JP5213161B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly to a pneumatic radial tire having a belt reinforcing layer made of organic fiber cords in the vicinity of a crossing belt layer.

  Along with the advancement of high-grade and high-quality vehicles, especially in passenger cars, low-vibration and improvement of ride comfort of vehicles have been rapidly progressing in recent years. Is required. In particular, reduction of noise generated in the vehicle is desired, and as one of such noises, it is generated based on the fact that the running tire spreads the unevenness of the road surface and the vibration is transmitted to vibrate the air in the vehicle The demand for improving so-called road noise has become extremely high. In addition, with the upgrading of vehicles, it is necessary to maintain road noise, riding comfort, handling stability, and the like at high levels.

  In particular, as a method for reducing road noise of a tire that has been improved in recent years, there is a method in which a reinforcing layer in which a cord is rubberized is arranged in the tire circumferential direction on the entire width or both ends of the outer layer side of the cross belt layer. For example, Patent Document 1 discloses a technique for reinforcing the circumferential rigidity of a belt by covering at least both ends of a belt layer with a reinforcing layer formed by winding a nylon cord in a spiral shape. . This technique is often originally implemented for the purpose of improving the high-speed durability of a steel radial tire, but at the same time, it is a technique capable of reducing road noise.

  Moreover, as said improvement technique aiming at the further significant reduction of road noise, for example, patent document 2, 3 uses a high elastic modulus cord for the reinforcement layer of the tire circumferential direction arrange | positioned on the outer side of a belt layer. Technology is disclosed. Further, Patent Document 4 discloses a composite cord in which a high elastic filament and a low elastic filament are twisted together with a reinforcing layer in the tire circumferential direction arranged outside the belt layer, and an inflection point is given to the stress-elongation curve. A technique using is disclosed.

  Furthermore, Patent Documents 5 to 7 disclose techniques for limiting the characteristics and materials of fiber cords used for a tire circumferential reinforcing layer disposed outside the belt layer, and Patent Document 8 discloses a belt layer. The tire circumferential direction reinforcing layer disposed outside the tire, at least in the center in the tire width direction is made of nylon cord, and at least one tire width direction both ends of the reinforcing layer is made of polyester cord It is disclosed.

However, among the conventional techniques for reducing the road noise described above, techniques such as those disclosed in Patent Document 1 and the like can achieve some effects in reducing road noise as well as improving high-speed durability. Still it was not satisfactory enough. In addition, the techniques according to Patent Documents 2 to 4 can be expected to have a moderate effect. In particular, according to the techniques according to Patent Documents 5 to 7, a large road noise reduction effect can be obtained. In particular, it was not satisfactory with respect to the push-up performance of the shock when riding over a step. Accordingly, there has been no prior art that sufficiently satisfies the riding comfort, which is an essential condition of the required performance of the current tire, and that can significantly reduce road noise.
JP-A-6-24208 (Claims etc.) JP-A-2-147407 (Claims etc.) JP-A-1-145203 (Claims etc.) JP-A-1-247204 (Claims etc.) JP-A-9-66705 (Claims etc.) Japanese Unexamined Patent Publication No. 2000-142025 (Claims etc.) Japanese Patent Laid-Open No. 10-86607 (Claims etc.) JP-A-11-208212 (Claims etc.)

  As described above, according to the above-described prior art, although a tire that is satisfactory with respect to road noise characteristics can be obtained, another problem is caused in that the vibration ride comfort performance deteriorates because the circumferential rigidity of the tire increases. It was. This is particularly important when driving on uneven and stepped road surfaces, and by adding such a circumferential reinforcing layer, the amount of hit (shock) over the step (shock) and its fit (dumping) are increased. There was a problem of making it worse. Therefore, it has been desired to establish a technology that can improve road noise characteristics without deteriorating vibration ride comfort when riding over a step.

  Accordingly, an object of the present invention is to provide a pneumatic tire excellent in both road noise performance and riding 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 determined that the elastic modulus of the fiber cord used for the belt reinforcing layer for improving road noise and the main crossing belt layer disposed below the belt reinforcing layer are predetermined. By satisfying the above relationship, when the above-mentioned belt reinforcing layer is more than conventional nylon fiber or processed with high elasticity of conventional nylon fiber, or when using fibers of other materials However, it has been found that a pneumatic tire can be obtained that can simultaneously satisfy the above-mentioned various characteristics.

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 belt reinforcing layer is disposed on the outer side in the tire radial direction of the crossing belt layer at the whole and / or both ends of the tread portion, and the belt reinforcing layer includes a plurality of organic fiber cords. A rubberized narrow strip is formed by wrapping the organic fiber cord spirally and endlessly so that the organic fiber cord is 0 ° to 5 ° with respect to the tire circumferential direction, and
The rigidity of the steel cord per unit width in the crossing belt layer 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)

  In the present invention, the tensile modulus of the organic fiber cord is preferably 4400 MPa or more. Further, the organic fiber cord is a cord in which 30% or more of the total displayed denier number is made of polyethylene-2,6-naphthalate (PEN) fiber, and 30% or more of the total displayed denier number is polyethylene terephthalate (PET) fiber. Cord composed of 30% or more of the total number of displayed deniers composed of aramid fibers, Composite cord composed of 30% or more of the total number of displayed deniers of aramid fibers and nylon fibers % Or more is preferably made of any of cords composed of polyolefin ketone (POK) fibers.

  According to the present invention, the above configuration makes it possible to realize a pneumatic tire that achieves both good road noise performance and vibration ride comfort performance and improved steering stability.

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 present invention, as shown in the drawing, at least one belt reinforcing layer 4 is disposed on the entire tread portion 11 and / or at both ends on the outer side in the tire radial direction of the crossing belt layer 3. In the illustrated example, one belt reinforcing layer 4 is disposed on the outer peripheral side of the crossing belt layer 3 over the entire tread portion 11 from the cereal side to the anti-cereal side, and the belt reinforcing layer 4 is provided at both ends on the outer peripheral side. One layer is arranged. The belt reinforcing layer 4 is formed by winding a rubberized narrow strip including a plurality of organic fiber cords spirally and endlessly so that the organic fiber cords are 0 ° to 5 ° with respect to the tire circumferential direction. This is a reinforcing layer in the tire circumferential direction.

  In this way, the belt reinforcing layer 4 is spirally wound around the entire tread and / or near the side portions at both ends of the tread portion, and in particular, the modulus of the cord used for the belt reinforcing layer 4 is increased to increase the tire circumference. By using a barrier-like reinforcing layer having high tension in the direction, the tension rigidity in the circumferential direction of the tread portion 11 is increased, and the so-called tagging effect of the belt is enhanced. As a result, it is difficult for the tread surface to spread vibrations on the road surface when the tires are running, reducing the vibrations transmitted from the tire side part to the rim part and the wheel and transmitted to the inside of the car, resulting in reduced road noise. The effect to do is acquired. In the present invention, the belt reinforcing layer 4 is preferably provided so as to extend to the outer side in the tire axial direction of the crossing belt layer 3 as illustrated.

  The organic fiber cord used for the belt reinforcing layer 4 is not particularly limited with respect to the cord diameter, the cord structure, the number of twists, etc., but is more preferably more elastic than general 66 nylon fibers, It is preferable to use one having a tensile elastic modulus of 4400 MPa or more, particularly 10800 MPa or more. By using an organic fiber cord having a high tensile elastic modulus, in addition to a road noise reduction effect, an improvement effect in steering stability can be obtained. Specifically, as the material of the organic fiber cord, for example, polyethylene-2,6-naphthalate fiber, polyethylene terephthalate fiber, aramid fiber, aramid-nylon composite cord, polyolefin ketone fiber and the like are very suitable. However, a certain effect can be obtained with 66 nylon fibers. More preferably, a cord in which 30% or more of the total number of displayed deniers is composed of polyethylene-2,6-naphthalate fiber, polyethylene terephthalate fiber, aramid fiber or polyolefin ketone fiber can be mentioned. Moreover, as an organic fiber cord, you may use what made the said organic fiber and the other organic fiber into the composite yarn or the composite cord other than what consists of single organic fiber. Specifically, for example, an aramid-nylon composite cord in which 30% or more, particularly 45% or more of the total displayed denier number is composed of an aramid fiber and a nylon fiber can be suitably used.

  On the other hand, in order to ensure the ride comfort in steps, the important characteristics necessary for the steel cords constituting the cross belt layer 3 are that the cords have low bending rigidity and high cord direction tensile rigidity. This is due to the following two reasons. (1) Since the steel cords constituting the crossing belt layer undergo 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, in the present invention, the use of a cord satisfying the following specific physical properties as the steel cord of the crossing belt layer 3 makes it possible to obtain the effect of improving the step riding comfort. That is, in the present invention, the rigidity of the steel cord per unit width in 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 ≦ 170
Use steel cords that satisfy this relationship. In terms of performance, a larger value of (A−800) / B is better. However, if it exceeds 170, a problem occurs in productivity and a problem of deterioration of the manufacturing defect rate appears.

  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.

  2 to 7 show cross-sectional views in one side in the width direction of a pneumatic tire according to another embodiment of the present invention. These are all examples of the arrangement of the belt reinforcing layer 4, but in the present invention, the arrangement of the belt reinforcing layer 4 is not limited to these examples. FIG. 2 shows a case where the belt reinforcing layer 4 is wound around both ends of the tread portion 13. FIG. 3 shows an example in which two layers of the belt reinforcing layer 4 are wound around both ends of the tread portion 13. FIG. 4 shows an example in which one layer is wound around the entire tread portion 13, and two layers are wound around both ends of the belt reinforcing layer 4. FIG. 5 shows an example in which the belt reinforcing layer 4 is wound around the entire tread portion 13. FIG. 6 shows an example in which two layers are wound around the entire tread portion 13, and one layer is wound around both ends of the belt reinforcing layer 4. FIG. 7 shows an example in which two layers of the belt reinforcing layer 4 are wound around the entire tread portion 13. For example, the structures shown in FIGS. 2 and 3 are preferably used for ordinary passenger cars from the viewpoint of weight reduction. Also, the structures as shown in FIGS. 1 and 4 to 6 are preferably used for heavy-duty passenger cars, sports cars that emphasize high-speed performance, and the like in terms of reinforcing effects.

  In the present invention, the steel cord used for the belt reinforcing layer and 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. Instead, it can be configured by appropriately selecting from conventionally known ones. For example, in the tire of the present invention, the number of crossing belt layers is at least two layers, preferably 1 to 4 layers, and the cords are overlapped so as to cross in different directions, and the tire circumferential direction is The angle can be, for example, 10 ° to 60 °, particularly 25 ° to 40 ° with respect to the tire circumferential direction. Further, the carcass 2 is preferably a radial carcass, and the number of disposed carcass 2 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.
Test tires having a tire size of 225 / 45R17 were produced according to the conditions shown below. 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 intersecting belt layer with respect to the tire circumferential direction is ± 27 °, and they are arranged so as to cross each other.

  The belt reinforcing layer is formed of organic fiber cords (polyolefin ketone fiber cord, polyethylene terephthalate fiber cord, polyethylene 2,6-naphthalate fiber cord, nylon-aramid composite twisted fiber cord, aramid fiber cord and 66 shown in the following table, respectively. A narrow rubberized strip including a plurality of nylon fiber cords was formed by wrapping endlessly in a spiral manner so that the organic fiber cord was 0 ° to 5 ° with respect to the tire circumferential direction. As the organic fiber cord of the belt reinforcing layer, the display decitex is 1670 dtex / 2, the lower twist is 39 times / 10 cm, the upper twist is 39 times / 10 cm (the number of twists is indicated as lower × up (times / 10 cm) 39 × 39) The thing of was used. In addition, the arrangement form is as shown in FIG. 5 for Example 6, as shown in FIG. 4 for Example 8, and all other arrangements are arranged as shown in FIG.

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

<Ride comfort test>
Each test tire was filled with a standard internal pressure and mounted on a standard rim defined in the JATMA standard, and an actual tire test was conducted. 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.

<Road noise test>
Each test tire is mounted on a sedan-type vehicle and all four wheels are run on the road noise evaluation road of the test course at a speed of 60 km / h. A rating of 1 to 5 is given, and each item is averaged for road noise. Scored. The evaluation was performed by three professional drivers, and the average of the scores of the three drivers was obtained. The higher this value, the better the road noise.

<Steering stability test>
Each test tire was mounted on a sedan-type vehicle and all four wheels were run on a steering stability evaluation test course. Specifically, each test tire is mounted on a passenger car, and an actual vehicle feeling test is performed at a speed of 60 to 200 km / hour. (I) Straight running stability, (ii) Turning stability, (iii) Rigidity, (Iv) Items such as handling were rated 1 to 5 points, and each item was averaged to give a handling stability score. The evaluation was performed by three professional drivers, and the average of the scores of the three drivers was obtained. The higher this value, the better the steering stability.

＊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 tires of the examples using the belt reinforcing layer and the crossing belt layer satisfying the conditions of the present invention, the step ride comfort can be improved while reducing road noise. Furthermore, it was confirmed that the handling stability could be improved.

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

Explanation of symbols

1 Bead core 2 Carcass 3 Intersection belt layer 4 Belt reinforcing layer 11 Bead portion 12 Side wall portion 13 Tread portion

Claims (7)

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 belt reinforcing layer is disposed on the outer side in the tire radial direction of the crossing belt layer at the whole and / or both ends of the tread portion, and the belt reinforcing layer includes a plurality of organic fiber cords. A rubberized narrow strip is formed by wrapping the organic fiber cord spirally and endlessly so that the organic fiber cord is 0 ° to 5 ° with respect to the tire circumferential direction, and
A pneumatic tire characterized in that the rigidity of the steel cord per unit width in the crossing belt layer satisfies 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)   The pneumatic tire according to claim 1, wherein the tensile modulus of the organic fiber cord is 4400 MPa or more.   The pneumatic tire according to claim 1 or 2, wherein the organic fiber cord is formed of a cord in which 30% or more of the total number of displayed deniers is composed of polyethylene-2,6-naphthalate fiber.   3. The pneumatic tire according to claim 1, wherein the organic fiber cord is made of a cord in which 30% or more of the total displayed denier is made of polyethylene terephthalate fiber.   The pneumatic tire according to claim 1 or 2, wherein the organic fiber cord is formed of a cord in which 30% or more of the total displayed denier number is composed of aramid fibers.   The pneumatic tire according to claim 1 or 2, wherein the organic fiber cord is composed of a composite cord in which 30% or more of the total displayed denier number is composed of an aramid fiber and a nylon fiber.   The pneumatic tire according to claim 1 or 2, wherein the organic fiber cord is made of a cord in which 30% or more of the total displayed denier number is composed of polyolefin ketone fibers.

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