Blade pivot of adjustable orientation and of reduced bulk for a turbomachine fan hub

Abstract

A blade pivot of adjustable orientation for a turbomachine fan hub includes: a block having a retaining device configured to retain a fan blade root and a coupling device for the transmission of a torque; a ball type rolling bearing for taking up centrifugal forces having an inner ring; a clamping nut screwed onto an external thread of the block in order to clamp the inner ring of the ball type rolling bearing for taking up centrifugal forces to the block; a rolling bearing for taking up transverse forces; a pitch setting transmission ring positioned inside the inner radial end of the block and equipped with a coupling device cooperating with the coupling device of the block, and a device for locking the pitch setting transmission ring on the block.

Claims

1. A blade pivot of adjustable orientation for a turbomachine fan hub comprising: a block having retaining means at an outer radial end configured to retain a fan blade root and coupling means at an inner radial end, for the transmission of a torque; a ball rolling bearing for taking up centrifugal forces having an inner ring mounted in transverse support against an outer radial portion of the block; a clamping nut screwed onto an external thread of the block in order clamp the inner ring of the ball rolling bearing for taking up centrifugal forces on the block; a rolling bearing for taking up transverse forces having an inner ring mounted in transverse support against an inner radial portion of the block; a pitch setting transmission ring positioned inside the inner radial end of the block and equipped with coupling means cooperating with the coupling means of the block; and means for locking the pitch setting transmission ring on the block.

2. The blade pivot according to claim 1, wherein the rolling bearing for taking up the transverse forces comprises an outer ring configured to be mounted in transverse support inside the turbomachine fan hub, the inner ring and the outer ring of the rolling bearing defining the rolling paths for a plurality of rolling elements.

3. The blade pivot according to claim 2, wherein the ball rolling bearing for taking up centrifugal forces comprises an outer ring to be mounted in transverse support inside the turbomachine fan hub, the inner ring and the outer ring of the ball rolling bearing defining the rolling paths for a plurality of balls.

4. The blade pivot according to claim 3, further comprising a second clamping nut configured to be screwed onto an internal thread of the turbomachine fan hub in order to clamp the turbomachine fan hub against it the respective outer rings of the ball rolling bearing for taking up centrifugal forces and of the rolling bearing for taking up transverse forces.

5. The blade pivot according to claim 2, wherein the outer ring of the rolling bearing for taking up transverse forces comprises a flexible flange.

6. The blade pivot according to claim 2, wherein the rolling elements of the rolling bearing for taking up transverse forces are needles or rollers.

7. The blade pivot according to claim 1, wherein the inner ring of the ball rolling bearing for taking up centrifugal forces is produced in two distinct portions in order to facilitate the assembly of the blade pivot.

8. The blade pivot according to claim 1, wherein the inner ring of the rolling bearing for taking up transverse forces is shrink-fit to the blade pivot.

9. A blade with variable a pitch setting angle for a turbomachine fan hub comprising an aerodynamic profile and a blade pivot according to claim 1.

10. A turbomachine comprising at least one turbomachine fan hub and at least one assembly of blades with a variable pitch setting angle according to claim 9.

11. A method for assembling a blade pivot according to claim 1 in a turbomachine fan hub, comprising in succession: lowering the blade pivot into the turbomachine fan hub; clamping the ball rolling bearing for taking up centrifugal forces by screwing the clamping nut onto the external thread of the blade pivot; mounting the rolling bearing for taking up transverse forces on the inner radial end of the blade pivot; mounting the pitch setting transmission ring inside the inner radial end of the block; and locking of said pitch setting transmission ring on the block.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a section view showing an adjustable orientation blade pivot according to one embodiment of the invention.

(2) FIG. 2 is a section view showing an adjustable orientation blade pivot according to another embodiment of the invention.

(3) FIGS. 3A to 3F show an example of assembly of a pivot according to the embodiment of FIG. 1.

DESCRIPTION OF THE EMBODIMENTS

(4) The invention applies to any turbomachine equipped with at least one shrouded or unshrouded fan, the fan blades of which (in the case of a shrouded fan) or the propeller blades (in the case of a non-shrouded fan) are equipped with a pitch setting system.

(5) The invention applies in particular to turbojets of the type comprising a fan with a very high bypass ratio (large fan diameter) and with a very low pressure ratio.

(6) The architecture of these types of turbojets is well known to a person skilled in the art and will therefore not be described in detail here. Briefly, these turbojets comprise a shrouded fan with a large diameter which is equipped with a fan blade pitch setting change system. Briefly, these turbojets comprise a large diameter shrouded fan which is equipped with a pitch setting change system of the blades of the fan.

(7) A pitch setting change system of this type can for example comprise lever arms (or eccentrics) coupled to each blade pivot and actuated in pivoting by a jack.

(8) More precisely, the pivot of each blade has as its function to ensure the retention of the fan blade on a rotating fan hub and guiding it for setting its pitch.

(9) To this end, the pivot of each fan blade is mounted radially in an opening of the fan hub which it passes through from side to side, the hub being centered on the longitudinal axis of the turbojet.

(10) As shown in FIG. 1, the pivot 2 of the fan blade according to the invention comprises several distinct elements which are assembled together so as to facilitate its assembly to/disassembly from the hub of the propeller.

(11) In particular, the pivot 2 comprises a block 4 which extends along the radial axis Z-Z of the pivot through an opening 6 of the hub 8 of the fan. This block 4 has, at one outer radial end (i.e. at its most distant end from the longitudinal axis of the turbojet), an attachment 10 in the form of a bulb which is intended to receive a root 12 of the fan blade. Of course, other blade root retaining means could be contemplated.

(12) At its inner radial end (i.e. at its closest end to the longitudinal axis of the turbojet), the block 4 comprises an opening 14 centered on the radial axis Z-Z and intended to receive a pitch setting transmission ring.

(13) Moreover, the opening 14 is equipped with inner grooves 16 for transmitting a torque. Of course, other coupling means for transmitting a torque can be contemplated.

(14) The pivot according to the invention also comprises a pitch setting transmission ring 18 (also called an eccentric) which is positioned in the opening 14 of the block and coupled to the latter by means of grooves 20 carried on its outer surface and cooperating with the inner grooves 16 of the opening.

(15) This pitch setting transmission ring 18 is intended to transmit the torque to the blade pivot to change its pitch setting. It is locked on the block by means of a screw 22 centered on the radial axis Z-Z and by a nut 24 clamped on said screw. The pitch setting transmission ring also allows locking the inner ring of the rolling bearing for taking on transverse forces supported against the inner portion of the block.

(16) The pivot according to the invention also comprises rolling bearings for taking up centrifugal forces (i.e. along the radial axis Z-Z) and transverse forces (i.e. along a plane perpendicular to the radial axis Z-Z) seen by the blade and its pivot.

(17) More precisely, the pivot according to the invention comprises a ball type rolling bearing 26 which is intended to take up centrifugal forces. This ball type rolling bearing 26 is equipped with an inner ring 28 which mounted in transverse support against the outer radial end of the block 4.

(18) Preferably, the inner ring 28 is formed of two distinct portions 28a, 28b. This feature allows facilitating the assembly of the pivot as will be detailed hereafter.

(19) This ball type rolling bearing 26 also comprises an outer ring 30 which is mounted in transverse support inside the opening 6 of the fan hub 8, the inner 28 and outer 30 rings defining rolling paths for a plurality of balls 32.

(20) To take up transverse forces, the pivot according to the invention comprises needle or roller type rolling bearing 34 which is offset radially toward the interior relative to the ball type rolling bearing 26.

(21) More precisely, this needle or roller type rolling bearing 34 comprises an inner ring 36 which is mounted in transverse support against the inner radial end of the block 4. This inner ring 36 can for example be shrink-fit on the block.

(22) The needle or roller type rolling bearing 34 also comprises an outer ring 38 which is mounted in transverse support inside the opening 6 of the fan hub 8, the inner 36 and outer 38 rings defining rolling paths for a plurality of needles or rollers 40.

(23) A first clamping nut 42 is screwed onto an external thread 44 of the block 4 in order to clamp the inner ring 28 of the rolling bearing for taking up centrifugal forces 26 on the block.

(24) A second clamping nut 46 is screwed onto an internal thread 48 of the hub 8 to provide clamping against it of the respective outer rings 30, 38 of the rolling bearing for taking up centrifugal forces and of the rolling bearing for taking up transverse forces.

(25) FIG. 2 shows a variant embodiment of the pivot according to the invention.

(26) This variant is distinguished from the embodiment previously described in that the outer ring 38′ of the needle or roller rolling bearing 34′ has, between its portion defining the rolling paths and its portion supported transversely inside the opening 6 of the fan hub 8, a flexible flange 38′a.

(27) This flexible flange 38′a has the advantage of conferring on the outer ring 38′ a flexibility allowing it to prevent the propagation of vibrations into the rest of the pitch setting system during flight events such as impacts on the fan blades by external elements. It can be obtained in several fashions: by giving it a crenelated shape, by reducing its thickness between its two ends or by using a more flexible material.

(28) In connection with FIGS. 3A to 3F, an example of assembly of the pivot according to the invention will now be described.

(29) During a first step illustrated by FIG. 1A, the outer ring 30 of the ball type rolling bearing is mounted in transverse support inside the opening 6 of the fan hub 8 (it is shrink-fit for example), then the balls 32 of this rolling bearing are assembled.

(30) As shown in FIG. 3B, the block 4 is then lowered radially into the opening 6 of the hub 8, the block previously being pre-equipped with a portion 28a of the inner ring of the ball type rolling bearing and of the inner ring 36 of the needle or roller rolling bearing (these rings 28a, 36 being shrink-fit for example).

(31) The other portion 28b of the internal ring of the ball type rolling bearing 26 is then mounted to form the inner ring 28, the latter being held by clamping the first locking nut 42 (FIG. 3C).

(32) The needles or rollers 40, as well as the outer ring 38 of the needle or roller rolling bearing 34 are then mounted. The respective outer rings 30, 38 are then locked by clamping the second locking nut 46 (FIG. 3D).

(33) The second locking nut 46 can itself be locked into position by means of an anti-rotation ring 50 and an elastic clamping ring 52 of the “circlip” type for example (see FIG. 1).

(34) During the following step illustrated by FIG. 3E, the pitch setting transmission ring 18 is mounted inside the opening 14 provided in the block 4 by causing their respective grooves 16, 20 to cooperate. The pitch setting transmission ring is then locked by mounting the screw 22 and clamping the nut 24.

(35) Finally, as shown in FIG. 3F, the root 12 of the blade can be mounted in the attachment 10 in the form of a bulb provided at the outer radial end of the block 4.