Variable Cam Timing Phaser Spool Valve Null Region Control
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Solution Overview
Problem
Conventional variable cam timing (VCT) systems face issues with delayed hydraulic adjustments and increased time required to position the cam phaser due to retarded cam torsions, leading to potential delays in engine commands and unwanted position changes.
Innovation Solution
A method is introduced where the spool valve of a cam torque-actuated VCT phaser is moved to a detent region between torsional pulses of the camshaft, and its commands are synchronized with cam torsion events to reduce the impact of retarded cam torsions, allowing for more accurate and reliable positioning of the cam phaser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the spool valve is commanded from a low retard region or advance region to the auto-lock region, then the cam phaser can be positioned at the desired location, but the spool valve must physically travel through a high retard region which causes delayed hydraulic adjustments and unwanted position changes
Solution Approach 1:
The system pre-positions the spool valve in the null region before commanding movement to the auto-lock region. This preliminary positioning prevents the spool valve from traveling through the high retard region, eliminating unwanted cam phaser position changes caused by retarded cam torsion during valve travel.
Solution Approach 2:
The null region acts as an intermediary position between the advance/retard regions and the auto-lock region. By routing the spool valve through this neutral intermediate zone, the system decouples the valve travel path from the high retard region, preventing harmful interactions while maintaining positioning capability.
2Ease of operation
If the spool valve travels through the high retard region, then it can reach the auto-lock region, but retarded cam torsion causes the cam phaser to change position by several degrees immediately before reaching the detent region
Solution Approach 1:
The system pre-positions the spool valve in the null region before commanding movement to the auto-lock region. This preliminary positioning prevents the spool valve from traveling through the high retard region, eliminating unwanted cam phaser position changes caused by retarded cam torsion during valve travel.
Solution Approach 2:
The null region acts as an intermediary position between the advance/retard regions and the auto-lock region. By routing the spool valve through this neutral intermediate zone, the system decouples the valve travel path from the high retard region, preventing harmful interactions while maintaining positioning capability.
3Measurement precision
If the detent circuit hydraulically adjusts the cam phaser position to the neutral position, then the cam phaser can be positioned accurately, but this process takes considerable time particularly if the cam phaser was already at the mid-lock position
Solution Approach 1:
The system pre-positions the spool valve in the null region before commanding movement to the auto-lock region. This preliminary positioning prevents the spool valve from traveling through the high retard region, eliminating unwanted cam phaser position changes caused by retarded cam torsion during valve travel.
Solution Approach 2:
The null region acts as an intermediary position between the advance/retard regions and the auto-lock region. By routing the spool valve through this neutral intermediate zone, the system decouples the valve travel path from the high retard region, preventing harmful interactions while maintaining positioning capability.
4Stability of the object's composition
If the locking pin is engaged to hold the cam phaser in position, then positioning stability is improved, but the time required to engage and disengage the locking pin increases
Solution Approach 1:
The system pre-positions the spool valve in the null region before commanding movement to the auto-lock region. This preliminary positioning prevents the spool valve from traveling through the high retard region, eliminating unwanted cam phaser position changes caused by retarded cam torsion during valve travel.
Solution Approach 2:
The null region acts as an intermediary position between the advance/retard regions and the auto-lock region. By routing the spool valve through this neutral intermediate zone, the system decouples the valve travel path from the high retard region, preventing harmful interactions while maintaining positioning capability.
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 reduces unwanted position adjustments and ensures consistent engagement of the locking pin, improving engine performance and reducing phasing errors, thereby enhancing fuel efficiency and emission control.
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 phaser may be cam torque actuated wherein 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.