Aircraft Actuator Torque Limiter With Thermal Clamping Compensation
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Solution Overview
Problem
Aircraft actuator torque limiters are thermally sensitive, leading to decreased triggering torque at low temperatures and increased internal friction, which requires overdimensioning of actuator parts and the aircraft structure to maintain functionality under cold conditions, resulting in inefficiency and excessive force at ambient temperatures.
Innovation Solution
Incorporating a movement member with a thermal expansion coefficient different from the rotary shaft, allowing differential contraction or expansion to adjust the clamping force of the friction pack, thereby maintaining effective torque transmission across temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the actuator is dimensioned for worst-case cold conditions to ensure functionality, then reliability at low temperatures is improved, but the device complexity and structural requirements increase due to overdimensioning at ambient temperatures
Solution Approach 1:
The invention changes the physical parameter of thermal expansion by introducing a movement member with a different thermal expansion coefficient than the rotary shaft. This causes differential expansion/contraction that automatically adjusts the clamping force of the friction pack according to temperature, eliminating the need for overdimensioning while maintaining reliability across temperature ranges.
Solution Approach 2:
The invention directly utilizes thermal expansion effects by selecting materials with different expansion coefficients for the rotary shaft and movement member. The differential thermal expansion creates automatic temperature compensation of the clamping force, allowing the actuator to maintain optimal performance without being overdimensioned for worst-case cold conditions.
2Ease of operation
If the torque limiter triggering torque is reduced to account for cold temperature effects, then ease of operation at low temperatures is improved, but the force available at ambient temperatures decreases due to overdimensioning requirements
Solution Approach 1:
The invention dynamically changes the clamping force parameter based on temperature through differential thermal expansion. The movement member's different expansion coefficient causes it to contract more than the rotary shaft in cold temperatures, automatically increasing clamping force to maintain triggering torque, thereby eliminating the need to reduce triggering torque for cold operation.
Solution Approach 2:
The system performs self-adjustment through automatic temperature compensation. The differential thermal expansion of the movement member relative to the rotary shaft automatically adjusts the clamping force according to temperature conditions without external intervention, maintaining optimal triggering torque across the temperature range.
3Reliability
If internal friction is increased to compensate for cold temperature effects, then reliability at low temperatures is improved, but energy loss increases due to decreased overall efficiency
Solution Approach 1:
The invention dynamically adjusts the internal friction parameter through temperature-dependent clamping force adjustment. The differential thermal expansion automatically increases clamping force in cold temperatures to maintain reliability, while at ambient temperatures the clamping force returns to normal levels, minimizing internal friction and energy loss.
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 efficient torque transmission at low temperatures without overdimensioning, reducing the force abatement between 20°C and −55°C by 20% compared to traditional systems, and limits the increase in triggering torque at higher temperatures, optimizing actuator performance and reducing structural requirements.
Implementation Method 1
the movement member being made from a second material having a thermal expansion coefficient different from the thermal expansion coefficient of the first material forming the rotary shaft
Data Source
AI summary
An aircraft actuator torque limiter includes a disengageable torque transmitter between a rotary shaft and a driven member. The disengageable transmitter includes a friction pack including at least one contact member mounted secured in rotation with the rotary shaft and a complementary contact member, mounted secured in rotation with the driven member. The transmitter includes a clamp of the friction pack and a mover of the clamp, able to contract or expand differentially relative to the rotary shaft along the axis of rotation during a temperature variation. The clamp mover is made from a second material having a thermal expansion coefficient different from that of the first material forming the rotary shaft.