Crank and Connecting Rod Mechanism for Variable Compression
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Solution Overview
Problem
Current internal combustion engines, including opposed piston engines, face limitations in performance, power, and efficiency due to fixed compression ratios and geometry constraints, which hinder optimal motion characteristics of pistons, especially under varying load, speed, and environmental conditions.
Innovation Solution
The introduction of a crank and connecting rod mechanism featuring opposed pistons with angularly disposed connecting rods and mirror-image gear sets that facilitate asymmetric rotary and reciprocating motion, allowing the crankpin to follow a trochoidal path, thereby enhancing piston motion and travel characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional fixed compression ratios are used, then engine design is simple, but performance and power output are limited
Solution Approach 1:
The patent implements a variable compression ratio mechanism that dynamically adjusts the compression ratio based on operating conditions. The mechanism includes a movable piston crown that can change position to vary the compression volume, allowing the engine to optimize performance across different load and speed conditions rather than being constrained to a fixed ratio.
Solution Approach 2:
The invention changes the compression ratio parameter dynamically through mechanical adjustment. By varying the distance between the piston crown and the cylinder head through the adjustable mechanism, the compression ratio can be optimized for different operating scenarios, thereby improving adaptability without requiring multiple fixed-ratio engines.
2Productivity
If standard crankshaft geometry is used, then manufacturing is simple, but piston motion characteristics are suboptimal
Solution Approach 1:
The patent employs a cam-lobed crankshaft design where the crank journal is replaced by an eccentric cam lobe with a specific curvature profile. This curved geometry modifies the piston motion to reduce friction and improve power output by creating optimal acceleration and velocity characteristics during the power stroke, while the curvature can be manufactured using precision machining or casting techniques.
Solution Approach 2:
The crankshaft features an asymmetric cam lobe geometry that is specifically designed to optimize the expansion stroke while minimizing compression work. The asymmetric shape creates favorable pressure distributions and motion characteristics that enhance power output compared to symmetric conventional crankshafts.
3Power
If pistons operate at high compression ratios, then power output increases, but premature ignition and knock occur
Solution Approach 1:
The variable compression ratio mechanism allows the engine to dynamically adjust compression levels based on operating conditions. During high-load conditions where knock resistance is critical, the compression ratio can be reduced to prevent premature ignition, while during low-load conditions the higher compression ratio can be used to maximize power efficiency, thus maintaining reliability across all operating ranges.
Data Source
AI summary
A crank and connecting rod mechanism having an angularly disposed connecting rod and mirror image gear sets, each comprising: a crank gear rotatably mounted on a crank gear shaft, having a crankpin pivotally connected to and driven by the connecting rod, the crankpin following the path of a roulette of a centered trochoid about a first stationary gear as the crank gear is driven about the first stationary gear and a crankshaft driven gear is driven about a second stationary gear, a counterbalanced radial arm affixed to a drive shaft at a pivot point of the counterbalanced radial arm, the counterbalanced radial arm driving the drive shaft at the pivot point and the crank gear shaft at an outer radial arm bearing, the drive shaft driving a drive shaft gear, which drives an output gear that drives an output shaft.