Hydraulically Lashed End Pivot Rocker Arm Eccentric Bearing
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Solution Overview
Problem
Conventional overhead valvetrain assemblies experience instability due to side loads and limited rocker arm rotation, leading to misalignment and increased flow resistance in intake and exhaust ports, which reduces engine performance.
Innovation Solution
A hydraulically lashed end pivot rocker arm assembly with an eccentric bearing assembly and offset hydraulic lash adjuster, allowing for increased valve lift and improved stability by mounting the rocker arm on nested eccentric shafts and using a stub shaft with a lug engaged by the hydraulic lash adjuster, which rotates to eliminate lash and provide lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the rocker arm is mounted using a convex-hemi-spherical feature on the hydraulic lash adjuster and a complementary concave-hemi-spherical feature on the rocker arm, then the rocker arm can be positioned without a fixed axis, but the rocker arm becomes unstable under side loads and limited rotation causes misalignment
Solution Approach 1:
The rocker arm assembly is segmented into multiple functional components: a rocker arm body, a separate eccentric bearing assembly with nested eccentric shafts, and a stub shaft with lug. This segmentation allows the positioning function to be separated from the stability function, with the eccentric shafts providing stable rotational support while the rocker arm maintains its positioning capability.
Solution Approach 2:
The eccentric bearing assembly acts as an intermediary between the fixed cylinder head mounting and the moving rocker arm. The nested eccentric shafts (inner shaft within outer shaft) provide a stable rotational axis that mediates between the fixed mounting points and the rocker arm's rotational motion, eliminating instability while preserving operational flexibility.
2Volume of moving object
If the hydraulic lash adjuster, rocker arm and valve stem are aligned in a vertical plane, then the assembly is compact, but this alignment creates protrusions in intake or exhaust ports that increase flow resistance
Solution Approach 1:
The hydraulic lash adjuster is repositioned from the traditional vertical plane alignment to an offset location in a different spatial dimension. The adjuster is mounted parallel to but offset from the vertical plane of motion of the rocker arm, allowing the assembly to maintain compactness while eliminating protrusions into the port flow paths. This dimensional repositioning removes the harmful interference with gas flow.
3Reliability
If the rocker arm is mounted on nested eccentric shafts with offset hydraulic lash adjuster, then valve lift capacity and stability are improved, but the device complexity increases
Solution Approach 1:
Multiple functions are merged into the eccentric bearing assembly: the outer shaft provides structural support and mounting, the inner eccentric shaft provides the rotational axis and stability, and the stub shaft with lug integrates the hydraulic lash adjuster mounting. This merging of functions into a single integrated assembly reduces the number of separate components and simplifies the overall structure despite the increased capability.
Solution Approach 2:
The eccentric bearing assembly serves multiple functions simultaneously: it provides a stable rotational axis for the rocker arm, supports the offset hydraulic lash adjuster, provides lubrication through the hollow inner shaft, and enables increased valve lift capacity. This multi-functionality reduces the need for separate components, thereby managing complexity while delivering enhanced performance.
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 configuration enhances engine performance by maintaining rocker arm stability, reducing flow resistance, and increasing valve lift capacity, thereby improving the overall efficiency of the valvetrain assembly.
Implementation Method 1
an eccentric bore, that is, a bore having an axis offset from and parallel to the axis of the bore in the rocker arm
Implementation Method 2
The inner shaft is hollow and provides high pressure oil to lubricate the inner shaft and eccentric bore interface and the stub shaft and rocker arm interface
Data Source
AI summary
A hydraulically lashed end pivot rocker arm assembly finds application in high performance valve trains of internal combustion engines. The rocker arm is mounted at one end upon an eccentric bearing assembly and includes a surface for engaging a valve stem at the opposite end and a roller engaged by a camshaft disposed between the ends. The eccentric bearing assembly includes a stub shaft or cylindrical body that is received within a bore in the rocker arm and an eccentric bore which receives an inner shaft which extends along the cylinder head and supports the eccentric bearings and the rocker arm assemblies. The stub shaft or cylindrical body includes an ear or lug which is engaged by a hydraulic lash adjuster disposed parallel to and offset from the vertical plane of motion of the rocker arm.