12/10/11

Overview: Delphi cam phasers

Delphi’s Variable Cam Phaser (VCP) replaces the standard pulley, sprocket or gear in an engine's valve train. It enables the cam lobe (lift event) timing to crank shaft timing to be changed while the engine is operating, based on the parameters of the engine. The cam lobe angular position, or phase relationship, is controlled by the internal vane mechanism of the VCP. Commands from the engine control module adjust the position of the oil control valve — see the schematic diagram below — which is mounted in the cylinder head and regulates engine oil flow to either side of the vanes.

Delphi cam phasers. Delphi produces a variety of variable cam phasers and oil control valves to meet individual customer requirements

The system includes an oil control valve, which controls the flow of oil to advance, retard or hold the camshaft position. Its high flow capacity provides fast phasing rates, and its integral filtration keeps it free of debris, avoiding the need for a separate filter while providing increased packaging flexibility.

Variable cam phasing changes the timing of the valve lift event. It can be used to shift the intake cam, the exhaust cam, or both on dual overhead cam engines. This helps increase engine efficiency, reduces emissions and improves idle stability. Clearly, this has a part to play in ‘downsizing’.

A standard rotor/stator pack in the VCP, and a remotely-mounted oil control valve, help packaging flexibility on the engine. When the engine is shut off, a mechanical locking pin maintains the default positions of the internal components.

Low-restriction (high flow-rate) four-way control valve provides low pressure operation and continuously variable position operation.

A Delphi variable cam phaser can be applied to virtually any engine to help fatten the torque curve, increase maximum power at higher crankshaft speeds, reduce hydrocarbon and NOx emissions, and help increase fuel-economy.

Delphi’s variable cam phasing technology balances response times, torque capacity and packaging size. Improvements in engine performance can be increased by fine-tuning the off-the-shelf produce for a specific engine.

Control
valve
Intake Exhaust Valve
overlap
Off Retard Advance Minimum
50% Intermediate:
flow is restricted to ‘hold’ position
100% Advance Retard Maximum

Importantly, the construction of the cam phaser and the oil control valve permits either two-position or continuously-variable operation. An intermediate lock-pin improves fuel economy and performance in dual (twin-camshaft) independent cam-phasing applications.

Implementation is simplified because of the vane configuration, which reduces mass and contributes to packaging flexibility.

Delphi manufactures cam phasing systems in North America, Europe and Asia.

http://delphi.com/

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