Protective reinforcement comprising differentiated layers for a pneumatic tire for a heavy-duty civil engineering vehicle

Abstract

A radial pneumatic tire for a heavy-duty civil engineering vehicle aims to reduce the risk of tread separation of the pneumatic tire, during driving on sharp rocks, while ensuring good resistance to cracking of the crown reinforcement. The pneumatic tire has a protective reinforcement with two protective layers, the radially innermost protective layer having elastic metal reinforcements with a diameter D1 which are axially distributed according to an axial pitch P1, and the radially outermost protective layer has elastic metal reinforcements with a diameter D2 which are axially distributed according to an axial pitch P2. In the tire the following relations are satisfied:
D1>D2
P1>P2
P1>=1.2*D1 and P2>=1.2*D2
2.5<=(D1*P1)/(D2*P2)<=5.

Claims

1. A tire for a heavy duty civil engineering type vehicle, comprising: a crown reinforcement radially on the inside of a tread and radially on the outside of a carcass reinforcement: the crown reinforcement comprising, radially from the outside to the inside, a protective reinforcement and a working reinforcement, the protective reinforcement comprising two protective layers each comprising elastic metal reinforcers having a tensile elastic modulus at most equal to 150 GPa, coated in an elastomeric material, which are mutually parallel and which form, with a circumferential direction (XX′) tangential to the circumference of the tire, an angle at least equal to 10° and which are crossed from one protective layer to the next, the radially innermost protective layer having an axial width LP1 and comprising elastic metal reinforcers having a diameter D1 at least equal to 3 mm and distributed axially with an axial spacing P1, the radially outermost protective layer comprising elastic metal reinforcers having a diameter D2 distributed axially with an axial spacing P2, the working reinforcement comprising two working layers respectively comprising inextensible metal reinforcers having a tensile elastic modulus greater than 150 GPa and at most equal to 200 GPa, coated in an elastomeric material, which are mutually parallel and which form, with the circumferential direction (XX), an angle at least equal to 15° and at most equal to 45° and which are crossed from one working layer to the next, the radially innermost working layer having an axial width LT1 at most equal to the axial width LP1, wherein the respective elastic metal reinforcers of the radially innermost protective layer and of the radially outermost protective layer satisfy the following relationships:
D1>D2
P1>P2
P1>=1.2*D1 and P2>=1.2*D2
2.5<=(D1*P1)/(D2*P2)<=5.

2. The tire according to claim 1, wherein the elastic metal reinforcers of the radially outermost protective layer have a diameter D2 at most equal to 2.5 mm.

3. The tire according to claim 1, wherein the respective elastic metal reinforcers of the radially innermost protective layer and of the radially outermost protective layer satisfy the relationship: 2.8<=(D1*P1)/(D2*P2)<=4.8.

4. The tire according to claim 1, wherein the elastic metal reinforcers of the radially innermost protective layer are radially positioned, with respect to the elastic metal reinforcers of the radially outermost protective layer, at a radial distance E at least equal to 0.8 mm and at most equal to 2 mm.

5. The tire according to claim 1, wherein the radially innermost protective layer has a force at break Rm1 at least equal to 1500 daN/cm.

6. The tire according to claim 1, wherein the radially outermost protective layer has a force at break Rm2 at most equal to 1200 daN/cm.

7. A tire for a heavy duty civil engineering type vehicle, comprising: a crown reinforcement radially on the inside of a tread and radially on the outside of a carcass reinforcement: the crown reinforcement comprising, radially from the outside to the inside, a protective reinforcement and a working reinforcement, the protective reinforcement comprising two protective layers each comprising elastic metal reinforcers having a tensile elastic modulus at most equal to 150 GPa, coated in an elastomeric material, which are mutually parallel and which form, with a circumferential direction (XX′) tangential to the circumference of the tire, an angle at least equal to 10° and which are crossed from one protective layer to the next, the radially innermost protective layer having an axial width LP1 and comprising elastic metal reinforcers having a diameter D1 distributed axially with an axial spacing P1, the radially outermost protective layer comprising elastic metal reinforcers having a diameter D2 distributed axially with an axial spacing P2, the working reinforcement comprising two working layers respectively comprising inextensible metal reinforcers having a tensile elastic modulus greater than 150 GPa and at most equal to 200 GPa, coated in an elastomeric material, which are mutually parallel and which form, with the circumferential direction (XX′), an angle at least equal to 15° and at most equal to 45° and which are crossed from one working layer to the next, the radially innermost working layer having an axial width LT1 at most equal to the axial width LP1, wherein the respective elastic metal reinforcers of the radially innermost protective layer and of the radially outermost protective layer satisfy the following relationships:
D1>D2
P1>P2
P1>=1.2*D1 and P2>=1.2*D2
2.5<=(D1*P1)/(D2*P2)<=5, wherein the elastic metal reinforcers of the protective layers are multistrand ropes of structure 1×N comprising a single layer of N strands wound in a helix, each strand comprising an internal layer of M internal threads wound in a helix and an external layer of K external threads wound in a helix around the internal layer.

8. The tire according to claim 7, wherein the single layer of N strands, wound in a helix, comprises N=3 or N=4 strands.

9. The tire according to claim 7, wherein the internal layer of M internal threads, wound in a helix, of each strand comprises M=1, 2, 3, 4 or 5 internal threads.

10. The tire according to claim 9, wherein, for the elastic metal reinforcers of the radially innermost protective layer, the internal layer of M internal threads, wound in a helix, of each strand, comprises M=3 internal threads.

11. The tire according to claim 9, wherein, for the elastic metal reinforcers of the radially outermost protective layer, the internal layer of M internal threads, wound in a helix, of each strand, comprises M=1 internal thread.

12. The tire according to claim 7, wherein the external layer of K external threads, wound in a helix around the internal layer of each strand, comprises K=5, 6, 7, 8, 9, 10 or 11 external threads.

13. The tire according to claim 12, wherein, for the elastic metal reinforcers of the radially innermost protective layer, the external layer of K external threads, wound in a helix around the internal layer of each strand, comprises K=8 external threads.

14. The tire according to claim 12, wherein, for the elastic metal reinforcers of the radially outermost protective layer, the external layer of K external threads, wound in a helix around the internal layer of each strand, comprises K=5 external threads.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The embodiments of the invention are illustrated in the schematic FIGS. 1 and 2, which are not to scale, with reference to a tire of size 53180R63:

(2) FIG. 1 is a meridian cross section through a crown of a tire for a heavy vehicle of dumper type according to the invention.

(3) FIG. 2 is a meridian cross section through a portion of protective reinforcement according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(4) FIG. 1 shows a meridian cross section through a tire 1 for a heavy-duty vehicle of civil engineering type of size 53/80R63, comprising a crown reinforcement 3 radially on the inside of a tread 2 and radially on the outside of a carcass reinforcement 4. The crown reinforcement 3 comprises, radially from the outside to the inside, a protective reinforcement 5, a working reinforcement 6 and a hoop reinforcement 7. The protective reinforcement 5 comprises two protective layers (51, 52) comprising elastic metal reinforcers that are coated in an elastomeric material, are mutually parallel and form an angle equal to 33° with a circumferential direction XX′ tangential to the circumference of the tire, the respective metal reinforcers of each protective layer being crossed from one protective layer to the next. The working reinforcement 6 comprises two working layers (61, 62), of which the respective metal reinforcers, which are inextensible, are coated in an elastomeric material, are mutually parallel and form with the circumferential direction XX′ angles respectively equal to 33°, in the case of the radially innermost working layer 61, and 24°, in the case of the radially outermost working layer 62, are crossed from one working layer to the next. The radially innermost protective layer 51 protrudes axially beyond the radially innermost working layer 61, which means to say that the radially innermost protective layer 51 has an axial width LP1 greater than the axial width LT1 of the radially innermost working layer 61. In the case depicted, the axial width LP1 is equal to 1.2 times the axial width LT1. The radially outermost protective layer 52 has an axial width LP2 less than the axial width LP1 of the radially innermost protective layer 51. The hoop reinforcement 7 comprises two hooping layers (71, 72), of which the respective metal reinforcers, which are coated in an elastomeric material, are mutually parallel and form an angle of between 6° and 10° with the circumferential direction XX′, are crossed from one hooping layer to the next.

(5) FIG. 1 shows a meridian cross section through a portion of protective reinforcement 5 according to the invention, comprising a radially innermost protective layer 51 and a radially outermost protective layer 52. The radially innermost protective layer 51 comprises large elastic metal reinforcers, having a large diameter D1, advantageously at at least equal to 3 mm, and distributed axially at an axial spacing P1 at least equal to 1.2*D1, the axial spacing being the axial distance between the respective centres of the circular cross sections of two consecutive reinforcers. The radially outermost protective layer 52 comprises small elastic metal reinforcers, having a small diameter D2, advantageously at at most equal to 2.5 mm, and distributed axially at an axial spacing P2 at least equal to 1.2*D2. The inter-reinforcer sections of the radially innermost protective layer 51 and of the radially outermost protective layer, respectively, are respectively equal to D1*P1, D1 being the radial thickness and P1 being the axial width of the section, and to D2*P2, D2 being the radial thickness and P2 being the axial width of the section. Furthermore, the elastic metal reinforcers of the radially innermost protective layer 51 are radially positioned, with respect to the elastic metal reinforcers of the radially outermost protective layer 52, at a radial distance E, advantageously at least equal to 0.8 mm and at most equal to 2 mm.

(6) The inventors have compared a tire according to the invention, I, against a reference tire R, for the tire size 53/80R63.

(7) Table 1 below gives the technical characteristics of the reference tire R and of the tire according to the invention, I, for the size 53/80R63 studied:

(8) TABLE-US-00001 TABLE 1 Crown layers for the size Tire according to 53/80R63 Characteristics Reference tire R the invention I Radially Type of 52.26 = 4*(4 + 9)*26 44.35 = 4*(3 + 8)*35 innermost reinforcer R1 protective layer Tensile elastic 100 GPa 120 GPa 51 modulus M1 of a reinforcer Force at break 770 daN 900 daN Fm1 of a reinforcer Diameter D1 of a 3.1 mm 3.7 mm reinforcer Axial spacing P1 3.7 mm 4.9 mm between reinforcers Angle A1 of the 24° 33° reinforcers, with respect to XX′ Force at break 2081 N/mm 1836 N/mm Rm1 of the protective layer Axial width LP1 1120 mm 1080 mm of the protective layer Radially Type of 52.26 = 4*(4 + 9)*26 24.26 = 4*(1 + 5)*26 outermost reinforcer R2 protective layer Tensile elastic 100 GPa 110 GPa 52 modulus M2 of a reinforcer Force at break 770 daN 250 daN Fm2 of a reinforcer Diameter D2 of a 3.1 mm 1.9 mm reinforcer Axial spacing P2 3.7 mm 2.5 mm between reinforcers Reinforcers angle 24° 33° A2, with respect to XX′ Force at break 2081 N/mm 1000 N/mm Rm2 of the protective layer Axial width LP2 850 mm 850 mm of the protective layer Protective Ratio of inter- 3.1*3.7/3.1*3.7 = 1 3.7*4.9/1.9*2.5 = 3.8 reinforcement 5 reinforcer sections D1*P1/D2*P2 Working Axial width LT1 1000 mm 950 mm reinforcement 6 of the radially innermost working layer 61

(9) So far as the reference tire R is concerned, the radially innermost protective layer has an axial width LP1 equal to 1120 mm, which is 120 mm greater than the axial width LT1 of the radially innermost working layer. The elastic metal reinforcers of the radially innermost protective layer are multistrand cords of structure 52.26, namely made up of N=4 strands, each strand comprising an internal layer of M=4 internal threads and an external layer of K=9 external threads wound in a helix around the internal layer, the threads having a section of diameter d=0.26 mm. In addition, these reinforcers have a tensile elastic modulus M1 equal to 100 GPa, a force at break Fm1 equal to 770 daN, a diameter D1 equal to 3.1 mm, are axially distributed at an axial spacing P1 equal to 3.7 mm, and make an angle A1 equal to 24° with the circumferential direction XX′. The radially outermost protective layer has an axial width LP2 equal to 850 mm and therefore less than the axial width LP1. The elastic metal reinforcers of the radially innermost protective layer are also multistrand cords of structure 52.26, having a tensile elastic modulus M2 equal to 100 GPa, a force at break Fm2 equal to 770 daN, a diameter D2 equal to 3.1 mm, axially distributed at an axial spacing P2 equal to 3.7 mm, and making an angle A2 equal to 24°, and the opposite of the angle A1, with the circumferential direction XX′.

(10) So far as the tire according to the invention I is concerned, the radially innermost protective layer has an axial width LP1 equal to 1080 mm, which is 130 mm greater than the axial width LT1 of the radially innermost working layer. The elastic metal reinforcers of the radially innermost protective layer are multistrand cords of structure 44.35, namely made up of N=4 strands, each strand comprising an internal layer of M=3 internal threads and an external layer of K=8 external threads wound in a helix around the internal layer, the threads having a section of diameter d=0.35 mm. In addition, these reinforcers have a tensile elastic modulus M1 equal to 120 GPa, a force at break Fm1 equal to 900 daN, a diameter D1 equal to 3.7 mm, are axially distributed at an axial spacing P1=4.9 mm, and make an angle A1 equal to 33° with the circumferential direction XX′. The radially outermost protective layer has an axial width LP2 equal to 850 mm and therefore less than the axial width LP1. The elastic metal reinforcers of the radially innermost protective layer are multistrand cords of structure 24.26, namely made up of N=4 strands, each strand comprising an internal layer of M=1 internal thread and an external layer of K=5 external threads wound in a helix around the internal layer, the threads having a section of diameter d=0.26 mm. In addition, these reinforcers have a tensile elastic modulus M2 equal to 110 GPa, a force at break Fm2 equal to 250 daN, a diameter D2 equal to 1.9 mm, are axially distributed at an axial spacing P2 equal to 2.5 mm, and make an angle A2 equal to 33°, and the opposite of the angle A1, with the circumferential direction XX′.

(11) The characteristics of the tire according to the invention I do indeed meet the essential conditions of the invention: D1, equal to 3.7 mm, is greater than D2, equal to 1.9 mm, P1, equal to 4.9 mm, is greater than P2, equal to 2.5 mm, P1 is equal to 1.32 times D1, therefore greater than 1.2 times D1, P2 is equal to 1.32 times D2, therefore greater than 1.2 times D2, the ratio D1*P1/D2*P2 is equal to 3.8, and therefore comprised between 2.5 and 5.

(12) The inventors have demonstrated, through experimental running via the client base, that the life of the tire according to the invention I, before being removed from the vehicle, was increased by approximately 10% with respect to that of the reference tire R.

(13) The scope of protection of the invention is not limited to the examples given hereinabove. The invention is embodied in each novel characteristic and each combination of characteristics, which includes every combination of any features which are stated in the claims, even if this feature or combination of features is not explicitly stated in the examples.