JP5303118B2 - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire with a bead having improved durability by suppressing the occurrence of permanent strain in a rubber member contacting a rim during travel while preventing the separation of ply cords from the rubber member and the pull-off of the ply cords during tire load rolling. <P>SOLUTION: The pneumatic tire comprises a bead part 1, a carcass ply 2 consisting of a body part 2a toroidally extending from a tread part through a sidewall part 3 to the bead part 1 and a turn-around part 2b turned around along the periphery of a bead core 4, and a wire chafer 6. At least one reinforcing layer 11 formed by covering a plurality of cords with a rubber is arranged on the outer face side of the wire chafer 6 in a range at least from a bead base part 8 to a bead back face part 9. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention has a bead base portion in contact with a rim base of a rim and a bead back surface portion in contact with a rim flange, a pair of bead portions provided with a bead core, and a toroidal shape from a tread portion to a bead portion through a sidewall portion. A carcass ply constituted by an extending main body portion and a rewinding portion wound around the bead core, and along the outer surface of the carcass ply from the main body portion of the carcass ply toward the rewinding portion. The present invention relates to a pneumatic tire comprising a wire chafer disposed in a row.

  In a pneumatic tire, in order to prevent pull-out of a ply cord during tire load rolling, normally, as shown in FIG. 4 (a), a carcass ply 100 is placed around a bead core 102 of a bead portion 101. A large amount of rewinding is performed from the inside to the outside in the tire width direction, and the rewinding portion 103 is embedded and fixed in a rubber member.

  However, in such a conventional bead structure, the carcass ply 100 shown in FIG. A pulling force F acts in the direction of the arrow, and repeated stress concentration occurs in the edge position 105 where the rigidity step exists and in the vicinity thereof, whereby separation from the rubber member of the ply cord is likely to occur. There was a problem of causing the bead cracks Cr as shown in FIG.

  As a means for preventing such separation and improving the durability of the bead part, as shown in FIG. 5A, the winding part 107 of the carcass ply 106 is further wound along the peripheral surface of the bead core 108. A bead portion structure has been proposed (see Patent Document 1).

  However, in such a bead portion structure, when a high load is applied to the tire, a large bending deformation occurs in the direction of arrow A with the rim flange 110 as a fulcrum as shown by a two-dot chain line in FIG. By repeating this bending deformation, the bead portion of the tire in contact with the rim flange is likely to be cracked, and the crack develops, and in the worst case, there is a risk of causing a bead portion failure.

Then, as a means for improving the bead part durability of the tire which has the said bead part structure, as shown in FIG. 6, the proposal which provides a wire chafer along the outer surface of the carcass ply 110 is made | formed (patent). Reference 2). As a result, it is possible to effectively suppress the bending deformation of the bead portion when a high load load is applied to the tire while preventing separation from the rubber member of the carcass ply.
Japanese Patent Laid-Open No. 2000-21916 JP 2001-191763 A

  However, even if the wire chafer is disposed along the outer surface of the carcass ply as in the bead structure shown in FIG. 6, the carcass ply 110 is still wound around the bead core 111, At the time of air filling, the rotation angle of the bead core in the direction of arrow B is increased by pulling the carcass ply 110 as compared with the tire having the conventional bead structure shown in FIG. This increase in the rotation angle of the bead core means that the contact pressure with respect to the rim of the bead base portion (portion contacting the rim base) and the bead back portion (portion contacting the rim flange) is greatly affected. The influence of the contact pressure is shown in the graph of FIG. 6 in comparison with the tire having the bead structure shown in FIG. This graph shows the contact pressure of the bead base portion and the back surface portion of the bead with respect to the rim. The solid line shows the contact pressure applied to the bead structure shown in FIG. 6, and the broken line shows the contact pressure applied to the bead structure shown in FIG. Show. As can be seen from this graph, when the carcass ply is wound around the bead core, the contact pressure with respect to the rim of the bead base portion and the back portion of the bead is higher on the heel side (the center of the bead core than when not wound (see FIG. 4)). More on the outer side in the tire width direction), and conversely on the toe side (inner side in the tire width direction than the center of the bead core). Therefore, there is a problem that plastic deformation, so-called sag occurs, in the rubber member (in particular, the heel side) that is in contact with the rim as the usage time increases. The rubber member sag causes unevenness of the cord path over the circumference of the bead core, which in turn induces deterioration of uniformity such as a so-called radial runout (RRO) that causes the tire to vibrate in the radial direction during running. It is very important to prevent not only the durability of the bead portion but also the steering stability.

  SUMMARY OF THE INVENTION An object of the present invention is to solve such problems of the prior art, and the purpose of the invention is to separate the ply cord from the rubber member and to pull out the ply cord during tire load rolling. It is to provide a pneumatic tire capable of improving the durability of the bead by suppressing the settling that occurs in the rubber member that is in contact with the rim as the usage time increases. .

In order to achieve the above object, the present invention provides a pair of bead portions each having a bead base portion in contact with a rim base of a rim and a bead back surface portion in contact with a rim flange and provided with a bead core, and a side from the tread portion. A carcass ply constituted by a main body extending toroidally through a wall part to a bead part and a rewinding part wound around the bead core, and from the main body part of the carcass ply to the rewinding part. A pneumatic chafer including a wire chafer disposed along an outer surface of the carcass ply toward the outer surface of the wire chafer from at least the bead base portion to the bead back surface portion. and, a plurality of cords comprises at least one layer of reinforcing layers formed by rubberized, code that constitutes the reinforcing layer, organic fiber The cord constituting the reinforcing layer extends in a radial direction, and the thickness of the rubber member between the reinforcing layer and the outer surface of the tire is between the reinforcing layer and the wire chafer. It is characterized by being smaller than the thickness of a certain rubber member . By adopting such a configuration, the reinforcing layer reinforces the rubber member that is in contact with the rim, and receives the pressing force from the bead core that is generated by the rotation of the bead core toward the rubber member, and further extends the reinforcing layer. Accordingly, the settling of the rubber member with the increase in the use time is suppressed, and the contact pressure is also made uniform. As used herein, “the thickness of the rubber member between the reinforcing layer and the outer surface of the tire” means that the reinforcing layer and the tire cross a normal line that stands perpendicular to the rim with the tire mounted on the rim. The thickness of the rubber member between the outer surface and the "thickness of the rubber member between the reinforcing layer and the wire chafer" means that the reinforcing layer and the wire chafer crossing the same normal line. The thickness of the rubber member in between.

  Note that the “bead rear surface in contact with the rim flange” referred to here is in contact with the rim flange when the tire is assembled to the applicable rim specified by JATMA and the air pressure and load specified in the same manner are applied. Not only the portion but also the portion that can contact the rim flange when the side wall portion is tilted to the rim flange side under the condition is included. The carcass ply "rewinding part" is formed not only by rewinding from the inner side to the outer side in the tire width direction but also by rewinding from the outer side to the inner side in the tire width direction. The case where it is done is also included. Furthermore, the “outer surface of the carcass ply” means the surface of the carcass ply that is closer to the surface of the tire.

  In addition, it is preferable that the reinforcing layer is disposed along the outer surface of the tire.

  According to the present invention, the carcass ply is wound around the bead core, and further, the reinforcing layer for reinforcing the rubber member that contacts the rim is provided on the outer surface side of the wire chafer. The durability of the bead part can be prevented by preventing the pull-out of the ply cord during separation and tire load rolling, and suppressing the settling on the rubber member in contact with the rim as the usage time increases. It is possible to provide a pneumatic tire capable of improving the tire.

  Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view in the tire width direction showing a bead portion of a pneumatic tire (hereinafter referred to as “tire”) according to the present invention mounted on a standard rim, and FIG. 2 is a bead of the pneumatic tire according to the present invention. FIG. 3 is an enlarged sectional view showing a part of the bead portion in FIG. 2.

  The tire having the bead portion 1 shown in FIG. 1 preferably has at least one carcass ply 2 (one piece in FIG. 1) obtained by rubberizing steel cords arranged substantially in the radial direction. A body portion 2a extending in a toroidal manner from the side wall portion 3 to the bead portion 1 and a rewinding portion 2b wound around the bead core 4 embedded in the bead portion 1, A wire chafer 6 along the outer surface of the carcass ply 2 from the body portion 2a of the carcass ply 2 toward the rewinding portion 2b in order to suppress bending deformation of the bead portion 1 when a high load load acts on the tire. And a belt (not shown) made of one or more cord rubberized layers for reinforcing the tread portion on the crown portion (not shown) of the carcass ply 2. Location and composed. The bead portion 1 has a bead base portion 8 that contacts the rim base Rb of the rim R and a bead back surface portion 9 that contacts the rim flange Rf. With this structure, separation of the ply cord from the rubber member and pull-out of the ply cord during tire load rolling can be prevented.

  The main feature of the present invention is that the carcass ply 2 is wound around the bead core 4 and the wire chain is formed along the outer surface of the carcass ply 2 from the main body portion 2a of the carcass ply 2 toward the rewinding portion 2b. In order to employ a bead structure in which the face 6 is disposed and to prevent the rubber member coming into contact with the rim R from being loosened, at least one reinforcing layer 11 formed by covering a plurality of cords with rubber is attached to the rubber member. More specifically, this reinforcing layer 11 is disposed on the outer surface side of the wire chafer 6 from at least the bead base portion 8 to the bead back surface portion 11.

  Accordingly, the reinforcing layer 11 effectively reinforces the rubber member between the bead base portion 8 and the bead back surface portion 9 that can come into contact with the rim R, and the reinforcing layer 11 is generated by the rotation of the bead core 4. Since it acts to receive the pressing force directed from the bead core 4 to the rubber member and further disperse it in the extension region of the reinforcing layer 11, it is possible to suppress the settling of the rubber member with an increase in usage time. The contact pressure on the rim between the base portion 8 and the bead back surface portion 9 can also be made uniform.

  It should be noted that the rigidity of the cords constituting the reinforcing layer 11 is preferably larger from the viewpoint of reinforcing the rubber member that contacts the rim R. However, when the rigidity is increased, a large force is required to bend the bead portion 1 and get over the rim flange Rf during the rim assembling work for assembling the tire to the rim R, and the rim assembling workability is significantly reduced. In particular, when the tire is for a heavy-duty vehicle such as a truck, a bus, or a construction vehicle, such a tendency is conspicuous because the basic rigidity of the tire is large. Therefore, in order to ensure proper reinforcement of the rubber member and not deteriorate the rim assembly property, the cord constituting the reinforcing layer 11 is preferably an organic fiber cord that is more flexible than a steel cord. For example, a rayon cord or an aramid (aromatic polyamide) cord is preferably used as the material of the organic fiber cord.

  Furthermore, the cord constituting the reinforcing layer 11 is preferably inclined with respect to the tire circumferential direction, and more preferably extended in the radial direction. In this way, the pressing force from the bead core 4 toward the rubber member can be received by more cords, and the received pressing force can be effectively dispersed. The contact pressure on the rim up to the back surface portion 9 can be made more uniform. Further, when the cord 1 is bent during the rim assembling work, no great tension is generated on the cord, so that the rim assembling property is not deteriorated.

  However, when the reinforcing layer 11 is arranged as shown in FIG. 1, when a high load is applied to the tire, the bead core 4 rotates as described above, and the bead base portion is shown in the graph of FIG. The contact pressure on the toe side of 8 decreases. This reduction in contact pressure means that the toe side of the bead base 8 moves in the direction of lifting from the rim base Rb, and not only can the proper adhesion between the bead 1 and the rim R be secured, The so-called rim slip easily occurs.

  Therefore, in addition to the above configuration, as shown in FIG. 2, the reinforcing layer 11 is preferably arranged along the outer surface of the tire, that is, along the bead base portion 8 and the bead back surface portion 9. Thereby, the reinforcing layer 11 not only acts to prevent the bead portion 1 from being lifted, but also acts to equalize the contact pressure of the bead base portion 8 and the bead back surface portion 9 with respect to the rim base Rb and the rim flange Rf. Therefore, it is possible to ensure proper adhesion between the bead portion 1 and the rim R, and to suppress rim slip.

In addition, as shown in FIG. 3, the thickness d ₁ of the rubber member between the reinforcing layer 11 and the outer surface of the tire crossing the normal m standing perpendicular to the rim R is the same normal m. It is preferable that the thickness is less than the thickness d2 of the rubber member between the reinforcing layer 11 and the wire chafer 6 that crosses. By doing in this way, since the rubber deformation amount of the bead base part 8 can be suppressed, the settling of the rubber member can be further suppressed.

  Next, since the pneumatic tire according to the present invention was manufactured and the durability of the bead portion was evaluated, it will be described below.

  In the test, the influence of the presence or absence of the reinforcing layer on the sag of the rubber member in contact with the rim and the RRO suppression effect was examined. The tires of the examples are radial tires having a tire size of TBR 495 / 45R22.5, and have the specifications shown in Table 1.

  For comparison, although the tire size and the bead portion structure are the same as those of the example, a tire of a conventional example having the specifications shown in Table 1 without having a reinforcing layer was also prototyped.

  Each of the test tires is mounted on a rim having a size of 17 × 22.5 inches to form a tire wheel. An air pressure of 900 kPa (relative pressure) is applied to the tire wheel, the tire load is 5.8 kN, and the traveling speed is 60 km / h. Measure the distance from the new tire and the bead core to the bead base and the back of the bead after running 100,000 km under the condition of room temperature 38 ° C on a drum tester. Then, the inhibitory effect of sag was evaluated. The evaluation results are shown in Table 1. In addition, the numerical value of the amount of stickiness in the table is obtained by indexing the average distance of the tire after traveling 100,000 km, where the average distance in a new tire is 100, and the closer the value is to 100, the smaller the amount of stickiness is Means that. Moreover, the evaluation method of the inhibitory effect of RRO measures and compares RPO before and after traveling 100,000 km. In addition, the numerical value of RRO in a table | surface means that uniformity is so good that it is small.

  From the results shown in Table 1, it can be seen that the tires of the examples are superior in the effect of suppressing sag and RRO as compared with the tires of the conventional examples.

  According to the present invention, the separation of the ply cord from the rubber member and the pull-out of the ply cord at the time of tire load rolling are prevented, and the settling that occurs in the rubber member that is in contact with the rim during traveling is suppressed. As a result, it has become possible to provide a pneumatic tire capable of improving the durability of the bead.

1 is a tire width direction cross-sectional view showing a pneumatic tire according to the present invention with a bead portion mounted on a standard rim. 1 is a tire width direction cross-sectional view showing a pneumatic tire according to the present invention with a bead portion mounted on a standard rim. It is an enlarged view which expands and shows a part of bead part of FIG. (A) is a tire width direction sectional view in the state where a bead part of a tire according to a prior art was attached to a standard rim, and (b) is used to explain a problem of a conventional tire (a Is a cross-sectional view similar to FIG. (A) is a tire width direction sectional view in the state where a bead part of a tire according to a prior art was attached to a standard rim, and (b) is used to explain a problem of a conventional tire (a Is a cross-sectional view similar to FIG. It is a tire width direction sectional view showing the bead part of the tire according to the prior art in the state where it was attached to the standard rim.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Carcass ply 2a Main body part 2b Rewinding part 3 Side wall 4 Bead core 6 Wire chafer 8 Bead base part 9 Bead back part 11 Reinforcement layer

Claims (2)

A pair of bead parts having a bead base part in contact with the rim base of the rim and a bead back part in contact with the rim flange and provided with a bead core, and a main body extending in a toroidal manner from the tread part to the bead part through the sidewall part And a carcass ply constituted by a rewinding portion wound around the bead core, and disposed along the outer surface of the carcass ply from the main body portion of the carcass ply toward the rewinding portion. In a pneumatic tire comprising a wire chafer,
Including at least one reinforcing layer formed by rubber-covering a plurality of cords disposed on the outer surface side of the wire chafer from at least the bead base portion to the bead back surface portion;
The cord constituting the reinforcing layer is an organic fiber cord,
The cord constituting the reinforcing layer extends in a radial direction ,
The pneumatic tire is characterized in that the thickness of the rubber member between the reinforcing layer and the outer surface of the tire is smaller than the thickness of the rubber member between the reinforcing layer and the wire chafer .   The pneumatic tire according to claim 1, wherein the reinforcing layer is disposed along an outer surface of the tire.

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