Ring for controlling a stage of variable-setting vanes for a turbine engine

Abstract

A control ring for a stage of variable-pitch vanes for a turbine engine includes at least one member for bearing on a casing and means for fixing the member. The member includes a bushing with an axial bore for the passage of the member or an element for supporting the member. A through-slot opens into the bore and allows for substantial radial deformation of the bushing. The member further include an outer thread for screwing the bushing into a complementary thread of a hole in the body, thereby deforming the bushing. The member or support can be mounted and moved inside the bore, to a second position, in which the bushing is radially constrained and is tightly mounted on the member or support, which is thus immobilized in relation to the bushing.

Description

TECHNICAL FIELD[0001]The present invention relates to a control ring for a stage of variable-pitch vanes for a turbine engine.PRIOR ART[0002]The prior art includes in particular EP-A2-1 696 134, EP-A1-1 820 942, FR-A1-2 882 577 and EP-A1-0 375 593.[0003]A stage of this type comprises an annular row of variable-pitch stator vanes (also referred to as VSV, an acronym for Variable Stator Vanes) that are supported by an outer annular casing, generally of a compressor of the turbine engine. Each vane comprises a blade, which is connected at its radially outer end, by a plate having a substantially circular contour, to a radial cylindrical pivot that defines the axis of rotation of the vane and is rotationally guided in a corresponding hole in the outer casing. The radially inner end of the blade of each vane generally comprises a second cylindrical pivot extending along the axis of rotation of the vane and rotationally guided in a hole in an inner casing of the compressor.[0004]The radia...

AI Technical Summary

Benefits of technology

[0016]It is thus understood that screwing the bushing fixes the bearing member or its support in relation to the casing. In the loose or unscrewed position, the bushing is free and unconstrained and the inner diameter of its inner bore allows the member or the support to be mounted and moved, and it in particular allows it to be precisely positioned in relation to the casing. In the screwed and tightened position, the bushing is radially constrained and the inner diameter of its inner bore is restricted. The bushing is thus tightly mounted on the member or the support in order to immobilise it in relation to the casing in the precise position. This technology has the advantage of limiting the risk of damaging the ring by limiting the direct transmission of torque thereto.

Problems solved by technology

However, it has been noted, particularly in the case of single-cylinder actuation means, that, depending on the opening and closing ranges of the variable-pitch vanes, the cold clearances cause off-centring of the control ring in relation to the casing, which negatively affects the precision of the pitch.

During operation, the presence of this clearance causes, under the action of the surrounding vibrations, a relative displacement between the parts, leading to the destruction of the threaded connection.

Consequently, the pad function is no longer provided.

Furthermore, this wear directly affects the pitch angle of the vanes during operation, which can affect the correct operation of the engine (surging in the event of a significant number of worn pads on the same stage).