JPH0687304A - Bias tire for construction vehicle - Google Patents

Abstract

PURPOSE:To lighten a bias tire for a construction vehicle without impairing abrasion resistance by changing the land/sea ratio of lug pattern in a tread center section and tread shoulder section in a specified range. CONSTITUTION:A right and left tread face 9R and 9L comprising a tread face 9 divided by the tire equator C are divided by pitch elements, and the distance A between the internal end E2 of the lug groove G provided in each area and the tire equator C is set in a range from 0.025 times of tread width WT. When the ground contact areas L1 and L2 of the in/out side rectangular areas Yi and Yo comprising each of the right and left tread faces 9R and 9L imaginarily divided by an intermediate line K and in/out side areas on the tread face are taken as S1 and S2, L1/S1=3.34 to 4.00 and L2/S2=1.00 to 1.14. In addition, the ratio of the peripheral length WG of the lug groove G at a tread edge (e) and the peripheral length of the ground contact face is set as 1.0 to 1.1, and the angle of a groove wall in a cross section orthogonal to the center line of the lug Groove G including a normal line to the normal line stood on the tread face 9 in the rectangular area Yo is set in a range of 28 deg. to 35 deg.. Therefore, a bias tire can be lightened without impairing abrasion resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bias tire for a construction vehicle which can achieve weight reduction without impairing wear life.

[0002]

2. Description of the Related Art For example, even in a bias tire for a construction vehicle in which a lug pattern consisting of a lug groove extending in the tire axial direction is provided to improve traction on a bad road, in recent years, loading capacity and fuel efficiency have been improved. Therefore, it is strongly desired to reduce the weight. Therefore, in recent years, in order to meet such demands, it has been proposed to increase the groove area of the tire and reduce the tread rubber weight.

[0003]

However, the increase of the groove area generally causes uneven wear, and there is a problem to be solved that the wear rate is accelerated and the service life of the tire is shortened by the increase of the ground contact pressure.

Therefore, the present inventor conducted a study on wear of bias tires. As a result, since the bias tire does not have the hoop effect due to the belt such as the radial tire, the center portion of the tread is smaller than the tread shoulder portion due to the centrifugal force due to the tire rolling as shown by the alternate long and short dash line in FIG. The outer diameter grows unevenly. Moreover, since there is no hoop effect, the carcass radius of curvature on the tread is smaller than the radius of curvature of the radial tire, that is, the rubber gauge thickness t1 at the center of the tread is smaller than the rubber gauge thickness t2 at the tread shoulder. There is little wear margin.
As a result, it has been found that in the bias tire, the center of the tread reaches the wear limit at an early stage, and the service life of the tread shoulder part ends with the wear margin left.

That is, the present invention is based on the fact that the land / sea ratio of the lug pattern in the central portion of the tread and the land / sea ratio in the tread shoulder portion are changed within a predetermined range, and the wear rates of the central portion of the tread and the shoulder portion are changed. It is an object of the present invention to provide a bias tire for a construction vehicle capable of increasing the groove area while achieving uniformization of the tire, and achieving weight reduction without impairing wear life.

[0006]

In order to achieve the above object, a bias tire for a construction vehicle according to the present invention is provided with a lug groove extending from a tread edge on the tread surface and interrupted in the vicinity of the tire equator at each circumferential pitch on both sides of the tire equator. A tire having a lug pattern in which the tread surface is divided into the lug groove and the ground contact surface that contacts the road surface, by providing the tread surface in a rectangular area Y in which the pitch length of the tread surface extends in the tire axial direction.
Is virtually divided into an outer rectangular area Yo from the middle line bisecting between the tread edge and the tire equator to the tread edge, and a rectangular area Yi inside the middle line to the tire equator. Area L of the ground plane in the rectangular region Yi of
1 and the area S1 of the lug groove on the tread surface L1 / S1
Is 3.34 to 4.00, the ratio L2 / S2 between the area L2 of the ground contact surface and the area S2 of the tread surface of the lug groove in the outer rectangular region Yo is 1.00 to 1.13, and at 1 pitch. , The circumferential length W of the lug groove at the tread edge
The ratio WG / WB between G and the circumferential length WB of the contact surface is 1.0
1.1, the ratio A / WT between the distance A between the tire axial inner end of the lug groove and the tire equator and the tread width WT is 0.
Further, the angle β formed by the groove line of the lug groove in the cross section perpendicular to the center line of the lug groove including the normal line of 025 to 0.05 and 28 in the outer rectangular region Yo is 28. It is set to ~ 35 degrees.

[0007]

The ratio L1 / S1 is set to 3.34 to 4.00, and the ratio L
2 / S2 is set to 1.00 to 1.13, and the inner rectangular area Yi
The ratio of the ground contact surface at is higher than the ratio of the ground contact surface at the outer rectangular area Yo. As a result, the wear speed at the central portion of the tread is reduced such that the ground contact pressure of the inner rectangular area Yi is reduced, and the progress of wear can be brought closer to the tread shoulder portion. This improves the wear life as a whole.
On the other hand, in the outer rectangular region Yo, the area of the lug groove is increased, so that the rubber weight is reduced. In particular, since the outer rectangular region Yo in the bias tire has a high rubber gauge thickness as described above, such an increase in the lug groove area in the outer rectangular region Yo can more effectively reduce the weight of the tire.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the figure, a construction vehicle bias tire 1 includes a tread portion 2, a sidewall portion 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 located at the radially inner end of each sidewall portion 3. In this example, the tire is formed as a dump truck tire having a tire size of 12.00-20 18PR.

A bead core 5 for reinforcement is embedded in the bead portion 4, a carcass 6 is bridged between the bead cores 5, 5, and the carcass 6 is radially outward and the tread portion 2 is inward. A breaker 7 is wound around.

In the present embodiment, the carcass 6 has an inner layer 6A composed of, for example, eight carcass plies 6a which are folded from the inside of the bead core 5 to the outside of the bead core 5 from the tread portion 2 to the sidewall portion 3 and the inner layer 6A. The inner layer 6A includes an outer layer B which is placed on the outer side of the inner layer 6A and covers the folded portion of the inner layer 6A and has both ends folded back from the outer side to both sides, for example, two carcass plies 6b. Carcass ply 6a, 6b
Are made by arranging organic carcass cords such as nylon at an angle of 30 to 45 degrees with respect to the tire equator C, and the carcass plies 6a and 6b are oriented so that the carcass cords cross each other. It is arranged as a different cross-ply structure. The number of plies of the carcass 6, the material of the carcass cord, the number of driving the carcass cord, and the like are appropriately set according to the required tire performance.

The breaker 7 outside the carcass 6 is, in this example, two breaker plies inside and outside, and each ply is
For example, by arranging organic breaker cords such as nylon at an angle of 30 to 45 degrees with respect to the tire equator, the tread portion 2 is reinforced, the impact from the road surface is alleviated, and the cut resistance is improved.

Then, on the tread surface 9 of the tread portion 2,
A rug pattern is formed. As shown in FIG. 2, the lug pattern divides the left and right tread single-sided areas 9L and 9R into which the tread surface 9 is divided into two by the tire equator C, with the pitch elements P in the circumferential direction, respectively, and the divided pitches. One lug groove G is formed in each element P. Therefore, the lug pattern divides the tread surface 9 into the lug groove G and the ground surface that is the rest of the tread surface 9 and contacts the road surface. As shown in FIG. 2, the pitch length M in the circumferential direction of each pitch element is constant, that is, an equal pitch array partitioned by one kind of pitch element P0, and as shown in FIG. Type, eg 3
A variable pitch array or the like, which is divided by using the pitch elements P1, P2, and P3 of various types, can also be adopted. The pitch elements P provided on the tread one-sided areas 9L and 9R are
It is preferable that the number is 25 to 36, respectively.

The outer end E1 of the lug groove G has a tread edge e.
The inner end E2 that is open at the end and extends inward in the tire axial direction is a lateral groove having an end that is interrupted near the tire equator C, and is a lug groove G.
Is formed by positioning its outer end E1 at an intermediate position in the circumferential direction of the pitch element P.

In this example, the lug groove G is bent in a zigzag shape and extends at a substantially right angle toward the tire equator C, and the groove width W, which is the length of the groove in the circumferential direction, extends from the outer end E1 to the inner end. It has reached E2 and is gradually decreasing. As described above, in this example, the lug groove G extends at a substantially right angle toward the tire equator C, so that the pitch element P has a rectangular shape. At this time, the pitch element P has a rectangular shape in which the pitch length A extends in the tire axial direction. It matches the region Y. When the lug groove G is largely inclined in the tire axial direction, the pitch element P has a quadrangle different from the rectangular region Y as shown in FIG. 5, for example.

The lug groove G has an inner end E2 and a tire equator C.
The distance A between and is set to 0.025 times or more and 0.05 times or less of the tread width WT. The distance A is 0.025
When it is smaller than WT and when the lug groove G crosses the tire equator C, the pattern rigidity of the central portion of the tread is lowered, and the tread surface of the central portion becomes easy to move, causing slippage with the road surface and shortening the wear life. . On the contrary, when it is more than 0.05 WT, the drainage property is poor and the wet grip property is deteriorated.

In such a lug pattern, the rectangular area Y is an outer rectangular area Y extending from the intermediate line K that bisects the tread edge e and the tire equator C to the tread edge e.
o is a rectangular area Y from the middle line K to the tire equator C
When virtually divided into i, the area L1 of the ground contact surface and the area S1 of the lug groove G on the tread surface in the rectangular area Yi.
And the ratio L1 / S1 of 3.34 to 4.00, and the ratio L2 / S2 of the area L2 of the ground contact surface in the outer rectangular region Yo and the area S2 of the lug groove G on the tread surface is 1.00.
It is set to 1.13. That is, the land / sea ratio in the inner rectangular area Yi is increased as compared with the land / sea ratio in the outer rectangular area Yo, and the ground contact pressure in the inner rectangular area Yi is reduced as compared with the outer rectangular area Yo. As a result, the wear rate on the inner rectangular region Yi, that is, the tread central portion side is reduced, and the progress of wear is approximated to the progress of wear on the tread shoulder portion side, whereby the overall wear life can be improved.
On the other hand, in the outer rectangular region Yo, the area of the lug groove is increased conversely, so that the rubber weight is reduced and the tire can be made lighter. Therefore, when either one or both of the ratio L1 / S1 and the ratio L2 / S2 deviates from the above range, both the wear of the tread shoulder portion and the tread central portion are promoted or the wear progress becomes unbalanced. The wear life is shortened or the weight of the tire is not sufficiently reduced.

The lug pattern has a ratio WG / WB of 1.0 to 1.1 and an angle β of 28 to 35 degrees in order to obtain a required pattern strength.

Here, the symbol WG is the circumferential length of the lug groove G at the tread edge within the one-pitch element P, and the symbol WB is the circumferential length at the tread edge e of the remaining contact surface. WG (= WG1 + WG2). When the ratio WG / WB is less than 1.0, the groove width becomes too small, which impairs drainage and makes it difficult to achieve weight reduction. On the contrary, when it is larger than 1.1, it causes uneven wear such as shoulder drop wear and also induces block chipping.

As shown in FIG. 3, the angle β is a normal line N standing on the tread surface 9 in the outer rectangular area Yo and a lug in a cross section including the normal line N and perpendicular to the center line Cg of the lug groove G. It is an angle formed by the groove walls ga and gb of the groove G. When the angle β is less than 28 degrees, the pattern rigidity is excessively reduced to impair the steering stability on a good road, and the abrasion with the road surface is accelerated due to the slip on the road surface. On the contrary, when the angle β is larger than 35 degrees, the traction performance on a rough road is deteriorated.

In order to further enhance the rigidity of the pattern, the angle α formed by the center line Cg of the lug groove G with respect to the tire axial direction is set to 5 in at least the outer half region of the outer rectangular region Yo. It is preferably set to 10 degrees.

The lug groove G may be bent in a zigzag shape in the outer half region. In such a case,
The angle of the zigzag with respect to the tire axial direction is in the range of 5 to 10 degrees, respectively. Also, different angles β1, β of the groove walls ga, gb
It may be inclined at 2, and in such a case, each angle β1,
β2 is in the range of 28 to 35 degrees.

(Concrete example) The structure shown in FIG.
Tire size with lug pattern is 12.00-2
A 0 18 PR tire was prototyped based on the specifications in Table 1, and the wear resistance, tire weight, and traction of the prototype tire were compared with the comparative tire.

[0023]

[Table 1] The abrasion resistance and the traction property were measured by the following tests, and compared by an index with the comparative example tire being 100. The larger the index, the better.

[0024]

As described above, since the bias tire for a construction vehicle according to the present invention is constructed, the weight of the tire can be reduced without impairing the wear life.

[Brief description of drawings]

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

FIG. 2 is a plan view showing an example of a tread pattern used for it.

FIG. 3 is a partial cross-sectional view showing a lug groove.

FIG. 4 is a schematic diagram illustrating another example of the pitch arrangement.

FIG. 5 is a schematic diagram illustrating a rectangular area.

FIG. 6 is a schematic diagram illustrating a conventional technique.

[Explanation of symbols]

 9 Tread surface A Pitch length C Tire equator e Tread edge G Lag groove K Intermediate line P Pitch

Claims (1)

[Claims] 1. A tread surface is provided on the tread surface, which extends from the tread edge and is interrupted in the vicinity of the tire equator, at each circumferential pitch on both sides of the tire equator so that the tread surface serves as the lug groove and the ground contact surface that contacts the road surface. A tire having a segmented lug pattern, in which a rectangular area Y in which the pitch length of the tread surface extends in the tire axial direction extends from an intermediate line bisecting between the tread edge and the tire equator to the tread edge. The rectangular area Yo and a rectangular area Yi extending from the middle line to the tire equator are virtually divided, and the rectangular area Y in the above is defined.
The ratio L1 / S1 of the area L1 of the ground contact surface and the area S1 of the lug groove on the tread surface is 3.34 to 4.00, and the area L2 of the ground surface in the outer rectangular region Yo and the tread surface of the lug groove The ratio L2 / S2 to the area S2 of 1.00 to 1.
13 and in one pitch, the circumferential length WG of the lug groove and the circumferential length WB of the ground contact surface at the tread edge.
And the ratio A / WT of the tread width WT and the distance A between the tire axially inner end of the lug groove and the tire equator are 0.025 to 0. 05, and
For a construction vehicle in which the angle β formed by the normal line standing on the tread surface in the outer rectangular area Yo and the groove wall of the lug groove in a cross section including this normal line and perpendicular to the center line of the lug groove is 28 to 35 degrees Bias tire.