JP2013063676A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve bead durability without reducing the performance of retaining air pressure.SOLUTION: A pneumatic tire includes: a carcass 6 formed of at least one carcass ply 7, a bead apex rubber 8, and a rim protector 9. A first bead face 12 extending from an end section 11e of an arc surface 11, and a second bead face 14 connected via a level difference face 13 are located on an outer face 4a of a bead section 4 in a tire axis direction. The level difference face 13 is positioned in the range of 0 to 2 mm from an outer face 5a of a bead core 5 in a tire radial direction, and a length of the level difference face 13 in a tire axis direction is 0.5 to 1.0 mm. A chamfer including an arc of a curvature radius r1 of 0.5 to 1.0 mm is formed at a connection section of the level difference face 13 and the second bead face 14.

Description

  The present invention relates to a pneumatic tire including a rim protector, and relates to a technique capable of improving bead durability without lowering air pressure holding performance.

  In pneumatic tires, the distance from the road surface of the rim flange decreases as the flattening ratio decreases, so that the rim flange is liable to be damaged by contacting the curb or the like, for example, when the vehicle is brought close to the road shoulder. There's a problem. Therefore, as shown in FIG. 4, by providing a rim protector a that protrudes outward in the tire axial direction in a region radially inward of the tire in the radial direction of the maximum width of the carcass on the outer side surface of the tire, the rim flange is curbed. A technique for preventing contact with the like has been proposed (see, for example, Patent Document 1).

JP 2000-71723 A

  However, as shown in FIG. 4, when the rim protector a is provided, the rubber member of the rim protector a serves as the rubber member of the bead portion outer surface b on the circular arc surface c continuous with the heel side of the bead base surface. Therefore, the rubber thickness gt beside the core, which is the total thickness of the rubber portions e1 and e2 between the bead core and the rim flange inner surface d, tends to increase.

  For this reason, during running, the surface pressure of the contact surface between the bead portion outer surface b and the rim flange inner surface d increases, and the amount of heat generated at the contact surface increases, particularly in the vicinity of the outer side in the tire radial direction of the bead core. There was a problem that durability was lowered, such as damage to the rubber parts e1 and e2 was likely to occur.

  Further, when the rubber thickness gt beside the core is reduced in order to reduce the surface pressure between the bead portion outer surface b and the rim flange inner surface d, the rubber portions e1 and e2 extend to the bead heel portion. The rubber thickness at the arc surface c may be reduced more than necessary, and the fitting property with the rim may be lowered, and the air pressure holding performance may be lowered.

  The present invention has been devised in view of the above problems, and extends on the outer surface in the tire axial direction of the bead portion from the end of the arc surface continuous to the heel side of the bead base surface to the outer side in the tire radial direction. A first bead surface, and a second bead surface extending outwardly in the tire radial direction from the first bead surface by being connected to the first bead surface via a stepped step surface. And providing a pneumatic tire capable of improving the durability of the bead portion without deteriorating the holding performance of the air pressure based on defining the position of the step surface and the width in the tire axial direction. The main purpose.

  In order to achieve the above-mentioned object, the invention of claim 1 of the present application relates to a folded portion that is folded from the inner side to the outer side in the tire axial direction around the bead core in a main body portion that extends from the tread portion through the sidewall portion to the bead core of the bead portion. A carcass formed of at least one carcass ply provided with a bead apex rubber that extends in a tapered manner from the bead core toward the outside in the tire radial direction between the main body portion and the folded portion, and a maximum width position of the carcass A pneumatic tire having a rim protector that protrudes outward in the tire axial direction and continuously extends in the tire circumferential direction in a region radially inward of the tire, and an outer side surface of the bead portion in the tire axial direction is The tire extends radially outward from the end of the arc surface connected to the heel side of the bead base surface that sits on the rim base surface of the regular rim. A first bead surface, and a second bead surface extending outward in the tire radial direction from the first bead surface by being connected to the first bead surface through a stepped step surface; The step surface is located in a range of 0 to 2 mm from the outer surface of the bead core in the tire radial direction to the outer side in the tire radial direction, and the length of the step surface in the tire axial direction is 0.5 to 1.0 mm. In addition, the connecting portion between the step surface and the second bead surface is provided with a chamfered portion formed of an arc having a radius of curvature of 0.5 to 1.0 mm. is there.

  According to a second aspect of the present invention, the connecting portion between the first bead surface and the stepped surface is provided with a chamfered portion made of an arc having a radius of curvature of 0.5 to 1.0 mm. This is a tire.

  According to a third aspect of the present invention, in a normal state in which a rim is assembled to a normal rim and a normal internal pressure is charged, the load is between the first bead surface, the rim flange inner surface of the normal rim, and the step surface. The pneumatic tire according to claim 1 or 2, wherein a space having a triangular cross-section in which the width in the tire axial direction gradually decreases toward the inside in the tire radial direction is formed.

  In the pneumatic tire of the present invention, the first bead in which the outer side surface in the tire axial direction of the bead portion extends outward in the tire radial direction from the end of the arc surface connected to the heel side of the bead base surface seated on the rim base surface of the regular rim. And a second bead surface extending outward in the tire axial direction from the first bead surface and extending outward in the tire radial direction by being connected to the first bead surface via a stepped step surface. doing. The step surface is located in a range of 0 to 2 mm from the outer surface of the bead core in the tire radial direction to the outer side in the tire radial direction, and the length of the step surface in the tire axial direction is 0.5 to 1.0 mm. Furthermore, a chamfered portion formed of an arc having a radius of curvature of 0.5 to 1.0 mm is provided at a connection portion between the step surface and the second bead surface.

  Since the pneumatic tire according to the present invention has the step surface, a space is generated between the outer surface in the tire axial direction of the bead portion and the inner surface of the rim flange when the rim is assembled and filled with the normal internal pressure. . The void suppresses an increase in the surface pressure between the rubber on the outer side of the bead core in the tire axial direction and the inner surface of the rim flange, and suppresses heat generation during running of the bead portion, thereby improving the durability of the bead portion.

  Further, since the step surface is located in the range of 0 to 2 mm from the outer surface of the bead core in the tire radial direction to the outer side in the tire radial direction, the void is located near the outer side in the tire radial direction of the bead core that generates a large amount of heat during driving. It is provided and exhibits a further effect of suppressing heat generation and improves the durability of the bead portion. In addition, since a chamfered portion made of an arc having a radius of curvature of 0.5 to 1.0 mm is provided at the connection portion between the step surface and the second bead surface, stress concentration at the connection portion is prevented. , It is possible to prevent cracking from the location.

  Furthermore, since the length in the tire axial direction of the step surface is 0.5 to 1.0 mm, the space is generated in an appropriate size, and the surface pressure is reduced without reducing the fitting force between the tire and the rim. Suppresses the increase, suppresses heat generation during running, and improves the durability of the bead portion. In addition, since the void is generated in an appropriate size near the outside of the bead core in the radial direction of the tire, there is no reduction in the rubber thickness on the arc surface connected to the heel side of the bead base surface, and the air pressure holding performance is reduced. To prevent.

It is sectional drawing which shows one Embodiment of the pneumatic tire of this invention. It is an expanded sectional view of the bead part of Drawing 1. It is an expanded sectional view of the bead part in a regular state. It is an expanded sectional view of the bead part of the conventional pneumatic tire provided with the rim protector.

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 the tire shaft of the pneumatic tire 1 of the present embodiment, and FIG. 2 is an enlarged cross-sectional view of the bead portion of FIG. 1 and 2 are cross-sectional views in a state where the rim is not assembled. FIG. 3 is an enlarged cross-sectional view of the bead portion in a normal state.

  Here, the “normal state” refers to a no-load state in which a tire is assembled on a normal rim and filled with a normal internal pressure. 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.

  In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in a state where the rim is not assembled.

  As shown in FIG. 1, the pneumatic tire 1 of the present embodiment includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of the bead portion 4, and the carcass 6 has an outer side in the tire radial direction and a tread. A belt layer 7 disposed inside the portion 2, a bead apex rubber 8 extending from the bead core 5 toward the outer side in the tire radial direction between the main body portion 6 a and the folded portion 6 b, and the carcass 6. A rim protector 9 that protrudes outward in the tire axial direction and extends continuously in the tire circumferential direction is provided in a region radially inward of the maximum width position.

  The carcass 6 includes at least one carcass ply 6A, a toroidal main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a tire axial direction around the bead core 5. And a folded portion 6b folded from the inside to the outside. 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 °. Yes. 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.

  Further, the folded portion 6b of the carcass ply 6A is preferably terminated at the outer side in the tire radial direction than the bead core 5 and the rim protector 9, and more preferably outside the outer end in the tire radial direction of the bead apex rubber 8. It is desirable to terminate at one side. Thereby, the rigidity of the bead part 4 improves and it contributes to the improvement of steering stability. The folded portion 6b of the present embodiment terminates near the tire maximum width position.

  The belt layer 7 includes at least one belt ply 7A, 7B in which a belt cord is inclined and 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 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.

  The bead apex rubber 8 is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A, and extends in a tapered manner from the bead core 5 toward the outer side in the tire radial direction. The position of the outer end of the bead apex rubber 8 in the tire radial direction is not particularly limited. However, from the viewpoint of securing the rigidity of the rim protector 9, it is desirable that the position of the bead apex rubber 8 is more outward in the tire radial direction than the most protruding position 9a of the rim protector 9.

  The rim protector 9 is formed so as to protrude outward in the tire axial direction in a region radially inward of the tire with respect to the maximum width position of the carcass 6. Such a rim protector 9 protects the rim flange 15a of the regular rim 15 from contact with a curb or the like during traveling. The cross-sectional shape of the rim protector 9 is not particularly limited, but a rim protector having a substantially triangular cross section or a substantially trapezoidal cross section is employed.

  As shown in FIG. 3, the regular rim 15 includes a rim base surface 15 b extending substantially linearly and a rim flange inner surface 15 d extending substantially vertically in the profile on the side in contact with the tire, And an arc-shaped rim heel surface 15c disposed between the two.

  As shown in FIG. 2, the tire radius extends from the end portion 11 e of the circular arc surface 11 connected to the heel side of the bead base surface 10 seated on the rim base surface 15 b of the regular rim 15 to the tire axial direction outer surface 4 a of the bead portion 4. A first bead surface 12 extending outward in the direction of the tire, and connecting to the first bead surface 12 via a stepped step surface 13 so as to protrude outward in the tire axial direction from the first bead surface 12 and in the tire radial direction And a second bead surface 14 extending outward.

  Further, the rubber members of the arc surface 11, the first bead surface 12, the step surface 13, and the second bead surface 14 are made of highly elastic rubber having excellent wear resistance according to the custom, and the bead due to friction with the regular rim 15 is used. Damage to the outer surface 4a is prevented.

  The arc surface 11 is in close contact with the rim heel surface 15c when the tire 1 is assembled into a rim and filled with internal pressure, thereby preventing air leakage from the tire lumen. Further, when the arc surface 11 is in close contact with the rim heel surface 15c, the bead portion 4 is reliably restrained, and high steering stability is exhibited.

  Since the pneumatic tire 1 of the present invention has the step surface 13 in the bead portion 4, as shown in FIG. 3, when the rim is assembled and the normal internal pressure is filled, the bead portion 4 has an outer surface in the tire axial direction. A space 16 is formed between 4a and the inner surface 15d of the rim flange. The void 16 suppresses an increase in surface pressure between the first bead surface 12 on the outer side in the tire axial direction of the bead core 5 and the inner surface 15d of the rim flange, and suppresses heat generation during travel of the bead portion 4, thereby reducing the bead portion 4. Improve durability.

  Further, as shown in FIG. 2, the step surface 13 is located in a range h of 0 to 2 mm from the outer surface 5 a of the bead core 5 in the tire radial direction to the outer side in the tire radial direction. If the stepped surface 13 is located outward in the tire radial direction from the range h, the space 16 may be separated from the vicinity of the outer surface 5a in the tire radial direction of the bead core 5 that generates a large amount of heat during traveling, and the heat generation suppressing effect may be reduced. There is. On the contrary, when the step surface 13 is located inward in the tire radial direction from the range h, a void 16 formed between the tire axial direction outer surface 4a of the bead portion 4 and the rim flange inner surface 15d becomes the arc surface 11. There is a risk that the air pressure holding performance will be reduced. From such a viewpoint, the range h is more preferably in the range of 0 to 1 mm.

  In the present embodiment, the bead core 5 has a rectangular cross section, but a bead core having a circular cross section may be used. In this case, the range h is a range of 0 to 2 mm from the tire axial direction line passing through the outermost end of the bead core in the tire radial direction to the outer side in the tire radial direction.

  Moreover, as shown in FIG. 2, the tire axial direction length W of the step surface 13 is 0.5 to 1.0 mm. When the length W is greater than 1.0 mm, the space 16 formed between the tire axial direction outer surface 4a of the bead portion 4 and the rim flange inner surface 15d becomes excessive when the rim is assembled, and the bead portion that is running In addition to the large deformation of 4, the air pressure holding performance may be reduced. Conversely, if the length W is less than 0.5 mm, the heat generation suppressing effect may be reduced.

  As shown in FIG. 2, a chamfered portion 17 formed of an arc having a radius of curvature r1 of 0.5 to 1.0 mm is provided at a connection portion between the step surface 13 and the second bead surface 14. The chamfered portion 17 prevents stress concentration at the connecting portion between the stepped surface 13 and the second bead surface 14 and prevents damage such as cracking from the portion.

  Further, as shown in FIG. 2, a chamfered portion 18 made of an arc having a radius of curvature r2 of 0.5 to 1.0 mm is provided at the connecting portion between the first bead surface 12 and the stepped surface 13. desirable. With this chamfer 18, the first bead surface 12, the step surface 13, and the second bead surface 14 are connected as a smooth curved surface in a state in which the rim is assembled and the normal internal pressure is filled, and stress concentration at each corner portion And, in turn, damage such as cracks is prevented.

  As shown in FIG. 3, the void 16 preferably has a triangular cross section in which the width in the tire axial direction gradually decreases gradually inward in the tire radial direction. When the cross-sectional shape of the void 16 is such a triangular shape, the contact pressure on the bead base surface 10 side can be increased, and a heat radiation effect can be exhibited while ensuring steering stability.

  As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, it cannot be overemphasized that this invention can be changed into various aspects, without being limited to said specific embodiment.

  A pneumatic tire having a size of 225 / 45R18 having the basic structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and bead durability and air pressure retention performance were tested for each sample tire. A conventional tire having the basic structure of FIG. 4 without the step surface was tested in the same manner as Comparative Example 1. The test method is as follows.

<Bead durability>
Each test tire is mounted on a regular rim of 18 x 7.5 JJ and run on a drum tester at a speed of 100 km / h under conditions of an internal pressure of 290 kPa and a longitudinal load of 8.23 kN until damage occurs to the bead part. The mileage of was measured. Evaluation is displayed by the index | exponent which makes the mileage of the comparative example 1 100. FIG. The larger the value, the higher the bead durability and the better.

<Air pressure retention performance>
Each test tire is mounted on a regular rim of 18 x 7.5 JJ and filled with an internal pressure of 230 kPa. It is left to stand indoors for 30 days, and the air pressure after being left is measured. Was measured. The amount of decrease in internal pressure of each test tire is displayed as an index with the amount of decrease in internal pressure of Comparative Example 1 being 100. The smaller the index, the better the amount of decrease in internal pressure. The test results are shown in Table 1.

  As a result of the test, it can be confirmed that in Examples 1 to 6, the bead durability is improved without deteriorating the air pressure holding performance as compared with Comparative Example 1. Further, it can be confirmed that in Comparative Examples 2 and 3 in which the position of the step surface is out of the scope of the present invention, the air pressure holding performance or bead durability is deteriorated as compared with Example 1. In addition, it can be confirmed that the air pressure holding performance is also deteriorated in Comparative Example 4 in which the tire axial direction length of the step surface is out of the range of the present invention.

  In Examples 1 to 3, the position of the step surface was changed within the scope of the present invention, but all confirmed that the bead durability was higher than Comparative Example 1 and the air pressure retention performance was maintained. it can. Similarly, in Examples 1, 4, and 5, the tire axial direction length of the step surface is changed within the scope of the present invention, but all have higher bead durability than Comparative Example 1 and maintain air pressure. It can be confirmed that the performance is maintained.

2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Belt layer 8 Bead apex rubber 9 Rim protector 11 Arc surface 12 First bead surface 13 Step surface 14 Second bead surface 16 Space

Claims (3)

A carcass composed of at least one carcass ply provided with a folded portion that is folded from the inner side to the outer side in the tire axial direction around the bead core in the main body portion extending from the tread portion to the bead core through the sidewall portion;
A bead apex rubber extending in a tapered manner from the bead core toward the outside in the tire radial direction between the main body portion and the folded portion;
A pneumatic tire comprising a rim protector that protrudes outward in the tire axial direction and continuously extends in the tire circumferential direction in a region radially inward of the tire in the radial direction from the maximum width position of the carcass,
The outer surface of the bead portion in the tire axial direction is
A first bead surface extending outward in the tire radial direction from an end of an arc surface connected to a heel side of a bead base surface seated on a rim base surface of a regular rim;
A second bead surface extending outward in the tire axial direction from the first bead surface and extending outward in the tire radial direction by being connected to the first bead surface via a stepped step surface;
The step surface is located in a range of 0 to 2 mm from the outer surface of the bead core in the tire radial direction to the outer side in the tire radial direction,
And the tire axial direction length of the said level | step difference surface is 0.5-1.0 mm,
In addition, the pneumatic tire is characterized in that a chamfered portion made of an arc having a radius of curvature of 0.5 to 1.0 mm is provided at a connection portion between the step surface and the second bead surface.   The pneumatic tire according to claim 1, wherein a chamfered portion made of an arc having a radius of curvature of 0.5 to 1.0 mm is provided at a connection portion between the first bead surface and the stepped surface. In the normal state in which the rim is assembled to the normal rim and the normal internal pressure is filled,
A space having a triangular cross-section in which the width in the tire axial direction gradually decreases inward in the tire radial direction is formed between the first bead surface, the inner surface of the rim flange of the regular rim, and the step surface. The pneumatic tire according to 1 or 2.

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