JP2001163007A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability at high speed. SOLUTION: This tire comprises a troidal carcass 6, a belt layer 7 placed on the outside thereof, and a buttress reinforcing layer 9. The buttress reinforcing layer 9 is extended from a region K as a starting point 9a ranging within 10 mm inside and outside a tire axial direction outer end 7e of an outer belt ply 7B in the tire axial direction to a terminal end point 9b on a side wall part side. The buttress reinforcing layer 9 consists of a cord ply 10 comprising an organic fiber cord inclined 10-180 deg. to the circumferential direction of the tire. The terminal end point 9b is placed on an outer side of the tire radial direction from a sectional maximum width position M of the tire, and a length L along a carcass outer plain of the buttress reinforcing layer 9 is 15 mm or more in a meridional section of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a pneumatic tire capable of improving high-speed durability.

[0002]

2. Description of the Related Art With the recent improvement in the performance of vehicles and the development of a highway network, there has been a strong demand for improvements in high-speed durability of pneumatic tires.
Conventionally, a standing wave is known as an obstacle to the high-speed durability of a radial tire. The standing wave refers to a phenomenon in which, when the tire runs at high speed, the deformation of the tread portion generated at the contact portion does not recover even after the contact with the ground and remains as a wave of vibration behind in the rotational direction.
Such a standing wave causes a rapid rise in the temperature of the tread portion, which leads to a thermal destruction of the tire and an adhesive destruction of components.

Conventionally, in order to suppress such a standing wave generation speed or shift to a high speed region side, an organic fiber cord is provided in the tire circumferential direction on the tire radial outer side of the belt layer for tightening the toroidal carcass. It is known to provide a so-called band to be wound.
However, in the above-described method of providing the band, the weight of the tread portion is increased, and strain is likely to concentrate near the end of the belt layer, which may adversely affect the durability.

[0004] The inventors conducted various experiments, and found that
When a reinforcing layer is provided on a buttress portion that is a connection portion between the tread portion and the sidewall portion of the tire, and the rigidity of the buttress portion is increased, a restoring force for restoring the deformation of the tread portion at the time of touchdown after touchdown increases, It has been found that the generation speed of the standing wave shifts to the high speed side. In particular,
By limiting the location of the buttress reinforcing layer that reinforces the buttress portion, the cord material, and further the shape, etc., higher speed durability can be obtained and other performances deteriorate, such as rolling resistance and ride comfort. We found that there was no damage.

[0005] As described above, an object of the present invention is to provide a pneumatic tire that can improve high-speed durability and is suitable as, for example, a radial tire for a passenger car.

[0006]

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 including at least two belt plies including an outer belt ply disposed on the tire radially outermost side,
And a buttress reinforcing layer, wherein the buttress reinforcing layer is
The outer belt ply extends from the outer end of the outer belt ply in the tire axial direction inward and outward in the tire axial direction to a terminal point on the side wall portion starting from a region within 10 mm, and the buttress reinforcing layer extends 10 to 10 in the tire circumferential direction. A cord ply having an organic fiber cord inclined at an angle of 80 °, and the terminal point is located radially outward of the tire maximum cross-sectional position from the tire maximum cross-sectional position, and along the carcass outer surface of the buttress reinforcing layer in the tire meridian cross-section. Characterized in that the length is 15 mm or more.

In the pneumatic tire having such a buttress reinforcing layer, the buttress portion of the carcass can be effectively reinforced, and the standing wave can be suppressed or the generation speed can be shifted to the high speed side. The durability is improved. In addition, by limiting the arrangement position of the buttress reinforcing layer, the cord ply material, the cord angle, and the like, it is possible to suppress a significant increase in tire weight and to prevent the rolling resistance from deteriorating.

[0008] The buttress reinforcing layer can be constituted by a cord ply made of an organic fiber cord covered with a topping rubber having a loss tangent (tan δ) smaller than 0.1. In this case, the topping rubber
As a result of being made of a rubber material having a small energy loss, heat generation in the buttress portion can be suppressed, and damage due to heat generation due to, for example, high-speed running can be prevented. Further, the sidewall portion may be provided with a concave portion formed by reducing the rubber thickness of the sidewall portion, at least in a part of the sidewall portion surface and the buttress region where the buttress reinforcing layer is disposed. . In this case, heat radiation of the buttress portion is promoted by the concave portion having a reduced rubber thickness, heat generation can be reduced, and durability can be improved.

Further, the cord ply may be formed to have a wavy portion in which a center line of the amplitude is repeatedly bent at substantially the same interval as the outer surface of the carcass in the tire meridian section. Thereby, the rigidity of the buttress reinforcing layer in the tire radial direction can be relatively reduced, so that the high-speed durability and the rolling resistance can be improved in a particularly balanced manner.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a right half sectional view showing one embodiment of the pneumatic tire of the present embodiment, and FIG. 2 is an internal structure diagram schematically showing the internal structure. In the figure, a pneumatic tire 1 includes a carcass 6 extending from a tread portion 2 to a bead core 5 of a bead portion 4 through a sidewall portion 3, a tire radially outside the carcass 6 and inside the tread portion 2, and It comprises a belt layer 7 composed of at least two belt plies including an outer belt ply 7B arranged on the outermost side in the radial direction, and a buttress reinforcing layer 9 for reinforcing the buttress portion B. Is exemplified.

The carcass 6 has at least one carcass ply 6 having a radial structure in which carcass cords are arranged at an angle of 75 ° to 90 ° with respect to the tire equator C.
A. As the carcass cord, a polyester cord is used in the present embodiment, but other than this, an organic fiber cord such as nylon or rayon, or an aramid cord or a steel cord may be used. Further, the carcass 6 has a main body 6a extending from the tread portion 2 to the bead core 5 of the bead portion 4 via the sidewall portion 3 and a folded portion 6b extending from the main body portion 6a and being turned around the bead core 5. .

The main body 6a and the folded portion 6b
A bead apex 8 extending from the bead core 5 in the tire radial direction and made of hard rubber is disposed between the two to effectively reinforce the bead portion 4. In the present embodiment, the folded portion 6b has a so-called high-turn-up structure in which the end portion is located outside the tire maximum width position M in the tire meridian section including the tire axis in the tire radial direction to increase the lateral rigidity of the tire. Is exemplified. However, the present invention is not particularly limited to this structure.

The belt layer 7 includes at least two cords arranged at a small angle of, for example, 10 to 45 ° with respect to the tire equator, in this example, an inner belt ply 7A in the radial direction of the tire and an outer belt ply 7A in the tire radial direction. And two belt plies of an outer belt ply 7B arranged on the outermost side in the tire radial direction, and the cords are overlapped in a direction crossing each other. In the present example, the width BW2 of the outer belt ply 7B in the tire axial direction is smaller than the width BW1 of the inner belt ply 7A in the tire axial direction. The width B
W2 is, for example, 80 to 100 of the tread contact width TW.
%, More preferably about 90 to 100%.
The cords arranged in the belt plies 7A and 7B are steel cords in this embodiment, but high elastic organic fiber cords such as aramid and rayon can be used if necessary.

The tread contact width refers to a maximum contact width in a state where the tire is assembled on a regular rim defined by a standard and a regular internal pressure and a regular load are applied. The "regular rim" is, for example, a standard rim for JATMA, and the "regular internal pressure" is the maximum air pressure for JATMA, but 180 kPa for passenger car tires, and the "regular load" is JATMA. If so, it is the maximum load capacity.

The buttress reinforcing layer 9 is provided on the outside of the carcass 6 in this embodiment.
B from the outer end 7e in the tire axial direction to 10
A start point 9a is provided in a region K within mm and extends from the start point 9a to an end point 9b on the side wall portion 3 side. According to various experiments by the inventors, even when the starting point 9a of the buttress reinforcing layer 9 is more than 10 mm from the outer end 7e of the outer belt ply 7B in the tire axial direction and inside the tire axial direction, the effect of improving high-speed durability is improved. Has reached a plateau, and is rather disadvantageous in increasing tire weight.

Further, at the outer end 7e of the outer belt ply 7B, a rigidity step is generated in the belt layer 7, and the rigidity of the tire becomes lower from the outer end 7e toward the outside in the tire axial direction. According to experiments by the inventors, when the starting point 9a of the buttress reinforcing layer 9 is located outside the tire axial direction outer end 7e of the outer belt ply 7B by more than 10 mm in the tire axial direction, the starting point 9a and the outer belt Outer end 7e of ply 7B
The low rigidity portion is locally created between the inner belt ply 7A and the strain generated during high-speed running is concentrated on the low rigidity portion, causing separation damage at the end of the inner belt ply 7A and the like. 9, it was found that the high-speed durability was rather deteriorated. From such a viewpoint, the starting point 9a of the buttress reinforcing layer 9 is within the tire axial direction from the tire axial outer end 7e of the outer belt ply 7B,
It must be provided within 10 mm outside. The starting point 9a is
When it is inside the outer end 7e of the outer belt ply 7B,
It is set inside the belt layer 7 in the tire radial direction.

The buttress reinforcing layer 9 must be formed from a cord ply 10 having an organic fiber cord such as nylon, polyester, rayon, or aramid inclined at an angle θ of 10 to 80 ° with respect to the tire circumferential direction. It is. The buttress reinforcing layer 9 exemplifies one formed by a single cord ply 10 in this example. For example, if the buttress reinforcing layer 9 is formed of a simple rubber sheet having no organic fiber cord, no improvement in high-speed durability can be expected. When a cord ply 10 having a steel cord is used for the buttress reinforcing layer 9, rubber is easily peeled off at the cut end surface of the steel cord having a low adhesive strength with rubber due to centrifugal force during high-speed running, so that high-speed durability is achieved. No improvement in sex is expected.

When the organic fiber cord is inclined at less than 10 ° with respect to the tire circumferential direction, the rigidity of the buttress portion B in the tire circumferential direction increases, but the effect of improving the rigidity in the tire radial direction decreases. Particularly, to improve the standing wave, it is necessary to increase the carcass rigidity in the tire radial direction rather than the tire circumferential rigidity of the buttress portion. Therefore, the organic fiber cord is set to the angle θ of 10 ° or more. Conversely, even if the organic fiber cord exceeds 80 ° with respect to the tire circumferential direction, the angle difference between the organic fiber cord and the radially structured carcass cord becomes small, and similarly, the carcass rigidity in the tire radial direction at the buttress portion B is expected to increase. Can not. From such a viewpoint, the angle θ is 12 to 78.
゜, more preferably 20 to 70 °, and the intersection angle of the outermost carcass ply 6A with the carcass cord is desirably set to 20 to 70 °.

The cord ply 10 forming the buttress reinforcing layer 9 is formed by, for example, coating an organic fiber cord with a small thickness of topping rubber. In this case, it is desirable that the topping rubber is made of, for example, a rubber material having a small energy loss of, for example, a loss tangent (tan δ) smaller than 0.1, for example, 0.06 to 0.08. By coating the organic fiber cord with such a topping rubber having a small loss tangent, heat generated due to distortion of the buttress portion B generated during running of the tire can be suppressed, and heat durability can be improved. The loss tangent tan δ is determined by cutting a strip-shaped sample and using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 2%.

As a result of various experiments, the buttress reinforcing layer 9 has the terminal point 9b located radially outward of the tire maximum sectional width position M in the tire radial direction, and the carcass of the buttress reinforcing layer 9 in the tire meridian section. It has been found that the length L (shown in FIG. 2) along the outer surface needs to be 15 mm or more. When the terminal point 9b is located radially inward of the tire maximum cross-sectional position M in the tire radial direction, the length of the buttress reinforcing layer 9 is increased, the tire weight is increased, and the rolling resistance is deteriorated. The length L along the carcass outer surface of the buttress reinforcing layer 9 is 15 mm.
If less, the buttress portion B cannot be reinforced within an effective range, and improvement in high-speed durability cannot be expected. More preferably, the length L of the buttress reinforcing layer 9 is 20 to 60 mm,
More preferably, it is desirable to set it to 30 to 50 mm.

In the pneumatic tire 1 having the buttress reinforcing layer 9 as described above, the buttress portion B of the carcass 6 can be effectively reinforced, and the standing wave is suppressed or the generation speed is shifted to a higher speed side. And the high-speed durability is improved. In addition, by limiting the arrangement position of the buttress reinforcing layer 9, the material of the cord ply 10, the cord angle, and the like, it is possible to suppress a large increase in tire weight and to prevent the rolling resistance from deteriorating.
Further, in the tire vulcanizing step, the inner liner rubber disposed on the tire inner surface is moved to the carcass side in the tire vulcanizing process, and the inner liner is sucked up, so that the tire inner surface is wavy and is called “cheese cut”. Although a defect is likely to occur, such a defect is prevented by disposing such a buttress reinforcing layer 9.

FIGS. 3A and 3B show another embodiment of the present invention. In the above-described embodiment, an example in which the buttress reinforcing layer 9 is provided outside the carcass 6 is illustrated. However, FIG. 3A shows an example in which the buttress reinforcing layer 9 is arranged inside the carcass 6 in the tire radial direction. In this embodiment, the same reinforcing effect as in the embodiment of FIG. 1 can be obtained, and the high-speed durability can be improved.

FIG. 3B shows the carcass 6 composed of two carcass plies 6A and 6B with the buttress reinforcing layer 9 interposed therebetween. In this embodiment, the buttress reinforcing layer 9 is
As a result of covering the inside and outside with A and 6B, a higher reinforcing effect is obtained as compared with the case where the buttress reinforcing layer 9 is arranged outside the carcass 6, so that high-speed durability can be greatly improved.

FIG. 4 shows still another embodiment of the present invention. In this example, the sidewall portion 3 is formed on the surface of the sidewall portion 3 and at least a part of the buttress region where the buttress reinforcing layer 9 is disposed by reducing the rubber thickness of the sidewall portion 3. The example in which the concave portion 12 is provided is illustrated. In this case,
The concave portion 12 having a reduced rubber thickness facilitates heat radiation of the buttress portion B, thereby reducing heat generation and improving durability. The concave portion 12 is, for example, 1.0-1.
It is desirable to reduce the rubber thickness by a thickness X of 5 mm. In particular, it is desirable to set the minimum rubber thickness t from the buttress reinforcing layer 9 to the outer surface of the tire in the concave portion 12 to, for example, 1.5 to 3.0 mm. .

FIG. 5 shows still another embodiment of the present invention. In the present embodiment, the cord ply 10 forming the buttress reinforcing layer 9 is formed to have a wavy portion 13 that repeats bending in which the center line CL of the amplitude extends at substantially the same interval as the outer surface of the carcass 6 in the tire meridian section. FIG. According to this embodiment, since the rigidity of the buttress reinforcing layer 9 in the tire radial direction can be relatively reduced, it is possible to achieve both high-speed durability and rolling resistance in a well-balanced manner.

The amplitude is, for example, 0.5 to 1.5 mm, more preferably 0.7 to 1.2 mm, and the bending pitch is, for example, 2.0 to 10.0 mm, more preferably 2.5 to 1.5 mm.
It is desirable to set it to 5.0 mm. In the example shown in the figure, a wavy shape is shown, but a zigzag shape may be used.

[0027]

Next, a more specific embodiment of the present invention will be described. A pneumatic radial tire for passenger cars having a tire size of 225 / 60R16 and specifications shown in Table 1 was prototyped, and high-speed durability, rolling resistance, and riding comfort were tested, and performance was compared. As a common specification of the tire, the carcass has a polyester cord inclined at an angle of 88 ° with respect to the tire equator. A two-layer belt ply inclined at 15 ° was used. The width of the outer belt ply was about 90% of the tread contact width. Also, the sixth embodiment has the concave portion 12 (X: 1.4 mm, t: 2.5 mm, width in the tire radial direction 20 mm) shown in FIG. 4, and the seventh embodiment has a wavy shape (amplitude 1.0 mm) as shown in FIG. , At a pitch of 3.0 mm).

As a high-speed durability test, a drum tester was used to mount the rim (16 × 7-JJ) on a rim (16 × 7-JJ), and a table drum durability test was performed based on the ECE high-speed durability test method.
In addition, the load was 5010N and the internal pressure was 3
20 kPa from 0 to 200 km / h for 10 minutes,
200km for 10 minutes, 210km for 10 minutes, 220
The vehicle was run for 10 minutes at km and for 20 minutes at 230 km. In this test, the test was continued at speed increases of 10 km / h for 20 minutes each and stepped up until the tire was broken. Then, the speed and time when the tire was broken were measured.

The rolling resistance was measured using a rolling resistance tester, and the tire assembled with the rim was subjected to an internal pressure of 200 kP.
a, the rolling resistance was measured at a speed of 80 km / h and a load of 4,413 N, and was indicated by an index with the rolling resistance of a comparative tire (Comparative Example 1) having no buttress reinforcing layer as 100.
The smaller the value, the smaller the rolling resistance and the better.

Regarding ride comfort, the rim-assembled tire was mounted on a 2000cc domestic FF passenger car with a displacement of 2000cc.
On a dry asphalt road, a bumpy road, a cobblestone road, a Bitzman road (a road with a small pebble), and the like, a sensory evaluation was performed with respect to ruggedness, pushing up, and dumping. evaluated. The higher the value, the better. Table 1 shows the test results.

[0031]

[Table 1]

As a result of the test, it was confirmed that the example had improved high-speed durability as compared with the comparative example. In addition, it was confirmed that the tire of the comparative example having the buttress reinforcing layer but not having its start point and end point properly arranged could not be expected to improve the high-speed durability.

[0033]

As described above, according to the first aspect of the present invention, the buttress portion of the carcass can be effectively reinforced by providing the predetermined buttress reinforcing layer in which the starting point and the ending point are appropriately regulated. Thus, the standing wave is suppressed or the generation speed is shifted to the high speed side, whereby the high speed durability is improved. In addition, by limiting the arrangement position of the buttress reinforcing layer, the cord ply material, the cord angle, and the like, it is possible to suppress a significant increase in tire weight and to prevent the rolling resistance from deteriorating.

According to the second aspect of the present invention, the buttress reinforcing layer is constituted by a cord ply made of an organic fiber cord covered with a topping rubber having a loss tangent (tan δ) smaller than 0.1. Heat generation at the buttress portion can be reduced, and heat damage can be prevented.

In the invention according to claim 3, the sidewall portion is formed on at least a part of a surface of the sidewall portion and in a buttress region where the buttress reinforcing layer is disposed.
By providing the concave portion formed by reducing the rubber thickness of the side wall portion, heat radiation of the buttress portion is promoted by the concave portion having reduced rubber thickness, and heat generation can be reduced and durability can be improved.

[0036] In the invention according to claim 4, the cord ply forming the buttress reinforcing layer has a wavy portion in the tire meridian section, in which the center line of the amplitude is repeatedly bent so as to extend at substantially the same interval as the outer surface of the carcass. By forming the buttress reinforcing layer, the rigidity of the buttress reinforcing layer in the tire radial direction can be relatively reduced, so that high-speed durability and rolling resistance can be improved in a particularly well-balanced manner.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram showing the internal structure.

FIGS. 3A and 3B are partially enlarged sectional views showing a buttress portion according to another embodiment of the present invention;

FIG. 4 is a partially enlarged cross-sectional view illustrating a buttress portion according to still another embodiment of the present invention.

FIG. 5 is a partially enlarged cross-sectional view of a buttress portion showing still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 7A Inner belt ply 7B Outer belt ply 7e Outer end of outer belt ply 9 Buttress reinforcing layer 9a Starting point of buttress reinforcing layer 9b Buttress reinforcing layer End point of 10 code plies

Claims (4)

[Claims] A carcass extending from a tread portion to a bead core of a bead portion via a sidewall portion, and an outer belt ply disposed radially outward of the carcass in the tire and inside the tread portion and further disposed radially outward of the tire. A belt layer consisting of at least two belt plies containing:
A buttress reinforcing layer, wherein the buttress reinforcing layer extends from the outer end of the outer belt ply in the tire axial direction to a region within 10 mm inward and outward in the tire axial direction from the starting point to the terminal point on the sidewall portion side, and The buttress reinforcing layer is one in the tire circumferential direction.
A cord ply having an organic fiber cord inclined at 0 to 80 °, wherein the terminal point is located outside the tire in the tire radial direction from the maximum cross-sectional width position of the tire, and the carcass outer surface of the buttress reinforcing layer in the tire meridian section A pneumatic tire characterized in that the length along the line is 15 mm or more. 2. The buttress reinforcing layer has a loss tangent (ta).
2. The pneumatic tire according to claim 1, further comprising a cord ply made of an organic fiber cord covered with a topping rubber having nδ) smaller than 0.1. 3. The side wall portion has a recess formed by reducing the rubber thickness of the side wall portion on at least a part of a surface of the side wall portion and in a buttress region where the buttress reinforcing layer is disposed. The pneumatic tire according to claim 1 or 2, wherein: 4. The cord ply according to claim 1, wherein, in the tire meridian cross section, a wavy portion in which the center line of the amplitude extends repeatedly at substantially the same interval as the outer surface of the carcass is repeatedly bent. Or the pneumatic tire according to 1.