Pitch change mechanism with fluidic circuit incorporating a pitch locking device

Abstract

This blower rotor (54) includes a plurality of blades (56) and a mechanism (70) for changing the pitch of the blades (56). The pitch-changing mechanism (70) includes a fluidic circuit (120) for supplying fluid to a cylinder (74). The fluidic circuit (120) includes a cylinder branch (130), a main branch (134), an auxiliary branch (136), and a valve system (138) for fluidly connecting the cylinder branch (130) selectively to one of the main (134) and auxiliary (136) branches. The valve system (138) has a control cylinder (74) immobilization configuration in which the cylinder branch (130) is fluidly isolated from the main (134) and auxiliary (136) branches. Figure for the abstract: Fig. 1

Description

Title of the invention: Pitch changing mechanism with fluidic circuit incorporating a pitch locking device. Field of the invention

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

[0002] A primary area of ​​application for the invention is that of unducted fan turbojets (better known by their English names "propfan", "open fan", "open rotor", and "unducted fan"). However, the invention also applies to turboprops with one or more propellers. Technological background

[0003] One of the ways currently being explored to improve the specific consumption of civil aircraft engines is the development of turbojets with unfaired fans, such as the one described in document FR 2 941 493. These turbojets include a conventional turboshaft engine gas generator, one or more turbine stages of which drive one or more unfaired 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 blades of this rotor(s), as in the case of conventional turboprop engines, have variable pitch, meaning that the angular position of these blades (called the pitch angle) can be modified during flight. As a reminder, the pitch angle of a blade corresponds to the angle, in a plane orthogonal to the blade's pivot axis, between the blade chord at 75% of the fan radius and a plane orthogonal to the fan's axis of rotation. It can vary from a value of 0°, corresponding to a so-called "sail" or "flat" position of the blade, to a value of 90°, corresponding to a so-called "flap" position of the blade. It can also take a value strictly less than 0°, typically approximately -5°, corresponding to a so-called "reverse" position of the blade.

[0005] As is known, this modification of the fan pitch angle during flight allows the engine thrust to be adjusted and the fan efficiency to be optimized according to the aircraft speed. Indeed, the fan speed is almost constant during all phases of operation, and it is the fan pitch that varies the thrust. Thus, during cruise flight, the fan blades are oriented such that The thrust is adjusted by minimizing the power drawn from the turbine shaft and fuel consumption, and by optimizing efficiency. Conversely, during takeoff, the blades are oriented to maximize thrust in order to accelerate and then lift off.

[0006] The blade orientation is commonly controlled by means of a pitch control mechanism comprising a control cylinder that is rotationally fixed to the fan hub. This control cylinder has a fixed part, which is translationally fixed to the fan hub, and another part that moves in translation along the fan axis. The translationally moving part is connected to the blade by a linkage system so as to convert the translation of the moving part into rotation of the variable-pitch blade. This control cylinder is generally a hydraulic cylinder supplied with fluid from a main source attached to the motor housing.This main source comprises, in a conventional manner, a pump for pressurizing the fluid, driven by the high-pressure body of the gas turbine via a gearbox, and a control unit for selectively directing the pressurized fluid exiting the pump to one or the other chamber of the control cylinder. A rotating fluid transfer mechanism ensures the transfer of the pressurized fluid between the casing and the blower rotor.

[0007] One difficulty encountered with variable-pitch blades is that, in the event of a malfunction of the primary power source, these blades tend, under their own centrifugal force, to move into a sail position. However, a blade stuck in this position generates little resistive torque and risks causing the engine to overspeed, with potential risks of engine damage. Furthermore, a blade stuck in this position also risks generating excessive and unacceptable drag for the aircraft's controllability and / or its range in the case of a diversionary mission.

[0008] To overcome this difficulty, it is known to use safety systems capable of returning the blades to the feathering position and / or preventing the variable-pitch blades from moving towards the small pitch position (i.e., towards the sail position) in the event of a failure of the main power source. Two main families of safety systems of this type can be distinguished: - 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 power source, typically an electric pump, attached of the casing intended to be activated in case 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 a movement of the cylinder towards the position in which the blades are in the flag position.

[0009] These solutions, however, are not entirely satisfactory. Indeed, in "passive" safety systems, the use of counterweights increases the weight of the blades, necessitating an oversized main power source and actuator. This results in an overall increase in the weight of the gas turbine engine, which consequently loses efficiency. And in "active" safety systems, it is necessary to provide a pitchlock device configured to engage with the moving part of the control actuator in the event of a main power source failure. This locks the blade pitch angle and thus prevents the blades from moving to the smaller pitch during the switchover from the main power source to the auxiliary power source. However, such a device is heavy and bulky. Description of the invention

[0010] One objective of the invention is to provide a compact solution for the safety shutdown of variable-pitch turbine blades in the event of a failure of the power supply system for the actuator controlling their orientation. Other objectives are to maximize the availability of the safety shutdown system, facilitate its maintenance, and minimize its impact on the weight of the turbomachine.

[0011] To this end, the invention relates, according to a first aspect, to a blower rotor for a gas turbine engine, comprising a hub, a plurality of variable-pitch blades each pivotable relative to the hub about its own pivot axis, and a pitch-changing mechanism for adjusting an angular position of each of the variable-pitch blades about its respective pivot axis, said pitch-changing mechanism comprising: - a frame attached to the hub, - a control cylinder with a fixed part attached to the frame and a movable part that can be moved relative to the fixed part, the fixed and movable parts of the control cylinder defining between them two fluidic chambers, each containing control fluid to control the movement of the movable part relative to the fixed part, - a linkage system connecting the moving part to the variable-pitch blade so as to convert a displacement of the moving part relative to the fixed part into a rotation of the variable-pitch blade around the pivot axis, - a fluidic circuit for supplying the control cylinder with control fluid to control the displacement of the moving part relative to the fixed part, the fluidic circuit comprising a cylinder branch in fluidic communication with the control cylinder, a main branch in fluidic communication with a main source of control fluid, an auxiliary branch in fluidic communication with an auxiliary source of control fluid, and a valve system for fluidly connecting the cylinder branch selectively to one of the main and auxiliary branches, the valve system having 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, - a pump, comprising the auxiliary control fluid source, including a pump body fixed to the hub and a pump rotor mounted to rotate freely relative to the pump body, and - an electric motor comprising a motor stator fixed to the hub and a motor rotor kinetically linked to the pump rotor for driving the pump rotor,

[0012] in which the valve system also has a control cylinder immobilization configuration in which the cylinder branch is fluidically isolated from the main branch and the auxiliary branch, each of the fluidic chambers of the control cylinder being fluidly isolated so as to prevent the control fluid from entering or leaving each of the fluidic chambers.

[0013] According to particular embodiments of the invention, the pitch change mechanism also has one or more of the following characteristics, taken individually or in any technically possible combination(s): - the valve system is configured to switch from the first configuration to the immobilization configuration in the event of a pressure loss in a test pipeline supplied by the main source; - the auxiliary source is configured to activate in case of pressure loss in the test pipeline; - the valve system is configured to switch from the immobilization configuration to the second configuration when fluid pressure in the auxiliary branch exceeds a predetermined threshold; - the valve system is configured to return from the second configuration to the immobilization configuration when the fluid pressure in the auxiliary branch falls below said predetermined threshold; the valve system includes a six-way valve with two primary ports fluidly connected to the cylinder branch, two secondary ports fluidly connected to the main branch, and two tertiary ports fluidly connected to the auxiliary branch; the valve system includes a first four-way valve with two primary ports fluidly connected to the cylinder branch and two secondary ports fluidly connected to the main branch, and a second four-way valve with two tertiary ports fluidly connected to the cylinder branch and two quaternary ports fluidly connected to the auxiliary branch; Each variable pitch blade is movable around its pivot axis between a sail position and a flag position, the fluidic circuit and the auxiliary source being configured so that, at least in a first mode, the auxiliary source supplies the control cylinder so as to cause a pivoting of the variable pitch blade towards its flag position; the fluidic circuit and the auxiliary source are configured so that, in a second mode, the auxiliary source supplies the control cylinder in order to cause a pivoting of the variable pitch blade towards its sail position; the cylinder branch includes a first cylinder line fluidly connected to a first of the fluidic chambers and a second cylinder line fluidly connected to a second of the fluidic chambers, and the auxiliary branch includes a first auxiliary line fluidly connected to a first port of the pump and a second auxiliary line fluidly connected to a second port of the pump, the pump being configured to draw fluid from one of the first and second ports and discharge this fluid to the other of the first and second ports, the valve system being configured to fluidly connect the first cylinder line to the first auxiliary line and the second cylinder line to the second auxiliary line when the cylinder branch is fluidly connected to the auxiliary branch; the pump is a bidirectional pump; The six-way valve has a first configuration in which the primary channels are fluidly connected to the secondary channels, the tertiary channels being fluidly isolated from the primary and secondary channels, a second configuration in which the primary channels are fluidly connected to the tertiary channels, the secondary channels being fluidly isolated from the primary and tertiary channels, and an intermediate configuration in which the primary, secondary and tertiary pathways are isolated from each other in pairs; - the six-way valve is configured to switch from the first configuration to the intermediate configuration in case of pressure loss in the test pipeline; - the six-way valve is configured to switch from the intermediate configuration to the second configuration when a fluid pressure in the auxiliary branch, in particular in one of the first and second auxiliary lines, exceeds a predetermined threshold; - the first four-way valve has a first configuration in which the primary channels are connected only to the secondary channels and a second configuration in which the primary channels are fluidically isolated from the secondary channels, and the second four-way valve has a first configuration in which the tertiary channels are isolated only from the quaternary channels and a second configuration in which the tertiary channels are fluidly connected to the quaternary channels, - the first four-way valve is configured to switch from the first to the second configuration in case of pressure loss in the test pipeline; - the second four-way valve is configured to switch from the first to the second configuration when a fluid pressure in the auxiliary branch, in particular in one of the first and second auxiliary lines, exceeds a predetermined threshold; - the fluidic circuit includes an accumulator to regulate the pressure in the auxiliary branch; - the pitch change mechanism includes a rotating fluid transfer mechanism to transfer the control fluid between the main source and the fluidic circuit; - the auxiliary source is positioned in an upstream end of the hub; and - the valve system is integral with the hub.

[0014] The invention also relates, according to a second aspect, to a gas turbine engine comprising a casing and a blower rotor according to the first aspect mounted movable in rotation relative to the casing.

[0015] According to a particular embodiment of the invention, the gas turbine engine also has the following characteristic: - the main source of control fluid is fixed in a reference point attached to the housing.

[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 features and advantages of the invention will become apparent from the following description, given solely by way of example and with reference to the accompanying drawings, in which: - Figure [1] is a top view of an aircraft according to an exemplary embodiment of the invention, - [Fig.2] is a simplified partial longitudinal cross-sectional view of a gas turbine engine from the aircraft of [Fig.1], - [Fig. 3] is a diagram of a pitch-changing mechanism for the gas turbine engine of [Fig. 2], according to a first variant, and - [Fig.4] is a diagram of the step change mechanism of [Fig.3], according to a second variant. Detailed description of an example of implementation

[0018] The aircraft 10 shown in [Fig.1] includes gas turbine engines 12 for propulsion.

[0019] In the example shown, the aircraft 10 is an airplane. It conventionally comprises a fuselage 14, a tail assembly 16, and two wings 18. The gas turbine engines 12 are two in number and are each housed under a respective wing 18. Alternatively (not shown), the gas turbine engines 12 are arranged along the fuselage 14, for example, near the tail assembly 16. In yet another alternative (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 can be seen in this Figure, the gas turbine engine 12 is elongated along a longitudinal axis X. It typically exhibits angular symmetry about said longitudinal axis X, that is to say, there is at least one angle for which the gas turbine engine is invariant under rotation about the longitudinal axis X.

[0022] Here and in the following, 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.

[0023] The gas turbine engine 12 conventionally comprises a casing 20, an internal channel 22 for circulating an airflow through the casing 20, a combustion chamber 24 housed in the channel 22, an engine 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 airflow through the vein 22.

[0025] The engine body 26 comprises a compressor 30, a turbine 32, and a drive shaft 34 coupling the turbine 32 to the compressor 30 for driving the compressor 30 by the turbine 32. The compressor 30 is located upstream of the combustion chamber 24 and supplies the combustion chamber 24 with compressed air. The turbine 32 is located downstream of the combustion chamber 24 and receives the exhaust gases exiting 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 housing 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 drive shaft 34 being a high-pressure shaft.

[0029] The low pressure body 40 includes 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 located upstream of the high-pressure compressor 30 and supplies the latter with compressed air. The low-pressure turbine 44 is located downstream of the high-pressure turbine 32 and receives the exhaust gases exiting the latter.

[0031] The low-pressure shaft 46 is guided in rotation relative to the housing 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 includes a blower 50 to drive the airflow into an external circulation channel 52 surrounding the casing 20. A primary airflow A (hot), consisting of the portion of the airflow driven into the internal circulation channel 22, is thus distinguished from a secondary airflow B (cold), consisting of the portion of the airflow driven into the external circulation channel 52.

[0034] The blower 50 includes a blower rotor 54. This blower rotor 54 is rotatably mounted relative to the housing 20 around the longitudinal axis X by means of a guide bearing 53. It includes a hub 55 provided with blower blades 56 extending substantially radially outwards from the hub 55. These vanes 56, when set in rotation, drive the airflow into the external circulation vein 52.

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

[0036] The blower rotor 54 is driven in rotation by the low-pressure turbine 44, via the low-pressure shaft 46. Preferably, this drive is achieved via a reduction gear (not shown) allowing the blower rotor 54 to rotate at a speed lower than that of the low-pressure shaft 46. Alternatively (not shown), this drive is direct, i.e., the blower rotor 54 is rotationally fixed to the low-pressure shaft 46.

[0037] In the example shown, the blower 50 also includes a blower stator 58 comprising fixed blades 59 arranged at the periphery of the housing 20, in the external circulation vein 52, along a plane orthogonal to the longitudinal axis X. This blower stator 58 is arranged here downstream of the blower rotor 54. In an alternative (not shown), the blower 50 includes, instead of the blower stator 58, a counter-rotating blower rotor.

[0038] Advantageously, the fan 50 is, as shown, unshod, i.e., the external circulation channel 52 has no peripheral delimitation. The turbomachine 12 is then constituted, as shown, by a turbojet with an unshod fan or, alternatively, by a turboprop. Alternatively (not shown), the external circulation channel 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 secondary flow rate B (cold) to the primary flow rate A (hot).

[0039] In the example shown, the gas turbine engine 12 is in particular of the "puller" type, that is to say, the fan 50 is located upstream of the internal circulation channel 22 and also drives the airflow into the latter. Alternatively (not shown), the gas turbine engine 12 is of the "pusher" type, that is to say, the fan 50 is located around the downstream half of the casing 20.

[0040] The blades 56 of the blower rotor 54 have variable pitch, that is to say, each blade 56 is mounted to pivot relative to the hub 55 about its own pivot axis P. This pivot axis P extends along 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 about 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 blower rotor 54 (and is therefore substantially parallel to the longitudinal axis X), and a so-called sail position, in in which the chord of the blade 56 is substantially contained within the 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 to that where the feathering position is located. Since the blades 56 are 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] To this end, each blade 56 is fixed, as seen in [Fig. 3], to a mounting piece 60 located at the base of the blade. This mounting piece 60 is rotatably mounted relative to the hub 55 around the pivot axis P. More precisely, the mounting 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 includes a pitch change mechanism 70 to adjust the pitch angle of each blade 56 around 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 includes a frame 72, a control cylinder 74, a linkage system 76 and a control system 78 for the cylinder 74.

[0045] The frame 72 is integral with the hub 55 and is typically made up of a part of the hub 55. It is thus fixed relative to the pivot axes P and mobile in rotation relative to the housing 20.

[0046] The control cylinder 74 comprises a fixed part 80, integral with the frame 72, and a movable part 82 that moves 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 about the longitudinal axis X through a small angle, for example on 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 includes in particular a body 84 forming one of the fixed part 80 and the moving part 82 and a piston 86 forming the other of the fixed part 80 and the moving part 82. Here, the body 84 forms the fixed part 80 and the piston 86 forms the moving part 82.

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

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

[0051] Here, the sum of the first and second volumes varies according to the position of the moving part 82 relative to the fixed part 80.

[0052] In an alternative (not shown), the control cylinder 74 is configured so that the sum of the first and second volumes is constant regardless of the position of the moving 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 fluidic chambers 92, 94. For this purpose, the internal cavity 90 and the piston 86 are typically designed so that the two fluidic chambers 92, 94 have the same cross-section.

[0053] The linkage system 76 connects the moving part 82 to each blade 56 so as to convert the translation of the moving part 82 along the longitudinal axis X and, where applicable, the rotation of the moving part 82 about the longitudinal axis X into a rotation of each blade 56 about its pivot axis P. In particular, the linkage system 76 connects the moving part 82 to each blade 56 so as to convert: - the translation of the moving part 82 along the longitudinal axis X towards its first position by a rotation of the variable-pitch blade 56 around the pivot axis P towards the flag position, and - the translation of the moving 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 fluidic chamber 92 will therefore be referred to hereafter as the "large pitch chamber," the increase in fluid pressure in said chamber causing a rotation of the blades 56 towards higher pitch angles, the second fluidic chamber 94 being called the "small pitch chamber" since the increase in fluid pressure in said chamber causes a rotation of the blades 56 towards lower pitch angles.

[0055] For this purpose, the linking system 76 includes a synchronizing ring 100 attached to the moving part 82 and, for each of the blades 56, a linking mechanism 102 of the blade 56 to the synchronizing ring 100.

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

[0057] Each linkage mechanism 102 comprises a first joint 106 integral with the moving part 82, a second joint 108 integral with the blade 56, away from the pivot axis P of said blade 56, and a linkage member 110 connecting the first joint 106 to the second joint 108.

[0058] The first joint 106 is carried by the synchronizing ring 100. Here it is constituted by a ball joint.

[0059] The second joint 108 is also formed 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 joint 106 and a second end (not referenced) articulated to the second joint 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 allows its length to be precisely adjusted when stopped so as to allow the pitch angle of each blade 56 to be controlled by the pitch change mechanism 70.

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

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

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

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

[0065] The cylinder branch 130 includes 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 134. 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 the main branch 134. In particular, the valve system 138 is configured to, in this first configuration, fluidly isolate the first auxiliary line 152 from the second auxiliary line 154.

[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 the auxiliary branch 136.

[0072] The valve system 138 also has an intermediate configuration (not shown) between the first and second configurations in which said valve system 138 fluidly isolates the cylinder branch 130 from the main branch 134 and the auxiliary branch 136 and fluidly isolates the cylinder lines 142, 144 from each other. In particular, in this intermediate configuration, the cylinder branch 130, the main branch 134, and the auxiliary branch 136 are all fluidly isolated from each other by the valve system 138. Preferably, the valve system 138 is also configured to fluidly isolate the first and second auxiliary lines 152, 154 from each other in this intermediate configuration.

[0073] The valve system 138 is configured to switch from the first configuration to the intermediate configuration in the event of a pressure loss in the test line 140, i.e., when the control fluid pressure in the test line 140 falls below a first predetermined threshold. Advantageously, the valve system 138 is also configured to return to the first configuration when the pressure in the test line 140 is restored, i.e., when the control fluid pressure in the test line 140 rises above said first predetermined threshold.

[0074] The valve system 138 is also configured to switch from the intermediate configuration to the second configuration when the fluid pressure in one of the lines 152, 154 of the auxiliary branch 136 exceeds a second predetermined threshold. Advantageously, the valve system 138 is also configured to return to the intermediate configuration when the fluid pressure in each of the lines 152, 154 of the auxiliary branch 136 falls below said second predetermined threshold.

[0075] It should be noted that, when the valve system 138 is in its intermediate configuration, said system 138 fluidly isolates each of the fluidic chambers 92, 94 of the control cylinder 74 so that it prevents the control fluid from entering or leaving each of said fluidic chambers 92, 94. The volume of control fluid contained in each of the fluidic chambers 92, 94 therefore remains substantially constant, thereby preventing the movement of the moving part 82 of the cylinder 80 and the pivoting of the vanes 56. The valve system 138 thus constitutes a pitch locking device 156 of the pitch change mechanism 70 having a cylinder 74 immobilization configuration constituted by the intermediate configuration.

[0076] Here, the valve system 138 consists of a six-way valve 158 with two primary ports 160, 161 fluidically connected to the cylinder branch 130, two secondary ports 164, 165 fluidly connected to the main branch 134, and two tertiary ports 166, 167 fluidly connected to the auxiliary branch 136. In particular: - a first primary channel 160 is fluidly connected to the first cylinder line 142, - a second primary channel 161 is fluidly connected to the second cylinder line 144, - a first secondary line 164 is fluidly connected to the first main line 146, - a second secondary line 165 is fluidly connected to the second main line 148, - a first tertiary line 166 is fluidly connected to the first auxiliary line 152, and - a second tertiary route 167 is fluidly connected to the second auxiliary conduit 154.

[0077] 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, while the tertiary ports 166, 167 are fluidly isolated from the primary and secondary ports 160, 161, 164, 165. In particular, in this first configuration, the first primary port 160 is fluidly connected to the first secondary port 164 so that the control fluid can flow in both directions, and the second primary port 161 is fluidly connected to the second secondary port 165 so that the control fluid can flow in both directions. Furthermore, the first and second tertiary ports 166, 167 are advantageously each closed.

[0078] This first configuration of the six-way valve 158 constitutes the first configuration of the valve system 138.

[0079] 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.

[0080] This second configuration of the six-way valve 158 constitutes the second configuration of the valve system 138.

[0081] The six-way valve 158 also has an intermediate configuration between the first and second configurations in which the primary ports 160, 161, secondary ports 164, 165 and tertiary ports 166, 167 are isolated from each other in pairs. In particular, in this intermediate configuration, each of the primary ports 160, 161, secondary ports 164, 165 and tertiary ports 166, 167 is closed.

[0082] The six-way valve 158 is configured to switch from the first configuration to the intermediate configuration in the event of a pressure loss in the test line 140. The six-way valve 158 is also configured to switch from the intermediate configuration to the second configuration when the fluid pressure in one of the lines 152, 154 of the auxiliary branch 136 exceeds the second predetermined threshold. Advantageously, the six-way valve 158 is also configured to return from the second configuration to the intermediate configuration when the fluid pressure in each of the lines 152, 154 of the auxiliary branch 136 falls below said second predetermined threshold, and from the intermediate configuration to the first configuration when the pressure in the test line 140 is restored.

[0083] To this end, the six-way valve 158 is, for example, made, as shown, in the form of a spool valve with a valve body 170 delimiting the ports 160, 161, 164, 165, 166, 167 and a spool 172 movably mounted inside the valve body 170. The spool 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 ports 160, 161, 164, 165, 166, 167 according to the first configuration of the six-way valve 158, and a second position (not shown) in which the passages connect the ports 160, 161, 164, 165, 166, 167 according to the second configuration of the valve six-way 158, and an intermediate position (not shown) between the first and second positions in which the passages connect the ways 160, 161, 164, 165, 166, 167 in accordance with the intermediate configuration of the six-way valve 158.

[0084] The spool valve also includes a return element 173, typically a spring, which forces the spool 172 towards its intermediate position, and a first counterbalancing cylinder 174 with a chamber (not shown) fluidically connected to the test line 140 and a piston (not shown) integral with the spool 172 and configured so that the pressure exerted on the spool by the fluid contained in the chamber is directed in the opposite direction to that of the force exerted on the return element 173 when the spool 172 is in its first position. The first counterbalancing cylinder 174 and the return element 173 are dimensioned so that the force exerted by the first counterbalancing cylinder 174 on the spool 172 overcomes that exerted by the return element 173 and maintains the spool 172 in its first position if and only if the pressure of the control fluid in the test line 140 is greater than the first predetermined threshold.

[0085] The spool valve further comprises a second counterbalancing cylinder 175 with a chamber (not shown) fluidically connected to an additional conduit 176 and a piston (not shown) integral with the spool 172 and configured so that the pressure exerted on the spool by the fluid contained in the chamber is oriented in the opposite direction to that of the excitation of the return member 173 when the spool 172 is in its second position. The second counterbalancing cylinder 175 and the return member 173 are dimensioned such that the force exerted by the second counterbalancing cylinder 175 on the spool 172 overcomes that exerted by the return member 173 and maintains the spool 172 in its second position if and only if the pressure of the control fluid in the additional conduit 176 is greater than the second predetermined threshold.

[0086] The additional line 176 is a line fluidically connected to the auxiliary branch 136 by means of a maximum pressure tapping mechanism 177 configured to put the additional line 176 into fluidic communication with that of the first and second auxiliary lines 152, 154 in which the control fluid pressure is highest by isolating the additional line 176 from the other auxiliary line 152, 154. In the example shown, this maximum pressure tapping mechanism 177 consists of a shuttle valve.

[0087] Alternatively (not shown), the six-way valve 158 is made in any other form suitable for fulfilling the aforementioned functions.

[0088] Preferably, the test pipe 140 is constituted, as shown, by an independent pipe fluidly connected to a third rotating port 178 of the rotating fluid transfer mechanism 124. Alternatively (not shown), the test 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.

[0089] The main source 122 includes a pressure generator 180 for raising the control fluid to a third pressure higher than the first and second pressures. It also includes a pressure control unit 182 for adjusting the pressure of the control fluid in the fluidic chambers 92, 94 by means of the third pressure.

[0090] 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.

[0091] The pressure generator 180 includes, for example, a pump capable of pumping the fluid to bring it to the third pressure, for example 100 bar. A pressure relief valve (not shown) allows a portion of the control fluid to be discharged to a return line (not shown) when the pressure of the control fluid downstream of the pressure generator 180 exceeds the third pressure.

[0092] 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 the small pitch chamber 94 via the rotating fluid transfer mechanism 124 and the fluidic 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 moving part 82 between its first and second positions.

[0093] For this purpose, the pressure control unit 182 includes 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 includes an input 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 depending on the control signal 192 received.

[0094] Here, the pressure control unit 182 is also capable of discharging control fluid from the fluidic chambers 92, 94 into the return line. For this purpose, it also includes an outlet port 194 fluidically connected to the return line and is configured to connect said outlet port 194: - to the second distribution port 187 when the first distribution port 185 is fluidly connected to the inlet port 184, and - to the first distribution port 185 when the second distribution port 187 is fluidly connected to the inlet port 184.

[0095] In the example shown, the pressure control unit 182 also includes a test 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 test port 196 to the inlet port 184 such that the control fluid pressure at said test port 196 is a reflection of the control fluid pressure at the outlet of the pressure generator 180 and is preferably substantially equal to the latter. Advantageously, the control unit pressure 182 is also configured to selectively fluidly isolate said witness port 56 from input port 184 on command from module 128.

[0096] The rotating fluid transfer mechanism 124 comprises a fixed body 200 integral with the housing 20 and a rotating body 202 integral with the hub 55 of the blower rotor 54. The fixed body 200 defines the fixed ports 186, 188, 198 and the rotating body 202 defines 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 connect fluidly 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.

[0097] Thus, the first connection port 185 of the pressure control unit 182 is fluidly connected, via the rotating fluid transfer mechanism 124, to the first main line 146, the second connection port 187 of the pressure control unit 182 is fluidly connected, via the rotating fluid transfer mechanism 124, to the second main line 148, and the sight port 196 is fluidly connected, via the rotating fluid transfer mechanism 124, to the sight line 140.

[0098] The rotating fluid transfer mechanism 124 consists, for example, of an oil transfer bearing as described in document WO 2022 / 195191 AL

[0099] The auxiliary source 126 includes a pump 210 for driving the control fluid in the fluidic circuit 120. Said pump 210 includes 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 blower rotor 54. Said pump 210 also includes a pump rotor 214 mounted to rotate freely relative to the pump body 212 such that the rotation of said rotor 214 relative to the pump body 212 causes the control fluid to move from one to the other of the first and second auxiliary ports 153, 155.

[0100] The auxiliary power source 126 also includes a drive mechanism 220 for driving the rotation of the pump rotor 214 relative to the pump body 212. This drive mechanism 220 includes an electric motor 222 whose stator (not shown) is fixed to the hub 55 of the blower rotor 54 and the rotor (not shown) is kinetically linked to the pump rotor 214 such that the rotation of the motor rotor 222 relative to its stator jointly drives the rotation of the pump rotor 214 relative to the pump body 212. This electric motor 222 is, for example, powered by a generator (not shown) driven by the rotation of the blower rotor 54 relative to the housing 20. Alternatively, the electric motor 222 is powered by a source attached to the housing 20.

[0101] The drive mechanism 220 is in particular configured to drive the rotation of the pump rotor 214 relative to the pump body 212 in such a direction that said rotation causes the control fluid to move 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 line 154 to the first auxiliary line 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 fluidic circuit 120 is therefore configured so that the pump 210 supplies the control cylinder 74 in such a way as to cause a pivoting of the vanes 56 towards their flag position.

[0102] Preferably, the drive mechanism 220 is reversible and can also drive the rotation of the pump rotor 214 relative to the pump body 212 in the opposite direction, so that said rotation causes the control fluid to move from the first auxiliary port 153 to the second auxiliary port 155. Thus, the pump 210 is bidirectional and also has a second operating mode in which it drives the control fluid in the auxiliary branch 136 from the first auxiliary line 152 to the second auxiliary line 154, so that the fluidic circuit 120 is also configured so that the pump 210 supplies the control cylinder 74 so as to cause the vanes 56 to pivot towards their sail position.

[0103] Advantageously, the auxiliary source 126 is configured so that the pump 210 is not flowing when the first and second auxiliary lines 152, 154 are fluidically isolated from each other, that is, in the example given here, when the valve system 138 is in its first configuration or in its intermediate configuration.

[0104] The auxiliary source 126 is advantageously positioned in an upstream end (not shown) of the hub 55 of the blower rotor 54. Such positioning is made possible by the space saving resulting from the absence of a mechanical pitch locking device permitted by the valve system 138. This positioning facilitates access to the auxiliary source 126 and its removal for maintenance.

[0105] The control module 128 is configured to receive a setting instruction 230 and a measurement 232 of the blade setting angle 56. It is also configured to deduce from this instruction 230 and this measurement 232 the control signal 192 transmitted to the pressure control unit 182.

[0106] 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 fluid pressure in the large pitch chamber 92 when the angle measurement 232 is less than the calibration instruction 230, and - an increase in fluid pressure in the small pitch chamber 94 when the angle measurement 232 is greater than the setting instruction 230.

[0107] The control module 128 is also configured so that the control signal 192 transmitted to the pressure control unit 182 commands an isolation of the witness port 196 under certain circumstances, for example when a failure of the pilot system 78 is detected.

[0108] The control module 128 is further configured to control the commissioning of the electric motor 222 in the event of failure of the control system 78.

[0109] In the example shown, the fluidic circuit 120 also includes an accumulator 236 to compensate for the variation in the sum of the volumes of the first and second fluidic chambers 92, 94 when the cylinder branch 130 operates in a closed circuit, which is typically the case when the valve system 138 is in its second configuration (cylinder branch 130 fluidically connected to the auxiliary branch 136). This accumulator 236 thus prevents cavitation of the pump 210.

[0110] To this end, the accumulator 236 is fluidically connected to the cylinder branch 130 in parallel with the control cylinder 74; that is, it has a first port 237 fluidly connected to the first cylinder line 142 and a second port 238 fluidly connected to the second cylinder line 144. It is further configured to deliver the additional volume of control fluid required when the sum of the volumes of the first and second fluidic chambers 92, 94 increases, and to limit the maximum pressure in the closed circuit when the sum of the volumes of the first and second fluidic chambers 92, 94 decreases. Those skilled in the art will readily be able to implement such an accumulator using their general knowledge.

[0111] A method for changing the pitch of the blades 56, implemented by the pitch changing mechanism 70 of [Fig.3], will now be described.

[0112] In the initial state, the pressure generator 180 is functional and the pressure control unit 182 fluidly connects the test 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 not 90. The auxiliary branch 136, however, is fluidically isolated from the rest of the fluidic circuit 120.

[0113] In a first step of this process, the control module 128 first receives a setting instruction 230 providing a setting angle greater than that of the measurement 232. The control module 135 then transmits a control signal 192 to the pressure control unit 182, intended to increase the fluid pressure in the large-pitch chamber 92. The pressure control unit 182 then fluidly 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 moving part 82 of the cylinder 74 moves to its first position, which, via the linkage system 76, causes the vanes to pivot. 56 towards the big strides (that is to say towards the flag position).

[0114] Once the measurement 232 equals the calibration instruction 230, the control module 135 transmits a control signal 192 to the pressure control unit 182 intended to stabilize the pressure in the chambers 92, 94 of the cylinder 74. The pressure control unit 182 then fluidly isolates the first and second distribution ports 185, 187 from the inlet port 184 and the outlet port 194. Without a new supply of control fluid to the chambers 92, 94, the fluid pressure in said chambers 92, 94 equilibrates, which stops the movement of the moving part 82 and immobilizes the vanes 56 in a fixed orientation.

[0115] During a second step of the pitch change process, the control module 128 receives a pitch instruction 230 specifying a pitch angle lower than that of measurement 232. The control module 135 then transmits a control signal 192 to the pressure control unit 182, intended to increase the fluid pressure in the small-pitch chamber 94. The pressure control unit 182 then fluidly connects the second distribution port 187 to the inlet port 184 and the first distribution port 185 to the outlet port 194, thereby 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 moving part 82 of the cylinder 74 moves to its second position, which, via the linkage system 76, causes the vanes to pivot. 56 towards small steps (that is to say towards the sail position).

[0116] Once the measurement 232 equals the calibration instruction 230, the control module 135 transmits a control signal 192 to the pressure control unit 182, intended to stabilize the pressure in the chambers 92, 94 of the cylinder 74. The pressure control unit 182 then fluidly isolates the first and second distribution ports 185, 187 of the inlet port 184 and of the outlet port 194. Without new supply of control fluid to chambers 92, 94, the fluid pressure in said chambers 92, 94 becomes balanced, which stops the movement of the moving part 82 and immobilizes the blades 56 in a fixed orientation.

[0117] Optionally, the pitch change process also includes, following the first or second step, a controlled step of locking the blades 56.

[0118] During this step, the control module 128 transmits to the pressure control unit 182 a command to disable the blades 56. Under the effect of this command, the pressure control unit 182 fluidly connects the test port 196 to the outlet port 194, causing a drop in fluid pressure in the test line 140.

[0119] This drop in fluid pressure in the test line 140 simultaneously causes a drop in pressure in the chamber of the first counterbalancing cylinder 174 of the six-way valve 158. This pressure is then no longer sufficient to counterbalance the load on the return element 173, which causes the six-way valve 158 to switch to its intermediate configuration. The fluid chambers 92, 94 of the control cylinder 74 are then fluidically isolated so that the control fluid can neither enter nor exit either of said fluid chambers 92, 94. The cylinder 74 is then immobilized and the pitch of the vanes 56 is locked until the control module 128 commands the unlocking of the vanes 56, either by restoring the pressure in the test line 140 or by activating the electric motor 222.

[0120] In the event of a malfunction of the pilot system 78, typically in the event of a 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 process includes an additional uncontrolled step of locking the blades 56.

[0121] During this step, the malfunction of the pilot system 78 causes a drop in fluid pressure in the test line 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.

[0122] This drop in fluid pressure in the test line 140 simultaneously causes a drop in pressure in the chamber of the first counterbalancing cylinder 174 of the six-way valve 158. This pressure is then no longer sufficient to counterbalance the load on the return element 173, which causes the six-way valve 158 to switch to its intermediate configuration. The fluid chambers 92, 94 of the control cylinder 74 are then fluidically isolated so that the control fluid can neither enter nor exit either of them. fluidic chambers 92, 94. The cylinder 74 is then immobilized and the angular position of the blades 56 is locked.

[0123] Preferably, this uncommanded step of locking the blades 56 is followed by a step of securing the blades 56 in the flag position.

[0124] During this step, the control module 128 commands the activation of the electric motor 222. The sending of this command is typically triggered by the detection, by the control module 128, of the malfunction of the pilot system 78. The pump 210 thus starts up.

[0125] The control is configured so that the electric motor 222 rotates in a first direction such that the pump 210 draws the control fluid towards the first auxiliary line 152 by sucking it from the second auxiliary line 154. This has the effect of increasing the fluid pressure in the first auxiliary line 152.

[0126] This pressure is transmitted to the additional line 176 via the maximum pressure sampling mechanism 177. The pressure in the additional line 176 thus passes above the second predetermined threshold, which causes the six-way valve 158 to switch to its second configuration: the first auxiliary line 152 is thus fluidly connected to the large pitch chamber 92 and the second auxiliary line 154 is fluidly connected to the small pitch chamber 94.

[0127] The fluid pressure in the large pitch chamber 92 is thus greater than the fluid pressure in the small pitch chamber 94.

[0128] The moving part 82 of the cylinder 74 then moves, under the effect of the greater fluid pressure in the large-pitch chamber 92, towards its first position, which, via the linkage system 76, causes the vanes 56 to pivot towards the large pitches (i.e., towards the flag position). This movement continues until the moving part 82 reaches its stop in its first position, the vanes 56 being in the flag position.

[0129] Once the blades 56 are in the flag position, the control module 128 commands the deactivation of the electric motor 222. The pump 210 stops, the pressure in the additional line 176 and in the chamber of the second counterbalancing cylinder 175 falls below the second predetermined threshold, and the six-way valve 158 returns to its intermediate configuration. The blades 56 are thus safely secured in the flag position and locked in this position.

[0130] This step of securing the blades 56 is advantageously followed by a step of moving the blades 56 out of the flag position, typically when the gas turbine engine is stopped.

[0131] During this step, the control module 128 sends a new activation command to the electric motor 222. The pump 210 thus starts up.

[0132] This new control is configured so that the electric motor 222 rotates in a second direction opposite to the first direction such that the pump 210 drives the control fluid towards the second auxiliary line 154, drawing it from the first auxiliary line 152. This has the effect of increasing the fluid pressure in the second auxiliary line 154.

[0133] This pressure is transmitted to the additional line 176 via the maximum pressure sampling mechanism 177. The pressure in the additional line 176 thus rises above the second predetermined threshold, which causes the six-way valve 158 to switch to its second configuration: the first auxiliary line 152 is then fluidly connected again to the large pitch chamber 92 and the second auxiliary line 154 is fluidly connected to the small pitch chamber 94.

[0134] The fluid pressure in the small pitch chamber 94 is thus greater than the fluid pressure in the large pitch chamber 92.

[0135] The moving part 82 of the cylinder 74 then moves, under the effect of the greater fluid pressure in the small-pitch chamber 94, to its second position, which, via the linkage system 76, causes the vanes 56 to pivot towards the small pitch (i.e., towards the sail position). This movement continues until the vanes 56 reach the desired position. Once this desired position is reached, the control module 128 commands the deactivation of the electric motor 222. The pump 210 stops, the pressure in the additional line 176 and in the chamber of the second counterbalancing cylinder 175 falls below the second predetermined threshold, and the six-way valve 158 returns to its intermediate configuration. The vanes 56 are thus locked in the desired position.

[0136] A variant of the pitch change mechanism 70 will now be described, with reference to [Fig.4].

[0137] The description of the variant in [Fig.3] applies in full to the variant in [Fig.4], except with regard to the details of the valve system 138. The latter variant differs from that of [Fig.3] in that the valve system 138 consists not of a six-way valve but of a set of two four-way valves 260, 262.

[0138] These valves 260, 262 comprise a first four-way valve 260 with two primary ports 264, 266 fluidly connected to the cylinder branch 130 and two secondary ports 268, 270 fluidly connected to the main branch 134, and a second four-way valve 262 with two tertiary ports 272, 274 connected fluidly connected to the cylinder branch 130 and two quaternary channels 276, 278 fluidly connected to the auxiliary branch 136. In particular: - a first primary channel 264 is fluidly connected to the first cylinder line 142, - a second primary channel 266 is fluidly connected to the second cylinder line 144, - a first secondary line 268 is fluidly connected to the first main line 146, - a second secondary line 270 is fluidly connected to the second main line 148, - a first tertiary route 272 is fluidly connected to the first cylinder line 142, - a second tertiary route 274 is fluidly connected to the second cylinder line 144, - a first quaternary track 276 is fluidly connected to the first auxiliary pipe 152, and - a second quaternary track 278 is fluidly connected to the second auxiliary pipe 154.

[0139] The first four-way valve 260 has a first configuration, shown in [Fig.4], in which the primary ports 264, 266 are fluidically connected to the secondary ports 268, 270. In particular, in this first configuration the first primary port 264 is fluidly connected to the first secondary port 268 so that the control fluid can flow in both directions, and the second primary port 266 is fluidly connected to the second secondary port 270 so that the control fluid can flow in both directions.

[0140] The first four-way valve 260 also has a second configuration (not shown) in which the primary ports 264, 266 are fluidically isolated from the secondary ports 268, 270. In particular, in this second configuration, each of the primary and secondary ports 264, 266, 268, 270 is closed.

[0141] The second four-way valve 262 has a first configuration, shown in [Fig.4], in which the tertiary paths 272, 274 are fluidically isolated from the quaternary paths 276, 278. In particular, in this second configuration, each of the tertiary and quaternary paths 272, 274, 276, 278 is closed.

[0142] The second four-way valve 262 also has a second configuration (not shown) in which the tertiary ports 272, 274 are fluidically connected to the quaternary ports 276, 278. In particular, in this second configuration the first tertiary port 272 is fluidly connected to the first quaternary port 276 so that the control fluid can flow in both directions, and the second tertiary path 274 is fluidly connected to the second quaternary path 278 so that the control fluid can flow in both directions.

[0143] When the first and second four-way valves 260, 262 are each in their first configuration, this constitutes the first configuration of the valve system 138. When the first four-way valve 260 is in its second configuration and the second four-way valve 262 is in its first configuration, this constitutes the intermediate configuration of the valve system 138. Finally, when the first and second four-way valves 260, 262 are each in their second configuration, this constitutes the second configuration of the valve system 138.

[0144] The first four-way valve 260 is configured to switch from the first to the second configuration in the event of a pressure loss in the test line 140. Advantageously, the first four-way valve 260 is also configured to return to its first configuration when the pressure in the test line 140 is restored.

[0145] To this end, the first four-way valve 260 is, for example, made, as shown, in the form of a spool valve with a valve body 280 delimiting the ports 264, 266, 268, 270 and a spool 282 movably mounted inside the valve body 280. The spool 282 has passages formed inside and is movable relative to the valve body 280 between a first position, shown in [Fig. 4], in which the passages connect the ports 264, 266, 268, 270 according to the first configuration of the first four-way valve 260, and a second position (not shown) in which the ports 264, 266, 268, 270 are closed according to the second configuration of the first four-way valve 260. The spool valve also includes a return element 284, typically a spring, forcing the drawer 282 towards its second position.It further includes a counterbalancing cylinder 286 with a chamber (not shown) fluidically connected to the test line 140 and a piston (not shown) integral with the spool 282 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 excitation of the return member 284. The counterbalancing cylinder 286 and the return member 284 are dimensioned so that the force exerted by the counterbalancing cylinder 286 on the spool 282 overcomes that exerted by the return member 284 and maintains the spool 282 in its first position if and only if the pressure of the control fluid in the test line 140 is greater than the first predetermined threshold.

[0146] The second four-way valve 262 is configured to switch from the first to the second configuration when the fluid pressure in the additional line 250 exceeds a second predetermined threshold. Advantageously, the second four-way valve 262 is also configured to return to its first configuration when the pressure in the additional line 250 falls below the second predetermined threshold.

[0147] To this end, the second four-way valve 262 is, for example, made, as shown, in the form of a spool valve with a valve body 290 delimiting the ports 272, 274, 276, 278 and a spool 292 movably mounted inside the valve body 290. The spool 292 has passages formed inside and is movable relative to the valve body 290 between a first position, shown in [Fig. 4], in which the ports 272, 274, 276, 278 are closed according to the first configuration of the second four-way valve 262, and a second position (not shown) in which the passages connect the ports 272, 274, 276, 278 according to the second configuration of the second four-way valve 262. The spool valve also includes a return element 294, typically a spring, pushing drawer 292 towards its first position.It further includes a counterbalancing cylinder 296 with a chamber (not shown) fluidly connected to an additional conduit 298 and a piston (not shown) integral with the spool 292 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 excitation of the return member 294. The counterbalancing cylinder 296 and the return member 294 are dimensioned so that the force exerted by the counterbalancing cylinder 296 on the spool 292 overcomes that exerted by the return member 294 and maintains the spool 292 in its second position if and only if the pressure of the control fluid in the additional conduit 298 is greater than the second predetermined threshold.

[0148] The additional line 298 is a line fluidically connected to the auxiliary branch 136 by means of a maximum pressure tapping mechanism 299 configured to put the additional line 298 in fluidic communication with that of the first and second auxiliary lines 152, 154 in which the control fluid pressure is highest by isolating the additional line 298 from the other auxiliary line 152, 154. In the example shown, this maximum pressure tapping mechanism 299 consists of a shuttle valve.

[0149] As an alternative (not shown), the first and second four-way valves 260, 262 are each made in any other form suitable to fulfill the aforementioned functions.

[0150] A method for changing the pitch of the blades 56, implemented by the pitch changing mechanism 70 of [Fig.4], will now be described.

[0151] In the initial state, the pressure generator 180 is functional and the pressure control unit 182 fluidly connects the test port 196 to the inlet port 184. The valve system 138 is therefore in its first configuration, so 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, however, is fluidly isolated from the rest of the fluid circuit 120.

[0152] In a first step of this process, the control module 128 first receives a calibration instruction 230 giving a calibration angle greater than that of the measurement 232. This first step takes place in the same way as the step change process implemented by the step change mechanism 70 of [Fig.3],

[0153] During a second step of the pitch change process, the control module 128 receives a calibration instruction 230 giving a calibration angle lower than that of the measurement 232. This second step takes place in the same way as that of the pitch change process implemented by the pitch change mechanism 70 of [Fig.3].

[0154] Optionally, the pitch change process also includes, following the first or second step, a controlled step of locking the blades 56.

[0155] During this step, the control module 128 transmits to the pressure control unit 182 a command to put the blades 56 into safety. Under the effect of this command, the pressure control unit 182 fluidly connects the test port 196 to the outlet port 194, causing a drop in fluid pressure in the test line 140.

[0156] This drop in fluid pressure in the test line 140 simultaneously causes a drop in pressure in the counterbalancing cylinder chamber 286 of the first four-way valve 260. This pressure is then no longer sufficient to counterbalance the load on the return element 284, which causes the first four-way valve 260 to switch to its second configuration, fluidly isolating the main branch 134 from the cylinder branch 130. With the electric motor 222 deactivated, the pressure in the auxiliary line 298 remains below the second predetermined threshold, and the second four-way valve 262 therefore remains in its first configuration. The valve system 138 is thus in its intermediate configuration.

[0157] Since the pressure in the additional line 298 does not vary and the cylinder 74 is fluidly isolated from the main branch 134 and auxiliary branch 136, the fluid The control module cannot enter or exit either of the fluidic chambers 92, 94. The vanes 56 are thus locked in position until the control module 128 commands the unlocking of the vanes 56, either by restoring the pressure in the test pipe 140, or by activating the electric motor 222.

[0158] In the event of a malfunction of the pilot system 78, typically in the event of a 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 process includes an additional uncontrolled step of locking the blades 56.

[0159] During this step, the malfunction of the pilot system 78 causes a drop in fluid pressure in the test line 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.

[0160] This drop in fluid pressure in the test line 140 simultaneously causes a drop in pressure in the counterbalancing cylinder chamber 286 of the first four-way valve 260. This pressure is then no longer sufficient to counterbalance the load on the return element 284, which causes the first four-way valve 260 to switch to its second configuration, fluidically isolating the main branch 134 from the cylinder branch 130. With the electric motor 222 deactivated, the pressure in the additional line 298 remains below the second predetermined threshold, and the second four-way valve 262 therefore remains in its first configuration. The valve system 138 is thus in its intermediate configuration.

[0161] Preferably, this uncommanded step of locking the blades 56 is followed by a step of securing the blades 56 in the flag position.

[0162] During this step, the control module 128 commands the activation of the electric motor 222. The sending of this command is typically triggered by the detection, by the control module 128, of the malfunction of the pilot system 78. The pump 210 thus starts up.

[0163] The control is configured so that the electric motor 222 rotates in a first direction such that the pump 210 draws the control fluid towards the first auxiliary line 152 by sucking it from the second auxiliary line 154. This has the effect of increasing the fluid pressure in the first auxiliary line 152.

[0164] This pressure is transmitted to the additional line 298 via the maximum pressure tapping mechanism 299. The pressure in the additional line 298 thus rises above the second predetermined threshold, causing the second four-way valve 262 to switch to its second configuration: the system valve 138 is thus found in its second configuration, the first auxiliary pipe 152 being fluidly connected to the large pitch chamber 92 and the second auxiliary pipe 154 being fluidly connected to the small pitch chamber 94.

[0165] The fluid pressure in the large pitch chamber 92 is thus greater than the fluid pressure in the small pitch chamber 94.

[0166] The moving part 82 of the cylinder 74 then moves, under the effect of the greater fluid pressure in the large-pitch chamber 92, towards its first position, which, via the linkage system 76, causes the vanes 56 to pivot towards the large pitches (i.e., towards the flag position). This movement continues until the moving part 82 reaches its stop in its first position, the vanes 56 being in the flag position.

[0167] Once the blades 56 are in the flag position, the control module 128 commands the deactivation of the electric motor 222. The pump 210 stops, the pressure in the additional line 298 and in the chamber of the counterbalancing cylinder 296 falls below the second predetermined threshold, and the second four-way valve 262 returns to its first configuration (and the valve system 138 to its intermediate configuration). The blades 56 are thus safely secured in the flag position and locked in this position.

[0168] This step of securing the blades 56 is advantageously followed by a step of moving the blades 56 out of the flag position, typically when the gas turbine engine is stopped.

[0169] During this step, the control module 128 sends a new activation command to the electric motor 222. The pump 210 thus starts up.

[0170] This new control is configured so that the electric motor 222 rotates in a second direction opposite to the first direction such that the pump 210 drives the control fluid towards the second auxiliary line 154, drawing it from the first auxiliary line 152. This has the effect of increasing the fluid pressure in the second auxiliary line 154.

[0171] This pressure is transmitted to the additional line 298 via the maximum pressure sampling mechanism 299. The pressure in the additional line 298 thus rises above the second predetermined threshold, which causes the second four-way valve 262 to switch to its second configuration: the valve system 138 is thus in its second configuration, with the first auxiliary line 152 being fluidly connected to the large pitch chamber 92 and the second auxiliary line 154 being fluidly connected to the small pitch chamber 94.

[0172] The fluid pressure in the small pitch chamber 94 is thus greater than the fluid pressure in the large pitch chamber 92.

[0173] The moving part 82 of the cylinder 74 then moves, under the effect of the greater fluid pressure in the small-pitch chamber 94, to its second position, which, via the linkage system 76, causes the vanes 56 to pivot towards the small pitch (i.e., towards the sail position). This movement continues until the vanes 56 reach the desired position. Once this desired position is reached, the control module 128 commands the deactivation of the electric motor 222. The pump 210 stops, the pressure in the additional line 298 and in the counterbalancing cylinder chamber 296 falls below the second predetermined threshold, and the second four-way valve 262 returns to its first configuration (and the valve system 138 to its intermediate configuration). The vanes 56 are thus locked in the desired position.

[0174] Thus, thanks to the invention described above, it is possible to do without a mechanical pitch locking device, the blades 56 being able to be locked in position by the action of the valve system 138 alone. The pitch locking mechanism 70 thus gains in compactness.

[0175] Furthermore, thanks to the use of an auxiliary source 126 housed in the blower rotor 54, failures in the rotating fluid transfer mechanism 124 do not affect the operation of the auxiliary source 126. The common failure modes between the auxiliary source 126 and the main source 122 are thus reduced, thereby increasing the availability of the blade safety system 56. This increase in availability is also achieved without impact on mass (or with minimal impact) since the mass of the auxiliary source 126 is comparable whether it is mounted on the housing 20 or on the hub 55 of the blower rotor 54.

[0176] Finally, thanks to the space saved by removing the mechanical step locking device, it is possible to position the auxiliary source in an upstream end of the hub 55 of the blower rotor 54. The auxiliary source 126 is thus more accessible, which facilitates maintenance.

Claims

1. Demands A blower 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 its own pivot axis (P), and a pitch-changing mechanism (70) for adjusting an angular position of each of the variable-pitch blades (56) about its respective pivot axis (P), said pitch-changing mechanism (70) comprising: - a frame (72) integral with the hub (55), - a control cylinder (74) with a fixed part (80) integral with the frame (72) and a movable part (82) detachable relative to the fixed part (80), the fixed part (80) and the movable part (82) of the control cylinder (74) delimiting between them two fluidic chambers (92, 94) each containing control fluid to control the movement of the movable part (82) relative to the fixed part (80), - a linkage system (76) connecting the moving part (82) to the variable pitch blade (56) so as to convert a displacement of the moving part (82) relative to the fixed part (80) into a rotation of the variable pitch blade (56) around the pivot axis (P), - a fluidic circuit (120) for supplying the control cylinder (74) with control fluid to control the movement of the moving part (82) relative to the fixed part (80), the fluidic circuit (120) comprising a cylinder branch (130) in fluidic communication with the control cylinder (74), a main branch (134) in fluidic communication with a main source (122) of control fluid, an auxiliary branch (136) in fluidic communication with an auxiliary source (126) of control fluid, and a valve system (138) for fluidically connecting the cylinder branch (130) selectively to one of the main (134) and auxiliary (136) branches, the valve system (138) having 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 arm (130) is fluidly connected to the auxiliary arm (136), - a pump (210), comprising the auxiliary control fluid source (126), including a pump body (212) integral with the hub (55) and a pump rotor (214) mounted to rotate freely relative to the pump body (212), and - an electric motor (222) including a motor stator integral with the hub (55) and a motor rotor kinetically linked to the pump rotor (214) for driving the pump rotor (214), in which the valve system (138) also has a control cylinder (74) immobilization configuration in which the cylinder arm (130) is fluidly isolated from the main arm (134) and the auxiliary arm (136), each of the fluidic chambers (92,94) of the control cylinder (74) being fluidically isolated so as to prevent the control fluid from entering or leaving each of the fluidic chambers (92, 94).

2. Blower rotor (54) according to claim 1, wherein the valve system (138) is configured to switch from the first configuration to the immobilization configuration in the event of a loss of pressure in a test line (140) supplied by the main source (122).

3. Blower rotor (54) according to claim 2, wherein the auxiliary source (126) is configured to activate in the event of a pressure loss in the test line (140).

4. Blower rotor (54) according to claim 3, wherein the valve system (138) is configured to switch from the immobilized configuration to the second configuration when a fluid pressure in the auxiliary branch (136) exceeds a predetermined threshold.

5. Blower rotor (54) according to claim 4, wherein the valve system (138) is configured to return from the second configuration to the immobilization configuration when the fluid pressure in the auxiliary branch (136) falls below said predetermined threshold.

6. Blower rotor (54) according to any one of the preceding claims, wherein the valve system comprises a six-way valve with two primary ports fluidly connected to the cylinder branch, two secondary ports fluidly connected to the main branch, and two tertiary ports fluidly connected to the auxiliary branch.

7. Blower rotor (54) according to any one of claims 1 to 5, wherein the valve system comprises a first four-way valve with two primary ports fluidly connected to the cylinder branch and two secondary ports fluidly connected to the main branch, and a second four-way valve with two tertiary ports fluidly connected to the cylinder branch and two quaternary ports fluidly connected to the auxiliary branch.

8. Gas turbine engine (12) comprising a casing (20) and a blower rotor (54) according to any one of the preceding claims mounted movable for rotation relative to the casing (20).

9. Aircraft (10) comprising at least one gas turbine engine (12) according to claim 8.

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