Rolling-Element Shaft Coupling for Low-Friction Torque Transmission

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Solution Overview

Problem

Conventional power transmission systems experience significant energy losses and vibration issues due to friction when transmitting high torques, particularly in turbomachines, where the mechanical strength requires a degree of freedom in longitudinal translation between shafts, leading to inefficient power transfer and potential system degradation.

Innovation Solution

A coupling assembly with a first shaft having axial grooves and a second coaxial shaft with internal grooves, featuring rolling elements and an annular cage that allows radial and tangential play, reducing friction and enabling translational movement while maintaining vibration behavior, by positioning rolling elements in housings and grooves to minimize contact points and optimize stress distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If conventional spline fittings are used to transmit high torques between shafts, then the torque transmission capability is improved, but the friction and energy loss increase significantly

Engineering Contradiction:

Improvetorque transmission capabilityVSAvoidenergy loss due to friction

Core Design Contradiction:

ForceVSLoss of energy

Solution Approach 1:

The patent replaces the conventional spline fitting mechanical system with a magnetic coupling system that uses magnetic fields to transmit torque. The magnetic coupling device includes magnetic elements on both shafts that interact through a magnetic field, eliminating direct mechanical contact and thus reducing friction and energy loss while maintaining high torque transmission capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If conventional spline fittings are used to allow relative axial translation between shafts, then the degree of freedom is improved, but the friction and local heating increase

Engineering Contradiction:

Improvedegree of freedom for axial translationVSAvoidlocal heating due to friction

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The magnetic coupling system replaces the mechanical spline contact with magnetic field interaction, allowing relative axial translation between shafts without direct mechanical contact. This eliminates the friction that causes local heating, enabling free axial movement while transmitting torque through the magnetic field.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Force

If conventional mechanical connections are used to transmit power between shafts, then the torque transmission is improved, but the vibration behavior and system stiffness are adversely affected

Engineering Contradiction:

Improvetorque transmissionVSAvoidsystem stiffness and vibration behavior

Core Design Contradiction:

ForceVSStability of the object's composition

Solution Approach 1:

The magnetic coupling system replaces rigid mechanical connections with a magnetic field-based transmission system. This allows torque to be transmitted while maintaining the natural vibration characteristics and stiffness of the system, as the magnetic coupling does not create the variable resistant effort that distorts eigenmodes in conventional mechanical connections.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 configuration significantly reduces energy losses and maintains the vibration behavior of the system, enhancing the reliability and service life of the mechanical connection by minimizing friction and stress peaks during high-torque transmission.

Implementation Method 1

a coupling device comprising a plurality of rolling elements and an annular cage, said rolling elements each being arranged on the one hand in a respective housing and on the other hand between one of the first axial grooves of the first shaft and one of the second axial grooves of the second shaft so as to couple the first and the second shaft in rotation

Methodology Applied

Scientific EffectRolling contact: Roller

Data Source

PatentEP3794243B1Torque transmission device with reduced friction

Publication Date: 2023.02.22 SAFRAN AIRCRAFT ENGINES SAS

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AI summary

The invention relates to a turbomachine comprising a low-pressure shaft (27) designed to rotatably drive a fan shaft (32) by means of a coupling unit comprising a first shaft (1) in which a plurality of first axial grooves (7) are formed, a second shaft (2) in which a plurality of second axial grooves (12) are formed, and a coupling device (4) comprising a plurality of rolling elements (13) and an annular cage (14) arranged between the first shaft (1) and the second shaft (2), the rolling elements (13) being arranged between one of the first axial grooves (7) and one of the second axial grooves (12), for rotatably coupling the first and the second shaft (1, 2), each first and second groove (7, 2) having a substantially flat first (16) and second (17) surface which are inclined in relation to each other and extend along the axis.