JP2009051453A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire enhancing wet performance, in the tire having a rib pattern. <P>SOLUTION: A level difference h is provided at height of a tread surface 5a at front and rear sides in a tire circumferential direction for clamping a thin groove 9 formed on the rib 7 in the circumferential direction, a wall surface of the thin groove 9b at a lower side of the level difference h is formed to a recessed bent surface, and a wide space 9s is formed between a wall surface 9a at an opposite side opposed to the bent surface and itself. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire in which wet performance is improved in a tire having a rib pattern.

  Conventionally, a tread pattern based on a rib pattern in which a plurality of ribs extending in the tire circumferential direction has been employed for heavy-duty pneumatic tires used particularly under high loads. And in order to improve braking / driving performance, it has been widely practiced to make the tread surface flexible by forming a large number of narrow grooves with both ends opened in the main grooves on both sides at intervals in the circumferential direction of the rib. (For example, see Patent Document 1).

The narrow grooves 9 formed in the ribs in this way are formed so that the planar groove walls 9a and 9b parallel to each other are generally orthogonal to the tread surface 5a, as shown in the tire circumferential cross section of FIG. Therefore, when the road surface of the tread is closed so that the walls 9a and 9b of the narrow groove 9 are brought into close contact with each other by a compressive load and the vehicle runs on a wet road surface, the water between the tread surface 5a and the road surface is closed. There was a problem that the film could not be taken into the narrow groove 9 and the frictional resistance when the tire was braked was lowered, so that the braking performance on the wet road surface was lowered.
JP-A-6-239109

  An object of the present invention is to solve the conventional problems described above, and to provide a pneumatic tire that improves wet performance in a tire having a rib pattern.

  In order to achieve the above object, the pneumatic tire of the present invention forms a plurality of main grooves extending in the tire circumferential direction on the tread surface, and has both ends spaced apart in the circumferential direction of the ribs defined by the main grooves. In the pneumatic tire in which a large number of narrow grooves opening in the main groove are formed, a step is provided in the height of the tread surface before and after the tire circumferential direction across the narrow grooves, and the narrow grooves on the low step side are provided. The wall surface is formed in a concave bent surface, and a widened space is formed between the opposite wall surface facing the bent surface.

Moreover, in the structure mentioned above, it is preferable to comprise as described in the following (1)-(5).
(1) The bending surface is formed into a concave curved surface having at least one bending point.
(2) The groove width on the tread surface of the narrow groove is set to 0.5 to 1.5 mm, and the arrangement interval in the tire circumferential direction is set to 25 to 50 mm.
(3) The maximum distance between both wall surfaces in the widened space is set to 0.5 to 3.0 mm.
(4) The size of the step is 15-30% of the depth of the narrow groove from the tread surface on the higher step side.
(5) Used as a heavy duty tire.

  According to the present invention, a step is provided in the height of the tread surface before and after the tire circumferential direction across the narrow groove formed in the circumferential rib, and the wall surface of the narrow groove on the lower side of the step is a concave bent surface. Since the widened space is formed between the wall surface on the opposite side opposite to the bent surface, the narrow groove on the tread surface at the time of tire contact is formed on the concave bent surface on the lower step side on the higher step side. By entering the wall surface so that it swells, the space between both wall surfaces is opened on the tread surface side so that the water film on the road surface can easily flow into the narrow groove. Thereby, the water film on a road surface reduces and the braking performance in a wet road surface can be improved. In addition, after the ground contact is completed, the water flowing into the narrow groove can be discharged to the outside by the centrifugal force of the tire along with the restoration of the wall surface of the narrow groove on the higher step side.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a half sectional view showing a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is a partial plan view showing an example of a tread surface of the tire of FIG.

  In FIG. 1, a pneumatic tire 1 includes a bead core 4 in which a carcass layer 3 is mounted between a pair of left and right bead portions 2 and 2, and both end portions 3 a and 3 a of the carcass layer 3 are embedded in bead portions 2 and 2, 4 is folded back from the inside to the outside of the tire. A belt layer 6 is disposed on the outer peripheral side of the carcass layer 3 in the tread portion 5.

  As shown in FIG. 2, a plurality of (four in the figure) main grooves 7 extending in the tire circumferential direction T are formed on the tread surface 5 a, and the ribs 8 defined by these main grooves 7, 7 are arranged in the circumferential direction. Are formed with a large number of narrow grooves 9 that open at both ends to the main grooves 7 and 7 with a distance p.

  In the pneumatic tire 1 of the present invention, as shown in the cross section in the tire circumferential direction of FIG. 3, a step h is provided at the height of the tread surface 5 a before and after the tire circumferential direction T across the narrow groove 9. The height of the surface 5a differs before and after the narrow groove 9 as a boundary with respect to the tire circumferential direction T. The wall surface 9b of the narrow groove 9 on the side where the level difference h is low is formed in a concave bent surface, and a widened space 9s is formed between the wall surface 9a on the opposite side facing the bent surface.

  Thus, the tread surface 5a in which the narrow groove 9 is formed in the rib 8 has a step h as shown in FIG. 4 (b) when the tire is grounded from the state of FIG. 4 (a) before the tire is grounded. The high-side wall surface 9a swells due to compression of the tread surface 5a, and is deformed so as to close the wide space 9s toward the bent surface of the low-side wall surface 9b. However, since both the wall surfaces 9a and 9b are opened outward on the tread surface 5a side, a water film interposed between the tread surface 5a and the road surface flows into the narrow groove 9 from the opening side of the wall surfaces 9a and 9b. By reducing the water film, the braking performance on the wet road surface can be improved. After the ground contact is completed, the water flowing into the narrow groove 9 is discharged to the outside by the centrifugal force of the tire due to the restoration of the wall surface 9a.

  As described above, since the concave bent surface is formed in the groove wall 9b, the rib rigidity is lowered on the side where the level difference h is low. However, since the wide space 9s is substantially closed due to the deformation of the wall surface 9a at the time of ground contact, the deformation of the wall surface 9a compensates for a decrease in the rib rigidity on the side where the level difference h is low, and has good uneven wear resistance. Can be held.

  FIG. 5 is a cross-sectional view corresponding to FIG. 3 showing another embodiment of the pneumatic tire 1 of the present invention. In the present embodiment, the tread surface 5a before and after the tire circumferential direction sandwiching the narrow groove 9 is formed in an inclined surface inclined in one direction, and a step is formed in the height of the tread surface 5a before and after the tire circumferential direction sandwiching the narrow groove 9 h is provided. And the wall surface 9b of the narrow groove 9 in the low side of the level | step difference h is formed in a concave bent surface, and the wide space 9s is formed between the wall surface 9a of the opposite side which opposes this.

  The operational effects of the embodiment of FIG. 5 are the same as in the case of FIG. The embodiment of FIG. 5 is preferably applied particularly to a tire in which the rotation direction is designated. That is, when applied to a tire whose rotation direction is designated, the tread surface 5a on the side where the level difference h is high is low when the tire contacts the ground by arranging the arrow Y direction in FIG. 5 in accordance with the rotation direction of the tire. Since the contact is made before the tread surface 5a on the side, the groove wall 9a is smoothly deformed toward the groove wall 9b and effectively acts on uneven wear resistance.

  However, when the embodiment of FIG. 5 is applied to a tire in which the rotation direction is not specified, the tread surface 5a is mutually between the adjacent ribs 7 and 7 or between the arbitrary ribs 7 and 7. It is preferable to arrange them so that the inclination directions of these are different.

  In the present invention, the concave bent surface of the wall surface 9b may be formed into a concave curved surface having at least one bent point 9z (two in the figure) as shown in FIG. As a result, as shown in FIG. 4B, when the tire is in contact with the ground, a gap is likely to remain between the wall surface 9a and the wall surface 9b, and the flow of the water film into the narrow groove 9 is promoted. Can do.

  The groove width w1 (see FIG. 4 (a)) at the opening of the narrow groove 9 with respect to the tread surface 5a is usually set to 0.5 to 1.5 mm, and the groove extends from the tread surface 5a on the higher step h side. The depth H of the narrow groove 9 to the bottom surface is set to 50 to 75%, preferably about 5 to 10 mm, of the depth of the main groove 7.

  On the other hand, the maximum interval w2 between both wall surfaces 9a and 9b in the wide space 9s in the narrow groove 9 is 0.5 to 3.0 mm, preferably 0.6 to 2 mm, depending on the size of the tire and the size of the step h. It is good to set to the range of 5 mm. Thereby, the space formation in the narrow groove 9 at the time of grounding can be made favorable, and good wet performance can be ensured. When the maximum interval w2 is smaller than the above range, the effect of improving the wet performance is reduced, and when it is larger than the above range, the uneven wear resistance is reduced.

  Furthermore, the size of the step h may be set to 15 to 30%, preferably 20 to 25%, of the narrow groove depth H (see FIG. 4A) from the tread surface 5a on the higher side of the step h. As a result, the water film on the road surface can easily flow into the narrow groove 9 to ensure good braking performance on the wet road surface. If the level difference h is less than 15% of the depth H, the effect of improving the wet performance is reduced, and if it exceeds 30%, uneven wear is caused.

  The interval p (see FIG. 2) between the narrow grooves 9 in the tire circumferential direction T may be a size adopted in a known tire, preferably 25 to 50 mm, and more preferably 30 to 40 mm. Thereby, dry performance and wet performance can be made to balance in a good balance. When the distance p is less than 25 mm, the dry performance is lowered, and when it is more than 50 mm, the wet performance is lowered.

  FIG. 6 is a partial plan view showing a tread surface 5a of a pneumatic tire 1 according to another embodiment of the present invention. In the central region of the tread surface 5a, three main grooves 7 extending in the tire circumferential direction T are formed. In both shoulder regions, lug grooves 10 extending in the tire width direction are formed at intervals in the tire circumferential direction. Then, in the circumferential direction of the rib 8 defined by these main grooves 7 and 7, a large number of narrow grooves 9 extending in the tire width direction with an interval p and having both ends opened to the main grooves 7 and 7 are formed. is doing. In addition, also about the narrow groove 9 by this embodiment, since the structure similar to FIG.3 and FIG.5 mentioned above is employ | adopted as it is and there exists the same effect, the overlapping description is abbreviate | omitted.

  As described above, the pneumatic tire 1 of the present invention is provided with a step h at the height of the tread surface 5a before and after the tire circumferential direction T across the narrow groove 9 formed in the circumferential rib 8. The wall surface of the narrow groove 9b on the low h side is formed in a concave bent surface, and the wall surface space 9s is formed between the wall surface 9a on the opposite side to the concave wall surface. The present invention can be widely applied to heavy-duty pneumatic tires in which circumferential ribs 8 are formed on the tread surface 5a for use under high loads.

  The tire size is 295 / 80R22.5, the tread pattern is FIG. 6, the step h in the tire circumferential direction across the narrow groove 9 formed in the two ribs 7, 7, and the tire circumferential cross-sectional shape of the narrow groove 9 A conventional tire, an inventive tire, and a comparative tire were produced by varying the maximum distance w2 between the wall surfaces 9a, 9b in the wide space 9s of the narrow groove 9 as shown in Table 1. In each tire, the circumferential interval p of the narrow grooves 9 was 30 mm, the width w1 of the opening of the narrow grooves 9 was 1.0 mm, and the depth H of the narrow grooves 9 was 12 mm.

  For these three types of tires, the braking performance on wet road surfaces was evaluated by the following test method, and the results are shown in Table 1 using an index with the conventional tire as 100. The larger the value, the better. Furthermore, in addition to the above test, the evaluation of uneven wear resistance was also carried out by the following test method, and the results are also shown in Table 1 as above.

[Brake performance on wet road surface]
Each tire is assembled in a rim (size: 22.5 × 8.25), filled with air pressure of 900 kPa, mounted on the front and rear wheels of a 2-D4 vehicle, and subjected to a braking test on an asphalt road surface with a water depth of 5 mm. Evaluation was based on the braking distance.

[Uneven wear resistance]
Each tire is assembled in a rim (size: 22.5 × 8.25), filled with air pressure of 900 kPa, and driven by an indoor drum tester at a speed of 80 km / h and a load of 35.7 kN for 60,000 km. The degree of uneven wear (uneven wear amount and size) on the tread surface of each tire after running was measured and evaluated based on the results.

  From Table 1, it can be seen that the inventive tire has improved braking performance on the wet road surface as compared with the conventional tire and the comparative tire.

1 is a half sectional view showing a pneumatic tire according to an embodiment of the present invention. It is a partial top view which shows an example of the tread surface of the tire of FIG. FIG. 3 is a cross-sectional view taken along line XX of FIG. 2 according to the embodiment of the present invention. (A) And (b) is explanatory drawing which shows the form of the tread surface before and behind a tire, respectively. FIG. 6 is a cross-sectional view taken along line XX of FIG. 2 according to another embodiment of the present invention. It is a partial top view which shows the tread surface of the pneumatic tire by other embodiment of this invention. It is sectional drawing of the tire peripheral direction which shows the form of the narrow groove in a conventional tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 5a Tread surface 7 Main groove 8 Rib 9 Narrow groove 9a, 9b Groove wall 9s Widening space 9z Bending point h Step p Interval of narrow groove in tire circumferential direction w2 Maximum space of both wall surfaces in widening space H of narrow groove Depth T Tire circumferential direction

Claims (6)

A pneumatic structure in which a plurality of main grooves extending in the tire circumferential direction are formed on the tread surface, and a plurality of narrow grooves having both ends opened to the main grooves at intervals in the circumferential direction of the ribs defined by the main grooves. In the tire,
A step is provided in the height of the tread surface before and after the tire circumferential direction across the narrow groove, and the wall surface of the narrow groove on the low step side is formed as a concave bent surface, and the opposite side facing the bent surface A pneumatic tire in which a wide space is formed between the wall and the wall.   The pneumatic tire according to claim 1, wherein the bent surface is formed as a concave curved surface having at least one bent point.   The pneumatic tire according to claim 1 or 2, wherein a groove width on a tread surface of the narrow groove is 0.5 to 1.5 mm, and an arrangement interval in a tire circumferential direction is 25 to 50 mm.   The pneumatic tire according to claim 1, 2 or 3, wherein a maximum distance between both wall surfaces in the widened space is 0.5 to 3.0 mm.   The pneumatic tire according to claim 1, 2, 3, or 4, wherein the size of the step is 15 to 30% of the depth of the narrow groove from the tread surface on the higher step side.   The pneumatic tire according to claim 1, wherein the pneumatic tire is a heavy duty tire.