JPH1178409A - Radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extensively improve high speed durability of a radial tire without having a harmful influence on other performance of the tire by using an organic fiber cord having a specific physical property as a cord to be used for a belt enforcing layer of a cap belt, etc. SOLUTION: A cord of a belt enforcing layer 5 is an organic fiber cord, and as a cord physical property, when a dry heat contraction coefficient at the time of a loading of 0.04 g/d is S1 (%) under atmospheric temperature 177 deg.C and a dry heat contraction coefficient at the time of a loading of 0.12 g/d is S2 (%) under atmospheric temperature 177 deg.C, S1 and S2 satisfies relation expressed by S1 >=5.5 and S2 <=S1 -2.5.

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 having improved high-speed durability, and more particularly, to a pneumatic radial tire having a belt reinforcing layer.
By using an organic fiber cord having specific physical properties,
The present invention relates to a radial tire with significantly improved high-speed durability.

[0002]

2. Description of the Related Art In recent years, with the remarkable improvement in the performance of passenger cars, the performance of passenger car tires has been required to be improved at a particularly high level. In particular, high-speed durability is of particular importance because it is a characteristic relating to occupant safety.
By the way, studies on improving the high-speed durability of tires have been actively conducted from the viewpoint of material characteristics and tire structure, and the role of the organic fiber reinforcing material plays a large role in the research. That is, recently, it is known that a tire provided with a belt reinforcing layer such as a so-called cap belt exhibits a good effect on high-speed durability. This cap belt is a cord layer that further reinforces the belt layer using organic fiber cords arranged in the tire circumferential direction as reinforcing cords, and a function for suppressing failure due to tread peeling due to generation of centrifugal force during high-speed running. Demonstrate. For this reason, the use of the cap belt significantly improved the high-speed durability of the tire. However, with the further improvement of passenger vehicle performance and the expansion of high-speed motorways, there is a strong demand for further improvement of high durability performance of tires. In fact, it is becoming increasingly difficult to make further improvements.

[0003]

The object of the present invention is to provide a tire having a specific property as a cord used for a belt reinforcing layer in such a situation, thereby adversely affecting other performances of the tire. It is an object of the present invention to provide a radial tire having significantly improved high-speed durability of the tire.

[0004]

Means for Solving the Problems The present inventors have studied the physical properties of organic fiber cords in order to achieve the above object, and in particular, have studied organic fiber cords generated during vulcanization in the tire manufacturing process. Focusing on the dry heat shrinkage rate of the rubber and the force of the rubber around the cord at the time of the dry heat shrinkage to prevent the cord from shrinking (restraining force of the rubber), as a result of a thorough study, the high-speed durability of the tire and the organic property of the cap belt The inventors have found that the physical properties of the fiber cords are closely related, and have completed the present invention. That is, a carcass consisting of a radially arranged one or more layers forming a toroid straddling between a pair of bead portions is provided as a body reinforcing material for a sidewall portion and a tread portion connected to the bead, and the carcass is one of them. A belt having a turn-up structure in which at least one layer is wound from the inside to the outside of the tire around the bead core of the bead portion, and a belt formed of a plurality of cord arrangement layers around a crown portion of the carcass; In a pneumatic radial tire provided with at least one belt reinforcing layer, the cords of which are arranged in the tire circumferential direction covering the end portions, the cord of the belt reinforcing layer is an organic fiber cord, and as cord physical properties, under ambient temperature 177 ° C., a dry heat shrinkage under a load of 0.04 g / d and S ₁ (%), One under ambient temperature 177 ° C., a dry heat shrinkage under a load of 0.12 g / d S
_{When 2} (%), S ₁ and S ₂ are expressed by the following formulas (1) and (2): S ₁ ≧ 5.5 (1) S ₂ ≦ S ₁ -2.5 (2) A radial tire that satisfies the relationship represented by: Further, the organic fiber cord has an intermediate elongation E (%) under a load of 2.44 g / d at an ambient temperature of 25 ° C., which satisfies the following formula (3): E ≦ 8.0 (3) Preferably, they are satisfied.

Here, the meaning of the g / d (gram / denier) display of the load applied to the cord when measuring S ₁ , S ₂ and E means the load (gram number) applied to the cord.
Is divided by the actually measured total denier (so-called positive fineness) of the code. Further, the dry heat shrinkage (hereinafter, simply referred to as heat shrinkage) means a heat shrinkage measured in a dry atmosphere as described later. The characteristic of the organic fiber cord defined in the present invention is the physical properties of the cord after the cord is subjected to an adhesive heat treatment at the time of tire production.

[0006] Incidentally, a tire undergoes a certain degree of circumferential expansion during molding to vulcanization, and becomes a tire as a final product. Therefore, the organic fiber cord used for the cap belt layer follows this, and is stretched to become a product yarn. Although the expansion ratio of this tire differs depending on the size and structure of the tire, generally, when comparing the center portion (center portion) of the cap belt and the end portion (shoulder portion) in the tire radial direction, the expansion ratio is larger in the center portion. Is known to be large. Also, when the tire is run at high speed, centrifugal force acts on the tire tread portion, and the tire tends to expand in the circumferential direction. Although the cap belt has the effect of suppressing the circumferential swelling, circumferential swelling also occurs in a tire using the cap belt. As a result of various studies, it has been found that, in order to improve the high-speed durability of the tire, it is better that the peripheral bulge (projection) is small and the difference between the projection amount of the tread center portion and the projection amount of the shoulder portion is small. That is, according to the present invention, the circumferential tightening effect at the center portion and the shoulder portion of the cap belt is made uniform, and the protrusion amount at the time of high-speed running is made uniform at the tread surface, thereby improving the durability at the time of high-speed running. It is based on the knowledge that it is effective for

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, in the present invention, a belt supplement will be described.
The characteristics of the organic fiber cord used for reinforcing the strong layer
explain about. The fiber cord used in the present invention is
As described above, the two thermal shrinkage ratios at a given temperature and load are
Satisfying the relations of the above-mentioned expressions (1) and (2) at the same time.
There must be. That is, the organic fiber in the present invention
The cord has a load of 0.04 g / d under an ambient temperature of 177 ° C.
The heat shrinkage rate under heavy load is S₁(%) And ambient temperature
The thermal shrinkage under a load of 0.12 g / d at 177 ° C
S_Two(%), S₁And S _TwoIs the following formula,
(1), (2) S₁≧ 5.5 ・ ・ ・ (1) S_Two≤S₁−2.5 It is necessary to satisfy the relationship expressed by (2). Where S
₁Measurement conditions of 0.04 g /
The time when the load of d is applied is that when the tire is vulcanized,
Organic fiber core wrapped around the belt layer in the circumferential direction
, The so-called cap belt cord is received in the mold
The temperature is usually 177 ° C.
Tire radial end of shoulder belt cord (shoulder)
Was set because the load received by was 0.04 g / d
Value. Here, the heat shrinkage S₁Is 5.5% or more
And the circumference of the cap belt cord at the shoulder
Higher durability with higher tightening effect than current cord
Effective for improvement.

Further, the measurement condition of S ₂ is set at an ambient temperature of 17
The reason why the load of 0.12 g / d was applied at 7 ° C. is that the center part (center part) of the cap belt in the tire radial direction during vulcanization of the tire receives the temperature and the restraining force (the load applied to the cord). ). Here, when S ₂ ≦ S ₁ -2.5 is satisfied, the circumferential tightening effect due to the heat shrinkage of the product tire can significantly improve the high-speed durability of the tire. Also, if S ₂ do not satisfy the preferred above range in the range of 3.5 to 4.0 (%), the circumferential direction of the cinching effect of cap belt results in a variation in the radial direction, and a center portion A difference occurs in the amount of protrusion at the shoulder portion, which impairs high-speed durability.

Further, the organic fiber cord of the belt reinforcing layer in the present invention has an ambient temperature of 25 ° C. and 2.44 g / d.
It is desirable that the intermediate elongation under load E (%) satisfies the following equation (3): E ≦ 8.0 (3) In general, it is known that the intermediate elongation E and the heat shrinkage rate are closely related. When E is increased, S ₁ and S ₂ are decreased. But E
If it exceeds 8.0%, the tightening effect as a cap belt cord is reduced, and it may not be possible to obtain high-speed durability, which is not preferable.

In the present invention, the cord satisfying the relations of the above formulas (1), (2) and (3) is obtained by spinning the corresponding polymer at a relatively low speed in the cord raw yarn production step, quenching the cord,
It is desirable to produce by stretching at an appropriate magnification. Also,
In the code dipping process during tire manufacturing,
After the cord is dipped in the adhesive liquid as a drip weave, it passes through each zone of the drying section, the first heating stretching section, and the second heating stretching section, and is wound. In the present invention, the final zone, the normalizing, The temperature of the zone (second heating and stretching zone) is set to 40 with respect to the heat setting zone (first heating and stretching zone).
A particularly effective effect can be obtained by subjecting the twisted cord to heat treatment (so-called dip treatment) under a condition of lowering the temperature in the range of ~ 80 ° C and setting the cord tension at 1/5 to 1/2 of that of the heat-setting zone. it can.

In the present invention, the type of the organic fiber cord material used for the belt reinforcing layer is not particularly limited as long as it satisfies the relations of the expressions (1) and (2) at the same time. However, for example, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polytetramethylene adipamide (nylon 4,6), polyhexamethylene adipamide (nylon 6,6), and polycapramide (nylon) 6), polyhexamethylene sebacamide (nylon 6,1
0), polyhexamethylene dodecamide (nylon 6,1
2) and the like. Among them, especially nylon fiber, by changing the conditions of the heat treatment (dip treatment) process when applying the adhesive in the tire manufacturing process,
It is preferable because desired physical properties can be obtained relatively easily. Usually, these fibers are those containing 85 mol% or more of the corresponding polymer. The method for producing the organic fiber may be a method for producing a fiber using a normal tire cord, and is not particularly limited.For example, in the case of a nylon cord, a solid The nylon having a predetermined molecular weight obtained by the polymerization is rapidly cooled under a spinneret in a gas atmosphere at 10 to 60 ° C., and at a spinning speed of 500 to 1000 m / min and a draw ratio of 3.0 to 4.0.
The original yarn can be obtained by selecting the optimum conditions within the range and spinning. In the organic fiber cord according to the present invention, the raw yarn is twisted, two or three of the yarns are combined, and the twisted yarn is twisted in the opposite direction to obtain an equation T = N × (0.139 × D / ρ) ^{1 / Two}
× 10 ^-3 [where, N: number of twists of cord (times / 10 c)
m), D: the actual measured total denier of the cord, ρ: the specific gravity of the cord] is preferably 0.30 to 0.75. If it is less than 0.30, the durability of the cord will be poor, and if it exceeds 0.75, snoring will occur and handling will be poor.

Next, the radial tire of the present invention will be specifically described with reference to the drawings. A radial tire which is an example of the present invention shown in FIG. 1 includes a carcass 3 which is locked by folding back at least one carcass ply end 2 around a bead core 1, and at least two layers radially outward of the carcass 3 in the tire radial direction. And a cord arrangement covering the belt outside the belt 5 has a belt reinforcing layer 5 in the tire circumferential direction, and a tread 6 outside the belt reinforcing layer. 70 for direction
It is arranged in a direction of up to 90 degrees. In the belt 4, non-stretched cords typified by aramid fibers and steel cords are arranged at an inclination angle of 10 to 30 degrees with respect to the circumferential direction (equatorial plane of the tire). They are superimposed so that they intersect. Here, the belt reinforcing layer applied to the radial tire of the present invention is one or more cord reinforcing layers disposed so as to cover at least the belt end, and the belt reinforcing layer is formed from one belt end to the other. A so-called cap belt in which the entire belt is covered up to the belt end is preferable (see FIG. 1), but a so-called cap layer layer in which only both ends of the belt are covered near the shoulder portion is also included (see FIG. 2). In the present invention, the high-speed durability of the radial tire can be significantly improved by using the organic fiber cord having the specific physical properties for the belt reinforcing layer of the tire.

[0013]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The tires of Examples and Comparative Examples were all tire sizes of 185 / 65R14, and the carcass cord was a tire using polyethylene terephthalate (PET), and was manufactured by an ordinary method. All the tire structures manufactured here have the same tubeless structure, the belt is a steel belt with two layers, the steel cord is 1 × 5 × 0.23, the number of shots is 34.0 / 5cm,
The angle of the first belt layer was 22 degrees left with respect to the circumferential direction, and the angle of the second belt layer was 22 degrees right with respect to the circumferential direction. Further, the belt reinforcing layer is a so-called cap belt in which the cords are arranged at 0 degrees in the circumferential direction and the entire belt end is covered from the belt end. In Examples and Comparative Examples, as the cap belt cord,
1260D / 2 nylon 6,6 (manufactured by DuPont, trade name Type728), 1500D / 2 PET or 15
A 00D / 2 aramid was used, and the number of twists was 39 × 39 (times / 10 cm) in each case. The number of shots was 50/50 mm. In addition, the denier number is shown by cutting off less than 10 denier using the actually measured denier (fineness) of the dip processing code.

Each of the above cords was treated under the following conditions in the dip treatment step in order to secure adhesion to rubber and obtain desired cord physical properties. After being immersed in the resorcinol-formalin-latex solution, the treatment temperature was 160 ° C. and the treatment time was 6 in the drying zone.
0 seconds. In the heat set zone, the processing temperature was 240 ° C., the processing time was 60 seconds, and the cord tension was 1.
It was set in the range of 0 g / d. Further, in the normalizing zone, the treatment temperature was set to 180 ° C., the treatment time was set to 60 seconds, and the cord tension was set to 0.5 g / d to dry the cord. Thus, a cord having the desired cord physical properties was obtained.

Next, the characteristics of the cords used in the examples and comparative examples were evaluated according to the cord test method shown below. Code in an oven maintained at [thermal shrinkage factor S _1, S ₂ of fiber] previously 177 ° C., in the case of thermal shrinkage rate S ₁ 0.04
g / d load, in the case of a heat shrinkage ratio S ₂ , the fiber was thermally shrunk by leaving it under a load of 0.12 g / d load for 30 minutes to measure the length of the cord at that time, before put in the oven, i.e. the amount that is shorter than the fiber length before heat shrinkage by dividing the previous code length put in the oven and heat shrinkage factor S ₁ or S ₂ of fibers. That is, it was obtained from the following equation. Heat shrinkage = ｛(fiber length before heat shrink-fiber length after heat shrink)
/ Fiber length before heat shrinkage｝ × 100 (%) [Intermediate elongation of fiber] According to the test method of JIS L1017 “constant load elongation”, let a so-called load-elongation curve be drawn by an autograph, and 2.44 g / D The elongation at the time of loading was read.

[Tire High-Speed Durability Test] Using a drum tester having a smooth drum surface made of copper and having a diameter of 1.707 m, the ambient temperature was controlled to 38 ± 3 ° C., and a JATMA standard rim size with a load of 470 kg was used. After running for 120 minutes at a speed of 81 km / hour, and after allowing to cool for 3 hours or more, the test air pressure was readjusted and the main running was started. The actual running starts at 121 km / h and the speed is increased by 8 every 30 minutes.
The speed was increased step by step at km / hour, and the speed at which the malfunction occurred and the running time were measured. The results are shown in Tables 1 and 2. The high-speed durability was indicated by an index based on a conventional example (current tire). The higher the value, the better the high-speed durability.

[0017]

[Table 1]

[0018]

[Table 2]

From the above results, the following was confirmed. In Examples 1 to 6, since the expressions (1) and (2) were simultaneously satisfied, it was found that the high-speed durability was significantly improved as compared with the conventional example (current tire). . The belt material of the current tire as a conventional example is
This is the same as that used in this embodiment. Further, Comparative Examples 1 and 2 use nylon of the same material as that of the above-mentioned Example, but Comparative Example 1 did not satisfy the above-mentioned formula (1) and Comparative Example 2
Does not satisfy the expression (2), so that the high-speed durability is not improved. Furthermore, Comparative Examples 3 and 4, as cap belt cords, are used PET and aramide respectively, for both the thermal shrinkage rate S ₁ is was less than 5.5%, high-speed durability was not improved .

[0020]

According to the present invention, by using an organic fiber cord having specific physical properties as a reinforcing cord used for a belt reinforcing layer, high-speed durability is significantly improved without adversely affecting other tire performances. The radial tire can be provided.

[Brief description of the drawings]

FIG. 1 is a right half sectional view of a radial tire according to the present invention.

FIG. 2 is a right half sectional view of another radial tire according to the present invention.

[Explanation of symbols]

 1: Bead core 2: Carcass end 3: Carcass 4: Belt 5: Belt reinforcement layer 6: Tread 7: Shoulder

Claims (3)

[Claims] 1. A carcass comprising a single or multilayer radially arranged carcass straddling between a pair of bead portions as a body reinforcing material for a sidewall portion and a tread portion connected to the bead. Has a turn-up structure in which at least one of them is wound up from the inside of the tire to the outside around the bead core of the bead portion, and at the outer periphery of the crown portion of the carcass, a belt composed of a plurality of cord arrangement layers, In a pneumatic radial tire having at least one belt reinforcing layer, in which cords are arranged in the tire circumferential direction so as to cover at least the belt end portion, the cord of the belt reinforcing layer is an organic fiber cord, physical properties, under the ambient temperature of 177 ° C., 0.04 g / dry heat shrinkage under a load of d S ₁ (%) And, and under the ambient temperature 177 ° C., a dry heat shrinkage under a load of 0.12 g / d S
_{When 2} (%), S ₁ and S ₂ are expressed by the following formulas (1) and (2): S ₁ ≧ 5.5 (1) S ₂ ≦ S ₁ -2.5 (2) A radial tire, which satisfies a relationship represented by: 2. The organic fiber cord of the belt reinforcing layer,
An intermediate elongation E (%) under a load of 2.44 g / d at an ambient temperature of 25 ° C. satisfies the relationship represented by the following formula (3): E ≦ 8.0 (3) Item 2. The radial tire according to item 1. 3. The radial tire according to claim 1, wherein the organic fiber cord is nylon.