Segmented Rocker Arm for Selective Valve Actuation
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Solution Overview
Problem
The proximity of the valve yoke to the rocker shaft in many engines prevents the use of single-valve engine brake actuation, necessitating lower pressures for both valves during braking, as there is no space for a hydraulic lash adjuster to actuate the inboard valve separately.
Innovation Solution
A valve opening arrangement with a yoke that moves only the first valve when contacted by a first contact surface and both valves when contacted by a second contact surface, allowing for flexible actuation and minimizing space occupancy, enabling single-valve actuation during engine braking and two-valve actuation during exhaust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the valve yoke is placed in close proximity to the rocker arm pivot shaft to save space, then the device complexity is reduced, but the ability to actuate only the closest valve during braking is lost
Solution Approach 1:
The rocker arm is segmented into two distinct contact surfaces: a first contact surface for engaging the inboard valve stem and a second contact surface for engaging the outboard valve stem. This segmentation allows the single rocker arm to provide selective actuation of different valves depending on which contact surface is engaged, resolving the contradiction between compact packaging and selective valve actuation capability.
Solution Approach 2:
The rocker arm is designed with multi-functionality by incorporating multiple contact surfaces that can engage different valves. The same rocker arm structure serves multiple purposes: it can actuate the inboard valve during braking operations and the outboard valve during exhaust operations, eliminating the need for separate actuation mechanisms and maintaining compact packaging while providing versatile valve control.
2Adaptability or versatility
If a hydraulic lash adjuster is used to actuate the inboard valve separately, then single-valve actuation is achieved, but the device complexity increases and more space is required
Solution Approach 1:
The invention extracts the selective actuation function from a separate hydraulic lash adjuster mechanism and integrates it directly into the rocker arm structure through differentiated contact surfaces. This eliminates the need for additional hydraulic components while maintaining the capability to actuate the inboard valve separately during braking operations.
Solution Approach 2:
The invention merges the selective actuation function with the existing rocker arm mechanism. By incorporating multiple contact surfaces into the rocker arm, the patent combines what would otherwise be separate actuation systems (hydraulic lash adjuster and rocker arm) into a single integrated mechanism, reducing device complexity while preserving single-valve actuation capability.
3Device complexity
If both valves are actuated during braking, then the valve train package is simplified, but higher cylinder pressures are required reducing braking efficiency
Solution Approach 1:
The rocker arm is designed with local quality differentiation through its two distinct contact surfaces: the first contact surface is positioned to engage the inboard valve stem, while the second contact surface is positioned to engage the outboard valve stem. This local differentiation allows selective engagement of different valves based on operational requirements, enabling single-valve actuation during braking to reduce cylinder pressure requirements and improve braking efficiency.
Data Source
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AI summary
A valve opening arrangement includes a first contact surface on a first member, and a second contact surface on a second member discrete from the first member. A first and a second opening are provided, and a first and a second valve movable to open and close the first and second opening, respectively, are provided. A yoke is arranged to move the first valve and not the second valve when contacted by the first contact surface and is arranged to move the first valve and the second valve when contacted by the second contact surface.