Turboprop Speed Reducer Spring Mount for Equal Torque Split

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Solution Overview

Problem

Existing speed reducers with two intermediate lines in turboprops face challenges in ensuring optimal power distribution between the intermediate lines due to hyperstatic systems, leading to uneven torque transmission and complexity in production, which affects reliability.

Innovation Solution

A speed reducer design featuring a spring surrounding a longitudinal portion of the input shaft, allowing radial movement to achieve an equilibrium position for equal power distribution between the intermediate lines, simplifying production and enhancing reliability by enabling free vertical and lateral movement of the input pinion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a rectangular part with compression spring is used to allow vertical movement of input pinion, then load distribution between intermediate lines is improved, but device complexity and production difficulty increase

Engineering Contradiction:
Improveload distributionVSAvoidproduction complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The invention extracts the essential function (radial movement for load distribution) from the complex rectangular part with compression spring system, implementing it through a simple cylindrical bore that allows the input shaft to move radially. This removes unnecessary structural complexity while preserving the load distribution capability.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The invention applies local quality by providing radial movement freedom only where needed (at the input shaft position) through a localized cylindrical bore, rather than implementing a complex mechanism throughout the entire gearbox structure. This targets the specific location requiring flexibility.

Inventive Principle:
Principle #3Local quality

2Reliability

If a rectangular part with compression spring is used to position input pinion, then torque distribution is improved, but reliability may be degraded due to production complexity

Engineering Contradiction:
Improvetorque distributionVSAvoidproduction ease
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The invention extracts the essential function (radial positioning for torque distribution) from the complex rectangular part with compression spring system, implementing it through a simple cylindrical bore that allows the input shaft to move radially. This removes unnecessary structural complexity while preserving the torque distribution capability.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of using an active mechanism (rectangular part with spring) to force the pinion into position, the invention inverts the approach by creating a passive constraint (cylindrical bore) that naturally guides the input shaft to the correct radial position through geometry alone, simplifying manufacturing.

Inventive Principle:
Principle #13The other way round (Inversion)

3Ease of manufacture

If the input pinion is constrained in position, then manufacturing is simplified, but optimal meshing and equal power distribution cannot be guaranteed

Engineering Contradiction:
Improvemanufacturing simplicityVSAvoidmeshing precision
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention applies dynamics by allowing the input shaft to move radially within the cylindrical bore, enabling the system to dynamically adjust to optimal meshing conditions. This dynamic capability ensures equal power distribution between intermediate lines while maintaining manufacturing simplicity through the straightforward bore geometry.

Inventive Principle:
Principle #15Dynamics

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

The solution ensures efficient torque distribution between the intermediate lines, reducing production complexity and improving reliability by allowing the input pinion to naturally position for balanced meshing forces, thus achieving equal torque transmission.

Implementation Method 1

a spring (24) surrounded a longitudinal portion (29) of the input shaft (a1)

Methodology Applied
Scientific EffectSpring: Spring

Data Source

PatentEP3384180B1Speed reducer with two intermediate lines for a turboprop engine, turboprop engine comprising said reducer
Publication Date: 2021.04.21 SAFRAN TRANSMISSION SYST
  • EP3384180B1 patent drawingFigure 1~2
  • EP3384180B1 patent drawingFigure 3~4
  • EP3384180B1 patent drawingFigure 5

AI summary

The invention relates to a speed reducer comprising two intermediate lines for a turboprop engine, said reducer comprising: - an input line comprising an input shaft (ai) bearing an input gear wheel, - a first intermediate line comprising a first intermediate shaft bearing a first intermediate gear wheel, - a second intermediate line comprising a second intermediate shaft bearing a second intermediate gear wheel, - a spring (24) held by a frame (25), the spring (24) surrounding a longitudinal portion (29) of the input shaft (ai) in order to allow a movement of the input gear wheel (10) towards an equilibrium position corresponding to an equal distribution of the transmission of the power coming from the input shaft (ai) to the first intermediate shaft (a2) of the first intermediate line (17) and the second intermediate shaft (a3) of the second intermediate line (18).