WO2004080557A1

WO2004080557A1 - Device for modifying the thrust orientation of an aircraft rotor, particularly for a model helicopter

Info

Publication number: WO2004080557A1
Application number: PCT/FR2004/000480
Authority: WO
Inventors: Jean-Marie Piednoir
Original assignee: Jean-Marie Piednoir
Priority date: 2003-03-04
Filing date: 2004-03-02
Publication date: 2004-09-23
Also published as: FR2851932A1

Abstract

The invention relates to a device which is used to modify the thrust orientation of an aircraft rotor. According to the invention, the aforementioned rotor consists of: a rotary assembly comprising two blades (20) which are connected by a hub (30); a rotary support on which the hub can be mounted, such that it can be oriented around a swivel axis in order to modify the angle of incidence of the blades; and a drive shaft which is used to rotate the aforementioned rotary support. The inventive device also comprises at least one permanent magnet which is solidly connected to the rotary assembly and at least one coil (60) which is fixed in relation to the frame of the aircraft and which is disposed such as to create a magnetic field that interacts with the magnet when supplied with an electric current. Said field generates a torque on the permanent magnet, which enables the rotary assembly to be rotated around the swivel axis and the angle of incidence of the blades to be modified.

Description

The present invention relates to devices making it possible to modify the orientation of the thrust of an aircraft rotor, in particular of a model of a helicopter. 'a helicopter. The invention is directed more particularly but not exclusively to the field of aeromodelling and to radio-controlled small helicopters whose main rotor is driven in rotation by an electric motor. The rotor of these helicopters has two blades connected by a hub which can freely pivot around an axis of rotation perpendicular to that of the drive shaft. To exert a torque on this assembly in order to act on the incidence of the blades as a function of the desired lateral and longitudinal cyclic pitches, the rotor is provided with a Bell bar, which has paddles at its ends. The incidence of the latter is controlled by connecting rods secured, by means of ball joints, to an upper swash plate. This rests on a bearing carried by a lower swashplate, the orientation of which, relative to the axis of the drive shaft, can be modified by means of two servomotors. Such a control device is relatively complex and makes radio controlled helicopters fragile, expensive, and complex to build.

It is also known on an experimental basis to modify the orientation of the blades of a rotor by means of piezoelectric actuators arranged between the blades and the hub. These actuators require an electrical current supply by rotary contacts, which can pose reliability problems.

International application WO 03/080433 published after the priority date from which the present invention benefits describes a device comprising a micromotor rotating with the rotor. Such a device requires rotating contacts which affect reliability and complicate manufacturing.

International application WO 02/070094 describes a device comprising a coil arranged to exert a force directed axially on a magnet. Such a device requires the use of a mechanism to transform the axial movement of the magnet into a pivoting of the blades. This application also describes an alternative embodiment in which the rotor carries a coil. This variant requires rotating contacts, which is not desirable. There has long been a need to simplify the devices making it possible to modify the orientation of the thrust of the rotor, in particular to allow large-scale commercialization at low cost of radio-controlled helicopters.

The object of the invention is therefore, according to a first of its aspects, a device making it possible to modify the orientation of the thrust of an aircraft rotor, this rotor comprising:

a rotary assembly comprising at least one blade connected to a hub, in particular at least two blades connected by a hub,

- a rotary support on which the hub can be mounted with a possibility of orientation around a pivot axis so as to modify the angle of incidence of the blades,

a rotation drive shaft of said rotary support, this device further comprising:

- at least one permanent magnet secured to the rotary assembly, - at least one coil arranged so as to create, when powered by an electric current, a magnetic field interacting with the magnet, so as to create a torque making it possible to rotate the rotary assembly around the pivot axis and to modify the angle of incidence of the blades.

The coil is fixed relative to a chassis of the aircraft. The coil creates on the magnet (s) the torque allowing the angle of incidence of the blades to be modified.

The invention makes it possible to manufacture a rotor having a particularly simple structure and to control the incidence of the blades without using a servomotor; the reliability of the rotor is thereby considerably increased and its price reduced. In addition, the invention makes it possible to manufacture a lighter radio-controlled helicopter, therefore with more autonomy or less dangerous to use.

The invention makes it possible in particular to avoid the use of rotary contacts, which increases reliability.

The device according to the invention may comprise one or more coils and the coil or coils used may comprise a core of magnetic material, if necessary, in order to channel the field lines. This or these coils can be fixed relative to a chassis supporting the motor used to drive the drive shaft in rotation. In the case of the use of a single coil, this preferably has an axis substantially parallel to that of the drive shaft.

In the case of the use of several coils, these preferably have axes substantially parallel to a plane perpendicular to the axis of the drive shaft. These coils can in particular have axes, preferably substantially intersecting, forming between them angles of 90 ° in the case of the use of two or four coils or of 120 ° in the case of the use of three coils. More coils can be used if necessary.

In a particular embodiment, the device thus comprises four coils associated in pairs, two coils of the same pair having substantially the same axis, the angle between the axes of the two pairs being substantially 90 °. Two coils of the same pair define between them a space in which said at least one permanent magnet can be arranged, so as to be exposed to the magnetic field created by the coils. Two coils of the same pair are advantageously electrically connected together in series so that the magnetic fields are added.

The reel (s) can be fixed on a support crossed by the drive shaft, this support comprising for example a section of tube, which can serve as accommodation if necessary for at least one bearing, for example ball, to the inside which the drive shaft is mounted. This support can be secured to a chassis on which is fixed at least one electric motor for driving the rotor.

When several coils are used, these can be supported by the same part, which can be produced for example by molding of plastic material or any other non-magnetic material. This part can comprise, in an exemplary embodiment, a central annular part traversed by the drive shaft and at its periphery teeth each serving as a core for a coil. The teeth may be, if necessary, terminated at the end opposite to the annular central part by a coil retaining head. These coils can be wound directly on the teeth. As a variant, the teeth can receive prefabricated coils. The coils can be fixed to the teeth by any known means, for example by gluing or, in the case of a plastic part, by bouteroUage the end of the teeth. The coils can also be fixed on the teeth by snap-fastening, for example. The coil (s) can comprise, for example, between 50 and 1000 turns, being produced with enameled wire whose diameter can for example be between 0.03 and 0.2 mm.

The hub can be arranged so as to allow the attachment of at least one magnet with the polar axis thereof oriented substantially perpendicular to the axis of the drive shaft when the blades are neutral, this is ie when the rotor generates a thrust in a direction substantially parallel to the axis of the drive shaft. Such an arrangement of said at least one magnet may be preferred when using a coil whose axis is substantially parallel to that of the drive shaft, preferably being coincident with the latter. Said at least one magnet can then be housed inside the coil. As a variant, two magnets arranged outside the coil, for example substantially at the mid-length thereof, may be used.

In another particular embodiment, the hub can be arranged so as to allow the fixing of at least one magnet with the polar axis of this magnet substantially parallel to that of the drive shaft. Such an arrangement can be used in particular when the device comprises a coil whose axis is substantially coaxial with the drive shaft and that the magnet or magnets are external to the coil, and in particular that two magnets are used placed at the above it eccentrically.

When the device comprises several coils whose axes are not parallel to that of the drive shaft, the hub may be arranged so as to allow the fixing of said at least one magnet with the polar axis of the latter substantially parallel to the axis of the drive shaft when the blades are neutral. Such an arrangement of said at least one magnet is particularly suitable for the use of at least two coils having their axes substantially perpendicular to that of the drive shaft or for the use of two pairs of coils, as indicated below. above.

The support on which the hub is mounted may include a yoke inside which the hub is at least partially engaged.

In a particular embodiment, the rotor comprises two magnets arranged with a spacing between them to allow the passage of an axis by which the hub is articulated on the yoke.

In another particular embodiment, the support comprises a tube in which is engaged an axis by which the hub is articulated on the support. The hub can then include, for example, two magnets on one side, these magnets being eccentric relative to the drive shaft and located above a coil coaxial with the drive shaft.

In yet another embodiment, the support is arranged to allow snap-fastening of the hub above. The support may in particular comprise at least two elastically deformable lugs and a housing for an axis of the hub, said lugs being arranged to retain the axis in the housing. The latter can be made so as to allow rotation of the axis relative to the support. Alternatively, the hub may include a tube internally traversed by an axis, and it is the tube which is arranged to snap into the housing of the support, this tube then being fixed relative to the support.

A snap-fastening of the hub on its support is advantageous because it simplifies the manufacture of the rotor and may also allow, if necessary, easier separation of the hub in the event of an aircraft crash, thereby reducing the risk of damage. rotor. In a particular embodiment, at least one pierced permanent magnet is used, which can be magnetized diametrically. Such a magnet can further increase the compactness of the device.

The rotor may comprise, if necessary, a collective pitch adjustment mechanism, for example a mechanism comprising links connected on the one hand to the blades and, on the other hand, directly or indirectly, to a collective pitch adjustment member , movable relative to the axis of the drive shaft, this adjusting member being able to be actuated by a servomotor.

The rotor can comprise a gyroscopic stabilization system which can be of any type known per se, comprising for example a Bell bar or weights in front of the center of gravity of the blades, having regard to the direction of rotation of the rotor. These weights can for example be present substantially at the leading edge of the blades, being integrated therein.

The control device may include a control device making it possible to control the electric current in the coil (s) so as to obtain the commands of the lateral cyclic step and of the longitudinal cyclic step desired.

The control device may include at least one sensor capable of delivering information relating to the angular position of the rotary assembly around the axis of the drive shaft. This sensor can be for example an optical, capacitive or magnetic sensor. The information concerning the position which it delivers can be useful in the case where the control device has only one coil coaxial with the drive shaft. In the case where the control device comprises several coils, the position sensor may not exist.

Another subject of the invention is, according to another of its aspects, a control device intended to be connected to one or more coils making it possible to exert a magnetic field on at least one rotating magnet with a rotor comprising at least two blades connected by a hub, this control device being arranged to deliver to the coil or coils a determined current so that the interaction between the magnetic field produced by the coil (s) and the magnet (s) generates a torque enabling the l orientation of the rotor thrust selectively.

This control device can optionally include a position sensor capable of delivering a predefined signal when the rotor passes through a predetermined angular position. In this case, the control device can be arranged to measure the duration of a revolution of the rotor and determine at least one time interval during which a current must be sent in at least one coil according to a setpoint.

The control device can also be arranged to supply at least two non-coaxial coils, in particular two coils having their axes arranged at 90 ° from one another, and be devoid of position sensor.

The invention applies particularly to the production of a radio controlled helicopter, in particular a helicopter whose main rotor is driven by an electric motor. The tail rotor can be driven by this electric motor through a mechanical transmission or by an independent electric motor. The helicopter may also be, for example, with a double main rotor, the two rotors being counter-rotating.

The invention also applies, according to another of its aspects, to the production of a radio-controlled aircraft, the rotor being for example placed at the front of the aircraft or on a wing or used in propulsion mode. back of the unit. The modification of the orientation of the thrust can make it possible to produce the aircraft without rudder or depth, for example.

The invention also applies to a convertible aircraft or an airship. The convertible aircraft may for example comprise an actuator making it possible to modify the orientation of the drive shaft relative to the longitudinal axis of the aircraft, so as to allow takeoff and vertical landing.

The aircraft can be equipped, if necessary, with at least one camera. Another subject of the invention is, according to another of its aspects, a device making it possible to modify the orientation of the thrust of an aircraft rotor, this device comprising: a rotary assembly comprising at least one blade connected to a hub , a rotary support on which the hub can be mounted with a possibility of orientation around a pivot axis so as to modify the angle of incidence of said at least one blade, a rotation drive shaft of said support rotary, at least one permanent magnet secured to the rotary assembly, at least one fixed coil relative to an aircraft chassis and arranged so as to create, when powered by an electric current, a magnetic field interacting with the magnet so as to generate on said at least one permanent magnet a torque making it possible to rotate the rotary assembly around the pivot axis and to modify the angle of incidence of said at least one blade.

The rotor can be the main rotor or a tail rotor. The invention will be better understood on reading the detailed description which follows, of non-limiting examples of implementation thereof, and on examining the appended drawing, in which:

- Figure 1 shows schematically and partially, in perspective, an example of rotor and control device, - Figure 2 shows in isolation, schematically, the upper end of the drive shaft of Figure 1 and the coil, FIG. 3 is a schematic bottom view of the hub of FIG. 1,

FIG. 4 schematically represents, in perspective, an alternative embodiment of the hub, - FIG. 5 is a side view, with cutaway, of another alternative embodiment,

FIG. 6 is a schematic and partial section on VI-VI of FIG. 5, FIG. 7 represents in isolation the upper end of the drive shaft of FIG. 5,

FIG. 8 schematically represents the electronic installation, FIG. 9 diagrammatically represents the control device, FIGS. 10 to 12 are time diagrams illustrating different possibilities of controlling the rotor, among others,

FIGS. 13 to 15 are schematic views illustrating other arrangements of coils and magnets,

FIG. 16 is a variant of the control device in the case of the use of several coils as in FIGS. 13 to 15,

FIG. 17 is a schematic exploded view showing in particular a part for supporting the coils,

- Figures 18 and 19 illustrate methods of fixing, among others, coils on the support piece of Figure 17, - Figures 20 and 21 schematically show a drive shaft end for attachment by snap-fastening of the hub, FIG. 21 being a view along arrow XXI of FIG. 20,

FIG. 20A is a view similar to FIG. 20, showing an alternative embodiment, - FIG. 22 partially and schematically represents an alternative embodiment of the hub,

FIG. 23 schematically and partially illustrates an exemplary embodiment of a collective pitch control mechanism,

FIG. 24 schematically represents a blade comprising a counterweight,

FIG. 25 schematically represents an alternative embodiment of a gyroscopic stabilization system, comprising a Bell bar,

FIG. 26 diagrammatically represents a helicopter equipped with a control device according to the invention, FIG. 27 diagrammatically represents an aircraft equipped with a control device according to the invention,

- Ligure 28 schematically represents a pierced magnet, FIG. 29 schematically represents a rotary assembly with one blade, and

- Figure 30 shows schematically an alternative embodiment of a rotary assembly with a blade. FIG. 1 shows an aircraft rotor 10 comprising on the one hand a drive shaft 11 rotated by an electric motor 12 about an axis R by means of a reduction gear 13 and on the other hand a rotary assembly producing the thrust, comprising two blades 20 connected by a hub 30, the latter being able to pivot about an axis P perpendicular to the axis R, so as to modify the angle of incidence of the blades. The increase in the angle of incidence of one blade 20 results in a decrease of the same value in the angle of incidence of the other blade 20, and vice versa. In the neutral position of the blades 20, the orientation of the thrust vector is substantially coaxial with the axis R.

The drive shaft 11 can be provided at the end, as can be seen in FIG. 2, with a tube 50 of axis P, intended to receive an axis 31 of the hub 30, the latter being shown partially at a enlarged scale in Figure 3.

In the example considered, a coil 60 is carried by a support 70 integral with the chassis 80 of the aircraft, this support 70 being traversed by the drive shaft 11. The coil 60 is connected to a control device 90, itself connected to a receiver 100 which transmits to the control device 90 information received from a transmitter not visible in FIG. 1 but shown schematically in FIG. 8.

There is shown in Figure 3 the face of the hub 30 disposed opposite the coil 60. The hub 30 has on this face two permanent magnets 110 and 111 formed in the example considered each by a disc whose large faces define the poles south and north of the magnet. The magnet 110 has for example its apparent north pole and the magnet 111 its apparent south pole. The magnets 110 and 111 are offset relative to the axis R and the coil 60, and are exposed to the magnetic field produced by the latter when it is supplied with current by the control device 90. The interaction between the magnets 110 and 111 and this magnetic field produces a torque around the axis P which tends to modify the angle of incidence of the blades 20. By choosing the moment when an electric current flows through the coil 60, we can act selectively on the rotary assembly, as will be explained later. Various modifications can be made to the hub and to the arrangement of the magnets without departing from the scope of the present invention.

In the example of FIG. 3, the polar axes of each of the magnets 110 and 111 are oriented substantially parallel to the axis R when the blades 20 are in neutral. In the variant illustrated in FIG. 4, the polar axes M of the magnets are substantially perpendicular to the axes R and P. The magnets 110 and 111 can be fixed for example as illustrated on the uprights 33 of the hub, these uprights 33 being arranged so so that the magnets 110 and 111 are located for example substantially half-length of the coil 60 and on each side thereof, to be exposed to the magnetic flux which leaves one side of the coil to join the other face.

It is also possible, as illustrated in FIGS. 5 to 7, to arrange the magnets 110 and 111 so that their polar axis M is perpendicular to the axes R and P, inside the coil 60.

The shaft 11 is provided in the example of these figures at its end with a yoke 120 which comprises two uprights 121 and 122 each provided with a bore 123 for the passage of an axis 124 which makes it possible to articulate the hub 30 on yoke 120 around the P axis.

The axis 124 is engaged in a tube 135 integral with the hub 30. The latter has two branches 131 connecting the blades to a central part 132 which extends downwards and supports the magnets 110 and 111, the north pole N of the one of these magnets being facing the south pole S of the other magnet, so that the magnetic fields generated by these magnets are added. A space 137 is formed between these magnets for the passage of the tube 135, the latter being shorter than the interval existing between the uprights 121 and 122 of the yoke. In the example of FIGS. 5 to 7, when an electric current flows through the coil 60, the magnets 110 and 111 tend to align with the field lines inside the coil 60. Depending on the direction of the current, a torque can be exerted on the magnets 110 and 111 which tends to rotate the hub 130 around the axis P.

The aircraft can be equipped, as seen in FIG. 8, in addition to the control device 90 and the receiver 100, with a variator 101 making it possible to vary the speed of rotation of the engine 12 and, in the case of a helicopter, a booster 103 or a auxiliary motor connected to the tail rotor. This servomotor 103 can be connected to the receiver 100 via a gyroscope 104, if necessary.

The transmitter comprises for example two sleeves 106 and 107 making it possible to respectively control the longitudinal cyclic step and the lateral cyclic step. The control device 90 comprises, in the example considered, two microcontrollers and power transistors controlled by the microcontrollers to send current pulses to the coil 60.

One of the microcontrollers is used for example to decode the information received from the receiver 100 in order to determine what are the instructions concerning the longitudinal cyclic step and the lateral cyclic step.

The other microcontroller can be arranged to send current pulses into the coil 60 at the right time, so as to create a torque on the hub causing the desired modification of the thrust vector.

The control device 90 may include a phase lock loop circuit which allows the angular position of the rotor to be known at any time. A position sensor 91 can send, as illustrated in FIG. 9, a signal each time the rotor passes through a reference position. This position sensor 91 can comprise for example a magnetic sensor and the rotor a magnet 92 fixed on a disc 93 rotating with the shaft 11, as shown in FIG. 1. The control device 90 can comprise an oscillator controlled in frequency by the signals from the position sensor 91, which oscillates at a multiple N of the frequency of rotation of the shaft, and makes it possible to split the duration of each revolution into N time intervals.

During the rotation of the rotor, each time interval defines an angular interval in ° equal to 360 / N. Thus, at the n ^th time interval since the transition to the reference position, the angular position of the rotor is in the n ^th section from the section corresponding to the reference position.

The duration of a revolution can be divided into four equal sectors, as can be seen in Figures 10 to 12. It is assumed in Figure 10 that the duration of each revolution is divided into four equal sectors if s ₄ . The duration of the journey of each sector is a quarter of the duration of a revolution. The command is carried out from two setpoints C _x and C _y , the X axis cuts the sectors s _t and s ₃ , while the Y axis cuts the sectors s ₂ and s ₄ .

The angular position t ₀ corresponds to the passage of the rotor through the reference position, detected by means of the sensor 91. It is assumed that the orientation of the polar axis M of the magnet (s) and the direction of the current in the coil 60 are such that a positive current pulse in the coil at a time interval Δt centered on the X axis in the first sector if causes a torque which tends, by gyroscopic effect, to modify the vector pushed forward, which allows for example to advance the helicopter. It is assumed that a positive current pulse in a time interval centered on the Y axis in the second dial makes it possible to modify the orientation of the vector pushed to the right. Similarly, a positive current pulse in the coil 60 in a time interval, centered in the X axis, in the third sector s ₃ makes it possible to tilt the vector pushed backwards and centered on the Y axis. in the fourth sector s ₄ to the left. In order to exert a greater or lesser torque on the hub 30 in order to incline the vector pushed more or less in the desired direction, the width Δt of the current pulse can be varied for example symmetrically with respect to the X or Y axis concerned.

The amplitude of displacement of the handle 106 controlling the longitudinal cyclical step on the transmitter of the radio-controlled can thus be translated by a more or less long current pulse in the first sector if or in the third sector s ₃ , depending on whether the handle is pushed forward or backward. The amplitude of movement of the handle 107 controlling the lateral cyclic step can be expressed by a more or less long current pulse in the second s ₂ or fourth s ₄ sectors. Alternatively, it is also possible to vary the amplitude of the current which is injected into the coil, with a constant duration for the current pulse.

It is also possible to vary both the duration of the pulse and its amplitude or to cut it with a variable duty cycle.

To cause the thrust vector to tilt forward, you can either send a positive current pulse in the coil in the first sector if, or send a negative current pulse in the opposite sector s ₃ , as illustrated in Figure 11 . Preferably, with each revolution, a pulse of polarity given in one of the sectors is associated with a pulse of opposite polarity in the diametrically opposite sector, as illustrated in FIG. 12.

Numerous modifications can be made to the examples which have just been described without departing from the scope of the present invention.

One can for example use at least two coils 160 and 161 whose axes A and B are contained in a plane substantially perpendicular to the axis R and at least one magnet whose polar axis is substantially parallel to the axis R, as illustrated in FIG. 13. It is also possible to use three coils 160, 161 and 162 of respective axes A, B, C, as shown respectively in FIG. 14. The axes A, B and C are arranged at 120 ° from each other other.

In Figure 15, there are shown four coils 160, 161, 162 and 163 whose respective axes A, B, C, D are arranged at right angles to each other. In this arrangement, it is advantageous to associate the coils in pairs, so that their magnetic fields are added, the magnet or magnets rotating in the space 165 formed between the pairs of coils.

In the case where at least two coils are used, as illustrated in FIGS. 13 to 15, the control device may no longer include a position sensor. Depending on the setpoints C _x and C _y , the control device sends a current in the coils which can be constant throughout a revolution for a fixed setpoint. In order to reduce energy consumption, it is also possible to synchronize the sending of a current pulse in a coil with the passage of the rotary assembly in a predefined position. When using at least two coils whose axes are contained in a plane substantially perpendicular to the axis of the drive shaft, the coils are advantageously arranged on a support piece 170, which may for example have the shape illustrated in FIG. 17 in the case of four coils associated in pairs.

This support comprises an annular central portion 171 on which four teeth 172 are connected and provided with heads 173 for retaining the coils. These heads 173 can be formed for example in a single piece with the rest of the part by molding or by injection, in which case the electrical conductors of the coils can be wound directly on the teeth 172.

As a variant, the teeth with their heads can be fixed on the central annular part 171 after placing the coils on the teeth or winding of these on the teeth, the teeth 172 being able to be fixed on the central annular part 171 by gluing , welding, snap-fastening or any other means of fixing.

The teeth can also be produced without heads, then the coils can be retained on the teeth 172 by bouteroUage their end 174, as illustrated in Figure 18. Alternatively, as shown in Figure 19, the teeth may have an end 175 arranged to allow snap fastening of the coils.

The fixing of the hub on the rest of the rotor can be carried out in various ways and it can be advantageous to fix the hub by snap-fastening on its support so as to facilitate the manufacture of the rotor and also, if necessary, to allow a separation of the blades and from the hub of the rest of the rotor in the event of a crash, which can reduce the risk of damaging the aircraft.

FIGS. 20 and 21 have illustrated an example of support 180 allowing the hub to be fixed by snap-fastening.

This support comprises for example two uprights 181 and 182 each provided with a housing 183 in which can be snap-fastened one end of an axis serving as a pivot to the hub or of a tube housing such an axis.

Each upright also comprises at least one elastic tab 184 which makes it possible to retain this axis or this tube in the housing 183.

FIG. 20A represents a variant in which the hub has elastic tabs 184 and the shaft 11 a corresponding axis 195.

The axis which allows the articulation of the hub on its support can be, if necessary, made integrally with the hub 30, as illustrated in FIG. 22. On the latter, the axis comprises two portions 190 which are for example intended to be fixed by snap-fastening in the aforementioned housings 183. In the variant illustrated in FIG. 28, a perforated magnet 110, diametrically magnetized, is used. This magnet 110 can be crossed by the axis 190 and be made integral with a support structure for the blades. The magnet 110 can for example be made integral with the Bell bar and the blades can be carried by a part (not shown) articulated on the Bell bar, the longitudinal axis of the blades being perpendicular to that of the Bell bar. Such an arrangement can improve stability. Using a holey magnet can help improve compactness and performance.

If necessary, the rotor can include a collective pitch control, as illustrated in FIG. 23.

The collective pitch control can be carried out in multiple ways and for example by means of a control rod 201 and a set of links 200.

In the example of FIG. 1, the rotary assembly is equipped with a gyroscopic stabilization system comprising two weights 40 in front of the center of gravity of the blades and their leading edge 21.

As a variant, the weights 41 can be integrated in the blades, in particular in their leading edge, as illustrated in FIG. 24.

In another variant, as illustrated in FIG. 25, the gyroscopic stabilization system can comprise a Bell bar 42, which can be provided at the end with pallets 43.

The invention is particularly suitable for controlling the orientation of the thrust vector of a radio-controlled helicopter such as, for example, that shown diagrammatically in FIG. 26.

Such a helicopter comprises, in addition to the main rotor, a tail rotor 220, which can be rotated by the same motor as the main rotor or by a different motor. The invention also applies to the control of the orientation of the thrust vector of the propeller of an aircraft, such as for example that shown schematically in FIG. 27.

The invention advantageously finds application in a rotor with a single blade, as illustrated in FIGS. 29 or 30. The rotor then comprises one or more counterweights 300 and if necessary the equivalent of a Bell bar, in the example in Figure 29. Such a rotor allows a collective pitch control signal to be superimposed on a control signal for varying the incidence of the blade as a function of the angle of rotation.

The rotor can then be used both as a main rotor and as a tail rotor.

This tail rotor can be connected by a shaft, belt or flexible transmission to the main rotor drive motor.

Many modifications can be made to the various examples of implementation of the invention which have just been described, and in particular to combine the characteristics of these.

Throughout the description, including the claims, the expression “comprising a” should be understood as being synonymous with “comprising at least one”, unless otherwise specified.

Claims

1. Device making it possible to modify the orientation of the thrust of an aircraft rotor, this rotor comprising: - a rotary assembly comprising two blades (20) connected by a hub (30),

- a rotary support on which the hub can be mounted with a possibility of orientation around a pivot axis (P) so as to modify the angle of incidence of the blades, a shaft (11) for driving in rotation of said rotary support, this device being able to be characterized by the fact that it further comprises:

- at least one permanent magnet (110; 111) secured to the rotary assembly,

- at least one coil (60; 160; 161; 162; 163) fixed relative to an aircraft chassis and arranged so as to create, when powered by an electric current, a magnetic field interacting with the magnet, so as to generate on said at least one permanent magnet a torque making it possible to rotate the rotary assembly around the pivot axis (P) and to modify the angle of incidence of the blades.

2. Device according to claim 1, characterized in that it comprises a single coil (60).

3. Device according to claim 2, characterized in that the axis of the coil (60) is substantially parallel to that (R) of the drive shaft (11).

4. Device according to claim 1, characterized in that it comprises several coils (160; 161; 162; 163).

5. Device according to claim 4, characterized in that the coils (160; 161; 162; 163) have axes (A; B; C; D) substantially parallel to a plane perpendicular to the axis (R) of the drive shaft (11).

6. Device according to one of claims 4 and 5, characterized in that it comprises at least two coils whose axes, preferably substantially intersecting, form an angle of 90 ° between them.

7. Device according to claim 6, characterized in that it comprises four coils associated in pairs, two coils of the same pair having substantially the same axis, the angle between the axes of the two pairs being substantially 90 °.

8. Device according to claim 7, characterized in that two coils of the same pair define between them a space (165) in which said at least one permanent magnet can be arranged, so as to be exposed to the magnetic field created by the coils.

9. Device according to any one of the preceding claims, characterized in that it comprises at least one coil fixed to a support through which the drive shaft passes.

10. Device according to any one of the preceding claims, characterized in that it comprises several coils supported by the same part (170).

11. Device according to the preceding claim, characterized in that said part comprises a central annular part (171) traversed by the drive shaft and at its periphery teeth (172) each serving as a core for a coil.

12. Device according to claim 1, characterized in that the hub (30) is arranged so as to allow the attachment of at least one magnet with the polar axis thereof oriented substantially perpendicular to the axis of l drive shaft when the blades are neutral.

13. Device according to claim 12, characterized in that it comprises a single coil (60) and in that said at least one magnet is arranged inside the coil.

14. Device according to claim 12, characterized in that it comprises a single coil (60) and in that it further comprises two magnets arranged outside the coil, substantially half the length of that -this.

15. Device according to claim 1, characterized in that the hub is arranged so as to allow the fixing of at least one magnet with the polar axis of this magnet substantially parallel to that (R) of the shaft training.

16. Device according to claim 15, characterized in that it comprises a single coil whose axis is substantially coaxial with the drive shaft and that the magnet or magnets are external to the coil.

17. Device according to claim 16, characterized in that it comprises two magnets disposed above the coil (60) eccentrically.

18. Device according to claim 1, characterized in that it comprises several coils whose axes are not parallel to that of the drive shaft, the hub being arranged so as to allow the fixing of said at least one magnet with the polar axis thereof substantially parallel to the axis of the drive shaft, when the blades are neutral.

19. Device according to claim 1, characterized in that the support on which the hub is mounted comprises a yoke inside which is engaged at least partially the hub.

20. Device according to claim 19, characterized in that the rotor comprises two magnets arranged with a spacing between them to allow the passage of an axis by which the hub is articulated on the yoke.

21. Device according to claim 1, characterized in that the support comprises a tube (50) in which is engaged an axis by which the hub is articulated on the support.

22. Device according to any one of the preceding claims, characterized in that the support is arranged to allow snap-fastening of the hub above.

23. Device according to claim 22, characterized in that the support comprises at least two elastically deformable tabs (184) and a housing (183) for an axis of the hub.

24. Device according to any one of the preceding claims, characterized in that the rotor includes a collective pitch adjustment mechanism.

25. Device according to any one of the preceding claims, characterized in that the rotor comprises a gyroscopic stabilization system.

26. Device according to any one of the preceding claims, characterized in that it comprises a control device making it possible to control the electric current in the coil (s) so as to obtain the commands of the lateral cyclic step and of the longitudinal cyclic step desired.

27. Device according to claim 1, characterized in that said at least one permanent magnet is pierced.

28. Device according to claim 27, characterized in that said at least one permanent magnet is diametrically magnetized.

29. Control device (90) intended to be connected to one or more coils enabling a magnetic field to be exerted on at least one rotating magnet with a rotor comprising at least two blades connected by a hub, this control device being arranged for delivering a determined current to the coil (s) so that the interaction between the magnetic field produced by the coil (s) and the magnet (s) generates a torque enabling the orientation of the rotor thrust to be changed selectively.

30. Device according to claim 29, characterized in that it comprises a position sensor (91) capable of delivering a predefined signal when the rotor passes through a predetermined angular position.

31. Aircraft equipped with a control device as defined in any one of claims 1 to 28.

32. Aircraft according to claim 31, characterized in that it constitutes a radio-controlled helicopter.

33. Device making it possible to modify the orientation of the thrust of an aircraft rotor, comprising: a rotary assembly comprising at least one blade connected to a hub, a rotary support on which the hub can be mounted with the possibility of orientation about a pivot axis so as to modify the angle of incidence of said at least one blade, a rotation drive shaft of said rotary support, at least one permanent magnet secured to the rotary assembly, at least a fixed coil relative to a chassis of the aircraft and arranged so as to create, when powered by an electric current, a magnetic field interacting with the magnet, so as to generate on said at least one permanent magnet a torque making it possible to rotate the rotary assembly around the pivot axis and modify the angle of incidence of said at least one blade

34. Device according to claim 33, characterized in that the rotor is a tail rotor.

35. Device according to claim 33, characterized in that the rotor is a main rotor