JP2007161192A - Traveling body with lug - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire 2 with a lug capable, which suppresses deposition of mud without impairing traveling performance. <P>SOLUTION: The tire 2 with the lug is provided with a tread 4 having a body 14 and a large number of lugs 16 outwardly projected from the body 14. An outer surface 18 of the tread 4 is constituted of: an apex surface 20 of the lug 16; an inclination surface inwardly inclined/extended from the apex surface 20; and a lug bottom 24 spread along the body 14 from the inclination surface 22. The lug bottom 24 is provided with a large number of projections. A cross section area of the projection 26 is 0.8 mm<SP>2</SP>to 13.0 mm<SP>2</SP>. Length of the projection 26 is 3 mm to 10 mm. When a plane at which a base of the projection 26 is positioned is made to a reference surface, an angle of the projection 26 relative to the reference surface is 60° to 90°. A clearance of the projections 26 is 3.0 mm to 5.0 mm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a traveling body with a lug 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 traveling body with a lug in consideration of workability in wet fields and soft ground. The traveling body includes a lug tire and a lug crawler.

  In tires with lugs, the tread has a number of lugs. The lug extends from the vicinity of the equator plane toward the end of the tread on the rear side in the rotational direction. The lugs are alternately arranged on the left and right in the rotation direction. This lug protrudes substantially outward in the radial direction from the tread surface. Propulsion is generated by this mud scratching mud on soft ground such as wetlands. The traction force of this tire is ensured by this lug.

  When the working machine equipped with the tire travels on a soft ground, mud adheres to the tire. If mud adheres between the lugs, the mud may fill the gaps between the lugs. In such a tire, traction is reduced. If mud sticks between the lugs, the machine will get stuck. In addition to such a case, since the tire is rotating, the mud may be lifted upward and fall due to its own weight. If this machine is a rice transplanter, the seedlings that have just been planted will be covered with mud, broken, and fallen. If this machine travels on a paved road with mud attached to the tire, the road may be soiled. If the mud is dried while attached to the tire, it may be difficult to remove the mud during car washing.

JP-A-8-268011 discloses a traveling body with a lug in which the adhesion of mud is suppressed without impairing traction. In this traveling body, a large number of cuts are formed in the tread surface located between the lugs.
JP-A-8-268011

  There is a tire in which a foamed rubber layer is provided on the surface of the tire in order to suppress adhesion of mud. This tire has a problem that its durability is inferior because the foamed rubber layer is worn during running.

  In order to suppress adhesion of mud, some tires have a large number of recesses on the surface of the tire. In this tire, since the movement of the tire surface is small, mud is clogged in the concave portion at a stage immediately after the start of traveling. The effect of preventing adhesion of mud by the recess is small.

  An object of the present invention is to provide a traveling body with a lug in which adhesion of mud is suppressed without impairing traveling performance.

The traveling body with a lug according to the present invention includes a tread having a main body and a number of lugs protruding outward from the main body. The outer surface of the tread is composed of a top surface of the lug, an inclined surface extending inwardly inclined from the top surface, and a lug bottom extending from the inclined surface along the main body. The lug bottom has a number of protrusions. Sectional area of the projection is 0.8 mm ² or more 13.0 mm ² or less. The length of this protrusion is 3 mm or more and 10 mm or less. When the plane on which the base of this protrusion is located is used as the reference plane, the angle formed by this protrusion with respect to the reference plane is 60 ° or more and 90 ° or less. The interval between the protrusions is 3.0 mm or greater and 5.0 mm or less.

  Preferably, in the traveling body, the inclined surface includes a large number of the protrusions. Preferably, in the traveling body, the protrusion is made of a crosslinked rubber. The hardness (durometer A hardness) of this protrusion is 50 or more and 90 or less.

This traveling body with a lug supports the body of the working machine. The traveling body is loaded with the load of the aircraft. The protrusion is a crosslinked rubber. This protrusion is deformed by this load, and is restored by removing the load. The mud adhering to the traveling body is separated from the traveling body by the restoring force of the protrusion. In this traveling body, the cross-sectional area of the projection is a 0.8 mm ² or more 13.0 mm ² or less, the projection is excellent in deformation recovery property. This protrusion does not pierce the mud. In this traveling body, since the length of the protrusion is 3 mm or more and 10 mm or less, the protrusion is excellent in deformation recovery property. Mud does not entangle with this protrusion. In this traveling body, the angle formed by the protrusion with respect to the reference surface is set to 60 ° or more and 90 ° or less, and thus the protrusion is excellent in deformation recovery property. In this traveling body, since the interval between the projections is set to 3.0 mm or more and 5.0 mm or less, mud cannot enter between the projections. In this traveling body, the shape and interval of the protrusions are optimized. This protrusion effectively suppresses adhesion of mud. In this traveling body, since the rigidity of the tread and the lug can be set to be equal to or higher than that of the conventional traveling body, the traveling performance of the traveling body is not impaired.

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

  FIG. 1 is a developed view showing a part of a lug-equipped tire 2 as a running body with a lug 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 partially enlarged cross-sectional view taken along line III-III in FIG. In FIG. 1, the left-right direction is the axial direction of the tire 2. What is indicated by an arrow A is the rotation direction of the tire 2. In FIG. 2, the vertical direction is the radial direction of the tire 2, and the horizontal direction is the axial direction of the tire 2. The lower side of FIG. 3 represents the outward direction of the tire 2 in the radial direction. An alternate long and short dash line CL in FIGS. 1 and 2 represents the equator plane of the tire 2. The tire 2 has a substantially bilaterally symmetric shape around the equator plane.

  The 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 such as a trencher and a dozer.

  The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, and a belt 12. Although not shown, the tire 2 includes a tube. This tube is filled with air.

  The tread 4 is made of a crosslinked rubber and has a shape protruding outward in the radial direction. The tread 4 includes a main body 14 and a large number of lugs 16 that protrude from the main body 14 substantially outward in the radial direction. The lug 16 extends rearward in the rotational direction from the vicinity of the equator plane toward the end of the tread 4. The lugs 16 are alternately arranged on the left and right in the rotation direction. The lug 16 scratches the mud to generate a driving force. The lug 16 ensures the traction force of the tire 2. The shape, interval, height, and the like of the lugs 16 are appropriately determined in consideration of adhesion of mud to the tire 2, traction force of the tire 2, and the like.

  The outer surface 18 of the tread 4 includes a top surface 20 of the lug 16, an inclined surface 22, and a lug bottom 24. The inclined surface 22 extends from the top surface 20 so as to be inclined substantially inward in the radial direction. The lug bottom 24 extends from the inclined surface 22 along the main body 14. On a smooth road surface such as a paved road, the top surface 20 contacts the road surface. The inclined surface 22 and the lug bottom 24 do not contact the road surface. On a soft ground such as a wet field, the lug 16 scratches the mud, so that the inclined surface 22 and the lug bottom 24 come into contact with the mud. In the tire 2, the lug bottom 24 includes a large number of protrusions 26.

  The protrusion 26 protrudes from the lug bottom 24 substantially outward in the radial direction. The protrusion 26 has a cylindrical shape. The protrusion 26 is made of a crosslinked rubber. The protrusion 26 is deformed when a load is applied, and is restored when the load is removed. In the tire 2, the protrusion 26 is made of the same material as the tread 4. The protrusion 26 may be made of a material different from that of the tread 4.

  The protrusions 26 are regularly arranged on the lug bottom 24. In the tire 2, the axial interval between the protrusions 26 and the rotational interval are the same. Note that the number, interval, shape, and the like of the protrusions 26 arranged on the lug bottom 24 are appropriately determined in consideration of adhesion of mud to the tire 2.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The sidewall 6 is made of a crosslinked rubber. The sidewall 6 absorbs an impact from the road surface by bending. Further, the sidewall 6 prevents the carcass 10 from being damaged.

  The bead 8 extends from the sidewall 6 substantially inward in the radial direction. The bead 8 includes a core 28 and an apex 30 that extends radially outward from the core 28. The core 28 has a ring shape and includes a plurality of non-stretchable wires (typically steel wires). The apex 30 has a tapered shape that tapers outward in the radial direction, and is made of a highly hard crosslinked rubber.

  The carcass 10 includes a first carcass ply 32 and a second carcass ply 34. The first carcass ply 32 and the second carcass ply 34 are bridged between the beads 8 on both sides, and are along the inside of the tread 4 and the sidewall 6. The first carcass ply 32 and the second carcass ply 34 are wound around the core 28 from the inner side to the outer side in the axial direction. One carcass ply may be used for the carcass 10. Three or more carcass plies may be used.

  Although not shown, the first carcass ply 32 is composed of a first cord and a topping rubber. The absolute value of the angle formed by the first cord with respect to the equator plane is usually 10 ° or more and 60 ° or less. The second carcass ply 34 includes a second cord and a topping rubber. The absolute value of the angle formed by the second cord with respect to the equator plane is usually 10 ° or more and 60 ° or less. In the tire 2, the angle formed by the first cord with respect to the equator plane is opposite to the angle formed by the second cord with respect to the equator plane. The first cord and the second cord are usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The belt 12 includes a belt ply 36. The belt ply 36 is located on the inner side in the radial direction of the tread 4. The belt ply 36 is laminated on the outer side in the radial direction of the carcass 10. The belt ply 36 reinforces the carcass 10. Two or more belt plies 36 may be used for the belt 12.

  Although not shown, the belt ply 36 is composed of a belt cord and a topping rubber. The absolute value of the angle formed by the belt cord with respect to the equator plane is usually 10 ° or more and 60 ° or less. Examples of a preferable material for the belt cord include steel and organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  FIG. 4 is a partially enlarged sectional view showing a state where the tire 2 of FIG. 1 is in contact with the ground 38. FIG. 4 shows a part of the tread 4 of the tire 2 and a ground 38 made of mud. The arrow line B represents the direction of the load applied to the tire 2. An arrow line C represents the rotation direction of the tire 2. The tire 2 supports the airframe. The tire 2 is loaded with the load of the machine body. When the projection 26 is in a position in contact with the ground 38, the projection 26 is deformed by this load. As shown in FIG. 4, the protrusion 26 falls backward in the rotational direction. The vicinity of the tip 40 of the protrusion 26 is in contact with the side surface 42 of the adjacent protrusion 26. The protrusion 26 covers the lug bottom 24. A space 44 is formed between the lug bottom 24 and the mud. In the tire 2, the lug bottom 24 does not come into direct contact with the ground 38.

  When the tire 2 rotates and deviates from a position where the protrusion 26 contacts the ground 38, the load applied to the protrusion 26 is removed. This protrusion 26 is restored. In the tire 2, the mud adhered to the tire 2 is separated from the tire 2 by the restoring force of the protrusions 26. In the tire 2, adhesion of mud is suppressed.

  In the tire 2, since mud adherence is suppressed, the lugs 16 continue to scrape the mud stably. Traction does not decrease during driving. Even if an agricultural machine equipped with the tire 2 runs on a paved road, the paved road is not soiled with mud.

  In the tire 2, the height at which the mud is separated from the tire 2 is low. The mud is not lifted above the tire 2. The impact when the mud separated from the tire 2 falls on the ground 38 is small. In the tire 2, seedlings and the like that have just been planted are not damaged by mud splashes or the like.

  As described above, in the tire 2, the protrusion 26 can be formed of the same material as the tread 4. In the production of the tire 2, a special process for forming the protrusions 26 is not necessary. In the tire 2, adhesion of mud is effectively suppressed without increasing the production cost. Since the rigidity of the tread 4 and the lug 16 can be set equal to or higher than that of the conventional tire, the performance such as traction force and durability of the tire 2 can be maintained equal to or higher than that of the conventional tire. In the tire 2, the running performance is not impaired.

In the tire 2, the protrusion 26 satisfies the following conditions.
(1) cross-sectional area of the projection 26 is 0.8 mm ² or more 13.0 mm ² or less.
(2) The length of the protrusion 26 is 3 mm or more and 10 mm or less.
(3) When the plane on which the root of the projection 26 is located is the reference plane, the angle formed by the projection 26 with respect to the reference plane is not less than 60 ° and not more than 90 °.
(4) The interval between the protrusions 26 is 3.0 mm or greater and 5.0 mm or less.

  FIG. 5 is a partially enlarged cross-sectional view showing the tire 2 of FIG. FIG. 5 shows an enlarged part of FIG. The lower side of FIG. 5 represents the outward direction of the tire 2 in the radial direction. FIG. 5 shows the protrusion 26 in a state where no load is applied. An alternate long and short dash line ML represents the main axis of the protrusion 26. The solid line TL passes through the base 46 of the protrusion 26. In this specification, the plane on which the base 46 of the protrusion 26 is located is the reference surface 48 of the protrusion 26. This solid line TL represents the reference plane 48. The reference surface 48 coincides with the lug bottom 24 in the protrusion 26. The area of the reference surface 48 is the cross-sectional area of the protrusion 26. A double arrow line HA represents a height from the reference surface 48 to the tip 40 of the protrusion 26. This height HA is the length of the protrusion 26. The angle α is an angle formed by the main axis ML of the protrusion 26 with respect to the reference plane 48. This angle α is the minimum angle that the main axis ML forms with respect to the reference plane 48. The upper limit value of the angle α is 90 °. A double arrow line LA is an interval between the protrusions 26. The interval LA between the protrusions 26 is represented by the distance between the bases 46 of the adjacent protrusions 26.

By setting the cross-sectional area of the protrusion 26 to 0.8 mm ² or more, the rigidity of the protrusion 26 increases. The restoring force of the protrusion 26 is increased. The protrusions 26 are excellent in deformation recovery properties. In the tire 2, adhesion of mud is suppressed. In this respect, the cross-sectional area, more preferably 1.0 mm ² or more, 2.0 mm ² or more is particularly preferable. By setting the cross-sectional area to 13.0 mm ² or less, it is possible to prevent the rigidity of the protrusion 26 from becoming excessive. This protrusion 26 does not pierce the mud. The deformation / restorability of the protrusion 26 can be maintained. In this respect, the cross-sectional area is more preferably 12.0 mm ² or less, 10.0 mm ² or less is particularly preferred.

  When the length HA of the protrusion 26 is set to 3 mm or more, the protrusion 26 is appropriately deformed. When the projection 26 comes into contact with the ground 38, the projection 26 effectively covers the lug bottom 24. In the tire 2, adhesion of mud is suppressed. In this respect, the length HA is more preferably 4 mm or more, and particularly preferably 5 mm or more. By setting the length HA to 10 mm or less, the entanglement of mud on the protrusions 26 is suppressed. In the tire 2, adhesion of mud is suppressed. In this respect, the length HA is more preferably 9 mm or less, and particularly preferably 8 mm or less.

  When the angle α is set to 60 ° or more, the protrusion 26 is appropriately deformed. The restoring force of the protrusion 26 is large. The protrusions 26 are excellent in deformation recovery properties. In the tire 2, adhesion of mud is suppressed. In this respect, the angle α is more preferably 70 ° or more, and further preferably 80 ° or more. When the angle α is 90 °, the amount that the protrusion 26 can be deformed by the load becomes the maximum. The restoring force of the protrusion 26 is also maximized. From this point of view, the angle α is particularly preferably 90 °.

  By setting the interval LA between the protrusions 26 to 3 mm or more, interference between adjacent protrusions 26 can be suppressed. When the projection 26 comes into contact with the ground 38, the projection 26 effectively falls in the half rotation direction. This protrusion 26 effectively covers the lug bottom 24. In the tire 2, adhesion of mud is suppressed. In this respect, the distance LA is more preferably equal to or greater than 3.1 mm, and particularly preferably equal to or greater than 3.2 mm. By setting the distance LA to 5.0 mm or less, in the tire 2 in which mud cannot enter between the protrusions 26, mud adhesion is suppressed. In this respect, the distance LA is more preferably 4.5 mm or less, and particularly preferably 4.0 mm or less.

  In the tire 2, the number of all the protrusions 26 is 5000 or more and 300000 or less. By setting the number of all the protrusions 26 to 5000 or more, mud cannot enter between the protrusions 26. In the tire 2, adhesion of mud is suppressed. In this respect, the number of all the protrusions 26 is more preferably 10,000 or more, and particularly preferably 20,000 or more. By setting the number of all the protrusions 26 to 300000 or less, interference between the adjacent protrusions 26 can be suppressed. When the projection 26 comes into contact with the ground 38, the projection 26 effectively falls in the half rotation direction. This protrusion 26 effectively covers the lug bottom 24. In the tire 2, adhesion of mud is suppressed. In this respect, the number of all the protrusions 26 is more preferably 200000 or less, and particularly preferably 100000 or less.

  In the tire 2, the ratio of the number of protrusions 26 that satisfies all of the above-described conditions (1) to (4) to the number of all protrusions 26 is 0.3 or more. By setting this ratio to 0.3 or more, the protrusions 26 effectively suppress mud adhesion. In this respect, the ratio is more preferably equal to or greater than 0.4, and particularly preferably equal to or greater than 0.5. Since it is particularly preferable that all the protrusions 26 satisfy all the conditions (1) to (4), the upper limit value of this ratio is 1.0.

  In the tire 2, it is preferable that the hardness (durometer A hardness) of the crosslinked rubber constituting the protrusion 26 is 50 or more and 90 or less. By setting the hardness to 50 or more, the rigidity of the protrusion 26 is increased. The restoring force of the protrusion 26 is increased. The protrusions 26 are excellent in deformation recovery properties. In the tire 2, adhesion of mud is suppressed. In this respect, the hardness is more preferably equal to or greater than 52, and particularly preferably equal to or greater than 55. By setting the hardness to 90 or less, it is possible to suppress the rigidity of the protrusion 26 from becoming excessive. This protrusion 26 does not pierce the mud. The deformation / restorability of the protrusion 26 can be maintained. In this respect, the hardness is more preferably 88 or less, and particularly preferably 85 or less.

  In the present invention, the hardness is measured by a type A durometer according to JIS-K6253. For this measurement, a test piece formed by crosslinking the rubber composition constituting the protrusions 26 is used. This test piece is obtained by holding the rubber composition in a mold having a temperature of 160 ° C. for 10 minutes. This hardness is measured under conditions where the temperature is 25 ° C.

  FIG. 6 is a developed view showing a part of a tire 50 with lugs as a running body with lugs according to another embodiment of the present invention. FIG. 7 is a partially enlarged sectional view taken along line VII-VII in FIG. In FIG. 6, the left-right direction is the axial direction of the tire 50. What is indicated by an arrow A is the rotational direction of the tire 50. The downward direction in FIG. 7 represents the outward direction of the tire 50 in the radial direction. 6 and 7 show the tread 52 of the tire 50. FIG. The tire 50 has the same configuration as the tire 2 in FIG. 1 except for the tread 52. 6 represents the equator plane of the tire 50. In FIG. The tire 50 has a substantially bilaterally symmetrical shape with the equator plane as the center.

  The tread 52 is made of a crosslinked rubber and has a shape protruding outward in the radial direction. The tread 52 includes a main body 54 and a large number of lugs 56 protruding from the main body 54 substantially outward in the radial direction. The lug 56 extends rearward in the rotational direction from the vicinity of the equator plane toward the end of the tread 52. The lugs 56 are alternately arranged on the left and right in the rotation direction. The lug 56 scratches the mud to generate a driving force. The lug 56 ensures the traction force of the tire 50.

  The outer surface 58 of the tread 52 includes a top surface 60 of the lug 56, an inclined surface 62, and a lug bottom 64. The inclined surface 62 extends from the top surface 60 so as to be inclined substantially inward in the radial direction. The lug bottom 64 extends from the inclined surface 62 along the main body 54. On a smooth road surface such as a paved road, the top surface 60 contacts the road surface. The inclined surface 62 and the lug bottom 64 do not contact the road surface. On the soft ground, the lugs 56 scrape the mud, so that the inclined surface 62 and the lug bottom 64 come into contact with the mud. In the tire 50, the inclined surface 62 and the lug bottom 64 are provided with a number of protrusions 66. The protrusions 66 are regularly arranged on the inclined surface 62 and the lug bottom 64. The protrusion 66 is made of a crosslinked rubber. The protrusion 66 is deformed when a load is applied, and is restored when the load is removed. The shape and the like of the protrusion 66 are the same as those of the tire 2 in FIG.

  In the tire 50, when the protrusion 66 is in a position in contact with the ground, a load is applied to the protrusion 66, so that the protrusion 66 is deformed. Although not shown, like the tire 2 in FIG. 1, the protrusion 66 falls backward in the rotational direction, and the tip 68 of the protrusion 66 contacts the side surface 70 of the adjacent protrusion 66. The protrusion 66 covers the inclined surface 62 and the lug bottom 64. A space is formed between the inclined surface 62 and the ground. A space is formed between the lug bottom 64 and the ground. In the tire 50, the inclined surface 62 and the lug bottom 64 are not in direct contact with the ground. When the tire 50 rotates and deviates from the position where the protrusion 66 contacts the ground, the load applied to the protrusion 66 is removed. This protrusion 66 is restored. In the tire 50, the mud adhered to the tire 50 is separated from the tire 50 by the restoring force of the protrusion 66. In the tire 50, adhesion of mud is suppressed. In this tire 50, since the protrusion 66 is also arranged on the inclined surface 62, adhesion of mud is suppressed more than in the tire 2 in FIG.

  In this tire 50, since the adhesion of mud is suppressed, the lug 56 continues to scrape the mud stably. While traveling, there is no reduction in traction due to mud adhesion. Even if an agricultural machine equipped with the tire 50 travels on a paved road, the paved road is not soiled with mud.

  In the tire 50, the height at which the mud is separated from the tire 50 is low. The mud is not lifted above the tire 50. The impact when the mud separated from the tire 50 falls to the ground is small. In the tire 50, seedlings and the like that have just been planted are not damaged by mud splashes or the like.

  As described above, in the tire 50, the protrusion 66 can be formed of the same material as the tread 52. In the production of the tire 50, a special process for forming the protrusion 66 is not necessary. In the tire 50, the adhesion of mud is effectively suppressed without increasing the production cost. Since the rigidity of the tread 52 and the lug 56 can be set to be equal to or higher than that of the conventional tire 50, performance such as traction force and durability of the tire 50 can be maintained to be equal to or higher than that of the conventional tire 50. In the tire 50, running performance is not impaired.

  The dimensions and angles of the tires 2 and 50 are measured in a state where the tires 2 and 50 are incorporated in a regular rim and the tires 2 and 50 are filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tires 2 and 50. In the present specification, the normal rim means a rim defined in a standard on which the tires 2 and 50 depend. “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 tires 2 and 50 depend. “Maximum air pressure” in the JATMA standard, “maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and “INFLATION PRESSURE” in the ETRTO standard are normal internal pressures.

  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 basic configuration shown in FIGS. 1 and 2 and having the specifications shown in Table 1 below was obtained. The tire size is 9.5-22 4PR. For the carcass, a first carcass ply and a second carcass ply were used. The material of the first cord used in the first carcass ply is nylon fiber. The angle formed by the first cord with respect to the equator plane is 35 °. The material of the second cord used for the second carcass ply is nylon fiber. The angle formed by the second cord with respect to the equator plane is 35 °. The angle formed by the first cord with respect to the equator plane is opposite to the angle formed by the second cord with respect to the equator plane. A belt ply was used for the belt. The material of the belt cord used for this belt ply is nylon fiber. The angle formed by the belt cord with respect to the equator plane is 30 °. The protrusion is disposed on the lug bottom. The hardness (durometer A hardness) of this protrusion is 59. The cross-sectional area of this protrusion is 2.3 mm ² . The length HA of this protrusion is 6 mm. An angle α formed by the protrusion with respect to the reference surface of the protrusion is 90 °. The distance LA between the protrusions is 3.3 mm.

[Comparative Examples 5 and 6 and Examples 4 and 5]
A lug-equipped tire was obtained in the same manner as in Example 1 except that the cross-sectional area of the protrusions was as shown in Table 1 below.

[Comparative Examples 4 and 7 and Example 6]
A lug-equipped tire was obtained in the same manner as in Example 1 except that the protrusion interval LA was as shown in Table 1 below.

[Comparative Examples 2 and 9 and Examples 3, 7 and 8]
A lug-equipped tire was obtained in the same manner as in Example 1 except that the length HA of the protrusions was as shown in Table 1 below.

[Comparative Example 1 and Example 2]
A lug-equipped tire was obtained in the same manner as in Example 1 except that the angle α was as shown in Table 1 below.

[Comparative Examples 3 and 8]
A lug-equipped tire was obtained in the same manner as in Example 1 except that the cross-sectional area of the protrusions and the interval LA between the protrusions were as shown in Table 1 below.

[Example 9]
A lug-equipped tire was obtained in the same manner as in Example 1 except that the protrusions were disposed on the inclined surface and the lug bottom.

[Comparative Example 10]
Comparative Example 10 is a conventional tire with lugs. The tire tread has no protrusions. The tread has a hardness (type A durometer) of 59.

[Evaluation of adhesion of mud]
A prototype tire was mounted on an agricultural tractor. The rim was 22 × W11 and the tire air pressure was 140 kPa. A running test was conducted on a test course that simulated fields and wetlands. After running this agricultural tractor for a predetermined time, the mass of mud adhering to the prototype tire was measured. This evaluation result is represented by a relative value in which the result of Comparative Example 11 is 100. It shows that adhesion of mud is suppressed, so that this figure is small. The results are shown in Tables 1 and 2 below. The ratio of the mass of moisture contained in the mud to the mass of mud in the test course is 18%.

  As shown in Table 1 and Table 2, in the tire with a lug of the example, adhesion of mud is effectively suppressed. From this evaluation result, the superiority of the present invention is clear.

  The traveling body with a lug according to the present invention can be mounted on various agricultural machines and light civil engineering construction machines.

FIG. 1 is a development view showing a part of a tire with lugs as a running body with lugs 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 partially enlarged cross-sectional view taken along line III-III in FIG. FIG. 4 is a partially enlarged sectional view showing a state where the tire of FIG. 1 is in contact with the ground. FIG. 5 is a partially enlarged cross-sectional view showing the tire of FIG. FIG. 6 is a development view showing a part of a lug tire as a lug traveling body according to another embodiment of the present invention. FIG. 7 is a partially enlarged sectional view taken along line VII-VII in FIG.

Explanation of symbols

2, 52 ... tire 4, 54 ... tread 6 ... sidewall 8 ... bead 10 ... carcass 12 ... belt 14, 56 ... main body 16, 58 ... lug 18 , 60 ... outer surface 20, 62 ... top surface 22, 64 ... inclined surface 24, 66 ... lug bottom 26, 68 ... projection 28 ... core 30 ... apex 32 .... First carcass ply 34 ... Second carcass ply 36 ... Belt ply 38 ... Ground 40, 50, 70 ... Tip 42, 72 ... Side 44 ... Space 46 ... Base 48 ... Reference plane

Claims (3)

A tread having a main body and a number of lugs projecting outward from the main body;
The outer surface of the tread is composed of a top surface of the lug, an inclined surface extending inwardly inclined from the top surface, and a lug bottom extending from the inclined surface along the main body.
This lug bottom has a number of protrusions,
Sectional area of the projections, is a 0.8 mm ² or more 13.0 mm ² or less,
The length of this protrusion is 3 mm or more and 10 mm or less,
When the plane on which the root of this protrusion is located is the reference plane, the angle formed by this protrusion with respect to the reference plane is 60 ° or more and 90 ° or less,
A traveling body with lugs in which the distance between the protrusions is 3.0 mm or greater and 5.0 mm or less.   The traveling body according to claim 1, wherein the inclined surface includes a plurality of the protrusions. The protrusion is made of a crosslinked rubber,
The traveling body according to claim 1 or 2, wherein the hardness (durometer A hardness) of the protrusion is 50 or more and 90 or less.

Images