Cam Torque Phaser Mid Position Lock
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Solution Overview
Problem
Existing Variable Cam Timing (VCT) systems lack the ability to lock the phaser in a mid position without relying on end stop limits, limiting the flexibility in varying the timing of intake and exhaust valve operations in internal combustion engines.
Innovation Solution
The introduction of a check valve in spool cam torque actuated (CTA) phaser with a mid position lock, utilizing a hydraulic detent circuit that allows for locking and unlocking of the phaser through a lock pin, which can be integrated with a detent valve, enabling the phaser to be locked at any intermediate position independent of fluid flow, using a spring mechanism and passages to align with advance and retard chambers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional VCT system uses end stop limits to lock the phaser, then the phaser can be locked at extreme positions, but the phaser cannot be locked at mid positions, limiting timing flexibility
Solution Approach 1:
A lock pin is introduced as an intermediary mechanical element that can engage with detent positions at any location along the phaser's travel path, not just at the end stops. This lock pin, actuated by a spool valve and hydraulic circuit, provides the capability to lock the phaser at intermediate positions, thereby enabling mid-position locking and improving timing flexibility
Solution Approach 2:
A hydraulic detent circuit is implemented using a spool valve controlled by a solenoid. This hydraulic system actuates the lock pin to engage or disengage detent positions, enabling precise control over phaser locking at various positions including mid positions, thus resolving the limitation of conventional end-stop-only locking
2Reliability
If the phaser relies on fluid flow to maintain position, then timing can be adjusted continuously, but the phaser cannot maintain position when oil pressure is low, such as during cranking
Solution Approach 1:
The lock pin is preliminarily positioned to engage with detent positions before fluid pressure conditions become critical. During low oil pressure conditions such as engine cranking, the lock pin mechanically maintains the phaser position without relying on fluid pressure, ensuring reliable position maintenance across a broader range of operational conditions
Solution Approach 2:
The hydraulic fluid pressure system is replaced with a mechanical lock pin and detent mechanism for position maintenance. This mechanical substitution ensures that the phaser can maintain its position reliably even when oil pressure is insufficient, thereby expanding the range of operational conditions where stable timing control is achievable
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 solution allows for precise control of camshaft timing, enabling the phaser to maintain a mid position lock during engine conditions where oil pressure is low, such as during cranking, and facilitates flexible timing adjustments without the need for internal bearings, enhancing engine performance and efficiency.
Implementation Method 1
A spring on a back side of the lock pin pushes the lock pin till the nose contacts a face of the endplate or sprocket
Implementation Method 2
The disclosed check valve in spool cam torque actuated (CTA) phaser with mid position lock allows a mid position lock with a hydraulic detent circuit in both a rotor and an endplate
Data Source
AI summary
A cam torque actuated variable cam timing phaser can include a rotor (20) enclosed by an endplate (64) within a housing (10). The housing (10) can have at least one cavity (10a) to be divided by a vane (22) rigidly attached to the rotor (20). The vane (22) can divide the cavity (10a) into a first chamber (16) and a second chamber (18). Passages (26, 28, 56, 58) can connect the first and second chambers (16, 18) facilitating oscillation of the vane (20) within the cavity (10a). A detent valve (50) can move between an open position and a closed position. When in the open position, the detent valve (50) can connect portions of a detent passage (56, 58) extending through the rotor (20) and through the endplate (64) allowing pressurized actuating fluid flow with respect to the first and second chambers (16, 18) in response to a relative angular position of the rotor (20) with respect to the endplate (64). A lock pin (60) can move between a locked position and a released position.