Zero Pressure Phaser Unlocking via Residual Oil Pumping
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Solution Overview
Problem
Existing variable cam timing (VCT) systems face challenges in unlocking the lock pin during engine start-up when oil pressure is insufficient, preventing the phaser from moving to desired positions, especially in 'stop-start' modes where the engine may not achieve a successful cold start if the intake camshaft phaser is locked at the full retard position.
Innovation Solution
A pumping chamber is created using an existing phaser control valve and solenoid to generate sufficient oil pressure to disengage the locking pin at all conditions, allowing the phaser to unlock and move to various positions, including the retard position, by utilizing a spool valve and pilot valve system that primes the pump chamber during engine shutdown and fills it with residual pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lock pin is engaged to lock the phaser at full retard position during engine shutdown, then the phaser maintains a desired position for stop-start mode, but the lock pin cannot be unlocked during engine cranking due to insufficient oil pressure
Solution Approach 1:
The system performs preliminary action by maintaining residual oil pressure in the phaser chambers during engine shutdown. The control valve directs oil pressure to both working chambers simultaneously, keeping the phaser in a neutral position and preventing the lock pin from engaging, thereby ensuring the phaser is ready for immediate operation during engine restart without requiring high pressure to unlock
Solution Approach 2:
The control valve acts as an intermediary by directing oil pressure to both working chambers simultaneously during shutdown, creating a balanced pressure state that prevents lock pin engagement. This intermediary action ensures that during restart, the lock pin remains disengaged and the phaser can move freely to the commanded position
2Productivity
If the oil control valve exhausts all oil from one working chamber to move the phaser to an extreme position, then the phaser reaches the desired extreme position, but the lock pin cannot be unlocked during engine start-up when oil pressure is low
Solution Approach 1:
The system performs preliminary action by maintaining residual oil pressure in both working chambers during engine shutdown. The control valve directs oil pressure to both chambers simultaneously, keeping the phaser in a neutral position and preventing the lock pin from engaging, thereby ensuring the phaser is ready for immediate operation during engine restart without requiring high pressure to unlock
Solution Approach 2:
The control valve changes the pressure distribution parameter by directing oil pressure to both working chambers simultaneously during shutdown, creating a balanced pressure state. This parameter change prevents the phaser from moving to extreme positions and ensures the lock pin remains disengaged during restart
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
Enables the phaser to unlock the lock pin during engine cranking and start-up, allowing for successful engine starting and reduced Noise Vibration and Harshness (NVH) during hot restarts, even when oil pressure is low, by ensuring the phaser can move to the required positions, such as the retard position, enhancing engine performance and efficiency.
Implementation Method 1
the solenoid 107 may also be linearly controlled by varying current or voltage
Implementation Method 2
A pumping chamber is created using an existing phaser control valve and solenoid to generate sufficient oil pressure to disengage the locking pin at all conditions
Data Source
AI summary
Using existing phaser control valve and a solenoid to create a pumping chamber which provides enough oil pressure to disengage a locking pin at all conditions.