JPH07144513A - Pneumatic tire for off-road travel - Google Patents

Abstract

PURPOSE:To improve the cutting resistance of a side wall part and suppress the increase of weight by disposing a protecting layer with a reinforcing rubber layer of specified hardness interposed in the specified position of the side wall part, and forming this protecting layer of a specified reinforcing ply. CONSTITUTION:A side wall part 3 is provided with a protecting layer 10 with a reinforcing rubber layer 9 interposed on the outside in the tire radial direction of a carcass 6 from a buttress part 8 on the outside in the radial direction to a position going radially inward over the maximum width position 13 of the maximum width W of the side wall part 3. This protecting layer 10 is formed of at least one reinforcing ply 11 with organic fiber cords inclined by 45-75 deg. to the circumferential direction of a tire 1. The reinforcing rubber layer 9 has a JISA hardness of 56-63 deg. and has a thickness 0,24-0.55 times as thick as the thickness of side wall rubber in the maximum width position 13. The weight increase of the tire can be thereby suppressed while improving the cutting-through resistance of the side wall part 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for traveling on rough terrain, which can improve the cut penetration resistance of a sidewall portion and suppress an increase in tire weight.

[0002]

2. Description of the Related Art In recent years, due to diversification of leisure and the like, demand for RV vehicles capable of actively driving over rough terrain such as off-road is increasing.
Sharp rocks, stones, etc. that rise up from the road surface are prone to damage such as cuts from the buttress portion to the sidewall portion.

In order to solve such a problem, the applicant of the present invention has proposed a pneumatic tire disclosed in Japanese Patent Laid-Open No. 4-163215.

As shown in FIG. 4, this pneumatic tire is provided with a protective layer C made of a reinforcing ply along the side wall portion A and outside the carcass B at a predetermined angle, and has a cut penetration resistance. It is a heightened one.

[0005]

However, in such a conventional configuration, when the cut is deep enough to penetrate the protective layer C, the cut causes the protective layer C to be repeatedly deformed by repeated deformation of the tire.
Since the inside of the coating rubber D located at the inside of the rubber grows relatively early to reach the carcass B, the cut penetration resistance is somewhat increased, but the effect is not sufficient.

It is also conceivable that the thickness of the coating rubber D between the carcass B and the protective layer C is increased to delay the growth of the cut, but such a method significantly increases the weight of the tire and reduces the fuel consumption of the vehicle. make worse.

The present invention has been devised in view of the above problems, and provides a pneumatic tire for traveling on rough terrain, which can suppress the increase in tire weight while improving the cut resistance of the sidewall portion. The purpose is to do.

[0008]

The present invention is directed to a carcass which is folded from the inside of the tire to the outside around the bead core of the bead part, passing through the sidewall part from the tread part, and inside the tread part and outside the carcass. A pneumatic tire for running on rough terrain having a belt layer arranged, wherein the sidewall portion has a maximum width position of the sidewall portion extending radially inward from a buttress portion radially outward of the sidewall portion. A protective layer extending outside the carcass in the axial direction of the tire and having a reinforcing rubber layer interposed between the carcass, and the protective layer includes a cord made of an organic fiber. The reinforcing rubber layer comprises at least one reinforcing ply inclined at an angle of 45 degrees or more and 75 degrees or less with respect to the circumferential direction, and the reinforcing rubber layer has a JIS A hardness of 56 ° to 63 °, The thickness is 0.25 to 0.55 times the thickness of the sidewall rubber at the maximum width position of the sidewall portion.
It is a pneumatic tire for running on rough terrain, which is doubled in length.

[0009]

According to the present invention, even if the cut is deep enough to penetrate the protective layer, there is a JISA between the protective layer and the carcass.
Since a reinforcing rubber layer with a hardness of 56 ° to 63 ° is interposed, the separation between the protective layer and the carcass due to the difference in rigidity can be prevented, and the cut can be prevented from growing to the carcass early and the cut resistance can be improved. Can be improved.

Further, the thickness of the reinforcing rubber layer is set to 0.2 of the thickness of the sidewall rubber at the maximum width position of the sidewall portion.
5 times to 0.55 times, that is, when the thickness of the sidewall rubber at the maximum width position of the sidewall portion is 2 to 4 mm, the thickness of the reinforcing rubber layer is regulated to 0.5 to 2.2 mm. As a result, it is possible to reduce the wall thickness, suppress a significant increase in tire weight, and reduce fuel consumption of the vehicle.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a pneumatic tire 1 for traveling on rough terrain
Is a carcass 6 which is folded from the inside of the tire to the outside around the bead core 5 of the bead portion 4 passing from the tread portion 2 to the sidewall portion 3, and the belt layer 7 and the protective layer 10 arranged outside the carcass 6. Composed of and.

The carcass 6 exemplifies a carcass cord having a radial structure in which the carcass cords are arranged at an angle of 90 degrees with respect to the tire equator. A bead apex which is made of hard rubber and stands radially outward from the bead core 5 is provided between the body portion 6A of the carcass 6 and the folded portions 6B at both ends to reinforce the bead portion 4.

The belt layer 7 is provided inside the tread portion 2 and outside the carcass 6, that is, in the present embodiment, a two-layer belt ply 1.
2 and 13 are arranged to reinforce the tread portion 2.

In the tread portion 2, a tread rubber 14 is arranged outside the belt layer 7. In this embodiment, the tread rubber is made of a relatively hard rubber having a hardness of 60 to 66 ° of JISA hardness.

The protective layer 10 has a sidewall portion 3
Further, a reinforcing rubber layer is provided on the tire axially outer side of the carcass 6 from the buttress portion 8 outwardly in the radial direction thereof to a position radially inwardly exceeding the maximum width position 13 forming the maximum width W of the sidewall portion 3. 9 are arranged.

The protective layer 10 is composed of at least one reinforcing ply 11 in which an organic fiber cord made of aromatic polyamide, nylon, rayon, polyester or the like is inclined at an angle of 45 degrees or more and 75 degrees or less with respect to the tire circumferential direction. Composed of.

The sidewall portion 3 is provided with a sidewall rubber 15 on the outer side of the protective layer. In this embodiment, the sidewall rubber 3 has a hardness lower than that of the tread rubber 14 of the tread portion 2, more specifically, a JIS A hardness. 53 ° to 59 °
Composed of.

The reinforcing rubber layer 9 has a JIS A hardness of 56.
It is not less than 0 ° and not more than 63 °, and its thickness is 0.25 to 0.55 times the thickness of the sidewall rubber at the maximum width position 13 of the sidewall portion 3. In addition, the sidewall rubber 15 at the maximum width position of the sidewall portion 15
Preferably has a thickness of 2 mm to 4 mm.

[0019]

SPECIFIC EXAMPLE Tires (Examples 1 to 3) having a tire size of 215SR15 and having the structure shown in FIG. 1 were prototyped and their performances were tested. Although the tire having the conventional structure without the protective layer 10 (Comparative Example 1) and the protective layer 10 are provided, the thickness of the reinforcing rubber layer 9 is 0.25 to 0.55 times the thickness of the sidewall rubber. A test was also conducted for those outside the range (Comparative Example 2) to compare the performance.

A) Cut resistance A so-called pendulum type sidewall impact test is conducted. As shown in FIG. 2, the weight 17 is attached with a wedge-shaped blade 16 at the lower end of the pendulum 18, and the sidewall of the tire T is impacted by the free fall method.
This is a test for obtaining and evaluating the breaking energy of the tire sidewall by using 7 and the drop height H. The blade 16
As shown in FIGS. 3 (a) and 3 (b), the blade edge 15A is formed by a flat body having a tapered cross-section with an arc tip. The longitudinal direction of the cutting edge 16A was evaluated parallel to the tire radial direction and parallel to the tire circumferential direction, and the index was set to 100 for Comparative Example 1, respectively.
The larger the value, the better the cut resistance of the sidewall portion.

B) Tire weight The tire weight of Comparative Example 1 is shown as an index with 100 being the weight.
The larger the value is, the heavier the tire weight is.

C) Durability The test prescribed in JIS D4230, Section 5.3 was conducted, and the test result was expressed as an index with Comparative Example 1 being 100. The larger the value, the better.

The test results are shown in Table 1.

[0024]

[Table 1]

As a result of the test, it was confirmed that the tires of Examples have improved cut resistance while suppressing an increase in tire weight, as compared with the tires of Comparative Examples. In addition, in the tire of Comparative Example 2 in which the thickness of the reinforcing rubber layer 9 is more than 0.25 to 0.55 times the thickness of the sidewall rubber, specifically 0.174 times, the cut resistance is improved. However, due to the thinning of the reinforcing rubber layer, separation occurred between the protective layer and the carcass, resulting in a marked decrease in durability.

[0026]

As described above, according to the present invention, an increase in tire weight can be suppressed while improving the cut penetration resistance of the sidewall portion.

[Brief description of drawings]

FIG. 1 is a meridional cross-sectional view of a pneumatic tire for running on uneven terrain according to an embodiment of the present invention.

FIG. 2 is a diagram showing a method for testing cut resistance.

FIG. 3 shows the shape of a blade used in the test method,
(A) is a plan view and (b) is a side view.

FIG. 4 is a cross-sectional view illustrating a conventional technique.

[Explanation of symbols]

 1 Pneumatic tire for running on rough terrain 2 Tread part 3 Sidewall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 8 Buttress part 9 Reinforcement rubber layer 10 Protective layer 11 Reinforcement ply 12 Belt ply 14 Tread rubber 15 Sidewall part

Claims (1)

[Claims] 1. A carcass that is folded back from the inside of the tire to the outside around the bead core of the bead portion, passing through the sidewall portion from the tread portion, and a belt layer disposed inside the tread portion and outside the carcass. A pneumatic tire for running on uneven terrain, ranging from the buttress portion radially outward to the sidewall portion to a position exceeding the maximum width position of this sidewall portion radially inward, of the carcass. A protective layer extending outside in the tire axial direction and having a reinforcing rubber layer interposed between the protective layer and the carcass is arranged, and the protective layer is a cord made of an organic fiber and is 45 degrees or more in the tire circumferential direction. And at least one reinforcing ply inclined at an angle of 75 degrees or less, and the reinforcing rubber layer has a JIS A hardness of 56 ° to 63 °.
The pneumatic tire for running on rough terrain, wherein the thickness is 0.25 to 0.55 times the thickness of the sidewall rubber at the maximum width position of the sidewall portion.