JP5355067B2 - Pneumatic tire and manufacturing method thereof - Google Patents

Description

    The present invention relates to a pneumatic tire having a reinforcing layer in which a reinforcing cord that intersects the tire equator at an angle of 45 to 90 degrees is embedded between a belt layer and a tread, and a method for manufacturing the same.

As conventional pneumatic tires, for example, those described in Patent Document 1 below are known.
JP 2006-151212 A

  This includes a carcass layer having both ends in the width direction folded back around the bead core and extending substantially in a toroidal shape, and a belt cord disposed radially outside the carcass layer and inclined with respect to the tire equator. A belt layer composed of two belt plies, a tread disposed radially outward of the belt layer, and an aroma disposed between the belt layer and the tread and intersecting the tire equator at a large angle inside. And a reinforcing layer in which a cord of a group polyamide is embedded.

  In this case, when a circumferential shear deformation occurs between the road surface and the belt layer due to high speed running, the cord of the aromatic polyamide embedded in the reinforcing layer is slightly bent following the deformation. However, since it functions as a resistor, the axial distribution of slip and tangential force between the outer surface of the tread and the road surface in the ground contact area is made uniform, thereby improving steering stability and uneven wear resistance. Yes.

    However, it has been found that the pneumatic tire as described above cannot be improved as much as expected for uneven wear resistance when actually running at high speed. Therefore, as a result of intensive studies to find out the cause, the present inventor has found the following. That is, when a green tire is stored in a vulcanization mold and vulcanized, the tread portion including the belt layer extends in the circumferential direction, so that the width of the belt layer is narrowed, but the tire is inclined at a large angle relative to the tire equator. Since the cord of the reinforcing layer is made of aromatic polyamide, it hardly shrinks in the longitudinal direction, that is, in the width direction of the belt layer even by vulcanization.

  As a result, the narrowness ratio in the width direction of the belt layer becomes larger than the heat shrinkage rate of the cord of the reinforcing layer. In this case, the cord of the aromatic polyamide is slackened and the length of the cord of the aromatic polyamide is equal to the length of the cord. Protrusions are projected in the radial direction or in the circumferential direction to generate a waveform. When such a waveform is generated, the rigidity of the reinforcing layer is reduced at the position of the waveform, causing uneven wear, and the effect of suppressing uneven wear described above is diminished.

  An object of the present invention is to provide a pneumatic tire capable of easily improving uneven wear resistance and a method for manufacturing the same.

The first purpose is that a carcass layer having both ends in the width direction folded back around the bead core and extending in a substantially toroidal shape, and a belt cord disposed radially outside the carcass layer and inclined with respect to the tire equator. A belt layer composed of at least two belt plies embedded therein, a tread disposed radially outward of the belt layer and having a plurality of main grooves formed on the outer surface, and between the belt layer and the tread A pneumatic tire having a reinforcing layer in which a reinforcing cord made of an organic fiber that intersects the tire equator at an angle of 45 to 90 degrees is embedded, and the width of the belt ply is radially outward The width of the reinforcing layer is made wider than the distance in the width direction between the pair of main grooves located on both outermost sides in the width direction, while the outermost belt It can be achieved by a pneumatic tire that is narrower than the lie, and further, the reinforcing layer is arranged in close contact with the outermost belt ply in the radial direction, and the thermal contraction rate of the reinforcing cord is in the range of 10 to 15%. it can.

Secondly, the carcass layer is bulged and deformed so as to extend in a substantially toroidal shape, and both end portions in the width direction are folded back around the bead core, while the belt cord is inclined to the tire equator on the radially outer side of the carcass layer. A tread having at least two belt plies embedded therein, a tread disposed radially outward of the belt layer and having a plurality of main grooves formed on the outer surface, the belt layer and the tread, A green belt is attached by attaching a cylindrical belt tread band with a reinforcing layer embedded with a reinforcing cord made of organic fibers that is arranged between and at an angle of 45 to 90 degrees to the tire equator. In the method for manufacturing a pneumatic tire, comprising the step of molding and the step of vulcanizing the green tire to form a pneumatic tire, The width of the reinforcing layer is gradually narrowed toward the outer side in the radial direction, and the width of the reinforcing layer is made wider than the distance in the width direction between the pair of main grooves located on the outermost sides in the width direction, while the outermost side in the radial direction. In addition, the reinforcing layer is arranged in close contact with the outermost belt ply in the radial direction , and a reinforcing cord having a thermal shrinkage within a range of 10 to 15% is embedded as the reinforcing layer. This can be achieved by a method for manufacturing a pneumatic tire using a rubberized cord layer.

  In this invention, since the thermal contraction rate of the reinforcing cord made of organic fibers embedded in the reinforcing layer and intersecting the tire equator at an angle of 45 to 90 degrees is set to 10% or more, the belt layer by vulcanization The thermal contraction rate of the reinforcing cord in the reinforcing layer becomes larger than the narrow ratio in the width direction, and as a result, the reinforcing layer becomes narrower than the belt layer, and the reinforcing cord is stretched in the longitudinal direction by the belt layer. There is no room for generating a radial or circumferential waveform. Thereby, the rigidity of the reinforcing layer becomes uniform, and the uneven wear resistance can be easily improved. However, if the thermal contraction rate of the reinforcing cord exceeds 15%, it becomes difficult to manufacture the reinforcing cord and the tire shape becomes unstable, so that it cannot be used practically.

According to the second aspect of the present invention, the reinforcing cord functions most effectively as a resistor against the above-described circumferential shear deformation, and the axial distribution of slip and tangential force in the ground contact region is effective. Can be made uniform. Furthermore, it is possible to be configured as described in claim 3, potently inhibit the diameter growth of the shoulder portion due to centrifugal force during high speed running.

Embodiment 1 of the present invention will be described below with reference to the drawings.
In FIGS. 1 and 2, reference numeral 11 denotes a pneumatic radial tire for a passenger car that can run at high speed. The pneumatic tire 11 includes a pair of bead portions 13 each having a bead core 12 embedded therein, and a radial direction from the bead portions 13. Side wall portions 14 extending outward, tread portions 15 having a larger diameter than these side wall portions 14 and having a substantially cylindrical shape, and radially outer ends of the sidewall portions 14 and both axial ends of the tread portions 15 And a shoulder portion 16 positioned therebetween.

  The pneumatic tire 11 has a carcass layer 18 extending between the bead cores 12 in a substantially toroidal shape to reinforce the sidewall portion 14, the tread portion 15, and the shoulder portion 16. The width direction of the carcass layer 18 Both end portions are folded around the bead core 12 from the inside to the outside. The carcass layer 18 is composed of at least one carcass ply 19 here, and a plurality of carcass cords 20 extending in the radial direction (the meridian direction) are embedded in the carcass plies 19. Here, the carcass cord 20 is made of nylon, but may be made of organic fibers such as steel, aromatic polyamide or polyester.

Reference numeral 24 denotes a belt layer disposed on the radially outer side of the carcass layer 18, and the belt layer 24 is configured by laminating at least two (here, two) belt plies 25, A large number of non-extensible belt cords 26 made of steel, aromatic polyamide or the like are embedded in the interior. The belt cords 26 of these belt plies 25 are inclined with respect to the tire equator S within a range of 10 to 45 degrees, and at least two belt plies 25 are inclined in the opposite direction with respect to the tire equator S. Further, the aforementioned belt ply 25 is arranged so that its width gradually decreases as it goes outward in the radial direction.

  Reference numeral 28 denotes a tread disposed radially outward of the carcass layer 18 and the belt layer 24. The outer surface (grounding surface) of the tread 28 is wide and has a plurality of, four in this example, continuously extending in the circumferential direction. The main groove 29 is formed. In addition, the outer surface of the tread 28 may be formed with a plurality of lateral grooves that are wide and extend substantially in the width direction and intersect the main groove 29.

  When the pneumatic tire having the carcass layer 18 and the belt layer 24 as described above is driven at a high speed, the tread 28 in the ground contact region undergoes a large shear deformation in the circumferential direction between the road surface and the belt layer 24. At this time, since the center part of the tread has a larger diameter than the end part of the tread due to the crown radius, the tangential force in the driving direction is applied to the outer surface of the tread center part, while the braking direction is applied to the outer surface of both end parts of the tread. The tangential force is generated. As a result, the slip and tangential force between the outer surface of the tread and the road surface in the ground contact region are greatly different at the position in the width direction.

For this reason, in this embodiment, the tread portion 15 between the belt layer 24 and the tread 28 includes at least one (here, one) reinforcing ply 32 and is slightly wider than the radially outermost belt ply 25. with placing the narrow Kushida reinforcing layer 33 is to that larger than the width direction distance between the pair of main grooves 29 located a width of the reinforcing layer 33 to the both widthwise outermost sides. As a result, the reinforcing layer 33 is disposed in close contact with the outermost belt ply 25 in the radial direction. Here, a plurality of linearly extending reinforcing cords 34 intersecting the tire equator S at an angle A of 45 to 90 degrees larger than the cord angle of the belt cord 26 inside the reinforcing layer 33 (reinforcing ply 32). Are embedded over the entire width, and these reinforcing cords 34 are made of organic fibers such as nylon, polyketone, and polyethylene terephthalate.

  At this time, since the reinforcing cord 34 is embedded in the reinforcing layer 33 over the entire width thereof, it functions as a resistor while slightly bending following the deformation by the tread 28, whereby the entire area in the grounding region is The distribution in the width direction of the slip and tangential force between the outer surface of the tread and the road surface is uniformly distributed. Here, when the crossing angle A of the reinforcing cord 34 with respect to the tire equator S is less than 45 degrees, the reinforcing layer 33 exhibits the effect, and the circumferential shear deformation in the tread 28 increases, so the crossing angle A Must be 45 degrees or more.

  If the reinforcing cord 34 intersects the tire equator S at substantially 90 degrees as in this embodiment, the reinforcing cord 34 functions most effectively as a resistor against the aforementioned circumferential shear deformation, This is preferable because the axial distribution of slip and tangential force in the ground contact area can be effectively uniformed. When the crossing angle A exceeds 90 degrees, the reinforcing cord 34 is only inclined in the opposite direction with respect to the tire equator S, and therefore the maximum value of the crossing angle A is 90 degrees.

  In addition, since the pneumatic tire 11 as described above is generally manufactured by vulcanizing a green tire, the tread portion 15 including the belt layer 24 extends in the circumferential direction during vulcanization, and the width of the belt layer 24 is increased. However, if the narrowing ratio in the width direction of the belt layer 24 is larger than the thermal contraction rate of the reinforcing cord of the reinforcing layer 33, the reinforcing cord is slackened and the longitudinal direction is reduced. A protruding waveform in the radial direction or the circumferential direction is generated at one location, and the rigidity of the reinforcing layer is reduced at the waveform portion.

  Here, the narrow ratio in the width direction of the belt layer 24 means that the width of the belt layer 24 in the green tire before vulcanization is B, and the width of the belt layer 24 in the vulcanized pneumatic tire 11 is E. The value obtained by subtracting the width E from the width B is divided by the width B, and the result is multiplied by 100. On the other hand, the thermal contraction rate of the reinforcing cord is a load of 0.1746 (mN / D) at room temperature. When the length in the longitudinal direction of the reinforcing cord when loaded is F, and the length in the longitudinal direction when dry-heat-shrinking for 30 minutes in a thermostatic bath at 177 degrees C while applying the load to the reinforcing cord is G, The value obtained by subtracting the longitudinal length G from the longitudinal length F is divided by the longitudinal length F, and the result is multiplied by 100.

  In order to avoid the above-described situation, in this embodiment, the thermal contraction rate in the longitudinal direction of the reinforcing cord 34 embedded in the reinforcing layer 33 is set to 10% or more, thereby the belt layer 24 by vulcanization. The thermal contraction rate of the reinforcing cord 34 in the reinforcing layer 33 is made larger than the narrow ratio in the width direction. As a result, when vulcanization is performed, the reinforcing layer 33 is significantly narrower in the width direction than the belt layer 24, and the reinforcing cord 34 is stretched in the longitudinal direction by the belt layer 24, whereby the reinforcing cord 34 has a radius as described above. Thus, there is no room for generating a waveform in the direction or the circumferential direction, the rigidity of the reinforcing layer 33 becomes uniform, and uneven wear resistance can be easily improved.

  However, if the thermal contraction rate of the reinforcing cord 34 exceeds 15%, it becomes difficult to manufacture the reinforcing cord 34, and the shape of the pneumatic tire 11 becomes unstable due to the large thermal contraction, so that the thermal contraction rate is 15 Reinforcing cord 34 exceeding% cannot be used practically. Thus, in this embodiment, it is necessary to use a rubberized cord layer in which a reinforcing cord 34 having a thermal contraction rate in the range of 10 to 15% is embedded as the reinforcing layer 33.

  Here, the reinforcing cord 34 having a high heat shrinkage rate as described above can be obtained by increasing the number of twists of the cord (the number of twists per 10 cm) or by increasing the dipping temperature of the cord, For example, in a reinforcing cord in which a filament bundle of nylon fiber is twisted by 37 x 37 (number of times twisted per 10 cm x number of times twisted), the heat shrinkage rate is 7.0%, which is less than 10%, but 50 x 50 It is 11.0% in the reinforcing cord subjected to the twist of, and is in the range of 10 to 15%. Then, by increasing the number of twists of the cord, when the thermal contraction rate of the reinforcing cord 34 is increased, the thermal contraction rate of the reinforcing cord 34 can be easily and reliably within the above range.

  37 is disposed between the belt layer 24 and the tread 28, in this case, in the tread portion 15 between the reinforcing layer 33 and the tread 28, and is a pair of belt auxiliary layers usually called layers, and these belt auxiliary layers 37 Since at least both ends in the width direction of the reinforcing layer 33 extend from the outside in the radial direction, and here the belt auxiliary layer 37 extends slightly from the both ends in the width direction of the belt layer 24 to the outside in the width direction. Both ends in the width direction of the layer 24 are also covered from the outside in the radial direction.

  The belt auxiliary layer 37 is composed of at least one (here, one) auxiliary ply 38, and a reinforcing element 39 extending substantially parallel to the tire equator S is embedded in the auxiliary ply 38. The reinforcing element 39 is composed of organic fiber, for example, nylon, a twisted cord of aromatic polyamide, a hybrid cord in which the nylon and the aromatic polyamide are twisted, or a steel cord bent in a wavy or zigzag shape. can do.

  When such a belt auxiliary layer 37 is arranged in the tread portion 15, the shoulder portion 16 overlapping the belt auxiliary layer 37 is caused by centrifugal force by the belt auxiliary layer 37 when the pneumatic tire 11 runs at a high speed. Diameter growth is strongly suppressed. Here, the belt auxiliary layer 37 described above can be formed, for example, by spirally winding a ribbon-like body in which one or a small number of reinforcing elements 39 are arranged and covered with rubber. In the present invention, a thin shock absorbing rubber layer is disposed between the belt layer 24 and the reinforcing layer 33, and the shock absorbing rubber layer absorbs part of the shear deformation in the circumferential direction, thereby reducing the width of the above-mentioned slip. The direction distribution may be further uniformized.

    The pneumatic tire 11 described above can be manufactured as follows. That is, first, while the cylindrical first forming drum 42 shown in FIG. 3 is driven and rotated by the driving unit 43, tire constituent members including the carcass ply 19 are successively supplied and wound around the first and second ends. The cylindrical ply band 44 including the carcass layer 18 is formed by bonding them together. Next, after the first conveying means 46 holding the bead core 12 with filler is moved toward the first molding drum 42 to surround the first molding drum 42 from the outside, the ply band 44 is The first forming drum 42 is reduced in diameter while being held from the outside by the conveying means 46.

  Next, the first conveying means 46 is moved along the guide rail 47 to a position surrounding the second molding drum 48 from the outside, and the gripping ply band 44 and the bead core 12 with filler are received by the second molding drum 48. hand over. At this time, the pair of bead lock bodies 49 of the second molding drum 48 is expanded in diameter, and the bead core 12 is gripped from the radially inner side via the ply band 44.

On the other hand, in the band forming drum (not shown), the belt ply 25, the reinforcing ply 32, the auxiliary ply 38, and the tread 28 in which a plurality of main grooves 29 are formed on the outer surface are wound one after another, and the belt layer 24, A cylindrical belt tread band 50 including a tread 28, a belt layer 24, a reinforcing layer 33 disposed between the tread 28, and a belt auxiliary layer 37 is formed around the belt. At this time, a rubberized cord layer in which a reinforcing cord 34 having a thermal shrinkage rate in the range of 10 to 15% is embedded is used for the reinforcing layer 33 described above. Further, at this time, the belt ply 25 is arranged so that the width gradually decreases toward the outer side in the radial direction, and the width of the reinforcing layer 33 is set between the pair of main grooves 29 located on both outermost sides in the width direction. The outermost belt ply 25 is radially narrower than the outermost belt ply 25 in the radial direction, and the reinforcing layer 33 is disposed in close contact with the outermost belt ply 25 in the radial direction.

  Next, the bead lock body 49 of the second forming drum 48 moves inward in the axial direction so as to approach each other together with the bead core 12, and air is supplied into the ply band 44, so that the ply band 44 (the carcass layer 18 between the bead cores 12). ) Bulges and deforms so as to extend in a toroidal cross section, and the folded bladder of the second forming drum 48 expands, and the ply bands 44 (both ends in the width direction of the carcass layer 18) on both outer sides in the axial direction from the bead core 12 Wrap around 12 times.

At this time, the second conveying means (not shown) holding the belt tread band 50 moves to a position surrounding the second forming drum 48 from the outside, and the belt tread band 50 is moved to the ply band 44 (carcass). A green tire is formed by sticking to the radially outer side of the layer 18). Next, the green tire is carried into the vulcanization mold (not shown) from the second molding drum 48 and vulcanized under high temperature and high pressure to obtain the pneumatic tire 11 .

  The present invention can be applied to the industrial field of pneumatic tires having a reinforcing layer between a belt layer and a tread.

1 is a meridian cross-sectional view of a pneumatic tire showing Embodiment 1 of the present invention. It is a partially broken plan view of the tread portion. It is a schematic front view explaining the manufacturing method.

11 ... Pneumatic tire 12 ... Bead core
18 ... Carcass layer 24 ... Belt layer
25 ... belt ply 26 ... belt cord
28… Tread 33… Reinforcing layer
34 ... Reinforcement cord 37 ... Belt auxiliary layer
39 ... Reinforcing element 50 ... Belt tread band S ... Tire equator

Claims (4)

A carcass layer whose both ends in the width direction are folded around a bead core and extend in a substantially toroidal shape, and at least two belts that are disposed radially outside the carcass layer and in which belt cords that are inclined with respect to the tire equator are embedded A belt layer composed of a ply, a tread disposed on the outer side in the radial direction of the belt layer and having a plurality of main grooves formed on the outer surface, and disposed between the belt layer and the tread. In a pneumatic tire provided with a reinforcing layer in which reinforcing cords made of organic fibers intersecting at an angle of 45 to 90 degrees are embedded , the width of the belt ply is gradually narrowed toward the outer side in the radial direction, and The width of the reinforcing layer is made wider than the distance in the width direction between the pair of main grooves located on both outermost sides in the width direction, but is made narrower than the belt ply on the outermost side in the radial direction. With the serial reinforcing layer adhered directly disposed radially outermost belt ply, pneumatic tire is characterized in that the thermal shrinkage of the reinforcing cord in the range of 10-15%.     The pneumatic tire according to claim 1, wherein the reinforcing cord intersects the tire equator at substantially 90 degrees.     The pneumatic tire according to claim 1, wherein a belt auxiliary layer that covers at least both ends in the width direction of the reinforcing layer from the outside in the radial direction and in which a reinforcing element that extends substantially parallel to the tire equator is embedded is disposed. The carcass layer is bulged and deformed so as to extend in a substantially toroidal shape, and both end portions in the width direction are folded back around the bead core, while a belt cord inclined with respect to the tire equator is embedded inside the carcass layer radially outside A belt layer composed of at least two belt plies, a tread disposed radially outward of the belt layer and having a plurality of main grooves formed on the outer surface, and disposed between the belt layer and the tread. A step of forming a green tire by attaching a cylindrical belt tread band comprising a reinforcing layer in which a reinforcing cord made of an organic fiber intersecting with the tire equator at an angle of 45 to 90 degrees is embedded; A pneumatic tire comprising a step of vulcanizing the green tire to form a pneumatic tire, wherein the belt ply has a radius The width of the reinforcing layer is made wider than the distance in the width direction between the pair of main grooves located on the outermost sides in the width direction, while the belt plies on the outermost side in the radial direction. Furthermore, the rubber layer is further narrowed, and the reinforcing layer is disposed in close contact with the outermost belt ply in the radial direction, and the reinforcing layer has a rubber cord embedded with a reinforcing cord having a thermal shrinkage within a range of 10 to 15%. A method of manufacturing a pneumatic tire, characterized by using a cord layer.

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