Fan Hub Blade Pivot Clamping for Zero-Clearance Radial Retention
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Solution Overview
Problem
Existing turbojet engines with high bypass ratios face issues in radial retention of fan blades due to residual mounting clearance, leading to contact wear and uneven force distribution, which can be critical under centrifugal forces.
Innovation Solution
A blade pivot with adjustable orientation is introduced, featuring a stud with a retaining ring and clamping parts that eliminate residual clearance through a 'keystone' type clamping mechanism, ensuring forces pass through a consistent path and preventing wear on other parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a segmented retaining ring is used to retain the pivot in a groove, then the pivot can be retained radially, but residual mounting clearance causes the pivot to fall and consume clearance, creating contact wear on inner bushings
Solution Approach 1:
The invention introduces a retaining ring as an intermediary element between the pivot and the groove. The retaining ring fits tightly in the groove and radially retains the pivot, eliminating the need for the pivot to fall into clearance. This intermediary component absorbs the retention function while preventing direct contact wear on the inner bushings of the rolling bearings.
Solution Approach 2:
The invention changes the geometric parameters of the retaining ring and groove interface to eliminate residual mounting clearance. By designing the groove width to precisely match the retaining ring dimensions and ensuring tight fit, the system transforms from having clearance to having zero clearance, preventing the pivot from falling and consuming clearance during operation.
2Ease of manufacture
If the groove is made wider than the retaining ring to accommodate tolerance dispersions, then assembly is easier, but mounting clearance is created that leads to pivot falling and wear
Solution Approach 1:
The invention optimizes the dimensional parameters of the retaining ring and groove to achieve a tight fit that eliminates clearance while accommodating normal tolerance dispersions. The groove width is designed to match the retaining ring dimensions with minimal clearance, and the retaining ring is designed with appropriate tolerances to ensure proper fit without creating excessive clearance that would allow the pivot to fall.
Solution Approach 2:
The retaining ring serves as a mediator that absorbs the tolerance dispersions between the groove and the pivot. By designing the retaining ring with appropriate dimensions and tolerances, it accommodates manufacturing variations while maintaining a tight fit that eliminates harmful clearance, thus resolving the contradiction between ease of assembly and precision requirements.
3Reliability
If centrifugal force is not immediately absorbed by the retaining ring during engine rotation, then forces pass through other propagation paths like threads, but this can be critical for parts not dimensioned to hold heavy loads
Solution Approach 1:
The invention implements preliminary action by ensuring the retaining ring is in place and the pivot is radially retained before centrifugal forces act on the system during engine rotation. The retaining ring is designed to immediately absorb centrifugal forces on the pivot, preventing these forces from being transmitted through unintended paths such as threads that are not dimensioned to handle heavy loads.
Solution Approach 2:
The retaining ring acts as an intermediary that intercepts and absorbs centrifugal forces before they can propagate through other parts of the assembly. By positioning the retaining ring to radially retain the pivot, it creates a dedicated force transmission path that is specifically designed to handle centrifugal loads, protecting weaker components like threaded parts from excessive stress.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides reliable radial retention and prevents wear on pivot parts by ensuring consistent force distribution, maintaining perfect holding during engine operation and at standstill, eliminating the need for other parts to absorb heavy loads.
Implementation Method 1
a rolling bearing for absorbing the centrifugal forces having an inner bushing mounted in transverse abutment against an external radial portion of the stud
Implementation Method 2
a clamping nut screwed onto an outer thread of the stud to come into conical abutment against the clamping parts such that said clamping parts ensure a clamping of the inner bushing of the rolling bearing on the stud and a clamping of the retaining ring in the groove
Data Source
AI summary
The invention relates to a blade pivot with adjustable orientation for a turbomachine fan hub, comprising a stud having means for retaining a fan blade root and coupling means for the transmission of a torsional torque, a rolling bearing for absorbing the centrifugal forces having an inner bushing mounted in transverse abutment against an external radial portion of the stud, a ring for radially retaining the stud relative to the rolling bearing housed in an annular groove formed in the stud, a plurality of clamping parts each mounted in transverse abutment against the retaining ring and in radial abutment against the inner bushing of the rolling bearing, and a clamping nut screwed onto an outer thread of the stud to come into conical abutment against the clamping parts such that said clamping parts ensure a clamping of the inner bushing of the rolling bearing on the stud and a clamping.