Crank Pin Hardness Reduction via Induction Tempering
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Solution Overview
Problem
Big end bearing failures in internal combustion engines lead to heat build-up and hardening of crank pin material, making repair expensive and time-consuming, often requiring replacement of the entire crankshaft due to persistent hardness issues after re-machining.
Innovation Solution
Measuring the surface hardness and depth of hardened spots on the crank pin, using an induction heating device to temper the affected areas, adjusting output power and heating time based on depth measurements to reduce hardness, and machining the crank pin to size post-treatment, allowing for in-situ repair without disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If re-machining is performed to remove the hardened layer, then the hardened material is removed, but the hardness may not drop to the allowed level and the entire crankshaft must often be changed
Solution Approach 1:
The patent applies heat treatment parameters (temperature, time, cooling rate) to change the physical state of the hardened layer, transforming it from a hard brittle state to a softer more ductile state, enabling repair while maintaining structural integrity
Solution Approach 2:
The patent converts the harmful hardened layer that causes repair difficulties into a beneficial treated zone by applying controlled heat treatment, which softens the hardened material to allow machining while maintaining the structural strength of the crankshaft
2Ease of repair
If heat treatment is applied to soften the hardened material, then the crank pin becomes softer and more repairable, but the hardness must be precisely controlled to maintain strength
Solution Approach 1:
The patent applies heat treatment locally to only the hardened zones of the crank pin rather than the entire crankshaft, softening only the affected areas while preserving the original strength characteristics of the non-hardened regions
Solution Approach 2:
The patent employs hardness measurement at multiple stages (before heat treatment, during cooling, and after heat treatment) to monitor and control the hardness reduction process, ensuring the crank pin achieves the desired softness for repair while maintaining sufficient strength
3Manufacturing precision
If the hardened layer is thick and the hardened area is wide, then the hardness removal by re-machining becomes insufficient, but removing more material may compromise the crankshaft structure
Solution Approach 1:
The patent changes the physical properties of the hardened layer through heat treatment parameters (temperature, time, cooling rate) to soften the material in place, avoiding the need to remove large amounts of material while maintaining structural integrity
Solution Approach 2:
The patent replaces the mechanical removal process (re-machining) with a thermal process (heat treatment) that softens the hardened layer, allowing for easier subsequent machining with minimal material removal while achieving the desired hardness reduction
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
Enables precise reduction of hardness in hardened areas, optimizing the heat treatment process to restore crank pin dimensions within specified limits, reducing the need for crankshaft replacement and extending engine life.
Implementation Method 1
During the heat treatment the hard spot or area is heated by an induction heating device
Implementation Method 2
the crank pin is first heated to a suitable temperature and thereafter cooled. As a result the hardened material of the crank pin becomes softer
Data Source
Figure 1
Figure 2
AI summary
Method for treating a crank pin (4) of a crank shaft (1). In the method hardness of the crank pin (4) surface is measured and when the hardness is over a predetermined limit value, depth of the hard spot (10) is measured. Heat treatment parameters are determined at least on the basis of the depth measurement and the hard spot (10) is heat treated. During the heat treatment the hard spot (10) is heated by an induction heating device (5).