JP5213160B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly to improvement of a pneumatic radial tire provided with a flipper or an insert reinforcing layer.

  In recent years, in a pneumatic radial tire, for the purpose of improving steering stability, it is common to increase the rigidity of the sidewall portion from the tire bead portion. Conventionally, for example, a configuration in which a reinforcement material including a bead core and a bead filler, a so-called flipper is provided from the bead portion to the sidewall portion, a configuration in which a so-called insert is provided from the bead portion to the sidewall portion, and the like are widely used. It has been adopted.

For example, in Patent Document 1, a cord reinforcing layer made of a cord extending at an angle in a range of 70 to 110 ° with respect to a radial line segment is disposed in a bead portion, and a material of a cord strand of this cord By specifying the above, a pneumatic tire has been disclosed that has improved driving stability while ensuring excellent vibration riding comfort and low vehicle interior noise. Patent Document 2 relates to a pneumatic radial tire including a cord reinforcing layer in which a radially inner end is positioned in the vicinity of a bead core and a radially outer end is positioned outward from the radially outer end of a bead filler. Improved techniques are disclosed.
JP 2001-187521 A (Claims etc.) JP 2001-130229 A (Claims etc.)

  With the above-described conventional technology, it is possible to improve steering stability by reinforcing a portion from the bead portion to the sidewall portion with a reinforcing layer such as a flipper or an insert to increase tire rigidity. However, in this case, since the rigidity in the vertical direction of the tire is also increased, another problem has arisen that the vibration riding comfort performance deteriorates.

  This is particularly important when driving on uneven or stepped road surfaces, and adding these reinforcing layers greatly deteriorates the size (shock) and the fit (dumping) when riding over a step. It was. Therefore, it has been desired to establish a technique capable of improving the steering stability without causing deterioration in ride comfort.

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

  As a result of intensive studies in order to solve the above problems, the present inventors have found the following. That is, as described above, the riding comfort performance that is most deteriorated by having a flipper or an insert reinforcing layer is the size (shock) and the fit (dumping) when hitting a step. Hereinafter, these strengths and fits are collectively referred to as “step ride comfort”.

  Here, in order to ensure ride comfort, the important characteristics required for the steel cord constituting the belt layer are that the cord has low bending rigidity and high tensile rigidity in the cord direction. 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 shock and damping generated when stepping over a step are 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, and the belt layer arrangement, for example, between the two belt layers The influence of the rubber layer thickness and 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. In addition, the step riding performance evaluation was carried out when the angle of the belt layer was changed from 45 degrees to 75 degrees, but no improvement in riding comfort was confirmed.

  From this point of view, as a result of further studies, the present inventor has improved the above-mentioned step ride comfort by using a cord that satisfies a specific physical property as a steel cord of a belt layer in a pneumatic tire having a flipper or an insert reinforcing layer. The inventors have found that an effect can be obtained and have completed the present invention.

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 toroid shape between the bead portions. In a pneumatic tire comprising: a carcass composed of at least one carcass ply for reinforcing the carcass; and at least two crossing belt layers that are disposed on the outer side in the radial direction of the crown portion of the carcass and use steel cords as a reinforcing material.
At least one flipper or insert reinforcing layer is disposed in at least a part of the region from the bead portion through the sidewall portion to the shoulder portion of the tread portion, and the unit width of the crossing belt layer The steel cord has a rigidity satisfying a relationship represented by the following formula.
(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 (pieces / 50 mm)

  According to the present invention, with the above configuration, it is possible to improve the vibration riding comfort performance of the vehicle in the pneumatic tire having the flipper or the insert reinforcing layer.

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.

  In addition, at least one carcass 2 extending in a toroidal shape between the bead portions 11, in the illustrated example, one carcass ply, extends from the inside of the tire around the bead core 1 embedded in each bead portion 11. They are folded back and locked to reinforce these parts 11-13. 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 tire of the present invention, at least one flipper or insert reinforcing layer, in the illustrated example, the insert reinforcing layer 4 is formed in at least a part of the region from the bead portion 11 through the sidewall portion 12 to the shoulder portion of the tread portion 13. Is arranged. Here, the flipper is disposed between the main body 2A and the folded portion 2B of the carcass 2 and includes at least a part of the bead core 1 and a bead filler (not shown) disposed on the outer side in the tire radial direction. It is a reinforcing material. The flipper is usually composed of an organic fiber cord such as Kevlar. The insert reinforcing layer is a reinforcing material arranged in the tire circumferential direction, and is usually composed of a steel cord. In the present invention, the cord structure, the number of driving, the arrangement angle, the arrangement range, etc. of the flipper and the insert reinforcing layer are not particularly limited. For example, the insert reinforcing layer 4 can be arranged as shown in FIGS. 2A to 2D, and the flipper 5 can be arranged as shown in FIGS. 3A and 3B.

In the tire of the present invention, the rigidity of the steel cord per unit width of the crossing belt layer 3 is expressed by the following formula:
(A-800) / B ≧ 20
It satisfies the relationship represented by Here, A and B are defined as follows.
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 (pieces / 50 mm)

By making the relationship between the bending rigidity (bending resistance) and tensile rigidity of the steel cord satisfy the above formula, the ride comfort of the step, which is evaluated by combining both shock and damping, is clearly improved. It becomes possible. 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. More preferably, the following formula:
25 ≦ (A−800) / B ≦ 110
Use steel cords that satisfy this relationship.

  As the steel cord used for the crossing belt layer 3, any steel cord having any twisted structure or filament diameter (elementary wire diameter) may be used as long as the above relational expression is satisfied. Can be improved. 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, a fine crack generated at the end of the steel cord grows between adjacent steel cords, and then between the belt laminations. The speed of crack growth leading to belt separation is significantly increased. 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 in-plane direction of the belt layer. Thereby, lower out-of-plane bending rigidity can be obtained, and in-plane rigidity required for steering stability can also be improved. Furthermore, it is effective for ensuring rubber penetrability (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.

  In the present invention, the steel cord used for the crossing belt layer only needs to satisfy the above conditions, and other details of the tire structure and the material of each member are not particularly limited, and are conventionally known. It can be configured by appropriately selecting from the above. For example, in the tire of the present invention, the number of crossing belt layers is at least 2, preferably 1 to 4, and the angle with respect to the tire circumferential direction is, for example, 0 ° to 70 ° with respect to the tire circumferential direction. It can be. The number of carcass 2 disposed can be 1 to 4. Further, although not shown, a bead filler is disposed outside the bead core 1 in the tire radial direction, a tread pattern is appropriately formed on the 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.
A test tire having a tire size 225 / 45R17 having an insert reinforcing layer 4 as shown in FIG. The insert reinforcing layer 4 was formed by applying a 30 × 50 mm width treat using a 1 × 3 × 0.30 mm cord at a width of 50 mm and a cord angle of 45 ° with respect to the lasil direction. The crossing belt layers were two layers, and steel cords having cord structures shown in the following table were respectively applied. The angle of the crossing belt layer with respect to the tire circumferential direction was ± 62 °.

  The following tests were performed on each of the obtained test tires. The results are also shown in the table below.

<Ride comfort performance test>
Each test tire was filled with an internal pressure of 2.1 kgf / cm ² and mounted on a standard rim defined in the JATMA standard, 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, (1) size (shock) and (2) fit of the push-up feeling when overcoming a bump difference of road surface width x height 2 cm x length 3 cm at a speed of 60 km / h (Damping) was given a score of 1 to 5 points, and each item was averaged to give a step ride 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.

＊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）
＊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）

* 1) 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)
* 2) A: Cord tensile stiffness (kg) defined by stress at 1% tension x Number of driven wires (pieces / 50mm)

  As shown in the above table, in the test tire of the example using the crossing belt layer that satisfies the conditions of the present invention, a good step difference compared to the test tire of the comparative example that does not satisfy the conditions of the present invention. It was confirmed that ride comfort was obtained.

It is a width direction one side sectional view of the pneumatic tire concerning one embodiment of the present invention. It is a fragmentary sectional view showing the variation of the arrangement position of an insert reinforcement layer. It is a fragmentary sectional view which shows the variation of the arrangement position of a flipper.

Explanation of symbols

1 Bead core 2 Carcass 3 Cross belt layer 4 Insert reinforcement layer 5 Flipper 11 Bead portion 12 Side wall portion 13 Tread portion

Claims (1)

From at least one carcass ply having a pair of left and right bead portions and sidewall portions, and a tread portion continuous between both sidewall portions, extending in a toroidal shape between the bead portions and reinforcing these portions. A pneumatic tire comprising: a carcass comprising: a carcass crown portion; and at least two crossing belt layers using a steel cord as a reinforcing material.
At least one flipper or insert reinforcing layer is disposed in at least a part of the region from the bead portion through the sidewall portion to the shoulder portion of the tread portion, and the unit width of the crossing belt layer A pneumatic tire characterized in that the rigidity of the steel cord satisfies the relationship represented by the following formula.
(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 (pieces / 50 mm)

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