Variable-Throat Turbocharger Drive Pin Cladding and Caulking
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Solution Overview
Problem
Existing methods for connecting constituent members in variable-throat exhaust turbochargers face challenges such as high manufacturing costs, low yield rates, and instability due to the use of wear-resistant materials, particularly when dealing with high-temperature conditions and the need for precise brazing welding, which can lead to defects and increased processing time.
Innovation Solution
A method involving the creation of shaft members with a two-stratum structure, where a wear-resistant material like Co—Mo alloy is clad onto a steel plate and cut to form drive pins, allowing for caulking to secure the connection without local heating, thereby maintaining firm connections under high temperatures and reducing material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wear-resistant material (Co-Mo alloy, nickel base, or cobalt base alloy) is used for sliding members to increase wear resistance, then wear resistance is improved, but plastic deformation such as caulking cannot be applied to fix the sliding members
Solution Approach 1:
The drive pin is divided into two distinct parts: a sliding portion made of wear-resistant material (Co-Mo alloy, nickel base, or cobalt base alloy) and a connecting portion made of steel material that can be easily caulked. This segmentation allows each part to have optimized properties for its specific function while avoiding the contradiction between wear resistance and ease of fixing.
Solution Approach 2:
The drive pin uses a composite structure combining wear-resistant material (for the sliding portion) with steel material (for the connecting portion). This composite approach allows the assembly to simultaneously achieve high wear resistance at the sliding interface and ease of manufacturing through caulking at the connecting portion.
2Strength
If press-in or shrinkage fit is adopted for firm connection of two members, then connection firmness is improved, but at high temperature (600°C or over) thermal expansion coefficient difference causes the drive pin to slip off
Solution Approach 1:
The material parameters (thermal expansion coefficients) are carefully selected so that the steel connecting portion has a thermal expansion coefficient similar to the drive ring, while the wear-resistant sliding portion can have different properties. This parameter matching ensures that at high temperatures, the thermal expansion differences do not cause loosening or slippage of the connection.
3Strength
If welding is used to fix the drive pin to the drive ring, then connection firmness is improved, but manufacturing cost increases and yield rate decreases due to sensitivity to crack
Solution Approach 1:
The welding process (thermal-chemical joining) is replaced with a mechanical joining method (caulking). The connecting portion of the drive pin is designed to be caulked into the drive ring, providing firm mechanical connection without the risks of welding such as cracking, high cost, and low yield rate associated with welding wear-resistant materials.
4Strength
If brazing welding is used to connect ceramic turbine rotor and metal compressor wheel, then connection rigidity is improved, but processing time increases and defects can occur
Solution Approach 1:
The brazing welding process (thermal-chemical joining) is replaced with mechanical joining methods (press-in or caulking). This substitution eliminates the lengthy brazing process and associated defects while achieving firm, rigid connections through properly designed mechanical interlocking structures.
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
This approach enables a stable, cost-effective, and efficient connection of drive pins to drive rings within the variable-throat mechanism, ensuring reliable operation under severe conditions with reduced material waste and processing time, while maintaining the necessary wear resistance and thermal stability.
Implementation Method 1
wear-resistant material is welded on the upper surface of a steel plate to form cladding
Implementation Method 2
the connecting shaft portion is pressed into the through-hole and caulked at the end thereof for firm connection
Data Source
AI summary
The present invention provides a variable-throat exhaust turbocharger equipped with a variable-throat mechanism of which connection of constituent members can be achieved with a small number of man-hour and at low cost and which is stable in quality with firm connection of constituent members maintained under severe operating conditions. Among constituent members of the variable throat-area mechanism of the variable-throat exhaust turbocharger for varying the blade angle of a plurality of nozzle vanes supported rotatably by a members in a turbine casing, shaft members to be inserted and fixed in through-holes in a member with through-holes are produced by a method in which wear-resistant material is welded to form cladding of a certain thickness on the upper surface of a steel plate, said material being harder than the steel plate, and then crude shafts for forming drive pins are cut out from the clad plate.