JP2012011916A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve gripping performance on a dry road surface by uniforming the ground contact pressure of blocks.SOLUTION: This pneumatic tire includes blocks 16 provided on a tread part 10 and sectioned by grooves. One or more protrusions 26 are provided only in a triangular region 30 located near at least one block angle portion 28 on each block surface 24 where ground contact pressure is low, for increasing ground contact pressure in the triangular region. The triangular region 30 is a region in a triangular shape which is encircled by a first boundary line L1 connecting points D, E located at 35-45% of lengths X, Y of two block sides to each other, and a second boundary line L2 and a third boundary line L3 existing Z=1-5 mm inside from the two block sides 32a, 32b and extending in parallel to the block sides, respectively.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire provided with blocks that are divided by grooves in a tread portion.

  Some pneumatic tires have a tread surface provided with blocks divided by longitudinal grooves extending in the tire circumferential direction and transverse grooves intersecting the longitudinal grooves.

  In a pneumatic tire having such a block pattern, the following Patent Document 1 provides a grip force by providing a plurality of spews that are rubber-like protrusions on the surface of the block located in the shoulder region, and biting the spew into the road surface. Is disclosed.

  Patent Document 2 below discloses providing spews at the four corners of the block surface and providing additional spews between two spews provided along the block sides. In patent document 2, since the bulging part is formed in the high elastic modulus base rubber layer by the rubber flow at the time of spew molding in the block edge part provided with the additional spew, the rigidity of the block edge part is locally It is described that this reduces uneven wear such as heel and toe wear and river wear.

  Patent Document 3 below discloses that a vent hole is provided in the tire mold at positions corresponding to the four corners of the block surface in order to eliminate the variation in the tread gauge caused by the difference in the size of the block.

JP 2009-190345 A JP 2007-191020 A JP-A-11-165319

  As described above, Patent Documents 1 and 2 disclose that protrusions such as spews are provided on the block surface. However, in Patent Document 1, the protrusion is provided near the center rather than near the corner of the block surface. Moreover, in patent document 2, this protrusion is provided not only in the corner | angular part vicinity of a block surface but in the area | region between them. As will be described later, the contact pressure distribution when the block is brought into contact with the dry road surface is such that the contact pressure in the triangular region located in the vicinity of the block corner is lower than the other portions. However, in Patent Documents 1 and 2, since the protrusions are also provided in the portion where the ground pressure is high, the ground pressure cannot be made uniform, and it is not intended to make the ground pressure uniform in the first place.

  On the other hand, Patent Document 3 shows that spews are formed at the four corners of the block surface by providing vent holes at positions corresponding to the four corners of the block surface and molding the block. As described in paragraph 0029 of the literature, the spew is removed by buffing or the like after vulcanization molding and does not attempt to equalize the ground pressure.

  An object of the present invention is to make the contact pressure uniform by providing protrusions in a region where the contact pressure is low on the block surface, thereby improving the grip performance on a dry road surface.

  The pneumatic tire according to the present invention includes a block divided by a groove in a tread portion, and the block is limited to a triangular region having a low contact pressure located near at least one block corner portion on the block surface. In addition, one or a plurality of protrusions for increasing the contact pressure in the triangular area are provided.

  More specifically, the triangular region is formed from the block corner along the first corner near the block corner and two block sides that form the block corner with respect to the first corner. It can be set as the triangular area | region comprised by the 2nd corner | angular part and 3rd corner | angular part which are each located in the side to leave | separate. More specifically, the triangular area includes a first boundary line connecting points located at 35 to 45% of the length of each block side from the block corner on each of the two block sides, and the 2 It is preferable that it is a triangular area surrounded by a second boundary line and a third boundary line extending in parallel with each block side 1-5 mm inside from one block side.

  The triangular region may be provided with a central protrusion for increasing the ground pressure near the first corner and side protrusions for increasing the ground pressure near the second and third corners as the protrusion. . In this case, it is preferable that the central projection has a larger cross-sectional area than the side projection. Alternatively, the projection may be a triangular projection in plan view corresponding to the triangular region.

  According to the present invention, by providing a protrusion in a triangular area with a low ground pressure near the block corner on the block surface, the ground pressure in the triangular area can be increased and the ground pressure can be made uniform. In addition, the grip performance on the dry road surface can be improved.

It is an expanded view showing the tread pattern of the tire concerning a 1st embodiment. It is a top view of the block concerning the embodiment. It is a principal part expansion perspective view of the block concerning the embodiment. It is a principal part enlarged side view of the block concerning the embodiment. It is a principal part expansion perspective view of the block which concerns on 2nd Embodiment. It is a principal part expansion perspective view of the block which concerns on 3rd Embodiment. It is a top view of the block concerning a 4th embodiment. It is a top view of the block concerning a 5th embodiment. It is a top view of the block concerning a 6th embodiment. It is an analysis figure which shows the ground pressure distribution of a block.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
The pneumatic tire according to the embodiment is not illustrated, but the pair of left and right bead portions and sidewall portions and the radially outer ends of the left and right sidewall portions are connected to each other between the sidewall portions. The tread portion 10 is provided, and includes a carcass extending between the pair of bead portions. The carcass is composed of at least one carcass ply having both ends locked by an annular bead core embedded in the bead portion through the sidewall portion from the tread portion 10 and reinforces each of the above portions. A belt composed of two or more rubber-coated steel cord layers is provided on the outer peripheral side of the carcass in the tread portion 10, and the tread portion 10 is reinforced at the outer periphery of the carcass.

  As shown in FIG. 1, the tread portion 10 is provided with a plurality of vertical grooves (main grooves) 12 that extend straight in the tire circumferential direction A, and a plurality of horizontal grooves 14 that intersect the vertical grooves 12. A plurality of blocks 16 divided by vertical grooves 12 and horizontal grooves 14 are provided. In this example, four longitudinal grooves 12 are provided in the tire width direction B, whereby in the tire width direction B, the center region 18 on the tire center line CL and an intermediate formed on both sides of the center region 18 are sandwiched. The regions 20 and 20 are divided into five regions including shoulder regions 22 and 22 at both ends formed further outside the intermediate region 20.

  In the intermediate region 20 and the shoulder region 22, the lateral grooves 14 are juxtaposed at a predetermined interval in the tire circumferential direction A, whereby the intermediate region 20 and the shoulder region 22 have a large number of blocks 16 aligned in the tire circumferential direction A. It is configured as a block row.

  Each block 16 is provided with a plurality of protrusions 26 on a block surface 24 that is a ground contact surface. Specifically, the block 16 includes a plurality of protrusions 26 that increase the contact pressure of the triangular region 30 by limiting to the triangular region 30 having a low contact pressure located near each block corner 28 on the block surface 24. Is provided.

  The triangular region 30 having a low ground pressure is a region having a low ground pressure when the projection 26 is not provided. FIG. 10 is a diagram showing a result of FEM analysis of the contact pressure distribution on a dry road surface (for example, μ = 0.7) having a high friction coefficient with respect to the block 16 where the protrusions 26 are not provided. When a ground load was measured by image processing while applying a vertical load (154 N) to the block 16, a region with a predetermined width along the block side 32 corresponding to the edge of the block 16 and a concentric shape from the center of the block. The ground pressure is high in the area where it spreads, and the ground pressure is low in the triangular area 30 located in the vicinity of the block corner portion 28 sandwiched therebetween. Such a contact pressure distribution has the same tendency even when force is applied in the front-rear and left-right directions. For this reason, the grip performance on the dry road surface is impaired by such uneven contact. Therefore, by providing the projection 26 only in the triangular region 30 having a low ground pressure, the ground pressure in the region 30 can be increased, and thereby the ground pressure over the entire block surface 24 can be made uniform.

  As shown in FIG. 2, the triangular region 30 includes a first corner portion 34 near the block corner portion 28 and two block sides 32 a and 32 b that form the block corner portion 28 with respect to the first corner portion 34. It is a triangular region composed of a second corner portion 36 and a third corner portion 38 that are respectively located on the side away from the block corner portion 28. The first corner portion 34 is an angle that forms the same direction and the same angle as the block corner portion 28 inside the block corner portion 28, and constitutes the apex angle of the triangular region 30. Therefore, the second corner portion 36 and the third corner portion 38 constitute the base angle of the triangular region 30.

  More specifically, the triangular region 30 includes a first boundary line L1 that intersects the two block sides 32a and 32b that form the block corner portion 28, and the block corner portion 28 side of the first boundary line L1. This is a triangular region surrounded by a second boundary line L2 and a third boundary line L3 that extend in parallel to the two block sides 32a and 32b, respectively. The intersection of the second boundary line L2 and the third boundary line L3 forms the first corner portion 34, and the first boundary line L1 constitutes the bottom of the triangular region 30 facing the first corner portion 34. . In this example, since the block 16 has a rectangular shape in plan view and the block corner portion 28 has a right angle, the first corner portion 34 also has a right angle. Therefore, the triangular region 30 has a right triangle shape.

  The first boundary line L1 connects points D and E located at 35 to 45% of the lengths X and Y of the block sides 32a and 32b from the block corner portion 28 on the two block sides 32a and 32b. It is a straight line. The second boundary line L2 and the third boundary line L3 are straight lines extending in parallel with each of the block sides 32a and 32b inside Z = 1 to 5 mm from the two block sides 32a and 32b. The triangular region 30 defined by the first to third boundary lines L1, L2, and L3 is based on the results of the FEM analysis including the FEM analysis and the blocks having various shapes shown in FIGS. As a result, it was confirmed that the contact pressure was low in the above region for various block shapes. Here, the distance Z from the block sides 32a and 32b to the second and third boundary lines L2 and L3 is more preferably 1 to 3 mm. For reference, since the length of the block side 32 is usually about 15 to 50 mm, the distance Z is 5 to 20% of the lengths X and Y of the block sides 32a and 32b, more preferably 10 to 15%. % Length.

  The protrusions 26 are formed over the entire triangular area 30 so as to increase the ground pressure of the triangular area 30 over the entire area. In this example, the plurality of protrusions 26 are provided in the region 30 so as not to protrude from the triangular region 30. In other words, the first to third boundary lines L1, L2, and L3 are respectively set at positions where the area of the region 30 is the smallest within a range where the plurality of protrusions 26 do not protrude from the triangular region 30, Therefore, at least one protrusion 26 contacts each boundary line L1, L2, L3 from the inside.

  More specifically, as the plurality of protrusions 26, a central protrusion 40 that is located in the vicinity of the first corner 34 and increases the contact pressure in the vicinity of the first corner 34, and the vicinity of the second and third corners 36 and 38. The side protrusions 42 and 42 are provided to increase the contact pressure in the vicinity of the second and third corners 36 and 38, respectively, and are arranged along the first boundary line L1. . In this example, two each of the side protrusions 42 are provided, and accordingly, five protrusions 26 are provided in the triangular region 30.

  As shown in FIGS. 2 to 4, each protrusion 26 has a circular shape in plan view, and the tip (upper end) has a spherical shape. The central protrusion 40 is a large protrusion located at the center of the triangular region 30, and has a cross-sectional area (that is, an outer diameter) set larger than that of the side protrusion 42 as shown in FIG. 2. The middle protrusions located on both sides adjacent to the central protrusion 40 are first side protrusions 42a, and are further provided on the second and third corners 36, 38 adjacent to both sides thereof. The small protrusions are the second side protrusions 42b, and the cross-sectional areas are sequentially reduced. As shown in FIG. 4, the height H of each protrusion 26 is set to be the same in this example, but the center protrusion 40 is set higher than, for example, the side protrusion 42 in order to make the ground pressure more uniform. May be. The height H of the protrusions 26 is not particularly limited, but is preferably about 1 to 3 mm.

  As shown in FIG. 2, in this example, a plurality of protrusions 26 are provided in the same arrangement configuration at all four corners 28 of the block 16. Further, as shown in FIG. 1, the protrusions 26 are similarly provided in all the blocks 16 of the intermediate region 20 and the shoulder region 22. In addition, such a protrusion 26 can be formed by providing a corresponding recess in a portion of the tire mold where the block surface is formed.

  In the block 16 according to the embodiment as described above, the projection 26 is provided only in the triangular area 30 having a low ground pressure near the block corner portion 28 on the block surface 24, so that the ground area of the triangular area 30 is grounded. The contact pressure can be made uniform by increasing the pressure. Therefore, the grip property on the dry road surface in the early stage of tire wear can be improved.

  In the present embodiment, with respect to the triangular region 30, the central protrusion 40 located in the vicinity of the first corner 34 and the side protrusions 42 positioned on the second and third corners 36, 38 side, respectively. In addition, the central protrusion 40 is a large protrusion, and side protrusions 42a and 42b composed of a middle protrusion and a small protrusion are appropriately provided on both sides according to the shape of the region 30. The contact pressure can be made more uniform.

(Second and third embodiments)
FIG. 5 is a diagram showing a main part of the block according to the second embodiment, and FIG. 6 is a diagram showing a main part of the block according to the third embodiment. These embodiments differ from the above-described embodiment in that one protrusion 26 is provided in the triangular area 30, and the protrusion 26 has a triangular shape in plan view corresponding to the triangular area 30.

  Specifically, in the example shown in FIG. 5, the protrusion 26 has a triangular frustum shape with the triangular region 30 as a bottom surface. Here, the triangular frustum is a solid obtained by cutting the triangular pyramid along a plane parallel to the bottom surface and excluding the portion including the apex. In the example shown in FIG. 6, the protrusion 26 has a triangular pyramid shape with the triangular region 30 as a bottom surface. By setting it as such a shape, the contact pressure can be made more uniform. In addition, including the setting of the triangular area | region 30, other structures are the same as that of 1st Embodiment, and there exists the same effect.

  A plurality of projections 26 provided in the triangular region 30 may be provided as in the first embodiment, or may be configured as one as in the second and third embodiments. Further, the shape of the protrusion 26 is not particularly limited, and for example, a plurality of protrusions having a cross-sectional triangle shape or a cross-sectional square shape may be provided in addition to the circular cross-sectional shape as in the first embodiment. Further, the case of forming with one protrusion 26 as in the second and third embodiments is not limited to the above-described triangular shape in plan view. For example, the plurality of protrusions 40 and 42 in the first embodiment are formed. There is no particular limitation as long as it can be connected to form a single protrusion, and the ground pressure of the triangular region 30 can be increased over the whole.

(Fourth to sixth embodiments)
7 to 9 are diagrams showing an embodiment in which the shape of the block 16 is changed.

  In the fourth embodiment shown in FIG. 7, the block 16 has a parallelogram shape in plan view. Therefore, the block corner portion 28 includes a pair of acute angle portions 28a and a pair of obtuse angle portions 28b. When the FEM analysis similar to that of the first embodiment was performed on such a parallelogram block 16 as well, it was confirmed that the ground pressure was low in the triangular region 30 as shown in the figure. Is defined by first to third boundary lines L1 to L3 similar to the above. In this example, as in the first embodiment, each triangular region 30 is provided with a plurality of protrusions 26. However, as in the second and third embodiments, one triangular shape in plan view is used. Various modifications such as providing the protrusions 26 are possible.

  In the fifth embodiment shown in FIG. 8, in the block 16, one of the block sides 32 has a curved line shape, and has a generally triangular shape in plan view as a whole. As for the block corner portion 28 sandwiched between the curved line-shaped block sides 32c, it is confirmed by the FEM analysis that the ground pressure is low in the triangular region 30 as shown in the figure. It is defined by the same first to third boundary lines L1 to L3.

  In the sixth embodiment shown in FIG. 9, the block 16 has a concave polygonal shape in plan view in which parallel obtuse obtuse angled portions are recessed inward. In the case of such a concave polygonal shape, it is confirmed by the FEM analysis that the contact pressure is low in the triangular region 30 as illustrated, and in the other block corner portions 28 except for the concave corner portion 44 larger than 180 °. In the same manner as in the fourth embodiment, a triangular region 30 is defined.

  In the example shown in FIGS. 8 and 9, as in the second and third embodiments, one triangular projection 30 is provided in each triangular region 30, but as in the first embodiment. Various modifications such as providing a plurality of protrusions 26 in each triangular region 30 are possible. The other configurations of the fourth to sixth embodiments are the same as those of the first embodiment, and the same functions and effects are achieved.

(Other embodiments)
In the above embodiment, the protrusions 26 are provided on all the block corners 28 of the block 16, but the present invention is not limited to the case where the projections 26 are provided on all the block corners 28. Preferably, the contact pressure in the vicinity of the corner is provided at the block corner 28 having an angle of 50 ° or more and less than 180 °, and more preferably at the right or obtuse block corner 28.

  Moreover, in the said embodiment, although the protrusion 26 was provided about all the blocks 16 located in the intermediate | middle area | region 20 and the shoulder area | region 22, this invention is not limited to the case where it provides in all the blocks 16. FIG. Although not enumerated one by one, various modifications can be made without departing from the spirit of the present invention.

  Dry performance of the tire of the example (size: 235 / 50R18) having the tread configuration of the first embodiment described above and the conventional tire (comparative example) in which the protrusion 26 is not provided on the tire of the example. (Grip performance on dry road surface) was evaluated.

  The setting of the triangular region 30 in the tire of the example is that in Example 1, X = 30 mm, Y = 30 mm, Z = 2 mm, the position of the point D = 12 mm (0.4X) from the block corner portion 28, and the point E Position = 12 mm (0.4Y) from the block corner 28, and the height H of the projection 26 = 2 mm. Here, the block size was 30 mm long × 30 mm wide × 8 mm high.

  In Example 2, Z = 1 mm, the position of the point D = 10.5 mm (0.35X) from the block corner 28, the position of the point E = 10.5 mm (0.35Y) from the block corner 28, and the others The setting was the same as in Example 1.

  In Example 3, Z = 5 mm, the position of the point D = 13.5 mm (0.45X) from the block corner 28, the position of the point E = 13.5 mm (0.45Y) from the block corner 28, and the others The setting was the same as in Example 1.

  The dry performance was evaluated by attaching tires assembled to rims to the vehicle, traveling on a dry road surface with an actual vehicle, performing a sensory test with a driver, and setting the result of the comparative example as 100. A larger index means better dry performance.

  As a result, in Example 1, the dry performance was 108, in Example 2, the dry performance was 105, and in Example 3, the dry performance was 105. In both cases, the dry performance was clearly improved compared to the comparative example.

DESCRIPTION OF SYMBOLS 10 ... Tread part 16 ... Block 24 ... Block surface 26 ... Protrusion 28 ... Block corner part 30 ... Triangular area 32 ... Block side 34 ... First corner part 36 ... Second corner part 38 ... Third corner part 40 ... Center protrusion 42 ... side projection L1 ... first boundary line L2 ... second boundary line L3 ... third boundary line X, Y ... length of block side

Claims (6)

In pneumatic tires with blocks divided by grooves in the tread part,
The block is provided with one or a plurality of protrusions for limiting the contact pressure of the triangular area only within a triangular area having a low contact pressure located near at least one block corner on the block surface. Pneumatic tire characterized by.   The triangular region is located on a side away from the block corner along a first corner near the block corner and two block sides that form the block corner with respect to the first corner. The pneumatic tire according to claim 1, wherein the pneumatic tire is a triangular region composed of a second corner portion and a third corner portion.   From the two block sides, a first boundary line connecting points located between 35 to 45% of the length of the block sides from the block corners on the two block sides, and the triangular region. 3. The pneumatic tire according to claim 2, wherein the pneumatic tire is a triangular region surrounded by a second boundary line and a third boundary line extending in parallel with each block side at an inner side of 1 to 5 mm.   The triangular region is provided with a central protrusion for increasing the ground pressure near the first corner and side protrusions for increasing the ground pressure near the second and third corners as the protrusion. The pneumatic tire according to claim 2 or 3, characterized in.   The pneumatic tire according to claim 4, wherein the central protrusion has a larger cross-sectional area than the side protrusion.   The pneumatic tire according to any one of claims 1 to 3, wherein the protrusion is a protrusion having a triangular shape in plan view corresponding to the triangular area.

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