Variable Cam Timing Phaser Viscous Damping
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Solution Overview
Problem
Variable cam timing systems produce significant noise, vibration, and harshness (NVH) due to rotor impacts with the stator during maximum advanced or retarded positions and cam torsional effects, leading to operator dissatisfaction.
Innovation Solution
The variable cam timing phaser incorporates a stator with inwardly-extending lobes and a rotor with outwardly-extending lobes, featuring hydraulic fluid orifices that seal off at terminal positions to equalize pressure between timing chambers, reducing noise by trapping hydraulic fluid and acting as a viscous damper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hydraulic pressure is increased in advance chambers to advance cam timing, then variable valve timing is achieved, but rotor impacts stator at significant velocity causing noise and vibration
Solution Approach 1:
The patent introduces a cushioning chamber between the rotor and stator that fills with hydraulic fluid before the rotor impacts the stator. This cushioning fluid absorbs the impact energy when the rotor reaches terminal position, preventing direct metal-to-metal contact and reducing noise and vibration while maintaining the variable timing function.
Solution Approach 2:
The cushioning chamber acts as an intermediary element between the rotor and stator. It contains hydraulic fluid that mediates the interaction between these two components during terminal positioning, preventing harmful impacts while allowing the necessary relative rotation for variable timing control.
2Adaptability or versatility
If hydraulic pressure is increased in retard chambers to retard cam timing, then variable valve timing is achieved, but rotor impacts stator at significant velocity causing noise and vibration
Solution Approach 1:
The cushioning chamber fills with hydraulic fluid before the rotor impacts the stator during retardation. This pre-positioned cushioning fluid absorbs the impact energy when the rotor reaches the fully retarded position, preventing direct contact and reducing noise and vibration while maintaining timing control capability.
Solution Approach 2:
The cushioning chamber serves as an intermediary between the rotor and stator during retardation, using hydraulic fluid to mediate the interaction and prevent harmful impacts while allowing the necessary relative rotation for variable timing.
3Adaptability or versatility
If cam torsional effects cause rotor to forcefully impact stator, then timing variation is achieved, but high NVH levels are produced
Solution Approach 1:
The cushioning chamber is positioned to receive hydraulic fluid before torsional impacts occur. When cam torsional effects cause the rotor to impact the stator, the cushioning fluid is already in place to absorb this impact energy, preventing the forceful contact that would generate high NVH levels while maintaining timing variation capability.
Solution Approach 2:
The cushioning chamber acts as an intermediary that mediates the torsional impact between rotor and stator. The hydraulic fluid in this chamber absorbs the energy from cam torsional effects, preventing direct impactful contact and reducing NVH levels while preserving the timing variation function.
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 design minimizes or eliminates NVH issues while maintaining the advantages of variable cam timing, providing a more satisfactory operating experience by reducing noise and vibration.
Implementation Method 1
trapping hydraulic fluid and acting as a viscous damper
Implementation Method 2
hydraulic pressure is increased in the advance chambers relative to the retard chambers, thereby producing a relative rotation between the rotor and stator
Data Source
AI summary
A variable cam-timing phaser, including a stator having a plurality of inwardly-extending stator lobes and a rotor having a plurality of outwardly-extending rotor lobes. The rotor is rotatably disposed within the stator so that the rotor lobes interleave with the stator lobes to form a first timing chamber and a second timing chamber between each of the stator lobes. The phaser further includes a hydraulic valve, where the phaser is configured so that, upon operation of the valve to selectively couple the second timing chambers to a hydraulic fluid supply and the first timing chambers to a hydraulic fluid sink, the rotor is caused to rotate toward a terminal position, in which at least one of the first timing chambers is at least partially sealed off from the hydraulic fluid sink, thereby producing a tendency toward pressure equalization between the first timing chambers and the second timing chambers.