Reversible electrical machine for an aircraft

Abstract

A reversible electrical machine (1) comprising: a first electrical device (10) having a first stator (11) and a first rotor (12); a second electrical device (20) including a second rotor (22) and a second stator (21) together with an outlet shaft (50) and first disengageable coupling means (30) enabling said first and second rotors (12, 22) to be associated and dissociated in rotation. Said reversible electrical machine (1) also includes second disengageable coupling means (40) that are disengageable under a predetermined force and that mechanically connect said second rotor (22) to said outlet shaft (50). Said first electrical device (10) is a motor for transmitting high mechanical power to said outlet shaft (50), while said second electrical device (20) is a motor-generator for operating in motor mode to transmit additional mechanical power to said outlet shaft (50), and in generator mode for receiving mechanical power from said outlet shaft (50).

Claims

1. A reversible electrical machine comprising: a first electrical device having a first rotor configured to cooperate with a first stator; a second electrical device including a second rotor configured to cooperate with a second stator; first disengageable coupling means enabling the first and second rotors to be associated and dissociated in rotation; and an outlet shaft; wherein the reversible electrical machine includes second disengageable coupling means that are disengageable under a first predetermined force and that mechanically connect the second rotor to the outlet shaft, the first electrical device being a motor for transmitting mechanical power to the outlet shaft and the second electrical device being a motor-generator for operating in motor mode to transmit additional mechanical power to the outlet shaft, and in generator mode for receiving mechanical power from the outlet shaft.

2. The reversible electrical machine according to claim 1 wherein the first rotor includes first magnets that are permanent.

3. The reversible electrical machine according to claim 1 wherein the second rotor includes second magnets that are permanent.

4. The reversible electrical machine according to claim 1 wherein the first rotor includes first magnets that are non-permanent.

5. The reversible electrical machine according to claim 1 wherein the second rotor includes second magnets that are non-permanent.

6. A reversible electrical machine comprising: a first electrical device having a first rotor configured to cooperate with a first stator; a second electrical device including a second rotor configured to cooperate with a second stator; first disengageable coupling means enabling the first and second rotors to be associated and dissociated in rotation; an outlet shaft; and second disengageable coupling means that are disengageable under a first predetermined force and that mechanically connect the second rotor to the outlet shaft; wherein the first electrical device is a motor for transmitting mechanical power to the outlet shaft and the second electrical device is a motor-generator for operating in motor mode to transmit additional mechanical power to the outlet shaft, and in generator mode for receiving mechanical power from the outlet shaft, and wherein the first rotor and the second rotor are rotatable about a common axis of rotation and the first coupling means include an intermediate shaft, the second coupling means, and third disengageable coupling means mechanically connecting the first rotor to the intermediate shaft, the intermediate shaft being associated with the outlet shaft, thereby enabling the first rotor to be mechanically connected to the second rotor.

7. The reversible electrical machine according to claim 6 wherein the third coupling means include a freewheel enabling the first rotor to be associated with the intermediate shaft, and consequently with the second rotor, in one direction of rotation, and to be dissociated from the intermediate shaft, and consequently from the second rotor in the opposite direction of rotation, the second coupling means being engaged.

8. The reversible electrical machine according to claim 7 wherein the intermediate shaft constitutes one end of the outlet shaft.

9. The reversible electrical machine according to claim 5 wherein the first rotor is formed by DC-powered non-permanent first magnets and the second rotor is formed by DC-powered non-permanent second magnets, the non-permanent first and second magnets being mechanically connected together in rotation, the first coupling means including inhibit means enabling the power supply to the non-permanent first magnets to be switched off while the non-permanent second magnets continue to be powered.

10. The reversible electrical machine according to claim 9 wherein the first coupling means include the second coupling means and fourth disengageable coupling means that are disengageable under a second predetermined force and that mechanically connect the first rotor with the outlet shaft, the second coupling means and the fourth coupling means thus enabling the first rotor and the second rotor to be mechanically coupled together in rotation by the outlet shaft.

11. The reversible electrical machine according to claim 2 wherein the first magnets of the first rotor rotate outside the first stator.

12. The reversible electrical machine according to claim 3 wherein the second magnets of the second rotor rotate inside the second stator.

13. The reversible electrical machine according to claim 1 wherein the first and second rotors rotate about a common axis of rotation, and the first and second stators form a single stator.

14. The reversible electrical machine according to claim 1 wherein at least one first magnet is oriented radially relative to the axis of rotation of the first rotor and at least one second magnet is oriented radially relative to the axis of rotation of the second rotor.

15. The reversible electrical machine according to claim 1 wherein the first motor includes multiple first magnets, and the second motor includes multiple second magnets, and wherein at least one first magnet is oriented radially relative to an axis of rotation of the first rotor and at least one second magnet is oriented radially relative to an axis of rotation of the second rotor.

16. A hybrid power plant of a rotary wing aircraft wherein the hybrid power plant includes a main gearbox connected to a main rotor of the aircraft, at least one engine mechanically connected to the main gearbox, and at least one reversible electrical machine according to claim 1 with the outlet shaft being mechanically connected to the main gearbox.

17. A hybrid power plant of a rotary wing aircraft wherein the hybrid power plant comprises a main gearbox connected to a main rotor of the aircraft, an engine having a free turbine and a compressor, together with at least one reversible electrical machine according to claim 1, with the outlet shaft being mechanically connected to the compressor of the engine, and the free turbine of the engine being mechanically connected to the main gearbox.

18. The reversible electrical machine according to claim 1 wherein the second disengageable coupling means are automatically disengageable under the first predetermined force.

19. The reversible electrical machine according to claim 1 wherein the first coupling means is configured to connect the first and second rotors with a first transmission ratio, and the second coupling means is configured to connect the second rotor to the outlet shaft with the first transmission ratio.

20. The reversible electrical machine according to claim 19 wherein the first transmission ratio is equal to 1.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The invention and its advantages appear in greater detail from the context of the following description of embodiments given by way of illustration and with reference to the accompanying figures in which:

(2) FIGS. 1 to 5 show various embodiments of the reversible electrical machine of the invention;

(3) FIG. 6 shows a rotary wing aircraft fitted with parallel hybridization with a reversible electrical machine; and

(4) FIG. 7 shows a rotary wing aircraft fitted with micro-hybridization with a reversible electrical machine.

(5) Elements that are present in more than one of the figures are given the same references in each of them.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIG. 1 shows an embodiment of a reversible electrical machine 1 of the invention having a first electrical device 10, a second electrical device 20, first disengageable coupling means 30, and an outlet shaft 50. The first device 10 is a motor and has a first rotor 12 co-operating with a first stator 11. Likewise, the second device 20 has a second rotor 22 co-operating with a second stator 21, however this second device is a motor-generator. Each stator 11, 21 is provided with non-permanent magnets 14, 24 made up of one or more windings of conductor wires serving to generate at least one stator magnetic field when passing an electric current. Each rotor 12, 22 is provided with permanent magnets 15, 25 generating respective first and second rotor magnetic fields.

(7) In FIG. 1, as in all of the figures, the non-permanent magnets 14, 24 and the permanent magnets 15, 25 are oriented radially relative to the axis of rotation of each rotor 12, 22, thus enabling the magnetic flux to flow radially between the non-permanent magnets 14, 24 of the stators 11, 21 and the permanent magnets 15, 25 of the rotors 12, 22.

(8) Nevertheless magnets 14, 24, 15, 25 may also be oriented axially relative to the axis of rotation of each rotor 12, 22, the magnetic flux then flowing axially between the magnets 14, 24 and 15, 25.

(9) In a reversible electrical machine 1, it is also possible to arrange some of these magnets 14, 24 axially and others of these magnets 14, 24 radially relative to the axis of rotation of each rotor 12, 22. Likewise, some of the magnets 15, 25 will then be oriented axially and others of the magnets 15, 25 will be oriented radially.

(10) Furthermore, the non-permanent magnets 14, 24 of each stator 11, 21 may be made up of one or more windings of conductor wires forming one or more phases, respectively, which may then generate one or more stator magnetic fields, respectively.

(11) The first disengageable coupling means 30 serve to connect the first and second rotors 12 and 22 together mechanically. Second disengageable coupling means 40 that are disengageable under a first predetermined force serve to connect the second rotor 22 mechanically with the outlet shaft 50. This outlet shaft may be connected to the power train of a vehicle, e.g. the MGB of a rotary wing aircraft.

(12) The first rotor 12 rotates outside the second stator 11, while the second rotor 22 rotates inside the second stator 21, the first rotor 12 and the second rotor 22 having the same axis of rotation. As a result, the first electrical device 10 is capable of delivering a high level of mechanical torque in motor mode, while the second electrical device is capable of delivering lower mechanical torque in motor mode and low magnetic torque in generator mode.

(13) The reversible electrical machine 1 may operate equally well in motor mode, in which the reversible electrical machine 1 transforms the electrical power it receives into mechanical power that is delivered to the outlet shaft 50, and also in generator mode, in which the outlet shaft 50 delivers mechanical power that the reversible electrical machine 1 transforms into electric power.

(14) The first coupling means 30 comprise an intermediate shaft 51, the second coupling means 40, and third disengageable coupling means 35. The intermediate shaft 51 is secured to the outlet shaft 50, and the third coupling means 35 connect the first rotor 12 mechanically to the intermediate shaft 51. As a result, the first rotor 12 is mechanically connected to the outlet shaft 50, while the third coupling means 35 is engaged, thereby enabling the first rotor 12 to be mechanically connected to the second rotor 22 by the second coupling means 40 that are disengageable under a first predetermined force.

(15) The third coupling means 35 include a freewheel enabling the first rotor 12 to be associated with the intermediate shaft 51 and consequently to the second rotor 22 in one direction of rotation, and to be disassociated from the intermediate shaft 51 and consequently the second rotor 22 in the opposite direction of rotation, the second coupling means 40 being engaged.

(16) The first disengageable coupling means 30 thus enable the first rotor 12 to drive the outlet shaft 50 in rotation when the first device 10 is in motor mode. While the reversible electrical machine 1 is in motor mode, the second electrical device 20 may also be in motor mode and may deliver additional mechanical power to the outlet shaft 50.

(17) Conversely, when the reversible electrical machine 1 is operating in generator mode, the second device 20 receives mechanical power from the outlet shaft 50 via the second coupling means 40 and consequently from the second rotor 22. Advantageously, the third coupling means 35 are disengaged in this mode of operation, and consequently the first coupling means 30 are likewise disengaged. The first electrical device 10 is then dissociated from the outlet shaft 50, and consequently from the second electrical device 20 and therefore does not operate in generator mode. Consequently, no resisting torque due to the permanent magnets 15 of the first rotor 11 appears in the reversible electrical machine 1. Consequently, the efficiency with which the mechanical energy from the outlet shaft 50 is transformed into electrical energy is optimized.

(18) FIG. 2 shows a preferred embodiment of the electrical machine 1 that has only one stator 5, replacing the first and second stators 11, 21 of FIG. 1, while the first coupling means 30, the second coupling means 40, and the outlet shaft 50 remain unchanged compared with the embodiment shown in FIG. 1. The single stator 5 is provided with one or more windings 6 of conductor wires enabling at least one stator magnetic field to be generated when carrying an electric current. The first rotor 12 and the second rotor 22 rotate respectively outside and inside the stator 5, the first rotor 12 and the second rotor 22 having the same axis of rotation. Each rotor 12, 22 has permanent magnets 15, 25 generating respective first and second rotor magnetic fields.

(19) Advantageously, the use of a single stator 5 for co-operating with both the first and the second rotors 12 and 22 enables the dimensions and the weight of the electrical machine to be reduced, and also enables its cost to be reduced.

(20) FIG. 3 shows another embodiment of the electrical machine 1 that has only one stator 5 provided with one or more windings 6 of conductor wires. The first rotor 12 and the second rotor 22 rotate respectively outside and inside the stator 5, the first and second rotors 12 and 22 having the same axis of rotation.

(21) Unlike the preferred embodiment, the first rotor 12 has permanent magnets 15, while the second rotor 22 has non-permanent magnets 26 constituted for example by coils of conductor wires conveying DC delivered by a battery or by capacitors. Thus, the rotor 12 generates a first rotor magnetic field permanently, whereas the rotor 22 is capable of generating a second rotor magnetic field solely when the non-permanent magnets 26 are conveying DC.

(22) Once more, first disengageable coupling means 30 comprise an intermediate shaft 51, the second coupling means 40, and third disengageable coupling means 35. The intermediate shaft 51 then constitutes one end of the outlet shaft 50, and the third coupling means 35 mechanically connect the first rotor 12 with this end of the outlet shaft 50. As a result, the first rotor 12 is mechanically connected to the outlet shaft when the third coupling means 35 are engaged, thereby enabling the first rotor 12 to be mechanically connected to the second rotor 22 via the second coupling means 40.

(23) Advantageously, the use of non-permanent magnets 26 on the second rotor 22 makes it possible to eliminate magnetic torque completely by switching off the electrical power supply to the coils constituting the non-permanent magnets 26 in the event of the braking of the second rotor not being sufficient to disengage the second coupling means 40 during a short circuit.

(24) Furthermore, the use of permanent magnets 15 on the first rotor 12 makes it possible to obtain better performance in motor mode, the third coupling means 35 serving to dissociate this first rotor 12 from the outlet shaft 50 in the event of the first rotor 12 braking, e.g. following a short circuit in the coils 6 of the stator 5.

(25) Furthermore, the use of a single stator 5 for co-operating with the first rotor 12 and the second rotor 22 makes it possible to reduce the dimensions and the weight of the reversible electrical machine 1, and thus to reduce its cost.

(26) Another embodiment of the reversible electrical machine 1 is shown in FIG. 4. The reversible electrical machine 1 has a single stator 5, and the first rotor 12 is formed by non-permanent first magnets 16 such as coils powered with DC and rotating outside the stator 5, while the second rotor 22 is formed by non-permanent second magnets 26 such as coils powered by DC and rotating inside the stator 5. Furthermore, the non-permanent first and second magnets 16, 26 are mechanically constrained to rotate together permanently about the common axis of rotation of the first and second rotors 12, 22.

(27) The first coupling means 30 then include inhibit means enabling the electrical power supply to the non-permanent first magnets 16 to be switched off, while the non-permanent second magnets 26 continue to be powered electrically. When the first coupling means 30 are engaged, the non-permanent first magnets 16 and the non-permanent second magnets 26 are powered with DC and they transmit torque to the first rotor 12 and to the second rotor 22 in motor mode. The first and second rotors 12, 22 thus rotate together about their axis of rotation and enable the electrical machine 1 to deliver maximum torque in motor mode.

(28) In contrast, when the first coupling means 30 are disengaged, i.e. when the inhibit means switches off the electrical power supply to the non-permanent first magnets 16, only the non-permanent second magnets 26 of the second rotor 22 are powered with DC. Consequently, only the second rotor 22 creates a rotor magnetic field, and as a result rotates about its axis of rotation, thereby enabling the electrical machine 1 to deliver just enough electric power in generator mode.

(29) Thus, this embodiment of the reversible electrical machine 1 makes it possible in particular to eliminate the third coupling means 35 of the preferred embodiment, thereby reducing the number of components of the reversible electrical machine 1, and consequently reducing its weight and its cost. Furthermore, this embodiment is particularly advantageous when the opposing torque created during a short circuit in the coil 6 of the stator 5 does not enable the second coupling means 40 to be disengaged under a first predetermined force.

(30) However, since the non-permanent first magnets 16 and the non-permanent second magnets 26 are mechanically connected to rotate together on a continuous basis, blocking of the first or second electrical device 10, 20 causes the second coupling means 40 to be disengaged, and consequently causes the motor and generator functions of the reversible electrical machine 1 to be lost.

(31) In a variant of this embodiment of the invention as shown in FIG. 5, the first coupling means 30 include not only the inhibit means, but also the second coupling means 40 and disengageable fourth coupling means 41. The normal operation of the reversible electrical machine 1 in this variant remains unchanged and is obtained in particular by using the inhibit means to switch on or off the electrical power supply to the non-permanent first magnets 16.

(32) However, the non-permanent first and second magnets 16, 26 are not mechanically linked together in rotation on a permanent basis, being linked via the second and fourth coupling means 40, 41 which are disengageable, and by the outlet shaft 50.

(33) These fourth coupling means 41 are disengageable under a second predetermined force, enabling the first rotor 12 to be dissociated from the outlet shaft 50 in the event of the first electrical device 10 becoming blocked. Thus, the reversible electrical machine 1 remains functional by means of the second device 20, which is connected to the outlet shaft 50 by the second coupling means 40.

(34) Likewise, in the event of the second electrical device 20 becoming blocked, the second coupling means 40 enable the second rotor 22 to be dissociated from the outlet shaft 50. For example, the second coupling means 40 may include a fuse element 42 that connects the outlet shaft 50 to a bore 43 associated with the second motor 22, and the fuse element 42 may be configured to break under a first predetermined force in order to dissociate the bore 43 from the outlet shaft 50. The electrical machine 1 thus remains operational, in motor mode only, by using the first device 10, which is connected to the outlet shaft 50 by the fourth coupling means 41.

(35) Advantageously, in the event of the first or the second electrical device 10, 20 becoming blocked, this variant thus makes it possible to maintain the reversible electrical machine 1 operational, at least in part.

(36) Furthermore, the reversible electrical machine 1 of the invention may be used in various types of vehicle. The reversible electrical machine 1 is preferably used in an aircraft 100 having a rotary wing. Such an aircraft 100 is shown in FIGS. 6 and 7 and includes a hybrid power plant 105 and at least one main rotor 102.

(37) This hybrid power plant 105 comprises at least one engine 103, at least one reversible electrical machine 1 as described above, and a main gearbox (MGB) 101 that is connected to the main rotor 102 of the aircraft 100.

(38) With parallel hybridization, as shown in FIG. 6, the outlet shaft 50 from the reversible electrical machine 1 is mechanically connected to the MGB 101.

(39) With micro-hybridization, as shown in FIG. 7, the outlet shaft 50 from the reversible electrical machine 1 is mechanically connected to the engine 103, and more precisely to the compressor 106 of the engine 103. The engine 103 also has a free turbine 107 that is mechanically connected to the MGB 101.

(40) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several embodiments are described, it will readily be understood that it is not conceivable to identify exhaustively all possible embodiments. It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.