US3587549A

US3587549A - Ignition system

Info

Publication number: US3587549A
Application number: US800139A
Authority: US
Inventors: Earl R Kebbon; Joel N Ashcraft
Original assignee: Ambac Industries Inc
Current assignee: Ambac Industries Inc
Priority date: 1969-02-18
Filing date: 1969-02-18
Publication date: 1971-06-28
Anticipated expiration: 1988-06-28

Abstract

AN IGNITION SYSTEM FOR AN ENGINE IS PROVIDED INCLUDING A SOURCE OF VOLTAGE, ENGINE FUEL IGNITION MEANS AND CONTROLLABLE SWITCH MEANS FOR SELECTIVELY COMPLETING A CIRCUIT WITH THE SOURCE OF VOLTAGE AND THE ENGINE FUEL IGNITION MEANS, THE SWITCH MEANS INCLUDING MAGNETICALLY SENSITIVE SEMICONDUCTIVE MEANS RESPONSIVE TO A MAGNETIC FIELD FOR ACTUATING THE

SWITCH MEANS TO COMPLETE THE CIRCUIT. A MAGNETIC ROTOR IS EMPLOYED FOR PRODUCING A MAGNETIC FIELD, THE MAGNETICALLY SENSITIVE SEMICONDUCTIVE MEANS BEING RESPONSIVE TO THE MAGNETIC FIELD OF THE ROTOR.

Description

United States Patent 231 972 10/1957 Gilbert Inventors Earl R. Kebbon;

Joel N. Ashcroft, Columbus, Miss. Appl. No. 800,139 Filed Feb. 18, 1969 Patented June 28, 1971 Assignee AMBAC Industries, Incorporated Columbus, Miss.

IGNITION SYSTEM 7 Claims,4 Drawing Figs.

US. Cl. 123/148, 123/149, 315/209 Int. F021) 3/06 Field ofSenrcli 123/148 Reierenoa Cited UNITED STATES PATENTS 2,924,635 2/1960 Sichling et al. 123/1485 3,241,538 3/1966 Hugenholtz l23/l48E 3,297,009 [/1967 Sasaki et al. 315/209 3,335,320 8/1967 Quinn 123/148E Primary Examiner- Laurence M. Goodridge Attorneyl-lowson and l-lowson ABSTRACT: An ignition system for an engine is providedineluding a source of voltage, engine fuel ignition means and controllable switch means for selectively completing a circuit with the source of voltage and the engine fuel ignition means,

the switch means including magnetically sensitive semiconductive means responsive to a magnetic field for actuating the switch means to complete the circuit. A magnetic rotor is employed for producing a magnetic field, the magnetically sensif' tive semiconductive means being responsive to the magnetic field of the rotor.

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FIG. 2.

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ATTYS.

IGNITION SYSTEM The present invention relates to an ignition system suitable for use with internal combustion engines, and, particularly, to improvements in such ignition systems of the class in which the usual breaker apparatus is replaced by electronic circuitry.

in conventional ignition systems, combustible fuel is ignited during sequential timed intervals synchronized with the phase of operation of the engine by means of a breaker and associated breaker points together with a mechanical rotating distributor, in a well known manner. In recent years, systems have been proposed in which the breaker apparatus is replaced by electronic circuitry for performing similar functions in response to electrical timing pulses produced in synchronism with engine operation. The present invention is concerned with such systems in which the mechanical breaker.

and associated breaker points are eliminated.

Many recent ignition systems have employed complex electronic circuitry in order to alleviate the undesirable breaker apparatus. Due to the complex circuitry and deviations from conventional ignition circuits, these systems have not been entirely satisfactory and capable of being substituted for conventional ignition system circuits to replace the breaker apparatus employed in an economical manner. Many of these systems have employed electronic switches and a triggering circuit with trigger coils to actuate the switches to a conductive state for connecting voltage pulses to the spark plugs of the engine. The present invention eliminates the use of such trigger coils and provides a more compact arrangement which is highly reliable. The present ignition system employs simple circuit components and preferably uses the available battery as a source of power. The ignition system of the present invention is also adapted to provide effective ignition despite adverse conditions, such as unclean spark plugs, for example. The present invention is also adapted to provide high engine effciency and is especially adapted for use with engines having a large number of cylinders. Furthermore, thev present ignition system is adaptable to provide a number of ignition pulses to each spark plug during each combustion stroke for better ignition in the engine cylinders.

In accordance with the present invention, a new and improved ignition system with novel features is provided which cooperates to facilitate a compact, economical and reliable ignition system. The present invention employs a source of voltage, engine fuel ignition means for igniting combustible fuel in the engine and controllable switch means for selectively completing a circuit with the source of voltage and the engine fuel ignition means. The controllable switch means includes magnetically sensitive semiconductive means responsive to a magnetic field for actuating the switch means to complete the circuit with the source of voltage and the ignition means. The present invention also employs a magnetic rotor for producing a magnetic field, the magnetically sensitive semiconductive means of the switch means being responsive to the magnetic field of the rotor for actuating the switch means.

Preferably, trigger means is provided which includes the magnetic rotor and circuit means supported by a stator. The magnetically sensitive semiconductive means is preferably a separate device from the switch means, which may be provided by a silicon-controlled rectifier, and the magnetically sensitive semiconductive device is preferably included as a part of the last-mentioned circuit means. In this arrangement, the magnetically sensitive semiconductive device is responsive to the magnetic field of the rotor to produce a control signal in the circuit means. The switch means is provided with a control terminal responsive to the control signal for having the control signal actuate the switch means to complete the circuit with the source of voltage and the ignition means. In the preferred embodiment of the invention, the circuit means includes a sensing circuit operable to produce the control signal when the magnetically sensitive semiconductive device is in the magnetic field of the rotor. The source of voltage preferably employs a battery, which is also connected to the circuit means to supply power to the circuit means for producing the control signal.

Preferably, the engine is provided with a plurality of cylinders and the ignition means provides a spark gap ignition device for each cylinder on the engine. In this arrangement, the ignition system may further include a distributor for connecting the controllable switch means to the ignition devices in synchronism with engine operation. Alternatively, instead of employing a distributor, the switch means may include a plurality of electronic switches, one for each spark gap ignition device, and the trigger means preferably includes a plurality of circuit means, each having a magnetically sensitive semiconductive device cooperable with the magnetic field of the rotor, one circuit means being associated with each electronic switch for producing control signals for actuating its associated electronic switch in synchronism with engine operation.

For a better understanding of these and other features and following drawings, in which:

FIG. 1 is a block diagram illustrating an overall ignition system in which the present invention is preferably employed;

FIG. 2 is a schematic diagram of an ignition system embodying one form of the present invention;

H6. 3 is another schematic diagram of an ignition system embodying another form of the present invention; and

FIG. 4 is a schematic diagram of an ignition system embodying still another form of the present invention.

Referring to FIG. 1, there is represented therein an ignition system in use in conjunction with an engine 10, which may be a conventional gasoline engine. For purposes of illustration, it will be assumed that the engine 10 has eight cylinders each with an associated spark plug for igniting combustible fuel in the corresponding cylinder and that the engine is of the usual four-cycle type. The proper timing relation for firing the fuel in the engine cylinders is provided by engine ignition means 12, which will ordinarily comprise circuitry including eight spark plugs, one for each cylinder of engine 10 and a distributor operable in synchronism with engine operation for connecting voltage pulses intermittently to the eight spark plugs. The function of the remainder of the ignition system of FIG. 1 is to provide appropriate voltage pulses to the ignition means in sequence so that each voltage pulse fires the appropriate spark plug at the proper time.

To provide the proper voltage pulses, there is provided a source of voltage 14, which may be a conventional DC battery. The voltage output from source of voltage 14 is supplied to controllable switch means 16, which may be provided by a silicon-controlled rectifier. The switch means has its output connected to the engine ignition means 12 and, particularly, the output of the switch means would be connected to the distributor which would operate to connect the voltage output from the switch means to different ones of the eight spark plugs in synchronism with engine operation. The output connection 18 of the switch means is effective to connect the output voltage from voltage source 14 to the ignition means when input line 20 is supplied with a trigger control signal for triggering the switch means. More specifically, input line 20 connects trigger control signals to the switch means to actuate the switch means to connect the output voltage of the voltage source 14 to fire one of the eight spark plugs in the ignition means. Therefore, to produce firing of any one of the eight cylinders by engine ignition means 12, it is only necessary to apply a trigger control signal to the input line 20 to render conductive the controllable switch means 16, thereby permitting current to flow from the voltage source to the appropriate spark plug.

To generate the necessary trigger control signal at the desired time in relation to the phase of engine operation for which fuel ignition is desired, there is preferably employed trigger means 22 having its output on line 20. The trigger means preferably comprises circuit means including a magnetically sensitive device supported by a stator member and a rotor having flux generating means, which is rotated about its center so as to have its magnetic field effect the magnetically sensitive device to generate a signal in the trigger circuit means, as will be explained more fully hereinafter. The rotor of the trigger means may be geared to crankshaft 24 of the engine by way of gearing 26 so that the trigger control signal is produced by the trigger means at a rate in sequence with engine operation to actuate the switch means to connect the source of voltage to fire the appropriate spark plug.

In other embodiments of the invention, as will be explained in regard to the detailed schematic circuit diagrams, the distributor may be omitted from the engine ignition means. In this instance, the ignition means will merely comprise circuitry including the eight spark plugs. In this arrangement without a distributor, the switch means would include eight switching devices, one associated with each spark plug, connected to the voltage source and adapted to connect the source of voltage to different ones of the eight spark plugs. Specifically, each switching device, which preferably is provided by a siliconcontrolled rectifier, would be effective to connect the output voltage from voltage source 14 to a different particular one of the spark plugs in the engine ignition means 12, depending upon which of the switching devices received a control signal for triggering the switching device. In this system, eight input lines would conduct control signals from the trigger means 22 to different ones of the eight switching devices. To generate the necessary trigger control signals at the required times in relation to the phase to engine operation, the trigger means would preferably be provided with eight circuits, each having a magnetically sensitive device which would be spaced circumferentially around the center of the magnetic rotor. The rotor is rotatable so as to have its magnetic field effect the magnetically sensitive devices to produce control signals in sequence in the eight trigger circuits. The sequence for triggering each of the eight circuits in the trigger means to produce the appropriate control signal to render the appropriate switching device conductive for effecting the desired sequence of spark plug firing may be selected in appropriate fashion for particular engine application.

Referring to FIG. 2, a detailed schematic diagram of the circuitry of a system embodying one form of the invention, in accordance with the overall system block diagram of FIG. 1, is shown. In the circuit of FIG. 2, engine ignition means 30 is provided comprising a distributor, generally designated 32, having eight output terminals, 34, 36, 38, 40, 42, 44, 46 and 48, located in a circumferentially spaced relation with respect to the axis of rotation of distributor contact arm 50. The distributor contact arm is geared to rotate in synchronism with engine operation to connect voltage pulses to fire appropriate spark plugs, such as spark plug 52, one spark plug being connected to each of the output terminals of the distributor in a conventional manner. Input terminal 54 of the distributor, which has the distributor contact arm 50 electrically connected thereto, is connected to secondary winding 56 of voltage step-up transformer 58, which has a primary winding 60. The primary winding 60 of the voltage step-up transformer is connected to source of power 62 by way of semiconductive switch means 64. In the present instance, controllable switch means 64 is provided by a silicon-controlled rectifier 66 having its anode element 68 connected to source of power 62, its cathode element 70 connected to primary winding 60 and its control terminal 72 connected to trigger means, generally designated 74. The silicon-controlled rectifier may be of the usual type which is nonconductive when its control terminal 72 is at the same potential as its cathode 70, but becomes strongly conductive when its control terminal 72 is made sufficiently positive with respect to its cathode 70. The trigger means generates the necessary control signal which is applied to the control terminal of the siliconcontrolled rectifier at the required time in relation to the phase of engine operation for having the source of voltage applied to the transformer and distributor for firing the appropriate spark plug in synchronism with engine operation.

The source of voltage 62 in FIG. 2 comprises a battery 80, which has its negative terminal connected to electrical ground and its positive terminal connected to one terminal 820 of ignition switch 82. The other terminal 82b of ignition switch 82 is electronically connected to a transformer oscillator circuit, generally designated 84, which is adapted to provide high voltage pulses through diode 86 to charge capacitor means 88 with pulses of positive polarity. The capacitor means may comprise an ordinary capacitor having one terminal connected to the cathode of diode 86 and the other terminal connected to electrical ground. Since the silicon-controlled rectifier 66 is nonconductive until a control signal is applied to its control terminal 72, current will not pass from the capacitor through the silicon-controlled rectifier, which provides a current blocking action. Resistor 90 connected in series with zener diode 92 provides a voltage limiting circuit connected in parallel with capacitor 88 to limit the charge established across capacitor 88.

The transformer oscillator 84 comprises a transformer, generally designated 94, having a primary winding 96 and two

secondary windings

98 and 100. The primary winding 96 has one end connected to terminal 82b of ignition switch 82 and its other end connected to the collector oftransistor 104, which has its emitter connected to electrical ground. Also, there is connected between terminal 82b of the ignition switch and electrical ground a voltage divider

circuit comprising resistors

106 and 108. One end of secondary winding 98 is connected between

resistors

106 and 108, and the other end of secondary winding 98 is connected to the base of transistor 104. Secondary winding 100 of the transformer has one end connected to the ground and its other end connected to the anode of diode 86.

In operation of the transformer oscillator, when ignition switch 82 is closed, transistor 104 is initially biased to its conductive state by the potential applied to its base through resistor 106 and secondary winding 98. With the transistor in its conductive state, current flows through primary winding 96 and the transistor and results in a voltage pulse being induced in

secondary windings

98 and 100. The voltage pulse induced in secondary winding 98 causes the transistor 104 to become nonconductive. The high voltage positive pulse induced in winding 100 passes through diode 86 and charges capacitor 88. The transformer 94 steps up the battery voltage to a desired level for storage in capacitor 88. When the voltage induced in secondary winding 98 by primary winding 96 drops below the potential required to bias the transistor to its nonconductive state, then the transistor returns to its conductive state to permit current to flow through primary winding 96 and the transistor, repeating the cycle to produce a high voltage pulse in secondary winding 100 for charging the capacitor to a desired level.

If a positive control signal is applied to the control terminal 72 of silicon-controlled rectifier 66, the charged capacitor 88 will discharge suddenly through the silicon-controlled rectifier and primary winding 60 of transformer 58, which will generate a high voltage pulse in secondary winding 56 of transformer 58. The high voltage pulse generated in secondary winding 56 is conducted to the appropriate spark plug through distributor 32 in a conventional manner. The transformer oscillator 84 oscillates at a frequency, which preferably is on the order of 3,000 cycles per second, to have capacitor 88 charged to the desired level and ready to be discharged through the switch means whenever a spark plug is ready to be fired.

In accordance with the present invention, the trigger means 74 generates the desired control signal to actuate silicon-controlled rectifier 66 to its conductive state in synchronism with engine operation, thereby permitting discharge of capacitor 88 to fire the appropriate one of the spark plugs. Generally, the trigger circuit 74 comprises a magnetic rotor for producing a magnetic field and circuit means on a stationary structure. The circuit means preferably includes a magnetically sensitive semiconductive device 122 responsive to the magnetic field of the rotor to produce the control signal in the circuit means, which is connected to control terminal 72 of switch means 66. The circuit means further includes a sensing circuit operable to produce the control signal when the magnetically sensitive semiconductive device is in the magnetic field of the rotor. The sensing circuit is provided by an amplifier, generally designated 124, and voltage sensitive switching means, which includes a unijunction transistor oscillator circuit, generally designated 126, operable with capacitor 128, which is discharged to produce the control signal. The battery 80 is connected to the circuit of trigger means 74 through line 130 to supply power to the circuit for producing the desired control signal when the magnetically sensitive semiconductive device is in the magnetic field of the rotor.

More specifically, the battery 80 is connected to the circuit of trigger means 74 by electrical line 130, which is connected in the trigger circuit to the source terminal of a field-effect transistor 132. The drain terminal of field-effect transistor 132 is connected to one side of-biasing resistor 134. The other side of resistor 134 is connected, first, to the gate terminal of fieldefiect transistor 132, second, to one terminal of magnetically sensitive semiconductive device 122, and third, to the base of transistor amplifier 124. The magnetically sensitive semiconductive device 122 has its other terminal connected to electrical ground, as shown in FIG. 2. In this arrangement, the fieldeffect transistor is connected as a constant current device and provides a constant current source with battery 80 for supplying current to the magnetically sensitive semiconductive device 122. The magnetically sensitive semiconductive device 122 is preferably provided by a solid state device of the type which changes its conductive characteristics when subjected to a magnetic field. The magnetically sensitive semiconductive device is preferably provided by a magnetodiode manufactured by the Sony Corporation of Tokyo, Japan. Other magnetically sensitive semiconductive devices could be employed, such as, a magnetoresistor manufactured by Siemens Akliengesellschaft of West Germany or a Hall effect device manufactured by F. W. Bell, Incorporated of Columbus, Ohio. These devices operated to' provide a change in current carried through the device or provide a change in voltage across the device when the device is subjected to a magnetic field. The magnetodiode preferably employed is used to provide a change in voltage across the device when the device is in the magnetic field of rotor 120.

The magnetic rotor 120 is preferably provided by a permanent magnet arranged to rotate about center 120a so that one of its poles 12% produces a magnetic field to effect the magnetically sensitive semiconductive device each revolution of the magnet rotor. The rotor is geared to the crankshaft of the engine by way of gearing which is also coupled to the rotatable contact arm 50 of distributor 32, as indicated in FIG. 2. Depending on the particular application of the ignition system, the rotor 120 could be provided with a plurality of poles, each pole being adapted to produce a magnetic field to effect the magnetically sensitive semiconductive device 122 to produce a control signal in the circuit of trigger means 74.

As previously stated, the base of transistor 124 is connected between resistor 134 and magnetically sensitive semiconductive device 122. The collector of transistor 124 is connected to battery 80 by way of line 130, and the emitter of the transistor is connected to one side of biasing resistor 136, which has its other side connected to one terminal of capacitor 128, the other terminal of capacitor 128 being grounded, as shown in FIG. 2.

The voltage sensitive switching means 126 is provided by a unijunction transistor, which is connected in a unijunction oscillator circuit with capacitor 128. More specifically, the emitter 126a of unijunction transistor 126 is connected between resistor 136 and capacitor 128. The unijunction transistor has one of its base terminals 126b connected in a voltage divider circuit between current limiting resistor 138, which is connected to line 130, and variable resistor 140, which is connected to electrical ground. The other base terminal 1260 of the unijunction transistor is connected, first, to biasing resistor 142, which has its other side grounded, and second, to control terminal 72 of rectifier 66 by way of coupling capacitor 144. Preferably, a resistor 146 is connected between control terminal 72 and cathode 70 of siliconcontrolled rectifier 66. Resistor 146 provides a desensitizing resistance to make the rectifier less susceptible to transient voltages which might turn on the silicon-controlled rectifier at undesired times. The desensitizing of. the silicon-controlled rectifier may be provided internally so that resistor 146 may be unnecessary.

In operation of trigger circuit 74 shown in FIG. 2, when magnetically sensitive semiconductive device 122 is out of the magnetic field of magnet rotor 120, current flows from battery through field-effect transistor 132 and magnetically sensitive semiconductive device 122. Transistor 124 is normally in its conductive state and, therefore, capacitor 128 is charged to a potential, which is less than the necessary potential to actuate unijunction transistor 126 to provide increased conductivity thereof.

When the magnet rotor rotates to a position to have its magnetic field effect the magnetically sensitive semiconductive device, the magnetically sensitive semiconductive device provides an increased voltage thereacross which is applied to capacitor 128 through transistor 124. This increased potential which charges capacitor 128 is greater than the critical value needed to actuate the unijunction transistor to permit capacitor 128 to discharge therethrough. The discharge of capacitor 128 through unijunction transistor 126 provides the control signal applied to control terminal 72 of silicon-controlled rectifier 66 to actuate the rectifier 66 to its conductive state. With capacitor 128 discharged, the unijunction transistor returns to low conduction state, and the cycle repeats itself, when the magnetically sensitive semiconductive device is again in the magnetic field of the rotor.

The positive control signal from trigger circuit 74 applied to the control terminal of silicon-controlled rectifier 66 actuates the rectifier to its conductive state to suddenly discharge storage capacitor 88 through primary winding 60v of transformer 58. The pulse delivered to primary winding 60 will generate a high-voltage pulse in the transformer secondary, which high-voltage pulse is conducted through distributor rotor arm 50 to fire an appropriate spark plug. The normal and desired order of events with respect to any spark plug and the ignition means is that first the capacitive means 88 is charged to the value of the charging pulses, then a trigger control signal renders the silicon-controlled rectifier conductive to connect the capacitor 88 to the appropriate spark plug through transformer 58 and distributor 32 to fire the desired spark plug. Then the silicon-controlled rectifier will become nonconductive so that the capacitor 88 may again be charged. The cycle repeats itself with another trigger control signal being produced to permit firing of another spark plug.

FIG. 3 illustrates an alternative circuit arrangement to FIG. 2 in which the mechanical distributor of FIG. 2 has been replaced by electronic circuitry. Specifically, the mechanical distributor is replaced by providing a separate switch means and trigger circuit for each

spark plug

200 and 202, for example, of the engine. In the modified circuit of FIG. 3, parts in the source of voltage circuit, and switch means and trigger circuit associated with spark plug 200, similar to those in the circuit of FIG. 2 are identified by the same number designator with the addition of primes thereto. Also, in FIG. 3, parts in the second switch means and second trigger circuit associated with spark plug 202, similar to the switch means and trigger circuit of FIG. 2, are identified by the same number designator with the addition of double primes thereto.

Electrical lead 204 may connect the source of voltage 62' to additional switch means circuits, in a manner similar to the connections to switch means circuits 64' and 64", for firing other spark plugs of the engine, as indicated in FIG. 3, and electrical lead 206 may connect battery 80' to additional trigger circuits in a manner similar to the arrangements for trigger circuits 74' and 74", one additional trigger circuit being provided for each additional switch means circuit and associated other spark plug. More specifically, in this arrangement, one switch circuit and an associated trigger circuit is provided for each spark plug of the engine, as shown with switch circuit 64' and associated trigger circuit 74' for spark plug 200. The primary difference in the circuits of FIGS. 2 and 3 lies in the use of a separate switch means and associated trigger circuit for each spark plug of the engine, instead of a single switch means and trigger circuit employed with a distributor. Each spark plug preferably has an associated voltage step-up transformer connected between the output of its associated switch means and the spark plug, such as transformer 210 associated with spark plug 200 and transformer 212 associated with spark plug 202.

In the system of FIG. 3, preferably, only one trigger rotor 120' is employed and cooperates with each of the magnetically sensitive semiconductive devices, such as devices 122' and 122". Specifically, a number of magnetically sensitive semiconductive devices, equal to the number of spark plugs of the engine, would be supported by a stator member and spaced from each other circumferentially around a center; and the rotor, which is provided by permanent magnet 120, is rotated about its center 120a so as to have its magnetic field sequentially effect the several magnetically sensitive semiconductive devices. As previously stated, the rotor 120' is geared to the crankshaft of the engine. In the spacing of the magnetically sensitive semiconductive devices with respect to the rotor, the arrangement is such that trigger control pulses are produced in the trigger circuits associated with each magnetically sensitive semiconductive device for effecting the desired sequence of spark plug firing, this sequence being selected in appropriate fashion for the particular engine application.

In the operation of the ignition system of FIG. 3, the capacitor 88' is charged to the desired value by the charging pulses applied thereto, then a trigger control signal is generated in one of the circuit means to actuate an associated switch means so as to fire the associated spark plug. As indicated in FIG. 3, the sources of voltage operates in exactly the same manner as the source of voltage circuit in FIG. 2. In a similar manner, each of the

trigger circuits

74, 74", etc., operates as described in regard to trigger circuit 74 in FIG. 2, as well as each switch means 66', 66", etc., operating the same as switch means circuit 66 in FIG. 2. In the arrangement of FIG. 3, the angular orientation of the magnetically sensitive

semiconductive devices

122, 122", etc., for a given position of the magnet rotor 120' is preferably adjusted so that the magnetic field actuates one device, for example device 122", at a time after the capacitor 88' has been charged. The trigger control signal generated in the associated trigger circuit 74", in this example, renders its associated switch means conductive so as to discharge capacitor 88' through switch means 66 and the primary winding 212a" of the transformer 212" to generate a high-voltage pulse in transformer secondary 212b" to fire spark plug 202 at the appropriate time in synchronism with engine operation. Similarly, capacitor 88' is again charged and the next appropriate spark plug will be fired in response to magnet rotor 120' being rotated to a position to have its magnetic field effect the magnetically sensitive semiconductive device associated with such spark plug. This cycle of operation repeats itself to fire all the spark plugs in the appropriate sequence in synchronism with engine operation.

It should be noted that by appropriate selection of circuit component values, the systems of FIGS. 2 and 3 can provide a number of ignition pulses to each spark plug at desired angular positions of the engine crankshaft. Thus, the present ignition system is adapted for multiple sparking of the spark plug during each combustion stroke of each engine cylinder. If the first ignition spark fails to properly ignite the fuel-air mixture in the cylinder, there is an opportunity for other sparks to ignite a fresh portion of the mixture during each combustion stroke, thereby insuring more complete combustion.

More specifically, the output of the oscillator 84 of the voltage source 62 oscillates at a frequency sufficiently high that capacitor means 88 in the voltage source is always adequately charged when it is desired to discharge it to provide an ignition pulse, for example. With the unijunction transistor oscillator 126 in the trigger circuit 74 having the required repetition rate of oscillations, as long as the magnetically sensitive semiconductive device 122, such as a magnetodiode, is in the magnetic field of the rotor 120, ignition pulses will be generated. Particularly, in the trigger circuit, when the semiconductive device is in the magnetic field of the rotor, capacitor 128 will be charged and discharged in the unijunction oscillator circuit 126 to actuate the switching device 66 between its nonconductive and conductive states to discharge capacitor 88 a number of times through the switch means 66 to produce a series of ignition pulses during each combustion stroke of each cylinder. The duration of producing ignition pulses for each firing interval for a cylinder will depend on the angular width and speed of the trigger rotor.

The circuitry in the trigger circuit of FIGS. 2 and 3 is especially advantageous for certain applications, particularly those in which multiple sparking of the spark plug during each combustion stroke is desired, but in certain instances where multiple firing is not needed and in other cases, a simpler and more economical system shown in FIG. 4 may be utilized. The simplified system of FIG. 4 is somewhat similar to the system of FIG. 2, and in the modified system of FIG. 4, parts in the source of voltage circuit and the switch means circuit similar to those in the circuit of FIG. 2 are identified by the same number designator with the addition of triple primes thereto. The primary difference in the systems of FIGS. 2 and 4 lies in the use of a greatly simplified trigger circuit 250 in FIG. 4 and having the primary winding 252 of ignition transformer 254 located in the anode circuit of switch means 64", instead of the cathode circuit as in FIG. 2.

More specifically, in FIG. 4 the primary winding 252 of ignition transformer 254, which is part of the engine ignition means 258, is connected between the output of source of voltage 62 and anode 68" of silicon-controlled rectifier 66". Secondary winding 256 of the ignition transformer is connected at one end to electrical ground and at its other end to distributor contact am 260 of distributor generally designated 262 having eight

output terminals

264, 266, 268, 270, 272, 274, 276 and 278, located in a circumferentially spaced relation with respect to the axis of rotation of distributor contact arm 260, in a manner similar to the arrangement in FIG. 2. As stated in regard to FIG. 2, the contact arm 260 in FIG. 4 is geared to rotate in synchronism with engine operation to connect voltage pulses to fire appropriate spark plugs, such as spark plug 280, one spark plug being connected to each of the output terminals of the distributor in a conventional manner. The position of the primary winding of the ignition transformer, in the anode circuit of the switch as in FIG. 4 or in the cathode circuit of the switch as in FIG. 2, will depend on the particular application of the system and the component elements employed.

The trigger circuit 250 is employed to generate the desired control signal to actuate silicon-controlled rectifier 66" to its conductive state in synchronism with engine operation to permit discharge of capacitor 88" to fire the appropriate one of the spark plugs. Trigger circuit 250 in the embodiment of FIG. 4 comprises a magnetorotor 282 and a magnetically sensitive semiconductive device 284 responsive to the magnetic field of the rotor for a predetermined interval each revolution of the rotor. The magnetically sensitive semiconductive device and rotor operate as described in regard to FIG. 2.

semiconductive device 284 has one terminal connected to electrical ground and its other terminal connected first to control terminal 72" of silicon-controlled rectifier 66" by way of coupling capacitor 144" and, second, to dropping resistor 286, which has its other side connected to battery by electrical line 288. The dropping resistor is employed to provide the proper bias voltage across the magnetically sensitive device from the battery so that the change in voltage across the magnetically sensitive semiconductive device, when it is in the magnetic field of the rotor, will be sufficient to provide an appropriate control signal to actuate the silicon-controlled rectifier 66". Resistor 146' in switch means circuit 64' permits the charge on the coupling capacitor 144" to be dissipated after each actuation of the rectifier.

In operation of the ignition system-of FIG. 4, the capacitor 88" in source of voltage 62' is charged to the desired value by the charging pulses applied thereto, as described in regard to FIG. 2, then a control signal from the trigger circuit will render the silicon-controlled rectifier conductive so that the capacitor 88" is discharged therethrough and through the primary of the transformer. The pulse thereby generated in the secondary of the transformer is conducted through the distributor to fire the appropriate one of the spark plugs in synchronism with engine operation.

The control signal in the trigger circuit 250 of FIG. 4 is produced to actuate rectifier 66", when the rotor 282 rotates to a position to have its magnetic field affect the magnetically sensitive semiconductive device 284. The device 284, when in the magnetic field of rotor 282, provides an increased voltage thereacross which is applied to control terminal 72" of silicon-controlled rectifier 66" to actuate the rectifier to its conductive state. With capacitor 88" discharged through rectifier 66", the cycle repeats itself when the magnetically sensitive semiconductive device is again in the magnetic field of the rotor.

It should be noted that other types of voltage sources could be employed in the FIG. 4 arrangement. For example, a conventional pulse generator could be employed to charge capacitor 88", or, without a capacitor in the voltage source, pulses could be applied to the anode of silicon-controlled rectifier in synchronism with engine operation.

It should also be appreciated that the magnetically sensitive semiconductive device, coupling capacitor, resistors and silicon-controlled rectifier could be contained in an integrated circuit module. Furthermore, the magnetically sensitive semiconductive device could be fabricated in the control terminal circuit of the switch means as an integral part thereof. Moreover, the switch means could be made of a magnetically sensitive semiconductive material and, in this manner, the functions of the switch means and the magnetically sensitive semiconductive device could be combined in a single, integral component.

It should be appreciated that the present invention provides an ignition system which is highly reliable and employs simple circuit components. The present ignition system eliminates the conventional breaker point apparatus, and the magnet rotor and magnetically sensitive semiconductive device arrangement can be made very compact with the magnetically sensitive semiconductive devices potted and encapsulated in a housing structure to provide a unit which is economical to manufacture and assemble and capable of operation in ad verse conditions without malfunction.

While the invention has been described with particular reference to specific embodiments thereof in the interest of complete definiteness, it will be understood that it may be embodied in a large variety of forms diverse from those specifically shown and described without departing from the scope and spirit of the invention as defined by the appended claims.

We claim:

1. An ignition system for an internal combustion engine having a plurality of cylinders comprising: a source of voltage; engine fuel ignition means including an ignition device for each cylinder of the engine; controllable switch means including a plurality of electronic switches, one electronic switch being associated with each ignition device and each electronic switch selectively completing a circuit with the source of voltage for causing a voltage potential to be applied to its associated ignition device, each electronic switch having a control terminal responsive to a suitable signal for actuating the electronic switch; and trigger means including a magnetic rotor for producing a magnetic field and a plurality of circuit means, one circuit means being associated with each electronic switch and each circuit means having a magnetically sensitive semiconductive device cooperable with the magnetic field of the rotor to produce a control signal In the circuit means, each circuit means being connected to the control terminal of one of the electronic switches for having its control signal actuate the associated electronic switch for firing each ignition device in synchronism with engine operation.

2. An ignition system for an internal combustion engine having a plurality of cylinders comprising: a source of voltage; engine fuel ignition means including an ignition device for each cylinder of the engine; controllable switch means including a plurality of electronic switches, one electronic switch being associated with each ignition device and each electronic switch being connected to the source of voltage for causing the occurrence of a voltage potential to operate its associated ignition device as the switch means is switched from a first state to a second state, each electronic switch having a control terminal responsive to a suitable signal for actuating the electronic switch from the first state to the second state; and trigger means including a magnetic rotor for producing a magnetic field and a plurality of circuit means, one circuit means being associated with each electronic switch and each circuit means having a magnetically sensitive semiconductive device cooperable with the magnetic field of the rotor to produce a control signal in the circuit means, each circuit means being connected to a control terminal of one of the electronic switches for having its control signal actuate the associated electronic switch for firing each ignition device in synchronism with engine operation.

3. The ignition system of claim 2 in which each circuit means further includes a capacitor and voltage sensitive switching means through which the capacitor is discharged to produce the control signal when the charge on the capacitor reaches the predetermined level, the capacitor being charged to the predetermined level when the magnetically sensitive semiconductive device of the circuit means is in the magnetic field of the rotor.

4. The ignition system of claim 2 in which each circuit means includes a sensing circuit operable to produce the control signal when the magnetically sensitive semiconductive device of the circuit means is in the magnetic field of the rotor.

5. The ignition system of claim 2 in which each magnetically sensitive semiconductive device comprises a magnetodiode.

6. The ignition system of claim 2 in which each magnetically sensitive semiconductive device comprises a magnetoresistor.

7. An ignition system for an internal combustion engine having a plurality of cylinders comprising: a source of voltage; engine fuel ignition means including an ignition device for each cylinder of the engine; controllable switch means including a plurality of electronic switches, one electronic switch being associated with each ignition device and each electronic switch being connected to the source of voltage for causing the occurrence of a voltage potential to operate the associated ignition device as the switch means is switched from a first state to a second state, each electronic switch including magnetically sensitive semiconductive means responsive to a magnetic field for actuating the electronic switch from its first state to its second state; and trigger means including a magnetic rotor for producing a magnetic field, each said magnetically sensitive semiconductive means being cooperable with the magnetic field of the rotor for actuating the associated electronic switch for firing each ignition device in synchronism with engine operation.