JPH04356203A - Heavy duty type pneumatic radial tire - Google Patents

Abstract

PURPOSE:To ensure durability of the tread portion of a heavy duty type pneumatic radial tire without causing lack of dimensional stability and belt durability by combining the merit of a tire having a first belt coverin the entire tread area with the merit of a tire formed of a split construction excluding the central area of the tread. CONSTITUTION:A reinforcement layer 6 formed by burying a cord in the radial direction from a tread portion 4 to a tire side portion 7 is laid along a carcass ply 1, in the case of tire of a split construction having a carcass ply 1 of one or more layers and a steel belt layer 3 of at least three layers with a first belt 3a counted from the carcass ply 1 in the tread direction, decomposed and arranged on the tread excluding its central area.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to the structure of a heavy-duty pneumatic radial tire used for large vehicles, in particular to a structure that does not cause a lack of dimensional stability or belt durability, and also maintains good durability on rough roads. It's about the tires you get.

0002

[Prior Art] As shown in Fig. 4, a conventional heavy-duty pneumatic radial tire has a bead core (
2) one or more carcass plies (1) wound and locked from the inside to the outside around the carcass ply (1); and a belt layer (3) consisting of a steel cord arranged on the outside of the carcass ply (1) in the tread part. have. This belt layer (3) consists of a first belt (3a) which is closest to the carcass ply (1) and has a large cord angle with respect to the tire circumferential direction, and a first belt (3a) which is laminated on top (outside) and has a cord with a large cord angle with respect to the tire circumferential direction. It is composed of two or three layers of belts (3b) that have a small angle and intersect with each other.

[0003] The first belt layer (
3a) includes a carcass ply (1) that is arranged over almost the entire area of the tread portion (4) and forms an angle direction (radial direction) of about 90° with respect to the tire circumferential direction, and a first belt (3a).
) two- or three-layer belt (3b) placed on top of the
In addition to serving as an interference layer with the belt, it also serves as reinforcement against internal pressure, increasing the rigidity of the entire belt and contributing to dimensional stability.

However, in the case of the above tire structure, due to the high belt rigidity, the ability to follow unevenness such as protrusions on the road surface is poor, and the center of the tread is easily damaged due to stress concentration due to protrusions on the road surface. In some cases, there were drawbacks such as the belt cord breaking inside the tread.

In other words, radial tires with a general structure having high belt rigidity are characterized by little deformation of the belt layer, and as a result, deformation of the tread rubber within the contact patch, internal friction caused by deflection due to load, etc. decreases, so
It has excellent shape retention and improves wear resistance. However, on the other hand, the movement of the belt layer following irregularities such as road surface protrusions is significantly reduced due to the above reasons, so the tread rubber on the belt deforms significantly when running over protrusions under high internal pressure and high load. Therefore, localized stress concentration on the tread rubber tends to occur, making the tread part susceptible to damage.

In order to improve these drawbacks, as shown in FIG. 5, the first belt (3a) of the belt layer (3) is divided into two parts near the shoulder part, excluding the central part of the tread. The belt-structured tire has a split structure that lowers the rigidity of the tread (4), which is susceptible to stress concentration, and makes it more flexible, reducing damage to the central tread area, making it particularly suitable for use on rough roads. It has been used as a subject.

In other words, when the belt rigidity is lowered as in this tire, the movement of the belt layer to follow the unevenness caused by protrusions is improved, and the belt layer can easily follow the unevenness, so that the belt layer and the road surface are This acts in the direction of relieving the pressure on the tread rubber caused by the tread rubber, that is, in the direction of relieving local stress concentration.

However, in the case of this tire structure, due to the split structure of the first belt (3a), the reinforcing effect of the first belt (3a) is reduced, and as a result, the outer periphery of the crown portion deteriorates during use. Growth tends to become large, and this increase in circumferential growth causes instability in the tread shape, resulting in poor shape retention, and has the disadvantage of increasing shear strain at the ends of No. 2 and No. 3 belts. .

[0009]

[Problems to be Solved by the Invention] As explained above, although the tire shown in Fig. 4 has high belt rigidity and the shape of the tread portion is stable, the tread portion has difficulty following changes in the road surface due to the high belt rigidity. However, the tire shown in Fig. 5, in which the first belt has a split structure, has the disadvantage that it is easily damaged by stress concentration due to unevenness of the road surface. On the other hand, there are disadvantages such as a decrease in the reinforcing effect of the belt against internal pressure, which leads to an increase in peripheral growth and makes it difficult to maintain the shape of the tread. It has characteristics that are contradictory to its rough road durability.

Therefore, the present invention combines the characteristics of the above-mentioned tire structures, especially the advantages of both, while ensuring the durability of the tread portion on rough roads, which is an advantage of the belt split structure.
To provide a pneumatic radial tire for heavy loads, which can maintain the shape of a tread part well and improve dimensional stability without causing insufficient belt durability.

[0011]

[Means for Solving the Problems] The present invention provides a tire in which the first belt has a split structure, and a reinforcing layer formed by embedding cords in the radial direction is provided along the carcass ply from the tread part to the tire side part. This arrangement solves the above problem.

That is, the heavy-duty pneumatic radial tire according to the present invention has one or more carcass plies wound around a bead core from the inside to the outside and locked in the bead portion, and a carcass ply wound on the outside of the carcass ply in the tread portion. at least three belt layers arranged;
In a tire with a split structure, in which the first belt in the belt layer counting from the carcass ply in the tread direction is divided and placed on both sides excluding the tread center area, the radial direction is divided from the tread part to the tire side part. It is characterized in that a reinforcing layer made of embedded cords is arranged along the carcass ply.

[0013] In the above, the width of the reinforcing layer is such that its side edge does not reach the bead on the side of the tire from the foot of the perpendicular line drawn down from the edge of the widest belt to the carcass ply. , Particularly preferably, the ratio (h/H) of the height (h) in the tire height direction at the side end position to the tire height (H) at the tire maximum width position is set to be 0.8 or more. This is what is being done. That is, unless the width of this reinforcing layer is made wider than the maximum width of the belt end, a sufficient outer diameter growth suppressing effect cannot be obtained. However, if the width is too wide and the reinforcing layer side end is located near the bead core that moves the most, it may cause a failure, which is not preferable.

[0014]

[Function] In the above-mentioned radial tire of the present invention, the first belt of the belt layer has a split structure in which it is divided except for the central region of the tread, which reduces the belt rigidity of the tread. The belt layer easily deforms following irregularities such as protrusions on the road surface, acts to relieve pressure on the tread rubber, and can relieve local stress concentration.

Moreover, in the case where the first belt has a split structure, a reinforcing layer formed by embedding cords in the radial direction is provided along the carcass ply from the tread part to the tire side part. This reinforcing layer can suppress the outer diameter growth that occurs due to a decrease in the reinforcing action of the tread belt, and maintains the shape of the tread center region. In particular, since the cord embedded in this reinforcing layer runs in the radial direction, the above-mentioned split structure provides belt flexibility and suppresses the growth of the outer diameter without significantly affecting the relaxation of stress concentration. can be accomplished.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a sectional view of a heavy-duty pneumatic radial tire according to an embodiment of the present invention, and FIG. 2 schematically shows the layer structure of a carcass and a belt.

In the figure, (1) is a carcass ply of one or more layers wound around a bead core (2) from the inside to the outside and locked in the bead part, and is mainly made of organic fibers such as polyester, nylon, and polyamide. Consists of cord or steel cord. The figure shows a case where the carcass plies are two layers. (3) is a belt layer made of at least three layers (four layers in the figure) of steel cords disposed outside the carcass ply (1) in the tread portion (4), and among this belt layer (3), No. 1 belt (3a) counting from the carcass ply (1) in the tread direction
The tread has a split structure in which the tread is divided and arranged in both side parts, that is, in the vicinity of the shoulder part (5), except for the central region of the tread. (3b) shows another belt placed outside the first belt (3a).

(6) is a reinforcing layer formed by embedding a cord at an angle of 90° to the tire circumferential direction (radial direction), and as shown in the figure, it extends from the tread part (4) to the tire side part (7). ) along the carcass ply (1). The cord used for this reinforcing layer (6) is made of the same textile cord of organic fibers such as polyester, nylon, and polyamide as the carcass ply (1).
As described above, they are arranged in the radial direction. When the carcass ply (1) has two layers as shown in the figure, this reinforcing layer (6) can be sandwiched between the layers. Of course, they can also be arranged along the inner or outer surface of the carcass ply (1). The same applies to the case where the carcass ply is one layer.

The width of this reinforcing layer (6) is determined from its side edge (6a
) does not reach the bead part of the tire side part (7), and the height (h) in the tire height direction at the side end (6a) position is the tire height at the position where the tire maximum width (W) It is set at a position that is 0.8 times or more of (H).

In addition, since the tire side portion (7) where the end of the reinforcing layer (6) is located has a particularly large amount of deformation due to the rolling of the tire, in order to prevent separation (peeling) of the reinforcing layer (6), As mentioned above, it is preferable to use textile cords made of organic fibers or steel cords with high initial elongation for the reinforcing layer.

Regarding the heavy-duty pneumatic radial tire shown in FIG. 1 according to the embodiment of the present invention described above, the outer diameter growth amount,
The results of measuring the static envelope characteristics are shown in Table 1 below. The tires used in the test had a rim width of 8.25 inches, 11r24.5, 16P.
This is a size R tubeless tire. Table 1 also shows the measurement results for the tires of Examples 1 and 2 and Comparative Examples 1 and 2.

Example 1 is a tire in which the height (h) at the side edge position of the reinforcing layer (6) is 1.5 times the tire height (H) at the tire maximum width (W) position. 2 is the same as 1.
This is a tire that is twice as large. Furthermore, the tire of Comparative Example 1 has a conventional structure in which the first belt is disposed over almost the entire tread portion, and differs from both Examples in this point and in that it does not have a reinforcing layer. The tire of Comparative Example 2 has a split structure in which the first belt is divided, and does not have a reinforcing layer.

[0023]

[Table 1]

*1: Test conditions for outer diameter growth amount/internal pressure 8.
4kg/cm2, load 3189kg, speed 48km/
H - After running for 24 hours at a speed of 48 km/H, the amount of growth in the outer diameter of the tire was measured, and the durability was judged from the dimensional stability. *2: Static envelope characteristics test conditions/internal pressure 7.7
kg/cm2, load 2800kg, protrusion: diameter 16
As a substitute characteristic for measuring the stress concentration of a column with a height of 8 m/m and a tread part, a tire is loaded under specified conditions on a columnar protrusion, and the non-contact area of the tread surface caused by the columnar protrusion is measured. The diameter (average value in the tire circumferential direction and width direction) was measured to determine the static envelope characteristics.

The outer diameter growth amount and the static envelope characteristic are each expressed as an index, with the case of Comparative Example 1, which is a tire with a non-split belt structure, set as 100.

As is clear from Table 1 above, the tire according to the embodiment of the present invention has improved static envelopment properties and has improved static envelopment compared to the tire of Comparative Example 1 in which the first belt extends over the entire tread area. It is almost as good as Comparative Example 2, in which the No. 1 belt has a split structure, and has sufficient rough road durability, and the amount of external growth is reduced compared to Comparative Example 2, which has a simple split structure. As a result, the shape retention of the tread portion can be improved.

FIG. 3 shows the ratio (h/ It is a graph illustrating the relationship between the value of H) and the amount of outer diameter growth. Points A in the figure correspond to the first embodiment described above, and points B correspond to the second embodiment.

As shown in FIG. 3, the ratio (h/H)
The value is the carcass ply (1) from the belt side edge of the maximum width.
If the perpendicular line is larger than the value at the foot position (a), that is, if the width is narrower than the maximum belt width, a sufficient effect of suppressing outer diameter growth cannot be obtained. Also, the above ratio (h/
If the value of H) is less than 0.8(b), there will be little effect of suppressing outer diameter growth, and not only will material be wasted, but also the Because the side edges of the reinforcing layer are located, it is easy to cause failure. Therefore, the ratio (h/H) is 0.8 or more, and the foot position (a
) is preferable.

[0029]

As described above, according to the present invention, as a pneumatic radial tire for heavy loads, a reinforcing layer formed by embedding cords in the radial direction is disposed along the carcass ply from the tread part to the tire side part. This allows the tire to have both the characteristics of a tire with a belt structure where the first belt covers the entire area and a tire with a split structure where the first belt has a split structure except for the central area, and the advantages of the split structure. It is possible to ensure the durability of the tread portion on rough roads, and also to maintain the shape of the tread portion well without causing a decrease in belt durability, and to improve the dimensional stability.

[Brief explanation of drawings]

FIG. 1 is a half sectional view of a tire showing one embodiment of the present invention.

FIG. 2 is a plan view schematically showing the layer structure of the belt, carcass, etc. of the same tire.

[Fig. 3] Graph showing the relationship between the height (h) in the tire height direction at the side end position of the reinforcing layer and the ratio (h/H) of the tire height (H) and the amount of outer diameter growth. It is.

FIG. 4 is a half-sectional view schematically showing a conventional tire in which the first belt has a non-split structure.

FIG. 5 is a half sectional view schematically showing a conventional tire in which the first belt has a split structure.

[Explanation of symbols]

(1) Carcass ply (3) Steel belt layer (3a) No. 1 belt (4) Tread section (6) Reinforcement layer (6a) Side edge of reinforcing layer (7) Tire side part

Claims (2)

[Claims] Claim 1: A carcass ply having one or more layers wound around a bead core from the inside to the outside and locked in the bead portion, and at least three belt layers disposed on the outside of the carcass ply in the tread portion. However, in a tire with a split structure in which the first belt in the belt layer counting from the carcass ply in the tread direction is divided and arranged on both sides except for the tread center area, the radial A pneumatic radial tire for heavy loads characterized by a reinforcing layer formed by embedding a directional cord along the carcass ply. [Claim 2] The width of the reinforcing layer is such that the side edge thereof does not reach the bead on the side of the tire from the foot of a perpendicular line drawn from the widest belt end to the carcass ply, and Height in the tire height direction at the side edge position (h)
and the tire height (H) at the tire maximum width position (h
The pneumatic radial tire for heavy loads according to claim 1, wherein: /H) is set to be 0.8 or more.