Asymmetric Balancer Shaft Mass Offset for Engine Noise
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Solution Overview
Problem
Conventional balancer shaft systems for reciprocating internal combustion engines face limitations in effectively reducing structure-borne noise and are often costly, with design compromises necessary to meet boundary conditions such as lubricant volume and foaming prevention, and deviations from ideal geometric conditions lead to suboptimal balance of inertial forces and moments.
Innovation Solution
The solution involves a mass balancing device with a first balancer shaft having a greater mass than the second balancer shaft and a height offset, allowing for defined lateral forces and residual transverse forces that counteract inertial moments, optimizing structure-borne noise reduction while being simpler and cost-effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional balance shaft systems are arranged as compact modules within the oil pan or in the crankcase area, then the structural integration is improved, but the acoustic effectiveness deteriorates due to deviations from ideal geometric conditions
Solution Approach 1:
The patent applies asymmetry by making the unbalanced masses of the two balance shafts unequal. Specifically, one balance shaft has an unbalanced mass that is 15-30% different from the other, creating an asymmetric force distribution that optimizes the counterbalancing effect for reducing structure-borne noise while maintaining practical structural integration
2Force
If the unbalanced masses of balance shafts are made equal for complete lateral force compensation, then the force balance is improved, but the structure-borne noise reduction deteriorates
Solution Approach 1:
The patent changes the mass parameter of the balance shafts from equal to unequal. By adjusting the unbalanced mass of one shaft to be 15-30% different from the other, the system optimizes the counterbalancing forces to specifically target and reduce structure-borne noise while maintaining acceptable lateral force compensation
3Volume of moving object
If balance shaft systems are integrated in the oil pan area, then the space utilization is improved, but the lubricant volume and foaming prevention are compromised
Solution Approach 1:
The patent segments the balance shaft system into two laterally separated channels within the crankcase area, each housing a balance shaft. This segmentation allows for optimized lubrication supply to each shaft independently while maintaining compact integration, thus preserving lubricant volume and preventing foaming while achieving space-efficient arrangement
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 achieves a 60% reduction in structure-borne noise with a 20% lighter second counterweight, improving acoustic effectiveness and reducing costs by allowing for more flexible design without major changes.
Implementation Method 1
the free inertial forces of the second order generated by the four-cylinder reciprocating internal combustion engine are balanced. This is achieved by mounting two parallel, counter-rotating balance shafts in a balance shaft housing and driving them at twice the crankshaft speed. The unbalanced masses used are dimensioned so that their forces acting in the vertical direction of the engine add up to compensate for the free inertial forces of the second order.
Implementation Method 2
This is achieved by offsetting the balance shafts vertically. This method takes advantage of the fact that while the lateral forces of the imbalances sum to zero, the vertical offset generates a moment that also acts around the crankshaft axis.
Data Source
Figure 1~2
Figure 3~4
Figure 4
AI summary
Device (1) for mass balancing for a reciprocating-piston internal combustion engine (2) having at least one piston which can be driven by a crankshaft via a connecting rod, wherein a first balancing shaft (3) with a first balancing weight (3') and a second balancing shaft (4) with a second balancing weight (4') are provided for the device (1), wherein the first balancing shaft (3) can be driven in rotation by the crankshaft in the opposite direction to the latter, and the second balancing shaft (4) can be driven in rotation by the crankshaft in the same direction as the latter, in each case at twice the crankshaft rotational speed, wherein the first balancing weight (3') has a greater mass than the second balancing weight (4'). On account of the design according to the invention, the invention offers primarily the advantage of providing a function, optimized in relation to the conventional prior art, in the form of body-borne noise reduction.