JP2011031812A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of restraining generation and growth of a crack in the vicinity of the folding-back end, by sufficiently reducing compressive strain acting on the folding-back end of a carcass ply. <P>SOLUTION: This pneumatic tire has a body part 40 inside in the tire width direction of an annular bead core 1a arranged in a bead part 1, and has a folding-back part 41 outside in the tire width direction of the bead core 1a, and has the carcass ply 4 folded back outside from the inside on the periphery of the bead core 1a. A recessed part 10 is formed on a tire outer surface between the folding-back end 4E of the carcass ply 4 and a tire maximum width position 9, and its recessed part 10 is scraped out inside in the tire radial direction so as to enter between the body part 40 and the folding-back part 41, and the deepest end 10E is arranged inside in the tire radial direction more than the folding-back end 4E. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire including a carcass ply folded around an annular bead core.

  In general, in a pneumatic tire, a side wall portion on the grounding side is bent and deformed during load rolling, and a large compressive strain is generated at the folded end of the carcass ply due to the internal stress associated therewith. When this compressive strain acts repeatedly, a crack is generated in the vicinity of the folded end of the carcass ply and may eventually develop into a separation.

  With respect to this problem, as shown in FIG. 6, a pneumatic tire in which a recess 15 is formed on the outer surface of the tire between the turn-back end 14 </ b> E of the carcass ply 14 and the tire maximum width position is proposed in Patent Document 1 below. ing. Patent Documents 2 to 4 listed below describe pneumatic tires in which the shape of the recess 15 is modified. In these tires, it is intended to reduce the compressive strain acting on the folded end 14E by blocking the internal stress accompanying the bending deformation of the sidewall portion by the recess 15.

  However, in these pneumatic tires, it has been found that the effect of reducing the compressive strain acting on the folded end 14E is not sufficient, and there is room for further improvement. As a result of extensive research by the present inventor, in the above pneumatic tire, when the sidewall portion is bent and deformed, the folded end is provided via the rubber 16 between the main body portion 14a and the folded portion 14b of the carcass ply 14. It was found that compressive strain acts on 14E, and cracks occur in the vicinity of the folded end 14E.

Japanese Patent Laid-Open No. 3-186409 JP-A-4-362406 JP-A-6-32122 JP 2000-185530 A

  The present invention has been made in view of the above circumstances, and its purpose is to sufficiently reduce the compressive strain acting on the folded end of the carcass ply and to suppress the generation and growth of cracks in the vicinity of the folded end. To provide tires.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire of the present invention has a main body portion on the inner side in the tire width direction of the annular bead core disposed in the bead portion, and has a folded portion on the outer side in the tire width direction of the bead core, and around the bead core. In the pneumatic tire including the carcass ply folded from the inside to the outside, a recess is formed on the outer surface of the tire between the folded end of the carcass ply and the tire maximum width position, and the recess includes the body portion and the The innermost portion of the concave portion is disposed so as to enter between the folded portions, and the deepest end of the concave portion is disposed on the inner side in the tire radial direction from the folded end.

  According to such a configuration, since rubber between the main body portion and the folded portion of the carcass ply is reduced, when the sidewall portion is bent and deformed, it is folded back via the rubber between the main body portion and the folded portion. The compressive strain acting on the end can be sufficiently reduced, and the generation and growth of cracks in the vicinity of the folded end can be effectively suppressed. Moreover, the effect of weight reduction and rolling resistance reduction by having formed the recessed part is also acquired.

  In the bead structure as described above, stress tends to easily act on the deepest end of the recess, and there is a concern about the generation of cracks starting from the deepest end. Therefore, in the present invention, when the perpendicular perpendicular to the normal of the main body passing through the folded end passes through the midpoint of the line segment from the intersection of the normal and the main body to the folded end, the concave portion It is preferable that the deepest end of the concave portion is disposed on the outer side in the tire width direction with respect to the perpendicular line, whereby the deepest end of the concave portion can be moved away from the main body portion. Since the movement of the carcass ply accompanying the bending deformation of the sidewall portion is larger in the main body than in the folded portion, the deepest end of the concave portion is arranged as described above, so that the influence of the movement of the main body portion is suppressed and the deepest of the concave portion is arranged. Cracks at the edges can be prevented.

  In the present invention, the reinforcing member is folded around the bead core from the inside of the main body portion to the outside of the folded portion, and the end portion of the reinforcing member adjacent to the main body portion passes through the deepest end of the concave portion. It is preferable to be located on the outer side in the tire radial direction from the intersection of the normal line of the main body part and the main body part. As described above, the movement of the carcass ply accompanying the bending deformation of the sidewall portion is large in the main body portion.According to the above configuration of the present invention, the movement of the main body portion in the bead portion is appropriately suppressed by the reinforcing member, Cracks at the deepest end can be prevented.

  Further, in the tire of the present invention, when the rubber thickness on the outside of the main body changes greatly in the vicinity of the recess, cracks tend to occur at that portion. Therefore, in the present invention, the rubber thickness on the outer side of the main body portion gradually decreases from the deepest end of the recess toward the outer side in the tire radial direction, and the outer surface of the tire is gently formed from the recess to the tire maximum width position. It is preferable. With such a configuration, since the outer surface of the tire is gently formed from the recess to the maximum tire width position, it is possible to satisfactorily suppress cracks resulting from changes in the rubber thickness.

Tire meridian half sectional view showing an example of the pneumatic tire of the present invention Sectional drawing which shows the principal part of the pneumatic tire Sectional drawing which shows the principal part of the pneumatic tire which concerns on another embodiment of this invention. Sectional drawing which shows the principal part of the pneumatic tire which concerns on another embodiment of this invention. Schematic explaining the arrangement of bead filler etc. Sectional drawing which shows the bead part of the pneumatic tire described in patent document 1

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a half sectional view of a tire meridian showing an example of a pneumatic tire according to the present invention. FIG. 2 is a cross-sectional view showing the main part of the pneumatic tire. The pneumatic tire includes a pair of bead portions 1, a sidewall portion 2 that extends outward in the tire radial direction from each of the bead portions 1, and a tread portion 3 that continues to each tire radial direction outer end of the sidewall portion 2. Is provided. The bead portion 1 is provided with an annular bead core 1a formed by covering a converging body such as a steel wire with rubber.

  A carcass ply 4 is arranged between the pair of bead portions 1 so as to be bridged in a toroid shape, and is folded back from the inside to the outside around the bead core 1a. The carcass ply 4 has a main body portion 40 on the inner side in the tire width direction of the bead core 1a, and has a folded portion 41 on the outer side in the tire width direction of the bead core 1a, and an outer end in the tire radial direction of the folded portion 41 is defined as a folded end 4E. Yes. An inner liner rubber 5 for maintaining air pressure is disposed on the inner peripheral side of the carcass ply 4.

  A belt 6 is laminated on the outer periphery of the carcass ply 4 of the tread portion 3, and a tread rubber 7 is further laminated on the outer periphery thereof. The outer side of the carcass ply 4 is covered with a rubber layer 8 from the bead portion 1 to the sidewall portion 2. A recess 10 is formed on the outer surface of the tire between the folded end 4E and the tire maximum width position 9. The concave portion 10 is wound inward in the tire radial direction so as to enter between the main body portion 40 and the folded portion 41, and the deepest end 10E is arranged on the inner side in the tire radial direction from the folded end 4E. That is, the relationship of R1> R2 is satisfied, where R1 is the diameter of the folded end 4E with reference to the tire axis center and R2 is the diameter of the deepest end 10E.

  The positional relationship described above may be obtained in a standard tire posture in which the tire is assembled to the standard rim 20 and filled with the maximum air pressure. The standard rim is a standard rim (or “Approved Rim” or “Recommended Rim”) in the applicable size described in the following standards. The maximum air pressure is the maximum of a single wheel in the applicable size described in the following standards. Air pressure corresponding to load (maximum load capacity). The standard is determined by an industrial standard effective in the region where the tire is produced or used. For example, “Year Book of The Tire and Rim Association Inc.” in the United States, “Standards Manual of The European Tire and Rim Technical Organization” in Europe, and “JATMA Year Book” of the Japan Automobile Tire Association in Japan.

  In such a bead structure, the rubber between the main body portion 40 and the turn-up portion 41 of the carcass ply 4 is reduced. Therefore, when the sidewall portion 2 is bent and deformed during traveling, the main body portion 40 is deformed. The compression strain acting on the folded end 4E via the rubber between the folded portion 41 and the folded portion 41 can be sufficiently reduced. As a result, the generation and growth of cracks in the vicinity of the folded end 4E can be effectively suppressed, and the advantages of weight reduction and rolling resistance reduction due to the formation of the recess 10 can be obtained.

  The recess 10 extends in an annular shape continuously in the tire circumferential direction, and is formed by recessing the outer surface of the tire inward in the tire width direction and inward in the tire radial direction. Note that the recess 10 may extend discontinuously. In order to sufficiently reduce the compressive strain acting on the folded end 4E while ensuring a gap between the main body 40 and the folded portion 41 and suppressing the movement of the main body 40, R1-R2 is 1 mm or more. 0 mm or less is preferable. The deepest end 10 </ b> E is a portion having the smallest diameter in the inner wall of the recess 10.

  The deepest end 10E is formed with a circular arc in cross section, and the radius of curvature is preferably 1.0 mm or greater and 4.0 mm or less. In this tire, since the recess 10 is provided, stress tends to act on the deepest end 10E when the sidewall portion 2 is bent and deformed. In this way, the deepest end 10E is formed in an arc. The stress can be dispersed to suppress cracks starting from the deepest end 10E.

  In the present embodiment, as shown in FIG. 2, a normal line L1 is drawn to the main body portion 40 so as to pass through the folded end 4E, and a perpendicular line L2 perpendicular to the normal line L1 is an intersection of the normal line L1 and the main body portion 40. When passing through the midpoint P2 of the line segment from P1 to the turn-back end 4E, the deepest end 10E of the recess 10 is disposed on the outer side in the tire width direction than the perpendicular L2. These lines and points are determined with reference to the center of the thickness of the carcass ply 4 as long as the positional relationship is obtained in the above standard tire posture.

  When the side wall portion 2 is bent and deformed, the main body portion 40 falls toward the folded-back portion 41, so that the movement of the carcass ply 4 is larger in the main body portion 40 than the folded-back portion 41. If this is the case, the tendency is particularly prominent. Therefore, there is a concern about cracks starting from the deepest end 10E of the concave portion 10, but with the bead structure as described above, the concave portion 10 can be moved away from the main body portion 40. Cracks at the end 10E can be prevented.

  FIG. 3 is a cross-sectional view of the tire of FIGS. 1 and 2 when the reinforcing member 11 that is folded from the inside of the main body 40 to the outside of the folded portion 41 around the bead core 1a is disposed. Such a structure in which the reinforcing member 11 is provided can improve the durability of the bead portion 1 and is particularly useful for a heavy duty pneumatic tire. As the reinforcing member 11, a conventionally known reinforcing body can be used without particular limitation, and examples thereof include a nylon chafer and a steel chafer.

  The end 11E of the reinforcing member 11 adjacent to the main body 40 is located on the outer side in the tire radial direction from the intersection P3 between the normal L3 of the main body 40 passing through the deepest end 10E and the main body 40. That is, when the diameter of the intersection P3 with reference to the tire axis center is R3 and the diameter of the end portion 11E is R4, the relationship of R3 <R4 is satisfied. For this reason, the movement of the main body portion 40 in the bead portion 1, particularly the movement of the main body portion 40 in the vicinity of the outer side in the tire radial direction from the normal line L3, is appropriately suppressed by the reinforcing member 11 to prevent cracks at the deepest end 10E. it can. The above lines and points are determined with reference to the center of the thickness of the carcass ply 4, and the positional relationship may be obtained as long as the standard tire posture is obtained.

  As shown in FIGS. 2 and 3, the rubber thickness on the outside of the main body portion 40 changes relatively greatly in the vicinity of the concave portion 10, and there is a concern about the occurrence of cracks in that portion (particularly around the point Q <b> 1). As a countermeasure against this crack, in the example of FIG. 4, the rubber thickness of the rubber layer 8 on the outer side of the main body portion 40 is gradually decreased gradually from the deepest end 10E toward the outer side in the tire radial direction. The outer surface of the tire is gently formed over the entire area.

  The virtual extension line L4 is an extension line drawn parallel to the carcass ply 4 so as to maintain the thickness of the rubber layer 8 at the tire maximum width position 9, and the branch point Q2 is an actual tire from the virtual extension line L4. This is the point where the outer surface branches. When the tire outer surface is formed smoothly as described above, the branch point Q2 is preferably separated from the deepest end 10E by 20 mm or more outward in the tire radial direction. Such positional relationship may be obtained as long as it is obtained in the standard tire posture.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that it has a bead structure as described above, and any conventionally known material, shape, structure, manufacturing method, etc. can be adopted in the present invention. it can.

  Although not shown in the above embodiment, a bead filler made of hard rubber is disposed outside the bead core 1a in the tire radial direction. In the pneumatic tire of the present invention, from the viewpoint of preventing the main body portion 40 from falling, it is preferable to dispose hard rubber 1c equivalent to the bead filler 1b on the inner side in the tire width direction of the folded portion 41 as shown in FIG. . In that case, the bead filler 1b and the hard rubber 1c may be separate members as shown in (a), or may be monolithically integrated members as shown in (b).

  The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention. Therefore, the number of carcass plies, the cord material, and the like can be changed as appropriate according to the application and conditions to be used.

  Since the durability test was performed in order to show concretely the composition and effect of the present invention, it explains below. In the durability test, the prototype tire (275 / 70R22.5) was assembled on the rim (8.25 × 22.5) and then on the indoor drum under the conditions of an internal pressure of 900 kPa, a speed of 60 km / h, and a load of 30.9 kN. The vehicle was run for 150,000 km, and the presence or absence of cracks at the folded end of the carcass ply and the deepest end of the recess was investigated.

  In this durability test, the example in which the concave portion was not formed on the outer surface of the tire was set as Comparative Example 1, and the type in which the concave portion as shown in FIG. In addition, examples in which the recesses as shown in FIG. 2 are formed are referred to as Examples 1 and 2, and in particular, the example in which the deepest end of the recess is located on the inner side in the tire width direction from the above-described normal line L2 is also the tire width. The one located outside in the direction (see FIG. 2) was taken as Example 2. The evaluation results are shown in Table 1.

  Further, the above test was performed by changing the load to 61.8 kN and the travel distance to 50,000 km. In the durability test under the high load condition, in addition to the above-described Example 2, Examples 3 and 4 in which reinforcing members as shown in FIG. In Examples 3 and 4, the value of R3 is the same but the value of R4 is different, and only Example 4 satisfies the relationship of R3 <R4. The evaluation results are shown in Table 2.

  From Table 1, it can be seen that in Examples 1 and 2, cracks at the folded end of the carcass ply can be suppressed compared to Comparative Examples 1 and 2, and the durability of the bead portion is excellent. And in Example 2, the crack in the deepest end of a recessed part can also be prevented. Table 2 also shows that cracks at the deepest end of the recess can be prevented by appropriately disposing the reinforcing member as in Example 4 even under high load conditions.

DESCRIPTION OF SYMBOLS 1 Bead part 1a Bead core 2 Side wall part 4 Carcass ply 4E Folding end 9 Tire maximum width position 10 Recess 10E Deepest end 11 Reinforcement member 11E End part 40 Main body part 41 Folding part L1 Normal line L2 of the main part passing through the folding end perpendicular line L3 Normal line P1 of the main body part passing through the deepest end of the recess P2 intersection point of the normal line L1 and the main body part P2 Midpoint P3 Intersection point of the normal line L3 and the main body part

Claims (4)

A carcass ply having a main body portion on the inner side in the tire width direction of the annular bead core disposed in the bead portion, a folded portion on the outer side in the tire width direction of the bead core, and folded back from the inner side to the outer side around the bead core. In a pneumatic tire comprising:
A concave portion is formed on the outer surface of the tire between the folded end of the carcass ply and the tire maximum width position, and the concave portion is wound inwardly in the tire radial direction so as to enter between the main body portion and the folded portion. A pneumatic tire characterized in that the deepest end of the recess is arranged on the inner side in the tire radial direction than the folded end.   When the perpendicular perpendicular to the normal of the main body passing through the folded end passes through the midpoint of the line segment from the intersection of the normal and the main body to the folded end, the deepest end of the recess is the perpendicular The pneumatic tire according to claim 1, wherein the pneumatic tire is arranged on the outer side in the tire width direction.   A reinforcing member that is folded around the bead core from the inside of the main body portion to the outside of the folded portion, and the end portion of the reinforcing member adjacent to the main body portion passes through the deepest end of the concave portion. The pneumatic tire according to claim 1, wherein the pneumatic tire is located on an outer side in a tire radial direction from an intersection of a normal line and the main body portion.   The rubber thickness on the outer side of the main body portion gradually decreases from the deepest end of the recess toward the outer side in the tire radial direction, and the outer surface of the tire is gently formed from the recess to the maximum tire width position. 3. The pneumatic tire according to any one of 3 above.

Images