GB2171067A

GB2171067A - Heavy duty pneumatic tire

Info

Publication number: GB2171067A
Application number: GB08602738A
Authority: GB
Inventors: Kenshiro Kato; Motoaki Taniguchi; Shigeki Yamada; Masanobu Takahashi; Kazuyuki Endo
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 1985-02-04
Filing date: 1986-02-04
Publication date: 1986-08-20
Also published as: FR2608515B1; GB2171067B; GB8602738D0; FR2608515A1

Abstract

A heavy duty pneumatic tire comprises a carcass (1) composed of at least one ply (a,b) of radially arranged cords which are arranged at an angle from 90 to 75 DEG with respect to the equatorial plane of the tire, and a belt (2) comprising a first group ( alpha ) of layers composed of cords arranged substantially parallel with said plane and a second group ( beta ) of layers composed of cords arranged at an angle from 15 to 65 DEG with respect to said plane. At least one of the belt layers in the first group has a width at least 1.10 times that of the normal ground contact width (W) of the tread portion, and the belt layers of the second group each have a different inclination direction with respect to the adjacent one of the second group, are each interposed between any combination among the carcass ply, the belt layers of the first group and the other belt layers of the second group, and have a width not greater than the width (W) and the width of the radially innermost and outermost layers of the first group. <IMAGE>

Description

SPECIFICATION Heavy duty pneumatic tire The present invention relates to a heavy duty pneumatic tire, and more particularly to a radial tire of such type for use in taxiing of aircraft.

The invention is particularly concerned with attaining both durability and cornering stability during high speed running, and also with the enhancement of the durable tire life with respect to the belt reinforcement.

In radial tires, the tread portion is reinforced by a plurality of belt layers in which cords are intersectingly arranged. When they are used as tires for aircraft, so-called standing waves are likely to be developed during high speed running due to insufficient tensile force of the belt along the circumference of the tread in the vicinity of the shoulder portion. Thus, there is a danger that the durability of the tires will be considerably adversely affected.

In attempting to overcome the above problems, Japanese Patent Publication No. 201,701/82 and Japanese Patent Publication No. 201,702/82 disclose that cord material having a higher extensibility at the side regions of the belt layers in the radial section as compared with the central region thereof may be used in belt layers composed of cords which are arranged at angles of not more than 30 relative to the circumference of the tread portion; and a carcass profile is employed such as to promote the growth of the shoulder portions when an internal pressure is applied to the tire.In addition, Japanese Patent Publication No. 201,704/82 discloses that a green tire with a plurality of belt layers composed of circumferential cords having extensibility and thermal contraction properties due to heating action may be vulcanizated in a mold of U-shape expanding outwardly in the radial direction. Even though all the above prior art proposals are effective in ensuring durability during high speed running corresponding to takingoff and landing of the aircraft, an undesirable reduction in the cornering power occurs. Therefore, there remains the problem that the cornering stability during taxiing is adversely affected.

The present invention aims to provide a heavy duty pneumatic tire having a tread portionreinforcing structure which can avoid the production of standing waves when running at a high speed, substantially unaccompanied by any reduction in the cornering power.

The invention also aims to provide a radial tire particularly suitable for aircraft which is provided with a belt structure combining a cord-circumferential belt layer and a cord-oblique belt layer and possessing satisfactory separation resistance and uneven wear resistanFe.

The present invention provides a heavy duty pneumatic tire comprising a toroidal carcass composed of at least one ply of radially arranged cords which are arranged in parallel at an angle from 90 to 75" with respect to the equatorial plane of the tire, and a belt composed of cords superimposed upon the crown portion of the carcass and arranged parallel with one another for reinforcing the tread portion, the said belt comprising a first group of layers composed of cords arranged substantially parallel with the tire equatorial plane and a second group of layers composed of cords arranged inclinedly at an angle from 15 to 650 with respect to the tire equatorial plane, at least one of the belt layers in the first group having a width at least 1. 10 times greater than that of the ground contact width of the tread portion under tire conditions of normal internal pressure and normal loading, and the belt layers of the second group each have a different inclination direction with respect to the adjacent one of the second group, and are each interposed between any combination of the carcass ply, the belt layers of the first group and the other belt layers of the second group, and have a width not greater than the said ground contact width of the tread portion and the width of the radially innermost and outermost belt layers of the first group.

According to a preferred embodiment of the present invention, the belt and/or carcass is composed of organic fiber cords.

In order to achieve a second aim of the present invention, there is provided a heavy duty pneumatic tire in which the interval between cords constituting the cord-circumferential belt layer located at least at the outermost side in the radial direction is arranged to be larger at the opposite side regions than at the central region of the belt layer.

The invention will be further described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a sectional view illustrating a heavy duty pneumatic tire according to the present invention; Figures 2a, 2b and 2c are sectional views illustrating the belt portions of pneumatic tires according to the present invention; and Figure 3 is a diagrammatic partially sectional view of a belt construction of an aircraft radial tire as another embodiment of the present invention.

In Fig. 1 is shown a sectional view of an embodiment of a pneumatic tire according to the present invention, and Figs. 2a, b and c show various modifications of belt layer lamination.

The tire shown in Fig. 1 has a carcass 1 comprising two radial plies a and b composed of organic fiber cords, and a belt 2. Reference numerals 3, 4, 5 and 6 respectively indicate a bead core, a chafer, and stiffeners of hard rubber and soft rubber. The carcass 1 may be a ply made of wire cords of a metal, particularly steel.

The belt 2 is composed of preferably organic fiber cords superimposed around the crown portion of the carcass 1 and arranged parallel with one another, and is divided into a first group a of layers (cord-circumferential belt layers) having cords arranged substantially parallel with the equatorial plane of the tire and a second group ss (cord-oblique belt layers) having cords arranged inclinedly at an angle of 15O to 65" with respect to the equatorial plane of the tire.

At least one of the belt layers in the first group a is arranged to be 1.10 times wider than the ground contact width W of the tread portion 7 under tire conditions of normal internal pressure and normal loading.

The belt layers of the second group ss which are cord-oblique belt layers are different from the adjacent cord-obiique belt layers thereof in terms of the direction in which they are inclined, and are interposed between any combination among the carcass ply, the belt layers of the first group a and the other belt layers in the second group ss, as shown in Fig. 1 and Fig. 2. The belt layers of the second group have a width not exceeding the ground contact width W of the tread portion under the tire conditions of normal internal pressure and normal loading as well as the arranged width of the belt layers in the first group a positioned nearest the innermost and outermost sides in the tire radial direction.

An embodiment of the present invention is shown in Fig. 3 which is an aircraft radial tire of a tire size of H 46X 18.0 R 20. Fig. 3 is a schematic diagrammatic partially sectional view showing the structure and the arrangement of the belt construction of this tire.

The tire shown in Fig. 3 has two carcass plies 11 and 12 composed of cords arranged perpendicular with respect to the circumferential direction, four circumferential belt layers 21, 22, 23 and 24 composed of cords arranged parallel with the circumferential direction, and oblique belt layers 31 and 32 inclinedly arranged with respect to the tire circumferential direction.

The cord-circumferential belt layers 21, 22, 23 and 24 are composed of aromatic polyamide fiber cords of 3,000 d/3, which are each divided into the ground region Cw having a width of about 85% of a ground contacting width Tw of the tread 7 under loading and the remaining opposite sides regions. The opposite side regions include regions LW, LW' positioned inwardly and outwardly in the axial direction of ground contacting edges P, respectively. The interval between the adjacent cords constituting the cord-circumferential belt layers is 1.4 mm in the central region and 2.4 mm in the opposite side regions. The hardness of cover rubber covering the cords at the cord-circumferential belt layers has a Shore A hardness of.75" at the central region and 60 at the opposite side regions.

The cord-oblique belt layers 31 and 32 are composed of aromatic polyamide fiber cords of 3,000 d/3 as in the case of the cord-circumferential belt layers, and the cords of the cordoblique belt layers are arranged inclinedly at 65" with respect to the circumferential direction.

The cord-oblique belt layers 31 and 32 are extended while being reversed to each other in the cord direction. These cord-oblique belt layers 31 and 32 are arranged between the first and second cord-circumferential belt layers 21 and 22 and between the second and third cordcircumferential belt layers 22 and 23, respectively, as viewed from the inside in the radial direction. The width of the cord-oblique belt layers 31 and 32 is about 95% of the ground contacting width Tw.

According to the present invention, at least one of the belt layers in the first group a is arranged to extend to the shoulder portion and the buttress portion such that the arranged width is not less than 1.10 times the ground contact width of the tread portion under the conditions of normal internal pressure and normal loading. Thereby, sufficiently high circumferential tensile force at the shoulder portion and the buttress portion can be obtained. Thus, speedy restoration of the flexural deformation and damping of vibrations due to loading can be promoted near the kicking portion of the tread portion during high speed running, so that the effect of retarding standing waves can be obtained and largely contribute to the improved durability of the belt portion.

Further, the presence of the cord-oblique belt layers in the second group ss further enhances the rigidity against the lateral deformation produced in the axial direction of a rotary shaft of the tire within the ground contact area in the loaded state as compared with a lamination structure of only the belt layers in the first group a. Particularly, in order to enhance this effect, it is necessary to restrict the cord angle of the cord-oblique belt layers to a range of from 15 to 65".

The following Table 1 shows values of cornering power when the belt layer construction shown in Fig. 1 was employed and the angle of the cord-oblique belt layers were varied. The cord-arranged directions of the belt layers in the second group were alternatively reversed. The value is indicated by index, and the value of the cornering power of a bias tire of the same size is taken as 100.

Table 1

Oblique belt angle e (degree) Oo 150 300 500 650 950 Cornering 50 80 100 90 80 60 power The cornering power can be further increased over the values in Table 1 by increasing the number of the cord-oblique belt layers.

In general, in the case of the cord-oblique belt layers only or the lamination structure composed of the cord-oblique belt layers and the cord-circumferential belt layers without taking any contrivance, mainly circumferential interlayer shearing deformation is caused between the belt layers in the vicinity of the edge portions thereof in the loading state, which becomes a main cause of difficulty at the belt edge portions during running.

Therefore, the arranged width of the cord-oblique belt layers should not be greater than the ground contact width W of the tread portion 7 under the normal internal pressure and normal loading conditions taking the durability of the belt edge portions into account. This is intended to mainly reduce the deformation input applied to the belt edge portions while avoiding a position from the ground contact edge to the buttress portion which undergoes the iargest circumferential elongation in a radially sectional plane due to bending when the belt portion iS bent under loading.

In addition, complete covering of all the width of the cord-oblique belt layers with the cordcircumferential belt layers nearest the radially innermost and outermost sides of the belt layers is necessary to effectively restrain the circumferential movement of the edges of each of the belt layers during deformation under loading. If the arranged width of the cord-oblique belt layer exceeds that of the radially inward or outward cord-circumferential belt layer sandwiching the cord-oblique belt layer, it was confirmed that the circumferential movement of the edge portions of the cord-oblique belt layer or the interlayer shearing strain becomes far larger to cause separation at the edge portions of the cord-oblique belt layer during the running initial stage.

On the other hand, the edge portions of the cord-oblique belt layer completely sandwiched between the cord-circumferential belt layers over the entire width can fully satisfy the durable level with respect to the lateral deformation of the belt which is produced in the axial direction of the rotary shaft of the tire within the ground contact area in the running state without suffering separation. Further, the rigidity against the side force produced in the direction of the rotation axis of the tire within the ground contact area affords the effects of increasing the apparent circumferential rigidity of the edges of the cord-obiique belt layer to increase the cornering power and enhance the cornering stability against excess lateral force.

In order to fully exhibit the effects due to the interval between the adjacent cords of the cordcircumferential belt layer being made different between the central region and the opposite side regions, it is desirable that the opposite side regions extend inwardly from the ground contacting edges of the tread in the axial direction, and include tread regions reaching a width of not more than 30% of the width of the tread.

Further, in order to more effectively mitigate shearing force produced at the interfaces of the cords when compression force is applied to the opposite side regions of the cord-circumferential belt layers in the axial direction, it is advantageous to cover the cords at the opposite side regions with a cover rubber having a lower hardness than that of rubber covering the cords at the central region, preferably a Shore A hardness of about 70 to 85% of the latter.

The invention will be further described with reference to the following illustrative Examples.

Examples In Fig. 1 is shown a construction of a belt portion used in an aircraft tire of a tire size of 40X 14-16. The tire contains two carcass plies both edge portions of which are wound around a pair of bead cores 3 provided at right and ieft sides, respectively. Belt layers are disposed in the tread of the tire. Aromatic polyamide cords of 3,000 d/3 are used in the radial carcass ply and the belt layer. The tire of this size has a contact area equal to 280 mm in width relative to a flat road surface under loading of 2,820 Lbs and an internal charge pressure of 170 psi.Tires having an axial width along the periphery of the belt specified in the following Table 2 were prepared in which the angle of the first, third and fifth belt layers were set at 0 (circumferential direction), and the second and fourth layers are set at +65 and 650, respectively, in Fig. 1.

The ratio maximum cord-circumferential belt width of Tire Nos. a, b and c to the ground contact width as mentioned above are 125, 1.10 and 0.93, respectively. Under the conditions of the above-mentioned loading and internal pressure, the running speed of the tire was increased. Speed at which standing waves were produced were compared by index, and the results are shown in the right column of Table 2.

Table 2

belt 1 belt 2 belt 3 belt 4 belt 5 Standing wave (mm) (mm) (mom) (mm) (mini) producing speed (index) a) 350 200 260 240 245 116 b) 310 200 260 240 245 100 c) 260 200 260 240 245 71 In comparison, the standing wave-producing speed in the conventional bias structural tire of the same size was taken as 100. In a high speed durability test adopting an acceleration from rest to a specified take-off speed as one cycle, Tire c produces peeling at the tread portion after repeated tests for several cycles.It was confirmed that Tires a and b exhibited satisfactory durability in the above test as well as in a running test under heavy load.

In order to confirm the functions and effects of the embodiment of the present invention as shown in Fig. 3, comparative experiments were carried out by using the following three tires.

1. A comparative tire in which the cord interval and the hardness of the cover rubber of the cord-circumferential belt layer were not varied between the opposite side regions and the central region. In this tire, the cord interval of the cord-circumferential belt layer is 1.4 mm, and the Shore A hardness of the cover rubber is 75".

2. A tire A according to a preferred embodiment of the present invention in which the cord interval of the cord-circumferential belt layer is 1.4 mm at the central region and 2.4 mm in the opposite side regions, the hardness of cover rubber is not varied between the central region and the opposite side regions, and the Shore A hardness is 70".

3. A tire B according to the present invention having the same construction as described in connection with the illustrated embodiment of Fig. 3.

After these tires were each subjected to a drum running test over 5,000 km under a normal load, uneven wear amount at the opposite side regions on the outer surface of the tread and the length of cracks due to separation in the axial direction of the outermost cord-circumferential belt layer were measured.

Measurement results shown in the following table were obtained.

Table 3

Comparative Invention Invention tire tire (A) tire (B) Cord interval ratio (opposite side region/ 1.0 1.7 1.7 central region) Cover rubber hardness ratio (opposite side region/ 1.0 1.0 0.8 central region) Uneven wear index (standard value: 100) 100 80 60 Crack length index (standard value: 100) 100 70 50 As apparent from the measurement results shown in the above table, the uneven wear at the opposite side regions on the outer surface of the tread and the separation of the cordcircumferential belt layer can be restrained by setting the cord interval of the cord-circumferential belt layer larger at the opposite side regions than at the central region, and the uneven wear resistance and the separation resistance can be further enhanced when the hardness of the cover rubber is set lower at the opposite side regions than at the central region. That is, according to the present invention, a radial tire suitable for aircraft having good functionality and satisfactory durability can be obtained.

As mentioned above, the durability at high speeds corresponding to take-off and landing is ensured by the presence of the cord-circumferential belt layers containing at least one belt layer with a belt layer width of not more than 1.10 at the ratio of the width to the ground contact width. Further, the rigidity in the direction of the rotation axis within the ground contact area which could not be attained by the cord-circumferential belt layer only can be increased by employing the cord-oblique belt layers in combination with the cord-circumferential belt layer, thereby restoring the cornering stability. Further, the durability force at the cord-oblique belt layer edge portions under the heavy loading use conditions is largely increased by completely covering the cord-oblique layers with the cord-circumferential belt layers over the entire width and specifying the cord-oblique belt layers within the ground contact width. In addition, the weight can be largely reduced by using organic fiber cords in the belt layers and the carcass ply layers as compared with reinforcement using steel cords in a tire with the same safety factor. This can lead to weight reduction of the whole aircraft and accordingly of the fuel consumption.

Claims

1. A heavy duty pneumatic tire comprising a toroidal carcass composed of at least one ply of radially arranged cords which are arranged in parallel at an angle from 90 to 75" with respect to the equatorial plane of the tire, and a belt composed of cords superimposed upon the crown portion of the carcass and arranged parallel with one another for reinforcing the tread portion, the said belt comprising a first group of layers composed of cords arranged substantially parallel with the tire equatorial plane and a second group of layers composed of cords arranged inclinedly at an angle from 15 to 65" with respect to the tire equatorial plane, at least one of the belt layers in the first group having a width at least 1. 10 times greater than that of the ground contact width of the tread portion under tire conditions of normal internal pressure and normal loading, and the belt layers of the second group each have a different inclination direction with respect to the adjacent one of the second group, and are each interposed between any combination of the carcass ply, the belt layers of the first group and the other belt layers of the second group, and have a width not greater than the said ground contact width of the tread portion and the width of the radially innermost and outermost belt layers of the first group.

2. A tire as claimed in claim 1, wherein the belt is composed of organic fiber cords.

3. A tire as claimed in claim 1 or 2, wherein the carcass is composed of organic fiber cords.

4. A tire as claimed in any of claims 1 to 3, wherein the interval between the adjacent cords constituting the cord-circumferential belt layer located at least at the outermost side in the radial direction is so arranged that the interval at the opposite side regions of the said belt layer is larger than that of the central region thereof.

5. A tire as claimed in claim 4, wherein the opposite side regions of the cord-circumferential belt layer in which the interval between the adjacent cords is set relatively larger are extended to the inside in the axial direction beyond the ground contacting edges of the tread and totally include regions having a width of not more than about 30% of the width of the tread.

6. A tire as claimed in claim 4 or 5, wherein the interval between the adjacent cords in the opposite side regions of the cord-circumferential belt layer in which the interval between the adjacent cords is set relatively larger is about 150 to 200% of that between the cords of the said belt layer at the central region.

7. A tire as claimed in any of claims 4 to 6, wherein the cords at the opposite side regions of the cord-circumferential belt layer in which the interval between the adjacent cords is set relatively larger is covered with rubber which has a lower hardness than that of the rubber covering the cords at the central region thereof.

8. A tire as claimed in claim 7, wherein the rubber covering the cords at the opposite side regions of the cord-circumferential belt layer in which the interval between the adjacent cords is set relatively larger has a Shore A hardness of about 70 to 85% of the rubber covering the cords at the central region of the belt layer.

9. A heavy duty pneumatic radial tire according to claim 1, substantially as herein described with reference to, and as shown in, any of the figures of the accompanying drawings.

10. A heavy duty pneumatic tire consisting, as a main reinforcement, of at least one toroidal carcass composed of a ply of radially arranged cords which are arranged in parallel at an angle from 90 to 75" with respect to an equatorial plane of the tire, and a tire tread-reinfocing belt composed of cords superimposed upon a crown portion of the carcass and arranged in parallel with one another for serving to reinforce the tread portion, said belt consisting of a first group of plural layers composed of cords arranged substantially in parallel with the tire equatorial plane and a second group of plural layers composed of cords arranged inclinedly at an angle from 15 to 65" with respect to the tire equatorial plane; at least one of the belt layers in the first group has an arranged width being more than 1.10 times as much as that of the ground contact width of the tread portion under the tire conditions of a normal internal pressure and à normal loading, and the belt layers of the second group each have a different inclination direction with respect to the adjacent one of the second group, are each interposed between any combination among the carcass ply, the belt layers of the first group and other belt layers of the second-group, and has an arranged width not exceed the ground contact width of the tread portion under the tire conditions of the normal internal pressure and the normal loading and the arranged width of the belt layers of the first group located nearest the radially innermost and outermost sides.