Heavy-duty pneumatic tires

Abstract

To enhance fuel consumption performance and on-snow performance.SOLUTION: Provided is a pneumatic tire 1 in which a heavy load is provided with a plurality of first lateral fine grooves 11, a plurality of second lateral fine grooves 12, a plurality of first crown blocks 14 and a plurality of second crown blocks 15 are provided in a crown region Cr. The first lateral fine grooves 11 and the second lateral fine grooves 12 are 3.0 mm or less in groove width. The first crown blocks 14 are regulated between the first lateral fine grooves 11 adjoining a tire circumferential direction and are hexagonal shape in a tread 14a. Each of the first crown blocks 14 contain three corner parts K adjoining crown circumferential direction grooves in tread plan view. The second crown blocks 15 are regulated between the second lateral fine grooves 12 adjoining the tire circumferential direction. There is provided a first concave part 17 in at least one of the three corner parts K.SELECTED DRAWING: Figure 1

Description

[[Technical Field]]

[0001] The present invention relates to a heavy-duty pneumatic tire. [[Background Art]]

[0002] The following Patent Document 1 describes a heavy-duty pneumatic tire in which a pair of circumferential main grooves is disposed in a tread portion. At least one narrow circumferential groove and a plurality of narrow widthwise grooves are disposed between the pair of circumferential main grooves, whereby a plurality of block-shaped land portions are partitioned and formed. [[Prior Art Literature]] [[Patent Literature]]

[0003] [[Patent Document 1]] Japanese Patent Laid-Open No. 2012-20714 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] In recent years, from the viewpoint of environmental protection, heavy-duty pneumatic tires excellent in fuel efficiency performance have been demanded. Further, since heavy-duty pneumatic tires require a great deal of labor for tire replacement, they are generally required to be usable for all-season travel, and it is particularly desired to improve performance on snow.

[0005] The present invention has been devised in view of the above-described actual situation, and a main object of the present invention is to provide a heavy-duty pneumatic tire capable of improving both fuel efficiency performance and performance on snow. [[Means for Solving the Problem]]

[0006] The present invention relates to a heavy-duty pneumatic tire having a tread portion, wherein the tread portion includes a pair of crown circumferential grooves and a crown region which is the region between the pair of crown circumferential grooves, wherein the pair of crown circumferential grooves are arranged such that the tire equator is located between them, each of the pair of crown circumferential grooves has a groove width greater than 3.0 mm, each of the pair of crown circumferential grooves extends continuously in the tire circumferential direction to form a plurality of first zigzag peaks, the crown region is provided with a plurality of longitudinal narrow grooves, a plurality of transverse narrow grooves and a plurality of crown blocks, each of the plurality of longitudinal narrow grooves and the plurality of transverse narrow grooves has a groove width of 3.0 mm or less, and each of the plurality of longitudinal narrow grooves extends in the tire circumferential direction to form a plurality of second zigzag peaks The multi-layered, continuously extending cross grooves include a first cross groove connecting pairs of adjacent first and second zigzag peaks in the tire axial direction, and a second cross groove connecting pairs of adjacent second zigzag peaks in the tire axial direction, and the multi-layered crown blocks include a multi-layered first crown block defined between adjacent first cross grooves in the tire circumferential direction and having a hexagonal tread surface, and a multi-layered second crown block defined between adjacent second cross grooves in the tire circumferential direction and having a hexagonal tread surface, and in a plan view of the tread, each of the multi-layered first crown blocks includes three corner portions adjacent to either of the pair of crown circumferential grooves, and at least one of the three corner portions is provided with a first recess, wherein the multi-layered, continuously extending cross grooves include a first cross groove connecting pairs of adjacent first and second zigzag peaks in the tire axial direction, and the multi-layered crown blocks include a multi-layered first crown block defined between adjacent second cross grooves in the tire circumferential direction and having a hexagonal tread surface, and in a plan view of the tread, each of the multi-layered first crown blocks includes three corner portions adjacent to either of the pair of crown circumferential grooves, and at least one of the three corner portions is provided with a first recess, wherein the multi-layered crown block is a pneumatic tire for heavy loads. [Effects of the Invention]

[0007] By adopting the above configuration, the heavy-duty pneumatic tire of the present invention can improve fuel efficiency and snow performance. [Brief explanation of the drawing]

[0008] [Figure 1] This is an enlarged plan view of the tread portion showing one embodiment of the heavy-duty tire of the present invention. [Figure 2] Figure 1 is a plan view of the tread section. [Figure 3] This is an enlarged view of the first crown block in Figure 1. [Figure 4] (A) is a schematic perspective view of the first crown block, and (B) is a perspective view of the first crown block in Figure 1. [Figure 5] This is an enlarged view of the first crown block in Figure 1. [Figure 6] Figure 1 is a perspective view of the first crown block. [Figure 7] Figure 1 shows enlarged views of the first and second crown blocks. [Figure 8] (A) is a cross-sectional view along line AA in Figure 7, and (B) is a cross-sectional view along line BB in Figure 7. [Figure 9] (A) is a plan view of the first crown block of another embodiment, and (B) is a perspective view of the first crown block of (A). [Figure 10] This is a perspective view of the first crown block of yet another embodiment. [Figure 11] (A) is a perspective view of the first crown block in yet another embodiment, and (B) is a perspective view of the first crown block in yet another embodiment. [Modes for carrying out the invention]

[0009] One embodiment of the present invention will be described below with reference to the drawings. Figure 1 is a plan view of the tread portion 2 of the heavy-duty pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 of this embodiment. The tire 1 of this embodiment is suitably used, for example, as an all-season tire that can also be used for driving on snowy roads.

[0010] As shown in Figure 1, the tread portion 2 of this embodiment includes a pair of crown circumferential grooves 3, 3 and a crown region Cr which is the area between the pair of crown circumferential grooves 3, 3. The crown region Cr is the area where a relatively large ground pressure acts during straight-line driving.

[0011] A pair of crown circumferential grooves 3, 3 are positioned so that the tire equator C is located between them. Each crown circumferential groove 3 has a groove width W1 greater than 3.0 mm. Furthermore, each crown circumferential groove 3 extends continuously in the circumferential direction of the tire to form multiple first zigzag peaks 5. Such crown circumferential grooves 3 can form large snow columns, thus providing basic snow performance.

[0012] The crown region Cr is provided with a plurality of longitudinal grooves 6, a plurality of transverse grooves 7, and a plurality of crown blocks 8. Each longitudinal groove 6 extends continuously in the circumferential direction of the tire to form a second zigzag apex 9. Each transverse groove 7 includes a first transverse groove 11 connecting a pair P1 of adjacent first zigzag apex 5 and second zigzag apex 9 in the axial direction of the tire, and a second transverse groove 12 connecting a pair P2 of adjacent second zigzag apex 9, 9 in the axial direction of the tire.

[0013] Each crown block 8 includes a plurality of first crown blocks 14 and a plurality of second crown blocks 15. Each first crown block 14 is defined between adjacent first transverse grooves 11 in the circumferential direction of the tire, and its tread surface 14a is hexagonal. Each second crown block 15 is defined between adjacent second transverse grooves 12 in the circumferential direction of the tire, and its tread surface 15a is hexagonal.

[0014] Each of the longitudinal grooves 6 and each of the transverse grooves 7 has a groove width W2 and W3 of 3.0 mm or less, respectively. As a result, when in contact with the ground, each of the first crown blocks 14 and each of the second crown blocks 15 support each other due to the deformation of each of the grooves 6 and 7, thereby increasing the apparent pattern rigidity of the crown region Cr. This reduces rolling resistance and improves fuel efficiency.

[0015] In a plan view of a tread, each first crown block 14 includes three corner portions K adjacent to either of the pair of crown circumferential grooves 3. A first recess 17 is provided in at least one of the three corner portions K. The first recess 17 allows a strong snow column to be formed continuously with the snow column formed by the crown circumferential grooves 3. Therefore, performance on snow is improved.

[0016] The tread portion 2 further includes, for example, a pair of shoulder regions Sh disposed on both sides of the crown region Cr in the tire axial direction. It is preferable that the width Wa of the crown region Cr in the tire axial direction is 45% to 65% of the tread width TW. It is preferable that the width Wb of the shoulder region Sh in the tire axial direction is 10% to 30% of the tread width TW.

[0017] As used herein, the "tread width TW" refers to the distance in the tire axial direction between tread edges Te, which are the outermost ground contact positions in the tire axial direction when the tire 1 in a normal state is loaded with a normal load and grounded on a flat surface with a camber angle of 0°.

[0018] The "normal state" refers to a state where the tire is assembled to a normal rim, filled with a normal internal pressure, and is in an unloaded state. Unless otherwise specified in the present specification, the dimensions and the like of each part of the tire 1 are values measured in the normal state.

[0019] The "normal rim" is a rim defined for each tire in the standard system including the standard on which the tire 1 is based. For example, it is a "standard rim" for JATMA, a "Design Rim" for TRA, and a "Measuring Rim" for ETRTO.

[0020] The aforementioned "standard internal pressure" is the air pressure specified for each tire in the standards system, including the standard on which Tire 1 is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0021] The aforementioned "standard load" is the load specified for each tire in the standards system, including the standard on which Tire 1 is based. For JATMA, it is the "maximum load capacity," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "LOAD CAPACITY."

[0022] In this embodiment, the crown region Cr is provided with two longitudinal grooves 6 located on either side of the tire equator C. As a result, the crown region Gr is provided with a second crown block 15 located on the tire equator C and first crown blocks 14 located on both sides of the second crown block 15. Note that the number of longitudinal grooves 6 is not limited to two.

[0023] The groove width W1 of the crown circumferential groove 3 is preferably 3% or more of the tread width TW, more preferably 4% or more, preferably 10% or less, and even more preferably 9% or less. The groove depth D1 of the crown circumferential groove (shown in Figure 8(A)) is preferably 8 mm or more, more preferably 9 mm or more, preferably 15 mm or less, and even more preferably 14 mm or less. Such a crown circumferential groove 3 has the effect of maintaining the pattern rigidity of the tread section 2 and increasing the shear force of snow columns.

[0024] Figure 2 is a plan view of the tread portion 2. As shown in Figure 2, the first zigzag apex 5 includes an inward-facing apex 5a that is convex toward the tire equator C and an outward-facing apex 5b that is convex toward the tread end Te. In this embodiment, the first zigzag apex 5 has the inward-facing apex 5a and the outward-facing apex 5b arranged alternately in the circumferential direction of the tire.

[0025] The groove width W2 of the longitudinal groove 6 (shown in Figure 1) is preferably 0.5 mm or more, more preferably 0.8 mm or more, and preferably 2.7 mm or less. The groove depth D2 of the longitudinal groove 6 (shown in Figure 8(B)) is preferably 8 mm or more, more preferably 9 mm or more, preferably 15 mm or less, and more preferably 14 mm or less. In this embodiment, the groove depth D2 of the longitudinal groove 6 is the same as the groove depth D1 of the crown circumferential groove.

[0026] The second zigzag apex 9 includes an inwardly curved apex 9a that is convex toward the tire equator C and an outwardly curved apex 9b that is convex toward the tread edge Te. In this embodiment, the inwardly curved apex 9a and the outwardly curved apex 9b of the second zigzag apex 9 are arranged alternately in the circumferential direction of the tire.

[0027] The first transverse groove 11 connects, for example, the inward-facing apex 5a of the crown circumferential groove 3 and the outward-facing apex 9b of the longitudinal groove 6. The second transverse groove 12 connects, for example, the inward-facing apex 9a, 9a of the longitudinal groove 6. In this embodiment, the first transverse groove 11 and the second transverse groove 12 extend in a straight line.

[0028] The groove width W3a of the first transverse narrow groove 11 and the groove width W3b of the second transverse narrow groove 12 are preferably 0.5 mm or more, more preferably 0.6 mm or more, preferably 1.5 mm or less, and more preferably 1.2 mm or less, respectively. The groove depth D3a of the first transverse narrow groove 11 (shown in Figure 8(A)) and the groove depth D3b of the second transverse narrow groove 12 (shown in Figure 8(B)) are preferably 5 mm or more, more preferably 6 mm or more, preferably 13 mm or less, and more preferably 12 mm or less, respectively. In this embodiment, the groove depth D3a of the first transverse narrow groove 11 is the same as the groove depth D3b of the second transverse narrow groove 12.

[0029] Each crown block 8 (the first crown block 14 and the second crown block 15) is barrel-shaped, with the width Wb in the axial direction of the tire at the central part 8c in the tire circumferential direction being greater than the width Wd in the axial direction of the tire at both ends 8e in the tire circumferential direction. Each crown block 8 is a block in which the maximum length Lm in the tire circumferential direction is greater than the maximum width Wm in the axial direction of the tire. Because such crown blocks 8 have high rigidity in the tire circumferential direction, rolling resistance can be further reduced.

[0030] Figure 3 is an enlarged view of the first crown block 14. As shown in Figure 3, the three corner sections K of the first crown block 14 (shown in Figure 1) include, for example, one corner section K1 formed by the outward-facing apex 5b and two corner sections K2 formed by the inward-facing apex 5a and the first transverse groove 11. The two corner sections K2 are formed, for example, a corner section K2a with the smallest interior angle α and a corner section K2b with a larger interior angle α than corner section K2a. Corner section K2b is formed with a smaller interior angle α than corner section K1, which is formed by the outward-facing apex 5b.

[0031] In this specification, the interior angle α is defined by two imaginary straight lines formed on the tread plane. Specifically, the interior angle α1 of the corner section K1 is the angle between a first straight line c1 and a second straight line c2 in a tread plane view. The first straight line c1 is formed by connecting the outer end 5t of the outward-facing apex 5b in the tire axial direction with the first protruding end t1 of the corner section K2a. The second straight line c2 is formed by connecting the outer end 5t of the outward-facing apex 5b with the second protruding end t2 of the corner section K2b. The first protruding end t1 is the end where one of the first transverse grooves 11, the crown circumferential groove 3, and the tread surface 14a intersect. The second protruding end t2 is the end where the other of the first transverse grooves 11, the crown circumferential groove 3, and the tread surface 14a intersect. The interior angle α2 of the corner section K2a is the angle between the first straight line c1 and the third straight line c3. The third straight line c3 is formed by connecting the first protruding end t1 and the third protruding end t3. The third protruding end t3 is the end where one of the first transverse narrow grooves 11, the vertical narrow groove 6, and the tread surface 14a intersect. The interior angle α3 of the corner section K2b is the angle between the second straight line c2 and the fourth straight line c4. The fourth straight line c4 is formed by connecting the second protruding end t2 and the fourth protruding end t4. The fourth protruding end t4 is the end where the other of the first transverse narrow groove 11, the vertical narrow groove 6, and the tread surface 14a intersect. If a recess (such as the first recess 17 or the second recess 20 described later) is provided in each corner section K, the outer end 5t and each protruding end t1 to t4 are defined by the groove wall and tread surface assuming that the recess is not provided.

[0032] While not particularly limited, the inner angle α1 of corner section K1 is, for example, 130 to 170 degrees. The inner angle α2 of corner section K2a is, for example, 90 to 110 degrees. The inner angle α3 of corner section K2b is, for example, 105 to 125 degrees. The first crown block 14 having such corner sections K suppresses a decrease in the pattern rigidity of the tread section 2.

[0033] The first recess 17 is provided, for example, in the corner portion K2 between the first zigzag top portion 5 (inward top portion 5a) and the first transverse narrow groove 11. In this embodiment, the first recess 17 is provided in the corner portion K2a, which has the smallest inner angle α2 among the three corner portions K. Such a first recess 17 helps to reduce rolling resistance by suppressing the decrease in rigidity of the corner portion K2a.

[0034] In this embodiment, the first recess 17 is provided in only one of the three corner sections K. Such a tire 1 helps to suppress an excessive decrease in pattern rigidity in the crown region Cr, thereby maintaining high fuel efficiency. To improve snow performance, the first recess 17 may also be provided in two corner sections K2 formed by the crown circumferential groove 3 and the first transverse narrow groove 11 (not shown).

[0035] Figure 4(A) is a perspective view of the first crown block 14. As shown in Figure 4(A), the first recess 17 has a first bevel surface 18 in this embodiment. The first bevel surface 18 is a triangular plane with vertices at points p1, p2, and p3. Point p1 is on the edge e1 where the crown circumferential groove 3 and the tread surface 14a intersect. This edge e1 extends in the circumferential direction of the tire. Point p2 is on the edge e2 where the first transverse narrow groove 11 and the tread surface 14a intersect. This edge e2 extends in the axial direction of the tire. Point p3 is on the edge e3 where the groove wall 3e of the crown circumferential groove 3 and the groove wall 11e of the first transverse narrow groove 11 intersect. This edge e3 extends in the radial direction of the tire. Thus, the first bevel surface 18 in this embodiment is formed as a so-called diamond cut. Such a first slope 18 makes it easy to discharge the snow columns formed by the first recess 17, so that new snow columns can be formed in the first recess 17 each time it touches the ground. As a result, the performance on snow is further improved. The first slope 18 may be, for example, a triangular curved surface.

[0036] As shown in Figure 3, in a plan view of the tread, the length w10 of the first slope 18 in the tire axial direction continuously decreases from the second point p2 toward the center of the first crown block 14 in the tire circumferential direction. The length h10 of the first slope 18 in the tire circumferential direction continuously increases from the second point p2 toward the third point p3. Such a first slope 18 facilitates the discharge of snow in the first recess 17 into the crown circumferential groove 3.

[0037] To form large snow columns while maintaining the pattern rigidity of the crown region Cr, the tire radial length d1 of the first slope 18 (shown in Figure 4(A)) is preferably 0.50 times or more, more preferably 0.70 times or more, and preferably 1.00 times or less of the groove depth D2 of the first transverse narrow groove 11. Similarly, the maximum tire axial length W10 of the first slope 18 is preferably 0.10 times or more, more preferably 0.20 times or more, preferably 0.60 times or less, and preferably 0.50 times or less of the maximum tire axial length Wm of the first crown block 14 (shown in Figure 2). Furthermore, the tire circumferential length H10 of the first slope 18 is preferably 0.02 times or more, more preferably 0.04 times or more, preferably 0.50 times or less, and preferably 0.40 times or less of the maximum tire circumferential length Lm of the first crown block 14 (shown in Figure 2). Figure 4(B) shows an embodiment in which the length d1 of the first slope 18 is 1.00 times the groove depth D2 of the first transverse narrow groove 11.

[0038] Figure 5 is a plan view of the first crown block 14. As shown in Figure 5, in a plan view of the tread, each first crown block 14 includes three corner sections K3 adjacent to the longitudinal grooves 6. The three corner sections K3 are formed, for example, one corner section K3a formed by the inward-facing apex 9a and two corner sections K3b formed by the outward-facing apex 9b and the first transverse groove 11. The two corner sections K3b have smaller interior angles than, for example, one K3a. The interior angles of the corner sections K3 are defined by two imaginary straight lines (not shown), similar to the interior angles α1 to α3 of the corner section K.

[0039] A second recess 20 is provided in at least one of the three corner sections K3. The second recess 20 is provided, for example, in the two corner sections K3 on both ends in the tire circumferential direction. In this embodiment, the second recess 20 is formed in the two corner sections K3b formed by the outward-facing apex 9b and the first transverse narrow groove 11. Such a second recess 20 suppresses a decrease in the pattern rigidity of the tread section 2.

[0040] Figure 6 is a perspective view of the first crown block 14. As shown in Figure 6, the second recess 20 includes a third inclined surface 21. The third inclined surface 21 is a quadrilateral with vertices at points 8, 9, 10, and 11. Point 8, p8, lies on edge e5 where the longitudinal groove 6 and the tread surface 14a intersect. Point 9, p9, lies on edge e6 where the groove wall 6e of the longitudinal groove 6 and the groove wall 11e of the first transverse groove 11 intersect. Point 10, p10, lies on the tread surface 14a of the first crown block 14, spaced inward in the tire circumferential direction from point Q on edge e2 where the groove wall 11e of the first transverse groove 11 and the tread surface 14a intersect. Point 11, p11, lies on the groove wall 11e of the first transverse groove 11, spaced inward in the tire radial direction from point Q. Such a third slope 21 helps to form large snow columns.

[0041] The second recess 20 further includes a fourth slope 22. The fourth slope 22 is triangular in shape, for example, including the tenth point p10, the eleventh point p11, and point Q. Such a fourth slope 22 exerts snow column shear force.

[0042] As shown in Figure 5, in a plan view of the tread, the third slope 21 has a tire axial length w11 that continuously decreases from the 10th point p10 toward the center of the tire circumferential direction of the first crown block 14. The third slope 21 has a tire circumferential length h11 that continuously increases from the 11th point p11 toward the outside of the tire axial direction of the first crown block 14 toward the 9th point p9. Such a third slope 21 helps to expel snow into the second recess 20.

[0043] The pair of second recesses 20, 20 facing each other across the first transverse groove 11 are formed with the same length w12 along the first transverse groove 11. This allows the first transverse groove 11 and the pair of second recesses 20, 20 to form one large snow column, and also reduces the difference in rigidity between the corner portions K3b, K3b of the first crown blocks 14, 14 adjacent to each other in the circumferential direction of the tire, thereby minimizing the impact on rolling resistance.

[0044] The length d2 of the third slope 21 in the tire radial direction (shown in Figure 6) is preferably 0.15 times or more the groove depth D3a of the first transverse narrow groove 11, more preferably 0.25 times or more, preferably 0.60 times or less, and more preferably 0.50 times or less. The maximum length W11 of the third slope 21 in the tire axial direction is preferably 0.10 times or more the maximum length Wm of the first crown block 14 in the tire axial direction (shown in Figure 2), more preferably 0.20 times or more, preferably 0.60 times or less, and more preferably 0.50 times or less. The maximum length H11 of the third slope 21 in the tire circumferential direction is preferably 0.02 times or more the maximum length Lm of the first crown block 14 in the tire circumferential direction (shown in Figure 2), more preferably 0.04 times or more, preferably 0.50 times or less, and more preferably 0.40 times or less.

[0045] Figure 7 is an enlarged view of the first crown block 14 and the second crown block 15. As shown in Figure 7, each first crown block 14 is provided with a first transverse groove 25 that crosses the first crown block 14. Such a first transverse groove 25 provides an edge effect to improve driving stability on snowy roads, especially on snowy and icy roads.

[0046] The first transverse groove 25 is inclined in the same direction with respect to the tire axis from the crown circumferential groove 3 to the longitudinal groove 6. The first transverse groove 25 includes a first portion 25a connected to the crown circumferential groove 3, a second portion 25b connected to the longitudinal groove 6, and a third portion 25c connecting the first portion 25a and the second portion 25b, which is inclined more significantly with respect to the tire axis than the first portion 25a and the second portion 25b. Although not particularly limited, the difference (β1c-β1a) between the angle β1c of the third portion 25c with respect to the tire axis and the angle β1a of the first portion 25a with respect to the tire axis is preferably 20 degrees or more, more preferably 25 degrees or more, preferably 40 degrees or less, and more preferably 35 degrees or less. The difference (β1c-β1b) between the angle β1c of the third part 25c and the angle β1b of the second part 25b with respect to the tire axis should ideally be the same as the difference (β1c-β1a).

[0047] The first transverse groove 25 is located in the central part 14f of the first crown block 14 in the tire circumferential direction. The first transverse groove 25 is located on both sides of the tire circumferential direction, centered on the midpoint of the first crown block 14 in the tire circumferential direction, within 30% of the maximum length Lm of the first crown block 14. Such a first transverse groove 25 moderately reduces the rigidity of the first crown block 14 in the tire circumferential direction, helping to make the rigidity of the first crown block 14 uniform both inside and outside the tire circumferential direction.

[0048] Figure 8(A) is a cross-sectional view along line AA in Figure 7. As shown in Figure 8(A), the groove depth D4 of the first transverse groove 25 is preferably 0.5 times or more, more preferably 0.6 times or more, preferably 1.0 times or less, and even more preferably 0.9 times or less, of the groove depth D3a of the first transverse groove 11. The groove width W4 of the first transverse groove 25 is preferably 0.5 mm or more, more preferably 0.6 mm or more, preferably 1.5 mm or less, and even more preferably 1.2 mm or less.

[0049] As shown in Figure 7, in a plan view of the tread, each second crown block 15 includes four corner sections K5 between the longitudinal grooves 6 and the second transverse grooves 12. In this embodiment, the second crown block 15 is provided with a third recess 27 in all four corner sections K5. This further improves snow performance.

[0050] In this embodiment, the third recess 27 includes a quadrilateral fourth slope 28 with four vertices, similar to the third slope 21 of the second recess 20. This third recess 27 also enhances snow column shear force and improves snow performance. The fourth slope 28 is formed in the same shape as the third slope 21. Thus, in the tread portion 2 of this embodiment, the quadrilateral fourth slope 28 and the third slope 21 are positioned closer to the tire equator C than the triangular first slope 18. In other words, during straight-line driving, the fourth slope 28 and the third slope 21 are positioned in areas where relatively large ground pressure acts, and the first slope 18 is positioned in areas where relatively small ground pressure acts. As a result, the snow column shear force can be further enhanced in areas where relatively large ground pressure acts, while the decrease in pattern rigidity of the crown block 8 is suppressed in areas where relatively small ground pressure acts.

[0051] The pair of third recesses 27, 27 facing each other across the second transverse groove 12 are formed with the same length w13 along the second transverse groove 12. This allows the second transverse groove 12 and the pair of third recesses 27, 27 to form one large snow column, and also reduces the difference in rigidity between the corner portions K5, K5 of the adjacent second crown blocks 15, 15 in the circumferential direction of the tire, thereby minimizing the impact on rolling resistance.

[0052] Each second crown block 15 further includes two corner sections K6 formed by the outward-facing apex 9b of the longitudinal groove 6. The interior angle of each corner section K5 is smaller than the interior angle of each corner section K6. No recess is formed in each corner section K6.

[0053] Each second crown block 15 is provided with a second transverse groove 35 that crosses the second crown block 15. Such a second transverse groove 35 provides an edge effect, improving driving stability on snowy roads, especially on snowy and icy roads.

[0054] The second transverse groove 35 is located in the central part 15f of the second crown block 15 in the tire circumferential direction. The second transverse groove 35 is located on both sides of the second crown block 15 from the midpoint in the tire circumferential direction, within 15% of the maximum length Lm of the second crown block 15 in the tire circumferential direction. Such a second transverse groove 35 moderately reduces the rigidity of the second crown block 15 in the tire circumferential direction, helping to make the rigidity of the second crown block 15 uniform both inside and outside the tire circumferential direction.

[0055] The second transverse groove 35 is inclined in the same direction with respect to the tire axis from one longitudinal groove 6 (left side in the figure) to the other longitudinal groove 6 (right side in the figure). The second transverse groove 35 includes a first portion 35a connected to one longitudinal groove 6, a second portion 35b connected to the other longitudinal groove 6, and a third portion 35c connecting the first portion 35a and the second portion 35b. The third portion 35c is inclined more significantly with respect to the tire axis than the first portion 35a and the second portion 35b. Although not particularly limited, the difference (β2c-β2a) between the angle β2c of the third portion 35c with respect to the tire axis and the angle β2a of the first portion 35a with respect to the tire axis is preferably 20 degrees or more, more preferably 25 degrees or more, preferably 40 degrees or less, and more preferably 35 degrees or less. The difference (β2c-β2b) between the angle β2c of the third part 35c and the angle β2b of the second part 35b with respect to the tire axis should ideally be the same as the difference (β2c-β2a).

[0056] In the tread portion 2 of this embodiment, the second transverse groove 12 is arranged so as to intersect with a virtual straight line c10, which connects the inner ends in the tire axial direction of adjacent first transverse grooves 25 in the tire axial direction. Similarly, the second transverse groove 35 is arranged so as to intersect with a virtual straight line c11, which connects the inner ends in the tire axial direction of adjacent first transverse grooves 11 in the tire axial direction. The straight line c11 intersects with the third portion 35c of the second transverse groove 35. As a result, the edge effect of the first transverse groove 25 and the edge effect of the second transverse groove 12 are exerted substantially simultaneously. Furthermore, the edge effect of the first transverse groove 11 and the edge effect of the second transverse groove 35 are exerted substantially simultaneously.

[0057] Figure 8(B) is a cross-sectional view along line BB in Figure 7. As shown in Figure 8(B), the groove depth D5 of the second transverse groove 35 is preferably 0.5 times or more, more preferably 0.6 times or more, preferably 1.0 times or less, and even more preferably 0.9 times or less, of the groove depth D3b of the second transverse groove 12. The groove width W5 of the second transverse groove 35 is preferably 0.5 mm or more, more preferably 0.6 mm or more, preferably 1.5 mm or less, and even more preferably 1.0 mm or less.

[0058] Figure 9(A) is a plan view of the first crown block 14 of another embodiment. Figure 9(B) is a perspective view of the first crown block 14 of another embodiment. Components that are the same as those in this embodiment are denoted by the same reference numerals and their descriptions may be omitted. As shown in Figure 9, in this embodiment, the first recess 17 includes a second bevel 19. The second bevel 19 is a quadrilateral with vertices at the fourth point p4, the fifth point p5, the sixth point p6, and the seventh point p7. The second bevel 19 has the same shape as the third bevel 21 and the fourth bevel 28. The fourth point p4 is on the edge e1 where the crown circumferential groove 3 and the tread surface 14a intersect. The fifth point p5 is on the edge e3 where the groove wall 3e of the crown circumferential groove 3 and the groove wall 11e of the first transverse narrow groove 11 intersect. The sixth point p6 is located on the tread surface 14a of the first crown block 14, spaced inward in the tire circumferential direction from point P on the edge e2 where the first transverse groove 11 and the tread surface 14a intersect. The seventh point p7 is located on the groove wall 11e of the first transverse groove 11, spaced inward in the tire radial direction from point P. In this embodiment, the first recess 17 includes a fifth inclined plane 23 which is a triangular plane with points p6, p7 and P as its vertices.

[0059] Figure 10 is a perspective view of the first crown block 14 of yet another embodiment. Components identical to those in this embodiment are denoted by the same reference numerals, and their description may be omitted. As shown in Figure 10, in this embodiment, the first recess 17 has a sixth bevel 41. The sixth bevel 41 is a quadrilateral with vertices at the first point p1, the second point p2, the 21st point p21, and the 22nd point p22. The sixth bevel 41 may be a curved surface or a flat surface. The 21st point p21 is located, for example, on edge e11 that passes through the third point p3 and extends parallel to edge e1. The 22nd point p22 is located, for example, on edge e12 that passes through the third point p3 and extends parallel to edge e2. In this embodiment, the edge connecting the first point p1 and the second point p2 and the edge connecting the 21st point p21 and the 22nd point p22 extend parallel to each other.

[0060] In this embodiment, the first recess 17 includes a seventh surface 42 connected to the sixth inclined surface 41. The seventh surface 42 is, for example, triangular in shape with vertices at the third point p3, the 21st point p21, and the 22nd point p22. The seventh surface 42 is formed, for example, parallel to the tread surface 14a. The seventh surface 42 may also be inclined outward in the tire radial direction from the third point p3 to the 21st point p21 and the 22nd point p22. Figure 10 shows an embodiment in which the length d11 of the sixth inclined surface 41 in the tire radial direction is 1.00 times the groove depth D2 of the first transverse narrow groove 11 (shown in Figure 4(A)).

[0061] Figure 11(A) is a perspective view of the first crown block 14 of yet another embodiment. Components identical to those in this embodiment are denoted by the same reference numerals and their descriptions may be omitted. As shown in Figure 11(A), in this embodiment, the second recess 20 includes an eighth bevel 43. The eighth bevel 43 is a quadrilateral with vertices at the eighth point p8, the tenth point p10, the twentieth point p23, and the twenty-fourth point p24. The eighth bevel 43 may be a curved surface or a flat surface. The twenty-third point p23 is located, for example, on edge e13 that passes through the ninth point p9 and extends parallel to edge e5. The twenty-fourth point p24 is located, for example, on edge e14 that passes through the eleventh point p11 and extends parallel to edge e5. In this embodiment, the edge connecting the 8th point p8 and the 10th point p10 extends parallel to the edge connecting the 23rd point p23 and the 24th point p24.

[0062] In this embodiment, the second recess 20 includes a ninth surface 44 connected to the eighth inclined surface 43. The ninth surface 44 is, for example, a quadrilateral with vertices at the ninth point p9, the eleventh point p11, the 23rd point p23, and the 24th point p24. The ninth surface 44 is formed, for example, parallel to the tread surface 14a. The ninth surface 44 has, for example, an edge connecting the ninth point p9 and the eleventh point p11, and an edge connecting the 23rd point p23 and the 24th point p24, extending parallel to each other.

[0063] Figure 11(B) is a perspective view of the first crown block 14 of yet another embodiment. Components identical to those in this embodiment are denoted by the same reference numerals, and their descriptions may be omitted. As shown in Figure 11(B), in this embodiment, the first recess 17 has a tenth bevel 45. The tenth bevel 45 is a quadrilateral with vertices at the fourth point p4, the sixth point p6, the twenty-fifth point p25, and the twenty-sixth point p26. The tenth bevel 45 may be a curved surface or a flat surface. The twenty-fifth point p25 is located, for example, on edge e15 that passes through the fifth point p5 and extends parallel to edge e1. The twenty-sixth point p26 is located, for example, on edge e16 that passes through the seventh point p7 and extends parallel to edge e1. In this embodiment, the edge connecting the fourth point p4 and the sixth point p6 extends parallel to the edge connecting the 25th point p25 and the 26th point p26.

[0064] In this embodiment, the first recess 17 includes an eleventh surface 46 connected to the tenth inclined surface 45. The eleventh surface 46 is, for example, a quadrilateral with vertices at the fifth point p5, the seventh point p7, the 25th point p25, and the 26th point p26. The eleventh surface 46 is formed, for example, parallel to the tread surface 14a. The eleventh surface 46 has, for example, an edge connecting the fifth point p5 and the seventh point p7, and an edge connecting the 25th point p25 and the 26th point p26, both extending parallel to each other.

[0065] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiments described above and can be implemented in various modified forms. [Examples]

[0066] A tire with the basic pattern shown in Figure 1 was prototyped based on the specifications in Table 1, and tested for fuel efficiency and snow performance. The common specifications and test methods are as follows. Size: 275 / 80R22.5 Rim: 22.5 x 8.25 Internal pressure: 900kPa

[0067] <Fuel efficiency> The rolling resistance was measured using a rolling resistance tester under the following conditions. The evaluation is expressed as an index with the value of Comparative Example 2 set to 100. A smaller number indicates lower rolling resistance and better fuel efficiency. Load: 28.76kN Speed: 60km / h

[0068] <Snow performance> The test tires were mounted on the test vehicle shown below, and the acceleration was calculated when the test driver accelerated from 10 km / h to 40 km / h on a snowy road. The results are shown as an index with the acceleration of Comparative Example 2 set to 100. A higher number indicates better snow performance. Test vehicle: Truck with a maximum load capacity of 10 tons (2-D vehicle) The test results are shown in Table 1.

[0069] [Table 1]

[0070] The test results show that the tires in the example have improved fuel efficiency or snow performance compared to the tires in the comparative example.

[0071] [Note] The present invention includes the following embodiments.

[0072] [Invention 1] A heavy-duty pneumatic tire having a tread section, The tread portion includes a pair of crown circumferential grooves and a crown region which is the region between the pair of crown circumferential grooves. The pair of crown circumferential grooves are arranged such that the tire equator is located between them. The pair of crown circumferential grooves each have a groove width greater than 3.0 mm. The pair of crown circumferential grooves each extend continuously in the tire circumferential direction so as to form a plurality of first zigzag peaks. The crown region is provided with a plurality of longitudinal grooves, a plurality of transverse grooves, and a plurality of crown blocks. Each of the aforementioned plurality of vertical narrow grooves and the plurality of horizontal narrow grooves has a groove width of 3.0 mm or less. Each of the aforementioned longitudinal grooves extends continuously in the circumferential direction of the tire so as to form a plurality of second zigzag peaks. The plurality of transverse grooves include a first transverse groove connecting pairs of the first and second zigzag peaks that are adjacent to each other in the tire axial direction, and a second transverse groove connecting pairs of the second zigzag peaks that are adjacent to each other in the tire axial direction. The plurality of crown blocks are defined between the first transverse grooves adjacent to each other in the circumferential direction of the tire, and the tread surface of the plurality of first crown blocks is hexagonal in shape, It includes a plurality of second crown blocks, which are defined between adjacent second transverse grooves in the circumferential direction of the tire and whose tread surfaces are hexagonal in shape, In a plan view of the tread, each of the plurality of first crown blocks includes three corner portions adjacent to one of the pair of crown circumferential grooves, A first recess is provided in at least one of the three corner portions. Heavy-duty pneumatic tires. [Invention 2] The heavy-duty pneumatic tire according to the present invention 1, wherein the first recess is provided in the corner portion between the first zigzag apex and the first transverse narrow groove. [Invention 3] The first recess is provided in the corner portion with the smallest inner angle among the three corner portions, as described in invention 1 or 2 of the present invention, for a heavy-duty pneumatic tire. [4th Invention] The first recess has a first inclined surface, The first slope is a triangular plane with the first, second, and third points as its vertices. The first point is located on the edge where the crown circumferential groove and the tread intersect, The second point is located on the edge where the first transverse groove and the tread intersect. The third point is located on the edge where the groove wall of the crown circumferential groove and the groove wall of the first transverse narrow groove intersect, as described in invention 1 or 2 of the present invention. [5th ​​Invention] The length of the first slope in the tire radial direction is 0.50 to 1.00 times the groove depth of the first transverse narrow groove. The maximum length of the first inclined plane in the tire axial direction is 0.10 to 0.60 times the maximum length of the first crown block in the tire axial direction. The pneumatic tire for heavy loads according to the present invention, wherein the maximum length of the first slope in the tire circumferential direction is 0.02 to 0.50 times the maximum length of the first crown block in the tire circumferential direction. [Invention 6] The first recess includes a second slope, The second slope is a quadrilateral with vertices at the 4th, 5th, 6th, and 7th points. The fourth point is located on the edge where the crown circumferential groove and the tread intersect. The fifth point is located on the edge where the groove wall of the crown circumferential groove and the groove wall of the first transverse narrow groove intersect. The sixth point is located on the tread surface, spaced inward in the tire circumferential direction from point P on the edge where the groove wall of the first transverse groove and the tread surface intersect, The seventh point is located on the groove wall of the first transverse narrow groove, which is spaced inward from point P in the radial direction of the tire, in the heavy-duty pneumatic tire according to invention 1 or 2. [7th Invention] In a plan view of the tread, each of the plurality of first crown blocks includes three corner portions adjacent to the longitudinal grooves. A heavy-duty pneumatic tire according to the present invention 1 or 2, wherein at least one of the three corner portions is provided with a second recess. [8th Invention] The second recess includes a third slope, The third slope is a quadrilateral with vertices at the 8th, 9th, 10th, and 11th points. The eighth point is located on the edge where the vertical groove and the tread intersect, The ninth point is located on the edge where the groove wall of the vertical narrow groove and the groove wall of the first horizontal narrow groove intersect. The tenth point is located on the tread surface, spaced inward in the tire circumferential direction of the first crown block from point Q on the edge where the groove wall of the first transverse narrow groove intersects with the tread surface. The 11th point is located on the groove wall of the first transverse narrow groove, which is spaced inward from point Q in the radial direction of the tire, in the heavy-duty pneumatic tire according to the present invention, as described in 7. [Invention 9] The length of the third slope in the tire radial direction is 0.15 to 0.60 times the groove depth of the first transverse groove. The maximum length of the third slope in the tire axial direction is 0.10 to 0.60 times the maximum length of the first crown block in the tire axial direction. The pneumatic tire for heavy loads according to the present invention, wherein the maximum length of the third slope in the tire circumferential direction is 0.02 to 0.50 times the maximum length of the first crown block in the tire circumferential direction. [Invention 10] The heavy-duty pneumatic tire according to the present invention, wherein the second recess is provided in the two corner portions on both ends of the tire circumferential direction among the three corner portions. [Invention 11] A heavy-duty pneumatic tire according to the present invention 1 or 2, wherein each of the plurality of first crown blocks is provided with a first transverse narrow groove that crosses the first crown block. [Invention 12] The groove depth of the first transverse groove is 0.5 to 1.0 times the groove depth of the first lateral groove. The heavy-duty pneumatic tire according to invention 11, wherein the groove width of the first transverse narrow groove is 1.5 mm or less. [Invention 13] The multiple crown blocks include multiple second crown blocks, The plurality of second crown blocks are divided between the plurality of longitudinal grooves and between the second transverse grooves adjacent to each other in the circumferential direction of the tire. The second crown block has a hexagonal tread surface. In a plan view of the tread, each of the plurality of second crown blocks includes four corner sections between the longitudinal groove and the second transverse groove. A heavy-duty pneumatic tire according to the present invention 1 or 2, wherein the four corner portions are provided with third recesses. [Explanation of symbols]

[0073] 1. Heavy-duty pneumatic tire 11. First transverse narrow groove 12. Second transverse narrow groove 14. First Crown Block 14a Tread 15. Second Crown Block 17. First recess Cr Crown Region K Corner Section

Claims

1. A heavy-duty pneumatic tire having a tread section, The tread portion includes a pair of crown circumferential grooves and a crown region which is the region between the pair of crown circumferential grooves. The pair of crown circumferential grooves are arranged such that the tire equator is located between them. The pair of crown circumferential grooves each have a groove width greater than 3.0 mm. The pair of crown circumferential grooves each extend continuously in the tire circumferential direction so as to form a plurality of first zigzag peaks. The crown region is provided with a plurality of longitudinal grooves, a plurality of transverse grooves, and a plurality of crown blocks. Each of the aforementioned plurality of vertical narrow grooves and the plurality of horizontal narrow grooves has a groove width of 3.0 mm or less. Each of the aforementioned longitudinal grooves extends continuously in the circumferential direction of the tire, forming a plurality of second zigzag peaks. The plurality of transverse grooves include a first transverse groove connecting pairs of the first and second zigzag peaks that are adjacent to each other in the tire axial direction, and a second transverse groove connecting pairs of the second zigzag peaks that are adjacent to each other in the tire axial direction. The plurality of crown blocks are defined between the first transverse narrow grooves adjacent to each other in the circumferential direction of the tire, and the tread surface of the plurality of first crown blocks is hexagonal in shape, It includes a plurality of second crown blocks, which are defined between adjacent second transverse grooves in the circumferential direction of the tire and whose tread surfaces are hexagonal in shape, In a plan view of the tread, each of the plurality of first crown blocks includes three corner portions adjacent to one of the pair of crown circumferential grooves. A first recess is provided in at least one of the three corner portions. The first recess includes a second inclined surface, The second slope is a quadrilateral with the fourth, fifth, sixth, and seventh points as its vertices. The fourth point is located on the edge where the crown circumferential groove and the tread intersect, The fifth point is located on the edge where the groove wall of the crown circumferential groove and the groove wall of the first transverse narrow groove intersect. The sixth point is located on the tread surface, spaced inward in the tire circumferential direction of the first crown block from point P on the edge where the groove wall of the first transverse narrow groove and the tread surface intersect. The seventh point is located on the groove wall of the first transverse groove, which is spaced inward from point P in the tire radial direction. Heavy-duty pneumatic tires.

2. The heavy-duty pneumatic tire according to claim 1, wherein the first recess is provided in the corner portion between the first zigzag apex and the first transverse narrow groove.

3. The first recess is provided in the corner portion with the smallest inner angle among the three corner portions, as described in claim 1 or 2.

4. The first recess has a first inclined surface, The first slope is a triangular plane with the first, second, and third points as its vertices. The first point is located on the edge where the crown circumferential groove and the tread intersect, The second point is located on the edge where the first transverse groove and the tread intersect. The third point is located on the edge where the groove wall of the crown circumferential groove and the groove wall of the first transverse narrow groove intersect, as described in claim 1 or 2, for a heavy-duty pneumatic tire.

5. The length of the first slope in the tire radial direction is 0.50 to 1.00 times the groove depth of the first transverse narrow groove. The maximum length of the first inclined plane in the tire axial direction is 0.10 to 0.60 times the maximum length of the first crown block in the tire axial direction. The heavy-duty pneumatic tire according to claim 4, wherein the maximum length of the first slope in the tire circumferential direction is 0.02 to 0.50 times the maximum length of the first crown block in the tire circumferential direction.

6. A heavy-duty pneumatic tire having a tread portion, The tread portion includes a pair of crown circumferential grooves and a crown region which is the region between the pair of crown circumferential grooves. The pair of crown circumferential grooves are arranged such that the tire equator is located between them. The pair of crown circumferential grooves each have a groove width greater than 3.0 mm. The pair of crown circumferential grooves each extend continuously in the tire circumferential direction so as to form a plurality of first zigzag peaks. The crown region is provided with a plurality of longitudinal grooves, a plurality of transverse grooves, and a plurality of crown blocks. Each of the aforementioned plurality of vertical narrow grooves and the plurality of horizontal narrow grooves has a groove width of 3.0 mm or less. Each of the aforementioned longitudinal grooves extends continuously in the circumferential direction of the tire, forming a plurality of second zigzag peaks. The plurality of transverse grooves include a first transverse groove connecting pairs of the first and second zigzag peaks that are adjacent to each other in the tire axial direction, and a second transverse groove connecting pairs of the second zigzag peaks that are adjacent to each other in the tire axial direction. The plurality of crown blocks are defined between the first transverse narrow grooves adjacent to each other in the circumferential direction of the tire, and the tread surface of the plurality of first crown blocks is hexagonal in shape, It includes a plurality of second crown blocks, which are defined between adjacent second transverse grooves in the circumferential direction of the tire and whose tread surfaces are hexagonal in shape, In a plan view of the tread, each of the plurality of first crown blocks includes three corner portions adjacent to one of the pair of crown circumferential grooves. A first recess is provided in at least one of the three corner portions. In a plan view of the tread, each of the plurality of first crown blocks includes three corner portions adjacent to the longitudinal grooves. A second recess is provided in at least one of the three corner portions. The second recess includes a third slope, The third slope is a quadrilateral with vertices at the 8th, 9th, 10th, and 11th points. The eighth point is located on the edge where the vertical groove and the tread intersect, The ninth point is located on the edge where the groove wall of the vertical narrow groove and the groove wall of the first horizontal narrow groove intersect. The tenth point is located on the tread surface, spaced inward in the tire circumferential direction of the first crown block from point Q on the edge where the groove wall of the first transverse narrow groove intersects with the tread surface. The 11th point is located on the groove wall of the first transverse groove, which is spaced inward from point Q in the tire radial direction. Heavy-duty pneumatic tires.

7. The length of the third slope in the tire radial direction is 0.15 to 0.60 times the groove depth of the first transverse groove, The maximum length of the third slope in the tire axial direction is 0.10 to 0.60 times the maximum length of the first crown block in the tire axial direction. The pneumatic tire for heavy loads according to claim 6, wherein the maximum length of the third slope in the tire circumferential direction is 0.02 to 0.50 times the maximum length of the first crown block in the tire circumferential direction.

8. The heavy-duty pneumatic tire according to claim 6, wherein the second recess is provided in the two corner portions on both ends of the three corner portions in the circumferential direction of the tire.

9. The heavy-duty pneumatic tire according to claim 1 or 2, wherein each of the plurality of first crown blocks is provided with a first transverse narrow groove that crosses the first crown block.

10. The groove depth of the first transverse groove is 0.5 to 1.0 times the groove depth of the first transverse groove. The pneumatic tire for heavy loads according to claim 9, wherein the groove width of the first transverse narrow groove is 1.5 mm or less.

11. The plurality of crown blocks include a plurality of second crown blocks, The plurality of second crown blocks are divided between the plurality of longitudinal grooves and between the second transverse grooves adjacent to each other in the circumferential direction of the tire. The second crown block has a hexagonal tread surface. In a plan view of the tread, each of the plurality of second crown blocks includes four corner portions between the longitudinal groove and the second transverse groove. The heavy-duty pneumatic tire according to claim 1 or 2, wherein the four corner portions are provided with third recesses.

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