Variable Geometry Turbine Crankshaft Torque Limiting Mechanism
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Solution Overview
Problem
Existing variable geometry turbochargers face challenges in maintaining precise control and durability due to harsh operational conditions, leading to unit-to-unit variation and increased wear, particularly in high-temperature exhaust environments.
Innovation Solution
A mechanism featuring a stop and setscrew arrangement that limits crankshaft travel, combined with a cam/gear system, reduces component stack-up and torque transmission to downstream parts, allowing for precise control and reduced wear by stopping rotation at the cam/gear, thus enhancing durability and repeatability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a variable geometry mechanism is used to control exhaust flow to the turbine, then turbine performance and emissions are improved, but the mechanism experiences increased wear and unit-to-unit variation due to harsh operational conditions
Solution Approach 1:
The patent extracts the torque-limiting function from the downstream variable geometry components and places it upstream at the crankshaft through a dedicated torque limiting device. This separates the wear-generating torque transmission path from the precision geometry control components, allowing the VGT mechanism to operate without bearing full actuation torque, thereby reducing wear and improving reliability.
2Adaptability or versatility
If multiple components are stacked to achieve variable geometry control, then control functionality is achieved, but manufacturing complexity and assembly variation increase
Solution Approach 1:
The patent combines the torque limiting function with the crankshaft assembly by integrating a torque limiting device directly onto the crankshaft. This merges multiple functions (actuation and torque protection) into a single integrated component rather than using separate stacked components, reducing assembly complexity and eliminating alignment variations between multiple parts.
Solution Approach 2:
The crankshaft assembly is designed to serve multiple functions: it provides the rotational actuation for variable geometry control and simultaneously houses the torque limiting device. This multi-functionality reduces the need for additional dedicated components, simplifying the overall device structure while maintaining control capability.
3Force
If full torque is transmitted to downstream components for geometry adjustment, then actuation force is sufficient, but wear on downstream components increases
Solution Approach 1:
The patent introduces a torque limiting device as an intermediary between the actuation source and the downstream variable geometry components. This intermediary device regulates the torque transmission, allowing sufficient actuation force to reach the VGT mechanism while preventing excessive torque from damaging downstream components, thereby extending their durability.
Data Source
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AI summary
An exemplary variable geometry turbine (126) includes a turbine wheel (260); a variable geometry assembly (300) that includes a rotatable control ring (312) that has a slot (314) and a plurality of vanes (302) where each vane (302) has a post pivotably controlled by rotation of the control ring (312) and where adjacent vanes (302) define nozzles to direct exhaust gas to the turbine wheel (260); a crankshaft (342) that has a pin (344) for receipt by the slot (314) of the control ring (312) where rotation of the crankshaft (342) rotates the control ring (312); and a center housing (280) that includes a rotatable stop (352) fixed to the crankshaft (342) and having a close stop surface (523), a secure component (420) and a translatable shaft (362) where the translatable shaft (362) comprises an engagement mechanism (560) to engage the rotatable stop (352); where translation of the shaft (362) causes rotation of the crankshaft (342) and where the close stop surface (523) establishes a contact with the secure component (420) to limit rotation of the crankshaft (342) and to establish a closed limit for the vanes (302).