JP2005126007A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of making controllability and stability on an ice/snow road surface in winter and controllability stability on a dry road surface at a usual time compatible from at a new product to intermediate stage on or after abrasion. <P>SOLUTION: The pneumatic radial tire has at least three circumferential main grooves on a tread stepping surface part and a tread pattern in which circumferential sub-grooves 3 are arranged on at least two land part rows 2 of a plurality of land part rows 2 partitioned by the circumferential main grooves 1. At least one side of wall surfaces of the circumferential main grooves 1 for partitioning the land part rows 2 having the circumferential sub-grooves 3 has a chamfered part 4 becoming a taper shape and difference of depth Dt of the chamfered part 4 and depth Ds of the circumferential sub-groove 3 is made to ±5% or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a pneumatic radial tire, and more particularly, to a pneumatic radial tire for a passenger car that achieves both driving stability (safety) on a snowy road surface in winter and driving stability on a dry road surface in a normal period. About.

  Conventionally, as a tread pattern of pneumatic radial tires for passenger cars, three or more circumferential main grooves have been provided for the purpose of improving drainage performance on wet road surfaces, and the circumferential main grooves define the tread pattern. There is a known pattern in which a plurality of circumferential sub-grooves are further arranged on the formed rib portion. In addition, in the tread pattern having such a circumferential main groove, many patterns having a chamfered portion (taper cut portion) on the groove wall surface of the circumferential main groove have been proposed.

  For example, in Patent Document 1, for the purpose of improving the ground contact property at the time of tire rolling, the tread circumferential direction is based on the idea that the ground contact pressure on the block surface is uniform over the entire surface in the tire contact surface. Thus, it has been proposed to make the radius of curvature of the block surface smaller than that of the outer contour line of the tread surface.

  Further, in Patent Document 2, a chamfered portion is provided on the groove wall surface, and a narrow groove-shaped concave portion is formed along the groove on the tread surface in the vicinity thereof, while ensuring excellent wet performance, There has been proposed a pneumatic tire that can be easily vulcanized and molded without causing demolding even with a mold.

Furthermore, in patent document 3, the chamfering part (taper cut part) which made the depth and inclination | tilt angle of the both edges of the straight groove provided in the specific position between the circumferential direction center of a tire tread surface and the tread edge part into a specific value is provided. Thus, it has been proposed to improve the motion characteristics on the wet road surface.
JP 11-115419 A (claims, etc.) JP 2001-163013 A (Claims etc.) JP-A-56-157606 (Claims etc.)

  However, in the pneumatic tire having a pattern having a chamfered portion on the groove wall surface of the circumferential main groove as described above, a large number of circumferential grooves are required to ensure steering stability on the road surface on ice and snow. On the other hand, in order to increase the edge effect, it is necessary to raise the groove angle of the circumferential groove as much as possible (decrease the angle of the groove wall surface with respect to the tire radial direction), but in a tread pattern tire with a simple groove angle, the pattern block Stiffness was reduced, and the stability and braking performance on dry roads was sacrificed. In any case, with conventional tread pattern pneumatic tires, it is possible to stably achieve both steering stability on snowy and snowy road surfaces and driving stability on dry roads from the new article to the middle wear period. could not.

  Accordingly, an object of the present invention is a pneumatic radial tire capable of achieving both handling stability on a snowy and snowy road surface in winter and handling stability on a dry road surface in a normal period from the time of a new article to after the middle stage of wear. Is to provide.

In order to solve the above problems, a pneumatic radial tire of the present invention has at least three circumferential main grooves on a tread tread surface portion, and a plurality of land portion rows defined by the circumferential main grooves. In a pneumatic radial tire having a tread pattern in which circumferential sub-grooves are arranged in at least two land portion rows,
At least one side of the wall surface of the circumferential main groove defining the land portion row having the circumferential sub-groove has a chamfered portion, and the depth Dt of the chamfered portion and the circumferential sub-groove The difference from the depth Ds is within ± 5%.

  The width of the circumferential main groove is preferably 5 to 12 mm, and the groove angle θg of the wall surface of the circumferential main groove with respect to the tire radial direction below the chamfered portion is preferably 0 to 10 °, more preferably. Is 3-7 °.

  Moreover, the width of the circumferential sub-groove is preferably 2 to 5 mm, and the depth is preferably 2 to 5 mm. Further, the depth Dt of the chamfered portion is preferably 2 to 5 mm, and the groove angle θt with respect to the tire radial direction is preferably 15 to 45 °.

  Note that the chamfered portion may be a chamfered portion if the groove angle θt gradually changes or may form a curved surface, and the groove angle θt is larger than the groove angle θg below the chamfered portion.

  According to the present invention, when the tire is new, the steering stability on the road surface on ice and snow can be ensured by the circumferential sub-groove, and the block rigidity of the pattern is improved by the chamfered portion, while the circumferential main direction is improved after the middle period of wear. Due to the edge effect of the grooves, the handling stability on the road surface on ice and snow is maintained close to when it is new. As a result, it is possible to realize both the steering stability on the snowy and snowy road surface in winter and the steering stability on the dry road surface in the normal period from the new article to the middle wear stage.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a cross section of a tread portion of a pneumatic radial tire for a passenger car according to an embodiment of the present invention. The tread surface T shown in the figure has three circumferential main grooves 1 and four land portion rows 2 defined by the circumferential main grooves 1. If the number of the circumferential main grooves 1 is less than 3, the steering stability on the icy and snowy road surface when the tire is new is insufficient. The width Wm of the circumferential main groove 1 is preferably 5 to 12 mm. Even if the width Wm is less than 5 mm, the steering stability on the icy and snowy road surface is not sufficient. On the other hand, if it exceeds 12 mm, the stability on the dry road surface is deteriorated, which is not preferable.

  In the illustrated example, as shown in FIGS. 1 and 2, the circumferential sub-grooves 3 are arranged one by one in the approximate center of the four land portion rows 2, for a total of four. The circumferential sub-grooves 3 are required to be arranged in at least two land portion rows 2. If the number is less than two, the steering stability on the icy and snowy road surface at the time of a new article is insufficient.

  The pneumatic radial tire for passenger cars of the present invention has a tapered shape on at least one side (both sides in the illustrated example) of the circumferential main groove 1 that defines the land portion row 2 having the circumferential sub-groove 3. It is important that the difference between the depth Dt of the chamfered portion 4 and the depth Ds of the circumferential sub-groove 1 is within ± 5%. Thereby, when the tire is new, the driving stability on the road surface on ice and snow can be ensured by the circumferential sub-groove 3 arranged in the land portion row 2, and the pattern is formed by the chamfered portion 4 of the circumferential main groove 1. By improving the block rigidity, it is possible to ensure steering stability on a dry road surface. Further, when the wear progresses due to traveling, the circumferential sub-groove 3 disposed in the land portion row 2 disappears, but the edge effect is easily exhibited by the groove angle θg of the circumferential main groove 1, so Steering stability on the road surface is maintained close to when it is new. If the difference between the depth Dt of the chamfered portion 4 and the depth Ds of the circumferential sub-groove 3 deviates from within ± 5%, the steering stability on the road surface on ice and snow from the time of the new article to the middle stage of wear is no longer possible. It becomes impossible to achieve a balance with handling stability on a dry road surface.

  The groove angle θg of the circumferential main groove 1 from the lower portion of the chamfered portion 4 to the groove bottom with respect to the tire radial direction of the wall surface is preferably 0 to 10 °, more preferably 3 to 7 °. If it exceeds °, steering stability on the road surface on ice and snow during wear will be insufficient.

  Moreover, the width of the circumferential sub-groove 3 is preferably 2 to 5 mm. If the width of the circumferential sub-groove 3 is less than 2 mm, the steering stability on the road surface on ice and snow is not sufficient. On the other hand, if the width exceeds 5 mm, the driving stability on the dry road surface is not sufficient. It is not preferable.

  Further, the depth Ds of the circumferential sub-groove 3 is preferably 2 to 5 mm. If the depth Ds is less than 2 mm, the steering stability on the road surface on ice and snow is not sufficient. On the other hand, if it exceeds 5 mm, the steering stability on the dry road surface is not sufficient, which is not preferable anyway.

  The depth Dt of the chamfered portion 4 is preferably 2 to 5 mm. If the depth Dt is less than 2 mm, the steering stability on the dry road surface is not sufficient. On the other hand, if it exceeds 5 mm, the steering stability on the road surface on ice and snow is not sufficient.

  Further, the groove angle θt of the chamfered portion 4 with respect to the tire radial direction is preferably 15 to 45 °. If the groove angle θt is less than 15 °, the steering stability on the dry road surface is not sufficient. On the other hand, if it exceeds 45 °, the steering stability on the road surface on ice and snow is not sufficient.

  The pneumatic radial tire for passenger cars according to the present invention can be appropriately provided with tire width direction grooves 5a and 5b in the land portion row 2 in order to improve driving performance, braking performance, etc. on snowy and snowy road surfaces. The angle, the groove width, and the groove depth with respect to are not particularly limited. Although not shown, sipes can be provided for the same purpose. Furthermore, the circumferential main groove 1 and the circumferential sub-groove 3 shown in FIG. 2 are both straight grooves, but the edge component is increased as a zigzag groove, and driving performance and braking performance are improved within a range that does not impair various performances. You can also.

Hereinafter, the present invention will be described based on examples.
Examples 1-3, conventional example, comparative example Pneumatic for test passenger car having size 195 / 65R15 having the basic pattern shown in FIGS. 1 and 2 and each basic pattern having the values shown in Table 1 below Radial tires were prepared for each. Next, this test tire was mounted on a 6JJ × 15 rim, and then mounted on the front and rear wheels of a 4WD type passenger car. The air pressure was 200 kPa for both. In addition, the cross section of the land part row | line | column in the tread surface part of each test tire is expanded and shown in FIG.

Evaluation on ice / snow road surface On a general snow / snow road surface, a chain is attached to the front wheel of a 4WD type passenger car equipped with a test tire, and the feeling evaluation by 5 drivers is an average of 5 people with 10 points being the perfect score. went.

Evaluation on a dry road surface In a test course capable of high speed running, a feeling evaluation by five drivers in a 4WD type passenger car equipped with a test tire was performed with an average of five evaluations with 10 points being a perfect score.
The obtained results are also shown in Table 1 below.

  INDUSTRIAL APPLICABILITY The present invention is useful as a pneumatic radial tire for passenger cars that can safely travel on snowy and snowy road surfaces and dry road surfaces over a long period of time.

It is sectional drawing of the tread part of the pneumatic radial tire for passenger cars which concerns on one embodiment of this invention. FIG. 2 is a partially developed plan view of a tread of the pneumatic radial tire for a passenger car shown in FIG. 1. It is sectional drawing of one land part row | line | column of each test tire used in the Example.

Explanation of symbols

1 circumferential main groove 2 land section row 3 circumferential sub groove 4 chamfered section 5 width direction groove

Claims (5)

The tread tread has at least three circumferential main grooves, and circumferential sub-grooves are arranged in at least two land portion rows of the plurality of land portion rows defined by the circumferential main grooves. In a pneumatic radial tire having a tread pattern,
At least one side of the wall surface of the circumferential main groove defining the land portion row having the circumferential sub-groove has a chamfered portion, and the depth Dt of the chamfered portion and the circumferential sub-groove The pneumatic radial tire is characterized in that the difference from the depth Ds is within ± 5%.   The pneumatic radial tire according to claim 1, wherein the circumferential main groove has a width of 5 to 12 mm.   The pneumatic radial tire according to claim 1 or 2, wherein a groove angle θg of a wall surface of the circumferential main groove with respect to a tire radial direction below the chamfered portion is 0 to 10 °.   The pneumatic radial tire according to any one of claims 1 to 3, wherein the circumferential sub-groove has a width of 2 to 5 mm and a depth of 2 to 5 mm.   The pneumatic radial tire according to any one of claims 1 to 4, wherein a depth Dt of the chamfered portion is 2 to 5 mm and a groove angle θt with respect to the tire radial direction is 15 to 45 °.

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