JP6965507B2 - tire - Google Patents

Description

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

Conventionally, for example, as shown in FIG. 3, a pair of main grooves a, a, main grooves a and a tread ground contact end Te that are continuous in the tire circumferential direction are communicated with the tread portion g and with respect to the tire axial direction. A tire t having an inclined groove b1 extending inclined and an inclined groove b2 extending inclined without communicating with the main groove a and the tread ground contact end Te is known. In such a tire, the main groove a and the inclined grooves b1 and b2 smoothly discharge the water film between the tread tread surface and the road surface, so that excellent drainage performance can be exhibited.

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 on the land portion c thereof. Further, when the inclined groove b2 is provided with a bent portion d extending in a bent shape as shown in the figure, an acute-angled second corner portion c2 sandwiched between the bent portions d is formed in the land portion c. Rubber tends to accumulate in the first corner portion c1 and the second corner portion c2 during tire vulcanization. Therefore, the tire t having the first corner portion c1 and the second corner portion c2 has a problem that the steering stability performance tends to deteriorate because the contact pressure becomes non-uniform.

JP 2015-131603

The present invention has been devised in view of the above circumstances, and a main object of the present invention is to provide a tire capable of improving drainage performance and steering stability performance in a well-balanced manner.

The present invention provides a tire provided with a pair of crown main grooves continuously extending 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 grooves, in the tread portion. 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 length in the tire axial direction on the tread tread, and each of the first lateral grooves is provided. Is an angle with respect to the tire axial direction and the inner portion extending outward in the tire axial direction at an inclination of an angle θ1 with respect to the tire axial direction from the inner end located at a distance A from the crown main groove to the outer side in the tire axial direction. Each of the second lateral grooves is provided between the first lateral grooves adjacent to the tire circumferential direction, and includes an outer portion extending so as to straddle the tread ground contact end with an inclination of θ2 (<θ1). The lateral groove has an inner end located outside the main groove of the crown in the tire axial direction and separated by a distance B smaller than the distance A, and is an angle larger than the angle θ1 with respect to the tire axial direction from the inner end. It is characterized in that it is inclined in the same direction as the first lateral groove at θ3 and extends outward in the tire axial direction, and the outer end ends without intersecting the tread ground contact end.

In the tire according to the present invention, a plurality of third lateral grooves having a shorter length in the tire axial direction on the tread tread than the second lateral groove are provided in each shoulder region, and each of the third lateral grooves is a tire. It is provided between the first lateral grooves adjacent to each other in the circumferential direction, and each of the third lateral grooves straddles the tread ground contact end from the inner end located outside the second lateral groove in the tire axial direction with a distance C. It is desirable that it extends.

In the tire according to the present invention, it is desirable that the distance C is 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 the 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 preferably ~ 50 °, and the angle θ4 of the third lateral groove is preferably 25 ° or less.

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

The tire of the present invention 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 the tread portion. It is a tire. The crown main groove continuous in the tire circumferential direction can smoothly drain the water film between the tread tread surface and the road surface, thus improving the drainage performance.

In each shoulder region, a plurality of first lateral grooves and a plurality of second lateral grooves are provided as lateral grooves in descending order of length in the tire axial direction on the tread tread. Each first lateral groove extends outward in the tire axial direction at an angle θ1 with respect to the tire axial direction from the inner end located at a distance A from the crown main groove to the outer side in the tire axial direction, and in the tire axial direction. On the other hand, it includes an outer portion extending so as to straddle the tread ground contact end at an inclination of an angle θ2 (<θ1). Since the first lateral groove has an outer portion on the tread ground contact end side, the water in the groove can be smoothly discharged by utilizing the lateral force during turning. Further, since the first lateral groove does not communicate with the crown main groove, an acute-angled land portion sandwiched between the first lateral groove and the crown main groove is not formed. As a result, rubber accumulation during tire vulcanization is suppressed, and non-uniform ground pressure is eliminated, so that steering stability performance is maintained high.

Each second lateral groove is provided between the first lateral grooves adjacent to each other in the tire circumferential direction. Each second lateral groove has an inner end located outside the main groove of the crown in the tire axial direction and separated by a distance B smaller than the distance A, and is an angle larger than the angle θ1 with respect to the tire axial direction from the inner end. At θ3, it is inclined in the same direction as the first lateral groove and extends outward in the tire axial direction, and the outer end is terminated without intersecting the tread ground contact end. Since such a second lateral groove does not communicate with the crown main groove, it does not form an acute-angled land portion with the crown main groove. Further, the second lateral groove is terminated without the outer end intersecting the tread ground contact end. Therefore, the second lateral groove maintains high rigidity of the land portion, and thus exhibits excellent steering stability performance. Further, since the distance B of the second lateral groove is smaller than the distance A of the first lateral groove, a large length of the second lateral groove in the tire axial direction is secured. Since the second lateral groove is inclined at an angle θ3 larger than the angle θ1 of the inner portion of the first lateral groove, a large actual length in the longitudinal direction of the second lateral groove is secured. Therefore, the second lateral groove exhibits high drainage performance.

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

It is a developed view of the tread part which shows one Embodiment of this invention. It is an enlarged view of the lateral groove of FIG. It is an enlarged view of the lateral groove of FIG. It is a development view of the tread part which shows the embodiment of the prior art.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a developed 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 air is not filled inside the tires. The tire 1 of the present embodiment is a pneumatic tire for a passenger car.

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 crown main groove 3 and a crown region 5 which is a region between the crown main grooves 3 and 3.

In the present embodiment, the crown main groove 3 extends linearly. Such a crown main groove 3 reduces the resistance to water passing through the groove and exhibits high drainage performance. The crown main groove 3 is not limited to such an embodiment, and may extend in a gentle wavy shape or a zigzag shape. Further, it is desirable that the pair of crown main grooves 3 are arranged symmetrically with respect to the tire equator Ca.

The groove width W1 of the crown main groove 3 is preferably, for example, 5% to 15% of the tread width TW. 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 high rigidity of the land portion while ensuring drainage performance, and exhibits excellent steering stability performance.

The "tread width TW" is a tread ground contact end Te defined as the outermost ground contact position in the tire axial direction when a normal load is applied to a tire 1 in a normal state and the tire 1 is grounded on a flat surface at a camber angle of 0 degrees. It is the distance between Tes in the tire axial direction. The "normal state" is a no-load state in which the tire 1 is rim-assembled on a normal rim (not shown) and is filled with a normal internal pressure. In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire 1 are values measured in this normal state.

A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, JATMA is a standard rim, TRA is "Design Rim", or ETRTO. If there is, say "Measuring Rim".

"Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. JATMA is the maximum air pressure, and TRA is the table "TIRE LOAD LIMITS AT VARIOUS". The maximum value described in "COLD INFLATION PRESSURES", "INFLATION PRESSURE" for ETRTO, but 180kPa uniformly if the tires are for passenger cars.

"Regular load" is the load defined for each tire in the standard system including the standard on which the tire is based. JATMA has the maximum load capacity, and TRA has the table "TIRE LOAD LIMITS AT". The maximum value described in "VARIOUS COLD INFLATION PRESSURES", "LOAD CAPACITY" for ETRTO, and 88% of the above load when the tires are for passenger cars.

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

The first lateral groove 7, the second lateral groove 8, and the third lateral groove 9 extend in an arc shape in the present embodiment. Further, the first lateral groove 7, the second lateral groove 8, and the third lateral groove 9 each have a center on one side (lower side in the figure) in the tire circumferential direction, and the other side (upper side in the figure) in the tire circumferential direction. It is formed in an arc shape that is convex to the surface. As a result, the length of the land portion between the lateral grooves 7 to 9 is secured, so that the rigidity of the land portion is maintained. The first lateral groove 7, the second lateral groove 8, and the third lateral groove 9 are not limited to such an embodiment.

In the present embodiment, each of the first lateral grooves 7 is an inner end 7i in the tire axial direction located apart from the crown main groove 3 on the outer side in the tire axial direction, and an outer end located on the outer side in the tire axial direction of the tread ground contact end Te. It has an end 7e. As a result, the first lateral groove 7 can efficiently discharge the water film between the tread tread and the road surface to the outside from the tread ground contact end Te. Further, since the inner end 7i of the first lateral groove 7 is separated from the crown main groove 3, an acute-angled corner portion sandwiched between the first lateral groove 7 and the crown main groove 3 is formed. (Not shown) is not formed. Therefore, when the tire is vulcanized, the formation of rubber pools is suppressed, so that the steering stability performance is maintained high.

If the inner end 7i is largely separated from the crown main groove 3, the length of the crown main groove 3 becomes small, and the drainage performance may be deteriorated. Therefore, it is desirable that the distance A between the inner end 7i of the first lateral groove 7 and the crown main groove 3 in the tire axial direction is, for example, 15% to 35% of the width Ws in the tire axial direction of the shoulder region 4.

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 in the tire axial direction from the inner end 7i at an angle θ1 with respect to the tire axial direction. The outer portion 12 extends so as to straddle the tread ground contact end Te at an angle θ2 with respect to the tire axial direction, which is smaller than the angle θ1 of the inner portion 11. Since the water in the first lateral groove 7 can be smoothly discharged from the outer portion 12 by utilizing a large lateral force during turning, the drainage performance is greatly improved. Further, the inner portion 11 can maintain a large rigidity in the tire circumferential direction inside the tire axial direction of the shoulder region 4 on which a large contact pressure acts.

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

The angle θ1 of the inner portion 11 is preferably 25 to 45 °. The angle θ2 of the outer portion 12 is preferably 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 deteriorate. If 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 smoothly discharged by utilizing 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 °, an acute-angled corner portion is likely to be formed in the region sandwiched between the inner portion 11 and the outer portion 12, and a rubber pool is formed during tire vulcanization, which deteriorates steering stability performance. There is a risk of When the angle α exceeds 170 °, the first lateral groove 7 becomes linear and the actual length in the longitudinal direction thereof becomes small, so that the drainage performance may deteriorate. The angle α is defined herein as an angle sandwiched between the virtual line Ec and the virtual line Ed.

As shown in FIG. 1, in the first lateral groove 7, the length L1 in the tire axial direction on the tread tread between the tread ground contact ends Te and Te is the length L1 in the tire axial direction on the tread tread of the second lateral groove 8. It is formed larger than the length L2. Such a first lateral groove 7 can exhibit a large 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 alternately provided with the first lateral grooves 7 in the tire circumferential direction.

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

The inner end 8i of the second lateral groove 8 is separated from the crown main groove 3 outward in the tire axial direction. As a result, an acute-angled corner portion sandwiched between the second lateral groove 8 and the crown main groove 3 is not formed. Therefore, when the tire is vulcanized, the formation of rubber pools is suppressed, so that the steering stability performance is maintained high.

The distance B between the inner end 8i of the second lateral groove 8 and the crown main groove 3 in the tire axial direction is formed to be smaller than the distance A between the inner end 7i of the first lateral groove 7 and the crown main groove 3 in the tire axial direction. .. The outer end 8e of the second lateral groove 8 is arranged in the shoulder region 4, but the outer end 7e of the first lateral groove 7 is arranged outside the tread ground contact end Te, so that the second lateral groove 8 is arranged in the first lateral groove 7. The length L2 in the tire axial direction tends to be smaller than that of the tire. Therefore, by making the distance B smaller than the distance A, a large tire axial length L2 of the second lateral groove 8 is secured, so that the drainage performance is improved. If 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 becomes small, and there is a possibility that rubber pools are likely to occur during tire vulcanization. Therefore, the distance B is preferably 35% to 65% of the distance A.

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

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

When the length of the lateral groove in the tire axial direction is less than 60% of the width Ws in the tire axial direction of the shoulder region 4, the contact pressure acting on the lateral groove and the lateral force during turning run are applied to the inner portion and the outer portion. , There is no big change. Therefore, in such a lateral groove, it is desirable that the angle of inclination is specified by the lateral groove itself in which the inner portion and the outer portion are combined. The angle of the lateral groove itself is specified by a virtual line Ef that connects the inner end E1 and the outer end and E2 of the groove edge portion 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 the virtual line Ef that connects the inner end E1 and the outer end E2 of the groove edge portion Ea with a straight line.

The angle θ3 of the second lateral groove 8 is formed to be larger than the angle θ1 of the inner portion 11. The inner end 8i of the second lateral groove 8 is provided on the crown main groove 3 side of the inner end 7i of the first lateral groove 7, that is, the inner end 11i of the inner portion 11. As a result, a contact pressure larger than that of the inner end 11i of the inner portion 11 acts on the inner end 8i of the second lateral groove 8. Therefore, by making the angle θ3 of the second lateral groove 8 larger than the angle θ1 of the inner portion 11, a large 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 preferably 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 tread and the road surface, and the drainage performance is improved. It 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 effectively collected, and the drainage performance may deteriorate. There is.

As shown in FIG. 1, in the second lateral groove 8, the length L2 in the tire axial direction on the tread tread is larger than the length L3 in the tire axial direction on the tread tread of the third lateral groove 9. desirable. As a result, the water film on the tread tread on the inner side of the shoulder region 4 in the tire axial direction, which 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 preferably 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 any one of the first lateral grooves 7 adjacent to each other in the tire circumferential direction in the tire circumferential direction. As a result, excellent drainage performance is further exhibited.

The third lateral groove 9 is provided between the first lateral grooves 7 and 7 adjacent to each other in the tire circumferential direction. The third lateral groove 9 of the present embodiment is inclined in the same direction as the first lateral groove 7 and is provided alternately with the first lateral groove 7 in 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 so as to straddle the tread ground contact end Te. As described above, 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 discharges the water in the third lateral groove 9 to the outside of the tread ground contact end Te, so that the drainage performance is improved.

The inner end 9i of the third lateral groove 9 is located at a distance from the second lateral groove 8 outward in the tire axial direction. In the present embodiment, the inner end 9i is located outside the outer end 8e of the second lateral groove 8 in the tire axial direction. As a result, the rigidity of the land portion of the shoulder region 4 between the first lateral grooves 7 and 7 is largely secured, so that 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 becomes small, so that the steering stability performance may deteriorate. When the distance C exceeds 12.5% of the tread width TW, the tire axial length L3 of the third lateral groove 9 on the tread tread or the tire axial length L2 of the second lateral groove 8 becomes smaller. Drainage performance may deteriorate.

It is desirable that the distance C is 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 tread on the land inside the tire axial direction, which is difficult to drain, may not be effectively discharged. If the distance C is excessively larger than the distance B, the water film on the tread tread on the land outside in the tire axial direction may not be discharged smoothly.

The distance D between the inner end 9i of the third lateral groove 9 and the outer end 8e of the second lateral groove 8 in the tire circumferential direction 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 deteriorate. 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 come close to each other, so that the tire shaft of the land portion between the first lateral groove 7 and the third lateral groove 9 Directional rigidity may be reduced.

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

As shown in FIG. 2, in the present embodiment, the third lateral groove 9 includes an inner portion 31 having an inner end 9i in the tire axial direction and an outer portion 32 having an outer end 9e in the tire axial direction. .. 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 at 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, which is smaller than the angle θ4a of the inner portion 31. Similarly to the first lateral groove 7, 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 ends E1 of the groove edge portion Ea having the maximum length of the groove edge E of the third lateral groove 9. It is defined by the intermediate position E3 and the 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 tread, which is less than 60% of the width Ws in the tire axial direction of the shoulder region 4. Therefore, the third lateral groove 9 is specified by an angle θ4 with respect to the tire axial direction of the virtual line Ef that connects the inner end E1 and the outer end E2 of the groove edge portion Ea with a straight line.

It is desirable that the angle θ4 of the third lateral groove 9 with respect to the tire axial direction is smaller than the angle θ2 of the outer portion 12 of the first lateral groove 7. As a result, edge components having different angles are provided in the third lateral groove 9 and the outer portion 12, so that the drainage performance is effectively enhanced. From this point of view, the angle θ4 of the third lateral groove 9 is preferably 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 groove 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 edge E of each of the first lateral groove 7 to the third lateral groove 9 of the lateral groove 6 is defined as follows. The groove edge E of the first lateral groove 7 includes a plurality of groove edge portions 15, 16 ... That are 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 side formed by the 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 the adjacent groove edge portions 15, 16 ... Of the first lateral groove 7 and having an angle β1, β2 ... Of 90 ° or more. , An acute-angled corner portion of less than 90 ° is not formed. As a result, the land portion around the first lateral groove 7 suppresses the formation of rubber pools during tire vulcanization, so that excellent steering stability performance is exhibited. The groove edge E of the second lateral groove 8 and the groove edge E of the third lateral groove 9 are also tread tread side formed by adjacent groove edge portions 15, 16 ... Like the groove edge E of the first lateral groove 7. It is desirable that the angles β1, β2, β3, β4, ... Can all be formed at 90 ° or more.

The above-mentioned effects are exhibited especially at the groove edge portion at the groove edge Et on the tread tread.

As shown in FIG. 1, it is desirable that the groove width W2 on the tread tread of the first lateral groove 7 is larger than the groove width W3 on the tread tread of the second lateral groove 8. It is desirable that the groove width W3 on the tread tread of the second lateral groove 8 is larger than the groove width W4 on the tread tread of the third lateral groove 9. The groove width W2 of the first lateral groove 7 is preferably, for example, 60% to 80% of the groove width W1 of the crown main groove 3. The groove width W3 of the second lateral groove 8 is preferably, for example, 50% to 70% of the groove width W1 of the crown main groove 3. The groove width W4 of the third lateral groove 9 is preferably, for example, 30% to 50% of the groove width W1 of the crown main groove 3. The groove widths W2 to W4 of each 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 without grooves or sipes 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 enhance the straight running stability performance. Is desirable.

Although the tire of the present invention has been described in detail above, it goes without saying that the present invention can be implemented by changing to various aspects without being limited to the above-mentioned specific embodiment.

A size 245 / 40R18 tire having the basic pattern shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and the drainage performance and steering stability performance of each test 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 ratios of the shoulder region and the crown region and the groove volume are the same.
Each comparative example and each embodiment satisfies the groove width W1 of the crown main groove> the groove width W2 of the first lateral groove> the groove width W3 of the second lateral groove> the groove width W4 of the third lateral groove.
The angle of the outer portion θ2: 21 ° (angle θ2: 15 ° of Example 7)
Distance A / width of shoulder area Ws: 25%

<Stable steering performance / drainage performance>
Free sample tires were installed on all wheels of passenger cars under the following conditions. Then, the test driver runs a test course on a dry asphalt road surface and a test course on a wet asphalt road surface with a water depth of 3 mm, and the running characteristics related to traction performance and turning performance at this time are evaluated by the test driver's sensuality. rice field. The result is displayed with a score of 100 in the conventional example. The larger the number, the better.
Vehicle: 4WD vehicle with a 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 tires of the examples have improved performance in a well-balanced manner as compared with the tires of the comparative examples. In addition, the test was conducted by changing the tire size, and the result was the same as this test result.

1 Tire 3 Crown main groove 4 Shoulder area 7 1st lateral groove 8 2nd lateral groove 8i Inner end 8e Outer end 11 Inner part 12 Outer part Te tread grounding end

Claims (6)

A tire provided with a pair of crown main grooves continuously extending 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 grooves, in the tread portion.
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 length in the tire axial direction on the tread tread.
Each of the first lateral grooves and the second lateral groove extends in an arc shape, respectively.
Each of the first lateral grooves has an inner portion extending outward in the tire axial direction at an inclination of an angle θ1 with respect to the tire axial direction from an inner end located outside the crown main groove with a distance A in the tire axial direction, and a tire shaft. Including an outer portion extending so as to straddle the tread ground contact end at an inclination of an angle θ2 smaller than the angle 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 outside the crown main groove in the tire axial direction and separated by a distance B smaller than the distance A, and the angle θ1 from the inner end with respect to the tire axial direction. At an angle θ3 larger than that, the tire is inclined in the same direction as the first lateral groove and extends outward in the tire axial direction, and the outer end is terminated without intersecting the tread ground contact end.
The groove edge of the first lateral groove and the groove edge of the second lateral groove are grooves having an arc direction that is continuously extended in either direction with respect to the tire circumferential direction and having a maximum length in the tire axial direction, respectively. Including the edge
The angle θ1 is relative to the tire axial direction of a virtual line connecting the inner end of the groove edge portion of the first lateral groove in the tire axial direction and the intermediate position of the length of the groove edge portion of the first lateral groove in a straight line. Is the angle
The angle θ2 is the tire axial direction of a virtual line connecting the outer end of the groove edge portion of the first lateral groove in the tire axial direction and the intermediate position of the length of the groove edge portion of the first lateral groove in a straight line. Is the angle to
The tire is characterized in that the angle θ3 is an angle with respect to the tire axial direction of a virtual line connecting the inner end and the outer end of the groove edge portion of the second lateral groove with a straight line. Each shoulder region is provided with a plurality of third lateral grooves having a length smaller in the tire axial direction on the tread tread than the second lateral groove.
Each of the third lateral grooves is provided between the first lateral grooves adjacent to each other in the tire circumferential direction.
The tire according to claim 1, wherein each of the third lateral grooves extends so as to straddle the tread ground contact end from the inner end located outside the second lateral groove in the tire axial direction with a distance C. The tire according to claim 2, wherein the distance C is 10% to 25% of the tread width. The third lateral groove is inclined in the same direction as the first lateral groove, and the angle θ4 with respect to the tire axial direction is smaller than the angle θ2 of the outer portion.
The third lateral groove extends in an arc shape.
The groove edge of the third lateral groove includes a groove edge portion in which the direction of the arc is continuously extended in either direction with respect to the tire circumferential direction and has the maximum length in the tire axial direction.
The tire according to claim 2 or 3, wherein the angle θ4 is an angle with respect to the tire axial direction of a virtual line connecting the inner end and the outer end of the groove edge portion of the third lateral groove with a straight line. 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 is provided, which is divided between the crown main grooves.
The tire according to any one of claims 1 to 5, wherein the width of the crown land portion in the tire axial direction is 10% to 20% of the tread width.

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