JP2011207319A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire attaining weight reduction and small rolling resistance and being in superior in side cut resistance and ozone crack resistance by making a side wall part and a carcass ply proper.SOLUTION: The pneumatic tire includes a recession part 12 deviated to an inner side in a tire width direction viewed from a tire width direction cross section on at least one outer surface of the bead part 20 and the side wall part 10, and in the state that the pneumatic tire is attached to an application rim and a standard internal pressure is filled, the carcass ply 33 at the outermost side in the tire width direction at a position H1 having 1.3 times of flange height H0 from a rim base line position LL of the application rim 40 is positioned at an inner side than a center of thickness G of the bead part 20.

Description

  The present invention relates to a pneumatic tire used for light trucks and the like, and more particularly, to a pneumatic tire that is reduced in weight and has low rolling resistance, and also has good side cut resistance and ozone crack resistance.

  In recent years, pneumatic tires have been demanded for low fuel consumption tires from the viewpoint of environment and economy, and as a countermeasure, there is a reduction in rolling resistance, and as one of the means for reducing rolling resistance, May reduce tire mass.

  For the purpose of reducing the mass of the tire, there is a method to reduce the number of ply cords driven as a carcass material, but in this case, the overall rigidity of the tire is reduced, so that the tire's motion performance, steering stability performance, etc. are reduced. Is concerned. A method of reducing the total rubber thickness of the tire sidewall and bead is also conceivable. However, since the rigidity of the sidewall and bead is reduced, there is a concern about deterioration of the side cut performance and the steering stability performance. Is done.

  In order to solve the above-mentioned problem, for example, in Patent Document 1, a recess is formed in the outer rubber layer between the tire maximum width position and the position where the outer surface of the bead part is separated from the rim flange, and the tire side in the recess is The total thickness of the portion is equal to or greater than the total thickness of the tire side portion at the tire maximum width position, and the maximum depth of the concave portion is equal to or greater than 1.5 mm, thereby reducing the rubber mass and reducing the weight of the tire. There is described a pneumatic tire intended to suppress heat storage and prevent thermal deterioration of the outer rubber layer.

  However, in the pneumatic tire described in Patent Document 1, although the weight of the tire can be reduced, a compressive strain and a radius directed inward in the tire radial direction are formed at a recessed portion formation portion (recessed portion) at the time of load rolling. Since tensile strain directed outward in the direction is repeatedly applied, further improvement has been desired in terms of rigidity in the tire width direction.

  Furthermore, the pneumatic tire described in Patent Document 1 is made of natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber and other highly unsaturated rubbers having a high content of double bonds in the main chain as main rubber components. Since the double bond part of the highly unsaturated rubber has the property of depolymerizing by reacting with ozone, the rubber of the side wall part (side rubber caused by standing or running for a long time) It has been desired to effectively suppress surface cracks (ozone cracks). In particular, when the change in the outer surface shape in the vicinity of the bead portion is large, the surface distortion of the side rubber increases, so that the ozone crack resistance is improved as compared with other portions of the bead portion and the sidewall portion. There is a need.

  As a technique for suppressing side cuts and ozone cracks accompanying a decrease in rigidity in the tire width direction as described above, for example, as shown in Patent Document 2, by optimizing the concave shape of the concave portion, Examples thereof include a pneumatic tire in which a certain bead portion durability is secured while reducing the tire mass.

  Patent Document 3 discloses a pneumatic tire that is lighter in weight and improved in bead portion durability by making the interval between beads before assembling the rim wider than the rim width of the applied rim.

  Patent Document 4 does not attempt to reduce the weight of the tire, but for the purpose of improving the durability of the bead portion, the position of the folded portion of the carcass ply and the hardness of the bead filler are optimized. Is disclosed.

JP 2000-158919 A Japanese Patent Laid-Open No. 10-193924 JP 2009-73369 A JP 2007-210363 A

  Here, in the pneumatic tire of Patent Document 2, although the tire mass can be reduced, the distortion in the vicinity of the folded portion of the carcass ply cannot be sufficiently relaxed, and the occurrence of side cuts and ozone cracks still occurring in the sidewall portions is still possible. The problem remained.

  Moreover, although the pneumatic tire of patent document 3 has a certain effect in improving side cut resistance and ozone crack resistance, the development of a technology that can further effectively improve side cut resistance and ozone crack resistance has been developed. It was desired.

  An object of the present invention is to provide a pneumatic tire that is reduced in weight and has low rolling resistance by optimizing a bead portion and a carcass ply, and further excellent in side cut resistance and ozone crack resistance. is there.

The inventor includes a pair of bead portions, a pair of sidewall portions, and a tread portion straddling the sidewall portions, which are formed of two or more carcass plies extending in a toroid shape between a pair of bead cores embedded in the bead portion. With regard to the pneumatic tire connected through the carcass, intensive studies were made to solve the above problems.
And, by forming a predetermined recess in the side rubber portion, it is possible to reduce the weight, and accordingly, to reduce rolling resistance, and further, the position of the outermost carcass ply in the tire width direction at the predetermined tire radial direction position. It has been found that by optimizing, the width of the side rubber sufficient to ensure the rigidity in the tire width direction can be secured, so that the side cut resistance and the ozone crack resistance can be improved.

The present invention has been made based on such findings, and the gist thereof is as follows.
(1) A carcass composed of two or more carcass plies extending in a toroid shape between a pair of bead cores embedded in a pair of bead portions, a pair of sidewall portions, and a tread portion straddling the sidewall portions. A pneumatic tire connected via an outer surface of at least one of the bead portion and the sidewall portion, and having a concave portion that is inward in the tire width direction, and the pneumatic tire is used as an applied rim. When mounted and filled with standard internal pressure, the outermost carcass ply in the tire width direction at a position 1.3 times the flange height measured from the baseline of the applicable rim is inside the thickness center of the bead portion. Pneumatic tire characterized by.

(2) The distance from the outer surface of the tire measured along the perpendicular to the inner carcass to the outermost carcass ply in the tire width direction at a position 1.3 times the height of the flange measured from the baseline of the applicable rim is the bead. The pneumatic tire according to (1) above, which is 65% or more of the thickness of the part.

(3) The carcass ply includes at least one layer of a turn-up ply comprising a main body portion extending between the bead cores and a folded portion extending around the bead core from the inner side to the outer side in the width direction of the tire, The pneumatic tire according to (1) or (2), further comprising at least one layer of a downply that covers the outer side of the folded portion in the tire width direction and extends at least to the inner side in the radial direction of the bead core.

(4) The air according to any one of (1) to (3), wherein the concave portion is formed of one or a plurality of arcs having a center of curvature on the outer side in the tire width direction when viewed in a cross section in the tire width direction. Enter tire.

(5) The pneumatic tire according to any one of (1) to (4), wherein a radius of curvature of the arc is in a range of 50 to 250 mm.

(6) The distance measured along the tire radial direction from the straight line drawn through the center of the bead core in parallel with the tire rotation axis to the inner end in the tire radial direction of the recess when viewed in the tire width direction cross section is 20 The pneumatic tire according to any one of (1) to (5) above, which is in a range of ˜40 mm.

(7) The distance measured along the tire radial direction from the straight line drawn through the center of the bead core in parallel with the tire rotation axis to the outer end in the tire radial direction of the recess when viewed in the tire width direction cross section The pneumatic tire according to any one of (1) to (6) above, wherein the pneumatic tire has a section height of 0.4 to 0.6 times.

  According to the present invention, it is possible to provide a pneumatic tire that is reduced in weight and has a low rolling resistance and further does not impair side cut resistance and ozone crack resistance.

(a) is the width direction sectional drawing about the pneumatic tire according to this invention, (b) is the figure which expanded and showed a part of bead part and side wall part of (a). It is width direction sectional drawing about the conventional pneumatic tire. It is width direction sectional drawing about the conventional pneumatic tire.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
FIG. 1 (a) is a half part of the pneumatic tire according to the present invention as seen in the cross section in the width direction, and FIG. 1 (b) is a bead portion and a sidewall of the pneumatic tire shown in FIG. 1 (a). It is an enlarged view of a part of the part.

  As shown in FIG. 1A, the present invention includes a pair of bead cores in which a pair of bead portions 20, a pair of sidewalls 10, and a tread portion 50 straddling the sidewall 10 portions are embedded in the bead portion 20. This is a pneumatic tire connected via a carcass 30 composed of two or more carcass plies (two in FIG. 1A, a turn-up ply 31 and a down ply 33 in FIG. 1A) extending between 21.

And in this invention, as shown in FIG.1 (b), the recessed part which swells into the tire width direction inner side seeing in the tire width direction cross section in the at least one outer surface of the said bead part 20 and the side wall part 10. As shown in FIG. 12 and the tire width at a position H1 that is 1.3 times the flange height H0 from the rim baseline position LL of the applied rim 40 in a state where the pneumatic tire is mounted on the applied rim and filled with the standard internal pressure. The outermost carcass ply (down ply 33 in FIG. 1B) is the inner carcass (the carcass at the innermost side in the tire width direction in H1. In FIG. 1B, the main body portion 31a of the carcass ply 31 is shown. (In other words, as shown in FIG. 1 (b), the down-pull is applied from the outer surface of the tire). Distance X measured along the normal to the inner carcass up is greater than the distance (1 / 2G) from the tire outer surface to the bead portion center) can be characterized.
Applicable rims are industrial standards effective in the areas where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) YEAR BOOK, in Europe, ETRTO (European Tire Rim Technical Organization) STANDARD MANUAL, In the United States, the rim defined in TRA (THE TIRE and RIM ASSOCIATION INC.) YEAR BOOK, etc. shall be used. The standard internal pressure is based on the applicable rim and air pressure-load capacity correspondence table corresponding to the size of the radial ply tire defined in the above-mentioned JATMA YEAR BOOK (Japan Automobile Tire Association Standard) and the like.

  That is, by forming the recess 12, the tire can be reduced in weight, and the rolling resistance of the tire can be effectively reduced. Furthermore, each carcass ply at the position H1 1.3 times the rim flange height H0 (in FIG. 1 (b), the main body portion 31a, the turn-up portion 31b, and the down ply 33) is the thickness G of the bead portion 20. Since the thickness of the side rubber 11 positioned on the outer side in the tire width direction of each of the carcass plies 31 and 33 can be secured even when the concave portion 12 is formed by being arranged inward from the center of the tire, Strength is improved and generation of side cuts and ozone cracks can be suppressed.

  In the case of a conventional pneumatic tire (not shown) in which the concave portion 12 is formed, the passing positions of the carcass plies 31 and 33 in the bead portion 20 are not optimized (the carcass ply is the bead portion 20). Since the thickness of the side rubber 11 on the outer side in the tire width direction of the folded portion 31b cannot be sufficiently secured, and the lateral rigidity of the tire cannot be obtained sufficiently. It was difficult to ensure high side cut resistance and ozone crack resistance.

  In addition, since the side cut resistance and the ozone crack resistance can be further improved, the tire measured along a perpendicular to the inner carcass at a position H1 which is 1.3 times the flange height H0 measured from the base line LL of the applied rim 40. The distance X from the outer surface to the outermost carcass ply 33 in the tire width direction is preferably 65% or more of the thickness G of the bead portion.

  In addition, as a reason for determining the passage position of the turned-up portion 31b with respect to the thickness G of the bead portion 20 at a position H1 which is 1.3 times the flange height H0 of the applied rim 40, the position H1 is generally determined as a tire. This is because the rubber thickness is the thinnest part, and is likely to be the starting point of failure. The flange height H0 from the rim base line LL is the height of the rim flange 40a as the name suggests, and can be calculated by setting the difference between the rim flange outer diameter and the rim diameter to ½.

  Here, as for the carcass plies 31, 32, and 33 constituting the carcass 30 of the present invention, other conditions are particularly limited as long as two or more are provided from the viewpoint of ensuring the strength in the width direction and the radial direction of the tire. I do not. For example, as shown in FIG. 1 (a), a turn-up ply comprising a body portion 31a extending between the bead cores 21 and a turn-up portion 31b extending around the bead core from the inner side to the outer side in the width direction of the tire. 31 and at least the down ply 33 extending to the inside in the radial direction of the bead core 21 can also be configured, and although not shown, each is composed of two carcass plies which are turn-up plies. It can also be configured. The number of carcass plies may be two or more, and the upper limit is not particularly limited.

  In addition, from the viewpoint of securing rigidity in the tire width direction, the carcass ply is formed on the inner side in the tire width direction around the bead core and the body portion 31a extending between the bead cores 21, as shown in FIG. At least one layer of a turn-up ply 31 consisting of a folded portion 31b that is wound and extended outward from the outer side, and at least one layer that extends to the inside in the radial direction of the bead core 21 so as to cover the outer side in the tire width direction of the folded portion 31b. It is preferable that the down ply 33 is included. In this case, in order to ensure desired side cut resistance and ozone crack resistance, the main body portion 31a and the turn-up portion 31b of the turn-up ply 31 and the down ply 33 are both 1.3 times the rim flange height H0. It is necessary to pass inside X1, X2, and X3 from the center of the thickness G of the bead portion 20 at the position H1.

  When the carcass ply 31 is a turn-up ply as shown in FIG. 1 (a), the height of the flange 31 from the base line LL of the applied rim is determined with respect to the position in the tire radial direction of the end 31c of the folded portion 31b. The height is preferably 2.2 to 3.7 times higher than H0. This is because the terminal end 31c can be disposed in a portion where the distortion of the sidewall portion 10 during tire compression is small, so that separation of the carcass ply end portion 31c can be effectively prevented.

  Further, the concave portion 12 of the pneumatic tire according to the present invention is a portion formed around the outer surface of the side rubber 11 located in at least one of the bead portion 20 and the sidewall portion 10 as shown in FIG. It can be seen that the shape and thickness of the side rubber 110 of the conventional bead portion shown in FIG. In addition, the recess 12 has one or more circular arcs (not shown) having a center of curvature on the outer side in the tire width direction when viewed in a cross section in the tire width direction from the viewpoint that weight can be effectively reduced while ensuring rigidity in the tire width direction. Further, it is preferable that the radius of curvature of the arc before assembling to the application rim is in the range of 50 to 250 mm. This is because if the radius of curvature of the arc is less than 50 mm, the resistance to ozone cracking may be reduced because the radius of curvature is too small. On the other hand, if the radius of curvature exceeds 250 mm, the weight cannot be sufficiently reduced.

  Further, as shown in FIG. 1 (a), from the straight line BC drawn in parallel to the tire rotation axis through the center of the bead core 21 as seen in the cross section in the tire width direction, from the tire radial direction outer end 12a of the recess 12 The distance M1 measured along the tire radial direction is preferably in the range of 0.4 to 0.6 times the tire section height (tire sectional height) SH. This is because if the distance M1 is less than 0.4 times the section height, the weight reduction due to the formation of the concave portion 12 is not sufficient, and the rolling resistance may not be reduced. On the other hand, the distance M1 exceeds 0.6 times the section height. This is because a sufficient side rubber gauge cannot be secured, which may cause a decrease in side cut performance.

  Further, as shown in FIG. 1 (a), from the straight line BC drawn parallel to the tire rotation axis through the center of the bead core 21 as seen in the cross section in the tire width direction, from the inner end 12b in the tire radial direction of the recess 12 The distance M2 measured along the tire radial direction is preferably in the range of 20 to 40 mm. When the distance M2 is less than 20 mm, the area of the outer surface of the tire in contact with the flange 40a of the applicable rim 40 becomes small, so that the durability may be reduced. On the other hand, when the distance M2 exceeds 40 mm, the recess 12 This is because the amount of curling of the side rubber 11 is reduced, and the weight reduction effect of the tire may be reduced.

  The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

Next, a pneumatic tire according to the present invention was prototyped and its performance was evaluated, which will be described below.
(Examples 1 and 2)
As Example 1 and 2, as shown to Fig.1 (a), a pair of bead part 20, the pair of sidewall part 10, and the tread part 50 straddling this sidewall 10 part were embed | buried under the said bead part 20. A carcass 30 composed of three carcass plies 31 and 33 extending in a toroidal shape between a pair of bead cores 21, and as shown in FIG. The outermost carcass ply (down ply 33 in the tire width direction) at a position H1 that is 1.3 times the flange height H0 from the base line LL of the applicable rim. ) Produced a pneumatic tire (size: LVR 225 / 75R16 118L, rim width: 6 inches, air pressure: 600 kPa) passing through the inside of the thickness G of the bead part 20.
The distance of the carcass ply 33 along the perpendicular to the carcass 31a located on the innermost side in the tire width direction from the outer surface of the tire at a position H1 1.3 times the flange height H0 of the applied rim 40 with respect to the thickness G of the bead portion (X / G), the presence / absence of the recess 12 and the radius of curvature R of the arc forming the recess 12 are shown in Table 1.

(Comparative Example 1)
In Comparative Example 1, as shown in FIG. 3, the side rubber 111 of the side wall portion 101 is not provided with the concave portion 12, the bead portion 20 is thick, and the down ply 33 is applied to the applied rim. A normal pneumatic tire (size: under the same conditions as in the example) except that it passes outside the center of the thickness G of the bead portion 20 at a position H1 that is 1.3 times the flange height H0 from the base line LL. LVR 225 / 75R16 118L, rim width: 6 inches, air pressure: 600 kPa).
The distance of the carcass ply 33 along the perpendicular to the carcass 31a located on the innermost side in the tire width direction from the outer surface of the tire at a position H1 1.3 times the flange height H0 of the applied rim 40 with respect to the thickness G of the bead portion (X / G), the presence / absence of the recess 12 and the radius of curvature R of the arc forming the recess 12 are shown in Table 1.

(Comparative Example 2)
In Comparative Example 2, as shown in FIG. 2, the concave portion 12 is not provided in the side rubber 110 of the sidewall portion 100, and the bead portion 20 is thick except under the same conditions as in the example. A pneumatic tire (size: LVR 225 / 75R16 118L, rim width: 6 inches, air pressure: 600 kPa) was produced.
The distance of the carcass ply 33 along the perpendicular to the carcass 31a located on the innermost side in the tire width direction from the outer surface of the tire at a position H1 1.3 times the flange height H0 of the applied rim 40 with respect to the thickness G of the bead portion (X / G), the presence / absence of the recess 12 and the radius of curvature R of the arc forming the recess 12 are shown in Table 1.

(Comparative Example 3)
Comparative Example 3 is the same as in the example except that the down ply 33 passes outside the center of the thickness G of the bead portion 20 at a position H1 that is 1.3 times the flange height H0 from the base line LL of the applied rim. A similar pneumatic tire (size: LVR 225 / 75R16 118L, rim width: 6 inches, air pressure: 600 kPa) was produced.
The distance of the carcass ply 33 along the perpendicular to the carcass 31a located on the innermost side in the tire width direction from the outer surface of the tire at a position H1 1.3 times the flange height H0 of the applied rim 40 with respect to the thickness G of the bead portion (X / G), the presence / absence of the recess 12 and the radius of curvature R of the arc forming the recess 12 are shown in Table 1.

(Evaluation)
The pneumatic tires of Examples and Comparative Examples 1 to 3 were evaluated by the following methods.

(1) Tire mass About each pneumatic tire of an Example and a comparative example, each mass was measured and it evaluated about weight reduction of a tire. Evaluation shows how much weight reduction is achieved from the mass of Comparative Example 1, and the smaller the value, the better the weight reduction, which is a good result. The evaluation results are shown in Table 1.

(2) Rolling resistance Each of the pneumatic tires of the examples and comparative examples was actually attached to a car and ran at 80 km / h with the maximum internal pressure (JATMA standard) and maximum vehicle load (JATMA standard). The rolling resistance was evaluated by measuring the resistance value at the time using a force type measurement tester. The evaluation results are shown as an index ratio when the rolling resistance of Comparative Example 1 is set to 100, and are shown in Table 1. In addition, the numerical value in Table 1 is a favorable result, so that rolling resistance is so small that it is small.

(3) Ozone crack resistance and side-cut resistance For each pneumatic tire of the example and comparative example, 60km / kg with a maximum internal pressure (JATMA standard) and 1.5 times the maximum load of the JATMA standard Evaluation was performed by running at h and measuring the distance traveled until a failure (side cut, ozone crack, etc.) occurred. Evaluation is expressed as an index ratio when the traveling distance of Comparative Example 1 is set to 100, and the larger the distance, the longer the traveling distance and the higher the durability. The evaluation results are shown in Table 1.

  From the results of Table 1, the pneumatic tires of Examples 1 and 2 have a smaller tire mass and reduced rolling resistance compared to the pneumatic tires of Comparative Examples 1 and 2 that do not have a predetermined recess. I understood. Further, the pneumatic tires of Examples 1 and 2 in which the position of the carcass ply on the outermost side in the tire width direction is optimized are the pneumatic tires of Comparative Examples 1 and 3 in which the optimization is not achieved. It was found that the bead durability is higher than that.

  According to the present invention, it is possible to provide a pneumatic tire that is reduced in weight and has a low rolling resistance, and further excellent in side cut resistance and ozone crack resistance.

DESCRIPTION OF SYMBOLS 10 Side wall part 20 Bead part 21 Bead core 22 Protrusion 23 Bead filler 30 Carcass 31, 32, 33 Carcass ply 31a Ply main-body part 31b Ply folding | turning part 40 Rim 40a Flange 50 Tread part

Claims (7)

A pair of bead portions, a pair of sidewall portions, and a tread portion straddling the sidewall portions are connected via a carcass composed of two or more carcass plies extending in a toroid shape between a pair of bead cores embedded in the bead portion. A pneumatic tire,
In the outer surface of at least one of the bead portion and the sidewall portion, there is a recess that is inward in the tire width direction, and the pneumatic tire is mounted on an applicable rim and filled with standard internal pressure, A pneumatic tire characterized in that a carcass ply on the outermost side in the tire width direction at a position 1.3 times the height of the flange measured from the base line of the applied rim is inside the thickness center of the bead portion.   The distance from the tire outer surface measured along the perpendicular to the inner carcass to the outermost carcass ply in the tire width direction at a position 1.3 times the flange height measured from the base line of the applied rim is the thickness of the bead portion. The pneumatic tire according to claim 1, wherein the pneumatic tire is 65% or more.   The carcass ply includes at least one turn-up ply including a main body portion extending between the bead cores and a folded portion extending from the inner side to the outer side in the width direction of the tire around the bead core; The pneumatic tire according to claim 1, further comprising at least one layer of a downply that covers the outer side in the tire width direction and extends at least radially inward of the bead core.   The pneumatic tire according to any one of claims 1 to 3, wherein the concave portion is composed of one or a plurality of arcs having a center of curvature on the outer side in the tire width direction when viewed in a cross section in the tire width direction.   The pneumatic tire according to claim 4, wherein a radius of curvature of the arc is in a range of 50 to 250 mm.   When viewed from the cross section in the tire width direction, the distance measured along the tire radial direction from the straight line drawn through the center of the bead core and parallel to the tire rotation axis to the outer end in the tire radial direction of the recess is the tire section height. The pneumatic tire according to any one of claims 1 to 5, wherein the pneumatic tire is in a range of 0.4 to 0.6 times.   The distance measured along the tire radial direction from the straight line drawn through the center of the bead core in parallel to the tire rotation axis to the inner end in the tire radial direction of the recess when viewed in the tire width direction cross section is 20 to 40 mm. It is a range, The pneumatic tire of any one of Claims 1-6 characterized by the above-mentioned.

Images