KR820000274B1 - Helicopter rotor and transmission mounting and vibration isolation system - Google Patents

Abstract

The rotor(16) & the transmission(14) of a helicopter are mounted on the fuselage(12) by a vibration isolating assembly. The assembly includes a number of elastomeric counts(20,22) each of which incorporates alternate layers of elastomer and metal laminates. The mounts are subject to compression & are located about the axis of the rotor. Four mounts are used, the axes of the forward two intersecting on the roll axis, & the axes of the rearward two also intersecting on the roll axis but further back.

Description

Helicopter rotorcraft power support and vibration isolation system

1 is a perspective view of the suspension and vibration blocking system of the present invention for supporting a helicopter powertrain and a rotorcraft from the body of the helicopter.

2 is a schematic plan view of a helicopter illustrating the configuration of the suspension system.

3 is a schematic plan view of a helicopter showing another configuration of the suspension system.

4 is a cross-sectional view of one of the elastomeric members used in the suspension system.

5 is an illustration of a transmission and a rotorcraft suspension system in a roll mode.

6 is an illustration of a transmission and a rotorcraft suspension system in a pitch mode.

7 is a perspective view of a single elastomer stack of one of the elastomeric members, showing the placement direction providing pitch and roll shear stiffness.

8 is a graph showing engine drive shaft misalignment with respect to pitch focus repair.

9 is a graph showing the yaw line of the suspension system versus the roller focus repair of the suspension system for pitch focus repair of the selected system.

10 is a graph showing the K (shear force roll) of suspension versus system roll focal repair for the roll natural frequency Wn (roll) of the selected system.

FIG. 11 is a graph showing K (shear force pitch) versus pitch focal repair for the pitch natural frequency Wn (pitch) of a selected system.

TECHNICAL FIELD The present invention relates to the support of a helicopter rotorcraft and a transmission from a helicopter body, and in particular, comprising a plurality of elastomeric members selectively arranged, which provide rigidity to the system without any other aids. A vibration isolation support system having a selected stiffness that provides selected torque and lift suppression and separates blade passing frequency from helicopter's electric pitch and natural freguency of the roll.

Prior arts include helicopter powered support systems that focus pitch and roll axes, such as U.S. Patent Nos. 3,858,831, 3,163,378, 3,921,940, and 2,761,638, but these prior art systems require that they be suspended. In addition to the device, it is mechanically complex, heavy, and expensive because it requires an auxiliary device to achieve yaw suppression, pitch and roll stiffness, motion limiting means, and mechanical properties of the device.

The primary object of the present invention includes a plurality of elastomeric members that support, selectively disposed, concentrated and assembled from a gas, such that the members provide roll and pitch stiffness, torque suppression and lift suppression of the system, Another object is to provide a vibration isolating system for a helicopter rotorcraft transmission that is configured to form a natural frequency of the system that is sufficiently less than the blade passage frequency to reduce the gas's response to forces and moments imparted by the helicopter rotorcraft.

According to the invention, such a system is provided having a roll axis extending in the longitudinal direction of the helicopter and positioned above the base of the transmission and a pitch axis extending laterally of the body and located below the base of the transmission, whereby the elastic members suppress the yaw of the device. Are arranged and concentrated to provide.

According to another feature of the invention, the elastomeric member can be arranged and concentrated to provide different stiffness in directions orthogonal to the member, providing the pitch and roll stiffness of the required system.

It is another feature of the present invention to provide the aforementioned vibration isolation system in which the pitch axis is selected to provide low gas response and maximum rotor blade direct response to ensure effective operation of the rotor blade absorber.

Another feature of the invention is that the elastic member is arranged and concentrated as described above so that torque suppression of the system is achieved by elastic compression in the elastic member.

A very important feature of the present invention is to provide a vibration isolating system in which the elastic member provides yaw suppression of the system and no aid for yaw suppression is required.

Another feature of the present invention is to provide a system as described above, wherein the elastic member itself provides a stop member to limit excessive movement between the powertrain and the aircraft, resulting in severe steering.

Another feature of the present invention is to provide a system as described above, wherein the elastic member eliminates metal-to-metal contact between the transmission and the aircraft surface and thereby reduces transmission of high frequency acoustic vibrations between them and thus reduces aircraft interior noise. It is.

Another feature of the present invention is to separate the pitch and roll modes of the helicopter transmission from the blade pass frequency to prevent resonance and thus to minimize gas response to forces and moments imparted to the helicopter by the rotorcraft. It is to provide a system as described above, wherein the pitch and roll axes of the device and the rigidity of the elastic member are selected such that the natural frequency of the suspension device is sufficiently lower than the blade passing frequency.

Another object of the invention is that the natural frequency of the system is determined by the position of the roll and pitch axis and the pitch and roll stiffness of the elastic member, and the torque suppression of the system is determined by the selected position of the pitch and roll axis and the compressive stiffness of the elastic member. It is to provide a system described above.

Another feature of the present invention is to provide a system as described above, wherein the elastomeric members are sufficiently preloaded to keep them compressed and untensioned over their entire operating range.

Another object of the present invention is that the flexible member used can be used to match the mechanical elements of the gas to minimize the response to the rotor poles, and the rotor blades in-plane acting to reduce the rotor blade funding. A suspension system is particularly suitable for use in conjunction with vibration absorbers.

The present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, a portion 10 of the helicopter includes a body 12, a main rotorcraft 14, and a main lift rotor 16. In FIG. In the conventional form, the transmission, ie gearbox 14, supports and drives the helicopter rotor blade 16 to rotate about the axis of rotation 18, such that the rotor blade 16 of any selected number of blades lifts and propels the helicopter 10. In addition, one or more rotary blade head vibration dampers 19 (preferably in the form of a bifilar described in US Pat. No. 3,181,815) are provided to damp the rotor blade plane vibrations. A typical engine (not shown) drives the transmission 14 to fulfill its rotor blade drive function. The transmission 14 and the rotor blade 16 are supported from the base 12 by a number of elastic members (hereinafter referred to as "flexmount"). Two of the flexible mounting members are shown as 20 and 22, the flexible mounting members only supporting the power transmission 14 and the rotor blade 16 from the helicopter body 12. Only two of such members are shown in FIG. 21, but as shown in FIGS. 2 and 3, the flexible mounting members are circumferentially disposed about the transmission 14, and as shown in FIG. 2. Likewise, four identical members 20, 22, 24 and 26 are in the form of a rectangle arranged in a rectangular corner and a rotation axis 18 is arranged in the center of the rectangle, or as shown in FIG. It will be apparent to those skilled in the art that the mounting members, denoted by 24 'and 26', can be arranged in trapezoidal corners and the axis of rotation 18 can be arranged in the center of the trapezoid. Flexible mounting members 20-26 constitute a support and vibration isolation system 27 for the main rotor blades and transmission.

Embodiments of this system are not limited to the structures of FIGS. 2 and 3, and the base can be well applied to a transmission that forms some geometric shape, and is not limited to four flexible mounting members, and also has a rotorcraft axis of rotation. The same may apply to the case where 18 is not centered. An advantage of the rectangular structure of FIG. 2 is the uniform distribution of shear and compression loads to the elastic member. The structure of the flexible mounting member is shown well in FIG. 4, one of which is shown in FIG. In the flexible mounting member 20, alternating laminations of elastic and metal are arranged between the transmission and the body, in particular a group of such alternating elastic and metal laminations is arranged between the transmission flange 28 and the plate member 30. . The plate member is supported from the base 12. The second strain of alternating redzium of the elastic body and the metal is arranged between the plate member 30 and the head 32 of the bolt member 34.

The bolt member passes through the hole 36 of the lamination and plate member 30 and screwes with the nut member 38 so that the laminations are sufficiently preloaded in order to remain compressed during operation and thereby avoid tension loads thereon. To be able. It will be appreciated by those skilled in the art that the preload and other methods of assembly may be used. Alternating stacks such as 40, 54, 42, 44, 60 and 48 and metal shims such as 52, 56, 58 and 62 provide load transfer paths to the body from the transmission and thus the metal between them. Avoiding contact of large metals prevents the transmission of high frequency vibrations through the flexible mounting member 20 from the transmission 14 to the body 12 and reduces the internal noise of the body. In the structure of the flexible mounting member 20, the axis 50 becomes the focal line of the member 20 as described below.

In FIG. 1, members 20, 22, 24 and 26 (only 20 and 22 are shown in FIG. 1), the focus line 50 of member 20 and the focus line 64 of member 24 intersect at point 65, while member 22 The focal line 66 of the member 26 and the focal line 68 intersect at point 70, concentrating so as to extend to the longitudinal axis of the helicopter 10 and form a system roll axis 72 located at the base of the transmission 14 or at least above and the members 20-26. It is important.

As can be seen in FIG. 1 the focal lines 50 and 66 of the flexible mounting members 20 and 22 are located on the left side of the transmission 14 and intersect at point 74 while the focal lines 64 and of the flexible mounting members 24 and 26 are intersected. 68 is located at the right side of the transmission 14 and intersects at a second point not shown in FIG. The second point cooperates with the intersection 74, so that the pitch of the system extends to the side of the helicopter 10 and is arranged side by side perpendicular to the roll axis 72 at one position below the base of the transmission 14 and below the mounting member 20-26. Form axis 76.

The concentration of such mounting members 20, 22, 24 and 26 forms the roller axis 72 and the pitch axis 74 of this system, and when these four flexible, mounting members are so arranged and concentrated, Provides suppression of the suspension system 27 without the need. It will be appreciated by those skilled in the art that the pitch axis 76 may be located above the transmission 14 and the lower axis 72 if desired.

This concentration concept is shown in more detail in FIGS. 5 and 6. 5 shows a transmission 14 represented by a roll mode from the rear, wherein the focal lines 50 and 64 of the mounting members 20 and 24 intersect the roll axis 72 respectively and are perpendicular to the focal line 50 of the mounting member 22. Shear line 78 is formed. Around that axis 72, a roll motion of the system takes place. Because of the high compressive force to shear stiffness ratio of the flexible mounting member, the elastic and metal stacks of the flexible mounting member 20 shown in FIG. 4 must deform parallel to the roll shear force line 78.

In FIG. 6, the transmission 14, shown as pitch mode, can be seen and the focal lines 50 and 66 of the mounting members 20 and 22 cross the pitch axis 76, respectively, so that all pitch movements of the suspension system 27 are centered on the axis 76. To form the pitch shear force line 80 of the member 20 perpendicular to the focal line 50 and to ensure that all elastic and metal laminates of the flexible mounting member 20 deform parallel to the pitch shear force line 80. In the pitch and roll modes and all their combined modes, the flexible mounting members 20-26 act as positive stop members of the transmission versus aerodynamic movement until the bolt 34 contacts the member 30 by lateral movement of the stack. This is because the bolt is operated to form the positive stop member.

The plane in which the elastic and metal stacks of the mounting member 20 are located should be parallel to the roll shear line 78 and the pitch shear line 80 to orient the stacks properly. The stacks of other mounting members 22, 24, 26 are similarly orientated appropriately to the roll shear and pitch shear lines formed by the roll and pitch modes of the transmission 14 about the roll and pitch axes 72 and 76.

One shear force stiffness of the flexible mounting member may need to be higher than the other shear force stiffness to match the natural frequency of the system. The shear shear lines 78 and the pitch shear lines 80 meet at orthogonal angles, so that there are two orthogonal different shear stiffnesses, one of the two shear forces stiffnesses nearly equal to the pitch shear force lines 80, and the other nearly parallel to the roll shear force lines 78 It allows the use of flexible mounting members oriented properly with respect to lines 50,64,66,68 to coincide. This is shown in detail in FIG. FIG. 7 passes through the roll shear force line 78 to impart a net load, and passes through the pitch shear force line 80 to impart a combined shear and compressive force load, thereby selectively stacking 40 and its flexible mounting member to be stronger at pitch than at the roll. An elastomeric stack 40 of any one of the oriented mounting members 20, 22, 24, 26 is shown.

The natural frequency of the transmission 14 is determined by the pitch and the position of the roll axes 76 and 72 and by the pitch and roll stiffness of the flexible mounting member 20-26. The torque suppression of the suspension system 27 is determined by the pitch and the roll axes 76 and 72 and by the compressive force stiffness of the flexible mounting member 20-26. The natural frequency of the transmission 14 is the blade passing frequency (blade number X rotor speed, ie for a rotor blade with four blades, which is lower than 4 / rotation, so that the blade passing frequency in-plane force and the moment the rotor gives the transmission It is an important point of the present invention that the roll and pitch axes of the suspension system and the flexible mounting member stiffness are selected so that vibrations from the gas to the body are blocked.The hardness of the elastic body used to assemble the elastomer stacks is also important. The shear force stiffness of and the hardness of the elastomer-laminated structure, ie the thickness of the elastomer and the thickness of the metal shims, determine the compressive force stiffness of the flexible mounting member.

The stiffness of the suspension system 27 and the manner in which the pitch and roll axes are determined in carrying out the spirit of the invention are described. Many compromises must be made in that manner to obtain the most desirable results for this suspension system. First, the natural frequency of the suspension system 27 should be selected so that a desirable result of separating the gas from the rotor blade stimulation can be obtained. It is assumed that the natural frequency Wn of the suspension system is selected as a multiple of the main rotor blade rotation speed.

In consideration of the roll or the pitch or both, the following equations can be expressed.

In other words,

Where Wn represents the system natural frequency at the roll or pitch, and K ₀ is the spring rate with respect to the pitch or roll focus. Equation (1) can be redefined as follows. In other words,

Where L is the distance from the flexible mounting member elastic body to the focal point, N is the number of flexible mounting members, M is the weight of the transmission and rotor, D is the distance from the focus to the center of the transmission. , I _o is the weight moment of inertia of the transmission relative to the center of the vibration system.

In Equation (2), Wn, I _o and M are constants and L and D are variables depending on the change of the focal axis of the system.

In equation (2), the following equation can be derived to find the answer of K (shear force).

In other words,

Equation (3) can be provided for K (shear force) at the roll and K (shear force) mode at the pitch.

The terms pitch water line and roll focus line are used in the following description, where the roll line line is where the roll axis of the suspension system passes through the axis of rotation of the rotor blade, and the pitch line line is also the suspension line. The pitch axis of the system passes through the extended axis of rotation of the rotor blades.

It can be seen from Eq. (3) that K (shear force) can be obtained using Eq. (3) by setting L and D at a given focus line.

In FIG. 8, it can be seen that the first of the four graphs is used as a tool for the selection of the roller and pitch axes and the selection of the rigidity of the suspension system.

In FIG. 8, the ordinate of the graph represents misalignment and pitch focus repair. The desired misalignment can be adjusted by selecting a predetermined pitch focus. The next factors to be selected are yaw stiffness and roll focus. Although it is desirable for this suspension system to have maximum unstable stiffness, i.e. suppression of unstable, the size of the flexible mounting member, the distance between the flexible mounting member and the transmission and the aircraft, the manner in which the flexible mounting member is attached to the transmission Tradeoffs should be made in the selection of yaw stiffness and roll focus to adapt to practical considerations such as loads on airframes, airframes and transmissions, vertical flexibility of the system, and so on.

In constructing the FIG. 9 graph, the selected pitch focus repair is used, and from the graph the yaw stiffness is a function of the compressive force stiffness of the flexible mounting member at various assumed roller repairs. It can be seen that the desired yaw stiffness is obtained with a predetermined pitch focus repair at two different roll focus repairs. The selected roller focus repair is consistent with the practical considerations mentioned above.

From the ninth road, select the roll focus repair, and in Fig. 10, create a graph representing the roll K (shear force) for the roll focus repair for the desired Wn to determine the required roll stiffness. Next, determine the required pitch shearing force from the eleventh degree which represents the K (shear force) of the pitch with respect to the pitch focus repair for the selected Wn pitch and represents the selected pitch focusing means.

Based on this data, the most suitable roll and pitch focus repairs for the suspension system 27 are selected, and these data are subtracted to form the pitch axis 76 and the roll axis 72, and the desired yaw stiffness and the special characteristics of the present invention. Pitch and roll focal lines are chosen to obtain optimal roll K and shear K for shear system considerations.

Another feature of this suspension system is that the pitch axis of the suspension system can be selected to provide low gas response to the rotor blade's power and maximum longitudinal response of the rotor blade head. This is done by keeping the pitch axis as far away as possible under the rotor blades, thus amplifying the small residual pitch response of the gas with the large in-plane response of the rotor blades required for effective operation of the rotor blade in-plane absorber. . By the pitch axis being located far below the transmission and the rotorcraft, the motion about that axis is generally in plane, thus increasing the effectiveness of the rotor blade in-plane vibration damper. Such effective rotor blade in-plane vibration dampers reduce the amplitude of vibrations transmitted from the rotor blades to the gas through the flexible mounting member 20-26.

It is to be understood that the present invention is not limited in the details and structures shown and described, and which is adapted for modification by those skilled in the art.

Claims (1)

In a support and vibration isolating system of a rotorcraft rotorcraft of a helicopter comprising a plurality of mounting members connected to a body and supporting the power unit from the body, wherein the mounting member comprises an elastic layer and a metal layer. Laminated and alternately arranged concentrically on the axis so as to be oriented perpendicular to the axis of the mounting member are constructed by overlapping arrangement in a compressed state between the base and the transmission, wherein each mounting member is a roll and pitch in each elastic laminate Forming a focal line coincident with the axis of the mounting member such that the shear force lines are perpendicular to the focal line, and wherein the focal line of each mounting member extends in the longitudinal direction of the body and is displaced vertically on one side of the mounting member The roll axis of the system, and transverse to the body and displaced perpendicularly from the roll axis at the other side of the mounting member. Intersect the corresponding focal line of the other mounting member to form a pitch axis of the mounting system, and the rolls and pitch axes are arranged from the mounting member by a selected interval to provide a unique transmission torque suppression means. Helicopter rotorcraft transmission support and vibration isolation system.

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