Switchable Finger Follower With DLC Coating and I-Beam Lever
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Solution Overview
Problem
Existing switchable roller finger followers for internal combustion engine valve trains are limited by space restrictions and increased mass moment of inertia due to their design, making them unsuitable for compact applications and reducing efficiency.
Innovation Solution
A switchable finger follower design featuring an inner lever with a sliding pad and a coupling pin that moves longitudinally within a bore, utilizing a DLC coating for reduced friction and an I-beam cross-section for reduced weight and compactness, allowing for efficient switching between valve lift modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a roller finger follower design is used to reduce friction, then friction is reduced, but the mass moment of inertia increases and space requirements increase
Solution Approach 1:
The patent changes the physical parameters of the cam contact surface by applying DLC (diamond-like carbon) coating, which provides low friction properties without requiring a roller design. This allows the flat-faced follower to maintain reduced friction while keeping the mass moment of inertia low.
Solution Approach 2:
The patent uses a simple flat-faced follower design with a lightweight coupling pin mechanism instead of a complex roller assembly. This simpler design achieves the switching function with less mass, reducing the mass moment of inertia while still providing the necessary friction reduction through DLC coating.
2Object-affected harmful factors
If a roller finger follower design is used to reduce friction, then friction is reduced, but the device occupies more space
Solution Approach 1:
The patent applies DLC coating to the flat cam contact surface, which reduces friction without requiring the additional space of a roller mechanism. The coated flat surface provides the necessary low-friction interface while maintaining a compact design.
Solution Approach 2:
The patent extracts the friction-reduction function from the mechanical roller structure and implements it through surface coating (DLC) on a flat surface. This separates the friction management function from the geometric structure, allowing a compact flat-faced design to achieve low friction without the space requirements of a roller.
3Weight of moving object
If a lightweight design with I-beam cross-section is used, then weight is reduced, but structural strength must be maintained
Solution Approach 1:
The patent uses composite construction with an I-beam cross-section for the inner lever, which provides high structural strength-to-weight ratio. The I-beam geometry distributes loads efficiently while minimizing material usage, achieving both weight reduction and strength maintenance.
Solution Approach 2:
The patent applies different properties to different parts of the structure - the I-beam cross-section provides strength where needed while maintaining lightweight characteristics. The DLC coating is applied locally to the cam contact surface where friction reduction is most critical, while the I-beam structure provides localized strength where mechanical loads are highest.
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
The design provides a more compact and lighter switchable finger follower that can operate in reduced space envelopes, enhancing efficiency by reducing lost motion spring and valve spring force requirements, thus improving overall engine performance.
Implementation Method 1
The sliding pad has at least one of an anti-friction coating or a surface finish of Ra 0.05 or better forming a cam contact surface
Data Source
AI summary
A switchable finger follower is provided having an inner lever with a sliding pad located between first and second inner lever ends. The sliding pad has at least one of an anti-friction coating or a surface finish of Ra 0.05 or better forming a cam contact surface. An outer lever supports the inner lever, and includes a first outer lever end mounted for pivoting movement at the first end of the inner lever by a pivot axle. A coupling pin is arranged on one of the inner or outer levers on an end opposite from the pivot axle. The coupling pin has a coupling projection with a first locking surface, and is moveable from a first, locked position with the first locking surface engaged with a second locking surface located on the other of the inner lever or the outer lever, to a second, unlocked position. A lost motion element is arranged between the inner lever and the outer lever.