US2389638A

US2389638A - Ignition system

Info

Publication number: US2389638A
Authority: US
Publication date: 1945-11-27
Anticipated expiration: 1962-11-27

Description

Nov. 27, 1945. s. RUBEN 2,389,638

IGNITION SYSTEM Filed April 14, 1942 INVENTOR. Jaimie! Hahn Patented Nov. 27, 1945 UNITED STATES PATENT OFFICE 2,889,638 IGNITION SYSTEM Samuel Ruben, New Rochelle, N. Y. Application April 14, 1942, Serial No. 438,884

8 Claims.

This invention relates to electric ignition systerns.

The present application is a continuation-inpart of my prior filed co-pending application, Serial No. 416,304, filed October 24, 1941.

An object of the invention is to improve electric ignition systems for internal combustion engines.

Other objects of the invention will be apparent from the following description and accompanying drawing taken in connection with the appended claims.

The invention comprises the features of construction, combination of elements, arrangement of parts, and methods of manufacture and operatlon referred to above or which will be brought out and exemplified in the disclosure hereinafter set forth, including the illustrations in the drawins.

In the drawing:

Figure 1 illustrates an ignition system embodying features of my invention; and

Figures 2, Sand 4 show modifications,

The present invention relates to an ignition system utilizing an alternating current source of substantially constant frequency in combination with a circuit which is thrown in and out of resonance in synchronism with the operating cycles of an internal combustion engine in such a manner as to develop a high alternating'voltage during resonance, the voltage being used to produce spark discharges at the spark plugs of the engine.

Referring to Figure 1 which shows an ignition system suitable for a nine cylinder aircraft engine, the source of ignition current is an alternating current generator or alternator l driven by a motor 9 supplied with power from any suitable source such as the battery circuit of the airplane. Alternator I0 generates an alternating current of substantially constant frequency. The frequency may be selected to be that most desirable for the conditions under which the engine is required to operate and preferably should be sufficiently high to provide two or more current oscillations during a spark discharge. The most suitable frequencies may fall within the range of 1,000 to 1'0;000 cycles per second, a 2,500 cycle generator being quite suitable.

' The alternating current from generator I0 is stepped up to a higher voltage such as about 1,000 volts by transformer II. The secondary H of transformer ll feeds a series resonant circuit I8 to vary the magnetic reluctance of the core and thus vary the inductance of winding I2. Rotor I6 comprises a disc of soft iron or other suitable magnetic permeable material provided with nine evenly spaced notches I! about its periphery andstationary iron core l5 has at the end of each of its arms three integral teeth 8 so spaced in relation to the periphery of rotor l6 that during the rotation of the rotor the teeth on both arms will come opposite six of the notches I! simultaneously. The disc I6 is driven by the engine at one-half engine speed so that during two complete revolutions of the engine which constitutes one firing cycle, there are nine times during which notches 11 come opposite to teeth 8, thus producing nine minimum inductance periods for inductance l2. The series resonant circuit comprising inductance l2 and condenser I3 is tuned to resonate at the frequency of alternator l0 when these minimum inductance points are reached.

A conductor I8 is connected to the series resonant circuit between inductance I2 and condenser l3 and extends to the rotary contact arm 20 of distributor l9. During the resonance periods just described a high alternating voltage will be developed on conductor [8, this voltage being much higher than the potential difference across secondary l4. Thus it may amount to 10,000 volts or more.

Distributor [9 comprises a frame 22 of insulating material having a series of nine evenly spaced molded-in conducting segments 23 distributed around its inner periphery. The inner periphery is cut with gear teeth and the rotating arm 20 of the distributor carries a toothed pinion wheel 2| at its end which rolls on the inner periphery of the distributor frame making contact with the segments 23 as it passes over them. Distributor arm 20 is driven in synchronism with rotor It; at one-half engine speed and is so positioned relative to the rotor notches that pinion gear 2! is substantially in the middle of a contact segment 23 when notches l1 come opposite teeth 8. Thus the rotating distributor contact is in contact with one of the stationary segments 23 each time the circuit reaches resonance. v

Segments 23 are connected by conductors 24 through the cable manifold of the ignition system to spark plugs 21 of the engine, the outer electrodes of the spark plugs being grounded to the frame 28 of the engine in the usual manner A series resistance 26 is preferably connected in series with each of conductors 24 near the spark plug terminal to reduce the initial discharge current density and thus reduce the erosion of the spark plug electrodes.

In one circuit arranged according to the present invention using a 2,500 cycle generator condenser l3 had a capacitance of .001 microfarad and the total inductance of the resonant circuit was 4.06 henrys. The primar of the transformer had 1,000 turns on a 4;" square iron core with a "secondary of 6,000 turns. The variable inductance I2 comprised 5,500 turns on a iron core section and the minimum gap between the rotor and stator 01 the variable core was about 3 mils,

In the operation of the system generator III of the motor generator set supplies an alternating potential across the output terminals of transformer ll. Rotor l6 rotates at one-half engine speed and when notches I! come opposite teeth 8 to increase the air gap of the core IS, the resonant circuit comprising inductance I2 and condenser I3 is brought into resonance at the frequency of the alternating current, thus generating a high alternating voltage on conductor I8. This alternating voltage preferably lasts for several alternating current cycles and is sufficient to provide a spark of the necessary duration at one of the spark plugs of the internal combustion engine. Distributor 19 connects the spark plugs to the resonant circuit in sequence and with such timing in relation to the position of notches I! that one of the spark plugs is connected to the resonant circuit just before a resonance peak is reached so that pinion gear contact 2| is not required to make and break a circuit carrying any substantial current, the current being developed in the circuit only after the connection has been made and being completed before the contact passes off the stationary segment.

The present system is suitable not only for aircraft engines, but also for other internal combustion engines such as those for tanks and automobiles. 4

The system provides a high voltage sparking impulse which can be accurately timed and the timing of which is not subject to slow change due to mechanical wear of cams or other parts.

Where it is desired to have a means for advancing or retarding the spark, this can be readily provided for by mounting stator [5 of the variable inductance for a limited degree of rotation so that teeth 8 may be advanced or retarded with respect to the position of notches l1.

Instead of periodically variable inductance l2 it is contemplated that in some instances inductance I 2 may be made of constant inductive value and that condenser [3 may be shunted with a relatively small capacitance variable condenser comprising a rotary plate and a stationary plate adapted to vary the resonant frequency of the circuit by varying the capacitance.

Figure 2 illustrates a modification of the ignition system wherein the inductance is varied by short-circuiting a portion of the inductive Winding to bring the circuit into resonance. The circuit is otherwise generally similar to that of Figure 1. In the circuit of Figure 2 the secondary winding Id of transformer ll feeds a series resonant circuit comprising an inductance 30, an inductance 3i and condenser l3, all in series across the output terminals of transformer secondary M. A pair of contacts 33 are connected across inductance 30 to short-circuit this inductance when the contacts are closed. These contacts are periodically closed by rotary cam 32 driven by the engine at such speed as to close the contacts each time a spark is required. As long as contacts 33 are open inductance 30 forms part of the output circuit of transformer secondary I4 and the circuit is not in resonance with the A. C. voltage developed across the secondary winding. Whenever contacts 33 are closed by cam 32, however, in-

ductance 30 is short-circulted and thus effectively removed from the circuit. Inductance 3| and capacitance l3 are of such values as to bring the circuit into resonance with the A. C. voltage under these conditions. Thus, each time contacts 33 are closed a high potential is developed on conductor IE to produce a spark at one of the plugs in the same manner as described in connection with Figure 1.

Since whenever contacts 33 are open the circuit is immediately thrown out of resonance, a high potential is prevented from developing across the contacts and, therefore, substantially no sparking or arcing at the contacts is experienced.

Figure 3 illustrates a further modified system which is generally similar to Figure 2 except that a condenser 40 is connected in the series resonant circuit in place of inductance 30 to throw the circuit out of resonance. In this case the circuit is brought into resonance when condenser 40 is shunted out by the closing of contacts 33 driven by cam 32.

Figure 4 illustrates a system in which a variable inductance 50 has its inductance varied by varying the air gap of a magnetic permeable core. In this figure the series resonant circuit comprises inductance 50 and condenser l3 which are connected in series across the output of transformer II. Inductance 50 is wound on a soft iron core 5i having a movable section 52 which is moved toward and away from the end of stationary core 5| by cam 32 driven by the engine. As the air gap is decreased, the inductance is thereby increased to bring the circuit into resonance at the point of minimum air gap. Spring 54 normally maintains the air gap at its widest point. Core 52 is mounted on a magnetic permeable plate 53 carried on the end of the cam operated arm pivoted at 55. Thus, when the high points of the cam engage the arm, the core 52 and its associated plate 53 are moved closer to the ends of the stationary core and its magnetic return path to decrease the air gap and increase the inductance and bring the circuit into resonance.

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. An ignition system for an internal combustion engine comprising a source of alternating current, a series resonant circuit fed thereby and having reactances therein comprising a capacitance and inductance in series, a spark distributor circuit connected to the common junction of said capacitance and inductance, and means for periodically varying one of said reactances to bring said resonant circuit periodically into resonance with said source of alternating current.

2. An ignition system for an internal combustion engine comprising a source of alternating current, a series resonant circuit fed thereby comprising a capacitance and an inductance in series, a spark distributor circuit connected to the common junction of said capacitance and inductance, said inductance being variable and means for periodically varying said inductance to bring said resonant circuit periodically into resonance and thereby develop a high voltage at said common junction.

3. An ignition system for an internal combustion engine comprising a source of alternating current, a series resonant circuit fed thereby comprising a capacitance and an inductance in series, a spark distributor circuit connected to the common junction of said capacitance and inductance, said inductance being variable between a maximum and a minimum value, said resonant circuit being in resonance with said alternating current when said inductance is at its minimum value, and means for periodically bringing said inductance to its minimum value at substantially equally spaced sparking intervals.

4. An ignition system for an internal combustion engine comprising a source of alternating current, a series resonant circuit fed thereby comprising a capacitance and an inductance in series, a spark distributor circuit connected to the common junction of said capacitance and inductance, said inductance having a core with a variable air gap and means for periodically varying said air gap to bring said resonant circuit periodically into resonance with said alternating current at substantially equally spaced sparking circuit into and out oi resonance with said alternating current.

6. An ignition'system for an internal combustion engine comprising a source oi. alternating current, a series resonant circuit fed thereby, and a spark distributor circuit connected to a point in said resonant circuit of high resonant voltage and means for periodically short-circuiting a reactance in said resonant circuit to periodically vary the resonant frequency of said circuit into and out of resonance with said alternating current.

7. An ignition system for an internal combustion engine comprising a constant frequency A. 0. generator, a series resonant circuit comprising an inductance and a capacitance fed thereby, said inductance having a stationary core with poles thereon and a rotor adjacent said poles having points of difierent minimum spacing from said poles whereby the air gap in the magnetic circuit of said inductance is varied by rotation of said rotor, said circuit being in resonance with said A, 0. generator at a predetermined air gap width only whereby said circuit is brought in and out of resonance periodically by said rotor, and a spark distribution circuit connected to a point of said resonant circuit of high resonant voltage.

8. An electric ignition system for an internal combustion engine comprising a source of alternating current, a series resonant circuit energized thereby, a series of spark plugs, a distributor for connecting said spark plugs sequentially to. a point of high resonant voltage in said resonant circuit, and means to produce periodic discharges in said plugs comprising a reactance in said resonant circuit and a device for varying said reactance periodically for periodically bring ing said circuit into resonance with said alternating current source.

SAMUH RUBEN.