JP2004338572A - Run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively suppress tread lift without degrading ride quality or increasing the weight of a tire. <P>SOLUTION: A belt-like body 7 comprising a band layer 9 adjacent to the outer side of a carcass 6 and a tread reinforcing rubber layer 10 disposed on the outer side thereof is provided within a tread part 2 of a run-flat tire 1 furnished with a side reinforcing rubber layer 11 having a roughly crescent cross section on a side wall part 3. The band layer 9 consists of a band ply 9A with a band cord spirally wound at the angle of ≤ 5° with respect to the circumferential direction of the tire, and the tread reinforcing rubber layer 10 is formed of low heat build-up which is higher in hardness and smaller in tangential loss than tread rubber 2G. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a run flat tire that can suppress a tread lift at the time of run flat and improve durability and steering stability.
[0002]
[Prior art]
As illustrated in FIG. 3 (A), a run-flat tire having a substantially crescent-shaped cross section can be used as a run-flat tire that can travel a relatively long distance even when air in the tire is released due to puncture or the like. A device provided with a reinforcing rubber layer b has been proposed (for example, see Patent Document 1). In addition, the code | symbol c in the figure is the carcass which carcass cord arranged radially, and the code | symbol d is the belt layer for tread reinforcement which arranged the belt code crosswise.
[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), as the sidewall portion a is bent and the shoulder portion e comes into contact with the ground, the center portion of the tread portion f rises from the road surface. A lift occurs.
[0005]
At this time, the ground pressure at the shoulder portion e becomes extremely high, causing abnormal wear at this portion e and increasing the deflection of the sidewall portion a, thereby promoting heat generation of the side reinforcing rubber layer b. Therefore, the durability at the time of run flat decreases. In addition, since the contact area is reduced and the contact property is impaired, steering stability and braking performance are also reduced.
[0006]
Conventionally, as means for suppressing the tread lift, a steel cord has been used as a belt cord, and the belt rigidity has been increased by increasing the diameter of the cord and increasing the cord density. However, such means has a problem that the ride comfort is impaired during normal running on inflation, and that the weight of the tire increases with an increase in the amount of steel.
[0007]
Therefore, the present invention provides a belt-like body consisting of a band layer in which a band cord is spirally wound and a tread reinforcing rubber layer using a high-hardness and low-heat-generating rubber instead of the conventional belt layer, which is adjacent to the outside of the carcass. On the basis of this, it is necessary to provide a run-flat tire that can effectively suppress a tread lift and improve durability and handling stability at the time of run-flat without causing a decrease in ride comfort and an increase in tire weight. The purpose is.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the present application is directed to 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 cross section disposed on the sidewall portion. With
A band layer disposed radially outside the carcass inside the tread portion, and a band layer disposed radially outside the band layer and having higher hardness and tangent loss (tan δ) than the tread rubber. While providing a belt-shaped body consisting of a tread reinforcing rubber layer using a small low heat-generating rubber,
The band layer is formed of a band ply in which a band cord is spirally wound at an angle of 5 ° or less with respect to a tire circumferential direction.
[0009]
Further, in the invention of claim 2, the tread reinforcing rubber layer has a tangent loss (tan δ) of 0.02 or more and 0.06 or less, and a rubber hardness (durometer A hardness) of 77 ° or more and 95 ° or less. It is characterized by:
[0010]
In the invention of claim 3, the band layer has a width W1 in the tire axial direction of 95% or more and 120% or less of the tread contact width WT.
[0011]
Further, in the invention of claim 4, the tread reinforcing rubber layer is characterized in that the width W2 in the tire axial direction is 80% or more and 120% or less of the tread contact width WT.
[0012]
In the invention of claim 5, the tread reinforcing rubber layer has a thickness t of 2 mm or more and 8 mm or less.
[0013]
Here, the "tread contact width WT" refers to a tire shaft between the tread contact ends when a regular load is applied to a tire with a regular internal pressure filled with a regular rim and a regular internal pressure filled with a regular internal rim. Mean width in direction. The "regular rim" is a rim defined for each tire in a 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 an air pressure defined for each tire according to the standard, and is the maximum air pressure for JATMA, and the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLASION PRESSURESRES” for TRA, In the case of ETRTO, it means "INFLATION PRESSURE". In the case of a tire for a passenger car, the pressure is 180 kPa. The "regular load" is a load defined for each tire by the standard. For JATMA, the maximum load capacity. For TRA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURESURES". , ETRTO means a load obtained by multiplying "LOAD CAPACITY" by 0.88.
[0014]
In this specification, unless otherwise specified, dimensions and the like of each part of the tire are values specified in the normal internal pressure state.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to illustrated examples.
FIG. 1 is a 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 of 50% or less.
[0016]
In FIG. 1, a run flat tire 1 is provided with a carcass 6 extending from a tread portion 2 to a bead core 5 of a bead portion 4 through a sidewall portion 3, and inside a tread portion 2 and outside a radial direction of the carcass 6. And a side reinforcing rubber layer 11 having a substantially crescent cross section disposed on the side wall portion 3.
[0017]
The carcass 6 is composed of one or more carcass plies 6A in which carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction, in this example, one carcass ply 6A. Organic fiber cords such as nylon and rayon are appropriately employed.
[0018]
In addition, the carcass ply 6A includes a series of ply folded portions 6b that are folded around the bead core 5 from the inside in the tire axial direction to the outside around the bead core 5 at both ends of the ply body 6a extending between 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 body 6a and the ply turn-up portion 6b.
[0019]
Next, the side reinforcing rubber layer 11 has a substantially crescent-shaped cross section extending gradually inward and outward in the tire radial direction from the central portion 11A having the maximum thickness T to increase the bending rigidity of the sidewall portion 3. , And serves to reduce the longitudinal deflection of the tire in a punctured state. For this purpose, the central portion 11A is located near the carcass maximum width position M (the height position where the ply body portion 6a protrudes most outward in the tire axial direction) where it is most likely to bend in a punctured state.
[0020]
This side reinforcing rubber layer 11 is preferably arranged on the tire lumen side of the carcass 6 as in this example from the viewpoint of increasing the bending rigidity. However, when the carcass 6 is formed of a plurality of carcass plies 6A, Can be arranged between the ply body portions 6a, 6a.
[0021]
In any case, the side reinforcing rubber layer 11 is located radially inward from the lower end EL of the bead apex rubber 8 inward in the tire axial direction relative to the tire axial outer end of the belt-shaped body 7. Preferably, it extends to the upper end EU. Thereby, the overlapping portions 12L and 12U are formed between the bead apex rubber 8 and the belt-shaped 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 of the upper overlapping portion 12U in the tire axial direction is preferably 5 to 20 mm. If the overlap lengths WL and WU are each smaller than 5 mm, bending deformation may occur at the upper end EU and the lower end EL. Unnecessary if the overlap lengths WL and WU are larger than 60 mm and 20 mm. Weight increase.
[0022]
From the viewpoint of weight increase and 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 manner in FIG. 2, the belt-like body 7 is provided with a band layer 9 disposed adjacent to the carcass 6 on the outside in the radial direction, and further disposed outside the band layer 9. And the tread reinforcing rubber layer 10.
[0024]
Of these, the band layer 9 is formed from one or more band ply 9A spirally wound at an angle of 5 ° or less with respect to the tire circumferential direction, in this example, one band ply 9A. The width W1 of the band layer 9 in the tire axial direction is 95% or more and 120% or less of the tread contact width WT, and substantially the entire tread portion 2 is restrained with a high rebound effect. As the band cord, a steel cord or an organic fiber cord such as nylon, polyester, rayon, or aromatic polyamide can be used as appropriate, but it is preferable to use an organic fiber cord from the viewpoint of weight reduction.
[0025]
When the product of the force (N) for extending one cord by 3% and the number of cords per 5 cm width (the number of cords) is defined as the ply elastic modulus, the ply elastic modulus of the band layer 9 is 400 ( It is preferably in the range of not less than (N · number) and up to 2,000 (N · number).
[0026]
The tread reinforcing rubber layer 10 is formed of a high-hardness, low-heat-generation rubber having a higher rubber hardness and a smaller tangent loss (tan δ) than the tread rubber 2G. 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 that of the hardest rubber and a rubber having the lowest heat generation among the tread rubbers 2G. The tangent loss (tan δ) is made smaller than that.
[0027]
In particular, the tread reinforcing rubber layer 10 preferably has a rubber hardness (durometer A hardness) of 77 ° or more and 95 ° or less, and a tangent loss (tan δ) of 0.02 or more and 0.06 or less. .
[0028]
Here, when a tread lift occurs in the tire, as shown in FIG. 3B, the carcass side of the tread portion is on the tension side, and the tread surface side is on the compression side. Therefore, by providing the band layer 9 adjacent to the carcass 6, the carcass cord in the radial direction and the band cord in the circumferential direction can bear the tension on the pull side, respectively. Can be effectively increased. Further, by arranging a tread reinforcing rubber layer 10 made of high-hardness rubber having excellent compression rigidity further radially outward of the band layer 9, the rigidity on the compression side can be effectively increased. And, by these synergistic effects, the drag on the tread lift is increased, and the generation thereof can be effectively suppressed.
[0029]
At this time, since the tangent loss (tan δ) of the tread reinforcing rubber layer 10 is 0.06 or less, the resilience from the bending deformation of the tread portion 2 is improved, and the road surface followability is increased, and the run flat running performance is improved. Can be further improved. In addition, since the heat generation is low, the rise in temperature is suppressed, and it is possible to contribute to the improvement of durability during run flat. If the tangent loss (tan δ) is less than 0.02, there is a possibility that the energy loss is small but the reinforcing property is 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 viscoelastic spectrum meter manufactured by Iwamoto Seisakusho.
[0031]
In order to effectively exhibit the effect of suppressing the tread lift, the thickness t of the tread reinforcing rubber layer 10 is preferably set to 2 mm or more and 8 mm or less. If the thickness t is less than 2 mm, the rigidity on the compression side becomes too small, and the effect of suppressing the tread lift becomes insufficient. Conversely, if it exceeds 8 mm, the ride comfort is disadvantageous and the tire weight tends to be unnecessarily increased. 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 a range of 77 ° or more and 95 ° or less, and more preferably in a range of 78 ° or more and 94 ° or less.
[0032]
In addition, the tire 1 needs to exhibit excellent cornering performance and envelope performance during normal running on inflated tires. However, since the tread reinforcing rubber layer 10 has high hardness and low heat build-up, it is possible to use a relatively soft rubber having excellent road grip properties as the tread rubber while securing the necessary tread rigidity. Thus, it is possible to improve the envelope performance while maintaining a high cornering performance.
[0033]
The width W1 of the band layer 9 is set to 95% or more and 120% or less of the tread contact width WT in order to stabilize the ground contact surface in the normal traveling, particularly in high-speed traveling, and to exert a high steering stability including cornering performance. It is preferable to set the width W2 of the tread reinforcing rubber layer 10 to 80% or more and 120% or less of the tread contact width WT. When the widths W1 and W2 are below the respective lower limits, the steering stability tends to be impaired. On the contrary, when the widths W1 and W2 are above the upper limits, the rigidity difference of the constituent materials at the shoulder portion having a large bending becomes large, and structural damage is caused. There is a problem that the fear of escalation increases.
[0034]
As described above, particularly preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.
[0035]
【Example】
A tire having the structure shown in FIG. 1 and having a tire size of 245 / 40R18 was prototyped according to the specifications shown in Table 1, and the amount of tread lift (distance h shown in FIG. 3 (B)), the tire weight, and the run flat durability of the test tires The vehicle was tested for performance, driving stability in normal driving, and riding comfort. Except for the specifications in Table 1, the specifications were the same.
[0036]
(1) Steering stability and ride comfort:
The test tires were mounted on four wheels of a vehicle (4300 cc) with a rim (8 × 8JJ) and internal pressure (230 kPa), and the steering stability (rigidity and handle response) when running on a tire test course on dry asphalt road surface ) And ride comfort were evaluated by a sensory evaluation of a driver, with the conventional example taken as 100. The higher the value, the better.
(2) Rolling resistance:
It measured using the rolling resistance tester, and evaluated it as 100 with the conventional example. Larger values are worse.
[0037]
[Table 1]

[0038]
As shown in the table, it can be confirmed that the product of the example can effectively suppress the tread lift while reducing the weight of the tire without impairing the steering stability and the riding comfort during normal running.
[0039]
【The invention's effect】
As described above, the present invention uses a belt-like body composed of a band layer formed by spirally winding a band cord and a tread reinforcing rubber layer using a rubber having high hardness and low heat generation, instead of the conventional belt layer. In addition, the tread lift can be effectively suppressed without lowering the ride comfort and increasing the tire weight, and the durability and steering stability at the time of run flat can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view showing one 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 a conventional technique and its problems.
[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 9A Band ply

Claims (5)

Carcass from the tread portion to the bead core of the bead portion via the sidewall portion, and a side reinforcing rubber layer having a substantially crescent cross section disposed on the sidewall portion,
A band layer disposed radially outside and adjacent to the carcass inside the tread portion, a band layer disposed radially outside the band layer and having higher hardness and tangent loss (tan δ) than tread rubber; While providing a belt-like body consisting of a tread reinforcing rubber layer using a small low heat-generating rubber,
The run flat tire, wherein the band layer is formed of a band ply in which a band cord is spirally wound at an angle of 5 ° or less with respect to a tire circumferential direction. The tread reinforcing rubber layer has a tangent loss (tan δ) of 0.02 or more and 0.06 or less, and a rubber hardness (durometer A hardness) of 77 ° or more and 95 ° or less. Runflat tire described The run-flat tire according to claim 1, wherein the band layer has a width W <b> 1 in the tire axial direction of 95% or more and 120% or less of a tread contact width WT. 4. The run-flat tire according to any one of claims 1 to 3, wherein the tread reinforcing rubber layer has a width W2 in the tire axial direction of 80% or more and 120% or less of a tread contact width WT. The run-flat tire according to any one of claims 1 to 4, wherein the tread reinforcing rubber layer has a thickness t of 2 mm or more and 8 mm or less.

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