Mechanical motion transmission system and an aircraft fitted with a corresponding system

Abstract

A mechanical system for transmitting rotary motion between firstly at least one inlet wheel driven in rotation by at least one engine, each inlet wheel being suitable for being driven in rotation by a corresponding dedicated engine, and secondly at least two distinct driven shafts of an accessory box, the at least one engine serving to drive rotation of one of the at least two driven shafts in isolation, or to drive the at least two driven shafts simultaneously, jointly with at least one aircraft rotor, the mechanical system including a selective rotary drive member that is movable axially between two distinct drive positions.

Claims

1. A mechanical system for transmitting rotary motion between at least one engine and at least two distinct driven shafts of an accessory box, wherein the at least two driven shafts for transmitting rotary motion to two propulsion rotors in a hybrid rotorcraft that does not include a tail rotor shaft, the at least one engine serving to drive rotation of one of the at least two driven shafts in isolation, or to drive the at least two driven shafts simultaneously together with at least one aircraft rotor, the mechanical system including a selective rotary drive member that is movable axially between two distinct drive positions, the mechanical system comprising: an inlet wheel adapted to be driven in rotation by the engine; a first drive position in which one of the at least one engine drives both the at least one rotor and a first driven shaft of the accessory box in rotation simultaneously; and a second drive position in which one of the at least one engine drives a second driven shaft of the accessory box in rotation, the second driven shaft being distinct from the first driven shaft; a first bevel gear having teeth, the first bevel gear being movable in rotation about a first axis; a bevel wheel provided with teeth, the bevel wheel being movable in rotation about a second axis intersecting the first axis of the first bevel gear, the respective teeth of the first bevel gear and of the bevel wheel co-operating with in mutually complementary manner, the bevel wheel driving the at least one rotor in rotation; a second bevel gear having teeth meshing with the teeth of the bevel wheel and transmitting rotary motion to the first driven shaft of the accessory box; and a takeoff shaft constantly driven in rotation by the inlet wheel, the takeoff shaft serving to transmit rotary motion constantly to the second driven shaft of the accessory box without driving the first bevel gear, the bevel wheel and the second bevel gear in rotation while in the second drive position of the selective drive member, and when the engine drives rotation of the inlet wheel, the inlet wheel drives rotation of the takeoff shaft and of the second driven shaft of the accessory box; wherein the takeoff shaft is arranged to rotate about a third axis of rotation distinct from the first axis of rotation, the third axis of rotation being arranged so that it does not coincide with the first axis of rotation; and wherein in the first drive position of the selective drive member, the inlet wheel simultaneously drives rotation of 1) the first bevel gear, the bevel wheel and the second bevel gear to drive the first driven shaft of the accessory box, and 2) the takeoff shaft to simultaneously drive the second driven shaft of the accessory box.

2. The mechanical system according to claim 1, wherein the third axis of rotation is arranged parallel to a plane defined by the first and second intersecting axes of rotation and in non-coplanar manner.

3. The mechanical system according to claim 1, wherein the selective drive member is formed by an activatable freewheel, the activatable freewheel including a movable part actuated by an actuator selected from the group comprising hydraulically controlled actuators, pneumatically controlled actuators, and electrically controlled actuators.

4. The mechanical system according to claim 1, wherein the mechanical system includes a pair of gears for adapting a speed of rotation of the inlet wheel and for driving rotation of the takeoff shaft and of the second driven shaft of the accessory box.

5. The mechanical system according to claim 4, wherein, in the first drive position of the selective drive member and at constant speed of rotation of the at least one engine, the pair of gears enable the second driven shaft of the accessory to be driven in rotation at a speed of rotation Ω2 that is distinct from a speed of rotation Ω1 of the first driven shaft of the accessory box.

6. The mechanical system according to claim 1, wherein the first and second driven shafts of the accessory box are movable in rotation about respective fourth and fifth axes of rotation that are mutually parallel.

7. The mechanical system according to claim 6, wherein the inlet wheel is movable in rotation about a sixth axis of rotation, with the fourth and fifth axes of rotation being arranged parallel to the sixth axis of rotation.

8. An aircraft having at least one engine and at least one rotor for providing the aircraft with propulsion and/or lift, wherein the aircraft includes at least one mechanical system according to claim 1, the mechanical system serving to transmit rotary motion between a drive shaft of the at least one engine and a driven shaft of the at least one rotor.

9. A mechanical system for transmitting rotary motion from an engine and driving at least two distinct driven shafts of an accessory box and driving two propulsion rotors in a hybrid rotorcraft without a tail rotor, the two rotors providing propulsion and controlling yaw movements of the hybrid rotorcraft, the mechanical system comprising: an inlet wheel adapted to be driven in rotation by the engine; a main drivetrain connected to the inlet wheel and adapted to drive the first driven shaft of the accessory box, the main drivetrain comprising: a first bevel gear having teeth, the first bevel gear being movable in rotation about a first axis; a bevel wheel movable in rotation about a second axis intersecting the first axis of the first bevel gear, wherein the first bevel gear cooperates with the bevel wheel to drive the bevel wheel, the bevel wheel adapted to thereby drive the at least one rotor in rotation; a second bevel gear cooperating with the bevel wheel and adapted to transmit rotary motion to the first driven shaft of the accessory box; an auxiliary drive train connected to the inlet wheel having a takeoff shaft adapted to transmit rotary motion constantly to the second driven shaft of the accessory box, wherein the takeoff shaft is arranged to rotate about a third axis of rotation distinct from and does not coincide with the first axis of rotation; and a selective rotary drive member that is movable axially between a first drive position and a second drive position, wherein in the first drive position of the selective drive member, the inlet wheel simultaneously drives rotation of main drivetrain and the auxiliary drivetrain.

10. The mechanical system according to claim 9, wherein the mechanical system includes a pair of gears connected to drive the first driven shaft at a first speed of rotation and drive the second driven shaft at a second speed different than the first speed.

11. The mechanical system according to claim 10, wherein, in the first drive position of the selective drive member and at constant speed of rotation of the at least one engine, the pair of gears enable the second driven shaft of the accessory to be driven in rotation at a speed of rotation Ω2 that is distinct from a speed of rotation Ω1 of the first driven shaft of the accessory box.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1 is a perspective view of an aircraft fitted with a mechanical system in accordance with the invention;

(3) FIGS. 2 and 3 are theoretical diagrams showing the operation of a first embodiment of a corresponding mechanical system, shown respectively in two positions POS1 and POS2 of the selective rotary drive member, in accordance with the invention;

(4) FIG. 4 is a diagrammatic side view of a second embodiment of a mechanical system in accordance with the invention; and

(5) FIG. 5 is a perspective view showing the first embodiment of the mechanical system.

DETAILED DESCRIPTION OF THE INVENTION

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

(7) As mentioned above, the invention relates to a mechanical system and to an aircraft fitted with such a mechanical system.

(8) As shown in FIG. 1, the aircraft 1 may be in the form of a rotorcraft and have an engine 2 such as a combustion engine or a turbojet. The engine 2 then serves to drive a drive shaft 5 in rotation and a mechanical system 4 serves to transmit the rotary motion of the drive shaft 5 to a driven shaft 6 with a change in angular orientation between the respective axes of rotation of the drive shaft 5 and the driven shaft 6.

(9) Such a driven shaft 6 then serves to drive rotation of at least one rotor 3 having blades for providing the aircraft 1 with lift and/or propulsion. Advantageously, the mechanical system 4 also serves to reduce the speed of rotation of the driven shaft 6 compared with the speed of rotation of the drive shaft 5.

(10) As shown diagrammatically in FIGS. 2 and 3, in a first embodiment of a mechanical system 4, a plurality of shafts or gears are movable in rotation about various different axes of rotation. In order to simplify the representation of the mechanical system 4, some of the axes are shown as being coplanar and capable of crossing, which is naturally not possible physically.

(11) Such a mechanical system 4 for transmitting rotary motion thus serves to transmit rotary motion between firstly at least one inlet wheel 8, 8′ driven in rotation by at least one engine 2, 2′, each inlet wheel 8, 8′ being driven in rotation by a respective one of the engines 2, 2′, and secondly at least two distinct driven shafts 40, 41 of an accessory box 42. In this first embodiment, the at least two drive shafts 41 and 42 of the driven box 42 are arranged in parallel.

(12) The engine(s) 2, 2′ thus serves to drive rotation of at least one of the two driven shafts 40, 41 in isolation or to drive both driven shafts 40 and 41 simultaneously while jointly driving at least one rotor 3, 103, 103′ of the aircraft 1. In this embodiment, the rotor 3 may be the main rotor for providing a hybrid rotorcraft with propulsion and/or lift, while the two rotors 103 and 103′ are two rotors for propelling the hybrid rotorcraft.

(13) As shown, such a mechanical system 4 also has a selective rotary drive member 9 that is axially movable between two distinct drive positions:

(14) a first drive position POST, shown in FIG. 2, in which the engine 2 drives rotation both of the rotor(s) 3, 103, 103′ and of a first driven shaft 40 of the accessory box 42; and

(15) a second drive position POS2, shown in FIG. 3, in which the engine 2 drives a second drive shaft 41 of the accessory box 42 in rotation, where the second drive shaft 41 is distinct from the first drive shaft 40.

(16) Furthermore, such a mechanical system 4 also has a bevel gear pair 7 with intersecting axes 11 and 21 made up of a first bevel gear 12 referred to as a “power” gear having teeth 13 and that is movable in rotation about a first axis 11, and a bevel wheel 22 having teeth 23 and that is movable in rotation about a second axis 21. The respective teeth 13 and 23 of the first bevel gear 12 and of the bevel wheel 22 are then suitable for co-operating in mutually complementary manner. The bevel wheel 22 is then suitable for driving the rotors 3, 103, and 103′ in rotation.

(17) In addition, the mechanical system 4 has a second bevel gear 32, referred to as the “accessory” gear, having teeth 33 meshing with the teeth 23 of the bevel wheel 22. Such an accessory gear 32 is also suitable for transmitting rotary motion to the first driven shaft 40 of the accessory box 42. Furthermore, the speed of rotation of the first driven shaft 40 may advantageously be distinct from the speed of rotation of the bevel gear 12 while conserving a parallel orientation between the first axis 11 and a fourth axis of rotation 43 about which the first driven shaft 40 rotates.

(18) Furthermore, the mechanical system 4 also includes a “takeoff” shaft 50 that is designed to be driven constantly in rotation by the inlet wheel 8. Such a takeoff shaft 50 then serves to transmit rotary motion continuously to the second drive shaft 41 of the accessory box 42 without driving the bevel gear pair 7 and the accessory gear 32 in rotation. In this example, the takeoff shaft 50 is shown as being movable in rotation about a third axis of rotation 51 that is distinct from the first axis of rotation 11.

(19) Such first and second driven shafts 40 and 41 can then be arranged so as to be free to rotate respectively about fourth and fifth axes of rotation 43 and 44 that are mutually parallel but that do not coincide, as shown in the first embodiment of the mechanical system 4.

(20) Such a third axis of rotation 51 is then arranged so that it does not coincide with the first axis of rotation 11, thereby avoiding any problem of interference with a bevel wheel shaft 26. Specifically, such a particular arrangement enables the third axis of rotation 51 to be positioned parallel to a plane defined by the first and second intersecting axes of rotation 11 and 21, without being coplanar therewith. As mentioned above, for reasons of simplifying the representation, the third axis of rotation 51 is shown, erroneously, as being coplanar with the first and second axes of rotation 11 and 21, but that does not correspond to reality since the second axis of rotation 21 and the third axis of rotation 51 cannot intersect.

(21) In addition, as shown in FIG. 2, when the selective drive member 9 is arranged in the first drive position POS1, the inlet wheel 8 then drives in rotation firstly the bevel gear pair 7, the accessory gear 32, and the first driven shaft 40 of the accessory box 42, and simultaneously also drives in rotation the takeoff shaft 50 and the second driven shaft 41 of the accessory box 42.

(22) Such a first drive position POS1 thus corresponds to the rotorcraft in a state of flight since it serves to drive rotation of the main rotor 3 enabling the rotorcraft at least to be provided with lift.

(23) An actuator 10 then enables the selective drive member 9 to be controlled using a rod held in a predetermined position. The actuator may itself be controlled by means of a hydraulic control, for example.

(24) Furthermore, such a selective drive member 9 may advantageously be formed by an activatable freewheel corresponding to a freewheel 29 that is activated or not activated by means of a movable part 19 forming dog clutch means between the freewheel 29 and a gear secured to the inlet wheel 8.

(25) Furthermore, the rod may be arranged coaxially with the inlet wheel 8, thus enabling the selective drive member 9 and more particularly the movable part 19 to be maintained in its first drive position POS1. Such a rod is then arranged on a sixth axis of rotation 17 of the inlet wheel 8.

(26) Such a sixth axis of rotation 17 is then advantageously arranged parallel to the fourth and fifth axes of rotation 43 and 44.

(27) Furthermore, the mechanical system 4 has adapter means 18, such as a pair of gears on parallel axes of rotation, for reducing or increasing the speed of rotation of the inlet wheel 8 and for driving the takeoff shaft 50 and the second driven shaft 41 of the accessory box 42 in rotation.

(28) Consequently, when the selective drive member 9 is placed in the first drive position POS1 and the engine 2 is rotating at a constant speed of rotation, the adapter means 18 can enable the second driven shaft 41 of the accessory box 42 to be driven in rotation at a speed of rotation Ω.sub.2 that is different from the speed of rotation Ω.sub.1 of the first driven shaft 40 of the accessory box 42.

(29) Furthermore, freewheels 70 and 71 are then arranged in the accessory box 42 so as to give precedence to the accessories being driven in rotation by the first driven shaft 40 if it is being driven by the bevel wheel 22.

(30) As shown in FIG. 3, when the selective drive member 9 is arranged in the second drive position POS2, the inlet wheel 8 then drives the takeoff shaft 50 and the second driven shaft 41 of the accessory box 42 in rotation without passing via the bevel gear pair 7, the accessory gear 32, or the first driven shaft 40.

(31) In outline, in this second drive position POS2, the actuator 10 keeps the rod in a position that enables the part 19 of the freewheel 29 to be spaced apart from the gear driven by the inlet wheel 8. For simplification and comprehension purposes, such a movable part 19 is shown herein as being a part that is outside the freewheel 29, however in another variant, such a movable part 19 could equally well be arranged inside the freewheel in order to enable balls or rolling elements that it includes to be moved and held in position.

(32) Such a second drive position POS2 then corresponds to a state of the rotorcraft being on the ground since the engine 2 can then no longer drive rotation of the main rotor 3 of the rotorcraft.

(33) Furthermore, the bevel wheel 22 may form one of two elements meshing with a single-piece transmission member 24 referred to as a “double” gear. A gear 25 thus rotates together with the bevel wheel 22 and co-operates with the teeth of an interlinking wheel 60 suitable for driving at least one main rotor 3 in rotation.

(34) As shown, such an interlinking wheel 60 may also co-operate with the teeth of another gear 25′ of a second double gear 24′.

(35) Under such circumstances and by analogy, another engine 2′ can also serve to drive in rotation another inlet wheel 8′, another power gear 12′, and another bevel wheel 22′ that is complementary to the second double gear 24′.

(36) Thus, such a particular embodiment makes it possible, when the selective drive member 9 is arranged in the first drive position POS1, to mitigate a potential failure of one of the two engines 2, 2′ in order to enable the first driven shaft 40 of the accessory box 42 to be driven constantly in rotation in flight by one or the other of the two engines 2 and 2′.

(37) In a second embodiment of the mechanical system 4 as shown in FIG. 4, the first and second driven shafts 40 and 41 may also be arranged so as to be free to rotate respectively about fourth and fifth axes of rotation 43 and 44 that coincide, by using shafts that are coaxial.

(38) As above, freewheels 70′ and 71′ are then arranged in the accessory box 42 so as to give precedence to the accessories being driven in rotation by the first driven shaft 40 if it is being driven by the bevel wheel 22.

(39) As shown in FIG. 5, the takeoff shaft 50 is shown offset relative to the sixth axis of rotation 17 of the inlet wheel 8. Such a lateral offset of the takeoff shaft 50 makes it possible to avoid interfering with the bevel wheel shaft 26 driven in rotation by the bevel wheel 22.

(40) Furthermore, such a lateral offset of the takeoff shaft 50 is obtained by the adapter means 18 serving to reduce or increase the speed of rotation of the takeoff shaft 50 relative to the speed of rotation of the inlet wheel 8.

(41) 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.