A VARIABLE-PITCHING TURBINE ENGINE STAGE

Abstract

The present invention relates to a stage (1) of variable pitch blades (2) comprising: - a row of blades (2), - a housing having an axis of revolution (X), and - a control ring (5) for the pitch control of the blades (2), comprising: - a body (50) which extends around the housing, - first connecting members of the body (50) to cylindrical pivots (22) of said blades (2), - a second connecting member (70) of the body (50) to an actuator (7) carried by the housing, and - third guiding members (8) of the body (50) around and at a distance from the housing, in which said third members (8) comprise levers (80) which each have a first end (80a) articulated on the housing about a radial axis (R80a) with respect to the axis (X), and a second end (80b) connected to the body (50). Figure for the summary: Figure 7

Description

Title of the invention: A VARIABLE PITCH BATTERY STAGE FOR A TURBOMACHINE technical field

[0001] The present invention relates to a variable pitch blade stage for a turbine, in particular for an aircraft. Technical background

[0002] A stage of variable-pitch stator blades for a turbomachine, particularly an aircraft turbomachine, comprises an annular array of variable-pitch stator blades (also called VSVs – an acronym for "Variable Stator Varies") which are mounted on an external annular housing, generally that of a turbomachine compressor. Each blade comprises a blade connected at its outer radial end by a plate with a substantially circular contour to a radial cylindrical pivot. This cylindrical pivot defines the axis of rotation of the blade and is guided in rotation within a corresponding orifice in the external housing. The inner radial end of each blade generally comprises a second cylindrical pivot. This second cylindrical pivot extends along the axis of rotation of the blade and is guided in rotation within an orifice in an internal housing of the compressor.

[0003] The radially external end of the cylindrical pivot of each blade is connected by a connecting rod (or lever) to a control ring that is rotated around the annular housing by actuators (such as jack-type or similar actuation means). The rotation of the control ring is transmitted by the connecting rods to the cylindrical pivots of the blades and causes them to rotate around their axes.

[0004] The angular pitching of the VSV blades 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.

[0005] Each of these blades is movable in rotation around its axis between a first "open" or "fully open" position in which each blade extends substantially parallel to the longitudinal axis of the turbomachine, and a second "closed" or "quasi-closed" position in which the blades are inclined with respect to the axis of the turbomachine and thus reduce the cross-section of the air passage through the blade stage.

[0006] The control ring must be centered and guided in rotation about its axis of rotation. In the current technique, the annular housing includes tracks on which the inner periphery of the control ring can cooperate by Friction. In particular, the control ring includes guiding elements, such as pads, on the tracks of the annular housing. These pads serve, firstly, to ensure the concentricity of the control ring around the annular housing by adjusting the clearance between the pads and the tracks, and secondly, to limit the deformation of the control ring caused by the aerodynamic forces on the variable-pitch blades acting on the kinematics during operation. It is indeed important to have radial clearances, known as cold clearances, between the pads and the tracks to allow for thermal expansion of the annular housing and ensure proper timing kinematics in all engine configurations. These radial clearances between the pads and the tracks can depend on the initial setting during assembly of the control ring and on the thermal conditions.Therefore, the quality of the guidance of the control ring by these guide elements can depend on the radial clearance between these pads and the tracks of the annular housing. Thus, this radial clearance (or in other words, the mounting clearance) between the pads and the tracks can be designed to optimize the clearance under the pads under thermal operating conditions (i.e., when hot), and to prevent the control ring from deforming, particularly under compression on the annular housing, for example, during the acceleration phases of the operating turbomachine.

[0007] It is known in the prior art to use mounting shims to adjust the radial clearance between the pads and the tracks. These shims have the necessary thickness to achieve the ideal theoretical radial clearance JT ([Fig. 1a]) to allow the two aforementioned functions, namely, optimizing the clearance under the pads 81 and preventing deformation of the control ring 5. However, if the radial clearance adjusted by the shims is too large, or in other words, an "open" radial clearance Jo ([Fig. 1b]), for example, compared to the theoretical radial clearance JT, the guidance of the control ring 5 by the pads 81 may be less secure. This can lead to the blades spreading apart. If the radial clearance adjusted by the shims is too small, or in other words, a "closed" radial clearance ([Fig. 1e]), there may be a risk of the control ring 5 clamping onto the annular housing 4.This could lead to a kinematic blockage of the variable pitch blade stage 1 and / or deterioration and breakage of the control ring 5. Furthermore, since the pads 81 are also designed to rub the tracks 46 of the annular housing 4, the friction surface of these tracks 46 can wear down and thus increase the radial clearance under the pads 81 and drift towards the open radial clearance profile Jo of [Fig.lb]. .

[0008] Another disadvantage of pads as guiding elements is that they generally only restrict the deformation of the control ring in one direction (for example, in a radial direction towards the inside, i.e., towards the annular housing). Thus, these pads may not be sufficient to restrict outward radial and / or axial deformations.

[0009] The number and position of the actuators can also affect the deformation of the control ring during operation. For example, the control ring 5 of [Fig. 2a] having a single actuator 7 can concentrate the forces at a single point and thus de-symmetrize the control ring 5. Figures 2b and 2c illustrate an example of two control rings 5 ​​having, respectively, first 50a and second 50b annular bodies with a connecting member 70 for a single actuator 7, in which the first annular body 50a exhibits deformations (such as ovalization) relative to the second annular body 50b, which is intact.

[0010] For example, [Fig. 3a] represents a model of the timing errors due to deformation (such as ovalization of the control ring) measured in degrees (°) on the ordinate with respect to the first (i.e., the opening position represented by circles) and second (i.e., the closing position represented by triangles) positions of the blades on the abscissa, in the case of the control ring 5 with a single actuator 7. In this [Fig. 3a], the single actuator 7, represented by an arrow and positioned at the first and approximately sixty-fifth blades of the stage, exhibits asymmetry of the blades between their first and second blade positions. This configuration increases the timing errors of the blades and can thus increase the deformation of the control ring.

[0011] Figures 3b and 3b also represent models of the timing errors due to deformation in the case of a control ring comprising two actuators 7 spaced 180° and 135° (or 225°) apart, respectively. In [Fig. 3b], with an equidistant distribution at 180° of the two actuators 7, which are represented by arrows at the first and approximately the sixty-fifth and thirty-fourth blades, the first and second blade positions are substantially symmetrical and the timing errors are lower than those in [Fig. 3a]. However, the integration of two actuators can increase the size, weight, and complexity of the operation and assembly of the variable-pitch blade stage. In [Fig.3c] with a distribution of the two actuators at 135° (or 225°) which are represented by arrows at the level of the first and about the sixty-fifth blades and about the twenty-eighth blade, the first and second blade positions are asymmetrical and can further deform the control ring.

[0012] In this context, it is advantageous to overcome the drawbacks of the prior art by proposing a reliable solution that limits the deformation of a control ring in a variable-pitch turbine stage of a turbomachine, while simultaneously improving the centering and guidance of the control ring during operation. Description of the invention

[0013] The present invention proposes a simple, effective and economical solution to at least some of the aforementioned problems.

[0014] The invention proposes a variable-pitch blade stage for an aircraft turbomachine, comprising: - an annular row of variable-pitch blades, each blade comprising a blade including a cylindrical pivot at its radially external end, this pivot defining a pitch axis C of the blade, - an annular housing having an axis of revolution X and comprising mounting housings for said cylindrical pivots, and - a control ring for adjusting the blade pitch, the ring comprising: - an annular body that extends around the annular casing, - of the first connecting elements of the annular body to the cylindrical pivots of said blades, - a second connecting element of the annular body to at least one actuator carried by the annular housing, and - third guiding elements of the annular body around and at a distance from the annular housing.

[0015] According to the invention, said third guiding members comprise levers which each have a first end articulated on the annular housing around a radial axis R80a with respect to the axis of revolution X, and a second end connected to the annular body.

[0016] The variable-pitch blade stage according to the invention makes it possible to replace the support and guide pads of the prior art with levers to limit the deformation of the control ring during operation. In particular, the levers make it possible to connect the control ring to the annular housing and to guide this control ring by minimizing (or even eliminating) radial (inward and / or outward with respect to the X-axis) and / or axial deformation(s). Indeed, the levers form a strong (or rigid) connection between the control ring and the annular housing to best contain and control the different modes of deformation regardless of the number and position of the actuator(s) in the blade stage.

[0017] Furthermore, the levers optimize the blade timing accuracy, notably by reducing the impact of thermal expansion on blade timing accuracy, thanks to the levers' ability to allow and transmit movements (such as pivoting, translation, rotation, etc.) between the control ring and the annular housing. Whereas in the prior art, radial play between the pads and the annular housing is the primary contributor to blade misalignment.

[0018] Furthermore, the solution of the invention also allows for a saving in assembly time (for example, elimination of mounting shims and radial play adjustment between the levers and the annular housing) and maintenance (e.g. removal of wear parts and readjustment of radial play of the pads) of the control ring and consequently of the blade stage.

[0019] The invention therefore has the advantage of being based on a simple design, offering very high reliability, and little penalizing in terms of costs, size and environmental impact, particularly of the aircraft turbomachine.

[0020] The term "articulated" means that the first end can be pivotally mounted on the annular housing around the radial axis R80a. The first end of the levers can thus be assembled on the housing to allow their rotation relative to each other around the radial axis R80a.

[0021] The variable-pitch blade stage according to the invention may comprise one or more of the following features, taken individually or in comparison with each other:

[0022] - the second end is articulated by a ball joint to a first fixing pin engaged in an orifice of the annular body;

[0023] - the first fixing pin has a radial orientation with respect to the axis of revolution X;

[0024] - the first end includes a mounting hole for a second fixing pin engaged in an opening of the annular casing;

[0025] - the first end has a thickness or radial dimension greater than that of the second end;

[0026] - said third guiding elements are of approximately two to twenty in number, preferably this number is between three and twelve;

[0027] - the levers are distributed regularly around the axis of revolution X;

[0028] - each of said third guiding members has an external diameter greater than an external diameter of the first connecting elements;

[0029] - the second end is located at a predetermined radial distance from the annular body;

[0030] - the radial axis of the first end is inclined at a predetermined angle α with respect to an axis perpendicular to the axis of revolution X;

[0031] — angle a is for example between 0° and 50°;

[0032] - angle a is for example between 5° and 50°;

[0033] — at least one internal surface (or internal periphery) of the first end and / or the second end of the levers is or are covered with an anti-wear coating, for example a lubricant made of plastic material;

[0034] — said wear-resistant coating comprises at least one chemical element, for example molybdenum or graphite;

[0035] — the levers are each made of aluminium, steel or titanium;

[0036] — the variable-pitch blade stage is a rectifier stage of a low-pressure compressor pressure or a high-pressure compressor of the turbomachine.

[0037] The present invention also relates to a turbomachine, in particular for aircraft, comprising at least one stage of blades with variable pitch according to one of the features of the invention.

[0038] The turbomachine can be a turbojet or a turboprop. Description of the figures

[0039] The invention will be better understood and other details, features and advantages of the invention will become more apparent upon reading the following description, given by way of non-limiting example and with reference to the accompanying drawings in which:

[0040] [Fig. la] la [Fig. la] represents very schematically a theoretical radial clearance called ideal between the pads of a control ring and the tracks of an annular housing of a variable pitch blade stage;

[0041] [Fig. 1b] [Fig. 1b] represents very schematically a radial clearance said to be open between the pads and the tracks of the variable pitch blade stage;

[0042] [Fig. le] the [Fig. le] represents very schematically a radial clearance said to be closed between the pads and the tracks of the variable pitch blade stage;

[0043] [Fig.2a] [Fig.2a] is a schematic top view of a control ring with a single cylinder actuator according to the prior art;

[0044] [Fig.2b] [Fig.2b] is a schematic view of a first deformed control ring compared to a second intact control ring with a single actuator according to the prior art;

[0045] [Fig.2c] [Fig.2c] is a schematic perspective and side view of the first and second control rings of [Fig.2b];

[0046] [Fig.3a] [Fig.3a] is a schematic view of the control ring with a single actuator of figures 2a to 2c and a modeling of the blade timing errors on this ring;

[0047] [Fig.3b] [Fig.3b] is a schematic view of a control ring with two actuators distributed at an equidistance of 180° according to the prior art and a modeling of the blade timing errors on this ring;

[0048] [Fig.3c] [Fig.3c] is a schematic view of a control ring with two actuators distributed at a distance of 135° according to the prior art and a modeling of the blade timing errors on this ring;

[0049] [Fig.4] [Fig.4] is a partial schematic half axial cross-sectional view of a variable pitch blade stage of a compressor module of a turbomachine according to the invention;

[0050] [Fig. 5] [Fig. 5] is a schematic side perspective view of a crankcase annular and control rings of the blade stage of the [Fig.4];

[0051] [Fig.6] [Fig.6] is a schematic perspective view of the control ring of [Fig.4] or [Fig.5], comprising levers according to an embodiment of the invention;

[0052] [Fig.7] [Fig.7] is a schematic, partial perspective view of the floor of dawns of the [Fig.6];

[0053] [Fig.8] [Fig.8] is another schematic perspective and partial view of the floor of dawns of the [Fig.6];

[0054] [Fig.9] [Fig.9] is a schematic, partial perspective view of the floor of the [Fig.4] or [Fig.5] blades, comprising the [Fig.6] lever assembled on the control ring and an annular housing;

[0055] [Fig. 10] [Fig. 10] is a schematic axial and partial cross-sectional view of the blade stage of [Fig. 9];

[0056] [Fig. 11] [Fig. 11] is another schematic axial and partial cross-sectional view of the blade stage of [Fig. 9] or [Fig. 10].

[0057] Elements having the same functions in the different implementations have the same references in the figures. Detailed description

[0058] Generally, in the following description, the terms "longitudinal" and "axial" refer to the orientation of structural elements extending along a longitudinal axis. This axis can be considered the axis of rotation of a turbomachine rotor. The term "radial" refers to the orientation of structural elements extending in a direction perpendicular to the longitudinal axis. The terms "inner" and "outer," and "internal" and "external," are used with reference to positioning relative to the longitudinal axis. Thus, a structural element extending along the axis has an inner face facing the axis and an outer surface opposite its inner surface. Similarly, the terms "upstream" and "downstream" are defined with respect to the direction of airflow in the turbomachine.

[0059] Figures 1a to 1e, 2a to 2c and 3a to 3c have been described above in the technical background of the present application and represent at least part of a variable pitch blade stage 1 according to the prior art comprising pads 81 as guide members 8 of a control ring 5 relative to an annular housing 4.

[0060] The present invention applies generally and without limitation to a turbomachine 10, in particular an aircraft turbomachine. The turbomachine 10 may be a turbojet or a turboprop.

[0061] Figures 4 and 5 schematically represent, in a non-limiting manner, at least one stage 1 of variable pitch blades 2 of a high-pressure compressor of the tur-bomachine 10. According to another embodiment, a low-pressure compressor of the tur-bomachine 10 may comprise one or more stages 1.

[0062] Floor 1 comprises: - an annular row of variable pitch blades 2, - an annular housing 4 having an axis of revolution X, and - a control ring 5 for the pitch of the blades 2.

[0063] Each stage 1 may also include an annular row of movable blades 3 carried by a rotor (not shown) of the turbomachine.

[0064] Each blade 2 comprises a blade 20 having a cylindrical pivot 22 at its radially external end. The cylindrical pivot 22 defines a pitching axis C of the blade 2.

[0065] The angular orientation of the blades 2 can be adjusted to optimize the gas flow in the compressor. In particular, the blades 2 can be rotated about their axes C between a closed or near-closed position and an open or fully open position.

[0066] In the closed position, the blades 20 of the turbine vanes are inclined with respect to a longitudinal axis of the turbomachine and define between them a minimum air passage cross-section in the duct. The longitudinal axis of the turbomachine corresponds substantially to the X-axis of the annular casing 4. The blades 2 are brought into this closed position when the turbomachine is at low speed or idle, at which point the air flow into the compressor is minimal. In the open position, the blades 20 of the turbine vanes extend substantially parallel to the axis of the turbomachine so that the air passage cross-section between the blades is maximized. The blades 2 are brought into this open position when the turbomachine is at full throttle, at which point the air flow into the compressor is maximum.

[0067] The blade 20 and the cylindrical pivot 22 can be connected by a disc or "plate" 28 extending perpendicularly to the axis C of the blade in a first corresponding housing 44 of the annular housing 4. A radially internal surface 21 of the disc 28 can be aligned with an internal wall 42 of the annular housing 4 so as not to oppose the gas flow.

[0068] The cylindrical pivot 22 of each blade 2 can extend inside a second housing 40 (such as a radial cylindrical chimney) of the annular housing 4 and its radially external end can be connected to the control ring 5 by a connecting rod 24. This control ring 5 extends around the annular housing 4 in Figures 4 and 5.

[0069] The annular housing 4 may include protruding tracks 46 on its outer periphery allowing the centering and guidance of the control ring 5, which are schematically represented by dashed lines in [Fig. 4]. These tracks 46 may have a cylindrical shape, as seen in Figures 9 to 11. Each track 46 may have a first thickness E46 (or, in other words, a radial dimension) measured, for example, along a plane perpendicular to the X-axis. As an example, the first thickness E46 may be at most approximately 100 mm. This first thickness E46 may vary depending on the dimensions of the variable-pitch blade stage 1 (such as the size and / or shape of the control ring 5, the annular housing 4, and / or the variable-pitch blades 2). Each track 46 may be located on a dimension (such as a radius or the first thickness E46) smaller than that of the cylindrical pivot 22 of the corresponding blade 2. Each control ring 5 can surround its track or tracks 46.

[0070] With reference to Figures 4 to 11, the control ring 5 comprises: - an annular body 50, - first connecting members 26 to cylindrical pivots 22, - a second connecting member 70 to at least one actuator 7, and - third guiding members 8 of the annular body 50 and at a distance from the housing 4.

[0071] The annular body 50 can extend around a longitudinal axis A corresponding substantially to the axis X of the annular housing 4.

[0072] The first connecting members 26 can be located on a circumference, in particular around the axis A, of the annular body 50. Each of the first connecting members 26 can have a first external diameter D26 measured in particular along a plane perpendicular to the axis A.

[0073] The second connecting element 70 to the actuator 7 may include a clevis carrying an axle on which is articulated one end of a piston rod of the actuator 7, when the latter is a cylinder for example.

[0074] The actuator 7 may comprise one (single) cylinder or several cylinders, for example hydraulic. This actuator 7 may include an element fixed to the annular housing 4 and a piston rod connected to the second component 70.

[0075] The actuator 7 allows the control ring 5 to be rotated in one direction or the other around the X axis to drive the blades 2 of an annular row in rotation around their axes C.

[0076] The annular body 50 may have first orifices 52 in which the first connecting members 26 (for example cylindrical pins) carried by the connecting rods 24 may be housed. Each connecting member 26 may generally be centered and guided in rotation in the first orifice 52 by at least one bushing bearing mounted in this first orifice 52.

[0077] The body 50 may also include second orifices 54 in which The third guide elements 8 can be housed there. These second orifices 54 can be distributed regularly around the axis A. These second orifices 54 can be located between two first orifices 52.

[0078] One of the features of the invention is that the third guiding members 8 comprise levers 80 (or, in other words, connecting rods). Figures 6 to 11 illustrate a non-limiting example of the lever 80 according to the invention. As mentioned above, the levers 80 allow the control ring 5 to be articulated relative to the annular housing 4 and vice versa to prevent deformation of the control ring 5 during operation.

[0079] Each of the levers 80 has a first end 80a articulated on the housing 4 around a first radial axis R80a with respect to the axis of revolution X, and a second end 80b connected to the annular body 50. With reference to the example in figures 7 to 11, the first end 80a is opposite the second end 80b and the first 80a and second 80b ends can be monoblocs (i.e. made from a single piece of material).

[0080] The first radial axis R80a can be inclined at a predetermined angle α with respect to an axis perpendicular to the X-axis. Inclining the first radial axis R80a further restricts the radial deflection of the control ring 5. This angle α can be between 0° and 50°. Advantageously, the angle α can be between 5° and 50°. In the example shown in Figures 9 to 11, the angle α can be approximately 10°. In an alternative not shown in the figures, the angle α can be zero; in this case, the first radial axis R80a can be perpendicular to the X-axis.

[0081] The first end 80a may have a second thickness E80a and the second end 80b may have a third thickness E80b. These second E80a and third E80b thicknesses (or, in other words, radial dimensions) are measured along a plane perpendicular to the axis A or the axis X. In the example of Figures 7 to 11, the second thickness E80a may be greater than the third thickness E80b.

[0082] In the example of Figures 7 to 11, the second end 80b can be located at a predetermined radial distance d80b from the annular body 50. This distance d80b can be less than 1 mm. This distance d80b can be zero when the second end 80b is mounted directly on the annular body 50 and an internal periphery of this second end 80b is abutted and in contact with the annular body 50 (not shown in the figures).

[0083] When the second end 80b is mounted directly on the annular body 50, this second end 80b may include, on its inner periphery (with respect to the X-axis), at least one second inner surface 800a covered with a wear-resistant coating (not shown in the figures). This wear-resistant coating may be a lubricant made of plastic material. The wear-resistant coating may include at least one chemical element, for example molybdenum or graphite, particularly to restrict the wear friction between the annular body 50 and the second end 80b of the levers 80 and thus extend the life of these levers 80.

[0084] The second end 80b can be articulated, in particular along a second radial axis Rsob relative to the X axis (or the A axis), on the annular body 50. The second radial axis R 80b can be substantially perpendicular to the A and X axes. In particular, the lever 80 can include a ball joint 82 and a first fixing pin 84. This ball joint 82 can be housed in a third mounting hole 81 of the second end 80b ([Fig. 11]). The second end 80b can thus be articulated by the ball joint 82 to the first fixing pin 84 engaged in the second hole 54 of the annular body 50. The ball joint 82 and the first fixing pin 84 can be one-piece (i.e., machined from a single piece of material). The second 52 and third 81 holes can be radially aligned with each other ([Fig. 11]).

[0085] The first pin 84 may have a radial orientation with respect to the axis of revolution X. In particular, the first pin 84 may be located at the level of the second radial axis R80b of each of the second ends 80b.

[0086] The first end 80a may include a fourth mounting hole 85 for a second fixing pin 86 engaged in a fifth hole 460 of the annular housing 4. More particularly, the fifth hole 460 may be provided in the track 46 of the annular housing 4. The fourth 85 and fifth 460 holes may be aligned radially with each other ([Fig. 11]).

[0087] The first end 80a may include, on its inner periphery (relative to the X-axis), at least one first internal surface 800b covered with a wear-resistant coating. This wear-resistant coating may be a lubricant made of plastic material. The wear-resistant coating may include at least one chemical element, for example molybdenum or graphite, particularly to restrict wear friction between the tracks 46 and the first end 80a of the levers 80 and to extend the service life of these levers 80.

[0088] The third guiding members 8 can be distributed regularly around the X axis. In particular, the levers 80 can be distributed regularly around the X axis.

[0089] The third guide members 8 can thus be located on a circumference, in particular around the axis A, of the annular body 50. Thus, each of the third guide members 8 (in particular the levers 80) can have a second external diameter D8 measured in particular along a plane perpendicular to the axis A. This second external diameter D8 can be larger than the first external diameter D26 of the first connecting members 26 (Figures 7 to 11). According to another variant not shown in the figures, the second external diameter D8 can be equal to the first external diameter D26 of the first connecting members 26. For this, the first thickness E46 of the track 46 can be reduced and / or the second E80a and third E80b thicknesses of the ends 80a, 80b of the levers 80 can be reduced.

[0090] The third guiding elements 8 may number from approximately two to twenty, preferably between three and twelve. In particular, the levers 80 may number from approximately two to twenty, preferably from approximately three to twelve. With reference to [Fig. 6], the levers 80 may number six, evenly distributed around axis A (or axis X).

[0091] The levers 80 of the third guiding members 8 can be made of a metallic material, such as titanium, steel or aluminum.

[0092] By way of example, Table 1 below summarizes the differences in blade alignment measured in a blade stage configuration comprising ten prior art pads 81 with a clearance of 0.03 mm and that comprising ten levers 80 of the invention with a clearance of 0.1 mm. These measured clearances may correspond to axial clearance, for example, at the first radial axis R80a. Thus, the lever 80 can move with the maximum clearance (or, in other words, total clearance) of approximately 0.1 mm around the first radial axis R 80a*

[0093] It is thus observed that for a clearance greater than the configuration of the pads 81, the differences in pitching are reduced in the configuration of the levers 80 according to the invention with one or two actuators 7. This demonstrates that the levers 80 of the invention restrict the deformations of the rings to preserve good kinematics of the pitching of the blades 2.

[0094] [Table 1] Configurations: Play (measured in millimeters) Maximum offset difference (measured in degrees) Single actuator 7 Two actuators 7 Ten pads 81 0.03 0.58 0.161 Ten levers 80 0.1 0.32 0.118

Claims

Claims

1. Stage (1) of variable-pitch blades (2) for an aircraft turbomachine (10), comprising: - an annular row of variable-pitch blades (2), each blade (2) comprising a blade (20) comprising a cylindrical pivot (22) at its radially outer end, this pivot (22) defining a pitch axis (C) of the blade (2), - an annular casing (4) having an axis of revolution (X) and comprising mounting housings (40) for said cylindrical pivots (22), and - a ring (5) for controlling the pitch of the blades (2), the ring (5) comprising: - an annular body (50) which extends around the annular casing (4), - first members (26) for connecting the annular body (50) to the cylindrical pivots (22) of said blades (2), - a second member (70) for connecting the annular body (50) to at least one actuator (7) carried by the annular casing (4), and - third members (8) for guiding the annular body (50) around and at a distance from the annular casing (4),characterized in that said third guide members (8) comprise levers (80) which each comprise a first end (80a) articulated on the annular casing (4) around a radial axis (R80a) relative to the axis of revolution (X), and a second end (80b) connected to the annular body (50).,

2. Variable-pitch blade stage according to claim 1, characterized in that the second end (80b) is articulated by a ball joint (82) to a first fixing pin (84) engaged in an orifice (52) of the annular body (50).

3. Variable-pitch blade stage according to claim 2, characterized in that the first fixing pin (84) has a radial orientation relative to the axis of revolution (X).

4. Variable-pitch vane stage according to any one of the preceding claims, characterized in that the first end (80a) comprises an orifice (85) for mounting a second fixing pin (86) engaged in an orifice (460) of the annular casing (4).

5. Variable-pitch blade stage according to any one of the preceding claims, characterized in that the first end (80a) has a thickness (E80a) or radial dimension greater than that of the second end (80b).

6. Stage of variable-pitch blades according to any one of the preceding claims, characterized in that said third guide members (8) are approximately two to twenty in number, preferably this number is between three and twelve.

7. Variable-pitch blade stage according to any one of the preceding claims, characterized in that the levers (80) are distributed regularly around the axis of revolution (X).

8. Stage of variable-pitch blades according to any one of the preceding claims, characterized in that each of said third guide members (8) has an external diameter (D8) greater than an external diameter (D26) of the first connecting members (26).

9. A variable-pitch vane stage according to any preceding claim, characterized in that the second end (80b) is located at a predetermined radial distance (d80b) from the annular body (50).

10. Stage of variable-pitch blades according to any one of the preceding claims, characterized in that the radial axis (R80a) of the first end (80a) is inclined at a predetermined angle (a) relative to an axis perpendicular to the axis of revolution (X), the angle (a) is for example between 5° and 50°.

11. Aircraft turbomachine (10) comprising at least one stage (1) of variable-pitch blades (2) according to any one of the preceding claims.

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