Hydraulic actuation circuit for actuating blades to lock them in a current position

Abstract

The invention relates to an actuation system (1) for adjusting the pitch of blades (20) of an aircraft engine fan, comprising a hydraulic supply source (3), a hydraulic cylinder (5) and a hydraulic circuit comprising a hydraulic path provided with a non-return valve (43) and a distribution valve (41) capable of selectively adopting two configurations, such that, when the distribution valve (41) is in the first configuration, the hydraulic cylinder (5) is configured such that its position is controlled by the hydraulic supply source (3), and when the distribution valve (41) is in the second configuration, the control fluid can circulate only from a retraction chamber (5f) to an extension chamber (5c) such that the piston of the hydraulic cylinder (5) moves in the first direction of movement, the fan blades being oriented into a safety position referred to as the "feathered position".

Description

[0001] DESCRIPTION

[0002] TITLE: HYDRAULIC CIRCUIT FOR ACCIDENTING VANES FOR LOCKING IN CURRENT POSITION

[0003] TECHNICAL FIELD

[0004] This disclosure relates to the general field of aircraft engines, and in particular to hydraulic circuits for adjusting the pitch of aircraft engine fan blades.

[0005] STATE OF THE ART

[0006] Climate change is a major concern, and there is an urgent need to reduce carbon emissions globally. Ambitious standards have been adopted to restrict emissions from civil aviation. Technological research efforts have thus led to very significant improvements in aircraft energy efficiency.

[0007] These efforts focus on new generations of aircraft engines, the reduction of aircraft weight, particularly through the materials used and lighter onboard equipment, and the development of the use of electric technologies to provide propulsion.

[0008] Improving existing systems is also necessary. Optimizing the fan blade pitch of the engine is a key factor in improving aircraft performance. By dynamically adjusting the blade orientation using an actuation system, it is possible to maximize propulsion during different flight phases, such as takeoff, cruise, and landing. This dynamic adaptation not only helps reduce fuel consumption but also better manages mechanical stresses on the engine, thus extending its lifespan. This helps meet the growing demands of the aerospace industry in terms of environmental performance and sustainability.

[0009] The actuation system typically includes a position-controlled hydraulic cylinder actuated by a flight control system via a hydraulic circuit. The hydraulic cylinder plays a crucial role in providing the force necessary to make precise and rapid adjustments, essential for the safety and efficiency of flight operations. For example, the actuation system helps control engine thrust while the aircraft is in flight and can brake the aircraft on the ground by reversing thrust. To meet safety requirements, a range of blade positions must be avoided during certain phases of flight, and therefore the associated positions of the hydraulic cylinder. This range, known as "small pitch," corresponds to a blade orientation in which thrust is at its maximum, with the blade opposing the airflow.When the blades are in their normal position, aerodynamic forces tend to push the hydraulic cylinder towards these positions. Therefore, if the actuation system is no longer able to counteract these forces, in the event of a failure or a lack of control, the blades will be gradually oriented towards the "small step" position range. Conversely, if a component of the position control system fails, the blades must be oriented to the "feathered" position, i.e., parallel to the airflow. This function of positioning the blades to the "feathered" position is ensured by an auxiliary hydraulic power supply system for the cylinder.

[0010] To lock the blades in their normal position, a hydromechanical pitchlock device is typically used. In this case, the hydraulic cylinder's piston is connected to a screw, which is initially held in place by a nut using a passively applied axial preload. Applying hydraulic pressure releases the preload, thus freeing the cylinder to be moved to a different position. This device requires a dedicated hydraulic valve and has several drawbacks. Firstly, this additional component adds significant mass, thereby reducing the aircraft's environmental performance. Secondly, there is a risk of the screw-nut system seizing, which could prevent the hydraulic cylinder from being actuated to orient the blades towards the "feathered" position if a component in the hydraulic cylinder's control system fails.

[0011] DESCRIPTION OF THE INVENTION

[0012] One purpose of this disclosure is to propose a solution to lock the blades in current position in case of failure of the servo chain in the position of the cylinder, of reduced mass, without additional energy input from the actuation system, limiting the risk of unavailability of the blade servo.

[0013] This goal is achieved by an aircraft engine fan blade pitch control actuation system, comprising a hydraulic power source, a hydraulic cylinder, the hydraulic cylinder comprising a cylinder and a piston, the piston delimiting within the cylinder a retraction chamber and an extension chamber, each of the retraction and extension chambers being designed to be supplied with a control fluid, so as to cause a displacement of the piston relative to the cylinder in a first direction of movement when a pressure of the control fluid in the extension chamber is greater than a pressure of the control fluid in the retraction chamber and to cause a displacement of the piston relative to the cylinder in a second direction of movement, opposite to the first direction of movement,when the control fluid pressure in the retraction chamber is greater than the control fluid pressure in the expansion chamber; the actuation system further comprising a hydraulic circuit supplied with control fluid by the hydraulic power source, the hydraulic circuit comprising a hydraulic channel equipped with a check valve, and a distribution valve comprising,

[0014] - a first power port and a second power port, each configured to be connected to the hydraulic power source;

[0015] - a first hydraulic port connected to the extension chamber;

[0016] - a second hydraulic port connected to the shrink chamber;

[0017] - a locking port configured to be connected to the retraction chamber via the hydraulic route, the check valve being configured to prevent circulation of the control fluid from the expansion chamber to the retraction chamber and to allow circulation of the control fluid from the retraction chamber to the expansion chamber; the distribution valve being adapted to selectively adopt a first configuration in which the first supply port is hydraulically connected to the first hydraulic port and the second supply port is connected to the second hydraulic port, the locking port being isolated, and a second configuration in which the first supply port is hydraulically connected to the second supply port, and the locking port is connected to the first hydraulic port, the second hydraulic port being isolated,so that when the distribution valve is in the first configuration, the hydraulic cylinder is configured to be position-controlled by the hydraulic power source, and when the distribution valve is in the second configuration, the control fluid can only flow from the retraction chamber to the extension chamber so that the hydraulic cylinder piston moves in the first direction of travel, the blower blades orienting themselves towards a safety position known as the "flag position".

[0018] On the one hand, when the cylinder position control system is active, the distribution valve is in the first configuration. The hydraulic circuit then connects the hydraulic cylinder to the hydraulic power supply, allowing for precise control of the cylinder's position. On the other hand, when the cylinder position control system is inactive, for example, due to a malfunction of the hydraulic power supply or the aircraft engine, the distribution valve is in the second configuration. The hydraulic circuit then isolates the hydraulic power supply from the hydraulic cylinder. In this position, the locking port associated with the check valve prevents the hydraulic cylinder piston from retracting, which would cause the fan blades to adopt a fine-pitch orientation, posing a risk to the aircraft.The presence of the check valve allows the control fluid to circulate, permitting the cylinder to extend and thus position the blades in the "feathered" position, but preventing the cylinder from retracting and therefore preventing the blades from moving towards the "small pitch" zone. The aerodynamic forces acting on the blades, which tend to retract the cylinder, are thus counteracted. The hydraulic cylinder is therefore locked in its normal position when the hydraulic power supply is unavailable, and thus without energy input, and can be extended to the "feathered" position of the blades by an auxiliary actuation system independent of the cylinder. The risk of blade control failure is thus limited by eliminating the risk of seizing, as the feathered position is enabled by the auxiliary actuation system.

[0019] The invention is advantageously complemented by the following features, taken individually or in any of their technically possible combinations:

[0020] - The first configuration is an active position reached when the distribution valve is electrically powered, and the second configuration is a passive position reached when the distribution valve is not electrically powered.

[0021] - The hydraulic path further includes a hydraulic restrictor configured to limit the flow of the control fluid in the hydraulic path.

[0022] - The hydraulic circuit further includes a return line equipped with a pressure relief valve, the distribution valve further includes a return port connected to the return line, and, when the distribution valve is in the second configuration, the first hydraulic port and the locking port are hydraulically connected to the return port, the pressure relief valve being configured to allow circulation of the control fluid in the return line only if a control fluid pressure in the return line is greater than a maximum value.

[0023] - The actuation system further includes a control unit, and the hydraulic power source includes an electric motor and a hydraulic pump, the electric motor being configured to drive the hydraulic pump in rotation, and the control unit being configured to drive the electric motor and electrically power the distribution valve.- The actuation system further includes an auxiliary actuator independent of the hydraulic power source, configured to orient the blower blades towards the safety position when the distribution valve is in the second configuration, the independent auxiliary actuator being chosen from: an auxiliary motor-pump unit connected to an auxiliary hydraulic circuit isolated from the hydraulic circuit and configured to supply the distribution valve with control fluid; an electromechanical actuator including a moving part capable of moving a moving part of the hydraulic cylinder 5, the moving part being the piston or the cylinder.

[0024] - The hydraulic circuit further includes a return path equipped with a pressure relief valve, the actuation system further includes a hydraulic circuit integrated with a hydraulic distributor, so that the assembly formed by the distribution valve, the check valve, and the pressure relief valve is configured to be driven in rotation by the blower.

[0025] According to another aspect, an aircraft engine is proposed comprising a fan mounted to rotate about a longitudinal axis X and a blade pitch actuation system as previously described, the fan comprising a plurality of blades configured to be actuated by the actuation system, so that, when the control fluid flows from the retraction chamber to the extension chamber, the hydraulic cylinder piston moving in the first direction of travel, the blades are configured to orient themselves parallel to the longitudinal axis X towards the large pitch position.

[0026] DESCRIPTION OF THE FIGURES

[0027] Other features, purposes and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0028] Figure 1 is a top view of an aircraft according to an example of an embodiment of the invention.

[0029] Figure 2 is a simplified partial longitudinal cross-sectional view of a gas turbine engine from the aircraft in Figure 1.

[0030] Figure 3 is a schematic representation of a pitch-changing mechanism for the gas turbine engine of Figure 2 in a general context. Figure 4 is a schematic representation of a blade pitch-adjustment actuation system for the gas turbine engine of Figure 2 according to the invention.

[0031] Figure 5 is a detailed hydraulic diagram of the actuation system of Figure 4.

[0032] Figure 6 is a schematic representation of the hydraulic circuit when the distribution valve is in the first configuration.

[0033] Figure 7 is a schematic representation of the hydraulic circuit when the distribution valve is in the second configuration.

[0034] Figure 8 is a schematic representation of a system for actuation of the pitch control of the blades of the gas turbine engine in another embodiment.

[0035] Figure 9 is a schematic representation of a system for actuation of the pitch control of the blades of the gas turbine engine in an alternative embodiment.

[0036] Across all figures, similar elements bear identical references.

[0037] DETAILED DESCRIPTION OF THE INVENTION

[0038] Aircraft 100 shown in Figure 1 includes gas turbine engines 110 for propulsion.

[0039] In the example shown, aircraft 100 is an airplane. It conventionally comprises a fuselage 114, a tail assembly 116, and two wings 118. The gas turbine engines 110 are two in number and are each housed under a respective wing 118. This disclosure extends more generally to other types of aircraft and propulsion systems; for example, the gas turbine engines 110 could be arranged along the fuselage 114, near the tail assembly 116, or aircraft 100 could comprise one or at least three gas turbine engines 110.

[0040] One of the gas turbine engines 110 is shown in Figure 2.

[0041] As can be seen in this figure, the gas turbine engine 110 is elongated along a longitudinal axis X. It typically exhibits angular symmetry around said longitudinal axis X, that is to say, there is at least one angle for which the gas turbine engine 110 is invariant under rotation around the longitudinal axis X.

[0042] Hereafter, the terms "interior" and "exterior", "internal" and "external", as well as their variations, are understood with reference to the X-axis, an element described as "interior" or "internal" being oriented towards the X-axis while an "exterior" or "external" element is oriented in the opposite direction to the X-axis. The gas turbine engine 110 conventionally comprises a casing 120, an internal channel 122 for the circulation of a gas flow through the casing 120, a combustion chamber 124 housed in the channel 122, a powerhead 126 and an exhaust nozzle 128.

[0043] In the following, the terms "upstream" and "downstream" are understood to refer to the direction of flow of a gas stream through vein 122.

[0044] The engine body 126 comprises a compressor 130, a turbine 132, and a drive shaft 134 coupling the turbine 132 to the compressor 130 for driving the compressor 130 by the turbine 132. The compressor 130 is located upstream of the combustion chamber 124 and supplies the combustion chamber 124 with compressed air. The turbine 132 is located downstream of the combustion chamber 124 and receives the exhaust gases exiting the combustion chamber 124.

[0045] The transmission shaft 134 has the longitudinal axis X as its axis of rotation. The transmission shaft 134 is guided in rotation relative to the housing 120 by means of bearings.

[0046] In the example shown, the turbomachine 110 is a multi-body turbomachine, in particular a double body, comprising a low-pressure body 140 in addition to the engine body 126. The engine body 126 then constitutes a high-pressure body, the compressor 130 being a high-pressure compressor, the turbine 132 being a high-pressure turbine and the drive shaft 134 being a high-pressure shaft.

[0047] The low pressure body 140 includes a low pressure compressor 142, a low pressure turbine 144 and a low pressure shaft 146 coupling the low pressure turbine 144 to the low pressure compressor 142 for driving the low pressure compressor 142 by the low pressure turbine 144.

[0048] The low-pressure compressor 142 is located upstream of the high-pressure compressor 130 and supplies the latter with compressed air. The low-pressure turbine 144 is located downstream of the high-pressure turbine 132 and receives the exhaust gases exiting the latter.

[0049] The low-pressure shaft 146 is guided in rotation relative to the housing 120 by means of bearings. The low-pressure shaft 146 is coaxial with the high-pressure shaft 134. Therefore, its axis of rotation is also the longitudinal axis X. In particular, the low-pressure shaft 146 extends inside the high-pressure shaft 134.

[0050] The turbomachine 110 also includes a blower 200 to drive the gas flow into an external circulation channel 152 surrounding the casing 120. A primary gas flow A (hot), consisting of the portion of the gas flow driven into the internal circulation channel 122, is thus distinguished from a secondary gas flow B (cold), consisting of the portion of the gas flow driven into the external circulation channel 152.

[0051] The blower 200 comprises a blower rotor 240. This blower rotor 240 is rotatably mounted relative to the housing 120 about the longitudinal axis X by means of a guide bearing. It includes a hub 250 provided with blower blades 20 extending substantially radially outwards from the hub 250. These blades 20, when rotated, drive the gas flow into the external circulation channel 152.

[0052] Each 20-bladed wing comprises, in a known manner, a leading edge, a trailing edge and a cord connecting the leading edge to the trailing edge.

[0053] The blower rotor 240 is driven in rotation by the low-pressure turbine 144, via the low-pressure shaft 146. Preferably, this drive is achieved via a reduction gear allowing the blower rotor 240 to rotate at a speed lower than that of the low-pressure shaft 146. In an embodiment not shown, the drive is direct, i.e. the blower rotor 240 is fixed in rotation to the low-pressure shaft 146.

[0054] In the example shown, the blower 200 also includes a blower stator 158 comprising fixed blades 159 arranged at the periphery of the housing 120, in the external circulation vein 152, along a plane orthogonal to the longitudinal axis X. This blower stator 158 is arranged here downstream of the blower rotor 240. In an alternative embodiment, the blower 200 may include, instead of the blower stator 158, a counter-rotating blower rotor.

[0055] Advantageously, the fan 200 is, as shown, unshod, meaning that the external circulation channel 152 has no peripheral delimitation. The turbomachine 110 then consists, as shown, of a turbojet with an unshod fan or, alternatively, a turboprop. Alternatively, the external circulation channel 152 is defined between the casing 120 and a nacelle surrounding the fan 200. The turbomachine 110 is then typically a turbojet with a high bypass ratio, the bypass ratio being defined as the ratio of the secondary flow rate B (cold) to the primary flow rate A (hot).

[0056] In the example shown, the gas turbine engine 110 is specifically of the "puller" type, meaning that the fan 200 is positioned upstream of the internal circulation channel 122 and also drives the gas flow within it. Alternatively, the gas turbine engine 110 can be of the "pusher" type, meaning that the fan 200 is located around the downstream half of the casing 120. The blades 20 of the fan rotor 240 have variable pitch, meaning that each blade 20 is mounted to pivot relative to the hub 250 about its own pivot axis P. This pivot axis P extends along the direction of blade elongation. It is orthogonal to the longitudinal axis X.

[0057] Each blade 20 is in particular capable of pivoting around the axis P relative to the hub 250 between a so-called "flag" or "large pitch" position, in which the blade chord 20 is substantially orthogonal to a plane of rotation of the blower rotor 240 (and is therefore substantially parallel to the longitudinal axis X), and a so-called "sail" or "small pitch" position in which the blade chord 20 is substantially contained in said plane of rotation of the blower rotor (and is therefore substantially orthogonal to the longitudinal axis X).

[0058] Preferably, each blade 20 is also capable of pivoting beyond the sail position, to a so-called "reverse" position, in which the chord of the blade 20 forms an angle, for example, approximately -5°, with the plane of rotation of the fan rotor 240, on the side of said plane opposite to that of the feathered position. Since the blades 20 are most often twisted, the chord used as a reference for measuring the pitch angle is, by convention, the chord of the blade at 75% of the radius of the fan rotor 240.

[0059] For this purpose, each blade 20 is fixed, as shown in Figure 3, to a mounting piece 210 located at the blade's base. This mounting piece 210 is rotatably mounted relative to the hub 250 around the pivot axis P. More precisely, the mounting piece 210 is rotatably mounted within a housing formed in the hub 250 by means of balls or other rolling elements.

[0060] With reference to Figure 3, the gas turbine engine 110 also includes a pitch change mechanism 1 to adjust the pitch angle of each blade 20 around its pivot axis P so as to adapt the performance of the turbomachine 110 to the different phases of flight.

[0061] The pitch change mechanism 1 includes a frame, a hydraulic cylinder 5, also called a control or actuation cylinder, a linkage system 21 and a cylinder piloting system 3.

[0062] The frame is integral with the hub 250 and is typically formed by a portion of the hub 250. It is thus fixed relative to each pivot axis P and free to rotate relative to the housing 120. The hydraulic cylinder 5 comprises a fixed main body or cylinder 51, integral with the frame. The cylinder 51 is cylindrical in shape and typically centered approximately on the longitudinal axis X.

[0063] The hydraulic cylinder 5 also includes a piston 52 that is movable in translation along the longitudinal axis X relative to the fixed part between a first position and a second position. Optionally, the piston 52 is also movable in rotation about the longitudinal axis X through a small angle, for example on the order of 5°, relative to the fixed part 51.

[0064] The cylinder 51 defines an internal cavity. The piston 52 includes at least one partition housed inside said internal cavity and defining within the cylinder 51 an extension chamber 5c and a retraction chamber 5f.

[0065] Each chamber is designed to be supplied with a control fluid, typically an oil, to cause a relative displacement of the piston 52 relative to the fixed cylinder 51.

[0066] When the pressure in the extension chamber 5c is greater than the pressure in the retraction chamber 5f, the piston 52 translates in a first direction of movement towards the first position, so that the linkage system 21 is configured to orient the vanes 20 towards higher pitch angles.

[0067] When the pressure in the retraction chamber 5f is greater than the pressure in the extension chamber 5c, the piston 52 translates in a second opposite direction of movement, towards the second position, so that the linkage system 21 is configured to take the blades 20 towards lower pitch angles.

[0068] According to a preferred embodiment, the piston 52 is fixed relative to the engine and the cylinder 51 is movable in translation. Thus, when the pressure in the extension chamber 5c is greater than the pressure in the retraction chamber 5f, the movable cylinder 51 translates in the first direction of movement, so that the linkage system 21 moves the blades 20 towards higher pitch angles, and conversely when the pressure in the retraction chamber 5f is greater than the pressure in the extension chamber 5c, the movable cylinder 51 translates in the second direction of movement, so that the linkage system 21 moves the blades 20 towards lower pitch angles.

[0069] The retraction chamber 5f has a first volume and the extension chamber 5c has a second volume, each of the first and second volumes depending on the position of the piston 52 in the main body 51. Preferably, the hydraulic cylinder 5 is symmetrical, meaning that the sum of the first and second volumes is constant regardless of the position of the piston 52. Thus, it is possible to control the hydraulic cylinder 5 by means of a simple closed-loop system without an accumulator, by transferring the control fluid from one chamber 5f to the other. For this purpose, the internal cavity and the piston 52 are typically designed so that the two chambers 5f and 5c have the same cross-section.

[0070] The linkage system 21 connects the piston 52 to each blade 20 so as to convert the translation of the piston 52 along the longitudinal axis X and, where applicable, the rotation of the piston 52 around the longitudinal axis X into a rotation of each blade 20 around its pivot axis P.

[0071] In particular, the linkage system 21 connects the piston 52 to each blade 20 so as to convert:

[0072] - the translation of the piston 52 along the longitudinal axis X in the first direction of movement by a rotation of the variable-pitch blade 20 around the pivot axis P towards the flag position, and

[0073] - the translation of the piston 52 along the longitudinal axis X in the second direction of movement in a rotation of the variable pitch blade 20 around the pivot axis P towards the sail position.

[0074] It is understood here that such a linkage system 21 can be adapted to the embodiment in which the cylinder 51 is mobile in translation and the piston 52 is fixed.

[0075] Typically, the linkage system 21 can be a crankshaft comprising a connecting rod 214 connected to the piston rod 53, and transmitting the force of the piston 52 to a crank 211 rotating about its axis at one end of the connecting rod 214, thus converting linear motion into rotary motion.

[0076] An example of a linkage system is detailed below for illustrative purposes. In the illustrated embodiment, the linkage system 21 comprises a synchronizing ring 213 fixed to the piston rod 53 and, for each of the blades 20, a linkage mechanism of the blade 20 to the synchronizing ring 213.

[0077] The synchronizing ring 213 extends in a radial plane around the piston 52. In particular, it is fixed to a longitudinal end of the piston rod 53.

[0078] Each linkage mechanism includes a first joint 215 attached to the piston 52, a second joint 212 attached to the blade 20, away from the pivot axis P of said blade 20, and a linking member 214 connecting the first joint 215 to the second joint 212.

[0079] The first joint 215 is supported by the synchronizing ring 213. It is, for example, a pivot joint or a ball joint. The second joint 212 can also be a pivot joint or a ball joint. It is eccentric relative to the pivot axis P.

[0080] The connecting member 213 has a first end articulated to the first joint 215 and a second end articulated to the second joint 212. Advantageously the connecting member 214 is rigid and of adjustable length, that is to say that the distance between the first and second ends can be modified, which allows its length to be precisely adjusted at rest so as to allow the pitch angle of each blade 20 to be controlled by the pitch change mechanism 1.

[0081] The connecting member 214 is here constituted by a connecting rod. In the example shown, each connecting mechanism also includes a crank 211 linking the attachment piece 210 to the second joint 212. The crank 211 is rigid and integral with the attachment piece 210. It extends, at least in part, in a direction orthogonal to the pivot axis P. It forms an arm for rotating the blade 20.

[0082] Figure 4 schematically illustrates an actuation system according to the invention.

[0083] The actuation system 1 includes a hydraulic power source 3, a hydraulic block 4, i.e. a hydraulic circuit 4, and the hydraulic cylinder 5 enabling the rotational actuation of the blade 20 around its own axis P.

[0084] In the embodiment shown, the hydraulic power source 3 is a main pump unit 3 or electro-hydrostatic actuator (EHA) of the hydraulic cylinder 5. The pump unit 3 is configured to control the position of the hydraulic cylinder 5. More precisely, it controls the position of the hydraulic cylinder 5 to the position requested by a centralized control system for the gas turbine engine 110. To achieve this, the actuation system 1 may include a vane position sensor 20, configured to measure the position of the vanes 20 and transmit the measured position to the centralized control system. Alternatively, the actuation system 1 may include a displacement sensor on the hydraulic cylinder 5, for example, a linear variable differential transducer (LVDT).The displacement sensor is configured to measure the relative position of the cylinder body 51 with respect to the piston 52, and transmit the position to the centralized control system. The centralized control system can then calculate the angular orientation of the vanes 20 from this measurement.

[0085] The motor-pump group 3 comprises an electric motor 31, a hydraulic pump 32 and a control unit 33.

[0086] The control unit 33 includes an electronic box configured to receive a position command from the centralized control system and to control the electric motor 31's rotational speed from the position command.

[0087] The electric motor 31 is thus connected to the control unit 33. Preferably, the control unit 33 also includes a second electronic box also connected to the electric motor 31. This increases the level of redundancy and compensates for a failure of the other electronic box.

[0088] The hydraulic pump 32 is connected to the electric motor 31 and driven in rotation by the electric motor 31. The hydraulic pump 32 is typically a reversible bidirectional pump, that is to say, it is configured to inject the control fluid into the hydraulic block 4 and to reverse the fluid flow to draw the control fluid from the hydraulic block 4.

[0089] Alternatively, the hydraulic power source 3 may include a servovalve powered by a hydraulic pressure generation system. In this conventional embodiment, which is not shown, the hydraulic cylinder 5 is position-controlled by the servovalve.

[0090] The actuation system 1 contributes to the function of blocking the blower blades 20 in the current position by blocking the hydraulic cylinder 5 in the current position, without energy input, while allowing the function of feathering the blade 20 to be performed by an auxiliary actuator independent of the main electrohydrostatic actuator, i.e., of the hydraulic power source 3. Advantageously, the independent auxiliary actuator is an electromechanical actuator (EMA) comprising a moving part capable of moving the moving part of the hydraulic cylinder 5 (piston 52 or cylinder 51 depending on the embodiment).The moving part of the auxiliary actuator can be mechanically connected to the moving part of the hydraulic cylinder 5, or, alternatively, can exert a force on a device fixed to the moving part of the hydraulic cylinder 5, to return the blades 20 to the "feathered" position. This eliminates the need for an auxiliary hydraulic power supply and limits common failure modes, offering a more robust solution, particularly in the event of a seizure of the auxiliary actuator. Alternatively, the actuation system 1 can include an auxiliary hydraulic power supply (not shown) connected to the hydraulic circuit or to an auxiliary hydraulic circuit isolated from the main hydraulic circuit and connected to the hydraulic cylinder 5, so as to ensure that the blades 20 are brought to the "feathered" position.

[0091] The hydraulic circuit 4 is configured to ensure hydraulic distribution from the hydraulic power source, here the motor pump unit 3, to the hydraulic cylinder 5.

[0092] The actuation system 1 further includes a reservoir 6. The reservoir 6 ensures the compensation of pressure variations within the hydraulic circuit 4 and the supply of the hydraulic pump 32. The reservoir 6 is typically a low pressure type reservoir.

[0093] The architecture of hydraulic block 4 is detailed in figure 5.

[0094] The hydraulic block 4 includes a distribution valve 41 (a "mode selector valve" or MSV). The distribution valve 41 is a monostable hydraulic distributor with six ports and two positions, directly electrically actuated.

[0095] The distribution valve 41 typically comprises a valve body and an electromagnetic coil or solenoid. The distribution valve 41 is designed to allow the circulation of control fluid in the hydraulic circuit 4 and to change the operating mode of the actuation system 1 between two operating modes. More specifically, the distribution valve 41 allows selection of the "passive" operating mode (the distribution valve 41 is in the rest position, not electrically powered, and isolates the hydraulic cylinder 5 from the hydraulic power supply 3) or the "active" operating mode (the distribution valve 41 is electrically powered and connects the hydraulic cylinder 5 to the hydraulic power supply 3).

[0096] The distribution valve 41 can be connected to the control unit 33, meaning that the position of the distribution valve depends on the power supply to the solenoid from the control unit 33. Preferably, the distribution valve 41 has a double winding and is also controlled by the optional second electronic control unit. This increases the level of redundancy.

[0097] The hydraulic circuit 4 includes a hydraulic channel with a check valve 43. Preferably, the hydraulic channel with the check valve 43 also includes a hydraulic restrictor 45. This allows the flow of the control fluid in the hydraulic channel to be limited.

[0098] In an illustrated embodiment where the actuation system 1 includes the reservoir 6, the hydraulic circuit 4 preferably includes a return line connecting a port of the distribution valve 41 to the reservoir 6. The return line includes a pressure relief valve 44 configured to open only if the control fluid pressure in the return line upstream of said valve exceeds a maximum pressure permitted by the hydraulic circuit 4. The optional presence of a return port and the pressure relief valve 44 helps to preserve the integrity of the hydraulic circuit in the event of overpressure generated by significant thermal expansion when the aircraft is stationary. Introducing the return port R without the pressure relief valve 44 would render inoperative the locking mechanism in the normal position, which prevents the retraction of the hydraulic cylinder 5.

[0099] The actuation system 1 further includes a rotary hydraulic distributor 7 ("Rotary connection"). The rotary hydraulic distributor 7 is designed to ensure the transfer of the control fluid between the fixed reference point of the hydraulic power supply 3 connected to the frame, and the rotating reference point connected to the blower 200.

[0100] Operation of the assembly consisting of the distribution valve 41, the non-return valve 43 and the r est ri et eu r 45

[0101] With reference to Figures 6 and 7, the distribution valve 41 comprises an actuating member 411, a spring 412, and a spool assembly or valve body 413, which designates both the moving and fixed parts of the valve 41. The actuating member 411 is, for example, an electromagnet configured to control the movement of the spool of the assembly 413 and change the configuration of the distribution valve 41 when it is electrically energized. The spring 412 is configured to exert a restoring force on the spool of the assembly 413, so as to maintain the distribution valve 41 in a default position when the actuating member 411 is not energized.

[0102] The distribution valve 41 is capable of selectively adopting a first configuration or a second configuration.

[0103] The distribution valve 41 includes a first supply port A and a second supply port B, each configured to be connected to the hydraulic supply source 3. By "connected" or "linked" means that the ports are hydraulically connected to the hydraulic supply source, via piping.

[0104] The distribution valve 41 comprises two ports connected to the two chambers of the hydraulic cylinder 5. More specifically, the distribution valve 41 includes a first hydraulic port C, called the "extension port," connected to the extension chamber 5c, and a second hydraulic port F, called the "retraction port," connected to the retraction chamber 5f. Optionally, the distribution valve 41 also includes a port R, called the "return port," connected to the reservoir 6 via the return line through the pressure relief valve 44.

[0105] The hydraulic distributor 41 has the particularity that it also includes an additional port called the locking port L. The locking port L is connected to the shrink chamber 5f via the hydraulic route including the check valve 43. This makes it possible to prevent the shrink chamber 5f from filling via the hydraulic route but to allow it to be emptied.

[0106] First configuration

[0107] Referring to Figure 6, when the distribution valve 41 is in the first configuration, it is open. In the first configuration, the distribution valve 41 is configured to connect the hydraulic power supply 3 to the hydraulic cylinder 5, thus allowing its supply of control fluid.

[0108] In the first configuration, the first supply port A is hydraulically connected to port C and the second supply port B is hydraulically connected to port F. Thus, the hydraulic pump 32 can pump the control fluid to the expansion chamber 5c while drawing the control fluid from the contraction chamber 5f, or, depending on the direction of rotation of the electric motor 31, draw the fluid from the expansion chamber 5c, while pumping the control fluid to the contraction chamber 5f.

[0109] The locking port L is isolated, meaning it is not connected to any port. Therefore, the hydraulic line with the return valve 43 is not connected to the hydraulic circuit 4.

[0110] The return port R is also isolated.

[0111] The distribution valve 41 is in its first configuration when it is electrically powered. This first configuration is the active position. More precisely, when the actuating element 411 is electrically powered by the mains supply, for example, by the control unit 33, the actuating element 411 is configured to exert a force on the spool of the assembly 413 greater than the restoring force exerted by the spring 412. The spring 412 is compressed, and the distribution valve 41 moves into the active position. This corresponds to the "active" operating mode of the actuation system 1.

[0112] Second configuration

[0113] Referring to Figure 7, when the distribution valve 41 is in the second configuration, it is closed. In the second configuration, the distribution valve 41 is configured to isolate the hydraulic power supply 3 from the hydraulic cylinder 5.

[0114] In the second configuration, the supply port A is hydraulically connected to the supply port B. Thus the hydraulic cylinder 5 is isolated from the hydraulic pump 32.

[0115] In the second configuration, the locking port L is hydraulically connected to port C, while port F is isolated. Thus, the extension chamber 5c of the hydraulic cylinder 5 is connected to the hydraulic line including the check valve 43.

[0116] As explained previously, the aerodynamic forces exerted on the blower 200 tend to push the blades 20 towards a position of small pitches, i.e. tend to retract the hydraulic cylinder 5, and therefore to push the control fluid from the extension chamber 5c towards the retraction chamber 5f.

[0117] The presence of the non-return valve 43 prevents the fluid contained in the extension chamber 5c of the hydraulic cylinder 5 from escaping through the locking port L.

[0118] The pressure in the extension chamber 5c of the hydraulic cylinder 5 therefore rises to a level sufficient to counteract the aerodynamic forces; the piston 52 of the hydraulic cylinder does not retract, or only retracts over a very short portion of its stroke due to the compressibility of the control fluid. The blades 20 of the blower 200 are thus locked in their normal position.

[0119] Furthermore, the fluid remains free to flow from the retraction chamber 5f to the extension chamber 5c in the forward direction of the non-return valve 43. This ensures the possibility of moving the piston 52 of the hydraulic cylinder 5 to the first position corresponding to a flagging position of the vanes 20 independently, even when the supply source 3 is not connected to the hydraulic cylinder 5.

[0120] The second configuration corresponds to the default position of the distribution valve 41, that is, its position when the distribution valve 41 is not electrically powered. This second configuration corresponds to the "passive" operating mode. More precisely, the distribution valve 41 is held in the passive position by the action of the spring 412. The valve spool is returned to the passive position when the actuating member 411 does not exert an opposing force on the valve spool, that is, when the electrical network is not supplying the distribution valve 41. This allows the distribution valve 41 to ensure that the blower blades remain locked in the current position when the system is no longer electrically powered, for example, following a failure. When the actuation system 1 is in the passive operating mode, the blades 20 can be feathered by the independent auxiliary actuator.The proposed actuation system 1 is compatible with an embodiment in which the independent auxiliary actuator is an auxiliary hydraulic power source connected to the hydraulic cylinder 5. Furthermore, unlike existing solutions, the actuation system 1 also allows the use of an electromechanical actuator. Thus, the presence of the distribution valve 41 enables the hydraulic cylinder 5 to be actuation independently of that performed by the main pump unit 3, without requiring an auxiliary hydraulic power source.

[0121] With reference to Figure 8, the port R connected to the return line via the pressure relief valve 44 is preferably also connected to the first hydraulic port C, and to the locking port L. This helps to limit the risk of overpressure, as the control fluid could escape to the reservoir 6 in the event of overpressure in either of the cylinder chambers.

[0122] Alternative embodiments

[0123] In the illustrated embodiment, the distribution valve 41 is arranged in the fixed frame linked to the frame of the actuation system 1 and therefore to the gas turbine engine 110 of the aircraft.

[0124] In a first alternative embodiment, the distribution valve 41 and the non-return valve 43 are arranged as close as possible to the hydraulic cylinder 5, in the rotating reference frame linked to the blower 200. This allows for a more robust actuation system 1 by reducing the risk of the cylinder retracting towards the "small steps" position in the event of a pipe rupture between the hydraulic circuit 4 and the rotating distributor 7.

[0125] In a second alternative embodiment illustrated in Figure 8, the actuation system 1 further includes an auxiliary power source 6. The auxiliary power source 6 is an auxiliary motor-pump unit comprising an auxiliary electric motor 61 and an auxiliary hydraulic pump 62.

[0126] According to a third alternative embodiment, illustrated in Figure 9, the actuation system 1 comprises an independent auxiliary actuator 6'. The independent auxiliary actuator is an electromechanical actuator, or "feathering" system. It is capable of moving or adjusting the moving part of the hydraulic cylinder 5 as required, and thus of changing the orientation of the blade 20. The present invention is described in the context of an actuation system for the fan blades 20 of an aircraft engine, but extends more generally to any hydraulic actuator requiring a locking function in the current position in one direction of travel without power input, while allowing movement in the opposite direction by means of an auxiliary actuation system independent of the hydraulic cylinder.

Claims

DEMANDS 1. Actuation system (1) for adjusting the pitch of the fan blades (20) of an aircraft engine, comprising a hydraulic power source (3), a hydraulic cylinder (5), the hydraulic cylinder (5) comprising a cylinder and a piston, the piston defining within the cylinder a retraction chamber (5f) and an extension chamber (5c), each of the retraction chamber (5f) and the extension chamber (5c) being suitable for being supplied with a control fluid, so as to cause a displacement of the piston relative to the cylinder in a first direction of movement when a pressure of the control fluid in the extension chamber (5c) is greater than a pressure of the control fluid in the retraction chamber (5f) and to cause a displacement of the piston relative to the cylinder in a second direction of movement, opposite to the first direction of movement,when a control fluid pressure in the retraction chamber (5f) is greater than a control fluid pressure in the expansion chamber (5c); the actuation system further comprising a hydraulic circuit supplied with control fluid by the hydraulic power source (3), the hydraulic circuit comprising a hydraulic channel equipped with a check valve (43), and a distribution valve (41) comprising, - a first power port (A) and a second power port (B), configured to be each connected to the hydraulic power source (3); - a first hydraulic port (C) connected to the extension chamber (5c); - a second hydraulic port (F) connected to the shrink chamber (5f); - a locking port (L) configured to be connected to the retraction chamber (5f) via the hydraulic route, the check valve (43) being configured to prevent circulation of the control fluid from the expansion chamber (5c) to the retraction chamber (5f) and to allow circulation of the control fluid from the retraction chamber (5f) to the expansion chamber (5c); the distribution valve (41) being adapted to selectively adopt a first configuration in which the first supply port (A) is hydraulically connected to the first hydraulic port (C) and the second supply port (B) is connected to the second hydraulic port (F), the locking port (L) being isolated, and a second configuration in which the first supply port (A) is hydraulically connected to the second supply port (B), and the locking port (L) is connected to the first hydraulic port (C), the second hydraulic port (F) being isolated, so that, when the distribution valve (41) is in the first configuration, the hydraulic cylinder (5) is configured to be position-controlled by the hydraulic power source (3), and when the distribution valve (41) is in the second configuration, the control fluid can only flow from the retraction chamber (5f) to the extension chamber (5c) so that the piston of the hydraulic cylinder (5) moves in the first direction of travel, the blower blades orienting themselves towards a safety position known as the "flag position".

2. Actuation system (1) according to claim 1, wherein the first configuration is an active position attained when the distribution valve (41) is electrically powered, and wherein the second configuration is a passive position attained when the distribution valve (41) is not electrically powered.

3. Actuation system (1) according to any one of claims 1 and 2, wherein the hydraulic path further comprises a hydraulic restrictor (45) configured to limit a flow of the control fluid in the hydraulic path.

4. Actuation system (1) according to any one of claims 1 to 3, wherein the hydraulic circuit further comprises a return path provided with a pressure relief valve (44), the distribution valve (41) further comprising a return port (R) connected to the return path, and wherein, when the distribution valve (41) is in the second configuration, the first hydraulic port (C) and the locking port (L) are hydraulically connected to the return port (R), the pressure relief valve (44) being configured to allow circulation of the control fluid in the return path only if a control fluid pressure in the return path is greater than a maximum value.

5. Actuation system (1) according to any one of claims 1 to 4, further comprising a control unit (33), and in which the hydraulic power source (3) comprises an electric motor (31) and a hydraulic pump (32), the electric motor (31) being configured to drive the hydraulic pump (32) in rotation, and the control unit being configured to drive the electric motor (31) and electrically supply the distribution valve (41).

6. Actuation system (1) according to any one of claims 1 to 5, further comprising an auxiliary actuator independent of the hydraulic power source (3), configured to orient the blower blades towards the safety position when the valve distribution (41) is in the second configuration, the independent auxiliary actuator being chosen from: an auxiliary motor-pump unit connected to an auxiliary hydraulic circuit isolated from the hydraulic circuit and configured to supply the distribution valve (41) with control fluid; an electromechanical actuator comprising a moving part capable of moving a moving part of the hydraulic cylinder 5, the moving part being the piston or the cylinder.

7. Actuation system (1) according to any one of claims 1 to 6, wherein the hydraulic circuit further comprises a return path provided with a pressure relief valve (44), the actuation system (1) further comprising a hydraulic circuit integrated into a hydraulic distributor (7), such that the assembly formed by the distribution valve (41), the check valve (43), and the pressure relief valve (44) is configured to be driven in rotation by the blower (200).

8. Aircraft engine comprising a fan (200) mounted for rotation about a longitudinal axis (X) and an actuation system (1) for setting blade pitch according to any one of claims 1 to 7, the fan (2) comprising a plurality of blades (20) configured to be actuated by the actuation system (1), such that, when the control fluid flows from the retraction chamber (5f) to the extension chamber (5c), the piston of the hydraulic cylinder (5) moving in the first direction of travel, the blades (20) are configured to orient themselves parallel to the longitudinal axis (X) towards the large pitch position.

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