Pitch changing mechanism with pitch locking device comprising planetary roller screws

Abstract

The invention relates to a pitch change mechanism (70) comprising a frame (72), a moving part (102) translatable along a longitudinal axis (X), and a locking device (160). The locking device (160) comprises a support member (162) and a screw-nut system (164), the support member being translatable along a longitudinal axis (X) between an operative position and a locked position. The screw-nut system (164) is formed by a planetary roller screw system (195) comprising a screw (176) translationally secured to the support member (162) and rotatably mounted about the longitudinal axis (X) and a nut (178) secured to the moving part (102). The screw (176) has an abutment surface (186) that is spaced from the frame (72) when the support member (162) is in the operative position and that supports against the frame (72) when the support member (162) is in the locked position.

Description

Technical Field

[0001] The invention relates to the general field of turbomachines equipped with at least one fan having variable-set blades, and more particularly to the control of the orientation of the fan airfoils of these turbomachines.

[0002] The preferred field of application of the invention is the field of turbojets with unducted fans (more commonly known as propeller fans, open fans, open rotors and unducted fans). However, the invention is also applicable to turboprop engines with one or more propulsion propellers. Background Art

[0003] One of the avenues currently being explored for improving 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 turbine gas generator, one or more turbine stages of which drive one or more unducted fans extending outside the nacelle of the engine.

[0004] As in the case of conventional turboprop engines, the blades of the fan or fans are variable setting blades, i.e. the angular position of these blades, known as the setting angle, can be varied during flight. As a reminder, the setting angle of the blade corresponds to the angle between the axis of rotation of the fan and the chord of the blade at 75% of the radius of the fan, in a plane orthogonal to the pivot axis of the blade. The setting angle of the blade can vary from a value equal to 90°, corresponding to a position of the blade known as the "flat" position, to a value equal to 0°, corresponding to a position of the blade known as the "feathered" position. The setting angle of the blade can also take values ​​strictly greater than 90° (generally approximately equal to 95°), corresponding to a position of the blade known as the "reverse" position.

[0005] As is known, this modification of the setting angle during flight makes it possible to vary the engine thrust and optimize the efficiency of the fan according to the speed of the aircraft. In fact, the rpm of the fan is almost constant in all operating phases, and the setting of the blades varies the thrust. Thus, in the cruising flight phase, the blades are oriented to regulate the thrust by minimizing consumption and the power extracted from the turbine shaft and by optimizing efficiency. Conversely, at takeoff, the blades are oriented to maximize the thrust in order to accelerate the aircraft and then take off.

[0006] The difficulty encountered with variable setting blades is that in the event of a failure of the system guiding the orientation of the variable setting blades, the blades tend to assume a flat position under their own centrifugal action. However, a blade blocked in this position produces little drag torque and risks causing an engine overspeed, which has the potential risk of damaging the engine. Furthermore, a blade blocked in this position also risks creating excessive and unacceptable drag on the aircraft's controllability and / or its range in the event of a turning mission.

[0007] To overcome this difficulty, it is known to use a safety system capable of returning the blade to the feathered position and / or resisting a displacement of the variably set blade towards a low pitch, that is to say towards a flat position, in the event of a failure of the airfoil orientation control system. Such systems are known, for example, from EP 1 832 509 and EP 3 400 169.

[0008] The safety system described in EP 1832509 uses a screw-nut system of the ball screw type coupled to a locking nut. In normal operation, the nut of the screw-nut system follows the displacement of the actuator that controls the orientation of the blade, causing the screw to rotate around its axis, while the locking nut follows the thread of the screw without contacting the thread of the screw (the thread of the locking nut is designed to have a slight clearance with the thread of the screw). In the event of a malfunction of the airfoil orientation control system, the screw of the screw-nut system is fixed (its rotation is blocked) and the locking nut engages with the screw, preventing the blade from pivoting towards a small pitch.

[0009] However, this safety system is not completely satisfactory. In fact, in order to function correctly, this safety system requires precise and complex management of the clearance between the locking nut and the screw thread. This safety system is also cumbersome and bulky. Summary of the invention

[0010] One object of the invention is to propose a simple system which is able to resist displacement of the variable setting blades towards a small pitch. Other objects are that the system be reliable, accurate, light and of reasonable cost.

[0011] To this end, according to a first aspect, the invention relates to a pitch changing mechanism for adjusting the angular position of at least one variably settable blade about a pivot axis of the blade, the pitch changing mechanism comprising:

[0012] - a frame, which is fixed relative to the pivot axis,

[0013] a control actuator comprising a fixed part fixed to the frame and a mobile part movable in translation along the longitudinal axis relative to the fixed part between a retracted position and a deployed position,

[0014] - a coupling system coupling the moving part to the variable-setting blade to convert a translation of the moving part along the longitudinal axis into a rotation of the variable-setting blade about the pivot axis, and

[0015] - a pitch locking device capable of preventing a translation of the mobile part relative to the fixed part along at least one path,

[0016] The pitch lock device includes:

[0017] - a support member movable in translation relative to the frame along the longitudinal axis between an operating position and a locking position,

[0018] - biasing means biasing the support member towards a locked position of the support member, and

[0019] - retaining means for retaining the support member in the operating position of the support member under normal operating conditions, and

[0020] -Screw-nut system, the screw-nut system has:

[0021] a screw, which is fixed in translation to the support member and is movably mounted to rotate relative to the support member about the longitudinal axis, the screw having an abutment surface which is located at a distance from the frame when the support member is in the operating position and which bears against the frame when the support member is in the locked position, and

[0022] a nut, which is fixed to the moving part and is coaxial with the screw, the nut cooperating with the screw such that translation of the nut along the longitudinal axis causes rotation of the screw about the longitudinal axis,

[0023] Therein, the screw-nut system is formed by a planetary roller screw system.

[0024] According to a particular embodiment of the invention, the pitch changing mechanism also has one or more of the following features, taken alone or in one or more any technically possible combination:

[0025] - the coupling system comprises a first hinge fixed to the mobile part, a second hinge fixed to the variable setting blade remote from the pivot axis, and a coupling member coupling the first hinge to the second hinge;

[0026] - the longitudinal axis is substantially orthogonal to the pivot axis;

[0027] -The planetary roller screw system is reversible;

[0028] - the control actuator comprises a first chamber and a second chamber, the first chamber containing a control fluid at a first pressure, the second chamber containing a control fluid at a second pressure, the pitch changing mechanism comprising a pressure generator and a pressure control unit, the pressure generator being used to bring the control fluid to a third pressure higher than the first pressure and the second pressure, the pressure control unit being used to adjust the first pressure and the second pressure by the third pressure, the holding device comprising a balancing actuator having a chamber, the chamber being supplied with the control fluid at the third pressure to counteract the bias of the biasing device;

[0029] - the frame comprises a stop against which an abutment surface of the screw bears when the support member is in the locked position, the variable-setting blade being movable about its pivot axis between a flat position and a feathered position, the coupling system being configured such that a displacement of the moving part towards the stop causes a rotation of the variable-setting blade towards the flat position;

[0030] - A planetary roller screw system comprises a plurality of rollers arranged between the screw and the nut, each roller engaging with the external thread of the screw and the internal thread of the nut;

[0031] - Each roller is fixed in translation to a nut or a screw;

[0032] - The planetary roller screw system consists of a recirculating planetary roller screw system or a planetary roller bearing screw system;

[0033] - the abutment surface is arranged at the downstream end of the screw, or respectively at the upstream end of the screw;

[0034] - the control actuator comprises a cylinder and a piston, the cylinder forming one of the fixed part and the moving part, the piston forming the other of the fixed part and the moving part, the cylinder defining an inner cavity, the piston dividing the inner cavity into two fluid chambers, each fluid chamber containing a control fluid for controlling the displacement of the moving part relative to the fixed part;

[0035] -The cylinders are continuous;

[0036] - the fluid chambers are adjacent;

[0037] - each fluid chamber is at least partially defined by an outer peripheral surface of the frame;

[0038] - the fluid chamber is closed at each of the longitudinal ends of the actuator;

[0039] - the pitch locking device is located outside the fluid chamber;

[0040] - the pitch change mechanism comprises a seal fluidically isolating the fluid chamber from the pitch lock;

[0041] - one of the two fluid chambers is in fluid communication with the interior of the housing, the control fluid constituting a lubricating fluid for the locking device;

[0042] - at least a portion of the pitch lock extends longitudinally away from the actuator;

[0043] - the pitch locking device is cantilevered relative to the frame in the longitudinal direction;

[0044] - the pitch changing mechanism comprises a collar, which couples the nut to the moving part of the actuator, the collar protruding longitudinally from the actuator, in particular, the collar protruding longitudinally upstream from the actuator;

[0045] - the locking device comprises a guide system for guiding the support member relative to the frame, the control actuator and the guide system being arranged longitudinally on the same side of the nut, preferably on the downstream side of the nut;

[0046] - the pitch locking device comprises a housing fixed to the nut and surrounding the nut, the screw and the support member;

[0047] - the housing at least partially defines an enclosure for the circulation of lubricating fluid of the pitch locking device;

[0048] - the housing comprises an inner cylinder carrying a nut on its inner surface and cooperating with an outer cylinder fixed to the frame so as to slide longitudinally inside the outer cylinder, the inner cylinder having at its outer periphery a seal in contact with the inner surface of the outer cylinder, the outer cylinder and the housing together defining an enclosure for the circulation of a lubricating fluid of the locking device;

[0049] - the pitch changing mechanism comprises means for guiding the nut relative to the frame, the guiding means comprising an inner cylinder fixed to the nut and an outer cylinder fixed to the frame, the inner cylinder cooperating with the outer cylinder so as to slide longitudinally inside the outer cylinder;

[0050] -The connection system enables:

[0051] o converting a translation of the moving member along the longitudinal axis in a first path into a rotation of the variable setting blade about the pivot axis towards the flat position, and

[0052] o converting a translation of the moving member along the longitudinal axis in a second path opposite to the first path into a rotation of the variably-set blade about the pivot axis towards a feathered position;

[0053] - the first articulation is arranged upstream of the second articulation, the first route extending from upstream to downstream, or, correspondingly, the first articulation is arranged downstream of the second articulation, the first route extending from downstream to upstream;

[0054] - the abutment surface is oriented along a first course;

[0055] - the support member moves by translation along a first path from an operating position of the support member to a locking position of the support member;

[0056] - The connecting member is composed of a connecting rod;

[0057] - the variable setting blade comprises a leading edge, a trailing edge and a chord connecting the leading edge to the trailing edge, the second hinge being arranged opposite the trailing edge relative to a plane orthogonal to the chord and containing the pivot axis; and

[0058] The frame comprises a stop against which the abutment surface of the screw bears when the support member is in the locked position, the control actuator and the stop being arranged longitudinally on the same side of the nut.

[0059] According to a second aspect, the present invention also relates to a fan rotor for a turbine, the fan rotor comprising a hub and a plurality of variable-setting blades, each variable-setting blade being pivotable relative to the hub about a specific pivot axis, the rotor also comprising a pitch changing mechanism according to the first aspect, the pitch changing mechanism being used to adjust the angular position of each of the variable-setting blades about its corresponding pivot axis.

[0060] According to a particular embodiment of the invention, the fan rotor also has one or more of the following features, taken alone or in one or more any technically possible combination:

[0061] - for each of the variable-setting blades, the coupling system of the pitch changing mechanism comprises a first hinge fixed to the moving part, a second hinge fixed to the variable-setting blade remote from the pivot axis, and a connecting rod coupling the first hinge to the second hinge; and

[0062] - The longitudinal axis constitutes the axis of rotation of the rotor.

[0063] According to a third aspect, the invention also relates to a turbomachine comprising a fan rotor according to the second aspect.

[0064] According to a particular embodiment of the present invention, the turbine also has the following features:

[0065] - The longitudinal axis constitutes the axis of elongation of the turbine.

[0066] According to a fourth aspect, the invention also relates to an aircraft comprising at least one turbomachine according to the third aspect.

[0067] Finally, according to a fifth aspect, the present invention relates to a method for changing the pitch of blades of a fan rotor of a turbine, each blade being pivotable about a specific pivot axis relative to the hub of the fan rotor, the method comprising adjusting the angular position of each of the blades about its corresponding pivot axis by means of a pitch changing mechanism according to the first aspect.

[0068] According to a particular embodiment of the present invention, the method further has the following characteristics:

[0069] - The method comprises the additional step of locking the orientation of the blades by means of pitch locking means. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Other characteristics and advantages of the invention will become apparent on reading the following description given by way of example only and with reference to the accompanying drawings, in which:

[0071] - Figure 1 is a top view of an aircraft according to an exemplary embodiment of the present invention,

[0072] - Figure 2 yes Figure 1 A simplified view of a partial longitudinal section of a turbine of an aircraft,

[0073] - Figure 3 According to the first embodiment Figure 2 A simplified view of a longitudinal section of a portion of a pitch changing mechanism of a turbine of FIG. 1 , the pitch changing mechanism being in a first configuration,

[0074] - Figure 4 is with Figure 3 A similar view of the pitch changing mechanism in the second configuration,

[0075] - Figure 5 yes Figure 3 The first variant of the pitch changing mechanism is Figure 3 A view similar to the view of

[0076] - Figure 6 yes Figure 3 The second variant of the pitch changing mechanism is Figure 3 A view similar to the view of

[0077] - Figure 7 yes Figure 3 The third variant of the pitch changing mechanism is Figure 3 A view similar to the view of

[0078] - Figure 8 It is used to make Figure 2 Simplified view of the radial axis of the rotating arm of the turbine's variable-setting blades,

[0079] - Fig. 9 yes Figure 3 A partial cross-sectional perspective view of the planetary roller screw of the pitch change mechanism,

[0080] - Fig.10 According to the second embodiment Figure 2 A simplified longitudinal cross-sectional view of a portion of a pitch changing mechanism of a turbine. DETAILED DESCRIPTION

[0081] Figure 1 The illustrated aircraft 10 includes a turbine 12 for propelling the aircraft.

[0082] In the example shown, the aircraft 10 is an airplane. The aircraft generally comprises a fuselage 14, a horizontal tail 16 and two wings 18. Here, the number of turbines 12 is two, and each turbine is housed under a respective wing 18. In a variant (not shown), the turbines 12 are arranged along the fuselage 14 (for example near the horizontal tail 16). As another variant (also not shown), the aircraft 10 comprises a single turbine 12 or at least three turbines 12.

[0083] exist Figure 2 One of the turbines 12 is shown in FIG.

[0084] As can be seen in this figure, the turbine 12 extends along a longitudinal axis X. The turbine generally has an angular symmetry about said longitudinal axis X, that is to say there is at least one angle for which the turbine is invariant by a rotation about the longitudinal axis X.

[0085] Here and hereinafter, the terms "inner" and "outer", "inner" and "outer" and their variations are to be understood with reference to the axis X, elements described as "inner" or "inner" being oriented toward the axis X, while "outer" or "outer" elements are oriented opposite to the axis X.

[0086] The turbomachine 12 generally includes a nacelle 20 , an internal flow path 22 for circulating air flow through the nacelle 20 , a combustion chamber 24 housed in the flow path 22 , an engine body 26 , and a gas exhaust nozzle 28 .

[0087] In the following, the terms “upstream” and “downstream” are to be understood with reference to the flow path of the air flow through the flow path 22 .

[0088] The engine body 26 includes a compressor 30, a turbine 32, and a transmission shaft 34, which couples the turbine 32 to the compressor 30 to drive the compressor 30 through the turbine 32. The compressor 30 is arranged upstream of the combustion chamber 24, and supplies compressed air to the combustion chamber 24. The turbine 32 is arranged downstream of the combustion chamber 24 and receives exhaust gas leaving the combustion chamber 24.

[0089] The transmission shaft 34 has a longitudinal axis X as a rotation axis.

[0090] The transmission shaft 34 is guided for rotation relative to the nacelle 20 by bearings (not shown).

[0091] In the example shown, the turbomachine 12 is a multi-body turbomachine, in particular a twin-body turbomachine, which includes a low-pressure body 40 in addition to the engine body 26. Thus, the engine body 26 constitutes a high-pressure body, the compressor 30 is a high-pressure compressor, the turbine 32 is a high-pressure turbine, and the transmission shaft 34 is a high-pressure shaft.

[0092] The low-pressure body 40 includes a low-pressure compressor 42 , a low-pressure turbine 44 , and a low-pressure shaft 46 that couples the low-pressure turbine 44 to the low-pressure compressor 42 to drive the low-pressure compressor 42 via the low-pressure turbine 44 .

[0093] The low-pressure compressor 42 is arranged upstream of the high-pressure compressor 30 and supplies compressed air to the high-pressure compressor. The low-pressure turbine 44 is arranged downstream of the high-pressure turbine 32 and receives exhaust gas leaving the high-pressure turbine.

[0094] The low pressure shaft 46 is guided for rotation relative to the nacelle 20 by bearings (not shown).

[0095] The low-pressure shaft 46 is coaxial with the high-pressure shaft 34 . The low-pressure shaft thus also has a longitudinal axis X as a rotation axis. In particular, the low-pressure shaft 46 extends within the high-pressure shaft 34 .

[0096] The turbine 12 further comprises a fan 50 for driving an air flow in an outer circulation flow path 52 around the nacelle 20. Thus, a distinction can be made between a primary air flow A (hot), which is constituted by the portion of the air flow driven in the inner circulation flow path 22, and a secondary air flow B (cold), which is constituted by the portion of the air flow driven in the outer circulation flow path 52.

[0097] The fan 50 comprises a fan rotor 54. The fan rotor 54 is mounted rotatably relative to the nacelle 20 about the longitudinal axis X. The fan rotor comprises a hub 55 ( Figure 3 ), the hub is provided with fan blades 56 extending generally radially outward from the hub 55. These blades 56 drive the air flow in the outer flow flow path 52 when rotating.

[0098] exist Figure 8 As can be seen in FIG. 5 , each blade 56 includes a leading edge 57A, a trailing edge 57B, and a chord C connecting the leading edge 57A to the trailing edge 57B.

[0099] return Figure 2 , the fan rotor 54 is driven in rotation by the low-pressure turbine 44 via the low-pressure shaft 46. In the example shown, the drive is direct, that is to say the fan rotor 54 is rotationally fixed to the low-pressure shaft 46. As a variant (not shown), the drive is done via a reducer that enables the fan rotor 54 to rotate at a lower speed than the speed of the low-pressure shaft 46.

[0100] In the example shown, the fan 50 also comprises a fan stator 58 comprising blades 59 arranged at the periphery of the nacelle 20 in the outflow flow path 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 a counter-rotating fan rotor instead of a fan stator 58.

[0101] Advantageously, as shown, the fan 50 is unducted, ie the outer flow path 52 has no peripheral limit. Thus, as shown, the turbomachine 12 is constituted by an unducted fan turbojet, or as a variant by a turboprop. In a variant (not shown), the outer flow path 52 is defined between the nacelle 20 and a fan casing surrounding the fan 50; thus, the turbomachine 12 is generally constituted by a turbojet with a high bypass ratio, the bypass ratio being defined as the ratio of the flow of the secondary flow B (cold) to the flow of the primary flow A (hot).

[0102] In the example shown, the turbine 12 is in particular of the "puller" type, that is to say the fan 50 is arranged upstream of the inner flow path 22 and also drives the air flow in the inner flow path. In a variant (not shown), the turbine is of the "pusher" type, that is to say the fan 50 is arranged around the downstream half of the nacelle 20.

[0103] The blades 56 of the fan rotor 54 are variably arranged blades, that is, each blade 56 is pivotally mounted relative to the hub 55 about a specific pivot axis P. The pivot axis P extends along the elongation direction of the blade 56. The pivot axis is orthogonal to the longitudinal axis X.

[0104] In particular, each blade 56 is pivotable relative to the hub 55 about the axis P between a position called a feathered position, in which the chord C of the blade 56 is substantially parallel to the longitudinal axis X, and a position called a flat position, in which the chord C of the blade 56 is substantially orthogonal to the longitudinal axis X. Preferably, each blade 56 is also pivotable beyond the flat position to reach a position called a reverse position, in which the chord C of the blade 56 forms an angle strictly greater than 90° (for example substantially equal to 95°) with the longitudinal axis X. Since the blades 56 are usually twisted, the chord C, which serves as a measurement reference for the setting angle, is usually formed by the chord of the blade at 75% of the radius of the fan rotor 54.

[0105] For this reason, as in Figure 3 As can be seen in FIG, each blade 56 is fixed to an attachment 60 arranged at the blade root. The attachment 60 is mounted rotatably relative to the hub 55 about a pivot axis P. More precisely, the attachment 60 is mounted rotatably in a housing 62 arranged in the hub 55 by means of balls 64 or other rolling elements.

[0106] The fan 50 also comprises a pitch changing mechanism 70 for adjusting the setting angle of each blade 56 about its pivot axis P, so as to adapt the performance of the turbine 12 to different flight phases.

[0107] Now refer to Figures 3 to 9 A first embodiment of the pitch changing mechanism 70 will be described.

[0108] Reference Figure 3 In this first embodiment, the pitch changing mechanism 70 comprises a frame 72 , a control actuator 74 , a system 76 for controlling the actuator 74 , and a coupling system 78 .

[0109] The frame 72 is fixed to the hub 55 and is generally constituted by a portion of the hub 55. The frame is thus fixed relative to the pivot axis P.

[0110] The frame 72 comprises a base 80. The base 80 is centered on the longitudinal axis X. Here, the base is traversed by the pivot axis P.

[0111] In the example shown, the base 80 delimits a housing 82 open toward downstream. This housing 82 is in particular a cylinder, in particular a cylinder of revolution, and is centered on the axis X. An oil-transmitting bearing 84 is received in said housing 82 .

[0112] The base 80 also defines a cavity 86 opening into the upstream face 88 of the base 80 through an orifice 90 , here centered on the axis X. This cavity 86 is in particular cylindrical (generally a cylinder of revolution) and centered on the axis X. The cavity is arranged between the upstream face 88 and the housing 82 .

[0113] The base 80 has a stop 92 directed upstream. The stop 92 is formed here by a portion of the upstream face 88. The stop extends substantially radially and is arranged in particular around the orifice 90.

[0114] In the example shown, the frame 72 also comprises a cylindrical body 94 protruding upstream from the base 80. This cylindrical body 94 is centered on the axis X and is open at its upstream end 95. The cylindrical body extends around the stop 92. This cylindrical body is generally a cylinder of revolution.

[0115] Here, the frame 72 also includes an outer peripheral cylindrical body 96 which is coaxial with the cylindrical body 94 and surrounds the cylindrical body 94 and projects upstream from the base 80. The cylindrical body 96 is open at its upstream end 97. The cylindrical body 96 is generally in the shape of a cylinder of revolution.

[0116] The base 80 and the outer peripheral cylinder 96 together define an outer peripheral surface 88 of the frame 72. The outer peripheral surface 88 is generally cylindrical and is centered on the axis X. The outer peripheral surface is oriented radially outwardly.

[0117] In the variant, Figure 5 As shown, the frame 72 does not include the cylindrical body 94 .

[0118] As another variation, Figure 6 As shown, the frame 72 does not include the peripheral cylinder 96. The outer peripheral surface 88 is therefore defined by the base 80 and the cylinder 94.

[0119] Back to Figure 3 The control actuator 74 includes a fixed component 100 and a movable component 102, the fixed component is fixed to the frame 72, and the movable component can be moved relative to the fixed component 100 along the longitudinal axis X in a retracted position (such as Figure 3 ) and the expanded position (as shown Figure 4 Optionally, the moving part 102 can also be rotated around the longitudinal axis X at a limited angle (eg, about 5°).

[0120] The control actuator 74 comprises in particular a continuous cylinder 104 forming one of the fixed part 100 and the moving part 102 and a piston 106 forming the other of the fixed part 100 and the moving part 102. Here, the cylinder 104 forms the moving part 102 and the piston 106 forms the fixed part 100.

[0121] Thus, in the example shown, the cylinder 104 surrounds and extends coaxially with the outer peripheral surface 88 of the frame 72 , and the piston 106 is formed by a collar 108 fixed to the frame 72 and extending radially outward from the outer peripheral surface 88 to the cylinder 104 .

[0122] The cylinder 104 defines an inner cavity 110. The piston 106 divides the inner cavity 110 into two adjacent fluid chambers 112, 114. Each fluid chamber contains a control fluid, typically consisting of oil, to control the displacement of the moving part 102 relative to the fixed part 100. The control fluid is at a first pressure in the first fluid chamber 112 and at a second pressure in the second fluid chamber 114. The first fluid chamber 112 and the second fluid chamber 114 are arranged so that a relative increase in the first pressure (that is, an increase relative to the second pressure) causes the piston 110 to be displaced toward the extended position of the piston, and a relative increase in the second pressure (that is, an increase relative to the first pressure) causes the piston 110 to be displaced toward the retracted position of the piston.

[0123] Here, each of the fluid chambers 112, 114 is bounded internally by the outer peripheral surface 88 of the frame 72 and externally by the cylinder 104. In addition, the first fluid chamber 112 is bounded at its downstream end by the piston 106, and the second fluid chamber 114 is bounded at its upstream end by the piston 106.

[0124] The control actuator 74 is therefore particularly compact, which enables the control actuator to be made lighter.

[0125] exist Figure 3 In the example shown, the moving part 102 also includes an upstream guide bushing 116 and a downstream guide bushing 118, each of which is fixed to the cylinder 104 and extends radially inward from the cylinder 104 to the outer peripheral surface 88 of the frame 72. The upstream guide bushing 116 is arranged upstream of the piston 106 and defines the upstream end of the first fluid chamber 112. The downstream guide bushing 118 is arranged downstream of the piston 106 and defines the downstream end of the second fluid chamber 114.

[0126] exist Figure 3 In the example shown, each of the upstream guide bushing 116 and the downstream guide bushing 118 constitutes a sealing bushing and respectively longitudinally closes the first fluid chamber 112 and the second fluid chamber 114. Thus, the fluid chambers 112, 114 are closed at each of the longitudinal ends of the control actuator 74.

[0127] In the variant, Figure 7As shown, only the downstream guide bushing 118 constitutes a sealing bushing. The upstream guide bushing 118 has a bore 119 enabling a control fluid to flow through the upstream guide bushing 118 .

[0128] In another variation, Figure 5 As shown, the moving component 102 does not include an upstream guide bushing 118 .

[0129] Back to Figure 3 The control system 76 includes a pressure generator 130, a pressure control unit 132, and a return line 136. The pressure generator is used to make the control fluid reach a third pressure higher than the first pressure and the second pressure. The pressure control unit is used to adjust the pressure of the control fluid in the first fluid chamber 112 and the second fluid chamber 114 by the third pressure. The return line is used to discharge the reduced pressure control fluid. The control system 76 also includes a main tank 133, a backup circuit 134, and a control module 135.

[0130] The pressure generator 130 comprises, for example, a pump capable of pumping the fluid to a third pressure, for example 100 bar. When the pressure of the control fluid downstream of the pressure generator 130 exceeds the third pressure, the main pressure relief valve 139A enables a portion of the control fluid to be discharged to the return line 136.

[0131] The pressure control unit 132 is supplied with control fluid at a third pressure by the pressure generator 130. The pressure control unit is fluidly connected to the first fluid chamber 112 and the second fluid chamber 114 via the oil transfer bearing 106. The pressure control unit is capable of distributing the control fluid between the first fluid chamber 112 and the second fluid chamber 114 to adjust the fluid pressure inside each of these chambers 112, 114, thereby adjusting the position of the piston 110 between the retracted position and the extended position of the piston. The pressure control unit is also capable of discharging the control fluid from the first fluid chamber 112 and the second fluid chamber 114 into the return line 136.

[0132] The main tank 133 is configured to collect the reduced pressure control fluid from the return line 136. The main tank supplies the pressure generator 130.

[0133] The backup circuit 134 is capable of supplying control fluid to the first fluid chamber 112 to move the piston 110 toward its deployed position in the event of a failure of the pressure generator 130. To this end, the backup circuit 134 comprises an auxiliary tank 137 and an auxiliary pump 138. In the example shown, the backup circuit also comprises an auxiliary pressure relief valve 139B.

[0134] The auxiliary tank 137 is configured to collect the pressure reduction control fluid from the return line 136. The auxiliary tank supplies the auxiliary pump 138. In the example shown, the auxiliary tank also supplies the main tank 133, and the pressure reduction control fluid from the return line 136 passes through the auxiliary tank 137 before reaching the main tank 133.

[0135] The auxiliary pump 138 is capable of pumping the control fluid into the auxiliary tank 137 to bring the control fluid to a third pressure. The auxiliary pump is fluidically connected to the pressure control unit 132 to supply the control fluid at the third pressure to the pressure control unit, and the pressure control unit 132 is configured to redirect all the control fluid from the auxiliary pump 138 toward the first fluid chamber 112.

[0136] When the pressure of the control fluid downstream of the auxiliary pump 138 exceeds the third pressure, the pressure reducing valve 139B is capable of discharging a portion of the control fluid towards the return line 136 .

[0137] The control module 135 is configured to receive a setting instruction (not shown) and derive a control signal from the setting instruction to be sent to the pressure control unit 132. In particular, the control module 135 is configured to send a control signal to the pressure control unit 132 to increase the fluid pressure in the first chamber 112 when the setting instruction is intended to increase the pitch of the blade 56, and to send a control signal to the pressure control unit 132 to increase the fluid pressure in the second chamber 114 when the setting instruction is intended to decrease the pitch of the blade 56.

[0138] The control module 135 is also configured to send a start-up command to the backup circuit 134 (more specifically, to the auxiliary pump 138 of the backup circuit) in the event of a failure of the pressure generator 130 .

[0139] The coupling system 78 couples the mobile part 102 to each blade 56 to convert the translation of the mobile part 102 along the longitudinal axis X and, if applicable, the rotation of the mobile part 102 about the longitudinal axis X into a rotation of each blade 56 about its pivot axis P. In particular, the coupling system 78 couples the mobile part 102 to each blade 56 to:

[0140] - converting a translation of the mobile member 102 along the longitudinal axis X on a first course into a rotation of the variable-set blade 56 about the pivot axis P towards the flat position, and

[0141] - Converting a translation of the mobile member 102 along the longitudinal axis X in a second direction opposite to the first path into a rotation of the variable-set blade 56 about the pivot axis P towards the feathered position.

[0142] To this end, the coupling system 78 comprises a synchronizing ring 140 fixed to the mobile part 102 and, for each of the blades 56 , means 142 for coupling the blade 56 to the synchronizing ring 140 .

[0143] The synchronizer ring 140 extends in a radial plane around the mobile part 102 . In particular, the synchronizer ring is fixed to an upstream end 143 of the mobile part 102 .

[0144] Each coupling mechanism 142 includes a first hinge 144 fixed to the moving part 102 , a second hinge 146 fixed to the blade 56 away from the pivot axis P of the blade 56 , and a coupling member 148 coupling the first hinge 144 to the second hinge 146 .

[0145] The first joint 144 is carried by the synchronizer ring 140. The first joint is formed here by a ball joint connection.

[0146] The second hinge 146 is also constituted by a ball joint connection. The second hinge is eccentric relative to the pivot axis P.

[0147] The coupling member 148 has a first end 150 hinged to the first hinge 144 and a second end 152 hinged to the second hinge 146. Advantageously, the coupling member 148 is rigid and has an adjustable length, that is, the distance between the first end 150 and the second end 152 can be changed, which makes it possible to accurately adjust the length of the coupling member in a fixed state so that the setting angle of each blade 56 can be manipulated by the pitch change mechanism 70.

[0148] In this case, the coupling component 148 is formed by a connecting rod 153 .

[0149] In the example shown, each coupling mechanism 142 also comprises a crank 154 coupling the attachment 60 to the second hinge 146. This crank 154 is rigid and fixed to the attachment 60. The crank extends at least partially in a direction orthogonal to the pivot axis P. The crank forms an arm for rotating the blade 56.

[0150] exist Figure 3 In the example shown, a first path extends from upstream to downstream, that is, a displacement of the mobile member 102 towards the stop 92 (in other words, towards the retracted position of the mobile member) causes each blade 56 to rotate towards the flat position of the blade, and a second path extends from downstream to upstream, that is, a displacement of the mobile member 102 away from the stop 92 (in other words, towards the deployed position of the mobile member) causes each blade 56 to rotate towards the feathered position of the blade. In addition, the first hinge 144 is arranged upstream of the second hinge 146.

[0151] For this reason, as in Figure 8 It can be seen in FIG. 1 that the second hinge 146 is arranged opposite the trailing edge 57B relative to a plane Q which is orthogonal to the chord C and contains the pivot axis P.

[0152] This particular arrangement enables the natural load of the blade 56 toward its flat position to enable the coupling member 148 to work in traction rather than compression when the pitch change mechanism 70 is fixed. Therefore, the risk of buckling of the coupling member 148 is very low, enabling the use of a relatively weak coupling member 148, thereby making the pitch change mechanism 70 lightweight.

[0153] The pitch changing mechanism 70 also comprises a pitch locking device 160 capable of blocking a translation of the mobile part 102 of the control actuator 74 along a first path, that is to say here towards the retracted position of the mobile part.

[0154] The locking device 160 includes a support member 162 and a screw-nut system 164 .

[0155] The support member 162 can be in an operating position ( Figures 3 to 7 The support member 162 is translated along a first path (that is, between a first position and a second position) and a locked position (not shown). Figure 3 In the example shown, the support member 162 is moved from its operating position to its locking position by translating from upstream to downstream. In other words, the operating position of the support member 162 is arranged upstream of the locking position of the support member.

[0156] The support member 162 comprises a body 166 extending along the longitudinal axis X and centered on the longitudinal axis X. The body 166 has a first longitudinal end 168 (in particular a downstream longitudinal end), the first longitudinal end being engaged by the orifice 90 of the frame 72, and a second free longitudinal end 170. Here, the body 166 is solid.

[0157] The first longitudinal end 168 and the aperture 90 of the frame 72 together form a guide system 172 for guiding the support member 162 relative to the frame 72 . The guide system 172 is arranged here on the downstream side of the screw-nut system 164 .

[0158] The support member 162 also includes a sleeve 174 secured to the body 166 and disposed about the second longitudinal end 170 of the body 166 .

[0159] The screw-nut system 164 includes a screw 176 and a nut 178 .

[0160] The screw 176 extends around the body 166 of the support member 162 and is coaxial with said body 166. The screw is fixed in translation to the support member 162 and is mounted movably to rotate relative to the support member 162 about the longitudinal axis X. To this end, the screw 176 is assembled to the support member 162 by means of a bearing 180. This bearing 180 is here arranged between a sleeve 174 of the support member 162 and an end portion 182 of the screw 176, which end portion of the screw is housed between the body 166 and the sleeve 174.

[0161] The screw 176 has a second longitudinal end portion 184 opposite the end portion 182. The second longitudinal end portion 184 defines a radial abutment surface 186. The abutment surface 186 is located at a distance from the frame 72 when the support member 162 is in the operating position and bears against the stop 92 of the frame 72 when the support member 162 is in the locking position.

[0162] Here, the second longitudinal end portion 184 flares from the threaded body 190 of the screw 176 to the abutment surface 186. Thus, the contact surface between the abutment surface 186 and the stop 92 increases, which increases the friction between the abutment surface 186 and the stop 92 and enables better transmission of braking and stopping forces.

[0163] The abutment surface 186 and the stop 92 are both smooth here. In a variant (not shown), the abutment surface 186 and / or the stop 92 have roughening to further increase the friction between the abutment surface 186 and the stop 92 and enable an even better transmission of forces.

[0164] In particular, the abutment surface 186 extends substantially radially. The abutment surface is oriented along a first path, that is, in Figure 3 In the example shown, it is oriented downstream. Here, the abutment surface is arranged at the downstream end of the screw 176.

[0165] The threaded body 190 extends from one of the end portions 182, 184 to the other end portion. The threaded body has external threads 192 at its circumference.

[0166] The threaded body 190 and the nut 178 are received within the cylindrical body 94 of the frame 72 .

[0167] The nut 178 is fixed to the moving part 102 of the actuator 74 and is coaxial with the screw 176. The nut 178 interacts with the screw 176 so that translation of the nut 178 relative to the screw 176 along the longitudinal axis X causes the screw 176 to rotate about the longitudinal axis X relative to the support member 162.

[0168] The nut 178 has an internal thread 194 .

[0169] The screw-nut system 164 is in particular formed by a reversible planetary roller screw system 195. Typically, in addition to the screw 176 and the nut 178, this planetary roller screw system 195 comprises a plurality of rollers 196 arranged between the screw 176 and the nut 178, each roller 196 extending parallel to the longitudinal axis X.

[0170] like Fig. 9 As shown, each roller 196 has threads 198 that engage with the external threads 192 of the screw 176 and the internal threads 194 of the nut 176. Each roller also includes external teeth 199 located at the end of the roller and extended by a smooth journal 200.

[0171] Typically, the planetary roller screw system 195 also has means 202 for guiding and retaining the rollers 196. The guide and retaining means 202 include a roller retaining portion 204 (also called a spacing bushing) mounted coaxially with the screw 176 between the screw and the nut 178, the roller retaining portion having a recess 206 that receives the journal 200 of the roller 196. The guide and retaining means also include a synchronizing tooth 210 in which the external teeth 198 located at the respective ends of the rollers 196 mesh. This meshing of the external teeth 198 in the synchronizing teeth 210 forms a planetary gear train, the function of which is to ensure the synchronization of the planetary motion (also called planetary motion or epicyclic motion) of the rollers 196, thereby smoothing the movement of the rollers 196 by helping them to roll easily on the threads 192 of the screw 176 and the threads 194 of the nut 178 with as little slippage as possible.

[0172] In the example shown, the planetary roller screw system 195 is of standard type, with the rollers 196 fixed in translation to the nut 178. The synchronizing teeth 210 consist of internal teeth of a ring 208 fixed to the nut 178 and mounted respectively at each longitudinal end of the nut 178, the longitudinal extension of the nut being substantially equal to that of the threaded portion of the rollers 196 and less than that of the threaded body 190 of the screw 176.

[0173] In a variant (not shown), the planetary roller screw system 195 is of the inverted type, the rollers 196 being fixed in translation to the screws 176. The synchronous teeth 210 are thus constituted by two external teeth of the screw 176 at each longitudinal end of the threaded body 190, the longitudinal extension of which is substantially equal to the longitudinal extension of the threaded portion of the rollers 196 and less than the longitudinal extension of the nut 178.

[0174] As another variant, the planetary roller screw system 195 is composed of a recycling planetary roller screw system (for example, the recycling planetary roller screw system described in document EP275504A2), or of a bearing roller screw system (for example, the bearing roller screw system described in document EP168942A1 or the bearing roller screw system described in document EP 671070A1).

[0175] This feature enables a good transmission of forces from the nut 178 to the screw 176 via the screw-nut system 164, while maintaining a small pitch in the helical coupling of the screw-nut system 164. In particular, this makes it possible to fix the nut 178 relative to the screw 176 even without a different locking nut, in the case where the rotation of the screw 176 is blocked. Thus, the use of a different locking nut can be omitted, which simplifies the manufacture of the mechanism and reduces costs, while increasing the reliability of the mechanism and minimizing its mass.

[0176] In a variant (not shown), the screw-nut system 164 consists of a screw-nut system similar to the one described in EP 1 832 509 .

[0177] return Figure 3 In the example shown in the figure, the pitch lock device 160 is located outside the fluid chambers 112, 114 of the control actuator 74. This arrangement enables the pitch lock device 160 and the actuator 74 to be assembled to the frame 72 independently of each other, which facilitates the installation of the pitch change mechanism 70 and thus reduces costs.

[0178] As in Figure 3 , a portion of the pitch lock device 160 even extends longitudinally away from the control actuator 74. In other words, there is a radial plane beyond which a portion of the pitch lock device 160 extends, while the actuator 74 does not extend beyond said radial plane. In particular, said portion of the pitch lock device 160 extends upstream of the actuator 74.

[0179] In order to enable such an arrangement to be formed, the pitch locking device 160 comprises a collar 193 which couples the nut 178 to the mobile part 102 of the actuator 74. This collar 193 here protrudes longitudinally towards upstream from the control actuator 74. In particular, the collar is frustoconical, the diameter of which decreases from a downstream end 193A of the collar attached to the actuator 74 to an upstream end 193B of the collar attached to the nut 178.

[0180] exist Figure 3In the example shown, the pitch lock 160 also forms a cantilever in the longitudinal direction relative to the frame 72. In other words, the entire portion of the frame 72 that supports the lock 160 is longitudinally located on the same side (here downstream) of the lock 160; the lock 160 is not longitudinally surrounded by the portion of the frame 72 that supports the lock. Due to this arrangement, the use of a support arranged upstream of the lock 160 is avoided, which facilitates access to the pitch change mechanism 70, in particular to the coupling system 78.

[0181] Therefore, in Figure 3 In the example shown, the control actuator 74 is arranged longitudinally on the same side of the nut 178 as the guide 172 and the stop 92 (here the downstream side).

[0182] In order to ensure good support of the locking device 160 even in the case of cantilevering, the pitch changing mechanism 70 comprises a device 220 for guiding the nut 178 relative to the frame 72. The guiding device 220 comprises an inner cylinder 222 fixed to the nut 178 and an outer cylinder 224 fixed to the frame 72, the inner cylinder 222 cooperating with the outer cylinder 224 to slide longitudinally inside the outer cylinder.

[0183] Specifically, the nut 178 is mounted on the inner surface 226 of the inner cylindrical body 222. The inner cylindrical body 222 has an upstream end 228 to which the upstream end 193B of the ferrule 193 is fixed.

[0184] Here, the outer cylindrical body 224 is formed by the cylindrical body 94 of the frame 72 .

[0185] The pitch lock device 160 requires lubrication. To this end, the lock device 160 comprises a housing 230 which at least partially defines an enclosure for the circulation of a lubricating fluid for the pitch lock device 160. This housing 230 is fixed to the nut 178 and surrounds the nut 178, the screw 176 and the support member 162.

[0186] exist Figure 3 , Figure 4 and Figure 6In the example of , the housing 230 includes an inner cylinder 222 and a plug portion 232, the plug portion closing an end (here, the upstream end 228) of the inner cylinder 222 opposite to the frame 72. The inner cylinder 222 has a seal 234 on its outer periphery that contacts the inner surface 236 of the outer cylinder 224. Therefore, the outer cylinder 224 and the housing 230 together define a capsule 238 for the circulation of the lubricating fluid of the locking device 160. The capsule 238 is fluidically isolated from the fluid chambers 112, 114 of the actuator 74 by the seal 234 and the upstream guide bushing 116. Therefore, the seal 234 and the guide bushing 116 form a seal of the pitch change mechanism 70, and the seal of the pitch change mechanism fluidly isolates the fluid chambers 112, 114 of the actuator 74 from the pitch locking device 160.

[0187] Advantageously, the lubricating fluid of the locking device 160 consists of oil. Thus, the pitch locking device 160 comprises an accumulation (not shown) making it possible to store lubricating fluid when the actuator 74 is in the retracted position and to deliver the lubricating fluid to the enclosure 238 when the actuator 74 moves towards its deployed position. As a variant, the lubricating fluid for the locking device 160 consists of grease deposited on the screw 176 and on the balls of the bearing 180.

[0188] exist Figure 5 (wherein the outer cylinder 224 and the upstream guide bushing 116 are not present) and Figure 7 (where the inner cylindrical body 222 and the upstream guide bushing 116 are perforated), the housing 230 is composed of the collar 193 and the plug portion 239 that closes the upstream end 193B of the collar 193. Therefore, the first fluid chamber 112 is in fluid communication with the interior of the housing 230, and the control fluid constitutes the lubricating fluid for the locking device 160.

[0189] This variant makes it possible to dispense with the use of an accumulation section. However, this variant requires a Figure 3 , Figure 4 and Figure 6 A variation of the flow rate pump 130 has a higher flow rate.

[0190] The locking device 160 further includes a biasing device 240 that biases the support member 162 toward the locked position of the support member and a retaining device 242 for retaining the support member 162 in the operating position of the support member when the pitch changing mechanism 70 is in normal operating conditions.

[0191] The biasing means 240 here consists of a compression spring which is compressed between the frame 72 and a shoulder 244 fixed to the support member 162. The biasing means is housed in the cavity 86, in particular between the shoulder 244 and the orifice 90.

[0192] The retaining device 242 includes a balancing actuator 250 including a balancing piston 252 and a balancing chamber 254 .

[0193] The balancing piston 252 is movably mounted in translation relative to the frame 72 along the longitudinal axis X. The balancing piston is in particular coaxial with the support member 162 . In the example shown, the balancing piston is arranged in the longitudinal extension of the support member 162 , between the support member 162 and the balancing chamber 254 .

[0194] The balancing chamber 254 is defined between the balancing piston 252 and the frame 72. In particular, the balancing chamber 254 is defined between the balancing piston 252 and a bottom 255 of the cavity 86 opposite the orifice 90; therefore, the guide system 172, the biasing device 240 and the retaining device 250 are all longitudinally arranged on the same side (here the downstream side) of the screw-nut system 164 (in particular the nut 178).

[0195] The balancing chamber 254 is fluidically connected to the pressure generator 130 via a fluid connection circuit 256 and is thus supplied with control fluid at a third pressure. The balancing chamber is intended to counteract the bias of the biasing device 240 when this supply is active.

[0196] To this end, the balancing actuator 250 is arranged so that the pressure exerted on the piston 252 by the fluid contained in the chamber 254 is directed in a direction opposite to the biasing direction of the biasing device 250: in the example shown, the balancing piston 252 is arranged between the chamber 254 and the shoulder 244, and the shoulder 244 is arranged between the piston 252 and the biasing device 240. Furthermore, the balancing piston 252 and the balancing chamber 254 are dimensioned so that when the chamber 254 is supplied with a control fluid at a third pressure, the force exerted by the control fluid on the piston 252 is greater than the biasing pressure of the biasing device 240.

[0197] Thus, when control fluid at the third pressure is supplied to chamber 254, the bias of biasing device 240 is removed and support member 162 remains in the operating position.

[0198] In the example shown, the pressure control unit 132 is fluidly disposed between the pressure generator 130 and the fluid connection circuit 256. The pressure control unit has a first configuration in which the pressure control unit isolates the fluid connection circuit 256 from the return line 136 and a second configuration in which the pressure control unit fluidly connects the fluid connection circuit 256 to the return line 136.

[0199] The pressure control unit 132 is configured to be normally in a first configuration of the pressure control unit, and to switch to a second configuration of the pressure control unit upon receiving a control instruction sent by the control module 135 .

[0200] A method for changing the pitch of the blades 56 implemented by the pitch changing mechanism 70 according to the first embodiment will now be described.

[0201] During a first step of the method, the control module 135 first receives a setting instruction intended to increase the pitch of the blade 56. The control module 135 then sends a control signal to the pressure control unit 132 intended to increase the fluid pressure in the first chamber 112. Due to the increase in the fluid pressure in the first chamber 112, the mobile part 102 of the actuator 74 moves in the second direction towards its deployed position, which causes the blade 56 to pivot towards a large pitch, that is to say towards a feathered position, via the coupling system 78.

[0202] Once the moving member 102 reaches the equilibrium position, the moving member stabilizes and the blades 56 maintain a fixed orientation.

[0203] During the second step of the pitch change method, the control module 135 first receives a setting instruction aimed at reducing the pitch of the blade 56. Then, the control module 135 sends a control signal to the pressure control unit 132 aimed at increasing the fluid pressure in the second chamber 114. Due to the increase in the fluid pressure in the second chamber 114, the mobile part 102 of the actuator 74 moves along a first path towards its retracted position, which causes the blade 56 to pivot towards a small pitch, that is to say towards a flat position, via the coupling system 78.

[0204] Once the moving member 102 reaches the equilibrium position, the moving member stabilizes and the blades 56 maintain a fixed orientation.

[0205] Optionally, the pitch changing method further comprises, after the first step or the second step, a step of locking the orientation of the blade 56 in a controlled manner.

[0206] During this step, the control module 135 sends a pitch lock control to the pressure control unit 132. Under the effect of this control, the pressure control unit 132 fluidically connects the fluid connection circuit 256 to the return line 136, causing a drop in the fluid pressure in the balancing chamber 254. As a result, the fluid pressure in said chamber 254 is insufficient to counteract the bias of the biasing device 240, which therefore causes the support member 162 to shift towards its locked position.

[0207] During this displacement, the screw 176 rotates around the longitudinal axis X while translating under the action of the resistance exerted by the assembly of the nut 178 and the roller 194 (the assembly of the nut and the roller is kept from moving in translation by the control actuator 74) until the abutment surface 186 of the screw bears against the stop portion 92 of the frame 72, thereby preventing the screw 176 from rotating around the longitudinal axis X and translating along the same axis X.

[0208] Thus, even in the event of a loss of fluid pressure in the first chamber 112 , the vanes 56 are blocked in their orientation.

[0209] In the event of a loss of pressure only in the second chamber 114, the mobile part 102 of the actuator 74 moves along the second path under the effect of the pressure difference between the two chambers 112, 114, thereby driving the screw 176 and the support member 162 by this movement, and the support member returns to its operating position. Therefore, the mobile part 102 is no longer fixed and can continue to move along the second path until the blade 56 is in the feathered position.

[0210] In the event of a failure of the control system 76 (typically, in the event of a failure of the pressure generator 130 ), the pitch variation method includes an additional step of locking the orientation of the blades 56 in an uncontrolled manner.

[0211] During this step, a failure of the control system 76 causes the fluid pressure in the balance chamber 254 to drop, typically because the pressure generator 130 is no longer able to bring the control fluid to the third pressure. As a result, the fluid pressure in the chamber 254 is insufficient to counteract the bias of the biasing device 240, which causes the support member 162 to shift toward its locked position.

[0212] During this displacement, the screw 176 drives the nut 178 and the roller 194 through this displacement, which no longer remain non-translationally mobile due to the loss of power controlling the actuator 74. The blade 56 therefore pivots slightly towards the small pitch until the abutment surface 186 of the screw 176 bears against the stop 92 of the frame 72, thereby preventing the screw 176 from rotating about the longitudinal axis X and from translating along the same axis X.

[0213] The blade 56 is thus prevented from pivoting towards a low pitch by the locking device 160 .

[0214] The uncontrolled locking step is followed by a safety protection step of the fan 50. During this step, the backup circuit 134 is activated and supplies control fluid to the first fluid chamber 112 to increase the fluid pressure in this chamber. Under the effect of this pressure increase, the mobile part 102 moves along the second path, thereby driving the screw 176 and the support member 162 through this movement, and the support member returns to its operating position. Therefore, the mobile part 102 is no longer fixed and can continue to move downstream until the blades 56 are in the feathered position.

[0215] Note that these different steps can be performed independently of each other.

[0216] Now refer to Fig.10 A second embodiment of the pitch changing mechanism 70 will be described.

[0217] In this embodiment, pitch changing mechanism 70 includes a frame 272 , a control actuator 274 , a system 276 for manipulating actuator 274 , and a coupling system 278 .

[0218] The frame 272 is fixed to the hub 55 and is generally constituted by a portion of the hub 55. The frame is thus fixed relative to the pivot axis P.

[0219] In the example shown, the frame 272 includes an upstream assembly 280 and a downstream assembly 282 spaced apart from each other along the longitudinal axis X. Each of these assemblies 280 , 282 is centered on the longitudinal axis X and extends from the longitudinal axis X toward the housing 62 , the upstream assembly 280 being arranged upstream of the housing 62 and the downstream assembly 282 being arranged downstream of the housing 62 .

[0220] The upstream assembly 280 is formed in particular by an upstream flange 284 of substantially dome shape, which houses at its center a blind cylinder 286. The blind cylinder 286 is closed at its upstream end 288 and is open at its downstream end 289. The blind cylinder projects upstream relative to the flange 284.

[0221] The upstream component 280 has an orifice 290 in its center that is open toward the downstream. This orifice 290 is particularly arranged in the upstream end 288 of the blind cylindrical body 286. The upstream component 280 also has a stop 291 that is oriented downstream. This stop 291 is formed here in the downstream face of the upstream end 288 of the blind cylindrical body 286. The stop extends substantially radially and is particularly arranged around the orifice 290.

[0222] Here, the downstream assembly 282 comprises a downstream flange 292 which houses at its center two concentric cylinders 294, 296: a central cylinder 294 which is closed at its upstream end 298 and a peripheral cylinder 296 which surrounds the central cylinder 294 and defines with the central cylinder 294 a peripheral cavity 300 which is closed at its downstream end 302. The central cylinder 294 defines a housing 304 in which an oil delivery bearing 306 is received.

[0223] The control actuator 274 includes a fixed component 308 and a movable component 309, wherein the fixed component is fixed to the frame 72 and the movable component can be moved relative to the fixed component 308 along the longitudinal axis X in a retracted position (eg, Fig.10 Optionally, the moving part 309 can also be rotated around the longitudinal axis X at a limited angle (eg, about 5°).

[0224] The control actuator 274 notably comprises a piston 310 forming the moving part 309 .

[0225] The control actuator 274 further includes a first fluid chamber 312 and a second fluid chamber 314, each of which is defined between the control piston 310 and the frame 272. The fluid chambers 312, 314 each contain a control fluid, typically composed of oil, at a first pressure in the first fluid chamber 312 and at a second pressure in the second fluid chamber 314. The first fluid chamber 312 and the second fluid chamber 314 are arranged such that a relative increase in the first pressure (that is, an increase relative to the second pressure) causes the piston 310 to shift toward a retracted position of the piston, and a relative increase in the second pressure (that is, an increase relative to the first pressure) causes the piston 310 to shift toward an extended position of the piston.

[0226] In the example shown, the piston 310 comprises a downstream sealing and guiding bushing 316, an upstream sealing and guiding bushing 318 and a cylindrical body 320 extending from the downstream sealing and guiding bushing 316 to the upstream sealing and guiding bushing 318. The downstream sealing and guiding bushing 316 is housed in the peripheral cavity 300 and extends from the central cylinder 294 to the peripheral cylinder 296 by forming a seal with each of these cylinders 294, 296. The upstream sealing and guiding bushing 318 is housed in the blind cylinder 286 and forms a seal with the peripheral wall 322 of the blind cylinder 286. Thus, the first fluid chamber 312 is delimited at its downstream end by the downstream sealing and guiding bushing 316, at its upstream end by the upstream end 288 of the blind cylinder 286, and at its periphery by the body 320 of the piston 310 and the peripheral wall 322 of the blind cylinder 286. The second fluid chamber 314 itself is constituted by the portion of the peripheral cavity 300 contained between a downstream sealing and guide bushing 316 and the downstream end 302 of said peripheral cavity 300 .

[0227] The control system 276 includes a pressure generator 330, a pressure control unit 332, and a return line 336. The pressure generator is used to make the control fluid reach a third pressure higher than the first pressure and the second pressure. The pressure control unit is used to adjust the pressure of the control fluid in the first fluid chamber 312 and the second fluid chamber 314 by the third pressure. The return line is used to discharge the reduced pressure control fluid. The control system 276 also includes a main tank 333, a backup circuit 334, and a control module 335.

[0228] The pressure generator 330 comprises, for example, a pump capable of pumping the fluid to a third pressure (eg 100 bar). When the pressure of the control fluid downstream of the pressure generator 330 exceeds the third pressure, the main pressure relief valve 339A enables a portion of the control fluid to be discharged to the return line 336.

[0229] The pressure control unit 332 is supplied with control fluid at a third pressure by the pressure generator 330. The pressure control unit is fluidly connected to the first fluid chamber 312 and the second fluid chamber 314 via the oil transfer bearing 306. The pressure control unit is capable of distributing the control fluid between the first fluid chamber 312 and the second fluid chamber 314 to adjust the fluid pressure inside each of these chambers 312, 314, thereby adjusting the position of the piston 310 between the retracted position and the extended position of the piston. The pressure control unit is also capable of discharging the control fluid from the first fluid chamber 312 and the second fluid chamber 314 into the return line 336.

[0230] The main tank 333 is configured to collect the reduced pressure control fluid from the return line 336. The main tank supplies the pressure generator 330.

[0231] The backup circuit 334 is capable of supplying control fluid to the second fluid chamber 314 to move the piston 310 to the retracted position of the piston in the event of a failure of the pressure generator 330. To this end, the backup circuit 334 includes an auxiliary tank 337 and an auxiliary pump 338. In the example shown, the backup circuit also includes an auxiliary pressure relief valve 339B.

[0232] The auxiliary tank 337 is configured to collect the pressure reduction control fluid from the return line 336. The auxiliary tank supplies the auxiliary pump 338. In the example shown, the auxiliary tank also supplies the main tank 333, and the pressure reduction control fluid from the return line 336 passes through the auxiliary tank 337 before reaching the main tank 333.

[0233] The auxiliary pump 338 is capable of pumping the control fluid into the auxiliary tank 337 to bring the control fluid to a third pressure. The auxiliary pump is fluidically connected to the pressure control unit 332 to supply the control fluid at the third pressure to the pressure control unit, and the pressure control unit 332 is configured to redirect all the control fluid from the auxiliary pump 338 to the second fluid chamber 314.

[0234] When the pressure of the control fluid downstream of the auxiliary pump 338 exceeds the third pressure, the pressure reducing valve 339B can discharge a portion of the control fluid towards the return line 336 .

[0235] The control module 335 is configured to receive a setting instruction (not shown) and derive a control signal from the setting instruction to be sent to the pressure control unit 332. In particular, the control module 335 is configured to send a control signal to the pressure control unit 332 to increase the fluid pressure in the second chamber 314 when the setting instruction is intended to increase the pitch of the blade 56, and to send a control signal to the pressure control unit 332 to increase the fluid pressure in the first chamber 312 when the setting instruction is intended to decrease the pitch of the blade 56.

[0236] The control module 335 is also configured to send a start-up command to the backup circuit 334 (more specifically, to the auxiliary pump 338 of the backup circuit) in the event of a failure of the pressure generator 330 .

[0237] The coupling system 278 couples the piston 310 to each blade 56 to convert a translation of the piston 310 along the longitudinal axis X and, where applicable, a rotation of the piston 310 about the longitudinal axis X into a rotation of each blade 56 about its pivot axis P.

[0238] To this end, the coupling system 278 includes a synchronizing ring 340 fixed to the piston 310 and, for each of the vanes 56 , a mechanism 342 for coupling the vane 56 to the synchronizing ring 340 .

[0239] The synchronizer ring 340 extends around the piston 310 in a radial plane.

[0240] Each coupling mechanism 342 includes a first hinge 344 fixed to the piston 310 , a second hinge 346 fixed to the blade 56 away from the pivot axis P of the blade 56 , and a connecting rod 348 coupling the first hinge 344 to the second hinge 346 .

[0241] The first articulation 344 is carried by the synchronizing ring 340. Here, the first articulation is formed by a ball joint connection.

[0242] The second hinge 346 is also constituted by a ball joint connection. The second hinge is eccentric relative to the pivot axis P.

[0243] The connecting rod 348 has a first end 350 hinged to the first hinge 344 and a second end 352 hinged to the second hinge 346. Advantageously, the connecting rod 348 has an adjustable length, that is, the distance between the first end 350 and the second end 352 can be changed, which enables the manipulation of the setting angle of each blade 56 to be precisely adjusted by the pitch change mechanism 70.

[0244] In the example shown, each coupling mechanism 342 also includes an eccentric 354 coupling the attachment 60 to the second hinge 346 .

[0245] The coupling system 278 is arranged so that a displacement of the piston 310 towards the stop 291 (i.e. towards the deployed position of the piston) causes each blade 56 to rotate towards the flat position of the blade, and a displacement of the piston 310 away from the stop 291 (i.e. towards the retracted position of the piston) causes each blade 56 to rotate towards the feathered position of the blade. To this end, the second hinge 346 is arranged on the side of the trailing edge 57B relative to a plane Q that is orthogonal to the chord C and contains the pivot axis P, that is to say relative to the pivot axis P and the second hinge 146 at Figures 4 to 9 The positions occupied in the embodiments are relative.

[0246] Note that Fig.10 In the example shown, the first hinge 344 is arranged upstream of the second hinge 346. The result of this is that, when the pitch change mechanism 70 is fixed, the natural load of the blade 56 towards its flat position causes the coupling member 348 to work under compression, resulting in the risk of buckling of said coupling member 348. In order to avoid the risk of buckling of the coupling member 348 and to be able to use a lighter coupling member 348, a variant (not shown) in which the first hinge 344 is arranged downstream of the second hinge 346 would be preferred. This particular arrangement (similar to that of the first embodiment) in fact makes it so that when the pitch change mechanism 70 is fixed, the natural load of the blade 56 towards its flat position causes the coupling member 348 to work under traction rather than under compression.

[0247] The pitch changing mechanism 70 further comprises a pitch locking device 360 ​​capable of preventing translation of the piston 310 relative to the frame 272 towards the deployed position of the piston.

[0248] The locking device 360 ​​includes a support member 362 and a screw-nut system 364 .

[0249] The support member 362 can be in an operating position ( Fig.10 The device can be translated to move between an unlocked position (shown) and a locked position (not shown).

[0250] The support member 362 comprises a body 366 extending along the longitudinal axis X and centered on the longitudinal axis X. The body 366 has a first longitudinal end 368 (in particular an upstream longitudinal end), the first longitudinal end being engaged by the orifice 290 of the frame 272, and a second free longitudinal end 372. Furthermore, in an example not shown, the body 366 is hollow and open at its two longitudinal ends 368, 372.

[0251] The support member 362 also includes a sleeve 374 secured to the body 366 and disposed about the second longitudinal end 372 of the body 366 .

[0252] The screw-nut system 364 includes a screw 376 and a nut 378 .

[0253] The screw 376 extends around the body 366 of the support member 362 and is coaxial with said body 366. The screw is fixed in translation to the support member 362 and is movably mounted to rotate relative to the support member 362 about the longitudinal axis X. To this end, the screw 376 is assembled to the support member 362 by means of a bearing 380. This bearing 380 is here arranged between a sleeve 374 of the support member 362 and an end portion 382 of the screw 376, which end portion of the screw is housed between the body 366 and the sleeve 374.

[0254] The screw 376 has a second longitudinal end portion 384 opposite the end portion 382. The second longitudinal end portion 384 defines a radial abutment surface 386. The abutment surface 386 is located at a distance from the frame 272 when the support member 362 is in the operating position and bears against the stop 291 of the frame 272 when the support member 362 is in the locking position.

[0255] Here, the second longitudinal end portion 384 flares from the threaded body 390 of the screw 376 to the abutment surface 386. Thus, the contact surface between the abutment surface 386 and the stop 291 increases, which increases the friction between the abutment surface 386 and the stop 291 and enables better transmission of braking and locking forces.

[0256] Here, the abutment surface 386 and the stop 291 are smooth. In a variant (not shown), the abutment surface 386 and / or the stop 291 have a roughening to further increase the friction between the abutment surface 386 and the stop 291 and enable a better transmission of force.

[0257] The threaded body 390 extends from one of the end portions 382, ​​384 to the other end portion. The threaded body has external threads 392 at its outer periphery.

[0258] The nut 378 is fixed to the piston 310 and is coaxial with the screw 376. The nut interacts with the screw 376 such that translation of the nut 378 relative to the screw 376 along the longitudinal axis X causes the screw 376 to rotate about the longitudinal axis X relative to the support member 362.

[0259] The nut 378 has an internal thread 394 .

[0260] The screw-nut system 364 is in particular formed by a reversible planetary roller screw system 395. Typically, in addition to the screw 376 and the nut 378, this planetary roller screw system 395 comprises a plurality of rollers 396 arranged between the screw 376 and the nut 378, each roller 396 extending parallel to the longitudinal axis X.

[0261] Preferably, the description of the planetary roller screw system 195 given above applies mutatis mutandis to the planetary roller screw system 395 .

[0262] This feature enables a good transmission of forces from the nut 378 to the screw 376 via the screw-nut system 364, while maintaining a small pitch in the helical coupling of the screw-nut system 364. In particular, this makes it possible to fix the nut 378 relative to the screw 376 even without a different locking nut, in the case where the rotation of the screw 376 is blocked. Thus, the use of a different locking nut can be omitted, which simplifies the manufacture of the mechanism and reduces costs, while increasing the reliability of the mechanism and minimizing its mass.

[0263] The locking device 360 ​​further includes a biasing device 420 that biases the support member 362 toward the locked position of the support member and a retaining device 422 for retaining the support member 362 in the operating position of the support member when the pitch changing mechanism 70 is in normal operating conditions.

[0264] The biasing device 420 is here constituted by a compression spring which is compressed between the frame 272 and a shoulder 424 fixed to the support member 362 .

[0265] The retaining device 422 includes a balancing actuator 430 including a balancing piston 432 and a balancing chamber 434 .

[0266] The balancing piston 432 is fixed to the support member 362 . The balancing piston is movably mounted in translation relative to the frame 272 along the longitudinal axis X. The balancing piston is in particular coaxial with the support member 362 . In the example shown, the balancing piston is arranged in the longitudinal extension of the support member 362 .

[0267] The balance piston 432 and the frame 272 together define a chamber 434 .

[0268] The balancing chamber 434 is fluidically connected to the pressure generator 330 via a fluid connection circuit 436 and is thus supplied with control fluid at a third pressure. The balancing chamber is intended to counteract the bias of the biasing device 420 when this supply is active.

[0269] To this end, the balancing actuator 430 is arranged so that the pressure exerted on the piston 432 by the fluid contained in the chamber 434 is directed in a direction opposite to the biasing direction of the biasing device 420: in the example shown, the balancing piston 432 is arranged between the chamber 434 and the shoulder 424, and the shoulder 424 is arranged between the piston 432 and the biasing device 420. Furthermore, the balancing piston 432 and the balancing chamber 434 are dimensioned so that when the chamber 434 is supplied with a control fluid at a third pressure, the force exerted by the control fluid on the piston 432 is greater than the biasing of the biasing device 420.

[0270] Thus, when control fluid at the third pressure is supplied to chamber 434, the bias of biasing device 420 is removed and support member 362 remains in the operating position.

[0271] In the example shown, the pressure control unit 332 is fluidly arranged between the pressure generator 330 and the fluid connection circuit 436. The pressure control unit has a first configuration in which the pressure control unit isolates the fluid connection circuit 436 from the return line 336 and a second configuration in which the pressure control unit fluidly connects the fluid connection circuit 436 to the return line 336.

[0272] The pressure control unit 332 is configured to be normally in a first configuration of the pressure control unit, and to switch to a second configuration of the pressure control unit upon receiving a control instruction sent by the control module 335 .

[0273] A method for changing the pitch of the blades 56 implemented by the pitch changing mechanism 70 according to the second embodiment will now be described.

[0274] During a first step of the method, the control module 335 first receives a setting instruction aimed at increasing the pitch of the blade 56. Then, the control module 335 sends a control signal to the pressure control unit 332 aimed at increasing the fluid pressure in the first chamber 312. Due to the increase in the fluid pressure in the first chamber 312, the control piston 310 moves towards its retracted position, which causes the blade 56 to pivot towards a large pitch, that is to say towards a feathered position, via the coupling system 278.

[0275] Once the piston 310 reaches the equilibrium position, the piston stabilizes and the vanes 56 maintain a fixed orientation.

[0276] During the second step of the pitch change method, the control module 335 first receives a setting instruction aimed at reducing the pitch of the blade 56. Then, the control module 335 sends a control signal to the pressure control unit 332 aimed at increasing the fluid pressure in the second chamber 314. Due to the increase in the fluid pressure in the second chamber 314, the control piston 310 moves towards its deployed position, which causes the blade 56 to pivot towards a small pitch, that is to say towards a flat position, via the coupling system 278.

[0277] Once the piston 310 reaches the equilibrium position, the piston stabilizes and the vanes 56 maintain a fixed orientation.

[0278] Optionally, the pitch changing method further comprises, after the first step or the second step, a step of locking the orientation of the blade 56 in a controlled manner.

[0279] During this step, the control module 335 sends a pitch lock control to the pressure control unit 332. Under the effect of this control, the pressure control unit 332 fluidically connects the fluid connection circuit 436 to the return line 336, resulting in a drop in the fluid pressure in the balance chamber 434. As a result, the fluid pressure in the chamber 434 is insufficient to counteract the bias of the biasing device 420, which results in the support member 362 being displaced toward its locked position.

[0280] During this displacement, the screw 376 rotates around the longitudinal axis X under the action of the resistance exerted by the assembly of the nut 378 and the roller 394 (the assembly of the nut and the roller is kept from moving in translation by the control actuator 274) until the abutment surface 386 of the screw bears against the stop portion 291 of the frame 272, thereby preventing the screw 376 from rotating around the longitudinal axis X and the screw from translating along the same axis X.

[0281] Thus, even in the event of a loss of fluid pressure in the first chamber 312 , the vanes 56 are blocked in their orientation.

[0282] In the event of a loss of pressure only in the second chamber 314, the piston 310 moves towards its retracted position under the effect of the pressure difference between the two chambers 312, 314, thereby driving the screw 376 and the support member 362 by this movement, which returns to its operating position. The piston 310 is therefore no longer fixed and can continue to move towards its retracted position until the blades 56 are in the feathered position.

[0283] In the event of a failure of the control system 276 (typically, in the event of a failure of the pressure generator 330 ), the pitch variation method includes an additional step of locking the orientation of the blades 56 in an uncontrolled manner.

[0284] During this step, a failure of the control system 276 causes the fluid pressure in the balance chamber 434 to drop, typically because the pressure generator 330 is no longer able to bring the control fluid to the third pressure. As a result, the fluid pressure in the chamber 434 is insufficient to counteract the bias of the biasing device 420, which causes the support member 362 to shift toward its locked position.

[0285] During this displacement, the screw 376 drives the nut 378 and the roller 394 through this displacement, which no longer remain non-translationally moved due to the loss of power controlling the actuator 274. The blade 56 thus pivots slightly towards the small pitch until the abutment surface 386 of the screw 376 bears against the stop 291 of the frame 272, thereby preventing the screw 376 from rotating about the longitudinal axis X and from translating along the same axis X.

[0286] The blade 56 is thus prevented from pivoting towards a low pitch by the locking device 360 ​​.

[0287] The uncontrolled locking step is followed by a safety protection step of the fan 50. During this step, the backup circuit 334 is activated and supplies control fluid to the first fluid chamber 312 to increase the fluid pressure in this chamber. Under the effect of this pressure increase, the piston 310 moves towards its retracted position, thereby driving the screw 376 and the support member 362 by this movement, and the support member returns to its operating position. Therefore, the piston 310 is no longer fixed and can continue to move downstream until the blades 56 are in the feathered position.

[0288] It should be noted that these different steps can be performed independently of each other.

[0289] Thus, due to the exemplary embodiment described above, it is possible to dispense with the use of a locking nut different from the nut 178, 378 of the screw-nut system 164, 364. This leads to simplified manufacturing, reduced costs and increased reliability of the locking device 160, 360 and thus of the pitch change mechanism 70.

[0290] Furthermore, due to the compactness of the control actuator 74 and the use of a less resistant and therefore lighter coupling member 148, Figures 3 to 9 The exemplary embodiment of makes it possible to make pitch changing mechanism 70 lighter.

[0291] Figures 3 to 9 The described exemplary embodiment of makes it possible to avoid the use of a support arranged upstream of the locking device 160 , which facilitates access to the pitch change mechanism 70 , in particular the coupling system 78 , after the pitch change mechanism has been assembled.

[0292] Figures 3 to 9These exemplary embodiments ultimately enable very precise manipulation of the setting angle of the blades 56 , which enables large blades 56 with complex geometries to be closely implanted on the hub 55 , thereby enabling increased efficiency of the turbine 12 .

Claims

1. A pitch changing mechanism (70) for adjusting the angular position of at least one variably settable blade (56) about a pivot axis (P) of the blade (56), the pitch changing mechanism (70) comprising: - a frame (72, 272) fixed relative to said pivot axis (P), a control actuator (74, 274) comprising a fixed part (100, 308) fixed to the frame (72, 272) and a mobile part (102, 309) movable in translation along a longitudinal axis (X) relative to the fixed part (100, 308) between a retracted position and a deployed position, a coupling system (78, 278) coupling the mobile part (102, 309) to the variable setting blade (56) for converting a translation of the mobile part (102, 309) along the longitudinal axis (X) into a rotation of the variable setting blade (56) about the pivot axis (P), and - a pitch locking device (160, 360) capable of preventing translation of the mobile part (102, 309) relative to the fixed part (100, 308) along at least one path, The pitch locking device (160, 360) comprises: a support member (162, 362) movable in translation along said longitudinal axis (X) relative to said frame (72, 272) between an operating position and a locking position, - a biasing device (240, 420) biasing the support member (162, 362) towards a locked position of the support member, and - retaining means (242, 422) for retaining the support member (162, 362) in an operating position of the support member under normal operating conditions, and - A screw-nut system (164, 364), comprising: a screw (176, 376) fixed in translation to the support member (162, 362) and movably mounted to rotate relative to the support member (162, 362) about the longitudinal axis (X), the screw (176, 376) having an abutment surface (186, 386) located at a distance from the frame (72, 272) when the support member (162, 362) is in the operating position and bearing against the frame (72, 272) when the support member (162, 362) is in the locking position, and a nut (178, 378) fixed to the mobile part (102, 309) and coaxial with the screw (176, 376), the nut (178, 378) cooperating with the screw (176, 376) such that translation of the nut (178, 378) along the longitudinal axis (X) causes rotation of the screw (176, 376) about the longitudinal axis (X), Therein, the screw-nut system (164, 364) is formed by a planetary roller screw system (195, 395).

2. The pitch changing mechanism (70) according to claim 1, wherein: The coupling system (78, 278) includes a first hinge (144, 344) fixed to the moving part (102, 309), a second hinge (146, 346) fixed to the variable setting blade (56) away from the pivot axis (P), and a coupling member (148, 348) coupling the first hinge (144, 344) to the second hinge (146, 346).

3. The pitch changing mechanism (70) according to claim 2, wherein: The first hinge (144) is arranged upstream of the second hinge (146), and the first route extends from upstream to downstream, or correspondingly, the first hinge is arranged downstream of the second hinge, and the first route extends from downstream to upstream.

4. The pitch changing mechanism (70) according to claim 2 or 3, wherein: The connecting member (148, 348) is composed of a connecting rod.

5. The pitch changing mechanism (70) according to any one of claims 2 to 4, wherein: The variable setting blade (56) includes a leading edge (57A), a trailing edge (57B), and a chord (C) connecting the leading edge (57A) to the trailing edge (57B), and the second hinge (146) is arranged opposite to the trailing edge (57B) relative to a plane that is orthogonal to the chord (C) and contains the pivot axis (P).

6. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The longitudinal axis (X) is generally orthogonal to the pivot axis (P).

7. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The planetary roller screw system (195, 395) is reversible.

8. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The control actuator (74, 274) comprises a first chamber (112, 312) and a second chamber (114, 314), wherein the first chamber contains a control fluid at a first pressure and the second chamber contains the control fluid at a second pressure, the pitch changing mechanism (70) comprises a pressure generator (130, 330) and a pressure control unit (132, 332), wherein the pressure generator is used to make the control fluid reach a third pressure higher than the first pressure and the second pressure, and the pressure control unit is used to adjust the first pressure and the second pressure by the third pressure, and the holding device (242, 422) comprises a balancing actuator (250, 430) having a chamber (254, 434), wherein the chamber is supplied with the control fluid at the third pressure to offset the bias of the biasing device (240, 420).

9. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The frame (72, 272) includes a stop portion (92, 291) against which an abutment surface (186, 386) of the screw (176, 376) bears when the support member (162, 362) is in the locked position, the variable setting blade (56) being movable about its pivot axis (P) between a flat position and a feathered position, the coupling system (78, 278) being configured such that displacement of the moving part (102, 309) toward the stop portion (92, 291) causes the variable setting blade (56) to rotate toward the flat position.

10. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The planetary roller screw system (195, 395) includes a plurality of rollers (196, 396) arranged between the screw (176, 376) and the nut (178, 378), each roller (196, 396) engaging with an external thread (192, 392) of the screw (176, 376) and an internal thread (194, 394) of the nut (178, 378).

11. The pitch changing mechanism (70) according to claim 10, wherein: Each roller (196, 396) is translationally fixed to the nut (178, 378) or the screw (176, 376).

12. The pitch changing mechanism (70) according to any one of claims 1 to 10, wherein: The planetary roller screw system (195, 395) consists of a recirculating planetary roller screw system or a planetary roller bearing screw system.

13. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The abutment surface (186, 386) is arranged at the downstream end of the screw (176, 376), or respectively at the upstream end of the screw.

14. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The control actuator (74, 274) includes a cylinder (104) and a piston (106), wherein the cylinder forms one of the fixed component (100, 308) and the movable component (102, 309), and the piston forms the other of the fixed component (100, 308) and the movable component (102, 309), the cylinder (104) defining an inner cavity (110), and the piston (106) dividing the inner cavity (110) into two fluid chambers (112, 114), each fluid chamber containing a control fluid for controlling the displacement of the movable component (102, 309) relative to the fixed component (100, 308).

15. The pitch changing mechanism (70) according to claim 14, wherein: The cylinders (104) are continuous.

16. The pitch changing mechanism (70) according to claim 14 or 15, wherein: The fluid chambers (112, 114) are adjacent.

17. The pitch changing mechanism (70) according to any one of claims 14 to 16, wherein: Each fluid chamber (112, 114) is at least partially defined by an outer peripheral surface (88) of the frame (72).

18. The pitch changing mechanism (70) according to any one of claims 14 to 17, wherein: The fluid chambers (112, 114) are closed at each of the longitudinal ends of the control actuator (74).

19. The pitch changing mechanism (70) according to any one of claims 14 to 18, wherein: The pitch lock device (160) is located outside the fluid chamber (112, 114).

20. The pitch change mechanism (70) of claim 19, comprising a seal (116, 234) fluidly isolating the fluid chamber (112, 114) from the pitch lock (160).

21. The pitch changing mechanism (70) according to any one of claims 14 to 19, wherein: The pitch locking device (160) includes a housing (230) fixed to the nut (178) and surrounding the nut (178), the screw (176) and the support member (162), one of the two fluid chambers (112, 114) being in fluid communication with the interior of the housing (230), and the control fluid constituting a lubricating fluid for the pitch locking device (160).

22. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The pitch lock device (160) includes a housing (230) fixed to the nut (178) and surrounding the nut (178), the screw (176) and the support member (162).

23. The pitch changing mechanism (70) according to claim 22, wherein: The housing (230) at least partially defines an enclosure (238) for the circulation of lubricating fluid for the pitch lock device (160).

24. The pitch changing mechanism (70) according to claim 22 or 23, wherein: The housing (230) includes an inner cylinder (222) which carries the nut (178) on an inner surface (226) and cooperates with an outer cylinder (224) fixed to the frame (72) to slide longitudinally within the outer cylinder, the inner cylinder (222) having a seal (234) at its outer periphery in contact with an inner surface (236) of the outer cylinder (224), the outer cylinder (224) and the housing (230) together defining a seal (238) for the circulation of a lubricating fluid for the pitch locking device (160).

25. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: At least a portion of the pitch lock (160) extends longitudinally away from the control actuator (74).

26. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The pitch locking device (160) forms a cantilever relative to the frame (72) in the longitudinal direction.

27. A pitch changing mechanism (70) according to any one of the preceding claims, comprising a collar (193) which connects the nut (178) to a moving part (102) of the control actuator (74), the collar (193) protruding longitudinally from the control actuator (74), in particular, the collar protruding longitudinally upstream from the control actuator.

28. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The pitch lock device (160) comprises a guide system (172) for guiding the support member (162) relative to the frame (72), the control actuator (74) and the guide system (172) being arranged longitudinally on the same side of the nut (178), preferably on the downstream side of the nut.

29. A pitch changing mechanism (70) according to any one of the preceding claims, comprising a guiding device (220) for guiding the nut (178) relative to the frame (72), the guiding device (220) comprising an inner cylinder (222) fixed to the nut (178) and an outer cylinder (224) fixed to the frame (72), the inner cylinder (222) cooperating with the outer cylinder (224) to slide longitudinally within the outer cylinder.

30. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The coupling system (78, 278) is capable of: - converting a translation of the mobile member (102, 309) along the longitudinal axis (X) in a first path into a rotation of the variable setting blade (56) about the pivot axis (P) towards the flat position, and - converting a translation of the mobile member (102, 309) along the longitudinal axis (X) in a second path opposite to the first path into a rotation of the variable-set blade (56) about the pivot axis (P) towards the feathered position.

31. The pitch changing mechanism (70) according to claim 30, wherein: The abutment surface (186, 386) is oriented along the first path.

32. The pitch changing mechanism (70) according to claim 30 or 31, wherein: The support member (162, 362) moves from an operative position of the support member to a locked position of the support member by translating along the first path.

33. A pitch changing mechanism (70) according to any one of the preceding claims, wherein: The frame (72) includes a stop portion (92) against which an abutment surface (186) of the screw (176) bears when the support member (162) is in the locked position, and the control actuator (74) and the stop portion (92) are longitudinally arranged on the same side of the nut (178).

34. A fan rotor (54) for a turbine, the fan rotor comprising a hub (55) and a plurality of variable-set blades (56), each variable-set blade being pivotable relative to the hub (55) about a specific pivot axis (P), the rotor (54) further comprising a pitch changing mechanism (70) according to any one of the preceding claims, the pitch changing mechanism being used to adjust the angular position of each of the variable-set blades (56) about its corresponding pivot axis (P).

35. The fan rotor (54) of claim 34, wherein: For each of the variable-set blades (56), the coupling system (78, 278) of the pitch changing mechanism (70) includes a first hinge (144, 344) fixed to the moving part (102), a second hinge (146, 346) fixed to the variable-set blade (56) away from the pivot axis (P), and a connecting rod (148, 348) connecting the first hinge (144, 344) to the second hinge (146, 346).

36. The fan rotor (54) according to claim 34 or 35, wherein: The longitudinal axis (X) constitutes the axis of rotation of the fan rotor (54).

37. A turbomachine (12) comprising a fan rotor (54) according to any one of claims 34 to 36.

38. The turbine (12) of claim 37, wherein: The longitudinal axis (X) constitutes the axis of elongation of the turbine (12).

39. An aircraft (10) comprising at least one turbine (12) according to claim 37 or 38.

40. A method for changing the pitch of blades (56) of a fan rotor (54) of a turbine, each blade being pivotable about a specific pivot axis (P) relative to a hub (55) of the fan rotor (54), the method comprising adjusting the angular position of each of the blades (56) about its corresponding pivot axis (P) by means of a pitch changing mechanism (70) according to any one of claims 1 to 33.

41. The method of claim 40, comprising the additional step of locking the orientation of the blade (56) by means of the pitch lock device (160, 360).

Images