Offset Reference Axis Crankshaft Counterweight Design
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Solution Overview
Problem
Internal combustion engines face challenges in mass balancing due to torsional vibrations caused by the crankshaft, leading to noise, reduced driving comfort, and potential fatigue, which existing solutions address inadequately, particularly in terms of space and cost efficiency.
Innovation Solution
A crank mechanism with a crankshaft featuring counterweights arranged on the opposite side of the crankshaft throws, having an arcuate shape with a varying distance from the crankshaft's longitudinal axis, allowing for a longer effective lever and reduced mass balancing requirements, potentially eliminating the need for external balancing shafts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional counterweights with constant distance from the crankshaft axis are used, then the mass balancing is achieved, but the required counterweight mass is large and occupies excessive space in the crankcase
Solution Approach 1:
The patent introduces a reference axis parallel to and offset from the crankshaft's longitudinal axis, creating a new dimensional reference frame. The counterweight's outer side is positioned at a constant distance from this reference axis rather than from the crankshaft axis, effectively utilizing the offset dimension to reduce the counterweight mass while maintaining balancing effectiveness within the same crankcase space.
2Reliability
If larger counterweights are used to achieve mass balancing, then the balancing efficiency is improved, but the engine weight and fuel consumption increase
Solution Approach 1:
By establishing a reference axis offset from the crankshaft axis, the patent enables the counterweight to achieve the same balancing effect with reduced mass. The offset distance creates an additional dimensional parameter that allows optimization of the counterweight geometry, reducing the required material while maintaining the balancing function.
3Object-affected harmful factors
If external balancing shafts are used to compensate for torsional vibrations, then the vibration control is improved, but the device complexity and cost increase
Solution Approach 1:
The patent integrates the balancing function directly into the crankshaft structure by optimizing the counterweight geometry relative to an offset reference axis. This merging of the balancing function into the existing crankshaft eliminates the need for separate external balancing shafts, thereby reducing system complexity while maintaining vibration control effectiveness.
4Ease of manufacture
If the counterweight outer side is positioned at constant distance from the crankshaft axis, then the manufacturing is simple, but the effective lever arm is short requiring larger counterweight mass
Solution Approach 1:
The patent positions the counterweight outer side at a constant distance from a reference axis that is offset from the crankshaft axis. This dimensional change effectively increases the perpendicular distance (lever arm) from the crankshaft axis to the counterweight outer side, allowing for shorter counterweights with sufficient balancing moment while maintaining manufacturing simplicity through the constant distance constraint.
Data Source
Figure 1
AI summary
The crank gear (1) has a crankshaft (2) supported in a crankcase and including crankshaft offsets (3) that are arranged at a distance from each other along a longitudinal axis (2a) of the crankshaft. A balance weight (4) formed as an unbalanced mass is arranged on the crankshaft for mass balance on opposite sides of the crankshaft offsets. The balance weight exhibits a non-circular arc shape on an outwardly facing side, where an outer side of the non-circular arc shape running in a peripheral direction exhibits identical magnitude in the longitudinal axis of the crankshaft.