Crankshaft Counterweight Positioning for Precise Balance Assembly
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Solution Overview
Problem
The connection of bolted counterweights to the crankshaft is not optimized, leading to potential misalignment and uneven force distribution, which can affect the balancing of static and dynamic moments in engines.
Innovation Solution
The use of independent positioning elements, such as positioning pins and recesses, to securely fix the counterweights on the crankshaft, allowing for better alignment and separate contact areas for the screws to improve force distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the counterweight is positioned as far away from the crankshaft axis as possible to achieve largest balancing moments, then the balancing effectiveness is improved, but the counterweight may collide with interference contours such as the piston or crankcase
Solution Approach 1:
The outer contour of the counterweight is designed to be dynamically adaptive to the piston's position. The contour follows a line of constant distance to the piston, allowing the counterweight to extend further from the crankshaft axis when the piston is retracted, while maintaining safe clearance when the piston is at bottom dead center. This dynamic contour optimization enables maximum balancing moment without collision.
Solution Approach 2:
Instead of using a simple circular contour centered on the crankshaft axis, the invention introduces a new geometric dimension by defining the outer contour based on constant distance to the piston. This transforms the counterweight's shape from a static circular form to an elliptical or oval form that optimizes mass distribution in the radial direction while accounting for the piston's vertical motion, thereby achieving larger balancing moments without interference.
2Object-affected harmful factors
If the counterweight has a non-circular outer contour to avoid interference, then the risk of collision is reduced, but the manufacturing complexity increases
Solution Approach 1:
The counterweight is designed as a separate, detachable component rather than an integrated part of the crankshaft. This segmentation allows the complex non-circular contour to be manufactured independently using standard casting or forging processes, then mounted onto the crankshaft using conventional fastening methods. The complexity is isolated to a single component that can be produced and inspected separately, simplifying the overall manufacturing process.
Solution Approach 2:
The counterweight is pre-manufactured with its optimized non-circular contour before assembly onto the crankshaft. This preliminary action allows the complex shape to be created using established manufacturing processes for counterweights, rather than attempting to form the complex geometry during crankshaft assembly. The pre-formed counterweight is then simply mounted and secured to the crankshaft, reducing the overall manufacturing complexity.
3Ease of operation
If the counterweight is bolted to the crankshaft using conventional methods, then the assembly is simple, but misalignment and uneven force distribution occur
Solution Approach 1:
A positioning element serves as an intermediary between the counterweight and the crankshaft, ensuring precise alignment before the counterweight is bolted in place. This positioning feature guides the counterweight into the correct angular and radial position, preventing misalignment during assembly. The positioning element maintains the precise orientation required for optimal balancing performance while allowing the assembly process to remain simple and tool-free.
Solution Approach 2:
The counterweight incorporates self-aligning features such as positioning keys, tapered surfaces, or interference-fit elements that automatically guide it into the correct position on the crankshaft during assembly. These self-service mechanisms eliminate the need for complex alignment tools or procedures, allowing the counterweight to self-position accurately while being mounted with simple fastening operations.
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
The present invention relates to a crankshaft with at least one counterweight, which is preferably screwed to the crankshaft by at least two screws, wherein the counterweight has a contact surface with which it rests against a corresponding contact surface of the crankshaft. The position of the counterweight on the crankshaft is determined by at least one positioning element that is independent of the screw connection.