Propulsion unit with foldable propeller blades and method for folding the blades

Abstract

The present invention relates to a propulsion unit (22) having a propeller (26), the propulsion unit comprising: - a nacelle (24); - a propeller (26) rotatably mounted in the nacelle (24) via a hub (28), the propeller (26) comprising blades (32) mounted in a blade sleeve (38) pivotable relative to the hub (28) about a pitch axis (Y), each blade (32) pivotable relative to the sleeve (38) about a folding axis (Z); - The folding device (50) includes an actuator (52) for folding the blade (32); the propulsion unit (22) is characterized in that the folding device (50) includes a control member (56) and a link (58), the control member being fixed to the blade sleeve (38) in rotation and driven by the actuator (52), the link being pivotally mounted on the root (34) of the associated blade (32) on one hand and on the movable control member (56) on the other.

Description

Technical Field

[0001] This invention relates to a propulsion unit with a propeller for an aircraft, the propulsion unit comprising:

[0002] - The cabin, which is designed to be attached to the structural elements of the aircraft;

[0003] - A propeller, which is rotatably mounted in the nacelle about a longitudinal axis of rotation via a hub, the propeller comprising blades, each blade being pivotally fixed to an associated blade sleeve about a radial pitch axis about a radial pitch axis about a folding axis about a blade sleeve about a folding axis about a radial pitch axis about a folding ... folding axis about a radial pitch axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a fold

[0004] - A folding device comprising a folding actuator that controls the pivoting of each blade relative to the blade sleeve between an extended position and a folded position, wherein in the extended position the blade extends radially relative to the axis of rotation and in the folded position the blade extends generally longitudinally against the nacelle. Background Technology

[0005] For example, this type of propeller propulsion unit is used in vertical takeoff and landing aircraft, also known as "VTOL (Vertical Take Off and Landing)". Of course, this propulsion unit can also be used in fixed-wing aircraft, also known as "CTOL (Classic Take Off and Landing)," which stands for "Classic Take Off and Landing." In this case, the aircraft can be equipped with multiple propeller propulsion units to distribute the thrust center and seek optimal propulsion efficiency on the aircraft.

[0006] These propeller propulsion units can be deactivated depending on the aircraft's flight configuration. When the propeller propulsion units are deactivated, the propellers may adversely affect the aircraft's aerodynamic performance, for example, by generating drag or by creating local disturbances in the airflow.

[0007] To address this issue, propulsion units equipped with foldable blade propellers have been proposed to remove these inactive blades from the local flow.

[0008] However, when folding is accidentally triggered and the blade is not in the predetermined folding pitch position, existing folding devices may apply force to the folding axis of the blade. For example, such a device is disclosed in document WO 2017 / 162561 A1.

[0009] Document US 2019 / 016441 A1 discloses a folding device that includes a control member formed by a lever mounted on a blade sleeve, the lever engaging with a linkage connected to the blade. Summary of the Invention

[0010] This invention proposes a propulsion unit with a propeller for an aircraft, the propulsion unit comprising:

[0011] - The cabin, which is designed to be attached to the structural elements of the aircraft;

[0012] - A propeller, which is rotatably mounted in the nacelle about a longitudinal axis of rotation via a hub, the propeller comprising blades, each blade being pivotally fixed to an associated blade sleeve about a radial pitch axis about a radial pitch axis about a folding axis about a blade sleeve about a folding axis about a radial pitch axis about a folding ... folding axis about a radial pitch axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a folding axis about a fold

[0013] - A folding device, comprising a folding actuator that controls the pivoting of each blade relative to the blade sleeve between an deployed position and a folded position, wherein in the deployed position the blade extends radially relative to the axis of rotation and in the folded position the blade extends generally longitudinally against the nacelle.

[0014] The folding device includes a transmission associated with each blade, each transmission including a movable control member and a link. The movable control member is fixedly mounted to the blade sleeve in rotation and is moved by a folding actuator. The link includes a first end and a second end. The first end is pivotally mounted eccentrically relative to the folding axis at the root of the associated blade, and the second end is pivotally mounted on the movable control member.

[0015] The characteristic feature is that the control component of each transmission device is formed by a slider, which is mounted to be able to slide radially between an inner limit position and an outer limit position in an associated blade sleeve, the inner limit position corresponding to one of the positions of the associated blade and the outer limit position corresponding to the other of the positions of the associated blade.

[0016] This folding device ensures that the linkage pulls the blade to pivot around the folding axis of the blade, regardless of the blade's pitch angle position, without applying force to the folding axis of the blade.

[0017] According to another feature of the propulsion unit of the invention, the sliding of the movable control member is actuated by a cam, and the movable control member is fixedly mounted to the cam follower in terms of sliding.

[0018] Another feature of the propulsion unit according to the invention is that the cam is mounted to slide longitudinally, and the cam follower is mounted to rotate about the pitch axis on a movable control member.

[0019] According to another feature of the propulsion unit of the invention, all cams of each transmission device in the transmission device are attached to a common rod of the folding actuator, which is slidable along the axis of rotation between a first position and a second position, the first position corresponding to the unfolded position of the blade and the second position corresponding to the folded position of the blade.

[0020] According to another feature of the propulsion unit of the invention, the propulsion unit includes means for detecting the position of the actuator rod in a first position and a second position of the actuator rod. This feature enables the pilot and / or the aircraft's electronic control unit to know the position of the propeller blades and detect malfunctions when appropriate.

[0021] According to another feature of the propulsion unit of the invention, the propulsion unit includes means for mechanically locking the actuator rod in a first position and a second position of the actuator rod. This feature enables ensuring that the blade remains in either the deployed or folded position, thereby preventing any unintentional pivoting of the blade.

[0022] The present invention also relates to a method for folding blades of a propeller of a propulsion unit manufactured according to the teachings of the present invention, characterized in that the method includes a folding step during which the blades are folded by a folding device, followed by a folding inspection step during which the blades are inspected by a detection device to check whether they have indeed been folded.

[0023] According to another feature of the method, if the blade is detected to be in a folded position during the folding inspection step, the mechanical locking device is controlled to lock the blade in the folded position. Attached Figure Description

[0024] Other features and advantages of the invention will become apparent from the following detailed description, and with reference to the accompanying drawings, in which:

[0025] Figure 1 It is a perspective view of an aircraft equipped with multiple propulsion units with propellers manufactured according to the teachings of the present invention.

[0026] Figure 2 It is shown Figure 1 A side view of the propulsion unit of an aircraft, in which the propeller blades are deployed at a pitch angle position that enables increased thrust.

[0027] Figure 3 Is with Figure 2A similar view, where the propeller blades are deployed at the folded pitch angle position.

[0028] Figure 4 Is with Figure 2 A similar view, in which the propeller blades are folded.

[0029] Figure 5 is based on Figure 10 The cross-sectional plane 5-5 shows an axial cross-sectional view of the rotating portion of the traction propulsion unit, wherein the propeller blades are deployed at a pitch angle position that enables increased thrust, and the traction propulsion unit is equipped with a folding device manufactured according to a first embodiment of the invention.

[0030] Figure 6 is based on Figure 12 Plane 6-6 shows an axial cross-sectional view of the rotating portion of the traction propulsion unit, wherein the propeller blades are deployed at the folding pitch angle position, and the traction propulsion unit is equipped with a folding device manufactured according to the first embodiment.

[0031] Figure 7 is based on Figure 13 Plane 7-7 shows an axial cross-sectional view of the rotating portion of the traction propulsion unit, wherein the propeller blades are folded, and the traction propulsion unit is equipped with a folding device manufactured according to the first embodiment.

[0032] Figure 8 It is a view similar to Figure 6, in which the traction propulsion unit is equipped with a folding device manufactured according to the second embodiment.

[0033] Figure 9 It is a view similar to Figure 7, wherein the traction propulsion unit is equipped with a folding device manufactured according to the second embodiment.

[0034] Figure 10 It shows Figure 1 A front view of the traction propulsion unit of an aircraft, wherein the propeller blades are deployed at a pitch angle position that enables increased thrust, and the propeller occupies any angular position about the axis of rotation of the propeller.

[0035] Figure 11 Is with Figure 10 A similar view shows the propeller blades deployed at the folded pitch angle position, with the propeller occupying any angular position around the propeller's axis of rotation.

[0036] Figure 12 Is with Figure 11 A similar view shows the propeller blades deployed at the folded pitch angle position, with the propeller occupying the division angle position around the propeller's axis of rotation.

[0037] Figure 13 Is with Figure 12A similar view shows the propeller blades folded into a housing in the nacelle.

[0038] Figure 14 It is shown schematically. Figure 1 A side view of the rotating portion of the propulsion unit of the aircraft in the first configuration, wherein the propeller is driven by an electric motor separate from the stepper motor.

[0039] Figure 15 Is with Figure 14 A similar view, in which the propulsion unit is manufactured in a second configuration, wherein the propeller is driven by an internal combustion engine separate from the stepper motor.

[0040] Figure 16 Is with Figure 14 A similar view, in which the propulsion unit is manufactured in a third configuration, wherein the propeller is driven by a stepper motor.

[0041] Figure 17 It is based on Figure 14 The cross-sectional plane 17-17 shows a radial cross-sectional view of the stepper motor according to the first embodiment.

[0042] Figure 18 Is with Figure 17 A similar view shows a stepper motor according to a second embodiment.

[0043] Figure 19 Is with Figure 17 A similar view shows a stepper motor according to a third embodiment.

[0044] Figure 20 It shows Figure 19 A perspective view of the rotor of a stepper motor.

[0045] Figure 21 This is a perspective view showing a stepper motor according to the fourth embodiment.

[0046] Figure 22 It is shown schematically. Figure 1 A perspective view of the propeller of the propulsion unit, which includes a device for locking the propeller rotating relative to the nacelle, the locking device being in an inactive state.

[0047] Figure 23 Is with Figure 22 A similar view, where the locked device is active.

[0048] Figure 24 This is a circuit diagram showing the angular position of a sensor for the propeller about its axis of rotation relative to the nacelle.

[0049] Figure 25 It shows the method for... Figure 1 A flowchart illustrating the steps involved in folding the blades of an aircraft's propulsion unit.

[0050] Figure 26 It shows the method for... Figure 1 A block diagram of the steps involved in the method of deploying the blades of the propulsion unit of an aircraft. Detailed Implementation

[0051] In the following description, elements with the same structure or similar function will be referred to by the same reference numerals.

[0052] In the remainder of the description, a longitudinal orientation will be used, as indicated by arrow "L" in the figure. This longitudinal orientation is locally associated with each propulsion unit within the propulsion unit. The longitudinal direction is oriented from front to back and is parallel to the axis of rotation of the propulsion unit's propeller.

[0053] A radial orientation should be used, which is orthogonal to the longitudinal direction and oriented from the inside out near the propeller's axis of rotation. A tangential orientation is also used, which is orthogonal to both the radial and longitudinal directions.

[0054] Figure 1 An aircraft 20 is shown, comprising a plurality of propeller propulsion units 22 manufactured according to the teachings of the present invention. This aircraft is a vertical takeoff and landing (VTOL) aircraft. In this respect, the aircraft 20 includes propulsion units 22 referred to as "lifting" units, which are designed to provide vertical thrust to the aircraft 20 for lifting. These lifting propulsion units 22 are here arranged on the tail fin and fuselage of the aircraft 20. The aircraft 20 also includes propulsion units 22 referred to as traction units, which are designed to provide longitudinal thrust to enable the aircraft 20 to move forward. The traction propulsion units 22 are here arranged on the wings of the aircraft 20.

[0055] Alternatively, the invention applies to a typical aircraft, also referred to simply as "CTOL," meaning "Typical Takeoff and Landing." Therefore, the aircraft comprises only a traction propulsion unit.

[0056] The propulsion unit 22 has a similar design. Therefore, the following description of a single propulsion unit 22 applies to the other propulsion units 22. Figures 2 to 4 As shown, the propulsion unit 22 includes a nacelle 24, which is designed to be mounted on a structural element of the aircraft 20, such as a wing or fuselage. The propulsion unit 22 is attached to the structural element, for example, via a strut (not shown). The nacelle 24 is equipped with an aerodynamic fairing.

[0057] The cabin 24 can be fixedly mounted on the structural element. When the structural element is fixed, the propulsion unit is fixed relative to the fuselage of the aircraft, thus forming a traction propulsion unit or a lifting propulsion unit. When the structural element is pivotally mounted relative to the fuselage of the aircraft, the propulsion unit alternately performs traction or lifting functions depending on the position of the structural element.

[0058] According to another variation of the invention, the nacelle is pivotally mounted on a structural element about a transverse axis, and the propulsion unit can alternately perform traction or lifting functions depending on the angular position of the nacelle on the structural element.

[0059] The propulsion unit 22 also includes a propeller 26, which is rotatably mounted in the nacelle 24 about a longitudinal axis of rotation “X” via a central hub 28. The front of the hub 28 typically covers the head 30 to improve the aerodynamic performance of the propulsion unit 22, particularly by reducing the drag of the propulsion unit.

[0060] The propeller 26 also includes a plurality of blades 32 extending along a main axis from a root 34 to a free end 36 called a blade tip, the blades 32 being linked to a hub 28 via the root. Each blade 32 has a profile extending from a leading edge to a trailing edge along the direction of rotation of the propeller 26. Each propeller 26 includes two blades 32. Of course, the invention is applicable to propellers comprising a large number of blades (e.g., three, four, or more blades).

[0061] The blades 32 are evenly distributed around the hub 28 at a defined angular pitch, such that the propeller 26 has rotational invariance about the given angular pitch around the axis of rotation “X”.

[0062] Each blade 32 can pivot relative to the hub 28 about a radial pitch axis “Y”, which, when the propeller 26 is deployed, substantially coincides with the main axis of the blade 32, as will be explained later. For this purpose, see Figures 5 to... Figure 9 As shown, hub 28 includes as many blade sleeves 38 as propeller 26 includes blades 32. Each blade sleeve 38 is pivotally mounted on hub 28 about pitch axis "Y". Each blade sleeve 38 is pivotally guided, for example, by rolling bearings. Each blade sleeve 38 is in the form of a sleeve that receives the root 34 of the associated blade 32, such that the blade 32 is rotationally secured to the blade sleeve 38 about pitch axis "Y".

[0063] Therefore, blade 32 can be controlled at pitch angle position "β" around the pitch axis "Y" within a range extending between the first limiting pitch angle position "β1" and the second limiting pitch angle position "β2". The thrust generated by the rotation of propeller 26 is determined according to the propeller's pitch angle position "β". The range includes the folded pitch angle position "β0", for which blade 32 is feathered.

[0064] Therefore, as Figure 3 and Figure 4 As shown, for the lifting propulsion unit 22, the folding pitch angle position "β0" corresponds to the orientation of the blade 32 extending in a plane orthogonal to the rotation axis "X", also known as the zero load capacity pitch angle position.

[0065] On the contrary, such as Figures 11 to 13 and Figure 6 to Figure 9 As shown, for the traction propulsion unit 22, the fold pitch angle position "β0" corresponds to the orientation of the blade 32 extending in a plane parallel to the rotation axis "X", and the blade 32 is "feathered".

[0066] Furthermore, each propeller 26 in the propulsion unit 22 has the special feature of foldable blades 32. In particular, this makes it possible to improve the aerodynamic performance of the aircraft 20 under certain flight conditions, such as when the aircraft 20 is flying at a speed sufficient for the aircraft's wings to provide lift alone, by folding the blades 32 of the propulsion unit 22.

[0067] Therefore, as shown in Figure 5 to... Figure 9 As shown, each blade 32 is pivotally mounted relative to its associated blade sleeve 38 about a folding axis “Z”, which extends orthogonally to the radial pitch axis “Y” of the blade 32. Therefore, the folding axis “Z” rotates together with the blade sleeve 38 about the pitch axis “Y”. More specifically, the blade 32 is hinged to the blade sleeve 38 such that when the blade 32 occupies the folding pitch angle position “β0” of the blade, the folding axis “Z” is orthogonal to the rotation axis “X”.

[0068] Therefore, the blades 32 of the propeller 26 can be controlled between an extended position and a folded position. In the extended position, such as... Figure 2 , Figure 3 Figure 5, Figure 6 Figure 8 as well as Figures 10 to 12 As shown, the main axis of blade 32 extends approximately radially relative to the rotation axis "X", and in the folded position, as... Figure 4 Figure 7 Figure 9 as well as Figure 13As shown, the main axis of blade 32 extends approximately longitudinally parallel to the rotation axis "X". In the folded position, blade 32 is longitudinally received against nacelle 24.

[0069] Advantageously, such as Figures 2 to 4 as well as Figures 10 to 13 As shown, in order to reduce the drag of the propulsion unit 22 when the blades 32 are in the folded position, the nacelle 24 includes housings 39, each designed to accommodate a blade 32 of the propeller 26 at its folded pitch angle position "β0". Therefore, the blades 32 in the folded position are integrated into the fairing of the nacelle 24. For this purpose, the nacelle 24 includes as many housings 39 as the propeller 26 includes blades 32.

[0070] In order to control the pitch angle position "β" of the blade 32, the propulsion unit 22 includes a pitch device 40 (Figure 5 to 10). Figure 9 As can be seen in the image, the pitch device controls the pivoting of the blade sleeve 38 about the radial pitch axis "Y" relative to the hub 28 to determine the pitch angular position "β" of each blade 32. Here, the pitch device 40 enables all blades 32 of the propeller 26 to be controlled to the same pitch angular position "β" simultaneously.

[0071] The pitch device 40 specifically includes a pitch actuator 42 comprising a control lever 44 that slides along a main axis coaxial with the rotation axis “X”. This pitch actuator is a linear electric actuator 42. Alternatively, the pitch actuator can also be a hydraulic or electro-hydraulic actuator. A radial plate 46 is attached to the free end of the control lever 44. Each blade 32 of the propeller 26 is connected to the plate 46 via a control link 48 having a first end hinged to the plate 46 and a second end hinged to a blade sleeve 38 in an eccentric manner relative to the pitch axis “Y”, forming a link / crank connection between the plate 46 and the blade 32. Therefore, the pitch angular position “β” of the blade 32 varies with the axial position of the control lever 44.

[0072] Here, the pitch actuator 42 can be fixedly mounted to the propeller 26 in terms of rotation. The pitch actuator 42 is arranged, for example, inside the nose 30.

[0073] In a variant not shown in this invention, the pitch actuator is fixedly mounted relative to the nacelle, and only the control board 46 can be fixedly mounted to the propeller 26 in terms of rotation.

[0074] Advantageously, the propulsion unit 22 includes means for determining the pitch angular position "β". This means is, for example, a pitch sensor 45, which enables the detection of the longitudinal position of the rod 44. The pitch sensor 45 is, for example, an inductive sensor.

[0075] Figure 5 to Figure 9 As shown, in order to control the blades 32 between their deployed and folded positions, the propulsion unit 22 includes a folding device 50, which includes an actuator 52 that controls the pivoting of each blade 32 relative to its blade sleeve 38 between the deployed and folded positions. The folding actuator 52 is common to all blades 32, such that the blades 32 are controlled simultaneously between their deployed and folded positions. The folding actuator 52 is here formed by an electric actuator.

[0076] The folding device 50 includes a transmission 54 associated with each blade 32, which functions to transmit motion of the folding actuator 52 to the blade 32. Each transmission 54 includes a movable control member 56, which is fixed in rotation to the associated blade sleeve 38 and movable by the folding actuator 52. Each transmission 54 also includes a link 58, which includes a first end pivotally mounted eccentrically to the root 34 of the associated blade 32 relative to the folding axis "Z" and a second end pivotally mounted to the movable control member 56. The link 58 forms a link / crank connection with the blade root 34, which allows motion of the control member 56 to be converted into pivoting motion of the blade 32 about the folding axis "Z" of the blade. For this purpose, the two ends of the link 58 are mounted such that the two ends can pivot about two axes parallel to the folding axis "Z".

[0077] according to Figure 8 and Figure 9 In the first embodiment of the folding device 50 shown, the control member 56 of each transmission device 54 is formed by a slider, which is mounted to slide radially in the associated blade sleeve 38 along the pitch axis "Y" between an inner limit position and an outer limit position, the inner limit position corresponding to one of the positions of the associated blade 32 and the outer limit position corresponding to another of the positions of the associated blade 32.

[0078] Figure 8 The external limit position of the control member 56 shown here corresponds to the deployed position of the associated blade 32, while Figure 9 The internal limit position of the control component shown corresponds to the folding position of the associated blade 32.

[0079] The sliding of the movable control member 56 is actuated here by a cam 60, which engages with the movable control member 56 via a cam follower 62. The cam follower 62 is fixedly mounted to the control member 56 in sliding direction along the pitch axis "Y".

[0080] More specifically, the cam 60 is mounted to slide longitudinally along the axis of rotation “X” between a first forward longitudinal position and a second rearward longitudinal position, the first forward longitudinal position here corresponding to Figure 8 The unfolded position of the blade 32 shown here corresponds to the second rear longitudinal position. Figure 9 The folding position of the blade 32 is shown. For this purpose, the cam 60 has an inclined profile extending from a front end to a rear end, the front end being arranged radially close to the axis of rotation "X", and the rear end being arranged at a greater radial distance from the axis of rotation "X".

[0081] Cam 60 is fixedly mounted to slide rod 64 of folding actuator 52 in sliding manner. Since all blades 32 are simultaneously controlled by the same folding actuator 52, all cams 60 of each transmission in transmission 54 are attached to the same slide rod 64. Slide rod 64 is coaxial with the rotation axis "X".

[0082] The folding actuator 52 is fixedly mounted to the propeller 26 in rotation around the rotation axis "X".

[0083] Alternatively, the folding actuator is fixedly mounted relative to the nacelle. In this case, regardless of the angular position of the propeller about the axis of rotation, the cam can be formed by a truncated cone that allows the cam to work in conjunction with a cam follower, or the cam can be rotatably mounted relative to the nacelle about the axis of rotation to accompany the rotation of the propeller and remain coincident with the cam follower of the associated blade.

[0084] Furthermore, the cam follower 62 is formed here by rollers that rotate about an axis orthogonal to the rotation axis "X" and the pitch axis "Y". The rollers are, for example, diabolo-shaped rollers with two parallel rolling surfaces on the cam 60. Advantageously, the cam follower 62 is laterally guided relative to the cam 60 via a longitudinal guide 66, which is carried by the cam 60, during sliding. Regardless of the pitch angle position "β" of the associated blade 32, in order to keep the cam follower 62 engaged in the guide 66, the cam follower is rotatably mounted on the movable control member 56 about the pitch axis "Y". Therefore, the cam follower 62 is carried by a U-shaped clip 70, which is pivotally mounted, for example, on the inner end of the movable control member 56 via rolling bearings. Therefore, regardless of the pitch angle position "β" of the associated blade 32, the rotation axis of the cam follower 62 remains orthogonal to the rotation axis "X", while the movable control member 56 can pivot freely and firmly with the blade sleeve 28 about the pitch axis "Y".

[0085] According to a second embodiment of the folding device 50 shown in Figures 5 to 7, a movable control member 56 is formed by a crank that is pivotally mounted in a blade sleeve 38 about a control axis "Z1" parallel to the folding axis "Z" between a first limit angle position and a second limit angle position, the first limit angle position corresponding to one of the positions of the associated blades 32, and the second limit angle position corresponding to the other of the positions of the associated blades 32. A second end of a connecting rod 58 is eccentrically pivotally mounted on the control member 56 relative to the control axis "Z1" of the connecting rod.

[0086] The pivoting of the movable control member 56 is actuated here by a rack 68, which engages with the toothed section 71 of the movable control member 56. More specifically, the rack 68 is mounted to slide longitudinally along the axis of rotation "X" between a first rear longitudinal position and a second front longitudinal position, the first rear longitudinal position corresponding here to the unfolded position of the blade 32 as shown in Figures 5 and 6, and the second front longitudinal position corresponding here to the folded position of the blade 32 as shown in Figure 7. The rack 68 extends parallel to the axis of rotation "X".

[0087] The rack 68 is fixedly mounted to the sliding rod 64 of the folding actuator 52 in a sliding manner. Since all blades 32 are simultaneously controlled by the same folding actuator 52, all racks 68 of each transmission in the transmission 54 are attached to the same sliding rod 64. The sliding rod 64 is coaxial with the rotational axis "X". The folding actuator 52 is fixedly mounted to the propeller 26 in a rotational manner around the rotational axis "X".

[0088] Regardless of the embodiment of the folding device 50, it is advantageous to be able to check whether the blades 32 of the propeller 26 are in the deployed or folded position. Therefore, the folding device 50 is equipped with a device for detecting the position of the blades 32. The detection device is formed, for example, by a first deployment sensor 72A and a second folding sensor 72B. The first deployment sensor 72A is arranged to detect that a movable element arranged on the transmission chain between the folding actuator 52 and the blades 32 occupies a specific position corresponding to the deployed position of the blades 32, while the second folding sensor 72B is arranged to detect that a movable element arranged on the transmission chain between the folding actuator 52 and the blades 32 occupies a specific position corresponding to the folded position of the blades 32. Here, the sensors 72A and 72B operate in an on / off manner, being activated only when the blades 32 occupy the associated deployed or folded position. These sensors are, for example, contact sensors 72A and 72B or sensing sensors 72A and 72B.

[0089] exist Figure 8 and Figure 9In the example shown, corresponding to the first embodiment of the folding device 50, the unfolding sensor 72A is activated by the free end of the control lever 64, while the folding sensor 72B is activated by the rear end of the cam 60.

[0090] In the example of the second embodiment corresponding to the folding device 50 shown in Figures 5 to 7, the unfolding sensor 72A is activated by the control member 56 at the angular position of the blade corresponding to the unfolded position of the blade 32, while the folding sensor 72B is activated by the front end of the control rod 64.

[0091] Furthermore, a mechanical locking device can be provided for the blade 32 in its deployed and folded positions. The locking device is, for example, formed by a latch 75 that engages with a movable element arranged on a drive chain between the folding actuator 52 and the blade 32. The latch 75 is arranged to prevent pivoting of the movable control member 56 when the blade 32 is in its deployed and folded positions. The latch 75 is actuated here by sliding of the rack 68.

[0092] On the other side of propulsion unit 22, such as Figures 14 to 16 As shown, the propulsion unit includes a rotor shaft 78, which is rotatably mounted in the nacelle 24 coaxial with the rotation axis "X" and is fixed to the propeller 26 in terms of rotation. The propulsion unit 22 also includes a propulsion device that drives the propeller 26 to rotate via the rotor shaft 78.

[0093] The propulsion unit 22 also includes an indexing device for stopping the propeller 26 about the axis of rotation "X" at at least one indexing angle position "θi", wherein the blades 32 in the deployed position coincide with the housing portion 34 of the nacelle 24. Due to the rotational invariance of the propeller 26, the propeller may have as many indexing angle positions "θi" as the blades 32.

[0094] The indexing device is formed by an electric stepper motor 82. In a known manner, this stepper motor 82 includes a rotor 84 rotatably mounted in a stator 86. The rotor 84 is coupled to the hub 28 of the propeller 26, while the stator 86 is fixed relative to the nacelle 24. The rotor 84 is here fixedly mounted to the rotor shaft 78 in rotation about the axis of rotation “X”.

[0095] The advantage of this stepper motor 82 is that it can decelerate the propeller 26 by reversing its rotation using a resistance torque. Furthermore, the stepper motor enables the supply of motor torque to the propeller 26, allowing it to be driven with high precision to one of the propeller's angular resolutions "θi". Finally, the stator 86 of the stepper motor 82 is arranged such that each angular resolution "θi" of the propeller 26 is matched to the pitch of the stepper motor 82, enabling the locking of the propeller 26's rotation at each of the propeller's angular resolutions "θi".

[0096] exist Figure 14 In the example shown, the propulsion device includes an electric propulsion motor 80 separate from the stepper motor 82. In this case, the stepper motor 82 is inserted between the propulsion motor 80 and the propeller hub 28 in the drive train of the motor torque generated by the propulsion motor 80. The stepper motor 82 is here directly mounted on the rotor shaft 78, which is permanently coupled to the motor shaft of the propulsion motor 80.

[0097] exist Figure 15 In the example shown, the propulsion motor 80 is an internal combustion engine. In this case, a stepper motor 82 is inserted between the propulsion motor 80 and the propeller hub 28 in the transmission chain of the motor torque generated by the propulsion motor 80. The stepper motor 82 is here directly mounted on the rotor shaft 78, which is controlled to the motor shaft of the propulsion motor 80 via a clutch 83.

[0098] exist Figure 16 In the example shown, the electric stepper motor 82 forms the propulsion device.

[0099] exist Figure 17 In the first embodiment of the indexing device shown, the electric stepper motor 82 is a variable reluctance motor, also known as a "variable reluctance stepper" or "switched reluctance motor" (SRM). In this stepper motor 82, the rotor 84 is made of a ferromagnetic material. The rotor 84 is formed, for example, by a stack of soft iron sheets, or the rotor 84 is made of a single integral portion of magnets. The rotor 84 includes external teeth with an even number of teeth 88.

[0100] The stator 86 is typically made of a stack of ferromagnetic metal sheets. The stator 86 includes internal teeth with an even number of teeth 90. The stator includes multiple coils 92. The coils 92, arranged around two opposing teeth 90, are powered in series to form two electromagnets, the polarities of which are radially directed towards the rotor 84.

[0101] The number of teeth on the rotor 84 is different from the number of coils on the stator 86, which makes it possible to determine the number of pitches of the stepper motor 82, i.e. the number of angular positions, wherein the rotor 84 can be stably stopped by supplying power to the two opposing coils 92 of the rotor 86.

[0102] By sequentially supplying power to the opposing pairs of electric coils 92, the rotor 84 can be rotated by attracting the rotor teeth 88 that are closest to the alignment of the electric coils 92.

[0103] In the second embodiment of the indexing device, the electric stepper motor 82 is a permanent magnet motor, also known as a "permanent magnet stepper".

[0104] The stator 86 is substantially the same as the stator of the variable reluctance stepper motor described in the first embodiment. However, the rotor 84 includes at least one permanent magnet, rather than teeth, comprising a north pole "N" and a south pole "S", the polarity axis of the at least one permanent magnet being radially oriented. The polarities "N" and "S" of the permanent magnet are arranged symmetrically with respect to the rotation axis "X", such that the north pole "N" and the south pole "S" are arranged alternately around the rotation axis "X".

[0105] This stepper motor 82 typically has higher torque than a variable reluctance motor.

[0106] exist Figure 19 and Figure 20 In the third embodiment of the indexing device shown, the electric stepper motor 82 is a hybrid motor, also known as a "hybrid synchronous stepper".

[0107] The stator 86 is substantially the same as the stator of the variable reluctance stepper motor described in the first embodiment.

[0108] On the other hand, the rotor 84 is formed here by two gears 84A and 84B made of ferromagnetic material, both gears having external teeth equipped with the same even number of teeth 88A and 88B. The two gears 84A and 84B are coaxially mounted with an axially inserted permanent magnet 94, with the north pole contacting one gear 84A and the south pole contacting the other gear 84B.

[0109] Due to this configuration, tooth 88A of the first gear 84A forms the north pole, while tooth 88B of the second gear 88B forms the south pole. The teeth 88A of the first gear 84A and the teeth 88B of the second gear 84B are offset at an angle. Therefore, in an axial view, the tooth 88A forming the north pole is angled between the two teeth 88B forming the south pole.

[0110] The resulting rotor 84 can be rotatably received within the stator 86. Therefore, supplying power to some of the coils 92 of the stator 86 will attract the teeth 88A, 88B of the rotor 84, which are of opposite sign.

[0111] The advantage of this hybrid stepper motor 82 is that it has a large number of steps, similar to the variable reluctance motor 82 described in the first embodiment, while having high motor torque, similar to the permanent magnet motor 82 described in the second embodiment.

[0112] Alternatively, for this third embodiment, such as Figure 21 As shown, the stepper motor is an axial-flow stepper motor 82, wherein the rotor 84 is formed of a disk, and a magnet 94 with alternating polarities is provided on the outer periphery of the disk. The stator 86 also includes an electromagnet formed of an electric coil 92 wound around a core of ferromagnetic material to generate a magnetic field oriented parallel to the rotation axis "X" of the rotor 84 along the outer periphery of the rotor 84.

[0113] Regardless of the type of stepper motor 82 implemented, the propulsion unit 22 advantageously includes a device 96 for mechanically locking the propeller 26 about its axis of rotation "X" relative to the nacelle 24 at each of the propeller's angular positions "θi". Furthermore, the locking device 96 is designed such that the propeller 26 can only be locked at the angular positions "θi".

[0114] like Figure 22 and Figure 23 As shown, the locking device 96 includes a disc 98 that is fixedly mounted to the propeller 26 in terms of rotation. The disc 98 is mounted coaxially with the axis of rotation “X”. The disc 98 is radially defined by an annular outer peripheral edge 100 and axially defined by two circular surfaces. The disc 98 includes at least one pawl 102, which corresponds to one of the angular resolution positions “θi”. The disc 98 includes a single pawl 102.

[0115] Alternatively, disk 98 may include a plurality of pawls 102, each pawl corresponding to a division angular position “θi”. Therefore, disk 98 may include a plurality of pawls 102 equal to the number of division angular positions “θi”. In particular, this allows for faster access to the division angular position “θi” without requiring another full propeller rotation.

[0116] Pawl 102 can engage locking member 104, which is mounted to move relative to nacelle 24 between a non-active position and an active position. In the non-active position, disk 98 can rotate freely. In the active position, when propeller 26 occupies one of the propeller's angular positions "θi", locking member 98 can be received in pawl 102 to fix propeller 26 about the axis of rotation "X" relative to nacelle 24 in terms of rotation. Locking member 104 is moved, for example, by an electric actuator.

[0117] exist Figure 22 and Figure 23 In the illustrated embodiment, the pawl 102 is formed in the outer peripheral edge 100 of the disk 98. The locking member 104 is here mounted to slide radially relative to the cabin 24 between a non-active position and an active position. In the non-active position, such as... Figure 22 As shown, the locking member is spaced apart from the outer peripheral edge 100. In the movable position of the locking member, as... Figure 23 As shown, the locking member is radially displaced toward the rotation axis "X" to coincide with the pawl 102. When the propeller 26 does not occupy one of the pitch angle positions "θi" of the propeller, the locking member 104 cannot be controlled to the active position of the locking member because the locking member will abut against the outer peripheral edge 100 of the disk 98.

[0118] In a variant of the invention (not shown), the pawl is formed on an annular track on one of the circular surfaces of the disk. In this case, the locking member can be mounted to slide relative to the cabin in the longitudinal direction.

[0119] The locking sensor 105 is, for example, a contact sensor or a sensing sensor, which enables the detection of when the locking member 104 is in the active position of the locking member.

[0120] Advantageously, each pawl 102 has a cam track shape equipped with two ramps converging toward a bottom 106. The bottom 106 is arranged such that when the locking member 104 is received in the bottom of the pawl 102, the propeller 26 occupies exactly one of the angular positions “θi” of the propeller. The locking member 104 includes rollers 108 or sliding coatings at its free end, which can roll or slide against the ramps of the pawl 102. Thus, when the propeller 26 stops at an angular position defined within a tolerance range [θi-λ; θi+λ] on both sides of one of the angular positions “θi” of the propeller, the rollers 108 contact one of the ramps of the pawl 102 when the locking member 104 is controlled toward the moving position of the locking member. The locking member 104 provides sufficient force to rotate the propeller 26 by engaging with the ramp of the pawl 102, as the locking member moves toward the active position of the locking member until the roller 108 is at the bottom 106 of the pawl 102, so as to precisely position the propeller 26 at the propeller's pitch angle position "θi".

[0121] In order to perform such an operation, the propeller 26 is preferably not subjected to any electric motor torque or resistance torque, except for the torque caused by friction of the rotational guide member of the propeller 26.

[0122] In addition, such as Figures 14 to 16 As shown, in order to ensure that the propeller 26 occupies all the angular positions "θi" of the propeller, or at least occupies an angular position within a tolerance range [θi-λ; θi+λ] defined on both sides of one of the angular positions "θi" of the propeller, the propulsion unit 22 includes a sensor 110 for the angular position of the propeller 26 relative to the nacelle 24.

[0123] For example, the inductive sensor 110 enables the measurement of the propeller's angular position without contact. Thus, the first rotor element 111 is fixedly mounted to the propeller 26 in terms of rotation, while the second stator element 113 enables the detection of the rotor element's angular position by an electromagnetic device.

[0124] like Figure 24As shown, the sensing sensor 110 is a resolver, also known as an "RVDT" or "Rotary Variable Differential Transformer." As a known non-limiting example, this sensor 110 includes a main coil 112 carried by a stator element 113 and two secondary coils 114, 116. The main coil 112 is powered by an alternating voltage "Vr". The two secondary coils 114, 116 are offset by 90° about the rotation axis "X". The rotor element 111 includes a reference coil 118. The reference coil 118 and the main coil 112 form a resolver 120. The secondary coils 114, 116 are energized by the rotation of the reference coil 118 carried by the rotor element 111. The voltage value in each of the secondary coils 114, 116 uniquely enables the determination of the angular position of the rotor element 111 about the rotation axis "X".

[0125] Alternatively, the sensing sensor 110 is made of a product with the trade name "Inductosyn", which enables high angular accuracy.

[0126] Now refer to Figure 25 A method for folding the blades 32 of the propeller 26 of the propulsion unit 22 is described. This method is implemented by an electronic control unit (not shown). The method can be triggered automatically or by manual command from the pilot. At the start of the method, the blades 32 of the propeller 26 are as follows: Figure 2 , Figure 3 Figures 5 and 6 Figure 8 As shown in the diagram. Figure 2 As shown in Figure 5, blade 32 occupies a pitch angle position "β", which may differ from the folding pitch angle position "β0" of the blade. Furthermore, propeller 26 is typically driven to rotate by a propulsion device.

[0127] In the first step, “E1-1”, certain flight conditions of the aircraft are checked to obtain authorization to continue with the folding method of blade 32.

[0128] For example, when step "E1-1" is applied to the lifting propulsion unit 22, it checks whether the aircraft 20 has reached a speed sufficient to provide load-bearing capacity for the aircraft's wings without requiring lifting thrust from the lifting propulsion unit 22. For example, it checks whether the forward speed "V" of the aircraft 20 is significantly higher than a determined first threshold speed "V0". If the forward speed of the aircraft is significantly higher than the determined first threshold speed, step "E1-2" to stop the next propulsion is triggered; otherwise, the folding method is interrupted.

[0129] According to another example, when step "E1-1" is applied to the traction propulsion unit 22, it is checked whether the aircraft 20 has reached a sufficient speed for economical cruise flight without needing to use all traction propulsion units 22 simultaneously to provide thrust to the aircraft 20. For example, it is checked whether the forward velocity "V" of the aircraft 20 is significantly higher than a determined second threshold velocity "V1". The blades 32 of the traction propulsion unit 22 can also be folded when the aircraft 20 is in hovering flight, since the blades of the traction propulsion unit are no longer needed. Then it is checked whether the forward velocity of the aircraft 20 is zero. If one of these conditions is selected, the next step "E1-2" is triggered; otherwise, the folding method is interrupted.

[0130] In the stopping step "E1-2" of propulsion, the driving torque provided by the propulsion device is interrupted, allowing the propeller 26 to rotate freely only due to the propeller's inertia.

[0131] When the propeller 26 is driven by the combustion propulsion motor 80, the clutch 83 is controlled to disengage, either at the start of step “E1-2” to stop the propulsion, or after a set time period determined for when the friction of the motor has begun to decelerate the propeller 26.

[0132] When the propeller 26 is driven by the electric propulsion motor 80, the propulsion motor 80 remains connected to the propeller 26 because the friction in such a motor is typically low.

[0133] At the end of step "E1-2" to stop propulsion, the pitch step "E1-3" is triggered. In this pitch step "E1-3", the blades 32 of the propeller 26 are controlled to the blade folding pitch angle position "β0", that is, controlled to the feathering position of the traction propulsion unit 22, as shown in Figure 6. Figure 8 and Figure 11 As shown, it may be controlled to the position where the lifting propulsion unit 22 has zero load-bearing capacity, such as... Figure 3 As shown.

[0134] Following pitch step "E1-3" is step "E1-4," during which the pitch angle position is checked. During this step, the pitch sensor 45 checks whether blade 32 occupies the folded pitch angle position "β0." A small offset "ε" of a few degrees from the folded pitch angle position "β0" along any orientation is generally tolerable. In this way, the pitch angle position "β" of blade 32 is checked more precisely to see if it falls within the pitch angle position range defined by the lower threshold "β0-ε" and the upper threshold "β0+ε". If the blade's pitch angle position falls within the range defined by the lower and upper thresholds, a method for stopping the rotation of propeller 26 at one of the propeller's division angle positions "θi" is triggered; otherwise, step "E1-3" is repeated.

[0135] The method for stopping the rotation of propeller 26 at one of the scaled angle positions "θi" of the propeller includes a step "E1-5" of checking the rotational speed "Nr", during which it is checked whether the rotational speed "Nr" of propeller 26 is less than or equal to a determined rotational speed "Nre".

[0136] If the rotational speed "Nr" of propeller 26 is higher than a certain rotational speed "Nre", braking step "E1-6" is triggered. During braking step "E1-6", stepper motor 82 is controlled to generate a resistance torque opposite to the free rotation of propeller 26 until the rotational speed "Nr" of propeller 26 is less than or equal to the predetermined rotational speed "Nre". The rotational speed "Nr" of propeller 26 is measured by a sensor (not shown), which is well-known and will not be described in detail below. At the end of braking step "E1-6", step "E1-5" of checking the rotational speed "Nr" is repeated.

[0137] If the rotational speed "Nr" of propeller 26 is less than or equal to a determined rotational speed "Nre", then step "E1-7" is triggered to stop the propeller at the division angle position. In this step, stepper motor 82 is controlled to stop propeller 26 at the division angle position "θi".

[0138] Following the blocking step "E1-7" is step "E1-8", which checks the angular position "θ" of the propeller 26 using the sensing sensor 110. If the measured angular position "θ" of the propeller 26 is within the tolerance range [θi-λ; θi+λ] defined on both sides of the graduated angular position "θi", then the locking step "E1-10" is triggered; otherwise, the adjustment step "E1-9" is triggered.

[0139] Adjustment step “E1-9” includes controlling stepper motor 82 to provide rotational torque that drives propeller 26 to rotate about the propeller’s rotation axis “X” toward one of the division angle positions “θi”.

[0140] During this adjustment step "E1-9", propeller 26 is driven to rotate only in one orientation. Therefore, when propeller 26 passes through the division angle position "θi", stepper motor 82 drives propeller 26 to rotate to the next division angle position "θi".

[0141] Alternatively, propeller 26 can be driven to rotate in two orientations by stepper motor 82, causing propeller 26 to rotate toward the nearest division angle position "θi".

[0142] After adjusting step "E1-9", repeat blocking step "E1-7".

[0143] Repeat adjustment steps “E1-9”, stop steps “E1-7”, and check steps “E1-8” until the angular position “θ” of propeller 26 is within the tolerance range [θi-λ; θi+λ] determined on both sides of one of the scale angle positions “θi”.

[0144] In the locking step "E1-10", as follows Figure 23 As shown, propeller 26 is rotatably locked relative to nacelle 24 at the propeller's angular resolution position "θi" by mechanical locking device 96. As previously explained, locking device 96 enables propeller 26 to be precisely brought into the propeller's angular resolution position "θi" by the engagement between locking member 104 and the ramp of pawl 102, the locking member being controlled to move toward the locking member.

[0145] At the end of locking step "E1-10", step "E1-11" for folding blade 32 is triggered. In this step, as previously described and as... Figure 4 Figure 7 Figure 9 and Figure 13 As shown, the blade 32 is folded into the corresponding receiving portion 39 of the blade by the folding device 50.

[0146] Then, in step "E1-12" of the folding inspection, sensor 72B is used to check whether blade 32 is folded correctly. Figure 25 As indicated by reference numeral "E1-14" in the attached diagram, if blade 32 is in the folded position, latch 75 is controlled in the final locking step "E1-13" to lock blade 32 in the folded position; otherwise, an incident is reported to the pilot of aircraft 20.

[0147] The aerodynamic design of the blades will take into account the requirement that the folded blades cannot be unintentionally deployed, that is, especially in the case that the blades are not effectively locked in the folded position. Under certain flight conditions that must be observed in such failure situations, the requirement that the folded blades cannot be unintentionally deployed will be taken into account.

[0148] Now refer to Figure 26 A method for deploying the blades 32 of the propulsion unit 22 is described. This method is implemented by an electronic control unit (not shown). The method can be triggered automatically or by manual command from the pilot.

[0149] In the first step “E2-1”, certain flight conditions of the aircraft 20 are checked, and these conditions must be met in order to obtain authorization for the continued deployment method of the blades 32.

[0150] For example, when step "E2-1" is applied to the lifting propulsion unit 22, it checks whether the speed of the aircraft 20 is decreasing and approaching a speed at which, without lifting thrust from the lifting propulsion unit 22, the aircraft's wings will no longer be sufficient to provide load-bearing capacity. For example, it checks whether the forward speed "V" of the aircraft 20 has decreased to a determined third threshold speed "V2". If the forward speed of the aircraft decreases to the determined third threshold speed, the subsequent deployment step "E2-2" is triggered; otherwise, the deployment method is not allowed.

[0151] According to another example, when step "E2-1" is applied to the traction propulsion unit 22, it is checked whether the speed of the aircraft 20 is below a sufficient economic cruise speed that requires all traction propulsion units 22 to be used simultaneously to provide thrust to the aircraft 20. For example, it is checked whether the forward velocity "V" of the aircraft 20 is significantly below a determined fourth threshold velocity "V3". The blades 32 of the traction propulsion unit 22 can also deploy as the aircraft 20 is about to leave hovering flight. If one of these conditions is selected, the next step "E2-2" is triggered; otherwise, the deployment method is interrupted.

[0152] In the unfolding step “E2-2”, the latch 75 is retracted and the folding actuator 50 is operated to unfold the blade 32.

[0153] In the subsequent inspection step "E2-3" after deployment, the deployment sensor 72A checks whether the blade 32 is in the deployed position. If the blade is in the deployed position, the step "E2-4" to unlock the propeller 26 is triggered; otherwise, the deployment step "E2-2" is repeated.

[0154] In the unlocking step “E2-4”, the locking member 104 of the mechanical locking device 96 of the propeller 26 is controlled to the inactive position of the locking member to release the rotation of the propeller 26.

[0155] In step "E2-5" of the unlock check, the locking sensor 105 checks whether the propeller 26 is unlocked and rotating. If so, the deployment method is completed and the propulsion unit 22 is ready for use; otherwise, the unlock step "E2-4" is repeated.

Claims

1. A propulsion unit (22) having a propeller (26) and for use in an aircraft (20), the propulsion unit comprising: - Cabin (24), which is intended to be attached to the structural elements of the aircraft (20); - A propeller (26) rotatably mounted in the nacelle (24) about a longitudinal axis of rotation (X) via a hub (28), the propeller (26) comprising blades (32), each of the blades being pivotally fixed to an associated blade sleeve (38), the blade sleeve being pivotally mounted relative to the hub (28) about a radial pitch axis (Y), and each blade (32) being pivotally mounted relative to the blade sleeve (38) about a folding axis (Z) orthogonal to the radial pitch axis (Y); - Folding device (50), the folding device including folding actuator (52) controlling the pivoting of each blade (32) relative to the blade sleeve (38) between an unfolded position and a folded position, in the unfolded position the blade (32) extends radially relative to the longitudinal axis of rotation (X), and in the folded position the blade (32) extends generally longitudinally against the nacelle (24); The folding device (50) includes a transmission (54) associated with each blade (32), each transmission (54) comprising: - A movable control member (56), which is fixedly mounted to the blade sleeve (38) in terms of rotation, and which is moved by the folding actuator (52), and - A link (58) comprising a first end and a second end, the first end being pivotally mounted eccentrically relative to the folding axis (Z) on the root (34) of an associated blade (32), and the second end being pivotally mounted on the movable control member (56). The movable control member (56) of each transmission device (54) is formed by a slider, which is mounted to be able to slide radially between an inner limit position and an outer limit position in an associated blade sleeve (38), the inner limit position corresponding to one of the positions of the associated blade (32) and the outer limit position corresponding to another of the positions of the associated blade (32).

2. The propulsion unit (22) according to claim 1, characterized in that The sliding of the movable control member (56) is actuated by the cam (60), and the movable control member (56) is fixedly mounted to the cam follower (62) in terms of sliding.

3. The propulsion unit (22) according to claim 2, characterized in that, The cam (60) is mounted to slide longitudinally, and the cam follower (62) is mounted to rotate about the radial pitch axis (Y) on the movable control member (56).

4. The propulsion unit (22) according to claim 3, characterized in that, All the cams (60) of each of the transmission devices (54) are attached to a common rod (64) of the folding actuator (52), the common rod being slidable along the longitudinal axis of rotation (X) between a first position and a second position, the first position corresponding to the unfolded position of the blade (32) and the second position corresponding to the folded position of the blade (32).

5. The propulsion unit (22) according to claim 4, characterized in that, The propulsion unit includes detection devices (72A, 72B) for detecting the position of the common rod (64) in a first position and a second position of the common rod.

6. The propulsion unit (22) according to claim 5, characterized in that, The propulsion unit includes a mechanical locking device (75) for mechanically locking the movable control member (56) at each of the positions of the movable control member corresponding to the unfolded position and the folded position of the blade (32).

7. The propulsion unit (22) according to claim 5, characterized in that, The cabin (24) is fixedly mounted on the structural element of the aircraft (20).

8. The propulsion unit (22) according to claim 5, characterized in that, The cabin (24) is pivotally mounted on the structural element of the aircraft (20).

9. The propulsion unit (22) according to claim 4, characterized in that, The propulsion unit includes a mechanical locking device (75) for mechanically locking the movable control member (56) at each of the positions of the movable control member corresponding to the unfolded position and the folded position of the blade (32).

10. The propulsion unit (22) according to any one of claims 1 to 4, characterized in that, The cabin (24) is fixedly mounted on the structural element of the aircraft (20).

11. The propulsion unit (22) according to any one of claims 1 to 4, characterized in that, The cabin (24) is pivotally mounted on the structural element of the aircraft (20).

12. A method for folding the blades (32) of the propeller (26) of the propulsion unit (22) according to any one of claims 5 to 8, characterized in that, The method includes a folding step (E1-11), during which the blade (32) is folded by the folding device (50), followed by a folding inspection step (E1-12), during which the blade (32) is inspected by the detection device (72A, 72B) to confirm that the fold has indeed been folded.

13. The method according to claim 12, characterized in that, The propulsion unit includes a mechanical locking device (75) for mechanically locking the movable control member (56) at each of the positions of the movable control member corresponding to the unfolded position and the folded position of the blade (32), wherein if the blade (32) is detected to be in the folded position during the inspection step (E1-12) of the folding, the mechanical locking device (75) is controlled to lock the blade (32) in the folded position.

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