JPH0976711A - Radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire which can improve partial wear resistance without worsening pattern noise, even when the number of sipes or pitch is finely set similarly to a customary one. SOLUTION: In a radial tire provided with longitudinal grooves in the circumferential direction, lateral grooves crossing with them, and block patterns divided with these grooves, on a tread face part, a block 3 is formed with a thin groove 4 crossing the block 3 on the nearly center in the circumferential direction of the tire, and one or a plurality of thin grooves 5 shallower than the center lateral groove respectively in the front and rear territories 3a, 3b continued through the thin groove 4. Difference between the thin wall 4 and the shallowest thin groove 5 is set to be 1.0-5.0mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire which is effective in reducing pattern noise and uneven wear resistance.

[0002]

BACKGROUND OF THE INVENTION A plurality of longitudinal grooves such as main grooves and sub-grooves in the tire circumferential direction, a large number of lateral grooves intersecting with the longitudinal grooves, and a large number of blocks defined by these grooves. There is known a so-called block pattern tire having a tire or a pattern tire in which a lateral groove crossing the rib-shaped land portion continuous in the tire circumferential direction is formed to form the land portion in a substantially block shape. .

At present, in designing a tire pattern of this type, it is general to design the sipes in the block to have the same depth on the circumference as shown in FIG. (1 in the figure
2) is a lateral groove, (13) is a block, and (14) is a sipe.

In a tire having such a pattern,
In order to improve the pattern noise reduction effect and to improve snow performance of studless tires, sipes in blocks are often inserted at relatively small intervals.

For this reason, the rigidity of the block in the pattern is lowered, and as a result, a wear tendency called so-called toe-and-heel wear, which causes a difference in wear at both ends in the tire circumferential direction of the block, is apt to occur, and uniform wear property is deteriorated. It will be.

That is, considering the wear mechanism of the block (13) containing the sipes (14), the ground contact state during tire rotation is as shown in FIG. 6 due to the relationship between the behavior of the block during running and the deformation due to load. Therefore, a difference occurs in friction energy between the tire stepping side (a) and the tire kicking side (b), and the friction energy is usually larger on the kicking side (b). Like

As the number of sipes increases and the distance between sipes decreases, the angle (α) due to wear decreases,
The tendency for toe and heel wear is even stronger. If the sipes have the same depth, the depression side (a) will be present in each of the parts (15) divided by the sipes (14).
And the energy difference on the kicking side (b) is about the same,
As shown in FIG. 7, the wear pattern is substantially the same on the circumference.

Further, if the sipes have the same depth, even if the wear progresses, the change in the above-mentioned tendency is small, and the state is maintained as it is or the step is further increased, which is a cause of the vibration or noise change. Will also be.

The friction energy (E) is equal to E
= Amount of displacement in the contact surface × energy defined by shear force in the contact surface.

The present invention has been made in view of the above, and does not deteriorate pattern noise even when the number of sipes and the pitch are set finely as in the conventional case in order to improve the no-vent hole and the snow performance. In addition, without deteriorating the effect of the fine groove formation such as snow performance,
Provided is a pneumatic radial tire capable of improving uneven wear resistance.

[0011]

DISCLOSURE OF THE INVENTION The present invention solves the above problems in a radial tire having a longitudinal groove in the circumferential direction and a lateral groove intersecting with the groove in the tread surface, and a block pattern defined by these grooves. In order to do so, the block is formed with a narrow groove that crosses the block at approximately the center in the tire circumferential direction, and one or a plurality of shallow grooves are formed in the front and rear regions that continue through the narrow groove, respectively, than the lateral groove at the approximately center. The thin groove is formed.

It is preferable that the difference between the approximately central groove and the shallowest shallow groove in the front and rear regions is 1.0 to 5.0 mm.

[0013]

According to the radial tire of the present invention having the above structure,
At the time of tire rotation, the energy difference between the tire step-in side and the kick-in side is different in each part divided by the narrow groove in the center of the tire circumferential direction and the shallow narrow groove in the front and rear areas in each block. Friction energy is dispersed.

Further, as the wear of the block progresses, the shallow fine grooves in the front and rear regions become further shallower and finally disappear. As a result, the form of division by the fine grooves formed in the block is different from the original one. An energy difference different from the above is generated in each of the regions, and energy dispersion occurs. That is, the block wear progresses while the block itself corrects the wear.

By setting the difference in depth between the above-mentioned thin groove in the approximate center and the shallowest thin groove in the front and rear regions to 1.0 to 5.0 mm, the energy dispersion of each portion can be improved. Is effectively done.

That is, if the difference in depth is less than 1.0 mm, the effect due to the difference in depth becomes small, and if the difference in depth exceeds 5.0 mm, the front and rear regions become thinner. The groove becomes too shallow, and the effect of forming a thin groove such as a sipe decreases.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partially developed view schematically showing the basic pattern of the radial tire of the present invention, and FIG. 2 is an enlarged perspective view of one block of the same.

As a tread pattern of this tire, a plurality of main grooves (1) are provided in the tread tread as longitudinal grooves in the tire circumferential direction, and lateral grooves (2) extending in the lateral direction intersecting with the main grooves (1). ) Are provided, and a large number of blocks (3) are arranged in the tire circumferential direction as land portions partitioned by these grooves, forming a so-called block pattern.

As shown in the enlarged view of FIG. 2, each of the blocks (3) is provided with a narrow groove (4) called a sipe that traverses the block (3) at approximately the center in the tire circumferential direction. In addition, a narrow groove (5) called a sipe similar to the above is shallower than the lateral groove (4) is formed in the front and rear regions (3a) and (3b) which are continuous with each other with the narrow groove (4) interposed therebetween. There is. Reference numerals (31), (32), (33) and (34) in the figure indicate the respective parts divided by the above-mentioned narrow grooves (4) and (5).

The fine grooves in the front and rear regions (3a) and (3b) are formed one by one as shown in FIG. 2, and as shown in FIG. 5) can be formed in advance, and in this case, the depth of the plurality of narrow grooves (5) can be the same, or the depth can be made smaller by making the grooves on the front and rear end sides of the block shallower. You can also make a difference.

The depths of the narrow groove (4) in the approximate center and the narrow groove (5) in the front and rear regions are the depths of the deep deep groove (4) and the shallowest narrow groove (5). It is preferable to set the difference of 1.0 to 5.0 mm from the viewpoint of the effect of fine grooves such as snow performance and the effect of preventing uneven wear. For example, the depth (d1) of the narrow groove (4) at the substantially center is set to be about 65 to 85% of the depth of the main groove as in the conventional sipe, and the depth (d2) of the narrow groove (5) in the front and rear regions is set. Is set to be shallow so that the above difference occurs.

Between the above-mentioned narrow grooves (4) and (5) and (5)
It is preferable that the interval of (5) is substantially the same, but the interval can be changed depending on the case. In any case, it is preferable to form each narrow groove so as to form a symmetrical shape in the front-rear direction with the narrow groove (4) at the substantially center interposed therebetween.

The groove width of each of the narrow grooves (4) and (5) is normally set to about 0.5 to 1.5 mm as in the conventional sipe, but as shown in FIG. (5) Both or either of the grooves of (5) may be formed in a slit shape wider than the sipe (groove width 1.5 to 4.0 mm).

For example, in the embodiment shown in FIG. 4, the slit (4) having a width wider than that of the sipe is provided for the narrow groove (4) at the substantially center.
It shows a case where a) is formed and a groove having a sipe-shaped narrow width (4b) is formed at the bottom thereof, and the narrow groove (5) in the front and rear regions is further formed as a slit-shaped groove. In this way, it is possible to form the cross-sectional shape of the fine grooves (4) and (5) in an irregular shape.

Further, as for the form of each of the fine grooves (4) and (5), in addition to the straight line which is substantially perpendicular to the tire circumferential direction as shown in the drawing, it is formed in an oblique direction depending on the block shape. Alternatively, it may be partially refracted, or may be formed with the side end of the block width slightly left.

As the block (3) in the present invention, a rib-shaped land portion continuous in the tire circumferential direction is formed with a lateral groove that crosses the land portion, and the land portion may be substantially block-shaped. It can be implemented by forming a thin groove in this block as described above.

In the case of a tire having a pattern having the blocks (3) in which the fine grooves (4) and (5) are formed as described above, for example, in the tire of FIG. 2, each block (3) is substantially centered in the tire circumferential direction. Relatively deep narrow groove (4) and front and rear area (3
a) It is divided into a plurality of parts by the shallow groove (5) formed in (3b), and since the narrow groove (5) in the front and rear regions is shallow, it is divided during tire rotation. Energy of the stepping side (a1) (a2) (a3) (a4) and the kicking side (b1) (b2) (b3) (b4) of each part (31) (32) (33) (34) Since the difference is small and each part (31) to (34) is different, and the behavior of each part (31) to (34) is also different, the energy distribution of the entire block (3) is effective. As a result, uneven wear such as toe and heel wear can be prevented.

As the wear of the block (3) further progresses, the shallow narrow grooves (5) in the front and rear regions (3a), (3b).
Will become shallower and eventually disappear, but at this time, the division form of the block (3) by the narrow groove is different from the original, and as a result, new energy is generated in each of the front and rear regions (3a) (3b). A difference is created and an energy dispersion occurs. That is, the block wear progresses while correcting the wear of the block itself, and it is possible to prevent the occurrence of an excessive uneven wear state. As a result, it is possible to prevent deterioration of vibration and pattern noise due to uneven wear.

In the case of a block in which a plurality of shallow fine grooves (5) are formed in the front and rear regions (3a) and (3b) as shown in FIG. 3, each block is divided by the fine grooves (4) and (5). The energy difference between the stepping side and the kicking side in each of the parts (31) to (36) is further reduced, and the individual energies of the parts (31) to (36) are also different. Therefore, the uniform wear property of the block (3) can be improved.

Also in the case of the block having the wide slit-like narrow grooves (4) and (5) as shown in FIG. 4, the energy dispersion of the entire block (3) occurs and the bias is generated almost in the same manner as in the case of FIG. It is possible to prevent the occurrence of wear.

In order to confirm the above-mentioned effects, regarding the tire (example) having a pattern shown in the block shown in FIG. 2 and the tire (comparative example) having a pattern shown in the block shown in FIG. ) Side is the depression side (a1) (b1) (a2) (b2) (a3) (b3
) (A4) (b4) 8 point tire energy was measured and the energy difference between the stepping side and the kicking side of each part (a) to (d) divided by the narrow groove (sipe). The (percentages) are shown in Table 1 below.

The tires used in the examples and comparative examples and the measurement conditions were as follows. Tire size: 195 / 65R15 91H Rim: 15 × 6-JJ Tire pressure: 2.1 kg / cm ² Load: 550 kgf Measurement position: Measured at the center of the width direction of each block, 5 mm from the front and rear ends or narrow groove did.

[0034]

[Table 1] As a result of the above measurement, regarding the energy difference, the tires of the examples of the present invention showed a clear improvement as compared with the comparative examples.

Further, the wear state of the tires of the same example and the comparative example as the above was examined by running, and it was found that the tire of the example had a step difference of about 30 as compared with the tire of the comparative example. % Reduced. Regarding pattern noise, the pitch peak sound was also reduced by about 1 dB.

[0036]

As described above, according to the tire of the present invention, in order to improve the snow performance, even if the number of sipes and the pitch in the block are set in the same manner as in the conventional case, the toe-and-heel wear state is unevenly distributed. The occurrence of wear can be reduced, and uniform wear can be significantly improved without deteriorating pattern noise and without reducing the effects of forming fine grooves such as snow performance.

[Brief description of drawings]

FIG. 1 is a partial development view schematically showing a basic pattern of a tire of the present invention.

FIG. 2 is an enlarged perspective view of one block of the above.

FIG. 3 is an enlarged perspective view of a block according to another embodiment.

FIG. 4 is an enlarged perspective view of a block according to still another embodiment.

FIG. 5 is an enlarged perspective view showing a block of a conventional tire.

FIG. 6 is a partial schematic cross-sectional view showing a grounded state of a block portion of a tire.

FIG. 7 is a schematic cross-sectional view of one block portion showing a worn state of a conventional tire.

[Explanation of symbols]

 (1) Vertical groove (2) Horizontal groove (3) Blocks (3a) (3b) Front and rear regions (4) Narrow groove in the center (5) Shallow thin groove

Claims (2)

[Claims] 1. A radial tire having a longitudinal groove in the circumferential direction, a lateral groove intersecting with the tread surface, and a block pattern defined by these grooves in a tread surface, wherein the block is provided at a substantially central portion in the tire circumferential direction. A radial tire, characterized in that a narrow groove is formed so as to traverse the block, and one or a plurality of narrow grooves, each of which is shallower than the central lateral groove, is formed in each of front and rear regions continuous through the narrow groove. 2. The radial tire according to claim 1, wherein the difference between the narrow groove in the approximate center and the shallowest narrow groove in the front and rear regions is 1.0 to 5.0 mm.