Electromechanical unit for a variable pitch propeller

Abstract

Described is an electromechanical unit for a propeller with variable pitch, comprising a containment structure (1) defining an inner chamber (2), a first shaft (3) positioned in the inner chamber (2) and rotatable about an axis (X), said first shaft (3) defining a power output and being connectable to a propeller unit with blades for rotating the propeller unit about the axis (X), a first electric motor (6) positioned in the inner chamber (2) and connected to the first shaft (3) for rotating said first shaft (3) about the axis (X), and a linear actuator (8) having a second shaft (9) translating along and / or parallel to said axis (X) and connectable to said propellor unit for determining a variation in the pitch of the blades of said propeller unit, the linear actuator (8) being mounted on the containment structure (1).

Description

[0001] ELECTROMECHANICAL UNIT FOR A VARIABLE PITCH PROPELLER

[0002] DESCRIPTION

[0003] This invention relates to an electromechanical unit for a variable pitch propeller, in particular for use in propulsion systems (aeronaval field) or in generators (wind, hydraulic) with a variable pitch propeller.

[0004] There are currently prior art propeller units equipped with a central hub and a plurality of blades arranged radially about the axis, which can be mounted in a rotatable fashion about a first axis for forming a drive thrust (aeronaval context) or for receiving a generating thrust from a fluid (in the field of wind, hydraulic or other generators). In order to optimise the aerodynamic / hydrodynamic interaction effect with the fluid, the propeller units are configured with variable pitch by means of adjustable assembly of the blades about respective adjustment axes which are perpendicular and incident with the first axis. This is described in detail in the prior art.

[0005] In particular, the aeronautical propellers have a limit on the speed of rotation, since the ends of the blades cannot reach supersonic speeds, otherwise there will be shock waves and a drop in aerodynamic efficiency. In order to increase the flight speed it is therefore not possible to increase in an arbitrary fashion the revolutions of the propeller, but it is necessary to increase the pitch of the blades. Having a variable pitch is equivalent to always having the “right gear” for the flight condition which the aircraft encounters at that moment, basically dependent on speed and flight altitude (air density), for example short pitch during take-off and climbing, long pitch during cruising.

[0006] Moreover, having the possibility of putting the blades parallel to the aerodynamic flow increases the safety of the flight since in the case of engine failure (malfunction with consequent blockage) undesired increases in the aerodynamic resistance and yawing effects are not generated (sudden movement of the aircraft towards the right or left about the vertical axis) linked to the faulty engine, the propeller of which would be rotated by the air.

[0007] Moreover, having the possibility of reversing the pitch of the propellers (on the ground) makes it possible to drastically reduce the space required for aborting a take-off in the event of a fault or to drastically reduce the space required for landing and reduce the wear of the brakes.

[0008] In this context, patent EP0436231 describes a propeller unit with an adjustment sleeve coaxial with the axis of rotation of the propeller unit meshed simultaneously, by conical threading, with respective pinions integral with the blades and defining respective axes for adjusting the blades. The adjustment sleeve adopts an adjustable position about the axis of rotation of the propeller unit by means of a cam interaction with a pin which can be moved along the axis by a respective adjustment rod in such a way that, irrespective of the current speed of rotation of the propeller unit, moving axially the adjustment rod obtains a corresponding rotational movement of the adjustment sleeve and, therefore, a variation of the angular position of the blades about the respective adjustment axes.

[0009] Also known from patent US5464324 is a system for adjustment of the pitch of the propeller which uses one or more adjustment bodies which can be translated axially by means of a control rod and each having a cam seat in which a pin is slidable that is in turn engaged eccentrically with an adjustment arm of the blade. Translating the control rod and, therefore, the adjustment bodies achieves a rotation of the arms for a travel depending on the translation of the control rod and, therefore, a predetermined rotation of the blades about the respective adjustment axes.

[0010] According to the prior art solutions, the command for adjusting the angular position of the blades is given by a hydraulic circuit (described for example in the first document EP0436231 mentioned above) which operates by moving the adjustment rod axially in both directions. This hydraulic circuit is generally driven by an internal combustion engine, for example where the hydraulic pump is directly moved by the engine, or by using pressurised oil already produced for operation of the engine and the auxiliary elements.

[0011] These solutions can be used in a traditional manner in the case of internal combustion engines which require pressurised oil to operate correctly.

[0012] The Applicant has found that these solutions are, however, not very suitable for use in the case of electric propulsion.

[0013] In fact, in these circumstances it would be necessary to provide an entire hydraulic system (pump, control unit, pipes, accumulator...) dedicated only to the actuation of the pitch of the propellers with an imaginable increase in weights and dimensions. Moreover, from the strictly technical point of view, passing pipes inside the electric motor to reach the nose-piece of the propeller, also considering the relative rotation, is not trivial in terms of seals, nor is it safe in the case of fluid leaks.

[0014] The technical purpose of the invention is therefore to provide an electromechanical unit for a variable pitch propeller which overcomes the above- mentioned drawbacks.

[0015] The aim of the invention is therefore to provide an electromechanical unit for a variable pitch propeller which is structurally simple and compact.

[0016] Another aim of this invention is to provide an electromechanical unit for variable pitch propellers which has a high standard of safety, with particular reference to the risk effects linked to hydraulic losses.

[0017] The technical purpose indicated and the specified aim are substantially achieved by an electromechanical unit comprising the technical features described in one or more of the accompanying claims.

[0018] Further features and advantages of the invention are more apparent in the nonlimiting description which follows of a non-exclusive embodiment of an electromechanical unit for a variable pitch propeller according to the invention.

[0019] The description is set out below with reference to the accompanying drawings which are provided solely for purposes of illustration without restricting the scope of the invention and in which: Figure 1 is a cross-section of an electromechanical unit according to the invention;

[0020] Figure 2 is a perspective view of the electromechanical unit of Figure 1 ;

[0021] Figure 3 corresponds to the view of Figure 2 with removal of an end guard to highlight some internal components.

[0022] In the accompanying drawings the numeral 100 denotes in its entirety an electromechanical unit according to the invention.

[0023] The electromechanical unit 100 is intended for actuating a propeller unit (not illustrated) with a variable pitch. This means that, structurally, the electromechanical unit 100 has a power output, which is rotary, and a further adjustment output (axial) for the command of angular adjustment of the blades of the propeller unit. Propeller units known for this purpose are fully described in the prior art (for example in EP0463231) and will not be described in detail.

[0024] The electromechanical unit 100 has a first side “A”, facing towards the propeller unit and to which it is configured to be connected, and an opposite side “B” and it extends between them with a preferably substantially cylindrical shape.

[0025] In more detail, the electromechanical unit 100 extends about an axis “X” which extends between side “A” and side “B”.

[0026] More in detail, the electromechanical unit 100 comprises a containment structure 1 with a hollow structure, defining an inner chamber 2 and defining a structural element for supporting the various components of the electromechanical unit 100 and also having the function of connecting to the frame an aircraft, a nautical vehicle or other installation suitable for assembly of the electromechanical unit 100.

[0027] Inside the inner chamber 2 there is a first shaft 3 rotatable about the axis “X” and defining a power output. The first shaft 3 is connectable, directly or indirectly, to a propeller unit with blades (not illustrated) for rotating the propeller unit about the axis “X”.

[0028] The first shaft 3 has the shape of a hollow shaft.

[0029] According to the embodiment illustrated, the first shaft 3 can be connected to a propeller unit indirectly by interposing a reduction gear unit. In particular, the electromechanical unit 100 comprises a reduction gear unit 4 (optional), preferably with epicyclic gear mechanisms, connected to an end of the first shaft 3 and in turn connectable to the propeller unit, preferably directly.

[0030] In more detail, the reduction gear unit 4 has an output drive flange 5 configured for connecting to the propeller unit in such a way that the propeller unit is connected to the first shaft 3 by interposing the reduction gear unit 4.

[0031] Preferably, the reduction gear unit 4 is positioned at an end of the containment structure 1 facing towards the propeller unit and included in a respective recess 6 of the containment structure 1. Preferably, the recess 6 defines a zone with a larger diameter of the containment structure 1.

[0032] The reduction gear unit 4 is described in detail below with reference to Figure 3.

[0033] The electromechanical unit 100 also comprises a first electric motor 6 positioned in the inner chamber 2 and connected to the first shaft 3 for rotating the first shaft 3 about the axis “X”. In particular, the first electric motor 6 has a stationary stator 6a and a rotor 6b fixed externally to the outer surface of the first shaft 3. For example, the rotor 6b is made from permanent magnets stably fixed to the first shaft 3, for example by gluing.

[0034] Preferably, the first shaft 3 is supported at its ends or close to its ends by respective bearings “Cl”, “C2” preferably of the ball type, the first electric motor 6 being positioned in an intermediate position between the bearings “Cl”, “C2”.

[0035] Moreover, according to the embodiment illustrated, comprising the reduction gear unit 4, the first shaft 3 is connected at the relative end facing towards the propeller unit to an inner rotor 4a of the reduction gear unit 4.

[0036] The electromechanical unit 100 also comprises a supporting element 7 fixed to the containment structure 1, in particular at the end opposite the propeller unit, and extending radially inwards and preferably also axially towards the other end.

[0037] Advantageously, according to the invention, the electromechanical unit 100 also comprises a linear actuator 8 mounted on the containment structure 1 and having a second shaft 9 translating along the axis “X” and / or parallel to the axis “X” and connectable to the propeller unit for determining a variation in the pitch of the blades of the propeller unit. The second shaft 9 is preferably coaxial with the first shaft 8 and / or the axis “X”.

[0038] Preferably, the linear actuator 8 is mounted in cantilever fashion on the containment structure 1, in particular at the end of the containment structure 1 opposite the propeller unit, by means of the supporting element 7 described above. The linear actuator 8 is therefore positioned inside the inner chamber 2.

[0039] Preferably, the linear actuator 8 extends inside the first shaft 3 along the axis “X” and in particular coaxially to it.

[0040] Preferably, the linear actuator 8 is positioned at least partly inside the first shaft 3, preferably the linear actuator 8 is positioned inside the first shaft 3 for at least 50% of its length and more preferably for at least 80% of its length.

[0041] The electromechanical unit 100 also comprises a roto-translational outlet element 10, having a first end rotatably connected to the second shaft 9 and a second end opposite the first end and connectable to the propeller unit for transmitting an axial drive movement for changing the pitch of the blades of the propeller unit.

[0042] Preferably, the first end of the roto-translational outlet element 10 is rotatably connected to the second shaft 9 by one or more roller bearings “C3” (two in the embodiment illustrated) and / or one or more circular guides, for example ball guides.

[0043] Preferably, the roto-translational outlet element 10 is supported exclusively by the second shaft 9 at the relative first end and extends in a cantilever fashion from the second shaft 9 towards the end of the containment structure 1 facing towards the propeller unit.

[0044] According to a variant embodiment not illustrated, the roto-translational outlet element 10 may also be supported in a relative zone different from the first end by means of a rotary and sliding support.

[0045] With reference to the linear actuator 8, it is preferably a linear electro-mechanical actuator and more preferably an electro-mechanical lead nut / screw actuator and / or with recirculating ball threaded transmission.

[0046] In more detail, the linear actuator 8 comprises a second electric motor 11 and a rotary element 12 (or “screw”) rotated by the second electric motor 11, where the above-mentioned second shaft 9 is coupled to the rotary element 12 by a threaded connection, preferably of the recirculating ball type. In other words, the connection between the second shaft 9 and the rotary element 12 is a nut-screw type coupling.

[0047] The linear actuator 8 also comprises an anti-rotation mechanism 13 (for example a linear guide, an anti-rotation tooth or other equivalent) acting on the second shaft

[0048] 9 to prevent a rotation of the second shaft 9 allowing the axial translation of the second shaft 9.

[0049] It follows that, in use, the first shaft 3 rotates the entire propeller unit whilst the second shaft has an axial adjustment movement, controlled by controlling the second electric motor 11 , which transfers to the roto-translational output element

[0050] 10 which, whilst rotating at the same speed as the propeller unit, has relative to it a component of axial movement given by the second shaft 9 and is therefore able to activate the change of angular position of the blades of the propeller unit about the respective adjustment axes.

[0051] Figure 2 is a perspective view of the electromechanical unit 100 in an mounted configuration, showing the drive flange 5 defining the power output directly connectable to the propeller unit. The drive flange 5 has connecting means 14 (in the form of holes) for the connection, preferably direct, to the propeller unit.

[0052] Moreover, Figure 2 shows the front end of the roto-translational outlet element 10, inside and coaxial with the drive flange 5.

[0053] Figure 3 is a perspective view of the electromechanical unit 100 wherein an end guard, on the side of the propeller unit, has been removed to highlight the internal components.

[0054] In detail, the epicyclic reduction gear unit 4 (optional) is visible, wherein the planetary gear 4b (external, facing towards the axis “X”) is fixed and wherein the satellite gears 4c are mounted on a shared hub 4d integral with the above- mentioned outlet drive flange 5 (hub 4d and drive flange 5 are preferably defined by a monolithic element). The drive flange 5 has a diameter smaller than the diameter of the trajectory travelled by the centres of the satellites 4c, that is to say, where the hub 4d is connected to the satellites 4c. Figure 3 also shows a roller bearing 15, associated with a circular seal 16, interposed between the drive flange 5 and the guard (also shown in Figure 1).

[0055] The present invention achieves the preset aims, overcoming the disadvantages of the prior art.

[0056] The electromechanical unit according to the invention is in effect very compact and entirely defined by electromechanical drives, and is therefore very reliable and free of components with a high risk of failure, such as pressurised oil ducts and joints.

Claims

CLAIMS1. An electromechanical unit for a variable pitch propeller, comprising:- a containment structure (1) defining an inner chamber (2);- a first shaft (3) positioned in the inner chamber (2) and rotatable about an axis (X), said first shaft (3) defining a power output and being connectable to a propeller unit with blades for rotating the propeller unit about said axis (X);- a first electric motor (6) positioned in the inner chamber (2) and connected to the first shaft (3) for rotating said first shaft (3) about the axis (X);- a linear actuator (8) having a second shaft (9) translating along and / or parallel to said axis (X) and connectable to said propeller unit for determining a variation in the pitch of the blades of said propeller unit; characterised in that said linear actuator (8) is mounted on said containment structure (1).

2. The electromechanical unit according to claim 1, wherein said linear actuator (8) is positioned inside said inner chamber (2).

3. The electromechanical unit according to claim 1 or 2, wherein said first shaft (3) is a hollow shaft and wherein said linear actuator (8) is at least partly positioned inside said first shaft (3), preferably said linear actuator (8) being positioned inside said first shaft (3) for at least 50% of its length and more preferably for at least 80% of its length.

4. The electromechanical unit according to any one of the preceding claims, wherein said linear actuator (8) is mounted in a cantilever fashion on the containment structure (1) by means of a supporting element (7), in particular at the end of the containment structure (1) opposite the said propeller unit.

5. The electromechanical unit according to any one of the preceding claims, wherein said linear actuator (8) is a linear electro-mechanical actuator.

6. The electromechanical unit according to any one of the preceding claims, wherein said linear actuator (8) is a lead screw and nut type electro-mechanical actuator and / or with recirculating ball threaded transmission.

7. The electromechanical unit according to claim 6, wherein said linear actuator (8) comprises a second electric motor (11) and a rotary element (12) rotated by said second electric motor (12), and wherein said second shaft (9) is coupled to the rotary element (12) by a threaded connection preferably of the recirculating ball type.

8. The electromechanical unit according to claim 7, wherein said linear actuator (8) also comprises an anti-rotation mechanism (13) acting on the second shaft (9) to prevent a rotation of said second shaft (9).

9. The electromechanical unit according to any one of the preceding claims, also comprising a roto-translational outlet element (10), having a first end rotatably connected to the second shaft (9), preferably by means of one or more rolling bearings (C3) and / or one or more circular guides, and a second end opposite the first end and connectable to the propeller unit for transmitting an axial drive movement for changing the pitch of the blades of said propeller unit.

10. The electromechanical unit according to claim 9, wherein said roto- translational outlet element (10) is supported exclusively by said second shaft (9) and extending in a cantilever fashion from the second shaft (9) towards an end of the containment structure (1) facing towards the propeller unit.

11. The electromechanical unit according to any one of the preceding claims, wherein the first shaft (3) and the second shaft (9) are coaxial with each other.

12. The electromechanical unit according to any one of the preceding claims, also comprising a reduction gear unit (4), preferably with epicyclic gear mechanisms,connected to said first shaft (3) and having a drive flange (5) configured for connecting to the propeller unit in such a way that the propeller unit is connected to the first shaft (3) by interposition of said reduction gear unit (4).

13. The electromechanical unit according to claim 12, wherein the reduction gear unit (4) is positioned at an end of the containment structure (1) facing towards the propeller unit and included in a respective recess (6) of the containment structure (1), preferably said recess defining a zone with a larger diameter of the containment structure (1).

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