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Publication numberUS3892219 A
Publication typeGrant
Publication dateJul 1, 1975
Filing dateSep 27, 1973
Priority dateSep 27, 1973
Publication numberUS 3892219 A, US 3892219A, US-A-3892219, US3892219 A, US3892219A
InventorsJohnston Richard W, Neuman John G, Preiser Mark E
Original AssigneeGen Motors Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Internal combustion engine ignition system
US 3892219 A
Abstract
An internal combustion engine ignition system which produces an ignition spark of a preselected duration for each cylinder of the engine. An arc-duration monostable multivibrator circuit produces an output timing signal of the preselected duration which operates a switching transistor conductive to complete the ignition coil primary winding energizing circuit. Each time the ignition coil primary winding energizing current reaches a predetermined magnitude, a control monostable multivibrator circuit produces a control signal which operates the switching transistor not conductive to interrupt the ignition coil primary winding energizing circuit. The ignition coil has a primary to secondary windings turns ratio such that, during the buildup of energizing current through the primary winding, a potential of sufficient magnitude to maintain the arc initiated across each spark plug gap is induced in the secondary winding and the primary winding is designed to have an inductance value which, with a predetermined magnitude of energizing current, will provide sufficient stored energy to maintain the arc initiated across each spark plug gap for a duration of time at least as long as the period between successive energizations thereof.
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United States Patent Preiser et a1.

July 1, 1975 1 1 INTERNAL COMBUSTION ENGINE IGNITION SYSTEM [75] Inventors: Mark E. Preiser, Santa Barbara,

Calif.; Richard W. Johnston, Troy; John G. Neuman, Grosse Pointe, both of Mich.

[731 Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Sept. 27, 1973 [211 Appl. No.: 401,505

[52] [1.5. CI. 123/148 E; 315/209 [51] Int. Cl. F02p 1/00 [58] Field of Search 123/148 E; 315/209 [56] References Cited UNITED STATES PATENTS 3.379.182 4/1968 Rittmann et a1. 123/148 E 3,394,690 7/1968 Bell 123/148 E 3,575,154 8/1971 Taylor i 123/148 E 3,593.696 7/1971 Guido r r 123/148 E 3,599,618 8/1971 Schuette 123/148 E 3,605,713 9/1971 Le Masters et a]. 123/148 OTHER PUBLICATIONS Pulse Digital & Switching Waveforms Milman & Taub, McGraw Hill, pg. 362, pgs. 404, 405.

Primary Examiner-Charles .1. Myhre Assistant Examiner-Paul Devinsky Attorney, Agent, or FirmRichard G. Stahr Q 15 7] ABSTRACT An internal combustion engine ignition system which produces an ignition spark of a preselected duration for each cylinder of the engine. An arc-duration monostable multivibrator circuit produces an output timing signal of the preselected duration which operates a switching transistor conductive to complete the ignition coil primary winding energizing circuit Each time the ignition coil primary winding energizing cur rent reaches a predetermined magnitude, a control monostable multivibrator circuit produces a control signal which operates the switching transistor not conductive to interrupt the ignition coil primary winding energizing circuit. The ignition coil has a primary to secondary windings turns ratio such that, during the buildup of energizing current through the primary winding, a potential of sufficient magnitude to maintain the are initiated across each spark plug gap is induced in the secondary winding and the primary winding is designed to have an inductance value which, with a predetermined magnitude of energizing current, will provide sufficient stored energy to maintain the are initiated across each spark plug gap for a duration of time at least as long as the period between successive energizations thereof.

2 Claims, 5 Drawing Figures III ENGINE SHEET UZRVZM WA I H SHEEI A IN PUT SIGNAL TIME E m T O O WPJO W5 O E G R L A A H N C m R S T m U P m w m 0 C B C TIME w Q I D5 L FR J i F iiiiiiiii .IiV I II; I

w F OW LU C Mm C w a mp (w m I P d5 WM 010 TF wD .Q P. 0 Y 2 mr TO BASE OF TRAN SISTDRw TO JUNCTION% TO JUNCTION 58 1 INTERNAL COMBUSTION ENGINE IGNITION SYSTEM This invention relates to an internal combustion engine ignition system and, more specifically, to an internal combustion engine ignition system which produces an ignition spark of a predetermined duration for each engine cylinder.

As is well known in the automotive art, the combustible fuel-air mixture in each of the cylinders of the engine during each compression stroke is ignited by an electrical spark produced by the associated ingition system. The ignition spark, therefore, must be of sufficient intensity to initiate combustion and should have sufficient power to maintain combustion during the power stroke. Therefore, an ignition system for internal combustion engines which provides an ignition spark of a sufficient magnitude to initiate combustion and of a duration long enough to maintain combustion during the power stroke, is desirable.

It is therefore, an object of this invention to provide an improved internal combustion engine ignition system.

It is an additional object of this invention to provide an improved internal combustion engine ignition system which produces an ignition spark and maintains the spark for a predetermined period of time.

In accordance with this invention, an internal combustion engine ignition system is provided wherein an arc-duration" monostable multivibrator circuit produces a timing signal of a predetermined duration which operates an electrical switching device to the electrical circuit closed condition to establish the ignition coil primary winding energizing circuit and another control monostable multivibrator circuit produces a control signal each time the ignition coil energizing current reaches a predetermined maximum to operate the electrical switching device to the electrical circuit open condition.

For a better understanding of the present invention, together with additional objects, advantages, and features thereof, reference is made to the following description and accompanying drawing in which:

FIG. 1 sets forth the internal combustion engine ignition system of this invention is schematic form;

FIG. 2 is a set of curves useful in understanding the operation of the circuitry of FIG. 1;

FIG. 3 is a set ofcurves useful in understanding a portion of the circuit of FIG. 1;

FIG. 4 sets forth an alternate embodiment of a portion of the ignition system of FIG. 1 in schematic form; and

FIG. 5 is an alternate embodiment of a portion of the circuit of this invention in schematic form.

As a point of reference or ground potential is the same point electrically throughout the system it has been represented in FIG. I by the accepted schematic symbol and referenced by the numeral 5.

In FIG. 1 of the drawing, the internal combustion engine ignition system of this invention is set forth in schematic form in combination with a source of direct current potential, which may be a conventional storage battery 3, and an ignition distributor 4 having a movable electrical contact 6, rotated in timed relationship with an associated engine, through which ignition spark potential is applied to the spark plugs of the engine individually, in a manner well known in the automotive art.

The internal combustion engine with which the ignition system of this invention may be used is set forth in block form, is referenced by the numeral 8 and is illustrated as having four spark plugs IS, 25, 3S, and 48, each having an arc gap, as is well known in the automotive art. It is to be specifically understood, however, that the ignition system of this invention may be used with internal combustion engines having more or less cylinders or also with rotary type engines.

Mounted within ignition distributor 4 is a pair of igni' tion distributor breaker contacts 7 which are operated to the electrical circuit open and closed conditions in timed relationship with engine 8 in a manner well known in the automotive art. A resistor 9 is connected in series with battery 3 and the ignition distributor breaker contacts 7 to provide a load for battery 3 when the breaker contacts 7 are closed. Capacitor 2 is the ignition capacitor connected across the breaker contacts 7.

To supply operating potential to the system, movable contact 11 of an electrical switch I3 may be closed to stationary contact 12 to supply battery potential across lead 14 and point of reference or ground potential 5. Movable contact 11 and stationary contact 12 may be a pair of normally open ignition contacts included in a conventional automotive ignition switch of the type well known in the automotive art. For purposes of this specification, it will be assumed that movable contact 11 is closed to stationary contact 12.

To supply a substantially constant direct current potential free of ripples and noise across lead l5 and point of reference or ground potential 5, battery potential may be regulated to a selected maximum value by Zener diode 16, which clips off positive polarity spikes greater than fifteen volts. Any negative polarity spikes are clipped by resistor 18 and Zener diode l6. Diode l7 prevents filter capacitor 19 from discharging through the battery with any momentary drop of bat tery potential.

The ignition coil 20 has a magnetic core 21, a primary windng 22 which, during the buildup of the flow of an energizing current therethrough, produces a magnetic flux in core 21 and a secondary winding 23, connected to the movable electrical contact 6 of ignition distributor 4. With none of the engine spark plugs fired, an ignition spark potential of sufficient magnitude to initiate an arc across the arc gap of each of the spark plugs IS, 25, 3S and 45 is induced by induction coil action in secondary winding 23 upon the interruption of the flow of energizing current through primary winding 22, in a manner well known in the automotive art. Primary winding 22 is designed to have an inductance value which, with a predetermined magnitude of energizing current, will provide sufficient stored energy to charge the total output capacitance to the desired peak output potential and to maintain the are initiated across each spark plug arc gap for a duration of time at least as long as the period between successive energizations thereofin a manner to be explained later in this specification. Ignition coil 20 is additionally designed to have a primary to secondary windings turns ratio such that, during the buildup of energizing current through primary winding 22, a potential of sufficient magnitude to maintain the are initiated across each spark plug arc gap is induced by transformer action in secondary winding 23. If desirable, ignition coil 20 may have an open magnetic core. That is, magnetic core 21 may have an air gap of the order of 0.015 inch, as is well known in the automotive art.

An electrical switching device having current carry ing members and being of the type which may be oper ated to the electrical circuit open and closed conditions in response to electrical signals is provided for establishing a circuit for the flow of energizing current from the source of direct current potential, battery 3, through the primary winding 22 of ignition coil 20. This switching device may be a type NPN transistor 30, however, any other electrical switching device having similar electrical characteristics may be substituted therefor without departing form the spirit of the invention. The ignition coil primary winding 22 and the current carrying members of the electrical switching device, collector electrode 32 and emitter electrode 33 of switching transistor 30. are connected in series across the source of direct current potential through a circuit which may be traced from the positive polarity terminal of battery 3, through switch 13, lead 14, primary winding 22, the collectoremitter electrodes of switching transistor 30, control impedance element 10, and point of reference or ground potential 5 to the negative polarity terminal of battery 3. This circuit is the ignition coil primary winding energizing circiut through which energizing current flows from the source of direct current potential through the ignition coil primary winding. Control impedance element is illustrated in the drawing as a resistor. It is to be specifically understood, however, that any other suitable electrical impedance element which will provide a potential drop thereacross with current flow therethrough may be substituted therefor without departing from the spirit of the invention.

While engine 8 is in the running mode, the ignition distributor breaker contacts 7 are operated to the electrical circuit open and closed conditions in timed relationship with the engine in a manner well known in the automotive art. While ignition distributor breaker contacts 7 are operated to the electrical circuit open condition, a potential ignition signal appears across junction 24 and point of reference or ground potential 5 of a positive polarity upon junction 24 with respect to point of reference or ground potential 5, curve A of FIG. 2, and while ignition distributor breaker contacts 7 are operated to the electrical circuit closed condition, junction 24 is at substantially ground potential. The ig nition signal appearing upon junction 24 may be filtered by the resistor 27 and capacitor 28 filter circuit combination and is applied through input resistor 29 to the positive polarity input terminal ofa comparator circuit 25. The comparator circuit is a commercially available logic circuit element well known in the art having a positive polarity input terminal and a negative polarity input terminal. Without intention or inference of a limitation thereto, in a practical application of the ignition system of this invention, a type MC-3302P comparator circuit marketed by Motorola, Inc. was employed. Comparator circuit produces a substantially ground output signal when an input signal applied to the positive polarity input terminal thereof is of a magnitude less positive than a signal applied to the negative polarity input terminal and an output signal of a positive polarity with respect to point of reference or ground potential 5 when an input signal applied to the positive polarity input terminal is of a magnitude more positive than a signal applied to the negative polarity input terminal. To provide the comparison signal applied to the negative polarity input terminal of comparator circuit 25, resistors 34 and 35 are connected across the regulated and filtered supply potential appearing across lead 15 and point of reference or ground potential 5 through leads 36 and 37. Resistors 34 and 35 are so porportioned that the potential upon junction 38, to which the negative polarity input terminal of comparator circuit 25 is connected, is of a magnitude less than the potential across junction 24 and point of reference or ground potential 5 while the ignition distributor breaker contacts 7 are operated to the electrical circuit open condition. Consequently, while ignition distributor breaker contacts 7 are operated to the elec trical circuit closed condition, comparator circuit 25 produces a substantially ground output signal and while ignition distributor breaker contacts 7 are operated to the electrical circuit open condition, comparator circuit 25 produces an output signal of a positive polarity with respect to point of reference or ground potential 5. Feedback resistor 26 serves to produce a sharp switching action, consequently, the output signal of comparator circuit 25 is of a square waveform pulse having substantially vertical leading and trailing edges corresponding to the time that ignition distributor breaker contracts 7 are operated to the electrical circuit open and closed conditions, respectively, curve B of FIG. 2. Comparator circuit 25, therefore, operates as a signal shaper circuit which shapes the potential signal appearing across junction 24 and point of reference or ground potential 5 while the ignition distirbutor breaker contacts 7 are operated to the electrical circuit open condition to a substantially square waveform signal upon output terminal 39 thereof of a positive polarity upon output terminal 39 with respect to point of reference or ground potential 5 and of a duration of time equal to the time the ignition distributor breaker contacts 7 are open.

Breifly, over the duration of each timing signal produced by arc-duration monostable multivibrator circuit 40, curve C of FIG. 2, ignition coil primary winding switching transistor 30 is operated conductive through the collector-emitter electrodes thereof to complete an energizing circuit for primary winding 22 between each output control signal produced by a control monostable multivibrator circuit 50, curve D of FIG. 2, and is operated not conductive through the collector-emitter electrodes in response to each output control signal produced by control monostable multivibrator circuit 50, curve D of FIG. 2, when the energizing current through ignition coil primary winding 22 has reached a predetermined magnitude, in a manner to be later explained.

As is well known in the art, the monostable multivibrator circuit normally operates in a stable state and may be switched to an alternate state by an electrical signal, in which it remains for a period of time as determined by an internal R-C timing network. After timing out, the device spontaneously returns to the stable state. The arc-duration monostable multivibrator circut 40 and the control monostable multivibrator circuit 50 each includes a type D flip-flop circuit, referenced by the numerals 4S and 55, respectively. The type D flip flop circiut is a commercially available logic circuit element well known in the art which in the "Set condition produces a logic 1 signal upon the Q output terminal and a logic 0 signal upon the Q output terminal in the Reset condition produces a logic 0 signal upon the Q output terminal and a logic l signal upon the Q output terminal and transfers the logic signal present upon the D input terminal to the 0 output terminal upon the application of a logic 1 signal to the C clock input terminal. A type D flip-flop circuit suitable for use with this application is marketed by RCA under the designation Type CD40l3". For purposes of this specification, a logic l signal is a potential signal of a positive polarity, a logic 0 signal is of ground potential and, when monostable multivibrator circuits 40 and 50 are operating in the stable state, respective type D flipflop circuits 45 and 55 are in the Reset" condition with a logic 0 signal upon the Q output terminal and a logic I signal upon the 6 output terminal. As the output signal of the arc-duration monostable multivibrator circuit 40 appears upon the Q output terminal of type D flip-flop circuit 45 and the output signal of the control monostable multivibrator circuit 50 appears upon the 6 output terminal of type D flip-flop circuit 55, when in the stable state, the output signal of arcduration multivibrator circuit 40 is a logic 0 and the output signal of control monostable multivibrator circuit 50 is a logic 1 and, when in the alternate state, the output signal of arc-duration monostable multivibrator circuit 40 is a logic 1 and the output signal of control monostable multivibrator circuit 50 is a logic 0 As the D input terminal of both type D flip-flop circuits 45 and 55 is connected to the regulated and filtered potential appearing across lead and point of reference or ground potential 5, a logic 1 signal is maintained upon these D input terminals. Consequently, the application of a logic 1 clock signal to the C clock input terminal of each will transfer the logic 1 signal present upon the D input terminal to the Q output terminal to place the flip-flop in the Set" condition and, consequently, the corresponding monostable multivibrator circuit in the alternate state.

Upon the initial operation of ignition distributor breaker contacts 7 to the electrical circuit open condition, the potential signal appearing across junction 24 and point of reference or ground potential 5 is filtered by the resistor 27 and capacitor 28 filter circuit combination, shaped to a substantially square waveform signal by comparator circuit 25 and applied as a logic 1 clock input signal, curve A of FIG. 3, to the C clock input terminal of type D flip-flop circuit 45 of arcduration monostable multivibrator circuit 40. Upon the rise of this signal, the logic 1 signal present upon the D input terminal is transferred to the Q output terminal, curve B of FIG, 3, to place type D flip-flop circuit 45 in the Set" condition and, consequently, arc duration monostable multivibrator circuit 40 in the alternate state with a logic 1 signal upon the output terminal. This logic l output signal charges capacitor 44 through resistor 41 and resistor 42. Resistor 42 is illustrated as a variable resistor but may be a fixed resistor if desired. As capacitor 44 charges, the potential upon junction 46 to which the R reset input terminal of type D flip-flop circuit 45 is connected, increases in a positive direction, curve C of FIG. 3, until it reaches a value of sufficient magnitude, point R of FIG. 3, to reset type D flip flop circuit 45 which places arc-duration monostable multivibrator circuit 40 in the stable state with a logic 0 signal present upon the output terminal. At this time, capacitor 44 discharges, curve C of FIG. 3, through diode 43, resistor 41 and the output transistor for the Q output terminal of type D flip-flop circuit 45 to point of reference or ground potential 5. From this description, it is apparent that arc-duration monostable multivibrator circuit 40 is triggered to the alternate state with the rise of the output signal of comparator circuit 25, remains in the alternate state for a period of time, period t of curve B of HG. 3, as determined by the RC time constant of the charging circuit of capacitor 44 and spontaneously returns to the stable state when capacitor 44 has become charged to a value of sufficient magnitude to reset type D flip-flop circuit 45. The logic 1 output signal of arc-duration monostable multivibrator circuit 40 is the timing signal, curve C of FIG. 2, during which an arc is to be maintained across each of the spark plugs of the engine. The duration of the timing signal produced by arc-duration monostable multivibrator circuit 40 is determined by the ohmic value of series resistors 41 and 42, consequently, the duration may be selectively varied by varying the ohmic value of variable resistor 42. If resistor 42 is a fixed resistor, the ohmic value of resistors 41 and 42 may be proportioned to provide a timing signal of a predetermined duration. Diode 43 provides a low impedance path in shunt with variable resistor 42 to permit capacitor 44 to discharge in a length of time shorter than it took to charge. As arc-duration monostable multivibrator circuit 40 produces a logic 1 output signal each time ignition distributor breaker contacts 7 are operated to the electrical circuit open condition, this device produces a timing signal corresponding to each spark plug ofthe engine in timed relationship with and during each revolution of the crankshaft of the engine and of a duration corresponding to the period of time ignition spark energy is to be applied to the spark plug to which it corresponds.

The logic 1 timing signal is applied to the cathode electrode of diode 61, consequently, this device is reverse biased thereby and the logic l signal produced by control monostable multivibrator circuit 50, operating in the stable state, is applied to the cathode electrode of diode 62 to reverse bias this device. With diodes 61 and 62 reverse biased, the filtered and regulated potential appearing across lead 15 and point of reference or ground potential 5 is applied across the series combination of resistor 63, Zener diode 64 and resistor 65. Zener diode is selected to have an inverse breakdown potential less than the potential present upon junction 66 with both diodes 61 and 62 reverse biased, consequently, Zener diode 63 breaks down and conducts in a reverse direction to complete a circuit through which base-emitter drive current is supplied to type NPN transistor 70 which may be traced from the positive polarity terminal of battery 3, through switch 13, resistor 18, diode 17, lead 15, resistor 63, Zener diode 64, the base-emitter electrodes of transistor 70 and point of reference or ground potential 5 to the negative polarity terminal of battery 3. This base drive current produces collector-emitter conduction through transistor 70 through a circuit which may be traced from the positive polarity terminal of battery 3, through switch l3, lead 14, series resistors 71 and 72, the collector-emitter electrodes of transistor 70 and point of reference or ground potential 5 to the negative polarity terminal of battery 3. While transistor 70 is conducting through the collector-emitter electrodes, a circuit is established thereby through which emitter-base drive current is supplied to type PNP transistor which may be traced from the positive polarity terminal of battery 3, through switch 13, lead 14, the emitter-base electrodes of transistor 80, resistor 72, the collector-emitter electrodes of transistor 70 and point of reference or ground potential S to the negative polarity terminal of battery 3. This emitter-base current flow through transistor 80 produces emitter-collector current flow therethrough which establishes a circuit through which base drive current is supplied to type NPN switching transistor 30 which may be traced from the positive polarity terminal of battery 3, through switch 13, lead 14, through the emitter-collector electrodes of transistor 80, resistor 73, the base-emitter electrodes of switching transistor 30, impedance element 10 and point of reference or ground potential to the negative polarity terminal of battery 3. This base-emitter drive current through switching transistor 30 produces collector-emitter con duction therethrough to complete the ignition coil primary winding energizing circuit, previously described, for the flow of ignition coil primary winding energizing current from the source of direct current potential, battery 3, through primary winding 22, the collectoremitter electrodes of switching transistor 30 and impedance element 10, curve E of FIG. 2. The flow of ignition coil primary winding energizing current through impedance element produces a potential drop thereacross which is of a positive polarity upon junction 74 with respect to point of reference or ground potential 5. Impedance element 10, therefore, is responsive to the flow of energizing current through the ignition coil primary winding energizing current for producing an electrical potential signal of a magnitude proportional to the magnitude of the flow of this energizing current. This electrical potential signal may be filtered by the resistor 77 and capacitor 78 filter circuit combination and applied to the positive polarity input terminal of comparator circuit 75 through lead 67 and current limiting resistor 68. Comparator circuit 75 may be the same as comparator circuit 25 previously described. To provide the comparison signal applied to the negative polarity input terminal of comparator circuit 75 with which the control potential signal produced across im pedance element 10 may be compared, resistors 8i and 82 are connected across the regulated and filtered supply potential appearing across lead and point of reference or ground potential 5 through lead 36. This potential is regulated to a desired constant magnitude by Zener diode 84 and may be filtered by the resistor 83 and capacitor 85 filter circuit combination. Resistors 81 and 82 are so proportioned that the potential upon junction 86, to which the negative polarity input terminal of comparator circuit 75 is connected, is of a mag nitude substantially equal to the magnitude of the control potential produced across control impedance element 10 when the ignition coil primary windng energizing current is of the predetermined magnitude. Consequently, when the electrical potential produced across control impedance element 10 is equal to the comparison potential signal appearing across junction 86 and point of reference or ground potential 5, comparator circuit 75 produces a logic 1 output signal having a substantially vertical leading edge, as feedback resistor 76 produces a rapid switching action, which is applied to the C clock input terminal of type D flip-flop circuit 55 of control monostable multivibrator circuit 50. Upon the rise of this logic 1 signal, the logic I signal present upon the D input terminal is transferred to the 0 output terminal to place type D flip-flop circuit 55 in the "Set condition and, consequently, control monostable multivibrator circuit 50 in the alternate state with a logic 0 control signal upon the output terminal, Control monostable multivibrator circuit 50, therefore, is responsive to the electrical potential signal of a predetermined magnitude, produced by impedance element 10, for producing an output logic 0 control signal when the ignition coil primary winding energizing current has reached a predetermined magnitude. The logic 0 control signal upon the output terminal of control monostable multivibrator circuit 50, curve D of FIG. 2, places a forward anode-cathode bias upon diode 62, consequently, the potential upon junction 66 reduces to a value below the inverse breakdown potential of Zener diode 64. As Zener diode 64 no longer conducts in a reverse direction at this time, the circuit through which base emitter drive current is supplied to transistor is interrupted, consequently, this device extinguishes. When transistor 70 extinguishes, the circuit through which emitter-base current is supplied to transistor is interrupted thereby, consequently, transistor 80 also extinguishes, When transistor 80 extinguishes, the circuit through which base-emitter drive current is supplied to switching transistor 30 is interrupted thereby, consequently, switching transistor 30 extinguishes to interrupt the ignition coil primary winding energizing circuit. Resistor 79 speeds up the cut-off or turn-off time of switching transistor 30. The resulting collapsing magnetic field induces, by induction coil action, a potential of a negative polarity in secondary winding 23 of ignition coil 20, curve F of FIG. 2. As secondary winding 23 is open-circuited at this time, the potential induced therein increases rapidly, curve F of FIG. 2, to a magnitude, for example 15 kilovolts, at which an arc is initiated across the arc gap of the one of the engine spark plugs to which this potential is directed through distributor 4. Upon the initiation of the arc across the arc gap of one of the engine spark plugs, the potential in secondary winding 23 falls rapidly to a magnitude, for example 3 kilovolts, which is sufficient to maintain the arc current, curve C] of FIG. 2, which is ofa maximum magnitude at the instant of spark initiation. While control monostable multivibrator circuit 50 is in the alternate state, the logic 1 signal upon the 0 output terminal of type D flip-flop circuit 55 charges capacitor 54 through resistor 51 and resistor 52. Resistor 52 is illustrated as a variable resistor but may be a fixed resistor if desired. As capacitor 54 charges, the potential upon junction 56, to which the R reset input terminal of type D flip-flop circuit 55 is connected, increases in a positive direction until it reaches a value of sufficient magnitude to reset type D flip-flop circuit 55 which places control monostable multivibrator circuit 50 in the stable with a logic 1 signal present upon the output terminal. At this time, capacitor 54 discharges through diode 53, resistor 51 and the output transistor for the Q output terminal of type D flip-flop circuit 50 to point of reference or ground potential 5. From this description, it is apparent that control monostable multivibrator circuit 50 is triggered to the alternate state when the ignition coil primary winding energizing current has reached the predetermined maximum in response to the electrical potential signal of a predetermined magnitude, remains in the alternate state for a period of time as determined by the R-C time constant of the charging circuit of capacitor 54 and spontaneously returns to the stable state when capacitor 54 has become charged to a value of sufficient magnitude to reset type D flip-flop circuit 55. when monostable multivibrator 50 has spontaneously returned to the stable state, the logic 1 output signal thereof again reverse biases diode 62. As timing signal produced by arcduration monostable multivibrator circuit 40 is still present to maintain a reverse bias upon diode 61, switching transitor 30 is again rendered conductive through the collector-emitter electrodes to complete the ignition coil primary winding energizing circuit in a manner previously described. The resulting flow of energizing current through ignition coil primary winding curve 22, curve B of FIG. 2, is initially of a magnitude determined by the arc current through the fired spark plug and increases in magnitude to the predetermined maximum to induce a potential, by transformer action, in secondary winding 23 of a sufficient magnitude to maintain the arc across the fired plug, curve F of FIG. 2. When the ignition coil primary winding energizing curent has again reached the predetermined maximum, the control monostable multivibrator circuit 50 is again triggered to the alternate state, in a manner previously explained, to place a forward anode-cathode bias upon diode 62, a condition which results in the interruption of the ignition coil primary winding energizing circuit in a manner previously explained. The resulting collapsing magnetic field induces a potential, by induction coil action, in secondary winding 23 which is limited to approximately 3 kilovolts, the magnitude required to maintain the arc of the fired plug, curve F of FIG. 2. From this description, it is apparent that, during each timing signal period, curve C of FIG. 2, switching transistor 30 is conductive through the collectoremitter electrodes thereof between each logic output signal of control monostable multivibrator circuit 50, curve D of FIG. 2, to complete the ignition coil primary winding energizing circuit through which energizing current flows through primary winding 22, curve E of FIG. 2, and is not conductive through the collectoremitter electrodes thereof during each output signal of control monostable multivibrator circuit 50 to interrupt the ignition coil primary winding energizing circuit. Upon each completion of the energizing circuit for ignition coil primary winding 22, the resulting expanding magnetic field produced by the flow of energizing current through primary winding 22 induces, by transformer action, a potential in secondary winding 23, curve F of FIG. 2, of a magnitude sufficient to maintain the arc across any fired plug and upon the interruption of the energizing circuit for ignition coil primary winding 22, the resulting collapsing magnetic field induces, by induction coil action, a potential in ignition coil secondary winding 23 of a magnitude sufficient to initiate a spark across the arc gap of any plug or, in the event a plug has already been fired, ofa sufficient magnitude to maintain the arc thereacross, as is shown by curve G of FIG. 2. Should the arc extinguish at any time during any of the timing signals, therefore, upon the next interruption of the flow of energizing current through ignition coil primary winding 22, the potential induced in secondary winding 23 by induction coil action increases rapidly to a magnitude at which the spark is again initiated across the arc gap of the plug to which the energy is directed through ignition distributor 4. It may be noted that the reversal of polarity of the potential induced in secondary winding 23 during transformer action and induction coil action does not extinguish the arc across any plug as this reversal of polarity occurs in a length of time less than that required for the arc gap to deionize. From this description, it is apparent that switching transistor 30 is responsive to each of the timing signals for establishing and to each of the control signals for interrupting the ignition coil primary winding energizing circuit.

During the transformer action period, the potential induced in secondary winding 23 may be of a magnitude of 3 kilovolts while the potential across the arc may be only 1 kilovolt. Consequently, 2 kilovolts must be dropped across the remainder of the circuit. To drop these 2 kilovolts, a resistor is connected in series with each of the engine spark plugs and is selected to have an ohmic value which will limit the arc current to a desired value, for example 50 milliamperes These resistors are referenced in the drawing by numerals IR, 2R, 33R and 4R, respectively.

In a practical application of the internal combustion engine ignition system of this invention, an ignition coil having a turns ratio of 250 to l with a primary voltage of 12 volts was employed to produce an output voltage of 3000 volts during the period of transformer action as the ignition coil primary winding energizing current builds up. This induced voltage by transformer action is of a sufficient magnitude to maintain the arc across any of the fired spark plugs. Furthermore, the primary winding was designed to have a sufficient inductance value, which, with a predetermined magnitude of energizing current, for exapmle 25 amperes, will provide sufficient stored energy to charge the total output capacitance to the desired output potential, for example 30 kilovolts, if the arc does not strike and to maintain the arc initiated across each spark plug for a duration at least as long as the period between successive energizations thereof; that is, for the period of each of the successive logic 0 output signals of control monostable multivibrator circuit 50. With this arrangement, the arc across any of the fired spark plugs is maintained during the entire period of the timing signal, as illustrated by curve H of FIG. 2, to provide substantial arc power.

The ignition signal, curve A of FIG. 2, is shown to be of a longer duration than the timing signal, curve C of FIG. 2. It is to be understood that these curves are illustrative of possible signal durations as the ignition signal may be of a shorter duration than the timing signal at higher engine speeds while the timing signal duration is constant at all engine speeds.

Diode 91 is included for the purpose of preventing the potential upon junction 92 from becoming greater than the potential across lead 15 and point of reference or ground potential 5 and diode 93 is included to pre vent negative polarity spikes from occuring upon junction 92 to prevent damage to comparator circuit 25. Diode 94 is included for the purpose of removing negative polarity spikes from lead 67 to prevent damage to comparator circuit 75. Resistors 95 and 96 provide pull-up" potential for respective comparator circuits 25 and 75.

As the output signal of comparator circuit 25 has substantially vertical leading and trailing edges corresponding to the times that ignition distributor breaker contacts 7 are operated to the electrical circuit open and closed conditions, respectively, and is, consequently, of a duration equal to the time that ignition distributor breaker contacts 7 are operated to the electrical circuit open condition, the logic 1 output signal of comparator circuit 25, curve B of FIG. 2, may be employed as the timing signal. This embodiment is schematically set forth in FIG. 4, wherein circuit elements the same as in FIG. 1 are assigned the same characters of reference, which sets forth the portion of the circuit of FIG. 1 which is changed by this embodiment. Output t..:rminal 39 of signal shaper circuit 25 is connected directly to the cathode electrode of diode 69 and monostable multivibrator circuit 40 is retriggerable in a manner to be later explained. The remainder of the circuit operates exactly the same way as herein previously described, so long as the timing signal output of comparator circuit 25 is present upon the cathode electrode of diode 69 and monostable multivibrator circuit 40 is in the alternate state. With this embodiment, however, the duration of the timing signal would be equal to the time that ignition distributor breaker contacts 7 are operated to the electrical circuit open condition. Consequently, the lobes of the distributor cam, not shown but well known in the automotive art, are designed to maintain ignition distributor breaker contacts 7 operated to the electrical circuit open condition for a predetermined number of degrees of engine crankshaft rotation which, at any engine speed, is the time ignition spark energy is to be supplied to the spark plugs. Therefore, as engine 8 rotates the distributor cam to operate the ignition distributor breaker contacts 7 to the electrical circuit open and closed conditions, each time breaker contacts 7 are operated to the electrical 1 open condition, a logic 1 timing signal corresponding to a spark plug of engine 8 is produced across output terminal 39 of comparator circuit 25 and point of reference or ground potential in timed relationship with and during each revolution of the crankshaft of engine 8 and for a duration of time corresponding to the period of time ignition spark energy is to be applied to the spark plug to which it corresponds. For example, and without intention of interference of a limitation thereto. should it be desired that ignition spark energy be applied to each of spark plugs 18, 28, 3S and 4S of engine 8 for a period of 45 crankshaft degrees, each one of the four lobes of the ignition distributor cam would be designed to maintain ignition distributor breaker contacts 7 open for 45 degrees of crankshaft rotation of engine 8. With this embodiment, therefore, the timing signal would not be of a constant duration regardless of engine speed, as with the embodiment employing an arc-duration monostable multivibrator circuit, but would be of a length of time proportional to engine speed, being longest with minimum engine speed and decreasing in duration with increasing engine speed. The R-C time constant of the charge circuit of capacitor 44, therefore, would be designed to insure that monostable multivibrator circuit 40 remains in the alternate state for a period of time longer than the longest timing signal. To prevent monostable multivibrator circuit 40 from timing out and returing to the stable state during alternate timing signals at high engine speeds, circuitry is provided through which this circuit is retriggered by each timing signal. Each positive polarity timing signal supplies base'emitter drive current for NPN transistor 60 through capacitor 47 and resistor 48. While base-emitter drive current is being supplied to transistor 60, capacitor 44 discharges through the collector-emitter electrodes thereof. When capacitor 47 has become charged, base-emitter drive circuit is no longer supplied to transistor 60, consequently, this device extinguishes and capacitor 44 begins to charge through circuitry previously described. The time constant of capacitor 47, resistor 48 and resistor 49 is selected to be of a duration only long enough to permit capacitor 44 to discharged. Diode 59 prevents reverse potential from damaging transistor 60 when capacitor 47 discharges at the conclusion of each timing signal,

With this embodiment, monostable multivibrator circuit 40 establishes a maximum arc-duration limit in the event movable Contact 11 of switch 13 is closed to stationary contact 12 while engine 8 is not in the running mode and ignition distributor breaker contacts 7 are operated to the elecrical circuit open condition. Under these conditions, without this limit circuitry, the system would continue producing a spark so long as switch 13 remains closed. As has been previously brought out, the R-C time constant of the charge circuit for capacitor 44 is designed to insure that monostable multivibrator circuit 40 remains in the alternate state for a period of time longer than the longest ignition signal. Therefore, in the absence ofa series of timing signals, this device times out and returns to the stable state and the logic 0 output signal thereof provides a forward anodecathode bias for diode 61. While diode 61 conducts at this time, the potential upon junction 66 is of an insufficient magnitude to cause Zener diode 64 to break down and conduct in a reverse direction. Consequently, switching transistor 30 is maintained extinguished.

In the two embodiments just described, the ignition signals appearing across junction 24 and point of reference or ground potential 5 are produced in response to the operation of ignition distributor breaker contacts 7 to the electrical circuit open condition. ln FIG. 5, wherein circuit elements the same as in FIG. I have been assigned the same characters of reference, an al ternate method for producing the required ignition signals by a magnetic pick-up type distributor is set forth. Magnetic pick-up type distributors of this type are well known in the automotive art and are comprised of a rotor member rotated by the associated internal combustion engine within the bore of a pole piece 112 which is magnetized by an annular permanent magnet, not shown. As rotor member 110 is rotated by the engine, an alternating current signal is induced in pickup coil 114, as shown, which is filtered by the resistor [15 and capacitor 116 filter circuit combination and supplied through input resistor 29 to the positive polarity input terminal of comparator circuit 25. When the signals induced in pickup coil 114 are of a magnitude less positive than the comparison signal present upon junction 38, a logic 0 signal appears upon the output terminal 39 of comparator circuit 25, as shown, and when these signals are of a magnitude more positive than the comparison signal upon junction 38, a logic l signal appears upon the output terminal 39 of comparator circuit 25, as shown, until the potential induced in the pickup coil 114 reduces to a magnitude less positive than the comparison signal upon junction 38. Comparator circuit 25, therefore, functions as a signal shaper circuit which produces an output signal of a square waveform having substantially vertical leading and trailing edges and of a duration of time equal to the period of time the signals induced in pickup coil 114 are of a magnitude greater than the comparison potential upon junction 38. Consequently, with this embodiment, comparator circuit functions as it does in the embodiments previously described except that in this embodiment it is responsive to an alternating current ignition signal rather than a direct current ignition signal. Output terminal 39 may be connected to the input terminal of arc duration monostable multivibrator circuit 40, or, alternatively, it may be connected directly to the cathode electrode of diode 61, in which event the output signal thereof is the timing signal.

It is apparent from the curves of FIG. 2 that from the beginning of the timing signal, curve C, to the initiation of the ignition spark which occurs at the beginning of arc current, curve G, there is a fixed time delay equal to the time period required for the ignition coil primary winding energizing current to reach a predetermined magnitude. The fixed time delay between the beginning of the timing signal and the initiation of the spark results in a retardation of the spark, as is well known in the automotive art. This spark retard is compensated for by the initial distributor tiiming and the use of the proper spark advance curve. For example, a spark retard of 0.5 milliseconds between the beginning of the timing signal and the initiation of the ignition spark requires a distributor spark advance compensation of 3 per 1000 engine rpm.

While specific electric circuit elements, logic circuit elements, transistor types, electrical circuits and electrical polarities have been set forth in detail in this specification, it is to be specifically understood that alternate electrical circuit elements, logic circuit elements, transistor types, electrical circuit elements and compatible electrical polarities may be substituted therefor without departing from the spirit of the invention.

While a preferred embodiment of the present invention has been shown and described, it will be obvious to those skilled in the art that various modifications and substitutions may be made without departing from the spirit of the invention which is to be limited only within the scope of the appended claims.

What is claimed is:

1. An internal combustion engine ignition system comprising in combination with a source of direct current potential and an ignition distributor having an electrical contact rotated in timed relationship with the engine through which ignition spark potential is applied to the spark plugs of the engine individually; a first monostable multivibrator circuit for producing a timing signal corresponding to each spark plug of said engine in timed relationship with and during each revolution of the crankshaft of said engine of a duration corresponding to the period of time ignition spark energy is to be applied to the said spark plug to which it corresponds; an ignition coil having a magnetic core, a primary winding which, during the buildup of the flow of an energizing current therethrough, produces a magnetic flux in said core and a secondary winding, connected to said electrical contact of said distributor, in which an ignition spark potential of sufficient magnitude to initiate an arc across the spark gap of each of said spark plugs is induced upon the interruption of the flow of energizing current through said primary winding, said primary winding having an inductance value which, with a predetermined magnitude of energizing current, will provide sufficient stored energy to maintain the are initiated across each spark plug spark gap for a predetermined duration of time and said ignition coil having a primary to secondary winding turns ratio such that, during the buildup of energizing current through said primary winding, a potential sufficient magnitude to maintain the arc initiated across each spark plug spark gap is induced in said secondary winding; an ignition coil primary winding energizing circuit through which energizing current flows from said source of direct current potential through said ignition coil primary winding; an impedance element included in said ignition coil primary winding energizing circuit for producing an electrical potential signal of a magnitude proportional to the magnitude of said flow ofenergizing current; a second monostable multivibrator circuit for producing a plurality of control signals during each said timing signal, each in response to said electrical potential signal of a predetermined magnitude; and means reponsive to said timing signal for establishing and to each of said control signals for interrupting said ignition coil primary winding energizing circuit.

2. An internal combustion engine ignition system comprising in combination with a source of direct current potential and an ignition distributor having an electrical contact rotated in timed relationship with the engine through which ignition spark potential is applied to the spark plugs of the engine individually; a first monostable multivibrator circuit for producing a timing signal corresponding to each spark plug of said engine in timed relationship with and during each revolution of the crankshaft of said engine of a duration corresponding to the period of time ignition spark energy is to be applied to the said spark plug to which it corresponds; an ignition coil having a magnetic core, a primary winding which, during the buildup of the flow of an energizing current therethrough, produces a magnetic flux in said core and a secondary winding, connected to said electrical contact of said distributor, in which an ignition spark potential of sufficient magnitude to initiate an arc across the spark gap of each of said spark plugs is induced upon the interruption of the flow of energizing current through said primary winding, said primary winding having an inductance value which, with a predetermined magnitude of energizing current, will provide sufficient stored energy to maintain the arc initiated across each spark plug gap for a predetermined duration of time and said ignition coil having a primary to secondary winding turns ratio such that, during the buildup of energizing current through said primary winding, a potential of sufficient magnitude to maintain the are initiated across each spark plug spark gap is induced in said secondary winding; an ignition coil primary winding energizing circuit through which energizing current flows from said source of direct current potential through said ignition coil primary winding; an impedance element included in said ignition coil primary winding energizing circuit for producing an electrical potential signal of a magnitude proportional to the magnitude of said flow of energizing current; an electrical potential comparator circuit reponsive to said electrical potential signal of a predetermined magnitude for producing an output signal; a second monostable multivibrator circuit for producing a plurality of control signals during each said timing signal, each in response to said output signal of said potential comparator circuit; and an electrical switching device of the type operable to electrical circuit closed and open conditions in response to electrical signals responsive to said timing signal for establishing and to each of said control signals for interrupting said ignition coil primary winding energizing circuit.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,892,219

DATED July 1, 1975 INVENTOR(5) I Mark E. Preiser et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown betow:

line line line line line line line line line line line line line line line line line line line Column 1, Column 3,

emitter Column 4,

Column 8, Column 9,

Column 11,

Column 12, Column 13, Column 14,

'[SEAL] after "is" should be in "collectoremitter" should be collectordelete "circuit" and insert current change "discharged" to discharge "tiiming" should be timing after "potential" insert of after "pluginsert spark change "repon" to respon Signed and Scaled this ninth Day Of December 1975 A ttest:

RUTH C. MASON Arresting Officer C. MARSHALL DANN Commissioner nj'larenrs and Trademarks

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Referenced by
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Classifications
U.S. Classification123/629, 123/634, 315/209.00R, 315/209.00T
International ClassificationF02P3/02, F02P3/05
Cooperative ClassificationF02P3/051
European ClassificationF02P3/05B