JPH106710A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for heavy load with improved vibration comfortableness. SOLUTION: In a pneumatic radial tire 1 for heavy load with a plurality of crossing belt layers 4, a split belt 5 is arranged, respectively, in a pair of right and left areas from 1/8 to 1/4 of the tread width from both ends of a tread 3 between a carcass 2 and the crossing belt layers 4. A buffer rubber layer 6 with the thickness of 5 to 10mm is arranged in an intermediate area between the pair of split belts 5, and a glass transition point of the buffer rubber layer 6 is -70 deg.C or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire for heavy loads, and more particularly, to a pneumatic radial tire for heavy loads suitable for use in underground mines, articulated dumps for tunnel work, etc., with improved vibration riding comfort. Regarding tires.

[0002]

2. Description of the Related Art Conventionally, a heavy-duty pneumatic radial tire reinforced with a steel belt is provided between a tread 3 of a tire 1 and a carcass ply 2 as shown in FIG. A belt cord layer (hereinafter, referred to as a “first belt”) disposed at a predetermined angle with respect to the tire circumferential direction, and a belt cord layer laminated on the first belt and intersecting with the cord of the first belt ( A belt cord layer (hereinafter, referred to as a "third belt") laminated on the second belt and intersecting with a cord of the second belt (hereinafter, referred to as a "third belt"). The layers 4 are stacked and configured.

[0003] In such a belt structure, various improvement techniques have conventionally been proposed in order to improve various performances of the tire. For example, it has been proposed to use the first belt as a so-called hollow structure (hereinafter sometimes abbreviated as a "split belt") in order to prevent the occurrence of separation at the end of the belt (Japanese Patent Laid-Open No. 61-1986). No. 54304, JP-A-61-54305 public reports). Further, it has been proposed to limit the width of the first steel belt and arrange organic fiber layers on both sides of the first steel belt in order to improve the durability of the belt portion and suppress the wandering phenomenon (Japanese Patent Application Laid-Open No. Sho 63). −
No. 13801)

Further, in order to prevent damage to the tread crown portion and breakage of the belt cord due to road surface protrusions, and to ensure belt durability for long-term use under heavy load conditions, the first
It has been proposed that the belt has a hollow structure, and two non-extensible fiber cord layers are arranged in the hollow portion so as to cross each other (Japanese Patent Laid-Open No. 64-1604).

Furthermore, in order to improve the belt durability under running on a rough road and running on a good road at high speed, it has been proposed that the first belt has a hollow structure and the composition of a rubber layer disposed therebetween is limited. (JP-A-63-134309).

[0006]

In a pneumatic radial tire for heavy loads, it has been conventionally known that a part of the belt layer is used as a split belt as described above. Since the thickness of the belt was at most equal to the thickness of the belt, there was a problem that the riding comfort was poor. In addition, in such a conventional heavy-duty pneumatic radial tire, the number of belts is four or more, which is problematic in terms of cost.

On the other hand, in a conventional heavy-duty pneumatic radial tire having three normal belt layers which is not a split belt, the internal pressure of the belt is particularly large at the center portion, that is, when the internal pressure is charged, the belt circumferential direction at the center portion is increased. There is a problem that the tension load is larger than the area from both ends of the tread to a point of 1/4 to 3/8 of the tread width, and the center pressure is increased, so that the riding comfort is deteriorated. I was

It is an object of the present invention to provide a pneumatic radial tire for heavy loads with improved riding comfort.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has arranged a pair of split belts in a specific region between the belt layer and the carcass, and By arranging the buffer rubber layer having a specific thickness in the hollow portion and having a glass transition point in a specific range, it has been found that the above object can be achieved,
The present invention has been completed.

[0010] That is, the pneumatic radial tire for heavy load of the present invention comprises a plurality of steel cord carcass folded back by a pair of bead cores and connected in a toroidal shape, and a tread arranged at a crown portion of the carcass. In a heavy-duty pneumatic radial tire having two crossed belt layers, a pair of right and left wheels between the carcass and the crossed belt layers and from both ends of the tread to 1/4 to 3/8 of the tread width. In each of the regions, a divided belt is disposed, and a buffer rubber layer having a thickness of 5 to 10 mm is disposed in a hollow region between the pair of divided belts, and the glass transition point of the buffer rubber layer is −70 ° C. or less. It is characterized by the following.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic radial tire for heavy loads according to the present invention will be specifically described with reference to the drawings. In the heavy-duty pneumatic radial tire 1 shown in FIG. 1, at least one steel cord carcass 2 folded back by a pair of bead cores 7 and connected in a toroidal shape, and the carcass 2
A plurality of crossed belt layers 3 between the tread 4 and the tread 4 disposed on the crown portion of the belt. In the present invention, in the tire having such a structure, the split belt 5 is formed between the carcass 2 and the cross-type belt layer 3 and from both ends (E) of the tread 4 to 1/8 to 1/4 of the tread width (L). Are arranged respectively in a pair of left and right regions reaching. Such a pair of split belts 5 has a tread width (L) of 1 from the tread end (E).
When it extends to the tread center side beyond / 4, the total belt tension at the center portion increases, and the riding comfort decreases. On the other hand, 1/8 of the tread width (L) from the tread edge
When it extends beyond the tread end (E) side, the belt durability deteriorates.

In the present invention, each of the pair of split belts is one steel cord belt, and the angle of the steel cord with respect to the tire circumferential direction (hereinafter referred to as “belt angle”) is 30 ° to 65 °. Preferably, the pair of split belts are two cross-type organic fiber cord belts, and the belt angle of the organic fiber cords is preferably 30 ° to 60 °. More preferably, the organic fiber cord is a nylon fiber cord.

In the present invention, a buffer rubber layer 6 having a thickness of 5 to 10 mm, preferably 5 to 7 mm is disposed in a hollow region between the pair of split belts 5. If the thickness is less than 5 mm, the desired vibration riding comfort cannot be obtained, while if it exceeds 10 mm, the durability of the belt in addition to the heat generation characteristics is reduced, and the effect of tightening the belt is reduced. It is preferable that the thickness be 7 mm or less from the viewpoint of heat generation characteristics.

Further, in the present invention, the buffer rubber layer 6 has a glass transition point of -70 or less, preferably -70.
It needs to be within the range of -110 ° C. If the glass transition point exceeds -70 ° C, the vehicle speed following performance of the cushioning rubber layer is inferior, and it becomes impossible to obtain a desired vibration riding comfort. If the temperature is lower than -110 ° C, the adhesiveness is deteriorated like silicone rubber. Therefore, the temperature is preferably higher than -110 ° C.

The pneumatic radial tire for heavy loads according to the present invention is preferably a steel cord crossed belt layer having a rim diameter of 25 inches or more and three crossed belt layers in order to fully utilize its characteristics. Preferably, there is.

[0016]

Next, the present invention will be specifically described based on examples and comparative examples. The tires of the examples and comparative examples are all heavy-load pneumatic radial tires having a tire size of ORR17.5R25. Each of these tires is 3
It has 3 crossed steel cord belt layers, the steel cord structure is 3 + 9 + 15 × 0.23, the number of driving is about 25.8 / 5cm, and the cord angle of the first belt is left to the circumferential direction. The cord angle of the second belt was 23 degrees to the right in the circumferential direction, and the cord angle of the third belt was 23 degrees to the left in the circumferential direction. The steel cord carcass is a single layer, and the number of shots is 18.6 / 5cm
And

A tire having such a structure, which does not have the split belt and the buffer rubber layer, is referred to as Comparative Example 1 (conventional example), and a tire having the split belt and the buffer rubber layer shown in Table 1 below is used in Example 1. ~ 3 and Comparative Example 2,
It was set to 3. The nylon fiber cord used for the split belt was a twist of two strands of 1500 denier, and the same steel cord as that of the steel cord belt layer was used.

With respect to these test tires, the riding comfort was evaluated by the following two methods. The results obtained are shown in Table 1 below. (B) G-meter measurement Accelerometers are installed above the axle of the vehicle and below the driver's seat, and the acceleration of vibration in three directions, up, down, left, right, front and back is measured.
Fourier analysis was performed for each direction. The magnitude of the vibration amplitude at each of the frequencies (all having the same value) that adversely affects the vibration riding comfort was compared with each of the examples and the comparative examples. The evaluation was indicated by an index with the result of Comparative Example 1 being 100. The smaller the value, the better.

(B) Feeling test An internal pressure of 5.5 kgf / cm ² was applied to the articulated dump.
, And feeling evaluation was performed by two operators. The evaluation was indicated by an index with the result of Comparative Example 1 (conventional example) being 100. The higher the numerical value, the better the obtained result. The results obtained are shown in Table 1 below.

[0020]

[Table 1]

[0021]

As described above, in the pneumatic radial tire for heavy load according to the present invention, a pair of split belts are arranged in a specific area between the belt layer and the carcass, and a hollow between the split belts is provided. By arranging a buffer rubber layer having a specific thickness in a part and a glass transition point in a specific range, the belt circumferential tension at the time of internal pressure filling is reduced in the center portion and increased in the divided belt region. In addition, the ground pressure is made uniform, and the riding comfort is greatly improved.

[Brief description of the drawings]

FIG. 1 is a left half sectional view of an example tire of the present invention.

FIG. 2 is a left half sectional view of a conventional tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic radial tire for heavy load 2 Steel cord carcass 3 Tread 4 Cross type belt layer 5 Split belt 6 Buffer rubber layer 7 Bead core

Claims (6)

[Claims] 1. A heavy-duty air having a plurality of crossed belt layers between at least one steel cord carcass folded back by a pair of bead cores and connected in a toroidal shape, and a tread arranged on a crown portion of the carcass. In the entering radial tire, a split belt is disposed between the carcass and the cross-type belt layer, and in a pair of left and right regions ranging from 両 端 to の of the tread width from both ends of the tread, 5 to 10 m thick in the hollow area between the pair of split belts
A pneumatic radial tire for heavy loads, wherein m rubber cushion layers are arranged, and the glass transition point of the rubber cushion layers is −70 ° C. or less. 2. The pneumatic radial tire for heavy loads according to claim 1, wherein each of the pair of split belts is a single steel cord belt, and an angle of the steel cord with respect to a tire circumferential direction is 30 ° to 65 °. 3. The heavy load air according to claim 1, wherein each of the pair of split belts is two cross-type organic fiber cord belts, and the angle of the organic fiber cords with respect to the tire circumferential direction is 30 ° to 60 °. Included radial tire. 4. The pneumatic radial tire for heavy pneumatic loads according to claim 3, wherein the organic fiber cord is a nylon fiber cord. 5. The pneumatic radial tire for heavy loads according to claim 1, wherein the thickness of the buffer rubber layer is 5 to 7 mm. 6. The pneumatic device for heavy loads according to claim 1, wherein a rim diameter is 25 inches or more, and the belt of the cross belt layer is a three-layer steel cord cross belt layer. Radial tire.