Camshaft Phaser Valve Spool Recirculation Passages
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Solution Overview
Problem
Camshaft phasers that utilize torque reversals to actuate oil flow between advance and retard chambers are complex and costly due to the requirement of multiple check valves, which increases the parasitic load on the engine's lubrication system and adds complexity to the system design.
Innovation Solution
A camshaft phaser design featuring a valve spool with diametrically opposed spool recirculation passages that segregate a phasing volume from a venting volume, allowing oil to be supplied from the retard chamber to the advance chamber and vice versa through a simple and economical check valve configuration, thereby increasing phasing rate and reducing system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple check valves are used to control oil flow between advance and retard chambers, then the camshaft phaser can achieve bidirectional phase adjustment, but the system complexity and cost increase
Solution Approach 1:
The patent combines multiple check valve functions into a single integrated check valve assembly. The valve spool integrates the first and second check valves into one component structure, where the valve spool itself acts as the sealing element for both check valves. This merging reduces the number of separate components and simplifies the overall system while maintaining bidirectional phase adjustment capability.
Solution Approach 2:
The valve spool serves multiple functions simultaneously: it acts as a moving valve element, provides sealing surfaces for both check valves, defines the recirculation passages, and controls oil flow in both directions. This multi-functionality reduces the number of separate components needed and simplifies the system architecture.
2Adaptability or versatility
If multiple check valves are used to control oil flow between advance and retard chambers, then the camshaft phaser can achieve bidirectional phase adjustment, but the manufacturing cost increases
Solution Approach 1:
The patent combines multiple check valve functions into a single integrated check valve assembly. The valve spool integrates the first and second check valves into one component structure, where the valve spool itself acts as the sealing element for both check valves. This merging reduces the number of separate components and simplifies the overall system while maintaining bidirectional phase adjustment capability.
3Ease of operation
If oil is supplied from the lubrication system to rotate the rotor, then the camshaft phaser can achieve phase adjustment, but the parasitic load on the engine increases
Solution Approach 1:
The patent enables the camshaft phaser to use its own operational characteristics (torque reversals during intake and exhaust strokes) to drive the phase adjustment mechanism. The camshaft torque reversals directly actuate the rotor without requiring additional oil supply from the engine's lubrication system, making the system self-powered and eliminating the parasitic load.
Solution Approach 2:
The patent converts the torque reversals, which are natural byproducts of the engine's intake and exhaust valve operation, into a useful driving force for phase adjustment. Instead of treating these torque variations as mere operational characteristics, the system harnesses them to power the camshaft phaser mechanism.
4Ease of manufacture
If check valves are located remotely from the valve spool, then the valve spool design is simplified, but the passage complexity increases
Solution Approach 1:
The patent combines the check valves with the valve spool by making the valve spool itself the sealing element. The first and second check valves are integrated into the valve spool structure, eliminating the need for separate check valve components and their associated remote passages.
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 design enhances oil flow efficiency, increases the phasing rate of the camshaft relative to the crankshaft, and simplifies the implementation of the check valve, reducing costs and complexity while minimizing the parasitic load on the engine's lubrication system.
Implementation Method 1
a first spool recirculation passage and a second spool recirculation passage diametrically opposed to the first spool recirculation passage, each extending from the valve spool bore to the advance chamber and the retard chamber such that oil is supplied to the advance chamber from the retard chamber through the first spool recirculation passage, the second spool recirculation passage, and the phasing volume in order to retard the timing of the camshaft relative to the crankshaft
Implementation Method 2
accommodate a check valve associated with the spool recirculation passage that is simple and economical to implement
Implementation Method 3
oil is moved directly from the advance chambers to the retard chambers or directly from the retard chambers to the advance chambers based on torque reversals imparted on the camshaft from intake and exhaust valves of the internal combustion engine
Data Source
AI summary
A camshaft phaser includes an input member and an output member defining an advance chamber and a retard chamber; a valve spool moveable along an axis between an advance position and a retard position and having a valve spool bore with a phasing volume and a venting volume defined therein such that the phasing volume is fluidly segregated from the venting volume, the valve spool having a first spool recirculation passage and a second spool recirculation passage which is diametrically opposed to the first spool recirculation passage. The first spool recirculation passage and the second spool recirculation passage provide paths for oil to flow from the advance chamber or the retard chamber to the phasing volume depending on the position of the valve spool.