Aircraft Actuator Torque Limiter With Thermal Clamping Compensation

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Solution Overview

Problem

Aircraft actuator torque limiters are thermally sensitive, leading to reduced tripping torque at low temperatures and increased internal friction, which necessitates oversizing of components and structures to maintain functionality under cold conditions, resulting in inefficiency and increased weight.

Innovation Solution

A torque limiter design that incorporates a thermosensitive disengageable system with a differential expansion mechanism between materials of varying thermal expansion coefficients, adjusting the clamping force to maintain torque threshold values across temperature variations, ensuring consistent performance without the need for oversized components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the torque limiter is calibrated to a certain trigger value to limit the force developed by the actuator, then the actuator is protected during breakdown or blocking, but the release torque varies with temperature causing the tripping torque to decrease at low temperatures

Engineering Contradiction:

Improveactuator protectionVSAvoidtemperature sensitivity of release torque

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent applies parameter changes by modifying the physical state of the friction elements through temperature-dependent friction coefficient variations. The friction torque naturally increases at low temperatures due to increased friction coefficients, compensating for the thermal sensitivity of the release torque mechanism and maintaining stable actuator protection across temperature ranges.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful effect of increased internal friction at low temperatures into a beneficial compensation mechanism. The increased friction at cold temperatures counteracts the decrease in release torque, transforming what was previously a detrimental effect into a self-regulating feature that maintains consistent protective functionality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If the actuator is sized for worst-case cold weather operating conditions, then compliant operation is ensured in cold weather, but the parts downstream of the actuator and the aircraft structure must be oversized

Engineering Contradiction:

Improvecold weather operation complianceVSAvoidweight of downstream parts and structure

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The torque limiter system provides self-service by automatically compensating for temperature effects through the natural variation of friction coefficients. The system uses its own operational characteristics (friction increases at low temperatures) to maintain stable tripping torque without requiring external compensation mechanisms or oversized components, thereby avoiding unnecessary weight increases.

Inventive Principle:

Principle #25Self-service

3Reliability

If the torque limiter is set to overcome friction due to cold and the load to be moved, then the actuator can move the control surface under maximum aerodynamic effort in cold, but at ambient temperature the force developed by the actuator is much greater than necessary

Engineering Contradiction:

Improvecold temperature operational capabilityVSAvoidenergy efficiency at ambient temperature

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent applies dynamics by allowing the friction torque to dynamically adapt to temperature conditions. The friction elements automatically provide higher torque at low temperatures when needed, and reduce resistance at ambient temperatures, creating a dynamic system that optimizes performance and energy efficiency across different operating conditions without requiring manual adjustment.

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 torque limiter maintains effective torque threshold values across temperature changes, reducing the effort reduction at low temperatures and minimizing the need for oversized parts and structures, thus enhancing efficiency and reducing weight.

Implementation Method 1

capable of contracting differently relative to the rotary shaft, along the axis, during a temperature variation

Methodology Applied

Scientific EffectThermal contraction: Thermal Contraction

Implementation Method 2

capable of expanding differently relative to the rotary shaft, along the axis, during a temperature variation

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP3800367B1Torque limiter for actuator of an aircraft, associated actuator, aircraft and method

Publication Date: 2022.04.27 DASSAULT AVIATION SA

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AI summary

This limiter (12) includes a disengageable torque transmission system (56) between a rotating shaft (50) and a driven member (54). The disengageable system (56) comprises a friction stack having at least one contact member (100) mounted rotationally fixed to the rotating shaft (50) and a complementary contact member (102) mounted rotationally fixed to the driven member (54). The system (56) includes a clamping member (106) for the friction stack and a displacement member (120) for the clamping member (106), adapted to contract or expand differentially with respect to the rotating shaft (50) along the axis of rotation (C-C') during a temperature change. The displacement member (120) is made of a second material having a coefficient of thermal expansion distinct from that of the first material forming the rotating shaft (50).