Variable Cam Timing Phaser Locking Pin Engagement Consistency

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Solution Overview

Problem

Conventional variable cam timing (VCT) systems face issues with inconsistent locking pin engagement due to spool valve travel through high retard regions, leading to delays in cam phaser position adjustments and engine command responses.

Innovation Solution

The method involves pre-positioning the cam phaser slightly advanced of the mid-lock position and then moving the spool valve to the detent region during cam torsional pulses to utilize these pulses for adjusting the phaser towards the neutral position, thereby reducing unwanted position changes and enhancing locking pin engagement consistency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the spool valve is commanded from a low retard region or the advance region to the detent region, it must physically travel through a high retard region, then the cam phaser may change its position by several degrees in the retarded direction immediately before reaching the detent region and auto-locking, which increases the time needed for the detent circuit to adjust the cam phaser position to the neutral position

Engineering Contradiction:

Improvelocking pin engagement consistencyVSAvoidtime required for cam phaser position adjustment

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The spool valve is pre-positioned in the high retard region before being commanded to the detent region. This preliminary positioning ensures that when the spool valve travels to the detent region, the cam phaser is already prepared to engage the locking pin without experiencing unwanted position changes, thereby reducing the time required for position adjustment and improving engagement consistency.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If the spool valve travels through the high retard region, retarded cam torsions may actuate the cam phaser position movement, then this creates delays in subsequent engine commands that require the cam phaser to be in a hard locked position

Engineering Contradiction:

Improvecam phaser positioningVSAvoidengine command response speed

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

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 the time required for locking pin engagement and improves the consistency of cam phaser positioning, enhancing engine performance and reducing phasing errors.

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

Methodology Applied

Scientific EffectHydraulic pressure: Pressure Gradient

Implementation Method 2

Alternatively, the phaser may be cam torque actuated wherein the actuation of the phaser is dependent on torque generated during cam actuation

Methodology Applied

Scientific EffectTorque: Torque

Data Source

PatentUS10465568B2Method and system for variable cam timing device

Publication Date: 2019.11.05 FORD GLOBAL TECH LLC

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.