US3496920A - Flywheel generator for charging the capacitor of a capacitor discharge ignition system - Google Patents

Description

.Feb. 24, 1970 c. L. SHANO E AL 3,496,920.

FLYWHEEL GENERATOR FOR CHARGING THE CAPACITOR OF A CAPACITOR DISCHARGE IGNITION SYSTEM Flled March 6, 1968 PULSE GEN.

LEVEL D51. 90

INVENTORS. DANIEL BOROVIK I CHARLES SHANO m W M ATTORNEYS.

United States Patent U.S. Cl. 123-148 4 Claims ABSTRACT OF THE DISCLOSURE The flywheel of an internal combustion engine has a ring gear about the periphery of it which induces a voltage in a variable reluctance pickup. A rectifying circuit connects the induced voltage to the ignition capacitor for charging the same after it has been discharged in synchronism with the engine through the ignition coil either by the operation if conventional ignition points or through an electronic trigger.

Background of the invention This invention pertains to a capacitor discharge ignition system for an internal combustion engine and more particularly to a unique device for charging the ignition capacitor after it has been discharged.

In the past ignition systems where the ignition capacitor has been electronically discharged have been complicated by the fact that circuitry must be provided for charging the ignition capacitor from battery potential. Furthermore, it is desirable that the energy stored in the discharge capacitor of the ignition system be independent of battery voltage. This is especially true in internal combustion engines which must operate continuously in remote areas such as along natural gas or fuel oil pipelines. These engines in many instances are remotely controlled from a location some distance from the engine. They are started, for example, by a potential source coupled to the engines directly from the central station. Their reliability, however, is reduced because of the dependence of the ignition system on local batteries.

Summary of the invention It is an object of this invention to provide a capacitor discharge ignition system for an internal combustion engine in which the ignition capacitor is independent of any battery for maintaining a charge thereon.

It is another object of this invention to provide a capacitor discharge ignition system for an internal combustion engine which is relatively simple and inexpensive to manufacture.

In one embodiment of this invention a capacitor discharge ignition system for an internal combustion engine is characterized by a flywheel which has a ring gear about the periphery thereof and which is driven past a plurality of variable reluctance pickups to induce a voltage in the pickups for charging the ignition capacitor. The variable reluctance pickups are connected in series to insure that there is suflicient induced voltage at low engine rpm. to charge the capacitor. A Zener diode circiut is connected across the ignition capacitor to limit the induced voltage from the pickups at high engine rpm. to prevent excessive charging thereof. The flywheel generator can be used in an ignition system in which the ignition capacitor is discharged by the operation of ignition points in the conventional manner, to provide a pulse for gating on an electronic switch, which discharges the capacitor through the ignition coil. The flywheel generator can also be used in an ignition system where both advance and distribution is provided electronically. In one typical circuit, the flywheel in addition to having the ring gear around the periphery of it also carries a flux varying element. The flux varying element induces a voltage in a magnetic pickup, which rises to a given level at a rotational position of the flywheel that varies in accordance with the speed of rotation of the same. A level detector is responsive to the voltage produced by the coil at the given level to energize a pulse generator which operates a semiconductor trigger to discharge the ignition capacitor through the ignition coil.

Description of the drawings FIG. 1 is a schematic wiring diagram illustrating an ignition circuit in accordance with this invention;

FIG. 2 is an expanded side elevation view of a portion of a flywheel generator in accordance with this invention; and

FIG. 3 is a schematic wiring diagram of a second embodiment of an ignition circuit utilizing the principles of this invention.

Detailed description Referring to the drawing, FIG. 1 illustrates an ignition system for an internal combustion engine, which includes an ignition coil 10 having a primary winding 12 and a secondary winding 14. The secondary winding 14 may be coupled to the center post of a distributor as is wellknown in the art. A silicon controlled rectifier 16 is connected in series with an ignition capacitor 18, which is across the primary winding 12 of the ignition coil 10. A diode 20 is connected across primary winding 12 and serves to reduce the amplitude of current reversals in the ignition coil secondary winding 14. This reduces the amount of electromagnetic radiation produced by the ignition coil and results in a corresponding reduction in radio interference and noise.

Silicon controlled rectifier 16 is triggered in synchronism with the internal combustion engine by pulses applied to the gate 16a thereof. These pulse are coupled to the gate 16a by means of a transformer 21 having a secondary winding 24 coupled between the gate 16a and the cathode of rectifier 16. Transformer 21 has a primary winding 26 which is connected through resistor 28 and ignition switch 30 to the battery 32. The opposite end of the primary winding 26 is connected to ground by intermittently operable breaker points 34. Breaker points 34 may be the well-known mechanical type breaker points synchronized with engine operation. A diode 36 connected across primary winding 26 of transformer 21 damps out reverse current transients.

When capacitor 18 is charged to the desired firing potential and silicon controlled rectifier 16 is fired by a pulse supplied to the gate 16a, capacitor 18 discharges through primary winding 12 of ignition coil 10. This produces a high voltage pulse in secondary winding 14, which is applied to the distributor for igniting the fuel in the cylinders of the internal combustion engine. Transients which could possibly fire the silicon controlled rectifier 16 at the wrong time are damped out by the diode 36.

In accordance with the principles of this invention, a unique generator is used to charge the capacitor 18 subsequent to it being discharged by the silicon controlled rectifier 16 through the ignition coil 10, The generator includes the engine flywheel 40, which is coupled to and driven by the internal combustion engine. Position in a spaced relation to the flywheel 40 is a variable reluctance pickup 42. About the circumference or periphery of the flywheel 40 is a ring gear 44 having a plurality of teeth. As shown in FIG. 2, the variable reluctance pickup includes a plurality of magnets 46 interposed between core laminations 48. Windings 50 are wound around the core laminations 48 so the induced voltage is additive and in a manner to connect the individual magnetic pickups in series. The individual laminations 48 are spaced so that the change of reluctance in each winding caused by flywheel rotation is in phase so that the output of the gen erator is the arithmetic sum of the voltage induced in each winding. As the flywheel 40 rotates, the teeth 52 of the ring gear 44 causes the reluctance of the flux path through the core laminations 48 to vary in a manner that produces a sinusoidal voltage in the windings 50. The output from the pickup 42 is coupled by transformer 54 to a full wave rectifier 56. The output of the rectifier 56 is coupled by resistor 58 to the ignition capacitor 18. In some operations, the transformer 54 can be eliminated, and the generator may be such that a half wave rectifier can -be used without deviating from the scope of this invention.

It is necessary that the storage capacitor by fully charged from the firing of one cylinder of the engine to the firing of the next cylinder, This means the flywheel generator must develop enough energy to charge capacitor 18 in a portion of a revolution of the flywheel. This can vary, for instance, from one charge per revolution for a one cylinder engine, to two for a two or four cylinder engine, to four per revolution for an eight cylinder engine. Because the output voltage is dependent on the velocity of the teeth past the pickup, it is necessary, in order to get suflicient charging potentials at a low flywheel r.p.m., to connect the pickups in series as shown in FIG. 2. At high engine speed, however, it is necessary to limit the voltage output of the generator to avoid damaging the ignition capacitor 18 with overvoltage. To accomplish this, a voltage limiting network 68 comprising three Zener diodes connected in series is connected across the ignition capacitor 18. In a typical operating installation the charge on capacitor 18 is in the area of 400 volts. It is, therefor, desirable to have the voltage limiting network calibrated to maintain the charge on the capacitor 18 substantially in this area.

In operation, initial cranking of the engine during starting causes the flywheel 40 to induce a voltage in variable reluctance pickup 42 to charge the ignition capacitor 18. During cranking the points 34 are closed grounding the primary 26 of transformer 21. Subsequent opening of the points generates a pulse in secondary winding 24 of the transformer to trigger silicon controlled rectifier 16. Triggering of the silicon controlled rectifier 16 discharges the ignition capacitor 18 through the ignition coil to produce a firing pulse for the engine. It can be seen therefore that compared to other more complicated networks for charging the ignition capacitor 18, the charging circuit of this invention is extremely simple and therefore relatively inexpensive to manufacture.

FIG. 3 illustrates another type of a capacitor discharge ignition system using the flywheel generator of this inven tion for charging the ignition capacitor. The circuit shown is for use with a four cylinder engine with a four stroke cycle. Thus two cylinders will go through their power stroke for each revolution of the engine flywheel. It is to be understood, however, that this ignition system can be adapted to engines of other numbers of cylinders within the scope of the invention. Each of the cylinders of the engine is provided with a spark gap or spark plug 6265 and separate ignition coils 67-70. The secondary windings of each of the coils are connected across their respective spark gaps.

A silicon controlled rectifier 72 connects the parallel connected primary windings of the ignition coils 68 and 70 in series across the ignition capacitor 75. Similarly, a silicon controlled rectifier 74 connects the parallel connected primary windings of ignition coils 67 and 69 in series across the ignition capacitor 75. Of the two cylinders associated with the ignition coils 67 and 69, one is ready to be fired and the other is on its exhaust stroke. Thus, only the cylinder to be fired is affected by the pulse through the ignition coils 67 and 69. This is also true of the ignition coils 68 and 70. Accordingly, two cylinders at a time are fired, one of which is on exhaust stroke and consequently is not affected.

In this system, two magnetic pickup units 81 and 82 are used in association with a single flux varying element 83 on the engine flywheel 85. As the flywheel 85 rotates, the flux varying element 83 will cause a change in flux in the windings 81 and 82 to generate a potential therein. The flywheel 85 rotates in a direction of the arrow in FIG. 3 so the pointed end of the flux varying element 83 passes by the pole pieces of the magnetic pickups 81 and 82 first. The space between the flux varying element 83 and the magnetic pickups 81 and 82 will decrease at a gradual rate until the stepped portion 86 of the flux varying element passes by the pole piece at which time the gap closes rapidly. At slow speeds, i.e., low flywheel r.p.m., sufficient potential to cause the level detectors 90 and 91 respectively to conduct will not be generated in the magnetic pickups 81 and 82 until the stepped portion 86 passes by them. That point at which the level detectors conduct is when the generated potential in the magnetic pickups 81 and 82 exceed the breakdown voltage of Zener diodes 93 and 93a. At higher speeds, and faster rotation of the flywheel 85, a potential great enough to cause the level detectors to conduct can be generated in the magnetic pickups 81 and 82 prior to the reaching of the stepped portion 86. The effect therefore of the shape portion is to provide electronic spark advance for the engine. An ignition system of this type is described in greater detail in Patent No. 3,356,896, issued Dec. 5, 1967 and assigned to the assignee of this application.

Conduction of the level detectors 90 and 91 applies a pulse to the base of NPN transistors 96 and 96a of the pulse generators 98 and 99. Conduction of the pulse generators 98 and 99 alternately trigger silicon controlled rectifiers 72 and 74 to discharge the ignition capacitor 75.

The flywheel 85 besides carrying the flux varying element 83, which provides the firing pulses for the ignition cylinders and also electronic advance, further carries a ring gear 100 around the periphery thereof similar to the ring gear 44 of the embodiment described in conjunction with FIG. 1. Also a variable reluctance pickup 102 similar to the variable reluctance pickup 42 described in conjunction with FIG. 1 is positionedvin a spaced relation to the teeth 104 of the ring gear 100. These two elements combine to form a flywheel generator for providing a substantially sinusoidal potential, which is rectified in rectifier 106 and coupled by resistors 108 to charge the ignition capacitor 75 subsequent to discharge thereof. Also, as was shown in the ignition circuit of FIG. 1, a voltage limiting circuit 110 comprising series connected Zener diodes is coupled across the ignition capacitor 75 to limit the charge on that capacitor at high engine speeds.

The flywheel generator of this embodiment also provides another important feature. Connected across the output of the rectifier 106 are current limiting resistor and Zener diode 117. Resistor 115 and Zener diode 117 form a step down voltage network for reducing the direct current output voltage of the flywheel generator from the rectifier 106 to between 10 and 14 volts. The output of this step down network is used to provide a DC potential through the resistors 120 and 121 for the direct current circuit of pulse generators 96 and 96a.

The flywheel generator described in conjunction with this 1 embodiment therefore not only greatly simplifies the circuit for charging the igintion capacitor 75, but, by providing the direct current for the pulse generators, makes the ignition system completely independent of the engine battery.

What has been described, therefore, is a relatively simple and inexpensive capacitor discharge ignition system for an internal combustion engine in which the ignition capacitor is independent of the engine battery for maintaining a charge thereon.

What is claimed is:

1. In a capacitor discharge ignition system for an internal combustion engine, including trigger circuit means for discharging the capacitor in synchronism with the engine to produce firing pulses, the combination including, a flywheel driven by the engine, a ring gear having a plurality of teeth, said ring gear being positioned about the periphery of the flywheel, pickup means positioned in a spaced relation with respect to said flywheel, said pickup means including a plurality of core laminations, a plurality of magnets interposed between said core laminations, and a plurality of windings each positioned about a core lamination, said flywheel being driven past said pickup means with said teeth of said ring gear causing the flux path through said core laminations to vary in a manner to produce a voltage in said windings, said windings being series connected and positioned about said laminations so that the voltages induced in each winding are additive, and circuit means connecting said induced voltage from said pickup means to the ignition capactor for charging the same subsequent to the discharge thereof.

2. The capacitor discharge ignition system of claim 1 wherein said circuit means includes rectifier means and voltage limiting means coupled between said rectifier means and the discharge capacitor, said voltage limiting means acting to limit the induced voltage from said pickup means at high engine rpm. to prevent excessive charging of the ignition capacitor.

3. The capacitor discharge ignition system of claim 1 in which the trigger means for discharging the capacitor in synchronism with the engine includes a silicon controlled rectifier having input, output and gate electrodes, and a pulse generating circuit connected to the gate electrode which is responsive to the opening of engine ignition points to energize said silicon controlled rectifier, and wherein the ignition capacitor is connected to the input of said silicon controlled rectifier, and an ignition coil is connected to the output of said silicon controlled 6 rectifier so that said flywheel generates an induced voltage in said pickup means to charge said capacitor with the same being discharged through the ignition coil by said ignition points operating to trigger said silicon controlled rectifier.

4. The capactor discharge ignition system of claim 1 wherein said trigger circuit means includes magneto pickup means including an inductance coil, level detector means, pulse generating means and semiconductor trigger means connected in that order to the ignition coil, and wherein said flywheel has a shaped flux varying portion thereon, said flux varying portion producing a voltage in said inductance coil which rises to a given level at a rotational position of said flywheel which varies in accordance with the speed of rotation thereof, said level detector means being responsive to the voltage produced by said inductance coil reaching the given level to energize said pulse generator means to operate said semiconductor means to discharge the ignition capacitor through the ignition coil, and said ring gear inducing a voltage in said pickup means to charge the ignition capacitor subsequent to the discharge thereof.

References Cited UNITED STATES PATENTS 359,552 3/1887 Bassett. 2,071,573 2/ 1937 Randolph et al. 3,240,198 3/1966 London et al. 3,311,783 3/1967 Gibbs et al. 3,326,199 6/1967 McMillen. 3,356,896 12/1967 Shano. 3,358,665 12/ 1967 Carmichael et al.

LAURENCE M. GOODRIDGE, Primary Examiner US. Cl. X.R. 310; 315-209

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