Fracture-Split Titanium Alloy Connecting Rod Rising Portions
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Solution Overview
Problem
The production of fracture-split type titanium-alloy connecting rods is challenging due to the high toughness of titanium alloys, which makes brittle fracture techniques difficult to implement, leading to issues with reassemblability and reproducibility of the inner diameter roundness when mounted on a crankshaft, and existing methods are not adequately established for these rods.
Innovation Solution
A fracture-split type titanium-alloy connecting rod with rising or protruding portions on the fractured surfaces, having a height of 0.4 mm or more, and a chromium nitride layer on the surface to improve assemblability and reassemblability, where the rising portions are designed to enhance alignment and the nitride layer buries gaps formed during fracture split, preventing misalignment during assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fracture technique is used to split the big end into rod portion and cap portion, then production yield is enhanced and machining complexity is reduced, but titanium alloy's high toughness prevents adequate brittle fracture and poor reassemblability
Solution Approach 1:
The patent applies parameter changes by controlling the chemical composition of the titanium alloy (specific Ti-6Al-4V with 6-8% Al, 3-5% V) and adjusting processing parameters during fracture splitting to achieve controlled brittle fracture. This resolves the contradiction by modifying material parameters to enable the fracture technique while maintaining reassemblability through proper composition control.
Solution Approach 2:
The patent introduces an intermediary mechanism by using specifically designed fracture surfaces with complementary roughness patterns that act as alignment guides during reassembly. This mediator enables the fractured surfaces to self-align, resolving the contradiction between using fracture technique and achieving good reassemblability.
2Device complexity
If conventional fracture technique is applied to titanium alloy connecting rod, then alignment processing is eliminated, but gaps on fractured surfaces cause misalignment and poor roundness reproducibility
Solution Approach 1:
The patent changes the surface parameters by creating controlled roughness patterns on the fractured surfaces through specific fracture techniques. These surface parameter modifications enable self-alignment during reassembly, eliminating the need for additional alignment processing while maintaining precise roundness reproducibility.
Solution Approach 2:
The patent converts the harmful effect of fracture surface gaps into a beneficial alignment feature. By controlling the fracture process to create complementary roughness patterns, the previously problematic gaps become self-aligning features that guide precise reassembly, eliminating the need for separate alignment processing.
3Weight of moving object
If titanium alloy is used for connecting rod, then weight is reduced, but machinability deteriorates and production cost increases
Solution Approach 1:
The patent extracts the need for post-fracture machining operations by using the fracture technique to create ready-to-assemble surfaces. This removes the problematic machining steps from the production process, resolving the contradiction between using titanium alloy and maintaining ease of manufacture.
Solution Approach 2:
The patent skips the traditional machining steps that would normally be required after separating the big end into rod portion and cap portion. By using controlled fracture to directly create the separating surfaces, the process rushes through the production sequence without the time-consuming machining operations that deteriorate titanium alloy producibility.
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 improves the assemblability and reproducibility of the inner diameter roundness of the big end when mounted on a crankshaft, enhancing the reassemblability and mechanical properties of the connecting rod, making it suitable for various internal combustion engines and automotive vehicles by minimizing bending stress and maintaining the structural integrity of the titanium alloy.
Implementation Method 1
a chromium nitride layer on the surface to improve assemblability and reassemblability, where the rising portions are designed to enhance alignment and the nitride layer buries gaps formed during fracture split
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
There is provided a fracture-split type titanium-alloy connecting rod exhibiting good reassemblability and a production method thereof. A connecting rod (1) is a split-type connecting rod made of a titanium alloy, including 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 being fracture-split into a rod portion (33) continuing from the other end of the rod main body and a cap portion (34) for coupling to the rod portion with a bolt (40). The rod portion and/or the cap portion include at least one rising portion (SP) protruding from an edge of a fractured surface (F).