JP5119601B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which the orientation of the front and back of the tire to a vehicle is specified, and more specifically, the driving performance on wet road surfaces and snow is improved while maintaining excellent driving performance on dry road surfaces. Related to pneumatic tires.

  2. Description of the Related Art Conventionally, pneumatic tires in which a tire front / back mounting direction with respect to a vehicle is designated have been widely used. In the pneumatic tire in which the mounting direction with respect to the vehicle is specified in this way, an asymmetric tread design is adopted, and optimal grooves are arranged in the region on the vehicle inner side and the region on the vehicle outer side when the vehicle is mounted, It is possible to maximize the tire characteristics (see, for example, Patent Documents 1 to 3).

However, even if an asymmetric tread design is adopted, it is difficult to achieve both driving performance on a dry road surface and driving performance on a wet road surface or snow. That is, if the groove area ratio in the tread portion is increased, it is possible to improve the running performance on a wet road surface or snow, but there is a problem that the running performance on a dry road surface is lowered accordingly.
JP 2005-53311 A JP-T-2004-523422 JP 2004-182090 A

  An object of the present invention is to provide a pneumatic tire that can improve the running performance on a wet road surface or snow while maintaining excellent running performance on a dry road surface.

In order to achieve the above object, the pneumatic tire of the present invention is a pneumatic tire in which the mounting direction of the front and back of the tire with respect to the vehicle is specified, and the four main grooves extending straight in the tire circumferential direction in the tread portion. When the main grooves are defined as the first main groove, the second main groove, the third main groove, and the fourth main groove in order from the outermost side when the vehicle is mounted, at least the grounding of the vehicle outside from the second main groove A plurality of first lug grooves extending to the end are arranged at an arbitrary pitch in the tire circumferential direction, and the central land portion is positioned in the central land portion between the second main groove and the third main groove. Are arranged at an arbitrary pitch in the tire circumferential direction, and these second lug grooves are reversed in a line symmetric direction with respect to the tire circumferential axis within the central land portion. Curved so that it intersects the adjacent second lug groove To make it, all of the second lug grooves contained in the central land portion is characterized in that configured so as to be continuous in the tire circumferential direction.

In the present invention, an asymmetric tread design is formed by combining four straight main grooves and at least two types of lug grooves, and the second lug grooves are positioned from the central land portion while ending in the central land portion. It extends to at least the ground contact end on the vehicle inner side, is curved so as to be reversed in a line-symmetrical direction with respect to the tire circumferential axis within the central land portion, and has a shape that intersects the adjacent second lug groove. As described above, the second lug groove is terminated in the central land portion, and a portion continuous in the tire circumferential direction is left in the central land portion, so that excellent running performance on a dry road surface can be ensured. In addition to providing four straight main grooves in the tread portion, arranging the first lug groove in the vehicle outer region, and arranging the second lug groove in the vehicle inner region, the second lug groove Since the groove component in the tire width direction and the groove component in the tire circumferential direction are mixed in the central land portion based on the shape of the tire, the running performance on wet road surfaces and snow can be improved.

  In the present invention, in order to maximize the driving performance on the dry road surface and the driving performance on the wet road surface or on the snow, the intersection between the second lug grooves is A, and the folding direction in which the inclination direction of the second lug groove is reversed When the point is B, the opening point from the central land portion of the second lug groove to the third main groove is C, and the end of the second lug groove is D, the turning point B from the opening point C of the second lug groove The ratio b / a between the length a up to a and the length b from the intersection A to the turn-around point B closer to the end than the intersection A is in the range of 0.3 to 0.6, and the end D of the second lug groove The ratio c / d between the distance c in the tire width direction from the second main groove to the third main groove and the distance d in the tire width direction from the second main groove to the third main groove is in the range of 0.1 to 0.5. The ratio e / f of the length e from the intersection A to the end D of the two lug grooves and the length f from the turn point B to the end D is set in the range of 0.1 to 0.5. Door is preferable.

  For the same reason as above, in the land portion between the first main groove and the second main groove, the first lug groove communicates with the first main groove from the wide width portion and the narrow width portion communicates with the second main groove. The ratio h / g of the distance h in the tire width direction from the groove width change point H to the second main groove and the distance g in the tire width direction from the first main groove to the second main groove is set to 0. A range of 1 to 0.5 is preferable.

  Furthermore, in order to improve the running performance on wet road surfaces and ice, it is preferable to provide sipes on land portions divided by the first main groove to the fourth main groove. Further, the edge portion where the side wall of at least one main groove of the first main groove to the fourth main groove and the tread surface intersect may be chamfered as necessary. In a tire with a main groove extending in the tire circumferential direction, the main groove interferes with the rain groove when traveling on a dry road surface having a rain groove (a groove for escaping water when it rains), and the steering wheel Although it may be caught, when chamfering as described above is performed, the steering stability on the dry road surface can be improved by suppressing the interference between the main groove and the rain groove.

  In the present invention, the grounding end is a portion of the tire that comes into contact with the flat surface when the tread portion of the tire is grounded on a flat surface under measurement conditions of a static load radius determined by a standard such as JATMA, TRA, or ETRTO. It means the end in the axial direction.

  The main groove means a groove whose groove width on the tread surface is 3% to 8% of the ground contact width. The tread portion needs to be provided with four main grooves that meet the above definition, but an auxiliary groove that extends in the tire circumferential direction and has a groove width narrower than the above specification may be added.

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. In the pneumatic tire of this embodiment, the mounting direction of the tire front and back with respect to the vehicle is specified. In FIG. 1, IN is the vehicle inner side, and OUT is the vehicle outer side.

  As shown in FIG. 1, the tread portion 1 is provided with four main grooves 11 to 14 extending straight in the tire circumferential direction. The first main groove 11 (first main groove) and the second main groove 12 (second main groove) counted from the vehicle outer side are arranged on the vehicle outer side than the tire equator CL, and the third main groove 11 counted from the vehicle outer side. The main groove 13 (third main groove) and the fourth main groove 14 (fourth main groove) are disposed on the vehicle inner side than the tire equator CL. Accordingly, the tread portion 1 is divided into five rows of land portions 21, 22, 23, 24, and 25 in order from the outside of the vehicle. An auxiliary groove 15 extending in the tire circumferential direction is disposed on the vehicle outer side than the main groove 11, and the land portion 21 is further subdivided into two rows of land portions 21a and 21b.

  A plurality of lug grooves 31 (first lug grooves) extending from the main groove 12 to at least the ground contact end Eo outside the vehicle are arranged at an arbitrary pitch in the tire circumferential direction in the vehicle outer region of the tread portion 1. Yes. This pitch may be constant or may vary in the tire circumferential direction. These lug grooves 31 extend in the tire width direction while being inclined with respect to the tire circumferential direction, and are bent toward the tire circumferential direction in a non-grounding region outside the ground contact edge Eo. The land portions 21 and 22 are each divided into a plurality of blocks by lug grooves 31.

On the other hand, in the area inside the vehicle of the tread portion 1, the terminal end is located in the land portion 23 (central land portion) between the main groove 12 and the main groove 13. A plurality of lug grooves 32 (second lug grooves) extending to Ei are arranged at an arbitrary pitch in the tire circumferential direction. This pitch may be constant or may vary in the tire circumferential direction. These lug grooves 32 extend in the tire width direction while being inclined with respect to the tire circumferential direction, and are bent toward the tire circumferential direction in a non-grounding region outside the ground contact edge Ei. The lug groove 32 is curved so as to be reversed in a line-symmetrical direction with respect to the tire circumferential axis within the land portion 23 without crossing the land portion 23, and intersects with the other lug groove 32 located adjacent thereto. Yes. As a result, the land portion 23 is divided into one rib 23a continuous in the tire circumferential direction by a lug groove 32 and a plurality of small blocks 23b scattered along the rib 23a. The lug groove 32 terminates inside the small block 23b. The land portions 24 and 25 are each divided into a plurality of blocks by lug grooves 32.

In the pneumatic tire, an asymmetric tread design in which four straight main grooves 11 to 14 and at least two kinds of lug grooves 31 and 32 are combined is formed. In particular, the lug groove 32 extends from the central land portion 23 to at least the ground contact Ei inside the vehicle while ending in the central land portion 23, and inverts in the line symmetrical direction with respect to the tire circumferential axis within the land portion 23. curved and shaped so as to intersect the adjacent lug grooves 32 to. In this way, the lug groove 32 is terminated in the central land portion 23, and the rib 23a continuous in the tire circumferential direction is left in the central land portion 23, so that the running performance on a dry road surface represented by steering stability is achieved. Can be maintained well. In addition to providing four straight main grooves 11 to 14 in the tread portion 1, arranging the lug groove 31 in the vehicle outer region, and arranging the lug groove 32 in the vehicle inner region, the lug groove Based on the shape of 32, since the groove component in the tire width direction and the groove component in the tire circumferential direction are mixed in the central land portion 23, it is possible to improve the running performance on a wet road surface or on snow.

  In the pneumatic tire, as shown in FIG. 2, the intersection of the lug grooves 32, 32 is A, the turning point at which the inclination direction of the lug groove 32 is reversed is B, and the main land portion 23 of the lug groove 32 is The opening point to the groove 13 is C, and the end of the lug groove 32 is D. However, the intersection point A, the turning point B, the opening point C, and the end point D are all specified on the center line of the lug groove 32.

  At this time, the ratio b / a of the length a from the opening point C of the lug groove 32 to the turning point B and the length b from the intersection point A to the turning point B closer to the terminal side than the intersection point A is 0.3 to The ratio c / d between the distance c in the tire width direction from the end D of the lug groove 32 to the main groove 13 and the distance d in the tire width direction from the main groove 12 to the main groove 13 is set to 0.6. The ratio e / f between the length e from the intersection A to the end D of the lug groove 32 and the length f from the turn point B to the end D is 0.1 to 0.5. The range. Thereby, the running performance on a dry road surface and the running performance on a wet road surface or snow can be maximized. According to the knowledge based on the experiment by the present inventors, when at least one of the ratio b / a, the ratio c / d, and the ratio e / f is out of the above range, the driving performance on the dry road surface and the driving on the wet road surface or snow. Compatibility with performance becomes difficult. In order to prevent the rigidity of the central land portion 23 from excessively decreasing due to the arrangement of the lug grooves 32, it is desirable that the depth of the lug grooves 32 in the central land portion 23 be gradually decreased toward the terminal side.

  Further, as shown in FIG. 2, in the land portion 22 between the main groove 11 and the main groove 12, the lug groove 31 communicates with the wide groove portion 31 a communicating with the main groove 11 on the vehicle outer side and the main groove 12 on the tire equator side. The ratio of the distance h in the tire width direction from the groove width change point H to the main groove 12 and the distance g in the tire width direction from the main groove 11 to the main groove 12 is h /. g is preferably in the range of 0.1 to 0.5. Thus, by arranging the narrow portion 31b on the tire equator side in the land portion 22, it becomes possible to improve the running performance on the dry road surface. However, according to the knowledge based on the experiments of the present inventors, when the ratio h / g falls below the lower limit of the above range, the effect of improving the running performance on the dry road surface decreases, and conversely, when the ratio h / g exceeds the upper limit of the above range. Driving performance on wet roads and snow will be reduced.

  As shown in FIG. 1, sipes 33 are preferably provided in the land portions 21 to 25 divided by the main grooves 11 to 14. The sipe 33 is a narrow groove having a groove width of 1.5 mm or less, and the depth is usually set in a range of 30% to 100% of the main groove depth. When such a sipe 33 is provided, the running performance on a wet road surface or ice can be improved by increasing the edge component.

  Of the main grooves 11 to 14, chamfering may be applied to the edge portion where the side wall of the at least one main groove and the tread surface intersect. For example, as shown in FIG. 3, the edge portion 11e where the side wall of the main groove 11 and the tread surface intersect can be chamfered. These chamfering processes may be performed only on the edge part 11e of the side wall on one side of the main groove, or may be performed on the edge part 11e of the side wall on both sides.

  In the pneumatic tires of the tire size 205 / 65R15, tires of Examples and Comparative Examples 1 and 2 in which only the tread pattern was varied were manufactured.

  An example is a tire provided with the tread pattern of FIG. 1 mentioned above. On the other hand, Comparative Examples 1 and 2 are tires in which the shape of the lug groove is different from that of the example. That is, in Comparative Example 1, the lug grooves extending from the ground contact end on the vehicle inner side toward the tire equator side are curved every other in the central land portion and communicated with the adjacent lug grooves (see FIG. 4). In Comparative Example 2, the sipe is extended from the end of the lug groove without bending the lug groove extending from the ground contact end on the vehicle inner side to the tire equator side at the central land portion, and the sipe is curved to intersect with the adjacent lug groove. (See FIG. 5).

  These test tires were evaluated for steering stability on dry road surfaces, turning performance on wet road surfaces, and steering stability on snow by the following test methods, and the results are shown in Table 1.

Steering stability on dry roads:
The test tire was mounted on a wheel with a rim size of 15 × 6.0 J, mounted on a vehicle with an air pressure of 210 kPa and a displacement of 2400 cc, and a sensory evaluation was performed by a test driver on a dry road test course. The evaluation results are shown as evaluation values by the 5-point method. This evaluation value has a reference level of 3 points, and the larger the value, the better the steering stability on the dry road surface.

Swivel on wet surfaces:
The test tire was assembled on a wheel having a rim size of 15 × 6.0 J and mounted on a vehicle having an air pressure of 210 kPa and a displacement of 2400 cc, and a sensory evaluation was performed by a test driver on a wet road surface test course. The evaluation results are shown as evaluation values by the 5-point method. This evaluation value means that the reference level is 3 points, and the larger the value, the better the turning performance on the wet road surface.

Steering stability on snow:
The test tire was mounted on a wheel having a rim size of 15 × 6.0 J, mounted on a vehicle having an air pressure of 210 kPa and a displacement of 2400 cc, and sensory evaluation was performed by a test driver on a test course on snow. The evaluation results are shown as evaluation values by the 5-point method. This evaluation value has a reference level of 3 points, and the larger the value, the better the steering stability on the dry road surface.

  As can be seen from Table 1, in comparison with Comparative Examples 1 and 2, the tires of the examples have drastically improved handling stability on dry road surfaces, turning performance on wet road surfaces, and driving stability on snow. It was.

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 principal part of FIG. It is XX arrow sectional drawing of FIG. 6 is a development view showing a tread pattern of Comparative Example 1. FIG. 6 is a development view showing a tread pattern of Comparative Example 2. FIG.

Explanation of symbols

1 tread 11 main groove (first main groove)
12 Main groove (second main groove)
13 Main groove (3rd main groove)
14 Main groove (4th main groove)
23 Land (Central land)
31 Lug groove (first lug groove)
32 lug groove (second lug groove)
33 Sipe IN Inside the vehicle OUT Outside the vehicle Ei Grounding end inside the vehicle Eo Grounding end outside the vehicle

Claims (3)

In a pneumatic tire in which the orientation of the front and back of the tire with respect to the vehicle is specified, four main grooves that extend straight in the tire circumferential direction are provided in the tread portion, and these main grooves are arranged in order from the outside of the vehicle when the vehicle is mounted. Are defined as the first main groove, the second main groove, the third main groove, and the fourth main groove, the plurality of first lug grooves extending from the second main groove to at least the ground contact end outside the vehicle are arranged around the tire circumference. A plurality of first extending from the central land portion to at least the ground contact end inside the vehicle, with the terminal ends being located in the central land portion between the second main groove and the third main groove. Two lug grooves are arranged at an arbitrary pitch in the tire circumferential direction, and the second lug grooves are curved so as to be reversed in a line symmetrical direction with respect to the tire circumferential axis in the central land portion, with respect to the adjacent second lug groove so as to intersect the second La all included in the central land portion A pneumatic tire having grooves configured so as to be continuous in the tire circumferential direction. The pneumatic tire according to claim 1 provided with a sipe land portion is divided by the first main groove to the fourth main groove. The pneumatic tire according to any one of claims 1 to 2 , wherein a chamfering process is performed on an edge portion where a side wall of at least one main groove and a tread surface of the first main groove to the fourth main groove intersect.

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