Pair of high-transverse-curvature tyres, in particular for two-wheeled vehicles, method of controlling the behaviour of such vehicles on a bend and front tyre of said pair

Abstract

A pair of high-transverse-curvature tires, in particular for equipping a two-wheeled vehicle, in which the belt structure of the rear tire comprises a layer of inextensible cords disposed at a substantially zero angle with respect to the equatorial plane of the tire, preferably wound on a sheet of elastomeric material reinforced with aramide pulp, whereas the belt structure of the front tire comprises at least one radially outer layer of inextensible cords disposed at a substantially zero angle with respect to the equatorial plane of the tire and distributed with an axially variable density, and preferably, another reinforcing layer at a radially underlying position. The zero-degree cords preferably are metallic cords, of the high elongation type, made of high-carbon steel. In the belt structure of the front tire the distribution density of said cords continuously increases from the centre to the belt ends starting from a value of about 6 cords/cm at an area of a width included between 10% and 30% of the axial extension of said belt, disposed on either side of the equatorial plane.

1 . A pair of tires for two-wheeled vehicles, said tires comprising a radial carcass of toric form of high transverse curvature, having a central crown and two sidewalls terminating with a pair of beads for anchoring the tire to a corresponding mounting rim, a tread band applied crown-wise to said carcass and a circumferentially inextensible belt structure, interposed between said carcass and tread band, characterized in that: 
 the belt structure of the rear tire comprises at least one radially outer layer formed of a plurality of axially side-by-side circumferential coils ( 7   a ) of a cord ( 7 ) wound at a substantially zero angle with respect to the equatorial plane of the tire,    the belt structure of the front tire comprises at least one radially outer layer provided with a plurality of cord coils, disposed at a substantially zero angle with respect to the equatorial plane of the tire, axially distributed with a varying density from one end to the other of said belt.    
     
     
         2 . A pair of tires for two-wheeled vehicles according to  claim 1 , characterized in that said tires have a curvature ratio not lower than 0.3, the rear tire having a curvature ratio lower than the front tire.  
     
     
         3 . A pair of tires for two-wheeled vehicles according to  claim 1 , characterized in that said cord layer of the belt structure in the rear tire is formed of a narrow band of rubberized fabric comprising 1 to 5 metallic cords, of the high-elongation type, spiralled on said carcass, from one end to the other of said crown portion, at an angle of a substantially zero value with respect to the equatorial plane of the tire.  
     
     
         4 . A pair of tires for two-wheeled vehicles according to  claim 1 , characterized in that said cord coils of the radially outer layer in the belt structure of the front tire comprise high-elongation metallic cords made of high-carbon steel wires.  
     
     
         5 . A pair of tires for two-wheeled vehicles according to  claim 4 , characterized in that the density of said cord coils progressively increases from the equatorial plane to the belt ends, being of a value not exceeding 8 cords/cm at a unit width area located on either side of the equatorial plane.  
     
     
         6 . A pair of tires for two-wheeled vehicles according to  claim 1 , characterized in that the cord coils of said radially outer layer in the belt structure of at least one of said tires are wound on at least another reinforcing layer in a radially inner position.  
     
     
         7 . A pair of tires according to  claim 6 , characterized in that said radially inner layer in the belt structure of at least one of said tires is broken at the equatorial plane of the tire over a portion of a width included between 10% and 30% of the axial extension of said belt.  
     
     
         8 . A pair of tires for two-wheeled vehicles according to  claim 6 , characterized in that said radially inner layer is made up of a sheet of elastomeric material ( 9 ), interposed between the belt structure ( 2 ) and the carcass ply ( 3 ), comprising bonding means dispersed in the elastomeric material of said sheet.  
     
     
         9 . A pair of tires for two-wheeled vehicles according to  claim 8 , characterized in that said bonding means is reinforcing fibrous fillings of a material selected from the group comprising textile, metallic or glass fibres.  
     
     
         10 . A pair of tires according to  claim 9 , characterized in that said reinforcing fibrous fillings are short fibril-structure aramide fibres.  
     
     
         11 . A pair of tires according to  claim 10 , characterized in that said reinforcing fibrous fillings are homogeneously dispersed in said elastomeric material with a density per unit volume included between 0.5% and 5% of the overall volume.  
     
     
         12 . A pair of tires according to  claim 9 , characterized in that said reinforcing fibrours fillings are oriented along a preferential direction, inclined to said equatorial plane.  
     
     
         13 . A pair of tires for two-wheeled vehicles according to  claim 6 , characterized in that in the belt structure of the front tire said radially inner layer is comprised of axially facing strips provided with reinforcing elements oriented in inclined directions in each strip and opposite to each other in said strips relative to the equatorial plane of the tire.  
     
     
         14 . A pair of tires for two-wheeled vehicles according to  claim 13 , characterized in that the reinforcing elements in said radially inner layer are selected from the group comprising textile cords and metallic cords.  
     
     
         15 . A pair of tires for two-wheeled vehicles according to  claim 13 , characterized in that said radially inner layer comprises two radially overlapping strips on each side of the equatorial plane, which are provided with reinforcing elements oriented in inclined directions in each strip and opposite to each other in the two strips, relative to the equatorial plane of the tire.  
     
     
         16 . A pair of tires for two-wheeled vehicles according to  claim 15 , characterized in that the reinforcing elements in one of said strips are of a different material than the reinforcing elements in the adjacent strip in the radial direction.  
     
     
         17 . A tire for two-wheeled vehicles comprising a radial carcass of toric form of high transverse curvature, with a curvature ratio not lower than 0,3, provided with a central crown and two sidewalls terminating with a pair of beads for anchoring the tire to a corresponding mounting rim, a tread band applied crown-wise to said carcass and a circumferentially inextensible belt structure, interposed between said carcass and tread band, characterized in that said belt structure comprises at least one radially outer layer provided with a plurality of cord coils, disposed at a substantially zero angle with respect to the equatorial plane of the tire, axially distributed with a varying density from one end to the other of said belt.  
     
     
         18 . A method of controlling the overall slip thrust in a pair of tires mounted on a motor-vehicle, said tires comprising a radial carcass of toric form of high transverse curvature having a central crown and two sidewalls terminating with a pair of beads for anchoring to a corresponding mounting rim, a tread band applied crown-wise to said carcass and a circumferentially-inextensible belt structure interposed between said carcass and tread band, characterized by coupling on said motor-vehicle: 
 a rear tire provided with a belt structure comprising at least one radially outer layer formed of a plurality of circumferential coils ( 7   a ) disposed in axial side by side relationship, of a cord ( 7 ) wound at a substantially zero angle with respect to the equatorial plane of the tire, and    a front tire provided with a belt structure comprising at least one radially outer layer provided with a plurality of cords disposed at a substantially zero angle with respect to the equatorial plane of the tire, axially distributed with a varying density from one end to the other of said belt.    
     
     
         19 . A method of controlling the behaviour of a motor-vehicle through the structure of the pair of tires forming its equipment, characterized by providing both tires with a belt structure comprising at least one radially outer layer provided with a plurality of reinforcing cord coils, disposed at a substantially zero angle with respect to the equatorial plane of the tire, the number of coils and their distribution along the axial extension of each belt structure being such that the behaviours of the two tires are combined with each other in order to achieve a neutral behaviour of the motor-vehicle in slip.  
     
     
         20 . A method according to  claim 19 , characterized by varying the density of said cord coils in the axial direction, at least in the belt structure of the front tire for controlling the slip thrust exerted by the motor-vehicle on curvilinear trajectories.