JP3364256B2 - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve run flat durability while holding excellent performance without adding a special reinforcing member by deviating respective bisected points of contour curves in respective cross sections in a specific condition in respective rubber reinforcing layers of sidewall parts on both the inner and outer sides. CONSTITUTION:Both rubber reinforcing layers 8u and 8i are formed of a crescent rubber stock whose cross section becomes thickest in the center and which tapers off along an inner surface of a carcass 1 in the whole area of both sidewall parts 6u and 6i, that is, in an area reaching the vicinity of the side end part of a tread part 5 from the vicinity on the outside in the tire radial direction of a bead core 2. In this case, in both the rubber reinforcing layers 8u and 8i, bisected points of contour curves in respective cross sections are set in Pu and Pi. The bisected point Pu is deviated to the side of the tread part 5 to a straight line L in parallel with the axis of rotation of a tire by passing through the largest width position Wm of the tire. On the other hand, the bisected point Pi is situated on the straight line L, or a piece deviated to the side of a bead part 7i is set in step shape arrangement.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle having a tire mounted thereon, which can travel a considerable distance under a punctured condition. Regarding a so-called run-flat pneumatic tire having a rubber reinforcing layer having a crescent-shaped rubber stock in cross section along the inner surface of the carcass, particularly, by arranging the rubber reinforcing layer appropriately, it is possible to puncture without additional special reinforcing members. The present invention relates to a pneumatic tire having excellent run-flat durability, which allows the vehicle to run safely over a longer distance without any progress of obstacles in comparison with a conventional run-flat tire. 2. Description of the Related Art Conventionally, a pneumatic tire mounted on an automobile has a reduced internal pressure or a zero pressure due to foreign matter such as a nail or a metal piece sticking into the tire for some reason during traveling. In the event that the vehicle becomes punctured (hereinafter referred to as puncture), the driver can safely drive the vehicle in a desired location, for example, a relatively short distance to a service station where tires can be changed without disadvantages such as further tire failure or steering problems. Various measures have been taken to keep the service running. As the simplest and most effective measure among these measures, a rubber reinforcing layer is provided on the inner surface of a carcass, which is called a flex zone, and covers almost the entire area of both flexible side walls, and the maximum thickness position is determined. The tire load, which is lined with the maximum width position of the tire and mainly supported by the internal pressure during normal internal pressure, is mainly supported by these rubber reinforcing layers during puncturing. Generally, a so-called run flat tire intended to support a shoulder is used. [0004] Under running in a punctured state, a sidewall portion of a general tire not provided with the rubber reinforcing layer cannot withstand the load of the wheel and is crushed to a folded state, particularly a pneumatic radial. In the case of tires, where the sidewall portion can lead to catastrophic failure in a short time, in run-flat tires, the rubber reinforcement layer depends on the shape and material that can exhibit some, if not sufficient, tire load support function. As a result, even if the tire is a pneumatic radial tire, it is possible to continue running without causing a significant failure in the constituent members of the sidewall portion, particularly the carcass, and without much trouble in driving. [0005] However, the above-mentioned run flat performance is generally applied to high performance tires, and in this respect, various tire performances to be exerted over almost the entire traveling distance, for example, steering. It is a major premise that stability and vibration comfort are maintained at the highest levels.Therefore, the provision of a rubber reinforcing layer to provide run-flat performance in case of emergency has a negative effect on tire performance Needed to be minimized. Therefore, when selecting the cross-sectional shape and material of the rubber reinforcing layer, it must be determined and adopted within a certain limited range of thickness and hardness, and a reinforcing member for improving run flat performance is required. The additional arrangement would otherwise increase the unsprung weight for run-flat tires of this type, for which it is inevitable to increase the weight compared to general tires, and depending on the type of vehicle, the ride comfort may be slightly reduced. With disadvantages. [0007] Therefore, although it is possible to drive safely for a predetermined distance in a punctured state, the sidewall portion near the tread portion, which cannot occur under normal internal pressure, comes into contact with the ground and slides with the road surface. It is inevitable that the carcass cord will be exposed to breakage due to premature abrasion of the rubber and breakage, and at the same time, the rubber reinforcing layer will be destroyed. However, in recent years, pneumatic tires of radial carcass, which are structurally disadvantageous in terms of run flat running, have become the mainstream, and the demand for further extending the safe running distance during puncturing tends to increase significantly. I couldn't respond and the improvement was strongly desired. Therefore, the shape and material of the rubber reinforcing layer along the inner surface of the carcass should be selected according to the conventional practice in a range that can maintain the highest standard of the tire, and without further adding a special reinforcing member. SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic tire having excellent run-flat durability that can further extend the mileage while maintaining sufficient safety without a tire failure in a punctured state. [0010] Carcass damage caused by running a conventional run-flat pneumatic radial tire under a punctured condition is remarkable in a sidewall portion facing outward when the tire is mounted on a vehicle. With this in mind, the present invention has been completed. That is, the pneumatic tire according to the present invention comprises a pair of bead portions and sidewall portions, and a tread portion connected to both sidewall portions, and at least reinforces these portions between the bead cores embedded in the bead portions. In addition to a one-ply radial carcass, a belt comprising at least two cord crossing layers for reinforcing the tread portion at the outer periphery of a crown portion of the carcass, and a cap comprising an organic fiber cord wound along the outer periphery In a pneumatic tire having a rubber reinforcing layer having a crescent-shaped rubber stock in cross section along the inner surface of the carcass over the entire area of both sidewall portions and having a rubber reinforcing layer for sharing and supporting the load on the tire, the tire is mounted on the vehicle in an outer position. Rubber of the side wall part facing the inside and the side wall part facing the inside Strong layer per, bisector point of their cross-section within the outline curve side War facing outwardly relative to the rotation axis and the straight line parallel to the tire through the maximum width position of the tire
In the left part, the side wall is biased toward the tread and faces inward.
The bead portion is characterized by a stepped arrangement located on the straight line or slightly biased toward the bead portion. The pneumatic tire of the present invention will be described more specifically with reference to FIGS. 1 (a) and 1 (b). FIG. 1 (a)
1B shows a cross section of the left half from the tire equatorial plane E facing outward in the mounting posture of the tire on the vehicle, and FIG. 1B shows a right half cross section facing the inside.
2 is a bead core, 3 is a belt, 4 is a cap, 5 is a tread portion, 6 is a sidewall portion, 7 is a bead portion, 8 is a rubber reinforcing layer, and the subscript u is outward when the tire is mounted on the vehicle. The subscript i indicates the part facing inward, respectively. 9 indicates an inner liner and 10 indicates a layer. The carcass 1 is composed of at least one ply (two ply in the illustrated example) radial ply having a large number of code arrangements substantially orthogonal to the tire equatorial plane E, and the bead cores 2 embedded in a pair of bead portions 7 are provided. The pair of bead portions 7 and the sidewall portions 6 and the tread portion 5 connected thereto are reinforced over the space. The belt 3 is composed of at least two cord crossing layers. In the illustrated example, the cords are shown as two layers 3-1 and 3-2.
Are arranged in directions different from each other with a small angle of intersection formed between the layers. The cap 4 is made of a rubberized layer of an organic fiber cord wound around the outer periphery of the belt 3 and serves as a layer for suppressing the growth of the belt 3 in the tire radial direction during high-speed running. 3, which is wider than that of the belt 3 and cooperates with the belt 3 to strengthen the tread portion 5 and further enhance the running performance of the high performance pneumatic tire. The rubber reinforcing layers 8u and 8i are preferably made of rubber having a higher hardness than the ply rubber of the carcass 1 and the rubber of the side wall portions 6u and 6i in accordance with the practice of this type of run flat tire. It functions as a supporting member for sharing the load of the tire under the internal pressure. However, the purpose of the purpose is to provide sufficient load support at the time of puncturing, which is impossible with the side rubber and the carcass ply in the side wall portions 6u and 6i. It is provided to make it possible even if it cannot be said, and in this sense, it plays the role of a stay. The rubber reinforcing layers 8u and 8i are provided on the carcass 1 in the entire region of the sidewall portions 6u and 6i, more specifically, in the region from the vicinity of the bead core 2 in the tire radial direction to the vicinity of the side end of the tread portion 5. A crimped rubber stock having a creeping cross-sectional profile along the inner surface of which the cross-section is the thickest at the center at the center. Further, as shown in the figure, when the bisecting points of the in-section contour curves are Pu and Pi, respectively, the rubber reinforcing layers 8u and 8i pass through the maximum width position Wm of the tire, and the rotational axis of the tire. (Not shown), the bisecting point Pu is biased toward the tread portion 5 with respect to the straight line L parallel to the straight line L.
i is located on this straight line L or is a step arrangement (example shown) slightly biased toward the bead portion 7i. Here, the cross-sectional contour curve is the carcass 1
Refers to a cross-sectional contour curve on a side other than the side in contact with, and, when this cross-sectional contour is compared to a bow, it corresponds to a curve on a chord side. Next, the distances Hu and Hi measured from the straight line L of the bisecting points Pu and Pi are determined by comparing the cross section height Sh of the tire measured from the bead base line BL of the tire with Hu by 50 to 50% of Sh. It is preferable that 75% and Hi be 50% or less of Sh. Note that the rubber reinforcing layers 8u and 8i are respectively placed on the maximum thickness position thereof at the bisecting points Pu and Pi.
It is desirable to have a shape having Further, the relationship between the lengths of the in-section contour curves of the rubber reinforcing layers 8u and 8i may be the same, but it is desirable to make the length of the rubber reinforcing layer 8u longer. Further, it is desirable that the rubber reinforcing layer 8u is arranged such that the end near the tread portion 5 extends into the contact area of the tread portion 5 under standard internal pressure and standard load. In FIG. 1, reference numeral 11 denotes a layer, which is a narrow cord layer in which an organic fiber cord is wound along the outer periphery of the belt 3 or the cap 4 for each width of a certain region divided in the tread width direction. In the illustrated example, both ends of the belt 3 and the cap 4 are covered, and together with the cap 4, contribute to high-performance at high speed. The puncture of a tire usually occurs only in one wheel apart from that under special circumstances, and if this puncture occurs, the dynamic load radius of a run-flat tire at normal internal pressure It is inevitable that it will decrease significantly more than that in. Therefore, in a vehicle in which the run flat tire is punctured, the vehicle body is inclined by an amount corresponding to the reduced amount of the dynamic load radius of the tire, so that the load burden on the outer sidewall portion 6u of the punctured tire is reduced by the inner sidewall portion. 6
i will be significantly higher than that of i. In addition, for example, in the case of a four-wheel independent suspension vehicle, a part of the load is increased as the load on the tire located opposite to the punctured tire decreases with the inclination of the vehicle body. Due to the inclination of the vehicle body and the large load, the position of the outer sidewall portion 6u where the degree of flexure becomes maximum is largely biased toward the tread portion 5 from the maximum width position Wm of the tire. Therefore, the outer side wall portion 6u of the conventional run flat tire in which the rubber reinforcing layer having the maximum thickness is disposed at a position corresponding to the maximum width position of the tire can only bear a significantly larger load than the inner side. However, the rubber thickness at the position where the degree of the bending becomes maximum is insufficient. Therefore, the outer side wall portion 6u in the conventional run flat tire cannot fully exert the load supporting function of the rubber reinforcing layer contrary to the original intention, and a wide area near the tread portion 5 is formed on the road surface. , The rubber rolls rapidly, and there is a concern that the carcass 1 may appear relatively early to cause breakage. However, the rubber reinforcing layer 8u on the outer side wall portion 6u is biased so that the bisecting point Pu is deviated toward the tread portion 5 from the straight line L passing through the maximum width position Wm of the tire. With the arrangement corresponding to the position where the degree of the music becomes maximum, the outer rubber reinforcing layer 8u can exhibit its load supporting function sufficiently effectively. As a result, the contact area between the side wall 6u and the road surface during puncturing is within a relatively narrow area occupied by tread rubber having a thick rubber gauge and a part of the rubber, which is excellent in abrasion resistance, near the tread section 5. Runflat durability is greatly improved. Regarding the inner side wall portion 6i, the position where the degree of bending is maximum is on the straight line L,
Alternatively, the rubber reinforcing layer 8i is arranged so that its bisecting point Pi matches the maximum position because it is slightly closer to the bead portion 7i. In addition to being the same as the reinforcing layer 8u, the length of the in-section contour curve of the rubber reinforcing layer 8i can be made shorter than that of the rubber reinforcing layer 8u. Contributes and suppresses an unfavorable increase in tire weight. EXAMPLE The size of a high performance pneumatic radial tire for a passenger car is P275 / 40ZR17, and its structure is shown in FIG.
Follow (a) and (b). The tread portion 5 has a left-right asymmetric pattern having directionality. The carcass 1 is a two-ply rayon cord ply, and the belt 3 has a steel cord intersection angle of 6 ply.
It consists of two layers of 0 °. Cap 4 is nylon cord 1
As the layer and the layer 10, one layer of a nylon cord was used as a pair. The rubber reinforcing layers 8u and 8i have a JIS hardness of 84 degrees, have a maximum thickness at the bisecting points Pu and Pi, and have a value of 7 mm. 87 mm and 70 mm in the latter case. The distances Hu and Hi from the straight line L to the bisecting points Pu and Pi were 13.6% of the tire section height Sh in the former and 4.5% in the latter. The height of the straight line L measured from the bead base line BL is 48.3 mm. A conventional tire according to the embodiment was prepared except that the lengths of the contour curves in the cross section of the outer and inner rubber reinforcing layers were both 83 mm, and their bisecting points were on a straight line L. Using this and the example as test tires, an actual vehicle test and run flat durability evaluation under the following conditions were performed. The test conditions were as follows: each test tire was mounted on the left front wheel of the vehicle, the valve core was removed, and the puncture state was reached.
The circuit was driven at km / h until significant damage occurred to the carcass 1 of the tire, and the evaluation was expressed by an index with the distance traveled before the occurrence of the damage set to 100 in comparison with the conventional example. Obtained. According to the present invention, it is possible to provide a pneumatic tire which maintains tire performance at the highest level and has excellent run flat durability without adding any special reinforcing member.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B show a left half and a right half of a pneumatic tire according to the present invention, respectively. [Description of Signs] 1 Carcass 3 Belt 4 Cap 5 Tread 6u Outer side wall 6i Inner side wall 8u Outer rubber reinforcing layer 8i Inner rubber reinforcing layer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B60C 17/00, 13/00

Claims (1)

(57) [Claim 1] A pair of bead portions and side wall portions, and a tread portion connected to both side wall portions, and these portions are reinforced between bead cores embedded in the bead portions. A belt consisting of at least one ply of radial carcass, at least two layers of cord crossing layers for reinforcing the tread portion at the outer periphery of the crown portion of the carcass, and a cap made of an organic fiber cord wound along the outer periphery. In addition to the pneumatic tires, which have a rubber reinforcing layer whose cross section along the inner surface of the carcass is crescent-shaped rubber stock over the entire area of both sidewalls and share and support the load on the tires, For each rubber reinforcing layer of the side wall part facing outward and the side wall part facing inward, The bisection points of the contour curves in the cross section are biased toward the tread portion in the side wall portion facing the straight line parallel to the rotation axis of the tire through the maximum width position of the tire, and the side facing inward. A pneumatic tire characterized by a stepped arrangement located on the straight line in the wall portion or slightly biased toward the bead portion.