JPH06156011A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To provide a pneumatic radial tire which improves fuel consumption and uneven abrasion resistance. CONSTITUTION:The carcass line shape at internal pressure of 0.5kg/cm<2> is set at R1>= R2>=R3, where the radius of curvature on the tire equatorial face is R1, the radius of curvature at the maximum width position of a belt is R2 and the radius of curvature at the maximum width position of a tire is R3. When filled at regular internal pressure, the neighborhood of the maximum width position of a carcass is deformed as recessed inward, a portion of a shoulder part is deformed as projected toward the outside of the tire and growth of the shoulder part is increased and tension burden of the belt is increased. Thus, rigidity of the belt is increased, collapse of the belt at grounding is reduced and loss at running is reduced and the low fuel consumption is achieved. Also, as growth of the shoulder part is increased, change in the crown radius is restrained and uneven abrasion is restrained.

Description

Detailed Description of the Invention

[0001]

[Industrial application] Pneumatic radial tires,
In particular, the present invention relates to a pneumatic radial tire having improved fuel economy and uneven wear resistance.

[0002]

2. Description of the Related Art In order to improve the fuel economy of automobiles,
Various fuel-efficient tires have been studied, but the main one was to reduce the loss of tread rubber. However, in recent years, research on low lost red has progressed considerably, and at present it is approaching its limit.

On the other hand, from the viewpoint of resource saving, it is also desired to extend the life of the tire by improving the uneven wear resistance of the tire.

[0004]

By the way, in the prior art,
It has been considered that it is preferable that the tire diameter growth be uniform, and that the belt at the time of filling with internal pressure has the same equatorial plane and shoulder portion elongation.

By the way, the carcass line is deformed so that the vicinity of the center of the arc of the large radius of curvature becomes convex toward the outside of the tire due to the filling of the internal pressure, and the adjacent small radius of curvature of the tire It tends to deform so as to be recessed inward. In such a conventional pneumatic radial tire, the diameter on the shoulder side tends to be smaller than the diameter on the equatorial plane when the internal pressure is filled, and it does not become a problem when it is new, but as the running amount increases the tread There is a problem that the shoulder side portion of the is dragged with respect to the road surface and uneven wear called shoulder drop wear occurs.

In view of the above facts, an object of the present invention is to provide a pneumatic radial tire which can improve fuel economy and uneven wear resistance.

[0007]

The pneumatic radial tire of the present invention is a pneumatic radial tire including at least two layers of belts, and the carcass line shape at an internal pressure of 0.5 kg / cm ² has a carcass maximum width. W, maximum belt width w, carcass height H from the carcass radial innermost position, carcass maximum width position height from the carcass radial innermost position h, on the tire equatorial plane The radius of curvature is R1, the radius of curvature at the belt maximum width position is R2,
When the radius of curvature at the tire maximum width position is R3, 2.
0w ≧ W ≧ 1.4w, 0.95H ≧ h ≧ 0.65H, R
It is characterized by satisfying 1 ≧ R2 ≧ R3.

[0008]

The pneumatic radial tire of the present invention has an internal pressure of 0.
When the carcass line shape is 5 kg / cm ² , the carcass maximum width is W, the belt maximum width is w, the carcass height is H from the tire radial innermost position, and the carcass tire radial direction is the innermost position. The height of the carcass maximum width position is h,
2.0w ≧ W ≧ 1.4w, 0.95H ≧ h, where R1 is the radius of curvature on the equatorial plane of the tire, R2 is the radius of curvature of the belt maximum width position, and R3 is the radius of curvature of the tire maximum width position.
It is formed so as to satisfy ≧ 0.65H and R1 ≧ R2 ≧ R3.

That is, the pneumatic radial tire of the present invention has a shape in which the carcass line at the time of low internal pressure is largely projected above the side portion, and the length from the tread end to the bead portion along the carcass is sufficient. Since there is a sufficient margin, the shoulder part can grow sufficiently when the internal pressure is increased, and at the time of normal internal pressure filling, the shoulder part where the radius of curvature of the carcass line is larger than the vicinity of the maximum width of the carcass is directed toward the outside of the tire. Then, the vicinity of the maximum width position of the carcass, which has the smallest radius of curvature, is deformed so as to be recessed toward the inside of the tire, and the shoulder portion grows larger and the tension load on the belt increases.

Since the belt bears a large tension load, the belt rigidity is increased, the collapse of the belt at the time of contact with the ground is reduced, and the loss during traveling is greatly reduced.

Further, a tire for front use generally has a smaller crown radius as it travels, and shoulder drop wear and railway wear are likely to occur. However, as the shoulder portion grows larger, this crown radius change Therefore, uneven wear can be suppressed at the same time.

If W is less than 1.4 w, the length along the carcass from the tread edge to the bead portion is insufficient, and sufficient rigidity cannot be given to the shoulder portion of the belt. On the other hand, when W exceeds 2.0 w, the shoulder portion grows excessively and the durability of the belt deteriorates.

If h is less than 0.65H, the length along the carcass from the tread edge to the bead portion is similarly insufficient, and sufficient rigidity cannot be given to the shoulder portion of the belt. On the other hand, when h exceeds 0.95H, the shoulder portion grows excessively and the durability of the belt deteriorates.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

In the pneumatic radial tire 10 of the present invention shown in FIG. 1, the carcass ply 12 extending radially is a carcass cord arranged in a direction orthogonal to the tire circumferential direction, and It is composed of a coating rubber for coating.

Both end portions of the carcass ply 12 in the tire width direction are folded back around the pair of bead cores 14 from the inner side to the outer side in the tire axial direction, and are respectively formed as folded back end portions 12A.

A belt layer 24 composed of at least two belts 23 is disposed on the outer side of the carcass ply 12 in the tire radial direction, and a tread 26 is disposed on the outer side of the belt layer 24 in the tire radial direction. Has been done. A predetermined tread pattern (not shown) is formed on the tread 26.

In the pneumatic radial tire 10 having such a structure, the carcass maximum width is W (the tread maximum width W is the tire axis from the tire equatorial plane to the shoulder side end on one side in the tire axial direction). The maximum belt width is w (the belt maximum width w here is the dimension along the tire axis from the equatorial plane of the tire to the outermost belt end in the axial direction). ), The carcass height from the innermost position in the tire radial direction of the carcass is H,
The height of the carcass maximum width position from the innermost position in the tire radial direction of the carcass is h, the radius of curvature on the tire equatorial plane is R1,
When the radius of curvature at the belt maximum width position is R2 and the radius of curvature at the tire maximum width position is R3, the rim is assembled to 0.5 kg.
The carcass line shape when filled with an internal pressure of / cm ² is
2.0w ≧ W ≧ 1.4w, 0.95H ≧ h ≧ 0.65
It is preferable that H and R1 ≧ R2 ≧ R3 are satisfied.

The pneumatic radial tire 10 of this embodiment has a tire size of 11 / 70RR22.5,
The radius of curvature of the carcass line is 800 mm for R1, 240 mm for R2, and 40 mm for R3, and the carcass height H is 16 mm.
The carcass maximum width position height h is 9 mm and the carcass maximum width position height is 135 mm.

Therefore, in the pneumatic radial tire 10 of this embodiment, the relationship between H and h is h = 0.8H.

Further, the carcass line has a curvature R4 at a position at a height of 50% of the carcass height H and a curvature R at a position at a height of 25% of the carcass height H on the tire shaft center side of the curvature R3.
5, R4 is 140 mm and R5 is 540 in this embodiment.
It is mm.

R4 and R5 are replaced by R1 ≧ R5 ≧ R2 ≧ R4
The durability of the bead portion can also be improved by setting ≧ R3. Further, in the pneumatic radial tire 10 of this embodiment, the carcass maximum width W is 14
2 mm, the maximum belt width w is 95 mm, and the relationship between W and w is W = 1.5 w.

Next, the operation of this embodiment will be described. When the pneumatic radial tire 10 of the present embodiment is filled with the normal internal pressure, as shown by the arrow in FIG. 1, the vicinity of the carcass maximum width position having the smallest radius of curvature is recessed inward in the tire axial direction (direction of arrow B in FIG. 1). The shoulder portion 34 in which the radius of curvature of the carcass line is larger than the vicinity of the maximum width of the carcass is deformed so as to be convex toward the outside of the tire. As a result, a force is exerted on the tread end portion to push it outward in the tire radial direction (direction of arrow A in FIG. 1), and as a result,
Since the vicinity of the tread end portion is deformed so as to be convex toward the outside of the tire, the growth of the shoulder portion 34 is increased and the tension load on the belt 23 is increased.

In particular, the pneumatic radial tire 10 of this embodiment has a shape in which the carcass line at low internal pressure overhangs above the side portion 30, and extends along the carcass from the tread end to the bead portion 32. Since the length has a sufficient margin, the shoulder portion 34 can be sufficiently grown outward in the radial direction (direction of arrow A).

Therefore, in the pneumatic radial tire 10 of the present embodiment, when the normal internal pressure is filled, the tension load on the belt 23 increases, the belt rigidity increases, and the crushing of the belt 23 at the time of ground contact decreases. The loss during traveling is greatly reduced.

Further, in the tire for front use, the crown radius generally becomes smaller as the tire runs, and shoulder wear and railway wear easily occur. However, in the pneumatic radial tire 10 of this embodiment, the shoulder portion 34 grows. Since the change in the crown radius is suppressed due to the increase of, the uneven wear can be suppressed.

If W is less than 1.4 w, the length from the tread edge to the bead portion 32 along the carcass is insufficient, and sufficient rigidity cannot be given to the shoulder portion side of the belt 23. On the other hand, when W exceeds 2.0 w, the growth of the shoulder portion 34 becomes excessive and the durability of the belt deteriorates.

If h is less than 0.65H, the length along the carcass from the tread end to the bead portion 32 is similarly insufficient, and sufficient rigidity can be given to the shoulder portion side of the belt 23. Can not. On the other hand, h is 0.9
If it exceeds 5H, the belt durability is deteriorated as well.

[Test Example] In order to see the effect of the pneumatic radial tire of this example, an actual vehicle fuel consumption test and an uneven wear resistance test were conducted.

The actual vehicle fuel consumption test was carried out using a new pneumatic radial tire of the present embodiment and a conventional pneumatic radial tire, and further, a pneumatic tire of the present embodiment in which the tread was buffed until the remaining groove depth became 0.5 mm. Using radial tires and conventional pneumatic radial tires, each rim was assembled and mounted on all wheels of the actual vehicle (2-DD, single track), and the test course (1 lap 8.5km under the same conditions of the same track) ) For 40 laps. In addition, superiority is 4
It was decided to judge by the fuel consumption of 0 laps. The test result is the conventional pneumatic radial tire (new tire)
Table 1 as an index display when the fuel consumption of 100
Shown in. The smaller the number, the less fuel consumption,
It shows that the fuel economy is excellent.

On the other hand, in the uneven wear resistance test, each test tire is assembled on a rim, filled with a regular internal pressure and mounted on the front axle of a semi-trailer to run, and the uneven wear width Wh (Fig. 2 reference, unit mm) was measured. The relationship between the uneven wear width Wh and the traveling distance is shown in the graph of FIG.

The pneumatic radial tire of this embodiment and the conventional pneumatic radial tire were different only in the shape of the carcass line, and the tread rubber, the rib pattern and the tire structure were the same. Conventional pneumatic radial tires have an R1 of 520 m at an internal pressure of 0.5 kg / cm ^2.
m, R2 is 380mm, R3 is 60mm, R4 is 90, R5
Is 400, the carcass maximum width W is 135 mm, the belt maximum width w is 100 mm, the carcass height H is 168 mm, and the carcass maximum width position height h is 90 mm.

[0033]

[Table 1]

From the test results shown in the above Table 1 and the graph of FIG. 3, it can be seen that the pneumatic radial tire of the present invention is superior in fuel economy and uneven wear resistance as compared with the conventional pneumatic radial tire. it is obvious.

[0035]

As described above, since the pneumatic radial tire of the present invention has the above-mentioned structure, it has an excellent effect of improving fuel economy and uneven wear resistance.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a tread showing an uneven wear width.

FIG. 3 is a graph showing the relationship between the uneven wear width and the traveling distance.

[Explanation of symbols]

 10 Pneumatic radial tire 12 Carcass ply 23 Belt 26 Tread

Claims (1)

[Claims] 1. A pneumatic radial tire including at least two layers of belts, wherein the carcass line shape at an internal pressure of 0.5 kg / cm ² has a carcass maximum width W, a belt maximum width w, and a carcass tire radius. The carcass height from the innermost position in the direction is H, the height of the carcass maximum width position from the innermost position in the tire radial direction of the carcass is h, the radius of curvature on the tire equatorial plane is R1, and the radius of curvature of the belt maximum width position is R2, where R3 is the radius of curvature of the tire maximum width position, 2.0w ≧ W ≧ 1.4w, 0.95H ≧ h ≧ 0.65H, R1 ≧ R2 ≧ R3 are satisfied. Pneumatic radial tire.