JP3075487B2 - Radial tires for construction vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire mounted on a large construction vehicle and having a flatness of 85% or less.

[0002]

2. Description of the Related Art Conventionally, as a radial tire mounted on a large construction vehicle, for example, a toroidal carcass layer composed of at least one carcass ply in which a steel cord extending in a meridian direction is embedded, A belt layer composed of at least two belt plies radially outward and having a steel cord embedded therein, and a tread radially outward of the belt layer, the outer surface of the tread in a meridional section being 2000 mm From
There is known one composed of an arc having a single radius of curvature of about 7000 mm.

[0003]

However, such conventional radial tires for construction vehicles have a problem that heat and distortion are large at the belt end, and as a result, separation is likely to occur at the belt end. is there. The reason is that when the radial tire is rolled under load, the sidewall portion is bent so as to bulge outward, so that the point C which is apart from the tire equatorial plane E by 0.25 times the tread width W is affected by the influence. The vicinity is depressed (buckled) inward in the radial direction, and as a result, the contact pressure at the tread portion is reduced as shown in FIG.
As shown by an imaginary line, it is low near the point C, and becomes high on both sides in the width direction of the point C, that is, near the tire equatorial plane E and near the point A that is 0.375 times the tread width W from the tire equatorial plane E. is there. In such a portion having a high ground pressure, a large distortion is generated at the time of touching the ground, so that heat is generated and the temperature becomes high. Of these portions having a high ground pressure, the belt end is generally located near the point A. As a result, large distortion and high temperature act on these belt ends, so that separation is easily generated at the belt ends. Such a problem becomes more remarkable as the flatness of the radial tire becomes lower, particularly when the flatness becomes 85% or less.

[0004] It is an object of the present invention to provide a radial tire for a construction vehicle capable of effectively suppressing belt end separation by reducing heat generation and distortion at a belt end.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a toroidal carcass layer comprising at least one carcass ply having a steel cord extending in a meridian direction embedded therein, and a carcass layer disposed radially outside the carcass layer. A radial tire for a construction vehicle, comprising: a belt layer including at least two belt plies in which a steel cord is embedded; and a tread disposed radially outside the belt layer, and having a flatness of 85% or less, a meridian. The outer surface of the tread in the cross section is at least 0.375 times the tread width W from the tire equatorial plane E, with the first area having the center in the width direction located on the tire equatorial plane E and being located on both outer sides in the width direction from the first area. A second area including a point A separated by only
A third region located between the region and the second region,
In addition, the first area is formed from an arc having a width D1 of 0.2 to 0.4 times the tread width W and a radius of curvature R1 of 3000 mm or more. Each second area is formed from a width D2 of 0.15 times the tread width W.
In the range of 0.375 times, each third region is formed from an arc having a radius of curvature R2 of 3000 mm or more and an arc having a radius of curvature R3 smaller than the radius of curvature R1 and R2 of the first and second regions. The radial distance L from the intersection B between the equatorial plane E and the first area to the point A is 0.003 of the tire outer diameter F at the intersection B.
It can be achieved by setting the range from 2 times to 0.012 times.

[0006]

It is now assumed that the tire mounted on the construction vehicle is rolling. At this time, since the sidewall portion of the tire is bent by the applied load, the vicinity of the point C is depressed (buckled) inward in the radial direction as described above.
The contact pressure at the tread portion is low near the point C,
It tends to be higher on both sides in the width direction of the point C, that is, near the tire equatorial plane E and near the point A. However, in the present invention, the first region having a large radius of curvature is provided near the tire equatorial plane E, and the second region having a large radius of curvature is provided also near the point A, so that the first region located between the first and second regions is provided. The vicinity of the three regions, that is, the vicinity of the point C is projected radially outward from the tread outer surface having the conventional single curvature radius. As a result,
The contact pressure near the point C increases, while the contact pressure decreases near the tire equatorial plane E and near the point A due to this effect. As a result, the contact pressure at the tread portion is shown by a solid line in FIG. Thus, they are almost uniform. Thereby, distortion and heat generation at the belt end located near point A are reduced, and separation at the belt end is effectively suppressed. In addition, as described in claims 2 and 3,
Even if the first and second regions are formed of straight lines, the same effects as described above can be obtained.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 11 denotes the flatness of a large construction vehicle such as a wheel loader or a scraper.
A pneumatic radial tire that is 85% or less, the tire 11 includes a pair of bead portions 13 in which beads 12 are respectively embedded, and a sidewall portion 14 extending substantially radially outward from the bead portions 13; And a substantially cylindrical tread portion 15 connecting the radially outer ends of the sidewall portions 14. The tire 11 is reinforced by a carcass layer 21 having a toroidal shape extending from one bead portion 13 to the other bead portion. Both end portions in the width direction of the carcass layer 21 are pivoted around the bead 12. It is folded from the inside in the direction to the outside in the axial direction. The carcass layer 21 is composed of at least one carcass ply 22, in this embodiment, one carcass ply 22, and each carcass ply 22 is perpendicular to the tire equatorial plane E (extends in the radial direction).
Many steel cords are buried. A belt layer 25 is disposed radially outward of the carcass layer 21. The belt layer 25 includes at least two belt plies 26 in this embodiment. In each belt ply 26, a number of steel cords embedded at an acute angle with respect to the tire equatorial plane E are embedded, and these steel cords cross each other at least in two adjacent belt plies 26. Both ends (belt ends) of the belt layer 25 in the width direction are 0.3 mm of the tread width W from the tire equatorial plane E.
It is located near point A, which is 75 times away. Here, the tread width W is an extension of the outer surface of the tread portion 15 and an extension of the outer surface of the sidewall portion 14 when the tread end 27 is formed of a small arc surface as in this embodiment. Measure between the intersections with A protective layer 30 is disposed radially outward of the belt layer 25, and the protective layer 30 includes at least one protective ply 31 in this embodiment. In each protective ply 31, a large number of steel cords having a large elongation whose inclination angle with respect to the tire equatorial plane E is substantially the same as the steel cord in the belt ply 26 are embedded. A tread 35 having a large number of grooves 34 formed on the outer surface is disposed radially outside the belt layer 25 and the protective layer 30.

The outer surface of the tread 35 in the meridian section of the tire 11 has at least first, second and third regions 41,
Three types of areas 42 and 43, and in this embodiment, a fourth area
It is composed of four types of areas, with 44 added. here,
The center of the first region 41 in the width direction is located on the tire equatorial plane E. As a result, the first region 41 extends by the same amount from the tread center toward both sides in the width direction, and the width D1 is the tread width. It is in the range of 0.2 to 0.4 times W. The first region 41 is formed by an arc having a radius of curvature R1 of 3000 mm or more or a straight line of infinity. Here, the width D1 of the first region 41 is in the range of 0.2 to 0.4 times the tread width W, and the radius of curvature R1 is 3000 mm or more because the width D1 or the radius of curvature R1 falls within the above range. If it deviates, the contact pressure near point A, which is 0.375 times the tread width W from the tire equatorial plane E, increases, and the contact pressure distribution in the tread portion 15 cannot be made uniform. Further, the second area 42 is the first area.
The point 41 is located on both outer sides in the width direction of the region 41 and includes the point A.
The width D2 of each second region 42 is 0.1 of the tread width W.
It is composed of an arc or an infinite straight line with a radius of curvature R2 of 3000 mm or more in a range of 5 to 0.375 times. The reason is that if the width D2 of the second region 42 is less than 0.15 times the tread width W, the contact pressure in the vicinity of the point A becomes high and the contact pressure distribution in the tread portion 15 cannot be made uniform. On the other hand, when D2 exceeds 0.375 times, the first, second and third regions 4
This is because the sum of the widths D1, D2, and D3 of 1, 42, and 43 exceeds the value of the tread width W, and further, the radius of curvature R2 is 3000
If it is less than mm, the contact pressure in the vicinity of the point A becomes high, and the contact pressure distribution in the tread portion 15 cannot be made uniform. The inner end of each second region 42, that is, the end on the tire equatorial plane E side is located at a position separated from the tire equatorial plane E by 0.125 to 0.225 times the tread width W. The radial distance L from the point A included in the second area 42 to the intersection B between the tire equatorial plane E and the first area 41 is the intersection B
Must be in the range of 0.003 times to 0.012 times the outer diameter F of the tire. The reason is that when the radial distance L is less than 0.003 times the tire outer diameter F, the outer surface of the tread 35 becomes almost the same as an arc having a single large radius of curvature, so that the contact pressure near the point A decreases. This is because the contact pressure distribution in the tread portion 15 cannot be made uniform due to the increase in the height.
When it exceeds 0.012 times, the outer surface of the tread 35 becomes almost the same as an arc having a small single radius of curvature, so that the contact pressure at the tread center (near the tire equatorial plane E) increases, and the contact pressure distribution becomes uniform. This is because it cannot be planned. The first and second
Between the regions 41 and 42, the width D3 is from 0.025 times the tread width W.
In the range of 0.125 times, the radius of curvature R3 is the first and second regions 41 and 42.
The third regions 43 each having an arc smaller than both the radii of curvature R1 and R2 are arranged, and the third regions 43 are arranged such that the first and second regions 41 and 42 directly collide with each other and tread.
The obtuse edge extending in the circumferential direction is prevented from being formed on the outer surface of the tire 35, thereby improving the appearance of the tire 11. Here, the radius of curvature R3 of each third region 43 is equal to the first and second regions 41,
20 less than the smaller one of the 42 radii of curvature R1 and R2
It is preferably smaller than 00 mm. The reason is that the difference is
If the length is less than 2000 mm, the above-described edge may be generated at the boundary between the third region 43 and the first and second regions 41 and 42. Further, the fourth regions 44 are respectively arranged outside the second regions 42 in the width direction.
Less than both R2.

When the tire 11 is mounted on a construction vehicle and rolled, the sidewall portion 14 of the tire 11 is bent by the applied load, and the vicinity of the point C is radially inward as described above. Recessed (buckled). As a result, the contact pressure in the tread portion 15 is low near the point C which is 0.25 times the tread width W from the tire equatorial plane E and is low on both sides in the width direction of these points C, that is, near the tire equatorial plane E and near point A. Try to get high. However, in the tire 11, the first region 41 having a large radius of curvature near the tire equatorial plane E and the second region 41 having a large radius of curvature near the point A as described above.
Since the region 42 is provided, between the first and second regions 41,
The vicinity of the third region 43 located at 42, that is, the vicinity of the point C is shown in FIG.
Projecting radially outward from the outer surface of the conventional tread having a single radius of curvature shown by the imaginary line, and as a result, the contact pressure near the point C becomes higher. The contact pressure in the vicinity of the point A decreases, and as a result, the contact pressure distribution in the tread portion 15 becomes substantially uniform.
Thereby, distortion and heat generation at the belt end located near point A are reduced, and separation at the belt end is effectively suppressed.

Next, test examples will be described. In this test, a conventional tire having an outer surface of a tread portion formed of an arc having a single curvature radius of 6000 mm and a test tire to which the present invention was applied were prepared. Here, each tire has a size
45/65 R45 L5, the flatness is about 65%, and the internal structure is as described in the previous embodiment. Further, regarding the first region 41 of the test tire, the width D1 (300 mm) is 0.297 times the tread width W (1010 mm), the curvature radius R1 is infinite (straight line), and the second region 42 is , Width D2
(215mm) is 0.213 times the tread width W and the radius of curvature R2 is
5000 mm, the inner end in the width direction is apart from the tire equatorial plane E by 0.208 times the tread width W. Further, for the third region 43, the width D3 (60 mm) is 0.06 times the tread width W and the radius of curvature R3 Is 800 mm, and for the fourth region 44,
The radius of curvature R4 was 1000 mm, and the radial distance L (16 mm) was 0.0059 times the tire outer diameter F (2730 mm). In this test tire, the axial distance M between the center of curvature O of the second region 42 and the tire equatorial plane E is about 135 mm. Next, after filling each such tire with an internal pressure of 5.25 kgf / cm ² , the tire is pressed against the drum while applying a load of 40 ton,
At that time, the contact pressure at each part of the tread part 15 was measured. The results are shown in FIG. 2. As can be seen from the figure, the difference between the maximum value and the minimum value of the contact pressure is empirically known as a value that does not cause a problem in the test tire. has become a 1kgf / cm ² within which it is. Also, while applying 32 ton (80% load) to each of the aforementioned tires,
Run at 5km / h for one day, then 40 ton (1
(00% road) for 3 days, 4t every 3 days
The load of on (10% load) was increased in a stepwise manner, and the tires were allowed to run on the tread portion 15 until a burst based on the belt end separation occurred. As a result, in the conventional tire, a burst occurred when the load reached 180% load, but in the test tire, no burst occurred up to 250% load, and the durability was improved.

In the above embodiment, the second region
Although the fourth region 44 is arranged outside the width direction of 42, the fourth region may not be provided in the present invention.

[0012]

As described above, according to the present invention, heat generation and distortion at the belt end can be reduced, and the belt end separation can be effectively suppressed.

[Brief description of the drawings]

FIG. 1 is a meridian sectional view showing one embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a position on a tread portion and a contact pressure.

[Explanation of symbols]

 11 ... radial tire for construction vehicles 21 ... carcass layer 22 ... carcass ply 25 ... belt layer 26 ... belt ply 35 ... tread 41 ... first area 42 ... second area 43 ... third area

Claims (3)

(57) [Claims] 1. A toroidal carcass layer comprising at least one carcass ply having a steel cord extending in a meridian direction embedded therein, and at least two carcass layers disposed radially outside the carcass layer and having the steel cord embedded therein. A construction vehicle radial tire having a belt layer composed of a belt ply and a tread disposed radially outward of the belt layer and having a flatness of 85% or less, at least the width of the tread outer surface in the meridian cross section in the width direction A first region whose center is located on the tire equatorial plane E, and a second region which is located on both outer sides in the width direction from the first region and includes a point A which is 0.375 times the tread width W from the tire equatorial plane E. And a third region located between the first region and the second region.
And the first region has a width D1 in the range of 0.2 to 0.4 times the tread width W and a radius of curvature R1 of 3000.
From the arc of not less than mm, each second area, width D2 tread width W
In the range of 0.15 to 0.375 times the radius of curvature R2 of 3000 mm or more, each third region, the radius of curvature R3 of the first and second
The radius of curvature L1 is smaller than the radius of curvature R1, R2 of the region, and the radial distance L from the intersection B between the tire equatorial plane E and the first region to the point A is the tire outer diameter F at the intersection B. Radial tires for construction vehicles, characterized in the range of 0.003 times to 0.012 times. 2. The radial tire for a construction vehicle according to claim 1, wherein said first region is constituted by a straight line having an infinite radius of curvature. 3. The radial tire for a construction vehicle according to claim 1, wherein said second region is constituted by a straight line having an infinite radius of curvature.