JP4456338B2 - Run flat tire - Google Patents

Description

【００３８】
表の如く、実施例品は、通常走行での操縦安定性や乗り心地性等を損ねることなく、かつタイヤの軽量化を図りながらトレッドリフトを効果的に抑制できるのが確認できる。
【００３９】
【発明の効果】
叙上の如く本発明は、従来のベルト層に代え、バンドコードを螺旋巻きしたバンド層と高硬度かつ低発熱性のゴムを用いたトレッド補強ゴム層とからなるベルト状体を用いているため、乗り心地性の低下やタイヤ重量の増加を招くことなく、トレッドリフトを効果的に抑制でき、ランフラット時における耐久性及び操縦安定性等を向上しうる。
【図面の簡単な説明】
【図１】本発明のランフラットタイヤの一実施例を示す断面図である。
【図２】そのトレッド部を拡大して示す断面図である。
【図３】（Ａ）、（Ｂ）は従来技術及びその問題点を説明する断面図である。
【符号の説明】
２ トレッド部
３ サイドウォール部
４ ビード部
５ ビードコア
６ カーカス
１１ サイド補強ゴム層
９ バンド層
２Ｇ トレッドゴム
１０ トレッド補強ゴム層
７ ベルト状体
９Ａ バンドプライ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a run flat tire that can suppress tread lift during run flat and improve durability and steering stability.
[0002]
[Prior art]
As shown in FIG. 3A, as a run flat tire that can travel relatively long distances even when air in the tire escapes due to puncture or the like, a side having a substantially crescent-shaped cross section is formed inside the sidewall portion a. The thing provided with the reinforced rubber layer b is proposed (for example, refer patent document 1). In the figure, reference numeral c denotes a carcass in which carcass cords are radially arranged, and reference numeral d denotes a tread reinforcing belt layer in which belt cords are arranged in a crossing manner.
[0003]
[Patent Document 1]
JP 2000-351307 A
[Problems to be solved by the invention]
In this type of tire, during run-flat running, as shown in FIG. 3 (B), a tread in which the central portion of the tread portion f rises from the road surface as the sidewall portion a bends and the shoulder portion e contacts the ground. Lift occurs.
[0005]
At this time, the ground contact pressure of the shoulder portion e becomes very high, abnormal wear occurs in the portion e, and the side wall rubber portion b is increased in bending, thereby promoting the heat generation of the side reinforcing rubber layer b. Therefore, the durability at the time of run flat is lowered. Further, since the ground contact area is reduced and the ground contact performance is impaired, the steering stability and the braking performance are also deteriorated.
[0006]
Conventionally, as a means for suppressing the tread lift, a steel cord is used for the belt cord, and the belt rigidity is increased by increasing the diameter of the cord and increasing the cord density. However, with such means, there is a problem that the ride comfort is impaired during normal running in inflation, and the tire weight is increased as the amount of steel increases.
[0007]
Therefore, in the present invention, instead of the conventional belt layer, a belt-like body composed of a band layer spirally wound with a band cord and a tread reinforced rubber layer using rubber having high hardness and low heat generation is adjacent to the outside of the carcass. Based on this, it is possible to provide a run-flat tire that can effectively suppress tread lift without causing a decrease in ride comfort and an increase in tire weight, and that can improve durability and handling stability during run-flat. It is aimed.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application includes a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a side reinforcing rubber layer having a substantially crescent-shaped cross section disposed on the sidewall portion. A band layer disposed radially inward of the carcass on the inner side of the tread portion, and a tread disposed on the outer side of the band layer in the radial direction and having an outer surface in direct contact with the tread rubber. A belt-like body comprising a reinforcing rubber layer is provided, and the tread reinforcing rubber layer has a tangent loss (tan δ) measured at a hardness higher than that of the tread rubber, a temperature of 70 ° C., a dynamic strain of 2%, and a frequency of 10 Hz. It is made of a small low heat-generating rubber, the tangent loss (tan δ) is 0.02 or more and 0.06 or less, and the rubber hardness (durometer A hardness) is 77 ° or more and The band layer is composed of a band ply in which the band cord is spirally wound at an angle of 5 degrees or less with respect to the tire circumferential direction.
[0009]
According to a second aspect of the present invention, the band layer has a ply elastic modulus of 400, which is a product of a force (N) for extending one band cord by 3% and the number of band cords driven per 5 cm width (pieces). It is characterized by -2000 (N · book) .
[0010]
According to a third aspect of the present invention, in the run flat tire according to the first or second aspect, the band cord is a rayon cord.
[0013]
Here, the “tread contact width WT” is a tire shaft between tread contact ends when a normal load is applied to a tire in a normal internal pressure state in which a normal rim is assembled and filled with a normal internal pressure, and a normal load is applied to a flat surface. It means the width of the direction. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure specified by the tire for each tire. The maximum air pressure in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, In the case of ETRTO, it means “INFLATION PRESSURE”, but in the case of passenger tires, it is 180 kPa. The “regular load” is the load specified by the standard for each tire. The maximum load capacity shown in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is the maximum load capacity for JATMA and TRA for TRA. In the case of ETRTO, it means a load obtained by multiplying "LOAD CAPACITY" by 0.88.
[0014]
In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified in the normal internal pressure state.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a case where the run flat tire of the present invention is a low-flat radial tire for a passenger car having a tire flatness ratio of 50% or less.
[0016]
In FIG. 1, a run-flat tire 1 is arranged on a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, inside the tread portion 2, and radially outside the carcass 6. A belt-like body 7 and a side-reinforcing rubber layer 11 having a substantially crescent-shaped cross section disposed on the sidewall portion 3.
[0017]
The carcass 6 includes one or more carcass cords arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction, in this example, one carcass ply 6A. As the carcass cord, for example, a steel cord or polyester, Organic fiber cords such as nylon and rayon are appropriately employed.
[0018]
The carcass ply 6A includes a series of ply folding portions 6b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the ply main body portion 6a straddling the bead cores 5 and 5. A bead apex rubber 8 having a triangular cross-section extending radially outward from the bead core is disposed between the ply main body 6a and the ply turn-up portion 6b.
[0019]
Next, the side reinforcing rubber layer 11 has a substantially crescent-shaped cross section in which the thickness gradually decreases inward and outward in the tire radial direction from the central portion 11A having the maximum thickness T, and the bending rigidity of the sidewall portion 3 is increased. It works to reduce the vertical deflection of the tire in the puncture state. For this purpose, the central portion 11A is positioned in the vicinity of the carcass maximum width position M (the height position at which the ply main body portion 6a protrudes most outward in the tire axial direction) that is most easily bent in the puncture state.
[0020]
The side reinforcing rubber layer 11 is preferably disposed on the tire lumen side of the carcass 6 as in this example from the viewpoint of increasing bending rigidity. However, when the carcass 6 is formed of a plurality of carcass plies 6A. Can also be arranged between the ply body portions 6a, 6a.
[0021]
In any case, the side reinforcing rubber layer 11 is located at the inner side in the tire axial direction from the outer end in the tire axial direction of the belt-like body 7 from the lower end EL in the radial direction from the outer end in the radial direction of the bead apex rubber 8. Preferably, it extends to the upper end EU. Thereby, overlapping portions 12L and 12U are formed between the bead apex rubber 8 and the belt-like body 7, respectively, and the rigidity steps at the upper end EU and the lower end EL are reduced. The overlapping length WL in the radial direction of the lower overlapping portion 12L is preferably 5 to 60 mm, and the overlapping length WU in the tire axial direction of the upper overlapping portion 12U is preferably 5 to 20 mm. If the overlapping lengths WL and WU are smaller than 5 mm, there is a risk of bending deformation at the upper end EU and the lower end EL, and unnecessary if the overlapping lengths WL and WU are larger than 60 mm and 20 mm. Cause a significant increase in weight.
[0022]
From the viewpoint of weight increase and the reinforcing effect, the maximum thickness T of the side reinforcing rubber layer 11 is preferably in the range of 5 to 15 mm.
[0023]
Next, as shown in an enlarged view in FIG. 2, the belt-like body 7 is arranged on the carcass 6 adjacent to the outer side in the radial direction and on the outer side of the band layer 9. The tread reinforcing rubber layer 10 is formed.
[0024]
Of these, the band layer 9 is formed of one or more band plies 9A, in this example, one band ply 9A, in which a band cord is spirally wound at an angle of 5 ° or less with respect to the tire circumferential direction. The width W1 in the tire axial direction of the band layer 9 is 95% or more and 120% or less of the tread ground contact width WT, and restrains substantially the entire tread portion 2 with a high tagging effect. As the band cord, a steel cord or an organic fiber cord such as nylon, polyester, rayon, aromatic polyamide or the like can be used as appropriate, but an organic fiber cord is preferably used from the viewpoint of weight reduction.
[0025]
When the product of the force (N) for stretching one cord by 3% and the number of cords driven per 5 cm width (the number) is defined as the ply elastic modulus, the ply elastic modulus of the band layer 9 is 400 ( N · book) and preferably in a range of ˜2000 (N · book) or less.
[0026]
The tread reinforcing rubber layer 10 is made of a rubber having a high hardness and a low heat generation property, which has a rubber hardness higher than that of the tread rubber 2G and a tangent loss (tan δ). When the tread rubber 2G is formed of a plurality of rubber layers, the tread reinforcing rubber layer 10 has a rubber hardness larger than the hardest rubber of the tread rubber 2G and has the lowest heat generation. Than the tangent loss (tan δ).
[0027]
In particular, the tread reinforced rubber layer 10 has a rubber hardness (durometer A hardness) of 77 ° to 95 ° and a tangent loss (tan δ) of 0.02 to 0.06 .
[0028]
Here, when the tread lift is generated in the tire, as shown in FIG. 3B, the carcass side of the tread portion is the tension side, and the tread surface side is the compression side. Therefore, by providing the band layer 9 adjacent to the carcass 6, the carcass cord can bear the tension on the tension side in the radial direction and the band cord in the circumferential direction. The rigidity of can be effectively increased. Further, the rigidity on the compression side can be effectively increased by disposing the tread reinforcing rubber layer 10 made of a hard rubber having excellent compression rigidity further outward of the band layer 9 in the radial direction. These synergistic effects increase the resistance to the tread lift and can effectively suppress the occurrence thereof.
[0029]
At this time, when the tangent loss (tan δ) of the tread reinforcing rubber layer 10 is 0.06 or less, the road surface followability is increased and the run-flat running performance is improved. It can be further improved. In addition, since the heat generation is low, the temperature rise is suppressed and it is possible to contribute to the improvement of durability at the time of run flat. When the tangent loss (tan δ) is less than 0.02, there is a possibility that although the energy loss becomes small, the reinforcement becomes low.
[0030]
The tangent loss (tan δ) is a value measured at a temperature of 70 ° C., a dynamic strain of 2%, and a frequency of 10 Hz using a rubber viscoelasticity spectrometer manufactured by Iwamoto Seisakusho.
[0031]
In order to effectively exhibit the tread lift suppressing effect, the thickness t of the tread reinforcing rubber layer 10 is preferably 2 mm or more and 8 mm or less. When the thickness t is less than 2 mm, the compression side rigidity is too small, and the tread lift suppressing effect is insufficient. On the contrary, if it exceeds 8 mm, it becomes disadvantageous for riding comfort and tends to unnecessarily increase the tire weight. Therefore, the thickness t is more preferably 3 mm or more and 7 mm or less. Similarly, if the rubber hardness is less than 77 °, the effect of suppressing the tread lift is insufficient, and if it exceeds 95 °, the ride comfort is deteriorated. From such a viewpoint, the rubber hardness is more preferably in the range of 77 ° to 95 °, and more preferably in the range of 78 ° to 94 °.
[0032]
Further, the tire 1 needs to exhibit excellent cornering performance and envelope performance during normal running in inflation. However, since the tread reinforced rubber layer 10 has high hardness and low heat build-up, it is possible to use a relatively soft rubber having excellent road surface grip properties while ensuring the necessary tread rigidity. The envelope performance can be improved while keeping the cornering performance high.
[0033]
The width W1 of the band layer 9 is 95% or more and 120% or less of the tread grounding width WT in order to stabilize the grounding surface in the normal traveling, particularly high-speed traveling, and to exhibit high steering stability including cornering performance. The width W2 of the tread reinforcing rubber layer 10 is preferably set to 100 % or more and 120% or less of the tread ground contact width WT. When the widths W1 and W2 are lower than their lower limits, the steering stability tends to be impaired. Conversely, when the widths W1 and W2 are higher than the upper limits, the rigidity difference of the constituent materials is increased at the shoulder portion having a large bend, resulting in structural damage. There is a problem that the fear of increasing.
[0034]
As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.
[0035]
【Example】
A tire having the structure shown in FIG. 1 and having a tire size of 245 / 40R18 was manufactured according to the specifications shown in Table 1, and the amount of tread lift of the sample tire (distance h shown in FIG. 3B), tire weight, run-flat durability Performance, driving stability in normal driving, and ride comfort were tested. The specifications other than those shown in Table 1 were the same.
[0036]
(1) Steering stability and ride comfort:
Steering tires (rigidity and steering response) when a sample tire is mounted on four wheels of a vehicle (4300cc) with a rim (8x8JJ) and internal pressure (230kPa) and running on a tire test course on a dry asphalt road surface The conventional example was evaluated as 100 by the sensory evaluation of the driver. A larger value is better.
(2) Rolling resistance:
The measurement was performed using a rolling resistance tester, and the conventional example was evaluated as 100. A larger value is worse.
[0037]
[Table 1]

[0038]
As shown in the table, it can be confirmed that the example products can effectively suppress the tread lift while reducing the weight of the tire without impairing the steering stability and the riding comfort in the normal running.
[0039]
【The invention's effect】
As described above, the present invention uses a belt-like body composed of a band layer in which a band cord is spirally wound and a tread reinforced rubber layer using a rubber having high hardness and low heat generation, instead of the conventional belt layer. The tread lift can be effectively suppressed without lowering the ride comfort and increasing the tire weight, and the durability and handling stability during run-flat can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a run flat tire of the present invention.
FIG. 2 is an enlarged sectional view showing the tread portion.
FIGS. 3A and 3B are cross-sectional views illustrating the prior art and its problems. FIGS.
[Explanation of symbols]
2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 11 Side reinforcing rubber layer 9 Band layer 2G Tread rubber 10 Tread reinforcing rubber layer 7 Belt-like body 9A Band ply

Claims (3)

A carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a side reinforcing rubber layer having a substantially crescent-shaped cross section disposed in the sidewall portion,
A band layer disposed radially inward of the carcass on the inner side of the tread portion, and a tread reinforcing rubber layer disposed on the outer side of the band layer in the radial direction and having an outer surface in direct contact with the tread rubber; A belt-shaped body made of
The tread reinforcing rubber layer is made of a low heat-generating rubber having a hardness higher than that of the tread rubber, a temperature of 70 ° C., a dynamic strain of 2%, and a low tangent loss (tan δ) measured at a frequency of 10 Hz , and Tangent loss (tan δ) is 0.02 or more and 0.06 or less, and rubber hardness (durometer A hardness) is 77 ° or more and 95 ° or less,
Moreover, the band layer is a run-flat tire comprising a band ply in which a band cord is spirally wound at an angle of 5 ° or less with respect to the tire circumferential direction.   The band layer has a ply elastic modulus of 400 to 2000 (N · line), which is a product of a force (N) for extending one band cord by 3% and the number of band cords driven per 5 cm width (line). The run flat tire according to claim 1. The run flat tire according to claim 1 or 2 , wherein the band cord is a rayon cord .

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