Dual Lock Pin Phaser for Variable Camshaft Timing
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Solution Overview
Problem
Existing variable camshaft timing (VCT) systems, particularly oil pressure actuated (OPA) and torsional assist (TA) systems, are limited in their ability to control phaser movement during engine start and shut down, as they default to extreme positions, restricting flexibility and efficiency in idling reduction and emissions control.
Innovation Solution
The implementation of a dual lock pin phaser mechanism with a remote piloted valve for hydraulic detent switching, allowing for mid-position locking and improved actuation rate, enabling the phaser to position the camshaft optimally for cold restarts and locking in full retard during stop-start mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single lock pin mechanism is used in traditional VCT systems, then the structure is simple, but the phaser can only lock at extreme positions (full advance or full retard) during engine start and shut down, limiting control flexibility
Solution Approach 1:
The single lock pin mechanism is segmented into two separate lock pins: a first lock pin for locking at intermediate phase angle positions and a second lock pin for locking at extreme positions (full advance or full retard). This segmentation allows the phaser to be locked at multiple discrete positions, providing flexibility for both cold restarts (intermediate position) and stop-start mode (extreme position) without requiring a completely new mechanism design
Solution Approach 2:
The dual lock pin mechanism serves multiple functions: the first lock pin enables intermediate positioning for cold restart capability, while the second lock pin enables extreme position locking for stop-start mode and traditional operation. This multi-functionality allows a single VCT system to handle various operating conditions (cold starts, hot restarts, stop-start mode, normal operation) without requiring different mechanisms for each scenario
2Reliability
If OPA or TA systems are used, then the phaser can be controlled during normal operation, but the system defaults to extreme positions during engine start and shut down when no oil pressure is available, limiting control capability
Solution Approach 1:
The system performs preliminary positioning of the phaser to intermediate positions (via the first lock pin) during engine cranking before oil pressure is available. This preliminary action ensures the phaser is in the correct position for cold restarts, and only after oil pressure is established does the system transition to oil-pressure-controlled operation or extreme position locking (via the second lock pin)
3Productivity
If the phaser is limited to extreme position locking during engine shut down, then the mechanism is simple to control, but fuel efficiency and emissions are compromised due to inability to optimize timing for hot restarts
Solution Approach 1:
Different locking strategies are applied to different operational scenarios: the first lock pin provides intermediate positioning specifically for cold restart scenarios where timing optimization is critical for fuel efficiency, while the second lock pin provides extreme position locking for stop-start mode and traditional operation. This local differentiation of locking behavior optimizes fuel efficiency when needed without overcomplicating the overall control system
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 solution enhances the VCT system's ability to manage engine timing during start and shut down, improving fuel efficiency and reducing emissions by allowing for intermediate phase angle positioning and fail-safe operation, even without electronic controls.
Implementation Method 1
a remote piloted valve for hydraulic detent switching
Data Source
AI summary
A system including a phaser with a first lock pin and a second lock pin in the rotor assembly. The first and second locks pins having a locked position where they engage a recess in the housing assembly and an unlocked position in which they do not engage the housing assembly. The first lock pin locks the rotor assembly to the housing assembly when the phaser is in or near an intermediate phase angle position. The second lock pin locks the rotor assembly to the housing assembly when the phaser is at a full retard position. Alternatively, the second lock pin can lock the rotor assembly to the housing assembly when the phaser is at a full advance position.