Fan-Shaped Three-Cylinder Engine Axial Crankpin Layout
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Solution Overview
Problem
Existing three-cylinder reciprocating piston internal combustion engines, such as the W3 and fan-type designs, face challenges with large cylinder angles that require significant installation space and result in a wide overall design, making them unsuitable for compact applications like motorcycles.
Innovation Solution
A reciprocating piston internal combustion engine with a fan-shaped configuration where the crankpin journals are arranged axially, allowing for flexible cylinder angles, enabling a more compact design by minimizing the overall width and replicating the sound of a V-twin engine, with optional unequal cylinder angles and a mass balancing shaft for improved NVH performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the cylinders are arranged in a V-arrangement with a middle cylinder inclined at a large angle, then the three-cylinder configuration can be achieved, but the overall width becomes large which is disadvantageous for motorcycle applications
Solution Approach 1:
The patent transitions from a traditional V-arrangement where all cylinders lie in one plane to a spatial arrangement where the middle cylinder is offset axially along the crankshaft. This dimensional change allows the cylinders to be distributed in three-dimensional space rather than confined to a single plane, reducing the overall width while maintaining the three-cylinder configuration
Solution Approach 2:
The crankshaft is segmented into multiple crankpin journals (first, second, and third crankpin journals) arranged axially. Each crankpin journal independently supports a connecting rod from each cylinder, allowing the cylinders to be positioned at different axial locations. This segmentation enables compact spatial arrangement of the three cylinders without requiring large cylinder angles
2Adaptability or versatility
If the cylinders are arranged in a fan-type configuration with all cylinders in one plane, then the three-cylinder design can be realized, but the cylinder angle becomes large requiring significant installation space
Solution Approach 1:
The invention moves away from the planar fan-type arrangement by introducing axial offset along the crankshaft. The middle cylinder's crankpin journal is positioned axially between or adjacent to the outer cylinders' crankpin journals, utilizing the third dimension (axial direction) to reduce the cylinder angle and overall installation footprint
3Device complexity
If multiple connecting rods share a common crankpin journal, then the device complexity is reduced, but the overall width increases making it unsuitable for compact applications
Solution Approach 1:
The crankshaft is divided into multiple separate crankpin journals (first, second, and third crankpin journals) arranged axially along the crankshaft. Each crankpin journal can support one or more connecting rods, but they are distributed axially rather than laterally. This segmentation maintains structural simplicity while reducing the overall width by utilizing axial spacing instead of lateral spacing
Data Source
AI summary
A reciprocating piston internal combustion engine includes at least one first, one second and one third cylinder and has a crank mechanism having a crankshaft, which is rotatably mounted in a crankcase, having a first, a second and a third crankpin. A first connecting rod having a first piston for the first cylinder is allocated to the first crankpin. A second connecting rod having a second piston for the second cylinder is allocated to the second crankpin. A third connecting rod having a third piston for the third cylinder is allocated to the third crankpin. The crankpins are arranged successively in an axial direction of the crankshaft, wherein the cylinders are arranged in a fan shape.