US2898392A - Ignition systems - Google Patents

Description

1959 R. L. JAESCHKE 2,398,392

IGNITION SYSTEMS Fi led Aug. 19. 1957 FIGB. 7/

IGNITION SYSTEMS Ralph L. Jaeschke, Kenosha, Wis., assignor to Eaton Manufacturing Company, Cleveland, Ohio, a corporation .of Ohio Application August 19, 1957, Serial No. 678,952 I 8 Claims. (Cl. 123- 149) This invention relates to ignition systems, and more: particularly to transistorized automotive ignition systems.-

Amongtheseveral objects of the invention may be noted the provision of ignition systems which automati-;

cally and precisely control the advance and retardation of spark in response to engine speed variations; the provision of ignition systems of the class described which insure improved flame propagation; and the provision of such ignition systems which are simple and inexpensive in.

Fig. 1 is a schematic and circuit diagram ofan ignition' system of the present invention;

Fig. 2 illustrates the wave patterns at certain points in the ignition system at low engine speeds; and,

. Fig. 3 illustrates the wave patterns at certain points in the ignition system at higher engine speeds.

Corresponding reference characters indicate corresponding parts throughout the several views of the draw- Referring now to Fig. 1, an automotive type distributor is indicated at D. A distributor rotor DR is interconnected by a wire 1 to a secondary TS of a step-up transformer T. Rotor DR is mechanically driven in the usual manner by an internal-combustion engine (usually from the cam shaft), so as to sweep the rotor across several distributor stator contacts D8 which are in turn electrically connected to the engine spark plugs as indicated. Transformer T, which is. preferably of the type used as the high voltage transformer in conventional television sets, has a primary winding TP. The TPzTS turns ratio is such that a secondary voltage of approximately 10 to kv. is developed. Transformer T may be of the laminated, air or compacted powdered iron core types. One end of primary T P is commonly connected to the other side of secondary TS and grounded, while the opposite terminal of TP is connected through a resistor R1 to the base B of a junction transistor JT. Primary TP is shunted by a condenser C1 to form an LC tank which resonates within a preferred frequency range of about 15 to kc. A tap of winding TP is connected to emitter E of transistor IT. The basic oscillator circuitry of Fig. 1 also includes an adjustable bias resistor R2, interconnecting the collector element of IT to its base B, and a source of DC. power B1, such as a 12 v. automotive storage battery interconnected through an ignition switch SW to collector C.

This oscillator circuit, constituted by transistor JT connected in a common-emitter configuration with its associated components including the LC tank and resistors R1 and R2, optionally but preferably also includes a resistor R3 and a protective limiter diode D1 series- 10 shunted across R1.

woundon two generator poles P1 and P2 magnetically;

connected between collector C and emitter E to protect:

In order to pulse or key this A.C. potential applied to DR, a pair of serially connected generator windings GWl and GW2 are shunt-connected by means of a wire 3, a resistor R4, a wire 5, and another conductor 7 across resistor R1. A diode limiter D2 is also electrically The windingsjGWl and GW2 are:

interconnected by the iron path providedby a generator stator elementGS. Aflux field through GS is estab-, lished by a polarized generator rotor GR positioned in a magnetic relationship between poles P1 and P2.. This rotor is of permanent magnetic material, such as Alnico,-

and is driven by the internal-combustion engine in a timed relationship therewith (half speed in the illustrated: embodiment). The rotation of rotorGRvaries the flux cutting windings GWl and GW2, thus generating an A.C. signalvhaving a frequency and an amplitude which are functions of engine speed, The .wave form of this; signal is preferably modified,- aswill be explained-m moredetail, hereinafterbythe R4 D 2 circuit and im,

. pressed across R1.--

j Operation is-as' follows:

Upon closing the ignition switch SW, the. D;C.' poi tential of battery B1 is applied across the transistor base-f collector circuit, which 'includes theLC tank circuit and R1 series-connected therewith. The parameters of;

R1 and R2'(e.g., 1009 .and 200tl, respectively) arejsuch that a small biasing potential of about- 1 v. is developed; across base B-collector C. by the voltage drop across R2.

'lhe generator G produces an.A.C'. Qsignal (across wires 3 and 7) having the wave shape X'-,('Fig.;2) or; some what truncated sine wave. The actionof D2 "and R4, limit the negative excursions of this A G sigIiaI, cutting oif the dashed portion of-wave'X.

" The signal of a wave shape as "indicated by the solid line portions of wave X causes a potential in accordance therewith to'be developed across resistor R1, which varying potential modifies the current through R2 and thus the potential between base B and collector C of transistor JT. At a predetermined point, referred to and illustrated as the trigger point (e.g., 3 v.), across wires 5 and 7, the net biasing potential becomes such that transistor J T conducts heavily, initiating oscillation in the LC tank. This trigger point value may be varied as desired by adjustment of rheostat R2. With a capacitance of about 50 to mfd, at C, the LC tank will provide an A.C. signal at a frequency of about 15 kc., the amplitude of which is stepped up by the transformer action of T to a potential of about 10 to 15 kv. This oscillation, indicated by the wave form Y, continues until the amplitude of the generator signal decreases and wave X becomes more positive than 3 v., the preselected trigger point. Thus, timed pulses of 15 kc. are produced, being initiated by the A.C. generator signal exceeding 3 v. in a negative direction and being cut 01f by the signal falling back below this trigger point level. The duration of this pulse is therefore controlled by the opertion of generator G. At higher engine speeds, the frequency and amplitude of the A.C. generator signal are increased, as shown in Fig. 3. The wave form of the signal is illustrated at XI. The slope of the fiat wave side steepens at this higher speed, thereby intersecting the trigger level at a point earlier along the time base. This action inherently advances the initiation of the 15 kc.

3 in that it prevents overdriving of transistor JT, which would cause modulation of the 15 kc. signal pulses at the rotational frequency of rotor GR.

It is to be noted that the four pole rotor GR is rotated at one. half the engine speed, mat the same speed as the cam shaft. For six and eight'cylinder engines the rotor configuration orspeed is appropriately modified. Also, the wave form of the output of generator G may bemodified from that shown by changing the shape of the rotor and/or faces of pole pieces P1 and P2. More than one spark pulse per cylinder explosion may be obtained by providing several notches in the rotor, instead of providing continuous ignition over each burning cycle, as is the case in the illustrated embodiment. Also, it is to be understood that junction transistors of the PNP as well as the NPN type may be used, if the customary In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

- As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In an ignition system for an internal-combustion engine having a plurality of spark plugs and a distributor having a rotor driven by the engine, said distributor being electrically interconnected to said plugsto supply sequentially thereto a series of timed high-voltage high-frequency electrical pulses; means for generating said series of timed high-voltage pulses comprising an oscillator having an LC resonant tank circuit, a step-up transformer including at least a portion of the inductance of said tank circuit in the primary winding thereof and having a secondary winding electrically connected to said distributor rotor, said oscillator including a transistor and a biasing resistor responsive to a voltage of predetermined amplitude to actuate said oscillator, and a generator driven by said engine in timed relation therewith, said generator being connected to vary the voltage across said biasing resistor and adapted to provide a series of shaped electrical pulses having a wave form the amplitude and slope of the leading edge of which are functions of engine speed, whereby the time of actuation of said oscillator is increasingly advanced as the engine speed increases.

2. In an ignition system as set forth in claim 1, said generator having a rotor and a stator, said rotor being of permanent magnetic material and driven from a cam shaft of said engine, and said stator having poles which are shaped relative to the generator rotor to provide a generally truncated sinusoidal wave form.

3. In an ignition system as set forth in claim 1, said biasing resistor being adjustable to vary the predetermined amplitude at which said transistor oscillator is actuated.

4. In an ignition system as set forth in claim 1, said transistor being connected in a common emitter configuration and having base, collector and emitter electrodes, said biasing resistor being connected between said base and collector, and said tank circuit being series connected with a source of DC. power between said base and collector.

5. In an ignition system as set forth in claim 4, a second resistor serially connected between said tank circuit and said transistor base, said generator being connected across said second resistor.

6. In an ignition system as set forth in claim 5, a diode limiter shunted across said second resistor whereby excursions of one polarity of said electrical pulse wave form are clipped.

7. In an ignition system as set forth in claim 6, a second diode and resistor being serially connected between said collector and emitter.

8. In an ignition system as set forth in claim 7, said components of said LC circuit having parameters which provide a resonant oscillator frequency of approximately 15 to 20 kc.

References Cited in the file of this patent UNITED STATES PATENTS 2,490,960 Hanchett Dec. 13, 1949 2,536,143 Short Jan. 2, 1951 FOREIGN PATENTS 1,137,949 France Jan. 21, 1957 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No., 2,8983%; August 4, 1959 Ralph Lo Jaeschlce It is herebfi certified that error appears in the -printed specification of the above numbered patent requiring correction and that the said Letters K Patent should read as corrected below.

Oolumn 3, line 16, after "customary" insert M polarity reversals are made, o

Signed and sealed this 12th day of January 1960.,

(SEAL) Attest:

KARL .AXLINE. ROBERT C. WATSON Attesting Officer Commissioner of Patents

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