Variable Compression Eccentric Layout Without Bearing Wall Weakening
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Solution Overview
Problem
Conventional methods for adjusting the compression ratio in reciprocating piston internal combustion engines compromise stability and performance due to thinner bearing walls in the adjusting drive, leading to stability issues and potential mechanical failures.
Innovation Solution
An apparatus featuring an externally toothed eccentric with a coupling unit using two takeoff shafts, an adjusting unit with an internal gear, and a synchronizing mechanism, allowing for compact design without stability losses by accommodating these components within the crankcase, web, or counterweight, enabling reliable adjustment of the compression ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional adjusting drive is used to change the compression ratio, then the compression ratio can be adjusted, but the bearing walls become thinner leading to stability problems
Solution Approach 1:
The adjusting drive components (eccentric, takeoff shafts, adjusting gear) are nested within existing crankshaft structures including the counterweight and web installation spaces. This nesting approach allows the adjusting mechanism to be accommodated without requiring additional external space that would thin bearing walls, thus maintaining structural stability while enabling compression ratio adjustment.
Solution Approach 2:
The invention utilizes the radial dimension by arranging takeoff shafts parallel to each other and spaced apart radially from the crankshaft axis. The first takeoff shaft is coupled to the eccentric and the second to the adjusting unit, creating a radial layout that efficiently uses available space within the crankcase without compromising bearing wall thickness.
2Adaptability or versatility
If the adjusting drive components are added to change compression ratio, then compression ratio variability is improved, but device complexity increases
Solution Approach 1:
The adjusting drive mechanism is merged with the existing crankshaft structure. The eccentric is positioned between the pin journal and connecting rod eye, utilizing existing structural elements. The first and second takeoff shafts are integrated into the crankcase space, and the adjusting gear is coupled to the crankshaft rotation, combining multiple functions into a unified structure that reduces overall complexity.
Solution Approach 2:
The crankshaft structure serves multiple functions: it provides the primary driving function while also housing the adjusting drive components (eccentric, takeoff shafts, adjusting gear). The counterweight and web installation spaces are utilized to accommodate adjusting mechanism components, making the crankshaft a multi-functional element that reduces the need for separate dedicated adjusting drive structures.
Data Source
AI summary
An apparatus configured to change a compression ratio of a reciprocating piston internal combustion engine includes an externally toothed eccentric, an adjusting unit, and a coupling unit. A first takeoff shaft is coupled mechanically to the external toothing system of the eccentric. A second takeoff shaft is coupled mechanically to the adjusting unit. The first and second takeoff shafts of the coupling unit, the eccentric and/or the adjusting unit are configured for the partial or complete arrangement in the interior of a crankcase of the crankshaft, within an installation space of a web of the crankshaft and/or within an installation space of a counterweight.