JPH092025A - Pneumatic radial tire having directional pattern - Google Patents

Abstract

PURPOSE: To effectively improve respective performances for wet/drainage, low noise, and control stability, without sacrificing the other performances. CONSTITUTION: This pneumatic racial tire is provided with at least a pair of main grooves in the circumferential direction extending in the circumferential direction of a tread on a pattern center zone, and a plurality of slant main grooves 4 extending from a pair of the main grooves 1 to the pattern end sides, slanting in the same directions against the main grooves 1, and opening at the tread grounding ends TE. The each slant main groove 4 is constituted of a steep slant part 5 positioned in the vicinity of the pattern center and a gentle slant part 6 positioned in the vicinity of the tread grounding end TE. The angle θ1 of the steep slant part 5 against the circumferential direction or the tread is set 0-30 deg., the similar angle θ2 of the gentle slant part 6 is set 70-90 deg., and the surface height of the tapering end part on the pattern center side of a land part 7 defined by the main groove 1 in the circumferential direction and the slant main groove 4 is smoothly lowered toward the extreme end side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having a so-called directional pattern and having excellent dynamic performance, and particularly to wet drainage performance, low noise performance and steering stability performance at the expense of other performance. It is intended to improve without.

[0002]

2. Description of the Related Art In order to make wet drainage performance and low noise performance compatible with each other, for example, the applicant first mentioned in Japanese Unexamined Patent Publication No.
As proposed as No. 319025, it is common to employ a tread pattern formed by combining circumferential grooves linearly extending in the tread circumferential direction and directional inclined grooves.

Further, in order to further improve the wet drainage performance, as compared with the general directional inclined groove as described above,
It is known that a steep groove with a smaller inclination angle with respect to the circumferential direction of the tread is effective. Furthermore, in order to improve hydroplaning resistance, it is necessary to increase the negative ratio to reduce noise. It is known to be effective, although it has the problem of deterioration.

[0004]

However, due to the demand for higher performance of tires in accordance with the higher performance of vehicles in recent years, wet drainage performance, low noise performance and steering stability performance are each reduced to other performances. There is no established technology to improve the whole area without sacrificing
In the case of adopting the steep groove as described above for the purpose of improving the wet drainage performance, the rigidity of the land portion defined by the steep groove, particularly in the tapered portion, becomes extremely low, This has the disadvantage of inevitably lowering the steering stability performance, and this also increases the wet drainage performance, and in the case of forming a circumferential groove in the pattern center, often in the tread center, ribs are formed in the tread center. As compared with the case where the vehicle is provided, there is an inconvenience that straight running stability performance, steering performance at a small steering angle, and the like are deteriorated. Therefore, this invention, while ensuring excellent wet drainage performance,
Provided is a pneumatic radial tire having a directional pattern, which effectively improves both low noise performance and steering stability performance.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a straight line stability performance and a steering performance at a small rudder angle are respectively provided by providing a rib that is continuous in the tread circumferential direction at a pattern center that normally corresponds to the tread center. On the premise of ensuring sufficient water drainage, from the viewpoint of optimal wet drainage performance, in addition to adopting a steep directional groove,
The pneumatic radial tire having a directional pattern of the present invention has been made by adding various studies to the configuration of the steep groove near the pattern center and the configuration near the tread ground contact end. , The pattern center area is provided with at least a pair of circumferential main grooves linearly extending in the circumferential direction of the tread to define circumferential ribs, and at least one of the circumferential main grooves is connected to the circumferential main groove together. Where a plurality of inclined main grooves that are inclined in the same direction and open to the tread ground contact end are provided by extending to the pattern end side, each inclined main groove is defined as a steeply inclined portion located in the vicinity of the pattern center. , And a gently sloping portion that is smoothly continuous to this steeply sloping portion and is located in the vicinity of the tread ground contact end. 0-3 the average angle of an acute form that
0 °, the same average angle of the gently sloping portion is 70 to 90 °, and the surface height of the tapered portion on the pattern center side of the land portion defined by the circumferential main groove and the inclined main groove is set to the tapered tip. Toward the side, the curved surface-shaped comb or the inclined flat surface is smoothly reduced.

[0006] Here, preferably, a sub steeply inclined groove extending from the gently inclined portion of the inclined main groove in the pattern center direction and substantially parallel to the steeply inclined portion is formed. In this case, it is more preferable to form the sub gentle sloping groove that extends from the sub steeply inclined groove toward the tread ground contact end, is substantially parallel to the gently sloping portion, and opens to the trend ground end.

More preferably, the inclined main groove is extended to the pattern end, and the extending direction of the inclined main groove in the vicinity of the pattern end is the same as that of the steeply inclined portion, and the extending portion is The average angle on the acute angle side with respect to the tread circumferential direction is 10 to 30 °. Further, in this case, it is more preferable that the auxiliary assisting inclined groove extends substantially parallel to the assisting inclined portion, and the auxiliary main inclined groove is opened in the inclined main groove in the vicinity of the pattern end to finish.

The above will be described more specifically based on the tread development diagram illustrated in FIG. In this example,
The pattern center C coincides with the tread center. Here, from the pattern center C to the tread contact width W of 5 to 1
Within the range of 0%, a pair of circumferential main grooves 1 and 1 extending linearly in the circumferential direction of the tread are provided.
The center rib 2 defined by 1 is provided with a circumferential sub-groove 3 having a somewhat narrow width which also extends linearly in the circumferential direction of the tread.

Further, here, a plurality of inclined main grooves 4 extending continuously from each circumferential main groove 1 to the pattern end E and inclined in the same direction with respect to the circumferential main groove 1 are provided. A portion of each of the inclined main grooves 4 near the pattern center, for example, from the pattern center C to the tread contact width W
10 to 25% of the range is a steeply inclined part 5 in which the average angle θ ₁ on the acute angle side with respect to the tread circumferential direction is in the range of 0 to 30 °, and the inclined main groove 4 has a tread ground end. A portion in the vicinity of TE, which is also within a range of 25 to 50% of the tread contact width W from the pattern center C, has an average angle θ ₂ on the acute side with respect to the circumferential direction of the tread within a range of 70 to 90 °. The gently sloping portion 6 is formed. Here, it goes without saying that the steeply sloped portion 5 and the gently sloped portion 6 are smoothly connected with a curved portion.

Further, the surface height of the tapered end portion on the pattern center side of the land portion 7 defined between the circumferential main groove 1 and the two inclined main grooves 4 and 4 is, for example, In the range of 20 to 40 mm in the lengthwise direction, as shown by hatching in the figure, it is smoothly reduced toward the tip side. This height reduction here can be performed, for example, not only by making the surface of the land portion a convex curved surface outward in the radial direction, but also by making it an inclined flat surface. The tread pattern configured in this way is
It is line-symmetric with respect to the pattern center C.

Further, in the illustrated preferred embodiment, a sub steep sloped groove 8 extending from the middle of the gentle sloped portion 6 toward the pattern center and substantially parallel to the steep sloped portion 6 is provided.
Is terminated in the land portion on the front side of the adjacent inclined main groove 4. In addition, here, a sub gentle sloped groove 9 is provided which extends from the middle of the sub steep sloped groove 8 toward the tread ground contact end side, opens at the ground contact end, and is substantially parallel to the gentle sloped portion 6.

Further, the extending direction of the inclined main groove 4 extending to the pattern end E in the vicinity of the pattern end is the same as that of the steeply inclined portion 5, and the extending portion 10 has a tread circumference. The average angle θ ₃ on the acute angle side with respect to the direction is in the range of 10 to 30 °. By the way, the sub gentle slant groove 9 extends substantially parallel to the gentle slant portion 6 also outside the tread ground contact end TE, and the slant main groove 4 is provided.
And ends in the extended portion 10.

[0013]

When the flow of water in the tread contact surface is observed in relation to the wet drainage performance, water is not found in the pattern center area (the area from the pattern center C to about 5 to 10% of the tread contact width W). It flows horizontally in the tread circumferential direction,
In a certain area outside of that area (area from the pattern center to about 10 to 25% of the tread ground contact width), the material flows at an angle of 0 to 30 ° with respect to the circumferential direction of the tread, and further outside area. In a region (about 25 to 50% of the tread ground contact width from the pattern center), the fluid flows at an angle of 70 to 90 ° while curving with respect to the tread circumferential direction and is discharged to the tread ground contact end.

Therefore, in the tire of the present invention, by providing at least a pair of circumferential main grooves 1 in the pattern center area, the drainage performance of the pattern center area is sufficiently ensured, and at the outside of the pattern center area. The drainage performance of a certain area is ensured by the steep slope portion 5 of the slope main groove 4, and the steep slope portion 5 is smoothly smoothed to the tread ground contact end by the gentle slope portion 6 which is continuous through the curved portion. Drain quickly.

Further, here, the height of the tapered end portion of the land portion 7 defined between the circumferential main groove 1 and the two inclined main grooves 4 and 4 is gradually reduced toward the tip. By increasing the rigidity of the end part, crushing at the time of grounding of the tapered end part, and by extension, preventing escape deformation into the groove, drainage is sufficiently smoothed, and at the same time, the contact of the end part The ground pressure can be increased to effectively contribute to the steering stability performance and the uneven wear resistance performance. By the way, the area where the surface height is reduced is set from the tip of the tapered end portion to 2 in the length direction thereof.
The range of 0 to 40 mm is that if it is less than 20 mm,
While the low rigidity land part will still remain,
When it exceeds 40 mm, the ground contact area of the block becomes too small, and the rigidity of the land part is reduced, so that the steering stability performance is inevitably reduced.

From the viewpoint of ensuring the steering stability, the tread pattern provided with only the inclined main groove 4 tends to have insufficient land rigidity, particularly in the pattern center area. By defining the center rib 2 by the pair of circumferential main grooves 1 and 1 provided in the, the rigidity of the land portion is enhanced, and excellent straight running stability and steering performance are secured. The center rib 2 also functions to effectively reduce the pattern noise as compared with the case where it is not provided.

Here, the land portion 7 defined by the circumferential main groove 1 and the inclined main groove 4 generally has a relatively large ground contact area in a portion existing between the gently sloping portions. Wet drainage performance is preferably supplemented by the provision of grooves.

Therefore, in the illustrated example, the sub steep inclined groove 8 and the sub gentle inclined groove 9 which are substantially parallel to the steeply inclined portion 5 and the gently inclined portion 6, respectively, are provided, and in the portion near the tread ground contact end TE. While maintaining the rigidity of the land, in other words, it improves wet drainage performance without lowering steering stability. In this case, if the angle of the sub steep inclined groove 8 with respect to the circumferential direction of the tread is reduced, the sub gentle inclined groove 9 is formed.
The difference in rigidity between the land portions located apart from each other is small, which is effective in suppressing uneven wear, and when the sub steeply inclined groove 8 is made substantially parallel to the steeply inclined portion 5, the wet drainage is performed. The performance can be further improved.

Further, in the illustrated example, by terminating the sub steep inclined groove 8 extending from the gently inclined portion 6 in the land portion,
Since the land area extends from the central area of the tread to the shoulder area, the rigidity of the land area is increased and steering stability is improved.

Further, by stopping the sub gentle sloped groove 9 without penetrating the sub steep sloped groove 8, the rigidity of the land portion in the central region of the tread becomes high, and a feeling of maneuverability at a small rudder angle is firmly felt. Moreover, since there is no increase in the lag component in the tread central region, it is possible to effectively suppress the occurrence of pattern noise.

If only the sub steep inclined groove 8 is provided without providing the sub gentle inclined groove 9, the ground pressure near the so-called 1/4 portion of the tread ground width is increased, and The water in the vicinity thereof can be smoothly guided to the gently inclined portion 6 that opens to the grounded end.

Further, in this tire, the inclined main groove 4
Is extended to the pattern end E beyond the tread ground contact end TE, and the average angle θ ₃ on the acute side of the extending portion 10 near the pattern end with respect to the tread circumferential direction is in the range of 10 to 30 °. In such a case, the land portion rigidity of the inner portion of the tread ground contact end TE is sufficiently ensured at the gently inclined portion 6, and then the drainage ejected obliquely forward from the tread ground contact end TE is extended. Since it can be discharged sufficiently smoothly, the drainage becomes more fluid and the drainage performance is further improved.

By the way, when the average angle θ ₃ exceeds 30 °, there is a high possibility that the ground contact contour line during turning of the vehicle overlaps with the groove shape and the generated noise increases, while it is less than 10 °. Then, from the gently inclined portion 6 to the extended portion 1
Since the bend of the groove until reaching 0 becomes large and it becomes difficult to guide the smooth flow of the drainage, the drainage efficiency decreases.

Further, in this case, when the sub gently slanted groove 9 extends substantially parallel to the gently slanted portion 6 and is opened to the extended portion 10 of the slanted main groove near the pattern end, the vehicle is When turning, the drainage performance is ensured and the required rigidity can be secured in the paddles contact area.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a development view of a tread showing an embodiment of the present invention, and its pattern configuration is as described above. In this example, the surface height of the tapered end portion on the pattern center side of the land portion 7 defined between the circumferential main groove 1 and the two inclined main grooves 4 and 4 is indicated by the diagonal lines in the figure. Within the indicated range,
As shown in the cross-sectional view of FIG. 2 toward the tip side, the shape is smoothly curved outward in the radial direction to form a convex curved surface. The function and effect of this surface height reduced portion are as described above.

Further, in this example, the circumferential auxiliary groove 3 formed in the central portion of the center rib 2 enhances the grounding pressure of the center rib 2 and enhances the grounding property near the limit of occurrence of the hydroplaning phenomenon, and at the same time, a small amount. It also improves the steering stability at the steering angle.

FIG. 3 is a development view of a tread showing another embodiment. In this example, the average angle θ4 of the sub steeply inclined groove 8 with respect to the circumferential direction of the tread is made slightly larger than that shown in FIG. 1, and the sub steeply inclined groove 8 is formed as the steeply inclined portion 5 of the inclined main groove 4. By making them substantially parallel to each other, the wet drainage performance can be enhanced more than that of the above-mentioned embodiment, and in addition, the land portion 7
By providing a plurality of sipes 11 and 12 which are substantially parallel to the sub steep sloped groove 8 and the sub gentle sloped groove 9, respectively, the steering stability on a wet road is improved based on the edge effect of the sipe edge, and It is possible to improve the ground contact property, and thus improve the wear resistance performance.

In the embodiment shown in FIG. 4, the end portion of the auxiliary steep groove 8 in the land portion 7 is sharpened in a wedge shape, and the auxiliary gentle inclination groove 9 is smoothly continued to the wedge-shaped tip portion thereof. By this, the flow resistance of the drainage to the sub gentle sloped groove 9 is reduced, and in the embodiment shown in FIG. 5, the end portion on the side of the sub gentle sloped groove 9 and the pattern center is directed downward in the drawing. Curved by an amount and averaged with respect to the tread circumferential direction θ ₅
Is 40 to 50 [deg.], And the tip thereof is smoothly continuous with the tip of the auxiliary steep groove 8, which also smooths the drainage. In this latter case, the surface height of the tapered land portion sandwiched between the two sub-inclined grooves 8 and 9 can be smoothly reduced toward the tip side to secure high land portion rigidity. It is preferable above.

By the way, according to the embodiments shown in FIGS. 4 and 5, the width of the shoulder land portion adjacent in the tread circumferential direction between the inclined main grooves can be made larger or smaller. It is preferable to balance the rigidity of the land portion by increasing the length in the circumferential direction and shortening the length in the circumferential direction for the wide land portion.

In the embodiment shown in FIG. 6, the sub gentle slanting groove 9 is separated from the sub steep slanting groove 8 and the end portion of the sub gentle slanting groove 9 on the pattern center side is curved slightly downward. It is a thing. In this example, since the land portion 7 is continuously formed as one, almost the same wet drainage performance as that in each of the above-described embodiments is ensured, yet smooth landing of the land portion 7 is ensured, and the pattern noise is ensured. Can be effectively suppressed.

Further, in the embodiment shown in FIG. 7, within the range from the pattern center C to 25% or less of the tread ground contact width W,
An inclined sub groove 13 whose angle to the circumferential direction of the tread is smaller than that of the steep inclined portion 5 of the inclined main groove 4 is provided in a branched manner, and the inclined sub groove 13 also has its tread ground end TE. In the vicinity of the slant main groove 4, a gentle slant sub-groove portion 14 extending substantially in parallel with the gently slant portion 6 of the slant main groove 4 is provided. While maintaining the parallel state, the inclined main groove 4 is opened in the extending portion 10 of the inclined main groove 4 in the vicinity of the pattern end E, beyond the tread ground contact end TE.

According to this example, in each of the land portions 7a and 7b which are tapered toward the pattern center side, the surface height of each tapered end portion is directed toward the tip end side,
For example, it is preferable to smoothly reduce the amount as shown in FIG.

According to this embodiment, in particular, the wet drainage performance is improved based on the action of the inclined sub-groove 13 that branches smoothly from the steeply inclined portion 5 of the inclined main groove 4 and opens at the tread ground contact end TE. It can be further improved.

Further, in this embodiment, the tread ground contact end T
By the action of the circumferential narrow groove 15 provided in the vicinity of E,
In particular, it is possible to effectively improve the ground contact property of the land portions 7a and 7b when turning.

[Comparative Example] A comparative test between the inventive tire and the conventional tire regarding wet drainage performance, steering stability performance on dry road surface, and low noise performance will be described below. ◎ Test tire Size 225/50 R16, tread ground width (W) 100mm tire. Inventive tire 1 A tire having the tread pattern shown in FIG.
Those having the dimensional specifications shown in Table 1.

[0036]

[Table 1]

Invention Tire 2 A tire having the tread pattern shown in FIG. 3,
Those having the dimensional specifications shown in Table 2.

[0038]

[Table 2]

Invention Tire 3 A tire having the tread pattern shown in FIG. 4,
Those having the dimensional specifications shown in Table 3.

[0040]

[Table 3]

Invention Tire 4 A tire having the tread pattern shown in FIG.
Those having the dimensional specifications shown in Table 4.

[0042]

[Table 4]

Invention Tire 5 A tire having the tread pattern shown in FIG.
Those having the dimensional specifications shown in Table 5.

[0044]

[Table 5]

Invention tire 6 is a tire having a tread pattern shown in FIG.
Those having the dimensional specifications shown in Table 6.

[0046]

[Table 6]

Conventional tire A tire having a tread pattern shown in FIG.
Those having the dimensional specifications shown in Table 7.

[0048]

[Table 7]

◎ Test method When the tire internal pressure was set to 2.2 kg / cm ² and the load was set to the equivalent of two passengers, the wet drainage performance was measured on a wet road surface with a water depth of 5 mm at 80 km / h and 90 km / h. It is evaluated by measuring the remaining contact area when driving straight ahead, and the steering stability performance on dry road surface is evaluated by the feeling of the test driver when running sports on the dry circuit course in various driving modes, And low noise performance is 10
The vehicle interior noise when coasting from 0 km / H was measured and evaluated. ◎ Test result The test result is shown in Table 8 as an index with the conventional tire as a control. The larger the index value, the better the result.

[0050]

[Table 8]

[0051]

As is apparent from the comparative test, according to the present invention, it is possible to effectively improve both the steering stability performance and the low noise performance while ensuring excellent wet drainage performance. it can.

[Brief description of the drawings]

FIG. 1 is a tread developed view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a mode of reducing the surface height of a tapered land portion.

FIG. 3 is a development view of a tread showing another embodiment.

FIG. 4 is a tread developed view showing another embodiment.

FIG. 5 is a development view of a tread showing another embodiment.

FIG. 6 is a development view of a tread showing still another embodiment.

FIG. 7 is a development view of a tread showing still another embodiment.

FIG. 8 is a development view of a tread showing a conventional example.

[Explanation of symbols]

1 Circumferential main groove 2 Center rib 3 Circumferential auxiliary groove 4 Inclined main groove 5 Steep sloped portion 6 Slowly sloped portion 7, 7a, 7b Land portion 8 Sub steeply sloped groove 9 Sub gentle slanted groove 10 Extended portion 11, 12 Sipe 13 inclined sub-groove 14 gently inclined sub-groove part 15 circumferential narrow groove C pattern center E pattern end TE tread ground end θ ₁ , θ ₂ , θ ₃ , θ ₄ , θ ₅ average angle L, L ₀ , L ₁ length W tread contact width

Claims (5)

[Claims] 1. A pattern center area is provided with at least a pair of circumferential main grooves extending linearly in a circumferential direction of a tread to define circumferential ribs, and at least one of the pair of circumferential main grooves is directed to a pattern end side. In a pneumatic radial tire having a plurality of inclined main grooves which extend and incline in the same direction with respect to the circumferential main groove and open at the tread ground contact end, each inclined main groove is provided in the vicinity of the pattern center. It is composed of a steeply inclined portion located and a gently inclined portion located in the vicinity of the tread ground contact end, and the average angle of the steeply inclined portion on the acute angle side with respect to the tread circumferential direction is 0 to 30 °. The same average angle is set to 70 to 90 °, and the surface height of the tapered end portion on the pattern center side of the land portion defined by the circumferential main groove and the inclined main groove is smoothly reduced toward the front end side. Let me A pneumatic radial tire having that directivity pattern. 2. A pneumatic with a directional pattern according to claim 1, further comprising a sub steep slope groove extending from the gentle slope portion of the slope main groove toward the pattern center and being substantially parallel to the steep slope portion. Radial tires. 3. The air having a directional pattern according to claim 2, wherein a sub gentle slant groove extending from the sub steep slant groove and opening to a tread ground contact end and substantially parallel to the gently slant portion is provided. Radial tires with. 4. The inclined main groove is extended to the pattern end, and the average angle of the inclined main groove on the acute angle side with respect to the tread circumferential direction is 10 to 10 near the pattern end.
A pneumatic radial tire having a directional pattern according to any one of claims 1 to 3, which has an angle of 30 °. 5. The air filled with a directional pattern according to claim 4, wherein the sub gentle sloping groove extends substantially parallel to the gradual slanting portion, and is opened to the slanting main groove in the portion near the pattern end. Radial tires.