FR3126018A1 - SYSTEM FOR CHANGING THE BLADES OF A FAN OF A PROPULSION ASSEMBLY - Google Patents

Abstract

The invention relates to a system (22) for changing the pitch of the blades for a propulsion assembly (2) of longitudinal axis (X), each blade (5) being pivotally mounted on a shaft (10) of the following propulsion assembly a pitch pin (Y), the system comprising a link mechanism (24) connected to each blade and a control means acting on the link mechanism, the control means comprising a cylindrical actuator having a fixed body (27) and a mobile body (25) integral in rotation with the shaft, the mobile body being in translation with respect to the fixed body, the actuator being arranged so as to move the link mechanism axially to cause the pitch change of the blades, in which the control device comprises a compass (28) connecting the fixed body (27) of the actuator to the movable body (25) of the actuator (23). Figure for abstract: Figure 1

Description

SYSTEM FOR CHANGING THE BLADES OF A FAN OF A PROPULSION ASSEMBLY

The present invention relates to a fan module with variable-pitch blades for a propulsion assembly, and more specifically to a device for setting the pitch of the blades adapted to such a fan.

A fan fitted with variable-pitch blades (known by the acronym VPF for “Variable Pitch Fan”) makes it possible to adjust the pitch (and more precisely the pitch angle) of the blades according to the flight parameters, and thus to optimize the operation of the fan, and in general of the propulsion assembly in which such a fan is integrated. As a reminder, the pitch angle of a blade corresponds to the angle, in a longitudinal plane perpendicular to the axis of rotation of the blade, between the chord of the blade and the plane of rotation of the fan.

Propulsion assemblies or turbomachines generally comprising a ducted fan or an unducted propeller equipped with variable-pitch moving blades, equipped with these pitch change systems are known.

In the category of turbomachines with at least one unducted propeller, also called by the English term "open rotor" or "unducted fan", there are those with a single unducted propeller and a rectifier comprising several stator vanes (known as the USF acronym for "Unducted Single Fan").

An open rotor type turbine engine mainly comprises, inside a fixed cylindrical casing carried by the structure of the aircraft, a "gas generator" part and a coaxial "propulsion" part. The gas generator part can be arranged upstream or downstream of the propulsion part. The terms “upstream” and “downstream” are defined with respect to the circulation of gases in the turbomachine. The propulsion part comprises at least one propeller driven in rotation by a turbine, in particular low pressure, of the gas generator part via a reducer, for example, with planetary gears. In some cases, the propulsion part may comprise two coaxial and counter-rotating propellers, respectively upstream and downstream which are driven, in opposite rotation to one another, by the turbine of the gas generator via the reducer. The propeller or propellers extend substantially radially with respect to the longitudinal axis transmission shaft outside the casing.

In general, the or each propeller comprises a substantially cylindrical rotating casing carrying a hub with an outer polygonal ring rotatably received around the longitudinal axis in the stator of the turbomachine. The ring comprises radial cylindrical housings distributed on its periphery around the longitudinal axis. Shafts with radial axes, perpendicular to the longitudinal axis of the turbomachine, integral with the roots of the blades are received in the housings of the polygonal rings and also pass through radial passages in the cylindrical casing.

To allow optimal operation of the turbine engine according to the different flight phases encountered, the blades of the propellers can rotate in the radial housings of the polygonal rings. For this, they are driven in rotation about their respective pivot axes, called pitch axis, by an appropriate system making it possible to vary the pitch of the blades during flight, that is to say the pitch of the propellers.

This system for changing the pitch of the blades of the propellers covers an angular range of rotation comprised between two extreme positions, namely an extreme position called "reverse" for which the blades exceed for example by 30° the plane transverse to the axis of the turbine engine (the direction of advance of the aircraft) to participate in the braking of the aircraft, in the manner of the usual thrust reversers, and an extreme position called "feathering" for which the blades are then erased as best as possible with respect to the direction of advance, for example, in the event of an engine failure or during a failure (or failure) of the blade pitch control device (for example a failure of a hydraulic actuator) so that the latter offer the least resistance (drag) possible.

In general, a system for changing the pitch of the blades of a propeller comprises a control device and a link mechanism connecting the control means to each blade of the propeller to ensure the desired angular pivoting of the blades.

In addition, the feathering of the blades is usually done via counterweights. Usually, the counterweights are placed on the foot of each blade and are potentially very heavy depending on the available space and come to load centrifugally and therefore increase the stresses of the foot of the blades and the bearings of the foot of the blades already very stressed.

Various solutions have been proposed for changing the pitch of the blades of a fan and performing the feathering of the blades on turbine engines of the "open rotor" or other type.

For example, document FR 3 066 559 discloses a system for changing the pitch of the blades comprising a single annular jack arranged on a fixed casing or internal stator with respect to the hub of the fan and a link mechanism comprising a transfer bearing , better known by the English acronym LTB for "Load Transfer Bearing", fixed on one side to the movable part of the cylinder and cooperating, on the other side, with a means for connecting the mechanism to the blades of the rotary hub, such that the load transfer bearing of the mechanism driven in rotation transmits the translational movement of the movable part of the fixed cylinder, to the connecting means of the rotary mechanism to change the orientation of the blades of the propeller. This pitch change system further comprises a device for feathering the blades comprising counterweights with a lever mechanism arranged in the rotating marker, linked to the outer ring of the load transfer bearing. The use of counterweights with a lever mechanism acting on the cylinder makes it possible to multiply the effort and to take advantage of an empty space to reduce the mass of the counterweights and not to solicit the foot of the blades.

Having a linear actuator in a fixed frame facilitates its oil supply and reduces the rotating masses. However, this solution requires a plane kinematics of the counterweight mechanism, implying for the pitch change mechanism to have a purely axial movement. This need for purely axial movement leads to an oversizing of the lever system. Moreover, if the pitch change mechanism is purely axial, it requires a greater force for actuation and this force translates into internal forces and therefore into additional mechanical stresses. Furthermore, the lever counterweight mechanism as presented is hyperstatic, making it difficult to design, manufacture and assemble.

The objective of the present invention is thus to propose a blade pitch change system in which the pitch change mechanism has a purely axial movement while avoiding oversizing of the lever system of the feathering device.

To this end, the invention relates to a system for changing the pitch of the blades for a propulsion assembly with a longitudinal axis X, each blade being pivotally mounted on a shaft of the propulsion assembly along a wedging axis, the system comprising a mechanism link connected to each blade and a control means acting on the link mechanism, the control means comprising a cylindrical actuator having a fixed body and a movable body integral in rotation with the shaft, the movable body being in translation relative to the body fixed along the longitudinal axis, the actuator being arranged so as to move the link mechanism axially to cause the pitch of the blades to change, and characterized in that the control means comprises a compass, called the main compass , connecting the fixed body of the actuator to the mobile body of the actuator.

Such a compass is dedicated and dimensioned to take up all the anti-rotation or anti-torque forces of the actuator, more precisely of the fixed body with respect to the mobile body of the actuator.

Preferably, the compass comprises a first arm, one end of which is connected to the fixed body of the actuator via a clevis by a first pivot connection and a second arm, one end of which is connected to the mobile body of the actuator via a clevis by a second pivot link, the opposite ends of the first arm and of the second arm being connected by a third pivot link, the pivot links having an entire axis of rotation perpendicular to the longitudinal axis.

Preferably, the actuator is a hydraulic cylinder comprising a cylinder secured to the shaft forming the fixed body of the actuator and a rod movable relative to the cylinder forming the movable body of the actuator.

Thus, the actuator is in a rotating frame along the longitudinal axis of the motor. The compass advantageously makes it possible to prevent the free rotation of the cylinder rod relative to the cylinder body and thus transforms the sliding pivot connection between the rod and the cylinder body into a sliding connection.

Thus, the invention allows the use of a passive flag return mechanism requiring a purely translating movement, like springs for example or like lever and cam counterweights.

The invention also makes it possible to simplify or de-constrain certain passive flag return mechanisms such as lever counterweight mechanisms or even lever and rack counterweights.

Also, since a compass is generally heavy, it can be used as a counterweight for a feathering mechanism, by positioning it in an area where there is room. Thus, it does not overload the blade root and blade root bearings unlike direct counterweights.

Advantageously, the pitch change system includes another compass, called an alternate compass, connecting the fixed body of the actuator to the mobile body of the actuator, the compasses being diametrically opposed. This second compass thus allows the unbalance that can be generated by the first compass.

Preferably, one of the pivot links of the substitute compass is mounted with a clearance or a flexible part in order to ensure operational safety redundancy, the second compass being able to replace the first compass in the event of failure of the latter while limiting the system hyperstatism. Thus, in the event of normal operation, only the first compass ensures the blocking of the rotation of the mobile body relative to the fixed body of the actuator.

By generalization, the control means comprises several substitute compasses connecting the fixed body of the actuator to the mobile body of the actuator, the compasses being regularly spaced around the cylindrical actuator.

Advantageously, the link mechanism comprises a synchronization ring integral with the moving body of the actuator and configured to drive the setting of the blades simultaneously and the system for changing the pitch of the blades comprises a device for feathering the blades, in particular in in the event of failure of the actuator of the control device, the feathering device comprising flyweights, each coupled to the synchronization ring and able, under the centrifugal effect, to be moved into a position in which said synchronization imposes a flag position on the blades.

Advantageously, the pivot links of the main compass are mounted with minimal play so that the mobile body moves relative to the fixed body without rotation.

Another object of the invention also relates to a fan module with variable-pitch blades for a propulsion assembly with a longitudinal axis, said module comprising a rotor carrying the blades and comprising an annular shaft and a system for changing the pitch of the blades according to the invention and as described above.

The invention also relates to a longitudinal axis propulsion assembly comprising such a fan module with variable-pitch blades or a system for changing the pitch of the blades according to the invention and as described above.

The present invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the description of a non-limiting example which follows, with reference to the appended drawings in which:

there , is an axial (or longitudinal) half-sectional view of a fan module comprising a blade pitch change system and a feathering system, in a first position, shown in the same plane as the axis rotation of a blade of the fan according to one embodiment;

there , is an axial half-sectional view of the fan module of the wherein the blade feathering device is in a second position;

there is a perspective detail view of a compass fitted to the pitch change system of the , And

there is an axial (or longitudinal) half-sectional view of a fan module comprising a blade pitch change system and a feathering system, in a first position, shown in the same plane as the axis of rotation of a blade of the fan according to another embodiment.

The elements having the same functions in the different implementations have the same references in the figures.

Claims (9)

System (22) for changing the pitch of the blades for a propulsion assembly (2) with a longitudinal axis (X), each blade (5) being pivotally mounted on a shaft of the propulsion assembly along a setting axis (Y), the system comprising a link mechanism (24) connected to each blade and a control means acting on the link mechanism, the control means comprising a cylindrical actuator (23) having a fixed body (27) and a movable body (25 ) integral in rotation with the shaft, the movable body being in translation relative to the fixed body, the actuator being arranged so as to move the link mechanism axially to cause the change in pitch of the blades,
characterized in that the control device comprises a compass (28), called main compass, connecting the fixed body (27) of the actuator to the movable body (25) of the actuator (23). Blade pitch change system according to claim 1, wherein the compass (28) comprises a first arm (29) one end (29A) of which is connected to the fixed body (27) of the actuator via a yoke (30) by a first pivot link (C1) and a second arm (31), one end (31A) of which is connected to the moving body (25) of the actuator via a yoke by a second pivot link (C2), the opposite ends (29B , 31B) of the first arm and of the second arm being connected by a third pivot link (C3), the first, second and third pivot links (C1, C2, C3) having an entire axis of rotation perpendicular to the longitudinal axis (X ). System for changing the pitch of the blades according to claim 1 or 2, in which the actuator (23) is a hydraulic cylinder comprising a cylinder integral with the shaft forming the fixed body of the actuator and a rod movable with respect to the cylinder forming the moving body of the actuator. System for changing the pitch of the blades according to one of claims 1 to 3, in which the control means comprises at least one other compass, called a substitute compass, connecting the fixed body of the actuator to the mobile body of the actuator, the compasses being regularly spaced around the cylindrical actuator. System for changing the pitch of the blades according to the preceding claim, in which one of the pivot links (C1, C2, C3) of the other substitute compasses is mounted with a clearance or a flexible part. Pitch change system according to any one of the preceding claims, in which the link mechanism (24) comprises a synchronization ring (34) integral with the movable body (25) of the actuator (23) and configured to drive the pitch of the blades (5) simultaneously and the system for changing the pitch of the blades comprises a feathering device (38) of the blades, in particular in the event of failure of the actuator (23), the feathering device ( 38) comprising flyweights (43) each coupled to the synchronization ring and able, under the centrifugal effect, to be moved into a position in which said synchronization ring (34) imposes a flag position on the blades. Pitch change system according to the preceding claim in combination with claim 2, in which the pivot links (C1, C2, C3) of the main compass are mounted with minimal play so that the movable body (25) moves relative to the fixed body (27) without rotation. Fan module with variable-pitch blades for a propulsion unit with a longitudinal axis (X), said module comprising a rotor (3) carrying the blades and comprising an annular shaft (10) and a pitch change system (22) of the blades (5) according to any one of the preceding claims. Longitudinal (X) axis propulsion assembly comprising a variable blade pitch fan module according to claim 8 or a blade pitch change system according to any one of claims 1 to 7.