JP2000238507A - Tire for heavy loarding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress asymmetric abrasion ultimately by arranging a block- shaped tread portion in the tire circumferential direction defined by longitudinal grooves with a depth larger than that of lateral grooves by a specific amount, and a rib-shaped tread portion defined by a depth smaller than that of the longitudinal grooves by a specific amount, while the rib-shaped tread portion having an expanded portion projected from a tread surface profile. SOLUTION: A tread portion comprises block-shaped tread portions 5i, 5o and a rib-shaped tread portion 6. Each of the block-shaped tread portion 5i, 5o extends in the direction to intersects longitudinal grooves 3a, 3i, 3o (3), and is defined by a lateral groove 7 arranged in the tire circumferential direction. The lateral groove 7 has a tread depth of 50% or more compared with that of a longitudinal groove 3. The rib-shaped tread portion 6 comprises either a rib arranged sequentially in the tire circumferential direction or a rib-shaped portion defined by lateral grooves 9a, 9b. The lateral grooves 9a, 9b intersect the longitudinal groove 3, having a tread depth of smaller than 50% compared to that of the longitudinal groove 3. Furthermore, the rib-shaped tread portion 6 has an expanded portion 12 which projects from a tread surface profile CR. Thereby generation of asymmetric abrasion can be suppressed for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy duty tire capable of improving abrasion resistance and the like.

[0002]

2. Description of the Related Art Many heavy duty tires to which a high load is applied employ a rib pattern or a rib lug pattern in order to enhance the wear resistance of the tread surface. However, tires having these patterns tend to cause slippage due to poor drainage properties, and particularly traction on wet roads. Therefore, in recent years, a pattern including a block row in which blocks are arranged in the tire circumferential direction is also being adopted for heavy load tires.

However, since the rigidity of the block in the circumferential direction of the tire is lower than that of the rib which is continuous in the circumferential direction of the tire, the effect of the braking force and the driving force when the block comes into contact with the road surface during load running of the tire and when the tire is released. Therefore, there is a problem that heel-and-toe wear, in which the heel of the block (first arrival portion on the road surface) or toe (the second arrival portion thereof) is locally worn, is particularly likely to occur. Such heel and toe wear is particularly likely to occur in the block row provided on the tread edge side.

The present invention has been devised in view of such problems, and includes a block array as described above on a tread surface to improve drainage and traction performance as compared with a rib pattern tire or the like. It is another object of the present invention to provide a heavy duty tire capable of suppressing uneven wear over a long period of time.

[0005]

According to the first aspect of the present invention, the tread surface is provided with two or more vertical grooves extending in the circumferential direction of the tire, so that the vertical grooves are provided between the vertical grooves or the vertical grooves. A land portion is formed between the tread edge and the tread edge, and the land portion extends in a direction intersecting with the vertical groove and has a circumferential groove having a groove depth of 50% or more of the groove depth of the vertical groove. A block-shaped land portion composed of blocks arranged in the direction, and 50% of the groove depth of the rib or the vertical groove continuous in the tire circumferential direction.
And a rib-shaped land portion comprising a rib-shaped portion divided by a shallow horizontal groove extending in a direction intersecting with the vertical groove, the rib-shaped land portion being at least the tread edge side and a tire. It is arranged on both outer sides in the axial direction,
And in the tire meridian section including the tire axis, the rib-shaped land portion has a bulge portion that protrudes outward in the tire radial direction from a tread surface contour line whose outer surface is determined by connecting the outer surface of the block-shaped land portion. It is a heavy duty tire provided.

The heavy duty tire of the present invention has a block-shaped land portion and a rib-shaped land portion on the tread surface, so that the drainage performance can be relatively improved as compared with the rib pattern tire, and the running performance on wet roads and the like can be improved. Can be increased. In the case of heavy load tires, uneven wear is likely to occur in the shoulder due to lateral force due to turning, difference in outer diameter of the tread surface, etc. By disposing the rib-shaped land portions having excellent properties on the tread edge side and both outer sides in the tire axial direction, uneven wear of the shoulder portion can be effectively suppressed.

Further, since the rib-shaped land portion is arranged on the tread edge side, a large amount of wear energy acts. Therefore, the wear amount of the rib-shaped land portion is larger than the wear amount of the block-shaped land portion. However, when the difference is larger, large wear energy is concentrated on the block-shaped land portion. This causes the blocks constituting the block-shaped land portion to move independently, and there is a problem that heel-and-toe wear, block punching, etc. occur simultaneously.

In order to prevent such a problem, in the present invention, the above-mentioned bulging portion is provided in the rib-shaped land portion, and the wear allowance of the rib-shaped land portion is set to be larger than that of the block-shaped land portion in advance. By doing so, it is possible to suppress a widening of the difference between the two wear amounts over a long period of time and improve the wear balance of the entire tread surface. As a result, it is possible to prevent concentration of wear energy on the block-shaped land portions, and to effectively suppress uneven wear of the tire as a whole over a long period of time.

Here, the bulging portion has a protruding amount (h) from the tread surface contour line of 0.05 to 0.20 times the groove depth of the vertical groove having the maximum groove depth. It is desirable to do.

In the present specification, "tread edge"
If a clear edge is formed at the end of the tread, it is the edge, but if there is no edge, the tread edge is a standard In this state, it is defined as the outer end of contact in the tire axial direction when a regular load is applied at a camber angle of 0 degree and the contact is made on a flat surface.

The "regular rim" is a rim defined for each tire in a standard system including the standard on which the tire is based. For example, a standard rim for JATMA and a "Design Rim" for TRA Or ETRTO
Then "Measuring Rim". In addition, "regular internal pressure"
Is the air pressure that each standard defines for each tire in a standard system that includes the standard on which the tire is based.
Maximum air pressure for TMA, table "TIRE L for TRA
OAD LIMITS AT VARIOUS COLD INFLATION PRESSURES "
RE ". Further," regular load "is a load defined for each tire in the standard system including the standard on which the tire is based. Maximum value, ETRTO
If so, use "LOAD CAPACITY".

The dimensions of the tire, such as the width and depth of each groove, are measured in the above-mentioned "standard state", and the groove width is particularly measured on the tread surface.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a tread pattern of a heavy-duty tire (hereinafter, may be simply referred to as “tire”) of the present embodiment, and FIG. 2 shows a cross section taken along line AA of FIG. 1 in a standard state. I have. In the figure, the tread surface 2 of the tire is provided with two or more (six in this example) vertical grooves 3 extending in the tire circumferential direction, so that the vertical grooves 3, 3 or between the vertical grooves 3 and the tread end are provided. Land part 4 between rim E
Is formed. The vertical groove 3 of the present embodiment includes a pair of vertical main grooves 3a, 3a.
a, a pair of vertical sub-grooves 3i, 3i, and a pair of outer vertical sub-grooves 3o, 3o.

The vertical main groove 3a has the largest groove width and groove depth among the vertical grooves 3. Although not particularly limited, the groove width W1 of the vertical main groove 3a is, for example, a tread width T which is a distance between the tread edges E and E in the tire axial direction.
2.5 to 6% of W and groove depth d1 (shown in FIG. 2)
Is particularly preferably 10 to 12% of the tread width TW. As a result, it is possible to secure a sufficient amount of drainage and to improve wet performance. The vertical main grooves 3a, 3a
In this example, the tires are arranged on both sides of the tire equator C, for example, from the tire equator C to the tread width TW of 15 to
It extends in the tire circumferential direction with a substantial groove center line gc at a position separated by a distance L of 25%.

The vertical sub-groove 3i is provided with the vertical main groove 3a,
3a and on both sides of the tire equator C are shown. Also, the outer vertical sub groove 3o is shown disposed between the vertical main groove 3a and the tread edge E. In the present embodiment, the inner and outer vertical sub-grooves 3i,
3o, the groove width and the groove depth are both formed smaller than those of the vertical main groove 3a. In this example, each groove width W2 is, for example, about 1.0 to 1.6% of the tread width TW, Also, each groove depth d
2 (shown in FIG. 2) is, for example, 7 to 9% of the tread width TW.
What is set to the degree is shown. The vertical sub-grooves 3i and 3o extend substantially in parallel with the vertical main groove 3a, for example, but are not limited thereto. In addition, each vertical groove 3 may be any one of zigzag, curve, and straight line or 2
It can be formed in various shapes obtained by combining the above.

The land portion includes a block-shaped land portion 5 and a rib-shaped land portion 6. In this example, the block-shaped land portion 5 includes an inner block-shaped land portion 5i formed between the inner vertical sub-groove 3i and the vertical main groove 3a, and the vertical main groove 3a and an outer vertical sub-groove. 3o, and a total of four rows are formed on the tread surface 2 including an outer block-shaped land portion 5o formed between the tread surface 3o and the outer block-shaped land portion 5o. Each of the block-shaped land portions 5i, 5o extends in a direction intersecting with the flute 3,
In addition, it is composed of blocks B arranged in the tire circumferential direction and divided by horizontal grooves 7 having a groove depth of 50% or more of the groove depth of the vertical grooves 3. For this reason, the effect of discharging the water film on the road surface to the outside of the tire via the vertical groove 3 and the horizontal groove 7 is enhanced, and wet performance can be improved.

The lateral groove 7 forming the block-shaped land portion 5
Is substantially 100% of the groove depth of the vertical main groove 3a in this example.
Has a groove depth d3 (shown in FIG. 2). The width W3 of the lateral groove 7 is, for example, 2.5 to 7 of the tread width TW.
%, More preferably about 3 to 6%, and in this example, it is larger than the groove width of the vertical main groove 3a, so that the wet performance can be suitably enhanced. In the present example, the vertical groove 3 and the horizontal groove 7 indicate that the block B has a substantially parallelogram shape. In addition, by forming a circumferential circumferential siping 13 at both ends of the block B in the block, the road rigidity of the block B can be improved while preventing a significant decrease in block rigidity.

In the present embodiment, the rib-shaped land portion 6 is a central rib-shaped land portion 6c formed between the inner vertical sub-grooves 3i, 3i.
And a rib-like land portion 6e at the end formed between the outer vertical sub-groove 3o and the tread edge E, and a total of three rows are formed on the tread surface 2. Such a rib-like land portion 6 has a rib continuous in the tire circumferential direction or a groove depth 5 of the longitudinal groove 3.
Any of rib-shaped portions having a groove depth of less than 0% and divided by a shallow horizontal groove 9 extending in a direction intersecting with the vertical groove 3 may be used. Such ribs also exhibit substantially similar wear characteristics to the ribs except for the initial stages of wear.

Here, "ribs continuous in the tire circumferential direction"
May be divided in the circumferential direction of the tire by a narrow groove having a groove width of 1.5 mm or less, and the “groove depth of the vertical groove 3” indicates the deepest vertical groove 3 (in this example, the vertical main groove 3 a). And "having a groove depth of less than 50% of the groove depth of the vertical groove 3" means that such a groove depth portion occupies at least 50% or more of the horizontal groove length. good.

In this embodiment, the shallow lateral groove 9 provided in the rib-like land portion 6e at the end is a cross section taken along the line ZZ in FIGS.
As shown in the figure, a main portion 9a having a groove depth of less than 50% of the groove depth d1 of the vertical main groove 3a and extending more than 50% of the length of the shallow horizontal groove 9; Groove depth d
1 as well as an auxiliary portion 9b having a groove depth of more than 50%. In this example, the auxiliary portion 9b is formed on both sides of the main portion 9a in the tire axial direction. The shallow lateral groove 9 is also formed with substantially the same groove width as the lateral groove 7.

In the main portion 9a, a siping S extending along the shallow lateral groove 9 is formed to suitably reduce the rigidity of the rib-like land portion 6 and reduce a remarkable difference in rigidity with the block-like land portion 5. And the wear balance of the tread surface 2 is improved. Such siping S depth d4 (shown in FIG. 4)
Is desirably 10% to 30% of the groove depth d3 of the lateral groove 7, for example. And such a rib-like land part 6 is, when the wear in which the vertical main groove 3a is completely removed is 100% wear,
At the time of 20 to 30% wear, the groove bottom of the main portion 9a of the shallow lateral groove 9 appears as the tread surface 2, as shown in FIG.
This is preferable because it changes to a rib that is substantially continuous in the tire circumferential direction, and the wear resistance can be further increased.

In the present embodiment, the central rib-shaped land portion 6c joins the constricted portion 16 whose rib width is locally reduced, and the constricted portions 16 on both sides in the axial direction, and connects the central rib-shaped land portion. 6C shows a thin groove 15 extending obliquely across 6c. As shown in FIG. 2 and FIG. 5 which is a partially enlarged sectional view thereof, the narrow groove 15 has a shallow groove portion 15a having a small groove depth,
Deep groove portions 1 having a groove depth larger than this shallow groove portion 15a and both sides
5b. The groove depth d5 of the shallow groove 15a
Is, for example, about 10 to 30% of the groove depth d1 of the vertical main groove 3a, and the groove depth d6 of the deep groove portion 15b is 60% or more of the groove depth d1 of the vertical main groove 3.

Therefore, as shown in FIG. 3, when the tread surface is worn by 20 to 30%, the central rib-like land portion 6c loses the shallow groove portion 15a of the narrow groove 15 and has higher rigidity. It is preferable because it can be changed to a rib to further enhance the wear resistance. Further, the shearing force acting on the central rib-shaped land portion 6c in the tire circumferential direction and the tire axial direction can be effectively absorbed by the deformation around the constricted portion 16, and the central rib-shaped land portion 6c can be effectively absorbed. It is also useful for suppressing uneven wear of steel.

In the case of a heavy load tire having a large outer diameter difference between the tire equator C side and the shoulder side on the tread surface 2 as in this example, the shoulder side wear becomes severe, but the block is located on the tread edge E side. By arranging the rib-shaped land portions 6e, 6e at the ends having better wear resistance than the land portions 5, it is possible to effectively suppress early wear on the shoulder side. If the width of the rib-like land portion 6e at the end is too small in the axial direction of the tire, sufficient rigidity cannot be maintained, and the movement (deformation) during running tends to increase. If it is too much, the abrasion resistance will be reduced. For example, in the standard condition when the product is new, the width We in the tire axial direction (average width in this example) is 8 to 30% of the tread width TW, more preferably 8 to 20%. It is desirable to do.

The tire equator C having the highest contact pressure is
By disposing the central rib-shaped land portion 6c at the position, the wear resistance of the crown portion can also be improved. In addition, the width of the rib-shaped land portion 6 is 0.8 to 2.2 times the width of the block B.
It is desirably 0 times, preferably 1.0 to 2.0 times.

Further, according to the present invention, as shown in FIG.
Is characterized in that the outer surface 10 has a bulging portion 12 which protrudes outward in the tire radial direction from a tread surface contour CR defined by connecting the outer surface 11 of the block-shaped land portion 5.

Generally, even if the rib-shaped land portion 6 is substantially continuous in the tire circumferential direction, a large amount of wear energy is unavoidable as long as it is arranged on the tread edge E side. Therefore, by providing such a bulging portion 12 on the rib-shaped land portion 6 and setting the wear allowance of the rib-shaped land portion 6 to be larger than that of the block-shaped land portion 5 in advance, both of the bulging portions 12 can be formed. An increase in the difference in the amount of wear can be suppressed over a long period of time, and the wear balance of the entire tread surface can be improved. By these,
Prevent the concentration of wear energy on the block-shaped land part 5,
As a whole, uneven wear of the tire can be effectively suppressed over a long period of time.

Here, the bulging portion 12 has a shallow lateral groove 9,
Except for the narrow groove 15 and the like, the groove is formed continuously in the tire circumferential direction, but the amount h of protrusion from the tread surface contour line CR is determined by the groove depth of the vertical main groove 3a having the maximum groove depth. Is preferably 0.05 to 0.20 times. When the protrusion amount h is less than 0.05 times the groove depth of the vertical main groove, the effect of the prevention portion 12 tends to relatively decrease. Part 12
The protruding amount tends to be too large, the distribution of the contact pressure is made uneven, and the rib-shaped land portion 6 largely moves independently upon contact with the road surface.
Tends to cause uneven wear such as track wear.

It is preferable that the bulging portion 12 has a uniform protrusion amount h in the axial direction of the tire, but it may be non-uniform. Further, the tread surface contour CR is specified in a state where the tire is assembled to a regular rim and filled with a regular internal pressure.
Outer surface 1 of two block-shaped land portions 5i, 5i, 5o, 5o
The radius of curvature centered on the tire equator C is 57
It shows a single arc of 5 mm.

The heavy-duty tire according to the present embodiment includes a radially structured carcass made of a steel cord and a belt layer on which cords inclined at a small angle with respect to the tire circumferential direction are arranged, and the radial tread surface has a high rigidity. It can be suitably used for tires. However, it can of course be applied to a tire having a bias structure.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to this embodiment, and can be modified into various forms. For example, the vertical groove 3 may be formed only by the vertical main groove. Needless to say, the number and the like can be variously changed. Further, the bulging portion 12 may not be provided in the central rib-like land portion 6c.

[0032]

EXAMPLES Tires (Examples 1 to 5) having a tire size of 295 / 75R22.5 and having specifications shown in Table 1 were prototyped, tested, and performance was compared. In the test, each tire was assembled on the rim (rim size 8.25 x 22.5,
(Internal pressure: 750 KPa), mounted on the drive wheels of the vehicle 2-DD-4-4, and traveled on a test course until the uneven wear occurred. . Further, for comparison, tires other than the present invention (Comparative Examples 1 and 2) were also prototyped, and the performance was compared.

[0033]

[Table 1]

As a result of the test, it can be confirmed that in the tire of the embodiment, the running distance until the occurrence of uneven wear is increased. In particular, for Examples 2 to 5 in which the amount of protrusion of the bulging portion was 0.05 to 0.20 times the groove depth of the vertical main groove,
Particularly good results were obtained.

[0035]

As described above, in the present invention, since the block-shaped land portion and the rib-shaped land portion are provided on the tread surface, the drainage can be relatively improved as compared with the tire having the rib pattern, so that it can be used on a wet road. Driving performance can be improved. In addition, since the rib-shaped land portions having excellent wear resistance are arranged on the tread edge side and on both outer sides in the tire axial direction, uneven wear of the shoulder portion can be suppressed.

Further, the rib-shaped land portion provided on the tread edge side is provided with a bulged portion whose outer surface protrudes outward in the tire radial direction from the tread surface contour line. By setting the wear allowance larger than that of the block-shaped land portion in advance, it is possible to suppress the difference in the wear amount between the two over a long period of time, and to improve the wear balance of the entire tread surface. As a result, it is possible to prevent concentration of wear energy on the block-shaped land portions, and to effectively suppress uneven wear of the tire as a whole over a long period of time.

[Brief description of the drawings]

FIG. 1 is a development view of a tread pattern showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a developed view of the tread pattern at the time of wear shown in FIG. 1;

FIG. 4 is a sectional view taken along the line ZZ of FIG. 1;

FIG. 5 is a partially enlarged view of a rib-like portion in FIG. 2;

FIG. 6 is a development view of a tread pattern of a comparative example.

[Explanation of symbols]

 2 Tread surface 3 Vertical groove 3a Vertical main groove 3i Vertical sub groove inside 3o Vertical sub groove outside 5 Block block land 5i Block land inside 5o Block land outside 6 6 Rib 6c Central rib Land portion 6e Rib-shaped land portion at end 7 Lateral groove 9 Shallow lateral groove 12 Swelling portion E Tread edge C Tire equator CR Tread surface contour

Claims (2)

[Claims] 1. A land portion is formed on a tread surface by providing two or more vertical grooves extending in a tire circumferential direction, and a land portion is formed between the vertical grooves or between the vertical grooves and a tread edge. A land portion extending in a direction intersecting with the vertical groove, and a block-shaped land portion formed of blocks arranged in the tire circumferential direction by horizontal grooves having a groove depth of 50% or more of the groove depth of the vertical groove; 5 of the depth of the continuous rib or the vertical groove
A rib-shaped land portion having a groove depth of less than 0% and defined by a shallow horizontal groove extending in a direction intersecting with the vertical groove, wherein the rib-shaped land portion is at least the tread edge side. And in the tire meridional section including the tire axis, the rib-shaped land portion is arranged on both outer sides in the tire axial direction, and the rib-shaped land portion has a tread surface profile defined by connecting the outer surface to the outer surface of the block-shaped land portion. A heavy duty tire having a bulge protruding outward in the tire radial direction from a line. 2. The bulging portion has a protruding amount (h) from the tread surface contour line of 0.05 to 0.20 times the groove depth of the vertical groove having the maximum groove depth. The heavy duty tire according to claim 1, wherein: