FR3072719A1 - CONTROL RING OF A VARIABLE SHIFT AUBRA STAGE FOR A TURBOMACHINE - Google Patents

Abstract

Ring (36) for controlling a variable-pitch blade stage for a turbomachine, comprising an annular body having an axis of revolution, and means configured to cooperate with the casing in order to center and guide said body, said third means comprising at least one bearing pad (44) on said casing, this pad being carried by an adjustment screw (46) which passes through a substantially radial housing (48) of said body, characterized in that said adjusting screw comprises one end radially internal having a symmetry of revolution about the axis (A) of the screw and having a generally inverted T-shaped section, which is engaged in a recess (62) of complementary shape of said pad or an element (54). ) of support of said pad, by displacement in a direction substantially parallel to said axis of revolution, said pad or said member comprising at least one flat (64) substantially parallel to a plane perpendicular to said axis of re evolution and cooperating by abutment with a wall (66) of said housing for the rotational locking of said pad or member around the axis of the screw.

Description

TECHNICAL AREA

The present invention relates in particular to a control ring for a stage of blades with variable setting for a turbomachine.

STATE OF THE ART

A stage of this type includes an annular row of stator vanes with variable setting (also called VSV - acronym of Variable Stator Varies) which are carried by an external annular casing, generally of a compressor of the turbomachine. Each blade comprises a blade which is connected at its radially outer end by a plate with a substantially circular outline to a radial cylindrical pivot which defines the axis of rotation of the blade and which is guided in rotation in a corresponding orifice of the outer casing. The radially inner end of the blade of each blade generally comprises a second cylindrical pivot extending along the axis of rotation of the blade and guided in rotation in an orifice of an internal casing of the compressor.

In the present application, the terms "radial", "radially", "axial", etc., refer to the longitudinal or revolution axis of the ring or of its annular body.

The radially outer end of the outer pivot of each blade is connected by a connecting rod to a control ring displaced in rotation around the outer casing by actuating means with a jack or the like. The rotation of the control ring is transmitted by the rods to the external pivots of the blades and makes them rotate around their axes.

The angular setting of the stator vanes in a turbomachine is intended to adapt the geometry of the compressor to its operating point and in particular to optimize the efficiency and the pumping margin of this turbomachine and to reduce its fuel consumption in the different flight configurations. .

Each of these blades is rotatable around its axis between a first "open" or "full open" position in which each blade extends substantially parallel to the longitudinal axis of the turbomachine, and a second "closed" or "almost closed" position in which the blades are inclined relative to the axis of the turbomachine and thus reduce the cross-section of air passage through the stage of blades.

The control ring must be centered and guided in rotation around its axis of rotation. In the current technique, the ring is equipped with projecting pads on which the outer periphery of the casing can come to cooperate by friction.

It is important to have radial cold clearances between the casing and the shoes of the ring, in order to allow thermal expansions of all the parts and to allow a good functioning of the kinematics of the setting of the blades in all engine configurations without system lockup.

The present invention provides an improvement to this technology.

STATEMENT OF THE INVENTION

The invention provides a control ring for a stage of variable-pitch blades for a turbomachine, comprising an annular body, first means configured to be connected to pivots of said blades, second means configured to be connected to means actuation for the rotation of said body around a casing of the turbomachine, and third means configured to cooperate with the casing in order to center and guide said body, this pad being carried by an adjustment screw which passes through a housing substantially radial of said body, characterized in that said adjusting screw comprises a radially internal end having a symmetry of revolution about the axis of the screw and having in section a general shape in inverted T, which is engaged in a recess of shape complementary to said pad or to a support member for said pad, by displacement in a direction substantially parallel to said axis of revolution, said pad or said member comprising at least one flat substantially parallel to a plane perpendicular to said axis of revolution and cooperating by abutment with a wall of said housing for the purpose of blocking the rotation of said pad or member around the axis of the screw.

According to the invention, the radially internal end of the nut has a symmetry of revolution and does not limit the rotation of the screw in the housing of the body. The cooperation of this end with the pad or its support member makes it possible to retain the pad vis-à-vis the screw, in a direction parallel to the axis of the screw. Furthermore, the skate, directly or through the body, is prevented from rotating around the axis of the screw by cooperation of the flat part (s) with the walls of the body of the ring. These flats are oriented so as to limit the size of the pad or its support member, as well as that of the body whose walls are intended to cooperate with this or these flats. The closer these body walls are to each other, the more the width or axial dimension of the body can be reduced.

The ring according to the invention may include one or more of the following characteristics, taken in isolation from one another or in comparison with each other:

- Said pad or said member comprises two flats parallel to a plane perpendicular to said axis of revolution and cooperating by abutment with side walls of said housing;

- Said flats are located at a distance substantially equal to the external diameter of the screw;

- Said screw comprises a radially external end for screwing a nut intended to bear on said body;

- said pad or said member comprises two hooks substantially in inverted L defining therebetween said recess

- The side walls of the housing are defined, at a radially internal part of the latter, by an annular channel arranged in the body of the ring, the housing further comprising a radially external substantially cylindrical part traversed by the adjusting screw and emerging in said channel.

The present invention also relates to a stage of variable setting vanes for a turbomachine, comprising an annular row of variable setting vanes each comprising a blade and a cylindrical pivot at its radially outer end, the stage further comprising an annular casing comprising mounting holes for the pivots of the blades, characterized in that said pivots are connected to a ring as described above.

The present invention also relates to a turbomachine, characterized in that it comprises at least one ring or at least one stage as described above.

DESCRIPTION OF THE FIGURES

The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the accompanying drawings in which:

- Figure 1 is a partial schematic half-view in axial section of stages of blades with variable setting of a turbomachine, according to the prior art;

- Figure 2 is a schematic perspective view of an adjustment screw and a support member of a shoe for a control ring according to the invention;

- Figure 3 is a schematic view of the ring according to the invention, partially shown and equipped with the member of Figure 2; and

- Figure 4 is a schematic view of the ring according to the invention, partially shown and fitted to the member and the adjustment screw of Figure 2.

DETAILED DESCRIPTION

In Figure 1, there is shown schematically, in axial section, a portion of a high-pressure compressor 10 of a turbomachine, in particular of an aircraft turbojet, with several stages, each stage comprising an annular row of movable blades 12 carried by the rotor (not shown) of the turbomachine and an annular row of fixed blades 14 forming rectifiers carried by a casing 16 of the stator of the turbomachine, the angular orientation of the blades 14 being adjustable to optimize the flow gas in compressor 10.

Each blade 14 comprises a blade 18 and a radially external cylindrical pivot 20, connected by an annular "plate" 22 extending perpendicular to the axis 24 of the blade in a corresponding housing 26 of the housing 16. The radially internal surface 28 of the plate is aligned with the internal wall 30 of the casing so as not to oppose the gas flow.

The cylindrical pivot 20 of each blade 14 extends inside a radial cylindrical chimney 32 of the casing 16 and its radially outer end is connected by a connecting rod 34 to a control ring 36 which surrounds the casing 16 and which is associated with actuating means (not shown) making it possible to rotate it in one direction or the other around the longitudinal axis of the casing 16 to drive the blades 14 of an annular row in rotation around their axes 24 .

Each ring 36 comprises radial orifices 40 in which are housed cylindrical pins 42 carried by the links 34. Each pin 42 is generally centered and guided in rotation in an orifice 40 by at least one bushing bearing mounted in the orifice 40 .

The body of the ring 36 further comprises means for connecting to an actuator, which may for example comprise a yoke carrying an axis on which is articulated one end of a piston rod of an actuator, when the latter is a cylinder for example.

The blades 14 can be moved in rotation around their axes 24 between a closed or almost closed position and an open or fully open position.

In the closed position, the blades 18 of the blades are inclined relative to the longitudinal axis of the turbomachine and define between them a minimum section of air passage in the stream. The blades 14 are brought into this position when the turbomachine is at low speed or at idle, the air flow flowing in the compressor then having a minimum value.

In the open position, the blades 18 of the blades extend substantially parallel to the axis of the turbomachine so that the air passage section between the blades is maximum. The blades 14 are brought into this position when the turbomachine is at full gas speed, the air flow flowing in the compressor then having a maximum value.

In the prior art, the casing 16 comprises at its outer periphery tracks 38 projecting from centering and guiding the rings 36, which are here schematically represented by dotted lines. Each ring 36 surrounds its guide track (s) 38. The reference J designates the radial clearances which are provided when cold between a ring 36 and its track (s) 38. These clearances J must be large enough to allow thermal expansion of the casing 16 but do not allow precise adjustment of the angular positions of the blades 14.

The invention provides an improvement to this technology which in particular makes it possible to precisely adjust the radial clearances between the ring 36 and the casing 16 by means of a ring more compact than those of the prior art.

Figures 2 to 4 show an embodiment of the invention in which the elements already described in the above are referenced by the same numbers.

The control ring 36 here comprises an annular body, which can be sectorized and formed by at least two sectors arranged circumferentially end to end and linked to each other.

As described in the foregoing, the body of the ring 36 may include radial orifices in which are housed cylindrical pins carried by the rods. The body of the ring 36 further comprises means for connecting to an actuator, which may for example comprise a yoke carrying an axis on which is articulated one end of a piston rod of an actuator, when the latter is a cylinder for example.

The ring 36 comprises at least one pad 44 for bearing on the casing 16, which is fixed to a radially internal end of an adjustment screw 46, directly or via a support member 54 as in the example shown.

The adjusting screw 46 comprises an external thread and is screwed into a housing 48 which is substantially radial from the body of the ring 36. In the mounting position shown in FIG. 4, the radially external end of the screw 46 projects from the body of the ring 36 and receives a radial immobilization nut of the screw 46. This nut is screwed from the outside onto the screw 46 and bears radially on the body of the ring 36 to radially immobilize the screw 46 vis- with respect to this body.

The radially internal end of the screw 46 comprises an external annular groove 52 and has, in cross section, a general shape in inverted T.

The housing 48 of the body of the ring 36 comprises a radially external part 48a which is substantially cylindrical and a radially internal part 48b of general shape delimiting at least one parallelepipedal space. The radially external part 48a comprises an internal thread for screwing the screw 46 and the radially internal part receives the support member 54 for the shoe 44.

The shoe 44 here has a generally substantially cylindrical shape whose axis of revolution is oriented substantially radially and aligned with the axis of the screw 46.

The member 54 can be crimped onto the shoe 44. It comprises a recess of complementary shape at the radially internal end of the screw 46 and intended to receive this screw, by displacement of the screw in a direction substantially perpendicular to its axis A and parallel to the axis of revolution of the ring (see arrow F).

The member 54 comprises a circular base 56 which is connected to two lateral hooks 58, 60 defining between them a recess 62 for receiving the T-end of the screw 46. The hooks 58, 60 each have a general L-shape inverted, and comprise two branches 58a, 60a parallel to each other connecting to the base 56, and two branches 58b, 60b oriented towards one another and therefore the free ends are intended to be engaged in the groove 52 of the T-end of the screw.

The member 54 comprises between two flats 64 parallel to a plane perpendicular to the axis of revolution of the ring. These flats 64 extend at least in part on the sides of the flanges 58, 60. They are located at a distance D1 from one another, which is substantially equal to the external diameter D2 of the screw.

The radially internal part of the housing 48 of the control ring 36, in which the member 54 is received, here comprises two parallel side walls 66, which extend in planes perpendicular to the axis of revolution of said ring, and which are intended to cooperate by abutment with the flats 64 opposite the member 54. This cooperation makes it possible to immobilize in rotation the member 54 about the axis A of the screw 46. Thus, the screwing of the screw 46 in the housing 48 causes a radial displacement of the member 54 and the shoe 44 without causing rotation of these parts. The walls 66 of the housing are located at a distance E1 substantially equal to the diameter E2 of the radially external part of the housing 48. Advantageously, to facilitate machining making it possible to determine the parallelepipedal space, the walls 66 of the housing, at its radially part internal, are for example defined by an annular channel arranged in the body of the ring. In this channel opens the radially external part 48a substantially cylindrical of each housing.

At rest of the turbomachine and when cold, the radial positions of the pads 44 can be adjusted radially to provide radial clearances J between these pads and the casing 16. In operation, the casing 16 can expand and these clearances J can cancel each other out . Depending on the angular setting of the blades 14, the control ring 36 has a rotational and translational movement around the casing 16. This movement is not called into question by the support and the sliding of the pad (s) on the outer surface of the housing 16.

Claims (8)

1. Ring (36) for controlling a stage of blades (14) with variable setting for a turbomachine, comprising an annular body having an axis of revolution, first means (40) configured to be connected to pivots (20 ) said blades, second means configured to be connected to actuation means for the rotation of said body around a casing (16) of the turbomachine, and third means configured to cooperate with the casing in order to center and guiding said body, said third means comprising at least one pad (44) for bearing on said casing, this pad being carried by an adjustment screw (46) which passes through a housing (48) substantially radial of said body, characterized in that said adjusting screw comprises a radially internal end having a symmetry of revolution about the axis (A) of the screw and having in section a general shape in inverted T, which is engaged in a recess (62) of complex shape ntaire of said pad or of a member (54) for supporting said pad, by displacement in a direction substantially parallel to said axis of revolution, said pad or said member comprising at least one flat (64) substantially parallel to a plane perpendicular to said axis of revolution and cooperating by abutment with a wall (66) of said housing for locking in rotation of said shoe or member about the axis of the screw. 2. control ring (36) according to claim 1, wherein said shoe (44) or said member (54) has two flats (64) parallel to a plane perpendicular to said axis of revolution and cooperating by abutment with side walls ( 66) of said housing. 3. Control ring (36) according to the preceding claim, wherein said flats (64) are located at a distance (D1) substantially equal to the external diameter (D2) of the screw (46). 4. control ring (36) according to claim 2 or 3, in which the side walls (66) of the housing are defined, at a radially internal part of the latter, by an annular channel arranged in the body of the ring, the housing further comprising a radially outer portion (48a) substantially cylindrical through which the adjusting screw (46) and opening into said channel. 5. Control ring (36) according to one of the preceding claims, wherein said screw (46) comprises a radially outer end for screwing a nut intended to bear on said body. 6. Control ring (36) according to one of the preceding claims, in which said shoe (44) or said member (54) comprises two hooks (58, 60) substantially in L-shape inverted defining between them said recess (62). 7. Stage of variable-pitch vanes for a turbomachine, comprising an annular row of variable-pitch vanes (14) each comprising a blade (18) and a cylindrical pivot (20) at its radially outer end, the stage comprising furthermore an annular casing (16) comprising mounting holes for the pivots of the blades, characterized in that said pivots are connected to a control ring (36) according to one of the preceding claims. 8. Turbomachine, in particular of an aircraft, characterized in that it comprises at least one control ring (36) according to one of claims 1 to 6 or at least one stage of variable pitch vanes according to claim 7 .