JP6805535B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of uniforming the wear rate-determining of the tread portion shoulder region and the center region to improve the uneven wear resistance performance of the tire.

Recent heavy-duty tires mounted on trucks and buses have a low flatness, while maintaining the shape of the tread portion by providing a circumferential reinforcing layer on the belt layer. Specifically, the circumferential reinforcing layer is arranged in the center region of the tread portion to exert a tag effect, thereby suppressing the diameter growth of the tread portion and maintaining the shape of the tread portion.

In a low flat tire provided with such a circumferential reinforcement layer, the tire outer diameter tends to grow in a region outside the tire width direction with respect to the arrangement region of the circumferential reinforcement layer. Further, since the tire contact width is generally wider than that of a highly flat tire, the tread portion shoulder region tends to be unevenly worn at the initial stage of tire wear. Further, in general, a high driving force acts on a tire mounted on a drive shaft of a vehicle, so that the tread portion center region tends to be unevenly worn. This tendency is the same for low flat tires. As a conventional pneumatic tire relating to such a problem, the technique described in Patent Document 1 is known.

Japanese Patent No. 5041104

An object of the present invention is to provide a pneumatic tire capable of making the wear rate-determining of the tread portion shoulder region and the center region uniform and improving the uneven wear resistance performance of the tire.

In order to achieve the above object, the pneumatic tire according to the present invention includes a carcass layer, a belt layer arranged on the outer periphery of the carcass layer, and a plurality of circumferential main grooves extending in the tire circumferential direction. A pneumatic tire having a plurality of land portions defined in the circumferential main groove on the tread surface, and the outermost circumferential main groove in the tire width direction is defined as the outermost peripheral main groove. The outermost land portion in the tire width direction is defined as the shoulder land portion, the land portion in the second row from the outside in the tire width direction is defined as the second land portion, and is closer to the tire equatorial plane side than the second land portion. The land portion is defined as the center land portion, and the belt layer includes a pair of intersecting belts having differently signed belt angles and a circumferential reinforcing layer having a belt angle of 5 [deg] or less in absolute value. , a tire meridian direction of cross section, the tire width direction outside of the perpendicular foot drawn from the edge portion to the tread profile of the circumferential reinforcing layer, Ri tread near the second land portion, the grounding of the shoulder land portion the area S1, and a ground area S2 of the second land portion, and the contact area S31 in the center land portion adjacent to said second land portion is, have a relation of S2 <S1 and S2 <S31, and the shoulder land The ground contact width W1 of the portion and the ground contact width W2 of the second land portion have a relationship of 1.03 ≦ W1 / W2 ≦ 1.20 .
Further, the pneumatic tire according to the present invention includes a carcass layer, a belt layer arranged on the outer periphery of the carcass layer, a plurality of circumferential main grooves extending in the tire circumferential direction, and the circumferential main groove. A pneumatic tire having a plurality of land portions divided into grooves on the tread surface, the outermost peripheral main groove in the tire width direction is defined as the outermost peripheral main groove, and the most in the tire width direction. The land area on the outside is defined as the shoulder land area, the land area in the second row from the outside in the tire width direction is defined as the second land area, and the land area on the tire equatorial plane side of the second land area is the center land area. Defined as a part, the belt layer includes a pair of intersecting belts having belt angles having different signs from each other and a circumferential reinforcing layer having a belt angle of 5 [deg] or less in absolute value, and is in the tire meridional direction. In a cross-sectional view, the foot of the perpendicular line drawn from the outer edge portion of the circumferential reinforcement layer in the tire width direction to the tread profile is on the tread surface of the second land portion, and the ground contact area S1 of the shoulder land portion and the second land portion. The ground contact area S2 of the land portion and the ground contact area S31 of the center land portion adjacent to the second land portion have a relationship of S2 <S1 and S2 <S31, and have a contact width W1 of the shoulder land portion. The ground contact width W31 of the center land portion adjacent to the second land portion has a relationship of 0.95 ≦ W1 / W31 ≦ 1.05.
Further, the pneumatic tire according to the present invention includes a carcass layer, a belt layer arranged on the outer periphery of the carcass layer, a plurality of circumferential main grooves extending in the tire circumferential direction, and the circumferential main groove. A pneumatic tire having a plurality of land portions divided into grooves on a tread surface, the outermost peripheral main groove in the tire width direction is defined as the outermost peripheral main groove, and the most in the tire width direction. The land area on the outside is defined as the shoulder land area, the land area in the second row from the outside in the tire width direction is defined as the second land area, and the land area on the tire equatorial plane side of the second land area is the center land area. Defined as a unit, the belt layer includes a pair of intersecting belts having belt angles with different symbols from each other and a circumferential reinforcing layer having a belt angle of 5 [deg] or less in absolute value, and is in the tire meridional direction. In a cross-sectional view, the foot of the perpendicular line drawn from the outer edge portion of the circumferential reinforcement layer in the tire width direction to the tread profile is on the tread surface of the second land portion, and the ground contact area S1 of the shoulder land portion and the second land portion. The ground contact area S2 of the land portion and the ground contact area S31 of the center land portion adjacent to the second land portion have a relationship of S2 <S1 and S2 <S31, and between the second land portions on the left and right of the tire. It is characterized in that the center land portion having three or more rows is provided, and the ground contact area S2 of the second land portion and the ground contact area S32 of the center land portion closest to the tire equatorial plane have a relationship of S2 <S32. And.

In the pneumatic tire according to the present invention, (1) the ground contact area S1 of the shoulder land portion and the ground contact area S2 of the second land portion have a relationship of S2 <S1, so that there is a relationship between the shoulder land portion and the second land portion. The difference in rigidity is made uniform, and uneven wear of the shoulder region of the tread portion is suppressed. Further, (2) Since the ground contact area S2 of the second land portion and the ground contact area S31 of the center land portion adjacent to the second land portion have a relationship of S2 <S31, the rigidity between the center land portion and the second land portion. The difference is made uniform, and uneven wear in the center region of the tread portion is suppressed. As a result, the wear rate-determining of the shoulder region and the center region of the tread portion is made uniform, and there is an advantage that the uneven wear resistance performance of the tire is improved.

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 an explanatory view showing a belt layer of the pneumatic tire shown in FIG. FIG. 3 is an explanatory view showing a belt layer of the pneumatic tire shown in FIG. FIG. 4 is a plan view showing the tread surface of the pneumatic tire shown in FIG. FIG. 5 is an enlarged view showing a main part of the tread pattern shown in FIG. FIG. 6 is an enlarged view showing a main part of the tread pattern shown in FIG. FIG. 7 is a sectional view taken along line A showing the second land portion 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.

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

[Pneumatic tires]
FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. The figure shows a cross-sectional view of one side region of the cross-sectional view in the tire radial direction. Further, the figure shows a heavy-duty radial tire mounted on a truck, a bus, etc. for long-distance transportation as an example of a pneumatic tire.

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

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 is an annular member formed by bundling a plurality of bead wires, and constitutes the cores of the left and right bead portions. The pair of bead fillers 12 and 12 are composed of a lower filler 121 and an upper filler 122, and are arranged on the outer periphery of the pair of bead cores 11 and 11 in the tire radial direction to form a bead portion.

The carcass layer 13 is bridged between the left and right bead cores 11 and 11 in a toroidal shape to form a tire skeleton. Further, both ends of the carcass layer 13 are wound and locked from the inside in the tire width direction to the outside in the tire width direction so as to wrap the bead core 11 and the bead filler 12. The carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material (for example, nylon, polyester, rayon, etc.) with coated rubber and rolling them, and has an absolute value of 85 [deg] or more 95. It has the following carcass angle (defined as the longitudinal tilt angle of the carcass cord with respect to the tire circumferential direction). In the configuration of FIG. 1, the carcass layer 13 has a single-layer structure composed of a single carcass ply, but the present invention is not limited to this, and the carcass layer 13 has a multi-layer structure in which a plurality of carcass plies are laminated. Is also good.

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 circumference of the carcass layer 13. The specific configuration of the belt layer 14 will be described later.

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

[Belt layer]
2 and 3 are explanatory views showing a belt layer of the pneumatic tire described in FIG. 1. In these figures, FIG. 2 shows a region on one side of the tread portion with the tire equatorial plane CL as a boundary, and FIG. 3 shows a laminated structure of the belt layer 14. In FIG. 2, the circumferential reinforcing layer 145 is hatched. Further, in FIG. 3, thin lines in the belt plies 141 to 145 schematically show the arrangement configuration of the belt cords.

The belt layer 14 is formed by laminating a high-angle belt 141, a pair of crossing belts 142 and 143, a belt cover 144, and a circumferential reinforcing layer 145, and is arranged so as to be hung around the outer periphery of the carcass layer 13. (See FIG. 2).

The high-angle belt 141 is formed by coating a plurality of belt cords made of steel or an organic fiber material with coated rubber and rolling them, and has an absolute value of 45 [deg] or more and 70 [deg] or less, preferably 54 [deg]. ] Or more and 68 [deg] or less (defined as the inclination angle of the belt cord in the longitudinal direction with respect to the tire circumferential direction). Further, the high-angle belt 141 is laminated and arranged on the outer side of the carcass layer 13 in the tire radial direction.

The pair of crossing belts 142 and 143 are formed by coating a plurality of belt cords made of steel or an organic fiber material with coated rubber and rolling them, and have an absolute value of 10 [deg] or more and 55 [deg] or less, preferably. It has a belt angle of 14 [deg] or more and 28 [deg] or less. Further, the pair of crossing belts 142 and 143 have belt angles having different symbols from each other, and are laminated so that the longitudinal directions of the belt cords cross each other (so-called cross-ply structure). Here, the cross belt 142 located inside the tire radial direction is referred to as an inner diameter side cross belt, and the cross belt 143 located outside the tire radial direction is referred to as an outer diameter side cross belt. In addition, three or more cross belts may be laminated and arranged (not shown). Further, the pair of crossing belts 142 and 143 are laminated and arranged on the outer side in the tire radial direction of the high angle belt 141.

Further, the belt cover 144 is formed by coating a plurality of belt cords made of steel or an organic fiber material with coated rubber and rolling them, and has an absolute value of 10 [deg] or more and 55 [deg] or less, preferably 14 [. It has a belt angle of deg] or more and 28 [deg] or less. Further, the belt covers 144 are laminated and arranged on the outer side in the tire radial direction of the cross belts 142 and 143. In this embodiment, the belt cover 144 has the same belt angle as the outer diameter side crossing belt 143, and is arranged on the outermost layer of the belt layer 14.

The circumferential reinforcement layer 145 is configured by spirally winding a steel belt cord coated with coated rubber in the tire circumferential direction, and has a belt angle of 5 [deg] or less in absolute value. Further, the circumferential reinforcing layer 145 is arranged so as to be sandwiched between the pair of crossing belts 142 and 143. Further, the circumferential reinforcing layer 145 is arranged inside the tire width direction with respect to the left and right edge portions of the pair of crossing belts 142 and 143. Specifically, one or a plurality of wires are spirally wound around the outer circumference of the inner diameter side crossing belt 142 to form the circumferential reinforcing layer 145. Further, the circumferential reinforcing layer 145 is continuous across the tire equatorial plane CL. The circumferential reinforcement layer 145 reinforces the rigidity in the tire circumferential direction, thereby improving the durability of the tire.

Further, in FIG. 3, the width Wb3 of the narrower crossing belt (outer diameter side crossing belt 143 in FIG. 1) among the inner diameter side crossing belt 142 and the outer diameter side crossing belt 143 and the width Ws of the circumferential reinforcing layer 145. And preferably have a relationship of 0.70 ≦ Ws / Wb3 ≦ 0.90. As a result, the width Ws of the circumferential reinforcing layer 145 is properly secured.

The width of the belt ply is the distance between the left and right ends of each belt ply in the direction of the tire rotation axis, and is measured as a no-load state while the tire is mounted on the specified rim to apply the specified internal pressure.

Further, as shown in FIG. 3, the circumferential reinforcing layer 145 is a narrower crossing belt (in FIG. 1, the outer diameter side crossing) of the pair of crossing belts (inner diameter side crossing belt 142 and outer diameter side crossing belt 143). It is arranged inside the left and right edges of the belt 143) in the tire width direction. Further, the width Wb3 of the outer diameter side crossing belt 143 and the distance S from the edge portion of the circumferential reinforcing layer 145 to the edge portion of the outer diameter side crossing belt 143 are 0.03 ≦ S / Wb3 ≦ 0.12. It is preferably in the range. As a result, the distance between the end of the width Wb3 of the outer diameter side crossing belt 143 and the end of the circumferential reinforcing layer 145 is properly secured.

The distance S is measured as the distance in the tire width direction when the tire is mounted on the specified rim, a specified internal pressure is applied, and no load is applied.

Further, in FIG. 3, the width Wb3 of the outer diameter side crossing belt 143 and the width Wb4 of the belt cover 144 preferably have a relationship of 0.75 ≦ Wb4 / Wb3 ≦ 0.95, and 0.80 ≦ Wb4. It is more preferable to have a relationship of / Wb3 ≦ 0.90. Therefore, the belt cover 144 is narrower than the outer diameter side crossing belt 143.

Further, in FIG. 3, it is preferable that the width Wb4 of the belt cover 144 and the width Ws of the circumferential reinforcing layer 145 have a relationship of 1.02 ≦ Wb4 / Ws. Therefore, the belt cover 144 is wider than the circumferential reinforcing layer 145. Further, as shown in FIG. 2, it is preferable that the belt cover 144 extends to the outside in the tire width direction from the main groove 21 in the outermost peripheral direction. The upper limit of the ratio Wb4 / Ws is not particularly limited, but is restricted in relation to the ratio Wb4 / Wb3 and the ratio Ws / Wb3 described above.

[Tread pattern]
FIG. 4 is a plan view showing the tread surface of the pneumatic tire shown in FIG. In the figure, the tire circumferential direction means the direction around the tire rotation axis. Further, reference numeral T is a tire ground contact end.

As shown in FIG. 4, the pneumatic tire 1 includes a plurality of circumferential main grooves 21 and 22 extending in the circumferential direction of the tire, and a plurality of land portions 31 to 21 divided into these circumferential main grooves 21 and 22. The tread surface is provided with 33 and a plurality of lug grooves 41 to 43 arranged in these land portions 31 to 33.

The main groove is a groove that is obliged to display a wear indicator specified in JATTA, and for heavy-duty tires, a groove width of 4.0 [mm] or more and a groove depth of 6.5 [mm] or more are generally provided. Have. Further, the lug groove described later is a lateral groove extending in the tire width direction, and generally has a groove width of 2.0 [mm] or more and a groove depth of 3.0 [mm] or more, so that the tire touches the ground. Sometimes it opens. Further, the sipe described later is a notch formed in the land portion, and generally has a sipe width of less than 2.0 [mm], so that the tire is closed when the tire touches the ground.

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

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

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

For example, in the configuration of FIG. 4, the pneumatic tire 1 has a left-right point-symmetrical tread pattern centered on a point on the tire equatorial plane CL. However, the present invention is not limited to this, and the pneumatic 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, and may have a directionality in the tire rotation direction. It may have a tread pattern to have (not shown).

Further, in the configuration of FIG. 4, seven circumferential main grooves 21 and 22 are arranged symmetrically with respect to the tire equatorial plane CL. Further, one circumferential main groove 22 is arranged on the tire equatorial plane CL, and the left and right regions with the tire equatorial plane CL as a boundary are provided with three circumferential main grooves 21 and 22, respectively. In addition, eight rows of land portions 31 to 33 are partitioned by these circumferential main grooves 21 and 22.

However, the present invention is not limited to this, and four to six or eight or more circumferential main grooves may be arranged, or the circumferential main grooves may be arranged asymmetrically around the tire equatorial plane CL (). Not shown). Further, the land portion may be arranged on the tire equatorial plane CL by arranging the circumferential main groove at a position deviating from the tire equatorial plane CL (not shown).

Further, 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 outermost peripheral direction main groove. Further, the circumferential main groove 22 located on the CL side of the tire equatorial plane with respect to the outermost peripheral direction main groove 21 is defined as the center circumferential main groove. Generally, the distance from the tire equatorial plane CL to the main groove 21 in the outermost peripheral direction (dimension symbols omitted in the drawing) is in the range of 65 [%] or more and 80 [%] or less of the tire contact width TW.

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

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

Further, of the plurality of land portions 31 to 33 partitioned by the circumferential main grooves 21 and 22, the outermost land portion 31 in the tire width direction is defined as the shoulder land portion. The shoulder land portion 31 is a land portion on the outer side in the tire width direction defined in the main groove 21 in the outermost peripheral direction, and has a tire ground contact end T on the tread surface. Further, the land portion 32 in the second row from the outside in the tire width direction is defined as the second land portion. The second land portion 32 is a land portion on the inner side in the tire width direction divided into the main groove 21 in the outermost peripheral direction, and is adjacent to the shoulder land portion 31 with the main groove 21 in the outermost outer peripheral direction interposed therebetween. Further, the land portion 33 on the CL side of the tire equatorial plane with respect to the second land portion 32 is defined as the center land portion.

Further, in the configuration of FIG. 4, each of the circumferential main grooves 21 and 22 has a straight shape. However, the present invention is not limited to this, and some or all of the circumferential main grooves 21 and 22 may have a zigzag shape or a wavy shape having an amplitude in the tire width direction (not shown).

Further, in the configuration of FIG. 4, the second land portion 32 and the center land portion 33 are provided with a plurality of through lug grooves 42 and 43, respectively. Further, these through lug grooves 42 and 43 have an open structure penetrating the land portions 32 and 33, and are arranged at predetermined intervals in the tire circumferential direction. As a result, the second land portion 32 and the center land portion 33 are divided in the tire circumferential direction by the through lug grooves 42 and 43 to form a block row composed of a plurality of blocks (reference numerals omitted in the drawing). On the other hand, the shoulder land portion 31 does not have a lug groove and has ribs that are continuous in the tire circumferential direction.

However, not limited to this, the second land portion 32 and the center land portion 33 are continuous in the tire circumferential direction by providing a lug groove having a semi-closed structure that terminates within the land portions 32 and 33 at one end. It may be a rib (not shown). Further, the shoulder land portion 31 may be a block row by providing a through lug groove having an open structure (not shown).

[Relationship of land contact area]
Recent heavy-duty tires mounted on trucks and buses have a low flatness, while maintaining the shape of the tread portion by providing a circumferential reinforcing layer on the belt layer. Specifically, the circumferential reinforcing layer is arranged in the center region of the tread portion to exert a tag effect, thereby suppressing the diameter growth of the tread portion and maintaining the shape of the tread portion.

In a low flat tire provided with such a circumferential reinforcement layer, the tire outer diameter tends to grow in a region outside the tire width direction with respect to the arrangement region of the circumferential reinforcement layer. Further, since the tire contact width is generally wider than that of a highly flat tire, the tread portion shoulder region tends to be unevenly worn at the initial stage of tire wear. Further, in general, a high driving force acts on a tire mounted on a drive shaft of a vehicle, so that the tread portion center region tends to be unevenly worn. This tendency is the same for low flat tires.

Therefore, in this pneumatic tire 1, the following configuration is adopted in order to make the wear rate-determining of the tread portion shoulder region and the center region uniform and improve the uneven wear resistance performance of the tire.

5 and 6 are enlarged views showing a main part of the tread pattern shown in FIG. In these figures, FIG. 5 shows three rows of land portions 31 to 33 adjacent to each other centering on the second land portion 32, and FIG. 6 shows the main groove 21 in the outermost peripheral direction of the second land portion 32 and the shoulder land portion 31. The edge part on the side is shown. Further, in FIGS. 5 and 6, the broken line 145e indicates the position of the edge portion of the circumferential reinforcing layer 145. FIG. 7 is a sectional view taken along line A showing the second land portion shown in FIG.

As shown in FIG. 2, in the cross-sectional view in the tire meridian direction, the foot of the perpendicular line drawn from the outer edge portion of the circumferential reinforcing layer 145 in the tire width direction to the tread profile is defined as point X. At this time, the point X needs to be on the tread surface of the second land portion 32. Further, it is preferable that the point X is outside the midpoint M of the ground contact width W2 of the second land portion 32 in the tire width direction.

The tread on the land is the contact surface between the tire and the flat plate when the tire is attached to 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. Defined in.

The ground contact width of the land portion is measured as the maximum linear distance of the tread surface of the land portion in the tire axial direction.

The tread profile is the contour line of the tread surface in the cross-sectional view in the meridian direction of the tire, and is measured by 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.

Point X is defined under the measurement conditions of the tread profile.

Further, as shown in FIG. 4, the second land portion 32 and the center land portion 33 are divided in the tire circumferential direction by the through lug grooves 42 and 43, and a block row composed of a plurality of blocks (reference numerals omitted in the drawing) is formed. It is formed. On the other hand, the shoulder land portion 31 is not provided with a lug groove and is a rib that is continuous in the tire circumferential direction.

Further, as shown in FIG. 5, the through lug groove 42 of the second land portion 32 and the lug groove 43 of the center land portion 33 are arranged in the tire circumferential direction with predetermined pitch lengths Pa, Pb, and Pc. Further, the through lug groove 42 of the second land portion 32 and the lug groove 43 of the center land portion 33 are arranged in the tire circumferential direction in synchronization with the phases of the pitch lengths Pa to Pc. Further, the pitch variation structure is formed by periodically changing these pitch lengths Pa to Pc toward the tire circumferential direction. In such a pitch variation structure, pattern noise caused by the arrangement of the through lug grooves 42 and 43 in the tire circumferential direction is reduced, and the noise performance of the tire is improved. In general pneumatic tires, 3 to 7 types of pitch lengths are used.

Further, in FIG. 5, the ground contact area S1 of the shoulder land portion 31 and the ground contact area S2 of the second land portion 32 have a relationship of S2 <S1. Therefore, the ground contact area S1 of the shoulder land portion 31 is larger than the ground contact area S2 of the second land portion 32. Specifically, the ratio S1 / S2 is preferably in the range of 1.05 ≦ S1 / S2 ≦ 1.15, and more preferably in the range of 1.07 ≦ S1 / S2 ≦ 1.13.

The ground contact area is the area of 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. Is defined as.

In the above configuration, since the edge portion of the circumferential reinforcement layer 145 is at the same position in the tire width direction with respect to the second land portion 32 (see FIG. 2), the edge portion in the tire width direction is outside the edge portion of the circumferential reinforcement layer 145. The outer diameter of the shoulder land portion 31 in is easy to grow. Therefore, the shoulder region of the tread portion tends to be unevenly worn. Therefore, as described above, the ground contact area S1 of the shoulder land portion 31 and the ground contact area S2 of the second land portion 32 have a relationship of S2 <S1, so that the ground contact area S1 of the shoulder land portion 31 is in the circumferential direction. It is set larger than the ground contact area S2 of the second land portion 32 having the edge portion of the reinforcing layer 145. As a result, the difference in rigidity between the shoulder land portion 31 and the second land portion 32 is made uniform, and uneven wear of the tread portion shoulder region is suppressed.

For example, in the configuration of FIG. 5, the second land portion 32 includes a plurality of through lug grooves 42. Further, the penetrating lug groove 42 has a bent shape that is bent in a step shape in the tire circumferential direction, penetrates the second land portion 32 in the tire width direction, and opens to the left and right edge portions. Further, these through lug grooves 42 are arranged at predetermined intervals in the tire circumferential direction to divide the second land portion 32 into a plurality of blocks.

Further, as shown in FIG. 6, the through lug groove 42 provides the bent portion 421 at the central portion of the block. The central portion of the block is defined as a region of 30 [%] or more and 70 [%] or less from one edge portion of the ground contact width W2 of the second land portion 32. Further, the bent portion 421 extends in the tire circumferential direction, and the inclination angle (dimension symbol omitted in the drawing) with respect to the tire circumferential direction is 5 [deg] or more and 20 [deg] or less in absolute value. Further, the through lug groove 42 includes a bottom upper portion 422 that raises the bottom of the region including the bent portion 421. The bottom upper portion 422 increases the rigidity of the second land portion 32. Further, the through lug groove 42 is provided with sipes 423 at both ends of the bottom upper portion 422, respectively. Further, the sipe 423 is arranged at a position separated from the bent portion 421 of the through lug groove 42. Further, the through lug groove 42 is provided with notches 424 at both ends of the bent portion 421. Further, the cutout portion 424 is arranged by widening the bending point of the bending portion 421 in the tire width direction.

Further, in FIG. 7, the groove depth H2 of the through lug groove 42 and the groove depth H0 of the main groove 21 in the outermost peripheral direction have a relationship of 0.80 ≦ H2 / H0 ≦ 1.00. In the figure, the maximum groove depth H2 of the through lug groove 42 and the groove depth H0 of the main groove 21 in the outermost peripheral direction are set to be the same. Further, the groove depth H2'of the through lug groove 42 in the bottom upper portion 422 and the maximum groove depth H2 of the through lug groove 42 have a relationship of 0.40 ≦ H2 ′ / H2 ≦ 0.80. Further, the maximum depth position of the sipe 423 formed in the bottom upper portion 422 is shallower than the maximum depth position of the through lug groove 42. Further, the maximum depth position of the notch portion 424 is shallower than the groove depth of the through lug groove 42 in the bottom upper portion 422.

Further, as shown in FIG. 6, the edge portion 145e (see FIG. 2) outside the tire width direction of the circumferential reinforcing layer 145 is arranged outside the bent portion 421 of the through lug groove 42 in the tire width direction. Further, in the figure, the edge portion 145e of the circumferential reinforcing layer 145 is arranged so as to overlap the bottom upper portion 422 of the through lug groove 42. In FIG. 6, the groove width Wg21 of the through lug groove 42 at the edge portion of the second land portion 32 and the groove width Wg22 of the bent portion 421 have a relationship of Wg22 <Wg21. Further, the second land portion 32 has a plurality of notch portions 5 at the edge portions of each block. These notches 5 are narrower than the groove width Wg21 of the lug groove 42, and as shown in FIG. 7, are shallower than the maximum groove depth H2 of the through lug groove 42.

Further, in FIG. 5, the shoulder land portion 31 includes only a plurality of non-penetrating lug grooves 41, and does not include a penetrating lug groove 42 such as the second land portion 32. Therefore, the shoulder land portion 31 is a rib that is continuous in the tire circumferential direction. As a result, the ground contact area S1 and the rigidity of the shoulder land portion 31 are secured. Further, the non-penetrating lug groove 41 opens at one end to the edge portion of the shoulder land portion 31 on the outermost peripheral direction main groove 21 side, and at the other end, is inside the ground contact surface of the shoulder land portion 31. Terminate with. Further, a plurality of non-penetrating lug grooves 41 are arranged at predetermined intervals in the tire circumferential direction along the edge portion on the outermost peripheral direction main groove 21 side of the shoulder land portion 31.

Further, it is preferable that the groove area ratio Sg1 of the shoulder land portion 31 and the groove area ratio Sg2 of the second land portion 32 have a relationship of Sg1 <Sg2. Specifically, the ratio Sg2 / Sg1 is preferably in the range of 1.05 ≦ Sg2 / Sg1 ≦ 1.15, and more preferably in the range of 1.07 ≦ Sg2 / Sg1 ≦ 1.13.

The groove area ratios Sg1 and Sg2 are defined by the groove area / (groove area + ground contact area) in each land area. The groove area means the opening area of the groove on the ground plane. Further, the groove means a lug groove and a notch formed in the land portion, and does not include a circumferential groove, a sipe, a calf, etc. of the tread portion. The ground contact area means the contact area between the land portion and the road surface. In addition, the groove area and ground contact area are the tires when the tire is mounted on the specified rim and the specified internal pressure is applied, 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 on the contact surface between the flat plate and the flat plate.

Further, the groove area ratio Sg2 of the second land portion 32 is preferably in the range of 0.10 ≦ Sg2 ≦ 0.30, and preferably in the range of 0.13 ≦ Sg2 ≦ 0.20. The above upper limit ensures the drainage property of the tire, and the above lower limit ensures the rigidity of the second land portion 32.

Further, in FIG. 6, the groove length Lg1 of the non-penetrating lug groove 41 and the ground contact width W1 of the shoulder land portion 31 are preferably in the range of 0.10 ≦ Lg1 / W1 <1.00. More preferably, it is in the range of 25 ≦ Lg1 / W1 ≦ 0.70. Further, the shoulder land portion 31 is provided with a plurality of notches 5 at the edge portion on the outermost peripheral direction main groove 21 side. Further, these notches 5 are arranged between adjacent non-penetrating lug grooves 41. Further, the notch portion 5 has a structure similar to that of the notch portion 5 of the second land portion 32.

Further, as a relationship between the shoulder land portion 31 and the second land portion 32, the ground contact width W1 of the shoulder land portion 31 (see FIGS. 2 and 5) and the ground contact width W2 of the second land portion 32 are 1.03 ≦ W1. It is preferable to have a relationship of / W2 ≦ 1.20, and more preferably to have a relationship of 1.05 ≦ W1 / W2 ≦ 1.18. Therefore, the ground contact width W1 of the shoulder land portion 31 is set wider than that of the second land portion 32.

Further, in FIG. 5, the groove width Wg1 of the non-penetrating lug groove 41 of the shoulder land portion 31 and the groove width Wg2 of the penetrating lug groove 42 of the second land portion 32 have a relationship of Wg2 <Wg1. Specifically, it is preferable to have a relationship of 1.00 <Wg1 / Wg2 ≦ 1.50, and more preferably to have a relationship of 1.10 ≦ Wg1 / Wg2 ≦ 1.40.

As described above, in the configuration of FIG. 5, the shoulder land portion 31 is a rib continuous in the tire circumferential direction, and the second land portion 32 is a block row partitioned into a plurality of through lug grooves 42. Further, the ground contact width W1 of the shoulder land portion 31 is slightly wider than the ground contact width W2 of the second land portion 32. Further, the groove width Wg1 of the non-penetrating lug groove 41 of the shoulder land portion 31 and the groove width Wg2 of the penetrating lug groove 42 of the second land portion 32 have a relationship of Wg2 <Wg1. Further, the groove area ratio of the shoulder land portion 31 is smaller than the groove area ratio of the second land portion 32. As a result, the ground contact area S1 of the shoulder land portion 31 is set to be larger than the ground contact area S2 of the second land portion 32 (S2 <S1).

Further, in FIG. 5, the ground contact area S2 of the second land portion 32 and the ground contact area S31 of the center land portion 331 adjacent to the second land portion 32 have a relationship of S2 <S31. Therefore, the ground contact area S31 of the center land portion 331 is larger than the ground contact area S2 of the second land portion 32. Further, when combined with the above-mentioned condition S2 <S1, the ground contact area S2 of the second land portion 32 is the smallest as compared with the ground contact areas S1 and S31 of the left and right land portions 31 and 331. Further, the ratio S31 / S2 is preferably in the range of 1.03 ≦ S31 / S2 ≦ 1.15, and more preferably in the range of 1.05 ≦ S31 / S2 ≦ 1.13.

In general, a high driving force acts on a tire mounted on a drive shaft of a vehicle, so that the center region of the tread portion tends to be unevenly worn. Therefore, as described above, the ground contact area S2 of the second land portion 32 and the ground contact area S31 of the center land portion 331 adjacent to the second land portion 32 have a relationship of S2 <S31, so that the center land portion 331 The ground contact area S31 is set to be larger than the ground contact area S2 of the second land portion 32. As a result, the difference in rigidity between the center land portion 331 and the second land portion 32 is made uniform, and uneven wear in the tread portion center region is suppressed.

For example, in the configuration of FIG. 5, the center land portion 331 adjacent to the second land portion 32 includes a plurality of through lug grooves 43. Further, the through lug groove 43 has a bent shape bent in a step shape, penetrates the center land portion 331 in the tire width direction, and opens to the left and right edge portions. Further, these through lug grooves 43 are arranged at predetermined intervals in the tire circumferential direction to divide the center land portion 331 into a plurality of blocks.

Since the configuration of the through lug groove 43 of the center land portion 331 is the same as the configuration of the through lug groove 42 of the second land portion 32 (see FIGS. 6 and 7), the description thereof will be omitted.

Further, as a relationship between the second land portion 32 and the center land portion 331, the ground contact width W2 of the second land portion 32 and the ground contact width W31 of the center land portion 331 adjacent to the second land portion 32 have a relationship of W2 <W31. Has. Therefore, the ground contact width W31 of the center land portion 331 is set wider than that of the second land portion 32. Further, it is preferable to have a relationship of 1.03 ≦ W31 / W2 ≦ 1.20, and more preferably to have a relationship of 1.05 ≦ W31 / W2 ≦ 1.18.

Further, in FIG. 5, the groove width Wg2 of the through lug groove 42 of the second land portion 32 and the groove width Wg31 of the through lug groove 43 of the center land portion 331 adjacent to the second land portion 32 are 0.95 ≦ Wg31 /. It has a relationship of Wg2 ≦ 1.05. Therefore, in the second land portion 32 and the center land portion 331, the groove widths Wg2 and Wg31 of the through lug grooves 42 and 43 are set to be substantially the same.

As described above, in the configuration of FIG. 5, the second land portion 32 and the center land portion 331 are block rows formed by being divided into a plurality of through lug grooves 42 and 43, respectively. Further, the ground contact width W31 of the center land portion 331 is slightly wider than the ground contact width W2 of the second land portion 32. Further, the groove width Wg2 of the through lug groove 42 of the second land portion 32 and the groove width Wg31 of the through lug groove 43 of the center land portion 331 are set to be substantially the same. Further, the groove area ratio of the center land portion 331 is slightly smaller than the groove area ratio of the second land portion 32. As a result, the ground contact area S31 of the center land portion 331 is set to be larger than the ground contact area S2 of the second land portion 32 (S2 <S31).

Further, as a relationship between the shoulder land portion 31 and the center land portion 331, the contact area S1 of the shoulder land portion 31 and the contact area S31 of the center land portion 331 adjacent to the second land portion 32 have a relationship of S31 <S1. Has. Therefore, considering the above condition S2 <S31, the ground contact area S1 of the shoulder land portion 31 is the largest (S2 <S31 <S1). Specifically, the ratio S1 / S31 is preferably in the range of 1.01 ≦ S1 / S31 ≦ 1.20.

Further, in FIGS. 2 and 5, the contact width W1 of the shoulder land portion and the contact width W31 of the center land portion 331 adjacent to the second land portion 32 have a relationship of 0.95 ≦ W1 / W31 ≦ 1.05. Have. Therefore, the ground contact width W1 of the shoulder land portion 31 and the ground contact width W31 of the center land portion 331 are set to be substantially the same.

Further, as shown in FIG. 4, in a configuration in which three or more rows of center land portions 33 are provided between the second land portions 32 and 32 on the left and right of the tire, the ground contact area S2 of the second land portion 32 and the tire equatorial plane CL The contact area S32 of the nearest center land portion 332 has a relationship of S2 <S32. Therefore, the ground contact area S32 of the center land portion 332 is set to be larger than the ground contact area S2 of the second land portion 32. Further, the ratio S32 / S2 is preferably in the range of 1.03 ≦ S32 / S2 ≦ 1.15, and more preferably in the range of 1.05 ≦ S32 / S2 ≦ 1.13.

The center land area closest to the tire equatorial surface CL corresponds to this center land area when the center land area is on the tire equatorial surface CL, and when the circumferential main groove is on the tire equatorial surface. , The center land area on the side closer to the second land area to be compared is applicable.

For example, in the configuration of FIG. 4, the four rows of center land portions 33 between the second land portions 32, 32 on the left and right of the tire have the same land width (W31 = W32. See FIG. 2). The through lug groove 43 having the same structure and the same dimensions is provided. Therefore, all the center land portions 33 have the same ground contact area (S31 = S32).

In the configuration of FIG. 2, as shown in FIG. 5, the through lug groove 42 of the second land portion 32 and the lug groove 43 of the center land portion 331 (332) have the phase of the periodic change of the pitch lengths Pa to Pc. Are arranged in the tire circumferential direction in synchronization. However, the present invention is not limited to this, and the lug groove 42 of the second land portion 32 and the lug groove 43 of the center land portion 33 may be arranged with their phases shifted in the tire circumferential direction (not shown). Further, not limited to the above, the lug grooves 41 to 43 of each land portion 31 to 33 may be arranged with a single pitch length in the tire circumferential direction (not shown).

[Modification example]
FIG. 8 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. The figure outlines the tread profile and the groove wall shape of the circumferential main groove.

In the configuration of FIG. 1, as shown in FIG. 2, all the circumferential main grooves 21 and 22 have a structure in which the groove width is gradually reduced at a constant ratio.

However, the present invention is not limited to this, and the circumferential main groove 22b closest to the tire equatorial plane CL may have a stepped shape in which the groove width is gradually narrowed. Specifically, as shown in FIG. 8, the groove widths of the tread treads of the circumferential main grooves 21, 22a, and 22b are the same, but at the groove bottom of the circumferential main groove 22b closest to the tire equatorial plane CL. The groove width is narrower than the groove width at the groove bottom of the main groove 21 in the outermost peripheral direction.

For example, in the configuration of FIG. 8, the left and right circumferential main grooves 21 and 22a that partition the second land portion 32 have a wide groove bottom and have a structure in which the groove width is gradually reduced at a constant ratio. On the other hand, the left and right circumferential main grooves 22b and 22b that partition the center land portion 332 closest to the tire equatorial plane CL have the above-mentioned narrow groove bottom and have a shape in which the groove width is gradually narrowed. Have. As a result, the rigidity of the center land portion 332 closest to the tire equatorial plane CL is reinforced.

[effect]
As described above, the pneumatic tire 1 includes a carcass layer 13 and a belt layer 14 arranged on the outer periphery of the carcass layer 13, and a plurality of circumferential main grooves 21 extending in the tire circumferential direction. The tread surface is provided with 22 and a plurality of land portions 31, 32, 331, and 332 partitioned by the circumferential main grooves 21 and 22 (see FIG. 1). Further, the belt layer 14 includes a pair of intersecting belts 142 and 143 having belt angles having different symbols from each other, and a circumferential reinforcing layer 145 having a belt angle of 5 [deg] or less in absolute value (see FIG. 3). ). Further, in the cross-sectional view in the tire meridian direction, the foot X of the perpendicular line drawn from the outer edge portion 145e in the tire width direction of the circumferential reinforcing layer 145 to the tread profile is on the tread surface of the second land portion 32 (see FIG. 2). .. Further, the ground contact area S1 of the shoulder land portion 31, the ground contact area S2 of the second land portion 32, and the ground contact area S31 of the center land portion 331 adjacent to the second land portion 32 have a relationship of S2 <S1 and S2 <S31. Has (see FIG. 5).

In such a configuration, (1) the ground contact area S1 of the shoulder land portion 31 and the ground contact area S2 of the second land portion 32 have a relationship of S2 <S1, and therefore the rigidity between the shoulder land portion 31 and the second land portion 32. The difference is made uniform, and uneven wear of the tread portion shoulder area is suppressed. Further, (2) Since the ground contact area S2 of the second land portion 32 and the ground contact area S31 of the center land portion 331 adjacent to the second land portion 32 have a relationship of S2 <S31, the center land portion 331 and the second land portion 32 The difference in rigidity between the tread and the ground is made uniform, and uneven wear in the center region of the tread is suppressed. As a result, there is an advantage that the wear rate-determining of the tread portion shoulder region and the center region is made uniform, and the uneven wear resistance performance of the tire is improved.

Further, in the pneumatic tire 1, the contact width W1 of the shoulder land portion 31 and the contact width W2 of the second land portion 32 have a relationship of 1.03 ≦ W1 / W2 ≦ 1.20 (see FIG. 5). .. In such a configuration, when W2 <W1, the rigidity of the shoulder land portion 31 becomes higher than that of the second land portion 32. This has the advantage of suppressing uneven shoulder wear, which is particularly likely to occur on low flat tires.

Further, in the pneumatic tire 1, the contact width W2 of the second land portion 32 and the contact width W31 of the center land portion 331 adjacent to the second land portion 32 have a relationship of W2 <W31 (see FIG. 5). As a result, the rigidity of the center land portion 33 becomes higher than that of the second land portion 32, and there is an advantage that center wear, which tends to occur particularly on the tire mounted on the drive shaft of the vehicle, is suppressed.

Further, in the pneumatic tire 1, the contact area S1 of the shoulder land portion 31 and the contact area S31 of the center land portion 331 adjacent to the second land portion 32 have a relationship of S31 <S1 (see FIG. 5). In such a configuration, since the ground contact area S1 of the shoulder land portion 31 is large, the rigidity of the shoulder land portion 31 is higher than that of the center land portion 331. This has the advantage of suppressing uneven shoulder wear, which is particularly likely to occur on low flat tires.

Further, in the pneumatic tire 1, the relationship between the ground contact width W1 of the shoulder land portion 31 and the ground contact width W31 of the center land portion 331 adjacent to the second land portion 32 is 0.95 ≦ W1 / W31 ≦ 1.05. (See FIG. 5). In such a configuration, the ground contact width W1 of the shoulder land portion 31 and the ground contact width W31 of the center land portion 331 are made uniform, so that the rigidity of the shoulder land portion 31 is higher than that of the center land portion 331. This has the advantage of suppressing uneven shoulder wear, which is particularly likely to occur on low flat tires. Further, while making the ground contact width W1 of the shoulder land portion 31 and the ground contact width W31 of the center land portion 331 uniform, the ground contact area S1 of the shoulder land portion 31 and the ground contact area S31 of the center land portion 331 are related to each other S31 <S1. By setting to, there is an advantage that the area for securing the amount of tension when the tire touches the ground can be maintained while maintaining the response force to the lateral force between each land portion 31 to 33.

Further, in the pneumatic tire 1, the shoulder land portion 31 and the second land portion 32 each include a plurality of lug grooves 41 and 42 arranged at predetermined intervals in the tire circumferential direction (see FIG. 5). Further, the groove area ratio Sg1 of the lug groove 41 of the shoulder land portion 31 and the groove area ratio Sg2 of the through lug groove 42 of the second land portion 32 have a relationship of Sg1 <Sg2. As a result, the rigidity of the shoulder land portion 31 is higher than that of the second land portion 32, and there is an advantage that uneven shoulder wear, which is particularly likely to occur in low flat tires, is suppressed.

Further, in the pneumatic tire 1, the shoulder land portion 31 and the second land portion 32 each include a plurality of lug grooves 41 and 42 arranged at predetermined intervals in the tire circumferential direction (see FIG. 5). Further, the groove width Wg1 of the lug groove 41 of the shoulder land portion 31 and the groove width Wg2 of the through lug groove 42 of the second land portion 32 have a relationship of Wg2 <Wg1. As a result, the rigidity of the shoulder land portion 31 is higher than that of the second land portion 32, and there is an advantage that uneven shoulder wear, which is particularly likely to occur in low flat tires, is suppressed.

Further, in the pneumatic tire 1, the second land portion 32 and the center land portion 331 adjacent to the second land portion 32 are provided with a plurality of through lug grooves 42 and 43 arranged at predetermined intervals in the tire circumferential direction, respectively (FIG. FIG. 5). Further, the groove width Wg2 of the through lug groove 42 of the second land portion 32 and the groove width Wg31 of the lug groove 43 of the center land portion 331 adjacent to the second land portion 32 are 0.95 ≦ Wg31 / Wg2 ≦ 1.05. Has a relationship of. This has the advantage that the groove widths of the through lug grooves 42 and 43 of the land portions 32 and 331 located on the CL side of the tire equatorial plane with respect to the main groove 21 in the outermost peripheral direction are made uniform.

Further, in the pneumatic tire 1, the shoulder land portion 31 is a rib continuous in the tire circumferential direction, and the second land portion 32 and the center land portion 331 adjacent to the second land portion 32 are block rows (FIG. 5). reference). As a result, the rigidity of the shoulder land portion 31 is higher than that of the second land portion 32, and there is an advantage that uneven shoulder wear, which is particularly likely to occur in low flat tires, is suppressed.

Further, in the pneumatic tire 1, in the cross-sectional view in the tire meridional direction, the foot X of the perpendicular line drawn from the outer edge portion 145e in the tire width direction of the circumferential reinforcing layer 145 to the tread profile is the tread surface of the second land portion 32. It is outside the tire width direction from the midpoint M (see FIG. 2). In such a configuration, the change in the contact pressure distribution in the tire width direction due to the presence or absence of the circumferential belt layer 145 in the second land portion 32 becomes small. This has the advantage of suppressing uneven wear of the second land portion 32.

Further, in the pneumatic tire 1, the second land portion 32 includes a plurality of through lug grooves 42 arranged at predetermined intervals in the tire circumferential direction (see FIG. 5). The through lug groove 42 of the second land portion 32 has a bent shape that is bent in a step shape in the tire circumferential direction (see FIG. 6). Further, the foot X of the perpendicular line drawn from the edge portion 145e outside the tire width direction of the circumferential reinforcing layer 145 to the tread profile is outside the bent portion 421 of the bent shape of the through lug groove 42 in the tire width direction. In such a configuration, since the through lug groove 42 has the bent portion 421, the edge component of the second land portion 32 increases. This has the advantage of ensuring the traction performance particularly required for the tires mounted on the drive shaft of the vehicle.

Further, the pneumatic tire 1 is provided with three or more rows of center land portions 33 between the second land portions 32 and 32 on the left and right sides of the tire (see FIG. 4). Further, the ground contact area S2 of the second land portion 32 and the ground contact area S32 of the center land portion 332 closest to the tire equatorial plane CL have a relationship of S2 <S32. In such a configuration, since the ground contact area S2 of the second land portion 32 and the ground contact area S32 of the center land portion 332 have a relationship of S2 <S32, the rigidity difference between the center land portion 332 and the second land portion 32 becomes uniform. Therefore, there is an advantage that uneven wear in the center region of the tread portion is suppressed.

Further, in the pneumatic tire 1, the circumferential main groove 22b closest to the tire equatorial plane CL has a stepped shape in which the groove width is gradually narrowed (see FIG. 8). In such a configuration, the rigidity of the center land portion 332 closest to the tire equatorial plane CL is reinforced, and the rigidity difference between the land portions 31 to 33 is made uniform. This has an advantage that uneven wear of the land portions 32 and 33 particularly in the tread portion center region is suppressed.

[Applicable target]
In general, a low flat tire having a flatness of 75 [%] or less tends to cause uneven wear in the center region described above because the ground contact width is wide. Further, since the heavy load tire has a larger load when the tire is used than the passenger car tire, the diameter growth difference between the arranged region and the non-arranged region of the circumferential reinforcement layer tends to be large, and the shoulder region described above Uneven wear tends to occur. Therefore, by applying such a low-flat heavy-duty tire, there is an advantage that the above-mentioned effect of improving the uneven wear resistance of the tire can be remarkably obtained.

FIG. 9 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment of the present invention.

In this performance test, a plurality of different test tires were evaluated for uneven wear resistance. In this evaluation, a test tire with a tire size of 445 / 50R22.5 20 is assembled to a rim with a rim size of 22.5 x 14.00, and the test tire is given an air pressure of 830 [kPa]. Then, the test tire is mounted on the drive shaft of the 4 × 2 tractor trailer, which is the test vehicle, and the actual vehicle is evaluated with a standard load of 45.37 [kN] applied. Then, the difference in the amount of wear of each land portion when the tire wear rate is 80 [%] is measured and evaluated. This evaluation is performed by an index evaluation based on the conventional example (100), and the larger the value, the smaller the difference in the amount of wear in each land area, which is preferable.

The test tires of Examples 1 to 7 have the configurations shown in FIGS. 1 to 4. However, in Examples 1 to 6, the shoulder land portion 31 is a block row having the same through lug grooves 42 and 43 as the second land portion 32 and the center land portion 33. On the other hand, in the seventh embodiment, the shoulder land portion 31 is a rib provided with a non-penetrating lug groove 41 (see FIG. 5). Further, the tire contact width TW (see FIG. 4) is 360 [mm], and the width Ws (see FIG. 3) of the circumferential reinforcing layer 145 is 300 [mm]. Further, the width W2 of the second land portion 32 is 38.5 [mm], and the groove width Wg2 of the through lug groove 42 is 2.8 [mm]. Further, the groove length Lg1 (see FIG. 6) of the non-penetrating lug groove 41 in Example 7 is 5.0 [mm].

In the test tire of the conventional example 1, the land width and the lug groove width are constant in the configuration of the first embodiment. Further, the lug groove in each land portion is a through lug groove having a constant groove width. The test tire of the conventional example 2 has a wide shoulder land portion in the test tire of the conventional example 1. The test tire of the conventional example 3 is a rib in which all the land portions do not have a lug groove in the test tire of the conventional example 1.

As the test results show, it can be seen that the test tires of Examples 1 to 7 improve the uneven wear resistance performance of the tire.

1: Pneumatic tire, 11: Bead core, 12: Bead filler, 121: Lower filler, 122: Upper filler, 13: Carcus layer, 14: Belt layer, 141: High angle belt, 142, 143: Cross belt, 144: Belt cover, 145: Circumferential reinforcement layer, 15: Tread rubber, 16: Sidewall rubber, 17: Rim cushion rubber, 21, 22, 22a, 22b: Circumferential main groove, 31: Shoulder land, 32: Second land Part, 331, 332: Center land part, 41-43: Rug groove, 421: Bending part, 422: Bottom top, 423: Sipe, 424: Notch part

Claims (15)

A carcass layer, a belt layer arranged on the outer periphery of the carcass layer, a plurality of circumferential main grooves extending in the tire circumferential direction, and a plurality of land portions partitioned by the circumferential main groove are provided. Pneumatic tires for the tread surface
The outermost peripheral main groove in the tire width direction is defined as the outermost main groove, the outermost land portion in the tire width direction is defined as the shoulder land portion, and the second row from the outside in the tire width direction. The land part is defined as the second land part, and the land part on the tire equatorial plane side of the second land part is defined as the center land part.
The belt layer includes a pair of intersecting belts having belt angles having different symbols from each other, and a circumferential reinforcing layer having a belt angle of 5 [deg] or less in absolute value.
A tire meridian cross-section view, a foot of a perpendicular line which said drawn from the tire width direction outer edge portion of the circumferential reinforcing layer in the tread profile, Ri tread near the second land portion,
Wherein a contact area S1 of the shoulder land portion, a contact area S2 of the second land portion, and the contact area S31 in the center land portion adjacent to said second land portion is, have a relation of S2 <S1 and S2 <S31 ,and,
A pneumatic tire characterized in that the ground contact width W1 of the shoulder land portion and the ground contact width W2 of the second land portion have a relationship of 1.03 ≦ W1 / W2 ≦ 1.20 . The pneumatic tire according to claim 1, wherein the ground contact width W2 of the second land portion and the ground contact width W31 of the center land portion adjacent to the second land portion have a relationship of W2 <W31. The pneumatic tire according to claim 1 or 2 , wherein the ground contact area S1 of the shoulder land portion and the ground contact area S31 of the center land portion adjacent to the second land portion have a relationship of S31 <S1. Any of claims 1 to 3 in which the ground contact width W1 of the shoulder land portion and the ground contact width W31 of the center land portion adjacent to the second land portion have a relationship of 0.95 ≦ W1 / W31 ≦ 1.05. Pneumatic tires listed in one. The shoulder land portion and the second land portion each include a plurality of lug grooves arranged at predetermined intervals in the tire circumferential direction, and
The pneumatic tire according to any one of claims 1 to 4 , wherein the groove area ratio Sg1 of the shoulder land portion and the groove area ratio Sg2 of the second land portion have a relationship of Sg1 <Sg2. The shoulder land portion and the second land portion each include a plurality of lug grooves arranged at predetermined intervals in the tire circumferential direction, and
The air according to any one of claims 1 to 5 , wherein the groove width Wg1 of the lug groove in the shoulder land portion and the groove width Wg2 of the lug groove in the second land portion have a relationship of Wg2 <Wg1. Tires with rugs. The second land portion and the center land portion adjacent to the second land portion are provided with a plurality of lug grooves arranged at predetermined intervals in the tire circumferential direction, respectively, and
The groove width Wg2 of the lug groove in the second land portion and the groove width Wg31 of the lug groove in the center land portion adjacent to the second land portion have a relationship of 0.95 ≦ Wg31 / Wg2 ≦ 1.05. The pneumatic tire according to any one of claims 1 to 6 . The first one of claims 1 to 7 , wherein the shoulder land portion is a rib continuous in the tire circumferential direction, and the second land portion and the center land portion adjacent to the second land portion are block rows. Pneumatic tires. In the cross-sectional view in the tire meridional direction, the foot of the perpendicular line drawn from the outer edge portion of the circumferential reinforcement layer in the tire width direction to the tread profile is outside the midpoint of the tread surface of the second land portion in the tire width direction. The pneumatic tire according to any one of claims 1 to 8 . The second land portion includes a plurality of lug grooves arranged at predetermined intervals in the tire circumferential direction.
The lug groove of the second land portion has a bent shape that is bent in a step shape in the tire circumferential direction, and
Any of claims 1 to 9 , wherein the foot of the perpendicular line drawn from the outer edge portion of the circumferential reinforcing layer in the tire width direction to the tread profile is outside the bent portion of the bent shape of the lug groove in the tire width direction. Pneumatic tires listed in one. The center land portion having three or more rows is provided between the second land portions on the left and right of the tire, and
The pneumatic tire according to any one of claims 1 to 10 , wherein the ground contact area S2 of the second land portion and the ground contact area S32 of the center land portion closest to the equatorial plane of the tire have a relationship of S2 <S32. .. Tire The pneumatic tire according to any one of claims 1 to 11 , wherein the main groove in the circumferential direction closest to the equatorial plane has a stepped shape in which the groove width is gradually narrowed. The pneumatic tire according to any one of claims 1 to 12 , which is a heavy-duty tire having a flatness of 40 [%] or more and 75 [%] or less. A carcass layer, a belt layer arranged on the outer periphery of the carcass layer, a plurality of circumferential main grooves extending in the tire circumferential direction, and a plurality of land portions partitioned by the circumferential main groove are provided. Pneumatic tires for the tread surface
The outermost peripheral main groove in the tire width direction is defined as the outermost main groove, the outermost land portion in the tire width direction is defined as the shoulder land portion, and the second row from the outside in the tire width direction. The land part is defined as the second land part, and the land part on the tire equatorial plane side of the second land part is defined as the center land part.
The belt layer includes a pair of intersecting belts having belt angles having different symbols from each other, and a circumferential reinforcing layer having a belt angle of 5 [deg] or less in absolute value.
A tire meridian cross-section view, a foot of a perpendicular line which said drawn from the tire width direction outer edge portion of the circumferential reinforcing layer in the tread profile, Ri tread near the second land portion,
Wherein a contact area S1 of the shoulder land portion, a contact area S2 of the second land portion, and the contact area S31 in the center land portion adjacent to said second land portion is, have a relation of S2 <S1 and S2 <S31 ,and,
The air-filled portion is characterized in that the ground contact width W1 of the shoulder land portion and the ground contact width W31 of the center land portion adjacent to the second land portion have a relationship of 0.95 ≦ W1 / W31 ≦ 1.05. tire. A carcass layer, a belt layer arranged on the outer periphery of the carcass layer, a plurality of circumferential main grooves extending in the tire circumferential direction, and a plurality of land portions partitioned by the circumferential main groove are provided. Pneumatic tires for the tread surface
The outermost peripheral main groove in the tire width direction is defined as the outermost main groove, the outermost land portion in the tire width direction is defined as the shoulder land portion, and the second row from the outside in the tire width direction. The land part is defined as the second land part, and the land part on the tire equatorial plane side of the second land part is defined as the center land part.
The belt layer includes a pair of intersecting belts having belt angles having different symbols from each other, and a circumferential reinforcing layer having a belt angle of 5 [deg] or less in absolute value.
A tire meridian cross-section view, a foot of a perpendicular line which said drawn from the tire width direction outer edge portion of the circumferential reinforcing layer in the tread profile, Ri tread near the second land portion,
Wherein a contact area S1 of the shoulder land portion, a contact area S2 of the second land portion, and the contact area S31 in the center land portion adjacent to said second land portion is, have a relation of S2 <S1 and S2 <S31 ,
The center land portion having three or more rows is provided between the second land portions on the left and right of the tire, and
A pneumatic tire characterized in that the ground contact area S2 of the second land portion and the ground contact area S32 of the center land portion closest to the equatorial plane of the tire have a relationship of S2 <S32 .

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