JP2001071709A - Pneumatic tire having directional pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having a directional pattern improved in steering stability and noise reduction performance while securing excellent drainage performance. SOLUTION: Two circumferential direction main grooves 2 are provided in a tread center area, and an inclining land part 5 symmetrically extending and inclining to a tread center line C is partitioned on each of side parts of the circumferential direction main grooves 2. A chamfer part 8 with the height gradually decreasing toward the tip end is provided on a tapered end part of the inclining land part 5 on a circumferential direction main groove side, and the chamfer part 8 is connected with another inclining land part 5 by a connection part 9 provided on an inclining groove 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-performance pneumatic tire having a so-called directional pattern and excellent in athletic performance. It is improved without sacrificing.

[0002]

2. Description of the Related Art Among the main performances of tires, drainage performance,
In order to improve steering stability performance and low noise performance,
It is common to adopt the following configurations, respectively.

[0003] First, with respect to the drainage performance, based on a block pattern consisting of a combination of a circumferential main groove and an inclined groove, drainage in the tire circumferential direction is performed by the circumferential main groove, and lateral drainage is performed by the inclined groove. In addition to promoting, increasing the negative rate, increasing the inflow efficiency of water into the groove, and adopting a high angle groove that makes the inclination of the inclined groove closer to the tread circumferential direction, especially in the central area of the tread It is widely practiced to quickly and smoothly drain the tire in the circumferential direction.

In order to improve the steering stability, it is necessary to increase the rigidity of the block by raising a part of the inclined groove or the like. Further, for the low noise performance, the inclined groove is opened in the circumferential main groove. It is widely practiced to stop without stopping to suppress the impact and vibration of the block to reduce the pattern noise.

[0005] However, if the above-mentioned configurations are combined and applied to improve these performances, the following inconveniences arise. That is, as represented by a circumferential main groove for drainage in the tire circumferential direction and an inclined groove for lateral drainage, under a configuration in which grooves having different angles cross or branch each other, The water flowing from each groove collides and the water flow is disturbed,
Bubbles may be generated and the drainage performance may be deteriorated.In addition, block stiffness and therefore steering stability are difficult to secure on the sloping land formed by the high-angle sloping grooves. If the operation is terminated without opening in the groove, the drainage performance is reduced.

[0006] Accordingly, a technique for improving the drainage performance, the steering stability performance, and the low noise performance without sacrificing other performances has not yet been sufficiently established.

[0007]

SUMMARY OF THE INVENTION In order to improve each of the above-mentioned performances, that is, the drainage performance, the steering stability performance and the low noise performance, first, the applicant has first made the following.
A pneumatic radial tire according to JP-A-9-2025 has been proposed.

[0008] This is a plurality of inclined main grooves extending in a pattern center area from a pair of circumferential main grooves toward the pattern end side, and inclining in the same direction with respect to the circumferential main grooves and opening at the tread grounding end. In a pneumatic radial tire provided with grooves, each inclined main groove is composed of a steeply inclined portion located in the vicinity of the pattern center area and a gentle inclined portion located in the vicinity of the tread contact edge. The angle with respect to the tread circumferential direction is 0 to 30 °, the same angle of the gentle slope portion is 70 to 90 °, and the land portion defined by the circumferential main groove and the inclined main groove has a tapered end on the tread central region side. The surface height of the portion is smoothly reduced toward the tip.

The present invention is a further improvement of such a pneumatic radial tire according to the earlier proposal of the applicant, and the object of the invention is to control the steering while ensuring excellent drainage performance. An object of the present invention is to provide a pneumatic tire with further improved stability performance and low noise performance.

[0010]

A pneumatic tire having a directional pattern according to the present invention is provided with at least one circumferential main groove in a central region of a tread and each side portion of the circumferential main groove. Pneumatic tire having a directional pattern that defines an inclined land portion extending symmetrically inclined with respect to the tread center line, wherein a tapered end portion on the circumferential main groove side of the inclined land portion has a tip. , A chamfered portion whose height gradually decreases is provided, and this chamfered portion is connected to one inclined land portion by a connecting portion located in an inclined groove contributing to the division of the inclined land portion.

In such a tire, since the inclined groove contributing to the section of the inclined land portion is opened in the circumferential main groove, high drainage performance can be provided.

Further, in this tire, a chamfered portion whose height gradually decreases toward the tip is provided at the tapered end portion of the inclined land portion on the circumferential main groove side, so that drainage performance can be further improved. In addition to this, it is possible to improve the ground contact property and the steering stability performance while increasing the block rigidity.

Moreover, in this tire, the chamfered portion is connected to one of the adjacent inclined land portions by a connecting portion provided in the inclined groove, thereby further increasing the block rigidity and further improving the steering stability performance. On the other hand, by making the inclined groove shallow by the connecting portion itself, the sound pressure can be suppressed by reducing the groove volume, and the pattern noise can be effectively reduced.

In such a tire, more preferably, the surface height of the connecting portion is changed to be the same as the surface height of the chamfered portion in a cross section along the inclined groove, and preferably the maximum surface height of the connecting portion is changed. Is 25 to 90% of the depth of the circumferential main groove as measured from the groove bottom of the circumferential main groove. Further, it is preferable that the cross-sectional shape of the connecting portion along the inclined groove is a substantially triangular shape extending in the groove bottom direction.

Here, when the surface height of the connecting portion is changed to be the same as the surface height of the chamfered portion, the drainage performance, the contact property, the steering stability performance, etc. are not sacrificed, and the slope land portion is not sacrificed. The stiffness of the tip can advantageously be increased.

When the maximum surface height of the connecting portion is in the range of 25 to 90% of the depth of the circumferential main groove, the steering stability and the low noise performance are ensured while ensuring excellent drainage performance. Can be compatible at a high level. That is, when the maximum surface height of the connecting portion is set to 90% or less of the depth of the circumferential main groove, a gap surely exists between the connecting portion and the tread contact surface. Just before the water enters the ground plane, the water drawn near the connection and chamfer is
It is possible to flow down the inclined groove sufficiently smoothly through the gap. On the other hand, when the maximum surface height of the connecting portion is set to a height exceeding 90%, the gap becomes extremely small, and the drainage performance is reduced.

When the maximum surface height of the connecting portion is set to 25% or less of the depth of the circumferential main groove, the height of the connecting portion becomes too low, and the reinforcing effect on the chamfered portion is reduced. Since the opening area of the inclined groove with respect to the circumferential main groove is too large, both the steering stability performance and the low noise performance are reduced.

In order to improve the drainage performance, steering stability performance and low noise performance in a high level in a well-balanced manner,
It is particularly preferable that the surface height of the connecting portion is 40 to 60% of the depth of the circumferential main groove.

If the cross section of the connecting portion is substantially triangular in shape extending in the groove bottom direction, the flow resistance of drainage due to the presence of the connecting portion is reduced, and excellent drainage performance is secured. can do. In addition, in this connection part shape, the stepping side part of it is a gentle slope,
The resistance to water flowing into the inclined groove can be reduced, and the kick-out side of the inclined groove also has a gentle slope, so that the drainage that exceeds the top of the connecting part is smooth without disturbing the flow. Can flow down.

[0020] More preferably, the connecting portion has a cross-sectional shape along the inclined groove, and the kick-out side portion has a gentler slope than the step-in side portion. In this case, it is particularly preferable that the inclination angle of the kick-out side portion with respect to the tire radial direction is 45 ° or more.

According to this, the cross-sectional shape of the connecting portion along the inclined groove has a gentler slope on the kick-out side than on the step-on side, thereby ensuring both block rigidity and smooth drainage. it can. That is, the gentle gradient effect on the kick-out side is large. In addition, since the head portion of the drainage becomes smaller by making the kick-out side portion of the connecting portion a gentle slope itself, the drainage performance increases and the chamfered portion becomes adjacent to the inclined portion over a longer distance. It can be connected to the land, and steering stability is also improved. Further, the lowering of the sound pressure due to the reduction of the groove volume improves the low noise performance.

Here, when the inclination angle of the kick-out side portion of the connecting portion is 45 ° or more, the generation of bubbles due to the turbulence of the water flow can be more reliably prevented, so that the drainage can be performed more smoothly. Will be By the way, this inclination angle is 60
If it is larger than °, the slope of the kick-out side part becomes too gentle, the volume of the inclined groove decreases, and the drainage performance must be reduced, so this inclination angle is in the range of 45 ° to 60 °. Is preferred.

Further, it is preferable that the chamfered portion of the tapered end portion of the inclined land portion has a surface formed by a curved surface whose height gradually changes toward the front end side and becomes convex outward in the radial direction. . In this case, crushing at the time of grounding of the tapered end portion, and eventually escape deformation into the groove is more effectively prevented, drainage is sufficiently smoothed, and at the same time, the contact surface pressure at the end portion is reduced. By appropriately increasing the steering stability, the steering stability performance can be advantageously improved.

More preferably, in such a tire, a rib-shaped land portion which is continuous in the circumferential direction is formed in the central region of the tread, and the steering stability performance especially at a small steering angle is improved under the rigidity of the rib-shaped land portion itself. Orient.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a development view of a tread pattern showing one embodiment. Here, a pair of circumferential main grooves 2 extending linearly continuously in the tread circumferential direction are provided in a central region of a tread portion 1 at the center of the tread. Formed symmetrically with respect to the line C, one rib-shaped land portion 3 extending continuously in the circumferential direction is defined at the center of the tread.

Then, on each side of the rib-shaped land portion 3 separated from the circumferential main groove 2 by a front view of the tire,
By forming the respective inclined grooves 4 extending in a direction away from each other upward from below, under a mutual offset state in the tread circumferential direction, from a position adjacent to the circumferential main groove 2, In the figure, each inclined land portion 5 reaching the vicinity of the tread end E via the tread ground contact end TE is sectioned so as to be symmetrically inclined with respect to the tread center line C.

At a substantially central position between the tread center line C and the tread end E, there is provided a single circumferential groove 6 extending in a zigzag manner in the circumferential direction of the tread. At the approximate center of the inclined grooves 4, the inclined grooves 4 are substantially extended from the position of the tread edge E to the position of the tread contact edge TE.
And an inclined sub-groove 7 extending substantially in parallel with.

Here, the surface height of the tapered end portion on the tread center line C side of the inclined land portion 5 defined by the circumferential main groove 2 and the two inclined grooves 4 is shown by hatching in the figure. As shown, a chamfered portion 8 is provided which is smoothly reduced toward its tip end and has a gradually changing height. Preferably, the height is reduced so that the chamfered portion 8 is located outside the tire in the radial direction. It is realized under the mode of forming a convex curved surface.

Here, such a chamfered portion 8 is
The connecting portion 9 provided in the inclined groove 4 contributing to the section of the inclined land portion 5 is connected to one adjacent inclined land portion 5. In this case, at least a part of the chamfered portion 8 is connected to a wall surface of the adjacent inclined land portion 5. Is preferred.

As shown in FIG. 2, which shows an enlarged sectional view taken along the line II-II of FIG. 1, the connecting portion 9 has a substantially triangular cross section along the inclined groove 4 as a whole. It has a stepping-side part X and a kick-out side part Y. Here, it is preferable that the surface height of the stepping-side portion X is changed in the same manner as that of the chamfered portion 8, and the inclination angle α of the kick-out side portion Y with respect to the tire radial direction is 45 ° to 60 °. This is particularly preferred.

It is preferable that the connecting portion 9 has such a sectional shape that the kick-out side portion Y has a gentler gradient than the step-side portion X, and the maximum surface height of the connecting portion 9 is circumferential. It is preferable that the depth is 25 to 90% of the depth of the circumferential main groove 2 measured from the groove bottom of the main groove 2.

Further, as shown in the figure, corresponding to the position where each inclined land portion 5 comes closest to the rib-shaped land portion 3, a circumferential main groove 2 is formed on each side of the rib-shaped land portion 3. A pseudo-land portion 10 having a substantially triangular shape gradually increasing in width toward the upper side of the figure is provided so as not to reach the entire width of the pseudo-land portion. It is almost equal to that of the part 5.

In addition, as shown in the figure, the height of the land portion divided by the zigzag-shaped circumferential groove 6 is increased toward the circumferential groove 6 at a portion adjacent to the circumferential groove 6. Tapered surfaces 11, 12, 13, 14 that are gradually reduced are provided. Here, these tapered surfaces 11, 12, 13, 1
4 and the above-described pseudo land portion 10 are each separated from the grooves 2 and 6 by the upright walls of the grooves 2 and 6 as illustrated in the cross-sectional view in FIG.

The tire constructed as described above, in particular,
In the tread pattern, by providing two circumferential main grooves 2, drainage in the tire circumferential direction is improved as compared with a single main groove 2, and the occurrence of the hydroplaning phenomenon is effectively prevented. In addition, the responsiveness at the time of a small steering angle can be enhanced by the rib-shaped land portion 3, and the steering stability performance on a dry road surface can be improved. In addition, this rib-shaped land portion 3
It also functions to effectively reduce pattern noise as compared to a case without it.

The angle of the inclined groove 4 with respect to the circumferential direction of the tread is gradually increased from the tread central region side toward the tread ground contact end side.
The, in the vicinity of the tread center region is steeper partial average angle theta ₁ is less, by a tread ground contact end near to the average angle theta ₂ is large gentle slope portion, the groove angle, the drainage in the contact surface of the tread Smooth drainage can be ensured by sufficiently approaching the streamline direction. The average angle θ ₃ of the circumferential groove 6 with respect to the tread circumferential direction can be sufficiently reduced to improve the drainage in the circumferential direction.
In addition, the circumferential groove 6 can effectively contribute to the improvement of the steering stability performance by promoting the blocking by dividing each inclined land portion 5 into two parts, thereby improving the contact property.

As described above, the chamfered portion 8 functions to prevent the tapered end portion of the inclined land portion from escaping into the groove, thereby sufficiently smoothing the drainage, and further, the tapered portion. The contact pressure at the end portion can be increased to effectively function the steering stability. By connecting the chamfered portion 8 to one of the adjacent inclined land portions by the connecting portion 9 provided in the inclined groove 4, the rigidity of the chamfered portion 8 is further increased, and the steering stability performance is further improved. In addition, the low noise performance can be improved under the condition that the inclined groove 4 is made shallow by the connecting portion itself.

Here, by changing the surface height of the stepping-side portion X of the connecting portion 9 in the same manner as that of the chamfered portion 8, as described above, without sacrificing drainage performance, etc. The rigidity of the tip portion of the inclined land portion 5 can be advantageously increased. In addition, by making the kick-out side portion Y gentler in gradient than the step-in side portion X, it is possible to achieve both effective block rigidity and effective drainage. and again,
By setting the inclination angle α of the kick-out side portion of the connecting portion 9 in the range of 45 ° to 60 °, drainage in the tread width direction is performed sufficiently smoothly and quickly without disturbing the water flow due to generation of bubbles. Can be made. In addition, by setting the maximum surface height of the connecting portion 9 to 25 to 90% of the depth of the circumferential main groove 2, as described above, while maintaining excellent drainage performance, the steering stability performance is improved. And low noise performance can be compatible at a high level.

By the way, the pseudo land portion 10 can effectively contribute to the smooth flow of drainage into the inclined groove in relation to its own shape, arrangement pitch, etc. 11, 12, 13, and 14 can function to advantageously prevent a decrease in land rigidity and provide excellent steering stability performance while improving drainage performance by the circumferential groove 6.

[0039]

EXAMPLES Hereinafter, comparative tests on drainage performance, steering stability on a dry road surface, and low noise performance performed on an example tire and a conventional tire will be described. ◎ Test tire size is 205 / 55R16, tread contact width (W)
Is a 170mm tire. Example tire A tire having a tread pattern shown in FIG. 1,
It had the dimensional specifications shown in Table 1.

[0040]

[Table 1]

Conventional tire A tire having a tread pattern shown in FIG.
It had the dimensional specifications shown in Table 2.

[0042]

[Table 2]

◎ Test method When the air pressure charged into the tire was 2.3 kg / cm ² and the load was equivalent to two passengers, the drainage performance was as follows:
Measure and evaluate the critical speed of hydroplaning when traveling straight on a wet road with a depth of 5 mm, and measure and evaluate the lateral limit G of the hydroplaning phenomenon when turning on a wet road with a radius of 80 m and a depth of 5 mm. did.
In addition, the steering stability performance was evaluated based on the feeling of a test driver during sports driving on a dry circuit course in various driving modes. The low noise performance was evaluated based on the feeling of the sound inside the vehicle when the vehicle was coasting from 100 km / h on a straight road.

試 験 Test Results The results of the tests are shown in Table 3 as indexes using the conventional tire as a control. The larger the index value, the better the result.

[0045]

[Table 3]

As shown in Table 3, it is clear that in the example tires, drainage performance, steering stability performance and low noise performance can be improved as compared with the conventional tires.

[0047]

As is clear from the above description, according to the present invention, sufficient drainage performance is ensured,
Both steering stability performance and low noise performance can be effectively improved.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3 is an explanatory sectional view of a pseudo land portion and a tapered surface.

FIG. 4 is a development view of a tread pattern showing a conventional tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tread part 2 Circumferential main groove 3 Rib-shaped land part 4 Inclined groove 5 Inclined land part 6 Peripheral groove 7 Inclined sub-groove 8 Chamfered part 9 Connection part 10 Simulated land part C Tread center line E Tread end TE Tread ground end X Depressed Side part Y Kick-out side part α Tilt angle

Claims (8)

[Claims] At least one circumferential main groove is provided in a central region of a tread, and an inclined land portion extending symmetrically with respect to a tread center line is provided on each side of the circumferential main groove. A pneumatic tire having a directional pattern formed by partitioning, wherein the inclined land portion is provided with a chamfered portion whose height gradually decreases toward the tip at a tapered end portion on a circumferential main groove side, and the chamfered portion is provided. A pneumatic tire having a directional pattern in which is connected to one adjacent inclined land portion by a connecting portion located in an inclined groove contributing to a section of the inclined land portion. 2. The pneumatic tire having a directional pattern according to claim 1, wherein the surface height of the connecting portion is changed to be the same as the surface height of the chamfered portion in a cross section along the inclined groove. 3. The directionality according to claim 1, wherein the maximum surface height of the connecting portion is 25 to 90% of the depth of the circumferential main groove as measured from the groove bottom of the circumferential main groove. A pneumatic tire having a pattern. 4. A cross-sectional shape of the connecting portion along the inclined groove is substantially triangular extending in a groove bottom direction.
A pneumatic tire having a directional pattern according to any one of claims 1 to 3. 5. A pneumatic pneumatic device having a directional pattern according to claim 1, wherein the connecting portion has a cross-sectional shape along the inclined groove, and the kick-out portion has a gentler slope than the step-in portion. tire. 6. The pneumatic tire having a directional pattern according to claim 1, wherein an inclination angle of a kick-out side portion of the connecting portion with respect to a tire radial direction is 45 ° or more. 7. The directional pattern according to claim 1, wherein the surface of the chamfered portion is constituted by a curved surface whose height gradually changes and becomes convex outward in the radial direction. Pneumatic tire. 8. A pneumatic tire having a directional pattern according to claim 1, wherein a circumferentially continuous rib-shaped land portion is formed in a central region of the tread.