JP2011251637A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having directional patters, in which wet performance, on-snow performance, and uneven wear property are improved.SOLUTION: The pneumatic tire includes a plurality of blocks 5 formed in a center C by a center main groove 1, an outside main groove 2, and a side groove 3, and a rag groove 4 formed in the rib 5 of a shoulder S. Directional patterns are formed such that the side grooves 3 located in both sides of a tire width direction with respect to the center main groove 1 are inclined to opposite directions with respect to a tire equator, the center side inclination angle θ1 of the side groove 3 is made a sharp angle, the side grooves 3 of both sides of the tire width direction of the center main groove 1 are arranged to be shifted from each other in a tire peripheral direction so that a peripheral component 3' projecting the side groove 3 in the tire peripheral direction is present in the entire tire periphery, and sipes 7 are formed in blocks 5 and ribs 6.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that improves wet performance and performance on snow and improves uneven wear resistance.

  In general, it is known that a tire in which a plurality of blocks are divided by a plurality of main grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction is excellent in snow performance and drainage performance. In such a pneumatic tire, it is known to employ a directional tread pattern on the tread surface in order to obtain higher drainage. For example, Patent Document 1 proposes that the tread pattern be a directional pattern provided with a plurality of main grooves extending in the circumferential direction and a plurality of lug grooves and sipes extending inclined in the tire width direction.

  On the other hand, the tires have different wear characteristics depending on the front and rear wheels of the vehicle and their mounting positions. Therefore, by periodically rotating the mounting positions, the wear of all tires is made uniform and lasts longer. Yes. However, in a tire having a tread pattern with a directional direction in which the tire rotation direction is specified, the rotation direction of the tire is fixed, so the rotation is limited to the replacement of the tire between the front and rear wheels mounted on the same side on both sides of the vehicle. Will be. For this reason, in tires where a heavy load is applied to the shoulder when turning, such as a light truck tire, if the tread pattern with the above-described direction is used, rotation can be performed only between the front and rear wheel tires on the same side. Therefore, uneven wear of the shoulder portion cannot be suppressed by rotation of the tire. Moreover, in order to suppress uneven wear, it is effective to increase the block rigidity by reducing the lateral grooves, but in that case, there is a concern that the performance on snow may be deteriorated. Therefore, it is difficult to achieve both wet performance, performance on snow, and uneven wear resistance.

JP 2007-161114 A

  An object of the present invention is to solve the above-described problems, and to provide a pneumatic tire that improves wet performance and on-snow performance and also improves uneven wear resistance in a tire having a directional pattern. It is in.

  In order to achieve the above object, a pneumatic tire according to the present invention includes, on a tread surface, a center main groove extending in the tire circumferential direction on the tire equator, and positioned in both sides of the center main groove in the tire width direction and extending in the tire circumferential direction. At least two outer main grooves, and a plurality of lateral grooves extending in the tire width direction and communicating with the center main groove and the outer main groove are provided between the center main groove and the outer main groove. The main groove, the outer main groove, and the lateral groove define a plurality of blocks in the center portion, and extend in the tire width direction from the outermost outer main groove to the shoulder portion on the outer side in the tire width direction and communicate with the outermost outer main groove. In a pneumatic tire in which a lug groove is provided and a rib is formed on the shoulder portion, the lateral grooves located on both sides in the tire width direction with respect to the center main groove are opposite to the tire equator The center-side inclination angle θ1, which is the angle formed with respect to the tire circumferential direction at the portion where the lateral groove communicates with the center main groove, is made an acute angle, and the circumferential component projected from the lateral groove in the tire circumferential direction is It is a directional pattern in which the lateral grooves on both sides in the tire width direction of the center main groove are shifted in the tire circumferential direction so as to exist over the entire circumference of the tire, and sipes are provided on the blocks and the ribs. And

  According to the present invention, the lateral grooves positioned on both sides in the tire width direction with respect to the center main groove are inclined to the opposite sides with respect to the tire center main groove, and the lateral grooves communicate with the center main groove in the tire circumferential direction. On the other hand, since the center side inclination angle θ1 is an acute angle, wet performance and performance on snow can be improved. In particular, the lateral grooves on both sides in the tire width direction of the center main groove are shifted in the tire circumferential direction so that the circumferential component that projects the lateral grooves in the tire circumferential direction exists over the entire tire circumference. The performance can be improved. Further, since the lug groove that is not in communication with the outermost outer main groove is provided in the shoulder portion, uneven wear resistance can be improved. Therefore, in a tire having a directional pattern, wet performance and on-snow performance can be improved and uneven wear resistance can be improved.

  In the present invention, a bottom-up narrow groove portion having a groove depth and a groove width smaller than those of the other portions of the lateral groove is formed at the communication portion of the horizontal groove with respect to the center main groove. The groove depth is preferably 40 to 60%, and the groove width is preferably 30 to 50% of the maximum groove width of the lateral groove. Thereby, the block rigidity of the center portion can be increased while ensuring the drainage performance, and the uneven wear resistance of the center portion can be improved.

  In the present invention, it is preferable that the center-side inclination angle θ1 is relatively small with respect to the shoulder-side inclination angle θ2, which is an angle formed with respect to the tire circumferential direction at a portion where the lateral groove communicates with the outer main groove. Thereby, since the drainage performance of a horizontal groove improves, the drainage performance which falls by providing a bottom raising narrow groove part can be supplemented. More preferably, the difference between the shoulder side inclination angle θ2 and the center side inclination angle θ1 is 5 to 30 °. Thereby, the drainage of a horizontal groove can be improved more. Moreover, it is preferable that center side inclination | tilt angle (theta) 1 is 40-65 degrees, and this can raise drainage performance and can improve abrasion resistance.

  In the present invention, a fine groove is provided on the surface of the block, and the pitch interval of the fine groove is 2.5 to 5 mm, the depth is 0.1 to 0.8 mm, and the width is 0.1 to 0.8 mm. Is preferred. Thereby, wet performance and on-snow performance can be improved.

  In the present invention, it is preferable to intermittently or continuously arrange a plurality of chamfered portions having a shape in which the chamfering amount periodically changes in the tire circumferential direction at the edge portion on the inner side in the tire width direction of the rib. As a result, the edge amount increases and the wet performance can be improved.

  In the present invention, it is preferable that the inclination angle θ3 of the lug groove with respect to the tire circumferential direction is 90 ± 10 °. Thereby, rib rigidity can be ensured and abrasion resistance can be improved.

  In the present invention, it is preferred that the JIS A type hardness at −10 ° C. of the rubber forming the tread portion is 55 to 70. Thereby, while making the rigidity of a block and a rib into an appropriate range and improving uneven wear resistance, performance on snow can be improved.

  Each of these pneumatic tires is preferably used as a light truck tire used under a condition of an air pressure of 350 kPa or more.

1 is a front view of a tread surface of a pneumatic tire according to an embodiment of the present invention. It is a front view which expands and shows the block adjacent to the center main groove | channel of the pneumatic tire of FIG. It is explanatory drawing which expands and shows the center part of the pneumatic tire of FIG. It is a top view which expands and shows a part of rib of the shoulder part of the pneumatic tire of FIG. It is a side view of the block adjacent to the center main groove of the pneumatic tire of FIG. It is sectional drawing which expands and shows the fine groove | channel provided in the block adjacent to the center main groove | channel of the pneumatic tire of FIG. It is a side view of the rib of the shoulder part of the pneumatic tire of FIG.

  In the pneumatic tire of the present invention shown in FIG. 1, the tread T has one center main groove 1 located on the tire equator E and extending in the tire circumferential direction, and tires located on both sides of the center main groove 1. Two outer main grooves 2 extending in the circumferential direction are provided. A plurality of lateral grooves 3 are intermittently arranged in the tire circumferential direction so as to obliquely communicate between the center main groove 1 and the outer main groove 2. The center main groove 1 has a straight shape and includes a see-through portion when projected in the tire circumferential direction. Further, the shoulder portion S outside the outer main groove 2 is provided with an endless lug groove 4 extending intermittently in the tire circumferential direction from the shoulder edge toward the outer main groove 2 so as not to be connected to the outer main groove 2. Has been placed. In this way, two rows of block rows made up of a plurality of blocks 5 are partitioned and formed in the center portion C inside the outer main groove 2. On the other hand, a rib 6 having a plurality of end lug grooves 4 is formed in the shoulder portion S outside the outer main groove 2. A large number of sipes 7 are formed on the surfaces of the blocks 5 and the ribs 6 in a zigzag shape in plan view and extending in the tire width direction.

  The number of main grooves extending in the circumferential direction provided in the tread T is not limited to three, that is, one center main groove 1 and two outer main grooves 2 as shown in FIG. Moreover, the shape of the sipe 7 is not particularly limited as long as it is formed so as to extend in the tire width direction.

  The tread pattern of the pneumatic tire according to the present invention has a directional pattern by the lateral grooves 3 positioned on both sides in the tire width direction with respect to the center main groove 1 being inclined to the opposite sides with respect to the tire equator E. Yes. The directional pattern having the lateral grooves 3 and the end lug grooves 4 that are inclined with respect to the tire circumferential direction has an extension component in the tire circumferential direction and an extension component in the tire width direction. Both the front / rear braking / driving effect of the vehicle and the anti-slip effect in the lateral direction can be achieved. However, such a directional pattern allows rotation of the tire only between the front and rear wheels on the same side of the vehicle. Therefore, when the row of blocks is arranged on the shoulder portion S, heel and toe wear is promoted and uneven wear occurs. It is difficult to suppress. However, as shown in FIG. 1, the shoulder portion S is provided with a lug groove 4 that is endless, the lug groove 4 is not communicated with the outer main groove 2, and the land portion continues to the shoulder portion S in the circumferential direction. By forming the rib 6, the change in rigidity of the shoulder portion S in the tire circumferential direction can be reduced, and uneven wear of the shoulder portion S can be suppressed.

  As shown in FIG. 2, an angle formed with respect to the tire circumferential direction at a portion where the lateral groove 3 communicates with the center main groove 1 is a center side inclination angle θ1. The center side inclination angle θ1 is set to an acute angle. Preferably, the center side inclination angle θ1 is 40 to 65 °. Here, the center-side inclination angle θ1 is an angle formed by the groove width center line of the lateral groove 3 with respect to the tire circumferential direction. Thus, by making the center side inclination angle θ1 an acute angle, in addition to the effect of the inclined lateral groove 3 described above, drainage can be further improved and uneven wear resistance can be improved. When the center-side inclination angle θ1 exceeds 65 °, the end of the block on the outer main groove 2 side becomes an acute angle, so that heel and toe wear easily occurs and uneven wear resistance becomes insufficient. On the other hand, when the center side inclination angle θ1 is less than 40 °, the drainage performance is not sufficiently improved.

  Further, the lateral grooves 3 located on both sides in the tire width direction of the center main groove 1 are shifted in the tire circumferential direction so that a circumferential component in which the lateral grooves 3 are projected in the tire circumferential direction exists over the entire tire circumference. That is, as shown in the explanatory view of FIG. 3, by disposing the lateral grooves 3 positioned on both sides of the center main groove 1 in the tire width direction in the circumferential direction, the circumferential component 3 ′ of these lateral grooves 3 is circumferentially arranged. Shift. Therefore, the circumferential component of the horizontal groove 3 in the other block row is arranged in a portion where the circumferential component 3 ′ of the horizontal groove 3 of one block row disappears. Accordingly, the circumferential components 3 ′ on both sides in the tire width direction of the center main groove 1 complement each other and continue to overlap with each other over the entire circumference of the tire. Thus, wet performance at the time of tire rolling can be improved by allowing the circumferential component 3 'to exist over the entire circumference of the tire. The method of shifting the lateral grooves 3 is not particularly limited, but preferably, the lateral grooves 3 may be shifted by a half pitch in the circumferential direction on both sides of the center main groove 1.

  As shown in FIG. 4, the end lug groove 4 provided in the shoulder portion S extends in the tire width direction. The inclination angle θ3 with respect to the tire circumferential direction is preferably in the range of 90 ± 10 °. Further, the lug grooves 4 positioned in the shoulder portions S on both sides in the tire width direction may be inclined in opposite directions with respect to the tire equator E. Thus, by making the direction of inclination of the lug groove 4 the tire width direction, the rib rigidity can be ensured and the wear resistance can be improved. When the inclination angle θ3 is out of the range of 90 ± 10 °, the wear resistance is insufficient. Here, the inclination angle θ3 is an angle formed by the groove width center line of the lug groove 4 with respect to the tire circumferential direction.

  Wet performance can be improved by providing sipes 7 on the surfaces of the blocks 5 and the ribs 6. Preferably, the sipe 7 extends to the end of the block or rib. Since the sipe 7 extends to the end of the block or rib, the wet performance can be improved by the sipe edge. The inclination angle θ4 of the block and rib sipe 7 with respect to the tire circumferential direction is preferably in the range of 90 ± 10 °. By setting the inclination angle of the sipe 7 within this range, the wet braking performance can be improved. In particular, by extending the sipe 7 provided on the rib 6 in the tire width direction, it is possible to supplement wet braking performance that is reduced by making the lug groove 4 non-communication with the outer main groove 2.

  As shown in FIGS. 2 and 5, a bottom-up narrow groove portion 3 a is formed at a portion where the lateral groove 3 communicates with the center main groove 1. The bottom raised narrow groove portion 3a is a portion formed so that the groove depth and the groove width are smaller than other portions of the lateral groove 3. The length L3a of the bottom raised narrow groove portion 3a is set to 20 to 40% of the length L3 of the lateral groove 3. Further, the groove width W3a of the bottom raised narrow groove portion 3a is set to 30 to 50% of the maximum groove width W3 of the lateral groove 3, and the groove depth D3a of the bottom raised narrow groove portion 3a is set to 40 to 60% of the groove depth D1 of the center main groove 1. Has been. Here, the length L3 of the lateral groove 3 is the length from the center main groove 1 side end of the horizontal groove 3 to the outer main groove 2 side end. The length L3a of the bottom raised narrow groove portion 3a is the length of the lateral groove 3 from the end portion on the center main groove 1 side. These are all the lengths measured along the groove width center line.

  As described above, the bottom raised narrow groove portion 3a is formed at the communication portion of the lateral groove 3 with respect to the center main groove 1, and the groove width W3a and the groove depth D3a of the lateral groove 3 are reduced, so that the block rigidity in the vicinity of the bottom raised narrow groove portion 3a is increased. It can be increased to suppress uneven wear. Moreover, since the bottom raising of the lateral groove 3 and the narrowing are combined, it is possible to ensure that the lateral groove 3 communicates with the center main groove 1 when increasing the block rigidity. Therefore, the drainage performance can be favorably maintained by the cooperation of the center main groove 1 and the lateral groove 3.

  At this time, by setting the length L3a of the bottom raised narrow groove portion 3a to 20 to 40% of the length L3 of the lateral groove 3, uneven wear can be suppressed without deteriorating steering stability on snow. If the length L3a of the bottom raised narrow groove portion 3a is smaller than 20% of the length L3 of the lateral groove 3, the effect of suppressing uneven wear cannot be sufficiently obtained. On the contrary, if the length L3a of the bottom raised narrow groove portion 3a is larger than 40% of the length L3 of the lateral groove 3, the effect of improving the steering stability on snow cannot be obtained sufficiently.

  By setting the groove depth D3a of the lateral groove 3 in the bottom raised narrow groove portion 3a to be 40 to 60% of the groove depth D1 of the center main groove 1, uneven wear is suppressed without deteriorating steering stability on snow. I can do it. If the ratio of the groove depth D3a of the bottom raised narrow groove portion 3a to the groove depth D1 of the center main groove 1 is smaller than 40%, the effect of improving uneven wear resistance is obtained, but the effect of improving drainage performance and snow drainage performance. Cannot be obtained sufficiently. On the contrary, if this ratio is larger than 60%, the difference in rigidity cannot be made sufficiently small, and the effect of improving the uneven wear resistance cannot be obtained sufficiently.

  By setting the groove width W3a of the lateral groove 3 in the bottom raised narrow groove portion 3a to 30 to 50% of the maximum groove width W3 of the lateral groove 3, uneven wear can be suppressed without reducing the steering stability on snow. If the ratio of the groove width W3a of the bottom raised narrow groove portion 3a to the maximum groove width W3 of the horizontal groove 3 is smaller than 30%, the effect of improving uneven wear resistance is obtained, but the effect of improving drainage performance and snow drainage performance is sufficient. I can't get it. On the contrary, if this ratio is larger than 50%, the block rigidity does not change much and the effect of improving the uneven wear resistance cannot be sufficiently obtained.

  As shown in FIG. 2, an angle formed with respect to the tire circumferential direction at a portion where the lateral groove 3 communicates with the outer main groove 2 is a shoulder side inclination angle θ2. It is preferable to make the center side inclination angle θ1 relatively small with respect to the shoulder side inclination angle θ2. By doing in this way, the drainage performance of the horizontal groove 3 can be improved. Accordingly, the drainage performance can be maintained even if the bottom raised narrow groove portion 3a in which the groove depth and groove width of the lateral groove 3 are reduced in order to improve uneven wear resistance as described above. The difference between the center side inclination angle θ1 and the shoulder side inclination angle θ2 is preferably 5 to 30 °. If this difference is less than 5 °, the drainage performance is not improved. On the contrary, if this difference is larger than 30 °, the block rigidity is lowered and it is difficult to suppress uneven wear. Here, the shoulder side inclination angle θ2 is an angle formed by the groove width center line of the lateral groove 3 with respect to the tire circumferential direction.

  In the pneumatic tire of the present invention, it is preferable that a large number of fine grooves 8 that are inclined with respect to the tire circumferential direction are arranged in parallel on each tread surface of the block 5. These fine grooves 8 are fine grooves shallower than the sipe 7. The new tires do not necessarily have sufficient running performance on icy and snowy road surfaces because the inherent characteristics of the tread rubber are not exhibited. However, by providing such a fine groove 8, the water film generated between the ice and snow road surface and the tread surface is effectively removed by the fine groove 8. Therefore, the performance on ice and the performance on snow in the initial use can be improved. Further, when the fine grooves 8 are provided on the tread surface of the block 5, the presence of these fine grooves 8 promotes the peeling of the tread surface, so that the time until the original characteristics of the tread rubber are exhibited can be shortened. It is done.

  As shown in FIG. 6, the fine groove 8 may have a groove width w of 0.1 mm to 0.8 mm and a groove depth d of 0.1 mm to 0.8 mm. If the groove width w is smaller than 0.1 mm, the fine groove 8 has an insufficient water film removing effect and an effect of improving the snow drainage performance. Conversely, if the groove width w is larger than 0.8 mm, the block rigidity is lowered. On the other hand, if the groove depth d is smaller than 0.1 mm, the effect of removing the water film and improving the snow removal performance is insufficient, and conversely if it is larger than 0.8 mm, the block rigidity is lowered.

  The pitch p of the fine grooves 8 is preferably in the range of 2.5 to 5.0 mm. By setting the pitch p of the fine grooves 8 within this range, it is possible to reliably avoid the fine grooves 8 from being crushed when a high load is applied to the tire. Therefore, it is possible to exhibit the effect of improving the performance on ice and the performance on snow even under high load conditions. When the pitch p of the fine grooves 8 is smaller than 2.5 mm, the effect of improving the performance on ice and the performance on snow under high load conditions becomes insufficient. On the contrary, if the pitch p is larger than 5.0 mm, the effect of improving the water film removal effect is insufficient.

  The inclination angle α of the fine groove 8 with respect to the tire circumferential direction is preferably set in the range of 40 ° to 60 °. By setting the inclination angle α of the fine groove 8 within this range, the braking performance can be improved and the skid of the tire can be prevented. If the inclination angle α of the fine groove 8 is smaller than 40 °, the edge of the fine groove 8 hardly contributes to the braking performance, and conversely if larger than 60 °, the edge of the fine groove 8 hardly contributes to prevention of skidding.

  As shown in FIGS. 4 and 7, a plurality of chamfered portions 9 having a shape in which the chamfering amount periodically changes in the tire circumferential direction are formed intermittently or continuously at the inner edge of the rib 6 in the tire width direction. It is preferable. Here, the change in the chamfering amount means that the sizes in the width direction and the depth direction change along the circumferential direction of the rib 6. As shown in FIG. 4, the maximum chamfered portion 9a with the largest chamfering amount is the portion that is chamfered the largest in the depth direction and the width direction, and the minimum chamfered portion 9b is the depth direction and the width direction. This is the part where the chamfering is minimized.

  The shape of the chamfered portion 9 allows the edge length to be increased and the edge component acting in the braking / driving direction to be added by periodically changing the amount of chamfering in the tire circumferential direction. Can be maintained. If the chamfered portion 9 has a uniform shape with the chamfering amount not changing over the entire circumference, the edge length cannot be increased, so that the effect of improving the performance on snow cannot be sufficiently obtained.

  The depth D9a and / or width W9a of the maximum chamfered portion 9a of the chamfered portion 9 may be 30 to 60% of the maximum depth D2 of the outer main groove 2. By setting this range, the edge length can be sufficiently increased, and the traction on snow can be improved. Preferably, the maximum depth D2 of the outer main groove 2 is 40 to 50%. If the depth D9a and / or the width W9a of the maximum chamfered portion 9a is smaller than 30% of the outer main groove depth D2, the force applied between the lug groove 4 and the outer main groove 2 cannot be released. The effect of improving wear is not sufficiently obtained. On the other hand, if the depth D9a and / or the width W9a of the maximum chamfered portion 9a is larger than 60% of the outer main groove depth D2, the block rigidity is excessively lowered, so that the effect of improving on-snow handling stability cannot be sufficiently obtained.

  The maximum chamfered portion 9a of the chamfered portion 9 is preferably disposed in a region on the extension line of the end lug groove 4 as shown in FIG. In the region on the extended line of the end lug groove 4, stress is more concentrated than in the other region of the rib 6. Therefore, the maximum chamfered portion 9 a is disposed in this region to reduce the rigidity, thereby concentrating. The distributed stress can be easily dispersed and uneven wear can be suppressed. If the maximum chamfered portion 9a is arranged away from the region on the extension line of the lug groove 4, stress is easily concentrated on the region on the extension line of the lug groove 4, and the effect of improving the uneven wear resistance cannot be sufficiently obtained.

  One chamfer 9 may be formed per 0.5 to 2 pitches of the end lug groove 4. Here, the pitch of the end lug grooves 4 is an interval in the tire circumferential direction between the adjacent end lug grooves 4. If the chamfered portions 9 are formed at a rate of one at intervals smaller than 0.5 pitch, the number of the chamfered portions 9 increases too much, so that the block rigidity is excessively lowered and the effect of improving uneven wear resistance cannot be obtained sufficiently. . On the contrary, if the chamfered portions 9 are formed at a rate of one piece with an interval larger than 2 pitches, a portion having high rigidity and a portion having low rigidity are formed on the edge portion of the rib 6 and the difference in rigidity becomes large. The effect of improving the property cannot be obtained sufficiently.

  The rubber forming the tread preferably has a JIS A type hardness at −10 ° C. of 55 to 70. By doing so, uneven wear resistance can be improved and performance on snow can be improved. If the hardness is less than 55, the rigidity of the block and the rib is lowered, so that the effect of improving the uneven wear resistance cannot be sufficiently obtained. If the hardness exceeds 70, the effect of improving the performance on snow cannot be obtained sufficiently. Here, the hardness of the JIS A type is a hardness measured at a temperature of −10 ° C. with a durometer type A in accordance with JIS K6253.

  The pneumatic tire of the present invention is preferably used as a light truck tire used under conditions of an air pressure of 350 kPa or more.

  11 types of pneumatic tires of Conventional Example 1, Comparative Examples 1 and 2, and Examples 1 to 8 with tire sizes common to 195 / 75R16C 107 / 105R and different specifications as shown in Tables 1 and 2 were manufactured. .

  About these 11 kinds of tires, they were assembled on a 16x51 / 2J rim, filled with air pressure of 280 kPa at the front and 450 kPa at the rear, and attached to a European VAN with a maximum loading capacity of 3.5 ton, respectively, by the following method. Uneven wear resistance, drainage performance, steering stability on wet road surface, and steering stability on snow were measured.

Uneven wear resistance The tire appearance after traveling 4000 km on a paved road with the above vehicle was visually evaluated. The evaluation results are shown as an index with the value of Conventional Example 1 being 100. The smaller the index value, the better the uneven wear resistance.

Drainage performance The vehicle traveled on a test course with a water depth of 10 ± 1 mm and a turning radius of 100 m, and the running speed of the test vehicle when the maximum lateral acceleration of the tire occurred was measured. The evaluation results are shown as an index with the value of Conventional Example 1 being 100. A larger index value means better drainage performance.

Steering stability on a wet road The steering stability was evaluated in a speed range of 0 to 100 km / h on a test course consisting of a wet road with the above vehicle. The evaluation results are shown as an index with the value of Conventional Example 1 being 100. The larger the index value, the better the steering stability on the wet road surface.

Handling stability on snow The driving stability of the above vehicle was evaluated in the speed range of 0 to 100 km / h on a test course consisting of a snow surface. The evaluation results are shown as an index with the value of Conventional Example 1 being 100. The larger the index value, the better the handling stability on snow.

  As is clear from the results in Tables 1 and 2, the pneumatic tires of Examples 1 to 8 improved the handling stability on snow, the handling stability on the wet road surface, and the drainage performance as compared with Conventional Example 1. Uneven wear resistance can be improved.

  On the other hand, as apparent from the results in Table 1, the pneumatic tire of Comparative Example 1 cannot improve uneven wear resistance because the shoulder portion is a block. In the pneumatic tire of Comparative Example 2, since the lateral groove does not communicate with the center main groove, wet steering stability and drainage performance are deteriorated.

DESCRIPTION OF SYMBOLS 1 Center main groove 2 Outer main groove 3 Horizontal groove 3a Bottom raising narrow groove part 4 Lug groove 5 Block 6 Rib 7 Sipe 8 Fine groove 9 Chamfer

Claims (10)

A center main groove extending in the tire circumferential direction on the tire equator on the tread surface, at least two outer main grooves positioned on both sides in the tire width direction of the center main groove and extending in the tire circumferential direction, the center main groove and the A plurality of lateral grooves extending in the tire width direction and communicating with the outer main grooves are provided between the outer main grooves and the outer main grooves. Air in which a block is defined, a lug groove extending in the tire width direction from the outermost outer main groove and extending in the tire width direction and not communicating with the outermost outer main groove is formed, and a rib is formed in the shoulder portion In entering tires,
The lateral grooves positioned on both sides in the tire width direction with respect to the center main groove are inclined to opposite sides with respect to the tire equator, and at an angle formed with respect to the tire circumferential direction at a portion where the lateral grooves communicate with the center main groove. The lateral grooves on both sides of the center main groove in the tire width direction are arranged in the tire circumferential direction so that a certain center side inclination angle θ1 is an acute angle and a circumferential component in which the lateral grooves are projected in the tire circumferential direction exists over the entire tire circumference. A pneumatic tire characterized by being a directional pattern in which the blocks and the ribs are provided with sipes.   A bottom raised narrow groove portion having a groove depth and a groove width smaller than other portions of the transverse groove is formed at a communication portion of the transverse groove with respect to the center main groove, and the groove depth of the bottom raised narrow groove portion is set to the center main groove. The pneumatic tire according to claim 1, wherein the groove depth is 40 to 60%, and the groove width of the bottom raised narrow groove portion is 30 to 50% of the maximum groove width of the lateral groove.   The center-side inclination angle θ1 is relatively small with respect to a shoulder-side inclination angle θ2, which is an angle formed with respect to a tire circumferential direction at a portion where the lateral groove communicates with the outer main groove. The pneumatic tire according to 1 or 2.   The pneumatic tire according to claim 3, wherein a difference between the shoulder side inclination angle θ2 and the center side inclination angle θ1 is 5 to 30 °.   The pneumatic tire according to any one of claims 1 to 4, wherein the center-side inclination angle θ1 is 40 to 65 °.   A fine groove is provided on the surface of the block, and the pitch interval of the fine groove is 2.5 to 5 mm, the depth is 0.1 to 0.8 mm, and the width is 0.1 to 0.8 mm. The pneumatic tire according to any one of claims 1 to 5.   A plurality of chamfered portions having a shape in which a chamfering amount periodically changes in a tire circumferential direction is intermittently or continuously arranged at an edge portion on the inner side in the tire width direction of the rib. The pneumatic tire according to any one of the above.   The pneumatic tire according to any one of claims 1 to 7, wherein an inclination angle θ3 of the lug groove with respect to a tire circumferential direction is in a range of 90 ± 10 °.   The pneumatic tire according to claim 1, wherein the rubber forming the tread portion has a JIS A type hardness at −10 ° C. of 55 to 70.   The pneumatic tire according to any one of claims 1 to 9, wherein the pneumatic tire is a light truck tire used under conditions of an air pressure of 350 kPa or more.

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