US 3368539 A
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Feb. 13,1968 D.G.KIDWELL 3,368,539
7 BREAKERLESS IGNITION SYSTEM I Filed Oct. 23, 1965 :8 mPSmEZE INVENTOR E .WQ\
DONALD 62 K/DWELL BY A ORNEYS United States Patent ()fitice 3,368,539 BREAKERLESS IGNITIUN SYSTEM Donald G. Kidwell, Chamblee, Ga., assignor of twentyfive percent to G. D. Murphy, Jr., and twenty-five percent to Erie Cocke, Jr.
Filed Oct. 23, 1965, Ser. No. 503,669 3 Claims. (Cl. 123-148) ABSTRACT OF THE DISCLQSURE A contactless ignition system for delivering pulses to an output transformer across a spark producing element of an internal combustion engine having in combination a slotted disc rotatable between a light source and a photoelectric device, transistorized circuitry for providing high voltage pulses to said transformer, and switching means for abruptly reversing the conducting state of the circuitry for retarding the spark when engine manifold vacuum drops.
This invention relates to a system for generating the electrical impulse for causing a spark to cross a spark plug and more particularly to an electronic system which is adapted for ready replacement for the standard breaker point system in the distributor housing.
A principal objective of this invention is to provide an electronic spark generating system with means for a positive spark retardation which enable systems of this type to be employed with engines having the varying rotational speeds normally associated with conventional automobiles.
A still further objective of this invention is to provide a novel photo-transistor for use in such a system which is manufactured by merely removing the top from a silicon, switching transistor and potting it with clear epoxy to thereby produce a sensitive transistor photocell.
Another objective of this invention is to provide circuitry for generating the pulse of this system which generates pulses which are relatively independent of the engine speed.
Another important objective of this invention is to provide a structural package which can replace the breaker point system in present-day internal combustion engines with the electronic design described herein, without requiring a great deal of skill and technical knowhow on the part of the installer.
Another important objective of this invention is to provide a device in which an electronic spark generating system cooperates with the power generating plant such that spark advance can be easily controlled and adjusted by a mechanic of ordinary skill and in which spark retardation is instantaneous upon a drop of manifold vacuum.
These and other objectives and advantages of the invention will become more apparent upon a reading of the following description of one system made in accordance with the invention as diagrammatically illustrated by way of example in drawings, in which:
FIGURE 1 is an elevation plan view showing the interior of the distributor housing with the convention-a1 breaker point switch removed and the apparatus of this invention mounted in place thereof;
FIGURE 2 is a plan view of FIGURE 1; and
FIGURE 3 is a schematic-diagrammatic view of the electrical system.
Referring now with more particularity to the drawings wherein like numerals indicate like parts, the numeral indicates the base of the distributor housing. A shaft 12 is rotatably mounted therein and is rotated by a rotating part of the engine (not shown) via a bevel or the like 3,368,539 Patented Feb. 13, 1968 14. The shaft and bevel are conventional in ignition systems of the prior art. The breaker points and all other components, except for cam 16 and the centrifugal advance parts of the conventional ignition switch, have been removed. In place thereof, a slotted disc 18 is secured to the shaft by way of a securing nut 20. The slotted disc is best seen in FIGURE 2. The disc includes eight equally spaced slots. The slots are designated by the numeral 22.
Mounted on the distributor base 24, is a housing 25 having an opening 26 formed in its lower portion 27. A miniature lamp 30 is supported in the opening and has its lead wires 32 extending to an electrical source. The housing 25 further includes an overhang portion 33. The overhang forms an arcuate opening 34 with lower portion 27. The arcuate slot 27 receives the peripheral border of slotted disc 18. An opening 35 is formed in overhang 233 immediately above the lamp 3t and supports a photo transistor 36. It is apparent from FIGURE 2 that the slotted disc alternately blocks and communicates the light source of lamp 30 to the photo-transistor 36 as the disc 18 is rotated by shaft 12.
The particular photo-transistor 36 disclosed is made by removing the top from a transistor and replacing it with a clear epoxy resin. A transistor of the silicon switching type is used. The transistor 36 is placed across a lead 38 and is comprised of emitter 40, collector 42 and base 44. A collector resistance 46 is placed in lead 38 between the collector and the voltage source. The voltage source is indicated by the letter E. The collector 42 is connected to the base 48 of a transistor 5!) through a base resistance 52. Transistor 56 is the beginning of a switching system commonly referred to as a Schmitt trigger. When light strikes the photocell 36, its resistance drops rapidly providing a positive voltage to the base 48 of the normally conducting transistor 50. The positive voltage turns the transistor 50 off.
Transistor 56 is disposed in lead 51 and has its emitter 53 and its collector 55 across the voltage source respectively through resistances 56 and 57. Collector is connected to the base 60 of a transistor 62 through the resistance 64 and capacitance 66 which are in a parallel relationship. A base resistance 65 is disposed between the base 60 and the voltage source. The emitter 63 of transistor 62 is connected to the emitter 53 and the collector 65 is led to ground through a resistance 69.
For spark retardation purposes, a relay switch 70, having contact points 71 and 73 and a switch arm 74, is placed in the system. The coil 8% of the relay is connected to a vacuum operated switch 81.
The collectors 55 and 65 of transistors 50 and 62 are respectively connected to contact points 71 and 73. A capacitance 75 is disposed between the switch and the input of the flip-flop.
The switches as disposed in FIGURE 3, are in their normal position with the collector 55 of transistor 50 normally connected to base 82 of a transistor 83.
When the switch arm spans the contacts 71 and 74, the collector 55 is routed to line 84 between the diode 83 and the base resistance 86. When engine vacuum drops, the switch 81, through coil 80, draws arm 78 to contact 73. When this happens, the input to transistor 83 is from the collector 65 of transistor 62, and the power transistor 94 is turned off as the light leaves the photo-transistor. Thus, there is instant spark retardation as the engine manifold vacuum drops.
The output from the flip-flop is fed to the base 92 of the PNP power transistor 94. The emitter and collector of transistor 94 are disposed in parallel relationship with a diode 95, and a capacitance 96. The power transistor rapidly switches the current to winding 99 to provide a high voltage output from winding 101.
The transistor 94 provides current to winding 99 of transformer liitl. The winding 101 is in series with the spark plug 105 through the distributor cap. The winding 99 is connected to the voltage through ignition contacts 104. A ballast resistor 1% is used in the system.
In review, it is apparent that photo-transistor 36 acts as a high resistance to prevent a positive voltage from reaching base 48 of transistor 50. However, when one of the slots 22 traverses the photo-transistor, a positive voltage is applied to base 48 and transistor 50 is turned on. As transistor 58 turns on, it provides a positive voltage to transistor 88. Transistors 88 and 9% are flip-flop transistors. Transistor 94 is non-conducting while light is provided to the photo-transistor 36. A resistor 110 in the line between the collector of transistor E and the base of 94 is used to limit base current. The current through resistor 110 places transistor 94 in saturation. The transistor 94 thus is used as a switch to provide the current to the coil. As transistor 94- shuts the current off, the primary 99 field collapses to produce high voltage output from the secondary 101.
As previously stated, during operation the disc 18 alternately permits light from the lamp 30 to shine on transistor 36. The transistor resistance drops rapidly thereby permitting a positive voltage to be applied to the base 48 causing actuation of transistor 50 of the Schmitt trigger. The pulse is taken from the collector of 56 and applied to the transistor 83. However, the pulse can be taken from the collector 65 for spark retardation purposes, thus transistor 83 turn on pulses the other flipfiop transistor W, and charges the coil when the light from lamp 30 is blocked from the photo-transistor 36. A 15 slot would therefore provide a 15 spark retardation. The retardation, of course, requires the cooperation of the vacuum switch 81. Transistor 62 is connected through to transistor 90 via transistor 83 and the normally open contacts of vacuum switch 81. When the engine vacuum drops, the vacuum switch 81 energizes the relay coil and the output from transistor 62 is directed to the flip-flop transistor 83.
The power transistor 94 acts as an electronic switch for supplying and cutting off current to the primary coil winding 99. As can be seen in FIGURE 3, the power transistor is protected from high voltage peaks caused by the field collapse in the coil, by a zener diode 95 and a capacitor $6. Since the photo-transistor unit of this invention is mounted in place of the regular points, the conventional centrifugal advance can be used. The width of the slots determines degrees of retardation.
The circuitry provides a means whereby the coil will charge most of the time. This insures a sufficient charge time even at very high revolutions per minute. When iight strikes the phototransistor 36, and when the vacuum operated switch 31 is in the position, shown in FIGURE 3, the power transistor will shut oii for a particular time I causing a high voltage output from the coil. When switch arm '74 is drawn to contact 73, the power transistor will be off for the time t as the light leaves the transistor 36, transistor 94 is turned off and produces a high voltage output.
In a general manner, while there has been disclosed an effective and efiicient embodiment of the invention, it should be well understood that the invention is not limited to such an embodiment, as there might be changes made in the arrangement, disposition, and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims:
1. An ignition system for an internal combustion engine having a spark producing element for igniting engine fuel, an output transformer across said element for producing a spark when current pulse is applied to said transformer and a shaft rotatable in time relationship with said engine, that improvement in a system for delivering current pulses to said transformer in timed relationship with the output of said shaft comprising:
a light source,
a photoelectric device,
a disc afiixed to said shaft and having a peripheral edge portion disposed between said source and said device,
said edge formed with a plurality of equally spaced slots which sequentially permit light of short duration to reach said device as said shaft rotates,
a first normally conducting transistor having an output element,
means to render said first transistor nonconductive when light strikes said device,
a power transistor having an input element providing high voltage pulses to said output transformer when said first transistor is nonconductive,
spark retardation switch connecting said output element to said input element, said switch having a first position wherein current from said output element is directed to said input element and a second position wherein the conducting state of said power transistor is reversed, and
means sensitive to a drop in engine manifold vacuum for moving said switch in said second position.
2. The invention as described in claim 1 wherein when said switch is in said second position an additional transistor is connected between said input element and said output element.
3. An ignition system for an internal combustion engine having a spark producing element for igniting engine fuel, an output transformer across said element for producing a spark when current pulse is applied to said transformer and a shaft rotatable in timed relationship with said engine, that improvement in a system for delivering current pulses to said transformer in timed relationship with the output of said shaft comprising a light source, a photoelectric device, a disc affixed to said shaft and having a peripheral edge portion disposed between said source and said device, said edge formed with a plurality of equally spaced slots which sequentially permit light of short duration to reach said device as said shaft rotates, a first normally conducting transistor having its base connected to the collector of said device such that when light strikes said device said first transistor is non-conductive, a second transistor having its base connected to the emitter of said first transistor, a power transistor providing high voltage pulses to said output transformer when said first transistor is nonconductive, connecting means for connecting the base of said power transistor to said first transistor, said connecting means including a switch having a first position wherein said switch is connected to the collector of said second transistor, and a second position wherein said switch is connected to the collector of said second transistor and means sensitive to a drop in engine manifold vacuum for moving said switch to said second position.
References Cited UNITED STATES PATENTS 2,787,649 4/1957 Ballard et al. 123-148 3,202,146 8/1965 Short et al l23l48 3,297,099 1/1967 Sasaki et al 123-448 LAURENCE M. GOODRIDGE. Primary Examiner.