DOHC Sliding Cam Valve Train for Cylinder Shutdown
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Solution Overview
Problem
Internal combustion engines with existing valve trains face challenges in reducing emissions across various operating modes, particularly in-line four-cylinder engines with overhead camshafts, as they require complex camshaft configurations to manage valve actuation efficiently.
Innovation Solution
A DOHC sliding cam valve train with two camshafts and four cam pieces, where each cam piece is movable between axial positions, actuates intake and exhaust valves using cams with different lobes, including zero stroke cams to enable cylinder shutdown and efficient operation in varying modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common cam piece actuates valves of two adjacent cylinders, then camshaft complexity is reduced, but the base circle angle must be adequately large limiting applicability to specific engine configurations
Solution Approach 1:
The camshaft is segmented into modular cam pieces that can be independently positioned axially. Each cam piece contains multiple cam lobes for actuating valves of different cylinders, allowing the camshaft to be adapted to various engine configurations (inline-4, V6, V8, etc.) while maintaining reduced complexity through the shared cam piece architecture.
2Adaptability or versatility
If multiple cam lobes with different strokes are used on adjacent cams, then variable valve stroke is enabled, but the cam piece structure becomes more complex
Solution Approach 1:
Multiple cam lobes with different stroke characteristics (including zero-stroke lobes for cylinder shutdown) are merged into single cam pieces. These cam pieces are arranged axially adjacent to each other on the same camshaft, allowing variable valve stroke functionality to be achieved without requiring separate camshafts or complex mechanisms, thereby managing structural complexity.
3Object-generated harmful factors
If zero stroke cams are included to enable cylinder shutdown, then emission reduction is improved, but the cam configuration requires precise coordination between multiple cam groups
Solution Approach 1:
The camshaft system is designed with universal multi-functionality to support both normal operation and cylinder shutdown modes. Each cam piece contains multiple cam lobes including zero-stroke lobes that can selectively actuate or deactivate valve pairs for different cylinders. The axial positioning of cam pieces allows the same physical camshaft structure to universally serve multiple operating modes (all cylinders active, selective cylinder shutdown, partial shutdown) without requiring mode-specific hardware changes.
Data Source
AI summary
The invention relates to a DOHC sliding cam valve train of an internal combustion engine with a four-cylinder in-line arrangement and cylinder shutoff. One of the two camshafts has two shared cam pieces for the respective adjacent engine cylinders.