JPH0577610A - Radial tire for heavy load - Google Patents

Abstract

PURPOSE:To restrain generation of biased abrasion such as one side dropped abrasion and truck abrasion, to heighten durability, to improve a drainage property and to heighten a braking performance on the wet road. CONSTITUTION:A plural number of longitudinal main grooves 3... compression of which is less than 70%, consisting of straight grooves in parallel with a tire equator C on a tread surface 2 and including an outer longitudinal main groove 3A adjacent to a tread edge are provided, an outer longitudinal groove distance GP which is length from a groove edge F of a tread edge side of the outer longitudinal main groove 3A to the tire equator C is made to be 0.2-0.325 times of a tread width TW and a groove width GW of the outer longitudinal main groove 3A is made to be 0.045-0.07 times of the aforementioned tread width TW.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention suppresses uneven wear such as shoulder drop wear and track wear that occurs along the vertical groove of a tire, improves durability, and also improves drainage performance for heavy loads. Regarding radial tires.

[0002]

2. Description of the Related Art In recent years, even for heavy-duty tires used for buses, trucks, etc., tires having a low flatness ratio have been widely adopted in order to increase the loading capacity. Particularly in the case of tires mounted on a trailer, the tendency of lowering the flatness ratio is remarkable due to the further increase of the loaded weight, the stability of running, and the ease of handling.

[0003]

However, in a heavy duty tire, if the flatness ratio is set to 0.7 or less, the restraining force of the belt layer tends to gradually decrease from the tire central portion toward the tread shoulder portion. On the other hand, the tire is
The outer diameter of the tire gradually increases due to the centrifugal force caused by rolling, the tread portion repeatedly deforming when it comes into contact with the ground and opening during running, and the occurrence of permanent strain due to high internal pressure. It occurs unevenly with the tread shoulder. In particular, when it is mounted on a trailer vehicle, in addition to the above-mentioned uneven outer diameter change, the trailer vehicle is dragged by a truck and travels, and since there is no steering device, the tire itself has a strange shape. The bad condition that lateral force is applied overlaps. Moreover, since the trailer vehicle does not have a drive unit and cannot run on its own, the trackion does not act on the tires.

When a tire is used for a trailer having such a condition, the shoulder falls along the vertical groove of the tread surface,
Uneven wear such as track wear is likely to occur.

On the other hand, in the case of heavy-duty tires, it is necessary to improve the drainage property in order to increase the loading capacity and the braking function, especially on the wet road surface.

As a result of repeated studies by the inventor of the present invention, in the conventional heavy-duty tire, the vertical grooves a formed on the tread surface as shown in FIG. 7 are zigzag grooves. Is formed and uneven wear occurs in the outer vertical groove a1 located closest to the tread edge.
It was also confirmed that the uneven wear of the outer vertical groove a1 is concentrated on the groove edge ridge of the zigzag groove. It was also found that the bending angle of the zigzag groove greatly affects drainage.

Therefore, the vertical grooves a ... Are only linear grooves and the position of the outer vertical groove a1 is moved away from the tread edge e, and
The inventors have completed the present invention by finding that even if the occurrence of uneven wear is suppressed by controlling the groove shape and the groove width dimension, drainage can be improved.

According to the present invention, the vertical main groove is formed by a straight groove, and the position of the vertical main groove closest to the tread edge and the width of the vertical main groove are regulated to suppress the occurrence of uneven wear and improve durability. The purpose of the present invention is to provide a heavy-duty radial tire capable of improving the drainage performance, braking performance on wet road surfaces, and running safety.

[0009]

The present invention has an aspect ratio of 70.
% Radial load heavy tires, the tread surface is provided with a plurality of vertical main grooves including a vertical groove parallel to the tire equator and including an outer vertical main groove close to the tread edge,
Outer longitudinal groove length (GP), which is the length in the tire axial direction from the groove edge on the tread edge side of the outer longitudinal main groove to the tire equator.
Is 0.2 times or more and 0.325 times or less of the tread width (TW), and the groove width (GW) of the outer vertical main groove is 0.045 times or more and 0. 0
It is a heavy-duty radial tire characterized by being set to 7 times or less.

[0010]

[Function] Since the vertical main groove is formed by a straight groove parallel to the tire equator, the drainage property is improved, and there is no ridge at the groove edge like the zigzag groove, which is likely to occur at the ridge. Occurrence of uneven wear can be suppressed.

Further, if the outer longitudinal main groove distance GP is less than 0.2 times the tread width TW, the longitudinal main grooves are concentrated in the central region of the tread,
Since there is no vertical main groove in the tread shoulder portion, the drainage performance of the tread shoulder portion is reduced and the braking performance on the wet road surface is reduced. On the other hand, when the outer longitudinal main groove distance GP exceeds 0.325 times the tread width TW, the contact pressure is lowered at the tire equator side groove edge of the outer longitudinal main groove, which results in the promotion of slip in the tire circumferential direction. As a result, uneven wear, which is so-called track wear, is likely to occur along the groove edge.

The groove width GW of the outer vertical main groove is the tread width T.
If it is less than 0.045 times W, the drainage performance is poor and braking performance on the wet road surface deteriorates, while if it exceeds 0.07 times, the ground contact area of the tire decreases and the ground contact pressure increases and wear resistance decreases. Become.

Therefore, by controlling the position of the outer longitudinal main groove from the tire equator and the groove width, wear resistance can be further enhanced and drainage can be improved, and it can be used for heavy loads, especially for trailers. Can be done. A large tire having a tread width of 250 mm or more can be effectively used because it can efficiently improve wear resistance and drainage resistance.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the drawing, the radial tire 1 for heavy load has an aspect ratio of 7 which is the ratio of the tire cross-section height H to the tire maximum width W.
The flat tire of 0% or less, and the heavy duty radial tire 1 has a bead core 15 of a bead portion 14 from a tread portion 12 forming a tread surface 2 to a sidewall portion 13.
It comprises a carcass 6 which is folded back around and a belt layer 17 which is arranged inside the tread portion 12 and outside the carcass 16.

The carcass 16 is a radial or semi-radial arrangement in which carcass cords made of organic fibers such as nylon, rayon, polyester, aromatic polyamide fibers or steel are arranged at an angle of 70 to 90 ° with respect to the tire equator C. The carcass ply of (1) is formed by a single sheet or a plurality of sheets, and in this example, one sheet.

The belt layer 17 is composed of four belt plies 17a ... In this embodiment, each belt ply 17a is made of nylon, rayon, polyester, aromatic polyamide fiber or other organic fiber or steel belt cord like the carcass ply. Are arranged side by side, and at least two belt plies are arranged so as to intersect with each other between the plies.

The tread surface 2 is provided with a plurality of vertical main grooves 3 ... Which are straight grooves extending in the tire circumferential direction and parallel to the tire equator C. The vertical main groove 3 is a four-way groove including an outer vertical main groove 3A close to the tread edge E and an inner vertical main groove 3B interposed between the outer vertical main groove 3A and the tire equator C. 5 ribs are formed on the tread surface 2.

In this embodiment, as shown in FIG. 1, between the outer and inner vertical main grooves 3A, 3B and between the inner vertical main grooves 3B, 3B sandwiching the tire equator C, the vertical main grooves 3, 3 on both sides are provided. , And small sipes 21 ..., 22 ... are arranged at equal intervals. Further, the outer vertical main groove 3A is provided with a discontinuous lateral groove 23 which extends toward the tread edge E and is interrupted on the way.

The outer vertical main groove 3A has its tread edge E.
The outer longitudinal main groove distance GP, which is the length in the tire axial direction from the side groove edge F to the tire equator C, is set to 0.2 times or more and 0.325 times or less of the tread width TW. The groove width GW at the open end of the other vertical main groove 3A is set to be 0.045 times or more and 0.07 times or less of the tread width TW. The groove depth GH is 0.02 to 0.0 of the tread width TW.
It is preferably four times.

Further, in this embodiment, the outer wall surface 2 of the vertical main groove is
Nos. 4 and 25 have a side wall surface 24 on the tread edge E side with an inclination angle α of 5 ° or more and 20 ° or less with respect to a normal line N orthogonal to the tread surface 2 in a cross section in the tire meridian direction, and a tire equator C side. The side wall surface 25 has a tilt angle β of 22 ° or more and 30 ° or less.

In the outer vertical main groove 3A, a deformation bending point is generated in the tread portion 2 by the outer vertical main groove itself, and as a result, a decrease in ground contact pressure is observed along the tire equator side groove edge. This decrease in ground contact pressure promotes slippage in the tire circumferential direction, which may increase track wear. By forming the wall surface 25 on the tire equator side as the side wall surface 25 that is gently inclined as in the present embodiment, the rigidity of the groove edge F1 is increased and the slip resistance is enhanced, so that the groove edge F1 on the tire equator side is formed. It is possible to further suppress the occurrence of track wear that tends to occur.

Moreover, when the rainwater that has entered the outer vertical main groove 3A is discharged, the groove cross-sectional shape is inclined and opened toward the tire equator C side, so that the rainwater from the vertical main groove 3A is located on the tire equator C side. It is possible to prevent water splashes scattered to the side of the tire.

[0023]

[Examples] Regarding track wear resistance The tire size is 385 / 65R 22.5 and the vertical main groove has a pattern formed by straight grooves or zigzag grooves, and the outer vertical main groove distance is set in multiple stages. A plurality of types of set tires were prototyped, and the presence or absence of track wear and the amount of wear due to actual vehicle running were measured. In the measurement, test tires were prototyped according to the specifications shown in Table 1. The composition of the carcass and the belt layer is shown in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

The test was conducted on each sample tire with an internal pressure of 8.5 kg / cm.
Add ² and mount on a 23 ton trailer, loading capacity 1
After running 50,000 km on a general road under the condition of 00%, the amount of track wear generated on the tread surface was measured. The amount of wear was calculated by measuring the volume M (shown by diagonal lines in the figure) that disappeared due to wear as shown in FIG. 7, and the measured value was shown as an index. An index value of 0 indicates that no wear has occurred, and the larger the value, the greater the wear.

The test results are shown in FIG. Test results,
The straight groove type (A group) produces less orbital wear than the zigzag groove type (B, C groups), and the straight groove type with a GP / TW ratio of 0.325 or less causes orbital wear. It turned out not to occur.

Regarding drainage, the tire size is 385 / 65R22.5 as in 1).
For tires with multiple types of patterns in which the vertical main groove is a straight groove or a zigzag groove, the width of the outer vertical main groove is set stepwise and the braking distance of the actual vehicle on the wet road surface is measured. By doing so, the drainage performance was investigated. At the time of measurement, the tires provided were prototyped according to the specifications shown in Table 3. The composition of the carcass and the belt layer is shown in Table 2.

[0029]

[Table 2]

The test was carried out on the same vehicle as in 1), and after running on a wet road surface at a speed of 80 km / H in an empty state, sudden braking was applied and the distance until the vehicle stopped was measured.

The measurement results are shown in FIG. In the table, GW / TW, which is the ratio of the groove width to the tread width, is 0 corresponds to the G group without the longitudinal main groove, and FIG. 5 shows the braking distance of this G group as an index. The smaller the value, the better.

As a result of the test, the straight groove (D group) has a smaller braking distance than those without the vertical main groove (G group) and the zigzag groove (E, F groups).
Even in the case of a straight groove, the GW / TW ratio is 0.045.
From the above, it was found that the braking performance was good.

[0033]

As described above, in the heavy duty radial tire of the present invention, the vertical main groove is formed by a straight groove, and the position of the vertical main groove closest to the tread edge and its groove width are regulated. Therefore, it is possible to suppress the occurrence of uneven wear that tends to occur at the groove edge, improve the durability, and also improve the drainage property, so that the braking performance on the wet road surface can be improved and the traveling safety can be improved.

When the radial tire for heavy loads of the present invention is used as a heavy load tire for a trailer which does not require driving, the effect is more remarkable.

[Brief description of drawings]

FIG. 1 is a plan view showing a tread surface of a heavy duty radial tire of the present invention.

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

FIG. 3 is an enlarged sectional view showing an outer vertical main groove.

FIG. 4 is a graph showing a relationship between an outer vertical main groove distance and a track wear amount.

FIG. 5 is a graph showing the relationship between the groove width of the outer vertical main groove and the braking distance.

FIG. 6 is a plan view showing a conventional tread pattern.

FIG. 7 is a cross-sectional view of an outer vertical main groove showing a state of track wear.

[Explanation of symbols]

 2 Tread surface 3 Vertical main groove 3A Outer vertical main groove C Tire equator E Tread edge F Groove edge GP Outer vertical main groove distance GW Groove width TW Tread width

[Table 3]

Claims (1)

[Claims] 1. A radial tire for heavy loads having an aspect ratio of 70% or less, wherein a plurality of longitudinal main grooves each having a linear groove parallel to the tire equator and having an outer longitudinal groove near the tread edge are provided on a tread surface. In addition, the outer longitudinal main groove distance (GP), which is the length in the tire axial direction from the groove edge on the tread edge side of the outer longitudinal main groove to the tire equator, is set to 0.
The width of the outer vertical main groove (GW) is not less than 2 times and not more than 0.325 times, and is not less than 0.045 times and not more than 0.07 times the tread width (TW). Radial tires for heavy loads.