Rocker Arm Lash Adjustment with Lost Motion Spring
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Solution Overview
Problem
In internal combustion engines with variable valve actuation systems, setting lash in rocker arm assemblies with a lost motion stroke is challenging due to the high stiffness of the lost motion spring, which makes it difficult to accurately assess and set the proper lash value using a feeler gauge.
Innovation Solution
A method involving a rocker arm with a lost motion shaft and collar, where a feeler gauge is inserted between the collar and the rocker arm, and an adjusting screw is used to set the desired lash, avoiding the direct influence of the lost motion spring's force, allowing for precise adjustment without premature pinching of the gauge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a lost motion spring with high stiffness is used in the rocker arm assembly, then the valve actuation force is improved, but the lash setting precision deteriorates due to difficulty in assessing proper lash value with feeler gauge
Solution Approach 1:
The invention divides the lash measurement process into two distinct phases: first measuring the lost motion stroke (segment 1) by inserting the feeler gauge between the valve bridge and e-foot, then separately adjusting the mechanical lash (segment 2) using the adjusting screw. This segmentation allows each parameter to be measured and adjusted independently, eliminating the interference caused by the high stiffness spring force during measurement.
Solution Approach 2:
The invention performs the lost motion stroke measurement as a preliminary action before the final lash adjustment. By first determining the lost motion stroke value with the feeler gauge while the spring is in its natural state, the operator establishes a baseline measurement that is not influenced by spring pressure. This preliminary measurement enables subsequent accurate adjustment of the mechanical lash component.
2Ease of operation
If a feeler gauge is inserted between the e-foot and valve bridge during lash adjustment, then the lash can be set, but the gauge may be prematurely pinched due to the lost motion spring force, leading to inaccurate adjustment
Solution Approach 1:
The invention introduces a dynamic, two-stage adjustment process where the feeler gauge is used in a controlled manner during the lost motion stroke measurement phase, then removed or repositioned for the mechanical lash adjustment phase. This dynamic approach adapts the measurement technique to the specific requirements of each adjustment stage, preventing premature pinching while maintaining ease of operation.
Solution Approach 2:
The feeler gauge serves as an intermediary tool that facilitates the lost motion stroke measurement without being subjected to the full force of the lost motion spring. By positioning the gauge between the valve bridge and e-foot during the measurement phase, it allows operators to assess the lost motion stroke value before the spring force becomes problematic during final lash setting.
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 method enables accurate and reliable setting of lash in rocker arm assemblies with lost motion strokes, ensuring proper valve operation by isolating the feeler gauge from the lost motion spring's force, thus providing consistent and precise lash adjustment.
Implementation Method 1
the lost motion shaft being biased toward a valve bridge by a lost motion spring
Data Source
AI summary
A method for setting lash on a rocker arm assembly having a lost motion stroke includes: providing a rocker arm having a lost motion shaft including a collar, the lost motion shaft being biased toward a valve bridge by a lost motion spring, the lost motion shaft being translatable along a bore defined in the rocker arm; inserting a feeler gage in an area between the collar and the rocker arm; and adjusting an adjusting screw until a desired lash is attained.