JP2012176694A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire that can reduce rolling resistance of the tire during vehicle traveling and concurrently maintain excellent air permeability resistance.SOLUTION: A pneumatic radial tire 1 includes: a carcass 6 comprised of a carcass body 6a and a folded part 6b; a bead filler 7 disposed on the outside in a radial direction of a bead core 5; and an inner liner 8 extending along the carcass on the inside of the carcass. A length BFh of a perpendicular falling from an outermost end 7out in a tire radial direction of the bead filler through a bead toe 9 to a line segment in parallel with a tire rotation axis is 10-20% of a cross-sectional height SH of the tire, and a length LTU of a perpendicular falling from an outermost end 6bout in a tire radial direction of the folded part through the bead toe to a line segment in parallel with the tire rotation axis is 10-40% of a cross-sectional height SH of the tire. The inner liner is a rubber composition containing clay and terminal parts of the inner liner are disposed within a bead part.

Description

  The present invention relates to a pneumatic radial tire having low rolling resistance and good air permeation resistance.

The reduction in tire rolling resistance not only reduces the amount of CO ₂ emission during vehicle travel, but also contributes significantly to improving the fuel consumption of the vehicle. Therefore, conventionally, for the purpose of reducing the rolling resistance of the tire, for example, as in the pneumatic radial tire disclosed in Patent Document 1, the height from the bottom to the top in the radial direction of the highly rigid bead filler is set to 35 mm or less. Therefore, it is common practice to optimize the tire rigidity. Thereby, the tire rigidity in a bead part falls and the rolling resistance of a tire can be reduced by improving the eccentricity of a tire effectively. In other words, when the tire receives a load, by displacing the tire in the direction perpendicular to the road surface, the energy loss at the crown portion is less than when the tire is crushed and displaced in a direction parallel to the road surface. As a result, the rolling resistance of the tire can be reduced.

JP 2003-276407 A

In recent years, there has been an increasing demand for further improvements in tire rolling resistance due to improved fuel economy and environmental considerations.
Therefore, the present inventors have investigated a method for realizing further reduction of the rolling resistance of the tire, and by improving the eccentricity of the tire by further simplifying the configuration of the bead portion and reducing the tire rigidity. I got the idea. However, in this case, although rolling resistance can be reduced, it has been found that it is difficult to maintain good air permeation resistance. That is, it has been found that if the tire rigidity is too low, a gap may be generated between the bead portion and the rim during rolling of the tire load, and in such a case, a decrease in internal pressure is caused.
As described above, it has been found that there is a tradeoff between reducing the rolling resistance of the tire by optimizing the tire rigidity and maintaining the air impermeability, and it is difficult to realize both at the same time.

  Accordingly, an object of the present invention is to propose a pneumatic radial tire that can simultaneously reduce the rolling resistance of the tire during traveling of the vehicle and maintain good air permeation resistance.

As a result of intensive research to realize reduction of rolling resistance of the tire, the inventors have found a more appropriate arrangement of the bead filler and turned the tire around the bead core from the inner side to the outer side in the tire width direction. Obtaining the knowledge that considering the length of the turn-up portion of the carcass extending radially outward also contributes to the improvement of the rolling resistance of the tire, we succeeded in finding the appropriate length.
Furthermore, in order to reduce rolling resistance and maintain good air permeation resistance, intensive studies focused on an inner liner that maintains the internal pressure of pneumatic radial tires and contributes significantly to a decrease in air permeability Repeated. As a result, it was found that by providing an appropriate configuration and arrangement for the inner liner, both reduction in rolling resistance and good air permeation resistance can be realized simultaneously, and the present invention was completed. It was.

That is, the gist of the present invention is as follows.
(1) A carcass body comprising a carcass body extending in a toroidal shape between a pair of bead cores, and a folded portion extending from the carcass body from the inside to the outside in the tire width direction around the bead core and extending outward in the tire radial direction along the carcass body. When,
A bead filler disposed radially outside the bead core;
A pneumatic tire comprising an inner liner extending along the carcass inside the carcass,
The length of the perpendicular drawn from the outermost end in the tire radial direction of the bead filler to the line parallel to the tire rotation axis through the bead toe is 10% to 20% of the tire cross-sectional height,
From the outermost end in the tire radial direction of the folded portion, the length of a perpendicular line that passes through the bead to the line segment parallel to the tire rotation axis is 10% to 40% of the tire cross-sectional height,
The inner liner is a rubber composition containing clay;
A pneumatic radial tire characterized in that an end portion of the inner liner is disposed in a bead portion.

  (2) The pneumatic radial tire according to (1), wherein an end portion of the inner liner is disposed beyond the bead core.

  (3) The pneumatic radial tire according to (1) or (2), wherein a thickness in a tire width direction of a sidewall portion of the pneumatic tire is 1.5 mm or more and less than 2.6 mm.

  According to the present invention, it is possible to provide a pneumatic radial tire that simultaneously achieves a reduction in rolling resistance of the tire during vehicle travel and good air permeation resistance.

It is a tire width direction sectional view of a pneumatic tire according to the present invention. It is tire width direction sectional drawing of the other pneumatic tire according to this invention.

  Hereinafter, a pneumatic radial tire according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view in the tire width direction of a pneumatic tire according to the present invention, and FIG. 2 is a sectional view in the tire width direction of another pneumatic tire according to the present invention.

  FIG. 1 is a sectional view in the tire width direction of a pneumatic radial tire 1 (hereinafter simply referred to as “tire”) according to the present invention, in which 2 is a tread portion, 3 is a sidewall portion, and 4 is a bead portion. Bead cores 5 and 5 are disposed in the bead portions 4 and 4, respectively, and a carcass 6 extending in a toroidal shape is provided between the pair of bead cores 5 and 5. The carcass 6 extends between the bead cores 5 and 5 and the carcass main body 6a and extends from the carcass main body 6a to the outer side in the tire width direction around the bead cores 5 and 5 and extends outward in the tire radial direction along the carcass main body 6a. It consists of a folded portion 6b.

  Bead fillers 7 and 7 are disposed outside the bead cores 5 and 5 in the tire radial direction and between the carcass main body 6a and the folded portion 6b. An inner liner 8 is disposed along the carcass 6 on the tire inner peripheral surface of the carcass 6.

And in the tire according to the present invention,
(A) The length of the perpendicular drawn from the outermost end in the tire radial direction of the bead filler to the line parallel to the tire rotation axis through the bead toe is 10% to 20% of the cross-sectional height of the tire. ,
(B) The length of the perpendicular drawn from the outermost end in the tire radial direction of the folded portion through the bead to the line parallel to the tire rotation axis is 10% to 40% of the tire cross-sectional height. ,
(C) the inner liner is a rubber composition containing clay;
(D) the end of the inner liner is disposed within the bead portion;
Is essential.

That is, first, the tire radial direction outermost end 7 _out of the bead filler 7, when minus perpendicular to the tire rotation axis parallel to the line segment L through the bead toe 9, the tire radial direction outermost end 7 _out It is important that the length BFh from the line segment L to the line segment L is 10% to 20% of the sectional height SH of the tire. Here, the sectional height SH of the tire means 1/2 of the difference between the outer diameter of the tire and the rim diameter as defined by JATMA.
The reason why the length BFh is in the above range is that if it is less than 10%, the function of the bead filler as a rigid member is impaired. On the other hand, when it exceeds 20%, the rigidity of the bead portion does not sufficiently decrease, the eccentricity of the tire cannot be improved, and as a result, the rolling resistance of the tire cannot be sufficiently reduced. .

Further, in the above configuration, when the perpendicular line is drawn from the outermost end 6b _out of the tire radial direction 6b _out of the carcass folded portion 6b through the bead toe 9 to the line segment L parallel to the tire rotation axis, It is important that the length LTU from the outer end 6b _out to the line segment L is 10% to 40% of the sectional height SH of the tire.
The carcass folding portion 6b has a function of increasing the rigidity of the bead portion by sandwiching the bead core 5 and the bead filler 7 between the carcass body 6a, but the length of the folding portion 6b is set to an appropriate length. As a result, the rigidity of the bead portion is appropriately reduced to improve the eccentricity of the tire, and the rolling resistance of the tire can be reduced while maintaining the steering stability and the actual vehicle riding comfort in a good state. . That is, when the length LTU is set within the above range, the bead core 5 and the bead filler 7 may be sandwiched between the carcass main body 6a and the turn-up portion 6b when the cross-sectional height SH is less than 10%. This is because the rigidity of the bead portion becomes too low without being able to be achieved, and on the other hand, when it exceeds 40%, the rigidity of the bead portion becomes high and the rolling resistance cannot be reduced.

  As described above, it is possible to improve the eccentricity of the tire by optimizing the rigidity in the bead portion and to reduce the rolling resistance of the tire. However, as a result of repeated studies by the inventors, it has been found that if the bead rigidity is lowered in this way, the air permeability may be lowered. Because, as described above, if the tire stiffness is too low, a gap may be generated between the bead portion and the rim during rolling of the tire load, and in such a case, the internal pressure may be reduced. Because.

Therefore, in the tire according to the present invention, it is important that the rubber composition used for the inner liner 8 extending along the inner surface of the carcass 6 contains clay in addition to the above-described configuration.
The inner liner is provided on the inner peripheral surface of the tire in order to prevent air leakage from the inside of the tire to the outside and maintain the internal pressure of the tire. Therefore, the rubber composition used for the inner liner is required to have low air permeability and excellent bending resistance. In response to this requirement, generally, the inner liner uses a rubber composition obtained by blending carbon black or the like with a halogenated butyl rubber that contributes to a reduction in air permeability and a diene rubber that contributes to bending resistance. Yes. However, the rubber composition as described above does not sufficiently satisfy the air permeation resistance of the inner liner, and there remains room for further improvement.
Therefore, the present invention employs a configuration in which the rubber composition used for the inner liner includes clay so that the air permeability of the inner liner is effectively reduced and the internal pressure of the tire can be effectively maintained. If the rubber composition includes clay, the clay particles are blended in the inner liner in a direction intersecting the thickness direction of the inner liner, and the air permeation path is blocked. This is because it is possible to improve the performance.
It is preferable to use a clay containing white kaolin clay or sericite clay, and the clay content in the rubber composition used for the inner liner is 80% by mass to 150% by mass. Is preferred.

Furthermore, in the tire according to the present invention, the inner liner 8 is extended so that the end portions 8e, 8e of the inner liner 8 are in the bead portion 4 in order to maintain good air permeation resistance. It is important to arrange them. Here, the inside of the bead portion 4 is a region from a line segment parallel to the tire rotation axis through the tire radial direction outermost end 7 _out of the bead filler 7 to a line segment L parallel to the tire rotation axis through the bead toe 9. Say the part in
Specifically, the end portion 8e, for example as shown in FIG. 1, the position of the radially inward of the tire radial direction outermost end 7 _out of the bead filler 7 in the tire radial direction inside of the carcass (carcass main 6a side) Placed in. As described above, since the inner liner 8 is disposed so as to extend to the position of the bead portion 4, the occurrence of air leakage from the inside of the tire to the outside is sufficiently suppressed, and the internal pressure of the tire is improved. It is possible to hold the state.
For example, as shown in FIG. 2, the end portion 8 e may be disposed beyond the bead core 5 in the tire radial direction inside the carcass (on the carcass main body 6 a side). More specifically, the inner liner 8 is disposed so as to be located radially inward from the tire radial direction outermost end of the bead core 5. Thus, by arranging the inner liner 8 so as to extend to the entire inside of the tire, the occurrence of air leakage from the inside of the tire to the outside is sufficiently suppressed, and the internal pressure of the tire is further improved. It becomes possible to hold.

Moreover, in the said structure, as shown in FIG. 1, it is preferable that the tire width direction thickness W of the sidewall part 3 of the tire 1 is 1.5 mm or more and less than 2.6 mm. Here, the thickness in the tire width direction of the sidewall portion 3 refers to the thickness of the sidewall portion at a position having the maximum tire width.
The tire rolling resistance is the energy consumed by the heat generated by repeated deformation of the tire when rolling the tire. Loss can be reduced, and as a result, tire rolling resistance is reduced.

  Next, an inventive tire according to the present invention, a conventional tire according to the prior art, and a comparative tire shown below were prototyped, and the rolling resistance of the tire was evaluated. Further, the air permeability resistance of the tire was evaluated by examining the internal pressure retention property of the tire.

  The inventive tire is a radial tire for a passenger car having the configuration shown in FIG. 1 and having a size of 155/65 R13. Each specification was as shown in Table 1.

  On the other hand, in the conventional tire, the bead filler length BFh, the length of the carcass turn-up portion LTU, and the thickness of the sidewall portion in the tire width direction are as shown in Table 1, and the rubber composition of the inner liner is clay. In addition to the fact that the end portion of the inner liner does not extend to the bead portion inside the tire, the configuration other than that of the tire according to the invention example is applied.

  Further, as the comparative example tire, the length of the folded portion of the carcass LTU is the tire cross-section height SH, and the tire width direction thickness of the sidewall portion has the values shown in Table 1. It was based on.

These inventive tires, conventional tires and comparative tires were respectively mounted on a vehicle, and the rolling resistance of the tire and the internal pressure retention of the tire were evaluated.
The rolling resistance of the tire was evaluated by measuring the resistance in the traveling direction generated on the contact surface when a constant load was applied to the tire and the tire was rotated at a constant speed using an indoor drum tester. . Specifically, a load of 73% of the maximum load capacity was applied, an air pressure of 210 kpa was applied, and the tire was rotated at a speed of 80 km / h. In addition, the evaluation of the internal pressure retention of the tire was performed by leaving a tire to which air pressure of 210 kpa was applied for 6 months and comparing the residual internal pressure of the tire. The results are shown in Table 2.

  From the results in Table 2, the bead filler length BFh is 10% to 20% of the cross-sectional height of the tire, the length LTU of the folded portion of the carcass is 10% to 40% of the cross-sectional height of the tire, Inventive tire made of a rubber composition containing an inner liner is found to be able to maintain a good internal pressure of the tire in addition to effectively reducing the rolling resistance of the tire compared to the conventional tire. It was.

  According to the present invention, it is possible to provide a pneumatic radial tire that simultaneously achieves a reduction in rolling resistance of the tire during vehicle travel and good air permeation resistance.

1 pneumatic radial tire 2 tread portion 3 sidewall portion 4 bead portion 5 bead core 6 Carcass 6a carcass body 6b tire diameter of the folded portion 6b _out carcass turnup portion in the tire radial direction outermost end 7 bead filler 7 _out bead filler of the carcass direction from the outermost edge 8 innerliner 9 bead toe BFh bead tire radial direction outermost end _{7 out} of the filler, through the bead toe 9
The length of the perpendicular line that is lowered to the line parallel to the tire rotation axis SH The cross-sectional height of the tire L-L A straight line parallel to the tire axis passing through the bead toe 9 LTU The outermost end 6b in the tire radial direction of the folded portion of the carcass _out , bead to
The length of the vertical line drawn through line 9 to the line parallel to the tire rotation axis W The thickness of the sidewall 3 in the tire width direction

Claims (3)

A carcass main body extending in a toroidal shape between a pair of bead cores, and a carcass formed of a folded portion extending from the carcass main body, folded around the bead core from the inner side in the tire width direction to the outer side, and extended outward in the tire radial direction along the carcass main body;
A bead filler disposed radially outside the bead core;
A pneumatic tire comprising an inner liner extending along the carcass inside the carcass,
The length of the perpendicular drawn from the outermost end in the tire radial direction of the bead filler to the line parallel to the tire rotation axis through the bead toe is 10% to 20% of the tire cross-sectional height,
From the outermost end in the tire radial direction of the folded portion, the length of a perpendicular line that passes through the bead to the line segment parallel to the tire rotation axis is 10% to 40% of the tire cross-sectional height,
The inner liner is a rubber composition containing clay;
A pneumatic radial tire characterized in that an end portion of the inner liner is disposed in a bead portion.   The pneumatic radial tire according to claim 1, wherein an end portion of the inner liner is disposed beyond the bead core.   The pneumatic radial tire according to claim 1 or 2, wherein a thickness in a tire width direction of the sidewall portion is 1.5 mm or more and less than 2.6 mm.

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