Single Actuator Shifting Cam System for Variable Valve Lift
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Solution Overview
Problem
Existing vehicle valve train systems require multiple actuators or have limited options for actuator placement, making them less efficient and less flexible in providing variable valve lift and timing.
Innovation Solution
A camshaft assembly with dual shifting camshaft cartridges, where a single actuator axially displaces a master cartridge, which is coupled to a follower cartridge, allowing for axial movement and variable valve lift without direct engagement of both cartridges, enabling the actuator to be positioned anywhere along the camshaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple actuators are used to directly engage both camshaft cartridges, then reliable axial displacement of both cartridges is achieved, but device complexity and packaging difficulty increase
Solution Approach 1:
The patent combines the function of two separate actuators into a single actuator that controls both camshaft cartridges. The master cartridge includes a master actuator interface that receives signals from the controller, and through the coupling mechanism (finger portions engaging between master and follower cartridges), this single actuator's movement is transmitted to both cartridges, eliminating the need for a second actuator while maintaining reliable control
Solution Approach 2:
The coupling mechanism acts as an intermediary between the master cartridge and follower cartridge. The finger portions that engage between the cartridges transmit the axial displacement movement from the master cartridge to the follower cartridge, enabling indirect control of the follower cartridge without requiring a direct actuator connection
2Ease of operation
If multiple actuators are used to directly engage both camshaft cartridges, then precise control of each cartridge is achieved, but packaging flexibility is reduced
Solution Approach 1:
By merging the control function into a single actuator on the master cartridge, the system reduces the number of components that need to be packaged. The follower cartridge is controlled indirectly through the coupling mechanism, eliminating the need for a second actuator and its associated mounting space, thereby improving packaging flexibility
3Device complexity
If a single actuator is used to control both camshaft cartridges, then device complexity is reduced, but the ability to independently control each cartridge is limited
Solution Approach 1:
The coupling mechanism provides dynamic control capability. The finger portions can engage or disengage based on operational requirements, allowing the system to switch between coupled operation (both cartridges move together) and independent operation (follower cartridge can be positioned independently). This dynamic capability maintains control flexibility while using a single actuator
Solution Approach 2:
The camshaft system is segmented into a master cartridge and a follower cartridge with distinct functions. The master cartridge contains the actuator interface and primary cam lobes, while the follower cartridge contains additional cam lobes for different valve events. This segmentation allows each cartridge to be optimized for specific functions while being controlled through a unified actuation mechanism
Data Source
AI summary
A camshaft assembly for a vehicle valvetrain having first and second engine valves includes a camshaft, and a first camshaft cartridge axially displaceable along the camshaft and including a plurality of first cam lobes configured to selectively impart movement to the first engine valve. A second camshaft cartridge is axially displaceable along the camshaft and includes a plurality of second cam lobes configured to selectively impart movement to the second engine valve. An actuator is configured to axially displace the first camshaft cartridge along the camshaft. A coupling is between the first camshaft cartridge and the second camshaft cartridge. Axial displacement of the first camshaft cartridge selectively imparts movement to the second camshaft cartridge for axial displacement of the second camshaft cartridge.