JP2009173150A - Radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radial tire improved high-speed durability, road noise characteristics, and driving stability by improving belt durability, and improved in fuel economy by suppressing weight increase and preventing increase of rolling resistance. <P>SOLUTION: The radial tire comprises a radial carcass 4 and a belt 5 composed of three or more belt layers. The belt 5 has two crossing belt layers 5a, 5b disposed to cross each other, and at least one circumferential belt layer 5c formed to arrange a plurality of steel cords substantially in parallel to the plane of the tire equator on the outer circumferential side. The width of the circumferential belt layer 5c is larger than the width of the second belt layer of the outside in the tire radial direction of the two crossing belt layers 5a, 5b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radial tire (hereinafter, also simply referred to as “tire”), and more specifically, in an ultra-high performance tire that is used for long-time high-speed running, by reducing belt resistance by improving belt durability, The present invention relates to a radial tire that improves high-speed durability, road noise, and steering stability while improving fuel efficiency.

  Conventionally, in a passenger car radial tire in which a belt layer is embedded on the outer peripheral side of the carcass layer in the tread portion, by providing a belt cover layer whose cord angle with respect to the tire circumferential direction is substantially 0 ° on the outer peripheral side of the belt layer, It is known that the tagging effect on the belt layer can be enhanced. As a result, it is possible to prevent the edge separation phenomenon caused by the rising of both ends of the belt layer due to the centrifugal force at the time of tire rotation, and at the same time, the high-frequency road noise characteristics of the tire are improved by increasing the tire circumferential rigidity. become.

  When such a belt cover layer is provided, an organic fiber cord such as a nylon cord is generally used as the cord, but it cannot be said that the belt cover layer made of the organic fiber cord has a sufficient tagging effect, and the tire When the cord is continuously rotated at a high speed for a long time, the cord is continuously subjected to centrifugal force at a high temperature, and permanent deformation due to creep growth specific to the organic fiber cord is inevitable. Therefore, it has been difficult for the belt cover layer using the organic fiber cord to further improve the high-speed durability and high-frequency road noise characteristics of the tire.

  In order to overcome such difficulties, a radial tire using a steel cord as a cord for the belt cover layer has been proposed. For example, Patent Document 1 discloses that a HE (High Elongation) steel cord having a breaking elongation of 4 to 8% and a double twist structure is used as a reinforcement cord for a belt cover layer (annular reinforcing structure). .

Patent Document 2 discloses that in the circumferential belt layer as the belt cover layer, the product of the cross-sectional area of the steel cord per 50 mm width and the number of cords to be driven is 3.0 mm ² or more, so that high speed durability is achieved. A radial tire with improved road noise and steering stability is disclosed.
JP-A-56-82609 (Claims etc.) JP 2006-69338 A (Claims etc.)

  However, in the radial tire described in Patent Document 1, the tension load acts on the normal belt and the belt cover layer so as to resist the stress at 2/3 and 1/3, respectively. The code will cause significant disruption to the power distribution. In addition, it is difficult to ensure sufficient rigidity as a tire effect of the tire, and there is a problem in terms of durability.

  Further, in the radial tire to which the circumferential belt layer described in Patent Document 2 is applied, although the tagging effect is obtained, the belt end portion has a smaller tagging effect than the belt center portion, and durability caused by the belt end such as belt edge separation. There was a concern about deterioration of the properties, and improvement was still desired.

  Accordingly, an object of the present invention is to solve the above problems and improve belt durability, thereby improving high-speed durability, road noise and steering stability, suppressing an increase in weight, and increasing rolling resistance. By preventing this, it is an object to provide a radial tire with improved fuel efficiency.

  As a result of intensive studies to solve the above problems, the inventor of the present invention, in the circumferential belt layer made of steel cords arranged on the outer peripheral side of a normal crossing belt layer, by setting the width to a predetermined width, The inventors have found that the above object can be achieved and have completed the present invention.

That is, the radial tire of the present invention includes a radial carcass made of one or more carcass plies, and a belt made of three or more belt layers disposed on the outer peripheral side of the crown portion of the radial carcass. However, there are two layers of crossing belt layers arranged so as to cross each other, and at least one layer in which a plurality of steel cords are arranged substantially parallel to the tire equatorial plane on the outer peripheral side of the two layers of crossing belt layers In a radial tire having a circumferential belt layer,
The width of the circumferential belt layer is equal to or greater than the width of the second belt layer on the tire outer periphery side of the two crossing belt layers.

In the present invention, it is preferable that the width of the circumferential belt layer is equal to or greater than the width of the first belt layer on the tire inner periphery side of the two cross belt layers. The steel cord is preferably a steel cord formed by twisting steel strands having a tensile strength of 2700 N / mm ² or more. Furthermore, the gauge between the tire groove bottom and the circumferential belt layer is preferably 0.5 mm or more.

  According to the present invention, the belt edge separation is suppressed and the belt durability is improved by the above configuration, thereby improving the high speed durability, the road noise and the steering stability, and the weight. Increase in fuel consumption performance can be improved by suppressing the increase and preventing the increase in rolling resistance.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional perspective view showing a radial tire according to an embodiment of the present invention with a part thereof removed by breaking. The illustrated radial tire includes a tread portion 1, a pair of sidewall portions 2 extending inward in the tire radial direction continuously on both sides of the tread portion 1, and a bead continuous on the inner peripheral side of each sidewall portion 2. Part 3.

  As shown in the figure, the tread portion 1, the sidewall portion 2, and the bead portion 3 are reinforced by a radial carcass 4 including a single carcass ply extending from one bead portion 3 to the other bead portion 3 in a toroidal shape. . Further, the tread portion 1 includes two layers of intersecting belt layers 5a and 5b disposed on the outer peripheral side of the crown portion of the radial carcass 4, and a single circumferential belt disposed on the outer peripheral side of these belt layers. Reinforced by a belt 5 comprising the layer 5c.

  Here, the carcass ply of the radial carcass 4 may be plural, and an organic fiber cord extending in a direction substantially orthogonal to the tire circumferential direction, for example, an angle of 70 to 90 °, can be preferably used.

  Further, the two intersecting belt layers 5a and 5b, which are the belt layers on the radial carcass 4 side, are arranged so that the cord driving angle is preferably 60 ° to 80 ° with respect to the tire axial direction and intersect with each other. To do. Steel can be used as the cords of the crossing belt layers 5a and 5b, and organic fiber cords such as polyamide fibers can be suitably used from the viewpoint of lightness.

  Furthermore, the circumferential belt layer 5c which is the belt layer on the tread portion 1 side has a cord driving angle of substantially 0 ° with respect to the tire circumferential direction. That is, the cords of the circumferential belt layer 5c are arranged substantially parallel to the tire equatorial plane. The circumferential belt layer 5c is one layer in the illustrated example, but may be a plurality of layers. Here, substantially 0 ° means that it is within a range of 2 °, for example.

  In the present invention, as shown in FIG. 1, it is important that the width of the circumferential belt layer 5c is equal to or greater than the width of the second belt layer 5b on the outer side in the tire radial direction of the two intersecting belt layers 5a and 5b. It is. When the width of the circumferential belt layer 5c is smaller than the width of the second belt layer 5b, the tagging effect is reduced, and the distortion at the belt end becomes larger during tire rolling, resulting in a decrease in durability caused by belt edge separation or the like. There is a risk.

  In the present invention, as shown in FIG. 2, the width of the circumferential belt layer 5c is preferably equal to or greater than the width of the first belt layer 5a on the inner side in the tire radial direction of the two cross belt layers. As a result, the hoop effect is further increased and the belt durability can be further improved.

  However, if the width of the circumferential belt layer 5c is too large, the cord may come out from the groove bottom of the tire, so that the gauge between the tire groove bottom and the circumferential belt layer can secure 0.5 mm or more. The width of the directional belt layer is preferable.

In the present invention, as the steel cord constituting the circumferential belt layer 5c, a steel cord formed by twisting steel strands having a tensile strength of 2700 N / mm ² or more, preferably 3200 to 4000 N / mm ² is preferably used. be able to. If the tensile strength of the steel strand to be used is less than 2700 N / mm ² , the belt strength may be reduced, and durability such as plunger energy may be deteriorated.

  The circumferential belt layer 5c can be easily formed by, for example, winding one or a plurality of steel cords spirally in the tire circumferential direction in a state where the steel cords are aligned and covered with rubber.

  In the tire of the present invention, the width of the circumferential belt layer 5c is important, and the details of the tire structure other than that, the material of each member, etc. are appropriately selected from known structures and materials in accordance with conventional methods. There is no particular limitation.

  For example, a tread pattern is appropriately formed on the surface of the tread portion 1, and an inner liner (not shown) is disposed on 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 in more detail with reference to examples.
(Belt tension distribution)
For a radial tire of tire size 225 / 45R17 (first belt layer width: 185 mm, second belt layer width: 175 mm, no circumferential belt), the belt tension distribution was determined by analysis, and the results shown in FIG. Got. It was confirmed from FIG. 3 that the tension distribution decreased near both ends in the width direction even when the crossing belt was arranged to suppress the deformation of the tire due to the centrifugal force and reduce the rolling resistance and wear.
(Examples 1 to 3, conventional example, comparative example)
A radial tire of tire size 225 / 45R17 having the belt structure shown in FIG. 1 or FIG. 2 was manufactured as follows.

  One radial carcass 4 was used and a rayon fiber cord was used. Further, the two intersecting belt layers 5a and 5b are the same, and the cord driving angles are + 62 ° and −62 ° with respect to the tire axial direction, and steel cords are used. Furthermore, the circumferential belt layer 5c (number of cords driven: 58/50 mm) was one layer, and steel cords according to the conditions shown in Table 1 below were used.

The following evaluation tests were carried out for each manufactured tire. The results are also shown in Table 1 below.

<Belt durability>
Each test tire was mounted on a standard rim defined in the JATMA standard, filled with an internal pressure corresponding to the maximum load capacity in JATMA YEAR BOOK, and mounted on a passenger car. After traveling 40,000 km on the paved road, the tires were dissected and the separation length of the belt end was examined. The results are displayed as an index with the conventional example as 100. Smaller values indicate better results.

<High-speed durability test>
Each test tire was mounted on a rim having a rim size of 7J × 17, the air pressure was set to 300 kPa, and a high speed durability test was performed by a speed step method according to the test method of JATMA standard. The results are shown as indexes with the speed at the time of tire failure of the conventional example as 100. The higher the number, the better the result.

<Road noise test>
In the road noise test, each test tire is assembled on a rim of 7J × 17, mounted on a passenger car with a displacement of 2000 cc with an air pressure of 220 kPa, and the sound when driving on a specific road noise test road with a road noise measuring instrument. This was done by measuring the pressure. Each result is shown as an index with the conventional tire as 100. The smaller the value, the lower the road noise and the better.

<Cornering power>
JIS standard normal internal pressure, a tire loaded with a load is pressed on a drum with an outer diameter of 3000 mm and preliminarily traveled at a speed of 30 km / h for 30 minutes, and then adjusted to the normal pressure again and traveled at the same speed. I let you. At this time, an angle (slip angle) with a maximum of 14 degrees between the rolling direction of the tire and the circumferential direction of the drum is continuously provided, and the cornering force (CF) corresponding to the positive and negative angles is measured. The average cornering power value was calculated from the following formula and evaluated.
CP = {CF (1 °) + CF (2 °) / 2 + CF (3 °) / 3 + CF (4 °) / 4} / 4

<Rolling resistance test>
A method of measuring by using a rotating drum having a smooth steel surface with an outer diameter of 1707.6 mm and a width of 350 mm and rotating at a speed of 0 to 180 km / h under the action of a normal internal pressure of JIS standard and a load of 450 kgf, so-called The rolling resistance was measured by the lame method. The results are expressed as an index when the conventional tire is set to 100. The smaller the value, the smaller the rolling resistance and the better.

＊）使用したスチールコードの引張り強さは全て３３７０Ｎ／ｍｍ²であり、ナイロン繊維コードの引張り強さは１００４Ｎ／ｍｍ²であった。

*) The tensile strength of all the steel cords used was 3370 N / mm ² , and the tensile strength of the nylon fiber cords was 1004 N / mm ² .

  As shown in Table 1 above, it was confirmed that the tires of the examples using the circumferential belt layer in accordance with the conditions according to the present invention were superior in belt durability as compared with the tires of the conventional example and the comparative example. It was. However, in Example 5, generation | occurrence | production of the crack was recognized by the shoulder groove bottom.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional perspective view showing a radial tire according to an embodiment of the present invention, with a part thereof removed by breaking. FIG. 6 is a cross-sectional perspective view showing a radial tire according to another embodiment of the present invention with a part thereof removed by breaking. It is a graph which shows the analysis result of the tension distribution of the belt in an example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Radial carcass 5 Belt 5a, 5b Crossing belt layer 5c Circumferential belt layer

Claims (4)

A radial carcass composed of one or more carcass plies, and a belt composed of three or more belt layers disposed on the outer peripheral side of the crown portion of the radial carcass, wherein the belts are arranged so as to cross each other. A radial tire having two intersecting belt layers and at least one circumferential belt layer in which a plurality of steel cords are arranged substantially parallel to the tire equatorial plane on the outer peripheral side of the two intersecting belt layers In
A pneumatic radial tire characterized in that the width of the circumferential belt layer is equal to or greater than the width of the second belt layer on the tire outer periphery side of the two cross belt layers.   2. The pneumatic radial tire according to claim 1, wherein the width of the circumferential belt layer is equal to or greater than the width of the first belt layer on the inner circumferential side of the two crossing belt layers. The radial tire according to claim 1 or 2, wherein the steel cord is a steel cord formed by twisting steel strands having a tensile strength of 2700 N / mm ² or more.   The radial tire according to any one of claims 1 to 3, wherein a gauge between the tire groove bottom and the circumferential belt layer is 0.5 mm or more.

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