Pitch changing mechanism with control actuator and pitch locking device outside actuator cavity

Abstract

The invention relates to a pitch change mechanism (70) comprising a frame (72), a control actuator (74) and a locking device (160). The control actuator (74) includes a cylinder (104) and a piston (106), one of which is fixed and the other being translatable relative to the frame (72). The cylindrical body (104) defines an interior cavity (110), and the piston (106) divides the interior cavity (110) into two fluid chambers (112, 114), each containing a control fluid for controlling movement of the cylindrical body (104) and the piston (106) relative to each other. The pitch locking device (160) is external to the fluid chambers (112, 114).

Description

Technical Field

[0001] The present invention relates to the general field of turbines equipped with at least one fan provided with variable pitch blades, and more particularly to the control of the orientation of the fan airfoils of these turbines.

[0002] One preferred field of application of the present invention is turbojet engines with an unducted fan (more widely known as propfan, open fan, open rotor and unducted fan). However, the present invention is also applicable to turboprop engines with one or more propellers. Background Art

[0003] One of the ways currently being explored to improve the specific fuel consumption of civil aircraft engines is to develop unducted fan turbojet engines, such as those described in document FR 2 941 493. These turbojet engines include a conventional turbine engine 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 / these fans are variable pitch blades, that is to say, the angular position (referred to as the pitch angle) of these blades can be modified during flight. As a reminder, the pitch angle of a blade corresponds to the angle between the axis of rotation of the fan and the chord of the blade at 75% of the fan radius in a plane orthogonal to the pivot axis of the blade. The pitch angle of the blade can vary from a value equal to 90° (corresponding to the position of the blade called the "web" or "flat pitch" position) to a value equal to 0° (corresponding to the position of the blade called the "feathered" position). The pitch angle of the blade can also take values strictly greater than 90°, generally substantially equal to 95°, corresponding to the position of the blade called the "reverse" position.

[0005] It is well known that this modification of the pitch angle during flight makes it possible to achieve the development of engine thrust and the optimization of fan efficiency, depending on the speed of the aircraft. In fact, the rotational speed of the fan is almost constant during all operating phases, and the pitch of the blades modifies the thrust. Thus, during the cruise flight phase, the blades are oriented to regulate the thrust by minimizing the power and fuel consumption taken from the turbine shaft and by optimizing the efficiency. Conversely, during takeoff, the blades are oriented to maximize the thrust in order to accelerate the aircraft and then take off.

[0006] The manipulation of the orientation of the blades is generally carried out by means of a pitch changing mechanism, which includes a control actuator and a connection system, the control actuator including a movable part that translates along the axis of the fan, the connection system connecting the movable part to the blade in order to convert the translation of the movable part into rotation of the variable pitch blade.

[0007] A difficulty encountered with variable pitch blades is that in the event of a failure of the system for manipulating the orientation of the variable pitch blades, the blades tend to move to the feather position under their own centrifugal action. However, the drag torque generated by the blades blocked in this position is small and there is a risk of engine overspeed, thus having a potential risk of degrading the engine. In addition, the blades blocked in this position also have a risk of generating excessive drag, which is unacceptable for the controllability of the aircraft and / or the range of the aircraft in the case of a diversion mission.

[0008] To overcome this difficulty, it is known to use a safety system capable of preventing the variable pitch blades from shifting towards a small pitch (i.e., towards the feather position) in the event of a failure of the blade orientation control system. Such a system is known, for example, from EP 3 400 169.

[0009] In particular, a safety system is known which integrates a ball screw type screw-nut system coupled to a locking nut into an actuator for controlling the orientation of the blade. In normal operation, the nut of the screw-nut system follows the displacement of the control actuator, causing the screw to rotate about its axis, while the locking nut follows the screw thread without contacting the screw (the thread of the locking nut is designed to provide a slight clearance with the screw thread). In the event of a failure of the blade orientation control system, the screw of the screw-nut system is fixed (rotation of the screw is blocked) and the locking nut engages with the screw, thus preventing the blade from pivoting towards a small pitch.

[0010] However, this safety system is not entirely satisfactory. In fact, assembling it into the control actuator is complex. In addition, a control actuator with a specific geometry is required, making the control actuator heavy and bulky. Moreover, once the control system is installed, it is difficult to access the connection system of the movable parts connecting the blade to the actuator. In addition, for correct operation, precise and complex management of the clearance between the locking nut and the screw thread is required. Summary of the Invention

[0011] An object of the present invention is to facilitate the assembly of a pitch changing mechanism that manipulates the orientation of variable pitch blades when the pitch changing mechanism includes pitch locking means. Other objects are to achieve lightweighting of the pitch changing mechanism in order to simplify the pitch changing mechanism and to facilitate access to the pitch changing mechanism when the pitch changing mechanism is assembled to a set of variable pitch blades.

[0012] To this end, according to a first aspect, the present invention relates to a pitch changing mechanism for adjusting the angular position of at least one variable pitch blade about a pivot axis of the blade, the pitch changing mechanism comprising:

[0013] - a frame fixed relative to the pivot axis,

[0014] - A control actuator, the control actuator including a fixed part and a movable part, the fixed part being fixed to the frame, the movable part being capable of translational movement relative to the fixed part between a retracted position and a deployed position along a longitudinal axis,

[0015] - A connection system, the connection system connecting the movable part to the variable pitch blade to convert the translation of the movable part along the longitudinal axis into the rotation of the variable pitch blade about a pivot axis, and

[0016] - A pitch locking device, the pitch locking device being adapted to block the translation of the movable part relative to the fixed part in at least one way,

[0017] wherein the control actuator includes a cylindrical body forming one of the fixed part and the movable part and a piston forming the other of the fixed part and the movable part, the cylindrical body defining an inner cavity, the piston dividing the inner cavity into two fluid chambers, each fluid chamber containing a control fluid to control the displacement of the movable part relative to the fixed part, and the pitch locking device being outside the fluid chambers.

[0018] According to a particular embodiment of the present invention, the pitch changing mechanism further has one or more of the following features taken individually or in any technically feasible combination:

[0019] - The cylindrical body is continuous;

[0020] - The fluid chambers are continuous;

[0021] - Each fluid chamber is at least partially defined by the outer peripheral surface of the frame;

[0022] - At least a part of the pitch locking device extends longitudinally away from the control actuator;

[0023] - The pitch changing mechanism includes a seal that fluidically isolates the fluid chambers from the pitch locking device.

[0024] - The pitch locking device includes:

[0025] ○ A support member, the support member being capable of translational movement relative to the frame between an operating position and a locking position along the longitudinal axis,

[0026] ○ A return device, the return device biasing the support member towards the locking position of the support member,

[0027] ○ A holding device, the holding device being for holding the support member in the operating position of the support member under normal operating conditions, and

[0028] ○ A screw-nut system, the screw-nut system having:

[0029] ■ A screw, which is translationally fixed to a support member and rotatably mounted relative to the support member about a longitudinal axis. The screw has an abutting surface which, when the support member is in the operating position, is at a distance from the frame, and which, when the support member is in the locked position, bears against the frame, and

[0030] ■ A nut, which is fixed to the movable part of a control actuator and is coaxial with the screw. The nut cooperates with the screw such that translation of the nut along the longitudinal axis causes rotation of the screw about the longitudinal axis;

[0031] - The pitch-changing mechanism includes a shroud connecting the nut to the movable part of the control actuator, the shroud projecting longitudinally from the control actuator, particularly projecting upstream longitudinally;

[0032] - The abutting surface is arranged at the downstream end of the screw;

[0033] - Fluid chambers are closed at each longitudinal end of the longitudinal ends of the control actuator;

[0034] - The connection system includes a first hinge fixed to the movable part, a second hinge fixed to the variable pitch blade away from the pivot axis, and a connection member connecting the first hinge to the second hinge;

[0035] - The connection system is adapted to effect the following conversions:

[0036] ○ Conversion of translation of the movable part in a first manner along the longitudinal axis into rotation of the variable pitch blade about the pivot axis towards the flat pitch position, and

[0037] ○ Conversion of translation of the movable part in a second manner, opposite to the first manner, along the longitudinal axis into rotation of the variable pitch blade about the pivot axis towards the feather position;

[0038] - The first hinge is arranged upstream or downstream of the second hinge, and the first manner means from upstream to downstream or from downstream to upstream;

[0039] - The abutting surface is oriented in a first manner;

[0040] - The support member is moved from the operating position of the support member to the locked position of the support member by translation in a first manner;

[0041] - The connection member consists of a connecting rod;

[0042] - The variable pitch blade includes a leading edge, a trailing edge, and a chord connecting the leading edge to the trailing edge. The second hinge is arranged relative to the plane orthogonal to the chord and containing the pivot axis opposite to the trailing edge;

[0043] - The frame includes a stop, against which the adjacent surface of the screw bears when the support member is in the locked position, and the control actuator and the stop are longitudinally arranged on the same side of the nut;

[0044] - The control actuator includes a cylindrical body forming one of the fixed part and the movable part and a piston forming the other of the fixed part and the movable part. The cylindrical body defines an inner cavity, and the piston divides the inner cavity into two fluid chambers, each fluid chamber containing a control fluid to control the displacement of the movable part relative to the fixed part.

[0045] - The pitch locking device is cantilevered longitudinally relative to the frame;

[0046] - The locking device includes a guiding system for guiding the support member relative to the frame, and the control actuator and the guiding system are longitudinally arranged on the same side of the nut, preferably on the downstream side of the nut;

[0047] - The pitch locking device includes a housing that is fixed to the nut and surrounds the nut, the screw, and the support member;

[0048] - The pitch changing mechanism includes an enclosed space for restricting and / or circulating the lubricating fluid for the pitch locking device;

[0049] - The housing at least partially defines the enclosed space;

[0050] - The enclosed space is a closed enclosed space;

[0051] - One of the two fluid chambers is in fluid communication with the interior of the housing, and the control fluid constitutes the lubricating fluid for the locking device;

[0052] - The housing includes an inner cylindrical body that bears the nut on its inner surface and mates with an outer cylindrical body fixed to the frame to slide longitudinally within the outer cylindrical body. The inner cylindrical body has a seal in contact with the inner surface of the outer cylindrical body at its outer periphery, and the outer cylindrical body and the housing together define an enclosed space for the circulation of the lubricating fluid for the locking device;

[0053] - The pitch changing mechanism includes guiding means for guiding the nut relative to the frame, the guiding means including an inner cylindrical body fixed to the nut and an outer cylindrical body fixed to the frame, the inner cylindrical body mating with the outer cylindrical body to slide longitudinally within the outer cylindrical body; and

[0054] - The longitudinal axis is substantially orthogonal to the pivot axis.

[0055] 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 pitch blades, each variable pitch blade being pivotable relative to the hub about its own pivot axis, the rotor further comprising a pitch changing mechanism according to the first aspect for adjusting the angular position of each variable pitch blade about its respective pivot axis.

[0056] According to a particular embodiment of the invention, the fan rotor further has the following characteristics:

[0057] - The longitudinal axis constitutes the axis of rotation of the rotor.

[0058] According to a third aspect, the present invention also relates to a turbine comprising a fan rotor according to the second aspect.

[0059] According to a particular embodiment of the invention, the turbine further has the following characteristics:

[0060] - The longitudinal axis constitutes the elongation axis of the turbine.

[0061] According to a fourth aspect, the present invention also relates to an aircraft comprising a turbine according to the third aspect.

[0062] Finally, according to a fifth aspect, the present invention relates to a method for changing the pitch of the blades of a fan rotor of a turbine, each blade being pivotable relative to the hub of the fan rotor about its own pivot axis, the method comprising adjusting the angular position of each of the blades about its respective pivot axis by means of a pitch changing mechanism according to the first aspect.

[0063] According to a particular embodiment of the invention, the method further has the following characteristics:

[0064] - The method comprises an additional step of locking the orientation of the blades by means of pitch locking means. Description of the Drawings

[0065] Other features and advantages of the present invention will become apparent when reading the following description given by way of example and with reference to the drawings, in which:

[0066] - Figure 1 is a top view of an aircraft according to an exemplary embodiment of the present invention,

[0067] - Figure 2 is Figure 1 a simplified view of a partial longitudinal section of the turbine of the aircraft of

[0068] - Figure 3 is according to a first variant of Figure 2Simplified view of a longitudinal section of a part of the pitch change mechanism of a turbine, the pitch change mechanism being in a first configuration,

[0069] - Figure 4 is similar to Figure 3 view, the pitch change mechanism being in a second configuration,

[0070] - Figure 5 is according to a second variant Figure 2 Simplified view of a longitudinal section of a part of the pitch change mechanism of a turbine,

[0071] - Figure 6 is according to a third variant Figure 2 Simplified view of a longitudinal section of a part of the pitch change mechanism of a turbine,

[0072] - Figure 7 is according to a fourth variant Figure 2 Simplified view of a longitudinal section of a part of the pitch change mechanism of a turbine,

[0073] - Figure 8 is a simplified view along the radial axis of the arm for rotating the variable pitch blades of the Figure 2 turbine, and

[0074] - Figure 9 is Figure 3 Perspective view and partial cross - sectional view of the satellite ball screw of the pitch change mechanism. Detailed Description

[0075] Figure 1 The illustrated aircraft 10 includes a turbine 12 for propelling the aircraft.

[0076] In the illustrated example, the aircraft 10 is an airplane. The aircraft generally includes a fuselage 14, a tail 16, and two wings 18. There are two turbines 12 here, and each turbine 12 is housed below a corresponding wing 18. As a variant (not shown), the turbines 12 are arranged along the fuselage 14, for example, near the tail 16. Still as a variant (also not shown), the aircraft 10 includes a single turbine 12 or at least three turbines 12.

[0077] Figure 2 One of the turbines 12 is shown.

[0078] As can be seen in this figure, the turbine 12 extends along a longitudinal axis X. The turbine generally has angular symmetry about the longitudinal axis X, that is, there is at least one angle that remains unchanged when the turbine rotates about the longitudinal axis X.

[0079] Herein and hereinafter, the terms "inner" and "outer", "interior" and "exterior" and their variants are understood with reference to the axis X. An element described as an "inner element" or "interior element" is oriented towards the axis X, while an "outer" or "exterior" element is oriented relative to the axis X.

[0080] The turbine 12 generally includes a nacelle 20, an internal flow path 22 for allowing an air flow to pass through the nacelle 20, a combustion chamber 24 accommodated in the flow path 22, a drive body 26, and an exhaust nozzle 28.

[0081] Hereinafter, the terms "upstream" and "downstream" refer to the manner in which the air flow passes through the flow path 22.

[0082] The drive body 26 includes a compressor 30, a turbine 32, and a drive shaft 34. The drive shaft 34 connects the turbine 32 to the compressor 30 for driving the compressor 30 by the turbine 32. The compressor 30 is provided upstream of the combustion chamber 24 and supplies compressed air to the combustion chamber 24. The turbine 32 is provided downstream of the combustion chamber 24 and receives the exhaust gas leaving the combustion chamber 24.

[0083] The drive shaft 34 has a longitudinal axis X as its axis of rotation.

[0084] The drive shaft 34 is guided to rotate relative to the nacelle 20 by means of bearings (not shown).

[0085] In the illustrated example, the turbine 12 is a multi-rotor turbine, particularly a dual-rotor turbine, which further includes a low-pressure body 40 in addition to the drive body 26. Then, the drive body 26 constitutes the high-pressure body, the compressor 30 is a high-pressure compressor, the turbine 32 is a high-pressure turbine, and the drive shaft 34 is a high-pressure shaft.

[0086] The low-pressure body 40 includes a low-pressure compressor 42, a low-pressure turbine 44, and a low-pressure shaft 46. The low-pressure shaft 46 connects the low-pressure turbine 44 to the low-pressure compressor 42 for driving the low-pressure compressor 42 by the low-pressure turbine 44.

[0087] The low-pressure compressor 42 is provided upstream of the high-pressure compressor 30 and supplies compressed air to the high-pressure compressor 30. The low-pressure turbine 44 is provided downstream of the high-pressure turbine 32 and receives the exhaust gas leaving the high-pressure turbine 32.

[0088] The low-pressure shaft 46 is guided to rotate relative to the nacelle 20 by means of bearings (not shown).

[0089] The low-pressure shaft 46 is coaxial with the high-pressure shaft 34. Therefore, the low-pressure shaft also has the longitudinal axis X as its axis of rotation. In particular, the low-pressure shaft 46 extends inside the high-pressure shaft 34.

[0090] The turbine 12 further includes a fan 50 that drives an air flow in an outer flow path 52 that surrounds the nacelle 20. Thereby, a primary air flow A (hot) formed by a part of the air flow driven in the inner flow path 22 and a secondary air flow B (cold) formed by a part of the air flow driven in the outer flow path 52 are separated.

[0091] The fan 50 includes a fan rotor 54. The fan rotor 54 is rotatably mounted relative to the nacelle 20 about a longitudinal axis X. The fan rotor includes a hub 55 ( Figure 3 ), and the hub 55 is provided with fan blades 56 that extend substantially radially outward from the hub 55. These blades 56 drive the air flow in the outer flow path 52 when rotating.

[0092] As Figure 8 can be seen, each blade 56 includes a leading edge 57A, a trailing edge 57B, and a chord C that connects the leading edge 57A to the trailing edge 57B.

[0093] Return Figure 2 , the fan rotor 54 is driven to rotate by the low-pressure turbine 44 via a low-pressure shaft 46. In the example shown, this drive is direct, that is, the fan rotor 54 is rotationally fixed to the low-pressure shaft 46. As a variant (not shown), this drive is achieved via a speed reducer that enables the fan rotor 54 to rotate at a speed lower than the speed of the low-pressure shaft 46.

[0094] In the example shown, the fan 50 further includes a fan stator 58. The fan stator 58 includes vanes 59 that are arranged at the outer periphery of the nacelle 20 in a plane orthogonal to the longitudinal axis X and are located in the outer flow path 52. Here, the fan stator 58 is arranged downstream of the fan rotor 54. As a variant (not shown), the fan 50 includes a counter-rotating fan rotor instead of the fan stator 58.

[0095] Advantageously, as shown, the fan 50 is ducted-free, that is, the outer flow path 52 has no outer perimeter defined. Thus, as shown, the turbine 12 consists of a turbojet engine with a ducted-free fan, or as a variant, consists of a turboprop engine. As a variant (not shown), the outer flow path 52 is defined between the nacelle 20 and a fan housing that surrounds the fan 50; the turbine 12 generally consists of a high-bypass ratio turbojet engine, and the bypass ratio is defined as the ratio of the flow rate of the secondary flow B (cold) to the flow rate of the primary flow A (hot).

[0096] In the example shown, the turbine 12 is in particular of the "puller" type, i.e., the fan 50 is arranged upstream of the internal flow path 22 and also drives the air flow in the internal flow path. As a variant (not shown), the turbine is of the "pusher" type, i.e., the fan 50 is arranged around the downstream half of the nacelle 20.

[0097] The blades 56 of the fan rotor 54 are variable pitch blades, i.e., each blade 56 is pivotally mounted relative to the hub 55 about its own pivot axis P. This pivot axis P extends along the elongation direction of the blade 56. This pivot axis is orthogonal to the longitudinal axis X.

[0098] Each blade 56 is in particular able to pivot relative to the hub 55 about the axis P between a position called the feather position and a position called the flat pitch position. In the feather position, the chord C of the blade 56 is substantially parallel to the longitudinal axis X. In the flat pitch position, the chord C of the blade 56 is substantially orthogonal to the longitudinal axis X. Preferably, each blade 56 is also able to pivot beyond the flat pitch position to a position called the reverse pitch 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 blade 56 is generally twisted, by convention, the chord C used as a reference for measuring the pitch angle is formed by the blade chord at 75% of the radius of the fan rotor 54.

[0099] For this purpose, as Figure 3 shown, each blade 56 is fixed to a fastener 60 provided at the blade root. This fastener 60 is rotatably mounted relative to the hub 55 about the pivot axis P. More specifically, the fastener 60 is rotatably mounted in a housing 62 by means of a ball 64 or other rolling elements, and the housing 62 is arranged in the hub 55.

[0100] The fan 50 further includes a pitch changing mechanism 70 for adjusting the pitch angle of each blade 56 about its pivot axis P to adapt the performance of the turbine 12 to different flight phases.

[0101] Referring to Figure 3 , this pitch changing mechanism 70 includes a frame 72, a control actuator 74, a control system 76 for operating the actuator 74, and a connection system 78.

[0102] The frame 72 is fixed to the hub 55 and is generally formed by a part of the hub 55. Thus, the frame is fixed relative to the pivot axis P.

[0103] The frame 72 includes a base 80. This base 80 is centered on the longitudinal axis X. Here, this base is penetrated by the pivot axis P.

[0104] In the example shown, the base 80 defines a housing 82 that opens downstream. The housing 82 is in particular cylindrical, typically rotationally cylindrical, and centered on the axis X. The oil supply bearing 84 is received in the housing 82.

[0105] The base 80 also defines a cavity 86 that communicates with the upstream surface 88 of the base 80 through an orifice 90, which is centered on the axis X here. The cavity 86 is in particular cylindrical, typically rotationally cylindrical, and centered on the axis X. The cavity 86 is inserted between the upstream surface 88 and the housing 82.

[0106] The base 80 has an upstream stop 92. The stop 92 is formed here by a part of the upstream surface 88. The stop 92 extends substantially radially and is particularly arranged around the orifice 90.

[0107] In the example shown, the frame 72 also includes a cylindrical body 94 that projects upstream from the base 80. The cylindrical body 94 is centered on the axis X and is open at its upstream end 95. The cylindrical body 94 extends around the stop 92. The cylindrical body 94 is typically rotationally cylindrical.

[0108] Here, the frame 72 also includes an outer peripheral cylindrical body 96 that 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 typically rotationally cylindrical.

[0109] The base 80 and the outer peripheral cylindrical body 96 together define the outer peripheral surface 88 of the frame 72. The outer peripheral surface 88 is generally cylindrical, centered on the axis X. The outer peripheral surface is oriented radially outward.

[0110] As a variant, as Figure 5 shown, the frame 72 does not include the cylindrical body 94.

[0111] Further as a variant, as Figure 6 shown, the frame 72 does not include the outer peripheral cylindrical body 96. The outer peripheral surface 88 is then defined by the base 80 and the cylindrical body 94.

[0112] Returning to Figure 3 , the control actuator 74 includes a fixed part 100 and a movable part 102. The fixed part 100 is fixed to the frame 72, and the movable part 102 is translatable relative to the fixed part 100 along the longitudinal axis X between Figure 3 the retracted position shown in Figure 4 and the deployed position shown in

[0113] The control actuator 74 particularly includes a continuous cylindrical body 104 forming one of the fixed part 100 and the movable part 102, and a piston 106 forming the other of the fixed part 100 and the movable part 102. Here, the cylindrical body 104 forms the movable part 102, and the piston 106 forms the fixed part 100. As a variant (not shown), conversely: the cylindrical body 104 forms the fixed part 100, and the piston 106 forms the movable part 102.

[0114] Thus, in the illustrated example, the cylindrical body 104 extends around the outer peripheral surface 88 of the frame 72, coaxial with the outer peripheral surface 88 of the frame 72, and the piston 106 is constituted by a flange 108 fixed to the frame 72, and the flange 108 extends radially outward from the outer peripheral surface 88 to the cylindrical body 104.

[0115] The cylindrical body 104 defines an inner cavity 110. The piston 106 divides the inner cavity 110 into two continuous fluid chambers 112, 114. Each fluid chamber accommodates a control fluid generally composed of oil to control the displacement of the movable part 102 relative to the fixed part 100. This 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 such that a relative increase in the first pressure (i.e., relative to the second pressure) causes the piston 110 to shift towards its deployed position, and a relative increase in the second pressure (i.e., relative to the first pressure) causes the piston 110 to shift towards its retracted position.

[0116] Here, each of the fluid chambers 112, 114 is internally defined by the outer peripheral surface 88 of the frame 72 and externally defined by the cylindrical body 104. In addition, the first fluid chamber 112 is defined by the piston 106 at its downstream end, and the second fluid chamber 114 is defined by the piston 106 at its upstream end.

[0117] Therefore, the control actuator 74 is particularly compact, which enables the control actuator to be lightweight.

[0118] In Figure 3 the illustrated example, the movable part 102 further includes an upstream guide bushing 116 and a downstream guide bushing 118. The upstream guide bushing 116 and the downstream guide bushing 118 are each fixed to the cylindrical body 104 and extend radially inward from the cylindrical body 104 to the outer peripheral surface 88 of the frame 72. The upstream guide bushing 116 is disposed upstream of the piston 106 and defines the upstream end of the first fluid chamber 112. The downstream guide bushing 118 is disposed downstream of the piston 106 and defines the downstream end of the second fluid chamber 114.

[0119] In Figure 3In the example shown, each of the upstream guide bushing 116 and the downstream guide bushing 118 forms a sealing bushing and longitudinally closes the first fluid chamber 112 and the second fluid chamber 114, respectively. Thus, the fluid chambers 112, 114 are closed at each longitudinal end of the longitudinal ends of the control actuator 74.

[0120] As a variant, as Figure 7 shown, only the downstream guide bushing 118 forms a sealing bushing. The upstream guide bushing 118 has a hole 119 through which control fluid can flow through the upstream guide bushing 118.

[0121] As another variant, as Figure 5 shown, the movable member 102 does not include the upstream guide bushing 118.

[0122] Returning to Figure 3 , the actuation system 76 includes a pressure generator 130, a pressure monitoring unit 132, and a return line 136. The pressure generator 130 is configured to bring the control fluid to a third pressure higher than the first pressure and the second pressure. The pressure monitoring unit 132 is configured to regulate the pressure of the control fluid in the first fluid chamber 112 and the second fluid chamber 114 by means of the third pressure. The return line 136 is configured to discharge the depressurized control fluid. The actuation system 76 further includes a main tank 133, a standby circuit 134, and a control module 135.

[0123] For example, the pressure generator 130 includes a pump that is capable of pumping fluid to bring the fluid to a third pressure of, 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 towards the return line 136.

[0124] The pressure monitoring unit 132 is supplied with the control fluid at the third pressure by the pressure generator 130. The pressure monitoring unit is fluidly connected to the first fluid chamber 112 and the second fluid chamber 114 via an oil feed bearing 106. The pressure monitoring unit is capable of distributing the control fluid between the first fluid chamber 112 and the second fluid chamber 114 to regulate the fluid pressure inside each of these chambers 112, 114, thereby regulating the position of the piston 110 between its retracted position and its deployed position. The pressure monitoring 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.

[0125] The main tank 133 is configured to collect the depressurized control fluid from the return line 136. The main tank supplies the pressure generator 130.

[0126] The standby circuit 134 is capable of supplying control fluid to the first fluid chamber 112 to move the piston 110 to its deployed position in the event of a failure of the pressure generator 130. To this end, the standby circuit 134 includes an auxiliary tank 137 and an auxiliary pump 138. In the example shown, the standby circuit also includes an auxiliary pressure relief valve 139B.

[0127] The auxiliary tank 137 is configured to collect the decompressed 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 decompressed control fluid from the return line 136 passes through the auxiliary tank 137 and then reaches the main tank 133.

[0128] 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 fluidly connected to the pressure monitoring unit 132 to supply the control fluid at the third pressure to the pressure monitoring unit 132, and the pressure monitoring unit 132 is configured to redirect the entire control fluid from the auxiliary pump 138 to the first fluid chamber 112.

[0129] When the pressure of the control fluid downstream of the auxiliary pump 138 exceeds the third pressure, the pressure relief valve 139B is capable of discharging a portion of the control fluid to the return line 136.

[0130] The control module 135 is configured to receive a pitch command (not shown) and derive a control signal sent to the pressure monitoring unit 132 based on the pitch command. In particular, the control module 135 is configured to send a control signal aimed at increasing the fluid pressure in the first chamber 112 to the pressure monitoring unit 132 when the pitch command is intended to increase the pitch of the blade 56, and to send a control signal aimed at increasing the fluid pressure in the second chamber 114 to the pressure monitoring unit 132 when the pitch command is intended to decrease the pitch of the blade 56.

[0131] The control module 135 is further configured to send a start command to the standby circuit 134, more specifically to the auxiliary pump 138 of the standby circuit, in the event of a failure of the pressure generator 130.

[0132] The connection system 78 connects the movable member 102 to each blade 56 to convert the translation of the movable member 102 along the longitudinal axis X and (where appropriate) the rotation of the movable member 102 about the longitudinal axis X into the rotation of each blade 56 about its pivot axis P. In particular, the connection system 78 connects the movable member 102 to each blade 56 to perform the following conversion:

[0133] - converting the translation of the movable member 102 along the longitudinal axis X in a first manner into the rotation of the variable pitch blade 56 about the pivot axis P towards the flat pitch position, and

[0134] - Convert the translation of the movable member 102 along the longitudinal axis X in a second manner opposite to the first manner into the rotation of the variable pitch blade 56 about the pivot axis P towards the feather position.

[0135] To this end, the connection system 78 includes a synchronizing ring 140 fixed to the movable member 102, and for each blade 56, the connection system 78 includes a mechanism 142 for connecting the blade 56 to the synchronizing ring 140.

[0136] The synchronizing ring 140 extends in a radial plane around the movable member 102. In particular, the synchronizing ring is fixed to the upstream end 143 of the movable member 102.

[0137] Each connection mechanism 142 includes a first hinge 144 fixed to the movable member 102, a second hinge 146 fixed to the blade 56 away from the pivot axis P of the blade 56, and a connection member 148 connecting the first hinge 144 to the second hinge 146.

[0138] The first hinge 144 is carried by the synchronizing ring 140. Here, the first hinge is constituted by a spherical joint connection.

[0139] The second hinge 146 is also constituted by a spherical joint connection. The second hinge is eccentric with respect to the pivot axis P.

[0140] The connection 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 connection member 148 is rigid and has an adjustable length, that is to say, the distance between the first end 150 and the second end 152 can be modified, which makes it possible to precisely adjust the length at rest so that the pitch angle of each blade 56 can be manipulated by the pitch change mechanism 70.

[0141] The connection member 148 is constituted by a connecting rod 153 here.

[0142] In the example shown, each connection mechanism 142 further includes a crank 154 connecting the fastener 60 to the second hinge 146. The crank 154 is rigid and fixed to the fastener 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.

[0143] In the example shown, the first mode is from upstream to downstream, that is, the displacement of the movable member 102 towards the stop 92 (in other words, towards its retracted position) causes each blade 56 to rotate towards its feather position, and the second mode is from downstream to upstream, that is, the displacement of the movable member 102 away from the stop 92 (in other words, towards its deployed position) causes each blade 56 to rotate towards its pitch position. Additionally, the first hinge 144 is arranged upstream of the second hinge 146.

[0144] To this end, as Figure 8 shown, the second hinge 146 is arranged relative to the plane Q which is orthogonal to the chord C and contains the pivot axis P and opposite to the trailing edge 57B.

[0145] As a variant (not shown), the first mode is from downstream to upstream and the first hinge 144 is arranged downstream of the second hinge 146. Then, the second hinge 146 is arranged on the same side as the trailing edge 57B relative to the plane Q which is orthogonal to the chord C and contains the pivot axis P.

[0146] When the pitch changing mechanism 70 is fixed, these specific arrangements allow the natural biasing of the blade 56 towards its feather position such that the connecting member 148 operates in a traction rather than a compression manner. Therefore, the risk of the connecting member 148 bending is very low, such that a connecting member 148 with relatively low resistance can be used, thereby reducing the weight of the pitch changing mechanism 70.

[0147] The pitch changing mechanism 70 further includes a pitch locking device 160 which is adapted to block the translational movement of the movable part 102 of the control actuator 74 in the first mode, that is, to block the translational movement of the movable part of the control actuator towards its retracted position here.

[0148] The locking device 160 includes a support member 162 and a screw - nut system 164.

[0149] The support member 162 is translatably movable relative to the frame 72 along the longitudinal axis X between an operating position (as Figures 3 to 7 shown) and a locking position (not shown). The support member 162 moves from the operating position of the support member 162 to the locking position of the support member 162 by translating in the first mode (that is, in the example shown, 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 162.

[0150] The support member 162 includes a body 166 that extends along a longitudinal axis X and is centered on the longitudinal axis X. The body 166 has a first longitudinal end 168 (particularly the downstream longitudinal end) that engages with an orifice 90 of the frame 72, and a second free longitudinal end 170. The body 166 is solid here.

[0151] The orifice 90 of the frame 72 and the first longitudinal end 168 together form a guiding system 172 for guiding the support member 162 relative to the frame 72. This guiding system 172 is provided on the downstream side of the screw-nut system 164 here.

[0152] The support member 162 further includes a sleeve 174 that is fixed to the body 166 and is arranged around the second longitudinal end 170 of the body 166.

[0153] The screw-nut system 164 includes a screw 176 and a nut 178.

[0154] The screw 176 extends around the body 166 of the support member 162 and is coaxial with the body 166. The screw is translationally fixed to the support member 162 and is movably mounted to rotate relative to the support member 162 about the longitudinal axis X. For this purpose, the screw 176 is assembled to the support member 162 by means of a bearing 180. This bearing 180 is inserted here between the sleeve 174 of the support member 162 and an end portion 182 of the screw 176, and the end portion 182 of the screw 176 is received between the body 166 and the sleeve 174.

[0155] The screw 176 has a second longitudinal end portion 184 that is opposite to the end portion 182. This second longitudinal end portion 184 defines a radially adjacent surface 186. When the support member 162 is in the operating position, this adjacent surface 186 is at a distance from the frame 72, and when the support member 162 is in the locked position, this adjacent surface 186 bears against a stop 92 of the frame 72.

[0156] Here, the second longitudinal end portion 184 tapers from the threaded body 190 of the screw 176 to the adjacent surface 186. Thus, the contact area between the adjacent surface 186 and the stop 92 increases, which increases the frictional force between the adjacent surface 186 and the stop 92 and enables better transmission of braking force and blocking force.

[0157] Here, both the adjacent surface 186 and the stop 92 are smooth. As a variant (not shown), the adjacent surface 186 and / or the stop 92 have roughness to further increase the frictional force between the adjacent surface 186 and the stop 92 and achieve greater force transmission.

[0158] In particular, the adjacent surface 186 extends substantially radially. The adjacent surface is oriented in a first manner, that is, in the illustrated example, the adjacent surface is oriented downstream. Here, the adjacent surface is disposed at the downstream end of the screw 176.

[0159] The threaded body 190 extends from one of the end portions 182, 184 to the other. The threaded body 190 has an external thread 192 on its circumference.

[0160] The threaded body 190 and the nut 178 are received inside the cylindrical body 94 of the frame 72.

[0161] The nut 178 is fixed to the movable member 102 of the actuator 74 and is coaxial with the screw 176. The nut 178 cooperates with the screw 176 such that the 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.

[0162] The nut 178 has an internal thread 194.

[0163] In particular, the screw-nut system 164 is formed by a reversible satellite ball screw system 195. Conventionally, in addition to the screw 176 and the nut 178, the satellite ball screw system 195 further includes a plurality of balls 196 inserted between the screw 176 and the nut 178, and each ball 196 extends parallel to the longitudinal axis X.

[0164] As Figure 9 shown, each ball 196 has a thread 198 that engages with the external thread 192 of the screw 176 and the internal thread 194 of the nut 176. Each ball 196 further includes external gear teeth 199 located at its ends and extended by smooth journals 200.

[0165] Still conventionally, the satellite ball screw system 195 also has means 202 for guiding and retaining the balls 196. The guiding and retaining means 202 includes a ball retainer 204 (also known as a spacer bushing) mounted coaxially with the screw 176 between the screw 176 and the nut 178, and the ball retainer has notches 206 for receiving the journals 200 of the balls 196. The guiding and retaining means also includes synchronizing gear teeth 210, and the external gear teeth 198 located at the corresponding ends of the balls 196 mesh in the synchronizing gear teeth. This meshing of the external gear teeth 198 in the synchronizing gear teeth 210 forms a planetary gear train, and the function of the planetary gear train is to ensure the synchronization of the satellite motion (also known as planetary motion or epicyclic motion) of the balls 196, thereby making the motion of the balls 196 smooth by helping the balls 196 to roll easily (with the minimum possible slip) on the threads 192 of the screw 176 and the threads 194 of the nut 178.

[0166] In the example shown, the satellite ball screw system 195 is of the standard type, and the balls 196 are translationally fixed to the nut 178. The synchronizing gear teeth 210 are formed by the internal gear teeth of the rings 208 that are fixed to the nut 178 and are respectively mounted at each longitudinal end of the nut 178. The longitudinal extension of the nut 178 is substantially equal to the longitudinal extension of the threaded portion of the balls 196 and is lower than the longitudinal extension of the threaded body 190 of the screw 176.

[0167] As a variant (not shown), the satellite ball screw system 195 is of the inverted type, and the balls 196 are translationally fixed to the screw 176. Then, the synchronizing gear teeth 210 are formed by two external gear teeth at each longitudinal end of the screw 176 on the threaded body 190. The longitudinal extension of the threaded body is substantially equal to the longitudinal extension of the threaded portion of the balls 196 and is lower than the longitudinal extension of the nut 178.

[0168] As a further variant, the satellite ball screw system 195 consists of a recirculating satellite ball screw system, such as the system described in document EP 275 504 A2, or consists of a roller bearing screw system, such as the system described in document EP 168942 A1 or the system described in document EP 671 070 A1.

[0169] This feature enables good force transfer from the nut 178 to the screw 176 through the screw-nut system 164 while maintaining a small pitch in the screw connection of the screw-nut system 164. In particular, in the case where the rotation of the screw 176 is blocked, this feature enables the nut 178 to be fixed relative to the screw 176 even without a separate locking nut. Therefore, the need for a separate locking nut can be eliminated, which simplifies the manufacture of the mechanism and reduces the cost of the mechanism, while increasing the reliability of the mechanism and minimizing the mass of the mechanism.

[0170] As a variant (not shown), the screw-nut system 164 consists of a screw-nut system similar to that described in EP 1 832 509.

[0171] Return Figure 3, the pitch locking device 160 is here located outside the fluid chambers 112, 114 of the control actuator 74, that is to say, the components of the pitch locking device 160 are not all received inside one of the fluid chambers 112, 114. Thus, this arrangement enables the pitch locking device 160 and the actuator 74, which are separated from each other, to be assembled on the frame 72, which is beneficial for installing the pitch changing mechanism 70, thereby reducing costs. Here, the pitch locking device 160 is even far from the fluid chambers 112, 114 of the control actuator 74, that is to say, except outside the fluid chambers 112, 114, the components of the pitch locking device 160 do not contribute to defining one of these chambers 112, 114.

[0172] As Figure 3 shown, a part of the pitch locking device 160 even extends longitudinally far from the actuator 74. In other words, there is a radial plane: a part of the pitch locking device 160 extends beyond this radial plane, while the actuator 74 does not extend beyond the said radial plane. In particular, the said part of the pitch locking device 160 extends upstream of the actuator 74.

[0173] To achieve this arrangement, the pitch locking device 160 includes a shroud 193 that connects the nut 178 to the movable part 102 of the actuator 74. This shroud 193 here projects longitudinally upstream from the control actuator 74. The shroud is in particular frustoconical, and the diameter of the shroud decreases from the downstream end 193A of the shroud attached to the actuator 74 to the upstream end 193B of the shroud attached to the nut 178.

[0174] Furthermore, in the example shown, the pitch locking device 160 is cantilevered longitudinally with respect to the frame 72. In other words, the entire part of the frame 72 that supports the locking device 160 is longitudinally located on the same side (here the downstream side) of the locking device 160; the locking device 160 is not longitudinally framed by the part of the frame 72 that supports the locking device. Due to this arrangement, it is not necessary to provide a support upstream of the locking device 160, which facilitates access to the pitch changing mechanism 70 and more specifically to the connection system 78.

[0175] Thus, the control actuator 74 is longitudinally arranged on the same side as the guide device 172 and the stop 92 of the nut 178, here the downstream side.

[0176] Despite this cantilever, in order to ensure good support for the locking device 160, the pitch changing mechanism 70 includes means 220 for guiding the nut 178 with respect to the frame 72. The guiding means 220 includes an inner cylindrical body 222 fixed to the nut 178 and an outer cylindrical body 224 fixed to the frame 72, and the inner cylindrical body 222 cooperates with the outer cylindrical body 224 to slide longitudinally inside the outer cylinder.

[0177] In particular, 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 shroud 193 is fixed.

[0178] Here, the outer cylindrical body 224 is constituted by the cylindrical body 94 of the frame 72.

[0179] The pitch locking device 160 requires lubrication. For this purpose, the locking device 160 includes a housing 230 that at least partially defines an enclosed space for the circulation of the lubricating fluid for the pitch locking device 160. The housing 230 is fixed to the nut 178 and surrounds the nut 178, the screw 176, and the support member 162.

[0180] This enclosed space enables the lubricating fluid to be restricted around the pitch locking device 160.

[0181] In Figure 3 , Figure 4 and Figure 6 example, the housing 230 includes the inner cylindrical body 222 and a plug 232 that closes one end of the inner cylindrical body 222 opposite the frame 72 (here, the upstream end 228). The inner cylindrical body 222 has a seal 234 at its outer periphery that contacts the inner surface 236 of the outer cylindrical body 224. Thus, the outer cylindrical body 224 and the housing 230 together define an enclosed space 238 for the circulation of the lubricating fluid for the locking device 160. This enclosed space 238 is fluidly isolated from the fluid chambers 112, 114 of the actuator 74 by the seal 234 and the upstream guide bushing 116. Thus, the seal 234 and the guide bushing 116 form a seal of the pitch changing mechanism 70, thereby fluidly isolating the fluid chambers 112, 114 of the actuator 74 from the pitch locking device 160.

[0182] Then, the enclosed space 238 is a closed enclosed space, that is, the interior of the enclosed space 238 is fluidly isolated from the components outside the enclosed space 238.

[0183] As a variant (not shown), in particular, when the frame 72 does not include the cylindrical body 74, the housing 230 is constituted by the shroud 193 and a plug that closes the upstream end 193B of the shroud 193. Then, the enclosed space 238 is fluidly isolated from the fluid chambers 112, 114 of the actuator 74 only by the upstream guide bushing 116. Then, the enclosed space 238 is again a closed enclosed space.

[0184] In these variants in which the enclosed space 238 is a closed enclosure, the lubricating fluid for the locking device 160 consists of a lubricant different from the control fluid. Advantageously, the lubricating fluid consists of oil. The pitch locking device 160 then includes a reservoir (not shown) that enables the lubricating fluid to be stored when the actuator 74 is in the retracted position and to be transferred into the enclosed space 238 when the actuator 74 moves towards its deployed position. As a variant, the lubricating fluid for the locking device 160 consists of a grease deposited on the rolling parts of the screw 176 and the bearing 180.

[0185] In Figure 5 (In Figure 5 which the outer cylindrical body 224 and the upstream guide bushing 116 are absent) and Figure 7 (In Figure 7 which the inner cylindrical body 222 and the upstream guide bushing 116 are perforated) example, the housing 230 consists of a shroud 193 and a plug 239 that closes the upstream end 193B of the shroud 193. Then, 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.

[0186] This variant eliminates the need for a reservoir. However, this variant requires a pump 130 with a higher flow rate than the Figure 3 , Figure 4 and Figure 6 variants.

[0187] The locking device 160 further includes a return device 240 and a holding device 242. The return device 240 biases the support member 162 towards its locking position, and the holding device 242 is used to hold the support member 162 in its operating position when the pitch change mechanism 70 is in the normal operating state.

[0188] Here, the return device 240 consists of a compression spring compressed between the frame 72 and a shoulder 244, and the shoulder 244 is fixed to the support member 162. The return device is particularly accommodated in the cavity 86, between the shoulder 244 and the orifice 90.

[0189] The holding device 242 includes a balance actuator 250, and the balance actuator 250 includes a balance piston 252 and a balance chamber 254.

[0190] The balance piston 252 is movably mounted to translate along the longitudinal axis X relative to the frame 72. In particular, the balance piston is coaxial with the support member 162. In the example shown, the balance piston is arranged in the longitudinal extension of the support member 162, between the support member 162 and the balance chamber 254.

[0191] The balance chamber 254 is defined between the balance piston 252 and the frame 72. In particular, the balance chamber 254 is defined between the balance piston 252 and the bottom 255 of the chamber 86 opposite the orifice 90; thus, the guide system 172, the return means 240 and the holding means 250 are all longitudinally arranged on the same side (here the downstream side) of the screw-nut system 164, and thus in particular on the same side of the nut 178.

[0192] The balance chamber 254 is fluidly connected to the pressure generator 130 via a fluid connection circuit 256 to be supplied with control fluid at a third pressure. When this supply is activated, this supply is intended to balance the bias of the return means 240.

[0193] For this purpose, the balance actuator 250 is arranged such that the pressure exerted on the piston 252 by the fluid contained in the chamber 254 is directed in a direction opposite to the bias direction of the return means 250: in the example shown, the balance piston 252 is inserted between the chamber 254 and the shoulder 244, and the shoulder 244 is inserted between the piston 252 and the return means 240. In addition, the balance piston 252 and the balance chamber 254 are dimensioned such that when the chamber 254 is supplied with control fluid at a third pressure, the force exerted on the piston 252 by the control fluid is greater than the bias of the return means 240.

[0194] Thus, when the chamber 254 is supplied with control fluid at a third pressure, the bias of the return means 240 is eliminated and the support member 162 is held in the operating position.

[0195] In the example shown, the pressure monitoring unit 132 is fluidly inserted between the pressure generator 130 and the fluid connection circuit 256. The pressure monitoring unit has a first configuration and a second configuration. In the first configuration, the pressure monitoring unit isolates the fluid connection circuit 256 from the return line 136, and in the second configuration, the pressure monitoring unit fluidly connects the fluid connection circuit 256 to the return line 136.

[0196] The pressure monitoring unit 132 is configured to normally be in its first configuration and to switch to its second configuration upon receipt of a control instruction sent by the control module 135.

[0197] A method for changing the pitch of the blade 56 implemented by the pitch changing mechanism 70 will now be described.

[0198] During the first step of the method, the control module 135 first receives a pitch command intended to increase the pitch of the blade 56. Then, the control module 135 sends a control signal to the pressure monitoring unit 132 intended to increase the fluid pressure in the first chamber 112. When the fluid pressure in the first chamber 112 increases, the movable member 102 of the actuator 74 moves towards its deployed position in a second manner, which causes the blade 56 to pivot towards a large pitch (i.e., towards the feather position) via the connection system 78.

[0199] Once the movable member 102 reaches the equilibrium position, the movable member remains stable and the blade 56 remains in a fixed orientation.

[0200] During the second step of the pitch changing method, the control module 135 first receives a pitch command intended to decrease the pitch of the blade 56. Then, the control module 135 sends a control signal to the pressure monitoring unit 132 intended to increase the fluid pressure in the second chamber 114. When the fluid pressure in the second chamber 114 increases, the movable member 102 of the actuator 74 moves towards its retracted position in a first manner, which causes the blade 56 to pivot towards a small pitch (i.e., towards the flat pitch position) via the connection system 78.

[0201] Once the movable member 102 reaches the equilibrium position, the movable member remains stable and the blade 56 remains in a fixed orientation.

[0202] Optionally, the pitch changing method further includes a step of locking the orientation of the blade 56 in a controlled manner after the first step or the second step.

[0203] During this step, the control module 135 sends a pitch locking command to the pressure monitoring unit 132. Under the effect of this command, the pressure monitoring unit 132 fluidly connects the fluid connection circuit 256 to the return line 136, thereby causing the fluid pressure in the balance chamber 254 to drop. Then, the fluid pressure in said chamber 254 is not sufficient to counteract the bias of the return device 240, which thus causes the support member 162 to shift towards its locking position.

[0204] During this shift, while translating, the screw 176 rotates about the longitudinal axis X under the action of the resistance exerted by the assembly of the nut 178 and the balls 194 (the nut and the balls are held stationary by the control actuator 74 and do not translate) until the abutment surface 186 of the screw 176 bears against the stop 92 of the frame 72, thereby blocking the rotation of the screw 176 about the longitudinal axis X and the translation of the screw 176 along the same axis X.

[0205] Thus, even in the case of a loss of fluid pressure in the first chamber 112, the blade 56 is blocked in its orientation.

[0206] In the case of a pressure loss only in the second chamber 114, the movable member 102 of the actuator 74 moves in a second manner under the action of the pressure difference between the two chambers 112, 114, thereby driving the screw 176 and the support member 162 through this movement, and the support member 162 returns to its operating position. Therefore, the movable member 102 is no longer fixed and can continue to move in a second manner until the blade 56 is in the feather position.

[0207] In the case of a failure of the actuation system 76, typically in the case of a failure of the pressure generator 130, the pitch change method includes an additional step of locking the orientation of the blade 56 in an uncontrolled manner.

[0208] During this step, the failure of the actuation system 76 causes a drop in the fluid pressure in the balance chamber 254, which is usually because the pressure generator 130 can no longer keep the control fluid at the third pressure. Then, the fluid pressure in the chamber 254 is not sufficient to counteract the bias of the return device 240, which therefore causes the support member 162 to shift towards its locking position.

[0209] During this shift, the screw 176 drives the nut 178 and the ball 194 through this shift. Since the control actuator 74 loses power, the nut 178 and the ball 194 are no longer held fixed and do not translate. Therefore, the blade 56 pivots slightly towards the fine pitch until the abutment surface 186 of the screw 176 bears against the stop 92 of the frame 72, thereby blocking the rotation of the screw 176 about the longitudinal axis X and the translation of the screw 176 along the same axis X.

[0210] Then, the blade 56 is prevented from pivoting towards the fine pitch by the locking device 160.

[0211] The uncontrolled locking step is followed by a step of fixing the fan 50. During this step, the standby circuit 134 is activated and supplies control fluid to the first fluid chamber 112 to increase the fluid pressure in this chamber. Under the action of this pressure increase, the movable member 102 moves in a second manner, thereby driving the screw 176 and the support member 162 through this movement, and the support member 162 returns to its operating position. Therefore, the movable member 102 is no longer fixed and can continue to move downstream until the blade 56 is in the feather position.

[0212] It should be noted that these different steps can be implemented independently of each other.

[0213] Therefore, due to the above exemplary embodiments, the installation of the pitch change mechanism 70 becomes easier and the installation cost of the pitch change mechanism is reduced.

[0214] Furthermore, due to the compactness of the control actuator 74 and due to the use of a connection member 148 with less resistance and thus less weight, the weight of the pitch changing mechanism 70 can be reduced.

[0215] The above exemplary embodiments also make it possible to eliminate the need for a lock nut different from the nut 178 of the screw-nut system 164. This results in a simplified manufacture, reduced cost and increased reliability of the locking device 160 as well as of the pitch changing mechanism 70.

[0216] The exemplary embodiments also make it possible to dispense with a support provided upstream of the locking device 160, which facilitates access to the pitch changing mechanism 70, and more particularly to the connection system 78, after assembly is completed.

[0217] These exemplary embodiments ultimately make it possible to very precisely manipulate the pitch angle of the blade 56, which allows large blades 56 with complex geometries to be tightly implanted on the hub 55, thus increasing the efficiency of the turbine 12.

Claims

1. A pitch changing mechanism (70) for adjusting the angular position of at least one variable pitch blade (56) about a pivot axis (P) of the blade (56), the pitch changing mechanism (70) comprising: - a frame (72) fixed relative to the pivot axis (P), - a control actuator (74) including a fixed member (100) and a movable member (102), the fixed member being fixed to the frame, the movable member being translatable relative to the fixed member (100) along a longitudinal axis (X) between a retracted position and an extended position, - a connection system (78) connecting the movable member (102) to the variable pitch blade (56) to convert translation of the movable member (102) along the longitudinal axis (X) into rotation of the variable pitch blade (56) about the pivot axis (P), and - a pitch locking device (160) adapted to block translation of the movable member (102) relative to the fixed member (100) in at least one way, wherein the control actuator (74) includes two fluid chambers (112, 114) defined between the fixed member (100) and the movable member (102), the fluid chambers (112, 114) each containing control fluid for controlling displacement of the movable member (102) relative to the fixed member (100), and the pitch locking device (160) is located outside the fluid chambers (112, 114).

2. The pitch changing mechanism (70) according to claim 1, wherein, At least a part of the pitch locking device (160) extends longitudinally away from the control actuator (74).

3. The pitch changing mechanism (70) according to claim 1 or 2, the pitch changing mechanism including seals (116, 234) fluidly isolating the fluid chambers (112, 114) from the pitch locking device (160).

4. The pitch changing mechanism (70) according to any one of the preceding claims, wherein, The pitch locking device (160) includes: - a support member (162) translatable relative to the frame (72) along the longitudinal axis (X) between an operating position and a locking position, - a return device (200) biasing the support member (162) towards the locking position of the support member, - a holding device (202) for holding the support member (162) in the operating position of the support member under normal operating conditions, and - a screw-nut system (164) having: · A screw (176) that is translationally fixed to the support member (162) and is movably mounted to rotate about the longitudinal axis (X) relative to the support member (162), the screw (176) having an abutment surface (186) that is spaced from the frame (72) by a distance when the support member (162) is in the operating position and that abuts against the frame (72) when the support member (162) is in the locked position, and · A nut (178) that is fixed to the movable member (102) of the control actuator (74) and is coaxial with the screw (176), the nut (178) cooperating with the screw (176) such that translation of the nut (178) along the longitudinal axis (X) causes rotation of the screw (176) about the longitudinal axis (X).

5. The pitch changing mechanism (70) according to claim 4, the pitch changing mechanism including a shroud (193) connecting the nut (178) to the movable member (102) of the control actuator (74), the shroud (193) protruding longitudinally from the control actuator (74), particularly upstream longitudinally.

6. The pitch change mechanism (70) according to claim 4 or 5, wherein, The abutment surface (186) is arranged at the downstream end of the screw (176).

7. The pitch changing mechanism (70) according to any one of the preceding claims, wherein, The pitch locking device (160) is lubricated with a lubricant different from the control fluid.

8. The pitch changing mechanism (70) according to claim 7, the pitch changing mechanism including an enclosed space (238) for restriction and / or circulation of the lubricant.

9. The pitch changing mechanism (70) according to claim 8 in combination with any one of claims 4 to 6, wherein, The pitch locking device (160) includes a housing (230) that is fixed to the nut (178) and surrounds the nut (178), the screw (176), and the support member (162), the housing (230) at least partially defining the enclosed space (238).

10. The pitch changing mechanism (70) according to any one of the preceding claims, wherein, The fluid chambers (112, 114) are closed at each longitudinal end of the control actuator (74).

11. The pitch changing mechanism (70) according to any one of the preceding claims, wherein, The pitch locking device (160) is remote from the fluid chambers (112, 114) of the control actuator (74).

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

13. A turbine (12) including the fan rotor (54) according to claim 12.

14. An aircraft (10) including the turbine (12) according to claim 13.

15. A method for changing the pitch of blades (56) of a fan rotor (54) of a turbine, each blade being pivotable about its own 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 respective pivot axis (P) by means of a pitch changing mechanism (70) according to any one of claims 1 to 11.

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