JP2007237922A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve steering stability while restraining lowering of cutting resistance and riding comfort to the minimum. <P>SOLUTION: A carcass 6 is constituted of an inner carcass ply 9i arranged on the extreme inside and one or two pieces of outer carcass plies 9o arranged on the outside of it. A carcass cord of the outer carcass ply 9o is made larger than 0.4 time of intermediate elongation el of the carcass cord of the inner carcass ply 9i in its intermediate elongation e2 and larger than 1.0 time of cord thickness D1 of the carcass cord of the inner carcass ply 9i and smaller than 1.5 times of it and its cord twisting number T2 is made larger than 0.75 time of the cord twisting number T1 of the carcass cord of the inner carcass ply 9i and smaller than 1.0 time of it. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that has improved steering stability while minimizing a decrease in cut resistance and ride comfort.

  A radial tire is known in which a carcass forming a skeleton of a tire is formed by two to three carcass plies, and the steering stability is improved by increasing tire rigidity. In this type of tire, the same carcass cord is usually used for each carcass ply.

  On the other hand, with the recent increase in speed and performance of vehicles, further improvement in steering stability is desired for pneumatic tires. Therefore, it is effective to use a cord having a low intermediate elongation and a small elongation as the carcass cord. For example, from nylon to a high modulus fiber such as polyethylene terephthalate (PET) and further polyethylene naphthalate (PEN). The transition is planned.

  However, such high modulus of the cord material has a problem that the ride comfort is lowered and the cut resistance in the sidewall portion is lowered. If the thickness of the carcass cord is increased to reduce the elongation of the cord, the ride comfort will be reduced, and if the number of twists of the carcass cord is reduced to reduce the elongation of the cord, the cut resistance and There is a problem of causing a decrease in ride comfort

  Therefore, the present invention provides a carcass cord having an intermediate elongation, a cord thickness, and a cord twist number different between the inner carcass ply, which is the innermost carcass ply, and the other outer carcass plies. The objective is to provide a pneumatic tire that can improve steering stability while minimizing the reduction in cut resistance and ride comfort, based on suppressing the elongation of the carcass ply cord.

JP 2003-200709 A JP 08-164707 A

In order to achieve the above object, the invention of claim 1 of the present application includes a single inner carcass ply having a ply body portion extending from the tread portion to the bead core of the bead portion through the sidewall portion, and the inner carcass ply of the inner carcass ply. A pneumatic tire comprising a carcass composed of one or two outer carcass plies having a ply main body arranged radially outside the ply main body,
The inner carcass ply and the outer carcass ply are both made of carcass cords using organic fibers,
The carcass cord of the outer carcass ply has an intermediate elongation e2 that is greater than 0.4 times and less than 0.8 times the intermediate elongation e1 of the carcass cord of the inner carcass ply, and the cord thickness D2 is the inner thickness e2. More than 1.0 times and less than 1.5 times the cord thickness D1 of the carcass ply of the carcass ply, and the cord twist number T2 is 0.75 times the cord twist number T1 of the carcass cord of the inner carcass ply. It is characterized by being larger and smaller than 1.0 times.

In the invention of claim 2, the outer carcass ply includes a first outer carcass ply adjacent to the inner carcass ply, and each of the first outer carcass ply and the inner carcass ply includes the ply body. A ply turn-around portion that is continuous with the bead core and is turned back from the inside in the tire axial direction to the outside, and at least one ply turn-up portion terminates beyond the tire maximum width position radially outward. It is said.
According to a third aspect of the present invention, the ply turn-up portions of the first outer carcass ply and the inner carcass ply each end beyond the tire maximum width position radially outward.
In the invention of claim 4, the outer carcass ply and the inner carcass ply are characterized in that each carcass cord is arranged at an angle of 60 to 88 ° with respect to the tire circumferential direction.

Here, the “intermediate elongation” is “elongation at constant load” measured according to “standard time test” in Section 8.7 of JIS L1017, and the constant load F is calculated by the following equation. Is done.
F (N) = 44 × (d2 / d1)
Where d1 is the reference fineness (dtex) determined by the type of fiber
d2: Display fineness of sample (dtex)

  Further, in this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified when the bead part is held in accordance with the rim width specified by the tire size in a non-rim assembled state. .

  In the tire according to the present invention, a carcass cord having a low intermediate elongation is used for an outer carcass ply which is another carcass ply with respect to an inner carcass ply which is the innermost side. Moreover, in the outer carcass ply, the carcass cord is thicker than the inner carcass ply and the number of twists is set to be small, and the elongation of the carcass cord is set to be lower. Therefore, for example, with respect to a tire in which the outer carcass ply is formed using the same carcass cord as the inner carcass ply (referred to as a conventional tire for the sake of convenience), the carcass cord of the outer carcass ply is less stretched and the steering stability is improved. Can be made.

  On the other hand, in the sidewall portion of the tire, the portion to which the impact force is applied is deformed into a concave shape, so that a large distortion occurs in the inner carcass ply at this portion. For this reason, the inner carcass ply has a great influence on the cut resistance, for example, the inner carcass ply is easily broken. However, in the tire of the present invention, the elongation characteristic of the carcass cord of the inner carcass ply is the same as that of the conventional tire. In addition, since the elongation of the carcass cord of the outer carcass ply is smaller than that of a conventional tire, deformation due to impact is suppressed, and particularly, the impact force is also reduced because the carcass cord of the outer carcass ply is thicker and the rigidity is increased. And by these interaction, the fall of cut resistance can be suppressed to the minimum.

  Further, since the inner carcass ply is separated from the deformation center at the time of rolling of the tire, it has a great influence on the riding comfort such as an increase in elongation at the time of deformation. However, in the tire of the present invention, the elongation characteristics of the carcass ply of the inner carcass ply are the same as in the case of the conventional tire, so that a decrease in riding comfort can be minimized.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a case where the pneumatic tire of the present invention is a passenger tire.
As shown in FIG. 1, a pneumatic tire 1 according to the present embodiment includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, a radially outer side of the carcass 6, and a tread portion. 2 and a belt layer 7 disposed inside.

  The belt layer 7 is formed of two or more belt plies 7A and 7B in this example in which high-strength belt cords such as steel cords are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction. The Each belt ply 7A, 7B enhances belt rigidity by crossing the belt cords between the plies, and reinforces substantially the entire width of the tread portion 2 with a tagging effect.

  On the outer side in the radial direction of the belt layer 7, a band layer 10 in which band cords of organic fibers such as nylon are arranged at an angle of, for example, 5 degrees or less with respect to the circumferential direction, mainly for the purpose of enhancing high-speed durability. Can be provided. As the band layer 10, a pair of left and right edge band plies that covers only the outer end portion in the tire axial direction of the belt layer 7 and a full band ply that covers substantially the entire width of the belt layer 7 can be used as appropriate. An example of one full band ply is shown.

  The carcass 6 includes one inner carcass ply 9i having a ply main body portion 11i straddling the bead cores 5 and 5, and one ply main body portion 11o arranged radially outward of the ply main body portion 11i or Two outer carcass plies 9o are formed. In other words, the carcass 6 is composed of a total of two to three carcass plies 9 having a ply main body 11 straddling the bead cores 5 and 5, and the ply that is the innermost in the radial direction is the inner carcass ply 9 i and the outer side thereof. The other ply arranged is called the outer carcass ply 9o.

  The outer carcass ply 9o includes a first outer carcass ply 9o1 adjacent to the inner carcass ply 9i. In this example, the case where there is one outer carcass ply 9o is illustrated, and in this case, the outer carcass ply 9o is formed by the first outer carcass ply 9o1. In this example, each of the first outer carcass ply 9o1 and the inner carcass ply 9i includes a ply folding portion 12 that is connected to each ply main body portion 11 and is folded around the bead core 5 from the inner side to the outer side in the tire axial direction. Yeah. That is, a 2-0 ply structure is adopted. At this time, it is preferable that at least one ply turn-up portion 12 has a so-called high turn-up (HTU) structure in which the tire maximum width position Pm is terminated outward in the radial direction. In this example, it is more preferable that both the ply turn-up portion 12i of the inner carcass ply 9i and the ply turn-up portion 12o of the first outer carcass ply 9o1 are terminated outward in the radial direction of the tire maximum width position Pm. Is illustrated. Reference numeral 8 in the figure is a bead apex rubber made of hard rubber and having a triangular cross section extending radially outward from the bead core 5. Reference numeral 20 denotes a reinforcing layer in which reinforcing cords are inclined with respect to the tire circumferential direction. In this example, the side wall portion 3 extends from the bead portion 4 in cooperation with the ply folding portion 12 and the bead apex rubber 8. Reinforce over.

  Next, in the inner carcass ply 9i and the outer carcass ply 9o, carcass cords using organic fibers are arranged at a cord angle of 60 to 90 ° with respect to the tire circumferential direction.

  At this time, between the carcass cord of the outer carcass ply 9o (referred to as the outer carcass cord for convenience) and the carcass cord of the inner carcass ply 9i (referred to as the inner carcass cord), the intermediate elongation of the cord and the thickness of the cord And the number of twists of the cords are made different from each other, thereby keeping the elongation of the outer carcass cord low compared to the inner carcass cord.

For more information,
(1) The intermediate elongation e2 of the outer carcass cord is set to be larger than 0.4 times and smaller than 0.8 times the intermediate elongation e1 of the inner carcass cord, and (2) of the outer carcass cord The cord thickness D2 is set to be larger than 1.0 times and smaller than 1.5 times the cord thickness D1 of the inner carcass cord, and (3) the cord twist number T2 of the outer carcass cord is It is set larger than 0.75 times the cord twist number T1 of the carcass cord and smaller than 1.0 times.

  Here, as described above, the intermediate elongations e1 and e2 are “elongation at constant load” measured in accordance with the “standard time test” in Section 8.7 of JIS L1017. It is indicated by the value of the carcass code after processing. In addition, as a method of giving a difference in the intermediate elongation, for example, various methods such as changing the cord material itself, changing the dipping treatment conditions, adjusting the heating temperature and heating time at the time of heating the cord, and the like. Can be adopted. The cord thicknesses D1 and D2 are expressed by the total display fineness (dtex) of the cord. The cord twist numbers T1 and T2 are represented by the number of upper twists per 10 cm of the cord length.

  As described above, in the tire 1 of the present embodiment, the intermediate elongation e2 of the outer carcass cord is set to be smaller than the intermediate elongation e1 of the inner carcass cord. The cord thickness is increased compared to the cord, and the number of cord twists is set small. Therefore, for example, with respect to a tire in which the outer carcass ply is formed by using the same cord as the inner carcass cord (referred to as a conventional tire for the sake of convenience), the carcass cord of the outer carcass ply 9o has a small elongation, so that steering stability is reduced. Can be improved.

  On the other hand, in the side wall part 3, since the site | part to which the impact force was added deform | transforms into a concave shape, there exists a tendency for an internal carcass cord to be easy to fracture | rupture, such as a big distortion generate | occur | produced by this internal carcass ply 9i. However, in the tire 1 of the present embodiment, the elongation characteristic of the carcass cord is the same as that of the conventional tire. Moreover, since the extension of the outer carcass cord is smaller than that of the conventional tire, deformation due to impact is suppressed, and the outer carcass cord is thicker and the rigidity is increased, so that the effect of mitigating impact force is enhanced. These interactions make it possible to minimize the reduction in cut resistance. Further, the inner carcass ply 9i is far from the deformation center line at the time of rolling of the tire as compared with the outer carcass ply 9o, so that it has a great influence on the riding comfort such as an increase in elongation at the time of deformation. However, in the tire 1 of the present embodiment, the elongation characteristics of the carcass cords in the tire 1 are the same as those in the case of the conventional tire, so that it is possible to minimize a decrease in riding comfort.

  Here, the ratio e2 / e1 of the intermediate elongations e1 and e2 is 0.8 or more, the ratio D2 / D1 of the cord thicknesses D1 and D2 is 1.0 or less, and the ratio T2 / T1 of the cord twist numbers T1 and T2. When 1.0 is 1.0 or more, it is not possible to sufficiently secure the steering stability improvement effect. In particular, from the viewpoint of improving the steering stability, it is preferable to set the difference between the intermediate elongations e1 and e2 (e1−e2) to be larger than 2.0%. When the ratio e2 / e1 is 0.4 or less, the ratio D2 / D1 is 1.5 or more, and the ratio T2 / T1 is 0.75 or less, there is an effect on cut resistance and riding comfort. As compared with the effect of improving steering stability, the effect of suppressing the reduction in cut resistance and ride comfort is greatly reduced.

  From such a viewpoint, the lower limit value of the ratio e2 / e1 is preferably 0.6 or more and the upper limit value is preferably 0.8 or less. The lower limit value of the ratio D2 / D1 is 1.1 or more and the upper limit value is 1.3. The lower limit of the ratio T2 / T1 is preferably 0.85 or more, and the upper limit is preferably 0.95 or less.

  Next, in this example, as described above, a 2-0 HTU structure is adopted in which the ply turn-up portions 12i, 12o of the carcass 6 are terminated radially outward from the tire maximum width position Pm. In this case, the outer carcass ply 9o having a low intermediate elongation is located on the side of the deformation center when the tire is deformed, and the inner carcass ply 9i having a high intermediate elongation is located on the side away from the deformation center. In addition, the effect of suppressing the decrease in riding comfort can be exhibited more greatly.

  In addition, as schematically shown in FIG. 2, even in the case of adopting a 2-0 HTU structure in which only one of the ply turn-up portions 12i, 12o is terminated radially outward of the tire maximum width position Pm. The effect of suppressing cut resistance and ride comfort is still inferior to that of the case where both are turned up, but can still be exerted greatly. In this case, it is preferable from the viewpoint of cut resistance and riding comfort that the ply turn-up portion 12i of the inner carcass ply 9i having a high intermediate elongation is turned up.

  Further, in the tire of the present invention, from the viewpoint of securing better cut resistance and ride comfort, a carcass cord having a higher intermediate elongation than the conventional cord can be adopted for the inner carcass ply 9i. By adopting a carcass cord having a high intermediate elongation, the tire rigidity tends to be insufficient. Therefore, in such a case, it is preferable to set the cord angle of the carcass cord as low as 88 ° or less, more preferably 80 ° or less within the range of 60 to 90 °.

  In the tire of the present invention, as schematically shown in FIG. 3 (A), the ply body portion 11o of the first outer carcass ply 9o1 is unrolled through the outer side in the tire axial direction of the bead apex rubber 8 and in the vicinity of the bead core 5. It is also possible to adopt a 1-1 structure terminated with.

  The outer carcass ply 9o can also be formed by two plies, that is, the first outer carcass ply 9o1 and the second outer carcass ply 9o2 arranged on the outside thereof. Also in such a case, as schematically shown in FIG. 3 (B), each carcass ply 9i, 9o1, 9o2 is folded around the bead core 5, and as schematically shown in FIG. 3 (C), It is possible to adopt a 2-1 structure in which the ply body 11o of the second outer carcass ply 9o2 is unrolled through the outside of the bead apex rubber 8 in the tire axial direction and terminated in the vicinity of the bead core 5.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A radial tire for passenger cars having a tire size of 195 / 55R15 having the structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the test tires were tested and compared with respect to cut resistance, ride comfort, and steering stability. All tires have the same specifications except for the different carcass cords.

(1) Cut resistance:
A pendulum side wall impact test was adopted. This is a wedge-shaped blade attached to the weight, provided at the lower end of the pendulum, and impacted on the sidewall of the tire by the free fall method, and the fracture energy of the tire sidewall was evaluated by the weight and the drop height. It is a test to do. Comparative Example 1 is indicated by an index of 100. It shows that cut resistance is excellent, so that a numerical value is large.

(2) Ride comfort and handling stability:
Rim (15 x 6 JJ), internal pressure (200 kPa), mounted on all wheels for passenger cars (2000cc, FF vehicles), ride comfort, steering wheel response, rigidity on the dry asphalt road surface of the tire test course The steering stability with respect to the grip and the like was evaluated by sensory evaluation of the driver, and evaluation was performed by a five-point method in which Comparative Example 1 was three points. The larger the number, the better.

  As shown in the table, it can be confirmed that the tires of the examples can improve steering stability while maintaining or improving cut resistance and ride comfort.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is sectional drawing which shows the other example of the carcass structure which can be employ | adopted for this invention. (A)-(C) are sectional drawings which show the further another example of the carcass structure which can be employ | adopted for this invention.

Explanation of symbols

2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 9i Inner carcass ply 9o Outer carcass ply 9o1 First outer carcass ply 11 Ply main body portion 12 Ply folded portion Pm Maximum tire width position

Claims (4)

One inner carcass ply having a ply main body extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a ply main body portion disposed on the radially outer side of the ply main body portion of the inner carcass ply A pneumatic tire having a carcass composed of one or two outer carcass plies,
The inner carcass ply and the outer carcass ply are both made of carcass cords using organic fibers,
The carcass cord of the outer carcass ply has an intermediate elongation e2 that is greater than 0.4 times and less than 0.8 times the intermediate elongation e1 of the carcass cord of the inner carcass ply, and the cord thickness D2 is the inner thickness e2. More than 1.0 times and less than 1.5 times the cord thickness D1 of the carcass ply of the carcass ply, and the cord twist number T2 is 0.75 times the cord twist number T1 of the carcass cord of the inner carcass ply. A pneumatic tire characterized by being larger and smaller than 1.0 times.   The outer carcass ply includes a first outer carcass ply adjacent to the inner carcass ply. The first outer carcass ply and the inner carcass ply are respectively connected to the ply main body portions and around the bead core. 2. The air according to claim 1, further comprising a ply turn-up portion that is turned back from the inner side in the tire axial direction, and at least one ply turn-up portion terminates radially beyond the tire maximum width position. Tires.   3. The pneumatic tire according to claim 2, wherein the ply turn-up portions of the first outer carcass ply and the inner carcass ply each end beyond the tire maximum width position radially outward.   3. The pneumatic tire according to claim 1, wherein the outer carcass ply and the inner carcass ply have each carcass cord arranged at an angle of 60 to 88 ° with respect to the tire circumferential direction.

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