US3329867A - Ignition system suitable for internal combustion engines - Google Patents

Description

D. E. STEARNS July 4, 1967 IGNITION SYSTEM SUITABLE FOR INTERNAL COMBUSTION ENGINES Filed Nov. 16, 1964 JYJTEM c R 0mm i m c .Dxck f. Jzeaxws INVENTOR.

ATTOFA/EVJ United States Patent 3,329,867 IGNITION SYSTEM SUITABLE FOR INTERNAL COMBUSTION ENGINES Dick E. Stearns, 3103 Ibervilie, Shreveport, La. 71109 Filed Nov. 16, 1964, Ser. No. 411,337 Claims. (Cl. 315-409) This invention relates to an ignition system suitable for internal combustion engines. It is primarily intended for a system in which an electronic switch is employed for controlling the discharge of a capacitor through a spark producing apparatus to produce a spark, and in which the electronic switch is triggered into conductivity by the application of a triggering current thereto upon the opening of the breaker points employed with such an ignition system. It has for its general object the inhibition of refiring which may be found to occur in such a system during breaker point reclosure action as a result of contact bounce charactrized by one or more unintended reopenings and reclosures of the breaker points pursuant to the initial breaker point reclosure after having fired the system. It is also applicable in its broadest aspects to other systems in which such premature refiring may occur.

In engine ignition systems obtaining spark-over voltage in the spark plugs by means of the discharge of an energy storing capacitor to the primary of an ignition transformer and utilizing breaker point opening as a means of initiating the discharge of such energy storing capacitor and hence of the spark formation, operation may be made inefiicient by breaker point chatter as the points close. This will result in energy wasting multiple discharges of the energy storage capacitor.

It is an object of this invention therefore to provide an ignition system, using breaker points of more or less conventional variety employed in distributors of internal combustion engines, said system having incorporated therein a means for inhibiting the misfiring of the ignition as a consequence of breaker point chatter upon closure of breaker points.

It is a further object of this invention to provide an ignition system employing breaker points of more or less conventional variety such as used in the distributors of internal combustion engines, in which the system, having once fired upon opening of the breaker points, instantaneously will assume a condition in which it is unable to cause firing, and will thereafter gradually recover to a condition able to cause firing only after the breaker points shall have closed and all chattering of the points has ceased.

It is a further object of this invention to provide an ignition system employing breaker points of more or less conventional variety as used in the distributors of internal combustion engines, in which the system, upon being switched on by a charging current through a firing control capacitor upon the opening of the breaker points, will inhibit further firing until said control capacitor is substantially discharged, and will upon reclosing of said points bleed off the charge from said capacitor at a gradual rate such as will reduce it enough to permit firing only after the breaker points shall have been closed and chattering thereof has ceased.

Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings wherein is set forth by way of illustration and example a specific embodiment of the invention.

In the drawing:

FIG. 1 is an electrical diagram of an ignition system constructed in accordance wtih this invention, illustrating in block form the source of power providing the energy for the creation of the spark.

FIG. 2 is an electrical diagram illustrating one suitable ice form of a source of power which has been found to operate most satisfactorily for the purpose of supplying power for sparking to the ignition system illustrated in FIG. 1, such ignition system being indicated in block form in FIG. 2.

Referring first to FIG. 1, there is illustrated in electrical diagram form an ignition system utilizing a capacitor discharge of an energy storing capacitor incorporated in a DC to DC power converter, such discharge taking place through an ignition transformer as a means of forming a high voltage impulse producing a spark in the sparkplug of an engine to obtain fuel ignition.

With more specific reference to FIG. 1, energy from the battery 1 is converted to a convenient voltage by a power converter 2 and stored in an energy storing capacitor 31 which is actually a part of the converter 2 but is shown in FIG. 1 externally thereof for clarity and convenience in description. The primary of an ignition transformer or so-called ignition coil 3 is connected to ground through a silicon controlled rectifier 4 which serves as an electronic switch providing for current flow in one direction from the primary of such transformer to the ground. Reverse flow of current from the ground to the primary of transformer 3 is provided for by means of a diode 5 connected therebetween in parallel with the silicon controlled rectifier 4. The output of the ignition transformer secondary is connected in well known fashion to the various spark plugs in the engine in a system designated and illustrated diagrammatically at 6. The primary of the transformer 3 is connected by a suitable conductor 7 to the positive side of the capacitor 31 Which serves as the energy storing capacitor for the power converter 2 with the opposite side of this capacitor being grounded, it will be seen that upon the application of a sufiicient signal in the form of a triggering current to the gate of the silicon controlled rectifier 4, the capacitor 31 will be discharged through the primary of the transformer 3 and will cause the firing of the spark plug or spark plugs through the system 6.

In the condition of the system illustrated in FIG. 1, the battery 1 provides a unidirectional current source and such source is employed for supplying a triggering current or signal to the electronic switch 4. Means for conducting a triggering current from the battery 1 to the switch 4 is provided in the form of a resistance 8, a capacitor 10, and a diode 9 polarized in a direction to permit current flow toward the switch 4, all three elements connected in series from the positive terminal of battery 1, to the gate of the switch 4. Shunted across the capacitor 10 is a high impedance connection or resistor 11. The means just described for conducting a triggering current from the battery 1 to the switch 4 is made up of components of such value as to permit a sufficient rate of current flow therethrough for a short period of time adequate to-trigger or fire the silicon controlled rectifier 4. Resistor 11 is of such high impedance as to render it incapable of passing current from battery 1 to the gate of switch 4 of any appreciable degree under any condition during the entire firing sequence between one spark and the next.

Breaker points 12 and 13 are provided interconnected with the battery 1 and the gate so that when closed they will short circuit the firing system by connecting the juncture between the resistor 8 and the capacitor 10-, to ground. Thus when these points are closed no current can flow and any previous current flow from battery 1 through the RC combination of condenser 10 and resistor 8 to the I gate of the silicon controlled rectifier 4 will be interrupted.

In other words, this closing of the points 12 and 13 connects resistor 8 to ground and thus completely cuts off current to the gate of switch 4.

Furthermore, it will be seen that by grounding a point of the circuit between resistor 8 and capacitor 10 the closing of the points 12 and 13 isolates the RC combination of capacitor 10 and resistor 11 between the aforesaid ground connection at one side of capictor 10 charged to a positive polarity, and the opposite side of capacitor 10 at a negative polarity blocked below ground potential from any effect on the gate of switch 4 by rectifier 9. Under these circumstances the charge on capacitor 10 will be gradually bled off by resistor 11 toward a condition of zero charge, at least until it reaches a condition of charge in which it will be ready to transmit a positive surge of sufficient current from the battery 1 through resistor 8 and capacitor 10 to trigger switch 4 when the breaker points 12 and 13 are next opened to produce a spark.

As is customary in ignition systems for internal combustion engines, there is provided in this instance a cam illustrated diagrammatically at 14 for opening the points 12 and 13 when the ignition system is to be fired. When the points 12 and 13 are opened by the cam 14, the full voltage of the current source 1 will be impressed across the combined resistor 8, the RC combination control capacitor 10 and resistor 11, diode 9, and the gate-cathode circuit of switch 4, with the result that a surge of current will take place therethrough to the gate of the silicon controlled rectifier or switch 4. It is to be noted that inasmuch as with the points 12 and 13 closed the two sides of the capacitor 10 would eventually reach the same potential due to bleed-off by resistor 11, and hence the capacitor 10 being at least substantially discharged at the time the points thereafter opened, its condition of remanent charge would be such as to enable it to conduct a charging surge of current to the gate of the switch 4 sufficient for triggering thereof.

As previously stated, the application of the surge of current to the switch 4 will serve to fire the same or render it conductive whereupon the energy storing capacitor 31 incorporated with the power converter 2 will be discharged through the primary of the transformer 3 and the electronic switch 4 to the ground. This discharge will provide the energy in the secondary of the transformer 3 to produce the desired spark which is the object of the system 6.

The anode-cathode circuit of switch 4 having been rendered c nductive by the gate current as just described, the surge of discharging current from the capacitor 31 through the inductance of the primary of the transformer 3 will initiate an oscillation beginning with a forward surge of current from capacitor 31 and culminating in a reverse surge of current from the ground back through the primary of the transformer 3 to the capacitor 31 of the power converter, but since such reverse surge cannot take place through the switch 4 the diode 5 is provided for this purpose. This leaves the energy storing capacitor 31 with its beginning charge partly restored and ready to be recharged by the power converter to the desired predetermined degree so as to be ready for producing another impulse of power to the transformer 3. The action of the reverse surge of current just described will, of course, produce a back biasing of the silicon controlled rectifier 4 as a result of which it will recover its ability, during the time required for passing through the said reverse surge, to block flow of current through its anodecathode circuit from the energy storing capacitor to the ground until the next deliberate firing of switch 4 by the opening of breaker points 12 and 13 as hereinbefore described.

After the firing of the system takes place in the manner just described, continued operation of the means for opening the points 12 and 13 will permit them to close, again establishing the condition in which the juncture between the resistor 8 and the capacitor 10 is connected to ground. When this occurs no further fiow of current from the battery 1 to the gate of switch 4 through the capacitor 10 can take place, and the charge placed on the control capacitor 10 by the previous surge of gating current, or

triggering current, to the switch 4 will begin to bleed off through the resistor 11. Resistor 11 is selected so that this bleeding action will result in control capacitor 10 being reduced in charge at least to a point which differs by at least a predetermined minimum from the ultimate charge which the potential of the battery 1 will enable it to place on the capacitor 10 with the points open, at which point of charge it will be capable of absorbing sufficient charging current to fire switch 4, as such charging current simultaneously flows into the gate thereof in series therewith, upon next deliberate opening of the breaker points 12 and 13. It will be recognized that immediately after the surge of current through the control capacitor 10 to the gate of the switch 4, capacitor 10 will have been charged to the full potential of the battery 1, and thus will terminate all flow of current from battery 1 to the gate of switch 4 except for the negligible and ineffectual current passing through the high impedance of bleeder resistor 11. It will be clear also to those skilled in the art that as the charge on the capacitor 10 approaches such full battery potential, the current therethrough to said gate will be reduced until its rate will be less than sufiicient to trigger the switch 4. Thereafter, until reduction of said charge to below said minimum no further firing can occur.

In accordance with this invention the bleeder resistor 11 is made of a value such that the charge on the capacitor 10 resulting from the firing current to the gate of switch 4 taking place upon the deliberate periodic opening of breaker points 12 and 13, will not, following subsequent periodic initial reclosure of breaker points 12 and 13, be bled down sufiiciently to enable it to again pass a gate current of a magnitude to cause firing of the switch 4 until sufiicient time has passed to permit all chattering of breaker points 12 and 13, i.e., a series of spurious rapid reopenings and reclosings, to cease. Thus, even though breaker points 12 and 13 bounce open and closed many times after coming together initially in their periodic action, the time of such bounce following the initial closing, as related to the bleed-off rate of capacitor 11} by the resistor 11, is such that upon the occurrence of any bounce there will still remain sufficient charge on the capacitor 10 to prevent the capacitor 10 from passing current at a suflicient rate to fire the switch 4. Thus the switch 4 will not become conductive during the bounce period and there will be no false firing. However, the resistor 11 must be chosen to be of such a value that it will bleed off the charge from the capacitor 10 after the last bounce sufiiciently topermit refiring, within a time interval less than that before the next periodic intentional reopening of the points 12 and 13 during the fastest contemplated operation of the device.

Reference is now had to FIG. 2 in which is illustrated one form of power converter which has been found highly satisfactory for the supplying of power to the ignition system of this invention as illustrated in FIG. 1.

The source of power for operating the power converter 2 may be the same battery 1 referred to in FIG. 1, the same having its negative side grounded at 20. The positive side of this battery is applied to the center tap 21 of the primary of the power transformer 22 having a linear magnetizing characteristic. The application of the potential of the battery 1 to the feedback position 23 of the primary winding will produce a signal current through the capacitor 24 and resistor 25 to the base of an electronic switch 26 causing the emiter collector circuit of this switch to become conductive and connect the lower end of the power input winding 27 of the transformer 22 to the ground.

The windings 23 and 27 are arranged in a positive feedback manner so that when the electronic switch 26 becomes conductive increased base current through the capacitor resistor combination 24, 25 to the transistor 26 is caused by the resulting transformer response. Similarly, reducing the transistor conductance through the transistor 26 causes a resulting decrease in base current through transformer response.

The transformer 22 has a secondary winding 28 connected across the terminals of a capacitor 29. The inductance of the winding 28 and the capacitance of the capacitor 29 provide a tuned oscillatory circuit adapted to operate at a predetermined frequency which establishes a frequency of operation for the converter. One of the terminals of the coil 28 and capacitor 29 is grounded and the other terminal of this combination is connected through a diode 30 to the energy storage capacitor 31, the opposite side of which is also grounded.

Interconnecting the juncture between the diode 30 and the capacitor -31 on one hand and the base of a second electronic switch or transistor 32 on the other hand is a conductor '33 having interposed therein a diode '34 and a zener diode 35. It will be appreciated that when the potential across the capacitor 31 exceeds the inherent impedance of the zener diode circuit and the zener voltage of the zener diode 35, a control current will flow therethrough to the base of the electronic switch 32 rendering its collector emitter circuit conductive. Inasmuch as this collector emitter circuit interconnects the base of the electronic switch 26 and ground, it will be understood that when it becomes conductive it will bleed oft any signal otherwise being passed to the base of the transistor 26 and make it impossible for such signal to render the transistor 26 conductive. Transistor 26 will then shut olf the how of current through the power input coil 27 and stop the feeding of power through the transformer 22 to the energy storing capacitor 31.

Diode 34 will prevent any negative surge of potential by the energy storing capacitor 31 from causing destructive reverse flow of current through the zener diode 35.

The converter circuit having been shut down by the charge on capacitor 31 exceeding a predetermined voltage and causing a shut-down signal to flow through the zener diode 35 as above described, when the voltage on the capacitor 31 again falls sufiiciently to permit the zener diode to hold the output voltage and stop passing control current, the transistor 32 will become nonconductive, the signal from winding 23 will again become effective to render the collector emitter circuit of the transistor 26 conductive, and the converter will resume oscillation and charging of the energy storage capacitor 31 back to the level at which a signal will be passed through the zener diode -35 to shut it off again.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed Without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described what is claimed is:

1. In an ignition system of the type having an energy storing capacitor, an ignition coil and an electronic switch interconnected therewith for connecting said capacitor to said coil to discharge therethrough and provide a spark when said switch is rendered conductive, said switch having a control gate and being of the type rendered conductive upon supply of a current to said gate at a triggering rate, and means including a unidirectional current source and breaker points interconnected with said current source and gate for alternately supplying and interrupting current flow to said gate upon make and break operation of said points, and in which said points in high speed operation tend to bounce open during a time interval after closing and thereby cause unwanted firing; the improvement which comprises: an electrical energy storing means connected between said current source and said gate to undergo a change in its electrical charge in one direction upon flow of current through the storing means to said gate in a triggering direction and to cause reduction in rate of such flow as said change in charge progresses until it reduces such flow to less than a triggering rate when its charge approaches within a predetermined minimum of the ultimate charge it could attain due to such flow, whereby while its charge is within said minimum of said ultimate charge additional firing is inhibited, and the circuit through said energy storing mean-s and said gate has a relatively low transient impedance, isolating means connected in series with said energy storing means and said gate responsive to breaker point action in said interrupting of current flow to said gate, and relatively high impedance means connected to said storing means for conducting reverse flow through said storing means at a rate to delay its return to a state of charge outside said minimum for a greater time than required for the termination of bouncing tendency of the breaker points after closing.

2. The improvement in an ignition system as set forth in claim 1 in which said isolating means includes a rectifier in series in the gate circuit to prevent the reverse flow from following the low impedance path through said gate.

3. The improvement in an ignition system as set forth in claim 1 in which said electrical energy storing means is a capacitor and in which the operation of said breaker points serves alternately to impress across said capacitor the voltage of said current source and to effectively remove the voltage of said current source from said capacitor to alternately charge and discharge said capacitor and in which current flowing through said capacitor to said gate causing change of the charge on said capacitor in one direction is provided with a low impedance path whereby such change may take place relatively rapidly, and the relatively high impedance means is the only path available for such reverse flow through said capacitor.

4. The improvement in an ignition system as set forth in claim 1 in which said electrical energy storing means is a capacitor and said isolating means is a rectifier in series between said current source and said gate to permit current flow therethrough in a triggering direction only, said high impedance means includes a resistor shunted across said capacitor of a resistance snflicient to prevent a reduction of the charge on said capacitor from the full charge which said current source is capable of impressing thereon to below said predetermined minimum for a greater time than required for the termination of bouncing tendency of the breaker points after closing, and in which there is a resistor in series with said breaker points across said current source.

5. A power supply and control circuit combination for use in an ignition system of the type wherein a spark is produced by discharging electrical energy through an ignition coil in consequence of the operation of a breaker point type switch between its open and closed positions and in which the breaker points of such switch in high speed operation tend to bounce open upon closing and thus cause unwanted firing, said power supply and control circuit component combination comprising: a power supply including an energy storing capacitor and means connected thereto for recharging said capacitor upon reduction of its charge below a predetermined condition of charge; an ignition coil; an electronic switch of the type having a control gate and rendered conductive by a triggering current to said control gate, said coil and switch being connected to said energy storing capacitor to receive a discharge of current from said capacitor through said coil and thereby produce a spark when said switch is rendered conductive; current conducting means connected to said control gate of said switch and adapted to be connected to a current source for producing triggering current to the control gate of said switch, said conducting means including: a second electrical energy storing means connected between said current source and said gate to undergo a change in its electrical charge in one direction upon flow of current through the storing means to said gate in a triggering direction and to cause reduction in the rate of such flow as said change in charge progresses until it reduces such flow to less than a triggering rate when its charge approaches within a predetermined minimum of the ultimate charge it could attain due to such flow, whereby while its charge is within said minimum of said ultimate charge additional firing is inhibited and the circuit through said second energy storing means and said gate has a relatively low transient impedance, isolating means connected in series with said second energy storing means and said responsive to said breaker point action in said interrupting of current flow to said gate and relatively high impedance means connected to said second storing means for conducting reverse flow through said second storing means at a rate to delay its return to a state of charge outside said minimum for a greater time than required for the termination of bouncing tendency of the breaker points after closing.

' References Cited UNITED STATES PATENTS 2,888,574 5/1959 Buon 315209 3,078,391 2/ 1963 Bunodiere 315-209 3,165,688 1/1965 Gutzwiller 315-100 JOHN W. HUCKERT, Primary Examiner.

D. O. KMFT, Assistant Examiner.

Claims (1)

1. IN AN IGNITION SYSTEM OF THE TYPE HAVING AN ENERGY STORING CAPACITOR, AN IGNITION COIL AND AN ELECTRONIC SWITCH INTERCONNECTED THEREWITH FOR CONNECTING SAID CAPACITOR TO SAID COIL TO DISCHARGE THERETHROUGH AND PROVIDE A SPARK WHEN SAID SWITCH IS RENDERED CONDUCTIVE, SAID SWITCH HAVING A CONTROL GATE AND BEING OF THE TYPE RENDERED CONDUCTIVE UPON SUPPLY OF A CURRENT TO SAID GATE AT A TRIGGERING RATE, AND MEANS INCLUDING A UNIDIRECTIONAL CURRENT SOURCE AND BREAKER POINTS INTERCONNECTED WITH SAID CURRENT SOURCE AND GATE FOR ALTERNATELY SUPPLYING AND INTERRUPTING CURRENT FLOW TO SAID GATE UPON MAKE AND BRAKE OPERATION OF SAID POINTS, AND IN WHICH SAID POINTS IN HIGH SPEED OPERATION TEND TO BOUNCE OPEN DURING A TIME INTERVAL AFTER CLOSING AND THEREBY CAUSE UNWANTED FIRING; THE IMPROVEMENT WHICH COMPRISES: AN ELECTRICAL ENERGY STORING MEANS CONNECTED BETWEEN SAID CURRENT SOURCE AND SAID GATE TO UNDERGO A CHANGE IN ITS ELECTRICAL CHARGE IN ONE DIRECTION UPON FLOW OF CURRENT THROUGH THE STORING MEANS TO SAID GATE IN A TRIGGERING DIRECTION AND TO CAUSE REDUCTION IN RATE OF SUCH FLOW AS SAID CHANGE IN CHARGE PROGRESSES UNTIL IT REDUCES SUCH FLOW TO LESS THAN A TRIGGERING RATE WHEN ITS CHARGE APPROACHES WITHIN A PREDETERMINED MINIMUM OF THE ULTIMATE CHARGE IT COULD ATTAIN DUE TO SUCH FLOW, WHEREBY WHILE ITS CHARGE IS WITHIN SAID MINIMUM OF SAID ULTIMATE CHARGE ADDITIONAL FIRING IS INHIBITED, AND THE CIRCUIT THROUGH SAID ENERGY STORING MEANS AND SAID GATE HAS A RELATIVELY LOW TRANSIENT IMPEDANCE, ISOLATING MEANS CONNECTED IN SERIES WITH SAID ENERGY STORING MEANS AND SAID GATE RESPONSIVE TO BREAKER POINT ACTION IN SAID INTERRUPTING OF CURRENT FLOW TO SAID GATE, AND RELATIVELY HIGH IMPEDANCE MEANS CONNECTED TO SAID STORING MEANS FOR CONDUCTING REVERSE FLOW THROUGH SAID STORING MEANS FOR CONDUCTING ITS RETURN TO A STATE OF CHARGE OUTSIDE SAID MINIMUM FOR A GREATER TIME THAN REQUIRED FOR THE TERMINATION OF BOUNCING TENDENCY OF THE BREAKER POINTS AFTER CLOSING.

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