JP2013107426A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for a heavy load compatibly achieving tire uneven wear resistance and driving stability.SOLUTION: This pneumatic radial tire for heavy load includes one or more belt reinforcing layers, two or more inclined belt layers and a tread in this order at the radial direction outside of a carcass toroidally stretching between a pair of bead portions. The width of a tire width direction of the belt reinforcing layer is 80% or more of a tread width TW, and the width of the tire width direction of at least one layer of the inclined belt layers is larger than the widths of the tire width direction of all the belt reinforcing layers. The tire includes two or more sipes extending in a tire peripheral direction at the radial direction inside of a tread end and at the radial direction outside of the inclined belt layer at the radial direction outermost side. Each of the sipes closes when the tire is assembled to a specified rim, specified internal pressure is filled and maximum load weight is loaded.

Description

  The present invention relates to a heavy-duty pneumatic radial tire, and more particularly to a heavy-duty pneumatic radial tire that achieves both uneven wear resistance and steering stability.

Conventionally, various devices for improving wear performance have been made in pneumatic radial tires for heavy loads such as truck and bus tires and construction vehicle tires.
In particular, as a technique for improving both wear resistance and uneven wear resistance of a tire, for example, in Patent Document 1, a belt reinforcing layer and an inclined belt layer are arranged in order on the radially outer side of the tire carcass. Tires are described.

According to the above structure, first, the inclined belt layer can increase the in-plane shear rigidity of the tread rubber in the surface composed of the tire circumferential direction and the width direction, thereby improving the wear resistance of the tire.
Along with this, a belt reinforcing layer made of a cord extending in the tire circumferential direction suppresses the tread rubber growth in the radial direction, uniformizing the tread rubber radial growth amount in the tire width direction and preventing uneven wear of the tire. Can be improved.
This structure is effective from the viewpoint of maintaining the shape of the tire and durability against the recent flattening and heavy weight of the tire.

JP 2009-184371

  However, in the tire described in Patent Document 1, the ground contact length of the portion reinforced by the belt reinforcing layer is smaller than that of other portions, and the ground contact area of the tire is reduced, which may reduce steering stability. It was.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a heavy-duty pneumatic radial tire that achieves both uneven wear resistance and steering stability of the tire.

The inventor has intensively studied to solve the above problems.
As a result, the inventor in the heavy load tire provided with the belt reinforcing layer and the inclined belt layer described above, by first widening the width of the belt reinforcing layer and the inclined belt layer in the tire width direction, It has been found that the uneven wear resistance of tires can be further improved over a wide range.

Further, the inventor has found that a tire in which the width of the belt reinforcing layer and the inclined belt layer in the tire width direction is wide has a large amount of wear in the vicinity of the ground contact edge.
The inventor has found that this does not extend the belt reinforcing layer to the corresponding position near the end portion, so that the contact pressure at this position is reduced, so that the tire rotates on the tread rubber while the tire is rolling. It was found that shear deformation in the direction opposite to the direction occurred and caused drag wear.
Therefore, the inventor pays attention to the fact that shear deformation in the same direction as the rotation direction can be applied to the tread rubber to cancel the shear deformation in the opposite direction, so that a plurality of sipes are provided at appropriate positions on the tire. We obtained new knowledge that is effective.

  Furthermore, the inventor suppresses an excessive decrease in rigidity in the vicinity of the end portion in the width direction of the tire and suppresses a decrease in steering stability of the tire by making the above sipe closed when the tire is loaded. I also found that I can do it.

This invention is based on said knowledge, The summary structure is as follows.
(1) A heavy-duty pneumatic radial tire comprising one or more belt reinforcing layers, two or more inclined belt layers, and a tread in order on the radially outer side of the carcass straddling a toroidal shape between a pair of bead portions. And
The width in the tire width direction of at least one layer of the belt reinforcing layer is 80% or more of the tread width TW,
The width in the tire width direction of at least one of the inclined belt layers is greater than the width in the tire width direction than any belt reinforcing layer of the two or more belt reinforcing layers,
The tire includes two or more sipes extending in the tire circumferential direction at the sidewall portion, radially inward from the tread end and radially outward from the radially innermost inclined belt layer,
Each of the two or more sipes is a heavy-duty pneumatic radial tire characterized in that the tire is incorporated in a prescribed rim, filled with a prescribed internal pressure, and closed when a maximum load is applied.
Here, the “specified rim” is a standard rim (or “Approved Rim” or “Recommended Rim”) in the applicable size described in the specified industrial standard, and the specified internal pressure is described in the standard. It is the air pressure corresponding to the maximum load (maximum load capacity) of a single wheel at a certain application size.
The maximum load is the maximum load (maximum load capacity) of a single wheel at the applicable size described in the standard.
For such industrial standards, there are standards that are valid in each region where tires are produced or used. For example, in the United States, “The Tire and Rim Association Inc. Year Book” (including design guides) ) In Europe according to the “The European Tire and Rim Technical Organization Standards Manual” and in Japan according to the “JATMA YEAR BOOK” of the Japan Automobile Tire Association.

(2) The heavy-duty pneumatic radial tire according to (1), wherein the sum of the cross-sectional areas of the two or more sipes is 20 mm ² or more in an arbitrary cross-section in the width direction on the tire circumference.

  (3) The heavy-duty pneumatic radial tire according to (1) or (2), wherein each of the two or more sipes has an opening width of 3 mm or less.

  (4) Each of the two or more sipes has an opening width of 1.5 mm or more and 3 mm or less, and a depth of 1.5 mm or more and 3 mm or less, according to any one of the above (1) to (3) Pneumatic radial tire for heavy loads.

  (5) The heavy-duty pneumatic radial tire according to any one of (1) to (4), wherein at least one of the sipes is positioned within 3 mm radially inward from a tread end.

  According to the present invention, it is possible to provide a heavy-duty pneumatic radial tire that achieves both unbalanced wear resistance and steering stability of the tire.

1 is a schematic cross-sectional view in the width direction of a tire according to an embodiment of the present invention. It is a width direction fragmentary sectional view of the tire concerning one embodiment of the present invention. It is a width direction fragmentary sectional view of the tire concerning other embodiments of the present invention. It is a width direction fragmentary sectional view of the tire concerning another embodiment of the present invention. It is a width direction fragmentary sectional view of the tire concerning a comparative example. It is a width direction fragmentary sectional view of the tire concerning a comparative example. It is a width direction fragmentary sectional view of the tire concerning a prior art example.

Hereinafter, the heavy-duty pneumatic tire of the present invention (hereinafter referred to as a tire) will be described in detail.
FIG. 1 is a cross-sectional view in the width direction of a tire according to the present invention, and schematically shows only a half portion having a tire equatorial plane CL as a boundary. FIG. 2 is a partial cross-sectional view in the width direction showing a state near the tread end TE of the tire shown in FIG.
FIGS. 1 and 2 show the state of the tire when the tire is assembled in a specified rim, filled with a specified internal pressure, and brought into a no-load state.
As shown in FIG. 1, the tire of the present invention, according to the conventional practice, has one or more belt reinforcing layers 3 and 2 on the radially outer side of the carcass 2 straddling a pair of bead portions (bead core 1 in the illustrated example) in a toroidal shape. An inclined belt 4 composed of layers or more and a tread 5 are sequentially provided.
In the illustrated example, the belt reinforcing layer 3 includes two layers of belt reinforcing layers 3a and 3b, and each layer includes a cord extending at an angle of 0 ° to 30 ° with respect to the tire circumferential direction. For example, a non-extensible steel cord can be used as the cord. Further, the cord may be linear, or may be a detoured cord such as a cord that has been wave-shaped (hereinafter referred to as a corrugated cord).
Further, in the illustrated example, the inclined belt 4 includes two layers of inclined belt layers 4a and 4b, and includes a cord that intersects between the layers. For example, the cord of the inclined belt is inclined at an angle of 40 ° to 70 ° with respect to the tire circumferential direction and extends linearly.
In the illustrated example, the inclined belt layer 4a extends in the radial direction with almost no displacement.

Here, in the tire of the present invention, the width in the tire width direction of at least one layer of the belt reinforcing layer 3 is 80% or more of the tread width TW.
In the inclined belt layer 4, the width in the tire width direction of at least one belt layer is larger than the width in the tire width direction of any layer of the belt reinforcing layer 3. In the illustrated example, the width of the inclined belt layer 4a in the tire width direction is larger than the width of any of the belt reinforcing layers 3 in the tire width direction.

Further, the tire shown in FIGS. 1 and 2 is provided with three narrow groove-shaped sipes 6 extending in the tire circumferential direction on the radially inner side from the tread end TE and on the radially outer side from the inclined belt layer 4a. In the illustrated example, the sipe 6 has a semi-elliptical shape in the cross section in the width direction.
Thus, in the tire of the present invention, it is important to include two or more sipes extending in the tire circumferential direction on the radially inner side from the tread end and on the radially outer side of the radially outermost inclined belt layer. It is.
In addition, it is important that each of the two or more sipes is closed when the tire is incorporated in a specified rim, filled with a specified internal pressure, and a maximum load is applied.
Hereinafter, the function and effect of the present invention will be described.

According to the present invention, the width of the belt reinforcing layer in the tire width direction is equal to or greater than 80% of the tread width TW so that the contact pressure on the tread tread is made uniform over a wide range in the tire width direction. Can do. For this reason, the uneven wear resistance of the tire can be improved.
In the tire of the present invention, since the width in the tire width direction of at least one belt layer among the inclined belt layers is larger than the width in the tire width direction of any layer of the circumferential belt layer, the in-plane shear rigidity described above. Can be increased in a wide range in the width direction, and the wear resistance of the tire can be improved.

  Further, the tire of the present invention includes two or more sipes extending in the tire circumferential direction on the radially inner side from the tread end and radially outer side of the radially innermost inclined belt layer. On the outer side in the width direction from the end of the belt layer, the deformation of the tread rubber being crushed in the radial direction is increased. Thereby, deformation of the tread rubber in the tire circumferential direction increases due to the incompressibility of the rubber, and shear deformation in the tire rotation direction increases. As a result, the shear deformation in the direction opposite to the tire rotation direction due to the drag wear described above is offset, and the decrease in contact pressure outside the end of the maximum width inclined belt layer is suppressed, thereby improving the uneven wear resistance of the tire. Can be made.

Here, each sipe is built into the specified rim, filled with the specified internal pressure, closed when the maximum load is applied, that is, the sipe walls are in contact with each other. Excessive deformation of the tread rubber can be suppressed, and a decrease in the steering stability of the tire can be suppressed.
This is particularly effective against a large deformation of the tread rubber when the vehicle turns when a large lateral force is generated.

The above sipe preferably has a total cross-sectional area of two or more sipes of 20 mm ² or more in an arbitrary cross section on the tire circumference.
This is because by setting the thickness to 20 mm ² or more, the effect of increasing the deformation of the above-described tread rubber being crushed in the radial direction can be exhibited.
Further, in order to secure a wear volume at the shoulder end, it is preferably 80 mm ² or less.
Each sipe does not have to be continuous over the entire circumference of the tire and may have discontinuous portions.

Further, each of the above sipes preferably has an opening width of 1.5 mm or more and 3 mm or less. This is because the effect of increasing the deformation of the above-mentioned tread rubber being crushed in the radial direction can be further exerted by setting it to 1.5 mm or more. It is because it becomes easy to be surely obstruct | occluded when it is filled and a maximum load is applied.
The depth of each sipe is preferably 1.5 mm or more and 3 mm or less. This is because the effect of increasing the deformation of the above-mentioned tread rubber being crushed in the radial direction can be further exerted by setting it to 1.5 mm or more. It is because it becomes easy to be surely obstruct | occluded when it is filled and a maximum load is applied.

Moreover, it is preferable that at least one of the above sipes is located within 10 mm in the radial direction from the tread end. This is because by positioning the sipe at a position close to the tread end, the above-described effect of appropriately reducing the rigidity in the vicinity of the tread end is ensured.
Here, “positioned” means that at least one sipe as a whole is located within 10 mm radially inward from the tread end.
The shape of the sipe may be gradually reduced toward the bottom of the sipe, but may be a so-called bag shape in which the width at the bottom is wider than the width at the opening.
Moreover, in order to prevent generation | occurrence | production of the crack in the bottom part of a sipe, it is preferable to make the bottom part of a sipe into a shape which has a curvature without having a corner | angular part. For example, the sipe can have a semi-elliptical narrow groove shape with a curved bottom portion, a cross-sectional flask shape, or the like.

Incidentally, in the tire of the present invention, the width in the tire width direction of at least one layer of the belt reinforcing layer 3 is preferably 70% or more, more preferably 75% or more and 90% or less of the tire width.
This is because the contact pressure on the tread surface can be made uniform over a wide range in the tire width direction by setting it to 70% or more, and the uneven wear resistance of the tire can be improved. Moreover, this effect can be exhibited more by setting it as 75% or more.
On the other hand, by setting it to 90% or less, durability can be secured.
Here, when the width of the belt reinforcing layer is 70% or more, a large interlaminar shear strain is generated at the end of the belt reinforcing layer during loading. In this case, in order to prevent separation starting from the belt end, it is preferable to provide an interlayer distance of 3 mm or more between the end of the belt reinforcing layer and the adjacent inclined belt layer 4a.
Further, as shown in FIG. 2, it is preferable to dispose an interlayer rubber 7 softer than the coating rubber of the belt reinforcing layer 3b between the end of the belt reinforcing layer 3b and the end of the inclined belt layer 4a.
The modulus of the interlayer rubber 7 (modulus at 100% elongation) is preferably 5 MPa or less. The modulus at 100% elongation is a value calculated by measuring the dynamic stress when dynamic strain is applied under the specified temperature, frequency, and strain conditions in accordance with JISK6251 (FY2004). is there.

Here, the inclined belt layer 4a adjacent to the belt reinforcing layer 3b preferably has a width in the tire width direction of 5 mm or more and more preferably 10 mm or more larger than the belt reinforcing layer 3b. This is because the in-plane shear rigidity can be increased over a wide range in the width direction to improve the wear resistance of the tire.
Furthermore, the end of the inclined belt layer 4b disposed on the radially outer side of the inclined belt layer 4a is preferably 5 mm or more inward in the width direction and more than 10 mm inward in the width direction from the end of the inclined belt layer 4a. Is more preferable. It is because durability is easy to ensure, so that a belt end is a width direction inner side.
On the other hand, the end of the inclined belt layer 4b is preferably 30 mm or less on the inner side in the width direction from the end of the inclined belt layer 4a. This is to ensure uneven wear resistance of the tire.
In order to enhance the above-described in-plane shear rigidity, the inclined belt layers preferably cross each other. Further, the inclined belt layer is preferably made of a cord that extends at an angle of 40 ° or more with respect to the tire circumferential direction, and more preferably, the cord extends at an angle of 50 ° or more. This is because by setting the angle to 40 ° or more, shear strain between the belt reinforcing layer and the tire can be prevented from being prematurely broken. By setting the angle to 50 ° or more, this effect can be obtained.
On the other hand, in order to ensure the cord foldability due to the compressive strain, the inclination angle of the inclined belt layer with respect to the circumferential direction of the cord is preferably set to 70 ° or less.

  Further, as shown in FIG. 2, in order to prevent the end of the inclined belt layer 4a from falling inward in the radial direction and to ensure the desired shape of the product tire, it is preferable to dispose the cushion rubber 8. . The cushion rubber 8 is preferably disposed in the radially inner side of the end portion of the inclined belt layer 4a and in a region adjacent to the end portions of the belt reinforcing layers 3a and 3b. As the cushion rubber, rubber having a modulus at the time of 100% elongation of 1.5 to 6.5 MPa can be used.

In order to confirm the effect of the present invention, the inventive tires 1 to 5 according to the present invention and the tires 1 to 3 according to the comparative example were made on a trial basis. Conventional tires were also prepared.
Inventive tires 1 to 5, as shown in Tables 1 and 2, have two layers of belt reinforcement layers and two layers of inclined belts having an appropriate width in the width direction according to the present invention, and further according to the present invention. Has a continuous sipe on top.
Further, the tire according to Comparative Example 1 does not include a sipe, and the width in the width direction of the circumferential belt layer and the inclined belt layer is different from that of the inventive tire.
Furthermore, the tires according to Comparative Examples 2 and 3 are different from the tires according to the inventions in that each of the tires according to Comparative Examples 2 and 3 has a recess 9 having a substantially semicircular cross section shown in FIG.
In addition, the conventional tire does not include sipes, and the width in the width direction of the circumferential belt layer and the inclined belt layer is significantly different from that of the invention example and the comparative example tire.
The specifications of each tire are shown in Tables 1 and 2.

Here, in Table 1, “angle” is an inclination angle with respect to the tire circumferential direction, and the two inclined belt layers 4a and 4b intersect each other. “Width” is the width in the tire width direction. The “ratio” represents the ratio of the width in the width direction of the belt reinforcing layer to the tread width in percentage.
Further, “3b-4a” is an interlayer distance (mm) between the belt reinforcing layer 3b and the inclined belt layer 4a, and “4a-4b” is an interval (mm) between the inclined belt layers.
Further, “the thickness at the end of 3b” is the thickness (mm) of the interlayer rubber at the end of the belt reinforcing layer 3b. “100% modulus” means the above-described modulus at 100% elongation.

In Table 2, “sipe” means having a sipe on the tire outer surface radially inward from the tread end and radially outward from the inclined belt layer 4a. Similarly, the “concave portion” means having a concave portion on the tire outer surface radially inward from the tread end and radially outward from the inclined belt layer 4a.
Here, “thin groove shape” means that the sipe is a narrow groove shape having a semi-elliptical cross section, and “flask shape” means that the sipe is a flask shape in the cross section in the width direction. The “semicircular shape” means that the concave portion has a semicircular shape in the cross section in the width direction.
Further, “N / A” indicates that each tire does not have a sipe or a recess, and therefore does not fall under the applicable item.
“Area” is the cross-sectional area in the width direction, and the cross-sectional area of sipe is the sum of the cross-sectional areas of a plurality of sipes. The “depth from the tire surface” is the depth from the tire surface (opening) to the bottom of the sipe or recess, and the “opening width” means the width of the opening of the sipe or recess.
In addition, all the sipes of the invention examples are located within 10 mm in the radial direction from the tread end. Further, the concave portion of the comparative example is also located within 10 mm radially inward from the tread end (the entire concave portion is located within 10 mm radially inward from the tread end).

In order to evaluate the performance of each of the above tires, each tire of tire size 495 / 45R22.5 was incorporated into a rim of rim size 17.00 × 22.5, the internal pressure was set to 900 kPa, the maximum load (56.9 kN) was applied, and the following tests were performed. It was.
《Uneven wear resistance》
The drum was run at a speed of 60 km / h, and the amount of wear at the end of the tread after a certain time was measured.
The test results are shown in Table 2. In Table 2, the test results are expressed as an index with the conventional example being 100, and the larger the numerical value, the smaller the amount of wear and the better the uneven wear resistance.
《Steering stability》
A slalom run was performed at 60km / h, and the driver's sensitivity was evaluated. The evaluation was performed with a maximum score of 5 and the results in Table 2 are shown. The numerical value indicates that the larger one is more sensitive and has better handling stability.

As shown in Table 3, it can be seen that the tires according to Invention Examples 1 to 5 are more excellent in uneven wear resistance than the tire according to the conventional example.
While the tires according to Comparative Examples 2 and 3 have lower steering stability than the tires according to the conventional examples, the tires according to Invention Examples 1 to 5 maintain the same steering stability as the conventional tires. .
In addition, the tires according to Invention Examples 1 to 5 are significantly superior in uneven wear resistance than the tire according to Comparative Example 1.

1 Bead core
2 Carcass
3 Belt reinforcement layer
4 Inclined belt layer
5 tread
6 Sipe
7 Interlayer rubber
8 Cushion rubber
9 Recess

Claims (5)

A heavy-duty pneumatic radial tire comprising one or more belt reinforcing layers, two or more inclined belt layers, and a tread in order on the radially outer side of the carcass straddling a toroidal shape between a pair of bead parts,
The width in the tire width direction of at least one layer of the belt reinforcing layer is 80% or more of the tread width TW,
The width in the tire width direction of at least one of the inclined belt layers is greater than the width in the tire width direction than any belt reinforcing layer of the two or more belt reinforcing layers,
The tire includes two or more sipes extending in the tire circumferential direction at the sidewall portion, radially inward from the tread end and radially outward from the radially innermost inclined belt layer,
Each of the two or more sipes is a heavy-duty pneumatic radial tire characterized in that the tire is incorporated in a prescribed rim, filled with a prescribed internal pressure, and closed when a maximum load is applied. 2. The heavy-duty pneumatic radial tire according to claim 1, wherein the sum of the cross-sectional areas of the two or more sipes is 20 mm ² or more in an arbitrary cross-section in the width direction on the tire circumference.   3. The heavy-duty pneumatic radial tire according to claim 1, wherein each of the two or more sipes has an opening width of 3 mm or less.   The heavy radial pneumatic radial according to any one of claims 1 to 3, wherein each of the two or more sipes has an opening width of 1.5 mm or more and 3 mm or less and a depth of 1.5 mm or more and 3 mm or less. tire.   5. The heavy-duty pneumatic radial tire according to any one of claims 1 to 4, wherein at least one of the sipes is located within 3 mm radially inward from a tread end.

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