Plasma ignition system for an internal combustion engine

• US 4,510,915 A
• Filed: 09/29/1982
• Issued: 04/16/1985
• Est. Priority Date: 10/05/1981
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Endo, Hiroshi, Ishikawa, Yasuki, Sone, Masazumi, Imai, Iwao
• Primary Examiner(s): ARGENBRIGHT, TONY MICHAEL
• Application Number:
  US06/428,229
• Time in Patent Office: 930 Days
• Field of Search: 123/620, 123/598, 123/605, 123/633, 123/143 B, 123/640, 123/643, 123/596
• US Class Current: 123/620
• CPC Class Codes: F02P 7/035 without mechanical switching means
• CPC Class Codes: F02P 9/007 by supplementary electrical discharge in the pre-ionised electrode interspace of the sparking plug, e.g. plasma jet ignition

Abstract

An N cylinder internal combustion engine plasma ignition system comprises a DC-DC converter for boosting low DC voltage to high DC voltage. Each of N ignition energy charging circuits includes a first capacitor connected between the DC-DC converter and ground via first and second diodes. The capacitor is charged by the DC-DC converter. Each of N reverse blocked thyristors connected to a junction of the first diode and first capacitor selectively grounds an electrode of the corresponding first capacitor to discharge ignition energy stored in the first capacitor. For each cylinder a transformer connected between the first capacitor and a spark plug boosts and feeds the discharged energy to the plug. One end of the transformer primary winding is grounded via a second capacitor to generate a damped oscillation when the corresponding thyristor grounds the first capacitor. An ignition trigger signal generator sequentially triggers the corresponding thyristor in a predetermined ignition order whenever the engine revolves through a predetermined angle and supplies a pulse to the DC-DC converter in synchronization with the ignition trigger signal. Derivation of the high DC voltage is halted for a period of time according to the pulsewidth. Each of N core-less inductors connected in series with the secondary winding of a transformer restricts an abrupt large current flow from the corresponding spark plug, to extend the discharge duration of each spark plug and ignite the air-fuel fixture stably without misfire.

Claims

1. A plasma ignition system for an internal combustion engine, comprising:

(a) a plurality of plasma spark plugs each having a discharge gap between a central electrode and a grounded side electrode, said discharge gap being located in a corresponding engine cylinder;

(b) a DC-DC converter for boosting a low DC voltage into a high DC voltage;

(c) a plurality of ignition energy charging means, each having a first diode connected to said DC-DC converter, a first capacitor having a first terminal connected to said first diode and a second terminal connected to ground via a second diode, the first capacitor being charged by the high DC voltage from said DC-DC converter via a series path including said first and second diodes;

(d) a plurality of reverse blocked triode thyristors, each having an anode connected to the first terminal of said first capacitor and a grounded cathode, each thryistor being selectively turned on so as to discharge the energy stored in the said first capacitor therethrough;

(e) a plurality of voltage boosting transformers, each having a primary winding and secondary winding and a magnetic core that couples the primary and secondary windings to each other, the magnetic core having a tendency to saturate in response to current resulting from discharges of the first capacitor, first and second ends of said primary winding of each transformer being respctively connected in series with the second terminal of said first capacitor and to ground via a second capacitor having a capacitance value smaller than said first capacitor whereby a damped oscillation is generated in the second capacitor when the capacitive energy is discharged from said first capacitor through said thyristor, first and second ends of said secondary winding being respectively connected in series with the second terminal of said first capacitor and to the central electrode of the corresponding plasma spark plug, whereby the voltage applied to said corresponding primary winding is boosted and the boosted voltage is applied to the corresponding spark plug;

(f) an ignition trigger signal generator for (1) circularly generating and coupling a trigger signal to a gate of said corresponding thyristor according to a predetermined ignition order of the engine cylinders in response to the engine revolving through a predetermined angle and (2) generating and coupling another pulse signal having a predetermined pulsewidth to said DC-DC converter in synchronization with the ignition trigger signal for halting derivation of the high DC voltage for a period of time determined by said pulsewidth of the pulse signal; and

(g) a plurality of core-less inductors each connected in series with the secondary winding of said corresponding voltage boosting transformer and the electrodes for restricting an abrupt large discharge current flow through the corresponding plasma spark plug discharge gap so as to extend the ignition energy flow through said gap by the corresponding plasma ignition plug.

2. A plasma ignition system as set forth in claim 1, wherein each of said core-less inductors is connected between the second end of the secondary winding of said corresponding voltage boosting transformer and the central electrode of said corresponding plasma spark plug.

3. A plasma ignition system as set forth in claim 1, wherein each of said core-less inductors has first and second terminals respectively connected to a common terminal for the first end of said primary winding and for the second terminal of the first capacitor and to the first primary winding and one end of the secondary winding of said corresponding voltage boosting transformer, the other end of the secondary winding being directly connected to the central electrode of said corresponding plasma spark plug.

4. A plasma ignition system for an internal combustion engine, comprising:

(a) a plurality of plasma spark discharge gaps, each gap being located in a corresponding engine cylinder so as to receive an air-fuel mixture;

(b) a plurality of high voltage energy charging capacitors each of which is charged to high voltage energy;

(c) a plurality of switching elements, each responsive to a signal produced according to a predetermined ignition order, for discharging the charged high voltage energy in the corresponding capacitor;

(d) a plurality of voltage boosting transformers each having a primary and secondary winding, one end of each primary winding thereof being connected to a second capacitor so that a damped oscillation is generated thereat when the corresponding high voltage ignition energy charged capacitor is discharged by means of said corresponding switching element, one end of each secondary winding thereof being connected to said corresponding discharge gap, the transformer boosting and applying the damped oscillation voltage generated at the primary winding thereof and coupling a subsequent high voltage ignition energy charged in said corresponding high voltage energy charging capacitor to said corresponding discharge gap, the primary and secondary windings being coupled to each other by a magnetic core having a tendency to saturate in response to current flowing to the gap in response to discharges of the high voltage energy, whereby there is a tendency for an abrupt large discharge current to flow in the gap; and

(e) a plurality of core-less inductors each connected in series with the secondary winding of said corresponding transformer for restricting the tendency for the abrupt large discharge current to flow through said corresponding discharge gap in response to the subsequent high voltage ignition energy charged in said corresponding high voltage energy charging capacitor being discharged to said corresponding discharge gap.

5. An electronic breakerless plasma ignition system responsive to a low voltage DC source, the system being provided for an internal combustion engine having N cylinders, each cylinder including a separate plasma spark discharge gap responsive to an air-fuel mixture, where N is an integer greater than one, the system comprising:

(a) N energy storing capacitors, one of said capacitors being provided for each of the gaps;

(b) means responsive to the low voltage source for charging the capacitors to a high DC voltage, so that each capacitor stores sufficient energy to establish an ignition discharge current through its corresponding gap;

(c) means synchronized with operation of the engine cylinders for separately and sequentially discharging energy stored in each capacitor through its corresponding gap to provide the ignition discharge current through each gap, the means for discharging for each capacitor and each gap including;

(i) means including semiconductor switch means and resonant circuit means for establishing a current having a tendency to oscillate, the semiconductor switch means being cut-off in response to a change in polarity of the current so that the current is cut-off in response to a change in polarity thereof, the establishing means including a transformer having a primary winding connected in series with the energy storing capacitor and the semiconductor switch means, whereby a voltage pulse is derived across the primary winding in response to the ignition discharge current flowing in the gap;

(ii) means for boosting the amplitude of the voltage pulse and for applying the boosted voltage pulse across the gap, the boosting means including a secondary winding of the transformer, the transformer having a magnetic core coupling the primary and secondary windings together, the core having a tendency to saturate in response to the ignition discharge current flowing to the gap, whereby there is a tendency for an abrupt large discharge current to flow in the gap; and

(iii) means for attenuating and for extending the duration of the abrupt large discharge current that tends to flow in the gap, said attenuating and extending means including a core-less inductor connected in series with the secondary winding and the gap.

6. The system of claim 5 wherein the core-less inductor is connected between a first terminal of the secondary winding and an ungrounded electrode of a plasma discharge device including the gap, a second terminal of the secondary winding being connected to an electrode of the capacitor.

7. The system of claim 5 wherein the core-less inductor is connected between a first terminal of the secondary winding and an electrode of the capacitor, a second terminal of the secondary winding being connected to an ungrounded electrode of a plasma discharge device including the gap.