Variable Cam Timing Phaser Series Check Valves
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Solution Overview
Problem
Existing cam timing phaser arrangements in commercial vehicles face issues with mechanical complexity, sensitivity to impurities, oil leakage, and durability, particularly due to the use of three-positional spool valves and compact, complex rotor designs with specialized check valves.
Innovation Solution
A variable cam timing phaser arrangement utilizing a rotor with vanes and a stator, featuring a control assembly with first and second check valves and a selective deactivation device, allowing unidirectional fluid flow between chambers based on pressure differences, reducing mechanical complexity and oil leakage, and enabling robust, cost-effective manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If three-positional spool valves and variable force solenoids are used to control oil flow in cam timing phasers, then precise control of camshaft timing is achieved, but mechanical complexity and sensitivity to impurities increase
Solution Approach 1:
The invention extracts and removes the complex three-positional spool valve and variable force solenoid from the cam timing phaser system. Instead, it uses a simple two-position spool valve controlled by a standard solenoid, eliminating the problematic components while maintaining timing control functionality through a simplified hydraulic circuit with check valves.
Solution Approach 2:
The invention replaces expensive, complex, and sensitive components (three-positional spool valve and variable force solenoid) with cheaper, simpler, and more robust components (two-position spool valve and standard solenoid). The simplified design is less sensitive to impurities and more durable, effectively trading component sophistication for reliability and ease of manufacture.
2Productivity
If compact rotor designs with specialized check valves are used, then cam torque actuation efficiency is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The invention uses standard, off-the-shelf check valves that can be sourced from general automotive suppliers rather than custom-specialized check valves. These standard check valves serve multiple functions in the system (controlling oil flow direction, preventing backflow, enabling cam torque actuation) and can be installed in various positions, simplifying manufacturing and supply chain management while maintaining actuation efficiency.
Solution Approach 2:
Instead of designing compact, complex rotor geometries to fit specialized check valves, the invention inverts the approach by using standard check valves and designing the rotor and housing to accommodate them. This reversal simplifies manufacturing processes, allows for easier quality control, and reduces costs while achieving the same cam torque actuation efficiency through proper hydraulic circuit design.
3Adaptability or versatility
If three-positional spool valves are used in cam phaser arrangements, then oil flow regulation is improved, but oil leakage increases
Solution Approach 1:
The invention extracts and removes the three-positional spool valve from the system, which is the primary source of oil leakage due to its multiple sealing surfaces and complex internal passages. The simplified two-position spool valve has fewer sealing requirements and simpler internal geometry, significantly reducing leakage paths while maintaining sufficient oil flow regulation capability for cam timing control.
Solution Approach 2:
The invention uses a simplified hydraulic circuit design that copies the essential functionality of the three-positional valve system (controlling oil flow to advance and retard chambers) but implements it with simpler components. The check valves replicate the directional control function with fewer moving parts and sealing surfaces, reducing oil leakage while preserving the adaptability needed for various operating conditions.
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 simplifies the cam phaser design, reduces oil leakage, and enhances durability by using fewer and more robust hydraulic components, allowing for precise control with a single on/off actuator, and enabling the use of established check valves, resulting in improved performance and reduced costs.
Implementation Method 1
The first check valve and the second check valve are arranged in series in a fluid passage between the first chamber and the second chamber. The first check valve is configured to prevent fluid flow in a first direction from the first chamber to the second chamber and to allow fluid flow in a second direction from the second chamber to the first chamber.
Implementation Method 2
Cam torque actuated phasers utilize these periodic torque variations to rotate the rotor in the chosen direction, thereby advancing or retarding the camshaft timing. In principle they operate as 'hydraulic ratchets', allowing fluid to flow in a single direction from one chamber to the other chamber due to the torque acting on the oil in the chambers and causing periodic pressure fluctuations.
Data Source
Figure 1
Figure 2a~2d
Figure 3
AI summary
A variable cam timing phaser arrangement (201) is disclosed, comprising: a rotor (3) having at least one vane (5); a stator (7) co-axially surrounding the rotor (3), having at least one recess (9) for receiving the at least one vane (5) of the rotor, wherein the at least one vane (5) divides the at least one recess into a first chamber (13) and a second chamber (15); and a control assembly for regulating hydraulic fluid flow from the first chamber (13) to the second chamber (15) or vice-versa. The control assembly comprises a first check valve (17), a second check valve (23) and a selective deactivation device (35). The check valves are arranged in series in a fluid passage between the first chamber (13) and the second chamber (15). The selective deactivation device (35) is deployable and is configured to selectively deactivate either the first check valve (17) or the second check valve (23) upon deployment. By timing the deployment of the deactivation device, the direction of flow between the first (13) and second chambers (15) can be controlled. A method of controlling camshaft timing is also disclosed, as well as an internal combustion engine and a vehicle comprising the disclosed variable cam timing phaser arrangement.