JP2013035348A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of a tire by preventing generation of new stress concentration.SOLUTION: The pneumatic tire is provided which includes a carcass 6, a belt layer 7, and a bead apex rubber 8. A recessed part 9 continuously extended in a tire circumferential direction is formed at an outer face of a side part which includes a side wall part 3 and a bead part 4. The recessed part 9 includes a bottom face 10, an outer face 11, and an inner surface 12 each of which has linearly extending cross-section. Moreover, the outer end of the bead apex rubber 8 in a tire radial direction is located outside an inner recessed corner part 14 in the tire radial direction and located inside an outer recessed corner part 15 in the tire radial direction.

Description

  The present invention relates to a pneumatic tire that suppresses damage in the vicinity of an outer end of a bead apex rubber in the tire radial direction and improves durability.

  2. Description of the Related Art Conventionally, a pneumatic tire is known in which bead apex rubber is disposed extending from the outer surface of a bead core embedded in the bead portion to the outer side in the tire radial direction in order to ensure the bending rigidity of the bead portion.

  However, normally, at the outer end of the bead apex rubber in the tire radial direction, the body portion of the carcass ply wound around the bead core from the inner side to the outer side in the tire axial direction overlaps with the hoisted portion. There was a problem that it was easy to be confined, the adhesive strength between the members was liable to be lowered, and it was easy to become a starting point of damage even after vulcanization molding.

  Conventionally, in order to solve such a problem, as shown in FIG. 6, the side of the tire corresponding to the outer end b1 in the tire radial direction of the bead apex rubber b extending in a tapered shape from the bead core a toward the outer side in the tire radial direction. A technique for providing a concave portion c having a substantially triangular cross section on the outer surface of a portion has been proposed in the following technical literature.

Japanese Utility Model Publication No. 7-35109

  However, as shown in FIG. 6, in the pneumatic tire in which the concave portion c having a substantially triangular cross section is provided on the outer surface of the side portion, the outer end b <b> 1 of the bead apex rubber b is formed at the time of vulcanization molding as illustrated in FIG. 7. The local stress is received from the convex part of the mold, and the air is not sufficiently discharged. Further, after the vulcanization molding, there is a problem that stress concentrates on the apex of the concave portion c, and this portion becomes a starting point of new damage to reduce the durability of the bead portion.

  The present invention has been devised in view of the above circumstances, and forms a recess continuously extending in the tire circumferential direction on the outer surface of the side portion, which is a region including the sidewall and the bead portion. Based on the improvement of the cross-sectional shape, etc., the molding pressure is applied to the outer end of the bead apex rubber in the radial direction of the tire at the time of vulcanization molding, and the adhesive strength of each member near the outer end is increased. The main object is to provide a pneumatic tire capable of improving durability by preventing generation of a new stress concentration portion by providing a concave portion while preventing occurrence of damage.

  The invention according to claim 1 of the present invention includes a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a belt layer disposed inside the tread portion and radially outside the carcass, A pneumatic tire comprising a bead apex rubber that extends in a tapered shape from the bead core toward the outer side in the tire radial direction, and on the outer surface of the side portion that is a region including the sidewall portion and the bead portion, in the tire circumferential direction In the meridian cross section including the tire rotation axis, the recess is connected to the bottom surface extending linearly in the tire radial direction and the tire axial direction toward the outer side in the tire radial direction. An outer surface that inclines outward and extends linearly, and is connected to the inner side in the tire radial direction of the bottom surface and outward in the tire axial direction toward the inner side in the tire radial direction. An outer side in the tire radial direction of the bead apex rubber is located on the outer side in the tire radial direction from an inner corner where the bottom surface and the inner side are connected, and The tire is located on the inner side in the tire radial direction than the outer corner where the bottom surface and the outer surface are connected.

  According to a second aspect of the present invention, in the meridional section including the tire rotation axis, the concave portion is a straight line connecting an end portion of the inner side surface in the tire radial direction and an end portion of the outer side surface in the tire radial direction. The depth which is the maximum distance measured at right angles to the straight line from the bottom to the bottom is 0.015 to 0.05 times the opening length of the concave portion in the tire radial direction. Tire.

  The invention according to claim 3 is the pneumatic tire according to claim 1, wherein the length of the bottom surface of the recess in the tire radial direction is 15 to 20% of the tire cross-section height. .

  The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein a length of the inner surface of the concave portion in a tire radial direction is 5 to 10% of a tire cross-sectional height. is there.

  According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects, the length of the outer surface of the concave portion in the tire radial direction is 5 to 10% of the tire cross-sectional height. is there.

  According to a sixth aspect of the present invention, the carcass includes at least one sheet including a main body portion extending from the tread through the sidewall portion to the bead core, and a winding portion wound around the bead core from the inner side to the outer side in the tire axial direction. 6. The pneumatic tire according to claim 1, wherein an outer end in a tire radial direction of the winding portion is positioned radially outward from the outer corner of the recess. .

  According to a seventh aspect of the present invention, in the sidewall portion, the rubber thickness from the outer corner portion to the outer surface in the tire axial direction of the carcass is such that the rubber thickness from the inner corner portion to the outer surface of the carcass The pneumatic tire according to any one of claims 1 to 6, wherein the pneumatic tire is smaller than a thickness.

  Further, in the meridian cross section including the tire rotation axis, the outer end of the bead apex rubber in the tire radial direction has a length of the bottom surface inward and outward in the tire radial direction from an intermediate point of the bottom surface. The pneumatic tire according to any one of claims 1 to 7, which is located within a range of 10%.

  In the present invention, a concave portion extending continuously in the tire circumferential direction is formed on the outer surface of the side portion. The concave portion includes a bottom surface extending linearly in a meridian cross section including a tire rotation axis, and an outer surface extending linearly by inclining outward in the tire axial direction toward the outer side in the tire radial direction and connected to the outer side in the tire radial direction of the bottom surface. And an inner side surface which is connected to the inner side in the tire radial direction of the bottom surface and inclines outward in the tire axial direction toward the inner side in the tire radial direction and extends linearly. The outer end of the bead apex rubber in the tire radial direction is located on the outer side in the tire radial direction from the inner corner where the bottom surface and the inner side surface are connected, and the outer side where the bottom surface and the outer side surface are connected. It is characterized by being inside the tire radial direction with respect to the corner.

  In such a pneumatic tire, a sufficient molding pressure can be applied to the vicinity of the outer end of the bead apex rubber by a convex portion of a mold for molding the concave portion at the time of vulcanization molding. In particular, since the recess has a bottom surface that extends linearly, a large molding pressure can be applied to the outer end of the bead apex rubber in the radial direction of the tire, and the vicinity of the outer end of the bead apex rubber is easy to trap air. In this case, a wide range and sufficient discharge of air can be expected, and the adhesive strength between members can be increased. Furthermore, since the concave portion having such a bottom surface is less likely to cause local stress concentration after the vulcanization molding like the concave portion having a substantially triangular cross section, it does not cause a new damage starting point, and the durability of the bead portion is effective. Improve.

It is sectional drawing which shows one Embodiment of the pneumatic tire of this invention. It is a perspective view which expands and shows the bead part of FIG. It is sectional drawing which expands and shows the recessed part of FIG. It is sectional drawing which shows the time of vulcanization molding of the pneumatic tire of this invention. (A) thru | or (c) are the fragmentary perspective views of the bead part of the tire of a comparative example. It is a fragmentary perspective view of the bead part of the conventional pneumatic tire. It is sectional drawing which shows the time of vulcanization molding of the conventional pneumatic tire.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a tire meridian cross-sectional view including a tire shaft in a normal state of the pneumatic tire 1 of the present embodiment, and FIG. 2 is a perspective view of a bead portion thereof.

  Here, the normal state means that the tire is assembled to a normal rim (not shown) and is in a no-load state in which the normal internal pressure is filled. The value measured in the state.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, JATMA is a standard rim, TRA is “Design Rim”, ETRTO Then "Measuring Rim". Furthermore, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA and the table “TIRE LOAD LIMITS AT” is TRA. Maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa for tires for passenger cars.

  The pneumatic tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. A bead apex rubber 8 extending in a tapered shape from the bead core toward the outside in the radial direction of the tire is provided. In this example, a radial tire for a passenger car is shown.

  The carcass 6 is composed of one or a plurality of carcass plies 6A in this embodiment. The carcass ply 6A is a cord ply in which a carcass cord is covered with a topping rubber. In the present embodiment, the carcass cord is inclined with respect to the tire equator C at an angle of, for example, 75 ° to 90 °. The carcass cord is preferably an organic fiber cord such as polyester cord, nylon, rayon, or aramid, and a steel cord can be adopted if necessary.

  In addition, the carcass ply 6A of the present embodiment is wound from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4 and the bead core 5 around the bead core 5 from the inner side to the outer side in the tire axial direction. And a winding portion 6b extending outward in the tire radial direction. Between the body portion 6a and the winding portion 6b, the bead apex rubber 8 made of hard rubber is disposed so as to taper outward from the bead core 5 in the tire radial direction.

  The belt layer 7 includes at least two belt plies 7A and 7B in which belt cords are arranged at a small angle of, for example, 10 to 40 ° with respect to the tire equator C, and in this example, two belt plies 7A and 7B on the outer side in the tire radial direction. Are overlapped in the direction of crossing each other. As the belt cord, a steel cord is employed in the present embodiment, but a highly elastic organic fiber cord such as aramid or rayon can also be used as necessary.

  As shown in FIG. 2, the pneumatic tire 1 of the present embodiment is provided with a recess 9 that continuously extends in the tire circumferential direction on the outer surface of the side portion, which is a region including the sidewall portion 3 and the bead portion 4. It is done. The recess 9 includes a bottom surface 10 extending linearly, an outer surface 11 connected to the bottom surface, and an inner surface 12 in a meridian cross section including the tire rotation axis.

  The outer surface 11 of the concave portion 9 is connected to the outer side in the tire radial direction of the bottom surface 10 and is inclined outward in the tire axial direction toward the outer side in the tire radial direction and extends linearly. Further, the inner side surface 12 of the recess 9 is connected to the inner side in the tire radial direction of the bottom surface 10, and inclines in the tire radial direction inner side in the tire axial direction and extends linearly.

  The outer end 13 of the bead apex rubber 8 in the tire radial direction is on the outer side in the tire radial direction with respect to the inner corner 14 where the bottom surface 10 and the inner side surface 12 are connected. It is on the inner side in the tire radial direction than the outer corner 15 that is connected to the outer surface 11.

  As shown in FIG. 4, during vulcanization molding of the pneumatic tire 1, the bead portion 4 and the sidewall portion 3 are pressed by a bladder 16 that expands from the tire lumen side to mold a recess. It is pressed against the 17 convex portions 17a. The molding pressure acting on the recess 9 acts uniformly in a wide range outside and in the tire radial direction of the outer end 13 of the bead apex rubber 8 mainly via the bottom surface 10 extending linearly, and air is confined. Sufficient air can be expected to be exhausted at the point where it is easy. For this reason, the main-body part 6a and the winding part 6b of the carcass ply 6A can be brought into close contact with each other, and the adhesive strength of each member can be increased.

  In addition, the cross-sectional shape of the recessed part 9 needs to be the above-mentioned shape. That is, as shown in FIG. 5 (c), when the recess has a circular cross section, the local stress concentration is smaller than that of a conventional recess having a substantially triangular cross section. Thus, since there is no bottom surface 10 extending linearly, it becomes difficult to apply a uniform molding pressure over a wide range in the vicinity of the outer end of the bead apex rubber 8. Further, in the concave portion having the circular arc section, the gloss is concentrated on one point of the circular arc, so that the appearance when the tire is completed is likely to be deteriorated.

  Further, as shown in FIG. 3, the depth d of the recess 9 is determined from a straight line N connecting the end portion 18 on the inner side surface 12 in the tire radial direction and the end portion 19 on the outer side surface 11 in the tire radial direction. The maximum distance is perpendicular to the straight line N up to the bottom surface 10. If the depth d of the concave portion is too small, the molding pressure by the convex portion of the mold for molding the concave portion 9 tends to be insufficient, and conversely if too large, the thickness of the side wall rubber of the concave portion 9 is inadequate. There is a risk of reducing the durability of the tire by reducing the thickness as necessary. From this point of view, the depth d of the recess is desirably 0.015 times or more, more preferably 0.02 times or more of the opening length h1 in the tire radial direction between the end portions 18 and 19, and preferably 0.02 times or more. Is 0.05 times or less, more preferably 0.03 times or less.

  The length h3 of the bottom surface 10 in the tire radial direction is preferably 15% or more, more preferably 17% or more, and preferably 20% or less, more preferably 18% or less of the tire cross-section height H. . If the length h3 of the bottom surface is less than 15% of the tire cross-section height H, the range in which a large molding pressure is applied during vulcanization molding is lowered, and air discharge may be deteriorated. Conversely, if the length h3 of the bottom surface 10 exceeds 20% of the tire cross-sectional height, the area of the bottom surface 10 becomes too large, and the bending rigidity of the bead portion after molding may be reduced.

  Further, if the length h4 of the inner side surface 12 in the tire radial direction and the length h2 of the outer side surface 11 in the tire radial direction are too small, the change in the cross-sectional shape at the sidewall portion 3 becomes excessive, and the inner entry Stress concentration tends to occur at the corner 14 and / or the outer corner 15. On the other hand, if the lengths h2 and h4 are too large, a portion having a small rubber thickness of the sidewall portion 3 is made wide, and the durability may be lowered. From such a viewpoint, the lengths h2 and h4 are preferably 5 to 10% of the tire cross-section height H, respectively.

  If the outer end 6c of the carcass ply winding portion 6b and the outer end 13 of the bead apex rubber 8 in the tire radial direction are close to each other, air tends to remain during vulcanization molding. Therefore, it is desirable that the outer end 6c of the winding portion 6b is positioned radially outward from the outer corner portion 15.

  Further, the bead apex rubber 8 increases the rigidity of the side portion toward the inner side in the tire radial direction. Such a rigidity distribution is suitable from the viewpoint of securing ride comfort and handling stability. Therefore, even when the concave portion 9 is provided, the rubber thickness t1 from the outer corner 15 to the outer surface of the carcass 6 in the tire axial direction is close to such a rigidity distribution. It is desirable that the thickness is smaller than the rubber thickness t2.

  Further, the outer end 13 of the bead apex rubber 8 is desirably provided at the center of the bottom surface 10 as much as possible from the viewpoint of applying a sufficient molding pressure during vulcanization molding. In particular, it is desirable that the outer end 13 is provided within a range of 10% of the bottom surface length h3 from the middle of the length of the bottom surface 10 in the tire radial direction to the inside and outside of the tire radial direction.

  Although the pneumatic tire of the present invention has been described in detail above, it is needless to say that the present invention is not limited to the specific embodiment described above and can be implemented in various forms.

  A pneumatic tire having a tire size of 195 / 65R15 having the basic structure shown in FIG. For comparison, a similar test was performed on a tire (comparative example) having the shape of the side portion of FIGS. 5 and 6. The tire shown in FIG. 5A is a tire having an arc (Ra = 90 mm) in which the cross-sectional shape of the side of the outer end b1 of the bead apex rubber b on the outer surface of the side portion is convex outward in the axial direction. is there. Moreover, the tire described in FIG.5 (b) is a tire whose said cross-sectional shape is linear form. Furthermore, the tire described in FIG. 5C is a tire having an arcuate recess (Rb = 57 mm) in the cross-sectional shape of the side portion. The test method is as follows.

<Drum durability>
Each sample tire was mounted on a 6.0J rim, and a drum with a diameter of 1.7 m was run at an internal pressure of 240 kPa, a longitudinal load of 9.05 kN (150% of the normal load), and a speed of 100 km / h until damage occurred. Travel time was measured. The results are displayed as an index with Comparative Example 1 being 100, and the larger the value, the higher the durability.
The test results are shown in Table 1.

  As a result of the test, it can be confirmed that the tires of the examples have significantly improved durability as compared with the comparative examples.

2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 6A Carcass ply 6a Carcass ply main body portion 6b Carcass ply winding portion 6c Outer end of carcass ply winding portion 7 Belt layer
7A, 7B Belt ply 8 Bead apex rubber 9 Recessed portion 10 Bottom surface 11 Outer side surface 12 Inner side surface 13 Outside end of bead apex rubber in the tire radial direction 14 Inner corner 15 Outer corner

Claims (8)

A carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, a belt layer disposed inward of the tread portion and radially outward of the carcass, and tapered from the bead core outward in the tire radial direction. Pneumatic tire with bead apex rubber
A recess extending continuously in the tire circumferential direction is formed on the outer surface of the side portion, which is a region including the sidewall portion and the bead portion,
In the meridional section including the tire rotation axis, the recess has a linearly extending bottom surface, and an outer surface that is connected to the outer side in the tire radial direction of the bottom surface and tilts outward in the tire axial direction and extends linearly. And an inner side surface that is connected to the inside of the bottom surface of the tire in the radial direction of the tire and that inclines outward in the axial direction of the tire toward the inside in the radial direction of the tire and extends linearly,
The outer end of the bead apex rubber in the tire radial direction is located on the outer side in the tire radial direction from the inner corner where the bottom surface and the inner side surface are connected, and the outer side where the bottom surface and the outer side surface are connected. A pneumatic tire characterized by being on the inner side in the tire radial direction from the corner.   In the meridional section including the tire rotation axis, the recess includes the straight line connecting the inner radial end of the inner surface and the outer radial end of the outer surface to the bottom surface. The pneumatic tire according to claim 1, wherein a depth, which is a maximum distance measured at a right angle, is 0.015 to 0.05 times the opening length of the concave portion in the tire radial direction.   The pneumatic tire according to any one of claims 1 and 2, wherein a length of the bottom surface of the concave portion in a tire radial direction is 15 to 20% of a tire cross-section height.   The pneumatic tire according to any one of claims 1 to 3, wherein a length of the inner surface of the concave portion in a tire radial direction is 5 to 10% of a tire cross-sectional height.   The pneumatic tire according to any one of claims 1 to 4, wherein a length of the outer surface of the concave portion in a tire radial direction is 5 to 10% of a tire cross-sectional height. The carcass is composed of at least one carcass ply including a main body portion extending from the tread through the sidewall portion to the bead core, and a winding portion wound around the bead core from the inner side to the outer side in the tire axial direction.
The pneumatic tire according to any one of claims 1 to 5, wherein an outer end in a tire radial direction of the winding portion is located on a radially outer side than the outer corner of the recess.   The rubber thickness from the outer corner to the outer surface of the carcass in the tire axial direction of the sidewall portion is smaller than the rubber thickness from the inner corner to the outer surface of the carcass. The pneumatic tire in any one of thru | or 6.   In a meridian cross section including a tire rotation axis, an outer end of the bead apex rubber in a tire radial direction is located within a range of 10% of a length of the bottom surface inward and outward in the tire radial direction from an intermediate point of the bottom surface. Item 8. The pneumatic tire according to any one of Items 1 to 7.

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