Switching Roller Finger Follower Resettable Starting Position
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Solution Overview
Problem
Existing overhead cam switching roller finger followers face challenges in setting the starting position of the inner arm due to variances in spring strength and tolerance stack-up, leading to difficulties in lash management and uneven presentation of the inner roller assemblies to the overhead cam.
Innovation Solution
A switching roller finger follower design incorporating a stop pin with a selective fit through an inner port and axle, allowing for adjustable lash management by varying the stop pin diameter to set the starting position, and featuring a latch assembly and return springs to bias the inner arm assembly toward the desired position, independent of the outer arms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring is used to bias the inner arm to return to starting position, then the inner arm can return to starting position, but variances in spring strength and tolerance stack up make it difficult to set starting position
Solution Approach 1:
The patent adjusts the starting position by changing the physical parameters of the stop pin (diameter, length) and its position within the inner arm assembly. By varying these parameters, the exact starting position can be precisely controlled regardless of spring strength variances or tolerance stack-up in other components.
Solution Approach 2:
The stop pin acts as an intermediary element between the inner arm assembly and the outer arms. It provides a fixed reference point that defines the starting position, mediating the interaction between components and eliminating the need to rely solely on spring force for position control.
2Manufacturing precision
If tolerance stack up is accommodated, then starting position can be set accurately, but device complexity increases
Solution Approach 1:
Instead of controlling tolerances throughout the entire assembly, the patent applies local quality control by using a stop pin with specific dimensional characteristics (clearance fit, crowned ends) that locally compensates for tolerance stack-up. This focused approach achieves accurate starting position without requiring complex control mechanisms throughout the entire device.
3Ease of operation
If stop pin is made adjustable, then lash management is improved, but manufacturing complexity increases
Solution Approach 1:
The stop pin is designed as a simple, inexpensive component with standardized features (crowned ends, clearance fit) that can be easily manufactured and replaced if needed. This approach allows for adjustable lash management without significant manufacturing complexity, as the stop pin itself is a simple element that can be produced cost-effectively.
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 design effectively manages both latch lash and roller lash, allowing for precise adjustment of the starting position and reducing scrap and re-design costs by enabling customer-specific variations without complete re-manufacture, while maintaining a low part count and minimizing scrap during production.
Implementation Method 1
At least one return spring biases the stop pin toward the inner shoulders so as to bias the inner arm assembly toward the starting position
Data Source
AI summary
A switching roller finger follower comprises an inner arm assembly. A pair of outer arms surround the inner arm assembly. A pivot axle connects the inner arm assembly to pivot with respect to the pair of outer arms from a starting position to a lost motion position. A latch assembly comprises a latch selectively movable from a latched position latching the inner arm assembly to move dependent with the outer arms and an unlatched position unlatching the inner arm assembly to pivot independent of the outer arms. A stop pin spans between the pair of outer arms and through an inner port in an axle of inner arm assembly. The stop pin comprises a clearance fit with the inner port, and the stop pin is configured pivotable independent of the outer arms. At least one return spring biases the stop pin toward the starting position.