TURBO MACHINE MODULE FOR A PROPELLER WITH VARIABLE PITCH BLADES AND TURBO MACHINE THEREFOR

Description

Technical field of the invention

[0001] The invention relates to variable-pitch propellers for turbomachines, whether the rotor is shrouded or not. It relates more particularly to the mechanisms for controlling the pitch of the blades of these propellers. Technical background

[0002] The technical background includes, in particular, documents US10288087B2 and US837110562.

[0003] It is known to increase the bypass ratio of turboprop engines, whether turboprop or open propeller, to improve their propulsive efficiency and reduce their specific consumption. This feature makes it possible to increase the bypass ratio of the engines, but it also has the disadvantage of working with reduced fan or propeller speeds, reducing its compression ratio and thus generating aerodynamic instabilities, for example reducing surge margins.

[0004] One solution to counter these instabilities is to use a variable-pitch propeller. The pitch change mechanism therefore becomes a major technological building block for these engines. Propellers made up of fan blades on turbojets or propellers on open-rotor turbomachines (with unducted propellers) have a large number of blades. In addition, the pitch change system must counter significant forces due to the size of the blades and the power transmitted. Also, the system must allow a large amplitude of variation of the pitch angle, between extreme operating positions.

[0005] In addition to systems using individual actuators per blade, which pose problems of integration, power supply to the actuators and complexity for adjustment, various systems are known using a synchronization ring to modify the timing of an annular row of blades or vanes as a whole. For example, document FR-A1-2 937 678 describes a system using a rotating ring driven by jacks in a plane transverse to the longitudinal axis and document FR-A1-2 997 724 describes a system using a ring driven in axial translation by a longitudinal jack.

[0006] Known systems pose problems at various levels of size, complexity and adjustment or routing of energy to the different actuators, especially in the case of hydraulic actuators.

[0007] The invention aims to address both the problems of integration into the propeller hub space, of energy delivery to one or more actuators, as well as to enable precise adjustment of the blade pitch and compensation for any manufacturing clearances.

[0008] A second objective is to minimize the impact of installing a pitch change mechanism on the modularity of the engine and its maintenance.

[0009] The solution also aims to improve the reliability of the system, particularly in the event of actuator failure. Summary of the invention

[0010] To this end, the invention relates to a longitudinal axis turbomachine module, the module comprising: a casing rotating around the longitudinal axis and carrying a propeller provided with a plurality of blades, a system for changing the pitch of the propeller blades comprising: ° a control means, and ° a mechanism for varying the pitch of the propeller blades.

[0011] The invention is remarkable in that said system is carried by the rotating casing, in that said control means comprise an annular row of rotary actuators distributed around said longitudinal axis, and in that said mechanism for varying the pitch of the blades comprises a synchronization ring which is driven in rotation by rotary output shafts of the actuators, the synchronization ring being guided in rotation relative to said rotating casing by guide means and meshed by a first toothing of the synchronization ring with pinions of the blades.

[0012] The use of a synchronizing ring allows the pitch of all the blades to be changed in a synchronized manner. The fact that the synchronizing ring is guided in rotation on the rotating casing allows the assembly comprising the rotating casing and the blade rotation mechanism to form a functional unit as close as possible to the blades with a reduced footprint. This facilitates its integration into the turbomachine.

[0013] In addition, the rotational guidance of the crown on the rotating casing contributes to the rigidity of the mechanism for precise blade timing. Adding to this the fact that the synchronization crown drives the blades by a gear on the pivots, the device ensures, thanks to the precision of the meshing, a very good relative error in the blade timing.

[0014] Furthermore, these characteristics allow the installation of an interface, as close as possible to the blades, to lock the entire kinematics and block the position of the latter in the event of an emergency.

[0015] As far as the sizing of the actuators is concerned, it is possible to minimize the torque they must provide by playing on the geometric parameters of the crown and its teeth.

[0016] Finally, using an annular row of multiple actuators meshing with the same synchronizing wheel allows, in the event of one actuator failure, for the other actuators to continue to operate. This improves reliability in the event of a failure. Furthermore, as part of the actuation strategy, this arrangement can allow for rotation between the actuators that supply power to allow the others to cool. This is important with electric actuators.

[0017] Preferably, the synchronizing crown is surrounded by a hub belonging to the rotating casing and carrying the blades.

[0018] This arrangement corresponds to a compact layout of the module, therefore easier to integrate and more rigid to ensure the precision of the blade timing.

[0019] Advantageously, the synchronizing crown comprises a radially external peripheral edge cooperating with at least one bearing carried by said rotating casing to form said rotational guide means.

[0020] By transferring the guiding means to the periphery of the synchronizing crown, this allows the transverse forces and torques exerted to maintain the latter to be distributed over a relatively large surface area. This contributes to the robustness and rigidity of the device.

[0021] Advantageously, the output shafts of the actuators have axes of rotation substantially parallel to said longitudinal axis.

[0022] Advantageously, the actuators are carried by a wall of said rotating casing, this wall being substantially perpendicular to said longitudinal axis.

[0023] Preferably, the first meshing toothing with said pinions of the blades is frustoconical.

[0024] Advantageously, the blade pinions are bevel gears which are directly attached to the blade feet.

[0025] Preferably, the synchronizing crown comprises a second toothing which is cylindrical and meshes with said rotating output shafts.

[0026] Preferably, said second toothing is located on a radially internal peripheral edge of the synchronizing crown.

[0027] The invention also relates to an aircraft turbomachine, comprising at least one module as described previously. Brief description of the figures

[0028] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: [ Fig. 1 ] there figure 1 schematically shows an axial half-section of a module according to the invention; [ Fig. 2 ] there figure 2 shows schematically, in circumferential section, different pitch positions of the blades of a propeller using the invention; [ Fig. 3 ] there figure 3 shows a schematic longitudinal half-section of an open-rotor type turbomachine using the device of the figure 1 ; And [ Fig. 4 ] there figure 4 shows a schematic longitudinal half-section of a ducted fan turbomachine using the device of the figure 1 . Detailed description of the invention

[0029] There figure 1 shows a general view of an embodiment of a device 1 according to the invention, driven in rotation around the longitudinal axis X of a turbomachine by a shaft 2 coming out of the engine part, not shown. The shaft 2 is itself guided in rotation on a fixed casing 3 of the turbomachine by bearings 4. The propeller is placed here in front of the engine. The blades 5 of the propeller are driven in rotation around the longitudinal axis X, and are designed to have a variable pitch each around a radial axis Y rotating with the propeller. A cover 6 isolates the device itself from the air flow in which the blades 5 of the propeller work.

[0030] The device 1 here comprises a journal 7, centered on the longitudinal axis X, which connects the shaft 2 to the hub 8 of the propeller, supporting the blades 5. The journal 7 comprises a substantially cylindrical central part 7a which is fitted onto the shaft 2. The connection 9 is here made by splines, which allows assembly / disassembly of the journal 7 from the front of the shaft 2. It is held in axial position by a nut. Substantially in line with the spline connection 9, the journal 7 comprises a disc 7b connected to the hub 8. The disc 7b is here positioned in front of the hub 8. A bolted connection allows the centering and fixing of the hub 8 on the periphery of the disc 7b. The hub 8 is a structural part comprising on the periphery an annular row of circular housings with known and non-detailed means, such as bearings, for installing pivots 10 rotating with the blades 5 around the radial axes Y.The journal 7 and the hub 8 form a rotating casing connecting the blades 5 of the propeller to the shaft 2 of the engine.

[0031] To produce the pitch change mechanism, a synchronizing crown 11 is mounted on the journal 7. The synchronizing crown 11 is here formed of a disc 11a carrying a cylindrical lug 11b on its rear face.

[0032] The synchronizing ring 11 is mounted between the disc 7b of the journal and the pivots 10 of the blades 5, under the hub 8. The periphery of the disc 11a of the synchronizing ring 11 is held in a bearing 12 fixed to the periphery of the disc 7a of the journal 7, under the hub 8. This bearing 12 comprises means, not detailed here, in particular a groove and bearings, which keep the synchronizing ring 11 centered on the axis X and in a determined axial position. The outer periphery of the disc 11a of the synchronizing ring 11 forms a track for the bearings of said bearing 10. These means therefore allow the synchronizing ring 11 to rotate freely around the longitudinal axis X relative to the journal 7, while taking up the forces to which it is subjected to keep it in the axial position.

[0033] The cylindrical lug 11b of the synchronizing crown 11 carries at its free end a toothed crown 13. Here, the surface carrying the teeth of the toothed crown 13 is frustoconical around the axis X, it follows a cone whose generating lines pass through the intersection between the axis X and the plane of the axes Y of the pivots 10 of the blades 5. The toothed crown 13 meshes with the teeth of bevel gears 14 fixed to the end of the pivot 10 of each blade 5. The surface carrying the teeth of the pinion 14 of each pivot 10 follows a cone centered on the axis Y of the pivot and whose generating lines pass through the intersection between the axis X and the plane of the axes Y of the pivots of the blades.

[0034] The precision of the meshes of the synchronizing crown 11 with the bevel gears 14 makes it possible to obtain good precision of the blade-to-blade timing, with a very low relative error.

[0035] Furthermore, the disc 11a of the synchronizing crown 11 has a central recess. The disc carries, at the periphery of this central recess, an internal and axial toothed crown 15.

[0036] The device also comprises an annular row of rotary actuators 16 having Z axes parallel to the X axis of the turbomachine, one of which is shown in the figure 1. The rotary actuators 16 are fixed on the disc 7b of the journal 7, in front of the latter. Each drives in rotation about its axis Z an output shaft 17 which passes through the disc 7b of the journal and carries a toothed wheel 18 which meshes with the internal toothed crown 15 of the disc 11b of the synchronizing crown 11. For example, eight actuators 16 identical to that shown are fixed on the disc of the journal, distributed circumferentially in a crown at the front of the latter. The number of actuators and their size can vary depending on the geometric parameters of the device and the individual power defined for each actuator. The number of actuators can typically be three, six or twelve.

[0037] Here, these are electric actuators. Rotating power transfer means 19 are installed at the rear of the journal 7, between the shaft 2 and the fixed casing 3 of the turbomachine. Wires 20 transmit the energy from these means 19 to the actuators 16. They are controlled in position around their axis of rotation Z by electrical pulses.

[0038] Alternatively, hydraulic actuators can be used. In this case, a rotating hydraulic transfer device must be installed between the fixed structure and the device to supply them with energy and control them.

[0039] The assembly forms a support module for the blades 5 of the propeller with control of the pitch angle, the size of which is reduced to a restricted volume at the hub 8 of the blades 5 of the propeller.

[0040] The journal 7, the hub 8 of the propeller form a rotating casing at the speed imparted by the shaft 2 of the propeller. The actuators 16 are controlled to rotate their output shaft 17 at the same speed and by the same value in a direction determined according to the desired pitch angle. The rotation of the output shafts 17 causes a rotation of the synchronization ring 11 in the frame of reference of the rotating casing and, by the gearing of the synchronization wheel 11 on the pinions 14 of the pivots 10 of the blades 5, a corresponding modification of the pitch of each blade 5 around the Y axis of its pivot 10.

[0041] By oversizing the actuators, this arrangement allows, in the event of an actuator failure, to continue to operate with the other actuators. Furthermore, as part of the actuation strategy, this arrangement can allow for rotation between the actuators that supply power in order to allow the others to cool. This point is important with electric actuators.

[0042] The kinematics of the assembly allow the setting angle to be modified over a large angular range. figure 2 illustrates different angular positions of the blades 5, for operating modes in feather C1, in climb C2, at takeoff C3, on the ground C4 and in reverse thrust C5. The variation in pitch angle is greater than 90° between the extreme positions.

[0043] Furthermore, the rigidity of the assembly, in particular thanks to the bearing 12 for guiding the rotation of the synchronizing crown 11 on the journal 7 and to the gear connections on the teeth 13 and 15, makes it possible, if necessary, to lock the entire kinematics and to block the stalled position of the blades 5 in the event of an emergency. The additional means to be installed on the journal 7 to perform this locking function in the event of a failure of the actuator are not described here.

[0044] The device which has been described can be installed for example on a turbomachine 21 of the “open-rotor” type. The figure 3 thus shows the device 1 placed under the upstream propeller 22 of such a turbomachine 21, with at the rear a crown of fixed blades 23 straightening the flow passing through the propeller 22 and the engine 24 itself, not detailed, which drives the propeller 22 by the shaft 2. Similarly, with reference to the figure 4, the device 1 can be installed to drive the ducted fan 25 of a dual-flow turbomachine 26, the engine 27 of which is not detailed.

Claims

1. A module (1) for a turbomachine, the module comprising: - a propeller comprising a plurality of blades, - a rotating casing (7-8) rotatable about a longitudinal axis (X) and supporting the propeller provided with a plurality of blades (5), - a system for changing the pitch of the blades (5) of the propeller comprising: ∘ a control means, and ∘ a mechanism for varying the pitch of the blades of the propeller, wherein said system is supported by the rotating casing (7-8), wherein said control means comprise an annular row of rotating actuators (16) distributed about said longitudinal axis (X), and wherein said mechanism for varying the pitch of the blades comprises a synchronization ring (11) which is rotatably driven by rotating output shafts (17) of the actuators (16), , the synchronization ring (11) being rotatably guided with respect to said rotating casing (7-8) by guiding means and meshed by a first toothing (13) with pinions (14) of the blades (5), characterised in that the output shafts (17) of the actuators (16) having axes of rotation (Z) substantially parallel to said longitudinal axis (X).

2. The module (1) according to claim 1, wherein the synchronization ring (11) is surrounded by a hub (8) belonging to the rotating casing and supporting the blades (5).

3. The module (1) according to claim 1 or 2, wherein the synchronization ring (11) comprises a radially external peripheral edge cooperating with at least one bearing (12) supported by said rotating casing (7-8) to form said rotatably guiding means.

4. The module (1) according to one of the preceding claims, wherein the actuators (16) are supported by a wall (7b) of said rotating casing, this wall (7b) being substantially perpendicular to said longitudinal axis (X).

5. The module (1) according to one of the preceding claims, wherein the first toothing (13) for meshing with said pinions (14) of the blades (5) is frustoconical.

6. The module (1) according to any of the preceding claims, wherein the pinions (14) of the blades (5) are conical pinions which are directly attached to roots of the blades (5).

7. The module (1) according to any of the preceding claims, wherein the synchronization ring (11) comprises a second toothing (15) which is cylindrical and meshes with said output rotating shafts (17).

8. The module (1) according to claim 7, wherein said second toothing (15) is located on a radially internal peripheral edge of the synchronization ring (11).

9. An aircraft turbomachine (21, 26) comprising at least one module (1) according to one of the preceding claims.