Pitch change mechanism with pitch lock device

Abstract

This pitch change mechanism (70) comprises a frame, a cylinder (74) with a movable part (82) movable relative to the frame, a main source (122) and an auxiliary source (126) for supplying the cylinder (74), and a locking device (240). A latching mechanism (244) is configured to latch the locking device (240) in the event of a loss of pressure in an engagement chamber (246). The pitch change mechanism (70) also comprises a control line (140) supplied by the main source (122), an additional line (250) fluidly connected to the auxiliary source (124), and a maximum pressure sampling mechanism (252) configured to fluidly connect the engagement chamber (246) to that of the additional line (250) and the control line (140) having the highest pressure. Figure for abstract: Fig. 3

Description

Title of the invention: Pitch changing mechanism with 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 provided with variable pitch blades, and more particularly to the control of the orientation of the fan blades of these gas turbine engines.

[0002] A preferred field of application of the invention is that of turbojets with unducted fans (better known under the English names "propfan", "open fan", "open rotor" and "unducted fan"). However, the invention also applies to turboprops with one or more propulsive propellers. Technological background

[0003] One of the avenues currently being explored to improve the specific consumption of civil aircraft engines is the development of unducted fan turbojets, such as that described in document FR 2 941 493. These turbojets comprise a conventional turboshaft engine gas generator, one or more turbine stages of which drive one or more unducted 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 or these rotor(s) are, as in the case of conventional turboprops, with variable pitch, that is to say 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 pivot axis of the blade, between the chord of the blade at 75% of the radius of the fan and a plane orthogonal to the rotation axis of the fan. It can vary from a value equal to 0°, corresponding to a so-called "sail" 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 pitch-lock devices capable of locking the pitch angle of the blades in the event of failure of the main source and thus preventing the blades from moving towards small pitches. Such a device is for example known from document EP 3 400 169.

[0009] These pitch locking devices are most often used in combination with an auxiliary source, typically an electric pump, secured to the casing and supplying fluid to the so-called “large pitch” chamber of the control cylinder. This auxiliary source is intended to be activated in the event of failure of the main source so as to cause the cylinder to move towards the position in which the blades are in the flag position.

[0010] However, these solutions are not entirely satisfactory. Indeed, in order for the activation of the auxiliary source to cause the blades to move towards their flag position, it is necessary to provide complex pitch locking devices. designed to automatically disengage in the event of an increase in pressure in the large pitch chamber. Such pitch locking devices are heavy and expensive. In addition, it becomes impossible, in the event of a failure of the main source, to reduce the pitch of the blades, while there are situations in which it would be desirable to reduce this pitch in a controlled manner. Finally, the auxiliary source has failure modes in common with the main source, such as cases of leakage in the rotating fluid transfer mechanism, so that the auxiliary source may be unavailable when necessary. For certain failures, it is therefore impossible to return the blades to the flag position despite the presence of the auxiliary source. Statement of the invention

[0011] One objective of the invention is to propose a simple solution for securing variable-pitch blades in the event of failure of the feed system of the actuator controlling their orientation. Other objectives are to minimize the impact of this solution on the weight of the turbomachine, to reduce its cost and to maximize its availability, but also to retain the possibility of reducing the pitch of the blades in a controlled manner even in the event of failure of said feed system.

[0012] To this end, the invention relates, according to a first aspect, to a pitch change mechanism for adjusting an angular position of at least one variable-pitch blade of an aircraft around a pivot axis of the blade, said pitch change mechanism comprising: - a frame fixed relative to the pivot axis, - a control cylinder with a fixed part secured to the frame and a part mobile movable relative to the fixed part, - a connecting system connecting the moving part to the blade so as to convert a movement of the moving part relative to the fixed part into a rotation of the blade around the pivot axis, - a fluid circuit for supplying the control cylinder with control fluid to control the movement of the movable part relative to the fixed part, the fluid circuit comprising a cylinder branch in fluid communication with the control cylinder, a main branch in fluid communication with a main source of control fluid, an auxiliary branch in fluid communication with an auxiliary source of control fluid, and a valve system for fluidically connecting the cylinder branch selectively to one of the main and auxiliary branches, and - a pitch locking device with a locking mechanism having a first configuration in which the movable part of the cylinder control device is free to move relative to the fixed part and a second configuration in which the pitch locking mechanism is engaged with the movable part so as to immobilize the movable part relative to the fixed part, the pitch locking device also comprising an engagement mechanism, comprising an engagement chamber in contact with a piston secured to the locking mechanism, configured to switch the locking mechanism from the first configuration into the second configuration in the event of a loss of pressure in said engagement chamber,

[0013] wherein the pitch change mechanism comprises a control pipe supplied by the main source and an additional pipe fluidly connected to the auxiliary branch, as well as a maximum pressure sampling mechanism configured to fluidly connect the engagement chamber to that of the additional pipe and the control pipe having the highest pressure.

[0014] According to particular embodiments of the invention, the pitch change mechanism also has one or more of the following characteristics, taken in isolation or in any technically possible combination(s): - the auxiliary source includes a pump; - the fixed part and the movable part of the control cylinder delimit between them two fluid chambers each containing control fluid to control the movement of the movable part relative to the fixed part, the cylinder branch comprising a first cylinder pipe fluidly connected to a first of said chambers and a second cylinder pipe fluidly connected to a second of said chambers, and the auxiliary branch comprises a first auxiliary pipe fluidly connected to a first port of the pump and a second auxiliary pipe fluidly connected to a second port of the pump, the pump being configured to suck fluid from one of the first and second ports and deliver 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 pitch change mechanism comprises a maximum pressure sampling mechanism for placing the additional line in fluid communication with that of the first and second auxiliary lines in which the pressure of the control fluid is the highest, said placing in fluid communication being achieved by isolating the additional pipe from the other auxiliary pipe; the pump is a two-way pump; the blade is movable around its pivot axis between a sail position and a flag position, the fluid 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 the blade to pivot towards its flag position; the fluid circuit and the auxiliary source are also configured so that, in a second mode, the auxiliary source supplies the control cylinder so as to cause the blade to pivot towards its sail position; the pitch change mechanism is configured so that the auxiliary source activates in the event of a loss of pressure in the control pipe; the auxiliary source comprises an electric motor for actuating the pump; 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 exit the first configuration in the event of a loss of pressure in the control pipe; the valve system is configured to switch to the second configuration in the event of a loss of pressure in the control pipe; the valve system is configured to switch 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 valve system has an intermediate configuration in which the cylinder branch is fluidically isolated from the main branch and the auxiliary branch, the valve system being configured to be in this intermediate configuration when a fluid pressure in the control pipe is below a first predetermined threshold and a maximum fluid pressure in the auxiliary branch, in particular in each of the first and second auxiliary pipes, is below a second predetermined threshold; the valve system comprises a six-way valve with two first ways fluidly connected to the cylinder branch, two second ways fluidly connected to the main branch, and two third ways fluidly connected to the auxiliary branch; the six-way valve has a first configuration in which the first ways are fluidly connected to the second ways, the third ways being fluidly isolated from the first and second ways, and a second configuration in which the first ways are fluidly connected to the third ways, the second ways being fluidly isolated from the first and third ways, the six-way valve being configured to switch from the first to the second configuration in the event of a loss of pressure in the control pipe; the valve system comprises a first four-way valve with two first ways fluidly connected to the cylinder branch and two second ways fluidly connected to the main branch, and a second four-way valve with two third ways fluidly connected to the cylinder branch and two fourth ways fluidly connected to the auxiliary branch; the first four-way valve has a first configuration in which the first ways are connected only to the second ways and a second configuration in which the first ways are fluidically isolated from the second ways, the first four-way valve being configured to switch from the first to the second configuration in the event of a loss of pressure in the control pipe; the second four-way valve has a first configuration in which the third ways are isolated only from the fourth ways and a second configuration in which the third ways are fluidically connected to the fourth ways, the second four-way valve being 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 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; and the fluid circuit includes an accumulator to regulate the pressure in the auxiliary branch.

[0015] The invention also relates, according to a second aspect, to a gas turbine engine comprising a fan rotor comprising a hub and a plurality of variable-pitch blades each pivotable relative to the hub around a specific pivot axis, the gas turbine engine further comprising a pitch change mechanism according to the first aspect for adjusting an angular position of each of the blades around its respective pivot axis, the frame of said pitch change mechanism being integral with the hub of the fan rotor.

[0016] According to particular embodiments of the invention, the gas turbine engine also has one or more of the following characteristics, taken in isolation or in any technically possible combination(s): the engine comprises a casing, the fan rotor being mounted to rotate relative to the casing; the auxiliary source is integral with the fan rotor hub; the auxiliary source comprises a pump, said pump comprising a pump body secured to the hub of the fan rotor; said pump comprises a pump rotor mounted to rotate relative to the pump body, rotation of said rotor relative to said body causing movement of the control fluid from a first port of the auxiliary source to a second port of the auxiliary source; and the valve system is integral with the hub of the fan rotor.

[0017] 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

[0018] 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

[0019] The aircraft 10 shown in [Fig.l] comprises gas turbine engines 12 for propel it.

[0020] 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.

[0021] One of the gas turbine engines 12 is shown in [Fig.2].

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] The transmission shaft 34 has the longitudinal axis X as its axis of rotation.

[0028] The transmission shaft 34 is guided in rotation relative to the casing 20 by means of bearings (not shown).

[0029] 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.

[0030] The low pressure body 40 comprises a low pressure compressor 42, a turbine low pressure 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.

[0031] 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.

[0032] The low pressure shaft 46 is guided in rotation relative to the casing 20 by means of bearings (not shown).

[0033] 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.

[0034] 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.

[0035] 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 they are rotated, drive the air flow in the external circulation vein 52.

[0036] Each blade 56 comprises, in known manner, a leading edge, a trailing edge and a chord connecting the leading edge to the trailing edge.

[0037] 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.

[0038] 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.

[0039] Advantageously, the fan 50 is, as shown, not ducted, 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).

[0040] 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.

[0041] 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.

[0042] Each blade 56 is in particular able to pivot 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 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 able to pivot 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 flag 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.

[0043] 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.

[0044] 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 tur- bomachine 12 in the different phases of flight.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 constituted by an oil, to control the movement 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 movement of the movable part 82 towards its first position, the relative increase in the second pressure (i.e. relative to the first pressure) causing the movement of the movable part 82 towards its second position.

[0051] 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.

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

[0053] As a variant (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 mobile part 82 relative to the fixed part 80. Thus, it is possible to control the cylinder control 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 are of the same section.

[0054] 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.

[0055] Thus, the relative increase in the first pressure causes the blades 56 to rotate toward their flag position and the relative increase in the second pressure causes the blades 56 to rotate toward 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 toward higher pitch angles, the second fluid chamber 94 being referred to as the “small pitch chamber” since the increase in the fluid pressure in said chamber causes the blades 56 to rotate toward lower pitch angles.

[0056] 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.

[0057] The synchronization ring 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.

[0058] 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.

[0059] The first articulation 106 is carried by the synchronization crown 100. Here it is constituted by a ball joint.

[0060] The second articulation 108 is also constituted by a ball joint. It is eccentric relative to the pivot axis P.

[0061] 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.

[0062] The connecting member 110 is here constituted by a connecting rod.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] The auxiliary branch 136 comprises a first auxiliary conduit 152 connected 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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 and second tertiary ports 166, 167 are advantageously each closed.

[0076] This first configuration of the six-way valve 158 constitutes the first configuration of the valve system 138.

[0077] 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.

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

[0079] 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.

[0080] 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 spool 172 has passages formed therein 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 in accordance with 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 in accordance with the second configuration of the six-way valve 158. The spool valve also includes a biasing member 174, typically a spring, biasing the spool 172 toward 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.

[0081] As a variant (not shown), the six-way valve 158 is produced in any other form suitable for fulfilling the aforementioned functions.

[0082] Preferably, the control 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 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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 able to distribute 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.

[0087] 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.

[0088] 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 return line and is configured to connect said outlet 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.

[0089] 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.

[0090] 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 arranged inside the fixed body 200 and the rotating body 202, these channels being configured to fluidly connect one to the other, whatever 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.

[0091] 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.

[0092] The rotating fluid transfer mechanism 124 consists for example of an oil transfer bearing as described in document WO 2022 / 195191 A1.

[0093] 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 so 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.

[0094] 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 an electric motor 222. This electric motor 222 is for example powered by a generator (not shown) driven by the rotation of the fan rotor 54 relative to the casing 20. Alternatively, the electric motor 222 is powered by a source secured to the casing 20.

[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 line 154 to the first auxiliary line 152. The valve system 138 is 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 fluidically 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] Preferably, the drive mechanism 220 is reversible and can also cause the pump rotor 214 to rotate relative to the pump body 212 in the opposite direction, such 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 conduit 152 to the second auxiliary conduit 154, such that the fluid circuit 120 is also configured so that the pump 210 powers the control cylinder 74 so as to cause the blades 56 to pivot to their sail position.

[0097] 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.

[0098] 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.

[0099] 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 in certain circumstances, for example when a failure of the pilot system 78 is detected.

[0100] 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.

[0101] In the example shown, the fluid circuit 120 also comprises an accumulator 236 to compensate for the variation in the sum of the volumes of the first and second fluid 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 makes it possible to avoid cavitation of the pump 210.

[0102] For this purpose, the accumulator 236 is here fluidically connected to the cylinder branch 130 in parallel with the control cylinder 74, that is to say 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 fluid 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 fluid chambers 92, 94 decreases. A person skilled in the art will easily be able to implement such an accumulator using his general knowledge.

[0103] The pitch change mechanism 70 further comprises a pitch locking device 240 for locking the angular position of the blades 56.

[0104] 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 switch the locking mechanism 242 from the first configuration into 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.

[0105] 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.

[0106] 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 change mechanism of step 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.

[0107] 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.

[0108] A method of changing the pitch of the blades 56, implemented by the pitch changing mechanism 70 of [Fig. 3], will now be described.

[0109] 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. As for the locking mechanism 242 of the pitch locking device 240, it is in its first configuration.

[0110] 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).

[0111] Once the measurement 232 is equal to the calibration 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 control fluid to the chambers 92, 94, 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.

[0112] 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 jack 74 moves to its second position, which, via the connection system 76, causes the pivoting of the blades 56 towards the small steps (i.e. towards the sail position).

[0113] 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.

[0114] Optionally, the pitch change method also comprises, following the first or second step, a controlled step of locking the blades 56.

[0115] 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.

[0116] This drop in fluid pressure in the control pipe 140 simultaneously causes a drop in pressure in the chamber 246 of the engagement mechanism 244 of the pitch locking device 240. This pressure is then no longer sufficient to counterbalance the stress on the return member, which causes the tilting of the locking mechanism 242 in its second configuration. The angular position of the blades 56 is then locked.

[0117] At the same time, the pressure in the additional pipe 250 becomes higher than the pressure in the control pipe 140, which has the effect of switching the first maximum pressure sampling mechanism 252 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.

[0118] Simultaneously, the valve system 138 switches to its second configuration under the effect of the loss of pressure 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.

[0119] With the electric motor 222 deactivated, the pressures in the chamber 246 and in the first and second fluid chambers 92, 94 remain unchanged. The pitch locking device 242 thus remains engaged and the blades 56 locked in position until the control module 128 commands the unlocking of the blades 56, either by restoring the pressure in the control pipe 140, or by activating the electric motor 222.

[0120] 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 locking the blades 56.

[0121] 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.

[0122] This drop in fluid pressure in the control pipe 140 simultaneously causes a drop in pressure in the chamber 246 of the engagement mechanism 244 of the pitch locking device 240. This pressure is then no longer sufficient to counterbalance the stress on the return member, which causes the locking mechanism 242 to tilt into its second configuration. The angular position of the blades 56 is then locked.

[0123] At the same time, the pressure in the additional pipe 250 becomes higher than the pressure in the control pipe 140, which has the effect of switching the first maximum pressure sampling mechanism 252 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 chamber 246 is then equal to that in the additional pipe 250.

[0124] 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.

[0125] Preferably, this uncontrolled step of locking the blades 56 is followed by a step of securing the blades 56 in the flag position.

[0126] 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 control system 78. The pump 210 thus starts up.

[0127] The control is configured so that the electric motor 222 rotates in a first direction such that the pump 210 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.

[0128] Since the movable part 82 of the jack 74 cannot move due to the action of the locking mechanism 242, the increase in pressure in the large pitch chamber 92 does not have the effect of causing said movable part 82 to move. Instead, the pressure in the large pitch chamber 92 and in the first auxiliary conduit 152 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 242 to its first configuration.

[0129] The movable part 82 of the cylinder 74 is then released and moves, under the effect of the greater fluid pressure in the large pitch chamber 92, 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 the flag position.

[0130] Once this position is reached, the control module 128 commands the deactivation of the electric motor 222. The pump 210 stops, the pressure in the chamber 246 returns below the threshold pressure, and the locking mechanism 242 returns to its second configuration. The blades 56 are thus placed in safety in the flag position and locked in this position.

[0131] This step of securing the blades 56 is advantageously followed by a step exit of the blades 56 from the flag position, typically when the gas turbine engine is stopped.

[0132] During this step, the control module 128 sends a new command to activate the electric motor 222. The pump 210 thus starts up.

[0133] This new control is configured so that the electric motor 222 starts rotating in a second direction opposite to the first direction such that the pump 210 drives the control fluid towards the small pitch chamber 94, via the second cylinder line 144 and the second auxiliary line 154, by sucking it from the large pitch chamber 92 via the first auxiliary line 152 and the first cylinder line 142. This has the effect of increasing the fluid pressure in the small pitch chamber 94 relative to the large pitch chamber 92.

[0134] Since the movable part 82 of the jack 74 cannot move due to the action of the locking mechanism 242, the increase in pressure in the small step chamber 94 does not have the effect of causing said movable part 82 to move. Instead, the pressure in the small step chamber 94 and in the second auxiliary conduit 154 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 242 to its first configuration.

[0135] The movable part 82 of the jack 74 is then released and moves, under the effect of the greater fluid pressure in the small pitch chamber 94, towards its second position, which, via the connecting system 76, causes the blades 56 to pivot towards the small pitches (i.e. towards the sail position). This movement continues until the movable part 82 reaches the stop in its second position, the blades 56 being in the sail 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 of [Fig. 3] applies entirely to the variant of [Fig. 4], except with regard to the details of the valve system 138. This latter variant differs in fact from that of [Fig. 3] in that the valve system 138 does not only have a first configuration and a second configuration, it also has an intermediate configuration (not shown) between the first and second configurations.

[0138] This intermediate configuration is a configuration in which the cylinder branch 130 is fluidically isolated from the main branch 134 and the auxiliary branch 136. In particular, in this intermediate configuration, the cylinder branch 130, the main branch 134 and the auxiliary branch 136 are all fluidically isolated from each other.

[0139] The valve system 138 is configured to switch from the first configuration to the intermediate 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 first 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 first predetermined threshold.

[0140] Advantageously, this first predetermined threshold is greater than or equal to the engagement threshold of the locking mechanism 242 and is typically equal to the latter.

[0141] The valve system 138 is also configured to switch from the intermediate configuration to the second configuration when the fluid pressure in the additional pipe 250 exceeds a second predetermined threshold, i.e. when the fluid pressure in one of the pipes 152, 154 of the auxiliary branch 136 exceeds said second predetermined threshold. Advantageously, the valve system 138 is also configured to return to the intermediate configuration when the pressure in the additional pipe 250 falls below the second predetermined threshold, i.e. when the fluid pressure in each of the pipes 152, 154 of the auxiliary branch 136 falls below said second predetermined threshold.

[0142] Advantageously, this second predetermined threshold is less than or equal to the engagement threshold of the locking mechanism 242 and is typically equal to the latter.

[0143] The variant of [Fig.4] also 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.

[0144] These valves 260, 262 comprise a first four-way valve 260 with two primary ways 264, 266 fluidly connected to the cylinder branch 130 and two secondary ways 268, 270 fluidly connected to the main branch 134, and a second four-way valve 262 with two tertiary ways 272, 274 fluidly connected to the cylinder branch 130 and two quaternary ways 276, 278 fluidly connected to the auxiliary branch 136. In particular: - a first primary channel 264 is fluidically connected to the first cylinder line 142, - a second primary channel 266 is fluidically connected to the second cylinder line 144, - a first secondary line 268 is fluidically connected to the first main line 146, - a second secondary line 270 is fluidically connected to the second main line 148, - a first tertiary channel 272 is fluidically connected to the first cylinder line 142, - a second tertiary channel 274 is fluidically connected to the second cylinder line 144, - a first quaternary channel 276 is fluidically connected to the first auxiliary pipe 152, and - a second quaternary channel 278 is fluidically connected to the second auxiliary pipe 154.

[0145] The first four-way valve 260 has a first configuration, shown in [Fig. 4], in which the primary ports 264, 266 are fluidly 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.

[0146] 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.

[0147] The second four-way valve 262 has a first configuration, shown in [Fig. 4], in which the tertiary ports 272, 274 are fluidically isolated from the quaternary ports 276, 278. In particular, in this second configuration, each of the tertiary and quaternary ports 272, 274, 276, 278 is closed.

[0148] The second four-way valve 262 also has a second configuration (not shown) in which the tertiary ways 272, 274 are fluidly connected to the quaternary ways 276, 278. In particular, in this second configuration the first tertiary way 272 is fluidly connected to the first quaternary way 276 so that the control fluid can flow in both directions, and the second tertiary way 274 is fluidly connected to the second quaternary way 278 so that the control fluid can flow in both directions.

[0149] 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.

[0150] The first four-way valve 260 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 first four-way valve 260 is also configured to return to its first configuration when the pressure in the control pipe 140 is restored.

[0151] For this purpose, the first four-way valve 260 is for example produced, as shown, in the form of a slide valve with a valve body 280 delimiting the ways 264, 266, 268, 270 and a slide 282 mounted movably inside the valve body 280. The slide 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 ways 264, 266, 268, 270 in accordance with the first configuration of the first four-way valve 260, and a second position (not shown) in which the ways 264, 266, 268, 270 are closed in accordance with the second configuration of the first four-way valve 260. The slide valve also comprises a return member 284, typically a spring, biasing the spool 282 towards its second position.It also comprises a counterbalancing cylinder 286 with a chamber (not shown) fluidically connected to the control pipe 140 and a piston (not shown) integral with the slide 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 stress 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 slide 282 prevails over that exerted by the return member 284 and maintains the slide 282 in its first position if and only if the pressure of the control fluid in the control pipe 140 is greater than the first predetermined threshold.

[0152] The second four-way valve 262 is configured to switch from the first to the second configuration when the fluid pressure in the additional pipe 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 pipe 250 falls below the second predetermined threshold.

[0153] For this purpose, the second four-way valve 262 is for example produced, as shown, in the form of a slide valve with a valve body 290 delimiting the ways 272, 274, 276, 278 and a slide 292 mounted movably inside the valve body 290. The slide 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 ways 272, 274, 276, 278 are closed in accordance with the first confi 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 in accordance with the second configuration of the second four-way valve 262. The slide valve also comprises a return member 294, typically a spring, biasing the slide 292 towards its first position. It further comprises a counterbalancing cylinder 296 with a chamber (not shown) fluidically connected to the additional conduit 250 and a piston (not shown) integral with the slide 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 biasing 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 slide 292 prevails over that exerted by the return member 294 and maintains the slide 292 in its second position if and only if the pressure of the control fluid in the additional pipe 250 is greater than the second predetermined threshold.

[0154] A method of changing the pitch of the blades 56, implemented by the pitch changing mechanism 70 of [Fig.4], will now be described.

[0155] 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. As for the locking mechanism 242 of the pitch locking device 240, it is in its first configuration.

[0156] 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],

[0157] 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].

[0158] Optionally, the pitch change method also comprises, following the first or second step, a controlled step of locking the blades 56.

[0159] 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 control, the pressure control unit 182 fluidly connects the indicator port 196 to the outlet port 194, causing a drop in fluid pressure in the indicator line 140.

[0160] This drop in fluid pressure in the control pipe 140 simultaneously causes a drop in pressure in the chamber 246 of the engagement mechanism 244 of the pitch locking device 240. This pressure is then no longer sufficient to counterbalance the stress on the return member, which causes the locking mechanism 242 to tilt into its second configuration. The angular position of the blades 56 is then locked.

[0161] At the same time, the pressure in the additional pipe 250 becomes higher than the pressure in the control pipe 140, which has the effect of switching the first maximum pressure sampling mechanism 252 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.

[0162] Simultaneously, the first four-way valve 260 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 cylinder branch 130. The electric motor 222 being deactivated, the pressure in the additional pipe 250 remains below the second predetermined threshold and the second four-way valve 262 therefore remains in its first configuration. The valve system 138 is therefore in its intermediate configuration.

[0163] The pressure in the additional pipe 250 not varying and the cylinder 74 being fluidically isolated from the main 134 and auxiliary 136 branches, the pressures in the chamber 246 and in the first and second fluid chambers 92, 94 also remain unchanged. The pitch locking device 242 thus remains engaged and the blades 56 locked in position until the control module 128 commands the unlocking of the blades 56, either by restoring the pressure in the control pipe 140, or by activating the electric motor 222.

[0164] In the event of a malfunction of the control 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 method comprises an additional non-controlled step of locking the blades 56.

[0165] 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.

[0166] This drop in fluid pressure in the control pipe 140 simultaneously causes a drop in pressure in the chamber 246 of the engagement mechanism 244 of the pitch locking device 240. This pressure is then no longer sufficient to counterbalance the stress of the return member, which causes the locking mechanism 242 to tilt into its second configuration. The angular position of the blades 56 is then locked.

[0167] At the same time, the pressure in the additional pipe 250 becomes higher than the pressure in the control pipe 140, which has the effect of switching the first maximum pressure sampling mechanism 252 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.

[0168] Simultaneously, the first four-way valve 260 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 cylinder branch 130. The electric motor 222 being deactivated, the pressure in the additional pipe 250 remains below the second predetermined threshold and the second four-way valve 262 therefore remains in its first configuration. The valve system 138 is therefore in its intermediate configuration.

[0169] Preferably, this uncontrolled step of locking the blades 56 is followed by a step of securing the blades 56 in the flag position.

[0170] 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 control system 78. The pump 210 thus starts up.

[0171] The control is configured so that the electric motor 222 rotates in a first direction so that the pump 210 drives 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.

[0172] This pressure is transmitted to the additional pipe 250 via the second maximum pressure sampling mechanism 254. The pressure in the additional pipe 250 thus passes above the second predetermined threshold, which causes the second four-way valve 262 to switch into its second configuration: the valve system 138 is thus in its second configuration, the first auxiliary pipe 152 being fluidically connected to the large pitch chamber 92 and the second auxiliary pipe 154 being fluidically connected to the small pitch chamber 94.

[0173] The fluid pressure in the large pitch chamber 92 is thus greater than the fluid pressure in the small pitch chamber 94. However, since the movable part 82 of the jack 74 cannot move due to the action of the locking mechanism 242, the increase in pressure in the large pitch chamber 92 does not have the effect of causing said movable part 82 to move. Instead, the pressure in the large pitch chamber 92 and in the first auxiliary pipe 152 continues to increase progressively, until the pressure in the additional pipe 250 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 242 to its first configuration.

[0174] The movable part 82 of the cylinder 74 is then released and moves, under the effect of the greater fluid pressure in the large pitch chamber 92, 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 the flag position.

[0175] It will be noted that, in the case where the second predetermined threshold is equal to the engagement threshold of the locking mechanism 242, the locking mechanism 242 returns to its first configuration at the same time as the valve system 138 switches to its second configuration. The movable part 82 of the jack 74 then begins to move towards its first position as soon as the valve system 138 switches to its second configuration.

[0176] Once the vanes 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 pipe 250 and in the chamber 246 returns below the predetermined thresholds, the second four-way valve 262 returns to its first configuration (and the valve system 138 to its intermediate configuration) and the locking mechanism 242 returns to its second configuration. The vanes 56 are thus secured in the flag position and locked in this position.

[0177] This step of securing the blades 56 is advantageously followed by a step of removing the blades 56 from the flag position, typically when the gas turbine engine is stopped.

[0178] During this step, the control module 128 sends a new command to activate the electric motor 222. The pump 210 thus starts up.

[0179] This new control is configured so that the electric motor 222 starts rotating in a second direction opposite to the first direction such that the pump 210 drives the control fluid towards the second auxiliary line 154, by sucking it from the first auxiliary line 152. This has the effect of increasing the fluid pressure in the second auxiliary line 154.

[0180] This pressure is transmitted to the additional pipe 250 via the second maximum pressure sampling mechanism 254. The pressure in the additional pipe 250 thus passes above the second predetermined threshold, which causes the second four-way valve 262 to switch into its second configuration: the valve system 138 is thus in its second configuration, the first auxiliary pipe 152 being fluidically connected to the large pitch chamber 92 and the second auxiliary pipe 154 being fluidically connected to the small pitch chamber 94.

[0181] The fluid pressure in the small pitch chamber 94 is thus greater than the fluid pressure in the large pitch chamber 92. However, since the movable part 82 of the jack 74 cannot move due to the action of the locking mechanism 242, the increase in pressure in the small pitch chamber 94 does not have the effect of causing said movable part 82 to move. Instead, the pressure in the small pitch chamber 94 and in the second auxiliary conduit 154 continues to increase progressively, until the pressure in the additional conduit 250 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 242 to its first configuration.

[0182] The movable part 82 of the jack 74 is then released and moves, under the effect of the greater fluid pressure in the small pitch chamber 94, towards its second position, which, via the connecting system 76, causes the blades 56 to pivot towards the small pitches (i.e. towards the sail position). This movement continues until the movable part 82 reaches the stop in its second position, the blades 56 being in the sail position.

[0183] It will be noted that, in the case where the second predetermined threshold is equal to the engagement threshold of the locking mechanism 242, the locking mechanism 242 returns to its first configuration at the same time as the valve system 138 switches to its second configuration. The movable part 82 of the jack 74 then begins to move towards its second position as soon as the valve system 138 switches to its second configuration.

[0184] Thus, thanks to the invention described above, it is easy to unlock the variable-pitch blades 56 when activating the auxiliary source 126. This unlocking is done simply by using the mechanism which normally maintains the pitch locking device 240 in the unlocked configuration. It is thus possible to do without heavy, expensive and complex pitch locking devices. In addition, this makes it possible to actuate the pitch change mechanism 70 by means of the auxiliary source 126 not only to increase the pitch of the blades 56 but also to reduce, which is not possible with existing solutions.

[0185] Furthermore, by using an auxiliary source 126 housed in the fan rotor 54, failures in 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.

Claims

Claims

1. A pitch change mechanism (70) for adjusting an angular position of at least one variable pitch blade (56) of an aircraft about a pivot axis (P) of the blade (56), said pitch change mechanism (70) comprising: - a frame (72) fixed relative to the pivot axis (P), - a control cylinder (74) with a fixed part (80) integral of the frame (72) and a movable part (82) movable relative to the fixed part (80), - a connecting system (76) connecting the mobile part (82) to the blade (56) so as to convert a movement of the mobile part (82) relative to the fixed part (80) into a rotation of the blade (56) around the pivot axis (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), the fluid circuit (120) comprising a cylinder branch (130) in fluid communication with the control cylinder (74), a main branch (134) in fluid communication with a main source (122) of control fluid, an auxiliary branch (136) in fluid communication with an auxiliary source (126) of control fluid, and a valve system (138) for fluidly connecting the cylinder branch (130) selectively to one of the main (134) and auxiliary (136) branches, and - a pitch locking device (240) with a locking mechanism (242) having a first configuration 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 in which the pitch 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 comprising an engagement mechanism (244), comprising an engagement chamber (246) in contact with a piston (248) integral with the locking mechanism (242), configured to tilt the locking mechanism (242) from the first configuration into the second configuration in the event of a loss of pressure in said engagement chamber (246),

2.

3.

4. wherein the pitch change mechanism (70) comprises a control line (140) supplied by the main source (122) and an additional line (250) fluidly connected to the auxiliary branch (136), as well as a maximum pressure sampling mechanism (252) configured to fluidly connect the engagement chamber (246) to that of the additional line (250) and the control line (140) having the highest pressure. The pitch change mechanism (70) of claim 1, wherein the auxiliary source (126) comprises a pump (210). A pitch change mechanism (70) according to claim 2, wherein the fixed portion (80) and the movable portion (82) of the control cylinder (74) delimit between them two fluid chambers (92, 94) each containing control fluid for controlling the movement of the movable portion (82) relative to the fixed portion (80), the cylinder branch (130) comprising a first cylinder line (142) fluidly connected to a first of said chambers (92, 94) and a second cylinder line (144) fluidly connected to a second of said chambers (92, 94), and the auxiliary branch (136) comprises a first auxiliary line (152) fluidly connected to a first port (153) of the pump (210) and a second auxiliary line (154) fluidly connected to a second port (155) of the pump (210), the pump (210) being configured to draw fluid from one of the first and second ports (153,155) and discharge this fluid towards the other of the first and second ports (153, 155), the valve system (138) being 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 the cylinder branch (130) is fluidly connected to the auxiliary branch (136)., The pitch change mechanism (70) of claim 3, comprising a maximum pressure tapping mechanism (254) for placing the additional conduit (250) in fluid communication with one of the first and second auxiliary conduits (152, 154). in which the pressure of the control fluid is the highest, said fluid communication being carried out by isolating the additional pipe (250) from the other auxiliary pipe (152, 154).

5. The pitch change mechanism (70) of any one of claims 2 to 4, wherein the pump (210) is a bidirectional pump.

6. A pitch change mechanism (70) according to any preceding claim, wherein the blade (56) is movable about its pivot axis (P) between a sail position and a flag position, the fluid circuit (120) and the auxiliary source (126) being configured so that, at least in a first mode, the auxiliary source (126) supplies the control cylinder (74) so ​​as to cause the blade (56) to pivot towards its flag position.

7. The pitch change mechanism (70) of claim 6, wherein the fluid circuit (120) and the auxiliary source (126) are also configured so that, in a second mode, the auxiliary source (126) powers the control cylinder (74) so ​​as to cause the blade (56) to pivot toward its sail position.

8. A pitch change mechanism (70) according to any preceding claim, configured so that the auxiliary source (126) activates in the event of a loss of pressure in the control line (140).

9. A gas turbine engine (12) comprising a fan rotor (54) having a hub (55) and a plurality of variable pitch blades (56) each pivotable relative to the hub (55) about a specific pivot axis (P), the gas turbine engine (12) further comprising a pitch change mechanism (70) according to any one of the preceding claims for adjusting an angular position of each of the blades (56) about its respective pivot axis (P), the frame (72) of said pitch change mechanism (70) being integral with the hub (55) of the fan rotor (54).

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

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