CN112976944A

CN112976944A - Heavy-duty tubeless tire and manufacturing method thereof

Info

Publication number: CN112976944A
Application number: CN202010894434.6A
Authority: CN
Inventors: 金谷资辉
Original assignee: Sumitomo Rubber Industries Ltd
Current assignee: Sumitomo Rubber Industries Ltd
Priority date: 2019-12-18
Filing date: 2020-08-31
Publication date: 2021-06-18
Anticipated expiration: 2040-08-31
Also published as: JP2021095012A; JP7463712B2; CN112976944B

Abstract

The invention provides a heavy-duty tubeless tire (2) which suppresses the influence on the uneven wear resistance and realizes the reduction of the rolling resistance and the improvement of the rim assembling property. In the tire (2), the carcass (12) includes a plurality of carcass cords (42) arranged in parallel, and the outer diameter of each carcass cord (42) is 0.6mm to 1.0 mm. In a standard state of the tire (2), the contour of the carcass (12) includes a sidewall arc, which is expressed as the contour of a portion overlapping the bead pad (16), and a lower arc, which is expressed as the contour of a portion from the maximum width position of the carcass (12) to the end PA of the bead (8). The ratio (Rb/Rs) of the radius Rb of the sidewall arc to the radius Rs of the lower arc to the sidewall arc is 1.00 to 1.10.

Description

Heavy-duty tubeless tire and manufacturing method thereof

Technical Field

The invention relates to a heavy-duty tubeless tire and a manufacturing method thereof.

Background

A large load acts on a heavy-duty tubeless tire mounted on a vehicle such as a truck or a bus. In this tire, the rigidity is adjusted to withstand a large load. A tire having high rigidity is difficult to assemble to a rim. It is considered to improve ease of assembly to a rim of a tire, that is, to improve assembling performance while securing a required rigidity (for example, patent document 1 below).

Documents of the prior art

Patent document

[ patent document 1] Japanese patent laid-open No. 2007-45375

Disclosure of Invention

Problems to be solved by the invention

If the jig width of the mold is set smaller than the width of the rim, improvement in the rim assembling performance can be achieved. However, when this tire is assembled to a rim and air is filled into the tire, a portion of the bead (hereinafter referred to as a bead portion) tends to largely collapse. In this case, since the tread radius in the shoulder portion of the tire is reduced, partial wear may occur.

For example, if the size of a bead disposed between the end of the belt layer and the carcass is increased, improvement in partial wear resistance can be achieved. However, in this case, since the flexible zone between the bead pad and the bead becomes narrow, the assembling property of the rim may be impaired. If a larger tire pad is used, the rolling resistance may increase.

The present invention has been made in view of such circumstances, and an object thereof is to provide a heavy-duty tubeless tire in which an influence on the uneven wear resistance is suppressed, and reduction in rolling resistance and improvement in rim assembling performance are achieved.

Means for solving the problems

The heavy-duty tubeless tire according to one embodiment of the present invention has a flat ratio of 60% to 80%. The tire has a pair of beads, a carcass bridged between one side bead and the other side bead, a belt located radially outside the carcass, and a pair of pads located between ends of the belt and the carcass. The carcass comprises a plurality of parallel carcass cords, and the outer diameter of each carcass cord is more than 0.6mm and less than 1.0 mm. The tire is mounted on a standard rim, the inner pressure of the tire is adjusted to a standard inner pressure, and no load is applied to the tire, and the profile of the carcass in a standard state includes a sidewall arc, which is an arc of the profile of a portion overlapping the bead pad, and a lower arc, which is an arc of the profile of a portion from the maximum width position of the carcass to the end of the bead. The ratio of the radius of the sidewall arc to the radius of the lower arc is 1.00 to 1.10.

Preferably, in the heavy-duty tubeless tire, a ratio of a radius of the lower arc to a radial distance from the bead base line to the end of the bead is 0.85 or more and 0.95 or less.

Preferably, in the heavy-duty tubeless tire, a ratio of a radial distance from an end of the bead to a longitudinal end of the bead pad to a radial distance from the bead base line to a top of the belt layer is 0.25 or more and 0.45 or less.

Preferably, in the heavy-duty tubeless tire, a ratio of a toe-opening interval, which is measured without applying a load other than its own weight and is expressed by an axial distance from one toe opening to the other toe opening, to a rim width of the standard rim is 0.80 to 0.88.

Preferably, in the heavy-duty tubeless tire, a ratio of a cross-sectional width of the tire to the toe-hole interval is 1.60 or more and 1.90 or less.

A method for manufacturing a heavy-duty tubeless tire according to an aspect of the present invention includes: (1) a step of preparing a green tire having a pair of beads, a carcass bridged between the bead on one side and the bead on the other side, a belt located radially outside the carcass, and a pair of pads located between ends of the belt and the carcass, and (2) a step of pressurizing and heating the green tire in a mold. The ratio of the width of the mold clip to the rim width of a standard rim on which the tire is mounted is 1.15 to 1.22.

Effects of the invention

The heavy-duty tubeless tire of the present invention suppresses the influence on the eccentric wear resistance, and achieves a reduction in rolling resistance and an improvement in rim assemblability.

Drawings

Fig. 1 is a cross-sectional view showing a part of a heavy-duty tubeless tire according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view along the equatorial plane of the tire shown in FIG. 1.

Fig. 3 is a sectional view showing the profile of the carcass of the tire shown in fig. 1.

Fig. 4 is a view illustrating a measuring method of the toe-hole interval of the tire.

Fig. 5 is a view for explaining a method of manufacturing the tire of fig. 1.

Description of the symbols

2. tire

4. tread

6. side wall

8. bead

10. chafer

12. tire body

14. Belt layer

16. tyre cushion

18. inner liner

32. 32s, 32M. circumferential groove

34. 34s, 34C, 34M, 34 s. land part

40. carcass ply

40A. ply body

40B. folding part

42. carcass cord

46. 46A, 46B, 46℃ layer

48. end of the belt 14

50. transverse end of the tire cushion 16

52. longitudinal ends of the cushion 16

54. vulcanizer

56. mould

58. capsule tube

60 chamber surface

Detailed Description

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

In the present invention, a state in which a tire is assembled to a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, and no load is applied to the tire is referred to as a standard state. In the present invention, unless otherwise specified, the dimensions and angles of the respective portions of the tire are measured in a standard state.

The standard rim means a rim specified in a specification under which the tire is based. The "standard Rim" in the JATMA specification, "Design Rim" in the TRA specification, and "Measuring Rim" in the ETRTO specification are standard rims.

The standard internal pressure is an internal pressure specified in a specification to which the tire is compliant. The "maximum air PRESSURE" in the JATMA specification, "the" maximum value "described in the" TIRE LOAD limit AT TIREs LOAD limitation under VARIOUS COLD INFLATION PRESSURES "in the TRA specification, and the" INFLATION PRESSURE "in the ETRTO specification are standard internal PRESSURES.

The standard load refers to a load specified in a specification under which the tire is based. The "maximum LOAD CAPACITY" in the JATMA specification, "the" maximum value "described in the" TIRE LOAD limit AT TIREs LOAD limitation AT VARIOUS COLD INFLATION PRESSURES "in the TRA specification, and the" LOAD CAPACITY "in the ETRTO specification are standard LOADs.

Fig. 1 shows a part of a heavy-duty tubeless tire 2 (hereinafter, simply referred to as "tire 2") according to an embodiment of the present invention. The tire 2 is a truck and bus tire.

Fig. 1 shows a portion of a section of a tyre 2 along a plane containing the axis of rotation of the tyre 2. In fig. 1, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the paper surface of fig. 1 is the circumferential direction of the tire 2. In fig. 1, a chain line EL indicates the equatorial plane of the tire 2. The tire 2 in fig. 1 is assembled on a rim R (standard rim). The tire 2 shown in fig. 1 is in a standard state.

In fig. 1, a solid line BBL extending in the axial direction is a bead base line. The bead base line is a line defining a rim diameter of the rim R (see JATMA and the like).

In fig. 1, a solid radially extending line RBL is a rim base line. The double arrow RW indicates the axial distance from one rim base line to the other. The distance RW is a rim width of the rim R on which the tire 2 is mounted (see JATMA and the like). The rim base line is a line that specifies the rim width RW.

In fig. 1, a symbol PW is an axially outer end of the tire 2. The outer end PW is specified based on a virtual outer surface obtained by assuming that there is no decoration such as a pattern, a letter, or the like on the outer surface of the tire 2. The double arrow MW is the axial distance from the outer end PW of one side to the outer end PW of the other side. The distance MW is a cross-sectional width of the tire 2 (see JATMA and the like).

In fig. 1, the symbol PT is the radially inner end of the tire 2. The inner end PT is also called the toe box. The toe opening PT is the boundary of the outer and inner surfaces of the tire 2.

The tire 2 has a tread 4, a pair of sidewalls 6, a pair of beads 8, a pair of chafers 10, a carcass 12, a belt 14, a pair of pads 16, an inner liner 18, a barrier layer 20, a pair of reinforcing layers 22, a pair of ply strips 24, and a pair of edge strips 26.

The tread 4 is in contact with the road surface at its outer surface 4s (i.e., tread surface 4 s). The symbol PE denotes the intersection of the tread surface 4s and the equatorial plane. The intersection point PE is the equator of the tire 2. The equator PE of the tire 2 is also the radially outer end of the tire 2.

In fig. 1, a double arrow HE is a radial distance from the bead base line to the equator PE. The distance HE is a sectional height of the tire 2 (see JATMA and the like).

The tread 4 has a base portion 28 and a cap portion 30 located radially outward of the base portion 28. The base 28 is made of a cross-linked rubber with low exothermicity. The cover portion 30 is made of a crosslinked rubber in consideration of wear resistance and grip performance.

A groove 32 (i.e., a circumferential groove 32) continuously extending in the circumferential direction is engraved on the tread 4. Thereby, a plurality of land portions 34 are formed on the tread 4 in parallel in the axial direction. The tread 4 has a plurality of land portions 34 divided by the circumferential groove 32.

In this tire 2, 4 circumferential grooves 32 are engraved on the tread 4, and 5 land portions 34 are formed. Of the 4 circumferential grooves 32, the circumferential groove 32 located on the outer side in the axial direction is a shoulder circumferential groove 32s, and the circumferential groove 32 located on the inner side of the shoulder circumferential groove 32s is an intermediate circumferential groove 32 m. Of the 5 land portions 34, the land portion 34 located axially outward and including the end TE of the tread surface 4s is a shoulder land portion 34 s. In the axial direction, the land portion 34 located on the inner side and including the equator PE is a central land portion 34 c. The land portion 34 located between the shoulder land portion 34s and the center land portion 34c is an intermediate land portion 34 m.

In the tire 2, the width of the circumferential groove 32 is preferably 1% or more and 10% or less of the width of the tread surface 4s from the viewpoint of contribution to drainage performance and traction performance. The depth of the circumferential groove 32 is preferably 10mm to 25 mm. The width of the tread surface 4s is represented by the length from one end TE to the other end TE of the tread surface 4 s. The length is measured along the tread surface 4 s.

Each sidewall 6 is connected to an end of the tread 4. The sidewalls 6 extend radially inward from the ends of the tread 4 along the carcass 12. The side wall 6 is made of cross-linked rubber.

Each bead 8 is located radially inward of the sidewall 6. The bead 8 has a core 36 and an apex (apex) 38.

The core 36 extends in the circumferential direction. Although not shown, the core 36 includes a coiled wire made of steel. Apex 38 is located radially outward of core 36. Apex 38 extends radially outward from core 36. The symbol PA is the radially outer end of the apex 38. This outer end PA is also the end of the bead 8.

In fig. 1, the double arrow HA is the radial distance from the bead base line to the end PA of the bead 8. This distance HA is also referred to as the height of the bead 8. In the tire 2, the height HA of the bead 8 is adjusted so that the ratio (HA/HE) of the height HA of the bead 8 to the cross-sectional height HE is 0.30 to 0.40. The ratio (HA/HE) is preferably 0.33 or more, preferably 0.37 or less.

The apex 38 has an inner apex 38u and an outer apex 38 s. The outer apex 38s is located radially outward of the inner apex 38 u. The inner apex 38u and the outer apex 38s are made of crosslinked rubber. The outer apex 38s is softer than the inner apex 38 u.

Each chafer 10 is located axially outward of the bead 8. The chafer 10 is located radially inward of the sidewall 6. The chafer 10 is in contact with the rim R. The chafer 10 is made of cross-linked rubber.

The carcass 12 is located inside the tread 4, sidewalls 6 and chafer 10. The carcass 12 is laid between the one side bead 8 and the other side bead 8. The carcass 12 has a radial configuration. The carcass 12 has at least one carcass ply 40. The carcass 12 of the tire 2 is made up of a carcass ply 40.

In this tire 2, the carcass ply 40 is folded around the core 36 from the axially inner side toward the outwardly side at each bead 8. The carcass ply 40 has a ply body 40a extending from one core 36 to the other core 36, and a pair of folded portions 40b connected to the ply body 40a and folded about the respective cores 36 from the axially inner side toward the outwardly side. In the tire 2, the end of the folded portion 40b is disposed at the same position as that of the conventional tire.

Fig. 2 shows a section of the tire 2 along the equatorial plane. In fig. 2, the left-right direction is the circumferential direction of the tire 2, and the up-down direction is the radial direction of the tire 2.

As shown in fig. 2, the carcass ply 40 forming the carcass 12 includes a plurality of juxtaposed carcass cords 42. These carcass cords 42 are covered with a topping rubber 44. In the tire 2, the material of the carcass cord 42 is steel. The carcass cord 42 is a steel cord.

In fig. 2, a double arrow CD is an outer diameter of the carcass cord 42. In the tire 2, the outer diameter CD of the carcass cord 42 is 0.6mm or more and 1.0mm or less.

The carcass cord 42 itself has appropriate rigidity by setting the outer diameter CD to 0.6mm or more. In the carcass ply 40 including the carcass cord 42, damage accompanied by cutting of the carcass cord 42 is less likely to occur. From this viewpoint, the outer diameter CD is preferably 0.7mm or more. By setting the outer diameter CD to 1.0mm or less, the influence of the carcass cords 42 on the rigidity of the carcass ply 40 is suppressed. In this tire 2, good rim assembling performance is maintained. The thinner carcass cord 42 contributes to the weight reduction of the tire 2. From this viewpoint, the outer diameter CD is more preferably 0.9mm or less.

In this tire 2, the ends of the carcass cords 42 included in the carcass ply 40 are preferably 20 or more, and preferably 40 or less. The ends of the carcass cords 42 are represented by the number of carcass cords 42 contained per 50mm width of the carcass ply 40.

The carcass ply 40 has appropriate rigidity by setting the ends of the carcass cords 42 to 20 or more. Since excessive deformation is suppressed, damage accompanying cutting of the carcass cords 42 is less likely to occur in the carcass ply 40. From this viewpoint, the number of ends of the carcass cord 42 is more preferably 25 or more. The rigidity of the carcass ply 40 is appropriately maintained by setting the ends of the carcass cords 42 to 40 or less. In this tire 2, good rim assembling property is maintained.

In the tire 2, from the viewpoint of effectively suppressing the occurrence of damage accompanying the cutting of the carcass cord 42, it is preferable that the outer diameter CD of the carcass cord 42 is 0.6mm or more and the number of ends of the carcass cord 42 is 20 or more. From the viewpoint of maintaining good rim assemblability, it is preferable that the outer diameter CD of the carcass cord 42 is 1.0mm or less and the number of ends of the carcass cord 42 is 40 or less.

As shown in fig. 1, the belt 14 is located radially inside the tread 4. The belt 14 is located radially outward of the carcass 12.

The belt layer 14 is constituted by a plurality of layers 46 laminated in the radial direction. In this tire 2, the belt layer 14 is composed of 3 layers 46. In this tire 2, the number of layers 46 constituting the belt layer 14 is not particularly limited. The structure of the belt layer 14 is appropriately determined in consideration of the specification of the tire 2.

Although not illustrated, each layer 46 includes a plurality of belt cords in parallel. Each belt cord is inclined with respect to the equatorial plane. The belted layer cord is made of steel.

In this tire 2, of the 3 layers 46, the second layer 46B located between the first layer 46A and the third layer 46C has the largest axial width. The radially innermost first layer 46A has the smallest axial width.

Each of the beads 16 is located radially between the end of the belt 14 and the carcass 12. The tire pad 16 is made of cross-linked rubber.

As shown in fig. 1, in this tire 2, the bead pad 16 has the largest thickness at the portion of the end 48 of the belt layer 14 (specifically, the end 48 of the second layer 46B). The tire pad 16 tapers axially inward from the portion having its greatest thickness. The tire pad 16 is tapered radially inward from the portion having its maximum thickness.

As shown in fig. 1, an end 50 (hereinafter referred to as a lateral end 50) of the bead 16 located on the equatorial plane side is located axially outside the shoulder circumferential groove. An end 52 (hereinafter referred to as a longitudinal end 52) of the layer of the bead pad 16 located on the bead 8 side is located radially outward of the axially outer end PW of the tire 2.

An inner liner 18 is positioned inside the carcass 12. The inner liner 18 constitutes the inner surface of the tire 2. The inner liner 18 is made of a crosslinked rubber excellent in air-shielding property.

The insulation layer 20 is located between the carcass 12 and the inner liner 18. The insulation 20 is joined to the carcass 12 and to the inner liner 18. In other words, the inner liner 18 is engaged with the carcass 12 via the insulation layer 20. The separation layer 20 is made of a crosslinked rubber in consideration of adhesiveness.

Each reinforcing ply 22 is located in a portion of the bead 8. The reinforcing layer 22 is folded along the carcass ply 40 from the axially inner side toward the outwardly side about the core 36. In this tire 2, the carcass ply 40 is located between the reinforcing layer 22 and the bead 8.

Although not shown, the reinforcing layer 22 includes a plurality of filler cords (filler cord) arranged side by side. In the reinforcing layer 22, the filler cords are covered with a topping rubber. The material of the filling cord is steel.

In the tire 2, one end portion (hereinafter referred to as an inner end) of the reinforcing layer 22 is located between the outer end of the inner apex 38u and the core 36 in the radial direction. The other end portion (hereinafter referred to as outer end) of the reinforcing layer 22 is located between the end portion of the folded portion 40b and the core 36 in the radial direction. As shown in fig. 1, in the tire 2, the outer end of the reinforcing layer 22 is located further inward in the radial direction than the inner end thereof.

The respective ply strips 24 are located between the outer apexes 38s of the beads 8 and the chafers 10. The interlayer strip 24 covers the end of the folded portion 40b and the outer end of the reinforcing layer 22. The interlayer strip 24 is made of cross-linked rubber.

Each edge strip 26 is located between the outer apex 38s of the bead 8 and the ply strip 24. A part of the end of the folded portion 40b is in contact with the edge band 26. In this tire 2, the end of the folded portion 40b is sandwiched between the edge band 26 and the interlayer strip 24. The edge strip 26 is made of cross-linked rubber. In this tire 2, the edge band 26 is made of the same material as that of the interlayer strip 24.

Fig. 3 shows a portion of the tire 2 shown in fig. 1. Fig. 3 shows a contour CL of the carcass 12 included in the tire 2. The contour CL of the carcass 12 is the contour of the specified ply body 40a in the tire 2 in the standard state. In fig. 3, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the paper of fig. 3 is the circumferential direction of the tire 2.

In fig. 3, the symbol PL is the intersection of a straight line extending in the radial direction through the lateral end 50 of the bead pad 16 and the contour CL of the carcass 12. The symbol PV is the intersection of a straight line extending in the axial direction through the longitudinal end 52 of the bead sheet 16 and the contour CL of the carcass 12. In the tire 2, a portion from the intersection point PL to the intersection point PV in the contour CL of the carcass 12 is a contour of a portion overlapping the bead pad 16.

In the tire 2, the outline of the portion overlapping the bead pad 16 is represented by a circular arc, and this circular arc is referred to as a sidewall circular arc. In fig. 3, the symbol CB is the center of the sidewall arc. In this tire 2, the center CB of the sidewall arc is specified as follows.

A vertical bisector (hereinafter referred to as a first vertical bisector L1) of a line segment connecting the intersection point PL and the intersection point PV is drawn. An intersection point P1 of the first vertical bisector L1 and the contour CL of the carcass 12 is found. A vertical bisector (hereinafter referred to as a second vertical bisector L2) of a line segment connecting the intersection point P1 and the intersection point PL is drawn. An intersection of the second vertical bisector L2 and the first vertical bisector L1 (hereinafter also referred to as a first intersection) is the center CB of the sidewall arc. Although not illustrated, the center CB of the sidewall arc may also be represented by an intersection point (hereinafter also referred to as a second intersection point) of the third vertical bisector L3 and the first vertical bisector L1 by drawing a vertical bisector (hereinafter also referred to as a third vertical bisector L3) of a line segment connecting the intersection point P1 and the intersection point PV.

In fig. 3, arrow Rb is the radius of the sidewall arc. In this tire 2, the average of the length from the center CB measured along the first vertical bisector L1 to the contour CL of the carcass 12 and the length from the center CB measured along the second vertical bisector L2 to the contour CL of the carcass 12 is represented as the radius Rb of this sidewall arc. When the intersection of the third vertical bisector L3 and the first vertical bisector L1, that is, the center CB of the sidewall arc is represented by the second intersection, the average of the length from the second intersection measured along the first vertical bisector L1 to the contour CL of the carcass 12 and the length from the second intersection measured along the third vertical bisector L3 to the contour CL of the carcass 12 is represented as the radius Rb of the sidewall arc. In the case where the intersection point of the second vertical bisector L2 and the first vertical bisector L1, that is, the first intersection point and the second intersection point coincide, the average of the length from the first intersection point measured along the first vertical bisector L1 to the contour CL of the carcass 12, the length from the first intersection point measured along the second vertical bisector L2 to the contour CL of the carcass 12, the length from the second intersection point measured along the first vertical bisector L1 to the contour CL of the carcass 12, and the length from the second intersection point measured along the third vertical bisector L3 to the contour CL of the carcass 12 is represented as the radius Rb of the sidewall arc. In the tire 2, when the distance between the first intersection and the second intersection is within 3mm, the first intersection and the second intersection may coincide with each other.

In fig. 3, the symbol PM is an axially outer end of the contour CL of the carcass 12. The carcass 12 exhibits a maximum width at the position of its outer end PM. The position indicated by the symbol PM is a position on the outline CL of the carcass 12 corresponding to the maximum width position of the carcass 12. In this tire 2, the axially outer end PM thereof is located on a straight line extending in the axial direction through the aforementioned axially outer end PW. The symbol PN is an intersection of a straight line extending in the axial direction through the end PA of the bead 8 and the contour CL of the carcass 12. In the tire 2, in the contour CL of the carcass 12, a portion from the axially outer end PM to the intersection point PN is a contour of a portion from the maximum width position of the carcass 12 to the end PA of the bead 8.

In the tire 2, the contour of a portion from the maximum width position of the carcass 12 to the end PA of the bead 8 is represented by a circular arc, and this circular arc is referred to as a lower circular arc. In fig. 3, the symbol CS is the center of the lower arc. In the tire 2, the center CS of the lower arc is specified as follows.

A vertical bisector (hereinafter referred to as a fourth vertical bisector L4) connecting the line segment connecting the outer end PM and the intersection PN is drawn. An intersection point P4 of the fourth vertical bisector L4 and the contour CL of the carcass 12 is found. A vertical bisector (hereinafter referred to as a fifth vertical bisector L5) of a line segment connecting the intersection point P4 and the intersection point PN is drawn. An intersection point (hereinafter also referred to as a third intersection point) of the fifth vertical bisector L5 and the fourth vertical bisector L4 is a center CS of the lower arc. Although not illustrated, a vertical bisector (hereinafter, referred to as a sixth vertical bisector L6) of a line segment connecting the intersection point P4 and the axially outer end PM is drawn, and may be indicated as the center CS of the lower arc by an intersection point (hereinafter, referred to as a fourth intersection point) of the sixth vertical bisector L6 and the fourth vertical bisector L4. In this tire 2, the center CS of the lower arc is preferably located on a straight line extending in the axial direction through the axially outer end PM.

In fig. 3, the arrow Rs is the radius of the lower arc. In this tire 2, the average of the length from the center CS measured along the fourth vertical bisector L4 to the contour CL of the carcass 12 and the length from the center CB measured along the fifth vertical bisector L5 to the contour CL of the carcass 12 is represented as the radius Rs of this lower circular arc. When the center CS of the lower arc is represented by the fourth intersection point, which is the intersection point of the sixth vertical bisector L6 and the fourth vertical bisector L4, the average value of the length from the fourth intersection point measured along the fourth vertical bisector L4 to the contour CL of the carcass 12 and the length from the fourth intersection point measured along the sixth vertical bisector L6 to the contour CL of the carcass 12 is represented as the radius Rs of the lower arc. In a case where the intersection point of the fifth vertical bisector L5 and the fourth vertical bisector L4, that is, the third intersection point and the fourth intersection point coincide, an average value of the length from the third intersection point measured along the fourth vertical bisector L4 to the contour CL of the carcass 12 and the length from the third intersection point measured along the fifth vertical bisector L5 to the contour CL of the carcass 12 and the length from the fourth intersection point measured along the fourth vertical bisector L4 to the contour CL of the carcass 12 and the length from the fourth intersection point measured along the sixth vertical bisector L6 to the contour CL of the carcass 12 is represented as the radius Rs of the lower arc. In the tire 2, when the distance between the third intersection and the fourth intersection is within 3mm, the third intersection and the fourth intersection may coincide with each other.

In a standard state in which the tire 2 is assembled to a rim R, that is, a standard rim, and the internal pressure is adjusted to the standard internal pressure without applying a load, the contour CL of the carcass 12 includes a sidewall arc, which is an arc of a contour of a portion overlapping with the bead pad 16, and a lower arc, which is an arc of a contour from the maximum width position of the carcass 12 to a portion of the end PA of the bead 8. Wherein the ratio (Rb/Rs) of the radius Rb of the sidewall arc to the radius Rs of the lower arc is 1.00-1.10.

In the tire 2, in the contour CL of the carcass 12 in the normal state, the difference between the radius Rb of the sidewall arc and the radius Rs of the lower arc is suppressed to be within 10% of the radius Rs of the lower arc. In this tire 2, the sidewall arc having the larger radius Rb is set by setting the lower arc having the larger radius Rs, compared to the conventional tire. In this tire 2, since collapse of the bead portion at the time of inflation is suppressed and reduction of the tread radius in the shoulder portion is suppressed, it is not necessary to increase the size of the bead pad 16 in order to achieve improvement of the uneven wear resistance as in the conventional tire. A smaller bead pad 16 can be used and the tire 2 can achieve a reduction in rolling resistance. In addition, in the tire 2, since the distance between the longitudinal end 52 of the bead pad 16 and the end PA of the bead 8, that is, the flexible region can be increased, the rim assembling property can be improved.

In the tire 2, the aspect ratio represented by the ratio of the section height HE to the section width MW is 60% to 80%. In other words, the tire 2 has a flat ratio of 60% to 80%. In this tire 2, compared to a tire having a flat ratio exceeding 80%, since a side portion bridging a part of the tread 4 (hereinafter referred to as a tread portion) and a bead portion becomes short, there is a situation in which it is difficult to secure a flexible region that affects rim assembling performance.

However, as described above, by setting the difference between the radius Rb of the sidewall arc and the radius Rs of the lower arc to be within 10% of the radius Rs of the lower arc, the uneven wear resistance can be improved even with a small bead pad 16 in the tire 2. In this tire 2, although the length of the side portion is limited, the flexible zone is sufficiently secured. The smaller tire pads 16 contribute to a reduction in rolling resistance. In the tire 2, the rolling resistance is reduced and the rim assembling property is improved while suppressing the influence on the uneven wear resistance.

In addition, in the tire 2, since the difference between the radius Rb of the sidewall arc and the radius Rs of the lower portion arc is small, the deformation is hard to concentrate on the carcass 12 having the contour CL. Since the force acting on the carcass 12 is dispersed, the durability of the tire 2 is also improved.

In the tire 2, the ratio of the radius Rs of the lower arc (Rs/HA) to the radial distance HA from the bead base line to the end PA of the bead 8 is preferably 0.85 or more and preferably 0.95 or less.

By setting the ratio (Rs/HA) to 0.85 or more, collapse of the bead portion at the time of inflation is effectively suppressed. In this tire 2, a small bead pad 16 can be employed, and a flexible region is sufficiently secured. In the tire 2, the influence on the uneven wear resistance is suppressed, and the reduction of the rolling resistance and the improvement of the rim assembling property are realized. From this viewpoint, the ratio (Rs/HA) is more preferably 0.87 or more.

By setting the ratio (Rs/HA) to 0.95 or less, the contour CL of the carcass 12 can be appropriately maintained, and therefore, the deformation is less likely to concentrate on the carcass 12. Since the force acting on the carcass 12 is dispersed, the durability of the tire 2 is improved. In particular, since the concentration of deformation on the end PA of the bead is effectively suppressed, an improvement in bead durability is achieved. From this viewpoint, the ratio (Rs/HA) is more preferably 0.93 or less.

In fig. 1, reference PB denotes the top of the belt layer 14. The apex PB is represented by the radially outer end of the belt 14. The double arrow HB is the radial distance from the bead base line to the top PB of the belt 14. The double arrow HF is the radial distance from the end PA of the bead 8 to the longitudinal end 52 of the bead pad 16. The distance HF is the radial length of the flexure zone in the tire 2. In this tire 2, the aforementioned axially outer end PW is located radially further outward than a position half the radial length HF of this flexible region.

In this tire 2, the ratio (HF/HB) of the radial distance HF from the end PA of the bead 8 to the longitudinal end 52 of the bead pad 16 to the radial distance HB from the bead base line to the apex PB of the belt 14 is preferably 0.25 or more and preferably 0.45 or less.

The flexible region is sufficiently ensured by setting the ratio (HF/HB) to 0.25 or more. Since the flexible region imparts appropriate flexibility to the side portion, the tire 2 achieves an improvement in rim assembling performance. From this viewpoint, the ratio (HF/HB) is more preferably 0.27 or more.

The size of the flexible region is appropriately maintained by setting the ratio (HF/HB) to 0.45 or less. In the tire 2, since the rigidity of the side portion is ensured, good durability is maintained. In particular, since the strain concentration of the end portion PA of the bead 8 is effectively suppressed, the improvement of the bead durability is achieved. From this viewpoint, the ratio (HF/HB) is more preferably 0.40 or less.

In this tire 2, the toe-mouth spacing, represented by the axial distance from one toe-mouth PT to the other, is also taken into account. The method of measuring the toe-hole interval will be described with reference to fig. 4.

In the toe-hole interval measuring method, as shown in fig. 4 (a), the tire 2 is not mounted on the rim R, but the tire 2 is stood on a flat road surface. The height of the tyre 2 indicated by the double arrow HT is measured. The position of half of the measured height HT, indicated by the dash-dot line HL, is specified. As shown in fig. 4 (b), the axial distance TW from one toe hole PT to the other toe hole PT in this position HL is measured. In the tire 2, the distance TW is a toe-to-toe distance TW measured in a state where a load other than its own weight is not applied.

In this tire 2, the ratio (TW/RW) of the toe-opening interval TW to the rim width RW of the rim R, which is measured in a state where no load other than the self-weight is applied, and which is represented by the axial distance from one toe opening PT to the other toe opening PT, is preferably 0.80 or more, and preferably 0.88 or less.

By setting the ratio (TW/RW) to 0.80 or more, collapse of the bead portion at the time of inflation is effectively suppressed. In this tire 2, a small bead pad 16 can be used to sufficiently secure the flexible region. In the tire 2, the influence on the uneven wear resistance is suppressed, and the reduction of the rolling resistance and the improvement of the rim assembling property are realized. From this viewpoint, the ratio (TW/RW) is preferably 0.82 or more.

By setting the ratio (TW/RW) to 0.88 or less, the contour CL of the carcass 12 is appropriately maintained, so that the deformation is less likely to concentrate on the carcass 12. Since the force acting on the carcass 12 is dispersed, the durability of the tire 2 is improved. In particular, since the concentration of deformation at the end PA of the bead portion is effectively suppressed, the bead durability is improved. From this viewpoint, the ratio (TW/RW) is more preferably 0.86 or less.

In the tire 2, the ratio of the cross-sectional width MW (MW/TW) to the toe-hole interval TW is preferably 1.60 or more, and preferably 1.90 or less.

By setting the ratio (MW/TW) to 1.60 or more, since the contour CL of the carcass 12 is appropriately maintained, it is difficult for deformation to concentrate on the carcass 12. Since the force acting on the carcass 12 is dispersed, the durability of the tire 2 is improved. In particular, since the concentration of deformation at the end PA of the bead portion is effectively suppressed, the improvement of the bead durability is achieved. From this viewpoint, the ratio (MW/TW) is more preferably 1.62 or more, and still more preferably 1.68 or more.

Collapse of the bead portion at the time of inflation is effectively suppressed by setting the ratio (MW/TW) to 1.90 or less. In this tire 2, a small bead pad 16 can be used to sufficiently secure the flexible region. In the tire 2, the rolling resistance is reduced and the rim assembling property is improved while suppressing the influence on the uneven wear resistance. From this viewpoint, the ratio (MW/TW) is more preferably 1.82 or less.

In the tire 2, from the viewpoint of suppressing the influence on the uneven wear resistance and achieving reduction in rolling resistance, rim assembling property, and improvement in bead durability, the ratio (TW/RW) of the toe-mouth spacing TW to the rim width RW of the rim R, which is expressed by the axial distance from one toe-mouth PT to the other toe-mouth PT and is measured in a state where no load other than the self-weight is applied, is 0.80 or more and 0.88 or less, and the ratio (MW/TW) of the cross-sectional width MW of the toe-mouth spacing TW is preferably 1.60 or more and 1.90 or less.

In fig. 1, the double arrow D1 represents the thickness of the tire 2 on the equatorial plane. The thickness D1 is represented by the distance from the inner surface to the outer surface of the tire 2 measured along the equatorial plane. The double arrow TC indicates the thickness of the tire pad 16. This thickness TC is represented by the maximum thickness of the tire pad 16 measured from the side of the carcass 12 opposite the tire pad 16, i.e., along the normal to the inner surface.

As described above, in this tire 2, the bead pad 16 is smaller than that of the conventional tire. The smaller tire pads 16 contribute to a reduction in rolling resistance. From this viewpoint, the ratio of the thickness TC of the bead pad 16 to the thickness D1 of the tire 2 (TC/D1) is preferably 0.35 or less, and more preferably 0.30 or less. From the viewpoint that the cushion 16 can effectively alleviate the load acting on the end portion of the belt layer 14, the ratio (TC/D1) is preferably 0.20 or more, and more preferably 0.25 or more.

In fig. 1, a double arrow C1 is a thickness from an axially outer end PW of the tire 2 to the outer face of the carcass 12. The thickness C1 is the thickness of the outer portion of the carcass 12 at the axially outer end PW.

In the tire 2, a ratio (2 · C1/MW) of a thickness C1 of an outer portion of the carcass 12 at the axially outer end PW to half of the section width MW is preferably 0.05 or less. Thereby, the carcass 12 is disposed further outside in the tire 2. In this tire 2, the carcass 12 having a longer cord path, specifically, the carcass 12 having the profile CL including the lower arc having the larger radius Rs and the sidewall arc having the larger radius Rb is obtained. In the tire 2, the reduction of the rolling resistance and the improvement of the rim assembling property and the bead durability are achieved while suppressing the influence on the uneven wear resistance. From this viewpoint, the ratio (2. C1/MW) is more preferably 0.04 or less. From the viewpoint of sufficiently protecting the carcass 12 and suppressing the occurrence of damage to the carcass 12, (2 · C1/MW) is preferably 0.02 or more, and more preferably 0.03 or more.

Next, a method for manufacturing the tire 2 will be described. In the manufacture of the tire 2, a green tire 2r, which is a tire 2 in an uncrosslinked state of the tire 2 shown in fig. 1, is prepared by combining the tread 4, the sidewall 6, and the like in a building machine (not shown). The green tire 2r is pressurized and heated in a mold 56 of a vulcanizer 54 described later to obtain a tire 2. The method of manufacturing the tire 2 includes a step of preparing a green tire 2r, and a step of pressurizing and heating the green tire 2r in the mold 56.

Fig. 5 shows a part of a vulcanizer 54 used in the method for manufacturing the tire 2. In fig. 5, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the paper of fig. 5 is the circumferential direction of the tire 2. In the vulcanizer 54, the green tire 2r is vulcanized. The vulcanizer 54 has a mold 56 and a bladder (loader) 58.

The mold 56 has a cavity surface 60 therein. The cavity surface 60 contacts the outer surface of the green tire 2r and forms the outer surface of the tire 2. Although not described in detail, the mold 56 is a split mold.

The bladder 58 is located inside the die 56. The bladder 58 is made of cross-linked rubber. The interior of the bladder 58 is filled with a heating medium such as steam. Thereby, the bag cartridge 58 is inflated. The bladder 58 is shown in fig. 5 in an inflated state filled with a heating medium. The bladder 58 contacts the inner surface of the green tire 2r and forms the inner surface of the tire 2. In addition, in the manufacture of the tire 2, a rigid core (not shown) made of metal may be used instead of the bladder 58. The rigid core has an annular outer surface. The shape of the outer surface is similar to the shape of the inner surface of the tire 2 filled with air and kept in a state where the internal pressure is 5% of the standard internal pressure.

In the manufacture of the tire 2, a green tire 2r is put into a mold 56 set to a predetermined temperature. After the plunge, the mold 56 is closed. The bladder 58 expanded by the filling of the heating medium presses the green tire 2r from the inside into the cavity surface 60. The green tire 2r is pressurized and heated in the mold 56 for a prescribed time. Thereby, the rubber composition of the green tire 2r is crosslinked, thereby obtaining the tire 2.

In fig. 5, a solid line MBL is a reference line corresponding to the bead base line described above. This reference line is also referred to as the die baseline. The symbol PC is the intersection of the mold base line and the cavity surface 60. This intersection point PC is also referred to as a jig width reference point. The double arrow CW is the axial distance from one jig width reference point PC to the other jig width reference point PC. The distance CW is the clamp width of the die 56.

In this manufacturing method, the jig width CW of the mold 56 is wider than the rim width RW of the rim R to which the tire 2 manufactured by this mold 56 is assembled. Specifically, the ratio (CW/RW) of the jig width CW of the mold 56 to the rim width RW of the rim R on which the tire 2 is assembled is 1.15 or more and 1.22 or less.

Since the ratio (CW/RW) is 1.15 or more, in the tire 2 manufactured by this mold 56, the contour CL of the carcass 12 is configured such that the difference between the radius Rb of the sidewall arc and the radius Rs of the lower arc described above is small and the lower arc has a large radius Rs. In this tire 2, collapse of the bead portion at the time of inflation is effectively suppressed. In this tire 2, a small bead pad 16 can be used to sufficiently secure the flexible region. In the tire 2, the rolling resistance is reduced and the rim assembling property is improved while suppressing the influence on the uneven wear resistance. In other words, according to this manufacturing method, the tire 2 is obtained in which the influence on the uneven wear resistance is suppressed and the reduction in rolling resistance and the improvement in rim assembling performance are achieved. From this viewpoint, the ratio (CW/RW) is preferably 1.16 or more.

Since the ratio (CW/RW) is 1.22 or less, the contour CL of the carcass 12 is appropriately maintained in the tire 2 manufactured by the mold 56. The deformation is hard to concentrate on the carcass 12 of the tire 2. Since the force acting on the carcass 12 is dispersed, the durability of the tire 2 is improved. In particular, since the concentration of deformation at the end PA of the bead 8 is effectively suppressed, the bead durability is improved. In other words, according to this manufacturing method, the tire 2 in which the improvement of the bead durability is achieved is obtained. From this viewpoint, the ratio (CW/RW) is more preferably 1.21 or less.

As is clear from the above description, the heavy duty tubeless tire 2 of the present invention suppresses the influence on the uneven wear resistance, and achieves a reduction in rolling resistance and an improvement in rim assembling performance. The present invention achieves a significant effect in a tire 2 having a flat ratio of 60% to 80%, and further in a tire 2 having a flat ratio of 60% to 80%, and an outer diameter of 850mm or less (see JATMA and the like), which are difficult to secure a flexible region.

Examples

The present invention will be described in further detail below with reference to examples, but the present invention is not limited to these examples.

[ example 1]

A heavy-duty tubeless tire (size 215/75R17.5) having the structure shown in fig. 1 and the specification shown in table 1 was obtained. The outer diameter of the tire was 770 mm.

In this example 1, a steel cord having an outer diameter CD of 0.76mm was used for the carcass cord. The ratio of toe-gap spacing TW to rim width RW of rim R (TW/RW) was 0.85. The ratio of the tire section width MW with respect to the toe-hole interval TW (MW/TW) is 1.65. The ratio of the radius RB of the sidewall arc to the radius Rs of the lower arc (RB/Rs) was 1.09. The ratio of the radius Rs of the lower arc to the radial distance HA from the bead base line to the end PA of the bead (Rs/HA) is 0.89. The ratio (HF/HB) of the radial distance HF from the end PA of the bead to the longitudinal end of the bead pad to the radial distance HB from the bead base line to the top PB of the belt layer was 0.30. The ratio (CW/RW) of the jig width CW of the mold used for manufacturing the tire to the rim width RW of the rim R was 1.21.

[ example 2]

The ratio (HF/HB) was as shown in Table 1 below, and tires of example 2 were obtained in the same manner as in example 1.

Comparative example 1

The outer diameters CD, the ratios (TW/RW), the ratios (MW/TW), the ratios (Rb/Rs), the ratios (Rs/HA), the ratios (HF/HB), and the ratios (CW/RW) were as shown in the following Table 1, and tires of comparative example 1 were obtained in the same manner as in example 1. Comparative example 1 is a conventional tire.

Comparative example 2

Outer diameter CD tires of comparative example 2 were obtained in the same manner as in example 1, except as shown in table 1 below.

[ quality ]

The quality of the test tires was measured. The results are indicated by the indices in table 1 below. The smaller the value the smaller the mass.

[ partial wear resistance ]

The test tire was assembled to a standard rim, filled with air, and the internal pressure was adjusted to 700 kPa. The tire was mounted on all wheels of a test vehicle (4t load truck). The test vehicle was driven on a normal road in a state where 50% of the standard load was loaded on the entire loading table. The distance traveled until the amount of wear needed to be replaced is measured. The results are shown by the indices in table 1 below. The larger the value, the more excellent the resistance to partial wear.

[ durability of bead ]

The test tire was assembled to a standard rim, filled with air, and the internal pressure was adjusted to a standard internal pressure. The tire was mounted on a roller tester. A tire was loaded with 33.31kN, and the tire was run on a drum (radius 1.7m) at a speed of 80 km/h. The travel time until bead damage was measured. The results are shown by the indices in table 1 below. The larger the value, the more excellent the bead durability.

[ assembling property of rim ]

The ease of assembling the test tire machine to the standard rim was evaluated. The results are shown by the indices in table 1 below. The larger the value, the easier the tire is assembled to the rim, and the more excellent the rim assembling property is.

[ Rolling resistance ]

The Rolling Resistance Coefficient (RRC) of each test tire was measured while running on a drum at a speed of 80km/h under the following conditions using a rolling resistance tester. The results are shown by the indices in table 1 below. The larger the value, the smaller the rolling resistance.

Rim: 6.0X 17.5

Internal pressure: 700kPa

Longitudinal load: 14.17kN

[ TABLE 1]

As shown in table 1, in the embodiment, the influence on the uneven wear resistance performance was suppressed, and the reduction of the rolling resistance and the improvement of the rim assembling performance were achieved. From the evaluation results, the advantages of the present invention are apparent.

Industrial applicability

The technique described above, which suppresses the influence on the uneven wear resistance and achieves reduction in rolling resistance and improvement in rim assembling performance, is applicable to various tires.

Claims

1. A heavy-duty tubeless tire having a flat ratio of 60% to 80%,

the disclosed device is provided with:

a pair of beads;

a carcass that is bridged between one bead and the other bead;

a belt layer located radially outside the carcass; and

a pair of beads located between ends of the belt and the carcass,

the carcass comprises a plurality of parallel carcass cords, the outer diameter of each carcass cord is more than 0.6mm and less than 1.0mm,

in a standard state where the tire is assembled to a standard rim, the internal pressure is adjusted to a standard internal pressure, and no load is applied,

the profile of the carcass comprises:

a sidewall arc as an arc representing an outline of a portion overlapping with the bead pad; and

a lower arc as an arc representing an outline of a portion from a maximum width position of the carcass to an end of the bead,

the ratio of the radius of the sidewall arc to the radius of the lower arc is 1.00 to 1.10.

2. The heavy-duty tubeless tire of claim 1 wherein,

the ratio of the radius of the lower arc to the radial distance from the bead base line to the end of the bead is 0.85 or more and 0.95 or less.

3. The heavy-duty tubeless tire according to claim 1 or 2, wherein,

the ratio of the radial distance from the end of the bead to the longitudinal end of the bead pad to the radial distance from the bead base line to the top of the belt is 0.25 to 0.45.

4. The heavy-duty tubeless tire according to any one of claims 1 to 3, wherein,

the ratio of the toe-opening interval, which is represented by the axial distance from one toe opening to the other, to the rim width of the standard rim, measured in a state where no load other than the self-weight is applied, is 0.80 or more and 0.88 or less.

5. The heavy-duty tubeless tire of claim 4, wherein,

the ratio of the cross-sectional width of the tire to the toe-hole interval is 1.60 to 1.90.

6. A method of manufacturing a tubeless tire for heavy loads, comprising:

preparing a green tire for a tire, the green tire having a pair of beads, a carcass bridged between one bead and the other bead, a belt located radially outside the carcass, and a pair of pads located between ends of the belt and the carcass; and

a step of pressurizing and heating the green tire in a mold,

the ratio of the jig width of the mold to the rim width of a standard rim on which the tire is mounted is 1.15 to 1.22.