JP2002283815A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in riding comfort as a result of long term use of a tire. SOLUTION: The tire has a tread part 1, a side wall part 2, a bead part 3, a radial carcass 5, a bead filler 6, and a reinforcement layer 10 which is comprised of a rubber-coated nonwoven fabric having 100 g/m<2> or less weight, has the distance H kept to be at least 10 mm between the tire radially outermost end of the reinforcement layer 10 and the tire radially outermost end of a rim flange in the tire width direction cross section when the tire is mounted to a rim R and under the air pressure filling up state, and has the dynamic storage elastic modulus of the coating rubber comprising the reinforcement layer kept to be 50% or less of the dynamic storage elastic modulus of the bead filler rubber.

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, and more particularly to a pneumatic radial tire which prevents deterioration of ride comfort due to long-term use of the tire.

[0002]

2. Description of the Related Art Conventionally, a purpose of the present invention is to allow a tire to accurately transmit a force received from one of a road surface and a vehicle to the other, and to secure tire circumferential rigidity and radial rigidity to required limits. As shown in FIG. 2, since the bead filler 11 made of high-hardness rubber is disposed from the position directly above the bead core 12 in the tire radial direction to the vicinity of the tire maximum width position, the rubber weight of the bead filler 11 increases. In addition to the problem that excellent fuel economy cannot be realized, when the tire is mounted on a vehicle and used for a long time, the bead core 12 is relatively long in the tire radial direction from the position directly above the tire radial direction to the vicinity of the tire maximum width position. The rubber of the disposed bead filler 11 is hardened by the re-crosslinking, which causes a problem of deteriorating ride comfort. It was.

[0003]

In order to solve these problems, in recent years, the height of the bead filler from the position directly above the radial direction of the bead core in the tire radial direction has been reduced to suppress an increase in tire weight due to the bead filler rubber. In addition to realizing excellent fuel efficiency, a bead filler rubber sheet made of rubber of the same kind as the bead filler rubber is arranged from the tire bead portion to the side wall portion, and the tire radial rigidity and width direction in the region are arranged. Proposals have been made to set the rigidity in a well-balanced manner and to ensure excellent steering stability performance and vibration riding comfort performance.

However, when a tire constructed according to this proposal is mounted on a vehicle and used for a long time,
There was still a problem that both the bead filler and the bead filler rubber sheet were hardened due to re-crosslinking, resulting in deterioration of ride comfort.

In recent years, in order to solve the problems of the prior art, the height of the bead filler from the position directly above the tire radial direction of the bead core has been reduced, thereby suppressing an increase in tire weight due to the rubber of the bead filler. Along with realizing fuel efficiency, a cord reinforcement layer consisting of a cord of steel wire etc. is arranged from the tire bead to the sidewall, and both the radial and circumferential rigidity of the tire in this area are set to be high to ensure stable driving. Proposals have been made to improve performance.

However, in the pneumatic radial tire constructed according to such a proposal, there is a problem that fuel efficiency is deteriorated due to an increase in tire weight due to a steel cord constituting a cord reinforcing layer. The reinforcing layer has a steel cord end portion, and if stress concentration occurs at that portion, the adhesive effect between the coating rubber and the steel cord may not be sufficiently exhibited, so that excellent durability performance can be realized. There was also a problem that it was difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and an object of the present invention is to enhance rigidity from a bead portion to a sidewall portion to provide excellent steering stability. On the premise of ensuring performance, prevent tire weight from increasing and fuel efficiency from deteriorating,
Moreover, it is an object of the present invention to provide a pneumatic radial tire that can advantageously suppress a decrease in ride comfort when a new tire is used due to long-term tire use.

[0008]

A pneumatic radial tire according to the present invention has a tread portion, respective sidewall portions extending radially inward from the tread portion, and an inner peripheral side of the sidewall portion. A radial carcass having a bead portion provided on the bead portion, extending toroidally between the bead cores disposed on each bead portion, and winding the side portion radially outward around the bead core, and a radial carcass. A bead filler arranged between the main body portion and the rewinding portion adjacent to the outer peripheral surface of the bead core, and a reinforcing layer on a radially outer side of the rewinding portion of the radial carcass are provided with a rubber coating on the reinforcing layer. And the basis weight of the nonwoven fabric is 100 g / m ^2.
The following, under the pneumatic filling state where the tire is assembled on the rim, the distance from the tire radial outermost end of the rim flange of the tire radial outermost end of the reinforcing layer in the tire width direction cross section is at least 10 mm. The dynamic storage elastic modulus of the coating rubber constituting the reinforcing layer is 50% or less of the dynamic storage elastic modulus of the bead filler rubber.

In this pneumatic radial tire, the reinforcing layer is made of a non-woven fabric coated with rubber, and the basis weight of the non-woven fabric is 100 g / m ² or less, so that the above-described cord reinforcing layer made of a steel cord can be used. The tire weight can be reduced as compared with the case where the tire is used, whereby the fuel efficiency can be improved.

[0010] In addition, under the pneumatic filling state where the tire is assembled on the rim, at least the distance between the tire radially outermost end of the reinforcing layer in the tire width direction cross section and the tire radially outermost end of the rim flange is set at least. By setting it to 10 mm, as in the case of using the above-described cord reinforcing layer, reinforcement from the bead portion to the sidewall portion can be sufficiently achieved, and thereby excellent steering stability performance can be realized. .

When the dynamic storage elastic modulus of the coating rubber constituting the reinforcing layer is set to 50% or less of the dynamic storage elastic modulus of the bead filler rubber, the rigidity from the bead portion to the sidewall portion becomes excessive. Prevent improvement,
Excellent ride comfort can be achieved.

[0012] Therefore, in this pneumatic radial tire, fuel efficiency is improved by using a nonwoven fabric with an appropriate basis weight for the reinforcing layer, and excellent steering stability performance is obtained by optimizing the arrangement position of the reinforcing layer. Excellent ride comfort performance by optimizing the dynamic storage modulus of the coating rubber constituting the reinforcing layer can be realized at the same time.

[0013] More preferably, in such a pneumatic radial tire, the cross-sectional width of the reinforcing layer composed of the nonwoven fabric and the coating rubber is set on a straight line passing through the outermost end of the rim flange in the tire radial direction and parallel to the center axis of the rim. 80% or more of the cross-sectional width of the filler rubber. According to this, the arrangement amount of the bead filler rubber can be reduced as compared with the conventional pneumatic radial tire, and therefore, when the tire is used for a long period, the bead filler rubber is re-crosslinked. The resulting hardening of the bead filler can be suppressed, and deterioration of ride comfort performance can be advantageously prevented.

[0014] Preferably, the coating rubber is constituted so that sulfur is not more than 3 parts by weight based on 100 parts by weight of the rubber polymer. According to such a pneumatic radial tire,
For long-term use of the tire, in order to suppress the curing of the reinforcing layer due to the re-crosslinking of the coating rubber, lower the compounding amount of sulfur that is dominant with respect to the re-crosslinking, and advantageously reduce the curing phenomenon of the reinforcing layer. This can prevent deterioration of ride comfort.

[0015] Preferably, the tensile stiffness characteristic of the nonwoven fabric constituting the reinforcing layer is determined by: (tensile stiffness in the direction (first direction) where tensile stiffness is maximum) / (direction perpendicular to the first direction (second direction) Direction), the tensile rigidity is 1.5 or more, and more preferably, the first direction is the tire circumferential direction. According to this, the arrangement of the fibers constituting the nonwoven fabric is increased, for example, by disposing more fibers extending in the tire circumferential direction as compared with fibers extending in the tire radial direction, so that the tire radial rigidity is improved. Since it is relatively low and the tire circumferential rigidity can be relatively high, the riding comfort performance can be further improved with the same amount of fibers while maintaining the steering stability performance.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view in the tire width direction showing an embodiment of the present invention.
Is a tread portion, 2 is a sidewall portion extending continuously inward in the tire radial direction on a side portion of the tread portion 1, and 3 is a bead portion provided continuously on an inner peripheral side of the sidewall portion 2. Show.

Here, each bead portion 3 is provided with a bead core 4 embedded and arranged therein to form a ring as a whole, and a rewinding portion 5a of a radial carcass 5 extending toroidally between the bead cores 4 is formed around the bead core 4. To rewind radially outward from the inner side in the tire width direction to the outer side, terminate the rewinding portion 5a with the sidewall portion 2, and provide a bead core between the rewinding portion 5a of the radial carcass 5 and the main body portion 5b. A bead filler 6 is arranged adjacent to the outer peripheral surface of the inner car 4, and an inner liner 7 and a canvas chafer 8 are arranged so as to surround the radial carcass 5 from the side wall part 2 to the bead part 3. A belt 9 composed of a belt layer 9a and a belt reinforcing layer 9b is disposed on the outer peripheral side of the crown portion of The radially outer side of the fifth rewinder portion 5a arranging the reinforcing layer 10.

In this case, the reinforcing layer 10 is made of a non-woven fabric coated with rubber, and the basis weight of the non-woven fabric is 100 g / m ² or less, and the tire width is adjusted under the pneumatic filling condition where the tire is assembled on the rim R. the radially outermost end of the reinforcing layer 10 in the cross section, the distance H from the radially outermost end of the rim flange R _F, at least 10
mm, and the dynamic storage elastic modulus of the coating rubber constituting the reinforcing layer 10 is set to 50% or less of the dynamic storage elastic modulus of the rubber of the bee filler 6.

Here, a straight line L that passes through the outermost end of the rim flange _{RF in} the tire radial direction and is parallel to the rim center axis is used.
Above, the cross-sectional width w of the reinforcing layer 10 made of the nonwoven fabric and the coating rubber is set to 80 times the cross-sectional width W of the bead filler 6.
%, The coating rubber constituting the reinforcing layer 10 is not more than 3 parts by weight of sulfur with respect to 100 parts by weight of the rubber polymer, and the tensile stiffness characteristic of the nonwoven fabric forming the reinforcing layer 10 is as follows. And (tensile rigidity in the direction (first direction)) / (tensile rigidity in the direction perpendicular to the first direction (second direction)) is 1.5 or more,
The first direction is defined as a tire circumferential direction.

According to the pneumatic radial tire described above, the reinforcing layer 10 using a non-woven fabric with an appropriate basis weight improves fuel efficiency and optimizes the arrangement position of the reinforcing layer 10. As a result, excellent ride stability can be realized by optimizing the dynamic storage modulus of the coating rubber constituting the reinforcing layer 10.

[0021]

EXAMPLES Next, a pneumatic radial tire according to the present invention was experimentally manufactured, and the evaluation of the riding comfort performance when the tire was new and when the oven was deteriorated was evaluated. Example tires 1, 2, 3, and Comparative example tire 1,
2 and 3 all have the structure shown in FIG. 1, and the comparative example tire 4 does not include the reinforcing layer 10, that is, has the structure shown in FIG.
2, 3 and Comparative Example Tires 1, 2, and 3, and Comparative Example Tire 5 has a cord reinforcing layer made of rubber-coated steel cord instead of reinforcing layer 10 made of rubber-coated nonwoven fabric. Except for the bead portion, the tire had the same structure as the example tires 1, 2, 3, and the comparative tires 1, 2, 3, 4. Note that the example tires 1, 2, 3, and the comparative tires 1, 2, 3, 4, 5 had the specifications shown in Table 1.

[0022]

[Table 1]* Here, the basis weight is the basis of the nonwoven fabric constituting the reinforcing layer 10.
The amount of sulfur is defined as the amount of coating
Rubber rubber in 100 parts by weight of rubber polymer
The parts by weight of sulfur are referred to as tensile stiffness characteristics.
Tensile rigidity in the tire circumferential direction (first direction) showing the maximum) /
(Tensile stiffness in the direction perpendicular to the first direction (second direction))
Good, distance H is pneumatic filling with tires assembled on rim R
Under the condition, the tire of the reinforcing layer 10 in the cross section in the tire width direction
Radial outermost rim flange R _FTire radial direction
It refers to the distance from the outermost end, and the elastic modulus ratio means that the reinforcing layer 10
Beef with dynamic storage modulus of the constituent coating rubber
The ratio of filler 6 to the dynamic storage modulus of rubber
The width ratio is the rim flange R_FTire outermost end
As measured on a straight line L parallel to the rim center axis
The sectional width of the reinforcing layer 10 with respect to the sectional width of the rubber of the filler 6 is
Good, and cord means steel cord
You. The measurement of the tensile stiffness was performed using a nonwoven fabric sample 50
Powerful moment at 10% elongation at 200 mm width and 200 mm length
Was measured with an Instron tensile tester.
(Measured temperature, 25 ° C). Measurement of dynamic storage modulus
Using a spectrometer manufactured by Seiki Co., Ltd., a sample piece: 1 m thick
m, width: 3 mm, length: 50 mm (or JIS S
1, S2, N1 or N2 type specimen)
Initial load: 50 g, average strain amplitude: 2%, frequency 1
Measured at a test temperature of 25 ° C. under the condition of 00 Hz.
Was.

Each of the test tires was 195/6 in size.
5 R15, each having the same tread pattern, each of the test tires before use, and each of the test tires that had been left in a 60 ° C. oven for one month when the oven was deteriorated were mounted on a foreign-made vehicle. The professional riders performed a feeling evaluation on the ride performance on a scale of 1 to 10. Table 2 shows the evaluation results.

[0024]

[Table 2]

As a result of the evaluation, the tires of Examples 1 to 3
In both cases, compared to the comparative tires, not only the ride comfort when new, but also the ride comfort when the oven is deteriorated, and the degree of decrease in ride comfort between when new and when the oven is deteriorated is low. I understand.

Thus, according to the present invention, it is possible to provide a pneumatic radial tire which prevents deterioration of ride comfort due to long-term use of the tire.

[Brief description of the drawings]

FIG. 1 is a tire width direction sectional view showing an embodiment of a pneumatic radial tire according to the present invention.

FIG. 2 is a sectional view in the tire width direction showing an embodiment of a pneumatic radial tire according to a conventional invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4,12 Bead core 5 Radial carcass 5a Rewinding part 5b Body part 6,11 Bead filler 7 Inner liner 8 Canvas chafer 9 Belt 9a Belt layer 9b Belt reinforcement layer 10 Reinforcement layer H Distance R Rim R _F Rim flange W Cross section width W of bead filler 6 Cross section width w of reinforcing layer 9

Claims (5)

[Claims] 1. A tread portion, a sidewall portion extending radially inward from a side portion of the tread portion, and a bead portion provided on an inner peripheral side of the sidewall portion. A radial carcass having a side portion wound radially outward around the bead core by extending in a toroidal manner between the bead cores arranged in the bead core, and a bead core of the radial carcass between the main body portion and the rewind portion. In a pneumatic radial tire having a bead filler arranged adjacent to the outer peripheral surface and a reinforcing layer on the tire radial direction outer side of the rewind portion of the radial carcass, the reinforcing layer is made of a nonwoven fabric coated with rubber. the basis weight of the nonwoven fabric and 100 g / m ² or less, under the air pressure filling state that formed a tire on the rim, the reinforcing layer in the tire widthwise sectional Of hate radially outermost end,
The pneumatic pneumatic tire in which the distance from the outermost end of the rim flange in the tire radial direction is at least 10 mm, and the dynamic storage elastic modulus of the coating rubber constituting the reinforcing layer is 50% or less of the dynamic storage elastic modulus of the bead filler rubber. Radial tire. 2. The cross-sectional width of the reinforcing layer made of the nonwoven fabric and the coating rubber is set to be 80 times the cross-sectional width of the bead filler rubber on a straight line parallel to the rim center axis and passing through the outermost end of the rim flange in the tire radial direction. %. The pneumatic radial tire according to claim 1, wherein the percentage is not less than%. 3. The coating rubber is a rubber polymer 1
The pneumatic radial tire according to claim 1 or 2, wherein the sulfur content is 3 parts by weight or less with respect to 00 parts by weight. 4. The tensile stiffness characteristic of the nonwoven fabric forming the reinforcing layer is defined as: (tensile stiffness in the direction (first direction) where the tensile stiffness is maximum) / (direction perpendicular to the first direction (second direction) 4) The pneumatic radial tire according to any one of claims 1 to 3, wherein the tensile rigidity is 1.5 or more. 5. The pneumatic radial tire according to claim 4, wherein the first direction is a tire circumferential direction.