JP2008030605A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire devised to simultaneously improve steering stability on a dried road surface and steering stability and a turning property on a snow road surface. <P>SOLUTION: A plurality of inclined grooves 6 inclined directions in the tire circumferential direction of which are different from a lug groove 3 are formed so as to terminate in a block 4 by continuously crossing more than two pieces of the lug grooves 3, 3 without straddling over a tire equator line CL on a wide land part 5b partitioned so as to straddle over the tire equator line CL by a main groove 2a positioned nearest to a shoulder side and a main groove 2b adjacent to it out of a plurality of the main grooves 2a, 2b, 2c, 2d extending in the tire circumferential direction formed on a tread surface 1 and are arranged so as to overlap with each other between end parts 6a, 6b of the inclined grooves 6 adjacent to each other in the tire circumferential direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having an asymmetric tread pattern that simultaneously improves steering stability on a dry road surface, steering stability on a snowy road surface, and turning performance.

  In general, a pneumatic tire for icy and snowy roads employs a block pattern as a tread pattern to increase the groove depth or groove area, as illustrated in FIG. 5, in order to ensure motion performance on a snowy road surface. Has been generally set (see, for example, Patent Document 1). However, in a tire having a wide groove area as described above, the surface area of the block (land) becomes small as a whole pattern, and there is a problem that steering stability on a dry road surface is inferior.

As described above, it is very difficult to simultaneously achieve the motion performance on the road surface on snow and the motion performance on the dry road surface. In order to solve this problem, many proposals have been made so far, but all have advantages and disadvantages, and there is still room for improvement.
JP 2004-25954 A

  An object of the present invention is to solve such a conventional problem, and to provide a pneumatic tire that simultaneously improves steering stability and turning performance on a snowy road surface and steering stability on a dry road surface. It is in.

  In order to achieve the above object, the pneumatic tire of the present invention forms, on the tread surface, a plurality of main grooves extending in the tire circumferential direction and a plurality of lug grooves extending obliquely in the tire circumferential direction intersecting therewith, In the pneumatic tire in which a large number of blocks are defined in the tire circumferential direction of the tread surface by the main grooves and the lug grooves, the main groove located on the most shoulder side of the main grooves and the main groove adjacent thereto are used for the tire. A plurality of inclined grooves with different inclination directions with respect to the tire circumferential direction are continuously connected to two or more lug grooves without straddling the tire equator line in the wide land portion partitioned so as to straddle the equator line. The gist of the present invention is that the end portions of the inclined grooves adjacent to each other in the tire circumferential direction are overlapped with each other.

Furthermore, the pneumatic tire of the present invention may be configured as follows.
(1) The width of the wide land portion is set to 25 to 35% of the tire ground contact width.
(2) A narrow land portion in which the width of the land portion is 8 to 20% of the tire ground contact width is disposed adjacent to the tire equator line side of the wide land portion.
(3) In the wide land portion, when the width of the region occupied by the inclined groove in the tire circumferential direction is X1, the width X2 of the region on the tire equator line side, and the width X3 of the region on the tire shoulder side, each width X1 , X2, and X3 regions, the relationship between the groove area ratios SX1, SX2, and SX3 is expressed as SX2
<SX3 <SX1, 0.70 × SX3 ≦ SX2 ≦ 0.95 × SX3.
(4) The tire circumferential direction interval L between the terminals in the overlap region of the inclined grooves adjacent to each other in the tire circumferential direction is made smaller than the tire circumferential direction interval R of the lug grooves.
(5) The intersection angle α on the acute angle side where the lug groove intersects the main groove is set to 50 to 80 °.
(6) The inclination angle β on the acute angle side with respect to the tire circumferential direction of the inclined groove is set to 15 to 40 °.
(7) The total width of the main grooves is 15-30% of the tire ground contact width.
(8) A sipe extending generally in the tire width direction is formed on the surface of the block.

  According to the pneumatic tire of the present invention, the main groove located on the most shoulder side among the plurality of main grooves formed in the tire circumferential direction formed on the tread surface and the main groove adjacent thereto straddle the tire equator line. A plurality of inclined grooves that intersect with two or more lug grooves and terminate in the block without straddling the tire equator line are provided in the partitioned wide land portion so as to be inclined in the opposite direction to the lug grooves, and in the tire circumferential direction. Since the end portions of the adjacent inclined grooves are arranged so as to overlap each other, the edge effect of the inclined grooves in the wide land portion can improve the steering stability and the turning performance on the road surface on snow. Is terminated in a region that does not cross the tire equator line, rigidity in the tread central region is ensured, and steering stability on a dry road surface can be improved.

  Moreover, since the tread surface is formed in an asymmetric pattern configuration with respect to the tire width direction, when emphasizing steering stability and turning performance on the snowy road surface, the tire is mounted so that the wide land portion side is outside the vehicle. However, when the steering stability on the dry road surface is emphasized, the tire can be used according to desired required characteristics by mounting the tire so that the wide land portion side is inside the vehicle.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a partial plan view showing a tread surface of a pneumatic tire according to an embodiment of the present invention. In FIG. 1, the tread surface 1 has a plurality of (three in the figure) main grooves 2a, 2b and 2c extending in the tire circumferential direction, and a plurality of lug grooves 3 extending incline in the tire circumferential direction intersecting therewith. The main grooves 2a, 2b, 2c and the lug grooves 3 define a large number of blocks 4 in the tire circumferential direction of the tread surface 1. Thereby, the tread surface 1 is divided into four land portions 5a, 5b, 5c, and 5d. In the present invention, the main grooves 2a, 2b, and 2c refer to grooves that extend straight in the tire circumferential direction with a groove width of 4 to 20 mm.

  The land portion 5 defined by the main groove 2a located on the most shoulder side (right side in the figure) of the main grooves 2a, 2b, and 2c and the main groove 2b adjacent thereto is a wide land portion (hereinafter referred to as a wide land portion 5b). Is formed so as to straddle the tire equator line CL. The wide land portion 5b is formed with a plurality of inclined grooves 6 having different inclination directions from the lug grooves 3, and these inclined grooves 6 are continuously provided with two or more (three in the figure) lug grooves 3. The crossing ends in the block 4 and the end portions 6a and 6b of the inclined grooves 6 adjacent in the tire circumferential direction are arranged so as to overlap each other.

  As a result, the edge effect of the inclined groove 6 in the wide land portion 5b improves the handling stability and turning performance on the snowy road surface, and the inclined groove 6 is terminated in a region that does not straddle the equator line CL. As a result, the steering stability on the dry road surface can be improved.

  In addition, since the tread surface 1 is formed in an asymmetric pattern configuration with respect to the tire width direction, when emphasizing steering stability and turning performance on a snowy road surface, the tire is so that the wide land portion 5b side is outside the vehicle. When attaching importance to steering stability on a dry road surface, the tire can be used according to desired required characteristics by attaching the tire so that the wide land portion 5b side is inside the vehicle. .

In the pneumatic tire of the present invention, the width X of the wide land portion 5b is 25 to 35 of the tire ground contact width W.
%, Preferably 28-32%. Thereby, the block rigidity in the wide land part 5b can be ensured appropriately, and the steering stability on the dry road surface can be further improved. If the width X of the wide land portion 5b is less than 25% of the tire ground contact width W, the rigidity of the wide land portion 5b decreases and the running performance on the dry road surface decreases, and if it exceeds 35%, the difference in rigidity from the adjacent other land portion Becomes too large and wear resistance decreases. In addition, the dotted line P in a figure has shown the position of the tire grounding end.

  When the three main grooves 2a, 2b, and 2c are formed on the tread surface 1 as in the embodiment of FIG. 1, the land portion 5c adjacent to the tire equator line CL side of the wide land portion 5b is the narrow land portion. The width Y of the narrow land portion 5c is set to 8 to 20%, preferably 10 to 15% of the tire ground contact width W. Thereby, the block rigidity in the narrow land part 5c can be hold | maintained appropriately, and the steering stability in a dry road surface can be improved reliably. If the width Y of the narrow land portion 5c is less than 8% of the tire ground contact width W, the block rigidity of the narrow land portion 5c is insufficient, and steering stability on a dry road surface is lowered, and the block of the narrow land portion 5c is blocked. 4 is prone to uneven wear, and if it exceeds 20%, the amount of rubber in the narrow land portion 5c increases excessively, and the durability decreases due to heat generation during high-speed running.

  In the present invention, the tire contact width W refers to the contact width of the tire in a state where the tire is filled with air pressure specified by JATMA and a load corresponding to 80% of the maximum load specified by JATMA is applied.

In the wide land portion 5b of the present invention, as shown in FIG. 2, the width of the region occupied by the inclined groove 6 with respect to the tire width direction is X1, the width of the region on the tire equator line CL side is X2, and the tire shoulder side (see FIG. When the width of the region on the right side) is X3, the groove area ratios SX1, SX2, SX3 in the regions of the respective widths X1, X2, and X3 are SX2 <SX3 <SX1, 0.70 × SX3 ≦ SX
Adjustment may be made so that 2 ≦ 0.95 × SX3. As a result, the tread surface 1
It is possible to appropriately ensure the rigidity in the central region of the vehicle, and to improve the steering stability on the dry road surface and the braking performance on the snowy road surface.

Note that the width X1 of the region occupied in the tire width direction of the inclined groove 6 described above refers to the maximum distance in the tire width direction between the both end portions 6a and 6b of the inclined groove 6, and the inclination arranged in the tire circumferential direction. When the both ends of the groove 6 are uneven with respect to the tire width direction, the ends located closest to the main grooves 2a, 2b among the both ends 6a, 6b of the inclined groove 6 arranged in the tire circumferential direction The width in the tire width direction that connects

  In the wide land portion 5b of the present invention, the tire circumferential direction interval L (see FIG. 2) between the terminals 6a and 6b in the overlap region of the inclined grooves 6 and 6 adjacent to each other in the tire circumferential direction is defined as the tire of the lug grooves 3 and 3. It may be set to be smaller than the circumferential interval R. If the distance L is larger than the distance R, the block 4 in the wide land portion 5b becomes too small, and the steering stability on the dry road surface and the uneven wear resistance of the block 4 are deteriorated. In addition, the tire circumferential direction space | interval R of the lug grooves 3 and 3 mentioned above means the space | interval of the tire circumferential direction in the intermediate position of the area | region which occupies with respect to the tire width direction of the inclined groove | channel 6.

  In the present invention, the intersection angle α (see FIG. 2) on the acute angle side where the lug groove 3 intersects the main grooves 2a, 2b and 2c is set to 50 to 85 °, preferably 60 to 80 °. When the crossing angle α is less than 50 °, the rigidity in the circumferential direction of the block 4 is insufficient, and the steering stability on the dry road surface and the uneven wear resistance of the block 4 are deteriorated. If it exceeds 85 °, the ground contact outline and the lug groove 3 at the time of rotation of the tire periodically coincide with each other to cause noise.

  Furthermore, the inclination angle β on the acute angle side with respect to the tire circumferential direction of the inclined groove 6 may be set to 15 to 40 °, preferably 20 to 30 °. If the inclination angle β is less than 15 °, the steering stability and turning performance on the snowy road surface will be reduced, and if it exceeds 40 °, the width of the wide land portion 5b and the width of the surrounding land portion 5a and the narrow land portion 5c. Is lost, the block rigidity in each land portion becomes non-uniform, and the uneven wear resistance of the block 4 in each land portion decreases.

  In the present invention, the total width of the main grooves 2a, 2b and 2c may be adjusted to be 15 to 30%, preferably 18 to 25% of the tire ground contact width W. If the total width of the main grooves 2a, 2b and 2c is less than 15% of the tire ground contact width W, the wet performance on the road surface on snow will be lowered, and if it exceeds 30%, the steering stability will be lowered.

  On the tread surface 1 of the pneumatic tire of the present invention, 2 to 4 and most preferably 3 main grooves are formed. When the two main grooves 2a and 2b are formed on the tread surface 1, a continuous groove in the tire circumferential direction is formed instead of the main groove 2c in FIG. 1, and the pattern of the narrow land portion 5c and the land portion 5d Change the configuration. The pattern configuration in this case is not particularly limited, and is set according to the type and size of the tire as long as it does not impair the handling stability on the dry road surface and the driving stability and turning performance on the snowy road surface. The

  FIG. 3 shows an embodiment in which four main grooves 2a, 2b, 2c, and 2d are formed on the tread surface 1. In this embodiment, on the shoulder side (left side of the figure) of the main groove 2c in FIG. A main groove 2d is formed to divide the tread surface 1 into five land portions 5a, 5b, 5c, 5d, and 5e. Even in the present embodiment, the width of the land portion 5d may be set to 8 to 20% of the tire ground contact width W in the same manner as the land portion 5c (the narrow land portion 5c) on the tire equator line CL side. The pneumatic tire according to the present embodiment is particularly used for a tire having a wide tread surface and a flat tire.

  In the pneumatic tire of the present invention, a narrow groove extending in the tire circumferential direction (not shown) may be formed in each land portion 5a, 5b, 5c, 5d, and 5e. Further, as shown in FIG. 4, a sipe extending generally in the tire width direction is generally formed in the block 4 in each of the land portions 5a, 5b, 5c, 5d, and 5e.

  As described above, the pneumatic tire of the present invention has an asymmetric pattern structure on the tread surface in the left and right direction in the tire width direction, and therefore has an advantage that desired required characteristics can be obtained by selecting the mounting position on the vehicle. Therefore, it can be widely applied to various tires including passenger car tires.

  A conventional tire having a tread pattern of FIG. 5 and a tire of the present invention having a tread pattern of FIG. 4 were manufactured with a tire size of 205 / 55R16.

  These two types of tires are assembled on a 6.5J rim, filled with 200kPa internal pressure and mounted on the four front and rear wheels of a 2000cc rear-wheel drive vehicle. The steering stability and turning performance were evaluated, and the results are shown in Table 1 using an index with the conventional tire as 100. The larger the value, the better.

[Operation stability on dry road surface]
A test course consisting of an asphalt road surface was run at an average speed of 120 km / h, and a comprehensive evaluation was conducted by a skilled test driver with a feeling that mainly consisted of race change characteristics and cornering characteristics.

[Steering stability on snowy road surface]
A test course consisting of a flat snowy road surface was run at an average speed of 60 km / h, and a comprehensive test was carried out by a skilled test driver with a feeling mainly based on race change characteristics and cornering characteristics.

[Swivel on snowy road surface]
A 15 m radius circular turning course consisting of a flat on-snow road surface was run at an average speed of 30 km / h, and evaluation by feeling was carried out by a skilled test driver.

  As a result, it can be seen that the tire of the present invention has improved steering stability on a dry road surface, steering stability on a snowy road surface, and turning performance at the same time as compared with a conventional tire.

It is a partial top view which shows the tread surface of the pneumatic tire which consists of embodiment of this invention. It is a partial top view equivalent to FIG. 1 for demonstrating the structure of the tread surface of FIG. It is a partial top view which shows the tread surface of the pneumatic tire which consists of other embodiment of this invention. It is a partial top view which shows the tread surface of the pneumatic tire of this invention made into the object of evaluation. It is a partial top view which shows the tread surface of the conventional pneumatic tire.

Explanation of symbols

1 tread surface 2a, 2b, 2c, 2d main groove 3 lug groove 4 block 5a, 5d, 5e land portion 5b land portion (wide land portion) 5c land portion (narrow land portion)
6 Inclined groove 6a, 6b End of inclined groove CL Tire equator line P Tread grounding end

Claims (9)

A plurality of main grooves extending in the tire circumferential direction and a plurality of lug grooves extending in the tire circumferential direction intersecting therewith are formed on the tread surface, and a large number in the tire circumferential direction of the tread surface is formed by these main grooves and lug grooves. In the pneumatic tire in which the block of
In the wide land portion that is divided so as to straddle the tire equator line by the main groove located on the most shoulder side among the main grooves and the main groove adjacent thereto, the inclination direction with respect to the tire circumferential direction is different from that of the lug grooves. The plurality of inclined grooves are formed so as to continuously intersect with two or more lug grooves without ending over the tire equator line and terminate in the block, and end portions of the inclined grooves adjacent to each other in the tire circumferential direction Pneumatic tires arranged so as to overlap each other.   The pneumatic tire according to claim 1, wherein a width of the wide land portion is 25 to 35% of a tire ground contact width.   The pneumatic tire according to claim 1 or 2, wherein a narrow land portion having a land portion width of 8 to 20% of a tire ground contact width is arranged adjacent to the tire equator line side of the wide land portion. In the wide land portion, when the width of the region occupied by the inclined groove in the tire width direction is X1, the width of the region on the tire equator line side is X2, and the width of the region on the tire shoulder side is X3, each width X1, The pneumatic tire according to claim 1, 2 or 3, wherein the groove area ratios SX1, SX2, SX3 in the region of X2, X3 have the following relationship.
SX2 <SX3 <SX1
0.70 × SX3 ≦ SX2 ≦ 0.95 × SX3   The pneumatic tire according to claim 1, 2, 3 or 4, wherein a tire circumferential direction interval L between terminals in an overlap region of the inclined grooves adjacent to each other in a tire circumferential direction is smaller than a tire circumferential direction interval R of the lug groove. .   The pneumatic tire according to claim 1, 2, 3, 4, or 5, wherein an intersection angle α on an acute angle side where the lug groove intersects the main groove is 50 to 85 °.   The pneumatic tire according to claim 1, wherein an inclination angle β on an acute angle side with respect to the tire circumferential direction of the inclined groove is 15 to 40 °.   The pneumatic tire according to claim 1, 2, 3, 4, 5, 6 or 7, wherein a total width of the main groove is 15 to 30% of a tire ground contact width.   The pneumatic tire according to claim 1, wherein a sipe extending substantially in the tire width direction is formed on a surface of the block.

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