JP2005186672A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of suppressing the cord loose condition in the carcass cords of a bead part or in various cord layers for a long period of time. <P>SOLUTION: The pneumatic tire 1 is furnished with a carcass 6 ranging from the tread part 2 to the bead core 5 of the bead part 4 via each side wall part 3. The bead part 4 is furnished with at least one projection 9 protruding to outside in the tire axial direction. The projection 9 is provided in a position contacting at least partially with a circular arc surface at the rim flange outer end of a normal rim when the tire is set on the rim and is filled with a normal internal pressure and in the loaded condition with the normal load being applied. The projection 9 has a circular arc shape with the forefront being convex to the outside in the tire axial direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire that can improve the durability of a bead portion.

  FIG. 7 shows a partial cross-sectional view of a bead portion b of a pneumatic tire assembled with a rim and filled with a predetermined air pressure. In the clinching region where the bead portion b repeatedly contacts and separates from the rim flange Jf of the rim J during load traveling, a clinching rubber c made of a relatively hard rubber having excellent wear resistance is usually disposed.

  When a load is applied to the tire, the bead portion b is deformed so as to fall outward in the tire axial direction with the outer end of the rim flange Jf as a fulcrum, as indicated by phantom lines. At the interface between the clinch rubber c and the carcass cord d (or its topping rubber), shear strain (indicated by an arrow in the figure) due to the difference in rigidity occurs between them. When this shear strain increases, looseness occurs at the interface between the carcass cord and the clinch rubber. This looseness spreads to the bead portion due to the load running, and eventually the tires cannot run.

  The inventors have conducted various studies on this type of damage. As a result, the outer end of the rim flange of the normal rim is loaded in a state where the tire is assembled on the normal rim and the normal internal pressure is filled and the normal load is applied. By providing a protrusion with a specific shape at a position in contact with the arcuate surface, the amount of bending deformation of the bead during load running is reduced, and the cord loose that tends to occur at the interface between the carcass cord and the clinch rubber c is prolonged. It was found that it can be suppressed over time.

  The following Patent Document 1 is known as a prior art in which a protrusion is provided on the outer surface of a bead or sidewall. However, the protrusion of Patent Document 1 is not provided at a position that contacts the arc surface of the outer end of the rim flange during load traveling. Therefore, Patent Document 1 and the present invention are different from each other in configuration, and Patent Document 1 cannot achieve various functions and effects described later that are expected by the present invention.

JP 2001-171318 A

  As described above, an object of the present invention is to provide a pneumatic tire capable of suppressing cord loose for a long time in a carcass cord or various cord layers in a bead portion.

  The invention according to claim 1 of the present invention is a pneumatic tire having a carcass extending from the tread portion to the bead core of the bead portion through the sidewall portion, and at least protruding outward in the tire axial direction from the bead portion. One protrusion is provided, and the protrusion is assembled to the normal rim and filled with the normal internal pressure, and at least part of the normal rim is loaded with a normal load. The protrusion is provided at a position in contact with the circular arc surface, and the protrusion has a circular arc shape with a tip portion protruding outward in the tire axial direction.

  In the present specification, 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 and a “Design Rim” for TRA. Or “Measuring Rim” for ETRTO. In this specification, “normal internal pressure” is the air pressure defined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum value described in TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES is "INFLATION PRESSURE" for ETRTO, but 180 kPa for tires for passenger cars. In this specification, “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” if ETRTO, and load equivalent to 88% of the above load if the tire is for passenger cars.

  According to a second aspect of the present invention, in the tire meridian cross section including the tire shaft, the protruding portion is continuous in the tire circumferential direction with a protruding height of 1.0 to 2.0 mm and a protruding width of 1 to 20 mm. The pneumatic tire according to claim 1, wherein

  The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, characterized in that the tip portion is formed of an arc surface having a curvature radius R3 of 1.0 to 2.0 mm.

  According to a fourth aspect of the invention, in the tire meridian cross section including the tire shaft, the bead portion is disposed on the outer side in the tire radial direction and has an outer arc surface with a curvature radius R1 that protrudes outward in the tire axial direction, and the tire radius. An outer surface including an inner circular arc surface having a radius of curvature R2 which is arranged inward in the tire direction and protrudes inward in the tire axial direction, and a protruding surface which is provided between the outer circular arc portion and the inner circular arc portion and forms the protruding portion It is a pneumatic tire in any one of Claims 1 thru | or 3 which has a shape.

  The invention according to claim 5 is the pneumatic tire according to any one of claims 1 to 4, wherein the road index is 100 or more.

  The pneumatic tire of the present invention is provided with a protrusion having a specific shape at a position where the bead portion comes into contact with the arc surface of the outer end of the rim flange during load running. This protrusion can increase the bending rigidity of the bead portion that contacts the arc surface, and can reduce the amount of local collapse of the bead portion with the rim flange as a fulcrum. Moreover, since the front-end | tip part makes circular arc shape, the protrusion part disperse | distributes the force received from the outer end of a rim flange to the wide range of a bead part. Therefore, unlike the prior art, a concentrated load is not transmitted from the arc surface of the outer end of the rim flange to the bead portion. By these synergistic actions, in the pneumatic tire of the present invention, the cord looseness at the bead portion is suppressed over a long period of time.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a tire meridian cross-sectional view including a tire shaft for an assembly of a pneumatic tire 1 and a regular rim J of this embodiment. The pneumatic tire 1 of the present embodiment is arranged in a carcass 6 that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4 and on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. A radial tire including the belt layer 7 is exemplified.

  The carcass 6 includes one or more (in this example, one) carcass plies having a radial structure in which carcass cords are arranged at an angle of, for example, 75 ° to 90 ° with respect to the tire equator C, in this example, substantially 90 °. 6A. As the carcass cord, a polyester cord is used in this example, but other than this, an organic fiber cord such as nylon, rayon, or aramid, or a steel cord if necessary.

  The carcass ply 6A includes a main body portion 6a straddling the pair of bead cores 5 and 5 in a toroid shape, and a folded portion 6b extending from the inner side in the tire axial direction around the bead core 5 extending from the main body portion 6a. Contains. The bead portion 4 is provided with a hard rubber, for example, a clinch rubber 20 having a JISA hardness of about 60 to 80 ° at a portion in contact with the rim J.

  A bead apex 8 made of hard rubber extending from the bead core 5 to the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A, and the bead portion 4 is appropriately reinforced. The belt layer 7 includes at least two belt plies 7A and 7B in which the belt cord is inclined and arranged at a small angle of, for example, 10 to 45 ° with respect to the tire equator. The cords are overlapped in a direction that intersects each other.

  As shown in FIGS. 1 and 2, the bead portion 4 of the pneumatic tire 1 is provided with at least one protrusion 9 that protrudes outward in the tire axial direction. FIG. 2 shows a contour diagram representing the outer shape of the bead portion 4. The outer surface shape of the bead portion 4 of the present embodiment includes an outer circular arc surface 10 having a radius of curvature R1 which is disposed on the outer side in the tire radial direction and protrudes outward in the tire axial direction, and is disposed on the inner side in the tire radial direction and in the tire axial direction. It includes an inner circular arc surface 11 having a curvature radius R2 that protrudes inward, and a protruding surface 12 that forms the protruding portion 9 provided between the outer circular arc surface 10 and the inner circular arc surface 11. A vertical surface 13 that extends substantially in the tire radial direction at the contact point P <b> 1 is connected to the inner circular arc surface 11, and a bead heel surface 14 and a bead seat surface 15 are sequentially connected to the inner side of the vertical surface 13. Reference sign BL indicates a bead baseline.

  FIG. 3 shows an enlarged view of part A of FIG. The projecting surface 12 forms a tip end portion 9a of the projecting portion 9 and protrudes outward in the tire axial direction with a central portion 12a having a radius of curvature R3 and the inner circular arc surface 11 from both ends of the inner arc surface 11 via contacts P2 or P3, respectively. Or it is comprised by the skirt parts 12b and 12b which continue to the outer circular arc surface 10 smoothly. Thus, the front-end | tip part 9a of the projection part 9 is formed in circular arc shape. Further, since the projecting surface 12 is formed smoothly between the outer circular arc portion 10 and the inner circular arc surface 11, it is preferable in that a large surface strain does not concentrate when the tire is loaded.

  Also, in FIG. 4, the outer surface shape of the bead portion 4 in the no-load state, in which the normal rim J is assembled with the normal rim J and is filled with the normal internal pressure and is not loaded, is indicated by a solid line, Are indicated by virtual lines. In this embodiment, the protruding portion 9 is provided at a position where it does not contact the rim flange Jf of the normal rim J in the no-load state but contacts the arc surface Jfr in the loaded state. The position where such a projection 9 is provided can be easily determined according to the lateral rigidity of the tire if the regular rim J is determined.

  The protruding portion 9 provided at the position as described above increases the bending rigidity of the bead portion 4 by locally increasing the thickness. Thereby, the fall deformation amount of the bead portion with the arc surface Jfr of the rim flange Jf as a fulcrum can be reduced.

  Further, since the protrusion 9 has an arc shape, the protrusion 9 functions to disperse the force received from the arc surface Jfr at the outer end of the rim flange in and out of the tire radial direction with the protrusion 9 as the center. Therefore, unlike the prior art, a local load is not transmitted to the bead portion 4 via the arc surface Jfr. By these synergistic actions, the pneumatic tire 1 of the present invention can reduce the shear strain between, for example, the carcass cord and the clinch rubber 20 in the bead portion 4, and consequently the cord looseness is suppressed over a long period of time. In addition, since the projection part 9 does not contact with the rim flange Jf in the unloaded state, the pneumatic tire 1 of the present embodiment does not impair the rim assemblability.

  As shown in FIG. 3, the protrusion portion 9 of the present embodiment is exemplified by a continuous protrusion in the tire circumferential direction with a maximum protrusion height h of 1.0 to 2.0 mm and a protrusion width w of 1 to 20 mm. Is done. The protrusion height h is measured with reference to a tangent line K that contacts the outer arc portion 10 and the inner arc portion 11 at the contacts P2 and P3. If the protrusion height is less than 1.0 mm or the protrusion width w is less than 1.0 mm, the effect of improving the bending rigidity of the bead portion 4 tends to be insufficient, and conversely the protrusion height h is 2 If it exceeds 0.0 mm, or if the protruding width w exceeds 20 mm, it tends to come off from the contact portion with the rim, which is not preferable because not only the effect is not exhibited but also the tire weight is increased. In particular, the protrusion width w is more preferably 10 mm or more and 15 mm or less.

  Moreover, as for the projection part 9, the curvature radius R3 of the center part 12a which forms the front-end | tip part 9a has desirable 1.0-2.0 mm. If the radius of curvature R3 is less than 1.0 mm, the rigidity of the tip of the projection 9 is insufficient, and there is a risk of rubber chipping or the like occurring relatively early, and conversely if it exceeds 2.0 mm. During load running, the ability to widely disperse the force received from the arc surface Jfr at the outer end of the rim flange in the bead portion 4 is not preferable.

  Although the embodiments of the present invention have been described above, the present invention can be applied to various categories of pneumatic tires. In particular, among radial tires, the present invention can be particularly preferably applied to tires having a road index of 100 or more, specifically, radial tires for light trucks. This is based on the fact that tires with a load index exceeding 100 are subjected to a large load, and in particular, cord looseness tends to occur in the bead portion.

  A pneumatic radial tire for a light truck having a tire size of 175 / 75R15 was prototyped based on the specifications shown in Table 1, and the durability of the bead portion was tested. Further, in order to compare the performance, as shown in FIG. 5, a tire having a protrusion having a substantially triangular cross section (Comparative Example 1) and a tire having no protrusion as shown in FIG. 6 (Comparative Example) We also prototyped 2) and compared the performance. Only the protrusions are different, and the internal structure of the tire and the rubber composition are the same. The specifications common to the outer shape of the bead portion were as follows.

Radius of curvature of outer arc surface R1: 85mm
Curvature radius of inner circular arc surface R2: 10.5mm
Projection height (Example and Comparative Example 1) h = 1.5 mm
Protrusion width (Example and Comparative Example 1) w = 12 mm
The test method is as follows.

<Durability of bead part>
Each test tire is assembled on a rim of size 15 x 5 1 / 2K, loaded with JATMA standard maximum air pressure and maximum load, running on a drum tester at a speed of 60km / H and a slip angle of 2 °, and 40000km It was done by running. In addition, about the thing where the bead part was damaged in the middle of a run, the run distance was recorded.
Table 1 shows the test results.

  As a result of the test, the tire of the example could complete 40000 km without damage, and a significant technical effect on the durability of the bead portion could be confirmed. In each of the comparative examples, a clear looseness is generated between the carcass cord and the clinch rubber, and it is presumed that this was the basis of damage.

It is sectional drawing of the pneumatic tire which shows embodiment of this invention. It is an outline figure which shows the outer surface shape of the bead part. It is the A section enlarged view. It is sectional drawing of the bead part which shows a normal state and a load state. 10 is a partial cross-sectional view showing a protrusion of Comparative Example 1. FIG. 10 is a partial outline view of a bead portion of Comparative Example 2. FIG. It is sectional drawing explaining the deformation-like body of the conventional bead part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 9 Protrusion part 9a Protrusion tip J Regular rim Jf Rim flange Jfr Arc surface of rim flange outer end

Claims (5)

A pneumatic tire having a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion,
The bead portion is provided with at least one protrusion protruding outward in the tire axial direction,
The protrusion is provided at a position where at least a part of the protrusion is in contact with the arc surface of the outer edge of the rim flange of the normal rim when the normal rim is assembled and the normal internal pressure is filled and the normal load is applied. Being
Moreover, the pneumatic tire is characterized in that the protruding portion has a circular arc shape with a tip portion protruding outward in the tire axial direction.   2. The air according to claim 1, wherein the protrusion has a protrusion height of 1.0 to 2.0 mm and a protrusion width of 1 to 20 mm in the tire meridian cross section including the tire axis, and is continuous in the tire circumferential direction. Enter tire.   3. The pneumatic tire according to claim 1, wherein the tip portion is an arc surface having a curvature radius R3 of 1.0 to 2.0 mm. In the tire meridian cross section including the tire shaft, the bead portion,
An outer arc surface having a radius of curvature R1 which is arranged on the outer side in the tire radial direction and protrudes outward in the tire axial direction;
An inner circular arc surface of a radius of curvature R2 that is arranged on the inner side in the tire radial direction and that protrudes inward in the tire axial direction;
The pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire has an outer surface shape including a projection surface provided between the outer arc portion and the inner arc portion and forming the projection portion.   The pneumatic tire according to any one of claims 1 to 4, wherein the road index is 100 or more.

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