JP6111808B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire suitable as an all-season tire, and more particularly to a pneumatic tire that can improve snow performance and quietness.

  All-season tires are required to exhibit excellent snow performance during snowfall. Therefore, in the conventional all-season tire, a plurality of main grooves extending in the tire circumferential direction are provided in the tread portion, and the land portions divided by the main grooves extend in the tire width direction and cross the land portions. A plurality of lug grooves are provided, and snow traction is ensured based on such lug grooves (see, for example, Patent Documents 1 and 2).

  However, if the number of lug grooves in the tread part is increased for the purpose of improving snow performance and the land part of the tread part is subdivided into a number of blocks, pattern noise during driving increases and tire noise increases. Become. On the other hand, in recent years, since it is required to increase the quietness of the pneumatic tire, an increase in noise due to the lug groove is a problem to be avoided.

  On the other hand, by providing a plurality of bent lug grooves on the land portion of the tread portion, it is possible to disperse the air column resonance generated in the main groove based on these lug grooves and reduce noise during traveling. It has been proposed (for example, see Patent Documents 3 to 4).

  However, merely providing a plurality of lug grooves having a bent shape in the land portion of the tread portion is not necessarily sufficient in improving the silence. In addition, the lug groove having a bent shape is likely to be clogged with snow, and thus there is a problem that snow performance cannot be sufficiently exhibited when such clogging occurs.

JP 2009-173241 A JP 2009-214761 A JP 2007-237816 A JP 2012-171479 A

  An object of the present invention is to provide a pneumatic tire that can improve snow performance and quietness.

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. In the pneumatic tire provided with a pair of bead portions arranged on the inner side in the tire radial direction of the tire, the tread portion is provided with a first main groove and a second main groove extending in the tire circumferential direction in a zigzag shape. A first land portion extending in the tire circumferential direction is defined between the one main groove and the second main groove, and a plurality of auxiliary grooves having a bent shape are provided in the first land portion, and one of the auxiliary grooves is provided. Of the first main groove and the second main groove, the other end of each auxiliary groove is closed within the first land portion, and each auxiliary groove is bent from the opening end. A first groove extending to the end and a second groove extending from the bending point to the closed end; Provided, the first groove portion of the groove width gradually narrows toward the bending point from the open end, has said second groove portion is bent to the first groove side from the bending point structure,
The first main groove has a side wall surface in which a long surface inclined to one side with respect to the tire circumferential direction and a short surface inclined to the other side with respect to the tire circumferential direction are alternately arranged. The second main groove has a side wall surface in which a long surface inclined to the other side with respect to the tire circumferential direction and a short surface inclined to the one side with respect to the tire circumferential direction are alternately arranged. It is a feature.

  In the present invention, since a plurality of auxiliary grooves having a bent shape are provided in the first land portion so that the first land portion is not subdivided into a large number of blocks, an increase in pattern noise can be avoided. In addition, since the first main groove and the second main groove have a zigzag shape, air column resonance generated in the first main groove and the second main groove can be suppressed. In addition, since the plurality of auxiliary grooves having a bent shape are communicated with the first main groove or the second main groove, the auxiliary grooves are generated in the first main groove or the second main groove based on the sound absorption effect of these auxiliary grooves. The air column resonance can be attenuated.

  Moreover, since the 1st main groove and the 2nd main groove have zigzag shape, wet performance and snow performance can be improved based on the edge effect. Further, since the auxiliary groove has a shape in which the second groove portion is bent from the bending point to the first groove portion side, the wet performance and the snow performance are improved based on the edge effect of the first groove portion and the second groove portion. be able to. In particular, the auxiliary groove has a structure in which the groove width of the first groove portion is gradually narrowed from the opening end toward the bending point, and when the snow is clogged in the auxiliary groove, the snow is likely to be detached. A decrease in snow performance can be avoided. Further, when the groove width of the first groove portion is gradually narrowed from the opening end toward the bending point, the flow of water in the auxiliary groove is improved, so that an effect of improving the wet performance can be expected.

  As a result, in the present invention, the quietness, snow performance and wet performance are all improved by the synergistic effect of the first main groove and the second main groove having a zigzag shape and a plurality of auxiliary grooves having a bent shape. Is possible.

  In the present invention, the first main groove has a side wall surface in which a long surface inclined to one side with respect to the tire circumferential direction and a short surface inclined to the other side with respect to the tire circumferential direction are alternately and repeatedly arranged. The second main groove has a side wall surface in which a long surface inclined to the other side with respect to the tire circumferential direction and a short surface inclined to the one side with respect to the tire circumferential direction are alternately arranged. It is preferable to have. In this way, the long surface constituting the side wall surface of the first main groove is inclined to one side with respect to the tire circumferential direction, and the long surface constituting the side wall surface of the second main groove is the other with respect to the tire circumferential direction. By inclining to the side, it becomes difficult for the first land portion to fall down when receiving a force in the tire circumferential direction, and snow performance can be improved.

  The zigzag pitch P1 in the tire circumferential direction of the first main groove, the zigzag pitch P2 in the tire circumferential direction of the second main groove, and the arrangement pitch P3 in the tire circumferential direction of the auxiliary grooves are P1 / P3 ≦ 1.0 and P2 / P3 ≦. A relationship of 1.0 is preferable. Thereby, it is possible to ensure good snow performance and good quietness.

  The groove depth of the first groove portion of the auxiliary groove is preferably shallower than the groove depths of the first main groove and the second main groove. Thereby, falling of the 1st land part can be prevented and snow performance can be improved.

  The groove depth of the first groove portion of the auxiliary groove is preferably gradually increased from the bending point toward the opening end. As a result, when the snow is clogged in the auxiliary groove, the snow is easily separated, so that it is possible to avoid a decrease in snow performance due to snow clogging. Moreover, since the flow of water in the auxiliary groove is improved, the wet performance can be improved. In this case, it is preferable that the groove depth at the opening end of the first groove portion of the auxiliary groove be 110% to 150% of the groove depth at the bending point.

  On the other hand, the groove width at the bending point of the first groove portion of the auxiliary groove is preferably 50% to 90% of the groove width at the opening end. Thereby, the snow clogged in the auxiliary groove is easily separated and the flow of water in the auxiliary groove is improved, so that the snow performance and the wet performance can be further improved.

  The bending angle α between the first groove portion and the second groove portion of the auxiliary groove is preferably less than 90 °. Thereby, the edge effect of the auxiliary groove can be sufficiently ensured and the snow performance can be improved.

  The first land portion is preferably provided with a plurality of narrow grooves having an inclination angle θ of 30 ° to 70 ° with respect to the tire circumferential direction. Thereby, snow performance and wet performance can be further improved based on the edge effect of the narrow groove. In this case, the groove width of the narrow groove is preferably 1.2 mm or less.

  In the present invention, the first main groove is disposed on the outer side in the tire width direction from the tire equatorial plane, while the second main groove is disposed on the outer side in the tire width direction from the first main groove, and one end portion of the auxiliary groove Is preferably opened in the second main groove. Thus, by opening one end portion of the auxiliary groove toward the outer side in the tire width direction, the snow performance can be further improved.

  Further, the first main grooves are arranged on both sides of the tire equator plane, while the second main grooves are arranged on the outer sides in the tire width direction of the respective first main grooves, and a pair of first main grooves located on both sides of the tire equator plane. It is preferable to partition the second land portion extending in the tire circumferential direction between the grooves. Thus, by arranging the second land portion at the position of the tire equator and arranging the first land portion having a plurality of auxiliary grooves on both sides of the second land portion, the braking performance on snow is improved and the snow is The performance can be further improved.

  The second land portion is provided with a plurality of notch grooves extending in the tire width direction, one end of each notch groove is opened to the first main groove, and the other end of each notch groove is the first end. It is preferable to block within the two land portion. As a result, the wet performance and snow performance can be further improved based on the edge effect of the notch groove without substantially increasing the pattern noise.

  It is preferable that a third land portion is disposed outside the second main groove in the tire width direction, and a plurality of lug grooves extending in the tire width direction are provided in the third land portion. Thereby, snow performance can further be improved. Thus, when providing a lug groove in a shoulder area | region, it is preferable to make the lug groove non-communication with respect to a 2nd main groove. Thereby, the passing sound resulting from the air column resonance generated in the second main groove can be suppressed. Furthermore, it is preferable to provide a circumferential narrow groove extending in the tire circumferential direction in the third land portion. Thereby, pattern noise can be suppressed.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is a top view which extracts and shows the 1st land part in the tread pattern of FIG. It is a notch perspective view which extracts and shows the 1st land part in the tread pattern of FIG. FIG. 3 is a plan view schematically showing an extracted first land portion in the tread pattern of FIG. 2. It is a top view which extracts and shows the 2nd land part in the tread pattern of FIG.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 6 show a pneumatic tire according to an embodiment of the present invention. As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions 2, 2 disposed on both sides of the tread portion 1. And a pair of bead portions 3 and 3 disposed inside the sidewall portion 2 in the tire radial direction.

  A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the inside of the tire to the outside around the bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery of the bead core 5.

  On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7. For the purpose of improving high-speed durability, at least one belt cover layer 8 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is disposed on the outer peripheral side of the belt layer 7. Yes. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

  As shown in FIG. 2, the tread portion 1 includes a pair of main grooves 11 (first main grooves) extending in the tire circumferential direction at positions on both sides of the tire equatorial plane E, and an outer side in the tire width direction than the main grooves 11. A pair of main grooves 12 (second main grooves) extending in the tire circumferential direction at the positions are formed. The main grooves 11 and 12 are both zigzag shaped, but the zigzag shape may meander while forming a corner, or meander while smoothly curving. . The dimensions of the main grooves 11 and 12 are not particularly limited. For example, the groove width measured in the tire width direction is set in the range of 5.0 mm to 15.0 mm, and the groove depth is 5.0 mm to 5.0 mm. The range is set to 15.0 mm.

  Thus, a land portion 21 (first land portion) extending in the tire circumferential direction is defined between the main groove 11 and the main groove 12, and the tire circumferential direction is between the pair of main grooves 11, 11. A land portion 22 (second land portion) extending in the region is defined. Further, a land portion 23 (third land portion) is disposed outside the main groove 12 in the tire width direction.

  Each land portion 21 is provided with a plurality of bent auxiliary grooves 31 at intervals in the tire circumferential direction. These auxiliary grooves 31 have a shape bent like a fishhook. Each auxiliary groove 31 has one end opened to the main groove 12 and the other end closed in the land portion 21. As shown in FIGS. 3 and 4, each auxiliary groove 31 includes a first groove portion 31A extending from the opening end S1 to the bending point S2, and a second groove portion 31B extending from the bending point S2 to the closing end S3. Yes. The groove width of the first groove portion 31A is gradually narrowed from the opening end S1 toward the bending point S2, and the second groove portion 31B is bent from the bending point S2 toward the first groove portion 31A. In each auxiliary groove 31, the first groove part 31A and the second groove part 31B are divided based on a virtual extension line (broken line) of the first groove part 31A.

  Further, each land portion 21 is provided with a plurality of narrow grooves 41 that are inclined with respect to the tire circumferential direction at intervals in the tire circumferential direction. These narrow grooves 41 intersect with the auxiliary grooves 31 and are formed so as to cross the land portion 21. The groove width of the narrow groove 41 is preferably 1.2 mm or less. The narrow groove 41 having such dimensions exhibits the edge effect without impairing the integrity of the land portion 11.

  The land portion 22 located on the tire equator plane E is provided with a plurality of cutout grooves 32 extending in the tire width direction along the both edges thereof at intervals in the tire circumferential direction. Each notch groove 32 has one end opened to the main groove 11 and the other end closed in the land portion 22. More specifically, each notch groove 32 terminates in front of the tire equator plane E without crossing the tire equator plane E. The groove width of each notch groove 32 is preferably set to 1.2 mm or less like the narrow groove 41.

  A plurality of lug grooves 33 extending in the tire width direction are provided in the land portion 23 located in the shoulder region of the tread portion 1 at intervals in the tire circumferential direction. The lug groove 33 is not in communication with the main groove 12. In each land portion 23, at least one narrow groove 43 extending in the tire width direction is formed between a pair of lug grooves 33 adjacent to each other in the tire circumferential direction. Like the narrow groove 41, the width of the narrow groove 43 is preferably set to 1.2 mm or less. Further, each land portion 23 is formed with a circumferential narrow groove 53 extending in the tire circumferential direction. The groove width of the circumferential narrow groove 53 is not particularly limited, but can be set in a range of 1 mm to 2.5 mm, for example.

  In the pneumatic tire described above, a plurality of auxiliary grooves 31 having a bent shape are provided in the land portion 21 located between the main grooves 11 and 12, and the land portion 21 is not subdivided into a large number of blocks. An increase in pattern noise can be avoided. Further, since the main grooves 11 and 12 have a zigzag shape, air column resonance generated in the main grooves 11 and 12 can be suppressed. In addition, since the plurality of auxiliary grooves 31 having a bent shape communicate with the main groove 12, the air column resonance generated in the main groove 12 can be attenuated based on the sound absorption effect of the auxiliary grooves 31. it can.

  Moreover, since the main grooves 11 and 12 have a zigzag shape, wet performance and snow performance can be improved based on the edge effect. Further, since the auxiliary groove 31 has a shape in which the second groove portion 31B is bent from the bending point P2 toward the first groove portion 31A, the wet performance is based on the edge effect of the first groove portion 31A and the second groove portion 31B. And snow performance can be improved. In particular, the auxiliary groove 31 has a structure in which the groove width of the first groove portion 31A is gradually narrowed from the opening end S1 toward the bending point S2, and when the snow is clogged in the auxiliary groove 31, the snow is likely to be detached. Therefore, it is possible to avoid a decrease in snow performance due to snow clogging. Further, when the groove width of the first groove portion 31A is gradually narrowed from the opening end S1 toward the bending point S2, the flow of water in the auxiliary groove 31 is improved, so that the effect of improving the wet performance is also obtained.

  As a result, due to the synergistic effect of the main grooves 11 and 12 having a zigzag shape and the plurality of auxiliary grooves 31 having a bent shape, it is possible to improve both quietness, snow performance and wet performance.

  In the pneumatic tire, the main groove 11 is disposed on the outer side in the tire width direction from the tire equatorial plane E, while the main groove 12 is disposed on the outer side in the tire width direction from the main groove 11. However, since one end portion of the auxiliary groove 31 is opened toward the outer side in the tire width direction, good snow performance can be exhibited. The auxiliary groove 31 can be communicated with the main groove 11 located on the inner side in the tire width direction.

  In the pneumatic tire, the main grooves 11 are arranged on both sides of the tire equatorial plane E, while the main grooves 12 are arranged on the outer sides in the tire width direction of the main grooves 11 and are located on both sides of the tire equatorial plane E. The land portion 22 extending in the tire circumferential direction is defined between the pair of main grooves 11, 11. In this way, the land portion 22 is arranged at the position of the tire equatorial plane E, and a plurality of auxiliary grooves 31 are formed. By arranging the land portions 21 provided on both sides of the land portion 22, the braking performance on snow can be enhanced and good snow performance can be exhibited.

  In the pneumatic tire, as shown in FIG. 5, the main groove 11 has a long surface 111 inclined to one side with respect to the tire circumferential direction C and a short surface 112 inclined to the other side with respect to the tire circumferential direction C. Have side wall surfaces 110 arranged alternately and repeatedly. The long surface 111 is longer in the tread surface than the short surface 112. On the other hand, the main groove 12 is a side wall surface in which a long surface 121 inclined to the other side with respect to the tire circumferential direction C and a short surface 122 inclined to the one side with respect to the tire circumferential direction C are alternately and repeatedly arranged. 120. The long surface 121 is longer in the tread surface than the short surface 122. 5 illustrates the structure of the side wall surfaces 110 and 120 of the main grooves 11 and 12, and therefore, the illustration of the inclined grooves 31 and the narrow grooves 41 is omitted in FIG.

  In this way, the long surface 111 constituting the side wall surface 110 of the main groove 11 is inclined to one side with respect to the tire circumferential direction C as indicated by the arrow A, and the long surface 121 constituting the side wall surface 120 of the main groove 12 is formed. By inclining to the other side with respect to the tire circumferential direction C as indicated by the arrow B, that is, by inclining the long surface 111 of the main groove 11 and the long surface 121 of the main groove 12 in different directions. Are less likely to fall down when the land portion 21 receives a force in the tire circumferential direction C than in the case of aligning the two in the same direction. Thereby, the snow effect can be improved by effectively functioning the edge effect based on the inclined groove 31 and the narrow groove 41 formed in the land portion 21.

  In the pneumatic tire, as shown in FIG. 3, the zigzag pitch P1 of the main groove 11 in the tire circumferential direction C is P1 / P3 ≦ 1.0 with respect to the arrangement pitch P3 of the auxiliary groove 31 in the tire circumferential direction C. More preferably, the relationship of 0.2 ≦ P1 / P3 ≦ 1.0 is satisfied. Similarly, the zigzag pitch P2 of the main groove 12 in the tire circumferential direction C is P2 / P3 ≦ 1.0, more preferably 0.2 ≦ P2 with respect to the arrangement pitch P3 of the auxiliary groove 31 in the tire circumferential direction C. It is preferable that the relationship /P3≦1.0 is satisfied. Thereby, it is possible to ensure good snow performance and good quietness. Here, if P1 / P3 or P2 / P3 is larger than 1.0, the edge effect of the main grooves 11 and 12 is reduced, so that the effect of improving snow performance is reduced. Since it becomes easy to produce column resonance sound, the improvement effect of quietness falls.

  Further, the step amount T1 in the tire width direction of the side wall surface 110 of the main groove 11 and the step amount T2 in the tire width direction of the side wall surface 120 of the main groove 12 are preferably in the range of 1.0 mm to 2.5 mm, respectively. By setting such step amounts T1 and T2, good snow performance and good quietness can be ensured. Here, when the step amounts T1 and T2 are smaller than 1.0 mm, the edge effect of the main grooves 11 and 12 is reduced, so that the effect of improving the snow performance is reduced, and air column resonance occurs in the main grooves 11 and 12. Since it becomes easy to produce a sound, the improvement effect of quietness falls.

  As shown in FIG. 4, the groove depth (maximum depth) of the first groove portion 31 </ b> A of the auxiliary groove 31 may be shallower than the groove depths of the main grooves 11 and 12. In particular, the groove depth (maximum depth) of the first groove portion 31 </ b> A of the auxiliary groove 31 is preferably 80% or less of the groove depth of the main grooves 11 and 12. Thereby, falling of the land part 21 can be prevented and snow performance can be improved.

  The groove depth of the first groove portion 31A of the auxiliary groove 31 is preferably gradually increased from the bending point S2 toward the opening end S1. As a result, when the auxiliary groove 31 is clogged with snow, it becomes easy for the snow to be detached, so that it is possible to avoid a decrease in snow performance due to snow clogging. Moreover, since the flow of water in the auxiliary groove 31 is improved, the wet performance can be improved. In this case, it is preferable that the auxiliary groove 31 has the shallowest portion of the bending point S2 and is deepened by 10% to 50% from the bending point S2 toward the opening end S1. In other words, the groove depth at the opening end S1 of the first groove portion 31A of the auxiliary groove 31 is preferably 110% to 150% of the groove depth at the bending point S2. By providing such a gradient, snow performance and wet performance can be effectively improved. In addition, if the difference between the groove depth at the opening end S1 and the groove depth at the bending point S2 is too large, not only the quietness is adversely affected, but there is a concern that other problems such as uneven wear may occur.

  On the other hand, it is preferable that the auxiliary groove 31 has the largest opening end S1 and is narrowed by 10% to 50% from the opening end S1 toward the bending point S2. In other words, the groove width at the bending point S2 of the first groove portion 31A of the auxiliary groove 31 is preferably 50% to 90% of the groove width at the opening end S1. Thereby, the snow clogged in the auxiliary groove 31 is easily separated and the flow of water in the auxiliary groove 31 is improved, so that the snow performance and the wet performance can be effectively improved. Note that if the difference between the groove width at the open end S1 and the groove width at the bending point S2 is too large, it not only adversely affects quietness but also may cause other problems such as uneven wear.

  As shown in FIG. 3, the bending angle α between the first groove 31A and the second groove 31B of the auxiliary groove 31 is preferably less than 90 °. Thereby, the edge effect of the auxiliary | assistant groove | channel 31 can fully be ensured, and snow performance can be improved. The first groove portion 31A and the second groove portion 31B can be extended linearly or curvedly, and in either case, the bending angle α is an angle formed by the first groove portion 31A and the second groove portion 31B at the bending point S2. . When the bending angle α is 90 ° or more, the edge effect becomes insufficient because the arrangement pitch P3 of the auxiliary grooves 30 needs to be increased.

  The land portion 21 is provided with a plurality of fine grooves 41 that are inclined with respect to the tire circumferential direction. The inclination angle θ of the fine grooves 41 with respect to the tire circumferential direction C is in the range of 30 ° to 70 °. good. Thereby, snow performance and wet performance can be further improved based on the edge effect of the narrow groove 41. In addition, by making the narrow groove 41 intersect the auxiliary groove 31, it is possible to prevent the land portion 21 from being tilted down due to the auxiliary groove 31. Here, when the inclination angle θ of the narrow groove 41 with respect to the tire circumferential direction C is out of the above range, the effect of improving snow performance and wet performance is reduced.

  In the pneumatic tire, as shown in FIG. 6, the land portion 22 has a plurality of notch grooves 32 that open at one end to the main groove 11 and close at the other end within the land portion 22. By forming, the wet performance and snow performance can be further improved based on the edge effect of the notch groove 32 without substantially increasing the pattern noise.

  In the pneumatic tire, as shown in FIG. 2, the land portion 23 is disposed outside the main groove 12 in the tire width direction, and a plurality of lug grooves 33 extending in the tire width direction are formed in the land portion 23. As a result, snow performance can be further improved. Thus, when providing the lug groove 33 in the shoulder region, it is desirable that the lug groove 33 is not communicated with the main groove 12. Thereby, the passing sound resulting from the air column resonance generated in the main groove 12 can be suppressed, and the quietness can be further improved.

The tire size is 255 / 40R18 99H and extends in the tire circumferential direction to form an annular tread portion, a pair of sidewall portions disposed on both sides of the tread portion, and the tire portion radially inward of the sidewall portions 2, a pair of first main grooves and a pair of second main grooves extending in the tire circumferential direction in a zigzag shape at the tread portion, as shown in FIG. 2. A first land portion extending in the tire circumferential direction between the first main groove and the second main groove, and a second land portion between the pair of first main grooves, While arranging the third land portion outside the second main groove, providing a plurality of auxiliary grooves having a bent shape in the first land portion, opening one end of each auxiliary groove to the second main groove, The other end of each auxiliary groove is closed in the first land, and bent to each auxiliary groove from the opening end. A first groove extending to the bending point and a second groove extending from the bending point to the closed end are provided, the groove width of the first groove is gradually narrowed from the opening end toward the bending point, and the second groove is bent. The tires of Reference Example 1 and Examples 1 to 7 in which a plurality of narrow grooves extending in the tire width direction with a groove width of 1.0 mm were provided on the first land portion were bent from the point toward the first groove portion side.

In Reference Example 1 and Examples 1 to 7 , the ratio P1 / P3 between the zigzag pitch P1 in the tire circumferential direction of the first main groove and the arrangement pitch P3 in the tire circumferential direction of the auxiliary groove is 0.3, and the second main groove The ratio P2 / P3 between the zigzag pitch P2 in the tire circumferential direction and the arrangement pitch P3 in the tire circumferential direction of the auxiliary grooves was set to 0.3. On the other hand, the inclination of the main groove, the groove depth and width at the opening end of the first groove portion of the auxiliary groove, the groove depth and width at the bending point of the first groove portion of the auxiliary groove, the bending angle of the auxiliary groove Table 1 shows α, the inclination angle θ of the narrow groove, the presence or absence of a notch groove in the second land portion of the center, and the shape of the lug groove in the third land portion of the shoulder.

  Regarding the inclination of the main groove, a side wall surface in which long surfaces and short surfaces are alternately arranged is provided in each of the first main groove and the second main groove having a zigzag shape, and the long surfaces of both are the same. The case of inclining in the direction is indicated by “same direction”, and the case in which both long surfaces are inclined in the opposite direction (see FIG. 5) is indicated by “reverse direction”. As for the shape of the shoulder lug groove, the case where the lug groove communicates with the second main groove is indicated by “communication”, and the case where the lug groove does not communicate with the second main groove (see FIG. 1). This is shown in “No communication”.

  For comparison, a conventional tire was prepared in which the shape of the main groove was a straight shape and a groove (groove width 6 mm, groove depth 6 mm) crossing the first land portion was provided as an auxiliary groove. In addition, the tire of Comparative Example 1 was prepared in which the main groove was formed in a zigzag shape, and a groove (groove width 6 mm, groove depth 6 mm) crossing the first land portion was provided as an auxiliary groove. Further, a tire of Comparative Example 2 was prepared in which the main groove was formed in a zigzag shape, a groove having a bent shape was provided as an auxiliary groove, and the groove width of the first groove portion of the auxiliary groove was constant.

In the conventional example, Comparative Examples 1 and 2 , Reference Example 1 and Examples 1 to 7 , the groove width of the main groove was 12 mm, and the groove depth of the main groove was 8 mm.

  These test tires were evaluated for snow performance and quietness by the following evaluation methods, and the results are also shown in Table 1.

Snow performance:
Each test tire is mounted on a wheel with a rim size of 18 x 9.0 JJ and mounted on a test vehicle (front-wheel drive vehicle) with a displacement of 3500 cc with an air pressure of 230 kPa. The braking distance from when the vehicle was stopped to when the vehicle stopped was measured. The evaluation results are shown as index values using the reciprocal of the measured values, with the conventional example being 100. A larger index value means a shorter braking distance and better snow performance.

Silence:
Each test tire is mounted on a wheel with a rim size of 18 × 9.0JJ and mounted on a 3500cc displacement test vehicle (front wheel drive vehicle) with an air pressure of 230 kPa and at a speed of 20-100 km / h on a test course consisting of a dry road surface. Sensory evaluation was performed by a test driver on the noise inside the vehicle during inertial driving. The evaluation results are shown as index values with the conventional example being 100. The larger the index value, the better the quietness.

As is clear from Table 1, in all the tires of Examples 1 to 7 , snow performance and quietness were improved in a well-balanced manner in comparison with the conventional example. On the other hand, in the tire of Comparative Example 1, the effect of improving snow performance and quietness was insufficient because the auxiliary groove was a groove crossing the first land portion. In the tire of Comparative Example 2, since the groove width of the first groove portion of the auxiliary groove is constant, the snow clogged in the auxiliary groove is difficult to separate and the effect of improving snow performance is insufficient.

1 Tread part 2 Side wall part 3 Bead part 11 Main groove (first main groove)
12 Main groove (second main groove)
21 Land (First Land)
22 Land (second land)
23 Land (third land)
31 Auxiliary groove 31A 1st groove part 31B 2nd groove part 32 Notch groove 33 Lug groove 41 Narrow groove E Tire equatorial plane

Claims (15)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. In the pneumatic tire provided, the tread portion is provided with a first main groove and a second main groove extending in the tire circumferential direction in a zigzag shape, and the tire circumferential direction is between the first main groove and the second main groove. A first land portion extending to the first land portion, and a plurality of auxiliary grooves having a bent shape are provided in the first land portion, and one end portion of each auxiliary groove is the first main groove and the second main groove. A first groove portion that extends from the opening end to the bending point, and extends from the bending point to the closing end. A second groove portion to be bent, and the groove width of the first groove portion is bent from the opening end. Gradually narrows toward has said second groove portion is bent to the first groove side from the bending point structure,
The first main groove has a side wall surface in which a long surface inclined to one side with respect to the tire circumferential direction and a short surface inclined to the other side with respect to the tire circumferential direction are alternately arranged. The second main groove has a side wall surface in which a long surface inclined to the other side with respect to the tire circumferential direction and a short surface inclined to the one side with respect to the tire circumferential direction are alternately arranged. A featured pneumatic tire. A tire zigzag pitch P1 in the tire circumferential direction of the first main groove, a zigzag pitch P2 in the tire circumferential direction of the second main groove, and an arrangement pitch P3 in the tire circumferential direction of the auxiliary groove are P1 / P3 ≦ 1.0 and P2 The pneumatic tire according to claim 1 , wherein a relationship of /P3≦1.0 is satisfied. The pneumatic tire according to claim 1 or 2 , wherein a groove depth of the first groove portion of the auxiliary groove is shallower than groove depths of the first main groove and the second main groove. The pneumatic tire according to any one of claims 1 to 3 , wherein a groove depth of the first groove portion of the auxiliary groove is gradually increased from the bending point toward the opening end. The pneumatic tire according to claim 4 , wherein a groove depth at the opening end of the first groove portion of the auxiliary groove is 110% to 150% of a groove depth at the bending point. The pneumatic tire according to any one of claims 1 to 5 , wherein a groove width at the bending point of the first groove portion of the auxiliary groove is 50% to 90% of a groove width at the opening end. . The pneumatic tire according to any one of claims 1 to 6 , wherein a bending angle α between the first groove portion and the second groove portion of the auxiliary groove is less than 90 °. The pneumatic tire according to any one of claims 1 to 7 , wherein a plurality of narrow grooves having an inclination angle θ with respect to a tire circumferential direction of 30 ° to 70 ° are provided in the first land portion. The pneumatic tire according to claim 8 , wherein a groove width of the narrow groove is 1.2 mm or less. The first main groove is disposed on the outer side in the tire width direction from the tire equatorial plane, while the second main groove is disposed on the outer side in the tire width direction from the first main groove, and one end portion of the auxiliary groove is formed. the pneumatic tire according to any one of claims 1 to 9, characterized in that an opening to the second main groove. The first main grooves are arranged on both sides of the tire equatorial plane, while the second main grooves are arranged on the outer sides in the tire width direction of the first main grooves, and a pair of first main grooves located on both sides of the tire equatorial plane. The pneumatic tire according to any one of claims 1 to 10, wherein a second land portion extending in the tire circumferential direction is defined between the grooves. A plurality of cutout grooves extending in the tire width direction are provided in the second land portion, one end of each cutout groove is opened in the first main groove, and the other end of each cutout groove is The pneumatic tire according to claim 11 , wherein the pneumatic tire is blocked in the second land portion. Said third land portion arranged in the tire width direction outer side of the second main grooves, according to claim 11 or 12, characterized in that a plurality of lug grooves extending in the tire width direction to said Sanriku portion Pneumatic tires. The pneumatic tire according to claim 13 , wherein the lug groove is not communicated with the second main groove. The pneumatic tire according to claim 13 or 14 , wherein a circumferential narrow groove extending in a tire circumferential direction is provided in the third land portion.

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