Switching Finger Follower Support for Partial-Engagement Prevention
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Solution Overview
Problem
Existing switching finger followers in internal combustion engines suffer from partial engagement issues leading to damage and failure, necessitate precise timing controls, and are limited in applicability to heavy and medium-duty engines, especially in multiple cylinder environments.
Innovation Solution
A switching finger follower system with an adjustable support assembly that eliminates partial engagement by providing consistent contact geometries and positively defined switching mechanism positions, allowing for simplified control and reduced complexity, applicable to single-source and lost motion systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a locking mechanism with lateral followers and locking bar is used to switch between lobes, then valve actuation motions can be selectively conveyed, but partial engagement occurs leading to damage and failure of the locking mechanism
Solution Approach 1:
The locking mechanism is segmented into a locking bar with multiple engagement surfaces and corresponding engagement features on the follower. This segmentation allows for multiple discrete engagement positions, eliminating partial engagement by providing distinct locked states at different lobes.
Solution Approach 2:
Different engagement surfaces on the locking bar are designed with specific geometries tailored to each lobe position. The locking mechanism transitions from a uniform design to one with localized variations in engagement surface geometry, optimizing each engagement point to prevent partial engagement and distribute stresses evenly.
2Adaptability or versatility
If a switching finger follower is used to enable auxiliary valve actuation motions, then multiple operating modes can be achieved, but precise timing controls are necessitated increasing system complexity
Solution Approach 1:
The finger follower design incorporates self-locking and self-latching features that automatically maintain engagement with the selected lobe without requiring active control during operation. The mechanism uses spring-loaded followers and cam-actuated locking that automatically engage and disengage based on cam profile, eliminating the need for external timing controls.
3Power
If conventional finger followers are used in heavy and medium-duty engines, then valve actuation can be achieved, but the high loading conditions cause failures due to partial engagement
Solution Approach 1:
The finger follower incorporates shock-absorbing elements and compliant mounting features that cushion the high loading conditions before they reach the locking mechanism. This beforehand cushioning protects the locking bar and engagement features from excessive stresses that would cause failure under heavy-duty operating conditions.
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 system enhances durability and accuracy of valve motion control, reduces costs by eliminating the need for precise timing controls, and supports multiple cylinder operations with a single solenoid, while enabling alternative valve motions like braking late intake valve closing and early exhaust valve opening.
Implementation Method 1
a cam, which receives a rotational motion from a crankshaft and provides a reciprocating motion to an engine valve
Implementation Method 2
a hydraulic lash adjuster (HLA), which receives the reciprocating motion from the cam and maintains a zero lash between the cam and a finger follower
Implementation Method 3
The finger follower typically comprises a motion receiving component, disposed between the ends of the lever, to receive the valve actuation motions from a motion source (such as a cam), which motions are then conveyed to the engine valves via the load end of the lever
Data Source
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AI summary
A switching finger follower for an engine valve train utilizes an adjustable support assembly that eliminates potential for partial engagement during operation. A lever engagement member or latch is disposed for movement on the follower body and interacts with a lever to provide a constant contact geometry. The finger follower may be configured as a lost motion device and may include a biasing assembly and a travel limiter. The latch may support the lever in at least one precise position and may support the lever in a second position for partial lost motion, or permit the lever to pivot free of the latch for complete lost motion, as in cylinder deactivation applications.