JP2017136937A - Lugged tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lugged tire excellent in durability and flaw resistance while maintaining a proper tire production cost and mass.SOLUTION: In a lugged tire 2 in this invention, a tread 4 comprises a tread body 16 and plural lugs 18 protruding from the tread body 16 toward outside. Each lug 18 extends from the central vicinity of the tread body 16 to the end TE of the body 16. A rib 12 of the tire 2 protrudes outside in an axial direction in the vicinity of a boundary between the body 16 and a sidewall 6 and extends in a circumferential direction. In the rib 12, the width A of a first portion 12a is wider than the width B of a second portion 12b when defining a portion having overlap with the lug 18 in a radial direction as the first portion 12a, and a portion having no overlap with the lug 18 in the radial direction as the second portion 12b.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a tire with lugs. More specifically, the present invention relates to a lug-equipped tire that can be attached to an agricultural machine and a light civil engineering construction machine that travel in wetlands, soft ground, and the like.

  A working machine such as an agricultural machine and a light civil engineering construction machine is equipped with a lug tire in consideration of workability in wet fields and soft ground. The tread of a tire with lugs is provided with a number of lugs protruding outward in the radial direction. The rug sinks into the mud. Rug scratches mud. Lugs can contribute to tire traction.

  A large load is applied to the lug-equipped tire during traveling in wetlands and soft ground. The lug-equipped tire is required to be durable enough to withstand this load. Examination of a tire with a lug excellent in durability is reported in Japanese Patent Application Laid-Open No. 2007-168684.

JP2007-168684A

  In the tire vulcanization step, a preformed raw cover is put into a mold. The raw cover is heated while being pressurized in a cavity surrounded by the mold and the bladder. The rubber composition of the raw cover flows in the cavity by pressurization and heating. The rubber causes a crosslinking reaction by heating, and a tire is obtained.

  In a tire provided with a lug, the rubber composition of the raw cover flows into a portion corresponding to the lug of the cavity in the vulcanization process. For this reason, the rubber thickness of the buttress portion (near the boundary between the tread and the sidewall) in the portion where the lug is disposed may be thinner than the rubber thickness of the buttress portion in the portion where the lug is not disposed. . In the buttress portion, distortion tends to concentrate when the tire rolls. In a tire where the rubber thickness of the buttress portion is thin, rubber cracks and carcass cord damage at this portion may occur earlier than in a tire where the rubber thickness of the buttress portion is thick. A buttress portion with a thin rubber thickness can cause a decrease in durability. Furthermore, since the buttress portion is close to the maximum width position of the tire, the buttress portion is likely to come into contact with plants, rocks, and the like during traveling. A buttress portion having a thin rubber thickness can be a factor in reducing the resistance to trauma to these obstacles.

  In order to prevent the rubber thickness of the buttress portion from being reduced in the vulcanization process, the rubber thickness of the buttress portion may be designed to be thick. Or the rib which protruded outside may be provided in a buttress part. In any tire, the rubber thickness is increased more than necessary in a portion where no lug exists. This leads to an increase in tire manufacturing costs and mass.

  An object of the present invention is to provide a tire excellent in durability and trauma resistance while maintaining an appropriate tire manufacturing cost and mass.

  The tire with a lug according to the present invention includes a tread, a pair of sidewalls, and a pair of ribs. The tread includes a main body and a plurality of lugs protruding outward from the main body. Each lug extends from the vicinity of the center of the main body to the end of the main body. Each sidewall extends substantially inward in the radial direction from the end of the main body. Each rib protrudes outward in the axial direction in the vicinity of the boundary between the main body and the sidewall and extends in the circumferential direction. Of the ribs, when the tire is viewed from the side, the portion that overlaps the lug in the radial direction is the first portion, and the portion that does not overlap the lug in the radial direction is the second portion, the first portion The width A is larger than the width B of the second portion.

  Preferably, the ratio (A / H) of the width A to the tire cross-section height H is 5% or more and 20% or less.

  Preferably, the ratio (B / A) of the width B to the width A is 30% or more and 80% or less.

  Preferably, when the angle between the radially outer surface and the axially outer surface of the lug is an outer corner, the radial height D from the outer corner to the radially outer end of the first portion is The ratio (D / C) to the radial height C from the outer corner to the end of the main body is 0.8 or more and 1.2 or less.

  Preferably, the height of the rib is 1 mm or more and 8 mm or less.

  In the tire with lugs according to the present invention, the rib protrudes outward in the axial direction and extends in the circumferential direction in the vicinity of the boundary between the main body of the tread and the sidewall. When the portion of the rib that overlaps the lug in the radial direction is the first portion and the portion that does not overlap the lug in the radial direction is the second portion, the width A of the first portion is the width of the second portion. Greater than B. The first portion having a large width effectively prevents the rubber thickness of the buttress portion from being reduced at the position where the lug is present. This tire is excellent in durability and damage resistance. In this rib, since the width of the second portion is small, the influence of the rib on the manufacturing cost and mass of the tire is suppressed. In this tire, an appropriate tire manufacturing cost and mass are maintained.

FIG. 1 is a development view showing a part of a lug-equipped tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a side view showing a part of the tire of FIG. 2. FIG. 4 is a cross-sectional view of a tire with lugs according to another embodiment of the present invention. FIG. 5 is a side view showing a part of the tire of FIG.

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

  FIG. 1 is a development view showing a part of a lug-equipped tire 2 according to the present invention. In FIG. 1, the vertical direction is the circumferential direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the radial direction of the tire 2. FIG. 2 is a cross-sectional view taken along line II-II in FIG. In FIG. 2, the up and down direction is the radial direction of the tire 2, the left and right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In the figure, the alternate long and short dash line CL represents the equator plane of the tire 2. In the figure, a solid line BBL represents a bead base line. The bead base line BBL corresponds to a line that defines the rim diameter (see JATMA) of the rim on which the tire 2 is mounted. The bead base line BBL extends in the axial direction. This lug-equipped tire 2 is attached to an agricultural machine. Examples of the agricultural machine include a tractor, a binder, a harvester, a combine, a rice transplanter, a transporter, and a tiller. The tire 2 may be attached to a light civil engineering construction machine.

  The tire 2 includes 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, the tire 2 includes a tube. This tube is filled with air.

  The tread 4 forms a tread surface 14 that contacts the ground. The tread 4 is made of a crosslinked rubber. The tread 4 includes a main body 16 and a lug 18. The main body 16 has a shape protruding outward in the radial direction. A lug 18 is formed on the outer side of the main body 16 in the radial direction. The lug 18 protrudes radially outward from the main body 16. A plurality of lugs 18 are provided. The outer surface 20 of the lug 18 in the radial direction has an outwardly convex shape. The outer surface 22 of the lug 18 in the axial direction extends substantially in the radial direction.

  In FIG. 2, the position TE is the end of the main body 16. The end TE of the main body 16 is a position where the outer surface 24 of the main body 16 and the outer surface 22 in the axial direction of the lug 18 intersect when a cross section perpendicular to the circumferential direction of the tire is viewed from the front. The end TE of the main body 16 at the position where the lug 18 is present has a virtual outer surface of the main body 16 when the lug 18 is not present and a surface 22 on the axially outer side of the lug 18 when this cross section is viewed from the front. Is the position where That is, in FIG. 2, the end TE2 of the main body 16 at the position where the lug 18 exists is a surface object with respect to the end TE1 of the main body 16 at the position where the lug 18 does not exist and the equator plane CL.

  As apparent from FIGS. 1 and 2, each lug 18 extends from the vicinity of the center of the main body 16 to the end TE of the main body 16. The lugs 18 extending from the vicinity of the center of the main body 16 to one end and the lugs 18 extending from the vicinity of the center of the main body 16 to the other end are alternately arranged. This lug 18 sinks into the mud constituting the farm field and scratches this mud. This lug 18 can contribute to the traction of the tire 2. The shape, interval, height, and the like of the lugs 18 are appropriately determined in consideration of the specifications of the tire 2 and the like.

  Each sidewall 6 extends from the end TE of the main body 16 substantially inward in the radial direction. The sidewall 6 is made of a crosslinked rubber. The sidewall 6 absorbs an impact from the road surface by bending. Furthermore, the sidewall 6 prevents the carcass 10 from being damaged. The vicinity of the boundary between the main body 16 and the sidewall 6 is a buttress portion of the tire 2.

  Each bead 8 is located substantially inward of the sidewall 6 in the radial direction. The bead 8 includes a core 26 and an apex 28 extending outward from the core 26 in the radial direction. The core 26 has a ring shape. The core 26 includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 28 is tapered outward in the radial direction. The apex 28 is made of a highly hard crosslinked rubber. In addition, this bead 8 may be comprised only with the core 26. FIG. In this case, the bead 8 does not include the apex 28.

  The carcass 10 includes a carcass ply 30. The carcass ply 30 is stretched between the beads 8 on both sides, and extends along the inside of the tread 4 and the sidewall 6. The carcass ply 30 is folded around the core 26 from the inner side to the outer side in the axial direction.

  Although not shown, the carcass ply 30 includes a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is usually 10 ° or more and 60 ° or less. In other words, the carcass 10 has a bias structure. The cord is usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  Each rib 12 is located near the boundary between the main body 16 and the sidewall 6. The rib 12 is located at the buttress portion of the tire 2. The rib 12 protrudes outward in the axial direction from the main body 16 or the sidewall 6. The rib 12 extends in the circumferential direction.

  FIG. 3 is a side view in which a part of the tire 2 of FIG. 2 is enlarged. In FIG. 3, a double arrow X indicates the circumferential direction of the tire 2, the direction perpendicular to the circumferential direction X is the radial direction of the tire 2, and the direction perpendicular to the paper surface is the axial direction of the tire 2. It is. In FIG. 3, only the side surface of the lug 18 is shown. In the figure, the alternate long and short dash line TE represents the end TE of the main body 16 at the position where the lug 18 exists.

  A portion of the rib 12 that overlaps the lug 18 in the radial direction when the tire 2 is viewed from the side is referred to as a first portion 12a. In detail, when the tire 2 is viewed from the side, the rib 12 has a portion overlapping the root of the lug 18 (radially inner end of the lug 18) in the radial direction and the lug 18. The part is the first part 12a. A portion of the rib 12 that does not overlap with the lug 18 is referred to as a second portion 12b. Of the rib 12, a portion other than the first portion 12a is the second portion 12b. In FIG. 3, three first portions 12a are shown. In FIG. 3, two second portions 12b and a part of the two second portions 12b are shown. In this embodiment, all the first portions 12a have the same shape. All the second portions 12b have the same shape.

  As shown in FIG. 3, the inner end 32 of the first portion 12 a is located on the sidewall 6 and the outer end 34 of the first portion 12 a is located on the lug 18. The inner end 36 of the second portion 12 b is located on the sidewall 6, and the outer end 38 of the second portion 12 b is located at the boundary between the main body 16 and the sidewall 6. In the radial direction, the inner end 32 of the first portion 12a and the inner end 36 of the second portion 12b are at the same position. In the radial direction, the outer end 34 of the first portion 12a is located outside the outer end 38 of the second portion 12b.

  In FIG. 3, a double arrow A is the width of the first portion 12a. Specifically, the width A is a distance between the inner end 32 and the outer end 34 of the first portion 12a in the radial direction. In FIG. 3, the double arrow B is the width of the second portion 12b. Specifically, the width B is a distance between the inner end 36 and the outer end 38 of the second portion 12b in the radial direction. In the tire 2, the width A is larger than the width B.

  Below, the effect of this invention is demonstrated.

  In a tire provided with a lug, the rubber thickness of the buttress portion in the portion where the lug is disposed may be reduced in the vulcanization process. A buttress portion with a thin rubber thickness can cause a decrease in durability. Furthermore, a buttress portion having a thin rubber thickness can be a cause of deterioration of the trauma resistance against an obstacle. In the vulcanization step, the rubber thickness of the buttress portion may be designed to be thick in order to prevent the rubber thickness of the buttress portion from becoming thin. Or the rib which protruded outside may be provided in a buttress part. In any tire, the rubber thickness is increased more than necessary in a portion where no lug exists. This leads to an increase in tire manufacturing costs and mass.

  In the lug-equipped tire 2 according to the present invention, the rib 12 protrudes outward in the axial direction and extends in the circumferential direction at the buttress portion. In the tire 2, the width A of the first portion 12a of the rib 12 is larger than the width B of the second portion 12b. The first portion 12a having a large width effectively prevents the buttress portion from being thinned at the position where the lug 18 is present. The tire 2 is excellent in durability and damage resistance. In this rib 12, since the width of the second portion 12b is small, the influence of the rib 12 on the manufacturing cost and mass of the tire 2 is suppressed. In the tire 2, an appropriate manufacturing cost and mass of the tire 2 are maintained.

  When an agricultural machine or a working machine travels in the field, mud adheres to the lug-equipped tire. If mud adheres to the side surface of the tire, the traction of the tire 2 decreases. If mud adheres to the side of the tire, the tire may slip. In the tire 2 with a lug according to the present invention, the rib 12 is provided in the buttress portion. The rib 12 makes it easier for mud adhered to the side surface of the tire 2 to fall off. In the tire 2, adhesion of mud to the side surface is suppressed. In the tire 2, a decrease in traction and a slip due to adhesion of mud are prevented.

  The rib 12 can be formed by changing the shape of the mold. The rib 12 can be formed by providing a recess corresponding to the rib 12 on the cavity surface of the mold. There is no need to add a special process for forming the rib 12. In the tire 2, good productivity is maintained.

  In FIG. 2, a double-headed arrow H represents the cross-sectional height of the tire 2. The height H is a height in the radial direction from the bead base line BBL to the outer end of the tread 4. In the tire 2, the ratio (A / H) of the width A to the height H is preferably 5% or more as a percentage. By setting the ratio (A / H) to 5% or more, the rib 12 effectively prevents the rubber thickness of the buttress portion from being reduced at the position where the lug 18 exists. The tire 2 is excellent in durability and damage resistance. Further, the rib 12 effectively prevents mud from adhering to the side surface of the tire 2. From this viewpoint, the ratio (A / H) is more preferably 7% or more. The ratio (A / H) is preferably 20% or less. By setting the ratio (A / H) to 20% or less, the influence of the rib 12 on the manufacturing cost and mass of the tire 2 is suppressed. In this respect, the ratio (A / H) is more preferably equal to or less than 15%.

  In the tire 2, the ratio (B / A) of the width B to the width A is preferably 30% or more as a percentage. By setting the ratio (B / A) to 30% or more, the rib 12 effectively reduces the rubber thickness of the buttress portion at both the position where the lug 18 exists and the position where the lug 18 does not exist. To prevent. The tire 2 is excellent in durability and damage resistance. In this respect, the ratio (B / A) is more preferably equal to or greater than 40%. The ratio (B / A) is preferably 80% or less. By setting the ratio (B / A) to 80% or less, the influence of the rib 12 on the manufacturing cost and mass of the tire 2 is suppressed. In this respect, the ratio (B / A) is more preferably equal to or less than 75%.

  The angle between the radially outer surface 20 of the lug 18 and the axially outer surface 22 of the lug 18 is referred to as the outer angle 40 of the lug 18. When this corner is rounded, the corner when this round is not present is the outer corner 40 of the lug 18. In FIG. 2, a double-headed arrow C is a radial height from the outer corner 40 of the lug 18 to the end TE of the main body 16. The double-headed arrow D is the radial height from the outer corner 40 of the lug 18 to the outer end 34 of the first portion 12a. The ratio of the height D to the height C (D / C) is preferably 0.8 or more, and preferably 1.2 or less. By doing in this way, this rib 12 effectively prevents the rubber thickness of the buttress portion from being reduced at the position where the lug 18 exists. The tire 2 is excellent in durability and damage resistance. In this respect, the ratio (D / C) is more preferably equal to or greater than 0.9 and more preferably equal to or less than 1.1.

  In FIG. 2, a double-headed arrow E is a height in the radial direction from the outer corner 40 of the lug 18 to the midpoint between the inner end 32 and the outer end 34 of the first portion 12a. The ratio of the height E to the height C (E / C) is preferably 0.9 or more, and preferably 1.4 or less. By doing in this way, this rib 12 effectively prevents the rubber thickness of the buttress portion from being reduced at the position where the lug 18 exists. The tire 2 is excellent in durability and damage resistance. In this respect, the ratio (E / C) is more preferably equal to or greater than 1.0 and is more preferably equal to or less than 1.3.

  In FIG. 2, the double arrow h is the height of the rib 12. Specifically, the height h is the maximum value of the distance between the virtual outer surface and the axially outer surface of the rib 12 measured along the normal line of the virtual outer surface of the tire 2 when the rib 12 is not present. The height h is preferably 1 mm or more. By setting the height h to 1 mm or more, the rib 12 effectively prevents the rubber thickness of the buttress portion from being reduced. The tire 2 is excellent in durability and damage resistance. Further, the rib 12 effectively prevents mud from adhering to the side surface of the tire 2. In this respect, the height h is more preferably 2 mm or more. The height h is preferably 8 mm or less. By setting the height h to 8 mm or less, the effect of the rib 12 on the manufacturing cost and mass of the tire 2 is suppressed. Further, mud remains on the side surface of the rib 12 is suppressed. Thereby, adhesion of mud on the side surface of the tire 2 is effectively suppressed. In this respect, the height h is more preferably 6 mm or less.

  In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 2. In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “Maximum air pressure” in JATMA standard, “maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures. The same applies to the following tires.

  FIG. 4 is a cross-sectional view showing a tire 52 according to another embodiment of the present invention. In FIG. 4, the vertical direction is the radial direction of the tire 52, the horizontal direction is the axial direction of the tire 52, and the direction perpendicular to the paper surface is the circumferential direction of the tire 52. The tire 52 includes a tread 54, a pair of sidewalls 56, a pair of beads 58, a carcass 60, and a pair of ribs 62. Although not shown, the tire 52 includes a tube. This tube is filled with air. The tire 52 is the same as the tire 2 in FIG. 2 except for the lug shape of the tread 54 and the ribs 62.

  The tread 54 includes a main body 66 and a lug 68. The main body 66 has a shape protruding outward in the radial direction. A lug 68 is formed on the outer side of the main body 66 in the radial direction. The lug 68 protrudes radially outward from the main body 66. A plurality of lugs 68 are provided. The radially outer surface 70 of the lug 68 has an outwardly convex shape. The outer surface 72 of the lug 68 in the axial direction extends substantially in the radial direction. In FIG. 4, the position TE (TE1 and TE2) is the end TE of the main body 66. Each lug 68 extends from the vicinity of the center of the main body 66 to the end TE of the main body 66. Lugs 68 extending from near the center of the main body 66 to one end and lugs 68 extending from near the center of the main body 66 to the other end are alternately arranged. This lug 68 sinks into the mud constituting the farm field and scratches this mud. The lug 68 can contribute to the traction of the tire 52. The shape, interval, height, and the like of the lug 68 are appropriately determined in consideration of the specifications of the tire 52 and the like.

  Each rib 62 is located in the vicinity of the boundary between the main body 66 and the sidewall 56. The rib 62 is located at the buttress portion of the tire 52. The ribs 62 protrude outward in the axial direction from the main body 66 or the sidewalls 56. The rib 62 extends in the circumferential direction.

  FIG. 5 is a side view in which a part of the tire 52 of FIG. 4 is enlarged. In FIG. 5, a double arrow X indicates the circumferential direction of the tire 52, the direction perpendicular to the circumferential direction X is the radial direction of the tire 52, and the direction perpendicular to the paper surface is the axial direction of the tire 52. .

  A portion of the rib 62 that overlaps the lug 68 in the radial direction when the tire 52 is viewed from the side surface is referred to as a first portion 62a. A portion of the rib 62 that does not overlap the lug 68 in the radial direction when the tire 52 is viewed from the side surface is referred to as a second portion 62b. As shown in FIG. 5, the inner end 72 and the outer end 74 of the first portion 62 a are located on the sidewall 56. The inner end 76 and the outer end 78 of the second portion 62 b are located on the sidewall 56. In the radial direction, the outer end 74 of the first portion 62a and the outer end 78 of the second portion 62b are at the same position. In the radial direction, the inner end 72 of the first portion 62a is located inside the inner end 76 of the second portion 62b. In this embodiment, all the first portions 62a have the same shape. All the second portions 62b have the same shape.

  In FIG. 5, the double arrow A is the width of the first portion 62a. The double arrow B is the width of the second portion 62b. In the tire 52, the width A is larger than the width B.

  In the lug-equipped tire 52 according to the present invention, the rib 62 protrudes outward in the axial direction and extends in the circumferential direction at the buttress portion. In the tire 52, the width A of the first portion 62a of the rib 62 is larger than the width B of the second portion 62b. The first portion 62a having a large width effectively prevents the rubber thickness of the buttress portion from being reduced at the position where the lug 68 is present. The tire 52 is excellent in durability and damage resistance. In the rib 62, since the width of the second portion 62b is small, the influence of the rib 62 on the manufacturing cost and mass of the tire 52 is suppressed. In the tire 52, an appropriate manufacturing cost and mass of the tire 52 are maintained.

  When an agricultural machine or a working machine travels in the field, mud adheres to the lug-equipped tire. If mud adheres to the side surface of the tire, the traction of the tire decreases. If mud adheres to the side of the tire, the tire may slip. In the tire 52 with a lug according to the present invention, the rib 62 is provided in the buttress portion. The rib 62 makes it easier for mud adhered to the side surface of the tire 52 to fall. In the tire 52, adhesion of mud to the side surface is suppressed. In the tire 52, a decrease in traction and a slip due to adhesion of mud are prevented.

  In FIG. 4, a double-headed arrow H represents the cross-sectional height of the tire 52. In the tire 52, the ratio (A / H) of the width A to the height H is preferably 5% or more, more preferably 7% or more in terms of percentage. The ratio (A / H) is preferably 20% or less, and more preferably 15% or less.

  In the tire 52, the ratio (B / A) of the width B to the width A is preferably 30% or more, more preferably 40% or more in terms of percentage. The ratio (B / A) is preferably 80% or less, and more preferably 75% or less.

  In FIG. 4, the double-headed arrow C is the radial height from the outer corner 80 of the lug 68 to the end TE of the main body 66. The double-headed arrow D is the height in the radial direction from the outer corner 80 of the lug 68 to the outer end 74 of the first portion 62a. The ratio of the height D to the height C (D / C) is preferably 0.8 or more, and preferably 1.2 or less. The ratio (D / C) is more preferably 0.9 or more, and more preferably 1.1 or less.

  In FIG. 4, the double-headed arrow E is the radial height from the outer corner 80 of the lug 68 to the midpoint between the inner end 72 and the outer end 74 of the first portion 62 a. The ratio of the height E to the height C (E / C) is preferably 0.9 or more, and preferably 1.4 or less. The ratio (E / C) is more preferably 1.0 or more, and more preferably 1.3 or less.

  In FIG. 4, the double arrow h is the height of the rib 62. The height h is preferably 1 mm or more, and more preferably 2 mm or more. The height h is preferably 8 mm or less, and more preferably 6 mm or less.

  As mentioned above, two types of embodiment was shown about the tire concerning the present invention. The shape of the rib is not limited to those shown here. The width A of the first part may be larger than the width B of the second part. For example, the inner end of the first part may be located inside the inner end of the second part, and the outer end of the first part may be located outside the outer end of the second part. Furthermore, in the embodiments shown so far, the shape of all the first parts was the same. The shape of all the second parts was the same. Depending on the location, the shape of the first portion may be different. Depending on the location, the shape of the second portion may be different.

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

[Example 1]
A tire with a lug of Example 1 having the configuration shown in FIGS. 4-5 was obtained. The size of this tire is 13.6-26-4PR. Table 1 shows the specifications of the tire ribs. In this tire, the ratio (A / H) is 6%.

[Comparative Example 1]
A tire with lugs was obtained in the same manner as in Example 1 except that the tire did not have ribs. This is a conventional tire with lugs.

[Example 2-5 and Comparative Example 2]
The lug-equipped tires of Example 2-5 and Comparative Example 2 were obtained in the same manner as in Example 1 except that the width B was changed as shown in Table 1 by changing the position of the inner end of the second part.

[Example 6-9]
A lug-equipped tire of Example 6-9 was obtained in the same manner as in Example 1 except that the rib height h was as shown in Table 2.

[mass]
The mass of the tire was measured. The results are shown in Table 1-2 below as index values with Comparative Example 1 as 100. It is shown that the smaller the numerical value, the smaller the mass. The smaller the value, the better.

[durability]
The tire was incorporated into a regular rim (26 × W11), and the tire was filled with air to adjust the internal pressure to 70 kPa. This tire was mounted on a running test machine, and a vertical load of 10.44 kN was applied to the tire. The tire was run on a drum at a speed of 20 km / h, and the running distance until the tire was damaged was measured. This result is shown in Table 1-2 as an index value with the result of Comparative Example 1 as 100. However, the test was terminated when no damage occurred when the vehicle traveled twice the distance of the tire of Comparative Example 1. Therefore, the maximum value of durability in Table 1-2 is 200. The larger the value, the better the durability. Larger numbers are preferable.

[Mud adhesion]
A prototype tire was mounted on an agricultural tractor (38 hp). The rim was 26 × W11 and the tire air pressure was 100 kPa. The paddy field before plowing (uncultivated land) was run straight and turned while rotary plowing with a tractor, and the adhesion of mud was evaluated. This evaluation result is shown in Table 1-2 as an index value with the mud adhesion amount of Comparative Example 1 being 100. The smaller this value is, the less mud adheres. The smaller this value, the better.

  As shown in Table 1-2, the tire of the example is superior in numerical value to the tire of the comparative example. From this evaluation result, the superiority of the present invention is clear.

  The tire according to the present invention can be mounted on various agricultural machines and light civil engineering construction machines.

2, 52 ... Tire 4, 54 ... Tread 6, 56 ... Sidewall 8, 58 ... Bead 10, 60 ... Carcass 12, 62 ... Rib 14 ... Tread surface 16 , 66... Main body 20, 70... Radial outer surface of lug 22, 72... Lug axially outer surface 24... External surface of main body 26. 30 ... Carcass ply 32,72 ... Inner end of first part 34,74 ... Outer end of first part 36,76 ... Inner end of second part 38,78 ... of second part Outer end 40, 80 ... Outer corner

Claims (5)

It has a tread, a pair of sidewalls and a pair of ribs,
The tread includes a main body and a plurality of lugs protruding outward from the main body,
Each lug extends from near the center of the main body to the end of the main body,
Each sidewall extends inward in the radial direction from the end of the main body,
Each rib protrudes outward in the axial direction in the vicinity of the boundary between the main body and the sidewall, and extends in the circumferential direction.
Of the ribs, when the tire is viewed from the side, the portion that overlaps the lug in the radial direction is the first portion, and the portion that does not overlap the lug in the radial direction is the second portion,
A tire with lugs in which the width A of the first part is larger than the width B of the second part.   The tire with a lug according to claim 1, wherein a ratio (A / H) of the width A to the tire cross-sectional height H is 5% or more and 20% or less.   The tire with a lug according to claim 1 or 2, wherein a ratio (B / A) of the width B to the width A is 30% or more and 80% or less.   When the angle between the outer surface in the radial direction and the outer surface in the axial direction of the lug is an outer angle, from the outer angle, the radial height D from the outer angle to the radially outer end of the first portion is The lug-equipped tire according to any one of claims 1 to 3, wherein a ratio (D / C) to a radial height C to an end of the main body is 0.8 or more and 1.2 or less.   The tire with a lug according to any one of claims 1 to 4, wherein a height of the rib is 1 mm or more and 8 mm or less.

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