JPS63188502A - Heavy duty pneumatic radial tire - Google Patents

Abstract

PURPOSE:To reduce inputs from a bumpy road surface without the resisting force of a tire against side force being lowered, by setting the shapes of a carcass, a belt layer and carcass side parts, and the relationship between the carcass and the belt layer so as to satisfy specific relational expressions. CONSTITUTION:The shape of a carcass 20 is set to satisfy such an expression as 0.85<=H/B<=1.00 where H is the cross-sectioned height of the carcass 20 and B is the cross-sectioned width thereof. Further, the shape of a belt layer 30 is set to satisfy such an expression as 0.164l-14.72<=a<=0.179l-13.17 where (a) is the distance between a specific imaginary line to the center of a first belt ply 30 in the equator plane, (l) is the distance between both side ends of the crossing area of belt plies. Further, the shape of a carcass side part 20s is set to satisfy such an expression as 0.3H/B+1.027<=B/J<=0.3H/B+1.057 where L is the distance between both bead parts 10. Further, the relationship between the carcass 20 and the belt layer 30 is set to satisfy such an expression as 0.27B<=L<=0.75l where L is the width of the close contact area between the carcass 20 and the belt layer 30.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the improvement of pneumatic radial tires for heavy loads, such as tires for trunks and tires for work vehicles, which are used for driving on so-called rough roads and unpaved roads. It is used as a tire with a lot of

[Conventional technology]

Tires such as truck tires and work vehicle tires that are often driven on rough or unpaved roads are prone to damage to the rubber on the tire tread surface by gravel, debris, etc.
Durability is likely to decrease, such as belt separation failure.

Therefore, it is necessary to reduce the input from gravel and debris, and conventional attempts have been made to (a) improve the material of the belt reinforcing material, that is, the cord, the combustion structure of the cord, etc.

(b) Improving the arrangement density and arrangement angle of the cords in the belt layer.

(C) The number of plies of the belt layer is increased by λ.

(d) Increase or decrease the width of each ply of the belt layer.

(el) To improve the physical properties of the belt coating rubber constituting each ply of the belt layer.

etc., improvements were made exclusively from the structural aspect of the belt layer.

[Problem that the invention seeks to solve]

However, structural improvements to the belt layer as described above tend to increase the weight of the tire, reduce productivity due to the increase in the number of component parts, and also reduce input from uneven road surfaces. However, there were problems such as a weakening of the resistance against lateral forces generated during cornering during driving, and a weakening of the resistance against belt separation.

The present invention was achieved as a result of experiments and studies aimed at solving the above-mentioned problems.

Therefore, it is an object of the present invention to focus on the shape of the carcass and belt layer, and to improve the structure of gravel without increasing the weight of the tire or reducing productivity, while also reducing the resistance to lateral forces associated with cornering during driving. An object of the present invention is to provide an excellent pneumatic radial tire for heavy loads that can reduce input from uneven road surfaces such as debris.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention includes a carcass with a radial structure extending toroidally from one bead to the other bead, and non-extensible cords arranged at a shallow angle in the crown part of the carcass with respect to the equatorial plane of the tire. In a tire including a belt layer in which at least several plies of the above-mentioned layers are overlapped such that the cords intersect with each other across the equatorial plane, and the first ply and the second ply are sequentially arranged in close contact with the carcass, the tire is attached to the rim. When assembled and filled to the working internal pressure, the shape of the carcass satisfies the following formula (1) and 0.85≦H
/B≦1. OO-・-1---------・-・・-・--
-m-・-----
-14.72≦a≦0.1791-13.17-(2)
a: Belt ply intersection area From an imaginary line connecting each point where a plane parallel to the tire's equatorial plane passing through both ends of the belt intersects with the center of the belt first ply to the center of the belt first ply on the equatorial plane Distance l: Distance between both ends of the belt ply intersection area The shape of the carcass side satisfies the following formula (3), 0.31
1/B +1.027≦B/J≦0.3 H/B +1
．． 057・−・・−・−・−・−・−−−−−−−−−
--(31J: Distance between both bead parts The relationship between the carcass and the belt layer is 0.278≦L≦0.75 j2
−・・・−・・−・・−・・−１−−−−・(
4) L: Characterized by the relationship between the width of the contact area between the carcass and the belt layer.

[Effect]

Since the shapes of the carcass and the belt layer are formed as described above, the present invention does not increase the weight of the tire or reduce productivity, and does not weaken the resistance to lateral forces associated with cornering during driving. It is possible to reduce input from uneven road surfaces such as gravel and debris.

〔Example〕

Hereinafter, the present invention will be specifically described by way of examples with reference to the drawings.

The figure is a radial half-sectional explanatory diagram showing a pneumatic tire for a heavy vehicle according to an embodiment of the present invention.

In the figure, E denotes a pneumatic tire for a heavy vehicle according to an embodiment of the present invention, in which a non-stretchable cord layer, typified by a steel cord extending toroidally from one bead 10 to the other bead (not shown), is used, for example, an l-ply. A carcass 20 with a radial structure consisting of a carcass 20, and at least two plies of layers in which non-extensible cords 30a, which are also typically steel cords, are arranged at a shallow angle with respect to the equatorial plane CL of the tire in the crown part of the carcass 20 (Fig. 31 in
．． 32), these cords 30a are connected to the above equatorial plane CL.
overlap so that they intersect with each other, and the carcass 20
It is composed of a belt layer 30 which is sequentially arranged in close contact with a first ply 31 and a second ply 32.

In particular, in the present invention, when the tire is assembled on a rim and filled with internal pressure for use, the shape of the carcass 20 satisfies the following formula (1), and the shape is 0.85.
≦H/B≦1.00・-1−−−−−・−・−−1−
・－－－－－－－－－－－－－－－－(1) H diagonal - cross-sectional height B of carcass 20: cross-sectional width of carcass 20 The shape of belt layer 30 is expressed by the following formula (2) satisfies 0.16
41! -14,72≦a≦0.1791-13.17-
(2) a: Belt ply intersection area From the imaginary line connecting each point where a plane parallel to the tire's equatorial plane passing through both ends of the belt intersects with the center of the belt first ply 31 to the belt first ply on the equatorial plane. Distance l to the center of the ply 31: Distance between both ends of the intersection area of the belt ply The shape of the side portion 20s of the carcass 20 satisfies the following formula (3), 0.3 HUB +1.027 ≦B/J ≦0 .3
HUB +1.057−−−−・−−−−1−−
・-----・-・・-(31J: The distance between both bead portions 10 The relationship between the carcass 20 and the belt layer 30 is 0.278≦
L≦0.751--------------
··························(4) L: Shaped so as to have a width relationship between the carcass 20 and the belt layer 30 in a close contact area.

To further explain this structure, in this embodiment, the first ply 31 and the second ply 32 constituting the belt layer 30 are two plies having the same cord angle, respectively.
Consists of ply. That is, on the carcass 20 side of the first ply 31, there is a first ply 31a with the cord facing in the same direction as that of the first ply 31 (the angle may be the same for both), and a tread T of the second ply 32. A second ply 32a is arranged on the side, with the second ply 32 and the cord facing in the same direction (the angle may be the same in both directions).

As shown in the figure, a cushion rubber 60 with a 100% modulus of about 60 kg/- is arranged on the tread end side of the first ply 31 and the second ply 32, which may cause separation failure at the end of the belt layer. This is to prevent this.

In the figure, 40 is a bead filler, which is composed of a lower bead filler 41 made of hard rubber and an upper bead filler 42 made of soft rubber.

Further, 50 is a chafer, which is arranged from the rim R side of the bead portion to the upper bead filler 42, and 70
Comes with an inner liner.

Further, the shape of the carcass 20, the shape of the belt layer 30, the shape of the side portion 20s of the carcass 20, and the shape of the carcass 20 described above.
The relationship between the belt layer 30 and the belt layer 30 will be explained as follows.

(1) Shape of the belt layer 30 (related to equation (2)) In order to improve the behavior of the tire with respect to the road surface and obstacles on the road surface during driving, conventionally, the tread T in the axial cross section of the tire has been It has been considered desirable to reduce the curvature of the tread, that is, to provide a flat tread shape.

Accordingly, the shape of the carcass 20 and belt layer 30 in the tread region likewise tended to reduce the curvature in the axial cross section.

In other words, with respect to obstacles, such as stones and other protrusions on the road surface, it has been thought that reducing the axial cross-sectional curvature will reduce the bending deformation in the width direction of the tire, which will affect the behavior of the tire. This is because it was thought that the disturbance would be small.

Similarly, when considering the reduction in human effort due to protrusions such as stones in the structure of the belt layer 30, only the control of bending deformation in the axial direction has been considered.

However, in the research conducted by the inventor of the present invention, it was found that this alone is not sufficient, and that controlling the bending deformation in the circumferential direction can reduce the protrusion input.

One of the methods is the above equation (2). That is, in order to reduce protrusion input with respect to bending deformation in the circumferential direction, it is preferable that the axial curvature of the belt layer 30 is large.

This is shown by the following. For the sake of simplicity, place the protrusion in the center of the tread T and press the tire from above. At this time, axial bending deformation occurs preferentially on the tire tread,
After the side edges of the tread T touch the ground sequentially starting from the center position, circumferential bending deformation occurs. At this time, the shape of the belt layer 30 exhibits a curvature opposite to the shape after filling with internal pressure on the axial cross section. In this case, the side with a larger initial curvature will have a smaller opposite curvature, and then bending deformation in the circumferential direction will occur, but this is because the side with a smaller opposite curvature bends on the protrusion when loaded. Cheap. This is because the moment of inertia of circumferential bending is small because the curvature is small.

Due to the above, it is desirable that the belt layer 30 has a large axial curvature.

(2) Shape of carcass 20 (related to equation (3)) In order to control bending deformation in the tire circumferential direction in order to alleviate the input from protrusions on the road, it is necessary to reduce the stress borne by the belt layer 30. was found to be effective.

The carcass shape for this purpose is defined by equation (3). This is achieved by setting the maximum value within the range of equation (3).

Providing the shape of the carcass 20 that reduces the stress borne by the belt layer 30 also produces the following effects.

Increasing the axial curvature of the belt layer 30 generally includes:
When the tire is rolling with no lateral force, belt layer 3
There is a tendency to increase the variation type at the 0 end. but,
The shape of the carcass 20 reduces the stress borne by the belt layer 30, so the belt layer 3
The circumferential elongation of 0 can be made small. For this reason, distortion at the end portions of the belt layer 30 can be reduced, and a decrease in durability of the belt layer 30 caused by an increase in variation due to an increase in the curvature of the belt layer 30 can be offset.

(3) Relationship between carcass 20 and belt layer 30 ((4
) formula According to the above provisions, the decrease in the durability of the Bell) PF 30 caused by the increase in the rolling fluctuation strain at the end of the belt layer 30 due to the increase in the radial curvature of the belt layer 30 is more completely offset. .

This increases the interaction between the belt layer 30 and the carcass 20. Therefore, the elongation of the belt layer 30 in the circumferential direction can be reduced, and Bell) J! The strain at the end of the tube 30 when the internal pressure is filled can be reduced.

Note that this effect has a large contribution due to the above-mentioned equation (2).

Generally, when the belt layer 30 shares the internal pressure, it does not only share the stress in the circumferential direction, but also the stress in the width direction, although the contribution is smaller. The internal pressure shared by this width direction stress increases as the curvature of the bell layer 30 increases.

Although it has been mentioned that the prescription of formula (4) increases the interaction between the belt layer 30 and the carcass 20, this mainly increases the stress in the width direction of the belt layer 30. Therefore, the effect of equation (4) can be increased by the presence of equation (2).

This has no effect on the reduction of protrusion input.

The above does not weaken the resistance force against the lateral force generated during cornering during driving, and therefore does not cause a decrease in the durability of the belt layer 30, and does not result in an increase in the number of structural members or weight. .

Note that, of course, the provisions of equations (2) and (3) are limited to the range in which cancellation in equation (4) is possible.

[Experiment example]

In order to confirm the effects of the present invention, the following items were measured after traveling 30,000 km.

(a) The number of cuts in the tread that reached the top of the belt layer 30.

(b) Abrasion resistance.

(C) Length of cracks generated at the end of the belt layer 30.

(Specifications of the tires used in the experiment) - Tire size: 11.0OR-20 - Internal pressure: 7.2
5 kg/co! ·rim··············
・・・・・・8.0vX20・Carcass・・・・・・
......L ply carcass cord...
Steel cord (3+ 9 +15) Xo, 75+
Tobel+-m・・・・・・・・・・・・・・・4 ply belt layer cord・・・Steel cord (3xO, 2
0+6 xo, 3B) ・Cord angle of belt layer 1st ply (31a)...48° right rising 1st
Ply (31) 18° right up 2nd
Ply (32)...18° left rising 2nd degree ply (32a)...18° left rising The specifications above are the same for the example tire of the present invention and the conventional tire, and other The specifications are shown in Table 1.

・(11 formula...0.85≦H/B≦1.OOH
/B =0.956 (Example) 0.914 (Conventional example) - (2) formula % formula % - (3) formula 0.311/B +1.027 ≦B/J ≦0.3
H/B+1.0571.314≦B/J≦1.344
(Example) 1.301≦B/J≦1.331 (Conventional example) B/J = 1.329 (Example) B/J = 1.378 (Conventional example) ・Equation (4)...・・0.278≦L≦0.75 /
81≦L≦132 (Example) 84≦L≦132 (Conventional Example) L=90 (Example) L=55 (Conventional Example) The results of the experimental examples are shown in Table 2. In addition, the results of the experimental example are shown as an index with the measurement result of the conventional tire as 100, and the Kaputo number of the trend that reached the top of the belt layer and the length of the crack that occurred at the end of the belt layer (marked with *) are as follows: The smaller the value, the better; and the larger the value, the better the wear resistance (marked with **).

From Table 2, it can be seen that the example tires of the present invention are superior to the conventional example tires.

〔Effect of the invention〕

Since the present invention is configured as described above, it does not cause an increase in the weight of the tire or a decrease in productivity, and it also eliminates uneven road surfaces such as gravel and debris without weakening the resistance against lateral force accompanying cornering during driving. It is possible to reduce the input from

[Brief explanation of the drawing]

The figure is a radial half-sectional view showing a pneumatic radial tire for heavy vehicles according to an embodiment of the present invention. 10... Bead 20... Carcass 30... Belt layer 30a... Cord

Claims (1)

[Scope of Claims] A carcass with a radial structure extending in a toroidal manner from one bead to the other bead, and at least two layers in which non-extensible cords are arranged at a shallow angle with respect to the equatorial plane of the tire in the crown portion of the carcass. In a tire that includes a belt layer in which the plies are overlapped so that these cords intersect with each other across the equatorial plane, and the first ply and the second ply are sequentially placed in close contact with the carcass, the tire is attached to a regular tube-type rim. When the rim is assembled and the normal internal pressure is filled, the shape of the carcass satisfies the following formula (1), 0.85≦H/B≦1.00………………………………
... (1) H: Cross-sectional height of the carcass B: Cross-sectional width of the carcass The shape of the belt layer satisfies the following formula (2), a: parallel to the equatorial plane of the tire passing through both ends of the intersection area of the belt plies. Distance l from the imaginary line connecting each point where the surface intersects with the center of the belt first ply to the center of the belt first ply on the equatorial plane: Distance between both ends of the intersection area of the belt ply on the carcass side The shape satisfies the following formula (3) and is 0.3H
/B+1.027≦B/J≦0.3H/B+1.057
………………………(3) J: Distance between both bead parts Relationship between carcass and belt layer is 0.27B≦L≦0.75l………………………………
(4) L: A pneumatic radial tire for heavy loads, characterized by a relationship between the widths of the contact area between the carcass and the belt layer.