US3504231A - Breakerless oscillator ignition system - Google Patents

Description

March 31, 1970 o. F. TIBBS 3,504,231

BREAKERLESS OSCILLATOR IGNITION SYSTEM Filed June 26, 1967 IO IO ITH 53 INVENTOR 9 OSCAR E TIBBS ATTORNEYS United States Patent 3,504,231 BREAKERLESS OSCILLATOR IGNITION SYSTEM Oscar F. Tibbs, Ripley, Tenn., assignor, by mesne assignments, to Andrews Manufacturing Company, a corporation of Tennessee Continuation-impart of application Ser. No. 580,795, Sept. 20, 1966. This application June 26, 1967, Ser. No. 648,903

Int. Cl. H05b 37/02, 39/04 US. Cl. 315212 12 Claims ABSTRACT OF THE DISCLOSURE A transistorized ignition system for a multi-cylinder engine which employs no breaker points and no mechanical moving parts and provides a constant voltage which is harmlessly absorbed by the system when the spark plugs are not firing, but which is ideal for an efficient ignition of the combustible gases in the cylinder when the spark plugs are firing.

Cross reference to related application This is a continuation-in-part of application Ser. No. 580,795, filed Sept. 20, 1966, now Patent No. 3,408,536.

Background of the invention Conventional ignition systems employ mechanical breaker points to time the flow of current through the ignition system to the distributor. However these mechanical devices suffer from several disadvantages, the most important of which is that the voltage of the current delivered to the spark plugs cannot be varied to adapt to changing load requirements. If the voltage is set too low the spark plugs will not fire effectively at high engine speeds; and if the voltage is set too high, the plugs and other elements of the ignition system will burn out during period when a low voltage drop 1s required in the system.

An early attempt to overcome this problem was the development of a magneto which varied the voltage in accordance with engine speed. However, the fact that the magneto depended for efficient operation on the precision of moving mechanical parts has caused many problems. Consequently, the magneto has not been accepted as a satisfactory means for overcoming the inherent disadvantages of the conventional breaker point t1m1ng mechanisms.

With the development of transistors, attempts were made to design solid state ignition systems which would overcome the disadvantages of mechanical timing means. At first, transistors were employed to supplement the ignition coil in developing a high voltage, low ampere oscillating current, thereby reducing the load on the breaker points. However, this merely eliminated some of the problems associated with breaker points, but it did not eliminate the need for breaker points and thus, it was still not possible to provide a sufficient voltage available during all the changing load requirements.

Thus, it is a purpose of the present invention to provide a radically different solid state ignition system having many of the advantages of previous ignition systems while eliminating the disadvantages. The present system not only eliminates mechanical timing means, but also allows control of the voltage, without mechanical moving parts, to adapt to changing load requirements during acceleration and other conditions.

In the present system pulsating DC current is generated continuously. The system is designed to counteract difiiculties which would normally be encountered during the periods when pulses are being generated by the system but not delivered to the distributor and to the spark plugs. By employing this entirely different approach, all mechanical breaker points and voltage varying means have been eliminated. In this respect, the present invention has the advantages (but not the disadvantages) of a magneto. Consequently, the present system may be referred to, for convenience, as a solid state magneto or an electronic magneto.

Tht periods when current is being delivered through the distributor to the spark plugs will be referred to as the load condition, and the periods when current is not being delivered through the distributor to the spark plugs will be referred to as the no load condition. In the prevous conventional ignition systems difiiculties such as damaging high voltage surges were avoided since the breaker points caused the current to be cut off during these off periods. With the present system, however, means are provided for absorbing these high voltage surges in such a manner that (1) these surges cause no harm to the elements of the ignition system, (2) the surges will not cause the pulsating DC current of the ignition system to be cut 01f, and (3) spurious AC current surges transmitted to the ignition system from the generator or alternator will not cause the pulsating current to cut 011.

Summary of the invention The solid state ignition system according to the present invention operates in the following manner. Direct current from the automotive battery is continuously converted to pulsating DC current in a transistor circuit with current then being delivered to the ignition coil and hence through the distributor to the spark plugs. As this pulsating DC current is generated continuously by the transistor circuit, a current is induced to flow to a standard automobile ignition coil, through a distributor and to the spark plugs only during the load condition of the system which is When the distributor rotor is in the vicinity of a terminal leading to a spark plug. During the no load condition, when the rotor is between spark plug terminals, current is not delivered from the ignition coil to the distributor either because the rotor and terminal are not close enough to conduct, or, if they are close enough, because the compression about the base of the spark plug in the engine cylinder is insufiicient to allow the spark plug to fire and the circuit to be completed to ground. During the no load condition high voltage surges build up. These surges are capable of damaging the elements of the system. However, in the present system, the ignition coil and the transistor circuit absorb the high voltage surges so that no damage results.

An important feature of the present invention is that the resistance at the spark plugs during the load condition will vary automatically with the compression in the combustion chamber. As that resistance increases, the sparking is retarded. In this way the voltage remains constant but the sparking across the spark plug gap is retarded until the correct combustion conditions are present regardless of whether the engine is being operated at high or low speed.

Many additional advantages are attributable to the present ignition system. The spark plugs themselves have a long life since the constant, high voltage spark pulses tend to clean carbon deposits off of the plugs and improve the efficiency thereof. Also, since the spark will automatically be retarded by the engine compression conditions it is possible to operate the automobile more efliciently due to more complete combustion. Also, with the present system the distributor cap and rotor are not pitted or burned by arcing.

Thus it is an object of the present invention to provide an improved solid state ignition system which overcomes many disadvantages of previous ignition systems.

It is another object of this invention to provide an ignition system in which the sparking at the spark plugs will be controlled by the compression in the cylinder to automatically time the engine.

It is still another object of this invention to provide an automotive ignition system in which conventional timing means are eliminated. v

It is still another object of this invention to provide a automotive ignition system in which a pulsating DC current is developed by a transistor circuit means for delivery to the spark plugs during the load position of the distributor and in which voltage generated during the no load condition are absorbed by the system without causing damage to the elements of the system.

Other objects and the attendant advantages of the present invention will become apparent in the detailed description to follow of a preferred embodiment of the invention together with the accompanying drawings.

Brief description of the drawing The figure is a schematic view illustrating a preferred embodiment of the present invention.

Description of the preferred embodiment The structure and operation of the invention will now be described with respect to a preferred embodiment of the invention as shown in the drawings. However, it should be understood that the particular values of the elements in the present embodiment are chosen for purposes of illustration and may be varied within the scope of the invention.

As shown in FIG. 1 a 12 volt DC battery is connected from ground 11 through a switch to a transformer 30 to which is connected a transistor circuit. From the transformer 30 an induced current is delivered thru conductor 39 to primary winding 51 of the ignition coil 50 where a very high voltage is induced in the secondary winding 52 and passed through the distributor cap 60 to the rotor 62, thence to terminals 63 and to spark plugs 61. In the described embodiment the ignition coil 50 has a turn ratio of 250:1, and this will govern the number of turns of the transformer 30. However, other standard ignition coil turn ratios such as 100:1 and 400:1 may also be used. To employ the present invention with an ignition coil having these other turn ratios it would only be necessary to change the number of turns of the transformer 30.

Although there is disagreement on the correct theoretical functioning of the circuit, the circuit is connected as follows. The transformer 30 has a primary winding 31 and a feedback winding 32 which is primary in the sense of being connected thru primary coil 31 to the input, but secondary in the sense of being wound, closely in parallel with secondary windings 33, 34 and 35. Each of the five windings, 3135 respectively, has an S or F at each end which designates start or finish. These designations are helpful as an aid in winding the transformer. Each layer of windings is separated by a .0025 inch thick plastic insulating tape. Connected in series between primary winding 31 and ground 29 is the power circuit of an alternately conducting and nonconducting transistor Q A second transistor Q is shown but is not required for operation of the circuit. Q is used only as a reserve so that if one of the transistors Q and Q fails, the inoperative transistor can be very simply removed and the ignition will again operate. The power circuit electrodes of Q are connected in parallel with those of Q While the base electrode of Q is connected to the base electrode of Q The primary winding 31 may be constructed of 20 gauge wire having approximately 125 turns. It has been found that 20 gauge wire will draw a sufficient current while avoiding heat problems. The 15 turns of winding 32 are wound in parallel with secondary windings 33, 34 and 35 to maximize the inductive coupling between these windings. Satisfactory results have been obtained if winding 32 has approximately 14-18 turns and is formed of 18 gauge wire. The first side of the Winding 32 is connected across a resistance 45 to the base electrode of the transistor while the other side is connected to the emitter 41 of the transistor.

The transistor Q1, cg. the RCA power transistor 2N3731, has an emitter electrode 41, a collector electrode 42 connected to ground at 29 and a control base electrode 43. Transistor Q is identified by the same designation with the addition of a prime symbol. Likewise resistor 45' and ground 29 corresponding to 45 and 29, respectively, are shown. A capacitor 44 is connected from the emitter 41' to ground 46. The capacitance of this capacitor is chosen so that it can absorb the charge developed in the circuit during the no load condition of the system. In the present embodiment a value of 0.5 ,uf. has been found to be suitable. It has also been found that by varying the value of capacitor 44 the timing of the on and off cycles of the transistors Q and Q can be adjusted.

The three windings 33, 34 and 35 each have the same number of turns, but each winding is constructed from a different gauge wire. In the illustrated embodiment the windings 33, 34 and 35 are of 24 gauge, 26 gauge and 28 gauge wire respectively. These three windings, like the primary and feedback windings, are wound together in parallel fashion in order to maximize inductive coupling between the windings. Winding 34 is connected to a filter capacitor 36, which may have a value of about .047 f, which is further connected to the 12 volt source. The other end of winding 34 is grounded at 47. Winding 35 is connected to the 12 volt source in series with a 500 ,uf. capacitor 37 and the other end is connected at 38 directly into the laminated core of transformer 30. Finally, winding 33 is the output wire from the transformer 30 which delivers the pulsing DC current from the transformer 30 through conductor 39 to the standard ignition coil 50.

It is essential that the core of transformer 30 not be grounded. To accomplish this it has been found effective to enclose the entire transformer, including the windings, with a conventional paper insulation. In addition it is desirable to inclose the paper-insulated transformer within a metal shield of the same material as the core laminations. Such shielding isolates the transformer from external frequency effects. But more important, the field of the transformer is controlled such that the device will operate continuously rather than to sporadically cut off or on when without the shield.

The ungrounded end of winding 33 is connected, via conductor 39, to one end of each of the inductively coupled ignition coil windings 51, 52. Primary winding 51 is connected at its other end to ground 54, and the other end of secondary winding 52 is connected with the distributor cap 60 via conductor 53. Windings 51 and 52 oppose each other and winding 52 is tapped to the core of the ignition coil at 52'. The standard spark plugs, shown schematically at 61 are grounded at 64. No structure modification is required in the cylinders for mounting the spark plugs. Any conventional means of installing the spark plugs will be satisfactory.

The present system operates as follows: The transistors Q and Q switch on and off at all times, thus causing pulsating DC current to be generated in the primary winding 31 and primary and secondary winding 32 which is induced through winding 33. Current is conducted through the distributor cap 60, thence to rotor 62, then to terminals 63 and finally to spark plugs 61. This is only when the rotor is in the vicinity of a terminal, that is, at the load condition. When rotor 62 is between terminals 63, it is insulated so that no current flows through the rotor 62 or the lead line 53. This is the no load" condition.

In previous systems it was necessary to terminate the current flowing to the ignition coil when the rotor 62 was in the no load condition. Otherwise the voltage surges developed at that point would burn out various elements of the system, such as for example the transistor, or other weak points of the system. However, the present system maintains a constant voltage which is utilized for spark ignition of the combustible air-fuel mixture when in the load condition, but which is harmlessly absorbed by the circuit when in the no load condition.

In the no load condition the voltage developed in the circuit cannot be delivered from the ignition coil 50 to the spark plugs since the end of rotor 62 is insulated (not near any terminal 63). In previous systems the voltage would gradually rise to a point at which it would damage the system. As a result it was necessary to interrupt the current flow to the ignition coil by mechanical timing means.

However, in the present invention this does not gradually rise because it is absorbed in the circuit. This current is discharged through the secondary winding 33 and through 51 to ground with any reflected surges being harmlessly absorbed. Therefore, there is no increase in voltage within the ignition coil and the elements of the circuit, such as, for example, the transistor, are not damaged.

During the load condition the sparking is controlled by the compression in the combustion chamber. The engine is timed so that as rotor 62 approaches a terminal 63 the piston is approaching top dead center (TDC). At this position compression in the cylinder will approach the maximum which is the most advantageous condition for the best spark. At this point the sparking across the spark plug gap greatly increases, and just after the piston passe's TDC the explosion in the cylinder is sufficiently complete to propel the piston away from the cylinder head. As is understood in the art this process occurs in each cylinder of the engine in the desired order of their firing.

The specific values of elements shown in the preferred embodiment of the present system are provided for il lustration and not for limitation. Of course the system could also be designed to operate efliciently with other transistor designs. It should be apparent that many other variations and modifications are possible within the spirit and scope of the invention as defined in the appended claims wherein.

I claim:

-1. An electronic device for providing a pulsating direct current output for use in an internal combustion engine ignition system comprising:

a transformer having a core, and

a primary winding with lead-in and lead-out conductors,

a feed-back secondary winding starting from said primary winding lead-out conductor and wound closely in parallel with first, second and third secondary windings, wherein a pulsating means is connected to the lead-out from said primary winding,

said feed-back secondary winding is connected to bias said pulsating means,

said first secondary winding is connected between ground and an output,

said second secondary winding is connected between ground and across a capacitance to the lead-in to said primary winding, and

said third secondary winding is connected between the core of said transformer and across a capacitance to the lead-in to said primary winding.

2. An electronic device as described in claim 1 wherein:

the core of said transformer is laminated, and said transformer is enclosed within a layer of insulating material and a layer of metal.

3. An electronic device as described in claim 2 wherein:

said layer of metal is of the same material as the transformer core laminations.

4. An electronic device as described in claim 1 wherein:

said pulsating means is a transistor having an emitter,

base, and collector, wherein said primary winding lead-out conductor is connected to said emitter,

said feed-back secondary winding is connected to said base,

said collector is grounded, and a capacitance is connected across said emitter and collector. 5. An electronic device as described in claim 4 wherein the turns of said primary, feed-back and secondary windings are in the ratio of 8:1:3, respectively.

6. An electronic device as described in claim 4 wherein: said primary winding leadin is connected across a switch means to a power source, and the output of said first secondary winding is connected to the primary winding of an automobile ignition coil,

which ignition coil is further connected through a distributor cap to a plurality of spark plugs, whereby a continuous voltage is supplied to the distributor cap for delivery to the spark plugs.

7. An automobile ignition system for an internal combustion engine comprising a source of continuous direct current electrical energy, circuit means for converting the direct current electrical energy produced by said source into pulsating direct current electrical energy, distributor means including an input rotor and a plurality of output terminals arranged sequentially with respect to said rotor, a plurality of spark plugs connected to said distributor output terminals, and coil means for continuously applying said pulsating direct current electrical energy to said rotor for positions of said rotor wherein current is conducted to a spark plug and for absorbing voltage surges occurring for positions of said rotor with respect to said distributor terminals wherein current is not conducted to a spark plug.

8. A system as claimed in claim 7 wherein said coil means comprises transformer means including a primary winding and a secondary winding, said primary winding diverting the output of said secondary winding to ground for positions of said rotor wherein current is not conducted to a spark plug from said rotor.

9. A system as claimed in claim 7 wherein said circuit means includes at least one transistor and means for alternately rendering said transistor conductive and non-conductive.

10. A system as claimed in claim 9 wherein said circuit means includes a laminated core transformer and a shield constructed of the same material as said transformer surrounding said transformer and insulated therefrom.

11. A system as claimed in claim 9 wherein said circuit means includes transformer means comprising a transformer comprising a core, a primary winding including lead-in and lead-out conductors, said lead-out conductor being connected to the output circuit of said at least one transistor, first, second and third secondary windings, a feedback secondary Winding connected to said primary winding lead-out conductor to control biasing of said at least one transistor and wound closely in parallel with said first, second and third secondary windings, one side of said first secondary winding being connected to ground and the other side of said first secondary winding forming the output of said transformer means, one side of said second secondary winding being connected to ground and the other side of said second secondary winding being connected through a capacitance to said primary winding lead-in conductor, and one side of said third secondary winding being connected to said transformer core and the other side of said third secondary winding being connected through a further capacitance to said primary winding lead-in conductor.

. 7 12. A system as claimed in claim 11 wherein said primary Winding is constructed of 20 gauge wire having approximately 100 to 125 turns, said first secondary winding is constructed of 24 gauge wire having approximately one-third the number of turns of said primary winding, said second secondary winding is constructed of 26 gauge wire having approximately one-third the number of turns of said primary winding, said third primary winding being constmcted of 28 gauge wire and having approximately one-third the number of turnsof said primary Winding, and said feedback secondary winding being constructed of 18 gauge wire having approximately 14 to 18 turns.

References Cited UNITED STATES PATENTS 3,175,123 3/1965 Dilger 315209 3,263,124 7/1966 Struermer 3152l2 3,408,536 10/1968 Tibbs 315-212 JAMES W.' LAWRENCE, Primary Examiner C. R. CAMPBELL, Assistant Examiner US. Cl. X.R.

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