JP3378815B2 - 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 increasing tire strength (plunger strength) and achieving weight reduction.

[0002]

2. Description of the Related Art In tires for heavy-duty vehicles such as trucks and buses, it is necessary to sufficiently enhance the rigidity and strength of a belt layer in order to support a high internal pressure and a high load. Therefore, as shown in FIG. 3, conventionally, four plies a1 to a4 of steel cords are used for the belt layer a, and the cord angle of the first ply a1 on the carcass side (innermost side) with respect to the tire equator CO is set. It is relatively large, 40 to 70 degrees, and the cord angle of the second to fourth plies a2 to a4 is 10
Within the range of up to 30 degrees, the cords of the second ply a2 are arranged in a direction intersecting the cords of the third and fourth plies a3, a4 to form a strong truss structure.

On the other hand, in order to promote energy saving in recent years, there is an increasing demand for weight reduction in heavy duty tires, and in particular, weight reduction in the belt layer a, which occupies a large weight in the tire weight, is strongly desired. There is.

[0004]

However, since a large load acts on the belt layer a, simply reducing the number of belt plies will cause the belt layer a to break when the tire steps on foreign matter such as rocks. It becomes difficult to secure the necessary tire strength (plunger strength), such as when it is easy to do. If the belt cord is thickened to increase the tire strength, the cost is increased and the weight is increased, which hinders the weight reduction.

Here, it is considered that the belt breakage occurs due to the following mechanism. That is, when the tire steps on a rock or the like, the belt layer a tends to bend inward in the radial direction while changing the cord angle. At this time, the belt layer a is separated into the second and third layers by the innermost first ply a1.
The movement of the cords of the plies a2 and a3 is restricted, and the cord angle is less likely to change. Further, when the inner ply is bent inward in the radial direction, the tensile strain is increased toward the inner ply, and the cord breaks due to the interaction thereof, particularly around the second ply a2.

Therefore, for example, in Japanese Unexamined Patent Publication (Kokai) No. 8-244407, by increasing the cord angle in the first ply and reducing the ply strength, the cord restraining force on the second and third plies is alleviated, and the tire is It has been proposed to flexibly change the belt cord angle in accordance with the bending of the belt layer when stepping on a rock or the like to suppress the cord breakage of the second and third plies.

However, in such means for increasing the cord angle and reducing the ply strength, the tightening force on the carcass is reduced over the entire width of the ply, so that the tread shoulder portion, which is particularly inferior in the hoop effect, protrudes (outer diameter growth ), The contour profile of the tread is changed, and the uneven wear resistance is impaired.

Therefore, according to the present invention, flexibility can be concentratedly imparted to the central portion of the tread of the innermost belt ply, the tread shoulder portion is prevented from protruding, and uneven wear is suppressed.
It is an object of the present invention to provide a heavy-duty tire that can effectively improve the strength of the plunger and greatly contribute to weight reduction.

[0009]

In order to achieve the above-mentioned object, the invention of a heavy duty tire according to claim 1 is one steel carcass extending from a tread portion to a sidewall portion to a bead core of a bead portion. A carcass consisting of a carcass ply using a cord, and three or more sheets of steel belt cords arranged inward of the tread portion and outward in the radial direction of the carcass and arranged in parallel with each other and overlapping inward and outward in the tire radial direction. The innermost belt ply includes a belt layer made of a belt ply, and the innermost belt ply is characterized in that a corrugated region where the belt cord is bent by corrugation in the ply surface is provided in the tire central portion including at least the tire equator. There is.

[0010] The invention according to claim 1, wherein the belt ply in the top is, on both sides of the corrugation regions, straight regions set extending linearly without belt cord is attached waves
It has been burned .

In the heavy-duty tire of claim 2, the width of the corrugated region in the tire axial direction is 0.4 to 0.6 times the ply width of the innermost belt ply, and the amplitude of the corrugation is It is characterized in that the corrugation reference line of the belt cord in the corrugated region of 2.0 to 4.0 mm and the belt cord in the straight region are inclined at an angle of 46 to 70 degrees with respect to the tire equator. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a heavy-duty tire 1 includes a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and beads arranged at inner ends of the sidewall portions 3 in the tire radial direction. Part 4
And with. Further, the heavy-duty tire 1 includes the bead portion 4,
A toroidal carcass 6 spanned between the four carcasses 4 and a tough belt layer 7 arranged radially outward of the carcass 6.
Reinforced by and.

The carcass 6 is formed of a single carcass ply 6A which is folded back from the tread portion 2 to the sidewall portion 3 around the bead core 5 of the bead portion 4, and the carcass ply 6A is made of steel. Carcass cords are arranged at an angle of 75 to 90 degrees with respect to the tire equator CO.

Further, the belt layer 7 is composed of three or more belt plies which are overlapped inward and outward in the radial direction of the tire, and in this example, the first, second, and the first, second, and so on are sequentially arranged from the carcass 6 side toward the tread surface 2A. Third belt ply 11, 12, 1
The case where three sheets of 3 are formed is illustrated.

The ply width W1 of the first belt ply 11 in the tire axial direction is smaller than the ply width W2 of the second belt ply 12 and substantially equal to the ply width W3 of the third belt ply 13, The maximum ply width W2 is 0.80 to 0.95 times the tread width TW, that is, 0.
90 times. As a result, the substantially entire width of the tread portion 2 is reinforced with a hoop effect. Both ends of the belt layer 7 are gradually separated from the carcass 6, and the relatively soft cushion rubber 8 is filled in the separated portions.

Further, each of the belt plies 11, 12, 13
Is a steel belt cord (steel cord) 20
Are formed from steel plies arranged in parallel to each other,
As shown in FIG. 2, the first and second belt plies 11, 1
The belt cords 20A and 20B of No. 2 are tire equator CO
In contrast, the belt cord 20C of the third belt ply 13 is inclined in the same direction (for example, an upward rightward direction), and is inclined in an opposite direction (for example, an upward leftward direction) to the belt cords 20A and 20B.

Of these, the second and third belt plies 1
2 and 13 are belt cords 20B and 20C as in the conventional case.
Extends linearly and the angle α with respect to the tire equator CO
2 and α3 are set to 10 to 30 degrees, respectively.

On the other hand, in the innermost first belt ply 11, the corrugated region Y1 of the belt cord 20A is provided in the tire central portion including the tire equator CO.

Here, the "corrugated region Y1" is a region in which the belt cord 20A is two-dimensionally corrugated within the ply surface, and the corrugated reference line N is repeatedly formed as a center to form unevenness. The corrugated reference lines N are arranged in parallel with each other. For the sake of uniformity, in this example, each belt cord 20A has a corrugation amplitude Py and a corrugation pitch length L.
Although y and the phase of corrugation are substantially equal to each other and are equally spaced in the circumferential direction, the amplitude P is set in a range in which adjacent belt cords 20A do not overlap.
The y, the pitch length Ly, the phase, etc. may be changed.

In this example, the amplitude Py of the corrugation is
The corrugation pitch length Ly is in the range of 2.0 to 4.0 mm, and the corrugation amplitude Py is 3.0 to 15.0.
It is set about twice.

The area width Wy of the corrugated area Y1 in the tire axial direction is 0.4 to 0.6 times the ply width W1 of the first belt ply 11 in this example. On both outer sides of the attachment area Y1, the straight area Y2 in which the belt cord 20A extends straight without corrugation,
It forms Y2. The corrugation reference line N of the belt cord 20A passing through the corrugated region Y1 and the belt cord 20A passing through the straight region Y2 are inclined at substantially the same inclination, and the angle α1 with respect to the tire equator CO is 46 to 7.
The range is 0 degree.

As described above, in the belt layer 7, the belt cords 20A, 20B and 20C intersect each other to form a strong triangle structure, while the first belt ply 11 is formed.
Exhibits excellent elongation characteristics in the corrugated region Y1. Therefore, the movements of the belt cords 20B and 20C in the triangle structure are moderated appropriately. As a result, in the central portion of the tread, the belt cord 20 is responsive to the deflection of the tread portion 2 when the tire steps on the rock or the like.
The angles of B and 20C can be changed flexibly, the cord breakage of the second and third belt plies 12 and 13 can be suppressed, and the plunger strength can be effectively improved.

Even when the belt layer 7 has a three-ply structure as in this example, the belt cord is thicker and the number of cords to be driven is increased as compared with the conventional four-ply structure. Since the required plunger strength can be secured without causing any damage, it can greatly contribute to the weight reduction of the tire.

On the other hand, since the first belt ply 11 has the non-stretchability in the straight regions Y2 on both outer sides, it restrains the tread shoulder portion with a strong hoop effect. Therefore, it is possible to suppress the protrusion of the tread shoulder portion and effectively prevent the tread contour shape from changing, and it is possible to prevent uneven wear such as shoulder drop wear while increasing the plunger strength.

The area width Wy of the corrugated area Y1 is
Less than 0.4 times ply width W1 or wavy amplitude Py
Is less than 2.0 mm, the width having the elongation property or the elongation property itself becomes insufficient, and the effect of improving the plunger strength cannot be sufficiently exhibited. On the other hand, when the area width Wy exceeds 0.6 times the ply width W1, the protrusion of the tread shoulder cannot be sufficiently suppressed, causing uneven wear in this portion, and the corrugation amplitude Py is 4.0 mm.
If it exceeds the range, the central portion of the tread is extruded, and uneven wear is caused at this portion, thereby deteriorating the uneven wear resistance.

In the present application, the belt cord 20A
The twisting structure (cord structure) and the number of hammers can be set to be the same as the twisting structure (cord structure) and the number of hammers of the other belt cords 20B and 20C, and further on the outside of the third belt ply 13. A fourth belt ply can also be provided.

[0027]

EXAMPLE Tire size 11R22.T having the structure of FIG.
No. 5 heavy-duty tire was prototyped based on the specifications shown in Table 1, and the plunger strength and uneven wear resistance of each sample tire were compared, and the results are shown in Table 1. The specifications other than the structure of the belt layer are common to all tires.

Plunger strength: 800 Kpa by mounting the trial tire on a regular rim (7.50 × 22.5)
Under the condition that the internal pressure of (1) was filled, a plunger destruction test according to JIS D4230 was performed. The breaking energy at that time was compared by an index with Comparative Example 1 as 100. The higher the number, the better.

Uneven wear resistance: A test tire mounted on a regular rim (7.50 × 22.5) and mounted on all wheels of a 2 / 2-D vehicle under the condition of being filled with an internal pressure of 800 Kpa. In addition, 3000 dry pavement test courses
The vehicle was run for 0 km, and the uneven wear amount at that time was evaluated by a 5-point method. The higher the number, the better.

[0030]

[Table 1]

[0031]

As described above, according to the present invention, since the cord corrugated region is formed in the innermost belt ply, flexibility can be imparted to the central portion of the tread, and the plunger strength can be effectively improved. It is possible to reduce the weight and the weight. Further, when the straight areas of the cord are provided on both outsides of the corrugated area, it is possible to prevent the tread shoulder from protruding, and it is possible to improve the uneven wear resistance and the like while maintaining the effect of improving the plunger strength. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is a plan view showing a code arrangement state of a belt layer.

FIG. 3 is a plan view showing a cord arrangement state of a conventional belt layer.

[Explanation of symbols] 2 tread section 3 Side wall part 4 bead section 5 bead core 6 carcass 6A carcass ply 7 Belt layer 11, 12, 13 Belt ply 20, 20A-20C belt cord CO tire equator N wave reference line Py amplitude of corrugation Y1 corrugated area Y2 straight area Wy Wavy area area width W1 Innermost belt ply width

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Claims (2)

(57) [Claims] 1. A carcass consisting of a carcass ply using one steel carcass cord extending from the tread portion to the side wall portion to the bead core of the bead portion, and the inside of the tread portion and the outside of the carcass in the radial direction. A belt layer composed of three or more belt plies arranged in parallel with each other and arranged in parallel to each other and overlapping inward and outward in the tire radial direction, and the innermost belt ply includes at least the tire equator. A corrugated region which is provided at the center of the tire and in which the belt cord is bent in the ply surface by corrugation, and the corrugated region
The belt cords provided on both sides of the
A heavy-duty tire having a straight region extending in a straight line . 2. The width of the corrugated region in the tire axial direction is
0.4 to 0.6 of the ply width of the innermost belt ply
Double and wavy amplitude 2.0-4.0mm
The belt cord corrugation reference line in the attachment area
The belt cord in the belt area is 46 with respect to the tire equator.
The inclination according to claim 1, which is inclined at an angle of 70 degrees.
Heavy duty tires listed.