WO2010072911A1

WO2010072911A1 - Aircraft propulsion equipment with an improved reduction gear transmission device

Info

Publication number: WO2010072911A1
Application number: PCT/FR2009/001421
Authority: WO
Inventors: Richard Wilby
Original assignee: Airbus
Priority date: 2008-12-22
Filing date: 2009-12-14
Publication date: 2010-07-01
Also published as: FR2940361B1; FR2940361A1

Abstract

The invention relates to propulsion equipment for an aircraft, including a first rotary body (6) referred to as a driving body, a second rotary body (1) referred to as a driven body, and a reduction gear transmission device (19) disposed between the driving body and the driven body, characterised in that the reduction gear transmission body (19) includes a first surface (22), referred to as a driving transmission surface, rigidly connected to the driving body (6), a second surface (23), referred to as a driven transmission surface, rigidly connected to the driven body (1), said driving and driven transmission surfaces being opposite each other with an electrorheological fluid (24) between said driving and driven transmission surfaces, and in that the aircraft propulsion equipment includes means (30, 31) for generating an electric field in said electrorheological fluid (24).

Description

Aircraft power plant with improved reducer transmission

The present invention relates to the technical field of aeronautics, and more particularly to aircraft power plants, such as for example turbofan engines and counter-rotating propellers. The invention more specifically relates to an aircraft power plant comprising a first body, a second body and a gear reduction transmission device between these two bodies.

A counter-rotating propeller comprises two coaxial propellers rotating in opposite directions. These two propellers, described here respectively as first and second bodies, are generally driven by the same engine. To this end, a gearbox gearbox transmission device is provided between the two propellers.

A turbofan engine usually comprises: an air inlet, a combustion chamber and a combustion gas ejection nozzle providing propulsion;

a high-pressure body comprising a high-pressure turbine downstream (with respect to the direction of flow of air and gases) of the combustion chamber and a high-pressure compressor driven by said turbine upstream of the combustion chamber;

a low-pressure body comprising a low-pressure turbine downstream of the high-pressure turbine and a low-pressure compressor (which may be a simple fan or comprise a fan and one or more stages of blades of smaller diameter) upstream of the high-pressure compressor; pressure, which low pressure compressor is driven by the low pressure turbine,

a nacelle delimiting the air intake and completely surrounding the high pressure and low pressure bodies,

- A central casing inserted into the nacelle and surrounding including the high pressure body and a downstream part of the low pressure body. The flow of air admitted into the air inlet is thus divided between a primary air flow through the entire engine (low pressure compressor, high pressure compressor, combustion chamber, high pressure turbine and low pressure turbine). and a secondary air stream which, after passing through at least one upstream portion (blower) of the low pressure compressor, is diverted into a annular channel defined by the nacelle and the central casing to be ejected by the ejection nozzle with the hot gases (primary flow) out of the low pressure turbine.

Certain turbojet engines, known as triple-body turbojet engines, also include a third body incorporating the large-diameter blower. The compressor of the low pressure body of these reactors is reduced to one or more stages of blades of smaller diameter than that of the blower. This third body is coupled to the low-pressure body by means of a transmission gearbox type transmission device. The third body is thus rotated by the low pressure body but at a different speed. The interposition of a gearbox between the low pressure body and the blower makes it possible to provide a rotational speed of the low-pressure body greater than that of the blower, thus increasing the maximum potential rotation speed of the low-pressure body and to thereby increase the energy extracted from the hot gas stream by the turbine. It is also possible, because of this energy gain, to reduce the number and / or the diameter of the vanes of the low pressure compressor and / or the low pressure turbine. The mass of the power plant and its maintenance costs are reduced accordingly. At the same time, the speed of rotation of the fan can now be reduced, it is possible to use larger diameter blowers and thus increase the dilution ratio of the turbojet engine (ratio between the flow rate of the secondary flow and that of the primary flow ). The interposition of a gearbox between the low pressure body and the blower has thus made it possible, by improving the efficiency of the turbojet engines, to significantly reduce (between 10 and 15%) the fuel consumption.

In return, the use of gearboxes has significantly increased the costs of manufacturing and maintenance of power plants. Given the driving powers to be transmitted, in constant growth, these gearboxes are indeed subject to significant mechanical and thermal constraints, which require the use of materials and effective surface treatments and to provide manufacturing tolerances and very weak mounting. Despite these precautions, known gearboxes tend to wear out quickly. These problems will become crucial for future generations of power plants, which will have to transmit powers two to three times higher than those currently transmitted.

Furthermore, the performance of known power plants are limited by the problems of stall and pumping. The term "stall" used for a compressor refers to the separation of air streams from the surface of the compressor blades. It generates pumping, that is to say an inverted circulation of air in the compressor. These phenomena occur when the pressure ratio between the outlet and the compressor inlet exceeds a threshold value, called the pumping pressure ratio. Compressors, and in particular low-pressure compressors, known power plants are usually designed to preserve a pumping margin, defined as being the difference between the pumping pressure ratio and a maximum operating pressure ratio -which can operate the compressor-. This pumping margin limits the performance of the power plant and it is therefore desirable to provide the lowest possible. In return, it is necessary to implement means to quickly return to a normal situation, for example by a sudden decrease in the mass of air passing through the compressor, when pumping occurs. For this purpose, the known compressors comprise variable-pitch stator blades, which make it possible to abruptly reduce the speed of rotation of the compressor (and therefore the mass of air) when necessary. These blades have the disadvantage of burdening the manufacturing and maintenance costs of the compressors and increasing their mass.

In this context, the invention aims to propose a power plant equipped with a more efficient gear transmission device, which induces lower manufacturing and / or maintenance costs than known gearboxes while being able to transmit safely. significant power-and especially powers far superior to those transmitted by gearboxes known-.

Another object of the invention is to propose a motor installation of mass lower than that of known motor installations. In a preferred version, the invention also aims at proposing a turbojet engine power plant in which the stall and pumping problems are solved with a compressor, and in particular a low pressure compressor, of mass and cost lower than those of the installations. known. To do this, the invention proposes an aircraft power plant comprising a first rotary body said driving body, a second rotary body said coφs led, and a gear reducer between the driving body and the driven body. It is characterized in that: - the reducing transmission device comprises

a first surface, said driving transmission surface, integral with the driving body,

a second surface, said transmitted transmission surface, integral with the driven body, said driven and driven transmission surfaces facing each other,

an electrorheological fluid between these driving and driven transmission surfaces,

the aircraft powerplant comprises means for generating an electric field in the electrorheological fluid. In the usual way, the term "electrorheological fluid" denotes a fluid whose rheological properties vary as a function of the intensity of the electric field to which it is subjected. In particular, the viscosity of such a fluid increases with the intensity of the electric field: in the absence of an electric field, the fluid is thus generally comparable to a lubricating oil; subjected to a high electric field, it becomes almost solid. These properties result from the composition of the electrorheological fluid: the latter comprises conductive particles suspended in an insulating fluid. Under the effect of the electric field, the conductive particles organize themselves by forming kinds of fibers parallel to the electric field, which increase the viscosity of the fluid and its resistance to shear.

The reducer transmission device according to the invention is much less subject to wear than the known gearboxes, the elements providing the transmission in this device not being in direct metal-to-metal contact. The maintenance costs of the power plant according to the invention are lower. In addition, the reducer transmission device according to the invention has a mass less than that of known gearboxes (gold mass is a major limiting factor in the field of aeronautics).

The power plant according to the invention may be a triple-body and double-flow turbojet engine. In this case, the driving body is advantageously a body low pressure comprising a turbine and preferably also a compressor, and the driven body is a fan body, the reducing transmission device being arranged between an upstream end of a shaft of the low pressure body and a downstream end of a shaft of the blower body. Advantageously, the reducing transmission device of the aircraft power plant according to the invention comprises means for controlling the generated electric field, able to modify the intensity of said electric field.

It is therefore possible to modulate the ratio, said transmission ratio, between the speed of rotation of the driven body and the speed of rotation of the driving body. This modulation can be performed in particular according to environmental conditions such as the altitude or the outside air temperature, and / or operational conditions such as the flight phase. This possibility is not offered by known gearboxes, which provide a fixed transmission ratio. When the power plant is a turbojet engine, it is also possible to reduce or even cancel the speed of rotation of the fan during the take-off and landing phases in order to limit the noise generated by the turbojet engine (which is largely due to the fan) and the resulting noise pollution for residents located near the airport. Apart from the take-off and landing phases, the transmission ratio is preferably adjusted so as to minimize fuel consumption. If necessary, the transmission ratio can be modified for example to provide greater thrust.

The possibility of acting independently on the rotation speeds of the driving and driven bodies is also useful in the case of a go-around or missed approach. The transmission ratio may advantageously initially be low to limit the inertia of the assembly formed by the low pressure body and the blower and thus obtain a rise in power of the low pressure body (driving body) faster. This ratio can then be increased gradually as the rotation speed of the low pressure body increases, in order to accelerate the blower (driven body). The response time of the power plant in case of go-around or missed approach is thus reduced.

In general, the independent adjustment of the speeds of rotation of the driving and driven bodies allows rapid changes in rotation speeds, which not only confers greater responsiveness to the power plant but also allows, in the case of a turbojet, to solve the pumping problems of the low pressure compressor. As explained above, when stalling and / or pumping phenomena occur in the low pressure compressor, a sudden decrease in the rotational speed of said compressor (and thus the mass of air passing through it) makes it possible to return to a situation normal. This objective is achieved with fixed vanes (whose manufacturing and maintenance costs are lower than those of the variable-pitch vanes of the previous compressors), thanks to the reduction transmission device according to the invention. To reduce abruptly the speed of rotation of the low pressure compressor in a turbojet according to the invention, it is sufficient to increase the transmission ratio abruptly by a sudden increase in the electric field in order to transmit the inertia of the fan ( which rotates at lower speed) to the low pressure body. The invention thus extends to a method for counteracting a phenomenon of stalling and / or pumping in a turbojet engine power plant according to the invention. According to this method, in response to detecting the realization of a condition reflecting the fact that a stall and / or pumping phenomenon has occurred or is about to occur, the electric field control means generated control means for generating the electric field so as to increase sharply the intensity of the generated field. This method can be implemented alone or in addition to known methods. It can for example be coupled, if necessary, to a sudden reduction in the fuel injection rate to reduce the speed of rotation of the high pressure body. Advantageously, the electric field generation means are integrated in the gear reducer, so that the operation of the gear transmission device is independent of the electrical sources of the aircraft out of the starting phase of the power plant. Preferably, these means for generating the electric field comprise a generator with permanent magnets comprising an armature secured to the driving body and an inductor integral with the driven body.

In the case of a turbojet engine or a counter-rotating propeller, the two bodies (driving and driven) are rotatably mounted substantially around the same axis of rotation. Advantageously, each of the driving transmission surfaces and conducted is performed by a plurality of trays extending substantially substantially orthogonal to said axis of rotation, the driving trays (trays of the driving transmission surface) being arranged alternately with the led trays (trays of the driven transmission surface) and separated from each other by the electrorheological fluid.

Advantageously, each led or driven plate has a section, in any plane containing the axis of rotation, which is sinusoidal or serrated, in order to increase the contact surface of the plate with the electrorheological fluid. Preferably, the reducing transmission device comprises a sealed envelope accommodating the trays and the electrorheological fluid. Advantageously, said envelope is integral with one of the bodies and the integral plates of the same body are carried by the envelope while the integral plates of the other body are carried by a shaft of said other body. Advantageously, the electrorheological fluid has a thermal conductivity which increases with the intensity of the electric field. The thermal energy generated by the transmission is partly absorbed by the electrorheological fluid. The fact that the fluid has an increasing conductivity with the electric field makes it possible to absorb a larger part of the thermal energy generated precisely when this is important (the larger the field, the higher the transmitted torque and the higher the significant shear, and the more the transmission is exothermic). This property of the electrorheological fluid makes it possible to avoid heating of the transmission surfaces.

Advantageously, the power plant further comprises one or more of the following characteristics:

- The electric field control means comprises a transmission control unit mounted on the driven body;

- the power plant includes a motor control unit mounted on a fixed part of the installation; - The power plant comprises data communication means between the engine control unit and the control unit of the transmission, which data communication means comprise an annular antenna. This annular antenna preferably comprises, on the one hand, an emitter comprising a conductive strip formed on a fixed annular portion of the power plant, and secondly a receiver comprising a conductive strip formed on a generally annular portion - necessarily rotating and preferably projecting - of the led body extending opposite and in proximity (but without contact ) of the fixed annular portion; - The power plant comprises activatable means for electrical connection between the reducer transmission device and an electrical network of a fixed part of the power plant, these activatable means of electrical connection being adapted to transmit a power supply current when they are activated, - preferably, these activatable means of electrical connection comprise a conductive strip formed in an annular groove formed in the driven body, and a movable contactor carried by a fixed part of the power plant and movable between a position retracted in which it is not in contact with the conductive strip when the electrical connection means are not activated, and an extended position in which it is in mechanical and electrical contact with said conductive strip when the electrical connection means are activated ,

the conductive strip of the activatable means of electrical connection and the conducting strip forming the receiver of the annular antenna are advantageously one and the same band,

the activation of the electrical connection means is controlled by an emergency control unit,

- The control means of the generated electric field are adapted to, on receipt of an emergency signal (for example issued by the engine control unit), cancel the electric field and redirect the current produced by the magnet generator permanent to the activatable means of electrical connection for the supply of this current to the electrical network. Therefore, in the event of an electrical problem in the power plant (or possibly in another part of the aircraft, depending on the operating conditions), the permanent magnet generator may serve as a backup generator, the driven body being for this purpose decoupled from the driving body so as to turn freely, under the effect of wind. The invention thus extends to a method of supplying an emergency electric current in the event of a malfunction in a power plant according to the invention, in which: activatable means of electrical connection are activated (this activation can be initiated automatically by the engine control unit in response to the detection of a malfunction, or initiated manually by the crew of the aircraft ), The control means of the generated electric field control the means for generating the electric field so as to cancel the generated field and thus decouple the driven body from the driving body, and redirect the current produced by the permanent magnet generator to the network electric via the activatable means of electrical connection; - The control means of the generated electric field are adapted for, at the start of the power plant, bypass the permanent magnet generator and generate an electric field from a current transmitted by the electrical network via the activatable means of electrical connection. In this case, the activatable means of electrical connection are thus used to transmit a supply current to the reducer transmission device while the permanent magnet generator does not yet produce enough current (due to a still too slow rotation of the leading body). The invention thus extends to a method of starting a power plant according to the invention, in which: the activatable means of electrical connection are activated

(this activation can be initiated automatically by the engine control unit in the context of a starter module or be initiated manually by the crew of the aircraft),

the control means of the generated electric field control the means for generating the electric field so as to generate a field from a current transmitted by the electrical network via the activatable means of electrical connection; if necessary, to do this, the control means of the generated electric field bypass the permanent magnet generator; the current transmitted by the electrical network can come from a park generator for example;

- In the case of a turbojet, at least a portion of the gear reducer device is accessible and preferably can be extracted from the power plant by removing a blower pan and optionally a removable central disc of a hub of the blower . Of Preferably, the transmission control unit can be extracted from the power plant by removing only the blower pan, and the permanent magnet generator and an excitation module can be removed from the power plant by removing moreover, the central disk of the hub of the fan.

The present invention extends to an aircraft comprising at least one powerplant according to the invention.

The invention also relates to a power plant characterized in combination by all or some of the characteristics described above and below. Other details and advantages of the present invention will appear on reading the following description, which refers to the attached schematic drawings and relates to preferred embodiments, provided as non-limiting examples. On these drawings:

FIG. 1 is a diagrammatic view in longitudinal section of a power plant according to the invention, of the turbojet type,

FIG. 2 is a schematic view in longitudinal section of a reduction transmission device of the power plant of FIG. 1,

FIG. 3 is a diagrammatic sectional view of an upstream part of the power plant of FIG. 1, on which two views of details are reported, one in longitudinal section and the other in perspective,

- Figure 4 is a block diagram of electronic means of the power plant of Figure 1.

FIG. 1 illustrates a power plant according to the invention, of the triple-body and double-flow turbojet engine type, mounted or intended to be mounted in an aircraft. This turbojet engine includes:

- A fan body 1, which forms a first rotating assembly rotating at a speed of rotation denoted Nf, which fan body comprises in particular a fan shaft 2, a fan 3, a hub 4 through which the fan 3 is mounted on the fan. blower shaft 2, a blower pan 5,

a low-pressure body 6, which forms a second rotary assembly rotating at a rotation speed denoted N1, which low-pressure body comprises in particular a low-pressure shaft 7, a low-pressure compressor 8, a low-pressure turbine 9, a high-pressure body 10, which forms a third rotary assembly rotating at a rotation speed denoted N2, which high-pressure body comprises in particular a high-pressure shaft 11, a high-pressure compressor 12, a high-pressure turbine 13; combustion 14 and fuel injectors 15,

a fixed casing 16 surrounding the low pressure and high pressure bodies,

a fixed fan support nacelle 17 surrounding in particular the fan 3 and forming an air inlet 18 upstream of said fan,

a gas ejection nozzle (fixed), not shown,

a reducing transmission device 19 between the low-pressure body 6 and the blower body 1. It should be noted that the blower bodies, the low-pressure body and the high-pressure body all rotate around the same axis of rotation rotation of the motor.

The reducing transmission device 19 comprises (see FIG. 2) a transmission housing 20 comprising an envelope 21, driving plates 22, led plates 23 and an electrorheological fluid 24 filling the envelope 21.

The casing 21 is integral with the low pressure body 6, so that it is rotated at the same rotation speed N1 as this one. To this end, it has an extension 25 forming a splined coupling sleeve, fitted on the upstream end - also fluted - of the low pressure shaft. The envelope 21 serves to contain the electrorheological fluid 24 and must as such be sealed to said fluid. Moreover, the envelope 21 carries the driving trays 22 as explained below.

The electrorheological fluid 24 is chosen as a function of the range of viscosities and / or shear strengths, the specific gravity (mass) and the desired thermal stability. For example, the electrorheological fluid 24 may be composed of polyaniline particles suspended in a pine oil. The polyaniline particles have appropriate mechanical and electrical properties in view of the intended application and are, moreover, non-abrasive, which limits the wear of trays 22 and 23. Pine oil is a good choice in terms of environment. The electrorheological fluid obtained advantageously offers a high shear strength as opposed to its shear rate. The leading trays 22 and led 23 are housed in the casing 21, so that they are immersed in the electrorheological fluid 24. The leading and driven trays extend substantially orthogonal to the axis of rotation of the engine. They are arranged alternately: a leading plate 22 succeeds to a led plate 23 and vice versa. The trays are spaced apart from each other so that two successive trays are separated by a layer of electrorheological fluid. The distance between two successive trays is optimized according to a desired transmission ratio range and expected accelerations and decelerations. The driving plates 22 are integral with the low pressure body 6: they are carried by the casing 21 and extend radially centripetally from the peripheral inner face of said casing. The driven plates 23 are integral with the fan body 1: they are carried by the fan shaft 2 and extend radially centrifugally from said fan shaft. They thus transmit directly to the fan shaft 2 the torque that they receive from the driving plates 22 via the electrorheological fluid 24. For this purpose, the fan shaft 2 comprises a downstream member 26 which extends into the housing 21 and whose upstream fluted end receives the downstream end - also fluted - of a main member 27 of the fan shaft. The downstream member 26 of the fan shaft and the casing 21 are separated by bearings 28, so that the casing and the fan shaft are freely rotatable relative to each other.

Each driving plate 22 or led 23 has, in any plane containing the axis of rotation of the motor, a serrated or sinusoidal section. This characteristic makes it possible to increase the contact area between each plate and the electrorheological fluid, and thus the mechanical exchange surface by shearing between them. It therefore makes it possible to limit the diameter of the transmission housing 20. The front faces of the driving plates 22 form a surface called said driving transmission surface, while the front faces of the driven plates 23 form a surface called said transmission surface.

In order to further increase the torque that can be transmitted between trays via the electrorheological fluid, it is possible to provide, in each front face of each plate, grooves (not shown) extending radially from the center of the plate to its periphery along a curved path. The grooves formed on two faces opposite one another in successive trays are advantageously oriented in opposite directions: the fluid being guided by the grooves, it is constrained in opposite directions between the two successive trays, which increases the shear forces generated and therefore the maximum transmissible torque. The driven trays 23 are made of an electrically conductive material, for example metallic, in order to be used, as explained below, to generate an electric field inside the envelope 21. The driving trays 22 are in a material permeable to the electric field, for example metallic. The electric field generated inside the envelope determines the viscosity of the electrorheological fluid 24 and therefore the shear strength that this fluid opposes. The stronger the electric field, the more the electro-rheological fluid is viscous and the higher the transmission ratio, defined as the ratio between the rotational speed Nf of the blower body (i.e. trays driven) on the rotation speed N1 of the low-pressure body (ie driving trays) is large. When the intensity of the electric field drops, the viscosity of the electrorheological fluid decreases and the blower body 1 is driven at a lower speed relative to that of the low pressure body 6.

The electric field is generated by means of generating an electric field belonging to the reducing transmission device. These means comprise a generator 30 with permanent magnets and an excitation module 31. They are controlled by means of control of the generated electric field comprising a control unit of the transmission 29.

The generator 30 with permanent magnets comprises a rotor 32, carried the fan shaft 2 and carrying permanent magnets 33. These rotor 32 and magnets 33 constitute the inductor of the generator. The permanent magnet generator further comprises a sleeve 34 integral with the low-pressure body 6 and freely rotatable with respect to the rotor 32; Although rotating, this sleeve is called the stator of the permanent magnet generator. This stator 34 carries coils 35 and 36. The stator 34 and the coils 35, 36 constitute the armature of the permanent magnet generator. In operation, the rotor 32 and the stator 34 rotate at different speeds (Nf for the rotor and N1 for the stator), so that a current is induced in the coils 35, 36. The coils 36 are dedicated to the supply of the control unit of the transmission 29, while the output current of the windings 35 is used for the supply of the excitation module 31. The latter current is modulated under the control of the control unit of the transmission before being delivered to the excitation module.

The excitation module 31 comprises a rotor 37 carried by the fan shaft 2, and a sleeve 38, said stator, integral with the low-pressure body 6 and freely rotatable with respect to said rotor 37. The stator 38 of the module excitation circuit carries one or more windings 39 receiving the modulated current (current produced by the permanent magnet generator and then modulated by the control unit of the transmission). This modulated current is used to control the electric field generated inside the envelope 21. For this purpose, the rotor 37 of the excitation module carries three windings forming three phases, and three silicon rectifiers or other diodes, powered by said phases (all of these elements being very schematically represented and identified by the reference 40). The three rectifiers convert the received alternating current into a direct current, which is supplied to the transmission housing 20. More precisely, this direct current is led to the conducted plates 23 via electrical cables 41 housed in the fan shaft 2 (hollow) As shown in FIG. 2, an electric field whose intensity depends on the current modulated by the transmission control unit is thus established between the trays inside the envelope 21. Preferably , the stator 34 of the permanent magnet generator and that of the excitation module 38 are constituted by a single piece. As previously explained, this part is part of the rotating body of the low pressure body 6. Its upstream end is freely rotatably mounted in the hub 4 of the fan, using bearings 42. Because of the bearings 28 and 42, the transmission of a torque between the low-pressure body 6 and the blower body 1 takes place only at the level of the driving plates 22 and led 23 and the electrorheological fluid 24.

To facilitate maintenance, the control unit of the transmission 29 is fixed against an upstream face of the hub 4 of the fan, using a support 43, and is accessible by removing the pan 5 of blower. The various components of the transmission control unit, which are mounted on one or more printed circuit boards, are therefore subjected, in operation, to significant centrifugal forces. In order to guarantee their electrical connection to said cards, they are advantageously contained by a rigid surface coating applied to the cards.

The control unit of the transmission 29 is electrically connected to the generator 30 with permanent magnets and the excitation module 31, via a connector 44 which passes through the hub 4 of the fan at its center and cables 67 (symbolized only on Figure 4) housed in the fan shaft 2. In normal operation and out of the start-up phase of the turbojet engine, the transmission control unit 29 is supplied by the permanent magnet generator 30 via these cables 67 and connector 44. The hub 4 comprises a removable central disc 45 which, when it is removed, leaving an opening through which the permanent magnet generator 30, the excitation module 31 and the fan shaft 2 can be removed from the turbojet engine (the fan shaft is then extracted from the envelope 21 ). This arrangement facilitates maintenance operations, which is all the more appreciable that the generator 30 with permanent magnets and the excitation module 31 constitute the least reliable elements of the reducing transmission device.

The control unit of the transmission 29, mounted on the hub 4 of the fan, is controlled by a motor control unit 46 (see Figures 1 and 4), which is preferably carried by the nacelle 17 of the fan. Note that this engine control unit 46 performs all the usual control functions necessary for the operation of a turbojet engine. In addition to these known functions, this motor control unit 46 controls the control unit of the transmission 29, in order to adjust the transmission ratio according to the environmental and operational conditions, to prevent stalling and / or pumping phenomena. , and to decouple the fan from the rest of the engine in case of failure or damage in the low pressure or high pressure body.

The control signals transmitted by the motor control unit 46 to the transmission control unit 29 are driven by high-speed data buses 47 arranged inside the nacelle 17 of FIG. The control signals are then transmitted between the casing 16-fixed and the fan body 1 -rotative- by an annular antenna 48. This annular antenna comprises on the one hand an annular transmitter 49 consisting of a copper conductor strip formed on an upstream annular lip 51 (leading edge) of the casing 16. The annular lip 51 and the transmitter 49 have, in any plane containing the axis of rotation of the motor, a convex profile. The annular antenna further comprises a receiver 50, which comprises first and foremost a conductive strip 59 of copper formed on reinforcements 52, provided on the downstream face (trailing edge) at the mid-length of the blades of the fan 3 in order to limit the oscillation of the latter. These reinforcements 52 extend opposite the annular lip 51 of the housing, at a distance from the latter. Preferably, the blower 3 is designed so that these reinforcements are in contact from one blade to the next. Given the relative flexibility of the blades, and in order to guarantee a good electrical contact in all conditions between the conductive strip portions formed on the different blades of the fan, the receiver 50 comprises in the second place metallic connections (not shown) of the tongue and mortise type (or groove and tongue) between each blade and the following blade, in the extension of the conductive strip portions. The receiver 50 advantageously has, in any plane containing the axis of rotation of the engine, a concave profile enveloping the convex profile of the transmitter

49 so that a certain proximity (but without mechanical contact) is guaranteed between the receiver and the transmitter. This concave profile is advantageously identical over the entire circumference of the receiver 50, both at the level of the conductive strip 59 and metal links between blades, for the reasons mentioned below. The control signals thus transmitted from the transmitter 49 to the receiver

50 are then led to the control unit of the transmission 29 by data buses 53 at high speed, housed in each blade of the fan 3. If the fan is made of composite material based on carbon fibers, said buses 53 are preferably embedded in the expanded foam core of said material. The fan 3 also includes (in one of its blades) an emergency power supply cable 54, which connects the control unit of the transmission 29 to the conductive strip 59 which constitutes the receiver 50. In case of failure the transmission control unit 29 isolates the permanent magnet generator 30 from the excitation module 31 and redirects the current produced by the said generator towards the cable 54. Simultaneously, an emergency control unit of the aircraft 55 (see also FIG. 4), preferably mounted on the nacelle 17 of a fan, activates a rocking solenoid 56 housed inside the aircraft. the annular lip 51 of the housing. The solenoid 56 deploys a piston 57 which engages a graphite contactor 58 in the previously described receiver 50. The contactor advantageously has a convex profile which, when the piston 57 is not deployed and that the switch is in a retracted position, follows the profile of the annular lip and which, when the piston and therefore the contactor are deployed, guarantees the establishment of a sliding mechanical and electrical contact between the contactor 58 and the conductive strip 59. The piston 57 incorporates a spring or any equivalent means for damping, on the one hand the shock experienced by the switch 58 during its deployment and its contact with the conductive strip 59, and secondly the vibrations transmitted to the contactor 58 due to the rotation of the fan 3. The current produced by the permanent magnet generator is thus provided to the unit emergency control 55, via the emergency power cable 54, the conductive strip 59, the contactor 58, the piston 57, the solenoid 56 and the distribution son 60. These elements make mo yens activatable electrical connection between the generator 30 to permanent magnets and a fixed electrical network of the turbojet engine (including the emergency control unit). The emergency control unit 55 uses this current in the event of an electrical emergency to power an essential bus 64 of the aircraft, as explained below.

The functional electronic diagram of the turbojet engine is illustrated in FIG. 4. The motor control unit 46 communicates with the transmission control unit 29 via the data buses 47, the antenna 48 and the data buses 53 previously described (which provide data communication means between the engine control unit and the transmission control unit). A speed sensor 61 provides the engine control unit 46 with a measurement of the rotational speed Nf of the fan, while a speed sensor 62 provides a measurement of the rotational speed N1 of the low pressure body, for real-time calculation of the transmission ratio. Usually, the engine control unit integrates thrust management functions of the turbojet engine. In this context, it receives, from a thrust management module 63 via a data bus 69, commands from the joystick gases (not shown) or the power lever (not shown) of the dashboard.

As previously mentioned, in the event of an electrical emergency, the emergency control unit 55 has the particular function of activating the essential bus 64 in response to a command signal sent by an electric charge management system 65 via discrete digital interfaces 66.

At the start of the turbojet engine, the transmission control unit 29 is powered by a bus bar 68 of the aircraft, itself powered by a starter connected to a generator set (on the ground) or to an auxiliary power unit. of the aircraft (not shown). The link between the bus bar 68 and the transmission control unit 29 is achieved via the contactor 58, which is deployed on command of the engine control unit 46. When starting the turbojet, the control unit of the transmission 29 thus directly feeds the excitation module 31, thus shunting the generator 30 with permanent magnets. When the low-pressure body 6 begins to rotate, the rotational speed of the armature of the permanent magnet generator 30, which is carried by the casing 21 and is therefore integral with the low-pressure body, is necessarily greater than that of the inductor integral with the blower body 1. The permanent magnet generator 30 then begins to generate an alternating current. However, as long as this current is insufficient to satisfy the needs of the gear reducer device, the transmission control unit 29 continues to directly supply the excitation module 31 with the electric energy supplied by the starter . The electric field generated by the direct current supplied by the excitation module 31 causes an increase in the viscosity of the electrorheological fluid 24 which makes it possible to progressively accelerate the coφs of the fan 1. As the motor accelerates, the current produced by the permanent magnet generator 30 increases (the rotation speed N1 of the low-pressure body increases more rapidly than the rotational speed Nf of the blower body). When the difference between the speeds N1 and Nf is sufficient, the motor control unit 46 emits a disconnection signal from the contactor 58, which causes the piston 57 to retract. The control unit of the transmission 29 is thus isolated from the bus bar 68 and the current produced by the generator 30 with permanent magnets is used to supply the excitation module 31 as well as the control unit of the transmission 29. Permanent and self-sustaining is established, defined by a constant difference between the rotational speeds N1 and Nf, a constant electric field in the electrorheological fluid 24, and a constant transmission ratio.

When the engine is accelerated to a take-off speed, the engine control unit 46 selects the most appropriate transmission ratio depending on environmental conditions (outside air temperature in particular) and operating conditions (weight of the engine). the aircraft, take-off distance available ...), so as to obtain maximum thrust while respecting the local requirements in terms of noise. Note that the authorized level of noise can be selected by the crew of the aircraft and relayed to the engine control unit via the thrust management module 63 via the data bus 69. 3 blower being responsible for the majority of the noise generated by the turbojet, a low level of noise requires to limit the rotation speed Nf of the blower. Gold ₁ in a turbojet engine with a high dilution ratio, 75% of the thrust is provided by the secondary flow and therefore by the fan. In prior known turbojet engines, the transmission ratio being fixed, the selection of a low noise level (limitation of the speed of rotation of the fan) therefore results in a proportional limitation of the speed of rotation of the low pressure body. ; the turbojet engine operates in reduced thrust, which can be problematic. In the turbojet according to the invention, a limitation of the rotational speed Nf of the blower can be compensated by an increase in the rotation speed N1 of the low-pressure body and a subsequent adjustment of the temperature of the compressed gases and the energy extracted from the hot gas stream. The transmission ratio is thus advantageously adjusted so that the rotational speed Nf of the blower body is compatible with the authorized noise level (within the limit of the maximum peripheral speed supported by the blades of the blower) and in such a way that the rotation speed N1 of the low pressure body is optimized in order to obtain maximum thrust. An optimum transmission ratio is thus calculated by the control unit of the motor 46 and transmitted to the control unit of the transmission 29, which consequently modulates the current delivered to the excitation module 30. For example, a decrease of this current causes a decrease in the generated electric field, in the viscosity of the electrorheological fluid 24 and therefore in the speed of Nf rotation of the blower.

Similarly, in the approach phase, in response to a corresponding selection of the crew, the engine control unit 46 can program a reduction in the rotational speed Nf of the blower body while maintaining rotational speeds. N1 of the low pressure body and N2 of the high pressure high body. This makes it possible to limit the noise generated by the turbojet while maintaining a high reactivity which may prove useful in the event of a missed approach.

When the relative speed between the blower body and the low pressure body decreases, for example if the blower body 1 is accelerated relative to the low pressure body 6, the current produced by the permanent magnet generator 30 also decreases. The control unit of the transmission 29 can then be made to modulate the current delivered to the excitation module 30 so as to maintain the latter and the subsequent electric field at constant levels. This modulation ensures that the transmitted torque does not decrease when the relative speed between the blower body and the low pressure body decreases.

In case of damage or failure in the low-pressure body or in the high-pressure coφs (rupture and / or loss of a blade, fire, locked rotor ...), a significant divergence between the rotation speeds N1 and N2 on the one hand and the fuel flow on the other hand is detected by the engine control unit 46, which is likely to be undamaged since it is mounted on the nacelle 17 of the fan. The motor control unit 46 then sends the transmission control unit 29 an emergency signal via the data buses 47 and 53 (and the antenna 48). The transmission control unit 29 electrically isolates the excitation module 31 from the permanent magnet generator 30, while the motor control unit 46 transmits a discrete signal corresponding to the emergency control unit 55, which triggers the deployment of the contactor 58. The excitation module 31 is no longer supplied, the electric field becomes zero and the electrorheological fluid 24 goes into a state of minimal viscosity. The blower body 1, uncoupled from the low pressure body 6, is freewheeling. This makes it possible to reduce the inertia which opposes the flow of primary air in the low pressure and high pressure bodies, and to avoid jamming of the fan. The control unit of the transmission 29 then connects the output of the permanent magnet generator 30 to the emergency power cable 54, which transmits the current produced by the generator to the emergency control unit 55 via the contactor 58 and the distribution wires 60. The emergency control 55 thus receives an alternating current of variable frequency. Optionally, it may be provided that the emergency control unit comprises a semiconductor switching and interrupt circuit capable of transforming the received variable frequency current into a 400Hz alternating current. This current (whether stabilized in frequency or not) is then transmitted to the bus bar 68 of the aircraft (whose supply, previously provided by a normal generator, could be interrupted by the damage). Depending on the nature of the damage, the emergency control unit 55 may also redirect this current (in whole or in part) to the essential bus 64 of the aircraft. Although having a priori a production capacity lower than that of a so-called normal generator, the generator 30 with permanent magnets is suitable, in such a configuration where the fan is in freewheel and where the low pressure body is blocked, broken or rotates at low speed, to produce a current sufficient for the operation of the main technical loads of the aircraft. If necessary, the electric charge management system 65 interrupts the power supply of certain commercial loads in order to optimize the available electrical capacity. The possibility of using the permanent magnet generator as a backup generator in this way is particularly appreciable in the case of a military aircraft, the turbojet engines of which are likely to suffer damage in combat.

The invention may be subject to numerous variations with respect to the illustrated embodiment, provided that these variants fall within the scope delimited by the claims.

For example, the power plant according to the invention may alternatively be a counter-rotating propeller.

Claims

1. Aircraft engine installation comprising a first rotary body (6) said coφs driving, a second rotary body (1) said driven body, and a gear transmission device (19) between the driving body and the driven body, characterized in the reduction transmission device (19) comprises a first surface (22), said driving transmission surface, integral with the driving body (6), a second surface (23), said driven transmission surface, integral with the driven body ( 1), said driving and driven transmission surfaces facing each other, an electrorheological fluid (24) between said driving and driven transmission surfaces, and that the aircraft power plant comprises means (30, 31) for generating an electric field in the electrorheological fluid (24).

2. Aircraft power plant according to claim 1, characterized in that the gear transmission device (19) comprises means (29) for controlling the generated electric field, able to change the intensity of said electric field.

3. Aircraft engine installation according to one of claims 1 or 2, characterized in that the electric field generation means are integrated in the gear transmission device (19) and comprise a generator (30) with permanent magnets comprising a armature (34-36) secured to the driving body (6) and an inductor (32, 33) integral with the driven body (1).

4. Aircraft power plant according to one of claims 1 to 3, characterized in that the two bodies (1, 6) are rotatably mounted substantially about the same axis of rotation, and in that each of the surfaces of driven (22) and driven (23) transmission is performed by a plurality of trays (22, 23) extending substantially substantially orthogonal to said axis of rotation, the driving trays (22) being arranged alternately with the trays (23) led and separated from each other by the electrorheological fluid (24), each tray having a section, in any plane containing the axis of rotation, which is sinusoidal or serrated.

5. Aircraft power plant according to claim 4, characterized in that the reducing transmission device comprises a sealed envelope (21) accommodating the plates (22, 23) and the electromagnetic fluid. rheological (24), in that said envelope is integral with one of the bodies (6), and in that the plates (22) integral with this same body are carried by the envelope (21) while the plates ( 23) secured to the other body (1) are carried by a shaft (2) of said other body.

6. Aircraft engine installation according to one of claims 1 to 5, characterized in that the electrorheological fluid has a thermal conductivity which increases with the intensity of the electric field.

7. Installation according to one of claims 1 to 6 and according to claim 2, characterized in that: - the electric field control means comprise a transmission control unit (29) mounted on the body (1) led ,

the power plant comprises an engine control unit (46) mounted on a fixed part of the installation,

the power plant comprises data communication means between the motor control unit (46) and the transmission control unit (29), which data communication means comprise an annular antenna (48), which annular antenna comprises an emitter (49) comprising a conductive strip formed on a fixed annular portion (51) of the power plant and a receiver (50) comprising a conductive strip (59) formed on a generally annular portion 52 of the driven body extending opposite and near the fixed annular portion (51).

8. Powerplant according to one of claims 1 to 7, characterized in that the power plant comprises activatable means (54, 58, 59, 60) for the electrical connection between the reducer transmission device and an electrical network (55 , 64, 68) of a fixed part of the power plant, these activatable means of electrical connection being adapted to transmit a supply current when they are activated.

9. Powerplant according to claim 8, characterized in that said activatable means of electrical connection comprise a conductive strip (59) formed in an annular groove in the driven body, and a movable contactor (58) carried by a fixed part of the power plant and movable between a retracted position in which it is not in contact with the conductive strip when the electrical connection means are not activated, and an extended position in which it is in contact mechanical and electrical with said conductive strip when the electrical connection means are activated.

10. Powerplant according to one of claims 8 or 9 and according to claims 2 and 3, characterized in that the means (29) for controlling the electric field generated are adapted for receiving an emergency signal, canceling the electric field and redirecting the current produced by the permanent magnet generator (30) to the activatable means of electrical connection for the supply of this current to the electrical network (55, 64, 68).

11. Power plant according to one of claims 8 to 10 and according to claims 2 and 3, characterized in that the means (29) for controlling the electric field generated are adapted for, at the start of the power plant, to implement deriving the permanent magnet generator (30) and generating an electric field from a current transmitted by the electrical network via the activatable means of electrical connection.

12. Powerplant according to one of claims 1 to 11, characterized in that it is a triple-body turbojet and dual flow, and in that the driving body is a low pressure body (6) to turbine and compressor and the driven body is a fan body (1), the reduction transmission device (19) being arranged between an upstream end of a shaft (7) of the low pressure body and a downstream end of a shaft ( 2) the blower body.

13. Powerplant according to claim 12, characterized in that at least a portion (29, 30, 31) of the gear reducer (19) is accessible and can be extracted from the power plant by removing a pan (5). ) of a fan and a central disk (45) removable from a hub (4) of the fan.

14. Aircraft characterized in that it comprises at least one powerplant according to one of claims 1 to 13.