JP2021024523A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire capable of improving heat generation resistance performance while maintaining uneven wear resistance performance of the tire.SOLUTION: A pneumatic tire 1 includes a pair of circumferential main grooves 2 and 2 extending in a tire circumferential direction, a pair of shoulder land parts 31 and 31 divided by the circumferential main grooves 2 and 2, and a single center land part 32 (see Fig. 2). Ground contact widths Wb1 of the pair of shoulder land parts 31 and 31 each has a relationship of 0.27≤Wb1/TW≤0.40 with respect to a tire ground contact width TW.SELECTED DRAWING: Figure 2

Description

The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of improving heat generation resistance while maintaining uneven wear resistance of the tire.

For example, a tire for a construction vehicle mounted on a harbor straddle carrier has a problem that uneven wear is likely to occur due to its rolling because the height of the mounted vehicle is high. For this reason, conventional tires for construction vehicles have a pair of circumferential main grooves, a pair of shoulder land portions divided into these circumferential main grooves, and a single tire in order to improve the uneven wear resistance of the tire. A tread pattern with a center land area is used. As a conventional tire for a construction vehicle adopting such a configuration, the techniques described in Non-Patent Documents 1 and 2 are known.

Internet <URL: https://www.michelinearthmover.com/eng_ca/tyres-straddle-carriers/michelin-x-straddle/81222> Internet <URL: https://tire.bridgestone.co.jp/tb/truck_bus/catalog/industrial-truck/premises-dump_straddle-carrier/vchr/index.html>

On the other hand, with tires for construction vehicles in recent years, there is a demand to enable high-speed running of about 25 [km / h] on paved roads, so there is a problem that the heat generation resistance of tires should be improved during high-speed running. is there.

Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of improving heat generation resistance while maintaining uneven wear resistance of the tire.

In order to achieve the above object, the pneumatic tire according to the present invention includes a pair of circumferential main grooves extending in the tire circumferential direction, a pair of shoulder land portions partitioned by the circumferential main groove, and a single tire. A pneumatic tire including a center land portion, and each of the ground contact widths Wb1 of the pair of shoulder land portions has a relationship of 0.27 ≦ Wb1 / TW ≦ 0.40 with respect to the tire ground contact width TW. It is characterized by.

In the pneumatic tire according to the present invention, (1) by arranging a single center land portion, the rigidity of the tread portion is increased and the rolling of the vehicle is reduced. This has the advantage of suppressing uneven wear caused by rolling and improving the uneven wear resistance performance of the tire. Further, (2) there is an advantage that the ground contact width Wb1 of the pair of shoulder land portions is optimized. Specifically, by the above lower limit, the ground contact width Wb1 of the shoulder land portion is secured, and the effect of suppressing the rolling of the vehicle is properly secured. In addition, the above upper limit secures the placement area of the center land area.

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 center land portion of the pneumatic tire shown in FIG. FIG. 4 is a sectional view taken along line A of the land portion of the center shown in FIG. FIG. 5 is a sectional view taken along line B of the land portion of the center shown in FIG. FIG. 6 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. FIG. 7 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. FIG. 8 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. FIG. 9 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention. FIG. 10 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 tire for a construction vehicle called an OR tire (Off the Road Tire) as an example of a pneumatic tire.

In the figure, the cross section in the tire meridian direction is defined as the cross section when the tire is cut on a plane including the tire rotation axis (not shown). Further, the tire equatorial plane CL is defined as a plane that passes through the midpoint of the measurement point of the tire cross-sectional width defined by JATTA and is perpendicular to the tire rotation axis. Further, the tire width direction is defined as a direction parallel to the tire rotation axis, and the tire radial direction is defined as a direction perpendicular to the tire rotation axis.

The pneumatic tire 1 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 and 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 portions to form 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 skeleton. 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 formed by coating a plurality of carcass cords made of steel with coated rubber and rolling them, and has a cord angle (tire circumferential direction) of 80 [deg] or more and 110 [deg] or less in absolute value. Is defined as the longitudinal tilt angle of the carcass cord with respect to.). Further, the cord diameter of the carcass cord is in the range of 1.5 [mm] or more and 2.5 [mm] or less.

The belt layer 14 is formed by laminating a plurality of belt plies 141 to 145, and is arranged so as to be hung around the outer periphery of the carcass layer 13. In particular, in an OR tire, 4 to 8 belt plies (5 in FIG. 1) are laminated to form a belt layer 14. Further, the belt plies 141 to 145 are formed by coating a steel cord with a coated rubber and rolling it. Further, each belt ply 141 to 145 has a code angle (defined as an inclination angle in the longitudinal direction of the belt cord with respect to the tire circumferential direction) with respect to the adjacent belt plies, and the inclination direction of the belt cord. Are alternately inverted and laminated. As a result, a cross-ply structure is formed, and the structural strength of the belt layer 14 is increased. Further, the outer diameter of the belt cord is in the range of 1.5 [mm] or more and 2.5 [mm] or less.

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 extend from the inside in the tire radial direction to the outside in the tire width direction of the rewinding portions of the left and right bead cores 11 and 11 and the carcass layer 13 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, as an example, the tread surface of a radial tire for a port straddle carrier. 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. In FIG. 2, hatching is provided in the narrow groove portion having a groove depth deeper than that of the first center fine groove 321 described later.

As shown in FIG. 2, the pneumatic tire 1 has a pair of circumferential main grooves 2 and 2 extending in the tire circumferential direction, and a pair of shoulder land portions divided into these circumferential main grooves 2 and 2. A tread surface is provided with 31, 31 and a single center land 32.

The main groove is a groove that is obliged to display a wear indicator specified in JATTA, and has a groove width of 20 [mm] or more and a groove depth of 40 [mm] or more.

The groove width is measured as the distance between the opposing 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 the configuration in which the notch or chamfer is provided in the groove opening, the groove width is measured at the intersection of the extension line of the tread tread and the extension line of the groove wall in the cross-sectional view parallel to the groove width direction and the groove depth direction. Is measured.

The groove depth is measured as 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 the configuration having a partial bottom upper portion, sipe or uneven portion in the groove bottom, these are excluded and the groove depth is measured.

The specified rim means the "standard rim" specified in JATMA, 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 passenger car tires, the specified internal pressure is an air pressure of 180 [kPa], and the specified load is 88 [%] of the maximum load capacity at the specified internal pressure.

For example, in the configuration of FIG. 2, the pneumatic tire 1 has a point-symmetrical tread pattern having a center point on the tire equatorial plane CL. Further, the left and right regions with the tire equatorial plane CL as a boundary have a single circumferential main groove 2 and 2, respectively. Further, these circumferential main grooves 2 and 2 have a straight shape and are arranged symmetrically with respect to the tire equatorial plane CL. Further, a pair of shoulder land portions 31, 31 and a single center land portion 32 are partitioned by these circumferential main grooves 2, 2. Further, the center land portion 32 is arranged on the tire equatorial plane CL.

Further, it is preferable that the groove width Wg of the circumferential main groove 2 is in the range of 0.05 ≦ Wg / TW ≦ 0.10. With respect to 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.

Further, in FIG. 2, the maximum contact width Wb1 of the shoulder land portion 31 is in the range of 0.27 ≦ Wb1 / TW ≦ 0.40 with respect to the tire contact width TW, and 0.30 ≦ Wb1 / TW ≦ 0. More preferably, it is in the range of 38. Further, the maximum contact width Wb2 of the center land portion 32 is preferably in the range of 0.10 ≦ Wb2 / TW ≦ 0.40 with respect to the tire contact width TW, and 0.15 ≦ Wb2 / TW ≦ 0.30. It is more preferable that it is in the range of.

The ground contact widths Wb1 and Wb2 of the land portion are the same as the land portion when the tire is mounted on the specified rim to apply the specified internal pressure and the tire is placed perpendicularly to the flat plate in a stationary state to apply a load corresponding to the specified load. It is measured as a linear distance in the tire axial direction on the contact surface with the flat plate.

In FIG. 1, the relationship between the shoulder drop amount Dt of the tread profile when the tire is mounted on the specified rim and the specified internal pressure is applied is 0.025 ≦ Dt / SH ≦ 0.070 with respect to the tire cross-sectional height SH. It is preferable to have, and it is more preferable to have a relationship of 0.035 ≦ Dt / SH ≦ 0.060.

The profile is a contour line in a cross-sectional view in the meridian direction of the tire, and is measured using a laser profiler in a no-load state in which the tire is mounted on a specified rim and filled with a specified internal pressure. As the laser profiler, for example, a tire profile measuring device (manufactured by Matsuo Corporation) is used.

The shoulder drop amount Dt is defined as the diameter difference in the tire radial direction of the tread profile at the tire equatorial plane CL and the tire ground contact end T.

The tire cross-sectional height SH is a distance of ½ of the difference between the tire outer diameter and the rim diameter, and is measured as a no-load state while the tire is mounted on the specified rim to apply the specified internal pressure.

Further, the shoulder drop amount Dt'of the tread profile when the tire is attached to the specified rim and an internal pressure of 0 [kPa] is applied is 0.030 ≤ Dt'/ SH'≤ with respect to the tire cross-sectional height SH'. It is preferable to have a relationship of 0.070, and more preferably to have a relationship of 0.040 ≦ Dt'/ SH' ≦ 0.065. The tread profile when an internal pressure of 0 [kPa] is applied corresponds to the shape of the tire molding die.

Further, in FIG. 1, the gauge Gtr1 of the tread rubber 15 on the tire equatorial plane CL is relative to the gauge Gtr2 of the tread rubber 15 at the end position of the outermost layer (second protective belt 144 in FIG. 1) of the belt layer 14. It is preferable to have a relationship of 0.90 ≦ Gtr1 / Gtr2 ≦ 1.35, and more preferably to have a relationship of 1.00 ≦ Gtr1 / Gtr2 ≦ 1.25. Further, the gauge Gtr1 of the tread rubber 15 on the tire equatorial plane CL is in the range of 65 [mm] ≦ Gtr1 ≦ 90 [mm].

The gauge of the tread rubber is measured as the length of a perpendicular line drawn from the tread profile to the belt cord surface of the outermost layer of the belt layer in a cross-sectional view in the tire meridian direction. The belt cord surface is defined as a surface connecting the outer ends of a plurality of belt cords constituting the belt ply in the tire radial direction.

[Center land area]
FIG. 3 is an enlarged view showing a center land portion of the pneumatic tire shown in FIG. 4 and 5 are an A sectional view (FIG. 4) and a B sectional view (FIG. 5) of the center land portion 32 described in FIG. These figures show cross-sectional views in the groove depth direction along the first center narrow groove 321 (FIG. 4) and the second center narrow groove 322 (FIG. 5), which will be described later.

As shown in FIG. 2, the center land portion 32 includes a plurality of first center narrow grooves 321 and a plurality of second center narrow grooves 322.

The first center narrow groove 321 penetrates the center land portion 32 in the tire width direction and opens to the left and right edge portions of the center land portion 32. Further, a plurality of first center narrow grooves 321 are arranged at predetermined intervals in the tire circumferential direction. In such a configuration, the heat generation resistance of the tire is improved by the cooling action of the first center narrow groove 321.

Further, in the configuration of FIG. 2, the first center narrow groove 321 has a linear shape. However, the present invention is not limited to this, and the first center narrow groove 321 may have a gently curved arc shape or an S-shape (not shown).

Further, in FIG. 3, the groove width W21 of the first center narrow groove 321 is preferably in the range of 2.5 [mm] ≦ W21 ≦ 7.5 [mm], and 4.0 [mm] ≦ W21 ≦. More preferably, it is in the range of 6.0 [mm]. Further, as shown in FIG. 3, it is preferable that the first center narrow groove 321 has a substantially constant groove width. Specifically, it is preferable that the ratio of the maximum value W21_max of the groove width W21 of the first center narrow groove 321 to the minimum value W21_min is in the range of 1.00 ≦ W21_max / W21_min ≦ 1.10.

Further, as shown in FIG. 3, the first center narrow groove 321 extends in the tire width direction while being inclined with respect to the tire circumferential direction. Further, the inclination angle θ21 of the first center narrow groove 321 is preferably in the range of 65 [deg] ≤ θ21 ≤ 88 [deg], and is preferably in the range of 75 [deg] ≤ θ21 ≤ 85 [deg]. More preferred.

The inclination angle θ21 of the first center narrow groove 321 is measured as an angle formed by a virtual straight line passing through the left and right openings of the first center narrow groove 321 and the tire circumferential direction.

Further, in FIG. 3, the pitch length P21 of the first center narrow groove 321 is preferably in the range of 0.75 ≦ P21 / Wb2 ≦ 1.00 with respect to the ground contact width Wb2 of the center land portion 32. More preferably, it is in the range of 85 ≦ P21 / Wb2 ≦ 0.90.

Further, in FIG. 4, the groove depth H21 of the first center narrow groove 321 is in the range of 0.025 ≦ H21 / Hg ≦ 0.150 with respect to the maximum groove depth Hg of the circumferential main groove 2. It is preferably in the range of 0.040 ≦ H21 / Hg ≦ 0.060. Further, it is preferable that the groove depth H21 of the first center narrow groove 321 is in the range of H21 ≦ 5.0 [mm]. Therefore, the groove depth H21 of the first center narrow groove 321 is set to be very shallow with respect to the maximum groove depth Hg of the circumferential main groove 2.

In the above configuration, the first center narrow grooves 321 having a very shallow groove depth H21 are arranged at predetermined intervals in the tire circumferential direction, so that the wear progress from the new tire in the center land portion 32 becomes uniform. Will be done. As a result, the uneven wear resistance performance of the tire is improved.

The second center narrow groove 322 has a bent shape having two or more bending points, extends in the tire width direction, and opens in the circumferential main groove 2 at at least one end. Further, a plurality of second center narrow grooves 322 are arranged at predetermined intervals in the tire circumferential direction.

In the configuration of FIG. 2, the second center groove 322 has a step shape having two bending points. In such a configuration, the rigidity of the center land portion 32 is ensured by engaging the groove walls of the second center narrow groove 322 when the tire touches the ground. However, the present invention is not limited to this, and the second center narrow groove 322 may have an S-shape having two inflection points (not shown).

Further, the periferi length L22 (not shown) of the second center narrow groove 322 in the center land portion 32 is in the range of 1.20 ≦ L22 / Wb2 ≦ 1.80 with respect to the ground contact width Wb2 of the center land portion 32. It is preferably in the range of 1.40 ≦ L22 / Wb2 ≦ 1.60. The periferi length is measured as the groove length along the second center groove 322.

Further, in the configuration of FIG. 2, the first center narrow groove 321 and the second center fine groove 322 are alternately arranged in the tire circumferential direction. However, the present invention is not limited to this, and a plurality of first center narrow grooves 321 may be arranged between adjacent second center fine grooves 322 (not shown).

Further, in the configuration of FIG. 2, the first and second center narrow grooves 321 and 322 penetrate the center land portion 32 in the tire width direction, so that the center land portion 32 is partitioned in the tire circumferential direction. Further, by arranging the first and second center narrow grooves 321 and 322 so as to be separated from each other, each region divided into the first and second center narrow grooves 321 and 322 is continuous in the tire width direction. It has a tired tread. In such a configuration, the rigidity of the center land portion 32 is increased, and the uneven wear resistance performance of the tire is improved. Further, since two types of first and second center narrow grooves 321 and 322 having different maximum depths H21 and H22 (FIGS. 4 and 5 described later) are arranged in the tire circumferential direction, shallow grooves ( Compared with the configuration in which only the deep groove (322) is arranged without providing 321), the heat generation resistance of the tire can be improved while maintaining the rigidity of the center land portion 32.

Further, in FIG. 3, the groove width W22 of the second center narrow groove 322 is preferably in the range of 2.5 [mm] ≦ W22 ≦ 7.5 [mm], and 4.0 [mm] ≦ W22 ≦. More preferably, it is in the range of 6.0 [mm]. Further, as shown in FIG. 3, it is preferable that the second center narrow groove 322 has a substantially constant groove width in the region excluding the bending point. Specifically, the ratio of the maximum value W22_max of the groove width W22 of the second center narrow groove 322 to the minimum value W22_min in the above region is preferably in the range of 1.00 ≦ W22_max / W22_min ≦ 1.10. Further, in the configuration of FIG. 3, the second center narrow groove 322 has a constant groove width over the entire area including the bending point, but the groove width of the second center narrow groove 322 is not limited to this and is at the bending point. The width may be widened (not shown). As a result, the generation of cracks starting from the bending point is suppressed.

Further, as shown in FIG. 3, the second center narrow groove 322 extends in the tire width direction while being inclined with respect to the tire circumferential direction. Further, the inclination direction of the first center narrow groove 321 with respect to the tire circumferential direction is opposite to the inclination direction of the second center fine groove 322. Further, a region of 30 [%] in the central portion of the center land portion 32 (a region of 35 [%] or more and 65 [%] or less from one measurement point of the extending length of the second center narrow groove 322 in the tire width direction. The inclination angle θ22 of the second center narrow groove 322 in) is preferably in the range of 20 [deg] ≤ θ22 ≤ 80 [deg], and 45 [deg] ≤ θ22 ≤ 65 [deg]. More preferably in the range.

Further, as shown in FIG. 3, the distance De in the tire circumferential direction between the opening of the first center narrow groove 321 and the opening of the second center narrow groove 322 with respect to the circumferential main groove 2 is the first center narrow groove 321. The pitch length P21 is preferably in the range of 0.30 ≦ De / P21 ≦ 0.70, and more preferably in the range of 0.35 ≦ De / P21 ≦ 0.65.

Further, as shown in FIG. 3, the second center narrow groove 322 opens substantially orthogonal to the circumferential main groove 2. Specifically, the inclination angle (not shown) of the groove center line with respect to the tire circumferential direction at the opening of the second center narrow groove 322 with respect to the circumferential main groove 2 is in the range of 70 [deg] or more and 110 [deg] or less. It is preferably in the range of 80 [deg] or more and 100 [deg] or less. As a result, a local decrease in block rigidity at the opening of the second center narrow groove 322 is suppressed.

Further, in FIG. 5, the groove depth H22 of the second center narrow groove 322 is in the range of 0.50 ≦ H22 / Hg ≦ 0.90 with respect to the maximum groove depth Hg of the circumferential main groove 2. It is preferably in the range of 0.70 ≦ H22 / Hg ≦ 0.85. Further, it is preferable that the groove depth H22 of the second center narrow groove 322 is in the range of 35 [mm] ≦ H22. Therefore, the groove depth H22 of the second center narrow groove 322 is set deeper than the groove depth H21 of the first center narrow groove 321 described above.

Further, as shown in FIGS. 3 and 5, the second center narrow groove 322 has bottom upper portions 3221 and 3221 at the openings for the circumferential main grooves 2 and 2, respectively. Further, the distance H22'(see FIG. 5) from the tread tread to the top surface of the bottom upper portion 3221 of the second center narrow groove 322 is 0.025 ≦ H22'with respect to the maximum groove depth Hg of the circumferential main groove 2. It is preferably in the range of / Hg ≦ 0.150, and more preferably in the range of 0.040 ≦ H22 ′ / Hg ≦ 0.060. Further, it is preferable that the distance H22'of the bottom upper portion 3221 is in the range of H22'≤ 5.0 [mm]. Therefore, the distance H22'of the bottom upper portion 3221 is set to be very shallow with respect to the maximum groove depth Hg of the circumferential main groove 2.

The distance H22'corresponds to the minimum groove depth of the second center narrow groove 322, and is measured as the minimum value of the distance from the tread tread to the top surface of the bottom upper portion 3221 of the second center narrow groove 322.

Further, in FIG. 3, the extension length L22'of the bottom upper portion 3221 of the second center narrow groove 322 in the tire width direction is 0.20 ≦ L22'/ Wb2 ≦ with respect to the ground contact width Wb2 of the center land portion 32. It is preferably in the range of 0.35.

The extending length L22'of the bottom upper portion 3221 is measured in a region where the distance H22'of the bottom upper portion 3221 satisfies the above ratio H22'/ Hg.

Further, in the configuration of FIG. 3, the second center narrow groove 322 has a step shape and is opened at both ends thereof at orthogonal to the left and right circumferential main grooves 2 and 2. The second center narrow groove 322 has a bottom upper portion 3221 at the left and right straight portions of the step shape, respectively. As a result, the opening of the second center narrow groove 322 with respect to the circumferential main groove 2 is reinforced by the bottom upper portion 3221, and the rigidity of the center land portion 32 is ensured.

[Shoulder land]
As shown in FIG. 2, the shoulder land portion 31 includes a plurality of first shoulder narrow grooves 311 and a plurality of second shoulder narrow grooves 312.

The first shoulder narrow groove 311 penetrates the shoulder land portion 31 in the tire width direction and opens to the edge portion of the shoulder land portion 31 on the circumferential direction main groove 2 side and the tire ground contact end T. Further, a plurality of first shoulder narrow grooves 311 are arranged at predetermined intervals in the tire circumferential direction. Further, in the configuration of FIG. 2, the first shoulder narrow groove 311 has a linear shape. However, the present invention is not limited to this, and the first shoulder narrow groove 311 may have a gently curved arc shape or an S-shape (not shown).

Further, the groove width W11 (dimension symbol omitted in the drawing) of the first shoulder narrow groove 311 is in the range of 2.5 [mm] ≤ W11 ≤ 7.5 [mm]. Further, the inclination angle θ11 (dimension symbol omitted in the drawing) of the first shoulder narrow groove 311 is in the range of 65 [deg] ≤ θ11 ≤ 90 [deg]. The groove depth H11 of the first shoulder narrow groove 311 (dimension symbol omitted in the drawing) is in the range of 0.025 ≦ H11 / Hg ≦ 0.150 with respect to the maximum groove depth Hg of the main groove 2 in the circumferential direction. .. Further, the groove width W11, the inclination angle θ11 and the groove depth H11 of the first shoulder narrow groove 311 are the same with respect to the groove width W21, the inclination angle θ21 and the groove depth H21 of the first center narrow groove 321. preferable.

Further, in the configuration of FIG. 2, the first shoulder narrow grooves 311 of the left and right shoulder land portions 31, 31 are arranged on the extension line of the first center narrow groove 321. Therefore, the first shoulder groove 311 and the first center groove 321 of all the land portions 31 and 32 are arranged on the same straight line, and a long shallow groove (311) that traverses the entire tire contact area. 321) is formed. As a result, the cooling action of the tread tread surface by the first shoulder narrow groove 311 and the first center narrow groove 321 is enhanced, and the heat generation resistance of the tire is improved.

As shown in FIG. 2, the second shoulder narrow groove 312 has a bent shape or a curved shape, penetrates the shoulder land portion 31 in the tire width direction, and is an edge of the shoulder land portion 31 on the circumferential direction main groove 2 side. It opens to the portion and the tire ground contact end T. Further, a plurality of second shoulder narrow grooves 312 are arranged at predetermined intervals in the tire circumferential direction. Further, in the configuration of FIG. 2, the second shoulder narrow groove 312 has a step shape having two bending points. However, the present invention is not limited to this, and the second shoulder narrow groove 312 may have an S-shape having two inflection points (not shown).

Further, the groove width W12 (dimension symbol omitted in the drawing) of the second shoulder narrow groove 312 is in the range of 2.5 [mm] ≤ W12 ≤ 7.5 [mm]. Further, the maximum groove depth H12 of the second shoulder narrow groove 312 (dimension symbols omitted in the drawing) is 0.025 ≦ H12 / Hg ≦ 0.150 with respect to the maximum groove depth Hg of the main groove 2 in the circumferential direction. In range. Further, the groove width W12 and the maximum groove depth H12 of the second shoulder narrow groove 312 of the shoulder land portion 31 are the same as the groove width W21 and the groove depth H21 of the first center narrow groove 321 of the center land portion 32. It is preferable to have.

Further, the second shoulder narrow groove 312 extends in the tire width direction while being inclined with respect to the tire circumferential direction. Further, the inclination direction of the first shoulder narrow groove 311 with respect to the tire circumferential direction is opposite to the inclination direction of the second shoulder narrow groove 312. Further, the inclination angle θ12 (dimension symbol omitted in the drawing) of the second shoulder narrow groove 312 in the region of the central portion 30 [%] of the shoulder land portion 31 is in the range of 20 [deg] ≤ θ12 ≤ 80 [deg]. It is preferably in the range of 35 [deg] ≤ θ12 ≤ 65 [deg].

[Modification example]
6 to 8 are explanatory views showing a modified example of the pneumatic tire shown in FIG. 2. In the figure, the same components as those shown in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

In the configuration of FIG. 2, as described above, the shoulder land portion 31 and the center land portion 32 are provided with a plurality of shoulder narrow grooves 311 and 312 and center narrow grooves 321 and 322. In such a configuration, the shoulder narrow grooves 311 and 312 and the center narrow grooves 321 and 322 are preferable in that the tread tread surface is effectively cooled and the heat resistance of the tire is improved.

However, the present invention is not limited to this, and as shown in FIG. 6, the shoulder narrow grooves 311 and 312 may be omitted. In the configuration of FIG. 6, the shoulder land portion 31 does not have a groove and has a tread surface continuous in the tire circumferential direction. Further, as shown in FIG. 7, the center narrow grooves 321 and 322 may be omitted. In the configuration of FIG. 7, the center land portion 32 does not have a groove and has a tread surface continuous in the tire circumferential direction. Further, in the configuration of FIG. 6, only some of the shoulder narrow grooves 311, 312 and the center fine grooves 321 and 322 may be omitted (not shown). Even with these configurations, the effect of cooling the tread surface by the fine grooves can be obtained.

Further, not limited to the above, as shown in FIG. 8, all of the shoulder narrow grooves 311 and 312 and the center narrow grooves 321 and 322 may be omitted.

[effect]
As described above, the pneumatic tire 1 includes a pair of circumferential main grooves 2 and 2 extending in the circumferential direction of the tire, and a pair of shoulder land portions 31 partitioned by the circumferential main grooves 2 and 2. It includes 31 and a single center land 32 (see FIG. 2). Further, each of the pair of shoulder land portions 31 and 31 having a contact width Wb1 has a relationship of 0.27 ≦ Wb1 / TW ≦ 0.40 with respect to the tire contact width TW.

In such a configuration, (1) by arranging the single center land portion 32, the rigidity of the tread portion is increased and the rolling of the vehicle is reduced. This has the advantage of suppressing uneven wear caused by rolling and improving the uneven wear resistance performance of the tire. Further, (2) there is an advantage that the ground contact width Wb1 of the pair of shoulder land portions 31, 31 is optimized. Specifically, by the above lower limit, the ground contact width Wb1 of the shoulder land portion 31 is secured, and the effect of suppressing the rolling of the vehicle is properly secured. Further, by the above upper limit, the arrangement area of the center land portion 31 is secured.

Further, in the pneumatic tire 1, the pair of circumferential main grooves 2 have a straight shape (see FIG. 2). Further, the groove width Wg of the circumferential main groove 2 is in the range of 0.05 ≦ Wg / TW ≦ 0.10. With respect to the tire contact width TW. In such a configuration, since the circumferential main groove 2 has a straight shape, there is an advantage that the cooling action of the tread tread is enhanced and the heat resistance of the tire is improved.

Further, in the pneumatic tire 1, the pair of circumferential main grooves 2, 2 have a groove width Wg of 20 [mm] or more (see FIG. 2) and a groove depth Hg of 40 [mm] or more (see FIG. 4). ). As a result, the groove width Wg and the groove depth Hg of the circumferential main groove 2 are secured, and there is an advantage that the heat dissipation effect of the circumferential main groove 2 is ensured.

Further, the pneumatic tire 1 includes a pair of bead cores 11 and 11, a carcass layer 13 spanning the bead cores 11 and 11, and a belt layer 14 arranged on the outer periphery of the carcass layer 13 (see FIG. 1). ). Further, the belt layer 14 is formed by laminating four or more belt plies 141 to 145 formed by coating a steel cord with a coated rubber. Further, the outer diameter of the steel cord is in the range of 1.5 [mm] or more and 2.5 [mm] or less. As a result, the cord diameters of the belt plies 141 to 145 are optimized, and the structural strength of the tread portion is optimized. This has the advantage that the wide shoulder land portion 31 can efficiently reduce the rolling motion of the vehicle.

Further, in the pneumatic tire 1, the shoulder drop amount Dt of the tread profile when the tire is mounted on the specified rim and the specified internal pressure is applied is 0.025 ≦ Dt / SH ≦ 0 with respect to the tire cross-sectional height SH. It has a relationship of .070 (see FIG. 1). In such a configuration, the shoulder drop amount Dt of the tread profile is optimized, so that the ground contact state of the shoulder land portion 31 is optimized. This has the advantage that the wide shoulder land portion 31 can efficiently reduce the rolling motion of the vehicle.

Further, in the pneumatic tire 1, the gauge Gtr1 of the tread rubber 15 on the tire equatorial plane CL is 0.90 ≦ Gtr1 / Gtr2 with respect to the gauge Gtr2 of the tread rubber 15 at the end position of the outermost layer 145 of the belt layer 14. It has a relationship of ≦ 1.35 (see FIG. 1). In such a configuration, the gauge ratio Gtr1 / Gtr2 of the tread rubber 15 at a predetermined position is optimized, and there is an advantage that the effect of reducing the rolling of the vehicle by the wide shoulder land portion 31 can be efficiently obtained.

Further, in the pneumatic tire 1, the shoulder land portion 31 is provided with a plurality of shoulder narrow grooves 311 and 312 which penetrate the shoulder land portion 31 in the tire width direction and are arranged at predetermined intervals in the tire circumferential direction (FIG. 2). reference). Further, the ratio of the groove depth of the shoulder narrow grooves 311 and 312 to the maximum groove depth of the circumferential main grooves 2 and 2 is in the range of 0.025 or more and 0.150 or less. In such a configuration, (1) the shoulder land portion 31 includes shoulder narrow grooves 311 and 312 that open in the circumferential main groove 2, and therefore, the heat dissipation performance of these shoulder narrow grooves 311 and 312 improves the heat generation resistance of the tire. There is an advantage to do. Further, (2) the shoulder narrow grooves 311 and 312 having a very shallow groove depth are arranged at predetermined intervals in the tire circumferential direction, so that the wear progress of the shoulder land portion 31 from the time when the tire is new is made uniform. To. This has the advantage of improving the uneven wear resistance of the tire, and as a result, has the advantage of improving the rolling resistance of the tire.

Further, the pneumatic tire 1 has an advantage that the groove width and the groove depth of the shoulder narrow grooves 311 and 312 are optimized.

Further, in the pneumatic tire 1, the ratio of the maximum value and the minimum value of the groove widths of the shoulder narrow grooves 311 and 312 is in the range of 1.00 or more and 1.10 or less. In such a configuration, since the shoulder narrow grooves 311 and 312 have a substantially constant groove width, there is an advantage that the rigidity of the shoulder land portion 31 is made uniform and the uneven wear resistance performance of the tire is improved.

Further, in the pneumatic tire 1, the inclination direction of the first shoulder groove 311 of the shoulder groove 311 and 312 with respect to the tire circumferential direction is opposite to the inclination direction of the second shoulder groove 312 ( See FIG. 2).

Further, in the pneumatic tire 1, the center land portion 32 penetrates the center land portion 32 in the tire width direction and has the first and second center narrow grooves 321 and 322 arranged at predetermined intervals in the tire circumferential direction. Prepare (see FIG. 2). Further, the groove depth H21 of the first center narrow groove 321 is in the range of 0.025 ≦ H21 / Hg ≦ 0.150 with respect to the maximum groove depth Hg of the main groove 2 in the circumferential direction (see FIG. 4). Further, the groove depth H22 of the second center narrow groove 322 is in the range of 0.50 ≦ H22 / Hg ≦ 0.90 with respect to the maximum groove depth Hg of the main groove 2 in the circumferential direction (see FIG. 5). In such a configuration, since the center land portion 32 includes the first and second center narrow grooves 321 and 322 that open in the circumferential main groove 2, the heat dissipation action of these first and second center narrow grooves 321 and 322 This has the advantage of improving the heat generation resistance of the tire. Further, since the groove depth H22 of the second center narrow groove 322 is deeper than the groove depth H21 of the first center narrow groove 321, the heat dissipation performance of the tire is effective due to the heat dissipation action of the second center fine groove 322. There is an advantage to improve.

Further, in the pneumatic tire 1, the first and second center narrow grooves 321 and 322 have groove widths W21 and W22 (see FIG. 3) of 2.5 [mm] or more and 5.0 [mm] or less. It has maximum groove depths H21, H22 (see FIGS. 4 and 5). This has the advantage that the groove width and groove depth of the center narrow grooves 321 and 322 are optimized.

Further, in the pneumatic tire 1, the ratio of the maximum values W21_max and W22_max of the groove widths W21 and W22 (see FIG. 3) of the first and second center narrow grooves 321 and 322 to the minimum values W21_min and W22_min is 1. It is in the range of .00 or more and 1.10 or less. In such a configuration, since the first and second center narrow grooves 321 and 322 have substantially constant groove widths, there is an advantage that the rigidity of the center land portion 32 is made uniform and the uneven wear resistance performance of the tire is improved. ..

Further, in the pneumatic tire 1, the second center narrow groove 322 has a bottom upper portion 3221 at an opening with respect to the circumferential main groove 2 (see FIGS. 3 and 5). Further, the distance H22'from the tread tread to the top surface of the bottom upper portion 3221 of the second center narrow groove 322 is 0.025 ≦ H22 ′ / Hg ≦ 0 with respect to the maximum groove depth Hg of the main groove 2 in the circumferential direction. It is in the range of 150 (see FIG. 5). In such a configuration, the rigidity of the center land portion 32 is ensured by the bottom upper portion 3221, and there is an advantage that the uneven wear resistance performance of the tire is improved. Further, the above lower limit has an advantage that the cooling action of the land portion by the second center narrow groove 322 is ensured. Further, the above upper limit has an advantage that the reinforcing action of the rigidity of the land portion by the bottom upper portion 3221 is ensured.

[Applicable target]
Further, the pneumatic tire 1 is a tire for a construction vehicle, and is particularly preferably a tire for a construction vehicle mounted on a port straddle carrier. By applying such a tire for a construction vehicle, there is an advantage that the effect of improving the uneven wear resistance and heat generation resistance of the tire can be effectively obtained.

9 and 10 are charts showing the results of performance tests of pneumatic tires according to the embodiment of the present invention.

In this performance test, (1) heat resistance and (2) uneven wear resistance were evaluated for a plurality of types of test tires. Further, a test tire having a tire size of 1600R25 is assembled to a rim having a rim size of 25 × 11.25-2.0, and an internal pressure of 1000 [kPa] and 85 [%] of a specified load of JATTA are applied to the test tire.

(1) In the evaluation of heat resistance performance, an indoor drum tester is used, and the heat generation amount of the tire after traveling at a speed of 25 [km / h] for 4 hours is measured. Then, based on this measurement result, an index evaluation based on the conventional example (100) is performed. The larger the numerical value, the more preferable this evaluation. Further, if the evaluation is 90 or more, it can be said that the uneven wear resistance is properly secured.

(2) In the evaluation of uneven wear resistance, the test tires are mounted on all the wheels of the port straddle carrier, which is the test vehicle. Then, uneven wear of the tires is observed after the test vehicle has traveled on the paved road at a speed of 25 [km / h] for 3000 hours. Then, based on this measurement result, an index evaluation based on the conventional example (100) is performed. The larger the numerical value, the more preferable this evaluation. Further, if the evaluation is 90 or more, it can be said that the uneven wear resistance is properly secured.

The test tire of the embodiment has the configuration of FIG. 2 and includes a pair of circumferential main grooves 2 and 2 having a straight shape, a pair of shoulder land portions 31, 31 and a single center land portion 32. Further, the shoulder land portion 31 and the center land portion 32 have a plurality of shoulder narrow grooves 311 and 312 and center narrow grooves 321 and 322, respectively, which penetrate the land portion. Further, the tire contact width TW is 360 [mm], and the groove depth Hg of the circumferential main groove 2 is 50 [mm].

In the test tire of the conventional example, in the test tire of Example 1, the shoulder land portion and the center land portion do not have a shallow groove and have a plain tread surface.

As the test results show, it can be seen that the test tires of the examples have both uneven wear resistance and heat generation resistance.

1 Pneumatic tire; 2 Circumferential main groove; 11 bead core; 12 bead filler; 13 carcass layer; 14 belt layer; 141-145 belt ply; 15 tread rubber; 16 sidewall rubber; 17 rim cushion rubber; 31 shoulder land 32 Center land area; 311 First shoulder tread; 312 Second shoulder tread; 321 First center tread; 322 Second center tread; 3221 Top of bottom; 323 Circumferential groove; 3231 Top of bottom

Claims (15)

A pneumatic tire including a pair of circumferential main grooves extending in the circumferential direction of the tire, a pair of shoulder land portions and a single center land portion partitioned by the circumferential main grooves.
A pneumatic tire characterized in that each of the ground contact widths Wb1 of the pair of shoulder land portions has a relationship of 0.27 ≦ Wb1 / TW ≦ 0.40 with respect to the tire ground contact width TW. The pair of circumferential main grooves have a straight shape, and the groove width Wg of the circumferential main grooves is in the range of 0.05 ≦ Wg / TW ≦ 0.10. With respect to the tire contact width TW. The pneumatic tire according to claim 1. The pneumatic tire according to claim 1 or 2, wherein the pair of circumferential main grooves has a groove width of 20 [mm] or more and a groove depth of 40 [mm] or more. A pair of bead cores, a carcass layer bridged over the bead cores, and a belt layer arranged on the outer periphery of the carcass layer are provided.
The belt layer is formed by laminating four or more belt plies formed by coating a steel cord with coated rubber, and
The pneumatic tire according to any one of claims 1 to 3, wherein the outer diameter of the steel cord is in the range of 1.5 [mm] or more and 2.5 [mm] or less. Claim 1 in which the shoulder drop amount Dt of the tread profile when the tire is mounted on the specified rim and the specified internal pressure is applied has a relationship of 0.025 ≤ Dt / SH ≤ 0.070 with respect to the tire cross-sectional height SH. Pneumatic tire according to any one of ~ 4. Claim that the gauge Gtr1 of the tread rubber on the equatorial plane of the tire has a relationship of 0.90 ≦ Gtr1 / Gtr2 ≦ 1.35 with respect to the gauge Gtr2 of the tread rubber at the end position of the outermost layer of the belt layer. The pneumatic tire according to any one of 1 to 5. The shoulder land portion penetrates the shoulder land portion in the tire width direction and is provided with a plurality of shoulder grooves arranged at predetermined intervals in the tire circumferential direction.
The pneumatic tire according to any one of claims 1 to 6, wherein the ratio of the groove depth of the shoulder narrow groove to the maximum groove depth of the circumferential main groove is in the range of 0.025 or more and 0.150 or less. .. The pneumatic tire according to claim 7, wherein the shoulder narrow groove has a groove width of 2.5 [mm] or more and a maximum groove depth of 5.0 [mm] or less. The pneumatic tire according to claim 7 or 8, wherein the ratio of the maximum value and the minimum value of the groove width of the shoulder narrow groove is in the range of 1.00 or more and 1.10 or less. The air according to any one of claims 7 to 9, wherein the inclination direction of the first shoulder groove with respect to the tire circumferential direction is opposite to the inclination direction of the second shoulder groove. Tires with. The center land portion is provided with first and second center grooves that penetrate the center land portion in the tire width direction and are arranged at predetermined intervals in the tire circumferential direction.
The groove depth H21 of the first center narrow groove is in the range of 0.025 ≦ H21 / Hg ≦ 0.150 with respect to the maximum groove depth Hg of the circumferential main groove, and
Any of claims 1 to 10, wherein the groove depth H22 of the second center narrow groove is in the range of 0.50 ≦ H22 / Hg ≦ 0.90 with respect to the maximum groove depth Hg of the circumferential main groove. Pneumatic tires listed in one. The pneumatic tire according to claim 11, wherein the first and second center narrow grooves have a groove width of 2.5 [mm] or more and a maximum groove depth of 5.0 [mm] or less. The pneumatic tire according to claim 11 or 12, wherein the ratio of the maximum value and the minimum value of the groove widths of the first and second center narrow grooves is in the range of 1.00 or more and 1.10 or less. The second center groove has a bottom upper portion at an opening with respect to the circumferential main groove, and
The distance H22'from the tread tread to the top surface of the bottom of the second center narrow groove is 0.025 ≤ H22'/ Hg ≤ 0.150 with respect to the maximum groove depth Hg of the circumferential main groove. The pneumatic tire according to any one of claims 11 to 13 in the range. The pneumatic tire according to any one of claims 1 to 14, which is a tire for a construction vehicle.

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