Propeller with blades and aircraft comprising at least one propeller

Abstract

The present invention relates to a propeller (1) comprising a hub (2), blades (3) rotatable about a pitch axis (AXP) relative to said hub (2), and a guide device (4) per blade (3) guiding said blade (3) in rotation about its pitch axis (AXP) relative to said hub (2). Each guide device (4) is arranged between said hub (2) and said blade (3) and comprises one or more bearings (5, 6). Each bearing (5, 6) is provided with an internal frame (51, 61) secured to said blade (3), and an external frame (52, 62) secured to said hub (2) as well as a sliding layer (53, 63) comprising a lubricating fluid, an anti-friction material and / or an anti-friction surface treatment, and located between said internal frame (51, 61) and said external frame (52, 62).The propeller (1) comprises an axial stop (8) causing a translational stop of said blade (3) relative to said hub (2) along said pitch axis (AXP) from the inside to the outside of said hub (2). Abbreviated figure: figure 1.

Description

Title of the invention: Propeller provided with blades and aircraft comprising at least one propeller

[0001] The present invention relates to the field of aircraft rotors, and in particular to propellers for advancing an aircraft. The present invention relates to a propeller provided with blades and to an aircraft comprising at least one such propeller.

[0002] A propeller, also referred to as a "propeller" for example, traditionally comprises a rotating hub and several blades connected to the hub. An aircraft may comprise one or more propellers, placed for example on either side of the fuselage, and possibly on a wing of the aircraft.

[0003] The pitch of the blades can vary collectively, namely identically for all the blades, in order to modify their incidence and, consequently, vary the thrust generated by the propeller. For this purpose, each blade is articulated to the hub by a pitch articulation, giving freedom of rotation to the blade around its pitch axis relative to the hub of the propeller.

[0004] Such a pitch articulation further ensures the transmission of various forces between the blade and the hub of the propeller, such as those exerted at the root of the blade, in particular a centrifugal force generated by the rotation of the hub and the blade around the axis of rotation of this hub, as well as bending moments and shear forces.

[0005] Such a pitch articulation also ensures the rotational guidance of the blade relative to the hub.

[0006] According to a widespread prior art, a pitch articulation of a blade comprises one or more bearings provided with rolling elements, such as balls or rollers for example. Such a bearing is arranged between the hub and the root of the blade in order to guide the blade in rotation around its pitch axis and to transmit to the hub the forces generated during the rotation of the blades.

[0007] In addition, a stop device, for example a shoulder, a pin or an elastic ring, forms an axial stop between the hub and the blade along the pitch axis of the blade. Such a stop stop can hold the blade in position towards the inside of the hub, in particular to retain the blade under the effect of its weight when the propeller is not rotating. Conversely, a stop stop can hold the blade in position towards the outside of the hub to retain the blade under the effect of centrifugal force when the propeller is rotating.

[0008] For example, a propeller may comprise, for each blade, two ball or roller bearings used in combination. Alternatively, a single angular contact ball bearing may be used, as described in US 2012 / 0099991.

[0009] Furthermore, a pitch articulation causes unusual operation of the bearing. Indeed, the pitch of a blade is not permanently modified and causes a rotation of the blade about the pitch axis over a limited angular range. As a result, the bearing is subject to low-speed oscillating movements about the pitch axis, these movements being quasi-static. The use of such ball or roller bearings for a pitch articulation can then have several disadvantages.

[0010] First of all, such a pitch articulation is subject to the false Brinell effect, which is characterized by the appearance of local degradations, such as hollows, on the inner and / or outer races of the bearing. These degradations are very localized and particularly difficult to detect, whether by empirical manual procedures or by modern monitoring means, of the vibratory or acoustic types for example. These degradations induce in particular an increase in the forces necessary to modify the pitch of the propeller blades, and can ultimately lead to a loss of the pitch control function and / or the guidance function around the pitch axis.

[0011] Furthermore, corrosion of the materials usually used for the manufacture of the components of these bearings may appear, independently of degradation by the false Brinell effect.

[0012] Then, these bearings generally require permanent lubrication, which requires periodic preventive maintenance to replace the lubricant in order to prevent the consequences of its degradation or possible pollution. Indeed, the degradation of the bearings can be aggravated, in intensity and / or in speed of propagation, in the event of corrosion and / or poor lubrication.

[0013] The rolling pitch joints of the blades of a propeller must therefore be subject to effective and precise monitoring, which in fact requires expensive, even complex, maintenance operations which may involve the complete dismantling of the propeller, further involving risks linked to the human factor.

[0014] The present invention therefore aims to propose an alternative propeller solution for aircraft making it possible to limit, or even eliminate, the maintenance operations to be carried out.

[0015] The present invention therefore relates to a propeller for aircraft comprising: - a hub, - at least two blades, each of the blades being rotatable about a pitch axis of the blade relative to the hub, and - a blade guide device, each guide device guiding the blade in rotation about its pitch axis relative to the hub, each guide device being arranged between the hub and the blade.

[0016] The propeller according to the invention is remarkable in that each guide device comprises at least one bearing, said at least one bearing being provided with an internal frame and an external frame as well as a sliding layer located between the internal frame and the external frame, the internal frame being integral with the blade, the external frame being integral with the hub.

[0017] The rotational guidance device thus forms a pitch articulation of the propeller blade according to the invention.

[0018] The sliding layer is positioned between the internal reinforcement and the external reinforcement and allows for a substantially continuous connection or contact surface between the external and internal reinforcements of the bearing. The sliding layer allows for minimizing friction between the internal reinforcement and the external reinforcement and thus allows rotation of the external reinforcement relative to the internal reinforcement.

[0019] The use of one or more bearings for the guide device advantageously makes it possible to ensure the rotational guidance of the blade relative to the hub and to transmit the forces and moments between the blade and the hub, while overcoming the disadvantages of the technology of bearings equipped with rolling elements.

[0020] Such forces transmitted between the blade and the hub may include, for example, centrifugal forces generated during rotation of the hub and the blades about an axis of rotation of the hub, oriented from the inside to the outside of the hub substantially parallel to the pitch axis of the blade, and thus transmitted from the root of the blade to the hub. These centrifugal forces constitute axial forces for the blades and radial forces for the hub. Such forces transmitted between the blade and the hub may also include shear forces and bending moments generated during rotation of the hub and the blades about said axis of rotation.

[0021] Indeed, the sliding layer makes it possible to replace the point or linear contacts obtained with rolling elements, by a surface contact between the external and internal armatures of the bearing. Consequently, the invention makes it possible to limit, or even avoid, the appearance of degradations, in particular according to the false Brinell effect, despite the low-speed oscillating and quasi-static movements of the bearing.

[0022] Such a bearing also has the advantage of not degrading, or only very slowly, for example by reducing the thickness of the sliding layer. Such degradation can advantageously be detected before causing a malfunction, for example by the appearance of wear generating a clearance which can be monitored and quantified. The detection of such damage can advantageously be carried out without disassembly, for example by monitoring an unbalance of the propeller which will increase continuously and slowly with the degradation of the bearing. The service life of these bearings can be defined by taking into account such slow degradation in order to guarantee their removal before the occurrence of any feared consequences. For example, it is possible to model the wear of the sliding layer of a bearing and calculate a service life at the end of which the bearing must be replaced, which is not possible with rolling bearings in the absence of reliable modeling of the false Brinell effect.

[0023] Furthermore, the use of this or these bearings makes it possible to simplify the mounting and assembly of the guide devices on the hub as well as their replacements if necessary, due to greater sensitivity of the bearings to the installation conditions.

[0024] The propeller according to the invention may further comprise one or more of the following characteristics, taken alone or in combination.

[0025] According to one possibility, the sliding layer may comprise a lubricating fluid forming a lubricant film between the internal frame and the external frame of the bearing. The sliding layer may in this case be viscous, or even liquid. This lubricant film is obtained for example thanks to the internal and external frames which are porous and whose pores contain the lubricating fluid. The lubricating fluid may comprise for example mineral oil or silicone. Such bearings may be referred to as “self-lubricating bearings”. The internal and external frames may for example be made of bronze and produced by sintering. Other materials, metallic or non-metallic, are of course conceivable.

[0026] Such bearings do not require any additional lubrication during their lifetime, and therefore advantageously no maintenance operations, consequently reducing the cost of their use.

[0027] Alternatively, the sliding layer may be solid and comprise an anti-friction material. An anti-friction material may comprise, for example, one or more fluoropolymers, in particular polytetrafluoroethylene (PTFE) or polyetheretherketone (PEEK), a phenolic resin, a polyamide and / or graphite. The sliding layer may, for example, comprise a ring formed by a thin layer of polytetrafluoroethylene. In addition, anti-friction surface treatments, such as electrochemical deposition containing, for example, chromium, or plasma deposition with a powder comprising, for example, a ceramic or a tungsten carbide, may be carried out on the internal frame and / or the external frame. Such bearings may be referred to as “plain bearings” or “self-lubricated bearings”.

[0028] Again, no maintenance operations are necessary during the lifetime of these bearings, also reducing the cost of their use.

[0029] Alternatively, each bearing comprising a sliding layer can be replaced by another technology, typically a laminated bearing provided with several successive layers of elastomer and metal. Such a laminated bearing allows degrees of freedom via the deformation of the elastomer layers, and in particular supports significant compressive loads.

[0030] According to a possibility compatible with the previous ones, at least one guide device can be arranged entirely inside the hub. In this way, regardless of the number of bearings that the guide device comprises, this or these bearings are arranged inside the hub. The interior of the hub is, for example, delimited by an external face of the hub in contact with an external medium, in which the part of the blade generating thrust is located.

[0031] Alternatively, when a guide device comprises at least two bearings, at least one of the bearings may be arranged inside the hub and at least one of the bearings may be arranged outside the hub.

[0032] According to a possibility compatible with the preceding ones, the internal frame and the external frame of at least one bearing among said at least one bearing may respectively comprise a conical external face and a conical internal face, the conical external face of this internal frame, and the conical internal face of this external frame facing each other, the conical external face and the conical internal face having as a common axis of revolution the pitch axis of the blade. The conical external face and the conical internal face are formed by circles centered on the pitch axis whose diameter decreases from the inside to the outside of the hub.

[0033] The conical outer face and the conical inner face thus approach the pitch axis from the inside to the outside of the hub. The apex of a cone formed by the conical outer and conical inner faces is thus located between the base of this cone and the external environment.

[0034] The sliding layer is also conical in shape having as its axis of revolution the pitch axis of the blade.

[0035] Such a bearing, the internal and external frames of which are respectively provided with a conical external face and a conical internal face, makes it possible to simultaneously ensure recovery, on the one hand, of the centrifugal forces generated during the rotation of the hub around its axis of rotation and, on the other hand, of the shear forces and bending moments transmitted between the blade and the hub.

[0036] Such a bearing, the internal and external frames of which are provided respectively with a conical external face and a conical internal face, is preferably arranged inside the hub so as to ensure the absorption of centrifugal forces between the bearing and the hub.

[0037] For example, the guide device comprises one or at least two bearings whose internal and external frames are provided respectively with a conical external face and a conical internal face.

[0038] Alternatively or in a complementary manner, the internal frame and the external frame of at least one of these at least two bearings may respectively comprise a toric external face and a toric internal face, the toric external face of the internal frame and the toric internal face of the external frame facing each other. The toric external face and the toric internal face have as a common axis of revolution the pitch axis of the blade and are formed respectively by the revolution of circular generatrices around this pitch axis.

[0039] The sliding layer is also toroidal in shape having the pitch axis as its axis of revolution.

[0040] Such a bearing, the internal and external frames of which are respectively provided with a toric external face and a toric internal face, makes it possible to obtain a pivot-type connection around the pitch axis. Consequently, such a bearing makes it possible to simultaneously ensure recovery, on the one hand, of the centrifugal forces generated during the rotation of the hub around its axis of rotation and, on the other hand, of the shear forces and bending moments transmitted between the blade and the hub.

[0041] Such a bearing, the internal and external frames of which are provided respectively with a toric external face and a toric internal face, is preferably arranged inside the hub so as to ensure the absorption of centrifugal forces between the bearing and the hub.

[0042] For example, the guide device comprises one or at least two bearings whose internal and external frames are respectively provided with a toric external face and a toric internal face. Alternatively, the guide device may comprise at least one bearing with a toric external face and a toric internal face, and at least one bearing, whose internal and external frames respectively comprise a conical external face and a conical internal face.

[0043] Alternatively or in a complementary manner, when a guide device comprises at least two bearings, the internal frame and the external frame of at least one of these at least two bearings may respectively comprise a spherical external face and a spherical internal face, the spherical external face of the internal frame and the spherical internal face of the external frame facing each other, the spherical external face and the spherical internal face having as a common center of revolution a point on the pitch axis.

[0044] The sliding layer is also spherical in shape having as its center of revolution the same point of the pitch axis.

[0045] Such a bearing, the internal and external frames of which are provided respectively with a spherical external face and a spherical internal face, makes it possible to obtain a ball-and-socket type connection, by allowing three degrees of freedom in rotation around three intersecting axes. Consequently, such a bearing makes it possible to ensure mainly a recovery of centrifugal forces. Indeed, the shear forces and the bending moments will tend to cause rotation between the internal and external armatures. This is why such a bearing is used in combination with another similar bearing, namely one having a spherical external face and a spherical internal face respectively, or a different one. Such a combination of at least two bearings thus allows for the absorption of shear forces and bending moments as well as obtaining a pivot-type connection between the blade and the hub.

[0046] The guide device may thus comprise two bearings respectively comprising a spherical external face and a spherical internal face. Alternatively, the guide device may comprise at least one bearing with a spherical external face and a spherical internal face, and at least one bearing, the internal and external frames of which respectively comprise a conical external face and a conical internal face, or a toric external face and a toric internal face.

[0047] Alternatively or in a complementary manner, the internal frame and the external frame of at least one bearing among said at least one bearing may respectively comprise a cylindrical external face and a cylindrical internal face, the cylindrical external face of the internal frame and the cylindrical internal face of the external frame facing each other, the cylindrical external face and the cylindrical internal face having as a common axis of revolution the pitch axis.

[0048] The sliding layer is also cylindrical in shape having as its axis of revolution the pitch axis of the blade.

[0049] Such a bearing, the internal and external frames of which are respectively provided with a cylindrical external face and a cylindrical internal face, makes it possible to ensure only a recovery of the shear forces and bending moments transmitted between the blade and the hub. Therefore, the guide device comprises an axial stop in order to take up the centrifugal forces generated during the rotation of the hub around its axis of rotation, and consequently also to limit the movement of the internal frame parallel to the pitch axis from the inside to the outside of the hub. Such an axial stop may for example be arranged at one end of the blade, this end being located inside the hub.

[0050] This axial stop can also be provided by another bearing of the guide device whose internal and external frames allow the absorption of centrifugal forces.

[0051] The guide device may comprise one or at least two bearings with cylindrical external and internal faces. Alternatively, the guide device may comprise at least one bearing with cylindrical external and internal faces and at least one bearing whose internal and external frames comprise, for example, respectively a conical external face and a conical internal face, or a toric external face and a toric internal face, or a spherical external face and a spherical internal face.

[0052] Alternatively or in a complementary manner, when a guide device comprises at least two bearings, the internal frame and the external frame of at least one of these at least two bearings may respectively comprise a flat external face and a flat internal face, the flat external face of the internal frame and the flat internal face of the external frame facing each other, the flat external face and the flat internal face being arranged perpendicular to the pitch axis.

[0053] The sliding layer is also planar and arranged perpendicular to the pitch axis.

[0054] Such a bearing, the internal and external frames of which are respectively provided with a flat external face and a flat internal face perpendicular to the pitch axis, makes it possible to obtain a flat connection. Consequently, such a bearing makes it possible to ensure mainly a recovery of centrifugal forces. This is why such a bearing is used in combination with another bearing of a different type, thus allowing a recovery of shear forces and bending moments in order to obtain a pivot-type connection between the blade and the hub.

[0055] The guide device may thus comprise a bearing whose internal and external frames respectively comprise a flat external face and a flat internal face, and at least one bearing whose internal and external frames respectively comprise a conical external face and a conical internal face, a toric external face and a toric internal face, a spherical external face and a spherical internal face or a cylindrical external face and a cylindrical internal face.

[0056] According to a possibility compatible with the previous ones, the internal frame of at least one bearing among said at least one bearing can be assembled directly to the blade.

[0057] According to a first embodiment, the internal frame of this bearing comprises a cavity, for example of square or circular section, in which the blade is positioned, and more precisely an area of ​​the blade called the “blade root”. This cavity of the internal frame can be assembled with a tight fit on the blade root, or even by shrink fitting, so as to secure the internal frame to the blade root at least in rotation, or even also in translation.

[0058] Alternatively, a securing device, at least in rotation, can be positioned between the bore and the blade root, such as a key, a flat for example, or even a cavity of square or rectangular section. A stop in translation along the pitch axis between the internal frame and the blade, in particular from the inside to the outside of the hub, is in the latter case ensured by an axial stop. An axial stop makes it possible to participate in the absorption of the centrifugal forces generated during the rotation of the hub around its axis of rotation, and consequently, makes it possible to limit the movement of the internal frame parallel to the pitch axis from the inside to the outside of the hub. Such an axial stop can be arranged on the blade root. A such axial thrust bearing may include, for example, one or more screws, one or more nuts, one or more pins, or even a shoulder on the blade root. A spacer may optionally be positioned between the axial thrust bearing and the internal frame of the bearing.

[0059] According to a second embodiment, the internal frame of this bearing comprises a body extending outside the hub on which the blade is fixed using an external fixing. The blade may for example comprise an orifice in which the body is positioned. Alternatively, the blade may comprise two sides separated by a space in which one end of the body is positioned, possibly provided with flat faces. The external fixing may comprise one or more screws, and / or one or more pins passing through the body of the internal frame and the blade, as well as possibly one or more nuts.

[0060] This second embodiment makes it possible to obtain simplified assembly and disassembly of the blade which are carried out entirely outside the hub using the external fixing, and in particular without intervening on the hub and without dismantling the guide device.

[0061] Alternatively, the internal frame of at least one bearing among said at least one bearing can be assembled to an intermediate shaft secured to the blade. For this purpose, the internal frame of this bearing comprises a bore in which the intermediate shaft is positioned. This bore of the internal frame can be assembled with a tight fit on the intermediate shaft, or even by shrink fitting, so as to secure the internal frame to this intermediate shaft.

[0062] Alternatively, a securing device, at least in rotation, can be positioned between the bore and the intermediate shaft, such as a key, a flat for example or others. As for the first embodiment previously described, a stop in translation along the pitch axis between the internal frame and the blade, in particular from the inside to the outside of the hub, is then ensured by an axial stop, also participating in the absorption of centrifugal forces as previously described.

[0063] The intermediate shaft extends outside the hub and is secured to the blade using an external fastener. The blade may, for example, have an orifice in which the intermediate shaft is positioned. Alternatively, the blade may have two sides separated by a space in which one end of the intermediate shaft, possibly provided with flat faces, is positioned. The external fastener may comprise one or more screws, and / or one or more pins passing through the intermediate shaft and the blade, as well as possibly one or more nuts.

[0064] This attachment of the blade to the intermediate shaft outside the hub also makes it possible to simplify the assembly and disassembly of the blade from the hub.

[0065] Furthermore, when the guide device comprises at least two bearings, an additional spacer can also be arranged between the two internal frames of two adjacent bearings in order to ensure continuity of contact between the axial stop and the internal frames of two bearings.

[0066] Furthermore, such an axial stop can also be used in the case of assembly with a tight fit of the internal frame on the blade root or on the intermediate shaft in order to have redundancy of the centrifugal force absorption function.

[0067] Furthermore, the assembly of the external frame of a bearing on the hub can be obtained by an assembly with a tight fit, or even by shrink fitting, so as to secure the external frame and the hub. A connecting device such as pins, screws or the like can be used alternatively or in addition.

[0068] According to a possibility compatible with the previous ones, when a guide device comprises at least two bearings, said at least two bearings can be assembled on the hub so that an axial clearance exists between the two external armatures of two adjacent bearings parallel to the pitch axis, one of these two external armatures being in axial abutment against the hub parallel to the pitch axis.

[0069] Thanks to this axial play, a single bearing is mainly involved in the absorption of centrifugal forces. The second bearing thus makes it possible to secure the guide device and ensure this absorption in the event of damage to the first bearing. Redundancy in the absorption of centrifugal forces is thus ensured.

[0070] The axial play can be defined by tests or simulations, or even calculations, so as to be less than or equal to the axial offset undergone by the first bearing under the repeated effects of centrifugal forces, combined with an acceptable level of wear of this first bearing. Indeed, following this axial offset between the internal and external reinforcements of the first bearing parallel to the pitch axis, the external reinforcement of the second bearing comes into contact with the external reinforcement of the first bearing, the second bearing then participating in turn in the absorption of centrifugal forces, and compensating for the degradation undergone by the first bearing.

[0071] According to a possibility compatible with the previous ones, the propeller may include an axial stop in order to limit the movement of the internal armature parallel to the pitch axis from the outside to the inside of the hub. Such an axial stop may be useful when the hub is not rotating, to maintain the blade in position relative to the hub from the outside to the inside of the hub and in particular to oppose the action of gravity on the blade. Such an axial stop may be obtained by a stop of the blade, the intermediate shaft or the internal armature on the hub, for example a shoulder of the blade resting on an external face of the hub, or an elastic ring attached to the blade, or by shrinking the blade or the intermediate shaft onto the internal armature, or any other stopping means.

[0072] The present invention also relates to an aircraft comprising at least one propeller as previously described.

[0073] The invention and its advantages will appear in more detail in the context of the description which follows with examples given for illustrative purposes with reference to the appended figures which represent: - [Fig.l], a propeller of an aircraft according to the invention, - [Fig.2], an aircraft comprising at least one propeller according to the invention, and - figures 3 to 11, partial sectional views of examples of propellers according to the invention.

[0074] Elements present in several distinct figures are assigned a single reference.

[0075] The propeller 1 shown in [Fig. 1] is intended for an aircraft, which may be fixed-wing and / or rotary-wing. For example, the aircraft 10 shown in [Fig. 2] comprises a rotary wing 12 and two propellers 1 according to the invention positioned on either side of a fuselage 11 of the aircraft 10. Alternatively, an aircraft 10 may comprise a single propeller 1 or more than two propellers 1.

[0076] Such a propeller 1 according to the invention comprises a hub 2 carrying at least two blades 3. The examples of propellers 1 shown in Figures 1 and 2 comprise six blades 3, although a different number of blades 3 can be used without compromising the implementation of the invention.

[0077] The blades 3 are driven by the hub 2 in rotation around the axis of rotation AXROT of the propeller 1. Each blade 3 can also rotate around its pitch axis AXP relative to the hub 2 in order to modify its pitch. This pitch axis AXP corresponds substantially to the longitudinal axis of the blade 3 and is oriented in a radial direction for the hub 2. A variation in the pitch of the blade 3 makes it possible to modify the incidence of the blade 3.

[0078] In order to modify the pitch of the blades 3, the propeller 1 may comprise a conventional pitch control system, not shown in the figures. Such a pitch control system may for example comprise a pitch lever per blade 3 cooperating with a pitch control device of the aircraft 1.

[0079] In order to allow the rotation of the blade 3 relative to the hub 2 around its pitch axis AXP, the propeller 1 comprises a guide device 4 per blade 3, arranged between the blade 3 and the hub 2. Each guide device 4 shown in the figures comprises at least one bearing 5, 6, and does not comprise any rolling bearing device. Figures 3 to 10 represent different examples of propellers 1 according to the invention comprising different guide devices 4. The different guide devices 4 may comprise various types of bearings 5, 6, which may also be installed in different ways relative to the hub 2.

[0080] Furthermore, a propeller 1 according to the invention may comprise one or more guide devices 4 provided with at least one bearing 5, 6, and possibly at least one rolling bearing device.

[0081] In a manner common to all these examples and with reference to [Fig. 6] for example, each bearing 5, 6 is provided with an internal frame 51, 61 and an external frame 52, 62 as well as a sliding layer 53, 63 located between the internal frame 51, 61 and the external frame 52, 62. The internal frame 51, 61 and the external frame 52, 62 are positioned around the pitch axis AXP, the internal frame 51, 61 being positioned between the external frame 52, 62 and this pitch axis AXP. The internal frame 51,61 is secured to the blade 3 while the external frame 52,62 is secured to the hub 2. Different usual securing devices can be used to secure the internal frame 51,61 to the blade 3 on the one hand and the external frame 52,62 to the hub 2 on the other hand.

[0082] The sliding layer 53, 63 may be viscous, or even liquid, and comprises a lubricating fluid. The sliding layer 53, 63 thus forms a lubricant film between the internal frame 51, 61 and the external frame 52, 62. The internal frame 51, 61 and external frame 52, 62 may, for example, in this case be metallic, and in particular porous.

[0083] Alternatively, the sliding layer 53,63 may be solid and comprise an anti-friction material. The sliding layer 53,63 may also be formed by an anti-friction surface treatment of the internal reinforcement 51,61 and / or the external reinforcement 52,62. The internal reinforcement 51,61 and external reinforcement 52,62 may for example be metallic in these two cases, or made of composite materials.

[0084] According to a first type of bearing 5, 6 shown in Figures 3, 4, 6 and 7, the internal frame 51, 61 and the external frame 52, 62 may respectively comprise a conical external face 511, 611 and a conical internal face 521, 621 facing each other, and separated by the sliding layer 53, 63. The conical external face 511, 611 and the conical internal face 521, 621 have the same axis of revolution which is the pitch axis AXP and have the same apex angle. The sliding layer 53, 63 is also conical in shape around the pitch axis AXP.

[0085] The conical external face 511,611 and the conical internal face 521,621 are tapered in a direction going from an interior space INT of the hub 2 towards an exterior space EXT of the hub 2 along the pitch axis AXP. The conical external face 511,611 and the conical internal face 521,621 are thus obtained respectively with straight and parallel generatrices between them, inclined with respect to the pitch axis AXP and secant to this pitch axis AXP, each generatrix approaching the pitch axis AXP going from the interior space INT towards the exterior space EXT. Such a bearing 5,6 of the first type thus allows a pivot type connection.

[0086] In this way, this bearing 5, 6 of the first type ensures on the one hand the rotational guidance of the blade 3 relative to the hub 2 around the pitch axis AXP of the blade 3, and on the other hand an axial stop of the blade 3 relative to the hub 2 radially with respect to the hub 2, namely along the pitch axis AXP, and from the internal space INT to the external space EXT. This bearing 5, 6 of the first type thus allows a take-up of the centrifugal forces generated by the blade 3 during its rotation around the rotation axis AXROT as well as bending moments and shear forces.

[0087] The guide device 4 may comprise a single bearing 5 of the first type, as shown in [Fig. 3] and [Fig. 4]. Alternatively, the guide device 4 may comprise two bearings 5, 6, including at least one bearing 5 of the first type and one bearing 6 of a different type, as shown in [Fig. 7], or even two bearings 5, 6 of the first type, as shown in [Fig. 6]. In the latter case where the guide device 4 may comprise two bearings 5, 6 of the first type, the conical external faces 511, 611 and the conical internal faces 521, 621 of the two bearings 5, 6 may have the same inclination relative to the pitch axis AXP or different inclinations relative to the pitch axis AXP.

[0088] According to a second type of bearing 5, 6 shown in Figures 5 and 8, the internal frame 51, 61 and the external frame 52, 62 may respectively comprise a toric external face 512, 612 and a toric internal face 522, 622 facing each other, and separated by the sliding layer 53, 63. The toric external face 512, 612 and the toric internal face 522, 622 have the same axis of revolution which is the pitch axis AXP.

[0089] The toric outer face 512,612 and the toric inner face 522,622 are formed respectively by the revolution of circular generators around the pitch axis AXP, each circular generator being centered, in the plane of FIGS. 5 and 8, respectively on the points PTR1, PTR2, PTR3 and PTR4. The sliding layer 53,63 is also of toric shape around the pitch axis AXP. Such a bearing 5,6 of the second type provided with toric outer faces 512,612 and toric inner faces 522,622 thus allows a pivot type connection.

[0090] In this way, this bearing 5, 6 of the second type ensures on the one hand the rotational guidance of the blade 3 relative to the hub 2 around the pitch axis AXP of the blade 3, and on the other hand an axial stop of the blade 3 relative to the hub 2 radially with respect to the hub 2, namely along the pitch axis AXP, and from the internal space INT to the external space EXT. This bearing 5, 6 of the second type thus allows a take-up of the centrifugal forces generated by the blade 3 during its rotation around the rotation axis AXROT as well as bending moments and shear forces.

[0091] The guide device 4 may comprise a single bearing 5 of the second type, as shown in [Fig. 5]. Alternatively, the guide device 4 may comprise two bearings 5, 6 of the second type, as shown in [Fig. 8], or even at least two bearings 5,6 including at least one bearing 5,6 of the second type, and at least one bearing 5,6 of a different type, for example the first type. In the case where the guide device 4 may comprise two bearings 5,6 of the second type, the toric external faces 512,612 and the toric internal faces 522,622 of the two bearings 5,6 may respectively have the same radii around the pitch axis AXP or different radii. Similarly, their circular generatrices may have the same radii or different radii around the points PTR1,PTR2 and the points PTR3,PTR4 respectively.

[0092] According to a third type of bearing 5, 6 shown in Figures 7 and 9, the internal frame 51, 61 and the external frame 52, 62 may respectively comprise a spherical external face 513, 613 and a spherical internal face 523, 623 facing each other, and separated by the sliding layer 53, 63. The spherical external face 513, 613 and the spherical internal face 523, 623 have the same center of revolution PTR, PTR' which is on the pitch axis AXP. The sliding layer 53, 63 is also spherical in shape around the same center of revolution PTR, PTR'. Such a bearing 5, 6 of the third type thus allows a ball-and-socket type connection between its internal 51, 61 and external 52, 62 frames.

[0093] In this way, this bearing 5, 6 of the third type ensures on the one hand the rotational guidance of the blade 3 relative to the hub 2 around the pitch axis AXP, and on the other hand an axial stop of the blade 3 relative to the hub 2 radially with respect to the hub 2, namely along the pitch axis AXP, and from the internal space INT to the external space EXT. The bearing 5, 6 of the third type thus mainly allows a take-up of the centrifugal forces generated by the blade 3 during its rotation around the rotation axis AXROT, but no take-up of the bending moments and shear forces.

[0094] Such a bearing 5, 6 of the third type must therefore be used in a guide device 4 comprising a combination of at least two bearings 5, 6. The guide device 4 may comprise a combination of two such bearings 5, 6 of the third type, as shown in [Fig. 9]. Alternatively, the guide device 4 may comprise such a bearing 6 of the third type, combined with another bearing 5 of another type, for example of the first type, as shown in [Fig. 7], or even of the second type. In the case where the guide device 4 may comprise two bearings 5, 6 of the third type, the spherical external faces 513, 613 and the spherical internal faces 523, 623 of the two bearings 5, 6 may have the same radii respectively around the centers of revolution PTR, PTR' or different radii.

[0095] According to a fourth type of bearing 5,6 shown in Figures 10 and 11, the internal frame 51,61 and the external frame 52,62 may respectively comprise a cylindrical external face 514,614 and a cylindrical internal face 524,624 facing each other, and separated by the sliding layer 53,63. The cylindrical external face 514,614 and the cylindrical inner face 524,624 have the same axis of revolution which is the pitch axis AXP. The cylindrical outer face and the cylindrical inner face are parallel to each other and defined by a generator parallel to the pitch axis AXP. The sliding layer 53,63 is also cylindrical in shape around the pitch axis AXP. Such a bearing 5,6 of the fourth type thus allows a sliding pivot type connection between its internal 51,61 and external 52,62 frames.

[0096] In this way, this bearing 5,6 of the fourth type ensures on the one hand the rotational guidance of the blade 3 relative to the hub 2 around the pitch axis AXP. This bearing 5,6 of the fourth type thus allows only the bending moments and shear forces to be taken up, but not the centrifugal forces generated by the blade 3 during its rotation around the rotation axis AXROT.

[0097] The guide device 4 may then comprise two such bearings 5, 6 of the fourth type in combination with a device for absorbing centrifugal forces as shown in [Fig. 10], or even a single bearing 5 of this fourth type. The device for absorbing centrifugal forces may for example comprise an axial stop 8, possibly combined with one or more spacers 55, 65 and a shoulder 34 of the blade.

[0098] The guide device 4 may comprise a combination of two bearings 5, 6, including a bearing 6 of the fourth type, and another bearing 5 of another type allowing the absorption of centrifugal forces as shown in [Fig. 1 1]. Such another bearing 5 allowing the absorption of centrifugal forces may for example be of the first, second or third type, or even of a different type.

[0099] According to a fifth type of bearing 5 shown in [Fig.l 1], the internal frame 51 and the external frame 52 may respectively comprise a flat external face 515 and a flat internal face 525 facing each other, and separated by the sliding layer 53. The flat external face 515 and the flat internal face 525 are arranged perpendicular to the pitch axis AXP. The sliding layer 53 is also of planar shape and arranged perpendicular to the pitch axis AXP. The flat external face 515 and the flat internal face 525 as well as the sliding layer 53 are parallel to each other and defined by a generatrix perpendicular to the pitch axis AXP.

[0100] In this way, this bearing 5 of the fifth type mainly ensures an axial stop of the blade 3 relative to the hub 2 along the pitch axis AXP, and from the internal space INT to the external space EXT. This bearing 5 of the fifth type thus allows a recovery of the centrifugal forces generated by the blade 3 during its rotation around the axis of rotation AXROT.

[0101] The guide device 4 then comprises such a bearing 5 of the fifth type, in combination with another bearing 6 allowing at least the rotational guidance of the blade 3 relative to the hub 2 around the pitch axis AXP. The guide device 4 can thus comprise two bearings 5,6, including at least one bearing 5 of the fifth type and one bearing 6 of the fourth type, as shown in [Fig. 11]. Alternatively, the guide device 4 can also comprise two bearings 5,6, including at least one bearing 5 of the fifth type and one bearing 6 of another type, for example of the first, second or third type.

[0102] The guide device 4 can thus comprise a single bearing 5, as shown in FIGS. 3 to 5. Alternatively, the guide device 4 can comprise a combination of at least two bearings 5, 6 of the same type or of different types, as shown in FIGS. 6 to 11.

[0103] A bearing 4,5 may therefore comprise an internal frame 51,61, an external frame 52,62 and a sliding layer 53,63 which are, as described previously, of the same shape, namely conical, toric, spherical, cylindrical or planar, in order to cooperate with each other. Alternatively, a bearing 4,5 may comprise an internal frame 51,61 and an external frame 52,62 having faces of different shapes, among conical, toric, spherical, cylindrical or planar faces, the sliding layer 53,63 then being of a non-regular thickness to allow these faces of different shapes to cooperate with each other.

[0104] Regardless of the number of bearings 5, 6 that the guide device 4 comprises and of the type of bearings 5, 6, the guide device 4 can be arranged in different ways with the hub 2.

[0105] For example, the guide device 4 may be arranged entirely inside the hub 2, as shown in FIGS. 3 to 8, 10 and 11. Alternatively, when the guide device 4 comprises at least two bearings 5, 6, at least one bearing 5 may be arranged inside the hub 2 and another bearing 6 may be arranged outside the hub 2 as shown in [Fig.9].

[0106] Furthermore, the external frame 52, 62 of the bearing 5, 6 can be secured to the hub 2 by various usual securing devices which may be combined. For example, the external frame 52, 62 can be secured to the hub 2 by shrink fitting, namely using a tight fit, as shown in FIGS. 3 and 7. Alternatively, or in a complementary manner, the external frame 52, 62 can be secured to the hub 2 for example using pins 25 or in an equivalent manner using screws and possibly nuts. In addition, the external frame 52 of a bearing 5 is axially supported on the hub 2, from the internal space INT to the external space EXT. This axial support allows the centrifugal forces generated by the blade 3 during the rotation of the hub 2 to be taken up and the transfer of these centrifugal forces to the hub 2.

[0107] Furthermore, the internal frame 51, 61 of the bearing 5, 6 can be assembled directly to the blade 3, or via an intermediate part, a sleeve for example.

[0108] For example, according to a first embodiment, the internal frame 51, 61 can be assembled to a blade root 31 of the blade 3, using a bore in the internal frame 51, 61 in which the blade root 31 is positioned. The connection of the internal frame 51, 61 and the blade root 31 can thus be obtained by shrink fitting, as shown in FIGS. 3 and 6 to 11. Alternatively, or in a complementary manner, a key can for example be positioned between the internal frame 51, 61 and the blade root 31 or a flat can be used.

[0109] In this case, the propeller comprises an axial stop 8 attached to the blade root 31 in order to form a translation stop along the pitch axis AXP between the internal frame 51, 61 and the blade 3, from the internal space INT to the external space EXT. This axial stop 8 also contributes to the absorption of centrifugal forces. Such an axial stop 8 may comprise, for example, a pin positioned in a hole passing radially through the blade root 31. The axial stop 8 may also comprise a screw, a nut, or any other translation stop device.

[0110] The axial stop 8 may bear along the pitch axis AXP directly against the internal frame 51, 61 of the or one of the bearings 5, 6 of the guide device 4, as shown in FIGS. 3, 6 and 7. A spacer 55, 65 may optionally be inserted between the axial stop 8 and the internal frame 51, 61 of the bearing 5, 6, as shown in FIGS. 8 to 11. In the case where the guide device 4 comprises at least two bearings 5, 6, a spacer 55, 65 may also be inserted between the internal frames 51, 61 of two adjacent bearings 5, 6. Each spacer 55, 65 thus makes it possible to transmit the centrifugal forces from the axial stop 8 to the internal frame(s) 51, 61.

[0111] According to a second embodiment, the internal frame 51 of a bearing 5 may comprise a body 59 extending outside the hub 2 as shown in [Fig.4]. This body 59 may form a single piece with the internal frame 51. Alternatively, the body 59 may be a separate piece from the internal frame 51 and secured to it by conventional means. The blade 3 is then fixed to the body 59 in the external space EXT by an external fixing 35. The external fixing 35 may for example comprise one or more screws, and / or one or more rods inserted into orifices passing through the body 59 and the blade 3. The external fixing 35 may optionally also comprise one or more nuts.

[0112] The internal frame 51, 61 of the bearing 5, 6 can alternatively be assembled to the blade 3 using an intermediate shaft 9. This intermediate shaft 9 is thus secured on the one hand to the internal frame 51, 61 of the bearing(s) 5, 6 of the guide device 4, and on the other hand to the blade 3. This intermediate shaft 9 can for example be assembled by shrink-fitting in a bore of the internal frame 51, 61. The blade 3 is fixed to the shaft intermediate 9 in the external space EXT by an external fixation 35 as previously described.

[0113] Regardless of the method of securing the blade 3 and the internal frame 51, 61, the propeller 1 may include an axial stop in order to limit the movement of the internal frame parallel to the pitch axis AXP from the external space EXT to the internal space INT. Such an axial stop may include, for example, a shoulder 33 of the blade 3 capable of bearing on an external face 22 of the hub 2, or be obtained using an elastic ring attached to the blade 3 or any other stopping means.

[0114] Furthermore, when the guide device 4 comprises at least two bearings 5, 6, the external armatures 52, 62 of two adjacent bearings 5, 6 can be assembled so as to be in contact with each other parallel to the pitch axis, namely assembled without axial play between them, as shown in FIGS. 8, 10 and 11. Consequently, the two adjacent bearings 5, 6 contribute simultaneously to the absorption in particular of the centrifugal forces. These centrifugal forces are thus distributed between these two adjacent bearings 5, 6, which are in fact less stressed before being transferred to the hub 2, via the external armature 52 of the bearing 5 in axial support on the hub 2.

[0115] Alternatively, a non-zero axial clearance J may be present between the external frames 52, 62 of two adjacent bearings 5, 6 during their assembly, as shown in FIGS. 6 and 7. In this case, the first bearing 5 whose external frame 52 is in axial support on the hub 2 mainly ensures alone the absorption of the centrifugal forces generated by the blade 3 during the rotation of the hub 2 and the transfer of these centrifugal forces towards the hub 2. The second bearing 6 is little, if at all, stressed by these centrifugal forces.

[0116] This first bearing 5 is therefore highly subjected to centrifugal forces and may be susceptible to degrade slowly to the point of causing a shift between its internal 51 and external 52 reinforcements. This axial shift between the internal 51 and external 52 reinforcements of the first bearing 5 has the effect of reducing the value of the axial clearance J. When this axial clearance J becomes zero, the external reinforcements 52, 62 of the two bearings 5, 6 are then in contact and the two bearings 5, 6 ensure the absorption of centrifugal forces, thus avoiding greater degradation of the first bearing 5, and consequently, a greater axial shift between the internal 51 and external 52 reinforcements of this first bearing 5. The second bearing 6 thus makes it possible to secure the guide device 4 and to ensure redundancy in the function of absorbing centrifugal forces.

[0117] Naturally, the present invention is subject to numerous variations as to its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all the embodiments possible. It is of course possible to replace a means described by an equivalent means without departing from the scope of the present invention.

Claims

Claims

1. Propeller (1) for aircraft (10) comprising: - a hub (2), - at least two blades (3), each of said blades (3) being rotatable about a pitch axis (AXP) of said blade (3) relative to said hub (2), and - a guide device (4) per blade (3), each guide device (4) guiding said blade (3) in rotation about its pitch axis (AXP) relative to said hub (2), each guide device (4) being arranged between said hub (2) and said blade (3), characterized in that each guide device (4) comprises at least one bearing (5, 6), said at least one bearing (5, 6) being provided with an internal frame (51, 61) and an external frame (52, 62) as well as a sliding layer (53, 63) located between said internal frame (51, 61) and said external frame (52,62), said internal frame (51,61) being integral with said blade (3), said external frame (52,62) being integral with said hub (2).

2. Propeller (1) according to claim 1, characterized in that at least one guide device (4) is arranged entirely inside the hub (2).

3. Propeller (1) according to claim 1, characterized in that a guide device (4) comprises at least two bearings (5, 6), at least one of said bearings (5, 6) being arranged inside the hub (2) and at least one of said bearings (5, 6) being arranged outside the hub (2).

4. Propeller (1) according to any one of claims 1 to 3, characterized in that the internal frame (51, 61) and the external frame (52, 62) of at least one bearing (5, 6) among said at least one bearing (5, 6) respectively comprise a conical external face (511, 611) and a conical internal face (521, 621), said conical external face (511, 611) of the internal frame (51, 61) and said conical internal face (521, 621) of the external frame (52, 62) facing each other, said conical external face (511, 611) and said conical internal face (521, 621) having as a common axis of revolution said pitch axis (AXP), said conical external face (511, 611) and said internal face conical (521,621) being formed by circles centered on said pitch axis (AXP) whose diameter decreases from the inside to the outside of said hub (2).

5. Propeller (1) according to any one of claims 1 to 4, characterized in that the internal frame (51, 61) and the external frame (52, 62) of at least one bearing (5, 6) among said at least one bearing (5, 6) respectively comprise a toric external face (512, 612) and a toric internal face (522, 622), said toric external face (512, 612) of the internal frame (51, 61) and said toric internal face (522, 622) of the external frame (52, 62) facing each other, said toric external face (512, 612) and said toric internal face (522, 622) having as common axis of revolution said pitch axis (AXP) and being formed respectively by the revolution of circular generatrices around said pitch axis (AXP).

6. Propeller (1) according to any one of claims 1 to 5, characterized in that a guide device (4) comprises at least two bearings (5, 6), and the internal frame (51, 61) and the external frame (52, 62) of at least one bearing (5, 6) among said at least two bearings (5, 6) respectively comprise a spherical external face (513, 613) and a spherical internal face (523, 623), said spherical external face (513, 613) of the internal frame (51, 61) and said spherical internal face (513, 613) of the external frame (52, 62) facing each other, said spherical external face (513, 613) and said spherical internal face (523, 623) having as a common center of revolution a point of said pitch axis (AXP).

7. Propeller (1) according to any one of claims 1 to 6, characterized in that the internal frame (51,61) and the external frame (52,62) of at least one bearing (5,6) among said at least one bearing (5,6) respectively comprise a cylindrical external face (514,614) and a cylindrical internal face (524,624), said cylindrical external face (514,614) of the internal frame (51,61) and said cylindrical internal face (524,624) of the external frame (52,62) facing each other, said cylindrical external face (514,614) and said cylindrical internal face (524,624) having as common axis of revolution said pitch axis (AXP).

8. Propeller (1) according to any one of claims 1 to 7, characterized in that a guide device (4) comprises two bearings (5, 6), the internal frame (51, 61) and the external frame (52, 62) of at least one bearing (5,6) among said at least two bearings (5,6) respectively comprise a flat external face (515,615) and a flat internal face (525,625), said flat external face (515,615) of the internal frame (51,61) and said flat internal face (525,625) of the external frame (52,62) facing each other, said flat external face (515,615) and said flat internal face (525,625) being arranged perpendicular to said pitch axis (AXP).

9. Propeller (1) according to claim 4, characterized in that a guide device (4) comprises two bearings (5, 6) of which the internal frame (51, 61) and the external frame (52, 62) respectively comprise said conical external face (511, 611) and said conical internal face (521, 621).

10. Propeller (1) according to claim 6, characterized in that said guide device (4) comprises two bearings of which the internal frame (51,61) and the external frame (52,62) respectively comprise said spherical external face (513,613) and said spherical internal face (523,623).

11. Propeller (1) according to any one of claims 1 to 10, characterized in that the internal frame (51, 61) of at least one bearing (5, 6) among said at least one bearing (5, 6) is assembled to said blade (3) outside said hub (2) using an external fixing (35).

12. Propeller (1) according to any one of claims 1 to 10, characterized in that the internal frame (51, 61) of at least one bearing (5, 6) among said at least one bearing (5, 6) is assembled to an intermediate shaft (9) secured to said blade (3).

13. Propeller (1) according to claim 12, characterized in that said intermediate shaft (9) is secured to said blade (3) outside said hub (2), using an external fixing (35).

14. Propeller (1) according to claim 12, characterized in that said intermediate shaft (9) is secured to said blade (3) and said guide device (4) comprises an axial stop (8), said axial stop (8) causing a translational stop of said blade (3) relative to said hub (2) along said pitch axis (AXP) from the inside to the outside of said hub (2).

15. Propeller (1) according to any one of claims 1 to 10, characterized in that the internal frame (51, 61) of at least one bearing (5, 6) among said at least one bearing (5, 6) is assembled to said blade (3) inside said hub (2) and said guide device (4) comprises an axial stop (8), said axial stop (8) causing a translational stop of said blade (3) relative to said hub (2) along said pitch axis (AXP) from the inside to the outside of said hub (2).

16. Propeller (1) according to any one of claims 1 to 15, characterized in that said sliding layer (53, 63) comprises a lubricating fluid, an anti-friction material and / or an anti-friction surface treatment.

17. Aircraft (10) comprising at least one propeller (1) according to any one of claims 1 to 16.

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