JP6776827B2 - 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. 4, 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 at an inclination and an inclined groove b2 extending at an inclination 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 brewing. 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 ground 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, second lateral grooves, and third lateral grooves are provided as the lateral grooves, and each of the first lateral grooves is outward from the crown main groove in the tire axial direction. Straddle the inner part extending outward in the tire axial direction with an inclination of θ1 with respect to the tire axial direction from the inner end located at a distance, and the tread ground contact end with an inclination of an angle θ2 (<θ1) with respect to the tire axial direction. Each of the second lateral grooves is provided between the first lateral grooves adjacent to the tire circumferential direction, and each of the second lateral grooves is separated from the crown main groove to the outside in the tire axial direction. It has an inner end located so as to be inclined in the same direction as the first lateral groove and extends outward in the tire axial direction from the inner end, and the outer end is terminated without intersecting the tread ground contact end. The three lateral grooves are provided between the first lateral grooves adjacent to the tire circumferential direction, and each of the third lateral grooves has a tread ground contact end from an inner end located apart from the second lateral groove on the outer side in the tire axial direction. The third lateral groove extends so as to straddle, and is characterized in that the length in the tire axial direction on the tread tread is smaller than that of the second lateral groove.

In the tire according to the present invention, it is desirable that the angle θ4 of the third lateral groove with respect to the tire axial direction is smaller than the angle θ3 of the second lateral groove with respect to the tire axial direction.

In the tire according to the present invention, the distance B between the inner end of the second lateral groove and the crown main groove in the tire axial direction is the distance between the inner end of the first lateral groove and the crown main groove in the tire axial direction. It is desirable that it is smaller than A.

In the tire according to the present invention, the groove edge of the first lateral groove, the groove edge of the second lateral groove, and the groove edge of the third lateral groove are inclined at different angles with respect to the tire axial direction. It is desirable that the angles on the tread tread side formed by the adjacent groove edges, including the portions, are all 90 ° or more in a plan view.

In the tire according to the present invention, it is desirable that the angle between the inner portion and the outer portion is 160 to 170 °.

The tire of the present invention is a tire in which a pair of crown main grooves extending continuously in the tire circumferential direction and a plurality of lateral grooves are provided in both shoulder regions, which are regions on both outer sides of the crown main grooves, in the tread portion. .. 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.

A plurality of lateral grooves in each shoulder region are provided, including a first lateral groove, a second lateral groove, and a third lateral groove. Each first lateral groove has 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 separated from the crown main groove outward in the tire axial direction, and relative to the tire axial direction. 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 corner 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 apart from the crown main groove on the outer side in the tire axial direction, is inclined in the same direction as the first lateral groove from the inner end, extends outward in the tire axial direction, and has an outer end. Terminates without crossing the tread ground end. Such a second lateral groove also does not form an acute-angled corner portion with the crown main groove. Therefore, the steering stability performance is maintained high. Further, since the water film between the tread tread and the road surface can be removed in the groove, drainage performance can be ensured.

Each third lateral groove is provided between the first lateral grooves adjacent to each other in the tire circumferential direction. Each third lateral groove extends so as to straddle the tread ground contact end from the inner end located apart from the second lateral groove on the outer side in the tire axial direction. Such a third lateral groove forms a land portion with the second lateral groove and suppresses a decrease in rigidity of the land portion, so that the steering stability performance is maintained high. Further, the third lateral groove can smoothly drain the water film between the tread tread and the road surface from the tread ground contact end, thus improving the drainage performance.

The third lateral groove is formed to have a smaller length in the tire axial direction on the tread tread than the second lateral groove. In this way, since the third lateral groove having a small length in the tire axial direction is arranged on the tread ground contact end side with respect to the second lateral groove, the shoulder on the tread ground contact end side on which a larger lateral force acts during turning. The rigidity of the land area of the area is maintained high.

Therefore, the tire of the present invention improves drainage performance and steering stability performance 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 is used for various tires such as various 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 this 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 a mode, 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. The distance between Tes in the tire axial direction. The "normal state" is a state in which the tire 1 is rim-assembled on a normal rim (not shown) and is filled with normal internal pressure without load. 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. The first lateral groove 7, the second lateral groove 8, and the third lateral groove 9 of the present embodiment each have a center on one side (lower side in the figure) in the tire circumferential direction, and the other side in the tire circumferential direction (in the figure). It is formed in an arc shape that is convex on the upper side). As a result, the rigidity of the land portion of the shoulder region 4 is maintained to be large. 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 outward in the tire axial direction, and an outer end located outside the tread ground contact end Te in the tire axial direction. 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, during tire vulcanization, the formation of rubber pools is suppressed, and the steering stability performance is maintained high.

When the inner end 7i is largely separated from the crown main groove 3, the length of the first lateral groove 7 becomes small, and the drainage performance may deteriorate. 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 having an inner end 7i and an outer portion 12 having 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 of the land portion on the inner side in 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. is there.

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 °. If 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 actual length of the first lateral groove 7 and the groove volume may be reduced, resulting in deterioration of drainage performance. is there. When the angle θ1 of the inner portion 11 exceeds 45 °, or the angle θ2 of the outer portion 12 exceeds 40 °, the lateral force during turning is used to smoothly flow the water in the first lateral groove 7 to the tread ground contact end. It may not be possible to discharge from Te.

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 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 in the same direction as the first lateral groove 7 from the inner end 8i and extends outward in the tire axial direction. As a result, the rigidity step in the tire circumferential direction in the land portion is maintained small 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, during tire vulcanization, the formation of rubber pools is suppressed, and the steering stability performance is maintained high.

It is desirable that 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 smaller than the distance A of the first lateral groove 7. 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, 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 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 ground 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 defined 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.

It is desirable that the angle θ3 of the second lateral groove 8 is 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 ground 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, the rigidity of the land portion around the second lateral groove 8 in the tire circumferential direction is largely 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 drain the water film between the tread tread and the road surface, and water is effective. It cannot be collected in the ditch, and the drainage performance may deteriorate. 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 smaller, and the water film on the tread tread cannot be collected in the groove, resulting in poor drainage performance. There is a risk of

As shown in FIG. 1, in order to effectively exert the above-mentioned action, the length L2 of the second lateral groove 8 on the tread tread in the tire axial direction is, for example, more than the length L1 of the first lateral groove 7. Is also desirable to be small, and further, it is desirable that the width Ws of the shoulder region 4 in the tire axial direction is 40% to 58%.

The second lateral groove 8 has an overlapping portion 8a that overlaps with any one of the first lateral grooves 7 adjacent 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. That is, the third lateral grooves 9 of the present embodiment are alternately provided with the first lateral grooves 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. 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 is located outside the tread ground contact end Te in the tire axial direction in the present embodiment. 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, thus improving the drainage performance.

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 length L3 of the third lateral groove 9 on the tread tread in the tire axial direction is formed to be smaller than the length L2 of the second lateral groove 8. That is, the third lateral groove 9 having a small length in the tire axial direction is arranged closer to the tread ground contact end Te side than the second lateral groove 8. Therefore, during turning, the rigidity of the land portion of the shoulder region 4 on the tread ground contact end Te side on which a larger lateral force acts is maintained high, so that the steering stability performance is improved. From this point of view, it is desirable that the length L3 of the third lateral groove 9 is 20% to 30% of the length L2 of the second lateral groove 8.

It is desirable that 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 larger than the distance B. As a result, the rigidity of the land portion on the tread ground contact end Te side on which a large lateral force acts during turning can be maintained high, so that the steering stability performance is improved. If the distance C is excessively large, the length L3 of the third lateral groove 9 in the tire axial direction on the tread tread or the length L2 of the second lateral groove 8 in the tire axial direction becomes small, and the drainage performance may deteriorate. There is. Therefore, the distance C is preferably 1.2 to 1.8 times the distance B.

In order to effectively exert the above-mentioned action, the distance C is preferably larger than the length L3 of the third lateral groove 9 in the tire axial direction, and further, 1.1 to 1.1 of the length L3 of the third lateral groove 9. 1.7 times is desirable.

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 are arranged close to each other, so that the land between the first lateral groove 7 and the third lateral groove 9 is provided. There is a risk that the rigidity of the part in the tire circumferential direction will decrease.

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 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 specified at the intermediate position E3 and the outer end E2.

In the present embodiment, the length L3 (shown in FIG. 1) of the third lateral groove 9 in the tire axial direction on the tread tread 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 defined 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 θ3 of the second lateral groove 8 with respect to the tire axial direction. As a result, the rigidity of the land portion on the tread ground contact end Te side in the tire circumferential direction is largely maintained, so that the steering stability performance is further improved. Further, the water in the third lateral groove 9 is smoothly discharged by utilizing the lateral force during turning. From this point of view, the angle θ4 of the third lateral groove 9 is preferably 25 degrees or less.

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 sides 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 of the first lateral groove 7 on the tread tread is larger than the groove width W3 of the second lateral groove 8 on the tread tread. 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 the lateral grooves 7 to 9 are specified by the maximum width in the direction perpendicular to the longitudinal direction.

In the present embodiment, the crown region 5 is formed as a plain rib without a groove or a sipe. 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.
Distance A / width of shoulder area 4 Ws: 20%
Length of third lateral groove L3 / width of shoulder area Ws: 12.5%
The angle α of the conventional example is the angle of the inclined groove b2.

<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 sensuality of the test driver. It was. 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 7i Inner end 8 2nd lateral groove 8e Outer end 9 3rd lateral groove 11 Inner part 12 Outer part Te tread grounding end

Claims (5)

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, in the tread portion.
Each shoulder region is provided with a plurality of first lateral grooves, second lateral grooves, and a plurality of third lateral grooves as the lateral grooves.
Each of the first lateral grooves is 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 apart from the crown main groove on the outer side in the tire axial direction, and in the tire axial direction. On the other hand, it includes an outer part extending so as to straddle the tread ground contact end at an inclination of an angle θ2 (<θ1).
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 apart from the crown main groove on the outer side in the tire axial direction, and is inclined from the inner end in the same direction as the first lateral groove and extends outward in the tire axial direction. And the outer end ends without crossing the tread grounding end,
Each of the third lateral grooves is provided between the first lateral grooves adjacent to each other in the tire circumferential direction.
Each of the third lateral grooves extends so as to straddle the tread ground contact end from the inner end located apart from the second lateral groove in the tire axial direction.
The third lateral groove is a tire characterized in that the length in the tire axial direction on the tread tread is smaller than that of the second lateral groove. The tire according to claim 1, wherein the angle θ4 of the third lateral groove with respect to the tire axial direction is smaller than the angle θ3 of the second lateral groove with respect to the tire axial direction. The distance B between the inner end of the second lateral groove and the crown main groove in the tire axial direction is smaller than the distance A between the inner end of the first lateral groove and the crown main groove in the tire axial direction. Or the tire according to 2. The groove edge of the first lateral groove, the groove edge of the second lateral groove, and the groove edge of the third lateral groove each include a plurality of groove edges inclined at different angles with respect to the tire axial direction.
The tire according to any one of claims 1 to 3, wherein the angles on the tread tread side formed by the adjacent groove edges are all 90 ° or more in a plan view. The tire according to any one of claims 1 to 4, wherein the angle between the inner portion and the outer portion is 160 to 170 °.

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