Sliding-pivot locking mechanism for variable valve lift
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Solution Overview
Problem
Internal combustion engines without variable valve timing must compromise between optimization at low or high engine speeds, sacrificing performance in non-elected ranges due to fixed cam profiles.
Innovation Solution
A locking mechanism for a rocker arm valve train assembly with axially sliding locking elements allows selective locking of secondary rocker arms to an active rocker arm, changing cam profiles in response to hydraulic pressure changes, enabling variable valve lift and timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed cam profile is used in the valve train, then the structure is simple and reliable, but the engine performance cannot be optimized across different engine speeds and loads
Solution Approach 1:
The patent applies the dynamics principle by making the valve train system adjustable through hydraulic actuation. The locking mechanism can dynamically switch between locked and unlocked states based on engine operating conditions, allowing the system to adapt valve timing and lift characteristics without requiring multiple fixed cam profiles or complex mechanical adjustment mechanisms.
Solution Approach 2:
The patent utilizes hydraulics principle by employing a hydraulic locking mechanism that uses fluid pressure to control the engagement state of the locking elements. Hydraulic fluid is supplied through galleries in the pivot shaft to actuate the locking mechanism, enabling smooth and reliable switching between different cam profile configurations without complex mechanical linkages.
2Adaptability or versatility
If multiple cam profiles are added to enable variable valve timing, then engine performance is optimized across different speeds, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the rocker arm system into modular components: active rocker arms that directly follow cam profiles, secondary rocker arms that can be selectively locked to active arms, and independent locking mechanisms for each secondary arm. This modular segmentation allows flexible configuration without requiring complete redesign of the entire valve train for each cam profile change.
Solution Approach 2:
The patent uses an intermediary locking mechanism as a mediator between the camshaft and rocker arms. This locking mechanism, housed within the rocker housing and actuated hydraulically, selectively couples or decouples secondary rocker arms from active rocker arms, enabling cam profile switching without direct mechanical complexity in the rocker arm structure itself.
3Ease of operation
If locking elements are placed outside the rocker arms, then the locking mechanism is accessible, but the rocker design becomes heavier and more complex
Solution Approach 1:
The patent applies the nesting principle by placing the locking elements and hydraulic actuation components inside the rocker housing and pivot shaft structure. The male locking elements are housed within female cavities in the rocker arms, and hydraulic galleries are integrated into the pivot shaft. This internal nesting achieves compact and lightweight rocker design while maintaining functionality through centralized access points.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for optimized engine performance across a wider range of operating conditions by changing cam profiles, reducing torque and complexity, and enabling a compact, lightweight rocker design without the need for additional structural elements.
Implementation Method 1
When hydraulic pressure is changed in response to changing engine conditions, the male elements slide between predetermined positions within the female cavities
Data Source
AI summary
A locking mechanism for a plural rocker arm valve train assembly is provided. The locking mechanism is adapted for use with a camshaft having a plurality of different cam lobes having a plurality of different profiles, which result in variable valve displacement and duration. A plurality of rocker arms are located on a pivot shaft which runs parallel to the camshaft, each rocker arm having structures configured to be acted upon by respective lobes of the camshaft. An active rocker arm has structure configured to act upon an engine valve or valves. A movable locking element is fully enclosed by the rocker arms and is capable of selectively moving along the pivot shaft to allow the active rocker arm to selectively engage one or more of the other rocker arms for common pivoting, resulting in varied displacement of the engine valve or valves.