FI125663B - air Tire - Google Patents

Description

pneumatic tire

Engineering

The present invention relates to a pneumatic tire, and in particular an pneumatic tire, which is formed to have better performance on wet road surfaces and snow and to provide better wear resistance.

The invention relates to an air tire according to the preamble of claim 1.

Prior art

Conventionally, tires with a plurality of lamella pieces separating a plurality of circumferential main grooves and a plurality of diagonal grooves in the tire width are known to have excellent snow performance and excellent dewatering performance. The use of tread-responsive tire-rolling is known to be a technology in such pneumatic tires that further improves the drainage capability of the tire. For example, patent document 1 describes the preparation of a ring pattern as a direction-sensitive pattern comprising a plurality of circumferential main grooves, a plurality of circumferential and inclined foot grooves, and lamellae.

On the other hand, since the wear characteristics vary depending on the wheel attachment and whether the tire is mounted on the front or rear wheels of the vehicle, the tire life can be increased by changing the tire location regularly so that all tires wear uniformly. However, in the case of tires with a directionally sensitive tire pattern that determines the direction of rotation of the tire, the tires can only be changed due to the fixed direction of rotation of the tires between the front and rear wheels mounted on the same side of the vehicle. Therefore, for tires with heavy load on the shoulder, such as light truck tires, due to the directional sensitivity of the tire described above, uneven wear on the shoulder cannot be prevented by changing only the front and rear wheels on the same side. In addition, while increasing the stiffness of the lamella piece by reducing the number of lateral grooves effectively prevents uneven wear, the problem remains in these cases that performance on the snow is impaired. Therefore, it has been difficult to strike a balance between performance on wet and snowy road surfaces and uneven wear.

Prior Art Documents Patent Document

Patent Document 1: Japanese Unexamined Patent Application No. 2007-1 611 14A

Summary of the Invention The problem that the invention solves

It is an object of the present invention to solve the problems described above by providing an pneumatic tire having a direction-sensitive tread pattern that improves both tire performance on wet road surfaces and snow and tire wear resistance.

Solutions to the problem

In order to accomplish the above object, the pneumatic tire of the present invention includes a central groove on the tread which runs parallel to the circumference of the tire and centered on the tire; at least two outer end grooves disposed in the tire width direction on either side of the center groove and extending in the circumferential direction of the tire; and a plurality of lateral grooves extending in the tire width direction between the central groove and the outer grooves and connecting the central groove and the outer grooves. The plurality of lamella pieces in the central section distinguish between the central groove, the outer grooves and the lateral grooves. A foot groove not communicating with the outermost outer head groove extending in the tire in its width direction is located in the shoulder portions of the tire disposed outwardly from the outermost outer head groove in the tire width direction; and ribs are formed on the shoulders. The lateral grooves on both sides of the central tire groove are inclined on opposite sides of the tire centerline. The center-side tilt angle Θ1, which is the angle formed in the circumferential direction of the tire to the point where the lateral grooves are connected to the center groove, is a sharp angle. The lateral grooves on both sides of the central tire groove are arranged so that they move in the circumferential direction of the tire such that the circumferential component of the tire, which is a circumferential projection of the lateral grooves, extends along the entire circumference of the tire. The lamella pieces and ribs have lamellae that form a direction-sensitive pattern.

Effect of the Invention

The invention relates to an pneumatic tire according to the characterizing part of claim 1.

According to the present invention, the lateral grooves on both sides of the center groove are inclined on opposite sides of the tire center groove and the center side tilt angle Θ1, which is the angle formed with the circumferential direction of the tire where the side grooves are connected to the center groove. Therefore, performance on wet roads and snow can be improved. In particular, the lateral grooves on both sides of the central tire groove are arranged so that they move in the circumferential direction of the tire such that the circumferential component of the tire, which is a circumferential projection of the lateral grooves, extends over the entire circumference of the tire. Therefore, the performance of a rotating tire on wet road stacks can be improved. In addition, the prevention of uneven wear can be improved by the presence of foot grooves in the shoulder that are not in contact with the outer outer main groove. Thus, the directional sensitivity of a pneumatic tire can improve both tire performance on wet road surfaces and snow, and tire wear resistance.

In the present invention, a raised narrow bottom groove portion having a groove depth and width smaller than corresponding dimensions of the other side groove portions is formed at the point where the lateral grooves are connected to the central groove. The groove depth of the raised narrow base groove is preferably 40-60% of the groove depth of the middle groove, and the groove width of the raised narrow base groove is preferably 30-50% of the maximum groove width of the lateral grooves. In this way, the stiffness of the lamella piece in the central part can be increased while at the same time guaranteeing good dewatering ability, and the uneven wear of the central part can be improved.

In the present invention, the center-side tilt angle Θ1 is made relatively smaller than the shoulder-side tilt angle Θ2, which is the angle formed in the circumferential direction of the ring to the point where the lateral grooves are connected to the outer ends. Thus, the drainage capacity of the lateral grooves is improved, as a result of which the reduced drainage capacity can be increased by introducing an elevated thin bottom groove portion. Further, the difference between the center-side tilt angle Θ1 and the shoulder-side tilt angle ul2 is preferably set at 5-30 degrees. Thus, the drainage capacity of the lateral grooves can be further improved. The center angle of the Li Saxon has an inclination angle Θ1 of preferably 40-65 °, and this angle value can improve both dewatering capacity and wear resistance.

In the present invention, the surface of the lamella block has fine grooves, and the groove spacing of these fine grooves is preferably 2.5-5 mm, depth 0.1-0.8 mm and width 0.1-0.8 mm. Thus, performance on wet road stacks and snow can be improved.

the tire width direction in the present invention, the ribs of the inner side edge portion is preferably continuously or at times, a plurality of tapered portions having such a shape that the chamfer amount varies periodically in the circumferential direction of the tire. This can increase the edge delimiter performance on wet road stacks.

In the present invention, the inclination angle Θ3 of the foot grooves with respect to the circumferential direction of the ring is preferably 90 ± 10 °. This ensures rigidity of the rib and increases wear resistance.

In the present invention, the JIS A hardness of the tread rubber at -10 ° C is preferably 55-70. Thus, the stiffness of the lamella pieces and the placement of the ribs in a suitable area allow for uneven wear resistance and improved snow performance.

In addition, each of these pneumatic tires is suitable for use as a light truck tire operating at a pressure of at least 350 kPa.

Brief Description of the Drawings

Fig. 1 is a diagram of a front view of the tread of a pneumatic tire according to an embodiment of the present invention.

Figure 2 is an enlarged front view showing a section of lamella adjacent the central groove of the pneumatic tire of Figure 1.

Fig. 3 is an enlarged explanatory drawing showing the central portion of the pneumatic tire of Fig. 1.

Figure 4 is an enlarged plan view showing a portion of a rib portion of the pneumatic tire of Figure 1.

Figure 5 is a side view of a section of lamella adjacent the central groove of the pneumatic tire of Figure 2.

Fig. 6 is an enlarged cross-sectional view showing fine grooves in a slice piece adjacent the central groove of the pneumatic tire of Fig. 2.

Figure 7 is a side view of the rib of the shoulder portion of the pneumatic tire of Figure 4.

Detailed explanation

In the pneumatic tire of the present invention, shown in Fig. 1, the tread T has one center groove 1 extending circumferentially with the tire centerline E, and two outer grooves 2 disposed in the tire width direction on either side of the center groove 1. A plurality of lateral grooves 3 are disposed locally in the circumferential direction of the ring between the central head groove 1 and the outer head grooves 2 so as to connect the central head groove 1 and the outer head grooves 2. The central head groove 1 is rectangular and has a viewable portion. In addition, the terminating foot grooves 4 extending from the shoulder edge towards the outer main groove 2 without being associated with the outer main groove 2 are disposed locally in circumferential direction of the ring on the shoulder parts S located outwardly of the outer outer groove 2. In this way, two rows of lamella pieces consisting of a plurality of lamellae pieces 5 are formed apart from one another in a central part C which is inwardly viewed from the outer main grooves 2. On the other hand, the ribs S are formed with ribs 6 having a plurality of terminating foot grooves 4; these shoulder portions S are located outwardly from the outer main skirt 2. On the surface of the lamella pieces 5 and ribs 6 there are a plurality of lamellae 7 which extend in the width direction of the ring, each of which is zigzag-shaped viewed from above.

The number of main grooves on the tread T in the circumferential direction of the ring is not limited to the three main grooves shown in Figure 1, more specifically to the single central main groove 1 and the two outer main grooves 2. Furthermore, the shapes 7 are not particularly limited in shape.

The surface pattern of the pneumatic tire of the present invention is formed as a direction-sensitive pattern by tilting the lateral grooves 3 disposed on either side of the central main groove 1 in the width direction of the tire towards the opposite side relative to the center line E of the tire. In such a directionally sensitive pattern having end leg grooves 4 and lateral grooves 3 inclined with respect to the circumferential direction of the tire, there is a circumferential component of the tire and a component extending in the tire width direction. Therefore, when the tire hits the snow, both traction and braking action in the front and rear directions of the vehicle and sideways anti-skidding action can be achieved. This can, however, change the type of the sensitive direction in Fig each other only of the same side of the front and rear tires. Therefore, in cases where a row of lamella pieces is disposed on the shoulder portions S, the front and rear wear of the lamella piece increases and it is difficult to prevent uneven wear. However, as shown in Fig. 1, the terminating foot grooves 4 are in the shoulder parts S and the terminating foot grooves 4 are not connected to the outer main grooves 2, and in addition, ribs 6 are formed on the shoulder parts S, which consist of a continuous contact surface. Therefore, the variation of the stiffness of the shoulder portions S in the circumferential direction is reduced and the uneven wear of the shoulder portions S can be prevented.

As shown in Fig. 2, the angle formed with respect to the circumferential direction of the ring at the point where the lateral grooves 3 are connected to the center end groove 1 is the center-side inclination angle Θ1. The center side tilt angle Θ1 is formed as a sharp angle. The center-side tilt angle Θ1 is preferably formed at an angle of 40-65 degrees. Here, the inclination angle Θ1 of the center side is the angle formed by the center line of the groove width of the side grooves 3 with respect to the circumferential direction of the ring. In addition to the effects of tilting the lateral groove 3 by forming a center angle of tilt Θ1, the dewatering ability and the durability of uneven wear can be improved. If the tilt angle Θ1 of the center side exceeds 65 °, the front and rear sections of the section slab will wear out easily, and the uneven wear will be insufficient because of the sharp edges of the sections of the outer main groove 2. On the other hand, if the center-tilt angle Θ1 is less than 40 °, the dewatering capacity is not sufficiently improved.

Further, the circumferential grooves 3 on both sides of the central groove 1 of the ring are arranged so that they move in the circumferential direction of the ring such that the circumferential component of the ring, which is a circumferential projection of the lateral grooves 3, extends. More specifically, as shown in Fig. 3, when the lateral grooves 3 on both sides of the central groove 1 of the ring are arranged so that they move in the circumferential direction of the ring, the circumferential component 3 'of the lateral grooves 3 moves in the circumferential direction. Therefore, the circumferential component of the side grooves 3 of one of the lamella pieces is located at the part where the circumferential component 3 'of the side grooves 3 of the second lamella piece ends. Thus, the circumferential components 3 'on either side of the tire central groove 1 are complementary to each other and are arranged so that they continuously cover the entire circumference of the tire. Since such a circumferential component 3 'of the tire is arranged to extend over the entire circumference of the tire, the performance of the tire on wet road surfaces as the tire rotates can be improved. The displacement space of the lateral grooves 3 is not necessarily limited, but each lateral groove 3 preferably displaces 1/2 of the grooves in the circumferential direction of the ring on both sides of the central main groove 1.

As shown in Fig. 4, the end leg grooves 4 in the shoulder parts S are in the width direction of the ring. Their inclination angle Θ3 with respect to the circumference of the ring is preferably 90 ± 10 °. In addition, the end leg grooves 4 on the shoulder parts S on both sides of the tire width are preferably inclined in opposite directions with respect to the tire centerline E. Thus, making the end leg grooves 4 tilt parallel to the tire width can ensure rib stiffness and improve wear resistance. If the heeling angle Θ3 is not within 90 ± 10 °, the abrasion resistance is insufficient. Here, the heeling angle Θ3 is the angle formed by the center line of the groove width of the terminating foot grooves 4 relative to the circumference of the ring.

By forming lamellae 7 on the surface of lamellae 5 and ribs 6, performance on wet road surfaces can be improved. The lamellas 7 preferably extend to the edges of the lamella pieces 5 or ribs 6. By extending the fins 7 to the edges of the fins 5 and ribs 6, the edges of the fins can improve performance on wet road surfaces. Preferably, the slats 7 of both lamella pieces 5 and ribs 6 have an inclination angle Θ4 with respect to the circumferential direction of the ring of 90 ± 10 °. By adjusting the tilt angle Θ4 of the lamellas 7 to this size, the braking performance on a wet road surface can be improved. By extending the ribs 7 in the ribs 6 in the tire width direction, it is particularly possible to increase the braking properties of the wet conditions, which are impaired because the terminating foot grooves 4 are not in contact with the outer head grooves 2.

As shown in Figures 2 and 5, the raised thin bottom groove portion 3a is formed at a position where the lateral grooves 3 are connected to the central main groove 1. The raised thin bottom groove portion 3a is a portion having a smaller groove depth and width than other portions of the lateral grooves 3. The length L3a of the raised narrow base groove portion 3a is set to 20-40% of the length L3 of the lateral grooves 3. Further, the groove width W3a of the raised narrow base groove 3a is set to 30-50% of the maximum groove width W3 of the lateral grooves 3, and the groove depth D3a of the raised narrow base groove 3a is set to 40-60% of the groove D1 of the middle groove 1. Here, the length L3 of the side grooves 3 is the length measured from the side edge opposite the central groove 1 of the side grooves 3 to the side edge of the outer grooves 2. Further, the length L3a of the raised narrow bottom groove portion 3a is the length of the side edge opposite the central groove 1 of the lateral grooves 3. Both of these lengths are measured along the centerline of the groove width.

By providing an elevated thin bottom groove portion 3a at a position where the lateral grooves 3 engage with the central groove 1, and reducing the groove width W3a and groove depth D3a of the lateral grooves 3 can increase the stiffness of the slab adjacent the raised narrow bottom groove 3a and prevent uneven wear. Further, raising the bottom of the lateral grooves 3 is accompanied by a narrowing of its width, and therefore, by increasing the rigidity of the lamella piece, a state in which the lateral grooves 3 engage with the central groove 1 can be guaranteed.

By adjusting the length L3a of the raised narrow bottom groove portion 3a to 20-40% of the length L3 of the lateral grooves 3 here, uneven wear can be prevented without reducing the steering stability on the snow. If the length L3a of the raised narrow bottom groove portion 3a is less than 20% of the length L3 of the side grooves 3, the prevention of uneven wear cannot be sufficiently improved. On the other hand, if the length L3a of the raised narrow bottom groove portion 3a exceeds 40% of the length L3 of the lateral grooves 3, the steering stability on the snow is not sufficiently improved.

By setting the groove depth D3a of the side grooves 3 in the raised narrow bottom groove portion 3a to 40-60% of the groove depth D1 of the central groove 1, uneven wear can be prevented without reducing steering stability on the snow. If the ratio of the groove depth D3a of the raised narrow bottom groove portion 3a to the groove depth D1 of the middle groove 1 is improved, the durability of uneven wear can be improved, but the drainage and snow removal capacity are not sufficiently improved. On the other hand, if this ratio exceeds 60%, the stiffness difference cannot be sufficiently reduced and the durability of uneven wear does not improve sufficiently.

By setting the groove width W3a of the lateral grooves 3 in the raised narrow bottom groove portion 3a to 30-50% of the maximum groove width W3 of the lateral grooves 3, uneven wear can be prevented without reducing steering stability on the snow. If the ratio of the groove width W3a of the raised narrow base groove 3a to the maximum groove width W3 of the lateral grooves 3 is less than 30%, uneven wear resistance can be improved, but dewatering and snow removal capacity are not sufficiently improved. If, on the other hand, this ratio exceeds 50%, the stiffness of the slab piece will not vary significantly and the durability of uneven wear will not be sufficiently improved.

As shown in Figure 2, the angle formed with respect to the circumferential direction of the ring at the point where the lateral grooves 3 engage the outer end groove 2 is the shoulder tilt angle Θ2. Preferably, the center-side tilt angle Θ1 is smaller than the shoulder-side tilt angle Θ2. Thus, the drainage capacity of the lateral grooves 3 can be improved. Thus, even when the ring has a raised narrow bottom groove portion 3a, whereby the groove depth and groove width of the lateral grooves 3 is reduced, the dewatering capability can be maintained to improve the uneven wear resistance as described above. The difference between the center-side tilt angle Θ1 and the shoulder-side tilt angle Θ2 is preferably set at 5-30 degrees. If this difference is less than 5 °, the drainage capacity will not improve. On the other hand, if the difference is greater than 30 °, the stiffness of the lamella piece will be reduced and it will be difficult to prevent uneven wear. Here, the shoulder tilt angle Θ2 is the angle formed by the center line of the groove width of the side grooves 3 relative to the circumference of the ring.

Preferably, a plurality of fine grooves 8 are disposed parallel to the road surface of each section 5 of the pneumatic tires of the present invention, which incline in the circumferential direction of the tire. The fine grooves 8 are fine grooves that are lower than the lamellae 7. The rotation properties of new tires on icy and snowy surfaces are not always sufficient because the true properties of the tread rubber cannot be revealed. However, if fine grooves 8 as described above are formed, these fine grooves 8 will effectively remove the water film formed between the tread and the icy or snowy road surface. In this way, performance on ice and snow at the start of use can be improved. Further, if the fine grooves 8 are on the road surface of the lamella pieces 5, the peeling of the tread increases due to the existence of the fine grooves 8. Thus, in practice, the time required for the actual properties of the tread rubber to occur can be reduced.

As shown in Figure 6, the grooves 8 of the fine grooves 8 preferably have a groove width of 0.1-0.8 mm and a groove depth d of preferably 0.1-0.8 mm. If the grooves 8 of the fine grooves 8 have a groove width less than 0.1 mm, the improvement of the water-film removal effect and snow removal ability is insufficient. On the other hand, if the groove width w exceeds 0.8 mm, the stiffness of the slab piece is reduced. In addition, if the groove depth d is less than 0.1 mm, the improvement in water-film removal and snow removal ability is insufficient. On the other hand, if the groove depth d exceeds 0.8 mm, the stiffness of the lamella block is reduced.

Preferably, the grooves 8 of the fine grooves 8 have a groove p of 2.5 to 5.0 mm. By setting the slot spacing of the fine grooves 8 to this interval, it is possible to reliably prevent the fine grooves 8 from piling up when the tire is subjected to a heavy load. Therefore, the performance of a tire on snow and ice can be improved even when subjected to heavy loads. If the grooves 8 of the fine grooves 8 are less than 2.5 mm, the performance on snow and ice under heavy loads will not be sufficiently improved. On the other hand, if the slot spacing exceeds 5.0 mm, the effectiveness of the water film removal effect is insufficient.

The inclination angle α of the fine grooves 8 with respect to the circumferential direction of the ring is preferably set at 40-60 degrees. By setting the inclination angle α of the fine grooves 8 between this distance, the braking properties can be improved and the sideways slip of the tire prevented. If the inclination angle α of the fine grooves 8 is less than 40 °, the edges of the fine grooves 8 cannot easily promote braking properties. On the other hand, if the inclination angle α is greater than 60 °, the edges of the fine grooves 8 are difficult to promote to prevent lateral skidding.

4 and 7 seen from the figures, the fins 6 of the tire inner side edge portion is located in the tire width direction continuously or at times the number of chamfered portions 9 having such a shape that the chamfer amount in fluctuations Lee intermittently in the tire circumferential direction. As used herein, the term "chamfer amount" means that the ribs 6 vary in size sideways and in depth in the circumferential direction of the tire. As shown in Fig. 4, the most chamfered portion in the depth and lateral direction is the most chamfered portion 9a with the largest chamfer and the portion chamfered in the least depth and width direction is the least chamfered portion 9b.

When the shape of the chamfered portions 9 is such that the amount of chamfer varies periodically in the circumferential direction of the tire, the edge length and the peripheral component acting in the braking and driving directions can be increased. Therefore, performance on snow can be considered better. If the chamfered portions 9 are formed so that the amount of chamfer is uniform and does not vary over the entire circumference, the edge length cannot be increased, which makes it impossible to improve snow performance.

The depth D9a and / or the width W9a of the most bevelled portion 9a of the bevelled portions 9 is preferably 30-60% of the maximum depth D2 of the outer ends 2. Within this range, the edge length can be increased sufficiently and snow grip improved. The depth D9a and / or the width W9a of the most bevelled portion 9a is preferably 40-50% of the maximum depth D2 of the outer ends 2. If the depth D9a and / or width W9a of the most chamfered portion 9a is less than 30% of the maximum depth D2 of the outer fins 2, the force between the terminating leg grooves 4 and the outer fins 2 cannot be attenuated, resulting in insufficient improvement in uneven wear. In addition, if the depth D9a and / or width W9a of the most bevelled portion 9a exceeds 60% of the maximum depth D2 of the outer ends 2, the steering stability on the snow cannot be sufficiently improved due to excessive weakening of the stiffness of the lamella block.

As shown in Fig. 4, the most bevelled portion 9a of the beveled portions 9 is preferably disposed within an area extending along the extended line of the terminating leg grooves 4. The strain is more concentrated on the extended line region of the terminating foot grooves 4 than on the other areas of the ribs 6. Therefore, decentralization of concentrated stress is promoted by reducing stiffness so that the most beveled portion 9a is located in this area, which can prevent uneven wear. If the most beveled portion 9a is located outside the extended line region of the terminating foot grooves 4, the stress is concentrated in the area of the extended line of the easily terminating foot grooves 4, resulting in an insufficient improvement in uneven wear.

Preferably, one bevelled portion 9 is formed per 0.5 to 2.0 grooves between the end leg grooves 4 Here, the "end leg groove 4 groove distance" refers to the circumferential spacing of the ring of the adjacent end leg 4. If the chamfered portions 9 are formed in such a proportion that each is less than 0.5 slot apart, the number of chamfered portions is too large, resulting in excessively weakening of the stiffness of the lamella piece and insufficient improvement in the prevention of uneven wear. On the other hand, if the chamfered portions 9 are formed in a ratio such that the distance of each to each other exceeds 2.0 groove spacing, areas of high and low stiffness with a large difference in stiffness are formed at the edge portion of the ribs 6. As a result, uneven wear is not sufficiently improved.

The hardness of the tread rubber according to the Japanese Industrial Standard (JIS) A at -10 ° C is preferably 55-70. In this case, both abrasion resistance and snow performance can be improved. If the hardness is less than 55, the uneven wear resistance will not be sufficiently improved due to deterioration of the lamella pieces and rib stiffness. If the hardness exceeds 70, the performance on the snow will not improve sufficiently. Here is the “JIS A

Hardness ”refers to the hardness measured at 10 ° C according to JIS K6253 using a Type A hardness gauge.

The pneumatic tire of the present invention is preferably used as a light truck tire operated at a pressure of at least 350 kPa.

eXAMPLES

Eleven different types of pneumatic tires were manufactured with a common 195 / 75R16C 107 / 105R tire size for conventional Example 1, Comparative Examples 1 and 2, and Working Examples 1-8. The specifications of each tire varied as shown in Tables 1 and 2.

These eleven types of tires were mounted on 16x51 / 2J wheels. The front tires were pumped at 280 kPa and the rear tires at 450 kPa and fitted to a European-made van with a maximum load of 3.5 tonnes. Subsequently, the following methods were used to measure the durability of uneven wear, dewatering, steering stability on wet road surfaces, and steering stability on snow.

Duration of uneven wear

Tires were visually evaluated each time the vehicle described above was driven on a 4,000 km paved road with tires. The results of the evaluation were expressed as a ratio, which was 100 in the traditional example 1. Lower values of the ratio are indicative of better durability of uneven wear.

Drainage capacity:

Each tire was used in the vehicle described above on a test track having a water height of 10 ± 1 mm and a turning radius of 100 m. The running speed of the test vehicle at which the tire was subjected to maximum lateral acceleration was measured. The results of the evaluation were expressed as a ratio which was 100 in the case of the traditional Example 1. Higher ratio values are indicative of better dewatering capacity.

Steering stability on wet roads

A sense of steering stability for evaluation at 0-100 km / h on a wet road test track using the vehicle described above. The results of the evaluation were expressed as a ratio, which in the case of the traditional example 1 was 100. Higher ratio values are indicative of better steering stability on a wet road surface.

Steering stability on snow:

Feeling of steering stability for evaluation at 0-100 km / h on a snowy road surface on a test track using the vehicle described above. The results of the evaluation were expressed as a ratio, which was 100 in the case of the traditional Example 1. Higher ratio values are indicative of better steering stability on snow.

As shown in the results in Tables 1 and 2, all of the pneumatic tires of Working Examples 1-8 were able to improve steering stability on snow, steering stability on wet road surfaces, dewatering ability, and uneven wear resistance compared to conventional Example 1.

On the other hand, as can be seen from the results of Table 1, since the shoulder portion of the pneumatic tire of Comparative Example 1 is in the form of a lamella, uneven wear cannot be improved. In addition, in the case of the pneumatic tire of Comparative Example 2, the lateral grooves are not connected to the central main groove, which results in reduced steering stability on wet road surfaces and dewatering capacity.

Claims (9)

An air tire comprising on a wear surface (T) a middle head groove (1) running parallel to the tire's periphery on the tire's center line (E); at least two outer head grooves (2) located on both sides of the middle head groove (1) in the width direction of the tire and running parallel to the circumference of the tire; and a plurality of side grooves (3) running in the tire width direction between the middle head groove (1) and outer head grooves (2) and joining together the middle head groove (1) and outer head grooves (2), the middle portion (C) of the tire wear surface (C) having ), which distinguish from the middle head groove, outer head groove (2) and side groove (3); a footprint (4) running in the tire's width direction is in the tire's shoulder portions (S) located in the tire's width direction outward from the outermost outer head grooves (2); wherein the side grooves (3) on both sides of the middle head groove (1) in the width direction of the tire are inclined to opposite sides relative to the center line of the tire (E); the intermediate inclination angle Θ1, which is in the direction of the circumference of the tire, an angle formed at the point where the side grooves (3) adhere to the middle head groove (1), is an acute angle; and the side grooves (3) on both sides of the tire's middle main groove (1) are arranged in the width direction of the tire so that they move in the direction of the tire's circumference so that a component parallel to the tire's periphery (3 ') is a projection parallel to the side tracks (3). tire periphery, is on the length of the tire's entire periphery; and the lamella pieces (5) and ribs (6) have lamellae (7) forming a directionally sensitive pattern, characterized in that the foot groove (4) is not in contact with the outermost outer head groove (2); the ribs (6) are formed in the shoulder portions (S); and the angle of inclination of the intermediate side id1 is made in proportion less than the angle of inclination of the shoulder side Θ2, which is an angle formed in the direction of the circumference of the tire at the point where the side grooves (3) connect to the outer head grooves (2). Air tire according to claim 1, characterized in that the raised narrow bottom groove part (3a), whose groove depth and width is less than the corresponding dimensions for the parts of the other side grooves (3), has been formed at a place where the side grooves (3) connect to the middle main track (1); the groove depth (D3a) of the raised narrow bottom groove part (3a) is 40-60% of the middle depth (D1) groove depth (D1); and the groove width (W3a) of the raised narrow bottom groove part (3a) is 30-50% of the maximum groove width (W3) of the side grooves (3). Air tire according to claim 1, characterized in that the difference between the inclination angle of the shoulder side, 02, and the inclination angle of the intermediate side, 01, is 5-30 °. Air tire according to any one of claims 1-3, characterized in that the inclination angle 01 of the intermediate side is 40-65 °. Air tire according to any one of claims 1-4, characterized in that there are fine grooves (8) on the surface of the slab (5) and the gap (p) of these fine grooves (8) is 2.5-5 mm, depth (d) 0. , 1-0.8 mm and width (w) 0.1-0.8 mm. An air tire according to any one of claims 1-5, characterized in that the tire portion of the inside of the tire ribs (6) is positioned continuously in the width direction of the tire or, in some cases, several beveled parts (9), which have such a shape that the number of their taper varies periodically. the direction of the tire's periphery. Air tire according to any one of claims 1-6, characterized in that the inclination angle 03 of the foot groove (4) in relation to the direction of tire circumference is 90 ± 10 °. Air tire according to any of claims 1-7, characterized in that the JIS A hardness of the rubber forming the wear surface (T) at 10 ° C temperature is 55-70. Air tire according to any one of claims 1-8, characterized in that the air tire is a tire used in light trucks and used at an air pressure of at least 350 kPa.