Improved linear electromechanical actuator

Abstract

Linear electromechanical actuator (1), comprising: a containment structure (2); a pusher (3) designed to translate with respect to the containment structure (2); a mechanical reduction apparatus (4) arranged in the containment structure (2) and rotatable around a rotation axis (X); motor means (5) arranged in the containment structure (2) and operatively connected with said mechanical reduction apparatus (4) to rotate it around said rotation axis (X); a shaft (6) inserted inside said mechanical reduction apparatus (4) and connected to said pusher (3), said shaft (6) being mechanically connected with said mechanical reduction apparatus (4) in such a way that a rotation of said mechanical reduction apparatus (4) causes a translation of the shaft (6) along said rotation axis (X); a nut (8) having a thread pitch; a longitudinal pushing element (9) along the rotation axis (A) and having a linear guide (9B), said nut (8) and said longitudinal pushing element (9) being independent of each other and rotatable around said rotation axis (X) under the action of said motor means (5); said longitudinal pushing element (9) being inserted inside said nut (8); coupling means (10, 11, 15, 16) configured to mechanically couple said nut (8) and said longitudinal pushing element (9) with said shaft (6), in such a way that a rotation of said nut (8) and / or said longitudinal pushing element (9) causes a translation of said shaft (6) along said rotation axis (X).

Description

[0001] TITLE: "Improved linear electromechanical actuator"

[0002] DESCRIPTION

[0003] Field of application

[0004] The object of the present description is a linear electromechanical actuator in accordance with the preamble of Claim 1.

[0005] In particular, but not exclusively, the present invention relates to a linear electromechanical actuator for controlling a steering surface of an aircraft, for example, for vertical take-off, of a boat or the steering system of a vehicle or similar applications.

[0006] A method for checking an electrical, electronic and / or mechanical failure in a linear electromechanical actuator is a further object of the present invention.

[0007] Description of the prior art

[0008] Linear electromechanical actuators equipped with control and command electronics are known which are actuated by an electric motor whose task is to transform the rotary motion of the electric motor into a linear displacement of a pusher so as to control the positioning of a steering surface.

[0009] To this end, the electric motor is connected, through a reduction apparatus, to the pusher which, in turn, is connected to the steering surface to steer the position that said surface must assume according to the commands received from the control and command electronics.

[0010] Usually, the reduction apparatus comprises a nut on which a screw runs (or a screw on which a nut runs), which, in turn, is connected to the pusher and, thanks to an anti-rotation device, the screw (or the nut) is allowed to move only linearly and non-rotationally so as to obtain the linear displacement motion of the pusher.

[0011] These linear electromechanical actuators have been used, for example, to control the so-called secondary steering surfaces of an aircraft, such as air brakes, switches, flaps, trimming flaps but also to make it possible to open doors as well as for other uses that require low power, speed and response times, i.e. for all those applications referred to as "non-safety critical".

[0012] Document US 4179944 describes an example of a linear electromechanical actuator equipped with two motors coupled directly to a shaft by means of recirculating ball nuts. This electromechanical actuator does not provide sufficient redundancy to guarantee a "fault tolerance" for faults of a mechanical, electrical and electronic nature. In fact, this electromechanical actuator allows the identification of only two types of mechanical faults mainly related to the moving shaft, therefore it guarantees a limited redundancy especially in the case of mechanical failure between motor and shaft. Furthermore, such an electromechanical actuator could have problems in case of electrical and / or electronic failure related to the electric motors. In fact, these motors should be sized to ensure operation both in operating conditions and in fault conditions such as, for example, to overcome torques due to mechanical failures in the event of a stall of one of the two motors.

[0013] Problem of the prior art

[0014] However, the reliability of an electromechanical actuator of the type previously mentioned in document US 4179944 does not allow its use in installations dedicated to the command of primary steering surfaces of an aircraft, the swashplate of a helicopter, the steering system of a vehicle or the rudder of a ship, that is, more generally, of all those applications referred to as "safety critical" .

[0015] This depends on the fact that the low reliability of the electromechanical actuator described above lies both in the electrical part, i.e. in the electric motor, in the control and command electronics as well as in the possibility of a seizure of the mechanical part (known as mechanical "jamming" .

[0016] To overcome this problem, architectures are now used, for example, that have two identical actuators that move the same steering surface, allowing for electrical, electronic and mechanical redundancy, but generally resulting in an increase in weight and complexity of the system, or a single actuator equipped with a differential gearbox that allows the use of two independent electric motors and two independent electronics that move the same mechanics.

[0017] In addition, "safety critical" applications, such as those reported above, require very fast operating dynamics that do not allow the use of differential gearboxes generally characterized by too high operating clearances.

[0018] Further documents US 2013249464, WO2010027701 and US 2005269887 describe examples of electromechanical actuators that do not provide sufficient redundancy to ensure a "fault tolerance" for faults of a mechanical, electrical and electronic nature.

[0019] In particular, documents "US 464" and "WO 701" describe actuators equipped with two electric motors dependent on each other and coupled directly to the shaft to be moved by means of recirculating ball nuts. Thus, a mechanical failure, for example relating to the motor-shaft coupling for one or both of the motors, results in the blockage of the actuator itself. In addition, the motors must be sized to generate a torque capable of guaranteeing operation both in operating conditions and in conditions of electrical and / or electronic failure of one of the two motors.

[0020] Document "US 887" instead describes an actuator equipped with a battery of electric motors coupled directly to the shaft to be moved by roller recycling. Therefore, also in this case, a mechanical failure related to the motor-shaft coupling results in the stalling of the actuator itself preventing the movement of the shaft.

[0021] Further documents describe electromechanical actuators that are bulky in terms of length in order to ensure a shaft stroke length suitable for specific applications. This longitudinal footprint results in construction and mounting problems within the relevant housing with specific dimensioning.

[0022] In addition, there is an increasing need to detect electrical, electronic and / or mechanical failures and in particular what are known as "latent failures" of the actuator or actuators that are part of the architectures described above. Latent failures, as is known, can act on a component, whether mechanical or electrical / electronic, on a circuit, or on a system and are those failures that have not yet occurred, but whose activation event has already occurred without there being an impossibility of using the architecture.

[0023] In particular, the architectures described above are tested during the scheduled periodic inspections and, if no anomalies are highlighted, these architectures are judged to be completely efficient and therefore usable. However, in the course of their use, undetected and / or undetectable faults may arise that have a more or less serious impact on efficiency, but such faults remain latent until the next inspection, thus jeopardising the guarantee offered by redundancy.

[0024] This is a serious problem especially if the electromechanical actuator is used in "safety critical" applications.

[0025] SUMMARY OF THE INVENTION

[0026] The object of the invention in question is to realise a linear electromechanical actuator capable of solving the problems of the state of the art just described.

[0027] These objects are achieved by a linear electromechanical actuator, in accordance with Claim 1 below.

[0028] A further object of the present invention is to provide a method for checking an electrical, electronic and / or mechanical fault in a linear electromechanical actuator capable of solving the problems of the state of the art just described.

[0029] Advantages of the invention

[0030] Thanks to an embodiment of the present invention, it is possible to realize a linear electromechanical actuator of the Fault Tolerant Differential type that is also applicable for the control of primary steering surfaces since it allows the translation of the pusher even in conditions of failure of the electrical part, of the control electronics and / or of a seizure of the mechanical part.

[0031] Furthermore, thanks to an embodiment of the present invention, it is possible to realize a linear electromechanical actuator whose dynamic performance is much higher than electromechanical actuators that provide for the use of differential systems such as gearboxes.

[0032] Furthermore, thanks to an embodiment of the present invention, it is possible to realize a linear electromechanical actuator with generally a reduced weight and dimensions compared to electromechanical actuators that provide for the use of gearboxes and other differential devices as well as the use of a large number of screw- nut couplings. Specifically, the present invention makes it possible to provide a longitudinally compact electromechanical actuator capable of maintaining the same stroke length of the shaft and therefore of the pusher for the specific applications.

[0033] Furthermore, thanks to an embodiment of the present invention, it is possible to make a linear electromechanical actuator with a high reliability compared to electromechanical actuators that provide for the use of gearboxes and other differential devices. Furthermore, thanks to an embodiment of the present invention, it is possible to realize a linear electromechanical actuator capable of guaranteeing electronic, electrical and mechanical fault tolerance. In particular, the use of an intermediate stage increases the redundancies of the system ensuring high reliability with respect to the electromechanical actuators currently employed in the prior art as described above.

[0034] In addition, thanks to an embodiment of the present invention, it is possible to realize a linear electromechanical actuator that makes it possible to minimize friction, especially at low temperatures, optimizing the overall efficiency of the actuator with respect to electromechanical actuators that provide for the use of gearboxes and other differential devices.

[0035] Furthermore, thanks to an embodiment of the present invention, it is possible to realize a linear electromechanical actuator that reduces the response time for the movement of the shaft in case of jamming.

[0036] Furthermore, thanks to an embodiment of the present invention, it is possible to realize a linear electromechanical actuator with smaller dimensions and weights.

[0037] BRIEF DESCRIPTION OF THE DRA WINGS

[0038] The features and advantages of the present invention will become apparent from the following detailed description of a possible practical embodiment thereof, illustrated by way of non-limiting example in the accompanying drawings, in which:

[0039] - Figure 1 shows a sectional view of the linear electromechanical actuator in accordance with a first embodiment of the present invention in a first retracted configuration;

[0040] - Figure 2 shows a sectional view of the linear electromechanical actuator in accordance with the embodiment of Figure 1 in a second extended configuration;

[0041] - Figure 3 shows a sectional view of the linear electromechanical actuator in accordance with the embodiment of Figure 1 in an extended configuration in the event of jammings

[0042] - Figure 4 shows a flow diagram of the method for checking the presence of an electrical, electronic and / or mechanical fault in a linear electromechanical actuator, in accordance with the present invention.

[0043] DETAILED DESCRIPTION

[0044] Even if not explicitly highlighted, the individual features described with reference to the specific embodiments shall be understood as accessory to and / or interchangeable with other features described with reference to other embodiments.

[0045] With reference to the attached figures, a linear electromechanical actuator in accordance with the present invention is represented as a whole by 1.

[0046] With reference to Figures 1-3, the actuator 1 comprises a containment structure 2, preferably of a rigid type, and a pusher 3. This containment structure extends from a bottom 2A to an outlet opening 2B extended along a prevailing direction of development.

[0047] The pusher 3 represents the active element of the actuator 1.

[0048] In particular, the pusher 3 is designed to translate with respect to the containment structure 2 to at least partially come out from the containment structure 2, preferably out of the outlet opening 2B, during the operation of the actuator 1.

[0049] The translation of the pusher 3 takes place through a special opening provided in the containment structure 2.

[0050] The actuator 1 comprises a mechanical reduction apparatus 4, arranged in the containment structure 2, which is configured to be rotatable around a rotation axis X.

[0051] The actuator 1 comprises motor means 5, associated with the containment structure 2, preferably arranged inside the containment structure 2, which are operatively connected with the mechanical reduction apparatus 4 to rotate it around the axis X.

[0052] The actuator 1 comprises a shaft 6, inserted inside the mechanical reduction apparatus 4, which is connected with the pusher 3.

[0053] In particular, the shaft 6 comprises a first terminal end 6’ and a second terminal end 6”, where the first terminal end 6’ is connected to a coupling eyelet 3’. Said first terminal end 6’ can come out with the pusher 3 at least partially from the containment structure 2 during the operation of the actuator 1.

[0054] The actuator 1 comprises an anti-rotation mechanism which is active on the shaft

[0055] 6 to prevent a rotation of the shaft itself about the rotation axis X. Specifically, the anti-rotation mechanism can be internal or external to the containment structure 2. In accordance with a preferred embodiment, the anti-rotation mechanism is indicated by

[0056] 7 in Figure 1.

[0057] The shaft 6 is therefore connected with the mechanical reduction apparatus 4 in such a way that a rotation of the mechanical reduction apparatus 4 causes a translation of the shaft 6 along the rotation axis X and therefore a linear displacement of the pusher 3.

[0058] Advantageously, the mechanical reduction apparatus 4 comprises a nut 8 and a longitudinal pushing element 9 which are independent of each other, i.e. they are two separate and distinct elements.

[0059] The nut 8 and the longitudinal pushing element 9 are rotatable about the rotation axis X under the action of the motor means 5.

[0060] It should be noted that the longitudinal pushing element 9 is inserted inside the nut 8 at least partially. The nut 8 has a first nut threading 8A having a preferably defined relative pitch.

[0061] The longitudinal pushing element 9 along the rotation axis X has a linear guide 9B preferably provided with a movement step.

[0062] Specifically, the longitudinal pushing element 9 may be a linear guide 9B. Preferably, in this embodiment the linear guide 9B defines a relative movement step.

[0063] In this case, the linear guide 9B has a relative outer surface that can have one or more substantially smooth longitudinal grooves 9A suitable for defining said linear guide 9B. It should be noted that such grooves 9A extend substantially the entire length of the longitudinal pushing element 9 and are configured to engage balls as described in detail below.

[0064] It should be noted that the nut 8 and the longitudinal pushing element 9 have a thread pitch and a movement pitch respectively.

[0065] The nut 8 and the pushing element 9 have a prevailing direction of development that coincides with the aforementioned rotation axis X.

[0066] Both the nut 8 and the pushing element 9 are enabled to only rotate about the rotation axis X while each of them is prevented from translation along the rotation axis X for example by means of special locking shoulders or other solutions known to the person skilled in the art and therefore not described.

[0067] In order to obtain the rotation of the nut 8 and of the longitudinal pushing element 9 about the rotation axis X, the actuator 1 comprises a pair of bearings 13, 13’ active at the ends of the containment structure 2 acting on the nut 8.

[0068] The actuator 1 further comprises a further pair of bearings 14 active at one end in the containment structure 2 acting on the longitudinal pushing element 9.

[0069] Then the nut 8 and the longitudinal pushing element 9 are rotatable around the rotation axis X under the action of the motor means 5, which are connected to the nut and to the longitudinal pushing element either by means of a kinematic chain (for example a gearbox comprising a differential) or directly connected to the nut 8 and to the longitudinal pushing element 9.

[0070] In accordance with a preferred embodiment, the nut 8 comprises a substantially cylindrical hollow body defining a pushing channel 8B configured to receive at least in part the shaft 6 and the longitudinal pushing element 9. Specifically, the hollow body of the nut 8 has a threaded inner surface where a first nut threading 8A is formed.

[0071] The longitudinal pushing element 9 comprises a cylindrical body defining the linear guide and inserted inside the hollow body 8B of the nut 8. This cylindrical body of the longitudinal pushing element 9 instead has the outer surface provided with the longitudinal grooves 9A.

[0072] According to an aspect, the mechanical reduction apparatus 4 comprises coupling means 10, 11, 15, 16 configured to mechanically couple the nut 8 and the longitudinal pushing element 9 with the shaft 6, such that a rotation of the nut 8 and / or the longitudinal pushing element 9 causes a translation of the shaft 6 along the rotation axis X.

[0073] In other words, the actuator 1 is able to ensure a translation of the shaft 6 along the rotation axis X even under conditions of failure of one of the motor means 5, or of the relative electronics, or of the seizure of the coupling means 11, 15 and 16 with a nut 8 and with the longitudinal pushing element 9 without distinction so as to guarantee the complete extraction of the shaft 6.

[0074] To this end, the coupling means 10, 11, 15 and 16 comprise an intermediate coupling stage 10 inserted between said nut 8 and said longitudinal pushing element 9.

[0075] Specifically, this configuration provides that the intermediate stage 10 is inserted inside the pushing channel 8B, i.e. at least in part inside the cavity of the hollow body associated with the nut 8.

[0076] This intermediate coupling stage 10 is configured to rotate, translate or rototranslate with respect to the pushing channel.

[0077] The intermediate coupling stage 10 is at least partly inserted into the nut 8 and the shaft 6.

[0078] The intermediate coupling stage 10 is configured to receive at least in part the longitudinal pushing element 9. Specifically, the longitudinal pushing element 9 is at least partly inserted inside the intermediate stage 10 and changes the portion inserted inside said stage according to the extraction and / or the presence of faults and / or jamming as the intermediate stage with respect to the pushing channel 8B.

[0079] It should be noted that the intermediate coupling stage 10 extends along a prevailing direction of development between a first end 10’ facing the bottom of the containment structure and an opposite second end 10”.

[0080] In accordance with a preferred embodiment, the coupling means 10, 11, 15 and 16 comprise:

[0081] - first and second mechanical connection means 15, 16 for respectively mechanically coupling said intermediate coupling stage 10 with said nut 8 and said intermediate coupling stage 10 with said longitudinal pushing element 9; and

[0082] - third mechanical connection means 11 configured for mechanically coupling said intermediate coupling stage 10 with said shaft 6.

[0083] In accordance with a preferred embodiment, the intermediate coupling stage 10 is inserted at least in part into the shaft 6 and changes the inserted portion according to the extraction and / or the presence of faults and / or jamming.

[0084] Preferably, the shaft 6 is connected to the intermediate coupling stage 10 through the third mechanical connection means 11.

[0085] According to one aspect, the intermediate coupling stage 10 develops around an axis that is coincident with said rotation axis X.

[0086] The intermediate coupling stage 10 has an internal cavity 10D, preferably of the through type, which extends along an axis, preferably coinciding with said rotation axis X and which therefore confers a tubular conformation to said intermediate coupling stage 10. In this way, the intermediate coupling stage 10 is configured to receive within the internal cavity 10D the longitudinal pushing element 9. This longitudinal pushing element changes the inserted portion as a function of the extraction and / or the presence of faults and / or jamming.

[0087] In accordance with a preferred embodiment, the shaft 6 is in turn a hollow shaft configured to receive within a relative shaft cavity 6C at least in part the intermediate coupling stage 10 and the longitudinal pushing element 9 in turn inserted at least in part inside the internal cavity 10D of the intermediate stage 10 as illustrated in the figures. It is noted that the shaft 6 is in turn inserted at least partly inside the nut 8 in the pushing channel 8B.

[0088] Specifically, the electromechanical actuator provides that:

[0089] - the shaft 6 has a relative cavity 6C configured to receive at least in part the intermediate coupling stage 10 and the longitudinal pushing element 9;

[0090] - the intermediate coupling stage 10 has an internal cavity 10D configured to at least partially receive the longitudinal pushing element 9;

[0091] - the nut 8 has a pushing channel 8B configured to receive at least in part the shaft 6, the longitudinal pushing element 9 and the intermediate coupling stage 10, in accordance with the previous relationships between the shaft 6, the longitudinal pushing element 9 and the intermediate coupling stage 10. In accordance with a preferred embodiment illustrated in the figures, it is found that the shaft 6 is coaxial with respect to both the intermediate coupling stage 10 and with respect to the nut 8 and the longitudinal pushing element 9 along the rotation axis X, and the intermediate coupling stage 10 is coaxial with respect to the nut 8 and the longitudinal pushing element 9 also along the rotation axis X.

[0092] According to one aspect, the earliest means of mechanical connection 15 comprise, preferably, a screw nut coupling or, alternatively, a coupling made by means of satellite rollers, recirculation of rollers or recirculating ball screws.

[0093] According to one aspect, the second mechanical connection means 16 comprise a recirculating ball coupling by means of longitudinal grooves 9A obtained or a groove-type coupling between the intermediate coupling stage 10 equipped with coupling grooves and the longitudinal grooves 9A.

[0094] In accordance with a preferred embodiment, the third mechanical connection means 11 comprise a screw nut coupling or, alternatively, a coupling realised by means of satellite rollers, recirculation of rollers or a recirculating ball screw between said shaft 6 and said intermediate coupling stage 10, in such a way that a rotation of said nut 8 and / or of said longitudinal pushing element 9 causes a rotation or a translation or a rototranslation of said intermediate coupling stage 10 along the rotation axis X, and that said intermediate coupling stage 10, in turn, causes a translation of said shaft 6 along the rotation axis X.

[0095] In accordance with the present preferred embodiment, the shaft 6 is at least partly threaded. The third mechanical connection means 11 comprise a screw nut coupling between the shaft 6 with the intermediate coupling stage 10. Specifically, the shaft 6 comprises a threading 6 A obtained internally, in other words on the entire surface of the hollow shaft 6A. It is noted that the shaft 6 may be a hollow shaft and the third mechanical connection means 11 comprise a screw nut coupling between the screw shaft 6 with the intermediate coupling stage 10.

[0096] Preferably, the threading of the shaft 6 is arranged near the second end of said shaft 6". Further, the shaft may have a smooth outer surface extending between said first and second ends 6’, 6”. In other words, the shaft 6 has a smooth portion 6B on the outer surface and a threaded portion 6A on the inner surface.

[0097] In accordance with a preferred embodiment, the intermediate coupling stage 10 is interconnected with the screw nut 8 through a respective screw nut coupling obtained with the respective first mechanical connection means 15. Alternatively, the first means of mechanical connection 15 can take the form of a mechanical coupling of the type satellite roller, recirculation of rollers or recirculating ball screw.

[0098] The intermediate coupling stage 10 is interconnected with the longitudinal pushing element 9 through a respective linear guide coupling obtained with the respective second mechanical connection means 16.

[0099] Following a rotation of the nut 8 and / or the longitudinal pushing element 9 imparted by the motor means 5, a rotation or a translation or a rototranslation of the intermediate coupling stage 10 along the rotation axis X is determined and the latter, i.e. the intermediate coupling stage 10, in turn causes a translation of the shaft 6 along said rotation axis X.

[0100] In accordance with a preferred embodiment, the intermediate coupling stage 10 has externally, i.e. on its outer surface, at the first end 10’ a first thread 10A configured to couple to the nut 8, preferably to the first nut threading 8A.

[0101] Furthermore, the intermediate coupling stage 10 has internally, i.e. on its inner surface, at the first terminal end 10’ a coupling element 10B for coupling with the respective longitudinal pushing element 9.

[0102] It should be noted that the first thread 10A preferably covers only a portion of the outer surface of the intermediate coupling stage 10 near the respective end 10’ and extends towards the central area of the intermediate coupling stage 10.

[0103] The coupling element 10B is arranged internally to the surface of the intermediate stage 10 in the vicinity of the first terminal end 10’ interposing between the intermediate coupling stage 10 and the longitudinal pushing element 9.

[0104] Specifically, the first thread 10A may cover only a portion of the intermediate coupling stage outer surface 10, in particular a portion originating from the respective terminal end 10’ and extending towards the central zone of the intermediate coupling stage 10. The remaining outer surface has a conformation such as to couple with the shaft 6 as set out below.

[0105] In accordance with a preferred embodiment, said coupling element 10B has a ball recirculation device 40 coupled to the linear guide 9B. To be specific, the device 40 is mechanically associated with the longitudinal grooves 9A by means of recirculating ball coupling.

[0106] In accordance with an alternative embodiment to the previous one, said coupling element 10B has the coupling grooves configured to couple with the longitudinal grooves 9A so as to define a grooved coupling. It should be noted that such coupling grooves may also extend along the intermediate stage being formed on the inner surface of the intermediate coupling stage 10. Preferably, said coupling element 10B may extend along the intermediate coupling stage 10.

[0107] According to one aspect, the longitudinal grooves 9A can have different shapes in the case of a recirculating ball coupling and in the case of a grooved coupling. Specifically, in the embodiment with a grooved coupling, the longitudinal grooves 9A and the relative coupling grooves may have a trapezoidal shape or other shapes known to the person skilled in the art.

[0108] Preferably, the coupling between the intermediate coupling stage 10 and the nut 8 is embodied in the coupling of the screw nut or, alternatively, a coupling made by means of satellite rollers, recirculation of rollers or recirculating ball screw, where for example the intermediate coupling stage 10 is the screw and the nut 8 is the nut and the coupling between the intermediate coupling stage 10 and the longitudinal pushing element 9 is embodied in the coupling between the linear guide 9B of the pushing element 9 and the recirculation of balls of the intermediate coupling stage 10 acting on the linear guide or grooved type.

[0109] For example, the first thread 10A is coupled with the thread of the nut 8 and the ball recirculation device 40 of the coupling element 10B is coupled with the outer surface of the longitudinal pushing element 9, i.e. the longitudinal grooves 9 A. Alternatively, the first thread 10A is coupled with the thread of the nut 8 and the coupling element 10B is coupled with the outer surface of the longitudinal pushing element 9, i.e. the longitudinal grooves 9A by relative coupling grooves.

[0110] Preferably, it should be noted that since the nut 8 and the longitudinal pushing element 9 are independent of each other, they are still mechanically bound with the engagement of the screw nut or, alternatively, a coupling by means of satellite rollers, recirculation of rollers or recirculating ball screw and linear recirculating ball screw guide with the intermediate coupling stage 10, then the first thread 10A and the recirculating ball screw device 40 of the coupling element 10B of the intermediate coupling stage 10 are also constrained to each other since they are made on the same intermediate coupling element 10.

[0111] In accordance with a preferred embodiment, the intermediate coupling stage 10 externally comprises a second thread IOC. Said second thread IOC is configured to couple with a threading 6A of the shaft 6. Preferably, said second thread IOC extends on the outer surface of the hollow body of the intermediate stage 10 preferably between the first thread 10A and the second end 10”.

[0112] In accordance with a preferred embodiment, the intermediate coupling stage 10 comprises a shoulder 10F between the first thread 10A and the second thread 10C. This shoulder 10F also defines a stroke limit for the shaft 6 against which it abuts. It should be noted that the first thread 10A and the second thread 10C of the intermediate coupling stage 10 are mutually spaced with respect to a direction perpendicular to the development direction X due to the presence of the shoulder 10F.

[0113] Specifically, the shaft 6 provides for a relative thread, which has a certain pitch and direction and which is interconnected with the second thread 10C so as to achieve the screw nut coupling between them.

[0114] Preferably, the pitch of the thread of the shaft 6 is different, for example greater or lesser or equal in modulus but opposite in sign, with respect to the pitch of the thread of the nut 8 and the movement pitch of the longitudinal pushing element 9.

[0115] As previously described, the nut 8 and the longitudinal pushing element 9 are rotatable about the rotation axis X under the action of the motor means 5, which, preferably, are connected to the nut and the longitudinal pushing element. To this end, the motor means 5 comprise two electric type motors 5A and 5B each of which is operatively connected and active on the nut 8 and on the longitudinal pushing element 9.

[0116] Specifically, the first electric motor 5A is directly connected with the nut 8 and comprises a stator fixed to the containment structure 2 and a rotor fixed to said nut 8. The second electric motor 5B is connected to the longitudinal pushing element 9 by means of a kinematic chain 5B’.

[0117] It should be noted that the rotor of the electric motor 5A is in rigid connection with the nut 8 which is rotated by the electromagnetic interaction of the respective rotor (generally with permanent magnets) and stator.

[0118] The actuator 1 comprises braking means 12 A, 12B active respectively on the nut 8 and on the longitudinal pushing element 9 for braking the rotation about the rotation axis X of one and / or both, depending on the operating conditions to which the actuator 1 is subjected as described in more detail below.

[0119] In particular, the braking means 12A, 12B comprise two electric brakes, each of which is active respectively on the nut 8 and on the longitudinal pushing element 9.

[0120] For example, the brakes are specifically electromagnetic coil brakes.

[0121] In accordance with a preferred embodiment, the actuator 1 comprises command and control electronics for each electric motor 5A, 5B and for the first and second braking means 12 A, 12B, hereinafter electric brakes. It should be noted that each electric motor 5A and 5B as well as each electric brake 12A and 12B is controlled by its own control electronics (not illustrated in the figures), which is responsible for controlling and commanding the operating state and the operation of the aforementioned electric motors 5 A and 5B and electric brakes 12A and 12B.

[0122] Thus, in the preferred embodiment described above, the actuator 1 comprises two independent electric motors 5A and 5B and two independent electronics moving a fully redundant mechanism (i.e., the nut 8, the longitudinal pushing element 9, an intermediate stage 10 and a shaft 6) and comprises the use of a nut 8 and a longitudinal pushing element 9, which are independent and to which the rotors of the two electric motors 5A and 5B are directly connected. The nut 8 and the longitudinal pushing element 9 engage the intermediate stage 10 having on the outside and on the inside relative coupling portions for engaging the nut 8 and the longitudinal pushing element 9 and the shaft 6. The intermediate stage 10 therefore has a threaded element that engages the thread of the shaft 6 which does not rotate thanks to the anti-rotation device.

[0123] In accordance with a preferred embodiment, the actuator comprises a plurality of sensors 17, 18 arranged inside said containment structure 2 operatively connected with the command and control electronics. The plurality of sensors 17, 18 are designed to detect the position of the shaft 6 (and the rotations of the motors 5 A and 5B) so as to detect its displacements along the axis X.

[0124] Specifically, the actuator comprises a plurality of sensors, arranged inside and / or outside the containment structure 2 and appropriately configured to be in signal communication with the command and control electronics, which are designed to detect the position of the shaft 6 so as to detect its movements along the axis X.

[0125] For example, the plurality of sensors may include one or more of the following types of sensors:

[0126] - a linear sensor (indicated with 17 according to the embodiment illustrated in the figures positioned inside the shaft 6), and configured to detect the axial position of the shaft 6;

[0127] - rotary sensors 18 associated respectively to the nut 8 and to the longitudinal pushing element 9 and each configured to detect the relative rotation;

[0128] - any sensors, not illustrated in the figures, configured to read the axial position of the intermediate coupling stage 10.

[0129] - current and / or voltage sensors, not illustrated in the figures, integrated into the control electronics.

[0130] These sensors are connected through the command / control electronics and suitable software in order to monitor the relative movements between the shaft 6, the nut 8, the longitudinal pushing element 9, the intermediate coupling stage 10 and the containment structure 2.

[0131] For example, the sensor that detects the axial position of the intermediate coupling element 10 and the linear sensor 17 are capable of homing the rotary sensors.

[0132] Advantageously, the sensor that detects the axial position of the intermediate coupling element lOe and the linear sensor identify a reference point for the first and second rotary sensors obtaining the position of the nut 8 and of the longitudinal pushing element 9.

[0133] Advantageously, the presence of multiple sensors ensures redundancy for measuring the axial position of the shaft 6.

[0134] It should be noted that only two sensors among the plurality provided would be sufficient to obtain, through mathematical correlations, the axial position of the shaft 6.

[0135] Advantageously, the control / command electronics correlates the sensor outputs to identify a mechanical failure (so-called "jamming”) between the shaft 6 and the intermediate coupling stage 10 or between the nut 8 and the longitudinal pushing element 9 and the intermediate coupling stage 10.

[0136] It should also be noted that the introduction of the longitudinal pushing element 9, given a certain linear stroke of the shaft 6, makes it possible to minimize:

[0137] - the strokes of the intermediate stage 10 on the respective nut 8 and on the longitudinal pushing element 9.

[0138] - the stroke of the shaft 6 on the respective intermediate stage 10.

[0139] Consequently, the axial length of the nut 8, the longitudinal pushing element 9 and the shaft 6 can be minimised with the following advantages in terms of dimensions and weights.

[0140] In addition, the use of a linear guide makes it possible to reduce the possible number of jammings.

[0141] It should be noted that in the event of jamming, the actuator 1 allows the shaft to be extracted as illustrated in Figure 3, fulfilling the task of extracting the shaft 6 in the event of failure.

[0142] The operation of the actuator 1 in its preferred embodiment will now be described.

[0143] Normal operating mode

[0144] During normal operation only the motor 5A is powered. The motor 5B is deenergized and held in position by the brake 12B. The nut 8 rotates while the longitudinal pushing element 9 is stationary. The intermediate stage 10 translates and the shaft 6 translates integrally with the intermediate stage 10, thanks to the antirotation device.

[0145] In this way, the displacement of the shaft 6 is realized.

[0146] Operating mode in case of failure (failure of the 5 A motor or related electronics without distinction)

[0147] In the event that there is a failure of the motor 5A or its electronics, only the motor 5B is powered. The motor 5 A is de-energized and held in position by the applied brake 12A following the failure of the motor 5A. In this way, the nut 8 is stopped. In this scenario, the longitudinal pushing element 9 rotates thanks to the activation of the relative motor 5B. With the rotation of the longitudinal pushing element 9, the intermediate stage 10 rotates-translates. The shaft 6, thanks to the action of the antirotation device, translates along the rotation axis X as a result of the translation and rotation of the intermediate stage 10. The translation of the shaft 6 allows the linear displacement of the pusher 3 to be obtained, always along the rotation axis X.

[0148] Operating mode in case of failure (seizure of the intermediate stage with the nut and / or the pushing element 9)

[0149] In the event that there is a mechanical failure (so-called "jamming") of the intermediate stage 10 with the nut 8 and / or with the longitudinal pushing element 9. The motors 5 A and 5B are powered. The nut 8 and the longitudinal pushing element 9 rotate at the same speed. The intermediate stage 10 rotates about the rotation axis X integrally with the nut 8 and the longitudinal pushing element 9. The shaft 6, thanks to the action of the anti-rotation device, translates along the rotation axis X so as to obtain the linear displacement motion, again along the rotation axis X, of the pusher 3

[0150] Operating mode in case of failure (seizure of the shaft with intermediate stage)

[0151] In the event that there is a failure (known as "jamming") of the shaft 6 with the intermediate stage 10, the actuator operates in the same way as the situation of the "Normal operating mode "

[0152] A further object of the present invention is to provide a method for checking an electrical, electronic and / or mechanical fault in the previously described linear electromechanical actuator 1.

[0153] Thanks to an embodiment of the present invention, it is possible to realize a method for checking in a linear electromechanical actuator, of the Fault Tolerant Differential type, any electrical, electronic and / or mechanical faults, such as latent faults.

[0154] Advantageously, the method according to the present invention makes it possible to identify the type of fault in a linear electromechanical actuator more quickly than in the prior art described above. Furthermore, thanks to an embodiment of the present invention, it is possible to realize a method that identifies the type of mechanical failure in the linear electromechanical actuator and that actuates the electric motors in order to overcome the failure found. In particular, the actuator is equipped with a series of sensors that cooperate with each other to identify the type of failure.

[0155] With reference to the operating modes described above, the method for checking the existence of any problems or faults, in particular latent faults, in the electromechanical actuator 1 in accordance with the diagram of figures 8 will now be described.

[0156] Operating mode to check for any faults

[0157] During normal operation, it is possible to check electrical, electronic, and / or mechanical faults in the linear electromechanical actuator 1 by means of the following steps:

[0158] - activating 23 the electric motor 5 A, block 23, to move the nut 8 rotationally and keep the brake 12B engaged to hold the longitudinal pushing element 9 stationary in position;

[0159] - checking 24, block 24, during said activation step 23, that the shaft 6 translates with respect to said containment structure 2.

[0160] In particular, thanks to the command and control electronics and the plurality of sensors 17, 18 it is possible to identify whether the shaft 6 is actually translated with respect to the containment structure 2.

[0161] According to one aspect, if there are no faults, YES branch of the block 24, then it is provided that the step of activation of the electric motor 5A occurs with a predetermined activation interval T, block 26.

[0162] For example, the activation interval T may have a repetition frequency of constant or variable duration.

[0163] If the shaft 6 does not move with respect to the containment structure 2, NO branch of the block 24, then it is expected to intervene according to one of the methods provided to ensure the correct operation of the actuator 1, block 27 step of determining the type of fault, and to signal the type of anomaly found, block 28.

[0164] In particular, in the event that the command and control electronics does not detect the translation of the shaft 6, then the control electronics enters a so-called failure mode of operation.

[0165] To this end, the command and control electronics identifies through the sensors which electrical or electronic component (for example one of the two electric motors or the electronics themselves) or mechanical component (for example seizure of the intermediate stage with one of the nut and longitudinal pushing element without distinction or seizure of the shaft with the intermediate stage) has a fault.

[0166] The following describes how to detect and remedy a fault in an electrical or electronic component or a mechanical component of the actuator 1.

[0167] In such scenarios, the method always involves reporting the detected fault, block 28.

[0168] Operating mode in case of failure of one of the two electric motors or their electronics without distinction

[0169] The method determines what type of fault has occurred, and, in the event that the failure is in one of the two electric motors 5A or 5B or in the relative electronics without distinction, block 29, then a step is provided to operate the electric brake 12A or 12B so as to block the rotation of the nut 8 or of the longitudinal pushing element 9 on the side of the non-working motor / electronics, block 30.

[0170] Operating mode in case of failure (seizure of the intermediate stage with the nut and / or with the longitudinal pushing element 9)

[0171] The method determines the type of fault that has occurred, and, in the event that the failure is a mechanical failure (so-called "jamming”) of the intermediate stage 10 with the nut 8 and / or the longitudinal pushing element 9, block 31, for example seizure of the intermediate stage 10 with the nut 8 and / or the longitudinal pushing element 9, then there is a step of driving the two electric motors 5A and 5B from the respective electronics in the same direction of rotation, block 32.

[0172] Operating mode in case of failure (seizure of the shaft with intermediate stage)

[0173] The method determines the type of fault that has occurred and in the event that the failure is a failure (so-called "jamming”) of the shaft 6 with the intermediate stage 10, block 33, then there is a step of activating the electric motor 5A from the respective electronics and operating the electric brake 12B, block 34.

[0174] Obviously, in order to satisfy specific and contingent needs, a person skilled in the art may apply numerous changes to the variants described above, all without departing from the scope of protection as defined by the following claims.

Claims

CLAIMS1. Linear electromechanical actuator (1), comprising:- a containment structure (2);- a pusher (3) designed to translate with respect to the containment structure (2) to at least partially come out from the containment structure during the operation of the actuator;- a mechanical reduction apparatus (4) arranged in the containment structure (2) and rotatable around a rotation axis (X);- motor means (5) arranged in the containment structure (2) and operatively connected with said mechanical reduction apparatus (4) to rotate it around said rotation axis (X);- a shaft (6) extending between a first end (6’) connected to the pusher (3) and an opposite second end (6”), said shaft (6) being inserted inside said mechanical reduction apparatus (4) and connected to said pusher (3), said shaft (6) being mechanically connected with said mechanical reduction apparatus (4) in such a way that a rotation of said mechanical reduction apparatus (4) causes a translation of the shaft (6) along said rotation axis (X);- an anti-rotation mechanism active on said shaft (6) to prevent a rotation of the shaft (6) around said rotation axis (X); characterized in that said mechanical reduction apparatus (4) comprises:- a nut (8) having a thread threading;- a longitudinal pushing element (9) along the rotation axis (A) having a linear guide (9B), said nut (8) and said longitudinal pushing element (9) being independent of each other and rotatable around said rotation axis (X) under the action of said motor means (5), said longitudinal pushing element (9) being inserted inside said nut (8);- coupling means (10, 11, 15, 16) configured to mechanically couple said nut (8) andsaid longitudinal pushing element (9) with said shaft (6), in such a way that a rotation of said nut (8) and / or said longitudinal pushing element (9) causes a translation of said shaft (6) along said rotation axis (X); said coupling means (10, 11, 15, 16) comprising:- an intermediate coupling stage (10) interposed between the nut (8) and the longitudinal pushing element (9), said intermediate coupling stage (10) being inserted at least partially in said shaft (6) and in said nut (8) and said longitudinal pushing element (9) being inserted at least partially in said intermediate stage (10) and in said shaft (6).

2. Linear electromechanical actuator according to claim 1, wherein said coupling means (10, 11, 15, 16) comprise:- first and second mechanical connection means (15, 16) for respectively mechanically coupling said intermediate coupling stage (10) with said nut (8) and said intermediate coupling stage (10) with said longitudinal pushing element (9);- third mechanical connection means (11) for mechanically coupling said intermediate coupling stage (10) with said shaft (6).

3. Linear electromechanical actuator according to claim 2, wherein:- said first mechanical connection means (15) comprise a coupling of screw nut or satellite rollers, recirculation of rollers or ball screw;- said second mechanical connection means (16) comprise a recirculating ball coupling by means of longitudinal grooves (9 A) obtained on the linear guide (9B) or a groovetype coupling between the intermediate coupling stage (10) equipped with coupling grooves and the longitudinal grooves (9 A).

4. Linear electromechanical actuator according to claim 3, wherein said intermediate coupling stage (10) extends along the axis (X) between a first end (10’) facing inwards of said containment structure (2) and an opposite second end (10”) and comprises:- externally at the first end (10’) a first threading (10A) configured to couple with the first nut threading (8A);- internally at the first end (10”) coupling element (10B) configured to couple with the respective longitudinal pushing element (9);5. Linear electromechanical actuator according to claim 4, wherein the coupling element (10B) has a recirculating ball device (40) coupled to the longitudinal grooves (9 A) of the linear guide (9B);6. Linear electromechanical actuator according to any one of claims 2 to 5, said third mechanical connection means (11) comprising a screw nut coupling, satellite rollers, recirculation of rollers or ball screw between said shaft (6) and said intermediate coupling stage (10), such that at a rotation of said nut (8) and / or said longitudinal pushing element (9) causes a rotation or a translation or a rototranslation of said intermediate coupling stage (10) along said rotation axis (X) and that said intermediate coupling stage (10), in turn, causes a translation of said shaft (6) along said rotation axis (X).

7. Linear electromechanical actuator according to any one of claims 4 to 6, wherein:- said intermediate coupling stage (10) externally comprises a second threading (10C) configured to couple with the shaft (6) and extending between the first threading (10A) and the second terminal end (10’, 10”);- said shaft (6) is a hollow shaft and internally comprises a threading (6A) configured to couple with the second threading (IOC) of the coupling intermediate stage (10),8. Linear electromechanical actuator according to claim 7, wherein- the thread of said shaft (6) is arranged near the second end of said shaft (6”) and configured to couple with the thread of said threaded element (10C).

9. Linear electromechanical actuator according to any one of claims 1 to 8, wherein said shaft (6) is coaxial with respect to both said intermediate coupling stage (10) and with respect to said nut (8) and said longitudinal pushing element (9) along said rotation axis (X), said intermediate coupling stage (10) being coaxial with respect to said nut (8) and said longitudinal pushing element (9) along said rotation axis (X).

10. Linear electromechanical actuator according to any one of claims 1 to 9, wherein- the motor means (5) comprise a first electric motor (5A) operatively connected with the nut (8) and a second electric motor (5B) operatively connected to the longitudinal pushing element (9) to rotate them around said rotation axis (X-X);- first and second braking means (12A, 12B) active respectively on said nut (8) and said longitudinal pushing element (9) to brake the rotation around said rotation axis (X-X);- a command and control electronics for each electric motor (5 A, 5B) and for the first and second braking means (12A, 12B) comprising a plurality of sensors (17- 18) arranged within said containment structure (2) operatively connected with the command and control electronics, said plurality of sensors (17-18) being designed to detect the position of the shaft (6) so as to detect its movements along the axis X andthe rotations of the motors (5 A, 5B).

11. Linear electromechanical actuator according to claim 10, wherein- the first electric motor (5 A) is directly connected with the nut (8) and comprising a stator fixed to the containment structure (2) and a rotor fixed to said nut (8);- the second electric motor (5B) is connected to the longitudinal pushing element (9) by means of a kinematic chain (5B’).

12. Method for checking the presence of an electrical, electronic and / or mechanical fault in a linear electromechanical actuator (1), said linear electromechanical actuator (1) comprising- providing a linear electromechanical actuator (1) according to any one of claims 1 to 11;- providing the motor means (5) with respective electric motors (5A, 5B) mechanically operative respectively on said nut (8) and on said longitudinal pushing element (9) to move said nut (8) and said longitudinal pushing element (9);- providing first and second braking means (12A, 12B) active respectively on said nut (8) and said longitudinal pushing element (9) to brake the rotation around said rotation axis (X);- providing a command and control electronics for the electric motors (5 A, 5B) and for the first and second braking means (12A, 12B) comprising a plurality of sensors (17-18) arranged within said containment structure (2) operatively connected with the command and control electronics, said plurality of sensors (17-18) being designed to detect the position of the shaft (6) so as to detect its movements along the axis (X);said method being characterized by the steps of:- activating (23) the electric motor (5 A) to move said nut (8) rotationally and keep the brake (12B) engaged to maintain the longitudinal pushing element (9) stationary;- checking (24), through said plurality of sensors (17, 18), during said step of activation of the electric motor (5 A), that said shaft (6) translates with respect to said containment structure (2) and if said shaft (6) does not translate with respect to the containment structure (2):- checking (31) whether there is a mechanical failure of the intermediate stage (10) with the nut (8) and / or with the longitudinal pushing element (9), so as to drive (23), the two electric motors (5A and 5B) in the same direction of rotation;- checking (33) whether there is a mechanical failure of the shaft (6) with the intermediate stage (10), so as to drive (34), the electric motor (5 A) and the electric brake (12B).

13. Method for checking the presence of an electrical, electronic and / or mechanical fault in a linear electromechanical actuator (1) according to claim 12, comprising the steps, if said shaft (6) does not translate with respect to the containment structure (2), of:- checking whether one or both of said two electric motors (5 A, 5B) or said control electronics are in failure (29);- activating (30) the first or second braking means (12A, 12B) so as to prevent the rotation of said nut (8) or said longitudinal pushing element (9) on the side of the non-operating motor means / electronics.

Images