JPS61119405A - Pneumatic tire with durability improved - Google Patents

Abstract

PURPOSE:To reduce shear strain between layer surface by arranging a composition of rubber with short fibers which has the stated dimensional and mixed with the stated ratio, in a space between numbers of rubber coated layers which compose a belt embedded between a carcass ply and a tread. CONSTITUTION:A pneumatic tire 1 includes a carcass ply 5 which is composed of a rubber coated cord layer where numbers of cords are arranged in parallel, a belt 8 which is located on the outer circumference of the carcass ply and is composed of numbers of rubber coated cord layers (belt layer) 7 that have a cord 6 where each of layers is arranged with the stated angle, and a tread 9 which is located on the outer circumference of the belt layer. In this case, a rubber sheet layer 10 which is composed of a composition or rubber with short fibers of more than 5 parts by weight, is arranged between two rubber coated layers 7 that are adjacent each other. Here, the short fibers have an average diameter of smaller than 1mum, and a ratio L/D or more than 8, where L represents an average length of the short fibers and D represent their average diameter. The thickness of the rubber sheet layer 10 is set to be from 0.3-1.0mm.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The pneumatic tire with improved durability of the present invention, e.g.
This invention relates to a pneumatic tire with improved durability by arranging a rubber sheet layer in which short fibers are oriented as much as possible between the belt layers.

(Conventional technology) Recently, tires with excellent durability have greatly improved with the advent of radial tires, but with the development of expressways and improvements in the performance of automobiles, long-term driving at high speeds and high loads has further increased. ing. Therefore, there is a desire for tires to withstand long-term high-speed running, and to have significantly improved performance. An example of a conventional pneumatic tire with excellent durability is the one shown in FIG. In Fig. 3, 31 is a conventional pneumatic tire with excellent durability;
The pneumatic tire 31 has a bead portion 32, a carcass ply 33, a belt 34, and a tread 35. The belt 34 is located on the outer peripheral surface of the carcass ply 33, is provided between the carcass ply feathers and the tread trail, and acts as a hoop to suppress the radial outward growth of the carcass ply. As shown in FIG. 4, the belt 34 usually has 2 to 4 layers (
FIG. 3 shows an example of four layers). The belt layer 36 includes coated rubber 39 covering steel cords 38 arranged at a predetermined angle.

Road surface irregularities or impacts that the pneumatic tire receives during running are alleviated as deformation strain, bending strain, and shear strain between the eyebrows of the steel cord of each layer of the belt 34, the coated rubber 39, and the rubber sheet layer 37. FIG. 4 shows a change in the magnitude of shear strain between the belt layers 36, as indicated by arrow A, and a large shear strain has occurred in the coated rubber 39. When running at high speed for a long period of time, the durability of the rubber sheet layer nails is insufficient, causing fatigue failure due to repeated large shear strain between the eyebrows, and the belt layer 36 peels off, causing failure. There is. If the hardness of the rubber sheet layer 37 is increased, a problem arises in that extremely large shear strain occurs between the rubber sheet layer groups, leading to breakage.

(Objective of the Invention) Therefore, the object of the present invention is to alleviate the large shear strain occurring between the belt layers as much as possible without changing the rigidity of the belt as a hoop.

This minimizes the shear stress or strain that occurs inside the belt due to tire pressure or load, especially the in-plane shear strain that occurs between the eyebrows of the belt layer, improving the durability of the belt. The purpose is to provide pneumatic tires.

(Structure of the Invention) The pneumatic tire of the present invention with improved durability consists of a bead wire located at the bead portion and a rubberized cord layer in which a large number of cords are arranged in parallel, and both ends are folded back at the bead portion. A belt consisting of a carcass ply secured to a bead wire, a plurality of rubber coated cord layers located on the outer peripheral surface of the carcass ply and each layer having cords arranged at a predetermined angle, and a tread located on the outer peripheral surface of the belt. In a pneumatic tire comprising: and, short fibers having an average diameter of 1 μm or less and an average length to average diameter ratio (L/D) of 8 or more are interposed between two adjacent rubber coated cord layers. It is characterized by comprising a rubber sheet layer made of a rubber composition containing 5 parts by weight or more. Further, it is preferable that the thickness of the rubber sheet layer of the rubber composition is 0.3 to 1.0 mm. Further, it is preferable that the angle between two adjacent rubber coated cord layers sandwiching the equatorial plane of the tire is 60 degrees or less, and a rubber sheet layer is provided between the two coated cord layers. In addition, in the rubber sheet layer after vulcanization, the elastic modulus M1 at 50% strain when pulled in the direction in which the short fibers are arranged, and the elastic modulus M2 at 50% strain when pulled in the direction perpendicular to the direction in which the short fibers are arranged. The ratio of (M
l/M2) is preferably 2.5 or more. Also,
It is preferable that the short fibers are made of a thermoplastic polymer having an amide group, and are grafted via a condensate of a rubber portion and a phenol formaldehyde resin. It is preferable that the orientation direction of the short fibers in the rubber sheet layer is at an angle of 0 degrees to 10 degrees with respect to the circumferential direction. Further, it is preferable that the orientation direction of the short fibers in the rubber sheet layer is at an angle of 80 degrees to 90 degrees with respect to the circumferential direction. Also,
The elastic modulus of the short fiber rubber sheet layer after vulcanization at 100% strain when pulled in the orientation direction of the short fibers is 1.5 times or more the elastic modulus of the belt coated rubber at 100% strain. preferable.

In the present invention, the average diameter of short fibers is limited to 1 μm or less for the following reasons.

Originally, when strain (stress) is applied to short fibers, large shearing stress is applied to both ends of the short fibers, and due to the shear stress, cracks occur and grow from both ends of the short fibers, resulting in a short fiber reinforced rubber composition. There was a strong tendency to produce large leaps characteristic of . It is known that the shear stress greatly depends on the shape of the short fibers, and it goes without saying that the smaller the short fibers are, the less strain will be applied to both ends of the short fibers, and the smaller the shear stress will be. Become.

As the short fibers become smaller, the reinforcing effect per short fiber becomes smaller, but since the number of short fibers increases, overall, the inclusion of short fibers increases fatigue resistance, especially creep after repeated strain. can be prevented. Furthermore, it is possible to exhibit high elastic modulus, excellent cut resistance, and high anisotropy utilized in the present invention, which are the objectives of short fiber reinforcement.

In order to bring out the merits of the short fiber reinforcement mentioned above, it is necessary that the aspect ratio (L/D) is 8 or more,
In order to maintain this aspect ratio at 8 or more and reduce the shear stress applied to both ends of the short fibers to a level that does not pose a problem,
The average diameter of short fibers must be 1 μm or less.

In the present invention, the reason why the amount of short fibers is limited to 5 parts by weight or more is that if it is less than 5 parts by weight, the effect of reinforcing short fibers, which is the object of the present invention, cannot be expected.

In the present invention, the thickness of the rubber sheet of the short fiber-reinforced rubber composition containing short fibers is limited to 0.3 to 1° OI. This is because the purpose is to minimize the in-plane shear strain that occurs between the eyebrows of the belt layer, so a sufficient effect cannot be expected with this thinness. Conversely, if it exceeds 1.0 mIn,
The distance between the eyebrows of two adjacent belt layers becomes too large, and the weight of the entire belt increases, which is not practical. Additionally, as the distance between the belt layers increases, the movement of the steel cord in the belt layers increases, making it easier for cracks to occur and grow (in the worst case, this can lead to separation failure between the belt layers). .

In the present invention, a rubber sheet layer is provided between two adjacent rubber-coated cord layers (i.e., belt layers) in which the angle between the cords sandwiching the equatorial plane E of the tire is 60 degrees or less. It is preferable to provide one for the following reason. Assuming that the belt layers constituting the belt are the first belt layer, second belt layer, third belt layer, and fourth belt layer from the carcass ply side, the angle of the steel cord in each belt layer with respect to the tire circumferential direction is from the outside to the inside. Looking at the tire's equatorial plane E, the angle is upward to the right (hereinafter abbreviated as R) 65 degrees (i.e. R65 degrees), R approximately 2
0 degree, upward left (hereinafter abbreviated as L) approximately 20 degrees, and L30 degrees. At this time, the shear strain that occurs between two adjacent belt layers is due to the fact that the interlayer P between the second belt layer and the third belt layer, where the angle between the cords sandwiching the equatorial plane E of the tire is 40 degrees, is large; This is because the rubber sheet layer of the invention is most effective when inserted into this interlayer P.

In the present invention, the angle θ between the circumferential direction of the tire and the orientation direction of the short fibers in the short fiber reinforced rubber (reinforcement rubber angle) is 0 degrees to
The angle θ is preferably 10 degrees or 80 degrees to 90 degrees, because the effect of anisotropy (the effect of preventing belt interlayer stress from concentrating on the belt coating rubber) can be best exhibited within this angle θ range. Here, the angle θ between the circumferential direction of the tire and the direction in which the short fibers in the short fiber reinforced rubber are arranged is measured as an "acute angle".

In the present invention, in the short fiber reinforced rubber after vulcanization, the elastic modulus M1 at 50% strain when pulled in the direction in which the short fibers are arranged, and the elastic modulus M1 at 50% strain when stretched in the direction perpendicular to the direction in which the short fibers are arranged. It is preferable that the ratio of elastic modulus M2 under strain (Ml/M2) is 2.5 or more, which indicates the degree of orientation of the short fibers, and contains short fibers oriented to this degree. As mentioned above, the short fiber reinforced rubber composition is prepared by adjusting the angle θ between the circumferential direction of the tire and the orientation direction of the short fibers in the short fiber reinforced rubber from 0 degrees to
The greatest effect is produced when the angle is 10 degrees or 80 to 90 degrees.

In the present invention, it is preferable to use a thermoplastic polymer having an amide group as the material for the short fibers.
This is because the short fibers have excellent fatigue resistance because polymers having amide groups are easy to crystallize, and orientation of crystals is relatively easy, making it difficult to form spherulites. Further, the crystal melting point of the polymer having an amide group is usually 200''C or higher, and there is no problem in terms of heat resistance.

In the present invention, it is preferable that the short fibers and the rubber portion are grafted via a condensate of phenol formaldehyde resin. This is because the fatigue resistance of rubber can be improved.

However, the material of the short fibers is not limited to this example.
It may also be a thermoplastic polymer such as polybutadiene or isotaftic polypropylene.

Examples will be described in more detail below.

(Examples 1 to 8) Example 1 shows that the pneumatic tire of the present invention is significantly improved in durability performance compared to conventional tires, and the orientation angle of short fibers is The preferred angles are 0 to 10 degrees and 80 to 90 degrees.

(1) Manufacturing method of reinforced rubber composition In a 00C Banbury mixer (manufactured by Kobe Steel), the temperature was adjusted to 150°C and the rotor rotation speed was adjusted to 1100 rpm.
Natural rubber 1400 with a Mooney viscosity of 25 at 100°C
g, and 14 g of N-(3methacryloyloxy-2-hydroxypropyl)-N'-phenyl-P-phenylenediamine [TSUKRAK G-1, manufactured by Daien Shinko Co., Ltd.] were added, and the wire was heated for 1 minute. Next, 6-nylon (product name: 1
030B, manufactured by Ube Industries, melting point 221°C, molecular weight 300
00) and kneaded for 7 minutes.

During this time, the temperature inside the Banbury mixer rose to 232°C, and the 6-nylon melted. Next, novolac type phenol formaldehyde initial condensate (Meisho Kasei ■
After mixing for 7 minutes, 3 g of hexamethylenetetramine was added, and 2.
After kneading for 5 minutes (during which time the temperature of the bump of the Banbury mixer was 230° C.) to cause a graft reaction, the mixture was dropped to the bottom of the Banbury mixer and taken out.

Next, the obtained kneaded material has a nozzle inner diameter of 2III
Using a 30 mmφ extruder (manufactured by Ikegai) with a circular die with a length to inner diameter ratio (L/D) of 2, the extrudate was extruded into a string at a set temperature of 235°C, and the extrudate was heated to 0°C. It was cooled and solidified with cooling water, and then wound up on a bobbin through a guide roll at a draft ratio of 9 and a speed of 35 m/min. After vacuum drying this roll at room temperature for a day and night to remove adhering water,
Approximately 500 of these rolls are bundled into a sheet (2 mm thick).
, medium 150 mm), this sheet-like material was rolled by a pair of rolling rolls with a roll gap of 0.2 mm and a temperature of 60°C.
A reinforced rubber composition (sample 1) reinforced with short fibers was obtained by roll rolling to a size of 0.

(2) Manufacturing method of short fiber reinforced rubber and rubber sheet layer The above-mentioned reinforced rubber composition was blended with the ingredients and blending ratios shown in Table 1, at a temperature of 70°C, a rotor rotation speed of 7 Orp, and a
, m in an OCC Banbury mixer (manufactured by Kobe Steel) to prepare a rubber composition 1 made of short fiber reinforced rubber.

For comparison, Rubber Composition 2 and Rubber Composition 3 were created using the same blending components and blending ratios that did not include the reinforced rubber composition, but with the same manufacturing process. Further, these rubber compositions 1 to 3 were formed into rubber sheet layers with a predetermined thickness of 0.7 mm using a normal rubber roll. Since the rubber composition 1 contains a predetermined amount of short fibers, the rubber sheet layer of the present invention has the short fibers oriented in the direction in which the rubber roll is pulled out.

(Hereinafter, this page margin) Table 1 (a) Liquid IR is LIR manufactured by Clarei Soprene Chemical ■
-50.

(b) Novolac-type cashew-modified phenolic resin is a novolak-type phenolic resin modified with 40 parts by weight of cashew oil per 100 parts by weight of phenol.

(C,) The anti-aging agent is Tsurank 810-NA manufactured by Iruuchi Shinko Kagaku Kogyo@.

(d) Nobs is Tsukusera MS manufactured by Iriuchi Shinko Kagaku Kogyo @
It is A-G.

(6) Amount of short fibers (parts by weight) is the amount of short fibers in Sample 1 expressed as the amount of short fibers contained per 100 parts by weight of rubber in the rubber composition.

(3) Tire structure Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of an embodiment of a pneumatic tire with improved high-speed durability according to the present invention.

First, the configuration will be explained. In FIG. 1, a pneumatic tire 1 according to the present invention consists of a bead wire 3 located in a bead portion 2, a rubberized cord layer 5a in which a large number of cords are arranged in parallel, and both end portions 5b. The carcass ply 5 is folded back at the bead portion 2 and is locked to the bead wire 3, and the cord 6 is located on the outer peripheral surface of the carcass ply 5 and each layer is arranged at a predetermined angle (for example,
a plurality of rubber-coated layers 7 with steel cords);
That is, it has a belt 8 made of a belt layer and a trend 9 located on the outer peripheral surface of the belt 8. The rubber sheet layer 10 is provided between two adjacent rubber coated layers 7, and has an average diameter of 1 μm or less and a ratio of average length to average diameter (L
A rubber composition containing 5 parts by weight or more of short fibers having /D) of 8 or more. Moreover, the thickness of this rubber sheet layer 10 is 0.3 to 1.01III. A cord 6 sandwiching the equatorial plane E of the tire between two adjacent rubber coated layers 7
The angle formed by the two coated cord layers 7 is less than or equal to the degree of closure, and a rubber sheet layer 10 is provided between the two coated cord layers 7. Also,
In the rubber sheet layer after vulcanization, the ratio of the elastic modulus M1 at 50% strain when pulled in the short fiber arrangement direction to the elastic modulus M2 at 50% strain when pulled in the direction perpendicular to the short fiber arrangement direction (
Ml/M2) is 2.5 or more. The short fibers are made of a thermoplastic polymer having an amide group, and are grafted through a condensate of a rubber part and a phenol-formaldehyde resin.

Moreover, the orientation direction of the short fibers in the rubber sheet layer is at an angle of 0 degrees to 10 degrees with respect to the circumferential direction. Further, the orientation direction of the short fibers in the rubber sheet layer is at an angle of 80 degrees to 90 degrees with respect to the circumferential direction. In addition, the elastic modulus of the short fiber rubber sheet layer after vulcanization at 50% strain when pulled in the direction in which the short fibers are arranged is 1.5 of the elastic modulus of belt coated rubber at 50% strain.
That's more than double that.

(4) Manufacture of tire and performance test results (function) The tire was manufactured by a normal method, that is, as unvulcanized members, bead wire 3, stiffener, rubberized cord layer 5a, 4 The layers (first belt layer 7a, second belt layer 7b, third belt layer 7C, and fourth belt layer 7d) include the rubber coated layer (belt layer) 7, tread 9, sidewall, and short fibers, and have a predetermined content. A rubber sheet layer 10 having a thickness of 0.4 ++ nn is prepared. Next, the rubber sheet layer 10 is attached to a predetermined position on the surface of the second belt layer 7b by a predetermined width. Next, these prepared members are pasted in a predetermined order using a predetermined tire molding machine so that the rubber sheet layer 10 is placed between the second belt layer 7b and the third belt layer 7C to form a so-called green. Manufacture cases. Next, it is pressurized and heated in a vulcanizer to produce product tires (Examples 1 to 8).

Further, a tire of a comparative example is manufactured in the same manner as in Example 1 using a rubber sheet layer that does not contain short fibers.

The tires of these examples and comparative examples were filled with air to a predetermined air pressure, a predetermined load was applied, and then
Two performance tests are conducted: a slip angle durability drum test on the drum of a tire drum testing machine, and a crack generation test after driving on a rough road on the road surface.

When the tire is filled with air to a predetermined air pressure (approximately 7 kg/cil), a large tension is applied to the steel cord 6 within the belt 8, and the angle of the steel cord 6 changes. This angle change of the steel cord 6 is caused by the belt layer 7
There are differences in the direction of change and the amount of change. Therefore, shear stress and shear strain occur inside the belt layer 7, the rubber sheet layer 10, and between the eyebrows of the belt 8.

FIG. 2 is a partially enlarged sectional view of the second and third belt layers of the belt 8, and shows the distribution of the magnitude of shear strain occurring inside the layer in the horizontal axis direction in relation to the position within the layer. be. Shear stress and shear strain inside the belt 8 occur due to the load applied to the tires, and also occur during high-speed running as described above. However, in the pneumatic tire of the present invention, as shown in FIG. 2, a rubber sheet layer 10 containing short fibers is provided between the second belt layer 7b and the third belt layer 7c. Therefore, the magnitude of the shear strain occurring between the belt layers 7 is the maximum So (indicated by the arrow, B), and in the case of a conventional pneumatic tire (the fourth
31 (shown in the figure), and the distribution of shear strain between the belt layers is also small in the form of a valley at the boundary between the belt layer 7 and the rubber sheet layer 10.

This shows that the effect of alleviating the in-plane shear strain of the rubber sheet layer 10 containing short fibers is extremely large. Because the shear strain inside the belt 8 is small, in Example 1, the running distance in the high-speed durability test was significantly improved compared to the comparative example, as will be described later. It can be seen that the effect of the rubber sheet layer is extremely large.

In addition, in the above-mentioned embodiment, the case where the rubber sheet layer was provided between the second belt layer 7b and the third belt layer 7c was described, but the present invention is not limited to this case. Any cord angle of the layer may be used as long as it is 60 degrees or less across the tire equatorial plane E. The test results are shown in Table 2, Table 3-1, and Table 3-2, respectively.

In Table 2, Table 3-1, and Table 3-2, Examples 1 to 8
The rubber sheet layer (rubber composition magnetic 1) made of short fiber reinforced rubber was used with a rubber sheet thickness of 0.4 mm and a reinforcing rubber angle of 0 degrees as shown in the table. Further, in Comparative Example 2, a normal rubber sheet layer not containing the short fiber reinforced rubber described in the table was used. Comparative Example 1 did not use a rubber sheet layer.

In Table 2, in the tire of Example 1, the rubber sheet layer 10 is provided between the second belt layer and the third belt layer (the Mardo angle is 40 degrees with the equatorial plane E in between). The in-plane shear strain is extremely small. Therefore, the number of slip angle durability drums is excellent at 1246 times, and the occurrence of cracks after running on rough roads is also reduced by 5% compared to the conventional tire (Comparative Example 1).

This shows that the effect of reducing the shear strain of the rubber sheet layer 10 is extremely large.

In addition, in Comparative Example 3.4, a rubber sheet layer containing short fibers is provided, but the cords of the belt layer are between 1.2 and 3.4 of the belt layer, respectively. There are more than 60 drums with E in between. Therefore, there is no effect of reducing shear strain.

From the above explanation, it can be seen that the pneumatic tire according to the present invention has significantly improved high-speed durability compared to conventional tires.

In Examples 2 to 8 in Tables 3-1 and 3-2, the rubber sheet layer is provided between the second belt layer and the third belt layer. Here, tests were conducted by changing the reinforcing rubber angle θ between the orientation direction of the short fibers in the rubber sheet layer and the circumferential direction of the tire.

From the test results, the reinforcing rubber angle θ is 0 to 10 degrees or 80 degrees.
It turns out that ~90 degrees is preferable.

(Hereinafter, this page margin) Table 2 (a) θ is the angle between the circumferential direction of the tire and the orientation direction of the short fibers of the short fiber reinforced rubber.

(b) The tire size is IIR22.5, and it is a radial tire with a total tire width of 11 inches, an aspect ratio of 90, and a rim diameter of 22.5 inches.

(C) The angles of the cords of each belt layer of the tire with respect to the tire circumferential direction are as follows. The cord angle of the first belt layer is R65 degrees, the cord angle of the second belt layer is R20 degrees,
The cord angle of the third belt layer is L20 degrees and the cord angle of the fourth belt layer is L30 degrees.

(d) The position between the rubber sheet layers of 2.3 indicates that the rubber sheet layer was provided between the second belt layer and the third belt layer.

(Hereinafter, this page margin) Table 3-1 Table 3-2 (a) Slip angle durability drum is JIS 100%
The value was evaluated by running at a load of 60 km and applying a slip angle of 3.5 degrees alternately on the left and right sides, and the number of cycles until tire failure occurred.

(b) For cracks after driving on rough roads, the test tire was installed on the drive wheel, and after driving for 20,000km+, it was dissected and the length of the crack at the belt end was calculated over the entire circumference of the tire, measured at 8 locations, and averaged. The obtained value was put into the following formula and evaluated.

Crack length on belt end of test tire Formula-X 100 Control tire (comparative example 1 tire) tire) crack length Therefore, those with smaller values are better.

(Examples 9 to 13) In Examples 9 to 13, the graft ratio of short fibers (a) used in the present invention was measured and calculated as follows.

2 g of the reinforced rubber composition obtained in Example 1 was mixed with 20 g of benzene.
0 ml at room temperature to dissolve the rubber component in the reinforced rubber composition, and the resulting slurry was centrifuged at room temperature to separate into a solution portion and a precipitate portion. After repeating the above operation seven times on the precipitated portion, the precipitated portion was dried to obtain nylon fibers. This nylon fiber was dissolved in a mixed solvent of phenol and orthodichlorobenzene (1:3 C weight ratio) and analyzed by nuclear magnetic resonance spectroscopy (NMR) using hydrogen nuclei H (internal standard: tetramethylsilane). The cut area method was used for each peak of the methyl group and methylene group originating from natural rubber, the methylene group adjacent to the CO group originating from 6-nylon, the methylene group adjacent to the NH group, and the other three methylene groups. Find the molar ratio of 6-nylon and natural rubber by
The grafting rate was calculated. Further, the shape of about 200 fibers was measured using a scanning electron microscope at a magnification of 10,000 times. The fibers were extremely thin short fibers with a circular cross section. Sample 3 has short fibers with an average diameter of 1.1 μm.
This exceeds the average diameter limit of 1 μm according to the present invention. In addition, the reinforced rubber compositions obtained according to Table 4 (Samples 2 to 6
), rubber compositions 4 to 8 were manufactured according to the manufacturing method of (2) short fiber reinforced rubber and rubber sheet layer in (Examples 1 to 5), and further, each rubber composition was used to manufacture rubber compositions 4 to 8, respectively. .

A reinforcing layer was produced. Here, the compounding components of rubber compositions 4 to 8 are shown in Table 5, and rubber composition 5 uses sample 3, and is a rubber composition in which the average diameter of short fibers exceeds 1°0 μm. be.

Next, as shown in Table 6, using the rubber sheet layers of the aforementioned rubber compositions 4 to 8, Examples 9 to 13 and Comparative Examples 5 to
No. 8 tires were manufactured according to the tire manufacturing process described above (Example 1), and then performance tests were conducted. Performance test results are shown in Table 6-1 and Table 6-2.

In Table 6-1, Examples 9 to 11 all used Sample 2, Sample 4, and Sample 6 in Table 4, each of which had short fibers with an average diameter of 1 μm or less, and the results of the two performance tests showed good results. It shows.

On the other hand, in the tire of Comparative Example 5, the average diameter of short fibers in the rubber composition was 1. Rubber composition 5 was used in excess of OIlm, and the two performance test results were poor.

That is, if the average diameter of the short fibers exceeds 1 μm, the short fibers will have a large foreign substance effect, which is not preferable.

From the above explanation, the average diameter of the short fibers is limited to 1 μm or less.

In addition, the tire of Comparative Example 8 has an aspect ratio of short fibers L/D
Sample 5 with 7.8 was used, and as shown in Table 6-2, the two performance test results were poor. This shows that the aspect ratio of the short fibers is preferably 8 or more.

(Hereinafter, this page margin) Table 5 Table 6-1 Table 6-2 (a) Table 6-1 and Table 6-2 include tire size 29
5/75 R22.5 tubeless tires were used.

(b) The belt structure consists of four belt layers, and the angle between the cords of each belt layer and the circumferential direction of the tire is as follows. The first belt layer is R65 degrees, the second belt layer is right 1
5 degrees, 3rd belt layer 15 degrees left, 4th belt layer 25 degrees left
degree.

(Example 14.15) In Example 14.15, the thickness of the short fiber reinforced rubber layer installed between the carcass ply and the dwarf wire was 0.31II.
It shows that it is limited to cA~1.0III11.

In Example 14.15 and Comparative Example 9.10, a rubber sheet layer of short fiber reinforced rubber was produced from rubber composition 4 using reinforced rubber composition sample 2) according to the manufacturing method of Example 1. Ta. Each tire was manufactured using a rubber sheet layer having the thickness shown in Table 7, and then a heat generation durability drum test was conducted. Based on the heat generation durability drum test in Table 7, the maximum load % at the time of tire failure
As can be seen from the results for the rubber sheet layer, the running distance was low even when the thickness of the reinforcing layer was less than 0.3III11 or more than 2.0 mm. From this, the thickness of the short fiber reinforced rubber layer is 0.3 yam to 2. OnuIl thickness is desired. This means that as the thickness of the rubber sheet layer containing short fibers increases, the hoop rigidity of the belt as a whole decreases.
This is because the diameter of the tire has grown, and as a result, the heat generation durability of the tire has decreased.

Table 7 (a) The cord angle of the belt layer is R6 for the first belt layer.
5 degrees, the second belt layer is R20 degrees, and the third belt layer is L2
0 degrees, and the fourth belt layer is 530 degrees.

(b) The heat generation durability drum test was conducted at a drum speed of 60 km/h.
First, the vehicle was run for 24 hours at 100% JIS load, and then for 24 hours at 120% load. After that, if there is no failure, increase the load by 20%.
The evaluation is based on whether the tire fails under load.

Examples 16.17 Examples 16.17 demonstrate that the amount of short fibers in the short fiber reinforced rubber is limited to 5 parts by weight or more.

A rubber composition was prepared in the same manner as in Example 1 using the aforementioned reinforced rubber composition (Sample 1) and using the compounding components in Table 8 so that the amount of short fibers in the short fiber reinforced rubber was 5 parts by weight or more. 9
．． 10 were manufactured. The amount (parts by weight) of short fibers was 3 parts by weight for rubber composition 9 and 5 parts by weight for rubber composition 10. Using these rubber compositions, a thickness of 0 was obtained in the same manner as in Example 1.
．． 5III11 rubber sheet layers were produced. Using this reinforcing layer, Example 16.17 and Comparative Example 9 in Table 9
．． Ten tires were manufactured in the same manner as in Example 1 and two tire tests were conducted. The excellent results of Examples 16.17 are shown in Tables 9-1 and 9-2. This shows that the amount of short fibers is required to be 5 parts by weight or more.

(Hereinafter, this page margin) Table 8 Table 9-1 Table 9-2 Table 10 In addition, 1s disclosed in Japanese Patent Application Laid-open No. 10632/1983
It is fully possible to arrange the o-polypropylene short fibers so as to exhibit "high anisotropy" which is an essential requirement of the present invention. Also, Special Publication No. 57-4527, Special Publication No. 57-4
The 5yn-1,2-polybutadiene short fibers disclosed in Japanese Patent Publication No. 530 and Japanese Patent Publication No. 57-30662 can also be used in any way. However, most preferred are the nylon short fibers used in the present invention.

Furthermore, the present invention is not limited to the above-mentioned embodiments, and can be used in radial tires using organic fibers as belts, bias tires with belts (belted bias tires), bias tires, etc., and can also be used in tires for passenger cars. It is also applicable to large tires as well.

(Effects of the Invention) As explained above, the short fiber reinforced rubber composition containing micro short fibers is sufficiently oriented, and the orientation direction of the short fibers is 0 to 10 degrees or 80 degrees to the circumferential direction of the tire. ~9
By placing this short fiber reinforced rubber composition (rubber sheet layer) between the belt layers so that the angle is 0 degrees,
The in-plane shear strain occurring between the second belt layer and the third belt layer can be significantly reduced without changing the belt's tassel v4C1 properties. In addition, angle changes occur in the steel cord of the belt due to tire air pressure or applied load, and the shear strain that occurs in the belt layer and rubber sheet layer due to the angle change of the steel cord also greatly increases the total thickness of the belt. Therefore, the strain distribution can be reduced. It is possible to provide a pneumatic tire with significantly improved high-speed durability.

[Brief explanation of drawings]

Figure 1.2 relates to the invention. An embodiment of a pneumatic tire with improved high-speed durability is shown, and FIG. 1 is a sectional view thereof, and FIG. 2 is a partially enlarged sectional view of a belt layer. Figure 3 is a cross-sectional view of a conventional pneumatic tire, and Figure 4 is a cross-sectional view of a conventional pneumatic tire.
FIG. 2 is a partially enlarged sectional view of the belt layer of the pneumatic tire shown in the figure. 1--------1 pneumatic tire, 2--------bead section, 3--bead wire, 5------1 carcass ply, 6--------cord (steel cord), 7 ------
-Rubber coated cord layer (belt layer), 8...---
-Belt, 9--Tread, 10--Rubber sheet layer. Figure 1 Figure 2 Date Figure 3

Claims (8)

[Claims] (1) A bead wire located at the bead portion, a carcass ply consisting of a rubberized cord layer with a large number of cords arranged in parallel, both ends of which are folded back at the bead portion and locked to the bead wire, and an outer peripheral surface of the carcass ply. A pneumatic tire comprising a belt consisting of a plurality of rubber-coated cord layers, each layer having cords arranged at a predetermined angle, and a tread located on the outer peripheral surface of the belt. A rubber sheet layer made of a rubber composition containing 5 parts by weight or more of short fibers having an average diameter of 1 μm or less and a ratio of average length L to average diameter D (L/D) of 8 or more is provided between the coated cord layers. A pneumatic tire with improved durability. (2) The thickness of the rubber sheet layer of the rubber composition is 0.3 to 1.
A pneumatic tire with improved durability according to claim 1, characterized in that the tire diameter is 0 mm. (3) A patent characterized in that, among two adjacent rubber coated cord layers, the angle between the cords sandwiching the equatorial plane of the tire is 60 degrees or less, and a rubber sheet layer is provided between the two coated cord layers. A pneumatic tire with improved durability according to claim 1. (4) Elastic modulus M1 at 50% strain when pulled in the direction of short fiber arrangement in the rubber sheet layer after vulcanization, and elastic modulus at 50% strain when pulled in the direction perpendicular to the short fiber arrangement direction. M2
2. A pneumatic tire with improved durability according to claim 1, wherein the ratio (M1/M2) is 2.5 or more. (5) Claim 1, characterized in that the short fibers are made of a thermoplastic polymer having an amide group, and are grafted via a condensate of a rubber part and a phenol formaldehyde resin. Pneumatic tires with improved durability as described. (6) The air with improved durability according to claim 1, characterized in that the orientation direction of the short fibers in the rubber sheet layer is at an angle of 0 degrees to 10 degrees with respect to the circumferential direction. Included tires. (7) The air with improved durability according to claim 1, wherein the orientation direction of the short fibers in the rubber sheet layer is at an angle of 80 degrees to 90 degrees with respect to the circumferential direction. Included tires. (8) The elastic modulus of the short fiber rubber sheet layer after vulcanization at 50% strain when pulled in the orientation direction of the short fibers is 1.5 times or more of the elastic modulus of the belt coated rubber at 50% strain. A pneumatic tire with improved durability as claimed in claim 1.