Switchable Roller Finger Follower De-aeration Path
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Solution Overview
Problem
Hydraulic switchable roller finger followers experience delays and inconsistency in switching time due to air bubbles in the hydraulic fluid path, which is unsuitable for applications requiring rapid switching.
Innovation Solution
A switchable roller finger follower design incorporating a coupling device with a coupling pin that moves between locked and unlocked positions, featuring a de-aeration flow path that opens when locked and closes when unlocked, allowing air to escape when the pin is locked and preventing fluid leakage when high pressure is applied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic pressure is used to activate the coupling element, then the switching function can be controlled, but air bubbles in the hydraulic fluid path cause lag time and inconsistency in switching
Solution Approach 1:
The patent extracts air bubbles from the hydraulic system by providing a dedicated de-aeration passage that allows air to escape from the actuator chamber before it interferes with the switching operation. This separates the air removal function from the normal hydraulic operation, ensuring consistent and timely switching without air-induced lag.
Solution Approach 2:
The de-aeration passage is designed to remove air bubbles from the hydraulic fluid before they can cause switching delays. By providing a pre-established escape path for air, the system prepares for potential air accumulation and eliminates it proactively, ensuring consistent switching timing.
2Ease of operation
If the coupling element is released by oil pressure for deactivation, then the inner lever can travel a lost motion stroke, but hydraulic fluid may leak when high pressure is applied
Solution Approach 1:
The coupling pin is designed to dynamically change position based on hydraulic pressure. At low pressure during deactivation, the pin moves to allow lever separation. At high pressure during activation, the pin shifts to block the de-aeration passage, preventing fluid leakage while maintaining the dynamic response needed for operation.
Solution Approach 2:
The de-aeration passage includes a localized blocking feature that is only active when needed. The coupling pin creates a local obstruction in the passage under high pressure conditions, allowing the rest of the system to function normally while preventing leakage at the critical location.
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 integrated de-aeration flow path effectively removes air bubbles, ensuring faster and more consistent switching operations by allowing air to exit when the pin is locked and preventing fluid loss when the pin is unlocked, thus enhancing the reliability and speed of the switching mechanism.
Implementation Method 1
Pressure from a hydraulic fluid from the oil passage moves the coupling pin into one of the locked or the unlocked positions
Implementation Method 2
The coupling device also includes a spring configured to bias the coupling pin in the other of the locked and unlocked positions
Implementation Method 3
a de-aeration flow path is formed between the oil passage and the opening for allowing air to move out of the oil passage, past the coupling pin, and exit through the opening
Data Source
AI summary
A switchable roller finger follower includes an inner lever, an outer lever pivotably mounted to the inner lever by a pivot axle, and a coupling device. The coupling device includes a coupling pin configured to move between a locked position in which the inner lever and the outer lever are connected together for movement in at least one direction and an unlocked position in which the inner lever is movable relative to the outer lever in the at least one direction. The coupling device also includes a spring configured to bias the coupling pin in the locked or unlocked position. A de-aeration flow path is formed between an oil passage and an opening for allowing air to move out of the oil passage, past the coupling pin, and exit through the opening. The de-aeration flow path switches between being open and closed based on a position of the coupling pin.