JP2023118383A - Tire with lug - Google Patents

Abstract

To provide a tire with lugs that is excellent in durability, in which bear is hardly produced in a buttress during manufacturing.SOLUTION: A tire with a lug has a tread including lugs 18. The lugs 18 include hems 38. The tire further has a rib 12 in a buttress. The rib 12 has a plurality of first elements 32, a plurality of second elements 34 and a plurality of gaps 36. Respective sizes in a radial direction of the first elements 32 are larger than sizes in a radial direction of the second elements 34 adjacent to the first elements 32. The gaps 36 respectively are positioned in boundaries between the first elements 32 and the second elements 34 adjacent to the first elements 32. Positions in a circumferential direction of the gaps 36 are different from positions in the circumferential direction of the hems 38 of the lugs 18.SELECTED DRAWING: Figure 5

Description

The present specification relates to a tire having multiple lugs in its tread.

Agricultural machines such as tractors run on mud. A tire with a lug is attached to this agricultural machine. Tires with lugs are also mounted on work vehicles such as civil engineering machinery. This lugged tire has a tread and sidewalls. This tread has many lugs. The tread also has grooves between the lug and other lugs adjacent to this lug. An example of a tire with lugs is disclosed in JP-A-2017-136937.

Japanese Patent Application Laid-Open No. 2017-136937

The lugged tire disclosed in the above publication has ribs on the buttress (near the boundary between the tread and sidewall). The rib has a first element and a second element. The circumferential position of the first element coincides with the circumferential position of the lug. The circumferential position of the second element coincides with the circumferential position of the groove. The radial size of the first element is greater than the radial size of the second element. This first element can suppress bears at the buttress even when the uncrosslinked rubber composition flows toward the cavity for the lug during the vulcanization process of the tire.

The rug has a foot. This skirt is located near the interface between the lug and the groove. Stress concentrates on this skirt when the tire rolls. The rib has a gap (step) at the boundary between the first element and the second element. Stress is concentrated in this gap when the tire rolls. In the lugged tire disclosed in the above publication, the circumferential position of the gap coincides with the circumferential position of the hem of the lug. Damage such as cracks is likely to occur in the vicinity of this gap. As the damage progresses, the tire reaches the end of its life.

The present applicant intends to provide a tire with lugs that is less likely to have bares on the buttress during manufacturing and that has excellent durability.

A lugged tire disclosed herein has a tread, a pair of sidewalls and a pair of ribs. The tread has a plurality of lugs and a plurality of grooves that alternate along the circumferential direction. Each sidewall extends generally radially inward from the edge of the tread. Each rib extends circumferentially near the interface between the tread and the sidewalls. The rib has a plurality of first elements, a plurality of second elements and a plurality of gaps. The radial size of each first element is greater than the radial size of the second element adjacent to the first element. Each gap is located at the boundary between a first element and a second element adjacent to the first element. The circumferential position of this gap is different from the circumferential position of the skirt of the lug.

In this lugged tire, the first element may restrain buttress bareness. This tire is less susceptible to buttress damage. Therefore, this tire is excellent in durability.

FIG. 1 is a perspective view showing a lugged tire according to one embodiment. 2 is a right side view showing the tire of FIG. 1; FIG. 3 is an exploded view showing the tread of the tire of FIG. 1. FIG. FIG. 4 is an enlarged cross-sectional view taken along line IV--IV of FIG. 5 is an enlarged view showing a portion of the tire of FIG. 2; FIG. 6 is an enlarged view showing a portion of the tire of FIG. 5; FIG. 7 is an enlarged view showing a portion of the tire of FIG. 4; FIG. FIG. 8 is an enlarged cross-sectional view taken along line VIII--VIII of FIG. 9 is an enlarged cross-sectional view taken along line IX-IX of FIG. 5. FIG. FIG. 10 is a right side view showing part of a lugged tire according to another embodiment. 11 is an enlarged view showing a portion of the tire of FIG. 10; FIG. FIG. 12 is a right side view showing part of a lugged tire according to still another embodiment. 13 is an enlarged view showing a portion of the tire of FIG. 12; FIG. FIG. 14 is a right side view showing part of a lugged tire according to still another embodiment. 15 is an enlarged view showing a portion of the tire of FIG. 14; FIG.

Hereinafter, preferred embodiments of the tire mold will be described in detail with reference to the drawings as appropriate.

The lugged tire 2 shown in FIGS. 1-4 has a tread 4 , a pair of sidewalls 6 , a pair of beads 8 , a carcass 10 and a pair of ribs 12 . Although not shown, this tire 2 includes a tube. This tube is filled with air. This tire 2 can be mounted on an agricultural machine. Examples of agricultural machinery include tractors, binders, harvesters, combine harvesters, rice transplanters, carts and tillers. This tire 2 may be mounted on a civil engineering and construction machine.

The tread 4 forms a tread surface 14 . The tread 4 is made of crosslinked rubber. The tread 4 has a main portion 16 and a plurality of lugs 18 . The main portion 16 has a shape that protrudes radially outward. Each lug 18 rises from main portion 16 .

The arrow R in FIGS. 1 and 3 represents the direction of rotation of the tire 2 . The tread 4 has a plurality of left lugs 18a and a plurality of right lugs 18b. These left lugs 18a and right lugs 18b are alternately arranged along the circumferential direction. Each left lug 18a extends from the equator CL of the tire 2 toward the rear in the direction of rotation as it goes leftward in FIG. Each right lug 18b extends from the equator CL of the tire 2 toward the rear in the direction of rotation toward the right in FIG. The area of the surface of main portion 16 sandwiched between lugs 18 and adjacent lugs 18 is groove 20 . A plurality of lugs 18 and a plurality of grooves 20 are alternately arranged along the circumferential direction. Note that FIG. 3 shows the tread 4 that is two-dimensionally developed.

As shown in FIG. 1, each lug 18 has a ground contact surface 22, a front surface 24, a back surface 26 and side surfaces 27. As shown in FIG. The tread 22 is part of the tread surface 14 (see FIGS. 2 and 4). The front surface 24 is positioned forward of the ground contact surface 22 in the rotational direction. The back surface 26 is located on the rear side of the ground contact surface 22 in the rotational direction. In FIG. 2, illustration of the front surface 24 and the back surface 26 is omitted.

As shown in FIG. 4 , each sidewall 6 extends radially generally inward from the edge of the tread 4 . This sidewall 6 is made of crosslinked rubber. The sidewall 6 absorbs the impact from the road surface by bending. Moreover, the sidewalls 6 protect the carcass 10 from trauma. Near the boundary between main portion 16 and sidewall 6 is buttress 28 .

Each bead 8 is positioned substantially radially inward of the sidewall 6 . The bead 8 has a core 29 and an apex 30 extending radially outward from the core 29 . The core 29 is ring-shaped. Core 29 includes a wound non-stretchable wire. A typical material for the wire is steel. Apex 30 tapers radially outward. The apex 30 is made of crosslinked rubber with high hardness. Tire 2 may have beads 8 that do not include apex 30 .

The carcass 10 consists of carcass plies 31 . The carcass ply 31 is stretched between the beads 8 on both sides and along the inner sides of the tread 4 and the sidewalls 6 . The carcass ply 31 is folded back around the core 29 from the inner side to the outer side in the axial direction.

Although not shown, the carcass ply 31 consists of a large number of parallel cords and a topping rubber. The absolute value of the angle formed by each cord with respect to the equatorial plane is 10° or more and 60° or less. In other words, this carcass 10 has a bias structure. A typical material for cords is organic fibres. Preferred organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers. The carcass 10 may have two or more carcass plies 31 . The carcass 10 may have carcass plies 31 with a radial structure.

Each rib 12 is located on a buttress 28 . The ribs 12 are made of crosslinked rubber. As can be seen from FIG. 2, the ribs 12 extend in the circumferential direction. This rib 12 is ring-shaped. Ribs 12 protrude from sidewalls 6 . In this embodiment, rib 12 is integral with sidewall 6 . Therefore, the material of the ribs 12 is the same as the material of the sidewalls 6 . This rib 12 does not reach the tread 4 . A buttress 28 may span the sidewall 6 and the tread 4 . The ribs 12 suppress damage to the sidewalls 6 .

FIG. 5 is an enlarged view showing a portion of the tire 2 of FIG. 2. FIG. An arrow R in FIG. 5 represents the direction of rotation of the tire 2 . The rib 12 is shown in FIG. This rib 12 has a plurality of first elements 32 and a plurality of second elements 34 . These first elements 32 and second elements 34 are alternately arranged along the circumferential direction (see also FIG. 2). This rib 12 also has a plurality of gaps 36 . Each gap 36 is located at the boundary between one first element 32 and one second element 34 adjacent to this first element 32 . The radial size of the first element 32 is larger than the radial size of the second element 34 . The first element 32 is partially radially inward of the second element 34 . The radially inner edges of the ribs 12 are therefore uneven. The radially outer edge of rib 12 is a smooth circle. Gap 36 is formed due to the difference in size of first element 32 and second element 34 . A two-dot chain line indicated by symbol PL in FIG. 5 separates the first element 32 and the second element 34 . FIG. 5 shows five demarcation lines. Since no edge exists between the first element 32 and the second element 34, the marking line PL cannot be visually recognized on the actual tire.

Front gap 36a and back gap 36b are shown in FIG. The front gap 36a is located at the boundary between the first element 32 and the second element 34 located on the front side of the first element 32 in the rotational direction. The back gap 36b is located at the boundary between the first element 32 and the second element 34 located behind the first element 32 in the rotational direction.

A lug 18 is also shown in FIG. FIG. 5 shows the side surfaces 27 of the lugs 18 . In FIG. 5, illustration of the front surface 24 and the back surface 26 is omitted. Lug 18 has two skirts 38 . Specifically, the lug 18 has a front hem 38a and a back hem 38b. The front hem 38a is a boundary between the lug 18 and the groove 20 located on the front side of the lug 18 in the rotational direction. The back hem 38b is a boundary between the lug 18 and the groove 20 located behind the lug 18 in the rotational direction. Each hem 38 is determined with reference to the side surface 27 . Therefore, the hem 38 is positioned above the side surface 27 . The location of this skirt 38 is determined by assuming that there is no rounding (corner buildup) between the lug 18 and the groove 20 .

FIG. 6 shows a further enlarged portion of the tire 2 of FIG. In FIG. 6, reference La denotes a straight line passing through the axis of the tire 2 and the front hem 38a. This straight line La represents the circumferential position of the front hem 38a. FIG. 6 shows two straight lines La. Reference character Lb is a straight line passing through the axis of the tire 2 and the back hem 38b. This straight line Lb represents the circumferential position of the back hem 38b.

The reference ZL in FIG. 6 represents the circumferential zone of the lug 18 . The circumferential zone ZL of the lug 18 extends from the straight line La to the straight line Lb on the rear side of this straight line La. Reference ZG denotes a circumferential zone of groove 20 . Circumferential zone ZG of groove 20 extends from straight line Lb to straight line La on the rear side of straight line Lb.

In FIG. 6, symbol Sa is a straight line passing through the axis of the tire 2 and the front gap 36a. This straight line Sa represents the circumferential position of the front gap 36a. The straight line Sa does not match the straight line La. In other words, the circumferential position of the front gap 36a is different from the circumferential position of the front hem 38a. Straight line Sa does not match straight line Lb. In other words, the circumferential position of the front gap 36a is different from the circumferential position of the back hem 38b.

Reference symbol Sb in FIG. 6 denotes a straight line passing through the axis of the tire 2 and the back gap 36b. This straight line Sb represents the circumferential position of the back gap 36b. Straight line Sb does not match straight line La. In other words, the circumferential position of the back gap 36b is different from the circumferential position of the front hem 38a. Straight line Sb does not match straight line Lb. In other words, the circumferential position of the back gap 36b is different from the circumferential position of the back hem 38b.

In this tire 2 , there is no gap 36 whose circumferential position coincides with the circumferential position of the hem 38 . When the tire 2 rolls, stress concentrates on the hem 38 and stress also concentrates on the gap 36 . Since the position of the gap 36 is different from the position of the skirt 38 in the circumferential direction, stress can be distributed in this tire 2 . In this tire 2, cracks in the vicinity of the gap 36 can be suppressed. This tire 2 is excellent in durability.

In FIG. 6, symbol θa represents the central angle between the circumferential position of the front gap 36a and the circumferential position of the hem 38 closest to the front gap 36a. From the viewpoint of durability, the central angle θa is preferably 1.0° (degree) or more, more preferably 2.0° or more, and particularly preferably 2.5° or more. The central angle θa is preferably 15° or less.

In FIG. 6, symbol θb represents the central angle between the circumferential position of the back gap 36b and the circumferential position of the hem 38 closest to the back gap 36b. From the viewpoint of durability, the central angle θb is preferably 1.0° or more, more preferably 2.0° or more, and particularly preferably 2.5° or more. The central angle θb is preferably 15° or less.

As shown in FIG. 6, the straight line Sa is sandwiched between a straight line La and a straight line Lb on the rear side of the straight line La. In other words, the circumferential position Sa of the front gap 36 a is included in the circumferential zone ZL of the lug 18 . Straight line Sb is sandwiched between straight line Lb and straight line La behind straight line Lb. In other words, the circumferential position Sb of the back gap 36 b is included in the circumferential zone ZG of the groove 20 . In this tire 2 , the first element 32 straddles the circumferential zone ZL of the lug 18 and the circumferential zone ZG of the groove 20 . The second element 34 straddles the circumferential zone ZG of the groove 20 and the circumferential zone ZL of the lug 18 . As mentioned above, the radial size of the first element 32 is large. In the vulcanization process of this tire 2, even if uncrosslinked rubber composition flows into the cavity for the lug 18, the first element 32 can restrain bears. As previously mentioned, the radial size of the second element 34 is small. This second element 34 can contribute to the weight of the tire 2 . The circumferential position Sa of the front gap 36 a may be included in the circumferential zone ZG of the groove 20 and the circumferential position Sb of the back gap 36 b may be included in the circumferential zone ZL of the lug 18 .

In the rib 12, the gap 36 whose circumferential position is different from the circumferential position of the skirt 38 and the gap 36 whose circumferential position matches the circumferential position of the skirt 38 may coexist. The ratio of the number of gaps 36 whose circumferential position is different from the circumferential position of the skirt 38 to the total number of gaps 36 is preferably 30% or more, more preferably 50% or more, and particularly preferably 60% or more.

FIG. 7 shows an enlarged view of a portion of the tire 2 of FIG. In FIG. 7 , the vertical direction is the radial direction of the tire 2 and the horizontal direction is the axial direction of the tire 2 . Arrow W1 in FIG. 7 represents the radial size of the first element 32 . From the viewpoint that bares near the lug 18 can be suppressed, the size W1 is preferably 10 mm or more, more preferably 13 mm or more, and particularly preferably 15 mm or more. From the viewpoint of light weight of the tire 2, the size W1 is preferably 40 mm or less. Arrow W2 represents the radial size of second element 34 . From the viewpoint of light weight of the tire 2, the difference (W1-W2) is preferably 2.0 mm or more, more preferably 3.0 mm or more, and particularly preferably 3.5 mm or more. From the viewpoint of suppressing cracks, the difference (W1-W2) is preferably 5 mm or less.

The symbol PM in FIG. 7 represents the maximum width point. The maximum width point PM is the outermost point in the profile of the sidewall 6 in the axial direction. This profile is the surface of sidewall 6 when sidewall 6 is assumed to be free of ribs 12 and other protrusions. The rib 12 is located radially outside the maximum width point PM. The rib 12 is spaced from the maximum width point PM. In this tire 2, cracks are less likely to occur.

Reference character HT in FIG. 4 represents the height of the tire 2 . The height HT is measured along the radial direction (vertical direction in FIG. 4) with reference to the baseline BL. The baseline BL defines the diameter of the rim on which the tire 2 is mounted. Symbol LR in FIG. 7 represents the radial distance between the rib 12 and the maximum width point PM. From the viewpoint of crack suppression, the ratio of the distance LR to the height HT is preferably 5.0% or more, more preferably 6.0% or more, and particularly preferably 7.0% or more. This ratio is preferably 15% or less.

As shown in FIG. 7, the profile has a first arc 40 and a second arc 42 . A first arc 40 exists between the point of maximum width PM and the rib 12 . The second arc 42 exists radially inward from the maximum width point PM. In FIG. 7, the symbol R1 represents the radius of curvature of the first circular arc 40 and the symbol R2 represents the radius of curvature of the second circular arc 42. As shown in FIG. In this embodiment, the radius of curvature R2 is different from the radius of curvature R1. Curvature radius R2 is smaller than curvature radius R1. In this tire 2, the stress is distributed to the inner edge EI of the rib 12 and the maximum width point PM. In this tire 2, cracks in the vicinity of the inner end EI can be suppressed. From the viewpoint of stress suppression, the ratio (R2/R1) is preferably 0.90 or less, more preferably 0.80 or less, and particularly preferably 0.75 or less. The ratio (R2/R1) is preferably 0.6 or more.

FIG. 8 is an enlarged cross-sectional view taken along line VIII--VIII of FIG. In FIG. 8 , the vertical direction is the radial direction of the tire 2 and the horizontal direction is the axial direction of the tire 2 . In FIG. 8 the first element 32, the tread 4 and the sidewalls 6 are shown. The surfaces of first element 32 include top surface 44 , inner slope 46 and outer slope 48 . The inner slope 46 is located radially inward of the top surface 44 . This inner slope 46 connects the top surface 44 and the sidewall 6 . The outer slope 48 is located radially outward of the top surface 44 . This outer slope 48 connects the top surface 44 and the tread 4 . In other words, the first element 32 is partially continuous with the lug 18 (see also Figure 5). An outer slope 48 may connect the top surface 44 and the sidewalls 6 . In tires 2 in which the outer slope 48 connects the top surface 44 and the sidewall 6 , the ribs 12 are spaced apart from the tread 4 .

The inner slope 46 points radially inward and axially inward. The inner slope 46 can suppress stress concentration on the rib 12 . In this embodiment, the inner slope 46 is curved. The inner slope 46 has an inwardly convex shape in the axial direction. The inner slope 46 contributes to suppression of stress concentration.

The outer slope 48 points radially outward and axially inward. This outer slope 48 can suppress stress concentration on the rib 12 . In this embodiment, the outer slope 48 is curved. This outer slope 48 has an inwardly convex shape in the axial direction. This outer slope 48 contributes to suppression of stress concentration.

Arrow T1 in FIG. 8 represents the height of the first element 32 . From the viewpoint of suppressing bareness, the height T1 is preferably 1.0 mm or more, more preferably 2.0 mm or more, and particularly preferably 2.5 mm or more. From the viewpoint of light weight of the tire 2, the height T1 is preferably 8 mm or less.

9 is an enlarged cross-sectional view taken along line IX-IX of FIG. 5. FIG. In FIG. 9 , the vertical direction is the radial direction of the tire 2 and the horizontal direction is the axial direction of the tire 2 . In Figure 9 the second element 34, the tread 4 and the sidewalls 6 are shown. The surfaces of second element 34 include top surface 50 , inner slope 52 and outer slope 54 . The inner slope 52 is positioned radially inward of the top surface 50 . This inner slope 52 connects the top surface 50 and the sidewall 6 . The outer slope 54 is located radially inward of the top surface 50 . This outer slope 54 connects the top surface 50 and the tread 4 . An outer slope 54 may connect the top surface 50 and the sidewalls 6 . In tires 2 in which the outer slope 54 connects the top surface 50 and the sidewall 6 , the rib 12 is spaced apart from the tread 4 .

The inner slope 52 points radially inward and axially inward. The inner slope 52 can suppress stress concentration on the rib 12 . In this embodiment, the inner slope 52 is a curved surface. The inner slope 52 has an inwardly convex shape in the axial direction. The inner slope 52 contributes to suppression of stress concentration.

The outer slope 54 points radially outward and axially inward. This outer slope 54 can suppress stress concentration on the rib 12 . In this embodiment, the outer slope 54 is curved. The outer slope 54 has an inwardly convex shape in the axial direction. This outer slope 54 contributes to suppression of stress concentration.

Arrow T2 in FIG. 9 represents the height of the second element 34 . The height T2 is preferably 1.0 mm or more, more preferably 2.0 mm or more, and particularly preferably 2.5 mm or more. From the viewpoint of light weight of the tire 2, the height T2 is preferably 8 mm or less. In this embodiment, the height T2 of the second element 34 is the same as the height T1 of the first element 32 (see also FIG. 7).

In the present invention, the dimensions and angles of each member of the tire 2 are measured with the tire 2 mounted on a regular rim and inflated to a regular internal pressure. No load is applied to the tire 2 during the measurement. In the present specification, a regular rim means a rim defined in the standard on which the tire 2 relies. A "standard rim" in the JATMA standard, a "design rim" in the TRA standard, and a "measuring rim" in the ETRTO standard are regular rims. In this 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 JATMA 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 regular internal pressures.

FIG. 10 is a right side view showing part of a lugged tire 56 according to another embodiment. Ribs 58 are shown in FIG. This rib 58 has a plurality of first elements 60 and a plurality of second elements 62 . These first elements 60 and second elements 62 are alternately arranged along the circumferential direction. This rib 58 also has a plurality of gaps 64 . Each gap 64 is located at the boundary between one first element 60 and one second element 62 adjacent to this first element 60 . The radial size of the first element 60 is larger than the radial size of the second element 62 . The first element 60 is partially radially inward of the second element 62 . Accordingly, the radially inner edge of rib 58 is uneven. The radially outer edge of rib 58 is a smooth circle. Gap 64 is formed due to the difference in size of first element 60 and second element 62 .

Front gap 64a and back gap 64b are shown in FIG. The front gap 64a is located at the boundary between the first element 60 and the second element 62 located on the front side of the first element 60 in the rotational direction. The back gap 64b is located at the boundary between the first element 60 and the second element 62 located behind the first element 60 in the rotational direction. The circumferential size of the first element 60 is larger than that of the first element 32 shown in FIG. The circumferential size of the second element 62 is smaller than that of the second element 34 shown in FIG. The configuration of the members of this tire 56 other than the ribs 58 is the same as those of the tire 2 shown in FIGS. 1-9. Lugs 66 and grooves 68 are also shown in FIG. The lug 66 has a front skirt 70a and a back skirt 70b.

FIG. 11 shows an enlarged portion of the tire 56 of FIG. In FIG. 11, reference La denotes a straight line passing through the axis of the tire 56 and the front hem 70a. This straight line La represents the circumferential position of the front hem 70a. FIG. 11 shows two straight lines La. Reference character Lb is a straight line passing through the axis of the tire 56 and the back hem 70b. This straight line Lb represents the circumferential position of the back hem 70b. FIG. 11 shows two straight lines Lb. Reference ZL in FIG. 11 represents the circumferential zone of the lug 66 . The circumferential zone ZL of the lug 66 extends from the straight line La to the straight line Lb on the rear side of this straight line La. Reference ZG denotes a circumferential zone of groove 68 . The circumferential zone ZG of the groove 68 extends from the straight line Lb to the straight line La on the rear side of this straight line Lb.

Reference Sa in FIG. 11 denotes a straight line passing through the axis of the tire 56 and the front gap 64a. This straight line Sa represents the circumferential position of the front gap 64a. The straight line Sa does not match the straight line La. In other words, the circumferential position of the front gap 64a is different from the circumferential position of the front hem 70a. Straight line Sa does not match straight line Lb. In other words, the circumferential position of the front gap 64a is different from the circumferential position of the back hem 70b.

Reference symbol Sb in FIG. 11 denotes a straight line passing through the axis of the tire 56 and the back gap 64b. This straight line Sb represents the circumferential position of the back gap 64b. Straight line Sb does not match straight line La. In other words, the circumferential position of the back gap 64b is different from the circumferential position of the front hem 70a. Straight line Sb does not match straight line Lb. In other words, the circumferential position of the back gap 64b is different from the circumferential position of the back hem 70b.

The tire 56 does not have a gap 64 whose circumferential position coincides with the circumferential position of the hem 70 . In this tire 56 stress can be distributed. In this tire 56, cracks near the gap 64 can be suppressed. This tire 56 is excellent in durability.

In FIG. 11, symbol θa represents the central angle between the circumferential position of the front gap 64a and the circumferential position of the skirt 70 closest to the front gap 64a. From the viewpoint of durability, the central angle θa is preferably 1.0° or more, more preferably 2.0° or more, and particularly preferably 2.5° or more. The central angle θa is preferably 15° or less.

In FIG. 11, symbol θb represents the central angle between the circumferential position of the back gap 64b and the circumferential position of the hem 70 closest to the back gap 64b. From the viewpoint of durability, the central angle θb is preferably 1.0° or more, more preferably 2.0° or more, and particularly preferably 2.5° or more. The central angle θb is preferably 15° or less.

As shown in FIG. 11, straight line Sa is sandwiched between straight line Lb and straight line La behind straight line Lb. In other words, the circumferential position Sa of the front gap 64 a is included in the circumferential zone ZG of the groove 68 . Straight line Sb is sandwiched between straight line Lb and straight line La behind straight line Lb. In other words, the circumferential position Sb of the back gap 64 b is included in the circumferential zone ZG of the groove 68 . In this tire 56 , the circumferential positions of all gaps 64 are contained in the circumferential zone ZG of grooves 68 . In this tire 56 the circumferential zone ZL of the lug 66 is included in the circumferential zone of the first element 60 . During the tire 56 vulcanization process, even if uncrosslinked rubber composition flows into the cavity for the lugs 66, the first element 60 is capable of restraining bears.

FIG. 12 is a right side view showing part of a lugged tire 72 according to still another embodiment. Ribs 74 are shown in FIG. This rib 74 has a plurality of first elements 76 and a plurality of second elements 78 . These first elements 76 and second elements 78 are alternately arranged along the circumferential direction. This rib 74 also has a plurality of gaps 80 . Each gap 80 is located at the boundary between one first element 76 and one second element 78 adjacent to the first element 76 . The radial size of the first element 76 is greater than the radial size of the second element 78 . The first element 76 is partially radially inward of the second element 78 . Accordingly, the radially inner edge of rib 74 is uneven. The radially outer edge of rib 74 is a smooth circle. Gap 80 is formed due to the difference in size of first element 76 and second element 78 .

FIG. 12 shows a front gap 80a and a back gap 80b. The front gap 80a is located at the boundary between the first element 76 and the second element 78 located on the front side of the first element 76 in the rotational direction. The back gap 80b is located at the boundary between the first element 76 and the second element 78 located behind the first element 76 in the rotational direction. The circumferential size of the first element 76 is smaller than that of the first element 32 shown in FIG. The circumferential size of the second element 78 is larger than that of the second element 34 shown in FIG. The configuration of the members of this tire 72 other than the ribs 74 are the same as those of the tire 2 shown in FIGS. 1-9. Lugs 82 and grooves 84 are also shown in FIG. The lug 82 has a front skirt 86a and a back skirt 86b.

FIG. 13 shows an enlarged portion of the tire 72 of FIG. In FIG. 13, reference La denotes a straight line passing through the axis of the tire 72 and the front hem 86a. This straight line La represents the circumferential position of the front hem 86a. Reference character Lb is a straight line passing through the axis of the tire 72 and the back hem 86b. This straight line Lb represents the circumferential position of the back hem 86b. Reference ZL in FIG. 13 represents the circumferential zone of the lug 82 . The circumferential zone ZL of the lug 82 extends from the straight line La to the straight line Lb on the rear side of this straight line La.

In FIG. 13, symbol Sa is a straight line passing through the axis of the tire 72 and the front gap 80a. This straight line Sa represents the circumferential position of the front gap 80a. The straight line Sa does not match the straight line La. In other words, the circumferential position of the front gap 80a is different from the circumferential position of the front hem 86a. Straight line Sa does not match straight line Lb. In other words, the circumferential position of the front gap 80a is different from the circumferential position of the back hem 86b.

Reference symbol Sb in FIG. 13 denotes a straight line passing through the axis of the tire 72 and the back gap 80b. This straight line Sb represents the circumferential position of the back gap 80b. Straight line Sb does not match straight line La. In other words, the circumferential position of the back gap 80b is different from the circumferential position of the front hem 86a. Straight line Sb does not match straight line Lb. In other words, the circumferential position of the back gap 80b is different from the circumferential position of the back hem 86b.

The tire 72 does not have a gap 80 whose circumferential position coincides with the circumferential position of the hem 86 . In this tire 72 stress can be distributed. In this tire 72, cracks in the vicinity of the gap 80 can be suppressed. This tire 72 is excellent in durability.

In FIG. 13, symbol θa represents the central angle between the circumferential position of the front gap 80a and the circumferential position of the hem 86 closest to the front gap 80a. From the viewpoint of durability, the central angle θa is preferably 1.0° or more, more preferably 2.0° or more, and particularly preferably 2.5° or more. The central angle θa is preferably 15° or less.

In FIG. 13, symbol θb represents the central angle between the circumferential position of the back gap 80b and the circumferential position of the hem 86 closest to the back gap 80b. From the viewpoint of durability, the central angle θb is preferably 1.0° or more, more preferably 2.0° or more, and particularly preferably 2.5° or more. The central angle θb is preferably 15° or less.

As shown in FIG. 13, the straight line Sa is sandwiched between a straight line La and a straight line Lb behind this straight line La. In other words, the circumferential position Sa of the front gap 80 a is included in the circumferential zone ZL of the lug 82 . Straight line Sb is sandwiched between straight line La and straight line Lb behind this straight line La. In other words, the circumferential position Sb of the back gap 80b is included in the circumferential zone ZL of the lug 82. As shown in FIG. In this tire 72 the circumferential positions of all gaps 80 are contained in the circumferential zone ZL of the lugs 82 . In this tire 72 the circumferential zone of the first element 76 is included in the circumferential zone ZL of the lug 82 . During the vulcanization process of this tire 72, even if uncrosslinked rubber composition flows into the cavity for the lugs 82, the first element 76 can restrain bears.

FIG. 14 is a right side view showing part of a lugged tire 88 according to still another embodiment. A rib 90 is shown in FIG. This rib 90 has a plurality of first elements 92 and a plurality of second elements 94 . These first elements 92 and second elements 94 are alternately arranged along the circumferential direction. This rib 90 also has a plurality of gaps 96 . Each gap 96 is located at the boundary between one first element 92 and one second element 94 adjacent to this first element 92 . The radial size of the first element 92 is greater than the radial size of the second element 94 . The first element 92 is partially radially outward of the second element 94 . Accordingly, the radially outer edge of rib 90 is uneven. The radially inner edge of rib 90 is a smooth circle. Gap 96 is formed due to the difference in size of first element 92 and second element 94 .

Front gap 96a and back gap 96b are shown in FIG. The front gap 96a is located at the boundary between the first element 92 and the second element 94 located on the front side of the first element 92 in the rotational direction. The back gap 96b is located at the boundary between the first element 92 and the second element 94 located behind the first element 92 in the rotational direction. The configuration of the members of this tire 88 other than the ribs 90 is the same as those of the tire 2 shown in FIGS. 1-9. Lugs 98 and grooves 100 are also shown in FIG. The lug 98 has a front hem 102a and a back hem 102b.

FIG. 15 shows an enlarged portion of the tire 88 of FIG. In FIG. 15, reference La denotes a straight line passing through the axis of the tire 88 and the front hem 102a. This straight line La represents the circumferential position of the front hem 102a. FIG. 15 shows two straight lines La. Reference character Lb is a straight line passing through the axis of the tire 88 and the back hem 102b. This straight line Lb represents the circumferential position of the back hem 102b. Reference ZL in FIG. 15 represents the circumferential zone of the lug 98 . The circumferential zone ZL of the lug 98 extends from the straight line La to the straight line Lb on the rear side of this straight line La. Reference ZG denotes a circumferential zone of groove 100 . Circumferential zone ZG of groove 100 extends from straight line Lb to straight line La on the rear side of straight line Lb.

Reference Sa in FIG. 15 indicates a straight line passing through the axis of the tire 88 and the front gap 96a. This straight line Sa represents the circumferential position of the front gap 96a. The straight line Sa does not match the straight line La. In other words, the circumferential position of the front gap 96a is different from the circumferential position of the front hem 102a. Straight line Sa does not match straight line Lb. In other words, the circumferential position of the front gap 96a is different from the circumferential position of the back hem 102b.

Reference symbol Sb in FIG. 15 denotes a straight line passing through the axis of the tire 88 and the back gap 96b. This straight line Sb represents the circumferential position of the back gap 96b. Straight line Sb does not match straight line La. In other words, the circumferential position of the back gap 96b is different from the circumferential position of the front hem 102a. Straight line Sb does not match straight line Lb. In other words, the circumferential position of the back gap 96b is different from the circumferential position of the back hem 102b.

The tire 88 does not have a gap 96 whose circumferential position coincides with the circumferential position of the hem 102 . In this tire 88 stress can be distributed. In this tire 88, cracks near the gap 96 can be suppressed. This tire 88 is excellent in durability.

In FIG. 15, symbol θa represents the central angle between the circumferential position of the front gap 96a and the circumferential position of the skirt 102 closest to the front gap 96a. From the viewpoint of durability, the central angle θa is preferably 1.0° or more, more preferably 2.0° or more, and particularly preferably 2.5° or more. The central angle θa is preferably 15° or less.

In FIG. 15, symbol θb represents the central angle between the circumferential position of the back gap 96b and the circumferential position of the hem 102 closest to the back gap 96b. From the viewpoint of durability, the central angle θb is preferably 1.0° or more, more preferably 2.0° or more, and particularly preferably 2.5° or more. The central angle θb is preferably 15° or less.

As shown in FIG. 15, the straight line Sa is sandwiched between a straight line La and a straight line Lb behind this straight line La. In other words, the circumferential position Sa of the front gap 96 a is included in the circumferential zone ZL of the lug 98 . Straight line Sb is sandwiched between straight line Lb and straight line La behind straight line Lb. In other words, the circumferential position Sb of the back gap 96 b is included in the circumferential zone ZG of the groove 100 . In this tire 88 , the first element 92 straddles the circumferential zone ZL of the lug 98 and the circumferential zone ZG of the groove 100 . The second element 94 straddles the circumferential zone ZG of the groove 100 and the circumferential zone ZL of the lug 98 . As previously mentioned, the radial size of the first element 92 is large. During the tire 88 vulcanization process, even if uncrosslinked rubber composition flows into the cavity for the lugs 98, the first element 92 is capable of restraining bears. As previously mentioned, the radial size of the second element 94 is small. This second element 94 can contribute to the light weight of the tire 88 . The circumferential position Sa of the front gap 96 a may be included in the circumferential zone ZG of the groove 100 and the circumferential position Sb of the back gap 96 b may be included in the circumferential zone ZL of the lug 98 .

In the rib 90 , gaps 96 whose circumferential position is different from the circumferential position of the skirt 102 and gaps 96 whose circumferential position matches the circumferential position of the skirt 102 may coexist. The ratio of the number of gaps 96 whose circumferential position is different from the circumferential position of the skirt 102 to the total number of gaps 96 is preferably 30% or more, more preferably 50% or more, and particularly preferably 60% or more.

The tire 88 may have ribs 90 that are uneven on the radially outer edge and also uneven on the radially inner edge.

[Disclosure items]
The following items are disclosures of preferred embodiments.

[Item 1]
It has a tread, a pair of sidewalls and a pair of ribs,
The tread has a plurality of lugs and a plurality of grooves alternately arranged along the circumferential direction,
each sidewall extending generally radially inward from the edge of the tread;
each rib extending circumferentially near a boundary between the tread and the sidewall;
wherein the rib has a plurality of first elements, a plurality of second elements and a plurality of gaps;
the radial size of each first element is greater than the radial size of the second element adjacent to the first element;
each gap is located at the boundary between the first element and a second element adjacent to the first element;
A lugged tire, wherein the circumferential position of the gap is different from the circumferential position of the skirt of the lug.

[Item 2]
The lugged tire according to item 1, wherein a central angle between the circumferential position of the gap and the circumferential position of the skirt is 1.0° or more.

[Item 3]
A lugged tire according to item 1 or 2, wherein said rib has said gap whose circumferential position is contained in the circumferential zone of said groove.

[Item 4]
A lugged tire according to item 1 or 2, wherein said rib has said gap whose circumferential position is contained in the circumferential zone of said lug.

[Item 5]
The rib
(1) said gap whose circumferential position is contained in the circumferential zone of said lug;
and (2) a lugged tire according to item 1 or 2, having said gap whose circumferential position is contained in the circumferential zone of said groove.

[Item 6]
The rib is positioned radially outward from the maximum width point of the tire, and the radial distance between the rib and the maximum width point is 5.0% or more of the tire height. 6. A lugged tire according to any one of items 1 to 5.

[Item 7]
said sidewall profile having a first arc located between said widest point and said rib and a second arc extending radially inward from said widest point;
7. A lugged tire according to item 6, wherein the radius of curvature of the second arc is smaller than the radius of curvature of the first arc.

[Item 8]
a surface of the first element having a top surface, an inner slope and an outer slope;
the inner slope is positioned radially inward of the top surface and connects the top surface and the sidewall;
the outer slope is located radially outward of the top surface and connects the top surface and the sidewall or the tread;
the inner slope is directed radially inward and axially inward;
A lugged tire according to any one of items 1 to 7, wherein said outer slope is directed axially inwards towards radially outwards.

[Item 9]
The inner slope has an inwardly convex shape in the axial direction,
9. A lugged tire according to item 8, wherein the outer slope has an axially inwardly convex shape.

[Item 10]
the surface of the second element has a top surface, an inner slope and an outer slope;
the inner slope is positioned radially inward of the top surface and connects the top surface and the sidewall;
the outer slope is located radially outward of the top surface and connects the top surface and the sidewall or the tread;
the inner slope is directed radially inward and axially inward;
A lugged tire according to any one of items 1 to 9, wherein said outer slope is directed axially inwards towards radially outwards.

[Item 11]
The inner slope has an inwardly convex shape in the axial direction,
11. A lugged tire according to item 10, wherein the outer slope has an inwardly convex shape in the axial direction.

The lugged tire described above can be mounted on various vehicles.

2 Lug Tire 4 Tread 6 Side Wall 12 Rib 18 Lug 20 Groove 22 Ground Surface 24 Front Surface 26 Back Surface 27 Side surface 28 Buttress 32 First element 34 Second element 36 Gap 38 Bottom 40 First arc 42 Second arc 44 Top surface 46 Inner slope 48 Outer slope 50 Top surface 52 Inner slope 54 Outer slope 56 Tire with lug 58 Rib 60 First element 62 Second element 64 Gap 66 Lug 68 Groove 70 Bottom 72 Tire with lug 74 Rib 76 First Element 78 Second element 80 Gap 82 Lug 84 Groove 86 Bottom 88 Tire with lug 90 Rib 92 First element 94 - Second element 96 Gap 98 Lug 102 Groove

Claims (11)

It has a tread, a pair of sidewalls and a pair of ribs,
The tread has a plurality of lugs and a plurality of grooves alternately arranged along the circumferential direction,
each sidewall extending generally radially inward from the edge of the tread;
each rib extending circumferentially near a boundary between the tread and the sidewall;
wherein the rib has a plurality of first elements, a plurality of second elements and a plurality of gaps;
the radial size of each first element is greater than the radial size of the second element adjacent to the first element;
each gap is located at the boundary between the first element and a second element adjacent to the first element;
A lugged tire, wherein the circumferential position of the gap is different from the circumferential position of the skirt of the lug. 2. The lugged tire according to claim 1, wherein a central angle between the circumferential position of the gap and the circumferential position of the skirt is 1.0[deg.] or more. A lugged tire according to claim 1 or 2, wherein said rib has said gap whose circumferential position is contained in the circumferential zone of said groove. A lugged tire according to claim 1 or 2, wherein said rib has said gap whose circumferential position is contained in the circumferential zone of said lug. The rib
(1) said gap whose circumferential position is contained in the circumferential zone of said lug;
and (2) said gap whose circumferential position is contained in the circumferential zone of said groove. The rib is positioned radially outward from the maximum width point of the tire, and the radial distance between the rib and the maximum width point is 5.0% or more of the tire height. A lugged tire according to any one of claims 1 to 5. said sidewall profile having a first arc located between said widest point and said rib and a second arc extending radially inward from said widest point;
7. The lugged tire of claim 6, wherein the radius of curvature of said second arc is less than the radius of curvature of said first arc. a surface of the first element having a top surface, an inner slope and an outer slope;
the inner slope is positioned radially inward of the top surface and connects the top surface and the sidewall;
the outer slope is located radially outward of the top surface and connects the top surface and the sidewall or the tread;
the inner slope is directed radially inward and axially inward;
8. A lugged tire according to any one of the preceding claims, wherein said outer slope is directed axially inwards towards radially outwards. The inner slope has an inwardly convex shape in the axial direction,
9. The lugged tire of claim 8, wherein said outer slope has an axially inwardly convex shape. the surface of the second element has a top surface, an inner slope and an outer slope;
the inner slope is positioned radially inward of the top surface and connects the top surface and the sidewall;
the outer slope is located radially outward of the top surface and connects the top surface and the sidewall or the tread;
the inner slope is directed radially inward and axially inward;
10. A lugged tire according to any one of the preceding claims, wherein said outer slope is directed axially inwards towards radially outwards. The inner slope has an inwardly convex shape in the axial direction,
11. The lugged tire of claim 10, wherein said outer slope has an axially inwardly convex shape.

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