Background of the invention
The present invention relates to the general field of compressors and aviation engine turbines (including aircraft or helicopter). It relates more precisely controlling the air inlet flap (IGV for Vanes Inlet Guides) gas turbine engine.
The IGV actuators are used to control the position of pre-rotation vanes located upstream of the compressor stages of the turbine engine helicopter (see for example US 2014/0286745). The function of this actuator is to direct the air flow entering the engine upstream of the compressor. The variation of the angular position of the pre-rotation blades to optimize the overall performance of the engine (Transitional and specific consumption).

The air inlet flap control function is usually provided by a hydraulic cylinder fed by the fuel system, the flow rate and pressure are directly indexed on the gas generator speed. Such an architecture, however, has many drawbacks.

First, because of their reversibility, current hydraulic cylinders are not "position memory" (also called fail-freeze), that is to say that in case of failure they do not hold the last controlled position. Then, these cylinders are designed for a wide range of pressure and flow, which, due to interactions with the fuel system, generates each call flow of real disturbances cylinder fuel dosing system. Indeed, the service pressure delta varies depending on the engine operating point (low delta P idling and high delta P at high speed). In addition, this oversizing has a significant impact on the weight of the engine and causes unnecessary heating fuel and indirectly unwanted power drain on the accessory box. Finally, these cylinders are not controllable in the case where the engine is in operation, which is particularly disadvantageous in the context of some daily maintenance operations, as endoscopies of the engine where the shutters must be moved without starting the engine, because it requires the use of an external power pack.

Known with the patent US7,096,657 of an air inlet control shutters by means of a redundant electrical actuator which may be either a DC brushless motor or an AC induction motor or variable reluctance. Or, use a brushless motor requires a particularly complex and restrictive control electronics of a point of view of electromagnetic compatibility and power involved are not sufficient in all flight conditions. Similarly, in case of short circuit of the variable reluctance motor or its control electronics, the braking torque generated by the short circuit is very low or even zero, which necessarily requires the use of an electric brake (energize-to -release-type brakes) external to freeze the last driven position. This information is indeed crucial if we are to move safely in a pilot mode degraded engine. It is the same with one or other of these two types of motor, in case of loss of power supply.

There is therefore a need today for controlling the air inlet shutters using a new actuator which does not exhibit the above constraints.

OBJECT AND SUMMARY OF THE INVENTION

The present invention therefore aims to overcome the above drawbacks by providing an efficient and optimized for the single actuator control function IGVS and also having a particularly secure behavior.

This object is achieved by an electrical actuator motor air inlet flaps gas turbine comprising a fixed part secured to a stationary portion of said motor and a movable part in mechanical connection with said input strands of air, characterized in that said electric actuator includes, regularly distributed on the periphery of said movable part and fixed to said fixed portion, the fixed electromagnets disposed between said fixed and mobile electromagnets electromagnets

each secured to opposite sides to first and second piezoelectric elements, said movable electromagnets and said first and second piezoelectric elements having a degree of freedom of movement relative to said movable portion.

With this new architecture electrical, structural oversizing of the prior art systems is eliminated and the fuel system can then be optimized independently of the control function IGVS.

Advantageously, the fixed part is a rotary actuator stator, the movable portion of a rotor rotary actuator and said degree of freedom of movement is a degree of freedom in rotation about an axis of rotation of said rotor.

Preferably, each piezoelectric element is formed of a series of N ceramics disposed in one or more layers.

Advantageously, said piezoelectric element comprises two superimposed layers of ten ceramics put in parallel.

Preferably, said fixed electromagnet is an integral portion of said stator of which they form an inner serration.

Advantageously, said fixed electromagnets are electrically connected in parallel to a first source of DC voltage DC1 and said movable electromagnets are electrically connected in parallel to a second source of DC voltage DC2.

Preferably, said DC voltage sources deliver two opposite signals.

Advantageously, said first piezoelectric element is electrically connected in parallel to a first alternating voltage source AC1 and said second piezoelectric element is electrically connected in parallel to a second alternating voltage source AC2.

Preferably, said alternating voltage sources deliver two sinusoidal voltages in phase opposition, characterized by the following relationships:

AC1 = A sin Gu (t) and AC2 = A sin (ω (ί) + n).

The invention also relates to a gas turbine engine comprising the at least one electric actuator.

Brief Description of Drawings

Other features and advantages of the present invention emerge from the description made below, with reference to the accompanying drawings which illustrate an embodiment having no limiting character. In the figures:

- Figure 1 is a schematic view of a gas turbine engine to which the invention is applied;

- Figure 2 shows a first example of an electric rotary actuator for controlling the air intake components of the motor of FIG 1 according to the invention;

- Figure 3 illustrates the various power supplies required for the operation of the actuator of Figure 2;

- Figures 4A-4D show the different stages of movement of the rotor of the actuator of Figure 2; and

- Figure 5 shows a second example of an electric linear actuator for controlling the air intake components of the motor of FIG 1 according to the invention.

Detailed Description of the Invention

Figure 1 schematically illustrates a gas turbine engine 10 typically includes a compressor 12, a combustor 14 and a turbine 16 for the drive motor of the blades (not shown). The input of the compressor 12 are arranged air inlet flaps (IGV 18) whose rotational movement is provided by one or more actuators (ACT 20) controlled from a central computer (FADEC 22) which also ensures the engine management and in particular the injection of gas at the combustion chamber.

According to the invention, the actuator of the air intake shutters is an electrical actuator which is in the form of the particular piezoelectric rotary motor shown in Figure 2.

The piezoelectric motor 100 includes a central rotor 102 surrounds an annular stator 104. The central rotor, advantageously perforated to a weight gain, is in fixed connection with the lever that actuates the air inlet flaps, the lever being in pivot connection with the motor housing when the stator is in fixed connection with a stationary part of the engine. Regularly distributed at the periphery of the rotor and mechanically fastened or glued to the stator, depending on the nature of the rotor material, magnetic body form with associated windings 106a -106h fixed electromagnets 108a - 108h positioned at regular intervals. The magnetic bodies may also be an integral part of the stator of which they form as an internal toothing.

Between these fixed electromagnets are arranged electromagnets 110a - Mobile HOH (each formed of magnetic body and associated coils 112a - 112h) each secured to both sides of a piezoelectric element 114a - 114h; 116a - 116h. Each piezoelectric element is formed of a series of ceramic disposed on one or more layers. In the illustrated example, which should not be considered limiting, the piezoelectric element comprises two superimposed layers of ceramic ten paralleled. The height of the one or more ceramic layers corresponds to that of fixed or movable magnetic bodies surrounding them, so that the inner face of these various constituents form one line of tangent contact with the central rotor 102. With this configuration, the mobile electromagnets 110a -HOh and the first and second piezoelectric elements 114a - 114h; 116a - 116h have a degree of freedom of rotational movement about the axis of the central rotor 102 without any friction between stator and rotor (due to the presence of a non-referenced gap), unlike a configuration piezoelectric motor of known type. This air gap associated with how to use the piezoelectric elements allows a counter of the main problems with this piezoelectric technology: the wear of the polymers on which adhere the piezoelectric components. By limiting / eliminating the friction increases the lifetime and availability of equipment, making it compatible with an aeronautical use.

Engine operation is now explained with reference to Figure 3 and Figures 4A to 4D which show the control signals and the corresponding displacement of the central rotor during an engine operating cycle.

As illustrated in Figure 4B, the fixed electromagnets 108a,

108b, 108c are electrically connected in parallel to a first

DC voltage source DC1 (curve 120 in Figure 3) and mobile electromagnets 110a, 110b are electrically connected in parallel to a second source of DC voltage DC2 (curve 122 in Figure 3), the sources DC1 and DC2 supplying signals opposed. The first piezoelectric element 114a, 114b is electrically connected in parallel to a first alternating voltage source AC1 (curve 124 in Figure 3) and the second piezoelectric 116a element 116b is electrically connected in parallel to a second source of AC2 alternating voltage (curve 126 in Figure 3). The AC voltage sources deliver two sinusoidal voltages of phase and are therefore characterized by the following relationships:

Then CS1 = ™ s (t) = A et CS2 that (™ s (t) + n)

To move the piezoelectric motor must supply the piezoelectric elements and the electromagnets defining four in two successive phases as follows:

Figure 4A shows the initial phase in which the fixed electromagnets 108a, 108b, 108c are traversed by a current (voltage source DC1 is positive) and thus maintain contact with the central rotor 102. The mobile electromagnets 110a, 110b are disabled (DC2 DC voltage source is at zero) and the first and second piezoelectric elements 114a, 114b; 116a, 116b are in the initial rest position.

4B, while the fixed electromagnets 108a, 108b, 108c through which a current, maintain contact with the central rotor 102, the first piezoelectric elements 114a, 114b is longer and the second piezoelectric elements 116a, 116b retract resulting in their movement elongation / simultaneous retraction (in the direction shown by the arrow) mobile electromagnets 110a, 110b unpowered (the DC voltage source DC2 is maintained at zero) to which they are attached.

In Figure 4C, the movement of extension / retraction of the piezoelectric elements is completed and the mobile electromagnets 110a, 110b are then fed (the voltage source DC2 is made positive) to maintain contact with the central rotor 102. Simultaneously , fixed electromagnets 108a, 108b, 108c are turned off (the DC voltage source DC1 is zeroed).

Figure 4D shows the last stage when the first piezoelectric elements 114a, 114b retract and the second piezoelectric elements 116a, 116b elongate to resume their original shape along with them the movable electromagnets 110a, 110b (in the direction illustrated by the arrow) and thus also the central rotor 102 on which they are held in contact. It is found with the rotation of the index 130, the actual rotation of the motor corresponding to a cycle of extension / retraction of the piezoelectric elements.

To operate the engine in reverse, reverse the direction of steering electromagnets or switch the phase difference between the first and second sources of AC voltage AC1 and AC2 so that the latter is ahead of the first.

Note that if the previous description has been made compared with a rotary engine configuration, it is clear that it was given as an example and a linear motor configuration may be equally suitable as shown in Figure 5.

Thus, such a linear piezoelectric motor 200 includes a movable portion 202 and a fixed portion 204. As in the previous embodiment, the movable part is in fixed connection with the lever that actuates the air inlet shutters and the movable part is in fixed connection with a stationary part of the engine. Regularly distributed at the periphery of the movable portion and fixed to the fixed portion, the magnetic body form with associated windings 206a - 206b fixed electromagnets 208a - 208b positioned at regular intervals. The magnetic bodies may also be an integral part of the fixed part. Between these fixed electromagnets are arranged electromagnets 210a - Mobile 210b (each formed of magnetic body and associated coils 212a - 212b) each secured to either side to a piezoelectric element 214a - 114b; 216a - 216b each formed of a series of ceramic disposed in one or more layers, the inner face of these various components forming a single line of tangent contact (a gap 218 near exaggeratedly enlarged for explanation purposes) with the movable part 202. With this configuration, the mobile electromagnets 210a - 210b and the first and second piezoelectric elements 214a - 214b; 216a - 216b have a degree of freedom

translational movement along the movable part 202, without any friction between stator and rotor.

Thus, with the invention, because of an electrical / mechanical direct conversion and share a simplified design of the control command, the weight gain is very important, the mass of the actuator (of the order of 500g) which can be reduced by a factor of 5 relative hydraulic actuator IGV weighing typically about 2500g.

In addition, the dynamic performance of a piezoelectric actuator are also much better: up to 200mm / s at full load (lOOdaN) against 8.5mm / s for a hydraulic actuator types RTM 322 and a gain in accuracy of a few micrometers (against + / -0,2mm on a RTM 322).

CLAIMS
1. An electric actuator motor air inlet flaps gas turbine comprising a stationary part (104, 204) secured to a stationary portion of said motor and a movable part (102, 202) mechanically connected to said flaps air inlet, characterized in that said electric actuator (100, 200) includes, regularly distributed on the periphery of said movable part and fixed to said fixed portion, the fixed electromagnets (108a - 108h; 208a - 208c) and electromagnets disposed between said fixed mobile electromagnets (110a - HOH; 210a -210c) each secured to opposite sides to first (114a - 114h; 214a - 214c) and second (116a, 116h; 216a, 216c) piezoelectric elements , said movable electromagnets and said first and second piezoelectric elements having a degree of freedom of movement relative to said movable portion.

2. An electric actuator according to claim 1, wherein the fixed part is a rotary actuator stator (104), the movable part a rotor rotary actuator (102) and said degree of freedom of movement is a degree of freedom in rotation about an axis of rotation of said rotor.

3. An electric actuator according to claim 1 or claim 2, wherein each piezoelectric element is formed of a series of N ceramics disposed in one or more layers.

4. An electric actuator according to claim 3, wherein said piezoelectric element comprises two superimposed layers of ceramic ten paralleled.

5. An electric actuator according to claim 3 or claim 4, wherein said fixed electromagnets constitute an integral portion of said stator of which they form an inner serration.

6. An electric actuator according to any one of claims 1 to 5, wherein said stationary electromagnets are electrically connected in parallel to a first voltage source

continuous DC1 and said movable electromagnets are electrically connected in parallel to a second source of DC voltage DC2.

7. An electric actuator according to claim 6, wherein said direct voltage sources deliver two opposite signals.

8. The electric actuator according to any one of claims 1 to 5, wherein said first piezoelectric element is electrically connected in parallel to a first alternating voltage source AC1 and said second piezoelectric element is electrically connected in parallel to a second AC voltage source AC2.

9. An electric actuator according to claim 8, wherein said alternating voltage sources deliver two sinusoidal voltages in phase opposition, characterized by the following relationships:

AC1 = A sin Gû(t) et AC2 = A sin (a>(t)+ n).

10. A gas turbine engine comprising at least an electric actuator according to any one of claims 1 to 9.