3D-printed spur gear teeth of a tilt-wing pivot mechanism

Abstract

The invention relates to a device for tilting a wing (4) of a tilt-wing aircraft relative to a fuselage of the tilt-wing aircraft, comprising a gear transmission comprising a first gear (1) with tooth flanks arranged around a complete circular circumference and comprising a second gear (2) with tooth flanks arranged around a circumference of a circular arc with an opening angle of less than 180°, wherein a radius of the second gear (2) is greater than that of the first gear (1), wherein the first gear (1) is coupled to an electric drive (3), the second gear (2) is connected to the wing (4) in a rotationally fixed manner, the first and second gears (1, 2) are spur gears and wherein the first gear (1) and the second gear (2) are in engagement with one another by means of helical gearing.

Description

[0001] The invention relates to a device for tilting a wing of a tilt-wing aircraft relative to a fuselage of the tilt-wing aircraft, as well as a method for producing such a device using additive manufacturing.

[0002] In tilt-wing aircraft, a wing is designed to rotate relative to a fuselage from a horizontal orientation to a substantially vertical orientation about a direction of extension of the wing. The purpose of this is to enable unhindered outflow of vertically acting propeller airflow, particularly in electrically powered unmanned aircraft capable of vertical landing and takeoff. The propellers can be arranged immovably relative to the wing, so that tilting the wing simultaneously allows for thrust vector adjustment, in that the tilting of the wing causes the change in the thrust direction of the propellers relative to the fuselage. Other thrust configurations are also conceivable; the purpose of rotating the wing relative to the fuselage can remain open for the following explanations.

[0003] In order to achieve rapid transitions between the aircraft state and to be able to perform corresponding maneuvers for the transition between hover and forward flight and vice versa, especially in smaller unmanned aircraft designed as tilt-wing aircraft, a fast and powerful drive mechanism for tilting the wing is required. The speed of the change in orientation of the wing relative to the fuselage determines which maneuvers can be performed at all and how well. At the same time, the drive mechanism must compensate for the applied load torque, which becomes significant due to increasing air forces or torques at higher flight speeds and aerodynamic angles of attack.

[0004] Such tilt-wing aircraft are known in the state of the art: DE 10 2010 021 022 A1, for example, relates to a tilt-wing aircraft with a tail propulsion and control unit designed to generate thrust and also to generate an upward or downward thrust component and / or a laterally directed thrust component during hovering and climbing of the aircraft.

[0005] DE 10 2016 001 771 A1 further relates to a tilt-wing convertible aircraft, comprising a plurality of wing units arranged substantially one behind the other in the horizontal flight direction and connected to a fuselage unit, each of which has a tiltable wing and at least one drive unit arranged immovably on the wing relative to the wing.

[0006] Various drive mechanisms for adjusting the orientation of the wing relative to the fuselage are also proposed in the state of the art: US 11 518 505 B1 shows a VTOL tilt-wing aircraft designed as a 4-6 passenger airliner for scheduled service between city centers, optimized for travel distances of 100-500 miles fully loaded with passengers and fuel. A worm gear is used to tilt the wing relative to the fuselage.

[0007] Furthermore, JP 2010-254 264 A shows a vertical take-off and landing aircraft with a twistable wing that is twisted by a belt drive.

[0008] CN 1 07 600 403 B also shows an unmanned aerial vehicle with a tilting wing using a linkage. Control rods are used to tilt the wing.

[0009] CN 1 15 503 951 A also shows a linkage in an aircraft with a tilting wing that is tilted with the linkage. Control rods can act as tension rods or compression rods.

[0010] Furthermore, gear drives for tilting wings are known in the prior art: CN 1 09 398 751 B relates to a method for detecting whether the wing of a UAV with a tilting mechanism is loose, wherein a tilting mechanism is shown; CN 1 13 562 172 A further relates to an unmanned cargo aircraft with a tiltable wing.

[0011] CN 2 17 673 199 U relates to a tilt-rotor aircraft with a distributed electric drive and a fuselage. The fuselage is provided with a tilting mechanism for driving the main wing to tilt the main wing. The tilting mechanism includes a motor located within the fuselage and a rotating rod rigidly connected to the output end of the motor, with a pinion encased on the rotating rod.

[0012] US 7 510 143 B1 further relates to an aircraft with a wing assembly arranged downstream of a propulsion source of the aircraft. The aircraft comprises a fuselage having a longitudinal axis, a wing assembly supported by the fuselage and a movable part movable relative to the fuselage, and a wing supported by the movable part. A first actuator is coupled to the movable part to move it relative to the fuselage in a direction parallel to the axis of the fuselage. A second actuator is coupled to the wing to move the wing relative to the movable part and between the first and second positions. The object of the invention is to achieve an improved system for rotating a wing of a tilt-wing aircraft relative to its fuselage.

[0013] The invention is based on the features of the independent claims. Advantageous developments and refinements are the subject of the dependent claims.

[0014] A first aspect of the invention relates to a device for tilting a wing of a tilt-wing aircraft relative to a fuselage of the tilt-wing aircraft, comprising a gear transmission comprising a first gear with tooth flanks arranged around a complete circumference and comprising a second gear with tooth flanks arranged around a circumference of a circle with an opening angle of less than 180°, wherein a radius of the second gear is greater than that of the first gear, wherein the first gear is coupled to an electric drive, the second gear is connected to the wing in a rotationally fixed manner, the first and second gears are spur gears and wherein the first gear and the second gear are in engagement with one another by means of helical gearing, wherein the first gear and the second gear are manufactured from plastic by additive manufacturing.

[0015] Because the second gear is non-rotatably connected to the vane and has a larger diameter than the first gear, a reduction gear is created from the electric drive to the vane. This means that the drive rotates at a higher speed than the vane when the first gear and the second gear mesh and the drive is activated. The first gear thus functions as a pinion, as it has the smaller diameter of the two gears.

[0016] The second gear can be designed to save mass and only run along a circular arc with an opening angle of essentially or exactly 90°. This is because the wing is typically intended to be rotated essentially or exactly 90°, and the wing moves with the movement of the second gear. The tooth flanks of the first gear, on the other hand, must be arranged around a full circumference, since the first gear will perform a rotational movement of at least several multiples of 360° when the second gear moves by 90°, with the total angle covered by the movement of the first gear depending on the transmission ratio to the second gear. The opening angle is preferably exactly 90°, or in the range >90° to 110° or up to 130° if the wing is intended to be tilted against the main forward flight direction.

[0017] Helical gears on the gears described above and below, when intended for an unmanned tilt-wing aircraft with a preferred mass of 250 kg or less, or 100 kg or less, and particularly preferably 50 kg or less, are very difficult to manufacture. This is especially true for herringbone gears.

[0018] Herringbone gears are formed from a multitude of pairs of tooth flanks converging at an angle. Compared to simple helical gears, they have the advantage that locally occurring axial forces neutralize each other, and the gears meshing with herringbone gears (first gear and second gear) generate no net axial force. Such herringbone gears are very difficult to manufacture, especially for the application mentioned above. For this reason, the first gear and the second gear are preferably manufactured using additive manufacturing.

[0019] Additive manufacturing is particularly suitable for materials with a low melting point or low glass transition temperature (compared to steel), making thermoplastics particularly suitable. Additive manufacturing describes a process in which raw material is applied layer by layer until a desired component is completed. Therefore, additive manufacturing is often referred to as 3D printing.

[0020] By means of additive manufacturing, not only can complex gear geometries such as helical gears be produced more easily compared to state-of-the-art solutions, but it can also achieve a compact design of a single-stage gearbox that can generate a relatively high torque on the wing.

[0021] The higher frictional force of a worm gear, as well as the typically more complex design associated with greater installation space for control rods, can thus be avoided. The high reduction ratios used in the prior art for high torques (in worm gears or linear actuators) or the low reduction ratios for low torques and high speeds (when using belts or multi-stage gears), with their disadvantages, can be discarded, and a single-stage gear with a desired ratio can be used instead. This is achieved in particular through additive manufacturing in production. Furthermore, the mechanisms shown in the above-mentioned prior art only achieve a significantly lower power density than the single-stage gear according to the invention.

[0022] When the tilting of the wing relative to the fuselage is mentioned above and below, this also includes the tilting of a left wing half and a right wing half if no continuous wing is used over the entire span of the aircraft, but rather independently mounted wing halves.

[0023] According to the invention, the first gear and the second gear are manufactured by additive manufacturing.

[0024] According to a further advantageous embodiment, a respective holder for the first gear and for the second gear is produced by additive manufacturing.

[0025] According to a further advantageous embodiment, the helical gearing is a herringbone gearing. A gear designed as a spur gear with herringbone gearing is also called a double helical gear.

[0026] According to a further advantageous embodiment, the herringbone toothing has curved tooth flanks. The curved tooth flanks are preferably used only on the pinion, i.e., on the first gear, while straight tooth flanks are used on the second gear. This improves the engagement of the tooth flanks of the first gear in the recesses between the tooth flanks of the second gear.

[0027] According to a further advantageous embodiment, two first gears and two second gears are provided, wherein the helical gears between a first pair of first gear and second gear and between a second pair of first gear and second gear are aligned in a mirror image to one another, so that axial forces of the helical gears between the pairs of gears cancel each other out.

[0028] According to this embodiment, the first gears are preferably arranged next to one another, preferably connected to one another in a rotationally fixed manner, and the second gears are also arranged next to one another and preferably connected to one another in a rotationally fixed manner. This can also be considered a respective two-part first gear and a two-part second gear. Alternatively, the first gears are arranged spaced apart from one another, and the second gears are arranged spaced apart from one another. In contrast to this embodiment, the respective herringbone toothing is provided on a one-part first gear and a one-part second gear.

[0029] According to a further advantageous embodiment, the first gear and the second gear are made of plastic, preferably thermoplastic plastic, furthermore preferably a plastic matrix of the gears comprises particles and / or fibers, for example made of carbon or glass.

[0030] According to a further advantageous embodiment, the radius of the second gear is at least six times the radius of the first gear, particularly preferably eight times.

[0031] According to a further advantageous embodiment, the device further comprises an auxiliary gear with an output gear part and a drive gear part engageable with the output gear part, wherein the output gear part is rotationally fixed to the second gear and wherein the drive gear part is rotationally fixed to a rotation angle meter and / or rotation rate meter.

[0032] The auxiliary gear provides the mechanical coupling between the tilting vane angle sensor and the yaw rate sensor, an angle sensor built into the servo motor. The tilting vane angle is measured at the vane shaft and transferred to the servo's angle sensor via a small torsion bar. This design makes it possible to bypass the angle limitation (usually 360°) of a standard angle sensor. However, this is not necessary for servo motors, which have unlimited angle control.

[0033] According to a further advantageous embodiment, the output gear part and the drive gear part are manufactured by additive manufacturing and have respective tooth flanks which can be brought into engagement with one another and which are each arranged around a circumference of a circular arc with an opening angle of less than 180°.

[0034] A further aspect of the invention relates to a method for producing a device for tilting a wing of a tilt-wing aircraft relative to a fuselage of the tilt-wing aircraft, wherein a gear transmission comprising a first gear with tooth flanks arranged around a complete circular circumference and comprising a second gear with tooth flanks arranged around a circumference of a circular arc with an opening angle of less than 180°, wherein a radius of the second gear is larger than that of the first gear, is produced by additive manufacturing, so that in the manufacturing process by means of additive manufacturing a helical toothing of the first gear and a helical toothing of the second gear are manufactured from plastic.

[0035] According to this manufacturing process, the first gear and the second gear are manufactured using additive manufacturing. This allows even complex tooth geometries, such as herringbone gears, to be produced cost-effectively for the respective spur gears. This manufacturing process is cost-effective and easily scalable, making it particularly suitable for gear transmissions for unmanned, electrically powered tilt-wing aircraft with a mass of less than 100 kg, particularly preferably less than 50 kg. Furthermore, additive manufacturing can be used to produce a mount for the first gear and / or the second gear, enabling a streamlined, integrated design.

[0036] According to a further advantageous embodiment, the respective helical gearing is designed as a respective herringbone gearing on the respective gearwheel.

[0037] According to a further advantageous embodiment, an auxiliary gear with an output gear part and a drive gear part that can be brought into engagement with the output gear part is produced in additive manufacturing, wherein the output gear part is brought into rotationally fixed relation to the second gear and wherein the drive gear part is brought into rotationally fixed relation to a rotation angle sensor and / or rotation rate sensor.

[0038] The output gear part and the drive gear part are also preferably designed with helical gearing produced by additive manufacturing.

[0039] Advantages and preferred developments of the proposed method result from an analogous and analogous transfer of the statements made above in connection with the proposed device.

[0040] Further advantages, features, and details will become apparent from the following description, in which at least one embodiment is described in detail—possibly with reference to the drawings. Identical, similar, and / or functionally equivalent parts are provided with the same reference numerals.

[0041] They show: Fig. 1: A device for tilting a wing of a tilt-wing aircraft according to an embodiment of the invention. Fig. 2: The device of Fig. 1 in a side view. Fig. 3: The device of Fig. 1 in a front view. Fig. 4: A device for tilting a wing of a tilt-wing aircraft according to another embodiment of the invention. Fig. 5: An aircraft structure with two tilting wings with devices according to Fig. 1 according to an embodiment of the invention in a plan view.

[0042] The representations in the figures are schematic and not to scale.

[0043] Fig. Figure 1 shows a device for tilting a wing 4 of a tilt-wing aircraft relative to a fuselage of the tilt-wing aircraft. An electric drive 3 is provided, which is connected to the first gear 1 via a shaft. The first gear 1 is manufactured by additive manufacturing. In this manufacturing process, a herringbone toothing was applied to a shell wall of the cylindrical first gear 1, so that the toothing and the remaining base body of the first gear 1 form a one-piece component.The first gear 1 is thus designed as a spur gear and forms the pinion in the single-stage transmission in interaction with the second gear 2, which has a larger diameter than the first gear 1, is also designed as a spur gear and was again manufactured in an additive manufacturing process with a herringbone toothing that can be brought into engagement with the herringbone toothing of the first gear 1, so that a torque transfer from the drive 3 to the first gear 1 can take place via a single-stage reduction to the second gear 2, the torque of which is in turn transmitted via a further shaft to a vane 4 (in . Fig. 1 not shown) in order to be able to tilt it relative to the fuselage and thus relative to a holder of the first gear 1 and a holder of the drive 3 about a transverse axis of the aircraft, ie about an axis parallel to a wing longitudinal direction. Fig. The device illustrated in Figure 1 by way of example with the gear transmission comprising the first gear 1 and the second gear 2, both of which were manufactured using additive manufacturing, together with a respective holder for the gears 1, 2, each of which was also manufactured using additive manufacturing, serves to tilt the wing 4 of the unmanned aerial vehicle. In the exemplary dimensioning, the gear transmission on the second gear 2 generates a torque of 20 Newton meters and allows the wing 4 to be tilted from a horizontal to a vertical position in under three seconds with a transmission ratio of 1:8. In this embodiment, the device achieves a total mass of 250 g, which would not be possible with a conventionally manufactured worm gear, with linear actuators or rods known from the prior art, and with belt drives.

[0044] Fig. Figure 2 shows a side view of the device of Fig. 1.

[0045] Fig. 3 shows the first gear 1 and the second gear 2 from the device of Fig. 1 from a front view. This shows the complex geometry of the respective herringbone gearing, which is obtained by applying the additive manufacturing process, preferably with a thermoplastic material.

[0046] Fig. 4 shows a variant of the device of the Fig. 1: In this variant compared to the device of the Fig. 1, an auxiliary gear is also provided, which can be used advantageously in particular when no rotation angle sensor with a detection range of over 360° is available - because when the first gear 1 rotates, which is intended to cause a 90° rotation of the second gear 2 and thus of the connected vane 4, a rotation angle range of at least a multiple of 360° on the first gear 1 is to be expected. For this purpose, an output gear part 6 and a drive gear part 7 that can be brought into engagement with the output gear part 6 are provided, wherein the output gear part 6 is rotationally fixed to a rotation angle sensor 5 and wherein the drive gear part 7 is rotationally fixed to the second gear 2. In this case, a movement or an angle of the output gear part 6 is transferred to the rotation angle sensor 5, decoupled from the angle and movement of the first gear 1, which is located in a common housing with the electric drive 3.For example, a second shaft from the output gear part 6 is guided within the first shaft, which connects the first gear 1 to the electric drive 3, wherein the first shaft and the second shaft are kinematically decoupled from one another. Again, the drive gear part 7 and the output gear part 6 are manufactured using an additive manufacturing process, preferably from plastic. Furthermore, both the drive gear part 7 and the output gear part 6 have herringbone toothing in order to mesh with one another with as little slippage and backlash as possible. Both the output gear part 6 and the drive gear part 7 have tooth flanks arranged around a respective circumference of a respective circular arc with an opening angle of less than 180°, in this example essentially 90°.

[0047] Fig. 5 shows the connection and integration of the device of the Fig. 1 into a fuselage of an unmanned tilt-wing aircraft with electric propulsion 3. The structure of the Fig. 5 is shown from a bird's eye view. This aircraft is a tandem tilt-wing configuration, which has two wings 4 and therefore two tilt-wing shafts (dashed in Fig. 5), which preferably also form a rotation axis. Several propellers are provided along a respective tilting wing 4, which can be tilted relative to the basic structure of a fuselage by means of the device. In the region of the longitudinal center of each wing 4, a housing is arranged, comprising a respective electric drive 3 and a first gear 1 for rotating the respective second gear 2 (not shown). Fig. 5) together with a respective tilting wing shaft.

[0048] Although the invention has been illustrated and explained in detail by preferred embodiments, the invention is not limited by the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention. It is therefore clear that numerous variations exist. It is also clear that exemplary embodiments are truly only examples and should not be construed as limiting the scope, possible applications, or configuration of the invention in any way.Rather, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete terms, whereby the person skilled in the art, with knowledge of the disclosed inventive concept, can make various changes, for example with regard to the function or the arrangement of individual elements mentioned in an exemplary embodiment, without departing from the scope of protection defined by the claims and their legal equivalents, such as further explanations in the description. List of reference symbols 1 first gear 2 second gear 3 electric drive 4 wings 5 angle meters 6 Output gear part 7 Drive wheel part

Claims

[1] Device for tilting a wing (4) of a tilt-wing aircraft relative to a fuselage of the tilt-wing aircraft, comprising a gear transmission comprising a first gear (1) with tooth flanks arranged around a complete circumference and comprising a second gear (2) with tooth flanks arranged around a circumference of a circle with an opening angle of less than 180°, wherein a radius of the second gear (2) is greater than that of the first gear (1), wherein the first gear (1) is coupled to an electric drive (3), the second gear (2) is connected in a rotationally fixed manner to the wing (4), the first and second gears (1, 2) are spur gears and wherein the first gear (1) and the second gear (2) are in engagement with one another by means of helical gearing, wherein the first gear (1) and the second gear (2) are produced from plastic by additive manufacturing. [2] Device according to claim 1, wherein a rotation angle sensor and / or rotation rate sensor is provided synchronized to the first gear, wherein the rotation rate sensor has a detection range of greater than 360°. [3] Device according to one of the preceding claims, further comprising an auxiliary gear with an output gear part (6) and a drive gear part (7) engageable with the output gear part (6), wherein the drive gear part (7) is rotationally fixed to the second gear (2) and wherein the output gear part (6) is rotationally fixed to a rotation angle sensor (5) and / or rotation rate sensor. [4] Device according to claim 3, wherein the output gear part (6) and the drive gear part (7) are manufactured by additive manufacturing and have respective tooth flanks which can be brought into engagement with one another and which are each arranged around a circumference of a circular arc with an opening angle of less than 180°. [5] Device according to one of the preceding claims, wherein the helical gearing is a herringbone gearing. [6] Device according to one of the preceding claims, wherein the radius of the second gear (2) is at least six times the radius of the first gear (1). [7] Method for producing a device for tilting a wing (4) of a tilt-wing aircraft relative to a fuselage of the tilt-wing aircraft, wherein a gear transmission comprising a first gear (1) with tooth flanks arranged around a complete circular circumference and comprising a second gear (2) with tooth flanks arranged around a circumference of a circular arc with an opening angle of less than 180°, wherein a radius of the second gear (2) is greater than that of the first gear (1), is produced by additive manufacturing, so that in the manufacturing process by means of additive manufacturing a helical toothing of the first gear (1) and a helical toothing of the second gear (2) are manufactured from plastic. [8] Method according to claim 7, wherein the respective helical toothing is designed as a respective herringbone toothing on the respective gear wheel (1, 2). [9] Method according to one of claims 7 to 8, wherein an auxiliary gear with an output gear part (6) and a drive gear part (7) which can be brought into engagement with the output gear part (6) are further produced in additive manufacturing, wherein the drive gear part (7) is brought in a rotationally fixed manner to the second gear (2) and wherein the output gear part (6) is brought in a rotationally fixed manner to a rotation angle sensor (5) and / or rotation rate sensor.

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