JP2014083892A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of both of improvement in driving stability and reduction in rolling resistance.SOLUTION: A plurality of lateral grooves 4 are arranged with an interval in a tire circumferential direction CD on a shoulder land part 2 located at the outermost side in the tire width direction. Each of the lateral grooves 4 comprise: a main body part 4a extending in the tire width direction so as to cross over a grounding edge E; and a turn-back part 4b at which the lateral groove 4 turn back from an outside end part in the tire width direction of the main body part 4a to inside in the tire width direction. The turn-back part 4b extends with inclination relative to the tire circumferential direction CD and terminates at a position outside of the grounding edge E in the tire width direction without connecting to the other grooves or sipes. Independent dimples 6 are formed between the outside edge in the tire width direction of the shoulder land part 2 and the turn-back part 4b.

Description

  The present invention relates to a pneumatic tire in which a plurality of lateral grooves are formed in a shoulder land portion at intervals in the tire circumferential direction.

  Among the plurality of land portions provided on the tread surface, in the shoulder land portion located on the outermost side in the tire width direction, the load during cornering tends to increase, which greatly affects the steering stability performance on the dry road surface. . This is particularly noticeable in tires mounted on minivans and one-box vehicles with heavy vehicle weight and high center of gravity, and it is desirable to take effective measures. In the shoulder land portion, for the purpose of improving drainage performance or the like, it is common to repeatedly form lateral grooves extending in the tire width direction in the tire circumferential direction.

  In the shoulder land portion provided so as to straddle the ground contact end, the outer portion in the tire width direction is arranged in the buttress portion. The buttress portion corresponds to an outer portion of the sidewall portion in the tire radial direction, and is a portion that does not come into contact with the ground during normal traveling on a flat paved road. In the structure where the lateral groove formed in the shoulder land part terminates in the ground contact surface without entering the buttress part, or the structure that terminates immediately beyond the ground contact end, the volume reduction of the shoulder land part due to the lateral groove is not sufficient, Therefore, the contribution to the reduction of rolling resistance is small.

  On the other hand, as shown in Patent Documents 1 and 2, in the structure in which the lateral groove reaches the outer end in the tire width direction of the shoulder land portion, or in the structure in which the lateral groove is connected to the annular groove continuous in the tire circumferential direction in the buttress portion, The movement of the sidewall portion accompanying the bending deformation of the tire during traveling tends to increase, and the steering stability performance on the dry road surface tends to decrease. This is considered to be caused by the decrease in rigidity of the shoulder land portion and the wiping of the buttress portion being promoted, and there is room for improvement.

Design Registration No. 1169838 Design Registration No. 954684

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire capable of achieving both improvement in steering stability performance and reduction in rolling resistance.

  The above object can be achieved by the present invention as described below. That is, in the pneumatic tire according to the present invention, a plurality of land portions defined by a plurality of main grooves extending along the tire circumferential direction are provided on the tread surface, and the outermost portion in the tire width direction among the plurality of land portions. In the pneumatic tire in which a plurality of lateral grooves are formed at intervals in the tire circumferential direction on the shoulder land portion located in the body, the lateral grooves extend along the tire width direction so as to cross the ground contact end, and And a folded portion that is folded back from the end on the tire width direction outer side of the main body portion toward the inner side in the tire width direction, the folded portion extends while being inclined with respect to the tire circumferential direction, and other grooves and Without being connected to a sipe, it terminates at a position on the outer side in the tire width direction from the ground contact end, and an independent dimple is formed between the outer end in the tire width direction of the shoulder land portion and the folded portion. Is shall.

  In this tire, the folded portion of the lateral groove extends obliquely with respect to the tire circumferential direction, is not connected to other grooves or sipes, and terminates on the outer side in the tire width direction from the ground contact end, so that the rigidity of the shoulder land portion decreases. And the wiping of the buttress part is suppressed well. Since the dimples are formed in the shoulder land portion in addition to the lateral grooves extended by the folded portion, the tire mass can be reduced by increasing the volume of the shoulder land portion. Further, since the dimples are independently formed between the outer end of the shoulder land portion in the tire width direction and the folded portion, a decrease in rigidity of the shoulder land portion due to the dimple is suppressed. As a result, according to this tire, it is possible to achieve both improvement in steering stability performance and reduction in rolling resistance.

  In the present invention, it is preferable that the shoulder land portion has a thin rib region continuously extending in the tire circumferential direction with the outer edge in the tire width direction of the shoulder land portion as an edge. Thereby, the rigidity reduction of a shoulder land part and the wiping of a buttress part can be suppressed effectively, and steering stability performance can be improved appropriately.

  In the present invention, the dimple is preferably composed of a plurality of small dimples. According to such a configuration, it is possible to further improve the steering stability performance by further suppressing the decrease in rigidity of the shoulder land portion due to the dimples.

  In the present invention, it is preferable that the length of the dimples in the tire circumferential direction is 45% or more of the repeated pitch length of the lateral grooves. As a result, the length of the dimple is secured, and the effect of reducing rolling resistance can be effectively enhanced.

  In the present invention, the depth of the dimple may be larger than the depth of the folded portion. In this case, since the depth of the folded portion of the lateral groove is relatively small, the rigidity of the shoulder land portion can be prevented from being lowered. Nevertheless, since the depth of the dimple is relatively large, the rolling resistance can be reduced by ensuring the volume reduction of the shoulder land portion.

Development view showing an example of tread surface of pneumatic tire An enlarged view showing a part of the tread surface of FIG. The enlarged view which shows a part of tread surface in another embodiment The enlarged view which shows a part of tread surface in another embodiment (A) Enlarged view showing a part of the tread surface in Comparative Example 1 and (B) Comparative Example 2 The enlarged view which shows a part of tread surface in the comparative example 3

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The tread surface Tr of the pneumatic tire shown in FIG. 1 has a plurality of (three in this embodiment) main grooves 1 extending along the tire circumferential direction CD and a plurality of (this embodiment) partitioned by them. There are four land areas. The plurality of land portions include a pair of shoulder land portions 2 located on the outermost side in the tire width direction and a pair of center land portions 3 located across the tire equator CL. The shoulder land portion 2 is provided so as to straddle the ground contact end E.

  A plurality of lateral grooves 4 are formed in the shoulder land portion 2 at intervals in the tire circumferential direction CD. The end of the lateral groove 4 on the inner side in the tire width direction may be terminated within the ground contact surface without being connected to the main groove 1. A cut-out sipe 5 is formed between the lateral grooves 4 arranged in the tire circumferential direction CD. In the present specification, a sipe having a width of 1.2 mm or less is defined as a sipe, and a groove having a width greater than this is defined as a groove. Therefore, the width W4 of the lateral groove 4 exceeds 1.2 mm, and the width W5 of the sipe 5 is 1.2 mm or less. The width W4 and the width W5 are each measured by the height of the surface of the shoulder land portion 2 in the ground plane.

  The ground contact E attaches the tire to a standard rim specified in JATMA YEAR BOOK (2007 edition, Japan Automobile Tire Association standard), and the maximum load capacity (internal pressure-load capacity) in the applicable size and ply rating in JATMAYEAR BOOK Fills 100% of the air pressure (maximum air pressure) corresponding to the bold load in the correspondence table as the internal pressure, and indicates the outermost contact portion in the tire width direction when the maximum load capacity is applied. When the TRA standard or ETRTO standard is applied in the place of use or manufacturing, the respective standards are followed.

  As shown in an enlarged view in FIG. 2, each of the lateral grooves 4 includes a main body portion 4 a extending along the tire width direction so as to cross the ground contact end E, and a tire width from an outer end portion of the main body portion 4 a in the tire width direction. And a folded portion 4b that is folded inward in the direction. The end of the main body 4a on the inner side in the tire width direction is located in the ground contact surface, and the end on the outer side in the tire width direction is located outside the ground contact surface. The main body 4a of the present embodiment is a straight groove inclined with respect to the tire width direction, but may extend in parallel with the tire width direction or may be gently curved.

  The folded portion 4b extends while inclining with respect to the tire circumferential direction CD, and is connected to the ground without being connected to other grooves (such as the adjacent lateral grooves 4 and the main groove 1) or sipes (sipe 5 and other sipes). Terminate at a position on the outer side in the tire width direction from the end E. And the independent dimple 6 is formed between the tire width direction outer side end E2 of the shoulder land part 2, and the folding | returning part 4b. The outer end E2 is also an end of the tread rubber, and a sidewall rubber (not shown) continues to the outside in the tire width direction. In the shoulder land portion 2, a pattern including the lateral grooves 4 and the dimples 6 is repeatedly formed in the tire circumferential direction CD.

  In this tire, since the folded portion 4b is inclined with respect to the tire circumferential direction CD, wiping of the buttress portion is satisfactorily suppressed. In order to ensure the effect of suppressing wiping, the inclination angle θ of the folded portion 4b with respect to the tire circumferential direction CD is preferably 15 to 45 °. Further, in order to enhance the rolling resistance reduction effect by forming the lateral grooves 4 longer, the length L4b of the folded portion 4b in the tire circumferential direction CD is preferably 35% or more of the repeated pitch length P of the lateral grooves 4. The inclination angle θ and the length L4b are determined based on the groove center line of the lateral groove 4, respectively.

  Further, the folded portion 4b is not connected to another groove or sipe, and is terminated at the outer side in the tire width direction from the ground contact end E, so that a decrease in rigidity of the shoulder land portion 2 can be suppressed. Nevertheless, since the dimple 6 is formed in the shoulder land portion 2 in addition to the lateral groove 4 extended by the folded portion 4b, the shoulder land portion 2 is compared with the case where the folded portion 4b and the dimple 6 are not formed. As a result, the volume of the tire increases and the tire mass can be reduced and the rolling resistance can be reduced.

  The dimple 6 is formed between the outer end E2 and the folded portion 4b, and is surrounded and independent so as not to be connected to other grooves or sipes. Stiffness reduction can be satisfactorily suppressed. Therefore, according to this pneumatic tire, it is possible to achieve both improvement in steering stability performance and reduction in rolling resistance. Further, not arranging the dimples 6 on the inner side in the tire width direction than the turned-up portion 4b is advantageous in securing the rigidity of the shoulder land portion 2 and improving the steering stability performance.

  Since the folded portion 4b is not connected to another groove or sipe, in the mold used for vulcanization molding, a projection for forming another groove or sipe is connected to the projection for forming the folded portion 4b. They do not form corners. As a result, locations where air is easily trapped when the tire is vulcanized can be reduced, which is convenient in preventing the occurrence of a dent scar called a bear. In particular, such a structure is advantageous because the buttress portion is a portion where it is difficult to perform spew trimming and the installation of a vent hole is avoided.

  The shoulder land portion 2 has a thin rib region 7 continuously extending in the tire circumferential direction with the outer end E2 of the shoulder land portion 2 as an edge. Both the lateral groove 4 and the dimple 6 face the fine rib region 7 and do not reach the outer end E2, but are separated from the outer end E2 by a distance corresponding to the width W7 of the fine rib region 7. Thereby, the rigidity reduction of the shoulder land part 2 and the wiping of a buttress part can be suppressed effectively, and steering stability performance can be improved appropriately. The width W7 of the fine rib region 7 is set to 1.5 to 5.0 mm, for example.

  The lateral groove 4 is formed in a V shape as a whole. The folded portion 4b is folded so as to form an acute angle with respect to the main body portion 4a, but may be a right angle or an obtuse angle. However, in order to appropriately set the angle of the main body portion 4a with respect to the tire width direction and the angle θ of the turned-up portion 4b with respect to the tire circumferential direction CD, a form having an acute angle as in the present embodiment is preferable. In order to increase the volume reduction of the shoulder land portion 2 by elongating the lateral groove 4, it is preferable to bring the end portion of the main body portion 4a on the outer side in the tire width direction closer to the outer end E2, and in this embodiment, a distance corresponding to the width W7. You are approaching.

  The length L6 of the dimple 6 in the tire circumferential direction CD is preferably 45% or more, more preferably 50% or more of the repeated pitch length P of the lateral groove 4 in order to increase the volume reduction of the shoulder land portion 2 by increasing the dimple 6. Preferably, 55% or more is more preferable. The dimple 6 is disposed in a triangular region surrounded by the folded portion 4b of the lateral groove 4, the main body portion 4a of another lateral groove 4 adjacent to the lateral groove 4, and the outer end E2, and corresponds to the region. It is formed in a triangular shape. The shape of the dimple 6 is not limited to this, and may be another polygonal shape or a circular shape.

  The dimple 6 faces the folded portion 4b in the tire circumferential direction CD. When the depth of the dimple 6 is larger than the depth of the folded portion 4b, for example, when the depth of the folded portion 4b is 0.5 to 1.2 mm and the depth of the dimple 6 is larger than that, the folded portion The rigidity reduction of the shoulder land portion 2 due to 4b can be suppressed, and the steering stability performance can be improved. Nevertheless, since the volume reduction of the shoulder land portion 2 by the dimple 6 is ensured, the rolling resistance can be reduced.

  As another embodiment, the depth of the dimple 6 may be smaller than the depth of the folded portion 4b. For example, when the depth of the folded portion 4b is the above-mentioned dimension and the depth of the dimple 6 is smaller than that, the volume reduction of the shoulder land portion 2 by the dimple 6 is smaller than the above, but the shoulder by the dimple 6 Steering performance can be improved by suppressing a decrease in rigidity of the land portion 2. Therefore, the embodiment places importance on steering stability performance. The depths of the dimple 6 and the turned-up portion 4b are measured as the maximum values.

  The embodiment shown in FIGS. 3 and 4 is the same as the above-described embodiment except for the configuration described below. Therefore, common points will be omitted and mainly the differences will be described. The same parts as those already described are denoted by the same reference numerals, and redundant description is omitted. FIG. 3 is an example in which the folded portion 4b is formed shorter than in FIG. 2 and the dimple 6 is formed larger. In this case, the volume reduction of the shoulder land portion 2 due to the dimple 6 increases, which can contribute to reduction of rolling resistance. In this example, the area of the dimple 6 measured by the height of the surface of the shoulder land portion 2 is larger than the area of the folded portion 4b.

  4A and 4B, the dimple 6 in FIGS. 2 and 3 is configured by a plurality of small dimples 6a and 6b, respectively. Thereby, the rigidity fall of the shoulder land part 2 by the dimple 6 can be suppressed, and steering stability performance can be improved more favorably. Each of these dimples 6 is formed in a triangular shape as a whole, and is divided into two small dimples 6a and 6b arranged in the tire width direction by minute ribs extending in the tire circumferential direction.

  In the present embodiment, an example in which the shoulder land portions having the above-described structure are provided on both sides in the tire width direction is shown, but this may be provided only on one side in the tire width direction. The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention.

  Since the internal structure of the pneumatic tire can be configured in the same manner as a general radial tire, description of the internal structure is omitted. The pneumatic tire of the present invention is the same as a normal pneumatic tire except that the shoulder land portion as described above is provided on the tread surface, and any conventionally known material, shape, structure, manufacturing method, etc. Can be adopted.

  Hereinafter, in order to specifically show the configuration and effect of the present invention, the steering stability performance and the rolling resistance will be evaluated and described. These performance evaluations are performed as follows (1) and (2). The tire size used for the evaluation is 195 / 65R15, the depth of the main groove is 7.7 mm, and the width of the lateral groove formed in the shoulder land portion is The depth is 6.7 mm.

(1) Steering stability performance The vehicle was mounted on a vehicle (2000 cc class sedan (FF car)), traveled on a dry road surface, and a sensory test was performed by a driver. The result of Comparative Example 1 is evaluated with an index of 100, and the larger the value, the better the steering stability performance.

(2) Rolling resistance The reciprocal number of the rolling resistance coefficient measured using the drum type rolling resistance tester was calculated. The result of Comparative Example 1 is evaluated with an index of 100, and the larger the value, the smaller the rolling resistance and the better the performance.

  The shapes of Comparative Example 1 and Comparative Example 2 are as shown in FIGS. 5A and 5B, respectively, and are the same as Example 1 except for the shape of the lateral grooves and dimples in the buttress portion. Moreover, the shape of the comparative example 3 is as having shown in FIG. 6, Comprising: It substantially corresponds to what connected the sipe 5 to the folding | returning part 4b in Example 1. FIG. In addition, the tire structure and the rubber composition not specifically described are common. Table 1 shows the evaluation results.

  As shown in Table 1, in Examples 1 to 3, the steering stability performance and rolling resistance are superior to those of Comparative Examples 1 to 3, and both improvement in steering stability performance and reduction in rolling resistance can be successfully achieved.

DESCRIPTION OF SYMBOLS 1 Main groove 2 Shoulder land part 4 Horizontal groove 4a Main body part 4b Folding part 6 Dimple 6a Small dimple 6b Small dimple 7 Fine rib area E Grounding edge E2 Tire width direction outer side edge P of shoulder land part Repeat pitch length

Claims (5)

A plurality of land portions defined by a plurality of main grooves extending along the tire circumferential direction are provided on the tread surface, and a plurality of lateral grooves are formed in a shoulder land portion located on the outermost side in the tire width direction among the plurality of land portions. In a pneumatic tire formed with an interval in the tire circumferential direction,
The lateral groove includes a main body portion extending along the tire width direction so as to cross the ground contact end, and a folded portion formed by folding back from the outer end portion of the main body portion in the tire width direction toward the inner side in the tire width direction. ,
The folded portion extends while being inclined with respect to the tire circumferential direction, and is terminated at a position on the outer side in the tire width direction from the ground contact end without being connected to other grooves or sipes,
An independent dimple is formed between an outer end in the tire width direction of the shoulder land portion and the folded portion.   2. The pneumatic tire according to claim 1, wherein the shoulder land portion has a thin rib region continuously extending in a tire circumferential direction with an outer end in a tire width direction of the shoulder land portion as an edge.   The pneumatic tire according to claim 1 or 2, wherein the dimple is constituted by a plurality of small dimples.   The pneumatic tire according to any one of claims 1 to 3, wherein a length of the dimple in the tire circumferential direction is 45% or more of a repetition pitch length of the lateral groove. The pneumatic tire according to claim 1, wherein a depth of the dimple is larger than a depth of the folded portion.

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