US3696257A

US3696257A - Electrical pulse source including a movable control element varying the reluctance of a magnetic field through a winding connected to a difference amplifier of a signal processing circuit

Info

Publication number: US3696257A
Application number: US41370A
Authority: US
Inventors: Charles L Shano
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-05-28
Filing date: 1970-05-28
Publication date: 1972-10-03
Anticipated expiration: 1989-10-03

Abstract

A pair of parallel connected transistors have a common input bias network with one of the transistors having its input connected to such bias network through a coil wound on a soft magnetic pole of a permanent magnet to provide a trigger source for actuating an ignition circuit for an internal combustion engine. A small rectangular magnetic disc of a ferrous metal is mounted on the distributor shaft and rotates past the end of the coil magnet. The flux changes generate a sharp voltage change at the time that the peak of the disc moves past the magnetic pole and an output voltage appears across the collectors of the transistors. A third transistor has its input elements connected to the collectors. A timing network connects the third transistor to a control transistor, the output of which is connected to turn off a normally ''''on'''' switching transistor. The switching transistor establishes a square-wave output triggering signal to actuate the ignition system. The timing network prevents false conduction of the control transistor and establishes an unambiguous control of the precise timing and firing point.

Description

United States Patent 1 3,696,257 Shane [45] Oct. 3, 1972 [5 ELECTRICAL PULSE SOURCE 3,538,444 11/1970 Adlhoch ..328/ 149 X INCLUDING A MOVABLE CONTROL ELEMENT VARYING THE Primary Examiner-Stanley D. Miller, Jr.

RELUCTANCE OF A MAGNETIC FIELD THROUGH A WINDING CONNECTED TO A DIFFERENCE AMPLIFIER OF A SIGNAL PROCESSING CIRCUIT Inventor: Charles L. Shano, 321 E. Wagon Wheel Drive, Phoenix, Ariz. 85020 Filed: May 28, 1970 Appl. No.: 41,370

US. Cl. ..307/309, 123/148 E, 307/235, 315/209 T, 328/146 Int. Cl. ..H01v 5/00, H03k 3/26 Field of Search ..123/148 E, 149; 315/209; 307/235, 309, 282; 328/146-149; 330/30 D,

References Cited UNITED STATES PATENTS Att0mey-Andrus, Sceales, Starke & Sawall ABSTRACT A pair of parallel connected transistors have a common input bias network with one of the transistors having its input connected to such bias network through a coil wound on a soft magnetic pole of a permanent magnet to provide a trigger source for actuating an ignition circuit for an internal combustion engine. A small rectangular magnetic disc of a ferrous metal is mounted on the distributor shaft and rotates past the end of the coil magnet. The flux changes generate a sharp voltage change at the time that the peak of the disc moves past the magnetic pole and an output voltage appears across the collectors of the transistors. A third transistor has its input elements connected to the collectors. A timing network connects the third transistor to a control transistor, the output of which is connected to turn off a normally on switching transistor. The switching transistor establishes a square-wave output triggering signal to actuate the ignition system. The timing network prevents false conduction of the control transistor and establishes an unambiguous control of the precise timing and firing point.

12 Claims, 5 Drawing Figures ELECTRICAL PULSE SOURCE INCLUDING A MOVABLE CONTROL ELEMENT VARYING THE RELUCTANCE OF A MAGNETIC FIELD THROUGH A WINDING CONNECTED TO A DIFFERENCE AMPLIFIER OF A SIGNAL PROCESSING CIRCUIT BACKGROUND OF THE INVENTION This invention relates to an electrical pulse train source and particularly to such a source for generating a pulse signal in response to movement of a control element with respect to a circuit element.

In various control circuits, the power supplied to the load is desirably controlled in a timed manner and particularly in synchronism with a given movement. This may desirably be established through a magnetic control wherein a movable magnetic member changes the permeability of a flux path and thereby changes the signal in a winding means associated with that path. For

example, applicants copending application entitled Capacitor Discharge Pulse Source, filed on the same day as the present application, discloses a capacitor discharge ignition system in which a triggered capacitor charging circuit is provided havinga convertor charging to a selected voltage capacitor which is subsequently discharged at an appropriate time to fire the appropriate cylinder. of an engine. Although the triggering of such circuits can be made responsive to the opening and closing of the conventional contact points, it is desirably triggered through a contactorless firingor triggering system to avoid the usual problems of contact bounce, contact wear and the like. As applied to an ignition system and the like, the triggering circuitry is severely limited in design as a result of the physical and operating conditions. Thus, the triggering circuit is preferably interconnected to the distributor to provide a proper timed operation. However, the total package must then conform more or less to the usual distributor housing while still generating a pulse signal sufficient to drive the capacitor discharge ignition system into an operating cycle. Further, the triggering circuit must operate over a reasonable range of varying input volt ages and temperatures while maintaining a relatively simple and reliable construction which permits practical mass production and subsequent servicing.

SUMMARY OF THE PRESENT INVENTION The present invention is particularly directed to a reliable and relatively simple solid state electronic circuitry providing a pulsed output in response to, movement of a control element and, in particular, providing a rapidly changing output signal in response to the movement of the control element. Generally, in accordance with the present invention, a difference amplifier includes a pair of parallel connected amplifying devices, such as transistors. The transistors are connected to a common input bias network with at least one of the transistors having its input connected to such bias network through a variable impedance control means, the impedance of which is responsive directly to a mechanically-driven timing element. Rotation of the element thus controls the relative conductivity of the parallel connected transistors and establishes a change across the output which is interconnected into a suitable amplifying and squaring network. Further, the output essentially equals the input voltage less the slight saturation voltage drop of a transistor. Applicant has found that the differential detector and amplifier produces a highly reliable triggering circuit with essentially vertical or sharp leading and trailing edges and in particular, a firing control circuit for a solid state ignition system. Thus, the timing element may be a special disc member attached to the distributor shaft and may even be constructed for mounting with existing distributors with the variable impedance or control signal actuated by the existing distributor cam. This is of substantial practical significance in applying the invention to existing internal combustion engines employed in vehicles and the like. In a particular novel aspect of the present invention, a coil is connected between the base of the one transistor and the bias network or, in an alternative construction, a pair of coils are connected one in each of the base circuits. The coils are wound on a suitable magnetic member and mounted adjacent a rotating magnetic member. One of the members establishes a magnetic field. As applied to an ignition system for a four or eight cylinder engine, a small rectangular magnetic element was mounted to the distributor. The coil and magnet assembly was mounted within the distributor with the rectangular element moving past the endof the coil core. The rotation of the element generates an alternating current wave with the flux variation changing most rapidly as the element approaches and leaves the position of the minimum air gap. At the instance of the minimum air gap, the change in flux will, of course, be zero and then will decrease most rapidly. As a result, the flux wave form creates a relatively high voltage at the instant or time that the element moves the corner or pointed portion of the element past the magnetic core. This, in turn, will provide for a relatively rapid change in the output voltage of the differential detector.

In a particularly satisfactory and novel construction, the amplifying section of the trigger circuit advantageously employs a transistor having its input elements connected to the output elements of the differential transistors and with the output elements connected in combination with a timing network to a control transistor. The output of the control transistor, in turn, is connected to control a normally ,on switching transistor. The timing network allows varying of the conduction of the control transistor to allow control of the maximum repetition rate which can be transmitted by the circuit as well as filtering spurious signals such as may be produced by the differential amplifier. This circuit preferably employs high gain transistors to avoid the necessity for feedback networks and the like. Further, in accordance with a further aspect of the present invention, a voltage reference is maintained across the transistor of the trigger circuit. The voltage regulation need not be highly accurate and the emitterto-base diode of a transistor will provide a suitable referencevoltage. If desired, of course, a series regulator or other regulating circuitry may be provided.

The present invention has been found to provide a highly desirable trigger circuit, particularly adapted to the triggering of a capacitor discharge ignition system and the like in automotive, marine and industrial applications.

The electrical circuit of this invention limits the repetition rate or period of pulse signals and thus produces an inherent speed governing capability. This may, of .course, be desirably applied-to internal combustion engines and the like.-The system can, however, be designed, where desired, to respond to a relatively rapid input without loss of 11 signal, for example, 1,000,000 pulses per-second. 2

The, circuit ofthisinventionrmay also be designed with a sufficient output to permit direct power application, such as the direct. driving and turn-on and turn-off of a transistor in series with. a conventional ignition coil.

The. relativesimplicity of the present invention pen mits interconnection or construction as a small, compact package and therefore permits its direct adaptation and connection'to'existing distributor designs for internal combustion engines. The simplicity also, of

course, contributes to a low cost construction with a consequent application .to commercial considerations. The system of this invention is not particularly sensitive to reasonable variations in supply voltage and thus can be practically. applied to 1. automotive, marine and similar internal combustion engines. Further, the circuit of this invention may employ integrated electronic circuits.

BRIEF DESCRIPTION OF DRAWING The drawing furnished herewith illustrates the best modes, presently contemplated by the inventor for carrying out-the subject invention and clearly discloses the above advantages and features as well as others which will be readily understood from the following description. I

In the-drawing:

FIG. 1 is a schematic circuit diagram showing the application applied to a capacitor discharge ignition system for an internal combustion engine;

FIG. 2 shows wave forms generated at various points in the circuit of the pulse source illustrating the govern Referring to the.-drawing; and particularly to FIG; 1, the. inventionis shown applied to acapacitor discharge ignition system for operating an internal combustion engine 1 which is diagrammatically illustrated, including a plurality; of spark plugs 2 for firing of the appropriate cylinders, not shown. The usual distributor 3 includes the several contacts'connected to the spark plugs 2 and a rotating contact 4 for sequentially interconnecting the spark plugs 2 to the output of a capaci tor discharge ignition system or power supply The illustrated capacitor power supply includes'a storage capacitor 6 interconnected to a battery 7 through a charging circuit 8 which particularly forms the subject' matter of applicants copending application entitled Capacitor Discharge Power Source, which was filed on the same-day as this application. A trigger circuit 9 is interconnectedto control the operation or initiation of the charging circuit 8.v The trigger circuit 9 is a preferred construction of a pulse source in accordance with the present invention and includes a rotating control element 10 for. periodically actuating the trigger circuit 9 to generate a trigger pulse. The element 10 is coupled to the distributor 3 as diagrammatically shown by the dashed coupling 11 toprovide the desired timed interaction as subsequently described. The trigger circuit 9 is separately connected to the battery 7 through an ignition switch 12 while the charging circuit 8 is directly connected to the battery 7. The capacitor 6 is periodically discharged to the distributor 3 through a control switch shown as a silicon controlled rectifier l3 and a pulse transformer 14 which are connected in series across the capacitor 6.

The trigger circuit9 periodically actuates the charging circuit 8 to charge the capacitor 6 to a given level. During the initial turn-on of the charging circuit 8, a pulse is simultaneously applied to the rectifier 13 to discharge the previous charge, on capacitor 6 through thepulse transformer 14 and thereby through the distributor 3 and appropriate spark plug 2 for firing of the engine 1.

The illustrated charging circuit 8 generally includes an energy storage and transfer transformer 15 having a secondary winding connected in series with a capacitor-charging diode 16 to one side of the capacitor 6. The opposite side of the capacitor is connected in series with a bypass and freewheeling diode 17 directly to the opposite side of the secondary winding 15a to bypass the pulse transformer 14 during the charging cycle. This provides for charging of the capacitor. The capacitor is discharged through the control rectifier 13 which is connected in parallel with the secondary winding 15a and the charging diode l6 and thus in series with the capacitor 6 and the pulse transformer 14. The gate 18 of the rectifier 13 is connected to the charging circuit 8 to fire the rectifier during the initiation of the charging circuit 8.

The storage transformer 15 includes a primary winding 19 connected in series with a pair of transistors connected in a Darlington circuit20 to the battery 7. A resistor-capacitor differentiating network 21 interconnects the input of the Darlington circuit 20 to the battery 7 in series with a holding transistor 22. a

The trigger circuit 9, which is more fully described hereinafter, is connected to the input of the Darlington circuit to initiate conduction through the Darlington circuit and transformer primary 19. A holdingtransistor voltage-dividing resistor network 23 is connected in series with the Darlington circuit 20 and in parallel with the primary winding 19. The input circuit of the holding transistor 22 .is connected across a resistor 23a of the 'voltage-dividing resistor network 23. I

Once conduction is initiated through the Darlington circuit, an input bias signal is applied to holding transistor22 which, in turn, provides a holding current tothe input of the Darlington circuit 20 thereby driving the Darlington circuit. into conduction. A cutoff transistor 24 isconnected across the biasnetwork 23 and, in particular, the resistor 23a. A sensing resistor 25 is connected in series. in the circuit of the primary winding 19 to sense the current supplied to the storage transformer 15. At a selected current level, the voltage across the sensing resistor is sufficient to bias the cutoff transistor 24 to conduct, thereby bypassing the holding transistor network 23 and cutting off the conduction thereof. This, in turn, opens the bias supply circuit to the Darlington circuit 20 and resets the charging circuit.

During the flow of charging current, the transformer 15 stores the energy in the transformer core as a result ,of the relative direction of winding of the primary 19 and the secondary 15a and the connection of the blocking diode 16. Upon termination of conduction, the polarity across the windings l9 and 15a reverse, thereby transferring the stored energy into the capacitor. At the initiation of the next cycle, as a result of the triggering of the charging circuit 8 from the trigger circuit 9, the storage of energy in the transformer 15 is again initiated. Simultaneously with the turn-on of holding transistor 22, a pulse is supplied to the gate 18 of the controlled rectifier as a result of a capacitive coupling of the gate 18 to the collector of transistor 22 to fire the rectifier and discharge the previously stored energy from the capacitor 6, thereby to fire the internal combustion engine.

The present invention is particularly directed to the construction of trigger circuit 9 to form a rapidly changing signal level. In FIG. 1, the trigger circuit 9 includes a differential amplifying section or detector 26 controlled by the rotating control element 10 to produce a signal charge in synchronism with the operation of the distributor 3 and the firing of the internal combustion engine 1. The output of the amplifying section 26 is connected to drive an output amplification stage 27 which, in turn, controls the triggering of the charging circuit 8.

- More particularly, the differential amplifying detector 26 includes a pair of similar transistors 28 and 29, shown as N PN-type transistors. The transistors 28 and 29 are connected in a parallel with each in a common emitter configuration with similar individual collectorresistor 30 connected respectively between the corresponding collectors and the positive side of battery 7 through a common supply resistor 31 and switch 12. The emitters are interconnected into each other and in series with a common emitter resistor 32 to the negative or ground line 33 to the corresponding side of battery 7. A bias network for controlling conduction of the transistors includes a pair of series-connected

resistors

34 and 35 in series with a temperature compensation diode 36. The junction of the

resistors

34 and 35 is connected in series with a fixed resistor 37 to the base of the transistor 29. The control winding 38 interconnects the junction of

resistors

34 and 35 to the base of the transistor 28. The control winding 38 is wound on a magnet core 39 and is mounted in flux exchange relationship with respect to the rotating element 10, as more clearly shown in FIG. 3.

In the illustrated embodiment of the invention, a four-cylinder engine is diagrammatically illustrated and the rotating element 10 is shown as a square magnetic element rotating in the plane of the core 39. As hereinafter particularly described, the changing air gap established by the square configuration creates a variation in the magnitude of the flux cutting or passing through the control winding 38, with a particularly rapid change associated with the pointed or corner portion of the illustrated rotating element 10 and a consequent substantial induced voltage in the winding 38. The bias supplied to the transistor 28 is therefore varied in timed relation and in synchronism with the rotation of the element 10. This in turn, varies the relative conduction of the transistors 28 and 29 and provides a voltage difference across the collectors. A pair of output leads 40 connect the collector voltage differenceas the input to the amplifying stage 27.

The stage 27 includes a transistor 41 connected in a common emitter circuit with the emitter-to-base junction connected respectively to the output leads 40. The output of transistor 41 is connected by a filter and timing network 42 as the input to a control transistor 43. Network 42 includes a pair of voltage-dividing

resistors

44 and 45 connecting the collector of transistor 41 to the ground or negative line 33. A timing and filtering capacitor 46 is connected in parallel with

resistors

44 and 45. Capacitor 46 serves to bypass spurious signals generated by the differential amplifier section 26 or the like and also serves as a pulse rate governor as hereinafter noted. The junction of the

resistors

44 and 45 is connected to the base of a cutoff or control transistor 43, the collector of which is connected in series with a load resistor 47 to the positive side of the battery 7 through switch 12 and resistor 31. The emitter of transistor 43 is connected directly to the ground or reference line 33.

When transistor 41 conducts, capacitor 46 is charged and transistor 43 driven on upon the capacitor voltage rising to the turn-on level. As a result of the direct connection of capacitor 46, transistor 43 is driven on essentially instantly. However, when the transistor 41 turns off, capacitor 46 discharges through the resistor 44 and transistor 43. The transistor 43 will be held on for a minimum period and as subsequently described, limits the maximum firing rate to govern the driven speed of engine 1. The transistor 43 controls the cutoff of a normally-conducting switching transistor 48, as follows. A resistor 49 is connected between the resistor 45 and the reference or ground line 33 and thus in parallel with the output circuit of the transistor 43. The base of a switching transistor 48 is connected to the common junction of the resistors 47 and 49. A collector resistor 50 is connected to the collector of transistor 48 and in series with a resistor 51 of the charging circuit 8 to the positive side of the battery 7. Resistor 50 protects the transistor 48 from accidental damage.

The resistors 47 and 49 define a voltage-dividing network providing an input signal to the transistor 48 to cause the transistor 48 to conduct. This, in turn provides a conducting path which holds the capacitor 21 and the input to the Darlington pair connected transistor circuit 20 essentially at ground potential. Consequently, the input power is bypassed from the input of the Darlington circuit 20 and the charging circuit is held off.

When the transistor 41 of the amplifying stage 27 conducts, however, the base of transistor 48 is grounded and the transistor 48 cut off. This, then, allows current to flow through the pulsing capacitor 21 and provides an input pulse to the Darlington circuit 20 which initiates a cycle of operation, as previously described.

A voltage regulating unit 52 is preferably connected in parallel with the power supply to the trigger circuit 9 with v. the current limited by the supply resistor 31. Although any suitable regulator can be employed, the degree of regulation need not be very great. The reference voltage may conveniently be established at approximately five volts for a suitable driving of the several transistors. Consequently, the well-known PNP transistor can be interconnected as a voltage regulator, as shown in FIG. 1. The base and collector of transistor 52 are connected to each other and the base-to-emitter circuit back-biased to establish a regulated voltage drop across the transistor which, in turn, is connected across the supply lines to trigger circuit 9. Alternatively," the conventional Zener diode or any other suitable regulator can, of course, be employed.

, When reverse voltage is applied to the positive and negative trigger unit leads, the shunt regulator transistor 52 or Zener diode becomes forward biased and exhibits a very small voltage drop compared to the voltage drop of resistor 31. The small voltage drop of the regulator prevents damage to the circuit components which it is in shunt with.

The output transistor 48 is protected by the reverse polarity diode in the convertor unit at the same time.

a capacitor 53 is preferably connected across regulating unit 52. Capacitor 53 charges and discharges slowly when switch 12 is closed or opened. When switch 12 is opened, capacitor 53 discharges into the resistance of the trigger circuit and maintains a current flow in series-connected resistors 47 and 49. This maintains conduction of transistor 48 and causes it to turn off slowly to prevent forming of a pulse signal and triggering of. the convertor section when the switch is turned off. When the switch is turned on, capacitor 53 charges through resistor 31 and minimizes a rapid rise of current through resistorv47. Transistor 48 therefore turns on at a slow rate. The action of capacitor 53 is substantially more pronounced during the turn-off of the switch 12. Generally, the capacitor 53 prevents spark generation during the switching of the trigger unit. The capacitor 53 also provides a safety feature when the ignition system is applied to a two-cycle engine which may start inadvertently before the starter is activated because the switch contacts bounce causing rapid opening and closing with subsequent ignition firing since these engines may tend to cause a hazard to the operator when the ignition switch is closed prior to starting of the engine.

The operation of the triggering circuit is briefly summarized with reference to the voltage trace as shown in FIG. 2. At the uppermost part of the figure, a square wave trace 54 is illustrated. This corresponds to the voltage appearing at the output lines 40. When the voltage rises to a relatively positive level, the transistor 41 will be biased to conduct and the output will be transmitted through the filter network 46 to the base of the control transistor 43..

During the period that the transistor 41 conducts, it provides a turn-on signal to the transistor 43 which, in turn, conducts thereby bypassing the transistor 48 causing it to turn oft" and permitting conduction to the input of the Darlington circuit of the charging circuit 8. The voltage thus applied to the base of the transistor 43, is at a maximum level during the periodthat the square wave signal of the difierential amplifier work 42, however, provides a charge source to maintain the transistor 43 conducting until such time as the charge drops below the conduction input level of the transistor. The input signal to transistor 43 is shown by trace 55 and superimposed upon the necessary input level for transistor 43 which is shown by the constant level voltage trace 56. During the positive period of trace 54, a positive input signal is impressed on the transistor 43. When trace 54 goes negative, capacitor 46 discharges. A discharge time is shown by the full line illustration 55 which is at a predetermined time constant depending upon the product of the resistance of the

resistors

44, 45 and the base-emitter impedance of 43 and the capacitance of capacitor 46. If the time constant is reduced, the capacitor will more rapidly discharge through the transistor 43, as shown by the dashed line trace 58. If the time constant is increased, the discharge time will increase resulting in a shifting of the curve in the opposite direction to a typical trace 59 and thereby maintaining the conduction of the transistor 43 for a longer period. This action varies the initiation of the cutoff of the transistor 43, the output of which appears at the collector of the transistor 43 as a square-wave output signal, such as shown in FIG. 2 at 60, 61, and 62 for the

several traces

57, 58 and 59.

When the capacitor voltage intersects with the conduction level line 56 of the transistor 43, the transistor 43 turns off and transistor 48 rapidly switches on. Thus, while the transistor43 is conducting during both the output of the differential amplifier 26 and the timing period established by the filter network 42, the transistor 48is held off and its collector will be at a relatively high voltage with respect to ground or reference. At the time that the capacitor 46 discharges to the conduction level of the transistor 43, resulting in a turn-off of transistor 43 and turn-on of transistor 48, the collector voltage of transistor 48 will rapidly drop to essentially the reference level, equalling such voltage less the saturation voltage of transistor 48 and a small drop-across the small resistor 50. This level is maintained until the differential amplifier 26 again establishes a positive voltage signal at lines 40 and initiates a similar cycle, with the transistor 48 cut off at the point of intersection causing the initiation of the charging circuit 8 and the simultaneous discharge of capacitor 6. The output of the transistor 48 is a squarewave signal with the leading control edge of the pulse signal directly dependent upon, the output of the differential amplifier 26 and the time constant of the filter network 42.

The filter network 42 will thus not only remove spurious signals generated within the differential amplifier 26, but its time constant will determine the length of time or period that the output signal of the trigger circuit 9 is in the off condition and thereby provide highly accurate means of limiting the maximum output repetition rate of the trigger circuit. This, in turn, effectively causes the device tofunction as a governor or speed control means since above the maximum repetition rate established by 46, 44 and 45, the transistor 48 will remain off and thereby prevent operation of circuit 8.

The output stage provided by the cascaded

transistors

43 and 48 is sufficiently great to establish a square-wave output signal having a rise and fall time at the leading andtrailing edges in the nano-second region. This, in turn, provides a highly desirable triggering input to the charging circuit 8.

The triggering circuit 9 of this invention is a relatively simple circuit employing a minimum number of reliable components such that it can be conveniently packaged as an integrated unit for mounting directly within a distributor. For example, referring particularly to FIG. 3, a distributor housing 63 is diagrammatically shown. Within the housing 63, a small trigger housing 64 is mounted to one side of the distributor shaft 65. Within this trigger housing 64, the several resistors, capacitors and other components of the trigger circuit, such as shown in FIG. 1, can be mounted, particularly including the winding 38 and core 39 with an appropriate magnet 66 coupled to core 39, as diagrammatically illustrated. The winding 38 is wound about the core 39 with the end of the core 39 located in radial alignment with the distributor shaft 65. The square rotating element 10 is mounted on the distributor shaft 65 and rotates in a desired time movement with respect to the core 39.

The square element 10 provides highly accurate location of the control points defined by the corners of element 10, and thereby permits turn-on and turn-off of the triggering amplifying stages.

The connection of the transformer coil 38 is such that the voltage induced in coil 38 is negative when the cam corner or peak is passing the core 39 and thus going through the minimum air gap position. The relative negative signal drives the base of the transistor 28 negative, and thus tends to drive the transistor 28 off. As a result, the collector voltage will rise relative to the collector of the fixed driven transistor 29. The output voltage across leads 40 is then of polarity to drive the transistor 41 on and complete the previously described cycle. Although the circuit can be made to operate in synchronism with normal breaker point operation, the illustrated embodiment of the present invention is constructed to maintain generation of a pulse upon turn-off of the trigger circuit and initiation of the charging cycle. Further, the ignition sensing may be directly responsive to existing distributor cams and thereby readily adapted to existing automotive, marine and other multiple cylinder internal combustion engines.

In FIG. 3, a modification to the control winding 38 is shown to permit alternative construction with respect to a differentiating amplifier 26. Thus, the winding 38 may be provided with a center tap 67 which may be connected to the junction of the voltage-dividing bias network resistors 34 and 35-of FIG. 1. The resistor 37 may be eliminated and the opposite ends of the winding 38 may be connected to the respective bases of the transistors 28 and 29. This would result in opposite bias potentials applied to the bases and oppositely varying the conductivity in response to the rotation of the rotating element 10. The opposite conductivity would result in a corresponding change in the output of the transistors 28 and 29 appearing at leads 40.

In the tapped coil system, the transistor 29 would be driven further into saturation to insure that its base voltage remains relatively constant, thereby further insuring the driving on of the transistor 41.

In the embodiment of the invention illustrated in FIG. 1, the ignition switch 12 is connected directly to only the trigger circuit 9 with the charging circuit separately connected to the battery 7. When switch 12 is opened, the voltage to circuit 9 drops to zero and positively holds the circuit off. In certain alternator systems wherein a charging alternator maintains the battery at a selected voltage level, the open ignition switch voltage will not drop directly to zero, particularly with a trigger unit such as forms the subject matter of the present invention which maintains a small load on the ignition switch. A circuit employing a trigger circuit of this invention is schematically shown in FIG, 4, modified to insure tum-off of the ignition system upon opening of an ignition switch 68. Although the trigger unit may be identical to that of FIG. 1, a modified circuit employing an integrated amplifier is illustrated in FIG. 4. The charging and output circuit shown in block diagram in FIG. 4 is connected to the positive side of the battery 7, as in FIG. 1. The modified trigger circuit 9 is connected to the contact 69 of the ignition switch 68, the contact arm 70 which is connected to the positive side of the battery 7 and selectively connected with contact 69 for supplying power to the trigger circuit 9. An alternator 71 is provided, the output of which is interconnected through a suitable regulator 72 to maintain a predetermined output voltage during the operation thereof. A rectifying diode 73 connects the output of the regulated alternator 71 to the battery 7.

The ignition switch 68 is a single-pole, double-throw unit having the contact arm 70 interconnected to the junction of the diode 73 and the positive side of the battery 7 to maintain the contact arm at a relatively positive voltage. The switch 68 selectively engages a dead or off" contact 74 and the ignition on contact 69 which is connected to the bias network of the supply of the trigger unit. In FIG. 4, an

output switching transistors

48 and 43 of FIG. 1, are similarly connected to control the charging circuit 8. A pair of input bias resistors 77 and 78 for transistor 75 are connected in series to the on contact 69 and the ground line. The input or base of transistor 75 is connected to the junction of resistors 77 and 78 and the output circuit of transistor 75 is connected to battery 7 and particularly capacitor charging circuit 8 as in the embodiment of FIG. 1.

A voltage-dropping resistor 79 is connected directly between the output of the alternator 71 and the on" contact 69 of the ignition switch 68. In accordance with the embodiment of FIG, 4, a ballast and cutoff resistor 80 is connected between the on contact 69 and the common return line 33.

With the ignition switch 68 turned on, the battery voltage is applied directly to the trigger unit 9 and the output of the alternator 71 is similarly applied directly to the trigger unit 9 through the charging diode 73, thus bypassing the resistor 79 and applying full battery voltage. Under these conditions, the voltage-regulating device maintains a 5-volt supply to the triggering unit. The voltage dividing network consisting of the resistors 77 and 78, which tend to drive the transistor on, requires that the input voltage be maintained at or above 5 volts to provide turn-on to the transistor. When the ignition switch 68 is opened,'the power is supplied from the alternator 71 through the small shut- 1 1 off resistor 79 to the bias network resistor 77-78 in series parallel with the ballast resistor 80. The voltage of the ballast resistor 80 is relatively small compared to the voltage-dividing network resistors 77 and 78 and with the ignition switch off, the voltage-division isessentially controlled by the shut-off resistor 79 and the ballast resistor 80. The network is selected such that the voltage appearing across the ballast resistor 80 and therefore the voltage-dividing network 77 and 78, drops below volts. This positively deactivates the ignition circuit.

Further, in the embodiment of FIG. 4, an integrated circuit amplifier 81 replaces the several separate differential and amplifying transistors 28, 29 and 41 to simplify the circuit construction somewhat. Amplifier 81 may be any suitable unit with a difference amplifying input stage, not shown, such as a 709 operational amplifier of an integrated circuit construction which is manufactured and sold by Fairchild Camera & Instrument which has been satisfactorily applied. The amplifier 81 includes a pair of input terminals connected to sensing coil 82 which is controlled by rotating element 83, as in FIG. 1.

Bias resistors

84 and 85 are connected in series to battery 7 with the common junction 86 connected to the one input of the amplifiers 81 to set the operating point of the integrated circuit. The output of the amplifier 81 is connected to'transistor 76 through a filtering and timing network as in FIG. 1. The network includes a pair of

resistors

87 and 88 connected across the input of the transistor 76 with the junction of the resistor connected to the output of the amplifier 81. An

output circuit capacitor 89 is connected to the amplifier.8l to compensate for the output circuit lag of amplifier 81 and in accordance with the present invention is selected or adjusted with

input resistors

87 and 88 to establish the filtering and the governing of the circuit in the manner of network 42 of FIG. 1. An input capacitor 2 90 is shown connected to amplifier 81 to compensate for input circuit lag.

The trigger circuit of FIG. 4 otherwise functions essentially the same as that of FIG. 1 and no further description thereof is given.

As previously noted, the present invention is particularly directed to establishing a triggering circuit for a capacitor discharge ignition system or the like and has been so described in the above two embodiments.

However, it may be employed to directly drive a load,

for example, as shown in FIG. 5, wherein the triggering unit directly controls the energy through an ignition coil. Thus, in. the embodiment of the invention shown in FIG. 5, the triggering unit 91, shown in block diagram, is connectedto the input circuit of an output transistor 92 which controls the conduction through an ignition coil 93. In the illustrated embodiment of the invention, the ignition transformer 93 includes a primary winding 94 connected in series with control transistor 92 between the positive side of battery 7 and ground. A resistor 95 interconnects the base of the transistor 92 to the positive side of the battery and thus biases the control transistor 92 to conduct and establish a current flow through the primary winding 94 of transformer 93. Trigger unit 91 is constructed as in FIG. 1 or FIG. 4, and the normally-conducting switching transistor, no separately shown, thus holds the base of transistor 92 at ground to prevent conduction. When the control element 10 of the trigger unit. 91 moves a corner of the unit past the core 39 of the pickup coil 38, the triggering unit 91 removes the ground from the base of transistor 92 and permits the transistor 92 to conduct. As a result, transistor 92 is rapidly driven on, providing a pulse of current through the primary winding 94. The secondary winding of the transformer 93 is interconnected through the distributor to the spark plugs and thus applies a firing pulse directly to the engine in synchronism with the rotation of the distributor and the interconnected rotating element 10.

As previously described, the output of the electronic trigger unit is generally a square-wave signal. It, therefore, can be employed in other applications, such as the driving of a tachometer, a digital-type counter, control solenoids and the like whenever it is desired to produce an output in response to a moving control element. The input of the differential amplifier may be from a magnetic transducer, as shown, or any other suitable means, such as a varistor, a thermistor, photocells, thermocouples and pressure-sensitive devices, or the like, which can produce a variable electrical signal responsive to a mechanical movement.

The invention, as illustrated, thus provides a relatively simple and inexpensive pulse-forming, square-wave forming network which can be reliably and inexpensively constructed. The circuitry is completely compatible with integrated circuiting means and thus can be combined with a separate power transistor in chip form to establish breakerless ignition system in a very compact and totally enclosed or contained housing which can be readily mounted within the conventional distributor housing.

Various modes of carrying out the invention are contemplatedas being within the scope of the following claims which particularly point out and distinctly claim the subject matter which is regarded as the invention.

lclaim:

1. An electrical pulse source, comprising a movable control element, a first and a second electronic amplifying means connected in parallel with each other to define a difference amplifier and each of said amplifying means having an output means, an input bias network means connected to both of said amplifying means, said network means including control winding means and a magnetic means establishing a control field through the winding, said control element movable relative to said magnetic means and varying the reluctance of the magnetic path and thereby varying the relative conductivity of said first and second amplifying means, means to move said control element to periodically and alternately couple and decouple the control element with the signal means to correspondingly change the output of the signal means and thereby sequentially establish a first relative conducting condition of said first and second amplifying means and a second different relative conducting condition of said first and second amplifying means, said second relative conducting. condition being of an opposite signal polarity with respect to said firstrelative conducting condition, and an output amplifying and shaping circuit means having a pair of input means connected one each to each of said output means and responsive to the relative conducting conditions of said first and second electronic amplifying means and establishing a series of pulse signals the leading edge of which changes abruptly in response to the change in the conducting condition of said amplifying means and in synchronism with the change in signal polarity caused by the movement of said control element.

2. The electrical pulse source of claim 1, wherein said bias network means including a common voltagedividing means connected to base elements of said transistors, one of said transistors having a base element connected to said voltage-dividing means in series with said winding means and a flux-generating field means periodically coupled to said flux-responsive means by said control element.

3. The electrical pulse source of claim 1, wherein each of said first and second amplifying means including a transistor connected in a common emitter configuration, said bias network including voltage-dividing resistor means having a common bias junction connected to base elements of said transistors, and at least one of said transistors having a base element connected to said common bias junction in series with said coil means.

4. The electrical pulse source of claim 1 wherein each of said first and second amplifying means including a transistor connected in a common emitter configuration, said input bias network means including voltage-dividing resistor means having a common bias junction connected to base elements of said transistors, one of said transistors having a base element connected to said common bias junction in series with said winding means, said control element being a rotating fluxcontrol disc member and having a plurality of equicircumferentially-spaced control portions, said magnetic means being located in the plane of said rotating disc member, said output amplifying and shaping circuit means including an output amplifying transistor having an emitter and base connected one each to collectors of said first and second transistors, a switching transistor having an input means biasing the switching transistor to conduct, and a control transistor connected to said input means to selectively bypass said input means of said switching transistor and having an input means connected to said output amplifying transistor to selectively cut off said switching transistor.

5. The electrical pulse source of claim 4 wherein said input means to said control transistor includes a capacitor connected to bypass spurious signals from said switching transistor.

6. The electrical pulse source of claim 1 wherein said control element is a rotating magnetic disc member having a plurality of equicircumferentially-spaced protrusions, said magnetic means including a permanent magnet core means and said winding means being a coil means wound on said core means, said disc moving in the plane of said core means to vary the magnetic flux passing through said core means.

7. The electrical pulse source of claim 6 wherein each protrusion of the movable control element is defined by a pair of intersecting planar sidewalls defining a sharp edge sequentially and cyclically aligned with said core means.

8. The pulse source of claim 1 wherein said output amplifying and shaping circuit means includes an amplifier with input elements connected one each to the output means of said first and second electronic amplifying means, a switching amplifier means having an input means biasing the switching amplifier means to conduct, and a control amplifier means connected to said input means of said switching amplifier means to selectively bypass said input means and correspondingly cut off said switching amplifier means.

9. The pulse source of claim 1, having a storage capacitor, a charging circuit for said capacitor having a triggered input means to initiate a charging cycle and separate cutoff means to terminate the charging cycle, and means connecting said amplifying and shaping circuit means to said triggered input means'to control initiation of a charging cycle.

10. The pulse source of claim 1, having a storage capacitor, a charging circuit for said capacitor and including an energy storage transformer connected in series with a charging transistor means, said charging transistor means having an input circuit means connected to said output amplifying and shaping circuit means to initiate conduction, a holding transistor means to maintain conduction through said charging transistor means, said charging circuit including means to sense the current in said transformer and to cut off said holding transistor at a selected current level, said energy storage transformer being connected to said capacitor in series with a half-wave rectifying means, and means to periodically discharge said capacitor in timed relation to the movement of said control element.

11. The pulse source of claim 10 .wherein the input circuit means of said charging transistor includes a capacitor connected to a supply means and to the transistor, and said output amplifying and shaping circuit means connects said capacitor to a reference potential means.

12. The electrical pulse source of claim 1 wherein said first and second electronic amplifying means are part of an integrated operational amplifier including a coupling amplifier stage connected to said pair of output means, said amplifying and shaping circuit means including said coupling amplifier stage and having an input transistor and an output switching transistor, a bias network connected to bias said output switching transistor to conduct, said input transistor being connected to said bias network to turn said output transistor off, and a resistor-capacitor coupling network connecting said input transistor to said coupling amplifier stage to actuate said input transistor in accordance with a preselected maximum movement of said control element.

Claims

1. An electrical pulse source, comprising a movable control element, a first and a second electronic amplifying means connected in parallel with each other to define a difference amplifier and each of said amplifying means having an output means, an input bias network means connected to both of said amplifying means, said network means including control winding means and a magnetic means establishing a control field through the winding, said control element movable relative to said magnetic means and varying the reluctance of the magnetic path and thereby varying the relative conductivity of said first and second amplifying means, means to move said control element to periodically and alternately couple and decouple the control element with the signal means to correspondingly change the output of the signal means and thereby sequentially establish a first relative conducting condition of said first and second amplifying means and a second different relative conducting condition of said first and second amplifying means, said second relative conducting condition being of an opposite signal polarity with respect to said first relative conducting condition, and an output amplifying and shaping circuit means having a pair of input means connected one each to each of said output means and responsive to the relative conducting conditions of said first and second electronic amplifying means and establishing a series of pulse signals the leading edge of which changes abruptly in response to the change in the conducting condition of said amplifying means and in synchronism with the change in signal polarity caused by the movement of said control element.

2. The electrical pulse source of claim 1, wherein said bias network means including a common voltage-dividing means connected to base elements of said transistors, one of said transistors having a base element connected to said voltage-dividing means in series with said winding means and a flux-generating field means periodically coupled to said flux-responsive means by said control element.

4. The electrical pulse source of claim 1 wherein each of said first and second amplifying means including a transistor connected in a common emitter configuration, said input bias network means including voltage-dividing resistor means having a common bias junction connected to base elements of said transistors, one of said transistors having a base element connected to said common bias junction in series with said winding means, said control element being a rotating flux-control disc member and having a plurality of equicircumferentially-spaced control portions, said magnetic means being located in the plane of said rotating disc member, said output amplifying and shaping circuit means including an output amplifying transistor having an emitter and base connected one each to collectors of said first and second transistors, a switching transistor having an input means biasing the switching transistor to conduct, and a control transistor connected to said input means to selectively bypass said input means of said switching transistor and having an input means connected to said output amplifying transistor to selectively cut off said switching transistor.

9. The pulse source of claim 1, having a storage capacitor, a charging circuit for said capacitor having a triggered input means to initiate a charging cycle and separate cutoff means to terminate the charging cycle, and means connecting said amplifying and shaping circuit means to said triggered input means to control initiation of a charging cycle.

11. The pulse source of claim 10 wherein the input circuit means of said charging transistor includes a capacitor connected to a supply means and to the transistor, and said output amplifying and shaping circuit means connects said capacitor to a reference potential means.