US3302058A - Capacitive discharge ignition system capable of multiple sparking at slow-engine speeds - Google Patents

Description

1967 J. H. OTTEMAN ETAL 3,302,058

CAPACITIVE DISCHARGE IGNITION SYSTEM CAPABLE OF MULTIPLE SPARKING AT SLOW-ENGINE SPEEDS Filed March 25, 1964 JNVENTORJ JOHN H. OTTEMA N. ALLEN s. HOFFMAN M1 A TTOE/VEYS.

United States Patent CAPACITHVE DHSCHARGE lENliTliON SYSTEM CAPABLE OF MUILTHPLE SPARKHNG AT SLOW-ENGINE SPEEDS John H. Utteman, 6768 Cord Ave, Pico Rivera, Calif. 90660, and Allen G. Hofiman, 8216 S. Broadway, Apt. N, Whittier, Caiif. 906% Filed Mar. 23, 1064, Ser. No. 353,711 7 Claims. (Cl. 315-207) This invention relates to ignition systems.

The ignition of a compressed charge in a gas engine is conventionally accomplished by an electrical discharge inside the cylinder at a time at or near the maximum compression of the charge. Perhaps the best known ignition system is that which utilizes a breaker device which with a coil generates a surge of electricity to create a spark at the appropriate time.

There are many well-recognized disadvantages to the conventional ignition system, not the least of which is the decreasing reliability of the mechanical elements as speed of the engine increases. Accordingly, there have been many efforts made tocreate alternative systems. Such systems have as their objective to be just as reliable, if not more reliable, at higher speeds than at lower speeds, relatively simple and rugged in construc tion, and relatively trouble-free. It is an object of this invention to provide such a system.

Another objective of this system is to provide for a multiple spark at slow-engine speeds, such as at or near to starting of the engine, at which conditions a multiplicity of sparks is an advantage. This is attained in this invention while still providing an assurance of a spark at the precise moment needed at every engine speed.

Still another object of this invention is to provide an electronic system compitable with conventional ignition components.

An ignition system according to this invention in cludes a spark gap Within an engine cylinder, an induction coil having a core and a primary and a secondary winding. Pulsing means is provided, the preferred embodiment of which is a pickup which has a core and a winding, and magnetic means movably disposed in ad jacency to the pickup, so disposed and arranged to pass the .pickup coil and induce a pulse therein at a frequency which is proportional to that of the engines speed. A multi-vibrator and a power supply are also provided, along with trigger means which is actuable by pulses from the pickup. The frequency of the multi-vibrator is determined by itself, so that one or a plurality of pulses may emanate from the multi-vibrator, depending on the duration of the pulse from the pickup. The trigger means discharges power which was stored in the system into the induction coil whereupon a high-voltage current flows to the spark gap.

According to a preferred but optional feature of this invention, the trigger means is linked to the power supply through a choke coil.

According to still another preferred but optional feature of the invention, the trigger means comprises a gated diode, and the multi-vibrator comprises a unijunction transistor.

The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawing in which the single figure is a combined schematic and physical drawing of the presently preferred embodiment of the invention.

The presently preferred embodiment of ignition system includes a power supply 10', a filter 11, trigger means 12, multi-vibrator 13, pulsing means comprising a pickup 14 and magnetic means 15, induction coil 16, spark gap 17,

and, optionally, a distributor 18. These elements will now be described in detail.

A battery 20, or other source of positive and negative potential, is connected by lead 21 to a circuit breaker or fuse 22. To the other terminal of the circuit breaker, there are connected leads 23 and 24. Lead 23 branches to connect to the emitters 25, 26 of a pair of PNP transistors 27, 28, respectively, which may conveniently by type 2N441. Bases 29, 30 of the transistors are connected by leads 31, 32, respectively, to terminals 33, 34 of one segment of a primary winding 34a of a transformer 3%. A suitable transformer is Triad TY81 manufactured by Triad Transformer Corporation at 4055 Redwood Avenue, Venice, California. This is a transformer suitable for transforming 12-volt DC. current from the battery to an AC. voltage to be rectified at about 200 volts, when used in combination with a pair of transistors.

Center tap terminal 35 of this segment of winding is connected to one terminal of a resistor 36 which has a rating of 3 ohms, 2 watts. The other end of this resistor is connected to lead 23. The first mentioned terminal of resistor 36 is also connected to a capacitor 37 and a resistor 38, which capacitor and resistor are connected in parallel with each other. Capacitor 37 has a rating of microfarads at 25 volts, and resistor 38 has a rating of 200 ohms, 2 watts. Junction 39, connecting one end of this parallel connection, is connected to ground 40 and also to center tap terminal 41 of still another primary winding 42 of transformer 34b.

Terminals 44, 45 of winding 42 are respectively connected to collectors 46, 47 of transistors 27 and 28.

The secondary win-ding 48 of transformer 34!) includes a pair of terminals 49, 50, which are connected to each other across a capacitor 51, which has a rating of 0.005 microfarads at 1 kv. Center tap terminal 52 of secondary winding iii is connected to junction 53 and through it to ground 54. A capacitor 55, having a rating of 8 microfarads at 350 volts DC, is connected to junction 53 and also to filter 11, through lead 56. Another capacitor 57 has a rating of 8 microfarads at 350 volts DC, and is connected to junction 53 and also to output junction 58 of the power supply.

Two rectifiers 59, 60 are connected to terminals 49, 50, respectively, and are mutually joined at junction 61, which junction is connected to one terminal of resistor 62, said resistor having a rating of 350* ohms at 20 watts. The other terminal of resistor 62 is connected to junction 58 which is the output point for the power supply.

Filter 11 includes a capacitor 65, having a rating of 50 microfarads at 25 volts. The filter also includes first and second resistors 66 and 67, which are connected at a junction 68 with the capacitor and with each other. One terminal of resistor 66 is connected to lead 24, and the other is connected to a junction 69. Resistors 66 and 67 have ratings of 10 ohms and 100' ohms at /2 watt, respectively.

Trigger means 12 comprises a gated diode, which in the preferred embodiment is a silicon-controlled rectifier (SCR) such as a Sarkes-Tarzian STCRH, 400-volt rating. This device includes anode, cathode, and gate terminals 70, 71, 72, respectively.

Multi-vibrator 13 comprises a unijunction transistor 75. This device is characterized as having a PN contact, referred to as an emitter 76, and two ohmic contacts '77, 78 at base 79. This type of device will, with proper circuitry, act as a selfcontained multi-vibrator. Other types of muiti-vibrators may be used in this device, but this is a simple and rugged device especially suitable for use with this invention. The presently preferred unijunction transistor for use in this circuit is a UIT, 2N167l. Ohmic contact '77 is connected to one terminal 3 of a resistor 80, which resistor has a rating of 390 ohms, /2 watt. The other terminal of this resistor is connected to junction 69.

Ohmic contact 78 is connected by lead 31 to gate terminal 72 of the trigger means. Lead 81 branches to conmeet to one terminal of a resistor 82, which has a rating of 240 ohms, /2 watt. The other terminal of resistor 82 joins to junction 83 which is connected to cathode terminal 71 and also to one terminal of a capacitor 84, which has a rating of 0.075 miorofarad at 200 volts. The other terminal of capacitor 84 is connected to junction 85, which junction is connected to emitter 76 of the unijunction transistor. A resistor 73 having a rating of 43 kilohms, /2 watt, is connected between junctions 69 and 85. The resistance of resistor '73 is selected in conjunction with the value of capacitor 84. These two elements determine the frequency of oscillation of the multivibrator.

A zener diode 86, type 1N7l4 (which zener diode is optional) is connected between junction 87 and junction 88, junctions 83 and 88 being interconnected. Junctions 83 and 88 are grounded at ground 89.

One terminal of a resistor 90, 1 ohm, 2 watt, is connected to junction 88, and the other to one terminal of still another rectifier 91, rectifier 91 preferably being type 1N207l. The other terminal of rectifier 91 is connected to lead 92, which lead 92 also connects to the anode terminal 70 of trigger means 12 and to one terminal of a rectifier 93, also type 1N207l. The other terminal of rectifier 93 is connected to a choke coil 94. Choke coil 94 has a rating between 0.5 and 0.75 henries, 200 milliampere current rating.

Lea-d 92 also connects to the first terminal of capacitor 95, which has a rating of l microfarad at 600 volts DC. The other terminal of capacitor 95 is connected to the first terminal 96 of the primary winding 97 of induction coil 16. Second terminal 98 of the primary winding is connected to second terminal 99 of the secondary winding 100. A center tap 101 between the two second terminals is connected to ground 89. The secondary winding (which has a greater number of turns than the primary winding) has a first terminal 102. The induction coil includes a core 103 of magnetic material.

One terminal of a resistor 104 is connected to junction 87 and the other to a lead 105. Resistor 104 has a rating selected to suit the installation, for example, in this case, 56 kilohms; however, this resistance is one which is subject to selection in order to compensate for tolerance errors in the system. Lead 106 connects the first terminal of the secondary winding on the induction coil to the center post 107 of distributor 18.

Pickup coil 14- may conveniently have a soft iron core, and comprise about 10,000 turns of 0.002" 0.13. copper wire, varnish insulated, wound over a core about OD. resulting in about 3000 ohms DC. resistance. The pickup coils is about /3" long.

Distributor 18 is conventional and includes a plurality of contacts 108, one for each spark gap (that is, one for each cylinder), with lead extending between the respective spark gap and contact. A rotary blade 109 sequentially interconnects the contacts so as to make sequential connections between the center post and the spark gaps.

It is to be understood that were this device to be utilized in connection with a one-cylinder engine, then no distributor would be necessary, and there would simply be a direct connection between lead 106 and 110, which lead 110 indicates a connection to a single spark gap 17. Obviously, were only one spark gap to be utilized, then no distributor is necessary. It will also be understood that a plurality of pickup coils could be utilized, one for each of the spark gaps so that instead of distributing the output derived from a signal derived from a single pickup coil through a distributor having a multiplicity of positions, it would be equally possible to derive signals from a plurality of pickup coils and to provide a respective multi-vibrator, trigger means and induction coil for each individual spark gap.

Spark gap 17 (for example, a standard spark plug) has a pair of terminals, one of which is connected to lead 110, and the other of which is connected to lead 111, lead 111 going to ground 89. Similarly, each of the other spark gaps in the illustrated embodiment would have its own equivalent of lead attached to a respective one of contacts 108, and have its other terminal brought back to connect to junction 112 and through it to ground 89.

To junction 112, there is connected the other terminal of battery 20, this being the batterys connection to ground. Also a lead 113 extends from the negative side of the battery through winding 114 of pickup 14. Pickup 14 includes a core 115 of magnetizable material. The other terminal of winding 114 is connected to lead 105.

The pulsing means produce a pulse in pickup 14 by the action of magnetic means 15. Means 15 is shown as including a body revolving around a center 121 in the direction illustrated by the arrow. Similarly, for convenience, an indicia 122 illustrates that the blade 109 of the distributor and the body 120 is interconnected for mutual and synchronous rotation. A convenient location for body 120 is on the shaft of the distributor, although it could equally well be placed on the crankshaft of the vehicle or at any other place where a magnet will be brought periodically into near registration with the pickup coil so as to pass by the same and induce a current therein.

Magnets 123 are shown imbedded in body 120, with their north poles all facing radially outward from the center. For a 6-cylinder engine, there will be six of these magnets; for an 8-cylinder, eight; and for a l-cylinder engine, only one. It has been found that it is desirable to have a flux density at the surface of the poles at least equal to about 400 gauss in order to cause a suitable pulse to be generated in the pickup winding, which is a coil wound around a core of magnetizable material. As is well known, the passage of a magnet past the coil as indicated will cause a sine wave pulse to be generated, which has a positive and a negative component. It is further evident from the aforesaid that there will be six of these pulses for every revolution of body 120 so that, with proper mechanical interlinkages, one of these pulses will occur just as blade 109 touches a contact 108 respective to a selected spark gap 17.

Power supply 11, capacitor 95, and primary winding 97 are connected in a first series circuit. Trigger means 12, capacitor 95, and primary winding 97 are connected in a second series circuit. It is evident that the capacitor and the primary winding form portions of both series circuits.

The operation of the system will now be described. The operation of power supply 10 requires no detailed description here. Alternating current is generated in the primary windings by the interaction of the two transistors 27, 28. The output of this power supply passes through rectifiers to output junction 58, where the output is direct current. It has been found desirable to provide the filter 11, because the signal input from pickup 14 is only on the order of about 50 millivolts, which is about equivalent to the noise level of a power supply of this type. This device will readily produce an output voltage of 200 volts to the choke coil.

In accordance with the standard operation of a choke coil, the field builds up when charging and, when the core is saturated, the field will collapse which about doubles the voltage, and produces at lead 92, a voltage of about 400 volts. The rating of the choke coil is selected such that its resonant frequency is higher than any of the frequencies which occur within the rest of the system in operation, so that the performance of the system will not be limited by the resonant frequency of the choke itself.

Now assuming for a moment that magnet 123a is just,

passing the pickup, the following is the operational situation. At this time, blade 109 will interconnect the center post and lead 110. Also, at this time, a sine wave voltage will be imposed upon lead 105 but will pass through resistor 104. Blade 109 touches the respective contact for a period of time at least equal to that during which the pulse is generated. Passage of the negative component will, by virtue of its connection with junction 85, and emitter terminal 76, cause the multi-vibrator to oscillate. The free-running frequency of the illustrated multivibrator is about 600 cycles. This is roughly equivalent to an engine speed of about 9500 rpm. for an S-cylinder motor, or about 12,000 r.p.m. for a 6-cylinder motor, both top speeds for these classes of engines.

When the multi-vibrator oscillates, then the signal which it produces in lead 81 is applied to the gate terminal of the trigger means which causes the trigger means (SCR) to conduct. Before this occurred, the choke will have charged capacitor 95, and that charge now awaits dis charge through the trigger means 12. The discharge connection is through junctions 83 and 88 to ground 89. The other discharge flow is through the primary winding of the induction coil, and lead 101 to ground 89. This induces a higher voltage in the secondary which is conducted through the distributor, if there is one, to spark gap 17, this circuit being completed to ground 89 through lead 111.

When there is no pulse from pickup 14, the multivibrator ceases to oscillate, which renders the trigger means non-conductive. Then the choke coil again charges the condenser.

The zener diode 86 is provided to limit the level of the input signal so that the unijunction transistor (multivibrator) cannot be saturated by the pickup.

From the foregoing, it will be seen that the trigger means will be actuated by the multi-vibrator at a frequency determined by the multi-vibrator and concurrent with the times at which a negative portion of a pulse from pickup 14 is present so as to actuate the multivibrator. Accordingly, there is a speed at which the magnet is moving so rapidly past the pickup that it will actuate the m-ulti-vibrator for only one pulse to the trigger means. This is the upper limit of the velocity of the system, and is selected so as to be at or above the maximum speed of the engine involved.

Similarly, as the speed decreases, then a signal of sutficient amplitude to actuate the multi-vibrator will remain on the multi-vibrator for a period of time longer than one of its single pulses whereupon the trigger means may be actuated for a period longer than one pulse, and in fact may be several pulses, which in turn will pass several spark discharges through the respective spark gap. Accordingly, this device provides the advantage of multi-sparking at low and starting speeds, while it always guarantees a hot spark suitably timed at the most rapid of the speeds.

The system given as an example utilizes a center-tapped induction coil, which is perhaps the most commonly used type. However, other circuits and other types of induction coils may readily be substituted by persons skilled in the art. The system of the invention is adapted to provide current pulses to the primary winding of an induction coil. Any secondary circuit which completes a circuit through the spark gap is suitable.

This system is quite compatible with standard ignition installations. Most conveniently, it may be installed simply by adding a pickup coil adjacent to the rotor location, and substituting the magnetic means and rotor for the standard rotor and contact points.

Inasmuch as this system is actuated by pulses, it is evident that the actual source of the pulse is not critical. The most convenient pulse source is the magnetic means as shown. However, electro-optical means, such as a beam of light and a photo-sensitive cell, with means such as slits or mirrors for interrupting or transmitting the beam in pulses, would work electrically as well as in the place of the pulse means shown.

This device enables a rugged pulse and pickup system to be made wherein magnets may simply be potted in a rotatable device next to a rugged pickup coil. There are no mechanical devices subject to flutter, or any inherent inadequacy at any specific rate of operation.

This invention thereby provides a simple, effective, and highly efiicient ignition system suitable for a wide range of engine types and numbers of cylinders.

This invention is not to be limted by the embodiments shown in the drawing and described in the description which is given by way of example and not of limitation, but only in accordance with the scope of the appended claims.

We claim:

1. An ignition system for an internal combustion engine to provide a spark in a spark gap disposed in an engine cylinder, whereby to ignite a combustible mixture in said cylinder, said system comprising: an induction coil which includes a primary and a secondary winding, said spark gap being operatively connected to the said secondary winding; capacitance means; power supply means providing a D.C. output; means connecting said primary winding, said capacitance means, and said power supply means in a first series circuit so as to charge said capacitor means; trigger means actuable by a control signal connected in a second series circuit with said capacitance means and said primary winding so as to allow said capacitance means to discharge through said primary winding only when said trigger means is actuated; a pulsing means for providing an electrical pulse of a duration proportional to engine speed; multi-vibrator means operatively connected to said pulsing means whereby to be actuable by said electrical pulse to produce an oscillatory control signal having a frequency inherent within the multi-vibrator means for the duration of said electrical pulse; means applying said oscillatory control signal to said trigger means; whereby said trigger means is repetitively actuated at said frequency of said oscillatory control signal, thereby repetitively discharging said capacitance means at said frequency of said oscillatory control signal during the time the electrical pulse actuates said multi-vibrator means.

2. An ignition system according to claim 1 in which .a choke coil is included in the said first series circuit between the power supply and the capacitance means.

3. An ignition system according to claim 2 in which the pulsing means comprises a light source, means for pulsing said light source, and means responsive thereto to produce an electrical pulse to the multi-vibrator.

4. An ignition system according to claim 2 in which the pulsing means comprises a pickup coil comprising a Winding and a core, and magnetic means so disposed and arranged as periodically to pass. by said pickup winding and induce an electrical pulse therein.

5. An ignition system according to claim 2 in which the trigger means comprises a gated diode.

6. An ignition system according to claim 2 in which the multi-vibrator comprises a unijunction transistor including an emitter and two ohmic contacts, the pickup being connected to the emitter whereby the pulse from the pickup is impressed upon the emitter to cause the unijunction transistor to oscillate, one of the ohmic contacts being connected to the gated diode whereby to cause the gated diode to conduct current at the frequency of the unijunction transistor and during the time it oscillates.

7. An ignition system according to claim 5 in which the multi-vibrator comprises a unijunction transistor including an emitter and two ohmic contacts, the pickup being connected to the emitter whereby the pulse from the pickup is impressed upon the emitter to cause the unijunction transistor to oscillate, one of the ohmic contacts being connected to the gated diode whereby to cause the 7 gated diode to conduct current at the frequency of the 2,981,865 unijunction transistor and during the time it oscillates. 3,045,148 3,175,123 References Cited by the Examiner 3 202 937 UNITED STATES PATENTS 5 2,787,649 4/1957 Ballard 315209 2,898,392 8/1959 Jaeschke 3l5209 Fernbach 315-206 McNulty 315- 209 Dilger 315209 Anderson 30788.5

JOHN W. HUCKERT, Primary Examiner.

D. O. KRAFT, Assistant Examiner.

Claims (1)

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE TO PROVIDE A SPARK IN A SPARK GAP DISPOSED IN AN ENGINE CYLINDER, WHEREBY TO IGNITE A COMBUSTIBLE MIXTURE IN SAID CYLINDER, SAID SYSTEM COMPRISING: AN INDUCTION COIL WHICH INCLUDES A PRIMARY AND A SECONDARY WINDING, SAID SPARK GAP BEING OPERATIVELY CONNECTED TO THE SAID SECONDARY WINDING; CAPACITANCE MEANS; POWER SUPPLY MEANS PROVIDING A D.C. OUTPUT; MEANS, AND CONNECTING SAID PRIMARY WINDING, SAID CAPACITANCE MEANS, AND SAID POWER SUPPLY MEANS IN A FIRST SERIES CIRCUIT SO AS TO CHARGE SAID CAPACITOR MEANS; TRIGGER MEANS ACTUABLE BY A CONTROL SIGNAL CONNECTED IN A SECOND SERIES CIRCUIT WITH SAID CAPACITANCE MEANS AND SAID PRIMARY WINDING SO AS TO ALLOW SAID CAPACITANCE MEANS TO DISCHARGE THROUGH SAID PRIMARY WINDING ONLY WHEN SAID TRIGGER MEANS IS ACTUATED; A PULSING MEANS FOR PROVIDING AN ELECTRICAL PULSE OF A DURATION PROPORTIONAL TO ENGINE SPEED; MULT-VIBRATORY MEANS OPERATIVELY CONNECTED TO SAID PULSING MEANS WHEREBY TO BE ACTUABLE BY SAID ELECTRICAL PULSE TO PRODUCE AN OSCILLATORY CONTROL SIGNAL HAVING A FREQUENCY INHERENT WITHIN THE MULTI-VIBRATOR MEANS FOR THE DURATION OF SAID ELECTRICAL PULSE; MEANS APPLYING SAID OSCILLATORY CONTROL SIGNAL TO SAID TRIGGER MEANS; WHEREBY SAID TRIGGER MEANS IS REPETITIVELY ACTUATED AT SAID FREQUENCY OF SAID OSCILLATORY CONTROL SIGNAL, THEREBY REPETITIVELY DISCHARGING SAID CAPACITANCE MEANS AT SAID FREQUENCY OF SAID OSCILLATORY CONTROL SIGNAL DURING THE TIME THE ELECTRICAL PULSE ACTUATES SAID MULTI-VIBRATOR MEANS.

Images