JP2006151326A - Pneumatic radial tire for small truck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for a small truck for suppressing creep deformation of carcass plies while suppressing an increase in weight of a tire and in manufacturing cost to enhance durability. <P>SOLUTION: In the pneumatic radial tire for the small truck with the carcass plies 4A, 4B composed of organic fibrous cord, having casing structure wherein belt layers 7A-7C having at least two layers are arranged on outer peripheral sides of the carcass plies 4A, 4B, wherein air pressure corresponding to the maximum load ability is in a range of 350-650 kPa, there is provided a side reinforcing layer 9 extending on a sidewall part 2 while overlapping with an end part of the belt layer 7B having at least maximum width, and composed of reinforcing cord in substantially parallel with the organic fibrous cord of the carcass plies 4A, 4B. Intermediate elongation of the reinforcing cord of the side reinforcing layer 9 is made smaller by 0.5-2.0% point than that of the organic fibrous cord of the carcass plies 4A, 4B. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire suitable for a small truck. More specifically, the present invention relates to a small truck that suppresses creep deformation of a carcass layer and improves durability while suppressing an increase in tire weight and manufacturing cost. The present invention relates to pneumatic radial tires.

  In a pneumatic radial tire for a small truck, an organic fiber cord is generally used for a carcass material for reasons such as manufacturing simplicity and weight reduction (see, for example, Patent Document 1). However, pneumatic radial tires for light trucks have high air pressure and are used under high load conditions, so that creep deformation may occur in the carcass layer as the car travels, and the carcass peripheral may be extended. . When creep deformation occurs in the carcass layer, the strain generated in the belt edge portion increases, and there is a problem that a peeling failure tends to occur in the belt edge portion until the end of wear.

As countermeasures, a technique is adopted in which the number of carcass layers straddling between a pair of bead portions is increased or the driving density of the organic fiber cord is increased. However, these methods have a problem of increasing tire weight and manufacturing cost, and further improvements are desired.
JP-A-6-24206

  An object of the present invention is to provide a pneumatic radial tire for a small truck that suppresses creep deformation of a carcass layer and improves durability while suppressing an increase in tire weight and manufacturing cost.

  In order to achieve the above object, a pneumatic radial tire for small trucks of the present invention has a casing structure in which a carcass layer is composed of an organic fiber cord, and two or more belt layers are arranged on the outer peripheral side of the carcass layer. A pneumatic radial tire for a small truck having an air pressure corresponding to the maximum load capacity in a range of 350 to 650 kPa, extending to a sidewall portion while overlapping with an end portion of a belt layer having at least a maximum width, and the carcass layer A side reinforcing layer made of a reinforcing cord substantially parallel to the organic fiber cord is provided, and an intermediate elongation of the reinforcing cord of the side reinforcing layer is set to 0.5 to 2 higher than an intermediate elongation of the organic fiber cord of the carcass layer. It is characterized by a reduction of 0.0 percentage points.

  In the present invention, in a pneumatic radial tire for a small truck having a carcass layer made of an organic fiber cord and having a relatively high working air pressure, a side reinforcing layer is disposed along the carcass layer on the side wall, and the side reinforcing Since the intermediate elongation of the reinforcing cord of the layer is made smaller than the intermediate elongation of the organic fiber cord of the carcass layer, the creep deformation of the carcass layer is suppressed, and the peeling failure at the belt edge due to the creep deformation is prevented. Can do. Therefore, it is possible to improve the durability particularly from the middle wear stage to the last wear stage. And since a side reinforcement layer is smaller than the carcass layer straddling between a pair of bead parts, the increase in a tire weight and manufacturing cost can be suppressed.

  In the present invention, in order to effectively suppress the creep deformation of the carcass layer by adding the side reinforcing layer, it is desirable to adopt the following structure. That is, the lap amount A between the side reinforcing layer and the maximum width belt layer is preferably 5 to 40 mm. The end of the side reinforcing layer on the outer side in the tire radial direction is preferably disposed between the carcass layer and the belt layer having the maximum width. The end portion of the side reinforcing layer on the inner side in the tire radial direction is preferably arranged on the inner side in the tire radial direction from the tip of the bead filler embedded in the bead portion, and the wrap amount B between the side reinforcing layer and the bead filler is preferably 10 to 25 mm. . The end of the side reinforcing layer on the inner side in the tire radial direction may be disposed between the bead filler and the carcass layer located on the inner side in the tire width direction of the bead filler.

  The pneumatic radial tire for a light truck according to the present invention may be provided with at least one carcass layer that passes under the belt layer and straddles between the pair of bead portions, but sufficiently secures the internal pressure holding capability. However, in order to avoid an increase in the tire weight, it is preferable that the carcass layer straddling between the pair of bead portions through the lower part of the belt layer is two layers. On the other hand, it is preferable to use an organic fiber cord for the reinforcing cord constituting the side reinforcing layer, similarly to the carcass layer.

  Note that the air pressure corresponding to the maximum load capacity is the air pressure corresponding to the maximum load capacity defined by the standard, for example, the air pressure defined in the air pressure-load capacity correspondence table of the JATMA Yearbook (2004 edition). It is.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a pneumatic radial tire for a small truck according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. Two carcass layers 4 </ b> A and 4 </ b> B are mounted between the pair of bead portions 3 and 3. Each of these carcass layers 4A and 4B is composed of a plurality of organic fiber cords oriented in the tire radial direction. As the organic fiber cord, nylon cord, polyester cord, or the like can be used. The carcass layers 4 </ b> A and 4 </ b> B are wound up from the tire inner side to the outer side so as to wrap the bead core 5 and the bead filler 6 embedded in the bead part 3.

  On the other hand, on the outer peripheral side of the carcass layers 4A, 4B in the tread portion 1, three belt layers 7A, 7B, 7C are embedded over the entire circumference of the tire. These belt layers 7A to 7C include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect each other between the layers. When counted from the carcass side, the first belt layer 7A is the narrowest, the second belt layer 7B is the widest, and the third belt layer 7C is wider than the belt layer 7A and narrower than the belt layer 7B. It has become. The difference between the total width of the first belt layer 7A and the total width of the second belt layer 7B is set in a range of 10 to 50 mm. Further, a belt cover layer 8 formed by winding an organic fiber cord substantially at 0 ° with respect to the tire circumferential direction is provided around the edge portions of the belt layers 7A to 7C.

  The pneumatic radial tire has a casing structure in which the carcass layers 4A and 4B are made of organic fiber cords, and the three belt layers 7A to 7C are arranged on the outer peripheral side of the carcass layers 4A and 4B. Is specified in the range of 350 to 650 kPa.

  In the pneumatic radial tire, the side reinforcing layer is formed of a reinforcing cord that overlaps at least the end portion of the belt layer 7B having the maximum width and is substantially parallel to the organic fiber cords of the carcass layers 4A and 4B. 9 is buried. The cord angle of the side reinforcing layer 9 with respect to the tire circumferential direction is preferably the same as the cord angle of the carcass layers 4A and 4B with respect to the tire circumferential direction, but is substantially parallel if the difference between the two is 5 ° or less. Is to be interpreted.

Although it is preferable to use the same organic fiber cord as the carcass layers 4A and 4B for the reinforcing cord of the side reinforcing layer 9, it is also possible to use a steel cord. In any case, the intermediate elongation of the reinforcing cords of the side reinforcing layers 9 is set to be 0.5 to 2.0% smaller than the intermediate elongation of the organic fiber cords of the carcass layers 4A and 4B. For example, when the intermediate elongation of the organic fiber cords constituting the carcass layers 4A and 4B is 7%, the intermediate elongation of the reinforcement cords constituting the side reinforcing layer 9 is set in the range of 5 to 6.5%. . However, the intermediate elongation referred to here is obtained by obtaining the elongation at a constant load by a tensile tester according to JIS L1017. Here, the constant load (F) is obtained by the following equation.
F = 44 × (d ₂ / d ₁ )
F: Constant load (N: Newton)
d ₁ : Standard fineness (dtex) shown in Table 4 of JIS L1017
d ₂ : Display fineness (dtex) of sample to be measured

  In the pneumatic radial tire for small trucks having the carcass layers 4A and 4B made of organic fiber cords as described above and having a relatively high working air pressure, the side reinforcing layers are provided along the carcass layers 4A and 4B in the sidewall portion 2. 9, the intermediate elongation of the reinforcing cord of the side reinforcing layer 9 is made smaller than the intermediate elongation of the organic fiber cord of the carcass layers 4A, 4B, thereby suppressing the creep deformation of the carcass layers 4A, 4B, The peeling failure at the belt edge portion due to the creep deformation can be prevented. Therefore, even if it is a pneumatic radial tire for small trucks using organic fiber cords for the carcass layers 4A and 4B, durability from the middle wear stage to the last wear stage can be improved. And since the side reinforcement layer 9 is smaller than the carcass layers 4A and 4B straddling between a pair of bead parts 3 and 3, the increase in a tire weight and manufacturing cost can be suppressed.

  Here, when the difference between the intermediate elongation of the organic fiber cord constituting the side reinforcing layer 9 and the intermediate elongation of the organic fiber cord constituting the carcass layers 4A and 4B is less than 0.5% point, creep deformation is suppressed. On the other hand, if it exceeds 2.0% point, the organic fiber cords of the carcass layers 4A and 4B are likely to bite into the side reinforcing layer 9 during vulcanization, which may cause vulcanization failure between the plies. is there.

  The lap amount A between the side reinforcing layer 9 and the maximum width belt layer 7B is preferably 5 to 40 mm. The wrap amount A is the overlapping width of the two measured along the belt layer 7B. If the wrap amount A is less than 5 mm, the effect of suppressing creep deformation is insufficient, and conversely if it exceeds 40 mm, the effect of reducing the weight is reduced. The most preferable range of the wrap amount A is 10 to 20 mm. Note that the side reinforcing layer 9 is not overlapped with the belt layer 7A having the minimum width, and the distance from the edge of the belt layer 7A is preferably 10 mm or less.

  The end portion on the outer side in the tire radial direction of the side reinforcing layer 9 may be disposed at any position with respect to the belt layers 7A to 7C, but is disposed between the carcass layers 4A and 4B and the belt layer 7B having the maximum width. Is most preferred. Thereby, the reinforcement effect with respect to carcass layer 4A, 4B becomes large. Further, when the end portion of the side reinforcing layer 9 is disposed between the carcass layers 4A and 4B and the belt layer 7B having the maximum width, the carcass layers 4A and 4B and the side reinforcing layer 9 may be laminated in advance when the tire is formed. This is advantageous from the viewpoint of productivity.

  The end portion of the side reinforcing layer 9 on the inner side in the tire radial direction is arranged on the inner side in the tire radial direction from the tip of the bead filler 6 embedded in the bead portion 3, and the lap amount B between the side reinforcing layer 9 and the bead filler 6 is 10 It is better to set it to ~ 25mm. The wrap amount B is the overlapping width of the two measured along the side reinforcing layer 9. If the wrap amount B is less than 10 mm, the effect of suppressing creep deformation is insufficient, and conversely if it exceeds 25 mm, the effect of reducing the weight is reduced. The most preferable range of the wrap amount B is 15 to 20 mm.

  The end of the side reinforcing layer 9 on the inner side in the tire radial direction may be disposed at any position with respect to the bead filler 6, but the bead filler 6 and the carcass layer 4 </ b> B located on the inner side in the tire width direction of the bead filler 6 Most preferably, it is disposed between. Thereby, the reinforcement effect with respect to carcass layer 4A, 4B becomes large. Further, when the end portion of the side reinforcing layer 9 is disposed between the bead filler 6 and the carcass layer 4B, the carcass layers 4A and 4B and the side reinforcing layer 9 can be laminated in advance when the tire is formed. This is also advantageous from the standpoint of sex.

  In the embodiment described above, the case of a pneumatic radial tire provided with three belt layers has been described, but the present invention can be applied to a pneumatic radial tire provided with at least two belt layers.

  Conventional examples 1 and 2 in which the casing structure (carcass layer, belt layer and side reinforcing layer) is different in a pneumatic radial tire for a small truck having a tire size of 235 / 85R16 and an air pressure corresponding to the maximum load capacity of 450 kPa. The tires of Examples 1 to 8 and Comparative Examples 1 and 2 were produced. In particular, in Examples 1 to 8 and Comparative Examples 1 and 2, the difference (%) in the intermediate elongation between the cord of the side reinforcing layer and the cord of the carcass layer, the lap amount A between the side reinforcing layer and the maximum width belt layer (Mm) and the amount of lap B (mm) between the side reinforcing layer and the bead filler were varied. Steel cords were used for the belt layer, and polyester cords were used for the carcass layer and the side reinforcement layers. The intermediate elongation of the polyester cord of the carcass layer was 7%, the intermediate elongation of the polyester cord of the side reinforcing layer was smaller than the intermediate elongation of the polyester cord of the carcass layer, and the difference between the two was set appropriately. The intermediate elongation of the polyester cord was adjusted based on the dip treatment.

  With respect to these test tires, the remaining peeling force of the belt portion, the tire weight, the tire breaking internal pressure, and the failure occurrence rate were evaluated by the following test methods, and the results are shown in Table 1.

Residual peeling force of belt part:
For each test tire, the peel strength of the belt portion was measured when it was new and after the drum durability test. The peeling force of the belt portion is a force required to peel the belt portion from the carcass layer. In the drum endurance test, the internal pressure was 133% of the air pressure corresponding to the maximum load capacity, the load was 130% of the maximum load capacity, the speed was 60 km / h, and the test tire was run on the indoor drum for 20000 km. For each tire, the peel force at the time of a new article was taken as 100, and the peel force remaining after the drum endurance test was shown as an index. The larger the index value, the greater the peeling force of the belt portion remaining after the drum durability test.

Tire weight:
The weight of each test tire was measured. The evaluation results are shown as an index with the conventional example 1 as 100, using the reciprocal of the measured value. A larger index value means lighter weight.

Tire breaking internal pressure:
Each test tire was assembled on a standard rim, and its internal fracture pressure was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. A larger index value means a higher tire breaking internal pressure.

Failure rate:
About each test tire, the vulcanization failure which arises between a carcass layer and a side reinforcement layer was investigated, and the failure occurrence rate was calculated | required. A case where the failure occurrence rate is less than 0.5% is indicated by “OK”, and a case where the failure occurrence rate is 0.5% or more is indicated by “NG”.

  As can be seen from Table 1, the tires of Examples 1 to 8 were lighter than Conventional Example 1, but the evaluation results of the residual peeling force of the belt portion and the tire breaking internal pressure were good. Although the tire of Conventional Example 2 is lighter than Conventional Example 1, the residual peeling force of the belt portion and the tire breaking internal pressure were insufficient. In the tire of Comparative Example 1, since there was no difference between the intermediate elongation of the reinforcing cord of the carcass layer and the intermediate elongation of the reinforcing cord of the side reinforcing layer, the improvement effect as in Examples 1 to 8 was not obtained. In the tire of Comparative Example 2, the difference between the intermediate elongation of the reinforcing cord of the carcass layer and the intermediate elongation of the reinforcing cord of the side reinforcing layer was excessive, and this was the cause of failure.

1 is a meridian half sectional view showing a pneumatic radial tire for a small truck according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4A, 4B Carcass layer 5 Bead core 6 Bead filler 7A, 7B, 7C Belt layer 8 Belt cover layer 9 Side reinforcement layer

Claims (7)

For small trucks that have a carcass layer composed of organic fiber cords and a casing structure in which two or more belt layers are arranged on the outer periphery of the carcass layer, and the air pressure corresponding to the maximum load capacity is in the range of 350 to 650 kPa A pneumatic radial tire is provided with a side reinforcing layer made of a reinforcing cord that extends to the sidewall portion while overlapping at least the end portion of the belt layer having the maximum width and is substantially parallel to the organic fiber cord of the carcass layer. A pneumatic radial tire for a small truck in which the intermediate elongation of the reinforcing cord of the side reinforcing layer is 0.5 to 2.0% smaller than the intermediate elongation of the organic fiber cord of the carcass layer. The pneumatic radial tire for a light truck according to claim 1, wherein a lap amount A between the side reinforcing layer and the belt layer with the maximum width is 5 to 40 mm. The pneumatic radial tire for a small truck according to claim 1 or 2, wherein an end of the side reinforcing layer on the outer side in the tire radial direction is disposed between the carcass layer and the belt layer having the maximum width. An end portion on the inner side in the tire radial direction of the side reinforcing layer is arranged on the inner side in the tire radial direction from the tip of the bead filler embedded in the bead portion, and a wrap amount B between the side reinforcing layer and the bead filler is 10 to 25 mm. The pneumatic radial tire for a light truck according to any one of claims 1 to 3. 5. The small truck according to claim 1, wherein an end of the side reinforcing layer on the inner side in the tire radial direction is disposed between the bead filler and a carcass layer located on the inner side in the tire width direction of the bead filler. Pneumatic radial tire. The pneumatic radial tire for a light truck according to any one of claims 1 to 5, wherein there are two carcass layers that pass under the belt layer and straddle between the pair of bead portions. The pneumatic radial tire for a light truck according to any one of claims 1 to 6, wherein the reinforcing cord of the side reinforcing layer is an organic fiber cord.

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