Hydraulic actuation system for landing gear and aircraft comprising it.

Abstract

A hydraulic actuation system (100) of at least one moving element, comprising at least one hydraulic main actuator (103, 104) having a first state and a second state, and a hydraulic distribution circuit (101) comprising a controllable distribution device (102, 1025) for connecting the main actuator (103, 104) to at least one external supply port and one external return port so as to selectively bring the main actuator (103, 104) into its two states in a nominal operating mode, the hydraulic distribution circuit (101) comprising at least one emergency valve (105, 106) provided with a spool (110) movable between a first position allowing nominal operation and a second position allowing emergency operation in which the main actuator (103, 104) can be freely moved from its first state to its second state, characterized in that the emergency valve (106) is a valve monostable,the drawer (110) being returned to its second position by an elastic element (107) and in that the system comprises a latch (108) movable between a protruding position in which the latch (108) cooperates with the drawer (110) to form a stop opposing its movement to its second position and a retracted position in which the latch (108) is disengaged from the drawer (110), and an electromechanical control actuator (109) actuating the latch (108) between its two positions. FIGURE IN ABRIDGED DIAGRAM: Fig. 1,

Description

Title of the invention: Hydraulic landing gear actuation system and aircraft comprising same.

[0001] The present invention relates to the field of aeronautics and more particularly to the field of aircraft landing gear.

[0002] BACKGROUND OF THE INVENTION

[0003] Aircraft generally comprise landing gears each comprising a leg having a free end provided with at least one wheel and, at the opposite end, an end articulated to the aircraft in such a way that the leg is movable between an extended or deployed position and a retracted or retracted position in a hold of the aircraft which is closed by a hatch.

[0004] The movement of the landing gear leg and the cargo hatch is ensured by a hydraulic actuation system comprising actuators and a hydraulic circuit comprising a distribution assembly and connecting chambers of the actuators to at least one supply port and one return port of a hydraulic supply circuit of the aircraft. Each hydraulic actuator comprises a body slidably receiving a piston dividing the body of the actuator into two chambers of variable volume, namely a first chamber (chamber controlling the opening of the hatch for the hatch actuator and chamber controlling the extension of the leg for the leg actuator) which is supplied during the extension phase of the leg and a second chamber (chamber controlling the closing of the hatch for the hatch actuator and chamber controlling the retraction of the leg for the leg actuator) which is supplied during the retraction phase of the leg.

[0005] It is provided that in the event of a malfunction the hold hatch opens to allow the leg to descend into its extended position under its own weight. To this end, the hydraulic circuit comprises emergency bistable valves comprising an isolation valve for cutting off the hydraulic circuit from the supply port and return valves for connecting the actuator chambers to the return port so as to allow the pistons to move freely so as not to hinder the descent of the leg as well as the opening of the hold hatch.

[0006] Emergency valves are traditionally actuated either by an electromechanical motor or by a hydraulic power supply different from that of the hydraulic circuit of the actuation system. These methods of actuation of emergency valves require relatively heavy, complex and bulky equipment, and generate significant energy consumption.

[0007] However, climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those in circulation and requires the implementation of technological solutions to make them compliant with current regulations. Aircraft manufacturers and equipment manufacturers have been mobilizing for several years now to contribute to the fight against climate change and have undertaken sustained research and development work on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter onboard equipment, and the development of the use of electrical technologies to ensure the operation of equipment and the propulsion of aircraft.

[0008] SUBJECT OF THE INVENTION

[0009] The invention is the result of technological research aimed at significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft. The invention aims in particular to remedy at least in part the aforementioned drawbacks. Summary of the invention

[0010] For this purpose, a hydraulic system for actuating at least one mobile element is provided, comprising at least one hydraulic main actuator having a first state and a second state, and a hydraulic distribution circuit comprising a controllable distribution device for connecting the main actuator to at least one external supply port and an external return port so as to selectively bring the main actuator into its two states in a nominal operating mode, the hydraulic distribution circuit comprising at least one emergency valve provided with a slide valve movable between a first position allowing nominal operation and a second position allowing emergency operation in which the main actuator can be freely driven from its first state to its second state.

[0011] According to the invention, the emergency valve is a monostable valve, the slide being returned to its second position by an elastic element and the system comprises a lock movable between a projecting position in which the lock cooperates with the slide to form a stop opposing its movement towards its second position and a retracted position in which the lock is disengaged from the slide, and an electromechanical control actuator actuating the lock between its two positions.

[0012] Thus, it is an elastic element which brings the drawer of the emergency valve into its second position; the control actuator only serves to unlock the drawer. This Unlocking requires a very short stroke (two or three millimeters are sufficient) and limited energy to simply overcome the friction of the lock on the drawer. The control actuator can therefore have a small, light and space-saving structure, preferably like that of a solenoid.

[0013] The actuation of the emergency valve can be controlled independently of the normal state of the actuation system.

[0014] According to additional characteristics, usable individually or in whole or in part in combination: - the emergency valve is a return valve for directly connecting the main actuator to the external return port in emergency operation; - the system comprises several emergency valves, namely an isolation valve for cutting off the hydraulic distribution circuit of the external supply port in emergency operation and a return valve for directly connecting the main actuator to the external return port in emergency operation; - the system comprises several main actuators each connected to one of the return valves, the isolation valve being common to the main actuators; - the control actuator is a solenoid; - the main actuator is connected to a moving element of the lander; - the lander comprises a leg and the main actuator in its first state moves the leg to a retracted position and the main actuator in its second state moves the leg to an extended position; - the lander comprises a hatch and the main actuator in its first state moves the hatch to a closed position and the main actuator in its second state moves the hatch to an open position; - the emergency valve is a return valve to directly connect the main actuator to the external return port in emergency operation.

[0015] The invention also relates to a landing gear and an aircraft comprising such a hydraulic actuation system.

[0016] The aircraft comprises at least one landing gear and a hydraulic supply circuit connected to the hydraulic distribution circuit. The leg of the landing gear is articulated to the aircraft between an extended position and a retracted position in a hold of the aircraft closed by a hatch movable between an open position and a closed position. The actuation system comprises at least a first main actuator, the first main actuator in its first state moving the leg to the retracted position and the first main actuator in its second state moving the leg to the extended position.

[0017] According to additional characteristics, usable individually or in whole or in part in combination: - the aircraft comprises at least one second main actuator, the second main actuator in its first state moving the hatch towards the closed position and the second main actuator in its second state moving the hatch towards the open position; - the emergency valve is a return valve common to all actuators to directly connect the actuators to the external return port in emergency operation; - the system includes several emergency valves including at least one return valve common to several actuators; - the emergency valves include at least one isolation valve for cutting off the hydraulic distribution circuit of the external supply port in emergency operation.

[0018] Other characteristics and advantages of the invention will emerge from reading the following description of particular and non-limiting embodiments of the invention. Brief description of the drawings

[0019] Reference will be made to the accompanying drawings, among which:

[0020] [Fig-1] [Fig.l] is a schematic front view of an aircraft according to the invention;

[0021] [Fig.2] [Fig.2] is a block diagram of an actuation system according to a first embodiment of the invention;

[0022] [Fig.3] [Fig.3] is a schematic axial sectional view of an emergency valve of a hydraulic actuation system according to the invention;

[0023] [Fig.4] [Fig.4] is a block diagram of an actuation system according to a second embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] With reference to [Fig. 1], the hydraulic actuation system according to the invention, bearing the general reference 100, is described here in application to an aircraft A provided with two main landing gears LGp, right and left, and a directional front landing gear LGf. Each landing gear LGp, LGf comprises a leg Lp, Lf having a free end provided with wheels W and an opposite end articulated to a structure of the aircraft A between an extended position illustrated in [Fig. 1] and a retracted position in a hold Sp, Sf of the aircraft. Each hold Sp, Sf is closed by one or more doors or hatches Tp, Ts movable between an open position and a closed position.

[0025] Also referring to [Fig.2], the hydraulic actuation system 100 comprises a hydraulic distribution circuit 101 connecting a distribution plate 102, on the one hand, to the hydraulic supply circuit H of the aircraft A and, on the other hand, to three main actuators 103 each dedicated to the movement of the leg Lp, Lf of one of the landing gears LGp and LGf between the retracted position and the extended position and to three main actuators 104 each dedicated to the movement of the hatch(es) Tp, Tf of one of the landing gears LGp and LGf between the closed position and the open position.

[0026] Each main actuator 103 is a hydraulic actuator comprising a body slidably receiving a piston dividing the body into two chambers of variable volumes, namely a retraction chamber 103.1 and an extension chamber 103.2.

[0027] Each main actuator 104 is a hydraulic actuator comprising a body slidably receiving a piston dividing the body into two chambers of variable volumes, namely a closing chamber 104.1 and an opening chamber 104.2.

[0028] The distribution plate 102 groups together hydraulic distributors known per se and is arranged to supply one of the chambers of each actuator with pressurized hydraulic fluid and simultaneously exhaust the other chamber of this actuator in such a way that: - when the retraction chamber 103.1 of one of the main actuators 103 is supplied with pressurized hydraulic fluid, the piston of the main actuator 103 moves the leg Lp, Lf from its extended position to its retracted position; - when the extension chamber 103.2 of one of the main actuators 103 is supplied with pressurized hydraulic fluid, the piston of the main actuator 103 moves the leg Lp, Lf from its retracted position to its extended position; - when the closing chamber 104.1 of one of the main actuators 104 is supplied with pressurized hydraulic fluid, the piston of the main actuator 104 moves the hatch Tp, Tf from its open position to its closed position; - when the opening chamber 104.2 of one of the main actuators 104 is supplied with pressurized hydraulic fluid, the piston of the main actuator 104 moves the hatch Tp, Tf from its closed position to its open position.

[0029] This corresponds to the nominal operating mode. The arrangement of the distribution board and this nominal operating mode are known in themselves and will not be described further here.

[0030] The hydraulic circuit 101 further comprises emergency valves, namely an isolation valve 105 and at least one return valve 106, here two return valves 106 (distinguished, like the landing gear, by the letters f and p in [Fig.2]).

[0031] The isolation valve 105 is a monostable type valve (on the one hand electrically controlled and, on the other hand, with a spring return), three ports, two positions; interposed between the distribution plate 102 and the hydraulic supply circuit H. The isolation valve 105 conventionally comprises a body comprising a first orifice connected to a supply port of the hydraulic supply circuit H (port through which the hydraulic supply circuit H supplies pressurized fluid), a second orifice connected to a return port of the hydraulic supply circuit H (port through which the hydraulic fluid returns to the hydraulic supply circuit H when it is discharged from the actuators 103, 104), a third orifice connected to the supply port of the distribution plate 102. The supply port and the return port of the hydraulic supply circuit H form an external supply port and an external return port relative to the hydraulic distribution circuit 101. The body of the isolation valve 105 receives a slide valve sliding between two positions, namely: - a nominal operating position in which the drawer places the first orifice and the third orifice in fluid communication, and closes the second orifice; - an isolation position in which the drawer connects the second port and the third port fluidically, and closes the first port to isolate the circuit from all hydraulic power when there is no need to extend or retract, thus preventing any untimely movement of the doors or trains in the event of a failure of the control system.

[0032] The return valve 106p is interposed between the actuators 103, 104 of the main landing gear LGp and the return port of the hydraulic supply circuit H; the return valve 106f is interposed between the actuators 103, 104 of the front landing gear LGf and the return port of the hydraulic supply circuit H. The return valves 106 have identical structures. Each return valve 106 is a monostable, three-port, two-position type valve. Each return valve 106 conventionally comprises a body comprising a first port connected to the return port of the hydraulic supply circuit H, a second port connected to each retraction chamber 103.1, a third port connected to each opening chamber 104.2. The body of each return valve 106 receives a slide valve sliding between two positions, namely: - a nominal operating position in which the drawer closes the first orifice, the second orifice and the third orifice; - an emergency position in which the drawer places the second orifice and the third orifice in fluid communication with the first orifice.

[0033] The drawer 110 of each emergency valve 106 is elastically returned to the emergency position by an elastic member, here a compression spring 107 (see on [Fig. 3]) or any other means capable of performing this function. The drawer 110 in the nominal operating position comprises a portion in abutment laterally against a lock 108 having a holding position in which it extends transversely relative to the direction of movement of the drawer between its two positions: the compression spring 107 therefore pushes the drawer against a side of the lock 108 which opposes the movement of the drawer 110 towards its emergency position. The lock 108 can be moved into a retracted position by an electrical control actuator, here a solenoid 109, a position in which the drawer 110 escapes from the lock 108 and can therefore move towards its emergency position under the force exerted by the spring 107.

[0034] It is therefore understood that, in the event of failure of the actuation of the landing gears in the extended position, it is possible to supply the solenoids 109 to bring the locks 108 into the retracted position, which has the effect of causing the displacement of the drawers 110 of the emergency valves 106 into the emergency position.

[0035] This simultaneously causes: - the isolation of the distribution plate 102 from the supply port of the hydraulic supply circuit H and the connection of the distribution plate 102 to the return port of the hydraulic supply circuit H; - a return of the chambers of the actuators 103, 104 by connecting them to the return port of the hydraulic supply circuit H.

[0036] The hatches Tp, Tf can then open and the legs Lp, Lf are released and can move towards their exit position by falling under their own weight. It will be noted that the hatches and landing gear must first have been unlocked to allow their movements, which is done in a conventional manner.

[0037] The solenoids 109 are only powered for the time required to release the lock 108 and it is the compression spring 107 which ensures the movement of the slide 110 towards its emergency position; furthermore, no energy is consumed by the emergency valves 106 in nominal operating mode: the electrical consumption linked to the emergency valves 106 is minimal.

[0038] Once the drawers 110 of the emergency valves 106 are in the emergency position and after landing of the aircraft A, it is necessary to resort to a maintenance operation to return the drawers of the emergency valves 106 to the nominal operating position and to lock them with the locks 108 in the projecting position. This is not detrimental, a maintenance operation being in any case necessary after each failure of the landing gear.

[0039] Elements identical or analogous to those previously described will bear a numerical reference identical to the latter in the following description of a second embodiment in relation to [Fig.4].

[0040] This second embodiment is more particularly intended for aircraft A in which the landing gears are held in the retracted position without a latching box, only by preventing hydraulic fluid from escaping from the retraction chamber of the main actuators 103.

[0041] In such a case, the distribution plate 102 is replaced by a single monostable distributor 1025 with four ports and three positions. The distributor 1025 comprises a body comprising a first port connected to the supply port of the hydraulic supply circuit H of the aircraft A, a second port connected to the return port of the hydraulic supply circuit H, a third port connected to an extension line 121 connected to the extension chamber of each actuator 103, a fourth port connected to a retraction line 122 connected to the retraction chamber of each actuator 103. The body of the distributor receives a slide valve sliding between two extreme positions on either side of a central equilibrium position, namely: - a first extreme position of exit of the landing gears in which the drawer puts the first orifice into fluid communication with the third orifice and the second orifice with the fourth orifice; - a second extreme position for retracting the landing gear in which the drawer places the first orifice in fluid communication with the fourth orifice and the second orifice with the third orifice.

[0042] In the central isolation position, the drawer closes the first orifice and places the second orifice in fluid communication with the third orifice and the fourth orifice.

[0043] Compression springs arranged on each side of the drawer return the drawer to the central position. The movement of the drawer to each of its extreme positions is ensured by a solenoid controlled in a conventional manner.

[0044] It is therefore understood that the distributor 1025 plays the role of the distribution plate 102 to control the actuators in nominal operating mode so as to retract and extend the landing gear. There is no isolation valve here to isolate the actuators from the supply port of the hydraulic supply circuit H of the aircraft A because, in this embodiment, it is provided that the hydraulic supply of the aircraft is switched on demand to the device.

[0045] The retraction line 122 comprises a non-return valve 111 controlled by the pressure of the lines supplying the extension chambers to be passing from the retraction chambers to the fourth orifice. It is noted that the extension line 121 is also connected to the non-return valve 111. When an extension is ordered, it is desired that the retraction chambers can empty, which is achieved by forcing the opening of the non-return valve 111 otherwise the pressure remains in the retraction chambers. The retraction line 122 is also connected, upstream of the non-return valve 111, to a line bypass 123 connected via a pressure limiter 112 directly to the return port of the hydraulic supply circuit H. Indeed, as a closed volume is formed downstream of the non-return valve 111, the pressure limiter 112 makes it possible to prevent, in the event of an increase in temperature, the expansion of the fluid from causing potentially catastrophic overpressure.

[0046] The hydraulic distribution circuit 101 comprises, as previously, a return valve 106 identical to that of the first embodiment. The return valve 106 comprises a body comprising a first orifice connected to the bypass line 123 downstream of the pressure limiter 112 and therefore to the return port of the hydraulic supply circuit H, a second orifice connected to the extension line 121 and therefore to the extension chambers of the actuators 103, and a third orifice connected to the retraction line 122 and therefore to the retraction chambers of the actuators 103. The body of the return valve 106 receives a slide valve sliding between two positions, namely: - a nominal operating position in which the drawer closes the first orifice, the second orifice and the third orifice; - an emergency position in which the drawer places the second orifice and the third orifice in fluid communication with the first orifice.

[0047] The slide 110 of the return valve 106 is elastically returned to the emergency position by an elastic member, here a compression spring 107. As previously, a lock 108 blocks the slide 110 in the nominal operating position and releases it under the action of a solenoid 109 powered via an emergency control relay 113 piloted by the pilot of the aircraft A.

[0048] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0049] In particular, two solenoids 109 may be provided for each lock 108 for redundancy purposes, to compensate for the failure of one of the solenoids. Two control actuators of different types may also be used per lock.

[0050] A button or lever may be provided on each emergency valve 105, 106 to mechanically return the slide 110 to the nominal operating position, the position of this button or lever, accessible and visible without dismantling the emergency valve 105, 106, making it possible to visually determine the position of the slide 110.

[0051] The number of return valves may be different from that indicated, a return valve may be associated with each main actuator or be common to all or part of the main actuators.

[0052] The isolation valve is optional. In addition, while it is common practice to isolate the circuit during emergency operation, it is entirely possible to consider a return valve 106 which allows all the fluid to pass through to the return even if valve 105 does not isolate the circuit.

[0053] In the case where the actuation system does not comprise a distribution plate grouping together several distributors, but separate distributors, there may be one isolation valve per distributor or one or more isolation valve(s) common to all or part of the distributors.

[0054] Preferably, the lock 108 is returned to protrusion by an elastic element or any other element capable of performing this function and the portion of the drawer 110 having a front face coming into abutment against the lock 108 comprises an inclined rear surface forming a ramp making it possible to temporarily bring the lock 108 into the retracted position when the drawer 110 is brought from its emergency position to its nominal operating position (ratchet effect).

[0055] The cylinder chambers can be reversed: "push to extend" cylinders or "push to retract" cylinders are used depending on the geometry of the landing gear.

[0056] It should be noted that extended cylinders can be used by pressurizing both chambers: it is the differential section between the full chamber and the annular chamber which generates the force during pressurization.

[0057] Preferably, the return valve is arranged to connect the two chambers of each actuator to the return port as in the architecture of [Fig.4]. That said, this is not mandatory: the important thing is not to block the evacuation of the fluid from the retraction chamber. The extension chambers will either fill up by fluid recirculation phenomena inside the circuit, or will cavitate, or the two phenomena will be combined. This depends on the architecture of the circuit.

[0058] The invention is not limited to an application to the control of landing gear or even to use on aircraft. The invention is applicable to the change of state of a valve, with low energy consumption, by means of a member with low mass and size.

[0059] The invention thus relates to any monostable emergency valve comprising: - a slide valve movable between first and second positions and returned to its second position by an elastic element; - a lock movable between a projecting position in which the lock cooperates with the drawer to form a stop opposing its movement towards its second position and a retracted position in which the lock is released from the drawer; - and an electromechanical control actuator operating the lock between its two positions.

Claims

Claims

1. Hydraulic actuating system (100) of at least one movable element, comprising at least one main hydraulic actuator (103, 104) having a first state and a second state, and a hydraulic distribution circuit (101) comprising a distribution device (102, 1025) controllable for connecting each main actuator (103, 104) to at least one external supply port and an external return port so as to selectively bring each main actuator (103, 104) into its two states in a nominal operating mode, the hydraulic distribution circuit (101) comprising at least one emergency valve (105, 106) provided with a slide (110) movable between a first position allowing nominal operation and a second position allowing emergency operation in which each main actuator (103, 104) can be freely driven from its first state to its second state,characterized in that the emergency valve (106) is a monostable valve, the slide (110) being returned to its second position by an elastic element (107) and in that the system comprises a lock (108) movable between a projecting position in which the lock (108) cooperates with the slide (110) to form a stop opposing its movement towards its second position and a retracted position in which the lock (108) is released from the slide (110), and an electromechanical control actuator (109) actuating the lock (108) between its two positions.,

2. The system of claim 1, wherein the backup valve is a return valve (106) for directly connecting each main actuator (103, 104) to the external return port in backup operation.

3. A system according to claim 1, comprising an isolation valve (105) for cutting off the distribution hydraulic circuit (101) from the external supply port in emergency operation and a return valve (106) for directly connecting each main actuator (103, 104) to the external return port in emergency operation.

4. System according to claim 3, comprising several main actuators (103, 104) each connected to one of the return valves (106), the isolation valve (105) being common to the main actuators (103, 104).

5. A system according to any preceding claim, in which the control actuator (109) is a solenoid.

6. Landing gear (LGp, LGf) comprising a system according to any one of the preceding claims, each main actuator (103, 104) being connected to a movable element of the landing gear.

7. A landing gear according to claim 6, comprising a leg (Lp, Lf) and wherein each main actuator (103) in its first state moves the leg (Lp, Lf) to a retracted position and each main actuator (103) in its second state moves the leg (Lp, Lf) to an extended position.

8. A landing gear according to claim 6, comprising a hatch (Tp, Tf) and wherein the main actuator (104) in its first state moves the hatch (Tp, Tf) to a closed position and the main actuator (104) in its second state moves the hatch (Tp, Tf) to an open position.

9. A landing gear according to claim 7 or 8, wherein the emergency valve is a return valve (106) for directly connecting each main actuator (103, 104) to the external return port in emergency operation.

10. Aircraft comprising at least one landing gear according to any one of claims 6 to 9 and a hydraulic supply circuit (H) connected to the hydraulic distribution circuit (101), in which the leg (Lp, Lf) of the landing gear (LGp, LGf) is articulated to the aircraft between an extended position and a retracted position in a hold (Sp, Sf) of the aircraft closed by a hatch (Tp, Tf) movable between an open position and a closed position and in which the actuation system (100) comprises at least a first main actuator (103), the first main actuator (103) in its first state moving the leg (Lp, Lf) towards the retracted position and the first main actuator (103) in its second state moving the leg (Lp, Lf) towards the extended position.

11. An aircraft according to claim 10, comprising at least one second main actuator (104), the second main actuator (104) in its first state moving the hatch (Tp, Tf) towards the closed position and the second main actuator (104) in its second state moving the hatch (Tp, Tf) towards the open position.

12. An aircraft according to claim 10 or 11, wherein the emergency valve is a return valve (106) common to all the actuators for directly connecting the actuators (103, 104) to the return port external in emergency operation.

13. Aircraft according to claim 10 or 11, comprising several emergency valves of which at least one return valve (106) is common to several actuators.

14. An aircraft according to claim 13, wherein the emergency valves comprise at least one isolation valve (105) for cutting off the hydraulic distribution circuit (101) of the external supply port in emergency operation.

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