High performance tire for vehicles

Abstract

A very high performance tire ( 1, 101 ) for vehicles comprises a tread ( 14 ) provided with a plurality of transversal grooves ( 15 ) circumferentially distributed along the tread ( 14 ) in groups alternately extending from opposite shoulder zones (F, G) of the tread ( 14 ). The transversal grooves ( 15 ) define in an equatorial zone (E) of the tread ( 14 ) a substantially isotropic matrix of substantially continuous portions ( 18 ) of the tread ( 14 ) terminating at an equatorial portion ( 17 ) of a same transversal groove ( 15 ) of the axially opposite group of grooves.

1 . A tire ( 1 ,  101 ) for vehicles having a curvature ratio not greater than 0.1, comprising: 
 a carcass structure ( 2 ) including a central crown portion ( 3 ) and two sidewalls ( 4 ,  5 ) ending in a couple of beads ( 9 ,  10 ) for anchoring to a rim ( 11 ) of a wheel;    a belt structure ( 12 ), coaxially associated to the carcass structure ( 2 );    a tread ( 14 ), coaxially extending around the belt structure ( 12 ), on the tread being defined: 
 i) an equatorial zone (E) extending on either side of the equatorial plane (Y-Y) of the tire ( 1 ,  101 ), and  
 ii) two shoulder zones (F, G) in axially opposite positions with respect to said equatorial zone;  
    said tread ( 14 ) comprising a plurality of transversal grooves ( 15 ) including a first shoulder portion ( 16 ) and a second equatorial portion ( 17 ),     characterized in that said transversal grooves ( 15 ) are circumferentially distributed along the tread ( 14 ) in groups alternately extending from said shoulder zones (F, G) of the tread ( 14 ), said groups of grooves ( 15 ) defining in the equatorial zone (E) of the tread ( 14 ) a plurality of substantially continuous portions ( 18 ) of the tread ( 14 ) ending at the equatorial portion ( 17 ) of a same transversal groove ( 15 ) of the axially opposed group of grooves ( 15 ).    
     
     
         2 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that the equatorial portion ( 17 ) of at least one of the transversal grooves ( 15 ) forms an angle (g) having a width comprised between 20° and 65° with respect to the equatorial plane (Y-Y) of the tire ( 1 ,  101 ).  
     
     
         3 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that at least one of said transversal grooves ( 15 ) comprises an equatorial portion ( 17 ) extending on either side of the equatorial plane (Y-Y) of the tire ( 1 ,  101 ).  
     
     
         4 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that at least one of said transversal grooves ( 15 ) comprises an equatorial portion ( 17 ) extending in a substantially rectilinear way within an equatorial half-zone (E/ 2 ) of the tread ( 14 ).  
     
     
         5 . The tire ( 1 ,  101 ) according to  claim 4 , characterized in that at least one of said transversal grooves ( 15 ) comprises an equatorial portion ( 17 ) extending in a substantially rectilinear way at least partly within one of said shoulder zones (F, G) of the tread ( 14 ).  
     
     
         6 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that in each of said groups the transversal grooves ( 15 ) comprise equatorial portions ( 17 ) at least partly substantially parallel to one another.  
     
     
         7 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that the equatorial portions ( 17 ) of said groups of grooves terminate at a distance comprised between 0 mm and 50% of the mean pitch of the tread pattern from the equatorial portion ( 17 ) of the same transversal groove ( 15 ) of the axially opposite group of grooves ( 15 ).  
     
     
         8 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that the equatorial portions ( 17 ) of the transversal grooves ( 15 ) is connected to said shoulder portion ( 16 ) by means of a substantially curvilinear intermediate portion ( 19 ) having a curvature radius (R) comprised between 30 and 60 mm.  
     
     
         9 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that the shoulder portion ( 16 ) of at least one transversal groove ( 15 ) forms with the equatorial plane (Y-Y) of the tire ( 1 ,  101 ) an angle (b) having a width comprised between 85° and 95°.  
     
     
         10 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that said transversal grooves ( 15 ) have a substantially constant width comprised between 5 and 10 mm along the tread ( 14 ) portion substantially corresponding to the straightway ground contacting area of the tire ( 1 ,  101 ).  
     
     
         11 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that the shoulder portion ( 16 ) of the transversal grooves ( 15 ) comprises an end portion ( 20 ) having a width comprised between 40% and 60% of the maximum width of the transversal grooves ( 15 ).  
     
     
         12 . The tire ( 1 ,  101 ) according to  claim 11 , characterized in that said end portion ( 20 ) substantially lies within the curve or drift ground contacting area of the tire ( 1 ,  101 ).  
     
     
         13 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that each of said groups of grooves ( 15 ) comprises 3 to 7 transversal grooves ( 15 ).  
     
     
         14 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that said traversal grooves ( 15 ) have a depth comprised between 5 and 9 mm.  
     
     
         15 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that the transversal grooves ( 15 ) of each of said groups are longitudinally staggered with respect to the grooves ( 15 ) of the axially opposite group by a distance equal to about 50% of the mean pitch of the tread pattern.  
     
     
         16 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that the tread ( 14 ) further comprises a central depression ( 29 ) formed astride the equatorial plane (Y-Y) of the tire ( 1 ,  101 ), having a maximum depth comprised between 40% and 60% of the depth of the transversal grooves ( 15 ) and a width comprised between 15 and 25 mm.  
     
     
         17 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that it further comprises a couple of longitudinal slots ( 21 ,  22 ) circumferentially extending on opposite sides of the equatorial plane (Y-Y) of the tire ( 1 ,  101 ) along said shoulder zones (F, G) of the tread ( 14 ).  
     
     
         18 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that it further comprises a plurality of transversal notches ( 28 ) formed in said shoulder zones (F, G) of the tread ( 14 ) and interposed between adjoining transversal grooves ( 15 ), said notches ( 28 ) having a depth comprised between 3 and 4.5 mm and a width comprised between 2 and 3.5 mm.  
     
     
         19 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that each of said groups comprises a plurality of grooves ( 15 ) having a length decreasing along the rolling direction (D) of the tire ( 1 ,  101 ).  
     
     
         20 . The tire ( 1 ,  101 ) according to  claim 1 , characterized in that said substantially continuous portions ( 18 ) of the tread ( 14 ) terminate at the equatorial portion ( 17 ) of the transversal groove ( 15 ) having a prevailing length of the axially opposite group of grooves ( 15 ).  
     
     
         21 . A tread ( 14 ) for vehicle tires, comprising a plurality of transversal grooves ( 15 ) including a first shoulder portion ( 16 ) and a second equatorial portion ( 17 ) formed in an equatorial zone (E) of the tread ( 14 ) extending on either side of the equatorial plane (Y-Y) of the tire ( 1 ,  101 ) and along at least one of two shoulder zones (F, G) defined on the tread ( 14 ) in axially opposite parts with respect to said equatorial zone (E), 
 characterized in that said transversal grooves ( 15 ) are circumferentially distributed in groups alternately extending from said shoulder zones (F, G) of the tread ( 14 ), said groups of grooves ( 15 ) defining in the equatorial zone (E) of the tread ( 14 ) a plurality of substantially continuous portions ( 18 ) of the tread ( 14 ) terminating at the equatorial portion ( 17 ) of a same transversal groove ( 15 ) of the axially opposed group of grooves ( 15 ).    
     
     
         22 . The tread ( 14 ) according to  claim 21 , characterized in that the equatorial portion ( 17 ) of at least one of the transversal grooves ( 15 ) forms an angle (g) having a width comprised between 20° and 65° with respect to the equatorial plane (Y-Y) of the tire ( 1 ,  101 ).  
     
     
         23 . The tread ( 14 ) according to  claim 21 , characterized in that at least one of the transversal grooves ( 15 ) comprises an equatorial portion ( 17 ) extending on either side of the equatorial plane (Y-Y) of the tire ( 1 ,  101 ).  
     
     
         24 . The tread ( 14 ) according to  claim 21 , characterized in that the equatorial portion ( 17 ) of the transversal grooves ( 15 ) is connected to said shoulder portion ( 16 ) by means of a substantially curvilinear intermediate portion ( 19 ) having a curvature radius (R) comprised between 30 and 60 mm.  
     
     
         25 . The tread ( 14 ) according to  claim 21 , characterized in that the shoulder portion ( 16 ) of at least one transversal groove ( 15 ) forms with the equatorial plane (Y-Y) of the tire ( 1 ,  101 ) an angle (b) having a width comprised between 85° and 95°.  
     
     
         26 . The tread ( 14 ) according to  claim 21 , characterized in that each of said groups of grooves comprises from 3 to 7 transversal grooves ( 15 ).  
     
     
         27 . The tread ( 14 ) according to  claim 21 , characterized in that it further comprises a central depression ( 29 ) formed astride said equatorial plane (Y-Y), having a maximum depth comprised between 40% and 60% of the depth of the transversal grooves ( 15 ) and a width comprised between 15 and 25 mm.  
     
     
         28 . The tread ( 14 ) according to  claim 21 , characterized in that each of said groups comprises a plurality of grooves ( 15 ) having a length decreasing along the rolling direction (D) of the tire ( 1 ,  101 ).  
     
     
         29 . The tread ( 14 ) according to  claim 21 , characterized in that said substantially continuous portions ( 18 ) of the tread ( 14 ) terminate at the equatorial portion ( 17 ) of the transversal groove ( 15 ) having a prevailing length of the axially opposed group of grooves ( 15 ).  
     
     
         30 . A set of tires ( 1 ,  101 ), comprising a first couple of tires ( 101 ) adapted to be mounted on the front wheels of a vehicle and a second couple of tires ( 1 ) adapted to be mounted on the rear wheels of a vehicle, said first and second couple of tires ( 1 ,  101 ) comprising a first and, respectively, a second tread ( 14 ) on each of which are defined: 
 i) an equatorial zone (E) extending on either side of the equatorial plane (Y-Y) of the tire ( 1 ,  101 ), and    ii) two shoulder zones (F, G) in axially opposite positions with respect to said equatorial zone (E);    said first and second treads ( 14 ) being provided with a plurality of transversal grooves ( 15 ) including a first shoulder portion ( 16 ) and a second equatorial portion ( 17 ),    characterized in that:    1) in the front tires ( 101 ) said transversal grooves ( 15 ) are circumferentially distributed along the first tread ( 14 ) in groups alternately extending from opposite shoulder zones (F, G) of the tread ( 14 ), each of said groups including from 3 to 5 grooves ( 15 ),    2) in the rear tires ( 1 ) said transversal grooves ( 15 ) are circumferentially distributed along the second tread ( 14 ) in groups alternately extending from opposite shoulder zones (F, G) of the tread ( 14 ), each of said groups including from 5 to 7 grooves ( 15 ),    said groups of grooves ( 15 ) defining in the equatorial zone (E) of said first and second treads ( 14 ) a corresponding plurality of substantially continuous portions ( 18 ) of the tread ( 14 ) terminating at the equatorial portion ( 17 ) of a same transversal groove ( 15 ) of the axially opposite group of grooves ( 15 ).    
     
     
         31 . The set of tires ( 1 ,  101 ) according to  claim 30 , characterized in that: 
 i) the equatorial portion ( 17 ) of at least one of the transversal grooves ( 15 ) of the first tread ( 14 ) forms an angle (g) substantially equal to 45° with respect to the equatorial plane (Y-Y) of the front tire ( 101 ),    ii) the equatorial portion ( 17 ) of at least one of the transversal grooves ( 15 ) of the second tread ( 14 ) forms an angle (g) substantially equal to 30° with respect to the equatorial plane (Y-Y) of the rear tire ( 1 ).    
     
     
         32 . The set of tires ( 1 ,  101 ) according to  claim 30 , characterized in that the front tire ( 101 ) has a chord shorter than the chord of the rear tire ( 1 ).  
     
     
         33 . The set of tires ( 1 ,  101 ) according to  claim 30 , characterized in that the first tread ( 14 ) is provided with groups comprising three transversal grooves ( 15 ) and the second tread ( 14 ) is provided with groups comprising five transversal grooves ( 15 ).  
     
     
         34 . The set of tires ( 1 ,  101 ) according to  claim 30 , characterized in that the first tread ( 14 ) further comprises a central depression ( 29 ) formed astride the equatorial plane (Y-Y) of the front tire ( 101 ).  
     
     
         35 . The set of tires ( 1 ,  101 ) according to  claim 34 , characterized in that said central depression ( 29 ) has a depth comprised between 40% and 60% of the depth of the transversal grooves ( 15 ) and a width comprised between 15 and 25 mm.  
     
     
         36 . The set of tires ( 1 ,  101 ) according to  claim 30 , characterized in that in at least one of the front ( 101 ) and rear ( 1 ) tires the shoulder portion ( 16 ) of the transversal grooves ( 15 ) comprises and end portion ( 20 ) having a reduced width comprised between 40% and 60% of the maximum width of the transversal grooves ( 15 ).  
     
     
         37 . A method of optimizing the road behavior of a vehicle equipped with a set of tires ( 1 ,  101 ), comprising the following steps: 
 a) mounting on the front steering axis of the vehicle a couple of tires ( 101 ) comprising a first tread ( 14 ) allowing a substantially neutral behavior to lateral and longitudinal stresses and combinations thereof;    b) mounting on the rear and tractive axis of the vehicle a couple of tires ( 1 ) comprising a second tread ( 14 ) having a preferred releasing direction of longitudinal stresses with respect to lateral stresses.    
     
     
         38 . The method according to  claim 37 , wherein: 
 a) each tread ( 14 ) comprises a plurality of transversal grooves ( 15 ) arranged in groups alternately extending from opposite shoulder zones (F, G) of each tread ( 14 ), said groups of grooves ( 15 ) defining in an equatorial zone (E) of each tread ( 14 ) a corresponding plurality of substantially continuous portions ( 18 ) terminating at the equatorial portion ( 17 ) of a same groove ( 15 ) of the axially opposite group,    b) the first tread ( 14 ) comprises: 
 i) equatorial portions ( 17 ) of the transversal grooves ( 15 ) forming an angle (g) substantially equal to 45° with respect to the equatorial plane (Y-Y) of the tire ( 101 ),  
 ii) a central depression ( 29 ) formed astride the equatorial plane (Y-Y) of the tire ( 101 ), and  
   c) the second tread ( 14 ) comprises equatorial portions ( 17 ) of the transversal grooves ( 15 ) forming an angle (g) comprised between 30° and 50° with respect to the equatorial plane (Y-Y) of the tire ( 1 ).