Optimized architecture of a civil engineering tire

Abstract

A tire (1) for a vehicle of the construction plant type, having a carcass reinforcement (4) and a crown reinforcement (3), with at least five crown layers (311, 312, 321, 322, 331, 332) having metal reinforcers. The protective layer (312) has elastic reinforcers having a tensile modulus at most equal to 110 GPa. The rubbers, referred to as crown decoupling rubbers (6), that are located around the axial ends of the crown layers (311, 312, 321, 322, 331, 332) have an elongation at break at least equal to 500%, and a dynamic loss tan at most equal to 0.06. A crown filler rubber (5) between the axial end of the axially widest working layer (321) and the carcass reinforcement (4) possibly has an elongation at break at least equal to 650% and a dynamic loss tan, at 100 C. at 10 Hz, at most equal to 0.07.

Claims

1. A tire for a vehicle of the construction plant type, comprising: a crown reinforcement, radially on the inside of a tread and radially on the outside of a carcass reinforcement, comprising metal reinforcing elements coated with elastomeric materials, referred to as skim compounds, the crown reinforcement, which is substantially symmetrical on either side of the median circumferential plane which is perpendicular to the axis of rotation of the tyre and passes through the middle of the tread, the crown reinforcement-comprising at least five crown layers comprising metal reinforcing elements coated with elastomeric materials referred to as skim compounds, the radially outermost crown layer being a protective layer of which the metal reinforcing elements are elastic, having a tensile modulus at most equal to 110 GPa, the crown reinforcement comprising at least one working layer of which the reinforcing elements form an angle at least equal to 15 with the median circumferential plane, on either side of the equatorial plane, a filler rubber, referred to as crown filler rubber, comprised between the axial end of the axially widest working layer and the carcass reinforcement, composed of at least one elastomeric material, on either side of the equatorial plane, rubbers referred to as crown-decoupling rubbers located between the axial ends of the crown layers and the crown layer closest to said end, the decoupling rubbers having a radial thickness at least equal to 0.5 mm, wherein the elongation at break at 100 C. in accordance with the standard NF T 46-002 of the crown-decoupling rubbers is at least equal to 500%, and the maximum dynamic loss tan of said crown-decoupling rubbers, measured in accordance with the same standard ASTM D 5992-96, at a temperature of 100 C. and at 10 Hz, is at most equal to 0.06.

2. The tire according to claim 1, wherein the elongation at break at 100 C. in accordance with the standard NF T 46-002 of the at least one elastomeric material from which the crown filler rubber is made is at least equal to 650% and the maximum dynamic loss tand of said rubber, measured in accordance with the standard ASTM D 5992-96, at a temperature of 100 C. at 10 Hz, is at most equal to 0.07 and the elongation at break at 100 C. in accordance with the standard NF T 46-002 of the crown-decoupling rubbers is at least equal to 500%, and the maximum dynamic loss tan of said crown-decoupling rubbers, measured in accordance with the same standard ASTM D 5992-96, at a temperature of 100 C. and at 10 Hz, is at most equal to 0.06.

3. The tire according to claim 1, wherein the elastomeric materials of the decoupling rubbers (6) comprise silica as main reinforcing filler at a content of at least 40 parts of filler to 100 parts of elastomer.

4. The tire according to claim 1, wherein the elastomeric materials of the crown filler rubber comprise silica as main reinforcing filler at a content of at least 30 parts of filler to 100 parts of elastomer.

5. The tire according claim 1 wherein a protective layer has the greatest axial width of all the crown layers.

6. The fire according to claim 1, wherein the reinforcing elements of at least one protective layer have a diameter at least equal to 2.5 mm, having a tensile modulus at most equal to 80 GPa, and the skim compound of said crown layer comprises natural rubber.

7. The fire according to claim 1, wherein an elastic modulus G at 35% strain at 100 C. and at 10 Hz of the crown filler rubber (6), measured in accordance with the standard ASTM D 5992-96, is at most equal to 1.2 MPa.

8. The tire according to claim 1, wherein an elastic modulus G at 35% strain at 100 C. and at 10 Hz of the decoupling rubbers-($), measured in accordance with the standard ASTM D 5992-96, is at most equal to 2.2 MPa.

9. The tire according to claim 1, wherein the decoupling rubbers have a radial thickness at least equal to 1.5 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The features of the invention are illustrated in FIG. 1, which is schematic and not to scale, with reference to a tire of size 59.80R63.

DETAILED DESCRIPTION OF THE DRAWINGS

(2) FIG. 1 shows a meridian cross section through the crown of a tire 1 for a heavy vehicle of the construction plant type, 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 31, a working reinforcement 32 and a hoop reinforcement 33. The protective reinforcement has two protective layers 311 and 312 comprising elastic metal reinforcers coated with an elastomeric material or coating compound, which are mutually parallel. The working reinforcement 32 comprises two working layers 321, 322, the respective metal reinforcers of which, which are inextensible, are coated with an elastomeric material, are mutually parallel and form angles equal to between 15 and 50 with the circumferential direction XX', are crossed from one working layer to the next. The protective layer 311 projects axially beyond the axially widest working layer, in this case the radially innermost working layer 322. The hoop reinforcement 33 comprises two hooping layers 331, 332, the respective metal reinforcers of which, which are coated in an elastomeric material, are mutually parallel and form an angle of between 5 and 10 with the circumferential direction XX, are crossed from one hooping layer to the next.

(3) A crown filler rubber 5 is disposed between the widest working layer and the carcass reinforcement. Decoupling rubbers 6 are disposed between the ends of the crown layers and the crown layer closest to the end in question.

(4) The invention also works with only 5 crown layers and one protective layer, which would not be projecting. FIG. 1 only shows one of the numerous possible variants of the invention.

(5) FIG. 1 only shows one example, among others, of the possible architectures of the tire of the construction plant type. The invention was tested or evaluated on tires of size 59.80R63. The tires according to the invention were compared with reference tires of the same size for each of the tests, running tests and analysis tests. The tread patterns of the various tires are the same. The reference tires and the tires according to the invention comprise 6 crown layers: 2 radially innermost hooping layers, the reinforcing elements of which are made up of 77 threads of 0.35 mm disposed at a pitch of 5.5 mm and forming an angle of +8/8 with the circumferential direction at the equatorial plane, the layers crossing one another, 2 working layers, the radially innermost one of the 2 working layers having metal reinforcing elements made up of 189 threads of 0.23 mm disposed at a pitch of 5.9 mm and forming an angle of +33 with the circumferential direction at the equatorial plane, the radially outermost working layer having reinforcing elements made up of 77 threads of 0.35 mm disposed at a pitch of 5.5 mm and forming an angle of 24 with the circumferential direction at the equatorial plane, 2 radially outer protective layers, the radially innermost one of the 2 protective layers having elastic metal reinforcing elements with a modulus of 50 GPa, made up of 52 threads of 0.26 mm, with a diameter of 3.1 mm, disposed at a pitch of 3.7 mm and forming an angle of +33 with the circumferential direction at the equatorial plane and being the widest layer, the radially outermost protective layer having elastic reinforcing elements with a modulus of 60 GPa, made up of 24 threads of 0.26 mm disposed at a pitch of 2.5 mm and forming an angle of 33 with the circumferential direction at the equatorial plane.

(6) The tires of the invention are identical to the reference tires except that the reference tires have crown filler rubbers of which the elongation at break is equal to 640% and the maximum dynamic loss tan, of said rubber, at a temperature of 100 C. at 10 Hz, is slightly greater than 0.07. The reference tires have crown-decoupling rubbers of which the elongation at break is equal to 470% and of which a maximum dynamic loss tan, at a temperature of 100 C. at 10 Hz, is slightly greater than 0.06.

(7) The compounds of the crown filler rubber of the tires according to the invention have an elongation at break equal to 680% and a maximum dynamic loss tan, of said rubber, at a temperature 100 C. at 10 Hz, is equal to 0.06. The compounds of the decoupling rubbers have an elongation at break equal to 600% and a maximum dynamic loss tan, of said rubber, at a temperature of 100 C. at 10 Hz, equal to 0.055. These properties were obtained by using, for each of the rubbers mentioned, silica as main reinforcing filler at contents of at least 30 parts of filler to 100 parts of elastomer for the crown-decoupling rubbers and 40 parts of filler to 100parts of elastomer for the crown filler rubbers.

(8) The invention and the reference tires were used on identical vehicles of the construction plant type on one and the same track corresponding to use in the mining sector, known to customers, with identical loading and unloading cycles. At the end of life, the tires were cut and analysed. The tires according to the invention exhibit a crack size at the end of the radially outermost working layer on average 30% smaller than the reference tires. This demonstrates the advantage of the invention as regards the endurance of tires of the construction plant type.

(9) 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.