Directionally adjustable and integrity protected blade pivot for turbine fan hub

Abstract

The invention relates to a direction-adjustable blade pivot (2) for a turbine fan hub, comprising: a contact pad (4) having an attachment piece (10) configured to hold a fan blade root (12) and a connection device (16) for transmitting torque; a spherical roller bearing (26) that absorbs centrifugal forces and has an inner ring (28) and an outer ring (30); a first clamping nut (50) for screwing to an inner thread (8A) of the fan hub to clamp the outer ring of the spherical roller bearing; a roller bearing (34) that absorbs lateral forces and has an inner ring (36) and a smooth outer ring (38); a wedge ring (44) mounted between the inner rings (28, 36) to provide corresponding lateral support to these inner rings; a break-resistant sleeve (42) that carries the inner ring (36) of the roller bearing that absorbs lateral forces, and whose terminal end extends laterally beyond the outer ring (38) of the bearing so as to constitute a stop when the contact pad is displaced radially; and a second clamping nut (52) that screws to an outer thread (4A) of the contact pad to clamp the inner ring of the roller bearing that absorbs centrifugal forces and the inner ring of the roller bearing that absorbs lateral forces.

Description

Technical Field

[0001] The present invention relates to the general field of turbines equipped with at least one shrouded or unshrouded fan, wherein the fan blades (for shrouded fans) or propeller blades (for unshrouded fans) are equipped with a pitch setting system, and more specifically to the directional control of the fan blades of such turbines.

[0002] A preferred application of the present invention is a turbojet engine, which includes a shrouded fan with a high bypass ratio (large fan diameter) and an extremely low pressure ratio. Existing technology

[0003] By introducing variability into the low-pressure module of the turbojet engine, the operability of the turbojet engine with a high bypass ratio is ensured. This variability is activated according to the flight phase to restore sufficient pumping margin.

[0004] It is known to use variable pitch systems with fan blades integrated into the fan hub to provide variability. Such blade-based variable pitch systems can also provide thrust reversal capabilities, a feature no longer present in the engine nacelles of such turbojet engines.

[0005] Furthermore, in the fan module of a turbojet engine with a high bypass ratio, the shape of the blade root and the receiving blade socket, the pivot and its rolling bearings to absorb the force on the blade, the fan blades to provide the radial holding force of the fan blades, and the pivot assembly integrated in the fan blades.

[0006] For example, reference may be made to disclosure FR 3046403, which describes an example of such a fan blade retaining structure. More precisely, in this disclosure, the radial retaining of each blade includes a pivot and two ball bearings, the pivot comprising fasteners in the form of spherical objects, the ball bearings absorbing aerodynamic forces, inertial forces, and centrifugal forces borne by the blade and its pivot, an eccentric wheel splined to the pivot, and a hub of an integrated pivot assembly.

[0007] For this type of structure, the size of the fan hub depends directly on the integration of the blade pitch mechanism and also on the size of the rolling bearings of each pivot.

[0008] In fact, in the structure described in disclosure FR 3046403, the inner rolling bearing absorbs all the centrifugal forces experienced by the blades and their pivots. To minimize the lateral forces borne by this bearing, the inner and outer rolling bearings are radially spaced considerably apart. Therefore, the inner rolling bearing is not only the largest but also placed on a very small radius of the hub, making the tangential space between the inner rolling bearings of two adjacent blades very limited. This, in turn, affects the diameter of the fan hub.

[0009] However, in order to optimize the efficiency of turbojet engine fans with high bypass ratios, it is necessary to minimize the diameter of the fan hub and / or integrate a greater number of blades with a hub of the same size. Summary of the Invention

[0010] Therefore, the object of the present invention is to provide a structure with a smaller volume for the pivot and its rolling bearing.

[0011] Another object of the present invention is to provide a structure that can ensure the retention of the blade under all conditions, particularly the retention of its rolling elements, even in the event of rolling element breakage. In fact, dimensional markings of the debris retention system (aircraft protective layer or engine retaining housing) on ​​all released debris, and ensuring the retention of the rolling elements, can limit the dimensional markings of the aircraft protective layer to the mass of the blade alone.

[0012] According to the present invention, this objective is achieved by a turbine fan hub with an adjustable blade pivot, the blade pivot comprising:

[0013] - A stud having a fastener at a first end configured to hold the root of a fan blade and a connecting device at a second end for transmitting torsional torque;

[0014] - A ball bearing for absorbing centrifugal force, having an inner ring laterally mounted and supported on the outer shoulder of a stud, and an outer ring laterally mounted and supported on the inner side of a fan hub.

[0015] - The first clamping nut is screwed into the internal thread of the fan hub to ensure that the outer ring of the ball bearing that absorbs centrifugal force is clamped.

[0016] - A rolling bearing that absorbs lateral forces, having an inner ring and a smooth outer ring for laterally mounting and supporting the fan hub.

[0017] - A locking ring, which is installed between the inner ring of the ball bearing that absorbs centrifugal force and the inner ring of the rolling bearing that absorbs lateral force, to ensure corresponding lateral support for these inner rings;

[0018] - A fracture-resistant sleeve for the inner ring of a rolling bearing that absorbs lateral forces, the end of which extends laterally beyond the outer ring of the rolling bearing to absorb lateral forces, so as to form a stop block when the stud moves radially; and

[0019] - Tighten the second clamping nut to the external thread of the stud to ensure clamping of the inner ring of the ball bearing that absorbs centrifugal force and the inner ring of the rolling bearing that absorbs lateral force.

[0020] Notably, this invention proposes a ball bearing with four contact points, which is radially positioned as far as possible from the engine shaft to benefit from maximum space and thus its size allows it to absorb centrifugal forces experienced by the blades and their pivot.

[0021] Similarly, due to its structure that prevents ball bearing failure, it can maintain these rolling elements that absorb centrifugal force even when the rolling elements break (fail-safe function). Therefore, the blades, pivot, and rolling elements as a whole lose self-control upon fracture, which is possible with existing pivots, and the ejected component does not produce high-energy debris that causes serious damage to the engine, and therefore more typically to the flight mission.

[0022] Any breakage of the ball bearing occurs at the contact guard blade pivot formed between the outer ring of the rolling bearing and the fracture-resistant component.

[0023] For lateral forces smaller than centrifugal force, they are absorbed by needle roller or roller bearings, which enables precise guidance and improves tightness.

[0024] Preferably, the fracture-resistant sleeve extends sequentially to a cylindrical portion, followed by an outwardly flared tapered portion including the end, and the junction between these two portions forms a lateral support for the inner ring of the rolling bearing that absorbs lateral forces.

[0025] The pivot may further include a position sensor positioned facing the end of the fracture-resistant sleeve and used to detect any radial movement of the stud, such as due to the breakage of a ball bearing that absorbs centrifugal force.

[0026] Advantageously, the locking ring installed between the inner ring of the ball bearing that absorbs centrifugal force and the inner ring of the rolling bearing that absorbs lateral force can be a centrifugal fusible ring.

[0027] Preferably, the fracture-resistant sleeve is retracted onto the pivot.

[0028] Advantageously, the inner ring of the ball bearing that absorbs centrifugal force and the inner ring of the rolling bearing that absorbs lateral force are clamped by the second clamping nut via the anti-fracture sleeve and the locking ring.

[0029] Preferably, the inner and outer rings of the ball bearing that absorbs centrifugal force are manufactured in two different parts to facilitate the installation of the pivot.

[0030] The invention also includes a turbine fan comprising at least one directionally adjustable blade, the hub of which is mounted on a pivot as defined above, and a turbine comprising such a fan.

[0031] The present invention also includes a method for mounting a pivot as defined above, comprising: lowering the pivot into a fan hub; mounting a ball bearing for absorbing centrifugal force to a first end of a stud; clamping the ball bearing for absorbing centrifugal force by screwing a first clamping nut onto the internal thread of the hub; mounting a retaining ring that carries a smooth outer ring of a rolling bearing for absorbing lateral force, which is laterally supported inside the hub; mounting a fracture-resistant sleeve to a second end of the stud, the fracture-resistant sleeve carrying the remaining portion of the rolling bearing for absorbing lateral force and a fusible locking ring; and clamping the rolling bearing for absorbing lateral force by screwing a second clamping nut.

[0032] Brief description of the attached figures

[0033] Figure 1 shows a cross-sectional view of an directional adjustable blade pivot according to an embodiment of the present invention.

[0034] Figures 2A-2F show an example of mounting a pivot according to the embodiment of Figure 1.

[0035] Figure 3 illustrates the construction of the pivot according to the invention during normal operation.

[0036] Figure 4 illustrates the construction of the pivot according to the present invention in the event of a failure. Detailed Implementation

[0037] Figure 1 shows a blade pivot comprising several different elements assembled together to facilitate the installation / removal of these elements in a rotating fan blade hub, and its function is to ensure that the fan blades are held on this rotating hub and to guide them in setting their pitch.

[0038] As is well known, the pivot of each fan blade is radially mounted in an opening in the fan hub that runs from one side to the other, with the center of the hub on the longitudinal axis of the turbojet engine. Its structure is well known to those skilled in the art and will not be described in detail here.

[0039] According to the invention, the pivot 2 includes a stud 4 extending along the radial axis ZZ of the pivot through an opening 6 in the hub 8 of the fan. The stud 4 has a fastener 10 in the form of a ball at its outer radial end (i.e., at its end furthest from the longitudinal axis of the turbojet engine) for receiving the root 12 of the fan blades. Of course, other methods of retaining the blade roots are also possible.

[0040] At its inner radial end (i.e., at its end closest to the longitudinal axis of the turbojet engine), the stud 4 includes an external spline 16 for transmitting torsional torque to the eccentric wheel 18 (also referred to as the "set transmission ring"), and is also equipped with a spline 20 carried on the inner surface for engaging with the external spline 16 of the stud 4. Of course, other connecting devices for transmitting torsional torque can be considered.

[0041] This setting transmission ring 18 is used to transmit torsional torque to the blade pivot to change its pitch setting. The setting transmission ring 18 is locked to the stud by a screw 22 centered on the radial axis ZZ and a nut 24 clamped on the screw.

[0042] The pivot also includes rolling bearings for absorbing the centrifugal force (i.e., along the radial axis ZZ) and lateral force (i.e., along the plane perpendicular to the radial axis ZZ) experienced by the blades and their pivot.

[0043] More precisely, the pivot includes a ball bearing 26 for absorbing centrifugal force. This ball bearing 26 is equipped with an inner ring 28, which is laterally mounted and supported on the outer shoulder of the stud 4.

[0044] Preferably, the inner ring 28 is formed by two distinct portions 28a and 28b. This feature facilitates the installation of the pivot, as will be described in detail later.

[0045] The ball bearing 26 also includes an outer ring 30 for laterally mounting and supporting inside the opening 6 of the fan hub 8, and can also be formed in two different portions 30a, 30b to facilitate pivot mounting. The inner ring 28 and the outer ring 30 define the rolling path of a plurality of balls 32 held in the central cage 32A.

[0046] To absorb lateral forces, the pivot also includes a needle or roller bearing 34 that is radially offset inward relative to the ball bearing 26.

[0047] The needle roller or roller bearing 34 includes an inner ring 36 and a smooth outer ring 38, which define the rolling path of a plurality of needle rollers or rollers 40 that may be held in a central cage.

[0048] More precisely, the inner ring 36 is mounted on the fracture-resistant sleeve 42, which retracts onto the stud 4 and sequentially comprises, along the ZZ axis, a cylindrical portion 42A, a transverse support portion 42B of the inner ring 36, and an outwardly flared tapered portion 42C. The transverse support portion 42B is further pressurized by a locking ring 44, advantageously centrifugally fused, and its dimensions can be calibrated so that the ring begins to burn under a certain centrifugal force. By detecting the radial force capable of damaging these rolling paths, the fused stop ring can be used as an indicator of the rolling path condition. In fact, if a large radial force is present, the fusible ring will be damaged, which is detected by at least one of the aforementioned sensors.

[0049] The smooth outer ring 38 itself is laterally mounted and supported inside the opening 6 of the fan hub 8 via a flexible flange or a perforated support ring 46, which is attached to the circumference of the hub 8 by screws, as shown by screw holes 47.

[0050] The advantage of the perforated support ring 46 (or serrated ring, if considered) is that it allows the smooth outer ring 38 to be flexible, which prevents vibrations from propagating into the rest of the pitch setting system during flight, such as impacts from external components on the fan blades. For example, by retaining the outer ring of the bearing, an anti-rotation ring or resilient clamping ring 48 of the "elastic retainer" type can lock this ring in place.

[0051] The tapered portion of the fracture-resistant sleeve includes a terminal 42D that extends laterally beyond the smooth outer ring 38 of the rolling bearing that absorbs lateral forces, thereby forming a stop block when the stud moves radially. This terminal portion then contacts the smooth outer ring, which is itself laterally supported on the hub 8 of the fan.

[0052] The first clamping nut 50, which is screwed onto the internal thread 8A of the hub 8, ensures that the outer ring 30 of the ball bearing 26, which absorbs centrifugal force, is clamped thereon.

[0053] The second clamping nut 52 is screwed onto the external thread 4A of the stud 4, thereby ensuring that the inner ring 28 of the ball bearing 26, which absorbs centrifugal force, is clamped onto the stud by a continuous support chain formed by the fracture-resistant sleeve 42, the inner ring 36 of the needle or roller bearing 34, and the locking ring 44.

[0054] A position sensor 54 is placed further facing the end 42D of the fracture-resistant sleeve 42 to detect the breakage of the ball bearing 26. In fact, the position sensor will detect signal changes or loss caused by radial movement of the fracture-resistant sleeve.

[0055] However, it should be noted that an engine imbalance detector can also detect this fault, as a bearing failure causes the blade root to shift, resulting in an imbalance on the rotor (however, if the fault only involves a single pivot).

[0056] Similarly, in the event of a bent fusible locking ring, the fracture-resistant sleeve will no longer face the position sensor. This could, for example, detect overspeed. In fact, a fan with a pitch setting could pass through a setting where the fan no longer consumes power and strongly accelerates overspeed propulsion.

[0057] Referring to Figures 2A to 2F, an example of installing the pivot according to the present invention will now be described.

[0058] In the first step shown in Figure 2A, the outer half ring 30a of the ball bearing 26 is mounted laterally and supported inside the opening 6 of the fan hub 8 (e.g., to retract it).

[0059] Then, as shown in Figure 2B, the stud 4 is radially lowered into the opening 6 of the hub 8, the stud previously equipped (e.g., by shrinking) with the inner half ring 28A of the ball bearing 26.

[0060] In the third step shown in Figure 2C, the other inner half ring 28b of the ball bearing 26 is then installed to form the inner ring 28, and then the balls 32 of the rolling bearing are installed together with its cage 32A.

[0061] In the step of Figure 2D, the outer half ring 30B of the ball bearing 26 is then installed and retained by clamping the first clamping nut 50.

[0062] In the following steps (Figure 2E), the smooth outer ring 38 of the needle roller or roller bearing 34 and the support ring 46 are sequentially installed inside the opening 6 of the fan hub 8. The support ring 46 is fastened to the hub 8 by screws (screw holes 47), and the assembly is locked in place by the anti-rotation ring 48.

[0063] Then in step 2F, the smooth outer ring 38 of the needle or roller bearing 34 and a plurality of rolling elements around the stud 4 engage with the locking ring 44 previously mounted on the anti-breakage sleeve 42 before being locked by clamping the second clamping nut 52.

[0064] Finally, in the final step (corresponding to Figure 1), the root 12 of the blade can be installed in a fastener 10 in the form of a ball provided at the outer radial end of the stud 4. It is understood that the transmission ring 18 has been previously installed at the end of the stud 4 by engaging its respective splines 16, 20, and locked by the mounting screw 22 and the clamping nut 24.

[0065] Figures 3 and 4 illustrate the construction of the pivot according to the invention under normal operation and in the event of a malfunction, respectively.

[0066] In the normal operating position, position sensor 54 is placed facing the end 42D of the tapered portion of the fracture-resistant sleeve. Label 60 indicates the radial load applied to the pivot, and label 62 indicates the load transfer towards the hub. It should be noted that the second clamping nut 52 located on the pivot will obstruct the entire assembly.

[0067] In the location of the failure, for the locking ring 44 (but this would be equivalent to the case of a broken ball bearing 26), radial outward movement of the component group connected to the pivot is observed, particularly the sliding of the roller 40 on the smooth outer ring 38. It should be noted that the ball 32 is adjacent to the remaining half-circle; however, radial load can still be transmitted toward the hub 8.

[0068] The offset of the anti-fracture sleeve relative to the position sensor can identify that the pivot is no longer in its normal operating position. The anti-fracture sleeve prevents further movement of the pivot that would otherwise be adjacent to the rolling support and thus avoid any component loss.

[0069] It is important to note that it is possible to place the fused elements at an angle and unevenly distributed only on certain blades. Therefore, only a portion of the blades will experience combustion of their fused components, resulting in an imbalance that may be detected by the engine's standard imbalance sensors.

[0070] It will also be noted that the position sensor can also be used as a pitch setting sensor, which avoids integrating additional sensors in already congested areas.

Claims

1. A turbine fan hub-oriented blade pivot, comprising: - A stud, having a fastener at a first end configured to retain the root of a fan blade, and a connection device at a second end for transmitting torsional torque; - A ball bearing for absorbing centrifugal force, the ball bearing for absorbing centrifugal force having an inner ring that is laterally mounted and supported on the outer shoulder of the stud, and an outer ring that is laterally mounted and supported on the inner side of the fan hub. - A first clamping nut, which is screwed into the internal thread of the fan hub to ensure clamping of the outer ring of the ball bearing that absorbs centrifugal force; - A rolling bearing for absorbing lateral forces, the rolling bearing having an inner ring and a smooth outer ring for laterally mounting and supporting the fan hub. - A locking ring, which is installed between the inner ring of the ball bearing that absorbs centrifugal force and the inner ring of the rolling bearing that absorbs lateral force, to ensure corresponding lateral support for these inner rings; - A fracture-resistant sleeve supporting the inner ring of the rolling bearing that absorbs lateral forces, the end of the fracture-resistant sleeve extending laterally beyond the outer ring of the rolling bearing that absorbs lateral forces, so as to form a stop block in the event of radial movement of the stud; and - A second clamping nut is screwed onto the external thread of the stud to ensure that the inner ring of the ball bearing that absorbs centrifugal force and the inner ring of the rolling bearing that absorbs lateral force are clamped.

2. The pivot according to claim 1, wherein, The fracture-resistant sleeve extends sequentially into a cylindrical portion, followed by an outwardly flared tapered portion including the terminal. The junction between these two portions forms the lateral support for the inner ring of the rolling bearing that absorbs lateral forces.

3. The pivot of claim 2, further comprising a position sensor arranged facing the end of the fracture-resistant sleeve and used to detect any radial movement of the stud.

4. The pivot according to claim 1, wherein, The locking ring installed between the inner ring of the ball bearing that absorbs centrifugal force and the inner ring of the rolling bearing that absorbs lateral force is a centrifugal fusible ring.

5. The pivot according to claim 1, wherein, The fracture-resistant sleeve is retracted onto the stud.

6. The pivot according to claim 1, wherein, The inner ring of the ball bearing that absorbs centrifugal force and the inner ring of the rolling bearing that absorbs lateral force are clamped by the second clamping nut via the anti-fracture sleeve and the locking ring.

7. The pivot according to claim 1, wherein, The inner and outer rings of the ball bearing that absorbs centrifugal force are manufactured in two different parts to facilitate the installation of the stud.

8. A turbine fan comprising at least one directionally adjustable blade, the hub of which is mounted on a pivot according to claim 1.

9. A turbine comprising the fan according to claim 8.

10. A method for installing a pivot according to claim 1, comprising: Lower the stud into the fan hub; install the centrifugal force-absorbing ball bearing onto the first end of the stud; clamp the centrifugal force-absorbing ball bearing by screwing the first clamping nut onto the internal thread of the hub; install a retaining ring that carries the smooth outer ring of the lateral force-absorbing rolling bearing that is laterally supported inside the hub; install a fracture-resistant sleeve onto the second end of the stud, the fracture-resistant sleeve carrying the remaining portion of the lateral force-absorbing rolling bearing and a fusible locking ring; and clamp the lateral force-absorbing rolling bearing by screwing the second clamping nut.

Images