JP7756541B2 - pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire, and more specifically to a pneumatic tire having a tread including circumferential grooves and shoulder land portions formed in a portion including the outer contact edge in the tire width direction.

Pneumatic tires with treads including multiple land portions separated by multiple circumferential grooves are known (see, for example, Patent Document 1). The tire disclosed in Patent Document 1 has an inner edge in the tire width direction defined by a circumferential groove on the outer side in the tire width direction, and a shoulder land portion is formed in a portion including the outer tire width direction ground contact edge. The shoulder land portion is formed with lug grooves extending in the tire width direction and lateral sipes that are adjacent to the lug grooves in the tire circumferential direction and are narrower than the maximum width of the lug grooves. The shoulder land portion is also formed with a narrow groove that has a portion inclined relative to the tire circumferential direction and is narrower than the lug grooves, located outside the ground contact edge in the tire width direction (Figures 3-5 of Patent Document 1).

U.S. Patent Application Publication No. 2018/0162170

In the shoulder land area, the area outboard of the contact edge in the tire width direction is called the buttress. It is conceivable to improve snow traction performance by forming narrow grooves inclined relative to the tire circumferential direction in these buttresses. Furthermore, forming narrow grooves inclined relative to the tire circumferential direction may improve drainage during cornering when the contact width to the buttress widens during cornering. Furthermore, forming narrow grooves inclined relative to the tire circumferential direction may also have the effect of suppressing lateral vehicle slippage (side slip) due to the edge effect during cornering. However, in the configuration of Patent Document 1, narrow grooves with portions inclined relative to the tire circumferential direction intersect with lug grooves, which tends to reduce the rigidity of the buttress in the shoulder land area. Therefore, there is room for improvement in terms of improving snow traction performance. Furthermore, the configuration of Patent Document 1, which reduces the rigidity of the buttress, leaves room for improvement in terms of suppressing side slippage during cornering due to the edge effect during cornering when the contact width to the buttress widens during cornering. Furthermore, in the configuration of Patent Document 1, some of the narrow grooves extend in the tire width direction, which shortens the lateral sipes that connect the narrow grooves, leaving room for improvement in terms of improving drainage in the shoulder land areas. Furthermore, in the configuration of Patent Document 1, some of the narrow grooves extend in the tire width direction, leaving room for improvement in terms of more efficiently guiding water that is expelled from the sipes during cornering into the narrow grooves, thereby improving drainage in the shoulder land areas during cornering.

Patent Document 1 also describes a configuration in the shoulder land area in which narrow grooves with portions inclined relative to the tire circumferential direction do not intersect with lug grooves (Figure 7 of Patent Document 1). However, even with this configuration, some of the narrow grooves extend in the tire width direction, and the lateral sipes to which the narrow grooves are connected become short, leaving room for improvement in terms of improving drainage in the shoulder land area. Furthermore, even with this configuration, there is room for improvement in terms of more efficiently guiding water discharged from the sipes during cornering into the narrow grooves, thereby improving drainage in the shoulder land area during cornering.

The object of the present invention is to provide a pneumatic tire that can improve snow traction performance and the effectiveness of suppressing sideslip during cornering, while also improving drainage in the shoulder land area, including during cornering.

The pneumatic tire according to the present invention is a pneumatic tire comprising a circumferential groove and a shoulder land portion whose inner end in the tire width direction is determined by the circumferential groove and formed in a portion including the outer ground contact edge in the tire width direction. The pneumatic tire further comprises: a plurality of lug grooves extending from the first side in the tire width direction to the second side between the plurality of shoulder land portions or in the shoulder land portion; a lateral sipe provided between two circumferentially adjacent lug grooves in the shoulder land portion, the lateral sipe having the same width over the entire length in the longitudinal direction and narrower than the maximum width of the lug groove; and a narrow groove inclined relative to the tire circumferential direction over the entire length, connected to the lateral sipe, on the tire width outer side of the ground contact edge, and narrower than the maximum width of the lug groove; the narrow groove being separated from the two lug grooves over the entire length within the shoulder land portion.

With the above-described pneumatic tire, narrow grooves inclined relative to the tire circumferential direction are formed in the shoulder land area known as the buttress. Furthermore, because the narrow grooves are not connected to adjacent lug grooves, the buttress rigidity can be increased. This improves snow traction performance and enhances the edge effect during cornering, thereby improving the vehicle's ability to suppress skidding. Furthermore, because the narrow grooves are connected to the lateral sipes, drainage is improved. Furthermore, because the narrow grooves are inclined in the same direction relative to the tire circumferential direction along their entire length, the lateral grooves, which can be made deeper, can be made longer while improving drainage in the narrow grooves. This improves drainage in the shoulder land area. Furthermore, because water discharged from the sipes during cornering can be more efficiently guided into the narrow grooves, drainage in the shoulder land area during cornering can be improved. This improves drainage in the shoulder land area, including during cornering.

The pneumatic tire according to the present invention can improve snow traction performance and suppress skidding during cornering, while also improving drainage in the shoulder land area, including during cornering.

1 is a perspective view of a pneumatic tire as an example of an embodiment. 1 is a plan view of a pneumatic tire that is an example of an embodiment, showing a portion of a tread. FIG. 2 is an enlarged plan view showing a part of the center region of the tread. FIG. 4 is an enlarged perspective view of a recess in the oblique circumferential groove of FIG. 3 . FIG. 5 is an enlarged plan view showing the recess shown in FIG. 4 . FIG. 6 is a cross-sectional view taken along the line A1-A1 in FIG. 5. FIG. 7 is a view corresponding to FIG. 6 and showing another example of a recess. FIG. 7 is a view corresponding to FIG. 6 and showing another example of a recess. 5 is a view corresponding to FIG. 4 showing another example of a recess; FIG. FIG. 2 is an enlarged plan view showing a portion of a center region of a tread in an example embodiment. FIG. 10 is an enlarged perspective view showing a connection portion between the first circumferential groove and the lug groove between the center blocks, which is the first land portion, in FIG. 9 . FIG. 10 is an enlarged perspective view showing FIG. 9 cut along line BB. FIG. 10 is an enlarged plan view of part C in FIG. 9 . FIG. 13 is a cross-sectional view taken along the line DD in FIG. 12. FIG. 10 is an enlarged cross-sectional view of line EE in FIG. 9. FIG. 10 is an enlarged perspective view of the example embodiment taken along line F-F in FIG. 9. 10 is an enlarged cross-sectional view showing a bridge corresponding to the second raised portion in part G of FIG. 9 . FIG. 16 is an enlarged cross-sectional view of line HH in FIG. 15. FIG. 10 is an enlarged cross-sectional view of a third raised portion in the third circumferential groove of FIG. 9 . FIG. 10 is a diagram corresponding to part I of FIG. 9 showing another example of the third raised portion. 3 is an enlarged view of a part of a shoulder block that is a fifth land portion on the outer side in the vehicle width direction of FIG. 2 . FIG. FIG. 21 is an enlarged perspective view of an outer end portion in the tire width direction of the shoulder block of FIG. 20. FIG. 21 is a perspective view showing the shoulder block of FIG. 20 cut along a plane including the ground contact end.

Below, one example of an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. Furthermore, the present invention includes selective combinations of the components of the multiple embodiments and variations described below.

In this specification, the terms wet road surface, snowy road surface, and dry road surface are used. A wet road surface refers to a road surface wet with rainwater or a road surface wet from melting snow and ice. A snowy road surface refers to a road surface covered with snow. A dry road surface refers to a dry road surface free of snow and ice. Below, for ease of explanation, wet road surfaces and snowy road surfaces may be collectively referred to as "snow and ice road surfaces." While the following does not specifically mention driving performance on frozen road surfaces (ice performance), the pneumatic tire, which is an example of an embodiment, has good ice performance in addition to good wet performance, snow performance, and dry performance.

Figure 1 is a perspective view of a pneumatic tire 1, which is an example of an embodiment. Figure 2 is a plan view of the pneumatic tire 1, showing a portion of the tread. As shown in Figures 1 and 2, the pneumatic tire 1 has a tread 10, which is the portion that comes into contact with the road surface. Hereinafter, "pneumatic tire 1" will be referred to as "tire 1." The tread 10 has a tread pattern including multiple blocks, and is formed in an annular shape along the tire circumferential direction. While tire 1 does not limit its "main rotational direction," which is the direction of rotation when the vehicle on which tire 1 is mounted is traveling forward, the following description will mainly focus on the case where the direction of arrow α in Figure 1 is the main rotational direction.

For ease of explanation, the terms "left and right" are used in this specification to describe tire 1 and its components. The "right side" of tire 1 means the right side when the tire 1 is mounted on a vehicle and viewed from the front of the vehicle, and the "left side" means the left side when the tire 1 is mounted on a vehicle and viewed from the front of the vehicle.

In the embodiment, the mounting direction of the front and back of the tire 1 relative to the vehicle is specified. That is, the outer and inner sides of the tire 1 in the vehicle width direction are specified. In Figure 1, the tire 1 is mounted on the vehicle so that the right side is the outer side (OUT side) in the vehicle width direction and the left side is the inner side (IN side) in the vehicle width direction. When using the tire 1 as the right wheel or the left wheel of the vehicle, the main rotation direction and left-right direction of the tire 1 can be reversed, allowing a common tire 1 to be used for both the left and right wheels.

The tread 10 has multiple circumferential grooves 20, 21, 22 and multiple lug grooves 25, 26 that extend in a curved manner from the left side, which is the first side in the tire width direction, to the right side, which is the second side. The tread 10 includes multiple blocks that are separated in the tire circumferential direction and the tire width direction by being partitioned by the multiple circumferential grooves 20, 21, 22 and the multiple lug grooves 25, 26.

The blocks are island-shaped regions that protrude radially outward in the tire direction. As shown in FIG. 2, the tread 10 has a plurality of center blocks 50, a plurality of intermediate blocks 60, 70, and a plurality of shoulder blocks 80, 90, each of which will be described later. The tire equator CL, which will be described later, passes through the center block 50. The intermediate block 60 and shoulder block 80 are located on the left side of the tread 10 in the width direction, and the intermediate block 70 and shoulder block 90 are located on the right side of the tread 10 in the width direction.

The multiple circumferential grooves 20, 21, 22 include a first circumferential groove 20 formed near the center of the tread 10 in the width direction, and a second circumferential groove 21 and a third circumferential groove 22 provided on both the left and right sides of the first circumferential groove 20. Furthermore, multiple oblique circumferential grooves 31, described below, are formed between the first circumferential groove 20 and the second circumferential groove 21 of the tread 10. The "tire width direction" and the "tread 10 width direction" are the same direction, and both terms will be used appropriately below.

The first circumferential groove 20 and the second circumferential groove 21 are arranged on either side of the tire widthwise center. Of the multiple circumferential grooves 20, 21, and 22, the first circumferential groove 20 is arranged closest to the tire equator CL, which is the center in the tire widthwise direction. The tire equator CL refers to a line running along the tire circumferential direction and passing through the tire widthwise center.

The tread 10 also has a center region 40, which is a predetermined region in the tire width direction defined by the first circumferential groove 20 and the second circumferential groove 21. The center region 40 is divided into center blocks 50 and intermediate blocks 60, separated to the right and left, at each of multiple positions around the tire by multiple oblique circumferential grooves 31 (described below). The center blocks 50 are positioned adjacent to the center of the first circumferential groove 20 in the tire width direction. The center blocks 50 correspond to a first land portion as a center land portion. A center block row 41 is formed by multiple center blocks 50 lined up around the tire circumferentially.

The mediate blocks 60 correspond to the second land portions. A plurality of mediate blocks 60 aligned in the tire circumferential direction form the mediate block row 44.

The tread 10 also has a shoulder block row 45 formed therein, which includes a plurality of shoulder blocks 80 whose inner ends in the tire width direction are defined by the second circumferential groove 21. The tread 10 also has an intermediate block row 46 formed therein, which includes a plurality of intermediate blocks 70 defined by the first circumferential groove 20 and the third circumferential groove 22. The tread 10 also has a shoulder block row 47 formed therein, which includes a plurality of shoulder blocks 90 whose inner ends in the tire width direction are defined by the third circumferential groove 22. The shoulder blocks 80 correspond to the third land portion of the shoulder land portion. The intermediate blocks 70 correspond to the fourth land portion. The shoulder blocks 90 correspond to the fifth land portion of the shoulder land portion. The circumferential grooves 20, 21, and 22 are aligned along the tire circumferential direction and have approximately the same width.

The multiple lug grooves 25, 26 extend while curving from left to right in the tire width direction and are spaced apart circumferentially. In each of the multiple block rows 41, 44-47, the multiple lug grooves 25, 26 are inclined toward the same side with respect to the tire width direction between adjacent blocks in the tire circumferential direction. The lug grooves 25, 26 in the center block row 41 and the intermediate block row 44 are inclined more sharply with respect to the tire width direction than the lug grooves 25, 26 in the other block rows 45-47. This facilitates improved lateral snow traction performance in the center of the tire width direction. The multiple lug grooves 25, 26 are also shallower than the multiple circumferential grooves 20-22.

Furthermore, the multiple lug grooves 25, 26 include multiple first lug grooves 25 and multiple second lug grooves 26 spaced apart in the tire circumferential direction. In the tread 10, one or more first lug grooves 25 and one or more second lug grooves 26 are alternately arranged in the tire circumferential direction. Below, a case where the first lug grooves 25 and the second lug grooves 26 are alternately arranged one by one in the tire circumferential direction in the tread 10 is described. However, multiple first lug grooves 25 and multiple second lug grooves 26 may be alternately arranged. The first lug grooves 25 are lug grooves that are crossed in the tire circumferential direction by the intermediate portions of the oblique circumferential grooves 31 described below in the center region 40. On the other hand, the second lug grooves 26 are lug grooves that are connected by both ends of the oblique circumferential grooves 21. The widths of the lug grooves 25, 26 are generally approximately the same, but the ends of each lug groove 25, 26 on the first circumferential groove 20 side in the intermediate block row 46 are narrower than the remaining portions.

In this embodiment, blocks of the same type and assigned the same reference numerals are arranged in a line along the tire circumferential direction. Furthermore, the same number of blocks are arranged in a line along the tire circumferential direction, separated into multiple positions along the tire circumferential direction, along the multiple lug grooves 25, 26 of the tread 10. In other words, the tread 10 is formed with the same number of center blocks 50, intermediate blocks 60, 70, and shoulder blocks 80, 90.

A number of thin sipes extending generally in the tire width direction or generally in the tire circumferential direction are formed on the contact surface of each block. Each sipe is a thin groove narrower than the circumferential grooves 20-22 and lug grooves 25, 26, enhancing the edge effect that catches snow and ice, achieving good braking/driving performance and handling stability on snowy and icy roads. A tire 1 with this type of tread pattern is suitable, for example, for all-season tires.

The tire 1 has sidewalls 12 formed annularly along the tire circumferential direction, similar to the tread 10, on both sides of the tread 10 in the width direction.

On the other hand, the shoulder blocks 80, 90 located at both widthwise ends of the tread 10 include a ground contact edge T (Figure 2), which is the outer edge of the ground contact surface in the tire width direction. The tire widthwise end of each shoulder block 80, 90 extends outward in the tire width direction from the ground contact edge T and curves gently radially inward in the tire so that the outer peripheral surface is convex outward. The portion of each shoulder block 80, 90 extending outward in the tire width direction from the ground contact edge T is called a buttress.

In this specification, the term "ground contact edge T" refers to both ends in the tire width direction of the portion that comes into contact with a flat road surface when an unused tire 1 is mounted on a standard rim, inflated to the standard internal pressure, and a load of 70% of the standard load (maximum load capacity) at the standard internal pressure is applied.

Here, a "regular rim" is a rim specified by tire standards, and is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. "Regular internal pressure" is the "maximum air pressure" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "INFLATION PRESSURE" for ETRTO. "Regular load" is the "maximum load capacity" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "LOAD CAPACITY" for ETRTO.

A reinforcing structure (not shown) is provided on the inner circumferential side of the tire 1. The reinforcing structure includes a carcass, which is a rubber-coated cord layer, and a belt positioned between the tread pattern and the carcass. The carcass is composed of, for example, two carcass plies, and forms the tire framework that can withstand loads, impacts, air pressure, etc. The belt is a reinforcing band stretched around the tire, tightly tightening the carcass to increase the rigidity of the tread 10. An inner liner, which is a rubber layer that maintains air pressure, is attached to the inner circumferential surface of the carcass.

The tire 1 also has a bead 13 that is connected to the inner circumferential edge of the sidewall 12, extends radially inward, and curves convexly toward the inside of the tire 1. The bead 13 is located on the inner side of the sidewall 12 in the tire width direction (toward the tire equator CL). The bead 13 is fixed to the wheel rim, and has a bead core and bead filler inside.

Furthermore, in this embodiment, oblique circumferential grooves 31 are formed at multiple positions around the tire circumference in the center region 40. These oblique circumferential grooves 31 improve the snow traction performance of the tire 1. The oblique circumferential grooves 31 will be described in detail later.

Furthermore, as shown in FIG. 2, in the center block row 41, bridges 100, 101 are formed as raised portions in the lug grooves 25, 26 between the center blocks 50. These bridges 100, 101 improve the rigidity of adjacent center blocks 50 in the tire circumferential direction. Raised portions 102, 103, 104, 105 are also provided in the lug grooves 25, 26 between the blocks of the intermediate block row 44, shoulder block row 45, intermediate block row 46, and shoulder block row 47. Each of the raised portions 102-105 improves the rigidity of adjacent blocks in the tire circumferential direction.

Furthermore, both ends of the bridge 100 formed in the second lug groove 26 between the center blocks 50 have tapered surfaces that slope downward toward the corresponding end. As described below, this increases the rigidity of the center block 50 and suppresses the effects of the tire rotation direction while also preventing a decrease in drainage performance in the center of the tire width direction.

Furthermore, in the second circumferential groove 21, two raised portions 106, 107 serving as first raised portions are formed at the groove bottom at positions sandwiching the second circumferential groove 21 side ends of the lug grooves 25, 26 between the shoulder blocks 80 of the shoulder block row 45. Furthermore, at the intersection of the second circumferential groove 21 with the extensions of the lug grooves 25, 26, a raised portion 108 serving as a third raised portion is formed at the groove bottom in a portion surrounded on three sides by the two raised portions 106, 107 and the raised portion 103 serving as the second raised portion. This improves snow traction performance, reduces rolling resistance, and reduces air pumping noise, as described below.

Furthermore, narrow grooves 109, 110 (described below) are formed in the portion of the shoulder block 90 that is outwardly circumferentially inclined relative to the tire's circumferential direction, in the tire width direction, from the ground contact edge T. This improves snow traction performance. Furthermore, the narrow grooves 109, 110 are connected to the lateral sipes 81, 82, but are not connected to the lug grooves 25, 26, improving the drainage performance of the shoulder block 90, including during cornering. Furthermore, the increased rigidity of the shoulder block 90 further improves snow traction performance and reduces skidding during cornering.

Next, we will explain in detail the configuration of the oblique circumferential groove 31, the portion of the second lug groove 26 on the first circumferential groove 20 side and the first circumferential groove 20, the connection between the second and third circumferential grooves 21, 22 and the lug grooves 25, 26, and the narrow grooves 109, 110 of the shoulder block 90. First, we will explain the oblique circumferential groove 31 using Figures 3 to 6.

Figure 3 is an enlarged plan view of a portion of the center region 40 of the tread 10. Figure 4 is an enlarged perspective view of the recess 31a in the oblique circumferential groove 31 in Figure 3. Figure 5 is an enlarged plan view of the recess 31a. Figure 6 is a cross-section taken along line A1-A1 in Figure 5.

The oblique circumferential grooves 31 are provided at multiple positions in the tire circumferential direction in the center region 40. Each oblique circumferential groove 31 crosses the first lug groove 25 in the tire circumferential direction and is inclined relative to the tire circumferential direction so that the first longitudinal end K1 is closer to the tire equator CL at the center in the tire width direction than the second longitudinal end K2. The oblique circumferential groove 31 crosses the first lug groove 25 and connects two second lug grooves 26.

At the position where the first end K1 of the oblique circumferential groove 31 penetrates the second lug groove 26, a recess 31a is formed at the first end K1 that extends into the wall surface 50a (Figure 5) of the center block 50. The recess 31a extends along the second lug groove 26 and is recessed from the contact surface of the center block 50 and has a generally isosceles triangular shape when viewed from the outside in the tire radial direction, i.e., as shown in Figure 5 in plan view.

More specifically, the shape of the recess 31a in a plan view is an isosceles triangle with three vertices P1, P2, and P3, a first long side L1, a second long side L2, and a short side L3, and one corner corresponding to vertex P1 is rounded. The lengths of the first long side L1 and the second long side L2 are approximately the same and are longer than the length of the short side L3. The first long side L1 is aligned along the longitudinal direction of the second lug groove 26. Furthermore, vertex P1 of the isosceles triangle, which is the intersection of the second long side L2 and the short side L3, is recessed into the wall surface 50a. Furthermore, vertex P is located farther from the tire equator CL at the center in the tire width direction than vertex P2 of the isosceles triangle, which is the intersection of the first long side L1 and the second long side L2. The one corner corresponding to vertex P1 of the isosceles triangle is the intersection of the second long side L2 and the short side L3.

Furthermore, a sloped surface 31b is formed on the bottom surface of the recess 31a so as to approach the ground contact surface 50b of the center block 50 toward the inside of the center block 50. Specifically, as shown in FIG. 4, the left end of the lower edge DL of the bottom surface of the recess 31a adjacent to the second lug groove 26 is sloped slightly toward the ground contact surface toward the left end of the recess 31a. The left end of the recess 31a is slightly recessed toward the inside of the center block 50, forming a sloped surface 31b that connects the upper edge UL and lower edge DL on the ground contact surface 50b. As a result, as shown in the cross-sectional view of FIG. 6, the cross section of the bottom surface of the recess 31a is linearly sloped toward the inside of the center block 50 in which the recess 31a is formed (the left side of FIG. 6) so as to approach the ground contact surface 50b of the center block 50. Therefore, a relatively large space is formed inside the recess 31a that extends from the wall surface 50a of the center block 50, allowing water to enter from the second lug grooves 26 and the oblique circumferential grooves 31. In this specification, when the terms "upper" and "lower" are used, the higher side in the direction of the protrusion of a block, protrusion, or other raised part will be referred to as "upper," and the lower side will be referred to as "lower."

Although not shown, in the cross sections taken along lines A2-A2 and A3-A3 in Figure 5, as in Figure 6, the cross section of the bottom surface of the recess 31a is linear, sloping linearly toward the inside of the center block 50 and approaching the contact surface 50b of the center block 50.

As shown in FIG. 2, the multiple oblique circumferential grooves 31 are connected around the entire circumference via portions of the second lug grooves 26 formed at multiple positions around the tire, forming a zigzag shape. As shown in FIG. 4, the portion of each oblique circumferential groove 31 excluding the recessed portion 31a is deeper than the portions of each lug groove 25, 26 excluding the intersections with the oblique circumferential groove 31. The depth of the portion of the oblique circumferential groove 31 excluding the recessed portion 31a may be approximately the same as the depth of each lug groove 25, 26.

This creates an oblique circumferential groove 31 that is inclined relative to the tire circumferential direction and crosses the first lug groove 25 located in the center region 40 of the tread 10. Furthermore, the recess 31a located at the first end K1 of the oblique circumferential groove 31 extends into the center block 50, and the first end K1 is closer to the tire equator CL (the tire widthwise center) than the second end K2. This improves the vehicle's handling stability and cornering performance on snow. For example, the portions of the oblique circumferential groove 31 other than the recess 31a are inclined relative to the tire circumferential direction, making it easier to trap and grip snow and ice in the circumferential and lateral directions of the tire. Furthermore, the recessed portion at the left end of the recess 31a near the tire widthwise center of the oblique circumferential groove 31 makes it easier to trap and grip snow and ice in the lateral directions of the tire 1. This improves the tire's circumferential and lateral snow traction performance. Furthermore, because the first end K1 where the recessed portion 31a of the diagonal circumferential groove 31 is located is closer to the center in the tire width direction than the second end K2, handling stability and cornering performance on snow are improved compared to when the recessed portion is located farther outward in the tire width direction.

Furthermore, the recess 31a at the first end K1 of the oblique circumferential groove 31 extends along the second lug groove 26. As a result, when the tire 1 rotates so that water flows from the second end K2 to the first end K1 within the oblique circumferential groove 31 during vehicle travel on a wet road surface, the space between the recess 31a and the road surface widens, preventing the wall or bottom of the recess 31a from acting as a resistance to water flow. Furthermore, the bottom of the recess 31a is formed with a slope 31b that approaches the contact surface 50b of the center block 50 toward the inside of the center block 50, preventing water from stagnating within the recess 31a. Furthermore, unlike when the innermost recess 31c is a right-angled corner, as shown by the two-dot chain line in Figure 6, this configuration prevents a decrease in the rigidity of the center block 50. This configuration provides excellent drainage from within the tire 1 groove, effectively preventing hydroplaning and preventing a decrease in the rigidity of the center block 50.

For example, when the tire 1 rotates in the direction of arrow α in Figure 3 while the vehicle is running, it is conceivable that a water flow heading from the tire widthwise center toward the tire widthwise outer side along the second lug grooves 26, as indicated by arrow β in Figure 3, and a water flow heading toward the rear of the tire 1 in the direction of rotation along the oblique circumferential grooves 31, as indicated by arrow γ in Figure 3, will merge. In this case, the recess 31a can increase the volume of the space at the merger, thereby reducing water flow resistance and improving drainage.

Furthermore, in tire 1, the shape of recess 31a in a plan view is an isosceles triangle with one corner rounded, corresponding to vertex P1. This prevents turbulence in the water flow at the back of recess 31a, allowing for smoother water flow within the grooves leading to recess 31a and improving drainage. Furthermore, unlike when recess 31a has a rectangular shape in a plan view, this prevents excessive growth of recess 31a while suppressing water flow resistance at the water flow confluence, thereby minimizing a decrease in the rigidity of center block 50.

Figure 7A shows a first example of another recess. In the configuration shown in Figure 7A, the upper end of the inclined surface 31e formed on the bottom surface of the recess 31d is located radially inward of the tire (toward the bottom of Figure 7A) than the contact patch 50b. With this configuration, the rigidity of the center block 50 may be slightly reduced compared to the configurations shown in Figures 3 to 6, but the space within the recess 31a can be made larger, further improving the effectiveness of suppressing hydroplaning.

Figure 7B shows a second example of a different recess. In the configuration shown in Figure 7B, the bottom surface of recess 31f is formed with a convex surface 31g with a curved cross section that convexes outward toward the center block 50's contact surface 50b toward the center block 50's inner side, and a concave surface 31h with an arc-shaped cross section that continues from the inner end of convex surface 31g and has rounded corners. This configuration may slightly reduce the rigidity of the center block 50 compared to the configurations shown in Figures 3 to 6, but it can increase the space within recess 31a, thereby improving hydroplaning suppression. Furthermore, it can smooth the flow of water between recess 31a and the groove, improving drainage.

Figure 8 shows a third example of a different recess. Unlike the configurations shown in Figures 3 to 6, the planar shape of the recess 31i is an isosceles triangle with no rounded corners. The second long side L2 connecting vertices P1 and P2 forms the upper edge UL on the bottom surface of the recess 31a, and an inclined surface 31j is formed connecting the upper edge UL with the lower edge DL on the bottom side of the groove. With this configuration, the area of the wall surface 31k at the left end of the recess 31i can be increased, further improving lateral snow traction performance.

Next, the configuration of the first circumferential groove 20 and the portion of the second lug groove 26 on the first circumferential groove 20 side will be described in detail using Figures 9 to 14. Figure 9 is an enlarged plan view of a portion of the center region 40 of the tread 10. Figure 10 is an enlarged perspective view of the connection between the first circumferential groove 20 and the second lug groove 26 between the center block 50 in Figure 9. Figure 11 is an enlarged perspective view of Figure 9 taken along line B-B. Figure 12 is an enlarged plan view of part C in Figure 9. Figure 13 is a cross-section taken along line D-D in Figure 12. Figure 14 is an enlarged cross-section taken along line E-E in Figure 9.

As shown in Figures 9 to 14, multiple center blocks 50 are arranged adjacent to each other on the tire widthwise center side of the first circumferential groove 20, which is close to the tire widthwise center. The lug grooves 25, 26 between the center blocks 50 extend to the right in the tire width direction and open toward the first circumferential groove 20. A bridge 100 with a raised bottom surface is formed in the portion of the second lug groove 26 between the center blocks 50 on the first circumferential groove 20 side. In Figure 12, the bridge 100 is represented by a sandy area.

The bridge 100 is provided to increase the rigidity of adjacent center blocks 50. As shown in Figures 12 and 13, the bridge 100 has a generally trapezoidal cross section. Specifically, the upper surface 100a of the bridge 100 is generally flat along the tire circumferential direction, and the side surfaces of the longitudinal center end of the second lug groove 26 and the first circumferential groove 20 end have tapered surfaces 100b, 100c that slope downward toward the corresponding longitudinal end of the bridge 100. In Figure 12, the arrows J1, J2 shown on both side surfaces of the bridge 100 indicate that the corresponding side surfaces slope downward from the upper surface toward the tip of the arrow.

A wide portion 111 is formed at the end of the second lug groove 26 on the side of the first circumferential groove 20. The wide portion 111 is a space that is approximately triangular in plan view, with the tire circumferential width being greater on the first circumferential groove 20 side than on the lug groove center side within the tire circumferential range W in Figure 12. The tapered surface 100c of the bridge 100 on the first circumferential groove 20 side is located within this wide portion 111.

As shown in FIG. 10, the widthwise ends of the bridge 100 are connected to the wall surface of the center block 50 via a rounded portion 123 having an arc-shaped cross section. Alternatively, the widthwise ends of the bridge 100 may be connected directly to this wall surface without a rounded portion. As shown in FIG. 13, the maximum height HB of the bridge 100 can be, for example, in the range of 30% to 40% of the depth HL of the second lug groove 26.

Although detailed explanation is omitted, as shown in Figure 9, a bridge 101 with a raised bottom surface is also formed in the middle of the first lug groove 25 between the center blocks 50, adjacent to the second lug groove 26. Similar to bridge 100, bridge 101 has a trapezoidal cross section with tapered sides at both ends that slope downward toward the corresponding longitudinal ends of bridge 101.

Furthermore, as shown in Figures 9 to 11 and 14, a tapered protrusion 112 is formed on the bottom surface of the first circumferential groove 20 adjacent to the first circumferential side of the wide portion 111 in the tire circumferential direction (the lower side in Figure 9, the left side in Figure 10). The tapered protrusion 112 has a generally triangular shape in a plan view and is formed to protrude radially outward in the tire. Furthermore, as shown in Figures 11 and 14, the upper surface of the tapered protrusion 112 is provided with a first inclined surface 113 that is higher on the left side, which is the side of the lug grooves 25, 26 between the center blocks 50, than on the right side, which is the side of the intermediate block 70.

Furthermore, as shown in Figures 9 and 10, a second inclined surface 114 is formed on the entire side surface of the tapered protrusion 112 on the second side in the tire circumferential direction (upper side in Figure 9, right side in Figure 10), which is inclined toward the second side in the tire circumferential direction toward the wide portion 111 in the tire width direction. As shown in Figure 9, the second inclined surface 114 roughly follows the wall surface 111a of the wide portion 111 on the tapered protrusion 112 side.

Furthermore, a third inclined surface 115 is formed on the side surface of the tapered protrusion 112 on the first side in the tire circumferential direction (lower side in Figure 9, left side in Figure 10), which is inclined generally toward the second side in the tire circumferential direction toward the center block 50 in the tire width direction. The third inclined surface 115 is positioned adjacent to the second side in the tire circumferential direction from the opening of the first lug groove 25 on the first circumferential groove 20 side. The third inclined surface 115 is inclined with respect to the tire circumferential direction so as to be approximately aligned with the longitudinal direction of the first lug groove 25.

With the above configuration, bridges 100, 101 are provided in the lug grooves 25, 26 between the center blocks 50, thereby increasing the rigidity of the center blocks 50. Furthermore, even when the tire rotates in a direction that causes water to flow from the first circumferential groove 20 near the center of the tire width direction to the lug grooves 25, 26 between the center blocks 50 when the vehicle is traveling on a wet road surface, the tapered surfaces 100c of each bridge 100, 101 make it easier for water to flow from the first circumferential groove 20 to the lug grooves 25, 26.

Specifically, when the tire 1 rotates in the direction of arrow α in FIG. 9, the tapered surface 100c (FIG. 12) of the bridge 100 facilitates water flow from the first circumferential groove 20 to the second lug groove 26 in the direction indicated by arrow M1 in FIG. 9. On the other hand, when the tire 1 rotates in the opposite direction to the direction of arrow α in FIG. 9, the tapered surface 100b (FIG. 12) of the bridge 100 facilitates water flow from the second lug groove 26 to the first circumferential groove 20, i.e., in the direction indicated by arrow M2 in FIG. 9. This allows for the realization of a tire 1 that can increase the rigidity of the center block 50 and suppress the effects of the tire rotation direction while suppressing a decrease in drainage performance in the tire widthwise center.

Furthermore, a tapered protrusion 112 having a first inclined surface 113 on its upper surface, which is higher on the lug grooves 25, 26 side between the center blocks 50, is formed on the bottom surface of the first circumferential groove 20. This makes it even easier for water to flow along the first inclined surface 113 from the first circumferential groove 20 to the second lug groove 26 between the center blocks 50 when the tire 1 rotates in the direction of arrow α in Figure 9. This further reduces the deterioration of drainage performance in the center portion in the tire width direction.

Furthermore, a wide portion 111 is formed at the end of the second lug groove 26 near the first circumferential groove 20, and a tapered protrusion 112 is disposed adjacent to the wide portion 111 on the first circumferential side of the tire. A second inclined surface 114 is formed on the side surface of the tapered protrusion 112 on the second circumferential side of the tire. As a result, when the tire rotates in the direction opposite to the direction of arrow α in FIG. 9 , water that flows from the second lug groove 26 into the first circumferential groove 20 can be drained by passing through the right side of the first circumferential groove 20 in the tire width direction and into the first circumferential groove 20, regardless of the presence of the tapered protrusion 112, due to the inclination of the first inclined surface 113 and the inclination of the second inclined surface 114 of the tapered protrusion 112.

Furthermore, a third inclined surface 115 is formed on the side surface of the tapered protrusion 112 on the first side in the tire circumferential direction. The third inclined surface 115 is inclined with respect to the tire circumferential direction so as to follow the longitudinal direction of the first lug groove 25. As a result, when the tire 1 rotates in the direction of arrow α in Figure 9, the third inclined surface 115 of the tapered protrusion 112 makes it easier for water to flow from the first circumferential groove 20 to the first lug groove 25. This further reduces the deterioration of drainage performance in the tire widthwise center.

In addition, in this example, the bridge 101, which has a trapezoidal cross section and is provided in the middle of the first lug groove 25 between the center blocks 50, can increase the rigidity of the center blocks 50 on both sides in the circumferential direction of the tire. Furthermore, like the bridge 100, it can improve drainage from the first circumferential groove 20 to the first lug groove 25.

Next, the configuration of the connection portions between the second and third circumferential grooves 21, 22 and the lug grooves will be described in detail. Figure 15 is an enlarged perspective view of an example embodiment, taken along line F-F in Figure 9. Figure 16 is an enlarged cross-sectional view showing the raised portion 103 of the second raised portion at part G in Figure 9. Figure 17 is an enlarged cross-section taken along line H-H in Figure 15.

Referring to Figures 9 and 15 above, in the second circumferential groove 21, two raised portions 106, 107 serving as first raised portions are formed in the groove bottom at positions sandwiching the second circumferential groove 21 side ends of each lug groove 25, 26, corresponding to each lug groove 25, 26. Each raised portion 106, 107 is formed so as to protrude radially outward in the tire. As shown in Figure 9, the shape of each raised portion 106, 107 in a plan view is approximately triangular, with the base connected to the wall surface of the shoulder block 80 and the apex connected to the wall surface on the intermediate block 60 side.

Furthermore, as shown in Figures 15 and 16, the upper surface of each raised portion 106, 107 forms an inclined surface S that slopes upward radially outward toward the shoulder block 80. As a result, when the vehicle is traveling on a wet road surface and the tire 1 rotates in the direction of arrow α in Figure 9 or in the direction opposite to the direction of arrow α, the inclined surface S of each raised portion 106, 107 makes it easier for water to flow from the second circumferential groove 21 to the lug grooves 25, 26 between the shoulder blocks 80. Therefore, even when raised portions 103 are provided in the lug grooves 25, 26 as second raised portions, as described below, drainage performance can be improved.

Specifically, as shown in Figures 9 and 16, a raised portion 103 that protrudes radially outward from the tire is provided at the groove bottom of the second circumferential groove 21 side portion of each lug groove 25, 26 between the shoulder blocks 80. Like the bridges 100, 101 provided in the lug grooves 25, 26 between the center blocks 50, the raised portion 103 has a generally trapezoidal cross section. Specifically, the raised portion 103 has a generally flat upper surface along the tire circumferential direction, and the side surfaces on both longitudinal sides of the lug grooves 25, 26 have two tapered surfaces 103a, 103b that slope downward toward the corresponding end of the raised portion 103. The raised portion 103 is provided to increase the rigidity of the shoulder block 80, and both widthwise ends are connected to the wall surfaces of the shoulder block 80 adjacent in the tire circumferential direction.

As described above, an inclined surface S is formed on the upper surface of each raised portion 106, 107 in the second circumferential groove 21. This makes it easier for water to flow from the second circumferential groove 21 to the lug grooves 25, 26 when the vehicle is traveling on a wet road surface, regardless of the presence of the bridge 100, thereby improving drainage.

On the other hand, when two raised portions 106, 107 are formed in the second circumferential groove 21 and raised portions 103 are provided in the lug grooves 25, 26, if the space at the intersection of the second circumferential groove 21 with the extensions of the lug grooves 25, 26 is relatively wide, air tends to accumulate in this space. As a result, when a vehicle fitted with the tire 1 is driven on a dry road surface, air trapped in the space at the intersection tends to cause air pumping noise.

In this example, to resolve this issue, as shown in Figures 9, 15, and 17, a third raised portion, ie, a raised portion 108, is formed at the groove bottom of the second circumferential groove 21, at the intersection with the extensions of the lug grooves 25, 26, in a portion surrounded on three sides by the two raised portions 106, 107 and the raised portion 103. The lowest part of the second circumferential groove 21 is the reference surface 21a (Figures 15 and 17), and the raised portion 108 protrudes radially outward so as to be higher than the reference surface 21a.

In Figure 9, the raised portion 108 is shown by the sanded portion in the second circumferential groove 21. As shown in Figure 9, the raised portion 108 is approximately trapezoidal in plan view, with both circumferential edges connected to the wall surfaces of the circumferential ends of the two raised portions 106, 107 on either side.

As shown in Figure 17, the upper surface of the raised portion 108 is generally flat and has a constant vertical height from the reference plane 21a. Both tire widthwise end edges of the raised portion 108 are connected to the wall surfaces of the second circumferential groove 21. As shown in Figure 15, the upper surface of the raised portion 108 is lower than the upper surfaces of the raised portions 106 and 107. In this example, the lowest ends of the inclined surfaces S of the raised portions 106 and 107 are approximately at the same height as the upper surface of the raised portion 108.

Furthermore, as shown in FIG. 9 , the second circumferential groove 21 side end of the lug grooves 25, 26 between the shoulder blocks 80 faces the wall surface of the intermediate block 60 at the tire width direction end, via the portion of the second circumferential groove 21 where the raised portion 108 is provided at the groove bottom, on the extension line of the lug grooves 25, 26.

With the above configuration, two raised portions 106, 107 are formed in the groove bottom of the second circumferential groove 21 at positions sandwiching the second circumferential groove 21-side ends of the lug grooves 25, 26. Furthermore, a raised portion 103 is formed in the groove bottom of the lug grooves 25, 26 on the second circumferential groove 21 side. This increases the rigidity of the shoulder block 80 adjacent to the raised portions 106, 107 of the second circumferential groove 21 and the shoulder block 80 adjacent to the raised portions 103 of the lug grooves 25, 26. Therefore, the rigidity of the shoulder block 80 is increased by one of the raised portions 106, 107 and the raised portion 103. This reduces energy loss due to block deformation during vehicle travel, thereby reducing the rolling resistance of the tire 1. Furthermore, the shear force acting on the packed snow in the grooves when traveling on snowy roads increases resistance between the tire 1 and the road surface, improving snow traction performance.

Furthermore, at the intersection of the second circumferential groove 21 with the extensions of the lug grooves 25, 26 between the shoulder blocks 80, a raised portion 108 is formed at the groove bottom in the area surrounded on three sides by the two raised portions 106, 107 and the raised portion 103. This reduces the volume of the space at the intersection, thereby reducing the amount of air trapped. This reduces air pumping noise during driving.

Furthermore, the second circumferential groove 21 side ends of the lug grooves 25, 26 between the shoulder blocks 80 face the wall surface of the mediate block 60 on the extension line of the lug grooves 25, 26, via the portion of the second circumferential groove 21 where the raised portion 108 is provided at the groove bottom. As a result, the above-mentioned intersection of the second circumferential groove 21 is surrounded on all four sides by the three raised portions 106, 107, 108 and the wall surface of the mediate block 60. This makes it more difficult for air to be discharged from the intersection when the vehicle is in motion, but the raised portion 108 reduces the amount of air trapped, making the effect of providing the raised portion 108 more pronounced.

In addition, in this example, as shown in FIG. 9 , two raised portions 116, 117 having a generally triangular shape in plan view are formed on the groove bottom of the third circumferential groove 22 at positions sandwiching the third circumferential groove 22-side ends of the lug grooves 25, 26 between the shoulder blocks 90. Furthermore, a raised portion 105 is formed on the groove bottom on the third circumferential groove 22 side of the lug grooves 25, 26 between the shoulder blocks 90. The raised portion 105 has a tapered surface that becomes lower toward the end only on the side surface of the longitudinal center end of the lug grooves 25, 26, and the third circumferential groove 22-side end coincides with the wall surface of the third circumferential groove 22, so no tapered surface is formed.

Furthermore, at the intersection of the third circumferential groove 22 with the extensions of the lug grooves 25, 26 between the shoulder blocks 90, a raised portion 118 is formed at the groove bottom in a portion surrounded on three sides by three raised portions 116, 117, 105. In Figure 9, the raised portion 118 is shown by the sanded portion within the third circumferential groove 22.

Figure 18 is an enlarged cross-sectional view of the raised portion 118 in the third circumferential groove 22. As shown in Figure 18, the upper surface of the raised portion 118, like the raised portion 108 in the second circumferential groove 21, is generally flat and has a constant vertical height from the reference plane 22a of the third circumferential groove 22. Both edge portions of the raised portion 118 in the tire width direction are connected to the wall surfaces of the second circumferential groove 21.

This also reduces the amount of air trapped at the intersection of the third circumferential grooves 22 with the extensions of the lug grooves between the shoulder blocks 90. This reduces air pumping noise during driving. As shown in FIG. 9 , at this intersection, unlike the intersection of the second circumferential grooves 21, the second circumferential groove 21 side end of the lug groove between the shoulder blocks 90 and the second circumferential groove 21 side end of the lug groove between the intermediate blocks 70 face each other on the extension lines of the respective lug grooves. Therefore, air is more easily discharged at the intersection of the third circumferential grooves 22 than at the intersection of the second circumferential grooves 21. The effect of providing the raised portions 108 is greater at the intersection of the second circumferential grooves 21.

Figure 19 is a diagram corresponding to part I in Figure 9 and shows another example of a third raised portion. The third raised portion 119 shown in Figure 19 has a thin linear shape extending in the tire width direction in plan view, and both circumferential ends of the tire are not connected to the walls of the two raised portions 106, 107. Therefore, while the effect is less than that of raised portion 108 in Figure 9, it does have the effect of reducing the volume of the space at the intersection of the second circumferential groove 21 with the extensions of the lug grooves 25, 26 between the shoulder blocks 80, thereby reducing air pumping noise during driving. In this way, the third raised portion may be configured to be formed only in a portion of the groove bottom surrounded on three sides by the two first raised portions and the second raised portion at the intersection of the circumferential groove with the extensions of the lug grooves.

Next, the narrow grooves 109, 110 of the shoulder block 90 will be described using Figures 20 to 22. Figure 20 is an enlarged view of a portion of the shoulder block 90 in Figure 2. Figure 21 is an enlarged perspective view of the outer end of the shoulder block 90 in the tire width direction. Figure 22 is an oblique view of the shoulder block 90 cut along a plane including the ground contact edge T.

A plurality of lug grooves 25, 26 are formed between the shoulder blocks 90 of the shoulder block row 47, extending from the left side to the right side in the tire width direction. The shoulder blocks 90 are separated in the tire circumferential direction by the lug grooves 25, 26. When the tire 1 is mounted on a vehicle, the shoulder blocks 90 are provided at the ends located on the outer side in the vehicle width direction.

Two lateral sipes, 81 and 82, extending from the left side to the right side in the tire width direction are provided on the contact surface of each shoulder block 90. Therefore, each sipe 81 and 82 is provided between two lug grooves 25 and 26 that are adjacent in the tire circumferential direction. In the shoulder block 90, each sipe 81 and 82 has the same width over its entire length, and is narrower than the maximum width of the two lug grooves 25 and 26 that are provided between the sipes 81 and 82.

Ends 81a, 82a, which are the inner ends in the tire width direction of each sipe 81, 82, open into the wall surface at the inner end in the tire width direction of the shoulder block 90. Ends 81b, 82b, which are the outer ends in the tire width direction of each sipe 81, 82, terminate within the shoulder block 90 and do not open into the wall surface of the shoulder block 90. A serpentine portion is provided in part of the sipes 81, 82, but the serpentine portion may be omitted.

Furthermore, between the two lug grooves 25, 26 sandwiching the sipes 81, 82 in the shoulder block row 47, i.e., on the tire widthwise outer side of the ground-contact edge T of the upper surface of the shoulder block 90, two narrow grooves 109, 110 are formed that are inclined to the same side along the entire length in the tire circumferential direction. Narrow groove 109 is longer than narrow groove 110, and the inner end of narrow groove 109 in the tire widthwise direction is connected to end 81b of sipe 81.

The narrow grooves 110 and the narrow grooves 109 are inclined toward the outside in the tire width direction, in the same direction as the tire circumferential direction. The narrow grooves 110 are connected at their inner ends in the tire width direction to the sipes 82, so that they branch off from near the outer ends of the sipes 82 in the tire width direction.

Each narrow groove 109, 110 is shallower than each sipe 81, 82 and has, for example, an arc-shaped cross section that widens toward the open end. The shape of the narrow groove is not limited to this, and it may have a generally rectangular cross section with an open top, or a generally flat bottom surface with wall surfaces on both sides in the width direction inclined relative to the bottom surface so that the width widens toward the open end.

Furthermore, each narrow groove 109, 110 is separated from the two lug grooves 25, 26 that define both circumferential ends of the shoulder block 90 within the shoulder block 90 over its entire length. As a result, each narrow groove 109, 110 is not connected to the lug grooves 25, 26 between the shoulder blocks 90.

Furthermore, the outer ends of each narrow groove 109, 110 in the tire width direction do not open onto the wall surface of the shoulder block 90, but terminate within the shoulder block 90. Therefore, each narrow groove 109, 110 does not open onto the wall surface of the shoulder block 90.

Furthermore, shallow grooves 120 that are J-shaped in plan view are formed on the upper surface of each shoulder block 90, in a portion located outside the tire width direction of the ground contact edge T and further outside the narrow grooves 109, 110. The shallow grooves 120 have straight portions 121 located outside the tire width direction of the curved portions 122, and run along the tire circumferential direction. The shallow grooves 120 have approximately the same depth as the narrow grooves 109, 110. The width of the shallow grooves 120 increases from the end on the curved portion 122 side toward the end on the straight portion 121 side at both longitudinal ends.

With the above configuration, narrow grooves 109, 110 inclined relative to the tire circumferential direction are formed in an area called the buttress, which is located on the tire widthwise outer side of the ground-contact edge T of the shoulder block 90. Furthermore, the narrow grooves 109, 110 are not connected to the sipes 81, 82 or the two lug grooves 25, 26 that sandwich the narrow grooves 109, 110. This increases the rigidity of the buttress. This not only improves snow traction performance, but also enhances the edge effect during cornering, thereby improving the effectiveness of suppressing vehicle skidding during cornering.

Furthermore, because the narrow grooves 109, 110 are connected to the sipes 81, 82, drainage is improved. Furthermore, because the narrow grooves 109, 110 are inclined in the same direction relative to the tire circumferential direction along their entire length, the sipes 81, 82, which can be made deeper, can be made longer while improving drainage in the narrow grooves 109, 110. This improves drainage in the shoulder blocks 90. Furthermore, unlike when the narrow grooves 109, 110 are connected to the sipes 81, 82 via portions extending in the tire width direction, the narrow grooves 109, 110 extend circumferentially closer to the sipes 81, 82. This allows water discharged from the sipes 81, 82 during cornering to be more efficiently guided into the narrow grooves 109, 110, improving drainage in the shoulder blocks 90 during cornering.

Furthermore, because the narrow grooves 109, 110 are shallower than the sipes 81, 82, even though the thickness of the rubber portion of the tire is reduced at the buttresses at the outer ends in the tire width direction, making the narrow grooves 109, 110 shallower prevents the thickness of the bottoms of the narrow grooves 109, 110 from becoming excessively thin. This makes it possible to suppress the occurrence of cracks at the groove bottoms of each narrow groove 109, 110. In particular, the buttresses are exposed to sunlight and the rubber tends to harden, but even in such cases, the occurrence of cracks is easily suppressed. This makes the effects of making the narrow grooves 109, 110 shallower more pronounced.

In the above-described embodiment, two narrow grooves are formed in each shoulder block 90, but each shoulder block may have only one narrow groove or three or more narrow grooves.

In addition, in the above embodiment, the shoulder land portion is described as being made up of multiple blocks divided circumferentially by lug grooves. However, the shoulder land portion may not be formed with lug grooves along the entire width of the tire, and may not be divided into multiple blocks circumferentially. In this case, too, narrow grooves may be formed along the entire length of the shoulder land portion, on the outer side of the tread edge in the tire width direction, that are inclined relative to the tire circumferential direction and connect to lateral sipes but are not connected to the lug grooves.

1 Tire, 10 Tread, 12 Sidewall, 13 Bead, 20 First circumferential groove, 21 Second circumferential groove, 21a Reference surface, 22 Third circumferential groove, 22a Reference surface, 25 First lug groove, 26 Second lug groove, 31 Oblique circumferential groove, 31a Recess, 31b Inclined surface, 31c, 31d Recess, 31e Inclined surface, 31f Recess, 31g Convex surface, 31h Concave surface, 31i Recess, 31j Inclined surface, 31k Wall surface, 40 Center region, 41 Center block row, 44 Intermediate block row, 45 Shoulder block row, 46 Intermediate block row, 47 Shoulder block row, 50 Center block, 50a Wall surface, 50b Contact surface, 60 Intermediate block, 70 Intermediate block, 80 Shoulder block, 81, 82 Sipes, 81a, 81b, 82a, 82b: ends, 90: shoulder blocks, 100, 101: bridges, 100a: upper surfaces, 100b, 100c: tapered surfaces, 102-108: raised portions, 109, 110: narrow grooves, 111: wide portions, 112: tapered protrusions, 113: first inclined surfaces, 114: second inclined surfaces, 115: third inclined surfaces, 116-118: raised portions, 120: shallow grooves, 121: straight portions, 122: curved portions, 123: R portions, CL: tire equator, T: ground contact edge.

Claims (3)

A pneumatic tire comprising: a circumferential groove; and a shoulder land portion whose inner end in the tire width direction is determined by the circumferential groove and which is formed in a portion including a ground contact end on the outer side in the tire width direction,
a plurality of lug grooves extending from a first side to a second side in the tire width direction between the plurality of shoulder land portions or in the shoulder land portions;
a lateral sipe provided between two lug grooves adjacent in the tire circumferential direction in the shoulder land portion, the lateral sipe having the same width over the entire length in the longitudinal direction and narrower than the maximum width of the lug groove;
a narrow groove formed on the outer side in the tire width direction than the ground contact edge, wherein open end edges at both ends in the width direction of the narrow groove are inclined toward the same side in the tire circumferential direction toward the outer side in the tire width direction with respect to the tire circumferential direction over the entire longitudinal length of the narrow groove, and the narrow groove is connected to the lateral sipe, and the narrow groove is narrower than the maximum width of the lug groove,
the narrow groove is separated from the two lug grooves over the entire length within the shoulder land portion, and is not connected to each of the two lug grooves via a groove on the outer side of the ground contact edge in the tire width direction;
Pneumatic tires. The depth of the narrow groove is shallower than the depth of the lateral sipe.
The pneumatic tire according to claim 1 . an outer end of the narrow groove in the tire width direction does not open to a wall surface of the shoulder land portion;
The pneumatic tire according to claim 1 or 2.