WO2014192661A1

WO2014192661A1 - Pneumatic tire

Info

Publication number: WO2014192661A1
Application number: PCT/JP2014/063736
Authority: WO
Inventors: 里美吉野
Original assignee: 株式会社ブリヂストン
Priority date: 2013-05-28
Filing date: 2014-05-23
Publication date: 2014-12-04
Also published as: JP2014231259A; WO2014192661A9

Abstract

Provided is a pneumatic tire which is provided with a carcass ply having a low turn-up structure, the pneumatic tire being configured so as to minimize strain near the turn-up ends of a carcass ply. A pneumatic tire (10) is configured so that a carcass ply (14) has body sections (14A) and turn-up sections (14B) and so that the turn-up ends (14C) of the turn-up sections (14B) are located on the outside, in the radial direction of the tire, of a bead base line (BL) at a position in the range of 15 to 28% of the cross-sectional height (SH) of the tire. The turn-up sections (14B) each have: a first region (A1) which extends from the inside toward the outside in the radial direction of the tire so as to gradually approach the body section (14A); a second region (A2) which is provided within the angle formed by a straight line (L1) passing through the center (O) of curvature of the rim flange (18) of a regular rim in an axial cross-section of the tire and extending inward in the axial direction of the tire so as to be parallel to the rotation axis of the tire, and by a straight line (L2) passing through the center (O) of curvature and extends inward in the tire width direction and outward in the radial direction of the tire at an angle of 45º, the second region (A2) extending along the body section (14A) so as to be close to or in contact with the body section (14A); and a third region (A3) which gradually extends away from the body section (14A).

Description

Pneumatic tire

The present invention relates to a heavy duty pneumatic tire suitable for a construction vehicle.

Japanese Patent Application Laid-Open No. 5-178039 discloses a so-called low turn-up structure in which the folded end of the carcass ply is located near the bead portion.

Generally, a strain is generated near the folded end of the carcass ply by pulling out the folded portion of the carcass ply due to internal pressure growth (first strain). In addition, near the folded end of the carcass ply, distortion due to the falling of the carcass ply when the internal pressure is applied and when the load is applied is generated (second distortion). Further, in the vicinity of the folded end of the carcass ply, distortion is caused by the rubber being pushed out at the inner side and the outer side in the tire width direction of the folded end due to the reaction force from the rim flange when the internal pressure is applied and when the load is applied (third). Distortion). In the case of the low turn-up structure as in the conventional example described above, the influence of these distortions at the folded end of the carcass ply becomes large.

The present invention has been made in consideration of the above facts, and it is an object of the present invention to be able to suppress distortion in the vicinity of the folded end of a carcass ply in a pneumatic tire having a carcass ply having a low turn-up structure.

The pneumatic tire according to the first aspect of the present invention includes a pair of bead portions in which a bead core is embedded, a body portion that straddles between the bead portions, and an inner side in the tire width direction of the bead core. And a folded end located at the end of the folded portion is located within a range of 15 to 28% of the tire cross-section height outward in the tire radial direction with respect to the bead baseline. The folded portion passes from the inner side in the tire radial direction to the outer side through the center of curvature of the rim flange of the normal rim in the cross section in the tire axial direction and through the straight line extending in parallel with the tire rotation axis in the tire axial direction and the center of curvature. A first region which is provided within an angle range formed by a straight line extending in the direction of 45 ° on the inner side in the tire width direction and on the outer side in the tire radial direction, and gradually approaches the main body portion; And a, a carcass ply having a second region adjacent or in contact along the body portion, and a third region away gradually from the main body portion.

In this pneumatic tire, since the first region, the second region, and the third region are provided in the folded portion of the carcass ply, it is difficult to pull out the folded end of the carcass ply due to internal pressure growth. For this reason, even if the position of the turn-up end of the carcass ply is close to the bead base line, the first distortion in the vicinity of the turn-up end can be suppressed.

In the second region, since the folded portion of the carcass ply is close to or in contact with the main body portion, the carcass ply falls when the internal pressure is applied and when the load is applied, and the rim flange when the internal pressure is applied and when the load is applied Extrusion of rubber on the inner side in the tire width direction at the turn-back end due to the reaction force from is suppressed. Moreover, since the width | variety of the tire axial direction from a tire outer surface to a folding | turning part is large in the tire width direction outer side of a 2nd area | region, the extrusion amount of the rubber per unit area decreases. Therefore, the second strain and the third strain near the folded end can be suppressed.

Thus, in the pneumatic tire according to claim 1, in the pneumatic tire having a carcass ply having a so-called low turn-up structure in which the position of the turn-up end of the carcass ply is close to the bead base line, distortion near the turn-up end is caused. Can be suppressed.

The second region includes a straight line passing through the center of curvature of the rim flange of the normal rim in the tire axial direction cross section and extending inward in the tire axial direction parallel to the tire rotation axis, passing through the center of curvature and inward in the tire width direction and tire radius. It is provided within an angle range formed by a straight line extending in the direction of 45 ° on the outer side in the direction.

Here, the region outside this angular range is a region where the influence of the reaction force from the rim flange at the time of load application is relatively small, and it is not meaningful to arrange the second region of the folded portion in this region.

As described above, since the second region of the folded portion is arranged in an angular range where the influence of the reaction force from the rim flange when the load is applied is relatively large, Distortion can be appropriately suppressed.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the tire radial length of the second region is 5 of the height in the tire radial direction from the bead base line to the turn-up end. The inter-ply gauge between the main body portion and the folded portion in the second region is 50 to 200% of the cord diameter of the carcass ply.

Here, if the length in the tire radial direction of the second region deviates from 5 to 30% of the height in the tire radial direction from the bead base line to the turned-up end, distortion near the turned-up end of the carcass ply can be suppressed. It becomes difficult. If the inter-ply gauge is less than 50% of the cord diameter, the cords of the carcass ply are too close to each other, which is not preferable. Further, when the inter-ply gauge exceeds 200% of the cord diameter, the rubber extrusion suppressing effect is reduced.

In this pneumatic tire, since the inter-ply gauge between the main body portion and the turned-up portion of the carcass ply is appropriately set, the occurrence of a failure between the plies can be suppressed.

As described above, according to the pneumatic tire according to the present invention, in the pneumatic tire having a carcass ply having a low turn-up structure, an excellent effect can be obtained that distortion near the folded end of the carcass ply can be suppressed. .

It is an expanded sectional view showing a bead part of a pneumatic tire concerning this embodiment in a tire axial direction section. Hatching for the cross section is omitted. In the pneumatic tire concerning this embodiment, it is a sectional view showing one side of a tire equator.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In FIG. 1, a pneumatic tire 10 according to the present embodiment relates to a heavy-duty pneumatic radial tire used for, for example, a construction vehicle, and includes a pair of bead portions 12 and a carcass ply 14. As shown in FIG. 2, the pneumatic tire 10 further includes a tread portion 5 and a buttress portion 9. In FIG. 1, only one bead portion 12 is shown. In FIG. 2, one side of the tire equator CL is shown in the pneumatic tire 10.

This pneumatic tire 10 has a rubber gauge (rubber thickness) of the tread portion 5 larger than that of a pneumatic tire mounted on a passenger car or the like. Specifically, the tire 1 satisfies DC / OD ≧ 0.015 when the tire outer diameter is OD and the rubber gauge of the tread portion 5 at the position of the tire equator line CL is DC.

A plurality (for example, six layers) of belt layers 11 are provided between the tread portion 5 and the carcass ply 14 in the tire radial direction.

In the present embodiment, the tire width direction is a direction parallel to the rotation axis (not shown) of the pneumatic tire 10, and is the left-right direction (arrow XO-XI direction) in FIG. An arrow XO indicates an outer side in the tire width direction, and an arrow XI indicates an inner side in the tire width direction. Further, the tire radial direction is a direction perpendicular to the tire rotation axis, and is the vertical direction (arrow RO-RI direction) in FIG. An arrow RO indicates the outer side in the tire radial direction, and an arrow RI indicates the inner side in the tire radial direction.

“Regular rim” refers to the standard rim in the applicable size specified in the 2012 YEAR BOOK issued by JATMA, for example. “Regular internal pressure” also applies to the applicable size and ply rating specified in the YEAR BOOK. The air pressure for the maximum load at.

The tire cross-section height refers to the distance from the bead base line BL to the maximum position in the tire radial direction when the pneumatic tire 10 is assembled to a standard rim, 80% of the normal internal pressure is filled, and the load is not applied. The bead base line BL refers to the position of the intersection of the contour of the beat base 18A and the contour of the rim flange 18F in the tire width direction cross section, and corresponds to the position of the rim diameter of the normal rim in the tire radial direction.

When the TRA standard or ETRTO standard is applied in the place of use or manufacturing, follow each standard.

The pair of bead portions 12 are portions where the bead cores 16 are respectively embedded, and are portions that are fitted to the rim 18 when the pneumatic tire 10 is assembled to the rim 18. In FIG. 1, only one bead portion 12 is shown.

The carcass ply 14 has, for example, a toroidal shape between the pair of bead portions 12, and a main body portion 14 </ b> A located between the bead cores 16, and a folded portion 14 </ b> B folded back from the inside in the tire width direction of the bead core 16. is doing. The carcass ply 14 is configured by covering a cord (not shown) with rubber.

In a state in which the pneumatic tire 10 is assembled to a regular rim, filled with 80% of the regular internal pressure, and no load is applied, the folded end 14C located at the end of the folded portion 14B is on the outer side in the tire radial direction with respect to the bead base line BL. Further, it is located in the range of 15 to 28% of the tire cross-section height SH. In other words, the height HC in the tire radial direction from the bead base line BL to the turn-back end 14C is 0.15 to 0.28SH. Accordingly, in the pneumatic tire 10, the position of the turn-back end 14C is close to the bead base line BL as compared with a conventional tire (not shown) in which the turn-up end of the carcass ply is near the center of the tire cross-section height. It has a so-called low turn-up structure. The bead base line BL corresponds to the position of the rim radius R.

Here, the reason why the lower limit of the numerical value range is set to 15% is that if the lower limit is reached, the height HC of the turn-up portion 14B becomes too low, and the function of the carcass ply 14 as a tire skeleton deteriorates. Moreover, the upper limit of the numerical range is set to 28% because if it exceeds this, the ply end (the folded end 14C of the carcass ply 14) is positioned in a range where deformation is large at the time of load, and the distortion of the ply end increases. is there.

The turn-up portion 14B passes through the first region A1 gradually approaching the main body portion 14A from the inner side toward the outer side in the tire radial direction and the center of curvature O of the rim flange 18F of the rim 18 (regular rim) in the tire axial direction cross section. A straight line L1 extending parallel to the tire rotation axis (not shown) on the inner side in the direction and a straight line L2 passing through the center of curvature O and extending in the direction of 45 ° outward in the tire width direction and outward in the tire radial direction are provided. It has 2nd area | region A2 which adjoins or contacts so that 14 A of main body parts may be followed, and 3rd area | region A3 which leaves | separates gradually from 14 A of main body parts. The end of the third region A3 on the outer side in the tire radial direction is a turn-back end 14C.

If the angle between the straight lines L1 and L2 is θ, the angle θ is 12 ° to 45 °. In other words, the position of the inner end in the tire radial direction of the second region A2 (position of the height H12 from the bead base line BL) and the position of the outer end of the tire radial direction (position of the height H23 from the bead base line BL) are as follows. In any case, the angle θ is in the range of 12 ° to 45 °.

Here, the region outside the angle range of θ = 0 to 45 ° is a region where the influence of the reaction force from the rim flange 18F at the time of load application is relatively small, and this region is the second region A2 of the folded portion 14B. There is little significance to arrange.

Note that not all of the second region A2 is necessarily included in this angular range, and a part of the second region A2 may exist beyond this angular range.

Further, the length in the tire radial direction of the second region A2 is 5 to 30% of the height HC in the tire radial direction from the bead base line BL to the turn-back end 14C. Specifically, 0.05HC ≦ H23−H12 ≦ 0.30HC.

Here, when the length in the tire radial direction (H23-H12) of the second region deviates from 5 to 30% of the height HC in the tire radial direction from the bead base line BL to the turn-back end 14C, the carcass ply 14 turns back. It becomes difficult to suppress distortion near the end 14C.

Note that the length of the second region A2 in the tire radial direction can be out of this range.

Furthermore, the inter-ply gauge G between the main body portion 14A and the folded portion 14B in the second region A2 is 50 to 200% of the cord diameter of the carcass ply 14. The inter-ply gauge G is the distance between the cord surfaces of the main body portion 14A and the folded portion 14B in the normal direction of the main body portion 14A in the cross section in the tire axial direction. The cord diameter is the diameter of the cord.

Here, when the inter-ply gauge G is less than 50% of the cord diameter, the cords of the carcass ply 14 are too close to each other, which is not preferable. Further, when the inter-ply gauge G exceeds 200% of the cord diameter, the rubber extrusion suppressing effect is reduced.

Note that the inter-ply gauge G is not limited to this numerical range.

In addition, in the pneumatic tire 10, a hard stiffener 22 made of hard rubber is disposed in a region surrounded by the bead core 16, the main body portion 14 </ b> A of the carcass ply 14, and the folded portion 14 </ b> B. The width of the hard stiffener 22 gradually decreases toward the outer side in the tire radial direction. The bead portion 12 is provided with a rubber chafer 28.

A soft stiffener 23 having a smaller hardness than the hard stiffener 22 is disposed inside the bead portion 12 and the sidewall portion 20. An alternate long and short dash line 32 indicates a boundary between the soft stiffener 23 and the rubber chafer 28 on the tire outer surface side, and indicates a boundary between the rubber chafer 28 and the inner rubber 38 on the tire inner surface side. An alternate long and short dash line 34 indicates a boundary between the rubber chafer 28 and the side rubber 36. An alternate long and short dash line 40 indicates a boundary between the side rubber 36 and the soft stiffener 23. The sidewall portion 20 is a portion that connects the bead portion 12 and the tread portion 5 via the buttress portion 9 in the pneumatic tire 10.

In the second region A2, rubber is disposed between the main body portion 14A and the folded portion 14B. The rubber is a hard stiffener 22, a soft stiffener 23, or the like. When the inter-ply gauge G between the main body portion 14A and the folded portion 14B is small and the rubbers covering the cords are in contact with each other, another rubber is disposed between the main body portion 14A and the folded portion 14B. It does not have to be.

(Function)
This embodiment is configured as described above, and the operation thereof will be described below. In FIG. 1, in the pneumatic tire 10 according to the present embodiment, the carcass ply 14 has a so-called low turn-up structure, and the folded region 14B of the carcass ply 14 has a first region A1, a second region A2, and a third region. A3 is provided. Therefore, even if tension is generated in the carcass ply 14 due to internal pressure growth, the folded end 14C is hardly pulled out. For this reason, even if the carcass ply 14 has a low turn-up structure, strain (first strain) in the vicinity of the turn-back end 14C can be suppressed.

In particular, in the second region A2, since the folded portion 14B of the carcass ply 14 is close to or in contact with the main body portion 14A, the carcass ply 14 falls when the internal pressure is applied, and the rim flange 18F when a load is applied. Extrusion of rubber on the inner side in the tire width direction of the turn-back end 14C due to the reaction force from the tire is suppressed. Moreover, since the width | variety of the tire axial direction from a tire outer surface to the folding | turning part 14B is large in the tire width direction outer side of 2nd area | region A2, the extrusion amount of the rubber per unit area becomes small. Accordingly, it is possible to suppress the distortion (second distortion) due to the fall of the carcass ply 14 in the vicinity of the turn-back end 14C and the distortion (third distortion) due to rubber extrusion on the inner and outer sides in the tire width direction of the turn-back end 14C.

In particular, since the second region A2 of the folded portion 14B is disposed in an angular range (θ = 0 to 45 °) where the reaction force from the rim flange 18F is relatively large when a load is applied, the rim flange 18F. The distortion (second and third distortions) near the turn-back end 14C due to the influence of the reaction force from can be appropriately suppressed.

Moreover, since the inter-ply gauge G between the main body portion 14A and the folded portion 14B in the carcass ply 14 is appropriately set, the occurrence of a failure between the plies between the main body portion 14A and the folded portion 14B is suppressed. can do.

Thus, in the pneumatic tire 10 according to the present embodiment, in the pneumatic tire having the carcass ply 14 having a so-called low turn-up structure in which the position of the turn-up end 14C of the carcass ply 14 is close to the bead base line BL, The distortion around 14C can be suppressed. Moreover, the mass and cost of the pneumatic tire 10 can be suppressed by making the carcass ply 14 a low turn-up structure.

It should be noted that the configuration of the bead portion 12 other than the carcass ply 14, for example, the configuration of the rubber layer or the reinforcing layer, can be appropriately changed without departing from the gist of the present invention.

(Test example)
About the heavy-duty pneumatic tire (conventional example) and the heavy-duty pneumatic tire according to the example (FIG. 1) that do not have a region corresponding to the second region A2 of the present embodiment in the folded portion of the carcass ply, A finite element analysis of shear strain was performed on the outer side and the outer side in the tire width direction of the folded end in the tire width direction cross section.
The analysis conditions are as follows.
Tire size: 23.5R25 VJTz
Rim size: 19.50 / 2.5
Internal pressure: 500kPa
Load (radial direction): 119.07kN (12.15t)
The analysis results are as shown in Table 1. H12 θ ° in FIG. 1 is an angle formed by the straight line L1 and the straight line L2 when the center of curvature O in FIG. 1 is connected to the inner end in the tire radial direction of the second region by a straight line L2. H23 θ ° in FIG. 1 is an angle formed by the straight line L1 and the straight line L2 when the center of curvature O in FIG. 1 is connected to the outer end in the tire radial direction of the second region by a straight line L2.
The numerical value of the shear strain is indicated by an index with the conventional example being 100, and the smaller the numerical value, the smaller the shear strain and the better the result.

As a result, in Examples 1 to 3, the shear strain was lower when compared with the conventional example, both at the inner pressure load, at the inner pressure and at the load load, and at both the inner side and the outer side of the folded end in the tire width direction. It turned out to decrease. Of these, the shear strain was found to be the smallest in Example 2 and the largest in Example 3. It is considered that the shear strain of Example 3 was the largest because the angle θ at the position of the height H23 was more than 45 ° and 50 °.

The disclosure of Japanese Patent Application No. 2013-111201 filed on May 28, 2013 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually described to be incorporated by reference, Incorporated herein by reference.

(Explanation of symbols)
DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Bead part 14 Carcass ply 14A Main part

14B Folding part

14C Folding end 16 Bead core 18 Rim 18F Rim flange A1 1st area A2 2nd area A3 3rd area BL Bead base line G Interply gauge L1 Straight line L2 Straight line O Curvature center R Rim radius SH Tire cross-section height

Claims

A pair of bead portions with embedded bead cores;
It has a main body part located between the bead cores across the bead parts, and a folded part folded back from the inside in the tire width direction of the bead core, and the folded end located at the end of the folded part is a bead. A first region which is located in a range of 15 to 28% of the tire cross-section height on the outer side in the tire radial direction with respect to the baseline, and in which the folded portion gradually approaches the main body portion from the inner side to the outer side in the tire radial direction A straight line passing through the center of curvature of the rim flange of the normal rim in the tire axial section and extending parallel to the tire rotation axis inward in the tire axial direction, passing through the center of curvature and in the direction of 45 ° toward the tire width direction and radially outward A second region which is provided within an angular range formed by a straight line extending to the main body and is close to or in contact with the main body, and a third region which is gradually separated from the main body. And the carcass ply having a door,
Pneumatic tire with
The tire radial direction length of the second region is 5-30% of the height in the tire radial direction from the bead base line to the folded end,
The pneumatic tire according to claim 1, wherein an inter-ply gauge between the main body portion and the folded portion in the second region is 50 to 200% of a cord diameter of the carcass ply.