US3211954A - Electronic ignition system with pickup utilizing alternating flux to produce timed pulses of opposite phase - Google Patents

Description

Oct. 12, 1965 c. L. SHANO 3,211,954

ELECTRONIC IGNITION SYSTEM WITH PICKUP UTILIZING ALTERNATING FLUX TO PRODUCE TIMED PULSES OF OPPOSITE PHASE Filed Dec. 20, 1962 5| FIG; 1a 1 I I I I I I T FIG 1 OISTR/BUTOR FIG. 4

\f Char/es L. Shana f\ BY Q MXM A/Tys.

L A INVENTOR.

United States Patent 3,211,954 ELECTRONIC IGNITION SYSTEM WETH PICKUP UTILIZING ALTERNATING FLUX TU PRODEMZE TIMED PULSES 0F 0PPOKTE PHASE Charles L. Shano, Morton Grove, lIll., assignor to Motorola, Inc, Chicago, Ill., a corporation of Illinois Filed Dec. 20, 1962, Ser. No. 246,172 11 Claims. (Cl. 3l5-2l8) This invention relates to ignition systems for internal combustion engines, and more particularly to an improved transistorized ignition system utilizing a magnetic pulsing unit.

Transistorized ignition systems utilizing magnetic pulsing uni-ts offer important advantages over the more conventional type systems which utilize breaker points and condensers. Nevertheless, numerous problems arise in connection with the transistorized systems. For example, at low cranking speeds the triggering pulses generated by the magnetic uni-ts are very weak and hence unsure in their triggering effect. Another difficulty with electronic systems is that transient signals may cause false triggering of the ignition system. Finally, at high speeds the voltage pulses generated in the ignition system may be suflicient to damage the transistor switching devices.

Accordingly an object of this invention is to provide a transistorized ignition system which produces good pulse voltage values at low cranking speeds.

Another object of the invention is to provide a reliable, sure triggering transistorized ignition system utilizing a pulse producing mechanism of rugged construction.

Another object of the invention is to provide a transistorized ignition system which reduces the danger of transient signals triggering the ignition circuit.

Another object of the invention is to provide means in a transistorized ignition system for preventing damage to the switching transistors at high operating speeds.

A feature of the invention is the provision in a transistorized ignition system, of a magnetic pulser producing pulses of alternate polarity With a transistorized switching circuit and a dual coil pickup, and of circuitry connecting the switching circuit to the pickup to trigger the transist-orized system on each of the alternate pulses.

Another feature of the invention is a megnetic pulser unit having a disk magnet sandwiched between a pair of pole plates, each of the pole plates having extensions with oblique pole faces thereon. A pickup member has similar pole faces so that magnetic flux theretrhrough is suddenly weakened at timed intervals, with alternate pairs of the extensions causing alternating flux directions through the pickup member.

Another feature of the invention is the provision, in an ignition system utilizing the above described magnetic pulser, of a single transistor and a pair of diodes for steering the pulses to cause the desired switching of the transistor.

A further feature of the invention is the provision, in such an ignition system, of a pair of switching transistors operating in alternating fashion to present triggering pulses to the high voltage output.

Still another feature of the invention is the provision, in the described ignition system, of protective means connected to the coil windings to shunt excessive voltages from the transistor switching circuits. The protective means may be in the form of varistors, Zener diodes or low pass filters for shunting high frequency high voltage pulses from the transistor switching circuits.

A still further feature of the invention is the provision of a bucking winding opposing the voltage induced in the coil of the pulser unit to reduce excessively high voltages therein and prevent damage to the transistors.

In the drawings:

FIG. 1, is a schematic diagram of the ignition system constructed in accordance with the invention;

FIG. 1a, is a side elevational view of the rotor of the pulsing unit of FIG. 1;

FIG. 2, is an enlarged broken away View depicting in phantom the motion of the pulse generator of FIGS. 1 and la,

FIG. 3 depicts the changes in flux and voltage in the pickup member of FIG. 1;

FIG. 4, is a schematic diagram of a second. embodiment of the invention; and

FIG. 5, is a schematic diagram of still another embodiment of the invention.

In practicing the invention, a pulsing unit is provided with a magnetic rotor assembly. This rotor assembly includes a permanent disc magnet sandwiched between two annular pole plates. The pole plates have interleaved projections extending outwardly therefrom so that as the assembly rotate-s, alternate north and south pole .pieces are presented to two aligned pole extensions of a pickup which completes a magnetic circuit between the alternating pole pieces. As the pole pieces pass by the aligned extensions of the pickup member, the oblique faces on the extensions of the pickup member and the projections: of the pole pieces present a gradually diminishing and then rapidly increasing air gap therebetween.

A center tapped coil on the pickup member has alternating voltages induced therein due to the changing directions of the flux through the pickup member. These pulses are used to trigger a first circuit which in turn triggers the high voltage output circuit supplying high voltage ignition pulses to the internal combustion engine. One version of the first circuits includes a pair of steering diodes and a single switching transistor, while another version includes a pair of transistors alternately switching on and olf. Protection from high voltage damage is afforded to the transistors in various ways, including a pair of varistors connected across the coils, a low pass filter network, and a pair of zener diodes connected across the coils, or by the use of a bucking Winding opposing the voltage induced in the coils.

Referring to FIG. 1, pulses for switching an ignition system for an internal combustion engine 11 are supplied by a magnetic pulsing unit which includes a pickup member 13 and a center tapped coil including windings 15 and 17. Flux is varied through the magnetic pickup member 13 by a rotor assembly 19. Referring also now to FIG. 1a, the construction of rotor assembly 19 may be seen. A disk shaped permanent magnet 21 is sandwiched between two annular pole plates 23 and 25 and the assembly may be driven in sychronism with internal combustion engine 11 on rotary drive shaft 27. With the polarity of magnet 21 as shown in FIG. la, pole plate 23 will provide north poles and plate 25 will provide south oles. p The pole plates 23 and 25 are provided with a plurality of projections 29. The number of projections 29 will be determined by the number of cylinders of the internal combustion engine 111. As will be apparent from the drawings, the projections 25' of the pole plates 23 and 25 are interleaved, and will alternately appear as rotor assembly 19 rotates in the direction of the arrow. Thus each time a pair of projections 29 align themselves with the extensions of pickup member 13, a flux path will be completed through member 13. The direction of this flux path will change as each succeeding pair of projections 29 are aligned therewith.

It will also be apparent that projections 29 are obliquely angled on their ends, as are the corresponding extensions of pickup 13. Because of this, as the projections 29 swing past the extensions of pickup member 13 the gap therebetween will gradually close and then open very suddenly. This is more clearly shown in FIG. 2. A rapid change of flux through member 13 occurs when the air gap is suddenly increased. These flux values are depicted in the top curve of FIG. 3, and the point where the rapid change occurs may be readily seen. Such a change in flux generates peak voltages of opposite polarities in windings 15 and 17, as shown in the lower curve of FIG. 3.

A pair of diodes 31 and 33 connect the ends of Windings 15 and 17 to the base 35 of a transistor 37. The other ends of windings 15 and 17 are connected through a common lead 39 to the emitter 41 of transistor 37. Windings 15 and 17 have voltages generated therein 180 out of phase with each other as indicated by the dots. When the voltage generated in windings 17 is in the direction to cause transistor 37 to conduct, the voltage generated in winding 15 is in the direction to reverse bias diode 33. The following pulse will reverse bias diode 31 and will conduct through diode 33. As a result, every pulse which appears in windings 15 and 17 will cause transistor 37 to conduct.

The emitter electrode 41 of transistor 37 is connected to a positive voltage source 43. The collector electrode 45 of transistor'37 is connected to the primary winding 47 of a high voltage transformer 49. Accordingly when transistor 37 is conductive, primary winding 47 of transformer 49 will be energized to induce a voltage in secondary winding 51. Secondary winding 51 of transformer 25 is connected across bias electrodes 53 and emitter electrodes 55 of output transistor 57. Thus when the voltage is induced in secondary winding 51, output transistor 57 will be turned on. Transistor 57 is connected to the primary winding 59 of a high voltage transformer 61 for energizing the same. Thus when transistor 57 is energized, high voltage will be supplied to transformer 61. The secondary winding 63 of transformer 61 is connected to distributor 13. Upon collapse of the field of high voltage transformer 61, the high voltage spike resulting therefrom is supplied to distributor 13 and hence to internal combustion engine 11 for igniting the fuel therein.

When transistor 37 conducts, current amplification occurs which causes output transistor 57 to conduct and saturate due to phase relationship in transformer 49. As the pulse disappears, transistor 57 suddenly changes from saturation to cutoff. This rapid change of current through primary winding 59 of transformer 61 creates the required flux linkages to cause the necessary high voltage to appear in the secondary winding 63 of transistor 61. The energy to arc across the sparkplug gap in the sparkplug of internal combustion engine 11 is thereby attained. A capacitor 67 connects the collector 69 of transistor 57 to the base 35 of transistor 37 in regenerative fashion such that it aids in speeding up the rate of current rise and decay in the primary 59 of transformer 61.

No temperature compensation is required in the circuit since the input pulse under all conditions of temperature and cranking speed will be adequate to cause transistor 37 to saturate. Because no forward bias is used on either of transistors 37 or 57, the circuit will not be sensitive to random line voltage changes.

During high speed operation, rapidly changing flux in pickup 13 may induce very high voltages in coils 15 and 17. Damage to transistor 37 may be prevented by connecting a pair of varistors 71 and 73 across coils 15 and 17 respectively. The varistors have the characteristic that their resistance is inversely proportional to the voltage applied thereto. Thus at low generator voltage, the resistance will be high with negligible effect on the system. At high voltages, however, the resistances will be low providing a heavy shunt on the coils at high speeds.

Referring now to FIG. 4, a further embodiment of the invention is shown. A pair of transistors 75 and 77 have their emitter electrodes 79 and 31 respectively connected to common lead 39. The collector electrodes 83 and 85 of transistors 75 and 77 respectively are connected to either end of the primary winding 47 of transformer 49.

Primary winding 47 has a grounded center tap 87. Regenerative feedback capacitors 89 and 91 are connected to the base electrodes 93 and 95 of transistors 75 and 77 respectively in the same manner as capacitor 67 in FIG. 1.

The embodiment shown in FIG. 4 should result in improved stability. When the pulse in coil 17 causes transistor 75 to conduct, the pulse in coil 15 will cause transistor 77 to be cut off. The following pulse causes the opposite effect. The two halves of primary winding 47' are connected to their respective collectors 83 and such that when either transistor 75 or transistor 77 is on, the secondary winding 51 of transformer 49 will cause transistor 57 to conduct in the manner previously described.

Varistors 71 and 73 of FIG. 1 could be used in a similar manner in the present embodiment.

Another way of limiting the voltage in either of these two embodiments would be the connection of a low pass filter network in the base circuit for each transistor. This is shown by resistor 97 and capacitor 99 in the circuit for base 93 of transistor 75, and by resistor 101 and capacitor 103 in the circuit for base of transistor 77. As the speed of rotation of rotor assembly 19 increases with the speed of internal combustion engine 11, and hence as the voltages generated in coils 15 and 17 increase, the frequency will increase accordingly. Thus, increasing amounts of the voltage will be shunted from the bases of the respective transistors. For improved filtering, resistors 97 and 101 could be replaced by inductors.

Another method of limiting the voltage generated in coils 43 and 45 is shown in FIG. 5. Here a flux bucking coil 105, which may be wound on the pickup member 13, is provided to oppose the current generated in coils 15 and 17. Thus as the voltage generated increases, the current in the flux bucking coil 105 is directed to set up a field opposing the flux in coils 43 and 45, causing a re duction in the voltage generated therein. A variable resistor 107 and a diode 109 complete the flux bucking coil circuit. Diode 109 in series with bucking coil 107 prevents current flow in the "bucking coil until the voltage across the bucking coil is large enough to overcome the forward bias of diode 109. Resistor 107 is adjusted to provide the correct current magnitude for control of the voltage applied to the bases of transistors 75 and 77.

FIG. 5 shows a further voltage safety device for the transistors. This involves the connection of a pair of zener diodes 111 and 113 across coils 43 and 45 respectively. Output voltages of the coils exceeding the zener breakdown value will cause the diodes to shunt current from the bases of the respective transistors to prevent damage thereto. The flux bucking winding and the zener diodes may each be used without the other to provide some protection against high generated voltages, as may be required.

It may therefore be seen that the invention provides an improved ignition system for an internal combustion engine, which system is reliable and of rugged construction. Good pulse values are obtained at all speeds of the engine, and features are included to prevent overload on the switching transistors at high operational speeds. Finally, transient signals and variations in the power supply will not affect the operation of the system.

I claim:

1. An ignition system for an internal combustion engine, including in combination, high voltage output means supplying high voltage ignition pulses to the internal combustion engine, transistor switching means controlling said high voltage output means, magnetic pulser means operable in synchronism with the internal combustion engine and having a magnetic structure including a pick up member wherein the direction of magnetic flux is alternately reversed in the operation of said pulser means, a pair of windings on said pickup member to produce alternating pulse voltage waves of opposite phase for controlling said transistor switching means, and circuit means connecting said windings to said transistor switching means for controlling same, said circuit means including first and second portions individually connected to said windings and each applying alternate half cycles of the voltage pulse waves induced in one of said windings to control operation of said transistor switching means, whereby said high voltage output means is supplied with control pulses for each of the alternate flux directions produced by said magnetic pulser means.

2. An ignition system for an internal combustion engine, including in combination, high voltage output means supplying high voltage ignition impulses to the internal combustion engine, transistor switching means controlling said :high voltage output means, magnetic pulser means operable in synchronism with the internal combustion engine and having a magnetic structure including a pickup member in which magnetic flux is alternately produced in opposite directions by the operation of said magnetic pulser means, a pair of windings on said pickup member in which alternating voltage pulses are induced for controlling said transistor switching means, and circuit means connecting said windings to said transistor switching means for controlling the same, said circuit means including first and second portions individually connected to said windings and each alternately applying the portion of the alternating voltage pulses of one polarity induced in one of said windings to switch on said transistor switching means, whereby said high voltage output means is supplied'with control pulses for each of the alternate flux directions produced by said magnetic pulser means.

3. An ignition system for an internal combustion engine including in combination, high voltage output means supplying high voltage ignition pulses to the internal combustion engine, a transistor switch controlling said high voltage output means, magnetic pulser means operable in synchronism with the internal combustion engine and having a pickup member wherein the direction of magnetic flux is alternately reversed in the operation of said pulser means, a pair of windings on said pickup member to produce alternating pulse voltage waves of opposite phase for controlling said transistor switch, and a pair of diodes each connected to one of said-windings and connected to the base of said transistor switch for providing bias current thereto, said diodes being poled to block positive pulses from passage therethrough, whereby said diodes will pass alternate half cycles of the voltage pulse waves induced in each of said windings to cause said transistor switch to conduct, whereby said high voltage output means is supplied with controlpulses for each of the alternate flux directions produced by said magnetic pulser means.

4. An ignition system 'for an internal combustion engine, including in combination, high volt-age output means supplying high voltage ignition pulses to the internal combustion engine, a pair of transistors connected to provide current for controlling said high voltage output means, magnetic pulser means operable in synchronism with the internal combustion engine and having a pickup member wherein the direction of magnetic flux is alternately reversed in the operation of said pulser means, a pair of windings on said pickup member to produce alternating pulse voltage waves of opposite phase for controlling said high voltage output means, and circuit means connecting each of said windings to respective ones of the base electrodes of said pair of transistors, whereby said transistors will be alternately turned on to control said high voltage output means during alternate half cycles of the voltage pulse waves induced in each of said windings, whereby said high voltage output means is supplied with control pulses for each of the alternate flux directions produced by said magnetic pulser means.

5. An ignition system for an internal combustion engine including in combination, high voltage output means supplying high voltage ignition pulses to the internal combustion engine, transistor switching means controlling said high voltage output means, magnetic pulser means operable in synchronism with the internal combustion engine and having a rotatable wheel therein with a plurality of oblique pole faces, said pulser means further including a pickup member having a pair of oblique pole faces adapted to mate with successive pairs of said plurality of oblique pole faces on said rotatable member, said pole faces operating to present a gradually diminishing and suddenly increasing air gap therebetween, said magnetic pulser means operating to alternately reverse the direction of magnetic flux through said pickup member, a pair of windings on said pickup member to produce alternating pulse voltage waves of opposite phase for controlling said transistor switching means, and circuit means connecting said winding to said transistor switching means for controlling same, said circuit means applying alternate half cycles of the voltage pulse waves induced in each of said windings to control operation of said transistor switching means, whereby said high voltage output means is supplied with control pulses for each of the alternate flux directions produced. by said magnetic pulser means.

6. An ignition system for an internal combustion engine including in combination, high voltage output means supplying high voltage ignition pulses to the internal combustion engine, transistor switching means controlling said high voltage output means, magnetic pulser means operable in synchronism with the internal combustion engine, said magnetic pulser means including a disc type magnet sandwiched between first and second plates, said first and second plates having alternate interleaved projections thereon, each of said projection-s having an oblique pole face, said magnetic pulser means further including a pickup member having a pair of oblique pole faces for alternately mating with successive pairs of said pole faces on said projections of said first and second plates, whereby the direction of magnetic flux in said pickup member is alternately reversed as said pole faces on said projections of said first and second plates pass by said pole faces on said pickup member, said pole faces presenting a gradually diminishing and suddenly opening air gap in the magnetic circuit, a pair of windings on said pickup member to produce alternating pulse voltage waves of opposite phase for controlling said transistor switching means, and circuit means connecting said windings to said transistor switching means for controlling the same, said circuit means applying alternate half cycles of the voltage pulse waves induced in each of said windings to control operation of said transistor switching means, whereby said high voltage output means is supplied with control pulses for each of the alternate flux directions produced by said magnetic pulser means.

7. An ignition system for an internal combustion engine including in combination, high voltage output means supplying high voltage ignition pulses to the internal combustion engine, transistor switching means controlling said high voltage output means, magnetic pulser means operable in synchronism with the internal combustion engine and having a pickup member in which magnetic fiux is alternately reversed in direction by the operation of said magnetic pulser means, a pair of windings on said pickup member in which alternating voltage pulses are induced for controlling said transistor switching means, circuit means connecting said windings to said transistor switching means for controlling the same, said circuit means alternately applying the portion of the alternating voltage pulses of one polarity induced in each of said windings to switch on said transistor switching means, whereby said high voltage output means supplied with control pulses for each of the alternate flux directions produced by said magnetic pulser means, said circuit means including shunt means connected across said windings on said pickup member and adapted to shunt current from said transistor switching means when the voltage generated in said windings on said pickup member exceeds a given value.

8. An ignition system for an internal combustion engine including in combination, high voltage output means supplying high voltage ignition pulses to the internal combustion engine, transistor switching means controlling said high voltage output means, magnetic pulser means operable in synchronism with the internal combustion engine and having a pickup member in which magnetic flux is alternately reversed in direction by the operation of said magnetic pulser means, a pair of windings on said pickup member in which alternatnig voltage pulses are induced for controlling said transistor switching means, circuit means connecting said windings to said transistor switching means for controlling the same, said circuit means alternately applying the portion of the alternating voltage pulses of one polarity induced in each of said windings to switch on said transistor switching means, whereby said high voltage output means is supplied with control pulses for each of the alternate flux directions produced by said magnetic pulser means, said circuit means including varistor means connected across said windings on said pickup member for shunting current from said transistor switching means when the voltage produced in said windings exceeds a given value.

9. An ignition system for an internal combustion engine including in combination, high voltage output means supplying high voltage ignition pulses to the internal combustion engine, transistor switching means controlling said high voltage output means, magnetic pulser means operable in synchronism with the internal combustion engine and having a pickup member in which magnetic flux is alternately reversed in direction by the operation of said magnetic pulser means, a pair of windings on said pickup member in which alternating voltage pulses are induced for controlling said transistor switching means, circuit means connecting said windings to said transistor switching means for controlling the same, said circuit means alternately applying the portion of the alternating voltage pulses of one polarity induced in each of said windings to switch on said transistor switching means, whereby said high voltage output means is supplied with control pulses for each of the alternate flux directions produced by said magnetic pulser means, said circuit means including means for shunting high frequency pulses produced in said Windings on said pickup member from said transistor switching means, whereby high voltages produced by high speed operation are prevented from damaging said transistor switching means.

10. An ignition system for an internal combustion engine including in combination, high voltage output means supplying high voltage ignition pulses to the internal combustion engine, transistor switching means controlling said high voltage output means, magnetic pulser means operable in synchronism with the internal combustion engine and having a pickup member in which magnetic fiux is alternately reversed in direction by the operation of said magnetic pulse means, a pair of windings on said pickup member in which alternating volt-age pulses are induced for controlling said transistor switching means, circuit means connecting said windings to said transistor switching means for controlling the same, said circuit means alternately applying the portion of the alternating voltage pulses of one polarity induced in each of said windings to switch on said transistor switching means, whereby said high voltage output means is supplied with control pulses for each of the alternate flux directions produced by said magnetic pulser means, said circuit means including zener diode means connected across said windings of said pickup member to shunt current from said transistor switching means when the voltage of said coils attains the zener breakdown value.

11. An ignition system for an internal combustion engine, including in combination, high voltage output means supplying high voltage ignition pulses to the internal combustion engine, transistor switching means controlling said high voltage output means, magnetic pulser means operable in synchronism with the internal combustion engine and having a pickup member in which magnetic flux is alternately reversed in direction by the operation of said magnetic pulser means, a pair of windings on said pickup member in which alternating voltage pulses are induced for controlling said transistor switching means, a bucking winding on said pickup member, and first circuit means connected to said bucking winding to cause same to be operable at a given value of voltage induced in said Windings, and second circuit means connecting said pair of windings to said transistor switching means for controlling the same, said second circuit means alternately applying the portion of the alternating voltage pulses of one polarity induced in each of said pair of windings to switch on said transistor switching means, whereby said high voltage output means is supplied with control pulses for each of the alternate flux directions produced by said magnetic pulser means.

References Cited by the Examiner UNITED STATES PATENTS DAVID J. GALVIN, Primary Examiner.

Claims (1)

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE, INCLUDING IN COMBINATION, HIGH VOLTAGE OUTPUT MEANS SUPPLYING HIGH VOLTAGE IGNITION PULSES TO THE INTERNAL COMBUSTION ENGINE, TRANSISTOR SWITCHING MEANS CONTROLLING SAID HIGH VOLTAGE OUTPUT MEANS, MAGNETIC PULSER MEANS OPERABLE IN SYNCHRONISM WITH THE INTERNAL COMBUSTION ENGINE AND HAVING A MAGNETIC STRUCTURE INCLUDING A PICK UP MEMBER WHEREIN THE DIRECTION OF MAGNETIC FLUX IS ALTERNATELY REVERSED IN THE OPERATION OF SAID PULSER MEANS, A PAIR OF WINDINGS ON SAID PICKUP MEMBER TO PRODUCE ALTERNATING PULSE VOLTAGE WAVES OF OPPOSITE PHASE FOR CONTROLLING SAID TRANSISTOR SWITCHING MEANS, AND CIRCUIT MEANS CONNECTING SAID WINDINGS TO SAID TRANSISTOR SWITCHING MEANS FOR CONTROLLING SAME, SAID CIRCUIT MEANS INCLUDING FIRST AND SECOND PORTIONS INDIVIDUALLY CONNECTED TO SAID WINDINGS AND EACH APPLYING ALTERNATE HALF CYCLES OF THE VOLTAGE PULSE WAVES INDUCED IN ONE OF SAID WINDINGS TO CONTROL OPERATION OF SAID TRANSISTOR SWITCHING MEANS, WHEREBY SAID HIGH VOLTAGE OUTPUT MEANS IN SUPPLIED WITH CONTROL PULSES FOR EACH OF THE ALTERNATE FLUX DIRECTIONS PRODUCED BY SAID MAGNETIC PULSER MEANS.

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