Optimized Architecture of a Civil Engineering Tire

A radial for a vehicle of construction plant type, comprising:

• a crown reinforcement, radially on the inside of a tread and radially on the outside of a carcass reinforcement,
• a median plane (M), which is perpendicular to the axis of rotation of the tire and passes through the middle of the tread,
• the crown reinforcement comprising at least five layers of metal reinforcing elements, including at least 3 working layers and 2 protective layers radially on the outside of the working layers,
• a first, radially innermost working layer, of axial width L1, comprising mutually parallel metal reinforcing elements forming an angle A1 at the median plane with the circumferential direction (XX′) tangential to the circumference of the tire,
• a second and a third working layer radially on the outside of the first working layer, referred to as composite working layers, of respective axial widths L2 and L3,
• the composite second working layer and third working layer each comprising 3 parts:
• a central part;
• and two axial parts positioned on either side of the central part,
• the central parts of the composite second and third working layers comprising, over respective axial widths L21 and L31 centred on the median plane (M), first mutually parallel metal reinforcing elements forming angles A21 and A31, respectively, at the median plane with the circumferential direction (XX′),
• the axial parts of the composite second and third working layers, on either side of the central parts, comprising second mutually parallel elastic metal reinforcing elements which have a tensile modulus at most equal to 130 GPa and form angles A22 and A23, respectively, with the circumferential direction (XX′),
• two radially outermost protective layers, of axial width LPN1 for the radially innermost protective layer and LPN2 for the radially outermost protective layer, said protective layers comprising mutually parallel elastic metal reinforcers which have a tensile modulus at least equal to 40 GPa and at most equal to 130 GPa, are coated with an elastomeric material and form respectively an angle APN1 for the radially innermost protective layer and APN2 for the radially outermost protective layer with a circumferential direction (XX′), the absolute values of the angles APN1 and APN2 being at least equal to 15°,
• wherein the absolute values of the angles A1, A21, A31 at the median plane that are formed by the metal reinforcing elements of the working layers with the circumferential direction (XX′) are at least equal to 20°,
• wherein the angles A1 and A31 formed at the median plane by the reinforcing elements of the first layer and third layer, respectively, with the circumferential direction (XX′) have the same sign, this being the opposite sign to the angle A21 formed by the reinforcing elements of the central part of the second working layer at the median plane with the circumferential direction (XX′),
• wherein the angles A22 and A32 formed by the elastic reinforcing elements of the axial parts of the second and third working layers with the circumferential direction (XX′) are at most equal to 8°, and
• wherein the axial width L1 of the first working layer is at least equal to the axial widths L2 and L3 of the second and third working layers, and at least one protective layer has an axial width LPN1, LPN2 at least equal to the axial width of the working layer of greater width.