JP2012076664A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of easily discharging a stone even if the stone is caught in a closed-tip type inclined groove.SOLUTION: In this pneumatic tire, a main groove 1 is provided to extend in the tire circumferential direction in a tread part T; land parts 10 are divided which extend in the tire circumferential direction in positions adjacent to the main groove 1; and the land part 10 is provided with a plurality of inclined grooves 11, opening in the main groove 1 in a basic end thereof and being closed at the tip thereof inside of the land part 10. The angle θ of inclination of the inclined grooves 11 against the tire circumferential direction is formed to be gradually reduced as it comes close to the tip, and the groove width of the inclined groove 11 is formed constant or so as to be gradually reduced as it comes close to the tip. In the tread part T, JIS hardness Hα of a rubber component in a groove end including region A1, in which the tips of the inclined grooves 11 are included, is set lower than the JIS hardness Hβ of a rubber component in a peripheral region A2 adjacent to the groove end including region A1 on both sides thereof in the tire cross direction.

Description

  The present invention relates to a pneumatic tire in which a tip closing type inclined groove is provided in a tread portion, and more specifically, when stone biting occurs in a tip closing type inclined groove, the stone can be easily discharged. Related to pneumatic tires.

  In a pneumatic tire, a tread portion is provided with a main groove extending in the tire circumferential direction, a land portion extending in the tire circumferential direction is defined at a position adjacent to the main groove, and a base end is opened to the main groove in the land portion. On the other hand, there is one provided with a plurality of inclined grooves whose tips are closed in the land portion (see, for example, Patent Document 1). Such an inclined groove has the advantage that it contributes to the improvement of drainage performance because it effectively guides the water on the road surface to the main groove and is less likely to cause uneven wear.

  However, since the inclination angle with respect to the tire circumferential direction gradually decreases toward the front end and the groove width decreases gradually toward the front end, the end portion of the inclined groove is often clogged with small stones. . And such a stone biting into the inclined groove not only deteriorates the appearance of the tire, but also causes a crack in the tread part starting from the stone biting part, and generates an unpleasant noise when the tire rolls It causes inconvenience.

International Publication No. WO2010 / 058627 Pamphlet

  An object of the present invention is to provide a pneumatic tire capable of easily discharging stones when stone biting occurs in a tip closing type inclined groove.

  In order to achieve the above object, a pneumatic tire of the present invention is provided with a main groove extending in the tire circumferential direction in a tread portion, and a land portion extending in the tire circumferential direction is defined at a position adjacent to the main groove, In a pneumatic tire provided with a plurality of inclined grooves whose base end opens in the main groove while the distal end is closed in the land portion, the inclination angle of the inclined groove with respect to the tire circumferential direction is directed toward the distal end. The groove width of the inclined groove is gradually reduced, and the groove width of the inclined groove is gradually or gradually reduced toward the tip, and the JIS hardness Hα of the rubber composition in the groove end inclusion region in which the tip portion of the inclined groove is included in the tread portion is set. It is characterized by being lower than the JIS hardness Hβ of the rubber composition in the peripheral region adjacent to both sides in the tire width direction.

  In the present invention, in a pneumatic tire provided with a tip closing type inclined groove in the tread portion, the inclination angle of the inclined groove with respect to the tire circumferential direction is gradually decreased toward the tip, and the groove width of the inclined groove is constant or the tip. When gradually decreasing toward the surface, because the JIS hardness Hα of the rubber composition in the groove end inclusion region including the tip of the inclined groove in the tread portion is lower than the JIS hardness Hβ of the rubber composition in the peripheral region, Even when a small stone is clogged in the tip portion of the inclined groove, the groove end inclusion region in the tread portion is easily deformed, so that the bitten stone can be easily discharged. For this reason, the appearance of the tire is prevented from deteriorating due to the stone biting in the inclined groove, and the tread portion is prevented from cracking starting from the stone biting portion, and further, an unpleasant sound of ticking is generated when the tire rolls. It can be prevented from occurring.

  In the present invention, the groove end inclusion region preferably includes a portion from the tip of the inclined groove to a position that is 10% or more and 50% or less of the length of the inclined groove. Thereby, it is possible to sufficiently obtain the stone biting suppressing effect while suppressing the occurrence of uneven wear.

  The JIS hardness Hα of the rubber composition in the groove end inclusion region is in the range of 45 ≦ Hα ≦ 70, and the difference γ between the JIS hardness Hα and the JIS hardness Hβ of the rubber composition in the peripheral region is in the range of 5 ≦ γ ≦ 25. It is preferable to be within. Thereby, it is possible to sufficiently obtain the stone biting suppressing effect while suppressing the occurrence of uneven wear.

  It is preferable to provide an extended groove that is wider than the inclined groove at the tip of the inclined groove. When the extended groove portion is provided at the tip of the inclined groove, the tip portion of the inclined groove is likely to be widened, so that the bite stone can be more easily discharged.

  It is preferable that the depth of the inclined groove is gradually reduced toward the tip. The stone sandwiched between the inclined grooves is less likely to be discharged as it moves toward the tip of the inclined groove, but by gradually decreasing the depth of the inclined groove toward the tip, the stone is moved toward the tip of the inclined groove. It can approach the tread surface side and make it easy to discharge.

  In the present invention, the JIS hardness is a durometer hardness at 20 ° C. measured using an A type durometer in a durometer hardness test specified in JIS K6253.

It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is a top view which expands and shows the center land part in the tread pattern of the pneumatic tire of FIG. It is sectional drawing which notched the center land part of FIG. 2 along the inclination groove | channel. It is a top view which shows the modification of an inclination groove | channel. It is a top view which shows the other modification of an inclination groove | channel. It is a top view which shows the other modification of an inclination groove | channel.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention, and FIGS. 2 and 3 show a center land portion thereof.

  As shown in FIG. 1, a plurality of main grooves 1 extending in the tire circumferential direction are formed in the tread portion T, and two rows of center land portions 10 and two rows of shoulder land portions 20 are partitioned by these main grooves 1. ing. Although the groove width and groove depth of the main groove 1 are not particularly limited, in order to ensure good drainage performance, for example, the groove width is set in a range of 8.0 mm to 20.0 mm, The depth is set in the range of 6.0 mm to 9.5 mm.

  In each center land portion 10, a plurality of inclined grooves 11 that are inclined with respect to the tire circumferential direction are formed at intervals in the tire circumferential direction. Each inclined groove 11 has a base end that opens into the main groove 1, and a distal end that is closed in the center land portion 10. Such an inclined groove 11 contributes to improving drainage performance because it effectively guides the water on the road surface to the main groove 1, and also has an advantage that uneven wear is unlikely to occur because the center land portion 10 is not divided. . As a more specific configuration, the inclined grooves 11 formed in the two rows of the center land portions 10 are open to the common main groove 1 located on the tire equator CL. Arranging the inclined grooves 11 so as to face each other is advantageous for improving drainage efficiency, but is not limited to such an arrangement.

  In the inclined groove 11, the inclination angle θ (see FIG. 2) with respect to the tire circumferential direction is gradually reduced toward the tip. The inclination angle θ is an inclination angle of the center line of the inclined groove 11 with respect to the tire circumferential direction, and is set, for example, in a range of 0 ° to 45 °. Further, the inclined groove 11 may have a constant groove width, but it is desirable that the groove width gradually decreases toward the tip as shown in the figure.

  On the other hand, in each shoulder land portion 20, a plurality of lug grooves 21 extending in the tire width direction are formed at intervals in the tire circumferential direction. These lug grooves 21 communicate with the main groove 1 adjacent to the shoulder land portion 20.

  In the pneumatic tire having the tread pattern as described above, as shown in FIGS. 2 and 3, the JIS of the rubber composition R1 disposed in the groove end inclusion region A1 of the tread portion T in which the tip portion of the inclined groove 11 is included. The hardness Hα and the JIS hardness Hβ of the rubber composition R2 disposed in the peripheral region A2 of the tread portion T adjacent to both sides in the tire width direction of the groove end inclusion region A1 have a relationship of Hα <Hβ. 2 and 3 show only the center land portion 10, the peripheral region A2 is the entire region except the groove end inclusion region A1 in the tread portion T. FIG. These two types of rubber compositions R1 and R2 are applied to at least the cap tread rubber layer.

  Thus, in the pneumatic tire in which the tip closed type inclined groove 11 is provided in the tread portion T, the inclination angle θ with respect to the tire circumferential direction of the inclined groove 11 is gradually reduced toward the tip, and the groove width of the inclined groove 11 is increased. Is gradually or gradually decreased toward the tip, the JIS hardness Hα of the rubber composition R1 in the groove end inclusion region A1 including the tip portion of the inclined groove 11 is set to be higher than the JIS hardness Hβ of the rubber composition R2 in the peripheral region A2. Since it is low, even if a small stone S is clogged at the tip of the inclined groove 11, the groove end inclusion region A1 in the tread portion T is easy to move, so that the bitten stone S can be easily discharged. . Thereby, in addition to preventing the deterioration of the appearance of the tire due to the stone biting into the inclined groove 11, the tread portion T is prevented from cracking starting from the stone biting part, and further, it is called ticking when the tire rolls An unpleasant sound can be prevented from being generated.

  In the pneumatic tire, the groove end inclusion region A1 preferably includes a portion from the tip of the inclined groove 11 to a position that is 10% to 50% of the length of the inclined groove 11. The length of the inclined groove 11 here is a length measured along the center line of the inclined groove 11, and the portion included in the groove end inclusion region A <b> 1 is determined based on the center position of the inclined groove 11. To do. Thus, by including the tip end portion of the inclined groove 11 over a predetermined length in the groove end inclusion region A1, it is possible to sufficiently obtain a stone biting suppressing effect while suppressing the occurrence of uneven wear. Here, if the length of the tip portion of the inclined groove 11 included in the groove end inclusion region A1 is less than 10% of the length of the inclined groove 11, the stone biting suppression effect becomes insufficient, and conversely the length of the inclined groove 11 If it exceeds 50%, the stepped region due to uneven wear during wear becomes large.

  The JIS hardness Hα of the rubber composition R1 in the groove end inclusion region A1 is in the range of 45 ≦ Hα ≦ 70, and the difference γ (γ = Hβ) between the JIS hardness Hα and the JIS hardness Hβ of the rubber composition R2 in the peripheral region A2. -Hα) is preferably in the range of 5 ≦ γ ≦ 25. Thereby, it is possible to sufficiently obtain the stone biting suppressing effect while suppressing the occurrence of uneven wear. Here, if the JIS hardness Hα is less than 45, the level difference due to uneven wear at the time of wear increases, and if it exceeds 70, the stone biting suppression effect becomes insufficient. Further, if the hardness difference γ is less than 5, the effect of suppressing stone biting becomes insufficient, while if it exceeds 25, the level difference due to uneven wear at the time of wear increases.

  As shown in FIG. 3, it is preferable that the depth of the inclined groove 11 is gradually reduced toward the tip, that is, the depth of the inclined groove 11 is gradually shallower from the base end toward the tip. Since the inclined groove 11 has a constant groove width or gradually decreases toward the tip, the stone S sandwiched between the inclined grooves 11 tends to be more difficult to be discharged as it moves toward the tip of the inclined groove 11. However, when the depth of the inclined groove 11 is gradually reduced toward the tip, the stone S comes closer to the tread surface side toward the tip of the inclined groove 11, so that the discharge is facilitated. Can do.

  4 to 6 each show a modified example of the inclined groove. 4 to 6, an extended groove 12 that is wider than the inclined groove 11 is formed at the tip of the inclined groove 11. The shape of the extended groove portion 12 is not particularly limited, and a shape such as a polygonal shape (FIG. 4), a circular shape (FIG. 5), and a constricted shape (FIG. 6) can be adopted. Thus, when the extended groove part 12 is provided in the front-end | tip of the inclination groove | channel 11, since the front-end | tip part of the inclination groove | channel 11 becomes easy to spread, it becomes easy to discharge | emit the stone S which bite further.

  The maximum width W1 of the extended groove portion 12 is preferably 1.5 times or more the groove width W0 of the inclined groove 11 immediately before spreading. If the ratio W1 / W0 is less than 1.5, the effect of facilitating the stone discharge cannot be expected. The upper limit value of the ratio W1 / W0 is 3.0. Moreover, the length L1 of the extended groove part 12 is good in it being 3 mm or more. If the length L1 of the extended groove portion 12 is less than 3 mm, the effect of facilitating the stone discharge cannot be expected. The upper limit of the length L1 is 10% or less of the length measured along the center line of the inclined groove 11.

  In the above-described embodiment, the case where the inclined groove is provided in the center land portion has been described. However, such an inclined groove can be provided in another land portion partitioned by the tread portion, in which case a soft rubber composition is formed. The groove end inclusion region to be arranged may be appropriately set in the tread portion according to the position of the tip portion of the inclined groove.

  Further, in the embodiment described above, the groove end inclusion region is provided in a belt shape continuous in the tire circumferential direction, but intermittently in the tire circumferential direction so as to include the tip portions of the inclined grooves arranged at intervals in the tire circumferential direction. May be provided. However, when the groove end inclusion region where the soft rubber composition is disposed is intermittently provided in the tire circumferential direction, it becomes difficult to match the tip end portion of the inclined groove and the groove end inclusion region with each other during tire vulcanization. It is desirable to set the inclusion region in a belt shape continuous in the tire circumferential direction.

  The tire size is 205 / 55R16, and as shown in FIG. 1, three main grooves extending in the tire circumferential direction are provided in the tread portion, and four rows of land portions extending in the tire circumferential direction are defined by these main grooves. In a pneumatic tire provided with a plurality of inclined grooves whose base ends open to the main groove at the center land portion and whose front ends are closed in the center land portion, the inclination angle of the inclined groove with respect to the tire circumferential direction is set at the tip. And gradually decreasing the width of the inclined groove toward the tip, and a groove end inclusion region in which the tip portion of the inclined groove is included in the tread portion and a peripheral region adjacent to both sides in the tire width direction. JIS hardness Hα of the rubber composition arranged in the groove end inclusion region, JIS hardness Hβ of the rubber composition arranged in the peripheral region, the tip of the inclined groove included in the groove end inclusion region with respect to the length of the inclined groove Tires of Examples 1 to 6 and Comparative Example 1 in which the length ratio of the end portions was set as shown in Table 1 were produced. For comparison, a conventional tire in which the JIS hardness of the rubber composition constituting the tread portion was made uniform was prepared.

  In the conventional example, Examples 1 to 5 and Comparative Example 1, the inclined groove has a groove width at the opening end of 5.0 mm, a groove depth at the opening end of 6.0 mm, and a groove width at the tip of 1. The groove depth at the tip was 6.0 mm, and the groove depth was fixed. On the other hand, in Example 6, the inclined groove has a groove width at the opening end of 5.0 mm, a groove depth at the opening end of 6.0 mm, a groove width at the tip of 1.0 mm, and a groove at the tip. The depth was 1.0 mm, and the groove depth was gradually decreased toward the tip. Further, in Examples 4 to 6 and Comparative Example 1, a circular or quadrangle-shaped extended groove portion that was wider than the inclined groove was provided at the tip of the inclined groove.

  These test tires were evaluated for stone biting performance by the following evaluation methods, and the results are shown in Table 1.

Stone resistance:
Each test tire is mounted on a wheel with a rim size of 16 × 6.5J and mounted on a front wheel drive vehicle with an air pressure of 230 kPa and a displacement of 1400 cc. The traveling road was traveled 5000 km, and the number of stone bites of the tire after traveling was measured. The evaluation results are shown as an index using a reciprocal number as a measurement value and setting the conventional example as 100. A larger index value means a smaller number of stone bites.

  As is clear from Table 1, the tires of Examples 1 to 6 were superior in stone biting performance as compared with the conventional examples. On the other hand, since the tire of Comparative Example 1 has a reverse relationship between the JIS hardness Hα of the rubber composition in the groove end inclusion region and the JIS hardness Hβ of the rubber composition in the peripheral region, the improvement effect of the stone biting performance is recognized. I couldn't.

DESCRIPTION OF SYMBOLS 1 Main groove 10,20 Land part 11 Inclination groove 12 Expansion groove part 21 Lug groove A1 Groove end inclusion area A2 Peripheral area T Tread part

Claims (5)

  A main groove extending in the tire circumferential direction is provided in the tread portion, a land portion extending in the tire circumferential direction is defined at a position adjacent to the main groove, and a distal end of the land portion is open to the main groove while the distal end In the pneumatic tire provided with a plurality of inclined grooves that are closed in the land portion, the inclination angle of the inclined grooves with respect to the tire circumferential direction is gradually decreased toward the tip, and the groove width of the inclined grooves is constant or The JIS hardness Hα of the rubber composition in the groove end inclusion region in which the tip portion of the inclined groove is included in the tread portion is gradually reduced toward the front end, and the peripheral rubber composition in the peripheral region adjacent to both sides in the tire width direction. A pneumatic tire characterized by being lower than JIS hardness Hβ.   2. The pneumatic tire according to claim 1, wherein the groove end inclusion region includes a portion from a tip of the inclined groove to a position not less than 10% and not more than 50% of the length of the inclined groove.   The rubber composition in the groove end inclusion region has a JIS hardness Hα of 45 ≦ Hα ≦ 70, and the difference γ between the JIS hardness Hα and the JIS hardness Hβ of the rubber composition in the peripheral region is 5 ≦ γ ≦ 25. The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire is within the range of.   The pneumatic tire according to any one of claims 1 to 3, wherein an extended groove portion that is wider than the inclined groove is provided at a tip of the inclined groove.   The pneumatic tire according to any one of claims 1 to 4, wherein the depth of the inclined groove is gradually reduced toward the tip.

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