JP2012218650A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make compatible the steering stability, the drainage performance and the noise resistance performance with a high dimension.SOLUTION: This pneumatic tire 1 has an asymmetrical tread pattern and keeps the setting direction fixed to a vehicle. The groove width Gcr of a crown vertical groove 3A, the groove width Gso of an outer shoulder vertical groove 4A and the groove width Gsi of the inner shoulder vertical groove 4B satisfy the following formula (1) and (2). Moreover, the width Wcr of the crown land part 5, the width Wmo of the outer middle land part 6A and the width Wmi of the inner middle land part 6B satisfy the following formula (3) and (4). The outer middle land part 6A and the inner middle land part 6B are provided with the outer slot 15A and the inner slot 15B, respectively, and the length L3a of the outer slot 15A is larger than the length L3b of the inner slot 15B.0.8≤Gso/Gcr≤1.1 (1), 0.8≤Gsi/Gcr≤1.1 (2), 1.0≤Wmo/Wcr≤1.2 (3), and 1.0≤Wmi/Wcr≤1.2 (4).

Description

  The present invention relates to a pneumatic tire that can achieve a high level of handling stability, drainage performance, and noise resistance.

  Conventionally, there has been proposed a pneumatic tire in which an asymmetric tread pattern with respect to the tire equator is formed in the tread portion of the tire and the mounting direction to the vehicle is designated. Such tires can be given different characteristics to the tread portion on the vehicle inner side and the vehicle outer side when the vehicle is mounted.

  For example, Patent Document 1 proposes a pneumatic tire in which two longitudinal main grooves extending continuously in the tire circumferential direction are arranged on the vehicle inner side and one on the vehicle outer side. Such a pneumatic tire has a relatively large tread rigidity on the outside of the vehicle to improve the steering stability performance.

Japanese Patent Laid-Open No. 10-217719

  However, the pneumatic tire as described above has a problem that the drainage performance tends to be lowered because the land ratio of the tread portion on the outside of the vehicle becomes excessively large. Furthermore, since the longitudinal main groove continuously extends in the tire circumferential direction, there is a problem that the resonance noise (air column resonance) of the air passing through the tire groove increases, and the noise resistance performance tends to be lowered.

  In addition, by providing a plurality of horizontal grooves in the tread, the water film interposed between the tread and the road surface can be smoothly discharged to the tread end side, and the air column can be disturbed to improve drainage performance and noise resistance. It is also conceivable to suppress performance degradation.

  However, if the lateral grooves are simply provided, there is a problem that the rigidity of the tread portion becomes excessively small, and the steering stability performance tends to be lowered.

  The present invention has been devised in view of the above situation, and the width Wcr of the crown land portion, the width Wmo of the outer middle land portion, the width Wmi of the inner middle land portion, and the groove width Gcr of the crown vertical groove. The groove width Gso of the outer shoulder vertical groove and the groove width Gsi of the inner shoulder vertical groove are defined within a certain range, and the outer slot length of the outer middle land portion is set to be longer than the inner slot length of the inner middle land portion. The main purpose is to provide a pneumatic tire that can achieve a high level of compatibility between steering stability performance, drainage performance, and noise resistance performance.

According to the first aspect of the present invention, in the tread portion, a pair of crown longitudinal grooves extending continuously in the tire circumferential direction on both sides of the tire equator, and a tire axial direction outer side of the crown longitudinal groove in the tire circumferential direction. By providing a pair of shoulder longitudinal grooves extending continuously, one crown land portion extending on the tire equator, a pair of middle land portions extending between the crown longitudinal groove and the shoulder longitudinal groove, A pneumatic tire in which a shoulder land portion extending between the shoulder longitudinal groove and a tread grounding end is divided, and the tread portion has an asymmetric tread pattern with respect to the tire equator and is attached to a vehicle. And the pair of crown flutes have the same groove width Gcr, and the groove width Gcr and the groove width of the outer shoulder flutes positioned outside the vehicle when mounted on the vehicle. Gso and the groove width Gsi of the inner shoulder longitudinal groove located inside the vehicle when the vehicle is mounted satisfy the following formulas (1) and (2), the width Wcr of the crown land portion in the tire axial direction, and the vehicle outer side when the vehicle is mounted The width Wmo in the tire axial direction of the outer middle land portion located in the vehicle and the width Wmi in the tire axial direction of the inner middle land portion located inside the vehicle when the vehicle is mounted satisfy the following formulas (3) and (4), The outer middle land portion and the inner middle land portion are each provided with an outer slot and an inner slot that extend from the outer edge that is the vehicle outer side when the vehicle is mounted to the vehicle inner side and terminate without reaching the inner edge of the vehicle inner side, respectively. The length of the outer slot in the tire axial direction is longer than the length of the inner slot in the tire axial direction.
0.8 ≦ Gso / Gcr ≦ 1.1 (1)
0.8 ≦ Gsi / Gcr ≦ 1.1 (2)
1.0 ≦ Wmo / Wcr ≦ 1.2 (3)
1.0 ≦ Wmi / Wcr ≦ 1.2 (4)

  The crown longitudinal groove and the shoulder longitudinal groove of the invention according to claim 2 are such that the outer groove wall positioned outside the vehicle when the vehicle is mounted is more tread than the inner groove wall positioned inside the vehicle when the vehicle is mounted. The pneumatic tire according to claim 1, wherein the pneumatic tire is inclined at a large angle with respect to the normal.

According to a third aspect of the present invention, the width Wcr in the tire axial direction of the crown land portion, the width Wso in the tire axial direction of the outer shoulder land portion positioned outside the vehicle when the vehicle is mounted, and the position inside the vehicle when mounted on the vehicle. The pneumatic tire according to claim 1 or 2, wherein a width Wsi of the inner shoulder land portion in the tire axial direction satisfies the following expressions (5) and (6).
1.3 ≦ Wsi / Wcr ≦ 2.5 (5)
1.3 ≦ Wso / Wcr ≦ 2.5 (6)

  According to a fourth aspect of the present invention, each shoulder land portion is provided with a shoulder lateral groove extending inward in the tire axial direction from the tread ground end, and the shoulder lateral groove is located on the outer side of the vehicle when the vehicle is mounted. An outer shoulder lateral groove provided on the inner portion and an inner shoulder lateral groove provided on an inner shoulder land portion located on the inner side of the vehicle when the vehicle is mounted. At least the outer shoulder lateral groove terminates without reaching the outer shoulder longitudinal groove. The pneumatic tire according to any one of claims 1 to 3.

  According to a fifth aspect of the present invention, each of the longitudinal grooves includes an outer arc connecting the groove bottom surface and an outer groove wall positioned outside the vehicle when the vehicle is mounted, and an inner position positioned inside the vehicle when the groove bottom surface and the vehicle are mounted. The pneumatic tire according to any one of claims 1 to 4, wherein a radius of curvature of an inner arc connecting the side groove walls is 3 to 5 mm.

  According to a sixth aspect of the present invention, the inner middle land portion has one end in the middle region in the tire axial direction of the inner middle land portion and the other end between the inner slots adjacent in the tire circumferential direction. 6. The pneumatic tire according to claim 1, wherein a middle sipe that communicates with the inner shoulder longitudinal groove is provided, and the middle sipe is inclined at an angle of 20 to 70 degrees with respect to a tire circumferential direction.

  The invention according to claim 7 is the pneumatic tire according to claim 6, wherein the angle of the middle sipe gradually decreases from the one end toward the other end.

  The dimensions of each part of the tire are values specified in a normal state in which the rim is assembled to a normal rim and the normal internal pressure is filled unless otherwise specified.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, JATMA is a standard rim, TRA is “Design Rim”, and ETRTO is a standard rim. If present, it means "Measuring Rim".

  The “regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for ETRA, Then, “INFLATION PRESSURE” is set, but when the tire is for a passenger car, the pressure is uniformly set to 180 kPa.

  In the pneumatic tire of the present invention, a pair of crown longitudinal grooves extending continuously in the tire circumferential direction on both sides of the tire equator on the tread portion, and the tire axial direction outside of the crown longitudinal grooves continuously extending in the tire circumferential direction. A pair of shoulder flutes are provided. As a result, the tread portion includes one crown land portion extending on the tire equator, a pair of middle land portions extending between the crown longitudinal groove and the shoulder longitudinal groove, and between the shoulder longitudinal groove and the tread grounding end. And the shoulder land that extends. Further, the tread portion has an asymmetric tread pattern with respect to the tire equator, and the mounting direction to the vehicle is designated.

The pair of crown longitudinal grooves each have the same groove width Gcr, and the groove width Gcr, the groove width Gso of the outer shoulder longitudinal groove positioned outside the vehicle when the vehicle is mounted, and the inner side of the vehicle when mounted on the vehicle. The groove width Gsi of the inner shoulder longitudinal groove satisfies the following formulas (1) and (2).
0.8 ≦ Gsi / Gcr ≦ 1.1 (1)
0.8 ≦ Gso / Gcr ≦ 1.1 (2)

  Thereby, the groove width Gcr of the crown vertical groove, the groove width Gso of the outer shoulder vertical groove, and the groove width Gsi of the inner shoulder vertical groove can be made substantially uniform. The water film can be discharged in a well-balanced manner, and drainage performance can be improved effectively.

Further, the width Wcr of the crown land portion in the tire axial direction, the width Wmo of the tire middle direction of the outer middle land portion located outside the vehicle when the vehicle is mounted, and the tire axial direction of the inner middle land portion positioned inside the vehicle when the vehicle is mounted The width Wmi satisfies the following expressions (3) and (4).
1.0 ≦ Wmi / Wcr ≦ 1.2 (3)
1.0 ≦ Wmo / Wcr ≦ 1.2 (4)

  Thereby, the rigidity of the crown land portion, the outer middle land portion, and the inner middle land portion can be made uniform, and the steering stability performance and the straight running stability performance can be improved in a balanced manner. Further, each land portion can suppress a large difference in the land ratio, and the groove width Gcr of the crown vertical groove, the groove width Gso of the outer shoulder vertical groove 4A, and the groove width Gsi of the inner shoulder vertical groove can be reduced. Since the above formulas (1) and (2) are satisfied, it is possible to effectively prevent a decrease in drainage performance in any state.

  Furthermore, the outer middle land portion and the inner middle land portion are each provided with an outer slot and an inner slot that extend from the outer edge that is the vehicle outer side when the vehicle is mounted to the vehicle inner side and terminate without reaching the inner edge of the vehicle inner side.

  Such outer and inner slots can improve the drainage performance because the water film interposed between the outer and inner middle land portions and the road surface can be discharged to the outside of the vehicle. In addition, since the outer and inner slits terminate without reaching the inner edge on the inner side of the vehicle, the rigidity of the outer and inner middle land portions can be suppressed from being excessively reduced, and the steering stability performance can be maintained. Further, the inner and outer slots can disturb the air column of each longitudinal groove, and can improve noise resistance.

  In addition, the length of the outer slot in the tire axial direction is larger than the length of the inner slot in the tire axial direction. As a result, the outer slot can effectively improve the drainage performance that tends to decrease outside the vehicle during turning, and can effectively disturb the air column of the longitudinal groove, thereby improving the noise resistance performance.

It is a tread development view of the pneumatic tire of this embodiment. It is AA sectional drawing of FIG. FIG. 3 is an enlarged view of FIG. 2. It is a figure which expands and shows the vehicle outer side of FIG. It is a figure which expands and shows the vehicle inner side of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a pneumatic tire (hereinafter sometimes simply referred to as a “tire”) 1 according to the present embodiment is a passenger car having a left-right asymmetric tread pattern in which the mounting direction of the vehicle is specified. It is configured as a summer tire for use.

  Further, the direction of mounting on the vehicle is clearly indicated by letters (for example, “INSIDE” and / or “OUTSIDE”) on the sidewall portion of the tire 1 (not shown).

  In the tread portion 2 of the tire 1, a pair of crown longitudinal grooves 3 extending continuously in the tire circumferential direction on both sides of the tire equator, and the tire longitudinal direction outside of the crown longitudinal grooves 3 continuously extending in the tire circumferential direction. A pair of shoulder longitudinal grooves 4 are provided. As a result, the tread portion 2 includes one crown land portion 5 extending on the tire equator C, a pair of middle land portions 6 extending between the crown vertical groove 3 and the shoulder vertical groove 4, and the shoulder vertical groove 4. Shoulder land portions 7 and 7 extending from the tread grounding end 2t are divided.

  In the present specification, the “tread ground contact 2t” is an edge when it can be identified by a clear edge in appearance, but when it cannot be identified, a normal load is applied to the tire 1 in the normal state. Thus, a tread grounding end 2t is defined as a grounding end that is grounded to the plane on the outermost side in the tire axial direction when the tread portion 2 is grounded to the plane with a camber angle of 0 degrees.

  The “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 specified for JATMA, and the table “TIRE LOAD LIMITS” is set for TRA. The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

  The crown longitudinal groove 3 and the shoulder longitudinal groove 4 are both straight grooves extending linearly along the tire circumferential direction. Such straight grooves can smoothly drain the water film interposed between the tread surface and the road surface in the tire circumferential direction during straight traveling and turning, and can improve drainage performance. Preferably, the groove depths D1 and D2 (shown in FIG. 2) of the longitudinal grooves 3 and 4 are about 7.0 to 8.5 mm.

  Further, as shown in FIG. 3, the crown vertical groove 3 and the shoulder vertical groove 4 have a groove bottom surface 11, a groove bottom surface 11, and an outer surface 2 </ b> S of the tread portion 2 in a groove cross section perpendicular to the groove length direction. And a pair of groove walls 12 extending with an inclination with respect to the tread normal N.

  The groove wall 12 includes an outer groove wall 12o positioned on the vehicle outer side when the vehicle is mounted and an inner groove wall 12i positioned on the vehicle inner side. The outer groove wall 12o is set such that the angle α1o with respect to the tread normal N is larger than the angle α1i of the inner groove wall 12i.

  Such an outer groove wall 12o can increase the lateral rigidity toward the inside of the vehicle while suppressing a decrease in the land ratio of each of the crown land portion 5, the middle land portion 6, and the shoulder land portion 7, and is capable of improving the steering stability performance. Can be improved.

  Here, the land ratio is the ratio of the contact area of the land portion to the surface area measured in a state where all the grooves of the outer surface 2S (shown in FIG. 2) of the tread portion 2 are filled in each of the land portions 5, 6, and 7. It is represented by

  If the angle α1o is small, there is a possibility that the above-described effects cannot be exhibited sufficiently. On the other hand, if the angle α1o is too large, the land ratio of each of the land portions 5, 6, and 7 may be excessively lowered, and the steering stability performance and the straight running stability performance may not be sufficiently exhibited. From such a viewpoint, the angle α1o is preferably 1.0 times or more, more preferably 1.1 times or more, more preferably 1.1 times or more, more preferably 3.0 times or less, more preferably the angle α1i of the inner groove wall 12i. Is desirably 2.0 times or less.

  Each longitudinal groove 3, 4 is provided with an outer arc 13 o that connects the groove bottom surface 11 and the outer groove wall 12 o in an arc shape, and an inner arc 13 i that connects the groove bottom surface 11 and the inner groove wall 12 i. Such outer and inner arcs 13o and 13i can disperse distortion that tends to occur at the corners of the groove bottom surface 11 and the outer and inner groove walls 12o and 12i, and each crown land portion 5 and middle land portion 6 can be dispersed. And the lateral rigidity of the shoulder land portion 7 can be effectively increased.

  Furthermore, it is desirable that the radius of curvature R1 of the outer arc 13o is larger than the radius of curvature R2 of the inner arc 13i. Thus, the outer arc 13o can increase the lateral rigidity toward the vehicle inner side due to the synergistic effect with the outer groove wall 12o, and can effectively improve the steering stability performance.

  In addition, when the curvature radius R1 of the outer arc 13o is small, there is a possibility that the above-described operation cannot be effectively exhibited. Conversely, if the radius of curvature R1 is too large, the groove volume of each of the longitudinal grooves 3 and 4 becomes small, and the drainage state may be lowered. From this point of view, the radius of curvature R1 is preferably 3.0 mm or more, more preferably 4.0 mm or more, and preferably 8.0 mm or less, more preferably 7.0 mm or less.

  From the same viewpoint, the radius of curvature R2 of the inner arc 13i is preferably 1.0 mm or more, more preferably 2.0 mm or more, and preferably 6.0 mm or less, more preferably 5.0 mm or less.

  As shown in FIG. 1, the crown longitudinal groove 3 is divided into an outer crown longitudinal groove 3A located on the vehicle outer side and an inner crown longitudinal groove 3B located on the vehicle inner side. The crown longitudinal grooves 3A and 3B of the present embodiment have the same groove widths Gcr and Gcr, respectively, and distances L1i and L1o in the tire axial direction between the groove center lines 3Ac and 3Bc and the tire equator C are respectively set. Set the same.

  These crown longitudinal grooves 3A and 3B can discharge the water film between the crown surface grooves 3A and 3B in the tire circumferential direction with good balance on the vehicle inner side and the outer side in the vicinity of the tire equator C. Preferably, the distances L1i and L1o are about 8 to 15% of the tread width TW. The tread width TW is a tire axial distance between the tread ground contact ends 2t and 2t in a normal state.

  The shoulder vertical groove 4 includes an outer shoulder vertical groove 4A located on the vehicle outer side and an inner shoulder vertical groove 4B located on the vehicle inner side. The shoulder longitudinal grooves 4A and 4B of the present embodiment are set to have the same distance L2i and L2o in the tire axial direction between the groove center lines 4Ac and 4Bc and the tire equator C, like the crown longitudinal grooves 3A and 3B. The

  Such shoulder longitudinal grooves 4A and 4B can smoothly discharge the water film between the road surface and the road surface on the tread grounding end 2t and 2t side inside and outside the vehicle. Preferably, the distances L2i and L2o are about 25 to 30% of the tread width TW.

In the present embodiment, the groove width Gcr of each of the crown vertical grooves 3A and 3B, the groove width Gso of the outer shoulder vertical groove 4A, and the groove width Gsi of the inner shoulder vertical groove 4B are expressed by the following formulas (1) and (2). Meet.
0.8 ≦ Gso / Gcr ≦ 1.1 (1)
0.8 ≦ Gsi / Gcr ≦ 1.1 (2)

  Accordingly, the groove width Gcr of each crown vertical groove 3A, 3B, the groove width Gso of the outer shoulder vertical groove 4A, and the groove width Gsi of the inner shoulder vertical groove 4B can be made substantially uniform. The water film between the road surface and the road surface can be discharged in a well-balanced manner, and the drainage performance can be effectively improved.

  If the ratio (Gso / Gcr) is less than 0.8, the groove width Gso of the outer shoulder vertical groove 4A is reduced, and the water film between the road surface and the tread portion 2 on the vehicle inner side is sufficiently discharged. It may not be possible. On the contrary, when the above (Gso / Gcr) exceeds 1.1, the groove width Gcr of each crown longitudinal groove 3A, 3B becomes small, and the water film between the road surface and the tire equator C cannot be sufficiently discharged. There is a fear. From such a viewpoint, the ratio (Gsi / Gcr) is preferably 0.85 or more, and more preferably 1.05 or less.

  Similarly, the ratio (Gsi / Gcr) is preferably 0.85 or more and preferably 1.05 or less. Furthermore, it is desirable that the groove width Gcr, the groove width Gso, and the groove width Gsi are the same.

  Next, the crown land portion 5 is composed of straight ribs extending linearly in the tire circumferential direction on the tire equator C, and in this embodiment, no siping or slots are provided. Such a crown land portion 5 can increase its rigidity and improve straight running stability performance.

  The middle land portion 6 includes an outer middle land portion 6A located outside the vehicle and an inner middle land portion 6B located inside the vehicle. The outer middle land portion 6A and the inner middle land portion 6B are also made of the same straight rib as the crown land portion 5, and can improve the lateral stability by improving the steering stability performance.

In the present embodiment, the width Wcr of the crown land portion 5 in the tire axial direction, the width Wmo of the outer middle land portion 6A in the tire axial direction, and the width Wmi of the inner middle land portion 6B in the tire axial direction are expressed by the following formula (3). And (4) is satisfied.
1.0 ≦ Wmo / Wcr ≦ 1.2 (3)
1.0 ≦ Wmi / Wcr ≦ 1.2 (4)

  Thereby, the crown land portion 5, the outer middle land portion 6A, and the inner middle land portion 6B can equalize their rigidity and improve the steering stability performance and the straight running stability performance in a balanced manner.

  Further, it is possible to suppress a large difference between the land ratio of the outer and inner middle land portions 6A and 6B and the land ratio of the crown land portion 5, and as described above, each crown longitudinal groove 3A, Since the groove width Gcr of 3B, the groove width Gso of the outer shoulder vertical groove 4A, and the groove width Gsi of the inner shoulder vertical groove 4B satisfy the above formulas (1) and (2), it is possible to effectively prevent a decrease in drainage performance. sell.

  If the ratio (Wmo / Wcr) is less than 1.0, the rigidity and land ratio of the outer middle land portion 6A become excessively small, and the steering stability performance and drainage performance may be deteriorated. On the contrary, if the ratio (Wmo / Wcr) exceeds 1.2, the rigidity of the crown land portion 5 and the land ratio are excessively small, and the drainage performance and the straight running stability performance may be deteriorated. From such a viewpoint, the ratio (Wmo / Wcr) is more preferably 1.05 or more, and further preferably 1.15 or less.

  Similarly, the ratio (Wmi / Wcr) is more preferably 1.05 or more, and further preferably 1.15 or less.

  Further, the outer middle land portion 6A and the inner middle land portion 6B have outer slots extending from the outer edges 6Ao and 6Bo on the vehicle outer side to the vehicle inner side and terminating without reaching the inner edges 6Ai and 6Bi on the vehicle inner side. 15A and an inner slot 15B are provided, respectively.

  As shown in an enlarged view in FIG. 4, the outer slot 15A is inclined linearly at an angle α3a of 60 to 90 degrees with respect to the tire circumferential direction, and is on the outer edge 6Ao side of the outer middle land portion 6A. The groove width W3a is gradually reduced from the inner edge 6Ai side. Such an outer slot 15A can smoothly drain the water film interposed between the outer middle land portion 6A and the road surface to the outer shoulder vertical groove 4A disposed on the outer side of the vehicle, thereby improving the drainage performance.

  Further, since the outer slot 15A terminates without reaching the inner edge 6Ai of the outer middle land portion 6A as described above, it is possible to suppress the rigidity of the outer middle land portion 6A from being excessively lowered, and to improve the steering stability performance. Can be maintained. Furthermore, the outer slot 15A can push air out to the outer shoulder longitudinal groove 4A, thereby disturbing the air column in the outer shoulder longitudinal groove 4A and improving noise resistance. Preferably, the groove width W3a of the outer slot 15A is about 1.5 to 4.5 mm, and the groove depth (not shown) is about 3.0 to 7.0 mm.

  In the present embodiment, the length L3a of the outer slot 15A in the tire axial direction is set to be larger than the length L3b of the inner slot 15B in the tire axial direction (shown in FIG. 5). As a result, the outer slot 15A can effectively improve the drainage performance that tends to decrease outside the vehicle when turning, and can effectively disturb the air column of the outer shoulder vertical groove 4A, improving the noise resistance performance. sell.

  It should be noted that if the length L3a of the outer slot 15A is too small, there is a possibility that the above action cannot be effectively exhibited. On the other hand, if the length L3a is too large, the rigidity of the outer middle land portion 6A becomes excessively small, and the steering stability performance may be degraded. From this point of view, the length L3a is preferably 1.2 times or more, more preferably 1.4 times or more of the length L3b (shown in FIG. 5) of the inner slot 15B. 3.0 times or less, more preferably 2.5 times or less are desirable.

  As shown in an enlarged view in FIG. 5, the inner slot 15B is inclined linearly at an angle α3b of 5 to 45 degrees with respect to the tire circumferential direction, and extends toward the outer edge 6Bo of the inner middle land portion 6B. The groove width W3b gradually decreases from the inner side toward the inner edge 6Bi. Such an inner slot 15B can also smoothly drain the water film interposed between the inner middle land portion 6B and the road surface to the inner crown vertical groove 3B disposed on the outer side of the vehicle, thereby improving drainage performance.

  Further, since the inner slot 15B also terminates without reaching the inner edge 6Bi of the inner middle land portion 6B, the lateral rigidity of the inner middle land portion 6B can be secured, and the steering stability performance can be improved. Further, the inner slot 15B can also extrude air into the inner crown vertical groove 3B, disturb the air column in the inner crown vertical groove 3B, and improve noise resistance. Preferably, the groove width W3b of the inner slot 15B is about 1.5 to 3.5 mm, and the groove depth (not shown) is about 3.0 to 7.0 mm.

  In the present embodiment, the inner middle land portion 6B has one end 16o in the middle region in the tire axial direction of the inner middle land portion 6B between the inner slots 15B and 15B adjacent in the tire circumferential direction, and the other end 16i. Is provided with a middle sipe 16 communicating with the inner shoulder longitudinal groove 4B. The middle sipe 16 is curved and extended from one end 16o to the other end 16i while gradually decreasing the angle α4 with respect to the tire circumferential direction within a range of 140 to 160 degrees.

  Such a middle sipe 16 can increase the edge component of the inner middle land portion 6B, and can improve the traction performance. In addition, since the middle sipe 16 is curved and extends as described above, the edge component can be effectively increased as compared with the linear shape. Preferably, the length L4 in the tire axial direction from one end 16o to the other end 16i of the middle sipe 16 is about 40 to 80% of the width Wmi of the inner middle land portion 6B.

  As shown in FIG. 1, the shoulder land portion 7 includes an outer shoulder land portion 7A located on the vehicle outer side and an inner shoulder land portion 7B located on the vehicle inner side. These outer and inner shoulder land portions 7A and 7B are also made of straight ribs, and can improve straight running stability performance and steering stability performance.

In this embodiment, the width Wcr of the crown land portion 5, the width Wso in the tire axial direction to the tread ground contact end 2 t of the outer shoulder land portion 7 A, and the tire axial direction to the tread ground contact end 2 t of the inner shoulder land portion 7 B. The width Wsi satisfies the following expressions (5) and (6).
1.3 ≦ Wsi / Wcr ≦ 2.5 (5)
1.3 ≦ Wso / Wcr ≦ 2.5 (6)

  As a result, the outer shoulder land portion 7A and the inner shoulder land portion 7B can suppress the occurrence of a large rigidity difference with the crown land portion 5 while ensuring sufficient rigidity. It is possible to achieve both straight running stability performance.

  When the ratio (Wso / Wcr) is less than 1.3, the rigidity of the outer shoulder land portion 7A becomes excessively small, and the steering stability performance may be lowered. On the contrary, if the ratio (Wso / Wcr) exceeds 2.5, the land ratio of each shoulder land portion 7A, 7B becomes excessively large and the rigidity of the crown land portion 5 becomes excessively small. , And the straight running stability performance may be reduced. From such a viewpoint, the ratio (Wmo / Wcr) is more preferably 1.4 or more, and further preferably 2.4 or less.

  Similarly, the ratio (Wsi / Wcr) is preferably 1.3 or more, more preferably 1.4 or more, and preferably 2.5 or less, more preferably 2.4 or less.

  The shoulder land portion 7 is provided with a shoulder lateral groove 17 extending from the tread grounding end 2t to the inside in the tire axial direction. The shoulder lateral groove 17 of the present embodiment includes an outer shoulder lateral groove 17A provided in the outer shoulder land portion 7A and an inner shoulder lateral groove 17B provided in the inner shoulder land portion 7B. Each of the shoulder lateral grooves 17A and 17B can smoothly discharge the water film interposed between the shoulder land portions 7A and 7B and the road surface to the tread ground contact end 2t side, and can improve drainage performance.

  As shown in FIG. 4, the outer shoulder lateral groove 17A extends from the tread grounding end 2t on the vehicle outer side to the vehicle inner side and terminates without reaching the outer shoulder vertical groove 4A. As a result, the outer shoulder lateral groove 17A can discharge the water film between the outer shoulder land portion 7A and the road surface to the tread grounding end 2t side while effectively suppressing steering stability and drainage performance. It can be compatible.

  Further, the outer shoulder lateral groove 17A is smoothly curved while gradually decreasing the angle α5a with respect to the tire circumferential direction from the vehicle outer side toward the vehicle inner side. Accordingly, the outer shoulder lateral groove 17A can increase the edge component of the outer shoulder land portion 7A, and can improve the traction performance. Preferably, the outer shoulder lateral groove 17A has a groove width W5a of about 2.0 to 6.0 mm, a groove depth (not shown) of about 4.0 to 8.0 mm, and a tire axial length L5a of the outer shoulder land portion. About 60 to 90% of the width Wso of 7A is desirable.

  In the present embodiment, a shoulder sub-groove 20 that connects the inner end 17Ai on the vehicle inner side of the outer shoulder lateral groove 17A and extends linearly in the tire circumferential direction is provided. The shoulder width W7 of the shoulder sub-groove 20 is set smaller than the groove width Gso (shown in FIG. 1) of the outer shoulder vertical groove 4A.

  Such a shoulder secondary groove 20 can smoothly discharge a water film interposed between the outer shoulder land portion 7A and the road surface, and can improve drainage performance. Moreover, since the groove width W7 of the shoulder sub-groove 20 is set to be smaller than the groove width Gso of the outer shoulder vertical groove 4A, it is possible to effectively suppress a decrease in rigidity of the outer shoulder land portion 7A. Further, since the shoulder minor groove 20 is connected to the outer shoulder lateral groove 17A, air is pushed out from the outer shoulder lateral groove 17A, and the air column in the shoulder minor groove 20 is disturbed, so that the noise resistance performance can be improved. .

  If the groove width W7 of the shoulder sub-groove 20 is small, there is a possibility that the water film between the shoulder surface and the road surface cannot be smoothly discharged. Conversely, even if the groove width W7 is too large, the rigidity of the outer shoulder land portion 7A may be excessively reduced. From such a viewpoint, the groove width W7 is preferably 0.8 mm or more, more preferably 1.0 mm or more, and preferably 2.0 mm or less, more preferably 1.8 mm or less.

  Similarly, as shown in FIG. 2, the groove depth D3 of the shoulder sub-groove 20 is preferably 20% or more, more preferably 30% or more of the groove depth D2 of the outer shoulder longitudinal groove 4A. Preferably, it is 80% or less, more preferably 70% or less.

  As shown in FIG. 5, the inner shoulder lateral groove 17B extends from the tread grounding end 2t on the vehicle inner side to the vehicle inner side and communicates with the inner shoulder vertical groove 4B. As a result, the inner shoulder land portion 7B has the inner shoulder blocks 22 divided by the inner shoulder vertical groove 4B, the tread grounding end 2t, and the inner shoulder lateral groove 17B spaced in the tire circumferential direction.

  Further, the inner shoulder lateral groove 17B extends smoothly from the vehicle inner side toward the vehicle outer side while gradually decreasing the angle α5b with respect to the tire circumferential direction.

  Such an inner shoulder lateral groove 17B can also effectively drain the water film interposed between the inner shoulder land portion 7B and the road surface, can increase edge components, and can improve drainage performance and traction performance. Preferably, the inner shoulder lateral groove 17B has a groove depth (not shown) of about 4.0 to 8.0 mm.

  The inner shoulder lateral groove 17B of the present embodiment has a wide portion 18 extending from the tread grounding end 2t to the vehicle outer side, a width communicating from the wide portion 18 to the inner shoulder vertical groove 4B, and a width smaller than the wide portion 18. The narrow portion 19 is included.

  Such an inner shoulder lateral groove 17B can effectively discharge the water film between the road surface and the drainage performance and control while effectively suppressing the rigidity reduction of the inner shoulder land portion 7B by the narrow portion 19. A stable performance can be achieved at a high level.

  If the length L6a of the narrow portion 19 in the tire axial direction is small, there is a possibility that the above-described action cannot be effectively exhibited. Conversely, even if the length L6a is too large, the water film between the road surface and the road surface may not be sufficiently discharged. From this point of view, the length L6a is preferably 5% or more, more preferably 10% or more, and preferably 40% or less, more preferably 10% or more of the length L6b of the wide portion 18 in the tire axial direction. Preferably it is 30% or less.

  Similarly, the groove width W6a of the narrow portion 19 is preferably 20% or more of the groove width W6b of the wide portion 18, more preferably 30% or more, and preferably 80% or less, more preferably 70% or less. Is desirable.

  Further, in the inner shoulder land portion 7B of the present embodiment, a shoulder sipe 21 that connects the inner shoulder vertical groove 4B and the tread grounding end 2t is provided between the inner shoulder lateral grooves 17B and 17B adjacent in the tire circumferential direction. .

  The shoulder sipe 21 is alternately arranged in the tire circumferential direction without the vehicle-side one end 21o and the vehicle-side other end 16i of the middle sipe 16 of the inner middle land portion 6B being adjacent to each other in the tire axial direction. Further, the shoulder sipe 21 extends substantially linearly from the one end 21o to the other end 21i inside the vehicle while being inclined at an angle α8 of 60 to 90 degrees with respect to the tire circumferential direction.

  Such a shoulder sipe 21 can increase the edge component of the inner shoulder land portion 7B, so that the traction performance can be improved. Moreover, the one end 21o of the shoulder sipe 21 is alternately arranged in the tire circumferential direction without being adjacent to the other end 16i of the middle sipe 16 in the tire axial direction, and therefore includes the inner middle land portion 6B and the inner shoulder land portion 7B. The rigidity of the tread portion 2 inside the vehicle can be suppressed from being partially reduced in the tire circumferential direction, and a decrease in steering stability performance can be effectively suppressed.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

Tires having the basic structure shown in FIG. 1 and having a center land portion, a middle land portion, a shoulder land portion and the like shown in Table 1 were manufactured, and their performance was evaluated. The common specifications are as follows.
Tire size: 255 / 55R18 109W
Rim size: 18 x 8.0
Tread width TW: 206mm
Crown flutes, shoulder flutes:
Groove depth D1: 8.0 mm
Groove depth D2: 7.4 mm
Outer and inner crown flutes:
Distance L1i, L1o: 18.5mm
Ratio (L1i / TW), Ratio (L1o / TW): 9.0%
Outer and inner shoulder flutes:
Distance L2i, L2o: 58.2mm
Ratio (L2i / TW), ratio (L2o / TW): 28.3%
Outer slot:
Angle α3a: 66 degrees Groove width W3a: 2.0 to 4.0 mm
Groove depth: 6.0 mm
Inner slot:
Angle α3b: 62 degrees Groove width W3b: 2.6 mm
Groove depth: 4.0mm
Middle sipe:
Angle α4: 140 to 150 degrees Middle sipe length L4: 24 mm
Outer shoulder lateral groove:
Groove width W5a: 4.0 mm
Length L5a: 27.4mm
Groove depth: 6.2 mm
Inner shoulder cross groove:
N6 length L6a: 8.1 mm
Narrow groove width W6a: 1.5 mm
Wide part length L6b: 31.8 mm
Wide part groove width W6b: 3.8 mm
Ratio (L6a / L6b): 25.5%
Ratio (W6a / W6b): 39.5%
Groove depth: 6.2 mm
Shoulder minor groove:
Groove width W7: 1.0mm
Groove depth: 1.0mm
Shoulder sipe angle α8: 75 to 85 degrees The test method is as follows.

<Noise resistance>
Each test tire was assembled to the rim, filled with 260 kPa front wheels and 290 kPa rear wheels, mounted on all wheels of a 4WD cc German 4WD vehicle, and noise was measured in accordance with JISO standard C-606. The evaluation was expressed as an index with Comparative Example 1 as 100. The larger the value, the better.

<Drainage performance>
Each test tire is assembled on the rim under the above conditions and mounted on all the wheels of the above vehicle, and the speed is gradually increased to a test course with a water pool of 5 mm depth and 20 m length on an asphalt road surface with a radius of 100 m. The vehicle was approached while increasing, and the average lateral acceleration of the front and rear wheels at a speed of 50 to 80 km / h was measured. The results are displayed as an index with the average lateral acceleration of Comparative Example 1 as 100. The larger the value, the better.

<Steering stability and straight running stability>
Each test tire is assembled on the rim under the above conditions and mounted on all wheels of the above vehicle, running on a dry asphalt road test course, steering stability performance (cornering power), responsiveness at lane change, Convergence and ground contact were evaluated by driver's sensory evaluation. A result is a score which sets the comparative example 1 to 100, and it is so favorable that a numerical value is large.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tires of the examples can achieve a high level of compatibility in handling stability performance, drainage performance, and noise resistance performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Crown vertical groove 4 Shoulder vertical groove 5 Crown land part 6 Middle land part 7 Shoulder land part 15A Outer slot 15B Inner slot

Claims (7)

The tread portion is provided with a pair of crown longitudinal grooves extending continuously in the tire circumferential direction on both sides of the tire equator, and a pair of shoulder longitudinal grooves extending continuously in the tire circumferential direction on the outer side of the crown longitudinal groove in the tire axial direction. And a pair of middle land portions extending between the crown longitudinal groove and the shoulder longitudinal groove, and between the shoulder longitudinal groove and the tread grounding end. It is a pneumatic tire that is separated from the extending shoulder land,
The tread portion has an asymmetric tread pattern with respect to the tire equator and is designated for mounting on the vehicle;
The pair of crown longitudinal grooves have the same groove width Gcr, and the groove width Gcr, the groove width Gso of the outer shoulder longitudinal groove located on the vehicle outer side when the vehicle is mounted, and the vehicle inner side when the vehicle is mounted. The groove width Gsi of the inner shoulder longitudinal groove located satisfies the following formulas (1) and (2),
The width Wcr in the tire axial direction of the crown land portion, the width Wmo in the tire axial direction of the outer middle land portion located outside the vehicle when the vehicle is mounted, and the tire axial direction of the inner middle land portion located inside the vehicle when the vehicle is mounted The width Wmi satisfies the following formulas (3) and (4),
The outer middle land portion and the inner middle land portion are each provided with an outer slot and an inner slot that extend from the outer edge, which is the outer side of the vehicle when the vehicle is mounted, to the inner side of the vehicle and terminate without reaching the inner edge of the inner side of the vehicle. ,
The pneumatic tire according to claim 1, wherein a length of the outer slot in the tire axial direction is larger than a length of the inner slot in the tire axial direction.
0.8 ≦ Gso / Gcr ≦ 1.1 (1)
0.8 ≦ Gsi / Gcr ≦ 1.1 (2)
1.0 ≦ Wmo / Wcr ≦ 1.2 (3)
1.0 ≦ Wmi / Wcr ≦ 1.2 (4)   In the crown longitudinal groove and the shoulder longitudinal groove, the outer groove wall located outside the vehicle when mounted on the vehicle is inclined at a larger angle with respect to the tread normal line than the inner groove wall located inside the vehicle when mounted on the vehicle. The pneumatic tire according to claim 1. The width Wcr in the tire axial direction of the crown land portion, the width Wso in the tire axial direction of the outer shoulder land portion located outside the vehicle when the vehicle is mounted, and the tire axial direction of the inner shoulder land portion located inside the vehicle when the vehicle is mounted The pneumatic tire according to claim 1 or 2, wherein the width Wsi satisfies the following expressions (5) and (6).
1.3 ≦ Wsi / Wcr ≦ 2.5 (5)
1.3 ≦ Wso / Wcr ≦ 2.5 (6) Each shoulder land portion is provided with a shoulder lateral groove extending inward in the tire axial direction from the tread grounding end,
The shoulder lateral groove includes an outer shoulder lateral groove provided in an outer shoulder land portion located on the outer side of the vehicle when mounted on the vehicle, and an inner shoulder lateral groove provided on an inner shoulder land portion positioned on the inner side of the vehicle when mounted on the vehicle,
The pneumatic tire according to claim 1, wherein at least the outer shoulder lateral groove terminates without reaching the outer shoulder longitudinal groove.   Each of the longitudinal grooves has an outer arc connecting the groove bottom surface and an outer groove wall located outside the vehicle when the vehicle is mounted, and an inner radius of curvature connecting the groove bottom surface and the inner groove wall positioned inside the vehicle when the vehicle is mounted. The pneumatic tire according to any one of claims 1 to 4, wherein is 3 to 5 mm. The inner middle land portion has a middle sipe having one end in an intermediate region in the tire axial direction of the inner middle land portion and the other end communicating with the inner shoulder longitudinal groove between the inner slots adjacent in the tire circumferential direction. Is provided,
The pneumatic tire according to any one of claims 1 to 5, wherein the middle sipe is inclined at an angle of 20 to 70 degrees with respect to a tire circumferential direction.   The pneumatic tire according to claim 6, wherein the middle sipe gradually decreases in angle from the one end toward the other end.

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