JP7640314B2 - Pneumatic tires - Google Patents

Description

The present invention relates to pneumatic tires.

For example, as disclosed in Patent Document 1, a pneumatic tire is known that has five ribs extending in the tire circumferential direction, with multiple slits in each rib that extend in the tire axial direction and bend along the way, and the slits are offset in the tire circumferential direction from the slits in the adjacent ribs.

In such pneumatic tires, traction is ensured by the effect of the slits extending in the tire axial direction, and traction is exerted in the entire tire circumferential direction because the slits of one rib are offset from the slits of the adjacent rib in the tire circumferential direction. In addition, because the slits not only extend in the tire axial direction but also bend in the middle, a certain degree of skid resistance is also ensured.

Special Publication No. 2015-512352

However, in the above pneumatic tires, the slits extend generally in the axial direction of the tire, so simply bending the slits does not ensure sufficient skid resistance. Also, when grooves are provided in the ribs to improve skid resistance, there is a problem that the rigidity of the tread decreases depending on how they are provided.

Therefore, the objective of the present invention is to provide a pneumatic tire that ensures sufficient skid resistance and tread rigidity.

In one embodiment, a pneumatic tire has four main grooves extending in a circumferential direction of the tire and five ribs formed by the main grooves. The ribs include one center rib on the tire equator, two quarter ribs adjacent to the center rib, and two shoulder ribs on the tire ground contact end side. Each rib has a plurality of slits arranged in the circumferential direction of the tire, each slit having one or more bending points and extending in the axial direction of the tire, and the slits of each rib are arranged in a line in the circumferential direction of the tire with respect to the slits of an adjacent rib. In this pneumatic tire, the center rib and the quarter rib have narrow grooves extending in a direction inclined with respect to the circumferential direction of the tire and connecting the two slits. The narrow grooves in the center rib and the quarter rib have an inclination direction opposite to the circumferential direction of the tire. The depth of the slits and the narrow grooves is 10 to 30% of the depth of the main groove .
In addition, a pneumatic tire according to an embodiment has four main grooves extending in a tire circumferential direction and five ribs formed by the main grooves, and the ribs include one center rib on the tire equator, two quarter ribs adjacent to the center rib, and two shoulder ribs on the tire ground contact end side. Each rib has a plurality of slits arranged in the tire circumferential direction, the slits having one or more bending points and extending in the tire axial direction, and the slits of each rib are offset in the tire circumferential direction from the slits of an adjacent rib. In this pneumatic tire, a narrow groove is formed in the center rib and the quarter rib, extending in a direction inclined with respect to the tire circumferential direction and connecting the two slits, the inclination direction of the narrow groove is opposite to that of the center rib and the quarter rib with respect to the tire circumferential direction, and sipes are provided at the bottom of the slits in the center rib and the quarter rib.

In the pneumatic tire of the embodiment, the slits and narrow grooves are provided as described above, so that the tire has sufficient skid resistance and the rigidity of the tread is also ensured.

Pneumatic tire tread pattern. 2 is a cross-sectional view taken along line AA in FIG. 1 . BB cross-sectional view of FIG.

The embodiment will be described with reference to the drawings. Note that the embodiment described below is merely an example, and any modifications that do not deviate from the spirit of the present invention are considered to be within the scope of the present invention.

The pneumatic tire of the embodiment has a typical cross-sectional structure of a pneumatic tire, except for the tread. Specifically, bead portions (bead portions are portions including a bead core and a bead filler) are provided on both sides in the tire axial direction, and a carcass ply is provided from one bead portion to the other bead portion in the tire axial direction. A belt is provided on the outer diameter side of the carcass ply, and a tread is provided on the outer diameter side of the belt. An inner liner is provided inside the carcass ply, and sidewall rubber is provided on both sides of the carcass ply in the tire axial direction. In addition to the above, a number of rubber members are provided to configure the pneumatic tire.

As shown in FIG. 1, the tread has two center main grooves 21 near the tire equator C and two shoulder main grooves 22 near the tire ground contact edge E as main grooves extending in the tire circumferential direction. These main grooves 21, 22 extend straight in the tire circumferential direction without bending. These main grooves 21, 22 have the same depth and are the deepest of the grooves provided in the tread. In addition, the center main groove 21 is narrower than the shoulder main grooves 22.

The main groove is a groove that extends in the circumferential direction of the tire and has a width that is at least half the width of the widest groove in the tread. Therefore, the width of the center main groove 21 is at least half the width of the shoulder main groove 22.

These main grooves 21, 22 form five ribs in the tread. The five ribs are a center rib 23 on the tire equator C, quarter ribs 24 on either side of the center rib 23, and shoulder ribs 25 on both axial sides of the tire at the tire's ground contact ends E.

Each of these ribs 23, 24, and 25 has a slit that has one or more bending points and extends in the tire axial direction. The slit is a groove that is narrower than the main grooves 21 and 22.

First, the center rib 23 has multiple center slits 30 spaced apart in the tire circumferential direction. The center slits 30 open into the center main grooves 21 on both sides of the center rib 23. The depth of the center slits 30 is 10 to 30% of the depth of the main grooves 21, 22.

The center slit 30 has two bending points 31, and is made up of a first straight section 32 from the bending point 31 to the bending point 31, and two second straight sections 33 from the bending point 31 to the opening end to the center main groove 21. The first straight section 32 and the second straight section 33 are inclined with respect to the tire axial direction, but the second straight section 33 is inclined in the opposite direction to the first straight section 32 with respect to the tire axial direction.

As shown in FIG. 2, a center sipe 34 narrower than the center slit 30 is provided at the bottom of the center slit 30. As shown in FIG. 1, the center sipe 34 also opens into the center main groove 21 on both sides of the center rib 23. The center sipe 34 is also bent at the same position as the center slit 30. The combined depth of the center slit 30 and center sipe 34 (i.e., the length from the opening end of the center slit 30 facing the ground contact surface to the bottom of the center sipe 34) is 50 to 90% of the depth of the main grooves 21, 22.

The quarter rib 24 also has multiple quarter slits 40 spaced apart in the circumferential direction of the tire. The quarter slits 40 open into the center main groove 21 and the shoulder main groove 22. The depth of the quarter slits 40 is 10 to 30% of the depth of the main grooves 21, 22.

The quarter slit 40 has two bending points 41, 42, and is made up of a first straight section 43 from the opening end to the center main groove 21 to the first bending point 41, a second straight section 44 from the first bending point 41 to the second bending point 42, and a third straight section 45 from the second bending point 42 to the opening end to the shoulder main groove 22. The first straight section 43 and the second straight section 44 are inclined with respect to the tire axial direction and arranged in a V shape. The third straight section 45 extends in the tire axial direction.

As shown in FIG. 3, a quarter sipe 46 narrower than the quarter slit 40 is provided at the bottom of the quarter slit 40. As shown in FIG. 1, the quarter sipe 46 also opens into the center main groove 21 and the shoulder main groove 22. The quarter sipe 46 is also bent at the same position as the quarter slit 40. The combined depth of the quarter slit 40 and the quarter sipe 46 (i.e., the length from the opening end of the quarter slit 40 toward the ground contact surface to the bottom of the quarter sipe 46) is 50-90% of the depth of the main grooves 21, 22.

The shoulder rib 25 is provided with multiple shoulder slits 50 spaced apart in the tire circumferential direction. One end of the shoulder slits 50 opens into the shoulder main groove 22. The other end of the shoulder slit 50 (hereinafter, this end will be referred to as the "closed end 51") is closed within the shoulder rib 25 and is located closer to the tire equator C than the tire ground contact edge E. The depth of the shoulder slits 50 is 10-30% of the depth of the main grooves 21, 22.

The shoulder slit 50 has two bending points 52, 53, and is made up of a first straight section 54 from the shoulder main groove 22 to the first bending point 52, a second straight section 55 from the first bending point 52 to the second bending point 53, and a third straight section 56 from the second bending point 53 to the closed end 51. The second straight section 55 is inclined with respect to the tire axial direction, but the first straight section 54 and the third straight section 56 extend in the tire axial direction. No grooves such as sipes are provided at the groove bottom of the shoulder slit 50.

These slits are arranged with a circumferential offset from the slits of the adjacent ribs. Specifically, the center slit 30 and the quarter slit 40 are arranged with a circumferential offset from each other in the tire circumferential direction and do not overlap in the tire axial direction. In addition, the quarter slit 40 of the quarter rib 24 and the shoulder slit 50 of the adjacent shoulder rib 25 are arranged with a circumferential offset from each other in the tire axial direction and do not overlap in the tire axial direction.

On the other hand, slits of non-adjacent ribs may have an overlapping area in the tire axial direction. However, the circumferential length of the area where the slits overlap in the tire axial direction is 10% or less of the pitch length. Here, the pitch length means the circumferential length of one repeating unit of the tread pattern, and is, for example, the circumferential distance P between the closed ends 51 of two circumferentially adjacent shoulder slits 50 (see the shoulder rib 25 on the right side of Figure 1).

For example, the center slit 30 and the shoulder slit 50 have an overlapping area in the tire axial direction. However, the length L (see FIG. 1) of the area where these slits 30, 50 overlap in the tire axial direction is 10% or less of the pitch length.

The quarter slit 40 of the quarter rib 24 has an area that overlaps in the tire axial direction with the quarter slit 40 of another quarter rib 24 and the shoulder slit 50 of the non-adjacent shoulder rib 25. However, the length of such an area that overlaps in the tire axial direction in the tire circumferential direction is 10% or less of the pitch length.

The center rib 23 and the quarter ribs 24 are provided with narrow grooves that extend at a slight incline relative to the tire circumferential direction. The narrow grooves are narrower than the main grooves 21 and 22.

The center rib 23 is provided with a center narrow groove 35 that extends in a direction inclined relative to the tire circumferential direction. The center narrow groove 35 connects two center slits 30 that are adjacent in the tire circumferential direction. The center narrow groove 35 does not open into the center main groove 21, but opens into the center slit 30. The depth of the center narrow groove 35 is 10 to 30% of the depth of the main grooves 21, 22. The center narrow groove 35 and the center slit 30 may be the same depth or different depths.

The two quarter ribs 24 each have a quarter narrow groove 47 extending in a direction inclined relative to the tire circumferential direction. The quarter narrow groove 47 connects two quarter slits 40 adjacent in the tire circumferential direction. The quarter narrow groove 47 does not open to the main grooves 21 and 22, but opens to the quarter slit 40. The depth of the quarter narrow groove 47 is 10 to 30% of the depth of the main grooves 21 and 22. The quarter narrow groove 47 and the quarter slit 40 may be the same depth or different depths.

The quarter narrow groove 47 is inclined in the opposite direction to the center narrow groove 35 with respect to the tire circumferential direction. Therefore, the extension line of the quarter narrow groove 47 intersects with the extension line of the center narrow groove 35. The quarter narrow groove 47 of one quarter rib 24 on one side in the tire axial direction is parallel to the quarter narrow groove 47 of the other quarter rib 24 on the other side in the tire axial direction. The shoulder rib 25 does not have a narrow groove extending in the tire circumferential direction.

A pneumatic tire with these characteristics is mounted, for example, on the front side of a vehicle.

As described above, the pneumatic tire of this embodiment has slits 30, 40, 50 extending in the tire axial direction in the center rib 23, quarter rib 24, and shoulder rib 25, respectively. These slits 30, 40, 50 allow the pneumatic tire to exhibit traction. And because these slits 30, 40, 50 each have a bending point and a portion inclined with respect to the tire axial direction, the pneumatic tire also exhibits skid resistance. Also, because each slit 30, 40, 50 in each rib 23, 24, 25 is positioned offset in the tire circumferential direction from the slits in the adjacent rib, the pneumatic tire exhibits traction in the entire tire circumferential direction.

In addition, the center rib 23 is provided with a center narrow groove 35 extending in the tire circumferential direction, and the quarter rib 24 is provided with a quarter narrow groove 47 extending in the tire circumferential direction, further improving the skid resistance of the pneumatic tire. Here, the center narrow groove 35 connects the two center slits 30, and the quarter narrow groove 47 connects the two quarter slits 40, so these narrow grooves 35, 47 are longer and the center rib 23 and quarter rib 24 are more likely to deform. This also improves the skid resistance of the pneumatic tire.

Furthermore, the center narrow groove 35 and the quarter narrow groove 47 are inclined in opposite directions relative to the tire circumferential direction. Therefore, when a force is applied to the tread in a direction that makes the center narrow groove 35 easy to close and the center rib 23 easy to deform (i.e., a direction perpendicular to the extension direction of the center narrow groove 35), the quarter narrow groove 47 is difficult to close and the quarter rib 24 is difficult to deform. Conversely, when a force is applied to the tread in a direction that makes the quarter narrow groove 47 easy to close and the quarter rib 24 easy to deform (i.e., a direction perpendicular to the extension direction of the quarter narrow groove 47), the center narrow groove 35 is difficult to close and the center rib 23 is difficult to deform. Therefore, regardless of the direction of force applied, the rigidity of each rib 23, 24, 25 is ensured, and the rigidity of the entire tread is ensured.

And because the rigidity of the tread is ensured, abrasion resistance and resistance to uneven wear are improved, and because tread deformation is minimal and energy loss is reduced, fuel efficiency is also improved.

In addition, the depth of each slit 30, 40, 50 and each narrow groove 35, 47 is 10% or more of the depth of the main grooves 21, 22, improving traction and skid resistance. In addition, the depth of each slit 30, 40, 50 and each narrow groove 35, 47 is 30% or less of the depth of the main grooves 21, 22, ensuring the rigidity of the tread and improving wear resistance, resistance to uneven wear, and fuel economy.

In addition, since a center sipe 34 is provided at the bottom of the center slit 30 and a quarter sipe 46 is provided at the bottom of the quarter slit 40, even if the center slit 30 or quarter slit 40 becomes shallow or disappears due to tread wear, the center sipe 34 and quarter sipe 46 remain, and the traction of the pneumatic tire is maintained.

On the other hand, a large force is applied to the shoulder rib 25, but since there are no sipes at the bottom of the shoulder slit 50, excessive deformation of the shoulder rib 25 is suppressed.

In addition, the combined depth of the center slit 30 and center sipe 34 is 50% or more of the depth of the main grooves 21 and 22, improving traction. In addition, the combined depth of the center slit 30 and center sipe 34 is 90% or less of the depth of the main grooves 21 and 22, ensuring the rigidity of the center rib 23 and improving wear resistance, resistance to uneven wear, and fuel economy.

In addition, the combined depth of the quarter slits 40 and quarter sipes 46 is 50% or more of the depth of the main grooves 21 and 22, improving traction. In addition, the combined depth of the quarter slits 40 and quarter sipes 46 is 90% or less of the depth of the main grooves 21 and 22, ensuring the rigidity of the quarter rib 24 and improving wear resistance, resistance to uneven wear, and fuel economy.

In addition, large lateral forces are applied to the front tires of a vehicle when the vehicle turns, but the pneumatic tire of this embodiment has excellent skid resistance, making it suitable as a front tire.

As described above, the circumferential length of the area where the center slit 30 and the shoulder slit 50 overlap in the axial direction of the tire is 10% or less of the pitch length. In this way, the center slit 30 and the shoulder slit 50 are arranged in a dispersed manner without concentrating in one place in the circumferential direction of the tire, so that traction is exerted throughout the entire circumferential direction of the tire.

As described above, the quarter slits 40 of one quarter rib 24 overlap with the quarter slits 40 of another quarter rib 24 and the shoulder slits 50 of the non-adjacent shoulder rib 25 in the tire axial direction, but the length of the axially overlapping area is 10% or less of the pitch length. In this way, the slits are dispersed and not concentrated in one place in the tire circumferential direction, so that traction is exerted throughout the entire tire circumferential direction.

Various modifications can be made to the above embodiments. For example, some or all of the center slit, quarter slit, and shoulder slit may have one or more bends, which will improve not only traction but also skid resistance.

In addition, some or all of the center main groove and shoulder main grooves may be zigzag-shaped main grooves extending circumferentially around the tire.

C...Tire equator, E...Tire ground contact edge, 21...Center main groove, 22...Shoulder main groove, 23...Center rib, 24...Quarter rib, 25...Shoulder rib, 30...Center slit, 31...Bending point, 32...First straight portion, 33...Second straight portion, 34...Center sipe, 35...Center narrow groove, 40...Quarter slit, 41...Bending point, 42...Bending point, 43...First straight portion, 44...Second straight portion, 45...Third straight portion, 46...Quarter sipe, 47...Quarter narrow groove, 50...Shoulder slit, 51...Closed end, 52...Bending point, 53...Bending point, 54...First straight portion, 55...Second straight portion, 56...Third straight portion

Claims (4)

The tire has four main grooves extending in a circumferential direction and five ribs formed by the main grooves,
The ribs include one center rib on the tire equator, two quarter ribs adjacent to the center rib, and two shoulder ribs on the tire ground contact end side.
Each rib has one or more bending points and is provided with a plurality of slits arranged in the tire circumferential direction, the slits having one or more bending points and extending in the tire axial direction,
In a pneumatic tire in which each slit of each rib is arranged to be shifted from each slit of an adjacent rib in the tire circumferential direction,
A narrow groove is formed in each of the center rib and the quarter rib, the narrow groove extending in a direction inclined with respect to the tire circumferential direction and connecting the two slits,
The inclination directions of the narrow grooves are opposite to each other with respect to the tire circumferential direction in the center rib and the quarter rib,
A pneumatic tire, characterized in that the depth of the slits and the narrow grooves is 10 to 30% of the depth of the main groove . The tire has four main grooves extending in a circumferential direction and five ribs formed by the main grooves,
The ribs include one center rib on the tire equator, two quarter ribs adjacent to the center rib, and two shoulder ribs on the tire ground contact end side.
Each rib has one or more bending points and is provided with a plurality of slits arranged in the tire circumferential direction, the slits having one or more bending points and extending in the tire axial direction,
In a pneumatic tire in which each slit of each rib is arranged to be shifted from each slit of an adjacent rib in the tire circumferential direction,
A narrow groove is formed in each of the center rib and the quarter rib, the narrow groove extending in a direction inclined with respect to the tire circumferential direction and connecting the two slits,
The inclination directions of the narrow grooves of the center rib and the quarter rib are opposite to each other with respect to the tire circumferential direction,
A pneumatic tire, wherein sipes are provided at bottoms of the slits in the center rib and the quarter ribs. The pneumatic tire according to claim 2 , wherein a combined depth of the slits and the sipes is 50 to 90% of a depth of the main groove. The pneumatic tire according to claim 2 or 3 , wherein there are no sipes at the bottom of the slit of the shoulder rib.

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