Variable Valve Lift Cam Assemblies with Axial Control Links
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Solution Overview
Problem
Modern automotive four-stroke internal combustion engines with camshaft-based valve operating systems face limitations in efficiently providing variable valve lift and timing, as they are susceptible to improvements in controlling the timing and duration of intake and exhaust valve openings.
Innovation Solution
A valve operating system with cam assemblies that include control links and cam members with multiple configurations, allowing axial movement and positioning along a rotary axis, coupled with a detent mechanism and actuator segments with ramp profiles, enabling the cam assemblies to switch between different lift profiles and timing positions, thereby providing variable valve lift and timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a camshaft with multiple sets of cam lobes is used to provide variable valve lift and timing, then valve operation flexibility is improved, but device complexity increases
Solution Approach 1:
The camshaft is divided into multiple independent cam assemblies, each capable of rotating about the rotary axis. Each cam assembly contains control links and cam members that can be independently positioned, allowing selective activation of different cam configurations without requiring a completely complex multi-lobe camshaft structure.
Solution Approach 2:
The cam assemblies are made dynamically reconfigurable through axial movement along the rotary axis. The control links enable cam members to switch between different cam configurations by moving axially, transforming a static complex multi-lobe camshaft into a dynamic system where simplicity is maintained through motion-based reconfiguration.
2Measurement precision
If cam assemblies are made slide-able along the rotary axis to switch between cam configurations, then valve timing control is improved, but manufacturing precision requirements increase
Solution Approach 1:
Control links serve as intermediary components between the cam members and the cam tube. These control links facilitate precise axial movement and positioning of cam members along the rotary axis, mediating the transformation of rotational motion into precise axial positioning without requiring extremely tight manufacturing tolerances on the cam assemblies themselves.
Solution Approach 2:
The detent mechanism provides self-locking capability that automatically secures cam assemblies in their intended positions along the rotary axis. This self-service positioning feature reduces the burden on manufacturing precision by providing inherent positional stability through mechanical engagement, allowing the system to achieve precise valve timing control without requiring ultra-precise manufacturing of all components.
3Reliability
If detent mechanisms are used to secure cam assemblies in position, then reliability is improved, but device complexity increases
Solution Approach 1:
The detent mechanism is merged with the cam tube structure, where detent features are integrated directly into the cam tube rather than being separate components. This combining approach provides reliable positional stability for cam assemblies while minimizing the increase in overall device complexity by consolidating functions into existing structural elements.
Data Source
AI summary
A valve operating system that includes a plurality of cam assemblies that are coupled for rotation about a rotary axis. Each of the cam assemblies has a control link and a first cam member. Each of the control links has a link body, which forms a majority of the control link, and that extends parallel to the rotary axis. Each of the first cam members is coupled to one of the control links for axial movement therewith along the rotary axis between first and second positions to alternate between first and second cam profiles, respectively.