Electronic Ignition System

Abstract

A solid state control unit for switching a device having means to smooth a control signal and protect the unit from transitory voltages and means to permit bypass of said control unit.

Description

BACKGROUND OF INVENTION

Ignition systems for internal combustion engines operate, as is well known, on the principle of stored inductive energy transfer. In such systems presently employed and proposed an impulse signal is generated by mechanical contacts, magnetic means and photosensitive devices to provide and interrupt current flow to a circuit connected to an ignition coil's primary winding. The providing of the current is known as the charging of the coil and the interruption of same permits the coil to discharge whereby a sparkplug is energized to initiate combustion in an engine cylinder. Various types of semiconductor means have been proposed whereby the charging and discharging aforesaid is controlled. It is to the simplification and improvement of such means, as one example of the utility of this invention, that the present invention is directed whereby the switching between current conduction and interruption is positive and definative so that, in regard to ignition systems above-mentioned as one utilization of this device, there is provided increased charging time between discharging of the ignition coil. As a result there is a 30 to 45 percent increase in spark potential available to the engine at higher engine speeds.

Another object of this invention is to provide means whereby the semiconductor means may be switched in and out of the ignition circuit whereby timing of the engine ignition means may be accomplished by the conventional dwell meters employed today. This has the advantage of adapting the advance brought to the art by such semiconductor means to the state of the art of the servicing devices known to be universally applied in automobile maintenance.

Another object of this invention is to construct a circuitry that provides a means to positively drive a switching device to permit limited functioning of the circuit to eliminate effects of any other than desired inputs tending to cause operation of the circuit.

DRAWING DESCRIPTION

FIG. 1 shows by way of graphical illustration the charging time for an ignition coil with conventional breaker point control at low engine speeds;

FIG. 2 shows by way of graphical illustration the charging time for an ignition coil with a switching circuitry according to the present invention at low engine speeds;

FIG. 3 shows by way of graphical illustration the charging time for an ignition coil with conventional breaker point control at high engine speeds;

FIG. 4 shows by way of graphical illustration the charging time for an ignition coil with the switching circuitry according to the present invention at high engine speeds; and,

FIG. 5 shows in schematic form the switching circuitry according to a preferred form of this invention.

DETAILED DESCRIPTION

In conventional ignition systems an impulse generating means, such as the breaker points within a distributor housing, create a square wave input signal 10 with a linear voltage rise 12 which has a duration 14 before reversing, as along 16. This voltage potential is applied to open a circuit to the ignition coil whereby current to the primary of an ignition coil is interrupted to introduce a high potential in a secondary that is transferred via a distributor rotor to an engine sparkplug. When the points finally close the circuit is closed again to permit recharging of the coil's primary winding. This charge builds up linearly as shown by the dash lines 18 of FIG. 1 until the coil is fully charged indicated by dash lines 19 that is held in the coil until the points open again as at 20 whereby the process aforedescribed is repeated. This represents an idling engine whereby the coil's primary winding is fully charged between successive point opening. In FIG. 2 there is shown how the dwell time, the time between point openings can be extended if the square wave form of FIG. 1 is differentiated to sharp pulses 22. As illustrated the charge build-up 24 reaches the coil capacity prior to the next successive point opening. This is shown by the dash lines 26 representing the plateau of the coil capacity. In FIGS. 3 and 4 the above processes are shown for higher engine speeds where the extended dwell provided by the sharp pulses 22 versus the square wave form 10 very demonstratively shows increased time for charge build-up 24 over 18 as well as greater charging of the coil between successive point opening.

It has been found that a simple circuit such as schematically illustrated by FIG. 5 will achieve the results aforementioned. In this circuit there is provided a semiconductor means interposed between an ignition switch 28, an ignition coil 30 and engine contact points 32. More specifically, a resistor 34 is connected to switch 28 and a lead 36 is connected to a lead 38 connected to a primary winding 40 and a secondary winding 42. A lead 44 connects the primary to a pair of switch arms 46 and 48 connected together to be manually operable between contacts 50, 52 and 54, 56 respectively. Contacts 52 and 56 are connected by a lead 58 to lead 60 from points 32. Contacts 50 and 54 are connected together, as at 62, to a lead 64 connected by lead 66 to collector 68 of a transistor 69 having a base 70 and an emitter 72. A lead 74 connects emitter 72 to a lead 76. It may, therefore, be realized that in accordance with the position of switch arms 46 and 48 either the points 32 or transistor 69 controls the connection or interruption of power source 78 to primary winding 40 whereby one or the other can cause the discharge of a high potential from secondary winding 42 to provide a spark discharge at spark plug 80.

Transistor 69 is normally positive biased upon closure of switch 28 in that lead 82 connects the source 78 through resistor 84 and diode 86 to base 70 to complete the circuit from the collector 68 to the emitter 72. The source 78 is also connected via lead 82 to a resistor 88 and thence via a lead 98 to lead 60 from points 32. Also a capacitor 92 is connected to lead 90 and to a base 100 of transistor 101 with a resistor 102 tapped into such connection which is connected to a lead 104 forming an RC differentiating circuit for control of transistor 101. Collector 106 of transistor 101 is connected by resistor 112 to resistor 114 and lead 116 to a Darlington amplifier 118 connected by lead 120 to diode 86 and resistor 120 and lead 122 to lead 104. Diode 124 connects lead 104 to lead 120, and zener diodes 126 and 128 are interposed with lead 68 and resistor 130 to clamp the voltage and so that reverse biasing of transistor 69 is prevented in that reverse current is bypassed to the coil. A capacitor 132 is connected as shown to enhance the system performance by resonating the coil to get longer pulse width at the sparkplug 80.

In operation the ignition switch 28 is closed uniting the DC source 78 to the system. As the engine is thereafter started the points 32 are opened and closed to open or complete the circuit. With the switch arms 46 and 48 in the position shown a positive potential is directed to lead 90 upon closure of ignition switch 28. If the points 32 are closed this potential is conducted by diodes 94 and 96 through the points 32 to ground. If the points are open it is directed to the capacitor 92 and thence to transistor 101 under control of the resistor 102 to drive the transistor 101 on, allowing the source 78 to be connected to the Darlington amplifier 118. Upon closure of switch 28 it should also be noted that the positive source is connected to the transistor 69 and primary winding 40. The transistor 69 is driven to connect the primary winding to ground in this circumstance such that the primary is being charged. If the switch arms 46 and 48 were manually moved onto contacts 52 and 56 this current flow to the primary would be direct from source 78, assuming ignition switch 28 is closed, to ground via the points 32 when closed.

However, when the Darlington amplifier is conducting the transistor 69 is non-conducting whereby the current flow, as in the case of the points 32 opening, is interrupted in the primary and a high potential is created in the secondary to provide a spark at the spark plug 80. In order to get a positive switching-off of transistor 101 after the coil is discharged the circuitry is arranged so that upon closure of the points, after momentarily opening, the positive potential from diodes 94 and 96 will be directed through the common ground back to the emitter 110 of transistor 101 to reverse bias to cut-off. This reverse bias occurs in that the value of resistor 114 is less than that of resistor 102 in the RC network. This will immediately allow the positive potential to bias transistor 69 on to permit charging of primary winding 40.

With this invention the point opening and engine timing can be adjusted by state of the art devices when the switch arms 46 and 48 are moved to block out of the circuitry other than that from the source to the coil 30 thence through the points 32 to ground. This allows the use of the more widely used equipment and techniques to set the points and time the engine.

It will be apparrent that the system described and illustrated in the accompanying drawings should be considered as illustrative of how such an electronic ignition system can be applied to a breaker-point engine ignition system. It is equally applicable to magnetic and photosensitive pick-ups and other devices proposed for engines. Further, the scope of this invention is considered to embrace structure equivalent to that disclosed now and hereafter either from a mechanical point of view or from an electronic one without departing from the spirit and intent of disclosure in return for these letter Patent.

Claims

What is claimed is:

1. For use in an engine ignition system having a means to interrupt charging of a primary winding to provide a high potential in a secondary winding of a coil that is used to provide a spark discharge an electronic means to increase charging time prior to interruption thereof, said electronic means including the improvement of:

A rc differentiating circuit controlling a transistor switching from non-conductive to conductive state; and

diode means connected to said RC differentiating circuit to permit reverse bias of said transistor upon interruption of a signal to said circuit.

2. For use in an ignition system having means to provide sequential impulse signals by interrupting the connection of a power source to an ignition coil for initiating combustion in an internal combustion engine, a semiconductor circuit comprising:

a second means connected to said first means to differentiate a signal from the latter to a fast decaying triggering pulse, said second means having a circuit comprised of diode means connected to the source to pass by way of said first means a positive potential upon decay of said triggering pulse to a resistance means;

a first transistor connected to said second means by having its base connected to a portion of said second means and an emitter connected to said resistance means tobe triggered on by a signal in the portion and off by a signal passed by the resistance means;

a third means to amplify a signal from the first transistor when it is on; and

a second transistor connected between the power source and the ignition coil to complete the circuit through the second transistor between the power source to the ignition coil in absence of a signal from said third means and to interrupt the circuit through the second transistor upon the event of receipt by said second transistor of a signal from said third means.

3. A means to connect a transistor to an ignition circuit comprising:

a lead connecting a collector of the transistor to a power source:

an RC differentiating means connecting the base of said transistor to the source;

diode means connected to said RC differentiating means and said source;

first switch means connected between said diodemeans and said source to cause current to bypass said RC differentiating means in one positionthereof to an emitter of said transistor and to said RC differentiating means in another position to drive said transistor to its non-conductive or its conductive state, respectively; and

resistance means of lessor resistance than said RC differentiating means connecting said source to said emitter ofsaid transistor in said one position of said switch means to reverse bias said transistor to its non-conductive state to there after eliminate spurious signals other than shall pass said RC differentiating means to affect said transistor when said first switch means is in said another position.

4. The structure of claim 3 and further comprising an amplifier connected to said transistor and operable by said transistor.

5. The structure of claim 4 and further comprising another transistor connected to said source, said lead being tapped to said amplifier such that said source can be diverted from said another transistor.

6. The structure of claim 5 and further comprising an ignition coil having a primary winding, a core and a secondary winding, said primary winding being connected to said another transistor and said source to be charged so long as said source is driving said transistor conductive.

7. The structure of claim 6 and further comprising:

a second switch means between said another transistor and said primary winding; and

a means to connect said second switch means to said first switch means for controlling whether said another transistor or said first switch means controls charging of said primary winding.