Pneumatic tyre and manufacturing method therefor

Abstract

The present invention has an object of providing a pneumatic tire that exhibits better uniformity by improving the wire wound body for constituting the bead core. The pneumatic tire 1 comprises a bead core 5 comprising a wire wound body 10 in which one bead wire 10 a is spirally wound in a continuous around a tire rotational axis CL so that a plurality of layers of the bead wire are formed in a radial direction of the tire. The wire wound body 10 comprises a first part 13 and a second part 14. The first part 13 comprises a plurality of layers of the bead wire 10 a each circumferentially extending with a constant radius from the tire rotational axis CL. The second part comprises a plurality of layers of the bead wire 10 a each circumferentially extending while changing its radius from the tire rotational axis CL.

1 . A pneumatic tire comprising
 a tread portion,   a pair of sidewall portions,   a pair of bead portions each with a bead core therein,   a carcass extending between the bead cores,   at least one of the bead cores comprising a wire wound body in which one bead wire is spirally wound in a continuous around a tire rotational axis so that a plurality of layers of the bead wire are formed in a radial direction of the tire, and   the wire wound body comprising a first part and a second part, the first part comprising a plurality of layers of the bead wire each extending in a circumferential direction of the tire having a constant radius from the tire rotational axis, the second part comprising a plurality of layers of the bead wire each extending in the circumferential direction of the tire while changing its radius from the tire rotational axis.   
     
     
         2 . The pneumatic tire according to  claim 1 ,
 wherein the second part constitutes a central angle in a range of from 4 to 20 degrees of the wire wound body.   
     
     
         3 . The pneumatic tire according to  claim 2 ,
 wherein the radius of each layer of the bead wire of the second part gradually increases from a side of a winding-starting end toward a side of a winding-terminal end of the bead wire.   
     
     
         4 . The pneumatic tire according to  claim 1 ,
 wherein the at least one of the bead cores comprises an axially inner portion disposed axially inward of the carcass, and an axially outer portion disposed axially outward of the carcass, and each of the axially inner portion and the axially outer portion is configured as the wire wound body.   
     
     
         5 . The pneumatic tire according to  claim 1 ,
 wherein each layer of the bead wire of the second part extends in a straight manner.   
     
     
         6 . The pneumatic tire according to  claim 1 ,
 wherein each layer of the bead wire of the second part extends in an arc manner.   
     
     
         7 . The pneumatic tire according to  claim 1 ,
 wherein the wire wound body has a winding-starting end and a winding-terminal end, and   the winding-terminal end is positioned on a radial line that passes through the tire rotational axis and the winding-starting end.   
     
     
         8 . A method for manufacturing the pneumatic tire according to  claim 1 , the method comprising
 a wire wound body forming step in which one bead wire is spirally wound in a continuous on a predetermined area of a side surface of an inner core to form the wire wound body,   wherein the wire wound body forming step comprises
 a wire fixing step in which a winding-starting end of the bead wire is pushed and fixed on the predetermined area, and then 
 a wire winding step in which the bead wire is spirally wound on the predetermined area by rotating the inner core around the tire rotational axis, 
 wherein the wire winding step comprises 
 a first rotating step in which the inner core rotates to wind the bead wire while maintaining an angle α 1  in constant between the tire rotational axis and a Y-axis direction that is a feeding direction of the bead wire to the inner core, and 
 a second rotating step in which the inner core rotates to wind the bead wire while gradually increasing the angle α 1 . 
   
     
     
         9 . The method for manufacturing the pneumatic tire according to  claim 8 ,
 wherein the angle α 1  is increased by turning the inner core around a radial axis passing through a point “O” at which a core equatorial plane and the tire rotational axis intersect.   
     
     
         10 . The method for manufacturing the pneumatic tire according to  claim 8 ,
 wherein the second rotating step further comprises moving the inner core backward along the Y-axis while increasing the angle α 1 .   
     
     
         11 . The pneumatic tire according to  claim 2 ,
 wherein the at least one of the bead cores comprises an axially inner portion disposed axially inward of the carcass, and an axially outer portion disposed axially outward of the carcass, and each of the axially inner portion and the axially outer portion is configured as the wire wound body.   
     
     
         12 . The pneumatic tire according to  claim 3 ,
 wherein the at least one of the bead cores comprises an axially inner portion disposed axially inward of the carcass, and an axially outer portion disposed axially outward of the carcass, and each of the axially inner portion and the axially outer portion is configured as the wire wound body.   
     
     
         13 . The pneumatic tire according to  claim 2 ,
 wherein each layer of the bead wire of the second part extends in a straight manner.   
     
     
         14 . The pneumatic tire according to  claim 3 ,
 wherein each layer of the bead wire of the second part extends in a straight manner.   
     
     
         15 . The pneumatic tire according to  claim 4 ,
 wherein each layer of the bead wire of the second part extends in a straight manner.   
     
     
         16 . The pneumatic tire according to  claim 2 ,
 wherein each layer of the bead wire of the second part extends in an arc manner.   
     
     
         17 . The pneumatic tire according to  claim 3 ,
 wherein each layer of the bead wire of the second part extends in an arc manner.   
     
     
         18 . The pneumatic tire according to  claim 4 ,
 wherein each layer of the bead wire of the second part extends in an arc manner.   
     
     
         19 . The pneumatic tire according to  claim 2 ,
 wherein the wire wound body has a winding-starting end and a winding-terminal end, and the winding-terminal end is positioned on a radial line that passes through the tire rotational axis and the winding-starting end.   
     
     
         20 . The pneumatic tire according to  claim 3 ,
 wherein the wire wound body has a winding-starting end and a winding-terminal end, and the winding-terminal end is positioned on a radial line that passes through the tire rotational axis and the winding-starting end.