Current control method and apparatus for electromagnetic valves

Claim 1

A method for controlling the operating current of an electromagnetic valve in response to a variable duration pulse, comprising the steps of: (a) coupling an energization voltage to an actuating coil of said electromagnetic valve in response to a leading edge of said pulse to initiate an energization current in said coil; (b) detecting when said energization current reaches a predetermined peak value; (c) decoupling said energization voltage from said coil to allow a circulating current to flow through a first path to decrease said circulating current at a higher rate; (d) detecting when said circulating current decreases to a medium current value; (e) switching said circulating current to a low resistance path to decrease said circulating current at a lower rate; (f) detecting when said circulating current reaches a lower holding current value necessary to hold said electromagnetic valve operated; (g) coupling said energization voltage to said coil to reinitiate said energization current; (h) detecting when said energization current reaches a higher holding current value lower than said medium current value; (i) decoupling said energization voltage from said coil to reinitiate said circulating current; and (j) repeating the steps (f) to (i) until the occurrence of a trailing edge of said pulse.

Claim 2

A method for controlling the operating current of an electromagnetic valve in response to a variable duration pulse, comprising the steps of: (a) coupling an energization voltage to an actuating coil of said electromagnetic valve in response to a leading edge of said pulse to initiate an energization current in said coil; (b) detecting when said energization current reaches a predetermined peak value; (c) decoupling said energization voltage from said coil to allow a circulating current to flow through a first path to decrease said circulating current at a higher rate; (d) detecting when said circulating current decreases to a medium current value; (e) switching said circulating current to a low resistance path to decrease said circulating current at a lower rate; (f) detecting when said circulating current reaches a lower holding current value necessary to hold said electromagnetic valve operated; (g) coupling said energization voltage to said coil to reinitiate said energization current; (h) detecting when said energization current reaches a higher holding current value lower than said medium current value; (i) decoupling said energization voltage from said coil to reinitiate said circulating current; and (j) repeating the steps (f) to (i) until the occurrence of a trailing edge of said pulse.

Claim 6

An apparatus for controlling the operating current of an electromagnetic valve in response to a variable duration pulse, comprising: a switching device connected in series with an actuating coil of said electromagnetic valve for coupling an energization voltage thereto when rendered conductive to generate an energization current and decoupling said voltage therefrom when rendered nonconductive to generate a circulating current; first means for successively generating a first switching signal when said energization current exceeds a peak current value and a second switching signal when said circulating current drops to a medium current value, and alternately generating a third switching signal when said circulating current drops to a lower holding current value and a fourth switching signal when said energization current rises to a higher holding current value lower than said medium current value; second means for rendering said switching device conductive in response to a leading edge of said pulse and said third switching signal and rendering said switching device nonconductive in response to said first and fourth switching signals and a trailing edge of said pulse; first energy absorbing circuit means connected in parallel with said coil for conducting said circulating current which is generated in response to said switching device being rendered nonconductive; and second energy absorbing circuit means connected in parallel with said coil for conducting said circulating current in response to said second switching signal.

Claim 7

An apparatus for controlling the operating current of an electromagnetic valve in response to a variable duration pulse, comprising: a switching device connected in series with an actuating coil of said electromagnetic valve for coupling an energization voltage thereto when rendered conductive to generate an energization current and decoupling said voltage therefrom when rendered nonconductive to generate a circulating current; first means for successively generating a first switching signal when said energization current exceeds a peak current value and a second switching signal when said circulating current drops to a medium current value, and alternately generating a third switching signal when said circulating current drops to a lower holding current value and a fourth switching signal when said energization current rises to a higher holding current value lower than said medium current value; second means for rendering said switching device conductive in response to a leading edge of said pulse and said third switching signal and rendering said switching device nonconductive in response to said first and fourth switching signals and a trailing edge of said pulse; first energy absorbing circuit means connected in parallel with said coil for conducting said circulating current which is generated in response to said switching device being rendered nonconductive; and second energy absorbing circuit means connected in parallel with said coil for conducting said circulating current in response to said second switching signal.