Two-Stage Balancer Shaft Design for Engine Vibration Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional balancer shaft designs for engines face challenges in reducing both the radial and axial sizes of the crankshaft while ensuring sufficient eccentric weight to effectively eliminate vibration caused by the crankshaft's rotation, leading to limitations in compactness and increased weight.
Innovation Solution
The balancer shaft design incorporates a pair of journal portions at both ends, with a first stage balance weight formed in a crank shape and a second stage balance weight positioned on the outer periphery, allowing for a compact arrangement by reducing the thickness and weight of the balancer shaft, and utilizing a sector shape to increase eccentric weight without significant axial expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the balance weight size in the axial direction is limited to pass between crank arms, then the radial size can be reduced, but the eccentric weight is insufficient
Solution Approach 1:
The patent transitions from a single-stage balance weight to a two-stage balance weight configuration. The first stage balance weight is positioned between the crank arms in the radial direction, while the second stage balance weight is added in the axial direction. This multi-dimensional arrangement allows the balancer shaft to achieve sufficient eccentric weight without increasing the radial size beyond the space between crank arms.
2Volume of moving object
If balance weights are provided on both ends of the balancer shaft, then the radial size is reduced, but the axial size increases
Solution Approach 1:
The patent employs a nested configuration where the second stage balance weight is positioned on the outer periphery of the first stage balance weight. This nesting arrangement allows both balance weights to occupy overlapping radial and axial spaces efficiently, reducing the overall axial length compared to having separate balance weights at both ends of the shaft.
3Volume of moving object
If the balancer shaft is brought close to the crankshaft, then the radial arrangement is compact, but the axial size increases
Solution Approach 1:
By introducing the second stage balance weight in the axial direction rather than extending the shaft axially, the patent achieves compact radial arrangement while controlling axial size. The two-stage configuration allows the balancer shaft to be positioned close to the crankshaft radially without requiring excessive axial length.
4Weight of moving object
If the diameter of the balance weight is enlarged to ensure eccentric weight, then the radial size increases, but the axial size can be reduced
Solution Approach 1:
The patent divides the balance weight into two separate stages: the first stage balance weight positioned between the crank arms and the second stage balance weight on its outer periphery. This segmentation allows the eccentric weight to be distributed across two smaller components rather than requiring one large diameter balance weight, thereby maintaining compact radial dimensions while achieving sufficient total eccentric weight.
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 configuration enables a more compact balancer shaft arrangement that effectively reduces weight, increases eccentric weight, and avoids contact with the crankshaft and connecting rod, while also providing an oil pull surface for lubrication, thereby enhancing engine vibration suppression and lubrication efficiency.
Implementation Method 1
the second stage balance weight further has an oil pull surface dipped in an oil reservoir in the crankcase, and the oil pull surface pulls up oil when the balancer shaft is rotating
Data Source
AI summary
A balancer shaft of an engine includes a pair of journal portions, a first stage balance weight and a second stage balance weight. The first stage balance weight is formed between the journal portions and eccentrically arranged with respect to an axis. The second stage balance weight is formed on a center part of the first stage balance weight in the axial direction and projects outward from the first stage balance weight in a radial direction. The balancer shaft has a recess portion on the opposite side of the eccentricity direction.