JP2010047200A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire excellent in both steering stability and vibration ride comfort. <P>SOLUTION: The pneumatic tire is provided with a crossing belt layer of at least two layers using a steel cord arranged at an outer side in a tire radial direction of a crown part of a carcass, as a reinforcement material. The pneumatic tire is attached to a standard rim stipulated in JATMA standard and has tire vertical spring constant at internal pressure of 230 kPa and load of 4,000 N of 200 N/mm or more. Rigidity of the steel cord per unit width of the crossing belt layer satisfies a relationship represented by a formula: (A-800)/B≥20, wherein A is cord traction rigidity (kg) defined by stress at 1% traction × the number of hitting (number/50 mm), and B is cord bending rigidity (g/mm) defined by inclination at 2-6 mm pushing-in deformation of stress-bending displacement curve obtained by cord 3-point bending test × the number of hitting (number/50 mm). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly to a pneumatic radial tire that can achieve both steering stability and vibration ride comfort performance at a high level.

  In recent years, in a pneumatic radial tire, it is common to increase the rigidity of a sidewall portion from a tire bead portion for the purpose of improving steering stability. Conventionally, for example, a reinforcing material containing a bead core and a bead filler, that is, a so-called flipper is disposed from the bead portion to the sidewall portion (Patent Document 1), and a so-called insert is disposed from the bead portion to the sidewall portion. The structure (patent document 2) etc. which are used are employ | adopted widely.

Further, in a pneumatic tire in which a carcass layer is mounted between a pair of bead portions and the carcass layer is wound around the bead core from the inside of the tire to the outside, the carcass cord of the carcass layer winding portion is connected to the body portion of the carcass layer. It has been proposed to ensure tire rigidity by crossing the carcass cord (Patent Documents 3 to 6).
JP 2001-130229 A JP 2001-187521 A Japanese Patent Laid-Open No. 2002-2216 JP 2002-127712 A JP 2003-226117 A JP 2007-83914 A

  By the above conventional technique, the steering stability is improved by reinforcing the tire rigidity by reinforcing the portion from the bead portion to the sidewall portion. However, since the vertical rigidity (longitudinal spring) of the tire also increases at the same time, another problem has arisen that the vibration ride comfort performance deteriorates.

  Vibration ride performance is particularly important when driving on uneven or stepped roads. When the tire vertical rigidity increases, the impact size (shock) when riding over a step and its fit (dumping) are greatly deteriorated. It was supposed to end up. Therefore, it has been desired to establish a technique capable of improving the steering stability without causing deterioration of the ride comfort on the step.

  Accordingly, an object of the present invention is to provide a pneumatic tire excellent in both steering stability and vibration ride comfort performance by improving the above-mentioned drawbacks of a conventional high-performance radial tire.

  As a result of intensive studies to solve the above problems, the present inventor has found the following. As described above, by increasing the rigidity of the sidewall from the tire bead part and increasing the vertical rigidity of the tire (longitudinal spring), the most deteriorating riding performance is shock and damping when overstepping (hereinafter referred to as these) The shock and damping are collectively referred to as “step ride comfort”).

  For example, if a tire with a longitudinal spring constant of 200 N / mm or more with an internal pressure of 230 kPa and a load of 4000 N is mounted on a standard rim defined in the JATMA standard, the deformation of the belt part is much larger than the deformation of the tire side part when stepping over a step. Thus, the influence of the belt layer characteristics on the step riding comfort is increased.

  In order to secure the step ride comfort of tires with a longitudinal spring constant of 200 N / mm or more, the important characteristics required for the steel cords constituting the belt layer are low bending rigidity of the cords and tensile rigidity in the cord direction. Is expensive. This is due to the following two reasons. (1) Since the steel cord constituting the belt layer is subjected to bending deformation when stepping over a step, the steel cord having a lower bending rigidity can lower the hit. (2) The fine vibration of the steel cord that occurs due to hitting over the step is attenuated faster and the fit is improved as the tensile tension in the cord direction is higher. Therefore, the steel cord needs to have high tensile rigidity.

  The level of ride comfort is greatly affected by the micro-vibration and damping characteristics of the steel cord, but the influence of the vibration of the entire belt layer is small. The influence of the belt angle is small. In addition, although this inventor actually changed the thickness of the intermediate | middle rubber layer from 0.1 mm to 2.0 mm and implemented level | step difference riding comfort evaluation, the improvement of riding comfort was not confirmed. Further, even when the angle of the belt layer was changed from 45 ° to 75 °, the step ride comfort evaluation was performed, but no improvement in ride comfort was confirmed.

  Based on these findings, the present inventor conducted further diligent investigations. The invention has been completed.

That is, the pneumatic tire of the present invention has a pair of left and right bead portions and sidewall portions, and a tread portion continuous between both sidewall portions, and extends in a toroidal shape between the bead portions. In a pneumatic tire comprising a carcass made of at least one carcass ply for reinforcing the carcass, and at least two cross belt layers using steel cords arranged on the outer side in the radial direction of the crown portion of the carcass as a reinforcing material,
A standard rim defined in JATMA standards is mounted, the tire longitudinal spring constant at an internal pressure of 230 kPa and a load of 4000 N is 200 N / mm or more, and the rigidity of the steel cord per unit width of the crossing belt layer is expressed by the following formula. It is characterized by satisfying the relationship.
(A-800) / B ≧ 20
A: Cord tensile stiffness (kg) defined by the stress at 1% tension × Number of driven wires (50 / 50mm)
B: Cord bending stiffness (g / mm) defined by the slope at the time of 2-6 mm indentation deformation of the stress-bending displacement curve obtained by the cord three-point bending test × number of driven (pieces / 50 mm).

  In the present invention, the distance between the steel cords adjacent in the crossing belt layer is preferably 0.3 mm or more, the cross-sectional shape of the steel cord is flat, and the longitudinal direction of the steel cord Are preferably arranged along the width direction of the crossing belt layer.

  According to the present invention, with the above configuration, it is possible to improve the vibration riding comfort performance of the vehicle in a tire having a longitudinal spring constant of 200 N / mm or more under the above-described conditions.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a cross-sectional side view in the width direction of a pneumatic tire according to a preferred embodiment of the present invention. As illustrated, the pneumatic tire of the present invention has a pair of left and right bead portions 11 and sidewall portions 12, and a tread portion 13 that is continuous between both sidewall portions 12. Further, at least one carcass 2 extending in a toroidal shape between both bead portions 11, in the illustrated example, one carcass ply is formed around the bead core 1 embedded in each bead portion 11 from the inside of the tire. They are folded back and locked to reinforce these parts 11 to 13. Further, at least two layers, in the illustrated example, of two intersecting belt layers 3 using a steel cord as a reinforcing material are disposed outside the carcass 2 in the crown portion tire radial direction.

  In the present invention, it is important that the tire longitudinal spring constant is 200 N / mm or more at an internal pressure of 230 kPa and a load of 4000 N, more preferably a tire longitudinal spring under specified conditions. The constant is in the range of 200 N / mm to 800 N / mm. Under the above conditions, steering stability is improved by reinforcing the tire rigidity by reinforcing the portion from the bead portion to the sidewall portion.

  The tire longitudinal spring constant is calculated by the following procedure. First, a tire is mounted on a standard rim specified in the JATMA standard, and a load is applied in the tire diameter direction at an internal pressure of 230 kPa to a value equal to the maximum load capacity in the air pressure-load capacity correspondence table of the JATMA standard. “Vertical deflection-loading load curve (measurement point is 40 points or more)” is measured. The relationship between the vertical deflection and the test load when each test load is applied is regressed by a quadratic equation, and the vertical spring constant (N / mm) is calculated from the differential value at a load of 4000 N.

  In FIG. 1, the insert reinforcing layer 4 is arranged as a means for setting the tire longitudinal spring constant to 200 N / mm or more, but other known methods other than this can also be used. For example, it is good also as a structure which arrange | positions a flipper from the above-mentioned bead part 11 to the sidewall part 12, and in the pneumatic tire which rolled up the carcass layer around the bead core 1 from the tire inner side to the outer side, It is good also as a structure which makes the carcass cord of a winding part cross | intersect with the carcass cord of the main-body part of a carcass layer.

In the present invention, the cross belt layer 3 is a steel belt using a steel cord as a reinforcing material, and the rigidity of the steel cord per unit width is expressed by the following formula:
(A-800) / B ≧ 20
(Here, A is the cord tensile stiffness (kg) defined by the stress at 1% tension) × the number of driving (lines / 50 mm), and B is 2 of the stress-bending displacement curve obtained in the cord three-point bending test. It is important to satisfy the relationship represented by the cord bending rigidity (g / mm) defined by the inclination at the time of ˜6 mm indentation deformation (the number of driving (lines / 50 mm)). By making the relationship between the bending rigidity and the tensile rigidity of the steel cord satisfy the above formula, the ride comfort on the step can be clearly improved. On the other hand, if the value of (A−800) / B is less than 20, both shock and damping cannot be achieved, and the step riding comfort deteriorates.

The larger the value of (A-800) / B, the better in terms of performance. However, if it exceeds 170, a problem occurs in productivity and a problem of deterioration in production failure rate occurs.
25 ≦ (A−800) / B ≦ 170
Use steel cords that satisfy this relationship.

  In the present invention, as long as the steel cord satisfies the above relational expression, any twisted structure and filament diameter (elementary wire diameter) may be used, thereby improving the step ride comfort. Can do. For example, the twisted structure may be any structure such as single twist, layer twist, double twist, no twist, and flat cross section.

  Further, in the present invention, the effect of the present invention can be used more advantageously as the number of driven cords having a smaller wire diameter is used, but the distance between adjacent steel cords in the layer is preferably 0.3 mm or more. If the distance between adjacent steel cords in the layer is less than 0.3 mm, fine cracks generated at the ends of the steel cords grow between adjacent steel cords, and then between the belt laminations. Will also expand rapidly, and the crack growth rate leading to belt separation will be significantly faster. The distance between adjacent steel cords in the layer is more preferably 0.4 mm or more, for example, in the range of 0.5 to 1.5 mm.

  Furthermore, in the present invention, it is preferable that the cross-sectional shape of the steel cord is flat and the flat cords are arranged so that the major axis direction is along the width direction of the belt layer. Thereby, lower out-of-plane bending rigidity can be obtained, and in-plane bending rigidity required for steering stability can also be improved. Furthermore, it is effective for ensuring rubber penetration (hereinafter referred to as “rubber penetration”).

  The steel cord structure with a flat cross-sectional shape includes a single-strand structure in which the spiral shape of the strands is crushed in one direction, and two strands that are parallel to each other without being twisted together. And a structure in which a sheath wire is wound. In particular, two parallel wires, such as 2 parallel + 4-7 structures, which are parallel to each other without being twisted, can be used as a core, and the remaining strands around the core can penetrate between at least one pair of adjacent wires. It is preferable to apply a steel cord having a twisted structure so as to have a large gap, whereby a higher in-plane bending rigidity, a lower out-of-plane bending rigidity, and good rubber penetrability can be obtained.

  The pneumatic tire of the present invention is a steel that is mounted on a standard rim defined by JATMA standard, has a tire longitudinal spring constant of 200 N / mm or more at an internal pressure of 230 kPa and a load of 4000 N, and is used for at least two crossing belt layers. The cord only needs to satisfy the above conditions, and the other details of the tire structure and the material of each member are not particularly limited, and may be appropriately selected from conventionally known ones. Can do. For example, in the tire of the present invention, the number of crossing belt layers is at least 2, preferably 2 to 4, and the angle with respect to the tire circumferential direction is, for example, 0 to 70 °. Can be 1 to 4 sheets. In addition, a bead filler is disposed outside the bead core in the tire radial direction, a tread pattern is appropriately formed on the back surface of the tread portion, and an inner liner is disposed in the innermost layer of the tire. Further, in the tire of the present invention, as the gas filled in the tire, it is possible to use normal or air having a changed oxygen partial pressure, or an inert gas such as nitrogen.

Hereinafter, the present invention will be described more specifically with reference to examples.
(Comparative Examples 1-1 to 1-9 and Comparative Examples 2-1 to 2-4)
The steel cords having the cord structures shown in Tables 1 and 2 below were applied to the two intersecting belt layers to prepare test tires having tire sizes 185 / 70R14 having different longitudinal spring constants. The angle of the crossing belt layer with respect to the tire circumferential direction was ± 22 °.

(Examples 1-1 to 1-9 and Comparative Examples 3-1 to 3-4)
The steel cords having the cord structures shown in Tables 3 and 4 below were applied to the two intersecting belt layers to prepare test tires having tire sizes 205 / 55R16 having different longitudinal spring constants. The angle of the crossing belt layer with respect to the tire circumferential direction was ± 26 °.

(Examples 2-1 to 2-9 and Comparative Examples 4-1 to 4-4)
The steel cords having the cord structures shown in Tables 5 and 6 below were applied to the two intersecting belt layers to prepare test tires having tire sizes 225 / 45R17 having different longitudinal spring constants. The angle of the crossing belt layer with respect to the tire circumferential direction was ± 28 °.

(Step comfort test)
Each of the obtained test tires was filled with an internal pressure of 230 kPa, and mounted on a standard rim defined in JATMA standards, and an actual tire test was performed. The test was carried out by attaching each test tire to a sedan-type vehicle with all four wheels, and two people getting on and running on a ride comfort evaluation test course. Specifically, at a speed of 60 km / hour, 1 to 5 points for (1) shock and (2) damping, respectively, of the feeling of pushing up over a bump difference of road surface width x height 2 cm x length 3 cm The average of each item was used as a step comfort score. The evaluation was performed by two professional drivers, and the average of the scores of the two drivers was obtained. If the overall evaluation of the step ride comfort is 3 points or more, there is no problem, and if it is less than 3 points, the driver clearly feels uncomfortable. The results are also shown in Tables 1 to 6 below.

※１ Ｂ：コード３点曲げ試験で得られる、応力‐曲げ変位曲線の２〜６ｍｍ押し込み変形時の傾きで定義されるコード曲げ剛性（ｇ／ｍｍ）×打込み本数（本／５０ｍｍ）の値である。
※２ Ａ：１％引張時の応力で定義されるコード引張剛性（ｋｇ）×打込み本数（本／５０ｍｍ）の値である。

* 1 B: Cord bending stiffness (g / mm) defined by the slope of 2-6mm indentation deformation of the stress-bending displacement curve obtained in the 3-point bending test of the cord x the number of driving (lines / 50mm) is there.
* 2 A: Cord tensile stiffness (kg) defined by stress at 1% tension x number of driven wires (pieces / 50 mm).

  As shown in Tables 1 to 6, in the test tire of the example using the cross belt layer that satisfies the conditions of the present invention, it is better than the test tire of the comparative example that does not satisfy the conditions of the present invention. It was confirmed that it was possible to obtain a smooth ride comfort.

It is a width direction one side sectional view of the pneumatic tire concerning one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Crossing belt layer 4 Insert reinforcement layer 11 Bead part 12 Side wall part 13 Tread part

Claims (3)

From at least one carcass ply that has a pair of left and right bead portions and sidewall portions, and a tread portion that is continuous between both sidewall portions, extends in a toroid shape between the bead portions, and reinforces these portions. A pneumatic tire comprising: a carcass, and at least two crossing belt layers using a steel cord disposed on the outer side in the radial direction of the crown portion of the carcass as a reinforcing material,
The tire longitudinal spring constant is 200 N / mm or more at an internal pressure of 230 kPa and a load of 4000 N, and the rigidity of the steel cord per unit width of the cross belt layer is expressed by the following formula. A pneumatic tire characterized by satisfying the relationship described above.
(A-800) / B ≧ 20
A: Cord tensile stiffness (kg) defined by the stress at 1% tension x Number of driven wires (pieces / 50mm)
B: Cord bending stiffness (g / mm) defined by the slope at the time of 2-6 mm indentation deformation of the stress-bending displacement curve obtained in the three-point bending test of the cord x number of driven wires (50/50 mm)   The pneumatic tire according to claim 1, wherein a distance between the steel cords adjacent in the crossing belt layer is 0.3 mm or more.   The pneumatic tire according to claim 1 or 2, wherein the steel cord has a flat cross-sectional shape and is arranged so that a longitudinal direction of the steel cord is along a width direction of the crossing belt layer.

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