Titanium Journal Support Pin With Steel Sleeve for Weight and Hardness
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Solution Overview
Problem
The inclusion of gear reduction in gas turbine engines to allow the fan rotor to rotate slower than the fan drive turbine adds weight, and existing journal support pins, typically made of hardened steel, are heavy and inefficient.
Innovation Solution
A journal support pin with a titanium body and an outer surface hardened with a steel sleeve or coating, such as silver or titanium nitride, to provide increased hardness and reduce weight while maintaining structural integrity and oil supply functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a steel journal support pin is used to support intermediate gears, then the hardness and durability are sufficient, but the weight increases significantly
Solution Approach 1:
The journal support pin uses a composite structure combining titanium alloy (Ti-6Al-4V) body with a hardened steel sleeve (AISI 4140 or AISI 4340). The titanium provides lightweight structural support while the steel sleeve provides the necessary hardness and wear resistance for gear support, achieving optimal weight-strength balance.
Solution Approach 2:
The steel sleeve is applied only to the outer surface and specific load-bearing regions of the titanium pin body, providing localized hardness where needed for gear contact while maintaining the lightweight titanium construction in non-critical areas. The sleeve thickness is optimized to provide sufficient hardness without excessive weight.
2Weight of moving object
If a titanium journal support pin is used to reduce weight, then the weight decreases, but the surface hardness is insufficient for supporting intermediate gears
Solution Approach 1:
The journal support pin uses a composite structure combining titanium alloy (Ti-6Al-4V) body with a hardened steel sleeve (AISI 4140 or AISI 4340). The titanium provides lightweight structural support while the steel sleeve provides the necessary hardness and wear resistance for gear support, achieving optimal weight-strength balance.
Solution Approach 2:
The steel sleeve is applied only to the outer surface and specific load-bearing regions of the titanium pin body, providing localized hardness where needed for gear contact while maintaining the lightweight titanium construction in non-critical areas. The sleeve thickness is optimized to provide sufficient hardness without excessive weight.
3Weight of moving object
If the outer surface thickness is reduced to minimize weight, then the weight decreases, but the oil supply holes may compromise structural integrity
Solution Approach 1:
The steel sleeve provides localized reinforcement at the oil hole regions, allowing thin-walled construction elsewhere for weight reduction while maintaining structural integrity at critical locations. The sleeve acts as a strengthening element precisely where the oil holes create potential weakness points.
Solution Approach 2:
The combination of titanium body with steel sleeve provides the necessary strength-to-weight ratio, allowing the design to achieve minimal weight while maintaining sufficient structural integrity even with reduced wall thickness and oil supply holes.
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 solution reduces the overall weight of the gear reduction system while maintaining the necessary hardness and durability to support intermediate gears, allowing for efficient operation in a gas turbine engine environment.
Implementation Method 1
an outer surface outside of the titanium body having a surface hardness that is harder than the body
Implementation Method 2
the outer surface is provided by nitriding
Implementation Method 3
oil supply holes extend from a central bore in the body through the surface
Data Source
AI summary
A gas turbine engine includes a propulsor and a fan drive turbine. The fan drive turbine drives the propulsor through a geared architecture. The geared architecture includes a sun gear, a ring gear, and intermediate gears supported on journal support pins. The sun gear engages the intermediate gears and the intermediate gears engages the ring gear. The journal support pins include a titanium body and an outer surface outside of the titanium body that has a surface hardness that is harder than the titanium body. The outer surface is provided by a steel sleeve. Oil supply holes extend from a central bore in the titanium body through the steel sleeve. At least one pin extends through the steel sleeve to secure the steel sleeve to the titanium body.