Fixed Block Shaft Bearing Geometry for Constant Generator Speed
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Solution Overview
Problem
The fixed block shaft in integrated drive generators faces design challenges due to varying input shaft speeds from gas turbine engines, leading to variable frequency generation, which requires a method to maintain constant output speed and frequency.
Innovation Solution
A method for replacing the fixed block shaft with a new design featuring a body extending from one end to another, a radially extending disc, and a bearing race with specific dimensions and ratios, along with a spline connection to drive the ring gear in the differential, ensuring consistent speed and frequency generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional fixed block shaft is used in the integrated drive generator, then the structure is simple and easy to manufacture, but the output speed and frequency vary due to varying input shaft speeds from the gas turbine engine
Solution Approach 1:
The patent applies parameter changes by optimizing the bearing race geometry parameters - specifically setting the ratio of bearing race width to length between 0.80 and 0.95, and the ratio of bearing race inner diameter to length between 4.30 and 4.50. These parameter optimizations improve the bearing performance and stability of the fixed block shaft, enabling it to maintain constant output speed and frequency despite varying input speeds from the gas turbine engine.
2Reliability
If the bearing race dimensions are optimized with specific ratios, then the constant speed and frequency performance is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for the bearing race dimensions to balance performance and manufacturability. The bearing race width to length ratio is set between 0.80 and 0.95, and the inner diameter to length ratio is set between 4.30 and 4.50. These ranges provide optimal bearing performance while accommodating normal manufacturing tolerances, avoiding overly stringent precision requirements.
Data Source
Figure 1
Figure 2~3
Figure 4A~4D
AI summary
A fixed block shaft (90)) has a body (140) extending from a first end (143) to a second end (145). A disc (144) extends radially outwardly of a shaft portion (142). The shaft portion (142) extends to the second end (145). The disc (144) extends radially outwardly from the shaft adjacent the first end with a boss (182) extending to the first end (143) from the disc (144). The boss (182) defines an inner peripheral surface and the inner peripheral surface has a bearing race (150). The bearing race (150) extends from the first end (143) to a bearing race end. An inner diameter of the bearing race (150) defines a first distance. An inner diameter of the bearing race (150) is defined as a first distance and the bearing race (150) extends along a central axis for a second distance. A ratio of the first distance to the second distance is between 4.30 and 4.50. An integrated drive generator (20) and a method are also disclosed.