Tire for a two-wheeled vehicle, including a specific belt structure

Abstract

A tire for a two-wheeled vehicle includes a carcass of toric form having a high transverse curvature, a tread band, and a circumferentially-inextensible belt structure. The belt structure is interposed between the carcass and the tread band, and includes reinforcing elements. Relative to an equatorial plane of the tire, the reinforcing elements may be randomly oriented, substantially oriented in an axial direction, or substantially oriented in an inclined direction. The belt structure further includes a radially-external layer provided with a plurality of cord coils disposed at a substantially-zero angle relative to the equatorial plane of the tire. The cord coils are positioned in axial side-by-side relationship and extend from one axial extremity of the belt structure to an opposite axial extremity. A density of the cord coils grows from the equatorial plane of the tire to the axial extremities of the belt structure.

1 . A tire for two-wheeled vehicles comprising a carcass of toric form having a high transverse curvature and provided with a central crown and two sidewalls terminating in a pair of beads for anchoring to a corresponding mounting rim, a tread band located on said crown and having a curvature ratio at least as high as 0.3 and a circumferentially-inextensible belt structure disposed between said carcass and tread band, in which that said belt structure at a radially external position is comprised of a layer of cord coils substantially disposed at a zero angle to the equatorial plane of the tire.  
     
     
         2 . A tire for two-wheeled vehicles comprising a carcass of toric form having a high transverse curvature and provided with a central crown and two sidewalls terminating in a pair of beads for anchoring to a corresponding mounting rim, a tread band located on said crown and a circumferentially-inextensible belt structure disposed between said carcass and tread band, which belt comprises a radially external layer provided with a plurality of cord coils disposed at a substantially zero angle to the equatorial plane of the tire, said plurality of cord coils being in axial side-by-side relationship and extended from one axial extremity to the other axial extremity of said belt, and at least one radially internal layer provided with reinforcing elements oriented in a crossed direction relative to the equatorial plane of the tire, in which said tire has a curvature ratio or tread camber at least as high as 0.3.  
     
     
         3 . A tire for two-wheeled vehicles comprising a carcass of toric form having a high transverse curvature and provided with a central crown and two sidewalls terminating in a pair of beads for anchoring to a corresponding mounting rim, a tread band located on said crown and a circumferentially-inextensible belt structure disposed between said carcass and tread band, which belt comprises a radially external layer provided with a plurality of cord coils disposed at a substantially zero angle to the equatorial plane of the tire, said plurality of cords being in axial side-by-side relationship and extended from one axial extremity to the other axial extremity of said belt, and at least one radially internal layer provided with reinforcing elements oriented in a crossed direction relative to the equatorial plane of the tire, in which the winding thickness according to which said cord coils at an angle of substantially zero degrees are distributed along the axial extension of said belt is given by the following relation:  
       
         
           
             
               Nx 
               = 
               
                 K 
                  
                 
                   
                     R 
                     2 
                   
                   
                     r 
                     2 
                   
                 
                  
                 No 
               
             
           
           
           
               
           
         
       
       wherein: 
 No is the number of cord coils disposed in a central portion of unitary length located on either side of the equatorial plane;  
 R is the distance between the center of said portion and the rotation axis of the tire;  
 r is the distance between the center of the unitary portion included the equatorial plane and the axial extremities of said radially external layer, and the rotation axis of the tire;  
 K is a parameter taking into account the constituent material and the cord formation, as well as the amount of rubber around the cord and the weight of the radially-internal layer section at said  
 unitary portion which is variable with the occurrence of variations in the material type and structural features of the belt strips along the crown profile that diverge from the reference values.  
 
     
     
         4 . A tire for two-wheeled vehicles comprising a carcass of toric form having a high transverse curvature and provided with a central crown and two sidewalls terminating in a pair of beads for anchoring to a corresponding mounting rim, a tread band located on said crown and a circumferentially-inextensible belt structure disposed between said carcass and tread band, which belt comprises a radially external layer provided with a plurality of cord coils disposed at a substantially zero angle to the equatorial plane of the tire, in axial side-by-side relationship and extended from one axial extremity to the other axial extremity of said belt, and at least one radially internal layer provided with reinforcing elements oriented in a crossed direction relative to the equatorial plane of the tire, in which 
 said tread band has a curvature ratio at least as high as 0.3,    the winding thickness of said cord coils increasingly grows from the equatorial plane to the belt extremities;    the winding thickness of said cord coils, in a right section of unitary width located on either side of the equatorial plane does not exceed 6 cords/cm.    
     
     
         5 . A tire according to  claim 4 , in which said winding thickness is between 4 and 6 cords/cm.  
     
     
         6 . A tire according to  claim 4 , in which said cords of the radially external layer comprise metallic high-elongation cords made of high-carbon steel wires.  
     
     
         7 . A tire according to  claim 4 , in which said cords of the radially external layer comprise textile cords made of aramid.  
     
     
         8 . A tire according to  claim 4 , in which said radially internal layer comprises two strips disposed axially in side by side relationship, provided with reinforcing elements oriented in directions that are inclined in each strip and opposite to each other in the two strips, relative to the equatorial plane of the tire.  
     
     
         9 . A tire according to  claim 4 , in which said radially internal layer comprises, from each axial side of the equatorial plane, two radially superposed strips provided with reinforcing elements oriented according to inclined directions in each strip and opposite to each other in the two strips, relative to the equatorial plane of the tire.  
     
     
         10 . A tire according to  claim 9 , in which the reinforcing elements in one of said strips are of a different material from that of the reinforcing elements in the adjacent strip in the radial direction.  
     
     
         11 . A tire according to  claim 4 , in which the reinforcing elements in said radially internal layer are selected from the group consisting of textile cords and metallic cords.  
     
     
         12 . A tire according to  claim 4 , in which said radially internal layer consists of a sheet of elastomeric material charged with fibrous reinforcing fillings dispersed in the elastomeric matrix.  
     
     
         13 . A tire according to  claim 12 , in which said fibrous reinforcing fibers are made of a material selected from the group comprising textile, metallic and glass fibers.  
     
     
         14 . A tire according to  claim 12 , in which said fibrous reinforcing fibers are short fibers formed with fibrils of aramid.  
     
     
         15 . A tire according to  claim 12 , in which said fibrous reinforcing fillings are oriented along a preferred direction inclined to said equatorial plane.  
     
     
         16 . A tire according to  claim 12 , in which said fibrous reinforcing fibers are distributed in said elastomeric matrix according to a density per unit of volume of between 0.5% and 5% of the overall volume.  
     
     
         17 . A tire according to  claim 4 , in which said radially internal layer is interrupted at the equatorial plane of the tire over a portion of a width of between 10% and 30% of the axial width of said belt.  
     
     
         18 . A tire according to  claim 4 , in which said beads comprise bead cores of aramidic fiber.  
     
     
         19 . A tire for two-wheeled vehicles comprising a carcass of toric form having a high transverse curvature and provided with a central crown and two sidewalls terminating in a pair of beads for anchoring to a corresponding mounting rim, a tread band located on said crown and having a curvature ratio at least as high as 0.3, and a belt structure interposed between said carcass and tread band, circumferentially inextensible, provided with reinforcing elements oriented in a crossed direction to the equatorial plane of the tire, in which: 
 said belt comprises a radially external layer provided with a plurality of cord coils disposed at a substantially zero angle relative to the equatorial plane of the tire, positioned in axial side-by-side relationship and extending from one belt axial extremity to the other axial extremity,    the thickness of said cord coils increasingly growing from the equatorial plane to the belt axial extremities according to a given relation.    
     
     
         20 . A tire for vehicles according to  claim 19 , in which: 
 said given relation keeps to a constant value the product of the mass of the cord coils disposed in a unitary portion of given value over the axial width of said belt by the square of the distance between the center of said portion and the rotation axis of the tire, so as to cause a uniform tension state in said belt structure under the effect of the centrifugal force acting on the tire under working conditions.