JP2021160572A - tire - Google Patents

Abstract

To provide a tire which can combine on-snow acceleration performance with low rolling resistance performance.SOLUTION: The tire comprises : a plurality of main grooves 21, 22 extending in a tire circumferential direction; and four or more rows of land portions 32, 33 constituted by being partitioned by the main grooves 21, 22. In addition, a middle land portion 32 and a center land portion 33 include a plurality of penetration lug grooves 321, 331 penetrating the land portions 32, 33 in a tire width direction. Pitch lengths λ2, λ3 of the penetration lug grooves 321, 331 fall in the range of 7[%] to 14[%] of a tire maximum grounding length. Further, the maximum groove depths H21, H31 (not shown in FIG.) of the penetration lug grooves 321, 331 fall in the range of 5[%] to 65[%] of the maximum groove depths Hg1, Hg2 of the main grooves 21, 22.SELECTED DRAWING: Figure 3

Description

The present invention relates to a tire, and more particularly to a tire capable of achieving both acceleration performance on snow and low rolling resistance performance of the tire.

In the conventional heavy-duty tire, a zigzag-shaped main groove is adopted in order to improve the acceleration performance on snow of the tire. As a conventional tire adopting such a configuration, the technique described in Patent Document 1 is known.

JP-A-2017-154708

On the other hand, in heavy-duty tires mounted on the steering shaft of a vehicle, there is a problem that the rolling resistance of the tire should be reduced.

In order to achieve the above object, the tire according to the present invention is a tire including a plurality of main grooves extending in the tire circumferential direction and four or more rows of land portions divided into the main grooves, and at least. The land portion in one row includes a plurality of penetrating lug grooves penetrating the land portion in the tire width direction, and the pitch length of the penetrating lug groove is 7 [%] or more and 14 [%] or less of the maximum tire contact length. The maximum groove depth of the through lug groove is in the range of 5 [%] or more and 65 [%] or less of the maximum groove depth of the main groove.

The tire according to the present invention has an advantage that the relationship between the pitch length of the through lug groove and the maximum groove depth is optimized, and the tire has both acceleration performance on snow and low rolling resistance performance. Specifically, the range of the pitch length of the through lug groove has the above lower limit and the range of the maximum groove depth of the through lug groove has the above upper limit, so that the rigidity of the land portion is secured and the rolling resistance of the tire is ensured. Deterioration is suppressed. Further, the range of the pitch length of the through lug groove has the above upper limit and the range of the maximum groove depth of the through lug groove has the above lower limit, so that the edge component of the land portion is secured and the snow road surface is traveling. The traction action of the through lug groove is ensured.

FIG. 1 is a cross-sectional view in the tire meridian direction showing a tire according to an embodiment of the present invention. FIG. 2 is a plan view showing the tread surface of the tire shown in FIG. FIG. 3 is an enlarged view showing a middle land portion and a center land portion of the tire shown in FIG. FIG. 4 is an enlarged view showing the middle land portion shown in FIG. FIG. 5 is a cross-sectional view of the middle land portion shown in FIG. FIG. 6 is a cross-sectional view of the middle land portion shown in FIG. FIG. 7 is an enlarged view showing the land area of the center shown in FIG. FIG. 8 is a chart showing the results of performance tests of tires according to the 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 those that are replaceable and self-explanatory while maintaining the identity of the invention. Further, the plurality of modifications described in this embodiment can be arbitrarily combined within a range self-evident by those skilled in the art.

[tire]
FIG. 1 is a cross-sectional view in the tire meridian direction showing a tire according to an embodiment of the present invention. The figure shows a cross-sectional view of one side region in the tire radial direction. In this embodiment, as an example of the tire, a pneumatic radial tire for heavy load mounted on the steering shaft of a truck and a tractor will be described.

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

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

The pair of bead cores 11 and 11 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. The carcass ply of the carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with coated rubber and rolling them, and has an absolute value of 80. It has a carcass angle of [deg] or more and 100 [deg] or less (defined as an inclination angle of the carcass cord in the longitudinal direction with respect to the tire circumferential direction).

The belt layer 14 is formed by laminating four layers of belt plies 141 to 144, and is arranged so as to be hung around the outer circumference of the carcass layer 13. The belt plies 141 to 144 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 a belt angle of 15 [deg] or more and 55 [deg] or less in absolute value. Further, the belt plies 141 to 144 have differently signed belt angles (defined as the inclination angles of the belt cords in the longitudinal direction with respect to the tire circumferential direction), and the belt cords are laminated so as to intersect each other in the longitudinal directions. (So-called cross-ply structure).

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 1. The pair of sidewall rubbers 16 and 16 are arranged on the outer sides of 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 tire 1 shown in FIG. The figure shows the tread surface of an all-season tire with a mud and snow mark "M + S". 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 tire 1 has a plurality of circumferential main grooves 21 and 22 extending in the tire circumferential direction, and a plurality of land portions 31, 32, which are defined by these circumferential main grooves 21 and 22. 33 is provided on the tread surface.

The main groove is a groove that is obliged to display a wear indicator specified in JATTA, and has a maximum groove width of 7.0 [mm] or more and a maximum groove depth of 12 [mm] or more.

The groove width is measured as 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.

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 a configuration in which the groove has a partially uneven portion or a sipe on the groove bottom, the groove depth is measured by excluding these.

The specified rim means the "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 JATMA, 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 tire 1 has a substantially point-symmetrical tread pattern having a center point on the tire equatorial plane CL. However, the present invention is not limited to this, and the tire 1 may have, for example, a left-right axisymmetric tread pattern or a left-right asymmetric tread pattern centered on the tire equatorial plane CL, or a tread having directionality in the tire rotation direction. It may have a pattern (not shown).

Further, in the configuration of FIG. 2, the left and right regions with the tire equatorial plane CL as a boundary have two circumferential main grooves 21 and 22, respectively. Further, these circumferential main grooves 21 and 22 are arranged symmetrically with respect to the tire equatorial plane CL. In addition, five rows of land portions 31 to 33 are partitioned by these circumferential main grooves 21 and 22. Further, one land portion 33 is arranged on the tire equatorial plane CL.

However, the present invention is not limited to this, and three or five or more circumferential main grooves may be arranged, or the circumferential main grooves may be arranged asymmetrically with respect to the tire equatorial plane CL (not shown). .. Further, by arranging one main groove in the circumferential direction on the tire equatorial plane CL, the land portion may be arranged at a position deviating from the tire equatorial plane CL (not shown).

Further, among the circumferential main grooves 21 and 22 arranged in one region with the tire equatorial plane CL as a boundary, the outermost circumferential main groove 21 in the tire width direction is defined as the shoulder main groove, and the tire equatorial line is defined. The circumferential main groove 22 on the surface CL side is defined as the center main groove.

Further, the land portion 31 on the outer side in the tire width direction divided in the shoulder main groove 21 is defined as the shoulder land portion. The shoulder land portion 31 is the outermost land portion in the tire width direction and is located on the tire ground contact end T. Further, the land portion 32 on the inner side in the tire width direction divided in the shoulder main groove 21 is defined as the middle land portion. The middle land portion 32 is adjacent to the shoulder land portion 31 with the shoulder main groove 21 interposed therebetween. Further, the land portion 33 on the CL side of the tire equatorial plane with respect to the middle land portion 32 is defined as the center land portion. The center land portion 33 may be arranged on the tire equatorial plane CL (see FIG. 2), or may be arranged at a position deviating from the tire equatorial plane CL (not shown).

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.

In the configuration including the four circumferential main grooves 21 and 22 as shown in FIG. 2, a pair of shoulder land portions 31 and 31, a pair of middle land portions 32 and 32, and a single center land portion 33 are provided. Is defined. Further, for example, in a configuration having five or more circumferential main grooves, two or more rows of center land areas are defined (not shown), and in a configuration having three circumferential main grooves, the middle land area is the center land area. Also serves as a part (not shown).

Further, in the configuration of FIG. 2, the maximum contact width Wb1 of the shoulder land portion 31 has a relationship of 0.15 ≦ Wb1 / TW ≦ 0.25 with respect to the tire contact width TW. Further, it is preferable that the maximum contact width Wb3 of the center land portion 33 closest to the tire equatorial plane CL has a relationship of 0.15 ≦ Wb3 / TW ≦ 0.25 with respect to the tire contact width TW, and 0.18 ≦. It is more preferable to have a relationship of Wb3 / TW ≦ 0.23. Further, in a configuration including four circumferential main grooves 21 and 22 and five rows of land portions 31 to 33 as shown in FIG. 2, the maximum ground contact width Wb2 of the middle land portion 32 is the maximum ground contact width of the shoulder land portion 31. It is slightly narrower than Wb1, and specifically, it is preferably in the range of 0.85 ≦ Wb2 / Wb1 ≦ 0.95.

Further, in the configuration of FIG. 2, the shoulder main groove 21 and the center main groove 22 have a zigzag shape or a wavy shape having an amplitude in the tire width direction. However, the present invention is not limited to this, and as will be described later, the shoulder main groove 21 and the center main groove 22 may have a straight shape at the groove opening (not shown).

Further, in FIG. 2, the snow traction index STI (so-called 0 [deg] snow traction index) with respect to the tire circumferential direction over the entire circumference of the tire is in the range of 130 ≦ STI.

The Snow Traction Index STI is an empirical formula of Uniroyal Co., Ltd. proposed by SAE (Society of Automotive Engineers), and is defined by the following formula (1). In the same formula, Pg is the groove density [1 / mm], and the groove length [mm] of all the grooves (all the grooves except the sipes) projected in the tire circumferential direction on the tire contact patch and the tire contact area. (Product of tire contact patch width and tire circumference length) Calculated as a ratio to [mm ^ 2]. Further, ρs is a sipe density [1 / mm], and is calculated as a ratio between the sipe length [mm] of all sipe projected in the tire circumferential direction on the tire contact patch and the tire contact area [mm ^ 2]. Will be done. Further, Dg is an average value of the groove depths [mm] of all the grooves projected in the tire circumferential direction on the tire contact patch.

STI = -6.8 + 2202 x Pg + 672 x ρs + 7.6 x Dg ... (1)

[Middle land]
FIG. 3 is an enlarged view showing the middle land portion 32 and the center land portion 33 of the tire 1 shown in FIG. FIG. 4 is an enlarged view showing the middle land portion 32 shown in FIG. 5 and 6 are cross-sectional views of the middle land portion 32 shown in FIG. In these figures, FIG. 5 shows a cross-sectional view of the middle land portion 32 cut along a through lug groove 321A having a groove bottom sipe 323, and FIG. 6 shows a through lug groove 321B having no groove bottom sipe. A cross-sectional view of the middle land portion 32 cut along the line is shown.

In the configuration of FIG. 2, as shown in FIG. 3, the groove openings of the shoulder main groove 21 and the center main groove 22 have a wavy shape formed by connecting a plurality of arcs convex on the CL side of the tire equatorial plane. ing. Therefore, the left and right edge portions of the middle land portion 32 have a wavy shape formed by connecting a plurality of arcs convex on the CL side of the tire equatorial plane.

Further, in FIG. 4, the wavy wavelengths λ2L and λ2R of the edge portion of the middle land portion 32 are in the range of 14 [%] or more and 28 [%] or less of the maximum tire contact length Lt (not shown). Further, the wavy wavelengths λ2L and λ2R of the left and right edge portions are set to be equal to each other.

The maximum tire contact length Lt 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 when 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 circumferential direction on the surface.

Further, as shown in FIG. 4, the circumferential length of the arc (dimension symbols omitted in the drawing) is 80 [%] or more and 85 [%] or more with respect to the wavy wavelengths λ2L and λ2R. Is preferable. Further, adjacent arcs are connected via a short straight line or an arc. Therefore, the edge portion of the middle land portion 32 has a wavy shape formed by connecting long arcs that are convex in the same direction. In such a configuration, uneven wear at the maximum protruding position of the edge portion is suppressed as compared with a configuration in which the edge portion has a zigzag shape or a sinusoidal shape.

Further, the wavy amplitudes A2L and A2R of the edge portion are in the range of 3.0 [%] or more and 10 [%] or less with respect to the maximum ground contact width Wb2 of the middle land portion 32, and 4.0 [%] or more. It is preferably in the range of 7.0 [%] or less. Further, the amplitudes A2L and A2R are preferably in the range of 1.0 [mm] or more and 15.0 [mm] or less, and preferably in the range of 1.2 [mm] or more and 10.0 [mm] or less. Further, the ratio of the wavy amplitudes A2L and A2R of the left and right edge portions is set in the range of 90 [%] or more and 110 [%] or less.

Further, the wavy phase φ2 of the left and right edge portions is in the range of 10 [%] or more and 40 [%] or less with respect to the wavelength λ2L.

The wavy wavelength, amplitude and phase of the edge of the land are measured under no load with the tire mounted on the specified rim and filled with the specified internal pressure.

Further, as shown in FIG. 3, the middle land portion 32 includes a plurality of through lug grooves 321 and a plurality of blocks 322.

The through lug groove 321 has an open structure that penetrates the middle land portion 32 in the tire width direction. Further, a plurality of through lug grooves 321 are arranged in the tire circumferential direction with a predetermined pitch length P21. Further, the pitch length P21 of the through lug groove 321 is in the range of 7 [%] or more and 14 [%] or less of the maximum tire contact length Lt (not shown). For example, in the configuration of FIG. 3, the through lug groove 321 is opened at the maximum amplitude position of the wavy shape of the left and right edge portions of the middle land portion 32, respectively. Further, the number of pitches of the through lug groove 321 is set to twice the number of pitches of the wavy shape of the edge portion. Further, the number of pitches of the through lug groove 321 on the entire circumference of the tire is in the range of 100 or more and 200 or less.

Further, in FIG. 4, the through lug groove 321 of the middle land portion 32 is a fine shallow groove, and has a maximum of 1.5 [mm] or more and 4.0 [mm] or less (preferably 3.0 [mm or less]). It has a groove width W21 and a maximum groove depth H21 (see FIG. 5) of 1.5 [mm] or more and 4.0 [mm] or less (preferably 3.0 [mm or less]). Further, in FIG. 5, the maximum groove depth H21 of the through lug groove 321 has a relationship of 0.05 ≦ H21 / Hg1 ≦ 0.65 with respect to the maximum groove depth Hg1 of the shoulder main groove 21. It is preferable to have a relationship of 10 ≦ H21 / Hg1 ≦ 0.30.

In the above configuration, the relationship between the pitch length P21 and the maximum groove depth H21 of the through lug groove 321 is optimized, and the tire acceleration performance on snow and low rolling resistance performance are compatible. Specifically, the range of the pitch length P21 of the through lug groove 321 has the above lower limit, and the range of the maximum groove depth H21 of the through lug groove 321 has the above upper limit, so that the rigidity of the middle land portion 32 is ensured. Therefore, the deterioration of the rolling resistance of the tire is suppressed. Further, the range of the pitch length P21 of the through lug groove 321 has the above upper limit, and the range of the maximum groove depth H21 of the through lug groove 321 has the above lower limit, so that the edge component of the middle land portion 32 is secured. The traction action of the through lug groove 321 when traveling on a snowy road surface is ensured.

Further, in FIG. 4, the inclination angle θ21 of the through lug groove 321 with respect to the tire circumferential direction is in the range of 60 [deg] ≤ θ21 ≤ 120 [deg]. In the configuration of FIG. 4, the wavy shapes of the left and right edge portions of the middle land portion 32 are arranged so as to be out of phase with each other, and the through lug groove 321 opens at the maximum amplitude position of the wavy shape of the left and right edge portions, respectively. , The entire through lug groove 321 is inclined with respect to the tire circumferential direction.

The inclination angle θ21 of the through lug groove 321 is measured as an angle formed by a virtual straight line connecting both ends of the through lug groove 321 and the tire circumferential direction.

Further, as shown in FIG. 4, the through lug groove 321 has a zigzag shape. Further, the amplitude of the zigzag shape of the through lug groove 321 is in the range of 2.0 [%] or more and 7.0 [%] or less with respect to the pitch length P21 of the through lug groove 321. Further, the zigzag-shaped wavelength of the through lug groove 321 is in the range of 16 [%] or more and 22 [%] or less with respect to the maximum ground contact width Wb2 of the middle land portion 32.

Further, as shown in FIGS. 3 to 6, a plurality of through lug grooves 321 have a first through lug groove 321A having a groove bottom sipe 323 (see FIG. 5) and a second through lug having no groove bottom sipe. It is composed of a groove 321B (see FIG. 6). As shown in FIG. 6, the second through lug groove 321B has a structure in which the groove bottom sipe 323 is omitted from the first through lug groove 321A in FIG. Further, in the configuration of FIG. 3, the first through lug groove 321A and the second through lug groove 321B are alternately arranged in the tire circumferential direction. However, the present invention is not limited to this, and two or three second through lug grooves 321B may be arranged between the adjacent first through lug grooves 321A and 321A (not shown).

The groove bottom sipe is a notch formed in the groove bottom of the lug groove, and has a maximum sipe width of less than 1.0 [mm] and a depth described later, so that the tire is closed when the tire touches the ground.

Further, the distance H23'from the groove bottom of the through lug groove 321 to the maximum depth position of the groove bottom sipe 323 is within the range of 0.06 ≦ H23' / Hg1 with respect to the maximum groove depth Hg1 of the shoulder main groove 21. Yes, it is preferably in the range of 0.10 ≦ H23 ′ / Hg1. Further, the distance H23 from the tread tread to the maximum depth position of the groove bottom sipe 323 is in the range of H23 / Hg1 ≦ 1.00 with respect to the maximum groove depth Hg1 of the shoulder main groove 21, and H23 / Hg1 ≦ 0. It is preferably in the range of .50.

The block 322 is divided into a plurality of through lug grooves 321. Further, the block 322 has a long shape in the tire width direction. Specifically, in FIG. 4, the pitch length of the block 322 (equal to the pitch length P21 of the through lug groove 321) is 45 [%] or more and 80 [%] with respect to the maximum ground contact width Wb2 of the middle land portion 32. It is in the following range, preferably in the range of 50 [%] or more and 75 [%] or less.

[Center land area]
FIG. 7 is an enlarged view showing the center land portion 33 described in FIG. In the figure, the same components as those shown in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted.

In the configuration of FIG. 2, as shown in FIG. 3, the groove openings of the left and right center main grooves 22 and 22 have a wavy shape formed by connecting a plurality of arcs convex on the CL side of the tire equatorial plane. There is. Therefore, the left and right edge portions of the center land portion 33 have a wavy shape formed by connecting a plurality of arcs that are convex inward in the width direction of the center land portion 33 on the CL side of the tire equatorial plane in the figure. ..

Further, in FIG. 7, the wavy wavelengths λ3L and λ3R of the edge portion of the center land portion 33 are in the range of 14 [%] or more and 28 [%] or less of the maximum tire contact length Lt (not shown). Further, the wavy wavelengths λ3L and λ3R of the left and right edge portions are set to be equal to each other. Further, the wavelength λ3L of the edge portion of the center land portion 33 partitioned in the center main groove 22 is 90 [%] or more and 110 [%] or less with respect to the wavelength λ2R (see FIG. 4) of the edge portion of the middle land portion 32. It is set in the range of.

Further, as shown in FIG. 7, the circumferential length of the arc (dimension symbols omitted in the drawing) is 80 [%] or more and 85 [%] or more with respect to the wavy wavelengths λ3L and λ3R. Is preferable. Further, adjacent arcs are connected via a short straight line or an arc. Therefore, the edge portion of the center land portion 33 has a wavy shape formed by connecting long arcs that are convex in the same direction. In such a configuration, uneven wear at the maximum protruding position of the edge portion is suppressed as compared with a configuration in which the edge portion has a zigzag shape or a sinusoidal shape.

Further, the wavy amplitudes A3L and A3R of the edge portion are in the range of 3.0 [%] or more and 10 [%] or less with respect to the maximum ground contact width Wb3 of the center land portion 33, and 4.0 [%] or more. It is preferably in the range of 7.0 [%] or less. Further, the amplitudes A3L and A3R are preferably in the range of 1.0 [mm] or more and 15.0 [mm] or less, and preferably in the range of 1.2 [mm] or more and 10.0 [mm] or less. Further, the ratio of the wavy amplitudes A3L and A3R of the left and right edge portions is set in the range of 90 [%] or more and 110 [%] or less. Further, the amplitude A3L of the edge portion of the center land portion 33 partitioned in the center main groove 22 is 90 [%] or more and 110 [%] or less with respect to the amplitude A2R (see FIG. 4) of the edge portion of the middle land portion 32. It is set in the range of.

Further, the wavy phase φ3 of the left and right edge portions is in the range of 10 [%] or more and 40 [%] or less with respect to the wavelength λ3L.

Further, as shown in FIG. 3, the center land portion 33 includes a plurality of through lug grooves 331 and a plurality of blocks 332.

The through lug groove 331 has an open structure that penetrates the center land portion 33 in the tire width direction. Further, a plurality of through lug grooves 331 are arranged in the tire circumferential direction with a predetermined pitch length P31. Further, the pitch length P31 of the through lug groove 331 is in the range of 7 [%] or more and 14 [%] or less of the maximum tire contact length Lt (not shown). For example, in the configuration of FIG. 3, the through lug groove 331 is opened at the maximum amplitude position of the wavy shape of the left and right edge portions of the center land portion 33, respectively. Further, the number of pitches of the through lug groove 331 is set to twice the number of pitches of the wavy shape of the edge portion. Further, the number of pitches of the through lug grooves 331 on the entire circumference of the tire is in the range of 100 or more and 200 or less. Further, the number of pitches of the through lug groove 331 of the center land portion 33 is equal to the number of pitches of the through lug groove 321 of the middle land portion 32.

Further, as shown in FIG. 3, the opening of the through lug groove 331 of the center land portion 33 and the opening of the through lug groove 321 of the middle land portion 32 with respect to the center main groove 22 are arranged so as to face each other. .. Specifically, the offset amount Da in the tire circumferential direction of the openings of the facing through lug grooves 321 and 331 is in the range of 0 ≦ Da / λ2 ≦ 0.10. With respect to the wavelength λ2 of the edge portion of the middle land portion 32. It is preferably in the range of 0 ≦ Da / λ2 ≦ 0.05, and more preferably in the range of 0 ≦ Da / λ2 ≦ 0.05.

Further, in FIG. 7, the through lug groove 331 of the center land portion 33 is a fine shallow groove, and has a maximum of 1.5 [mm] or more and 4.0 [mm] or less (preferably 3.0 [mm or less]). It has a groove width W31 and a maximum groove depth H31 (not shown) having a groove width of 1.5 [mm] or more and 4.0 [mm] or less (preferably 3.0 [mm or less]). Further, the maximum groove depth H31 of the through lug groove 331 has a relationship of 0.05 ≦ H31 / Hg2 ≦ 0.65 with respect to the maximum groove depth Hg2 (not shown) of the center main groove 22. It is preferable to have a relationship of 10 ≦ H31 / Hg2 ≦ 0.30.

In the above configuration, the relationship between the pitch length P31 and the maximum groove depth H31 of the through lug groove 331 is optimized, and there is an advantage that the tire acceleration performance on snow and low rolling resistance performance are compatible with each other. Specifically, the rigidity of the center land portion 33 is ensured by having the range of the pitch length P31 of the through lug groove 331 having the above lower limit and the range of the maximum groove depth H31 of the through lug groove 331 having the above upper limit. Therefore, the deterioration of the rolling resistance of the tire is suppressed. Further, the range of the pitch length P31 of the through lug groove 331 has the above upper limit, and the range of the maximum groove depth H31 of the through lug groove 331 has the above lower limit, whereby the edge component of the center land portion 33 is secured. Therefore, the traction action of the through lug groove 331 when traveling on a snowy road surface is ensured.

Further, in FIG. 7, the inclination angle θ31 of the through lug groove 331 with respect to the tire circumferential direction is in the range of 60 [deg] ≤ θ31 ≤ 120 [deg]. In the configuration of FIG. 7, the wavy shapes of the left and right edge portions of the center land portion 33 are arranged so as to be out of phase with each other, and the through lug grooves 331 are opened at the maximum amplitude positions of the wavy shapes of the left and right edge portions, respectively. , The entire through lug groove 331 is inclined with respect to the tire circumferential direction. Further, as shown in FIG. 3, the inclination direction of the through lug groove 331 of the center land portion 33 is opposite to the inclination direction of the through lug groove 321 of the middle land portion 32.

Further, as shown in FIG. 7, the through lug groove 331 has a zigzag shape. Further, the amplitude of the zigzag shape of the through lug groove 331 is in the range of 2.0 [%] or more and 7.0 [%] or less with respect to the pitch length P31 of the through lug groove 331. Further, the zigzag-shaped wavelength of the through lug groove 331 is in the range of 16 [%] or more and 22 [%] or less with respect to the maximum ground contact width Wb3 of the center land portion 33.

Further, as shown in FIGS. 3 and 7, the plurality of through lug grooves 331 are composed of a first through lug groove 331A having a groove bottom sipe 333 and a second through lug groove 331B having no groove bottom sipe. Will be done. For example, in the configuration of FIG. 7, the first through lug groove 331A and the second through lug groove 331B are alternately arranged in the tire circumferential direction. However, the present invention is not limited to this, and two or three second through lug grooves 331B may be arranged between adjacent first through lug grooves 331A and 331A (not shown). Further, as shown in FIG. 3, the first through lug groove 331A of the center land portion 33 having the groove bottom sipe 333 and the first through lug groove 321A of the middle land portion 32 having the groove bottom sipe 323 are the tire circumferences. Arranged in a staggered pattern in the direction. In other words, the first through lug groove 331A of the center land portion 33 having the groove bottom sipe 333 and the first through lug groove 321A of the middle land portion 32 having the groove bottom sipe 323 face each other with the center main groove 22 in between. Through lug grooves 321A, 321B, 331A, and 331B of the land portions 32 and 33 are arranged so as not to prevent them.

Further, the distance H33'(not shown) from the groove bottom of the through lug groove 331 to the maximum depth position of the groove bottom sipe 333 is 0.06 with respect to the maximum groove depth Hg2 (not shown) of the center main groove 22. It is preferably in the range of ≦ H33 ′ / Hg2 and preferably in the range of 0.10 ≦ H33 ′ / Hg2. Further, the distance H33 (not shown) from the tread tread to the maximum depth position of the groove bottom sipe 333 is in the range of H33 / Hg2 ≦ 1.00 with respect to the maximum groove depth Hg2 of the center main groove 22, and is H33. It is preferably in the range of / Hg2 ≦ 0.50.

The block 332 is divided into a plurality of through lug grooves 331. Further, the block 332 has a long shape in the tire width direction. Specifically, in FIG. 7, the pitch length of the block 332 (equal to the pitch length P31 of the through lug groove 331) is 45 [%] or more and 80 [%] with respect to the maximum ground contact width Wb3 of the center land portion 33. It is in the following range, preferably in the range of 50 [%] or more and 75 [%] or less.

[Shoulder land]
In the configuration of FIG. 2, as described above, the shoulder land portion 31 is a rib having a tread surface continuous in the tire circumferential direction, and is not divided in the tire circumferential direction by a lug groove or a sipe. Further, the edge portion of the shoulder land portion 31 on the shoulder main groove 21 side has a wavy shape formed by connecting a plurality of convex arcs on the CL side of the tire equatorial plane as described above.

Further, as shown in FIG. 2, the shoulder land portion 31 includes a plurality of shallow grooves 311.

The shallow groove 311 has a U-shape with the opening facing the tire ground contact end T side. That is, the U-shape of the narrow shallow groove 311 extends from the top thereof to the outside in the tire width direction in a bifurcated manner and ends. Further, the shallow groove 311 has a closed structure that terminates in the ground contact surface of the shoulder land portion 31. Therefore, the narrow shallow groove 311 is not connected to the tire ground contact end T and the shoulder main groove 21, and is arranged away from the edge portion of the tread surface of the shoulder land portion 31. Further, a plurality of shallow grooves 311 are arranged at predetermined intervals in the tire circumferential direction.

The edge portion of the shoulder land portion 31 on the shoulder main groove 21 side may have a plurality of fine multisipes (reference numerals omitted in the drawing). These multisipes have a width of less than 1.0 [mm] and a extending length of less than 5.0 [mm]. With these multi-sipes, uneven wear of the edge portion of the shoulder land portion 31 is suppressed.

[effect]
As described above, the tire 1 includes a plurality of main grooves 21 and 22 extending in the tire circumferential direction, and four or more rows of land portions 31 to 33 divided into the main grooves 21 and 22 (). (See FIG. 2). Further, at least one row of land portions (middle land portion 32 and center land portion 33 in FIG. 2) includes a plurality of through lug grooves 321; 331 that penetrate the land portion 32; 33 in the tire width direction (FIG. 3). reference). The pitch length P21; P31 of the through lug groove 321; 331 is in the range of 7 [%] or more and 14 [%] or less of the maximum tire contact length Lt (not shown). Further, the maximum groove depth H21 (see FIG. 5); H31 (not shown) of the through lug groove 321; 331 is 5 [%] or more and 65 [%] of the maximum groove depth Hg1; Hg2 of the main groove 21; 22. It is in the following range.

In such a configuration, the relationship between the pitch length λ2; λ3 and the maximum groove depth H21; H31 of the through lug grooves 321; 331 is optimized, and there is an advantage that the tire has both acceleration performance on snow and low rolling resistance performance. Specifically, the range of the pitch length P21; P31 of the through lug groove 321; 331 has the above lower limit, and the range of the maximum groove depth H21; H31 of the through lug groove 321; 331 has the above upper limit. The rigidity of the portions 32; 33 is ensured, and the deterioration of the rolling resistance of the tire is suppressed. Further, the range of the pitch length P21; P31 of the through lug groove 321; 331 has the above upper limit, and the range of the maximum groove depth H21; H31 of the through lug groove 321; 331 has the above lower limit, so that the land portion 32; The edge component of 33 is secured, and the traction action of the through lug groove 321; 331 when traveling on a snowy road surface is secured.

Further, in this tire 1, the maximum groove width W21; W31 of the through lug groove 321; 331 is in the range of 1.5 [mm] or more and 4.0 [mm] or less. This has the advantage that the maximum groove widths W21; W31 of the through lug grooves 321; 331 are optimized.

Further, in this tire 1, the through lug grooves 321; 331 have a zigzag shape (FIG. 3). Further, the amplitude of the through lug groove 321; 331 (not shown) is in the range of 2.0 [%] or more and 7.0 [%] or less with respect to the pitch length (not shown) of the through lug groove 321; 331. .. Further, the wavelength of the through lug groove 321; 331 is in the range of 16 [%] or more and 22 [%] or less with respect to the maximum ground contact width Wb2; Wb3 of the land portion 32; 33. This has the advantage that the zigzag shape of the through lug grooves 321; 331 is optimized, and the effect of improving the traction performance of the tire by the through lug grooves 321; 331 is ensured.

Further, in the tire 1, the inclination angle θ21; θ31 of the through lug groove 321; 331 with respect to the tire circumferential direction is in the range of 60 [deg] or more and 120 [deg] (see FIGS. 4 and 7). The above lower limit ensures the effect of improving the traction performance by the through lug grooves 321; 331, and the above upper limit has the advantage of appropriately ensuring the rigidity of the land portion 32; 33.

Further, in the tire 1, a part of the plurality of through lug grooves 321; 331, 321A; 331A, has a groove bottom sipe 323; 333 (see FIGS. 4 and 7). Further, through lug grooves 321A; 331A having groove bottom sipes 323; 333 and at least one through lug groove 321B; 331B having no groove bottom sipes are alternately arranged in the tire circumferential direction. In such a configuration, since the through lug grooves 321A; 331A have the groove bottom sipe 323; 333, there is an advantage that the acceleration performance on snow of the tire is improved. Further, since the through lug groove 321A; 331A having the groove bottom sipe 323; 333 and the through lug groove 321B; 331B having no groove bottom sipe are alternately arranged in the tire circumferential direction, the rigidity of the land portion 32; 33 There is an advantage that the rolling resistance of the tire is reduced.

Further, in this tire 1, the distance H23'(see FIG. 5); H33'from the groove bottom of the through lug groove 321; 331 to the maximum depth position of the groove bottom sipe 323; 333 is the maximum of the main groove 21; 22. Groove depth Hg1; in the range of 6 [%] or more with respect to Hg2. Further, the distance H23; H33'from the tread tread to the maximum depth position of the groove bottom sipe 323; 333 is in the range of 100 [%] or less with respect to the maximum groove depth Hg1; Hg2 of the main groove 21; 22. .. This has the advantage that the depth of the groove bottom sipe 323; 333 is optimized. Specifically, the above lower limit secures the effect of improving the acceleration performance on snow by the groove bottom sipe 323; 333, and the above upper limit secures the rigidity of the land portion 32; 33 and reduces the rolling resistance of the tire. There are advantages.

Further, in the tire 1, adjacent land portions 32 and 33 are provided with through lug grooves 321 and 331, respectively (see FIG. 3). Further, one of the pair of through lug grooves 321 and 331 facing each other across the main groove 22 321A; 331A has a groove bottom sipe 323; 333, and the other 331B; 323B does not have a groove bottom sipe. As a result, there is an advantage that the rigidity between the adjacent land portions 32 and 33 is made uniform and the rolling resistance of the tire is reduced.

Further, in the tire 1, the maximum contact width Wb2; Wb3 of the land portion 32; 33 is in the range of 15 [%] or more and 25 [%] or less with respect to the tire contact width TW (see FIG. 2). This has the advantage that the land portion 32; 33 is optimized.

Further, in the tire 1, the first and second edge portions of the land portion 32; 33 have a zigzag shape or a wavy shape having an amplitude in the tire width direction, and are arranged so as to be out of phase in the tire circumferential direction (the tire 1 has a zigzag shape or a wavy shape). (See FIG. 3). Further, the through lug grooves 321; 331 extend while being inclined with respect to the tire circumferential direction to connect the maximum amplitude positions of the first and second edge portions. In such a configuration, since the edge portion of the land portion 32; 33 has a zigzag shape or a wavy shape, the acceleration performance on snow of the tire is improved as compared with the configuration in which the edge portion of the land portion has a straight shape (not shown). There is an advantage to do. Further, since the through lug groove 321; 331 opens at the maximum amplitude position of the edge portion of the land portion, there is an advantage that the uneven wear of the land portion 32; 33 is reduced as compared with the configuration of opening at other positions. ..

Further, in the tire 1, the first and second edge portions of the land portion 32; 33 have a wavy shape formed by connecting a plurality of arcs having amplitudes in the tire width direction (see FIG. 3). Further, the circumferential length of the arc (not shown) is in the range of 80 [%] or more with respect to the wavy wavelength λ2; λ3. Such a configuration has an advantage that uneven wear of the land portion 32; 33 is suppressed as compared with a configuration including a land portion having a zigzag shape or a sinusoidal edge portion.

Further, in the tire 1, the wavy shape of the first and second edge portions of the land portion 32:33 is formed by connecting a plurality of arcs that are convex toward the CL side of the tire equatorial plane (see FIG. 3). This has the advantage that uneven wear of the land portion 32; 33 is effectively suppressed.

[Applicable target]
Further, the tire 1 is a heavy load tire mounted on a steering shaft of a vehicle. By applying such a tire, there is an advantage that the effect of improving the uneven wear resistance and the tier performance of the tire can be effectively obtained, and there is an advantage that the requirement for the snow acceleration performance of the all-season tire is satisfied. ..

Further, in this embodiment, as described above, a pneumatic tire has been described as an example of the tire. However, the present invention is not limited to this, and the configuration described in this embodiment can be arbitrarily applied to other tires within the scope of those skilled in the art. Examples of other tires include airless tires and solid tires.

FIG. 8 is a chart showing the results of performance tests of tires according to the embodiment of the present invention.

In this performance test, (1) snow acceleration performance and (2) low rolling resistance performance were evaluated for a plurality of types of test tires. Further, a test tire having a tire size of 315 / 70R22.5 is assembled to a rim having a rim size of 22.5 × 9.00 ″, and an internal pressure of 900 [kPa] and a specified load of JATTA are applied to the test tire. The test tires are mounted on the steer shaft of a 4x2 tractor.

(1) Evaluation of acceleration performance on snow is required for acceleration from the specified initial speed to terminal velocity under test conditions in accordance with R117-2 (Regulation No. 117 Revision 2) of the ECE (Economic Commission for Europe). The distance is measured and an evaluation is made. The larger the numerical value, the more preferable this evaluation.

(2) In the evaluation of low rolling resistance performance, a drum tester with a drum diameter of 1707 [mm] was used, and the load was 33.3 [kN], the air pressure was 900 [kPa], and the speed was 80 [km / h] in accordance with ISO28580. ], The rolling resistance coefficient of the test tire was calculated. This evaluation is performed by an index evaluation based on the conventional example (100), and the larger the value, the more preferable.

In the test tire of Example 1, in the configurations of FIGS. 1 and 2, the edge portions of the shoulder main groove 21 and the center main groove 22 have a zigzag shape. Further, the groove depth of the shoulder main groove 21 and the center main groove 22 is 14.6 [mm], and the groove width is 15.3 [mm]. Further, each of the through lug grooves 321 and 331 has a zigzag shape, and has inclination angles θ21 and θ31 of 75 [deg] with respect to the tire circumferential direction. Further, the tire contact width TW is 268 [mm], the maximum contact width Wb1 of the shoulder land portion 31 is 49.5 [mm], and the maximum contact width Wb2 of the middle land portion 32 is 36.0 [mm]. Yes, the maximum ground contact width Wb3 of the center land portion 33 is 36.0 [mm]. The test tires of the other examples are modifications of the test tires of the first embodiment.

In the test tire of the comparative example, the pitch lengths P21 and P31 of the through lug grooves 321 and 331 of the middle land portion 32 and the center land portion 33 are largely set in the test tire of the first embodiment.

As shown by the test results, it can be seen that the test tires of the examples have both the acceleration performance on snow and the low rolling resistance performance of the tires.

1 tire; 11 bead core; 12 bead filler; 13 carcass layer; 14 belt layer; 141, 142 cross belt; 15 tread rubber; 16 sidewall rubber; 17 rim cushion rubber; 21 shoulder main groove; 22 center main groove; 31 shoulder Land; 311 Shallow groove; 32 Center land; 32 Middle land; 321, 321A, 321B Penetrating lug groove; 322 block; 323 Groove bottom sipe; 33 Center land; 331, 331A, 331B Penetrating lug groove; 332 Block; 333 groove bottom sipe

Claims (12)

A tire having a plurality of main grooves extending in the circumferential direction of the tire and four or more rows of land portions divided into the main grooves.
At least one row of the land portion comprises a plurality of through lug grooves penetrating the land portion in the tire width direction.
The pitch length of the through lug groove is in the range of 7 [%] or more and 14 [%] or less of the maximum tire contact length, and
A tire characterized in that the maximum groove depth of the through lug groove is in the range of 5 [%] or more and 65 [%] or less of the maximum groove depth of the main groove. The tire according to claim 1, wherein the maximum groove width of the through lug groove is in the range of 1.5 [mm] or more and 4.0 [mm] or less. The through lug groove has a zigzag shape and has a zigzag shape.
The amplitude of the through lug groove is in the range of 2.0 [%] or more and 7.0 [%] or less with respect to the pitch length of the through lug groove, and
The tire according to claim 1 or 2, wherein the wavelength of the through lug groove is in the range of 16 [%] or more and 22 [%] or less with respect to the maximum contact width of the land portion. The tire according to any one of claims 1 to 3, wherein the inclination angle of the through lug groove with respect to the tire circumferential direction is in the range of 60 [deg] or more and 120 [deg]. A part of the plurality of through lug grooves has a groove bottom sipe, and
Any one of claims 1 to 4, wherein the through lug groove having the groove bottom sipe and at least one through lug groove having no groove bottom sipe are alternately arranged in the tire circumferential direction. Tires listed in. The distance from the groove bottom of the through lug groove to the maximum depth position of the groove bottom sipe is in the range of 6 [%] or more with respect to the maximum groove depth of the main groove, and
The tire according to claim 5, wherein the distance from the tread tread to the maximum depth position of the groove bottom sipe is in the range of 100 [%] or less with respect to the maximum groove depth of the main groove. Adjacent land portions each include the through lug groove, and the land portion is provided with the through lug groove.
The tire according to any one of claims 1 to 6, wherein one of the pair of through lug grooves facing the main groove has the groove bottom sipe and the other does not have the groove bottom sipe. The tire according to any one of claims 1 to 7, wherein the maximum contact width of the land portion is in the range of 15 [%] or more and 25 [%] or less with respect to the tire contact width. The first and second edge portions of the land portion have a zigzag shape or a wavy shape having an amplitude in the tire width direction, and are arranged so as to be out of phase in the tire circumferential direction.
The tire according to any one of claims 1 to 8, wherein the through lug groove extends while being inclined with respect to the tire circumferential direction to connect the maximum amplitude positions of the first and second edge portions. .. The first and second edge portions of the land portion have a wavy shape formed by connecting a plurality of arcs having amplitudes in the tire width direction, and have a wavy shape.
The pneumatic tire according to any one of claims 1 to 9, wherein the circumferential length of the arc is in the range of 80 [%] or more with respect to the wavy wavelength. The pneumatic tire according to claim 10, wherein the wavy shape of the first and second edge portions of the land portion connects the plurality of arcs that are convex toward the equatorial plane of the tire. The tire according to any one of claims 1 to 11, which is a heavy-duty tire mounted on a steering shaft of a vehicle.

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