JP7669844B2 - tire - Google Patents

Description

This disclosure relates to tires.

The following Patent Document 1 describes a pneumatic tire that is said to improve wet handling stability while ensuring dry handling stability. The pneumatic tire is provided with a communicating lug groove that extends continuously from a first shoulder land portion across the tire equatorial plane to a second land portion and terminates within the second land portion, and a secondary groove that passes through the terminal end of the communicating lug groove and is spaced apart from a second outermost main groove that is arranged axially outside the second land portion.

JP 2018-79903 A

In recent years, there has been a demand for further improvements in wet and snow performance. At the same time, there is also a need to prevent a decline in steering stability.

This disclosure was devised in light of the above-mentioned circumstances, and its main objective is to provide a tire that can improve wet and snow performance while suppressing deterioration of steering stability.

The present disclosure relates to a tire having a tread portion, the tread portion comprising a middle land portion divided by a shoulder circumferential groove and a middle circumferential groove, the middle land portion being divided into a plurality of middle block elements by a plurality of middle lateral grooves, each of the plurality of middle lateral grooves including a first portion extending from the shoulder circumferential groove, a second portion on the side of the middle circumferential groove inclined relative to the first portion, and a communicating portion connecting the first portion and the second portion, such that each of the middle block elements includes a convex corner portion that is convex toward the block outer side at the communicating portion, and the block sidewall of the convex corner portion includes a first sidewall extending along the first portion, a second sidewall extending along the second portion, and a triangular third sidewall that spans the first sidewall, the second sidewall, and the block tread surface, and the third sidewall terminates radially outward of the groove bottom of the middle lateral groove.

By adopting the above configuration, the tire disclosed herein can improve wet and snow performance while suppressing deterioration of steering stability.

FIG. 2 is an enlarged plan view of a tread portion showing one embodiment of the present disclosure. FIG. 2 is an enlarged view of the vicinity of the middle lateral groove in FIG. 1 . FIG. 2 is a perspective view of a convex corner portion of FIG. 1 . FIG. FIG. 5 is a cross-sectional view taken along line AA in FIG. 4. FIG. FIG. 2 is a plan view of a tread portion including a shoulder land portion.

Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings.
1 is an enlarged plan view of a tread portion 2 of a tire 1 according to the present embodiment. The tire 1 according to the present embodiment is suitable for use as a pneumatic tire for winter or all seasons, for example, for commercial vehicles or small trucks. However, the present disclosure can be used for pneumatic tires for heavy loads or passenger cars, or non-pneumatic tires that are not filled with compressed air.

As shown in FIG. 1, the tread portion 2 of this embodiment has a middle land portion 5 divided into a shoulder circumferential groove 3 and a middle circumferential groove 4. The middle land portion 5 is a land portion on which a relatively large ground pressure acts during both straight running and cornering, and has a large impact on steering stability, wet performance, and snow performance. This disclosure focuses on this middle land portion 5 and aims to improve the above-mentioned performance.

The middle land portion 5 has a plurality of middle lateral grooves 7. As a result, the middle land portion 5 in this embodiment is divided into a plurality of middle block elements 5a.

Each of the middle lateral grooves 7 includes a first portion 11 extending from the shoulder circumferential groove 3, a second portion 12 on the side of the middle circumferential groove 4 that is inclined relative to the first portion 11, and a connecting portion 13 where the first portion 11 and the second portion 12 are connected. Such middle lateral grooves 7 provide multi-directional edge components, improving wet and snow performance. The middle block element 5a of this embodiment includes a convex corner portion 15 that is convex toward the outside of the block at the connecting portion 13.

Figure 2 is an enlarged view of the vicinity of the middle lateral groove 7 in Figure 1. Figure 3 is a perspective view of the convex corner portion 15. As shown in Figures 2 and 3, the block side wall 8 (first lateral side wall 8a described later) of the convex corner portion 15 includes a first side wall 17, a second side wall 18, and a third side wall 19. The first side wall 17 extends along the first portion 11. The second side wall 18 extends along the second portion 12. The third side wall 19 is triangular across the first side wall 17, the second side wall 18, and the block tread surface 9. Such a third side wall 19 increases the groove volume in the communication portion 13, which has a large drainage resistance and is prone to clogging with snow, and smooths the drainage and discharge of snow in the communication portion 13, thereby enhancing these discharge functions. Therefore, wet performance and snow performance are improved.

The third side wall 19 terminates radially outward of the groove bottom 7s of the middle lateral groove 7. This prevents the stiffness of the middle block element 5a from decreasing, and thus prevents deterioration of steering stability.

Figure 4 is a plan view of the tread portion 2. As shown in Figure 4, the tread portion 2 of this embodiment is provided with two shoulder circumferential grooves 3 and one middle circumferential groove 4 arranged between the shoulder circumferential grooves 3, 3. As a result, the tread portion 2 includes, for example, a pair of middle land portions 5 and a pair of shoulder land portions 6 divided between each shoulder circumferential groove 3 and the tread end Te. Note that the tread portion 2 is not limited to this form, and may have a pair of shoulder land portions, a pair of middle land portions, and a crown land portion (not shown) divided into two middle circumferential grooves by two shoulder circumferential grooves and two middle circumferential grooves.

The tread end Te is the axially outermost contact point when the tire 1 is mounted on a standard rim (not shown), filled to standard internal pressure, and unloaded in a standard state, and is placed on the ground with a standard load and a camber angle of 0°. Unless otherwise specified, the dimensions of each part of the tire 1 are values measured in the standard state. The axial distance between the tread ends Te on both sides of the tire is the tread width TW.

The "regular rim" is a rim that is defined for each tire 1 by the standard system that includes the standard on which tire 1 is based, such as a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO.

The "normal internal pressure" is the air pressure set for each tire 1 by each standard in the standard system including the standard on which tire 1 is based, and is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "INFLATION PRESSURE" for ETRTO.

The "normal load" is the load that is determined for each tire 1 by each standard in the system of standards, including the standard on which tire 1 is based. In the case of JATMA, it is the "maximum load capacity." In the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." In the case of ETRTO, it is the "LOAD CAPACITY."

In this embodiment, the shoulder circumferential groove 3 extends continuously in the tire circumferential direction. For example, the shoulder circumferential groove 3 extends in a straight line along the tire circumferential direction. Such a shoulder circumferential groove 3 improves drainage performance.

In this embodiment, the middle circumferential groove 4 extends continuously in the tire circumferential direction. The middle circumferential groove 4 extends, for example, in a zigzag shape. Such a middle circumferential groove 4 has a high snow column shear force. The middle circumferential groove 4 is formed with alternating small inclined portions 4A inclined at a small angle to the tire circumferential direction and large inclined portions 4B inclined at an angle larger than the small inclined portions 4A. The middle circumferential groove 4 is disposed on the tire equator C. Note that the middle circumferential groove 4 and the shoulder circumferential groove 3 are not limited to such a form, and each may adopt a form extending in a straight line, a zigzag shape, or a wavy shape.

The groove width W2 of the middle circumferential groove 4 is preferably larger than the groove width W1 of the shoulder circumferential groove 3. This ensures high drainage on the tire equator C side where drainage is difficult. Although not particularly limited, the groove width W2 of the middle circumferential groove 4 is preferably 1.1 times or more, more preferably 1.2 times or more, more preferably 1.5 times or less, and even more preferably 1.4 times or less of the groove width W1 of the shoulder circumferential groove 3. The groove width W2 of the middle circumferential groove 4 is, for example, preferably 3.0% or more of the tread width TW, more preferably 4.0% or more, more preferably 8.0% or less, and even more preferably 7.0% or less. The groove width W2 of the middle circumferential groove 4 is the groove width at the small inclination portion 4A.

Figure 5 is a plan view of the middle land area 5. As shown in Figure 5, in this embodiment, the block side walls 8 are configured with surfaces that extend in the tire radial direction so as to form the groove walls of each groove. The block side walls 8 are connected to, for example, the block tread surfaces 9 that come into contact with the road surface.

In this embodiment, the block sidewall 8 includes a first lateral sidewall 8a that forms the convex corner portion 15, a second lateral sidewall 8b that faces the first lateral sidewall 8a, a first vertical sidewall 8c that forms the shoulder circumferential groove 3, and a second vertical sidewall 8d that forms the middle circumferential groove 4. The first lateral sidewall 8a and the second lateral sidewall 8b form the middle lateral groove 7. The first lateral sidewall 8a includes a first sidewall 17, a second sidewall 18, and a third sidewall 19.

In this embodiment, the first portion 11 of the middle lateral groove 7 extends in a straight line. This first portion 11 maintains high rigidity of the middle land portion 5.

The angle α1 of the first portion 11 relative to the tire axial direction is preferably 20 degrees or less. This allows for greater traction when driving on snowy roads. In this embodiment, the angle α1 of the first portion 11 at the axial middle 5c of the middle land portion 5 is 0 degrees. In this specification, the middle 5c is the position where the maximum axial width Wm of the middle land portion 5 is divided into two equal parts in the tire axial direction. The angle α1 and the angle α2, which will be described later, are determined by the groove center line 7c of the middle lateral groove 7 (shown in FIG. 4).

The second portion 12 extends, for example, in an arc shape in a plan view of the tread. Such a second portion 12 can distribute the load caused by contact with the ground, which helps to suppress deformation of the middle lateral grooves 7 and maintain a high groove volume. The angle α2 (shown in FIG. 7) of the second portion 12 with respect to the tire axial direction continuously decreases toward the outside in the tire axial direction. The second portion 12 may extend in a straight line.

The second portion 12 extends from the middle circumferential groove 4. In other words, the middle lateral groove 7 crosses the middle land portion 5. Such middle lateral grooves 7 have high drainage and snow column shear strength, improving wet and snow performance. In this embodiment, the middle block element 5a is formed as a middle block 5R that is divided by the middle lateral grooves 7, 7 adjacent in the tire circumferential direction. Note that the middle lateral groove 7 is not limited to this form, and for example, the inner end (not shown) in the tire axial direction may terminate within the middle land portion 5.

The second portion 12 is inclined at a larger angle relative to the tire axial direction than the first portion 11. Such second portion 12 increases the groove volume of the middle lateral groove 7, and can effectively drain the water film between the tread surface of the middle land portion 5 (same as the block tread surface 9) and the road surface.

The angle β between the second portion 12 and the middle circumferential groove 4 is preferably 50 degrees or more, more preferably 55 degrees or more, more preferably 80 degrees or less, and even more preferably 75 degrees or less. Since the angle β is 50 degrees or more, the decrease in rigidity of the middle land portion 5 adjacent to the second portion 12 is suppressed. In addition, water and snow in the second portion 12 are smoothly discharged to the middle circumferential groove 4. Since the angle β is 80 degrees or less, the deformation of the middle land portion 5 at the time of contact with the ground is suppressed, and the groove width of the second portion 12 is secured. This improves wet performance and snow performance. In this specification, the angle β is the angle between the second vertical sidewall 8d and the second lateral sidewall 8b at a position 10 mm outward in the tire axial direction from the intersection K between the second vertical sidewall 8d and the second lateral sidewall 8b.

Figure 6 is a cross-sectional view of line A-A in Figure 4. As shown in Figures 5 and 6, it is desirable that the groove width Wa at the groove bottom 12s of the second portion 12 is constant over the entire length of the second portion 12. Such a second portion 12 increases the rigidity of the axially inner portion of the middle land portion 5, suppressing deterioration of steering stability. In this specification, the groove width Wa at the groove bottom 12s is the distance between the inner ends in the tire radial direction of the first lateral side wall 8a and the second lateral side wall 8b that form the middle lateral groove 7. The inner end is formed in an arc portion 8r that is convex toward the outside of the middle lateral groove 7 and has the smallest radius of curvature.

As shown in FIG. 5, the groove width W3 of the first portion 11 is preferably larger than the groove width W4 of the second portion 12. This makes it possible to suppress a decrease in rigidity in the axially inner portion of the middle land portion 5, which is subject to particularly large ground contact pressure, thereby maintaining steering stability. Although not particularly limited, the groove width W3 of the first portion 11 is preferably 1.1 times or more, more preferably 1.2 times or more, more preferably 1.5 times or less, and even more preferably 1.4 times or less of the groove width W4 of the second portion 12. In addition, the groove width W3 of the first portion 11 is preferably 5% or more of the maximum width Wm of the middle land portion 5, more preferably 10% or more, more preferably 25% or less, and even more preferably 20% or less.

The groove depth of the first portion 11 (not shown) is preferably equal to the groove depth d2 (shown in FIG. 6) of the second portion 12. The groove depth of the first portion 11 is preferably 85% or more of the groove depth d2 of the second portion 12, more preferably 95% or more, and more preferably 115% or less, and even more preferably 105% or less.

The communication portion 13 is arranged closer to the tire equator C than the axial middle 5c of the middle land portion 5. This ensures a large length for the portion 11 with a small angle α1, which produces high snow column shear force, and the communication portion 13, which is prone to snow clogging, is arranged closer to the middle circumferential groove 4, which allows snow to be discharged more smoothly. In order to more effectively exert the above-mentioned effect, the axial distance La between the communication portion 13 and the middle circumferential groove 4 is preferably 3 mm or more, more preferably 4 mm or more, more preferably 7 mm or less, and even more preferably 6 mm or less. More specifically, the distance La is the axial distance between the connection portion 29 described later and the axial inner end 12i of the groove center line 12c of the second portion 12 (the same as the center line 7c of the middle lateral groove 7).

As shown in FIG. 2, the third side wall 19 does not connect to the middle circumferential groove 4, but terminates within the middle lateral groove 7. Such a third side wall 19 ensures a high edge effect of the second portion 12, improving snow performance.

3, in this embodiment, the third side wall 19 includes a tread side edge 21 that is the boundary with the block tread 9, a first edge 22 that is the boundary with the first side wall 17, and a second edge 23 that is the boundary with the second side wall 18. Each of the first edge 22 and the second edge 23 is inclined inward in the tire radial direction toward a connection portion 29 between the first edge 22 and the second edge 23. In this embodiment, the connection portion 29 is included in the communication portion 13. The connection portion 29 forms, for example, a bend between the first edge 22 and the second edge 23. The connection portion 29 in this embodiment divides the first portion 11 and the second portion 12.

The tread side edge 21 is formed longer than the first edge 22 and the second edge 23. Such a tread side edge 21 further suppresses the decrease in rigidity of the convex corner portion 15.

The length L1 (shown in FIG. 2) of the tread side edge 21 is greater than the shortest length L2 (shown in FIG. 2) between the connection portion 29 and the tread side edge 21 in a plan view of the tread. Such a third side wall 19 further suppresses the decrease in rigidity of the convex corner portion 15.

Although not particularly limited, the length L1 of the tread side edge 21 is preferably 10% or more of the maximum width Wm (shown in FIG. 5) of the middle land portion 5, more preferably 15% or more, more preferably 30% or less, and even more preferably 25% or less. Also, the minimum length L2 is preferably 3 mm or more, more preferably 4 mm or more, more preferably 7 mm or less, and even more preferably 6 mm or less.

The connection portion 29 is preferably located within a range of 30% to 50% of the maximum groove depth d (shown in FIG. 3) of the middle lateral groove 7 from the block tread surface 9. This allows for smooth drainage and removal of snow from the middle lateral groove 7 and prevents a decrease in the rigidity of the middle land portion 5, thereby improving wet and snow performance while preventing a deterioration in steering stability. To achieve this effect more effectively, it is even more preferable for the connection portion 29 to be located within a range of 35% to 45% of the maximum groove depth d.

7 is a plan view of the middle land portion 5. As shown in FIG. 7, in the plan view of the tread, the second lateral side wall 8b includes a fourth side wall 24 extending from the shoulder circumferential groove 3 and a fifth side wall 25 extending from the middle circumferential groove 4, which has a larger angle with respect to the tire axial direction than the fourth side wall 24. The connection portion (hereinafter sometimes referred to as the "second connection portion") 30 between the fourth side wall 24 and the fifth side wall 25 is misaligned in the tire axial direction from the connection portion (hereinafter sometimes referred to as the "first connection portion") 29 between the first edge 22 and the second edge 23. As a result, during the rolling of the tire 1, the deformation of the middle lateral groove 7 is promoted at a position separated from the first connection portion 29 and the second connection portion 30, so that snow is discharged more smoothly. The distance L3 in the tire axial direction between the first connection portion 29 and the second connection portion 30 is formed to be smaller than the length L1 of the tread side edge 21, for example. This helps prevent a decrease in steering stability and improves snow performance. To effectively achieve this effect, the distance L3 is preferably 35% or more of the length L1 of the tread edge 21, more preferably 40% or more, more preferably 55% or less, and even more preferably 50% or less.

The second vertical side wall 8d includes, for example, a pair of vertical wall portions 26, 26 extending from both ends of the middle block 5R in the tire circumferential direction, and a horizontal wall portion 27 connecting the pair of vertical wall portions 26, 26. The horizontal wall portion 27 is formed with a smaller angle of inclination with respect to the tire axial direction than each vertical wall portion 26. In addition, in a plan view of the tread, the angles θ1, θ2 between each vertical wall portion 26 and the horizontal wall portion 27 (which are smaller than 180 degrees) are preferably 80 degrees or more, more preferably 85 degrees or more, more preferably 100 degrees or less, and even more preferably 95 degrees or less. Since the angles θ1, θ2 are 80 degrees or more and 100 degrees or less, the reduction in rigidity of the portion formed by each vertical wall portion 26 and the horizontal wall portion 27 of the middle block 5R is suppressed, and the snow column shear force can be secured. This improves steering stability and snow performance.

In this embodiment, the middle land portion 5 further includes a middle lug groove 31, a first middle sipe 32, and a second middle sipe 33. In this specification, "sipe" means a notch-like body with a width of less than 1.5 mm. In addition, in this specification, "groove", which includes a circumferential groove, a lateral groove, and a lug groove, means a groove-like body with a groove width of 1.5 mm or more.

In this embodiment, the middle lug grooves 31 extend from the shoulder circumferential grooves 3 toward the inside in the tire axial direction and terminate within the middle block 5R. The middle lug grooves 31 extend, for example, parallel to the tire axial direction. Such middle lug grooves 31 increase the snow column shear force. In this specification, the term "parallel to the tire axial direction" includes not only an angle of 0 degrees with respect to the tire axial direction, but also an angle of 20 degrees or less.

In this embodiment, the first middle sipe 32 extends from the middle circumferential groove 4 toward the outside in the tire axial direction. The first middle sipe 32 overlaps, for example, with the middle lug groove 31 in the tire circumferential direction. Such a first middle sipe 32 reduces the rigidity of the middle block 5R near the middle lug groove 31, increases the vibration caused by the rolling of the tire 1, promotes the deformation of the middle lug groove 31, and makes the discharge of snow smoother. Although not particularly limited, the tire axial distance L5 between the tire axial outer end 32e of the first middle sipe 32 and the tire axial inner end 31i of the middle lug groove 31 is preferably 2% or more of the maximum width Wm (shown in FIG. 5), more preferably 3% or more. Moreover, the distance L5 is preferably 6% or less of the maximum width Wm, more preferably 5% or less.

In this embodiment, the second middle sipe 33 extends from the shoulder circumferential groove 3 toward the inside in the tire axial direction and terminates within the middle block 5R. The inner end 33i of the second middle sipe 33 in the tire axial direction overlaps with the third side wall 19 in the tire axial direction. Such a second middle sipe 33 has a large water absorption effect and improves drainage performance. The axial length L7 of the first middle sipe 32 and the second middle sipe 33 is preferably 55% or more of the maximum width Wm of the middle land portion 5, more preferably 60% or more, more preferably 75% or less, and even more preferably 70% or less.

Figure 8 is a plan view including the shoulder land portion 6 of Figure 4. As shown in Figure 8, the shoulder land portion 6 is provided with shoulder lateral grooves 40 that cross the shoulder land portion 6, shoulder inclined sipes 41 that are inclined with respect to the tire axial direction, and shoulder longitudinal sipes 42 that extend in the tire circumferential direction.

In this embodiment, the shoulder lateral groove 40 extends from the shoulder circumferential groove 3 toward the tire axially outward beyond the tread edge Te. The shoulder lateral groove 40 includes, for example, an axial portion 40A extending parallel to the tire axial direction, and an inclined portion 40B connected to the axial portion 40A and extending at a larger inclination than the axial portion 40A. In this embodiment, the axial portion 40A has a groove edge extending in the longitudinal direction formed in a straight line in a tread plan view. The axial portion 40A is, for example, disposed outside the inclined portion 40B in the tire axial direction. In this embodiment, the inclined portion 40B has a groove edge extending in the longitudinal direction formed in an arc shape in a tread plan view. The inclined portion 40B is, for example, formed in the shoulder land portion 6.

The connection position 40c between the axial portion 40A and the inclined portion 40B is located closer to the tread end Te than the axial middle position 6c of the shoulder land portion 6. The axial distance L8 between the connection position 40c and the tread end Te is preferably 3 mm or more, more preferably 4 mm or more, more preferably 7 mm or less, and even more preferably 6 mm or less. In this specification, the connection position 40c is the axially innermost end 40e of the groove edge of the axial portion 40A.

The groove width W5 of the axial portion 40A is preferably smaller than the groove width W6 of the inclined portion 40B. This allows water in the shoulder lateral groove 40 to be smoothly discharged from the tread edge Te to the outside. The groove width W5 of the axial portion 40A is preferably, for example, 3 mm or more, more preferably 4 mm or more, more preferably 7 mm or less, and even more preferably 6 mm or less. The groove width W6 of the inclined portion 40B is preferably 2 mm or more, and more preferably 3 mm or less. The groove width W5 of the axial portion 40A is the width at the buttress region B described below.

Two shoulder inclined sipes 41 are provided between the shoulder lateral grooves 40, 40 adjacent in the tire circumferential direction. The shoulder inclined sipes 41 extend, for example, from the shoulder circumferential groove 3 toward the outside in the tire axial direction and terminate within the shoulder land portion 6. The axial outer ends 41e of the shoulder inclined sipes 41 overlap with the shoulder longitudinal sipes 42 in the tire circumferential direction.

In this embodiment, the shoulder longitudinal sipe 42 is formed to include a main portion 43 extending parallel to the tire circumferential direction within the shoulder land portion 6, and a pair of secondary portions 44, 44 that are connected to both ends of the main portion 43 and extend beyond the tread end Te in a direction away from the main portion 43 in the tire circumferential direction. Such a shoulder longitudinal sipe 42 reduces only the circumferential rigidity of the shoulder land portion 6, thereby reducing the self-aligning torque power (SATP). This increases the equivalent cornering power (equivalent CP) of the entire tire, and further suppresses the deterioration of steering stability. The equivalent CP is a value obtained by dividing the cornering power by the SATP. The SATP is the self-aligning torque (SAT) when a slip angle of 1 degree is applied to the tire 1 during running. Furthermore, the SAT is expressed as the sum of the braking force and the driving force on the tire circumferential line of the tread contact surface. In this specification, "parallel to the tire circumferential direction" includes cases where the angle with respect to the tire circumferential direction is 0 degrees, as well as cases where the angle is 20 degrees or less.

The circumferential length L9 of the shoulder longitudinal sipes 42 is preferably 50% or more of the circumferential distance L10 between the circumferentially adjacent shoulder lateral grooves 40, 40. This allows the above-mentioned effects to be effectively achieved. More specifically, the length L9 of the shoulder longitudinal sipes 42 is preferably 55% or more of the distance L10 between the shoulder lateral grooves 40, 40, more preferably 60% or more, more preferably 75% or less, and even more preferably 70% or less. This prevents a decrease in the axial stiffness of the shoulder land portion 6, and more adequately maintains steering stability.

From the same viewpoint, the shortest distance L11 between the shoulder vertical sipe 42 and the shoulder inclined sipe 41 is preferably 10% or more of the axial width Ws of the shoulder land portion 6, more preferably 15% or more, more preferably 30% or less, and even more preferably 25% or less.

In the tire 1 of this embodiment, multiple outer sipes 50 are provided in a buttress region B arranged on the axially outer side of the tread edge Te. The outer sipes 50 terminate within the buttress region B without contacting the tread edge Te. Two outer sipes 50 are provided between axial portions 40A adjacent in the tire circumferential direction. The outer sipes 50 extend parallel to the tire axial direction. The outer sipes 50 overlap with the shoulder longitudinal sipes 42 in the tire circumferential direction. The buttress region B is a region that is not in contact with the ground when the tire 1 in a normal state is placed on a flat surface with a normal load and a camber angle of 0°.

Although a tire according to one embodiment of the present disclosure has been described in detail above, the present disclosure is not limited to the specific embodiment described above and can be modified and implemented in various ways.

Prototype tires were made with the basic pattern shown in Figure 4. The steering stability, wet performance, and snow performance of each prototype tire were then tested. The common specifications and test methods for each prototype tire are as follows:

<Steering stability, wet and snow performance>
Each sample tire was mounted on the following test vehicle. A test driver ran the test vehicle on a test course with a dry asphalt road surface, a wet asphalt road surface, and a snow road surface, and evaluated the steering stability performance, wet performance, and snow performance based on the stability and operability of each test vehicle by sensory evaluation. The results are shown in a score based on Example 1 being 100. The higher the value, the better the performance.
Tire size: 205/65R16
Rim: 16 x 6.5J
Internal pressure (kPa): 390 (front wheel) / 420 (rear wheel)
Vehicle: Commercial vehicle with 2000cc displacement The test results are shown in Table 1.
The "range of the connection portion" in Table 1 is the ratio of the distance between the connection portion and the block tread surface in the tire radial direction to the maximum depth of the shoulder lateral groove.

The test results confirmed that the tire of the embodiment suppresses the deterioration of steering stability. In addition, the tire of the embodiment has excellent wet and snow performance.

[Additional Notes]
The present disclosure includes the following aspects.

[Disclosure 1]
A tire having a tread portion,
The tread portion includes a middle land portion divided by a shoulder circumferential groove and a middle circumferential groove,
The middle land portion is divided into a plurality of middle block elements by a plurality of middle lateral grooves,
each of the plurality of middle lateral grooves includes a first portion extending from the shoulder circumferential groove, a second portion on the side of the middle circumferential groove inclined with respect to the first portion, and a communication portion connecting the first portion and the second portion, so that each of the middle block elements includes a convex corner portion that is convex toward an outer side of the block at the communication portion,
the block side wall of the convex corner portion includes a first side wall extending along the first portion, a second side wall extending along the second portion, and a triangular third side wall spanning the first side wall, the second side wall, and the block tread surface,
The third side wall terminates radially outward of a groove bottom of the middle lateral groove.
tire.
[Disclosure 2]
The third side wall includes a tread side edge that is a boundary with the block tread, a first edge that is a boundary with the first side wall, and a second edge that is a boundary with the second side wall,
The tire of Disclosure 1, wherein the tread side edge is longer than the first edge and the second edge.
[Disclosure 3]
The tire according to Disclosure 2, wherein a connection portion between the first edge and the second edge is located in a range of 30% to 50% of a maximum groove depth of the middle lateral groove.
[Disclosure 4]
The tire according to Disclosure 3, wherein the length of the tread side edge is greater than the shortest length between the connection portion and the tread side edge in a plan view of the tread.
[Disclosure 5]
The tire of disclosure 4, wherein the shortest length is between 3 and 7 mm.
[Disclosure 6]
The tire according to any one of disclosures 1 to 5, wherein the second portion extends from the middle circumferential groove.
[Disclosure 7]
The tire according to any one of claims 1 to 6, wherein the communication portion is disposed closer to the tire equator than a middle portion in the axial direction of the middle land portion.
[Disclosure 8]
The tire according to any one of claims 1 to 7, wherein a groove width of the first portion is larger than a groove width of the second portion.
[Disclosure 9]
The tire according to any one of claims 1 to 8, wherein the angle of the first portion with respect to the tire axial direction is 20 degrees or less.
[Disclosure 10]
The tire according to any one of the disclosures 1 to 9, wherein an angle between the middle circumferential groove and the second portion is 50 to 80 degrees.
[Disclosure 11]
The tire according to any one of disclosures 1 to 10, wherein a groove width at a groove bottom of the second portion is constant over the entire range of the length of the second portion.

Reference Signs List 1 Tire 5 Middle land portion 7 Middle lateral groove 7s Groove bottom 5a Middle block element 8A Block side wall 8B Block tread surface 11 First portion 12 Second portion 13 Connecting portion 15 Convex corner portion 17 First side wall 18 Second side wall 19 Third side wall

Claims (10)

A tire having a tread portion,
The tread portion includes a middle land portion divided by a shoulder circumferential groove and a middle circumferential groove,
The middle land portion is divided into a plurality of middle block elements by a plurality of middle lateral grooves,
each of the plurality of middle lateral grooves includes a first portion extending from the shoulder circumferential groove, a second portion on the side of the middle circumferential groove inclined with respect to the first portion, and a communication portion connecting the first portion and the second portion, so that each of the middle block elements includes a convex corner portion that is convex toward an outer side of the block at the communication portion,
the block side wall of the convex corner portion includes a first side wall extending along the first portion, a second side wall extending along the second portion, and a triangular third side wall spanning the first side wall, the second side wall, and the block tread surface,
the third side wall terminates radially outward of the groove bottom of the middle lateral groove ,
the communication portion is disposed closer to the tire equator than a middle portion in the axial direction of the middle land portion,
tire. A tire having a tread portion,
The tread portion includes a middle land portion divided by a shoulder circumferential groove and a middle circumferential groove,
The middle land portion is divided into a plurality of middle block elements by a plurality of middle lateral grooves,
each of the plurality of middle lateral grooves includes a first portion extending from the shoulder circumferential groove, a second portion on the side of the middle circumferential groove inclined with respect to the first portion, and a communication portion connecting the first portion and the second portion, so that each of the middle block elements includes a convex corner portion that is convex toward an outer side of the block at the communication portion,
the block side wall of the convex corner portion includes a first side wall extending along the first portion, a second side wall extending along the second portion, and a triangular third side wall spanning the first side wall, the second side wall, and the block tread surface,
the third side wall terminates radially outward of the groove bottom of the middle lateral groove,
A groove width at a groove bottom of the second portion is constant over the entire range of the length of the second portion.
tire. The third side wall includes a tread side edge that is a boundary with the block tread, a first edge that is a boundary with the first side wall, and a second edge that is a boundary with the second side wall,
The tire according to claim 1 or 2 , wherein the tread side edge is longer than the first edge and the second edge . 4. The tire according to claim 3 , wherein a connection portion between the first edge and the second edge is located in a range of 30% to 50% of a maximum groove depth of the middle lateral groove . The tire according to claim 4 , wherein a length of the tread side edge is greater than a shortest length between the connection portion and the tread side edge in a plan view of the tread . 6. The tire according to claim 5 , wherein said minimum length is between 3 and 7 mm . The tire according to claim 1 , wherein the second portion extends from the middle circumferential groove . The tire according to any one of claims 1 to 7, wherein the groove width of the first portion is greater than the groove width of the second portion. The tire according to any one of claims 1 to 8, wherein the angle of the first portion with respect to the tire axial direction is 20 degrees or less. The tire according to any one of claims 1 to 9, wherein the angle between the middle circumferential groove and the second portion is 50 to 80 degrees.

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