Camshaft Phaser Hydraulic Fail-Safe Lock Pin Engagement
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Solution Overview
Problem
Existing camshaft phasers rely on bias springs to return to a predetermined aligned position in case of phasing oil control valve failure, which may not be sufficient for reliable engagement of the intermediate lock pin, potentially affecting engine performance and starting conditions.
Innovation Solution
A hydraulic circuit with diverter valves and check valves is introduced to assist in returning the camshaft phaser to a predetermined aligned position, ensuring reliable engagement of the lock pin without relying solely on bias springs, by controlling oil flow between advance and retard chambers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bias spring is used to return the camshaft phaser to the predetermined aligned position, then the phaser can be returned to the aligned position upon valve failure, but the reliability of lock pin engagement is insufficient under all engine conditions
Solution Approach 1:
The patent employs a hydraulic circuit with check valves and diverter valves to control oil flow between advance and retard chambers. This hydraulic system provides reliable return force to engage the lock pin at the predetermined aligned position, overcoming the insufficiency of mechanical bias springs while maintaining system reliability under all engine operating conditions.
Solution Approach 2:
The patent introduces check valves and diverter valves as intermediary components that mediate the oil flow between chambers. These intermediaries enable controlled hydraulic action to return the rotor to the aligned position, ensuring reliable lock pin engagement without requiring direct mechanical spring force.
2Reliability
If the phasing oil control valve fails, then the camshaft phaser must be locked at the predetermined aligned position, but the existing return mechanism may not ensure engagement under all conditions
Solution Approach 1:
The hydraulic circuit with check valves is designed to automatically return the rotor to the predetermined aligned position upon phasing oil control valve failure. The system self-activates using existing oil pressure and the check valve mechanism, eliminating the need for external intervention or complex additional actuators, thereby maintaining ease of operation while ensuring fail-safe reliability.
Solution Approach 2:
The check valves and hydraulic circuit are pre-configured to provide compensatory return force before failure occurs. When the phasing oil control valve fails, the pre-established hydraulic pathway with check valves immediately activates to return the rotor to the aligned position, ensuring the fail-safe mechanism operates reliably without requiring additional complex control systems.
3Reliability
If a hydraulic circuit with diverter valves and check valves is introduced, then the lock pin engagement reliability is improved, but the device complexity increases
Solution Approach 1:
The hydraulic circuit with diverter valves and check valves serves multiple functions: it controls oil flow between chambers during normal operation, provides fail-safe return force upon valve failure, and ensures reliable lock pin engagement. By consolidating these functions into a single integrated hydraulic system, the patent improves reliability while minimizing the increase in overall device complexity compared to adding separate mechanical return mechanisms.
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 provides a robust fail-safe mechanism for engaging the lock pin, ensuring the camshaft phaser can maintain a stable phase relationship between the crankshaft and camshaft under all conditions, enhancing engine reliability and performance.
Implementation Method 1
a first check valve that allows oil to flow from the one of the retard chambers to the one of the advance chambers when the first diverter valve permits communication between the one of the advance chambers and the first check valve and the second check valve allows oil to flow from the one of the advance chambers to the one of the retard chambers
Implementation Method 2
a first diverter valve that is switchable between two positions of 1) blocking communication between the phasing oil control valve and only one of the advance chambers while permitting communication between the one of the advance chambers and a first check valve and of 2) permitting communication between the phasing oil control valve and the one of the advance chambers while blocking communication between the one of the advance chambers and the first check valve
Implementation Method 3
Engine oil is selectively supplied to one of the advance and retard chambers and vacated from the other of the advance and retard chambers by a phasing oil control valve in order to rotate the rotor within the stator and thereby change the phase relationship between an engine camshaft and an engine crankshaft
Data Source
AI summary
A camshaft phaser includes a stator having a plurality of lobes and a rotor coaxially disposed within the stator and having a plurality of vanes interspersed with the lobes defining a plurality of alternating advance chambers and retard chambers such that a phasing valve supplies and vents oil to and from the advance and retard chambers. A first check valve allows oil to flow from only one of the retard chambers to only one of the advance chambers when a first diverter valve permits communication between the one of the advance chambers and the first check valve and a second check valve allows oil to flow from the one of the advance chambers to the one of the retard chambers when a second diverter valve permits communication between the one of the retard chambers and the second check valve.