JP6344088B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more specifically, while maintaining high drainage performance and sufficiently ensuring running performance (wet performance) on a wet road surface, noise performance is improved by suppressing passing sound, In addition, the present invention relates to a pneumatic tire that can maintain a high steering stability performance (dry performance) on a dry road surface.

  In conventional pneumatic tires, the straight main grooves that generally extend in the tire circumferential direction are important because it is important to improve drainage performance in order to ensure driving performance (wet performance) on road surfaces wet with rain. The drainage performance is improved by forming. However, such a straight main groove has a problem in that it is difficult to suppress air column resonance and it is difficult to reduce noise. Thus, it has been proposed to provide both the wet performance and the noise performance by providing a plurality of main grooves having different shapes to suppress the generation of air column resonance while maintaining the drainage performance.

  For example, in the pneumatic tire described in Patent Document 1, a straight main groove is arranged on the tire equator, and a plurality of arc-shaped grooves are continuously repeated in the tire circumferential direction on both sides of the straight main groove in the tire width direction. An arc-shaped curved main groove formed is arranged, an auxiliary groove having a narrow groove width is arranged outside the arc-shaped curved main groove in the tire width direction, and a plurality of inclined grooves are arranged so as to cross the auxiliary groove diagonally. doing. By configuring the tread pattern in this manner, it is possible to improve the noise performance by suppressing the generation of air column resonance due to the straight main groove while ensuring the drainage performance and maintaining the wet performance.

  However, in the pneumatic tire having such a tread pattern, although the generation of air column resonance sound due to the straight main groove can be suppressed, the air column resonance sound generated in the arc-shaped curved main groove or auxiliary groove is high frequency. Transmission of road noise as a road noise from a plurality of inclined grooves to the outside of the tire cannot be sufficiently suppressed, and there is a problem that sufficient noise performance cannot be obtained.

JP 2004-168142 A

  The object of the present invention is to maintain high drainage performance and ensure sufficient running performance (wet performance) on wet road surfaces, while improving noise performance by suppressing passing sound and stable steering on dry road surfaces. The object is to provide a pneumatic tire capable of maintaining high performance (dry performance).

In order to achieve the above object, the pneumatic tire of the present invention is provided with a plurality of main grooves extending in the tire circumferential direction on both sides of the tire equator on the tread surface, and a plurality of rows of land portions are formed by the plurality of main grooves. a pneumatic tire which is defined and formed, first a plurality of extending in the tire width direction in the shoulder land portion located on the outer side in the tire width direction outermost main groove located at the outermost side in the tire width direction of the major groove of the plurality of 1 is provided and a second lug grooves a plurality of extending lug grooves and the tire width direction, the first lug grooves of the plurality of the one end of the first lug groove of the plurality of while communicating to the outermost main groove The other end portion of the plurality of second lug grooves is terminated in the shoulder land portion without reaching the tire ground contact end, and one end portions of the plurality of second lug grooves are terminated in the shoulder land portion without reaching the outermost main groove. while the second lug of the plurality of One end of the other end portion extend beyond the tire ground contact end, was what end position of the other end of the first lug groove of the plurality of causes is matched on the circumference of the tire of the second lug grooves of the plurality of was what end position of the parts are matched on the circumference of the tire, and, said plurality of other end of the first lug grooves and the plurality of second end portion of the lug groove of having cash S overlap in the tire width direction As described above, while the plurality of first lug grooves and the plurality of second lug grooves are alternately arranged in the tire circumferential direction, the groove width is 1 mm on each extension line of the plurality of first lug grooves. In the following, a sipe extending in the tire width direction is formed discontinuously with the other end portions of the plurality of first lug grooves, and the shoulder land portion is configured in a rib shape continuous in the tire circumferential direction.

  In the present invention, excellent drainage performance in the shoulder land portion can be ensured by the outermost main groove and the first and second lug grooves, and the running stability performance (wet performance) on the wet road surface can be improved. Also, the lug groove existing between the outermost main groove and the tire ground contact edge is interrupted in the middle of the shoulder land portion (that is, the two types of lug grooves of the first lug groove and the second lug groove having different shapes). Therefore, the air column resonance generated in the outermost main groove is suppressed from being transmitted to the outside of the tire through a plurality of lug grooves as high-frequency road noise, thus improving the noise performance. be able to. At this time, since the sipe extending in the tire width direction is formed discontinuously with the other end portion of the first lug groove on the extension line of the first lug groove and extending in the tire width direction, the first lug groove becomes the ground contact end. Even if it is not open (it does not communicate with the second lug groove), the drainage performance is not impaired. Further, since the above-described sipes are provided instead of the lug grooves, the rigidity of the shoulder land portion does not decrease, and the steering stability performance (dry performance) on the dry road surface can be sufficiently maintained. Furthermore, the terminal positions of the first lug groove and the second lug groove coincide with each other on the tire circumference, and there is an overlap between the first lug groove and the second lug groove, and the length of each lug groove is sufficient. Even if there is no lug groove where the first lug groove and the second lug groove are discontinuous and the outermost main groove and the grounding end are crossed across the shoulder land, the drainage performance Will not be damaged. Moreover, since the length and positional relationship of the first lug groove and the second lug groove are optimized by the overlapping arrangement of the first lug groove and the second lug groove, the wet performance, the dry performance, and the noise performance Can be achieved at a high level.

  In the present invention, the sipe extends outward in the tire width direction beyond the tire ground contact edge, and the length Ls of the sipe in the tire width direction and the length L from the outermost main groove to the tire ground contact edge is 0.4. It is preferable to satisfy the relationship of × L ≦ Ls ≦ 1.2 × L. As a result, the sipe opens at the tire ground contact end and a sufficient sipe length is ensured, so that drainage performance can be improved while maintaining dry performance and noise performance.

  In the present invention, it is preferable that the length Ls of the sipe in the tire width direction and the overlap margin S satisfy the relationship of 0.1 × Ls ≦ S ≦ 0.5 × Ls. As a result, the sipe length Ls and the overlap margin S can be optimized, which is advantageous in achieving both high wet performance, dry performance, and noise performance.

  In the present invention, the groove depth of the first lug groove is gradually reduced toward the end portion in the overlapping region where the other end portion of the first lug groove and the one end portion of the second lug groove have an overlap margin S. In addition, the groove depth of the second lug groove is gradually decreased toward the end portion thereof, and the maximum groove depth D1a of the first lug groove and the maximum groove depth D2a of the second lug groove are arbitrarily set in the overlapping region. It is preferable that the groove depth D1b of the first lug groove and the groove depth D2b of the second lug groove satisfy the relationship of 0.2 × (D1a + D2a) ≦ D1b + D2b ≦ 0.8 × (D1a + D2a). By changing the groove depth of the first lug groove and the second lug groove in this way, the rigidity of the shoulder land portion can be maintained even if the first lug groove and the second lug groove are provided, and the dry performance is improved. It is advantageous to improve the wet performance while maintaining.

  In the present invention, the overlap margin S, the maximum groove depth D1a of the first lug groove, and the maximum groove depth D2a of the second lug groove are 0.8 × D1a ≦ S ≦ 2 × D1a or 0.8 × D2a. It is preferable to satisfy the relationship of ≦ S ≦ 2 × D2a. Thereby, the overlap margin S and the groove depth of the first lug groove and the second lug groove can be optimized to maintain the rigidity of the shoulder land portion, and to improve the wet performance while maintaining the dry performance. Become advantageous.

  In the present invention, a third lug groove is provided in an intermediate land portion adjacent to the inner side in the tire width direction of the outermost main groove, and one end portion of the third lug groove is terminated in the intermediate land portion, while the third lug groove The end portion communicates with the outermost main groove, and the communication position with the outermost main groove at the other end of the third lug groove communicates with the outermost main groove at one end portion of the first lug groove adjacent in the tire circumferential direction. It is preferable to arrange between positions. Thereby, while ensuring the drainage performance by the 3rd lug groove and improving wet performance further, dry performance can be maintained highly by optimization of the arrangement.

  At this time, the groove depth D3c at the communication position with the outermost main groove of the third lug groove and the groove depth GD of the outermost main groove have a relationship of 0.4 × GD ≦ D3c ≦ 0.8 × GD. It is preferable to satisfy. By raising the bottom at the position where the third lug groove communicates with the outermost main groove in this way, it is possible to suppress a decrease in rigidity of the intermediate land portion with an increase in the third lug groove. It is advantageous to maintain high performance.

  In the present invention, the relationship between the groove depth D1c at the communication position of the first lug groove with the outermost main groove and the groove depth GD of the outermost main groove is 0.4 × GD ≦ D1c ≦ 0.8 × GD. It is preferable to satisfy. Since the first lug groove is raised at the position where the first lug groove communicates with the outermost main groove in this way, it is possible to suppress the rigidity of the shoulder land portion from being lowered by the first lug groove. It is advantageous to maintain.

  In this invention, it is preferable that the distance of the tire circumferential direction between the other end part of a 1st lug groove and the one end part of a 2nd lug groove is 5 mm or more and 15 mm or less. By setting the distance between the first lug groove and the second lug groove in this way, the rigidity of the shoulder land portion can be optimized, and in order to achieve both high wet performance, dry performance, and noise performance. Become advantageous.

  In the present invention, the tire ground contact end is an end in the tire axial direction when a normal load is applied by placing the tire on a normal rim and filling the normal internal pressure in a vertical state on a plane. . The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESURE” for ETRTO, but 180 kPa when the tire is a passenger car. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFORATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO, but if the tire is a passenger car, the load is equivalent to 88% of the load.

1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. 1 is a front view showing a tread surface of a pneumatic tire according to an embodiment of the present invention. It is sectional drawing explaining the structure of a 1st lug groove, a 2nd lug groove, and a 3rd lug groove.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the tire width direction is a direction parallel to the rotation axis of the pneumatic tire, and the inner side in the tire width direction is the direction toward the tire equator in the tire width direction, and the outer side in the tire width direction. Is the direction opposite to the direction toward the tire equator in the tire width direction. Further, the tire radial direction is a direction orthogonal to the rotation axis of the pneumatic tire, and the tire circumferential direction is a direction of rotation about the rotation axis of the pneumatic tire. Further, the vehicle inner side is a direction that is located inside the vehicle body when a pneumatic tire is assembled to a regular rim and mounted on the vehicle body, and the vehicle outer side is a direction that is located outside the vehicle body at this time. It is.

  In FIG. 1, the symbol CL represents the tire equator. The pneumatic tire T of the present invention includes a tread portion 1, a sidewall portion 2, and a bead portion 3. A carcass layer 4 is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back around the bead core 5 disposed in each bead portion 3 from the vehicle inner side to the outer side. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4. On the other hand, a plurality of layers (two layers in FIG. 1) of belt layers 7 and 8 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each of the belt layers 7 and 8 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and is disposed so that the reinforcing cords cross each other between the layers. In these belt layers 7 and 8, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set, for example, in a range of 10 ° to 40 °. Further, a belt reinforcing layer 9 is provided on the outer peripheral side of the belt layers 7 and 8. The belt reinforcing layer 9 includes an organic fiber cord oriented in the tire circumferential direction. In the belt reinforcing layer 9, the organic fiber cord has an angle with respect to the tire circumferential direction set to, for example, 0 ° to 5 °.

  The present invention is applied to such a general pneumatic tire, but its cross-sectional structure is not limited to the basic structure described above.

  As shown in FIG. 2, the tread surface 10 that is the outer surface of the tread portion 1 has a plurality of main grooves extending in the tire circumferential direction, specifically, a pair of first grooves positioned on both sides of the tire equator CL. A main groove 11 and a pair of second main grooves 12 located on the outer side in the tire width direction of the first main groove are provided. In the example of FIG. 2, the first main groove 11 and the second main groove 12 are both straight main grooves parallel to the tire equator CL. In the example of FIG. 2, the second main groove 12 among the plurality of main grooves is the outermost main groove located on the outermost side in the tire width direction. Since it is advantageous to improve the drainage by providing the main groove at a position close to the tire equator CL side, the main groove on the outermost side in the tire width direction from the tire equator CL (in the case of FIG. 2, the second main groove 12). ) To the outer side wall is 0.3 × (length from the tire equator CL to one of the contact ends E, that is, 1/2 of the contact width TW (that is, TW / 2). (TW / 2) ≦ L0 ≦ 0.6 × (TW / 2), preferably 0.33 × (TW / 2) ≦ L0 ≦ 0.55 × (TW / 2). preferable. Moreover, it is preferable to set the groove width of the outermost main groove (second main groove 12) to, for example, 5 mm or more and 20 mm or less in order to achieve both wet performance and noise performance.

  The first main groove 11 and the second main groove 12 define a plurality of rows of land portions. Specifically, between the shoulder land portion 13 located on the outer side in the tire width direction of the outermost main groove (second main groove 12), and between the outermost main groove (second main groove 12) and the first main groove 11 The two intermediate land portions 14 located at the center and the center land portion 15 located between the two first main grooves 11 are partitioned.

  In these land portions (shoulder land portion 13, intermediate land portion 14, and center land portion 15), a plurality of lug grooves extending in the tire width direction are provided at intervals in the tire circumferential direction. In the present invention, at least the shoulder land portion 13 is provided with the first lug groove 16 and the second lug groove 17. In the example of FIG. 2, a later-described third lug groove 18 is provided in the intermediate land portion 14, and a later-described fourth lug groove 19 is provided in the center land portion 15.

The first lug groove 16 provided in the shoulder land portion 13 has one end portion (end portion in the tire width direction) communicating with the outermost main groove (second main groove 12), while the other end portion (tire width). The end portion on the outer side in the direction does not reach the tire ground contact end E and terminates in the shoulder land portion 13. On the other hand, the second lug groove 17 provided in the shoulder land portion 13 has one end portion (end portion on the inner side in the tire width direction) that does not reach the outermost main groove (second main groove) and is within the shoulder land portion 13. On the other hand, the other end portion (end portion on the outer side in the tire width direction) extends beyond the tire ground contact end E to the outer side in the tire width direction. In the example of FIG. 2, the first lug groove 16 and the second lug groove 17 are both curved in the tire circumferential direction. In addition, the bending directions of the first lug groove 16 and the second lug groove 17 are opposite on the vehicle inner side (left side in FIG. 2) and the vehicle outer side (right side in FIG. 2). The first lug groove 16 and the second lug groove 17 are discontinuous without crossing each other. The other end of the first lug grooves 16 provided plural is to do its end position is matched on the lap tire. Similarly, the terminal positions of one end portions of the plurality of second lug grooves 17 that are provided coincide with each other on the tire circumference. The first lug groove 16 and the second lug groove 17 are in the tire circumferential direction so that the other end portion of the first lug groove 16 and the one end portion of the second lug groove 17 have an overlap margin S in the tire width direction. Are alternately arranged. Thereby, the shoulder land part 13 is comprised by the rib shape which follows a tire circumferential direction.

  In the shoulder land portion 13 thus configured, a sipe 20 having a groove width of 1 mm or less and discontinuous with the other end portion of the first lug groove 16 is formed on the extension line of the first lug groove 16. Has been. The sipe 20 has a sufficiently small groove width and groove depth as compared with the first lug groove 16 and the second lug groove 17, and does not divide the shoulder land portion 13. As described above, since the sipe 20 is formed along the extension line of the first lug groove 16, it does not intersect the first lug groove 16 and the second lug groove 17.

  Since the shoulder land portion 13 is configured in this way, excellent drainage performance is obtained by the outermost main groove (second main groove 12), the first lug groove 16, and the second lug groove 17, and stable running on a wet road surface is achieved. Performance (wet performance) can be improved. Further, two types of lug grooves (first lug groove 16 and second lug groove 17) having different shapes are arranged in the shoulder land portion 13, and the outermost main groove (second main groove 12), the tire ground contact edge E, Since the lug groove existing between them is interrupted in the middle of the shoulder land portion 13, the air column resonance generated in the outermost main groove (second main groove 12) causes a plurality of lug grooves as high-frequency road noise. Therefore, the noise performance can be improved. At this time, the sipe 20 is formed on the extension line of the first lug groove 16 so that the groove width is 1 mm or less and is discontinuous with the other end portion of the first lug groove 16 and extends in the tire width direction. Even if it is not open to the tire ground contact edge E (not communicated with the second lug groove 17), the drainage performance is not impaired. Moreover, since the sipe 20 having a small groove width and groove depth as described above is provided instead of the groove, the rigidity of the shoulder land portion 13 does not decrease, and the steering stability performance (dry performance) on the dry road surface is sufficient. Can be maintained. Further, the end positions of the first lug groove 16 and the second lug groove 17 coincide with each other on the tire circumference, and the first lug groove 16 and the second lug groove 17 have an overlap S. Since the lengths of the lug grooves 16 and 17 are sufficiently secured, the first lug groove 16 and the second lug groove 17 are discontinuous from this point as well. A decrease in drainage performance due to the absence of a lug groove that connects the outer main groove (second main groove 12) and the tire ground contact edge E is suppressed. In addition, by arranging the first lug groove 16 and the second lug groove 17 so as to have an overlapping region in this way, the length and positional relationship of the first lug groove 16 and the second lug groove 17 are optimized. Therefore, it is possible to achieve a high degree of compatibility between wet performance, dry performance, and noise performance.

  As described above, the sipe 20 is separated from the other end of the first lug groove 16 (end on the outer side in the tire width direction), but preferably has a sufficient length to improve drainage performance. Therefore, the sipe 20 extends beyond the tire ground contact edge E to the outside in the tire width direction, and the tire width direction length Ls of the sipe 20 and the outermost main groove (second main groove 12) to the tire ground contact edge E. It is preferable to satisfy the relationship of 0.4 × L ≦ Ls ≦ 1.2 × L. Thereby, since the sipe 20 opens to the tire ground contact end E and a sufficient sipe length is ensured, drainage performance can be improved while maintaining dry performance and noise performance. At this time, if the above-mentioned length Ls is smaller than 0.4 times the length L, the sipe 20 does not have a sufficient length, so it is difficult to improve drainage performance. If the length Ls is larger than 1.2 times the length L, the sipe 20 becomes too long, and it is difficult to secure the rigidity of the shoulder land portion 13 by separating the first lug groove 16 and the sipe 20. Become.

  The length Ls of the sipe 20 in the tire width direction preferably further satisfies the relationship of the overlap margin S between the first lug groove 16 and the second lug groove 17 and 0.1 × Ls ≦ S ≦ 0.5 × Ls. . Thus, by optimizing the relationship between the length of the sipe 20 and the overlap margin S, it is advantageous to achieve both high wet performance, dry performance, and noise performance. At this time, if the overlap allowance S is smaller than 0.1 times the length Ls, it is difficult to ensure sufficient drainage performance. If the overlap margin S is larger than 0.5 times the length Ls, the rigidity of the shoulder land portion 13 is lowered and it is difficult to maintain the dry performance.

  As illustrated in FIG. 3, in the region where the first lug groove 16 and the second lug groove 17 overlap (hereinafter referred to as “overlapping region”), the groove depth of the first lug groove 16 is the end portion thereof, That is, it gradually decreases toward the other end (the outer end in the tire width direction), and the groove depth of the second lug groove 17 is the terminal end, that is, one end (the end in the tire width direction). It is preferable to make it gradually smaller toward. In particular, the maximum groove depth of the first lug groove 16 is D1a, the maximum groove depth of the second lug groove 17 is D2a, the groove depth of the first lug groove 16 at an arbitrary position in the overlapping region is D1b, and the overlapping range. If the groove depth of the second lug groove 17 at an arbitrary position (the same position as the position where the depth D1b is measured) is D2b, these depths D1a, D2a, D1b, D2b are 0.2 × (D1a + D2a). ) ≦ (D1b + D2b) ≦ 0.8 × (D1a + D2a). Thus, by changing the groove depth and setting the magnitude relationship, the rigidity of the shoulder land portion 13 can be maintained even if the first lug groove 16 and the second lug groove 17 are provided, and the dry performance is improved. It is advantageous to improve the wet performance while maintaining. At this time, if the sum (D1b + D2b) of the depth D1b and the depth D2b is smaller than 0.2 times the sum (D1a + D2a) of the depth D1a and the depth D2a, the first lug groove 16 and the first The sum of the groove depths of the two lug grooves 17 becomes too small, making it difficult to obtain sufficient drainage performance. When the sum (D1b + D2b) of the depth D1b and the depth D2b is greater than 0.8 times the sum (D1a + D2a) of the depth D1a and the depth D2a, the first lug groove 16 and the second lug groove in the overlapping region The sum total of the groove depths 17 becomes too large, and it becomes difficult to sufficiently secure the rigidity of the shoulder land portion 13 (particularly, the overlapping region), and it becomes difficult to maintain excellent dry performance. The depths D1a, D2a, D1b, and D2b are all smaller than the outermost main groove (second main groove 12), preferably the outermost main groove (second main groove 12). The depth GD should be 45% to 90%.

  Furthermore, the overlap margin S, the maximum groove depth D1a of the first lug groove 16, and the maximum groove depth D2a of the second lug groove 17 are 0.8 × D1a ≦ S ≦ 2 × D1a or 0.8 It is preferable to satisfy the relationship of × D2a ≦ S ≦ 2 × D2a. Thus, by optimizing the overlap margin S and the groove depths of the first lug groove 16 and the second lug groove 17, the rigidity of the shoulder land portion 13 can be maintained, and wet performance is maintained while maintaining dry performance. It will be advantageous to improve. At this time, if the overlap margin S is smaller than 0.8 times the depths D1a and D2a, it becomes difficult to sufficiently secure the overlapping region, and the first lug groove 16 and the second lug groove 17 are overlapped. The effect cannot be obtained sufficiently. If the overlap margin S is larger than twice the depths D1a and D2a, the overlap region becomes too wide and the overlap of the first lug groove 16 and the second lug groove 17 increases, so that the rigidity of the shoulder land portion 13 is sufficiently increased. It becomes difficult to maintain, and it becomes difficult to maintain dry performance.

  A lug groove can also be provided in the intermediate land portion 14 adjacent to the innermost side in the tire width direction of the outermost main groove (second main groove 12). Preferably, as shown in FIG. A third lug groove 18 is provided in which the inner end portion is terminated in the intermediate land portion 14 while the other end portion (the outer end portion in the tire width direction) communicates with the outermost main groove (second main groove 12). Good. In this example, the third lug groove 18 is slightly curved so as to protrude inward in the tire width direction. When the third lug groove 18 is provided in this manner, the communication position with the outermost main groove (second main groove 12) at the other end is one end of the first lug groove 16 adjacent to the tire circumferential direction (tire width). It is preferable to dispose between the communication positions with the outermost main groove (second main groove 12) at the inner end in the direction. By configuring the third lug groove 18 in this way, the dry performance can be maintained at a high level by optimizing the arrangement while improving the wet performance by obtaining drainage by the third lug groove 18. . Although the maximum groove depth D3a of the third lug groove 18 is not particularly limited, the groove depth is preferably smaller than the outermost main groove (second main groove 12), and more preferably, the third lug groove 18 is. The maximum groove depth D3a may be 45% to 90% of the groove depth GD of the outermost main groove (second main groove 12).

  When the third lug groove 18 is provided in this way, as shown in FIG. 3, the third lug groove 18 communicating with the outermost main groove (second main groove 12) is the outermost main groove (second main groove 12). It is preferable to raise the bottom at a position communicating with the. Specifically, when the groove depth at the communication position of the third lug groove 18 with the outermost main groove (second main groove 12) is D3c, the groove depth D3c is the outermost main groove (second main groove). It is preferable to satisfy the relationship of the groove depth GD of the groove 12) and 0.4 × GD ≦ D3c ≦ 0.8 × GD. By raising the bottom in this manner, it is possible to suppress a decrease in the rigidity of the intermediate land portion 14 with an increase in the third lug groove 18, which is advantageous in maintaining high dry performance. At this time, if the groove depth D3c is smaller than 0.4 times the groove depth GD, the groove depth at the communication position of the third lug groove 18 with the outermost main groove (second main groove 12) is too small. It becomes difficult to obtain excellent drainage performance. If the groove depth D3c is larger than 0.8 times the groove depth GD, there is almost no difference from the case where the bottom elevation is not provided, and the effect of increasing the rigidity of the intermediate land portion 14 cannot be sufficiently obtained.

  Similarly to the third lug groove 18, the first lug groove 16 communicating with the outermost main groove (second main groove 12) also has an outermost main groove (second main groove 12) as shown in FIG. 3. It is preferable to raise the bottom at the communicating position. Specifically, when the groove depth at the communication position with the outermost main groove (second main groove 12) of the first lug groove 16 is D1c, the groove depth D1c is the groove depth of the second main groove 12. It is preferable to satisfy the relationship of the length GD and 0.4 × GD ≦ D1c ≦ 0.8 × GD. By raising the bottom as described above, it is possible to suppress the rigidity of the shoulder land portion 13 from being lowered by the first lug groove 16, which is advantageous in maintaining high dry performance. At this time, if the groove depth D1c is smaller than 0.4 times the groove depth GD, the groove depth at the communication position of the first lug groove 16 with the outermost main groove (second main groove 12) is too small. It becomes difficult to obtain excellent drainage performance. If the groove depth D1c is larger than 0.8 times the groove depth GD, there is almost no difference from the case where the bottom elevation is not provided, and the effect of increasing the rigidity of the shoulder land portion 13 cannot be obtained sufficiently.

  As described above, the first lug grooves 16 and the second lug grooves 17 are alternately arranged in the tire circumferential direction. In this case, in order to achieve both wet performance, dry performance, and noise performance, It is preferable that the first lug groove 16 and the second lug groove 17 be arranged at a predetermined interval. Specifically, the distance in the tire circumferential direction between the other end portion (the outer end portion in the tire width direction) of the first lug groove 16 and one end portion (the end portion in the tire width direction) of the second lug groove 17. It is preferable that d is 5 mm or more and 15 mm or less. By setting the distance between the first lug groove 16 and the second lug groove 17 in this way, the rigidity of the shoulder land portion 13 can be optimized, and the wet performance, dry performance, and noise performance are highly compatible. It will be advantageous to. At this time, if the distance d is smaller than 5 mm, the rigidity of the shoulder land portion 13 becomes too small, and it becomes difficult to sufficiently improve the dry performance. If the distance d is greater than 15 mm, the rigidity of the shoulder land portion 13 becomes too large and pattern noise is likely to occur, so that it is difficult to sufficiently improve the noise performance.

  The shape of the lug groove formed in the center land portion 15 is not particularly limited. For example, as shown in FIG. 2, the lug groove is inclined with respect to the tire width direction, and one end portion (end portion on the inner side in the tire width direction) is the tire equator CL. It is possible to provide a fourth lug groove 19 that terminates in the center land portion 13C without exceeding and whose other end portion (end portion on the outer side in the tire width direction) communicates with the first main groove 11. In the example of FIG. 2, a plurality of center lug grooves 14 </ b> C communicating with each of the first main grooves 11 on both sides of the tire equator CL are provided at intervals in the tire circumferential direction. The center lug grooves 14C provided on one side and the other side of the tire equator CL have the same inclination angle with respect to the tire width direction.

  The tire size is 215 / 60R16, has the cross-sectional shape illustrated in FIG. 1 and is based on the tread pattern of FIG. 2, and the presence / absence of sipe in the shoulder land portion and the presence / absence of communication between the sipe and the first lug groove (sipe The relationship between the length Ls of the sipe in the tire width direction to the length L from the second main groove to the tire ground contact end, the ratio Ls / L of the sipe to the tire width direction length Ls. S / Ls, whether or not the groove depth of each lug groove gradually decreases in the region where the first lug groove and the second lug groove overlap (whether or not the lug groove depth decreases in the overlapping region), The maximum groove depth of the first lug groove which is the sum of the groove depth D1b of the first lug groove and the groove depth D2b of the second lug groove at an arbitrary position in the overlapping region of the 1 lug groove and the second lug groove Ratio (D1) to the sum of the depth D1a and the maximum groove depth D2a of the second lug groove + D2b) / (D1a + D2a), the ratio S / D1a of the first lug groove of the overlap margin S to the maximum groove depth D1a, the ratio S / D2a of the second lug groove of the overlap margin S to the maximum groove depth D2a, the third lug Opening position of groove, presence / absence of bottom raising at communication position of first lug groove with second main groove, presence / absence of bottom raising at communication position of third lug groove with second main groove, second main groove of first lug groove The ratio D1c / GD of the groove depth D1c at the communication position to the groove depth GD of the second main groove, and the second main groove of the groove depth D3c at the communication position of the third lug groove with the second main groove Comparative example in which the ratio D3c / GD with respect to the groove depth GD and the distance d in the tire circumferential direction between the other end of the first lug groove and one end of the second lug groove are set as shown in Tables 1 and 2, respectively. 30 types of pneumatic tires of 1-4 and Examples 1-26 were produced.

  In Comparative Example 1, the first lug groove extends beyond the tire ground contact end to the same position as the outer end in the tire width direction of the second lug groove in the tread pattern of FIG. This is an example of communication with two main grooves. Comparative Example 2 is an example in which sipes are eliminated from the tread pattern of FIG. Comparative Example 3 is an example in which the sipe is connected to the other end of the first lug groove (the end on the outer side in the tire width direction) in the tread pattern of FIG. The comparative example 4 is an example in which the first lug groove and the second lug groove do not overlap and do not have the overlap margin S in the tread pattern of FIG.

  In addition, regarding the column of “Open position of third lug groove” in Tables 1 and 2, the open end (one end part) of the first lug groove where the open end (other end part) of the third lug groove is adjacent in the tire circumferential direction. The case where it is arranged between the two is indicated as “between lug grooves”, and the position of the opening end (other end) of the third lug groove and the position of the opening end (one end) of the first lug groove are the tire circumference. The case where the direction matches is indicated as “lag groove”.

  About these 30 types of pneumatic tires, noise performance, wet performance, and dry performance were evaluated by the following evaluation methods, and the results are also shown in Tables 1 and 2.

Noise performance Each test tire is mounted on a wheel with a rim size of 16 × 7J, mounted on a 2L front-wheel drive vehicle (test vehicle) with an air pressure of 220 kPa, and a passing sound when traveling on a rough road at a speed of 60 km / h The sensory evaluation about was performed. The evaluation results are shown on a 10-point scale with Comparative Example 1 as a reference (5 points). The larger this value, the lower the sound pressure of the passing sound and the better the noise performance.

Wet performance Each test tire is mounted on a wheel with a rim size of 16x7J, mounted on a 2L front-wheel drive vehicle (test vehicle) with an air pressure of 220kPa, and handling stability by five test drivers on a wet road surface Sensory evaluation was performed. The evaluation was performed with a maximum of 10 points using Comparative Example 1 as a reference (5 points), and the average value of the evaluation by each driver was shown as the evaluation result. The larger this value, the better the steering stability on a wet road surface, and the better the wet performance.

Dry performance Each test tire is mounted on a wheel with a rim size of 16x7J, mounted on a 2L front-wheel drive vehicle (test vehicle) with an air pressure of 220kPa, and handling stability by five test drivers on a dry road surface Sensory evaluation was performed. The evaluation was performed with a maximum of 10 points using Comparative Example 1 as a reference (5 points), and the average value of the evaluation by each driver was shown as the evaluation result. The larger this value, the better the steering stability on the dry road surface, and the better the dry performance.

  As is clear from Tables 1 and 2, all of Examples 1 to 26 have a plurality of noise performance, wet performance, and dry performance while maintaining at least the conventional level (Comparative Example 1). The performance was improved from the conventional level (Comparative Example 1).

  On the other hand, the comparative example 2 which does not have a sipe was worse in wet performance than the comparative example 1. In Comparative Example 3 in which the sipe communicated with the first lug groove, the dry performance was worse than that in Comparative Example 1. In Comparative Example 4 in which the first lug groove and the second lug groove do not overlap and have no overlap margin S, the wet performance is worse than that of Comparative Example 1.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7, 8 Belt layer 9 Belt reinforcement layer 10 Tread surface 11 1st main groove 12 2nd main groove 13 Shoulder land part 14 Middle land part 15 Center Land portion 16 First lug groove 17 Second lug groove 18 Third lug groove 19 Fourth lug groove 20 Sipe CL Tire equator E Grounding end

Claims (9)

In the pneumatic tire in which a plurality of main grooves extending in the tire circumferential direction are provided on both sides of the tire equator on the tread surface, and a plurality of rows of land portions are defined by the plurality of main grooves,
Among the plurality of main grooves, the plurality of first lug grooves extending in the tire width direction extend in the tire width direction on the shoulder land portion positioned on the outer side in the tire width direction of the outermost main groove positioned on the outermost side in the tire width direction. It provided a second lug grooves of the plurality of the one end of the first lug groove of the plurality of the tire ground contact end and the other end of the first lug groove of the plurality of while communicating to the outermost main groove is terminated within the shoulder land portion without reaching, the plurality of second the plurality of second lug one end of the lug grooves while terminating at the shoulder land portion in the without reaching the outermost main groove The other end portion of the groove extends beyond the tire ground contact end, the end positions of the other end portions of the plurality of first lug grooves are aligned on the tire circumference, and the plurality of second lug grooves was what end position of the one end are matched on the circumference of the tire, and, the The one end portion of the second lug groove of the plurality of the other end portion of the first lug grooves of several that the first lug groove of the plurality of to have cash S overlap in the tire width direction of the plurality of and 2 lug grooves while arranging alternately in the tire circumferential direction, the plurality groove width on each extension of the first lug groove of the book of the plurality of first lug grooves in 1mm below the other end portion and the non A pneumatic tire characterized in that sipes continuously extending in the tire width direction are formed and the shoulder land portion is formed in a rib shape continuous in the tire circumferential direction.   The sipe extends outward in the tire width direction beyond the tire ground contact edge, and the length Ls of the sipe in the tire width direction and the length L from the outermost main groove to the tire ground contact edge is 0. The pneumatic tire according to claim 1, wherein a relationship of 4 × L ≦ Ls ≦ 1.2 × L is satisfied.   3. The pneumatic tire according to claim 1, wherein a length Ls of the sipe in the tire width direction and the overlap margin S satisfy a relationship of 0.1 × Ls ≦ S ≦ 0.5 × Ls.   In the overlapping region where the other end portion of the first lug groove and the one end portion of the second lug groove have the overlap allowance S, the groove depth of the first lug groove gradually decreases toward the terminal portion. In addition, the groove depth of the second lug groove gradually decreases toward the terminal portion, the maximum groove depth D1a of the first lug groove and the maximum groove depth D2a of the second lug groove, and the overlapping region The groove depth D1b of the first lug groove and the groove depth D2b of the second lug groove at any position within the range satisfy the relationship of 0.2 × (D1a + D2a) ≦ D1b + D2b ≦ 0.8 × (D1a + D2a) The pneumatic tire according to any one of claims 1 to 3.   The overlap margin S, the maximum groove depth D1a of the first lug groove, and the maximum groove depth D2a of the second lug groove are 0.8 × D1a ≦ S ≦ 2 × D1a or 0.8 × D2a ≦ The pneumatic tire according to claim 1, wherein a relationship of S ≦ 2 × D2a is satisfied.   A third lug groove is provided in an intermediate land portion adjacent to the innermost side in the tire width direction of the outermost main groove, and one end portion of the third lug groove is terminated in the intermediate land portion, while the other end of the third lug groove is provided. The outermost main groove at one end portion of the first lug groove adjacent to the tire circumferential direction at a position where the other end portion of the third lug groove communicates with the outermost main groove. The pneumatic tire according to any one of claims 1 to 5, wherein the pneumatic tire is disposed between communication positions with the groove.   The groove depth D3c at the communication position of the third lug groove with the outermost main groove and the groove depth GD of the outermost main groove have a relationship of 0.4 × GD ≦ D3c ≦ 0.8 × GD. The pneumatic tire according to claim 6, wherein the pneumatic tire is satisfied.   The groove depth D1c at the communication position of the first lug groove with the outermost main groove and the groove depth GD of the outermost main groove have a relationship of 0.4 × GD ≦ D1c ≦ 0.8 × GD. The pneumatic tire according to claim 1, wherein the pneumatic tire is satisfied.   The distance of the tire peripheral direction between the other end part of the said 1st lug groove and the one end part of the said 2nd lug groove is 5 mm or more and 15 mm or less, The Claim 1 characterized by the above-mentioned. Pneumatic tire.

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