Pitch changing mechanism with cantilevered pitch locking device

Abstract

The present invention relates to a pitch changing mechanism (70) comprising: a frame (72); a control actuator (74) comprising a fixed part (100) rigidly connected to the frame (72) and a movable part (102) translatable along a longitudinal axis (X); a connection system (78) connecting the movable part (102) to the variable pitch blades (56) to convert translation of the movable part (102) into rotation of the variable pitch blades (56); a pitch locking device (160) capable of blocking translation of the movable part (102) relative to the fixed part (100) in at least one manner. The pitch locking device (160) is cantilevered in the longitudinal direction relative to the frame (72).

Description

Field of the Invention

[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 a 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 the development of unducted fan turbojet engines, such as the turbojet engine 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 or fans are variable pitch blades, that is to say, the angular position (called 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 so as 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 the rotation of the variable pitch blade.

[0007] One 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, 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, 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. In addition, precise and complex management of the clearance between the locking nut and the screw thread is required for correct operation. Summary of the Invention

[0011] An object of the present invention is to facilitate access to a pitch changing mechanism that manipulates the orientation of variable pitch blades when the pitch changing mechanism includes pitch locking means and is assembled to a set of variable pitch blades. Other objects are to achieve weight reduction of the pitch changing mechanism to enable simplification of the pitch changing mechanism and facilitate its assembly.

[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, and 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 a variable pitch blade to convert the translation of the movable part along the longitudinal axis into rotation of the variable pitch blade about a pivot axis, and

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

[0017] Wherein, the pitch locking device is cantilevered longitudinally relative to the frame.

[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 pitch locking device includes:

[0020] o 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.

[0021] o A guiding system, the guiding system guiding the support member relative to the frame.

[0022] o A return device, the return device biasing the support member towards the locking position of the support member, o A holding device, the holding device for holding the support member in the operating position of the support member under normal operating conditions, and

[0023] o A screw-nut system, the screw-nut system having:

[0024] ■ A screw, the screw being translationally fixed to the support member and movably mounted to rotate about the longitudinal axis relative to the support member, the screw having an abutment surface which is at a distance from the frame when the support member is in the operating position and which abuts against the frame when the support member is in the locking position, and

[0025] ■ A nut, the nut being fixed to the movable part of the actuator and 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;

[0026] - 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;

[0027] - The pitch changing mechanism includes guiding means for guiding a nut relative to a 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 cooperating with the outer cylindrical body to slide longitudinally within the outer cylindrical body;

[0028] - The pitch locking device includes a housing fixed to the nut and surrounding the nut, the screw, and the support member;

[0029] - The control actuator includes a cylindrical body forming one of a fixed part and a 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;

[0030] - One of the two fluid chambers is in fluid communication with the interior of the housing, and the control fluid constitutes a lubricating fluid for the locking device;

[0031] - The fluid chambers are closed at each longitudinal end of the actuator;

[0032] - The housing at least partially defines an enclosed space for the circulation of the lubricating fluid for the pitch locking device;

[0033] - The pitch changing mechanism includes a seal that fluidly isolates the fluid chambers from the pitch locking device;

[0034] - The housing includes an inner cylindrical body that bears the nut on its inner surface and cooperates with an outer cylindrical body fixed to the frame to slide longitudinally within the outer cylindrical body, the inner cylindrical body having a seal at its outer periphery that contacts the inner surface of the outer cylindrical body, and the outer cylindrical body and the housing together define an enclosed space for the circulation of the lubricating fluid for the locking device;

[0035] - The connection system includes a first hinge member fixed to the movable part, a second hinge member fixed to the variable pitch blade away from the pivot axis, and a connection member connecting the first hinge member to the second hinge member;

[0036] - The connection system is adapted to effect the following conversions:

[0037] o converting a translation of the movable part in a first manner along the longitudinal axis into a rotation of the variable pitch blade about the pivot axis towards the flat pitch position, and

[0038] o converting a translation of the movable part in a second manner opposite to the first manner along the longitudinal axis into a rotation of the variable pitch blade about the pivot axis towards the feather pitch position;

[0039] - The first hinge member is disposed upstream or downstream of the second hinge member, and the first manner refers to from upstream to downstream or from downstream to upstream;

[0040] - The adjacent surfaces are oriented in a first manner;

[0041] - The support member is moved from its operating position to its locking position by translation in the first manner;

[0042] - The connecting member consists of a connecting rod;

[0043] - The variable pitch blade includes a leading edge, a trailing edge, and a chord connecting the leading edge to the trailing edge, and the second hinge is arranged relative to the trailing edge with respect to a plane orthogonal to the chord and containing the pivot axis;

[0044] - The frame includes a stop, and when the support member is in the locking position, the adjacent surface of the screw bears against the stop, and the control actuator and the stop are longitudinally arranged on the same side of the nut;

[0045] - The cylindrical body is continuous;

[0046] - The fluid chamber is continuous;

[0047] - Each fluid chamber is at least partially defined by the outer peripheral surface of the frame;

[0048] - The adjacent surface is arranged at the downstream end or the upstream end of the screw;

[0049] - The pitch locking device is outside the fluid chamber;

[0050] - At least a part of the pitch locking device extends longitudinally away from the actuator;

[0051] - The pitch changing mechanism includes a shroud connecting the nut to the movable part of the actuator, the shroud protruding longitudinally from the actuator, in particular protruding longitudinally upstream; and

[0052] - The longitudinal axis is substantially orthogonal to the pivot axis.

[0053] According to a second aspect, the invention also relates to a fan rotor for a turbine, the fan rotor including a hub and a plurality of variable pitch blades, each variable pitch blade being pivotable relative to the hub about its own pivot axis, and the rotor further including a pitch changing mechanism according to any one of the preceding claims to adjust the angular position of each variable pitch blade of the variable pitch blades about its respective pivot axis.

[0054] According to a particular embodiment of the invention, the fan rotor further has the following features:

[0055] - The longitudinal axis constitutes the axis of rotation of the rotor.

[0056] According to a third aspect, the invention also relates to a turbine comprising a fan rotor according to the second aspect.

[0057] According to a particular embodiment of the invention, the turbine also has the following characteristics:

[0058] - The longitudinal axis constitutes the elongation axis of the turbine.

[0059] According to a fourth aspect, the invention also relates to an aircraft comprising at least one turbine according to the third aspect.

[0060] Finally, according to a fifth aspect, the invention relates to a method for changing the pitch of the blades of the fan rotor of a turbine, each blade being pivotable about its own pivot axis relative to the hub of the fan rotor, said method comprising adjusting the angular position of each of said blades about its respective pivot axis by means of a pitch-changing mechanism according to the first aspect.

[0061] According to a particular embodiment of the invention, the method also has the following characteristics:

[0062] - The method comprises an additional step of locking the orientation of the blades by means of pitch locking means. Description of the Drawings

[0063] Other features and advantages of the invention will become apparent when reading the following description given by way of example and with reference to the drawings, in which:

[0064] - Figure 1 is a top view of an aircraft according to an exemplary embodiment of the invention,

[0065] - Figure 2 is Figure 1 a simplified view of a partial longitudinal section of the turbine of the aircraft,

[0066] - Figure 3 is a simplified view of a longitudinal section of a part of a pitch-changing mechanism of a turbine according to a first variant, Figure 2 in a first configuration,

[0067] - Figure 4 is a view similar to Figure 3 in a second configuration,

[0068] - Figure 5 is a simplified view of a longitudinal section of a part of a pitch-changing mechanism of a turbine according to a second variant, Figure 2

[0069]

[0069] - Figure 6 is a simplified view of a longitudinal section of a part of a pitch-changing mechanism of a turbine according to a third variant, Figure 2Simplified view of a longitudinal section of a part of the pitch-changing mechanism of a turbine

[0070] - Figure 7 is according to a fourth variant Figure 2 Simplified view of a longitudinal section of a part of the pitch-changing mechanism of a turbine

[0071] - Figure 8 is a simplified view along the radial axis of the arm for rotating the variable pitch blade of the Figure 2 turbine, and

[0072] - Figure 9 is Figure 3 perspective view and partial cross-sectional view of the satellite ball screw of the pitch-changing mechanism of DETAILED DESCRIPTION

[0073] Figure 1 The illustrated aircraft 10 includes a turbine 12 for propelling the aircraft

[0074] 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

[0075] Figure 2 One of the turbines 12 is shown

[0076] As can be seen in this Figure 2 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

[0077] Hereinafter and hereinafter, the terms "inner" and "outer", "inside" and "outside", and their variants are understood with reference to the axis X. An element described as an "inner element" or "inner component" is oriented towards the axis X, while an "outer" or "external" element is oriented relative to the axis X

[0078] 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 housed in the flow path 22, a drive body 26, and an exhaust nozzle 28

[0079] Hereinafter, the terms "upstream" and "downstream" refer to the way the air flow passes through the flow path 22

[0080] The drive body 26 includes a compressor 30, a turbine 32, and a drive shaft 34. The drive shaft 34 couples the turbine 32 to the compressor 30 for driving the compressor 30 by the turbine 32. The compressor 30 is disposed upstream of the combustion chamber 24 and supplies compressed air to the combustion chamber 24. The turbine 32 is disposed downstream of the combustion chamber 24 and receives the exhaust gas leaving the combustion chamber 24.

[0081] The drive shaft 34 has a longitudinal axis X as its axis of rotation.

[0082] The drive shaft 34 is guided to rotate relative to the nacelle 20 by means of bearings (not shown).

[0083] 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.

[0084] 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 couples the low-pressure turbine 44 to the low-pressure compressor 42 for driving the low-pressure compressor 42 by the low-pressure turbine 44.

[0085] The low-pressure compressor 42 is disposed upstream of the high-pressure compressor 30 and supplies compressed air to the high-pressure compressor 30. The low-pressure turbine 44 is disposed downstream of the high-pressure turbine 32 and receives the exhaust gas leaving the high-pressure turbine 32.

[0086] The low-pressure shaft 46 is guided to rotate relative to the nacelle 20 by means of bearings (not shown).

[0087] The low-pressure shaft 46 is coaxial with the high-pressure shaft 34. Thus, 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.

[0088] The turbine 12 further includes a fan 50 for driving an air flow in an outer flow passage 52 around the nacelle 20. Thereby, a primary air flow A (hot) constituted by a part of the air flow driven in the inner flow passage 22 and a secondary air flow B (cold) constituted by a part of the air flow driven in the outer flow passage 52 are separated.

[0089] The fan 50 includes a fan rotor 54. The fan rotor 54 is rotatably mounted relative to the nacelle 20 about the longitudinal axis X. The fan rotor includes a hub 55 ( Figure 3 ), and the hub 55 is provided with fan blades 56 extending substantially radially outward from the hub 55. These blades 56 drive the air flow in the outer flow passage 52 when rotating.

[0090] 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.

[0091] Return Figure 2 , the fan rotor 54 is driven to rotate by the low-pressure turbine 44 via the 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 that of the low-pressure shaft 46.

[0092] 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.

[0093] Advantageously, as shown, the fan 50 is ducted-free, that is, the outer flow path 52 has no outer periphery defined. Thus, as shown, the turbine 12 is composed of a turbojet engine with a ducted-free fan, or as a variant, is composed of a turboprop engine. As a variant (not shown), the outer flow path 52 is defined between the nacelle 20 and a fan casing surrounding the fan 50; the turbine 12 is generally composed 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).

[0094] In the example shown, the turbine 12 is in particular of the "puller" type, that is, the fan 50 is arranged upstream of the inner flow path 22 and also drives the air flow in the inner flow path. As a variant (not shown), the turbine is of the "pusher" type, that is, the fan 50 is arranged around the downstream half of the nacelle 20.

[0095] The blades 56 of the fan rotor 54 are variable pitch blades, that is, each blade 56 is pivotally mounted relative to the hub 55 about its own pivot axis P. The pivot axis P extends along the elongation direction of the blade 56. This pivot axis is orthogonal to the longitudinal axis X.

[0096] Each blade 56 is in particular able to pivot relative to the hub 55 about an axis P between a position called the feather position, in which the chord C of the blade 56 is substantially parallel to the longitudinal axis X, and a position called the 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 able to pivot beyond the flat 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 serving as a reference for measuring the pitch angle is formed by the blade chord at 75% of the radius of the fan rotor 54.

[0097] For this purpose, as Figure 3 shown, each blade 56 is fixed to a fastener 60 provided at the blade root. The 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 element, the housing 62 being arranged in the hub 55.

[0098] The fan 50 also includes a pitch changing mechanism 70 for adjusting the pitch angle of each blade 56 about its pivot axis P so as to adapt the performance of the turbine 12 to different flight phases.

[0099] With reference to Figure 3 , the pitch changing mechanism 70 includes a frame 72, a control actuator 74, a control system 76 for actuating the actuator 74, and a connection system 78.

[0100] 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.

[0101] The frame 72 includes a base 80. The base 80 is centered on the longitudinal axis X. Here, the base is pierced by the pivot axis P.

[0102] In the example shown, the base 80 delimits a housing 82 opening downstream. The housing 82 is in particular cylindrical, generally of revolution cylindrical, and centered on the axis X. An oil supply bearing 84 is received in the said housing 82.

[0103] The base 80 also delimits a cavity 86 which opens to the upstream surface 88 of the base 80 through an orifice 90 which is here centered on the axis X. The cavity 86 is in particular cylindrical, generally of revolution cylindrical, and centered on the axis X. The cavity 86 is inserted between the upstream surface 88 and the housing 82.

[0104] The base 80 has an upstream-facing stop 92. This stop 92 is here formed by a part of the upstream surface 88. The stop 92 extends substantially radially and is in particular arranged around the orifice 90.

[0105] In the example shown, the frame 72 also includes a cylindrical body 94 protruding 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 generally rotationally cylindrical.

[0106] 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 protrudes upstream from the base 80. The cylindrical body 96 is open at its upstream end 97. The cylindrical body 96 is generally rotationally cylindrical.

[0107] The base 80 and the outer peripheral cylindrical body 96 together define the outer peripheral surface 88 of the frame 72. This outer peripheral surface 88 is substantially cylindrical, centered on the axis X. The outer peripheral surface is oriented radially outwards.

[0108] As a variant, as Figure 5 shown, the frame 72 does not include the cylindrical body 94.

[0109] 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.

[0110] 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 movable 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

[0111] The control actuator 74 in particular 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.

[0112] Thus, in the illustrated example, the cylinder 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, the flange 108 extending radially outward from the outer peripheral surface 88 to the cylinder 104.

[0113] The cylinder 104 defines an inner cavity 110. The piston 106 divides the inner cavity 110 into two consecutive fluid chambers 112, 114. Each fluid chamber accommodates a control fluid, typically constituted by oil, to control the displacement of the movable member 102 relative to the fixed member 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 displace towards its deployed position, and a relative increase in the second pressure (i.e., relative to the first pressure) causes the piston 110 to displace towards its retracted position.

[0114] 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 cylinder 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.

[0115] Thus, the control actuator 74 is particularly compact, which enables the control actuator to be lightweight.

[0116] In Figure 3 the illustrated example, the movable member 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 cylinder 104 and extend radially inward from the cylinder 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.

[0117] In Figure 3 the illustrated example, each of the upstream guide bushing 116 and the downstream guide bushing 118 constitutes 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 control actuator 74.

[0118] As a variant, as Figure 7 shown, only the downstream guide bushing 118 constitutes a sealing bushing. The upstream guide bushing 118 has a hole 119 that enables the control fluid to flow through the upstream guide bushing 118.

[0119] As another variant, as Figure 5 shown, the movable member 102 does not include the upstream guide bushing 118.

[0120] Returning to Figure 3 , the actuating 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 a control fluid to a third pressure that is 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 actuating system 76 further includes a main tank 133, a standby circuit 134, and a control module 135.

[0121] For example, the pressure generator 130 includes a pump that is capable of pumping a fluid to bring 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 towards the return line 136.

[0122] 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 the oil supply 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, and thus to regulate 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.

[0123] 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.

[0124] The standby circuit 134 is capable of supplying the 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 further includes an auxiliary pressure relief valve 139B.

[0125] The auxiliary tank 137 is configured to collect the depressurized 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 depressurized control fluid from the return line 136 passes through the auxiliary tank 137 and then reaches the main tank 133.

[0126] The auxiliary pump 138 is capable of pumping the control fluid into the auxiliary tank 137 so that the control fluid reaches the 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. The pressure monitoring unit 132 is configured to redirect the entire control fluid from the auxiliary pump 138 to the first fluid chamber 112.

[0127] 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 part of the control fluid into the return line 136.

[0128] 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 according to 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.

[0129] 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.

[0130] 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 conversions:

[0131] - 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

[0132] - converting 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 pitch position.

[0133] 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.

[0134] 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.

[0135] Each connecting mechanism 142 includes a first hinge member 144 fixed to the movable member 102, a second hinge member 146 fixed to the blade 56 away from the pivot axis P of the blade 56, and a connecting member 148 connecting the first hinge member 144 to the second hinge member 146.

[0136] The first hinge member 144 is carried by the synchronizing ring 140. Here, the first hinge member is constituted by a ball joint connector.

[0137] The second hinge member 146 is also constituted by a ball joint connector. The second hinge member is eccentric with respect to the pivot axis P.

[0138] The connecting member 148 has a first end 150 hinged to the first hinge member 144 and a second end 152 hinged to the second hinge member 146. Advantageously, the connecting 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 modified, which enables precise adjustment of the length at rest so that the pitch angle of each blade 56 can be manipulated by the pitch changing mechanism 70.

[0139] The connecting member 148 is constituted by a connecting rod 153 here.

[0140] In the example shown, each connecting mechanism 142 further includes a crank 154 connecting the fastener 60 to the second hinge member 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.

[0141] 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 flat pitch position. Additionally, the first hinge member 144 is disposed upstream of the second hinge member 146.

[0142] For this purpose, as Figure 8 shown, the second hinge member 146 is disposed relative to the plane Q orthogonal to the chord C and containing the pivot axis P opposite to the trailing edge 57B.

[0143] As a variant (not shown), the first mode is from downstream to upstream and the first hinge member 144 is disposed downstream of the second hinge member 146. Then, the second hinge member 146 is disposed on the same side as the trailing edge 57B relative to the plane Q orthogonal to the chord C and containing the pivot axis P.

[0144] 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 tension rather than compression. Therefore, the risk of bending of the connecting member 148 is very low, allowing the use of a connecting member 148 with relatively low resistance, thereby reducing the weight of the pitch changing mechanism 70.

[0145] 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 a first manner, that is to say, to block the translational movement of the movable part of the control actuator towards its retracted position here.

[0146] The locking device 160 includes a support member 162 and a screw-nut system 164.

[0147] 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 is moved from the operating position of the support member 162 to the locking position of the support member 162 by translating in a first manner (that is to say, in the example shown, by translation 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.

[0148] The support member 162 includes a body 166 which extends along the longitudinal axis X and is centered on the longitudinal axis X. The body 166 has a first longitudinal end 168 (in particular a downstream longitudinal end) which engages with the orifice 90 of the frame 72, and a second free longitudinal end 170. The body 166 is solid here.

[0149] 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 arranged on the downstream side of the screw-nut system 164 here.

[0150] The support member 162 further includes a sleeve 174 which is fixed to the body 166 and is arranged around the second longitudinal end 170 of the body 166.

[0151] The screw-nut system 164 includes a screw 176 and a nut 178.

[0152] 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 about the longitudinal axis X relative to the support member 162. For this purpose, the screw 176 is assembled to the support member 162 by means of a bearing 180. The bearing 180 is here inserted between the sleeve 174 of the support member 162 and the 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.

[0153] The screw 176 has a second longitudinal end portion 184 opposite to the end portion 182. The second longitudinal end portion 184 defines a radially adjacent surface 186. When the support member 162 is in the operating position, the adjacent surface 186 is at a distance from the frame 72, and when the support member 162 is in the locked position, the adjacent surface 186 abuts against the stop 92 of the frame 72.

[0154] 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 is increased, which increases the frictional force between the adjacent surface 186 and the stop 92 and enables better transmission of braking force and blocking force.

[0155] 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 has roughness to further increase the frictional force between the adjacent surface 186 and the stop 92 and achieve greater force transmission.

[0156] In particular, the adjacent surface 186 extends substantially radially. The adjacent surface is oriented in a first manner, that is, in the example shown, the adjacent surface is oriented downstream. Here, the adjacent surface is arranged at the downstream end of the screw 176.

[0157] 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.

[0158] The threaded body 190 and the nut 178 are received inside the cylindrical body 94 of the frame 72.

[0159] The nut 178 is fixed to the movable part 102 of the actuator 74 and is coaxial with the screw 176. The nut 178 cooperates with the screw 176 such 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.

[0160] The nut 178 has an internal thread 194.

[0161] 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.

[0162] 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 a smooth journal 200.

[0163] 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 further 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 smallest possible slip) on the threads 192 of the screw 176 and the threads 194 of the nut 178.

[0164] 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 rings 208 fixed to the nut 178 and respectively mounted at each longitudinal end of the nut 178, and 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.

[0165] 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 threaded body 190 of the screw 176, and 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.

[0166] 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 of a roller bearing screw system, such as the system described in document EP 168 942 A1 or in document EP 671 070 A1.

[0167] This property enables a good transmission of force 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 property enables the nut 178 to be fixed relative to the screw 176 even in the absence of a different locking nut. Thus, the need for a different 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.

[0168] 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.

[0169] Return Figure 3 , the pitch locking device 160 is located outside the fluid chambers 112, 114 of the control actuator 74 here. 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 advantageous for the installation of the pitch changing mechanism 70, thereby reducing costs.

[0170] As Figure 3 shown, a part of the pitch locking device 160 even extends longitudinally away 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.

[0171] To achieve this arrangement, the pitch locking device 160 includes a shroud 193 that connects the nut 178 to the movable member 102 of the actuator 74. This shroud 193 projects longitudinally upstream from the control actuator 74 here. 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.

[0172] Furthermore, the pitch locking device 160 is longitudinally cantilevered relative to the frame 72. In other words, the entire portion 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 portion of the frame 72 that supports the locking device, and there is no component fixed to the frame 72 that supports the end of the pitch locking device 160 opposite to the end supported by the frame 72. Due to this arrangement, it is not necessary to provide a support member upstream of the locking device 160, which facilitates access to the pitch changing mechanism 70 and more specifically to the connection system 78.

[0173] Therefore, the control actuator 74 is longitudinally disposed on the same side as the guiding device 172 and the stop 92 of the nut 178, here the downstream side.

[0174] Despite this cantilever, in order to ensure good support for the locking device 160, the pitch changing mechanism 70 includes a device 220 for guiding the nut 178 relative to the frame 72. The guiding device 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 within the outer cylindrical body.

[0175] 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.

[0176] Here, the outer cylindrical body 224 is constituted by the cylindrical body 94 of the frame 72.

[0177] The pitch locking device 160 requires lubrication. To this end, 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.

[0178] In Figure 3 、 Figure 4 and Figure 6In the example, the housing 230 includes an inner cylindrical body 222 and a plug 232 that closes one end of the inner cylindrical body 222 opposite to 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 for the pitch changing mechanism 70, thereby fluidly isolating the fluid chambers 112, 114 of the actuator 74 from the pitch locking device 160.

[0179] Advantageously, the lubricating fluid for the locking device 160 consists of oil. The pitch locking device 160 then includes a reservoir (not shown) that enables the storage of the lubricating fluid when the actuator 74 is in the retracted position and the transfer of the lubricating fluid 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 grease deposited on the rolling parts of the screw 176 and the bearing 180.

[0180] In Figure 5 (In Figure 5 where the outer cylindrical body 224 and the upstream guide bushing 116 are absent) and Figure 7 (In Figure 7 where the inner cylindrical body 222 and the upstream guide bushing 116 are perforated) examples, 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.

[0181] 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.

[0182] 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 changing mechanism 70 is in the normal operating state.

[0183] Here, the return device 240 consists of a compression spring compressed between the frame 72 and the 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.

[0184] The holding device 242 includes a balancing actuator 250 which includes a balancing piston 252 and a balancing chamber 254.

[0185] The balancing piston 252 is movably mounted for translation along a longitudinal axis X relative to the frame 72. In particular, the balancing piston is coaxial with the support member 162. In the example shown, the balancing piston is disposed in the longitudinal extension of the support member 162, between the support member 162 and the balancing chamber 254.

[0186] 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 the bottom 255 of the cavity 86 opposite the orifice 90; thus, the guiding system 172, the return device 240 and the holding device 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.

[0187] The balancing chamber 254 is fluidly connected to the pressure generator 130 through 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 device 240.

[0188] To this end, the balancing 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 device 250: in the example shown, the balancing 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 device 240. Moreover, the balancing piston 252 and the balancing 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 device 240.

[0189] Thus, when the chamber 254 is supplied with control fluid at a third pressure, the bias of the return device 240 is eliminated and the support member 162 is held in the operating position.

[0190] 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.

[0191] The pressure monitoring unit 132 is configured to normally be in its first configuration and to switch to its second configuration upon receiving a control instruction sent by the control module 135.

[0192] A method for changing the pitch of the blade 56 implemented by the pitch changing mechanism 70 will now be described.

[0193] 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.

[0194] Once the movable member 102 reaches the equilibrium position, the movable member remains stable and the blade 56 maintains a fixed orientation.

[0195] 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.

[0196] Once the movable member 102 reaches the equilibrium position, the movable member remains stable and the blade 56 maintains a fixed orientation.

[0197] 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.

[0198] During this step, the control module 135 sends a pitch locking command to the pressure monitoring unit 132. Under the action 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 the chamber 254 is insufficient to counteract the bias of the return device 240, which therefore causes the support member 162 to shift towards its locking position.

[0199] 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.

[0200] Thus, even in the case of a fluid pressure loss in the first chamber 112, the vane 56 is blocked in the orientation of the vane 56.

[0201] 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. Thus, the movable member 102 is no longer fixed and can continue to move in a second manner until the vane 56 is in the feather position.

[0202] In the case of a failure of the actuating 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 vane 56 in an uncontrolled manner.

[0203] During this step, the failure of the actuating system 76 causes a drop in the fluid pressure in the balance chamber 254, which is typically 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 thus causes the support member 162 to shift towards its locking position.

[0204] 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. Thus, the vane 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.

[0205] Then, the vane 56 is prevented from pivoting towards the fine pitch by the locking device 160.

[0206] 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. Thus, the movable member 102 is no longer fixed and can continue to move downstream until the vane 56 is in the feather position.

[0207] It should be noted that these different steps can be implemented independently of each other.

[0208] Thus, due to the above-described exemplary embodiments, the support member provided upstream of the locking device 160 can be omitted, which facilitates access to the pitch-changing mechanism 70, and more particularly to the connection system 78, after assembly is completed.

[0209] In addition, the installation of the pitch-changing mechanism 70 becomes easier, and the installation cost of the pitch-changing mechanism is reduced.

[0210] In addition, due to the compactness of the control actuator 74 and due to the use of connection members 148 with less resistance and thus less weight, the weight of the pitch-changing mechanism 70 can be reduced.

[0211] The above-described exemplary embodiments also make it possible to eliminate the need for a locking nut different from the nut 178 of the screw-nut system 164. This results in simplified manufacture, reduced cost, and increased reliability of the locking device 160 and the pitch-changing mechanism 70.

[0212] These exemplary embodiments ultimately enable very precise manipulation of the pitch angle of the blade 56, which allows large blades 56 with complex geometries to be closely implanted on the hub 55, thereby improving 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 part (100) and a movable part (102), the fixed part being fixed to the frame (72), the movable part being translatable relative to the fixed part (100) along a longitudinal axis (X) between a retracted position and a deployed position, the movable part (102) extending around the fixed part (100), - a connection system (78) connecting the movable part (102) to the variable pitch blade (56) to convert the translation of the movable part (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 the translation of the movable part (102) relative to the fixed part (100) in at least one way, wherein the pitch locking device (160) is cantilevered longitudinally relative to the frame (72).

2. The pitch changing mechanism (70) according to claim 1, wherein, The pitch locking device (160) comprises: - a support member (162) translatable relative to the frame (72) along the longitudinal axis (X) between an operating position and a locking position, - a guiding system (172) guiding the support member (162) relative to the frame (72), - a return device (240) biasing the support member (162) towards the locking position of the support member, - a holding device (242) 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) translationally fixed to the support member (162) and movably mounted to rotate about the longitudinal axis (X) relative to the support member (162), the screw (176) having an abutment surface (186) which is at a distance from the frame (72) when the support member (162) is in the operating position and which abuts against the frame (72) when the support member (162) is in the locking position, and · a nut (178) fixed to the movable part (102) of the actuator and 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).

3. The pitch changing mechanism (70) according to claim 2, wherein, The control actuator (74) and the guiding system (172) are longitudinally arranged on the same side of the nut (178), preferably on the downstream side of the nut.

4. The pitch changing mechanism (70) according to claim 2 or 3, the pitch changing mechanism comprising guiding means (220) for guiding the nut (178) relative to the frame (72), the guiding means (220) comprising an inner cylindrical body (222) fixed to the nut (178) and an outer cylindrical body (224) fixed to the frame (72), the inner cylindrical body (222) cooperating with the outer cylindrical body (224) to slide longitudinally within the outer cylindrical body.

5. The pitch changing mechanism (70) according to any one of claims 2 to 4, wherein, The pitch locking device (160) comprises a housing (230) which is fixed to the nut (178) and surrounds the nut (178), the screw (176) and the support member (162).

6. The pitch changing mechanism (70) according to any one of the preceding claims, wherein, The control actuator (74) comprises a cylindrical body (104) forming the movable member (102) and a piston (106) forming the fixed member (100).

7. The pitch changing mechanism (70) according to claim 6, wherein, The cylindrical body (104) defines an inner cavity (110), the piston (106) dividing the inner cavity (110) into two fluid chambers (112, 114), each fluid chamber containing control fluid for controlling the displacement of the movable member (102) relative to the fixed member (100).

8. The pitch changing mechanism (70) according to claims 5 and 7, wherein, One of the two fluid chambers (112, 114) is in fluid communication with the interior of the housing (230), the control fluid constituting lubricating fluid for the locking device (160).

9. A fan rotor (54) for a turbine, the fan rotor comprising 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 comprising a pitch changing mechanism (70) according to any one of the preceding claims for adjusting the angular position of each variable pitch blade (56) about its respective pivot axis (P).

10. A turbine (12) comprising a fan rotor (54) according to claim 9.

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

12. A method for changing the pitch of the blades (56) of a fan rotor (54) of a turbine, each blade being pivotable relative to the hub (55) of the fan rotor (54) about its own pivot axis (P), 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 8.

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