Feedforward Dynamic Spool Valve

Abstract

The present invention describes a method of controlling a spool valve through a feedback and feedforward mechanism. In one example, the method includes actuating a spool valve via a solenoid to advance and retard a hydraulic variable cam timing actuator coupled to a camshaft and commanded to zero to maintain the current cam timing by means of A component whose frequency is synchronized with the engine firing frequency modulates the solenoid to counteract cam torque oscillations. In this way, the spool can be maintained at zero despite high cam torque oscillation frequency, thereby preserving oil in the solenoid assembly and improving cam timing.

Description

technical field [0001] The invention relates to a feedforward dynamic slide valve. Background technique [0002] Internal combustion engines may use variable cam timing (VCT) to improve a vehicle's fuel economy and emissions performance. One of these methods is variable cam timing using an oil-actuated device such as a vane cam phaser. The phaser can be controlled by an electromechanically actuated spool valve that directs oil flow to one side of the vane or the other. The performance of the device is thus dependent on the oil pressure, which may be a function of engine speed and leakage through various oil systems. [0003] An exemplary VCT system uses a spool valve with one inlet flow and two outlet flows. The spool valve thus has two functions - controlling the entry of oil and the exit of oil. Feedback and / or feedforward methods are often used to control VCT position when controlling oil inlet. [0004] The inventors herein have recognized that when cam timing is ma...

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Problems solved by technology

This can lead to unwanted engine knock and subsequent degradation of engine parts

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