In-line Four Cylinder Engine Crankshaft Balance Optimization
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Solution Overview
Problem
Existing in-line four-cylinder engines for vehicles face challenges in achieving a compact design while improving acceleration feeling and reducing vibrations, as they struggle to balance the additional weight of crank webs without increasing engine size or causing interference with other components.
Innovation Solution
The engine design features a crankshaft with crank pins arranged on two virtual planes with specific phase differences, utilizing balance ratios and distances to distribute the weight of half crank webs in a way that forms a substantially circular vector of primary inertia couple, allowing for a compact and balanced engine with improved acceleration feeling and reduced vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the additional weight of crank web is increased to improve balance, then the acceleration feeling is improved, but the engine size increases and interference with other components occurs
Solution Approach 1:
The patent divides the crank web into two separate half crank webs (left and right) with different balance ratios. This segmentation allows independent optimization of each half's weight and position, enabling improved balance characteristics without proportionally increasing the overall engine size. The left half crank web has a first balance ratio and the right half crank web has a second balance ratio, allowing precise control over the distribution of additional weight.
Solution Approach 2:
The patent applies different balance ratios to different parts of the crank web structure. Specifically, the left half crank web and right half crank web have different balance ratios tailored to their respective positions and functions. This local quality approach allows the heavier balance weights to be strategically placed only where needed, rather than uniformly distributing weight throughout the entire crank web, thus improving acceleration feeling while minimizing overall engine size increase.
2Ease of operation
If the rotational radius is enlarged to achieve better balance, then the acceleration feeling is improved, but the crankshaft becomes larger
Solution Approach 1:
The patent changes the balance ratio parameter differently for the left and right half crank webs instead of uniformly increasing the rotational radius. By adjusting the balance ratios (first balance ratio for left half, second balance ratio for right half) and their respective distances from the crankshaft center, the patent achieves the desired balance effect through parameter optimization rather than geometric enlargement, thus improving acceleration feeling while keeping the crankshaft compact.
3Stability of the object's composition
If the additional weight of crank web is set at 1/2 of reciprocating portion weight, then the balance is improved, but interference with other gears and bearings occurs
Solution Approach 1:
The patent segments the additional weight into two separate half crank webs with different balance ratios. Instead of concentrating 1/2 of the reciprocating portion weight in a single location, the weight is distributed between the left and right half crank webs. This segmentation allows the weight to be placed in positions that achieve the desired balance effect while avoiding interference with gears and bearings by utilizing available space on both sides of the crankshaft center.
Solution Approach 2:
The patent employs asymmetric balance ratios for the left and right half crank webs. The first balance ratio for the left half and the second balance ratio for the right half are different, creating an asymmetric weight distribution that optimizes balance characteristics while fitting within the spatial constraints of the engine layout, thereby avoiding interference with surrounding components.
Data Source
AI summary
A two-plane type crankshaft is provided. The weight of crank webs for the respective cylinders is divided between left and right half webs and balance ratios kL and kR of the half webs for the respective cylinders are set so as to be (kL−0.25)·(0.25−kR)≅DR/DL to form a track of a vector of a primary inertial couple into a substantial circle. A primary balancer offsets the primary inertia couple.