tire

Abstract

This tire provides high control performance while suppressing a decrease in the shear rigidity of the blocks. [Solution] The tire 1 is provided with a plurality of blocks 5. Each block 5 includes a tread surface 6 surrounded by a plurality of block edge pieces 8 with different extending directions, and a recess 7 formed by indenting the tread surface 6. The recess 7 includes an open edge 11 that extends along the tread surface 6 without intersecting any of the block edge pieces 8. The open edge 11 is a polygonal shape formed by connecting a plurality of open edge pieces 15. At least one of the open edge pieces 15 has an extending direction different from any of the extending directions of the block edge pieces 8. The open edge piece 15 is connected to at least one rib 20 that locally protrudes into the recess 7 and extends in the radial direction of the tire.

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Patent Document 1 below describes a tire having a tread portion. The tread portion includes a plurality of lateral grooves, a plurality of longitudinal grooves, and a plurality of blocks defined by the plurality of lateral grooves and the plurality of longitudinal grooves. Further, on the ground contact surface of the block, there are provided a lateral edge defined by the lateral groove, a longitudinal edge defined by the longitudinal groove, and a second interrupted groove that interrupts without connecting to the lateral groove or the longitudinal groove. The second interrupted groove is inclined in the same direction as the longitudinal groove.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] This invention was devised in view of the above-described circumstances, and its main objective is to provide a tire that can be expected to have high control performance while suppressing a decrease in the shear rigidity of the blocks. [Means for solving the problem]

[0006] The present invention relates to a tire including a tread portion, wherein the tread portion is provided with a plurality of blocks, at least one of the plurality of blocks includes a tread surrounded by a plurality of block edge pieces with different extending directions, and a recess formed by recessing the tread portion, the recess includes an opening edge extending along the tread without intersecting any of the plurality of block edge pieces, and a recess wall extending radially inward from the opening edge, the opening edge is a polygonal shape formed by connecting a plurality of linearly extending opening edge pieces, at least one of the plurality of opening edge pieces has an extending direction different from any of the extending directions of the plurality of block edge pieces, and at least one rib is connected to at least one of the plurality of opening edge pieces, locally protruding into the recess and extending radially inward. [Effects of the Invention]

[0007] By adopting the above-described configuration, the tire of the present invention can be expected to provide high control performance while suppressing a decrease in the shear rigidity of the blocks. [Brief explanation of the drawing]

[0008] [Figure 1] This is a developed view of the tread portion showing one embodiment of the tire of the present invention. [Figure 2] Figure 1 is a cross-sectional perspective view of the block provided in the tread area. [Figure 3] Figure 2 is a plan view of the block. [Figure 4] This is a cross-sectional view along line AA in Figure 3. [Figure 5] This is a cross-sectional perspective view of a block in another embodiment. [Figure 6](A) is a plan view of the tread surface of the block in Figure 5, and (B) is a cross-section of (A) along line BB. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. The drawings contain exaggerations and representations that differ from the actual structural dimensional ratios in order to aid in understanding the content of the present invention. Furthermore, the same or common elements are denoted by the same reference numerals throughout each embodiment, and redundant explanations may be omitted. Moreover, the specific configurations shown in the embodiments and drawings are for the purpose of understanding the content of the present invention. For this reason, the present invention is not limited to the specific configurations shown in the drawings.

[0010] Figure 1 is an exploded view of the tread portion 2 of tire 1 in this embodiment. Figure 1 shows a standard pneumatic tire for passenger cars. The present invention is particularly desirable to be applied to pneumatic tires for driving on rough terrain (dirt roads) such as sand and mud, and for rally use. The present invention may also be applied to heavy-duty pneumatic tires for trucks and buses, and to non-pneumatic tires that are not filled with compressed air.

[0011] The aforementioned "normal condition" refers to a state in which, for tires with defined standards, the tire is mounted on a standard rim (not shown), filled to the standard internal pressure, and is unloaded. For tires without defined standards, the aforementioned normal condition means a standard operating condition according to the tire's intended use, and is unloaded. In this specification, unless otherwise specified, the dimensions of each part are values ​​measured in the aforementioned normal condition.

[0012] A "standard rim" is the rim defined for each tire within the standards system that the tire is based on. For example, it is the "standard rim" for JATMA, the "Design Rim" for TRA, and the "Measuring Rim" for ETRTO.

[0013] The "normal internal pressure" is the air pressure defined for each tire in a standard system including the standards on which the tire is based. In the case of JATMA, it is the "maximum air pressure"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "INFLATION PRESSURE".

[0014] As shown in FIG. 1, the tread portion 2 of the present embodiment is provided with a plurality of blocks 5.

[0015] FIG. 2 is a perspective sectional view of one of the plurality of blocks 5 shown in FIG. 1. FIG. 3 is a plan view of the block 5 in FIG. 2. As shown in FIGS. 2 and 3, the block 5 includes a tread surface 6 and a recess 7 that recesses the tread surface 6. The tread surface 6 is surrounded by a plurality of block edge pieces 8 having different extending directions. The recess 7 includes an opening edge 11 that extends along the tread surface 6 without intersecting any of the plurality of block edge pieces 8, and a recess wall surface 12 that extends inward in the tire radial direction from the opening edge 11.

[0016] Further, the opening edge 11 is a polygon formed by connecting a plurality of linearly extending opening edge pieces 15. Such a plurality of block edge pieces eight and opening edge 11 exhibit a large frictional force.

[0017] Furthermore, at least one of the plurality of opening edge pieces 15 has an extending direction different from the extending direction of any of the plurality of block edge pieces 8. Such an opening edge piece 15 exerts a frictional force in a direction different from that of the block edge piece 8, so that the difference between the frictional force in the edge normal direction and the frictional force in a direction different from the edge normal direction is suppressed from increasing. As a result, the frictional force exerted according to the turning angle during turning travel is made uniform, and thus the control performance is improved. <了

[0018] Furthermore, at least one of the plurality of opening edge pieces 15 is connected to at least one rib 20 that locally protrudes into the recess 7 and extends in the tire radial direction. Such a rib 20 can increase the edge component of the opening edge piece 15 provided with the rib 20 while suppressing a decrease in the shear rigidity of the block 5, and can further enhance the frictional force. Thus, the tire 1 of the present invention can be expected to have high control performance while suppressing a decrease in the shear rigidity of the block 5. The rib 20 is a portion protruding from the recess wall surface 12.

[0019] The tread surface 6 is, in this specification, the area that contacts the ground plane in the normal load condition. The "normal load condition" refers to the state in which the normal load is applied to the tire 1 in the normal state and the tire contacts the ground plane at a camber angle of 0°. The "normal load" is the load determined for each tire in a standard system including the standard on which the tire 1 is based. In the case of JATMA, it is the "maximum load capacity", in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "LOAD CAPACITY". Also, in the case of a tire for which various standards are not defined or a non-pneumatic tire, the "normal load" refers to the load acting on one tire in the standard mounting state of the tire. The "standard mounting state" refers to the state in which the tire is mounted on a standard vehicle according to the purpose of use of the tire and the vehicle is stationary on a flat road surface in a state where it can run.

[0020] In this specification, the "linear shape" includes not only those in which the opening edge piece 15 is composed of a straight line, but also those composed of one arc and having a radius of curvature R1 of 200 mm or more. Also, in this specification, the "polygonal shape" includes not only the mode in which adjacent opening edge pieces 15 are directly butted and connected, but also the mode in which they are connected to an arc (not shown) having a radius of curvature R2 of 10 mm or less. This is considered in view of the fact that the tire 1 is a rubber molded product.

[0021] In this specification, "different (extending direction)" means not only that in a plan view of the tread surface 6, the angle θA between the block edge piece 8 and the opening edge piece 15 is 15 degrees or more, but may also include the case where the angle θA is 10 degrees or more, or even 5 degrees or more. Furthermore, "different (extending direction)" may also include the case where the block edge piece 8 and the opening edge piece 15 are not parallel (θA > 0 degrees).

[0022] The configuration of this embodiment will be described in more detail below. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-described effects even without the configurations described below. Furthermore, even if any one of the configurations described below is applied individually to a tire of the present invention having the above-described features, an improvement in performance corresponding to each configuration can be expected. Moreover, if several of the configurations described below are applied in combination, a combined improvement in performance corresponding to each configuration can be expected.

[0023] The tread portion 2 has a specified orientation for mounting on the vehicle. As shown in Figure 1, the tread portion 2 includes an inner tread end Ti located on the inside of the vehicle when mounted on the vehicle, and an outer tread end To located on the outside of the vehicle when mounted on the vehicle. The inner tread end Ti and the outer tread end To correspond to the outermost contact point in the tire axial direction when the tire 1 under the normal load condition is in contact with the plane. In addition, the rotation direction N of the tread portion 2 in this embodiment is also specified. Note that the tire 1 is not limited to those with a specified orientation for mounting on the vehicle and those with a specified rotation direction N.

[0024] In this embodiment, the tread portion 2 includes a plurality of lateral grooves 3 extending in the tire axial direction and a plurality of longitudinal grooves 4 extending in the tire circumferential direction. In this specification, "extending in the tire axial direction" means that the groove extends with an angle θB of 35 degrees or less between a virtual straight line n1 connecting both ends of the groove width centerline c1 and the tire axial direction. In this specification, "extending in the tire circumferential direction" means that the groove extends with an angle θB exceeding 35 degrees. In this specification, grooves including lateral grooves 3 and longitudinal grooves 4 refer to recesses with a groove width of 1.5 mm or more, and are clearly distinguished from notched sipes with a width of less than 1.5 mm.

[0025] In this embodiment, the lateral groove 3 includes a main lateral groove 3A that connects the inner tread end Ti and the outer tread end To, and a secondary lateral groove 3B whose ends terminate within the tread portion 2. The lateral groove 3 is inclined such that, for example, the angle with respect to the tire axis increases from the inner tread end Ti side toward the outer tread end To.

[0026] In this embodiment, the longitudinal grooves 4 extend to connect adjacent transverse grooves 3 in the circumferential direction of the tire. Multiple longitudinal grooves 4 are arranged in a row, for example, in the axial direction of the tire. In this embodiment, the angle θB of the longitudinal grooves 4 is larger for the longitudinal grooves 4 located on the outer tread edge To side than for the longitudinal grooves 4 located on the inner tread edge Ti side.

[0027] Block 5 includes, for example, a first block 5A and a second block 5B. The first block 5A is divided into adjacent main lateral grooves 3A and sub-lateral grooves 3B in the tire circumferential direction and adjacent longitudinal grooves 4 in the tire axial direction. The second block 5B is divided into adjacent main lateral grooves 3A in the tire circumferential direction and adjacent longitudinal grooves 4 in the tire axial direction. In this embodiment, a plurality of first blocks 5A and a plurality of second blocks 5B are arranged between adjacent main lateral grooves 3A in the tire circumferential direction.

[0028] The block edge piece 8 includes a first block edge piece 8A along the transverse groove 3 and a second block edge piece 8B along the longitudinal groove 4.

[0029] As shown in Figure 1, in a plan view of the tread surface 6, the first block 5A is formed, for example, in a trapezoidal shape. In this embodiment, the first block 5A includes a notch K in which the upper or lower base of the trapezoid is cut out on the centroidal side of the tread surface 6. The first block 5A is formed as a horizontally elongated block 5x in which the maximum length of the second block edge piece 8B is smaller than the maximum length of the first block edge piece 8A. Such a first block 5A also exhibits frictional force in multiple directions.

[0030] In a plan view of the tread surface 6, the second block 5B is formed as a longitudinally elongated block 5y in which the maximum length of the second block edge piece 8B is greater than the maximum length of the first block edge piece 8A. Between adjacent main transverse grooves 3A in the circumferential direction of the tire, for example, each of the multiple second blocks 5B is located on the outer tread edge To side than each of the multiple first blocks 5A. Among the multiple second blocks 5B1 arranged between adjacent main transverse grooves 3A in the circumferential direction of the tire, the second block 5B located on the innermost tread edge Ti side intersects with the tire equator C. Note that the tread portion 2 is not limited to this pattern, and various patterns can be employed.

[0031] In this embodiment, the recess 7 of the present invention is provided in the second block 5B. In other words, the recess 7 is provided in the elongated block 5y located on the outer tread end To side, where a relatively large lateral force acts during cornering. This allows the frictional force from the opening edge 11 of the recess 7 to be greatly increased. Note that the recess 7 is not limited to being provided in the second block 5B; for example, it may be provided only in the first block 5A, or in both the first block 5A and the second block 5B.

[0032] As shown in Figures 2 and 3, the tread surface 6 of block 5 (the second block 5B (hereinafter the same) having the recess 7) is, for example, polygonal. In other words, the tread surface 6 of this embodiment is polygonal, formed by connecting a plurality of linearly extending block edge pieces 8. In this specification, "linear" and "polygonal" are the same as "linear" and "polygonal" as described for the opening edge piece 15.

[0033] Specifically, the tread surface 6 in this embodiment is parallelogram-shaped and formed by four block edge pieces 8. Preferably, the tread surface 6 is triangular to octagonal, formed by, for example, three to eight block edge pieces 8. For the triangular shape, isosceles, right, or equilateral triangles are desirable. For the quadrilateral shape, in addition to the parallelogram shape, rhombic, rectangular, or square shapes are desirable. For other polygonal shapes, regular polygons are desirable.

[0034] The area SA of the virtual tread surface 6A of block 5 (shown in Figure 1) is 450 mm². 2 The above is preferable, 700mm 2 The above is even more desirable, 1100mm 2 The following is preferable, 800mm 2 The following is even more desirable: The virtual tread surface 6A is obtained by filling the recess 7 up to the opening edge 11. The area SA is the sum of the area Sa of the tread surface 6 and the area Sb enclosed by the opening edge 11 (Sa + Sb). In addition, the height H1 of the block 5 in the tire radial direction (shown in Figure 4) is preferably 6 mm or more, more preferably 9 mm or more, preferably 11 mm or less, and more preferably 10 mm or less.

[0035] Furthermore, the ratio (Sa / SA) of the area Sa of the tread surface 6 to the area SA of the virtual tread surface 6A is preferably 40% or more, more preferably 50% or more, preferably 70% or less, and more preferably 60% or less.

[0036] In this embodiment, the opening edge 11 is formed in a rhombus shape by connecting four opening edge pieces 15. The opening edge 11 can be, for example, a triangular shape formed by connecting three opening edge pieces 15, or an octagonal shape formed by connecting eight opening edge pieces 15 (not shown). Furthermore, it is even more desirable for the opening edge 11 to be a square shape formed by connecting four opening edge pieces 15, or a hexagonal shape formed by connecting six opening edge pieces 15. For the triangular shape, isosceles triangles, right triangles, and equilateral triangles are desirable. For the square shape, in addition to the rhombus, parallelograms, rectangles, and squares are also desirable. For other polygonal shapes, regular polygons are desirable.

[0037] In this embodiment, each of the multiple open edge pieces 15 has an extension direction different from the extension direction of any of the multiple block edge pieces 8. As a result, the open edge pieces 15 exert frictional force in multiple directions different from the block edge pieces 8, making it possible to reduce the difference between the frictional force in the direction normal to the edge and the frictional force in directions different from the edge normal. Therefore, the frictional force exerted by the turning angle during turning is made more uniform, further improving control performance.

[0038] The shortest distance Ln between the block edge piece 8 and the opening edge piece 15 is preferably 2 mm or more, more preferably 4 mm or more, preferably 8 mm or less, and more preferably 5 mm or less. Since the shortest distance Ln is 2 mm or more, the decrease in the shear stiffness of the block 5 is suppressed. Since the shortest distance Ln is 8 mm or less, the length of the opening edge piece 15 of the recess 7 can be made larger, and the frictional force generated by the opening edge piece 15 can be increased.

[0039] The recessed wall surface 12 has, for example, an inner end 12i located furthest inward in the tire radial direction. The recessed wall surface 12 is divided into a plurality of recessed wall surface portions 13 extending radially inward from each opening edge piece 15. As a result, the inner end 12i in this embodiment is divided into a plurality of inner end portions 14 provided on each of the plurality of recessed wall surface portions 13. Adjacent inner end portions 14 are connected to each other so as to form a bent portion 18.

[0040] Figure 4 is a cross-sectional view taken along line AA in Figure 3. Figure 4 shows a cross-section of the opening edge piece 15 (recessed wall surface portion 13). As shown in Figures 2 to 4, the recess 7 has a bottom surface portion 16 connected to the inner end 12i. In this embodiment, the bottom surface portion 16 is formed as a plane parallel to the opening edge 11. Such a bottom surface portion 16 can exert a high shear force against dirt roads, thereby improving control performance.

[0041] The maximum depth D1 of the recess 7 is preferably 2 mm or more, more preferably 4 mm or more, preferably 8 mm or less, and even more preferably 6 mm or less. Since the maximum depth D1 of the recess 7 is 2 mm or more, it provides basic shear force against dirt roads. Since the maximum depth D1 of the recess 7 is 8 mm or less, the decrease in the shear stiffness of the block 5 is suppressed. From this viewpoint, the maximum depth D1 of the recess 7 is preferably 20% or more of the height H1 of the block 5 in the tire radial direction, more preferably 40% or more, preferably 100% or less, and even more preferably 80% or less.

[0042] The angle α1 between the recessed wall surface 12 and the tread surface 6 is preferably 90 degrees or more, more preferably 100 degrees or more, preferably 170 degrees or less, and more preferably 120 degrees or less. When the angle α1 is 90 degrees or more, the shear rigidity of the block 5 is maintained at a high level. When the angle α1 is 170 degrees or less, the frictional force exerted by the open edge piece 15 is high. In this embodiment, the recessed wall surface 12 is inclined toward the block edge piece 8 toward the outward direction in the radial direction of the tire. As shown in Figure 4, the recessed wall surface 12 in this embodiment extends in a straight line, but for example, it may extend in a convex arc toward the outward direction in the radial direction of the tire, or conversely, it may extend in a convex arc toward the inward direction in the radial direction of the tire.

[0043] In this embodiment, the ribs 20 are provided on each of the multiple open edge pieces 15. This further suppresses the decrease in shear stiffness of the block 5, while increasing the edge component of the open edge piece 15 on which the ribs 20 are provided, thereby further increasing the frictional force. In this embodiment, four ribs 20 are provided on the block 5.

[0044] It is desirable that the rib 20 be provided at a position that overlaps with the midpoint 15c (shown in Figure 3) of the extending direction of the opening edge piece 15. This further suppresses the decrease in the shear stiffness of the block 5. In this embodiment, the midpoint 20c of the rib 20 in the extending direction coincides with the midpoint 15c of the opening edge piece 15 in the extending direction.

[0045] The rib 20 has, for example, a cross-sectional area Sc (shown in Figure 2) that continuously decreases toward the inward direction in the tire radial direction. When the block 5 wears down due to tire running, such a rib 20 suppresses the decrease in the volume of the recess 7, thereby suppressing the decrease in shear force on the dirt road. Note that the rib 20 is not limited to this configuration, and the cross-sectional area Sc may be the same size at any position in the tire radial direction. In this embodiment, the protrusion length p (shown in Figure 4) of the rib 20 from the recess wall surface 12 continuously decreases toward the inward direction in the tire radial direction.

[0046] In this embodiment, the rib 20 extends from the opening edge piece 15 to the inner end 12i. Such a rib 20 can suppress the decrease in the shear stiffness of the block 5 over a long period of time. However, the rib 20 is not limited to this configuration, and for example, it may terminate radially outward from the inner end 12i (not shown).

[0047] The cross-section of the rib 20 is, for example, rectangular. Such a rib 20 can further suppress the decrease in shear stiffness of the block 5 while increasing the edge component of the open edge piece 15 on which the rib 20 is provided. The maximum protruding length p1 of the rib 20 is rectangular and smaller than the length w1 (shown in Figure 3) of the opening edge piece 15 of the rib 20 in the extending direction. The maximum protruding length p1 is the length of the rib 20 at its outer end in the tire radial direction.

[0048] The width w1 of the rib 20 is preferably 5% or more, more preferably 10% or more, 25% or less, and even more preferably 20% or less, of the length W1 (shown in Figure 3) of the opening edge piece 15 on which the rib 20 is located. The maximum protruding length p1 of the rib 20 is preferably 55% or more, more preferably 60% or more, 95% or less, and even more preferably 90% or less, of the w1 of the rib 20. Although not particularly limited, the length h1 of the rib 20 in the tire radial direction is preferably 80% or more, and even more preferably 85% or more, of the maximum depth D1 of the recess 7.

[0049] Figure 5 is a cross-sectional perspective view of block 5 (second block 5B) of another embodiment. Figure 6(A) is a plan view of the tread surface 6 of block 5 in Figure 5, and Figure 6(B) is a cross-sectional view of Figure 6(A) along line BB. As shown in Figures 5 and 6, in this embodiment, the bottom surface 16 includes a top portion 25 located radially outward from the inner end 12i, and an inclined surface 26 extending radially outward from the inner end 12i toward the top portion 25. The top portion 25 can make contact with the ground when the tire is running. The term "when the tire is running" includes, of course, the top portion 25 making contact with the ground when the tire 1 is new, but also includes the state in which the top portion 25 makes contact with the ground for the first time when the tread portion 2 has worn down to a certain extent. With such a bottom surface 16, as the tire 1 wears down, the top portion 25, which has a smaller contact area, makes contact first. As wear progresses further, the contact area continuously increases. Thus, the bottom portion 16 of this embodiment can reduce the change (increase rate) of the contact area due to the progression of wear, and therefore reduces the change in ground pressure and thus the frictional force, thereby improving control performance. Furthermore, when the top portion 25 makes contact with the bottom portion 16, ground pressure is concentrated in this area, increasing the coefficient of friction on low-friction surfaces such as muddy roads and icy roads. As a result, the change (difference) in the coefficient of friction between low-friction surfaces and non-low-friction surfaces is reduced, enabling stable driving and improving control performance. Moreover, this bottom portion 16 can suppress the decrease in the shear rigidity of the block 5. The top portion 25 of this embodiment is formed as the apex.

[0050] In this embodiment, the inclined surface 26 is formed in a pyramidal shape, including one apex 25 and a plurality of ridge-like portions 27. As wear progresses, such an inclined surface 26 forms a plurality of linearly extending bottom edge pieces 28 between adjacent ridge-like portions 27, thereby further increasing the frictional force. As the length of the bottom edge pieces 28 increases with wear, the change in ground pressure and thus the frictional force can be further reduced. The bottom portion 16 is not limited to this configuration, and may also include a plurality of apex portions 25 (not shown), or the apex portions 25 may be formed in a planar shape (not shown).

[0051] As shown in Figure 6(B), the ridge-like portion 27 of this embodiment extends linearly from each bent portion 18 toward the apex 25. The ridge-like portion 27 may also extend in a convex arc outward in the radial direction of the tire from each bent portion 18 toward the apex 25, or it may extend in a convex arc inward in the radial direction of the tire from each bent portion 18 toward the apex 25 (not shown).

[0052] The height h2 of the top 25 is preferably 40% or more of the maximum depth D1 of the recess 7 (shown in Figure 4), more preferably 45% or more, preferably 80% or less, and even more preferably 75% or less. Since the height h2 of the top 25 is 40% or more of the maximum depth D1 of the recess 7, the top 25 can remain in contact with the ground for a long period of time, thus reducing the change in frictional force. Since the height h2 of the top 25 is 80% or less of the maximum depth D1 of the recess 7, the shear force against the mud by the recess 7 can be exerted at a high level. The height h2 of the top 25 is the radial separation distance between the inner end 12i and the top 25 of the tire.

[0053] Although particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above and can be implemented in various modified forms. [Examples]

[0054] A test tire with the basic pattern shown in Figure 1 was prototyped based on the specifications in Table 1. The control performance and wear resistance of the prototype test tire were then tested. The common specifications and test methods for each test tire are as follows.

[0055] <Common Specifications> Tire size: 205 / 65R15 Rim size: 15×7.0J Air pressure: 200kPa Test vehicle: 2000cc four-wheel drive vehicle Test course: Dirt road (unpaved road)

[0056] <Control performance and wear resistance> The control performance of a test vehicle equipped with test tires on all wheels was evaluated subjectively by a test driver while driving on a test course. Furthermore, the wear condition of the tread was also evaluated subjectively by the test driver after the drive. Each result is shown on a scale where Comparative Example 1 is rated at 60, with higher numbers indicating better performance. The test results are shown in Table 1.

[0057] [Table 1]

[0058] The test results confirmed that the tire of the embodiment had improved control performance compared to the tire of the comparative example. Furthermore, the tire of the embodiment also showed improved wear resistance compared to the tire of the comparative example. It should be understood by those skilled in the art that the tire of the embodiment, with its ribs, has greater shear rigidity of the blocks compared to the comparative example tire without ribs.

[0059] [Note] The present invention includes the following embodiments.

[0060] [Invention 1] A tire including a tread portion, The tread portion is provided with a plurality of blocks, At least one of the plurality of blocks includes a tread surrounded by a plurality of block edge pieces with different extending directions, and a recess formed by indenting the tread, The recess includes an opening edge that extends along the tread without intersecting any of the plurality of block edge pieces, and a recess wall surface that extends radially inward from the opening edge in the tire direction. The aforementioned opening edge has a polygonal shape formed by connecting multiple opening edge pieces that extend in a straight line. At least one of the plurality of opening edge pieces has an extension direction different from any of the extension directions of the plurality of block edge pieces. At least one of the plurality of opening edge pieces is connected to at least one rib that protrudes locally into the recess and extends in the radial direction of the tire. tire. [Invention 2] The tire according to the present invention 1, wherein each of the plurality of open edge pieces has an extension direction different from any of the extension directions of the plurality of block edge pieces. [Invention 3] The tire according to invention 1 or 2, wherein the ribs are provided on each of the plurality of open edge pieces. [4th Invention] The tire according to any one of inventions 1 to 3, wherein the area of ​​the cross-section of the rib decreases continuously toward the radially inward direction of the tire. [5th ​​Invention] The tire according to any one of inventions 1 to 4, wherein the cross-section of the rib is rectangular. [Invention 6] The recessed wall surface has an inner end that is located furthest inward in the tire radial direction, The recess has a bottom surface portion connected to the inner end, The tire according to any one of inventions 1 to 5, wherein the bottom surface portion includes a top portion located radially outward from the inner end and an inclined surface extending radially outward from the inner end toward the top portion. [7th Invention] The aforementioned top portion is capable of making contact with the ground when the tire is running, as described in invention 6. [8th Invention] The tire according to claim 6 or 7 of the present invention, wherein the height of the top portion is 40% to 80% of the maximum depth of the recess. [Invention 9] The tire according to any one of inventions 1 to 8, wherein the angle between the recessed wall surface and the tread surface is 90 to 170 degrees. [Invention 10] The tire according to claim 9 of the present invention, wherein the angle between the recessed wall surface and the tread surface is 100 to 120 degrees. [Invention 11] The tire according to any one of inventions 1 to 10, wherein the maximum depth of the recess is 2 to 8 mm. [Invention 12] The tire according to any one of inventions 1 to 11, wherein the maximum depth of the recess is 20% to 100% of the height of the block in the tire radial direction. [Invention 13] The tire is a tire according to any one of inventions 1 to 12, which is for driving on rough terrain. [Explanation of Symbols]

[0061] 1 tire 5 blocks 6 Tread 7 recesses 8 block edge pieces 11 Opening edge 15 Open edge piece 20 Ribs

Claims

1. A tire including a tread portion, The tread portion is provided with a plurality of blocks, At least one of the plurality of blocks includes a tread surface surrounded by a plurality of block edge pieces with different extending directions, and a recess formed by indenting the tread surface. The recess includes an opening edge that extends along the tread without intersecting any of the plurality of block edge pieces, and a recess wall surface that extends radially inward from the opening edge in the tire direction. The aforementioned opening edge has a polygonal shape formed by connecting multiple opening edge pieces that extend in a straight line. At least one of the plurality of opening edge pieces has an extension direction different from any of the extension directions of the plurality of block edge pieces. At least one of the plurality of open edge pieces is connected to at least one rib that protrudes locally into the recess and extends in the radial direction of the tire. tire.

2. The tire according to claim 1, wherein each of the plurality of open edge pieces has an extension direction different from any of the extension directions of the plurality of block edge pieces.

3. The tire according to claim 1, wherein the ribs are provided on each of the plurality of open edge pieces.

4. The tire according to claim 1, wherein the area of ​​the cross-section of the rib decreases continuously toward the radially inward direction of the tire.

5. The tire according to claim 1, wherein the cross-section of the rib is rectangular.

6. The recessed wall surface has an inner end that is located furthest inward in the tire radial direction, The recess has a bottom surface portion connected to the inner end, The tire according to any one of claims 1 to 5, wherein the bottom surface includes a top portion located radially outward from the inner end and an inclined surface extending radially outward from the inner end toward the top portion.

7. The tire according to claim 6, wherein the top portion is capable of making contact with the ground when the tire is running.

8. The tire according to claim 6, wherein the height of the top portion is 40% to 80% of the maximum depth of the recess.

9. The tire according to any one of claims 1 to 5, wherein the angle between the recessed wall surface and the tread surface is 90 to 170 degrees.

10. The tire according to claim 9, wherein the angle between the recessed wall surface and the tread surface is 100 to 120 degrees.

11. The tire according to any one of claims 1 to 5, wherein the maximum depth of the recess is 2 to 8 mm.

12. The tire according to any one of claims 1 to 5, wherein the maximum depth of the recess is 20% to 100% of the height of the block in the tire radial direction.

13. The tire is the tire according to any one of claims 1 to 5, which is for driving on rough terrain.

Images