Switchable Camshaft Phaser Combining Torque and Oil Pressure
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Solution Overview
Problem
Conventional variable cam timing (VCT) phasers face limitations in oil dependency and actuation efficiency, particularly at low RPMs for Torsional Assist (TA) phasers and high RPMs for Camshaft Torque Actuation (CTA) phasers, leading to non-symmetrical actuation rates and oil consumption issues.
Innovation Solution
A switchable VCT phaser design that selectively uses either CTA mode, TA mode, or both simultaneously, employing a control valve with recirculation check valves and spool-dependent variable vents to optimize actuation based on engine conditions, allowing independent tuning of TA venting for advance and retard directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If Torsional Assist (TA) phaser is used, then variable cam timing is achieved, but oil dependency increases and actuation rate is limited at low RPM
Solution Approach 1:
The patent combines TA and CTA technologies into a single VCT phaser that can operate in either mode or both simultaneously. The control valve enables selective engagement of TA mode (using engine oil pressure) and CTA mode (recirculating oil internally), allowing the system to merge the advantages of both approaches while mitigating their individual limitations across different RPM ranges
Solution Approach 2:
The control valve is designed to dynamically switch between TA and CTA modes based on operating conditions. The spool mechanism can position itself to enable TA actuation at low RPM when oil pressure is available, then transition to CTA mode at high RPM where camshaft torque is sufficient, optimizing performance across the entire RPM spectrum
2Quantity of substance
If Camshaft Torque Actuation (CTA) phaser is used, then oil consumption is reduced, but actuation capability diminishes at high RPM
Solution Approach 1:
The patent merges CTA and TA technologies into a hybrid system where the control valve can engage CTA mode (recirculating oil internally) to reduce oil consumption, while providing the option to switch to TA mode when additional actuation power is needed at high RPM, thus combining the oil efficiency of CTA with the high-RPM capability of TA
Solution Approach 2:
The control valve is designed with multi-functionality to handle both CTA and TA modes. It can recirculate oil internally for CTA operation to minimize oil consumption, or open pathways for engine oil pressure to actuate the phaser in TA mode when high actuation power is required, making the system universally capable across all operating conditions
3Adaptability or versatility
If switchable VCT phaser control valve is used, then both CTA and TA modes are enabled, but device complexity increases
Solution Approach 1:
The control valve is segmented into distinct functional zones with separate ports and passages for CTA and TA modes. The spool is divided into multiple lands that independently control different fluid pathways, allowing each mode to be managed separately while maintaining a unified valve structure, thus reducing complexity through functional segmentation
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 enhances hydraulic efficiency, reduces oil consumption, and balances actuation rates in both directions, enabling improved performance and efficiency across various operating conditions by leveraging both camshaft torque and engine oil pressure.
Implementation Method 1
Within the body of the spool 28 is a first central passage 29, a second central passage 30, a CTA recirculation check valve 2, and an inlet check valve 1
Implementation Method 2
A blending or combining of the CTA and TA technologies into one VCT phaser offers a solution to address both the TA and CTA VCT limitations while creating a VCT phaser design that minimizes the use of oil while actuating
Data Source
AI summary
A variable cam timing phaser with a control valve that can selectively user either CTA mode, TA mode or both CTA and TA mode simultaneously to actuate the phaser.