Patent Number: 6,332,454

Title: Electromagnetic valve driving apparatus having current limit switching function

Abstract: A driving apparatus for an electromagnetic valve which supplies fuel to an engine comprises a conduction control circuit and a current-limit-value setting circuit. The conduction control circuit turns on and off an FET so that a conduction current flowing through a coil of the electromagnetic valve has a magnitude equal to a predetermined current limit value while a microcomputer is outputting a driving signal to the conduction control circuit. The predetermined current limit value used in the conduction control circuit is set at a first current limit value during a predetermined period starting at a point of time the microcomputer outputs the driving signal. When the predetermined period has lapsed, the predetermined current limit value is switched from the first current limit value to a second current limit value which is smaller than the first current limit value. In addition, when the microcomputer detects a start state of the engine or a low level state of a battery voltage, the second current limit value is raised to the first current limit value to thereby improve the starting characteristics of the engine.

Inventors: Itabashi; Toru (Anjo, JP), Yamada; Atsushi (Kariya, JP)

Assignee: Denso Corporation

International Classification: F02D 41/20 (20060101); F02M 59/36 (20060101); F02M 59/20 (20060101); F02M 051/00 (); F02M 037/08 ()

Expiration Date: 12/25/2018