JP2012086664A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the partial-wear-resistant performance of a shoulder part without degrading pinch-cut-resistant performance.SOLUTION: A plurality of dimples opened in an outer surface of a tire are separately formed in the tire circumferential direction in a buttress deflection area Qa between the first axial line passing through an outermost end in the tire axial direction of a belt layer and the second axial line separate from the first axial line inward of the tire radial direction by the distance K1 of 0.3 time the height HB in the tire radial direction from a bead base line to the outermost end in the tire axial direction. The center of an open surface of each dimple is located on the outer side in the tire axial direction from a pinch cut area Qb between the positions separate by 8 mm and by 13 mm, respectively, outward of the tire axial direction from the tire radial line passing through the rim width position.

Description

  The present invention relates to a pneumatic radial tire in which uneven wear resistance performance of a shoulder portion is improved without deteriorating pinch cut resistance performance.

  In a pneumatic radial tire, since the tread portion is reinforced with a tough belt layer, the rigidity of the tread portion is large and hardly deformed. Therefore, for example, during turning, a large load acts on the shoulder portion outside the turning radius, and the ground contact surface shape and the contact pressure are likely to change at the shoulder portion, causing uneven wear at the shoulder portion. Arise.

  Therefore, for example, as shown in FIG. 7 (A), a circumferential groove b extending continuously in the tire circumferential direction is formed in the buttress portion a, and the rigidity of the buttress portion a is reduced to reduce the load change or camber change. It has been proposed to absorb the deformation of the buttress portion a and suppress changes in the shape of the ground contact surface and the contact pressure (see, for example, Patent Documents 1 and 2).

  However, as a result of the inventor's research, it has been found that when the circumferential groove b is formed in the buttress portion a as described above, the pinch cut resistance is deteriorated such that pinch cut is likely to occur. This pinch cut is assumed to occur as follows. For example, as shown in FIG. 7B, when the tire t rides on a curbstone or the like, a large deflection occurs in the sidewall part b, and the sidewall part c is between the curbstone and the rim flange Rf. The compression force in the shearing direction acts on the carcass cord e impactively. A state in which the sidewall portion c is sandwiched between the curbstone and the rim flange Rf may be referred to as a pinch state. At this time, when the circumferential groove b is formed at the sandwiched position, the rubber thickness is small, so that the impact force is not relieved and the carcass cord e undergoes compressive deformation, which causes breakage. It is thought to progress.

Japanese Patent Laid-Open No. 64-52503 JP-A-6-320919

  Therefore, the present invention is based on the fact that a plurality of dimples are spaced apart in the tire circumferential direction instead of the circumferential groove, and the impact force in the pinch state can be reduced while improving the uneven wear resistance performance of the shoulder portion. An object of the present invention is to provide a pneumatic radial tire that can suppress pinch cuts by reducing the compressive force in the shear direction acting on the carcass cord.

In order to solve the above-mentioned problem, the invention of claim 1 of the present application includes a carcass that extends from a tread portion to a bead core of a bead portion through a sidewall portion, and a belt disposed radially outside the carcass and inside the tread portion. A pneumatic radial tire comprising a layer,
In the meridian cross section including the tire core in the normal internal pressure state in which the tire is assembled to the normal rim and filled with the normal internal pressure,
A first axial line passing through the outermost end in the tire axial direction of the belt layer and a distance K1 that is 0.3 times the height HB in the radial direction of the tire from the bead base line to the outermost end in the tire axial direction. A plurality of dimples that open on the outer surface of the tire are spaced apart in the tire circumferential direction in a buttress deflection region Qa that is a region between the first axial direction line and a second axial line that is spaced inward in the tire radial direction. ,
The opening surface of the dimple is located on the outer side in the tire axial direction outside the pinch cut region Qb between the position separated by 8 mm and the position separated by 13 mm from the tire radial direction line passing through the rim width position of the regular rim. The center is located.

  In the invention of claim 2, the dimples adjacent in the tire circumferential direction have a tire circumferential distance Lc between the centers of the opening surfaces of 1.5 to 3.0 of the tire circumferential direction length LD of the opening surface of the dimples. It is characterized by being doubled.

  In the invention of claim 3, the dimple has a deepest portion where a depth from the outer surface of the tire is maximum, and a depth HD at the deepest portion is 0.5 to 3.0 mm. It is characterized by.

  The invention of claim 4 is characterized in that the dimple has a circular or elliptical shape on the opening surface.

  In the invention of claim 5, the dimple has a tire circumferential length LD of 6 to 18 mm in the opening surface.

  In the invention of claim 6, the dimple has a deepest portion where the depth from the outer surface of the tire is maximum, and when viewed from the front, the deepest portion is closer to the center of the opening surface. Is also located inside the tire radial direction.

  In the invention of claim 7, when the dimple is viewed from the front, the maximum position of the tire circumferential length of the opening surface is located on the inner side in the tire radial direction from the center of the opening surface. It is a feature.

  In the present specification, 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, a standard rim for JATMA and a “Design” for TRA. “Rim” or “Measuring Rim” for ETRTO. The “regular internal pressure” is the air pressure defined by the standard for each tire. If JATMA, the maximum air pressure, if TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” If it is ETRTO, it means “INFLATION PRESSURE”, but in the case of a passenger car tire, it is 180 kPa.

  In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified in the normal internal pressure state.

  In the present invention, a plurality of dimples are spaced apart in the tire circumferential direction in the buttress deflection region Qa, thereby reducing the bending rigidity of the buttress deflection region Qa. Therefore, the load change and camber change in the tread portion can be absorbed and relaxed by the bending deformation of the buttress bending region Qa while maintaining the tread rigidity. As a result, as in the case of the conventional circumferential groove, the uneven wear resistance performance of the shoulder portion can be improved by suppressing changes in the contact surface shape and contact pressure.

On the other hand, since the dimples are spaced apart in the tire circumferential direction, thick portions where the rubber thickness is not reduced remain between the dimples. And this thick part can relieve | shock the impact force at the time of a pinch state, can reduce the compressive force of the shear direction which acts on a carcass cord, and can suppress the fracture | rupture of a carcass cord, ie, a pinch cut.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is sectional drawing which shows a buttress bending area | region with a dimple. It is the schematic which shows the arrangement | sequence state of a dimple. It is sectional drawing which expands and shows a dimple. (A)-(D) are sectional drawings which show the other example of a dimple. The front view which shows the other example of the opening surface of a dimple. (A) is sectional drawing of the tire which shows a prior art, (B) is sectional drawing which shows the pinch state of a tire.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 shows a tire meridional section including a tire shaft in a normal internal pressure state in which a pneumatic radial tire 1 of the present invention is assembled to a normal rim R and filled with a normal internal pressure and is loaded with a normal internal pressure.

  In FIG. 1, a pneumatic radial tire 1 is a flat radial tire for a passenger car having a flatness ratio of 0.5 or less in this example, and a bead core 5 of a bead portion 4 from a tread portion 2 to a sidewall portion 3. And a belt layer 7 disposed on the outer side in the radial direction of the carcass 6 and inside the tread portion 2.

  The carcass 6 includes a toroid-shaped main body portion 6a straddling between the bead cores 5 and 5, and a turn-back portion 6b that is continuous at both ends thereof and is turned around from the bead core 5 to the outside in the tire axial direction. Further, a bead apex rubber 8 is provided between the main body 6a and the turn-up portion 6b. The bead apex rubber 8 extends from the bead core 5 outward in the tire radial direction and cooperates with the turn-up portion 6b. Reinforce over the wall 3. The carcass 6 is formed of one or more carcass plies 6A and 6B in this example, in which carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction. As the carcass cord, a polyester cord is used in this example, but other than this, an organic fiber cord such as nylon, rayon, or aramid is preferably used.

  The belt layer 7 is formed of two or more belt plies 7A and 7B in this example, in which belt cords are arranged at, for example, about 10 to 35 ° with respect to the tire circumferential direction. In this example, the belt ply 7A on the inner side in the tire radial direction is wider than the outer belt ply 7B, and the position of the ply end is made different so that stress is applied at the outer end in the tire axial direction of the belt layer 7. Concentrated to prevent damage. In addition, the belt layer 7 has a belt cord that crosses between the plies so that the belt rigidity is increased, and substantially the entire width of the tread portion 2 is strongly reinforced with a tagging effect. As the belt cord, a steel cord is employed in this example, but high modulus organic fiber cords such as polyethylene naphthalate (PEN), polyethylene terephthalate (PET), and aromatic polyamide can also be used as necessary.

  On the outer side in the radial direction of the belt layer 7, a band layer 9 in which a band cord such as nylon is spirally wound is disposed for the purpose of improving high-speed durability. As the band layer 9, a pair of left and right edge band plies that covers only the outer end portion of the belt layer 7 and a full band ply that covers substantially the entire width of the belt layer 7 can be used as appropriate. In this example, a single full band ply is illustrated.

  Next, in the tire 1 of the present embodiment, the first axial line X1 passing through the outermost end 7E in the tire axial direction of the belt layer 7 and the tire from the bead base line BL to the outermost end 7E in the axial direction of the tire. A buttress deflection region Qa, which is a region between the first axial line X1 and the second axial line X2 separated from the first axial line X1 by a distance K1 of 0.3 times the radial height HB, A plurality of dimples 10 opened at the tire outer surface S are spaced apart in the tire circumferential direction. As shown in FIG. 3, the shape of the opening surface 10S of the dimple 10 is preferably a circular shape or an elliptical shape (including an oval shape and an oval shape), and thereby stress on the opening surface 10S due to tire deformation. Reduces concentration and prevents cracking. Further, the dimples 10 are arranged in a row at equal intervals Lc on one circumferential line J centered on the tire axis.

  The buttress bending region Qa is a region that receives bending when a load is applied to the tread portion 2. By providing the dimple 10 in the buttress bending region Qa, its bending rigidity is locally reduced, and the bending is reduced. Can be promoted. Therefore, while maintaining the tread rigidity, the load change and camber change in the tread portion 2 can be absorbed and relaxed by the bending of the buttress bending region Qa, and the change in the contact surface shape and the contact pressure can be suppressed. The uneven wear resistance performance of Sh can be improved.

  Moreover, since the buttress deflection region Qa is adjacent to the tread portion 2, the load change and camber change can be absorbed and relaxed more accurately and with good responsiveness. The impact on stability can be minimized.

  Further, since the dimples 10 are spaced apart in the tire circumferential direction, a thick portion 11 (shown in FIG. 3) in which the rubber thickness is not reduced remains between the adjacent dimples 10 and 10. Therefore, the thick-walled portion 11 can reduce the impact force in the pinch state, reduce the compressive force in the shear direction acting on the carcass cord, and suppress the carcass cord breakage damage. That is, the anti-pinch cut performance can be improved.

  In addition, in this embodiment, as shown in FIG. 2, in order to further improve the anti-pinch cut performance, the center j (corresponding to the centroid) of the opening surface 10S of the dimple 10 is located outside the pinch cut region Qb in the tire axial direction. Is located). Hereinafter, the center j of the opening surface 10S may be referred to as the opening center j. The pinch cut region Qb means a region between a position 8 mm away from the tire radial direction line Y1 passing through the rim width position Pr of the normal rim R and a position 13 mm away from the tire axial direction. This region Qb is a region where the carcass cord is most easily broken and damaged by being pinched between the road surface and the rim flange Rf when in a pinch state. Therefore, when the dimple 10 is formed, the opening center j is positioned on the outer side in the tire axial direction of the pinch cut region Qb, so that the compressive force in the shear direction acting on the carcass cord is reduced, and the anti-pinch cut performance is improved. Yes.

  Here, as shown in FIG. 3, in the dimples 10 and 10 adjacent in the tire circumferential direction, the tire circumferential distance Lc between the opening centers j and j is the tire circumferential length of the opening surface 10S of the dimple 10. It is preferably 1.5 to 3.0 times the LD. When the distance Lc is less than 1.5 times the length LD, the width of the thick portion 11 becomes too small, and it is difficult to sufficiently enhance the effect of improving the anti-pinch cut performance. On the contrary, when the distance Lc exceeds 3.0 times the length LD, it becomes difficult to absorb and relax the load change and camber change in the tread portion 2, and the tendency to reduce the uneven wear resistance performance of the shoulder portion Sh. Become. The tire circumferential length LD of the opening surface 10S of the dimple 10 is preferably in the range of 6 to 18 mm.

  Next, as shown in FIG. 4 of the meridional section passing through the opening center j, the dimple 10 has a deepest portion 10a having the maximum depth from the tire outer surface S, and the deepest portion 10a The depth HD is preferably in the range of 0.5 to 3.0 mm. If the depth HD is less than 0.5 mm, the dimple 10 does not function sufficiently because it is too shallow, and it becomes difficult to improve the uneven wear resistance of the shoulder portion Sh. On the other hand, when the depth HD exceeds 3.0 mm, the buttress flexure region Qa is too deep and the rigidity of the buttress bending region Qa becomes too low, and the steering stability is adversely affected, and stress is concentrated on the deepest portion 10a. This may cause cracks and the like. From such a viewpoint, the lower limit of the depth HD is preferably 1.0 mm or more, and the upper limit is preferably 2.0 mm or less. In this example, the dimple 10 has a bottom that is curved with a small arc, and thus the deepest portion 10a appears as a deepest point 10P. In this case, stress concentration at the bottom is alleviated, which is advantageous in suppressing the occurrence of cracks from the bottom. In particular, as in this example, when the depth of the dimple 10 gradually increases gradually from the periphery of the opening surface 10S to the deepest point 10P, it is advantageous to suppress the generation of cracks. Although it is disadvantageous for the generation of cracks, the deepest portion 10a can be formed as a flat surface as shown in FIGS. 5 (A) to (C).

  In addition, when the dimple 10 is viewed from the front, it is also preferable that the deepest portion 10a is positioned on the inner side in the tire radial direction from the opening center j as shown in FIG. This is because the deepest portion 10a can be moved away from the pinch cut region Qb where pinch cut is most likely to occur by positioning the deepest portion 10a on the inner side in the tire radial direction from the opening center j. This is advantageous for improving pinch cut performance. When the deepest portion 10a is a plane, the center i of the plane is positioned on the inner side in the tire radial direction with respect to the opening center j as shown in FIG. 5A, 5B, and 5D, the deepest portion 10a can be formed at the same position in the tire radial direction as the opening center j.

  When the dimple 10 is viewed from the front, as shown in FIG. 6, it is also preferable that the maximum position N of the length in the tire circumferential direction of the opening surface 10S is located on the inner side in the tire radial direction from the opening center j. Also in this case, the maximum position N can be moved away from the pinch cut region Qb, which is advantageous in improving the anti-pinch cut performance.

  In the buttress bending region Qa, fine decorative circumferential grooves extending continuously in the tire circumferential direction have a depth of 0.4 mm or less and a width of 3.0 mm or less for the purpose of improving the design. It does not matter if it is provided.

  In this example, in order to protect the rim flange Rf from damage, a rim protector 15 is formed on the sidewall portion 3 as shown in FIG. The rim protector 15 includes a protruding surface portion 15c that protrudes most outward in the tire axial direction, an inclined surface portion 15a that smoothly extends from the inner edge of the protruding surface portion 15c in the tire radial direction to the outer surface of the bead portion 4, and a protruding surface portion 15c. It is formed from a raised body having a substantially trapezoidal cross section surrounded by an outer sloped portion 15b smoothly connected to the outer surface of the sidewall portion 3 from the outer edge in the tire radial direction. The protruding surface portion 15c protrudes outward in the tire axial direction from the rim flange Rf. The projecting surface portion 15c is formed radially inward from the carcass maximum width point Cm at which the main body portion 6a of the carcass 6 projects most outward in the tire axial direction. In the tire having the rim protector 15 as described above, the longitudinal rigidity of the sidewall portion 3 is increased by the rim protector 15 so that it is difficult to bend and deform. Therefore, uneven wear resistance at the shoulder portion Sh is more likely to occur. . Therefore, this invention can exhibit a higher effect in such a tire.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A tire for a passenger car radial tire (tyre size 235 / 40R19) having the tire structure shown in FIG. 1 was prototyped according to the specifications shown in Table 1, and vertical springs, lateral springs, pitch cut resistance performance, shoulder portions of each sample tire. Were tested for uneven wear resistance, and the results are shown in Table 1. Except as described in Table 1, the specifications are substantially the same.

  The conventional example is an example in which neither the dimples nor the circumferential grooves are formed in the buttress flexure region Qa. In Comparative Example 1, a circumferential groove is formed as shown in FIG. 7A instead of the dimples. This is an example. The circumferential groove has a groove width of 13.0 mm and a groove depth of 8.2 mm.

(1) Vertical spring:
The ratio of longitudinal load / longitudinal deflection amount under the conditions of the rim (8.5), internal pressure (230 kPa), and longitudinal load (5 kN) was measured as a longitudinal spring constant, and is represented by an index where Conventional Example 1 is 100. The larger the value, the higher the spring constant.

(2) Lateral spring:
The ratio of lateral load / lateral deflection under the conditions of the rim (8.5), internal pressure (230 kPa), and longitudinal load (4.6 kN) was measured as a lateral spring constant, and the conventional example 1 was expressed as an index of 100. Yes. The larger the value, the higher the spring constant.

(3) Pitch cut resistance:
The tires are mounted on four wheels of a domestic FR car with a displacement of 3500cc under the conditions of rim (8.5) and internal pressure (230 kPa), and the test tire is at a 45 ° angle to the curb and at a speed of 5 km / h. I entered it and got on. The curb is 110 mm in height and width. And after getting on the curb, it was inspected for pinch cuts. Then, such a test was performed while increasing the approach speed by 5 km / h until a pinch cut occurred, and displayed as an index with the speed at which the pinch cut occurred in the conventional example being 100. The larger the value, the better the pinch cut resistance.

(4) Uneven wear resistance of shoulder portion:
After running 20,000 km on an asphalt tire test course using the above vehicle, the amount of uneven wear generated on the shoulder land was determined and displayed as an index with the conventional example being 100. The larger the value, the better the uneven wear resistance.

As shown in the table, it can be confirmed that the tires of the examples can reduce the impact force in the pinch state while improving the uneven wear resistance performance of the shoulder portion, and can improve the pinch cut performance.

2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Belt layer 7E Tire axial direction outermost end 10 Dimple 10a Deepest portion 10S Opening surface BL Bead base line N Maximum position in tire circumferential length Pr Rim width position R Regular rim S Tire outer surface X1 First axial line X2 Second axial line

Claims (7)

A pneumatic radial tire comprising a carcass extending from a tread portion through a sidewall portion to a bead core of the bead portion, and a belt layer disposed radially outside the carcass and inside the tread portion,
In the meridian cross section including the tire core in the normal internal pressure state in which the tire is assembled to the normal rim and filled with the normal internal pressure,
A first axial line passing through the outermost end in the tire axial direction of the belt layer and a distance K1 that is 0.3 times the height HB in the radial direction of the tire from the bead base line to the outermost end in the tire axial direction. A plurality of dimples that open on the outer surface of the tire are spaced apart in the tire circumferential direction in a buttress deflection region Qa that is a region between the first axial direction line and a second axial line that is spaced inward in the tire radial direction. ,
The opening surface of the dimple is located on the outer side in the tire axial direction outside the pinch cut region Qb between the position separated by 8 mm and the position separated by 13 mm from the tire radial direction line passing through the rim width position of the regular rim. A pneumatic radial tire characterized in that the center is located.   In the dimples adjacent to each other in the tire circumferential direction, a tire circumferential distance Lc between the centers of the opening surfaces is 1.5 to 3.0 times a tire circumferential direction length LD of the opening surface of the dimple. The pneumatic radial tire according to claim 1.   The dimple has a deepest portion where a depth from the outer surface of the tire is maximum, and a depth HD at the deepest portion is 0.5 to 3.0 mm. 2. A pneumatic radial tire according to 2.   The pneumatic radial tire according to any one of claims 1 to 3, wherein a shape of the opening surface of the dimple is a circular shape or an elliptical shape.   The pneumatic radial tire according to any one of claims 1 to 4, wherein the dimple has a tire circumferential length LD of 6 to 18 mm on an opening surface.   The dimple has a deepest portion having a maximum depth from the outer surface of the tire, and when the dimple is viewed from the front, the deepest portion is located on the inner side in the tire radial direction from the center of the opening surface. The pneumatic radial tire according to any one of claims 1 to 5, wherein   4. The dimple has a maximum position in the tire circumferential direction length of the opening surface when the dimple is viewed from the front, and is located on the inner side in the tire radial direction from the center of the opening surface. The pneumatic radial tire according to any one of 5 and 6.

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