Electric Cam Phasing System Locking Mechanism
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Solution Overview
Problem
Conventional electric cam phasing systems face challenges in maintaining valve timing during engine start-up and shutdown, as they require movement of the camshaft to learn its position, which is inefficient and can lead to misalignment.
Innovation Solution
An electric cam phasing system with a locking mechanism that uses oil pressure to selectively engage a center fastener, allowing for adjustable phasing between the camshaft and sprocket, and maintains the locked position during engine shutdown and start-up by utilizing a bias spring and a locking pin activated by oil pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the camshaft is allowed to move freely during engine start-up and shutdown, then the system can learn its position, but the valve timing becomes unstable and may misalign
Solution Approach 1:
The lock mechanism transitions between locked and unlocked states dynamically. During normal operation, the lock is engaged to maintain stable valve timing. During engine start-up and shutdown, the lock is disengaged to allow camshaft movement for position learning. This dynamic state change resolves the contradiction by providing stability when needed and freedom of movement when required.
Solution Approach 2:
The system uses the engine's own oil pressure to automatically control the lock mechanism. When oil pressure is sufficient (during normal operation), the lock engages automatically. When oil pressure drops (during start-up/shutdown), the lock disengages automatically, allowing the camshaft to move freely without external intervention.
2Reliability
If a lock mechanism is added to prevent rotation during engine start-up and shutdown, then valve timing stability is maintained, but the system complexity increases
Solution Approach 1:
The lock mechanism is actuated by hydraulic pressure from the engine's oil system. High oil pressure during normal operation forces the lock into the engaged position, while low oil pressure during start-up/shutdown allows automatic disengagement. This hydraulic actuation eliminates the need for complex mechanical linkages, electronic sensors, or control systems, adding minimal complexity while effectively preventing rotation.
Solution Approach 2:
The lock mechanism serves as an intermediary between the camshaft and the gearbox housing. It provides a simple mechanical interface that either allows or prevents rotation based on oil pressure, without requiring complex control systems or additional components.
3Reliability
If the lock is continuously engaged to prevent rotation, then valve timing is maintained, but the camshaft cannot be adjusted for phasing
Solution Approach 1:
The lock mechanism operates periodically rather than continuously. It is engaged during normal operation to maintain valve timing and disengaged during specific periods (engine start-up and shutdown) when camshaft movement is required. This periodic engagement pattern allows both valve timing maintenance and phasing adjustment to occur at appropriate times.
Solution Approach 2:
The system changes the operational state parameter of the lock based on engine conditions. During normal operation, the lock is in the engaged state to maintain timing. During start-up and shutdown, the lock transitions to the disengaged state to allow phasing adjustment. This parameter change enables the system to adapt to different operational requirements.
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
The system ensures precise control over valve timing by locking the gearbox during engine shutdown and start-up, preventing relative rotation between the camshaft and sprocket, thus maintaining consistent valve timing until sufficient oil pressure is restored.
Implementation Method 1
maintains the locked position during engine shutdown and start-up by utilizing a bias spring and a locking pin activated by oil pressure
Implementation Method 2
utilizing a bias spring and a locking pin activated by oil pressure
Data Source
AI summary
An electric cam phasing system is provided. The electric cam phasing system includes an electric motor including a center shaft; a camshaft; a center fastener extending into a center of the camshaft and a gearbox including a sprocket and a drive unit. The drive unit includes an input shaft coupling connected to the center shaft. The drive unit is configured for coupling the camshaft to the sprocket in a manner such that relative phasing of the camshaft with respect to sprocket is adjustable via the electric motor driving the drive unit. The electric cam phasing system also includes a lock positioned axially between the center shaft and the camshaft, the lock being configured for selectively engaging the center fastener to lock the gearbox.