JPH0373481B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is characterized in that a tread is circumferentially divided into a plurality of land portions by a transverse main groove, and the transverse main groove as a whole has a chevron shape (inverted V It has a unique asymmetrical tread pattern in which the peaks of the chevrons are offset from the tire's equatorial plane in an offset herringbone arrangement. In addition, by appropriately distributing the negative ratio of the tread under the asymmetric tread pattern mentioned above, this greatly improves turning performance regardless of the dryness or wetness of the road surface. This article relates to a pneumatic tire that can be realized. In recent years, as vehicles have become faster, the performance requirements for pneumatic tires have been increasing, and in particular there is a high demand for improved drainage performance during rain, and in addition to improved turning performance on dry roads. (Prior Art) Of the above, in order to improve tire performance when turning, asymmetrical tread patterns regarding the negative ratio of the tread pattern are being studied, focusing on load transfer when a vehicle turns. In other words, in order to improve tire performance when turning, it is necessary to increase the rigidity of the land area on the outside of the tire, where more load is applied to the tire when mounted on the vehicle, and to increase the ground contact area. Therefore, in order to minimize the number of grooves located on the outside of the tire in terms of the tread pattern, axial lateral grooves that open on the side edges of the tread intersect with the main grooves arranged along the tread circumference of the tire. It is an asymmetrical tread pattern that is essentially rib-shaped by eliminating it on the outside, but while this improves turning performance on dry roads, the lack of groove arrangement on the outside of the tire worsens drainage performance. However, there are problems with stable running at high speeds on wet roads such as during rain, and it has not yet been put into practical use. Therefore, in consideration of drainage performance, tires with a tread pattern as shown in Figure 3, in which horizontal grooves in the axial direction are left on the outside of the tire mounted on the vehicle, are mainly used. Since it is not possible to increase the rigidity of the land portion on the outside, turning performance is difficult, and in addition, the drainage performance required during rainy weather is still insufficient, and there are still problems with stable running. (Problems to be Solved by the Invention) Not only is it convenient to avoid a decrease in the land stiffness on the outside of the tire when mounted on a vehicle, but it is also particularly advantageous for water drainage performance on the outside of the tire. It is a first object of the present invention to propose an asymmetric tread pattern that can significantly improve high-speed driving performance on wet road surfaces. A second object of the present invention is to propose an asymmetric tread pattern that can improve stable turning performance even in dry conditions. (Means for Solving the Problems) The present invention provides a means for solving problems from one side edge _E1 of the tread T to the other side edge _E2.
It extends continuously between the two side edges E ₁ ,
A pneumatic tire has a tread pattern in which the tread T is divided into a plurality of land areas L by transverse main grooves 1 each opening at E ₂ , and the transverse main groove 1 extends from one side edge E ₁ of the tread T. A central diagonal groove _1a that occupies a central area having a width that is substantially 1/2 of the ground contact width W extending up to the other side edge E2 and is inclined at an angle α of 5° to 20° with respect to the tire circumferential direction; A bent diagonal groove 1b extends from one side end e ₁ of the diagonal groove 1a to one edge E ₁ of the tread T at an angle β increasing from 45° to 80°, and from the other side end e ₂ of the tread T. It consists of an inverted oblique groove 1C that is inclined at an angle γ increasing from 100° to 135° over the other side edge _E2 of T,
A pneumatic tire having an asymmetrical tread pattern characterized by an offset herringbone arrangement, wherein the tread pattern is formed on one side edge of the tread T of the central diagonal groove 1a.
The tread T is extended from the side end e ₁ which is closer to E ₁ at the same angle as the inclination angle α of the central oblique groove 1 a, and then bent substantially parallel to the bent oblique groove 1 b.
at least one auxiliary groove 2 opening on one side edge E ₁ of
a, 2b, and the inverted oblique groove 1C adjacent in the circumferential direction
The inverted diagonal groove 1 is formed independently of the transverse main groove 1 between
C and at least one additional groove 3 extending substantially parallel to said tread T and opening into the other side edge E ₂ of said tread T, and having a negative ratio in the central area 4 of said tread T.
15 to 30%, the refractive oblique groove 1b and the auxiliary groove 2
40 to 45 in one side area 5 of Toledo T including a and 2b
%, and in the other side region 6 of the tread T including the inverted oblique grooves 1C and the additional grooves 3, it is more preferable that they are each set in the range of 10 to 15%. According to the present invention, when the tire having the asymmetric tread pattern is mounted on a vehicle, the plurality of land portions of the tread defined by the transverse main grooves arranged in the offset herringbone pattern are arranged at a chevron-shaped peak located toward the outside of the tire. The direction of contact with the road surface should be set in advance from the tire, and for this reason it is desirable to attach an arrow mark to the side of the tire to indicate this direction. In the above, one side area and the other side area of the tread are separated from each side edge by a distance equivalent to 1/4 of the tread ground contact width W from one side edge of the tread to the other side edge, and the remaining area is the area in the center. area. In the present invention, it is sufficient that the central area is substantially occupied by the central diagonal groove. In other words, even if the side end _e1 of the central diagonal groove 1a is within the one side area 5 of the tread T, the central area may be occupied by the central diagonal groove. 4 and one side area 5 of the tread T, and even if the side edge _e2 of the central diagonal groove 1a is within the one side area 6 of the tread T, it is almost the same as the central area 4 and the other side area 6 of the tread T. In short, it is important to form an offset herringbone arrangement that is biased toward the outside of the tire at the chevron-shaped top of the transverse main groove 1 where the central diagonal groove 1a intersects with the inverted diagonal groove 1c. . (Function) In the present invention, first, the transverse main groove 1 provided in the tread 1 has an inclination of 5° to 20° in the central diagonal groove 1a with respect to the tire circumferential direction, that is, the tire equatorial plane as a plane including the tread circumference line c. Since the number of grooves is small within the range of In particular, the central diagonal groove 1a and the reverse diagonal groove 1c
Since the chevron-shaped peak formed by the intersection of the two is located on the outside of the tire in the mounting position on the vehicle with respect to the tread circumference line c, when driving on a wet road surface, stagnant water on the front of the tire will be absorbed by the tire. By stepping into contact with the ground, the tire is pushed more towards the inside front of the tire, that is, toward the vehicle, and the intrusion into the outside contact area of the tire is reduced, and moreover, water drainage in the bent diagonal grooves 1b and especially the reversed diagonal grooves 1c, which act as lateral grooves. As the capacity is fully demonstrated, drainage characteristics have been improved which can significantly reduce the occurrence of hydroflaning phenomenon caused by thickening of water film in the outer contact area of the tire, improving straight running performance. In addition, even under cornering conditions, the increase in water film thickness on the stepping side is suppressed even in the outer region of the tire on the outside of the corner, where the load increases, resulting in stable high-speed running performance. It can be sustained. In addition to these basic functions, the second invention further improves the above-mentioned drainage characteristics by adding the auxiliary groove 2.
a, 2b and the additional grooves 3, but also these auxiliary grooves 2a, 2b and the additional grooves 3 can reduce the negative ratio of the tread by 15 to 30% in the central area 4 of the tread T, and by 15% to 30% in the one side area 5. So 40-45
%, and the other side area 6 is set in the range of 10 to 15%.By doing so, the land area stiffness of the tread is properly distributed on the outer side of the tire, which is higher than other areas, and the dryness of the road surface is controlled. It is possible to achieve good turning performance without any problems. Now, since the inclination of the central diagonal groove 1a is virtually no different from the circumferential groove at an angle of less than 5 degrees, when the tire is pressed down, water stagnant on the road in front is diverted more strongly toward the inside of the tire. On the other hand, if the angle is larger than 20°, the water surface will collide with the groove edge, making the above-mentioned effect of strengthening the diversion insufficient. The reason for the limitation is that by doing so, adequate drainage can be ensured under various usage environments of the tire. Next, if the angle β to be increased for the diagonal groove 1b is less than 45°, at the front of the tire on the depression side,
This makes it difficult for the discharge of a stronger branch flow toward the vehicle, and on the other hand, if it is larger than 80 degrees, it becomes disadvantageous in that the resistance to the flow of the branch flow becomes stronger. If it is defined as
The reason for this limitation is to appropriately guide the divided flow from the central oblique groove 1a to realize effective drainage. Also, the angle γ to be increased for the reverse oblique groove 1c
If the angle is smaller than 100°, the action as a horizontal groove becomes too strong, and drainage is trapped in the groove, making it difficult to remove excess water left from the above-mentioned diversion, while if it is larger than 135°, the action of the circumferential groove becomes too strong. The reason for this limitation is that it is similar to the above and impedes drainage. In this way, the refracted oblique groove 1b and the inverted oblique groove 1c
Generally, the arrangement is made to have an inclination angle that is symmetrical with respect to the tire equatorial plane. In addition, the auxiliary grooves 2a, 2b and the additional grooves 3 are designed to further improve the drainage performance.
The distribution of the negative ratio of the tread pattern is determined according to the number of the auxiliary grooves 2a, 2b and the additional grooves 3. If the negative ratio in zone 4 is less than 15%, it will not be possible to obtain a drainage flow rate that can advantageously promote the above-mentioned diversion, while if it exceeds 30%, the land stiffness in the central zone will be reduced locally. This is because if the negative ratio is less than 40% in one side area 5 of the tread T, it will be difficult to secure the necessary drainage flow rate. If it exceeds 45%, this one-sided area 5
If the negative ratio in the other side area 6 is less than 10%, it will be difficult to achieve the required drainage performance, while if it exceeds 15%, stability will depend on the land rigidity of the one side area 6. Since it becomes difficult to ensure good turning performance, it is necessary to appropriately distribute the negative ratio as described above. In addition to the above points, the central diagonal groove 1a constituting the transverse main groove 1 is installed at an inclination angle of 5° to 20° with respect to the circumferential direction, so that the general circumferential grooves are arranged in the central area. It also prevents the air column resonance sound that occurs when the pedal is pressed, as well as the pitch sound that occurs when the groove edge hits the road surface when stepping on the ground, which is particularly noticeable when the contact shape and the land edge shape are close. In addition to contributing effectively, the installation of so-called rain grooves prevents the formation of a water film on the road surface by constructing a road surface in which many small grooves are lined up parallel to the direction of travel, allowing rainwater to flow into the grooves and preventing the formation of a water film on the road surface. On the road, the tire sideways slip phenomenon caused by the reaction force generated when the tire groove edge enters the rain groove, so-called rain groove wander (the phenomenon where the steering wheel becomes loose due to the tire sideways slipping), can also occur due to the central diagonal groove with the above-mentioned inclined arrangement. 1
This is advantageously prevented by the arrangement of a. The central diagonal groove occupies a central area divided from both sides of the tread at a point separated from each side edge by a distance corresponding to substantially 1/4 of the ground contact width of the tread extending from one side edge of the tread to the other side edge. It is sufficient to have the above-mentioned effect as long as it is in the central area, and it is not necessary to strictly occupy the central area. In the present invention, the auxiliary groove 2 is installed in the tread side area 5 on the inside of the tire, and its negative ratio is set to 40.
By increasing the range to ~45%, drainage to the inside of the vehicle can be made more efficient, and therefore the negative ratio in the other side area 6 of the toledo can be reduced to 10~15%.
Even if it is made small, drainage is maintained well. Therefore, the land portion rigidity and ground contact area of the tread on the outside of the tire away from the vehicle can be increased, providing excellent turning performance. If an additional groove 3 independent of the transverse main groove is connected to the other side area 6 on the outside of the tire away from the vehicle so that the negative ratio is preferably within the range of 10 to 15%, drainage can be achieved while ensuring tread rigidity. This will allow you to further improve your sexuality. The tread pattern of the present invention can be applied to any type of tire, such as a radial tire or a bias tire, but at least one cord layer arranged substantially in the radial direction is applied as a carcass that reinforces the tread part and both sidewall parts. However, it is more preferably used as a pneumatic radial tire in which the crown portion of the tread is reinforced with at least two belts made of cord layers that intersect with each other at a relatively small angle in the tire circumferential direction. (Example) FIG. 1 is a developed view showing the tread pattern of an example tire of the present invention, and FIG. 2 shows the footprint of the tire on the road surface. In the drawings, reference numeral 1 denotes a transverse main groove that extends continuously from one side edge _E1 of the tread T to the other side edge _E2 , and opens at both side edges _E1 and _E2, respectively. This transverse main groove 1 divides the tread T into a plurality of land portions L. The transverse main groove 1 has a central oblique groove 1a with a slight gentle inclination α in the range of 5° to 20° with respect to the plane containing the tread circumference line C (equatorial plane), on both sides of this central oblique groove 1a. From the ends e ₁ and e ₂ , one side edge E ₁ of the above tread T
Until reaching the refractive oblique groove 1b and the other side area _E2 of the tread T, the above-mentioned intersection angle remains an acute angle and becomes a steep slope β increasing to a range of 45° to 80°. is connected to the inverted diagonal groove 1c which has a steep slope γ increasing to form an obtuse angle in the range of 100° to 135°, thus forming an offset herringbone arrangement as a whole. The central diagonal groove 1a extends from each side edge _{E1, E2} by a distance corresponding to substantially 1/4 of the ground contact width W of the tread 1 extending from one side edge _E1 of the tread T to the other side edge _E2 . It almost occupies the center area 4 divided from the area 5 on one side and the area 6 on the other side of the tread. In the embodiment (Fig. 1), the side end _c1 of the central oblique groove 1a is the tread T.
The central diagonal groove 1a extends into the one side area 5 of the tread, and the side end _e2 of the central diagonal groove 1a is slightly wider than the boundary between the central area 4 and the other side area 6 of the tread circle. It is located near Line C. Each transverse main groove 1 is arranged to extend from the side end e ₁ closer to one side edge E ₁ of the central oblique groove 1a with a gentle slope α and then bent substantially parallel to the bent oblique groove 1b on one side of the tread T. At least one auxiliary groove 2a, 2b in the illustrated example, which opens at the edge _E1 , is connected to the central diagonal groove 1a in parallel to each other. Further, between the inverted oblique grooves 1c, an additional groove 3 is provided which is substantially parallel to these grooves and opens to the other side edge _E2 of the tread T independently without being connected to the transverse main groove 1. There is. Here, three central diagonal grooves 1a are opened in parallel at equal intervals in the front and back at the contact area of the tread T, substantially between the stepping side 7 and the kicking side, as shown in the footprint of Fig. 2. It is arranged like this. However, the number of extending central diagonal grooves is not limited to three, and may be appropriately selected from one to six. Further, the auxiliary grooves 2a, 2b and the additional groove 3 are not limited to the example shown in the drawings, and when auxiliary grooves are provided, the negative ratio is 40 to 45 in the one side area 5 of the tread T, as described above. %, other side area 6
It can be determined by increasing or decreasing it as appropriate within the range of 10 to 15%. The transverse main groove 1, auxiliary grooves 2a, 2b, and additional grooves 3 arranged in this way have a groove width in the range of 2 to 6% of the tread contact width W, and have a groove depth that is normally applied as a tread groove. Just set it up. It has the tread pattern shown in Fig. 1, and the angle of intersection with the plane containing the tread circumference line C is 14° (α),
56゜(β), 124゜(γ), groove width W is 8mm, total number of arrays is 16
For comparison, a prototype asymmetrical tire of size 205/60 R15 is shown in Fig. 3, in which a tread land portion in an offset herringbone arrangement is formed by the main transverse main groove 1, auxiliary grooves 2a, 2b, and additional grooves 3. As shown, four circumferential grooves 9 parallel to each other are provided in the central area, which is approximately 1/2 of the tread contact width W, and two bent portions in opposite directions are also provided in the central area in the shape of a trifold folding screen. A comparison tire of the same size was prepared having a conventional point symmetrical tread pattern with 64 axial grooves 10 forming a diameter. Regarding the tread T of the asymmetrical tire tested above, the negative ratio was 20% in the center area 4, 40% in the tread one side area 5, and 10% in the other tread side area 6, making the overall average about 23%. In the case of the comparison tire, the center area is 40%, and each of the two areas on one side and the other side is 35%.
%, and the overall average was approximately 38%. Next, attach both tires to the actual vehicle, and the speed is 0.
The ground contact area at Km/Hr is 100, the speed is 60Km/
The remaining ground contact area was measured at each speed of Hr, 80 Km/Hr, and 100 Km/Hr, and wet performance was evaluated based on hydroplaning performance, that is, drainage performance. The results obtained are shown in Table 1. For this measurement, a glass plate was fitted over the pit.
A water film with a thickness of 5 mm was formed on a glass plate, and the remaining ground surface area was measured by taking photographs from below the glass plate as a car passed over the water film at various speeds.

[Table] (Note) The values in the table were evaluated by measuring only the main parts where the ground contact was clearly visible.
The cornering power, cornering force (maximum value), and self-aligning torque of both tires were measured using an indoor test chamber under the conditions of an internal pressure of 2.0 kg/ ^cm2 and a load of 400 kg, and dry performance was evaluated based on turning performance. The results obtained are shown in Table 2 using an index with the evaluation value of the conventional tire set as 100, and the larger the index, the better the buildup.

[Table] From the results in Tables 1 and 2, the tires of the example showed significantly improved hydroplaning prevention performance, especially when running at high speeds, compared to the comparative tires, and the dry performance also improved by about 10 to 20%. It is clear that there are. This is because the tread pattern of the example tire is asymmetric and directional, whereas the conventional tire has a point symmetrical tread pattern and no directional. (Effects of the Invention) As explained above, the present invention provides a remarkable effect in that the wet performance, especially during high-speed running, is simultaneously improved in accordance with the dry performance.

[Brief explanation of drawings]

FIG. 1 is a developed view illustrating the tread pattern of a tire according to the present invention, FIG. 2 is a footprint diagram showing road surface conditions, and FIG. 3 is a developed view showing the tread pattern of a conventional tire used for comparison. It is a diagram. 1... Transverse main groove, 1a... Central oblique groove, 1b... Bent oblique groove, 1c... Inverted oblique groove, 2a, 2b... Auxiliary groove, 3...
Additional groove, 4...Central area, 5...Tread one side area, 6
...Tread other side area, 7...Stepping side, 8...Kicking side, T...Tread, _E1 ...One side edge, _E2 ...Other side edge,
C...Treasured circumference line.

Claims (1)

[Scope of Claims] 1. The main transverse groove 1 extends continuously from one side edge E ₁ of the tread T to the other side edge E ₂ and opens at both side edges E ₁ and E ₂ . The pneumatic tire has a tread pattern in which the tread T is divided into a plurality of land areas L, and the transverse main groove 1 is substantially 1 of the ground contact width W extending from one side edge _E1 of the tread T to the other side edge _E2 . a central diagonal groove 1a that substantially occupies a central area having a width of /2 and is inclined at an angle α of 5° to 20° with respect to the tire circumferential direction;
A bent oblique groove 1b extends from one side end _e1 of the central oblique groove 1a to one side edge _E1 of the tread T at an angle β increasing from 45° to 80°, and the other side end
100°~ from e ₂ to the other side edge E ₂ of the above tread T
A pneumatic tire with an asymmetric tread pattern characterized by an offset herringbone arrangement consisting of inverted diagonal grooves 1C inclined at an angle γ increased to 135°. 2 The tread pattern includes one side edge E ₁ of the tread T of the central diagonal groove 1a.
At least one extending from the nearer side end _e1 at the same angle as the inclination angle α of the central oblique groove 1a, bent substantially parallel to the bent oblique groove 1b, and opening at one side edge _E1 of the tread T. 1 auxiliary groove 2a,
2b, and at least one additional groove extending substantially parallel to the reversed diagonal groove 1C independently of the transverse main groove 1 between the circumferentially adjacent reversed diagonal groove 1C and opening to the other side edge _E2 of the tread. a groove 3 and a negative ratio in the central region 4 of said tread T;
15 to 30%, the refractive oblique groove 1b and the auxiliary grooves 2a, 2
It is characterized in that it is set in the range of 40 to 45% in one side area 5 of the tread T including b, and in the range of 10 to 15% in the other side area 6 of the tread T including the inverted diagonal groove 1C and the additional groove 3. Claim No. 1
A pneumatic tire with an asymmetric tread pattern as described in Section 1.