US3478249A

US3478249A - Spark ignition apparatus for internal combustion engines

Info

Publication number: US3478249A
Application number: US613518A
Authority: US
Inventors: Norman Alfred Jukes
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1966-02-16
Filing date: 1967-02-02
Publication date: 1969-11-11
Anticipated expiration: 1986-11-11
Also published as: DE1539231A1; FR1510665A; DE1539231B2; GB1160991A; DE1539231C3; ES337614A1

Description

Nov. 11, 1969 N. A. JUKES 3,478,249

SPARK IGNITION APPARATUS FOR INTERNAL COMBUSTION ENGINES Filed Feb. 2, 1967 FT Z PRIOR ART PRIOR ART United States Patent US. Cl. 315-209 6 Claims ABSTRACT OF THE DISCLOSURE The spark ignition apparatus comprises a spark generating circuit for supplying sparks to the plugs of the engine in turn, a trigger circuit which when biased by an input permits the spark generating circuit to produce a spark, a continuously running oscillator for providing the biasing input to the trigger circuit, and magnetic means driven by the engine for coupling the oscillator to the trigger circuit when a spark is required, the design of the trigger circuit being such that irrespective of engine speed only one spark is produced each time the oscillator is coupled to the trigger circuit.

This invention relates to spark ignition apparatus for internal combustion engine-s.

This invention has for an object to provide spark ignition apparatus comprising a spark generating circuit for supplying sparks to the plugs of the engine in turn, a trigger circuit which when biased by an input permits the spark generating circuit to produce a spark, a continuously running oscillator for providing the biasing input to the trigger circuit, and magnetic means driven by the engine for coupling the oscillator to the trigger circuit when a spark is required, and in which the design of the trigger circuit is such that irrespective of engine speed only one, i.e., a single spark is produced each time the oscillator is coupled to the trigger circuit.

It is a further object of the invention to provide spark ignition apparatus as set forth in the foregoing object, and in which the trigger circuit includes a feed-back path which accelerates the switching action and is useful particularly at low speeds to assure the emission of such single spark.

Further and more specific objects will be apparent from the accompanying drawings, in which:

FIGURE 1 is a circuit diagram illustrating an embodiment of the invention, and

FIGURES 2 and 3 are, respectively, diagrammatic side and front elevational views of a form of magnetic coupling arrangement for use in the circuit of FIGURE 1.

Referring to the drawings, there are provided a positive supply line 11 which in use is connected to the positive terminal of the battery of the vehicle through an ignition switch 12, and a negative line 13 which conveniently is earthed. Connected between the lines 11, 13 are a free running oscillator, a trigger circuit, and a spark generating circuit.

The oscillator includes a capacitor 14 connected between the lines 11, 13 in parallel with a series circuit including a resistor 15 and a capacitor 16. A point inter mediate the resistor 15 and capacitor 16 is connected through the secondary winding 17 of a transformer 18 to the base of an n-p-n transistor 19, the collector of which is connected to the line 11. The emitter of the transistor 19 is connected to one end of a resistor 21, the other end of which is connected to the line 13 through the primary winding 22 of the transformer 18 and a capacitor 23 in parallel, and is also connected to an output terminal 24.

The trigger circuit is in the form of an amplifier with AC. feed back, and includes a resistor 25, one end of which is connected to the line 11 and the other end of which is connected to the base of an n-p-n transistor 26, and to the collector of an n-p-n transistor 27. The transistor 26 has its collector connected to the line 11 through a resistor 28, and its emitter connected to the line 13 through a resistor 29, while the transistor 27 has its emitter connected to the line 13, and its base connected to the line 13 through a resistor 31. The base of the transistor 27 is further connected to the line 13 through a diode 32 and the capacitor 33 in series, and a point intermediate the diode 32 and capacitor 33 is connected to an input terminal 34. The AC. feed back is provided by way of a resistor 35 and a capacitor 36 connected in series between the collector of the transistor 26 and the base of the transistor 27.

The spark generating circuit includes an ignition coil 37 having a secondary winding 38 which is connected to the spark plugs of the engine in turn through a distributor in the usual way, and a primary winding 39 one end of which is connected to the line 11, and the other end of which is connected to the collector of an n-p-n transistor 41, the emitter of which is connected to the line 13, and the collector and emitter of which are bridged by a voltage-dependent resistor 42. The spark generating circuit is coupled to the trigger circuit by way of a connection from the base of the transistor 41 to the emitter of the transistor 26. There is further provided magnetic means for coupling the oscillator to the trigger circuit at the instant when a spark is required. This magnetic means includes an output coil 43 connected between the terminal 24 and the line 13, and a pick-up coil 44 connected between the terminal 34 and the line 13. The pick-up coil 44 is tuned to the operating frequency of the oscillator. The magnetic means is preferably contained within the distributor of the road vehicle, and may be of the form illustrated in United States Patent No. 3,277,340 which is described briefly herein in connection with FIGS. 2 and 3. The magnetic circuit for

coils

43 and 44 comprises an open rectangular core 49 which is split along one of its long sides. The

windings

43 and 44 are wound on the limbs or opposite sides of the split in the core, and the arrangement is such that the air gap between the windings is sufficient for magnetic coupling. Rotatable about an axis parallel to one of the longer sides of the core is a disc 51 which is driven by, and at a speed dependent on, the speed of the engine with which the ignition circuit is associated. Thus, conveniently the disc 51 may be driven by the distributor shaft diagrammatically shown at 53.

The disc is made of conductive material and includes four slo s 51 which extend inwardly towards the center of the disc from its circumference and which are mutually at right angles. The disc is rotated so that it passes between the windings or

coils

43 and 44, and when a slot 52 is aligned with the two portions of the broken limb on which

windings

43 and 44 are wound, the windings are coupled magnetically. The windings are not coupled at any oher time. The disc described is suitable for use with a four cylinder engine, and in other cases the number of slots will be equal to the number of cylinders, Moreover, the disc 51 could be driven indirectly by the engine through step-up or step-down gearing, in which case the number of slots could be a fraction of or a multiple of, the number of engine cylinders.

In use, between the production of sparks, current flows through the resistor 25 to switch the transistor 26 on, and the transistor 26 in turn switches on the transistor 41, so that current flows in the primary winding 39. The

oscillator operates in known manner, and in a typical case may have a frequency of 600 kilocycles per second.

At the instant when a spark is required, the

windings

43, 44 are coupled magnetically, and the output from the oscillator is rectified by the diode 32 and fed to the base of the transistor 27, so turning the transistor 27 on. The base current supplied to the transistor 26 now fiows through the transistor 27 instead, and so the transistor 26 is turned off, with consequent turning off of the transistor 41. The resultant fall in flux in the ignition coil 37 produces the spark.

While the transistor 27 is switching on and the

transistors

26, 41 are switching off, the voltage at the collector of the transistor 26 rises, so that the capacitor 36 is charged by way of the resistor 35. This feed back signal accelerates the switching action, so that the rate of fall of collector current in the transistor 41 is less dependent on the rate of rise of the current in the winding 44,

It -will be appreciated that the transistor 27 is held off until a signal of sufficieut amplitude appears at the terminal 34. Because of the design of the circuit, only one spark will be applied to a plug each time the

windings

43, 44 are coupled, and by virtue of this arrangement the design of apparatus for use with engines having a large number of cylinders, for example, in excess of six, is considerably simplified as compared with arrangements in which at speeds below a predetermined engine speed each plug may have more than one spark applied thereto each time the

windings

43, 44 are coupled.

In practice, it is convenient to house the oscillator, the trigger circuit and the transistor 41 and resistor 42 in the same container, and this container can be the distributor. In this case, the distributor is designed to act as a heat sink for the transistor 41.

The purpose of the resistor 21 is to provide negative feed back within the oscillator, which assists in stabilizing the frequency of the oscillator against changes in the supply voltage. The capacitor 16 provides a low impedance path in the feed back circuit of the oscillator, and the resistor 15 is provided to ensure that the oscillator starts satisfactorily.

The voltage dependent resistor 42 prevents damage to the transistor 41 as a result of the back when the flux in the ignition coil 37 collapses, and also prevents damage as a result of transient Volta-gm reflected from the windings 38 during production of a spark. The resistor 29 also protects the transistor 41 when the spark is produced.

It should now be appreciated that among the important features of the invention is the ability to tune the oscillator into resonance with the output winding of the pick-up coil, as well as the provision of the AC. positive feed back for the A.C. amplifier connection of transistors to insure the desired operation at low speeds. Also, the use of the voltage dependent resistance enables the suppression of transients at the collector of transistor 41.

Thus, it will be appreciated that the characteristics and features of the principle of the invention enable the positive control of the production of a single spark for each cylinder to be fired. From a reading of the description hereof other and further modifications may occur to those skilled in the art and accordingly it is intended that the invention be limited only by the scope of the appended claims.

What is claimed is:

1. Spark ignition apparatus for an internal combustion engine, comprising a spark generating circuit for supplying a single spark to each of the plugs of the engine in turn, a trigger circuit connected to said spark generating circuit comprising a first transistor and a second transistor interconnected for mutually exclusive operation and which circuit is normally in one condition of operation but when biased by an input assumes a second condition of operation to cause the spark generating circuit to produce a single spark, a continuously operating fixed frequency oscillator for providing the biasing input to said trigger circuit, magnetic means driven by the engine for coupling said oscillator to said trigger circuit when a spark is required to drive said trigger circuit from said one condition to said second condition, said trigger circuit remaining in said second condition until said trigger circuit is decoupled from said oscillator, and a feedback circuit from the second transistor to the first transistor to accelerate the switching action from said first condition of operation to said second condition of operation.

2. The apparatus of claim 1 wherein said transistors of the trigger circuit are connected in DC. amplifier fashion and said feed back circuit comprises a positive feed back circuit.

3. The apparatus of claim 1 wherein said spark generating circuit comprises a transistor connected to be operated simultaneously with the second transistor; and further comprising a voltage dependent resistance connected between the emitter and collector electrodes of the spark generating circuit transistor.

4. The apparatus of claim 1 comprising pick-up coil means for transferring energy from the oscillator to the first transistor; said pick-up coil means being tuned to resonance with the oscillator.

5. The apparatus of claim 1 further comprising rectifying means interposed between the oscillator and the transistors to permit the latter to operate in DC amplifier fashion.

6. Spark ignition apparatus for an internal combustion engine of the spark plug type, comprising a spark generating circuit for intermittently supplying a single spark for each explosion, said spark generating circuit comprising a spark generating transistor, a trigger circuit comprising a first transistor and a second transistor connected in circuit and to the spark generating transistor, said trigger circuit normally characterised by conduction of said second transistor and non-conduction-of said first transistor but when biased by input shifting conduction from the second transistor to the first transistor with the second transistor and spark generating transistor becoming non-conductive to generate a spark, a continuously operable oscillator for providing the bias input, pick-up winding 'means tuned to the frequency of said oscillator, and magnetic means driven by the engine for coupling said oscillator to said trigger circuit via said winding means each time a spark is required for explosion, said trigger circuit returning to conduction in said second transistor and non-conduction in said first transistor when said trigger circuit is decoupled from said oscillator, and said trigger circuit including a positive feedback path between the second transistor and the first transistor for increasing the speed at which the first trausistor becomes conductive when the trigger circuit is coupled to the oscillator.

References Cited UNITED STATES PATENTS 3,161,803 12/1964 Knittweis 315-209 3,240,199 3/1966 Neopolitokis 123-448 3,277,340 10/1966 Iukes et a1. 3l5214 3,291,110 12/1966 Peters 123l48 3,299,874 1/1967 Elkind 123148 JOHN W. HUCKERT, Primary Examiner SIMON BRODER, Assistant Examiner US. Cl. X.R. 3l5218