JP7064352B2 - Run flat tire - Google Patents

Description

The present invention relates to a run-flat tire having excellent durability.

The following Patent Document 1 is arranged in a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, a belt layer arranged on the outside of the carcass and inside the tread portion, and inside the carcass of the sidewall portion. We are proposing run-flat tires with side reinforcement rubber layers.

In a run-flat tire at the time of a flat tire, a tread lift is generated in which the tread portion is dented inward in the radial direction of the tire as the internal pressure decreases during running under a load. When a tread lift occurs, the buttress portions on both outer sides of the tread portion tend to touch the ground. When the buttress portion touches the ground, the load acting on the tire is concentrated on the side reinforcing rubber layer, and there is a problem that the side reinforcing rubber layer is destroyed at an early stage due to heat generation or the like.

Japanese Patent Application Laid-Open No. 2003-341308

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a run-flat tire capable of improving durability during run-flat running.

The present invention includes a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, a belt layer arranged outside the carcus and inside the tread portion, and inside the carcass of the sidewall portion. A run-flat tire with a side reinforcing rubber layer arranged on the tire meridional cross section in a punctured state where the tire is assembled on a regular rim, the internal pressure is zero, and a regular load is applied. The outer end in the tire axial direction is characterized in that it is located within the range of the ground contact surface in the tire axial direction.

In the run-flat tire according to the present invention, it is desirable that the outer end of the belt layer is located at the buttless portion on the outer side in the tire axial direction from the tread end of the tread portion in the tire meridional cross section.

The run-flat tire according to the present invention has a tire cross-sectional height H and a maximum tire width position from the bead baseline in a tire meridional cross section under a normal state of no load, which is rim-assembled on a regular rim and is filled with a regular internal pressure. It is desirable that the distance L1 in the tire radial direction up to and the distance L2 in the tire radial direction from the bead baseline to the outer end of the belt layer satisfy the following relationship.
L1 + 0.5 (H-L1) ≤ L2 ≤ L1 + 0.8 (H-L1)

In the run-flat tire according to the present invention, the width of the belt layer in the tire axial direction is the maximum tire width in the tire meridional cross section in a normal state with no load, which is rim-assembled on a regular rim and filled with a regular internal pressure. It is preferably in the range of 85% to 90%.

The run-flat tire of the present invention has a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, a belt layer arranged on the outside of the carcass and inside the tread portion, and inside the carcass of the sidewall portion. It has a side reinforcing rubber layer arranged.

In this run-flat tire, the outer end of the belt layer in the tire axial direction is the tire shaft of the ground contact surface in the tire meridional cross section in a punctured state where the rim is assembled on the regular rim, the internal pressure is zero, and the regular load is applied. It is located within the range of the direction. Therefore, during the run-flat running, the reaction force from the road surface acting on the ground contact surface is dispersed in the belt layer and the side reinforcing rubber layer, and the distortion of the side reinforcing rubber layer is reduced. As a result, in the run-flat tire of the present invention, heat generation of the side reinforcing rubber layer can be suppressed for a long period of time, and durability during run-flat running can be improved.

FIG. 3 is a cross-sectional view taken along the meridian of a tire in a normal state according to an embodiment of the present invention. It is a partially enlarged view near the sidewall portion of FIG. 1. It is a meridian cross-sectional view of a punctured tire in contact with a road surface.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional view of a tire meridian including a tire rotation axis in a normal state of a run-flat tire (hereinafter, may be simply referred to as a “tire”) 1 of the present embodiment. The run-flat tire 1 of the present embodiment can be suitably used, for example, for a passenger car.

The "normal state" is a state in which the tire is rim-assembled on a normal rim (not shown) and is filled with normal internal pressure without load. In the present specification, unless otherwise specified, the dimensions of each part of the tire are the values in the normal state.

A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, "standard rim" for JATTA and "Design Rim" for TRA. If it is ETRTO, it is "Measuring Rim".

"Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For example, "maximum air pressure" for JATTA and "TIRE" for TRA. The maximum value described in LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES, or "INFLATION PRESSURE" for ETRTO.

As shown in FIG. 1, the tire 1 of the present embodiment is arranged in the carcass 6 from the tread portion 2 to the bead core 5 of the bead portion 4 via the sidewall portion 3 and outside the carcass 6 and inside the tread portion 2. The belt layer 7 is provided, the side reinforcing rubber layer 8 arranged inside the carcass 6 of the sidewall portion 3, and the bead apex rubber 9 arranged on the bead portion 4.

The carcass 6 is formed of at least one carcass ply, and in this embodiment, one carcass ply 6A. The carcass ply 6A includes, for example, a main body portion 6a and a folded portion 6b.

The main body portion 6a extends between the bead cores 5 of the pair of bead portions 4. The folded-back portion 6b is folded back from the inside to the outside in the tire axial direction around the bead core 5.

It is desirable that the folded-back portion 6b is terminated on the outer side in the radial direction of the tire, for example, with respect to the outer end 9b of the bead apex rubber 9. It is desirable that the folded-back portion 6b of a more preferable embodiment is sandwiched between the main body portion 6a and the belt layer 7 and terminated. It is desirable that the folded-back portion 6b of a more preferable embodiment is terminated inside the tire radial direction of the vertical groove 11 which continuously extends the most tread end Te side of the tread portion 2 in the tire circumferential direction. Such a carcass 6 is useful for increasing the rigidity of the sidewall portion 3 in a wide range and, by extension, improving the durability during run-flat running.

The "tread end" is a position on the outermost side in the tire axial direction of the ground contact surface when a normal load is applied to the tire in a normal state and the tire is grounded on a flat surface at a camber angle of 0 °.

The "regular load" is the load defined for each tire in the standard system including the standard on which the tire is based. For example, "maximum load capacity" for JATTA and "table" for TRA. The maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

The carcass ply 6A is formed, for example, by covering the carcass cord with a topping rubber. The carcass cord of the present embodiment is arranged at an angle of, for example, 75 to 90 degrees with respect to the tire equator C. As the carcass cord, a metal fiber cord such as steel or an organic fiber cord such as polyester, nylon, rayon or aramid can be adopted. In this embodiment, the organic fiber cord can be preferably adopted.

FIG. 2 shows a partially enlarged view of the vicinity of the sidewall portion 3 on one side of FIG. 1. As shown in FIG. 1 or 2, the bead apex rubber 9 of the present embodiment is arranged between the main body portion 6a and the folded-back portion 6b of the carcass ply 6A.

The bead apex rubber 9 extends in a tapered shape from the bottom surface 9a in contact with the outer surface of the bead core 5 in the radial direction of the tire toward the outer end 9b in the radial direction of the tire. The bead apex rubber 9 is formed of, for example, a hard rubber harder than the rubber forming the tread portion 2 and the sidewall portion 3, for example, a rubber having a JIS A hardness of 65 ° or more. Such a bead apex rubber 9 increases the rigidity of the bead portion 4, reduces the deflection during run-flat running in cooperation with the side reinforcing rubber layer 8, and helps to improve the durability during run-flat running.

It is desirable that the outer end 9b of the bead apex rubber 9 has a height Ha in the tire radial direction from the bead baseline BL in the range of, for example, 10 to 50% of the tire cross-sectional height H. When the height Ha in the tire radial direction is less than 10% of the tire cross-sectional height H, the deflection during run-flat running becomes large, and the run-flat durability may decrease. On the contrary, when the height Ha in the tire radial direction is larger than 50% of the tire cross-sectional height H, the tire mass may increase and the ride quality may deteriorate.

The side reinforcing rubber layer 8 of the present embodiment has a thickness reduced from the central portion to the inside and outside in the radial direction of the tire, and is formed in a substantially crescent shape in cross section. Preferably, the maximum thickness t of the side reinforcing rubber layer 8 is in the range of 5% to 10% of the height H in the radial direction of the tire. It is desirable that such a side reinforcing rubber layer 8 is formed of, for example, a hard rubber, like the bead apex rubber 9.

The inner end 8a of the side reinforcing rubber layer 8 in the tire radial direction is adjacent to the inner side surface of the bead apex rubber 9 in the tire axial direction via, for example, the main body portion 6a of the carcass ply 6A. On the other hand, the outer end 8b of the side reinforcing rubber layer 8 in the tire radial direction extends to, for example, the inside of the tread end Te in the tire radial direction. Such a side reinforcing rubber layer 8 increases the rigidity of the sidewall portion 3, particularly the bending rigidity near the maximum width position M which is the maximum width Wm of the tire, reduces the deflection during run-flat running, and reduces the bending during run-flat running. Can improve durability.

It is desirable that the height Hb in the tire radial direction between the inner end 8a and the outer end 8b of the side reinforcing rubber layer 8 is, for example, in the range of 35 to 70% of the tire cross-sectional height H. When the height Hb in the radial direction of the tire is less than 35% of the height H of the cross section of the tire, the deflection during the run-flat running becomes large, and the run-flat durability may decrease. On the contrary, when the height Hb in the radial direction of the tire is larger than 70% of the cross-sectional height H of the tire, the tire mass may increase and the ride quality may deteriorate.

The belt layer 7 is formed of, for example, at least one belt ply 7A and 7B in this embodiment. Each belt ply 7A and 7B includes, for example, a belt cord arranged at an angle of 10 to 35 ° with respect to the tire equator C. The belt plies 7A and 7B are overlapped so that the belt cords intersect each other. For the belt cord, for example, a steel cord is suitable, but a highly elastic organic fiber cord such as aramid or rayon can also be adopted.

In the present embodiment, the band layer 10 is arranged on the outside of the belt layer 7. The band layer 10 includes band cords arranged at an angle of, for example, 5 degrees or less with respect to the tire circumferential direction. For the band cord, for example, an organic fiber cord such as nylon or aramid is adopted.

FIG. 3 shows a tire meridian cross-sectional view of the punctured tire 1. The punctured state is a state in which the tire 1 is rim-assembled on a regular rim, the internal pressure is zero (gauge pressure), a regular load is applied, and the tire 1 is pressed against the horizontal plane HP at a camper angle of 0 degrees.

As shown in FIG. 3, in the punctured tire 1, a so-called tread lift is generated in which the vicinity of the tire equator C of the tread portion 2 is recessed inward in the radial direction of the tire. Therefore, the contact patch S of the tire 1 is formed separately on both sides of the tire equator C, and each of them is formed from the end side of the tread portion 2 to the sidewall portion 3. Since the contact patch S in such a punctured state is located outside the contact patch in the tire axial direction larger than the contact patch during normal running, the conventional tire tends to have insufficient strength against contact.

In the present invention, in view of such an actual situation, the outer end 7a of the belt layer 7 in the tire axial direction is positioned within the range of the ground contact surface S in the tire axial direction in the tire meridional cross section in the punctured state. In the tire 1, the reaction force from the road surface acting on the ground contact surface S is distributed and borne by the belt layer 7 and the side reinforcing rubber layer 8 during the run-flat running. As a result, in the tire 1 of the present embodiment, the distortion of the side reinforcing rubber layer 8, particularly the distortion near the outer end 8b covered with the belt layer 7, is effectively reduced. Therefore, the heat generation of the side reinforcing rubber layer 8 is suppressed, and its destruction is prevented for a long period of time. Therefore, the tire 1 has improved durability during run-flat running. Further, in such a tire 1, the rigidity in the vicinity of the tread end Te of the tread portion 2 is increased, and the wear resistance performance in the vicinity of the tread end Te of the tread portion 2 is improved.

The ground contact surface S of the punctured tire 1 is formed including, for example, the buttress portion 12. Therefore, in a more preferred embodiment, the outer end 7a of the belt layer 7 is located at the buttless portion 12 outside the tread end Te of the tread portion 2 in the tire axial direction in the tire meridian cross section in the punctured state.

In a more preferred embodiment, in the tire meridional cross section in the punctured state, the tire axial distance a of the belt layer 7 included in the range of the ground contact surface S is 40% or more, more preferably 40% or more of the ground contact width Ws of the ground contact surface S in the punctured state. It is desirable that it is 50% or more. With such a tire 1, the durability during run-flat running can be further improved.

In order to obtain the action of the belt layer 7 as described above, as shown in FIG. 1 or 2, in the tire meridian cross section in the normal state, the width Wb of the belt layer 7 in the tire axial direction is, for example, the maximum tire width. It is preferably in the range of 85% to 90% of Wm. When the width Wb of the belt layer 7 is less than 85% of the maximum tire width Wm, the outer end 7a of the belt layer 7 is located near the tread end Te in the range of the ground contact surface S in the tire axial direction in the punctured state, and the run Durability during flat driving may not be sufficiently improved. On the contrary, when the width Wb of the belt layer 7 is larger than 90% of the maximum tire width Wm, the tire mass may increase excessively.

From the same viewpoint as above, in the tire meridional cross section in the normal state, the tire cross section height H, the distance L1 in the tire radial direction from the bead baseline BL to the tire maximum width Wm, and the belt layer 7 from the bead baseline BL. It is desirable that the distance L2 in the tire radial direction to the outer end 7a of the tire satisfies the following relationship.
L1 + 0.5 (H-L1) ≤ L2 ≤ L1 + 0.8 (H-L1)

In the above relationship, when the distance L2 is less than L1 + 0.5 (H-L1), the outer end 7a of the belt layer 7 is located near the sidewall portion 3, and the tire 1 is generally provided due to repeated bending in the sidewall portion 3. Durability may be reduced. On the contrary, when the distance L2 is larger than L1 + 0.8 (H—L1), it may not be possible to expect an improvement in durability during run-flat running.

Although the particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these embodiments and can be modified into various embodiments.

Tires (size: 225 / 60RF18) having the basic structure shown in FIG. 1 and based on the specifications in Table 1 were prototyped and their performance was tested. As a comparative example, a tire in which the outer end of the belt layer was not included in the range of the ground contact surface in the tire axial direction in the punctured tire meridian cross section was prototyped and tested in the same manner.
The test method is as follows.

<Runflat durability>
Each test tire is attached to the rim (6.5J) with the valve core removed, and in a punctured state with zero internal pressure, a drum test is conducted under the following conditions in accordance with the ECE30 regulations, and running until the tire breaks. The time was measured. The evaluation is an index with a comparative example of 100, and the larger the value, the better.
Speed: 80km / h
Load: 65% of maximum load load

<Tire mass>
The mass of each test tire before it was assembled to the rim was measured. The evaluation is an index with a comparative example of 100, and the smaller the value, the better.

<Abrasion resistance>
Each test tire attached to the rim (6.5J) with an internal pressure of 210 kPa is attached to all wheels of the test vehicle, and after traveling 15,000 km on a test course on a dry road surface, at three points on the tire circumference, near the tread end of the tread part. The amount of wear was measured. The evaluation is an index with the comparative example as 100 based on the reciprocal of averaging the amount of wear, and the larger the value, the better.

As shown in Table 1, it was confirmed that the tires of each embodiment had improved run-flat durability.

2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 7a Outer end 8 Side reinforcement rubber layer S Ground surface

Claims (2)

The carcass from the tread portion to the bead core of the bead portion through the sidewall portion, the belt layer arranged on the outside of the carcass and inside the tread portion, and the side arranged inside the carcass of the sidewall portion. A run-flat tire with a reinforced rubber layer,
The carcass is formed from at least one carcass ply including a main body portion of a pair of the bead portions straddling between the bead cores and a folded portion that is folded back from the inside to the outside in the tire axial direction around the bead core. ,
The folded portion is sandwiched between the main body portion and the belt layer and terminated.
In the tire meridional cross section in a punctured state where the rim is assembled to the regular rim, the internal pressure is zero, and the regular load is applied, the outer end of the belt layer in the tire axial direction is within the range of the ground plane in the tire axial direction. Position to,
The tire axial distance of the belt layer included in the range of the ground contact surface in the punctured state is 50% or more of the ground contact width of the ground contact surface in the punctured state.
The outer end of the belt layer is located at the buttress portion outside the tread end in the tire axial direction in the tire meridian cross section.
The folded portion ends on the inner side of the tire radial direction of a vertical groove that continuously extends in the tire circumferential direction at the most tread end side of the tread portion.
In the tire meridional cross section in the normal state with no load, which is assembled on the regular rim and filled with the regular internal pressure, the tire cross-sectional height H, the distance L1 in the tire radial direction from the bead baseline to the tire maximum width position, and A run-flat tire characterized in that the distance L2 in the tire radial direction from the bead baseline to the outer end of the belt layer satisfies the following relationship.
L1 + 0.5 (H-L1) ≤ L2 ≤ L1 + 0.8 (H-L1) A claim that the width of the belt layer in the tire axial direction is in the range of 85% to 90% of the maximum tire width in the tire meridian cross section in a normal state with no load assembled to the normal rim and filled with the normal internal pressure. Item 1. The run-flat tire according to Item 1.

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