JP2872283B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention can be used throughout the seasons, that is, it travels not only on a dry road surface but also on a slippery road surface covered with rain or snow and ice. The present invention relates to a pneumatic tire that can be provided for:

(Prior Art) Tires require greatly different performance depending on the condition of the road on which they are to be run. They exhibit excellent performance on dry and wet roads, so-called "summer tires", and are excellent on ice and snow. They can be broadly categorized into "winter tires" that perform well and "all-season tires" for use throughout the year.

Summer tires usually emphasize drainage on the tread contact surface, for example, usually 3 to 3 extending in the tire circumferential direction.
Five substantially linear circumferential grooves are arranged at substantially equal intervals in the width direction, while lateral grooves intersecting these circumferential grooves are arranged at substantially equal intervals in the tire circumferential direction. It is provided with a row of blocks partitioned by a lateral groove, and in order to achieve both steering stability on a dry road surface (dry performance) and steering stability on a wet road surface (wet performance), these circumferential grooves and Various arrangements have been made for the arrangement of the lateral grooves.

On the other hand, winter tires are preferably used as a circumferential groove and a lateral groove, in which a groove bent in a zigzag shape and having a large groove width and a large groove depth are used. Attention has been paid to enhancing the driving and braking performance of the tire by increasing the grip force.

Then, as shown in FIG. 4, for example, the all-season tire 10 has a plurality of circumferential grooves 14 extending in the tire circumferential direction in a zigzag manner in the central portion of the tread portion 12 in the tire width direction. The zigzag wide transverse grooves 16 and the wide transverse grooves adjacent to each other are arranged at predetermined intervals and extend between the circumferential grooves adjacent to each other. The narrow lateral grooves 18 provided are formed in three rows of blocks 20 each of which is disposed at substantially equal intervals in the tire circumferential direction,
Cuts 22a and 22b are formed between adjacent circumferential grooves and extend substantially parallel to the transverse grooves to divide each block into three block elements in the tire circumferential direction and to provide a rigidity of each block. Is set low to improve the grounding performance.

(Problems to be Solved by the Invention) A tire having such a tread pattern is not suitable for running on icy and snowy roads due to an improvement in the frictional force of the tire due to a cut edge that divides each block into a plurality of elements. However, when a force can be exerted in a direction perpendicular to the cuts, such as during driving and braking, although the predetermined performance can be substantially exerted, the cuts are arranged so that each block is disposed. When the elements are easily moved and the vehicle travels on a dry road surface, the wear of the tread rubber on the kick-out side of each block element is remarkably accelerated as compared with that on the step-in side.

For this reason, uneven wear having a sawtooth shape in the circumferential direction occurs in the middle of the life of the tire, which causes a problem that tire performance is deteriorated and appearance is impaired. This problem exists regardless of the internal structure of the tire, that is, whether it is a bias tire or a radial tire.

The present invention has been made in view of such a problem, and an object thereof is to provide a pneumatic tire that is excellent in dry and wet performance, and also excellent in uneven wear resistance, and can be used throughout the four seasons. I do.

(Means for Solving the Problems) In order to achieve this object, in the present invention, a plurality of circumferential grooves formed in a tread portion and separated from each other in a tire width direction and extending in a tire circumferential direction. And a plurality of lateral grooves extending between the circumferential grooves and spaced apart from each other in the tire circumferential direction, and a block row defined by at least the circumferential grooves and the lateral grooves. In the tire, each block of each block row has a pair of narrow grooves each having one end opened in a circumferential groove adjacent to each other and extending inward substantially in parallel with the lateral groove, and a pair of narrow grooves. A central notch connected to the other end thereof, and a pair of inclined cuts extending at an acute angle with respect to the central notch and extending from the vicinity of each joint of the narrow groove and the central notch to an adjacent lateral groove.

FIG. 1 shows a tread pattern of a pneumatic tire 30 to which the present invention is applied. The tread portion 32 of the tire 30 has, depending on the tire size, usually two to five circumferential grooves extending substantially in the tire circumferential direction, and in this embodiment, four circumferential grooves 34, 34. And 36, 36 are arranged apart from each other in the tire width direction.

The groove width of the pair of circumferential grooves 34 arranged adjacent to each other in the tread center portion is different from that of the other circumferential grooves 36 which are arranged to be spaced apart outward in the width direction of the grooves and form a pair with each other. The groove depth is set larger than the groove width, while the groove depth is set deeper. Thereby, sufficient drainage in the tire circumferential direction can be secured.

Then, the adjacent circumferential grooves 34, 34 and 34 and 36 are obliquely oblique to the tire equatorial plane in one direction within an angle range of 15 ° to 35 °, and are separated by a certain distance in the circumferential direction. Direction groove
By communicating at 38, three block rows 40, 42
And section 42.

The width of the lateral grooves 38 is narrower than that of the circumferential grooves 34, but the narrowest portion has a groove width of 50% or more of the groove width of the circumferential grooves 34. This is because the minimum groove width is such that a snow column shearing effect in the ground contact surface that obtains important traction when traveling on a snowy road is obtained.

On the other hand, the groove depth of the lateral groove 38 is at least partly shallower than that of the circumferential groove 34, and a value within a range of 0 to 50% of a value measured from the groove bottom of the circumferential groove 34. The rigidity of the block defined by the circumferential groove and the lateral groove is relatively high.

In this example, the shoulder portion 44 of the tire 30 is also provided with a circumferential groove 46 extending in the tire circumferential direction, and the tread portion 32
A plurality of lateral grooves 48 which are oblique to the circumferential grooves 36 and are spaced apart from each other in the tire circumferential direction extend to the shoulder portion to form a shoulder block row 50.

The angle formed by these lateral grooves 48 in the circumferential groove 36 of the tread portion 32 with respect to the tire equatorial plane is the angle formed by the lateral grooves 38 provided in the tread portion with respect to the tire equatorial plane. It has almost equal parts. Further, the lateral groove 48 is bent in a direction opposite to the equatorial plane at an intermediate portion thereof, and opens in a circumferential groove 46 provided in the shoulder portion 44.

In the present embodiment, the width of the lateral groove 48 provided at the end of the tread portion 32 from the portion that opens to the circumferential groove 36 to the bent portion thereof is determined in the lateral direction of the tread portion. The groove width from the bent portion to the portion that opens to the circumferential groove 46 has a groove width substantially equal to that of the circumferential groove 34 of the tread portion 32, and the groove depth is the same as that of the groove 38. As in 38, the circumferential groove may be equal to or shallower than the circumferential groove, and a part thereof may be shallower. And the lateral groove 48 is
It is formed at a pitch substantially equal to the pitch between the lateral grooves 38 of the tread portion and shifted by a half pitch in the tire circumferential direction. This leads to a reduction in pattern noise.

Of course, the extending direction and width of the lateral groove 38 of the shoulder portion may be changed as necessary.

Each block element of the shoulder block row 50 is bisected by a notch extending substantially parallel to the lateral groove 48 that defines each block element, and the notch enlarges a portion opening into the circumferential groove 36 at the tread end. To form a notch and increase its edge effect.

By the way, the block row formed in the center of the tread part
For example, as shown in FIG. 1 (b), each of the blocks 52 forming the 40 and 42 includes a pair of narrow grooves each having one end opened in circumferential grooves 34 and 36 separated from each other in the tire width direction.
54 is provided.

The narrow grooves 54 are disposed substantially parallel to the circumferential grooves at positions that divide the interval between the lateral grooves 38, 38 that are spaced apart from each other in the tire circumferential direction substantially in the circumferential direction. 34 and
Each end of each length 1 ₁ and 1 ₂ by narrow grooves 38 extending in the block inwardly from 36, interconnected by a central cut 56.

The narrow groove 54 has a groove width of 1.5 mm to 3 mm, preferably about 2 mm, and has a groove depth similar to that of the lateral groove 38. By setting the groove width and groove depth within such a range, the narrow groove does not close unless a transient external force acts on the tread portion, and it is possible to expect a sufficient edge effect by the narrow groove. it can.

On the other hand, the width of the central cut 56 connecting the pair of narrow grooves is 0.
It shall be selected from the range of 5 mm to 1 mm, the cut depth is set to be approximately the same as the groove depth of the narrow groove 54 or slightly shallower,
By ensuring that the cuts always close in the ground plane,
A decrease in the rigidity of the block can be minimized.

Here, the length k of the center cuts 56 shall be set to the sum of the fine grooves 54 of the pair bisected value, i.e. (1 ₁ +1 ₂₎ / 2 and substantially equal to or slightly more long. Therefore, if you set equal length 1 ₁ and 1 ₂ of the narrow groove, 1 ₁ = 1 ₂ = k
Becomes

Then, in the vicinity of the joint between the pair of narrow grooves 54 and the central cut 56, in the present embodiment, from the joint, the respective blocks 52
Each lateral groove separated in the circumferential direction of the tire that defines
A pair of inclined cuts 58 extending to 38 are provided. This forms an S-shape or a Z-shape together with the cut 56.

The angle of the inclined cut 58 with respect to the central cut 56 is smaller than 90 °, that is, arranged at an acute angle with respect to the central cut 56, and each block 52 is divided into four block elements 52a, 52b, 52c and 52d. To divide. In addition, inclined cut
The groove width and groove depth 58 are equivalent to the groove width and groove depth of the central cut 56.

In the embodiment shown in FIG. 1 (b), each of the block elements 52a and 52b and the elements 52c and 52d, which are adjacent in the tire width direction and defined by the narrow groove 54 and the central cut 56, By setting the block element lengths of the block elements 52b and 52c in the tire circumferential direction to be longer than those of the other block elements 52a and 52c, the width of the portion of the lateral groove 38 that opens into the circumferential groove 36 is increased. At the same time, the width of the middle part of the lateral groove 38 is set small,
A pair of block elements 52a and 5 adjacent to each other in the tire width direction
2b and the pair of block elements 52c and 52d may be offset from each other in the tire width direction, and the circumferential grooves 34 and 36 may extend in the tire circumferential direction in a right and left manner in a crank shape. Of course, if these block elements are arranged without being shifted in the tire width direction, the circumferential grooves 34 and 36 can be substantially extended straight on the tire equatorial plane, and the combination of each block element is changed. By doing so, various changes are possible.

Incidentally, the internal structure of the tire 30 to which the present invention is applied,
As shown in FIG. 2, an organic fiber cord represented by nylon, polyester, rayon, or the like is formed by stacking at least one ply, at most three plies, arranged at an angle of approximately 90 ° with respect to the tire equatorial plane S. A layer of carcass 62 is toroidally connected between a pair of bead rings 60, and a non-extensible cord represented by a steel cord or an aromatic polyamide fiber is provided on the outer periphery of the carcass 62 with respect to the tire equatorial plane S. A plurality of plies arranged in one direction in a shallow angle, for example, in an angle range of 10 ° to 30 °, such that a plurality of plies are obliquely oblique to each other, so that the belt main body and, in some cases, the outer periphery of the belt main body A belt 64 having an auxiliary layer formed by spirally winding a nylon cord substantially parallel to the equatorial plane S is provided, and a belt made of rubber in contact with the road surface is provided on the outer periphery of the belt 64. It has a so-called radial structure provided with a red portion 32.

On the other hand, in another embodiment of the present invention shown in FIG.
The lateral groove 48 and the lateral groove 48 in the shoulder portion 44 are curved and extend in a curved shape so that the length of each block element in the tread 32 in the tire circumferential direction is substantially equal, and the narrow groove 54 and the center are formed. A pair of block elements partitioned in the tire circumferential direction by the cuts 56 are arranged without relatively shifting in the tire width direction, thereby forming substantially linear circumferential grooves 34 and 36. The configuration is the same as that of the embodiment shown in FIG. 1 (a) except that a cutout which opens substantially orthogonally to the lateral groove 48 that defines the shoulder block row 50 is provided.

(Operation) In such a tire, one end of each block of the block row arranged in the tread portion 32 is opened in a circumferential groove adjacent in the tire width direction, and substantially in the lateral direction. Four narrow narrow grooves extending parallel to the groove 38 and a narrow central cut communicating the narrow grooves, and four narrow inclined cuts extending at an acute angle to the central cut and extending to the lateral groove 38 The narrow groove portion does not close in the ground contact surface, so that the edge effect of the block can be enhanced, and the both ends of the central cut are provided unless excessive external force acts on the tread during traveling. Communicates with the narrow groove having a smaller groove width than the groove width of the circumferential groove,
The rigidity of the block element against external force acting in the tire circumferential direction does not decrease as compared with the case where the cut directly opens in the circumferential groove, and therefore, the movement of the block element at the end of the narrow groove can be reduced. In addition, the wear resistance and the wet braking performance are not deteriorated. In addition, even when the vehicle travels on a road surface having a relatively small coefficient of friction, the notch connected to the narrow groove can be expected to have a synergistic effect with the edge effect of the narrow groove.

In addition, since the center cut and the inclined cut are dimensioned so that they can be closed to each other at the time of contact with the ground, and a reduction in rigidity of the block element is minimized, a synergistic effect with the edge effect of the narrow groove can be expected.

As described above, since the narrow groove, the center cut, and the inclined cut that partition the block element are organically arranged, even when an external force acts in the tire circumferential direction, such as during driving and braking, each block is formed. The movement is effectively suppressed, so that uneven wear does not occur, and due to the edge effect of the narrow grooves and cuts, the vehicle can travel sufficiently even on a road surface having a small coefficient of friction.

(Example) Dry performance, wet performance, and on-snow fee were measured using inventive tires A and B having the tread pattern shown in FIGS. 1 (a) and 3 and conventional tire C having the tread pattern shown in FIG. Comparative running tests were performed on rings and abrasion resistance.

◎ Test tires: ・ Both the inventive tire and the conventional tire have a carcass in which a ply of 1500d / 2 thick polyester cord is disposed in two layers and disposed at an angle of approximately 90 ° with respect to the tire equator. A ply consisting of steel cords arranged in one direction at an angle of 20 ° to the tire equator, with a belt having two layers arranged so that each cord crosses each other, size 195 / 70R14, tread width 140 mm , The negative ratio is about 35
% Passenger car tires, the specifications of which are shown in the following table.

試 験 Test method: Each tire was mounted on an actual vehicle, and each test was performed under internal pressure and load conditions based on JIS standards.

-Dry performance: Various runs were performed on a circuit course on a dry road surface, and a comprehensive feeling evaluation such as straightness and turning performance was evaluated to evaluate the index.

-Wet performance: Comprehensive feeling evaluation such as turning performance and braking performance on a wet road surface with a water depth of 0 to 1 mm was evaluated and index evaluation was performed.

-Feeling on snow: Comprehensive feeling evaluation such as starting, climbing, turning, and straightness on a slippery snow-covered road was evaluated by index.

-Uneven wear characteristics: The presence or absence of uneven wear when traveling 1000 km on a general road was visually inspected and evaluated by index.

Table 2 shows the results of the above test. The larger the index, the better the performance.

As is clear from Table 2, it has been confirmed that the tire according to the present invention has improved performance as compared with the conventional tire.

(Effects of the Invention) Thus, according to the present invention, the dry performance and the uneven wear resistance can be improved without impairing the wet performance and the feeling on snow, and the life of the tire can be greatly extended.

[Brief description of the drawings]

FIG. 1 (a) is a diagram showing a tread pattern of the tire of the present invention, FIG. 1 (b) is an explanatory diagram showing an enlarged block of the tire shown in FIG. 1 (a), and FIG. FIG. 3 is a sectional view showing the internal structure of the tire shown in FIG. 1, FIG. 3 is a view showing a tread pattern of another embodiment of the present invention, and FIG. 4 is a view showing a tread pattern of a conventional tire. It is. 10,30 tires, 12,32 tread parts 14,16,34,36,46 circumferential grooves 16,18,38,48 lateral grooves 20,40,42,50 blocks Row 52: Block, 54: Narrow groove 56: Center notch, 58: Inclined notch

Claims (1)

(57) [Claims] 1. A plurality of circumferential grooves formed in a tread portion and extending in the tire circumferential direction while being spaced apart from each other in a tire width direction, and extending between the circumferential grooves and extending in the tire circumferential direction. In a pneumatic tire including a plurality of lateral grooves spaced apart from each other and at least a block row defined by the circumferential grooves and the lateral grooves, each block of each block row is arranged in a circumferential direction adjacent to each other. A pair of narrow grooves each having one end open to the groove and extending substantially inwardly substantially parallel to the lateral groove, a central notch connected to the other end of each of the narrow grooves, and an acute angle with the central notch And a pair of inclined cuts extending from the vicinity of each of the narrow groove and the center cut to the adjacent lateral groove.