Pitch changing mechanism with locking device

Abstract

The invention relates to a pitch change mechanism (70) comprising a frame (72), a moving portion (102) movable in translation along a longitudinal axis (X), and a locking device (160) for fixing the moving portion (102) relative to the frame (72). The locking device (160) includes a blocking surface (162), a guide surface (164), and a blocking member (166) interposed between the blocking surface and the guide surface. The locking device further comprises a biasing member (200) urging the guide surface (164) and the blocking member (166) towards one configuration and retaining means (202) for retaining the guide surface (164) and the blocking member (166) in the other configuration under predetermined conditions.

Description

TECHNICAL FIELD

[0001] The present invention relates to the general field of actuators intended to control the orientation of variable setting vanes, such as the variable setting vanes equipped on the fans of certain turbomachines.

[0002] The preferred field of application of the invention is the field of turbojet engines with unducted fans, better known under the names "propfan", "open fan" and "open rotor". However, the invention is also applicable to turboprop engines with one or more propeller screws and to ducted turbojet engines with variable setting fan vanes. BACKGROUND

[0003] One of the ways currently being explored to improve the specific consumption of the engines of civil aircraft is the development of unducted fan turbojet engines, such as the one described in document FR 2 941 493. These turbojet engines comprise a conventional turbine shaft gas generator whose turbine stage(s) drive(s) one or more unducted fans that extend outside the engine nacelle.

[0004] As in the case of conventional turboprop engines, the vanes of this or these fans are variable setting fans, that is to say, the angular position of these vanes, called setting angle, can be modified during flight. As a reminder, the setting angle of a vane corresponds to the angle between the rotation axis of the fan and the chord of the vane located at 75% of the radius of the fan, in a plane orthogonal to the pivot axis of the vane. This angle can vary from a value substantially equal to 90°, which corresponds to the position of the vane called "zero thrust position" or "low pitch", to a value substantially equal to 0°, which corresponds to the position of the vane called "feathered" position. This angle can also take a value strictly greater than 90°, generally a value substantially equal to 95°, which corresponds to the position of the vane called "reverse" position.

[0005] As is known, this modification of the setting angle during flight makes it possible to vary the engine thrust and to optimize the efficiency of the fan as a function of the speed of the aircraft. Indeed, the speed of the fan is almost constant throughout the operating phases, it is the setting of the vanes that varies the thrust. Thus, during the cruising flight phase, the vanes are oriented to regulate the thrust by minimizing the power taken from the turbine shaft and consumed and by optimizing the efficiency. Conversely, during takeoff, the vanes are oriented to maximize the thrust in order to accelerate then take off the aircraft.

[0006] The control of the orientation of the blades is generally performed by a pitch change mechanism comprising a control actuator comprising a mobile part that is movable translationally along the axis of the fan, and a connection system connecting the mobile part to the blades to translate the translation of the mobile part into a rotation of the variable setting blades.

[0007] The difficulty encountered with variable setting blades is that, in the event of failure of the system controlling the orientation of the variable setting blades, said blades tend to switch to the zero-thrust position under their own centrifugal action. However, a blade stuck in this position generates a very small resistance moment, there being a risk of causing the engine to overspeed, with the potential risk of damaging the engine. Furthermore, in the event of an emergency landing mission, a blade stuck in this position also risks generating an excessive resistance, which is unacceptable for the controllability of the aircraft and / or its range.

[0008] To overcome this difficulty, it is known to use a safety system capable of preventing the variable setting blades from moving towards small pitch, i.e. towards the zero-thrust position, in the event of 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 that integrates a screw-nut system of the ball screw type, coupled to a locking nut, in the actuator controlling the orientation of the blades. In normal operation, the nut of the screw-nut system follows the movement of the control actuator, thus causing the screw to rotate about its axis, while the locking nut follows the thread of the screw but is always out of contact with it (the threading of the locking nut is designed to provide a small gap between it and the thread of the screw). In the event of failure of the blade orientation control system, the screw of the screw-nut system is immobilized (preventing the screw from rotating) and the locking nut engages with said screw, thus preventing the blades from pivoting towards small pitch.

[0010] However, this safety system is not entirely satisfactory. To make it work properly, it is necessary to precisely and complexly manage the gap between the locking nut and the thread of the screw. SUMMARY

[0011] One object of the present invention is to be able to lock the blade setting angle in at least one direction in a simple and robust manner. Other objects are to be able to lock the blade setting angle in its current orientation, possibly with a certain tolerance, to be able to lock without supplying power to the actuator, to be able to lock and / or unlock with a small force, and to limit the size of the locking mechanism.

[0012] To this end, according to a first aspect, the application relates to a pitch varying mechanism for adjusting an angular position of at least one variable setting blade of an aircraft turbomachine about a pivoting axis of the blade, the pitch varying mechanism comprising:

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

[0014] - a control actuator comprising a fixed part integral with the frame, and a mobile part,

[0015] - a connection system connecting the mobile part to the variable setting blade to translate a movement of the mobile part relative to the fixed part into a rotation of the variable setting blade about the pivoting axis, and

[0016] - a pitch locking device adapted to prevent a movement of the mobile part relative to the fixed part in at least one direction,

[0017] wherein the pitch locking device comprises:

[0018] - a blocking surface integral with the frame, or movable with the mobile part relative to the frame,

[0019] - a guiding surface facing the blocking surface and comprising a surface portion located at a first fixed distance from the blocking surface,

[0020] - a blocking member interposed between the blocking surface and the guiding surface and having a guiding face facing the guiding surface, said blocking member having an unlocked configuration in which the face is located at a second distance from the blocking surface, the second distance being greater than the first distance, and a locked configuration in which the face is located at the first distance from the blocking surface, the blocking member having an engagement with the blocking surface so as to immobilize the mobile part relative to the frame,

[0021] the guiding surface and the blocking member being movable relative to each other parallel to the blocking surface between a first configuration in which the surface portion is spaced apart from the face, and a second configuration in which the face abuts against the surface portion,

[0022] the pitch locking device further comprising:

[0023] - a biasing member urging the guiding surface or the blocking member towards the second configuration, and

[0024] - a retaining means for retaining the guiding surface and the blocking member in the first configuration under certain predetermined conditions.

[0025] According to a particular embodiment of the application, the pitch- varying mechanism also has one or more of the following features, taken separately or in any technically possible combination:

[0026] - the predetermined condition comprises a supply pressure of the chamber controlling the actuator greater than a threshold value, said threshold value being less than a minimum supply pressure of the chamber controlling the actuator under normal operating conditions;

[0027] - the blocking surface is movable jointly with the mobile portion with respect to the frame, preferably the blocking surface is integral with the mobile portion,

[0028] - in the first configuration, the blocking member is free in its unlocked configuration, and in the second configuration, the blocking member is forced in its locked configuration;

[0029] - the guiding surface is translatable with respect to the blocking surface, parallel to the blocking surface;

[0030] - the guiding surface converges towards the blocking surface;

[0031] - the guiding surface converges towards the blocking surface along a first direction, the biasing member exerts a force on the guiding surface oriented along a second direction opposite to the first direction, and / or the biasing member exerts a force on the blocking member oriented along said first direction;

[0032] - the blocking member comprises a blocking face facing the blocking surface, the guiding face converges towards said blocking face;

[0033] - the guiding face converges towards the blocking face along a first direction, the biasing member exerts a force on the guiding surface oriented along a second direction opposite to the first direction, and / or the biasing member exerts a force on the blocking member oriented along said first direction;

[0034] - the guiding face is substantially parallel to the guiding surface;

[0035] - the blocking surface is cylindrical, the blocking member is annular and substantially coaxial to the blocking surface, the blocking member is divided in a plurality of sections which are movable with respect to each other between an approach configuration, in which the blocking member has a reduced diameter, and a separation configuration, in which the blocking member has an increased diameter, the approach configuration constituting one of the locked and unlocked configurations of the blocking member, and the separation configuration constituting the other of said locked and unlocked configurations;

[0036] - the blocking surface is cylindrical, and the blocking member comprises a split sleeve substantially coaxial to the blocking surface;

[0037] - the blocking member surrounds the blocking surface;

[0038] - the blocking surface surrounds the blocking member;

[0039] - the guiding surface is annular and substantially coaxial to the blocking surface;

[0040] - the holding means comprise a counter-actuator having a counter-chamber in contact with a piston movable with the guiding surface or the blocking member, said counter-chamber being able to receive a pressurized fluid to counterbalance the thrust of the biasing means;

[0041] - the mobile part is translatable with respect to the fixed part along a longitudinal axis;

[0042] - one of the blocking surface and the blocking member is interposed between the longitudinal axis and the other of the blocking surface and the blocking member;

[0043] - the blocking surface is cylindrical and substantially coaxial to the longitudinal axis;

[0044] - one of the guiding surface and the blocking member is translatable with respect to the frame along a secondary translation direction substantially parallel to the blocking surface, the other of the guiding surface and the blocking member being substantially fixed with respect to the frame along said secondary translation direction,

[0045] - the secondary translation direction is substantially parallel to the longitudinal axis;

[0046] - the control actuator comprises a high-pitch chamber and a low-pitch chamber, the high-pitch chamber being adapted so that a relative increase in pressure in said high-pitch chamber causes the variable setting vane to rotate towards a high-pitch, the low-pitch chamber being adapted so that a relative increase in pressure in said low-pitch chamber causes the variable setting vane to rotate towards a low-pitch;

[0047] - the guiding surface converges towards the blocking surface along a direction from the high-pitch chamber towards the low-pitch chamber; and

[0048] - the guiding surface converges towards the blocking surface along a direction from the high-pitch chamber towards the low-pitch chamber.

[0049] According to a second aspect, the application also relates to a fan rotor for a turbomachine, the fan rotor comprising a hub and a plurality of variable setting vanes, each of the plurality of variable setting vanes being pivotable with respect to the hub about a specific pivot axis, the rotor further comprising a pitch varying mechanism according to the first aspect to adjust the angular position of each of the variable setting vanes about its respective pivot axis.

[0050] According to a particular embodiment of the application, the fan rotor further has the following features:

[0051] - the longitudinal axis constitutes a rotation axis of the rotor.

[0052] According to a third aspect, the application also relates to a gas turbine engine comprising a fan rotor according to the second aspect.

[0053] According to a particular embodiment of the application, the gas turbine engine also has the following features:

[0054] - the longitudinal axis constitutes an elongation axis of the gas turbine engine.

[0055] According to a fourth aspect, the application also relates to an aircraft comprising at least one gas turbine engine according to the third aspect.

[0056] Finally, according to a fifth aspect, the application relates to a method for varying the pitch of the blades of a fan rotor of a turbomachine, each of the blades being pivotable about a specific pivot axis with respect to a hub of the fan rotor, said method comprising adjusting the angular position of each of the blades about its respective pivot axis by means of a pitch varying mechanism according to the first aspect.

[0057] According to a particular embodiment of the application, the method also has the following features:

[0058] - the method comprises an additional step of locking the orientation of the blades by means of a pitch locking device. BRIEF DESCRIPTION OF DRAWINGS

[0059] Other features and advantages of the application will appear from the following description, given by way of example only, and with reference to the appended drawings, in which:

[0060] - Figure 1 is a top view of an aircraft according to an exemplary embodiment of the application,

[0061] - Figure 2 is a simplified longitudinal sectional view of a gas turbine engine of the aircraft of Figure 1 ,

[0062] - Figure 3 is a partial simplified view in longitudinal section of a first embodiment of a pitch varying mechanism of the gas turbine engine of Figure 2 ,

[0063] - Figure 4 is a partial simplified view in longitudinal section of a first variant of a pitch locking device of the pitch varying mechanism of Figure 3 ,

[0064] - Figure 5 is a view similar to Figure 4 , in which the pitch locking device is in a second configuration,

[0065] - Figure 6 is a simplified view along a radial axis of a rotating arm of a variable setting blade of the turbomachine of Figure 2 ,

[0066] - Figure 7 and Figure 8 is Figure 4 and Figure 5 front view of the blocking member of the locking device of

[0067] - Figure 9 is Figure 2 view of a second embodiment of a pitch change mechanism of a gas turbine engine, similar to Figure 3 ,

[0068] - Figure 10 is Figure 9 partial simplified view of a longitudinal section of a first variant of a pitch locking device of the pitch change mechanism of

[0069] - Figure 11 is a view similar to Figure 10 , in which the pitch locking device is in a second configuration,

[0070] - Figure 12 is Figure 9 partial simplified view of a longitudinal section of a second variant of a pitch locking device of the pitch change mechanism of

[0071] - Figure 13 is a view similar to Figure 12 , in which the pitch locking device is in a second configuration,

[0072] - Figure 14 is Figure 9 partial simplified view of a longitudinal section of a third variant of a pitch locking device of the pitch change mechanism of

[0073] - Figure 15 is a view similar to Figure 14 , in which the pitch locking device is in a second configuration. DETAILED DESCRIPTION

[0074] Figure 1 The aircraft 10 shown comprises a turbomachine 12, which forms a gas turbine engine to propel the aircraft 10.

[0075] In the example shown, the aircraft 10 is an airplane. In a conventional manner, this aircraft comprises a fuselage 14, a horizontal tail 16 and two wings 18. Here, the number of gas turbine engines 12 is two and each gas turbine engine is housed under a respective wing 18. As a variant (not shown), the gas turbine engines 12 are arranged along the fuselage 14, for example close to the horizontal tail 16. As a further variant (also not shown), the aircraft 10 comprises a single gas turbine engine 12 or at least three gas turbine engines 12.

[0076] In Figure 2 One of the turbomachines 12 is shown in

[0077] As can be seen in this Figure 2 The turbomachine 12 is elongated along a longitudinal axis X. The turbomachine 12 generally has an angular symmetry about said longitudinal axis X, that is to say that there is at least one angle which is invariant for the turbomachine by rotation about the longitudinal axis X.

[0078] Here and in the following, the terms "internal" and "external", "inner" and "outer" and their variants are to be understood with reference to the axis X, the elements described as "internal" or "inner" being oriented towards the axis X, while the "external" or "outer" elements are oriented opposite the axis X.

[0079] In a conventional manner, the turbomachine 12 comprises a nacelle 20, an internal flow path 22 for the passage of a flow of gas through the nacelle 20, a combustion chamber 24 housed in the flow path 22, an engine core 26 and an exhaust nozzle 28.

[0080] In the following, the terms "upstream" and "downstream" are to be understood with reference to the direction of flow of the flow of gas through the flow path 22.

[0081] The engine core 26 comprises a compressor 30, a turbine 32 and a transmission shaft 34 coupling the turbine 32 to the compressor 30 to drive the compressor 30 by the turbine 32. The compressor 30 is arranged upstream of the combustion chamber 24 and supplies compressed air to the combustion chamber 24. The turbine 32 is arranged downstream of the combustion chamber 24 and receives exhaust gases leaving the combustion chamber 24.

[0082] The transmission shaft 34 has the longitudinal axis X as its axis of rotation.

[0083] The transmission shaft 34 is guided in rotation relative to the nacelle 20 by bearings (not shown).

[0084] In the example shown, the turbomachine 12 is a multi-spool turbomachine, in particular a two-spool turbomachine, comprising, in addition to the engine spool 26, a low-pressure spool 40. The engine spool 26 thus constitutes a high-pressure spool, the compressor 30 is a high-pressure compressor, the turbine 32 is a high-pressure turbine, and the transmission shaft 34 is a high-pressure shaft.

[0085] The low-pressure spool 40 comprises a low-pressure compressor 42, a low-pressure turbine 44, and a low-pressure shaft 46 coupling the low-pressure turbine 44 to the low-pressure compressor 42 for driving the low-pressure compressor 42 by the low-pressure turbine 44.

[0086] The low-pressure compressor 42 is arranged upstream of the high-pressure compressor 30 and supplies the high-pressure compressor 30 with compressed air. The low-pressure turbine 44 is arranged downstream of the high-pressure turbine 32 and receives exhaust gases leaving the high-pressure turbine 32.

[0087] The low-pressure shaft 46 is guided in rotation relative to the nacelle 20 by bearings (not shown).

[0088] The low-pressure shaft 46 is coaxial with the high-pressure shaft 34. The low-pressure shaft 46 thus also has the longitudinal axis X as its axis of rotation. In particular, the low-pressure shaft 46 extends within the high-pressure shaft 34.

[0089] The turbomachine 12 further comprises a fan 50 for driving an airflow in an outer flow-through flow path 52 around the nacelle 20. A primary (hot) airflow A is thus distinguished, which consists of the part of the airflow driven in the inner flow-through flow path 22, and a secondary (cold) airflow B, which consists of the part of the airflow driven in the outer flow-through flow path 52.

[0090] The fan 50 comprises a fan rotor 54. This fan rotor 54 is rotatably mounted relative to the nacelle 20 about the longitudinal axis X. The fan rotor 54 comprises a hub 55 Figure 3 and Figure 9 provided with fan blades 56 extending substantially radially outward from the hub 55. When these blades 56 are rotated, they drive the airflow within the outer flow-through flow path 52.

[0091] As seen in Figure 6 each blade 56 comprises a leading edge 57A, a trailing edge 57B, and a chord C connecting the leading edge 57A to the trailing edge 57B.

[0092] Returning to Figure 2The fan rotor 54 is rotated by the low-pressure turbine 44 via the low-pressure shaft 46. This drive is preferably implemented by means of a reduction gear (not shown) which makes it possible for the fan rotor 54 to rotate at a speed which is less than the speed of the low-pressure shaft 46. Alternatively, this drive is a direct drive, that is to say the fan rotor 54 rotates integrally with the low-pressure shaft 46.

[0093] In the example shown, the fan 50 also comprises a fan stator 58 comprising fixed blades 59 which are arranged along a plane which is orthogonal to the longitudinal axis X, at the periphery of the nacelle 20, in the external flow-through flow path 52. Here, this fan stator 58 is arranged downstream of the fan rotor 54. As a variant (not shown), the fan 50 comprises a fan rotor which rotates in the opposite direction, instead of the fan stator 58.

[0094] Advantageously, as shown, the fan 50 is an unducted fan, that is to say the external flow-through flow path 52 is not delimited by an outer perimeter. Thus, as shown, the turbomachine 12 is constituted by a turbojet having an unducted fan, or as a variant by a turboprop. As a variant (not shown), the external flow-through flow path 52 is delimited between the nacelle 20 and a fan casing which surrounds the fan 50; then, the turbomachine 12 is generally constituted by a turbojet having a high bypass ratio, the bypass ratio being defined as the ratio of the flow rate of the secondary (cold) flow B to the flow rate of the primary (hot) flow A.

[0095] In the example shown, the turbomachine 12 is a turbomachine of the "puller" type, that is to say the fan 50 is arranged upstream of the internal flow-through flow path 22 and also drives the airflow in the internal flow-through flow path 22. As a variant (not shown), the turbomachine is a turbomachine of the "pusher" type, that is to say the fan 50 is placed approximately halfway downstream of the nacelle 20.

[0096] The blades 56 of the fan rotor 54 are variable-pitch blades, that is to say each blade 56 is mounted pivotally about a specific pivot axis P with respect to the hub 55. This pivot axis P extends along the elongation direction of the blade 56. This pivot axis P is substantially orthogonal to the longitudinal axis X.

[0097] In particular, each blade 56 is able to pivot about the axis P, with respect to the hub 55, between a position called feathered position, in which the chord C of the blade 56 is substantially parallel to the longitudinal axis X, and a position called zero-thrust 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 zero-thrust position to reach a position called reversed position, in which the chord C of the blade 56 forms an angle with the longitudinal axis X strictly greater than 90°, for example substantially equal to 95°. Since the blades 56 are generally twisted, the chord C given as a reference to measure the setting angle is generally constituted by the chord of the blade at 75% of the radius of the fan rotor 54.

[0098] To this end, as can be seen in Figure 3 and Figure 9 , each blade 56 is integral with an attachment assembly 60 arranged at the root of the blade. This attachment assembly 60 is rotatably mounted with respect to the hub 55 about the pivot axis P. More precisely, the attachment assembly 60 is rotatably mounted by means of balls 64 or other rolling elements within a housing 62 formed in the hub 55.

[0099] The fan 50 also comprises a pitch change mechanism 70 for adjusting the setting angle of each blade 56 about its pivot axis P so as to adapt the performance of the turbomachine 12 to different flight phases.

[0100] With reference to Figures 3 to 5 A first exemplary embodiment of this pitch change mechanism 70 will now be described.

[0101] As can be seen in Figure 3 , the pitch change mechanism 70 comprises a frame 72, a control actuator 74, a control system 76 for the control actuator 74, and a connection system 78.

[0102] The frame 72 is integral with the hub 55, generally constituted by a portion of the hub 55. The frame 72 is thus fixed with respect to the pivot axis P.

[0103] The frame 72 comprises a base 80. This base 80 is centred on the longitudinal axis X. Here, the base 80 is traversed by the pivot axis P.

[0104] In the example shown, the base 80 delimits a housing 82 which is open downstream. This housing 82 is in particular cylindrical, generally revolved cylindrical, and centred on the axis X. An oil feed bearing 84 is housed in said housing 82.

[0105] In the example shown, the frame 72 also comprises a barrel 86 which projects upstream from the base 80. This barrel 86 is centred on the axis X. The barrel 86 is generally revolved cylindrical.

[0106] The base 80 and the peripheral cylinder 86 together delimit an outer peripheral surface 88 of the frame 72. This outer peripheral surface 88 is substantially cylindrical and centred on the axis X. The outer peripheral surface 88 is oriented radially outwards.

[0107] The control actuator 74 comprises a fixed part 100 integral with the frame 72 and a mobile part 102 that is translationally mobile relative to the fixed part 100 along the longitudinal axis X between a retracted position, shown, and a deployed position, not shown. Optionally, the mobile part 102 is also rotationally mobile about the longitudinal axis X over a limited angle, for example of the order of 5°. Figure 3

[0108] The control actuator 74 comprises in particular a continuous cylinder 104 forming one of the fixed part 100 and the mobile part 102 and a piston 106 forming the other of the fixed part 100 and the mobile part 102. Here, the cylinder 104 forms the mobile part 102 and the piston 106 forms the fixed part 100. As a variant, not shown, the situation is reversed: the cylinder 104 forms the fixed part 100 and the piston 106 forms the mobile part 102.

[0109] Thus, in the example shown, the cylinder 104 extends around the outer peripheral surface 88 of the frame 72, coaxially with the outer peripheral surface 88 of the frame 72, and the piston 106 is constituted by a collar 108 integral with the frame 72, extending radially outwards from the outer peripheral surface 88 to the cylinder 104.

[0110] The piston 106 has an outer surface 109 in contact with the cylinder 104.

[0111] The cylinder 104 delimits an inner cavity 110. The piston 106 divides said inner cavity 110 into two adjacent fluid chambers 112, 114. Each fluid chamber contains a control fluid, generally constituted by oil, for controlling the movement of the mobile 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 move towards its deployed position, and a relative increase in the second pressure, i.e. relative to the first pressure, causes the piston 110 to move towards its retracted position.

[0112] Here, each of the fluid chambers 112, 114 is internally delimited by the outer peripheral surface 88 of the frame 72 and externally delimited by the cylinder 104. Furthermore, the first fluid chamber 112 is delimited by the piston 106 at its downstream end and the second fluid chamber 114 is delimited by the piston 106 at its upstream end.

[0113] ​The control actuator 74 is thus particularly compact, which makes it lighter.

[0114] In the example shown, the mobile part 102 further comprises an upstream guide ring 116 and a downstream guide ring 118, each of which is integral with the cylinder 104 and extends radially inwardly from the outer peripheral surface 88 of the frame 72. The upstream guide ring 116 is arranged upstream of the piston 106 and delimits an upstream end of the first fluid chamber 112. The downstream guide ring 118 is arranged downstream of the piston 106 and delimits a downstream end of the second fluid chamber 114.

[0115] In the example shown, each of the upstream guide ring 116 and the downstream guide ring 118 constitutes a sealing ring and respectively longitudinally closes the first fluid chamber 112 and the second fluid chamber 114. The fluid chambers 112, 114 are thus closed at each of the longitudinal ends of the control actuator 74.

[0116] As a variant (not shown), only the downstream guide ring 118 constitutes a sealing ring. The upstream guide ring 116 has an aperture, so that the control fluid can flow through the upstream guide ring 116.

[0117] As a further variant (not shown), the mobile part 102 does not comprise the upstream guide ring 116.

[0118] The control system 76 comprises a pressure generator 130 for bringing the control fluid to a third pressure higher than the first pressure and the second pressure, a pressure control unit 132 for regulating the pressure of the control fluid in the first fluid chamber 112 and in the second fluid chamber 114 by the third pressure, and a return line 136 for discharging the control fluid at reduced pressure. The control system 76 further comprises a main reservoir 133, an emergency circuit 134, and a control module 135.

[0119] The pressure generator 130 comprises, for example, a pump able to pump the fluid to bring it to the third pressure (for example 100 bar). When the pressure of the control fluid downstream of the pressure generator 130 exceeds the third pressure, a main pressure relief valve 139A enables a portion of the control fluid to be discharged to the return line 136.

[0120] The pressure control unit 132 is fluidically connected to the first fluid chamber 112 and the second fluid chamber 114 via the oil feed bearing 84. The pressure control unit 132 is capable of distributing control fluid between the first fluid chamber 112 and the second fluid chamber 114 to adjust the fluid pressure inside each of these chambers 112, 114 and, thus, the position of the piston 110 between its retracted position and its deployed position. The pressure control unit 132 is also capable of discharging control fluid from the first fluid chamber 112 and the second fluid chamber 114 into the return line 136.

[0121] The main reservoir 133 is configured to collect depressurized control fluid from the return line 136. The main reservoir 133 feeds the pressure generator 130.

[0122] The emergency circuit 134 is capable of supplying control fluid to the first fluid chamber 112 to move the piston 110 towards its deployed position in case of failure of the pressure generator 130. To this end, the emergency circuit 134 comprises an auxiliary reservoir 137 and an auxiliary pump 138. In the example shown, the emergency circuit 134 also comprises an auxiliary pressure relief valve 139B.

[0123] The auxiliary reservoir 137 is configured to collect depressurized control fluid from the return line 136. The auxiliary reservoir 137 feeds the auxiliary pump 138. In the example shown, the auxiliary reservoir 137 also feeds the main reservoir 133, wherein the depressurized control fluid from the return line 136 passes through the auxiliary reservoir 137 before reaching the main reservoir 133.

[0124] The auxiliary pump 138 is capable of pumping control fluid into the auxiliary reservoir 137 to bring the control fluid to the third pressure. The auxiliary pump 138 is fluidically connected to the pressure control unit 132 to supply control fluid to the pressure control unit 132 at the third pressure, the pressure control unit 132 being configured to redirect all control fluid from the auxiliary pump 138 to the first fluid chamber 112.

[0125] The pressure relief valve 139B is adapted to discharge a portion of the control fluid to the return line 136 when the pressure of the control fluid downstream of the auxiliary pump 138 exceeds the third pressure.

[0126] The control module 135 is configured to receive a setting instruction (not shown) and to derive from the setting instruction a control signal sent to the pressure control unit 132. In particular, the control module 135 is configured to send to the pressure control unit 132 a control signal intended to increase the fluid pressure in the first chamber 112 when the setting instruction is intended to increase the pitch of the blade 56, and to send to the pressure control unit 132 a control signal intended to increase the fluid pressure in the second chamber 114 when the setting instruction is intended to decrease the pitch of the blade 56. Thus, the first chamber 112 constitutes a high-pitch chamber, adapted so that a relative increase in the pressure in said chamber 112 causes the blade 56 to rotate towards a high pitch, and the chamber 114 constitutes a low-pitch chamber, adapted so that a relative increase in the pressure in said chamber 114 causes the blade 56 to rotate towards a low pitch.

[0127] The control module 135 is also configured to send a start instruction to the emergency circuit 134, more particularly to the auxiliary pump 138 of the emergency circuit 134, in the event of failure of the pressure generator 130.

[0128] The connection system 78 connects the mobile part 102 to each blade 56, so as to translate the translation of the mobile part 102 along the longitudinal axis X and, where appropriate, the rotation of the mobile part 102 around the longitudinal axis X into a rotation of each blade 56 around its pivot axis P. In particular, the connection system 78 connects the mobile part 102 to each blade 56 so as to:

[0129] - translate the translation of the mobile part 102 along the longitudinal axis X in a first direction into a rotation of the variable-setting blade 56 around the pivot axis P towards the zero-thrust position, and

[0130] - translate the translation of the mobile part 102 along the longitudinal axis X in a second direction opposite to the first direction into a rotation of the variable-setting blade 56 around the pivot axis P towards the feathered position.

[0131] To this end, the connection system 78 comprises a synchronizing crown 140 integral with the mobile part 102, and for each blade 56, the connection system 78 comprises a connection mechanism 142 for connecting the blade 56 to the synchronizing crown 140.

[0132] The synchronizing crown 140 extends in a radial plane around the mobile part 102. In the first embodiment described herein, the synchronizing crown 140 is fixed to the intermediate portion of the mobile part 102.

[0133] Each connection mechanism 142 comprises a first articulation 144 integral with the mobile part 102, a second articulation 146 integral with the blade 56 and separated from the pivot axis P of said blade 56, and a connection member 148 connecting the first articulation 144 to the second articulation 146.

[0134] The first articulation 144 is carried by the synchronous crown 140. Here, the first articulation 144 is composed of a spherical joint.

[0135] The second articulation 146 is also composed of a spherical joint. The second articulation 146 is arranged eccentrically with respect to the pivot axis P.

[0136] The connection member 148 has a first end 150 articulated to the first articulation 144 and a second end 152 articulated to the second articulation 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 adjust the length of the connection member 148 precisely in the rest position, so as to be able to control the setting angle of each blade 56 by the pitch variation mechanism 70.

[0137] Here, the connection member 148 is composed of a connecting rod 153.

[0138] In the example shown, each connection mechanism 142 also comprises a crank 154 connecting the attachment assembly 60 to the second articulation 146. This crank 154 is rigid and integral with the attachment assembly 60. The crank 154 extends at least partly in a direction orthogonal to the pivot axis P. The crank 154 forms an arm for rotating the blade 56.

[0139] In the example shown, the first direction is from upstream to downstream, that is to say, the movement of the movable member 102 towards its retracted position causes the rotation of each blade 56 towards its zero-thrust position, and the second direction is from downstream to upstream, that is to say, the movement of the movable member 102 towards its deployed position causes the rotation of each blade 56 towards its feathered position. Furthermore, the first articulation 144 is arranged upstream of the second articulation 146.

[0140] To this end, as can be seen in Figure 6 , the second articulation 146 is placed opposite the trailing edge 57B with respect to a plane Q orthogonal to the chord C and containing the pivot axis P.

[0141] As a variant (not shown), the first direction is from downstream to upstream, the first articulation 144 being arranged downstream of the second articulation 146. The second articulation 146 is then placed on the same side of the trailing edge 57B with respect to a plane Q orthogonal to the chord C and containing the pivot axis P.

[0142] These particular arrangements make it possible for the natural thrust of the blade 56 towards its zero-thrust position to cause the connection member 148 to work in tension rather than in compression when the pitch variation mechanism 70 is immobilized. The risk of flexing of the connection member 148 is therefore very low, making it possible to use a relatively fragile connection member 148, which makes it possible to reduce the weight of the pitch variation mechanism 70.

[0143] The pitch changing mechanism 70 further comprises a pitch locking device 160, which is able to at least prevent the translation of the mobile part 102 of the control actuator 74 in a direction which would cause the rotation of the blade 56 towards a small pitch. In the first embodiment described herein, said locking device 160 is housed inside the control actuator 74.

[0144] An exemplary embodiment of this locking device 160 will now be described with reference to Figure 4 and Figure 5 the accompanying drawings.

[0145] The locking device 160 comprises a blocking surface 162, which is movable with the mobile part 102 with respect to the fixed part 100, a guide assembly 163, which delimits a guide surface 164 facing the blocking surface 162, and a blocking member 166, which is interposed between the blocking surface 162 and the guide surface 164 to fix the mobile part 102 with respect to the fixed part 100 by engaging the blocking surface 162.

[0146] In particular, the blocking surface 162 is integral with the mobile part 102.

[0147] The blocking surface 162 is translationally movable with respect to the frame 72 along a main translation direction. This main translation direction is substantially parallel to the blocking surface 162. Advantageously, said main translation direction is constituted by the direction of the larger dimension of the blocking surface 162.

[0148] Advantageously, the blocking surface 162 is cylindrical, that is to say, it has the shape of a cylinder. The main translation direction is then preferably parallel to the axis of said cylinder. Moreover, advantageously, said axis of the cylinder substantially coincides with the axis X, that is to say, the blocking surface is substantially coaxial with the axis X.

[0149] In particular, the blocking surface 162 is directly carried by the mobile part 102. In the first embodiment described herein, the blocking surface 162 constitutes the inner surface of the cylinder 104.

[0150] In general, the blocking surface 162 is substantially smooth.

[0151] The guide surface 164 is positioned with respect to the blocking surface 162 so that one of the guide surface 164 and the blocking surface 162 is interposed between the axis X and the other of the guide surface 164 and the blocking surface 162. Thus, in the first embodiment described herein, the guide surface 164 is interposed between the axis X and the blocking surface 162; then, the blocking surface 162 is oriented radially inwards and the guide surface 164 is oriented radially outwards.

[0152] Here, the guide surface 164 is annular and substantially coaxial with the blocking surface 162. Therefore, the guide surface 164 is positioned relative to the blocking surface 162 such that one of the guide surface 164 and the blocking surface 162 surrounds the other. Specifically, in the first embodiment described herein, the blocking surface 162 surrounds the guide surface 164.

[0153] The guide surface 164 is translatably movable relative to the blocking surface 162, parallel to the blocking surface 162. Specifically, the guide surface 164 is translatably movable relative to the blocking surface 162 along a primary translational direction. Therefore, in the exemplary implementation described herein, the guide component 163 is translatably movable relative to the frame 72 independently of the blocking surface 162.

[0154] The guide surface 164 is located at a substantially fixed distance from the blocking surface 162, meaning that the guide surface 164 can neither move to separate itself from the blocking surface 162 nor move toward the blocking surface 162. In other words, the guide surface 164 is substantially fixed in terms of translation relative to the blocking surface 162 along a direction perpendicular to the blocking surface 162.

[0155] The guide surface 164 can also be positioned relative to the blocking member 166 along the secondary translation direction. Figure 4 The first construction shown is Figure 5 The second configuration shown moves translationally between the components. For this purpose, one of the guide component 163 and the blocking member 166 is constituted by a movable component 168, which is translatably movable relative to the frame 72 along the secondary translational direction, while the other of the guide component 163 and the blocking member 166 is substantially fixed relative to the frame 72 along the secondary translational direction. In the exemplary implementation described herein, it is precisely the movable component 168 that constitutes the guide component 163.

[0156] The secondary translation direction is parallel to the blocking surface 162. In particular, the secondary translation direction is parallel to the primary translation direction. Therefore, here, the secondary translation direction is essentially parallel to the axis X.

[0157] The guide surface 164 is composed of a plurality of surface portions 170 juxtaposed with each other along the secondary translation direction. Each surface portion 170 is typically composed of a basic portion of the guide surface 164, which extends over the entire width of the guide surface 164 perpendicular to the secondary translation direction, and the dimension of the basic portion of the guide surface 164 parallel to the secondary translation direction is very small. In an extreme case, each surface portion 170 is composed of a line extending along the guide surface 164 perpendicular to the secondary translation direction.

[0158] Each surface portion 170 is located at a fixed distance do from the blocking surface 162.

[0159] In the illustrated example, the guiding surface 164 converges towards the blocking surface 162 parallel to the secondary translation direction. In other words, the distance from the guiding surface 164 to the blocking surface 162, parallel to the secondary translation direction, decreases from the first end 172 to the opposite second end 174 of the guiding surface 164. Thus, for each pair of juxtaposed surface portions 170, the one of said surface portions 170 that is closest to the second end 174 is located at a distance do from the blocking surface 162 that is smaller than or equal to the distance do from the other surface portion 170 to the blocking surface 162.

[0160] The guiding surface 164 converges along a first convergence direction towards the blocking surface 162. Preferably, as illustrated, said first convergence direction is oriented from the large-pitch chamber 112 towards the small-pitch chamber 114.

[0161] Here, the guiding surface 164 converges continuously towards the blocking surface 162, that is to say, the distance from the guiding surface 164 to the blocking surface 162 decreases continuously from the first end 172 to the second end 174. Advantageously, the slope of the guiding surface 164 is substantially constant between the first end 172 and the second end 174.

[0162] Generally, the guiding surface 164 is substantially smooth.

[0163] The blocking member 166 is positioned relative to the blocking surface 162 such that one of the blocking member 166 and the blocking surface 162 is interposed between the axis X and the other of the blocking member 166 and the blocking surface 162. Thus, in the first embodiment described herein, the blocking member 166 is interposed between the axis X and the blocking surface 162.

[0164] Preferably, as illustrated, the blocking member 166 is annular and substantially coaxial with the blocking surface 162. Thus, the blocking member 166 is positioned relative to the blocking surface 162 such that one of the blocking member 166 and the blocking surface 162 surrounds the other of the blocking member 166 and the blocking surface 162. In particular, in the first embodiment described herein, the blocking surface 162 surrounds the blocking member 166.

[0165] The blocking member 166 is also substantially coaxial with the guiding surface 164.

[0166] The blocking member 166 is translatable relative to the blocking surface 162 parallel to the blocking surface 162. In particular, the blocking member 166 is translatable relative to the blocking surface 162 along the primary translation direction.

[0167] The blocking member 166 can also move, with respect to the blocking surface 162, in a direction perpendicular to said surface 162, between an unlocked configuration (as shown in Figure 4 Figure 1 1 ) in which the blocking member 166 is spaced apart from the blocking surface 162, and a locked configuration (as shown in Figure 5 Figure 12) in which the blocking member 166 is engaged with the blocking surface 162 so that the mobile portion 102 is fixed with respect to the frame 72.

[0168] To this end, here the blocking member 166 is divided, in the circumferential direction, into a plurality of segments 190 that can move with respect to one another between a Figure 7 proximity configuration, in which the blocking member 166 has a reduced diameter, and a Figure 8 spacing configuration, in which the blocking member 166 has an increased diameter. The number of these segments 190 is at least two. Preferably, the number of these segments 190 is greater than or equal to 4. In the example shown, the number of segments 190 is four.

[0169] The diameter of the blocking member 166 can thus vary between a first value, in which the blocking member 166 is spaced apart from the blocking surface 162, the blocking member 166 then being in the unlocked configuration, and a second value, in which the blocking member 166 is engaged with the blocking surface 162, the blocking member 166 then being in the locked configuration. One of the proximity configuration and the spacing configuration thus constitutes the unlocked configuration of the blocking member 166, and the other of the proximity configuration and the spacing configuration constitutes the locked configuration.

[0170] In particular, in the first embodiment described herein, the proximity configuration constitutes the unlocked configuration, and the spacing configuration constitutes the locked configuration.

[0171] Each segment 190 is rigid. Each segment 190 is generally made of metal.

[0172] Advantageously, the blocking member 166 also comprises a biasing element 192 that urges the segments 190 towards the one of the spacing configuration and the proximity configuration that constitutes the unlocked configuration. Here, this biasing element 192 is formed by an elastic ring, for example an O-ring, that delimits the inside of the blocking member 166, the outside of which is attached to the segments 190. The unlocked configuration thus constitutes the configuration of the blocking member 166 at rest.

[0173] As a variant (not shown), the blocking member 166 consists of a split sleeve. In a known manner, the split sleeve is an annular assembly interrupted by a slot. The lips of the split sleeve can be moved relative to each other between a close configuration, in which the diameter of the sleeve is reduced, and a split configuration, in which the diameter of the sleeve is increased. Thus, one of the close configuration and the split configuration constitutes the unlocked configuration of the blocking member 166, and the other of the close configuration and the split configuration constitutes the locked configuration.

[0174] Returning to Figure 4 and Figure 5 The blocking member 166 has a blocking face 182 facing the blocking surface 162 and a guiding face 184 facing the guiding surface 164.

[0175] In at least one of the locked configuration and the unlocked configuration of the blocking member 166, the blocking face 182 is substantially parallel to the blocking surface 162. In the exemplary implementation described herein, the blocking face 182 is substantially parallel to the blocking surface 162 in both the locked configuration and the unlocked configuration of the blocking member 166.

[0176] The guiding face 184 consists of a plurality of face portions 186 juxtaposed to each other along a secondary translation direction. Each face portion 186 generally consists of a substantial portion of the guiding face 184 extending over the entire width of the guiding face 184 perpendicular to the secondary translation direction, and the dimension of the substantial portion of the guiding face 184 parallel to the secondary translation direction is very small. In an extreme case, each face portion 186 consists of a line extending along the guiding face 184 perpendicular to the secondary translation direction.

[0177] In the example shown, the guiding face 184 converges towards the blocking face 182 parallel to the secondary translation direction. In other words, the distance from the guiding face 184 to the blocking face 182 parallel to the secondary translation direction decreases from a first end 187 of the guiding face 184 to an opposite second end 188. Thus, for each pair of juxtaposed face portions 186, the one of the face portions 186 closest to the second end 188 is located at a distance from the blocking face 182 smaller than or equal to the distance from the other face portion 186 to the blocking face 182.

[0178] The guiding face 184 converges towards the blocking face 182 along a second convergence direction. Preferably, as shown, the second convergence direction has the same orientation as the first convergence direction. Thus, here, the second convergence direction is oriented from the large-pitch chamber 112 towards the small-pitch chamber 114.

[0179] Here, the guiding face 184 continuously converges towards the blocking face 182, that is to say, the distance from the guiding face 184 to the blocking face 182 continuously decreases from the first end 187 to the second end 188. Advantageously, the slope of the guiding face 184 is substantially constant between the first end 187 and the second end 188.

[0180] Preferably, in at least one of the locked configuration and the unlocked configuration of the blocking member 166, the guiding face 184 is substantially parallel to the guiding surface 164. In the exemplary implementation described herein, the guiding face 184 is substantially parallel to the guiding surface 164 in both the locked configuration and the unlocked configuration of the blocking member 166.

[0181] When the blocking member 166 is in the locked configuration, each face portion 186 is located at a first distance dl from the blocking surface 162 ( Figure 5 ), and when the blocking member 166 is in the unlocked configuration, each face portion 186 is located at a second distance d2 from the blocking surface 162 ( Figure 4 ). Advantageously, for at least a portion of the face portions 186, the first distance dl is less than the second distance d2 for each face portion 186. Among the face portions 186, there is at least one face portion 186 for which the first distance dl is equal to the distance do between the blocking surface 162 and a surface portion called the corresponding surface portion 170.

[0182] In the exemplary implementation described herein, the first distance dl of each face portion 186 is less than the second distance d2 of the face portion 186. To this end, each segment 190 is movable in translation perpendicularly to the blocking surface 162 between the locked configuration and the unlocked configuration of the blocking member 166. In particular, each segment 190 is connected to the frame 72 by a link 193, thereby enabling this degree of freedom.

[0183] Furthermore, in the exemplary implementation described herein, for a plurality of face portions 186, there is a corresponding surface portion 170 located at a distance do from the blocking surface 162 equal to the first distance dl from the face portion 186 to the blocking surface 162 when the blocking member 166 is in the locked configuration.

[0184] When the guiding surface 164 and the blocking member 166 are in their first configuration ( Figure 4 ), each face portion 186 is separated from the corresponding surface portion 170; thus, the blocking member 166 is free to be in its unlocked configuration.

[0185] When the guiding surface 164 and the blocking member 166 are in their second configuration ( Figure 5) the at least one face 186 abuts against the corresponding surface portion 170 and is interposed between said corresponding surface portion 170 and the blocking surface 162; the blocking member 166 is thus forced into its locked configuration. Here, when the guiding surface 164 and the blocking member 166 are in their second configuration, the plurality of faces 186 abut against the corresponding surface portion 170 and are interposed between said corresponding surface portion 170 and the blocking surface 162. Advantageously, therefore, when the guiding surface 164 and the blocking member 166 are in their second configuration, the guiding face 184 abuts against the guiding surface 164 over at least 50% of its axial length.

[0186] The movement of the blocking member 166 from the first configuration to the second configuration with respect to the guiding surface 164 is oriented in the same direction as the first converging direction and the second converging direction, that is to say, here, a movement from the large-pitch chamber 112 towards the small-pitch chamber 114. The contact between the guiding surface 164 and the guiding face 184 is therefore progressive, which facilitates the movement of the blocking member 166 with respect to the guiding surface 164.

[0187] Still with reference to Figure 4 and Figure 5 The movement assembly 168 is housed in a recess 194, here a circular recess centred on the axis X, formed in a support 195 integral with the frame 72. This recess 194 opens through an opening 196 in a face 197 of said support 195 facing the blocking surface 162. The recess 194 is delimited opposite the blocking surface 162 by a bottom 198 arranged rearward with respect to said face 197. The recess 194 is also delimited along the secondary translation direction by two opposite end walls 199A, 199B.

[0188] The bottom 198 is in particular cylindrical and coaxial with the longitudinal axis X. The walls 199A, 199B are themselves substantially radial.

[0189] In the first embodiment described herein, said support 195 is constituted by the piston 106, the face 196 being constituted by the outer surface 109 of said piston 106.

[0190] Furthermore, in the exemplary implementation described herein, the opening 196 extends from one of the end walls 199A, 199B to the other. Advantageously, the opening 196 also extends over the entire circumference of the face 197.

[0191] Still in the exemplary implementation described herein, the first end wall 199A carries the connection 193, each segment 190 being connected to the frame 72 by the connection 193.

[0192] Still with reference to Figure 4 and Figure 5The locking device 160 further comprises a biasing member 200 which urges the guiding surface 164 and the blocking member 166 towards the second configuration, and a retaining means 202 for retaining the guiding surface 164 and the blocking member 166 in the first configuration under certain predetermined conditions, typically when the third pressure is greater than a threshold value which is less than the minimum supply pressure of the fluid chambers 112, 114 under normal operating conditions. This minimum supply pressure of the fluid chambers 112, 114 under normal operating conditions is the minimum pressure supplied by the pressure generator 130 in the absence of any malfunction, in particular in the absence of a leak or a breakdown.

[0193] The biasing member 200 is arranged to exert opposite forces on the guiding surface 164 and the blocking member 166, the force exerted on the guiding surface 164 urging said surface 164 towards the blocking member 166, and the force exerted on the blocking member 166 urging said blocking member 166 towards the guiding surface 164. In particular, the force exerted on the guiding surface 164 is oriented in a direction opposite to the first converging direction and the second converging direction, and the force exerted on the blocking member 166 is oriented in a direction identical to the first converging direction and the second converging direction.

[0194] To this end, here the biasing member 200 comprises at least one compression spring compressed between a first shoulder 204 which is movable with the mobile assembly 168 along the secondary translation direction, and a second shoulder 206 carried by the frame 72. In the exemplary implementation described herein, the second shoulder 206 is carried by the second wall 199B (that is to say, by the wall delimiting the recess 194 opposite the wall 199A which carries the slide 193), and the first shoulder 204 is carried by the mobile assembly 168.

[0195] For example, the biasing member 200 comprises a single compression spring centred on the axis X. As a variant, the biasing member 200 comprises a plurality of compression springs distributed circumferentially around the axis X.

[0196] By means of the biasing member 200, the configuration of the guiding surface 164 and the blocking member 166 at rest is the second configuration. This makes it possible to force the blocking member 166 into its locking configuration even in the event of failure.

[0197] The retaining means 202 comprises a counter-actuator 210 having a counter-piston 212 and a counter-chamber 214.

[0198] The counterbalance piston 212 is mounted to translate jointly with the mobile member 168 with respect to the frame 72 along the secondary translation direction. In the exemplary implementation described herein, the counterbalance piston 212 is an integral piece, in particular made of the mobile member 168, which can benefit in terms of compactness.

[0199] The counterbalance piston 212 is also substantially coaxial with the guide surface 164 and the blocking member 166.

[0200] The counterbalance chamber 214 is delimited between the counterbalance piston 212 and the frame 72 along the secondary translation direction. The counterbalance chamber 214 is thus in contact with the counterbalance piston 212. In particular, in the exemplary implementation described herein, the counterbalance chamber 214 is delimited between the first wall 199A and the guide surface 164 along the secondary translation direction.

[0201] In the exemplary implementation described herein, the counterbalance chamber 214 is also delimited between the bottom 198 and the blocking surface 162 perpendicularly to the blocking surface 162. To this end, the face 197 of the support 195 and the counterbalance piston 212 each form a sealing contact, in particular a sealing annular contact, with the blocking surface 162.

[0202] The counterbalance chamber 214 is fluidically connected to the pressure generator 130 by a fluid connection circuit 218 Figure 3 ) to supply the counterbalance chamber 214 with control fluid at a third pressure. When this supply is activated, the counterbalance chamber 214 is intended to counterbalance the thrust of the biasing means 200.

[0203] To this end, the counterbalance actuator 210 is arranged so that the pressure exerted by the fluid contained in the chamber 214 on the piston 212 is oriented in a direction opposite to the thrust direction of the biasing means 200. Thus, here, the counterbalance piston 212 is interposed between the chamber 214 and the biasing means 200, and the shoulder 204 is interposed between the biasing means 200 and the piston 212. Furthermore, the counterbalance piston 212 and the counterbalance chamber 214 are dimensioned so that, when the chamber 214 is supplied with control fluid at a pressure higher than a threshold value, the force exerted by the control fluid on the piston 212 is greater than the thrust of the biasing means 200.

[0204] Thus, as long as the pressure supplied to the chamber 214 is greater than the threshold value, the thrust on the biasing means 200 is counteracted, causing the guide surface 164 and the blocking member 166 to remain in their first configuration. On the other hand, when the supply of control fluid to the chamber 214 at a pressure greater than the threshold value is no longer present, typically when the pressure generator 130 is deactivated, the force of the biasing means 200 prevails, switching the guide surface 164 and the blocking member 166 to their second configuration.

[0205] Returning to Figure 3Here, the pressure control unit 132 is fluidly interposed between the pressure generator 130 and the fluid connection circuit 218. The pressure control unit 132 has a first configuration, in which it isolates the fluid connection circuit 218 from the return line 136, and a second configuration, in which it fluidly connects the fluid connection circuit 218 to the return line 136.

[0206] The pressure control unit 132 is configured to be in its first configuration under normal conditions and to switch to its second configuration upon reception of a control command sent by the control module 135.

[0207] Now, the method implemented by the pitch variation mechanism 70 for varying the pitch of the blade 56 will be described.

[0208] In a first step of the method, the control module 135 first receives a set instruction to increase the pitch of the blade 56. Then, the control module 135 sends a control signal to the pressure control unit 132 to increase the fluid pressure in the first chamber 112. When the fluid pressure in the first chamber 112 increases, the moving part 102 of the actuator 74 moves in the second direction towards its deployed position, which causes the blade 56 to pivot towards a high pitch, i.e. towards a feathered position, via the connection system 78.

[0209] Under the action of the push of the biasing element 192, the blocking member 166 remains in an unlocked configuration, spaced apart from the blocking surface 162, and thus does not hinder the movement of the moving part 102.

[0210] Once the moving part 102 reaches the equilibrium position, the moving part 102 stabilizes and the blade 56 remains in a fixed orientation.

[0211] In a second step of the pitch variation method, the control module 135 first receives a set instruction to decrease the pitch of the blade 56. Then, the control module 135 sends a control signal to the pressure control unit 132 to increase the fluid pressure in the second chamber 114. When the fluid pressure in the second chamber 114 increases, the moving part 102 of the actuator 74 moves in the first direction towards its retracted position, which causes the blade 56 to pivot towards a low pitch, i.e. towards a zero-thrust position, via the connection system 78.

[0212] Here, again under the action of the push of the biasing element 192, the blocking member 166 remains in an unlocked configuration, spaced apart from the blocking surface 162, and thus does not hinder the movement of the moving part 102.

[0213] Once the moving part 102 reaches the equilibrium position, the moving part 102 stabilizes and the blade 56 remains in a fixed orientation.

[0214] Optionally, the pitch variation method further comprises a step of controlled locking of the orientation of the blade 56 after the first step or the second step.

[0215] During this step, the control module 135 sends a pitch lock control to the pressure control unit 132. Under the effect of this control, the pressure control unit 132 fluidically connects the fluid connection circuit 218 to the return line 136, causing the fluid pressure in the counterbalance chamber 214 to drop. Then, the fluid pressure in said chamber 214 drops below the threshold value, and is therefore insufficient to counterbalance the thrust of the biasing means 200, which therefore causes the movement of the mobile assembly 168 along the axis X.

[0216] Then, the guide surface 164 presses on the guide face 184 of the blocking member 166. Since the guide surface 164 and the guide face 184 are each inclined with respect to the longitudinal direction (since the guide surface 164 converges towards the blocking surface 162 and the guide face 184 converges towards the blocking face 182), the bearing force of the guide surface 164 on the guide face 184 has a radial component (this would also be the case if only the guide surface 164 or the guide face 184 were inclined with respect to the longitudinal direction). Thus, the guide surface 164 pushes the blocking member 166 towards the blocking surface 162.

[0217] Thus, the blocking member 166 moves under the effect of this thrust towards the blocking surface 162 until the blocking member 166 engages with the blocking surface 162. There, the movement of the mobile assembly 168 along the axis X stops, which can only occur jointly with the movement of the blocking member 166 towards the blocking surface 162, which then prevents the movement of the mobile assembly 168 along the axis X.

[0218] Then, the force of the biasing means 200 on the mobile member 168 is converted by the wedge effect into a force that presses the blocking member 166 against the blocking surface 162. This generates an adhesion force at the interface between the blocking member 166 and the blocking surface 162 that prevents any movement of the blocking surface 162 relative to the blocking member 166.

[0219] Then, the mobile part 102 can no longer move relative to the fixed part 100. Thus, the blade 56 is blocked in its orientation even in the event of loss of fluid pressure in one of the chambers 112, 114.

[0220] In the event of a malfunction of the control system 76, typically in the event of a malfunction of the pressure generator 130, the pitch variation method comprises an additional step of uncontrolled locking of the orientation of the blade 56.

[0221] During this step, a failure of the control system 76 causes the fluid pressure in the counterbalance chamber 214 to drop, generally because the pressure generator 130 is no longer able to raise the third pressure above the threshold value. The fluid pressure in said chamber 214 is then insufficient to counterbalance the thrust of the biasing means 200, and this causes the movement assembly 168 to move along the axis X.

[0222] The guiding surface 164 then presses on the guiding face 184 of the blocking member 166. Since the guiding surface 164 and the guiding face 184 are each inclined with respect to the longitudinal direction (since the guiding surface 164 converges towards the blocking surface 162 and the guiding face 184 converges towards the blocking face 182), the bearing force of the guiding surface 164 on the guiding face 184 has a radial component (this would also be the case if only the guiding surface 164 or the guiding face 184 were inclined with respect to the longitudinal direction). The guiding surface 164 thus pushes the blocking member 166 towards the blocking surface 162.

[0223] The blocking member 166 thus moves under the effect of this thrust towards the blocking surface 162 until the blocking member 166 engages with the blocking surface 162. There, the movement of the movement assembly 168 along the axis X stops, which can only occur jointly with the movement of the blocking member 166 towards the blocking surface 162, which then prevents the movement of the movement assembly 168 along the axis X.

[0224] The force of the biasing means 200 on the movable member 168 is then converted by the wedge effect into a force that presses the blocking member 166 against the blocking surface 162. This creates an adhesion force at the interface between the blocking member 166 and the blocking surface 162 that prevents any movement of the blocking surface 162 relative to the blocking member 166.

[0225] The movement portion 102 is then no longer able to move relative to the fixed portion 100. The orientation of the vane 56 thus blocks the vane 56.

[0226] Preferably, the uncontrolled locking step is followed by a step of fixing the fan 50. During this step, the emergency circuit 134 is activated and supplies control fluid to the first fluid chamber 112 and to the counterbalance chamber 214 in order to increase the fluid pressure in these chambers. Under the effect of the increase in pressure in the chamber 214, the bearing force of the blocking member 166 on the blocking surface 162 disappears. There is then no longer any adhesion between the blocking member 166 and the blocking surface 162 (or at least this adhesion becomes very weak). The movement portion 102 is then no longer fixed but can move downstream under the effect of the increase in pressure in the first fluid chamber 112 until the vane 56 is in the feathered position.

[0227] It should be noted that these different steps can be implemented independently of one another.

[0228] Thus, thanks to the above-described example embodiment, it is made possible to lock the current orientation of the blade 56, which can have a certain tolerance, in a simple and robust manner. This locking can be performed even without supplying power to the actuator 74, even with a small force. Moreover, this locking is achieved without significantly increasing the size of the mechanism 70.

[0229] In particular, the above-described first embodiment has proven to be advantageous because it is particularly compact in the radial direction and simplifies the design of the mechanism 70 by facilitating the supply of the counterbalance chamber 214 via the oil feed bearing 84.

[0230] A second embodiment of the pitch variation mechanism 70 will now be described with reference to Figures 9 to 15 Figure 6.

[0231] This second embodiment differs from the first embodiment in that the locking device 160 is arranged radially outside, in particular around, the control actuator 74. Thus, in this second embodiment:

[0232] - the blocking surface 162 constitutes an outer surface of the cylinder 104,

[0233] - the blocking surface 162 is interposed between the axis X and the guiding surface 164,

[0234] - the blocking surface 162 is oriented radially outward, the guiding surface 164 being oriented radially inward,

[0235] - the guiding surface 164 surrounds the blocking surface 162,

[0236] - the blocking surface 162 is interposed between the axis X and the blocking member 166,

[0237] - the blocking member 166 surrounds the blocking surface 162,

[0238] - the split configuration of the blocking member 166 constitutes its unlocked configuration, the approach configuration constituting its locked configuration,

[0239] - the support 185 is arranged radially outside the blocking member 166 and the control actuator 74,

[0240] - the support 185 extends around the blocking member 164, and

[0241] - the face 186 constitutes an inner face of said support 185 oriented toward the axis X.

[0242] Compared to the above-described first embodiment, this second embodiment can have a counterbalance chamber 214 with a larger radial section, which makes it possible to use a biasing member 200 that can exert a greater force and thus to increase the blocking force of the locking device 160.

[0243] Furthermore, in this second embodiment, the synchronization crown 140 is fixed to the upstream end 143 of the mobile part 102, instead of the intermediate portion of the mobile part 102. This is a consequence of the gain in longitudinal compactness achieved by the second embodiment.

[0244] Now, the first embodiment of the locking device 160 will be described with reference to Figures 10 to 15 Other exemplary implementations of the locking device 160 will be described. It should be noted that, although these other exemplary implementations are described with respect to the second embodiment, in which the locking device 160 is arranged radially outside the control actuator 74, these other exemplary implementations are also applicable to the first embodiment, in which the locking device 160 is arranged radially inside the control actuator 74.

[0245] A first variant implementation of the locking device 160 is illustrated in Figure 10 and Figure 11 , in which Figure 10 the blocking member 166 and the guiding surface 164 are shown in their first configuration, Figure 11 the blocking member 166 and the guiding surface 164 are shown in their second configuration. This first variant is identical to the first implementation described above.

[0246] A second variant implementation of the locking device 160 is illustrated in Figure 12 and Figure 13 , in which Figure 12 the blocking member 166 and the guiding surface 164 are shown in their first configuration, Figure 13 the blocking member 166 and the guiding surface 164 are shown in their second configuration. This second alternative differs from the first implementation described above by several features.

[0247] First, the recess 194 is not open by an opening 196 passing from one of the walls 199A, 199B of the recess 194 to the other. On the contrary, the recess 194 is partially closed by a wall 220 opposite the bottom 195 and interposed between the bottom 195 and the blocking surface 162. The opening 196 is formed by a groove 222 formed through said wall 220. In particular, the wall 220 is cylindrical and the groove 222 is annular and substantially coaxial to the wall 220.

[0248] Then, each segment 190 of the blocking member 166 is not connected to the frame 72 by a link 193 carried by the first wall 199A of the recess 194. On the contrary, each segment 190 has a longitudinal extension slightly smaller than the longitudinal extension of the groove 222 and engages in said groove 222. Thus, the groove 222 acts as a guide to guide the radial translation of each segment 190 with respect to the blocking surface 162, while the blocking member 166 is fixed with respect to the frame 72 along the longitudinal direction X.

[0249] A further difference lies in the fact that the counterbalance chamber 214 is not delimited longitudinally between the first wall 199A and the guiding surface 164, and not radially between the bottom 195 of the recess 194 and the blocking surface 162. On the contrary, the counterbalance chamber 214 is delimited longitudinally between the first wall 199A and a face 224 of the counterbalance piston 212 distinct from the guiding surface 164, and radially between the bottom 195 and a wall 220. The guiding surface 164 and the blocking member 166 are arranged outside the counterbalance chamber 214; in particular, the guiding assembly 163 and the blocking member 166 are each interposed between said face 224 of the piston 212 and the biasing member 200. This prevents the control fluid from entering between the blocking face 182 and the blocking surface 162, which can increase the adhesion coefficient between the blocking member 166 and the blocking surface 162. The locking of the locking device 160 is thus more effective.

[0250] Finally, the counterbalance piston 212 is not integral with the mobile assembly 168. The counterbalance piston 212 is simply interposed between the counterbalance chamber 214 and the mobile assembly 168, which makes it possible for the counterbalance piston 212 to remain pressed against the mobile assembly 208 and thus to move jointly with the mobile assembly 208 along the secondary translation direction, due to the pressure exerted on the piston 212 by the fluid present in the chamber 214 on the one hand, and the opposite pressure exerted on the mobile assembly 208 by the biasing member 200 on the other hand. It should be noted, however, that this latter difference is optional, as in other variants the counterbalance piston 212 can also be integral with the mobile assembly 168.

[0251] A third alternative implementation of the locking device 160 is shown in Figure 14 and Figure 15 , Figure 14 showing the blocking member 166 and the guiding surface 164 in their first configuration, Figure 15 showing the blocking member 166 and the guiding surface 164 in their second configuration. This second variant differs from the first implementation described above by several features.

[0252] First, the guiding assembly 163 is integral with the frame 72, and the mobile assembly 168 is constituted by the blocking member 166.

[0253] Then, the shoulder 204 is not carried by the mobile assembly 168. On the contrary, the shoulder 204 is carried by a plate 230 interposed between the biasing member 200 and the mobile assembly 168. This plate 230 is substantially fixed in terms of radial translation. It should be noted, however, that this plate 230 is optional, as in other variants the shoulder 204 can also be carried by the mobile assembly 168.

[0254] Another difference lies in the fact that the counterbalance chamber 214 is not longitudinally delimited between the first wall 199A and the guiding surface 164. On the contrary, the counterbalance chamber 214 is longitudinally delimited between the first wall 199A and a face 232 of the counterbalance piston 212 distinct from the guiding surface 164. The guiding surface 164 and the blocking member 166 are arranged outside the counterbalance chamber 214; in particular, the guiding assembly 163 and the blocking member 166 are each interposed between said face 232 of the piston 212 and the biasing member 200.

[0255] An additional difference lies in the fact that the counterbalance piston 212 is not integral with the mobile assembly 168. The counterbalance piston 212 is simply interposed between the counterbalance chamber 214 and the mobile assembly 168, which makes it possible for the counterbalance piston 212 to remain pressed against the mobile assembly 208 and thus to move jointly with the mobile assembly 208 along the secondary translation direction, as a result of the pressure exerted on the piston 212 by the fluid present in the chamber 214 on the one hand and the opposite pressure exerted on the mobile assembly 208 by the biasing member 200 on the other hand.

[0256] Finally, each section 190 of the blocking member 166 is not connected to the frame by means of a connecting piece 193 carried by the first wall 199A of the recess 194. On the contrary, each section 190 is longitudinally interposed between the plate 230 and the piston 212, thereby acting as a guide to guide the radial translation of each section 190 with respect to the blocking surface 162, while the movement of the blocking member 166 with respect to the frame 72 along the longitudinal direction X takes place.

[0257] This latter variant is advantageous because it makes it possible to immobilize the fan 50 without having to refill the counterbalance chamber 214. Indeed, in the event of an increase in the pressure in the large-pitch chamber 112, the blocking member 166 will be pushed apart from the guiding surface 164 by the adhesion forces, which will then be reduced, and then this adhesion force will be insufficient to oppose the movement of the mobile part 102 with respect to the fixed part 100.

[0258] It should be noted that, although the above description has been given for an exemplary embodiment in which the cylindrical surface 162 is movable jointly with the mobile part 102 with respect to the frame 72, the application is by no means limited to this single case. Thus, in other exemplary embodiments (not shown), the blocking member 166 is movable jointly with the mobile part 102 with respect to the frame 72, and then the cylindrical surface 162 is integral with the frame 72. The person skilled in the art will be able to easily make the necessary adjustments.

Claims

1. A pitch variation mechanism (70) for adjusting the angular position of at least one variable setting blade (56) of a turbomachine (12) of an aircraft around a pivot axis (P) of said blade (56), said pitch variation mechanism (70) comprising: - a frame (72) fixed relative to said pivot axis (P), - a control actuator (74) comprising a fixed part (100) integral with said frame (72) and a mobile part (102), - a connection system (78) connecting said mobile part (102) to said variable setting blade (56) to translate the movement of said mobile part (102) relative to said fixed part (100) into a rotation of said variable setting blade (56) around said pivot axis (P), and - a pitch locking device (160) adapted to block the movement of said mobile part (102) relative to said fixed part (100) in at least one direction, wherein said pitch locking device (160) comprises: - a blocking surface (162) integral with said frame (72) or movable jointly with said mobile part (102) relative to said frame (72), - a guiding surface (164) facing said blocking surface (162) and comprising a surface portion (170) located at a fixed first distance (do) from said blocking surface (162), - a blocking member (166) interposed between said blocking surface (162) and said guiding surface (164) and having a guiding face (184) facing said guiding surface (164), said blocking member (166) having an unlocked configuration in which a face (186) of said guiding face (184) is located at a second distance (d2) from said blocking surface (162), said second distance (d2) being greater than said first distance (do), and a locked configuration in which said face (186) is located at said first distance (do) from said blocking surface (162), said blocking member (166) being engaged with said blocking surface (162) so as to immobilize said mobile part (102) relative to said frame (72), said guiding surface (164) and said blocking member (166) being movable relative to each other parallel to said blocking surface (162) between a first configuration in which said surface portion (170) is spaced apart from said face (186) and a second configuration in which said face (170) abuts against said surface portion (186), said pitch locking device (160) further comprising: - a biasing member (200) urging said guiding surface (164) or said blocking member (166) towards said second configuration, and - a locking member (190) interposed between said guiding surface (164) and said blocking member (166) and having a face (192) facing said guiding surface (164), said biasing member (200) being interposed between said face (192) and said guiding surface (164) so as to urge said guiding surface (164) towards said second configuration. - a retaining device (202) for retaining the guiding surface (164) and the blocking member (166) in the first configuration under certain predetermined conditions, wherein the guiding surface (164) converges towards the blocking surface (162) so that, when the guiding surface (164) and the blocking member (166) are in the second configuration, the force of the biasing device (200) on the guiding surface (164) or on the blocking member (166) is converted by a wedge effect into a force pressing the blocking member (166) against the blocking surface (162) so that an adhesion force is generated at the interface between the blocking member (166) and the blocking surface (162), the dimensions of the biasing device (200) being designed so that the adhesion force prevents any movement of the blocking surface (162) relative to the blocking member (166).

2. The pitch varying mechanism (70) according to claim 1, wherein, the guiding surface (164) converges along a first direction towards the blocking surface (162), the biasing member (200) exerts a force on the guiding surface (164) oriented along a second direction opposite to the first direction, and / or the biasing member exerts a force on the blocking member (166) oriented along the first direction.

3. The pitch varying mechanism (70) according to claim 1 or 2, wherein the blocking member (166) comprises a blocking face (182) facing the blocking surface (162), the guiding face (184) converging towards the blocking face (182).

4. The pitch varying mechanism (70) according to any of the preceding claims, wherein, the guiding face (184) is substantially parallel to the guiding surface (164).

5. The pitch varying mechanism (70) according to any of the preceding claims, wherein, the blocking surface (162) is cylindrical, the blocking member (166) is annular and substantially coaxial to the blocking surface (162), the blocking member being divided circumferentially into a plurality of segments (190) movable relative to each other between an approach configuration, in which the blocking member (166) has a reduced diameter, and a distancing configuration, in which the blocking member (166) has an increased diameter, the approach configuration constituting one of a locked configuration and an unlocked configuration of the blocking member (166) and the distancing configuration constituting the other of the locked configuration and the unlocked configuration.

6. The pitch varying mechanism (70) according to any of the preceding claims, wherein, the retaining device (202) comprises a counteracting actuator (210) having a counteracting chamber (214) in contact with a piston (212) movable with the guiding surface (164) or with the blocking member (166), the counteracting chamber (214) being able to receive a pressurized fluid to counteract the thrust of the biasing device (200).

7. The pitch varying mechanism (70) according to any of the preceding claims, wherein, between said fixed portion (100) and said movable portion (102), said two fluid chambers being arranged so that an increase in fluid pressure in one of said fluid chambers (112, 114) with respect to the fluid pressure in the other fluid chamber (112, 114) causes said movable portion (102) to move with respect to said fixed portion (100), said predetermined condition comprising a supply pressure of said fluid chambers (112, 114) being greater than a threshold value, said threshold value being lower than a minimum supply pressure of said fluid chambers (112, 114) under normal operating conditions.

8. A fan rotor (54) for a turbomachine comprising a hub (55) and a plurality of variable setting blades (56), each of said plurality of variable setting blades being pivotable with respect to said hub (55) about a specific pivot axis (P), said rotor (54) further comprising a pitch varying mechanism (70) according to any one of the preceding claims to adjust the angular position of each of said variable setting blades (56) about its respective pivot axis (P).

9. A gas turbine engine (12) comprising a fan rotor (54) according to claim 8.

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

11. A method for varying the pitch of blades (56) of a fan rotor (54) for a turbomachine, each of the blades being pivotable about a specific pivot axis (P) with respect to a hub (55) of the fan rotor (54), the method comprising: to adjust the angular position of each of said blades (56) about its respective pivot axis (P) by means of a pitch varying mechanism (70) according to any one of claims 1 to 7.

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