RU2777706C2 - Vibration damping device for helicopter - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: invention relates to the field of aviation, in particular to structures of bearing systems of helicopters. Helicopter (2) contains fuselage (3) and propeller (4), at least one device (15) adapted for damping vibrations transmitted from propeller (4) to fuselage (2), and designed for placement between fuselage (2) and propeller (4). Device (15) contains first threaded element (21; 20) functionally connected to propeller (4) and adapted for vibration, when operated in parallel with first axis (B), second threaded element (20; 21) functionally connected to fuselage (4) and functionally connected to first threaded element (21; 20) so that, during the operation, to rotationally vibrate around first axis (B), and a set of threaded rollers (22), which are screwed on first and second threaded elements (21, 20; 20, 21). Rollers (22) can rotate around their corresponding second axes (C) in parallel and separately from first axis (B) relatively to first and second threaded elements (21, 20), rollers (22) can also rotate around first axis (B) relatively to first threaded element (21; 20) and second threaded element (20; 21).

EFFECT: compactness and accuracy of a device, and possibility of damping vibrations of a large amplitude are provided.

14 cl, 5 dwg

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority over European Patent Application No. 18186028.9, filed July 27, 2018, the entire content of which is hereby incorporated by reference.

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The present invention relates to a kit for a helicopter.

BACKGROUND OF THE INVENTION

It is known that helicopters contain a fuselage, a main rotor located on the upper part of the fuselage and rotating around its axis, and a tail rotor located at the end of the fuselage.

In more detail, the screw, in turn, contains:

- supporting body;

- a sleeve rotating about said axis and provided with a plurality of blades radially attached to and protruding from said sleeve; and

- a shaft that can be connected to the drive element and operatively connected to the sleeve to cause it to rotate.

The fuselage is usually connected to the propeller with a plurality of connecting rods and a torque parry plate; in other words, the fuselage is "suspended" on the supporting body.

During operation, the operation of the screw causes the creation of high-frequency and low-frequency vibrations. More specifically, the low frequency vibrations are generated by the wake that separates from the blades and from the center of the hub. This separation occurs at the center of the hub and affects the vertical and horizontal airfoils of the tail and tail rotor.

During operation, the rotation of the blades at high angular speeds leads to the occurrence of high-frequency vibrations, which are transmitted to the shaft and, consequently, to the fuselage, creating discomfort for those inside the fuselage.

It is known in the industry that vibration loads acting on a propeller have impulses equal to N*Ω and multiples of them in a single frame of reference with the fuselage, where Ω is the shaft rotation speed and N is the number of propeller blades.

In other words, the sleeve and the shaft transmit the impulses of the vibrational aerodynamic load acting in the plane of the blades to the aforementioned impulses.

Based on the foregoing, the industry clearly feels the need to limit the transmission from the shaft to the fuselage of vibrations with the above-mentioned values of impulses equal to N * Ω, and their multiple values.

For this purpose, passive and active damping devices are used.

Passive damping devices contain masses elastically suspended on a shaft or sleeve on springs. The vibration of these suspended masses makes it possible to at least partially absorb vibrations on the shaft and bushing.

The aforementioned damping devices convert the kinetic energy into the movement of the aforementioned masses on an elastic support and generate a damping force proportional to the elasticity of the spring and the displacement of the masses.

Active damping devices are actuators that apply a sinusoidal damping force to a bushing or shaft that counteracts the force generated by vibrations.

Damping devices that operate by absorbing vibration through a passive vibrating element require the use of mass and spring combinations in standard arrangements and have minimum overall dimensions that limit flexibility of use.

Active damping devices are expensive and difficult to manufacture.

Another recently developed solution is represented by the so-called "inertial" devices, known as "inertors".

These devices are located between the first and second points and exert a force on them proportional to the difference in acceleration between the first and second points, the purpose being the acceleration components along the line connecting the two points.

By timely calibration of the inertia values, it is possible to reduce or eliminate this vibration transmission force at a given frequency between the first and second points.

One of the first examples of such inertial type devices is described in EP-B-1402327 and contains:

- rod connected to the first point;

- a body connected to the second point, and the rod can slide relative to it; and

- a flywheel connected to the rod and rotating inside the housing as a result of the rod sliding due to vibrations at the first point.

US-A-2009/0108510 describes yet another inertia-type damping device.

It is known in the industry that there is a need for an inertial-type damping device that is easily integrated into known types of helicopters without changing the aerodynamic configuration of the helicopter.

The industry is also aware of the need for an inertial-type damping device that is particularly compact, particularly accurate, and capable of damping large amplitude vibrations.

The industry is also aware of the need for an inertial type damping device that is durable, has a high load capacity, and generates the lowest possible friction.

JP-A-S6078130 discloses a kit for the restrictive part of paragraphs 1 and 9.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a kit for a helicopter which will make it possible to satisfy at least one of the aforementioned needs in a simple and inexpensive manner.

The above object is realized by the present invention relating to the helicopter kit according to claim 1.

The present invention also relates to a helicopter kit according to claim 9.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, the following is a preferred embodiment solely as a non-limiting example and with reference to the accompanying drawings, in which:

- Fig.1 is a lateral perspective view of the main rotor of a helicopter with a kit in accordance with the present invention, with parts removed for clarity;

- figure 2 is a section on an enlarged scale along the axis II-II of figure 1 kit component with parts removed for clarity;

- figure 3 is a section on an enlarged scale along the line III-III of figure 2 kit component with parts removed for clarity;

- figure 4 is a section along the line IV-IV of figure 3; and

- Figure 5 is a very enlarged perspective view of a helicopter incorporating the kit of Figures 1-4.

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in figure 1, reference numeral 1 denotes kit for helicopter 2.

As shown in figure 5, the helicopter 2 includes a fuselage 3, the main rotor 4 located on the top of the fuselage 3 and rotating about the axis A, and the tail rotor located at one end of the fuselage 3 and rotating about its own axis transverse to the axis A .

In more detail, screw 4 is only shown in relation to:

- supporting body 5;

- a shaft 6 rotating about axis A, connected in a way not shown to a drive unit, for example, a turbine, mounted on a helicopter 1 and functionally connected to a hub (not shown) on which a plurality of blades (also not shown) are hinged.

The helicopter 2 also contains a plurality of rods 7 which extend along respective axes B, which are inclined to the axis A and have respective ends 8 and 9 opposite each other, respectively attached to the body 5 and to the top 10 of the fuselage 3.

The rods 7 are pivotally connected to the respective anchors 12 and 13, which are held by the upper part 10 and the body 5, respectively, about the respective axes D and E.

Set 1 contains a plurality of devices 15 for damping vibrations transmitted to the fuselage 3 by the propeller 4.

In the example shown, there are four devices 15 associated with respective rods 7.

As shown in figures 2-4, the devices 15 extend along the respective axes B, are hollow and accommodate the respective rods 7.

Since the devices 15 are identical, only one device 15 will be described below.

Preferably the device 15 comprises (FIGS. 2-4):

- nut 21 connected to screw 4 and adapted to vibrate parallel to axis B;

a screw 20 connected to the fuselage 3, operatively connected to the nut 21 to vibrate rotationally about the axis B; and

- a plurality of threaded rollers 22 which have threads 23 screwed onto the screw 20 and onto the nut 21, which can rotate about their respective axes C, parallel to and separate from the axis B, and can also rotate about the axis B relative to the screw 20 and the nut 21.

The device 15 thus implements an inertor, namely a device capable of applying force to the fuselage 3 and to the body 5 in proportion to the difference in acceleration between the fuselage 3 and the body 5.

This force allows you to dampen the vibrations that occur during the operation of the screw 4, and limit their transmission to the fuselage 3.

In more detail, device 15 comprises:

- tubular axial tip 30 attached to the body 5; and

- a tubular axial tip 31, axially opposite the tip 30 and attached to the upper part 10 of the fuselage 2.

The tips 30 and 31 are hinged on the respective anchors 12 and 13 about the respective axes D and E.

As a consequence, the tip 30 is subjected to an alternating movement of axial vibration parallel to axis B, which is caused by the vibration loads transmitted by the housing 5.

The device 15 also contains between the tips 30 and 31:

- a tubular body 32 attached to the tip 30 and containing in the part axially opposite the tip 30, the nut 21; as well as

- a tubular body 33 attached to the tip 31 and containing a screw 20 in the part axially opposite the tip 30.

In particular, the tubular body 32 contains, in turn, at their mutually opposite axial ends:

- a cup-shaped part 35 connected to the tip 30; and

- a cup-shaped part 36, having a larger diameter than part 35, and containing a nut 21.

In turn, the tubular body 33 contains:

- a cup-shaped part 37 connected to the tip 31; and

- a part 38, having a greater length than part 37, and a smaller diameter than part 37, and containing a screw 20.

Part 38 of tubular body 33 has a smaller diameter than part 36 of tubular body 32.

Part 38 of tubular body 33 is placed inside part 36 of tubular body 32.

Screw 20 and nut 21 have multiple threads.

Screw 20 and nut 21 are located radially opposite each other and radially spaced relative to axis B.

The rollers 22 are located in a position radially placed between the screw 20 and the nut 21 in a direction radial to the axis B.

The rollers 22 run along their respective axes C and each has an external thread 23.

Thread 23 is simultaneously screwed onto nut 21 and onto screw 20.

Rollers 22 run along respective axes C and are angled at equal distances from each other about axis B, and in the case shown there are nine.

Rollers 22:

- can rotate around C-axes with rotational motion; and

- can simultaneously rotate around axis B with rotational motion.

Preferably, the rollers 22 are movable together with the nut 21 in a direction parallel to axis B.

Preferably, the thread angle 23 on the rollers 22 is equal to the thread angle of the nut 21.

Due to the connection between the thread 23 and the screw 20, the movement of the rollers 22 along the axis B causes the tubular body 33 to rotate about the axis B.

Each 22 roller also contains:

- two mutually opposite axial ends 27 and 28; and

- two gear wheels 45 and 46 located next to the respective ends 27 and 28.

The threads 23 of the rollers 22 are single start threads.

It is important to emphasize that the angles of the threads 23 of the rollers 22, the screw 20 and the nut 21 shown in the accompanying figures are purely indicative.

The connection between the threads 23 of the rollers 22 and the screw 20 and the nut 21 is reversible.

The device 15 also contains a pair of crowns 47 and 48 respectively attached to the nut 21 and made integral with the nut 21.

Crowns 47 and 48 are coaxial with axis B and spaced apart along axis B.

Each crown 47 and 48 has an internal tooth 49 meshing with the respective gear wheels 45 and 46 of each roller 22.

Thus, the gears 45 and 46 are engaged with the tooth 49 (figure 4) when the rollers 22 rotate around the axis B.

The device 15 also contains two disk-shaped bearings 25 on axis B, spaced apart from each other along axis B and rotating relative to the nut 21 and the screw 20.

Each support 25 forms a plurality of nests 26 located at an angle at equal distances from each other around the axis B and connected by axial ends 27 of the corresponding rollers 22.

In the embodiment shown, there is a radial play between the supports 25 and the part 36.

In an alternative embodiment, between the supports 25 and part 26 with the nut 21 can be placed elements with a low coefficient of friction.

Device 15 also contains:

- a flywheel 40 rotating about the axis B and aligned in the angular direction with the screw 20; and

- two bearings 41, radially mounted between the part 37 of the tubular body 33 and the tip 31.

In the example shown, the flywheel 40 is located on a shoulder formed by parts 37 and 38 of the housing 33.

The flywheel 40 rotates together with the screw 20 due to the vibration of the tubular body 32 along axis B.

The flywheel 40 is sized to obtain the desired value for the rotating masses, equal to the sum of the masses of the rollers 22, the tubular body 32 and the flywheel 40. This value of the rotating masses tunes the device 15 to a predetermined value of the vibration frequency of the body 5, the transmission of which to the fuselage is to be weakened.

The bearings 41 allow the relative rotation of the tubular body 33 in relation to the tip 31 about the axis B and support the axial loads transmitted by the screw 20.

The ends 8 and 9 of the rod 7 are placed inside the tips 30 and 31, respectively.

Rod 7 extends from end 8 to end 9 along axis B, inside tip 30, tubular body 32, tubular body 33 and tip 31.

In particular, the diameter of the rod 7 is smaller than the inner diameter of the screw 23.

During operation, shaft 6 rotates the hub and blades around axis A.

The rotation of the hub and blades creates aerodynamic loads on the blades and subsequent vibrations, which are transmitted to the shaft 6.

The rods 7 connect the fuselage 3 with the body 5 of the propeller 4.

The principle of operation of the helicopter 2 is explained below with reference to one rod 7 and one device 15.

The operation of the screw 4 causes the appearance of vibration loads.

The pivoting of the tip 30 about the E axis prevents the nut 21 from rotating around the B axis.

Therefore, vibration loads cause alternate transient vibration of the tip 30, the tubular body 32 and the nut 21 parallel to axis B.

The alternating displacement of the nut 21 causes the coupling between the threads 23 of the rollers 22 and the nut 21 to alternately rotate the supports 25 about axis B and the rollers 22 about their respective axes C.

At the same time, the rollers 22 perform an alternating rotational movement about axis B because the respective gears 45 and 46 mesh with the teeth 49 of the respective crowns 47 and 48.

The rotation of the rollers 22 about their respective axes C, as a result of the engagement between the threads 23 of the rollers 22 and the nut 21, causes the screw 20, the tubular body 33 and the flywheel 40 to rotate alternately about the axis B.

The bearings 41 prevent this rotation from being transmitted to the fuselage 3 through the tip 31 and support the axial loads transmitted by the propeller 20.

The device 15 thus generates an inertial vibrational moment on the flywheel 40 resulting from the translational vibrational motion transmitted from the housing 5 to the tubular housing 32.

More specifically, this inertial vibrational moment is due to the alternate rotation of rollers 22, screw 20 and flywheel 40.

Due to the alternate rotation of the rollers 22, the tubular body 33, the screw 20 and the flywheel 40, the device 15 applies two equal forces at the points of contact of the tips 30 and 31 with the body 5 and the fuselage 3, respectively. These forces are opposite to each other and proportional to the relative acceleration between the aforementioned points of contact.

These torsional forces dampen the vibrations transmitted to the fuselage 3 as they tend to neutralize the vibrational forces transmitted by the rod 7, thereby improving the comfort of the passengers of the helicopter 2.

In other words, device 15 implements an inertor.

Based on the results of the consideration of kit 1 according to the present invention, the advantages that can be achieved by its implementation are obvious.

In particular, the kit 1 contains a plurality of damping devices 15 of the inertial type. Each of the devices 15 comprises a plurality of rollers 22 screwed onto a respective screw 20 and nut 21 and rotating about respective axes B and C as a result of axial vibrations transmitted from the body 5 to the tubular body 32 and to the nut 21.

Therefore, the device 15 is capable of converting the axial vibrations of the tubular body 32 into an alternate rotation of the rollers 22 about axes B and C and the screw 20 and flywheel 40 about their respective axes B.

This variable rotation creates a force acting on the anchors 12 and 13, which is proportional to the relative acceleration of the anchors 12 and 13.

This force restrains the transmission of vibrations to the anchor 13 and hence to the fuselage 3, improving the comfort of the passengers inside the helicopter 2.

Due to the presence of rollers 22 inserted between the respective screws 20 and nuts 21, the devices 15 of kit 1 have low friction, long life and durability in relation to the inertial devices of the known type described in the introductory part of this description.

In addition, the presence of rollers 22 inserted between the screws 20 and nuts 21 makes the devices 15 particularly compact and precise.

This makes the use of the helicopter 2 particularly advantageous.

Each device 15 contains a rod 7 and is pivotally connected to the corresponding anchors 12 and 13 relative to the same hinge axes D and E of the corresponding rod 7 with anchors 12 and 13.

Consequently, the devices 15 do not require any significant modification of the helicopter 1 and use the already installed anchors 12 and 13 to fasten the rods 7 between the body 5 and the upper part 10 of the fuselage 3.

In addition, this makes the kit 1 suitable for retrofitting existing helicopters 2 equipped with rods 7 in a particularly simple and inexpensive way.

To do this, it is enough to hang the device 15 on the already existing anchors 12 and 13 around the axes D and E.

The flywheel 40 makes it possible to adjust the force generated by the respective device 15 with respect to a specific vibration frequency value to be damped. In fact, it is sufficient to increase or decrease the moment of inertia of rotation of the flywheel 40 in order to change the frequency of the vibrations, which are mainly damped by the corresponding device 15.

The crowns 47 and 48 allow the rotation of the rollers 22 about the respective common axis B by engagement between the respective teeth 49 and the gears 45 and 46 of the rollers 22.

The support 25 of each device 1 holds the respective rollers 22 at an angle around axis B.

Finally, of course, in the kit 1 described and illustrated here, modifications and variations can be made without going beyond the scope defined by the claims.

In particular, the nut 21 can be connected to the fuselage 3 through the lug 31, and the screw 20 can be connected to the body 5 through the lug 30.

Moreover, in addition to rotating about axis B relative to screw 20, rollers 22 can also freely move axially relative to nut 21 parallel to axis B.

In addition, the devices 15 can be placed inside the respective rods 7 or connected to other appropriate structural elements located between the upper part 10 of the fuselage 3 and the body 5.

In addition, kit 1 can contain only one support 25 and only one crown 47 or 48.

Finally, the tubular bodies 32 and 33 of each device 15 can be directly attached to the corresponding rod 7.

Claims (42)

1. Vibration damping device for a helicopter (2) containing a fuselage (3) and a propeller (4), made with the possibility of damping vibrations transmitted from the specified propeller (4) to the specified fuselage (2), and for installation between the specified fuselage (2 ) and the specified screw (4); and the specified device (15), in turn, contains - the first threaded element (21; 20), functionally connected with the specified screw (4) and adapted for vibration during operation parallel to the first axis (B); - a second threaded element (20; 21) functionally connected to said fuselage (4) and functionally connected to said first threaded element (21; 20) in order to vibrate rotationally around said first axis (B) during operation; and - a plurality of threaded rollers (22) that are screwed onto said first and second threaded elements (21, 20; 20, 21); moreover, said rollers (22) can rotate about their respective second axes (C), parallel and separate from said first axis (B), relative to said second threaded element (20; 21); moreover, these rollers (22) can also rotate around the specified axis (B) relative to the specified first threaded element (21; 20) and the specified second threaded element (20; 21); characterized in that said second threaded element (20; 21) is a screw (20) screwed onto said rollers (22), and said first threaded element (21; 20) is a nut (21) screwed onto said rollers ( 22); wherein said nut (21) forms a second thread which is internal to said first axis (B) and is screwed onto said rollers (22); wherein said screw (20) forms a third thread which is external with respect to said first axis (B) and is screwed onto said rollers (22). 2. Vibration damping device according to claim 1, characterized in that said rollers (22) are movable together with said first threaded element (21; 20) in a direction parallel to said first axis (B). 3. Vibration damping device according to claim 1 or 2, characterized in that said device (15) is an inertor. 4. Vibration damping device according to any one of the preceding claims, characterized in that said rollers (22) and said first threaded element (21; 20) have the same thread angles; while these rollers (22) contain the first single thread (23); and the specified first threaded element and the second threaded element (21, 20; 20, 21) contain the second and third multiple threads, respectively. 5. Vibration damping device according to claim 4, characterized in that it contains - tubular axial tip (31) for fixing the specified second threaded element (20; 21) on the specified fuselage (2); and - bearing (41) located between said first threaded element (21; 20) and tubular axial tip (30) to ensure relative rotation of said second threaded element (20; 21) relative to said tubular axial tip (30) around said first axis (B). 6. Vibration damping device according to any one of the preceding claims, characterized in that it comprises a flywheel (40) rotating around said first axis (B) and operatively connected to said rollers (22) and said second threaded element (20; 21). 7. Vibration damping device according to claim 6, characterized in that said flywheel (40) is angularly aligned with said second threaded element (20; 21). 8. Vibration damping device according to any one of the preceding paragraphs, characterized in that it contains at least one crown (47) attached to the specified second threaded element (20; 21); wherein said crown (47) comprises a tooth (49) facing said first axle (B) and engaged by a plurality of gears (45, 46) located on respective rollers (22). 9. Vibration damping device for a helicopter (2) containing a fuselage (3) and a propeller (4), made with the possibility of damping vibrations transmitted from the specified propeller (4) to the specified fuselage (2), and for installation between the specified fuselage (2 ) and the specified screw (4); and the specified device (15), in turn, contains - the first threaded element (21; 20), functionally connected with the specified screw (4) and adapted for vibration during operation parallel to the first axis (B); - a second threaded element (20; 21) functionally connected to said fuselage (4) and functionally connected to said first threaded element (21; 20) in order to vibrate rotationally around said first axis (B) during operation; and - a plurality of threaded rollers (22) that are screwed onto said first and second threaded elements (21, 20; 20, 21); moreover, said rollers (22) can rotate about their respective second axes (C), parallel and separate from said first axis (B), relative to said second threaded element (20; 21); moreover, these rollers (22) can also rotate around the specified axis (B) relative to the specified first threaded element (21; 20) and the specified second threaded element (20; 21); characterized in that it contains at least one crown (47) attached to the specified second threaded element (20; 21); wherein said crown (47) comprises a tooth (49) facing said first axle (B) and engaged by a plurality of gears (45, 46) located on respective rollers (22). 10. Vibration damping device according to any one of the preceding claims, characterized in that it comprises a support (25) forming a plurality of sockets (26) engaged with said respective rollers (22) at a fixed angle; moreover, the specified support (25) is made with the possibility of angular movement around the specified first axis (B) relative to the specified first threaded element (21; 20) and the specified second threaded element (20; 21). 11. Helicopter containing - specified fuselage (2); - specified screw (4); - supporting body (5) of the specified screw (4); and - a plurality of rods (7) located between said fuselage (2) and said supporting body (5); characterized in that it contains for each said rod (7) a vibration damping device according to any one of the preceding paragraphs; wherein said damping device (15) is located between said body (5) and said fuselage (2). 12. Helicopter according to claim 11, characterized in that said first threaded element (21; 20) and said second threaded element (20; 21) are attached to the corresponding said rod (7). 13. The helicopter according to claim 11 or 12, characterized in that at least one specified rod (7) and the specified corresponding device (15) are hinged to the specified fuselage (2) around the third axes (D), coinciding with each other; moreover, the specified at least one rod (7) and the specified corresponding device (15) are pivotally connected with the specified screw (4) about the same corresponding fourth axes (E), coinciding with each other. 14. Helicopter according to any one of claims 11-13, characterized in that one of said rods (7) and said device (15) are placed inside another said rod (7) and said device (15).

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