Patent Application
20100154965
This invention relates to a pneumatic tire having a carcass and a belt reinforcing structure, and, more particularly, to a heavy load radial ply tire having a carcass and a high strength belt structure.
In a conventional pneumatic tire, a large number of belt plies, which stiffen the crown area, are sandwiched on top of one another and are susceptible to cracks inside the belt layers. These cracks may subsequently grow both axially and radially outward, causing a sudden cut/peel off and scattering of the belt/tread during operation.
In one conventional tire, zigzag belt layers have been utilized for the radially inner belt layers with the cord angles progressively increasing from the radially inner belt layers toward the radially outer belt layers. Thus, inner belt plies may contain cords extending substantially in a zigzag path at a cord angle of 5 degrees to 15 degrees in the circumferential direction with respect to the equatorial plane, while being bent at both sides, or lateral edges, of the plies. Each of the outer belt plies may contain cords having a cord angle B larger than the cord angle A of the inner belt plies.
In another conventional tire, each of the side end portions between adjoining inner zigzag belt plies is provided with a further extra laminated portion of a strip continuously extending in the circumferential direction. Further, the extra laminated portions may be sandwiched one upon another in the radial direction. It has been found that the circumferential rigidity of this tire in the vicinity of the lateral edge of each ply end or tread edge is locally increased in this manner so that the radial growth in the vicinity of the tread edge portion during running at high speed may be reduced.
Still another conventional tire has a carcass and a composite belt reinforcing structure having a pair of radially outer zigzag layers and a spirally wound belt layer with cords inclined at an inclination of 5 degrees or less in the circumferential direction with respect to the equatorial plane and located radially inward of, and adjacent to, the radially outer zigzag belt layers. The radially outer zigzag belt layers have cords inclined at 5 degrees to 30 degrees in the circumferential direction with respect to the equatorial plane and extending in alternation to turnaround points at each lateral edge of the belt layer. At each turnaround point, the cords are folded or preferably bent to change direction across the crown of the carcass thus forming a zigzag cord path. The radially inner zigzag belt layers are positioned between the carcass and the spirally wound belt layer. Each of the radially inner zigzag belt layers has cords wound at an inclination of 5 degrees to 30 degrees in the circumferential direction with respect to the equatorial plane and extending in alternation to turnaround points at each lateral edge of the belt layers.
In accordance with one example embodiment of the present invention, a pneumatic tire has a carcass and a belt reinforcing structure. The belt reinforcing structure includes a first zigzag belt layer having a first amplitude and a first wavelength and a second zigzag belt layer having a second amplitude and a second wavelength. The first wavelength of the first zigzag layer is out of phase with the second wavelength of the second zigzag layer.
According to another aspect of the present invention, the first zigzag belt layer comprises cords inclined an amount in the range of 3.0 to 8.5 degrees relative to an equatorial plane of the pneumatic tire.
According to still another aspect of the present invention, the second zigzag layer comprises cords inclined an amount in the range of 3.0 to 8.5 degrees relative to an equatorial plane of the pneumatic tire.
According to yet another aspect of the present invention, the pneumatic tire further includes a circumferential spirally wound layer interposed between the first zigzag layer and the second zigzag layer.
According to still another aspect of the present invention, the circumferential spirally wound layer comprises cords inclined an amount in the range of 0 to 5 degrees relative to an equatorial plane of the pneumatic tire.
According to yet another aspect of the present invention, the first zigzag layer is out of phase by Π/2 radians with the second zigzag layer.
According to still another aspect of the present invention, the first zigzag layer is disposed radially inward of the second zigzag layer.
In accordance with another example embodiment of the present invention, a pneumatic tire has a carcass and a belt reinforcing structure. The belt reinforcing structure includes a first zigzag belt layer having a first amplitude and a first wavelength and a second zigzag belt layer having a second amplitude and a second wavelength. The first wavelength of the first zigzag layer is 90 degrees out of phase with the second wavelength of the second zigzag layer.
According to another aspect of the present invention, the first zigzag belt layer comprises cords inclined an amount in the range of 3.0 to 8.5 degrees relative to an equatorial plane of the pneumatic tire.
According to still another aspect of the present invention, the second zigzag layer comprises cords inclined an amount in the range of 3.0 to 8.5 degrees relative to an equatorial plane of the pneumatic tire.
According to yet another aspect of the present invention, the pneumatic tire further includes a circumferential spirally wound layer interposed between the first zigzag layer and the second zigzag layer.
According to still another aspect of the present invention, the circumferential spirally wound layer comprises cords inclined an amount in the range of 0 to 5 degrees relative to an equatorial plane of the pneumatic tire.
According to yet another aspect of the present invention, the first zigzag layer is disposed radially inward of the second zigzag layer.
According to still another aspect of the present invention, the first amplitude is greater than the second amplitude.
According to yet another aspect of the present invention, the first zigzag layer, the second zigzag layer, and the circumferential spirally wound layer are formed from a continuous strip of material.
“Apex” means a non-reinforced elastomer positioned radially above a bead core.
“Aspect ratio” of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100% for expression as a percentage.
“Axial” and “axially” mean lines or directions that are parallel to the axis of rotation of the tire.
“Bead” means that part of the tire comprising an annular tensile member wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.
“Cut belt” or “cut breaker reinforcing structure” means at least two cut layers of plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 10 degrees to 33 degrees with respect to the equatorial plane of the tire.
“Bias ply tire” means a tire having a carcass with reinforcing cords in the carcass ply extending diagonally across the tire from bead core to bead core at about a 25-50 degree angle with respect to the equatorial plane of the tire. Cords run at opposite angles in alternate layers.
“Carcass” means the tire structure apart from the belt structure, tread, undertread, and sidewall rubber over the plies, but including the beads.
“Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.
“Chafers” refer to narrow strips of material placed around the outside of the bead to protect cord plies from the rim, distribute flexing above the rim, and to seal the tire.
“Chippers” mean a reinforcement structure located in the bead portion of the tire.
“Cord” means one of the reinforcement strands of which the plies in the tire are comprised.
“Equatorial plane (EP)” means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.
“Flipper” means a reinforced fabric wrapped about the bead core and apex.
“Footprint” means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load and pressure
“Innerliner” means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating fluid within the tire.
“Net-to-gross ratio” means the ratio of the tire tread rubber that makes contact with the road surface while in the footprint, divided by the area of the tread in the footprint, including non-contacting portions such as grooves.
“Nominal rim diameter” means the average diameter of the rim flange at the location where the bead portion of the tire seats.
“Normal inflation pressure” refers to the specific design inflation pressure and load assigned by the appropriate standards organization for the service condition for the tire.
“Normal load” refers to the specific design inflation pressure and load assigned by the appropriate standards organization for the service condition for the tire.
“Ply” means a continuous layer of rubber-coated parallel cords.
“Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire.
“Radial-ply tire” means a belted or circumferentially-restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65-90 degrees with respect to the equatorial plane of the tire.
“Section height” (SH) means the radial distance from the nominal rim diameter to the outer diameter of the tire at its equatorial plane.
“Zigzag belt reinforcing structure” means at least two layers of cords or a ribbon of parallel cords having 2 to 20 cords in each ribbon and laid up in an alternating pattern extending at an angle between of 2-30 degrees between lateral edges of the belt layers.
As shown in the half cross-section of
The carcass 31 may include at least one carcass ply 32 (
A belt structure 40 is arranged between the carcass 31 and the tread portion 25. The belt structure 40, according to an example embodiment of the present invention, comprises an inner belt layer 41 disposed radially adjacent the carcass 31 and an outer belt layer 42 disposed radially adjacent the tread portion 25. As shown in
The rubberized strip 43 may be further wound many times while the strip is shifted approximately a width of the strip in the circumferential direction so as not to form a gap between adjoining strips 43. As a result, the cords 46 extend substantially zigzag in the circumferential direction while changing the bending direction at a turnaround point 48 at both lateral edges 44, 45. The cords 46 may be further embedded uniformly throughout the inner belt layer 41. Moreover, the cords 46 may overlap one another such that multiple plies of the inner belt layer 41 are formed while crossing the cords 46 with each other.
Similarly, as shown in
The cords 46 of the inner belt layer 41 and outer belt layer 42 may cross with each other at a cord angle A of 2 degrees to 16 degrees, or more specifically 3.0 degrees to 8.5 degrees such as 5 degrees or 6.54 degrees, with respect to the equatorial plane EP of the tire 10 when the strip 43 is reciprocated at least once between both lateral edges 44, 45 of the inner layer within every 360 degrees of the circumference of the tire, as shown in
If the cord 46 was a nylon cord and the compressive strain would exceed 25%, cord fatigue could result. However, when a ratio of R/W (R is a radius of curvature (mm) of the strip 43 at the side lateral edges 44, 45 of the inner belt layer 41, and W is a width (mm) of the strip 43) is 2.0 or greater, as shown in
In addition to a case where the strip 43 is bent at both side lateral edges 44, 45 of the inner belt layer 41 in an arc configuration, as shown in
In the example embodiment, the layers 41, 39, and 42 may all be formed from a continuous strip 43 that simply forms the radially inner zigzag layer(s) 41 and then continues to form the at least one spirally wound layer 39 and then continues on to form the radially outer zigzag layer(s) 42. Alternatively, the spirally wound layer(s) 39 could be formed as a separate layer from another strip 43. This alternative permits the cords 46 to be of different size or even of different materials from the inner and outer zigzag layers 41, 42 (i.e., a steel inner layer and an aramid outer layer).
The circumferential, spirally wound layer 39, between the inner and outer zigzag layers 41, 42, may reduce the circumferential growth of the tire 10, not only in the lateral edges 44, 45, but also the crown area of the tread pattern 36. Thus, the circumferential, spirally wound layer 39, by resisting growth in the crown area of the tire 10, may greatly reduce cut propensity due to foreign object damage and also reduce tread cracking, particularly under the tread grooves.
In order to further improve uniformity, footprint shape, high load capability and durability, and wear evenness, as shown in
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 can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.
