Linear electro-mechanical actuator

Abstract

Described is a linear electro-mechanical actuator (100), comprising a containment frame (200), a movement unit and a transmission element (300) extending along a main axis (X) and comprising a first threaded portion (3a) and a second threaded portion (3b). The transmission element (300) is configured to translate and simultaneously rotate about the main axis (X). The actuator (100) also comprises a first rotary element (400) provided with a first thread (4a) suitable for engaging rotatably with the first threaded portion (3a) to define a first threaded connection (3a, 4a) and a second rotary element (500) provided with a second thread (5b) suitable for engaging rotatably with the second threaded portion (3b) to define a second threaded connection (3b, 5b). The actuator (100) comprises an element (600) translating along the main axis (X) and connected to the transmission element (300) to rotate freely relative to the transmission element (300) and to have translation movement integral with the axial component of the roto-translational movement of the transmission element (300).

Description

[0001] LINEAR ELECTRO-MECHANICAL ACTUATOR

[0002] DESCRIPTION

[0003] The present invention relates to a linear electro-mechanical actuator and is used in particular in the aeronautical field in particular for landing carriages, flight surfaces and more generally where electrical and electronic redundancy is requested.

[0004] Linear electro-mechanical actuators are known in the prior art comprising an electric motor and a two-state transmission with different pitches, in such a way as to obtain an optimised reduction ratio and with a compact structure.

[0005] The Applicant has found that these actuators can be further improved in order to guarantee the versatility of utilisation, in particular according to different uses or with use in different operating conditions. The prior art architecture allows, in effect, optimisation for a specific situation but does not allow adaptation to different situations of use.

[0006] Moreover, particularly in the aeronautical field, there is the need for actuators which are increasingly reliable and which are therefore able to operate with a high safety margin.

[0007] In this context, the invention relates to a linear electro-mechanical actuator comprising a containment frame, a movement unit and a transmission element extending along a main axis and comprising a first threaded portion and a second threaded portion. The transmission element is configured to translate along the main axis and simultaneously rotate about the main axis.

[0008] The actuator, according to this invention, also comprises a first rotary element moved by the movement unit in rotation about the main axis.

[0009] The first rotary element is provided with a first thread suitable for engaging rotatably with the first threaded portion of the transmission element in such a way as to define a first threaded connection.

[0010] The actuator, according to this invention, also comprises a second rotary element moved by the movement unit in rotation about the main axis. The second rotary element is provided with a second thread suitable for engaging rotatably with the second threaded portion of the transmission element in such a way as to define a second threaded connection.

[0011] Preferably, the first and the second threaded connections have opposite spiral angles.

[0012] Alternatively, the first and the second threaded connections have concordant spiral angles. In the latter case, it is preferable that the first and the second threaded connections have a different module value.

[0013] Preferably, the first and the second threaded connections have identical module values. This is preferably provided in the case of threads having opposite spiral angles.

[0014] Even more preferably, the first and the second threaded connections have a pitch of between 1 mm and 100 mm.

[0015] Alternatively, the first and the second threaded connections may have a different module values. This is preferably provided in the case of threads with concordant spiral angles.

[0016] The actuator according to the invention also comprises an output translating element, translating along the main axis and connected to the transmission element in such a way as to rotate freely relative to the transmission element and in such a way as to have translation movement integral with the axial component of the roto-translational movement of the transmission element.

[0017] Preferably, the output translating element is connected to the transmission element by one or more bearings.

[0018] Preferably, the bearings are ball or roller bearings. As an alternative to the bearings, there may be one or more sliding supports, for example bushings.

[0019] In this way, the rotary component of the movement of the transmission element is absorbed by the bearings and not transmitted to the output translating element, which, on the other hand, receives the entire component of axial movement of the transmission element.

[0020] Preferably, the movement unit comprises a first motor operatively associated with the first rotary element and a second motor operatively associated with the second rotary element.

[0021] Preferably, the first and the second motors can be controlled independently of each other.

[0022] Preferably, the first and the second motors are mounted on the containment frame, in particular inside respective dedicated compartments.

[0023] According to the preferred embodiment, the first and second motors have respective axes of rotation coinciding with the main axis and the first and second motors are axially spaced from each other along the main axis.

[0024] According to an alternative embodiment, the first and the second motors could be concentric with each other. More specifically, the two motors might be nested inside one another. In the latter configuration, one of the two motors is preferably inserted inside the transmission element and is configured with an external rotor, in particular engaged on the inner surface of the respective rotary element.

[0025] According to the preferred embodiment, the first and the second motors are electric motors and have respective rotors fixed, preferably externally, respectively to the first and to the second rotary elements.

[0026] In this situation, the first rotary element is coaxial with the first motor and integral with the rotor of the first motor, whilst the second rotary element is coaxial with the second motor and integral with the rotor of the second motor.

[0027] According to an alternative embodiment, the first and second motors have the respective axes of rotation parallel to the main axis and have the respective rotors connected to the respective rotary element by means of a connection with gears.

[0028] According to a variant embodiment, the invention may also be performed by means of a mechanical transmission wherein the first and the second motors are absent and wherein they are replaced by respective power sockets (inlet shafts) which can be engaged by respective external motors and in particular protruding from the frame. In this configuration the actuator adopts more precisely the structure of a mechanical transmission which can be coupled to respective motors by means of corresponding power couplings, for example splined receiving shafts or seats.

[0029] According to an aspect of the invention, the transmission element is made in the form of a hollow body and the threaded connections are positioned on opposite surfaces of the transmission element.

[0030] In particular, one of the threaded connections is made on an inner surface of the transmission element and the other threaded connection is positioned on the outer surface of the transmission element in such a way that the transmission element is positioned between the first rotary element and the second rotary element.

[0031] In other words, the first threaded connection and the second threaded connection are positioned on surfaces opposite to each other, that is to say, on the outer cylindrical surface and on the inner cylindrical surface, of the transmission element.

[0032] According to the preferred embodiment, the transmission element, for example being made by means of a tubular shape, has a central hole and the first rotary element is inserted in the hole whilst the second rotary element is positioned outside the transmission element.

[0033] The first threaded connection and the second threaded connection may be positioned in a superposed position or partly superposed in an axial direction or occupy respective regions axially offset from each other.

[0034] Preferably, the threaded connections are at least partly superposed on each other in an axial direction.

[0035] Further features and advantages of the present invention are more apparent in the illustrative and therefore non-limiting description of an embodiment of a linear electro-mechanical actuator according to the invention.

[0036] The description is set out below with reference to the accompanying drawing, which are provided solely for purposes of illustration without restricting the scope of the invention and in which Figure 1 shows a cross-section view of an actuator according to this invention.

[0037] With reference to the accompanying drawings, the numeral 100 denotes in its entirety a linear electro-mechanical actuator according to the invention.

[0038] The actuator 100 comprises a containment frame 200, preferably box-shaped and defining an inner space.

[0039] The actuator 100 also comprises a movement unit in particular motor-driven and in particular positioned in the containment space.

[0040] The actuator 100 comprises a transmission element 300 extending along a main axis “X” and comprising a first threaded portion 3a and a second threaded portion 3b.

[0041] The transmission element 300 is configured to translate along the main axis “X” and simultaneously rotate about the main axis “X”.

[0042] In other words, the transmission element 300 is configured to adopt a component of rotary movement about the main axis “X” and a component of axial movement along the main axis “X”, that is to say, for roto-translating.

[0043] The actuator 100 also comprises a first rotary element 400 moved by the movement unit in rotation about the main axis “X”.

[0044] The first rotary element 400 is provided with a first thread 4a suitable for engaging rotatably with the first threaded portion 3a of the transmission element 300 in such a way as to define a first threaded connection 3a, 4a.

[0045] The actuator 100 also comprises a second rotary element 500 moved by the movement unit in rotation about the main axis “X” and provided with a second thread 5b suitable for engaging rotatably with the second threaded portion 3b of the transmission element 300 in such a way as to define a second threaded connection 3b, 5b.

[0046] According to the embodiment illustrated, the first and the second threaded connections 3a, 4a; 3b, 5b have identical module values.

[0047] Preferably, the module value is between 1 mm and 100 mm.

[0048] According to the embodiment illustrated, the first and the second threaded connections 3a, 4a; 3b, 5b have opposite spiral angles.

[0049] According to a further possible embodiment not illustrated, the first and the second threaded connections 3a, 4a; 3b, 5b have identical module values and concordant spiral angles.

[0050] According to a further possible embodiment not illustrated, the first and the second threaded connections 3a, 4a; 3b, 5b have different module values and opposite spiral angles.

[0051] According to a further possible embodiment not illustrated, the first and the second threaded connections 3a, 4a; 3b, 5b have different module values and concordant spiral angles.

[0052] In use, therefore, when the first and the second rotary elements 400, 500 are rotated about the main axis “X”, the first and the second threaded connections 3a, 4a; 3b, 5b are such that the transmission element 300 rotates about the main axis “X” and, simultaneously, translates along the main axis “X”.

[0053] Preferably, in order to operate the first and the second rotary elements 400, 500, the movement unit comprises a first motor “Ml” operatively associated with the first rotary element 400 and a second motor “M2” operatively associated with the second rotary element 500.

[0054] Preferably, the first and second motors “Ml”, “M2” are housed in the containment space of the containment frame, in particular in a dedicated compartment or in respective dedicated compartments.

[0055] Preferably, the first and second motors “Ml”, “M2” can be controlled independently of each other.

[0056] According to the embodiment shown in Figure 1, the first and the second motors “Ml”, “M2” have respective axes of rotation coinciding with the main axis “X” and are axially spaced from each other along the main axis “X”. In this situation, the first and second motors “Ml”, “M2” are electric motors and have respective rotors fixed, preferably externally, respectively to the first and to the second rotary elements 400, 500.

[0057] According to an embodiment not illustrated, on the other hand, the first and the second motors “Ml”, “M2” have the respective axes of rotation parallel to the main axis “X” and have the respective rotors connected to the corresponding rotary elements 400, 500 by means of a gear connection.

[0058] According to another embodiment not illustrated, the axes of rotation of the first and second motors “Ml”, “M2” have respective axes of rotation coincident with each other. More specifically, the first and second motors “Ml”, “M2” might adopt a nested configuration wherein one motor is radially inside the other motor. With reference to the embodiment shown in Figure 1, the transmission element 300 is made in the form of a hollow body and the threaded connections 3a, 4a; 3b, 5b are positioned on opposite surfaces of the transmission element 300.

[0059] In particular, one of the threaded connections 3a, 4a; 3b, 5b is made on an inner surface of the transmission element 300 and the other threaded connection 3a, 4a; 3b, 5b is positioned on the outer surface of the transmission element 300 in such a way that the transmission element 300 is positioned between the first rotary element 400 and the second rotary element 500.

[0060] Preferably, the threaded connections 3a, 4a; 3b, 5b are at least partly superposed on each other in an axial direction. In other words, the threaded connections 3a, 4a; 3b, 5b are positioned in such a way that one of them is at least partly (that is to say, at least for a relative axial portion) nested inside the other.

[0061] Alternatively, the threaded connections 3a, 4a; 3b, 5b could be axially spaced from each other in such a way as to not be superposed in an axial direction, preferably remaining one positioned inside and one positioned outside on the transmission element 300.

[0062] Preferably, the transmission element 300 has the shape of a tubular element and has a central hole. In this situation, the first rotary element 400 is inserted in the hole for engaging inside the transmission element 300 by means of the first threaded connection 3a, 4a whilst the second rotary element 500 is positioned outside the transmission element 300 and engages with it by means of the second threaded connection 3b, 5b. In this situation, preferably, the first threaded portion 3 a (engaged with the first thread 4a of the first rotary element 400) has an axial extension less than the axial extension of the second threaded portion 3b (engaged with the second thread 5b of the second rotary element 500).

[0063] The actuator 100 also comprises an output translating element 600, translating along the main axis “X” and connected to the transmission element 300 in such a way as to rotate freely relative to the transmission element 300 and in such a way as to have translation movement integral with the axial component of the roto- translational movement of the transmission element 300.

[0064] In other words, the rotary motion of the transmission element 300 is not transmitted to the output translating element 600 (except for any friction torque) whilst the translating motion of the transmission element 300 is transmitted to the output translating element 600.

[0065] Preferably, the translating element 600 is connected to the transmission element 300 by one or more bearings, for example ball or roller bearings.

[0066] Alternatively, the translating element 600 is connected to the transmission element 300 by one or more sliding supports, for example bushings.

[0067] In use, therefore, the output translating element 600 is slidable along the main axis “X” and is connected to the transmission element 300 in such a way as to have a translational movement integral (that is to say, synchronous and integral) with the translational component of the movement of the transmission element 300.

[0068] This invention also relates to a method for operating the actuator 100 as described above.

[0069] The method comprises a step of actuating the movement unit for rotating the first rotary element 400 and the second rotary element 500 with respective speeds of rotation individually selected in such a way as to move in a roto-translation the transmission element 300 and, consequently, translate the output translating element 600.

[0070] Preferably, the actuating step is performed by activating the first and second motors “Ml”, “M2” independently of each other.

[0071] Once the motors “Ml”, M2” are activated and the first and second rotary elements 400, 500 rotate, the transmission element 300 roto-translates along the main axis “X” (or, if necessary, only translates as a function of the speeds of rotation of the rotary elements 400, 500). In this situation, thanks to the presence of the bearings, the rotational component of motion of the transmission element 300 is not transmitted to the output translating element 600 whilst the translating component of motion of the transmission element 300 is transmitted to the output translating element 600 which therefore translates along the main axis “X”.

[0072] According to another aspect of the invention, for each rotary element 400, 500, the actuator 100 comprises a respective braking device “B” acting on the rotary element 400, 500 and / or on the rotor of the respective motor “Ml”, “M2”, which can be individually activated, in a controlled fashion, for blocking the rotation of the respective rotary element 400, 500. The braking device “B” may operate by friction, preferably by electromagnetic interaction.

[0073] In this way, the braking action exerts a locking action on the rotary element 400, 500 associated with the braked motors “Ml”, “M2” in such a way that the respective thread 4a, 5b is stationary like a fixed thread. This brings about a possible operating condition of the actuator 100, which can be operated in a similar fashion to a traditional double-thread actuator. The braked motor "Ml", "M2" is therefore like an electromechanical redundancy, which may remain inactive allowing the operation of the actuator 100, increasing the overall reliability of the actuator 100.

[0074] This aspect is particularly advantageous, for example, if one of the two motors “Ml”, “M2” fails, that is to say, if one of the two motors “Ml”, “M2” is not operational. In this situation, since one of the two motors “Ml”, “M2” is non- operational, that is to say, braked, the actuator 100 can be operated, and in particular can be operated in a similar manner to a traditional double-thread actuator.

[0075] In other words, the architecture of the actuator 100 according to this invention makes it possible to obtain, if one of the two motors “Ml”, “M2” were not operational, a redundant system of the “fail-safe” type, that is to say, a system which is still able, even though affected by a “failure”, to have a considerable strength and reliability.

[0076] The present invention achieves the preset aims, overcoming the drawbacks of the prior art.

[0077] In effect, the actuator is extremely versatile. Further, the particular embodiment of the actuator allows an increase in reliability.

Claims

CLAIMS1. A linear electro-mechanical actuator (100), comprising:- a containment frame (200);- a movement unit;- a transmission element (300) extending along a main axis (X) and comprising a first threaded portion (3a) and a second threaded portion (3b), said transmission element (300) being configured to translate along said main axis (X) and simultaneously rotate about said main axis (X);- a first rotary element (400), moved by said movement unit in rotation about the main axis (X) and provided with a first thread (4a) designed to engage rotatably with said first threaded portion (3a) of the transmission element (300) in such a way as to define a first threaded connection (3a, 4a);- a second rotary element (500) moved by said movement unit in rotation about the main axis (X) and provided with a second thread (5b) designed to engage rotatably with said second threaded portion (3b) of said transmission element (300) in such a way as to define a second threaded connection (3b, 5b);- an output translating element (600), translating along said main axis (X) and connected to the transmission element (300) in such a way as to rotate freely relative to the transmission element (300) and in such a way as to have translation movement integral with the axial component of the roto-translational movement of the transmission element (300).

2. The actuator according to claim 1, wherein said movement unit comprises a first motor (Ml) operatively associated with said first rotary element (400) and a second motor (M2) operatively associated with said second rotary element (500), said first and second motors (Ml, M2) being controllable independently of each other.

3. The actuator according to claim 2, wherein said first and second motors (Ml, M2) have respective axes of rotation coinciding with said main axis (X) andwherein said first and second motors (Ml, M2) are axially spaced from each other along said main axis (X).

4. The actuator according to claim 3, wherein said first and second motors (Ml, M2) are electric motors and have respective rotors fixed, preferably externally, respectively to the first and to the second rotary elements (400, 500).

5. The actuator according to claim 2, wherein said first and second motors (Ml, M2) have the respective axes of rotation parallel to the main axis (X) and have the respective rotors connected to the respective rotary element (400, 500) by means of a gear connection.

6. The actuator according to any one of the preceding claims, wherein said transmission element (300) is made in the form of a hollow body and wherein said threaded connections (3a, 4a; 3b, 5b) are positioned on opposite surfaces of said transmission element (300), in particular one of said threaded connections (3a, 4a; 3b, 5b) being made on an inner surface of the transmission element (300) and the other threaded connection (3a, 4a; 3b, 5b) being positioned on the outer surface of the transmission element (300) in such a way that said transmission element (300) is positioned between said first rotary element (400) and said second rotary element (500).

7. The actuator according to claim 6, wherein said threaded connections (3a, 4a; 3b, 5b) are at least partly superposed on each other in an axial direction.

8. The actuator according to any one of the preceding claims, wherein the first and the second threaded connections (3a, 4a; 3b, 5b) have identical module values.

9. The actuator according to any one of the preceding claims, wherein the first and the second threaded connections (3a, 4a; 3b, 5b) have opposite helical angles.

10. The actuator according to any one of the preceding claims, wherein the translating element (600) is connected to the transmission element (300) by one or more bearings, preferably said bearings being ball or roller bearings.

11. The actuator according to any one of the preceding claims, comprising for each rotary element (400, 500), a respective braking device (B) which can be activated individually, in a controlled fashion, for locking the rotation of said respective rotary element (400, 500).

12. A method for operating the actuator (100) according to any one of the preceding claims, comprising a step of actuating said movement unit for rotating said first rotary element (400) and said second rotary element (500) with respective speeds of rotation individually selected in such a way as to move the transmission element (300) in a roto-translation and, consequently, translate the translating element (600).

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