JP2021112999A - tire - Google Patents

Abstract

To provide a tire capable of enhancing wear resistance, dry braking performance and wet braking performance.SOLUTION: The tire comprises: circumferential main grooves 2 extending in a tire circumferential direction in a tread portion; blocks 5 which are land portions partitioned by the circumferential main grooves 2; sipes 7 each penetrating the block 5 in a tire width direction; and chamfered portions 8 provided in the sipes 7. A ratio Wm/Wb of a length Wm of the chamfered portion 8 in the tire width direction to a ground contact width Wb of the block 5 in the tire width direction is 0.2 or more and 1.0 or less. A number N of sipes 7 having the chamfered portions 8 is 10 or more and 180 or less on a tire circumference. A tire meridional cross section has a value of {Wi×N×(Wm/Wb)×2×π×Rc}/(E/Rc) of 0.44 or less where E is an average thickness in a tire circumferential direction of rubber of the block 5, Rc is an average circumferential curvature radius of the ground plane of the block 5, and Wi is a width of the sipe 7.SELECTED DRAWING: Figure 3

Description

The present invention relates to a tire.

In recent tires, a sipe may be provided on the tread portion to ensure drainage. Further, the tread portion may be provided with a notched sipe having a notch portion on the wall surface of the sipe. As a conventional tire adopting such a configuration, the technique described in Patent Document 1 is known.

Japanese Unexamined Patent Publication No. 2014-237398

However, there is room for improvement in wear resistance, dry braking performance and wet braking performance of the above-mentioned conventional tires.

The present invention has been made in view of the above, and an object of the present invention is to provide a tire capable of improving wear resistance, dry braking performance and wet braking performance.

In order to solve the above-mentioned problems and achieve the object, the tire according to an embodiment of the present invention includes a circumferential main groove extending in the tire circumferential direction in the tread portion, a land portion partitioned by the circumferential main groove, and a land portion. A sipe that penetrates the land portion in the tire width direction and a chamfered portion provided on the sipe are provided, and the length of the chamfered portion in the tire width direction with respect to the ground contact width Wb in the tire width direction of the land portion. The ratio Wm / Wb of Wm is 0.2 or more and 1.0 or less, the number N of chamfered sipe which is a sipe provided with the chamfered portion is 10 or more and 180 or less on the tire circumference, and the tire meridional cross section. When the average thickness of the rubber in the land portion in the tire circumferential direction is E, the average circumferential radius of curvature of the ground contact surface of the land portion is Rc, and the width of the sipe is Wi, {Wi × N × (Wi × N × ( The value of Wm / Wb) × 2 × π × Rc} / (E / Rc) is 0.44 or less.

In the chamfered sipe, the ratio Wm / Ws of the length Wm of the chamfered portion in the tire width direction to the length Ws of the sipe in the tire width direction is preferably 0.2 or more.

When the groove depth of the circumferential main groove is D, the depth of the sipe is Ds, and the depth of the chamfered portion is Dm, it is preferable that D> Ds ≧ Dm.

When the width of the chamfered portion in the direction orthogonal to the extending direction of the sipe on the tread surface of the land portion is ML, it is preferable that ML> Dm with respect to the depth Dm of the chamfered portion. ..

The chamfered portion may be provided on at least one of the groove wall surfaces of the sipe.

The product N × (Wm / Wb) of the ratio Wm / Wb and the number N is preferably 5 or more and 90 or less.

In the chamfered sipe, the chamfered portions are not provided at both ends in the tire width direction, and the lengths of the both end portions without the chamfered portions are preferably 3 mm or more and 6 mm or less. ..

In the chamfered sipe, the chamfered portions are provided at both ends in the tire width direction, the chamfered portions are not provided at the portions other than the both end portions, and the chamfered portions are provided. The length of the non-chamfered portion is preferably 6 mm or more and 12 mm or less.

In the chamfered sipe, the chamfered portion is not provided at one side end portion in the tire width direction, and the length of the one side end portion without the chamfered portion is 6 mm or more and 12 mm or less. Is preferable.

According to the tire according to the present invention, wear resistance, dry braking performance and wet braking performance can be improved.

FIG. 1 is a cross-sectional view in the tire meridian direction showing a tire according to an embodiment of the present invention. FIG. 2 is a plan view showing the tread surface of the tire shown in FIG. FIG. 3 is an enlarged view showing a first example of the block shown in FIG. FIG. 4 is a cross-sectional view of a portion AA in FIG. FIG. 5 is an enlarged view showing a second example of the block shown in FIG. FIG. 6 is an enlarged view showing a third example of the block shown in FIG. FIG. 7 is an enlarged view showing a fourth example of the block shown in FIG. FIG. 8 is an enlarged view showing a fifth example of the block shown in FIG. FIG. 9 is an enlarged view showing a sixth example of the block shown in FIG. FIG. 10 is an enlarged view showing a seventh example of the block shown in FIG. FIG. 11 is a cross-sectional view of a portion AA in FIG. FIG. 12 is an enlarged view showing an eighth example of the block shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description of each embodiment, the same or equivalent components as those of the other embodiments are designated by the same reference numerals, and the description thereof will be simplified or omitted. The present invention is not limited to each embodiment. In addition, the components of each embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. It should be noted that the plurality of modifications described in this embodiment can be arbitrarily combined within a range self-evident by those skilled in the art.

[tire]
FIG. 1 is a cross-sectional view in the tire meridian direction showing a tire according to an embodiment of the present invention. Further, FIG. 2 is a plan view showing a tread surface of the tire shown in FIG. FIG. 1 shows a cross-sectional view of a one-sided region in the tire radial direction. Further, FIG. 1 shows a studless tire for a passenger car as an example of a tire. The tire according to the present embodiment is preferably a pneumatic tire, and the gas to be filled in the tire is not only normal air or air adjusted for oxygen partial pressure, but also an inert gas such as nitrogen, argon, and helium. Can be used.

In FIG. 1, the cross section in the tire meridian direction refers to a cross section when a tire is cut on a plane including a tire rotation axis (not shown). Further, the reference numeral CL is a tire equatorial plane, and refers to a plane that passes through the center point of the tire in the tire rotation axis direction and is perpendicular to the tire rotation axis. The tire width direction means a direction parallel to the tire rotation axis, and the tire radial direction means a direction perpendicular to the tire rotation axis.

The tire 1 has an annular structure centered on a tire rotation axis, and has a pair of bead cores 11 and 11, a pair of bead fillers 12 and 12, a carcass layer 13, a belt layer 14, and a pair of tread rubber 15. The sidewall rubbers 16 and 16 and a pair of rim cushion rubbers 17 and 17 are provided (see FIG. 1).

The pair of bead cores 11 and 11 have an annular structure in which one or a plurality of bead wires made of steel are wound around in a plurality of manners, and are embedded in the bead portion to form the cores of the left and right bead portions. The pair of bead fillers 12 and 12 are arranged on the outer periphery of the pair of bead cores 11 and 11 in the tire radial direction to form a bead portion.

The carcass layer 13 has a single-layer structure composed of one carcass ply or a multi-layer structure formed by laminating a plurality of carcass plies, and is bridged between the left and right bead cores 11 and 11 in a toroidal shape to form a tire skeleton. Configure. Further, both ends of the carcass layer 13 are wound and locked outward in the tire width direction so as to wrap the bead core 11 and the bead filler 12. The carcass ply of the carcass layer 13 is composed of a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) coated with coated rubber and rolled, and has an absolute value of 80. It has a carcass angle of [deg] or more and 95 [deg] or less (defined as an inclination angle of the carcass cord in the longitudinal direction with respect to the tire circumferential direction).

The belt layer 14 is formed by laminating a pair of intersecting belts 141 and 142 and a belt cover 143 as a reinforcing material, and is arranged so as to be hung around the outer periphery of the carcass layer 13. The pair of crossing belts 141 and 142 are formed by coating a plurality of belt cords made of steel or an organic fiber material with coated rubber and rolling them, and have an absolute value of 20 [deg] or more and 55 [deg] or less. Have. Further, the pair of crossing belts 141 and 142 have differently signed belt angles (defined as inclination angles in the longitudinal direction of the belt cord with respect to the tire circumferential direction), and the longitudinal directions of the belt cords intersect each other. (So-called cross-ply structure). The belt cover 143 is formed by coating a belt cord made of steel or an organic fiber material with a coated rubber, and has a belt angle of 0 [deg] or more and 10 [deg] or less in absolute value. Further, the belt cover 143 is, for example, a strip material formed by coating one or a plurality of belt cords with coated rubber, and the strip material is applied a plurality of times in the tire circumferential direction with respect to the outer peripheral surfaces of the cross belts 141 and 142. And it is composed by winding it in a spiral shape.

The tread rubber 15 is arranged on the outer periphery of the carcass layer 13 and the belt layer 14 in the tire radial direction to form the tread portion 10 of the tire. The pair of sidewall rubbers 16 and 16 are arranged outside the carcass layer 13 in the tire width direction, respectively, to form the left and right sidewall portions. The pair of rim cushion rubbers 17 and 17 are arranged inside the left and right bead cores 11 and 11 and the rewinding portion of the carcass layer 13 in the tire radial direction, respectively, to form a rim fitting surface of the bead portion.

[Tread pattern]
FIG. 2 shows a typical block pattern. In FIG. 2, the tire circumferential direction means the direction around the tire rotation axis. Further, the reference numeral T is a tire contact end, and the dimension symbol TW is a tire contact width.

As shown in FIG. 2, the tire 1 includes a plurality of circumferential main grooves 2 extending in the tire circumferential direction, a plurality of land portions 3 partitioned by these circumferential main grooves 2, and these land portions 3. A plurality of lug grooves 4 arranged in the tread surface are provided. Of the plurality of land portions 3, the land portion 3 close to the tire equatorial plane CL is the center land portion 3C. The land portion 3 on the outer side in the tire width direction of the center land portion 3C is the shoulder land portion 3S.

The main groove is a groove that is obliged to display a wear indicator specified in JATTA, and has a groove width of 3.0 mm or more and a groove depth of 5.0 mm or more. The lug groove is a lateral groove extending in the tire width direction, has a groove width of 1.0 mm or more and a groove depth of 3.0 mm or more, and opens when the tire touches the ground to function as a groove.

The groove width is measured as the maximum value of the distance between the left and right groove walls at the groove opening in a no-load state in which the tire is mounted on the specified rim and the specified internal pressure is filled. In a configuration in which the land portion has a notch or a chamfered portion at the edge portion, the groove width is measured at the intersection of the tread tread and the extension line of the groove wall in a cross-sectional view with the groove length direction as the normal direction. Is measured. Further, in the configuration in which the grooves extend in a zigzag shape or a wavy shape in the tire circumferential direction, the groove width is measured with the center line of the amplitude of the groove wall as a measurement point.

The groove depth is measured as the maximum value of the distance from the tread tread to the groove bottom in a no-load state in which the tire is mounted on the specified rim and the specified internal pressure is filled. Further, in a configuration in which the groove has a partially uneven portion or a sipe on the groove bottom, the groove depth is measured by excluding these.

The specified rim means the "applicable rim" specified in JATTA, the "Design Rim" specified in TRA, or the "Measuring Rim" specified in ETRTO. The specified internal pressure means the "maximum air pressure" specified in JATTA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or "INFLATION PRESSURES" specified in ETRTO. The specified load means the "maximum load capacity" specified in JATTA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or the "LOAD CAPACITY" specified in ETRTO. However, in JATTA, in the case of a passenger car tire, the specified internal pressure is an air pressure of 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

Further, among two or more circumferential main grooves (including the circumferential main grooves arranged on the tire equatorial surface CL) arranged in one region with the tire equatorial plane CL as a boundary, the tire width direction The outermost circumferential main groove is defined as the outermost peripheral main groove. The outermost peripheral direction main groove is defined in each of the left and right regions with the tire equatorial plane CL as a boundary. The distance from the tire equatorial plane CL to the main groove in the outermost peripheral direction (dimension symbols omitted in the drawing) is in the range of 20 [%] or more and 35 [%] or less of the tire contact width TW.

The tire contact width TW is the contact surface between the tire and the flat plate when the tire is mounted on the specified rim to apply the specified internal pressure and the tire is placed perpendicular to the flat plate in a stationary state and a load corresponding to the specified load is applied. It is measured as the maximum linear distance in the tire axial direction in.

The tire ground contact end T is a contact surface between the tire and the flat plate when the tire is mounted on the specified rim to apply a specified internal pressure and the tire is placed perpendicular to the flat plate in a stationary state and a load corresponding to the specified load is applied. It is defined as the maximum width position in the tire axial direction in.

Further, the land portion 3 on the outer side in the tire width direction, which is defined in the main groove 2 in the outermost peripheral direction, is defined as the shoulder land portion. The shoulder land portion 3 is the outermost land portion in the tire width direction and is located on the tire ground contact end T.

Further, in the configuration of FIG. 2, as described above, each land portion 3 is provided with a plurality of lug grooves 4. Further, these lug grooves 4 have an open structure penetrating the land portion 3 and are arranged at predetermined intervals in the tire circumferential direction. As a result, all the land portions 3 are divided in the tire circumferential direction by the lug grooves 4, and a block row composed of a plurality of blocks 5 is formed. However, the present invention is not limited to this, and the land portion 3 may be a rib that is continuous in the tire circumferential direction (not shown).

The ground contact width Wb of each block 5 is the block and the flat plate when the tire is attached to the specified rim to apply the specified internal pressure and the block and the flat plate are placed perpendicular to the flat plate in a stationary state and a load corresponding to the specified load is applied. It is measured as the maximum linear distance in the tire axial direction on the contact surface of.

Further, in the configuration of FIG. 2, the circumferential main groove 2 and the lug groove 4 are arranged in a grid pattern to form a rectangular block 5. However, the block 5 can have any shape. For example, the circumferential main groove 2 may have a zigzag shape having an amplitude in the tire width direction, or the lug groove 4 may have a bent or curved shape (not shown). Further, for example, instead of the circumferential main groove 2 and the lug groove 4 in FIG. 2, the tire 1 is inclined to a plurality of inclined main grooves extending at a predetermined angle with respect to the tire circumferential direction, and the inclined main grooves adjacent to each other. A lug groove for communicating the grooves and a plurality of blocks defined by these inclined main grooves and lug grooves may be provided (not shown). In these configurations, the blocks can have long and complex shapes.

Further, although not shown in FIG. 2, each block 5 has a sipe and a chamfered portion formed on the sipe, as will be described later.

[Block sipes and chamfers]
FIG. 3 is an enlarged view showing a first example of the block shown in FIG. FIG. 3 shows a plan view of a single block 5 in the center land portion 3C.

As shown in FIG. 3, the block 5 includes a plurality of sipes 7 and a chamfered portion 8 provided on each sipes 7. The sipe 7 and the chamfered portion 8 are arranged in a row. The sipe 7 is a notch formed in the tread tread, and has a groove width of 0.4 mm or more and 1.0 mm or less and a groove depth of 3 mm or more and 6 mm or less. The sipe 7 is blocked when the tire touches the ground.

The sipe 7 penetrates the block 5, that is, the land portion (see FIG. 2) in the tire width direction. In the portion where the sipe 7 is arranged, the sipe 7 has a length of 100% with respect to the length in the tire width direction. When the block 5 is rectangular, the sipe 7 has a length of 100% with respect to the minimum length of the block 5 in the tire width direction. When the block 5 is rectangular, the sipe 7 has a length of 100% with respect to the maximum length of the block 5 in the tire width direction. The sipe 7 divides the block 5 at the portion where the sipe 7 is provided. When the block 5 is rectangular, the minimum length and the maximum length of the block 5 in the tire width direction coincide with the ground contact width Wb, so that the sipe 7 has a length of 100% with respect to the ground contact width Wb.

FIG. 3 shows a case where two sipes 7 are provided in a block 5 partitioned by a pair of circumferential main grooves 2 and a lug groove. The number of sipes 7 is not limited to two, and more sipes 7 may be provided.

In FIG. 3, the sipe 7 of this example is provided with one chamfered portion 8. The chamfered portion 8 is a portion that connects the edge portions of adjacent surfaces with a flat surface (for example, C chamfered) or a curved surface (for example, R chamfered). That is, the groove wall surface of the sipe 7 and the ground contact surface of the block 5 are adjacent to each other, and the portion connecting the edge portions of the adjacent surfaces with a flat surface or a curved surface is the chamfered portion 8. In the following description, among the sipes 7 provided with the chamfered portion 8, the ratio Wm / Ws of the length Wm of the chamfered portion 8 in the tire width direction to the length Ws of the chamfer 7 in the tire width direction is 0. Those with 2 or more are defined as "chamfered sipes".

In the first example shown in FIG. 3, the length Wm of the chamfered portion 8 in the tire width direction corresponds to the length Ws of the sipe 7 in the tire width direction. That is, the length Wm of the chamfered portion 8 in the tire width direction is 100% with respect to the length Ws of the sipe 7 in the tire width direction. Here, the ratio Wm / Wb of the length Wm of the chamfered portion 8 in the tire width direction to the ground contact width Wb of the land portion 3 in the tire width direction is preferably 0.2 or more and 1.0 or less. When the ratio Wm / Wb is 0.2 or more and 1.0 or less, the rigidity of the land portion 3 can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

The width of the circumferential main groove 2 in the direction perpendicular to the extending direction is, for example, 5 mm or more and 12 mm or less. The width of the chamfered portion 8 in the direction perpendicular to the extending direction is, for example, 1.0 mm or more and 3.0 mm or less.

FIG. 4 is a cross-sectional view of a portion AA in FIG. In FIG. 4, when the depth of the sipe 7 is Ds, the depth of the chamfered portion 8 (the depth of the deepest portion) is Dm, and the groove depth of the circumferential main groove is D, the relationship between the depths is D> Ds ≧ Dm. With such a depth relationship, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

The depth of the circumferential main groove 2 is, for example, 4 mm or more and 8 mm or less. The depth of the sipe 7 is, for example, 3 mm or more and 6 mm or less. The depth of the chamfered portion 8 (depth of the deepest portion) is, for example, 1 mm or more and 2 mm or less.

When the width of the chamfered portion 8 in the direction orthogonal to the extending direction of the sipe 7 on the tread surface of the block 5 of the land portion 3 is ML, the relationship of the depth with respect to the depth Dm of the chamfered portion 8 is ML> Dm. That is, the width ML of the chamfered portion 8 becomes narrower toward the deepest portion Mb. With such a depth relationship, the block rigidity can be maintained and the dry braking performance and the wet braking performance can be improved.

Here, the number N on the tire circumference of the chamfered sipe is preferably 10 or more and 180 or less. When the number N is 10 or more and 180 or less, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

Further, the product N × (Wm / Wb) of the ratio Wm / Wb of the length Wm of the chamfered portion 8 in the tire width direction to the ground contact width Wb in the tire width direction of the land portion 3 and the number N is 5 or more. It is preferably 90 or less. When the product N × (Wm / Wb) is 5 or more and 90 or less, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

By the way, when the groove width of the sipe 7 is Wi, the average thickness of the tread rubber 15 of the land portion 3 in the tire circumferential direction is E, and the average circumferential radius of curvature of the ground contact surface of the land portion 3 is Rc.
{Wi x N x (Wm / Wb) x 2 x π x Rc} / (E / Rc)
The value of (hereinafter, may be referred to as a void ratio) is preferably 0.44 or less. When the void ratio is 0.44 or less, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

In the above values, the groove width Wi of the sipe 7 is the length in the direction orthogonal to the extending direction of the sipe 7. In the above values, the average thickness E is the average value of the thickness between the ground contact surface of the land portion 3 and the belt cover 143 which is a reinforcing material in the tire circumferential direction. The average thickness E is measured at the position of the middle portion of the ground contact width Wb in the tire width direction of the land portion 3. In the above values, the average radius of curvature Rc in the circumferential direction is the average value of the radius of curvature of the ground plane of the land portion 3 in the tire circumferential direction. The average radius of curvature Rc in the circumferential direction is measured at the position of the intermediate portion of the ground contact width Wb in the tire width direction of the land portion 3. In the above values, π is the pi.

[Other Embodiments]
FIG. 5 is an enlarged view showing a second example of the block shown in FIG. FIG. 5 shows a plan view of a single block 5 in the center land portion 3C. FIG. 5 shows a case where two sipes 7 are provided in a block 5 partitioned by a pair of circumferential main grooves 2 and a lug groove, as in the first example shown in FIG. The number of sipes 7 is not limited to two, and more sipes 7 may be provided.

In the second example shown in FIG. 5, unlike the first example shown in FIG. 3, the length Wm of the chamfered portion 8 in the tire width direction is shorter than the length Ws of the sipe 7 in the tire width direction. The length Wm of the chamfered portion 8 in the tire width direction is less than 70% of the length Ws of the sipe 7 in the tire width direction. When the length Wm is less than 70% of the length Ws, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved. Of the length Ws of the sipe 7 in the tire width direction, the chamfered portion 8 is provided for the portions of the lengths Ws1 and Ws2 at both ends, excluding the portion of the chamfered portion 8 having the length Wm in the tire width direction. Only the sipe 7 is provided.

The ratio Wm / Ws of the length Wm of the chamfered portion 8 in the tire width direction to the length Ws of the sipe 7 in the tire width direction is 0.2 or more. When the ratio Wm / Ws is 0.2 or more, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved. For example, when the length Ws of the sipe 7 in the tire width direction is 3 mm or more and 36 mm or less, the length Wm of the chamfered portion 8 in the tire width direction is 3 mm or more and 36 mm or less.

In FIG. 5, the lengths Ws1 and Ws2 of both ends where the chamfered portion 8 is not provided are preferably 3 mm or more and 6 mm or less, respectively. When the lengths Ws1 and Ws2 are 3 mm or more and 6 mm or less, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

FIG. 6 is an enlarged view showing a third example of the block shown in FIG. FIG. 6 shows a plan view of a single block 5 in the center land portion 3C. In this example, two chamfered portions 8a and 8b are provided for one sipe 7. The chamfered portions 8a and 8b are connected to separate circumferential main grooves 2.

The total length of the chamfered portion 8a in the tire width direction Wm1 and the chamfered portion 8b in the tire width direction Wm2 is less than 70% of the length Ws of the sipe 7. If the total length of the length Wm1 and the length Wm2 is less than 70% of the length Ws, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved. Can be done. The chamfered portion 8 is not provided in the portion of the length Ws of the sipe 7 in the tire width direction except for the lengths Wm1 and Wm2 at both ends. That is, the chamfered portion 8 is not provided in the portion of the length Ws1 of the sipe 7, excluding the lengths Wm1 and Wm2 at both ends, and only the sipe 7 is provided.

The ratio (Wm1 + Wm2) / Ws of the total length (Wm1 + Wm2) of the length Wm1 and the length Wm2 to the length Ws in the tire width direction of the sipe 7 is 0.2 or more. When the ratio (Wm1 + Wm2) / Ws of the total length of the length Wm1 and the length Wm2 to the length Ws is 0.2 or more, the block rigidity can be maintained and the wear resistance performance can be improved, and dry braking can be performed. Performance and wet braking performance can be improved.

In FIG. 6, the chamfered portion 8 is not provided in the intermediate portion between the chamfered portion having a length Wm1 and the chamfered portion having a length Wm2, which are provided at both ends in the tire width direction. Only the sipe 7 is provided in the portion where the chamfer portion 8 is not provided. The length Ws1 of the intermediate portion where the chamfered portion 8 is not provided is preferably 6 mm or more and 12 mm or less. When the length Ws1 is 6 mm or more and 12 mm or less, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

When the depth of the sipe 7 is Ds, the depth of the chamfered portion 8d (the depth of the deepest portion) is Dm, and the groove depth of the circumferential main groove is D, the relationship between the depths is D>. Ds ≧ Dm. With such a depth relationship, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

FIG. 7 is an enlarged view showing a fourth example of the block shown in FIG. FIG. 7 shows a plan view of a single block 5 in the center land portion 3C. In this example, one chamfer portion 8d is provided for one sipe 7. The chamfered portion 8d is connected to one circumferential main groove 2 in the tire width direction and is not connected to the other circumferential main groove 2.

The length Wm of the chamfered portion 8a in the tire width direction is less than 70% of the length Ws of the sipe 7. When the length Wm is less than 70% of the length Ws, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved. Of the length Ws of the sipe 7 in the tire width direction, the portion of the length Ws1 excluding the length Wm of the chamfered portion 8 in the tire width direction is not provided with the chamfered portion 8 and the sipe 7 is not provided. Is provided.

In FIG. 7, the length Ws1 of the one-sided end portion where the chamfered portion 8 is not provided is preferably 6 mm or more and 12 mm or less. When the length Ws1 is 6 mm or more and 12 mm or less, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

The ratio Wm / Ws of the length Wm of the chamfered portion 8 in the tire width direction to the length Ws of the sipe 7 in the tire width direction is 0.2 or more. When the ratio Wm / Ws is 0.2 or more, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

When the width of the chamfered portion 8 in the direction orthogonal to the extending direction of the sipe 7 on the tread surface of the block 5 of the land portion 3 is ML, the relationship of the depth with respect to the depth Dm of the chamfered portion 8 is ML> Dm. That is, the width ML of the chamfered portion 8 becomes narrower toward the deepest portion Mb. With such a depth relationship, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

FIG. 8 is an enlarged view showing a fifth example of the block shown in FIG. FIG. 8 shows a plan view of a single block 5 in the center land portion 3C. In this example, two chamfered portions 8e and 8f are provided for one sipe 7. The chamfered portions 8e and 8f are not connected to the circumferential main groove 2.

The total length of the chamfered portion 8e in the tire width direction Wm1 and the chamfered portion 8f in the tire width direction Wm2 is less than 70% of the length Ws of the sipe 7. If the total length of the length Wm1 and the length Wm2 is less than 70% of the length Ws, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved. Can be done. Of the lengths Ws of the sipe 7 in the tire width direction, the chamfered portions 8e and 8f are provided with chamfered portions, excluding the lengths Wm1 and Wm2 in the tire width direction. It is not provided, and a sipe 7 is provided.

The ratio (Wm1 + Wm2) / Ws of the total length (Wm1 + Wm2) of the length Wm1 and the length Wm2 to the length Ws in the tire width direction of the sipe 7 is 0.2 or more. When the ratio (Wm1 + Wm2) / Ws of the total length of the length Wm1 and the length Wm2 to the length Ws is 0.2 or more, the block rigidity can be maintained and the wear resistance performance can be improved, and dry braking can be performed. Performance and wet braking performance can be improved.

When the width of the chamfered portion 8 in the direction orthogonal to the extending direction of the sipe 7 on the tread surface of the block 5 of the land portion 3 is ML, the relationship of the depth with respect to the depth Dm of the chamfered portion 8 is ML> Dm. That is, the width ML of the chamfered portion 8 becomes narrower toward the deepest portion Mb. With such a depth relationship, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

FIG. 9 is an enlarged view showing a sixth example of the block shown in FIG. FIG. 9 shows a plan view of a single block 5 in the center land portion 3C. In this example, three chamfered portions 8a, 8b, and 8c are provided for one sipe 7. The chamfered portions 8a and 8b are connected to separate circumferential main grooves 2. The chamfered portion 8c is not connected to the circumferential main groove 2.

The total length of the chamfered portion 8a in the tire width direction Wm1, the chamfered portion 8b in the tire width direction Wm2, and the chamfered portion 8b in the tire width direction Wm3 is the length of the sipe 7. It is less than 70% with respect to Ws. If the total length of the length Wm1, the length Wm2 and the length Wm3 is less than 70% of the length Ws, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved. Can be improved. Of the length Ws of the sipe 7 in the tire width direction, the lengths Ws1 and Ws2 excluding the lengths Wm1, Wm2 and Wm3 of the chamfered portions 8a, 8b and 8c in the tire width direction are the chamfered portions. Is not provided, but a sipe 7 is provided.

The ratio (Wm1 + Wm2 + Wm3) / Ws of the total length (Wm1 + Wm2 + Wm3) of the lengths Wm1, Wm2 and Wm3 to the length Ws in the tire width direction of the sipe 7 is 0.2 or more. When the ratio (Wm1 + Wm2 + Wm3) / Ws of the total length (Wm1 + Wm2 + Wm3) to the length Ws is 0.2 or more, the block rigidity can be maintained and the wear resistance performance can be improved. It is possible to improve dry braking performance and wet braking performance.

When the width of the chamfered portion 8 in the direction orthogonal to the extending direction of the sipe 7 on the tread surface of the block 5 of the land portion 3 is ML, the relationship of the depth with respect to the depth Dm of the chamfered portion 8 is ML> Dm. That is, the width ML of the chamfered portion 8 becomes narrower toward the deepest portion Mb. With such a depth relationship, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

FIG. 10 is an enlarged view showing a seventh example of the block shown in FIG. FIG. 10 shows a plan view of a single block 5 in the center land portion 3C. In FIG. 10, the sipe 7 of this example is provided with one chamfered portion 8. In this example, the chamfered portion 8 is provided only on one of the groove wall surfaces of the sipe 7. The chamfered portion 8 is not provided on the other side of the groove wall surface of the sipe 7. That is, the chamfered portion 8 is provided only on one of the groove wall surfaces on both sides of the sipe 7. Also in this example, the sipe 7 penetrates the block 5 which is a land portion in the tire width direction. The length of the chamfered portion 8 provided on the sipe in the tire width direction coincides with the length Ws of the sipe 7 in the tire width direction. That is, the length Wm of the chamfered portion 8 in the tire width direction is 100% with respect to the length Ws of the sipe 7 in the tire width direction. Similar to the case of the first example shown in FIG. 3, the ratio Wm / Wb of the length Wm of the chamfered portion 8 in the tire width direction to the ground contact width Wb of the land portion 3 in the tire width direction is 0.2 or more and 1 It is preferably 0.0 or less. When the ratio Wm / Wb is 0.2 or more and 1.0 or less, the rigidity of the land portion 3 can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

Also in the seventh example shown in FIG. 10, the product N × (Wm / Wb) of the ratio Wm / Wb of the length Wm of the chamfered portion 8 in the tire width direction and the number N is 5 or more and 90 or less. Is preferable. Further, the void ratio is preferably 0.44 or less.

FIG. 11 is a cross-sectional view of a portion AA in FIG. In FIG. 11, when the depth of the sipe 7 is Ds, the depth of the chamfered portion 8 (the depth of the deepest portion) is Dm, and the groove depth of the circumferential main groove is D, the relationship between the depths is D> Ds ≧ Dm. With such a depth relationship, the block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

As described with reference to FIGS. 10 and 11, the chamfered portion 8 is provided on at least one of the groove wall surfaces of the sipe 7, so that the chamfered portion 8 is provided in the same manner as in the case described with reference to FIGS. 3 and 4. , The block rigidity can be maintained and the wear resistance performance can be improved, and the dry braking performance and the wet braking performance can be improved.

FIG. 12 is an enlarged view showing an eighth example of the block shown in FIG. FIG. 12 shows a plan view of a single block 5 in the center land portion 3C. In FIG. 12, the sipe 7 of this example is provided with one chamfered portion 8. In this example, as in the third example shown in FIG. 5, the chamfered portion 8 is provided only on one of the groove wall surfaces of the sipe 7. The chamfered portion 8 is not provided on the other side of the groove wall surface of the sipe 7. That is, the chamfered portion 8 is provided only on one of the groove wall surfaces on both sides of the sipe 7. Also in this example, the sipe 7 penetrates the block 5 which is a land portion in the tire width direction. The length of the chamfered portion 8 provided on the sipe in the tire width direction is less than 70% of the length of the sipe 7 in the tire width direction. The ratio Wm / Ws of the length Wm of the chamfered portion 8 in the tire width direction to the length Ws of the sipe 7 in the tire width direction is 0.2 or more.

In FIGS. 3 and 6 to 10, the sipe 7 may be curved or bent (not shown). As shown in FIGS. 6, 8 and 9, when a plurality of chamfered portions are provided on one sipe 7, some of the chamfered portions are provided on only one of the groove wall surfaces of the sipe 7. May be (not shown).

[Example]
Tables 1 to 5 are tables showing the results of tire performance tests according to the present embodiment.

In this performance test, a plurality of types of test tires were evaluated for wear resistance, dry braking performance, and wet braking performance. Further, a test tire having a size of 205 / 55R16 was assembled on a wheel having a size of 16 × 6.5J, and the air pressure was set to 200 kPa, and the test tire was attached to a test vehicle of an FF sedan passenger car (total displacement 1600 cc).

Regarding the wear resistance performance, the distance traveled by the test vehicle on the test course of the dry road surface until the tread surface is completely worn, that is, the distance traveled until the wear indicator provided in the circumferential main groove 2 is exposed. It was measured and evaluated by indexing the measured mileage. The larger the index value, the better the wear resistance. Regarding the dry braking performance, the braking distance was measured on a dry road surface at a speed of 100 km / h. The reciprocal of the measured value is used, and the larger the index value, the better the dry performance. Regarding the wet braking performance, the braking distance was measured on a wet road surface at a speed of 100 km / h and a water depth of 1 mm. The reciprocal of the measured value is used, and the larger the index value, the better the wet performance.

The tires of Examples 1 to 40 are provided on a sipe, a circumferential main groove extending in the tire circumferential direction, a land portion partitioned by the circumferential main groove, a sipe penetrating the land portion in the tire width direction, and a sipe. The chamfered portion is provided, the ratio Wm / Wb is 0.2 or more and 1.0 or less, the number N on the tire circumference of the chamfered sipe is 10 or more and 180 or less, and the void ratio is 0.44 or less. The relationship between the depth Ds of the sipe and the depth Dm of the chamfered portion is Ds ≧ Dm, the relationship between the width ML of the chamfered portion and the depth Dm of the chamfered portion is ML> Dm, and the product N × (Wm / Wb) is 5 or more and 90 or less. When the ratio Wm / Wb is 0.7, 0.5, 0.4, 0.3, 0.2, the lengths Ws1 and Ws2 of both ends where the chamfered portion is not provided are 3 mm or more. The length Ws1 of the intermediate portion without the chamfered portion was set to 6 mm or more and 12 mm or less, and the length Ws1 of the one-sided end portion without the chamfered portion was set to 6 mm or more and 12 mm or less.

The tire of the conventional example is a tire having a sipe in the tread portion but not having a chamfered portion of the sipe. The tire of the comparative example is a tire having a sipe and a chamfered portion in the tread portion, and has a ratio Wm / Wb of 1.0.

As shown in Tables 1 to 5, the ratio Wm / Wb is 0.2 or more and 1.0 or less, the number N on the tire circumference of the chamfered sipe is 10 or more and 180 or less, and the void ratio is 0.44. The relationship between the depth Ds of the sipe and the depth Dm of the chamfered portion is Ds ≧ Dm, and the relationship between the width ML of the chamfered portion and the depth Dm of the chamfered portion is ML> Dm. It can be seen that when the product N × (Wm / Wb) is 5 or more and 90 or less, good results can be obtained with respect to the wear resistance performance, the dry braking performance and the wet braking performance.

1 Tire 2 Circumferential main groove 3 Land part 3C Center Land part 3S Shoulder land part 4 Rug groove 5 Block 7 Sipe 8, 8a, 8b, 8c, 8d, 8e, 8f Catch part 10 Tread part 11 Bead core 12 Bead filler 13 Carcus layer 14 Belt layer 15 Tread rubber 16 Side wall rubber 17 Rim cushion rubber 141, 142 Cross belt 143 Belt cover CL Tire equatorial plane T Tire ground contact end TW Tire ground contact width

Claims (9)

A circumferential main groove extending in the tire circumferential direction in the tread portion, a land portion partitioned by the circumferential main groove, a sipe penetrating the land portion in the tire width direction, and a chamfered portion provided on the sipe. With
The ratio Wm / Wb of the length Wm in the tire width direction of the chamfered portion to the ground contact width Wb in the tire width direction of the land portion is 0.2 or more and 1.0 or less.
The number N of chamfered sipes, which are chamfered sipes having the chamfered portion, is 10 or more and 180 or less on the tire circumference.
When the average thickness of the rubber in the land portion in the tire circumferential direction in the tire meridional cross section is E, the average radius of curvature in the circumferential direction of the ground contact surface of the land portion is Rc, and the width of the sipe is Wi.
A tire having a value of {Wi × N × (Wm / Wb) × 2 × π × Rc} / (E / Rc) of 0.44 or less. The tire according to claim 1, wherein in the chamfered sipe, the ratio Wm / Ws of the length Wm of the chamfered portion in the tire width direction to the length Ws of the sipe in the tire width direction is 0.2 or more. .. Claim 1 or claim 2 in which D> Ds ≧ Dm when the groove depth of the circumferential main groove is D, the depth of the sipe is Ds, and the depth of the chamfered portion is Dm. Tires listed in. 3. Claim 3 in which ML> Dm with respect to the depth Dm of the chamfered portion, where ML is the width of the chamfered portion in the direction orthogonal to the extending direction of the sipe on the tread surface of the land portion. Tires listed in. The tire according to any one of claims 1 to 4, wherein the chamfered portion is provided on at least one of the groove wall surfaces of the sipe. The tire according to any one of claims 1 to 5, wherein the product N × (Wm / Wb) of the ratio Wm / Wb and the number N is 5 or more and 90 or less. In the chamfered sipe, the chamfered portions are not provided at both ends in the tire width direction, and the lengths of the both end portions without the chamfered portions are 3 mm or more and 6 mm or less. The tire according to any one of claims 6. In the chamfered sipe, the chamfered portions are provided at both ends in the tire width direction, the chamfered portions are not provided at the portions other than the both end portions, and the chamfered portions are provided. The tire according to any one of claims 1 to 6, wherein the length of the non-existent portion is 6 mm or more and 12 mm or less. In the chamfered sipe, the chamfered portion is not provided at one side end portion in the tire width direction, and the length of the one side end portion without the chamfered portion is 6 mm or more and 12 mm or less. The tire according to any one of claims 1 to 6.

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