JP2018076037A - tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire improving drainage performance and steering stability with good balance.SOLUTION: In a tire 1, first lateral grooves 7 and second lateral grooves 8 are provided in plural numbers in each shoulder region 4 in the descending order of lengths in a tire shaft direction. The first lateral grooves 7 have an inner part 11 extending at an angle θ1 of inclination to outside in the tire shaft direction, from a crown main groove 3 to outside in the tire shaft direction across a distance A and an outer part 12 extending at an angle θ2(<θ1) of inclination to stride across a tread grounding end Te. The second lateral grooves 8, provided between the first lateral grooves 7 and 7, have an inner end 8i positioned from the crown main groove 3 to outside in the tire shaft direction across a distance B smaller than the distance A. The second lateral grooves 8 extend at an angle θ3 of inclination larger than the angle θ1 in the same direction as the first lateral grooves 7 from the inner end 8i, an outer end 8e of which terminates without crossing the tread grounding end Te.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a tire in which drainage performance and steering stability performance are improved in a well-balanced manner.

  Conventionally, for example, as shown in FIG. 3, a pair of main grooves a and a continuous in the tire circumferential direction are connected to the tread portion g, and the main groove a and the tread ground contact Te are connected to the tire axial direction. There is known a tire t including an inclined groove b1 extending in an inclined manner and an inclined groove b2 extending in an inclined manner without communicating with the main groove a or the tread ground contact Te. In such a tire, the main groove a and the inclined grooves b1 and b2 smoothly discharge the water film between the tread surface and the road surface, and thus can exhibit excellent drainage performance.

  However, in this type of tire t, an acute-angled first corner portion c1 sandwiched between the main groove a and the inclined groove b1 is formed in the land portion c. In addition, when the bent portion d extending in a bent shape as shown in the figure is provided in the inclined groove b2, a sharp corner-shaped second corner portion c2 sandwiched between the bent portions d is formed in the land portion c. Such first corner portion c1 and second corner portion c2 tend to accumulate rubber during tire vulcanization. Accordingly, the tire t having the first corner portion c1 and the second corner portion c2 has a problem that the grounding pressure becomes non-uniform and the steering stability performance is likely to deteriorate.

JP2015-131603A

  The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire that can improve drainage performance and steering stability performance in a well-balanced manner.

  The present invention provides a tire in which a tread portion is provided with a pair of crown main grooves extending continuously in the tire circumferential direction, and a plurality of lateral grooves provided in both shoulder regions which are regions on both outer sides of the crown main groove. In each shoulder region, a plurality of first lateral grooves and a plurality of second lateral grooves are provided as the lateral grooves in descending order of the length in the tire axial direction on the tread surface. Is an inner portion extending outwardly in the tire axial direction with an inclination of an angle θ1 with respect to the tire axial direction from an inner end located at a distance A outward from the crown main groove in the tire axial direction, and an angle with respect to the tire axial direction. each of the second lateral grooves is provided between the first lateral grooves adjacent to each other in the tire circumferential direction, and includes an outer portion extending across the tread contact edge at an inclination of θ2 (<θ1). The lateral groove An inner end located at a distance B smaller than the distance A on the outer side in the tire axial direction from the main groove, and the first end at an angle θ3 larger than the angle θ1 with respect to the tire axial direction from the inner end. Inclined in the same direction as one lateral groove, extends outward in the tire axial direction, and terminates without the outer end intersecting the tread grounding end.

  In the tire according to the present invention, each shoulder region is provided with a plurality of third lateral grooves whose length in the tire axial direction on the tread surface is smaller than that of the second lateral grooves. It is provided between the first lateral grooves adjacent to each other in the circumferential direction, and each of the third lateral grooves extends from the inner end located at a distance C to the outer side in the tire axial direction from the second lateral groove so as to straddle the tread ground contact end. It is desirable to extend.

  In the tire according to the present invention, the distance C is desirably 10% to 25% of the tread width.

  In the tire according to the present invention, it is desirable that the third lateral groove is inclined in the same direction as the first lateral groove, and an angle θ4 with respect to the tire axial direction is smaller than the angle θ2 of the outer portion.

  In the tire according to the present invention, the angle θ1 of the inner portion is 25 to 45 °, the angle θ2 of the outer portion is 15 to 40 °, and the angle θ3 of the second lateral groove is 30. It is desirable that the angle θ4 of the third lateral groove is 25 ° or less.

  The tire according to the present invention is preferably provided with a crown land portion divided between the crown main grooves, and a width of the crown land portion in a tire axial direction is 10% to 20% of a tread width.

  In the tire of the present invention, the tread portion is provided with a pair of crown main grooves extending continuously in the tire circumferential direction, and a plurality of lateral grooves provided in both shoulder regions which are regions on both outer sides of the crown main groove. Tire. Since the crown main groove continuous in the tire circumferential direction can smoothly drain the water film between the tread surface and the road surface, drainage performance is improved.

  Each shoulder region is provided with a plurality of first and second lateral grooves in the order of increasing length in the tire axial direction on the tread surface as lateral grooves. Each first lateral groove includes an inner portion extending outward in the tire axial direction at an angle θ1 with respect to the tire axial direction from an inner end located at a distance A outward from the crown main groove at a distance A in the tire axial direction, and in the tire axial direction. On the other hand, it includes an outer portion extending across the tread grounding end at an angle θ2 (<θ1). Since the first lateral groove has an outer portion on the tread grounding end side, the water in the groove can be smoothly discharged using the lateral force during turning. Furthermore, since the 1st horizontal groove is not connected with the crown main groove, the acute-angle land part pinched by the 1st horizontal groove and the crown main groove is not formed. As a result, rubber accumulation during tire vulcanization is suppressed, and uneven contact pressure is eliminated, so that steering stability is maintained high.

  Each second lateral groove is provided between first lateral grooves adjacent in the tire circumferential direction. Each second lateral groove has an inner end located at a distance B smaller than the distance A on the outer side in the tire axial direction from the crown main groove, and an angle larger than the angle θ1 with respect to the tire axial direction from the inner end. At θ3, it inclines in the same direction as the first lateral groove and extends outward in the tire axial direction, and the outer end terminates without crossing the tread ground contact end. Such a second lateral groove is not in communication with the crown main groove, and therefore does not form an acute-angle land portion with the crown main groove. In addition, the second lateral groove terminates without the outer end crossing the tread grounding end. For this reason, since the 2nd horizontal groove maintains the rigidity of a land part highly, it exhibits the outstanding handling stability performance. Furthermore, since the distance B of the second lateral groove is smaller than the distance A of the first lateral groove, the length of the second lateral groove in the tire axial direction is ensured to be large. Since the second horizontal groove is inclined at an angle θ3 larger than the angle θ1 of the inner portion of the first horizontal groove, the actual length in the longitudinal direction of the second horizontal groove is ensured to be large. For this reason, a 2nd horizontal groove exhibits high drainage performance.

  Therefore, the tire of the present invention improves drainage performance and steering stability performance in a well-balanced manner.

It is an expanded view of the tread part which shows one Embodiment of this invention. It is an enlarged view of the horizontal groove of FIG. It is an enlarged view of the horizontal groove of FIG. It is an expanded view of the tread part which shows embodiment of a prior art example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread portion 2 of a tire 1 showing an embodiment of the present invention. The present invention can be used for various tires such as pneumatic tires for passenger cars and heavy loads, and non-pneumatic tires in which the tire is not filled with air. The tire 1 of this embodiment is a pneumatic tire for passenger cars.

  As shown in FIG. 1, the tread portion 2 is provided with a pair of crown main grooves 3 and 3 extending continuously in the tire circumferential direction. As a result, the tread portion 2 is formed with shoulder regions 4 and 4 which are regions on both outer sides of the main crown groove 3 and a crown region 5 which is a region between the main crown grooves 3 and 3.

  In this embodiment, the crown main groove 3 extends linearly. Such a crown main groove 3 reduces resistance to water passing through the groove and exhibits high drainage performance. In addition, the crown main groove 3 is not limited to such an embodiment, and may be one that extends in a gentle wave shape or zigzag shape. Further, it is desirable that the pair of crown main grooves 3 be arranged symmetrically about the tire equator Ca.

  The groove width W1 of the crown main groove 3 is preferably 5% to 15% of the tread width TW, for example. The groove depth (not shown) of the crown main groove 3 is preferably about 5 to 12 mm, for example. Such a crown main groove 3 maintains excellent rigidity of the land portion while ensuring drainage performance, and exhibits excellent steering stability performance.

  The “tread width TW” is a tread ground contact edge Te that is determined as a ground contact position on the outermost side in the tire axial direction when a normal load is applied to the tire 1 in a normal state and grounded on a flat surface with a camber angle of 0 degrees, This is the distance in the tire axial direction between Te. The “normal state” is a no-load state in which the tire 1 is assembled on a normal rim (not shown) and filled with a normal internal pressure. In this specification, when there is no notice in particular, the dimension of each part of the tire 1 is a value measured in this normal state.

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

 “Normal 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 is TIRE LOAD LIMITS AT VARIOUS The maximum value described in “COLD INFLATION PRESSURES”, “INFLATION PRESSURE” if it is ETRTO, but if the tire is for a passenger car, it is uniformly 180 kPa.

  “Regular load” is the load that each standard defines 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 AT for TRA” If the maximum value described in “VARIOUS COLD INFLATION PRESSURES”, ETRTO is “LOAD CAPACITY”, if the tire is for a passenger car, the load is equivalent to 88% of the load.

  A plurality of lateral grooves 6 are provided in each shoulder region 4, 4. In this embodiment, the lateral groove 6 includes a first lateral groove 7, a second lateral groove 8, and a third lateral groove 9.

  In the present embodiment, the first lateral groove 7, the second lateral groove 8, and the third lateral groove 9 extend in an arc shape. The first lateral groove 7, the second lateral groove 8, and the third lateral groove 9 each have a center on one side in the tire circumferential direction (lower side in the figure) and the other side in the tire circumferential direction (upper side in the figure). It is formed in the circular arc shape which becomes convex. Thereby, since the length of the land part between each horizontal groove 7 thru | or 9 is ensured, the rigidity of a land part is maintained. In addition, the 1st horizontal groove 7, the 2nd horizontal groove 8, and the 3rd horizontal groove 9 are not limited to such an aspect.

  In the present embodiment, each of the first lateral grooves 7 is an inner end 7i in the tire axial direction that is located apart from the crown main groove 3 in the tire axial direction, and an outer position that is located on the outer side in the tire axial direction of the tread ground contact Te. It has an end 7e. Thereby, the 1st horizontal groove 7 can discharge | emit the water film between a tread tread surface and a road surface efficiently from the tread grounding edge Te to the outer side. Further, since the inner end 7 i of the first lateral groove 7 is separated from the crown main groove 3, an acute angle corner portion sandwiched between the grooves 3, 7 is provided between the first lateral groove 7 and the crown main groove 3. (Not shown) is not formed. Accordingly, since the formation of a rubber pool is suppressed during tire vulcanization, the steering stability performance is maintained high.

  If the inner end 7i is greatly separated from the crown main groove 3, the length of the crown main groove 3 is reduced, and the drainage performance may be deteriorated. For this reason, the distance A in the tire axial direction between the inner end 7i of the first lateral groove 7 and the crown main groove 3 is preferably 15% to 35% of the width Ws of the shoulder region 4 in the tire axial direction, for example.

  In the present embodiment, the first lateral groove 7 includes an inner portion 11 including an inner end 7i and an outer portion 12 including an outer end 7e.

  As shown in FIG. 2, the inner portion 11 extends outward from the inner end 7i in the tire axial direction with an inclination of an angle θ1 with respect to the tire axial direction. The outer portion 12 extends so as to straddle the tread ground contact Te with an inclination of an angle θ2 with respect to the tire axial direction that is smaller than the angle θ1 of the inner portion 11. Such an outer portion 12 can smoothly drain the water in the first lateral groove 7 by using a large lateral force during turning, greatly improving the drainage performance. Further, the inner portion 11 can maintain a large rigidity in the tire circumferential direction on the inner side in the tire axial direction of the shoulder region 4 where a large contact pressure acts.

  In the present specification, the angle θ1 of the inner portion 11 and the angle θ2 of the outer portion 12 of the first lateral groove 7 are defined as follows. First, in the groove edge E of the first lateral groove 7, a groove edge portion Ea having a maximum length in the tire axial direction and the direction of the arc extending continuously in any direction with respect to the tire circumferential direction is specified. . The angle θ1 of the inner portion 11 is an angle with respect to the tire axial direction of an imaginary line Ec that connects the inner end E1 of the groove edge Ea in the tire axial direction and the intermediate position E3 of the length of the groove edge Ea with a straight line. Further, the angle θ2 of the outer portion 12 is an angle with respect to the tire axial direction of the imaginary line Ed that connects the outer edge E2 of the groove edge portion Ea in the tire axial direction and the intermediate position E3 of the length of the groove edge Ea with a straight line. is there.

  The angle θ1 of the inner portion 11 is preferably 25 to 45 °. The angle θ2 of the outer portion 12 is desirably 15 to 40 °. When the angle θ1 of the inner portion 11 is less than 25 ° or the angle θ2 of the outer portion 12 is less than 15 °, the groove volume of the first lateral groove 7 becomes small, and the drainage performance may be deteriorated. When the angle θ1 of the inner portion 11 exceeds 45 °, or the angle θ2 of the outer portion 12 exceeds 40 °, there is a risk that the water in the first lateral groove 7 cannot be discharged smoothly using the lateral force during turning. There is.

  The angle α sandwiched between the inner portion 11 and the outer portion 12 is preferably 160 to 170 °. When the angle α is less than 160 °, sharp corners are easily formed in a region sandwiched between the inner portion 11 and the outer portion 12, and a rubber pool is formed during tire vulcanization, so that steering stability performance is deteriorated. There is a risk. When the angle α exceeds 170 °, the first lateral groove 7 becomes linear, and the actual length in the longitudinal direction becomes small, so that the drainage performance may be deteriorated. In the present specification, the angle α is defined as an angle between the virtual line Ec and the virtual line Ed.

  As shown in FIG. 1, the first lateral groove 7 has a length L1 in the tire axial direction on the tread surface between the tread grounding ends Te and Te, and a tire axial direction length on the tread surface of the second lateral groove 8 in the tire axial direction. It is formed larger than the length L2. Such a 1st horizontal groove 7 can exhibit big drainage performance.

  In the present embodiment, the second lateral groove 8 is provided between the first lateral grooves 7 and 7 adjacent to each other in the tire circumferential direction. That is, the second lateral grooves 8 of the present embodiment are provided alternately with the first lateral grooves 7 in the tire circumferential direction.

  The second lateral groove 8 has an inner end 8 i in the tire axial direction disposed in the shoulder region 4 and an outer end 8 e in the tire axial direction disposed in the shoulder region 4. The second lateral groove 8 is inclined in the same direction as the first lateral groove 7 from the inner end 8i and extends outward in the tire axial direction. Thereby, since the rigidity step in the tire circumferential direction is reduced between the first lateral groove 7 and the second lateral groove 8, the steering stability performance is improved.

  The inner end 8 i of the second lateral groove 8 is separated from the crown main groove 3 to the outer side in the tire axial direction. Thereby, an acute-angle corner portion sandwiched between the grooves 3 and 8 is not formed between the second lateral groove 8 and the crown main groove 3. Accordingly, since the formation of a rubber pool is suppressed during tire vulcanization, the steering stability performance is maintained high.

  The distance B in the tire axial direction between the inner end 8i of the second lateral groove 8 and the crown main groove 3 is formed smaller than the distance A in the tire axial direction between the inner end 7i of the first lateral groove 7 and the crown main groove 3. . Although the outer end 8e of the second lateral groove 8 is disposed in the shoulder region 4, the outer end 7e of the first lateral groove 7 is disposed on the outer side of the tread grounding end Te, so that the second lateral groove 8 is the first lateral groove 7. Compared to the above, the length L2 in the tire axial direction tends to be small. For this reason, since the tire axial direction length L2 of the 2nd horizontal groove 8 is ensured large by making the distance B smaller than the distance A, drainage performance improves. When the distance B is excessively smaller than the distance A, the rigidity of the land portion sandwiched between the crown main groove 3 and the second lateral groove 8 is reduced, and there is a possibility that rubber accumulation is likely to occur during tire vulcanization. For this reason, the distance B is preferably 35% to 65% of the distance A.

  As shown in FIG. 2, the second lateral groove 8 includes an inner portion 21 having an inner end 8i in the tire axial direction and an outer portion 22 having an outer end 8e in the tire axial direction in the present embodiment. . In the present embodiment, the inner portion 21 of the second lateral groove 8 extends outward in the tire axial direction from the inner end 8i with an inclination of an angle θ3a with respect to the tire axial direction. In this embodiment, the outer portion 22 of the second lateral groove 8 is inclined at an angle θ3b with respect to the tire axial direction that is smaller than the angle θ3a of the inner portion 21.

  In the present specification, the angle θ3a of the inner portion 21 and the angle θ3b of the outer portion 22 of the second transverse groove 8 are the same as the first transverse groove 7 and the groove edge portion Ea having the maximum length of the groove edge E of the second transverse groove 8. Defined by an inner end E1, an intermediate position E3, and an outer end E2.

  When the length of the transverse groove in the tire axial direction is less than 60% of the width Ws of the shoulder region 4 in the tire axial direction, the contact pressure acting on the transverse groove and the lateral force during cornering are reduced in the inner part and the outer part. There is no big change. For this reason, in such a lateral groove, it is desirable that the inclination angle is specified by the lateral groove itself that combines the inner part and the outer part. The specification of the angle of the lateral groove itself is defined by an imaginary line Ef that connects the inner end E1, the outer end, and E2 of the groove edge Ea having the maximum length in the tire axial direction with a straight line. In the present embodiment, the length L2 of the second lateral groove 8 in the tire axial direction is less than 60% of the width Ws of the shoulder region 4 in the tire axial direction. Therefore, the second lateral groove 8 is specified by an angle θ3 with respect to the tire axial direction of an imaginary line Ef that connects the inner end E1 and the outer end E2 of the groove edge Ea with a straight line.

  The angle θ3 of the second lateral groove 8 is formed larger than the angle θ1 of the inner portion 11. The inner end 8 i of the second lateral groove 8 is provided closer to the crown main groove 3 than the inner end 7 i of the first lateral groove 7, that is, the inner end 11 i of the inner portion 11. As a result, a larger ground pressure acts on the inner end 8 i of the second lateral groove 8 than on the inner end 11 i of the inner portion 11. Therefore, by making the angle θ3 of the second lateral groove 8 larger than the angle θ1 of the inner portion 11, the rigidity in the tire circumferential direction of the land portion around the second lateral groove 8 is ensured, so that excellent steering stability is achieved. Performance is demonstrated.

  The angle θ3 of the second lateral groove 8 is desirably 30 to 50 °. When the angle θ3 of the second lateral groove 8 is less than 30 degrees, the actual length of the second lateral groove 8 cannot be increased on the tire equator Ca side where it is difficult to discharge the water film between the tread surface and the road surface, and drainage performance is reduced. May get worse. When the angle θ3 of the second lateral groove 8 exceeds 50 °, the length L2 of the second lateral groove 8 in the tire axial direction becomes small, the water film cannot be collected effectively, and the drainage performance may be deteriorated. There is.

  As shown in FIG. 1, in the second lateral groove 8, the length L2 in the tire axial direction on the tread surface is larger than the length L3 in the tire axial direction on the tread surface of the third lateral groove 9. desirable. As a result, the water film on the tread surface on the inner side in the tire axial direction of the shoulder region 4 that is difficult to be discharged can be smoothly collected in the second lateral groove 8, so that the drainage performance is improved. The length L2 of the second lateral groove 8 is desirably 3 to 5 times the length L3 of the third lateral groove 9.

  The second lateral groove 8 has an overlapping portion 8a that overlaps with one of the first lateral grooves 7 adjacent in the tire circumferential direction in the tire circumferential direction. Thereby, the outstanding drainage performance is exhibited further.

  The third lateral groove 9 is provided between the first lateral grooves 7 and 7 adjacent in the tire circumferential direction. The third horizontal grooves 9 of the present embodiment are inclined in the same direction as the first horizontal grooves 7 and are alternately provided in the first horizontal grooves 7 and the tire circumferential direction.

  The third lateral groove 9 has an inner end 9i in the tire axial direction and an outer end 9e in the tire axial direction. In the present embodiment, the third lateral groove 9 extends from the inner end 9i to straddle the tread grounding end Te. Thus, the outer end 9e of the third lateral groove 9 of the present embodiment is located outside the tread ground contact end Te in the tire axial direction. Such a third lateral groove 9 also smoothly drains the water in the third lateral groove 9 to the outside of the tread ground contact Te, so that the drainage performance is improved.

  The inner end 9 i of the third lateral groove 9 is located away from the second lateral groove 8 on the outer side in the tire axial direction. In the present embodiment, the inner end 9 i is located on the outer side in the tire axial direction with respect to the outer end 8 e of the second lateral groove 8. Thereby, since the rigidity of the land portion of the shoulder region 4 between the first lateral grooves 7 and 7 is ensured, the steering stability performance is maintained high.

  The distance C in the tire axial direction between the inner end 9i of the third lateral groove 9 and the outer end 8e of the second lateral groove 8 is preferably 5% to 12.5% of the tread width TW. When the distance C is less than 5% of the tread width TW, the rigidity of the land portion on the tread ground contact end Te side on which a large lateral force acts during turning travel is reduced, so that the steering stability performance may be deteriorated. When the distance C exceeds 12.5% of the tread width TW, the tire axial direction length L3 on the tread surface of the third lateral groove 9 or the tire axial direction length L2 of the second lateral groove 8 is reduced. Drainage performance may be deteriorated.

  The distance C is preferably larger than the distance B. When the distance C is smaller than the distance B, that is, when the distance B is larger than the distance C, the water film on the tread surface of the land portion on the inner side in the tire axial direction that is difficult to drain may not be effectively discharged. When the distance C is excessively larger than the distance B, the water film on the tread surface of the land portion on the outer side in the tire axial direction may not be smoothly discharged.

  The distance D in the tire circumferential direction between the inner end 9i of the third lateral groove 9 and the outer end 8e of the second lateral groove 8 is preferably 4% to 12% of the length Lb of the second lateral groove 8 in the tire circumferential direction. . When the distance D is less than 4% of the length Lb of the second lateral groove 8, the rigidity of the land portion between the third lateral groove 9 and the second lateral groove 8 becomes small, and the steering stability performance may be deteriorated. When the distance D exceeds 12% of the length Lb of the second lateral groove 8, the first lateral groove 7 and the third lateral groove 9 approach each other, so that the tire axis of the land portion between the first lateral groove 7 and the third lateral groove 9 There is a risk that the directional rigidity is reduced.

  In order to improve drainage performance and steering stability performance in a well-balanced manner, the tire axial direction length L3 of the third lateral groove 9 is desirably 5% to 25% of the width Ws of the shoulder region 4 in the tire axial direction.

  As shown in FIG. 2, the third lateral groove 9 includes an inner portion 31 having an inner end 9 i in the tire axial direction and an outer portion 32 having an outer end 9 e in the tire axial direction in the present embodiment. . In the present embodiment, the inner portion 31 of the third lateral groove 9 extends outward in the tire axial direction from the inner end 9i with an inclination of an angle θ4a with respect to the tire axial direction. In the present embodiment, the outer portion 32 of the third lateral groove 9 is inclined at an angle θ4b with respect to the tire axial direction that is smaller than the angle θ4a of the inner portion 31. The angle θ4a of the inner portion 31 of the third lateral groove 9 and the angle θ4b of the outer portion 32 are also the inner end E1 of the groove edge portion Ea of the maximum length of the groove edge E of the third lateral groove 9, as in the first lateral groove 7. It is defined by an intermediate position E3 and an outer end E2.

  In the present embodiment, the third lateral groove 9 has a length L3 (shown in FIG. 1) in the tire axial direction on the tread surface that is less than 60% of the width Ws of the shoulder region 4 in the tire axial direction. For this reason, the third lateral groove 9 is specified by an angle θ4 with respect to the tire axial direction of an imaginary line Ef that connects the inner end E1 and the outer end E2 of the groove edge Ea with a straight line.

  The angle θ4 of the third lateral groove 9 with respect to the tire axial direction is desirably smaller than the angle θ2 of the outer portion 12 of the first lateral groove 7. Thereby, since the edge component of a different angle is provided in the 3rd horizontal groove 9 and the outer side part 12, drainage performance is improved effectively. From such a viewpoint, the angle θ4 of the third lateral groove 9 is desirably 25 degrees or less. In the present embodiment, the angle θ4 of the third lateral groove 9 is the smallest among the angles of the lateral grooves 6. In the present embodiment, the angle θ3 of the second lateral groove 8 is the largest among the angles of the lateral groove 6.

  As shown in FIG. 3, in the present embodiment, it is desirable that the groove edges E of the first to third lateral grooves 7 to 9 of the lateral groove 6 are defined as follows. The groove edge E of the first lateral groove 7 includes a plurality of groove edge portions 15, 16... Inclined at different angles with respect to the tire axial direction. It is desirable that the angles β1, β2, β3, β4,... On the tread tread surface side formed by adjacent groove edge portions 15, 16 provided in the first lateral groove 7 are all 90 ° or more. In other words, the land portion around the first lateral groove 7 is formed by land portions having angles β1, β2,... Of 90 ° or more by the adjacent groove edge portions 15, 16,. , An acute angle corner portion of less than 90 ° is not formed. Thereby, since the formation of a rubber pool is suppressed in the land part around the 1st horizontal groove 7 at the time of tire vulcanization, the outstanding steering stability performance is exhibited. The groove edge E of the second transverse groove 8 and the groove edge E of the third transverse groove 9 are the tread tread side formed by adjacent groove edge portions 15, 16, like the groove edge E of the first transverse groove 7. It is desirable that the angles β1, β2, β3, β4,... Can be formed at 90 ° or more.

  The above-described effects are exhibited particularly at the groove edge portion at the groove edge Et on the tread surface.

  As shown in FIG. 1, the groove width W2 of the first lateral groove 7 on the tread surface is desirably larger than the groove width W3 of the second lateral groove 8 on the tread surface. The groove width W3 of the second lateral groove 8 on the tread surface is preferably larger than the groove width W4 of the third lateral groove 9 on the tread surface. The groove width W2 of the first transverse groove 7 is preferably 60% to 80% of the groove width W1 of the crown main groove 3, for example. The groove width W3 of the second lateral groove 8 is preferably 50% to 70% of the groove width W1 of the crown main groove 3, for example. The groove width W4 of the third lateral groove 9 is preferably 30% to 50% of the groove width W1 of the crown main groove 3, for example. The groove widths W2 to W4 of the lateral grooves 7 to 9 are specified by the maximum width in the direction perpendicular to the longitudinal direction.

  As shown in FIG. 1, the crown region 5 is formed as a plain rib in which no groove or sipe is provided in the present embodiment. Although not particularly limited, the width Wc in the tire axial direction of the crown region 5 is 10% to 20% of the tread width TW in order to increase the rigidity of the land portion of the crown region 5 and improve the straight running stability performance. It is desirable that

  Although the tire according to the present invention has been described in detail above, it is needless to say that the present invention is not limited to the specific embodiment described above, and can be implemented in various forms.

Tires of size 245 / 40R18 having the basic pattern of FIG. 1 were prototyped based on the specifications in Table 1, and the drainage performance and steering stability performance of each sample tire were tested. The common specifications and test methods for each sample tire are as follows.
In each comparative example and each example, the groove width and the groove depth are adjusted so that the land ratio and the groove volume of the shoulder region and the crown region are the same.
Each comparative example and each example satisfy the groove width W1 of the crown main groove> the groove width W2 of the first transverse groove> the groove width W3 of the second transverse groove> the groove width W4 of the third transverse groove.
Outside portion angle θ2: 21 ° (angle θ2 of Example 7: 15 °)
Distance A / width Ws of shoulder region: 25%

<Operation stability and drainage performance>
Sample tires were installed on all passenger cars under the following conditions. Then, the test driver runs a dry asphalt road test course and a wet asphalt road test course with a water depth of 3 mm. It was. The results are displayed with a score of 100 for the conventional example. The larger the value, the better.
Vehicle: 4WD vehicle with displacement of 2000cc Internal pressure: 230kPa
The test results are shown in Table 1.

  As a result of the test, it can be confirmed that the performance of the tire of the example is improved in a well-balanced manner as compared with the tire of the comparative example. In addition, the test was performed while changing the tire size, and the test result was the same.

DESCRIPTION OF SYMBOLS 1 Tire 3 Crown main groove 4 Shoulder area | region 7 1st horizontal groove 8 2nd horizontal groove 8i Inner end 8e Outer end 11 Inner part 12 Outer part Te Tread grounding end

Claims (6)

The tread portion is a tire provided with a pair of crown main grooves extending continuously in the tire circumferential direction, and a plurality of lateral grooves provided in both shoulder regions which are regions on both outer sides of the crown main groove,
Each shoulder region is provided with a plurality of first lateral grooves and a plurality of second lateral grooves in order of increasing length in the tire axial direction on the tread surface as the lateral grooves,
Each of the first lateral grooves includes an inner portion extending outward in the tire axial direction at an angle θ1 with respect to the tire axial direction from an inner end positioned at a distance A outward from the crown main groove in the tire axial direction, and a tire shaft An outer portion extending across the tread ground end at an angle θ2 (<θ1) with respect to the direction,
Each of the second lateral grooves is provided between the first lateral grooves adjacent to each other in the tire circumferential direction,
Each of the second lateral grooves has an inner end located at a distance B smaller than the distance A on the outer side in the tire axial direction from the crown main groove, and the angle θ1 with respect to the tire axial direction from the inner end. The tire is inclined in the same direction as the first lateral groove at a larger angle θ3 and extends outward in the tire axial direction, and the outer end terminates without crossing the tread ground contact end. Each shoulder region is provided with a plurality of third lateral grooves that are smaller in length in the tire axial direction on the tread surface than the second lateral grooves,
Each of the third lateral grooves is provided between the first lateral grooves adjacent in the tire circumferential direction,
2. The tire according to claim 1, wherein each of the third lateral grooves extends from the inner end located at a distance C to the outer side in the tire axial direction from the second lateral groove so as to straddle the tread ground contact end.   The tire according to claim 2, wherein the distance C is 10% to 25% of a tread width.   The tire according to claim 2 or 3, wherein the third lateral groove is inclined in the same direction as the first lateral groove, and an angle θ4 with respect to a tire axial direction is smaller than the angle θ2 of the outer portion. The angle θ1 of the inner portion is 25 to 45 °,
The angle θ2 of the outer portion is 15 to 40 °,
The angle θ3 of the second lateral groove is 30 to 50 °,
The tire according to claim 4, wherein the angle θ4 of the third lateral groove is 25 ° or less. A crown land portion divided between the crown main grooves is provided;
The tire according to any one of claims 1 to 5, wherein a width of the crown land portion in a tire axial direction is 10% to 20% of a tread width.

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