Variable Stroke Engine Camshaft Positioning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing variable stroke engines face size constraints due to the need to avoid interference between the camshaft and link member, leading to increased engine and crankcase dimensions.
Innovation Solution
The camshaft is positioned close to the crankshaft by overlapping part of its trajectory with the link member's trajectory in a plane perpendicular to the crankshaft axis, and its rotational phase is set to avoid interference, allowing for a more compact engine design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the camshaft is disposed at a position spaced apart from the crankshaft to avoid interference between the link member and cams, then the interference problem is solved, but the size of the crankcase and entire engine is increased
Solution Approach 1:
The patent applies dimensional change by moving the camshaft from a position in the horizontal plane to a position in the vertical plane (above the crankshaft axis). This three-dimensional rearrangement allows the camshaft to be closer to the crankshaft without horizontal interference, as the link member operates in a different vertical zone during its stroke cycle.
Solution Approach 2:
The patent utilizes dynamic motion analysis to resolve the interference issue. By carefully designing the camshaft rotational phase and the link member trajectory, the patent ensures that the cam profile and link member end portion do not occupy the same spatial zone simultaneously. The camshaft rotation is phased so that when the link member is at its extreme position, the cam is in a position that avoids contact.
2Volume of stationary object
If the camshaft is disposed at a position close to the crankshaft to reduce engine size, then the engine compactness is improved, but interference between the link member and cams occurs
Solution Approach 1:
The patent resolves the interference issue by transitioning from two-dimensional planar arrangement to three-dimensional spatial arrangement. The camshaft is positioned above the crankshaft axis in the vertical dimension, allowing close proximity without horizontal interference. The link member's trajectory in the vertical plane is designed to pass below the camshaft projection, eliminating overlap.
Solution Approach 2:
The patent applies local quality by creating zone-specific clearances. The cam profile is designed with specific local dimensions and the link member end portion is shaped to avoid the cam zone. The rotational phase is locally optimized at the camshaft-crankshaft interface to ensure no overlap between the cam operating zone and link member position zone.
Data Source
AI summary
A variable stroke engine includes an end portion of a connecting rod, which is connected at one end portion thereof to a piston by a piston pin, and an end portion of a control rod, which is connected at one end portion thereof to an eccentric shaft, and which are linked to each other by a link member rotatably supported on a crankshaft. A rotative power of the crankshaft is transmitted to the camshaft. The camshaft is disposed at such a position that part of a trajectory drawn by the intake-side and exhaust-side cams overlaps a trajectory drawn by the link member in a projection on a plane perpendicular to an axis of the crankshaft, and a rotational phase of the camshaft is set so that the interference, of the intake-side and exhaust-side cams with an end portion, on the camshaft side, of the link member, is avoided.