JP5130751B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve the tire's low rolling resistance performance while maintaining the wet performance and snow braking performance of the tire.

  In recent pneumatic tires, width direction grooves are arranged in the center region and the shoulder region of the tread portion in order to ensure the braking / driving performance of the tire. Such a tread pattern is called a traction pattern.

  However, in the configuration in which many grooves in the width direction are arranged in the tread portion center region, the displacement of the tread portion center region toward the outer side in the tire radial direction increases during inflation. For this reason, the change of the tire shape at the time of tire grounding becomes large, and there exists a subject that the rolling resistance of a tire deteriorates.

  In view of this problem, recent pneumatic tires employ a configuration in which the width of the widthwise groove is narrowed or a structure in which the depth of the widthwise groove is shallow. However, with these configurations, it is difficult to maintain tire wet performance and snow braking performance.

  In addition, the technique described in patent document 1 is known for the conventional pneumatic tire relevant to this invention. In the conventional pneumatic tire, at least a pair of circumferential grooves extending along the tire circumferential direction is arranged in the tread, and the tread is arranged at least on the tire land side row on the tire equatorial plane and on the tire shaft of the center land row. Pneumatically divided into a plurality of land portion rows with both side land portion rows arranged on the outer side in the direction, and at least a plurality of lateral grooves extending in the tire axial direction are arranged in the tire land direction in the central land portion row and the both side land portion rows The transverse groove disposed in at least the central land portion row of the tire extends at least 15% or more of a width in the tire axial direction of the central land portion row from both ends of the land portion toward the inward portion of the land portion. The row or block is a false block, and the block or the false block of the central land portion row is near the corner on one side in the tire circumferential direction facing the circumferential groove, and its depth toward the circumferential main groove. Gradually The forming a chamfered portion widthwise side near the central land portion row along the tire circumferential direction by irregularities, and wherein the. Further, the lateral groove on one side in the tire axial direction of the central land portion row and the lateral groove on the other side in the tire axial direction are connected by a first narrow groove having a narrower width than the lateral groove. To do.

International Publication No. 2004/041556 Pamphlet

  An object of the present invention is to provide a pneumatic tire that can improve the low rolling resistance performance of the tire while maintaining the wet performance and snow braking performance of the tire.

In order to achieve the above object, a pneumatic tire according to the present invention includes at least three circumferential main grooves extending in the tire circumferential direction, a plurality of widthwise grooves extending in the tire width direction, and the circumferential direction. A pneumatic tire having, in a tread portion, a main groove and a plurality of block rows defined by the width direction groove, and is based on the width direction groove inclined upward in a plan view of the tread portion. The block row and the block row based on the widthwise groove inclined to the left are arranged adjacent to each other, and the groove width of the widthwise groove in the tread shoulder region is the center line of the block row The width of the groove in the width direction groove in the outer region in the tire width direction is increased by starting to widen from the outer region in the tire width direction with the boundary to the opening on the outer side in the tire width direction of the width direction groove. And the inclination angle of the width direction groove is increased as the direction from the block row of the inner side in the tire width direction in the block row in the tire width direction outer side with respect to the tire circumferential direction and the groove depth of the widthwise grooves h2 And the groove depth h1 of the circumferential main groove have a relationship of 0.30 ≦ h2 / h1 ≦ 0.70, and the groove width w2 of the widthwise groove and the groove width w1 of the circumferential main groove are It has a relationship of 0.20 ≦ w2 / w1 ≦ 0.50.

  In this pneumatic tire, (1) a block row based on a widthwise groove inclined to the right and a block row based on a widthwise groove inclined to the left are arranged adjacent to each other. The groove width direction of the width direction groove of the matching block row is different. For this reason, opening of each width direction groove | channel at the time of inflation of a tire is suppressed by what is called a twist effect. Thereby, the change of the tire shape at the time of tire contact is suppressed, and there is an advantage that the low rolling resistance performance of the tire is improved. Moreover, (2) Since the groove volume of the width direction groove | channel is expanded in the at least one opening part of the width direction groove | channel, the drainage property of each width direction groove | channel improves. Thereby, there exists an advantage which the wet performance of a tire improves. (3) Since the inclination angle of the width direction groove with respect to the tire circumferential direction increases from the block row on the inner side in the tire width direction toward the block row on the outer side in the tire width direction, the tire in the tread portion center region at the time of inflation The displacement outward in the radial direction is smaller than the displacement outward in the tire radial direction of the tread portion shoulder region. Thereby, the change of the tire shape at the time of tire contact is suppressed, and there is an advantage that the low rolling resistance performance of the tire is improved. Further, (4) the ratio h2 / h1 between the groove depth h2 of the width direction groove and the groove depth h1 of the circumferential main groove, and the groove width w2 of the width direction groove and the groove width w1 of the circumferential main groove Since the ratio w2 / w1 is optimized, the groove volume of the width direction groove is appropriately secured. Thereby, there exists an advantage by which the snow braking performance of a tire is maintained.

  In the pneumatic tire according to the present invention, the groove in the width direction in the center region of the tread portion expands the groove volume at the openings on both sides.

  A high contact pressure acts on the center area of the tread portion when the tire contacts the ground. Moreover, the width direction groove | channel expands the groove volume in the opening part of both sides, and the drainage property of the width direction groove | channel improves. Therefore, this pneumatic tire has an advantage of improving the wet performance of the tire because the drainage performance in the tread portion center region where the contact pressure is high is improved.

  In the pneumatic tire according to the present invention, when the area of 70 [%] of the contact width T of the tire centering on the center line CL is taken, the five circumferential main grooves are arranged in the area. The

  In this pneumatic tire, the drainage performance is improved by the circumferential main groove, and the contact pressure of each block row is made uniform to control the distortion of the tread portion. Thereby, there exists an advantage which can reduce the rolling resistance of a tire, maintaining the wet performance of a tire.

  Further, the pneumatic tire according to the present invention includes a block width R1 of the block row defined by the inner three circumferential main grooves among the five circumferential main grooves, and an outer circumferential main groove. The block width R2 of the partitioned block row has a relationship of 0.95 ≦ R1 / R2 ≦ 1.05.

  In this pneumatic tire, the relationship between the block widths R1 and R2 of each block row in the tread portion center region is optimized, so that the contact pressure of each block row at the time of tire contact is made uniform. Thereby, there is an advantage that uneven wear of the block row is suppressed.

  In the pneumatic tire according to the present invention, the total groove area A of the circumferential main grooves and the total groove area B of the width direction grooves on the ground contact surface of the tire are 0.25 ≦ B / (A + B) ≦ 0. There are 45 relationships.

  In this pneumatic tire, the ratio B / (A + B) of the total groove area B of the width direction groove to the total groove area A + B of the tire ground contact surface is optimized, whereby the block rigidity of the block row is optimized. Thereby, there is an advantage that the rolling resistance of the tire is reduced, and there is an advantage that the uneven wear resistance performance of the tire is improved.

  In the pneumatic tire according to the present invention, the ratio G of the sum A + B of the total groove area A of the circumferential main grooves and the total groove area B of the width direction grooves on the ground contact surface of the tire and the ground contact area X of the tire G = (A + B) / X is in the range of G ≦ 0.25.

  In this pneumatic tire, since the ratio of the total groove area A + B to the ground contact area X is optimized, the rigidity of the entire block row is ensured. Thereby, the distortion of the block row at the time of tire contact is suppressed, and there is an advantage that the rolling resistance of the tire is reduced.

  In the pneumatic tire according to the present invention, the groove wall angle θ of at least one of the circumferential main grooves is in the range of θ ≧ 8 [deg].

  In this pneumatic tire, since the range of the groove wall angle θ of the circumferential main groove is optimized, there is an advantage that the rolling resistance of the tire is reduced.

  Further, in the pneumatic tire according to the present invention, the groove wall angle θ of at least one of the circumferential main grooves changes as it goes in the tire circumferential direction.

  In this pneumatic tire, the rigidity of the land portion (block row) is increased by changing the groove wall angle θ. Thereby, the fall of the land part is suppressed and there exists an advantage which the rolling resistance of a tire increases.

  In the pneumatic tire according to the present invention, a narrow groove extending in the tire circumferential direction is formed at the outer end in the width direction of the tread portion.

  In this pneumatic tire, uneven wear of the block row is suppressed by the positive wear of the fine ribs formed by the fine grooves when the tire contacts the ground. Thereby, there exists an advantage which the uneven wear-proof performance of a tire improves.

  In the pneumatic tire according to the present invention, a narrow groove extending in the tire circumferential direction is formed in the buttress portion.

  In this pneumatic tire, the narrow groove is closed when the tire is in contact with the ground, whereby the contact pressure in the shoulder region (block row) of the tread portion is reduced and uneven wear is suppressed. Thereby, there exists an advantage which the uneven wear-proof performance of a tire improves.

  Further, in the pneumatic tire according to the present invention, when the belt reinforcing layer is disposed in the tread portion, the thickness of the tread rubber from the groove bottom of the circumferential main groove in the center region of the tread portion to the belt reinforcing layer. t is in the range of 3.0 [mm] ≦ t ≦ 5.5 [mm].

  In this pneumatic tire, since the thickness t of the tread rubber under the circumferential main groove is optimized, there is an advantage that the rolling resistance of the tire is effectively reduced.

  In the pneumatic tire according to the present invention, the tan δ of the tread rubber when heated at 100 ° C. is in the range of 0.01 ≦ tan δ ≦ 0.10.

  In this pneumatic tire, since tan δ of the tread rubber is optimized, the hysteresis loss of the tread portion is reduced. Thereby, there exists an advantage by which the rolling resistance of a tire is reduced effectively.

  In the pneumatic tire according to the present invention, the opening of the width direction groove is expanded in both the groove width direction and the groove depth direction.

  In this pneumatic tire 1, the groove volume of the width direction groove is efficiently expanded at the opening of the width direction groove. Thereby, since the drainage property in a width direction groove | channel improves, there exists an advantage which the wet performance of a tire improves.

  The pneumatic tire according to the present invention is applied to a heavy-duty pneumatic radial tire.

  In a heavy-duty pneumatic radial tire, the rolling resistance of the tire tends to increase. Therefore, there is an advantage that the effect of reducing the rolling resistance can be obtained more remarkably by applying such a pneumatic tire.

  In the pneumatic tire according to the present invention, (1) a block row based on a widthwise groove inclined upward and a block row based on a widthwise groove inclined upward and left are arranged adjacent to each other. Therefore, the groove width directions of the width direction grooves of adjacent block rows are different. For this reason, opening of each width direction groove | channel at the time of inflation of a tire is suppressed by what is called a twist effect. Thereby, the change of the tire shape at the time of tire contact is suppressed, and there is an advantage that the low rolling resistance performance of the tire is improved. Moreover, (2) Since the groove volume of the width direction groove | channel is expanded in the at least one opening part of the width direction groove | channel, the drainage property of each width direction groove | channel improves. Thereby, there exists an advantage which the wet performance of a tire improves. (3) Since the inclination angle of the width direction groove with respect to the tire circumferential direction increases from the block row on the inner side in the tire width direction toward the block row on the outer side in the tire width direction, the tire in the tread portion center region at the time of inflation The displacement outward in the radial direction is smaller than the displacement outward in the tire radial direction of the tread portion shoulder region. Thereby, the change of the tire shape at the time of tire contact is suppressed, and there is an advantage that the low rolling resistance performance of the tire is improved. Further, (4) the ratio h2 / h1 between the groove depth h2 of the width direction groove and the groove depth h1 of the circumferential main groove, and the groove width w2 of the width direction groove and the groove width w1 of the circumferential main groove Since the ratio w2 / w1 is optimized, the groove volume of the width direction groove is appropriately secured. Thereby, there exists an advantage by which the snow braking performance of a tire is maintained.

  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. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  FIG. 1 is a plan view showing a tread surface of a pneumatic tire according to an embodiment of the present invention. 2 to 4 and 6 are explanatory views illustrating the widthwise grooves of the pneumatic tire illustrated in FIG. 1. FIG. 5 is an explanatory view showing a circumferential main groove of the pneumatic tire shown in FIG. 1. 7-11 is explanatory drawing which shows the modification of the pneumatic tire described in FIG. FIG. 12 is a chart showing the results of the performance test of the pneumatic tire according to the present invention.

[Pneumatic tire]
The pneumatic tire 1 includes at least three circumferential main grooves 21 to 23 extending in the tire circumferential direction, and a plurality of width direction grooves (including narrow grooves) 31 to 33 extending in the tire width direction. The tread portion includes a plurality of block rows 41 to 43 defined by the circumferential main grooves 21 to 23 and the width direction grooves 31 to 33 (see FIG. 1). Thereby, a traction pattern based on the block row is formed.

  For example, in this embodiment, five circumferential main grooves 21 to 23 are formed (see FIG. 1). In the tread portion center region, a plurality of widthwise grooves 31 (32) that connect adjacent circumferential main grooves 21, 22 (22, 23) are arranged in the tire circumferential direction. Further, in the tread portion shoulder region, a plurality of width direction grooves 33 that connect the circumferential main grooves 23 located on the outermost side in the tire width direction and the tread portion end portions are arranged in the tire circumferential direction. These circumferential main grooves 21 to 23 and width direction grooves 31 to 33 form four block rows 41 and 42 in the center region of the tread portion, and one block on each side of the tread portion shoulder region. A row 43 is formed.

  In this pneumatic tire 1, (1) in plan view of the tread portion, the block row 42 based on the width direction grooves 32 inclined upward and the width direction grooves 31 and 33 inclined upward to the left are based. Block rows 41 and 43 to be arranged are arranged next to each other (see FIG. 1). That is, in at least a pair of adjacent block rows 42 and 41 (42, 43), the inclination direction with respect to the tire circumferential direction of the width direction groove 32 in one block row 42 and the width direction in the other block row 41 (43). Each width direction groove | channel 31-33 is arrange | positioned so that the inclination direction with respect to the tire circumferential direction of the groove | channels 31 and 33 may mutually differ.

  For example, in this embodiment, three right and left block rows 41 to 43 are formed from the center line CL toward the outer side in the tire width direction (see FIG. 1). In the block row 41 closest to the center line CL, the width direction groove 31 is inclined in a direction that rises to the left in plan view of the tread portion. Further, in the second block row 42, the width direction grooves 32 are inclined in the direction of rising to the right. Further, in the block row 43 located on the outermost side in the tire width direction, the width direction groove 33 is inclined in a direction that rises to the left in a plan view of the tread portion. For this reason, the inclination directions of the width direction grooves 31 to 33 of the block rows 41 to 43 are alternately reversed from the center line CL toward the outer side in the tire width direction.

  In addition, (2) the groove volume of the width direction grooves 31 to 33 is expanded in at least one opening of the width direction grooves 31 to 33 (see FIGS. 1 to 4). That is, at least one of the opening portions of the width direction grooves 31 to 33 (opening portions to the circumferential main grooves 21 to 23 or opening portions to the tread end portions), The groove depth is enlarged and the groove volume of the opening is increased.

  For example, in this embodiment, in the block row 41 closest to the center line CL, the groove width of the width direction groove 31 is widened at both the opening portions on the tire width direction inner side and the tire width direction outer side (FIG. 1). And FIG. 2). In the second block row 42, the groove width of the width direction groove 32 is widened only at the opening on the outer side in the tire width direction (see FIGS. 1 and 3). Further, in the block row 43 located on the outermost side in the tire width direction, the width of the width direction groove 33 is widened only at the opening on the outer side in the tire width direction (see FIGS. 1 and 4). Further, the groove widths of the width direction grooves 31 to 33 start to widen from the end side of the block relative to the center line l of the block and reach the opening (see FIGS. 2 to 4).

  (3) The inclination angles D1 to D3 (0 [deg] <D1 to D3 ≦ 90 [deg]) of the width direction grooves 31 to 33 with respect to the tire circumferential direction are the tire widths from the block rows 41 and 42 on the inner side in the tire width direction. It increases as it goes to the block rows 42 and 43 on the outer side in the direction (see FIG. 1). That is, the inclination angle D1-D3 of the width direction grooves 31-33 tends to approach the right angle in the block row 42 (43) on the outer side in the tire width direction than the block row 41 (42) on the inner side in the tire width direction.

  For example, in this embodiment, the inclination angle D1 of the width direction groove 31 of the block row 41 closest to the center line CL, the inclination angle D2 of the width direction groove 32 of the second row of block rows 42, and the tire width direction most. The inclination angle D3 of the width direction groove 33 of the block row 43 on the outside has a relationship of D1 <D2 <D3 (see FIG. 1). Further, the relationship between the inclination angles D1 to D3 (D1 <D2 <D3) is maintained in the left and right regions of the tire with the center line CL as a boundary.

  The inclination angles D1 to D3 of the width direction grooves 31 to 33 are defined as follows (see FIGS. 2 to 4). First, in the substantially straight width direction grooves 31 and 32, a straight line along the longest block edge side is drawn, and an acute angle formed by this straight line and a straight line in the tire circumferential direction is an inclination angle D1 of the width direction grooves 31 and 32, Let D2 (see FIGS. 2 and 3). Further, in the arc-shaped or curved width direction groove 33, a straight line connecting the center points of the respective openings of the width direction groove 33 is drawn, and an acute angle formed by this straight line and a straight line in the tire circumferential direction is inclined to the width direction groove 33. The angle is D3 (see FIG. 4).

  (4) The groove depth h2 of the widthwise grooves 31 to 33 and the groove depth h1 of the circumferential main grooves 21 to 23 have a relationship of 0.30 ≦ h2 / h1 ≦ 0.70. Further, the groove width w2 of the width direction grooves 31 to 33 and the groove width w1 of the circumferential direction main grooves 21 to 23 have a relationship of 0.20 ≦ w2 / w1 ≦ 0.50 (see FIGS. 5 and 6). That is, when the shallow groove is formed in the block of the tread portion shoulder region, the shallow groove is not considered as the width direction grooves 31 to 33.

[effect]
As described above, in the pneumatic tire 1, (1) a block row 42 based on the width direction grooves 32 inclined to the right and the blocks based on the width direction grooves 31 and 33 inclined to the left. Since the rows 41 and 43 are arranged adjacent to each other (see FIG. 1), the width directions of the width direction grooves 31 and 32 (32 and 33) of the adjacent block rows 41 and 42 (42 and 43) are different. For this reason, opening of each width direction groove | channel 31, 32 (32, 33) at the time of inflation of a tire is suppressed by what is called a twist effect. Thereby, the change of the tire shape at the time of tire contact is suppressed, and there is an advantage that the low rolling resistance performance of the tire is improved. For example, in a tread pattern in which the inclination direction of the width direction groove is uniform, the width direction groove opens in the same direction, so that the change in the tire shape outward in the tire radial direction during inflation is large. For this reason, there exists a possibility that the rolling contact resistance of a tire may deteriorate due to a change in the ground contact shape of the tire.

  Moreover, (2) Since the groove volume of the width direction grooves 31-33 is expanded in at least one opening part of the width direction grooves 31-33 (refer FIGS. 1-4), each width direction groove | channel 31-33. The drainage performance is improved. Thereby, there exists an advantage which the wet performance of a tire improves.

  (3) Since the inclination angles D1 to D3 of the width direction grooves 31 to 33 with respect to the tire circumferential direction increase from the block row 41 on the inner side in the tire width direction toward the block row 43 on the outer side in the tire width direction, The displacement of the tread portion center region toward the outer side in the tire radial direction is smaller than the displacement of the tread portion shoulder region toward the outer side in the tire radial direction. Thereby, the change of the tire shape at the time of tire contact is suppressed, and there is an advantage that the low rolling resistance performance of the tire is improved.

  (4) Ratio h2 / h1 between the groove depth h2 of the width direction grooves 31 to 33 and the groove depth h1 of the circumferential direction main grooves 21 to 23, and the groove width w2 and the circumference of the width direction grooves 31 to 33 Since the ratio w2 / w1 with the groove width w1 of the direction main grooves 21-23 is optimized, the groove volume of the width direction grooves 31-33 is ensured appropriately. Thereby, there exists an advantage by which the snow braking performance of a tire is maintained.

[Additional matter 1]
In the pneumatic tire 1, it is preferable that the width direction grooves 31 and 32 in the center region of the tread part increase the groove volume at the openings on both sides (see FIGS. 1 and 2). A high contact pressure acts on the center area of the tread portion when the tire contacts the ground. Moreover, the width direction groove | channels 31 and 32 expand the groove volume in the opening part of both sides, and the drainage property of the width direction grooves 31 and 32 improves. Accordingly, the drainage performance in the tread portion center region where the contact pressure is high is improved, and there is an advantage that the wet performance of the tire is improved.

  For example, in this embodiment, the block row 41 closest to the center line CL enlarges the groove volume at the openings on both sides (see FIG. 2). Thereby, the drainage property in the tread part center area | region is improved.

[Additional matter 2]
Moreover, in this pneumatic tire 1, when taking the area | region of 70 [%] of the contact width T of the tire centering on the centerline CL, the five circumferential main grooves 21-23 are arrange | positioned in this area | region. (See FIG. 1). In such a configuration, the drainage performance is improved by these circumferential main grooves, and the contact pressure of each of the block rows 41 to 43 is made uniform, so that the distortion of the tread portion is controlled. Thereby, there exists an advantage which can reduce the rolling resistance of a tire, maintaining the wet performance of a tire.

  For example, in this embodiment, an area of 35 [%] (T / 2 × 0.7) of the tire contact width T is taken in the left-right direction of the tire around the center line CL, and five circumferences are included in this area. Direction main grooves 21 to 23 are arranged (see FIG. 1).

  Note that the tire contact width T means that the tire is attached to the applicable rim and applied with a specified internal pressure and is placed perpendicular to the flat plate in a stationary state and applied with a load corresponding to the specified load. The maximum linear distance in the tire axial direction at the contact surface between the tire and the flat plate.

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

  Moreover, in said structure, block width R1 of the block row | line | column 41 divided by three inner circumferential main grooves 21 and 22 among five circumferential main grooves 21-23, and the outer circumferential main groove It is preferable that the block width R2 of the block row 42 partitioned by 23 has a relationship of 0.95 ≦ R1 / R2 ≦ 1.05 (see FIG. 1). In such a configuration, since the relationship between the block widths R1 and R2 of the block rows 41 and 42 in the tread portion center region is optimized, the contact pressure of the block rows 41 and 42 at the time of tire contact is made uniform. Thereby, there is an advantage that uneven wear of the block rows 41 and 42 is suppressed.

  The block widths R1 and R2 of the block rows 41 and 42 are defined by the width dimensions when the tire is mounted on the applicable rim and applied with a specified internal pressure and is in a no-load state.

[Additional matter 3]
Moreover, in this pneumatic tire 1, the total groove area A of the circumferential main grooves 21 to 23 and the total groove area B of the width direction grooves 31 to 33 on the ground contact surface of the tire are 0.25 ≦ B / (A + B) ≦. It is preferable to have a relationship of 0.45. That is, the ratio S = B / X of the total groove area B of the width direction grooves 31 to 33 on the tire contact surface and the tire contact area X is taken. Further, the ratio G + (A + B) / the sum A + B of the total groove area A of the circumferential main grooves 21 to 23 and the total groove area B of the width direction grooves 31 to 33 on the ground contact surface of the tire and the ground contact area X of the tire Take X. At this time, the ratio S / G (= B / (A + B)) between the ratio G and the ratio S preferably has a relationship of 0.25 ≦ S / G ≦ 0.45.

  In such a configuration, the ratio B / (A + B) of the total groove area B of the width direction grooves 31 to 33 to the total groove area A + B of the tire ground contact surface is optimized, whereby the block rigidity of the block rows 41 to 43 is optimized. Is done. Thereby, there is an advantage that the rolling resistance of the tire is reduced, and there is an advantage that the uneven wear resistance performance of the tire is improved. For example, when B / (A + B) <0.25, the block rigidity increases and uneven wear tends to occur in the block. In addition, when 0.45 <B / (A + B), the block rigidity is reduced and the rolling resistance of the tire is deteriorated.

  The contact surface of the tire is the contact surface between the tire and the flat plate when the tire is mounted on the applicable rim and applied with the specified internal pressure and is placed perpendicular to the flat plate in a no-load and stationary state. Say. Then, with reference to the ground contact surface of the tire, the total groove area A of the circumferential main grooves 21 to 23, the total groove area B of the width direction grooves 31 to 33, and the tire ground contact area X on the tire ground contact surface are defined. The

  Further, in this pneumatic tire 1, the sum A + B of the total groove area A of the circumferential main grooves 21 to 23 and the total groove area B of the width direction grooves 31 to 33 on the ground contact surface of the tire, and the ground contact area X of the tire The ratio G = (A + B) / X is preferably in the range of G ≦ 0.25. Furthermore, the ratio G = (A + B) / X is more preferably in the range of 0.21 ≦ G ≦ 0.22.

  In such a configuration, since the ratio of the total groove area A + B to the ground contact area X is optimized, the rigidity of the entire block rows 41 to 43 is ensured. Thereby, the distortion of the block rows 41 to 43 at the time of tire contact is suppressed, and there is an advantage that the rolling resistance of the tire is reduced.

[Additional matter 4]
In the pneumatic tire 1, the groove wall angle θ of at least one circumferential main groove 21 to 23 is preferably in the range of θ ≧ 8 [deg] (see FIG. 5). In such a configuration, since the range of the groove wall angle θ of the circumferential main grooves 21 to 23 is optimized, there is an advantage that the rolling resistance of the tire is reduced. For example, when θ <8 [deg], when the distortion of the tread portion increases during rolling of the tire, the block collapses and the rolling resistance of the tire increases. Therefore, by making the cross-sectional shape of the block trapezoidal with θ ≧ 8 [deg], the collapse of the block is suppressed, and the rolling resistance of the tire increases. The groove wall angle θ is defined by an inclination angle between a perpendicular to the tread of the land portion and a groove wall surface of the circumferential main grooves 21 to 23 in a sectional view of the circumferential main grooves 21 to 23 in the groove depth direction. The

  Moreover, in this pneumatic tire 1, it is preferable that the groove wall angle θ of at least one of the circumferential main grooves 21 and 22 changes as it goes in the tire circumferential direction (see FIG. 7). For example, in this embodiment, in the plan view of the tread portion, the groove wall angle θ of the circumferential main grooves 21 to 23 changes to a wave shape or a zigzag shape as it goes in the tire circumferential direction. In such a configuration, the rigidity of the land portion (block rows 41 to 43) is increased by the change in the groove wall angle θ. Thereby, the fall of the land part is suppressed and there exists an advantage which the rolling resistance of a tire increases.

[Additional matter 5]
Moreover, in this pneumatic tire 1, it is preferable that the narrow groove extended in a tire circumferential direction is formed in the width direction outer side edge part of a tread part (refer FIG. 8). For example, in this embodiment, the narrow grooves 431 are formed in the block row 43 located on the outermost side in the tire width direction. The narrow groove 431 extends in the tire circumferential direction along the outer end in the width direction of the block row 43. The narrow groove 431 forms a thin rib 432 at the outer end in the width direction of the block row 43. In such a configuration, when the tire is in contact with the ground, the fine ribs 432 formed by the fine grooves 431 are positively worn, whereby uneven wear of the block row 43 is suppressed. Thereby, there exists an advantage which the uneven wear-proof performance of a tire improves.

  In the pneumatic tire 1, it is preferable that a narrow groove 433 extending in the tire circumferential direction is formed in the buttress portion (see FIG. 9). In such a configuration, the narrow groove 433 is closed when the tire is in contact with the ground, whereby the contact pressure in the tread portion shoulder region (block row 43) is reduced and uneven wear is suppressed. Thereby, there exists an advantage which the uneven wear-proof performance of a tire improves.

[Additional matter 6]
Further, in the pneumatic tire 1, when the belt reinforcing layer 5 is disposed in the tread portion, the thickness of the tread rubber from the groove bottoms of the circumferential main grooves 21 and 22 in the center region of the tread portion to the belt reinforcing layer 5 is increased. The thickness t is preferably in the range of 3.0 [mm] ≦ t ≦ 5.5 [mm] (see FIG. 10). In such a configuration, since the thickness t of the tread rubber under the grooves of the circumferential main grooves 21 and 22 is optimized, there is an advantage that the rolling resistance of the tire is effectively reduced. For example, when 5.5 [mm] <t, the distortion of the tread rubber at the time of tire contact increases, the block collapses, and the tire rolling resistance increases. Further, when t <3.0 [mm], damage due to stone drilling or the like easily reaches the belt reinforcing layer, so that it is likely to cause a failure and cracks are likely to occur.

  In the pneumatic tire 1, tan δ when the tread rubber is heated at 100 [° C.] is preferably in the range of 0.01 ≦ tan δ ≦ 0.10. In such a configuration, since tan δ of the tread rubber is optimized, the hysteresis loss of the tread portion is reduced. Thereby, there exists an advantage by which the rolling resistance of a tire is reduced effectively. For example, when 0.10 <tan δ, the amount of heat generated by the tread rubber during tire rolling increases, and the rolling resistance of the tire increases. Further, when tan δ <0.01, the productivity of the tire is deteriorated.

[Additional matter 7]
Moreover, in this pneumatic tire 1, it is preferable that the opening part of the width direction grooves 31-33 is expanded to both a groove width direction and a groove depth direction (refer FIG. 11). In such a configuration, the groove volume of the width direction grooves 31 to 33 is efficiently expanded at the openings of the width direction grooves 31 to 33. Thereby, since the drainage property in the width direction grooves 31-33 improves, there exists an advantage which the wet performance of a tire improves.

  For example, in this embodiment, by chamfering the opening of the width direction groove 31 (32, 33), the groove width of the opening becomes 2 toward the circumferential main groove 21 (22, 23). Widened in stages (see FIG. 11). Further, by providing a step in the opening of the width direction groove 31 (32, 33), the groove depth of the opening is enlarged toward the circumferential main groove 21 (22, 23).

[Applicable to]
The pneumatic tire 1 is preferably a heavy-duty pneumatic radial tire. In such a pneumatic tire, the rolling resistance of the tire tends to increase. Therefore, there is an advantage that the effect of reducing the rolling resistance can be obtained more remarkably by applying such a pneumatic tire.

[performance test]
In this example, performance tests on (1) low rolling resistance performance, (2) snow braking performance, (3) wet performance, and (4) uneven wear resistance performance were performed on a plurality of pneumatic tires with different conditions. (See FIG. 12). In this performance test, a pneumatic tire having a tire size of 275 / 80R22.5 is mounted on an applicable rim specified by JATMA, and a specified internal pressure is applied to the pneumatic tire.

  (1) In a performance test related to low rolling resistance performance, a drum type rolling resistance tester loads a pneumatic tire with a load of 30.89 [kN] and measures rolling resistance. And index evaluation is performed based on this measurement result. This evaluation is indicated by an index value based on a conventional pneumatic tire (conventional example) as a reference (100), and the larger the index value, the more preferable the rolling resistance tends to decrease.

  (2) In the performance test related to snow braking performance, pneumatic tires are mounted on a heavy load vehicle having a total vehicle weight of 25 [t] (6 × 2), and braking from a running speed of 40 [km / h] on a snow road surface is performed. The distance is evaluated. This evaluation is indicated by an index value based on a conventional pneumatic tire (conventional example) as a reference (100), and the larger the index value, the more preferable.

  (3) In the performance test relating to wet braking performance, pneumatic tires are mounted on a heavy load vehicle having a total vehicle weight of 25 [t] (6 × 2), and braking from a traveling speed of 40 [km / h] on a wet road surface is performed. The distance is evaluated. This evaluation is indicated by an index value based on a conventional pneumatic tire (conventional example) as a reference (100), and the larger the index value, the more preferable.

  (4) In the performance test for uneven wear resistance, a pneumatic tire is mounted on a heavy-duty vehicle having a total vehicle weight of 25 [t] (6 × 2) and travels 30,000 [km] on a general pavement. The degree of uneven wear is observed and evaluated. This evaluation is indicated by an index value based on a conventional pneumatic tire (conventional example) as a reference (100), and the larger the index value, the more preferable.

  The conventional pneumatic tire has a traction pattern based on a block row. In this conventional example, the inclination direction of the width direction groove with respect to the tire circumferential direction is defined as one direction. Further, the width of the width direction groove is not widened at the opening.

  The pneumatic tires 1 to 3 of the invention are based on the block rows 42 based on the width direction grooves 32 inclined upward to the right and the width direction grooves 31 and 33 inclined upward to the left in plan view of the tread portion. Are arranged adjacent to each other (see FIG. 1). Moreover, the groove volume of the width direction grooves 31-33 is expanded in the at least one opening part of the width direction grooves 31-33. Further, the inclination angles D1 to D3 of the width direction grooves 31 to 33 with respect to the tire circumferential direction increase from the block row 41 on the inner side in the tire width direction toward the block row 43 on the outer side in the tire width direction. Further, the groove depth h2 of the width direction grooves 31 to 33 and the groove depth h1 of the circumferential direction main grooves 21 to 23 have a relationship of 0.30 ≦ h2 / h1 ≦ 0.70, and the width direction grooves 31 to 31. The groove width w2 of 33 and the groove width w1 of the circumferential main grooves 21 to 23 have a relationship of 0.20 ≦ w2 / w1 ≦ 0.50.

  As shown in the test results, it can be seen that in the pneumatic tires 1 of Invention Examples 1 to 3, the low rolling resistance performance is improved and the snow braking performance, the wet performance and the uneven wear resistance performance are maintained. Further, when Invention Example 1 and Invention Example 2 are compared, it can be seen that the low rolling resistance performance of the tire is improved in the case where the number of the circumferential main grooves 21 to 23 is five than in the case where the number is three. . In addition, when Invention Example 2 and Invention Example 3 are compared, the ratio w2 / w1 between the groove width w2 of the width direction grooves 31 to 33 and the groove width w1 of the circumferential main grooves 21 to 23 is optimized. It can be seen that the rolling resistance of the tire decreases.

  As described above, the pneumatic tire according to the present invention is useful in that it can improve the low rolling resistance performance of the tire while maintaining the wet performance and snow braking performance of the tire.

It is a top view which shows the tread surface of the pneumatic tire concerning the Example of this invention. It is explanatory drawing which shows the width direction groove | channel of the pneumatic tire described in FIG. It is explanatory drawing which shows the width direction groove | channel of the pneumatic tire described in FIG. It is explanatory drawing which shows the width direction groove | channel of the pneumatic tire described in FIG. It is explanatory drawing which shows the circumferential direction main groove of the pneumatic tire described in FIG. It is explanatory drawing which shows the width direction groove | channel of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is a graph which shows the result of the performance test of the pneumatic tire concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 5 Belt reinforcement layers 21-23 Circumferential main grooves 31-33 Width direction grooves 41-43 Block row | line 431 Narrow groove 432 Narrow rib 433 Narrow groove

Claims (14)

A plurality of block rows defined by at least three circumferential main grooves extending in the tire circumferential direction, a plurality of width direction grooves extending in the tire width direction, and the circumferential main grooves and the width direction grooves And a pneumatic tire having a tread portion,
In a plan view of the tread portion, the block row based on the width direction groove inclined to the right and the block row based on the width direction groove inclined to the left are arranged adjacent to each other,
The groove width of the width direction groove in the tread portion shoulder region starts to widen from the outer region in the tire width direction with the center line of the block row as a boundary, and reaches the opening in the tire width direction outer side of the width direction groove. By expanding the groove volume of the width direction groove in the outer region in the tire width direction,
The inclination angle of the width direction groove with respect to the tire circumferential direction increases from the block row inside in the tire width direction toward the block row outside in the tire width direction, and
The groove depth h2 of the widthwise groove and the groove depth h1 of the circumferential main groove have a relationship of 0.30 ≦ h2 / h1 ≦ 0.70, and the groove width w2 of the widthwise groove and the circumference A pneumatic tire characterized by having a relationship of 0.20 ≦ w2 / w1 ≦ 0.50 with the groove width w1 of the directional main groove.   The pneumatic tire according to claim 1, wherein the groove in the width direction in the center region of the tread expands the groove volume at openings on both sides.   The pneumatic according to claim 1 or 2, wherein the five main grooves in the circumferential direction are arranged in the region when a region of 70% of the ground contact width T of the tire centering on the center line CL is taken. tire.   Of the five circumferential main grooves, the block width R1 of the block row defined by the inner three circumferential main grooves, and the block width R2 of the block row defined by the outer circumferential main grooves, The pneumatic tire according to claim 3, having a relationship of 0.95 ≦ R1 / R2 ≦ 1.05.   The total groove area A of the circumferential main grooves and the total groove area B of the width direction grooves on the tire contact surface have a relationship of 0.25 ≦ B / (A + B) ≦ 0.45. The pneumatic tire according to any one of the above.   The ratio G + (A + B) / X of G + (A + B) / X where G ≦ 0.25 is the sum of the total groove area A of the circumferential main grooves and the total groove area B of the widthwise grooves on the tire contact surface. The pneumatic tire according to any one of claims 1 to 5, wherein the pneumatic tire is in a range of.   The pneumatic tire according to claim 1, wherein a groove wall angle θ of at least one of the circumferential main grooves is in a range of θ ≧ 8 [deg].   The pneumatic tire according to any one of claims 1 to 7, wherein a groove wall angle θ of at least one of the circumferential main grooves changes in the tire circumferential direction.   The pneumatic tire according to any one of claims 1 to 8, wherein a narrow groove extending in a tire circumferential direction is formed at an outer end portion in a width direction of the tread portion.   The pneumatic tire according to any one of claims 1 to 9, wherein a narrow groove extending in the tire circumferential direction is formed in the buttress portion.   When the belt reinforcing layer is disposed in the tread portion, the thickness t of the tread rubber from the groove bottom of the circumferential main groove in the center region of the tread portion to the belt reinforcing layer is 3.0 [mm] ≦ t ≦ The pneumatic tire according to any one of claims 1 to 10, which is in a range of 5.5 [mm].   The pneumatic tire according to any one of claims 1 to 11, wherein tan δ when the tread rubber is heated at 100 [° C] is in a range of 0.01? Tan?   The pneumatic tire according to any one of claims 1 to 12, wherein an opening of the width direction groove is expanded in both a groove width direction and a groove depth direction.   The pneumatic tire according to claim 1, which is applied to a heavy-duty pneumatic radial tire.

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