Switchable Roller Finger Follower with Pre-Assembled Outer Arms
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Solution Overview
Problem
Existing switchable roller finger followers in overhead cam-type internal combustion engines face issues with friction generated by sliding surface contact, which complicates manufacturing and performance.
Innovation Solution
A switchable roller finger follower design featuring an inner lever with a slot, an outer lever with pocketed arms, and separate outer rollers supported by bearing needles and retainers, allowing for pre-assembly and reduced friction through the use of a coupling device with a locking mechanism and lost motion springs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sliding surface contact is used in conventional roller finger followers, then the structure is simpler, but friction is generated which worsens performance
Solution Approach 1:
The patent introduces an intermediary element (the roller) between the cam surface and the lever to reduce direct sliding contact. The roller rotates on its axis while rolling along the cam surface, converting sliding friction into rolling friction, thereby reducing the harmful friction effect while maintaining the overall structural simplicity of the finger follower mechanism.
Solution Approach 2:
The patent replaces the sliding mechanical contact system with a rolling contact system. Instead of direct sliding between the cam and lever surfaces, a roller is introduced that rotates on bearing needles, substituting the sliding friction mechanism with a rolling friction mechanism, which significantly reduces friction and improves performance.
2Reliability
If outer rollers are separately mounted on outer arms, then assembly is simplified and reliability is improved, but the device complexity increases
Solution Approach 1:
The patent segments the outer roller mounting into separate, independent components. Each outer roller is separately mounted on its respective outer arm using individual bearing needles and retainers, rather than being part of a unified complex assembly. This segmentation allows for easier assembly and disassembly while improving reliability through modular design.
Solution Approach 2:
The patent enables preliminary assembly of the outer rollers on the outer arms before final assembly of the complete finger follower. The outer rollers can be pre-mounted on the outer arms with their bearing needles and retainers, creating ready-to-install sub-assemblies that simplify the final assembly process and improve overall assembly reliability.
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 simplifies assembly, reduces friction, and enhances performance by enabling easy pre-assembly of components and maintaining reliable operation across high and low lift modes.
Implementation Method 1
a lost motion spring connected between the inner lever and the outer lever
Implementation Method 2
outer rollers supported by bearing needles
Data Source
AI summary
A switchable finger follower, including an inner lever and an outer lever. The outer lever includes a pocket defined by two outer arms that extend along longitudinal sides of the inner lever. The outer lever is mounted for pivoting movement at the first end of the inner lever by a pivot axle, and a respective outer roller is separately mounted on an outer side of each of the two outer arms. A coupling device is located on one of the inner or outer levers and has a coupling 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 method of assembling a finger lever with outer rollers connected to the two outer arms is also provided.