Titanium Alloy Connecting Rod Bolt Phosphate Coating
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Solution Overview
Problem
Conventional split-type connecting rods made of titanium alloy face issues with seizing during bolt fastening, leading to unstable axial force and increased weight due to the use of steel nuts or molybdenum grease, which is difficult to manage in mass production.
Innovation Solution
A split-type connecting rod with a steel bolt featuring a zinc phosphate coating on its surface, preventing direct contact with the titanium alloy and eliminating the need for nuts or grease, thereby ensuring a stable axial force without weight increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steel nuts are used to prevent seizing during bolt fastening, then seizing is prevented, but the weight of the connecting rod increases
Solution Approach 1:
A phosphate coating layer is applied on the bolt surface as an intermediary between the steel bolt and titanium alloy connecting rod. This coating prevents direct contact and seizing while maintaining a compact structure without additional nuts, thus resolving the contradiction between seizing prevention and weight reduction.
2Reliability
If molybdenum grease is applied to prevent seizing, then seizing is prevented, but the manufacturing process becomes complex and axial force becomes unstable due to fluctuating grease application
Solution Approach 1:
The invention replaces the reusable but difficult-to-control molybdenum grease with a phosphate coating that is applied during the manufacturing process. This coating provides consistent anti-seizing properties without requiring precise control of application amount, simplifying the manufacturing process and ensuring stable axial force.
3Force
If high-strength steel bolts are used to generate sufficient axial force, then the required axial force (40-50 kN) is achieved, but seizing is more likely to occur at the screw surface
Solution Approach 1:
The phosphate coating serves as a mediator between the high-strength steel bolt and the titanium alloy connecting rod. It allows the bolt to generate the required 40-50 kN axial force while preventing direct metal-to-metal contact that would cause seizing, thus resolving the contradiction between force generation and seizing resistance.
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 zinc phosphate coating prevents seizing and stabilizes the axial force, eliminating the need for nuts and grease, resulting in a consistent and weight-efficient axial force generation.
Implementation Method 1
The fixing member, e.g. bolt, may comprise a phosphate coating, which may be provided on at least part or all of the surface of the main body, e.g. the bolt main body.
Implementation Method 2
When the applied amount fluctuates, the friction coefficient will fluctuate, thus resulting in large fluctuation in the snug torque
Data Source
Figure 1A~1B
Figure 2(a)~2(c)
Figure 3A~3B
AI summary
There is provided a split-type connecting rod (1) made of a titanium alloy which can generate a stable axial force without an unwanted increase in weight when its cap portion (34) is coupled with fixing members or bolts (40). A split-type connecting rod (1) which is made of a titanium alloy includes a rod main body (10), a small end (20) provided at one end of the rod main body, and a big end (30) provided at another end of the rod main body. The big end is split into a rod portion (33) continuing from the other end of the rod main body and a cap portion (34) to be coupled to the rod portion. The connecting rod further includes a fixing member or bolt (40) for coupling the cap portion to the rod portion. The fixing member or bolt includes a main body (40a) made of steel, and a phosphate coating (40b) provided on the surface of the main body.