JP2013241043A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving cut resistance and rolling resistance in good balance while achieving weight reduction.SOLUTION: A sidewall rubber layer is formed by a two layer structure comprising a rubber layer constructing a rim cushion 6 extending from the bottom face of a bead section 2 toward the outside in the tire diametrical direction and a rubber layer constructing a black sidewall 7 positioned on the outside and extending from the inside toward the outside in the tire diametrical direction. A height Hr of an upper end 6a of the rim cushion rubber 6 is changed in a wavy shape within a range of 0.5-0.7 times as much as a tire cross-sectional height SH along the tire peripheral direction, and the average height is set to be not more than 0.6 times as much as the tire cross-sectional height SH.

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which cut resistance and rolling resistance are improved in a well-balanced manner while reducing weight.

  In general, since the side stiffness of a tire has a great influence on the motion performance of the tire, many proposals have been made regarding the reinforcing structure of the sidewall portion (see, for example, Patent Documents 1 and 2).

  Among these, in patent document 1, in order to suppress the deterioration of riding comfort and the fall of braking performance which arise by raising side rigidity, the inner side rubber which consists of a high modulus rubber which extends a sidewall part from a bead part to a belt end It has been proposed to improve the braking performance by increasing the front and rear rigidity while avoiding the deterioration of ride comfort by using a two-layer structure of a layer and an outer rubber layer made of a low modulus rubber disposed on the outer layer. . However, in this proposal, since the inner rubber layer made of high modulus rubber is extended to the belt end, there is a problem that the rolling resistance is lowered.

  Further, in Patent Document 2, in order to improve the crack growth resistance in the sidewall portion, the sidewall rubber has a two-layer structure of an inner rubber layer made of high modulus rubber and an outer rubber layer made of low modulus rubber, It has been proposed that the outer rubber layer has a cut resistance function and the inner rubber layer has a cut scratch growth prevention function.

  On the other hand, as a measure for improving rolling resistance and noise resistance, efforts have been made to downsize the bead filler embedded in the bead portion. However, in this type of tire, there is a problem in that side rigidity is insufficient and steering stability is lowered, and at the same time, there is a problem that cracks are likely to occur in the sidewall due to external impact, and there are various measures to supplement these Has been studied.

  In view of the above-mentioned background, the applicant has made an inner rubber layer made of a high modulus rubber extending from the bead portion to the outer side in the tire radial direction, and an outer rubber layer made of a low modulus rubber disposed on the outer side. By adjusting the height of the inner rubber layer, it is possible to improve the cut resistance in the sidewall portion while improving the rolling resistance while reducing the weight of the tire. As a result of obtaining the knowledge that it can be performed and intensive studies based on this knowledge, the present invention has been completed.

JP 2003-31213 A JP 2006-21671 A

  An object of the present invention is to solve such a conventional problem, and to provide a pneumatic tire in which cut resistance and rolling resistance are improved in a balanced manner while reducing weight.

  In order to achieve the above object, the pneumatic tire of the present invention has a bead filler disposed on the outer peripheral side of a bead core embedded in a pair of left and right bead portions, and the bead core is directed from the inner side toward the outer side in the tire axial direction. It is provided with at least one carcass layer folded back so as to wrap the filler, and is exposed outside in the tire axial direction adjacent to the carcass layer on the tire axial direction outside, and from the tire radial inner side toward the outer side. A pneumatic tire in which an extending rim cushion is disposed and a black sidewall extending from the upper end in the tire radial direction of the exposed portion toward the outer side in the tire radial direction is laminated on the outer side in the tire axial direction of the rim cushion. The height of the upper end of the rim cushion is within a range of 0.5 to 0.7 times the tire cross-sectional height along the tire circumferential direction. And the average height of the upper end of the rim cushion is 0.6 times or less of the tire cross-section height, and the hardness Ks of the rubber constituting the black sidewall and the rubber constituting the rim cushion The relationship between the hardness Kr and the hardness Kf of the rubber constituting the bead filler is Ks <Kr <Kf.

Furthermore, in the structure mentioned above, it is preferable to comprise as described in the following (1)-(7).
(1) The height of the upper end of the rim cushion is formed in a wave shape with a period of 18 or more along the tire circumferential direction.
(2) The height of the upper end of the bead filler is 5 to 40% of the tire cross-sectional height.
(3) The height of the lower end of the black sidewall is set to 0.3 to 0.4 times the tire cross-sectional height.
(4) The thickness of the rim cushion is gradually decreased toward the outer side in the tire radial direction, and the total thickness of the rim cushion and the black sidewall in the laminated portion of the rim cushion and the black sidewall is increased. It is made substantially constant in the tire radial direction.
(5) The thickness of the rim cushion in the laminated portion of the rim cushion and the black sidewall is 0.5 to 2.0 mm.
(6) The relationship between tan δTs at 60 ° C. of the rubber constituting the black sidewall, tan δTr at 60 ° C. of the rubber constituting the rim cushion, and tan δTf at 60 ° C. of the rubber constituting the bead filler is Tr <Ts < Let Tf.
(7) The lower end of the rim cushion is extended to the inside of the bead core in the tire axial direction so as to wrap the bead core.

  According to the present invention, a rim cushion tire is disposed on the outer side in the tire axial direction adjacent to the carcass layer, the rim cushion being exposed on the outer side in the tire axial direction of the bead portion and extending from the inner side in the tire radial direction toward the outer side. A black sidewall extending from the upper end in the tire radial direction of the exposed portion toward the outer side in the tire radial direction is laminated on the outer side in the axial direction, and the height of the upper end of the rim cushion is equivalent to 0.7 times the tire cross-sectional height. The relationship between the hardness Hs of the rubber constituting the black sidewall and the hardness Hr of the rubber constituting the rim cushion and the hardness Hf of the rubber constituting the bead filler is Hs < Since Hr <Hf, an appropriate side rigidity can be ensured by the arrangement of the rim cushion made of high-hardness rubber, and the upper end of the rim cushion can be secured. By suppressed is, it is possible to improve the rolling resistance.

  In addition, the height of the upper end of the rim cushion is changed in a wave shape within the range of 0.5 to 0.7 times the tire cross-sectional height along the tire circumferential direction, and the average height is set to 0 of the tire cross-sectional height. Since it is suppressed within 6 times, the effect of improving the cut resistance and the effect of improving the rolling resistance can be ensured in a well-balanced manner by the fluctuation of the rim cushion height on the tire circumference.

It is a half sectional view showing the outline of the pneumatic tire by the embodiment of the present invention. It is sectional drawing which expands and shows the principal part in the tire of FIG. It is an image figure for demonstrating the condition where the height of the upper end of a rim cushion changes along a tire peripheral direction.

  Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing an outline of a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view showing a main part of the tire of FIG.

  As shown in FIG. 1, the pneumatic tire 1 according to the present invention has a bead filler 4 disposed on the outer peripheral side of a bead core 3 embedded in a pair of left and right bead portions 2, and the periphery of the bead core 3 extends from the inner side to the outer side in the tire axial direction. And at least one carcass layer 5 that is folded back so as to wrap the bead filler 4 (in the figure), and is exposed outside in the tire axial direction of the bead portion 2 outside the tire axial direction adjacent to the carcass layer 5. And a rim cushion 6 extending from the inner side in the tire radial direction toward the outer side, and extending from the upper end in the tire radial direction of the exposed portion of the rim cushion 6 toward the outer side in the tire radial direction on the outer side in the tire axial direction of the rim cushion 6. Existing black sidewalls 7 are laminated.

  In the present invention, the height Hr (see FIG. 2) of the upper end 6a of the rim cushion 6 is changed in a wave shape within the range of 0.5 to 0.7 times the tire cross-section height SH along the tire circumferential direction. In addition, the average height of the upper end 6a of the rim cushion 6 is 0.6 times or less of the tire cross-section height SH, and the hardness Ks of the rubber constituting the black sidewall 7 and the hardness of the rubber constituting the rim cushion 6 are included. The relationship between Kr and the hardness Kf of the rubber constituting the bead filler 4 is Ks <Kr <Kf. FIG. 3 is an image view seen from the side of the tire showing a state in which the height Hr of the upper end 6a of the rim cushion 6 changes in a wavy shape along the tire circumferential direction.

  In this way, the rim cushion 6 that is exposed outside the bead portion 2 in the tire axial direction and extends from the inner side in the tire radial direction toward the outer side is disposed outside the tire axial direction adjacent to the carcass layer 5. A black sidewall 7 extending from the upper end in the tire radial direction of the exposed portion of the rim cushion 6 toward the outer side in the tire radial direction is laminated on the outer side in the tire axial direction of the tire, and the height Hr of the upper end 6a of the rim cushion 6 is set to the tire cross section. The rubber hardness Ks constituting the black side wall 7 and the rubber hardness Kr constituting the rim cushion 6 and the bead filler 4 are suppressed to a height lower than the height corresponding to 0.7 times the height SH. By setting Ks <Kr <Kf as the relationship with the hardness Kf of the rubber component, appropriate side rigidity is ensured by the arrangement of the rim cushion 6 made of high-hardness rubber. It is possible to, by suppressing the height Hr of the upper end of the rim cushion 6, it is possible to improve the rolling resistance.

  In addition, the height Hr of the upper end 6a of the rim cushion 6 is changed in a wave shape within the range of 0.5 to 0.7 times the tire cross-section height SH along the tire circumferential direction, and the average height is changed to the tire cross-section. Since the height SH is suppressed to 0.6 times or less, the effect of improving the cut resistance and the effect of improving the rolling resistance can be ensured in a well-balanced manner by changing the height of the rim cushion on the tire circumference.

  Here, when the height Hr of the upper end 6a of the rim cushion 6 is less than 0.5 times the tire cross-section height SH, the cut resistance is lowered, and when it exceeds 0.7 times, the rolling resistance is lowered. It will be. Further, if the average height exceeds 0.6 times the tire cross-section height SH, the balance between the improvement effect of cut resistance and the improvement effect of rolling resistance is lost, and the improvement effect of rolling resistance is insufficient. become.

  Further, when the hardness Kr of the rubber constituting the rim cushion 6 is larger than the hardness Kf of the rubber constituting the bead filler 4, the rolling resistance is deteriorated, and the rubber constituting the rim cushion 6. When the hardness Kr is made smaller than the hardness Ks of the rubber constituting the black sidewall 7, the side rigidity is insufficient and the steering stability is lowered.

  From such a viewpoint, in the pneumatic tire 1 of the present invention, the rubber constituting the black sidewall 7 has a JISA hardness of 40-60 at 20 ° C., and the rubber constituting the rim cushion 6 has a JISA hardness at 20 ° C. It is preferable to use rubber having a JISA hardness of 80 to 95 at 20 ° C. for the rubber constituting the bead filler 4 of 70 to 85.

  The fluctuation of the height Hr along the tire circumferential direction of the upper end 6a of the rim cushion 6 is a waveform that gently changes with respect to the tire circumferential direction from the viewpoint of suppressing a rapid change in side rigidity on the tire circumference as much as possible. Preferably, it is formed so as to have a waveform that changes sinusoidally. Therefore, in this invention, the case where the fluctuation | variation of this height Hr changes to a step shape along a tire circumferential direction is excluded.

  In the present invention, the height Hr of the upper end 6a of the rim cushion 6 may be formed in a wave shape having a period of 18 or more, preferably 72 or less along the tire circumferential direction. Thereby, cut resistance and rolling resistance can be improved with good balance. Here, if the wavy period is less than 18, the fluctuation of the side stiffness in the tire circumferential direction becomes too large and the uniformity of the tire is destroyed. If it exceeds 72, the effect of improving the cut resistance and the rolling resistance are improved. It becomes difficult to ensure a good balance between the effects.

  As described above, in the pneumatic tire 1 of the present invention, the height Hr of the upper end 6a of the rim cushion 6 made of high-hardness rubber is 0.5 to 0.7 times the tire cross-section height SH along the tire circumferential direction. Therefore, even when the bead filler 4 is downsized, appropriate side rigidity can be ensured. Therefore, in the present invention, the height Hf of the upper end of the bead filler 4 can be 5 to 40% of the tire cross-section height SH. Here, if it is less than 5%, the side rigidity is insufficient and the steering stability is lowered, and the cut resistance is lowered. If it exceeds 40%, the rolling resistance is lowered.

  In the pneumatic tire 1 of the present invention, the height Hs of the lower end 7b of the black sidewall 7 is preferably adjusted to be 0.3 to 0.4 times the tire cross-section height SH. Thereby, favorable cut resistance can be ensured while ensuring the durability of the bead part 2. Here, if the height Hs of the lower end 7b of the black sidewall 7 is less than 0.3 times the tire cross-section height SH, the durability of the bead portion 2 is reduced. This may cause a decrease in cutting performance.

  In the present invention, the thickness of the rim cushion 6 is gradually reduced toward the outer side in the tire radial direction, and the total thickness of the rim cushion 6 and the black sidewall 7 in the laminated portion of the rim cushion 6 and the black sidewall 7 is determined. It is good to adjust so that becomes substantially constant in the tire radial direction. Thereby, cut resistance and rolling resistance can be improved in a more balanced manner while suppressing rapid fluctuations in rigidity in the tire radial direction.

  More preferably, the thickness of the rim cushion 6 in the laminated portion of the rim cushion 6 and the black sidewall 7 is adjusted to be 0.5 to 2.0 mm. By adjusting the thickness of the rim cushion 6 on the outer side in the tire radial direction to 0.5 mm, it is possible to suppress a sudden change in rigidity in the vicinity of the upper end 6a of the rim cushion 6, and the thickness on the inner side in the tire radial direction. By adjusting to 2.0 mm, the balance between cut resistance and rolling resistance can be reliably improved. Here, when the thickness of the rim cushion 6 on the outer side in the tire radial direction is less than 0.5 mm, the cut resistance is reduced, and when the thickness on the inner side in the tire radial direction exceeds 2.0 mm, the rolling resistance is reduced. Will do.

  Further, in the pneumatic tire 1 of the present invention, tan δTs of the rubber constituting the black sidewall 7 at 60 ° C., tan δTr of the rubber constituting the rim cushion 6 at 60 ° C., and tan δTf of the rubber constituting the bead filler 4 at 60 ° C. It is preferable that Tr <Ts <Tf. As a result, it is possible to efficiently suppress heat generated in the sidewall portion during traveling and to ensure good durability. Here, if the tan δTs at 60 ° C. of the rubber constituting the black sidewall 7 is larger than the tan δTf at 60 ° C. of the rubber constituting the bead filler 4, it becomes difficult to suppress the heat generated in the sidewall portion during traveling.

  From such a point of view, in the pneumatic tire 1 of the present invention, the rubber constituting the rim cushion 6 has a tan δTr at 60 ° C. of 0.10 or less, and the rubber constituting the black sidewall 7 has a tan δTs at 60 ° C. of 0. .12 or less, it is preferable to use a rubber having a tan δTf at 60 ° C. of 0.18 or less as the rubber constituting the bead filler 4.

  In the present invention, more preferably, the lower end 6 b of the rim cushion 6 may be extended to the inside of the bead core 3 in the tire axial direction so as to wrap the bead core 3. Thereby, without disposing a new reinforcing layer on the bottom surface of the bead portion 2, it is possible to ensure good rim displacement resistance.

  As described above, the pneumatic tire of the present invention includes a rim cushion rubber that extends from the bottom surface of the bead portion toward the outer side in the tire radial direction and the outer side of the side wall rubber layer that is disposed on the outer side in the tire axial direction of the carcass layer. The upper end of the rim cushion rubber has a tire cross-section height along the tire circumferential direction, with a two-layer structure of black sidewall rubber extending from the inner side to the outer side in the tire radial direction. By changing it to a wave shape within a range of 0.5 to 0.7 times the height and ensuring that the average height is not more than 0.6 times the tire cross-section height, appropriate side rigidity is ensured. However, it improves the cutting resistance and rolling resistance in a well-balanced manner, and can be applied to tires with bead fillers that are especially downsized. It can be widely used for the pneumatic tire for passenger cars.

  The tire size is 195 / 65R15, the tire structure is shown in FIG. 1, and the configurations of the black sidewall, rim cushion and bead filler are different as shown in Table 1, respectively. Conventional tire (conventional example), tire of the present invention (Example 1) To 3) and comparative tires (Comparative Examples 1 to 5), respectively. In each tire, all specifications except the specifications in Table 1 were made common.

  These nine types of tires were evaluated for weight reduction, cut resistance, and rolling resistance by the following methods, respectively, and the results are also shown in Table 1 using an index with the conventional tire as 100. The larger the value, the better.

[Evaluation of weight reduction]
The weight of each tire was measured, and the result was used for evaluation of weight reduction.

[Evaluation of cut resistance]
Each tire is fitted to a rim (size: 15 x 6 JJ) and filled with air pressure 230 kPa, and is mounted on a domestic car (2.0 L, sedan), and a 30 cm high curb at a speed of 10 km / h. After climbing at an angle of 5 ° and repeating this five times, the damage of the sidewall portion was measured, and the result was evaluated as cut resistance.

[Evaluation of rolling resistance]
Each tire is fitted to a rim (size: 15 × 6JJ) and filled with an air pressure of 230 kPa. A load of 4.5 kN is applied by an indoor drum tester (drum diameter: 1706 mm), and the speed is 80 km / h. After preliminarily running for a minute, the rolling resistance value was measured, and the reciprocal of the result was used to evaluate the rolling resistance.

  From Table 1, it was confirmed that the tire of the present invention improved the cut resistance and rolling resistance in a well-balanced manner while reducing the weight of the tire as compared with the conventional tire and the comparative tire.

  More specifically, in Comparative Example 1, the cut resistance was lowered because the height of the bead filler was lowered compared to the conventional tire, and in Comparative Example 2, the rolling resistance was deteriorated because the height of the rim cushion was increased. On the other hand, in Example 1, since the upper end height of the rim cushion was changed in a sine wave shape with respect to the tire circumferential direction, the cut resistance and the rolling resistance were improved in a well-balanced manner. In comparison example 4, the rolling resistance deteriorates because the height variation along the tire circumferential direction of the rim cushion is increased in Comparative Example 4, and the rim cushion height decreases. It was confirmed that the cut resistance deteriorated because the height variation along the tire circumferential direction of the cushion was formed in steps.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Bead core 4 Bead filler 5 Carcass layer 6 Rim cushion 6a Upper end of rim cushion 6b Lower end of rim cushion 7 Black sidewall 7b Lower end of black sidewall SH Tire sectional height Hr Height of upper end of rim cushion Height Hf Height of the upper end of the bead filler Hs Height of the lower end of the black sidewall

Claims (8)

A bead filler is disposed on the outer peripheral side of a bead core embedded in a pair of left and right bead portions, and includes at least one carcass layer folded back so as to wrap around the bead core from the inner side to the outer side in the tire axial direction. And a rim cushion that is exposed outside in the tire axial direction of the bead portion and extends from the inner side toward the outer side in the tire radial direction, on the outer side in the tire axial direction adjacent to the carcass layer, and the tire of the rim cushion A pneumatic tire in which a black sidewall extending from the upper end in the tire radial direction of the exposed portion toward the outer side in the tire radial direction is laminated on the outer side in the axial direction,
The height of the upper end of the rim cushion is changed in a wave shape within a range of 0.5 to 0.7 times the tire cross-sectional height along the tire circumferential direction, and the average height of the upper end of the rim cushion is changed to the tire cross-section. Relationship between the hardness Ks of the rubber constituting the black sidewall, the hardness Kr of the rubber constituting the rim cushion, and the hardness Kf of the rubber constituting the bead filler Is a pneumatic tire with Ks <Kr <Kf.   The pneumatic tire according to claim 1, wherein the height of the upper end of the rim cushion is formed in a wave shape having a period of 18 or more along the tire circumferential direction.   The pneumatic tire according to claim 1, 2, or 3, wherein a height of an upper end of the bead filler is 5 to 40% of a tire cross-sectional height.   The pneumatic tire according to claim 1, 2, or 3, wherein a height of a lower end of the black sidewall is 0.3 to 0.4 times a tire cross-sectional height.   While gradually decreasing the thickness of the rim cushion toward the outer side in the tire radial direction, the total thickness of the rim cushion and the black sidewall in the laminated portion of the rim cushion and the black sidewall is the tire radial direction. The pneumatic tire according to claim 1, 2, 3, or 4, which is substantially constant.   The pneumatic tire according to claim 1, 2, 3, 4, or 5, wherein a thickness of the rim cushion in a laminated portion of the rim cushion and the black sidewall is 0.5 to 2.0 mm.   The relationship between tan δ Ts at 60 ° C. of the rubber constituting the black sidewall, tan δ Tr at 60 ° C. of the rubber constituting the rim cushion, and tan δ Tf at 60 ° C. of the rubber constituting the bead filler is Tr <Ts <Tf. The pneumatic tire according to claim 1, 2, 3, 4, 5 or 6.   The pneumatic tire according to claim 1, 2, 3, 4, 5, 6 or 7, wherein a lower end of the rim cushion extends to an inner side in a tire axial direction of the bead core so as to wrap the bead core.

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