JP2020026171A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire excellent in durability and steering stability.SOLUTION: In a pneumatic tire 2, a bead 10 comprises a first apex 30 and a second apex 32 positioned outside in a shaft direction of the first apex 30. A folded-back part 38b of a carcass ply passes through a space between the first apex 30 and the second apex 32. The tire 2 comprises a strip apex 22 extending in a radial direction between a main part 38a and the folded-back part 38b of the carcass ply. A ratio (Hw/Lw) of a height Hw in a radial direction from a bead base line BBL to a maximum width position Pw of the tire 2 to a maximum width Lw of the tire 2 is 35% or more. In the radial direction, an outside end 50 of the strip apex 22 is positioned closer to outside than an outside end 42 of the folded-back part, where a ratio (Hd/Hw) of a distance Hd between the ends to the height Hw is 5% or more.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire.

  The bead portion of the tire fits over the rim. In the running state, a large load is applied to the bead portion. In order to achieve good tire durability, the rigidity of the bead portion is important. Further, the structure of the bead portion affects the steering stability. In order to improve tire durability and steering stability, various studies have been made on the configuration of the bead portion.

  In the tire reported in Japanese Patent Application Laid-Open No. 2012-025280, the bead is located at a position smaller than the conventional apex (first apex) in the axial direction outside of the first apex for durability and steering stability. Apex (second apex). In this tire, durability is improved by sandwiching the folded portion of the carcass between the first apex and the second apex. In addition, this structure also contributes to steering stability because the in-plane torsional rigidity of the bead portion is improved.

JP 2012-025280 A

  Further, there is a demand for a tire having improved bead durability. Further, since a large force is repeatedly applied to the bead portion during traveling, the bead portion is likely to generate heat. In order to realize more excellent steering stability, tires are also required to suppress performance deterioration (thermal sag) due to this heat generation.

  An object of the present invention is to provide a tire excellent in durability and steering stability.

  The tire according to the present invention includes a pair of beads, a carcass, and a pair of strip apex. Each bead includes a core, a first apex extending radially outward from the core, and a second apex located axially outward of the first apex. The carcass is provided with a carcass ply, and the carcass ply is provided between a main portion extending from the inside in the axial direction of one bead to the inside in the axial direction of the other bead, and the first apex and the second apex. And a turn-back portion extending in the radial direction. The strip apex extends in a radial direction between the main portion and the folded portion. The ratio (Hw / Lw) of the radial height Hw from the bead baseline to the maximum width position Pw of the tire to the maximum width Lw of the tire is 35% or more. In the radial direction, the outer end of the strip apex is located outside the outer end of the folded portion, and the ratio (Hd / Hw) of the distance Hd to the height Hw therebetween is 5% or more. It is.

  Preferably, the profile of the side surface of the tire includes an arc C1 extending radially outward from the maximum width position Pw and an arc C2 extending radially inward from the maximum width position Pw, and a radius of curvature of the arc C1. R1 is 70 mm or more, and the absolute value of the difference between the radius of curvature R1 and the radius of curvature R2 of the arc C2 is 10 mm or less.

  Preferably, the present tire further includes a clinch located outside the second apex in the axial direction, and the outer end of the second apex is located outside the outer end of the clinch in the radial direction. ing.

  Preferably, a ratio (Hs / Hw) of the height Hs from the bead baseline to the outer end of the strip apex to the height Hw in the radial direction is 105% or more and 140% or less.

  Preferably, the ratio (Hr / Hw) of the height Hr from the bead base line to the outer end of the folded portion to the height Hw in the radial direction is 80% or more and 125% or less.

  The inventors have studied the structure of a tire having a first apex and a second apex in which the bead has improved durability. As a result, it was found that the ratio (Hw / Lw) of the height Hw in the radial direction from the bead base line to the maximum width position to the maximum width Lw (Hw / Lw) of 35% or more contributed to the improvement of durability. The inventors further insert a strip apex between the main portion of the carcass and the folded portion, and appropriately adjust the position of the outer end thereof, so that even a tire having a large ratio (Hw / Lw) has a bead portion. Was found to be able to suppress the distortion and to disperse the distortion position. This contributes to suppression of heat generation at the bead portion. Thereby, even in a tire having a large ratio (Hw / Lw), heat sag can be suppressed, and good steering stability can be realized.

  In this tire, the ratio (Hw / Lw) is 35% or more. This tire has a strip apex between the main portion of the carcass and the turn-up portion, and an outer end of the strip apex is located outside the outer end of the turn-up portion, and a height Hw of a distance Hd between them. (Hd / Hw) is 5% or more. With these combinations, the tire achieves good durability and steering stability.

FIG. 1 is a sectional view showing a part of a pneumatic tire according to one embodiment of the present invention. FIG. 2 is an enlarged sectional view showing a part of the tire of FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

  FIG. 1 shows a pneumatic tire 2 according to one embodiment of the present invention. In FIG. 1, the up-down direction is the radial direction of the tire 2, the left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper is the circumferential direction of the tire 2. An alternate long and short dash line CL indicates the equatorial plane of the tire 2. The solid line BBL represents a bead baseline. The bead base line BBL corresponds to a line that defines the rim diameter of the rim (see JATMA). Bead base line BBL extends in the axial direction. The shape of the tire 2 is symmetrical with respect to the equatorial plane except for the tread pattern.

  In this specification, the contour of the outer surface of the tire 2 is called a profile. When a projection or a groove is provided on the outer surface, this profile is represented using a virtual outer surface obtained assuming that there is no protrusion or groove. In FIG. 1, the symbol Pw indicates a position (maximum width position) where the tire 2 has the maximum width on the profile of the side surface.

  The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of clinch 8, a pair of beads 10, a carcass 12, a belt 14, a band 16, an inner liner 18, a pair of chafers 20, and a pair of strip apex 22. Have. The tire 2 is a tubeless type.

  The tread 4 has a shape convex outward in the radial direction. The tread 4 forms a tread surface 5 that contacts the road surface. A groove 7 is cut in the tread 4. The groove 7 forms a tread pattern. The tread 4 has a base layer 24 and a cap layer 26. The cap layer 26 is located radially outside the base layer 24. The cap layer 26 is laminated on the base layer 24. The base layer 24 is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 24 is a natural rubber. The cap layer 26 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  Each sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. A radially outer portion of the sidewall 6 is joined to the tread 4. A radially inner end of the sidewall 6 is joined to the clinch 8. The sidewall 6 is made of a crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 6 prevents the carcass 12 from being damaged.

  Each clinch 8 is located substantially inside the sidewall 6 in the radial direction. The clinch 8 is located outside the bead 10 and the carcass 12 in the axial direction. The clinch 8 is made of a crosslinked rubber having excellent wear resistance. The clinch 8 abuts the flange of the rim.

  Each bead 10 is located axially inward of the clinch 8. In the tire 2, the bead 10 includes the core 28, the first apex 30, and the second apex 32.

  The core 28 is ring-shaped and includes a wound non-stretchable wire. A typical material of the wire is steel. The first apex 30 extends radially outward from the core 28. The first apex 30 tapers radially outward. The first apex 30 is made of a high-hardness crosslinked rubber. The second apex 32 is located outside the first apex 30 in the axial direction. The second apex 32 is located between the clinch 8 and the carcass 12 in the axial direction. The second apex 32 tapers in a radially outward direction and also tapers in a radially inward direction. In the radial direction, the outer end 34 of the second apex 32 is located outside the tip 36 of the first apex 30. The second apex 32 is made of a high-hardness crosslinked rubber.

  The carcass 12 is bridged between the beads 10 on both sides, and extends along the tread 4 and the sidewall 6. The carcass 12 has a carcass ply. In this embodiment, the carcass 12 includes two carcass plies, a first ply 38 and a second ply 40.

  The first ply 38 is folded around the core 28. The first ply 38 has a main portion 38a and a folded portion 38b. The main portion 38a extends from the inside of one bead 10 in the axial direction to the inside of the other bead 10 in the axial direction. The main portion 38a extends along the inside of the second ply 40. The main portion 38a is laminated outside the inner liner 18. The folded portion 38b extends radially outside the first apex 30 and inside the second apex 32 in the axial direction. The folded portion 38b passes between the first apex 30 and the second apex 32. As is clear from the drawing, the outer end 42 of the folded portion 38b of the first ply 38 is located near the maximum width position Pw of the tire 2. The carcass 12 of the tire 2 has a “high turn-up (HTU)” structure.

  The second ply 40 is folded around the core 28. The second ply 40 includes a main portion 40a and a folded portion 40b. The main portion 40a extends from the inside of one bead 10 in the axial direction to the inside of the other bead 10 in the axial direction. The main portion 40a extends along the outside of the first ply 38. The folded portion 40b extends radially outside the first apex 30 and inside the second apex 32 in the axial direction. The folded portion 40b passes between the first apex 30 and the second apex 32. The folded portion 40b of the second ply 40 is located inside the folded portion 38b of the first ply 38 in the axial direction. In the radial direction, the outer end 44 of the folded portion 38b of the second ply 40 is located inside the outer end 42 of the folded portion 38b of the first ply 38.

  Each of the first ply 38 and the second ply 40 is composed of a number of cords and topping rubber arranged in parallel. The absolute value of the angle formed by each cord with respect to the equatorial plane CL is 75 ° to 90 °. In other words, the carcass 12 has a radial structure. The cord is made of organic fibers. Preferred organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers. The carcass 12 may be formed only from the first ply 38.

  The belt 14 is located inside the tread 4 in the radial direction. The belt 14 is laminated on the carcass 12. The belt 14 reinforces the carcass 12. The belt 14 includes an inner layer 46 and an outer layer 48. Although not shown, each of the inner layer 46 and the outer layer 48 is composed of a number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equatorial plane CL. A typical absolute value of the tilt angle is 10 ° or more and 35 ° or less. The direction of inclination of the cord of the inner layer 46 with respect to the equatorial plane CL is opposite to the direction of inclination of the cord of the outer layer 48 with respect to the equatorial plane CL. The preferred material of the cord is steel. Organic fibers may be used for the cord.

  The band 16 is located radially outside the belt 14. In the axial direction, the width of the band 16 is larger than the width of the belt 14. Although not shown, the band 16 is made of a cord and a topping rubber. The cord is spirally wound. This band 16 has a so-called jointless structure. The cord extends substantially circumferentially. The angle of the cord with respect to the circumferential direction is 5 ° or less, and further 2 ° or less. The cord is made of organic fibers. Preferred organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers.

  The inner liner 18 is located inside the carcass 12. The inner liner 18 is joined to the inner surface of the carcass 12. The inner liner 18 is made of a crosslinked rubber having excellent air shielding properties. A typical base rubber for the inner liner 18 is butyl rubber or halogenated butyl rubber. The inner liner 18 holds the internal pressure of the tire 2.

  Each chafer 20 is located near the bead 10. When the tire 2 is mounted on the rim, the chafer 20 comes into contact with the rim. By this contact, the vicinity of the bead 10 is protected. In this embodiment, the chafer 20 is made of a cloth and a rubber impregnated in the cloth. The chafer 20 may be integral with the clinch 8. In this case, the material of the chafer 20 is the same as the material of the clinch 8.

  Each strip apex 22 is located between the main portion 38a of the first ply 38 and the folded portion 38b in the axial direction. The strip apex 22 is located between the main portion 40a of the second ply 40 and the folded portion 40b in the axial direction. The strip apex 22 extends in the radial direction. The strip apex 22 is made of a high-hardness crosslinked rubber.

  FIG. 2 shows the side part of FIG. 1 in an enlarged manner. In FIG. 2, a double-headed arrow Hw indicates a radial height from the bead base line BBL to the maximum width position Pw. In FIG. 1, the double arrow Lw indicates the maximum width of the tire 2. This is the distance between the position Pw of one side surface and the position Pw of the other side surface in the axial direction. In the tire 2, the ratio (Hw / Lw) of the height Hw to the maximum width Lw is 35% or more. In FIG. 2, the hatch of the sidewall 6 is omitted for easy viewing.

  In FIG. 2, the double-pointed arrow HSo indicates a radial height from the bead base line BBL to the outer end 50 of the strip apex 22. The double-headed arrow Hr indicates the radial height from the bead base line BBL to the “outer end of the folded portion”. When there are a plurality of folded portions as in the present embodiment, the outer end located at the outermost position in the radial direction is the outer end when measuring the height Hr. In the present embodiment, the height Hr is a height up to the outer end 42 of the folded portion 38b of the first ply 38. As is clear from FIG. 2, in the tire 2, the outer end 50 of the strip apex 22 is located outside the outer end 42 of the folded portion in the radial direction. That is, the height HSo is larger than the height Hr. The ratio (Hd / Hw) of the distance Hd (Hd = HSo-Hr) between them in the radial direction to the height Hw is 5% or more.

  Hereinafter, the operation and effect of the present invention will be described.

  In the tire 2, the bead 10 has the first apex 30 and the second apex 32, and the folded portion 38b of the first ply 38 and the folded portion 40b of the second ply 40 It passes between the second apex 32. This structure contributes to good durability. Furthermore, in the tire 2, the ratio (Hw / Lw) of the height Hw in the radial direction to the maximum width position Pw to the maximum width Lw is 35% or more. By increasing the maximum width position Pw in this way, the folded portions (the folded portions 38b of the first ply 38 and the folded portions 40b of the second ply 40) pass through the inside of the second apex 32 in the axial direction. It does not bend suddenly outward in the axial direction. The folded portions 38b and 40b extend radially outward while gently curving outward in the axial direction. This suppresses the concentration of distortion and contributes more effectively to durability. This tire 2 has excellent durability.

  The tire 2 includes the strip apex 22 between the main part of the carcass ply (the main part 38a of the first ply 38 and the main part 40a of the second ply 40) and the folded parts 38b, 40b. The outer end 50 of the strip apex 22 is located outside the outer end 42 of the folded portion, and the ratio (Hd / Hw) of the distance Hd between them to the height Hw is 5% or more. . The strip apex 22 suppresses distortion of the bead 10 and disperses the distortion position in the tire 2 having a ratio (Hw / Lw) of 35% or more. This contributes to the suppression of heat generation at the bead 10. This suppresses heat sag and contributes to realizing good steering stability. In the tire 2, good durability and steering stability are realized by combining the ratio (Hw / Lw) with 35% or more and the strip apex 22.

  The ratio (Hw / Lw) is more preferably 37% or more. By setting the ratio (Hw / Lw) to 37% or more, the concentration of distortion can be further suppressed. This effectively contributes to durability. The ratio (Hw / Lw) is preferably 45% or less. By setting the ratio (Hw / Lw) to 45% or less, the balance of the entire side portion can be appropriately maintained. This side portion can flex flexibly. This contributes to a good ride.

  The ratio (Hd / Hw) is more preferably at least 7%. By setting the ratio (Hd / Hw) to 7% or more, the strip apex 22 suppresses the distortion of the bead 10 and disperses the distortion position. This contributes to the suppression of heat generation at the bead 10. This suppresses heat sag and contributes to realizing good steering stability. The ratio (Hd / Hw) is preferably 30% or less. By setting the ratio (Hd / Hw) to 30% or less, the influence of the strip apex 22 on the vertical spring constant can be suppressed. In the tire 2, good riding comfort is maintained. In this respect, the ratio (Hd / Hw) is more preferably equal to or less than 25%.

  In the tire 2, the outer end 50 of the strip apex 22 is preferably located outside the maximum width position Pw in the radial direction. That is, the ratio (HSo / Hw) is preferably greater than 100%. By doing so, the strip apex 22 suppresses the distortion from the bead 10 to the vicinity of the maximum width position Pw of the tire 2 and disperses the distortion position. This suppresses heat sag and contributes to realizing good steering stability. In the tire 2, good durability and steering stability are realized. In this respect, the ratio (HSo / Hw) is more preferably equal to or greater than 105%.

  The ratio (HSo / Hw) is preferably 140% or less. By setting the ratio (HSo / Hw) to 140% or less, the influence of the strip apex 22 on the vertical spring constant is suppressed. In the tire 2, good riding comfort is maintained.

  In FIG. 2, the double-headed arrow HSi represents the radial height from the bead base line BBL to the inner end 52 of the strip apex 22. The double-headed arrow H1 indicates the radial height from the bead base line BBL to the tip 36 of the first apex 30. In this tire 2, the ratio (HSi / H1) is preferably 150% or less. By setting the ratio (HSi / H1) to 150% or less, the strip apex 22 suppresses the distortion of the bead 10 and disperses the distortion position. This suppresses heat sag and contributes to realizing good steering stability. In the tire 2, good durability and steering stability are realized. In this respect, the ratio (HSi / H1) is more preferably equal to or less than 130% and further preferably equal to or less than 110%. From the viewpoint of suppressing the influence of the strip apex 22 on the mass of the tire 2, this ratio is preferably 80% or more. In the embodiment of FIG. 2, the height HSi is equal to the height H1. That is, the ratio (HSi / H1) is 100%.

  In FIG. 2, the double-headed arrow Hc indicates a radial height from the bead base line BBL to the outer end 54 of the clinch 8. The double-headed arrow H2 indicates a radial height from the bead base line BBL to the outer end 34 of the second apex 32. In the tire 2, the outer end 34 of the second apex 32 is preferably located outside the outer end 54 of the clinch 8 in the radial direction. That is, the ratio (H2 / Hc) is preferably larger than 100%. By doing so, the change in rigidity becomes smooth from the part of the bead 10 to the vicinity of the maximum width position Pw. The distribution of the stiffness in this portion is appropriate. This contributes to durability and steering stability. In this respect, the ratio (H2 / Hc) is more preferably equal to or greater than 110%. From the viewpoint of suppressing the influence of the second apex 32 on the mass of the tire 2, the ratio is preferably equal to or less than 150%.

  As described above, the outer end 42 of the folded portion is located near the maximum width position Pw of the tire 2. In the tire 2, the ratio (Hr / Hw) of the height Hr of the outer end 42 of the folded portion to the height Hw of the position Pw is preferably 80% or more. By setting the ratio (Hr / Hw) to 80% or more, the folded portion contributes to the rigidity of the side portion. This suppresses the distortion of the side part. This folded portion contributes to durability. The ratio (Hr / Hw) is preferably 125% or less. By setting the ratio (Hr / Hw) to 125% or less, the influence of the folded portion on the vertical spring constant can be suppressed. In the tire 2, good riding comfort is maintained.

  As shown in FIG. 2, the profile of the side surface includes an arc C1 extending radially outward from the position Pw and an arc C2 extending radially inward from the position Pw. The absolute value Da (Da = | R1-R2 |) of the difference between the radius of curvature R1 of the arc C1 and the radius of curvature R2 of the arc C2 is preferably 10 mm or less. By setting the absolute value Da to 10 mm or less, the side portions are uniformly inflated. This contributes to suppressing distortion concentration. This contributes to the durability and steering stability of the tire 2. In the tire 2, good durability and steering stability are realized. Further, from the viewpoint of suppressing the concentration of distortion, the radius of curvature R1 is preferably equal to or greater than 70 mm.

  The complex elastic modulus Es of the strip apex 22 is preferably 60 MPa or more. By setting the complex elastic modulus Es to 60 MPa or more, the strip apex 22 suppresses the distortion of the bead 10 and disperses the distortion position. This suppresses heat sag and contributes to realizing good steering stability. In the tire 2, good durability and steering stability are realized. The complex elastic modulus Es is preferably 70 MPa or less. By setting the complex elastic modulus Es to 70 MPa or less, the influence of the strip apex 22 on the vertical spring constant is suppressed. In the tire 2, good riding comfort is maintained.

  In the tire 2, the complex elastic modulus E1 of the first apex 30 is preferably 60 MPa or more. By setting the complex elastic modulus E1 to 60 MPa or more, the first apex 30 contributes to the rigidity of the bead 10. This tire 2 has excellent durability. The complex elastic modulus E1 is preferably 70 MPa or less. By setting the complex elastic modulus E1 to 70 MPa or less, the influence of the first apex 30 on the vertical spring constant is suppressed. In the tire 2, good riding comfort is maintained.

  In this tire 2, the complex elastic modulus E2 of the second apex 32 is preferably 60 MPa or more. The second apex 32 contributes to the rigidity of the bead 10 by setting the complex elastic modulus E2 to 60 MPa or more. This tire 2 has excellent durability. The complex elastic modulus E2 is preferably 70 MPa or less. By setting the complex elastic modulus E2 to 70 MPa or less, the influence of the second apex 32 on the vertical spring constant is suppressed. In the tire 2, good riding comfort is maintained.

In the present invention, the complex elastic modulus Es, the complex elastic modulus E1, and the complex elastic modulus E2 are measured in accordance with the provisions of "JIS K6394". The measurement conditions are as follows.
Viscoelastic spectrometer: "VESF-3" of Iwamoto Seisakusho
Initial distortion: 10%
Dynamic distortion: ± 1%
Frequency: 10Hz
Deformation mode: tensile Measurement temperature: 70 ° C

  In the present invention, the dimensions and angles of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 2.

  In this specification, the regular rim means a rim defined in a standard on which the tire 2 depends. The “standard rim” in the JATMA standard, the “Design Rim” in the TRA standard, and the “Measuring Rim” in the ETRTO standard are regular rims. In this specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 depends. “Maximum air pressure” in the JATMA standard, “maximum value” published in “TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and “INFLATION PRESSURE” in the ETRTO standard are normal internal pressures. In the present specification, the normal load means a load determined in a standard on which the tire 2 depends. “Maximum load capacity” in the JATMA standard, “maximum value” published in “TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and “LOAD CAPACITY” in the ETRTO standard are normal loads.

  Hereinafter, the effects of the present invention will be clarified by examples, but the present invention should not be construed as being limited based on the description of the examples.

[Example 1]
A pneumatic tire of Example 1 having the structure shown in FIGS. 1 and 2 and having the specifications shown in Table 1 below was obtained. The size of this tire is 185R14C. In this tire, the ratio (Hr / Hw) was set to 118%, and the ratio (HSi / H1) was set to 100%. The ratio (H2 / Hc) was set to 122%. Therefore, in this tire, the height H2 is larger than the height Hc. This is described as “Yes” in the column “H2> Hc” in Table 1. The absolute value Da was set to 0.0 mm, and the radius of curvature R1 was set to 90 mm.

[Comparative Example 1]
The tire of Comparative Example 1 did not include the strip apex. Table 1 shows values of the ratio (Hw / Lw) of the tire. In this tire, the height H2 is smaller than the height Hc. This is described as “No” in the column “H2> Hc” in Table 1. Other than these, the tire of Comparative Example 1 is the same as the tire of Example 1.

[Comparative Example 2, Example 2]
Tires of Comparative Example 2 and Example 2 were obtained in the same manner as in Example 1 except that the height (Hw / Lw) at the maximum width position was changed and the ratio (Hw / Lw) was as shown in Table 1.

[Comparative Example 3, Example 3-4]
Tires of Comparative Example 3 and Example 3-4 were obtained in the same manner as in Example 1 except that the ratio (Hd / Hw) was changed as shown in Table 2 by changing the height of the outer end of the strip apex. Was.

[Example 5]
A tire of Example 5 was obtained in the same manner as Example 1 except that the height H2 was smaller than the height Hc.

[durability]
The tire was mounted on a regular rim (14 × 5.5 J), and the tire was filled with air to have an internal pressure of 450 kPa. The tire was mounted on a running test machine, and a vertical load of 11.63 kN was applied to the tire. The tire was run on a drum having a radius of 1.7 m at a speed of 80 km / h. The mileage until tire damage was confirmed was checked. This value is an index with Comparative Example 1 being 100, and is shown in Tables 1 and 2. The larger the value, the better the durability. The larger the value, the better.

[Driving stability]
The tire was mounted on a regular rim (14 × 5.5 J), which was mounted on the front and rear wheels of a commercially available light truck. The internal pressure of the front tire was 340 kPa, and the internal pressure of the rear tire was 420 kPa. The vehicle was loaded with luggage so that the load applied to these tires was half of the normal load. The driver drove this vehicle on the test course. In this running, in order to evaluate the influence of the heat sag on the driving stability, a running-in operation was performed at a speed of 60 km / h for 2 minutes, and then lanes were changed for three lanes. Furthermore, after traveling at a speed of 120 km / h for 5 minutes, lane changes for three lanes were performed. Steering stability at this time was confirmed. The results are shown in Tables 1 and 2 as an index with Comparative Example 1 being 100. The larger the value, the better.

  As shown in Tables 1 and 2, the example tires are generally superior to the comparative example tires. From the evaluation results, the superiority of the present invention is clear.

  The pneumatic tire described above can be applied to various vehicles.

2 ... tire 4 ... tread 5 ... tread surface 6 ... sidewall 7 ... groove 8 ... clinch 10 ... bead 12 ... carcass 14 ... belt 16 ...・ Band 18 ・ ・ ・ Inner liner 20 ・ ・ ・ Chafer 22 ・ ・ ・ Strip apex 24 ・ ・ ・ Base layer 26 ・ ・ ・ Cap layer 28 ・ ・ ・ Core 30 ・ ・ ・ First apex 32 ・ ・ ・Second apex 34 ... Outer end of second apex 36 ... Tip of first apex 38 ... First ply 40 ... Second ply 42 ... Outer end of folded portion 44 ..The outer end of the folded portion of the first ply 46 ... the inner layer 48 ... the outer layer 50 ... the outer end of the strip apex 52 ... the inner end of the strip apex 54 ... the clinch Outer edge

Claims (5)

It has a pair of beads, a carcass and a pair of strip apex,
Each bead includes a core, a first apex extending radially outward from the core, and a second apex located axially outside the first apex,
The carcass includes a carcass ply, and the carcass ply extends between an inner side of one bead in an axial direction and an inner side of the other bead in an axial direction, between the first apex and the second apex. And a folded portion extending in the radial direction through
The strip apex extends radially between the main portion and the folded portion,
A ratio (Hw / Lw) of a height Hw in a radial direction from a bead base line to a maximum width position Pw of the tire to a maximum width Lw of the tire is 35% or more;
The outer end of the strip apex is located outside the outer end of the folded portion in the radial direction, and the ratio (Hd / Hw) of the distance Hd to the height Hw therebetween is 5% or more. There is a pneumatic tire. The profile of the side surface of the tire includes an arc C1 extending radially outward from the maximum width position Pw and an arc C2 extending radially inward from the maximum width position Pw,
The radius of curvature R1 of the arc C1 is 70 mm or more;
The tire according to claim 1, wherein an absolute value of a difference between the curvature radius R1 and the curvature radius R2 of the arc C2 is 10 mm or less. It further comprises a clinch positioned axially outside the second apex,
The tire according to claim 1, wherein an outer end of the second apex is located outside an outer end of the clinch in a radial direction.   The ratio (HSo / Hw) of the height HSo from the bead baseline to the outer end of the strip apex to the height Hw in the radial direction is not less than 105% and not more than 140%. The tire described in Crab.   The ratio (Hr / Hw) of the height Hr from the bead base line to the outer end of the folded portion to the height Hw in the radial direction is 80% or more and 125% or less. The tire described in the above.

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