Selective Impact Hardening of Crankshaft Transition Radii
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Solution Overview
Problem
Existing methods for impact hardening of crankshafts, such as those used in internal combustion engines, require complex and expensive mechanical components to introduce internal compressive stresses effectively, leading to increased fatigue strength but with high outlay and potential damage risks.
Innovation Solution
A method where transition radii of crankshafts are impact-hardened by defining highly loaded, lightly loaded, and intermediate regions along the transition radius, focusing the impact force primarily on the highly loaded regions to introduce internal compressive stresses, thereby maximizing fatigue strength without fully encircling impact hardening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex mechanical components (transmissions, clutches, spring systems) are used to stop crankshaft rotation during impact tool action, then the introduction of internal compressive stresses is reliable and synchronized, but the device complexity increases and installation becomes complex and expensive
Solution Approach 1:
The invention extracts and removes the complex mechanical components (transmissions, clutches, spring systems) from the system. Instead of using these components to stop the crankshaft, the method allows the crankshaft to rotate continuously while the impact tool moves axially to apply forces at specific angular positions, eliminating the need for rotational stopping mechanisms
Solution Approach 2:
The invention transitions from a static approach (stopping rotation) to a dynamic approach (continuous rotation). The crankshaft maintains continuous rotational movement, and the impact tool dynamically adjusts its axial position to apply forces at the desired angular positions, creating a more flexible and simpler system
2Strength
If full encircling impact hardening is performed, then fatigue strength is maximized, but processing time increases and risk of damage to connecting-rod bearing journals increases
Solution Approach 1:
The invention applies local quality by concentrating impact forces on the highly loaded regions (transition radii) rather than applying uniform forces around the entire crankshaft. The method identifies and treats only the critical areas where fatigue stresses are highest, optimizing the balance between fatigue strength improvement and processing efficiency
Solution Approach 2:
The invention uses partial action by applying impact forces only to the necessary regions (highly loaded areas) rather than performing complete encircling hardening. This selective approach achieves sufficient fatigue strength improvement while reducing processing time and damage risk
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 enhances the fatigue strength of crankshafts while reducing processing complexity and costs, allowing for efficient and economical production with minimized risk of damage, such as to connecting-rod bearing journals at top dead center.
Implementation Method 1
Impact hardening in particular is an advantageous method for increasing the fatigue strength, in particular the bending fatigue strength and the torsional fatigue strength, of crankshafts. The increase in the fatigue strength is achieved here by virtue of impact forces being introduced into the crankshaft by cold working
Implementation Method 2
The increase in the fatigue strength is achieved here by virtue of impact forces being introduced into the crankshaft by cold working, preferably hammering by means of special impact tools
Data Source
AI summary
The invention relates to a method for the impact treatment of transition radii (8) of a crankshaft (4), in particular transition radii (8) between connecting rod bearing journals (5) and crank webs (7) and/or transition radii (8) between main bearing journals (6) and the crank webs (7) of the crankshaft (4). In order to apply an impact force (FS) to at least one of the transition radii (8) along the respective transition radius (8) circulating about the crankshaft (4) in an annular manner, a heavily loaded region (BMAX), a lightly loaded region (BMIN), and intermediate regions (BZW) lying therebetween are defined, and an impact treatment is then carried out such that the impact force (FS) introduced into the intermediate regions (BZW) is increased in the direction of the heavily loaded region (BMAX).