Electromechanical actuator for operating a flight control application

Abstract

The invention relates to an electromechanical actuator for actuating a flight control application of an aircraft, comprising an external rotor motor for driving an output shaft for actuating a flight control application, wherein the external rotor motor has a stator for generating a magnetic field and a rotor circumferentially surrounding the stator, and the rotor has a bell that is rotatable relative to the stator and is provided with magnets on its inner surface facing the stator in order to cause the bell to rotate relative to the stator in conjunction with the magnetic field of the stator.

Description

[0001] The present invention relates to an electromechanical actuator for actuating a flight control application of an aircraft. Electromechanical actuators are generally used in aircraft to actuate control surfaces and therefore play a crucial role in flight safety, particularly in actuating control surfaces that are essential for the maneuverability and stability of aircraft. Electromechanical actuators convert electrical energy into precise mechanical movements to adjust control surfaces such as flaps, rudders, and spoilers.

[0002] Despite the long-standing use of electromechanical actuators in aircraft for operating control surfaces, challenges remain regarding energy efficiency, size, weight, moment of inertia, cost and adaptability to specific application requirements.

[0003] The object of the present invention is to provide an electromechanical actuator that is particularly advantageous for actuating a flight control application. This is achieved with an electromechanical actuator that has all the features of claim 1. Further advantageous embodiments of an actuator according to the invention are described in the dependent claims.

[0004] According to the present invention, an electromechanical actuator according to the invention for actuating a flight control application of an aircraft comprises an external rotor motor for driving an output shaft for actuating a flight control application, wherein the external rotor motor has a stator for generating a magnetic field and a rotor circumferentially surrounding the stator, and the rotor has a bell that is rotatable relative to the stator and is provided with magnets on its inner surface facing the stator in order to cause the bell to rotate relative to the stator in conjunction with the magnetic field of the stator.

[0005] According to the state of the art, brushless inrunner electric motors are used to operate a flight control application of an aircraft; these have already proven themselves over a longer period and are also used in the latest aircraft developments.

[0006] Using an electromechanical actuator, specifically an outrunner motor, offers numerous advantages, particularly in flight control applications. Outrunner motors typically have a very high number of pole pairs, resulting in lightweight rotor magnets that are less susceptible to the vibrations common in aircraft. Furthermore, the large number of magnets allows for precise positioning of the rotor relative to the stator using a Hall-effect sensor, eliminating the need for the additional effort typically required to determine the rotor's position.

[0007] Furthermore, the arrangement of the magnets on the inside of the bell also has the positive effect that the centrifugal forces generated by the rotating bell cannot cause any adhesive bond or similar connection between the bell and the magnet to loosen. This eliminates the need for a special mounting band for the magnets, which is necessary for internal rotor motors. As a result, a smaller air gap can be achieved between the stator coils and the rotor magnets, which has a beneficial effect on the efficiency and power density of the electromechanical actuator.

[0008] According to the present invention, an electromechanical actuator with an external rotor motor can be used to actuate a control surface of an aircraft. In the prior art, only an internal rotor motor was considered for actuating a control surface of an aircraft.

[0009] According to an optional further development of the present invention, it can be provided that the rotor, in particular the bell, comprises aluminium, preferably made of aluminium or an aluminium alloy.

[0010] By making the rotor or bell out of aluminum or an aluminum alloy, the motor moment of inertia can be reduced compared to an internal rotor motor, despite a larger rotor diameter. This means that the structure, which is subjected to stress when the electromechanical actuator moves against an end stop or against "jams", needs to be less massive.

[0011] According to the invention, at least one Hall-effect sensor can be provided to determine the exact rotational position of the bell relative to the stator. A satisfactory position resolution of the rotor relative to the stator is only possible with an external rotor, as it has a high number of pole pairs of magnets. If, however, the number of pole pairs is too low, the accuracy of the position resolution also decreases, so that a special position detection unit is required to determine the position of the rotor relative to the stator. According to the present invention, however, a single Hall-effect sensor is sufficient to determine the position of the rotor relative to the stator with sufficient accuracy. This also contributes to a simplified design of the electromechanical actuator, since the Hall-effect sensor is significantly less complex in its design and signal processing than the position detection units commonly used.

[0012] According to the present invention, it can be provided that at least ten magnets, preferably at least 16 magnets and preferably at least 20 magnets are arranged equidistant from each other and at the same height of the longitudinal axis running parallel to the axis of rotation of the bell on the inner circumferential side of the bell.

[0013] According to a further advantageous modification of the present invention, it can be provided that the magnets of the rotor are individually arranged in a respective magnet receptacle of a bell of the rotor, wherein each of the several magnet receptacles is a recess on the inside of the bell facing the stator, which in a cross-sectional view, the normal of which is parallel to the axis of rotation of the rotor, has the form of a dovetail hole to receive a correspondingly shaped magnet in the form of a dovetail groove in order to create a dovetail connection between magnet and magnet receptacle.

[0014] The dovetail joint between the magnet holder and the magnet, visible in the cross-section, relieves the normally used bonding between the rotor or bell and a respective magnet, as the dovetail joint shown in the cross-section offers excellent support even under vibrations.

[0015] It can be provided that each magnet is inserted into its corresponding magnet holder by a sliding motion that runs parallel to the longitudinal axis (which is identical to the rotational axis of the rotor) of the external rotor motor. This prevents the magnet from slipping out radially, even under strong vibration, because the magnet holder tapers radially towards the stator, so that a correspondingly shaped magnet cannot slip out of the magnet holder in the radial direction.

[0016] A further advantage of the design of the magnet holder as a dovetail hole (in a cross-sectional view) is that even at high speeds, the centrifugal force acting on the respective magnets is not directed against an adhesive bond, as is regularly the case with an internal rotor.

[0017] According to a further optional modification of the present invention, it can be provided that the output shaft has the form of a threaded spindle, a longitudinal axis of the threaded spindle is identical to the rotational axis of the bell, and the external rotor motor surrounds the spindle at least partially circumferentially, so that the rotor has a recess for inserting or passing through the threaded spindle.

[0018] In this particularly compact design of the electromechanical actuator, the stator is provided with a central recess into which the threaded spindle can be inserted or removed. The stator is thus arranged circumferentially around the threaded spindle and serves to accommodate the extendable or retractable spindle. The bell housing, or a component rigidly connected to the bell housing, acts on the threaded spindle and converts the rotational movement of the bell housing into a linear movement of the spindle parallel to the longitudinal axis of the outer rotor (which is parallel to the rotational axis of the rotor).

[0019] According to a further development of the present invention, it can be provided that the bell, the threaded spindle and balls arranged between the threaded spindle and the bell generate a ball screw drive, which leads to a movement of the threaded spindle that depends on the direction of travel of the bell.

[0020] The bell can have a section extending towards the outer circumference of the threaded spindle, which, for example, extends over at least one thread in the longitudinal direction of the spindle and accommodates a ball in the space between the thread of the spindle and the section extending towards the threaded spindle, preventing rotation of the bell, so that when the bell (and therefore necessarily also the section extending towards the threaded spindle) is rotated in the longitudinal direction, a rotation of the ball along the inclined thread of the threaded spindle causes the spindle to move in the linear direction.

[0021] By arranging the stator around the threaded spindle, a particularly compact design of the electromechanical actuator is created, which requires little space in the longitudinal direction.

[0022] According to an optional further development of the present invention, it can be provided that a planetary gear is further provided, and that a planet gear of the planetary gear is arranged between an outer housing fixed to the stator and the rotor, in particular the bell, which is in a meshing connection with both the outer housing and the rotor, in particular the bell.

[0023] This design implements a gearbox in a very space-saving manner, with the bell or a component rigidly connected to the bell acting as the sun gear. The planetary gear set can then function as a reduction gear through the stationary ring gear (inside the outer housing) and the driven sun gear, further increasing the torque force transmitted by the bell to the bridge connecting the multiple planet gears.

[0024] According to an optional modification of the present invention, it can further be provided that the outer housing has a circumferential toothing on its inner side facing the external rotor motor and the rotor, in particular the bell, has a circumferential toothing on a side facing the outer housing, wherein the planetary gear engages simultaneously in the toothing of the outer housing and in the toothing of the rotor, in particular the bell.

[0025] Advantageously, it can be provided that the shaft, which is driven by the movement of the planet gears along the circumference of the sun gear, has an axis of rotation that is identical to the axis of rotation of the rotor.

[0026] According to the invention, it can further be provided that the bell is connected in a rotationally fixed manner to a worm shaft which interacts with a worm wheel to form a self-locking worm gear, wherein preferably an axis of rotation of the worm wheel is perpendicular to an axis of rotation of the worm shaft.

[0027] The self-locking property of the worm gear is particularly advantageous for positioning the air deflectors of an aircraft, as a high force typically acts on a positioned air deflector. The self-locking gear ensures that, after the desired actuation of the electromechanical actuator, which positions the air deflector, no additional energy is required to hold the positioned air deflector in the desired position.

[0028] According to a further optional embodiment of the present invention, it can be provided that a braking device for braking the rotor of the external rotor motor is also provided, which achieves a braking effect by a frictional engagement of a brake block on the rotor, in particular the bell, preferably wherein the brake block is arranged on an inner side of the outer housing in a rotationally fixed manner relative to the rotor, in particular the bell, but is movable back and forth in one direction along the axis of rotation of the rotor.

[0029] According to the invention, it can therefore be provided that a brake block of a braking device acts directly on the rotating bell of the outer rotor.

[0030] According to an optional embodiment of the present invention, the braking device may have a brake block which is arranged in a rotationally fixed manner relative to the rotor, in particular the bell, but which is movable back and forth in one direction along the axis of rotation of the rotor, preferably wherein a spring unit is provided to push the brake block towards the rotor to engage in a frictional engagement, and movement in the opposite direction can be generated by means of an electromagnet exerting a magnetic force on the brake block.

[0031] The axial movement of the brake pad can therefore be effected by an electromagnet, which, in its active state, exerts an attractive magnetic force on the brake pad to move it out of its braking position. An elastic spring element, such as a coil spring or the like, can push the brake pad towards its braking position, so that when the electromagnet is inactive, the braking device brakes the rotor of the external rotor. The attractive force exerted by the electromagnet is greater than the force exerted by the elastic spring element, so that when the electromagnet is active, the braking device is moved into the releasing position.

[0032] According to a further advantageous embodiment of the present invention, it can be provided that the rotor, in particular the bell, has two magnets spaced apart from each other in the longitudinal direction, each of which interacts with different coils of different stators to generate a duplex motor in a side-by-side configuration.

[0033] By using a duplex motor, the torque of the outer rotor can be easily increased. Furthermore, by providing a second stator that interacts with a second rotating array of magnets, also mounted on the bell, an additional torque is generated to move the bell. The bell is equipped with longitudinally offset magnet receptacles. First magnets located in these receptacles interact with a first stator or with first coils located within the first stator, while the longitudinally offset second magnet receptacles accommodate magnets that interact with a second stator or coils of the second stator, which are also longitudinally offset from the first stator. The bell containing these longitudinally spaced magnet receptacles can be constructed as a single piece or at least as a rigid structure.

[0034] According to a further optional modification of the present invention, the electromechanical actuator can be provided to have a minimum power range of at least 200 W, preferably at least 1000 W and preferably at least 2000 W, and a maximum power range of at most 4000 W, preferably at most 3000 W and preferably at most 2500 W.

[0035] The invention further relates to an aircraft, in particular an airplane, with an electromechanical actuator according to one of the aspects discussed above, preferably wherein the electromechanical actuator serves to move a control surface of the aircraft.

[0036] Further features, details, and advantages of the invention will become apparent from the following description of the figures. These show: Fig. 1: a sectional view of the electromechanical actuator according to the invention, which has a planetary gear, Fig. 2: a sectional view of the electromechanical actuator according to the invention with a worm gear, Fig. 3: a sectional view of the electromechanical actuator according to the invention with a braking device, Fig. 4: a sectional view of the electromechanical actuator according to the invention with a duplex motor, Fig. 5: a cross-sectional view of the rotor showing the dovetail joint between the magnet and the bell, and Fig. Figure 6: a sectional view of the electromechanical actuator according to the invention with a threaded spindle.

[0037] Fig. Figure 1 shows a sectional view of the electromechanical actuator 1 according to the invention, which has a planetary gear 14.

[0038] The stator 4 with its electromagnets is visible, as are the magnets 7 arranged radially outwards, which are fixedly connected to the bell 6. The bell 6 then rotates together with the magnets 7 around the axis of rotation X, with the planetary gear 14 having a planet gear 16 that meshes with a sun gear 18, which can be part of the bell 6 or at least non-rotatably connected to it. Furthermore, the planet gear 16 meshes with a toothed section arranged circumferentially on the outer housing 15, so that the toothed section projecting inwards from the outer housing 15 serves as a ring gear. The shaft 17 rotates around the sun gear 18 in the circumferential direction depending on the positional movement of the several planet gears 16. This results in a reduced rotational speed compared to the bell, but increases the torque.

[0039] Fig. Figure 2 shows a sectional view of the electromechanical actuator 1 according to the invention with a worm gear 2. The basic structure of bell 6, magnet 7 and stator 4 remains constant. Fig. 1 and corresponds to the characteristic arrangement of an external rotor. The worm shaft 19 can be formed as a single unit with the bell 6, but is at least rotationally fixed to it. It is clear to those skilled in the art that the worm shaft 19 can also be designed as part of the rotor 5 or part of the bell 6, and in this case, it interacts with a worm wheel 20 arranged transversely to the direction of rotation of the worm shaft 19. The worm gear 21 is self-locking, which is advantageous with regard to the typically high restoring force acting on the airfoils of an aircraft. Ultimately, no energy needs to be expended to hold a position of an airfoil, as this task is performed by the self-locking worm gear 21.

[0040] Fig. Figure 3 shows a sectional view of the electromechanical actuator 1 according to the invention with a braking device 22. According to this embodiment of the present invention, there is a braking device 22 designed to bring an axially reciprocating brake block 23 into frictional contact with a component of the bell 6 or to lift it away from it. A spring unit 24 may also be provided, which serves to push the brake block 23 towards the bell 6 so that the brake block 23 comes into physical contact with the bell 6 and its rotation is slowed. To release this braking state, an electromagnet 25 is activated, which exerts an attractive force on the brake block 23 that is directed opposite to the force exerted by the spring 24.Since the force exerted on the brake pad 23 by means of the electromagnet 25 is greater than the force exerted by the spring unit 24, the brake pad 23 moves away from the bell 6. The brake pad can be mounted on an outer housing 15 so that it is rotationally fixed but axially movable.

[0041] Fig. Figure 4 shows a sectional view of the electromechanical actuator 1 according to the invention with a duplex motor.

[0042] This cross-sectional view shows the arrangement of axially spaced stators 4, each interacting with axially spaced magnets 7. The two axially spaced magnets 7 are arranged on a common bell 6, so that the torque generated by each magnet (naturally with the help of the coils of the stators 4) is summed at the bell 6, resulting in a greater torque at the bell and thus at the output shaft 3, which is non-rotatably connected to the bell 6.

[0043] Fig. Figure 5 shows a cross-sectional view of the rotor 5, from which the dovetail connection of magnet 7 and bell 6 can be seen. In this cross-sectional view, whose plane of view is formed by the normal which runs parallel to the axis of rotation X, the dovetail connection of magnet 7 and magnet holder 8, which holds the magnet in the bell 6, can be seen.

[0044] Fig. Figure 6 shows a sectional view of the electromechanical actuator 1 according to the invention, including a threaded spindle 11. It can be seen that the stator 4, with its coils and windings or laminated cores, has a receptacle into which the threaded spindle 11 can be inserted or passed. The stator 4 is thus built circumferentially around the threaded spindle 11, resulting in a particularly compact design. The bell 6 has a section projecting inwards towards the axis of rotation X, which extends longitudinally along the threaded spindle 11. At least one receptacle for at least one ball 13 is provided between the threaded spindle 11 and the section of the bell 6, so that rotation of the bell 6, or rotation of the inwardly projecting section, causes a linear movement of the threaded spindle 11. Reference symbol list: 1 Electromechanical actuator 2 external rotor motors 3 Output wave 4 Stator 5 Rotor 6 Bell 7 Magnet 8 Magnetic recording 9 dovetail holes 10 dovetail grooves 11 Threaded spindle 12 Exclusion 13 balls 14 planetary gears 15 Outdoor housings 16 planetary gear 17 Bridge wave 18 sun wheel 19 worm shaft 20 worm gear 21 worm gears 22 Brake device 23 brake pad 24 spring unit 25 Electromagnet X axis of rotation

Claims

[1] Electromechanical actuator (1) for actuating a flight control application of an aircraft, comprising: an external rotor motor (2) for driving an output shaft (3) for actuating a flight control application, wherein the external rotor motor (2) has a stator (4) for generating a magnetic field and a rotor (5) circumferentially surrounding the stator (4), and the rotor (5) has a bell (6) which is rotatable relative to the stator (4) and is provided with magnets (7) on its inner side facing the stator (4) in order to cause the bell (6) to rotate relative to the stator (4) in conjunction with the magnetic field of the stator (4). [2] Electromechanical actuator (1) according to the preceding claim, wherein the rotor (5), in particular the bell (6), comprises aluminium, preferably made of aluminium or an aluminium alloy. [3] Electromechanical actuator (1) according to one of the preceding claims, wherein at least one Hall sensor is provided to determine the exact rotational position of the bell (6) relative to the stator (4). [4] Electromechanical actuator (1) according to one of the preceding claims, wherein the magnets (7) of the rotor (5) are individually arranged in a respective magnet receptacle (8) of a bell (6) of the rotor (5), wherein each of the multiple magnet receptacles (8) is a recess on the inside of the bell (6) facing the stator (4), which in a cross-sectional view, the normal of which is parallel to the axis of rotation (X) of the rotor (5), has the form of a dovetail hole (9) to receive a correspondingly shaped magnet (7) in the form of a dovetail groove (10) to create a dovetail connection between magnet (7) and magnet receptacle (8). [5] Electromechanical actuator (1) according to any one of the preceding claims, wherein the output shaft (3) has the form of a threaded spindle (11), a longitudinal axis of the threaded spindle (11) is identical to the rotational axis (X) of the bell (6), and the external rotor motor (2) surrounds the threaded spindle (11) at least partially on its circumference, so that the rotor (5) has a recess (12) for inserting or passing the threaded spindle (11). [6] Electromechanical actuator (1) according to the preceding claim, wherein the bell (6), the threaded spindle (11) and balls (13) arranged between the threaded spindle (11) and the bell (6) create a ball screw drive which results in a movement of the threaded spindle (11) which depends on the direction of travel of the bell (6). [7] Electromechanical actuator (1) according to one of the preceding claims 1-4, wherein a planetary gear (14) is further provided, and a planet gear (16) of the planetary gear (14) is arranged between an outer housing (15) fixed to the stator (4) and the rotor (5), in particular the bell (6), which is in a meshing connection with both the outer housing (15) and the rotor (5), in particular the bell (6). [8] Electromechanical actuator (1) according to the preceding claim, wherein the outer housing (15) has a circumferential toothing on its inner side facing the external rotor motor (2) and the rotor (5), in particular the bell (6), has a circumferential toothing on a side facing the outer housing (15), wherein the planet gear (16) engages simultaneously in the toothing of the outer housing (15) and in the toothing of the rotor (5), in particular the bell (6). [9] Electromechanical actuator (1) according to the preceding claim, wherein the shaft (17) which is driven by the movement of the planet gears (16) along the circumference of the sun gear (18) has an axis of rotation which is identical to the axis of rotation (X) of the rotor (5). [10] Electromechanical actuator (1) according to any one of the preceding claims 1-4, wherein the bell (6) is rotationally fixed to a worm shaft (19) which interacts with a worm wheel (20) to form a self-locking worm gear (21), wherein preferably an axis of rotation of the worm wheel is perpendicular to an axis of rotation of the worm shaft. [11] Electromechanical actuator (1) according to one of the preceding claims, wherein a braking device (22) for braking the rotor (5) of the external rotor motor (2) is further provided, which achieves a braking effect by frictional engagement of a brake block (23) with the rotor (5), in particular the bell (6), preferably wherein the brake block (23) is arranged on an inner side of the outer housing (15) in a rotationally fixed manner relative to the rotor (5), in particular the bell (6), but is movable back and forth in one direction along the axis of rotation (X) of the rotor (5). [12] Electromechanical actuator (1) according to the preceding claim, wherein the braking device has a brake block (23) which is arranged in a rotationally fixed manner relative to the rotor (5), in particular the bell (6), but is movable back and forth in one direction along the axis of rotation (X) of the rotor (5), preferably wherein a spring unit (24) is provided to push the brake block (23) towards the rotor (5) to engage in a frictional engagement, and movement in the opposite direction can be generated by means of an electromagnet (25) exerting a magnetic force on the brake block (23). [13] Electromechanical actuator (1) according to one of the preceding claims, wherein the rotor (5), in particular the bell (6), has two longitudinally spaced magnets (7) which each interact with different coils of different stators (4) to generate a duplex motor in a side-by-side configuration. [14] Electromechanical actuator (1) according to any of the preceding claims, wherein the electromechanical actuator (1) has a minimum power range of at least 200 W, preferably at least 1000 W and preferably at least 2000 W and has a maximum power range of at most 4000 W, preferably at most 3000 W and preferably at most 2500 W. [15] Aircraft, in particular airplane, with an electromechanical actuator (1) according to one of the preceding claims, preferably wherein the electromechanical actuator (1) serves to move a control surface of the aircraft.

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