Multi-Link Piston-Crank Mechanism for Compact Engine Design
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Summary
Problems
The multi-link piston-crank mechanism in internal combustion engines faces challenges with stress concentration and increased load due to torsional torque, leading to difficulties in achieving a compact design while maintaining rigidity and strength, especially with the shortened crankthrow which enhances engine mountability and compression ratio.
Innovation solutions
The pin-side opening of the oil passage is formed in ranges other than the traditional 90° or -90° angular positions relative to the crankpin decentering direction, thereby alleviating stress concentration and allowing for a reduced crankpin diameter while ensuring required strength and rigidity, and optimizing the oil passage layout to prevent inadequate oil film formation.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If the crankthrow is shortened to enhance engine mountability and compression ratio, then the engine size is reduced and compression ratio is improved, but the load on the crankpin increases due to torsional torque
Why choose this principle:
The patent applies local quality by positioning the oil-passage pin-side opening at specific angular ranges (0°≤θ < 90° or 270° < θ≤360°) relative to the crankpin decentering direction. This localized positioning avoids high-stress zones while maintaining lubrication function, allowing the crankpin to withstand higher loads despite the shortened crankthrow.
Principle concept:
If the crankthrow is shortened to enhance engine mountability and compression ratio, then the engine size is reduced and compression ratio is improved, but the crankpin diameter must be increased to maintain strength
Why choose this principle:
The patent positions the oil-passage pin-side opening in angular ranges that avoid stress concentration zones. This allows the crankpin to maintain sufficient strength with a smaller diameter, as the opening is located where it does not compromise the structural integrity needed to handle the increased loads from the shortened crankthrow.
Application Domain
Data Source
AI summary:
The pin-side opening of the oil passage is formed in ranges other than the traditional 90° or -90° angular positions relative to the crankpin decentering direction, thereby alleviating stress concentration and allowing for a reduced crankpin diameter while ensuring required strength and rigidity, and optimizing the oil passage layout to prevent inadequate oil film formation.
Abstract
In a crankshaft of an internal combustion engine wherein a crankthrow is shortened by the use of a multi-link mechanism, a stress concentration caused by a torsional torque in the vicinity of a pin-side opening (21) of an oil passage (20), which is open at the outer peripheral surface of a crankpin, is alleviated. The crankthrow from the axis of a main journal (2) to the axis of the crankpin (3) is set shorter than one-half of a piston stroke. The oil passage (20) is formed to supply lubricating oil to a bearing portion of the crankpin (3). The pin-side opening (21) of the oil passage (20), which is open at the outer peripheral surface of the crankpin (3), is formed in ranges other than angular ranges of 0°, 90°, 180°, and 270° with respect to a reference line (X1) extending from the axis of the main journal (2) toward the axis of the crankpin (3) in a decentering direction (X) of the crankpin.