BLADE ADJUSTING MECHANISM WITH A HYDRAULIC ACTUATOR SURROUNDING A LIQUID TRANSFERRING BEARING

Description

DOMAINE DE L'INVENTION

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

[0002] A key area of ​​application for the invention is that of unducted fan turbojets (better known by their English names "propfan", "open fan", "open rotor" and "unducted fan"). However, the invention also applies to turboprops with one or more pusher propellers. ARRIERE-PLAN TECHNOLOGIQUE

[0003] One of the avenues currently being explored to improve the specific consumption of civil aircraft engines is the development of turbojets with unfaired fans, such as the one described in document FR 2 941 493. These turbojets include a conventional turboshaft engine gas generator, one or more turbine stages of which drive one or more unfaired fan rotor(s) extending outside the engine nacelle, most often via a reduction gear allowing the fan rotor to rotate at a lower speed than the turbine stage(s).

[0004] The blades of this rotor(s), as in the case of conventional turboprop engines, have variable pitch, meaning that the angular position of these blades (called the pitch angle) can be modified during flight. As a reminder, the pitch angle of a blade corresponds to the angle, in a plane orthogonal to the blade's pivot axis, between the fan's axis of rotation and the blade chord at 75% of the fan's radius. It can vary from a value of 90°, corresponding to a "sail" or "flat" blade position, to a value of 0°, corresponding to a "flap" blade position. It can also take a value strictly greater than 90°, typically approximately 95°, corresponding to a "reverse" blade position.

[0005] As is well known, this adjustment of the fan blade pitch angle during flight allows the engine thrust to be varied and the fan efficiency to be optimized according to the aircraft's speed. Indeed, the fan speed is almost constant throughout all phases of operation, and it is the blade pitch that varies the thrust. Thus, during cruise flight, the blades are angled to adjust the thrust while minimizing the power drawn from the turbine shaft and fuel consumption, and optimizing efficiency. Conversely, during takeoff, the blades are angled to maximize thrust in order to accelerate and then lift off.

[0006] The blade pitch control is commonly achieved using a pitch control mechanism comprising a control cylinder with a moving part that translates along the fan axis and a linkage system connecting the moving part to the blade so as to convert the translation of the moving part into rotation of the variable-pitch blade. This control cylinder is generally a hydraulic cylinder supplied with fluid from a source attached to the turbomachine nacelle, which necessitates a rotary transfer between the stationary portion of the pipe in the nacelle frame and the portion of the pipe rotating with the fan rotor. This rotary transfer is most often achieved using a rotary fluid transfer mechanism commonly called a "fluid transfer bearing."Document EP 1 832 509 B1 describes another example of a pitch change mechanism for adjusting an angular position of at least one variable pitch blade around a blade pivot axis.

[0007] Typically, the fluid transfer bearing is positioned upstream of the gearbox, around the blower shaft. However, this arrangement has many disadvantages: The blower shaft passing through the fluid transfer bearing makes it particularly bulky, and by inserting the fluid transfer bearing between the cylinder and the reducer, the turbomachine is lengthened and, as a result, its weight is increased, which increases its consumption.

[0008] To address these problems, it was proposed to place the fluid transfer bearing downstream of the gearbox and connect it to the actuator via a tube passing through the gearbox. This is the arrangement found today on most turboprop engines. While this arrangement is well-suited to turbomachinery where the fan shaft is offset from the turbine shaft, as is the case with the vast majority of turboprop engines, it presents difficulties when integrated into a turbomachine where the fan shaft is coaxial with the turbine shaft, as in turbojets with unshod fans. Indeed, in such a case, the following constraints arise: Access to the fluid transfer bearing is made difficult, and since the fluid transfer bearing is traversed by the turbine shaft, it ends up being particularly bulky.

[0009] Thus, none of the existing solutions are satisfactory when it comes to equipping a turbomachine whose blower shaft is coaxial with the turbine shaft with a fluid transfer bearing intended to supply a pitch change mechanism of a blower rotor. EXPOSE DE L'INVENTION

[0010] One objective of the invention is to facilitate access to a fluid transfer bearing intended to supply a pitch-change mechanism of a fan rotor equipping a turbomachine whose fan shaft is coaxial with the turbine shaft, while minimizing the length of the turbomachine. Another objective is to minimize the overall size of the fluid transfer bearing.

[0011] To this end, the invention relates, according to a first aspect, to a pitch-changing mechanism for adjusting the angular position of at least one variable-pitch blade around a blade pivot axis, said pitch-changing mechanism comprising: a fixed frame relative to the pivot axis, a control cylinder comprising a fixed part integral with the frame and a movable part movable in translation along a longitudinal axis relative to the fixed part between a retracted position and a deployed position, a linkage system connecting the movable part to the variable-pitch blade so as to convert the translation of the movable part along the longitudinal axis into a rotation of the variable-pitch blade around the pivot axis, and a fluid transfer bearing for supplying the control cylinder with control fluid from a source relative to which the control cylinder is movable in rotation around the longitudinal axis, in which the control cylinder extends at least partially around the fluid transfer bearing.

[0012] According to particular embodiments of the invention, the pitch change mechanism also has one or more of the following characteristics, taken individually or in any technically possible combination(s): the control cylinder is coaxial with the fluid transfer bearing; the control cylinder extends around more than half, advantageously around more than three-quarters, of the fluid transfer bearing;the pitch change mechanism includes a pitch locking device suitable for blocking the translation of the moving part relative to the fixed part in at least one direction, said pitch locking device comprising: ∘ a locking member, movable in translation relative to the frame along the longitudinal axis between an operating position and a locking position, ∘ a return device urging the locking member towards its locking position, and ∘ a holding device to maintain the locking member in its operating position under normal operating conditions, the holding device comprising a counterbalancing cylinder having a counterbalancing chamber supplied with control fluid to counterbalance the urging of the return device, the fluid transfer bearing being configured to supply the counterbalancing cylinder with control fluid from the source;The fluid transfer bearing comprises a stator and a rotor movable jointly with the control cylinder around the longitudinal axis relative to the stator, the rotor extending around the stator; the fluid transfer bearing comprises a plurality of circuits independent of each other, at least one of said circuits comprising: ∘ an axial conduit formed in the stator, ∘ at least one radial orifice formed in the stator and connecting the axial conduit to the periphery of the stator, ∘ a circumferential groove formed between the rotor and the stator and into which the radial orifice or orifices open, and ∘ at least one radial conduit, formed in the rotor, extending radially from the groove to a feed channel formed in the frame or between the frame and the fluid transfer bearing; the axial conduits of the different circuits are coaxial;The control cylinder comprises a first and a second fluidic chamber, each containing control fluid to control the movement of the moving part relative to the fixed part, and the fluid transfer bearing comprises a first circuit fluidically connected to the first fluidic chamber for supplying said first fluidic chamber with control fluid provided by the source, and a second circuit fluidly connected to the second fluidic chamber for supplying said second fluidic chamber with control fluid provided by the source;

[0013] The invention also relates, according to a second aspect, to a blower rotor for a turbomachine comprising a hub and a plurality of variable pitch blades each pivotable relative to the hub around its own pivot axis, the rotor further comprising a pitch change mechanism according to the first aspect to adjust an angular position of each of the variable pitch blades around its respective pivot axis.

[0014] According to particular embodiments of the invention, the blower rotor also has one or more of the following characteristics, taken individually or in any technically possible combination(s): the blower rotor includes a guide bearing for guiding rotation about the longitudinal axis of said blower rotor relative to a turbomachine nacelle, said guide bearing having an internal diameter greater than an external diameter of the fluid transfer bearing; and the longitudinal axis constitutes an axis of rotation of the rotor.

[0015] The invention also relates, according to a third aspect, to a turbomachine comprising a blower rotor according to the second aspect.

[0016] According to a particular embodiment of the invention, the turbomachine also has the following characteristic: The longitudinal axis constitutes an elongation axis of the turbomachine.

[0017] The invention also relates, according to a fourth aspect, to an aircraft comprising at least one turbomachine according to the third aspect.

[0018] Finally, the invention relates, according to a fifth aspect, to a method for changing the pitch of the blades of a turbomachine blower rotor, each pivotable relative to a hub of the blower rotor around its own pivot axis, said method comprising adjusting an angular position of each of said blades around its respective pivot axis by means of a pitch changing mechanism according to the first aspect.

[0019] According to a particular embodiment of the invention, the process also has the following characteristic: The process includes an additional step of locking the orientation of the blades by means of the pitch locking device. BREVE DESCRIPTION DES FIGURES

[0020] Other features and advantages of the invention will become apparent from the following description, given solely by way of example and with reference to the accompanying drawings, in which: there Figure 1 is a top view of an aircraft according to an exemplary embodiment of the invention, the Figure 2 is a simplified partial longitudinal cross-sectional view of a turbomachine from the aircraft of the Figure 1 , there Figure 3 is a simplified longitudinal cross-sectional view of part of a pitch-change mechanism of the turbomachine of the Figure 2 According to a first embodiment, the step change mechanism being in a first configuration, the Figure 4 is a view similar to that of the Figure 3 , the step change mechanism being in a second configuration, the Figure 5 is a view similar to that of the Figure 3 of a first variant of the step change mechanism of the Figure 3 , there Figure 6 is a view similar to that of the Figure 3 of a second variant of the step change mechanism of the Figure 3 , there Figure 7 is a view similar to that of the Figure 3 of a third variant of the step change mechanism of the Figure 3 , there Figure 8 is a simplified view along a radial axis of a rotating arm for a variable-pitch turbine blade of the turbomachine. Figure 2 , there Figure 9 is a perspective and partial cross-sectional view of a satellite roller screw of the pitch change mechanism of the Figure 3 , there Figure 10 is a detailed view of a fluid transfer bearing of the pitch change mechanism of the Figure 3 , there Figure 11 is a simplified longitudinal cross-sectional view of part of a pitch-change mechanism of the turbomachine of the Figure 2 according to a second embodiment, and the Figure 12 is a detailed view of a fluid transfer bearing of the pitch change mechanism of the Figure 11 DESCRIPTION DETAILLEE D'UN EXEMPLE DE REALISATION

[0021] Aircraft 10 shown on the Figure 1 includes 12 turbomachines to propel it.

[0022] In the example shown, aircraft 10 is an airplane. It conventionally comprises a fuselage 14, a tail assembly 16, and two wings 18. The turbomachines 12 are two in number and are each housed under a respective wing 18. Alternatively (not shown), the turbomachines 12 are arranged along the fuselage 14, for example, near the tail assembly 16. In yet another alternative (also not shown), aircraft 10 comprises a single turbomachine 12 or at least three turbomachines 12.

[0023] One of the 12 turbomachines is shown on the Figure 2 .

[0024] As can be seen in this Figure, the turbomachine 12 is elongated along a longitudinal axis X. It typically exhibits angular symmetry around said longitudinal axis X, that is to say, there is at least one angle for which the turbomachine is invariant under rotation around the longitudinal axis X.

[0025] Here and in the following, the terms "interior" and "exterior", "internal" and "external", as well as their variations, are understood in reference to the X axis, an element described as "interior" or "internal" being oriented towards the X axis while an "exterior" or "external" element is oriented in the opposite direction to the X axis.

[0026] The turbomachine 12 includes, in a conventional manner, a nacelle 20, an internal channel 22 for circulating an airflow through the nacelle 20, a combustion chamber 24 housed in the channel 22, a powerhead 26 and a gas exhaust nozzle 28.

[0027] In the following, the terms "upstream" and "downstream" are understood to refer to the direction of flow of an airflow through vein 22.

[0028] The engine body 26 comprises a compressor 30, a turbine 32, and a drive shaft 34 coupling the turbine 32 to the compressor 30 for driving the compressor 30 by the turbine 32. The compressor 30 is located upstream of the combustion chamber 24 and supplies the combustion chamber 24 with compressed air. The turbine 32 is located downstream of the combustion chamber 24 and receives the exhaust gases exiting the combustion chamber 24.

[0029] The transmission shaft 34 has the longitudinal axis X as its axis of rotation.

[0030] The transmission shaft 34 is guided in rotation relative to the nacelle 20 by means of bearings (not shown).

[0031] In the example shown, the turbomachine 12 is a multi-body turbomachine, in particular a double-body turbomachine, comprising a low-pressure body 40 in addition to the engine body 26. The engine body 26 then constitutes a high-pressure body, the compressor 30 being a high-pressure compressor, the turbine 32 being a high-pressure turbine and the drive shaft 34 being a high-pressure shaft.

[0032] The low pressure body 40 includes 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.

[0033] The low-pressure compressor 42 is located upstream of the high-pressure compressor 30 and supplies the latter with compressed air. The low-pressure turbine 44 is located downstream of the high-pressure turbine 32 and receives the exhaust gases exiting the latter.

[0034] The low-pressure shaft 46 is guided in rotation relative to the nacelle 20 by means of bearings (not shown).

[0035] The low-pressure shaft 46 is coaxial with the high-pressure shaft 34. It therefore also has the longitudinal axis X as its axis of rotation. In particular, the low-pressure shaft 46 extends inside the high-pressure shaft 34.

[0036] The turbomachine 12 also includes a blower 50 to drive the airflow into an external circulation duct 52 surrounding the nacelle 20. Thus, a primary airflow A (hot), consisting of the portion of the airflow driven into the internal circulation duct 22, and a secondary airflow B (cold), consisting of the portion of the airflow driven into the external circulation duct 52, are distinguished.

[0037] The blower 50 includes a blower rotor 54. This blower rotor 54 is rotatably mounted relative to the nacelle 20 about the longitudinal axis X via a guide bearing 53. It includes a hub 55 ( Figure 3 ) provided with blower blades 56 extending substantially radially outwards from the hub 55. These blades 56, when set in rotation, drive the airflow into the external circulation vein 52.

[0038] As seen on the Figure 8 , 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.

[0039] Back to the Figure 2 The blower rotor 54 is driven in rotation by the low-pressure turbine 44, via the low-pressure shaft 46. Preferably, this drive is achieved through a reduction gear (not shown) allowing the blower rotor 54 to rotate at a speed lower than that of the low-pressure shaft 46. Alternatively (not shown), this drive is direct, i.e., the blower rotor 54 is fixed in rotation to the low-pressure shaft 46.

[0040] In the example shown, the blower 50 also includes a blower stator 58 comprising fixed blades 59 arranged at the periphery of the nacelle 20, in the external circulation vein 52, in a plane orthogonal to the longitudinal axis X. This blower stator 58 is arranged here downstream of the blower rotor 54. In an alternative (not shown), the blower 50 includes, instead of the blower stator 58, a counter-rotating blower rotor.

[0041] Advantageously, the fan 50 is, as shown, unshod, meaning that the external circulation duct 52 has no peripheral delimitation. The turbomachine 12 then consists, as shown, of a turbojet with an unshod fan or, alternatively, of a turboprop. Alternatively (not shown), the external circulation duct 52 is defined between the nacelle 20 and a fan casing surrounding the fan 50; the turbomachine 12 then typically consists of a turbojet with a high bypass ratio, the bypass ratio being defined as the ratio of the secondary flow rate B (cold) to the primary flow rate A (hot).

[0042] In the example shown, the turbomachine 12 is of the "puller" type, meaning that the fan 50 is positioned upstream of the internal circulation duct 22 and also draws the airflow into it. Alternatively (not shown), the turbomachine is of the "pusher" type, meaning that the fan 50 is located around the downstream half of the nacelle 20.

[0043] The blades 56 of the blower rotor 54 have variable pitch, meaning that each blade 56 is mounted to pivot relative to the hub 55 around its own pivot axis P. This pivot axis P extends along the direction of elongation of the blade 56. It is orthogonal to the longitudinal axis X.

[0044] Each blade 56 is specifically capable of pivoting about the axis P relative to the hub 55 between a so-called "flag" position, in which the chord C of the blade 56 is substantially parallel to the longitudinal axis X, and a so-called "sail" position, in which the chord C of the blade 56 is substantially orthogonal to the longitudinal axis X. Preferably, each blade 56 is also capable of pivoting beyond the sail position, to a so-called "reverse" position, in which the chord C of the blade 56 forms an angle strictly greater than 90°, for example, substantially equal to 95°, with the longitudinal axis X. Since the blades 56 are most often twisted, the chord C taken as a reference for measuring the pitch angle is, by convention, constituted by the chord of the blade at 75% of the radius of the fan rotor 54.

[0045] To this end, each 56-bladed blade is interconnected, as can be seen on the Figure 3 , of an attachment piece 60 arranged at the base of the blade. This attachment piece 60 is mounted to rotate relative to the hub 55 around the pivot axis P. More precisely, the attachment piece 60 is mounted to rotate inside a housing 62 provided in the hub 55 by means of balls 64 or other rolling elements.

[0046] The fan 50 also includes a pitch change mechanism 70 to adjust the pitch angle of each blade 56 around its pivot axis P so as to adapt the performance of the turbomachine 12 to the different phases of flight.

[0047] A first embodiment of the pitch change mechanism 70 will now be described, with reference to the Figures 3 à 9 .

[0048] With reference to the Figure 3 , the pitch change mechanism 70 comprises, in this first embodiment, a frame 72, a control cylinder 74, a control system 76 for the cylinder 74 and a linkage system 78.

[0049] The frame 72 is integral with the hub 55 and is typically made up of a part of the hub 55. It is thus fixed relative to the pivot axes P.

[0050] The frame 72 includes a base 80. This base 80 is centered on the longitudinal axis X. Here, it is crossed by the pivot axes P.

[0051] In the example shown, the base 80 defines a housing 82 open to the downstream side. This housing 82 is in particular cylindrical, typically a cylindrical of revolution, and centered on the X axis.

[0052] Back to the Figure 3 The base 80 also defines a cavity 86 opening into an upstream face 88 of the base 80 through an orifice 90 which is here centered on the X axis. This cavity 86 is in particular cylindrical, typically cylindrical of revolution, and centered on the X axis. It is interposed between the upstream face 88 and the housing 82.

[0053] The base 80 has a stop 92 oriented upstream. This stop 92 is formed here by a part of the upstream face 88. It extends substantially radially and is in particular arranged around the opening 90.

[0054] In the example shown, the frame 72 also includes a cylinder 94 projecting upstream from the base 80. This cylinder 94 is centered on the X axis and open at its upstream end 95. It extends around the stop 92. It is typically cylindrical of revolution.

[0055] Here, the frame 72 still includes a peripheral cylinder 96, coaxial with the cylinder 94 and surrounding the latter, projecting upstream from the base 80. This cylinder 96 is open at its upstream end 97. It is typically cylindrical of revolution.

[0056] The base 80 and the peripheral cylinder 96 together define an external peripheral surface 88 of the frame 72. This external peripheral surface 88 is substantially cylindrical and centered on the X axis. It is oriented radially outwards.

[0057] Alternatively, as shown on the Figure 5 , frame 72 does not include cylinder 94.

[0058] Alternatively, as shown on the Figure 6 The frame 72 does not include the peripheral cylinder 96. The external peripheral surface 88 is then delimited by the base 80 and the cylinder 94.

[0059] Back to the Figure 3 The control cylinder 74 comprises a fixed part 100, integral with the frame 72, and a movable part 102 that moves in translation along the longitudinal axis X relative to the fixed part 100 between a retracted position, shown on the Figure 3 , and a deployed position represented on the Figure 4 Optionally, the movable part 102 is also movable in rotation around the longitudinal axis X over a restricted angle, for example on the order of 5°.

[0060] The control cylinder 74 is also substantially centered on the longitudinal axis X. The control cylinder 74 therefore has the longitudinal axis X as its axis.

[0061] The control cylinder 74 includes in particular a continuous cylinder 104, forming one part of the fixed part 100 and the moving part 102 and a piston 106 forming the other part of the fixed part 100 and the moving part 102. Here, the cylinder 104 forms the moving part 102 and the piston 106 forms the fixed part 100.

[0062] Thus, in the example shown, the cylinder 104 extends around the external peripheral surface 88 of the frame 72, coaxially with the latter, and the piston 106 is made up of a collar 108 attached to the frame 72 extending radially outwards from the external peripheral surface 88 to the cylinder 104.

[0063] The cylinder 104 defines an internal cavity 110. The piston 106 divides said internal cavity 110 into two contiguous fluidic chambers 112, 114. Each contains a control fluid, typically an oil, to control the movement of the moving part 102 relative to the fixed part 100. This control fluid is at a first pressure in the first fluidic chamber 112 and at a second pressure in the second fluidic chamber 114. The first and second fluidic chambers 112, 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 extended 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.

[0064] Here, each of the fluidic chambers 112, 114 is delimited internally by the external peripheral surface 88 of the frame 72 and externally by the cylinder 104. The first fluidic chamber 112 is also delimited at its downstream end by the piston 106 and the second fluidic chamber 114 is delimited at its upstream end by the piston 106.

[0065] The control cylinder 74 is therefore particularly compact, which allows it to be made lighter.

[0066] In the example shown on the Figure 3 The moving part 102 also includes an upstream guide ring 116 and a downstream guide ring 118, each integral with the cylinder 104 and extending radially inwards from the cylinder 104 to the external peripheral face 88 of the frame 72. The upstream guide ring 116 is located upstream of the piston 106 and defines an upstream end of the first fluidic chamber 112. The downstream guide ring 118 is located downstream of the piston 106 and defines a downstream end of the second fluidic chamber 114.

[0067] In the example shown on the Figure 3 Each of the upstream and downstream guide rings 116, 118 constitutes a sealing ring and longitudinally closes the first fluidic chamber 112, respectively the second fluidic chamber 114. The fluidic chambers 112, 114 are thus closed at each of the longitudinal ends of the control cylinder 74

[0068] Alternatively, as shown on the Figure 7 Only the downstream guide ring 118 acts as a sealing ring. The upstream guide ring 118 has holes 119 allowing the control fluid to flow through it.

[0069] Alternatively, as shown on the Figure 5 , the moving part 102 does not include an upstream guide ring 118.

[0070] Back to the Figure 3 The pilot system 76 includes a pressure generator 130 for raising the control fluid to a third pressure higher than the first and second pressures, a pressure control unit 132 for adjusting the control fluid pressure in the first and second fluidic chambers 112, 114 by means of the third pressure, and a return line 136 for evacuating the depressurized control fluid. The pilot system 76 also includes a main reservoir 133, a backup circuit 134, and a control module 135.

[0071] The pressure generator 130 includes, for example, a pump capable of pumping the fluid to bring it to the third pressure, for example 100 bar. A main pressure relief valve 139A allows a portion of the control fluid to be discharged to the return line 136 when the pressure of the control fluid downstream of the pressure generator 130 exceeds the third pressure.

[0072] The pressure control unit 132 is supplied with control fluid at the third pressure by the pressure generator 130. It is fluidically connected to the first fluid chamber 112 and the second fluid chamber 114. It is capable of distributing the control fluid between the first fluid chamber 112 and the second fluid chamber 114 in order to adjust the fluid pressure inside each of these chambers 112 and 114, and thus adjust the position of the piston 110 between its retracted and extended positions. It is also capable of evacuating control fluid from the first and second fluid chambers 112 and 114 into the return line 136.

[0073] The main tank 133 is configured to collect depressurized control fluid from the return line 136. It supplies the pressure generator 130.

[0074] The backup circuit 134 is capable of supplying the first fluidic chamber 112 with control fluid so as to move the piston 110 to its deployed position in the event of failure of the pressure generator 130. For this purpose, the backup circuit 134 includes an auxiliary reservoir 137 and an auxiliary pump 138. In the example shown, it also includes an auxiliary pressure relief valve 139B.

[0075] The auxiliary tank 137 is configured to collect depressurized control fluid from the return line 136. It supplies the auxiliary pump 138. In the example shown, it also supplies the main tank 133, the depressurized control fluid from the return line 136 passing through the auxiliary tank 137 before reaching the main tank 133.

[0076] The auxiliary pump 138 is capable of pumping the control fluid into the auxiliary reservoir 137 to bring it to the third pressure. It is fluidically connected to the pressure control unit 132 so as to supply it with control fluid at the third pressure, the pressure control unit 132 being configured to redirect all of the control fluid from the auxiliary pump 138 to the first fluidic chamber 112.

[0077] The pressure relief valve 139B is suitable for venting part 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.

[0078] The control module 135 is configured to receive a timing instruction (not shown) and derive a control signal transmitted to the pressure control unit 132. In particular, the control module 135 is configured to transmit to the pressure control unit 132 a control signal intended to increase the fluid pressure in the first chamber 112 when the timing instruction aims to increase the pitch of the blades 56, and to transmit to the pressure control unit 132 a control signal intended to increase the fluid pressure in the second chamber 114 when the timing instruction aims to reduce the pitch of the blades 56.

[0079] The control module 135 is also configured to transmit to the backup circuit 134, more specifically to its auxiliary pump 138, a start instruction in the event of failure of the pressure generator 130.

[0080] The piloting system 76 is fixed in the frame attached to the nacelle 20. Thus, the control cylinder 74 is mobile in rotation around the longitudinal axis X relative to said piloting system 76.

[0081] The linkage system 78 connects the moving part 102 to each blade 56 so as to convert the translation of the moving part 102 along the longitudinal axis X and, where applicable, the rotation of the moving part 102 about the longitudinal axis X into a rotation of each blade 56 about its pivot axis P. In particular, the linkage system 78 connects the moving part 102 to each blade 56 so as to convert: the translation of the moving part 102 along the longitudinal axis X in a first direction in a rotation of the variable pitch blade 56 around the pivot axis P towards the sail position, and the translation of the moving part 102 along the longitudinal axis X in a second direction opposite to the first direction in a rotation of the variable pitch blade 56 around the pivot axis P towards the flag position.

[0082] For this purpose, the linking system 78 includes a synchronizing ring 140 attached to the moving part 102 and, for each of the blades 56, a mechanism 142 for linking the blade 56 to the synchronizing ring 140.

[0083] The synchronizing ring 140 extends in a radial plane around the moving part 102. It is in particular fixed to an upstream end 143 of the moving part 102.

[0084] Each linkage mechanism 142 comprises a first joint 144 attached to the moving part 102, a second joint 146 attached to the blade 56, away from the pivot axis P of said blade 56, and a linking member 148 connecting the first joint 144 to the second joint 146.

[0085] The first joint 144 is carried by the synchronizing ring 140. Here it is made up of a ball joint.

[0086] The second joint 146 is also made up of a ball joint. It is eccentric relative to the pivot axis P.

[0087] The connecting 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 connecting member 148 is rigid and of adjustable length, that is to say that the distance between the first and second ends 150, 152 can be modified, which allows its length to be precisely adjusted at rest so as to allow the pitch angle of each blade 56 to be controlled by the pitch change mechanism 70.

[0088] The connecting element 148 is here constituted by a connecting rod 153.

[0089] In the example shown, each linkage mechanism 142 also includes a crank 154 connecting the attachment piece 60 to the second articulation 146. This crank 154 is rigid and integral with the attachment piece 60. It extends at least in part in a direction orthogonal to the pivot axis P. It forms an arm for rotating the blade 56.

[0090] In the example shown on the Figure 3 The first direction is from upstream to downstream; that is, the movement of the movable part 102 towards the stop 92 (in other words, towards its retracted position) causes each blade 56 to rotate towards its sail position. The second direction is from downstream to upstream; that is, the movement of the movable part 102 away from the stop 92 (in other words, towards its deployed position) causes each blade 56 to rotate towards its flag position. Furthermore, the first joint 144 is located upstream of the second joint 146.

[0091] For this purpose, the second joint 146 is, as can be seen on the Figure 8 , placed opposite the trailing edge 57B relative to a plane Q orthogonal to the chord C and containing the pivot axis P.

[0092] This particular arrangement allows, when the pitch change mechanism 70 is immobilized, for the natural forces exerted by the blade 56 towards its sail position to cause the connecting member 148 to work in tension rather than compression. The risk of buckling of the connecting member 148 is therefore very low, making it possible to use a relatively weak connecting member 148 and thus lighten the pitch change mechanism 70.

[0093] The pitch change mechanism 70 also includes a pitch locking device 160 designed to block the translation of the moving part 102 of the control cylinder 74 in the first direction, i.e. here towards its retracted position.

[0094] This locking device 160 includes a support member 162 and a screw-nut system 164.

[0095] The support member 162 is movable in translation relative to the frame 72 along the longitudinal axis X between an operating position, represented on the Figures 3 à 7 , and a locking position (not shown). The support member 162 moves from its operating position to its locking position by translation in the first direction, that is, in the example shown on the Figure 3 , by translation from upstream to downstream. In other words, the operating position of the support member 162 is located upstream of its locking position.

[0096] The support member 162 comprises a body 166 elongated along the longitudinal axis X and centered on the longitudinal axis X. Said body 166 has a first longitudinal end 168, in particular a downstream longitudinal end, engaged through the orifice 90 of the frame 72, and a second free longitudinal end 170. The body 166 is solid here.

[0097] The first longitudinal end 168 and the orifice 90 of the frame 72 together form a guide system 172 guiding the support member 162 relative to the frame 72. This guide system 172 is here arranged on a downstream side of the screw-nut system 164.

[0098] The support member 162 also includes a skirt 174 integral with the body 166 and arranged around the second longitudinal end 170 of the body 166.

[0099] The screw-nut system 164 includes a screw 176 and a nut 178.

[0100] The screw 176 extends around the body 166 of the support member 162 and is coaxial with said body 166. It is fixed in translation to the support member 162 and mounted to rotate freely 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. This bearing 180 is interposed here between the skirt 174 of the support member 162 and an end portion 182 of the screw 176, housed between the body 166 and the skirt 174.

[0101] The screw 176 has a second longitudinal end portion 184 opposite the end portion 182. This second longitudinal end portion 184 defines a radial stop surface 186. This stop surface 186 is at a distance from the frame 72 when the support member 162 is in the operating position and bears against the stop 92 of the frame 72 when the support member 162 is in the locking position.

[0102] Here, the second longitudinal end portion 184 flares out from a threaded body 190 of the screw 176 to the stop surface 186. Thus, the contact area between the stop surface 186 and the stop 92 is increased, which increases the friction forces between the stop surface 186 and the stop 92 and allows better transmission of braking and locking forces.

[0103] The abutment surface 186 and the stop 92 are each smooth here. Alternatively (not shown), the abutment surface 186 and / or the stop 92 have asperities, so as to further increase the friction forces between the abutment surface 186 and the stop 92 and allow for even greater force transmission.

[0104] The abutment surface 186 extends particularly radially. It is oriented in the first direction, that is to say, in the example shown on the Figure 3 , downstream. Here, it is provided at a downstream end of screw 176.

[0105] The threaded body 190 extends from one end portion 182, 184 to the other. It has an external thread 192 on its circumference.

[0106] The threaded body 190 and the nut 178 are housed inside the cylinder 94 of the frame 72.

[0107] The nut 178 is fixed to the moving part 102 of the cylinder 74 and coaxial with the screw 176. It cooperates with the screw 176 so that a translation of the nut 178 along the longitudinal axis X relative to the screw 176 causes the screw 176 to rotate around the longitudinal axis X relative to the support member 162.

[0108] Nut 178 has an internal thread 194.

[0109] The screw-nut system 164 is in particular formed by a reversible satellite roller screw system 195. In a conventional manner, this satellite roller screw system 195 comprises, in addition to the screw 176 and the nut 178, a plurality of rollers 196 interposed between the screw 176 and the nut 178, each roller 196 being elongated parallel to the longitudinal axis X.

[0110] As seen on the Figure 9 , each roller 196 has a thread 198 in contact with the external thread 192 of the screw 176 and the internal tapping 194 of the nut 176. It further includes external teeth 199 located at its ends and extended by smooth trunnions 200.

[0111] The satellite roller screw system 195 also features, in a conventional manner, a guide and retaining device 202 for the rollers 196. This guide and retaining device 202 includes roller carriers 204 (also called spacer rings) which are mounted coaxially to the screw 176, between it and the nut 178, with notches 206 to accommodate the trunnions 200 of the rollers 196. It also includes a synchronizing gear 210 in which the external gears 198 located at the respective ends of the rollers 196 mesh.This external gearing 198 in the synchronizing gear 210 forms a planetary train whose role is to ensure synchronization of the satellite, also called planetary or epicycloidal, movement of the rollers 196, thus smoothing the movement of the rollers 196 by helping them to roll easily, with the least possible slippage, on the thread 192 of the screw 176 and the tapping 194 of the nut 178.

[0112] In the example shown, the satellite roller screw system 195 is of the standard type, the rollers 196 being fixed in translation to the nut 178. The synchronizing teeth 210 are made up of the internal teeth of crowns 208 fixed to the nut 178 and mounted respectively at each longitudinal end of the nut 178, the latter having a longitudinal extension substantially equal to that of the threaded portion of the rollers 196 and less than that of the threaded body 190 of the screw 176.

[0113] In an alternative (not shown), the satellite roller screw system 195 is of the inverted type, the rollers 196 being fixed in translation to the screw 176. The synchronizing teeth 210 are then made up of two external teeth of the screw 176 at each longitudinal end of the threaded body 190, the latter having a longitudinal extension substantially equal to that of the threaded portion of the rollers 196 and less than that of the nut 178.

[0114] Alternatively, the satellite roller screw system 195 consists of a recirculating satellite roller screw system such as, for example, that described in document EP 275 504 A2, or of a roller screw system with bearing such as, for example, that described in document EP 168 942 A1 or that described in document EP 671 070 A1.

[0115] This feature ensures efficient transmission of forces from nut 178 to screw 176 via the screw-nut system 164, while maintaining a small pitch in the helical connection of the screw-nut system 164. Specifically, if screw 176 becomes blocked from rotating, it allows nut 178 to be immobilized relative to screw 176 even without a separate locking nut. This eliminates the need for a separate locking nut, simplifying manufacturing and reducing the cost of the mechanism, while simultaneously increasing its reliability and minimizing its weight.

[0116] As an alternative (not shown), the screw-nut system 164 consists of a screw-nut system similar to that described in EP 1 832 509.

[0117] Back to the Figure 3 , the pitch locking device 160 is, in the example shown in this Figure, outside the fluidic chambers 112, 114 of the control cylinder 74. This arrangement allows the pitch locking device 160 and the cylinder 74 to be assembled separately from each other to the frame 72, which facilitates the assembly of the pitch changing mechanism 70 and thus reduces costs.

[0118] As seen on the Figure 3 A portion of the pitch locking device 160 extends longitudinally away from the cylinder 74. In other words, there is a radial plane beyond which a portion of the pitch locking device 160 extends without the cylinder 74 extending beyond said radial plane. In particular, this portion of the pitch locking device 160 extends upstream of the cylinder 74.

[0119] To enable this arrangement, the pitch locking device 160 includes a ferrule 193 connecting the nut 178 to the moving part 102 of the cylinder 74. This ferrule 193 here projects longitudinally upstream from the control cylinder 74. It is in particular frustoconical, its diameter decreasing from its downstream end 193A, attached to the cylinder 74, to its upstream end 193B, attached to the nut 178.

[0120] In the example shown on the Figure 3 The pitch locking device 160 is also longitudinally cantilevered relative to the frame 72. In other words, the entire portion of the frame 72 supporting the locking device 160 is located longitudinally on the same side, here downstream of the locking device 160; the locking device 160 is not longitudinally framed by the portion of the frame 72 supporting it. This arrangement eliminates the need for a support located upstream of the locking device 160, thus facilitating access to the pitch changing mechanism 70 and, more specifically, to the linkage system 78.

[0121] Thus, the control cylinder 74 is, in the example shown on the Figure 3 , arranged longitudinally on the same side of the nut 178, here the downstream side, as the guide device 172 and the stop 92.

[0122] To ensure good support of the locking device 160 despite this overhang, the pitch changing mechanism 70 includes a guide device 220 for the nut 178 relative to the frame 72. This guide device 220 has an internal cylinder 222 attached to the nut 178 and an external cylinder 224 attached to the frame 72, the internal cylinder 222 cooperating with the external cylinder 224 so as to slide longitudinally inside the latter.

[0123] The nut 178 is in particular mounted on an internal face 226 of the internal cylinder 222. The internal cylinder 222 has an upstream end 228 to which is fixed the upstream end 193B of the ferrule 193.

[0124] The external cylinder 224 is here constituted by the cylinder 94 of the frame 72.

[0125] The pitch locking device 160 requires lubrication. For this purpose, the locking device 160 includes a housing 230 which at least partially encloses a circulation chamber for a lubricating fluid in the pitch locking device 160. This housing 230 is integral with the nut 178 and surrounds the nut 178, the screw 176, and the support member 162.

[0126] In the examples of Figures 3 , 4 And 6The housing 230 comprises the inner cylinder 222 and a plug 232 closing one end of the inner cylinder 222 opposite the frame 72, here the upstream end 228. The inner cylinder 222 has a seal 234 at its periphery in contact with an inner face 236 of the outer cylinder 224. Thus, the outer cylinder 224 and the housing 230 together define a chamber 238 for the circulation of a lubricating fluid for the locking device 160. This chamber 238 is fluidically isolated from the fluidic chambers 112, 114 of the cylinder 74 by the seal 234 and the upstream guide ring 116. The seal 234 and the guide ring 116 thus form seals for the pitch-changing mechanism 70, fluidly isolating the fluidic chambers 112, 114 of the cylinder from the pitch-locking device 160. 74.

[0127] Advantageously, the lubricating fluid for the locking device 160 is an oil. The pitch locking device 160 then includes an accumulator (not shown) that stores the lubricating fluid when the cylinder 74 is in the retracted position and transfers the lubricating fluid into the housing 238 when the cylinder 74 moves to its extended position. Alternatively, the lubricating fluid for the locking device 160 is grease applied to the screw 176 and the bearings of the housing 180.

[0128] In the example of the Figure 5 , where the external cylinder 224 and the upstream guide ring 116 are absent, as well as in the Figure 7 where the internal cylinder 222 and the upstream guide ring 116 are drilled, the housing 230 is formed by the ferrule 193 and by a plug 239 closing the upstream end 193B of the ferrule 193. The first fluidic chamber 112 is then in fluidic communication with the interior of the housing 230, the control fluid constituting the lubrication fluid of the locking device 160.

[0129] This variant eliminates the need for an accumulator. However, it requires a 130 pump with a higher flow rate than the variant of Figures 3 , 4 And 6 .

[0130] The locking device 160 also includes a return device 240 which forces the support member 162 towards its locking position and a holding device 242 to hold the support member 162 in its operating position when the pitch changing mechanism 70 is in normal operating conditions.

[0131] The return device 240 here consists of a compression spring compressed between the frame 72 and a shoulder 244 integral with the support member 162. It is in particular housed in the cavity 86, between the shoulder 244 and the orifice 90.

[0132] The holding device 242 includes a counterbalancing cylinder 250 comprising a counterbalancing piston 252 and a counterbalancing chamber 254.

[0133] The counterbalancing piston 252 is mounted to move in translation along the longitudinal axis X relative to the frame 72. In particular, it is coaxial with the support member 162. In the example shown, it is arranged in the longitudinal extension of the support member 162, between the support member 162 and the counterbalancing chamber 254.

[0134] The counterbalancing chamber 254 is delimited between the counterbalancing piston 252 and the frame 72. In particular, the counterbalancing chamber 254 is delimited between the counterbalancing piston 252 and a bottom 255 of the cavity 86 opposite the orifice 90; the guide system 172, the return device 240 and the retaining device 242 are thus all arranged longitudinally on the same side, here the downstream side, of the screw-nut system 164 and therefore in particular of the nut 178.

[0135] The counterbalancing chamber 254 is fluidically connected to the pressure generator 130 by a fluid connection circuit 256 so as to be supplied with control fluid at the third pressure. It is intended to counterbalance the stress on the return device 240 when this supply is active.

[0136] To this end, the counterbalancing cylinder 250 is arranged so that the pressure exerted on the piston 252 by the fluid contained in the chamber 254 is oriented in a direction opposite to that of the stress on the return device 240: in the example shown, the counterbalancing piston 252 is interposed between the chamber 254 and the shoulder 244 and the shoulder 244 is interposed between the piston 252 and the return device 240. Furthermore, the counterbalancing piston 252 and the counterbalancing chamber 254 are dimensioned so that, when the chamber 254 is supplied with control fluid at the third pressure, the force exerted by the control fluid on the piston 252 is greater than the stress on the return device 240.

[0137] Thus, when the supply of control fluid to chamber 254 at the third pressure is active, the activation of the return device 240 is cancelled and the support member 162 is maintained in the operating position.

[0138] In the example shown, the pressure control unit 132 is fluidly interposed between the pressure generator 130 and the fluid connection circuit 256. It has a first configuration, in which it isolates the fluid connection circuit 256 from the return line 136, and a second configuration, in which it fluidly connects the fluid connection circuit 256 to the return line 136.

[0139] The pressure control unit 132 is configured to normally be in its first configuration and to switch to its second configuration upon receipt of a command instruction transmitted by the control module 135.

[0140] Still referring to the Figure 3 , the pitch change mechanism 70 finally includes a fluid transfer bearing 257 intended for supplying the control cylinder 74 with control fluid from the pilot system 76.

[0141] For this purpose, the fluid transfer bearing 257 is configured to transfer the control fluid from the fixed reference mark attached to the nacelle 20 to the rotating reference mark attached to the blower rotor 54 and more particularly to the first and second chambers 112, 114 of the cylinder 74.

[0142] For this purpose, the fluid transfer bearing 257 includes, with reference to the Figure 10 , a stator 258 fixed relative to the nacelle 20 and a rotor 259 movable jointly with the blower rotor 54 (and therefore with the control cylinder 74) around the longitudinal axis X relative to the stator 258. It also includes a first circuit 260 fluidically connected to the first fluidic chamber 112 for supplying said first fluidic chamber 112 with control fluid provided by the pilot system 76 and a second circuit 261 fluidically connected to the second fluidic chamber 114 for supplying said second fluidic chamber 114 with control fluid provided by the pilot system 76.

[0143] The stator 258 is cylindrical in shape, specifically a solid cylinder, coaxial with the longitudinal axis X. It is connected at its downstream end 262 to a structure 263 ( Figure 3 ) of gondola 20.

[0144] The rotor 259 is in the form of a cylinder of revolution coaxial with the longitudinal axis X. It extends around the stator 258. Its periphery is in contact with the frame 72. It is guided in rotation around the axis X relative to the stator 258 by means of bearings 264 interposed between the rotor 259 and the stator 258.

[0145] The fluid transfer bearing 257 is thus coaxial with the X axis. It is therefore also coaxial with the control cylinder 74.

[0146] The first circuit 260 includes a first axial conduit 265A formed in the stator 258, a plurality of first radial orifices 265B (only one of them being shown here) formed in the stator 258 and connecting the axial conduit 265A to the periphery of the stator 258, a first circumferential groove 265C formed between the rotor 259 and the stator 258 and into which each radial orifice 265B opens, and a plurality of first radial conduits 265D, formed in the rotor 259, extending radially from the groove 265C to a first feed channel 266 of the first fluidic chamber 112 formed in the frame 72.

[0147] The first axial conduit 265A has an axial extension parallel to the X-axis. In the example shown, it is specifically straight and coaxial with the X-axis. Alternatively (not shown), the first axial conduit 265A is curved and / or also has a radial extension in a direction orthogonal to the X-axis.

[0148] Furthermore, the first axial conduit 265A has, in the example shown, an annular radial section, that is to say, it is solid in its center.

[0149] Each first radial orifice 265B has a radial extension along a radial direction orthogonal to the X-axis. In the example shown, each first radial orifice 265B is, in particular, straight along a radial direction. Alternatively (not shown), at least one first radial orifice 265B is curved and / or also has an axial extension parallel to the X-axis.

[0150] The first circumferential groove 265C extends parallel to a radial plane orthogonal to the X axis.

[0151] Each first radial conduit 265D has a radial extension along a radial direction orthogonal to the X-axis. In the example shown, each first radial conduit 265D is, in particular, straight along a radial direction. Alternatively (not shown), at least one first radial conduit 265D is curved and also has an axial extension parallel to the X-axis and / or a circumferential extension along a direction orthogonal to both the X-axis and the radial direction.

[0152] The first supply channel 266 extends from an outlet of the first radial conduits 265D to an inlet of the first fluidic chamber 112. In the example shown, it is substantially straight and extends substantially parallel to the X axis.

[0153] The second circuit 261 includes a second axial conduit 267A formed in the stator 258, a plurality of second radial orifices 267B (only one of them being shown here) formed in the stator 258 and connecting the axial conduit 267A to the periphery of the stator 258, a second circumferential groove 267C formed between the rotor 259 and the stator 258 and into which each radial orifice 267B opens, and a plurality of second radial conduits 267D, formed in the rotor 259, extending radially from the groove 267C to a second feed channel 268 of the second fluidic chamber 114 formed in the frame 72.

[0154] The second axial conduit 267A has an axial extension parallel to the X-axis. Advantageously, it is coaxial with the first axial conduit 265A. In the example shown, it is, in particular, straight and coaxial with the X-axis. Alternatively (not shown), the second axial conduit 267A is curved and / or also has a radial extension in a direction orthogonal to the X-axis.

[0155] Furthermore, the second axial conduit 267A, in the example shown, has an annular radial cross-section, meaning it is solid in its center. Here, it extends around the first axial conduit 265A.

[0156] Each second radial orifice 267B has a radial extension along a radial direction orthogonal to the X-axis. In the example shown, each second radial orifice 267B is, in particular, straight along a radial direction. Alternatively (not shown), at least one second radial orifice 267B is curved and / or also has an axial extension parallel to the X-axis.

[0157] Each second radial orifice 267B is here arranged axially downstream of the first radial orifices 265B.

[0158] The second circumferential groove 267C extends parallel to a radial plane orthogonal to the X axis. Here it is arranged axially downstream of the first circumferential groove 265C.

[0159] Each second radial conduit 267D has a radial extension along a radial direction orthogonal to the X-axis. In the example shown, each second radial conduit 267D is, in particular, straight along a radial direction. Alternatively (not shown), at least one second radial conduit 267D is curved and also has an axial extension parallel to the X-axis and / or a circumferential extension along a direction orthogonal to both the X-axis and the radial direction.

[0160] Each second radial conduit 267D is here arranged axially downstream of the first radial conduits 265D.

[0161] The second supply channel 268 extends from an outlet of the second radial conduits 266D to an inlet of the second fluidic chamber 114. In the example shown, it is substantially straight and extends substantially parallel to the X axis.

[0162] The first and second circuits 260, 261 are independent circuits, that is to say they are not in fluidic communication with each other.

[0163] Here, the fluid transfer bearing 257 is also configured to supply the counterbalancing cylinder 250 with control fluid from the pilot system 76. For this purpose, the fluid transfer bearing 257 includes a third circuit 269 independent of the first and second circuits 260, 261.

[0164] The third circuit 261 includes a third axial conduit 270A formed in the stator 258, a plurality of third radial ports 270B (only one of them being shown here) formed in the stator 258 and connecting the axial conduit 270A to the periphery of the stator 258, a third circumferential groove 270C formed between the rotor 259 and the stator 258 and into which each radial port 270B opens, and a plurality of third radial conduits 270D, formed in the rotor 259, extending radially from the groove 270C to a third feed channel 271 for the counterbalancing cylinder 250, formed in the frame 72.

[0165] The third axial conduit 270A has an axial extension parallel to the X-axis. Advantageously, it is coaxial with the first and second axial conduits 265A and 267A. In the example shown, it is, in particular, straight and coaxial with the X-axis. Alternatively (not shown), the third axial conduit 270A is curved and / or also has a radial extension in a direction orthogonal to the X-axis.

[0166] Furthermore, the third axial conduit 270A has, in the example shown, a solid radial section. Here, it extends to the center of the first and second axial conduits 265A, 267A.

[0167] Each third radial orifice 270B has a radial extension along a radial direction orthogonal to the X-axis. In the example shown, each third radial orifice 270B is, in particular, straight along a radial direction. Alternatively (not shown), at least one third radial orifice 270B is curved and / or also has an axial extension parallel to the X-axis.

[0168] Each third radial orifice 270B is here arranged axially upstream of the first and second radial orifices 265B, 267B.

[0169] The third circumferential groove 270C extends parallel to a radial plane orthogonal to the X axis. Here it is arranged axially upstream of the first and second circumferential grooves 265C, 267C.

[0170] Each third radial duct 270D has a radial extension along a radial direction orthogonal to the X-axis. In the example shown, each third radial duct 270D is, in particular, straight along a radial direction. Alternatively (not shown), at least one third radial duct 270D is curved and also has an axial extension parallel to the X-axis and / or a circumferential extension along a direction orthogonal to both the X-axis and the radial direction.

[0171] Each third radial conduit 270D is here arranged axially upstream of the first and second radial orifices 265D, 267D.

[0172] The third feed channel 271 extends from an outlet of the third radial conduits 266D to an inlet of the counterbalancing chamber 254. In the example shown, it comprises a straight axial portion extending substantially parallel to the X-axis upstream from the outlet of the third radial conduits 266D to an end of said portion and a straight radial portion extending substantially orthogonally to the X-axis from the upstream end of the axial portion to the inlet of the counterbalancing chamber 254.

[0173] Back to the Figure 3 The guide bearing 257 has an external diameter smaller than the internal diameter of the guide bearing 53 of the blower rotor 54. It is located upstream of the reducer and is in particular housed in the housing 82 delimited by the base 80.

[0174] The guide bearing 257 is thus surrounded, at least in part, by the control cylinder 74. In particular, the control cylinder 74 extends along the X-axis around more than half, advantageously around more than three-quarters, of the fluid transfer bearing 257. To arrive at this measurement, the axial ends of the control cylinder 74 and the guide bearing 257 are taken into consideration, these being defined as follows: for the control cylinder 74, its axial ends are constituted by the stroke limits of the moving part 102; for the guide bearing 257, its axial ends are constituted by the limits beyond which the rotor 259 and the stator 258 no longer coexist (that is to say, starting from the center of the guide bearing, the first axial end of the rotor 259 or the stator 258 encountered delimits an axial end of the guide bearing 257).

[0175] A method for changing the pitch of the blades 56, implemented by the pitch changing mechanism 70 according to the first embodiment, will now be described.

[0176] In the first stage of this process, the control module 135 first receives a timing instruction aimed at increasing the pitch of the blades 56. The control module 135 then transmits to the pressure control unit 132 a control signal intended to increase the fluid pressure in the first chamber 112. As the fluid pressure in the first chamber 112 increases, the moving part 102 of the cylinder 74 moves in the second direction, towards its deployed position, which, via the linkage system 78, causes the blades 56 to pivot towards the large pitches (i.e. towards the flag position).

[0177] Once the moving part 102 has reached an equilibrium position, it stabilizes, the blades 56 maintaining a fixed orientation.

[0178] In a second step of the pitch change process, the control module 135 first receives a setting instruction aimed at reducing the pitch of the blades 56. The control module 135 then transmits to the pressure control unit 132 a control signal intended to increase the fluid pressure in the second chamber 114. As the fluid pressure in the second chamber 114 increases, the moving part 102 of the cylinder 74 moves in the first direction towards its retracted position, which, via the linkage system 78, causes the blades 56 to pivot towards the small pitch (i.e. towards the sail position).

[0179] Once the moving part 102 has reached an equilibrium position, it stabilizes, the blades 56 maintaining a fixed orientation.

[0180] Optionally, the pitch change process also includes, following the first or second step, a controlled locking step of the orientation of the blades 56.

[0181] During this step, the control module 135 transmits a step-lock command to the pressure control unit 132. Under the effect of this command, the pressure control unit 132 fluidly connects the fluid connection circuit 256 to the return line 136, resulting in a drop in fluid pressure in the counterbalancing chamber 254. The fluid pressure in said chamber 254 is then insufficient to counterbalance the load on the return device 240, which thus causes the support member 162 to move towards its locking position.

[0182] During this movement, the screw 176, while translating, rotates around the longitudinal axis X under the effect of the resistance imposed by the assembly of the nut 178 and the rollers 194 (which are held immobile in translation by the control cylinder 74) until its stop surface 186 comes to rest against the stop 92 of the frame 72, blocking the rotation of the screw 176 around the longitudinal axis X and its translation along the same axis X.

[0183] The blades 56 are thus locked in their orientation even in the event of loss of fluid pressure in the first chamber 112.

[0184] In the event of a pressure loss in the second chamber 114 only, the moving part 102 of the cylinder 74 is displaced in the second direction by the pressure difference between the two chambers 112 and 114, carrying with it the screw 176 and the support member 162, which returns to its operating position. The moving part 102 is therefore no longer immobilized and can continue to move in the second direction until the vanes 56 reach the flag position.

[0185] In the event of a malfunction of the pilot system 76, typically in the event of a failure of the pressure generator 130, the pitch change process includes an additional step of uncontrolled locking of the orientation of the blades 56.

[0186] During this step, a malfunction in the pilot system 76 causes a drop in fluid pressure in the counterbalancing chamber 254, typically because the pressure generator 130 is no longer able to bring the control fluid to the third pressure. The fluid pressure in said chamber 254 is then insufficient to counterbalance the load on the return device 240, which thus causes the support member 162 to move towards its locking position.

[0187] During this movement, the screw 176 takes with it the nut 178 and the rollers 194, which are no longer held immobile in translation due to the loss of supply to the control cylinder 74. The blades 56 therefore pivot slightly towards the small steps, until the stop surface 186 of the screw 176 comes to rest against the stop 92 of the frame 72, blocking the rotation of the screw 176 around the longitudinal axis X and its translation along the same axis X.

[0188] The pivoting of the blades 56 towards the small steps is then prevented by the locking device 160.

[0189] The uncontrolled locking step is followed by a blower 50 safety shutdown step. During this step, the backup circuit 134 is activated and supplies the first fluidic chamber 112 with control fluid to increase the fluid pressure in this chamber. Under the effect of this pressure increase, the moving part 102 moves in the second direction, carrying with it the screw 176 and the support member 162, which returns to its operating position. The moving part 102 is therefore no longer immobilized and can continue moving downstream until the blades 56 reach the flagging position.

[0190] It should be noted that these different steps can be implemented independently of each other.

[0191] A second embodiment of the pitch change mechanism 70 will now be described, with reference to the Figure 11 .

[0192] In this embodiment, the pitch change mechanism 70 includes a frame 272, a control cylinder 274, a control system 276 for the cylinder 274 and a linkage system 278.

[0193] The frame 272 is integral with the hub 55 and is typically made up of a part of the hub 55. It is thus fixed relative to the pivot axes P.

[0194] In the example shown, the building 272 comprises an upstream set 280 and a downstream set 282 spaced apart along the longitudinal axis X. Each of these sets 280, 282 is centered on the longitudinal axis X and extends from the longitudinal axis X to the dwelling 62, the upstream set 280 being located upstream of the dwelling 62 and the downstream set 282 being located downstream of the dwelling 62.

[0195] The upstream assembly 280 is in particular formed by an upstream flange 284 in the general shape of a dome housing in its center a blind cylinder 286. The blind cylinder 286 is closed at its upstream end 288 and open at its downstream end 289. It projects upstream relative to the flange 284.

[0196] The upstream assembly 280 has an orifice 290 opening downstream at its center. This orifice 290 is formed in the upstream end 288 of the blind cylinder 286. The upstream assembly 280 also has a stop 291 oriented downstream. This stop 291 is formed in the downstream face of the upstream end 288 of the blind cylinder 286. It extends substantially radially and is arranged around the orifice 290.

[0197] Here, the downstream assembly 282 includes a downstream flange 292 housing in its center two concentric cylinders 294, 296: a central cylinder 294, closed at its upstream end 298, and a peripheral cylinder 296 surrounding the central cylinder 294 and defining with the central cylinder 294 a peripheral cavity 300 closed at its downstream end 302. The central cylinder 294 defines a housing 304.

[0198] The control cylinder 274 comprises a fixed part 308, integral with the frame 72, and a movable part 309 that moves in translation along the longitudinal axis X relative to the fixed part 308 between a retracted position, shown on the Figure 11 , and a deployed position shown (not shown). Optionally, the movable part 309 is also movable in rotation around the longitudinal axis X over a restricted angle, for example on the order of 5°.

[0199] The control cylinder 274 includes in particular a piston 310 forming the moving part 309.

[0200] The control cylinder 274 also includes a first fluidic chamber 312 and a second fluidic chamber 314, each delimited between the control piston 310 and the frame 272. Said fluidic chambers 312, 314 each contain a control fluid, typically consisting of an oil, which is at a first pressure in the first fluidic chamber 312 and at a second pressure in the second fluidic chamber 314. The first and second fluidic chambers 312, 314 are arranged such that the relative increase of the first pressure (i.e., relative to the second pressure) causes the piston 310 to move towards its retracted position, and the relative increase of the second pressure (i.e., relative to the first pressure) causes the piston 310 to move towards its extended position.

[0201] In the example shown, the piston 310 comprises a downstream sealing and guiding ring 316, an upstream sealing and guiding ring 318, and a cylindrical body 320 extending from the downstream sealing and guiding ring 316 to the upstream sealing and guiding ring 318. The downstream sealing and guiding ring 316 is housed in the peripheral cavity 300 and extends from the central cylinder 294 to the peripheral cylinder 296, forming a seal with each of these cylinders 294 and 296. The upstream sealing and guiding ring 318 is housed in the blind cylinder 286 and forms a seal with the peripheral wall 322 of the blind cylinder 286. The first fluidic chamber 312 is thus delimited at its downstream end by the downstream sealing and guiding ring 316, and at its upstream end by the upstream end. 288 of the blind cylinder 286, and at its periphery by the body 320 of the piston 310 and by the peripheral wall 322 of the blind cylinder 286.The second fluidic chamber 314, for its part, is constituted by the portion of the peripheral cavity 300 included between the downstream sealing and guiding ring 316 and the downstream end 302 of said peripheral cavity 300.

[0202] The pilot system 276 includes a pressure generator 330 for raising the control fluid to a third pressure higher than the first and second pressures, a pressure control unit 332 for adjusting the control fluid pressure in the first and second fluidic chambers 312, 314 by means of the third pressure, and a return line 336 for evacuating the depressurized control fluid. The pilot system 276 also includes a main reservoir 333, a backup circuit 334, and a control module 335.

[0203] The pressure generator 330 includes, for example, a pump capable of pumping the fluid to the third pressure, for example 100 bar. A main pressure relief valve 339A allows a portion of the control fluid to be discharged to the return line 336 when the pressure of the control fluid downstream of the pressure generator 330 exceeds the third pressure.

[0204] The pressure control unit 332 is supplied with control fluid at the third pressure by the pressure generator 330. It is fluidically connected to the first fluid chamber 312 and the second fluid chamber 314. It is capable of distributing the control fluid between the first fluid chamber 312 and the second fluid chamber 314 in order to adjust the fluid pressure inside each of these chambers 312 and 314, and thus adjust the position of the piston 310 between its retracted and extended positions. It is also capable of returning control fluid from the first and second fluid chambers 312 and 314 to the return line 336.

[0205] The main tank 333 is configured to collect depressurized control fluid from the return line 336. It supplies the pressure generator 330.

[0206] The backup circuit 334 is capable of supplying the second fluidic chamber 314 with control fluid so as to move the piston 310 to its retracted position in the event of a failure of the pressure generator 330. For this purpose, the backup circuit 334 includes an auxiliary reservoir 337 and an auxiliary pump 338. In the example shown, it also includes an auxiliary pressure relief valve 339B.

[0207] The auxiliary tank 337 is configured to collect depressurized control fluid from the return line 336. It supplies the auxiliary pump 338. In the example shown, it also supplies the main tank 333, the depressurized control fluid from the return line 336 passing through the auxiliary tank 337 before reaching the main tank 333.

[0208] The auxiliary pump 338 is capable of pumping the control fluid into the auxiliary reservoir 337 to bring it to the third pressure. It is fluidically connected to the pressure control unit 332 so as to supply it with control fluid at the third pressure, the pressure control unit 332 being configured to redirect all of the control fluid from the auxiliary pump 338 to the second fluid chamber 314.

[0209] The pressure relief valve 339B is suitable for venting part of the control fluid to the return line 336 when the pressure of the control fluid downstream of the auxiliary pump 338 exceeds the third pressure.

[0210] The control module 335 is configured to receive a timing instruction (not shown) and derive a control signal transmitted to the pressure control unit 332. In particular, the control module 335 is configured to transmit to the pressure control unit 332 a control signal intended to increase the fluid pressure in the second chamber 314 when the timing instruction aims to increase the pitch of the blades 56, and to transmit to the pressure control unit 332 a control signal intended to increase the fluid pressure in the first chamber 312 when the timing instruction aims to reduce the pitch of the blades 56.

[0211] The control module 335 is also configured to transmit to the backup circuit 334, more specifically to its auxiliary pump 338, a start instruction in the event of failure of the pressure generator 330.

[0212] The linkage system 278 connects the piston 310 to each blade 56 so as to convert the translation of the piston 310 along the longitudinal axis X and, where applicable, the rotation of the piston 310 around the longitudinal axis X into a rotation of each blade 56 around its pivot axis P.

[0213] For this purpose, the linkage system 278 includes a synchronizing ring 340 attached to the piston 310 and, for each of the blades 56, a linkage mechanism 342 connecting the blade 56 to the synchronizing ring 340.

[0214] The synchronizing ring 340 extends in a radial plane around the piston 310.

[0215] Each linkage mechanism 342 includes a first joint 344 integral with the piston 310, a second joint 346 integral with the blade 56, away from the pivot axis P of said blade 56, and a connecting rod 348 linking the first joint 344 to the second joint 346.

[0216] The first joint 344 is carried by the synchronizing ring 340. Here it is made up of a ball joint.

[0217] The second joint 346 is also made up of a ball joint. It is eccentric relative to the pivot axis P.

[0218] The connecting rod 348 has a first end 350 articulated to the first articulation 344 and a second end 352 articulated to the second articulation 346. Advantageously the connecting rod 348 is of adjustable length, that is to say that the distance between the first and second ends 350, 352 can be modified, which allows precise adjustment of the piloting of the pitch angle of each blade 56 by the pitch changing mechanism 70.

[0219] In the example shown, each linking mechanism 342 also includes an eccentric piece 354 connecting the attachment piece 60 to the second joint 346.

[0220] The linkage system 278 is arranged so that the movement of the piston 310 towards the stop 291, i.e., towards its deployed position, causes each blade 56 to rotate towards its sail position, and that the movement of the piston 310 away from the stop 291, i.e., towards its retracted position, causes each blade 56 to rotate towards its flag position. To this end, the second hinge 346 is placed, relative to the plane Q orthogonal to the chord C and containing the pivot axis P, on the trailing edge side 57B, i.e., opposite, relative to the pivot axis P, the position occupied by the second hinge 146 in the embodiment of the Figures 4 à 10 .

[0221] It should be noted that, in the example shown on the Figure 11 The first joint 344 is located upstream of the second joint 346. Consequently, when the pitch change mechanism 70 is immobilized, the natural forces exerted on the blade 56 towards its sail position cause the connecting member 348 to work in compression, implying a risk of buckling of said connecting member 348. To avoid this risk of buckling of the connecting member 348 and to be able to use a lighter connecting member 348, a variant (not shown) is preferred in which the first joint 344 is located downstream of the second joint 346. This particular arrangement, like that of the first embodiment, ensures that the natural forces exerted on the blade 56 towards its sail position cause the connecting member 348 to work in tension and not in compression when the pitch change mechanism 70 is immobilized.

[0222] The pitch change mechanism 70 also includes a pitch locking device 360 ​​designed to block the translation of the piston 310 relative to the frame 272 towards its deployed position.

[0223] This 360 locking device includes a support member 362 and a screw-nut system 364.

[0224] The support member 362 is movable in translation relative to the frame 272 along the longitudinal axis X between an operating position, represented on the Figure 11 , and a locking position (not shown).

[0225] The support member 362 comprises a body 366 elongated along the longitudinal axis X and centered on the longitudinal axis X. This body 366 has a first longitudinal end 368, in particular an upstream longitudinal end, engaged through the opening 290 of the frame 272, and a second free longitudinal end 372. Furthermore, in the example shown, the body 366 is hollow and open at both its longitudinal ends 368 and 372.

[0226] The support member 362 also includes a skirt 374 integral with the body 366 and arranged around the second longitudinal end 372 of the body 366.

[0227] The screw-nut system 364 includes a screw 376 and a nut 378.

[0228] The screw 376 extends around the body 366 of the support member 362 and is coaxial with said body 366. It is fixed in translation to the support member 362 and mounted to rotate about the longitudinal axis X relative to the support member 362. For this purpose, the screw 376 is assembled to the support member 362 by means of a bearing 380. This bearing 380 is interposed here between the skirt 374 of the support member 362 and an end portion 382 of the screw 376, housed between the body 366 and the skirt 374.

[0229] The screw 376 has a second longitudinal end portion 384 opposite the end portion 382. This second longitudinal end portion 384 defines a radial stop surface 386. This stop surface 386 is at a distance from the frame 272 when the support member 362 is in the operating position and bears against the stop 291 of the frame 272 when the support member 362 is in the locking position.

[0230] Here, the second longitudinal end portion 384 flares out from a threaded body 390 of the screw 376 to the stop surface 386. Thus, the contact area between the stop surface 386 and the stop 291 is increased, which increases the friction forces between the stop surface 386 and the stop 291 and allows for better transmission of braking and locking forces.

[0231] The abutment surface 386 and the stop 291 are each smooth here. Alternatively (not shown), the abutment surface 386 and / or the stop 291 have asperities, so as to further increase the friction forces between the abutment surface 386 and the stop 291 and allow for even greater force transmission.

[0232] The threaded body 390 extends from one end portion 382, ​​384 to the other. It has an external thread 392 at its periphery.

[0233] The nut 378 is integral with the piston 310 and coaxial with the screw 376. It cooperates with the screw 376 so that a translation of the nut 378 along the longitudinal axis X relative to the screw 376 causes the screw 376 to rotate around the longitudinal axis X relative to the support member 362.

[0234] Nut 378 has an internal thread 394.

[0235] The screw-nut system 364 is in particular formed by a reversible satellite roller screw system 395. In a conventional manner, this satellite roller screw system 395 comprises, in addition to the screw 376 and the nut 378, a plurality of rollers 396 interposed between the screw 376 and the nut 378, each roller 396 being elongated parallel to the longitudinal axis X.

[0236] Preferably, the above description of the 195 satellite roller screw system applies mutatis mutandis to the satellite roller screw system 395.

[0237] This feature ensures efficient transmission of forces from nut 378 to screw 376 via the screw-nut system 364, while maintaining a small pitch in the helical connection of the screw-nut system 364. In particular, if screw 376 becomes blocked from rotating, it allows nut 378 to be immobilized relative to screw 376 even without a separate locking nut. This eliminates the need for a separate locking nut, simplifying manufacturing and reducing the cost of the mechanism, while simultaneously increasing its reliability and minimizing its weight.

[0238] The locking device 360 ​​also includes a return device 420 which forces the support member 362 towards its locking position and a holding device 422 to hold the support member 362 in its operating position when the pitch changing mechanism 70 is in normal operating conditions.

[0239] The return device 420 here consists of a compression spring compressed between the frame 272 and a shoulder 424 integral with the support member 362.

[0240] The holding device 422 includes a counterbalancing cylinder 430 comprising a counterbalancing piston 432 and a counterbalancing chamber 434.

[0241] The counterbalancing piston 432 is integral with the support member 362. It is mounted to move in translation along the longitudinal axis X relative to the frame 272. In particular, it is coaxial with the support member 362. In the example shown, it is arranged in the longitudinal extension of the support member 362.

[0242] The counterbalancing piston 432 and the frame 272 together define the chamber 434.

[0243] The counterbalancing chamber 434 is fluidically connected to the pressure generator 330 by a fluid connection circuit 436 so as to be supplied with control fluid at the third pressure. It is intended to counterbalance the stress on the return device 420 when this supply is active.

[0244] To this end, the counterbalancing cylinder 430 is arranged so that the pressure exerted on the piston 432 by the fluid contained in the chamber 434 is oriented in a direction opposite to that of the stress on the return device 420: in the example shown, the counterbalancing piston 432 is interposed between the chamber 434 and the shoulder 424, and the shoulder 424 is interposed between the piston 432 and the return device 420. Furthermore, the counterbalancing piston 432 and the counterbalancing chamber 434 are dimensioned so that, when the chamber 434 is supplied with control fluid at the third pressure, the force exerted by the control fluid on the piston 432 is greater than the stress on the return device 420.

[0245] Thus, when the supply of control fluid to chamber 434 at the third pressure is active, the activation of the return device 420 is cancelled and the support member 362 is maintained in the operating position.

[0246] In the example shown, the pressure control unit 332 is fluidly interposed between the pressure generator 330 and the fluidic connection circuit 436. It has a first configuration, in which it isolates the fluidic connection circuit 436 from the return line 336, and a second configuration, in which it fluidly connects the fluidic connection circuit 436 to the return line 336.

[0247] The pressure control unit 332 is configured to normally be in its first configuration and to switch to its second configuration upon receiving a command instruction transmitted by the control module 335.

[0248] Still referring to the Figure 11 , the pitch change mechanism 70 finally includes a fluid transfer bearing 457 intended for supplying the control cylinder 274 with control fluid from the pilot system 276.

[0249] For this purpose, the fluid transfer bearing 457 is configured to transfer the control fluid from the fixed reference mark attached to the nacelle 20 to the rotating reference mark attached to the blower rotor 54 and more particularly to the first and second chambers 312, 314 of the cylinder 274.

[0250] For this purpose, the fluid transfer bearing 457 includes, with reference to the Figure 12 , a stator 458 fixed relative to the nacelle 20 and a rotor 459 movable jointly with the blower rotor 54 (and therefore with the control cylinder 274) around the longitudinal axis X relative to the stator 458. It also includes a first circuit 460 fluidically connected to the first fluidic chamber 312 for supplying said first fluidic chamber 312 with control fluid provided by the pilot system 276 and a second circuit 461 fluidically connected to the second fluidic chamber 314 for supplying said second fluidic chamber 114 with control fluid provided by the pilot system 76.

[0251] The stator 458 is in the form of a cylinder of revolution coaxial to the longitudinal axis X. It is connected by its downstream end 462 to a structure (not shown) of the nacelle 20.

[0252] The rotor 459 is in the form of a cylinder of revolution coaxial with the longitudinal axis X. It extends around the stator 458. Its periphery is in contact with the frame 272. It is guided in rotation around the axis X relative to the stator 458 by means of bearings 464 interposed between the rotor 459 and the stator 458.

[0253] The fluid transfer bearing 457 is thus coaxial with the X axis. It is therefore also coaxial with the control cylinder 274.

[0254] The first circuit 460 includes a first axial conduit 465A formed in the stator 458, a plurality of first radial orifices 465B (only one of them being shown here) formed in the stator 458 and connecting the axial conduit 465A to the periphery of the stator 458, a first circumferential groove 465C formed between the rotor 459 and the stator 458 and into which each radial orifice 465B opens, and a plurality of first radial conduits 465D, formed in the rotor 459, extending radially from the groove 465C to a first feed channel 466 of the first fluidic chamber 112 formed between the frame 72 and the rotor 459.

[0255] The first axial conduit 465A has an axial extension parallel to the X-axis. In the example shown, it is specifically straight and coaxial with the X-axis. Alternatively (not shown), the first axial conduit 465A is curved and / or also has a radial extension in a direction orthogonal to the X-axis.

[0256] Furthermore, the first axial conduit 465A has, in the example shown, an annular radial section, that is to say, it is solid in its center.

[0257] Each first radial orifice 465B has a radial extension along a radial direction orthogonal to the X-axis. In the example shown, each first radial orifice 465B is, in particular, straight along a radial direction. Alternatively (not shown), at least one first radial orifice 465B is curved and / or also has an axial extension parallel to the X-axis.

[0258] The first circumferential groove 465C extends parallel to a radial plane orthogonal to the X axis.

[0259] Each first radial conduit 465D has a radial extension along a radial direction orthogonal to the X-axis. In the example shown, each first radial conduit 465D is, in particular, straight along a radial direction. Alternatively (not shown), at least one first radial conduit 465D is curved and also has an axial extension parallel to the X-axis and / or a circumferential extension along a direction orthogonal to both the X-axis and the radial direction.

[0260] The first supply channel 466 extends from an outlet of the first radial conduits 465D to an inlet of the first fluidic chamber 312. In the example shown, it is substantially straight and extends substantially parallel to the X axis.

[0261] The second circuit 461 includes a second axial conduit 467A formed in the stator 458, a plurality of second radial ports 467B (only one of them being shown here) formed in the stator 458 and connecting the axial conduit 467A to the periphery of the stator 458, a second circumferential groove 467C formed between the rotor 459 and the stator 458 and into which each radial port 467B opens, and a plurality of second radial conduits 467D, formed in the rotor 459, extending radially from the groove 467C to a second feed channel 468 of the second fluidic chamber 114 formed between the frame 72 and the rotor 459.

[0262] The second axial conduit 467A has an axial extension parallel to the X-axis. Advantageously, it is coaxial with the first axial conduit 465A. In the example shown, it is, in particular, straight and coaxial with the X-axis. Alternatively (not shown), the second axial conduit 467A is curved and / or also has a radial extension in a direction orthogonal to the X-axis.

[0263] Furthermore, the second axial conduit 467A, in the example shown, has an annular radial cross-section, meaning it is solid in its center. Here, it extends around the first axial conduit 465A.

[0264] Each second radial orifice 467B has a radial extension along a radial direction orthogonal to the X-axis. In the example shown, each second radial orifice 467B is, in particular, straight along a radial direction. Alternatively (not shown), at least one second radial orifice 467B is curved and / or also has an axial extension parallel to the X-axis.

[0265] Each second radial orifice 467B is here arranged axially downstream of the first radial orifices 465B.

[0266] The second circumferential groove 467C extends parallel to a radial plane orthogonal to the X axis. Here it is arranged axially downstream of the first circumferential groove 465C.

[0267] Each second radial conduit 467D has a radial extension along a radial direction orthogonal to the X-axis. In the example shown, each second radial conduit 467D is, in particular, straight along a radial direction. Alternatively (not shown), at least one second radial conduit 467D is curved and also has an axial extension parallel to the X-axis and / or a circumferential extension along a direction orthogonal to both the X-axis and the radial direction.

[0268] Each second radial conduit 467D is here arranged axially downstream of the first radial conduits 465D.

[0269] The second supply channel 468 extends from an outlet of the second radial conduits 466D to an inlet of the second fluidic chamber 314. In the example shown, it is substantially straight and extends substantially parallel to the X axis.

[0270] The first and second circuits 460, 461 are independent circuits, that is to say they are not in fluidic communication with each other.

[0271] Back to the Figure 11 The guide bearing 457 has an external diameter smaller than the internal diameter of the guide bearing 53 of the blower rotor 54. It is located upstream of the reducer and is in particular housed in the housing 304 delimited by the central cylinder 294.

[0272] The guide bearing 457 is thus surrounded, at least in part, by the control cylinder 274. In particular, the control cylinder 274 extends along the X-axis around more than half, advantageously around more than three-quarters, of the fluid transfer bearing 457. To arrive at this measurement, the axial ends of the control cylinder 274 and the guide bearing 457 are taken into consideration, these being defined as follows: for the control cylinder 274, its axial ends are formed by the ends 288, 302 of the fluidic chambers 312, 314; for the guide bearing 457, its axial ends are formed by the limits beyond which the rotor 459 and the stator 458 no longer coexist (that is to say, starting from the center of the guide bearing, the first axial end of the rotor 459 or the stator 458 encountered delimits an axial end of the guide bearing 457).

[0273] In particular, in the example shown, the control cylinder 274 extends along the X axis around the entire fluid transfer bearing 457.

[0274] Unlike the fluid transfer bearing 257, the fluid transfer bearing 457 is not configured here to supply the counterbalancing cylinder 430 with control fluid from the pilot system 276. Instead, the stator 458 is axially drilled in its center and traversed by a central conduit 470 intended to supply the counterbalancing cylinder 430.

[0275] This central conduit 470 is here straight and collinear with the longitudinal axis X. It extends through the fluid transfer bearing 257, but also through the support member 362 and the counterbalancing piston 432, up to the counterbalancing chamber 434.

[0276] The central pipe 470 is typically fixed in the nacelle frame 20. Alternatively, it is fixed in the rotating frame of the blower rotor 54.

[0277] A seal is made at the periphery of the central pipe 470, between the central pipe 470 and the counterbalancing piston 432. Advantageously, a second seal is also made at the periphery of the central pipe 470, between the central pipe 470 and the upstream end 298 of the central cylinder 294, which the central pipe 470 passes through in its center.

[0278] A method for changing the pitch of the blades 56, implemented by the pitch changing mechanism 70 according to the second embodiment, will now be described.

[0279] In the first stage of this process, the control module 335 first receives a timing instruction to increase the pitch of the blades 56. The control module 335 then transmits to the pressure control unit 332 a control signal intended to increase the fluid pressure in the first chamber 312. As the fluid pressure in the first chamber 312 increases, the control piston 310 moves to its retracted position, which, via the linkage system 278, causes the blades 56 to pivot towards the large pitches (i.e., towards the flag position).

[0280] Once the piston 310 has reached an equilibrium position, it stabilizes, the blades 56 maintaining a fixed orientation.

[0281] In a second step of the pitch change process, the control module 335 first receives a pitch instruction to reduce the pitch of the blades 56. The control module 335 then transmits to the pressure control unit 332 a control signal intended to increase the fluid pressure in the second chamber 314. As the fluid pressure in the second chamber 314 increases, the control piston 310 moves to its deployed position, which, via the linkage system 278, causes the blades 56 to pivot towards the small pitch (i.e., towards the sail position).

[0282] Once the piston 310 has reached an equilibrium position, it stabilizes, the blades 56 maintaining a fixed orientation.

[0283] Optionally, the pitch change process also includes, following the first or second step, a controlled locking step of the orientation of the blades 56.

[0284] During this step, the control module 335 transmits a step-lock command to the pressure control unit 332. Under the effect of this command, the pressure control unit 332 fluidly connects the fluid connection circuit 436 to the return line 336, resulting in a drop in fluid pressure in the counterbalancing chamber 434. The fluid pressure in said chamber 434 is then insufficient to counterbalance the load on the return device 420, which thus causes the support member 362 to move to its locking position.

[0285] During this movement, the screw 376 rotates around the longitudinal axis X under the effect of the resistance imposed by the assembly of the nut 378 and the rollers 394 (which are held immobile in translation by the control cylinder 274) until its stop surface 386 comes to rest against the stop 291 of the frame 272, blocking the rotation of the screw 376 around the longitudinal axis X and its translation along the same axis X.

[0286] The blades 56 are thus locked in their orientation even in the event of loss of fluid pressure in the first chamber 312.

[0287] In the event of a pressure loss in the second chamber 314 only, the piston 310 is moved towards its retracted position by the pressure difference between the two chambers 312 and 314, carrying with it the screw 376 and the support member 362, which returns to its operating position. The piston 310 is therefore no longer immobilized and can continue to move towards its retracted position until the vanes 56 reach the flag position.

[0288] In the event of a malfunction of the pilot system 276, typically in the event of a failure of the pressure generator 330, the pitch change process includes an additional step of uncontrolled locking of the orientation of the blades 56.

[0289] During this step, a malfunction in the pilot system 276 causes a drop in fluid pressure in the counterbalancing chamber 434, typically because the pressure generator 330 is no longer able to bring the control fluid to the third pressure. The fluid pressure in said chamber 434 is then insufficient to counterbalance the load on the return device 420, which thus causes the support member 362 to move to its locking position.

[0290] During this movement, the screw 376 takes with it the nut 378 and the rollers 394, which are no longer held immobile in translation due to the loss of supply to the control cylinder 274. The blades 56 therefore pivot slightly towards the small steps, until the stop surface 386 of the screw 376 comes to rest against the stop 291 of the frame 272, blocking the rotation of the screw 376 around the longitudinal axis X and its translation along the same axis X.

[0291] The pivoting of the 56 blades towards the small steps is then prevented by the 360 ​​locking device.

[0292] The uncontrolled locking step is followed by a blower 50 safety shutdown step. During this step, the backup circuit 334 is activated and supplies the first fluidic chamber 312 with control fluid to increase the fluid pressure in this chamber. Under the effect of this pressure increase, the piston 310 moves to its retracted position, carrying with it the screw 376 and the support member 362, which returns to its operating position. The piston 310 is therefore no longer immobilized and can continue moving downstream until the blades 56 reach the flagging position.

[0293] It should be noted that these different steps can be implemented independently of each other.

[0294] Thus, thanks to the embodiment examples described above, the fluid transfer bearing 257, 457 is made easily accessible, since it is located upstream of the reducer, without this being at the expense of the length of the turbomachine 12, thanks to the clever positioning of the fluid transfer bearing 257, 457 inside a cavity surrounded by the cylinder 74, 274. In addition, the size of the fluid transfer bearing 257, 457 itself is minimized.

[0295] These embodiment examples also make it possible to do without the use of a locking nut separate from the nut 178, 378 of the screw-nut system 164, 364. This results in a locking device 160, 360 and, therefore, a pitch changing mechanism 70 whose manufacture is simplified, costs reduced and reliability increased.

[0296] Furthermore, examples of the implementation of Figures 3 à 9 allow the pitch change mechanism 70 to be lightened thanks to the compactness of the control cylinder 74 and the use of less resistant and therefore lighter connecting elements 148.

[0297] The aforementioned examples of implementation of Figures 3 à 9 also allow saving the need for a support positioned upstream of the locking device 160, which facilitates access to the pitch changing mechanism 70, and more particularly to the linking system 78, once it is assembled.

[0298] These examples of the implementation of Figures 3 à 9 finally allow a high degree of precision in controlling the angle of the blades 56, which allows on the hub 55 the close implantation of large blades 56 with complex geometry, thus increasing the efficiency of the turbomachine 12.

Claims

1. A pitch change mechanism (70) for adjusting an angular position of at least one variable-setting blade (56) around a pivot axis (P) of the blade (56), said pitch change mechanism (70) comprising: - a frame (72, 272) which is fixed in relation to the pivot axis (P), - a control actuator (74, 274) including a fixed part (100, 308) secured to the frame (72, 272) and a movable part (102, 309), translationally movable along a longitudinal axis (X) in relation to the fixed part (100, 308) between a retracted position and an extended position, - a linking system (78, 278) linking the movable part (102, 309) to the variable-setting blade (56) so as to convert the translation of the movable part (102, 309) along the longitudinal axis (X) into a rotation of the variable-setting blade (56) about the pivot axis (P), and - a fluid transfer bearing (257, 457) for supplying the control actuator (74, 274) with actuating fluid coming from a source (76, 276) in relation to which the control actuator (74, 274) is rotationally movable about the longitudinal axis (X), characterized in that the control actuator (74, 274) extends at least partially around the fluid transfer bearing (257, 457).

2. The pitch change mechanism (70) as claimed in claim 1, wherein the control actuator (74, 274) is coaxial with the fluid transfer bearing (257, 457).

3. The pitch change mechanism (70) as claimed in claim 1 or 2, wherein the control actuator (74, 274) extends around more than half, advantageously around more than three quarters, of the fluid transfer bearing (257, 457).

4. The pitch change mechanism (70) as claimed in any of the preceding claims, comprising a pitch locking device (160) suitable for locking the translation of the movable part (102) in relation to the fixed part (100) in at least one direction, said pitch locking device (160) comprising: - a locking member (162), translationally movable in relation to the frame (72) along the longitudinal axis (X) between an operating position and a locking position, - a biasing device (240) biasing the locking member (162) towards its locking position, and - a retaining device (242) for retaining the locking member (162) in its operating position under normal operating conditions, the retaining device (242) comprising a counterbalance actuator (250) including a counterbalance chamber (254) supplied with actuating fluid to counterbalance the biasing of the biasing device (240), the fluid transfer bearing (257) being configured to supply the counterbalance actuator (250) with actuating fluid coming from the source (76).

5. The pitch change mechanism (70) as claimed in any of the preceding claims, wherein the fluid transfer bearing (257, 457) comprises a stator (258, 458) and a rotor (259, 459) jointly movable with the control actuator (74, 274) about the longitudinal axis (X) in relation to the stator (258, 458), the rotor (259, 459) extending around the stator (258, 458).

6. The pitch change mechanism (70) as claimed in claim 5, wherein the fluid transfer bearing (257, 457) comprises a plurality of circuits (260, 261, 269, 460, 461) independent from one another, at least one of said circuits (260, 261, 269, 460, 461) comprising: - an axial duct (265A, 267A, 270A, 465A, 466A) fashioned in the stator (258, 458), - at least one radial orifice (265B, 267B, 270B, 465B, 466B) fashioned in the stator (258, 458) and linking the axial duct (265A, 267A, 270A, 465A, 466A) to the periphery of the stator (258, 458), - a circumferential groove (265C, 267C, 270C, 465C, 466C) fashioned between the rotor (259, 459) and the stator (258, 458) and into which the or each radial orifice (265B, 267B, 270B, 465B, 466B) opens, and - at least one radial duct (265D, 267D, 270D, 465D, 466D), fashioned in the rotor (259, 459), extending radially from the groove (265C, 267C, 270C, 465C, 466C) all the way to a supply channel (266, 268, 271, 466, 468) formed in the frame (72, 272) or between the frame (72, 272) and the fluid transfer bearing (257, 457).

7. The pitch change mechanism (70) as claimed in claim 6, wherein the axial ducts (265A, 267A, 270A, 465A, 466A) of the different circuits (260, 261, 269, 460, 461) are coaxial.

8. The pitch change mechanism (70) as claimed in any of the preceding claims, wherein the control actuator (74, 274) comprises a first fluid chamber (112, 312) and a second fluid chamber (114, 314) each containing actuating fluid for actuating the displacement of the movable part (102, 309) in relation to the fixed part (100, 308), and the fluid transfer bearing (257, 457) comprises a first circuit (260, 460) fluidly connected to the first fluid chamber (112, 312) for supplying said first fluid chamber (112, 312) with actuating fluid provided by the source (76, 276) and a second circuit (261, 461) fluidly connected to the second fluid chamber (114, 314) for supplying said second fluid chamber (114, 314) with actuating fluid provided by the source (76, 276).

9. A fan rotor (54) for a turbomachine comprising a hub (55) and a plurality of variable-setting blades (56) each pivotable in relation to the hub (55) about a respective pivot axis (P), the rotor (54) further comprising a pitch change mechanism (70) as claimed in any of the preceding claims for adjusting an angular position of each of the variable-setting blades (56) around its respective pivot axis (P).

10. The fan rotor (54) as claimed in claim 9, comprising a guide bearing (53) for rotationally guiding, about the longitudinal axis (X), said fan rotor (54) in relation to a turbomachine nacelle (20), said guide bearing (53) having an inner diameter greater than an outer diameter of the fluid transfer bearing (257, 457).

11. The fan rotor (54) as claimed in claim 9 or 10, wherein the longitudinal axis (X) constitutes an axis of rotation of the fan rotor (54).

12. A turbomachine (12) comprising a fan rotor (54) as claimed in any of claims 9 to 11.

13. An aircraft (10) comprising at least one turbomachine (12) as claimed in claim 12.

14. A method for changing the pitch of the blades (56) of a fan rotor (54) for a turbomachine, each one pivotable in relation to a hub (55) of the fan rotor (54) about respective a pivot axis (P), said method comprising adjusting an angular position of each of said blades (56) around its respective pivot axis (P) by means of a pitch change mechanism (70) as claimed in any of claims 1 to 8.

15. The method as claimed in claim 14, comprising an additional step of locking the orientation of the blades (56) by means of the pitch locking device (160).