Elongated Lock Pin Camshaft Phaser for Torque Control
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Solution Overview
Problem
Existing camshaft phasers face challenges in providing multiple locking positions to manage torque during engine restarts in automatic stop mode, as commonly used lock pins with cylindrical shapes often result in fluid communication between advance and retard chambers, leading to undesired performance or loss of phase angle authority.
Innovation Solution
A vane-type camshaft phaser with elongated lock pins and seats in the radial direction, where the lock pin width is less than the length, preventing relative rotation while avoiding fluid communication between advance and retard chambers, allowing for selective engagement at different angular positions to manage torque effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple lock pin seats are provided at different angular positions to allow selective locking, then torque control during engine restart is improved, but the risk of fluid communication between advance and retard chambers increases
Solution Approach 1:
The lock pin is designed with an asymmetric rectangular cross-section where the width in the circumferential direction is less than the length in the radial direction. This asymmetric geometry allows the lock pin to engage with lock pin seats at multiple angular positions for torque control while preventing fluid communication between chambers, resolving the contradiction between adaptability and reliability
Solution Approach 2:
The solution moves from considering only angular positioning to incorporating radial dimension considerations. By making the lock pin elongated in the radial direction with width less than length, the design utilizes the radial dimension to prevent fluid communication while maintaining angular positioning capability, thus achieving both multiple locking positions and preventing harmful fluid communication
2Reliability
If lock pin width in circumferential direction is reduced to prevent fluid communication, then reliability is improved, but locking strength may be compromised
Solution Approach 1:
The lock pin employs asymmetric rectangular cross-section with width less than length. This asymmetric design strategically places the greater dimension (length in radial direction) in the direction critical for preventing fluid communication, while the smaller dimension (width in circumferential direction) suffices for locking engagement, thus maintaining both reliability and strength
Solution Approach 2:
The lock pin exhibits different dimensional characteristics in different directions: elongated in the radial direction for preventing fluid communication and narrower in the circumferential direction for locking engagement. This local quality differentiation optimizes the lock pin's performance for its specific dual functions without requiring uniform dimensions
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 solution enables precise control of phase relationship between the crankshaft and camshaft, minimizing torque issues during engine restarts at normal operating temperatures, maintaining desired performance and phase angle authority.
Implementation Method 1
a lock pin which is selectively seated with a lock pin seat to prevent relative rotation between the rotor and the stator at a predetermined aligned position between the rotor and the stator
Implementation Method 2
Engine oil is selectively supplied to one of the advance and retard chambers and vented from the other of the advance and retard chambers in order to rotate the rotor within the stator
Implementation Method 3
The lock pin has a lock pin width in a circumferential direction relative to the camshaft axis and a lock pin length perpendicular to the lock pin width and to the lock pin axis such that the lock pin width is less than the lock pin length
Data Source
AI summary
A camshaft phaser for varying the phase relationship between a crankshaft and a camshaft includes stator having a plurality of lobes. A rotor rotatable about a camshaft axis is disposed coaxially within the stator and has a plurality of vanes interspersed with the lobes to define advance chambers and retard chambers. A lock pin is slidably disposed along a lock pin axis within the rotor for selective engagement with a first lock pin seat and for selective engagement with a second lock pin seat. The lock pin has a lock pin width in a circumferential direction relative to the camshaft axis and a lock pin length perpendicular to the lock pin width and to the lock pin axis such that the lock pin width is less than the lock pin length.