JP2014201222A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire having two laminated belt layer structure, in which both maintenance of excellent belt edge separation resistance-performance and decrease in tire rolling resistance can be achieved by particularly structuring the belt layer.SOLUTION: In a pneumatic radial tire, which is configured by laminating two of belt layers having a plurality of steel cords embedded parallely in rubber so that the steel cords intersect with one another at angles of 15-45 degrees relative to a tire equator surface, a diameter Do of steel cords composing a belt layer arranged outside in a radial direction is set to be smaller than a diameter Di of steel cords composing a belt layer arranged inside in the radial direction.

Description

  The present invention relates to a pneumatic radial tire.

  More specifically, in a pneumatic radial tire having a belt layer structure in which two steel layers are laminated so that each steel cord intersects at an angle of 15 to 45 degrees with respect to the tire equatorial plane, the steel used in the two layers. The present invention relates to a pneumatic radial tire that realizes reduction in tire rolling resistance and retention of excellent belt edge separation resistance by making cords different from each other in a special combination.

  When the present inventors examined measures for improving the belt edge separation resistance, it is effective to increase the thickness of the steel cord used for the belt layer and reduce the driving density, but the belt layer is thicker. Thus, it was found that the tire rolling resistance deteriorates.

  Conventionally, in a pneumatic radial tire having a two-layered belt layer structure as described above, each belt layer has the same specifications regarding the cord thickness, driving density, belt layer thickness, etc. of the steel cord used therein. However, when the present inventors repeated research on the relationship between the tire structure and tire performance, two belt layers with the same specifications were used. In the case of not making it, the knowledge that the belt edge separation may be improved without deteriorating the rolling resistance was obtained.

  Thus, as a prior art that does not use two-layer belts of the same specification, for example, a pneumatic tire for a passenger car that can reduce road noise while maintaining good riding comfort and ground contact. For the purpose of providing, in a pneumatic tire for a passenger car in which a plurality of belt layers using steel cords are arranged between a tread portion and a carcass, an inner belt layer arranged inside the tire and an outer belt arranged outside the tire There is a proposal for a pneumatic tire for a passenger car that is formed so that the damping rate differs between layers (claim 1 of Patent Document 1).

  Specifically, in Patent Document 1, the attenuation rate of the inner belt layer is set higher than the attenuation rate of the outer belt layer. For example, the value of the inner belt layer is set to the value of the outer belt layer. Pneumatic tires for passenger cars having a size of 1.1 to 2.1 times are proposed (Claims 2 and 3 of Patent Document 1), and the wire diameter of the steel cord constituting the inner belt layer is set to the outer belt. There has been proposed a pneumatic tire for a passenger car that is thinner than the wire diameter of a steel cord constituting the layer (claim 4 of Patent Document 1).

  However, the proposal of this Patent Document 1 is intended to reduce road noise while maintaining good riding comfort and ground contact, and durability (belt edge separation resistance) It is not intended to achieve both tire rolling resistance reduction.

In particular, in a pneumatic radial tire having three or more belt layers such as three layers or four layers for the purpose of suppressing belt end separation and improving the durability of the belt, the steel cord is adjacent to each other. The two intersecting layers have a value of (cord interval of belt layer on the outer side in the tire radial direction) / (cord interval of belt layer on the inner side in the tire radial direction) of 1.2 or more and 3.0 or less, and on the inner side in the tire radial direction. The cord space of the belt layer is set to 0.3 mm or more, and the total area in the tire width direction cross section of the steel cord per 50 mm width of the belt layer on the inner side in the tire radial direction of the cross belt layer is defined as S _in (mm ² ) When the total area in the tire width direction cross section of the steel cord per 50 mm width of the belt layer on the outer side in the tire radial direction is S _out (mm ² ),
25 mm ² ≦ S _in + S _out ≦ 30 mm ²
There has been proposed a pneumatic radial tire that satisfies the above requirements (Patent Document 2).

  However, the pneumatic radial tire proposed in Patent Document 2 is a prior art based on the premise that there are three or more belt layers such as three layers or four layers. It is different.

JP 2004-182114 A JP 2011-11595 A

  The object of the present invention is to achieve both excellent belt edge separation resistance and reduced tire rolling resistance by making the structure of the belt layer special in a pneumatic radial tire having a belt layer structure of two-layer lamination. The object is to provide a pneumatic radial tire to be realized.

  The pneumatic radial tire of the present invention that achieves the above-described object has the following configuration (1).

(1) A belt in which a plurality of steel cords are aligned and embedded in rubber so that two steel layers are laminated so that the steel cords intersect at an angle of 15 to 45 degrees with respect to the tire equator plane. In a pneumatic radial tire having a layer structure, the diameter Do of the steel cord constituting the belt layer arranged radially outside is smaller than the diameter Di of the steel cord constituting the belt layer arranged radially inside Pneumatic radial tire characterized by that.

  The pneumatic radial tire of the present invention preferably has any one of the following configurations (2) to (5).

(2) The product SoEo of the wire cross-sectional area So (mm ² ) and the driving density Eo (lines / 50 cm) of the steel cord of the belt layer disposed on the radially outer side, and the belt layer disposed on the radially inner side The product SiEi of the wire cross-sectional area Si (mm ² ) of the steel cord and the driving density Ei (lines / 50 cm) is
SoEo <SiEi
The pneumatic radial tire according to (1) above, characterized in that:

(3) The product SoEo of the wire cross-sectional area So (mm ² ) and the driving density Eo (lines / 50 cm) of the steel cord of the belt layer disposed on the radially outer side, and the belt layer disposed on the radially inner side The product SiEi of the wire cross-sectional area Si (mm ² ) of the steel cord and the driving density Ei (lines / 50 cm) is
0.75 × SiEi <SoEo <0.95 × SiEi
The pneumatic radial tire according to the above (1) or (2), characterized in that:

(4) The cord diameter Do of the steel cord of the belt layer disposed on the radially outer side and the cord diameter Di of the steel cord of the belt layer disposed on the radially inner side,
0.5 × Di ≦ Do ≦ 0.8 × Di
The pneumatic radial tire according to any one of the above (1) to (3), characterized in that:

(5) The thickness To of the belt layer disposed on the radially outer side and the thickness Ti of the belt layer disposed on the radially inner side are:
0.4 × Ti ≦ To ≦ 0.9 × Ti
The pneumatic radial tire according to (4) above, characterized in that:

(6) The pneumatic radial tire according to any one of (1) to (5), wherein the steel cord constituting the belt layer disposed on the radially outer side is a monofilament cord.

(7) The pneumatic cord according to any one of (1) to (6) above, wherein the steel cord constituting the belt layer disposed on the radially outer side has a tensile breaking strength of 3500 to 4200 MPa. Radial tire.

  According to the first aspect of the present invention, in a pneumatic radial tire having a two-layered belt layer structure, the structure of the two belt layers is made special so that excellent belt edge separation resistance is achieved. It is possible to provide a pneumatic radial tire that achieves both the maintenance of the tire and the reduction in tire rolling resistance.

  According to the pneumatic radial tire of the present invention concerning any one of claims 2-7, while having the effect of the pneumatic radial tire of the present invention concerning claim 1 mentioned above, it has the effect more certainly and greatly. A pneumatic radial tire can be provided.

FIG. 1 is a tire meridian cross-sectional view illustrating a pneumatic radial tire according to the present invention. FIG. 2 is a tire meridian cross-sectional view illustrating an enlarged main portion of the tire meridian cross section shown in FIG. 1 in order to explain the pneumatic radial tire according to the present invention.

  Hereinafter, the present invention will be described in more detail.

  The pneumatic radial tire of the present invention has a belt layer in which a plurality of steel cords are aligned and embedded in rubber so that the steel cords intersect each other at an angle of 15 to 45 degrees with respect to the tire equatorial plane. In a pneumatic radial tire having a belt layer structure formed by laminating layers, the diameter Do of the steel cord constituting the belt layer disposed on the radially outer side is set to be equal to that of the steel cord constituting the belt layer disposed on the radially inner side. It is characterized by being thinner than the diameter Di.

  1 and 2 are tire meridian cross-sectional views illustrating a pneumatic radial tire T according to the present invention, respectively, and FIG. 2 is an enlarged view of a main part of the tire meridian cross section shown in FIG. is there.

  1 and 2, a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 made of an organic fiber cord is provided inside the tire so as to extend from the tread portion 1 to the left and right sidewall portions 2 and the bead portion 3, and both ends of the tire extend around the bead core 5 from the inside to the outside of the tire Wrapped. On the outer periphery of the carcass layer 4, there is provided a belt layer 6 made of two steel cords (a belt layer on the inner side in the tire radial direction is 6i, and a belt layer on the outer side in the tire radial direction is 6o). On the outer side in the tire radial direction of 6i and 6o, a belt cover layer 7 in which an organic fiber cord is wound in the tire circumferential direction is provided so as to cover both left and right edge portions of both belt layers. The belt layer 6 is formed by aligning a plurality of steel cords and embedding them in rubber. The two belt layers 6i and 6o are disposed at an angle of 15 to 45 degrees with respect to the tire equatorial plane. It has a belt layer structure that is laminated so as to intersect with each other.

  Therefore, what exhibits a belt layer structure of three or more layers is not included in the present invention.

  As shown in the enlarged portion of FIG. 2, the pneumatic radial tire T of the present invention has a belt layer in which the diameter Do of the steel cord constituting the belt layer 6o disposed on the radially outer side is disposed on the radially inner side. The diameter is smaller than the diameter Di of the steel cord constituting 6i.

  In the present invention, the deterioration of rolling resistance is suppressed by arranging the thin cord on the outer side in the tire radial direction in this way. The reason for this is that by arranging a thin cord on the outer side in the tire radial direction, the outer belt layer 6o can be made thinner than the inner belt layer 6i, thereby reducing the bending deformation resistance of the tread. It is considered. On the tread surface, the outer belt layer 6o undergoes a compressive deformation relative to the inner belt layer 6i in the circumferential direction. It is considered that rubber that is subjected to a compressive action (hydraulic) usually has a positive effect because it can be made thinner and less.

  On the other hand, if a thick cord having the same diameter is used for both the outer belt layer 6o and the inner belt layer 6i, the cord interval in the belt layer 6 can be ensured and the separation resistance is excellent. Resistance gets worse. If thin cords having the same diameter are used for both the outer belt layer 6o and the inner belt layer 6i, it is generally not possible to secure a cord interval in the belt layer, and the belt edge separation resistance is inferior. .

  In the present invention, it is important that the diameter Do of the steel cord constituting the belt layer 6o disposed on the radially outer side is thinner than the diameter Di of the steel cord constituting the belt layer 6i disposed on the radially inner side. The diameter Do and the diameter Di preferably satisfy the relationship of 0.5Di ≦ Do ≦ 0.8Di, and more preferably satisfy the relationship of 0.52Di ≦ Do ≦ 0.75Di. Further, the diameter Di of the steel cord constituting the belt layer 6i arranged on the radially inner side is preferably 0.60 to 0.90 mm, and the steel cord constituting the belt layer 6o arranged on the radially outer side The diameter Do is preferably 0.32 to 0.70 mm.

In the pneumatic radial tire of the present invention, preferably, the wire cross-sectional area So (mm ² ) of the steel cord of the belt layer disposed on the radially outer side, the product SoEo of the driving density Eo (lines / 50 cm), and the diameter The product SiEi of the wire cross-sectional area Si (mm ² ) and the driving density Ei (lines / 50 cm) of the steel cord of the belt layer arranged on the inner side in the direction,
SoEo <SiEi
It is preferable that the relationship is This is because, by satisfying this relationship, the amount of steel wire in the outer belt layer is reduced and the cord interval is widened, whereby the belt edge separation resistance is further improved.

More preferably,
0.75 × SiEi <SoEo <0.95 × SiEi
If this relationship is satisfied, belt edge separation resistance and rolling resistance can be obtained with a good balance.

In the invention, it is practical that the thickness of each belt layer corresponds to the cord diameters Do and Di of the steel cords used in each belt layer. However, as described above, the belt disposed radially inward. The cord diameter Di of the steel cord of the layer is
0.5 × Di ≦ Do ≦ 0.8 × Di
Therefore, since the thickness of each belt layer is preferably the thickness To of the belt layer disposed on the radially outer side and the thickness Ti of the belt layer disposed on the radially inner side,
0.4 × Ti ≦ To ≦ 0.9 × Ti
It is preferable that the relationship is

  This is because, as described above, if the belt layer can be thinned, the bending deformation resistance of the tread surface is thereby reduced.

  Further, the steel cord constituting the belt layer disposed on the outer side in the radial direction is preferably a monofilament cord because energy loss due to friction between the strands in the cord is eliminated, so that the rolling resistance can be further reduced. .

  Furthermore, it is preferable that the steel cord constituting the belt layer disposed on the radially outer side has a tensile breaking strength within a range of 3500 to 4200 MPa. By being in this range, it is possible to obtain a further effect of improving belt edge separation resistance without deteriorating belt folding durability.

  Hereinafter, specific configurations and effects of the pneumatic radial tire of the present invention will be described with reference to examples and the like.

  205 / 55R16 was used as a test tire, and eight tires were produced and evaluated for each example and each comparative example.

  The cord specifications of the belt layer of each pneumatic radial tire of each example, each conventional example, and each comparative example are as shown in Table 1 and Table 2, and for each test tire, the rolling resistance index, the belt resistance Edge separation and belt folding durability were evaluated. Specifically, the belt edge separation resistance was tested and evaluated in the following (2) and (3). “(Severe condition)” means a forced test under very severe conditions.

The test / evaluation method is as follows.
The steel cord diameter was measured according to JIS G3510.
The thickness of the belt layer (after tire vulcanization molding) is measured for each of the two belt layers before vulcanization molding, and the thickness of the belt layer after vulcanization molding is measured for each layer. The thickness of each layer (after tire vulcanization molding) was estimated and obtained according to the ratio of the thickness of the tire.

(1) Rolling resistance index (RRC index)
A test tire incorporated in a rim having a rim size of 16 × 6.5 JJ at a test internal pressure of 200 kPa is used in a drum tester having a smooth drum surface made of steel and having a diameter of 1707 mm, and the maximum in the air pressure described in JATMA YEAR BOOK 2009 edition The rolling resistance was measured when the vehicle was run at a speed of 80 km / hr with a load corresponding to 85% of the load applied and pressed against the drum.

  The evaluation results are shown as an index with the reciprocal of the measured value of the conventional tire 1 (conventional example 1) being 100. It means that rolling resistance is so small that this index value is large. An index value of 96 or more is an acceptable range.

(2) Durability of belt edge separation After holding a test tire in which oxygen is sealed in a rim having a rim size of 16 × 6.5JJ at an internal pressure of 240 kPa in a chamber maintained at a room temperature of 60 ° C. for 2 weeks, the internal oxygen is released and air is released. At 160 kPa. The test tire pretreated in this way is made of steel with a smooth drum surface and a drum tester having a diameter of 1707 mm, the ambient temperature is controlled to 38 ± 3 ° C., the running speed is 50 km / hr, and the slip angle. Under a fluctuation condition of 0 ± 3 ° and a load of 70% ± 40% of the maximum load described in JATMA YEAR BOOK 2009 edition, the load and slip angle were fluctuated with a rectangular wave of 0.083 Hz, and the vehicle was run for 5000 km for 100 hours. After running, the tire was incised, and the presence or absence of a peeling portion having a separation length of 5 mm or more in the width direction at the end in the belt width direction was confirmed. If there is no belt peeling, it means that the belt edge separation durability is excellent. The evaluation results are shown in two stages, an example in which a peeled part having a length of 5 mm or more exists is “x (failed)”, and an example in which a peeled part having a length of 5 mm or more is not present is indicated by “◯ (passed)”. It was.

(3) Belt edge separation durability (harsh conditions)
A test tire in which oxygen is sealed in a rim having a rim size of 16 × 6.5 JJ at an internal pressure of 240 kPa is held for two weeks in a chamber maintained at a room temperature of 60 ° C., then the internal oxygen is released and air is filled at 160 kPa. The test tire pretreated in this way is made of steel with a smooth drum surface and a drum tester having a diameter of 1707 mm, the ambient temperature is controlled to 38 ± 3 ° C., the running speed is 50 km / hr, and the slip angle. Under a fluctuation condition of 0 ± 4 ° and a load of 70% ± 50% of the maximum load described in JATMA YEAR BOOK 2009 edition, the load and the slip angle were fluctuated with a rectangular wave of 0.083 Hz, and the vehicle was run for 5000 km for 100 hours. After running, the tire was incised, and the presence or absence of a peeling portion having a separation length of 5 mm or more in the width direction at the end in the belt width direction was confirmed. If there is no belt peeling, it means that the belt edge separation durability is excellent. The evaluation results are shown in two stages, an example in which a peeled part having a length of 5 mm or more exists is “x (failed)”, and an example in which a peeled part having a length of 5 mm or more is not present is indicated by “◯ (passed)”. It was.

(4) Belt folding durability (harsh conditions)
Using a drum tester having a smooth drum surface made of steel and a diameter of 1707 mm, the peripheral temperature was controlled at 38 ± 3 ° C., and a test tire incorporated into a rim having a rim size of 16 × 6.5 JJ at a test internal pressure of 160 kPa, Traveling speed 30km / hr, slip angle 0 ± 5 °, load JATMA YEAR BOOK Under the fluctuation condition of 70% ± 40% of the maximum load described in 2009 edition, the load and slip angle are changed with 0.083Hz rectangular wave The vehicle was run for 300 km for 10 hours. After running, the tire was incised and examined for belt cord breakage.

  The evaluation results are shown in two stages, an example in which belt cord breakage occurred “x (failed)”, and an example in which belt cord breakage did not occur was represented by “◯ (passed)”.

Examples 1-7, Conventional Examples 1-2, Comparative Example 1
Each Example 1-7 is a thing of this invention, and Conventional Examples 1-2 is what made the steel cord diameter of each belt layer of the inner side of a tire radial direction, and the outer side of a tire radial direction the same, Example 1 uses a thin cord (diameter 0.65 mm), and Conventional Example 2 uses a thick cord (diameter 0.88 mm).

  In Comparative Example 1, the steel cord diameter of each belt layer on the inner side in the tire radial direction and on the outer side in the tire radial direction is reduced by the belt layer on the inner side in the tire radial direction (0.65 mm), and the belt layer on the outer side in the tire radial direction This is the reverse relationship to the present invention of thickening (0.88 mm).

  The evaluation results of Examples, Conventional Examples 1 and 2, and Comparative Example 1 are as described in Tables 1 and 2.

  As can be seen from Tables 1 and 2, the pneumatic radial tire of the present invention achieves both excellent belt edge separation resistance and reduced tire rolling resistance.

1: Tread part 2: Side wall part 3: Bead part 4: Carcass layer 5: Bead core 6: Belt layer 6i: Belt layer arranged inside in the tire radial direction 6o: Belt layer arranged outside in the tire radial direction 7 Belt cover layer T covering the belt layer: Pneumatic radial tire

Claims (7)

  A belt layer structure in which a plurality of steel cords are aligned and embedded in rubber so that two steel layers are laminated so that each steel cord intersects at an angle of 15 to 45 degrees with respect to the tire equator plane. In the pneumatic radial tire having the above, the diameter Do of the steel cord constituting the belt layer arranged radially outside is made smaller than the diameter Di of the steel cord constituting the belt layer arranged radially inside Pneumatic radial tire characterized by. A product SoEo of the wire cross-sectional area So (mm ² ) and driving density Eo (lines / 50 cm) of the steel cord of the belt layer disposed on the radially outer side, and the steel cord of the belt layer disposed on the radially inner side The product SiEi of the wire cross-sectional area Si (mm ² ) and the implantation density Ei (lines / 50 cm) is
SoEo <SiEi
The pneumatic radial tire according to claim 1, wherein: A product SoEo of the wire cross-sectional area So (mm ² ) and driving density Eo (lines / 50 cm) of the steel cord of the belt layer disposed on the radially outer side, and the steel cord of the belt layer disposed on the radially inner side The product SiEi of the wire cross-sectional area Si (mm ² ) and the implantation density Ei (lines / 50 cm) is
0.75 × SiEi <SoEo <0.95 × SiEi
The pneumatic radial tire according to claim 1 or 2, characterized in that: The cord diameter Do of the steel cord of the belt layer disposed on the radially outer side and the cord diameter Di of the steel cord of the belt layer disposed on the radially inner side,
0.5 × Di ≦ Do ≦ 0.8 × Di
The pneumatic radial tire according to any one of claims 1 to 3, wherein: The thickness To of the belt layer disposed on the radially outer side and the thickness Ti of the belt layer disposed on the radially inner side are:
0.4 × Ti ≦ To ≦ 0.9 × Ti
The pneumatic radial tire according to claim 4, wherein:   The pneumatic radial tire according to any one of claims 1 to 5, wherein the steel cord constituting the belt layer arranged on the radially outer side is a monofilament cord.   The pneumatic radial tire according to any one of claims 1 to 6, wherein the steel cord constituting the belt layer disposed on the radially outer side has a tensile breaking strength of 3500 to 4200 MPa.

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