JP2008222117A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve steering stability without damaging ride comfort. <P>SOLUTION: A profile of a tire outer surface is formed by a plurality of arcs having a radius of curvature gradually reduced from an intersection of the tire outer surface and a tire equatorial plane to a ground contact end side. A tread part 2 includes a center vertical groove 13 continuously extended to a tire peripheral direction and having a groove width GW1 of 15-25 mm, an outer pattern part Po provided on the vehicle outer side thereof, and an inner pattern part Pi provided on the vehicle inner side of the center vertical groove 13. The outer pattern part Po includes a large block row 20 wherein large blocks B1 are aligned in the tire peripheral direction. The inner pattern part Pi includes small block rows 23 and 24 wherein small blocks B2 and B3 having the width and the tire peripheral length shorter than the large block B1 are aligned in the tire peripheral direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that can improve driving stability without impairing riding comfort and drainage performance.

  Conventionally, a pneumatic tire in which a profile of a tread outer surface is formed by a plurality of arcs whose curvature radius gradually decreases from the tire equator toward the contact end side has been proposed (see Patent Document 1 below). This type of pneumatic tire has a very small change in contact shape due to a change in the slip angle, and also provides a "potential contact area" that can be contacted only when the load is increased in the tread portion to deform the contact shape similarly. As a result, the limit at the time of cornering can be increased, and the steering stability can be improved.

  However, the riding comfort and handling stability of a pneumatic tire are trade-offs, and in order to improve the riding comfort, it is necessary to improve the tread pattern suitable for the above-described profile. In addition, it is necessary to fully consider drainage.

Japanese Patent No. 2999489

  The present invention has been devised in view of the above situation, and the profile of the tire outer surface is formed by a plurality of arcs whose radius of curvature gradually decreases from the tire equator toward the ground contact end, and a novel improved to that. The main object is to provide a pneumatic tire that can improve steering stability, ride comfort and drainage in a well-balanced manner by combining various tread patterns.

  The invention according to claim 1 of the present invention includes a carcass having at least one carcass ply that is folded and locked by a bead core of a bead portion through a sidewall portion from a tread portion, and a radially outer side of the carcass and A pneumatic tire having a belt layer arranged inside the tread portion and having a direction to be mounted on the vehicle, which is assembled with a normal rim and filled with a normal internal pressure. In the tire meridian cross section including a tire rotation axis in a normal state, the profile of the tire outer surface is formed by a plurality of arcs whose radius of curvature gradually decreases from the intersection of the tire outer surface and the tire equatorial plane toward the ground contact end side. The tread portion extends continuously in the tire circumferential direction and has one central longitudinal groove having a groove width of 15 to 25 mm and an outer pad provided on the outer side of the vehicle. And an inner pattern portion provided on the vehicle inner side of the central longitudinal groove, the outer pattern portion includes a large block row in which large blocks are arranged in the tire circumferential direction, and the inner pattern portion is A small block having both a width and a tire circumferential direction length smaller than the large block includes a small block row arranged in the tire circumferential direction.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein a length of the large block in the tire circumferential direction is 2.0 to 4.0 times a length of the small block in the tire circumferential direction. .

  The invention according to claim 3 is characterized in that the outer pattern portion is formed by one outer longitudinal groove extending in the tire circumferential direction, and the large block row provided between the outer longitudinal groove and the central longitudinal groove. The rib is divided into a rib provided between the outer vertical groove and the ground contact end outside the vehicle. The rib extends from the ground contact end outside the vehicle to the tire equator side and communicates with the outer vertical groove. The pneumatic tire according to claim 1 or 2, wherein a shoulder lug groove that terminates without separation is provided.

According to a fourth aspect of the present invention, in the tire meridian cross section including the tire rotation axis in the normal state, the profile of the tire outer surface is the tire maximum width (SW) from the intersection (CP) of the tire outer surface and the tire equatorial surface. When the point on the tire outer surface separating the distance (SP) of 45% is (P), the radius of curvature (RC) of the tire outer surface gradually decreases in the section from the intersection (CP) to the point (P). And a pneumatic tire according to any one of claims 1 to 3, which satisfies the following relationship.
0.05 <Y60 / H ≦ 0.1
0.1 <Y75 / H ≦ 0.2
0.2 <Y90 / H ≦ 0.4
0.4 <Y100 / H ≦ 0.7
(Where Y60, Y75, Y90 and Y100 are the tire axial distances of 60%, 75%, 90% and 100% of the half width (SW / 2) of the maximum tire width in the tire axial direction from the intersection (CP). (The distances in the tire radial direction between the points P60, P75, P90 and P100 on the outer surface of the tire and the intersections (CP), and H is the tire cross-section height.)

  In the pneumatic tire of the present invention, steering stability can be improved by grounding more large blocks of the outer pattern portion during turning. Further, during normal running, the ride comfort can be prevented from deteriorating by grounding the small block of the inner pattern portion. In addition, the profile of the outer surface of the pneumatic tire of the present invention has a radius of curvature that gradually decreases toward the ground contact end, and a central vertical groove having a large groove width is provided between the outer pattern portion and the inner pattern portion. It is done. By these, the fall of drainage performance can be prevented. Thus, in the pneumatic tire of the present invention, steering stability can be improved without impairing riding comfort and drainage performance.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional view of the pneumatic tire 1 of the present embodiment in a normal state. Here, the “normal state” uniquely defines the posture of the tire and is a no-load state in which the rim is assembled to the normal rim J and the normal internal pressure is filled. Unless otherwise specified, the values of the tires are shown in the normal state.

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

  Furthermore, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA and the table “TIRE LOAD LIMITS AT” is TRA. The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” if it is ETRTO, but if the tire is for passenger cars, it is uniformly 180 kPa.

  A pneumatic tire 1 includes a carcass 6 having at least one carcass ply 6A that is folded and locked by a bead core 5 of a bead portion 4 from a tread portion 2 through a sidewall portion 3, and a tire radial direction of the carcass 6 A belt layer 7 disposed outside and inside the tread portion 2, a band layer 8 disposed outside the belt layer 7, and a bead apex 9 extending outwardly from the outer surface of the bead core 5 in the tire radial direction. The thing for passenger cars containing is illustrated. The pneumatic tire 1 of the present embodiment is configured as a so-called run-flat tire in which a pair of side reinforcing rubber layers 10 having a substantially crescent cross section are provided in the sidewall region inside the carcass 6.

  The pneumatic tire 1 of the present embodiment is configured for a large and high-powered passenger car having a tire maximum width SW of 245 to 400 mm, a flatness ratio of 20 to 55%, and a rim diameter of 18 to 25 inches, for example. The tire maximum width SW is the maximum width of the tire outer surface excluding characters and rim protectors provided on the sidewall portion 3.

  In the present embodiment, the carcass 6 is formed from one carcass ply 6A. The carcass ply 6A is formed by covering a carcass cord with a topping rubber. As the carcass cord, an organic fiber such as nylon, polyester, rayon, or aromatic polyamide is suitably used. In this embodiment, a polyester cord is employed. In addition, the carcass cord is desirably arranged to be inclined with respect to the tire equator C at an angle of 75 to 90 degrees, more preferably 90 degrees.

  The carcass ply 6A includes a main body portion 6a straddling a pair of bead cores 5 and 5 in a toroidal shape, and is connected to both ends of the main body portion 6a, and the bead core 5 is folded back from the inner side in the tire axial direction to the outer side. And a folded portion 6b extending along the outer side surface of the apex 9 in the tire axial direction. In this example, the outer end 6be of the folded portion 6b is terminated at a position beyond the outer end 7e in the tire axial direction of the belt layer 7 inward in the tire axial direction.

  Such a carcass ply 6A can effectively reinforce the sidewall portion 3 with a small number of sheets. Further, the outer end 6be of the folded portion 6b having low durability is located away from the side wall portion 3 having a large deflection during run-flat travel, and is positioned between the belt layer 7 having a small distortion and the main body portion 6a of the carcass ply. As a result, damage such as separation starting from the outer end 6be is suppressed, and run-flat durability is improved.

  The bead apex 9 extends in a tapered manner from the outer surface of the bead core 5 to the outside in the tire radial direction, and is preferably formed of a hard rubber having a JISA hardness of 65 to 95 degrees, more preferably about 70 to 95 degrees. . As a result, the bending rigidity of the bead portion 4 can be increased, the steering stability can be improved, and the vertical deflection of the tire 1 during the run-flat running is suppressed. In addition, in this specification, JISA hardness means the hardness by durometer type A based on JIS-K6253.

  The belt layer 7 is composed of two belt plies 7A and 7B in which a belt cord made of, for example, steel is inclined with respect to the tire equator C at, for example, about 10 to 35 °. As the belt cord, a highly elastic organic fiber material such as aramid or rayon can be used as necessary in addition to the steel material.

  The band layer 8 is formed of, for example, at least one band ply in which organic fiber cords are arranged along the tire circumferential direction (at an angle of 5 degrees or less with respect to the tire equator C). Thereby, lifting of the belt layer 7 and the like are effectively suppressed.

  As shown in FIG. 2, the side reinforcing rubber layer 10 has a substantially crescent cross section, and gradually increases in thickness from the thick central portion toward the inner end 10i and the outer end 10o in the tire radial direction. As a whole, the cross section is formed in a substantially crescent shape. The inner end 10 i is preferably located on the inner side in the tire radial direction than the outer end 9 T of the bead apex 9 and on the outer side in the tire radial direction than the bead core 5. Further, it is desirable that the outer end 10 o of the side reinforcing rubber layer 10 reaches the inner cavity side of the tread portion 2 and is terminated at a position on the inner side in the tire axial direction from the outer end 7 e of the belt layer 7.

  Such a side reinforcing rubber layer 10 can reinforce the rigidity of the tire in the entire region of the sidewall portion 3. Therefore, even in a run-flat state in which the air from the tire has escaped, the amount of longitudinal deflection of the tire is suppressed, and the vehicle travels continuously at a certain high speed (for example, 60 km / H). Is possible).

  In order to effectively suppress the longitudinal deflection of the tire during run-flat running, the JISA hardness of the side reinforcing rubber layer 10 is preferably 65 degrees or more, more preferably 70 degrees or more, and further preferably 74 degrees or more. On the other hand, if the JISA hardness of the side reinforcing rubber layer 10 is too large, the vertical spring of the tire becomes large and the ride comfort during normal running tends to be remarkably deteriorated. Therefore, it is preferably 99 degrees or less, more preferably 90 degrees. The following is desirable.

  Further, the side reinforcing rubber layer 10 according to the present embodiment has a plurality of recesses 11 in which an inner surface facing the tire lumen side is recessed in the tire circumferential direction. In such a run flat tire 1, the volume of the side reinforcing rubber layer 10 is reduced by the recess 11, and the side reinforcing rubber layer 10 can be reduced in weight as compared with the conventional run flat tire. This helps to increase the fuel efficiency of the vehicle and the riding comfort during normal driving.

  FIG. 3 shows a profile TL of the tire outer surface in a tire meridian cross section including a tire rotation axis in a normal state. The profile TL is specified on the assumption that there is no groove in the tread portion 2. The profile TL is formed by a plurality of arcs in which the radius of curvature RC gradually decreases from the intersection point CP between the tire outer surface and the tire equatorial plane toward the ground contact end, preferably an arc curve in which the radius of curvature RC continuously changes. . However, the radius of curvature RC can be decreased step by step.

  The “grounding end” is a position on the outermost side in the tire axial direction of the grounding surface when a normal load is applied in the normal state and the tire is pressed against a plane with a camber angle of 0 degrees. In addition, the normal 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 JATA and the table "TIRE LOAD LIMITS" is TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” if it is ETRTO, but if the tire is a passenger car, the load is equivalent to 88% of the load.

  Since such a profile TL can form the outer surface of the tread portion 2 in a round shape, the grounding shape has a small grounding width and a large grounding length. This reduces tire noise during travel and improves hydroplaning performance. In addition, such a profile TL increases the area where the tread portion 2 is easily bent, but shortens the area of the sidewall portion 3. For this reason, the pneumatic tire 1 having the profile TL can significantly reduce the weight of the tire. Accordingly, a substantial increase in tire mass is suppressed as compared with a pneumatic tire having a conventional tread profile.

As a preferable specific profile TL, when a point on the tire outer surface that is separated by a distance SP of 45% of the maximum tire width SW from the intersection CP of the tire outer surface and the tire equatorial plane is P, the point P from the intersection CP It is desirable that the radius of curvature RC of the outer surface of the tire gradually decreases toward the outer side in the tire axial direction and satisfies the following relationship.
0.05 <Y60 / H ≦ 0.1
0.1 <Y75 / H ≦ 0.2
0.2 <Y90 / H ≦ 0.4
0.4 <Y100 / H ≦ 0.7
Here, Y60, Y75, Y90, and Y100 separate the tire axial distances of 60%, 75%, 90%, and 100% of the half width (SW / 2) of the maximum tire width in the tire axial direction from the tire equator C, respectively. The distances in the tire radial direction between the points P60, P75, P90 and P100 on the tire outer surface and the intersection point CP. The “H” is a tire cross-sectional height.

RY60 = Y60 / H
RY75 = Y75 / H
RY90 = Y90 / H
RY100 = Y100 / H
A range satisfying the above relationship is shown as a graph in FIG. Therefore, the preferred profile TL will pass through the range shown in this graph.

  FIG. 5 shows a development view of the tread portion 2 of the pneumatic tire 1 of the present embodiment. The direction of mounting the pneumatic tire 1 on a vehicle is determined. That is, in FIG. 5, the right side is mounted on the vehicle outer side and the left side is mounted on the vehicle inner side when the vehicle is mounted. Such a pneumatic tire is provided with a display (for example, “INSIDE” or “OUTSIDE”) indicating the direction of mounting on the vehicle on the sidewall portion 3 or the like in order to reliably exhibit the performance. Note that the rotation direction of the tire is not particularly defined.

  The tread portion 2 continuously extends in the tire circumferential direction and is provided with one central longitudinal groove 13, whereby the outer pattern portion Po provided on the vehicle outer side and the vehicle of the central longitudinal groove 13 are provided. The inner pattern portion Pi provided inside is divided.

  In the present embodiment, the central longitudinal groove 13 extends linearly on the tire equator C and has a groove width GW1 of 15 to 25 mm, more preferably 15 to 20 mm. By providing such a central longitudinal groove 13 in a region where the contact pressure is high, a water film existing near the tire equator can be effectively drained backward in the running direction. The central longitudinal groove 13 may be formed in a zigzag shape or a wave shape, but a linear shape that minimizes the drainage resistance as in this embodiment is particularly desirable.

  Further, the groove width GW1 of the central vertical groove 13 is 15 to 25 mm, and is set larger than that of a general vertical groove. This is also wide for large size tires for passenger cars. In the pneumatic tire 1 of the present invention, sufficient drainage is ensured by such a wide central longitudinal groove 13. Preferably, the groove width GW1 is preferably about 3 to 15% of the tread ground contact width TW (distance in the tire axial direction between the ground contact ends Ei and Eo). The groove depth of the central longitudinal groove 13 can be determined according to customary practice, but is preferably 6 mm or more, more preferably, in order to prevent a significant decrease in the pattern rigidity of the tread portion 2 while ensuring sufficient drainage. Is desirably 8 mm or more, preferably 12 mm or less, more preferably 10 mm or less.

  In addition, it is most preferable that the central vertical groove 13 is disposed on the tire equator C where there is a high possibility of grounding during both turning and straight traveling, that is, the tire equator C exists in the central vertical groove 13. However, in order to increase the rigidity of the outer pattern portion Po on which a large lateral force acts during turning, the central longitudinal groove 13 can be arranged close to the vehicle inner side. At this time, in order to ground the central vertical groove 13 even during turning, the distance in the tire axial direction between the groove center line of the central vertical groove 13 and the tire equator C is preferably 20 mm or less.

  The outer pattern portion Po is a portion on the vehicle outer side than the central vertical groove 13. In the present embodiment, the outer pattern portion Po is provided with one outer vertical groove 14 extending in the tire circumferential direction. A large block row 20 formed between the outer vertical grooves 14 and a shoulder rib 21 formed between the outer vertical grooves 14 and the ground contact end Eo outside the vehicle are divided.

  In order to obtain effective drainage performance, the outer longitudinal groove 14 is exemplified by a straight line extending in the tire circumferential direction. Further, the outer longitudinal groove 14 is a region that divides a position substantially in the middle of the tire axial direction width OW of the outer pattern portion Po, specifically, 40 to 60% of the width OW from the groove edge outside the vehicle of the central longitudinal groove 13. It is provided in the inside. This is useful for balancing the rigidity of the outer pattern portion Po and suppressing the occurrence of uneven wear and the like.

  Although not particularly limited, the groove width GW2 of the outer vertical groove 14 is preferably smaller than the groove width GW1 of the central vertical groove 13 in order to balance steering stability and drainage performance during turning. More preferably, it is 1 mm or more, and further preferably 2 mm or more, while preferably 15 mm or less, more preferably 10 mm or less. Similarly, the groove depth of the outer longitudinal groove 14 is preferably 6 mm or more, more preferably 8 mm or more, and preferably 12 mm or less, more preferably 10 mm or less.

  The large block row 20 includes a large block B1 that is divided by a central longitudinal groove 13, an outer longitudinal groove 14, and middle lateral grooves 17 that extend between the central longitudinal groove 13 and the outer longitudinal groove 14 and that are separated in the tire circumferential direction. Are formed side by side.

  The middle lateral groove 17 is preferably inclined at, for example, about 20 to 80 degrees with respect to the tire circumferential direction in order to ensure steering stability and drainage. In addition, the middle lateral groove 17 of the present embodiment is exemplified by a curve that is curved in a smooth arc shape so that the inclination angle θ1 with respect to the tire circumferential direction gradually increases from the central longitudinal groove 13 side toward the outer longitudinal groove 14 side. Such a middle lateral groove 17 reduces drainage resistance on the central vertical groove 13 side where the contact pressure is high and improves drainage, while the outer vertical groove 14 side on which a large lateral force is easily applied during cornering has a block rigidity lateral rigidity. Helps to increase and improve steering stability.

  The arrangement pitch of the middle lateral grooves 17 in the tire circumferential direction is set to be relatively large. As a result, the large block B1 having a large ground contact area is defined. In the outer pattern portion Po, in order to ensure sufficient rigidity and prevent the drainage from being deteriorated, the length BL1 of the large block B1 in the tire circumferential direction is preferably 20 mm or more, more preferably 25 mm or more, Preferably it is 40 mm or less, more preferably 35 mm or less. Similarly, the width BW1 in the tire axial direction of the large block B1 is preferably 40 mm or more, more preferably 45 mm or more, and preferably 60 mm or less, more preferably 55 mm or less.

  Further, the large block B1 of the present embodiment is provided with an auxiliary inclined groove 18 that extends from the outer longitudinal groove 14 inward in the tire axial direction and terminates in front of the taper without communicating with the central longitudinal groove 13. Two auxiliary inclined grooves 18 are provided for each large-sized block B1, and are provided at positions that substantially divide the block circumferential length BL1 of the block B1 into three equal parts. Further, the auxiliary inclined groove 18 extends substantially parallel to the middle lateral groove 17. Such auxiliary inclined grooves 18 increase the heat dissipation of the large-sized block B1 that easily stores heat, ensure durability, and moderately moderate the block rigidity, thereby suppressing uneven wear.

  Further, the auxiliary inclined groove 18 is tapered and ends inside the large block B1, thereby leaving a land portion continuous in the tire circumferential direction on the side of the central vertical groove 13 of the large block B1 where the ground pressure increases. This can prevent deterioration in steering stability during turning as well as stability during straight traveling. The groove width of the auxiliary inclined groove 18 is preferably smaller than that of the middle lateral groove 17.

  The shoulder rib 21 is provided with a shoulder lug groove 19 which extends inward in the tire axial direction from the ground contact end Eo outside the vehicle and terminates in front of the shoulder rib 21 without communicating with the outer longitudinal groove 14. Since such a shoulder rib 21 has a portion continuous in the tire circumferential direction on the inner side in the tire axial direction, the lateral rigidity and the tire circumferential rigidity can be maintained high. Therefore, it is useful for securing a steering stability by generating a large lateral force during turning.

  Here, the distance (in other words, the minimum width of the shoulder rib 21) S between the inner end 19T of the shoulder lug groove 19 in the tire axial direction and the outer longitudinal groove 14 is not particularly limited, but is too large. And drainage performance may be deteriorated. From such a viewpoint, the distance S is preferably 20 mm or less, more preferably 10 mm or less.

  On the other hand, the distance S can be made zero, that is, the shoulder lug groove 19 can be communicated with the outer longitudinal groove 14. However, in such an embodiment, pattern air or pumping noise is likely to occur because the air compressed in the outer vertical groove 14 is discharged to the outside through the shoulder lug groove 19 during traveling. Therefore, in order to suppress tire noise, the distance S is preferably 1 mm or more, more preferably 2 mm or more.

  In addition, the shoulder lug groove 19 of the present embodiment includes a first shoulder lug groove 19a having a large groove width and a second shoulder lug groove 19b having a groove width smaller than that of the first shoulder lug groove 19a. In this embodiment, the first shoulder lug grooves 19a are spaced apart in the tire circumferential direction at a pitch in the tire circumferential direction substantially equal to the length BL1 in the tire circumferential direction of the large block B1 (the first shoulder lug grooves 19a). Is equal to the number of middle lateral grooves 17).

  In addition, two second shoulder lug grooves 19b are arranged between the first shoulder lug grooves 19a and 19a adjacent in the tire circumferential direction. By disposing the first shoulder lug grooves 19a having a large width at a large pitch, a reduction in the rigidity of the shoulder ribs 21 can be prevented. Moreover, by providing the second shoulder lug grooves 19b having a small width at a small pitch, it is possible to ensure sufficient drainage performance by including more shoulder lug grooves 19 in the ground contact surface.

  Although not particularly limited, in order to balance the rigidity and drainage of the shoulder rib 21, the groove width GW3 of the first shoulder lug groove 19a is preferably 3 mm or more, more preferably 5 mm or more. Preferably, it is 15 mm or less, more preferably 10 mm or less. Similarly, the groove width GW4 of the second shoulder lug groove 19b is preferably 20% or more, more preferably 30% or more, preferably 80% or less of the groove width GW3 of the first shoulder lug groove 19a. More preferably, 70% or less is desirable. Furthermore, the groove depth of each shoulder lug groove 19a or 19b is preferably 5 mm or more, more preferably 6 mm or more, and preferably 10 mm or less, more preferably 9 mm or less.

  The shoulder lug groove 19 of the present embodiment is inclined in the direction opposite to the middle lateral groove 17 and the angle θ2 with respect to the tire circumferential direction is set larger than the inclination angle θ1 of the middle lateral groove 17. In particular, the latter configuration is useful for further improving the lateral rigidity of the shoulder rib 21.

  In the present embodiment, the inner pattern portion Pi extends linearly in the tire circumferential direction and linearly extends in the tire circumferential direction with the first inner vertical groove 15 disposed on the central longitudinal groove 13 side. Two longitudinal grooves are provided with the second inner longitudinal groove 16 arranged on the grounding end Ei side inside the vehicle. Thereby, the inner pattern portion Pi is divided into three land portions of the center rib 22, the first small block row 23, and the second small block row 24 in order from the central longitudinal groove 13 side.

  The center rib 22 is formed between the central longitudinal groove 13 and the first inner longitudinal groove 15, and is formed by connecting an arc that protrudes toward the central longitudinal groove 13 in the tire circumferential direction. And a plurality of first inclined grooves 26 having one end connected to the wavy narrow groove 25 and the other end opened by the first inner longitudinal groove 15.

  The wavy narrow groove 25 extends substantially in the middle of the width direction of the center rib 22 in the tire circumferential direction. The wavy narrow groove 25 is formed with a very small groove width GW5 as compared with the central vertical groove 13 and the vertical grooves 14 to 16. Specifically, in order to prevent the rigidity of the center rib 22 from decreasing, the groove width GW5 of the wavy narrow groove 25 is preferably formed with a small width of about 0.5 to 3 mm. Further, a plain rib 27 is formed between the wavy narrow groove 25 and the central longitudinal groove 13 without substantial grooves or siping. This improves the rigidity of the tread central region where the contact pressure is large, and improves the straight running stability. Further, since the width of the plain rib 27 repeatedly increases and decreases in the tire circumferential direction, it helps to reduce the tread rigidity in the contact surface.

  The first inclined grooves 26 are provided at a pitch that is approximately a half of the pitch in the tire circumferential direction of the wavy narrow grooves 25. Thereby, the water film of the tread crown portion is effectively drained into the first inner longitudinal groove 15. The groove width GW6 of the first inclined groove 26 is not particularly limited, but is preferably 1 mm or more, more preferably 2 mm or more, and preferably 7 mm or less, more preferably 5 mm or less.

  The first small block row 23 is divided by a first inner longitudinal groove 15, a second inner longitudinal groove 16, and a second inclined groove 29 extending between the first inner longitudinal groove 15 and the tire circumferential direction. Blocks B2 are formed side by side in the tire circumferential direction. Similarly, the second small block row 24 is divided by a second inner longitudinal groove 16, a ground contact end Ei inside the vehicle, and a third inclined groove 30 that inclines between them with respect to the tire circumferential direction. The small blocks B3 are arranged in the tire circumferential direction.

  The small blocks B2 and B3 are formed such that the widths BW2 and BW3 in the tire axial direction are smaller than the width BW1 in the tire axial direction of the large blocks B1. The small blocks B2 and B3 are formed such that the lengths BL2 and BL3 in the tire axial direction are smaller than the length BL1 in the tire axial direction of the large block B1.

  In the inner pattern portion Pi, the lengths BL2 and BL3 in the tire circumferential direction of the small blocks B2 and B3 are preferably 10 mm or more, and more preferably 15 mm, in order to improve riding comfort without significantly reducing the driving stability. While the above is desirable, it is preferably set to 30 mm or less, more preferably 25 mm or less. Similarly, the widths BW2 and BW3 in the tire axial direction of the small blocks B2 and B3 are preferably 10 mm or more, more preferably 15 mm or more, and preferably 45 mm or less, more preferably 40 mm or less.

  Further, in order to achieve both a sufficient ride comfort on the inside of the vehicle and an improvement in steering stability on the outside of the vehicle, it is desirable to define the ratio of the contact area per block. For example, when the value obtained by the product (BLi × BWi) of the tire circumferential length BLi and the tire axial width BWi is approximately regarded as the block ground contact area Ai, the block of the large block B1 The ratio A1 / A2 (or A1 / A3) of the ground contact area A1 and the block ground contact area A2 (or A3) of the small block B2 (or B3) is preferably 2.2 or more, more preferably 2.4 or more. On the other hand, it is preferably 3.8 or less, more preferably 3.6 or less. When the ratio A1 / A2 (or A1 / A3) is less than 2.2 or exceeds 3.8, in either aspect, either steering stability or riding comfort tends to be sacrificed.

  The second and third inclined grooves 29 and 30 are preferably inclined at, for example, 30 to 60 ° with respect to the tire circumferential direction. Thereby, the small blocks B2 and B3 are formed in a substantially parallelogram shape. Moreover, by making the inclination directions of the second inclined groove 29 and the third inclined groove 30 reverse, it is possible to effectively prevent a single flow or the like depending on the pattern shape. The groove widths GW9 and GW10 of the inclined grooves 29 and 30 are preferably about 1.0 to 3.0 mm.

  The pneumatic tire as described above can exhibit a remarkable effect when it is mounted on a vehicle with a negative camber, for example. The camber represents a tilt angle of the tire when the four-wheeled vehicle is viewed from the front, and a state where the upper side of the tire is tilted toward the inside of the vehicle is referred to as a negative camber.

  When the pneumatic tire according to the present embodiment is mounted on a four-wheeled vehicle with a negative camber, the inner pattern portion Pi contacts the road surface more than the outer pattern portion Po during normal driving. For this reason, flexible impact absorbing ability of the tread portion 2 is obtained by the small blocks B2 and B3, and the ride comfort is further improved by reducing the ground contact area of the large block B1 having high rigidity. Moreover, since the profile TL of the tire outer surface is formed by a plurality of arcs whose curvature radii gradually decrease from the tire equator toward the contact end side, the contact pressure on the contact end Ei, Eo side is reduced. The drainage performance can be improved. Such an effect also makes it possible to reduce the depth of the other vertical grooves, which in turn helps to reduce air column resonance noise and the like.

  Further, during turning, the ground contact area of the small blocks B2 and B3 can be reduced by the load movement accompanying the centrifugal force, and the ground contact area of the large large block B1 and the shoulder rib 21 provided in the outer pattern portion Po can be increased. . Thereby, the handling stability at the time of turning is improved. Since the wide central longitudinal groove 13 on the tire equator C can be grounded to the road surface during both straight running and turning, sufficient drainage performance can be ensured.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.

  In order to confirm the effect of the present invention, a plurality of types of pneumatic tires of size 275 / 40R20 were prototyped based on the pattern of FIG. 5 and the specifications of Table 1, and the turning performance, riding comfort, noise performance and drainage performance were tested. The parameters other than those shown in Table 1 are the same. In addition, for the block width change,

Moreover, the following two types a and b were adopted as the profile of the tire outer surface.
<Profile a>
RY60 = 0.06
RY75 = 0.08
RY90 = 0.19
RY100 = 0.57
<Profile b>
RY60 = 0.09
RY75 = 0.14
RY90 = 0.37
RY100 = 0.57
The test method is as follows.

<Turning performance and ride comfort>
Each test tire was mounted on four wheels of a vehicle (European 4WD vehicle with 4800cc displacement) under the conditions of a rim (20 × 9.0 J) and an internal pressure (220 kPa). The test course on the dry asphalt road surface was run in various modes including turning, with one driver on board. Evaluation of steering stability and riding comfort is based on the driver's sensation, and is indicated by a score of Comparative Example 1 being 100. A larger index is better.

<Noise performance>
Using a vehicle having the same conditions as described above, a smooth road surface was run at a speed of 50 km / H, and the magnitude of the pattern noise was evaluated by the feeling of the driver. A result is a score which sets the prior art example 1 to 100, and shows that pattern noise is so small that a numerical value is large.

<Drainage performance>
On the asphalt road surface with a radius of 100m, on the course with a puddle with a depth of 5mm and a length of 20m, the vehicle is approached while increasing the speed stepwise, and the lateral acceleration (lateral G) is measured, 50-80km / The average lateral G of the front wheels at the speed of h was calculated. A result is displayed by the index | exponent which sets the comparative example 1 to 100, and it is so favorable that a numerical value is large.
Table 1 shows the test results.

  As a result of the test, it was confirmed that the tires of the examples improved the steering stability without impairing the ride comfort and drainage performance.

It is sectional drawing of the pneumatic tire which shows embodiment of this invention. It is a fragmentary perspective view of the sidewall part. It is a diagram which shows the profile of a tire outer surface. It is a diagram which shows the range of RYi in each position of a tire outer surface. It is an expanded view of a tread part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 13 Center vertical groove 20 Large block row 23 First small block row 24 Second small block row B1 Large block B2, B3 Small size Block Po Outer pattern part Pi Inner pattern part

Claims (4)

A carcass having at least one carcass ply that is folded and locked by a bead core of the bead portion from the tread portion through the sidewall portion, and a belt layer disposed radially outside the carcass and inside the tread portion. A pneumatic tire having a mounting direction on the vehicle,
In a tire meridian cross section including a normal tire rotating shaft that is assembled with a normal rim and filled with a normal internal pressure, the profile of the tire outer surface is a contact end side from the intersection of the tire outer surface and the tire equatorial plane. And the tread portion extends continuously in the tire circumferential direction and has a single central longitudinal groove with a groove width of 15 to 25 mm, and the vehicle outer side. An outer pattern portion provided on the inner longitudinal pattern portion and an inner pattern portion provided on the vehicle inner side of the central longitudinal groove,
The outer pattern portion includes a large block row in which large blocks are arranged in the tire circumferential direction,
The pneumatic tire according to claim 1, wherein the inner pattern portion includes a small block row in which small blocks having both a width and a tire circumferential direction length smaller than the large block are arranged in the tire circumferential direction.   2. The pneumatic tire according to claim 1, wherein a tire circumferential length of the large block is 2.0 to 4.0 times a tire circumferential length of the small block. The outer pattern portion is a large block row provided between the outer vertical groove and the central vertical groove by one outer vertical groove extending in the tire circumferential direction;
It is divided into a rib provided between the outer longitudinal groove and the ground contact end outside the vehicle,
The pneumatic tire according to claim 1 or 2, wherein a shoulder lug groove that extends from the ground contact end on the outer side of the vehicle toward the tire equator and terminates without communicating with the outer longitudinal groove is provided in the rib. In the tire meridian cross section including the tire rotation axis in the normal state, the profile of the tire outer surface is a distance (SP) of 45% of the maximum tire width (SW) from the intersection (CP) between the tire outer surface and the tire equatorial plane. When the point on the outer surface of the tire that is separated is defined as (P), the radius of curvature (RC) of the outer surface of the tire gradually decreases and satisfies the following relationship in the section from the intersection (CP) to the point (P). The pneumatic tire according to any one of claims 1 to 3.
0.05 <Y60 / H ≦ 0.1
0.1 <Y75 / H ≦ 0.2
0.2 <Y90 / H ≦ 0.4
0.4 <Y100 / H ≦ 0.7
(Where Y60, Y75, Y90 and Y100 are the tire axial distances of 60%, 75%, 90% and 100% of the half width (SW / 2) of the maximum tire width in the tire axial direction from the intersection (CP). (The distances in the tire radial direction between the points P60, P75, P90 and P100 on the outer surface of the tire and the intersections (CP), and H is the tire cross-section height.)

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