JP6790368B2 - Pneumatic tires for heavy loads - Google Patents

Description

The present invention relates to a pneumatic tire for heavy loads.

Heavy-duty pneumatic tires are installed on trucks, buses, and the like. In this tire, the radial outside of the carcass is reinforced with a tough belt. This tire has a longer durable life for carcass, belts, etc. than the wear life of the tread. Therefore, when the tread wears, the tread rubber is replaced and reused. This tire will be reused as a rectified tire. As described above, a tire used as a rectifying tire is disclosed in Japanese Patent Application Laid-Open No. 11-334316.

Japanese Unexamined Patent Publication No. 11-334316

Tires with more worn treads naturally have thinner treads. The surface of the tread may be scratched due to the tire stepping on a stone. This flaw can reach the belt. In particular, tires that are near the end of use with advanced tread wear are prone to flaws even on the belt. If there are many such defects on the belt, it cannot be used as a rectified tire.

By increasing the thickness of the tread under the groove formed on the tread surface, it is possible to prevent the belt from being scratched. However, increasing the thickness of the tread under the groove increases rolling resistance.

An object of the present invention is to provide a heavy-duty pneumatic tire having low rolling resistance and suitable for a rectified tire.

The heavy-duty pneumatic tire according to the present invention includes a tread forming a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the end of the tread, and each axially inward of the sidewall. A pair of bead located, a carcass laid between one bead and the other bead along the inside of this tread and sidewall, a belt laminated between the tread and the carcass, and a tread. It is provided with a rubber reinforcing layer laminated between the belt and the belt. This tread has a cap layer and a base layer.
The tensile strength is TB, the elongation at cutting is EB, and Et obtained by the following formula is the fracture energy. At this time, the fracture energy of the cap layer after deterioration is 2000 MPa ·% or more. At this time, the fracture energy of the rubber reinforcing layer after deterioration is 1000 MPa ·% or more.
Et = TB / EB / 2

Preferably, the loss tangent tan δ of the rubber reinforcing layer is 0.16 or less.

Preferably, the complex elastic modulus E ^* of the rubber reinforcing layer is 3 MPa or more and 15 MPa or less.

Preferably, the thickness Tp of the rubber reinforcing layer is 0.5 mm or more and 2.0 mm or less.

Preferably, a groove is formed on the tread surface. The thickness Tg under the groove from the bottom of the groove to the belt is 3 mm or more and 5 mm or less.

Preferably, a main groove extending in the circumferential direction is formed on the tread surface. The inclination angle α of the wall surface of the main groove with respect to the normal line perpendicular to the tread surface is 5 ° or more and 20 ° or less.

In the heavy-duty pneumatic tire according to the present invention, the rubber reinforcing layer protects the belt. Since this rubber reinforcing layer has a large destructive energy after deterioration, it protects the belt even at the end of use of the tire. The belt is prevented from being scratched without increasing the thickness of the tread. This tire has low rolling resistance because the tread does not become thick. This tire is suitable for rectified tires.

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 explanatory view of 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 the pneumatic tire 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 the figure, the alternate long and short dash line CL represents the equatorial plane of the tire 2. The straight line BL represents the bead baseline. The shape of the tire 2 is symmetrical with respect to the equatorial plane CL except for the tread pattern. The tire 2 is mounted on a truck, a bus, or the like. The tire 2 is a heavy load pneumatic tire. This tire 2 is a tubeless type.

The tire 2 includes a tread 4, a sidewall 6, a clinch 8, a bead 10, a carcass 12, a belt 14, a bead filler 16, a cover rubber 18, an inner liner 20, an insulation 22, a cushion layer 24 and a chafer 26. .. The tire 2 is further provided with a rubber reinforcing layer 28.

The tread 4 has a shape that is convex outward in the radial direction. The tread 4 is made of crosslinked rubber. The tread 4 forms a tread surface 30 in contact with the road surface.

The tread 4 includes a base layer 32 and a cap layer 34. The cap layer 34 is located radially outside the base layer 32. The cap layer 34 is laminated on the base layer 32. Usually, the base layer 32 is made of crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 32 is a natural rubber. Usually, the cap layer 34 is made of crosslinked rubber having excellent wear resistance, heat resistance and grip.

The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The radial outer edge of the sidewall 6 is joined to the tread 4. The radial inner edge of the sidewall 6 is joined to the clinch 8. The sidewall 6 is made of crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 6 prevents damage to the carcass 12.

The 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. Although not shown, when the tire 2 is incorporated into the rim, the clinch 8 comes into contact with the flange of the rim (not shown). The clinch 8 is made of a crosslinked rubber having excellent wear resistance.

The bead 10 is located inside the sidewall 6 in the radial direction. The bead 10 includes a core 36 and an apex 38 extending radially outward from the core 36. The apex 38 includes a hard apex 40 extending radially outward from the core 36 and a soft apex 42 extending radially outward from the hard apex 40. The core 36 is ring-shaped and includes a wound non-stretchable wire. A typical material for wire is steel. The rigid apex 40 is tapered outward in the radial direction. The hard apex 40 is made of a high hardness crosslinked rubber. The soft apex 42 is made of a crosslinked rubber that is softer than the hard apex 40.

The carcass 12 is composed of a carcass ply 44. The carcass ply 44 spans between the beads 10 on both sides and runs along the inside of the tread 4 and sidewall 6. The carcass ply 44 is folded around the core 36 from the inside to the outside in the axial direction. Due to this folding, the carcass ply 44 is formed with a main portion 44a and a folded portion 44b. The main portion 44a is located between the beads 10 on both sides. The folded-back portion 44b is located on the outer side in the axial direction of the bead 10. The outer end 44e of the folded-back portion 44b is located outside the apex 38 in the axial direction. In the tire 2, the outer end 44e is located on the axially outer side of the soft apex 42. The stress concentration at the outer end 44e is relaxed by the soft apex 42.

Although not shown, the carcass ply 44 comprises a large number of parallel cords and topping rubbers. The absolute value of the angle that each code makes with respect to the equatorial plane CL is 45 ° to 90 °, and further 75 ° to 90 °. In other words, the carcass 12 has a radial structure. The cord consists of, for example, steel. The carcass 12 may be formed from two or more carcass plies 44.

The belt 14 extends in the axial direction. The belt 14 is located inside the tread 4 in the radial direction. The belt 14 is located on the outer side in the radial direction of the carcass 12. The belt 14 reinforces the carcass 12. In the tire 2, the belt 14 is composed of a first layer 46a, a second layer 46b, a third layer 46c, and a fourth layer 46d. In the tire 2, of the first layer 46a, the second layer 46b, the third layer 46c, and the fourth layer 46d constituting the belt 14, the second layer 46b has the largest width in the axial direction. In the tire 2, the end 46e of the second layer 46b is the end of the belt 14.

Although not shown, each of the first layer 46a, the second layer 46b, the third layer 46c and the fourth layer 46d consists of a large number of parallel cords and topping rubbers. Each cord is made of steel. This code is inclined with respect to the equatorial plane CL. The absolute value of the angle that this code makes with respect to the equatorial plane CL is 15 ° to 70 °.

Although not shown, the tire 2 may include a band. The band covers the radial outside of the belt 14. The band consists of a cord and a topping rubber. Since the belt 14 is restrained by this cord, the lifting of the belt 14 is suppressed.

The bead filler 16 is wrapped around the core 36. The bead filler 16 is laminated with the carcass ply 44. The bead filler 16 is wound around the core 36 to form an inner piece portion 16a and an outer piece portion 16b. The bead filler 16 suppresses the deformation of the bead 10. The bead filler 16 can contribute to the improvement of the durability of the tire 2. The bead filler 16 is composed of a large number of parallel cords and a topping rubber. The bead filler 16 is made of, for example, a steel filler. Each cord is made of steel.

The cover rubber 18 is located axially outward of the soft apex 42. As shown, the cover rubber 18 covers the outer end 44e of the folded-back portion 44b. The cover rubber 18 can relieve the stress concentration of the folded-back portion 44b on the outer end 44e.

The inner liner 20 constitutes the inner surface of the tire 2. The inner liner 20 is made of crosslinked rubber. Rubber having excellent air shielding properties is used for the inner liner 20. 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.

The insulation 22 is located outside the inner liner 20. The insulation 22 is located inside the carcass 12. The insulation 22 is sandwiched between the carcass 12 and the inner liner 20. The insulation 22 is made of crosslinked rubber having excellent adhesiveness. The insulation 22 is firmly bonded to the carcass 12 and also firmly to the inner liner 20. The insulation 22 suppresses the peeling of the inner liner 20 and the carcass 12.

The cushion layer 24 is laminated with the carcass 12 in the vicinity of the end 46e of the belt 14. The cushion layer 24 is made of soft crosslinked rubber. The cushion layer 24 absorbs the stress of the end 46e of the belt 14. The cushion layer 24 suppresses the lifting of the belt 14.

The chafer 26 is located in the vicinity of the bead 10. When the tire 2 is incorporated into the rim, the chafer 26 comes into contact with the rim. This contact protects the vicinity of the bead 10. In this embodiment, the chafer 26 is integral with the clinch 8. Therefore, the material of the chafer 26 is the same as that of the clinch 8. The chafer 26 may consist of a cloth and rubber impregnated in the cloth.

The rubber reinforcing layer 28 is located inside the tread 4 in the radial direction. The rubber reinforcing layer 28 is located on the outer side in the radial direction of the belt 14. The rubber reinforcing layer 28 is located between the tread 4 and the belt 14 in the radial direction. The rubber reinforcing layer 28 covers the outer surface of the belt 14. In the tire 2, the rubber reinforcing layer 28 extends axially outward from the edge Et of the tread surface 30. The axial end portion of the rubber reinforcing layer 28 is laminated on the outer side in the radial direction of the cushion layer 24. The rubber reinforcing layer 28 is made of crosslinked rubber.

A main groove 48 and a main groove 50 extending in the circumferential direction are formed on the tread surface 30. The main groove 48 and the main groove 50 each go around the tread surface 30 in the circumferential direction. The main groove 48 is formed inside the main groove 50 in the axial direction.

As shown in FIG. 2, the main groove 48 includes a wall surface 54 and a wall surface 56 extending from the groove bottom 52 to the tread surface 30. The wall surface 54 and the wall surface 56 are opposed to each other and extend in the circumferential direction. The main groove 50 includes a wall surface 60 and a wall surface 62 extending from the groove bottom 58 to the tread surface 30. The wall surface 60 and the wall surface 62 are opposed to each other and extend in the circumferential direction.

The double-headed arrow α1 in FIG. 2 indicates the inclination angle of the wall surface 54 of the main groove 48 and the inclination angle of the wall surface 56. The double-headed arrow α2 indicates the inclination angle of the wall surface 60 of the main groove 50 and the inclination angle of the wall surface 62. The inclination angle α1 and the inclination angle α2 are measured as inclination angles with respect to the normal line perpendicular to the tread surface 30. The inclination angle α1 and the inclination angle α2 are measured at the openings of the main groove 48 and the main groove 50 of the tread surface 30. In the tire 2, the inclination angle α1 and the inclination angle α2 are collectively referred to as an inclination angle α.

The double-headed arrow Tp indicates the thickness of the rubber reinforcing layer 28. The double-headed arrow Tg indicates the thickness under the groove from the groove bottom 52 of the main groove 48 to the belt 14. This thickness Tg is measured as the thickness from the groove bottom 52 to the outer surface of the belt 14. This thickness Tg is measured at the position where it is the smallest when the groove bottom thickness 52 and the groove bottom 58 are different in measured under-groove thickness. In this tire 2, the thickness Tg is measured at the groove bottom 52. The thickness Tp and the thickness Tg are measured as linear distances in the radial direction.

In this tire 2, the cap layer 34 of the tread 4 is worn by use. The cap layer 34 deteriorates due to use. In the tire 2 in which the cap layer 34 has deteriorated, defects are likely to occur in the cap layer 34. This flaw may grow and reach the belt 14. In particular, in the tire 2 in which the cap layer 34 is worn and thinned, the flaw easily reaches the belt 14.

The cap layer 34, which has a large breaking energy, can suppress the occurrence of flaws. In particular, the cap layer 34, which has a large fracture energy after deterioration, suppresses the occurrence of flaws. From this point of view, the fracture energy of the cap layer 34 after deterioration is 2000 MPa ·% or more, preferably 3000 MPa ·% or more. The fracture energy of the cap layer 34 after deterioration is preferably 5000 MPa ·% or less, and more preferably 4000 MPa ·% or less. How to obtain this destructive energy will be described later.

Further, the tire 2 is provided with a rubber reinforcing layer 28. The reinforcement 28 prevents the flaw from reaching the belt 14. The rubber reinforcing layer 28 protects the belt 14. By providing the rubber reinforcing layer 28 having a large fracture energy after deterioration, it is possible to prevent the belt 14 from being damaged. From this point of view, the fracture energy of the rubber reinforcing layer 28 after deterioration is 1000 MPa ·% or more, preferably 1500 MPa ·% or more, further preferably 2000 MPa ·% or more, and particularly preferably 3000 MPa ·% or less. Is. The fracture energy of the rubber reinforcing layer 28 after deterioration is preferably 5000 MPa ·% or less, and more preferably 4000 MPa ·% or less.

In the tire 2, the outer surface of the base layer 32 is recessed inward in the radial direction inside the groove bottom 52. Since the rubber reinforcing layer 28 is provided, the base layer 32 can be made thinner than before at the groove bottom 52. Further, since the breaking energy of the cap layer 34 is large, the thickness of the cap layer 34 can be made thinner than before. As a result, even if the thickness Tg is made thinner than before, the generation and growth of flaws are suppressed at the groove bottom 52. The rubber reinforcing layer 28 is particularly suitable for reinforcing the tire 2 in which the outer surface of the base layer 32 is recessed inward in the radial direction.

In the tire 2 having a large thickness Tp of the rubber reinforcing layer 28, the belt 14 is unlikely to be scratched. From this viewpoint, the thickness Tp is preferably 0.5 mm or more, and more preferably 0.7 mm or more. On the other hand, the tire 2 having a small thickness Tp has a small rolling resistance. From this viewpoint, the thickness Tp is preferably 2.0 mm or less, and more preferably 1.5 mm or less.

In the tire 2 in which the loss tangent tan δ of the rubber reinforcing layer 28 is small, the rolling resistance is small. From this viewpoint, the loss tangent tan δ is preferably 0.16 or less, more preferably 0.15 or less, and particularly preferably 0.14 or less. This loss tangent tan δ is preferably 0.03 or more.

In the tire 2 having a large complex elastic modulus E ^* of the rubber reinforcing layer 28, it is difficult for the external force generated by the stepping stone or the like to be transmitted to the belt 14. The belt 14 is protected by the hard rubber reinforcing layer 28. From this point of view, the complex elastic modulus E ^* is preferably 3 MPa or more, and more preferably 4 MPa or more. On the other hand, in the tire 2 having a small complex elastic modulus E ^* , peeling of the rubber reinforcing layer 28 is suppressed. The soft rubber reinforcing layer 28 suppresses the occurrence of cracks. From this point of view, the complex elastic modulus E ^* is preferably 15 MPa or less, more preferably 12 MPa or less.

The tire 2 having a small inclination angle α1 of the wall surface 54 and the wall surface 56 of the main groove 48 tends to bite a foreign substance such as a stone into the main groove 48. The tire 2 is prone to scratches on the belt 14. From this point of view, the inclination angle α1 is preferably 5 ° or more, and more preferably 6 ° or more.

On the other hand, in the tire 2 having a large inclination angle α1, the area of the tread surface 30 in contact with the road surface becomes small. In this tire 2, the wear resistance of the cap layer 34 is inferior. From this viewpoint, the inclination angle α1 is preferably 20 ° or less, and more preferably 18 ° or less.

Similar to the inclination angle α1 of the wall surface 54 and the wall surface 56 of the main groove 48, the inclination angle α2 of the wall surface 60 and the wall surface 62 of the main groove 50 is preferably 5 ° or more, and more preferably 6 ° or more. Similar to the tilt angle α1, the tilt angle α2 is preferably 20 ° or less, and more preferably 18 ° or less.

In the tire 2 having a large thickness Tg under the groove from the groove bottom 52 to the belt 14, it is difficult for the belt 14 to have a flaw. From this viewpoint, the thickness Tg is preferably 3.0 mm or more, and more preferably 3.5 mm or more. In the tire 2 having a small thickness Tg, the rolling resistance is small. From this viewpoint, the thickness Tg is preferably 5.0 mm or less, more preferably 4.5 mm or less.

In the present invention, the fracture energy after deterioration is determined in accordance with the provisions of "Vulcanized rubber and thermoplastic rubber-How to determine tensile properties" of "JIS K6251". After this deterioration, the tire 2 is thermally deteriorated at 80 ° C. for one week. A test piece cut out from the deteriorated tire 2 can be obtained. The tensile strength (TB) and elongation at cutting (EB) of this test piece are measured in a room at 23 ° C. In the present invention, the fracture energy Et is calculated by the following mathematical formula from the tensile strength (TB) and the elongation at break (EB).
Et = (TB) ・ (EB) / 2

The loss tangent tan δ and the complex elastic modulus E ^* of the present invention are measured in accordance with the provisions of “JIS K 6394”. A 130 mm × 130 mm × 2 mm rubber slab sheet is produced from the crosslinked rubber composition in which the loss tangent tan δ and the complex elastic modulus E ^* are measured. A 40 mm × 4 mm × 2 mm measurement test piece is cut out from this rubber slab sheet. The loss tangent tan δ and the complex elastic modulus E ^* are measured using this measurement test piece under the following conditions.
Measuring device: Viscoelastic spectrometer "VES / F-3 type" (manufactured by Iwamoto Seisakusho)
Initial distortion: 10%
Dynamic distortion: 2%
Frequency: 10Hz
Deformation mode: tension
Measurement temperature: 70 ° C

In the present invention, the dimensions and angles of each member of the tire 2 are measured in a cross section cut out from the tire 2, as shown in FIG. 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. As used herein, the normal internal pressure means the internal pressure defined in the standard on which the tire 2 relies. The "maximum air pressure" in the JATMA standard, the "maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are regular internal pressures.

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 of Example 1 having the basic configuration shown in FIG. 1 was obtained. This tire size was "11R22.5". The fracture energy of the cap layer, the fracture energy of the rubber reinforcing layer, the loss tangent tan δ, the complex elastic modulus E ^* and the thickness Tp, the inclination angle α (α1 and α2) of the wall surface of the main groove, and the thickness under the groove of this tire. The Tg was as shown in Table 1 below. The fracture energy in Table 1 means the fracture energy after deterioration of the present invention. The items in Tables 2 to 6 below are the same as in Table 1.

[Comparative Example 1]
The rubber layer used for commercial tires was prepared. This rubber layer is laminated between the tread and the belt in order to bond them together. The breaking energy of this rubber layer was as shown in Table 1. With this rubber layer instead of the reinforcing rubber layer, the groove thickness Tg was set to 5.5 mm. Tires were obtained in the same manner as in Example 1 in other configurations.

[Comparative Example 2]
A tire was obtained in the same manner as in Example 1 except that the rubber layer was provided as in Comparative Example 1.

[Example 2 and Comparative Example 3]
Tires were obtained in the same manner as in Example 1 except that the fracture energy of the tread cap layer after deterioration was as shown in Table 1 below.

[Example 3]
A tire was obtained in the same manner as in Example 1 except that the fracture energy of the rubber reinforcing layer after deterioration was as shown in Table 1 below.

[Example 4]
A tire was obtained in the same manner as in Example 1 except that the fracture energy of the rubber reinforcing layer after deterioration was as shown in Table 2 below.

[Example 5-8]
A tire was obtained in the same manner as in Example 4 except that the loss tangent tan δ of the rubber reinforcing layer was as shown in Table 2 below.

[Example 9-14]
Tires were obtained in the same manner as in Example 4 except that the complex elastic modulus E ^* of the rubber reinforcing layer was as shown in Table 3 below.

[Example 15-20]
Tilt angle α of the wall surface of the main groove Tires were obtained in the same manner as in Example 4 except that the tires were as shown in Table 4 below. In this tire, the inclination angle α1 of the main groove on the inner side in the axial direction was measured.

[Example 21-25]
Under-groove thickness Tg of the main groove Tires were obtained in the same manner as in Example 4 except that the tires were as shown in Table 5 below.

[Example 26-31]
Thickness of rubber reinforcement layer Tp Tires were obtained in the same manner as in Example 4 except that the tires were as shown in Table 6 below.

[Rolling resistance]
The rolling resistance was measured under the following measurement conditions using a rolling resistance tester.
Rim used: 7.5 x 22.5
Internal pressure: 800 kPa
Load: 29.42kN
Speed: 80km / h
This result is shown in Tables 1 to 6 below as an index with the tire of Comparative Example 1 as 100. The larger the value of this index, the more preferable.

[Abrasion resistance]
The tires were incorporated into the regular rim "7.5 x 22.5". Air was filled so that the internal pressure of this tire became the JATMA standard internal pressure. This tire was mounted on a drum type running tester, and a vertical load of JATTA standard load was applied to the tire. This tire was run on the drum. The mileage until the cap layer was fully worn was measured. This result is shown in Tables 1 to 6 below as an index with the tire of Comparative Example 1 as 100. The larger the value of this index, the more preferable.

[Belt defect]
The tires were incorporated into the regular rim "7.5 x 22.5". Air was filled so that the internal pressure of this tire became the JATMA standard internal pressure. A drum-type running tester in which protrusions were formed on the drum was prepared. This tire was mounted on this drum type running tester, and a vertical load of JATTA standard load was applied to the tire. The tire was run on this drum for 600 hours. The number and size of scratches on the tire belt after running were inspected. The inspection results of the number and size of the flaws on the belt are shown in Tables 1 to 6 below as an index with the tire of Comparative Example 1 as 100. The larger the value of this index, the more preferable.

[Belt peeling]
In addition to the belt defect inspection described above, the presence or absence of peeling between the belt and the tread was inspected. The size of the peeling of the tire belt after running was inspected. The inspection result of the peeling of the belt is shown in Tables 1 to 6 below as an index with the tire of Comparative Example 1 as 100. The larger the value of this index, the more preferable.

As shown in Tables 1 to 6, in the tires of the examples, the rolling resistance is reduced and the damage to the belt is suppressed. This tire is suitable for rectified tires. From this evaluation result, the superiority of the present invention is clear.

The tires described above can be widely applied to heavy load tires.

2 ... Tire 4 ... Tread 6 ... Sidewall 10 ... Bead 12 ... Carcass 14 ... Belt 16 ... Bead filler 28 ... Rubber reinforcement layer 30 ... Tread surface 32・ ・ ・ Base layer 34 ・ ・ ・ Cap layer 44 ・ ・ ・ Carcass ply 48, 50 ・ ・ ・ Main groove 52, 58 ・ ・ ・ Groove bottom 54, 56, 60, 62 ・ ・ ・ Wall surface

Claims (7)

The tread forming the tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the end of the tread, a pair of beads each axially inside the sidewall, and the tread and sides. A carcass straddled between one bead and the other along the inside of the wall, a belt laminated between the tread and the carcus, and a rubber reinforcement layer laminated between the tread and the belt. And have
This tread has a cap layer and a base layer,
When the tensile strength is TB and the elongation at cutting is EB, when Et obtained by the following formula is used as the fracture energy,
The fracture energy of this cap layer after deterioration is 2000 MPa ·% or more.
The rubber reinforcing layer is Ri der fracture energy 1500 MPa ·% or more after deterioration,
This belt has a first layer, a second layer, a third layer and a fourth layer, and each of the first layer, the second layer, the third layer and the fourth layer has a large number of cords and topping rubbers arranged in parallel. Consists of
The main grooves extending in the circumferential direction on the tread surface is formed, the thickness of the rubber reinforcing layer in the groove bottom of the main groove is thinner than the thickness of the capping layer, rather thin than the thickness of the base layer,
A pneumatic tire for heavy loads , in which the thickness Tg under the groove from the bottom of the groove to the belt is 5 mm or less, and the thickness Tp of the rubber reinforcing layer is 1.5 mm or less .
Et = TB / EB / 2 The tire according to claim 1, wherein the loss tangent tan δ of the rubber reinforcing layer is 0.16 or less. The tire according to claim 1 or 2, wherein the complex elastic modulus E ^* of the rubber reinforcing layer is 3 MPa or more and 15 MPa or less. The tire according to any one of claims 1 to 3, wherein the thickness Tp of the rubber reinforcing layer is 0.5 mm or more . A groove is formed on the tread surface,
The tire according to any one of claims 1 to 4, wherein the thickness Tg under the groove from the groove bottom to the belt is 3 mm or more . A main groove extending in the circumferential direction is formed on the tread surface.
The tire according to any one of claims 1 to 5, wherein the inclination angle α of the wall surface of the main groove with respect to the normal line perpendicular to the tread surface is 5 ° or more and 20 ° or less. The tread forming the tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the end of the tread, a pair of beads each axially inside the sidewall, and the tread and sides. A carcass straddled between one bead and the other along the inside of the wall, a belt laminated between the tread and the carcus, and a rubber reinforcement layer laminated between the tread and the belt. And have
This tread has a cap layer and a base layer,
When the tensile strength is TB and the elongation at cutting is EB, when Et obtained by the following formula is used as the fracture energy,
The fracture energy of this cap layer after deterioration is 3000 MPa ·% or more.
The fracture energy of this rubber reinforcing layer after deterioration is 1000 MPa ·% or more.
This belt has a first layer, a second layer, a third layer and a fourth layer, and each of the first layer, the second layer, the third layer and the fourth layer has a large number of cords and topping rubbers arranged in parallel. Consists of
A main groove extending in the circumferential direction is formed on the tread surface, and the thickness of the rubber reinforcing layer at the groove bottom of this main groove is thinner than the thickness of the cap layer and thinner than the thickness of the base layer.
A pneumatic tire for heavy loads, in which the thickness Tg under the groove from the bottom of the groove to the belt is 5 mm or less, and the thickness Tp of the rubber reinforcing layer is 1.5 mm or less.
Et = TB / EB / 2

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