JP2004306771A - Runflat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a runflat tire which doubly satisfies durability performance at the time of runflat travelling and riding comfortability performance at the time of normal travelling. <P>SOLUTION: This runflat tire 1 having a reinforced rubber region 8 making a cross-section roughly crescent shape on the inside of a carcass layer 6 of a side wall part 3 is constituted as a first reinforced rubber layer 8a hardness by a durometer hardness test (type A) of JISK6253 of which is more than 65 to 100° and a second reinforced rubber layer 8b hardness by the durometer hardness test (type A) of JISK6253 of which is more than 45° and set lower by 5 to 55° than the hardness of the first reinforced rubber layer 8a are alternately laminated in more than three layers along the tire diametrical direction and are laminated so that a volumetric ratio of the first reinforced rubber layer 8a increases toward the tire inner surface side on the reinforced rubber region 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

実施例１及び２の結果が示すように、本発明に係るランフラットタイヤによれば、ランフラット走行時の耐久性能を阻害することなく、通常走行時の乗り心地を従来例よりも改善することができた。特に、実施例２では乗り心地性能が大幅に改善されており、上述した硬度の範囲から数値を選択することが好ましいことが分かる。また、第１の硬度及び第２の硬度を変化させることにより、耐久性能と乗り心地性能のバランスを変化させることができることがわかる。
【００４４】
比較例１は、乗り心地性能は優れているものの、第２の硬度が低いため、補強ゴム領域による荷重支持が不十分となり、耐久性能が大幅に悪化する。比較例２の場合、耐久性能が悪化し、乗り心地の良化代は小さい。比較例３のように、第１補強ゴム層と第２補強ゴム層の硬度を実施例１の逆にした場合、第２補強ゴム層の非圧縮性を利用することができないため、ランフラット走行時の耐久性能は悪化する。したがって、表１の結果から本発明に係るランフラットタイヤの効果を確認することができる。
【図面の簡単な説明】
【図１】本発明に係るランフラットタイヤの一例を示す断面図
【図２】別実施形態に係るランフラットタイヤを示す断面図
【符号の説明】
１ ランフラットタイヤ
３ サイドウォール部
６ カーカス層
８ 補強ゴム領域
８ａ 第１補強ゴム層
８ｂ 第２補強ゴム層
Ｃ タイヤ赤道線[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a run flat tire having a reinforcing rubber region in a sidewall portion.
[0002]
[Prior art]
A run flat tire refers to a tire that can travel a certain distance even if a decrease in air pressure inside the tire occurs due to an obstacle such as a puncture. As one of tire structures for enabling such run-flat running, a tire structure in which an inner surface of a sidewall portion is reinforced by a reinforcing rubber layer is known.
[0003]
Since the durability during run-flat running is required for the reinforcing rubber layer, rubber having relatively high hardness has been used. However, the higher the hardness of the reinforcing rubber layer is, the lower the vibration absorption is. Therefore, there has been a problem that the riding comfort during normal running (in a state where the flat tire is not punctured) is impaired.
[0004]
In order to solve the above problem, a reinforcing structure has been proposed in which a reinforcing rubber region is divided into a plurality of regions, and a rubber having a relatively low hardness is used as a reinforcing rubber layer in addition to a rubber having a high hardness.
[0005]
For example, the safety tire disclosed in Patent Literature 1 below has, in a sidewall portion, a first reinforcing rubber layer occupying a radially outer side and a second reinforcing rubber layer occupying a radially inner side. The hardness increases in the order of the first reinforcing rubber layer, the second reinforcing rubber layer, and the rubber filler.
[0006]
Further, the run-flat pneumatic tire disclosed in Patent Literature 2 below has a large number of sidewall wedges stacked in the sidewall portion so that the hardness is gradually reduced in the inward direction of the tire diameter.
[0007]
Further, in the safety tire disclosed in Patent Literature 3 below, the inside of the carcass layer of the sidewall portion is reinforced by a crescent-shaped reinforcing rubber layer. The reinforcing rubber layer has a high elastic rubber layer disposed on a carcass layer mainly including a central portion of the sidewall portion, and a crack resistant portion having a portion located on the shoulder portion and overlapping the high elastic rubber layer on the inner side in the tire axial direction. And a conductive rubber layer.
[0008]
Further, the run flat tire disclosed in Patent Document 4 below arranges a first rubber portion in a reinforcing rubber layer such that a maximum thickness portion thereof is close to a tire maximum width position, The second rubber portion having a small hardness has its maximum thickness portion spaced radially inward or outward from the maximum thickness portion of the first reinforcing rubber layer.
[0009]
[Patent Document 1]
JP-A-4-345505 (2nd tribute, FIG. 1)
[Patent Document 2]
JP-A-2000-343914 (2nd tribute, FIG. 2)
[Patent Document 3]
JP-A-62-279107 (Section 1, FIGS. 1 and 2)
[Patent Document 4]
Japanese Patent Application Laid-Open No. 2002-212216 (2nd tribute, FIG. 1)
[Problems to be solved by the invention]
However, in general, the lower the hardness of the reinforcing rubber layer, the better the ride comfort performance tends to be. On the other hand, the durability of the reinforcing rubber layer is preferably high in terms of durability performance during run flat running. Therefore, the durability performance during run flat running and the riding comfort performance during normal running are contradictory.
[0010]
The inventions described in Patent Literatures 1 to 4 provide a run-flat tire in which not only durability performance but also riding comfort performance is considered by providing a plurality of reinforcing rubber layers. However, it has been found that these reinforcing rubber layers have large deformation of the reinforcing rubber layer during run-flat running and a small effect of improving the durability performance due to the presence of rubber having low hardness which contributes to improvement of the riding comfort performance.
[0011]
The present invention has been made in view of the above circumstances, and an object of the present invention is to make use of the incompressibility of rubber having low hardness to achieve both durability performance during run-flat driving and riding comfort performance during normal driving. It is to provide a run flat tire that can perform the test.
[0012]
[Means for Solving the Problems]
To solve the above problems, the run flat tire according to the present invention,
A run-flat tire having a reinforcing rubber region having a substantially crescent cross section inside a carcass layer of a sidewall portion,
In the reinforcing rubber region, a first reinforcing rubber layer having a hardness of 65 to 100 ° according to a durometer hardness test (Type A) of JIS K6253 and a hardness of 45 ° according to a durometer hardness test (Type A) of JIS K6253. As described above, the second reinforcing rubber layer set to be lower than the hardness of the first reinforcing rubber layer by 5 to 55 ° is alternately laminated in three or more layers along the tire radial direction, and is formed on the tire inner surface side. , The first reinforcing rubber layers are laminated such that the volume ratio of the first reinforcing rubber layers increases.
[0013]
In the above, it is preferable that the volume ratio of the first reinforcing rubber layer / the second reinforcing rubber layer is 3/7 to 7/3.
[0014]
Further, it is preferable that the second reinforcing rubber layer is surrounded by the carcass layer and the first reinforcing rubber layer.
[0015]
[Effects]
The operation and effect of the run flat tire according to the present invention are as follows.
[0016]
In the configuration according to the present invention, the second reinforcing rubber layer is laminated between the first reinforcing rubber layers, and further laminated such that the volume ratio of the first reinforcing rubber layer increases toward the inner side in the tire width direction. Have been. Since the carcass layer is arranged outside the reinforcing rubber region, the second reinforcing rubber layer is less likely to escape in the tire width direction when the tire is deformed during run flat running. That is, the reinforcing rubber region is less likely to be deformed, and the incompressibility of the second reinforcing rubber layer does not impair durability during run-flat running. In addition, the second reinforcing rubber layer having a relatively low hardness absorbs vibration during normal running, so that ride comfort performance can be ensured.
[0017]
Although the compressive strain at the time of tire deformation increases toward the tire inner surface side in the reinforcing rubber region, the volume ratio of the relatively high hardness first reinforcing rubber layer increases as going toward the tire inner surface side, The reinforced rubber region has a sufficient load supporting ability, and can exhibit durability performance during run flat running.
[0018]
In addition, the first reinforcing rubber layer and the second reinforcing rubber layer are alternately laminated in three or more layers along the tire radial direction, so that durability and ride comfort during run-flat running can be achieved over the entire area of the sidewall portion. Can be taken into account.
[0019]
As a result, it is possible to provide a run flat tire that can achieve both durability performance during run flat running and riding comfort performance during normal running.
[0020]
Further, when the volume ratio of the first reinforcing rubber layer / the second reinforcing rubber layer is 3/7 to 7/3, the effect of improving the durability performance can be improved while increasing the ratio of the rubber having low hardness as compared with the conventional case. Obtainable. That is, it is possible to satisfactorily achieve both the durability performance during run flat running and the riding comfort performance during normal running.
[0021]
Further, by configuring the second reinforcing rubber layer so as to be surrounded by the carcass layer and the first reinforcing rubber layer, it is possible to substantially completely eliminate the escape of the second reinforcing rubber layer when the tire is deformed. As a result, the effect due to the incompressibility of the second reinforcing rubber layer is sufficiently exerted, and the effect of improving the durability performance during run flat running is greatly obtained.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of a run flat tire according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an example of a run flat tire according to the present invention. Since the tire 1 is targeted in the tire width direction, only the right half of the tire equator line C is shown.
[0023]
The tire 1 has a tread portion 2 that contacts a road surface, a sidewall portion 3 located on a side surface, and a rim strip portion 4. Further, it has a pair of bead portions 5 in the axial direction of the tire (the left-right direction in FIG. 1), and has a carcass layer 6 so as to be bridged between the pair of bead portions 5. The carcass layer 6 is formed of a single carcass ply, and the carcass ply is formed of a carcass cord wound around the tire equator C at a predetermined angle. Organic fibers are mainly used as the material of the carcass cord.
[0024]
In the tread portion 2, the belt layer 7 is provided immediately outside the carcass layer 6 in the tire radial direction, and the radially inner first belt ply 7a is overlapped with the outer side of the first belt ply 7a. And a second belt ply 7b to be arranged. Each of the belt plies 7a and 7b is formed by, for example, arranging steel cords at an angle of 15 ° to 35 ° with respect to the tire equator line C. The arrangement of the cords in the first belt ply 7a and the arrangement of the cords in the second belt ply 7b cross each other. The carcass layer 6 is provided so as to be folded from the inside toward the outside in the bead portion 5, and a bead apex rubber 10 is provided so as to be sandwiched between the folded portions.
[0025]
When the air in the tire is released due to a puncture of the tire and the internal pressure becomes zero, the flexural deformation of the tire increases. In order to suppress this deformation, a reinforcing rubber region 8 having a substantially crescent cross section is provided inside the carcass layer 6 of the side wall portion 3, thereby suppressing the bending deformation of the side wall portion 3. Can be.
[0026]
As shown in FIG. 1, the reinforcing rubber region 8 is configured by alternately stacking three or more first reinforcing rubber layers 8a and second reinforcing rubber layers 8b along the tire radial direction. Here, assuming that the rubber hardness of the first reinforcing rubber layer 8a is a first hardness and the rubber hardness of the second reinforcing rubber layer 8b is a second hardness, the first hardness is determined by a durometer hardness test (type A) of JISK6253. The hardness is set to 65 to 100 °, and the second hardness is 45 ° or more according to the durometer hardness test (type A) of JIS K6253, and is 5 to 55 ° lower than the hardness of the first reinforcing rubber layer 8a. It is set to be. Further, the reinforcing rubber regions 8 are stacked such that the volume ratio of the first reinforcing rubber layer 8a increases toward the tire inner surface side.
[0027]
As a result, it becomes difficult for the second reinforcing rubber layer 8b to escape inward in the tire width direction when the tire is deformed by run flat running. That is, due to the incompressibility of the second reinforcing rubber layer 8b, the reinforcing rubber region 8 is hardly deformed, and does not impair the durability during run flat running. Also, during normal traveling, the second reinforcing rubber layer 8b absorbs vibration, so that ride comfort performance can be ensured.
[0028]
Further, although the compressive strain during deformation of the tire increases toward the inner surface of the tire, since the volume ratio of the first reinforcing rubber layer 8a having relatively high hardness increases toward the inner surface of the tire, the reinforcement is increased. The rubber region 8 has a sufficient load supporting ability, and can exhibit durability performance during run flat running. On the other hand, on the tire outer surface side of the reinforcing rubber region 8, since the compressive strain during tire deformation is small, the effect of the second reinforcing rubber layer 8b on the durability performance is small.
[0029]
In addition, by alternately laminating the first reinforcing rubber layer 8a and the second reinforcing rubber layer 8b into three or more layers along the tire radial direction, the durability performance during run-flat running over the entire region of the sidewall portion 3 is improved. The configuration can be made in consideration of the riding comfort performance.
[0030]
As a result, it is possible to provide a run flat tire that can achieve both durability performance during run flat running and riding comfort performance during normal running.
[0031]
As a preferred embodiment of the present invention, the first hardness is 70 to 90 ° according to JIS K6253 durometer hardness test (type A), and the second hardness is JIS K6253 durometer hardness test (type A). The hardness is set so as to be 50 to 55 °. As shown in Examples described later, it is preferable to select the above numerical values for the hardness of each reinforcing rubber layer.
[0032]
FIG. 1 shows an example in which the volume ratio of the first reinforcing rubber layer 8a / the second reinforcing rubber layer 8b is set to 5/5, but in the present invention, the ratio of the first reinforcing rubber layer 8a / the second reinforcing rubber layer 8b is set. It is preferable that the volume ratio is 3/7 to 7/3. As a result, the effect of improving the durability performance can be obtained while increasing the proportion of the rubber having a lower hardness than the conventional one.
[0033]
In addition, as a method of forming the laminated structure of the reinforcing rubber region 8 according to the present invention, for example, Japanese Patent Application Laid-Open No. 2001-179848 by the present applicant and Japanese Patent Application No. 2000-380018, which have different hardnesses. A method of winding two types of rubber strips can be adopted. The thickness of each reinforcing rubber layer is not limited to a specific value.
[0034]
[Other embodiments]
(1) As shown in FIG. 2, the second reinforcing rubber layer 8b may be configured to be surrounded by the carcass layer 6 and the first reinforcing rubber layer 8a. As a result, the escape area of the second reinforcing rubber layer 8b can be almost completely eliminated when the tire is deformed, so that the effect of incompressibility is sufficiently exerted, and the effect of improving the durability performance during run flat running is greatly obtained.
[0035]
In the above description, the first reinforcing rubber 8a may have a surface in contact with the carcass layer 6 on the tire outer surface side of the reinforcing rubber region 8, as shown in FIG. Alternatively, it may not be provided as shown in FIG. These can be appropriately selected from the more convenient methods for forming the reinforcing rubber region 8.
[0036]
(2) In the present embodiment, two types of the first reinforcing rubber layer 8a and the second reinforcing rubber layer 8b are used for the reinforcing rubber region 8, but have a different hardness from the first and second hardness. A structure in which a reinforcing rubber layer is added may be adopted. Even in that case, as the volume goes to the inner surface of the tire, the rubber is laminated so that the volume ratio of the relatively hard rubber increases, and the durability is secured by utilizing the incompressibility of the relatively low hardness rubber. By arranging, the effect according to the present invention is exhibited.
[0037]
(3) In the above-described embodiment, an example is shown in which the carcass layer 6 is formed as a single layer, and the winding end reaches the end of the belt layer 7. However, in the present invention, the carcass layer 6 is formed of two or more layers. May be configured. Further, any or all of the winding ends of the carcass layer 6 may be arranged on the inner circumferential side of the tire from the end of the belt layer 7.
[0038]
【Example】
Hereinafter, examples and the like that specifically show the effects of the present invention will be described.
[0039]
(1) Durability (appearance failure occurrence time)
A running test was performed using a drum having a drum diameter of 1.7 m and a camber angle of 0 °. The running conditions were as follows: air pressure = 0 kPa, speed = 80 km / h, load = 5423N, and 245 / 40ZR18 was used for the tire.
[0040]
The evaluation was performed by measuring a traveling distance until a breakage caused by a crack or the like occurred in an area above the sidewall portion, and performing an index evaluation. When the tire of the conventional example is set to 100, a smaller index indicates that the durability performance during run flat running is inferior.
[0041]
(2) Ride Comfort Performance Sensory evaluation was performed on a good road and a bad road by using an actual vehicle (domestic vehicle, two passengers) using 245 / 40ZR18 as a tire. Based on the conventional example, if the points are plus, it indicates that the ride comfort is better than the conventional example.
[0042]
Table 1 shows the test results. The reinforcing rubber region in the example had the configuration shown in FIG. 1 and the volume ratio of the first reinforcing rubber layer / the second reinforcing rubber layer was 5/5. Further, the second hardness in the table is represented by a difference from the first hardness.
[0043]
[Table 1]

As shown by the results of Examples 1 and 2, according to the run-flat tire according to the present invention, it is possible to improve the riding comfort during normal running as compared with the conventional example without impairing the durability performance during run-flat running. Was completed. In particular, in Example 2, the riding comfort performance was significantly improved, and it can be seen that it is preferable to select a numerical value from the hardness range described above. Further, it can be seen that the balance between the durability performance and the riding comfort performance can be changed by changing the first hardness and the second hardness.
[0044]
In Comparative Example 1, although the ride comfort performance is excellent, the second hardness is low, so that the load support by the reinforcing rubber region is insufficient, and the durability performance is significantly deteriorated. In the case of Comparative Example 2, the durability performance deteriorates, and the improvement in ride comfort is small. When the hardness of the first reinforcing rubber layer and the hardness of the second reinforcing rubber layer are reversed from those in Example 1 as in Comparative Example 3, run-flat running cannot be performed because the incompressibility of the second reinforcing rubber layer cannot be used. The durability performance at the time deteriorates. Therefore, the effect of the run flat tire according to the present invention can be confirmed from the results in Table 1.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of a run flat tire according to the present invention. FIG. 2 is a sectional view showing a run flat tire according to another embodiment.
REFERENCE SIGNS LIST 1 run flat tire 3 side wall portion 6 carcass layer 8 reinforcing rubber region 8a first reinforcing rubber layer 8b second reinforcing rubber layer C tire equator

Claims (3)

A run-flat tire having a reinforcing rubber region having a substantially crescent cross section inside a carcass layer of a sidewall portion,
A first reinforcing rubber layer having a hardness of 65 to 100 ° in a durometer hardness test (type A) according to JIS K6253;
A second reinforcing rubber layer having a hardness of 45 ° or more according to the durometer hardness test (type A) of JISK6253 and being set at 5 to 55 ° lower than the hardness of the first reinforcing rubber layer,
It is configured by being alternately laminated into three or more layers along the tire radial direction,
A run-flat tire, wherein the first reinforcing rubber layer is laminated such that a volume ratio of the first reinforcing rubber layer increases toward an inner surface side of the tire. The run-flat tire according to claim 1, wherein a volume ratio of the first reinforcing rubber layer / the second reinforcing rubber layer is 3/7 to 7/3 in the reinforcing rubber region. The run-flat tire according to claim 1 or 2, wherein the second reinforcing rubber layer is surrounded by the carcass layer and the first reinforcing rubber layer.

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