Variable Nozzle Assembly Engagement for Stable Turbocharger Flow
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Solution Overview
Problem
The positioning of the variable nozzle unit in a turbocharger is compromised due to reduced frictional force caused by deformation of the disc spring under heating, leading to circumferential shift and changes in gas flow rate.
Innovation Solution
An engagement structure is implemented to restrict the circumferential shift of the variable nozzle unit by engaging it with the turbine housing in a region radially outside the movable range of the nozzle vane, using mechanisms like pins and notches or protrusions and recesses to maintain positional stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a pin with clearance is used to position the variable nozzle unit, then the nozzle unit can be easily positioned in the axial direction, but the frictional force decreases under heating and causes circumferential shift
Solution Approach 1:
A positioning protrusion is introduced as an intermediary element between the pin and the variable nozzle unit. The protrusion fits into a positioning groove on the nozzle unit, creating a positive mechanical engagement that prevents circumferential shift while maintaining ease of axial positioning through the disc spring mechanism
Solution Approach 2:
The solution adds a circumferential dimension of constraint through the positioning protrusion and groove mechanism, while maintaining the axial positioning function through the disc spring. This multi-dimensional constraint approach resolves the contradiction by addressing both positioning ease and positional stability in different spatial dimensions
2Difficulty of detecting and measuring
If the disc spring load is reduced due to heating deformation, then thermal expansion is accommodated, but frictional force decreases causing circumferential shift
Solution Approach 1:
The positioning protrusion acts as a mechanical intermediary that provides circumferential constraint independent of the disc spring load. This positive engagement mechanism ensures positional stability even when the disc spring deforms due to thermal effects, as the protrusion-groove interface maintains the nozzle unit's circumferential position
3Adaptability or versatility
If the variable nozzle unit is allowed to shift circumferentially, then clearance compensation is achieved, but gas flow rate changes occur
Solution Approach 1:
The positioning protrusion and groove mechanism serves as a mediator that prevents unwanted circumferential movement while allowing the nozzle vane to maintain proper alignment. This ensures consistent gas flow characteristics by eliminating positional variability that would otherwise cause flow rate changes
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 engagement structure effectively suppresses circumferential shift, thereby stabilizing the gas flow rate and ensuring consistent operation of the turbocharger.
Implementation Method 1
a disc spring by which the variable nozzle unit is biased and pressed against a turbine housing
Implementation Method 2
an engagement structure structured so that a predetermined part thereof engages with the variable nozzle unit so as to restrict shifting of the variable nozzle unit in a circumferential direction
Data Source
AI summary
A variable capacity turbocharger includes: a turbine impeller; a turbine housing accommodating the turbine impeller; a nozzle flow passage located around the turbine impeller in the turbine housing; a variable nozzle assembly having a nozzle vane located in the nozzle flow passage, and a drive mechanism configured to drive the nozzle vane; and an engagement mechanism configured to restrict a rotational position of the variable nozzle assembly. The engagement mechanism is located in a region radially outside a movable range of the nozzle vane in a radial direction of rotation of the turbine impeller.