Variable Cam Timing Oil Pressure Control for Phaser Jamming

Solution Overview

Problem

Variable cam timing (VCT) phasers in internal combustion engines may fail to reach desired positions due to high temperatures or wear, exacerbated by lower oil pressure settings for fuel economy, leading to reduced phasing velocity and engine performance issues.

Innovation Solution

The method involves adjusting the oil pressure supplied to the hydraulic camshaft timing actuator based on the camshaft phaser position, temporarily reducing pressure to unlock a locking pin and then increasing it to achieve the desired phaser position, using a control algorithm to boost oil pressure and compensate for phasing errors, and estimating the age of the VCT phasers for proactive control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If lower oil pressure is used for fuel economy, then fuel consumption is reduced, but VCT phasers may not reach desired position and phasing velocity is reduced

Engineering Contradiction:

Improvefuel consumptionVSAvoidVCT phaser position achievement

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The oil pressure system transitions from a static fixed-pressure design to a dynamic variable-pressure design. The oil pressure is adjusted in real-time based on engine operating conditions, phaser temperature, and phaser position feedback, allowing the system to optimize between fuel economy and reliable VCT operation across different operating scenarios.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the oil pressure parameter dynamically rather than maintaining a constant pressure. By varying oil pressure based on phaser temperature, phaser position, and engine load conditions, the system ensures sufficient pressure for phaser actuation when needed while reducing pressure for fuel economy during normal operation.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If higher oil pressure is used to ensure VCT phaser reaches desired position, then phasing reliability is improved, but fuel economy deteriorates

Engineering Contradiction:

ImproveVCT phaser position achievementVSAvoidfuel consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The oil pressure system transitions from a static fixed-pressure design to a dynamic variable-pressure design. The oil pressure is adjusted in real-time based on engine operating conditions, phaser temperature, and phaser position feedback, allowing the system to optimize between fuel economy and reliable VCT operation across different operating scenarios.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the oil pressure parameter dynamically rather than maintaining a constant pressure. By varying oil pressure based on phaser temperature, phaser position, and engine load conditions, the system ensures sufficient pressure for phaser actuation when needed while reducing pressure for fuel economy during normal operation.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If oil pressure is reduced to unlock locking pin, then pin jamming is prevented, but cam phaser movement is delayed

Engineering Contradiction:

Improvelocking pin operationVSAvoidcam phaser response time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary action by reducing oil pressure before the phasing command is executed to proactively unlock the locking pin. This preliminary pressure reduction ensures the pin is in the correct state before high pressure is applied, preventing jamming and ensuring smooth subsequent phaser movement.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The oil pressure is applied in periodic cycles: reduced pressure for pin unlocking, then increased pressure for phaser movement. This periodic pressure modulation allows the system to sequentially accomplish pin unlocking and phaser actuation without interference between these two functions.

Inventive Principle:

Principle #19Periodic 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 ensures VCT control while maintaining lower oil pressure for fuel economy, enhancing engine response and turbo spool-up time, and preventing cam phaser jamming, thereby improving Brake Specific Fuel Consumption and extending phaser lifespan.

Implementation Method 1

an Oil Pressure Actuated device (OPA), such as a vane type cam phaser. The phaser may be controlled by an electromechanically actuated spool valve that directs oil flow to one side or the other of the vane.

Methodology Applied

Scientific EffectHydraulic pressure: Hydraulic Press

Implementation Method 2

VCT phasers are equipped with a locking pin in their home position to prevent rattle noise.

Methodology Applied

Scientific EffectMechanical locking: Mechanical Fastener

Data Source

PatentUS8714123B2Oil pressure modification for variable cam timing

Publication Date: 2014.05.06 FORD GLOBAL TECH LLC

AI summary

Systems and methods for modifying oil pressure for a variable cam timing system are provided. In one example approach, a method comprises, in response to an operating condition, adjusting a valve coupled to a hydraulic variable camshaft timing actuator to initiate camshaft phasing and adjusting an oil pressure supplied to the valve based on a camshaft phaser position. If a camshaft phaser locking pin is in a home position, the method may further comprise reducing the oil pressure supplied to the valve for a predetermined time interval to a threshold amount to unlock the locking pin but not move the camshaft phaser and then increasing the oil pressure supplied to the valve to move the camshaft phaser.