JP6780687B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of achieving both dry steering stability performance and wet steering stability performance.

With recent pneumatic tires, there is a demand to improve sports performance not only when driving on a circuit but also when driving in urban areas and highways. Therefore, there is a problem that the dry performance and the wet performance of the tire should be compatible with each other. As a conventional pneumatic tire relating to such a problem, the techniques described in Patent Documents 1 and 2 are known.

Japanese Patent No. 4755709 Japanese Patent No. 5629283

An object of the present invention is to provide both dry steering stability performance and wet steering stability performance.

In order to achieve the above object, the pneumatic tire according to the present invention includes a plurality of circumferential main grooves extending in the tire circumferential direction and a land portion defined by the adjacent circumferential main grooves. The tire includes a chamfered portion formed on the edge portion of the land portion on the tire contact end side, and a lug groove and a narrow groove arranged corresponding to the chamfered portion. The chamfered portion widens the chamfered width in the tire circumferential direction on the tread surface of the land portion, and the lug groove is terminated in the land portion at one end and at the other end. The chamfered portion is opened in the central portion in the longitudinal direction, and the narrow groove is opened at one end portion at the edge portion of the land portion on the tire equatorial plane side, and at the other end portion, the surface is described. Terminate in the vicinity of the maximum width position of the chamfered portion while leaving a slight gap between the maximum width position of the chamfered portion, and the other end portion of the narrow groove and the maximum width position of the chamfered portion. The distance Gs to and from is in the range of Gs ≤ 1.5 [mm].
Further, the pneumatic tire according to the present invention includes a plurality of circumferential main grooves extending in the tire circumferential direction, and a shoulder land portion and a second land portion defined by the adjacent circumferential main grooves. In the tire, the second land portion has a chamfered portion formed on the edge portion on the tire ground contact end side of the second land portion, and a lug groove and a narrow groove arranged corresponding to the chamfered portion. The chamfered portion widens the chamfered width toward the tire circumferential direction at the tread surface of the second land portion, and the lug groove terminates in the second land portion at one end and the other. The end of the chamfer opens in the center of the chamfer in the longitudinal direction, and the groove opens at one end to the edge of the second land on the tire equatorial side and the other end. The second land portion, which terminates in the vicinity of the maximum width position of the chamfered portion or is connected to the maximum width position, is provided between the narrow grooves adjacent to each other in the tire circumferential direction. The ground contact width Wb2 of the second land portion having no other groove to divide has a relationship of 0.70 ≦ Wb2 / Wb1 ≦ 1.20 with respect to the ground contact width Wb1 of the shoulder land portion, and the shoulder The land portion includes a lug groove having a groove center line inclined in the same direction as the groove center line of the lug groove of the second land portion, and the groove center line of the lug groove and the second land of the shoulder land portion. The intersection points P1 and P2 of the groove center line of the lug groove and the groove center line of the circumferential main groove that divides the shoulder land portion and the second land portion are defined, respectively, and the intersection points P1 and P2 The distance Dp in the tire circumferential direction is in the range of 0.10 ≦ Dp / Pc ≦ 0.40 with respect to the pitch length Pc of the chamfered portion of the second land portion.

In the pneumatic tire according to the present invention, the lateral groove that opens in the center of the chamfered portion is a wide lug groove, and the lateral groove that ends or opens at the maximum width position of the chamfered portion is a narrow narrow groove. It has the following advantages. That is, as compared with (a) a configuration in which all the grooves arranged in the land portion are wide lateral grooves, the rigidity of the land portion is ensured and the dry performance of the tire is ensured. Further, (b) the drainage property of the land portion 32 is improved and the wet steering stability performance of the tire is improved as compared with the configuration in which all the grooves arranged in the land portion are narrow grooves or sipes. ..

FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view showing the tread surface of the pneumatic tire shown in FIG. FIG. 3 is an enlarged view showing a second land portion and a shoulder land portion in the vehicle width direction inner region described in FIG. FIG. 4 is an enlarged plan view showing the second land portion shown in FIG. FIG. 5 is a cross-sectional view showing the second land portion shown in FIG. FIG. 6 is an explanatory view showing a modified example of the lug groove in the second land portion shown in FIG. FIG. 7 is an explanatory view showing a modified example of the narrow groove in the second land portion described in FIG. FIG. 8 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In addition, the components of this embodiment include substitutable and self-explanatory components while maintaining the identity of the invention. Further, the plurality of modifications described in this embodiment can be arbitrarily combined within the range of those skilled in the art.

[Pneumatic tires]
FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. The figure shows a cross-sectional view of one side region in the tire radial direction. Further, the figure shows a radial tire for a passenger car as an example of a pneumatic tire.

In the figure, the cross section in the tire meridian direction refers to the cross section when the tire is cut on a plane including the 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.

Further, the inside in the vehicle width direction and the outside in the vehicle width direction are defined as the directions with respect to the vehicle width direction when the tires are mounted on the vehicle. Further, the left and right regions with the tire equatorial plane as a boundary are defined as an outer region in the vehicle width direction and an inner region in the vehicle width direction, respectively. Further, the pneumatic tire includes a mounting direction display unit (not shown) indicating the tire mounting direction with respect to the vehicle. The mounting direction display portion is composed of, for example, marks and irregularities attached to the sidewall portion of the tire. For example, ECE R30 (Article 30 of the European Economic Commission for Europe) requires that a display unit in the vehicle mounting direction be provided on a sidewall portion that is outside in the vehicle width direction when the vehicle is mounted.

The pneumatic tire 10 has an annular structure centered on the tire rotation axis, and includes 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 tread rubber 15. , A pair of sidewall rubbers 16 and 16 and a pair of rim cushion rubbers 17 and 17 (see FIG. 1).

The pair of bead cores 11, 11 are formed by winding one or a plurality of bead wires made of steel in an annular shape and 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 reinforce the 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 frame. To 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. Further, 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 90 [deg] or less (defined as an inclination angle in the longitudinal direction of the carcass cord 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, 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 cover 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 cover cords with coated rubber, and a plurality of the strip materials are provided in the tire circumferential direction with respect to the outer peripheral surfaces of the cross belts 141 and 142. It can be constructed 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 a tread portion 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 is a plan view showing the tread surface of the pneumatic tire shown in FIG. The figure shows the tread pattern of all-season tires. In the figure, 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 pneumatic tire 10 includes a plurality of circumferential main grooves 21 to 23 and circumferential fine grooves 24 extending in the tire circumferential direction, and a plurality of the pneumatic tires 10 partitioned by the circumferential grooves 21 to 24. The land portion 31 to 35 of the above is provided on the tread surface.

The main groove is a groove that is obliged to display a wear indicator specified in JATTA, and generally has a groove width of 3.0 [mm] or more and a groove depth of 6.0 [mm] or more. Further, the lug groove described later is a lateral groove extending in the tire width direction, and opens when the tire touches the ground to function as a groove. Further, the sipe described later is a notch formed in the tread tread surface, and is distinguished from a lug groove in that it closes when the tire touches the ground.

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 in which the groove length direction is 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 a "standard rim" specified by JATMA, a "Design Rim" specified by TRA, or a "Measuring Rim" specified by 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.

For example, in the configuration of FIG. 2, the pneumatic tire 10 has a left-right asymmetric tread pattern centered on the tire equatorial plane CL. Further, the vehicle width direction inner region having the tire equatorial plane CL as a boundary has two circumferential main grooves 21 and 22, and the vehicle width direction outer region is one circumferential main groove 23 and one circumferential direction. It is provided with a narrow groove 24. Further, these circumferential grooves 21, 22; 23, 24 are arranged symmetrically with respect to the tire equatorial plane CL. In addition, five rows of land portions 31 to 35 are partitioned by these circumferential grooves 21 to 24. Further, one land portion 33 is arranged on the tire equatorial plane CL.

Further, the land portions 31 and 35 on the outer side in the tire width direction defined in the main groove 21 in the outermost peripheral direction in the inner region in the vehicle width direction or the circumferential groove 24 in the outer region in the vehicle width direction are defined as shoulder land portions. The shoulder land portions 31 and 35 are the outermost land portions in the tire width direction and are located on the tire ground contact end T. Further, the land portions 32 and 34 on the inner side in the tire width direction divided into the outermost peripheral direction main groove 21 or the circumferential direction narrow groove 24 are defined as the second land portions. Therefore, the second land portions 32 and 34 are adjacent to the shoulder land portions 31 and 35 with the main grooves 21 and 24 in the outermost peripheral direction interposed therebetween. Further, the land portion 33 located on the CL side of the tire equatorial plane with respect to the second land portions 32 and 34 is defined as the center land portion.

[Inner area in the vehicle width direction]
FIG. 3 is an enlarged view showing a second land portion and a shoulder land portion in the vehicle width direction inner region described in FIG.

In the configuration of FIG. 2, the vehicle width direction inner region with the tire equatorial plane CL as a boundary is divided into two circumferential main grooves 21 and 22 and the shoulder land portion 31 divided into these circumferential main grooves 21 and 22. , A second land portion 32 and a center land portion 33 are provided.

Further, the two circumferential main grooves 21 and 22 have a straight shape having a constant groove width. Further, the distance Dm from the tire equatorial plane CL to the groove center line of the main groove 21 in the outermost peripheral direction is in the range of 8 [%] or more and 12 [%] or less with respect to the tire contact width TW. Further, the distance Dn from the tire equatorial plane CL to the groove center line of the other circumferential main groove 22 is in the range of 26 [%] or more and 32 [%] or less with respect to the tire contact width TW.

The groove center line of the circumferential main groove is defined as a straight line passing through the midpoints of the left and right measurement points of the groove width of the circumferential main groove and parallel to the tire circumferential direction.

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 groove widths of the circumferential main grooves 21 and 22 are in the range of 5.0 [mm] or more and 25.0 [mm] or less, and the groove depth is 5.0 [mm] or more and 12.0 [mm] or less. It is in the range of (dimension symbols omitted in the figure).

[Inner shoulder land]
As shown in FIG. 3, the shoulder land portion 31 includes a lug groove 311 and a narrow groove 312. The lug groove 311 and the narrow groove 312 terminate in the shoulder land portion 31 at one end without penetrating the shoulder land portion 31, extend in the tire width direction, and intersect the tire ground contact end T. Therefore, the edge portion of the shoulder land portion 31 on the outermost peripheral direction main groove 21 side has a plain structure having no groove and sipe opening, and extends continuously in the tire circumferential direction. As a result, the noise performance of the tire is improved.

Further, the distance D11 between the lug groove 311 and the narrow groove 312 and the edge portion of the shoulder land portion 31 has a relationship of 0.10 ≦ D11 / Wb1 ≦ 0.40 with respect to the ground contact width Wb1 of the shoulder land portion 31. Is preferable, and it is more preferable to have a relationship of 0.15 ≦ D11 / Wb1 ≦ 0.25.

The ground contact width is the contact 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 on the surface.

Further, it is preferable that the contact width Wb1 of the shoulder land portion 31 has a relationship of 0 ≦ Wb1 / TW ≦ 0.30 with respect to the tire contact width TW.

Further, in the configuration of FIG. 3, the lug groove 311 and the narrow groove 312 have a gentle arc shape curved in the tire circumferential direction. However, the present invention is not limited to this, and the lug groove 311 and the narrow groove 312 may have a linear shape and may extend substantially parallel to the tire width direction (not shown). Further, a plurality of lug grooves 311 and narrow grooves 312 are alternately arranged in the tire circumferential direction at a predetermined pitch. However, the present invention is not limited to this, and a plurality of narrow grooves 312 may be arranged between adjacent lug grooves 311 and 311 (not shown).

[Inner second land area]
4 and 5 are an enlarged plan view (FIG. 4) and a cross-sectional view (FIG. 5) showing the second land portion described in FIG.

As shown in FIG. 3, the second land portion 32 includes a chamfered portion 321 and a lug groove 322 and a narrow groove 323 (first and second lateral grooves) having different groove widths.

The chamfered portion 321 is formed on the edge portion of the second land portion 32 on the tire ground contact end T side (that is, the outermost peripheral direction main groove 21 side), and is formed on the tread surface of the second land portion 32 and the groove wall surface of the outermost outer peripheral direction main groove 21. And are connected by a plane or a curved surface. Further, the chamfered portion 321 has a shape in which the chamfered width Wc (see FIG. 4) is widened in the tire circumferential direction on the tread surface of the second land portion 32. Further, a plurality of chamfered portions 321 are arranged at predetermined intervals in the tire circumferential direction. By increasing the groove volume of the main groove 21 in the outermost peripheral direction by these chamfered portions 321, the wet performance of the tire is enhanced.

Further, the maximum width Wc of the chamfered portion 321 preferably has a relationship of 0.05 ≦ Wc / Wb2 ≦ 0.30 with respect to the maximum width Wb2 of the second land portion 32, and 0.15 ≦ Wc / Wb2 ≦. It is more preferable to have a relationship of 0.25.

The width of the chamfered portion is measured as the distance in the tire width direction from the edge portion of the land portion to the ridgeline of the chamfered portion on the tread surface of the land portion. Further, the edge portion of the land portion is defined as the intersection of the extension line of the groove wall of the circumferential main groove and the tread surface of the land portion. The ridgeline of the chamfered portion is defined as the boundary line between the wall surface of the chamfered portion and the tread of the land portion.

Further, it is preferable that the ground contact width Wb2 of the second land portion 34 has a relationship of 0.70 ≦ Wb2 / Wb1 ≦ 1.20 with respect to the ground contact width Wb1 of the shoulder land portion 35, and 0.90 ≦ Wb2 / Wb1 ≦. It is more preferable to have a relationship of 1.00. As a result, the ground contact widths Wb1 and Wb2 of the left and right land portions 31 and 32 partitioned by the circumferential main grooves 21 and 22 are optimized.

Further, in FIG. 4, the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321 is 0, with respect to the pitch length Pc (see FIG. 3) of the chamfered portion 321. It is preferable to have a relationship of 60 ≦ Lc / Pc ≦ 1.00, and more preferably to have a relationship of 0.80 ≦ Lc / Pc ≦ 0.95. As a result, the widening region of the chamfer width Wc is properly secured. The chamfered portions 321 and 321 adjacent to each other in the tire circumferential direction may be connected to each other or may be separated from each other on the premise that the above-mentioned ratio Lc / Pc condition is satisfied.

Further, in FIG. 5, the maximum depth Hc of the chamfered portion 321 preferably has a relationship of 0.20 ≦ Hc / Hg1 ≦ 0.70 with respect to the maximum depth Hg1 of the circumferential main groove 21. It is more preferable to have a relationship of .30 ≦ Hc / Hg 1 ≦ 0.50.

For example, in the configurations of FIGS. 4 and 5, the chamfered portion 321 has a triangular pyramid shape with the minimum width position 3212 as the apex. Further, as shown in FIG. 4, the chamfered portion 321 connects the long portion (the portion composed of the reference numerals 3213 and 3214) and the short portion (the reference numerals are omitted in the drawing) on the tread surface of the second land portion 32. The chamfered width of the chamfered portion 321 gradually increases in one direction in the tire circumferential direction at the elongated portion thereof. Further, as shown in FIG. 5, the chamfered portion 321 is C chamfered, and the tread surface of the second land portion 32 and the groove wall surface of the main groove 21 in the outermost peripheral direction are connected by a plane. However, the present invention is not limited to this, and the chamfered portion 321 is R chamfered, and the tread surface of the second land portion 32 and the groove wall surface of the main groove 21 in the outermost peripheral direction may be connected by a curved surface. Further, adjacent chamfered portions 321 and 321 are arranged in a row without leaving a gap. As a result, the ridgeline of the chamfered portion 321 has a zigzag shape extending in the tire circumferential direction along the edge portion of the second land portion 32.

The lug groove 322 is a first lateral groove arranged corresponding to the chamfered portion 321 and, as shown in FIG. 3, is terminated in the second land portion 32 at one end and at the other end. The chamfered portion 231 is opened in the central portion in the longitudinal direction and communicates with the main groove 21 in the outermost peripheral direction.

Further, in FIG. 4, it is preferable that the extending length D22 of the lug groove 322 in the tire width direction has a relationship of 0.20 ≦ D22 / Wb2 ≦ 0.80 with respect to the maximum width Wb2 of the second land portion 32. , 0.40 ≦ D22 / Wb2 ≦ 0.60, more preferably. Therefore, it is preferable that the lug groove 322 is terminated at a substantially central portion of the second land portion 32.

The extending length of the lug groove is measured as the distance in the tire width direction from the edge portion on the main groove side in the circumferential direction of the land portion to the end portion of the lug groove.

Further, the maximum groove width W22 of the lug groove 322 is 0.03 ≦ W22 / Lc ≦ 0.10 with respect to the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321. It is preferable to have the relationship of 0.04 ≦ W22 / Lc ≦ 0.07. Further, it is preferable that the maximum groove width W22 of the lug groove 322 is in the range of 2.5 [mm] ≦ W22 ≦ 6.5 [mm].

The maximum groove width of the lug groove is measured as the maximum width of the lug groove on the land tread. When the lug groove is a chamfered sipe as described later, the maximum groove width is measured as the maximum width including the chamfered portion.

Further, the inclination angle θ22 of the lug groove 322 with respect to the tire circumferential direction is preferably in the range of 30 [deg] ≤ θ22 ≤ 85 [deg], and is preferably in the range of 50 [deg] ≤ θ22 ≤ 70 [deg]. Is preferable.

The inclination angle of the lug groove is measured as the angle formed by the virtual line connecting both ends of the lug groove and the tire circumferential direction.

Further, the distance L22 in the tire circumferential direction from the maximum width position 3211 of the chamfered portion 321 to the opening position of the lug groove 322 with respect to the chamfered portion 321 is the tire from the maximum width position 3211 of the chamfered portion 321 to the minimum width position 3212. It is preferable to have a relationship of 0.35 ≦ L22 / Lc ≦ 0.65 with respect to the maximum length Lc in the circumferential direction, and more preferably to have a relationship of 0.40 ≦ L22 / Lc ≦ 0.60. Therefore, the lug groove 322 opens at the center of the chamfered portion 321 in the longitudinal direction.

Further, in FIG. 5, the maximum groove depth H22 of the lug groove 322 preferably has a relationship of 0.40 ≦ H22 / Hg1 ≦ 0.85 with respect to the maximum depth Hg1 of the circumferential main groove 21. It is more preferable to have a relationship of .50 ≦ H22 / Hg1 ≦ 0.75. Further, as shown in FIG. 5, the maximum groove depth H22 of the lug groove 322 is set to be larger than the maximum depth Hc of the chamfered portion 321.

For example, in the configurations of FIGS. 4 and 5, the lug groove 322 has a short straight line shape or a gentle arc shape, and is open to the central portion of the long portion 3213 of the chamfered portion 321. Further, the number of arrangements of the lug grooves 322 is the same as the number of arrangements of the chamfered portion 321, and a single lug groove 322 is opened in one chamfered portion 321. As a result, the long portion 3213 of the chamfered portion 321 is divided in the tire circumferential direction by the lug groove 322. Further, the inclination angle φ1 of the lug groove 322 with respect to the ridgeline of the long portion 3213 of the chamfered portion 321 is in the range of 35 [deg] ≦ φ1 ≦ 80 [deg].

The narrow groove 323 is a second lateral groove arranged corresponding to the chamfered portion 321. At one end, the narrow groove 323 opens at the edge of the second land portion 32 on the CL side of the tire equatorial plane, and the other end. Terminates near the maximum width position 3211 of the chamfered portion 321 at. Further, the narrow groove 323 may be connected to the maximum width position 3211 of the chamfered portion 321 at the other end portion, as will be described later.

Further, in FIG. 4, the maximum groove width W23 of the narrow groove 323 preferably has a relationship of 0 <W23 / W22 ≦ 0.80 with respect to the maximum groove width W22 of the lug groove 322, and 0 <W23 / W22 ≦. It is more preferable to have a relationship of 0.50. Therefore, the groove width of the narrow groove 323 is set sufficiently narrower than the groove width of the lug groove 322.

Further, the maximum groove width W23 of the narrow groove 323 is preferably in the range of 0.4 [mm] ≤ W23 ≤ 1.5 [mm], and 0.5 [mm] ≤ W23 ≤ 1.0 [mm]. It is more preferable that it is in the range of. Further, it is preferable that the narrow groove 323 is a sipe that closes when the tire touches the ground.

Further, the inclination angle θ23 of the narrow groove 323 with respect to the tire circumferential direction is preferably in the range of 30 [deg] ≤ θ23 ≤ 85 [deg], and is preferably in the range of 50 [deg] ≤ θ23 ≤ 70 [deg]. Is more preferable.

Further, the maximum groove depth H23 of the narrow groove 323 preferably has a relationship of 0.20 ≦ H23 / Hg1 ≦ 0.70 with respect to the maximum depth Hg1 of the circumferential main groove 21, and 0.40 ≦ H23. It is more preferable to have a relationship of / Hg1 ≦ 0.60. Further, the maximum groove depth H23 of the narrow groove 323 is set smaller than the maximum groove depth H22 of the lug groove 322.

For example, in the configurations of FIGS. 4 and 5, the narrow groove 323 has a short straight line shape or a gentle arc shape. Further, the number of fine grooves 323 arranged is the same as the number of arrangements of the chamfered portion 321, and a single fine groove 323 is arranged so as to face one chamfered portion 321. Further, the inclination angle φ2 of the narrow groove 323 with respect to the ridgeline of the long portion 3213 of the chamfered portion 321 is in the range of 35 [deg] ≦ φ2 ≦ 80 [deg].

Further, as shown in FIG. 4, the chamfered portion 321 is terminated in the vicinity of the maximum width position 3211. Further, the distance Gs between the end portion of the narrow groove 323 and the maximum width position 3211 of the chamfer portion 321 is in the range of Gs ≤ 1.5 [mm]. In such a configuration, during tire vulcanization molding, a minute gap can be formed between the molding blade of the fine groove 323 and the molding blade of the chamfering portion 321 in the tire molding die (not shown), so that the tire is vulcanized by an air pool. It is preferable because it can reduce vulcanization failure. The lower limit of the distance Gs is not particularly limited, but if it is 0.3 [mm] or more, the air flow path is secured and the above-mentioned vulcanization failure reduction effect is ensured.

Further, as shown in FIG. 4, only the narrow narrow groove 323 is opened at the edge portion of the second land portion 32 on the CL side of the tire equatorial plane, and other wide lateral grooves are not opened. As a result, the rigidity of the edge portion of the second land portion 32 on the CL side of the tire equatorial plane is ensured, and the dry performance of the tire is enhanced.

[Modification example]
FIG. 6 is an explanatory view showing a modified example of the lug groove in the second land portion shown in FIG. The figure shows a cross-sectional view of the lug groove 322 in the groove depth direction.

In the configuration of FIG. 4, the lug groove 322 has a U-shaped cross-sectional shape (not shown) and has a substantially constant groove width from the initial stage to the middle stage of wear. However, the present invention is not limited to this, and the lug groove 322 may be a chamfered sipe as shown in FIG. That is, the lug groove 322 may be composed of a narrow sipe portion 3221 that closes when the tire touches the ground, and a chamfered portion 3212 that is formed in the opening of the sipe portion 3221 to widen the groove width W22.

FIG. 7 is an explanatory view showing a modified example of the narrow groove in the second land portion described in FIG. The figure shows the positional relationship between the other end of the narrow groove 323 and the maximum width position 3211 of the chamfered portion 321.

In the configuration of FIG. 4, as described above, the narrow groove 323 is terminated inside the second land portion 32 without being connected to the chamfered portion 321. Further, a gap (distance Gs) between the end portion of the narrow groove 323 and the maximum width position 3211 of the chamfer portion 321 is appropriately secured. However, the present invention is not limited to this, and as shown in FIG. 7, the narrow groove 323 may be connected to the maximum width position 3211 of the chamfered portion 321. Further, if the connection point between the fine groove 323 and the chamfered portion 321 is within a distance of 2.5 [mm] from the maximum width position 3211 of the chamfered portion 321, the fine groove 323 is the chamfered portion 321. It can be said that it is connected to the maximum width position 3211.

[Additional matters]
As shown in FIG. 3, the chamfered portion 321 and the lug groove 322 of the second land portion 32 are arranged at substantially the same positions in the tire circumferential direction with respect to the lug groove 311 of the shoulder land portion 31. Specifically, the entire lug groove 311 of the shoulder land portion 31 in the tire contact patch is within the range of the circumferential length Lc (see FIG. 4) of the long portion 3213 of the chamfered portion 321 of the second land portion 32. It is in. As a result, the drainage property of the tire is improved.

Further, as shown in FIG. 3, the groove center line of the lug groove 322 of the second land portion 32 and the groove center line of the lug groove 311 of the shoulder land portion 31 are inclined in the same direction with each other, and also in the tire circumferential direction. They are placed offset from each other. Specifically, when defining the intersections P1 and P2 between the groove center lines of the lug grooves 311 and 322 and the groove center lines of the outermost peripheral direction main groove 21, the distances between these intersections P1 and P2 in the tire circumferential direction. The Dp is preferably in the range of 0 ≦ Dp / Pc ≦ 0.50 with respect to the pitch length Pc of the chamfered portion 321 of the second land portion 32, and is in the range of 0.10 ≦ Dp / Pc ≦ 0.40. More preferably. Further, the number of pitches of the lug groove 311 of the shoulder land portion 31 and the number of pitches of the lug groove 322 of the second land portion 32 are the same, and are in the range of 20 or more and 80 or less.

[effect]
As described above, the pneumatic tire 10 includes a plurality of circumferential main grooves 21 and 22 extending in the circumferential direction of the tire, and a land portion 32 formed by adjacent circumferential main grooves 21 and 22. Prepare (see FIG. 3). Further, the land portion 32 includes a chamfered portion 321 formed on the edge portion of the land portion 32 on the tire ground contact end side, and a lug groove 322 and a narrow groove 323 arranged corresponding to the chamfered portion 321. (See FIG. 4). Further, the chamfered portion 321 is formed at the edge portion of the land portion 32 on the tire ground contact end T side, and the chamfered width Wc is widened in the tire circumferential direction on the tread surface of the land portion 32. Further, the lug groove 322 is terminated in the land portion 32 at one end and opens at the center portion in the longitudinal direction of the chamfered portion 321 at the other end. Further, the narrow groove 323 opens at one end to the edge of the land portion 32 on the CL side of the tire equatorial plane, and terminates at the other end near the maximum width position 3211 of the chamfered portion 321 ( (See FIG. 4) or connect to the maximum width position 3211 (see FIG. 7).

In such a configuration, (1) the land portion 32 includes a chamfered portion 321 and a lug groove 322 formed on the edge portion on the tire ground contact end T side, so that the drainage property of the land portion 32 is improved and the tire is wet. Steering stability performance is improved. Further, since (2) the lug groove 322 does not penetrate the land portion 32, the rigidity of the land portion 32 is ensured, and the dry steering stability performance of the tire is ensured. Further, since (3) the lug groove 322 opens in the central portion in the longitudinal direction of the chamfered portion 321, the drainage property of the land portion 32 is improved, and the wet steering stability performance of the tire is improved.

Further, (4) the lateral groove that opens in the central portion of the chamfered portion 321 is a wide lug groove 322, and the lateral groove that ends or opens at the maximum width position 3211 of the chamfered portion 321 is a narrow narrow groove 323. , Has the following advantages. That is, as compared with (a) a configuration in which all the grooves arranged in the land portion 32 are wide lateral grooves (not shown), the rigidity of the land portion 32 is ensured and the dry performance of the tire is ensured. Further, as compared with (b) a configuration in which all the grooves arranged in the land portion 32 are narrow grooves or sipes (not shown), the drainage property of the land portion 32 is improved, and the tires are wet-controlled. Stability performance is improved. Further, as compared with (c) a configuration in which a wide lug groove opens at the maximum width position of the chamfered portion and a narrow narrow groove or sipe ends or opens at the central portion of the chamfered portion (not shown). Since the rigidity of the land portion 32 at the maximum width position 3211 of the chamfered portion 321 can be secured while ensuring the drainage action from the lug groove 322 to the chamfered portion 321, both the dry steering stability performance and the wet steering stability performance of the tire are compatible. There are advantages that can be done.

Further, in the pneumatic tire 10, the maximum width Wc of the chamfered portion 321 has a relationship of 0.05 ≦ Wc / Wb2 ≦ 0.30 with respect to the maximum width Wb2 of the land portion 32 (see FIG. 4). The lower limit ensures the drainage property improving effect of the chamfered portion 321, and the upper limit has the advantage of ensuring the rigidity of the land portion 32.

Further, in the pneumatic tire 10, the maximum length Lc (see FIG. 4) in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321 is the pitch length Pc of the chamfered portion 321 (FIG. 4). 3) has a relationship of 0.60 ≦ Lc / Pc ≦ 1.00. The above lower limit ensures the effect of improving the drainage property of the chamfered portion 321, and the above upper limit has an advantage that the planar shape of the chamfered portion 321 is optimized.

Further, in the pneumatic tire 10, the chamfered portion 321 has a triangular shape formed by connecting the long portion and the short portion on the tread surface of the land portion 32 (see FIG. 3). This has the advantage of improving the drainage action of the chamfered portion 321.

Further, in the pneumatic tire 10, the extending length D22 of the lug groove 322 in the tire width direction has a relationship of 0.20 ≦ D22 / Wb2 ≦ 0.80 with respect to the maximum width Wb2 of the land portion 32 ( (See FIG. 4). The lower limit ensures the drainage property improving effect of the lug groove 322, and the upper limit has the advantage of ensuring the rigidity of the land portion 32.

Further, in the pneumatic tire 10, the maximum groove width W22 of the lug groove 322 is 0.03 ≦ with respect to the maximum length Lc in the tire circumferential direction from the maximum width position 3211 to the minimum width position 3212 of the chamfered portion 321. It has a relationship of W22 / Lc ≦ 0.10. (See FIG. 4). The lower limit ensures the drainage property improving effect of the lug groove 322, and the upper limit has the advantage of ensuring the rigidity of the land portion 32.

Further, in the pneumatic tire 10, the inclination angle θ22 of the lug groove 322 with respect to the tire circumferential direction is in the range of 30 [deg] ≤ θ22 ≤ 85 [deg] (see FIG. 4). This has the advantage that the inclination angle θ22 of the lug groove 322 is optimized.

Further, in the pneumatic tire 10, the distance L22 in the tire circumferential direction from the maximum width position 3211 of the chamfered portion 321 to the opening position of the lug groove 322 with respect to the chamfered portion 321 is from the maximum width position 3211 of the chamfered portion 321. It has a relationship of 0.35 ≦ L22 / Lc ≦ 0.65 with respect to the maximum length Lc in the tire circumferential direction up to the minimum width position 3212 (see FIG. 4). In such a configuration, since the lug groove 322 opens in the central portion in the longitudinal direction of the chamfered portion 321, there is an advantage that the drainage action by the combination of the lug groove 322 and the chamfered portion 321 is further improved.

Further, in the pneumatic tire 10, the inclination angle θ23 of the narrow groove 323 with respect to the tire circumferential direction is in the range of 30 [deg] ≤ θ23 ≤ 85 [deg] (see FIG. 4). This has the advantage that the inclination angle θ23 of the narrow groove 323 is optimized.

Further, in the pneumatic tire 10, the maximum groove width W23 of the narrow groove 323 has a relationship of 0 <W23 / W22 ≦ 0.80 with respect to the maximum groove width W22 of the lug groove 322. In such a configuration, the groove width ratio of the lug groove 322 and the narrow groove 323 is optimized, so that the balance between the drainage improving action of the lug groove 322 and the reinforcing action of the land rigidity by the fine groove 323 is optimized. There are advantages.

Further, in the pneumatic tire 10, the maximum groove width W22 of the lug groove 322 is in the range of 2.5 [mm] ≤ W22 ≤ 6.5 [mm] (see FIG. 4). The lower limit ensures the drainage property improving effect of the lug groove 322, and the upper limit has the advantage of ensuring the rigidity of the land portion 32.

Further, in the pneumatic tire 10, the maximum groove width W23 of the narrow groove 323 is in the range of 0.4 [mm] ≤ W23 ≤ 1.5 [mm] (see FIG. 4). The lower limit ensures the drainage property improving effect of the narrow groove 323, and the upper limit has the advantage of ensuring the rigidity of the land portion 32.

Further, in the pneumatic tire 10, the distance Gs (see FIGS. 4 and 7) between the other end of the narrow groove 323 and the maximum width position 3211 of the chamfered portion 321 is Gs ≤ 1.0 [mm]. It is in the range. As a result, the extending length of the narrow groove 323 is secured, and the effect of improving the drainage property of the fine groove 323 is ensured.

Further, in the pneumatic tire 10, the other end portion of the narrow groove 323 is arranged apart from the maximum width position 3211 of the chamfered portion 321 (see FIG. 4). In such a configuration, during tire vulcanization molding, a minute gap can be formed between the molding blade of the fine groove 323 and the molding blade of the chamfering portion 321 in the tire molding die (not shown), so that the tire is vulcanized by an air pool. It has the advantage of reducing vulcanization failure.

Further, in the pneumatic tire 10, only the narrow groove 323 is opened at the edge portion of the land portion 32 on the CL side of the tire equatorial plane, and other wide lateral grooves (for example, the lug groove 322) are not opened (FIG. 4). reference). As a result, the rigidity of the edge portion of the land portion 32 on the CL side of the tire equatorial plane is ensured, and there is an advantage that the dry performance of the tire is enhanced.

FIG. 8 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention.

In this performance test, (1) dry steering stability performance and (2) wet steering stability performance were evaluated for a plurality of types of test tires. Further, a test tire having a tire size of 245 / 40R18 97Y is assembled to a rim having a rim size of 18 × 8.5J, and a specified internal pressure and a specified load of JATTA are applied to this test tire. Further, the test tires are mounted on all the wheels of the passenger car which is the test vehicle.

(1) In the evaluation of dry steering stability performance, the test vehicle travels on a dry road surface test course having a flat circuit at 60 [km / h] to 100 [km / h]. Then, the test driver performs a sensory evaluation on the steerability at the time of change and cornering and the stability at the time of going straight. This evaluation is performed by an index evaluation based on Conventional Example 2 (100), and the larger the value, the more preferable. If the evaluation is 98 or more, it can be said that the dry performance is maintained.

(2) In the evaluation of wet steering stability performance, the test vehicle runs on a predetermined test course under rainy weather conditions, and the lap time is measured. Then, the index evaluation is performed based on the measurement result. This evaluation is performed by an index evaluation based on Conventional Example 2 (100), and the larger the value, the more preferable.

The test tires of Examples 1 to 14 have the configurations shown in FIGS. 1 to 3, and the two circumferential main grooves 21 and 22 and the shoulder land portion 31 and the second land portion 32 are defined by the tire equatorial plane CL. Prepare for the inner area in the vehicle width direction. Further, the second land portion 32 includes a chamfered portion 321 and first and second lateral grooves (wide non-penetrating lug groove 322 and narrow narrow groove 323) arranged corresponding to the chamfered portion 321. .. Further, in FIG. 2, the tread width TW is 200 [mm], the distance Dm of the circumferential main groove 21 on the tire contact end T side is 60.0 [mm], and the circumferential main on the tire equatorial plane CL side. The distance Dn of the groove 22 is 25.0 [mm]. Further, the groove widths of the main grooves 21 and 22 in the circumferential direction are 15.0 [mm], the width Wb1 of the shoulder land portion 31 is 36.0 [mm], and the width Wb2 of the second land portion 32 is 27.0. It is [mm]. Further, the pitch length Pc of the chamfered portion 321 is 73 [mm], and the number of pitches is 30. Further, the distance Ga between the chamfered portion 321 and the end portion of the narrow groove 323 is 0 [mm] (see FIG. 7).

The test tires of Conventional Examples 1 and 2 and Comparative Examples have different configurations of the inner region in the vehicle width direction as compared with the test tires of Example 1. Specifically, the conventional example 1 does not include the first lateral groove (lug groove 322) that opens in the central portion of the chamfered portion 321 in the test tire of the first embodiment, and the maximum width position of the chamfered portion 321 is not provided. A wide through lug groove is provided in place of the second lateral groove (narrow narrow groove 323) that opens in 3211. In the conventional example 2, the test tire of the first embodiment does not have a first lateral groove (lug groove 322) that opens in the central portion of the chamfered portion 321 but opens at the maximum width position 3211 of the chamfered portion 321. It is provided with only a second lateral groove (narrow groove 323).

As shown by the test results, it can be seen that the dry steering stability performance and the wet steering stability performance of the tires are improved in the test tires of Examples 1 to 14.

10 Pneumatic tires; 11 bead cores; 12 bead fillers; 13 carcass layers; 14 belt layers; 141, 142 cross belts; 143 belt covers; 15 tread rubber; 16 sidewall rubber; 17 rim cushion rubber; 21-23 circumferential main Groove; 24 Circumferential tread; 31 Inner region shoulder tread; 311 Rug groove; 312 Tread; 32 Inner region second land; 321 Tread; 3211 Maximum width position; 3212 Minimum width position; 3213 Long Part; 322 lug groove; 3221 sipe part; 3222 chamfered part; 323 narrow groove

Claims (16)

A pneumatic tire including a plurality of circumferential main grooves extending in the circumferential direction of the tire and a land portion defined by the adjacent circumferential main grooves.
The land portion includes a chamfered portion formed on the edge portion on the tire ground contact end side of the land portion, and a lug groove and a narrow groove arranged corresponding to the chamfered portion.
The chamfered portion widens the chamfered width in the tire circumferential direction on the tread surface of the land portion.
The lug groove terminates in the land at one end and opens at the center of the chamfer in the longitudinal direction at the other end.
The narrow groove opens at one end to the edge of the land on the equatorial side of the tire, and at the other end, a slight gap is provided between the chamfer and the maximum width position of the chamfer. While terminating near the maximum width position of the chamfered portion,
A pneumatic tire, wherein the distance Gs between the other end of the narrow groove and the maximum width position of the chamfered portion is in the range of Gs ≤ 1.5 [mm]. The pneumatic tire according to claim 1, wherein the maximum width Wc of the chamfered portion has a relationship of 0.05 ≦ Wc / Wb2 ≦ 0.30 with respect to the maximum width Wb2 of the land portion. The maximum length Lc in the tire circumferential direction from the maximum width position to the minimum width position of the chamfered portion has a relationship of 0.60 ≦ Lc / Pc ≦ 1.00 with respect to the pitch length Pc of the chamfered portion. The pneumatic tire according to claim 1 or 2. The pneumatic tire according to any one of claims 1 to 3, wherein the chamfered portion has a triangular shape formed by connecting a long portion and a short portion on a tread surface of the land portion. The pneumatic tire according to claim 1, wherein the extending length D22 of the lug groove in the tire width direction has a relationship of 0.20 ≦ D22 / Wb2 ≦ 0.80 with respect to the maximum width Wb2 of the land portion. The maximum groove width W22 of the lug groove has a relationship of 0.03 ≦ W22 / Lc ≦ 0.10. With respect to the maximum length Lc in the tire circumferential direction from the maximum width position to the minimum width position of the chamfered portion. The pneumatic tire according to any one of claims 1 to 5. The pneumatic tire according to any one of claims 1 to 6, wherein the inclination angle θ22 of the lug groove with respect to the tire circumferential direction is in the range of 30 [deg] ≤ θ22 ≤ 85 [deg]. The distance L22 in the tire circumferential direction from the maximum width position of the chamfered portion to the opening position of the lug groove with respect to the chamfered portion is the maximum length in the tire circumferential direction from the maximum width position to the minimum width position of the chamfered portion. The pneumatic tire according to any one of claims 1 to 7, which has a relationship of 0.35 ≦ L22 / Lc ≦ 0.65 with respect to Lc. The pneumatic tire according to any one of claims 1 to 8, wherein the inclination angle θ23 of the narrow groove with respect to the tire circumferential direction is in the range of 30 [deg] ≤ θ23 ≤ 85 [deg]. The pneumatic tire according to any one of claims 1 to 9, wherein the maximum groove width W23 of the narrow groove has a relationship of 0 <W23 / W22 ≦ 0.80 with respect to the maximum groove width W22 of the lug groove. .. The pneumatic tire according to any one of claims 1 to 10, wherein the maximum groove width W22 of the lug groove is in the range of 2.5 [mm] ≤ W22 ≤ 6.5 [mm]. The pneumatic tire according to any one of claims 1 to 11, wherein the maximum groove width W23 of the narrow groove is in the range of 0.4 [mm] ≤ W23 ≤ 1.5 [mm]. The air according to any one of claims 1 to 12, wherein the distance Gs between the other end of the narrow groove and the maximum width position of the chamfered portion is in the range of Gs ≦ 1.0 [mm]. Chamfered tire. The pneumatic tire according to claim 13, wherein the other end of the narrow groove is arranged apart from the maximum width position of the chamfered portion. The pneumatic tire according to any one of claims 1 to 14, wherein only the narrow groove is opened and the other wide lateral groove is not opened at the edge portion on the equatorial side of the tire on the land portion. A pneumatic tire including a plurality of circumferential main grooves extending in the circumferential direction of the tire, and a shoulder land portion and a second land portion defined by the adjacent circumferential main grooves.
The second land portion includes a chamfered portion formed on the edge portion on the tire ground contact end side of the second land portion, and a lug groove and a narrow groove arranged corresponding to the chamfered portion.
The chamfered portion widens the chamfered width in the tire circumferential direction on the tread surface of the second land portion.
The lug groove terminates in the second land portion at one end and opens in the longitudinal central portion of the chamfered portion at the other end.
The narrow groove opens at one end to the edge of the second land portion on the equatorial side of the tire, and ends at the other end near the maximum width position of the chamfer, or the above. Connect to the maximum width position,
The second land portion does not have another groove that divides the second land portion between the narrow grooves adjacent to each other in the tire circumferential direction.
The ground contact width Wb2 of the second land portion has a relationship of 0.70 ≦ Wb2 / Wb1 ≦ 1.20 with respect to the ground contact width Wb1 of the shoulder land portion.
The shoulder land portion comprises a lug groove having a groove center line inclined in the same direction as the groove center line of the lug groove of the second land portion.
The groove centerline of the lug groove in the shoulder land portion, the groove centerline of the lug groove in the second land portion, and the groove centerline of the circumferential main groove that divides the shoulder land portion and the second land portion. Intersection points P1 and P2 are defined, respectively, and
Air characterized in that the distance Dp in the tire circumferential direction of the intersection points P1 and P2 is in the range of 0.10 ≦ Dp / Pc ≦ 0.40 with respect to the pitch length Pc of the chamfered portion of the second land portion. Chamfered tire.

Images