JP2021123197A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire 2 excellent in steering stability and durability.SOLUTION: The tire 2 has a carcass 14, an apex 42, a first strip 24, a second strip 26 and a third strip 28. A part of the first strip 24 is sandwiched between a surface in an axial direction inside of the apex 42 and the carcass 14. The second strip 26 is positioned outside in the axial direction of the first strip 24. A part of the second strip 26 is sandwiched between a surface outside in the axial direction of the apex 42 and the carcass 14. The third strip 28 is positioned outside in the axial direction of the second strip 26.SELECTED DRAWING: Figure 2

Description

The present invention relates to a pneumatic tire. In particular, the present invention relates to a tire having strips on the sides.

The tire has a pair of beads. A carcass is hung between the beads on both sides. Each bead has a core and an apex extending radially outward from this core. The carcass ply is folded back at the core.

The material of Apex is high hardness crosslinked rubber. This apex contributes to the rigidity of the tire. Tires with high rigidity have excellent steering stability.

When the tires are running, the beads are loaded. This load creates a local stress in the vicinity of the apex. This stress impairs the durability of the tire.

Japanese Unexamined Patent Publication No. 2016-147567 discloses a tire having an apex and a filler located outside the apex in the axial direction. In this tire, a part of the carcass is sandwiched between the apex and the filler. In this tire, the filler contributes to durability.

JP-A-2016-147567

Even in the tire disclosed in JP-A-2016-147567, the rigidity in the vicinity of the bead is insufficient. If the size of the apex is set large in this tire, a large rigidity can be achieved. However, the large apex invites looseness between the carcass and the filler. With the tires disclosed in JP-A-2016-147567, it is difficult to achieve both steering stability and durability.

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

The pneumatic tire according to the present invention has a tread, a pair of sidewalls, a pair of beads, a carcass, a pair of first strips, a pair of second strips and a pair of third strips. Each bead has a core and an apex extending radially outward from this core. The carcass spans between one bead and the other along the inside of the tread and sidewalls. A portion of each first strip is sandwiched between the axially inner surface of the apex and the carcass. Each second strip is located axially outward of the first strip. Part of this second strip is sandwiched between the axially outer surface of the apex and the carcass. Each third strip is located axially outward of the second strip.

Preferably, the complex elastic modulus E ^* (1) of the first strip at 70 ° C. ^{is larger than the complex elastic modulus E *} (2) of the second strip at 70 ° C., and the complex elastic modulus of the third strip at 70 ° C. E ^* Larger than (3). Preferably, the complex elastic modulus E ^* (2) is ^{larger than the complex elastic modulus E *} (3).

Preferably, the loss tangent tan δ (2) of the second strip at 70 ° C. is smaller than the loss tangent tan δ (1) of the first strip at 70 ° C. Preferably, the loss tangent tan δ (3) of the third strip at 70 ° C. is smaller than the loss tangent tan δ (1) of the first strip at 70 ° C. Preferably, the loss tangent tan δ (3) is smaller than the loss tangent tan δ (2).

Preferably, the rate of change in the thickness of the first strip is within ± 25% / mm. Preferably, the rate of change in the thickness of the second strip is within ± 25% / mm. Preferably, the rate of change in the thickness of the third strip is within ± 25% / mm.

Preferably, the inner edge of the first strip is located inward in the radial direction with respect to the outer edge of the apex. Preferably, the outer edge of the first strip is located radially outside the outer edge of the apex. Preferably, the inner edge of the second strip is located inward in the radial direction with respect to the outer edge of the apex. Preferably, the outer edge of the second strip is located radially outside the outer edge of the apex. Preferably, the inner edge of the third strip is located inward in the radial direction with respect to the outer edge of the apex. Preferably, the outer edge of the third strip is located radially outside the outer edge of the apex.

Preferably, the inner edge of the second strip is located inward in the radial direction with respect to the inner edge of the first strip. Preferably, the inner edge of the third strip is located inward in the radial direction with respect to the inner edge of the second strip.

Preferably, the outer edge of the second strip is located radially outside the outer edge of the first strip. Preferably, the outer edge of the third strip is located radially outside the outer edge of the second strip.

Preferably, the maximum thickness of the first strip is 1.0 mm or less. Preferably, the maximum thickness of the second strip is 1.0 mm or less. Preferably, the maximum thickness of the third strip is 2.0 mm or less.

Preferably, the inner edge of the first strip is located radially inward of the starting point of contact with the flange of the rim on which the tire is mounted. Preferably, the outer edge of the first strip is located radially outside the contact start point. Preferably, the inner end of the second strip is located inward in the radial direction with respect to the contact start point. Preferably, the outer edge of the second strip is located radially outside the contact start point. Preferably, the inner end of the third strip is located inward in the radial direction with respect to the contact start point. Preferably, the outer edge of the third strip is located radially outside the contact start point.

In the pneumatic tire according to the present invention, the first strip, the second strip and the third strip contribute to the rigidity in the vicinity of the bead. This tire has excellent steering stability. These strips do not significantly impair the durability of the tire. This tire has excellent steering stability and durability.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a part of the tire of FIG. FIG. 3 is an enlarged cross-sectional view showing a part of the tire of FIG. FIG. 4 is an enlarged cross-sectional view showing a part of the tire of FIG. FIG. 5 is an enlarged cross-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.

Pneumatic tires 2 are shown in FIGS. 1 and 2. In FIG. 1, the vertical 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 surface is the circumferential direction of the tire 2. In FIG. 1, the alternate long and short dash line CL represents the equatorial plane of the tire 2. The shape of the tire 2 is symmetrical with respect to the equatorial plane except for the tread pattern. In FIG. 1, the solid line BBL is a bead baseline. The bead baseline is a line that defines the rim diameter (see JATTA) of the rim 4 on which the tire 2 is mounted. This bead baseline BBL extends axially. In FIG. 1, the arrow Ht indicates the height of the tire 2 from the bead baseline BBL. Usually, the height Ht is 110 mm to 200 mm.

The tire 2 includes a tread 6, a pair of sidewalls 8, a pair of clinches 10, a pair of beads 12, a carcass 14, a belt 16, a band 18, an inner liner 20, a pair of chafers 22, and a pair of first strips 24. It has a pair of second strips 26 and a pair of third strips 28. This tire 2 is a tubeless type. The tire 2 is mounted on a light truck.

The tread 6 has a shape that is convex outward in the radial direction. The tread 6 forms a tread surface 30 that is in contact with the road surface. A plurality of grooves 32 are carved in the tread 6. These grooves 32 form a tread pattern.

The tread 6 has a base layer 34 and a cap layer 36. The cap layer 36 is located radially outside the base layer 34. The cap layer 36 is laminated on the base layer 34. The base layer 34 is made of crosslinked rubber having excellent adhesiveness. The cap layer 36 is made of crosslinked rubber having excellent wear resistance, heat resistance and grip.

Each sidewall 8 extends substantially inward in the radial direction from the end of the tread 6. The sidewall 8 is made of crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 8 prevents damage to the carcass 14.

Each clinch 10 is located approximately inside the sidewall 8 in the radial direction. The clinch 10 is joined to the radial inner edge of the sidewall 8. The clinch 10 extends substantially inward in the radial direction from the inner end of the sidewall 8. The clinch 10 is located outside the bead 12 and the carcass 14 in the axial direction. The clinch 10 is made of crosslinked rubber having excellent wear resistance. The clinch 10 comes into contact with the flange 38 of the rim 4.

The surface of the clinch 10 has a contact starting point Ps. The surface of the clinch 10 is in contact with the flange 38 on the inner side in the radial direction from the contact start point Ps. The surface of the clinch 10 is separated from the flange 38 on the outer side in the radial direction from the contact start point Ps. The contact start point Ps is determined in a state where the tire 2 is incorporated in the normal rim and the tire 2 is filled with air so as to have a normal internal pressure. At the time of determination, no load is applied to the tire 2.

Each bead 12 is located axially inside the clinch 10. The bead 12 has a core 40 and an apex 42. The core 40 is ring-shaped and includes a wound non-stretchable wire. A typical material for wire is steel.

The apex 42 extends radially outward from the core 40. Apex 42 is tapered outward in the radial direction. Apex 42 is made of high hardness crosslinked rubber. Apex 42 has an outer end Ea (see FIG. 2). The outer end Ea is located on the outermost side in the radial direction. The complex elastic modulus E ^* of Apex 42 is preferably 60 MPa or more. Apex 42 having a complex elastic modulus E ^* of 60 MPa or more contributes to the rigidity of the bead 12. This tire 2 has excellent durability. From this viewpoint, the complex elastic modulus E ^* is particularly preferably 63 MPa or more. The complex elastic modulus E ^* is preferably 70 MPa or less. Apex 42 having a complex elastic modulus E ^* of 70 MPa or less does not hinder the ride quality of the tire 2. From this viewpoint, the complex elastic modulus E ^* is particularly preferably 67 MPa or less.

In the present specification, the complex elastic modulus E ^* and the loss tangent tan δ of the rubber member are measured in accordance with the provisions of “JIS K 6394”. The measurement conditions are as follows.
Viscoelastic spectrometer: "VESF-3" from Iwamoto Seisakusho
Initial distortion: 10%
Dynamic distortion: ± 1%
Frequency: 10Hz
Deformation mode: Tension measurement temperature: 70 ° C

The carcass 14 is composed of a first ply 44 and a second ply 46. The first ply 44 and the second ply 46 are bridged between the beads 12 on both sides and run along the tread 6 and the sidewall 8. The first ply 44 is folded around the core 40 from the inside to the outside in the axial direction. As a result of this folding, a main portion 48 and a folded portion 50 are formed on the first ply 44. The second ply 46 is folded around the core 40 from the inside to the outside in the axial direction. As a result of this folding, a main portion 52 and a folded portion 54 are formed on the second ply 46. The end of the folded portion 50 of the first ply 44 is located outside the end of the folded portion 54 of the second ply 46 in the radial direction.

Each of the first ply 44 and the second ply 46 is composed of a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle each code makes with respect to the equatorial plane is 75 ° to 90 °. In other words, the carcass 14 has a radial structure. The cord consists of organic fibers. Preferred organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers. The carcass 14 may be formed from a single ply. The carcass 14 may be formed from three or more plies. The preferred number of plies for the carcass 14 is one or two. The tire 2 having the carcass 14 composed of one or two plies is lightweight. This tire 2 is excellent in fuel efficiency. From the viewpoint of durability and fuel efficiency, the ideal number of plies in the carcass 14 is 2.

The belt 16 is located inside the tread 6 in the radial direction. The belt 16 is laminated with the carcass 14. The belt 16 reinforces the carcass 14. The belt 16 is composed of an inner layer 56 and an outer layer 58. As is clear from FIG. 1, the width of the inner layer 56 is slightly larger than the width of the outer layer 58 in the axial direction. Although not shown, each of the inner layer 56 and the outer layer 58 consists of a number of parallel cords and topping rubbers. Each cord is tilted with respect to the equatorial plane. The general 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 56 with respect to the equatorial plane is opposite to the direction of inclination of the cord of the outer layer 58 with respect to the equatorial plane. The preferred material for the cord is steel. Organic fibers may be used for the cord. The axial width of the belt 16 is preferably 0.7 times or more the maximum width of the tire 2. The belt 16 may include three or more layers.

The band 18 is located on the outer side in the radial direction of the belt 16. In the axial direction, the width of the band 18 is larger than the width of the belt 16. Although not shown, the band 18 consists of a cord and a topping rubber. The cord is spirally wound. The band 18 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is 5 ° or less. Preferably, this angle is 2 ° or less. Since the belt 16 is restrained by this cord, the lifting of the belt 16 is suppressed. The cord consists of organic fibers. Preferred organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers. The tire 2 may have an edge band.

The belt 16 and the band 18 form a reinforcing layer. The reinforcing layer reinforces the carcass 14. The reinforcing layer may be formed only from the belt 16. The reinforcing layer may be formed only from the band 18.

The inner liner 20 is located inside the carcass 14. The inner liner 20 is joined to the inner surface of the carcass 14. The inner liner 20 is made of crosslinked rubber having excellent air shielding properties. A typical base rubber of the inner liner 20 is butyl rubber or halogenated butyl rubber. The inner liner 20 holds the internal pressure of the tire 2.

Each chafer 22 is located in the vicinity of the bead 12. In this embodiment, the cheffer is integrated with the clinch 10. Therefore, the material of the chafer 22 is the same as that of the clinch 10. The material of the chafer 22 may be different from the material of the clinch 10.

Each first strip 24 is formed by cross-linking a rubber sheet. The first strip 24 does not contain a cord. As shown in FIG. 2, the first strip 24 has an inner end E1i and an outer end E1o. The inner end E1i is located on the innermost side in the radial direction. The outer end E1o is located on the outermost side in the radial direction. In the vicinity of the inner end E1i, the first strip 24 is sandwiched between the axially inner surface of the apex 42 and the main portion 52 of the second ply 46. In other words, a part of the first strip 24 is sandwiched between the axially inner surface of the Apex 42 and the carcass 14.

Each second strip 26 is located axially outward of the first strip 24. The second strip 26 is formed by cross-linking a rubber sheet. The second strip 26 does not contain a cord. As shown in FIG. 2, the second strip 26 has an inner end E2i and an outer end E2o. The inner end E2i is located on the innermost side in the radial direction. The outer end E2o is located on the outermost side in the radial direction. In the vicinity of the inner end E2i, the second strip 26 is sandwiched between the axially outer surface of the apex 42 and the folded portion 54 of the second ply 46. In other words, a part of the second strip 26 is sandwiched between the axially outer surface of the apex 42 and the carcass 14. The first strip 24 is in contact with the second strip 26 on the radial outer side of the outer end Ea of the apex 12.

Each third strip 28 is located axially outward of the second strip 26. The third strip 28 is further located axially outward of the carcass 14. Therefore, the third strip 28 is not in contact with the second strip 26, which is in contact with the first strip 24. The third strip 28 is formed by cross-linking a rubber sheet. The third strip 28 does not contain a cord. As shown in FIG. 2, the third strip 28 has an inner end E3i and an outer end E3o. The inner end E3i is located on the innermost side in the radial direction. The outer end E3o is located on the outermost side in the radial direction.

In the tire 2, the first strip 24, the second strip 26, and the third strip 28 function as reinforcing members and can contribute to high rigidity in the vicinity of the bead 12. Therefore, the tire 2 is excellent in steering stability. In this tire 2, stress can be dispersed because each strip has a "strip shape". Therefore, in this tire 2, looseness between the carcass 14 and the reinforcing member (filler), which is seen in the tire 2 disclosed in Japanese Patent Application Laid-Open No. 2016-147567, is suppressed. This tire 2 has excellent durability.

In the present embodiment, the complex elastic modulus E ^{* (1) of the first strip 24 at 70 ° C. is larger than the complex elastic modulus E *} (2) of the second strip 26 at 70 ° C., and 70 ° C. of the third strip 28. More than the complex elastic modulus E ^* (3) in. Since the complex elastic modulus E ^* (1) of the first strip 24 is large, the first strip 24 contributes to steering stability in this tire 2. In the tire 2, a complex elastic modulus of the second complex elastic modulus of the strip 26 ^E * (2) and the third strip 28 ^E * (3) are not excessive. Therefore, the second strip 26 and the third strip 28 do not impair durability.

From the viewpoint of achieving both steering stability and durability, the ratio (E ^* (1) / E ^* (2)) of the ^{complex elastic modulus E *} (1) to the complex elastic modulus E ^{* (2) is 1.} 5 or more is preferable, and 2.0 or more is particularly preferable. The ratio (E ^* (1) / E ^* (2)) is preferably 4.0 or less.

From the viewpoint of achieving both steering stability and durability, the ratio (E ^* (1) / E ^* (3)) of the ^{complex elastic modulus E *} (1) to the complex elastic modulus E ^{* (3) is 1.} 5 or more is preferable, and 2.0 or more is particularly preferable. The ratio (E ^* (1) / E ^* (3)) is preferably 4.0 or less.

In the present embodiment, the complex elastic modulus E ^* (2) of the second strip 26 at 70 ° C. is larger than the ^{complex elastic modulus E *} (3) of the third strip 28 at 70 ° C. In other words, the tire 2 satisfies the following formula.
E ^* (1)> E ^* (2)> E ^* (3)
In this tire 2, stress is dispersed. This tire 2 has excellent durability.

From the viewpoint of durability, the ratio (E ^* (2) / E ^* (3)) of the ^{complex elastic modulus E *} (2) to the complex elastic modulus E ^{* (3) is preferably 1.1 or more.} 2 or more is particularly preferable. The ratio (E ^* (2) / E ^* (3)) is preferably 2.0 or less.

From the viewpoint of steering stability, the complex elastic modulus E ^* (1) of the first strip 24 is preferably 30 MPa or more, more preferably 50 MPa or more, and particularly preferably 65 MPa or more. From the viewpoint of durability, the complex elastic modulus E ^* (1) is preferably 80 MPa or less, more preferably 76 MPa or less, and particularly preferably 73 MPa or less.

From the viewpoint of steering stability, the complex elastic modulus E ^* (2) of the second strip 26 is preferably 20 MPa or more, more preferably 25 MPa or more, and particularly preferably 27 MPa or more. From the viewpoint of durability, the complex elastic modulus E ^* (2) is preferably 50 MPa or less, more preferably 40 MPa or less, and particularly preferably 35 MPa or less.

From the viewpoint of steering stability, the complex elastic modulus E ^* (3) of the third strip 28 is preferably 15 MPa or more, more preferably 20 MPa or more, and particularly preferably 22 MPa or more. From the viewpoint of durability, the complex elastic modulus E ^* (3) is preferably 45 MPa or less, more preferably 35 MPa or less, and particularly preferably 30 MPa or less.

In the present embodiment, the loss tangent tan δ (2) of the second strip 26 at 70 ° C. is smaller than the loss tangent tan δ (1) of the first strip 24 at 70 ° C. 3) is also smaller than the loss tangent tan δ (1) of the first strip 24 at 70 ° C. In this tire 2, heat generation is suppressed in the second strip 26 and the third strip 28. This tire 2 has excellent durability. In this tire 2, the loss tangent tan δ (1) of the first strip 24 is not too small. Therefore, the first strip 24 can contribute to steering stability.

From the viewpoint of achieving both steering stability and durability, the ratio (tan δ (2) / tan δ (1)) of the loss tangent tan δ (2) and the loss tangent tan δ (1) is preferably 0.8 or less. 7 or less is particularly preferable. The ratio (tan δ (2) / tan δ (1)) is preferably 0.3 or more.

From the viewpoint of achieving both steering stability and durability, the ratio (tan δ (3) / tan δ (1)) of the loss tangent tan δ (3) and the loss tangent tan δ (1) is preferably 0.8 or less. 7 or less is particularly preferable. The ratio (tan δ (3) / tan δ (1)) is preferably 0.3 or more.

In this embodiment, the loss tangent tan δ (3) of the third strip 28 at 70 ° C. is smaller than the loss tangent tan δ (2) of the second strip 26 at 70 ° C. In other words, the tire 2 satisfies the following formula.
tanδ (1) ＞ tanδ (2) ＞ tanδ (3)
In this tire 2, stress is dispersed. This tire 2 has excellent durability.

From the viewpoint of durability, the ratio (tan δ (3) / tan δ (2)) of the loss tangent tan δ (3) and the loss tangent tan δ (2) is preferably 0.9 or less, and particularly preferably 0.8 or less. The ratio (tan δ (3) / tan δ (2)) is preferably 0.5 or more.

From the viewpoint of steering stability, the loss tangent tan δ (1) of the first strip 24 is preferably 0.15 or more, and particularly preferably 0.18 or more. From the viewpoint of durability, the loss tangent tan δ (1) is preferably 0.25 or less, and particularly preferably 0.22 or less.

From the viewpoint of steering stability, the loss tangent tan δ (2) of the second strip 26 is preferably 0.08 or more, and particularly preferably 0.11 or more. From the viewpoint of durability, the loss tangent tan δ (2) is preferably 0.18 or less, and particularly preferably 0.15 or less.

From the viewpoint of steering stability, the loss tangent tan δ (3) of the third strip 28 is preferably 0.05 or more, and particularly preferably 0.08 or more. From the viewpoint of durability, the loss tangent tan δ (3) is preferably 0.15 or less, and particularly preferably 0.12 or less.

As described above, the first strip 24 is formed by cross-linking the rubber sheet. Therefore, the thickness of the first strip 24 is generally uniform. Stress is less likely to concentrate on the first strip 24. From this viewpoint, the rate of change in the thickness of the first strip 24 is preferably within ± 25% / mm. In other words, it is preferable that the thickness T1X at a certain point X of the first strip 24 and the thickness T1Y at a point Y 1.0 mm away from this point X satisfy the following formula.
0.75 <T1Y / T1X <1.25
It is preferable that the above formula holds in all zones except the vicinity of the inner end E1i (that is, the tapered portion) and the vicinity of the outer end E1o (that is, the tapered portion).

As described above, the second strip 26 is formed by cross-linking the rubber sheet. Therefore, the thickness of the second strip 26 is substantially uniform. Stress is less likely to concentrate on the second strip 26. From this viewpoint, the rate of change in the thickness of the second strip 26 is preferably within ± 25% / mm. In other words, it is preferable that the thickness T2X at a certain point X of the second strip 26 and the thickness T2Y at a point Y 1.0 mm away from this point X satisfy the following formula.
0.75 <T2Y / T2X <1.25
It is preferable that the above formula holds in all zones except the vicinity of the inner end E2i (that is, the tapered portion) and the vicinity of the outer end E2o (that is, the tapered portion).

As described above, the third strip 28 is formed by cross-linking the rubber sheet. Therefore, the thickness of the third strip 28 is generally uniform. Stress is less likely to concentrate on the third strip 28. From this viewpoint, the rate of change in the thickness of the third strip 28 is preferably within ± 25% / mm. In other words, it is preferable that the thickness T3X at a certain point X of the third strip 28 and the thickness T3Y at a point Y 1.0 mm away from this point X satisfy the following formula.
0.75 <T3Y / T3X <1.25
It is preferable that the above formula holds in all zones except the vicinity of the inner end E3i (that is, the tapered portion) and the vicinity of the outer end E3o (that is, the tapered portion).

The maximum thickness T1M of the first strip 24 is preferably 1.0 mm or less. In the tire 2 having the first strip 24, the stress can be dispersed. From this viewpoint, the maximum thickness T1M is more preferably 0.9 mm or less, and particularly preferably 0.8 mm or less. From the viewpoint of steering stability, the maximum thickness T1M is preferably 0.5 mm or more.

The maximum thickness T2M of the second strip 26 is preferably 1.0 mm or less. In the tire 2 having the second strip 26, the stress can be dispersed. From this viewpoint, the maximum thickness T2M is more preferably 0.9 mm or less, and particularly preferably 0.8 mm or less. From the viewpoint of steering stability, the maximum thickness T2M is preferably 0.5 mm or more.

The maximum thickness T3M of the third strip 28 is preferably 2.0 mm or less. In the tire 2 having the third strip 28, the stress can be dispersed. From this viewpoint, the maximum thickness T3M is more preferably 1.6 mm or less, and particularly preferably 1.3 mm or less. From the viewpoint of steering stability, the maximum thickness T3M is preferably 0.8 mm or more.

The reference numeral La in FIG. 3 represents the length of the apex 42. The length La is the radial distance from the core 40 to the outer end Ea of the apex 42. From the viewpoint of steering stability, the length La is preferably 18 mm or more, more preferably 21 mm or more, and particularly preferably 23 mm or more. From the viewpoint of durability, the length La is preferably 40 mm or less, more preferably 37 mm or less, and particularly preferably 35 mm or less.

Reference numeral L1 in FIG. 3 represents the length of the first strip 24. The length L1 is a radial distance from the inner end E1i to the outer end E1o. From the viewpoint of steering stability, the ratio (L1 / Ht) of the length L1 to the height Ht (see FIG. 1) of the tire 2 is preferably 0.10 or more, and particularly preferably 0.15 or more. From the viewpoint of durability, this ratio (L1 / Ht) is preferably 0.35 or less, and particularly preferably 0.30 or less.

Reference numeral L2 in FIG. 3 represents the length of the second strip 26. The length L2 is a radial distance from the inner end E2i to the outer end E2o. From the viewpoint of steering stability, the ratio (L2 / Ht) of the length L2 to the height Ht (see FIG. 1) of the tire 2 is preferably 0.15 or more, and particularly preferably 0.20 or more. From the viewpoint of durability, this ratio (L2 / Ht) is preferably 0.40 or less, and particularly preferably 0.35 or less.

Reference numeral L3 in FIG. 3 represents the length of the third strip 28. The length L3 is a radial distance from the inner end E3i to the outer end E3o. From the viewpoint of steering stability, the ratio (L3 / Ht) of the length L3 to the height Ht (see FIG. 1) of the tire 2 is preferably 0.20 or more, and particularly preferably 0.25 or more. From the viewpoint of durability, this ratio (L3 / Ht) is preferably 0.45 or less, and particularly preferably 0.40 or less.

In FIG. 4, the tire 2 is further enlarged and shown. Reference numeral Ha in FIG. 4 is the height of the outer end Ea of the apex 42 from the bead baseline BBL.

Reference numeral H1i in FIG. 4 is the height of the inner end E1i of the first strip 24 from the bead baseline BBL. The inner end E1i is located inside the outer end Ea of the Apex 42 in the radial direction. Therefore, the height H1i is smaller than the height Ha. In other words, the first strip 24 overlaps the apex 42 in the radial direction. This overlap contributes to the uniform stiffness distribution. From this viewpoint, the difference (Ha-H1i) is preferably 3 mm or more, more preferably 6 mm or more, and particularly preferably 8 mm or more. The difference (Ha-H1i) is preferably 30 mm or less.

Reference numeral H2i in FIG. 4 is the height of the inner end E2i of the second strip 26 from the bead baseline BBL. The inner end E2i is located inside the outer end Ea of the Apex 42 in the radial direction. Therefore, the height H2i is smaller than the height Ha. In other words, the second strip 26 overlaps the apex 42 in the radial direction. This overlap contributes to the uniform stiffness distribution. From this viewpoint, the difference (Ha-H2i) is preferably 6 mm or more, more preferably 9 mm or more, and particularly preferably 11 mm or more. The difference (Ha-H2i) is preferably 30 mm or less.

Reference numeral H3i in FIG. 4 is the height of the inner end E3i of the third strip 28 from the bead baseline BBL. The inner end E3i is located inside the outer end Ea of the Apex 42 in the radial direction. Therefore, the height H3i is smaller than the height Ha. In other words, the third strip 28 overlaps the apex 42 in the radial direction. This overlap contributes to the uniform stiffness distribution. From this viewpoint, the difference (Ha-H3i) is preferably 9 mm or more, more preferably 12 mm or more, and particularly preferably 14 mm or more. The difference (Ha-H3i) is preferably 30 mm or less.

As is clear from FIG. 4, the inner end E2i of the second strip 26 is located inward in the radial direction with respect to the inner end E1i of the first strip 24. In other words, the height H2i is smaller than the height H1i. In this tire 2, stress is dispersed. From this viewpoint, the difference (H1i-H2i) is preferably 2 mm or more, more preferably 4 mm or more, and particularly preferably 6 mm or more. The difference (H1i-H2i) is preferably 30 mm or less.

As is clear from FIG. 4, the inner end E3i of the third strip 28 is located inward in the radial direction with respect to the inner end E1i of the first strip 24. In other words, the height H3i is smaller than the height H1i. In this tire 2, stress is dispersed. From this viewpoint, the difference (H1i-H3i) is preferably 2 mm or more, more preferably 4 mm or more, and particularly preferably 6 mm or more. The difference (H1i-H3i) is preferably 30 mm or less.

As is clear from FIG. 4, the inner end E3i of the third strip 28 is located inward in the radial direction with respect to the inner end E2i of the second strip 26. In other words, the height H3i is smaller than the height H2i. In this tire 2, stress is dispersed. From this viewpoint, the difference (H2i-H3i) is preferably 2 mm or more, more preferably 4 mm or more, and particularly preferably 6 mm or more. The difference (H2i-H3i) is preferably 30 mm or less.

Reference numeral H1o in FIG. 5 is the height of the outer end E1o of the first strip 24 from the bead baseline BBL (see FIG. 1). The outer end E1o is located outside the outer end Ea of the Apex 42 in the radial direction. Therefore, the height H1o is larger than the height Ha. The first strip 24 contributes to steering stability. From this viewpoint, the difference (H1o-Ha) is preferably 20 mm or more, more preferably 30 mm or more, and particularly preferably 35 mm or more. The difference (H1o-Ha) is preferably 100 mm or less.

Reference numeral H2o in FIG. 5 is the height of the outer end E2o of the second strip 26 from the bead baseline BBL. The outer end E2o is located outside the outer end Ea of the Apex 42 in the radial direction. Therefore, the height H2o is larger than the height Ha. The second strip 26 contributes to steering stability. From this viewpoint, the difference (H2o-Ha) is preferably 25 mm or more, more preferably 35 mm or more, and particularly preferably 40 mm or more. The difference (H2o-Ha) is preferably 100 mm or less.

Reference numeral H3o in FIG. 5 is the height of the outer end E3o of the third strip 28 from the bead baseline BBL. The outer end E3o is located outside the outer end Ea of the Apex 42 in the radial direction. Therefore, the height H3o is larger than the height Ha. The third strip 28 contributes to steering stability. From this viewpoint, the difference (H3o-Ha) is preferably 30 mm or more, more preferably 40 mm or more, and particularly preferably 45 mm or more. The difference (H3o-Ha) is preferably 100 mm or less.

As is clear from FIG. 5, the outer end E2o of the second strip 26 is located outside the outer end E1o of the first strip 24 in the radial direction. In other words, the height H2o is larger than the height H1o. In this tire 2, stress is dispersed. From this viewpoint, the difference (H2o-H1o) is preferably 2 mm or more, more preferably 4 mm or more, and particularly preferably 6 mm or more. The difference (H2o-H1o) is preferably 30 mm or less.

As is clear from FIG. 5, the outer end E3o of the third strip 28 is located outside the outer end E1o of the first strip 24 in the radial direction. In other words, the height H3o is larger than the height H1o. In this tire 2, stress is dispersed. From this viewpoint, the difference (H3o-H1o) is preferably 2 mm or more, more preferably 4 mm or more, and particularly preferably 6 mm or more. The difference (H3o-H1o) is preferably 30 mm or less.

As is clear from FIG. 5, the outer end E3o of the third strip 28 is located outside the outer end E2o of the second strip 26 in the radial direction. In other words, the height H3o is larger than the height H2o. In this tire 2, stress is dispersed. From this viewpoint, the difference (H3o-H2o) is preferably 2 mm or more, more preferably 4 mm or more, and particularly preferably 6 mm or more. The difference (H3o-H2o) is preferably 30 mm or less.

As is clear from FIG. 2, the inner end E1i of the first strip 24, the inner end E2i of the second strip 26, and the inner end E3i of the third strip 28 are located inward in the radial direction from the contact start point Ps. ing. The outer end E1o of the first strip 24, the outer end E2o of the second strip 26, and the outer end E3o of the third strip 28 are located outside the contact start point Ps in the radial direction. In other words, each of the first strip 24, the second strip 26 and the third strip 28 overlaps the contact start point Ps in the radial direction. In this tire 2, stress concentration in the vicinity of the contact start point Ps is unlikely to occur. This tire 2 has excellent durability.

In the present invention, unless otherwise specified, 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. As used herein, the term "regular rim" means a rim defined in the standard on which Tire 2 relies. The "standard rim" in the JATTA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means the internal pressure defined in the standard on which the tire 2 relies. The "maximum air pressure" in the JATTA standard, the "maximum value" in the "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are normal internal pressures. When the tire 2 is for a passenger car, the dimensions and the angle are measured in a state where the internal pressure is 180 kPa.

Hereinafter, the effects of the present invention will be clarified by Examples, but the present invention should not be construed in a limited manner based on the description of these Examples.

[Example 1]
A pneumatic tire having the structure shown in FIG. 1-5 was obtained. The size of this tire was "225 / 75R15C 110 / 108Q". This tire has a first strip as a first layer, a second strip as a second layer, and a third strip as a third layer. The thickness of the first strip is almost uniform except for the vicinity of the inner end and the vicinity of the outer end. The thickness of the second strip is almost uniform except for the vicinity of the inner end and the vicinity of the outer end. The thickness of the third strip is almost uniform except for the vicinity of the inner end and the vicinity of the outer end.

[Example 2-9]
The tires of Example 2-9 were obtained in the same manner as in Example 1 except that the specifications of each strip were as shown in Table 1-3 below.

[Comparative Example 1]
A tire of Comparative Example 1 was obtained in the same manner as in Example 1 except that the second strip was not provided.

[Comparative Example 2]
A tire of Comparative Example 2 was obtained in the same manner as in Example 1 except that a filler was provided instead of the strip as the third layer. The shape of this filler is equivalent to the shape of the filler disclosed in JP-A-2016-147567. The thickness of this filler is not uniform. The material of this filler is crosslinked rubber. This filler does not contain cord.

[Maneuvering stability]
The tire was incorporated into a regular rim, and the tire was filled with air to set the internal pressure to 600 kPa. The rim and tires were mounted on a light truck. At the racing circuit, I let the driver drive this light truck. This driver was made to evaluate the steering stability. The results are shown in Table 1-3 below as indices.

[durability]
The tire was incorporated into a regular rim, and the tire was filled with air to set the internal pressure to 600 kPa. This tire was run on a drum. The conditions during running were as follows.
Load on tire: 20kN
Speed: 80km / h
The mileage until the tire was damaged was measured. The results are shown in Table 1-3 below as indices.

[Productivity]
The rate of scrap that would be generated in the tire manufacturing process was calculated by simulation. The results are shown in Table 1-3 below.

As shown in Table 1-3, the tires of each embodiment are excellent in steering stability, durability and productivity. From this evaluation result, the superiority of the present invention is clear.

The tire according to the present invention can be mounted on various vehicles.

2 ... Pneumatic tires 6 ... Treads 8 ... Sidewalls 10 ... Clinch 12 ... Beads 14 ... Carcass 16 ... Belts 18 ... Bands 24 ... First strips 26 ... 2nd strip 28 ... 3rd strip 38 ... Flange 40 ... Core 42 ... Apex 44 ... 1st ply 46 ... 2nd ply 48 ... 1st Main part of ply 50 ・ ・ ・ Folded part of first ply 52 ・ ・ ・ Main part of second ply 54 ・ ・ ・ Folded part of second ply

Claims (13)

It has a tread, a pair of sidewalls, a pair of beads, a carcass, a pair of first strips, a pair of second strips and a pair of third strips.
Each bead has a core and an apex extending radially outward from this core.
The carcass is bridged between one bead and the other along the inside of the tread and sidewall.
A part of each first strip is sandwiched between the axially inner surface of the apex and the carcass.
Each second strip is located axially outside the first strip, and a portion of the second strip is sandwiched between the axially outer surface of the apex and the carcass.
Pneumatic tires in which each third strip is located axially outside the second strip. The complex elastic modulus E ^{* (1) of the first strip at 70 ° C. is larger than the complex elastic modulus E *} (2) of the second strip at 70 ° C., and the complex elastic modulus E of the third strip at 70 ° C. ^* The pneumatic tire according to claim 1, which is larger than (3). The pneumatic tire according to claim 2, wherein the complex elastic modulus E ^* (2) is ^{larger than the complex elastic modulus E * (3).} The loss tangent tan δ (2) of the second strip at 70 ° C. is smaller than the loss tangent tan δ (1) of the first strip at 70 ° C.
The pneumatic tire according to any one of claims 1 to 3, wherein the loss tangent tan δ (3) of the third strip at 70 ° C. is smaller than the loss tangent tan δ (1) of the first strip at 70 ° C. The pneumatic tire according to claim 4, wherein the loss tangent tan δ (3) is smaller than the loss tangent tan δ (2). The rate of change in the thickness of the first strip is within ± 25% / mm, the rate of change in the thickness of the second strip is within ± 25% / mm, and the rate of change in the thickness of the third strip. The pneumatic tire according to any one of claims 1 to 5, wherein the tire is within ± 25% / mm. The inner end of the first strip is located inward in the radial direction with respect to the outer end of the apex.
The outer end of the first strip is located on the outer side in the radial direction with respect to the outer end of the apex.
The inner end of the second strip is located inward in the radial direction with respect to the outer end of the apex.
The outer end of the second strip is located on the outer side in the radial direction with respect to the outer end of the apex.
The inner end of the third strip is located inward in the radial direction with respect to the outer end of the apex.
The pneumatic tire according to any one of claims 1 to 6, wherein the outer end of the third strip is located outside the outer end of the apex in the radial direction. The tire according to claim 7, wherein the inner end of the second strip is located inside the inner end of the first strip in the radial direction. The tire according to claim 7 or 8, wherein the inner end of the third strip is located inside the inner end of the second strip in the radial direction. The tire according to any one of claims 7 to 9, wherein the outer end of the second strip is located outside the outer end of the first strip in the radial direction. The tire according to any one of claims 7 to 10, wherein the outer end of the third strip is located outside the outer end of the second strip in the radial direction. The maximum thickness of the first strip is 1.0 mm or less.
The maximum thickness of the second strip is 1.0 mm or less,
The tire according to any one of claims 1 to 11, wherein the maximum thickness of the third strip is 2.0 mm or less. The inner end of the first strip is located inward in the radial direction from the contact start point of the rim on which the tire is mounted.
The outer end of the first strip is located on the outer side in the radial direction from the contact start point.
The inner end of the second strip is located inward in the radial direction from the contact start point.
The outer end of the second strip is located on the outer side in the radial direction from the contact start point.
The inner end of the third strip is located inward in the radial direction from the contact start point.
The pneumatic tire according to any one of claims 1 to 12, wherein the outer end of the third strip is located outside the contact start point in the radial direction.

Images