Planetary Gearbox Clutch Layout for Aircraft Accessory Speed Shifting
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Solution Overview
Problem
Modern aircraft engines face challenges in meeting increasing electric power demands due to the limited power extraction potential of high pressure spools, necessitating an efficient transmission system to manage varying speed ratios between aircraft accessories and the low pressure spool.
Innovation Solution
A transmission system featuring a gear system with axially aligned and radially offset clutches, hydraulically controlled pistons, and splines that engage in parallel to shift rotational speeds, allowing for efficient power transfer and speed ratio conversion from a wide input range (8:1) to a narrower output range (2:1) for aircraft accessories.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a transmission system is designed to handle a wide input speed ratio range (8:1), then the system can accommodate varying accessory speed requirements, but the device complexity increases due to the need for multiple clutches and hydraulic control mechanisms
Solution Approach 1:
The transmission system is segmented into multiple independent clutch mechanisms (first clutch, second clutch, third clutch, fourth clutch) that can be engaged or disengaged independently. Each clutch handles specific speed ratio conversions, allowing the system to manage a wide 8:1 input speed ratio range through modular components rather than a single complex mechanism.
Solution Approach 2:
The clutches are arranged in both axial and radial dimensions, with axially aligned clutches and radially offset clutches creating a three-dimensional configuration. This spatial arrangement allows multiple clutch mechanisms to coexist in a compact footprint, managing complexity through efficient use of available space.
2Adaptability or versatility
If multiple clutches are used to achieve various gear speeds, then the adaptability for different speed ratios is improved, but the manufacturing precision requirements increase due to the need for precise alignment of axially aligned and radially offset clutches
Solution Approach 1:
The clutch mechanisms are designed with universal engagement features through spline connections. The first and second clutches engage the input shaft, while the third and fourth clutches engage intermediate shafts, creating a standardized multi-functional engagement system that reduces manufacturing precision requirements by using repeatable, standardized interfaces.
Solution Approach 2:
Intermediate shafts serve as mediators between the input shaft and output shaft, allowing the clutches to engage at different radial positions without requiring direct precision alignment between all components. The intermediate shafts absorb some alignment tolerances and facilitate smooth power transfer between misaligned components.
3Ease of operation
If hydraulically controlled pistons are used to engage clutches, then the ease of operation is improved through automated control, but the device complexity increases due to the hydraulic control system and multiple ports
Solution Approach 1:
The hydraulic control system is designed to be self-regulating, where the engagement and disengagement of clutches is automatically controlled by hydraulic pressure differentials. The system uses its own operational state to control itself, eliminating the need for external actuators or complex control mechanisms while maintaining ease of operation.
Solution Approach 2:
Hydraulic pistons are used to engage the clutches, replacing mechanical linkages with fluid pressure control. The hydraulic system provides smooth, controlled engagement and disengagement of clutches through pressure differentials, improving ease of operation while consolidating control functions into a single integrated system rather than multiple separate mechanisms.
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 system effectively converts a large input speed ratio range into a smaller output speed ratio range, enhancing engine efficiency, reducing brake wear, and preventing 'doorbelling' at shift points, while maintaining optimal accessory speed ratios.
Implementation Method 1
a plurality of pistons that are configured to engage the respective plurality of clutches, the plurality of pistons being hydraulically controlled and adapted to receive fluid from a respective plurality of ports in the output shaft
Data Source
AI summary
Disclosed is a transmission having: an input shaft configured to rotationally communicate with a gas turbine engine; an output shaft configured to rotationally communicate with an aircraft accessory; and a gear system connected between the input shaft and the output shaft, the gear system including: a plurality of clutches that are axially aligned and radially offset, the plurality of clutches configured to engage in parallel the output shaft and shift the transmission to generate a plurality gear speeds; and a plurality of pistons that are configured to engage the respective plurality of clutches, the plurality of pistons being hydraulically controlled and adapted to receive fluid from a respective plurality of ports in the output shaft.