JP2000108612A - Pneumatic tire and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving high-speed performance. SOLUTION: This pneumatic tire is provided with a carcass 6 and a belt layer 7 composed of at least two piece of belt ply 7A, 7B which are disposed outward in a tire radius direction of the carcass 6 and within a tread 2, and arranging steal cords in such a way to lean to a tire equator C. In this case, a tread rubber layer 9 disposed outward in the tire radius direction of the belt layer 7 is composed of a reinforcing rubber layer 10 disposed in the outside of the belt layer 7 and having a thickness of 0.2 to 1.0 mm, and a tread rubber layer 11 disposed outward in the tire radius direction of the reinforcing rubber layer 10. The reinforcing rubber layer 10 is made from a rubber composition including a rubber reinforcing short fiber of at least 10 to 30 weight part to 100 weight part of a rubber base material and organic acid cobalt salt of 0.5 to 2.5 weight part. Furthermore, the short fiber is substantially orientated in a tire circumferencial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving high-speed performance and a method for manufacturing a pneumatic tire.

[0002]

2. Description of the Related Art In recent years, radial structures have become widespread for pneumatic tires, especially for pneumatic tires for passenger cars and light trucks. In such a radial structure, since a belt layer made of a tough steel cord is arranged on the tread, there is an advantage that the abrasion resistance of the tread and the steering stability at high speed running are superior to the bias structure tire. is there.

However, in recent years, higher output and higher performance of vehicles have demanded further improvement in high-speed performance of tires. Generally, when running at an ultra-high speed with a radial tire, a so-called lifting phenomenon occurs in which both end edges of the belt layer float outward in the tire radial direction. At this time, the end of the steel cord of the belt layer having a low adhesive strength to the rubber is peeled off from the surrounding rubber, and the adhesive is broken to reduce the durability at high speed.

In order to solve such a problem, for example, as shown in FIG. 6, an organic fiber cord is spirally wound around the belt layer b made of steel cord in the tire radial direction substantially along the tire circumferential direction. It has been proposed to provide a turned band f (for example, JP-A-8-40013).

[0005] Such a band f can improve the high-speed performance by suppressing the lifting of the belt layer b, but increases the cost of manufacturing the tire, and requires a work process for winding the organic fiber cord. There is a problem that the productivity of the tire is reduced due to the increase.

The present invention has been made in view of such circumstances, and in the invention according to claim 1, a reinforcing rubber layer containing short fibers oriented substantially in the tire circumferential direction instead of the band. It is an object of the present invention to provide a pneumatic tire capable of improving high-speed performance without causing a significant increase in tire cost and a decrease in productivity, based on the fact that the tire is provided outside the belt layer in the tire radial direction.

According to the second and third aspects of the present invention, a sheet-like reinforcing rubber layer in which short fibers are oriented substantially in the circumferential direction and extruded is provided on the tread rubber of the tire.
The tread rubber layer disposed on the outside is formed using a raw composite rubber body that is integrally molded, improving the dimensional stability of the tread rubber, improving productivity and improving the high-speed performance with high accuracy. It is an object of the present invention to provide a pneumatic tire manufacturing method capable of manufacturing a pneumatic tire that can be manufactured.

[0008]

According to a first aspect of the present invention, there is provided a carcass extending from a tread portion through a sidewall portion to a bead core of a bead portion, a carcass outside of the carcass in a tire radial direction and an inside of the tread portion. And a belt layer composed of at least two belt plies in which steel cords are arranged at an angle to the tire equator C, wherein the tread portion has a radially outer side of the belt layer with respect to the tread portion. Is arranged outside the belt layer and has a thickness of 0.2 to 1.
A reinforcing rubber layer having a thickness of 0 mm and a tread rubber layer disposed radially outside the reinforcing rubber layer in the tire radial direction, and the reinforcing rubber layer is at least 10 to 30 parts by weight based on 100 parts by weight of the rubber base material. And a rubber composition containing 0.5 to 2.5 parts by weight of an organic acid cobalt salt, and the short fibers are substantially oriented in the tire circumferential direction.

According to a second aspect of the present invention, there is provided a carcass extending from a tread portion to a bead core of a bead portion via a sidewall portion, and a belt layer disposed outside the carcass in the tire radial direction and inside the tread portion. And a tread rubber disposed on the tire radial direction outside of the belt layer of the tread portion, a sheet-like reinforcing rubber layer in which short fibers are substantially oriented in a circumferential direction, and a tread disposed outside the sheet-like reinforcing rubber layer. A pneumatic tire manufacturing method, characterized in that the pneumatic tire is formed using a raw composite rubber body integrally molded with a rubber layer.

According to a third aspect of the present invention, the tread rubber layer comprises a cap rubber forming a tread surface and a base rubber layer disposed radially inward of the tire in the tread rubber layer. 3. The method for manufacturing a pneumatic tire according to claim 2, comprising a three-layer structure of a reinforcing rubber layer, a base rubber layer, and a cap rubber layer.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the pneumatic tire according to this embodiment includes a tread portion 2 and a sidewall portion 3.
And a carcass 6 reaching the bead core 5 of the bead portion 4 through
The outer side of the carcass 6 in the tire radial direction and the tread portion 2
And a belt layer 7 disposed inside the vehicle.

The carcass 6 has at least one carcass cord having a radial structure in which carcass cords are arranged at an angle of 75 ° to 90 ° with respect to the tire equator C, in this embodiment, one carcass ply 6.
A. In the present embodiment, the carcass cord employs a polyester cord, but other than this, an organic fiber cord such as nylon or rayon can be favorably employed. Note that an aramid cord, a steel cord, or the like may be employed as the carcass cord according to the type of tire.

The carcass 6 passes through the bead core 5 of the bead portion 4 from the tread portion 2 through the sidewall portion 3.
And a folded portion 6b which is continuous with the body portion 6a and is turned around the bead core 5 from inside to outside in the tire axial direction. A bead apex 8 extending from the bead core 5 in the tire radial direction and made of hard rubber is disposed between the main body 6a and the folded portion 6b to reinforce the bead portion 4.

In the present embodiment, the belt layer 7 is composed of at least two belt plies 7A and 7B in which steel cords are arranged at a small angle of 10 to 35 ° with respect to the tire equator, in this embodiment two inner and outer belt plies. Are overlapped in a direction in which the cords cross each other. Note that the belt ply 7A in the radial direction is formed wider than the outer belt ply 7B, and the rigidity step at the end of the belt layer 7 is reduced.

In the present embodiment, the tread portion 2
The tread rubber 9 disposed outside the belt layer 7 in the tire radial direction is disposed outside the belt layer 7 and has a thickness t.
Is exemplified by a reinforcing rubber layer 10 having a thickness of 0.2 to 1.0 mm and a tread rubber layer 11 disposed radially outside the reinforcing rubber layer 10 in the tire radial direction. Further, the tread rubber layer 11 of the present embodiment includes a cap rubber 11a forming a tread surface 2a which is an outer surface of the tread portion 2,
Base rubber layer 11b disposed radially inward of the tire
Are exemplified.

The reinforcing rubber layer 10 contains at least 10 to 30 parts by weight of short fibers for reinforcing rubber and 0.5 to 2.5 parts by weight of an organic acid cobalt salt with respect to 100 parts by weight of a rubber base material. One of the features is that the short fibers are made of a rubber composition, and the short fibers are substantially oriented in the tire circumferential direction.

In the reinforcing rubber layer 10, the short fibers are substantially oriented in the tire circumferential direction, so that the elastic modulus in the tire circumferential direction can be increased without increasing the rigidity in the tire radial direction. it can. For this reason, the reinforcing rubber layer 10 covers the outer side of the belt layer 7 in the tire radial direction, thereby suitably restraining the displacement of the belt layer 7 in the same manner as the conventional band. Lifting at both edges can be suppressed. Further, such a reinforcing rubber layer 10 can suppress the vibration of the belt layer 7 and also reduce the occurrence of road noise. Further, such a reinforcing rubber layer containing short fibers is inexpensive and excellent in productivity as compared with a band formed by winding an organic fiber cord.

In the present embodiment, the reinforcing rubber layer 10 is
The belt layer 7 is illustrated over substantially the entire width. This is preferable in that the lifting of the belt layer 7 can be suppressed over a wide range. It is to be noted that such a reinforcing rubber layer 10 can be provided only at both edges of the belt layer 7 where the lifting amount is the largest.

As the short fibers for reinforcing rubber contained in the reinforcing rubber layer 10, for example, organic fiber materials such as nylon, rayon, polyester, aromatic polyamide, cellulose resin, crystalline polybutadiene and cotton thread are preferable. In addition, inorganic fiber materials such as carbon fiber, metal fiber, whisker, boron and glass fiber can be used.

The short fibers have a diameter of, for example, greater than 1 μmm and 0.1 mm or less, and a length of, for example, 2 μm.
Those having a thickness of 0 μmm to 2 mm are preferred. The reason for limiting the diameter and length of the short fibers in this way is that the rubber reinforcing effect is relatively inferior when the diameter and length of the short fibers are smaller than the above values,
This is because if the value exceeds the above value, the fatigue resistance of the reinforcing rubber layer 10 tends to deteriorate. The expression "the short fibers are substantially oriented in the tire circumferential direction" includes those in which the inclination of the short fibers in the longitudinal direction with respect to the tire circumferential direction is in the range of 0 to 20 °.

The short fibers are kneaded with a rubber substrate or the like, and when the reinforcing rubber layer 10 is continuously formed into a sheet by rolling using, for example, a calender roll r as shown in FIG. The orientation direction of F can be substantially aligned with the material feeding direction. Alternatively, extrusion from an extruder provided with a forming die may be used.

Here, the thickness t of the reinforcing rubber layer 10 is 0.2
If it is less than mm, the orientation of the short fibers will be very excellent, but the material will be too thin and it will be difficult to handle in the process of molding the tire, and the general durability of the tire will tend to decrease It is in. Conversely, if the thickness t of the reinforcing rubber layer 10 exceeds 1.0 mm, there is a problem that the orientation of short fibers tends to decrease and the weight of the tire increases. From such a viewpoint, the thickness of the reinforcing rubber layer 10 is 0.2 to 0.2.
It is desirably 1.0 mm, preferably 0.3 to 1.0 mm, and more preferably 0.5 to 1.0 mm.

In the rubber composition constituting the reinforcing rubber layer 10, if less than 10 parts by weight of the short fibers are blended in 100 parts by weight of the rubber base material, the effect of reinforcing the rubber in the circumferential direction by the short fibers is reduced. I can't get it. Conversely, 30 short fibers
If the amount is more than 10 parts by weight, the adhesion to the rubber base material is deteriorated, and the adhesion to rubber and the durability after vulcanization are reduced. It is particularly preferable to include 10 to 28 parts by weight of short fibers with respect to 100 parts by weight of the rubber base material.

The rubber composition of the reinforcing rubber layer 10 contains 0.5 parts by weight of an organic acid cobalt salt per 100 parts by weight of a rubber base material.
２．５2.5 parts by weight. That is,
In order to improve the high-speed running performance, it is very important to prevent the steel cord of the belt layer 7 from peeling off from the surrounding rubber. However, the reinforcing rubber layer 10 and the steel Cord belt layer 7
And the high-speed durability can be further improved in combination with the restraining effect of the belt layer 7. In addition, although cobalt stearate is preferable as an organic acid cobalt salt, cobalt naphthenate, cobalt rhodisonate, etc. can also be used.

The reinforcing rubber layer 10 may be made of various types of rubber base materials in accordance with the customary manner. For example, one or two or more rubbers such as natural rubber and diene-based synthetic rubber may be blended and appropriately. It goes without saying that, in addition to the short fibers and the organic acid cobalt salt, an appropriate compounding agent such as carbon black, an antioxidant, zinc oxide, sulfur, and a vulcanization accelerator can be added.

Further, since the cap rubber 11a is in direct contact with the road surface, rubber having high wear resistance and rubber having excellent wet running properties can be preferably used. On the other hand, the base rubber 11b has heat generation resistance. Rubber or the like having excellent properties can be used as needed.

In such a pneumatic tire, when manufacturing a raw cover, as shown in FIG. 2, the tread rubber 9 is extruded into a sheet-like and unformed sheet in which short fibers are oriented substantially in the circumferential direction. A vulcanized reinforcing rubber layer 10 and an unvulcanized tread rubber layer 11 disposed outside thereof are molded using a green composite rubber body G1 integrally molded, and vulcanized. Is particularly preferred.

In such a raw composite rubber body G1, since the tread rubber layer 11 and the reinforcing rubber layer 10 are integrated,
The dimensional change of the tread rubber layer 11, which is liable to shrink or expand in a pre-vulcanized state by itself, is prevented by the reinforcing rubber layer 10, which is reinforced with short fibers and thus hardly causes a dimensional change even in an unvulcanized state. Tread rubber 9 which is excellent in quality. Therefore, the pneumatic tire formed by using this also has excellent productivity while improving accuracy and yield.

In this embodiment, the tread rubber layer 11
Is composed of the cap rubber 11a, a base rubber layer 11b disposed radially inward of the tire, and a wing rubber 12 having a substantially triangular cross section attached to both sides thereof. The figure shows a three-layer structure including a reinforcing rubber layer 10, a base rubber layer, and a cap rubber layer. The tread rubber layer 11 and the wing rubber 12 can be integrally extruded by, for example, an extruder, adhered to the reinforcing rubber layer 10 rolled by a calendar roll, and integrated to form the raw composite rubber body G1. The reinforcing rubber layer may be extruded together with the extruder.

FIG. 3 shows another embodiment of the present invention. In this example, the reinforcing rubber layer 10 is composed of a first layer 10F covering almost the entire width of the belt layer 7, and a second layer 10E disposed radially inward and covering both ends of the belt layer 7. Is exemplified. As described above, since the lifting amount of the belt layer 7 is particularly large at both edges, the two layers of the tread rubber have only two end portions so that the first layer can be formed when the tire is formed. , And the second layers 10F and 10E are preferably configured so that both end portions of the belt layer can be more constrained than the center portion. At both ends of the belt layer 7, the thickness of the reinforcing rubber layer is 2.
Acceptable up to 0 mm.

FIG. 4 shows still another embodiment of the present invention. In this example, the tread rubber 9 has the second layer 10E attached only to both ends. At this time, an undertread layer B having a thickness of 0.2 to 1.0 mm is provided inside the tread rubber layer 11 in the tire radial direction.
Is preferably arranged.

Although the embodiment of the present invention has been described in detail, the present invention can be suitably applied to a tire for a motorcycle such as a tire for a small truck.

[0033]

EXAMPLES A pneumatic tire having a tire size of 195/65 HR14 and having a basic structure shown in FIG. 1 was prototyped (Examples 1 to 7, Comparative Examples 1 and 2), high-speed performance, road noise, and process work. And general durability, and compared the performance. The rubber composition of the reinforcing rubber layer was the same except for the short fibers and the organic acid cobalt salt (cobalt stearate). The test conditions are as follows.

(1) High-speed performance The test tire was assembled on a rim and the internal pressure was 280 kPa and the load was 4.5.
The vehicle was preliminarily driven on the drum at a speed of 0 to 170 km / h at 6 kN for 10 minutes. Thereafter, the speed was increased from 170 km / h to 200 km / h in steps of 10 km / h every 10 minutes. The evaluation is indicated by an index with Comparative Example 1 being 100, and the larger the numerical value, the better.

(2) Road Noise Using a test vehicle equipped with test tires, the vehicle was driven on a road made of rough asphalt at a speed of 60 km / H, and a microphone was installed at a position corresponding to the driver's right ear to obtain overall noise. The level dB (A) was measured.
It was indicated by an index of 0. The higher the value, the lower the noise level and the better.

(3) Process workability The workability in molding the test tire was evaluated for the reinforcing rubber layer in the following three stages. ：: good △: slightly inconvenient ×: difficult to produce

(4) General durability The test tire is assembled on a rim, the internal pressure is 190 kPa, and the load is 6.
The vehicle was run on the drum at a speed of 57 km and a speed of 80 km / h, and the running distance until the tire was broken was compared. The result is
It is indicated by an index with Comparative Example 1 being 100, and the larger the numerical value, the better. Table 1 shows the test results and the like.

[0038]

[Table 1]

Next, the dimensional stability of the tread rubber (raw composite rubber body) in which the reinforcing rubber layer is integrated with the tread rubber layer and the tread rubber without the reinforcing rubber layer (standard raw rubber body) Cut into a predetermined length). As a result, as shown in Table 2, it was confirmed that the variation was very small when the reinforcing rubber layer was integrated with the tread rubber layer.

[0040]

[Table 2]

[0041]

As described above, according to the first aspect of the present invention, since the reinforcing rubber layer orients the short fibers substantially in the tire circumferential direction, it does not increase the rigidity in the tire radial direction. The elastic modulus in the tire circumferential direction can be increased. For this reason, the reinforcing rubber layer can suitably restrain the belt layer by covering the outer side of the belt layer in the tire radial direction, and can suppress lifting at both edges of the belt layer during high-speed running without impairing ride comfort. In addition, since the reinforcing rubber layer contains the organic acid cobalt salt, the adhesive strength between the steel cord and the belt layer is high, and the rubber peeling is further suppressed.

In addition, the occurrence of road noise can be reduced by suppressing the vibration of the belt layer. Further, such a reinforcing rubber layer containing short fibers can be produced at a lower cost than a band formed by winding an organic fiber cord.

According to the second or third aspect of the present invention, since the raw composite rubber body in which the tread rubber layer and the reinforcing rubber layer are integrated is used as the tread rubber, shrinkage or expansion occurs in a simple state before vulcanization. Since the dimensional change of the tread rubber layer that is easy to occur is reinforced by short fibers, the reinforced rubber layer that does not easily change in size even in an unvulcanized state is prevented, and a tread rubber having excellent dimensional stability can be provided. Therefore, the pneumatic tire formed by using this also has excellent productivity while improving accuracy and yield.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a pneumatic tire showing one embodiment of the present invention.

FIG. 2 is a sectional view showing an example of a raw composite rubber body used for a tread rubber.

FIG. 3 is a cross-sectional view showing another example of the raw composite rubber body used for the tread rubber.

FIG. 4 is a cross-sectional view showing another example of the raw composite rubber body used for the tread rubber.

FIG. 5 is a perspective view showing a manufacturing process of a reinforcing rubber layer.

FIG. 6 is a sectional view of a conventional pneumatic tire.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 6a Carcass ply main body 6b Carcass ply folded part 7 Belt layer 9 Tread rubber 10 Reinforcement rubber layer 11 Tread rubber layer 11a Cap rubber layer 11b Base rubber layer

Claims (3)

[Claims] 1. A carcass extending from a tread portion to a bead core of a bead portion via a sidewall portion, a carcass disposed radially outward of the carcass and inside the tread portion, and having a steel cord inclined with respect to the tire equator C. A pneumatic tire comprising a belt layer comprising at least two belt plies, wherein a tread rubber disposed radially outside the belt layer of the tread portion is disposed outside the belt layer. And a reinforcing rubber layer having a thickness of 0.2 to 1.0 mm, and a tread rubber layer disposed radially outward of the reinforcing rubber layer in the tire radial direction. At least 10 to 30 parts by weight of short fibers and 0.5 to 2.5 parts by weight
A pneumatic tire comprising a rubber composition containing a part by weight of an organic acid cobalt salt, and wherein the short fibers are substantially oriented in the tire circumferential direction. 2. A carcass extending from a tread portion to a bead core of a bead portion via a sidewall portion, and a belt layer disposed radially outward of the carcass and inside the tread portion, and The tread rubber disposed radially outward of the belt layer in the tire radial direction is integrally formed with a sheet-like reinforcing rubber layer in which short fibers are substantially oriented in the circumferential direction, and a tread rubber layer disposed outside thereof. A method for manufacturing a pneumatic tire, characterized in that the method is formed by using a raw composite rubber body obtained as described above. 3. The raw composite rubber body comprises a reinforcing rubber layer and a base rubber, wherein the tread rubber layer comprises a cap rubber forming a tread surface and a base rubber layer disposed radially inward of the tire. 3. The method for manufacturing a pneumatic tire according to claim 2, comprising a three-layer structure including a layer and a cap rubber layer.