Aeroplane tire with crown and carcass both having a concave portion

Abstract

The tire comprises a tread, a crown reinforcement and at least one crown layer. The crown layer has an axial width (L.sub.2) that is at least two-thirds of a maximum axial width (L.sub.1) of the tire and has a concave portion with axial limits (M.sub.2, M′.sub.2) on either side of an equatorial plane (XZ). The tire further includes a carcass reinforcement which has at least one carcass layer with a concave portion that has axial limits (M.sub.3, M′.sub.3) on either side of the equatorial plane (XZ). The radial distance (d) between the respective concave portions is at a maximum in the equatorial plane (XZ) and decreases continuously from the equatorial plane (XZ) as far as the axial limits (M.sub.2, M′.sub.2) of the said concave portions axially closest to the equatorial plane (XZ), where it reaches a minimum value (d.sub.M).

Claims

1. An aeroplane tire comprising: a tread, a crown reinforcement radially on the inside of the tread and comprising at least one crown layer, the radially interior crown layer having an axial width (L.sub.2) at least equal to two-thirds of the maximum axial width (L.sub.1) of the tire and comprising a concave portion of which the axial limits (M.sub.2, M′.sub.2), on either side of the equatorial plane, are the radially exterior points of the said radially interior crown layer, two beads and two sidewalls connecting the tread to the beads, a carcass reinforcement radially on the inside of the crown reinforcement and comprising at least one carcass layer, each carcass layer connecting the two beads, the radially exterior carcass layer comprising a concave portion of which the axial limits (M.sub.3, M′.sub.3), on either side of the equatorial plane, are the radially exterior points of the radially exterior carcass layer, wherein the radial distance (d) between the respective concave portions of the radially interior crown layer and of the radially exterior carcass layer is at a maximum in the equatorial plane and decreases continuously from the equatorial plane as far as the axial limits (M.sub.2, M′.sub.2) of the said concave portions axially closest to the equatorial plane, where it reaches a minimum value (d.sub.M).

2. The aeroplane tire according to claim 1, wherein the maximum radial distance (d.sub.C) between the concave portions is at least equal to 1.75 times the minimum radial distance (d.sub.M) between the concave portions.

3. The aeroplane tire according to claim 2, wherein the maximum radial distance (d.sub.C) between the concave portions is at least equal to 2.5 times the minimum radial distance (d.sub.M) between the concave portions.

4. The aeroplane tire according to claim 1, wherein the maximum radial distance (d.sub.C) between the concave portions is at least equal to 2.3 mm.

5. The aeroplane tire according to claim 4, wherein the maximum radial distance (d.sub.C) between the concave portions is at least equal to 3.3 mm.

6. The aeroplane tire according to claim 1, wherein the minimum radial distance (d.sub.M) between the concave portions is at least equal to 1.3 mm and at most equal to 2.5 mm.

7. The aeroplane tire according to claim 1, wherein an amplitude of concavity (a.sub.2) of the radially interior crown layer, defined as being the radial distance between a point (C.sub.2) positioned in the equatorial plane and one of the axial limits (M.sub.2, M′.sub.2) of the concave portion, is at least equal to 1 mm.

8. The aeroplane tire according to claim 1, wherein an amplitude of concavity (a.sub.3) of the radially exterior carcass layer, defined as being the radial distance between the point (C.sub.3) positioned in the equatorial plane and one of the axial limits (M.sub.3, M′.sub.3) of the concave portion, is at least equal to 1 mm.

9. The aeroplane tire according to claim 1, further comprising a hooping reinforcement comprising at least one hooping layer, each hooping layer having an axial width (L.sub.4) at most equal to half the maximum axial width (L.sub.1) of the tire and comprising reinforcing elements that are parallel to one another and inclined, with respect to a circumferential direction, by an angle of between +10° and −10°, wherein the hooping reinforcement is radially on the inside of the concave portion of the radially interior crown layer and radially on the outside of the concave portion of the radially exterior carcass layer.

10. The aeroplane tire according to claim 9, wherein the hooping reinforcement comprises two of the hooping layers.

11. The aeroplane tire according to claim 9, wherein the reinforcing elements of the at least one hooping layer are each made of aliphatic polyamides, aromatic polyamides, or a combination of aliphatic polyamides and of aromatic polyamides.

12. The aeroplane tire according claim 1, wherein each crown layer comprises reinforcing elements that are parallel to one another and inclined, with respect to a circumferential direction, by an angle of between +20° and −20°, wherein the reinforcing elements of the at least one crown layer are each made of aliphatic polyamides, aromatic polyamides, or a combination of aliphatic polyamides and of aromatic polyamides.

13. The aeroplane tire according to claim 1, wherein each carcass layer comprises reinforcing elements that are parallel to one another and perpendicular to a circumferential direction, wherein the reinforcing elements of the at least one carcass layer are each made of aliphatic polyamides, aromatic polyamides or a combination of aliphatic polyamides and of aromatic polyamides.

Description

BRIEF DESCRIPTION OF DRAWING

(1) The features and other advantages of embodiments of the invention will be better understood from FIG. 1 which shows a meridian section of a crown of a tire according to the preferred embodiment of the invention, with a hooping reinforcement interposed between the respective concave portions of the radially interior crown layer and of the radially exterior carcass layer.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

(2) In order to make the invention easier to understand, FIG. 1 has been depicted in simplified form and not to scale.

(3) FIG. 1 shows a meridian section, i.e. a section in a meridian plane, of the crown of a tire according to the invention comprising a tread 1, a crown reinforcement 2 radially on the inside of the tread 1, a radial carcass reinforcement 3 radially on the inside of the crown reinforcement 2 and a hooping reinforcement positioned radially between the crown reinforcement 2 and the radial carcass reinforcement 3.

(4) The respective radial, axial and circumferential directions are the directions ZZ′, YY′ and XX′. The equatorial plane XZ is defined by the radial and circumferential directions.

(5) The crown reinforcement 2 is made up of several crown layers of which the radially innermost one is the radially interior crown layer 21. The axial width L.sub.2 of the radially interior crown layer 21, which is the axial distance between its axial ends E.sub.2 and E′.sub.2, is at least equal to two-thirds of the maximum axial width L.sub.1 of the tire. The maximum axial width L.sub.1 of the tire is measured at the sidewalls, with the tire mounted on its rim and lightly inflated, i.e. inflated to a pressure equal to 10% of its recommended nominal pressure.

(6) The radially interior crown layer 21 comprises a concave portion of which the axial limits M.sub.2 and M′.sub.2, on either side of the equatorial plane XZ, are the radially exterior points of the said crown layer, positioned at the radial distance R.sub.2. The radially interior crown layer 21 further comprises two convex portions axially on the outside of the said concave portion. These convex portions are respectively bounded axially on the inside by the axial limits M.sub.2 and M′.sub.2 of the concave portion and axially on the outside by the ends E.sub.2 and E′.sub.2 of the crown layer.

(7) The concave portion of the radially interior crown layer 21 comprises a part that is concave in the mathematical sense, axially delimited by the points of inflection I.sub.2 and I′.sub.2, and, on either side of the said concave part, a part that is convex in the mathematical sense, axially bounded on the outside by an axial limit M.sub.2 or M′.sub.2 of the said concave portion. The axial width b.sub.2 of the concave portion is the axial distance between the axial limits M.sub.2 and M′.sub.2 of the concave portion. The amplitude of concavity a.sub.2 is the difference between the radial distance R.sub.2 of the axial limits M.sub.2 and M′.sub.2 and the radial distance r.sub.2 of the point C.sub.2 situated in the equatorial plane XZ.

(8) The carcass reinforcement 3 is made up of several carcass layers the radially outermost of which is the radially exterior carcass layer 31. In the crown region, radially on the inside of the crown reinforcement 2, the radially exterior carcass layer 31 comprises a concave portion of which the axial limits M.sub.3 and M′.sub.3, on either side of the equatorial plane XZ, are the radially exterior points of the said carcass layer, positioned at the radial distance R.sub.3.

(9) The concave portion of the radially exterior carcass layer 31 comprises a part that is concave in the mathematical sense, axially delimited by the points of inflection I.sub.3 and I′.sub.3, and, on either side of the said concave part, a part that is convex in the mathematical sense, bounded axially on the outside by an axial limit M.sub.3 or M′.sub.3 of the said concave portion. The axial width b.sub.3 of the concave portion is the axial distance between the axial limits M.sub.3 and M′.sub.3 of the concave portion, which in the case depicted in FIG. 1 is greater than the axial width b.sub.2 of the concave portion of the radial interior crown layer 21. The amplitude of concavity a.sub.3 is the difference between the radial distance R.sub.3 of the axial limits M.sub.3 and M′.sub.3 and the radial distance r.sub.3 of the point C.sub.3 situated in the equatorial plane XZ.

(10) The radial distance d.sub.C, between the radially interior points (C.sub.2, C.sub.3) of the respective concave portions of the radially interior crown layer 21 and radially exterior crown layer 31 is the difference between the respective radial distances (R.sub.2, R.sub.3) of C.sub.2 and C.sub.3.

(11) Furthermore, FIG. 1 depicts a preferred embodiment of the invention in which a hooping reinforcement 4 is positioned radially between the radially interior crown layer 21 and the radially exterior carcass layer 31. This hooping reinforcement is characterized by a narrow axial width L.sub.4, i.e. a width at most equal to half the maximum axial width L.sub.1 of the tire.

(12) The inventors have carried out the invention according to the preferred embodiment, with a hooping reinforcement, for an aeroplane tire of dimension 46×17R20, the use of which is characterized by a nominal pressure of 15.9 bar, a nominal static load of 20473 daN and a maximum reference speed of 225 km/h.

(13) In the tire studied, the crown reinforcement is made up of seven crown layers, the reinforcing elements of which are of hybrid type. The radially interior crown layer has an axial width of 300 mm, namely 0.83 times the maximum axial width of the tire. The width of concavity of the said radially interior crown layer is 160 mm, and the amplitude of concavity is 7.3 mm.

(14) The carcass reinforcement is made up of five carcass layers, of which the reinforcing elements are made of nylon. The radially exterior carcass layer has a width of concavity of 160 mm, and an amplitude of concavity of 10 mm.

(15) The hooping reinforcement is made up of two hooping layers, of which the reinforcing elements are of hybrid type. The axial width of the hooping reinforcement is 56 mm, namely 0.15 times the maximum axial width of the tire.

(16) The inventors have demonstrated by using finite element numerical simulation, on a tire running at a steady speed of 10 km/h, under a nominal static load of 20.5 tonnes and a nominal pressure of 15.9 bar, that the highest temperature measured at the shoulder at the end of the crown reinforcement decreases by at least 2° when the thickness of the crown in this shoulder region decreases by 2 mm. In other words, the saving on heat in this shoulder region is at least 2° C. when the thickness of the shoulder region is decreased by 2 mm. The weight of the tire is correspondingly reduced by around 1.7 kg, namely 2.25% of the weight of the tire.