WO2015145910A1

WO2015145910A1 - Pneumatic tire

Info

Publication number: WO2015145910A1
Application number: PCT/JP2014/084486
Authority: WO
Inventors: 和也石黒
Original assignee: 横浜ゴム株式会社
Priority date: 2014-03-28
Filing date: 2014-12-26
Publication date: 2015-10-01
Also published as: DE112014006530B4; AU2014388518A1; JP2015189350A; DE112014006530T5; AU2014388518B2; CN106132729B; CN106132729A; JP5796655B1

Abstract

Provided is a pneumatic tire enabling an increase in noise performance while achieving both steering stability on dry road surface and driving performance on wet road surface. In a pneumatic tire (T) including a center land portion (13), an inner central land portion (14), an outer central land portion (15), an inner shoulder land portion (17), and an outer central land portion (18) which are separately formed by at least four main grooves (11), the pneumatic tire having a designated vehicle mount direction, the center land portion (13) is formed with center lug grooves (20) that open only to one of the main grooves (11) on the vehicle inner side, the inner central land portion (14) is formed with inner central lug grooves (21) that open only to another of the main grooves on the vehicle inner side, each of the lug grooves (20, 21) comprising a first inclination portion (20A, 21A) positioned on an opening end side and having a relatively large inclination angle and a second inclination portion (20B, 21B) positioned on a terminal side and having a relatively small inclination angle, and an inner central sipe (22) is formed at the terminal portion of each of the inner central lug grooves (21) terminating within the inner central land portion (14), wherein the relationships L1 > L2 and L3 > L4 are satisfied, where L1 is the length of the center lug groove (20), L2 is the length of the inner central lug groove (21), L3 is the sum of the length L2 and the length of the inner central sipe (22), and L4 is the width of the inner central land portion (14).

Description

Pneumatic tire

The present invention relates to a pneumatic tire having at least four main grooves extending in the tire circumferential direction on a tread surface. More specifically, the present invention relates to noise while maintaining both steering stability performance on a dry road surface and running performance on a wet road surface. The present invention relates to a pneumatic tire capable of improving performance.

In recent years, with the progress of road maintenance and higher performance of vehicles, for pneumatic tires, the driving performance on dry roads (dry performance) and the driving performance on wet roads (wet performance) during high-speed driving There is a strong demand to improve noise performance while achieving compatibility.

Generally, as a method for improving wet performance, in addition to a main groove extending in the tire circumferential direction on the tread surface of the tire, a lug groove or sipe extending in the tire width direction is formed to ensure drainage. . However, in such a method, since the rigidity of the land portion formed on the tread surface is lowered, there is a problem that it is difficult to ensure the dry performance and the noise performance is deteriorated.

Conventionally, as a measure to improve noise performance while achieving both dry performance and wet performance, it has been proposed to specify the direction of the lug groove and its arrangement after specifying the mounting direction of the tire on the vehicle. (For example, refer to Patent Document 1).

However, in the structure of Patent Document 1, although some lug grooves communicate with both of two adjacent main grooves in order to ensure drainage performance, these some lug grooves are particularly outside when the vehicle is mounted. The noise performance does not improve sufficiently because it is open in the main groove on the side, and the block row is formed by some of these lug grooves, so the tread rigidity is low and the dry performance cannot be secured sufficiently There is a problem. Therefore, it is conceivable that some of these lug grooves are not opened with respect to the main groove on the outer side when the vehicle is mounted. However, such simple modification only balances the shape of the lug grooves and their arrangement. Therefore, the dry performance, wet performance, and noise performance to the extent obtained with the structure of Patent Document 1 cannot be obtained. Therefore, further improvement for improving noise performance is demanded while achieving both dry performance and wet performance.

Japanese Unexamined Patent Publication No. 2008-162390

An object of the present invention is to provide a pneumatic tire that can improve noise performance while achieving both stable driving performance on a dry road surface and traveling performance on a wet road surface.

In order to achieve the above object, the pneumatic tire of the present invention has at least four main grooves extending in the tire circumferential direction on the tread surface, and a plurality of circumferential land extending in the tire circumferential direction between adjacent main grooves. In the pneumatic tire in which a shoulder land portion is defined on the outer side in the tire width direction of each of the outermost main grooves in the tire width direction and the mounting direction with respect to the vehicle is specified. The center land portion located on the tire equator in the circumferential land portion of the tire extends in the tire width direction and communicates with a main groove that is inward with respect to the vehicle when mounted on the vehicle, while outside with respect to the vehicle when mounted on the vehicle. A plurality of center lug grooves that terminate in the center land portion without communicating with the main groove to be formed are spaced apart in the tire circumferential direction, and the center land portion of the plurality of circumferential land portions is Also While extending in the tire width direction to the inner intermediate land portion on the inner side with respect to the vehicle when both are mounted, it communicates with the main groove that is on the inner side with respect to the vehicle when mounted on the vehicle, while on the outer side with respect to the vehicle when mounted on the vehicle A plurality of inner intermediate lug grooves that terminate in the inner intermediate land portion without communicating with the main groove to be formed are spaced apart in the tire circumferential direction, and each of the center lug groove and the inner intermediate lug groove is Each inner intermediate lug is composed of a first inclined portion with a relatively large inclination angle with respect to the tire circumferential direction located on the opening end side and a second inclined portion with a relatively small inclination angle with respect to the tire circumferential direction located on the terminal end side. An inner intermediate sipe extending in the extending direction of the second inclined portion of each inner intermediate lug groove and terminating in the inner intermediate land portion is formed at the end of the groove, and the length of the center lug groove is set to L1. The inner middle When the groove length is L2, the sum of the length L2 and the length of the inner intermediate sipe is L3, and the width of the inner intermediate land portion is L4, the lengths L1 to L4 satisfy L1> L2 and L3> L4. It is characterized by satisfying the relationship.

In the present invention, as described above, the lug grooves (the center lug groove and the inner intermediate lug groove) formed in the center land portion and the inner intermediate land portion are all opened in the main groove that is inward with respect to the vehicle when the vehicle is mounted. On the other hand, since it does not open in the main groove that is outside the vehicle when the vehicle is mounted, the pumping sound and pattern noise during driving will be radiated inward to the vehicle, reducing the noise outside the vehicle. Can do. The lug grooves (center lug groove and inner intermediate lug groove) are both composed of a first inclined portion and a second inclined portion, and the inclination angle with respect to the tire circumferential direction on the opening end side is the tire circumferential direction on the terminal end side. Since it is larger than the inclination angle with respect to, drainage performance can be improved. Furthermore, since the inner intermediate sipe is extended from the end portion of the inner intermediate lug groove, even if one end of the inner intermediate lug groove is terminated in the land portion for noise performance as described above, the inner intermediate sipe is wet by the inner intermediate sipe. Performance can be supplemented. In particular, since the magnitude relationship between the lengths L1 to L4 is set as described above, the dry performance, wet performance, and noise performance can be improved in a well-balanced manner, and these performances can be made highly compatible.

In the present invention, the center land portion and the inner intermediate land portion are chamfered at a portion where the inclination angle of the first inclined portion is an acute angle among the corner portions formed by the main groove and the center lug groove or the inner intermediate lug groove. It is preferable. By chamfering in this way, the water can easily flow in the lug groove, and the drainage performance can be further improved. Moreover, uneven wear can be suppressed.

At this time, it is preferable to make the chamfering depth larger than the effective groove depth and smaller than the main groove depth. By setting the chamfering depth in this way, excellent drainage performance can be maintained until the end of wear.

In the present invention, of the plurality of circumferential land portions, the tire extends in the tire width direction to the outer intermediate land portion on the side that is on the outer side of the vehicle with respect to the vehicle than the center land portion. While communicating with the inner main groove, the outer intermediate lug grooves that terminate in the outer intermediate land portion without communicating with the main groove that becomes the outer side with respect to the vehicle when the vehicle is mounted are spaced apart in the tire circumferential direction. One of the shoulder land portions that is open and extends in the tire width direction to the outer shoulder land portion on the outer side with respect to the vehicle when the vehicle is mounted, and communicates with the main groove that is on the inner side with respect to the vehicle when the vehicle is mounted Thus, it is preferable to form a plurality of outer shoulder lug grooves that terminate in the outer shoulder land portion at intervals in the tire circumferential direction. As a result, the lug grooves (outer intermediate lug groove and outer shoulder lug groove) are also disposed in the land portions (outer intermediate land portion and outer shoulder land portion) on the outer side of the tire equator when mounted on the vehicle. Therefore, drainage performance can be improved. In addition, since the lug grooves (the outer intermediate lug groove and the outer shoulder lug groove) are opened only in the main groove that is inside with respect to the vehicle when the vehicle is mounted, the noise performance is not deteriorated.

In the present invention, the plurality of shoulder land portions that extend in the tire width direction to the inner shoulder land portion on the inner side with respect to the vehicle when the vehicle is mounted and do not communicate with the main groove that becomes the outer side with respect to the vehicle when the vehicle is mounted. The inner shoulder lateral groove of the book is formed at intervals in the tire circumferential direction, and is connected to a main groove that extends from the terminal end of the inner shoulder lateral groove in the extending direction of the inner shoulder lateral groove and that is outward with respect to the vehicle when the vehicle is mounted. It is preferable to provide an inner shoulder sipe. Thereby, although the drainage performance can be enhanced by the inner shoulder lateral groove, the inner shoulder lateral groove is not opened in the main groove on the outer side with respect to the vehicle when the vehicle is mounted, so that the noise performance is not deteriorated. In addition, instead of opening the inner shoulder lateral groove to the main groove on the outer side when the vehicle is mounted, the presence of the inner shoulder sipes can further improve the drainage performance without reducing the noise performance. it can.

In the present invention, a plurality of shoulder land portions that extend in the tire width direction to the outer shoulder land portion on the outer side with respect to the vehicle when the vehicle is mounted and do not communicate with the main groove that is on the inner side with respect to the vehicle when the vehicle is mounted. Preferably, the outer shoulder lateral grooves of the book are formed at intervals in the tire circumferential direction. Thereby, drainage performance can be further improved. In addition, since the outer shoulder lateral groove does not communicate with the main groove, even if noise (air column resonance) due to the main groove occurs, this noise will not be emitted outside the vehicle through the outer shoulder lateral groove. Noise performance is not degraded.

In the present invention, the shoulder land portion extends in the tire width direction to the outer shoulder land portion on the outer side with respect to the vehicle when the vehicle is mounted, and does not communicate with the main groove that is on the inner side with respect to the vehicle when the vehicle is mounted. It is preferable that a plurality of outer shoulder sipes ending in the outer shoulder land portion are formed at intervals in the tire circumferential direction, and the shoulder sipes are configured to have a bent portion. Thereby, since the edge effect by a sipe is obtained, preventing the rigidity of an outer side shoulder land part from falling too much because a sipe has a bending part, drainage performance and dry performance can be improved further. .

In the present invention, it is preferable to provide a plurality of dimples in the outer end region of the shoulder land portion in the tire width direction. As a result, it is possible to reduce running resistance during vehicle running and improve fuel efficiency.

FIG. 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a front view showing a tread surface of the pneumatic tire according to the embodiment of the present invention. FIG. 3 is an explanatory diagram showing an enlarged part of the tread surface of the pneumatic tire according to the embodiment of the present invention. FIG. 4 is an enlarged perspective view showing a chamfered portion of the pneumatic tire according to the embodiment of the present invention. FIG. 5 is an explanatory view showing the structure of the outer shoulder sipe of the pneumatic tire according to the embodiment of the present invention.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, the pneumatic tire T is designated with respect to the mounting direction with respect to the vehicle, the symbol IN is the side that is on the inner side of the vehicle when the vehicle is mounted (hereinafter referred to as the vehicle inner side), Side (hereinafter referred to as the vehicle outside), the symbol CL represents the tire equator. The pneumatic tire T includes a tread portion 1, sidewall portions 2, and bead portions 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 from the tire inner side to the outer side around the bead core 5 disposed in each bead portion 3. 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 in the range of 10 ° to 40 °, for example. 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 of, for example, 0 ° to 5 ° with respect to the tire circumferential direction.

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 illustrated in FIG. 2, a plurality of (four in FIG. 2) main grooves 11 extending in the tire circumferential direction are provided on the outer surface of the tread portion 1 of the pneumatic tire of the present invention, that is, the tread surface 10. It has been. The main groove 11 has a groove width of, for example, 5 mm to 10 mm, and a groove depth of, for example, 7 mm to 9 mm. A plurality of (three in FIG. 2) circumferential land portions 12 extending in the tire circumferential direction are defined between adjacent main grooves 11. Among these circumferential land portions 12, the land portion located on the tire equator is the center land portion 13, and the land portion located inside the vehicle with respect to the center land portion 13 is the inner intermediate land portion 14 and the center land portion 13. The land portion located outside the vehicle is referred to as an outer intermediate land portion 15. Further, on both sides of the tire equator CL in the tire width direction, a shoulder land portion 16 is defined on the outer side in the tire width direction of the outermost main groove 11 in the tire width direction. Of these shoulder land portions 16, the land portion located inside the vehicle is referred to as an inner shoulder land portion 17, and the land portion located outside the vehicle is referred to as an outer shoulder land portion 18. Of the plurality of circumferential land portions 12, the center land portion 13 and the inner intermediate land portion 14 extend in the tire width direction and communicate with the main groove 11 on the vehicle inner side, while A plurality of lug grooves 19 that terminate in the circumferential land portion 12 without communication are formed at intervals in the tire circumferential direction. The lug groove 19 formed in the center land portion 13 is referred to as a center lug groove 20, and the lug groove 19 formed in the inner intermediate land portion 14 is referred to as an inner intermediate lug groove 21. These lug grooves 19 (center lug groove 20 and inner intermediate lug groove 21) have a groove width of, for example, 2 mm to 4 mm, and a groove depth that is shallower than the main groove 11, for example, 4 mm to 7 mm.

As shown in FIG. 3 in an enlarged manner, the center lug groove 20 has different inclination angles with respect to the tire circumferential direction between the first inclined portion 20A on the opening end side and the second inclined portion 20B on the terminal end side. When the inclination angle of the first inclined portion 20A with respect to the tire circumferential direction is θ1a and the inclination angle of the second inclined portion 20B of the center lug groove 20 with respect to the tire circumferential direction is θ1b, the inclination angle θ1a and the inclination angle θ1b are θ1a> The relationship is θ1b. In other words, the center lug groove 20 has the first inclined portion 20A having a relatively large inclination angle with respect to the tire circumferential direction located on the opening end side and the second inclination angle with respect to the tire circumferential direction located on the terminal end side being relatively small. It is comprised from the inclination part 20B. Similarly, the inner intermediate lug groove 21 has different inclination angles with respect to the tire circumferential direction between the first inclined portion 21A on the opening end side and the second inclined portion 21B on the terminal end side, and the first inclined portion of the inner intermediate lug groove 21 When the inclination angle of 21A with respect to the tire circumferential direction is θ2a and the inclination angle of the second inclined portion 21B of the inner intermediate lug groove 21 with respect to the tire circumferential direction is θ2b, the inclination angle θ2a and the inclination angle θ2b have a relationship of θ2a> θ2b. is there. In other words, the inner intermediate lug groove 21 has a first inclined portion 21A having a relatively large inclination angle with respect to the tire circumferential direction located on the opening end side and a first inclination portion with a relatively small inclination angle with respect to the tire circumferential direction located on the terminal end side. 2 inclined portions 21B.

As shown in FIG. 3, the lug groove 19 (the center lug groove 20 and the inner intermediate lug groove 21) has a first inclined portion curved with a predetermined radius of curvature (r1, R1) and a second inclined portion. It is curved with a predetermined curvature radius (r2, R2), and has a shape in which the first inclined portion and the second inclined portion are smoothly connected by a connecting portion having a predetermined curvature radius. At this time, the center points of the open ends of the lug grooves 19 (the center lug groove 20 and the inner intermediate lug groove 21) are p1, P1, the center line (curvature radius r1, R1) of the first inclined portion, and the second inclined portion, respectively. Assuming that the intersections with the center line (curvature radius r2, R2) are p2 and P2, respectively, and the center points of the terminal portions are p3 and P3, respectively, the inclination angle θ1a is a straight line connecting the points p1 and p2 with respect to the circumferential direction. The tilt angle θ2a is an angle formed by a straight line connecting the points P1 and P2 with respect to the circumferential direction, and the tilt angle θ1b is a straight line connecting the points p2 and p3 with respect to the circumferential direction. The inclination angle θ2b is an angle formed by a straight line connecting the points P2 and P3 with respect to the circumferential direction. In FIG. 3, the center line of the connecting portion connecting the first inclined portion and the second inclined portion and the radius of curvature thereof are omitted.

An inner intermediate sipe 22 extending in the extending direction of the second inclined portion 21B of each inner intermediate lug groove 21 and terminating in the inner intermediate land portion 15 is formed at the terminal portion of each inner intermediate lug groove 21. ing. In the present invention, the sipe (the above-described inner intermediate sipe 22 and the inner shoulder sipe 27 and the outer shoulder sipe 29 described later) is a fine groove having a width of 0.5 mm to 1.0 mm and a depth of 4 mm to 7 mm. It is.

Regarding the circumferential land portion 12 and the lug groove 19 arranged in this way, the length of the center lug groove 20 is L1, the length of the inner intermediate lug groove 21 is L2, the length L2 of the inner intermediate lug groove 21 and the inside thereof When the sum of the length of the inner intermediate sipe 22 extending from the end portion of the intermediate lug groove 21 is L3 and the width of the inner intermediate land portion 14 is L4, the lengths L1 to L4 satisfy L1> L2 and L3> L4. Satisfies the relationship. The lengths L1 to L3 are the lengths measured along the center line of each lug groove 19 as shown in FIG. 3, and the length L4 is the length of the inner intermediate land portion 14 in the tire width direction. It is.

By configuring the tread surface 10 in this way, the lug groove 19 opens only in the main groove 11 inside the vehicle and does not open in the main groove 11 outside the vehicle. Will be emitted toward the inside of the vehicle. Therefore, the noise outside the vehicle is reduced and the noise performance can be improved. Further, the lug groove 19 (the center lug groove 20 and the inner intermediate lug groove 21) is composed of the first

inclined portions

20A and 21A and the second

inclined portions

20B and 21B, and is inclined with respect to the tire circumferential direction on the opening end side. Since the angles (θ1A, θ2A) are larger than the inclination angles (θ1B, θ2B) with respect to the tire circumferential direction on the terminal end side, water easily flows in the lug grooves 19 and the drainage performance can be improved. Furthermore, since the inner intermediate sipe 22 is extended from the end portion of the inner intermediate lug groove 21, even if one end of the inner intermediate lug groove 21 is terminated in the land portion for noise performance as described above, The sipe 22 can supplement the wet performance. In addition, since the magnitude relationship between the lengths L1 to L4 is set as described above, the dry performance, wet performance, and noise performance can be improved in a well-balanced manner, and these performances can be made highly compatible.

At this time, a groove having a shape different from the above-described lug groove 19 (the center lug groove 20 and the inner intermediate lug groove 21) is formed in the circumferential land portion 12, for example, the main groove 11 on the vehicle inner side and the vehicle outer side extending in the tire width direction. If a groove communicating with the main groove 11 is formed, the flow of rainwater and the like is improved and the wet performance is improved. However, the pumping sound and pattern noise during driving are also radiated to the outside of the vehicle. It cannot be reduced. Further, since the circumferential land portion 12 is divided in the circumferential direction, the rigidity of the circumferential land portion 12 is reduced, and the dry performance is deteriorated.

If the inclination angles θ1a, θ1b, θ2a, and θ2b deviate from the above-described magnitude relationship, the water does not easily flow through the lug groove 19 as in the case of satisfying the above-described magnitude relationship, and thus the effect of improving drainage performance cannot be obtained. . The inclination angles θ1a, θ1b, θ2a, and θ2b only need to satisfy at least the above magnitude relationship. For example, the inclination angle θ1a is in the range of 10 ° to 30 °, and the inclination angle θ1b is in the range of 40 ° to 70 °. It is preferable that the inclination angle θ2a is set in the range of 10 ° to 30 ° and the inclination angle θ2b is set in the range of 40 ° to 70 °. Setting the range of the inclination angle in this way is advantageous for improving the drainage performance.

If the lengths L1 to L4 deviate from the above magnitude relationship, the dry performance, wet performance, and noise performance cannot be improved in a balanced manner. Specifically, when the length L1 is smaller than the length L2, the dry performance cannot be improved, and when the length L3 is smaller than the length L4, the wet performance cannot be improved. The lengths L1 to L4 need only satisfy at least the above-described magnitude relationship. For example, the length L1 is in the range of 25 mm to 35 mm, the length L2 is in the range of 15 mm to 20 mm, and the length L3 is in the range of 25 mm to 35 mm. The range and length L4 are preferably set in the range of 20 mm to 25 mm. Setting the length range in this way is advantageous for improving the dry performance, wet performance, and noise performance in a well-balanced manner.

As illustrated in FIG. 4, in the circumferential land portion 12 (center land portion 13 and inner intermediate land portion 14), the main groove 11 and lug groove 19 (center lug groove 20 or inner intermediate lug groove 21) are formed. It is preferable to chamfer a portion of the corner portion 23 where the inclination angle of the first inclined portion is an acute angle. By chamfering in this way, the connecting portion between the main groove 11 and the center lug groove 20 or the inner intermediate lug groove 21 becomes gentle, so that drainage performance can be further improved and uneven wear can be suppressed.

At this time, it is preferable that the chamfering depth is larger than the effective groove depth and smaller than the main groove depth. By setting the chamfering depth in this way, excellent drainage performance can be maintained until the end of wear. The effective depth is a depth obtained by subtracting the height of the wear indicator from the main groove depth, and specifically, a depth obtained by subtracting 1.6 mm from the main groove depth. If the depth of the chamfer is smaller than the effective groove depth, the chamfer does not remain until the end of wear, so that excellent drainage performance cannot be maintained until the end of wear.

When chamfering may be set the volume of the missing portion by chamfering (triangular pyramid volume drawn by the dotted line in the drawing) in a range of, for example, 6mm ^³ ~ 8mm ^3. This is advantageous for improving drainage and suppressing uneven wear.

The outer intermediate land portion 15 extends in the tire width direction and communicates with the main groove 11 located inside the vehicle, while terminating in the outer intermediate land portion 15 without communicating with the main groove 11 located outside the vehicle. The plurality of outer intermediate lug grooves 24 are preferably formed at intervals in the tire circumferential direction. The outer shoulder land portion 18 has a plurality of outer shoulder lug grooves 25 that extend in the tire width direction and communicate with the main groove 11 located on the inner side of the vehicle while terminating in the outer shoulder land portion 18. It is preferable to form it at intervals in the circumferential direction. By providing the outer intermediate lug groove 24 and the outer shoulder lug groove 25 in this way, the lug groove 19 (outer intermediate lug) is also formed in the land portion (the outer intermediate land portion 15 and the outer shoulder land portion 18) outside the vehicle on the tire equator. Since the groove 24 and the outer shoulder lug groove 25) are disposed, drainage performance can be improved. Moreover, since the lug groove 19 (the outer intermediate lug groove 24 and the outer shoulder lug groove 25) is opened only in the main groove 11 on the vehicle inner side, the noise performance is not deteriorated.

A plurality of inner shoulder lateral grooves 26 that extend in the tire width direction and do not communicate with the main groove 11 located outside the vehicle are formed in the inner shoulder land portion 17 at intervals in the tire circumferential direction. It is preferable to provide an inner shoulder sipe 27 that extends in the extending direction of the inner shoulder lateral groove 26 from the end of the inner shoulder sipe and is connected to the main groove 11 located outside the vehicle. Thereby, although the drainage performance can be enhanced by the inner shoulder lateral groove 26, the inner shoulder lateral groove 27 does not open to the main groove 11 outside the vehicle, so that the noise performance is not deteriorated. Further, instead of opening the inner shoulder lateral groove 26 to the main groove 11 outside the vehicle, the presence of the inner shoulder sipe 27 can further enhance the drainage performance without deteriorating the noise performance.

The outer shoulder land portion 18 is preferably formed with outer shoulder lateral grooves 28 extending in the tire width direction and not communicating with the main groove 11 located on the inner side of the vehicle, spaced apart in the tire circumferential direction. Thereby, drainage performance can be further improved. Further, since the outer shoulder lug groove 28 is not in communication with the main groove 11, it is possible to prevent the air column resonance generated from the main groove 11 from being emitted outside the vehicle through the outer shoulder lug groove 28.

In addition, although the edge part of the tire width direction outer side of the inner side shoulder horizontal groove 26 and the outer side shoulder horizontal groove 28 may each terminate in the shoulder land part 16, it terminates in the shoulder land part 16 as shown in FIG. It is preferable not to extend to the outer side in the tire width direction of each shoulder land portion 16. Thereby, drainage performance can be further improved.

The outer shoulder land portion 18 has a plurality of outer shoulder sipes 29 extending in the tire width direction and not communicating with the main groove 11 located on the inner side of the vehicle while terminating in the outer shoulder land portion 18 in the tire circumferential direction. It is preferable to form it at intervals. At this time, it is preferable that the shape of the outer side shoulder sipe 20 is not a linear shape but a shape having a bent portion. Thereby, since the edge effect by a sipe is obtained, preventing the rigidity of an outer side shoulder land part from falling too much because a sipe has a bending part, drainage performance and dry performance can be improved further. .

In particular, as shown in FIG. 5, the shape of the outer shoulder sipe 29 is linear at the portion 29A on the tread surface side (upper side in the figure), while it is zigzag at the portion 29B on the groove bottom side (lower side in the figure). It is preferable to constitute so that. In this manner, zigzag sipe, which is harder to reduce rigidity than linear sipe, appears on the tread surface in the late stage of wear, when the rigidity of the land portion is reduced compared to the initial wear. As a result, the rigidity of the land portion can be effectively maintained. In FIG. 5, the outer shoulder sipe 29 is shown by a solid line while the outer shoulder land portion 18 (a part thereof) is shown by an alternate long and short dash line so that the structure of the outer shoulder sipe 29 becomes clear. An auxiliary line (broken line) is drawn so that the positional relationship between the tread surface side portion 29A of the sipe 29 and the groove bottom side portion 29B (particularly the groove bottom portion) becomes clear.

As in the embodiment shown in FIG. 2, a circumferential narrow groove 30 may be formed in the outer shoulder land portion 18. The circumferential narrow groove 30 has a groove width of 2 mm to 3 mm, a groove depth of 4 mm to 6 mm, a groove depth and a groove width smaller than those of the main groove 11, and a groove depth and a groove width larger than those of the sipe. It is a groove. The circumferential narrow groove 30 is disposed on the outer side in the tire width direction with respect to the end portion of the outer shoulder lug groove 25 and on the inner side in the tire width direction with respect to the end portions on the tire equator CL side of the outer shoulder lateral groove 28 and the outer shoulder sipes 29. The outer shoulder lug groove 25, the outer shoulder lateral groove 28, and the outer shoulder sipes 29 are preferably not communicated with each other. By doing in this way, drainage performance can be improved, suppressing the rigidity fall of a land part like the case where the main groove 11 is provided. Further, since the circumferential narrow groove 30 does not communicate with any of the outer shoulder lug groove 25, the outer shoulder lateral groove 28, and the outer shoulder sipe 29, even if air column resonance is generated due to the circumferential narrow groove 30, It can be prevented from being radiated to the outside of the vehicle, and noise performance is not deteriorated.

The number of the main grooves 11 is not particularly limited as long as at least four main grooves 11 are formed. From the relationship between the drainage performance by the grooves and the rigidity of the tread surface, four main grooves 11 as in the embodiment of FIG. 11 is preferably provided. That is, it is preferable to partition and form three circumferential land portions 12 and one (two in total) shoulder land portions 16 on both sides in the tire width direction.

The width of the circumferential land portion 12 may be constant, but may be different from each other as in the embodiment shown in FIG. Specifically, when the width of the center land portion 13 is W1, the width of the inner intermediate land portion 14 is W2 (= L4), and the width of the outer intermediate land portion 15 is W3, the widths W1 to W3 are W1> W2 It is preferable to satisfy the relationship> W3.

It is preferable to provide a plurality of dimples 32 in the end region 31 on the outer side in the tire width direction of the shoulder land portion 18. As a result, it is possible to reduce running resistance and improve fuel efficiency during vehicle running.

The tire size is 215 / 60R17 96H, has the cross-sectional shape illustrated in FIG. 1, is based on the tread pattern of FIG. 2, and the shape of the center lug groove (open / non-open with respect to the main groove on the vehicle inside / outside), Inclination angle θ1a, θ1b, length L1, presence / absence of chamfering at corner formed by center lug groove, chamfering depth (effective groove depth ratio), inner intermediate lug groove and inner intermediate sipe structure (groove and / or Presence / absence of sipe), shape (opening / non-opening with respect to main groove inside / outside of vehicle), inclination angles θ2a, θ2b, lengths L2, L3, presence / absence of chamfering at corners formed by inner intermediate lug grooves, chamfering depth (Effective groove depth ratio), inner intermediate land width L4, outer intermediate lug groove shape (opening / non-opening with respect to vehicle inner / outer main groove), outer shoulder lug groove shape (main inner vehicle width) / Opening / non-opening to circumferential narrow groove), shape of outer shoulder lateral groove (opening / non-opening to circumferential narrow groove), presence / absence of inner shoulder lateral groove, shape (opening / non-opening to main groove outside vehicle), inside Conventional Example 1, Comparative Examples 1 to 3, and Example 1 in which the presence / absence and shape of the shoulder sipe (opening / non-opening with respect to the main groove outside the vehicle), the presence / absence of the outer shoulder sipe and the shape are set as shown in Tables 1 and 2, respectively. 17 types of pneumatic tires of 13 to 13 were produced.

In the conventional example 1, there is no inner intermediate sipe, the inner intermediate lug groove also opens in the main groove on the vehicle outer side, the inner intermediate land portion forms a block row, and the end portion on the vehicle outer side instead of the inner shoulder lateral groove. Is a non-opening with respect to the main groove outside the vehicle, while an end portion on the vehicle inner side is provided with a sipe (linear shape) that terminates in the inner shoulder land portion. Further, in Comparative Examples 1 to 3 and Examples 1 to 13, the outer end portions of the inner shoulder lateral grooves and the outer shoulder lateral grooves in the tire width direction are not terminated in the shoulder land portions as shown in FIG. As shown in FIG. 2, the outer shoulder sipe extends to the outer side in the tire width direction of the shoulder land portion, and one end portion does not communicate with the circumferential narrow groove, and the other end portion is the outer shoulder land. Terminates within the department.

In the column of “chamfering depth (effective groove depth ratio)” in the table, “110%” in Example 7 indicates that the chamfering depth exceeds the effective groove depth and is the same as the main groove depth. Means that In the column of “shape” of “outer shoulder sipe” in the table, “2D” means a straight sipe, and “3D” means that the tread surface side is straight and the groove bottom side is as shown in FIG. It means a sipe that is zigzag shaped.

These 17 types of pneumatic tires were evaluated for noise performance, dry performance, wet performance, and fuel efficiency 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 17x6.5J, mounted on a test vehicle (front-wheel drive vehicle) with a displacement of 2.4L with air pressure of 230kPa, and EEC / ECE tires that comply with European passing sound regulations The passing sound was measured according to the measurement method based on the single noise regulation. The evaluation results are shown as an index with the conventional example 1 as 100, using the reciprocal of the measured value. The larger the index value, the smaller the passing noise and the better the noise performance.

Dry performance Dry asphalt in which each test tire is assembled to a wheel with a rim size of 17 × 6.5J, mounted on a test vehicle (front-wheel drive vehicle) with a displacement of 2.4 liters with a pneumatic pressure of 230 kPa, and pylons installed at intervals of 35 m The time required for the test driver to run on the slalom on the 175 m slalom test road consisting of the road surface was measured. The evaluation results are shown as an index with the conventional example 1 as 100, using the reciprocal of the measured value. The larger the index value, the shorter the required time and the better the dry performance.

Wet performance Each test tire is mounted on a wheel with a rim size of 17 × 6.5J, mounted on a test vehicle (front-wheel drive vehicle) with a displacement of 2.4L with an air pressure of 230kPa, and pylons installed at 35m intervals. The time required for the test driver to run on a slalom was measured on a 175 m slalom test road consisting of a 3 mm asphalt road surface. The evaluation results are shown as an index with the conventional example 1 as 100, using the reciprocal of the measured value. The larger the index value, the shorter the required time and the better the wet performance.

Fuel consumption performance Each test tire is mounted on a wheel with a rim size of 17 x 6.5 J, mounted on a test vehicle (front-wheel drive vehicle) with a displacement of 2.4 L with an air pressure of 230 kPa, and traveling for 1 hour at a speed of 100 km / h Fuel consumption (mileage per unit capacity of fuel) was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. A larger index value means better fuel efficiency.

As is apparent from Table 1, Examples 1 to 13 all improved noise performance, dry performance, wet performance, and annual performance compared to Conventional Example 1.

On the other hand, in Comparative Example 1 in which the magnitude relationships of the inclination angles θ1a, θ1b, θ2a, and θ2b of the center lug groove and the inner intermediate lug groove were reversed, the drainage performance was worse than that of the conventional example 1. In Comparative Example 2 having no inner intermediate sipe (that is, an example in which the inner intermediate lug groove is not opened with respect to the main groove outside the vehicle in Conventional Example 1), the noise performance is higher than that of Conventional Example 1. However, the wet performance was worse than that of Conventional Example 1. In Comparative Example 3 in which the magnitude relationship between the lengths L1 to L4 was reversed, the dry performance and wet performance were worse than those in Conventional 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 Main groove 12 Circumferential land part 13 Center land part 14 Inner intermediate land part 15 Outer intermediate part Land portion 16 Shoulder land portion 17 Inner shoulder land portion 18 Outer shoulder land portion 19 Lug groove 20 Center lug groove 20A First inclined portion 20B Second inclined portion 21 Inner intermediate lug groove 21A First inclined portion 21B Second inclined portion 22 Inside Intermediate sipe 23 Corner 24 Outer intermediate lug groove 25 Outer shoulder lug groove 26 Inner shoulder lateral groove 27 Inner shoulder sipe 28 Outer shoulder lateral groove 29 Outer shoulder sipe 30 Circumferential narrow groove 31 End region 32 Dimple CL Tire equator

Claims

The tread surface has at least four main grooves extending in the tire circumferential direction, a plurality of circumferential land portions extending in the tire circumferential direction are defined between adjacent main grooves, and each outermost portion in the tire width direction is defined. In a pneumatic tire in which a shoulder land portion is defined on the outer side in the tire width direction of the main groove, and the mounting direction with respect to the vehicle is specified,
Among the plurality of circumferential land portions, the center land portion located on the tire equator extends in the tire width direction and communicates with a main groove that is inward with respect to the vehicle when the vehicle is mounted. A plurality of center lug grooves that terminate in the center land portion without communicating with a main groove that is on the outside are formed at intervals in the tire circumferential direction, and the center of the plurality of circumferential land portions is formed. Extends in the tire width direction to the inner intermediate land portion on the inner side with respect to the vehicle when the vehicle is mounted than the land portion, and communicates with the main groove on the inner side with respect to the vehicle when the vehicle is mounted. A plurality of inner intermediate lug grooves that terminate in the inner intermediate land portion without communicating with the main groove that is on the outer side, are formed at intervals in the tire circumferential direction, and the center lug groove and the inner intermediate lug Each groove is located on the open end side It is composed of a first inclined portion with a relatively large inclination angle with respect to the tire circumferential direction and a second inclined portion with a relatively small inclination angle with respect to the tire circumferential direction located on the end side, and at the end portion of each inner intermediate lug groove An inner intermediate sipe extending in the extending direction of the second inclined portion of each inner intermediate lug groove and terminating in the inner intermediate land portion is formed, and the length of the center lug groove is L1, and the inner intermediate lug groove When the length of L1 is L2, the sum of the length L2 and the length of the inner intermediate sipe is L3, and the width of the inner intermediate land portion is L4, the lengths L1 to L4 satisfy the relationship of L1> L2 and L3> L4. A pneumatic tire characterized by satisfying.
Of the corners formed by the main groove and the center lug groove or the inner intermediate lug groove in the center land portion and the inner intermediate land portion, chamfering is performed on a portion where the inclination angle of the first inclined portion is an acute angle. The pneumatic tire according to claim 1, wherein
The pneumatic tire according to claim 2, wherein the chamfering depth is larger than the effective groove depth and smaller than the main groove depth.
Of the plurality of circumferential land portions, the tire extends in the tire width direction to the outer intermediate land portion on the outer side with respect to the vehicle when the vehicle is mounted than the center land portion, and becomes the inner side with respect to the vehicle when the vehicle is mounted. While communicating with the main groove, a plurality of outer intermediate lug grooves that terminate in the outer intermediate land portion without communicating with the main groove that is outside the vehicle when the vehicle is mounted are spaced apart in the tire circumferential direction. While forming and extending in the tire width direction to the outer shoulder land portion on the side that becomes the outer side with respect to the vehicle when the vehicle is mounted, and communicates with the main groove that becomes the inner side with respect to the vehicle when the vehicle is mounted. The pneumatic tire according to any one of claims 1 to 3, wherein a plurality of outer shoulder lug grooves that terminate in the outer shoulder land portion are formed at intervals in the tire circumferential direction.
A plurality of inner shoulders that extend in the tire width direction and do not communicate with a main groove that is outward with respect to the vehicle when the vehicle is mounted on the inner shoulder land portion that is on the inner side with respect to the vehicle when the vehicle is mounted. An inner shoulder sipe that forms a transverse groove at intervals in the tire circumferential direction and extends from the terminal end of the inner shoulder transverse groove in the extending direction of the inner shoulder transverse groove and is connected to a main groove that is outside the vehicle when the vehicle is mounted. The pneumatic tire according to any one of claims 1 to 4, further comprising:
A plurality of outer shoulders that extend in the tire width direction and do not communicate with a main groove that is inward with respect to the vehicle when the vehicle is mounted, on the outer shoulder land portion on the outer side with respect to the vehicle when the vehicle is mounted. 6. The pneumatic tire according to claim 1, wherein the lateral grooves are formed at intervals in the tire circumferential direction.
Of the shoulder land portion, the outer shoulder land portion on the outer side with respect to the vehicle when mounted on the vehicle extends in the tire width direction and does not communicate with the main groove on the inner side with respect to the vehicle when mounted on the vehicle. The plurality of outer shoulder sipes ending in the shoulder land portion are formed at intervals in the tire circumferential direction, and the shoulder sipes are configured to have a bent portion. Pneumatic tire described in 2.
The pneumatic tire according to any one of claims 1 to 7, wherein a plurality of dimples are provided in an end region on the outer side in the tire width direction of the shoulder land portion.