JP4526363B2 - Pneumatic tire - Google Patents

Description

    The present invention relates to a pneumatic tire provided with a belt reinforcing layer in which a non-stretchable reinforcing element substantially parallel to the tire equator is embedded.

As conventional pneumatic tires, for example, those described in Patent Document 1 below are known.
JP-A-6-297905

  This is a carcass layer with both ends in the width direction folded back around the bead core and extending in a substantially toroidal shape, and a belt cord that is arranged radially outside the carcass layer and inclined in the opposite direction to the tire equator is embedded inside A belt layer composed of at least two belt plies, a tread disposed radially outward of the belt layer, and disposed between the belt layer and the tread, and substantially parallel to the tire equator therein. A non-stretchable composite cord made of stretched organic fibers (for example, aromatic polyamide) and steel is embedded, and a belt reinforcing layer (layer) overlapping at both ends in the width direction of the belt layer is provided.

  And this thing suppresses the diameter growth of the tread part by the centrifugal force at the time of high-speed running, especially the diameter growth of the tread end part where a large amount of rubber is arranged by the belt reinforcing layer, and the diameter growth. Uniformity improves handling stability and reduces the distortion generated at the outer edge in the width direction of the belt layer to improve durability.

    However, in such a conventional pneumatic tire, since the belt reinforcing layer capable of strongly suppressing the elongation in the circumferential direction of the tire is disposed so as to overlap the both ends in the width direction of the belt layer, The diameter growth at the tread edge during high-speed running of the tire is strongly suppressed by both the belt layer and the belt reinforcing layer, while the diameter growth at the center of the tread is suppressed only by the belt layer. The diameter grows larger than that at the end, and the outer diameter increases as the tire equator is approached. In addition, since the outer surface of the tread of the pneumatic tire is usually provided with a crown radius, it has a convex shape similar to that described above.

  Here, when the pneumatic tire is driven at a high speed, the tread in the ground contact area undergoes a large shear deformation between the road surface and the belt layer. Since the diameter is large, a tangential force in the driving direction is generated on the outer surface of the tread central portion, while a tangential force in the braking direction is generated on the outer surfaces of both ends of the tread. As a result, the slippage and tangential force between the outer surface of the tread and the road surface in the ground contact area are greatly different in the position in the width direction, and the steering stability is lowered, and both ends in the width direction of the tread are slipped in the braking direction. There was a problem that partial wear occurred due to early wear.

  In Patent Document 1, a non-extensible composite cord extending substantially parallel to the tire equator is embedded between the belt layer and the tread, and a belt reinforcing layer (cap) that overlaps the belt layer in the entire width is provided. Although the pneumatic tire provided is also described, this also generates a tangential force in the driving direction on the outer surface of the central portion of the tread and a tangential force in the braking direction on the outer surfaces of both end portions of the tread. As a result, there is a problem that steering stability is lowered and uneven wear occurs.

  An object of the present invention is to provide a pneumatic tire capable of effectively improving both steering stability and uneven wear resistance.

    For this purpose, the carcass layer whose both ends in the width direction are folded back around the bead core and extend in a substantially toroidal shape, and the belt cord disposed radially outside the carcass layer and inclined in the opposite direction with respect to the tire equator A belt layer composed of at least two belt plies embedded in the belt, a tread disposed radially outward of the belt layer, and disposed between the tread and the carcass layer, and substantially inside the tire equator. A belt reinforcing layer in which non-stretchable reinforcing elements extending in parallel are embedded; a thin buffer rubber layer disposed between the tread and the belt layer and the belt reinforcing layer; and between the tread and the buffer rubber layer. This can be achieved by providing a reinforcing layer that is disposed and has a reinforcing cord embedded therein and embedded with a reinforcing cord inclined in a range of 45 to 90 degrees with respect to the tire equator.

  In the present invention, there is a belt reinforcing layer between the tread and the carcass layer, a buffer rubber layer between the tread and the belt layer, a belt reinforcing layer, and a reinforcing layer between the tread and the buffer rubber layer. Since each of them is disposed, a buffer rubber layer and a reinforcing layer are sequentially disposed between the belt reinforcing layer and the tread toward the tread. As a result, the circumferential shear deformation that occurs between the road surface and the belt layer or the belt reinforcing layer when the pneumatic tire is traveling at a high speed is reduced in the ground contact region by the deformation of the buffer rubber layer interposed in the middle. Since the portion is absorbed, the circumferential shear deformation in the tread is relieved, and thereby, the widthwise distribution of slip and tangential force between the outer surface of the tread and the road surface in the ground contact region is made uniform.

  At this time, shear deformation of the buffer rubber layer and the tread is transmitted to the reinforcing layer to deform the reinforcing layer, and a reinforcing cord inclined in a range of 45 to 90 degrees with respect to the tire equator is included in the reinforcing layer. Since it is embedded over the entire width, these reinforcing cords function as a resistor against the deformation and bend slightly following the deformation, so that there is a gap between the tread outer surface and the road surface in the ground contact area. The width direction distribution of sliding and tangential force in the case is further uniformized.

  Here, when the inclination angle of the reinforcing cord with respect to the tire equator is less than 45 degrees, the reinforcing layer starts to exert the same effect as the belt reinforcing layer, and the circumferential shear deformation in the tread tends to increase. The inclination angle must be 45 degrees or more. In addition, the diameter growth of the tread due to the centrifugal force during high-speed driving is suppressed by the belt reinforcing layer arranged between the cushioning rubber layer and the carcass layer, so durability and handling stability compared to conventional tires There is almost no drop in the.

According to the second aspect of the present invention, a belt layer and a reinforcing layer are interposed in addition to the buffer rubber layer between the belt reinforcing layer and the tread. Since the coating rubber of the layer can also slightly absorb the circumferential shear deformation, the circumferential shear deformation of the tread can be further reduced.
Furthermore, if constituted as in claim 3, it is possible to strongly suppress the diameter growth of the belt layer at the portion overlapping the belt reinforcing layer during high speed running, and to strongly suppress the distortion generated at the belt end. Can be reduced.

According to the fourth aspect of the present invention, since the reinforcing cord having high bending rigidity functions as a resistor against circumferential shear deformation, it is provided between the outer surface of the tread and the road surface in the ground contact region. The widthwise distribution of slip and tangential force can be strongly made uniform.
Further, when configured as described in claim 5, the shear shear deformation generated between the road surface and the belt layer (belt reinforcing layer) is sufficiently absorbed while suppressing an increase in centrifugal force during high-speed traveling. can do.

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 are provided, and a substantially cylindrical tread portion 15 that connects the outer ends in the radial direction of the side wall portions 14 is provided.

  The pneumatic tire 11 has a carcass layer 18 that extends between the bead cores 12 in a substantially toroidal shape and reinforces the sidewall portion 14 and the tread portion 15. Both end portions in the width direction of the carcass layer 18 are The bead core 12 is folded from the inner side in the axial direction toward the outer side in the axial direction. 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 steel or aromatic polyamide.

  Reference numeral 24 denotes a belt layer disposed on the radially outer side of the carcass layer 18, and this 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. The belt cords 26 of these belt plies 25 are inclined with respect to the tire equator S within a range of 10 to 70 degrees, and at least two belt plies 25 are inclined in the opposite direction with respect to the tire equator S.

  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. Although not shown, a large number of lateral grooves extending in the width direction may be formed on the outer surface of the tread 28. 32 is a belt reinforcing layer disposed in the tread portion 15 between the tread 28 and the carcass layer 18, here, between the belt layer 24 and the carcass layer 18. The belt reinforcing layer 32 is wider than the belt layer 24. The tread width W is almost the same width. As a result, the belt reinforcing layer 32 is generally called a cap, and overlaps at least at both ends in the width direction of the belt layer 24, here, the entire width of the belt layer 24.

  Here, the belt reinforcing layer 32 is composed of at least one (here, one) reinforcing ply 33. The reinforcing ply 33 extends substantially parallel to the tire equator S, and is made of steel, aromatic polyamide, or the like. A reinforcing element 34 made of a non-stretchable material is embedded. When the reinforcing element 34 is made of aromatic polyamide, it is possible to easily achieve both durability and steering stability of the pneumatic tire 11.

  For this reason, the tread portion 15 (including both end portions in the width direction of the belt layer 24) that overlaps the belt reinforcing layer 32 is in contact with the belt reinforcing layer 32 when the pneumatic tire 11 runs at high speed. Thus, the diameter growth due to centrifugal force is strongly suppressed. Thereby, distortion generated at the outer end in the width direction of the belt layer 24 is reduced, and there is almost no deterioration in durability and steering stability as compared with the conventional tire. Here, the above-described belt reinforcing layer 32 can be formed by, for example, winding a ribbon-like body in which one or a small number of reinforcing elements 34 are arranged side by side and covered with rubber spirally around the outside of the carcass layer 18.

  Then, when the pneumatic tire 11 including the carcass layer 18, the belt layer 24, and the belt reinforcing layer 32 as described above is driven at high speed, the tread 28 in the ground contact region has the road surface, the belt layer 24, and the belt reinforcing layer 32. At this time, the center of the tread has a larger diameter than the end of the tread due to the crown radius, so that the tangential force in the driving direction is applied to the outer surface of the center of the tread, while the tread ends. A tangential force in the braking direction is generated on the outer surface of the part.

  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. In the case where the belt reinforcing layer 32 is a layer that overlaps only at both ends in the width direction of the belt layer 24, the central portion of the tread grows in diameter due to centrifugal force based on high-speed running and becomes larger in diameter than the end portion of the tread. The sliding and tangential forces of the slabs are much different.

  Therefore, in this embodiment, a thin buffer rubber layer 36 is disposed in the tread portion 15 between the tread 28 and the belt layer 24 and the belt reinforcing layer 32. Here, the buffer rubber layer 36 is wider than the belt layer 24 but slightly narrower than the tread width W. It is preferable for the rubber constituting the buffer rubber layer 36 that the JIS hardness of the rubber constituting the tread 28 is lower than that of the rubber constituting the tread 28 in order to effectively exhibit a buffering action, and the width thereof is In order to effectively exhibit the action, the tread width W is preferably 0.3 times or more.

  As a result, the buffer rubber layer 36 is interposed between the tread 28, the belt layer 24, and the belt reinforcing layer 32. As a result, the road surface, the belt layer 24, and the belt reinforcement when the pneumatic tire 11 travels at a high speed. A part of the circumferential shear deformation generated between the layer 32 and the layer 32 is absorbed in the ground contact region by the deformation of the buffer rubber layer 36 interposed therebetween. For this reason, the circumferential shear deformation in the tread 28 is alleviated by the amount of absorption, and thereby, the widthwise distribution of the slip and tangential force between the outer surface of the tread and the road surface in the above-described ground contact region is made uniform throughout. Is done.

  Here, the wall thickness t of the buffer rubber layer 36 is preferably in the range of 0.5 to 3.0 mm. The reason is that if the thickness t is less than 0.5 mm, the circumferential shear deformation generated between the road surface and the belt layer 24 (belt reinforcing layer 32) cannot be sufficiently absorbed. This is because if it exceeds 3.0 mm, the centrifugal force in the tread portion 15 during high-speed running increases and circumferential shear deformation increases.

  The tread portion 15 between the buffer rubber layer 36 and the tread 28 is provided with a reinforcing layer 40 including at least one reinforcing ply 39 (here, one reinforcing ply 39). Since the rubber layer 36 and the tread 28 are interposed, the shear deformation of the buffer rubber layer 36 and the tread 28 described above is transmitted and similarly deformed. However, in this embodiment, the reinforcing layer 40 is wider than the belt layer 24 and slightly narrower than the tread width W, like the cushioning rubber layer 36, and the reinforcing layer 40 (reinforcing ply 39). A plurality of linearly extending reinforcing cords 41 inclined in the range of 45 to 90 degrees with respect to the tire equator S are buried over the entire width.

  As a result, the reinforcing cord 41 in the reinforcing layer 40 is bent slightly following the deformation while functioning as a resistor against the deformation caused by the buffer rubber layer 36 and the tread 28, and thereby, The distribution in the width direction of the slip and tangential force between the outer surface of the tread and the road surface is further dispersed and made uniform. Here, if the reinforcing cord 41 is made of steel, the reinforcing cord 41 with high bending rigidity functions as a resistor, and the width of the slip and tangential force between the outer surface of the tread and the road surface in the ground contact area. The reinforcing cord 41 is preferably made of steel because the direction distribution can be strongly uniformed throughout the entire area.

  At this time, when a twisted cord constituted by twisting a plurality of steel filaments as the reinforcing cord 41 is used, since the bending rigidity is high, a great effect as the resistor can be expected. When the steel monofilament is used, since the diameter is small, crack generation at the outer end in the width direction of the reinforcing layer 40 can be effectively suppressed. Further, the reinforcing cord 41 may be made of aromatic polyamide, but in this case, the occurrence of cracks at the outer end in the width direction of the reinforcing layer 40 can be effectively suppressed. As described above, the material of the reinforcing cord 41 may be appropriately determined in consideration of uneven wear resistance and crack suppression effects.

  Here, when the inclination angle A of the reinforcing cord 41 with respect to the tire equator S is less than 45 degrees, the reinforcing layer 40 starts to exert the same effect as the belt reinforcing layer 32, and the circumferential shear deformation in the tread 28 is caused. In order to increase, the inclination angle A must be 45 degrees or more. When the inclination angle A exceeds 90 degrees, the reinforcement cord 41 only inclines in the opposite direction with respect to the tire equator S, so the maximum value of the inclination angle A is 90 degrees.

  The width of the reinforcing layer 40 described above is 0.3 times the tread width W in order to effectively uniformize the widthwise distribution of slip and tangential force between the outer surface of the tread and the road surface in the ground contact area. The above is preferable. Further, as described above, the belt reinforcing layer 32 is provided between the tread 28 and the carcass layer 18, the buffer rubber layer 36 is provided between the tread 28 and the belt layer 24, and the belt reinforcing layer 32, and the tread 28 and the buffer rubber layer are provided. Since the reinforcing layer 40 is disposed between the belt reinforcing layer 32 and the tread 28, the buffer rubber layer 36 and the reinforcing layer 40 are sequentially disposed toward the tread 28.

  Further, if the belt reinforcing layer 32 is disposed between the belt layer 24 and the carcass layer 18 as described above, the belt layer 24 and the reinforcing member in addition to the buffer rubber layer 36 are provided between the belt reinforcing layer 32 and the tread 28. Although the layer 40 is interposed, since the coating rubber of the belt layer 24 and the reinforcing layer 40 can also slightly absorb the circumferential shear deformation, the circumferential shear deformation of the tread 28 can be further relaxed. it can.

    FIG. 3 is a diagram showing Embodiment 2 of the present invention. In this embodiment, the belt reinforcing layer 32 is disposed between the belt layer 24 and the buffer rubber layer 36. In this case, when traveling at high speed, it is possible to strongly suppress the diameter growth of the entire belt layer 24 including the belt end at the portion overlapping the belt reinforcing layer 32, here the belt layer 24. Thus, the distortion generated at the belt end can be strongly reduced.

    Next, Test Example 1 will be described. In this test, a belt layer between a carcass layer and a tread, a belt reinforcing layer (cap), a conventional tire in which the belt reinforcing layer (cap) is sequentially arranged toward the outside in the radial direction, and a belt reinforcing layer between the carcass layer and the tread, Example tires 1, 2, and 3 in which a belt layer, a shock absorbing rubber layer, and a reinforcing layer are sequentially arranged outward in the radial direction, and a belt layer, a belt reinforcing layer, a shock absorbing rubber layer, and a reinforcement between the carcass layer and the tread. An implementation tire 4 in which layers were arranged in this order toward the outside in the radial direction was prepared.

  Here, each of the tires described above was a tire for a high-performance passenger car, and the size was 225 / 50R16. In addition, the skeleton structure of these tires consists of a carcass layer composed of two carcass plies embedded with a nylon cord that intersects the tire equator S at 90 degrees, and a steel twist of 45 degrees rising to the tire equator S. A belt layer with a width of 225 mm and an aromatic polyamide that extends substantially parallel to the tire equator S A non-stretchable reinforcing element is embedded and a belt reinforcing layer having a width of 235 mm is provided. In addition, the inclination angle with respect to the tire equator S of the steel stranded cord embedded in the belt ply only in the conventional tire was 35 degrees.

  On the other hand, the buffer rubber layer had a thickness t of 1.0 mm and a width of 235 mm. In addition, the reinforcing layer has a width of 230 mm and a large number of reinforcing cords inclined at 90 degrees with respect to the tire equator S are embedded therein. In the implementation tire 2, a steel monofilament having a diameter of 0.7 mm is formed by twisting three steel filaments having a wire diameter of 0.3 mm. In the implementation tire 3, the diameter of twisted aromatic polyamide filaments is used. The one with 0.8 mm was used.

  Next, while applying a load of 6 kN to each of the tires described above, the vehicle started running on a 3 m diameter drum at a slip angle of 1 degree and 100 km / h, and then the speed was increased in steps of 10 km / h every 5 minutes. The vehicle was run until the belt end failed, and high speed durability was determined. As a result, assuming that the conventional tire has an index of 100, the implementation tires 1 and 4 have an index of 95, the implementation tire 2 has an index of 100, and the implementation tire 3 has an index of 110. Here, the conventional tire has been evaluated as a tire having excellent high-speed durability in the market, and the implementation tire also maintained substantially the same high-speed durability.

  Next, after mounting each of the above tires on a domestic passenger car, driving on the road combining highways, city roads, mountain slopes, etc., and running on the tire equator S for 3200, 9600, 16000km respectively. The amount of wear at the tread and the amount of wear at the end of the tread were measured. The wear ratio M of these measurement results, that is, the value of the wear amount on the tire equator S / the wear amount at the end of the tread is shown in the following Table 1 as an evaluation index of uneven wear. As is clear from Table 1, the uneven wear resistance of each of the tires was greatly improved.

  Next, after each tire was mounted on a high-performance passenger car, the test course was run, and the steering stability was evaluated by a skilled test driver with a feeling. As a result, when the perfect score was 10 points, it was 6 points for the conventional tire, but 8 points for the working tire 3 and 9 points for all of the working tires 1, 2, and 4.

    In the above-described embodiment, the belt reinforcing layer 32 is wider than the belt layer 24 and has a cap structure that overlaps with the belt layer 24 in the entire width. However, in the present invention, the belt reinforcing layer is formed only at both ends in the width direction of the belt layer. It is good also as a layer structure which overlaps.

  The present invention can be applied to the industrial field of pneumatic tires.

It is meridian sectional drawing which shows Embodiment 1 of this invention. It is a partially broken plan view of the tread portion. It is meridian sectional drawing which shows Embodiment 2 of this invention.

Explanation of symbols

11 ... Pneumatic tire 12 ... Bead core
18 ... Carcass layer 24 ... Belt layer
25 ... belt ply 26 ... belt cord
28 ... Tread 32 ... Belt reinforcement layer
34 ... Reinforcing element 36 ... Buffer rubber layer
40 ... Reinforcement layer 41 ... Reinforcement cord S ... Tire equator

Claims (5)

    A carcass layer whose both ends in the width direction are folded back around the bead core and extend in a substantially toroidal shape, and a belt cord which is disposed radially outside the carcass layer and which is inclined in the opposite direction with respect to the tire equator is embedded in at least A belt layer composed of two belt plies, a tread disposed radially outward of the belt layer, and a non-extensible structure disposed between the tread and the carcass layer and extending substantially parallel to the tire equator. A belt reinforcing layer in which a reinforcing element is embedded; a thin buffer rubber layer disposed between the tread and the belt layer and the belt reinforcing layer; and a tire inside the tread and the buffer rubber layer. A pneumatic tire comprising: a reinforcing layer in which a reinforcing cord inclined at an angle of 45 to 90 degrees with respect to the equator is embedded.     The pneumatic tire according to claim 1, wherein the belt reinforcing layer is disposed between the belt layer and the carcass layer.     The pneumatic tire according to claim 1, wherein the belt reinforcing layer is disposed between the belt layer and the buffer rubber layer.     The pneumatic tire according to claim 1, wherein the reinforcing cord embedded in the reinforcing layer is made of steel.     The pneumatic tire according to any one of claims 1 to 4, wherein a thickness of the buffer rubber layer is in a range of 0.5 to 3.0 mm.

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