JP2014159178A - Tire for rough terrain running vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motorcycle tire 2 for rough terrain which can be manufactured easily and is good in traction performance.SOLUTION: A tire tread includes many blocks 24. The block 24 includes a land 40, two first side surfaces 42 and two second side surfaces 44. The block 24 further includes two first peripheral edge ridges 46, two second peripheral edge ridges 48 and four corner ridges 50. Each of the first peripheral edge ridges 46 is located between the land 40 and the first side surfaces 42. Each of the second peripheral edge ridges 48 is located between the land 40 and the second side surfaces 44. Each of the corner ridges 50 is located between the first side surfaces 42 and the second side surfaces 44. Each ridge has a width of 2.00 mm or more and 3.00 mm or less and a height of 2.00 mm or more and 3.00 mm or less.

Description

  The present invention relates to a tire for a rough terrain vehicle. In particular, the present invention relates to an improvement in the tread of this tire.

  A motorcycle tire traveling on rough terrain such as a mountain forest has a tread having a block pattern. This block pattern includes a large number of blocks. Due to the edge effect of these blocks, the tire exhibits excellent traction performance on rough terrain.

  Japanese Unexamined Patent Application Publication No. 2008-279996 discloses a motorcycle tire for rough terrain in which a concave portion is formed on the ground contact surface of the block. In this tire, the edge effect is enhanced by the recess.

JP 2008-279996 A

  The mold for a tire disclosed in Japanese Patent Application Laid-Open No. 2008-279996 has a complicated shape. In the crosslinking / molding process using this mold, air tends to remain between the cavity surface and the raw cover (uncrosslinked tire). The remaining air causes a bear on the surface of the tire. In the manufacture of tires using this mold, the defect rate is high.

  An object of the present invention is to provide a tire for a rough terrain vehicle that is easy to manufacture and excellent in traction performance.

  The rough terrain vehicle tire according to the present invention includes a tread having a number of blocks. Each block includes a land, a side surface, and a ridge positioned between the land and the side surface. The cross-sectional shape of this ridge is an arc. The ridge has a width of 2.0 mm to 3.0 mm and a height of 2.0 mm to 3.0 mm.

  Preferably, the block includes a first side surface, a second side surface, and a ridge positioned between the first side surface and the second side surface.

  According to another aspect, the tire mold according to the present invention includes a vent hole and a recess that is present in the cavity surface and for molding the block. The recess has a bottom surface, an inner wall, and a groove located between the bottom surface and the inner wall. The vent hole has an opening in a groove in the vicinity of the bottom corner.

  Since the tire for rough terrain vehicle according to the present invention includes a ridge, the traction performance is excellent. The shape of the mold for this tire is simple. In this mold, air hardly remains. The defective rate of this tire is small.

FIG. 1 is a cross-sectional view illustrating a portion of a tire for a rough terrain vehicle according to an embodiment of the present invention. FIG. 2 is an enlarged perspective view showing a part of the tread surface of the tire of FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is a cross-sectional view showing a part of a mold for forming the tire of FIG. FIG. 7 is an enlarged cross-sectional view showing the mold viewed from the direction of arrow VII in FIG.

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

  FIG. 1 shows a motorcycle tire 2 as a tire for a rough terrain vehicle. The tire 2 travels in a forest, a wilderness or the like. The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 12, a chafer 14, and an inner liner 16. The tire 2 is a tube type. In FIG. 1, the vertical direction is the radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. The tire 2 has a substantially left-right symmetric shape centered on a one-dot chain line CL in FIG. This alternate long and short dash line CL represents the equator plane of the tire 2.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 includes a tread surface 18. The tread 4 includes a base 20 and a cap 22. The base 20 is made of a crosslinked rubber. The cap 22 is located outside the base 20 in the radial direction. The cap 22 is made of a crosslinked rubber.

  The cap 22 includes a number of blocks 24 that protrude substantially outward in the radial direction. Adjacent blocks 24 are separated by a recess 26. The recess 26 and the numerous blocks 24 form a toledo pattern. The ratio of the area of the block 24 to the area of the recess 26 on the tread surface 18 is referred to as a land / sea ratio. From the viewpoint of durability and grip properties, the land / sea ratio is preferably 10/90 or more and 30/70 or less.

  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. Furthermore, the sidewall 6 prevents the carcass 10 from being damaged. In the present embodiment, the material of the sidewall 6 is the same as the material of the base 20. The sidewall 6 and the base 20 are integrally formed.

  The bead 8 is located substantially inward of the sidewall 6 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. In the core 28, the non-stretchable wire is wound many times. A typical material for non-stretchable wire is steel. The apex 30 is tapered outward in the radial direction.

  The carcass 10 includes a first ply 32 and a second ply 34. The first ply 32 and the second ply 34 are bridged between the beads 8 on both sides, and extend along the inside of the tread 4 and the sidewall 6. The first ply 32 is laminated on the inner liner 16. The first ply 32 is folded around the core 28 from the inner side to the outer side in the axial direction. The second ply 34 is laminated on the first ply 32. The second ply 34 is folded around the core 28 from the inner side to the outer side in the axial direction.

  Although not shown, the first ply 32 and the second ply 34 are composed of 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 65 ° to 90 °. In other words, the carcass 10 has a radial structure. When the absolute value of the inclination angle is less than 90 °, the inclination direction of the cord of the first ply 32 is opposite to the inclination direction of the cord of the second ply 34.

  In the tire 2, the cord of each ply is usually made of an organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The belt 12 is located on the radially outer side of the carcass 10. The belt 12 is laminated with the carcass 10. The belt 12 reinforces the carcass 10. The belt 12 includes an inner layer 36 and an outer layer 38. In the cross section shown in FIG. 1, the inner layer 36 and the outer layer 38 extend in the axial direction. The inner layer 36 and the outer layer 38 overlap in the radial direction. The inner layer 36 is laminated on the outer side in the radial direction of the carcass 10. The outer layer 38 is laminated on the radially outer side of the inner layer 36.

  Although not shown, each of the inner layer 36 and the outer layer 38 is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The absolute value of the tilt angle is not less than 10 ° and not more than 35 °. The cord inclination direction of the inner layer 36 is opposite to the cord inclination direction of the outer layer 38. As this cord, a cord made of an organic fiber is preferably used. The cord material may be steel.

  In FIG. 2-5, block 24 is shown. In FIG. 5, the left-right direction is the axial direction of the tire 2, and the up-down direction is the circumferential direction of the tire 2. The block 24 includes a land 40, two first side surfaces 42, and two second side surfaces 44. The land 40 coincides with the tread surface 18. In the present embodiment, the land 40 is generally rectangular. The land 40 may have other shapes. In the present embodiment, each first side surface 42 extends substantially along the axial direction. In the present embodiment, each second side surface 44 extends substantially along the circumferential direction.

  The block 24 further includes two first peripheral ridges 46, two second peripheral ridges 48 and four corner ridges 50. Each first peripheral ridge 46 is located between the land 40 and the first side surface 42. In the present embodiment, the first peripheral ridge 46 extends substantially along the axial direction. Each second peripheral ridge 48 is located between the land 40 and the second side surface 44. In the present embodiment, the second peripheral ridge 48 extends substantially along the circumferential direction. Each corner ridge 50 is located between the first side surface 42 and the second side surface 44.

  In FIG. 3, the left-right direction is the circumferential direction. As shown in FIG. 3, the surface shape of the first peripheral ridge 46 in a cross section perpendicular to the length direction is an arc shape. The first peripheral ridge 46 protrudes from the first side surface 42 in the circumferential direction and protrudes from the land 40 in the radial direction.

  In FIG. 4, the left-right direction is the axial direction. As shown in FIG. 4, the surface shape of the second peripheral ridge 48 in the cross section perpendicular to the length direction is an arc shape. The second peripheral ridge 48 protrudes from the second side surface 44 in the axial direction and protrudes from the land 40 in the radial direction.

  In FIG. 5, the horizontal direction is the axial direction, and the vertical direction is the circumferential direction. As shown in FIG. 5, the surface shape of the corner ridge 50 in a cross section perpendicular to the length direction is an arc shape. The corner ridge 50 protrudes from the first side surface 42 in the circumferential direction and protrudes from the second side surface 44 in the axial direction.

  When the motorcycle travels on a hard and smooth road surface, the land 40, the first peripheral ridge 46 and the second peripheral ridge 48 come into contact with the road surface. As described above, the first peripheral ridge 46 and the second peripheral ridge 48 protrude from the land 40. Accordingly, the first peripheral ridge 46 and the second peripheral ridge 48 exhibit an edge effect during traveling. This edge effect improves the traction performance of the tire 2.

  On a soft road surface, a part of the block 24 is buried in the road surface. On soft road surfaces, this block 24 scratches mud. As described above, the corner ridge 50 protrudes from the first side surface 42 and protrudes from the second side surface 44. Therefore, the corner ridge 50 exhibits an edge effect when traveling. This edge effect enhances the traction performance of the tire 2 on a soft road surface.

  As described above, the cross-sectional shapes of the first peripheral ridge 46, the second peripheral ridge 48, and the corner ridge 50 are arcs. Fabrication of molds to obtain these ridges is easy.

  In FIG. 3, what is indicated by an arrow W <b> 1 is the width of the first peripheral ridge 46. The width W1 is preferably 2.00 mm or greater and 3.00 mm or less. The first peripheral ridge 46 having a width W1 of 2.00 mm or more is not easily worn away. In this respect, the width W1 is more preferably equal to or greater than 2.20 mm, and particularly preferably equal to or greater than 2.40 mm. The first peripheral ridge 46 having the width W1 of 3.00 mm or less is excellent in the edge effect. In this respect, the width W1 is more preferably equal to or less than 2.80 mm, and particularly preferably equal to or less than 2.60 mm.

  In FIG. 3, what is indicated by an arrow H <b> 1 is the height of the first peripheral ridge 46. The height H1 is preferably 2.00 mm or greater and 3.00 mm or less. The first peripheral ridge 46 having a height H1 of 2.00 mm or more is not easily worn away. In this respect, the height H1 is more preferably equal to or greater than 2.20 mm, and particularly preferably equal to or greater than 2.40 mm. The first peripheral ridge 46 having a height H1 of 3.00 mm or less is excellent in the edge effect. In this respect, the height H1 is more preferably equal to or less than 2.80 mm, and particularly preferably equal to or less than 2.60 mm.

  In FIG. 3, what is indicated by an arrow h <b> 1 is the height of the first peripheral ridge 46 from the land 40. The height h1 is preferably 1.00 mm or greater and 1.50 mm or less. The first peripheral ridge 46 having a height h1 of 1.00 mm or more is not easily worn away. In this respect, the height h1 is particularly preferably equal to or greater than 1.20 mm. The first peripheral ridge 46 having a height h1 of 1.50 mm or less is excellent in edge effect. In this respect, the height h1 is particularly preferably 1.30 mm or less.

  In FIG. 4, what is indicated by an arrow W <b> 2 is the width of the second peripheral ridge 48. The width W2 is preferably 2.00 mm or greater and 3.00 mm or less. The second peripheral ridge 48 having a width W2 of 2.00 mm or more is not easily worn away. In this respect, the width W2 is more preferably equal to or greater than 2.20 mm, and particularly preferably equal to or greater than 2.40 mm. The second peripheral ridge 48 having the width W2 of 3.00 mm or less is excellent in the edge effect. In this respect, the width W2 is more preferably equal to or less than 2.80 mm, and particularly preferably equal to or less than 2.60 mm.

  In FIG. 4, what is indicated by an arrow H <b> 2 is the height of the second peripheral ridge 48. The height H2 is preferably 2.00 mm or greater and 3.00 mm or less. The second peripheral ridge 48 having a height H2 of 2.00 mm or more is not easily worn away. In this respect, the height H2 is more preferably equal to or greater than 2.20 mm, and particularly preferably equal to or greater than 2.40 mm. The second peripheral ridge 48 having a height H2 of 3.00 mm or less is excellent in the edge effect. In this respect, the height H2 is more preferably equal to or less than 2.80 mm, and particularly preferably equal to or less than 2.60 mm.

  In FIG. 4, what is indicated by an arrow h <b> 2 is the height of the second peripheral ridge 48 from the land 40. The height h2 is preferably 1.00 mm or greater and 1.50 mm or less. The first peripheral ridge 46 having a height h2 of 1.00 mm or more is not easily worn away. In this respect, the height h2 is particularly preferably equal to or greater than 1.20 mm. The second peripheral ridge 48 having a height h2 of 1.50 mm or less is excellent in the edge effect. In this respect, the height h2 is particularly preferably 1.30 mm or less.

  In FIG. 5, an arrow W <b> 3 indicates the width in the axial direction of the corner ridge 50. The width W3 is preferably 2.00 mm or greater and 3.00 mm or less. The corner ridge 50 having a width W3 of 2.00 mm or more is not easily worn away. In this respect, the width W3 is more preferably equal to or greater than 2.20 mm, and particularly preferably equal to or greater than 2.40 mm. The corner ridge 50 having the width W3 of 3.00 mm or less is excellent in the edge effect. In this respect, the width W3 is more preferably equal to or less than 2.80 mm, and particularly preferably equal to or less than 2.60 mm.

  In FIG. 5, what is indicated by an arrow W <b> 4 is the circumferential width of the corner ridge 50. The width W4 is preferably 2.00 mm or greater and 3.00 mm or less. The corner ridge 50 having a width W4 of 2.00 mm or more is not easily worn away. In this respect, the width W4 is more preferably equal to or greater than 2.20 mm, and particularly preferably equal to or greater than 2.40 mm. The corner ridge 50 having the width W4 of 3.00 mm or less is excellent in the edge effect. In this respect, the width W4 is more preferably equal to or less than 2.80 mm, and particularly preferably equal to or less than 2.60 mm.

  In FIG. 5, what is indicated by an arrow h <b> 3 is the height of the corner ridge 50 from the first side surface 42. The height h3 is preferably 1.00 mm or greater and 1.50 mm or less. The corner ridge 50 having a height h3 of 1.00 mm or more is not easily worn away. In this respect, the height h3 is particularly preferably equal to or greater than 1.20 mm. A corner ridge having a height h3 of 1.50 mm or less has an excellent edge effect. In this respect, the height h3 is particularly preferably 1.30 mm or less.

  In FIG. 5, what is indicated by an arrow h <b> 4 is the height of the corner ridge 50 from the second side surface 44. The height h4 is preferably 1.00 mm or greater and 1.50 mm or less. The corner ridge 50 having a height h4 of 1.00 mm or more is not easily worn away. In this respect, the height h4 is particularly preferably 1.20 mm or more. A corner ridge having a height h4 of 1.50 mm or less has an excellent edge effect. In this respect, the height h4 is particularly preferably 1.30 mm or less.

  The tire may include a block that does not have the first peripheral ridge 46. The tire may include a block that does not have the second peripheral ridge 48. The tire may include a block that does not have the corner ridge 50.

  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.

  6 and 7 show a mold 52 for vulcanizing and forming the tire 2 of FIG. The mold 52 includes a main portion 54 and a back plate 56. The main portion 54 includes a vent hole 58 and a recess 60. The recess 60 is present on the cavity surface of the mold 52. The recess 60 includes a bottom surface 62, a first inner wall 64, a second inner wall 66, a first peripheral groove 68, a second peripheral groove 70, and a corner groove 72. The first peripheral groove 68 is located between the bottom surface 62 and the first inner wall 64. The second peripheral groove 70 is located between the bottom surface 62 and the second inner wall 66. The corner groove 72 is located between the first inner wall 64 and the second inner wall 66.

  The first peripheral groove 68, the second peripheral groove 70, and the corner groove 72 can be formed by cutting a corner of the recess 60. The mold 52 is easy to manufacture.

  The vent hole 58 has an opening 74. The shape of the opening 74 is a circle. The opening 74 exists in the grooves 68 and 70 near the corner of the bottom surface 62. The vent hole 58 extends from the opening 74 to the boundary between the main portion 54 and the back plate 56.

  In manufacturing the tire 2, a raw cover is put into the mold 52. The raw cover is pressurized and heated in the mold 52. The rubber composition of the raw cover flows by pressurization and heating. The rubber composition flows into the recess 60. By heating, the rubber composition causes a crosslinking reaction, and the tire 2 is obtained. From the recess 60, the block 24 is formed. A first peripheral ridge 46 is formed from the first peripheral groove 68, a second peripheral ridge 48 is formed from the second peripheral groove 70, and a corner ridge 50 is formed from the corner groove 72.

  When the rubber composition flows into the recess 60, the air in the recess 60 is smoothly discharged to the outside through the first peripheral groove 68, the second peripheral groove 70, and the vent hole 58. In the mold 52, the remaining of air hardly occurs. In the tire 2 obtained by the mold 52, bear is hardly generated. The defective rate of the tire 2 is small. Air may be discharged by means other than the vent hole 58.

  The rubber composition also flows into the vent hole 58. A spew is formed by the vent hole 58. In light of not forming an excessive spew, the inner diameter of the opening 74 is preferably 1.5 mm or less, and particularly preferably 1.2 mm or less. From the viewpoint that air hardly remains, the inner diameter is preferably 0.5 mm or more.

  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]
The mold shown in FIGS. 6 and 7 was prepared. The mold includes two first peripheral grooves, two second peripheral grooves, four corner grooves, and four vent holes. The inner diameter of each vent hole opening is 1.2 mm. A low cover was put into this mold, and it was pressurized and heated to obtain a tire of Example 1. This tire is shown in FIGS. 1-5. The size of this tire is 120 / 80-19. The tire includes a first peripheral ridge, a second peripheral ridge, and a corner ridge. The size of each ridge is shown in Table 1 below.

[Example 4]
A tire of Example 4 was obtained in the same manner as Example 1 except that a mold having no vent hole was used.

[Examples 3 and 6 and Comparative Examples 1 and 2]
Tires of Examples 3 and 6 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1 except that a mold having a groove having a size different from that of the mold used in Example 1 was used. The size of each tire ridge is shown in Tables 1 and 2 below.

[Examples 2 and 5]
The tires of Examples 2 and 5 were obtained in the same manner as in Example 1 except that a mold having a different size from the groove of the mold used in Example 1 and having no vent hole was used. It was. The size of each tire ridge is shown in Tables 1 and 2 below.

[Comparative Example 3]
A tire of Comparative Example 3 was obtained in the same manner as in Example 1 except that a mold having no grooves and vent holes was used.

[Example 7-9]
A tire of Example 7 was obtained in the same manner as in Example 1 except that a mold having no second peripheral groove and no corner groove was used. A tire of Example 8 was obtained in the same manner as Example 1 except that a mold having no first peripheral groove and no corner groove was used. A tire of Example 9 was obtained in the same manner as in Example 1 except that a mold having no first peripheral groove and no second peripheral groove was used.

[sensory evaluation]
The tires were mounted on a motorcycle rear rim (WM 2.15) with a displacement of 450 cc and dedicated to motorcycle racing. The tire was filled with air so that the internal pressure was 80 kPa. A commercially available tire was attached to the front rim of the motorcycle. This motorcycle was run on a motocross course, and the rider evaluated traction performance, grip performance and ground contact feeling. The results are shown in Tables 1-3 below as indices. The larger this value, the better the performance.

  As shown in Table 1-3, the tire of each example is excellent in various performances. From this evaluation result, the superiority of the present invention is clear.

  The tire according to the present invention can be mounted on various vehicles traveling on rough terrain.

2 ... motorcycle tire 4 ... tread 6 ... sidewall 8 ... bead 10 ... carcass 12 ... belt 24 ... block 40 ... land 42 ... first Side surface 44 ... Second side surface 46 ... First peripheral ridge 48 ... Second peripheral ridge 50 ... Corner ridge 52 ... Mold 58 ... Vent hole 60 ... Recess 62 ... Bottom 64 ... First inner wall 66 ... Second inner wall 68 ... First peripheral groove 70 ... Second peripheral groove 72 ... Corner groove 74 ... Opening

Claims (3)

It has a tread with many blocks,
Each block has a land, a side surface, and a ridge located between the land and the side surface,
The cross-sectional shape of the ridge is an arc,
The tire for rough terrain vehicles in which the ridge has a width of 2.00 mm to 3.00 mm and a height of 2.00 mm to 3.00 mm.   The tire according to claim 1, wherein the block includes a first side surface, a second side surface, and a ridge positioned between the first side surface and the second side surface. It has a vent hole and a recess that is present in the cavity surface and for molding the block,
The concave portion has a bottom surface, an inner wall, and a groove located between the bottom surface and the inner wall,
A mold for a tire, wherein the vent hole has an opening in a groove near a corner of the bottom surface.

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