Aircraft Generator Disconnect with Hydraulic Hold and Zero-Speed Release
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Solution Overview
Problem
Existing disconnect devices for aircraft engine generators face challenges such as insufficient actuating force, sensitivity to manufacturing tolerances, short service life, and inability to disconnect at zero speed, limiting their reliability and effectiveness in ensuring safe disconnection during mechanical failures.
Innovation Solution
A fail-safe hydraulic disconnect device using a spring-based disconnect biasing means and a fluid cavity to maintain the drive transfer means in a connected configuration, which automatically disconnects upon loss of pressure, ensuring reliable disconnection even in failure scenarios, and incorporating a vent valve for controlled fluid removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If mechanical power is extracted from the rotating drive shaft to operate a disconnect mechanism, then very high actuating forces and rapid disconnection are achieved, but the device requires very accurate tolerances and proves unreliable in the event of rotor bearing failure
Solution Approach 1:
The spring is pre-compressed during assembly to store potential energy, creating a ready-to-actuate disconnect mechanism. This preliminary action ensures that when the fluid cavity depressurizes, the spring immediately drives the disconnect mechanism without requiring accurate tolerances or rotor power extraction, thereby resolving the contradiction between high actuating force and reliability.
2Reliability
If a large actuator and mechanical advantage generating mechanism are used, then the assembly process becomes more robust and reliable, but the axial force produced is limited and insufficient to guarantee disconnection
Solution Approach 1:
The invention uses a fluid cavity (hydraulic or pneumatic) to apply axial force to the spring, enabling the spring to be compressed to a degree that generates sufficient disconnecting force. This fluid pressure mechanism overcomes the force limitation of pure mechanical actuators while maintaining the robust assembly process, resolving the contradiction between reliability and axial force.
3Force
If hydraulic pressure from the oil cooling system is used to provide axial force, then very high disconnecting forces are achieved, but the method fails in the event of oil cooling system failure
Solution Approach 1:
The spring is pre-compressed and held in place by fluid pressure in the cavity. When the fluid system fails or depressurizes, the spring automatically drives the disconnect mechanism. This preliminary energy storage ensures the disconnect function remains reliable even when the hydraulic system fails, resolving the contradiction between high disconnecting force and reliability.
4Reliability
If the disconnect device requires the generator shaft to be turning at low speed or uses an additional layshaft, then disconnection can be achieved, but the power to weight ratio of the generator is reduced
Solution Approach 1:
The invention extracts the power source (spring) from the rotating drive shaft, eliminating the need for rotor power extraction and additional layshafts. The spring is mounted on the stationary stator assembly, removing rotating mass and improving power to weight ratio while maintaining disconnect capability through fluid-pressure-activated spring release.
5Reliability
If the disconnect device uses rotor energy to provide disconnection force, then disconnection can be achieved, but the device becomes sensitive to manufacturing tolerances and has short service life
Solution Approach 1:
The invention replaces the mechanical rotor energy extraction system with a fluid-pressure-activated spring system. The spring is pre-compressed by fluid pressure in the cavity and releases to drive disconnection. This substitution eliminates sensitivity to manufacturing tolerances and extends service life by removing the complex mechanical interactions required in rotor-based systems.
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 provides a reliable and high-force disconnect mechanism that operates at zero speed, ensuring safe disconnection of the generator from the aircraft engine, overcoming limitations of existing devices by offering a robust and compact design with controlled fluid management.
Implementation Method 1
a disconnect biasing means, configured to bias the drive transfer means to the disconnected configuration
Implementation Method 2
a fluid cavity, configured such that provision of a pressurised fluid in the fluid cavity biases the drive transfer means toward, and can retain the drive transfer means in, the connected configuration
Data Source
AI summary
The present invention relates to a generator drive disconnect device, of a generator arranged to be driven by an aircraft engine. The disconnect device comprises: a drive transfer means (1) having a first, connected configuration, and a second, disconnected configuration; a disconnect biasing means (200), configured to bias the drive transfer means to the disconnected configuration; and a fluid cavity (300), configured such that provision of a pressurised fluid in the fluid cavity biases the drive transfer means to the connected configuration.