Protection for a circuit for controlling the orientation of propeller blades of an aircraft engine, allowing the orientation of these blades to be locked

Abstract

The invention relates to a hydraulic control circuit (17) for actuating a double-acting orientation cylinder (21) for orienting blades (3) of a propulsion propeller of an aircraft engine, said double-acting cylinder (21) comprising a first and a second chamber (18, 19), and the circuit (17) comprising: - a high-pressure pipe (23) and a low-pressure pipe (24); - a distributor valve (26) for connecting the first chamber (18) to the high-pressure pipe (23) and the second chamber (19) to the low-pressure pipe (24), or vice versa, or for isolating the two chambers (18, 19) from the high-pressure and low-pressure pipes; - a controlled valve (36) arranged between the first chamber (18) and the distributor valve (26), and controlled by a high-pressure control line (37), so as to be locked in a closed state in the event of a drop in pressure in the high-pressure control line (37).

Description

[0001] DESCRIPTION

[0002] TITLE: Protection for aircraft engine propeller blade orientation control circuit for locking the orientation of these blades

[0003] TECHNICAL FIELD

[0004] The invention relates to an aircraft engine comprising variable-pitch blades making it possible to control and / or reverse the thrust generated by this engine, and it relates to protection to prevent, in the event of failure of the control system, accidental thrust reversal when the aircraft is in flight.

[0005] STATE OF THE PRIOR ART

[0006] In a turboprop aircraft engine with variable pitch, air passes through a propeller or fan having a series of rotating blades or vanes, i.e. with variable pitch.

[0007] The orientation of these rotating blades around their span axis, which extends radially relative to the engine's rotational axis, can be changed in flight, so that such an engine can provide thrust reversal using the variable-pitch propeller blades or vanes.

[0008] In this case, the blades can occupy a propulsion orientation so that the engine generates thrust directed towards its downstream direction, and a so-called thrust reversal orientation, in which it generates thrust directed towards its upstream direction, the latter being intended to be used only when the aircraft is on the ground to decelerate it.

[0009] In practice, propulsion orientations are usually referred to as large pitches, and thrust reversal orientations are referred to as small pitches.

[0010] The transition from the propulsion orientation to the thrust reversal orientation is typically achieved by rotating the blades through 90°, with the orientation control generally being provided by a hydraulic circuit. Several failures can lead to a drift of the pitch in flight towards the thrust reversal position. This may be a failure of the pitch control unit, i.e. a computer controlling the hydraulic circuit, or a failure of the hydraulic circuit itself.

[0011] In this context, a protection system integrated into the hydraulic circuit ensures that the blades cannot switch to the thrust reversal orientation when the aircraft is, for example, in cruising flight, such protections being described in patent documents FR2981684A1, FR2978953A1, FR2985284A1 and FR3014153A1.

[0012] Thus, when it is detected that the blades are or are approaching a thrust reversal orientation while the engine is in flight configuration, the protection is activated to act on the hydraulic circuit so that it returns them to a propulsion orientation.

[0013] This type of protection can be implemented in an unducted turboprop or open rotor engine with a contra-rotating twin propeller, or in a ducted engine such as a turbojet with variable pitch fan blades.

[0014] The aim of the invention is to provide a passive protection solution constituting an alternative to existing solutions.

[0015] STATEMENT OF THE INVENTION

[0016] To this end, the invention relates to a hydraulic control circuit for actuating a double-acting orientation cylinder for orienting blades of an aircraft engine propulsion propeller, this double-acting cylinder comprising a first and a second chamber, this circuit comprising:

[0017] - a high pressure line and a low pressure line;

[0018] - a distributor valve for connecting the first chamber to the high pressure line and the second chamber to the low pressure line or vice versa, or for isolating the two chambers from the high pressure and low pressure lines; characterized in that:

[0019] - it comprises a controlled valve interposed between the first chamber and the distributor valve; - this controlled valve is controlled by a high pressure control line connected to the high pressure pipe to be blocked in the event of a drop in pressure in the high pressure control line and to be open in the event of sufficiently high pressure in the high pressure control line.

[0020] With this arrangement, a drop in pressure in the hydraulic circuit immediately blocks the orientation of the propeller blades, passively.

[0021] The invention also relates to a circuit thus defined, in which the high pressure control line is connected to the high pressure pipe by a blocking valve capable of occupying a deactivated state in which it places the high pressure control line in communication with the high pressure pipe, and an activated state in which it places the high pressure control line in communication with the low pressure pipe.

[0022] The invention also relates to a circuit thus defined, comprising a blocking solenoid valve which controls the blocking valve, and a computer controlling this blocking solenoid valve.

[0023] The invention also relates to a circuit thus defined, in which the blocking solenoid valve is arranged to control the blocking valve in order to activate it when this blocking solenoid valve is not electrically powered by the computer.

[0024] The invention also relates to a circuit thus defined, in which the double-acting cylinder is carried by an element rotating with the blades of the propulsion propeller, the upstream and downstream pipes being connected to the chambers of this cylinder by a hydraulic transfer bearing, in which the controlled valve is interposed between the cylinder and the hydraulic transfer bearing, and in which the high-pressure control line is connected to the controlled valve via the hydraulic transfer bearing.

[0025] The invention also relates to a circuit thus defined, in which the controlled valve comprises a blocking member capable of coming to bear on a seat or of being spaced from this seat to be either in a blocked state or in a passing state, a return spring tending continuously to press the blocking member onto the seat, a piston subjected to the pressure of the control line while being rigidly secured to the blocking member, the pressure of the control line acting on the piston against the return spring to tend to move the blocking member away from the seat.

[0026] The invention also relates to an aircraft engine comprising a circuit thus defined.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] [Fig. 1] is a longitudinal sectional view of a bypass turbojet engine;

[0029] [Fig. 2] is a view along the span axis of a propulsive propeller blade having a propulsive orientation;

[0030] [Fig. 3] is a view along the span axis of a pusher propeller blade having a thrust reversal orientation;

[0031] [Fig. 4] is a schematic view of the control circuit according to the invention;

[0032] [Fig. 5] is a sectional view of a valve operated in the open state;

[0033] [Fig. 6] is a sectional view of a controlled valve in the closed state.

[0034] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0035] In an aircraft engine such as engine 1 in Figure 1, air is admitted into an inlet sleeve 2 located upstream AM to pass through the blades 3 of a propeller, called a fan and comprising a series of rotating blades, before splitting into a central primary flow and a secondary flow surrounding the primary flow. These two flows circulate in its longitudinal direction AX, from upstream AM to downstream AV of this engine when it generates propulsion thrust.

[0036] The primary flow is admitted into an air intake 4 located downstream of the fan and extending around the longitudinal axis AX, to then be compressed in low pressure 5 and high pressure 6 compressors before arriving in a combustion chamber 7. This primary flow is then expanded in a high pressure turbine 8 and a low pressure turbine 9 before being evacuated downstream. The secondary flow is propelled directly downstream by the fan in a vein delimited externally by a nacelle 11 carrying the entire engine.

[0037] Such a double-body engine comprises a so-called low-pressure body by which the fan is coupled to the low-pressure turbine 9, and a so-called high-pressure body by which the high-pressure compressor 6 is coupled to the high-pressure turbine 8, these two bodies being coaxial and independent in rotation. These bodies are surrounded by a set of casings 12 succeeding one another along the longitudinal axis which they surround.

[0038] In Figure 3, a variable-pitch fan blade 3 has a lower surface face and an upper surface face extending between a leading edge 14 and a trailing edge 16. This blade 3 extends along a span axis EV radial to the axis AX, from a root by which it is secured to a rotor element, to a tip which is its free end located opposite the internal face of the nacelle 11.

[0039] The blade pitch angle is the angle between the chord axis Ac, which passes through the leading edge 14 and the trailing edge 16 extending in a plane normal to the axis EV, and the plane PS of the propeller which is normal to the axis AX. In the following, when such a pitch angle has a positive value, it corresponds to a propulsion downstream of the air flow in which the rotating blade is immersed, that is to say a propulsion direction. A negative value corresponds to a propulsion of the air flow upstream.

[0040] In Figure 3, the blade 3 occupies a propulsion orientation, corresponding for example to a so-called cruising regime: the chord axis Ac is inclined by a positive pitch angle Ce relative to the plane PS.

[0041] In the configuration corresponding to a propulsion orientation of Figure 3, the pitch angle of the blade 13 is positive, so that by being driven in rotation in the direction marked by R in the figures, it propels the air flow from upstream AM to downstream AV. The direction of rotation R corresponds to the clockwise direction when looking at the propeller along the axis AX, from the front, that is to say from its upstream AM.

[0042] This blade is of the variable pitch type: its orientation around the axis

[0043] EV is adjustable according to the engine operating conditions. In the situation of Figure 3, the orientation of the blade 13 corresponds to engine operation in propulsion, that is to say in which the flow F passing through the engine is propelled from upstream AM to downstream AV.

[0044] In the thrust reversal phase, for example when the aircraft is landing and the engine is used to brake it, the propeller blades are commanded to change their orientations. They then pivot around their span axes, to move from the propulsion orientation corresponding to Figure 3, to the thrust reversal orientation corresponding to the situation shown in Figure 4.

[0045] In the example of Figures 2 and 3, the blade pivots in the forward direction to change from the propulsion orientation to the thrust reversal orientation, so that its leading edge is downstream of its trailing edge at the thrust reversal orientation. When changing from one orientation to the other, the blade passes through a transient position called 0° in which its chord axis passes through the PS plane of the propeller. It is important that the blade remains in this transient position for a short time, which can cause engine overspeed.

[0046] It is also possible to provide a different configuration, in which the blade rotates in the opposite direction to pass from the propulsion orientation to the thrust reversal orientation, its trailing edge then remaining upstream of its leading edge when it is in the thrust reversal orientation. When passing from one orientation to the other, the blade passes through a so-called feathered position in which its chord axis is parallel to the axis AX.

[0047] In Figure 4, a hydraulic circuit 17 ensures the pressurization of a first upstream chamber 18 or a second downstream chamber 19 of a double-acting orientation cylinder 21 acting on the longitudinal position of a pitch setting device. This makes it possible to maintain the propeller blades at a predetermined pitch angle by maintaining this pitch setting device at a given position and to modify the pitch angle by moving this device.

[0048] This cylinder 21 is carried by the pitch setting device which rotates with the blades of the propeller which it carries, being powered by the control circuit which is carried by fixed elements of the engine, thanks to a hydraulic transfer bearing 22 surrounding the pitch setting device.

[0049] This circuit 17 comprises a high pressure supply line 23 supplied by a pump 25, and a low pressure return line 24 opening into a tank not shown.

[0050] The supply 23 and return 24 lines are connected to the cylinder 21 via a three-position distributor valve 26, comprising a central neutral position corresponding to that which it occupies in Figure 4, as well as a pitch increase position and a pitch reduction position.

[0051] This distributor valve 26, which is here a distributor slide, is connected to the upstream chamber 18 by an upstream pipe T1 and by the bearing 22, and it is connected to the downstream chamber 19 by a downstream pipe 28 and by the bearing 22.

[0052] In the neutral position of Figure 4, the pipes 23 and 24 are isolated from the chambers 18 and 19, which are at pressures of intermediate value between high pressure and low pressure, the blades 3 of the propeller therefore having their orientation angle immobilized at a fixed value.

[0053] When the distributor valve 26, which is here a distributor slide, is placed in its pitch increase position, that is to say offset to the right with respect to its position in Figure 4, and the valve 36 is open, this distributor valve puts the upstream chamber 18 into communication with the high pressure supply pipe 23, and the downstream chamber 19 into communication with the low pressure return pipe 24. This has the effect of moving the rod of the cylinder 21 to the right in Figure 4, to increase the pitch angle Ce of the blades 3 in order to place them in a propulsion orientation.

[0054] When the distributor valve 26 is in its pitch reduction position as in Figure 5, that is to say offset to the left with respect to its position in Figure 4, and the valve 36 is open, this valve connects the upstream chamber 18 with the return pipe 24, and the downstream chamber 19 with the high pressure pipe 23. This has the effect of moving the rod of the cylinder 21 to the left in Figure 4 to reduce the pitch angle Ce of the blades 3 in order to place them in a thrust reversal orientation. The circuit 17 incorporates a protection system so that the blades 3 cannot accidentally reach a thrust reversal orientation while the aircraft is in flight. It comprises a protection solenoid valve 31, an amplification valve 32, as well as a first protection valve 33 and a second protection valve 34.

[0055] When the two protection valves 33 and 34 are deactivated, the position of the cylinder 21, and therefore the angle of the blades 3, is governed by the distributor valve 26, which makes it possible to increase or decrease the angle of these blades 3, as indicated above.

[0056] If a drift in the orientation of the blades towards their thrust reversal orientation is detected, the FADEC computer electrically controls the protection solenoid valve 31 in order to activate the amplification valve 32, and thereby the protection valves 33 and 34.

[0057] When the two protection valves 33 and 34 are activated, the upstream chamber 18 is pressurized and the downstream chamber 19 is depressurized, which moves the rod of the cylinder 21 to the right in the figures to return the pitch angle of the blades 3 to a propulsion orientation.

[0058] According to the invention, the controlled valve 36 is interposed between the first chamber 18 and the distributor valve 26, and this valve 36 is controlled by a high pressure control line 37 to be blocked in the event of a drop in pressure in the line 37.

[0059] Thus, in the event of a pressure drop in the high-pressure circuits, the valve 36 switches to a blocked state, i.e. non-passing, so as to prevent the first chamber 18 from emptying, to immobilize the cylinder in order to lock the pitch of the blades so as to prevent them from switching to a thrust reversal orientation.

[0060] The valve 36 is controlled passively by the pressure of the hydraulic circuit, so that in the event of a drop in this pressure, this valve 36 closes, in order to immediately lock the blade pitch angle so that it does not drift under the effect of the aerodynamic forces to which the blades are subjected. In practice, and as illustrated in Figure 4, this controlled valve 36 is similar to a pressure-controlled non-return valve. It comprises a return spring which is compressed by the pressure of its control line 37 when this pressure is sufficient. When this pressure becomes insufficient, the spring pushes the movable element of the valve, so as to lock it in a closed state.

[0061] The high pressure control line 37 is supplied by the high pressure pipe 23 which is advantageously equipped with a blocking valve 38 controlled by a blocking solenoid valve 39 which can be actuated by the FADEC computer which is the engine computer. The valve 38 is advantageously a double-way valve, which can be in a deactivated state in which it puts the line 37 in communication with the high pressure pipe 23, or in an activated state in which it puts the line 37 in communication with the low pressure pipe 24.

[0062] With this arrangement, if an abnormal variation in the orientation of the blades, or another anomaly, is detected, the FADEC computer commands the blocking solenoid valve 39 to activate the valve 38 in order to drop the pressure in the control line 37. In this case, the control pressure of the valve 36 drops so that it closes to lock the orientation of the blades at their current value.

[0063] In practice, the airflow incident on the blades tends to place them in the thrust reversal position if there is no pressure in the chambers of the cylinder 21. Thus, by preventing the chamber 18 from emptying in the event of a loss of pressure in the pipe 23, the blades are prevented from approaching their thrust reversal position. This is how the orientation of the blades is locked.

[0064] The FADEC computer can thus act to lock the blade pitch to their current orientation in the event of detection of an anomaly such as a servo control failure or deterioration of the hydraulic circuit seal.

[0065] The computer can also be used to perform a self-test of the sealing of the first chamber, for example at startup or just before stopping the engine. In this case, the engine is running at ground idle speed, and the computer controls the blocking of the valve 36 while monitoring the orientation of the blades, so that in this situation, the detection of a drift in the orientation of the blades is significant of a sealing defect in the first chamber 18.

[0066] The blocking solenoid valve 39 is advantageously configured to activate the blocking valve if it is not electrically powered by the FADEC computer, which makes it possible to lock the pitch in the event of an electrical failure at the level of this computer.

[0067] As illustrated in Figure 5, the controlled valve 36 is located between the first chamber 18 and the hydraulic transfer bearing 22, so as to ensure that even in the event of a leak at the transfer bearing 22, the blocking of this controlled valve 36 makes it possible to ensure locking of the pitch of the blades.

[0068] In this context, the control line 37 is connected to the valve 36 via the transfer bearing 22, in the same way that the upstream T1 and downstream 28 pipes are connected to the first and second chambers via this same transfer bearing 22. In other words, the transfer bearing 22 ensures the transfer of three hydraulic channels.

[0069] The controlled valve 36 which is symbolized in Figure 4 by a non-return valve connected to line 37 is advantageously of the type illustrated in Figure 5. It comprises a blocking member 41 housed in a main channel 42 while being located opposite a seat 43, so that the valve is open when the member 41 is spaced from the seat 43, and it blocks or closes the main channel when this member 41 is resting on the seat.

[0070] The member 41 is continuously returned by a spring 44 to its locking position, and it is extended by a rod 46 passing in a sealed manner through the main channel and the end of which carries a piston 47 subjected to the pressure of the control line 37 which is exerted against the return spring. The assembly formed by the member 41, the rod 46 and the piston 47 is a rigid whole constituting the moving assembly of the valve.

[0071] As will be understood, when the pressure in the control line is sufficiently high, it moves the member 41 away from its seat 43 so that the valve is open. Conversely, when the pressure in the control line becomes insufficient with respect to the stiffness of the spring 44, the member 41 comes to bear on the seat 43 under the effect of the spring 44, so that the valve then becomes blocked.

[0072] In the example of the figures, the invention is implemented on a turbojet engine equipped with variable-pitch fan blades, but it can be implemented in an unducted engine of the turboprop type or of the “open rotor” type with a contra-rotating double propeller.

Claims

CLAIMS 1. Hydraulic control circuit (17) for actuating a double-acting orientation cylinder (21) for orienting blades (3) of an aircraft engine propulsion propeller, this double-acting cylinder (21) comprising a first and a second chamber (18, 19), this circuit (17) comprising: - a high pressure line (23) and a low pressure line (24); - a distributor valve (26) for connecting the first chamber (18) to the high pressure line (23) and the second chamber (19) to the low pressure line (24) or vice versa, or for isolating the two chambers (18, 19) from the high pressure and low pressure lines; characterized in that: - it comprises a controlled valve (36) interposed between the first chamber (18) and the distributor valve (26); - this controlled valve (36) is controlled by a high pressure control line (37) connected to the high pressure pipe (23) to be blocked in the event of a drop in pressure in the high pressure control line (37) and to be open in the event of sufficiently high pressure in the high pressure control line (37).

2. Circuit according to claim 1, in which the high pressure control line (37) is connected to the high pressure pipe (23) by a blocking valve (38) capable of occupying a deactivated state in which it puts the high pressure control line (37) into communication with the high pressure pipe (23), and an activated state in which it puts the high pressure control line (37) into communication with the low pressure pipe (24).

3. Circuit according to claim 2, comprising a blocking solenoid valve (39) which controls the blocking valve (38), and a computer (FADEC) controlling this blocking solenoid valve (39).

4. Circuit according to claim 3, in which the blocking solenoid valve (39) is arranged to control the blocking valve (38) in order to activate it when this blocking solenoid valve (39) is not electrically powered by the computer (FADEC).

5. Circuit according to one of the preceding claims, in which the double-acting cylinder (21) is carried by an element rotating with the blades of the propulsion propeller, the upstream and downstream pipes (27, 28) being connected to the chambers (18, 19) of this cylinder (21) by a hydraulic transfer bearing (22), in which the controlled valve (36) is interposed between the cylinder (21) and the hydraulic transfer bearing (22), and in which the high-pressure control line (37) is connected to the controlled valve (36) via the hydraulic transfer bearing (22).

6. Circuit according to one of the preceding claims, in which the controlled valve (36) comprises a blocking member (41) capable of coming to bear on a seat (43) or of being spaced from this seat (43) to be either in a blocked state or in a passing state, a return spring (44) tending continuously to press the blocking member (41) on the seat (43), a piston (47) subjected to the pressure of the control line (37) while being rigidly secured to the blocking member (41), the pressure of the control line acting on the piston (47) against the return spring (44) to tend to move the blocking member (41) away from the seat (43).

7. Aircraft engine comprising a circuit according to one of the preceding claims.

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