FAN ROTOR INCORPORATING A PITCH CHANGE MECHANISM PUMP

Abstract

This fan rotor for a gas turbine engine comprises a hub, a plurality of variable-pitch blades (56) and a pitch-changing mechanism (70) for adjusting an angular position of each of the blades (56). The pitch-changing mechanism (70) comprises a control cylinder (74) with a fixed part (80) and a movable part (82), a fluid circuit (120) for supplying the control cylinder (74) with control fluid for controlling the movement of the movable part (82) relative to the fixed part (80), and a pump (210) for driving the control fluid in the fluid circuit (120). The pump (210) comprises a pump body (212) secured to the hub (55). Figure for abstract: Fig. 3

Description

Title of the Invention: Blower Rotor Incorporating a Gearbox Pump Field of the Invention

[0001] The present invention relates to the general field of gas turbine engines equipped with at least one blower rotor having variable timing blades, and more particularly to the control of the orientation of the blower blades of these gas turbine engines.

[0002] A preferred field of application of the invention is that of non-cased blower turbofans (better known by the English names "propfan", "open fan", "open rotor" and "unducted fan"). However, the invention also applies to turboprop engines with one or more propulsive propellers. Technological Background

[0003] One of the current approaches being explored to improve the specific fuel consumption of civil aircraft engines is the development of non-cased fan turbofans, such as that described in document FR 2 941 493. These turbofans include a conventional turbomachine gas generator, one or more turbine stages of which drive one or more uncased fan rotor(s) extending outside the engine casing, most often via a reduction gear allowing the fan rotor to rotate at a speed lower than that of the turbine stage(s).

[0004] The leading edges of this or these rotor(s) are, as in the case of conventional turbopropellers, of variable pitch, that is to say that the angular position of these blades (called pitch angle) can be modified during flight. For reminder, the pitch angle of a blade corresponds to the angle, in a plane orthogonal to the axis of pivoting of the blade, between the chord of the blade at 75% of the radius of the blower and a plane orthogonal to the axis of rotation of the blower. It can vary from a value equal to 0°, corresponding to a so-called "veil" or "flat" position of the blade, to a value equal to 90°, corresponding to a so-called "flag" position of the blade. It can also take a value strictly less than 0°, typically substantially equal to - 5 °, corresponding to a so-called "reverse" position of the blade.

[0005] As is known, this modification of the pitch angle during flight makes it possible to change the engine thrust and optimize the efficiency of the fan as a function of the aircraft speed. Indeed, the fan speed is almost constant over all operating phases, and it is the pitch of the blades which varies the thrust. Thus, in the cruising flight phase, the blades are oriented so as to adjust the thrust by minimizing the power taken from the turbine shaft and consumption and optimizing efficiency. Conversely, during takeoff, the blades are oriented to maximize thrust in order to accelerate and then take off the aircraft.

[0006] The control of the orientation of the blades is commonly carried out by means of a pitch change mechanism comprising a control cylinder integral in rotation with the hub of the fan, this control cylinder comprising a fixed part, integral in translation with the hub of the fan, and another part movable in translation along the axis of the fan. The part movable in translation is connected to the blade by a connection system so as to convert the translation of the movable part into rotation of the variable-pitch blade. This control cylinder is generally a hydraulic cylinder supplied with fluid by a main source integral with the engine casing.This main source conventionally comprises a pump capable of pressurizing the fluid, driven by the high-pressure body of the gas turbine via a gearbox, and a control unit capable of directing the pressurized fluid leaving the pump, selectively, towards one or other of the chambers of the control cylinder. A rotating fluid transfer mechanism ensures the transfer of the pressurized fluid between the casing and the fan rotor.

[0007] A difficulty encountered with variable-pitch blades is that, in the event of a malfunction of the main source, said blades tend, under their own centrifugal effect, to move into the sail position. However, a blade blocked in this position generates little resistive torque and risks causing the engine to overspeed, with potential risks of engine damage. In addition, a blade blocked in this position also risks generating excessive drag that is unacceptable for the controllability of the aircraft and / or its range in the case of a diversion mission.

[0008] To overcome this difficulty, it is known to use safety systems capable of returning the blades to the flag position and / or of preventing the variable pitch blades from moving towards the small pitches (i.e. towards the sail position) in the event of failure of the main source. There are two main families of safety systems of this type: - so-called “passive” safety systems capable of returning the blades to the flag position without external action; these systems most often use the centrifugal force of a counterweight to return the blades to the flag position, as described for example in publications WO 2012 / 066240 and FR 2,957,329, and - so-called "active" safety systems requiring external action to return the blades to the flag position; these systems most often include an auxiliary source, typically an electric pump, integral with the casing intended to be activated in the event of failure of the main source, this auxiliary source supplying fluid to the so-called “large pitch” chamber of the control cylinder so as to cause the cylinder to move towards the position in which the blades are in the flag position.

[0009] However, these solutions are not entirely satisfactory. Indeed, in "passive" safety systems, the use of counterweights makes the blades heavier, requiring oversizing of the main source and the cylinder. This results in a general increase in weight of the gas turbine engine, which consequently loses efficiency. And in "active" safety systems, the auxiliary source has failure modes common to the main source, such as cases of leakage in the rotating fluid transfer mechanism, so that the auxiliary source may be unavailable when necessary. This has two implications: - it may be impossible to return the blades to the flag position, and - it is necessary to provide a pitch lock device to block the blade pitch angle in the event of failure of the main source and thus prevent the blades from moving towards small pitches during the switching time from the main source to the auxiliary source. Statement of the invention

[0010] An objective of the invention is to enable variable-pitch blades to be made safe in the event of failure of the supply system of the cylinder controlling their orientation, so as to maximize the availability of the safety system while minimizing the impact on the weight of the turbomachine.

[0011] To this end, the invention relates, according to a first aspect, to a fan rotor for a gas turbine engine, comprising a hub, a plurality of variable-pitch blades each pivotable relative to the hub around a specific pivot axis, and a pitch-changing mechanism for adjusting an angular position of each of the blades around its respective pivot axis, the pitch-changing mechanism comprising: - a control cylinder with a fixed part secured to the hub, and a mobile part movable relative to the fixed part, - a connection system connecting the moving part to each variable-pitch blade so as to convert a movement of the moving part relative to the fixed part into a rotation of the variable-pitch blade around the pivot axis, - a fluid circuit for supplying the control cylinder with control fluid to control the movement of the moving part relative to the fixed part, the fixed part, and - a pump for driving the control fluid in the fluid circuit,

[0012] in which the pump comprises a pump body secured to the hub.

[0013] According to particular embodiments of the invention, the fan rotor also has one or more of the following characteristics, taken individually or in any technically possible combination(s): - the pump comprises a pump rotor mounted rotatably relative to the pump body, the fan rotor further comprising a drive train configured to couple the pump rotor to a casing of the gas turbine engine such that rotation of the fan rotor relative to said casing jointly drives rotation of the pump rotor relative to the pump body; - each blade is movable around its pivot axis between a sail position and a flag position, the fluid circuit being configured so that the pump supplies the control cylinder so as to cause the blades to pivot towards their flag position; - the fluid circuit comprises a cylinder branch in fluid communication with the control cylinder, a main branch in fluid communication with a rotating fluid transfer mechanism for transferring the control fluid between a casing of the gas turbine engine and the fan rotor, an auxiliary branch in fluid communication with the pump, and a valve system for fluidly connecting the cylinder branch selectively to one of the main and auxiliary branches; - the fluid circuit comprises a control pipe which is in fluid communication with the rotating fluid transfer mechanism; - the valve system has a first configuration in which the cylinder branch is fluidly connected to the main branch and a second configuration in which the cylinder branch is fluidly connected to the auxiliary branch, the valve system being configured to switch from the first configuration to the second configuration in the event of a loss of pressure in the control pipe; - the pitch change mechanism comprises a pitch locking device with a locking mechanism having a first configuration in which the movable part of the control cylinder is free to move relative to the fixed part and a second configuration in which the locking mechanism is engaged with the movable part so as to immobilize the movable part relative to the fixed part, the device step lock also comprising an engagement mechanism configured to switch the locking mechanism from the first configuration to the second configuration in the event of a loss of pressure in the control pipe; - the fan rotor comprises an additional pipe fluidly connected to the auxiliary branch, the engagement mechanism comprising a return member urging the locking mechanism towards its second configuration, a chamber in contact with a piston secured to the locking mechanism so that the fluid contained in said chamber exerts on the piston a pressure oriented in a direction opposite to that of the urging of the return member, and a maximum pressure sampling mechanism configured to fluidly connect the chamber to that of the additional pipe and the control pipe having the highest pressure; - the valve system is configured so that, in the first configuration, the auxiliary branch forms a closed hydraulic circuit; - the valve system comprises a six-way valve with two primary ways fluidly connected to the cylinder branch, two secondary ways fluidly connected to the main branch, and two tertiary ways fluidly connected to the auxiliary branch; - the fixed part and the movable part of the control cylinder delimit between them two fluid chambers each containing a control fluid for controlling the movement of the movable part relative to the fixed part, a first of said fluid chambers having a first volume and the second of said fluid chambers having a second volume, each of the first and second volumes depending on the position of the movable part relative to the fixed part, the control cylinder being configured so that the sum of the first and second volumes is constant whatever the position of the movable part relative to the fixed part.

[0014] The invention also relates, according to a second aspect, to a gas turbine engine comprising a fan rotor according to the first aspect.

[0015] According to a particular embodiment of the invention, the gas turbine engine also has the following characteristic: - the gas turbine engine comprises a casing relative to which the fan rotor is rotatably mounted, the pump comprising a pump rotor kinematically coupled to said casing such that rotation of the fan rotor relative to this casing jointly drives rotation of the pump rotor relative to the pump body.

[0016] The invention also relates, according to a third aspect, to an aircraft comprising at least one gas turbine engine according to the second aspect. Brief description of the Figures

[0017] Other characteristics and advantages of the invention will appear on reading the description which follows, given solely by way of example and with reference to the appended drawings, in which: - [Fig.l] is a top view of an aircraft according to an exemplary embodiment of the invention, - [Fig.2] is a simplified view in partial longitudinal section of a gas turbine engine of the aircraft of [Fig.l], - [Fig.3] is a diagram of a pitch change mechanism of the gas turbine engine of [Fig.2], according to a first variant, and - [Fig.4] is a diagram of the pitch change mechanism of [Fig.3], according to a second variant. Detailed description of an example of implementation

[0018] The aircraft 10 shown in [Fig.l] includes gas turbine engines 12 to propel it.

[0019] In the example shown, the aircraft 10 is an airplane. This aircraft comprises, in a conventional manner, a fuselage 14, a tailplane 16 and two wings 18. The gas turbine engines 12 are here two in number and are each housed under a respective wing 18. As a variant (not shown), the gas turbine engines 12 are arranged along the fuselage 14, for example near the tailplane 16. As a further variant (also not shown), the aircraft 10 comprises a single gas turbine engine 12 or at least three gas turbine engines 12.

[0020] One of the gas turbine engines 12 is shown in [Fig.2].

[0021] As seen in this Figure, the gas turbine engine 12 is elongated along a longitudinal axis X. It typically has angular symmetry around said longitudinal axis X, i.e. there is at least one angle for which the gas turbine engine is rotationally invariant around the longitudinal axis X.

[0022] Here and hereinafter, 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 opposite the X axis.

[0023] The gas turbine engine 12 comprises, in a conventional manner, a casing 20, an internal vein 22 for circulating an air flow through the casing 20, a combustion chamber 24 housed in the vein 22, a motor body 26 and a gas exhaust nozzle 28.

[0024] In the following, the terms “upstream” and “downstream” are understood to refer to a direction of flow of an air flow through the vein 22.

[0025] The engine body 26 comprises a compressor 30, a turbine 32 and a transmission shaft 34 coupling the turbine 32 to the compressor 30 for driving the compressor 30 by the turbine 32. The compressor 30 is arranged upstream of the combustion chamber 24 and supplies the combustion chamber 24 with compressed air. The turbine 32 is arranged downstream of the combustion chamber 24 and receives the exhaust gases leaving the combustion chamber 24.

[0026] The transmission shaft 34 has the longitudinal axis X as its axis of rotation.

[0027] The transmission shaft 34 is guided in rotation relative to the casing 20 by means of bearings (not shown).

[0028] In the example shown, the turbomachine 12 is a multi-body turbomachine, in particular a double-body turbomachine, comprising a low-pressure body 40 in addition to the engine body 26. The engine body 26 then constitutes a high-pressure body, the compressor 30 being a high-pressure compressor, the turbine 32 being a high-pressure turbine and the transmission shaft 34 being a high-pressure shaft.

[0029] The low pressure body 40 comprises a low pressure compressor 42, a low pressure turbine 44 and a low pressure shaft 46 coupling the low pressure turbine 44 to the low pressure compressor 42 for driving the low pressure compressor 42 by the low pressure turbine 44.

[0030] The low pressure compressor 42 is arranged upstream of the high pressure compressor 30 and supplies the latter with compressed air. The low pressure turbine 44 is arranged downstream of the high pressure turbine 32 and receives the exhaust gases leaving the latter.

[0031] The low pressure shaft 46 is guided in rotation relative to the casing 20 by means of bearings (not shown).

[0032] The low pressure shaft 46 is coaxial with the high pressure shaft 34. It therefore also has the longitudinal axis X as its axis of rotation. In particular, the low pressure shaft 46 extends inside the high pressure shaft 34.

[0033] The turbomachine 12 also comprises a fan 50 for driving the air flow in an external circulation vein 52 surrounding the casing 20. A primary air flow A (hot) is thus distinguished, consisting of the portion of the air flow driven in the internal circulation vein 22, and a secondary air flow B (cold), consisting of the portion of the air flow driven in the external circulation vein 52.

[0034] The fan 50 comprises a fan rotor 54. This fan rotor 54 is rotatably mounted relative to the casing 20 around the longitudinal axis X by means of a guide bearing 53. It comprises a hub 55 provided with fan blades 56 extending substantially radially outwards from the hub 55. These blades 56, when rotated, drive the air flow into the external circulation vein 52.

[0035] Each blade 56 comprises, in known manner, a leading edge, a trailing edge and a chord connecting the leading edge to the trailing edge.

[0036] The fan rotor 54 is driven in rotation by the low-pressure turbine 44, via the low-pressure shaft 46. Preferably, this drive is done via a reducer (not shown) allowing the fan rotor 54 to rotate at a speed lower than that of the low-pressure shaft 46. In a variant (not shown), this drive is direct, that is to say that the fan rotor 54 is integral in rotation with the low-pressure shaft 46.

[0037] In the example shown, the fan 50 also comprises a fan stator 58 comprising fixed blades 59 arranged at the periphery of the casing 20, in the external circulation duct 52, along a plane orthogonal to the longitudinal axis X. This fan stator 58 is here arranged downstream of the fan rotor 54. As a variant (not shown), the fan 50 comprises, instead of the fan stator 58, a counter-rotating fan rotor.

[0038] Advantageously, the fan 50 is, as shown, unducted, that is to say that the external circulation vein 52 has no peripheral delimitation. The turbomachine 12 is then constituted, as shown, by a turbojet with an unducted fan or, alternatively, by a turboprop. As a variant (not shown), the external circulation vein 52 is defined between the casing 20 and a nacelle surrounding the fan 50; the turbomachine 12 is then typically constituted by a turbojet with a high bypass ratio, the bypass ratio being defined as the ratio of the flow rate of the secondary flow B (cold) to the flow rate of the primary flow A (hot).

[0039] In the example shown, the gas turbine engine 12 is in particular of the “puller” type, that is to say that the fan 50 is arranged upstream of the internal circulation vein 22 and also drives the air flow in the latter. As a variant (not shown), the gas turbine engine 12 is of the “pusher” type, that is to say that the fan 50 is placed around the downstream half of the casing 20.

[0040] The blades 56 of the fan rotor 54 are variable-pitch, that is to say that each blade 56 is pivotally mounted relative to the hub 55 around its own pivot axis P. This pivot axis P extends in the direction of elongation of the blade 56. It is orthogonal to the longitudinal axis X.

[0041] Each blade 56 is in particular capable of pivoting around the axis P relative to the hub 55 between a so-called flag position, in which the chord of the blade 56 is substantially orthogonal to a plane of rotation of the fan rotor 54 (and is therefore substantially parallel to the longitudinal axis X), and a so-called sail position, in which the chord of the blade 56 is substantially included in said plane of rotation of the fan rotor (and is therefore substantially orthogonal to the longitudinal axis X). Preferably, each blade 56 is also capable of pivoting beyond the sail position, to a so-called reverse position, in which the chord of the blade 56 forms an angle, for example substantially equal to - 5°, with the plane of rotation of the fan rotor 54, on the side of said plane opposite that where the flag position is located. The blades 56 being most often twisted, the chord taken as a reference for measuring the pitch angle is, by convention, constituted by the chord of the blade at 75% of the radius of the fan rotor 54.

[0042] For this purpose, each blade 56 is secured, as visible in [Fig. 3], to an attachment piece 60 arranged at the blade root. This attachment piece 60 is rotatably mounted relative to the hub 55 around the pivot axis P. More precisely, the attachment piece 60 is rotatably mounted inside a housing (not shown) formed in the hub 55 by means of balls or other rolling elements.

[0043] With reference to [Fig. 3], the gas turbine engine 12 also comprises a pitch change mechanism 70 for adjusting the pitch angle of each blade 56 about its pivot axis P so as to adapt the performance of the turbomachine 12 to the different phases of flight.

[0044] The pitch change mechanism 70 comprises a frame 72, a control cylinder 74, a connection system 76 and a system 78 for controlling the cylinder 74.

[0045] The frame 72 is integral with the hub 55 and is typically constituted by a part of the hub 55. It is thus fixed relative to the pivot axes P and movable in rotation relative to the casing 20.

[0046] The control cylinder 74 comprises a fixed part 80, integral with the frame 72, and a movable part 82 movable in translation along the longitudinal axis X relative to the fixed part 80 between a first position and a second position. Optionally, the movable part 82 is also movable in rotation around the longitudinal axis X over a restricted angle, for example of the order of 5°, relative to the fixed part 80.

[0047] The control cylinder 74 is typically substantially centered on the longitudinal axis X. The control cylinder 74 therefore has the longitudinal axis X as its axis.

[0048] The control cylinder 74 comprises in particular a body 84 forming one of the fixed part 80 and the movable part 82 and a piston 86 forming the other of the fixed part 80 and the movable part 82. Here, the body 84 forms the fixed part 80 and the piston 86 forms the movable part 82.

[0049] The body 84 delimits an internal cavity 90. The piston 86 comprises at least one partition 88 housed inside said internal cavity 90 and delimiting with the body 84 two fluid chambers 92, 94 inside the internal cavity 90. Each contains a control fluid, typically consisting of an oil, to control the placement of the movable part 82 relative to the fixed part 80. This control fluid is at a first pressure in the first fluid chamber 92 and at a second pressure in the second fluid chamber 94. The first and second fluid chambers 92, 94 are arranged so that the relative increase in the first pressure (i.e. relative to the second pressure) causes the movable part 82 to move towards its first position, the relative increase in the second pressure (i.e. relative to the first pressure) causing the movable part 82 to move towards its second position.

[0050] The first fluid chamber 92 has a first volume and the second fluid chamber 94 has a second volume, each of the first and second volumes depending on the position of the movable part 82 relative to the fixed part 80.

[0051] The control cylinder 74 is advantageously configured so that the sum of the first and second volumes is constant regardless of the position of the movable part 82 relative to the fixed part 80. Thus, it is possible to control the control cylinder 74 by means of a simple closed-loop system without an accumulator, by transferring the control fluid from one to the other of the fluid chambers 92, 94. For this purpose, the internal cavity 90 and the piston 86 are typically designed so that the two fluid chambers 92, 94 have the same cross-section.

[0052] Alternatively, the sum of the first and second volumes varies depending on the position of the movable part 82 relative to the fixed part 80.

[0053] The connecting system 76 connects the movable part 82 to each blade 56 so as to convert the translation of the movable part 82 along the longitudinal axis X and, where appropriate, the rotation of the movable part 82 around the longitudinal axis X into a rotation of each blade 56 around its pivot axis P. In particular, the connecting system 76 connects the movable part 82 to each blade 56 so as to convert: - the translation of the movable part 82 along the longitudinal axis X towards its first position into a rotation of the variable-pitch blade 56 around the pivot axis P towards the flag position, and - the translation of the movable part 82 along the longitudinal axis X towards its second position in a rotation of the variable-pitch blade 56 around the pivot axis P towards the sail position.

[0054] Thus, the relative increase in the first pressure causes the blades 56 to rotate towards their flag position and the relative increase in the second pressure causes the blades 56 to rotate towards their sail position. The first fluid chamber 92 will therefore be referred to hereinafter as the “large pitch chamber”, the increase in the fluid pressure in said chamber causing the blades 56 to rotate towards their sail position. blades 56 towards higher pitch angles, the second fluid chamber 94 being called the “small pitch chamber” since the increase in fluid pressure in said chamber causes the blades 56 to rotate towards lower pitch angles.

[0055] For this purpose, the connection system 76 comprises a synchronization ring 100 secured to the mobile part 82 and, for each of the blades 56, a mechanism 102 for connecting the blade 56 to the synchronization ring 100.

[0056] The synchronization crown 100 extends in a radial plane around the mobile part 82. It is in particular fixed to a longitudinal end 104 of the mobile part 82.

[0057] Each connecting mechanism 102 comprises a first articulation 106 secured to the movable part 82, a second articulation 108 secured to the blade 56, away from the pivot axis P of said blade 56, and a connecting member 110 connecting the first articulation 106 to the second articulation 108.

[0058] The first articulation 106 is carried by the synchronization crown 100. Here it is constituted by a ball joint.

[0059] The second articulation 108 is also constituted by a ball joint. It is eccentric relative to the pivot axis P.

[0060] The connecting member 100 has a first end (not referenced) articulated to the first articulation 106 and a second end (not referenced) articulated to the second articulation 108. Advantageously, the connecting member 110 is rigid and of adjustable length, that is to say that the distance between the first and second ends can be modified, which makes it possible to precisely adjust the length when stopped so as to allow the control of the setting angle of each blade 56 by the pitch change mechanism 70.

[0061] The connecting member 110 is here constituted by a connecting rod.

[0062] In the example shown, each connecting mechanism 102 also comprises a crank 112 connecting the attachment part 60 to the second articulation 108. This crank 112 is rigid and integral with the attachment part 60. It extends at least partly in a direction orthogonal to the pivot axis P. It forms an arm for rotating the blade 56.

[0063] The control system 78 comprises a fluid circuit 120, integral with the hub 55, for supplying the control cylinder 74 with control fluid to control the movement of the movable part 82 relative to the fixed part 80. It also comprises a main source of control fluid 122, fixed in the reference attached to the casing 20, a rotating fluid transfer mechanism 124 for transferring the control fluid between the main source 122 and the fluid circuit 120, an auxiliary source of control fluid 126, and a control module 128.

[0064] The fluid circuit 120 comprises a cylinder branch 130 in fluid communication with the control cylinder 74, a main branch 134 in fluid communication with the rotating fluid transfer mechanism 124 and, via the rotating fluid transfer mechanism 124, with the main source 122, an auxiliary branch 136 in fluid communication with the auxiliary source 126, and a valve system 138 for fluidly connecting the cylinder branch 130 selectively to one of the main and auxiliary branches 134, 136. It also comprises a control pipe 140 which is in fluid communication with the rotating fluid transfer mechanism 124.

[0065] The cylinder branch 130 comprises a first cylinder line 142 fluidly connected to the large pitch chamber 92 and a second cylinder line 144 fluidly connected to the small pitch chamber 142.

[0066] The main branch 134 comprises a first main conduit 146 fluidly connected to a first rotating port 147 of the rotating fluid transfer mechanism 124 and a second main conduit 148 fluidly connected to a second rotating port 149 of the rotating fluid transfer mechanism 124.

[0067] The auxiliary branch 136 comprises a first auxiliary conduit 152 fluidly connected to a first auxiliary port 153 of the auxiliary source 126 and a second auxiliary conduit 154 fluidly connected to a second auxiliary port 155 of the auxiliary source 126.

[0068] The valve system 138 has a first configuration, shown in [Fig. 3], in which said valve system 138 fluidly connects the cylinder branch 130 to the main branch 132. In particular, in this first configuration, the valve system 138 fluidly connects the first cylinder line 142 to the first main line 146 and the second cylinder line 144 to the second main line 148.

[0069] The valve system 138 is also configured to, in this first configuration, fluidly isolate the auxiliary branch 136 from the cylinder branch 130 and from the main branch 134. In particular, the valve system 138 is configured to, in this first configuration, fluidly connect the first auxiliary line 152 to the second auxiliary line 154 so that the auxiliary branch 136 forms a closed hydraulic circuit.

[0070] The valve system 138 also has a second configuration (not shown) in which said valve system 138 fluidly connects the cylinder branch 130 to the auxiliary branch 136. In particular, in this second configuration, the valve system 138 fluidly connects the first cylinder line 142 to the first auxiliary line 152 and the second cylinder line 144 to the second auxiliary line 154.

[0071] The valve system 138 is also configured to, in this second configuration, fluidly isolate the main branch 134 from the cylinder branch 130 and from the auxiliary branch 136.

[0072] The valve system 138 is configured to switch from the first configuration to the second configuration in the event of a loss of pressure in the control pipe 140, i.e. when the control fluid pressure in the control pipe 140 falls below a predetermined threshold. Advantageously, the valve system 138 is also configured to return to the first configuration when the pressure in the control pipe 140 is restored, i.e. when the control fluid pressure in the control pipe 140 returns above said predetermined threshold.

[0073] Here, the valve system 138 consists of a six-way valve 158 with two primary ways 160, 161 fluidly connected to the cylinder branch 130, two secondary ways 164, 165 fluidly connected to the main branch 134, and two tertiary ways 166, 167 fluidly connected to the auxiliary branch 136. In particular: - a first primary way 160 is fluidly connected to the first cylinder line 142, - a second primary channel 161 is fluidically connected to the second cylinder line 144, - a first secondary line 164 is fluidically connected to the first main line 146, - a second secondary line 165 is fluidically connected to the second main line 148, - a first tertiary channel 166 is fluidically connected to the first auxiliary pipe 152, and - a second tertiary channel 167 is fluidically connected to the second auxiliary pipe 154.

[0074] The six-way valve 158 has a first configuration in which the primary ports 160, 161 are fluidically connected to the secondary ports 164, 165, the tertiary ports 166, 167 being fluidically isolated from the primary and secondary ports 160, 161, 164, 165. In particular, in this first configuration the first primary port 160 is fluidically connected to the first secondary port 164 so that the control fluid can flow in both directions, and the second primary port 161 is fluidically connected to the second secondary port 165 so that the control fluid can flow in both directions. In addition, the first tertiary port 166 is advantageously fluidically connected to the second tertiary port 167.

[0075] This first configuration of the six-way valve 158 constitutes the first confi- 138 valve system configuration.

[0076] The six-way valve 158 also has a second configuration in which the primary ports 160, 161 are fluidly connected to the tertiary ports 166, 167, the secondary ports 164, 165 being fluidly isolated from the primary and secondary ports 160, 161, 166, 167. In particular, in this second configuration the first primary port 160 is fluidly connected to the first tertiary port 166 and the second primary port 161 is fluidly connected to the second tertiary port 167. In addition, the first and second secondary ports 164, 165 are advantageously each closed.

[0077] This second configuration of the six-way valve 158 constitutes the second configuration of the valve system 138.

[0078] The six-way valve 158 is configured to switch from the first to the second configuration in the event of a loss of pressure in the control pipe 140. Advantageously, the six-way valve 158 is also configured to return to the first configuration when the pressure in the control pipe 140 is restored.

[0079] For this purpose, the six-way valve 158 is for example produced, as shown, in the form of a slide valve with a valve body 170 delimiting the ways 160, 161, 164, 165, 166, 167 and a slide 172 mounted movably inside the valve body 170. The slide 172 has passages formed inside and is movable relative to the valve body 170 between a first position, shown in [Fig. 3], in which the passages connect the ways 160, 161, 164, 165, 166, 167 in accordance with the first configuration of the six-way valve 158, and a second position (not shown) in which the passages connect the ways 160, 161, 164, 165, 166, 167 in accordance with the second configuration of the six-way valve 158. The slide valve also includes a return member 174, typically a spring, biasing the slide 172 towards its second position.It also comprises a counterbalancing cylinder 176 with a chamber (not shown) fluidically connected to the control pipe 140 and a piston (not shown) integral with the slide 172 and configured so that the pressure exerted on the latter by the fluid contained in the chamber is oriented in a direction opposite to that of the stress of the return member 174. The counterbalancing cylinder 176 and the return member 174 are dimensioned so that the force exerted by the counterbalancing cylinder 176 on the slide 172 prevails over that exerted by the return member 174 and maintains the slide 172 in its first position if and only if the pressure of the control fluid in the control pipe 140 is greater than the predetermined threshold.

[0080] As a variant (not shown), the six-way valve 158 is produced in any other form suitable for fulfilling the aforementioned functions.

[0081] Preferably, the control pipe 140 is constituted, as shown, by a independent pipe fluidly connected to a third rotating port 178 of the rotating fluid transfer mechanism 124. Alternatively (not shown), the control pipe 140 is constituted by an independent pipe fluidly connected to one of the first and second rotating ports 147, 149 of the rotating fluid transfer mechanism 124, or by one of the first and second main pipes 146, 148.

[0082] The main source 122 comprises a pressure generator 180 for bringing the control fluid to a third pressure higher than the first and second pressures. It also comprises a pressure control unit 182 for adjusting the pressure of the control fluid in the fluid chambers 92, 94 by means of the third pressure.

[0083] The third pressure is greater than the pressure threshold in the control pipe 140 below which the valve system 138 switches to the second configuration.

[0084] The pressure generator 180 comprises for example a pump capable of pumping the fluid to bring it to the third pressure, for example 100 bars. A pressure relief valve (not shown) makes it possible to evacuate a portion of the control fluid to a return line (not shown) when the pressure of the control fluid downstream of the pressure generator 180 exceeds the third pressure.

[0085] The pressure control unit 182 is supplied with control fluid at the third pressure by the pressure generator 180. It is fluidically connected to the large pitch chamber 92 and to the small pitch chamber 94 via the rotating fluid transfer mechanism 124 and the fluid circuit 120. It is capable of distributing the control fluid between the large pitch chamber 92 and the small pitch chamber 92 so as to adjust the fluid pressure inside each of these chambers 92, 94 and, thus, adjust the position of the movable part 82 between its first and second positions.

[0086] For this purpose, the pressure control unit 182 comprises an inlet port 184 fluidly connected to an outlet of the pressure generator 180, a first distribution port 185 fluidly connected to a first fixed port 186 of the rotating fluid transfer mechanism 124, and a second distribution port 187 fluidly connected to a second fixed port 188 of the rotating fluid transfer mechanism 124. It also comprises an inlet 190 for receiving a control signal 192 from the control module 128. It is configured to fluidly connect the inlet port 184 selectively to one of the first and second distribution ports 185, 187 as a function of the received control signal 192.

[0087] Here, the pressure control unit 182 is also capable of discharging control fluid from the fluid chambers 92, 94 into the return line. For this purpose, it also comprises an outlet port 194 fluidly connected to the line return and is configured to connect said output port 194: - to the second distribution port 187 when the first distribution port 185 is fluidically connected to the input port 184, and - to the first distribution port 185 when the second distribution port 187 is fluidically connected to the inlet port 184.

[0088] In the example shown, the pressure control unit 182 also comprises a control port 196 fluidly connected to a third fixed port 198 of the rotating fluid transfer mechanism 124, the pressure control unit 182 being configured to fluidly connect this control port 196 to the inlet port 184 so that the pressure of the control fluid at said control port 196 is an image of the pressure of the control fluid at the outlet of the pressure generator 180 and is preferably substantially equal to the latter. Advantageously, the pressure control unit 182 is also configured to selectively fluidly isolate said control port 196 from the inlet port 184 upon command from the module 128.

[0089] The rotating fluid transfer mechanism 124 comprises a fixed body 200 secured to the casing 20 and a rotating body 202 secured to the hub 55 of the fan rotor 54. The fixed body 200 delimits the fixed ports 186, 188, 198 and the rotating body 202 delimits the rotating ports 147, 149, 178. Channels (not shown) are provided inside the fixed body 200 and the rotating body 202, these channels being configured to fluidly connect to each other, regardless of the angular position of the rotating body 202 relative to the fixed body 200: - the first fixed port 186 and the first rotating port 147, - the second fixed port 188 and the second rotating port 149, and - the third fixed port 198 and the third rotating port 178.

[0090] Thus, the first connection port 185 of the pressure control unit 182 is fluidically connected, via the rotating fluid transfer mechanism 124, to the first main pipe 146, the second connection port 187 of the pressure control unit 182 is fluidically connected, via the rotating fluid transfer mechanism 124, to the second main pipe 148, and the control port 196 is fluidically connected, via the rotating fluid transfer mechanism 124, to the control pipe 140.

[0091] The rotating fluid transfer mechanism 124 consists for example of an oil transfer bearing as described in document WO 2022 / 195191 AL

[0092] The auxiliary source 126 comprises a pump 210 for driving the control fluid in the fluid circuit 120. Said pump 210 comprises a pump body 212 delimiting the first and second auxiliary ports 153, 155. This pump body 212 is integral with the hub 55 of the fan rotor 54. Said pump 210 also comprises a pump rotor 214 mounted to rotate relative to the pump body 212 such that rotation of said rotor 214 relative to the pump body 212 causes movement of the control fluid from one to the other of the first and second auxiliary ports 153, 155.

[0093] The auxiliary source 126 also comprises a drive mechanism 220 for driving the rotation of the pump rotor 214 relative to the pump body 212. This drive mechanism 220 here comprises a kinematic chain 222 kinematically coupling the pump rotor 214 to the casing 20 of the gas turbine engine 12 so that the rotation of the fan rotor 54 relative to said casing 20 jointly drives the rotation of the pump rotor 214 relative to the pump body 212. For example, said kinematic chain 222 comprises a shaft 224 secured to the pump rotor 214 and the casing 20 so that the pump rotor 214 is fixed in rotation about the longitudinal axis X relative to the casing 20.

[0094] Alternatively (not shown), the drive mechanism 220 comprises an electric motor.

[0095] The drive mechanism 220 is in particular configured to drive the rotation of the pump rotor 214 relative to the pump body 212 in a direction such that said rotation causes the movement of the control fluid from the second auxiliary port 155 to the first auxiliary port 153. Thus, the pump 210 drives the control fluid in the auxiliary branch 136 from the second auxiliary conduit 154 to the first auxiliary conduit 152.The valve system 138 being further configured to fluidly connect the first cylinder line 142 to the first auxiliary line 152 and the second cylinder line 144 to the second auxiliary line 154 when it is in its second configuration, and the first cylinder line 142 being fluidly connected to the large pitch chamber 92, the fluid circuit 120 is therefore configured so that the pump 210 supplies the control cylinder 74 so as to cause the blades 56 to pivot towards their flag position.

[0096] The control module 128 is configured to receive a setting instruction 230 and a measurement 232 of the setting angle of the blades 56. It is also configured to deduce from this instruction 230 and from this measurement 232 the control signal 192 transmitted to the pressure control unit 182.

[0097] In particular, the control module 128 is configured so that the control signal 192 transmitted to the pressure control unit 182 commands: - an increase in the fluid pressure in the large pitch chamber 92 when the angle measurement 232 is less than the setting instruction 230, and - an increase in the fluid pressure in the small pitch chamber 94 when the angle measurement 232 is greater than the setting instruction 230.

[0098] The control module 128 is also configured so that the signal of command 192 transmitted to the pressure control unit 182 commands isolation of the witness port 196 in certain circumstances, for example when a failure of the pilot system 78 is detected.

[0099] A method of changing the pitch of the blades 56, implemented by the pitch changing mechanism 70 of [Fig. 3], will now be described.

[0100] In the initial state, the pressure generator 180 is functional and the pressure control unit 182 fluidly connects the control port 196 to the inlet port 184. The valve system 138 is therefore in its first configuration, such that the first distribution port 185 is fluidly connected to the large pitch chamber 92 and the second distribution port 187 is fluidly connected to the small pitch chamber 90. The auxiliary branch 136 is fluidly isolated from the rest of the fluid circuit 120 and forms a closed loop inside which the pump 210, actuated by the rotation of the fan rotor 54 relative to the casing 20, drives the control fluid.

[0101] In a first step of this method, the control module 128 first receives a setting instruction 230 giving a setting angle greater than that of the measurement 232. The control module 135 then transmits to the pressure control unit 182 a control signal 192 intended to increase the fluid pressure in the large pitch chamber 92. The pressure control unit 182 then fluidically connects the first distribution port 185 to the inlet port 184 and the second distribution port 187 to the outlet port 194, which has the effect of increasing the fluid pressure in the large pitch chamber 92 relative to the small pitch chamber 94. As the fluid pressure in the large pitch chamber 92 increases, the movable part 82 of the cylinder 74 moves towards its first position, which, via the connection system 76, causes the pivoting of the blades 56 towards the large steps (i.e. towards the flag position).

[0102] Once the measurement 232 is equal to the setting instruction 230, the control module 135 transmits to the pressure control unit 182 a control signal 192 intended to stabilize the pressure in the chambers 92, 94 of the cylinder 74. The pressure control unit 182 then fluidically isolates the first and second distribution ports 185, 187 from the inlet port 184 and from the outlet port 194. Without a new supply of the chambers 92, 94 with control fluid, the fluid pressure in said chambers 92, 94 equilibrates, which stops the movement of the movable part 82 and immobilizes the blades 56 in a fixed orientation.

[0103] During a second step of the pitch change method, the control module 128 receives a setting instruction 230 giving a setting angle less than that of the measurement 232. The control module 135 then transmits to the pressure control unit 182 a control signal 192 intended to increase the fluid pressure in the small pitch chamber 94. The pressure control unit 182 then fluidically connects the second distribution port 187 to the inlet port 184 and the first distribution port 185 to the outlet port 194, which has the effect of increasing the fluid pressure in the small pitch chamber 94 relative to the large pitch chamber 92. As the fluid pressure in the small pitch chamber 94 increases, the movable part 82 of the cylinder 74 moves to its second position, which, via the connection system 76, causes the blades 56 to pivot towards the small pitches (i.e. towards the sail position).

[0104] Once the measurement 232 is equal to the setting instruction 230, the control module 135 transmits to the pressure control unit 182 a control signal 192 intended to stabilize the pressure in the chambers 92, 94 of the cylinder 74. The pressure control unit 182 then fluidically isolates the first and second distribution ports 185, 187 from the inlet port 184 and from the outlet port 194. Without a new supply of the chambers 92, 94 with control fluid, the fluid pressure in said chambers 92, 94 equilibrates, which stops the movement of the movable part 82 and immobilizes the blades 56 in a fixed orientation.

[0105] Optionally, the pitch change method also comprises, following the first or second step, a controlled step of securing the blades 56.

[0106] During this step, the control module 128 transmits to the pressure control unit 182 a command to secure the blades 56. Under the effect of this command, the pressure control unit 182 fluidically connects the indicator port 196 to the outlet port 194, causing a drop in the fluid pressure in the indicator pipe 140.

[0107] The valve system 138 then switches to its second configuration, fluidly isolating the main branch 134 from the rest of the fluid circuit 120 and fluidly connecting the auxiliary branch 136 to the cylinder branch 130. The pump 210, which is still actuated by the rotation of the fan rotor 54 relative to the casing 20, then instantaneously drives the control fluid towards the large pitch chamber 92, via the first auxiliary line 152 and the first cylinder line 142, by sucking it from the small pitch chamber 94 via the second cylinder line 144 and the second auxiliary line 154. This has the effect of increasing the fluid pressure in the large pitch chamber 92 relative to the small pitch chamber 94.

[0108] As the fluid pressure in the large pitch chamber 92 increases, the movable part 82 of the cylinder 74 moves towards its first position, which, via the connecting system 76, causes the blades 56 to pivot towards the large pitches (i.e. towards the flag position). This movement continues until the movable part 82 reaches its stop in its first position, the blades 56 being in flag position.

[0109] In the event of a malfunction of the control system 78, typically in the event of a breakdown of the pressure generator 180 or in the event of a leak at the level of the rotating fluid transfer mechanism 124, the pitch change method comprises an additional non-controlled step of securing the blades 56.

[0110] During this step, the malfunction of the control system 78 causes a drop in the fluid pressure in the control pipe 140, typically because the pressure generator 180 is no longer able to bring the control fluid to the third pressure or because the pressure loss through the rotating fluid transfer mechanism 124 is too great.

[0111] The valve system 138 then switches to its second configuration, fluidly isolating the main branch 134 from the rest of the fluid circuit 120 and fluidly connecting the auxiliary branch 136 to the cylinder branch 130. The pump 210, which is still actuated by the rotation of the fan rotor 54 relative to the casing 20, then instantaneously drives the control fluid towards the large pitch chamber 92, via the first auxiliary line 152 and the first cylinder line 142, by sucking it from the small pitch chamber 94 via the second cylinder line 144 and the second auxiliary line 154. This has the effect of increasing the fluid pressure in the large pitch chamber 92 relative to the small pitch chamber 94.

[0112] As the fluid pressure in the large pitch chamber 92 increases, the movable part 82 of the cylinder 74 moves towards its first position, which, via the connecting system 76, causes the blades 56 to pivot towards the large pitches (i.e. towards the flag position). This movement continues until the movable part 82 reaches a stop in its first position, the blades 56 being in the flag position.

[0113] A variant of the pitch change mechanism 70 will now be described, with reference to [Fig.4].

[0114] The description of the variant of [Fig. 3] applies in full to the variant of [Fig. 4]. This latter variant differs from that of [Fig. 3] in that the pitch change mechanism 70 further comprises a pitch locking device 240 for locking the angular position of the blades 56.

[0115] This pitch locking device 240 comprises a locking mechanism 242 having a first configuration (not shown) in which the movable part 82 of the control cylinder 74 is free to move relative to the fixed part 80 and a second configuration (not shown) in which the locking mechanism 242 is engaged with the movable part 82 so as to immobilize the movable part 82 relative to the fixed part 80. The pitch locking device 240 also comprises an engagement mechanism 244 configured to tilt the locking mechanism 242 of the first configuration in the second configuration in the event of a loss of pressure in the control pipe 140, i.e. when the control fluid pressure in the control pipe 140 falls below a predetermined threshold. This predetermined threshold is typically equal to the switching threshold of the valve system 138 in the second configuration.

[0116] This engagement mechanism 244 comprises a return member (not shown), typically a spring, urging the locking mechanism 242 towards its second configuration. It also comprises a chamber 246 fluidly connected to the control pipe 140 and a piston 248 secured to the locking mechanism 242. The chamber 246 is in contact with said piston 248 so that the fluid contained in said chamber 246 exerts on the piston 248 a pressure oriented in a direction opposite to that of the urging of the return member.The chamber 246, the piston 248 and the return member are dimensioned so that the force exerted by the fluid contained in the chamber 246 on the piston 248 and, via this, on the locking mechanism 242 prevails over that exerted by the return member and maintains the locking mechanism 242 in its first configuration if and only if the pressure of the control fluid in the chamber 246 is greater than the predetermined threshold.

[0117] In order to allow the blades 56 to be feathered and to prevent them from locking in the event of a loss of pressure in said control pipe 140, the pitch change mechanism 70 also comprises an additional pipe 250 fluidly connecting the auxiliary branch 136 to the chamber 246, as well as a first maximum pressure sampling mechanism 252 configured to fluidly connect the chamber 246 to that of the additional pipe 250 and the control pipe 140 having the highest pressure by fluidly isolating it from the other. This first maximum pressure sampling mechanism 252 is here constituted by a first shuttle valve.

[0118] In the example shown, the additional pipe 250 is fluidically connected to the auxiliary branch 136 via a second maximum pressure sampling mechanism 254 configured to place the additional pipe 250 in fluid communication with that of the first and second auxiliary pipes 152, 154 in which the pressure of the control fluid is the highest by isolating the additional pipe 250 from the other auxiliary pipe 152, 154. This second maximum pressure sampling mechanism 254 here consists of a second shuttle valve. Alternatively (not shown), the additional pipe 250 is directly fluidically connected to the first upstream auxiliary pipe 152.

[0119] A method of changing the pitch of the blades 56, implemented by the pitch changing mechanism 70 of [Fig.4], will now be described.

[0120] In the initial state, the pressure generator 180 is functional and the pressure control unit 182 fluidly connects the control port 196 to the inlet port 184. The valve system 138 is therefore in its first configuration, such that the first distribution port 185 is fluidly connected to the large pitch chamber 92 and the second distribution port 187 is fluidly connected to the small pitch chamber 90. The auxiliary branch 136 is fluidly isolated from the rest of the fluid circuit 120 and forms a closed loop inside which the pump 210, actuated by the rotation of the fan rotor 54 relative to the casing 20, drives the control fluid. As for the locking mechanism 242 of the pitch locking device 240, it is in its first configuration.

[0121] During a first step of this method, the control module 128 first receives a setting instruction 230 giving a setting angle greater than that of the measurement 232. This first step takes place in an identical manner to that of the pitch change method implemented by the pitch change mechanism 70 of [Fig. 3],

[0122] During a second step of the pitch change method, the control module 128 receives a setting instruction 230 giving a setting angle less than that of the measurement 232. This second step takes place in an identical manner to that of the pitch change method implemented by the pitch change mechanism 70 of [Fig.3].

[0123] Optionally, the pitch change method also comprises, following the first or second step, a controlled step of securing the blades 56.

[0124] During this step, the control module 128 transmits to the pressure control unit 182 a command to secure the blades 56. Under the effect of this command, the pressure control unit 182 fluidically connects the indicator port 196 to the outlet port 194, causing a drop in the fluid pressure in the indicator pipe 140.

[0125] The pressure in the additional pipe 250 thus becomes greater than the pressure in the control pipe 140, which has the effect of causing the first maximum pressure sampling mechanism 252 to switch into a new configuration in which it fluidly connects the chamber 246 to the additional pipe 250 by fluidly isolating it from the control pipe 140. The pressure in the chamber 246 is then equal to that in the additional pipe 250. Depending on this pressure (lower or higher than the threshold pressure), the locking mechanism 242 is maintained in its first unlocked configuration or switches into its second locked configuration.

[0126] Simultaneously, the valve system 138 switches to its second configuration under the effect of the pressure loss in the control pipe 140, fluidly isolating the main branch 134 from the rest of the fluid circuit 120 and fluidly connecting the auxiliary branch 136 to the cylinder branch 130. The pump 210, which is actuated by the rotation of the fan rotor 54 relative to the casing 20, then instantaneously drives the control fluid towards the large pitch chamber 92, via the first auxiliary pipe and the first cylinder pipe 142, by sucking it from the small pitch chamber 94 via the second cylinder pipe 144 and the second auxiliary pipe 154. This has the effect of increasing the fluid pressure in the large pitch chamber 92 relative to the small pitch chamber 94.

[0127] In the case where the locking mechanism 242 has switched to the locked configuration, the increase in pressure in the large pitch chamber 92 does not, however, have the effect of causing a displacement of said movable part 82, the movable part 82 of the jack 74 not being able to move due to the action of the locking mechanism 242. The pressure in the large pitch chamber 92 and in the first auxiliary pipe 152 (which is transmitted to the chamber 246 of the engagement mechanism 244 via the shuttle valves 252, 254 and the additional pipe 250) then increases progressively, until it reaches a value sufficient for the pressure in the chamber 246 of the engagement mechanism 244 to counterbalance the stress of the return device and return the locking mechanism to its first unlocked configuration.

[0128] It will be noted that, in the event of a failure of the pump 210, the pressure in the additional pipe 250 cannot be raised to a level sufficient to restore the pressure in the chamber 246 above the threshold pressure. The locking mechanism 242 then remains in its second configuration locking the orientation of the blades 56 and can only be released by a pressure command at the level of the control pipe 140.

[0129] Thus, in all cases (locking mechanism 242 maintained in unlocked configuration or switched to unlocked configuration) and excluding failure of the pump 210, a stage is reached where the locking mechanism 242 is in unlocked configuration (because it has remained in this configuration or because it has returned to it) and where the fluid pressure in the large pitch chamber 92 is greater than that in the small pitch chamber 94. Under the effect of this greater fluid pressure in the large pitch chamber 92, the movable part 82 of the cylinder 74 then moves towards its first position. This causes, via the connecting system 76, the pivoting of the blades 56 towards the large pitches (i.e. towards the flag position). This movement continues until the movable part 82 reaches the stop in its first position, the blades 56 being in the flag position.

[0130] In the event of a malfunction of the control system 78, typically in the event of failure of the pressure generator 180 or in the event of a leak at the level of the rotating fluid transfer mechanism 124, the pitch change method comprises an additional non-controlled step of securing the blades 56.

[0131] During this step, the malfunction of the control system 78 causes a drop in the fluid pressure in the control pipe 140, typically because the pressure generator 180 is no longer able to bring the control fluid to the third pressure or because the pressure loss through the rotating fluid transfer mechanism 124 is too great.

[0132] The pressure in the additional pipe 250 thus becomes greater than the pressure in the control pipe 140, which has the effect of causing the first maximum pressure sampling mechanism 252 to switch into a new configuration in which it fluidly connects the chamber 246 to the additional pipe 250 by fluidly isolating it from the control pipe 140. The pressure in the chamber 246 is then equal to that in the additional pipe 250. Depending on this pressure (lower or higher than the threshold pressure), the locking mechanism 242 is maintained in its first unlocked configuration or switches into its second locked configuration.

[0133] Simultaneously, the valve system 138 switches to its second configuration under the effect of the pressure loss in the control pipe 140, fluidly isolating the main branch 134 from the rest of the fluid circuit 120 and fluidly connecting the auxiliary branch 136 to the cylinder branch 130. The pump 210, which is actuated by the rotation of the fan rotor 54 relative to the casing 20, then instantaneously drives the control fluid towards the large pitch chamber 92, via the first auxiliary pipe and the first cylinder pipe 142, by sucking it from the small pitch chamber 94 via the second cylinder pipe 144 and the second auxiliary pipe 154. This has the effect of increasing the fluid pressure in the large pitch chamber 92 relative to the small pitch chamber 94.

[0134] In the case where the locking mechanism 242 has switched to the locked configuration, the increase in pressure in the large pitch chamber 92 does not, however, have the effect of causing a displacement of said movable part 82, the movable part 82 of the jack 74 not being able to move due to the action of the locking mechanism 242. The pressure in the large pitch chamber 92 and in the first auxiliary pipe 152 (which is transmitted to the chamber 246 of the engagement mechanism 244 via the shuttle valves 252, 254 and the additional pipe 250) then increases progressively, until it reaches a value sufficient for the pressure in the chamber 246 of the engagement mechanism 244 to counterbalance the stress of the return device and return the locking mechanism to its first unlocked configuration.

[0135] It will be noted that, in the event of a failure of the pump 210, the pressure in the additional pipe 250 cannot be raised to a level sufficient to restore the pressure in the chamber 246 above the threshold pressure. The locking mechanism 242 then remains in its second configuration locking the orientation of the blades 56 and can only be released by a pressure command at the level of the control pipe 140.

[0136] Thus, in all cases (locking mechanism 242 maintained in unlocked configuration or switched to unlocked configuration) and excluding failure of the pump 210, a stage is reached where the locking mechanism 242 is in unlocked configuration (because it has remained in this configuration or because it has returned to it) and where the fluid pressure in the large pitch chamber 92 is greater than that in the small pitch chamber 94. Under the effect of this greater fluid pressure in the large pitch chamber 92, the movable part 82 of the cylinder 74 moves towards its first position. This causes, via the connecting system 76, the vanes 56 to pivot towards the large pitches (i.e. towards the flag position). This movement continues until the movable part 82 reaches the stop in its first position, the vanes 56 being in the flag position.

[0137] Thanks to the invention described above, failures at the level of the rotating fluid transfer mechanism 124 do not impact the operation of the auxiliary source 126. The common failure modes between the auxiliary source 126 and the main source 122 are thus reduced, which increases the availability of the blade safety system 56. This increase in availability is also achieved without impact on the mass (or with minimal impact) since the mass of the auxiliary source 126 is comparable whether it is mounted on the casing 20 or on the hub 55 of the fan rotor 54.

[0138] Furthermore, thanks to the continuous drive of the pump 210 by the rotation of the fan rotor 54, the auxiliary source 126 can instantly take over from the main source 122, which makes it possible to do without a pitch locking device and therefore a weight saving.

[0139] Finally, the mechanical drive of the pump 210 by the rotation of the fan rotor 54 makes it possible to dispense with the need for an electric motor mounted on the fan rotor 54, which avoids the problems of power supply and control of such a motor and again allows a weight saving.

Claims

Claims

1. Fan rotor (54) for a gas turbine engine (12), comprising a hub (55), a plurality of variable-pitch blades (56) each pivotable relative to the hub (55) about a specific pivot axis (P), and a pitch-changing mechanism (70) for adjusting an angular position of each of the blades (56) about its respective pivot axis (P), the pitch-changing mechanism (70) comprising: - a control cylinder (74) with a fixed part (80) secured to the hub (55), and a movable part (82) movable relative to the fixed part (80), - a connecting system (76) connecting the movable part (82) to each variable-pitch blade (56) so as to convert a displacement of the movable part (82) relative to the fixed part (80) into a rotation of the variable-pitch blade (56) about the axis pivoting (P),- a fluid circuit (120) for supplying the control cylinder (74) with control fluid to control the movement of the movable part (82) relative to the fixed part (80), and - a pump (210) for driving the control fluid in the fluid circuit (120), in which the pump (210) comprises a pump body (212) secured to the hub (55).,

2. The fan rotor (54) of claim 1, wherein the pump (210) comprises a pump rotor (214) rotatably mounted relative to the pump body (212), the fan rotor (54) further comprising a drive train (222) configured to couple the pump rotor (214) to a casing (20) of the gas turbine engine (12) such that rotation of the fan rotor (54) relative to said casing (20) jointly drives rotation of the pump rotor (214) relative to the pump body (212).

3. A fan rotor (54) according to claim 1 or 2, wherein each blade (56) is movable about its pivot axis (P) between a sail position and a flag position, the fluid circuit (120) being configured so that the pump (210) powers the control cylinder (74) so ​​as to cause the blades (56) to pivot towards their flag position.

4. A fan rotor (54) according to any preceding claim, wherein the fluid circuit (120) comprises a cylinder branch (130) in fluid communication with the control cylinder (74), a main branch (134) in fluid communication with a rotating fluid transfer mechanism (124) for transferring the control fluid between a housing (20) of the gas turbine engine (12) and the fan rotor (54), an auxiliary branch (136) in fluid communication with the pump (210), and a valve system (138) for fluidly connecting the cylinder branch (130) selectively to one of the main and auxiliary branches (134, 136).

5. The fan rotor (54) of claim 4, wherein the fluid circuit (120) comprises a witness line (140) that is in fluid communication with the rotating fluid transfer mechanism (124).

6. The fan rotor (54) of claim 5, wherein the valve system (138) has a first configuration in which the cylinder branch (130) is fluidly connected to the main branch (134) and a second configuration in which the cylinder branch (130) is fluidly connected to the auxiliary branch (136), the valve system (138) being configured to switch from the first configuration to the second configuration in the event of a loss of pressure in the control pipe (140).

7. A fan rotor (54) according to claim 5 or 6, wherein the pitch change mechanism (70) comprises a pitch lock device (240) with a locking mechanism (242) having a first configuration in which the movable portion (82) of the control cylinder (74) is free to move relative to the fixed portion (80) and a second configuration in which the locking mechanism (242) is engaged with the movable portion (82) so as to immobilize the movable portion (82) relative to the fixed portion (80), the pitch lock device (240) also comprising an engagement mechanism (244) configured to switch the locking mechanism (242) from the first configuration to the second configuration in the event of a loss of pressure in the control pipe (140).

8. A fan rotor (54) according to claim 7, comprising an additional conduit (250) fluidly connected to the auxiliary branch (136), wherein the engagement mechanism (244) comprises a return member urging the locking mechanism (242) towards its second configuration, a chamber (246) in contact with a piston (248) secured to the locking mechanism (242) so that the fluid contained in said chamber (246) exerts on the piston (248) a pressure oriented in a direction opposite to that of the urging of the return member, and a maximum pressure sampling mechanism (252) configured to fluidly connect the chamber (246) to that of the additional conduit (250) and the control pipe (140) having the highest pressure.

9. A gas turbine engine (12) comprising a fan rotor (54) according to any preceding claim.

10. A gas turbine engine (12) according to claim 9, comprising a casing (20) relative to which the fan rotor (54) is rotatably mounted, the pump (210) comprising a pump rotor (214) kinematically coupled to said casing (20) such that rotation of the fan rotor (54) relative to said casing (20) jointly drives rotation of the pump rotor (214) relative to the pump body (212).

11. An aircraft (10) comprising at least one gas turbine engine (12) according to claim 9 or 10.

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