Variable Cam Timing Phaser Vent Path for Air Ingress Prevention
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Solution Overview
Problem
Conventional variable cam timing systems experience oscillations due to torsional forces, leading to air ingestion through vent paths, which reduces performance by overcoming hydraulic fluid pressure and causing the rotor to move back and forth within advance and retard chambers.
Innovation Solution
A control valve assembly with a vent path configured to prevent air from being sucked into the variable cam timing phaser, using a design that includes a valve housing, a rotor, and a control sleeve to direct hydraulic fluid and prevent air ingress, ensuring smooth rotation by maintaining hydraulic fluid pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the exhaust port is fluidly connectable with a sump through a vent path in conventional control valve assemblies, then hydraulic fluid can be exhausted from the system, but air may be drawn back into the advance or retard chamber through the vent path during torque reversals, causing rotor oscillation and decreased performance
Solution Approach 1:
A check valve is introduced as an intermediary component in the vent path between the exhaust port and the sump. This check valve allows hydraulic fluid to flow from the advance or retard chamber to the sump during normal operation, but prevents air from being drawn back into the chamber during torque reversals when pressure differentials would otherwise cause air ingestion through the vent path.
Solution Approach 2:
The system maintains an inert hydraulic fluid environment in the advance and retard chambers by preventing air ingress through the vent path. The check valve ensures that the hydraulic fluid environment remains free of air bubbles, which would otherwise be drawn in during torque reversals and cause oscillation and performance degradation.
2Adaptability or versatility
If the rotor moves between advance and retard positions under torsional forces, then the phaser can adjust cam timing, but the vanes move back and forth within the chambers, overcoming hydraulic fluid pressure and causing excessive oscillation
Solution Approach 1:
The check valve acts as a mediator that stabilizes the hydraulic pressure environment in the advance and retard chambers. By preventing air ingress during torque reversals, it ensures that hydraulic fluid pressure remains consistent and effective in controlling vane position, thereby reducing rotor oscillation while maintaining the ability to adjust cam timing.
Solution Approach 2:
The system maintains optimal hydraulic pressure parameters in the advance and retard chambers by preventing air ingestion. The check valve ensures that the pressure differential across the vanes remains sufficient to overcome torsional forces and maintain stable rotor position, enabling reliable cam timing adjustment without excessive oscillation.
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 effectively reduces oscillations of the rotor by preventing air ingestion during torque reversals, maintaining hydraulic fluid flow and pressure, and enhancing the overall performance of the variable cam timing system.
Implementation Method 1
maintaining hydraulic fluid pressure
Implementation Method 2
direct hydraulic fluid and prevent air ingress
Data Source
AI summary
A variable cam timing phaser of a variable cam timing system includes a housing and a rotor moveable with respect to the housing. The rotor and the housing define advance and retard chambers. The variable cam timing phaser also includes a control valve assembly. The control valve assembly includes a valve housing defining a valve housing interior, a supply port, first and second working ports, and an exhaust port. The control valve assembly also includes a piston moveable for controlling flow of the hydraulic fluid through the valve housing interior. The exhaust port is fluidly connectable with a sump through a vent path that is defined by at least one of the valve housing and the rotor. The vent path is configured to prevent air from being sucked into the variable cam timing phaser through the vent path.