Patent ID: 7137369
Filing Date: 2006-11-21
Classification: F01L

Abstract:
1. A method of controlling a variable cam timing (VCT) system for an internal combustion engine including: a camshaft and a crankshaft; a camshaft sensor and a crankshaft sensor, each producing measurement pulses; and a variable cam timing phaser having: a housing having an outer circumference for accepting drive force; a rotor for connection to a camshaft coaxially located within the housing, the housing and the rotor defining at least one vane separating a plurality of chambers, the vane being capable of rotation to shift the relative angular position of the housing and the rotor; a spool valve comprising a slidable spool for controlling fluid flow between the plurality of chambers; and an on/off solenoid for controlling the position of the spool, the method comprising the steps of: determining a measured angular phase between the camshaft and the crankshaft using measurement pulses; determining a switch value equal to the difference between a set point and the measured angular phase; and controlling the on/off solenoid based on the switch value, wherein if the switch value is greater than zero, the on/off solenoid is turned on, allowing fluid to flow in a first direction between the plurality of chambers and if the switch value is less than zero, the on/off solenoid is turned off, allowing fluid to flow in a second direction, opposite the first direction between the plurality of chambers.