EP0765992A1 - Actuating system for variable stator vanes - Google Patents

Abstract

The mechanism consists of blades (3) connected by levers (9) to control rings (10) which are pivoted to cams (15), each turning about a first fixed axis (17). Each cam is linked to a control lever (21) which rotates about a second fixed axis (26) lying parallel to the first one by means of an arm (22). The arm is pivoted to the cam and control lever at points which are separate from the two fixed axes. The cams (15a, 15b, 15c) which are connected to other control rings (10) are linked to a synchronising bar (20) at points identical to that of the first cam (15).

Description

The invention relates to a device for controlling a stage of pivoting or variable-pitch blades.

We meet such blades on the stators of certain aircraft engines: depending on the engine speed, we feel the need to more or less straighten the flow of gas passing through these stages of blades, which we therefore rotate around their axis under the action of a control mechanism located on the other side of the stator.

The pivots of the blades, which pass through the stator, are joined to control levers all connected to a control ring which surrounds the stator and which a control mechanism rotates.

There are many kinds of control mechanisms, which involve the use of an actuating member such as a jack and a transmission mechanism composed of levers, connecting rods, etc. The characteristics of these transmissions are quite varied and some allow non-linear control of the blades, that is to say that the rotation of the latter is not proportional to the movement of the actuator. The invention belongs to this kind of control devices and its essential advantage is that the transmission is particularly simple.

In the most general form, the invention relates to a device for controlling a stage of variable-pitch vanes provided with levers joined to a control ring, the control ring being articulated to a cam pivoting around a first fixed axis, characterized in that the cam is joined to a control crank rotating around a second fixed axis parallel to the first axis by a link articulated to the cam and to the rotating crank at points distinct from the fixed axes.

The control device can moreover relate to several stages of blades and several control rings at the same time. To apply the invention, it is then possible to have other articulated cams by pivoting around other first fixed axes to other control rings of other stages of blades with variable setting, the cams being interconnected by a synchronization bar articulated to the cams at identical positions relative to the first fixed axes. Or, in a different design, there are other cams articulated by pivoting around other first axes fixed to other control rings of other stages of blades with variable setting, the other cams being interconnected and to the rotating crank by a synchronization bar articulated to the other cams and to the crank in identical positions with respect to the other first fixed axes and to the second fixed axis.

• la figure 1 représente une vue générale d'implantation de l'invention,
• les figures 2 et 3 représentent une première réalisation de l'invention, et
• la figure 4 représente une autre réalisation de l'invention.

The invention will now be described in more detail with the aid of the following figures, which are annexed by way of illustration and not limitation:

• FIG. 1 represents a general view of the implantation of the invention,
• FIGS. 2 and 3 represent a first embodiment of the invention, and
• Figure 4 shows another embodiment of the invention.

FIG. 1 represents the inlet of a turbomachine with in particular a low pressure compressor section 1 and a high pressure compressor section 2. It is on this that the invention is established. Each of the compressors is above all composed of stages of fixed vanes 3 and movable vanes 4 which alternate, some attached to a stator 5 which surrounds the annular vein 6 of gas circulation and the others fixed to a rotor 7 delimiting vein 6, and turning with it.

The fixed blades 3 can actually pivot around a pivot 8 passing through the stator 5. The pivot 8 of each of the blades 3 is terminated by a lever 9. The levers 9 of each of the blade stages are united to a ring of command 10 common.

It can be seen in FIGS. 2 and 3 that the meeting of the levers 9 of a stage with the associated control ring 10 is made by articulations 11 which hold the control ring 10 while nevertheless allowing it to turn on itself . This can be accomplished by providing the control ring with a transmission rod 12, one end 13 of which is articulated to it, so as to allow angular displacements of the transmission rod 12, and the other end of which is articulated. to a cam 15 in the form of a bent lever and more precisely at the end of one of the arms 16 of this bent lever.

A pin 17 fixed on the stator is established at the elbow of the cam 15 to allow it to rotate, and its other arm 18 extends opposite the transmission rod 12 and carries at its end another articulation 19 intended to support a synchronization bar 20 perpendicular to the control ring 10, that is to say arranged in the axial direction of the machine. The synchronization bar 20 is similarly articulated to other cams 15 assigned to the control of other stages of fixed blades 3 by transmissions similar to that just described and which notably include a control ring 10 for each of the floors. The only difference is that the other cams, noted 15a, 15b, 15c, etc., have arms 16a, 16b or 16c, etc. articulated to the transmission rods 12 of different lengths ℓ, ℓa, ℓb, ℓc, etc. This will make it possible, as will be clearly seen shortly, to control the stages of fixed blades 3 differently, that is to say to impose different rotations on them. But the second arms 18 are all the same length and are parallel, so that the synchronization bar 20 is articulated to the cams 15, 15a, 15b, 15c, etc., at an identical position with the fixed axes 17, 17a, 17b, 17c, etc.

The control mechanism, unlike a solution previously adopted by the applicant, does not consist of a lever fixed to the fixed axis 17 of the cam 15 considered first, and the purpose of which is to rotate the latter to pull or push on the control rods 12 via all the cams 15 and the synchronization bar 20. Instead, there is a crank 21 rotating around a second fixed axis 26 parallel to the first fixed axes 17, 17a, 17b, 17c, etc., and a connecting rod 22 whose ends are articulated, for the first 23 at the end of the crank 21, and for the second 24 to a part of the second arm 18 distant from the fixed axis 17.

où t est une racine de l'équation t²(Z-K)+2tT-Z-K=0, avec T=[R₂sin(α₀-α)-x], E=[-R₂cos(α₀-α) +y] et $$\text{K =}\frac{{\text{L}}^{\text{2}}\text{-}\left({\text{T}}^{\text{2}}{\text{+ Z}}^{\text{2}}{\text{+ R}}_{\text{1}}^{\text{2}}\right)}{{\text{2R}}_{\text{1}}}\text{;}$$

x et y étant les mesures de la distance entre l'axe fixe 26 et l'axe fixe 17, projetée sur les axes parallèles respectivement à la barre de synchronisation 20 et aux anneaux de commande 10 une fois projetés dans le plan des figures 2 et 3.The laws controlling the angle β of rotation of the blades 3 as a function of the angle α of rotation of the crank 21 essentially depend on the length L of the connecting rod 22 between the joints 23 and 24 and of radii R ₁ and R ₂ measured on the cams 15 between the fixed axis 17 and the joints 14 and 24. Finally, with this mechanism we obtain the crank 21, the connecting rod 22, the cams 15, 15a, 15b, 15c, etc., the bar synchronization 20 and the control rods 12 extend substantially in a perpendicular plane fixed axes 17, 17a, 17b, 17c, etc. and 26, the following formula from angular positions of origin α ₀ and β ₀ : $$\frac{{\text{β + β}}_{\text{0}}}{\text{2}}\text{= Arc tg t,}$$

where t is a root of the equation t ² (ZK) + 2tT-ZK = 0, with T = [R ₂ sin (α ₀ -α) -x], E = [- R ₂ cos (α ₀ -α ) + y] and $$\text{K =}\frac{{\text{L}}^{\text{2}}\text{-}\left({\text{<figure-callout id="2" label="T" filenames="imgf0001.png" state="{{state}}">T</figure-callout>}}^{\text{2}}{\text{+ <figure-callout id="2" label="Z" filenames="imgf0001.png" state="{{state}}">Z</figure-callout>}}^{\text{2}}{\text{+ R}}_{\text{1}}^{\text{2}}\right)}{{\text{2R}}_{\text{1}}}\text{;}$$

x and y being the measurements of the distance between the fixed axis 26 and the fixed axis 17, projected onto the axes parallel respectively to the synchronization bar 20 and to the control rings 10 once projected in the plane of FIGS. 2 and 3.

The angle β is therefore a sinusoidal function of the angle α.

The crank 21 can be turned by the rod 27 of a jack 28 articulated at a fixed point 29, according to a usual design.

The angles β of rotation imposed on the levers 9 and on the blades 3 are different for the various stages, and more precisely, they are proportional to the lengths ℓ, ℓa, ℓb, ℓc, etc., of the arms 16 between the fixed axis 17 and the articulation 14 of the transmission rod 12, that is to say that the laws of rotation are all sinusoidal.

In the design of FIG. 4, one of the stages of fixed blades 3, the one on the left in the figure, is likewise displaced according to a non-linear law, but the others obey a proportional law with the displacements of the actuator . With the notations of FIGS. 2 and 3, there is the synchronization bar 20 to which the cams 15b, 15c are articulated, etc. The modifications relate to the cams 15 and 15a: the cam 15, now denoted 115, is not connected to the synchronization bar 20 and its second arm 18 is replaced by an arm 118 of another shape intended to receive a joint 123 uniting it at one end of a connecting rod 122 similar or similar to the connecting rod 22 and the other end of which is joined by a joint 124 to a protrusion 125 formed on a cam 115a moreover similar to the cam 15a and situated in the same place. Another difference consists in that the fixed axis 117a of articulation of the cam 115a is not an inert axis but a control axis dependent on the actuator member. In a word, the crank 21 of the previous embodiment is eliminated and the cam 115a is a motor lever.

Claims (3)

Control device for a stage of vanes (3) with variable setting provided with levers (9) joined to a control ring (10), the control ring (10) being articulated to a cam (15, 115) pivoting around a first fixed axis (17), characterized in that the cam (15, 115) is joined to a control crank (21, 115a) rotating around a second fixed axis (26, 117a) parallel to the first fixed axis (17) by a link (22, 122) articulated to the cam and to the rotating crank at points distinct from the fixed axes. Control device according to claim 1, characterized in that it comprises other cams (15a, 15b, 15c, ...) articulated by pivoting around other first fixed axes (17a, 17b, 17c, ... ) to other control rings (10) of other stages of blades (3) with variable setting, the cams being connected together by a synchronization bar (20) articulated to the cams in identical positions relative to the first fixed axes. Control device according to claim 1, characterized in that it comprises other cams (15b, 15c, ...) articulated by pivoting around other first fixed axes (17b, 17c, ...) at d ' other control rings of other stages of variable-pitch blades, the other cams being connected to each other and to the rotating crank (115a) by a synchronization bar (20) articulated to the other cams and to the rotating crank at positions identical with respect to the other first fixed axes and to the second fixed axis (117a).

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