JP4751070B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a land portion composed of blocks or ribs partitioned by a circumferential main groove and a width direction sub-groove, and more particularly to a pneumatic tire that suppresses a decrease in rigidity of a shoulder land portion.

  Conventionally, pneumatic tires called so-called statless tires are used in the tread part in the tire circumferential direction as a means to improve icy and snow performance (overall performance such as drainage performance, straight running performance, turning performance, and stopping performance) on icy and snowy road surfaces. A sipe is formed in the tread width direction on a land portion composed of blocks or ribs defined by a plurality of circumferential main grooves provided toward the tread and a plurality of width direction subgrooves provided in the tread width direction. It is known to do.

For example, if the width of the shoulder sipe formed on the shoulder land portion located on the tread shoulder portion is wider than the width of the center sipe formed on the center land portion located on the tread center portion, further turning on an icy and snowy road surface A pneumatic tire for a passenger car with improved performance (ability to turn straight ahead) is disclosed (for example, Patent Document 1).
Japanese Patent Laid-Open No. 2000-142035 (page 2 to page 3, FIG. 1)

  However, in the conventional pneumatic tire, the shoulder sipe width is wider than the center sipe width, so that the rigidity of the shoulder land portion is reduced, so that the wear resistance of the shoulder land portion is reduced. There was a problem. In addition, in the case of a commercial tire mounted on a one-box / van-based vehicle with a large load capacity, the wear resistance of the shoulder land portion further decreases as the rigidity of the shoulder land portion decreases. There was a problem.

  Therefore, the present invention has been made in view of the above-described problems, and an object thereof is to provide a pneumatic tire that secures ice / snow performance on an ice / snow road surface and suppresses a decrease in rigidity of a shoulder land portion.

In order to solve the above-described problems, the present invention has the following features. First, the feature of the present invention is that in the tread portion (tread portion 15), a plurality of circumferential main grooves (circumferential main grooves 2) provided in the tire circumferential direction and a tread width direction are provided. Pneumatic tire (pneumatic tire) having land portions (land portions 4a, 4b, 5a, 5b, 6, 7a, 7b) composed of blocks or ribs partitioned by a plurality of width direction sub grooves (width direction sub grooves 3) A tire land 1) that is divided into a plurality of circumferential main grooves and is formed at the tread center portion of the tread portion, and is located outside the tread portion in the tread width direction. It is formed between the shoulder land portion (shoulder land portion 7a, 7b) formed in the tread shoulder portion (tread shoulder portion S1, S2) and the center land portion and the shoulder land portion, and the tire circumference Middle land portions (middle land portions 4a, 4b) that are continuous in the direction, shoulder sipes (shoulder sipes 71, 72) are formed in the shoulder land portions in the tread width direction, A center sipe (center sipe 61) is formed in the center land portion in the tread width direction, and the width (W7) of the shoulder sipe in the tire circumferential direction is the width of the center sipe in the tire circumferential direction ( The width of the shoulder circumferential main groove adjacent to the shoulder land portion is narrower than W6) and is 25 to 35% of the width of the center circumferential main groove adjacent to the center land portion, and the shoulder circumferential main groove The gist of the depth is 50 to 70% of the depth of the center circumferential main groove .

  According to this invention, since the center sipe and the shoulder sipe are formed in the center land portion and the shoulder land portion, the edge effect on the icy and snowy road surface can be sufficiently obtained, and the icy and snowy performance on the icy and snowy road surface can be ensured.

  Further, since the width of the shoulder sipe is narrower than the width of the center sipe, a decrease in rigidity of the shoulder land portion is suppressed, and the wear resistance of the shoulder land portion that is particularly easily worn is improved. This pneumatic tire is preferably mounted on a one-box / van-based vehicle that has a large load and is likely to cause uneven wear (shoulder wear or one-side wear).

  Further, by improving the wear resistance of the shoulder land portion, it is possible to suppress the occurrence of uneven wear (shoulder wear, side wear, polygonal wear). Here, the polygonal wear is wear in which uneven wear (shoulder wear or fall-off wear) progresses obliquely rearward toward the tread shoulder portion, and finally becomes a polygon of about octagons to dodecagons.

  In the present invention, the shoulder sipe width (W7) is 0.1 to 0.4 mm, and the difference between the shoulder sipe width (W7) and the center sipe width (W6) is 0.1 to 0.3 mm. It is a summary.

  According to this invention, the width of the shoulder sipe is 0.1 to 0.4 mm, and the difference between the width of the shoulder sipe and the width of the center sipe is 0.1 to 0.3 mm. The decrease in rigidity can be further suppressed, and the wear resistance of the shoulder land portion is further improved.

  In the present invention, the shoulder sipe is formed on the outer side in the tread width direction from the position 35% (35% position F) from the tire equator line (tire equator line CL) in the tread contact width. To do.

  According to this invention, the shoulder sipe is disposed on the outer side in the tread width direction than the position of 35% from the tire equator line in the tread ground contact width, so that the tire equator line side (that is, the 35% position) Ice / snow performance can be ensured at the center land portion that contributes greatly to ice / snow performance, and the wear resistance can be improved at the outer side in the tread width direction (shoulder land portion that is easily worn) than the 35% position.

  In the present invention, the width (W2a) of the shoulder circumferential main groove (circumferential main groove 2a) adjacent to the shoulder land portion is equal to that of the center circumferential main groove (circumferential main groove 2) adjacent to the center land portion. It is 25 to 35% of the width (W2), and the depth (D2a) of the shoulder circumferential direction main groove is 50 to 70% of the depth (D2) of the center circumferential direction main groove.

  According to this invention, the width of the shoulder circumferential main groove is 25 to 35% of the width of the center circumferential main groove, and the depth of the shoulder circumferential main groove is 50 to the depth of the center circumferential main groove. By being 70%, even if wear occurs in the shoulder land portion, the progress of wear can be blocked by the shoulder circumferential main groove. As a result, wear is less likely to occur in the center land portion, which contributes greatly to ice / snow performance, and ice / snow performance can be ensured.

  ADVANTAGE OF THE INVENTION According to this invention, while ensuring the snow and snow performance in a snowy and snowy road surface, the pneumatic tire which suppresses the fall of the rigidity of a shoulder land part can be provided.

  Next, an example of a pneumatic tire according to the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Composition of pneumatic tire)
FIG. 1 is a cross-sectional view in the tread width direction of a pneumatic tire 1 according to the present embodiment. As shown in FIG. 1, the pneumatic tire 1 has a pair of bead portions 11 including at least a bead core 11a and a bead filler 11b. Specifically, a steel cord or the like is used for the bead core 11a constituting the bead unit 11.

  The pneumatic tire 1 has a carcass layer 12 that is a skeleton of the pneumatic tire 1. A belt layer 13 (a first belt layer 13a and a second belt layer 13b) is disposed on the outer side of the carcass layer 12 in the tire radial direction. Further, a tread portion 15 that is in contact with the road surface is disposed on the outer side of the belt layer 13 in the tire radial direction.

  Next, the above-described tread portion 15 will be described with reference to FIG. FIG. 2 is a development view of the tread portion 15 of the pneumatic tire 1.

  As shown in FIG. 2, the tread portion 15 is partitioned by circumferential main grooves 2 a and 2 b provided in the tire circumferential direction and a width-direction sub-groove 3 provided in the tread width direction. Land portions 4a, 4b, 5a, 5b, 6, 7a, 7b made of blocks or ribs are arranged.

  Specifically, the tread portion 15 includes at least a ground end E that is an end of the tread ground width that contacts the ground, and the shoulder land portions 7a and 7b located in the tread shoulder portions S1 and S2 face the tread width direction. A plurality of zigzag shoulder sipes 71 and 72 are formed.

  A plurality of zigzag center sipes 61 are formed in the center land portion 6 located in the tread center portion C in the tread width direction. In addition, the center land part 6 should just be arrange | positioned at the tread center part C, for example, may be arrange | positioned including the tire equator line CL, and may be arrange | positioned in the tire equator line CL vicinity.

  Further, the middle land portions 4a, 4b, 5a and 5b located in the middle portions M1, M2, M3 and M4 provided between the tread center portion C and the tread shoulder portions S1 and S2 are respectively zigzag-shaped middle sipes. A plurality of 41, 42, 51, and 52 are formed.

  Here, as shown in FIGS. 3 and 4, the width (W7) of the shoulder sipes 71, 72 provided in the shoulder land portions 7a, 7b is equal to the width (W6) of the center sipes 61 provided in the center land portion 6. ). Since the shoulder land portion 7a and the shoulder land portion 7b have the same configuration, only the shoulder land portion 7a is shown in FIG.

  The width (W7) of the shoulder sipes 71 and 72 is 0.1 to 0.4 mm, and the difference between the width (W7) of the shoulder sipes 71 and 72 and the width (W6) of the center sipes 61 is 0.1 to 0. .3 mm is preferable. In this case, the width of the middle sipes 41, 42, 51, 52 may be the same as the width (W 6) of the center sipe 61, and the middle sipes 41, 42, 51, 52 may be configured to narrow in order from the center sipe 61 to the shoulder sipes 71, 72.

  If the width (W7) of the shoulder sipes 71 and 72 is smaller than 0.1 mm, it may be difficult to manufacture. Further, if the width (W7) of the shoulder sipes 71 and 72 is larger than 0.4 mm, the rigidity of the shoulder land portions 7a and 7b may be lowered.

  On the other hand, if the difference between the width (W7) of the shoulder sipes 71 and 72 and the width (W6) of the center sipe 61 is smaller than 0.1 mm, the drainage performance effect on the icy and snowy road surface may not be sufficiently obtained. Further, if the difference between the width (W7) of the shoulder sipes 71 and 72 and the width (W6) of the center sipe 61 is larger than 0.3 mm, the rigidity of the shoulder land portions 7a and 7b may be lowered.

  The shoulder sipes 71 and 72 are more preferably arranged on the outer side in the tread width direction than the position F of 35% from the tire equator line CL in the tread ground contact width.

  When the shoulder sipes 71 and 72 are disposed on the inner side in the tread width direction from the position F at 35% from the tire equator line CL, the shoulder sipes 71 and 72 having a width narrower than the width (W6) of the center sipe 61 The ice / snow performance may be deteriorated because it is arranged at a position that contributes to the above.

  Furthermore, as shown in FIG. 5, the width (W2a) of the circumferential main groove 2a (shoulder circumferential main groove) adjacent to the shoulder land portions 7a and 7b is equal to the circumferential main groove 2 ( The width (W2) of the center circumferential direction main groove) is 25 to 35%, and the depth (D2a) of the circumferential direction main groove 2a is 50 to 70% of the depth (D2) of the circumferential direction main groove 2 Preferably there is.

  Since the shoulder land portion 7a and the shoulder land portion 7b have the same configuration, and the middle land portions 4a and 5a and the middle land portions 4b and 5b have the same configuration, the shoulder land portion in FIG. Only 7a and middle land portions 4a and 5a are shown.

  If the width (W2a) of the circumferential main groove 2a is less than 25% of the width (W2) of the circumferential main groove 2, when the vehicle turns, the circumferential main groove 2a closes, and the turning performance deteriorates. May end up. Further, when the width (W2a) of the circumferential main groove 2a exceeds 35% of the width (W2) of the circumferential main groove 2, land portions (middle land portions 4a, 4b and shoulders) that are adjacent to the circumferential main groove 2a. The rigidity of the land portions 7a and 7b) may decrease.

  On the other hand, if the depth (D2a) of the circumferential main groove 2a is less than 50% of the depth (D2) of the circumferential main groove 2, the wear may occur in the vicinity of the circumferential main groove 2a. The direction main groove 2a disappears early, and ice / snow performance (particularly, drainage performance and turning performance) may not be ensured. Further, when the depth (D2a) of the circumferential main groove 2a exceeds 70% of the depth (D2) of the circumferential main groove 2, a land portion (middle land portion 4a, 4b) adjacent to the circumferential main groove 2a. In addition, the rigidity of the shoulder land portions 7a and 7b) may be reduced.

(Action / Effect)
According to the pneumatic tire 1 according to the present embodiment described above, the center sipe 6 and the shoulder sipes 71 and 72 are formed in the center land portion C and the shoulder land portions S1 and S2, so that the edge on the icy and snowy road surface is formed. A sufficient effect can be obtained, and ice / snow performance on an ice / snow road surface can be ensured.

  Further, since the width (W7) of the shoulder sipes 71 and 72 is narrower than the width (W6) of the center sipe 6, the lowering of the rigidity of the shoulder land portions 7a and 7b is suppressed, and the shoulder land portion 7a that is particularly easily worn. , 7b is improved.

  Further, by improving the wear resistance of the shoulder land portions 7a and 7b, it is possible to suppress the occurrence of uneven wear (shoulder wear, side wear, polygonal wear).

  The width (W7) of the shoulder sipes 71 and 72 is 0.1 to 0.4 mm, and the difference between the width (W7) of the shoulder sipes 71 and 72 and the width (W6) of the center sipes 6 is 0.1. By being -0.3mm, the fall of the rigidity of shoulder land part 7a, 7b can further be suppressed, and the abrasion resistance of shoulder land part 7a, 7b further improves.

  Further, since the shoulder sipes 71 and 72 are arranged on the outer side in the tread width direction from the position F of 35% from the tire equator line CL in the tread contact width, the tire equator line CL side from the position F of 35%. (In other words, the center land portion 6 that contributes greatly to ice and snow performance) ensures snow and snow performance, and the wear resistance is improved on the outer side in the tread width direction (the shoulder land portions 7a and 7b that are easily worn) than the position F of 35%. Can be made.

  Further, the width (W2a) of the circumferential main groove 2a is 25 to 35% of the width (W2) of the circumferential main groove 2 and the depth (D2a) of the circumferential main groove 2a is the width of the circumferential main groove 2. By being 50 to 70% of the depth (D2), even if wear occurs in the shoulder land portions 7a and 7b, the progress of wear can be blocked by the circumferential main groove 2a. This makes it difficult for wear to occur in the center land portion 6 that contributes greatly to the snow and snow performance, and the snow and snow performance can be ensured.

  Although the contents of the present invention have been disclosed through the embodiments of the present invention as described above, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention.

  From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  Next, in order to further clarify the effects of the present invention, the results of tests performed using pneumatic tires according to the following comparative examples and examples will be described. In addition, the data regarding each pneumatic tire were measured on the conditions shown below.

・ Tire size: LYR 195 / 80R15 107L
・ Wheel size: 6.0J × 15
-Vehicle type: 1 box (displacement 2.500cc)
-Internal pressure conditions: Normal internal pressure Hereinafter, the stop performance, wear resistance, and uneven wear resistance of the pneumatic tires according to Comparative Examples 1 to 3 and Example 1 will be described. Table 1 shows the sipe width and test results for each pneumatic tire. Each pneumatic tire is the same except for the width of the sipe (including the sipe depth), and is constituted by a tread portion shown in FIG.

  As shown in Table 1, in the pneumatic tire according to Comparative Example 1, the width of the center sipe is 0.4 mm, and the width of the shoulder sipe is 0.4 mm. In the pneumatic tire according to Comparative Example 2, the center sipe width is 0.6 mm and the shoulder sipe width is 0.6 mm.

  In the pneumatic tire according to Comparative Example 3, the center sipe width is 0.4 mm and the shoulder sipe width is 0.6 mm. In the pneumatic tire according to Example 1, the width of the center sipe is 0.6 mm, and the width of the shoulder sipe is 0.4 mm.

<Stopping performance>
Each pneumatic tire is attached to a vehicle (no load), runs on a test course on an icy road surface at a constant speed, and the vehicle equipped with the pneumatic tire according to Comparative Example 1 stops after a full lock brake is applied. The stop performance of the pneumatic tires according to Comparative Example 2, Comparative Example 3, and Example 1 was indicated by an index. In addition, it shows that it is excellent in stop performance, so that the value of an index | exponent is large.

  As a result, it was found that the pneumatic tires according to Comparative Example 2 and Example 1 were superior in stopping performance as compared with the pneumatic tires according to Comparative Example 1 and Comparative Example 3. That is, it was found that a pneumatic tire having a wide center sipe has excellent stopping performance.

<Abrasion resistance>
Each pneumatic tire is mounted on a vehicle (constant load), and after traveling 15000 km on a dry road test course, the groove depth (remaining groove) of the pneumatic tire according to Comparative Example 1 mounted on the rear of the vehicle is set to “ The groove depth in the pneumatic tires according to Comparative Example 2, Comparative Example 3 and Example 1 mounted on the rear of the vehicle was indicated by an index. In addition, it shows that it is excellent in abrasion resistance, so that the value of an index | exponent is large.

  As a result, it was found that the pneumatic tires according to Comparative Example 3 and Example 1 were superior in wear resistance as compared with the pneumatic tires according to Comparative Example 1 and Comparative Example 2. That is, it has been found that a pneumatic tire having a difference between the width of the center sipe and the width of the shoulder sipe can ensure wear resistance.

<Uneven wear resistance>
Each pneumatic tire is mounted on a vehicle (constant load), the groove depth located at the tread shoulder portion in the pneumatic tire according to Comparative Example 1 mounted on the rear of the vehicle after running on a dry road test course for 15000 km. The difference between the (remaining groove) and the depth of the groove located in the tread center portion is “100”, and the tread shoulder portion in the pneumatic tires according to Comparative Example 2, Comparative Example 3 and Example 1 mounted on the rear of the vehicle The difference between the groove depth (remaining groove) located in the groove and the depth of the groove located in the tread center portion was indicated by an index. In addition, it shows that it is excellent in uneven wear resistance, so that the value of an index | exponent is large.

  As a result, it was found that the pneumatic tires according to Comparative Example 1 and Example 1 were more excellent in uneven wear resistance than the pneumatic tires according to Comparative Example 2 and Comparative Example 3. That is, it was found that a pneumatic tire with a narrow shoulder sipe has excellent uneven wear resistance.

It is a tread width direction cross section of the pneumatic tire concerning this embodiment. It is an expanded view of the tread part in the pneumatic tire concerning this embodiment. It is an enlarged view of a shoulder land part concerning this embodiment. It is an enlarged view of the center land part concerning this embodiment. It is an enlarged view of the center land part, middle land part, and shoulder land part which concern on this embodiment, and sectional drawing of the circumferential direction main groove.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2, 2a ... Circumferential main groove, 3 ... Width direction subgroove, 4a, 4b, 5a, 5b ... Middle land part, 6 ... Center land part, 7a, 7b ... Shoulder land part, 11 ... Bead part, 11a ... Bead core, 11b ... Bead filler, 12 ... Carcass layer, 13 ... Belt layer, 13a ... First belt layer, 13b ... Second belt layer, 15 ... Tread part, 41, 42, 51, 52 ... Middle sipe, 61 ... Center sipe, 71,72 ... Shoulder sipe

Claims (3)

The tread portion has a land portion composed of blocks or ribs partitioned by a plurality of circumferential main grooves provided toward the tire circumferential direction and a plurality of width direction auxiliary grooves provided toward the tread width direction. A pneumatic tire,
A center land portion that is partitioned into a plurality of the circumferential main grooves and formed in the tread center portion of the tread portion;
A shoulder land portion formed in a tread shoulder portion located outside the tread width direction of the tread portion;
And a middle land portions continuous in the tire circumferential direction is formed between the center land portion and the shoulder land portion,
In the shoulder land portion, a shoulder sipe is formed in the tread width direction,
In the center land portion, a center sipe is formed in the tread width direction,
The width of the shoulder sipe in the tire circumferential direction is narrower than the width of the center sipe in the tire circumferential direction,
The width of the shoulder circumferential main groove adjacent to the shoulder land portion is 25 to 35% of the width of the center circumferential main groove adjacent to the center land portion,
The depth of the shoulder circumferential main groove is 50 to 70% of the depth of the center circumferential main groove. The width of the shoulder sipe is 0.1 to 0.4 mm,
The pneumatic tire according to claim 1, wherein a difference between a width of the shoulder sipe and a width of the center sipe is 0.1 to 0.3 mm.   3. The pneumatic tire according to claim 1, wherein the shoulder sipe is formed on the outer side in the tread width direction with respect to the tread contact width at a position 35% from the tire equator line.

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