VARIABLE GEOMETRY CONTROL SURFACE SYSTEM FOR AIRCRAFT WINGS

Description

Technical field

[0001] The present invention relates to a variable geometry aircraft control surface. State of the art

[0002] Typically, an aircraft control surface, such as an aileron, is moved around a hinge axis using an actuator. This hinge axis also corresponds to an attachment axis of the control surface to a wing of the aircraft. The control surface is rigid. Moving such a control surface to a deflection angle associated with a desired lift coefficient requires a fairly significant expenditure of energy from the actuator.

[0003] Document US 2010 / 259046 describes a variable geometry wind turbine blade. Document US 2006 / 186269 describes a variable geometry control surface. The objects described in these documents are not fully satisfactory. Statement of the invention

[0004] The present invention aims to overcome this drawback. To this end, it relates to a variable geometry control system for an aircraft wing, the wing comprising an upper plane and a lower plane.

[0005] According to the invention, the steering system comprises at least: an upper flexible skin intended to be fixed to the wing in the extension of the upper plane of the wing; a lower flexible skin intended to be movable in the extension of the lower plane of the wing by means of a plane-plane connection, the lower flexible skin being fixed to the upper flexible skin along a trailing edge of the control surface; at least one actuator intended to generate a movement of the lower flexible skin relative to the lower plane of the wing, the displacement of the lower soft skin causing a curvature of the upper soft skin and a curvature of the lower soft skin, the curvature of the upper soft skin and the curvature of the lower soft skin having a concavity oriented in the same direction, the upper flexible skin having a greater thickness in an area located at the trailing edge and in an area located at the level of attachment of the upper flexible skin to the upper plane of the wing than in a central area located between the area located at the trailing edge and the area located at said attachment, the thickness ratio between the area located at the trailing edge and the central area being between 2 and 3, the thickness ratio between the area located at said attachment and the central area being between 4 and 5.

[0006] Thus, thanks to the deformation of the flexible skins according to a curvature, the necessary deflection angle of the steering system is less important than the necessary deflection angle of a rigid steering system for the same lift coefficient. Thus the quantity of energy to be supplied by the actuator is much less important than the quantity of energy to be supplied by the actuator of a rigid steering system for the same lift coefficient.

[0007] Additionally, the at least one actuator comprises at least one actuator shaft arranged to be moved longitudinally between the upper flexible skin and the lower flexible skin, the at least one actuator shaft having one end attached to an inner surface of the lower flexible skin.

[0008] Further, the actuator(s) are attached to an inner surface of the lower plane of the wing.

[0009] According to one feature, the actuator shaft(s) are configured to each slide through an opening in a rear spar of the wing.

[0010] For example, the steering system includes at least one linear ball guide bushing configured to be mounted on the at least one opening through which the at least one actuator shaft is slidable.

[0011] Furthermore, the steering system further comprises at least one auxiliary axis parallel to the actuator axis or axes, the auxiliary axis or axes having a first end fixed to the rear spar and a second free end directed towards the trailing edge of the steering system, the steering system further comprising at least one auxiliary bushing fixed to the internal surface of the lower flexible skin, the second free end being able to slide in the auxiliary bushing.

[0012] According to a particular feature, the steering system further comprises an internal frame between the upper flexible skin and the lower flexible skin, the internal frame having a rigidity in compression and in tension along an axis substantially perpendicular to the upper flexible skin or the lower flexible skin greater than a rigidity of the internal frame in shear along an axis substantially parallel to the upper flexible skin or the second lower flexible skin.

[0013] The invention also relates to an aircraft, in particular a transport aircraft, comprising at least one control system, as described above, equipping each of its wings. Brief description of the figures

[0014] The attached figures will make it clear how the invention can be implemented. In these figures, identical references designate similar elements. The figure 1represents a cross-sectional view of a steering system in two different positions. The figure 2 represents a schematic cross-sectional view of a steering system in two different positions. The figure 3 represents a perspective view of an aircraft wing equipped with the variable geometry control surface system. The figure 4 represents a low-angle view of a section of a steering system. The Figure 5 represents a bird's eye view of a section of a steering system. The figure 6 represents, on the right, a view of a cross-section along an actuator axis of a steering system and, on the left, a detail of the cross-section. The figure 7 represents, on the right, a view of a cross-section along an auxiliary axis of a steering system and, on the left, a detail of the cross-section. The figure 8represents a cross-section of the two flexible skins highlighting the transverse evolution of their thickness. The figure 9 represents a perspective view of an embodiment of the steering system comprising an internal framework. The figure 10 represents a perspective view of an aircraft whose wings are equipped with control systems. Detailed description

[0015] There figure 1 represents the variable geometry control system 1 for an aircraft wing 2 AC ( figure 10 ). The variable geometry rudder system 1 may correspond to a variable geometry aileron system ("morphing aileron" in English).

[0016] A variable geometry control surface corresponds to a non-rigid control surface which can deform to change its geometric shape.

[0017] The wing 2, which the steering system 2 is intended to equip, comprises an upper plane 3 and a lower plane 4.

[0018] The steering system 1 comprises at least one upper flexible skin 5 and one lower flexible skin 6. The upper flexible skin 5 and the lower flexible skin 6 join to form a trailing edge 7 of the steering system 1. In a non-limiting manner, the flexible skins 5 and 6 can be made from a thermoplastic composite or a thermosetting composite.

[0019] The upper flexible skin 5 is intended to be fixed to the wing 2 in the extension of the upper plane 3 of the wing 2. By way of non-limiting example, the upper flexible skin 5 can be fixed to the upper plane 3 of the wing 2 using countersunk screws.

[0020] The lower flexible skin 6 is intended to be movable in the extension of the lower plane 4 of the wing 2 by means of a plane-plane connection between the lower plane 4 and the lower flexible skin 6. The lower flexible skin 6 is fixed to the upper flexible skin 5 along the trailing edge 7.

[0021] By way of non-limiting example, the lower flexible skin 6 is fixed to the upper flexible skin 5 along the trailing edge 7 by welding in the case where the upper 5 and lower 6 flexible skins are manufactured from thermoplastic composite. They can also be fixed to each other along the trailing edge 7 by co-firing in the case where they are manufactured from thermoplastic or thermosetting composite. They can also be fixed to each other along the trailing edge 7 by gluing or by rivets.

[0022] As shown in the figure 8, the upper flexible skin 5 has a greater thickness in a zone Z51 located at the trailing edge 7 and in a zone Z52 located at the level of the attachment of the upper flexible skin 5 to the upper plane 3 of the wing 2 than in a central zone Z53 located between the zone Z51 and the zone Z52. Advantageously, the lower flexible skin 6 has a greater thickness in a zone Z61 located at the level of the trailing edge 7 and in a zone Z62 located at the level of the plane-plane connection between the lower flexible skin 6 and the lower plane 4 of the wing 2 than in a central zone Z63 located between the zone Z61 and the zone Z62.

[0023] The dotted lines on the figure 8 designate the approximate boundaries of the different zones.

[0024] The thickness ratio between the Z51 zone and the central Z53 zone is between 2 and 3. The thickness ratio between the Z52 zone and the central Z53 zone is between 4 and 5. For example, the Z51 zone has a thickness between 2.20 mm and 1.95 mm. The Z52 zone has a thickness between 2.5 mm and 3 mm. The Z53 zone has a thickness between 0.715 mm and 0.975 mm.

[0025] Similarly, and without limitation, the thickness ratio between zone Z61 and central zone Z63 is between 2 and 3. The thickness ratio between zone Z62 and central zone Z63 is between 4 and 5. For example, zone Z61 has a thickness between 2.20 mm and 1.95 mm. Zone Z62 has a thickness between 2.5 mm and 3 mm. Zone Z63 has a thickness between 0.715 mm and 0.975 mm.

[0026] These thickness ratios allow the curvature shape of the flexible skins 5 and 6 to be controlled.

[0027] According to one embodiment, the thickness between the zones Z51, Z52, Z53, Z61, Z62, Z63 can evolve continuously. According to another embodiment, the thickness between the zones Z51, Z52, Z53, Z61, Z62, Z63 can evolve in stair steps as shown in the figure 8 .

[0028] As shown in the figure 3 , the control system 1 further comprises at least one actuator 8 intended to generate a displacement D of the soft skin 6 relative to the lower plane 4 of the wing 2. On the figure 1 , there figure 6 and the figure 7 , the displacement D generated by the actuator(s) 8 is represented by a double arrow.

[0029] The actuator(s) 8 are configured to generate a linear displacement of the lower flexible skin 6 in two opposite directions. The direction of displacement D of the lower flexible skin 6 can be directed alternately towards the trailing edge 7 or directed away from the trailing edge 7.

[0030] The displacement D of the lower flexible skin 6 causes a curvature of the upper flexible skin 5 and a curvature of the lower flexible skin 6. The curvature of the upper flexible skin 5 and the curvature of the lower flexible skin 6 have a concavity C1, C2 oriented in the same direction, as shown in the figure 1 and the figure 2 . On the figure 1 , a position P1 and a second position P1a have been represented. On the figure 2, a position P1b is shown in which the flexible skins 5 and 6 have a substantially zero curvature and a position P1 in which the flexible skins 5 and 6 have a non-zero curvature. The direction of the concavity C1, C2 generated by a displacement D directed towards the trailing edge 7 is opposite to the direction of the concavity C1, C2 generated by a displacement D directed away from the trailing edge 7.

[0031] The actuator(s) 8 comprise at least one actuator shaft 9 arranged to be moved longitudinally between the upper flexible skin 5 and the lower flexible skin 6. The actuator shaft(s) 9 comprise an end 10 fixed to an inner surface 61 of the lower flexible skin 6. As shown in the figure 4 , there Figure 5 and the figure 6, the end 10 may be fixed to the inner surface 61 of the lower flexible skin 6 by means of an axle support. The axle support may comprise a surface 19 fixed to the inner surface 61 of the lower flexible skin 6 and a flange 20 in which the end 10 is blocked or fixed ( figure 1 , figure 4 And figure 6 ). The inner surface 61 of the lower flexible skin 6 corresponds to a surface of the lower flexible skin 6 directed towards the upper flexible skin 5.

[0032] Advantageously, as shown in the figure 6, the actuator(s) 8 are fixed on an internal surface 41 of the lower plane 4 of the wing 2. Thus, the actuator axis(es) 9 move linearly relative to the wing 2. The internal surface 41 of the lower plane 4 of the wing 2 corresponds to a surface of the lower plane 4 directed towards the upper plane 3 of the wing 2. Furthermore, the actuator axis(es) 9 contribute to maintaining the plane-plane connection between the lower flexible skin 6 and the lower plane 4.

[0033] Thus, when the actuator(s) 8 are actuated, the actuator shaft(s) 9 move linearly along their respective longitudinal axes. With the end 10 of the actuator shaft(s) 9 being attached to the lower flexible skin 6, the lower flexible skin 6 is driven by the actuator shaft(s) 9. With the lower flexible skin 6 attached to the upper flexible skin 5 along the trailing edge 7, the lower flexible skin 6 and the upper flexible skin 5 deform to form the curvature described above.

[0034] Between the upper plane 3 and the lower plane 4 of the wing 2, the wing 2 may comprise a rear spar 12 extending over the entire span of the wing 2. This rear spar 12 is located as close as possible to the trailing edge of the wing 2.

[0035] The actuator shaft(s) 9 may be configured to each slide through an opening 11 in the rear spar 12 of the wing 2. The rear spar 12 may then serve as a guide for the actuator shaft(s) 9.

[0036] The steering system 1 may also comprise at least one linear ball guide bushing 13 configured to be mounted on the opening(s) 11 of the rear spar 12 through which the actuator shaft(s) 9 are capable of sliding.

[0037] Advantageously, as shown in the figure 7, the steering system 1 may further comprise at least one auxiliary shaft 15. The auxiliary shaft(s) 15 are parallel to the actuator shaft(s) 9. The auxiliary shaft(s) 15 have an end 16 fixed to the rear spar 12 and a free end 18 directed towards the trailing edge 7 of the steering system 1. The steering system 1 further comprises at least one auxiliary bushing 17 fixed to the inner surface 61 of the lower flexible skin 6. The free end 18 is capable of sliding in the auxiliary bushing 17. The auxiliary bushing(s) 17 serve as a guide for the auxiliary shaft(s) 15. The auxiliary bushing(s) may be fixed to the inner surface 61 using shaft support. The shaft support may comprise a surface 21 fixed to the inner surface 61 of the lower flexible skin 6 and a flange 22 on which the auxiliary bushing is mounted ( figure 7). Thus, when the actuator(s) 8 are actuated, the actuator axis(es) 9 drive the lower flexible skin 6. Driving the lower flexible skin 6 makes it possible to generate a movement of the lower flexible skin 6. The movement of the lower flexible skin 6 drives the auxiliary bushing(s) 17 which then move around the auxiliary axis(es) 15. Furthermore, the auxiliary axis(es) 15 contribute to maintaining the plane-plane connection between the lower flexible skin 6 and the lower plane 4.

[0038] The actuator(s) 8 and the auxiliary axes 15 have dimensions allowing their integration into a wing 2.

[0039] In addition, the variable geometry steering system 1 makes it possible to reduce the necessary travel of the actuator axis 9 and the necessary load provided by the actuator(s) 8 compared to the necessary travel and the necessary load of a rigid steering system for the same lift coefficient.

[0040] As shown in the figure 9 , the steering system may further comprise an internal frame 14 between the upper flexible skin 5 and the lower flexible skin 6. The internal frame 14 has a rigidity in compression and in tension along an axis substantially perpendicular to the upper flexible skin 5 or the lower flexible skin 6 greater than a rigidity of the internal frame 14 in shear along an axis substantially parallel to the upper flexible skin 5 or the lower flexible skin 6.

Claims

1. Morphing control surface system for an aircraft wing, the wing (2) comprising an upper plane (3) and a lower plane (4), the morphing control surface system comprising at least: - an upper flexible skin (5) intended to be fixed to the wing (2) in the extension of the upper plane (3) of the wing (2); - a lower flexible skin (6) intended to be movable in the extension of the lower plane (4) of the wing (2) via a plane-to-plane link, the lower flexible skin (6) being fixed to the upper flexible skin (5) along a trailing edge (7) of the control surface (1); - at least one actuator (8) intended to generate a displacement (D) of the lower flexible skin (6) with respect to the lower plane (4) of the wing (2), the displacement (D) of the lower flexible skin (6) causing a curvature of the upper flexible skin (5) and a curvature of the lower flexible skin (6), the curvature of the upper flexible skin (5) and the curvature of the lower flexible skin (6) having a concavity (C1, C2) oriented in a same direction, charaterized in that the upper flexible skin (5) has a greater thickness in a zone (Z51) situated at the trailing edge (7) and in a zone (Z52) situated at the fixing of the upper flexible skin (5) to the upper plane (3) of the wing (2) than in a central zone (Z53) situated between the zone (Z51) situated at the trailing edge (7) and the zone (Z52) situated at said fixing, the thickness ratio between the zone (Z51) situated at the trailing edge (7) and the central zone Z53 being comprised between 2 and 3, the thickness ratio between the zone (Z52) situated at said fixing and the central zone (Z53) being comprised between 4 and 5.

2. Control surface system as claimed in claim 1, characterized in that the actuator or actuators (8) comprise at least one actuator axis (9) arranged to be displaced longitudinally between the upper flexible skin (5) and the lower flexible skin (6), the actuator axis or axes (9) comprising an end (10) fixed to an inner surface (61) of the lower flexible skin (6).

3. Control surface system as claimed in either one of claims 1 and 2, characterized in that the actuator or actuators (8) are fixed onto an inner surface (41) of the lower plane (4) of the wing (2).

4. Control surface system as claimed in either one of claims 2 and 3, characterized in that the actuator axis or axes (9) are configured to each slide through an aperture (11) of a rear spar (12) of the wing (2).

5. Control surface system as claimed in claim 4, characterized in that it comprises at least one linear ball-type guide bushing (13) configured to be mounted on the aperture or apertures (11) through which the actuator axis or axes (9) can slide.

6. Control surface system as claimed in any one of claims 2 to 5, characterized in that it further comprises at least one auxiliary axis (15) parallel to the actuator axis or axes (9), the auxiliary axis or axes (15) having a first end (16) fixed to the rear spar (12) and a free second end (18) directed toward the trailing edge (7) of the control surface system (1), the control surface system (1) further comprising at least one auxiliary bushing (17) fixed onto the inner surface (61) of the lower flexible skin (6), the free second end (18) being able to slide in the auxiliary bushing (17).

7. Control surface system as claimed in any one of claims 1 to 6, characterized in that it further comprises an internal skeleton (14) between the upper flexible skin (5) and the lower flexible skin (6), the internal skeleton (14) having a compressive and tensile strength on an axis substantially at right angles to the upper flexible skin (5) or the lower flexible skin (6) greater than a shear strength of the internal skeleton (14) on an axis substantially parallel to the upper flexible skin (5) or the lower flexible skin (6).

8. System as claimed in any one of claims 1 to 7, characterized in that the lower flexible skin (6) has a greater thickness in a zone (Z61) situated at the trailing edge (7) and in a zone (Z62) situated at the plane-to-plane link between the lower flexible skin (6) and the lower plane (4) of the wing (2) than in a central zone (Z63) situated between the zone (Z61) situated at the trailing edge (7) and the zone (Z62) situated at said plane-to-plane link.

9. System as claimed in claim 8, characterized in that the thickness ratio between the zone (Z61) situated at the trailing edge (7) and the central zone (Z63) is between 2 and 3, and the thickness ratio between the zone (Z62) situated at said plane-to-plane link and the central zone (Z63) is between 4 and 5.

10. Aircraft, characterized in that it comprises at least one control surface system (1) as claimed in any one of claims 1 to 9 equipping each of its wings (2).