Combined-Cycle Three-Cylinder Engine NVH Control
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Solution Overview
Problem
Three-cylinder engines face issues with noise, vibration, and harshness (NVH) and deteriorated engine performance due to structural characteristics that lead to similar displacement in two- and four-cycle combustion cylinders, resulting in poor combustion efficiency and reduced merchantable quality.
Innovation Solution
A combined-cycle combustion control type three-cylinder engine design where the bore, stroke, and valve timing of a two-cycle cylinder differ from those of a four-cycle cylinder, allowing for simultaneous four- and two-cycle combustion, controlled by a controller that manages intake and exhaust timings using a crankshaft and camshaft system with variable valve timing, ensuring equal power generation across cylinders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If all three cylinders are controlled by the same combustion process (either four-cycle or two-cycle), then the engine structure is simple and easy to control, but NVH performance deteriorates due to identical bore, stroke, and valve timing in all cylinders
Solution Approach 1:
The patent divides the three cylinders into two distinct groups: two cylinders operate on four-cycle combustion process while one cylinder operates on two-cycle combustion process. This segmentation allows different combustion characteristics in different cylinders, improving NVH performance by creating vibration cancellation effects while maintaining relatively simple control structure through the existing ECU.
Solution Approach 2:
The patent applies different combustion process characteristics to different cylinders: four-cycle process with specific intake/exhaust timing for two cylinders, and two-cycle process with different timing for one cylinder. This local differentiation in combustion quality enables NVH improvement through varied piston motion patterns while keeping the overall engine structure compact.
2Object-affected harmful factors
If two-cycle combustion is used in one cylinder to improve NVH, then noise and vibration are reduced, but engine performance (power and torque) deteriorates due to poor combustion efficiency in two-cycle mode
Solution Approach 1:
The patent merges four-cycle and two-cycle combustion processes in a single three-cylinder engine, combining the NVH benefits of two-cycle operation with the combustion efficiency of four-cycle operation. The two cylinders using four-cycle process maintain high power output, while the one cylinder using two-cycle process contributes to vibration cancellation, achieving overall performance improvement.
Solution Approach 2:
The patent creates asymmetric combustion operation where two cylinders use four-cycle process and one cylinder uses two-cycle process. This asymmetric configuration optimizes the balance between power output and NVH performance, leveraging the strengths of each combustion type in different cylinders rather than using a uniform approach.
3Ease of manufacture
If the bore, stroke, and valve timing of two-cycle and four-cycle cylinders are made equal, then manufacturing is simplified, but combustion efficiency deteriorates and engine performance is reduced
Solution Approach 1:
The patent changes the operational parameters (combustion process type, intake/exhaust timing) for each cylinder based on its designated role. Two cylinders operate with four-cycle timing parameters optimized for power output, while one cylinder operates with two-cycle timing parameters optimized for vibration control, allowing each cylinder to be tuned for its specific function while using a common physical platform.
Data Source
AI summary
A combined-cycle combustion control type three-cylinder engine includes: a cylinder block; and cylinders arranged in a row in the cylinder block and consisting of first, second, and third cylinders so that four-cycle combustion is performed in two of the first, second, and third cylinders and two-cycle combustion is performed in the remaining cylinder. A crankshaft is provided in first, second, and third pistons and converting reciprocating motions of the respective first, second, and third cylinders into rotational motions. A camshaft receives a rotational force from the crankshaft to control intake and exhaust timings for each of the first, second, and third cylinders.