JP2012144096A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving high speed durability of a tire by restraining tread separation.SOLUTION: This pneumatic tire 1 includes, in a tread, a plurality of circumferential directional main grooves 21-24 extending in the tire circumferential direction, and lands 31-35 partitioned by the circumferential directional main grooves 21-24. A groove width W1_sh of a first shoulder main groove 23 and a groove width W2_sh of a second shoulder main groove 24 have the relationship of W1_sh>W2_sh. A groove under gauge T_sh of the first shoulder main groove 23 and a groove under gauge T_ce of a center main groove 21 also have the relationship of T_sh<T_ce. The pneumatic tire 1 also includes a belt reinforcing layer 17 arranged outside in the tire radial direction of a pair of crossing belt plies 141 and 142 and under a groove of the first shoulder main groove 23. This belt reinforcing layer 17 is formed by arranging a plurality of belt cords, and an inclination θ to the tire circumferential direction of the belt cords falls within a range of 60[deg]≤θ≤120[deg].

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that can suppress tread separation and improve high-speed durability performance of the tire.

  In a pneumatic tire having an asymmetric tread pattern, the groove widths of the circumferential main grooves on the left and right sides of the tire may be different. In such a pneumatic tire, a configuration is known in which a belt reinforcing layer is disposed below the circumferential main groove in one side region of the tread portion. As a conventional pneumatic tire employing such a configuration, a technique described in Patent Document 1 is known. In the pneumatic tire of Patent Document 1, a belt reinforcing layer is disposed in order to improve the steering stability performance of the tire.

Japanese Patent Laid-Open No. 08-244408

  By the way, in a pneumatic tire, there exists a subject which should suppress tread separation. Tread separation is a phenomenon in which tread rubber is peeled off.

  Therefore, the present invention has been made in view of the above, and an object thereof is to provide a pneumatic tire that can suppress tread separation and improve high-speed durability performance of the tire.

  In order to achieve the above object, a pneumatic tire according to the present invention includes a carcass layer, a belt layer that has at least a pair of crossed belt plies laminated and is disposed on the outer periphery in the tire radial direction of the carcass layer, and the belt layer. The tread portion includes a plurality of circumferential main grooves extending in the tire circumferential direction and a land portion defined by the circumferential main grooves. In the pneumatic tire, among the plurality of circumferential main grooves, the left and right circumferential main grooves on the outermost side in the tire width direction are referred to as a first shoulder main groove and a second shoulder main groove, and the tire equator When the circumferential main groove between the line and the first shoulder main groove is called a center main groove, the groove width W1_sh of the first shoulder main groove and the groove width W2_sh of the second shoulder main groove W1_sh> W2_sh, and the lower shoulder gauge T_sh of the first shoulder main groove and the lower groove gauge T_ce of the center main groove have a relationship of T_sh <T_ce, and the pair of cross belt plies A belt reinforcing layer is disposed on the outer side in the tire radial direction and below the first shoulder main groove, the belt reinforcing layer is formed by arranging a plurality of belt cords, and the inclination angle θ of the belt cord with respect to the tire circumferential direction is It is in the range of 60 [deg] ≦ θ ≦ 120 [deg].

  In the pneumatic tire according to the present invention, a gauge difference T_ce−T_sh between the sub-groove gauge T_ce of the center main groove and the sub-groove gauge T_sh of the first shoulder main groove is 0.3 [mm] ≦ T_ce−. It is preferable to be within the range of T_sh ≦ 2.5 [mm].

  In the pneumatic tire according to the present invention, it is preferable that a sub-groove gauge T_ce of the center main groove is in a range of 2.0 [mm] ≦ T_ce ≦ 4.0 [mm].

  In the pneumatic tire according to the present invention, it is preferable that a sub-groove gauge T_sh of the first shoulder main groove is in a range of 1.5 [mm] ≦ T_sh ≦ 3.5 [mm].

  In the pneumatic tire according to the present invention, the end portion on the inner side in the tire width direction of the belt reinforcing layer is outside in the tire width direction with respect to the groove opening portion of the center main groove and the groove opening portion of the first shoulder main groove. The end of the belt reinforcing layer on the outer side in the tire width direction is on the outer side in the tire width direction with respect to the groove opening portion of the first shoulder main groove and the tire width direction of the cross belt ply. It is preferable that it exists in a tire width direction inner side rather than an outer edge part.

  In the pneumatic tire according to the present invention, the groove width W1_sh of the first shoulder main groove is in the range of 10 [mm] ≦ W1_sh ≦ 30 [mm], and the groove depth of the first shoulder main groove is The thickness H_sh is preferably in the range of 7.5 [mm] ≦ H_sh ≦ 10.0 [mm].

  Moreover, in the pneumatic tire according to the present invention, it is preferable that the first shoulder main groove side is mounted on the vehicle with the vehicle width direction inner side facing.

  In the pneumatic tire according to the present invention, the sub-groove gauge T_sh of the wide first shoulder main groove and the sub-groove gauge T_ce of the center main groove have a relationship of T_sh <T_ce, and the groove of the first shoulder main groove By disposing the belt reinforcing layer below, the movement of the shoulder land portion with the first shoulder main groove as a node is suppressed. Thereby, generation | occurrence | production of the tread separation in this position is suppressed, and there exists an advantage which the high-speed durability performance of a tire improves.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view showing a main groove of the pneumatic tire shown in FIG. FIG. 3 is a table showing the results of the evaluation test of the pneumatic tire according to the embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 1 shows a pneumatic radial tire for passenger cars as an example of a pneumatic tire.

  The pneumatic tire 1 includes a bead core 11, a bead filler 12, a carcass layer 13, a belt layer 14, a tread rubber 15, and a sidewall rubber 16 (see FIG. 1). The bead core 11 has an annular structure and is configured as a pair of left and right. The bead filler 12 is disposed on the outer periphery of the bead core 11 in the tire radial direction and reinforces the bead portion of the tire. The carcass layer 13 has a two-layer structure in which a pair of carcass plies 131 and 132 are stacked, and is spanned between the left and right bead cores 11 and 11 in a toroidal shape to form a tire skeleton. Further, both end portions of the carcass layer 13 are folded and locked outward in the tire width direction so as to wrap the bead filler 12.

  The belt layer 14 is configured by laminating a pair of cross belt plies 141 and 142, a belt cover layer 143 and an edge cover layer 144, and is disposed on the outer periphery of the carcass layer 13 in the tire radial direction. The pair of cross belt plies 141 and 142 are formed by arranging and rolling a plurality of belt cords made of steel material or organic fiber material. These cross belt plies 141 and 142 have a belt angle within a range of 30 [deg] or more and 60 [deg] or less. The belt angle refers to the inclination angle of the belt cord with respect to the tire circumferential direction. Moreover, these cross belt plies 141 and 142 are laminated so that the fiber directions of the belt cords cross each other by having belt angles with different signs (cross-ply structure). The belt cover layer 143 is formed by arranging and rolling a plurality of belt cords made of an organic fiber material. The belt cover layer 143 has a belt angle within a range of −10 [deg] or more and +10 [deg] or less, and is disposed on the outer side in the tire radial direction of the cross belt plies 141 and 142. The edge cover layer 144 is formed by arranging and rolling a plurality of belt cords made of an organic fiber material. The edge cover layer 144 has a belt angle within a range of −10 [deg] or more and +10 [deg] or less, and is disposed at an edge portion of the belt cover layer 143 on the outer side in the tire radial direction. The belt layer 14 may further include another belt ply (not shown).

  The tread rubber 15 is disposed on the outer circumference in the tire radial direction of the carcass layer 13 and the belt layer 14 to constitute a tread portion of the tire. The sidewall rubber 16 is configured as a pair of left and right sides, and is disposed on the outer side in the tire width direction of the carcass layer 13 to constitute a sidewall portion of the tire.

  The pneumatic tire 1 includes a plurality of circumferential main grooves 21 to 24 that extend in the tire circumferential direction and a plurality of land portions 31 to 35 that are partitioned by the circumferential main grooves 21 to 24. (See FIG. 1). The circumferential main grooves 21 to 24 are a groove width of 5.0 [mm] or more and 20.0 [mm] when the tire is mounted on a specified rim and applied with a specified internal pressure and is not loaded. ] A circumferential groove having the above groove depth. In this embodiment, the pneumatic tire 1 includes four circumferential main grooves 21 to 24 having a straight shape, and the center land portion 31 and a pair of left and right second land portions are provided by the circumferential main grooves 21 to 24. 32 and 33 and a pair of left and right shoulder land portions 34 and 35 are defined. Thereby, a tread pattern based on the rib-like land portions 31 to 35 is formed. The pneumatic tire 1 may have a tread pattern based on a block-shaped land portion (not shown).

  In this embodiment, the prescribed rim refers to “applied rim” prescribed in JATMA, “Design Rim” prescribed in TRA, or “Measuring Rim” prescribed in ETRTO. The specified internal pressure means “maximum air pressure” specified by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” specified by TRA, or “INFLATION PRESSURES” specified by ETRTO. The specified load means the “maximum load capacity” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO. However, in JATMA, in the case of tires for passenger cars, the specified internal pressure is air pressure 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

  Moreover, the pneumatic tire 1 has designation | designated of the mounting direction with respect to a vehicle (refer FIG. 1). This designation is displayed by, for example, unevenness formed on the sidewall portion of the tire.

  The pneumatic tire 1 has a tread pattern that is asymmetric with respect to the tire equator line CL (see FIG. 1). With this asymmetric tread pattern, both wet performance and dry performance of the tire can be achieved. If the groove widths W1_sh and W2_sh of the circumferential main grooves 23 and 24 on the left and right sides of the tire on the outermost side in the vehicle width direction are different, it can be said that the asymmetric tread pattern is obtained.

[Under groove gauge and belt reinforcement layer]
Generally, in a pneumatic tire having an asymmetric tread pattern, the groove widths of the circumferential main grooves on the left and right sides of the tire may be different. When a high-speed durability test is performed on such a tire, tread separation may occur in a circumferential main groove having a wider groove width among the left and right circumferential main grooves on the outermost side in the tire width direction. Tread separation is a phenomenon in which tread rubber is peeled off.

  This tread separation is considered to occur when the shoulder land portion rises with the wide circumferential main groove as a node due to high-speed rotation of the tire, and the shoulder land portion moves to generate heat.

  Therefore, the pneumatic tire 1 has the following configuration in order to suppress tread separation and improve the high-speed durability performance of the tire (see FIGS. 1 and 2).

  First, out of the plurality of circumferential main grooves 21 to 24, the left and right circumferential main grooves 23 and 24 on the outermost side in the tire width direction are referred to as a first shoulder main groove and a second shoulder main groove (see FIG. 1). ). The circumferential main groove 21 between the tire equator line CL and the first shoulder main groove 23 is referred to as a center main groove. Further, in the tire meridian direction end view, lengths D1 and D2 from the tire equator line CL to the left and right ends of the tires of the cross belt plies 141 and 142 are respectively taken. Then, a center region and a shoulder region of the tread portion are defined with a position 60% of the lengths D1 and D2 (positions of 0.6 × D1 and 0.6 × D2) from the tire equator line CL as a boundary.

  At this time, at least one center main groove 21 is disposed in the center region of the tread portion on the first shoulder main groove 23 side. For example, in this embodiment, the first shoulder main groove 23 and the second shoulder main groove 24 are arranged at positions of 0.6 × D1 and 0.6 × D2 from the tire equator line CL, respectively. The center region of the tread portion and the left and right shoulder regions are partitioned by these circumferential main grooves 23 and 24. Further, in the center region between the tire equator line CL and the first shoulder main groove 23 and between the tire equator line CL and the second shoulder main groove 24, that is, in the left and right tread center regions with the tire equator line CL as a boundary. Main grooves 21 and 22 are arranged respectively.

  Further, the groove width W1_sh of the first shoulder main groove 23 and the groove width W2_sh of the second shoulder main groove 24 have a relationship of W1_sh> W2_sh (see FIG. 1). Specifically, the pneumatic tire 1 is mounted on the vehicle with the first shoulder main groove 23 side in the vehicle width direction. At this time, the groove width W1_sh of the first shoulder main groove 23 on the inner side in the vehicle width direction is wider than the groove width W2_sh of the second shoulder main groove 24 on the outer side in the vehicle width direction. Thereby, an asymmetric tread pattern with respect to the tire equator line CL is formed. At this time, by setting the groove width W1_sh of the first shoulder main groove 23 on the inner side in the vehicle width direction to be wide, the wet performance of the tire is ensured. On the other hand, by setting the groove width W2_sh of the second shoulder main groove 24 on the outer side in the vehicle width direction to be narrow, the rigidity of the shoulder land portion 35 is ensured and the dry performance of the tire is enhanced.

  Further, the sub-groove gauge T_sh of the first shoulder main groove 23 and the sub-groove gauge T_ce of the center main groove 21 have a relationship of T_sh <T_ce (see FIG. 2). That is, the sub-groove gauge T_sh of the first shoulder main groove 23 having a wide groove width W1_sh is set small. Thereby, the rising of the shoulder land portion 34 at the time of high-speed rotation of the tire is suppressed, and the occurrence of tread separation at this position is suppressed.

  Further, the above configuration is adopted only in the region on the first shoulder main groove 23 side of the tread portion, and in the region on the other side of the second shoulder main groove 24, the sub-groove gauge of the second shoulder main groove 24 and the tire thereof. It is preferable that the sub-groove gauge of the center main groove 22 on the equator line CL side is set to be the same. Thereby, the rise of the shoulder block is relieved.

  The pneumatic tire 1 includes a belt reinforcing layer 17 (see FIGS. 1 and 2). The belt reinforcing layer 17 is formed by arranging and rolling a plurality of belt cords made of an organic fiber material. The belt reinforcing layer 17 is disposed on the outer side in the tire radial direction of the pair of cross belt plies 141 and 142 and below the first shoulder main groove 23. At this time, the inclination angle θ of the belt cord with respect to the tire circumferential direction is preferably in the range of 60 [deg] ≦ θ ≦ 120 [deg], and in the range of 75 [deg] ≦ θ ≦ 105 [deg]. It is more preferable.

  For example, in this embodiment, the ends of the pair of cross belt plies 141 and 142 extend to the outer side in the tire width direction from the first shoulder main groove 23 (see FIG. 2). Further, the belt reinforcing layer 17 has a belt-like structure and is disposed around the cross belt plies 141 and 142 by being wound from the outer side in the tire circumferential direction. Further, the belt reinforcing layer 17 is disposed so as to cover the lower portion of the first shoulder main groove 23. Further, the sub-groove gauge T_sh of the first shoulder main groove 23 is narrowed by the thickness of the belt reinforcing layer 17, and the relationship (T_sh <T_ce) with the sub-groove gauge T_ce of the center main groove 21 is adjusted. A belt cover layer 143 is disposed so as to cover the cross belt plies 141 and 142 and the belt reinforcing layer 17 from the outer side in the tire radial direction. Further, the edge cover layer 144 is located on the outer side in the tire radial direction from the belt reinforcing layer 17, and is disposed at a position different from the belt reinforcing layer 17 in a plan view.

  In such a configuration, when the tire rolls, the belt reinforcing layer 17 is disposed below the first shoulder main groove 23, so that the movement of the shoulder land portion 34 with this position as a node is suppressed. Thereby, the rising of the shoulder land portion 33 at the time of high-speed rotation of the tire is suppressed, and the occurrence of tread separation at this position is suppressed. Further, the function of the belt reinforcing layer 17 is appropriately ensured by optimizing the inclination angle θ of the belt reinforcing layer 17 with respect to the tire circumferential direction of the belt cord (60 [deg] ≦ θ ≦ 120 [deg]). The

  In this pneumatic tire 1, the gauge difference T_ce−T_sh between the lower groove gauge T_ce of the center main groove 21 and the lower groove gauge T_sh of the first shoulder main groove 23 is 0.3 [mm] ≦ T_ce−T_sh ≦ It is preferably in the range of 2.5 [mm] (see FIGS. 1 and 2). In addition, the sub-groove gauge T_ce of the center main groove 21 is preferably in the range of 2.0 [mm] ≦ T_ce ≦ 4.0 [mm]. In addition, the sub-groove gauge T_sh of the first shoulder main groove 23 is preferably in the range of 1.5 [mm] ≦ T_sh ≦ 3.5 [mm]. By these, generation | occurrence | production of tread separation is suppressed effectively.

  Here, the sub-groove gauges T_sh and T_ce are measured as the distance from the groove bottom of the circumferential main groove to the outermost layer of the belt layer 14 (the distance to the belt cord constituting the outermost layer of the belt layer 14). The outermost layer of the belt layer 14 includes a belt cover layer 143 and an edge cover layer 144.

  In the pneumatic tire 1, the end portion 171 on the inner side in the tire width direction of the belt reinforcing layer 17 is located on the outer side in the tire width direction from the groove opening portion of the center main groove 21 and from the groove opening portion of the first shoulder main groove 23. Is also preferably on the inner side in the tire width direction (see FIG. 2). In other words, the end portion 171 on the inner side in the tire width direction of the belt reinforcing layer 17 is more on the inner side of the land portion than the left and right edge portions of the second land portion 32 partitioned by the center main groove 21 and the first shoulder main groove 23. Placed in.

  In addition, the end 172 of the belt reinforcing layer 17 on the outer side in the tire width direction is wider than the end of the first shoulder main groove 23 in the tire width direction and the outer side of the cross belt ply 142 in the tire width direction. It is preferable to be inside in the direction (see FIG. 2). In other words, the end portion 172 of the belt reinforcing layer 17 on the outer side in the tire width direction is located on the outer side in the tire width direction of the land portion with respect to the inner edge portion in the tire width direction of the shoulder land portion 34 defined by the first shoulder main groove 23. is there. Further, the end portion 172 of the belt reinforcing layer 17 on the outer side in the tire width direction is on the inner side in the tire width direction than the end portion of the cross belt ply 142 on the outer side in the tire radial direction.

  In the above configuration, the belt reinforcing layer 17 has a width that is at least larger than the groove width W1_sh of the first shoulder main groove 23 and is disposed over the entire region below the first shoulder main groove 23. Thereby, generation | occurrence | production of tread separation is suppressed effectively. Further, by installing the belt reinforcing layer 17 in a necessary and sufficient range, an increase in tire weight is prevented.

  In the above configuration, the end portion 172 of the belt reinforcing layer 17 on the outer side in the tire width direction is disposed with an interval of 5 mm or more on the inner side in the tire width direction with respect to the end portion of the cross belt ply 142. Is preferred. Thereby, the stress concentration at the end of the cross belt ply 142 is alleviated, and belt edge separation is suppressed.

  Further, in the pneumatic tire 1, the groove width W1_sh of the first shoulder main groove 23 is in the range of 10 [mm] ≦ W1_sh ≦ 30 [mm], and the groove depth H_sh of the first shoulder main groove 23 is set. Is preferably in the range of 7.5 [mm] ≦ H_sh ≦ 10.0 [mm] (see FIG. 2). Thereby, the groove width W1_sh and the groove depth H_sh of the first shoulder main groove 23 are optimized. The belt reinforcing layer 17 is set according to the groove width W1_sh of the first shoulder main groove 23 as described above.

[effect]
As described above, the pneumatic tire 1 includes the carcass layer 13 and the belt layer 14 that has at least one pair of crossed belt plies 141 and 142 stacked and is disposed on the outer periphery in the tire radial direction of the carcass layer 13. The tread rubber 15 is provided outside the belt layer 14 in the tire radial direction (see FIG. 1). The pneumatic tire 1 has a plurality of circumferential main grooves 21 to 24 extending in the tire circumferential direction and land portions 31 to 35 defined by the circumferential main grooves 21 to 24 as tread portions. Prepare. Further, the groove width W1_sh of the first shoulder main groove 23 and the groove width W2_sh of the second shoulder main groove 24 have a relationship of W1_sh> W2_sh. Further, the sub-groove gauge T_sh of the first shoulder main groove 23 and the sub-groove gauge T_ce of the center main groove 21 have a relationship of T_sh <T_ce. The pneumatic tire 1 also includes a belt reinforcing layer 17 disposed on the outer side in the tire radial direction of the pair of cross belt plies 141 and 142 and below the groove of the first shoulder main groove 23. The belt reinforcing layer 17 is formed by arranging a plurality of belt cords, and an inclination angle θ of these belt cords with respect to the tire circumferential direction is in a range of 60 [deg] ≦ θ ≦ 120 [deg].

  In such a configuration, the sub-groove gauge T_sh of the wide first shoulder main groove 23 and the sub-groove gauge T_ce of the center main groove 21 have a relationship of T_sh <T_ce. By arranging the belt reinforcing layer 17, the movement of the shoulder land portion 34 with the first shoulder main groove 23 as a node is suppressed. Thereby, generation | occurrence | production of the tread separation in this position is suppressed, and there exists an advantage which the high-speed durability performance of a tire improves. Further, the belt reinforcing layer 17 is disposed under the first shoulder main groove 23, so that there is an advantage that the sub-groove gauge T_sh of the first shoulder main groove 23 can be adjusted.

  Further, in this pneumatic tire 1, the gauge difference T_ce−T_sh between the groove depth gauge T_ce of the center main groove 21 and the groove width gauge T_sh of the first shoulder main groove 23 is 0.3 [mm] ≦ T_ce−T_sh ≦ It is in the range of 2.5 [mm] (see FIGS. 1 and 2). Thereby, since the sub-groove gauge difference T_ce-T_sh is optimized, there is an advantage that occurrence of tread separation is effectively suppressed. For example, if T_ce−T_sh <0.3 [mm], the effect of suppressing the movement of the shoulder land portion 34 with the first shoulder main groove 23 as a node cannot be sufficiently obtained, which is not preferable. Further, when 2.5 [mm] <T_ce−T_sh, the rectangular ratio of the tire ground contact shape becomes inappropriate, and the deflection of the shoulder land portion 34 increases, which is not preferable.

  Moreover, in this pneumatic tire 1, the sub-groove gauge T_ce of the center main groove 21 is in the range of 2.0 [mm] ≦ T_ce ≦ 4.0 [mm] (see FIGS. 1 and 2). Thereby, since the sub-groove gauge T_ce of the center main groove 21 is optimized, there is an advantage that generation of tread separation is effectively suppressed. For example, when T_ce <2.0 [mm], the tire ground contact shape tends to buckle (a phenomenon in which the center region ground contact shape is shortened), and a load is easily applied to the shoulder land portion, which is not preferable. In addition, 4.0 [mm] <T_ce is not preferable because heat storage in the center land portion increases and tread separation is likely to occur in the center land portion.

  Moreover, in this pneumatic tire 1, the sub-groove gauge T_sh of the first shoulder main groove 23 is in the range of 1.5 [mm] ≦ T_sh ≦ 3.5 [mm] (see FIGS. 1 and 2). Thereby, since the sub-groove gauge T_sh of the first shoulder main groove 23 is optimized, there is an advantage that the occurrence of tread separation is effectively suppressed. For example, when T_sh <1.5 [mm], belt separation tends to occur, and when 3.5 [mm] <T_sh, tread separation due to heat storage tends to occur, which is not preferable.

  In the pneumatic tire 1, the end portion 171 on the inner side in the tire width direction of the belt reinforcing layer 17 is located on the outer side in the tire width direction from the groove opening portion of the center main groove 21 and from the groove opening portion of the first shoulder main groove 23. Is also on the inner side in the tire width direction, and the end 172 on the outer side in the tire width direction of the belt reinforcing layer 17 is outside in the tire width direction with respect to the groove opening of the first shoulder main groove 23 and in the tire width direction of the cross belt ply 142. It is inside the tire width direction from the outer end (see FIG. 2). With such a configuration, there is an advantage that occurrence of tread separation is effectively suppressed by installing the belt reinforcing layer 17 in a necessary and sufficient range. For example, if the installation range of both ends of the belt reinforcement layer 17 is too narrow, the effect of suppressing the tread separation cannot be sufficiently obtained. Conversely, if the installation range of both ends of the belt reinforcement layer 17 is too wide, the tire weight is increased. Since it increases and rolling resistance deteriorates, it is not preferable.

  Further, in the pneumatic tire 1, the groove width W1_sh of the first shoulder main groove 23 is in the range of 10 [mm] ≦ W1_sh ≦ 30 [mm], and the groove depth H_sh of the first shoulder main groove 23 is set. Is in the range of 7.5 [mm] ≦ H_sh ≦ 10 [mm] (see FIG. 2). In such a configuration, since the groove width W1_sh and the groove depth H_sh of the first shoulder main groove 23 are optimized, there is an advantage that occurrence of tread separation is effectively suppressed.

  FIG. 3 is a table showing the results of the evaluation test of the pneumatic tire according to the embodiment of the present invention. In this performance test, a test on high-speed durability performance was performed for a plurality of different pneumatic tires.

  In the high-speed durability test, a pneumatic tire having a tire size of 225 / 45R17 was assembled on a rim of 17 × 7.5 J, and a pneumatic pressure of 280 [kPa] and a load of 5.0 [kN] were applied to the pneumatic tire. Is done. In the indoor drum testing machine, the traveling speed is increased by 10 [km / h] every 240 minutes from 240 [km / h]. Then, the number of steps (the number of increases in travel speed) until the tire breaks down is measured and evaluated. This evaluation is recognized as superior in two or more steps.

  The pneumatic tire 1 of Examples 1-5 has the structure described in FIG. 1 and FIG. In the pneumatic tire 1, the sub-groove gauge T_sh of the first shoulder main groove 23 having a wide groove width and the sub-groove gauge T_ce of the center main groove 21 have a relationship of T_sh <T_ce. Further, a belt reinforcing layer 17 made of organic fiber is disposed on the outer side in the tire radial direction of the pair of cross belt plies 141 and 142 and below the first shoulder main groove 23. Further, the end portion 171 on the inner side in the tire width direction of the belt reinforcing layer 17 is on the outer side in the tire width direction with respect to the center main groove 21 and on the inner side in the tire width direction with respect to the first shoulder main groove 23. Further, the end portion 172 of the belt reinforcing layer 17 on the outer side in the tire width direction is on the outer side in the tire width direction with respect to the first shoulder main groove 23 and on the inner side in the tire width direction with respect to the end portion of the cross belt ply 142.

  In the pneumatic tire of Conventional Example 1, the sub-groove gauge T_sh of the first shoulder main groove having the wide groove width is the same as the sub-groove gauge T_ce of the center main groove, and no belt reinforcing layer is provided. The pneumatic tire of Conventional Example 2 has the same lower groove gauge T_sh of the first shoulder main groove and the lower groove gauge T_ce of the center main groove having a wide groove width, but includes a belt reinforcing layer made of organic fibers. Yes. Further, the inner end of the belt reinforcing layer in the tire width direction is between the tire equator line and the center main groove. Further, the end of the belt reinforcing layer on the outer side in the tire width direction is on the outer side in the tire width direction with respect to the first shoulder main groove and on the inner side in the tire width direction with respect to the end portion of the cross belt ply.

  Each of these pneumatic tires has an asymmetric tread pattern because the groove width W1_sh of the first shoulder main groove and the groove width W2_sh of the second shoulder main groove have a relationship of W1_sh> W2_sh. .

  As shown in the evaluation results, it can be seen that in the pneumatic tire 1 of Examples 1 to 5, the high-speed durability performance of the tire is improved as compared with the pneumatic tires of Conventional Examples 1 and 2 (see FIG. 3). Further, when Examples 1 and 2 and Comparative Example 1 are compared, the high-speed durability performance of the tire is improved by optimizing the belt angle (belt cord inclination angle with respect to the tire circumferential direction) θ of the belt reinforcing layer 17. I understand that. Further, when Examples 1 and 3 and Comparative Example 2 are compared, it is understood that the high-speed durability performance of the tire is improved by optimizing the sub-groove gauge difference T_ce−T_sh. Moreover, when Examples 1 and 4 are compared, it can be seen that the high-speed durability performance of the tire is maintained by optimizing the sub-groove gauge T_sh of the first shoulder main groove 23. Moreover, when Examples 1 and 5 are compared, it can be seen that the high-speed durability performance of the tire is improved by optimizing the installation range of the belt reinforcing layer 17. In addition, since the tire weight increases as the width of the belt reinforcing layer increases, it is not preferable.

  DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 11 Bead core, 12 Bead filler, 13 Carcass layer, 131, 132 Carcass ply, 14 Belt layer, 141, 142 Cross belt ply, 143 Belt cover layer, 144 Edge cover layer, 15 Tread rubber, 16 Side wall Rubber, 17 Belt reinforcing layer, 171, 172 End, 21, 22 Center main groove, 23 First shoulder main groove, 24 Second shoulder main groove, 31 Center land portion, 32, 33 Second land portion, 34, 35 Shoulder Land

Claims (7)

A carcass layer, a belt layer having at least a pair of crossed belt plies stacked and disposed on the outer periphery in the tire radial direction of the carcass layer; and a tread rubber disposed on the outer side in the tire radial direction of the belt layer; A pneumatic tire including a plurality of circumferential main grooves extending in the tire circumferential direction and a land portion defined by the circumferential main grooves in a tread portion,
Among the plurality of circumferential main grooves, the left and right circumferential main grooves on the outermost side in the tire width direction are referred to as a first shoulder main groove and a second shoulder main groove, and the tire equator line and the first shoulder main groove When the circumferential main groove between the grooves is called the center main groove,
The groove width W1_sh of the first shoulder main groove and the groove width W2_sh of the second shoulder main groove have a relationship of W1_sh> W2_sh, and the sub-groove gauge T_sh of the first shoulder main groove and the groove of the center main groove The lower gauge T_ce has a relationship of T_sh <T_ce, and
A belt reinforcing layer is disposed on the outer side in the tire radial direction of the pair of cross belt plies and below the first shoulder main groove, and the belt reinforcing layer is formed by arranging a plurality of belt cords. A pneumatic tire having an inclination angle θ with respect to a circumferential direction in a range of 60 [deg] ≦ θ ≦ 120 [deg].   Gauge difference T_ce-T_sh between sub-groove gauge T_ce of the center main groove and sub-groove gauge T_sh of the first shoulder main groove is within a range of 0.3 [mm] ≦ T_ce−T_sh ≦ 2.5 [mm]. The pneumatic tire according to claim 1.   The pneumatic tire according to claim 1 or 2, wherein a sub-groove gauge T_ce of the center main groove is in a range of 2.0 [mm] ≤ T_ce ≤ 4.0 [mm].   The pneumatic tire according to any one of claims 1 to 3, wherein a sub-groove gauge T_sh of the first shoulder main groove is in a range of 1.5 [mm] ≤ T_sh ≤ 3.5 [mm].   An end of the belt reinforcing layer on the inner side in the tire width direction is on the outer side in the tire width direction with respect to the groove opening part of the center main groove and on the inner side in the tire width direction with respect to the groove opening part of the first shoulder main groove, and An end of the belt reinforcing layer on the outer side in the tire width direction is on the outer side in the tire width direction with respect to the groove opening of the first shoulder main groove and on the inner side in the tire width direction with respect to the end on the outer side in the tire width direction of the cross belt ply. The pneumatic tire according to any one of claims 1 to 4.   The groove width W1_sh of the first shoulder main groove is in the range of 10 [mm] ≦ W1_sh ≦ 30 [mm], and the groove depth H_sh of the first shoulder main groove is 7.5 [mm] ≦ H_sh The pneumatic tire according to claim 1, which is in a range of ≦ 10.0 [mm].   The pneumatic tire according to any one of claims 1 to 6, wherein the pneumatic tire is attached to a vehicle with the first shoulder main groove side facing inward in the vehicle width direction.

Images