JP2008222145A - Pneumatic tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for heavy loads capable of effectively enhancing rim-slipping resistance by achieving effective function of a hard rubber body 25. <P>SOLUTION: Since the hard rubber body 25 is arranged between a bead core 12 and a carcass layer 21, the hard rubber body 25 is covered and restricted from a side not only by a wire chafer 23 but also by the carcass layer 21. As a result, deformation and flow of the hard rubber body 25 are regulated during vulcanization, the hard rubber body 25 can be easily arranged at an adequate position for increasing the contact pressure, and the deformation of the hard rubber body 25 can be firmly suppressed during the load rolling. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

    The present invention relates to a heavy duty pneumatic tire having improved rim slip resistance by disposing a hard rubber body in a bead portion.

As a conventional heavy-duty pneumatic tire with good rim slip resistance, for example, those described in Patent Document 1 below are known.
JP 2003-72325 A

  This is a triangular shape that forms a mountain shape toward the bead toe in the cross section of the tire width direction between the radial carcass and the wire chafer in the region near the bead toe radially inward from the center of the bead core and inside the tire width direction. Hard rubber with a shape is provided, which restrains deformation and the like during vulcanization and load rolling of the hard rubber with a wire chafer and increases the contact pressure of the bead part against the inclined bead sheet part over a wide range. The value is retained.

    Here, in recent years, as the performance of pneumatic tires has improved, the load capacity of pneumatic tires has gradually increased, and as a result, in pneumatic tires as described in the prior art, the rim and pneumatic during load rolling There has been a case where circumferential slip with the bead portion of the tire, that is, rim slip cannot be sufficiently suppressed.

  An object of the present invention is to provide a heavy duty pneumatic tire capable of effectively improving rim slip resistance by effectively functioning a hard rubber body.

    The purpose of this is to provide a rim having an inclined bead seat portion provided with a bead portion in which the width direction end portion of the carcass layer is wound around the bead core and a wire chafer is disposed around the turned-up portion of the carcass layer. In a heavy-duty pneumatic tire that is assembled and constitutes a wheel, a hard rubber body having a substantially triangular shape with a tapered cross section from the bead core toward the bead toe is disposed between the bead core and the carcass layer on the bead toe side from the center of the bead core. This can be achieved.

  In the present invention, since the hard rubber body is disposed between the bead core and the carcass layer, the hard rubber body is covered and restrained by the carcass layer in addition to the wire chafer. As a result, deformation and flow of the hard rubber body at the time of vulcanization are regulated, and the hard rubber body can be easily disposed at an optimum position for improving the contact pressure, and the hard rubber body at the time of load rolling Can be strongly suppressed. As a result, the contact pressure of the bead portion in the vicinity of the bead toe with respect to the inclined bead sheet portion is increased, the clamping force in a wide range of the bead portion is maintained at a high value, and the rim slip resistance is effectively improved.

  According to the second aspect of the present invention, it is possible to effectively suppress the deterioration of the rim assembly property and the occurrence of separation near the bead heel while strongly suppressing the rim slip. Furthermore, if comprised as claimed in claim 3, it is possible to further increase the tightening force of the bead portion against the inclined bead seat portion while suppressing cracking in the rubber during rim assembly, rim unwinding, and the like. According to the fourth aspect of the present invention, most of the internal stress based on the deformation of the hard rubber body is received by the linear side of the bead core facing the bead toe, and the hard rubber body Separation with the bead core is effectively suppressed.

  Furthermore, if it comprises as described in Claim 5, the occupation ratio of the hard rubber in the radial inside of a bead core will increase, and the clamping force with respect to the inclination bead seat part of a bead part can further be increased. According to the sixth aspect of the present invention, the occupation ratio of the hard rubber in the bead portion is increased, and the tightening force can be further increased. Furthermore, if comprised as described in Claim 7, the gauge of the rubber chafer between a hard rubber body and a bead base will become thin, and the clamping force with respect to an inclination bead seat part will become reliable. Furthermore, if it comprises as described in Claim 8, the failure generation based on abrasion of a bead base can be suppressed effectively.

Embodiment 1 of the present invention will be described below with reference to the drawings.
1 and 2, reference numeral 11 denotes a heavy-duty pneumatic radial tire mounted on a truck, a bus, a large construction vehicle or the like. The tire 11 includes a pair of bead portions 13 each having a bead core 12 embedded therein, and these bead portions. Side wall portions extending substantially radially outward from 13 and substantially cylindrical tread portions connecting the outer ends in the radial direction of the sidewall portions. In this embodiment, a hexagonal bead having a hexagonal cross section in the tire width direction is used as the bead core 12 described above.

  The tire 11 is reinforced by a carcass layer 21 extending from one bead portion 13 to the other bead portion 13, and both end portions in the width direction of the carcass layer 21 are wound around the bead core 12. Yes. As a result, the carcass layer 21 includes a pair of winding portions 21a that surround the bead core 12 from the periphery in the bead portion 13, a main body portion 21b that connects the inner ends of the winding portions 21a and extends in a substantially toroidal shape, It is comprised from a pair of folding | turning part 21c extended toward the outer side of a substantially radial direction from the outer end of the return part 21a. The carcass layer 21 is composed of at least one carcass ply 22 in this embodiment, and each carcass ply 22 is substantially orthogonal to the tire equator plane (an angle of 80 to 90 degrees with respect to the tire equator plane). The reinforcing cord is made of a large number of steels and the like and is coated with a coating rubber.

  Reference numerals 23 denote wire chafers arranged around the winding portion 21a in the bead portion 13, and these wire chafers 23 are reinforcing cords composed of a plurality of steel wires arranged at equal intervals from each other. Is covered with a coating rubber. The reinforcing cords of the wire chafer 23 are inclined at an angle of 45 to 80 degrees with respect to the meridian direction.

  Reference numeral 25 denotes a hard rubber body disposed on the bead toe 26 side from the center O of each bead core 12 and disposed between the bead core 12 and the winding portion 21a of the carcass layer 21 and the wire chafer 23. Has a substantially triangular shape with a tapered section from the bead core 12 toward the bead toe 26. The tire 11 having such a bead portion 13 is assembled to a rim 31 having a pair of inclined bead seat portions 30 inclined at about 5 degrees or 15 degrees so as to go radially inward as approaching the center in the width direction. It becomes a wheel. Such a structure is suitable for a tire for a large construction vehicle having a tread gauge of 25 mm or more and a rim diameter of 25 inches or more.

  Here, the above-mentioned rim 31 is a standard rim (or “DESIGN RIM”, “Recommended Rim”) in an applicable size described in the following standard. The standards are determined by industrial standards that are valid for the region where tires are produced or used. For example, “The Tire and Rim Association Inc. Year Book” in the United States and “The European Tire and Rim Technical Organization's Standards Manual ”corresponds to“ JATMA Year Book of Japan Automobile Tire Association ”in Japan.

  Then, when the hard rubber body 25 is arranged between the bead core 12 and the carcass layer 21 in this way, the hard rubber body 25 is covered and restrained by the carcass layer 21 in addition to the wire chafer 23, and as a result. The deformation and flow of the hard rubber body 25 at the time of vulcanization are restricted, and the hard rubber body 25 can be easily disposed at the optimum position for improving the contact pressure, and the hard rubber body at the time of load rolling 25 deformations can be strongly suppressed. Thereby, the contact pressure of the bead portion 13 in the vicinity of the bead toe 26 with respect to the inclined bead seat portion 30 is increased, the clamping force in a wide range of the bead portion 13 is maintained at a high value, and the rim slip resistance is effectively improved. It is.

  Here, when the thickness of the rubber compressed and deformed by the inclined bead sheet portion 30 on the radial line segment L passing through the center O of the bead core 12 is N as indicated by a virtual line in FIG. The compression ratio P defined as the ratio of the total rubber portion existing radially inward of the bead core 12 to the thickness M before compression deformation is preferably in the range of 0.25 to 0.50. The reason for this is that when the compression ratio P is less than 0.25, the contact pressure against the inclined bead seat portion 30 in the entire bead portion 13 may be insufficient, and rim slip may occur. This is because the deterioration may occur or separation due to rubber deformation may occur in the vicinity of the bead heel 34, but such a situation can be effectively suppressed within the aforementioned range.

  The radial line segment L passing through the center O of the bead core 12 described above refers to a radial line segment in a state where the tire 11 (bead portion 13) is in the assembled posture to the rim 31. It doesn't matter whether it is actually assembled to a standard rim. Further, in the definition of the compression ratio P, the “thickness M before compressive deformation of all rubber portions existing radially inward from the bead core 12” means from the bead core 12 to the bead base 35 measured on the radial line segment L. The thickness obtained by subtracting the diameters of the reinforcing cords of the carcass layer 21 and the wire chafer 23 from the thickness of the carcass layer 21, for example, when the carcass layer 21 is composed of one carcass ply 22, one reinforcing member This is a value obtained by subtracting the cord diameter of the cord and the cord diameter of one reinforcing cord of the wire chafer 23 from the thickness.

  In addition, if the hard rubber body 25 is made of rubber having a 100% modulus value in the range of 4.1 to 5.9 MPa, the bead 13 has an inclined bead 13 while suppressing cracking in the rubber during rim assembly and rim unwinding. This is preferable because the tightening force on the seat portion 30 can be further increased. Further, when the bead core 12 is composed of a hexagonal bead as described above, the bead toe of the hard rubber body 25 is placed on one of the perpendicular lines Q to the side 12a facing the bead toe 26 of the bead core 12 in the cross section in the tire width direction. When the apex R on the 26 side is arranged, most of the internal stress due to the deformation of the hard rubber body 25 is received by the straight side 12a of the bead core 12 facing the bead toe 26, and the hard rubber body 25 and This is preferable because separation between the bead cores 12 can be effectively suppressed.

  Further, when the outer end 25a in the tire width direction of the hard rubber body 25 is positioned on the outer side in the width direction from the radial line segment L passing through the center O of the bead core 12, the occupation ratio of the hard rubber on the inner side in the radial direction of the bead core 12 Is increased, and the tightening force of the bead portion 13 on the inclined bead seat portion 30 can be further increased. Therefore, the configuration as described above is preferable. Furthermore, if the radially outer end 25b of the hard rubber body 25 is positioned radially outward from a line segment passing through the center O of the bead core 12 and parallel to the tire axis, the hard rubber occupying ratio in the bead portion 13 increases. Since the tightening force further increases, it is preferable to configure as described above.

  Further, in the cross section in the tire width direction, the side 25c on the bead base 35 side of the hard rubber body 25 is inclined in parallel with the bead base 35 or gradually approaching the bead base 35 from the bead heel 34 toward the bead toe 26. It is preferable. The reason for this is that, conversely, if the slope is gradually separated from the bead base 35 toward the bead toe 26, the gauge of the rubber chafer between the hard rubber body 25 and the bead base 35 becomes thicker. It is easily deformed and the tightening force on the inclined bead seat portion 30 is weakened. However, when configured as described above, the gauge of the rubber chafer becomes thin, and the tightening force on the inclined bead seat portion 30 is ensured. .

  Furthermore, when the tire 11 is not assembled to the rim 31, if the wire chafer 23 of the tire 11 is arranged radially outward from the rim base line S (the outer surface line of the inclined bead seat portion 30), The occurrence of a failure due to wear of the bead base 35 can be effectively suppressed, which is preferable. The hard rubber body 25 is preferably made of hard rubber having a JIS A hardness of 60 to 80 degrees.

  The reason is that if it is less than 60 degrees, it is difficult to sufficiently restrain the deformation in the vicinity of the bead toe 26, so it is difficult to sufficiently increase the tightening force on the inclined bead seat portion 30, while it exceeds 80 degrees. This is because the brittleness of the rubber becomes obvious, and there is a high possibility that the hard rubber body 25 will be cracked when the rim of the tire 11 is assembled and the rim is unwound. Here, the above-mentioned JIS A hardness is a value measured at a measurement temperature of 25 ° C. using a durometer hardness test / tire A tester according to JIS K6253-1993.

    Next, test examples will be described. In this test, a conventional tire 1 in which a hard rubber body having a substantially triangular shape tapered toward the bead toe is disposed between the wire chafer and the bead toe on the bead toe side of the wire chafer, and the center of the bead core. The conventional tire 2 in which a hard rubber body having the same shape and the same cross-sectional area as the conventional tire 1 is disposed between the carcass layer and the wire chafer on the bead toe side, and the bead core and the carcass layer on the bead toe side from the center of the bead core. In the meantime, an implementation tire in which a hard rubber body having substantially the same shape and the same cross-sectional area as that of the conventional tire 1 was provided was prepared.

  Here, the size of each tire was 26.5R25, and each tire was mounted on a rim of 22.00 × 250 / 4.5, and the compression ratio at this time was 0.35. Further, a hard rubber having a 100% modulus value of 5.9 MPa and a JIS A hardness of 70 degrees was used as the hard rubber body. Next, after filling each wheel with an internal pressure of 650 kPa, the tread surface is pressed against the plate while applying a load of 150 kN to the wheel by a rim slip tester, and the tire is braked while the brake is applied. The rim drag force (tangential force acting between the tire and the rim) when the rim slip started was measured. As a result, when the conventional tire 1 is indicated as 100, the rim slip resistance is improved up to 115 in the case of the conventional tire 2 as compared with 109 in the conventional tire 2. Here, the larger the index value, the better the result.

  The present invention can be applied to the industrial field of heavy duty pneumatic tires.

It is a tire width direction sectional view of a bead part showing Embodiment 1 of this invention. It is a tire width direction sectional view of a bead part and a rim.

Explanation of symbols

11 ... Pneumatic tire 12 ... Bead core
12a ... Side 13 ... Bead part
21 ... Carcass layer 21a ... Rewind part
23 ... Wire chafer 25 ... Hard rubber
25a ... Outer end in the axial direction 25b ... Outer end in the radial direction
25c ... side 26 ... bead toe
30 ... Inclined bead seat 31 ... Rim
34 ... Bead heel 35 ... Bead base O ... Center L ... Radial line segment Q ... Perpendicular N ... Rubber thickness M ... Thickness S ... Rim baseline

Claims (8)

    The end of the carcass layer in the width direction is rolled back around the bead core, and the bead portion is provided with a wire chafer around the turned-up portion of the carcass layer, and is assembled to a rim having an inclined bead seat portion. In the heavy-duty pneumatic tire, a hard rubber body having a substantially triangular shape with a tapering cross section from the bead core toward the bead toe is disposed between the bead core and the carcass layer on the bead toe side from the center of the bead core. Heavy duty pneumatic tire.     It is defined as the ratio of the rubber thickness compressed and deformed at the inclined bead sheet portion on the radial line segment passing through the center of the bead core to the thickness before compression deformation of all rubber portions existing radially inward from the bead core. The heavy duty pneumatic tire according to claim 1, wherein the compression ratio is in the range of 0.25 to 0.50.     The heavy-duty pneumatic tire according to claim 1 or 2, wherein the hard rubber body is made of rubber having a 100% modulus value in a range of 4.1 to 5.9 MPa.     The bead toe apex of the hard rubber body is arranged on any perpendicular to the side of the beaco core facing the bead toe in the tire width direction cross section when the bead core is formed of a hexagonal bead. The heavy-duty pneumatic tire described.     The heavy-duty pneumatic tire according to any one of claims 1 to 4, wherein an outer end in the tire width direction of the hard rubber body is positioned on the outer side in the width direction from the radial line segment passing through the center of the bead core.     The heavy-duty pneumatic tire according to any one of claims 1 to 5, wherein the radially outer end of the hard rubber body is positioned radially outward from a line segment passing through the bead core center and parallel to the tire axis.     The bead base side of the hard rubber body is inclined parallel to the bead base or gradually approaching the bead base as it goes from the bead heel to the bead toe in the tire width direction cross section. Heavy duty pneumatic tire as described in 1.     The heavy duty pneumatic tire according to any one of claims 1 to 7, wherein when not assembled to the rim, the wire chafer is disposed radially outward from the rim base line.

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