JP2007176304A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of enhancing the controllability and stability by increasing the side rigidity without increasing the tread rigidity too much and of suppressing a drop of the durability due to heat accumulation. <P>SOLUTION: The pneumatic tire having at least one carcass layer 4A, 4B and belt layers 6A and 6B embedded at their peripheries is structured so that carcass cords C of the carcass layers 4A and 4B are arranged in the radial direction in the belt lower part C1, and in the side part C2 and turnup part C3, arranged in the direction inclined relative to the radial direction, while the side wall part 2 is furnished at the surface with a plurality of band-shaped projections 11 extending in inclination relative to the radial direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire with optimized tread rigidity and side rigidity, and more specifically, improves steering stability by increasing side rigidity without increasing the tread rigidity more than necessary, and further durability by heat storage. The present invention relates to a pneumatic tire that can suppress the deterioration of the property.

  In pneumatic tires used in harsh driving environments such as sports competitions, it is required to increase side rigidity in view of higher output of vehicles and higher grip of cap compounds.

  In view of such requirements, in a pneumatic tire, a plurality of carcass layers are stacked, the cord angle of these carcass layers with respect to the tire circumferential direction is made smaller than 90 °, and the cords cross each other between the layers. A so-called half radial structure has been proposed (see, for example, Patent Document 1). Further, as means for increasing the side rigidity, a reinforcing layer including a reinforcing cord is added to the sidewall portion (see, for example, Patent Document 2), or the bead filler is enlarged (for example, Patent Document 3). reference).

However, when the half radial structure is adopted, not only the side rigidity but also the tread surface rigidity is increased, so that the ground contact property is deteriorated, and as a result, the steering stability is deteriorated. On the other hand, when a reinforcing layer including a reinforcing cord is added to the sidewall or the bead filler is enlarged, the handling stability decreases due to an increase in unsprung mass, and further, the reinforcing layer is added and the bead filler volume is increased. With this, there is a problem that heat dissipation is reduced and durability is reduced due to heat storage.
JP-A-1-321939 JP-A-8-324213 JP 2000-313205 A

  An object of the present invention is to provide a pneumatic tire which can improve steering stability by increasing side rigidity without increasing the tread rigidity more than necessary, and further can suppress a decrease in durability due to heat storage. There is.

  In order to achieve the above object, a pneumatic tire according to the present invention includes at least one carcass layer folded from a tread portion through a sidewall portion by a bead core of a bead portion, and an outer peripheral side of the carcass layer in the tread portion. In a pneumatic tire having an embedded belt layer, the carcass cords of the carcass layer are arranged in a radial direction at a lower belt portion located below the belt layer, and from the vicinity of the end of the belt layer to the bead core. In the turn-up portion folded by the side portion and the bead core, it is arranged in a direction inclined with respect to the radial direction, and a plurality of strip-like protrusions extending on the surface of the sidewall portion while being inclined with respect to the radial direction are provided. It is characterized by providing.

  In the present invention, the carcass cords of the carcass layer are arranged in the radial direction at the lower part of the belt, and arranged in the direction inclined with respect to the radial direction at the side part and the turn-up part. That is, a so-called radial structure is adopted in the belt lower portion, and a so-called half radial structure is adopted in the side portion and the turn-up portion. Thereby, the side rigidity can be increased without increasing the tread rigidity more than necessary. Further, by providing a plurality of strip-shaped protrusions extending while inclining with respect to the radial direction on the surface (inner surface or outer surface or both surfaces) of the sidewall portion, the side rigidity can be further increased. As a result, the steering stability can be improved by combining the tread surface rigidity and side rigidity with the carcass layer and the reinforcing effect with the protrusions.

  In addition, unlike the case where a reinforcing layer including a reinforcing cord is added to the sidewall portion or the bead filler is increased in size, a decrease in steering stability due to an increase in unsprung mass is avoided, and durability due to heat storage is reduced. The decrease can be suppressed. For tires that do not require high steering stability, the reinforcement layer embedded in the sidewall can be removed or downsized, or the bead filler can be downsized (volume down). An improvement effect can be obtained.

  In the present invention, in order to ensure side rigidity, the protrusions are preferably arranged so as to be inclined in the direction opposite to the cord inclination direction of the closest carcass layer, and may be arranged in a lattice pattern. In any case, the inclination angle of the protrusion with respect to the tire circumferential direction is 45 ° to 85 ° at the tire maximum width position, and the cord angle of the carcass layer with respect to the tire circumferential direction is 50 ° to 86 ° at the side portion and the turn-up portion. It is preferable that The width of the protrusions is preferably 2 mm or more and 10 mm or less, the distance between the protrusions is 3 mm or more and 15 mm or less, and the height of the protrusions is preferably 2 mm or more and 8 mm or less. The width of the protrusion may be partially changed depending on the required rigidity.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. Two carcass layers 4A and 4B are mounted between the pair of left and right bead portions 3 and 3, and end portions of the carcass layers 4A and 4B are folded around the bead core 5 from the inside to the outside of the tire. The carcass layer 4A located on the inner side and the carcass layer 4B located on the outer side each include a plurality of carcass cords C aligned. On the outer peripheral side of the carcass layer 4 in the tread portion 1, two belt layers 6A and 6B are arranged over the entire tire circumference. These belt layers 6A and 6B include reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords intersect each other between the layers. Further, a belt cover layer 7 is disposed on the outer peripheral side of the belt layers 6A and 6B.

  FIG. 2 shows the casing structure of the pneumatic tire of FIG. As shown in FIG. 2, the carcass cords C of the carcass layers 4A and 4B are arranged in the radial direction (direction perpendicular to the tire circumferential direction) in the belt lower portion C1 positioned below the belt layers 6A and 6B. The side portion C2 from the vicinity of the ends of 6A and 6B to the bead core 5 and the turnup portion C3 folded back by the bead core 5 are arranged in a direction inclined with respect to the radial direction. The cord angle θ1 with respect to the tire circumferential direction measured at the center position in the tread width direction of the carcass layers 4A and 4B is substantially 90 °. Further, the cord angle θ2 with respect to the tire circumferential direction at the side portion C2 of the carcass layers 4A and 4B and the cord angle θ3 with respect to the tire circumferential direction at the turn-up portion C3 of the carcass layers 4A and 4B are both smaller than 90 °, more preferably. Is set in the range of 50 ° to 86 °.

  On the other hand, in FIG. 1, a plurality of strip-shaped protrusions 11 extending while inclining with respect to the radial direction are formed on the outer surface of the sidewall portion 2 extending between the tread portion 1 and the bead portion 3. ing. More specifically, the protrusion 11 is inclined in the direction opposite to the cord inclination direction of the closest carcass layer 4A (turn-up portion) from the vicinity of the tire maximum width position to the bead portion 3. Thereby, the protrusion 11 and the carcass cord C of the carcass layer 4A adjacent to the protrusion 11 intersect with each other to form a good reinforcing structure.

  The protrusion 11 can also be formed from the vicinity of the end portions of the belt layers 4A and 4B to the bead portion 3. As described above, it is sufficient that the protrusions 11 are inclined in one direction, but the protrusions 11 may be arranged in a lattice shape (stitch shape) by combining inclinations in other directions. In this case, it is possible to remove or reduce the reinforcing layer including the reinforcing cord inserted into the sidewall portion 2 in order to ensure the circumferential rigidity, and it is possible to reduce the bead filler that has been enlarged for the same purpose. become.

  In the pneumatic tire, the belt lower portion C1 adopts a radial structure, while the side portion C2 and the turn-up portion C3 adopt a half radial structure. By adopting a radial structure in the belt lower portion C1 in this way, it is possible to suppress an excessive increase in the tread surface rigidity, and to suppress a ground contact property with the road surface, particularly a deterioration in the ground contact property under a low load condition. Further, by adopting a half radial structure in the side portion C2 and the turn-up portion C3, and by providing a plurality of belt-like protrusions 11 extending on the surface of the sidewall portion 2 while inclining in the radial direction, the side rigidity is improved. The steering stability can be improved. In addition, unlike the case where a reinforcing layer is added to the sidewall portion 2 or the bead filler is enlarged, a decrease in handling stability due to an increase in unsprung mass is avoided, and a decrease in durability due to heat storage is suppressed. be able to.

  Here, the angle of the protrusion 11 with respect to the tire circumferential direction is preferably 45 ° to 85 ° at the tire maximum width position. If this angle deviates from the above range, the reinforcing effect due to the intersection with the carcass cord C becomes insufficient. When the angle of the protrusion 11 with respect to the tire circumferential direction is 50 ° to 70 °, a more preferable effect is obtained.

  On the other hand, the cord angles θ2 and θ3 of the carcass layers 4A and 4B with respect to the tire circumferential direction are preferably set to 50 ° to 86 °. When these cord angles θ2 and θ3 are less than 50 °, the durability is lowered. Conversely, when the cord angles θ2 and θ3 are more than 86 °, the reinforcing effect due to the intersection becomes insufficient. A more preferable effect is obtained when the cord angles θ2 and θ3 of the carcass layers 4A and 4B with respect to the tire circumferential direction are set to 70 ° to 82 °.

  The width of the protrusion 11 is preferably 2 mm or more and 10 mm or less. If the width of the protrusion 11 is less than 2 mm, the effect of increasing the rigidity in the tire circumferential direction is insufficient, and conversely if it exceeds 10 mm, the tire mass increases. A preferred width is 4 mm to 7 mm. Further, the width of the protrusion 11 may be partially changed according to the required rigidity. For example, the rigidity balance may be optimized by partially widening the width of the protrusion 11 in the vicinity of the tire maximum width position where the greatest force is applied. However, the ratio of the maximum width to the minimum width is desirably 2.0 or less.

  The interval between the protrusions 11 is preferably 3 mm or more and 15 mm or less. If the distance between the protrusions 11 is less than 3 mm, the adjacent protrusions 11 may interfere with each other when the deformation of the sidewall portion 2 is large, causing a sudden change in rigidity (abrupt behavior change). If it exceeds, the effect of increasing the rigidity in the tire circumferential direction becomes insufficient. A preferable interval is 5 mm to 8 mm. Moreover, you may change the space | interval of the projection part 11 partially according to the required rigidity. For example, the rigidity balance may be optimized by partially narrowing the interval between the protrusions 11 in the vicinity of the tire maximum width position where the greatest force is applied.

  The height of the protrusion 11 is preferably 2 mm or more and 8 mm or less. If the height of the protrusion 11 is less than 2 mm, the effect of increasing the rigidity in the tire circumferential direction becomes insufficient. Conversely, if the height exceeds 8 mm, no further effect is obtained, and only an increase in weight is caused. A preferred height is 4 mm to 6 mm.

  FIG. 3 shows a casing structure of a pneumatic tire according to another embodiment of the present invention. In the embodiment of FIGS. 1 and 2 described above, the inclination directions of the carcass cords C of the carcass layers 4A and 4B are the same on both sides of the tire equator CL. However, in the embodiment of FIG. The inclination directions of the carcass cords 4A and 4B are opposite on both sides of the tire equator CL. Even in such a case, the same effects as described above can be obtained.

  FIG. 4 shows a pneumatic tire according to still another embodiment of the present invention. In the embodiment of FIGS. 1 and 2 described above, the protrusion 11 is formed on the outer surface of the sidewall portion 2. However, in the embodiment of FIG. 4, the protrusion 11 is formed on the outer surface and the inner surface of the sidewall portion 2. Forming. Even in such a case, the same effects as described above can be obtained. The protrusions 11 can be formed on the outer surface, the inner surface, or both surfaces of the sidewall portion 2, but the reinforcing effect is higher when arranged on the inner surface than the outer surface, and a higher reinforcing effect is obtained when arranged on both surfaces.

  In the above-described embodiment, the case where the reinforcing layer including the reinforcing cord is not embedded in the sidewall portion has been described. However, in the present invention, the reinforcing layer including the reinforcing cord can be embedded in the sidewall portion as necessary. . In the case where a reinforcing layer is embedded in the sidewall portion and it is desired to increase the rigidity in the vicinity of the bead portion, the protrusion provided on the surface of the sidewall portion and the cord of the reinforcing layer may be arranged so as to cross each other. In addition, when it is desired to increase the rigidity of the reinforcing layer from the upper end portion on the outer side in the tire radial direction to the shoulder portion, the protrusion provided on the surface of the sidewall portion and the carcass cord of the carcass layer should be arranged so as to intersect each other. Is desirable.

  In the above-described embodiment, the pneumatic tire provided with two carcass layers has been described. However, the present invention can be applied to a pneumatic tire provided with at least one carcass layer. When providing a plurality of carcass layers, it is desirable to arrange the carcass cords so as to cross each other.

  In the pneumatic tire of tire size 235 / 45R17 93W, tires of Conventional Examples 1 and 2 and Examples 1 to 3 in which the casing structure and the surface shape of the sidewall portion were varied were produced.

  The tire of Conventional Example 1 includes two carcass layers and two belt layers, the carcass cords of the carcass layer are arranged in a direction inclined with respect to the radial direction, and one reinforcing layer is formed along the bead filler. (8) is embedded, and the surface of the sidewall portion is substantially smooth (see FIG. 5). The tire of Conventional Example 2 has the same structure as that of Conventional Example 1 except that two reinforcing layers are embedded along the bead filler. The tire of Example 1 includes two carcass layers and two belt layers, and the carcass cords of the carcass layer are arranged in the radial direction in the lower part of the belt, and in the radial direction in the side part and the turn-up part. A plurality of strip-shaped protrusions that are arranged in an inclined direction and extend while being inclined with respect to the radial direction are provided on the surface of the sidewall portion, and an angle with respect to the tire circumferential direction is set to 50 °. The tire of Example 2 has the same structure as Example 1 except that the angle of the belt-like protrusions with respect to the tire circumferential direction is 65 °. The tire of Example 3 has the same structure as Example 1 except that the angle of the belt-like protrusions with respect to the tire circumferential direction is 80 ° and one reinforcing layer is embedded along the bead filler. . The width of the protrusions was 6 mm, the distance between the protrusions was 9 mm, and the height of the protrusions was 5 mm. The cord angle of the reinforcing layer with respect to the tire circumferential direction was 20 °.

  About these test tires, tire mass, durability, steering stability, running time, and circumferential rigidity were evaluated by the following test methods, and the results are shown in Table 1.

Tire mass:
The mass of the test tire was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. It means that it is so light that this index value is small.

durability:
The test tire was assembled on a wheel with a rim size of 17 x 9 JJ, the air pressure was set to 220 kPa, and after performing the durability test specified in JIS D4230 using a drum tester, the load was continuously increased by 10% every 4 hours. The test was continued, and the distance traveled until the tire broke down was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. The larger the index value, the better the durability.

Steering stability:
The test tire is mounted on a wheel with a rim size of 17 x 9 JJ, mounted on a four-wheel drive vehicle equipped with a motor with a supercharger with a displacement of 2000 cc, and the air pressure after warm-up is 220 kPa. Evaluation was performed. The evaluation results are shown as an index with Conventional Example 1 as 100. The larger the index value, the better the steering stability.

Travel time:
The test tire is mounted on a wheel with a rim size of 17 x 9 JJ and mounted on a four-wheel drive vehicle equipped with a motor with a supercharger of 2000 cc class. The time required for the section travel was measured. The evaluation results are shown as an index with the conventional example 1 as 100, using the reciprocal of the measured value. The larger the index value, the shorter the traveling time and the better the traveling performance.

Circumferential rigidity:
Using a side stiffness tester, the tire circumferential stiffness was measured under conditions of a rim size of 17 × 9 JJ and an air pressure of 220 kPa. The evaluation results are shown as an index with Conventional Example 1 as 100. A larger index value means higher circumferential rigidity.

この表１に示すように、実施例１〜３のタイヤは、従来例１，２との対比において、タイヤ質量、耐久性、操縦安定性、走行タイム、周剛性の評価結果が良好であった。

As shown in Table 1, the tires of Examples 1 to 3 had good evaluation results of tire mass, durability, steering stability, running time, and circumferential rigidity in comparison with Conventional Examples 1 and 2. .

  Next, tires of Examples 4 to 8 were produced in the pneumatic tire of tire size 235 / 45R17 93W, in which the surface shape of the sidewall portion was varied while keeping the casing structure constant. The tires of Examples 4 to 8 are different from Example 2 in the width of the protrusions, the interval between the protrusions, and the height of the protrusions.

For these test tires, the circumferential rigidity was evaluated by the test method described above, and the results are shown in Table 2. The evaluation result of the circumferential rigidity is shown by an index with the conventional example 1 as 100.

この表２に示すように、実施例４〜８のタイヤは、従来例１との対比において、周剛性の評価結果が良好であった。

As shown in Table 2, the tires of Examples 4 to 8 had good evaluation results of peripheral rigidity in comparison with Conventional Example 1.

  Next, tires of Examples 9 to 11 in which the surface shape of the sidewall portion was variously changed while keeping the casing structure constant in the tire size 235 / 45R17 93W were prepared. The tires of Examples 9 to 11 have the same casing structure as that of Example 1, and have different arrangement surfaces of the protrusions.

For these test tires, the circumferential rigidity was evaluated by the test method described above, and the results are shown in Table 3. The evaluation result of the circumferential rigidity is shown by an index with the conventional example 1 as 100.

この表３に示すように、実施例９〜１１のタイヤは、従来例１との対比において、周剛性の評価結果が良好であった。

As shown in Table 3, the tires of Examples 9 to 11 had good evaluation results of the circumferential rigidity in comparison with Conventional Example 1.

1 is a perspective cross-sectional view showing a pneumatic tire according to an embodiment of the present invention with a part cut away. FIG. 2 is a development view showing a casing structure of the pneumatic tire of FIG. 1. It is an expanded view which shows the casing structure of the pneumatic tire which consists of other embodiment of this invention. FIG. 6 is a perspective sectional view showing a pneumatic tire according to still another embodiment of the present invention with a part cut away. It is an expanded view which shows the casing structure of the conventional pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4A, 4B Carcass layer 5 Bead core 6A, 6B Belt layer 7 Belt cover layer 11 Protrusion part C Carcass cord C1 Belt lower part C2 Side part C3 Turn-up part

Claims (6)

  A pneumatic tire having at least one carcass layer folded from a tread portion through a sidewall portion by a bead core of a bead portion and a belt layer embedded on an outer peripheral side of the carcass layer in the tread portion. The carcass cords of the layers are arranged in the radial direction in the lower belt portion located below the belt layer, and in the radial direction in the side portion from the end of the belt layer to the bead core and the turn-up portion folded by the bead core. A pneumatic tire provided with a plurality of belt-like projections arranged in a direction inclined with respect to the sidewall and extending while inclining with respect to a radial direction on the surface of the sidewall portion.   The pneumatic tire according to claim 1, wherein the protrusions are arranged so as to be inclined in a direction opposite to a cord inclination direction of the nearest carcass layer.   The pneumatic tire according to claim 1, wherein the protrusions are arranged in a lattice pattern.   The inclination angle of the protrusion with respect to the tire circumferential direction is 45 ° to 85 ° at the tire maximum width position, and the cord angle of the carcass layer with respect to the tire circumferential direction is 50 ° to 86 ° at the side portion and the turn-up portion. The pneumatic tire according to any one of claims 1 to 3.   The pneumatic according to any one of claims 1 to 4, wherein the width of the protrusions is 2 mm or more and 10 mm or less, the interval between the protrusions is 3 mm or more and 15 mm or less, and the height of the protrusions is 2 mm or more and 8 mm or less. tire. The pneumatic tire according to any one of claims 1 to 4, wherein a width of the protrusion is partially changed.

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