Switchable Roller Finger Follower Lash Adjustment
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Solution Overview
Problem
Existing switchable roller finger followers for internal combustion engines lack lash adjustment capability between the inner and outer levers, which is essential for optimal valve train operation.
Innovation Solution
A switchable roller finger follower design that includes a locking pin with adjustable flat height and clearance, allowing for precise mechanical lash adjustment between the inner and outer levers, enabling selection of locking pins with different flat heights to set desired lash values within a range of 25 to 200 microns, and an anti-rotation pin to prevent locking pin rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a locking pin with adjustable flat height is used, then lash adjustment capability is improved, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by providing locking pins with different flat heights (e.g., first flat height for first lash value, second flat height for second lash value) to adjust the mechanical lash between inner and outer levers. This allows precise control of the coupling device lash by selecting appropriate locking pins, directly resolving the need for lash adjustment capability while maintaining a relatively simple overall device structure.
2Adaptability or versatility
If multiple locking pins with different flat heights are provided, then adaptability is improved, but manufacturing complexity increases
Solution Approach 1:
The invention provides multiple locking pins with different flat heights (first flat height, second flat height, etc.) to enable different lash settings (first lash value, second lash value). This parameter variation approach improves adaptability by allowing selection of appropriate lash values for different operating conditions, while the manufacturing complexity is managed by using identical pin structures with only dimensional variations.
Solution Approach 2:
The coupling device allows dynamic adjustment of lash values by selecting different locking pins based on operational requirements. The ability to change lash settings dynamically (by replacing locking pins) enhances adaptability while maintaining ease of manufacture through standardized pin designs that differ only in flat height dimensions.
3Measurement precision
If the locking pin flat height is precisely controlled, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies different flat heights for locking pins to achieve different lash values, requiring precise control of the flat height parameter during manufacturing. This direct parameter control approach ensures that the lash measurement accuracy is maintained by precisely controlling the flat height dimension, accepting tighter tolerances on this critical parameter to achieve the desired measurement precision.
Solution Approach 2:
The invention replaces complex mechanical adjustment mechanisms with a simpler system of pre-manufactured locking pins having different flat heights. This substitution approach improves measurement precision by eliminating the need for complex adjustment mechanisms, while managing manufacturing precision requirements through standardized pin production with controlled flat height dimensions.
4Reliability
If an anti-rotation pin is added, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent incorporates an anti-rotation pin to prevent the locking pin from rotating within the coupling device. This beforehand protective measure ensures that the locking pin maintains its intended orientation and prevents premature disengagement or malfunction, thereby improving reliability by anticipating and preventing potential failure modes related to locking pin rotation.
Solution Approach 2:
The anti-rotation pin serves as an intermediary element that prevents unwanted rotation of the locking pin. This additional component mediates between the locking pin and the coupling device housing, ensuring stable operation and improving reliability by eliminating a potential source of failure without requiring major structural changes to the overall device.
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
Enables adjustable lash settings for improved mechanical coupling, enhancing the operational efficiency and adaptability of the valve train by ensuring optimal lift mode transitions between high lift and low lift or no lift modes.
Implementation Method 1
oil from an oil source is used to activate the coupling element. When the coupling element is activated, it locks the outer lever to the inner lever
Implementation Method 2
the motion being absorbed by a lost-motion spring
Implementation Method 3
a lost motion spring is connected between the inner lever and the outer lever
Data Source
AI summary
A switchable finger follower, including an inner lever and an outer lever. The outer lever is mounted for pivoting movement to the inner lever. A coupling device is located on one of the inner or outer levers and has a locking pin arranged to move between a locking position, in which the inner and outer levers are connected together for movement in an activation direction, and an unlocked position, in which the inner lever is pivotable relative to the outer lever. A coupling projection is located on the other of the inner or outer lever. The locking pin engages beneath the projection in the locking position, and the locking pin includes a flat at a defined flat height that contacts the coupling surface in the locking position and is selected from a number of locking pins having different flat heights to set a desired mechanical coupling device lash.