JP5144290B2 - Pneumatic run flat tire - Google Patents

Description

  The present invention relates to a pneumatic run-flat tire, and more particularly to a pneumatic run-flat tire that enables safe traveling over a certain distance even when the internal pressure is reduced due to puncture or the like.

Conventionally, as a pneumatic run-flat tire for ordinary passenger cars, a side-reinforced pneumatic run-flat tire having a side reinforcing rubber layer having a crescent-shaped cross section on a tire side portion has been proposed (for example, Patent Document 1). reference.). This type of pneumatic run-flat tire has a thick side-reinforcing rubber layer, two carcass layers, or a carcass layer in order to run a predetermined distance while supporting the load of ordinary passenger cars during run-flat running. The durability was ensured by adding a fiber reinforced layer even with one sheet.
Japanese Patent Laid-Open No. 2-147417 Japanese Patent Laid-Open No. 3-176213 JP 2002-500587 A

However, normal tires for light passenger cars are simpler and more comfortable than ordinary passenger car tires. However, if the same structure as normal passenger cars is applied to pneumatic run-flat tires for light passenger cars, Rigidity becomes too high as compared with heavy weight, which significantly impairs the ride comfort. Further, there is a concern that the input to the vehicle body is also large, which affects the durability of the vehicle.
The present invention has been made in order to solve the above-mentioned problems, and when used in a relatively lightweight vehicle, a pneumatic run flat tire capable of suppressing deterioration in ride comfort while ensuring run flat durability. The purpose is to provide.

  As a result of repeating various experimental studies, the inventor has optimized the carcass structure, the fineness of the carcass cord, and the thickness of the side reinforcing rubber layer, thereby ensuring the run-flat running performance and reducing the ride comfort. I found out that it can be suppressed.

The pneumatic run-flat tire according to claim 1 has a pair of bead cores, a belt layer, and a bead core extending from one bead core to the other bead core in a toroidal shape, and an end portion folds the bead core from the tire inner side to the tire radial direction outer side. A single carcass ply in which a plurality of carcass cords of three rayon cords arranged in parallel with each other and covered with rubber, and a main body portion of the carcass ply extending from one bead core to the other bead core, A bead filler disposed between the folded portion of the carcass ply and extending gradually from the bead core toward the outer side in the tire radial direction; and disposed on the inner side in the tire axial direction of the carcass ply; And a side reinforcing rubber layer that gradually decreases in thickness toward the tread portion side, and folding the carcass ply The heel end is located at the tire side portion between the end portion of the belt layer and the outer end in the tire radial direction of the bead filler, and the maximum thickness T1 of the side reinforcing rubber layer is It is set within a range of 30 to 40% of the thickness T0 of the tire side portion measured at the maximum thickness portion, and a rubber gauge between the main body portion and the folded portion of the carcass ply is a diameter of the carcass cord. An overlapping region set within a range of 1.0 to 1.5 times is provided on the end side of the folded portion .

Next, the operation of the pneumatic run flat tire according to claim 1 will be described.
In the pneumatic run-flat tire according to claim 1, the carcass ply has one piece, but the carcass cord is made of three rayon cords, and the maximum thickness T1 of the side reinforcing rubber layer is set to the thickness of the tire side portion. By setting it within the range of 30 to 40% of T0, when used in a relatively light vehicle (for example, a vehicle weight of 950 kg or less), it is possible to improve ride comfort while ensuring run-flat durability. it can.

For example, when a tire side part undergoes a large deformation due to an impact from a road surface projection caused by a rough road, an excessive tensile stress acts on the carcass inside the bead filler, so a carcass having a two-stranded carcass cord. Although there is a concern that the ply 1 layer is insufficient in strength, in the present invention, the cord fineness of the cord used for the carcass ply is set to 1840 dtex / 3 or more, thereby ensuring sufficient durability.
Compared to the conventional product where the ply end overlaps the belt layer by arranging the folded end of the carcass ply on the tire side part between the end of the belt layer and the outer end of the bead filler in the tire radial direction. It is lightweight and can improve ride comfort.
In addition, rayon cords are suitable for run flat running because they generate less heat.
Here, when the maximum thickness T1 of the side reinforcing rubber layer is less than 30% of the thickness T0 of the tire side portion, the run-flat durability is insufficient. On the other hand, when the maximum thickness T1 of the side reinforcing rubber layer exceeds 40% of the thickness T0 of the tire side portion, the ride comfort is deteriorated.

Further, the carcass ply of the present invention including the carcass cord in which the three-layered rayon cord is twisted is thicker than the carcass ply including the two-stranded carcass cord. Increased in comparison with carcass ply including twisted carcass cord. For this reason, in the pneumatic run flat tire according to claim 1, the rubber gauge between the main body portion and the folded portion of the carcass ply is set within a range of 1.0 to 1.5 times the diameter of the carcass cord. The distortion can be suppressed by providing the overlapping region on the end portion side of the folded portion. Thereby, generation | occurrence | production of the separation from the edge part of the folding | turning part of a carcass can be suppressed.

It should be noted that if the rubber gauge between the carcass ply main body portion and the turn-up portion in the overlapping region is less than 1.0 times the diameter of the carcass cord, the distortion at the end of the carcass cannot be suppressed.
On the other hand, if the rubber gauge between the carcass ply main body portion and the turned-up portion in the overlapping region exceeds 1.5 times the diameter of the carcass cord, there is a concern that the rubber volume increases so that the heat generation durability deteriorates. The

  In addition, the overlapping region where the rubber gauge between the carcass ply main body portion and the folded portion is set within a range of 1.0 to 1.5 times the diameter of the carcass cord is the inner side in the tire radial direction from the end portion of the folded portion. It is preferable to ensure at least 10 mm along the hekacas ply.

Invention according to claim 2, the pneumatic run-flat tire according to claim 1, wherein the belt layer is composed of two belt plies, the tire radial direction outside of the belt layer, the belt layer A belt reinforcing layer including a plurality of nylon cords is disposed so as to cover the entirety of the cord, and the nylon cord is a one-sided cord obtained by bundling nylon filaments and applying only a lower twist. .

Next, the operation of the pneumatic run-flat tire according to claim 2 will be described .
A belt layer composed of two belt plies buckles during run-flat travel, and there is a concern about belt breakage. For this reason, buckling can be suppressed by disposing a belt reinforcing layer including a plurality of nylon cords so as to cover the entire belt layer on the outer side in the tire radial direction of the belt layer.
In addition, the single twisted cord can improve durability against cord breakage while suppressing out-of-plane rigidity and suppressing deterioration in ride comfort performance as compared with a phase twisted cord.

As described above, since the pneumatic run flat tire according to claim 1 has the above-described configuration, it is possible to suppress the deterioration of the ride comfort while ensuring the run flat running performance , and further from the folded end of the carcass. It has an excellent effect that the occurrence of separation can be suppressed .
Moreover, since the pneumatic run-flat tire according to claim 2 has the above-described configuration, it has an excellent effect that durability against cord breakage of the belt can be improved.

[First Embodiment]
As shown in FIG. 1, the pneumatic run-flat tire 10 of the present embodiment is for a mini passenger car, and includes a pair of bead portions 12, a pair of tire side portions 14, and a tread portion 16 that is continuous with both tire side portions 14. And a carcass 20 straddling between the bead cores 18 embedded in the pair of bead portions 12 in a toroid shape, and a belt 22 for reinforcing the tread portion 16 on the outer periphery of the carcass 20.

The carcass 20 of the present embodiment is composed of a single carcass ply 24 in which a plurality of carcass cords are arranged in parallel to each other and covered with rubber. The end portion of the carcass ply 24 is folded back around the bead core 18 from the inside to the outside of the tire, the portion straddling the bead cores 18 is a main body portion 24A, and the folded portion is a folded portion 24B.
The folded portion 24B has an end portion located on the tire side portion 14.

  Here, the tire side portion 14 is a normal line perpendicular to the tangent line of the main body portion 24A of the carcass ply 24 that passes through the outer end portion of the bead filler 28 in the tire radial direction in the pneumatic run flat tire 10 described later. This is a portion indicated by an arrow A between L1 and a normal line L2 perpendicular to the tangent to the main body part 24A of the carcass ply 24 through the end of the belt 22 described later, and the tire diameter is larger than the normal line L1. The inside of the direction is a bead portion 12.

The carcass cord used in the carcass ply 24 of this embodiment is a three-strand rayon cord. The fineness of the carcass cord is preferably set in the range of 1840 dtex / 3 to 1900 dtex / 3.
Further, the number of carcass cords driven in the carcass ply 24 is preferably 40 to 60/5 cm.

In the carcass 20 of the present embodiment, the end portion side of the folded portion 24B of the carcass ply 24 is in intimate contact with the main body portion 24A, and this intimate portion is used as an overlapping area SA. The overlapping area SA is preferably secured at least 10 mm along the carcass ply 24 from the end of the folded portion 24B to the inside in the tire radial direction.
Further, in the overlapping region SA, as shown in FIG. 2, the rubber gauge G between the main body 24A and the folded portion 24B is set within a range of 1.0 to 1.5 times the diameter of the carcass cord 23. Is preferred. In FIG. 2, reference numeral 25 denotes a coating rubber covering the carcass cord 23.

The belt 22 of the present embodiment is composed of two belt plies 26 in which a plurality of steel cords arranged in parallel to each other are covered with rubber.
A tread rubber layer 34 that forms the tread portion 16 is disposed outside the belt 22 in the tire radial direction.
A side rubber layer 36 that forms the tire side portion 14 is disposed outside the carcass 20 in the tire axial direction.
A bead filler 28 made of rubber harder than the side rubber layer 36 and extending in a tapered manner from the outer peripheral surface of the bead core 18 toward the outer side in the tire radial direction is disposed between the main body portion 24A and the folded portion 24B of the carcass ply 24. Has been.
Further, a rubber chafer 40 forming a bead toe is disposed in the bead portion 12, and the outer surface of the rubber chafer 40 is covered with a cover rubber 42.
An inner liner 33 having excellent air impermeability is provided on the inner surface of the pneumatic run-flat tire 10.

In the pneumatic run flat tire 10 of the present embodiment, the cross section is gradually crescent-shaped (inner side in the tire radial direction and outer side in the tire radial direction) on the inner surface side of the main body part 24A of the carcass 20 extending from the bead part 12 to the tread part 16. The side reinforcing rubber layer 30 having a shape in which the thickness gradually decreases is provided.
Even if the tire internal pressure becomes zero, the side reinforcing rubber layer 30 stably supports the total weight of the running vehicle, prevents the rim 32 from being fitted with the pneumatic run-flat tire 10, and prevents air from being removed. In order to prevent the entering run-flat tire 10 from being broken, it is made of rubber harder than the side rubber layer 36.

The side reinforcing rubber layer 30 is thickest at a substantially central portion in the tire radial direction, and its maximum thickness T1 is 30 to 40% of the thickness T0 of the tire side portion 14 measured at the maximum thickness portion of the side reinforcing rubber layer 30. It is set within the range.
In the case of a mini passenger tire, the side reinforcing rubber layer 30 preferably has a rubber hardness in the range of 90 to 100 (JIS A) and a maximum thickness T1 in the range of 4 to 6 mm. The side reinforcing rubber layer 30 of the present embodiment has a hardness of 98 ° (after vulcanization) and a maximum thickness of 5 mm.

(Function)
In the pneumatic run flat tire 10 of the present embodiment, the carcass ply 24 is one, but the carcass cord is made of three twisted rayon cords, and the maximum thickness T1 of the side reinforcing rubber layer 30 is set to the tire side. Since it is set within a range of 30 to 40% of the thickness T0 of the portion 14, even when used in a light vehicle such as a light passenger car, the ride comfort should be improved while ensuring run-flat durability. Can do.
Since the turn-up end of the carcass ply 24 is arranged on the tire side portion 14, the ride comfort can be improved with light weight as compared with the conventional product in which the turn-up end overlaps the belt layer.

  If the maximum thickness T1 of the side reinforcing rubber layer 30 is less than 30% of the thickness T0 of the tire side portion 14, the run-flat durability is insufficient, and the maximum thickness T1 of the side reinforcing rubber layer 30 is the tire side portion. If it exceeds 40% of the thickness T0 of 14, the ride comfort is deteriorated.

  In addition, an overlapping area SA in which the rubber gauge G between the main body portion 24A and the folded portion 24B of the carcass ply 24 is set within a range of 1.0 to 1.5 times the diameter of the carcass cord is an end portion of the folded portion 24B. Since it is provided on the side, the coating rubber 25 between the carcass cords serves as a cushioning material, and distortion at the end of the carcass during run-flat traveling can be suppressed.

  If the rubber gauge G between the main body portion 24A and the folded portion 24B of the carcass ply 24 in the overlapping area SA is less than 1.0 times the diameter of the carcass cord 23, distortion at the end of the carcass cannot be suppressed, There is a concern that the generation of separation from the end of the folded portion 24B cannot be suppressed. On the other hand, if the rubber gauge G between the main body portion 24A and the turn-up portion 24B of the carcass ply 24 in the overlapping area SA exceeds 1.5 times the diameter of the carcass cord 23, the volume of the coating rubber 25 increases too much and the heat generation durability is increased. There is concern about the deterioration of sex.

  Further, when the length of the overlapping area SA is less than 10 mm, there is a concern that the distortion at the end of the carcass cannot be suppressed and the occurrence of separation from the end of the folded portion 24B cannot be suppressed. On the other hand, if the overlap area SA is too long, the run-flat durability is lowered due to the lower bead filler 28, or the upper end of the ply is increased and the end of the member is cracked and the end of the member is cracked. The upper limit is preferably 20 mm or less.

[Second Embodiment]
Next, a pneumatic run flat tire 10 according to a second embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same structure as 1st Embodiment, and the description is abbreviate | omitted.
As shown in FIG. 3, in the pneumatic run flat tire 10 of the present embodiment, an organic fiber cord layer 44 is provided outside the belt 22 in the tire radial direction so as to cover the entire belt 22. The organic fiber cord layer 44 of this embodiment is formed by arranging a plurality of nylon cords in parallel with each other and covering them with a coating rubber.
The nylon cord of this embodiment is a single twist cord in which nylon filaments are bundled and subjected only to a lower twist. In this embodiment, a 1400 dtex / 2 nylon cord is used, but the present invention is not limited to this.

  By arranging such an organic fiber cord layer 44 on the outer side of the belt 22 in the tire radial direction, the entire belt 22 is reinforced, and buckling that causes belt breakage during run-flat traveling can be suppressed. The durability against the cord breakage of 22 can be improved.

(Test example)
In order to confirm the effect of the present invention, a pneumatic run flat tire of a conventional example, a pneumatic run flat tire of a comparative example, and a pneumatic run flat tire of an example to which the present invention was applied were prepared, and the tire weight, and The carcass breaking load was examined.

The test tire is described below.
Example 1: The tire according to the first embodiment described above (the cord fineness of the carcass ply cord is 1840 dtex / 3), and the folded end is disposed on the tire side portion.
Example 2: A tire according to the second example described above (Example 1 + belt reinforcing layer).
Comparative example: The same configuration as in the example except that the cord fineness of the carcass ply cord is 1840 dtex / 2.
The tire size is 155 / 65RF14. Other specifications are as described in Tables 1 and 2 below.

Next, test items and test methods will be described.
Run-flat durability: The test tire is assembled on a 4.5J × 14 rim, the internal pressure is 0 kPa, the load is 255 kg with a drum testing machine, the ambient temperature is 38 ± 3 ° C, and the speed is increased to 80 km / h. In order to evaluate the running time until a failure occurred and the vibration level increased rapidly. The travel time to be secured in this size is shown as an index with 100 as the travel time. The larger the index value, the better the run-flat durability.
-Riding comfort: The test tire was mounted on a vehicle, and the comparative example was displayed as an index with the comparative example being 100 with the feeling of the test driver as a control. The larger the index value, the better the ride.
・ Buckling: The test tire is assembled on a 4.5J × 14 rim, and is pressed against a flat plate with an internal pressure of 0 kPa and a load of 265 kg. A CT scan is taken, and the distance from the ground contact surface to the tread is measured at the center in the width direction of the tire. Measurement. The reciprocal of the measured value was displayed as an index. The result shows that the value of the comparative example is 100, and the larger the index value, the less buckling.
-Anti-separation performance at the turn-back: The test tire is assembled on a 4.5 x 14 rim, the internal pressure is 300 kPa, the load is 775 kg, the ambient temperature is 38 ° C, and the vehicle runs at a speed of 60 km / h. The time until was evaluated. The travel time that should be secured as the actual size is shown as an index with 100 as the travel time. The larger the index value, the better the separation resistance.
The test results are as described in Tables 1 and 2 below.

As a result of the test, it can be seen that the tires of Examples 1 and 2 to which the present invention is applied can improve the ride comfort while ensuring the run-flat durability. Moreover, in Example 2, it turns out that buckling has decreased by addition of the belt reinforcement layer.
Moreover, although the comparative example has run-flat durability more than necessary, it can be seen that the ride comfort is poor compared to the examples.

1 is a cross-sectional view of a pneumatic run flat tire according to a first embodiment to which the present invention is applied. It is sectional drawing of the overlap area | region of a carcass. It is sectional drawing of the pneumatic run flat tire which concerns on 2nd Embodiment to which this invention was applied. It is sectional drawing of the conventional pneumatic run flat tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic run-flat tire 12 Bead part 14 Tire side part 16 Tread part 18 Bead core 20 Carcass 22 Belt 24 Carcass ply 24A Body part 24B Fold-up part SA Overlapping area 26 Belt ply 28 Bead filler 30 Side reinforcement rubber layer 34 Tread rubber layer 36 Side rubber layer

Claims (2)

A pair of bead cores;
Belt layer,
A plurality of carcass cords arranged in a toroid form from one bead core to the other bead core, with end portions folded back from the tire inner side to the tire radial direction outer side, and three twisted rayon cords arranged in parallel to each other One carcass ply covered with rubber,
A bead filler disposed between a main body portion of the carcass ply extending from one bead core to the other bead core and a folded portion of the carcass ply and extending while gradually decreasing the thickness from the bead core toward the outer side in the tire radial direction; ,
A side reinforcing rubber layer that is disposed on the inner side in the tire axial direction of the carcass ply and gradually decreases in thickness toward the bead portion side and the tread portion side;
With
The folded end of the carcass ply is located at the tire side portion between the end portion of the belt layer and the outer end in the tire radial direction of the bead filler,
The maximum thickness T1 of the side reinforcing rubber layer is set within a range of 30 to 40% of the thickness T0 of the tire side portion measured at the maximum thickness portion of the side reinforcing rubber layer ,
An overlapping region in which the rubber gauge between the carcass ply main body portion and the folded portion is set in a range of 1.0 to 1.5 times the diameter of the carcass cord is located on the end side of the folded portion. A pneumatic run-flat tire characterized by being provided . The belt layer is composed of two belt plies,
A belt reinforcing layer including a plurality of nylon cords is disposed on the outer side in the tire radial direction of the belt layer so as to cover the entire belt layer,
2. The pneumatic run-flat tire according to claim 1, wherein the nylon cord is a single-twist cord obtained by bundling a nylon filament and performing only a lower twist. 3.

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