Switchable Camshaft Valvetrain for Variable Valve Lift
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Solution Overview
Problem
Existing valvetrain systems in combustion engines face limitations in dynamically adjusting valve timing and lift profiles due to static cam profiles, which compromise between fuel consumption, power, and emissions, and are influenced by temperature, pressure, and viscosity of hydraulic oil in electro-hydraulic systems, and are complex and costly in solenoid-type actuation systems.
Innovation Solution
A valvetrain assembly with a main camshaft, main rocker arms, auxiliary cam, and a latch system controlled by an auxiliary camshaft, allowing for switching between main and auxiliary cam profiles to provide adjustable valve lift and timing, enabling multiple profiles for selected valves or cylinders, and incorporating electric drive means for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a static cam profile is used in the valvetrain, then the structure is simple and reliable, but the valve timing and lift cannot be dynamically adjusted, resulting in compromised fuel consumption, power, and emissions performance
Solution Approach 1:
The patent applies dynamics by making the cam profile switchable between different configurations. The camshaft can dynamically change between a main cam profile and an auxiliary cam profile based on engine operating conditions, allowing the valvetrain to adapt valve timing and lift characteristics without requiring a completely complex reconfigurable system. This resolves the contradiction by introducing controlled variability into an otherwise simple cam-based system.
Solution Approach 2:
The camshaft is segmented into multiple functional components: a main camshaft with main cams and an auxiliary camshaft with auxiliary cams. Each camshaft can independently provide different cam profiles, and they can be selectively engaged or disengaged. This segmentation allows the system to offer multiple valve timing strategies while maintaining the simplicity of individual cam profiles, thus improving adaptability without proportionally increasing overall system complexity.
2Adaptability or versatility
If electro-hydraulic variable valve actuation is used to change cam profile, then valve timing and lift can be adjusted, but the system becomes influenced by temperature, pressure, and hydraulic oil viscosity
Solution Approach 1:
The patent replaces the electro-hydraulic actuation system with a purely mechanical solution. Instead of using hydraulic fluid and electric valves to change cam profiles, the invention uses mechanically actuated switchable camshafts where the main and auxiliary camshafts can be selectively engaged through mechanical means. This eliminates the reliability issues associated with hydraulic fluid viscosity changes, temperature effects, and pressure variations, while maintaining cam profile adjustability.
3Adaptability or versatility
If solenoid type actuation system is used to operate valves without cams, then valve timing can be controlled, but the system becomes complex and costly with an actuator needed for each valve
Solution Approach 1:
The patent applies universality by using a single camshaft system that serves multiple functions. The main camshaft and auxiliary camshaft together provide multiple valve timing profiles for all valves, rather than requiring individual actuators for each valve. The switchable cam mechanism allows one mechanical system to perform the work of multiple independent actuators, reducing both complexity and cost while maintaining adaptive valve timing control.
Data Source
AI summary
A valvetrain assembly has valves each having a valve stem; a main camshaft with main cams, a main cam corresponding to each valve; main rocker arms each corresponding to a valve and having a valve stem actuation portion, a pivot axis parallel to the main cam shaft, and a main cam follower for following the corresponding main cam, wherein the valve stem actuation portion, pivot axis, and main cam follower are arranged along the main rocker arm length distanced from each other; an auxiliary cam on the main camshaft; an auxiliary cam follower for each auxiliary cam, following the auxiliary cam, wherein each auxiliary cam follower is movable on one main rocker arm between a first and second position; a latch on respective main rocker arm(s) for locking the auxiliary cam follower in the first position; and an auxiliary camshaft with a selector cam for each latch, controlling the latch.