Multi-step Valve Actuation System with Latching Follower Arms
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Solution Overview
Problem
The multi-step valve actuation system is not feasible in overhead valve, camshaft-in-block internal combustion engines due to space constraints, as it requires increased packaging space and design modifications to accommodate the necessary components.
Innovation Solution
A multi-step valve actuation system is implemented using pivotably mounted rocker arms, pushrods, and follower arms that engage with multiple cams on a camshaft, allowing for selective valve lift profiles and incorporating a lash adjuster to manage clearances, with friction-reducing roller assemblies and latching mechanisms for unitary movement, enabling efficient packaging within limited spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multi-step valve actuation system is implemented in an overhead valve, camshaft-in-block internal combustion engine, then the engine can achieve multiple valve lift profiles for improved performance and fuel efficiency, but the space requirements increase making the system infeasible due to limited packaging space
Solution Approach 1:
The patent combines multiple follower arms (first, second, and third follower arms) into a single integrated valve actuation mechanism that operates from one camshaft. The follower arms are positioned at different radial distances from the camshaft center and can be selectively engaged to provide different valve lift profiles, merging what would traditionally require separate actuation systems into one compact unit.
Solution Approach 2:
The single camshaft with multiple cams (first, second, and third cams at different radial distances) serves multiple functions by providing different valve lift profiles through selective engagement of follower arms. This multi-functional design allows the same physical component to deliver first maximum valve lift, second maximum valve lift, and third maximum valve lift based on operating conditions, eliminating the need for multiple separate camshafts or actuation systems.
2Adaptability or versatility
If follower arms are selectively latchable for unitary movement to achieve different valve lifts, then multi-step valve actuation is enabled, but the device complexity increases with additional latching mechanisms
Solution Approach 1:
The follower arms are designed with dynamic latching capabilities that allow them to be selectively engaged or disengaged from the cam lobes based on camshaft rotation position. The latching mechanism transitions between locked and unlocked states dynamically, enabling the system to switch between different valve lift profiles (first, second, and third maximum lifts) without requiring complex mechanical linkages or multiple separate mechanisms.
Solution Approach 2:
The latching mechanism appears to be designed for automatic or self-actuating engagement based on the camshaft position and follower arm movement. The system utilizes the natural motion of the follower arms relative to the cam lobes to trigger latching or unlatching actions, reducing the need for external actuation mechanisms and simplifying the overall device complexity while maintaining selective valve lift control capability.
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 efficient operation of internal combustion engines with multiple valve lift profiles, reducing space requirements and enabling efficient packaging, thereby enhancing engine performance and fuel efficiency by allowing for valve deactivation and optimized engine modes like Active Fuel Management.
Implementation Method 1
Each of the first, second, and third follower arms may rotatably support friction reducing roller assemblies
Data Source
AI summary
A multi-step valve actuation system is provided to selectively open a poppet valve of an internal combustion engine having a camshaft rotatably supported by a cylinder block. The multi-step valve actuation system includes a rocker arm operable to selectively open the poppet valve and a pushrod operable to bias the rocker arm. A first follower arm is engageable with a first cam of the camshaft and operates to selectively bias the pushrod. A lash adjuster is disposed between the first follower arm and the pushrod. A second follower arm is engageable with a second cam of the camshaft and selectively latchable with respect to the first follower arm, while a third follower arm is engageable with a third cam of the camshaft and selectively latchable with respect to the first follower arm. An internal combustion engine incorporating the multi-step valve actuation system of the present invention is also disclosed.