US3718125A

US3718125A - Capacitor discharge ignition system

Info

Publication number: US3718125A
Application number: US00130950A
Authority: US
Inventors: T Posey
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-04-05
Filing date: 1971-04-05
Publication date: 1973-02-27
Anticipated expiration: 1990-02-27

Abstract

An improved capacitor discharge ignition system which produces controlled multiple ignition sparks for each opening of the distributor breaker points. Upon applying a direct current potential across the input terminals of a conventional DC to DC inverter circuit, the inverter power transistors begin oscillating, thereby driving the primary of the inverter transformer which produces a high voltage potential in the secondary windings. A diode bridge circuit rectifies this potential which is applied to a storage capacitor in series with the primary winding of a conventional ignition coil. When the storage capacitor reaches a predetermined voltage potential the silicon controlled rectifier control transistor is forward biased due to the voltage at the junction of a fixed resistor and variable resistor which are in series and connected across the high voltage supply. Upon opening of the distributor breaker points, a capacitor in series with the collector of the control transistor begins to charge causing a current flow through the gate cathode junction of the silicon controlled rectifier sufficiently to forward bias the anode cathode junction of the SCR. The storage capacitor discharges through the SCR and primary of the ignition coil causing an ignition spark to be produced. This discharge of the storage capacitor causes the base potential of the control transistor to drop to zero volts thereby raising the collector emitter resistance which reduces the SCR gate current flow below trigger level, and due to the zero potential between the anode and cathode electrodes of the SCR. the SCR turns off. Immediately the storage capacitor starts to recharge and again upon reaching a predetermined voltage potential, the circuit repeats as stated above to produce another ignition spark, provided the previously mentioned capacitor in series with the control transistor''s collector has not reached a charged state which would prevent sufficient SCR gate trigger current. The capacitor''s RC time constant is controlled by a variable resistor which may be adjusted to produce from one to as many ignition sparks as desired, depending on the frequency of the ignition sparks as determined by the variable resistor associated with the base electrode of the control transistor and the duration of the opening of the breaker points. Upon closing of the breaker points, the control transistor''s collector capacitor is discharged through the breaker points and a fixed resistor thereby resetting the circuit for the next ignition cycle.

Description

United States Patent 1 Posey Feb. 27, 1973 CAPACITOR DISCHARGE IGNITION SYSTEM [76] Inventor: Thad W. Posey, 2402 Apple Hill Rd., Alexandria, Va. 22308 [22] Filed: April 5, 1971 [21] Appl. N0.: 130,950

[52] US. Cl. ..l23/l48 E [51] Int. Cl ..F02p 3/06 [58] Field ofSearch ..173/l48 E [56] References Cited UNITED STATES PATENTS 3,620,201 11/1971 Warren ..l23/l48 E 3,383,556 5/1968 Tarter ...l23/l48 E 3,489,129 1/1970 Issler et a1. ..l23/148 E 3,626,910 12/1971 Porsche ....123/148 E 3,277,340 10/1966 Jukes et a1. ....123/l48 E 3,386,000 5/1968 Farr ....123/148 E 3,367,314 2/1968 Hirosawa et al. ..123/148 E Primary ExaminerLaurence M. Goodridge Assistant ExaminerCort R. Flint [5 7] ABSTRACT ignition coil. When the storage capacitor reaches a predetermined voltage potential the silicon controlled rectifier control transistor is forward biased due to the voltage at the junction of a fixed resistor and variable resistor which are in series and connected across the high voltage supply. Upon opening of the distributor breaker points, a capacitor in series with the collector of the control transistor begins to charge causing a current flow through the gate cathode junction of the silicon controlled rectifier sufficiently to forward bias the anode cathode junction of the SCR. The storage capacitor discharges through the SCR and primary of the ignition coil causing an ignition spark to be produced. This discharge of the storage capacitor causes the base potential of the control transistor to drop to zero volts thereby raising the collector emitter resistance which reduces the SCR gate current flow below trigger level, and due to the zero potential between the anode and cathode electrodes of the SCR. the SCR turns off. Immediately the storage capacitor starts to recharge and again upon reaching a predetermined voltage potential, the circuit repeats as stated above to produce another ignition spark, provided the previously mentioned capacitor in series with the control transistors collector has not reached a charged state which would prevent sufficient SCR gate trigger current. The capacitors RC time constant is contro led by a variable resistor which may be addischarged through the breaker points and a fixed :resistor thereby resetting the circuit for the next ignition cycle.

3 Claims, 1 Drawing Figure CAPACITOR DISCHARGE IGNITION SYSTEM SUMMARY OF THE INVENTION This invention pertains to an improved capacitor discharge ignition system specifically for but not limited to the internal combustion engine requiring timed ignition sparks. The intent of this invention is to improve the combustion process of an internal combustion engine by employing unique circuit means to produce controlled multiple ignition sparks for each ignition cycle thereby improving the efficiency of the engine and reducing exhaust emissions due to poor and incomplete internal combustion.

It has been determined that prior single spark capacitor discharge ignition systems may produce a spark of relatively short duration which will not ignite certain cylinder charge mixtures properly for good combustion. Other suggested continuous firing ignition arrangements when used with the conventional automotive distributor do not provide means to adequately control the continuous ignition sparks to guard against pre-ignition at high engine revolutions per minute.

The object of this invention is to employee circuit means which can produce multiple ignition sparks where the second ignition spark is produced approximately 400 microseconds after the initial ignition spark of a given cycle, which effectively results in a longer ignition spark. This is accomplished by taking advantage of the ignition coils inductance to recharge the storage capacitor after an initial discharge through the ignition coil. Additional ignition sparks are produced thereafter depending on circuit means adjustment for spark frequency and circuit means adjustment for quantity of sparks desired for each ignition cycle.

DESCRIPTION OF DRAWING The schematic drawing shows a preferred circuit diagram of the invention with numerical designators depicting circuit components.

DETAILED DESCRIPTION Referring to the schematic diagramit will be noted there are three major sections of which comprises the entire system. They are, the DC to DC inverter circuit which is commonly used to convert a lower voltage direct current source to a higher voltage source; the controlled trigger circuit which controls the electronic switch, and the spark discharge circuit made up of a high voltage storage ignition capacitor and a silicon controlled rectifier used in this circuit as an electronic switch.

The following description explains the operation of this circuit in detail: Upon applying a positive voltage to input battery terminal 16 and a negative voltage to input battery terminal 17 which is grounded, the two power transistors 13 and 14 begin oscillating, driving the primary of the transformer 12. Bias resistors and 1 l aid in starting the inverter circuit when power is first applied and oscillator drive winding 15 sustains inverter drive once the circuit has started. Secondary winding 18 is magnetically coupled to the primary winding 12 and due to the turns ratio, the secondary winding 18 will have induced across its winding approximately 550 volts. Diode bridge 19 rectifies this potential into a direct current source and starts charging storage capacitor 41 which is in series with the primary winding of the ignition coil 42 to ground. A fixed resistor 21 and a variable resistor 23 are connected in series 22 and across the

high voltage source

20 and 17. At the junction 22 of the two

resistors

21 and 23 is connected the base electrode 25 of the SCR control transistor 27. As the storage capacitor 41 charges, the potential at junction 22 as determined by variable resistor 23 raises to suflicient value to forward bias control transistor 27. Upon opening of the distributor breaker points 44, trigger capacitor 32 begins to charge from the positive low voltage battery 16 through current limiting resistor 33 and through the collector 26, emitter 24 of transistor 27, through resistor 34, and through the gate 37, cathode 38 of silicon controlled rectifier 39 and through diode 45 to ground. This current flow through the SCR gate 37 forward biases the SCR anode 40, cathode 38 junction thereby turning on the SCR 39 which discharges the storage capacitor 41 through diode 45 to ground 17, and through the primary of the ignition coil 42 to ground 17 producing an ignition spark. This on" condition of the SCR 39 also short circuits the high voltage supply 20 to ground 17 which stops inverter drive and drops the junction 22 and base electrode 25 of control transistor 27 to zero volts which raises the collector 26, emitter 24 junction resistance thereby reducing SCR gate 37 current flow below SCR 39 trigger level. Immediately SCR 39 turns off due to the zero volts potential between the SCR anode 40 and cathode 38. The inverter circuit again starts as previously described and begins recharging the storage capacitor 41. Again when the voltage potential at junction 22 reaches a value sufficient to forward bias control transistor 27 and provided trigger capacitor 32 has not reached a charged state through variable resistor 28 and diode 30, the SCR 39 will turn on and discharge the storage capacitor 41, producing another ignition spark as previously described. The circuit will continue to repeat this firing cycle as described above during the entire duration of the breaker points 44 opening. Upon closing of the breaker points 44, the positive charge on capacitor 32 is discharged through fixed resistor 29 and diode 31 and through the breaker points 44. This fixed resistor 29 and diode 31 provide a fixed time constant which controls the trigger capacitor 32 discharge, thereby requiring a predetermined breaker points 44 closure duration prior to opening, eliminating firing the SCR 39 on breaker point 44 bounce. As long as breaker points 44 remain closed the trigger capacitor 32 cannot charge therefore the SCR 39 cannot go into conduction even though the control transistor 27 may be forward biased due to the voltage potential at junction 22 which causes a base 25, emitter 24 small current flow below SCR 39 trigger level.

Variable resistor 28 may be adjusted to control the charge time of trigger capacitor 32 providing from one to multiple firing of the SCR 39 for each opening of the breaker points 44. Variable resistor 23 may be set to forward bias the control transistor 27 at various voltage potentials applied to the storage capacitor 41. In this way the frequency and power of the ignition sparks may be controlled as well as the number of sparks per breaker point 44 opening.

Previously unexplained diode 45 is used to aid in turning off the SCR 39, by clamping the cathode 38 of the SCR 39 slightly positive during conduction of the SCR 39. Resistor 35 is used to establish a ground potential on the gate 37 of SCR 39 during the off condition of the SCR 39. Capacitor 36 is used to filter out transient noise spikes on the gate 37 of the SCR 39 for protection against false firing of the SCR 39.. Resistor 34 is used to aid in turning off the control transistor 27 when the base 25 voltage drops near zero volts.

Extensive testing of this circuit has revealed very good performance can be achieved by setting variable resistor 23 to forward bias control transistor 27 at approximately 300 volts charge on the storage capacitor 41. This will take advantage of the energy returned to the storage capacitor 41 by the inductance of the igni- -tion coil 42 when the storage capacitor 41 has been discharged through the ignition coil 42 from approximately 550 volts on the initial opening of the breaker points 44. The coils inductance will recharge the storage capacitor 41 to approximately 300 volts in approximately 400 microseconds and produce a second spark which effectively results in a longer ignition spark on initial breaker points 44 opening. Additional sparks will be produced at a somewhat longer time interval depending on the power supply restart capability etc., and may also be controlled by variable resistor 28 to shorten the charge time of trigger capacitor 32 to limit the number of sparks per breaker point 44 opening.

Tests have also revealed that excessive ignition sparks during breaker point 44 opening may result in pro-ignition at high engine revolutions per minute due to the relative position of the distributor rotor button just prior to breaker point 44 closure. It is therefore essential that a means to limit the number of ignition sparks per breaker point 44 opening be provided as described in the preceding disclosure for proper operation of an internal combustion engine.

The foregoing description of the invention as related to test and performance have been made in accordance with application statutes and is not intended to limit this invention, but merely as being descriptive thereof.

I claim:

1. A multiple firing capacitor discharge ignition system for internal combustion engines comprising an ignition coil with primary and secondary windings; spark initiation means timed to the relative position of the engine's pistons; a source of DC voltage; a DC to DC inverter circuit to convert a lower voltage source to a high voltage source with a diode bridge circuit to rectify this high voltage to a direct current source; a storage capacitor with one side connected to said high voltage source and the other side to the primary of said ignition coil; a silicon controlled rectifier with its anode connected to said high voltage source, its cathode connected to ground, its gate connected to circuit means connected to the base of a silicon controlled rectifier control transistor; a second circuit means adapted to control the silicon controlled rectifier comprising said silicon controlled rectifier control transistor with its emitter connected to the gate of the said silicon controlled rectifier; a third circuit means adapted to initiate an ignition spark and limit the number of ignition sparks per breaker points opening consisting of a silicon controlled rectifier trigger capacitor with one side connected to the collector of the said silicon controlled rectifier control transistor and a variable resistor and diode in series to ground and a fixed resistor and diode in series to ground, whose values determine the charge and discharge time of said trigger capacitor, thereby controlling the number of ignition sparks per breaker points opening, and the other side of the trigger capacitor connected to the said low voltage positive battery terminal through a resistor and breaker points connected at the resistor capacitor junction operating to ground. 1

2. A system according to claim 1 wherein said first circuit means to control the frequency and energy of said multiple ignition sparks consists of a voltage divider with a fixed resistor and variable resistor connected across the high voltage DC supply, whose values determine the ignition spark frequency and spark energy by allowing the said silicon controlled rectifier control transistor to trigger the said silicon controlled rectifier only after the said storage capacitor reaches a predetermined voltage charge.

3. A system according to claim 1 wherein said second circuit means to control the silicon controlled rectifier consists of a transistor with its base connected to the junction of said voltage divider, emitter connected to the silicon controlled rectifier gate and collector connected to a trigger capacitor. The said silicon controlled rectifier control transistor circuit so arranged will upon breaker points opening provide trigger current to the gate of the said silicon controlled rectifier until the silicon controlled rectifier turns on discharging the said storage capacitor which turns off the silicon controlled rectifier control transistor thereby removing the silicon controlled rectifier gate trigger current.

Claims

1. A multiple firing capacitor discharge ignition system for interNal combustion engines comprising an ignition coil with primary and secondary windings; spark initiation means timed to the relative position of the engine''s pistons; a source of DC voltage; a DC to DC inverter circuit to convert a lower voltage source to a high voltage source with a diode bridge circuit to rectify this high voltage to a direct current source; a storage capacitor with one side connected to said high voltage source and the other side to the primary of said ignition coil; a silicon controlled rectifier with its anode connected to said high voltage source, its cathode connected to ground, its gate connected to circuit means adapted to produce multiple triggers to the said silicon controlled rectifier for each breaker points opening; a first circuit means adapted to take advantage of the energy returned to the said storage capacitor after an initial ignition spark thereby providing a second ignition spark approximately 400 microseconds after the first spark and means to control the frequency and energy of said multiple sparks thereafter comprising a voltage divider circuit between the said high voltage supply and ground with the voltage divider junction connected to the base of a silicon controlled rectifier control transistor; a second circuit means adapted to control the silicon controlled rectifier comprising said silicon controlled rectifier control transistor with its emitter connected to the gate of the said silicon controlled rectifier; a third circuit means adapted to initiate an ignition spark and limit the number of ignition sparks per breaker points opening consisting of a silicon controlled rectifier trigger capacitor with one side connected to the collector of the said silicon controlled rectifier control transistor and a variable resistor and diode in series to ground and a fixed resistor and diode in series to ground, whose values determine the charge and discharge time of said trigger capacitor, thereby controlling the number of ignition sparks per breaker points opening, and the other side of the trigger capacitor connected to the said low voltage positive battery terminal through a resistor and breaker points connected at the resistor capacitor junction operating to ground.