JPH0891025A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE: To remarkably improve the wet drainage performance and improve the abrasion resistance by securing the excellent steering stability, etc. CONSTITUTION: A plurality of' inclined main grooves 2 which extend in the direction spreading upwardly from the lower part are formed, having a pattern center C as boundary, in the plane view of a tire in the installation attitude onto a vehicle, and the first inclined subgroove 4 is branched from each inclined subgroove 2 toward the tread end side, and the second inclined subgroove 5 is branced from the first inclined subgroove 4, and these inclined subgrooves 4 and 5 are extended free from the crossing with any other groove, and each branched point is positioned within 1/4 of the tread width TW from the pattern center C, and the change of the angle for the tire circumferential direction of each groove 2, 4, 5 is set at most 30 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tread pattern of a pneumatic radial tire, in particular, a so-called high-performance tire having excellent exercise performance, which provides excellent steering stability on a dry road surface and generates noise. It is sufficiently suppressed and still exhibits excellent wet drainage performance.

[0002]

2. Description of the Related Art In a conventional high performance tire, a so-called directional pattern formed by combining linear circumferential grooves extending in the tire circumferential direction and respective inclined grooves extending in a substantially V shape in a front view of the tire is combined. Is widely practiced, and the better wet drainage performance of such tires is often ensured by increasing the negative rate.

On the other hand, in the center area of the tread, each of the inclined grooves extending in a V-shape in a front view of the tire and the inclined grooves extending in the same direction as the inclined grooves have an inclination angle with respect to the tire circumferential direction. In particular, a combination of small steep grooves is provided, and in the tread side area, a gentle slant groove for draining the tire to the side is also provided by bending from each of the slant grooves. It has been confirmed that the performance can be improved.

[0004]

By the way, in such a conventional technique, in forming a tread pattern, a straight circumferential groove and a slant groove, or a slant groove and a steep groove, etc. are mutually connected. Since, when the tire rolls under load, the water on the road surface is drained through each of these grooves, and where water confluence occurs, the turbulence of the flow due to the confluence, Where the flow branches, the flow turbulence occurs due to the large change of the flow direction at the branch point, and each of them has a disadvantage that the drainage efficiency is lowered.

In addition, in the above-mentioned prior art in which the grooves must intersect with each other, the rigidity of the land portion defined by each groove is naturally low, and it is difficult to ensure sufficient wear resistance. There was also a problem that it would be difficult to ensure excellent steering stability.

The present invention has been made as a result of studies aimed at solving such problems of the prior art, and the object of the present invention is not only wear resistance but also steering stability. (EN) It is possible to provide a pneumatic radial tire that can be sufficiently secured and that the generated noise can be effectively suppressed and the wet drainage performance can be greatly improved.

[0007]

A pneumatic radial tire of the present invention has a tread tread portion which gradually expands from the lower side to the upper side at a pattern center as seen in a front view of a mounting posture of the tire on a vehicle. A plurality of inclined main grooves extending in the opening direction are provided, the first inclined sub-grooves are branched from each inclined main groove toward the tread end side, and the first inclined sub-grooves are separated from the second inclined sub-grooves. The groove is further branched toward the tread end side, and each of these inclined sub-grooves is continuously extended in a curved shape without intersecting with any of the other grooves, and each inclined sub-groove is extended. All branch points of are located within 1/4 of the tread width from the pattern center,
Change in the angle of each groove with respect to the tire circumferential direction by 30 °
It is as follows.

Here, the angle of the inclined main groove with respect to the tire circumferential direction is preferably 5 to 40 °, more preferably 10 to 3
In the range of 0 °, the same angle of the first inclined sub groove is set to 20 to 6
The angle of the second inclined sub-groove is extended in the range of 0 °, more preferably in the range of 30 to 50 °, and in the range of 40 to 90 °, and more preferably in the range of 50 to 80 °.

Further, preferably, each of the inclined main grooves located apart from the pattern center is extended to the pattern center together to form a circumferential groove which is substantially continuous in the tire circumferential direction, or By terminating each inclined main groove at the front side position of the pattern center,
An annular land portion that extends including the pattern center and is continuous in the tire circumferential direction is provided.

Further, preferably, the land portions and / or the first inclined sub-grooves, which are defined between the inclined main grooves and taper toward the pattern center side, and the inclined main groove and the first inclined sub groove. The surface height of the taper portion of each land portion that is defined between the two inclined sub-grooves and tapers toward the pattern center side is gradually reduced toward the pattern center side.

Further, the respective inclined main grooves which are located apart from the pattern center are formed in a substantially V shape with each other, or
It is preferable to form them by offsetting each other in the tire circumferential direction, and it is preferable to form a sipe extending substantially parallel to the second inclined sub-groove on each land portion defined by each groove.

[0012]

[Operation] When observing the flow of water in the contact surface of the tire,
In the pattern center area, water is 30 ° from the tire circumferential direction.
The tendency is to discharge to the front side in the range of, and in the side area, there is a tendency to be discharged to the front side somewhat from the side, so if you pay attention only to this point, the inclined groove extending to the pattern center area , The angle range of 0 to 30 ° with respect to the tire circumferential direction, and the gently sloping groove extending to the side area is 60 to 90.
An angle range of ° is effective.

However, when the slanted groove and the gently slanted groove are simply combined, the bending angle from the slanted groove to the gently slanted groove becomes large, and the turbulence of the flow due to the large change of the flow direction causes the drainage. There is the inconvenience of reducing efficiency.

Therefore, in this tire, the first inclined sub groove is smoothly branched from the inclined main groove extending at a small angle with respect to the tire circumferential direction toward the tread end side, and
From the first slanted sub-groove, the second slanted sub-groove is further smoothly branched toward the tread end side, both of the slanted sub-grooves are continuously curved, and each of the grooves is By setting the angle change with respect to the tire circumferential direction to be 30 ° or less, when the tire rolls under load, drainage to the front side of the tire is performed mainly by the inclined main groove and to the side of the tire. The drainage of 2 is provided by both inclined sub-grooves.

In this case, the change in the angle of each groove with respect to the tire circumferential direction is 30 ° or less, and since each of the inclined sub-grooves smoothly branches, the drainage flow and There is no turbulence in the flow due to abrupt changes in the direction of the flow in each of the divergent flows, and the respective drainage flows smoothly in the direction of the observed streamlines. The efficiency can be effectively improved.

By the way, the total flow rate of the water drained through the inclined groove gradually increases toward the downstream side, considering the amount of water flowing into the inclined groove on the way, but To gradually widen the groove width toward the downstream side to a necessary and sufficient extent, the groove width may be too wide and pattern noise may be significantly deteriorated, and the area of the block may be reduced. Since there is a problem in that the rigidity and the ground contact area are reduced, which is also disadvantageous in terms of maneuverability, here, the inclined main groove is changed to the first inclined auxiliary groove, and the first inclined auxiliary groove is changed to the first inclined auxiliary groove. In addition to the inclined main groove, each of the inclined sub-grooves is branched, and in some cases, further inclined sub-grooves are branched to ensure a sufficient total volume of the groove. Large amounts of It makes it possible to smoothly Naru drainage. The reason why the number of the inclined sub-grooves is at least two is to secure a sufficient drainage capacity, and it is undeniable that the drainage capacity is insufficient with only one of them.

Further, here, each of the inclined sub-grooves is extended particularly continuously in a curved shape so that the branch point of the branch groove is close to a tangent circle, and a smooth water shunt that is not bent is formed. It will be possible. Further, the curved groove allows efficient and smooth drainage from the center of the tread to the side.

Further, by extending each of the inclined sub-grooves without intersecting with any of the other grooves, generation of flow turbulence due to flow merging is prevented, and drainage efficiency is improved. Further improvement can be brought about, and in addition, the definition of a small land portion can be prevented, and the land portion rigidity can be sufficiently enhanced. As a result, excellent maneuvering stability can be realized.

Moreover, in this tire, by dividing each inclined sub-groove at a position within 1/4 of the tread width from the pattern center, a sufficient total groove volume is obtained in the central region where wet drainage is dominant. It is possible to obtain the effect of ensuring that the water is drained toward the ground end by quickly branching. In other words,
When at least one of the inclined sub-grooves is branched at a position exceeding 1/4 of the tread width, wet drainage performance is deteriorated due to lack of groove volume at the center of the tread, and conversely 1 of the tread width. Outside / 4, the number of grooves is too large and the effective ground contact surface is reduced, so that maneuverability is disadvantageous.

Here, the angle of the inclined main groove with respect to the tire circumferential direction is in the range of 5 to 40 °, and that of the first and second inclined auxiliary grooves is 20 to 60 ° and 40 to 90, respectively.
In the range of °, the central part of the tread has drainage,
The smooth grounding reduces pattern noise at the same time, and the shoulder part has both drainage toward the grounding end and lateral rigidity of the block to ensure stability. The middle part plays a role in connecting each smoothly.

That is, below the lower limit of each of the above angle ranges, the block rigidity cannot be secured mainly, so that the wear surface and the steering control surface are deteriorated. On the contrary, when the upper limit is exceeded, the block surface deviates from the streamline direction in the tread surface. As a result, the drainage property deteriorates significantly.

In this tire, when each of the inclined main grooves located apart from the pattern center is extended to above the pattern center to form a circumferential groove that is substantially continuous in the tire circumferential direction, It is possible to further improve the drainage performance. On the other hand, when an annular land portion that extends including the pattern center and is continuous in the tire circumferential direction is provided, pattern noise can be reduced. .

By the way, it is defined between the inclined main grooves and / or between the first inclined sub groove and the inclined main groove and the second inclined sub groove, and is tapered toward the pattern center side. When the surface height of the tapered portion of each land portion is gradually reduced toward the pattern center side, the tapered portion is crushed at the time of grounding, and by extension, into the groove of the tapered portion. The escape deformation can be sufficiently prevented, the flow of the drainage can be made extremely smooth, and the drainage efficiency can be further improved.

Moreover, the reduction of the surface height of the tapered portion is
On the other hand, since it contributes to secure the rigidity of the land portion and also secures the contact pressure, it is possible to realize excellent uneven wear resistance and steering stability.

Further, when the inclined main grooves that are separated from each other by the pattern center are formed in a substantially V shape, they are drained to the left and right at the same time, so that the drainage property can be further enhanced. On the other hand, when the inclined main grooves are formed so as to be offset from each other in the tire circumferential direction, the blocks are alternately grounded, so that impact noise can be dispersed and pattern noise can be reduced.

In addition, in this tire, when a sipe extending substantially parallel to the second inclined sub-groove is formed in each land portion defined by each groove, the ground contact property of the tread is improved. At the same time, since the sipes exert an edge effect, grip on a low μ road surface is improved.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a development view illustrating a tread pattern of an invention tire. Since the internal reinforcing structure of the tire is similar to that of a general radial tire, the illustration is omitted here.

In the drawing, C indicates a pattern center, and the pattern center C can be aligned with the tread center as shown, or can be offset from the tread center in the required direction to some extent.

In this example, a plurality of slopes extending in a direction of gradually expanding from the lower side to the upper side with the pattern center C as a boundary in front view of the tire mounting posture on the tread tread portion 1 are shown. The main groove 2 is provided, and each of the inclined main grooves 2 is located at a half pitch in the tire circumferential direction at each half of the pattern center C. In the figure, D indicates the rotation direction of the tire.

Here, each inclined main groove 2 has angles θ ₀ and θ ₁ in the range of 5 to 40 °, preferably 10 to 30 ° with respect to the tire circumferential direction, and the inner end portion thereof has It extends in the tire circumferential direction on the pattern center to provide therewith a circumferential groove 3 which is substantially continuous in the tire circumferential direction, and the outer end of which does not open at the tread end but before this. End at the side position. The outer end of the inclined main groove 2 may be opened at the tread end.

Here, from the inclined main groove 2 at a position within 1/4 of the tread width TW from the pattern center C,
A first inclined sub grooves 4 by smoothly branched, the first inclined sub groove 4, 20 to 60 ° with respect to the tire circumferential direction, preferably an angle theta ₂ in the range of 30 to 50 °, theta ₃ Then, it is extended to the tread end side from the inclined main groove 2 without intersecting any other groove. Incidentally, as shown in the drawing, the first inclined sub-groove 4 which is terminated at the front side position of the tread end can be opened at the tread end.

Further, also at a position within 1/4 of the tread width TW from the pattern center C, the second inclined sub-groove 5 is smoothly branched from the first inclined sub-groove 4, and the 2 inclined sub-grooves 5 with 4 in the tire circumferential direction
The tread is extended at an angle θ ₄ or θ ₅ in the range of 0 to 90 °, preferably 50 to 80 ° to the tread end side from the first inclined sub groove 4 without intersecting any other groove. Open at the end.

Therefore, the second inclined sub-groove 5 can be branched at a position almost the same as the branch position of the first inclined sub-groove 4 or a position near the same.

In addition, in this tire, each groove 2, 4, 5
Of the angle with respect to the tire circumferential direction (θ ₁ −θ ₀ ),
30 for both (θ ₃ −θ ₂ ) and (θ ₅ −θ ₄ ).
The value should be less than °.

In the tire constructed as described above, water in the ground contact surface is discharged through the grooves 2, 4 and 5 in the front and side directions of the tire, respectively. As described above, excellent wet drainage performance can be provided, and by extending the inclined sub-grooves 4 and 5 without intersecting with any other groove, the land rigidity is sufficiently enhanced. As a result, the wear resistance of the land portion can be improved, and the steering stability can be greatly improved.

Further, the branch position of each of the inclined sub-grooves 4 and 5 is changed from the pattern center C to 1 of the tread width TW.
By setting the position within / 4, the groove volume in the central part of the tread becomes sufficient, and excellent wet drainage performance can be exhibited.

By the way, in the embodiment shown here, in addition to the above, between the inclined main grooves 2 and between the first inclined sub-groove 4 and the inclined main groove 2 and the second inclined sub-groove 5. In each of the land portions 6, 7, and 8 which are respectively defined and taper toward the pattern center side, the surface height of each taper portion is preferably indicated by hatching in the figure, Within the range of 10 to 30 mm in the length direction, the width is gradually reduced toward the pattern center side. FIG. 2 is a cross-sectional view along the length direction of the land portion 6, which illustrates this. Here, the surface height of the land portion 6 is reduced by a curved surface that is convex outward in the radial direction of the tire. There is. It should be noted that the reduction of the surface height of each of the land portions 6, 7 and 8 can be realized even with a flat surface.

When the surface height of the tapered portions of the land portions 6, 7, and 8 is reduced in this way, as described above, the drainage efficiency is further improved and the uneven wear resistance and the uneven wear resistance are improved. The steering stability can also be improved.

Further, in the illustrated example, the sipe 9 extending substantially parallel to the second inclined sub-groove 5 is formed in each of the land portions defined by the respective grooves 2, 4 and 5, so that The landing of the land portion is improved, and in addition, by extending the sipe 9 substantially parallel to the second inclined sub-groove 5, the land portion is divided, and the land portions adjacent to each other in the circumferential direction are separated from each other. It is possible to prevent the difference in rigidity from becoming extremely large and prevent uneven wear.

FIG. 3 is a view showing another embodiment of the present invention, in which the portion near the pattern center of the inclined main groove 2 is gradually narrowed toward the pattern center C, and the pattern center side thereof is provided. By arranging the edge of the pattern on the front side of the pattern center C,
An annular land portion 10 that extends to include the pattern center C and is continuous in the circumferential direction is formed, and an auxiliary groove 11 that extends from the tread end portion to the buttress portion is substantially parallel to the first inclined sub groove 4. It was formed in.

Therefore, here, between the inclined main grooves 3,
The land portion that is gradually tapered toward the pattern center side is not formed.

On the other hand, the first inclined sub-groove 4 and
Between the inclined main groove 2 and the second inclined sub-groove 5, land portions 7 and 8 having the same tapered end portions as described above are defined, so that the land portions 7 and 8 are formed. In the taper portion of, the surface height is reduced in the same manner as described above.

The other construction of the tire of this example is almost the same as that of the above-mentioned embodiment except that the sipe is not formed in any land portion.

Therefore, according to this tire, it is possible to obtain the same effect as that of the above-described embodiment, and it is possible to reduce the pattern noise by the smooth rotary grounding due to the existence of the annular land portion 10. .

[Comparative Example] A comparative test of the invention tire and the conventional tire regarding wet drainage performance, steering stability performance on dry road surface, uneven wear resistance performance and pattern noise will be described below.

◎ Test tire size is 225/50 R16 and tread width is 200
mm passenger car tires.

Invention Tire 1 A tire having the tread pattern shown in FIG.
Those having the dimensional specifications shown in Table 1.

[Table 1]

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

[Table 2]

Conventional tire A tire having a tread pattern shown in FIG. This pneumatic tire is a typical example of a tread pattern of a conventional pneumatic tire, and includes five circumferential grooves and a plurality of circumferentially-spaced directional inclined grooves as shown in the figure. Are arranged. Tire size is 225 / 50R
16, the tread width TW is about 200 mm, which are the same as those in the above embodiment. The circumferential groove 21 provided at the center of the tread is a narrow groove having a width of 4 mm, and a pair of circumferential grooves 22 having a groove width of 11 mm are provided on the left and right sides of the tread. A pair of circumferential grooves 23 having a groove width of 10 mm are provided at a position corresponding to about 1/4 of the width, and the four thick circumferential grooves and a large number of directional inclined grooves 24, 25, 26 are wet on the wet road surface. It contributes to the drainage of water.

◎ Test method Each tire was mounted on an actual vehicle with a filling internal pressure of 2.3 kg / cm ² , and under a load condition equivalent to one person's riding, wet drainage performance was measured when running straight on a wet road surface with a water depth of 5 mm. , The rate of occurrence of hydroplaning phenomenon was measured and evaluated. In addition, the wet road surface with a water depth of 5 mm had a radius of 8 mm.
In addition to measuring the limit lateral G when turning at 0 m, the speed at which the hydroplaning phenomenon occurred was measured and evaluated, and the steering stability performance on dry road surface was determined by sports running on a dry circuit course in various modes. Evaluated by the feeling of a test driver, the uneven wear resistance is 5000 on general roads (city areas, highways, mountain slope curves).
The degree of wear of the tread surface after traveling in the km mode was visually evaluated, and the pattern noise was evaluated by measuring the noise inside the vehicle when coasting from 100 km / h on a straight smooth road.

◎ Test Results The results of the above tests are shown in Table 3 with an index of 100 using the conventional tire as a control. The larger the index value, the better the result.

[0052]

[Table 3]

[0053]

As is apparent from the above comparative example, according to the present invention, excellent steering stability on a dry road surface can be ensured, and pattern noise can be suppressed sufficiently low to increase wet drainage performance. It is possible to improve the wear resistance and also effectively improve the wear resistance.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a tread pattern of an invention tire.

FIG. 2 is a diagram illustrating a manner of reducing the height of a tapered land portion.

FIG. 3 is a diagram illustrating another tread pattern of the invention tire.

FIG. 4 is a diagram illustrating a tread pattern of a conventional tire.

[Explanation of symbols]

1 tread tread 2 inclined main groove 3 circumferential groove 4 first inclined auxiliary groove 5 second inclined auxiliary groove 6, 7, 8 land portion 9 sipes 10 annular land portion 11 auxiliary groove C pattern center TW tread width θ ₀ ~ Θ ₅ angle

Claims (9)

[Claims] 1. A plurality of inclined main grooves extending in a direction of gradually expanding from a lower side to an upper side with a pattern center as a boundary in a front view of a tire mounting posture on a vehicle are provided on a tread surface. , From each inclined main groove, the first inclined sub-groove is branched toward the tread end side, and from this first inclined sub-groove, the second inclined sub-groove is further branched toward the tread end side, Each of these inclined sub-grooves is made to extend continuously in a curved shape without intersecting any of the other grooves, and the branch points of each of the inclined sub-grooves are set to the tread width from the pattern center. Position within 1/4 and change the angle of each groove with respect to the tire circumferential direction by 30 °
The following pneumatic radial tires. 2. The angle of the inclined main groove with respect to the tire circumferential direction is set to 5 to 40 °, and the same angles of the first and second inclined sub grooves are set to 20 to 60 ° and 40 to 90 °, respectively. The pneumatic radial tire according to claim 1. 3. A circumferential groove that is substantially continuous in the tire circumferential direction is formed by extending the respective tilted main grooves that are located apart from the pattern center up to the pattern center. 2. The pneumatic radial tire described in 2. 4. The pneumatic radial tire according to claim 1, further comprising an annular land portion extending in a circumferential direction of the tire including the pattern center. 5. The surface height of the tapering portion of each land portion defined between the inclined main grooves and tapering toward the pattern center side is gradually reduced toward the pattern center side. The pneumatic radial tire according to any one of claims 1 to 4. 6. A first inclined sub groove, an inclined main groove and a second inclined sub groove.
7. The surface height of the taper portion of each land portion which is defined between the inclined sub-groove and the taper toward the pattern center side is gradually reduced toward the pattern center side. The pneumatic radial tire according to any one of 1 to 5. 7. The pneumatic radial tire according to any one of claims 1 to 6, wherein each of the inclined main grooves located apart from the pattern center is formed in a substantially V shape. 8. The pneumatic radial tire according to any one of claims 1 to 6, wherein each of the inclined main grooves located apart from the pattern center is formed by offsetting each other in the tire circumferential direction. 9. The pneumatic device according to claim 1, wherein sipes extending substantially parallel to the second inclined sub-groove are formed in each land portion defined by each groove. Radial tires.