JP4758144B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire capable of improving the vehicle behavior stability at the limit, and is mainly suitable for a pneumatic radial tire.

Conventionally, in a vehicle such as a passenger car in which a pneumatic radial tire is used, cornering is achieved by reducing the inclination angle of a reinforcing belt built in the tire to reduce the rigidity in the circumferential direction of the tire. Reducing the load dependency of power and increasing the vertical and lateral springs by increasing the height and hardness of the bead filler improve the stability of the vehicle at the limit of high loads such as cornering. It is done for that purpose.
Japanese Patent Laid-Open No. 3-25003

  However, particularly in small vehicles, for the purpose of increasing the living space, there has been a tendency in recent years that the center of gravity of the vehicle increases as the vehicle height increases. As a result, the roll of the vehicle becomes large during cornering. As a result, the vehicle may become unstable due to an oversteer tendency at the limit.

On the other hand, conventional structural changes such as belts and bead fillers cannot sufficiently stabilize the behavior at the limit, and a sufficient effect for improving the running stability of the vehicle can be obtained. There wasn't.
In view of the above facts, an object of the present invention is to provide a pneumatic tire capable of improving the behavior stability of a vehicle at the limit.

A plurality of carcasses are arranged on each of the pair of side portions, and one is formed on the tire equatorial plane of the tread formed of a rubber material and positioned between the pair of side portions , and a pair of circumferential directions on the outer side in the tread width direction. Grooves are arranged,
A pneumatic tire having an outer portion of a circumferential groove located on the outer side in the tread width direction of the tread tire equatorial plane as a shoulder region, and a region between these shoulder regions as a center region,
When the width direction edge component length of the center region is C and the width direction edge component length of the shoulder region is S, the relationship 2.3 ≧ S / C ≧ 2 is established.
The rubber material constituting the shoulder region has the same or lower hardness than the rubber material constituting the center region.

The operation of the pneumatic tire according to claim 1 will be described below.
In the pneumatic tire according to the present invention, a plurality of carcasses are disposed on each of the pair of side portions, and a tread formed of a rubber material is positioned between the pair of side portions. In addition, a plurality of circumferential grooves are arranged in the tread, and outer portions of the circumferential grooves located on the outermost side of the tread are respectively shoulder regions, and a region between the shoulder regions is a center region.

Furthermore, in this claim, when the width direction edge component length of the center region is C and the width direction edge component length of the shoulder region is S, the relationship is 2.3 ≧ S / C ≧ 2. . Further, the hardness of the rubber material constituting the shoulder region is the same as or lower than the hardness of the rubber material constituting the center region.

  Therefore, in this claim, by arranging a plurality of carcasses on each of the pair of side portions to increase rigidity and increasing the vertical spring and the horizontal spring respectively, the roll of the vehicle can be directly suppressed, and at the limit time The behavior of the vehicle can be stabilized.

  Furthermore, the width of the edge component in the width direction of the tread is more than double the shoulder region in comparison with the center region, and the hardness of the rubber material of the tread in the shoulder region is the same or lower than in the center region. As a result, the block rigidity of the land portion constituting the shoulder region is lowered. As a result, it is possible to effectively stabilize the behavior of the vehicle by suppressing the generation of cornering power at the time of a limit high load where the ground pressure in the shoulder region increases.

  On the other hand, since the rigidity of the center region of the overall rigidity of the pneumatic tire is dominant during normal load, cornering power and self-aligning torque can be maintained to ensure steering stability during normal load.

  As described above, in the pneumatic tire according to the present invention, the plurality of carcasses are arranged on each of the pair of side portions, whereby the vertical spring and the horizontal spring are enhanced, and the width direction edge component length ratio is further increased. Suppressing cornering power by regulation and cornering power by regulating the hardness ratio of the tread rubber material stabilized the vehicle behavior at the limit very effectively.

The operation of the pneumatic tire according to claim 2 will be described below.
In this claim, it has the same configuration as in claim 1 and operates in the same way. However, the carcass is folded back by the bead core, and the end of the folded carcass reaches the belt located at the lower part of the tread. And it has the structure that two carcass are arrange | positioned at the side part.

  Accordingly, the carcass is formed in the envelope structure as described above, and the two carcasses are arranged on the side portions, so that the vertical spring and the horizontal spring of the pneumatic tire are reliably increased. As a result, the effect of the first aspect of stabilizing the behavior of the vehicle at the limit by directly restraining the roll of the vehicle can be achieved more reliably.

The operation of the pneumatic tire according to claim 3 will be described below.
The present invention has the same configuration as that of the first aspect and operates in the same manner, but further, the bias angle that is inclined in the extending direction of the cord forming the carcass is in the range of 2 ° to 16 °, Each carcass is arranged in such a manner that the extending directions of the cords between the matching carcasses are inclined opposite to each other.

  Therefore, not only a plurality of carcasses having a bias angle in the range of 2 ° to 16 ° are arranged on the side portion, but also the extending directions of the cords between the adjacent carcasses as described above are inclined in the opposite directions. The vertical springs and the horizontal springs are reliably enhanced by the structure in which each carcass is disposed in the vertical direction. Accordingly, the operation and effect of claim 1 that stabilizes the behavior of the vehicle at the limit by directly restraining the roll of the vehicle is more reliably achieved.

The operation of the pneumatic tire according to claim 4 will be described below.
This claim has the same configuration as that of claims 1 to 3 and operates in the same manner, but further has a configuration in which the radius of curvature of the outer surface of the tread in the shoulder region is set to 28 mm or less.

  Therefore, by reducing the radius of curvature of the outer surface in the shoulder region to 28 mm or less, an increase in the contact width of the tread at the time of heavy load is suppressed, and the generation of cornering power at the time of the heavy load is suppressed. The action and effect of claim 1 that stabilizes the behavior of is now more reliably achieved.

  As described above, according to the above configuration of the present invention, it has an excellent effect that it can provide a pneumatic tire that can improve the behavioral stability of the vehicle at the limit, and is mainly excellent in a pneumatic radial tire. Demonstrate.

A pneumatic tire according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 and FIG. 2 show a vehicle tire having a radial structure as an example of the pneumatic tire 10 according to the present embodiment, and the outer peripheral side of the pneumatic tire 10 is formed into a circular arc shape. The crown portion 12 is configured.

  In the present embodiment, as shown in FIG. 1, a carcass 14 constituting a skeleton of the pneumatic tire 10 is embedded in the crown portion 12 so as to penetrate the crown portion 12. Nylon cords are arranged in a direction orthogonal to the equator plane CL of the pneumatic tire 10.

  The crown portion 12 is provided with a tread 16 that is an outer skin that is formed of a rubber material and is in contact with the road surface. A steel belt is provided between the carcass 14 and the tread 16 in the crown portion 12. A belt 18 formed by bundling a number of cords is arranged for reinforcement.

  On the other hand, a pair of bead cores 22 in which steel wires are wound and bundled in a ring shape are arranged at lower portions of both ends of the pneumatic tire 10. The pair of bead cores 22 are folded back so that portions near both ends of the carcass 14 are wound around each other. Are buried.

  The carcass 14 is formed in an envelope structure in which the end E of the carcass 14 folded back by the bead core 22 reaches the belt 18 positioned below the tread 16, and accordingly, the bead core 22, the crown portion 12, Two carcasses 14 are arranged on each of the pair of side portions 26 of the pneumatic tire 10 which is a portion connecting the two.

On the other hand, as shown in FIG. 2, the tread 16 has, for example, its circumferential direction into three circumferential grooves 28 which Ru extending substantially along are arranged. The tread pattern is defined by the circumferential grooves 28 so that the outer surface of the tread 16 is divided into a plurality of land portions 30 and the sipe 32, which is a narrow groove, is disposed in each land portion 30. The pneumatic tire 10 of the present embodiment has.

Further, the outermost portions of the left and right circumferential grooves 28 located on the outermost side among these three circumferential grooves 28 are respectively shoulder regions 16A, and the region between these shoulder regions 16A is the center region 16B. It is said that. In this shoulder region 16A, the width direction edge component length per unit length dimension L along the circumferential direction of the tread 16 in the shoulder region 16A is S, and the width per unit length dimension L along the circumferential direction of the tread 16 in the center region 16B. When the direction edge component length is C, 2.3 ≧ S / C ≧ 2.

  The width direction edge component length is a length obtained by projecting the edge portion of the land portion 30 formed by a groove such as the sipe 32 per unit length along the circumferential direction of the tread 16 shown in the X direction of FIG. This is the cumulative total. Accordingly, the tread 16 has an edge portion of the land portion 30 due to the circumferential groove 28 extending along the circumferential direction, for example. Depending on the edge portion of the circumferential groove 28, the widthwise edge component length That will not happen.

  In this embodiment, the rubber material constituting the shoulder region 16A in the tread 16 and the rubber material constituting the center region 16B are made of different materials, and the hardness of the rubber material constituting the center region 16B is determined. The hardness of the rubber material constituting the shoulder region 16A is low. The curvature radius R of the outer surface of the tread 16 in the shoulder region 16A is set to 28 mm or less.

Next, the operation of the pneumatic tire 10 according to the present embodiment will be described below.
In the pneumatic tire 10 according to the present embodiment, the end portion E of the carcass 14 folded back by the bead core 22 is positioned below the tread 16 formed of a rubber material as shown in FIGS. 1 and 2. Therefore, two carcasses 14 are arranged on each of the pair of side portions 26.

  A plurality of circumferential grooves 28 are arranged in the tread 16 located between the pair of side portions 26. In this embodiment, the outer portion of the circumferential groove 28 located on the outermost side of the tread 16 Each of the shoulder regions 16A is a center region 16B.

Further, the width direction edge component length ratio is 2.3 ≧ S / C ≧ 2, and the width direction edge component length of the tread 16 is more than doubled in the shoulder region 16A in comparison with the center region 16B. Further, the hardness of the rubber material constituting the shoulder region 16A is made lower than the hardness of the rubber material constituting the center region 16B, and the hardness ratio of the rubber material based on the hardness of the rubber material in the shoulder region 16A is 1 or more. The curvature radius R of the outer surface of the tread 16 in the shoulder region 16A is set to 28 mm or less.

  Therefore, in the present embodiment, two carcass 14 are arranged on each of the pair of side portions 26 as an envelope structure in which the end E of the carcass 14 folded back by the bead core 22 reaches the belt 18 positioned at the lower part of the tread 16. I tried to do it. In other words, by arranging two carcass 14 on the side portion 26 and increasing the vertical spring and the lateral spring of the pneumatic tire 10, respectively, the roll of the vehicle can be directly suppressed, and the behavior of the vehicle at the limit is stabilized. I was able to.

  Furthermore, the width of the tread 16 in the width direction edge component length is more than twice the shoulder region 16A in comparison with the center region 16B, and the hardness of the rubber material of the tread 16 in the shoulder region 16A is reduced in comparison with the center region 16B. The block rigidity of the land portion 30 that configures the shoulder region 16A in comparison with the center region 16B is reduced. As a result, it is possible to suppress the occurrence of cornering power and effectively stabilize the behavior of the vehicle at the time of the limit high load where the ground pressure in the shoulder region 16A increases.

  On the other hand, since the rigidity of the center region 16B out of the overall rigidity of the pneumatic tire 10 becomes dominant during normal load, cornering power and self-aligning torque can be maintained to ensure steering stability during normal load. .

  As described above, in the pneumatic tire 10 according to the present embodiment, the longitudinal springs and the lateral springs of the pneumatic tire 10 are enhanced by substantially arranging two carcasses 14 on each of the pair of side portions 26. In addition, by suppressing cornering power by regulating the width direction edge component length ratio and by suppressing cornering power by regulating the hardness ratio of the rubber material constituting the tread 16, the behavior of the vehicle at the limit is very effective. It was possible to stabilize.

  On the other hand, in the present embodiment, since the radius of curvature R of the outer surface of the tread 16 in the shoulder region 16A is reduced to 28 mm or less, an increase in the contact width of the tread 16 under a heavy load is suppressed, which is also a limit. The generation of cornering power at high loads is suppressed, and the behavior of the vehicle at the limit can be more reliably stabilized.

Next, a pneumatic tire according to a second embodiment of the present invention will be described with reference to FIGS. In addition, the same code | symbol is attached | subjected to the member same as the member demonstrated in 1st Embodiment, and the duplicate description is abbreviate | omitted.
In the pneumatic tire 10 according to the present embodiment shown in FIGS. 3 and 4, as in the first embodiment, the relationship of 2.3 ≧ S / C ≧ 2 is established, and the widthwise edge of the tread 16 is determined. The shoulder length 16A is doubled or more in comparison with the center region 16B, and the hardness of the rubber material constituting the shoulder region 16A is lower than the hardness of the rubber material constituting the center region 16B.

  However, in the present embodiment, instead of the carcass 14 having an envelope structure, as shown in FIG. 4, the bias angle θ that is the inclination in the extending direction of the cord K forming the carcass is 2 ° to 16 °. The carcass 14A, 14B is in a so-called X structure in which the carcass 14A, 14B are arranged in a shape in which the extending directions of the cord K between the adjacent carcass 14A, 14B are opposite to each other. A plurality of sheets (two in the present embodiment) are embedded in the entering tire 10.

  That is, the cord K is arranged linearly while the bias angle θ of the cord K constituting the carcass 14A with respect to the axis V along the tire width direction shown in FIG. 4 is an angle in the range of 2 ° to 16 °. The bias angle θ of the cord K constituting the carcass 14B adjacent to the carcass 14B is also an angle in the range of 2 ° to 16 °, but the extending direction of the cord K is reversed.

  Therefore, in the present embodiment, a carcass 14A, 14B that is arranged in a plurality on the side portion 26 is adopted such that the bias angle is in the above range, and each adjacent carcass 14A, By adopting the X structure in which the carcass 14A and 14B are arranged in the shape in which the directions of the cord K extending between the 14Bs are opposite to each other, the longitudinal spring and the lateral spring of the pneumatic tire 10 are reliably increased. Became.

  Accordingly, as in the first embodiment, the cornering power due to the regulation of the width direction edge component length ratio is suppressed, and the cornering power due to the regulation of the hardness ratio of the rubber material of the tread 16 is suppressed. In addition, by adopting the carcass 14A and 14B as described above, the vertical and lateral springs are reliably increased, so that the roll of the vehicle is directly suppressed, and the behavior of the vehicle at the limit is controlled. It became possible to stabilize.

Next, the test results of the pneumatic tire according to the embodiment of the present invention and the conventional example will be described.
First, as shown in Table 1, as a sample used for the test, not only the ply structure which is a carcass structure is a normal structure, but also the width direction edge component length ratio and the rubber material hardness ratio are set to 1.0, respectively. In the conventional example, the shoulder region has a curvature radius R of 35 mm.

  On the other hand, as an example corresponding to the embodiment of the present invention, the ply structure is an envelope structure or an X structure, and the width direction edge component length ratio is 2.3. Four types of samples were prepared. Further, regarding the hardness ratio of the rubber material of each of these examples, the hardness ratio of the rubber material of Example 3 was set to 1.2, and the hardness ratio of the rubber material of the other examples was set to 1.0. Furthermore, regarding the curvature radius R of the shoulder region, the curvature radius R of the shoulder region of Example 4 was set to 15 mm, and the curvature radius R of the shoulder region of the other examples was set to 35 mm.

  However, the tire size of each of these examples and conventional examples was 185 / 60R15 and the wheel was 5.5 JJ. The air pressure was 220 kPa, and the applied loads were 3.5 kPa and 2.5 kPa.

  The evaluation items shown in Table 1 include vertical springs, horizontal springs, cornering power (represented as CP in Table 1), and actual vehicle feeling. These evaluation results are expressed as an index with the conventional example being 100. . As a guideline for evaluation, the vertical spring and the horizontal spring are good when the value is large, and the cornering power is the value obtained by subtracting the rear load from the front load of the vehicle, and the case where this value is small is good. The actual vehicle feeling is good when the value is large.

  From Table 1 showing the results of this test, the vertical springs, the horizontal springs and the actual vehicle feeling are all higher in Examples 1 to 4 than in the conventional example. Up to this point, the cornering power was lower than that of the conventional example, and each example was superior to the conventional example.

  In the second embodiment, the number of carcasses is two, but a plurality of three or more may be used. Further, the pneumatic tire according to the present embodiment is mainly used for passenger cars, but may be applied to tires of other vehicles.

1 is a cross-sectional view showing a pneumatic tire according to a first embodiment of the present invention. 1 is a partially broken plan view showing a pneumatic tire according to a first embodiment of the present invention. It is sectional drawing which shows the pneumatic tire which concerns on the 2nd Embodiment of this invention. It is the partially broken top view which shows the pneumatic tire which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 14 Carcass 14A Carcass 14B Carcass 16 Tread 16A Shoulder area 16B Center area 26 Side part 28 Circumferential groove

Claims (4)

A plurality of carcasses are arranged on each of the pair of side portions, and one is formed on the tire equatorial plane of the tread formed of a rubber material and positioned between the pair of side portions , and a pair of circumferential directions on the outer side in the tread width direction. Grooves are arranged,
A pneumatic tire having an outer portion of a circumferential groove located on the outer side in the tread width direction of the tread tire equatorial plane as a shoulder region, and a region between these shoulder regions as a center region,
When the width direction edge component length of the center region is C and the width direction edge component length of the shoulder region is S, the relationship 2.3 ≧ S / C ≧ 2 is established.
A pneumatic tire characterized in that the hardness of the rubber material constituting the shoulder region is the same or lower than the hardness of the rubber material constituting the center region.   2. The pneumatic tire according to claim 1, wherein the carcass is folded back by a bead core, and two carcasses are arranged on a side portion by the end portion of the folded carcass reaching a belt positioned at a lower portion of the tread. .   The bias angle, which is the inclination of the extending direction of the cord forming the carcass, is in the range of 2 ° to 16 °, and each carcass is arranged in a shape in which the extending directions of the cords are opposite to each other between the adjacent carcasses. The pneumatic tire according to claim 1.   The pneumatic tire according to any one of claims 1 to 3, wherein a radius of curvature of an outer surface of the tread in the shoulder region is set to 28 mm or less.

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