Aircraft turbine engine including variable pitch propeller blades

Abstract

A variable pitch propeller blade (10) for an aircraft turbine engine is disclosed, the blade (10) comprising an airfoil (12) connected to a root (14), the root (14) comprising a body (24) housed in an annular barrel (26) extending around the pitch axis (A) of the blade, characterized in that the body (24) comprises: a free end (28) opposite the airfoil (12); a shoulder (30) facing the airfoil (12); and a ball (32) located between the free end (28) and the shoulder (30), the ball (32) having a cross section called the middle section having a maximum value Sm, the barrel (26) being fixed to the body (24) and covering and matching at least a portion of the shoulder (30) and the ball (32).

Description

Technical Field

[0001] The present invention relates to the field of aircraft turbine engines and in particular to propellers for these turbine engines, the propellers comprising variable-pitch blades. Background Art

[0002] The prior art includes in particular documents FR-A1-3 017 163, US-A1-2016 / 272299, CH-A-194 633, DE-A1-42 03 205, US-A1-2002 / 008177, US-A1-2015 / 110633 and FR-A1-3080 322.

[0003] Aircraft turbine engine propellers may be ducted (such as in the case of a fan) or unducted (such as in the case of an open rotor architecture).

[0004] The propeller comprises blades which may be of variable pitch. The turbine engine then comprises a mechanism which enables the pitch angle of the blades to be varied in order to adapt the thrust generated by the propeller to the different flight phases.

[0005] The design of propeller blades involves multiple disciplines with often conflicting objectives. The design of a propeller blade must allow for optimal aerodynamic performance (i.e. providing thrust while maximizing efficiency), guarantee the mechanical strength of the blade (i.e. withstanding the mechanical constraints resulting from static and dynamic loads), while limiting mass and acoustic signature. In particular, an improvement in the aerodynamic performance of a propeller tends to result in an increase in the Bypass Ratio (BPR), which translates into an increase in the propeller's external diameter and, therefore, the blade's span.

[0006] At the same time, in some turbine engine architectures, the engine is started with a very open pitch, known as drapeau. In fact, this starting position allows the power to be consumed by torque, which ensures the safety of the machine by ensuring a low propeller speed. More precisely, according to simple considerations, the power is proportional to the product of speed and torque. However, the torque increases with increasing angle of attack, which can be increased by means of pitch. In fact, those skilled in the art of aerodynamics understand that, in a first approximation, the resultant force on the blade profile is perpendicular to the chord and can be decomposed into two components: the thrust along the engine axis and the drag of the blade on the propeller plane. Therefore, with increasing pitch of the blade, the resultant force is shifted towards the propeller plane, so that the drag of the aerodynamic profile increases and the thrust decreases.

[0007] Thus, in the feathering start condition, the thrust generated by the propeller is zero, torque is maximum, and speed is minimum. However, the angle of attack becomes so large that the blades experience turbulent, highly lifted aerodynamic flow, resulting in strong vibration excitation. This excitation is both broadband due to small vortices in the lifted region and strong at certain specific frequencies due to large Karman recirculation (which causes significant aerodynamic oscillations). In particular, on blades with large chords and spans, which generate significant drag, these forces are significant even at low speeds.

[0008] In the current state of the art, it is common practice to attach the blade to its support using an attachment known as a broached attachment. The blade comprises a root having a generally dovetail shape and intended to engage in a form-fitting manner in a slot in the support, the slot usually being produced by broaching.

[0009] For blades with broached attachments, these aerodynamic forces are so strong that they can cause rigid solid motions of the blade root within the slot cavity at the blade root, similar to rotation. During feathering startup, the reduction in fan speed does not generate sufficient centrifugal forces to prevent these aerodynamically induced motions. This results in friction damage to the blade and the wedge inserted between the root and the bottom of the slot cavity within just a few cycles. For the same reason, this problem can arise in windmilling training situations after an engine failure, as variable-pitch blades are often equipped with a feathering system.

[0010] Furthermore, strong vibration excitations can also occur at higher speeds on non-ducted architectures due to the influence of the direction of the engine installation on the aircraft and the infinite flow upstream. In fact, non-ducted engines are subject to the influence of the ground and the fuselage, which can lead to distortions in the propeller feed and flow rate depending on the engine azimuth angle. This leads to a vibration response of the propeller blades on the first engine orders 1N, 2N and 3N (and possibly higher). On the other hand, in the absence of an air inlet sleeve, the direction of the air flowing through the blades is not parallel to the engine axis. This sideslip angle generates a force called "1P", which causes a vibration response of the propeller blades on the engine order 1N. Similarly, these forces 1P can also occur during the climb or approach phase of the aircraft when the air flows through the blades at an angle of attack. If the attachments of the blades are not suitable, these high speed vibration excitations can lead to the same friction damage discussed above.

[0011] For all of these reasons, broaching attachments is not currently a viable solution for variable pitch, high chord, and long span propeller blades.

[0012] Therefore, there is a need for a variable pitch propeller blade attachment technique that enables blade rotation to be restricted during all phases of flight that may excite vibration modes of the blade. Summary of the Invention

[0013] According to a first aspect, the invention relates to a variable pitch propeller blade for an aircraft turbine engine, comprising a blade connected to a root comprising a solid body housed in an annular barrel extending around a pitch axis for the blade,

[0014] It is characterized in that the main body includes:

[0015] a free end situated on the side opposite the blade, configured to cooperate in a form-matched manner with a system for controlling the pitch of the blade and comprising a cross section known as a low section having a non-circular shape and a value Sb,

[0016] a strut situated on one side of the blade, comprising a cross section called the high section having a value Sh, and

[0017] a bulb located between the free end and the support, which bulb has, in section, a convex circular shape extending between the free end and the support and which includes, at the top of this shape, a cross section called the middle section, which has a maximum value Sm that is greater than Sh and Sb,

[0018] A cylinder is attached to the body and covers and fits at least a portion of the strut and the ball, the cylinder having a shape complementary in section to the ball at the level of the intermediate section and complementary in section to the strut at the level of the high section.

[0019] In the present application, a cross section is defined as a section perpendicular to the pitch axis of the blade.A bulb is a convex or domed portion, ie in this case comprising a convexity or dome, which extends around the pitch axis.

[0020] The present invention therefore proposes a blade equipped with an improved root particularly suitable for limiting the risks of rotation described above.

[0021] The peculiarity of the root of the blade is particularly related to the combination of a bulb of large cross-section, which enables the blade to be optimally held along its axis, and a strut of smaller cross-section, which limits the risk of aerodynamic disturbances of the air flow passing through the blade and close to its root during operation.

[0022] Compared to current broached attachments, the invention makes it possible to limit premature wear of the blade during flight phases that could excite vibration modes of the blade. Furthermore, the blade root is very advantageous in terms of overall dimensions and aerodynamic refinement of the profile.

[0023] The blade according to the invention may include one or more of the following features, taken alone or in combination with each other:

[0024] --The root or body does not include any hollow or concave part;

[0025] --The cylinder is independent of the control system;

[0026] - The low section is eccentric with respect to the pitch axis;

[0027] --The low cross section is oval, oblong, rectangular, square, etc.;

[0028] - the middle cross-section has a circular shape; alternatively, the middle cross-section has a non-circular shape (such as an elliptical, oblong, rectangular, square, etc.);

[0029] - The high section has a non-circular shape;

[0030] --The high cross section is oval, oblong, rectangular, square, etc.;

[0031] - the cylinder is made of two shell halves mounted and attached to the body, the shell halves being joined at the level of a joining plane passing through said pitch axis;

[0032] -The barrel is glued to the body;

[0033] at least one shrink-fit ring mounted around the shell half to hold it fast against the body, the shrink-fit ring extending around the pitch axis;

[0034] - a lower shrink-fit ring mounted on the lower cylindrical surface of the barrel and extending around at least a portion of the free end of the body;

[0035] - an upper shrink-fit ring is mounted on the high cylindrical surface of the barrel and extends around a portion of the ball portion of the body;

[0036] - a claw engagement ring extending about the pitch axis and captively mounted about the strut between the ball and the blade, the claw engagement ring including external claw teeth configured to cooperate with the system;

[0037] - The claw engagement ring is configured to fit over the high cylindrical surface of the barrel.

[0038] The invention also relates to an assembly comprising a blade as described above and a system for controlling the pitch of the blade, wherein the system comprises at least two rolling guide bearings extending around a pitch axis.

[0039] Advantageously, the first guide bearing is located between the low section and the middle section or at the connection between the free end of the body and the ball, and the second guide bearing is located between the middle section and the high section or at the connection between the ball and the support.

[0040] Preferably, the first guide bearing extends at least partially around the lower shrink-fit ring and the second guide bearing extends at least partially around the upper shrink-fit ring.

[0041] The guide bearings receive the mechanical forces generated by the aerodynamic and centrifugal forces applied to the blade during operation. The lower bearing can be configured to ensure centrifugal retention of the blade, and the upper bearing can be configured to receive the bending moments generated by the aerodynamic and centrifugal forces. The distance between the bearings along the pitch axis creates sufficient leverage to prevent the blade from rotating in any phase of flight.

[0042] Advantageously, the system comprises a cup extending around the pitch axis and inserted between the cylinder and the guide bearing, the cup comprising a bottom wall extending transversely to the axis and having a recess for receiving the free end of the body, the recess having a shape complementary in section to that of the free end at the level of said low section.

[0043] Preferably, the cup includes internal claw teeth configured to cooperate with external claw teeth of said claw engagement ring.

[0044] The invention also relates to a turbine engine, in particular for an aircraft, comprising at least one blade or at least one assembly as described above.

[0045] According to a second aspect, the invention relates to a system for controlling the angular pitch of a propeller blade of an aircraft turbine engine, characterized in that the system comprises:

[0046] a cup-shaped portion comprising an annular wall extending around an axis intended to be the pitch axis of the blade, the annular wall comprising a lower axial end closed by a bottom wall and an open upper axial end, the upper axial end being configured so that the root of the blade can be mounted inside the cup-shaped portion, the bottom wall being configured to cooperate in a form-fitting manner with the free end of said root in such a way that the cup-shaped portion is rotationally fixed to the root around said axis, and

[0047] a fixing ring extending around said axis and configured to be mounted around the root, configured to be mounted inside the cup and to cooperate with the annular walls of the root and the cup respectively to ensure that the root is axially retained in the cup.

[0048] The present invention thus proposes a system particularly suitable for facilitating the installation and removal of propeller blades.

[0049] The system according to the present invention may include one or more of the following features, taken alone or in combination with each other:

[0050] -The system also includes:

[0051] a lower rolling guide bearing extending around said axis and mounted around the lower portion of the annular wall,

[0052] an upper rolling guide bearing extending around said axis and mounted around the upper portion of the annular wall;

[0053] At least one of the guide bearings has an inner ring integrated into the cup.

[0054] - at least one of the guide bearings is angular contact;

[0055] The bottom wall comprises a recess having a non-circular cross section and configured to receive the free end of the root of the blade.

[0056] - the recess is eccentric relative to the pitch axis;

[0057] - the system further comprises an elastically deformable member extending around the pitch axis and mounted inside the cup, the member being axially supported on the bottom wall and being configured to bias the root of the blade axially towards the outside of the cup;

[0058] - the fixing ring is a claw-engaging ring comprising external claw teeth configured to cooperate with complementary internal claw teeth of the annular wall of the cup;

[0059] - the system further includes a locking ring configured to axially engage between the inner claw teeth and the outer claw teeth to prevent the claw engagement ring from rotating within the cup, and an annular snap ring mounted in the cup to axially lock the locking ring in the cup;

[0060] The cross section of the retaining ring is wedge-shaped and is configured to be biased axially outwards from the cup under the action of centrifugal force during operation and to keep the blade root axially secured by a wedge effect.

[0061] The invention also relates to an assembly comprising a system as described above and a variable pitch propeller blade comprising a blade connected to a root comprising a body housed in an annular cylinder extending around the pitch axis of the blade.

[0062] The invention also relates to a turbine engine, in particular for an aircraft, comprising at least one system or component as described above.

[0063] Finally, the present invention relates to a method for installing the assembly described above, wherein the method comprises the following steps:

[0064] a) inserting the root of the blade into the cup of the system by displacing the blade in a direction parallel to the pitch axis,

[0065] b) engaging the free end of the root in a recess in the bottom wall of the cup to rotationally secure the cup to the root of the blade, and

[0066] c) Engaging a fixing ring previously installed or present around the root of the blade in the cup and installing this ring in the cup and on the root of the blade to ensure that the root remains axially in the cup.

[0067] Advantageously, during step a) and / or step b), the root of the blade is supported on the elastically deformable member and axially compresses the elastically deformable member.

[0068] Preferably, during step c), the fixing ring is mounted in the cup by means of claw engagements. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Other features and advantages will emerge from the following description of non-limiting embodiments of the invention and with reference to the accompanying drawings, in which:

[0070] [ Figure 1 ] Figure 1 is a schematic perspective view of a propeller blade for an aircraft turbine engine and illustrating the present invention,

[0071] [ Figure 2 ] Figure 2 yes Figure 1 and showing the root of the blade,

[0072] [ Figure 3 ] Figure 3 Is a Figure 1 A schematic perspective view of a partially exploded view of the root of a blade,

[0073] [ Figure 4 ] Figure 4 yes Figure 1A schematic perspective view of the body of the root of the blade,

[0074] [ Figure 5 ] Figure 5 yes Figure 1 Another schematic axial cross-section of the root of a blade and a guide bearing, the cross-section extending along the chord of the blade of the blade,

[0075] [ Figure 6 ] Figure 6 yes Figure 1 Schematic axial section through the root of a blade and a guide bearing, the section extending transversely to the chord of the blade of the blade,

[0076] [ Figure 7 ] Figure 7 It is along Figure 5 Another schematic cross-sectional view of line VII-VII,

[0077] [ Figure 8 ] Figure 8 yes Figure 1 a schematic axial cross-sectional view of the root of a blade and an embodiment of a system according to the invention for controlling the angular pitch of this blade,

[0078] [ Figure 9 ] Figure 9 yes Figure 8 A schematic perspective view of the cup portion of the system,

[0079] [ Figure 10 ] Figure 10 yes Figure 8 Schematic perspective view of a claw-shaped engagement ring of the system in

[0080] [ Figure 11 ] Figure 11 yes Figure 8 A schematic perspective view of a locking ring of the system in FIG.

[0081] [ Figure 12 ] Figure 12 yes Figure 8 Schematic perspective view of the root of the blade and a partial axial section of the system, showing the first installation step,

[0082] [ Figure 13 ] Figure 13 yes Figure 8 Schematic perspective view of the root of the blade and a partial axial section of the system, showing the second installation step,

[0083] [ Figure 14 ] Figure 14 yes Figure 8 Schematic perspective view of the root of the blade and a partial axial section of the system, showing the third installation step,

[0084] [ Figure 15 ] Figure 15 yes Figure 8 Schematic perspective view of the root of the blade and a partial axial section of the system, showing the fourth installation step,

[0085] [ Figure 16 ] Figure 16 yes Figure 8 Schematic perspective view of the root of the blade and a partial axial section of the system, showing the fifth installation step,

[0086] [ Figure 17 ] Figure 17 yes Figure 8 a schematic perspective view of a partial axial section of the root of the blade and of the system, showing the sixth installation step, and

[0087] [ Figure 18 ] Figure 18 yes Figure 1 Schematic axial section through the root of a blade and an alternative embodiment of a system according to the invention for controlling the angular pitch of this blade. DETAILED DESCRIPTION

[0088] Figure 1 A blade 10 is shown for a propeller of an aircraft turbine engine, the propeller being of the ducted or non-ducted type.

[0089] The blade 10 includes a blade 12 connected to a root 14 .

[0090] The blade 12 has an aerodynamic profile and comprises a soffit 12a and a dorsum 12b connected by an upstream leading edge 12c and a downstream trailing edge 12d, the terms “upstream” and “downstream” referring to the flow of gases around the blade in operation.

[0091] The blade 12 has a free upper end, called the tip, and a lower end connected to a root 14 .

[0092] In the example shown, the blade 10 is made of composite material by an infusion method known as Resin Transfer Molding (RTM). This method involves preparing a fiber preform 18 by three-dimensional weaving, then placing the preform in a mold and injecting a polymerizable resin (such as epoxy resin) that impregnates the preform. After the blade 12 has cured and hardened, its leading edge 12 c is typically reinforced by a metal sheath 20 that is mounted and attached, for example, by gluing.

[0093] The blade 10 here comprises a spar 22 comprising: a portion forming the core of the blade 12 and intended to be inserted into the preform 18 before resin injection; and a portion (called body 24 ) extending from the side opposite the tip of the blade 14 to form part of the root 14 .

[0094] Preferably, the spar 22 is made of a 3D woven carbon fiber reinforced epoxy organic matrix composite material, in which the warp threads are oriented primarily radially and the weft threads are oriented primarily along the chord of the blade at the aerodynamic duct height. However, the spar can also be a more mechanically advantageous component made of a different organic matrix composite material (thermoset, thermoplastic or elastomer) reinforced with long fibers (carbon, glass, aramid, polypropylene) in different fiber arrangements (woven, braided, knitted, unidirectional).

[0095] Although not shown, the blade 12 may be hollow or solid and include an internal cavity filled with a foam or honeycomb type filler material mounted around the spar 22 and covered with an organic matrix composite skin to increase the blade's impact resistance.

[0096] The sheath 20 may be titanium or a titanium alloy, stainless steel, steel, aluminum, nickel, etc. The soffit 12a or even the dome 12b of the blade 12 may be covered with a polyurethane film for preventing erosion.

[0097] The root 14 essentially comprises two parts, namely the body 24 and an annular cylinder 26 extending around the axis A of the body and the blade.

[0098] Axis A is the axis of elongation of the blade 10 and of the blade 12 and is in particular the pitch axis of the blade (i.e. the axis about which the angular position of the blade is adjusted). Axis A is also generally a radial axis and therefore extends along a radius from the axis of rotation of the propeller equipped with the blade.

[0099] The body 24 of the root 14 has Figures 3 to 7 The specific shape that can be clearly seen in the

[0100] The main body 24 basically consists of three parts:

[0101] a free end 28 situated on the side opposite the blade 12 ,

[0102] - a support 30 located on one side of the blade, and

[0103] - A ball 32 situated between the free end and the support.

[0104] In the example shown, the free end 28 has a substantially parallelepiped shape. Figure 7 As can be seen in FIG, this end 28 is offset from the axis A to enable rotational adjustment or indexing, as will be explained in more detail below.

[0105] Pb is defined as a transverse plane (ie, a plane perpendicular to the axis A) measured along the axis A through approximately the middle of the end portion 28. This plane Pb is referred to as the bottom plane or lower plane. Figure 7 The cross-sectional shape of the end portion 28 in this plane Pb is shown. This cross-section (called the low cross-section) has a value or surface area (eg maximum value) denoted Sb and is generally rectangular in shape in the example shown.

[0106] As will be described further below, end portion 28 is configured to cooperate with a system 34 for controlling the pitch of the blade.

[0107] The pillar 30 has a relatively complex shape and can be considered to include:

[0108] - two lateral ribs 30a, 30b, situated respectively on the side of the soffit 12a and the dome 12b of the blade 12, which converge towards each other along the axis A and in the direction of the tip of the blade 12 (see Figure 4 and Figure 6 ),as well as

[0109] - two edges, respectively an upstream edge 30 c and a downstream edge 30 d , which diverge from one another along the axis A and in the direction of the tip of the blade 12 (see Figure 4 and Figure 5 ).

[0110] Ph is defined as a transverse plane passing through the strut 30, particularly through the lower end of the strut. This plane Ph is referred to as the elevation plane or upper plane. In this plane, the strut may have a non-circular shape in cross-section (e.g., elliptical, oblong, square, or rectangular). This cross-section (referred to as the elevation) has a value or surface area (e.g., a maximum value), denoted as Sh.

[0111] The ball portion 32 has a generally convex or dome shape that extends about the axis A.

[0112] Pm is defined as the mid-plane passing through the ball 32 and particularly in the portion of the ball with the largest cross-section (labeled Sm). This plane Pm is referred to as the mean plane. In this plane, the ball 32 may have a circular shape in cross section, although this cross section is not limiting.

[0113] It will be appreciated that plane Pm lies between planes Pb and Ph. The cross-section of ball portion 32 decreases from plane Pm (Sm) to plane Ph, and from plane Pm to plane Pb. Therefore, it will be appreciated that Sm is greater than both Sb and Sh. Furthermore, in the example shown, Sh is greater than Sb.

[0114] As in Figure 3 As can be seen in FIG, the barrel 26 is composed of two shell halves 26a, 26b mounted and attached to the body 24, for example one shell half on the side of the soffit 12a of the blade and the other shell half on the side of the dome 12b of the blade 12. The shell halves 26a, 26b are thus joined at a joining plane passing through the axis A and extending substantially parallel to the chord of the blade 12.

[0115] Advantageously, the cylinder 26 is attached to the body 24, preferably by gluing. The adhesive extends around the axis A between the cylinder and the body.

[0116] Preferably, the cylinder 26 is made of metal (steel, titanium or a titanium alloy such as TA6V). The adhesive is, for example, an epoxy adhesive filled with a thermoplastic or elastomer mass or reinforced with fabric. This gluing method is particularly suitable because the contact surface area between the cylinder cavity and the body, which can be composite, is large. The presence of the adhesive joint is advantageous because it allows slight shape defects to be corrected. The adhesive joint also prevents friction at the metal / composite interface, thereby increasing the service life of the blade.

[0117] Several possibilities are envisioned for attaching the barrel 26 to the main body 24. The first is to intentionally leave a gap between the two shell halves 26a, 26b of the barrel 26 once they have been assembled, allowing for proper pressure to be applied while the adhesive bond cures. This curing phase can be completed in an autoclave, with the entire paddle inside a vacuum bag. However, this operation can also be performed in a press. However, the disadvantage of leaving a gap between the two shell halves 26a, 26b is that the positioning of the two halves is less controllable, necessitating reworking of the exterior surfaces. A second possibility is to attach the shell halves around the main body without any existing gap by placing one shell half against the other. This strategy is possible, for example, by machining a blank that has already been cut into two parts and held together during machining to ensure the geometry of the exterior surfaces once the shell halves are reassembled. This allows for control over the positioning and geometry of the exterior surface of the barrel 26 without requiring additional machining after gluing. In any case, positioning pins or stops may be considered to secure the relative position of the shell halves of the cartridge.

[0118] However, it is not mandatory to have an adhesive joint between the body and the cylinder, although it is very advantageous. Alternatively, a prestressed washer (or spring) can be used between the cylinder and the composite body to radially push the body against the bearing surface of the cylinder. The geometry of the cylinder can also be used to slightly "clamp" the body when the two shell halves of the cylinder are installed around the ball. In this case, it is the deformation of the cylinder that creates the prestress. Therefore, tools must be provided to maintain this position before final assembly.

[0119] As in Figure 5 and Figure 6 As can be seen in the drawing, the cylinder 26 covers and adapts to at least a portion of the ball 32 and at least a portion of the support 30 and has a cross-sectional shape complementary to that of the ball 32 at the level of the intermediate section Sm and to that of the support 30 at the level of the high section Sh.

[0120] More specifically, in the example shown, the barrel 26 comprises three parts,

[0121] - a lower end portion 36, which is generally annular in shape (see Figures 5 to 7 ), and extending at the level of and around the free end 28 of the root,

[0122] an upper end 38 extending at the level of the plane Ph and comprising two lateral lips 40 applied to the ribs 30a, 30b of the support 30, and

[0123] An intermediate portion 42 which is applied to the ball 32 and closely adapts to the shape of the ball.

[0124] The lip 40 is supported on the ribs 30 a , 30 b of the strut 30 and makes it possible to stiffen the root 14 of the blade and to increase its resistance to torsion about the pitch axis A.

[0125] Furthermore, the lips enable energy to be absorbed in the event of an impact, such as the ingestion of a bird, on the blade 10. Fillets may be present on these lips in order to prevent local wear or damage to the body.

[0126] The inner surface of the barrel 26, which contacts the main body 24, serves as the bearing surface. Compared to a broached attachment, the bearing surface is maximized by utilizing the entire circumference of the blade's base. In a broached attachment, only two distinct surfaces of the blade's root, located on the soffit and the apses, are supported on the bearing surface, while the surfaces of the blade's root, located on the leading and trailing edges, are free. The bearing surface is also much greater in the radial direction than with a broached attachment, which also contributes to a significant increase in its surface area. This large bearing surface reduces contact pressure under all operating conditions.

[0127] The barrel 26 comprises two cylindrical surfaces 44, 46a for mounting shrink-fit rings 48, 50. The shrink-fit rings 48, 50 make it possible to keep the shell halves 26a, 26b fastened to each other and to the body 24. The shrink-fit rings 48, 50 extend around the axis A.

[0128] The surface 44 is located on the lower end 36 and is oriented radially outwardly relative to the axis A. This surface receives, by means of a shrink fit, a ring 48 which is engaged from below and is supported axially on a cylindrical bearing surface located at the junction of the end 36 and the intermediate portion 42 of the barrel 26 .

[0129] The surface 46a is situated on the intermediate portion 42 and is oriented radially outwards with respect to the axis A. This surface receives, by shrink fit, a ring 50 which is engaged from above and is supported axially on a cylindrical bearing surface situated in the vicinity of the plane Pm.

[0130] It can be seen that the surface 46a is located in close proximity to a cylindrical surface 46b which is intended to receive a retaining ring 52 as will be described below.

[0131] In the example shown, the surfaces 44 , 46 a and the rings 48 , 50 have different diameters. The diameter of the surface 46 a is greater than the diameter of the surface 44 , and thus the diameter of the ring 50 is greater than the diameter of the ring 48 .

[0132] Surfaces 46a, 46b may have the same or different diameters. For example, surface 46b may have a slightly smaller diameter than the diameter of surface 46a. This is particularly true in the case where ring 50 should be installed with a predetermined radial clearance relative to this surface 46b.

[0133] from Figure 5 and Figure 6 It can be seen that the ring 50 is located between the planes Ph and Pm, and the ring 48 is located between the planes Pm and Ps.

[0134] Figure 5 and Figure 6Also shown are the positions of the rings 48 , 50 and the planes Pm, Ph, Ps relative to the rolling bearings 54 , 56 extending around the axis A and the root 14 .

[0135] Here, the number of bearings 54 and 56 is two, which are a lower bearing 54 and an upper bearing, respectively.

[0136] The bearings 54, 56 are of ball rolling type. In the example shown, the bearings have different diameters, and the balls of the bearings also have different diameters.

[0137] The bearing 54 extends substantially between the planes Pm and Pb and therefore extends around the lower portion of the ball 32. This bearing also extends around the ring 48. This bearing 54 has a smaller diameter than the other bearing 56, and the balls of this bearing have a larger diameter than the balls of the other bearing 56.

[0138] The bearing 54 is also angular contact. In the example shown, the support points or surfaces of the balls on the raceways of the rings 54a, 54b of balls are located on a frustoconical surface S1 extending along the axis A and having its largest diameter on the side of the blade's tip.

[0139] The bearing 56 extends approximately between the planes Pm and Ph, and therefore extends around the upper portion of the spherical portion 32. This bearing also extends around the ring 50. The bearing 56 is also angular contact. In the example shown, the bearing points or surfaces of the balls on the raceways of the rings 56 a, 56 b of the balls are located on a frustoconical surface S2 extending along the axis A and having its largest diameter on the side of the free end of the root of the blade.

[0140] The position of the intermediate section between the two bearings 54, 56 is very advantageous in terms of the overall radial dimensions, since part of the height of the bearing surface between the intermediate section and the high section is located inside the cup 58, unlike the prior art broached attachments integrated into the pivot. This contributes to reducing the overall radial dimensions of the control system 34.

[0141] Figures 8 to 17 A first embodiment of the system, in particular of the fixing ring 52, is shown, and Figure 18 Alternative embodiments of the system and the ring are shown.

[0142] The system 34 comprises a cup 58 including an annular wall 58a extending around the axis A. This wall 58a comprises a lower axial end closed by a bottom wall 58b and an open upper axial end configured to allow the root 14 of the blade to be mounted inside the cup.

[0143] The bottom wall 58b is configured to cooperate in a form-fitting manner with the free end of the root 14 and, therefore, with the end 28 of the body 24 so that the cup is rotationally fixed to the root about the axis.

[0144] In the present case, it will be understood that the bottom wall 58b comprises a recess 60 having a non-circular, in particular rectangular, cross section and configured to receive the end 28 ( Figure 8 ). As in Figure 5 As can be seen in FIG, the recess 60 is eccentric relative to the axis A in a similar manner to the end 28 (see FIG. Figure 7 ). This eccentricity allows for indexing and rotational adjustment when the root is inserted and installed in the cup 58, so that only one engaged position of the end 28 in the recess 60 is possible.

[0145] The recess 60 is located on the upper or inner face of the bottom wall 58b of the cup 58 so that the recess is located within the cup and is oriented toward the root.

[0146] System 34 generates a torque at the blade root that counteracts the torsional moment generated by aerodynamic and centrifugal forces. Like the rest of the main body 24 of the root 14, the end 28 of the root 14 can be enclosed in the barrel 26. In this case, this end also has a non-circular shape to restrict its rotation. However, as described above, it is advantageous to have this end of the main body protrude from the barrel to directly restrict its rotation. This provides a more direct force path, where torsional moments are applied directly to the main body. The dimensions of the low section are strictly smaller than the maximum dimension of the mid-section to limit the overall circumferential dimension to this height. As a result, the overall circumferential dimension of the barrel at this height is also smaller than that at the level of the mid-section. This enables the diameter of the lower bearing, located below the mid-section, to be reduced. Consequently, the blade root can be integrated lower in the radial direction, significantly reducing the theoretical hub ratio associated with root integration. As is known to those skilled in the art, a low hub ratio improves engine performance, particularly by making the engine more compact and, therefore, lighter. This last point is a very important advantage of the present technical solution compared to competitors, which generally propose cartridges with a cylindrical outer shape.

[0147] The bottom wall 58 b comprises a lower or external face situated on the opposite side of the root 14 and comprising a cylindrical extension 62 extending along the axis A and comprising an external thread or external straight spline 64 for coupling the system in rotation with a pitch changing mechanism not shown and common to the different systems 34 and the blade 10 of the propeller.

[0148] An elastically deformable member 66, such as a coil spring, extends around the axis A and is mounted inside the cup 58. This member 66 is supported axially on the upper surface of the bottom wall 58 b, in the example shown, at the outer periphery of this surface, and is configured to bias the root of the blade axially towards the outside of the cup, i.e. towards the side of the tip of the blade.

[0149] The member 66 is supported on the cylindrical bearing surface 68 of the barrel 26. In the example shown, the member 66 is centered by engaging its upper end on and around a cylindrical rim 70 of the barrel and by engaging its lower end on and around a cylindrical rim 72 of the cup located at the outer periphery of the bottom wall 58b.

[0150] In this case, the component 66 extends around the shrink-fit ring 48 .

[0151] As in Figure 8 As can be seen in FIG, the cup 58 is designed to support bearings 54 , 56 which ensure centering and guidance of the cup about the axis A relative to the casing 74 or the fixed structure of the turbine engine.

[0152] The bearings 54, 56 may be part of a control system. In particular, at least one of the guide bearings may have an inner ring of the guide bearing integrated into the cup.

[0153] This is the case with lower bearing 54, whose inner ring 54a is integrated into cup 58. In practice, this means that the cup includes a raceway 54aa at its outer periphery, on which the balls of bearing 54 roll directly. This raceway comprises an annular surface with a concavely curved cross-section. This raceway is located at the lower end of the cup and at the lower end of wall 58a. Outer ring 54b of bearing 54 is attached to housing 74, for example, by shrink-fitting. Furthermore, cup 58 is advantageously designed to apply prestressing force to bearing 54.

[0154] The outer ring 56b of the bearing 56 is attached to the housing 74, for example by shrink fitting. The inner ring 56a of the bearing engages on and around the free upper end of the cup 58 and the free upper end of the wall 58a. This end of the wall 58a comprises an outer cylindrical surface 76 for mounting the inner ring 56a and an outer thread for screwing on a nut 78 intended to be axially supported on the inner ring 56a to keep it axially tightened against the outer cylindrical shoulder 80 of the cup 58.

[0155] The wall 58a of the cup also comprises, at the inner periphery of the wall, a part configured to cooperate with the aforementioned fixing ring 52 .

[0156] The retaining ring 52 extends about the axis A and is configured to fit around the root 14. The retaining ring 52 is configured to fit within the cup and cooperate with the root 14 and annular wall 58a of the cup 58, respectively, to ensure that the root is axially retained in the cup.

[0157] exist Figures 8 to 17 In the embodiment of FIG. 5 , the retaining ring 52 is a pawl-engaging ring that includes external pawl teeth 84 configured to mate with complementary internal pawl teeth 82 of the annular wall 58 a of the cup 58 .

[0158] exist Figure 9 The teeth 82 of the cup 58 can be clearly seen in FIG. These teeth are evenly spaced about the axis A. In the non-limiting example shown, there are six teeth. For example, each of these teeth has an angular extension about the axis A of between approximately 20° and 30°.

[0159] Each of the teeth 82 comprises, at the inner periphery of the tooth, a groove 86 , which is oriented circumferentially relative to the axis A. The grooves 86 of the teeth 82 form discontinuous valleys around the axis A.

[0160] exist Figure 10 The claw-shaped engagement ring can be clearly seen in FIG. The teeth 84 of the claw-shaped engagement ring are regularly spaced about the axis A. In the non-limiting example shown, there are six teeth. For example, each of these teeth has an angular extension about the axis A of between approximately 20° and 30°.

[0161] The teeth 84 are complementary to the teeth 82 and are configured to mate with these teeth by means of a claw engagement (crabotage). Crabotage is a well known method of mounting in the aerospace field and will be explained in detail in the following examples. Figures 12 to 17 To explain.

[0162] The ring 52 comprises an internal cylindrical surface 52 a intended to cooperate by sliding with the aforementioned surface 76 of the cup 58 .

[0163] Ring 52 includes a second set of teeth 88 extending axially upward on the side of the tip of blade 10. These teeth 88 are also regularly spaced about axis A. In the example shown, there are six of these teeth. These teeth may be staggered relative to teeth 84, i.e., the circumferential spaces between teeth 88 and teeth 84 are axially aligned. As a non-limiting example, each of teeth 88 has an angular extension about axis A of between approximately 10° and 20°.

[0164] Each of the teeth 88 comprises, at the inner periphery of the tooth, a groove 90 oriented circumferentially with respect to the axis A. The grooves 90 of the teeth 88 form discontinuous valleys around the axis A.

[0165] Figure 11 A locking ring 92 is shown that is configured to engage axially between the claw teeth 82 , 84 to prevent the ring 52 from rotating within the cup 58 .

[0166] This annulus 92 comprises slide rails 94 (in the non-limiting example shown, they number six) intended to engage in the inter-tooth spaces extending between the teeth 82, 84. It will therefore be understood that these slide rails 94 have a shape complementary to that of these spaces and are regularly spaced about the axis A.

[0167] In the example shown, the rails 94 are secured to one another by bridges 96 extending circumferentially between the rails 94. There are five bridges 96, each extending between two adjacent rails 94. Intentionally, no two of the rails 94 are connected together by the bridges, so that the ring 92 is open. This simplifies assembly when the ring is installed in the system 34 by allowing the rails to be moved away from or toward one another.

[0168] Each of the rails 94 includes a groove 98 at the inner periphery of the rail, the groove being oriented circumferentially relative to the axis A. The grooves 98 in the rails 94 form discontinuous valleys about the axis A.

[0169] The system also includes an annular snap ring 100, which is only Figure 17 Visible in.

[0170] A snap ring 100 is mounted in the cup 58 to block the locking ring 92 axially in the cup 58. The snap ring 100 may also be split or open to facilitate its installation and is intended to engage in the grooves 86 of the teeth 82 of the cup and in the grooves 98 of the rails 94 of the ring 92 when these grooves 86, 98 are all located in the same plane perpendicular to the axis A and are arranged circumferentially relative to each other to form a complete valley around the axis A (see FIG. Figure 16 and Figure 17 ).

[0171] Now refer to Figures 12 to 17 , Figures 12 to 17 shows the installation by Figure 1 The blade 10 shown and Figure 8 The system 34 shown is formed by a method of assembly.

[0172] exist Figure 12In the first step shown, the root 14 of the blade 10 is engaged in the cup 58 of the system 34 by axial translation along the axis A until the end 28 of the body 24 of the root is engaged in the recess 60 of the cup 58. As can be seen in the figures, the shrink fit ring has been captively mounted around the support 30 of the body of the root. Although not shown in the figures, when the root 14 is inserted into the cup 58, the member 66 ( Figure 8 ) is compressed.

[0173] exist Figure 12 and Figure 13 In the second step shown, the shrink fit ring is angularly positioned about axis A so that its teeth 84 are aligned with the spaces between the teeth 82 of the cup. The ring 52 is then displaced axially in translation within the cup 58 until the ring 52 engages the surface 46b of the barrel 26 and the teeth 84 are located just below the teeth 82, as shown. Figure 13 The grooves 90 provided on the teeth can be used to grip the ring 52 with a suitable tool.

[0174] exist Figure 13 and Figure 14 In the third step shown, the ring 52 is rotationally displaced about the axis A so that the teeth 82, 84 are axially aligned with each other. Due to the angular extension of the teeth in the example shown, this angular displacement is about 25° to 30°. The teeth 88 can be used to clamp the ring 52 and rotate the ring by the aforementioned tool. The member 66 (not shown) biases the root axially outward from the cup so that the teeth 84 are axially supported on the teeth 82. The root is thus axially retained within the cup and the system 34. In operation, the centrifugal forces applied to the blade are transmitted to the cup 58 via the teeth 82, 84, and these forces are directly received by the bearing 54, the inner ring 54a of which is integrated into the cup 58.

[0175] exist Figure 15 and Figure 16 In the fourth step shown, the ring 92 is angularly positioned about the axis A so that its rails 94 are aligned with the spaces between the teeth 82, 84. The ring 92 is then displaced axially in translation within the cup 58 until the rails 94 engage in these spaces. The bridge 96 can then be supported on the teeth 84 of the ring 52. Thus, the ring 92 prevents any rotation of the ring 52 within the cup 58.

[0176] exist Figure 17 In the final step shown, the snap ring 100 is engaged in the grooves 86, 98 that are circumferentially aligned with each other. The snap ring 100 prevents the ring 92 from being accidentally disassembled.

[0177] It will be appreciated that the blade is disassembled by performing the aforementioned steps in reverse order. It will also be appreciated that one of the essential steps in installing and disassembling the root is the securing ring 52. This ring 52 can be manipulated from outside the turbine engine, which is particularly advantageous during maintenance operations. The blade can be disassembled and removed from the propeller by disassembling and removing a minimum number of parts.

[0178] Reference Figure 18 , Figure 18 An alternative embodiment of a retaining ring 52' is shown. The ring 52' is wedge-shaped in cross section and is configured to be biased axially outwardly from the cup 58 under centrifugal force during operation and to hold the root 14 of the blade axially secured by a wedging effect.

[0179] In the example shown, the axial semi-cross section of the ring 52 ′ is generally trapezoidal and comprises a lower surface 102 and two lateral surfaces, an inner lateral surface 104 and an outer lateral surface 106 .

[0180] The ring 52 ′ engages around the root 14 and in the cup and is axially supported on the shrink-fit ring 50 by means of its surface 102 , here by means of a washer 108 .

[0181] The outer surface 106 of the ring cooperates, by support and axial sliding, with a complementary ring 110 mounted inside the cup and around the ring 52 ′.

[0182] The ring 52 ′ is segmented and is formed by a plurality of segments arranged at a circumferential distance from one another around the axis A. By way of example, there are six segments evenly distributed around the axis A.

[0183] Finally, the nut 112 is screwed onto the internal thread of the upper end of the cup 58 and cooperates with the internal surface 104 of the ring 52 ′ by support and axial sliding.

[0184] Tightening and tightening the nut 112 causes axial displacement of the segments of the ring 52' supported on the washer 108 and radial biasing of these segments against the complementary-shaped ring 110. Any mounting play is then removed.

[0185] The barrel 26 comprises a cylindrical shoulder 114 which is supported against a complementary cylindrical shoulder 116 of the cup 58 (here at the junction between the middle portion 42 and the lower end of the barrel 26). This variant has the advantage of receiving the centrifugal forces in order to retain the blade and also replaces the previously mentioned member 66 by applying the prestressing force directly between the barrel 26 (and therefore the root 14 of the blade) and the inner ring 54a of the bearing 54.

[0186] Other variant embodiments not shown are possible, including:

[0187] The shell halves 26a, 26b of the cylinder 26 can be mounted to the main body 24 by bolting, riveting, welding, etc.;

[0188] The adhesive used to connect the barrel 26 to the body 24 may be an epoxy adhesive, but the adhesive may also be an elastomeric or thermoplastic adhesive. A non-stick film may also be used to enable relative movement while limiting wear due to friction.

[0189] Still regarding the problem of the cylinder / body interface, it is possible to combine several of the technical solutions proposed (gluing, prestressing by washers or springs, prestressing by the geometry of the cylinder); these solutions can be combined independently of the presence of a gap between the two parts of the cylinder;

[0190] • Although less advantageous, the radial position of the bearings ensuring the centrifugal retention of the blade can be opposite to the radial position of the bearings receiving the bending moments generated by the aerodynamic and centrifugal forces.

Claims

1. A variable pitch propeller blade (10) for an aircraft turbine engine, the blade (10) comprising a blade (12) connected to a root (14), the root (14) comprising a solid body (24) housed in an annular barrel (26) extending around the pitch axis (A) of the blade, It is characterized by: The main body (24) comprises: a free end (28) situated on the side opposite to the blade (12), configured to cooperate in a form-matched manner with a system (34) for controlling the pitch of the blade and comprising a cross section known as a low section having a non-circular shape and a surface area Sb, a strut (30) situated on one side of the blade (12), comprising a cross section called a high section, the surface area of ​​which is Sh, and - a spherical portion (32) situated between the free end (28) and the support (30), the spherical portion (32) having, in cross section, a convex circular shape extending between the free end and the support and comprising, at the top of the convex circular shape, a cross section called the middle section, the surface area of ​​which is Sm, which is greater than Sh and Sb, The cylinder (26) is attached to the body (24) and covers and fits at least a portion of the support (30) and the ball (32), the cylinder (26) having a shape that is complementary in section to the ball (32) at the level of the intermediate section and complementary in section to the support (30) at the level of the high section, wherein a claw engagement ring (52) extends about the pitch axis (A) and is captively mounted about the strut (30) between the ball (32) and the blade (12), the claw engagement ring (52) including external claw teeth (84) configured to mate with the system (34).

2. The blade (10) according to claim 1, wherein: The low section is eccentric relative to the pitch axis (A).

3. The blade (10) according to claim 1 or 2, wherein: The intermediate cross-section has a circular shape.

4. The blade (10) according to claim 1 or 2, wherein: The high cross-section has a non-circular shape.

5. The blade (10) according to claim 1 or 2, wherein: The cylinder (26) is made of two shell halves (26a, 26b) mounted and attached to the body (24), the shell halves (26a, 26b) being joined at the level of a joining plane passing through the pitch axis (A).

6. The blade (10) according to claim 5, wherein: The cylinder (26) is glued to the main body (24).

7. The blade (10) according to claim 5, wherein At least one shrink-fit ring is mounted around the shell halves (26a, 26b) to hold them secured against the body (24), the shrink-fit ring extending around the pitch axis (A).

8. The blade (10) according to claim 7, wherein The at least one shrink fit ring includes an upper shrink fit ring (50) and a lower shrink fit ring (48), the lower shrink fit ring (48) being mounted on the lower cylindrical surface (44) of the barrel (26) and extending around at least a portion of the free end (28) of the body (24).

9. The blade (10) according to claim 8, wherein The upper shrink fit ring (50) is mounted on the high cylindrical surface (46a) of the barrel (26) and extends around a portion of the ball portion (32) of the body (24).

10. The blade (10) according to claim 9, wherein The claw-shaped engagement ring (52) is configured to be mounted on the high cylindrical surface (46a) of the barrel (26).

11. An assembly comprising a variable pitch propeller blade (10) for an aircraft turbine engine and a system (34) for controlling the pitch of said blade, wherein The system (34) comprises at least two rolling guide bearings extending around the pitch axis (A), The blade (10) comprises a blade (12) connected to a root (14), said root (14) comprising a solid body (24) housed in an annular cylinder (26) extending around the pitch axis (A) of the blade, Characterized in that the main body (24) comprises: a free end (28) situated on the side opposite to the blade (12), configured to cooperate in a form-matched manner with a system (34) for controlling the pitch of the blade and comprising a cross section known as a low section having a non-circular shape and a surface area Sb, a strut (30) situated on one side of the blade (12), comprising a cross section called a high section, the surface area of ​​which is Sh, and - a spherical portion (32) situated between the free end (28) and the support (30), the spherical portion (32) having, in cross section, a convex circular shape extending between the free end and the support and comprising, at the top of the convex circular shape, a cross section called the middle section, the surface area of ​​which is Sm, which is greater than Sh and Sb, The cylinder (26) is attached to the body (24) and covers and fits at least a portion of the support (30) and the ball (32), the cylinder (26) having a shape that is complementary in section to the ball (32) at the level of the intermediate section and complementary in section to the support (30) at the level of the high section, wherein a first guide bearing (54) is located between the low section and the middle section or at the connection between the free end (28) of the body (24) and the ball portion (32), and a second guide bearing (56) is located between the middle section and the high section or at the connection between the ball portion (32) and the support (30), wherein a lower shrink fit ring (48) is mounted on the lower cylindrical surface (44) of the barrel (26) and extends around at least a portion of the free end (28) of the body (24), wherein an upper shrink fit ring (50) is mounted on the high cylindrical surface (46a) of the barrel (26) and extends around a portion of the ball portion (32) of the body (24), The first guide bearing (54) extends at least partially around the lower shrink fit ring (48), and the second guide bearing (56) extends at least partially around the upper shrink fit ring (50).

12. An assembly comprising a variable pitch propeller blade (10) for an aircraft turbine engine and a system (34) for controlling the pitch of said blade, wherein The system (34) comprises at least two rolling guide bearings extending around the pitch axis (A), The blade (10) comprises a blade (12) connected to a root (14), said root (14) comprising a solid body (24) housed in an annular cylinder (26) extending around the pitch axis (A) of the blade, Characterized in that the main body (24) comprises: a free end (28) situated on the side opposite to the blade (12), configured to cooperate in a form-matched manner with a system (34) for controlling the pitch of the blade and comprising a cross section known as a low section having a non-circular shape and a surface area Sb, a strut (30) situated on one side of the blade (12), comprising a cross section called a high section, the surface area of ​​which is Sh, and - a spherical portion (32) situated between the free end (28) and the support (30), the spherical portion (32) having, in cross section, a convex circular shape extending between the free end and the support and comprising, at the top of the convex circular shape, a cross section called the middle section, the surface area of ​​which is Sm, which is greater than Sh and Sb, The cylinder (26) is attached to the body (24) and covers and fits at least a portion of the support (30) and the ball (32), the cylinder (26) having a shape that is complementary in section to the ball (32) at the level of the intermediate section and complementary in section to the support (30) at the level of the high section, In which, the system (34) comprises a cup (58) extending around the pitch axis (A) and inserted between the cylinder (26) and the rolling guide bearing, the cup (58) comprising a bottom wall (58b) extending transversely to the pitch axis (A) and having a recess (60) for receiving the free end (28) of the body (24), the recess (60) having a shape complementary in cross section to the free end (28) at the level of the low section.

13. The assembly of claim 12, wherein: A claw engagement ring (52) extends about the pitch axis (A) and is captively mounted about the support post (30) between the ball portion (32) and the blade (12), the claw engagement ring (52) including external claw teeth (84) configured to mate with the system (34), wherein the cup portion (58) includes internal claw teeth (82) configured to mate with the external claw teeth (84) of the claw engagement ring (52).

14. A turbine engine comprising at least one assembly according to any one of claims 11 to 13.

15. The turbine engine according to claim 14, wherein: The turbine engine is a turbine engine for an aircraft.

Images