JP2703172B2 - Heavy duty tire - Google Patents

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 preventing rib tear caused by a circumferential narrow groove provided in a tread shoulder and maintaining wandering resistance and wear resistance against shoulder drop.

2. Description of the Related Art In recent years, with improvement of road networks and performance of vehicles, tires used for trucks, buses, and the like have three to five circumferential main grooves on a tread surface. While the rib pattern is provided, the belt layer is formed tough using a steel cord or the like, and the rigidity of the entire tread portion is increased by the tag effect. However, this increases the rigidity even in the tread shoulder portion which has a large effect of suppressing lateral blurring, and reduces the adaptability to the road surface and the followability. As a result, when traveling on a rutted road surface, a so-called wandering phenomenon in which the steering wheel is subjected to a large external force when escaping from the rutted is likely to occur.

Therefore, conventionally, as shown in FIG. 7, a narrow groove b extending in the circumferential direction is formed on the outermost outer rib a in the tire axial direction. The narrow groove b enhances the wandering property to alleviate the rigidity of the outer portion a1, and can prevent so-called shoulder drop wear that progresses from the tread end.

[0003]

However, when the vehicle is driven at a high speed, it can be used at a relatively early stage of use.
For example, a rib tear such as a crack e is induced on the groove wall surface f1 inside the narrow groove b starting from the intersection p with the siping s (FIG. 8) provided on the outer rib a.

An object of the present invention is to provide a heavy-duty tire capable of preventing a rib tear of an outer rib while maintaining wandering properties, abrasion resistance against shoulder droppings, and rocking performance by the narrow grooves.

[0005]

In order to achieve the above object, a first aspect of the present invention is to provide the tread surface with a plurality of ribs by providing three to five main grooves extending in the tire circumferential direction on the tread surface. A tire having a divided rib pattern, which linearly extends in the tire circumferential direction on the outermost outer rib in the tire axial direction and near the tread edge Te among the plurality of ribs, and has a depth of the main groove. while forming the narrow grooves constant or reduced toward GD less and yet have a 9mm or more groove depth gd groove width to the groove bottom, in the outer ribs, and the narrow groove
Providing a siping connecting the main groove closest to the narrow groove
In addition, of the groove walls sandwiching the narrow groove, the corner portion where the inner groove wall on the inner side in the tire axial direction intersects with the tread surface is cut out, and is inclined linearly inward in the radial direction toward the narrow groove. the br /> beauty Ru inclined plane provided, and with an angle of 80-95 degrees formed between the groove walls and the tread surface, the inclined plane of the tire axial direction width WA1 of 2.0mm or less and radially This is a heavy duty tire having a depth WA2 of 2.0 mm or less.

A second invention is a tire having a rib pattern in which the tread surface is divided into a plurality of ribs by providing three to five main grooves extending in a tire circumferential direction in a tread portion. Among the ribs, extends linearly in the tire circumferential direction on the outermost outer rib in the tire axial direction and in the vicinity of the tread edge Te, and has a depth not more than GD of the main groove and 9 mm.
While forming a narrow groove having the above groove depth gd and having the groove width constant or reduced toward the groove bottom, the outer ribs
A groove connecting the narrow groove and the main groove closest to the narrow groove.
In addition to providing a ping, of the groove walls sandwiching the narrow groove, the corner portion where the inner groove wall on the inner side in the tire axial direction intersects with the tread surface is cut out, and is inclined in a radially inward convex arc shape toward the narrow groove. The angle between the inner groove wall and the tread surface is set to 80 to 95 degrees, and the width WB1 in the tire axial direction and the depth WB2 in the radial direction of the inclined curve are set to 1. This is a heavy duty tire having a thickness of 0 mm or more and 3.0 mm or less.

[Action] The narrow groove extending in the circumferential direction of the tire moderately reduces the rigidity of the outer tread edge, improves wandering performance, and reduces the contact pressure at the tread edge when lateral force acts. The occurrence of the origin of shoulder drop wear and the inward growth of the wear beyond the narrow groove are suppressed.

[0007] Further, since an inclined plane or an inclined curved surface formed by a notch having a predetermined dimension is formed at a corner where the inner groove wall of the narrow groove and the tread surface intersect, a gap between the corner and the road surface is formed. The snag in the axial direction of the tire is reduced, and the lateral force during cornering is reduced from being concentrated on the edge of the inner surface of the narrow groove. As a result, the occurrence of cracks inside the groove bottom surface can be suppressed and rib tear can be prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the first invention and the second invention of the present application will be described below with reference to the drawings. 1 to 3 showing the first invention, a heavy duty tire 1A has bead portions 3 on both sides through which a bead core 2 passes, a sidewall portion 4 extending outward from each bead portion 3 in the tire radial direction, and an upper end thereof. And a tread portion 5 connecting between them. A carcass 6 that wraps around the bead core 2 from the tread portion 5 through the sidewall portion 4 is bridged between the bead portions 3 and 3 and radially outside the carcass 6 and inside the tread portion 5. Is wound with a belt layer 7.

The belt layer 7 has at least one or more, in this example, first, second, third, and fourth belt plies 7a, 7b,
7c and 7d.

Each of the belt plies 7a to 7d is composed of a cord array in which steel belt cords are arranged at an angle of 10 to 70 degrees in the tire radial direction, and the second belt ply 7b is arranged in the tire axial direction. The ply width BW is formed larger than the other belt plies 7a, 7c, 7d. The maximum ply width BW is 0.85 to 0.95 of the tread width TW.
It has twice the width, and thus the tread portion 5 is reinforced firmly over substantially the entire width with a hammer effect.

[0011] tread surface T s is the outer surface of the tread portion 5 in this example consists of a convex circular arc having a center on the tire equatorial plane, the tread surface T s in the tread edge Te is its outer end, The side wall portion 4 is connected via a small circular arc surface J to a buttress surface BS connected by a concave circular arc.

[0012] Also on the tread surface T s is the rib pattern is formed consisting of the main grooves G of three to five extending in the tire circumferential direction. In this example, four main grooves G extending linearly in the circumferential direction is provided, the tread surface T s Thus, the rib R1 of extending on the tire equator, and the rib R2 in both sides , And is further divided into five ribs, namely, an outer rib R3 disposed on the outer side and located on the outermost side in the tire axial direction. Note each main grooves G, in the tread surface T s, 1
It has a groove width GW of 0 to 15 mm.

The outer rib R3 has a rib width RW of 0.10 to 0.18 times the tread width TW, and the outer rib R3 is provided on the outer rib R3 and in the vicinity of the tread edge Te. R3 is a rib body portion R3A and a rib outer edge portion R3B outside the rib body portion R3A.
Are arranged. Said sub groove g is a straight groove extending linearly in the tire circumferential direction, 0.10-0.25 times the groove width GW of the main groove G the groove width gw on the tread surface T s (e.g. 2-3 mm)
The groove width is a parallel groove or a tapered groove that is constant or reduced toward the groove bottom. Note that the vicinity of the tread edge Te means a region Y from the tread edge Te to a position at a distance of 0.3 times the rib width RW inward in the tire axial direction.

The narrow groove g is not less than 9 mm and the main groove
Have a depth GD less groove depth gd of G, it is substantially perpendicular formed with the tread surface T s.

Here, a narrow groove g
When the ribs are formed, the rigidity of the rib outer edge portion R3B becomes large, and it is difficult to obtain the effects of improving the wandering performance and the wear resistance against shoulder drop. Similarly, when the groove width gw is smaller than 0.1 times the groove width GW of the main groove G and when the groove depth gd is smaller than 9 mm,
It is difficult to obtain the above-mentioned effects, and conversely, the groove width gw is not more than 0.
When the groove depth is larger than 25 times and when the groove depth gd is larger than the depth GD, the strength of the rib outer edge portion R3B becomes excessively small, causing chipping or the like. The rib outer edge portion R3B is formed integrally and continuously in the circumferential direction without being divided by, for example, siping, lug grooves, or the like.

[0016] By forming the narrow groove g approximately perpendicular to the tread surface T s, and the inner groove wall F1 in the tire axial direction inner side of the thin groove g sandwiching the groove wall F1, F2, the tread surface T s Is in the range of 80 to 95 degrees to maintain the balance between the strength of the rib outer edge R3B at the bottom of the narrow groove and the strength of the rib body R3A at the upper end of the outer end.

[0017] Moreover in the present invention, the corners of the inner and groove wall F1 and the tread surface T s intersect, are provided notch.

The cutout portion 10 is, in the first invention, between the inner groove wall F1 and the tread surface T s, the inclined plane inclined in a straight line radially inwardly toward the narrow groove g gs1 Consists of Inclined plane gs1, the angle 30 to 60 degrees with respect to the normal on the tread surface T s, for example, a plane inclined at approximately 45 °, 2.0 mm and the tire axial direction of the width WA1
And the depth WA2 in the radial direction is set to 2.0 mm or less. The inclined plane gs1 has an effect of alleviating the lateral force acting on the outer edge of the rib body portion R3A among the lateral forces acting at the time of turning, thereby reducing the occurrence of cracks at this portion and preventing rib tear. When the width W A1 is larger than 2.0 mm,
Starting from the notched inclined plane gs1, shoulder rib-shaped uneven wear is liable to be caused on the rib body portion R3A.
When A2 is larger than 2 mm, stone grind easily occurs in the narrow groove.
When the width W A1 and the depth W A2 are smaller than 0.5 mm, the rib tear prevention effect cannot be sufficiently exerted. Therefore, the width W A1 and the depth W A2 are preferably 0.5 mm. or more, more preferably 1.0mm or more.

[0019] Also before Symbol rib main body R3A, rib in R2,
For example, a laterally S-shaped siping S that divides these ribs in the circumferential direction of the tire is formed on each of the inner ribs R1 to enhance road grip performance.

As shown in FIGS. 4 and 5, in the heavy duty tire 1B according to the second invention, the notch 10 is
And is formed by an inclined curved surface gs2 which inclines in a convex arc shape inward in the radial direction toward. The tire structure other than the notch 10 is the same as that of the heavy load tire 1A.

In the present embodiment, the inclined curved surface gs2 is formed as shown in FIG.
As shown enlarged in the said groove wall F1 and consists arcuate surface of a radius of curvature Rd inscribed in the tread surface T s, the tire axial direction of the width WB1 of 3.0mm or less and the radial depth WB2 3.0 mm or less. Inclined surface gs2
Has a width WB1 of 3.0 mm like the inclined plane gs1.
More time of large, to lead to shoulder wear, Matafuka of WB2 is 3.
Time of greater than 0mm, to induce God stone to narrow groove g. In addition, width W
B1, depth WB2 is, to give full play to the Ributea prevention effect
In order to achieve this, the thickness is preferably 1.0 mm or more, and more preferably 1.
5 mm or more.

[0022] Note that as an inclined curved surface gs2, as shown in FIG. 6, one of the inner groove wall F1 and the tread surface T s, or can be formed by an arc surface of a radius of curvature Rd intersecting both shoulder wear The radius of curvature Rd is preferably 6.0 mm or less, and more preferably 3.0 mm or less, in order to suppress rock formation.

(Specific Example) Tire size 285 / 75R having the structure shown in FIGS.
A 24.5 tire was prototyped based on the specifications in Tables 1 and 2, and the test tires were compared for rib tear resistance, shoulder drop abrasion resistance, and stone bite resistance by actual vehicle running tests.

The running conditions of the actual vehicle are: mounted rim; 8.25 × 24.5 internal pressure; 8.44 ksc (8.28 × 10 ⁵ Pa) mounted vehicle; front axle of tractor head vehicle with two drive shafts Traction conditions: 20 tons Tow a loaded trailer Car Road; General road Running conditions; Ratio of highway to general road is 2: 1 and 1
Traveled 000 km. (For the stone resistance test, run on Jari Road 2000m.)

1) The rib tear resistance is as shown in FIG.
Of the rebirth that occurred after traveling 10,000 km,
The product of the product of the length LA and the width WA, LA × WA, which is the largest, was defined as the rib tear value, and Comparative Example 5 was set to 100 and indicated as an index. The smaller the index, the better.

2) The shoulder drop abrasion resistance is defined as the wear value of the shoulder drop abrasion generated after running, where the product WB × DB of the width WB and the depth DB is the largest, as shown in FIG. An index is indicated by setting Comparative Example 5 to 100. The smaller the index, the better.

3) Stone bite resistance is measured by measuring the number of stone blocks generated after traveling, and averaging the results of repeating this five times.
An index is indicated by setting Comparative Example 5 to 100. The smaller the index, the better.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

As described above, the heavy duty tire of the present invention has the following features.
A narrow groove in the circumferential direction is provided near the tread edge, and a predetermined notch-shaped slope is provided at the corner between the inner groove wall and the tread surface. The rib tear caused by the narrow groove can be prevented while maintaining the property.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a heavy duty tire according to the first invention.

FIG. 2 is a plan view of a tread portion showing the tread pattern.

FIG. 3 is a partial cross-sectional view showing an enlarged narrow groove of the first invention.

FIG. 4 is a sectional view showing one embodiment of a heavy duty tire according to the second invention.

FIG. 5 is an enlarged partial sectional view showing the narrow groove.

FIG. 6 is a cross-sectional view showing another example of a narrow groove.

FIG. 7 is a cross-sectional view of a tire illustrating a conventional technique.

FIG. 8 is a plan view of a tread portion for explaining a conventional technique.

FIG. 9 is a diagram illustrating the rib tear property shown in Tables 1 and 2.

FIG. 10 is a diagram illustrating shoulder drop abrasion shown in Tables 1 and 2.

[Description of Signs] F1 Inner groove wall G Main groove g Narrow groove gs1 Inclined plane gs2 Inclined curved surface R3 Outer rib T s Tread surface θ Angle

Continuation of front page (56) References JP-A-5-85105 (JP, A) JP-A-4-176711 (JP, A) JP-A-3-273908 (JP, A) JP-A-3-235701 (JP) JP-A-3-136906 (JP, A) JP-A-3-253408 (JP, A) JP-A-3-217304 (JP, A)

Claims (2)

(57) [Claims] The tire extends in the circumferential direction of the tire on the tread surface.
A tire having a rib pattern in which the tread surface is divided into a plurality of ribs by providing five main grooves, wherein the plurality of ribs are located on outermost outer ribs in the tire axial direction and near a tread edge Te. Forming a narrow groove extending linearly in the tire circumferential direction and having a groove depth gd of not more than 9 mm and not more than the depth GD of the main groove and having a constant or reduced groove width toward the groove bottom; The outer rib is provided with the narrow groove and the main groove closest to the narrow groove.
And a notch at the corner where the inner groove wall on the inner side in the tire axial direction intersects with the tread surface among the groove walls sandwiching the narrow groove, and a straight line is formed radially inward toward the narrow groove. an inclined plane Ru extending inclined provided, and said groove walls and the angle between the tread surface with a 80-95 °, the tire axial direction and 2.0mm below the width WA1 of the radial direction of the inclined plane A heavy duty tire having a depth WA2 of 2.0 mm or less. 2. A tire extending in a circumferential direction of a tire on a tread portion.
A tire having a rib pattern in which the tread surface is divided into a plurality of ribs by providing five main grooves, wherein the plurality of ribs are located on outermost outer ribs in the tire axial direction and near a tread edge Te. While forming a narrow groove extending linearly in the tire circumferential direction and having a groove depth gd of not more than 9 mm and not more than the depth GD of the main groove and having a constant or reduced groove width toward the groove bottom; The outer rib is provided with the narrow groove and the main groove closest to the narrow groove.
And a notch at the intersection of the inner groove wall on the inner side in the tire axial direction and the tread surface among the groove walls sandwiching the narrow groove, and a convex circle radially inward toward the narrow groove. An inclined curved surface extending in an arc shape is provided, and the angle between the inner groove wall and the tread surface is set to 80 to 95 degrees, and the width WB1 in the tire axial direction and the depth WB2 in the radial direction of the inclined curved surface are reduced. Heavy load tires each having a thickness of 1.0 mm or more and 3.0 mm or less.