Variable Cam Timing Phaser Spool Valve Control
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Solution Overview
Problem
Conventional variable cam timing (VCT) systems face issues with the locking pin becoming side-loaded when attempting to adjust the cam phaser from a mid-lock position, leading to delayed or prevented phasing requests and mechanical stress on the locking machinery.
Innovation Solution
A method involving a spool valve duty cycle control to jump from the detent region to outside the null region and ramp through it while monitoring for cam timing movement away from the locked position, ensuring reliable disengagement of the locking pin before adjusting the cam phaser, thereby reducing side-loading and improving valve timing control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the cam phaser is held at the mid-lock position with the locking pin engaged, then the cam timing is stable, but the locking pin becomes side-loaded when actuation is attempted before full disengagement, causing delayed phasing requests and mechanical stress
Solution Approach 1:
The system performs preliminary disengagement of the locking pin by commanding the spool valve to exit the detent region before initiating cam phaser actuation. This preliminary action ensures the locking pin is fully disengaged and positioned to follow the vane, preventing side-loading during subsequent actuation attempts and ensuring reliable execution of phasing requests.
2Stability of the object's composition
If the spool valve is commanded to the detent region to hold the cam phaser, then the cam timing is maintained, but the locking pin cannot disengage promptly when actuation is commanded, leading to side-loading
Solution Approach 1:
Before commanding actuation, the system executes a preliminary action to move the spool valve out of the detent region, allowing the locking pin to disengage in advance. This preliminary disengagement action ensures the locking pin is ready to follow the vane movement without delay, preventing side-loading while maintaining the ability to hold cam timing when needed.
Solution Approach 2:
The system dynamically adjusts the spool valve position based on operational requirements. When actuation is commanded, the spool valve transitions from the static detent region to dynamic regions that allow the locking pin to disengage and follow the vane. This dynamic adjustment ensures the locking pin can transition from a held position to an active following position without side-loading.
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 approach ensures reliable disengagement of the locking pin and reduces mechanical stress, enhancing engine performance and emissions by preventing side-loading during phaser adjustments.
Implementation Method 1
The spool valve may direct flow of a hydraulic fluid, such as oil, from one side of the vane to the other, such as from a retard side to an advance side.
Implementation Method 2
the actuation of the phaser is dependent on torque generated during cam actuation
Data Source
AI summary
Methods and systems are described for an engine with a cam torque actuated variable cam timing phaser. Phaser positioning control is improved by reducing inaccuracies resulting from inadvertent spool valve and/or phaser movement when the spool valve is commanded between regions. In addition, improved spool valve mapping is used to render phaser commands more consistent and robust.