Breakerless Pulse Distribution System and Opto-Electrical Distributor Therefor

1. Field of the Invention

This invention relates to breakerless ignition systems for internal combustion engines and to distributors therefor.

2. Prior Art

The ignition system for an internal combustion engine generates timing pulses which indicate the instant during the piston stroke that the spark plugs should be fired and distributes these pulses to the individual spark plugs to cause them to fire in a preset order. In the conventional ignition system, mechanical breakers are used to generate the timing pulses and a rotating mechanical distributor directs the pulses to the appropriate spark plugs in sequence. Since the high voltage required to fire the spark plugs greatly limited the life of the mechanical breakers, ignition systems were developed in which the switching of the high voltage necessary to fire the individual spark plugs was accomplished by breakerless electronic switches such as silicon controlled rectifiers (SCRs). This significantly improved the life of the mechanical breakers which were still used for timing pulse generation. Subsequent developments have replaced the mechanical breakers for generating timing signals with magnetic and optical pulse generators. Many of the optical timing pulse generators, however, operate with a continuous light source which requires substantial electric power and therefore limits their use with magneto equipped internal combustion engines.

Further developments have resulted in a substitute for the conventional rotating mechanical distributor in the form of a transformer distributor. In such a system, the timing pulses are applied to a rotor which induces trigger pulses in angularly distributed secondary coils to fire the appropriate SCR controlled spark generating circuit. While the transformer distributor requires little power and has a long life, it is not suitable for use in a system with small firing angles because pulses can be induced under these conditions in two adjacent secondary coils simultaneously. This possibility of double firing also limits the amount of timing pulse advance that can be utilized with a transformer distributor.

A light activated system for applying energizing pulses to the injectors of an electronic fuel injection system is disclosed in commonly owned U.S. Pat. No. 3,895,612. In this system a single, continuously illuminated radiant energy source is used to sequentially activate the fuel injectors through a fiber optic which directs the radiant energy radially outward from the center of a disc rotated in synchronism with the engine to sequentially turn on circularly arranged photodetectors associated with the fuel injector activation circuits. No means are provided for advancing or retarding the pulses thus generated.

It is a primary object of this invention to provide a novel and improved internal combustion engine breakerless ignition system with a simple, inexpensive but reliable distribution means.

It is also an object of the invention to provide such a system which can operate at small firing angles.

It is another object of the invention to provide such a system which can accept full advance of the timing signal.

It is a further object of the invention to provide such a system which requires a minimum amount of power to operate.

In accordance with the invention, a breakerless distributor for sequentially distributing electrical pulses to a plurality of electrically energizable output lines (8, 10, 12, 14) at intervals determined by pulses on a single input line (72), comprises a plurality of electrically activated radiant energy sources (73, 75, 77, 79) such as light emitting diodes (LEDs), equal in number to the number of output lines (8, 10, 12, 14), all connected in series to the input line (72) such that all the radiant energy sources (73, 75, 77, 79) are energized simultaneously for the duration of each pulse on the input line (72). A photosensitive switch (83, 85, 87, 89) arranged in spaced confronting relation to each radiant energy source (73, 75, 77, 79) is connected to complete the circuit of one of the output lines (8, 10, 12, 14) when turned on by the associated radiant energy source. A shutter member (91) arranged for movement between the radiant energy sources (73, 75, 77, 79) and the photosensitive switches (83, 85, 87, 89), blocks reception of radiant energy by all but one of the photosensitive switches at a time and is driven in synchronism with the pulses on the input line (72) to sequentially turn on one photosensitive switch after the other for each successive pulse on the input line, whereby pulses are sequentially generated on the output lines.

The spaced confronting radiant energy sources (73, 75, 77, 79) and the photosensitive switches (83, 85, 87, 89) are each arranged in a circle (121, 123) and the shutter member (91), which has a section (93) through which radiant energy may pass, is mounted for rotation between the radiant energy sources and the photosensitive switches. In a preferred embodiment of the invention, the radiant energy sources (73, 75, 77, 79) and the photosensitive switches (83, 85, 87, 89) are arranged in concentric circles (121, 123) and the shutter (91) is a cup member mounted for rotation about the common center and having a slot (93) in the wall (127) thereof through which radiant energy may pass to a preselected number, in most cases one, photosensitive switch at a time. The invention may be applied to distributing timing pulses to the spark plug energizing circuits of a gasoline engine or to the solenoids of fuel injectors in diesel engines. Where the photosensitive switches (83, 85, 87, 89) are arranged to connect the individual spark plug firing circuits (7, 9, 11, 13) or fuel injector solenoids to a common tank capacitor (25), shunting capacitors (106) may be provided across each photosensitive switch to eliminate double firing due to radio frequency interference.

Since the radiant energy source-photosensitive switch combinations operate on narrow beams of radiation, they can be placed close together to provide very small firing angles where required. They also permit the slot (93) in the cup shaped shutter (91) to be made almost as wide as the angle between adjacent photosensitive switches (83, 85, 87, 89) so that full adjustment of the timing may be accomplished without danger of double firing.

For very small or irregular firing angles, additional pairs of radiant energy sources and photosensitive switches (131-139, 133-141, 135-143, 137-145) may be arranged in additional concentric circles with an additional slotted cup (14) mounted for rotation between the additional radiant energy sources and the photosensitive switches. Separate timing pulses may be provided to simultaneously energize the additional radiant energy sources.

As an alternative to placing the radiant energy sources (73, 75, 77, 79) and photosensitive switches (83, 85, 87, 89) in concentric circles, they may be arranged in axially spaced circles. In such an arrangement, the shutter member may take the form of a slotted disc (129) mounted for rotation about the common axis.

In order to use the system with a magnetic timing pulse generator (3) at small firing angles and/or high speeds, a two step timing pulse generator has been developed. The magnetic pickup (51, 53) triggers a first gate controlled electronic switch (47) which discharges a first capacitor (31) into the gate of a second gated electronic switch (69) which in turn discharges a second capacitor (33) through the distribution LEDs (73, 75, 77, 79). While the first capacitor (31) might not recharge rapidly enough between pulses at high speed or small firing angles to turn on the LEDs (73, 75, 77, 79) due to the characteristics of the pulses from the magnetic pickup (51, 53), it will have enough charge to trigger the second gated electronic switch (69). Since the second capacitor (33) is relatively small, and the trigger pulses for the second gated electronic switch (69) are relatively short, this second switch only remains on to turn on the LEDs (73, 75, 77, 79) for a short duration thereby permitting the second capacitor to fully recharge for the next timing pulse.

FIG. 1 is a schematic circuit diagram of a breakerless ignition system for an internal combustion engine incorporating the invention;

FIG. 2 is an isometric exploded view of a distributor according to the invention showing the physical relationship of part of the system shown in FIG. 1;

FIG. 3 is an isometric view of another embodiment of the invention; and

FIG. 4 is an isometric exploded view of a modification of the distributor shown in FIG. 2.

As illustrated in FIG. 1, the invention will be described as applied to the ignition system for a four cylinder, magneto equipped internal combustion engine, although it is to be understood that the invention is suitable for use with engines equipped with alternators or generators and with any number of cylinders. The system illustrated includes a magneto 1, a timing pulse generating circuit 3, a distributor 5, spark plug energizing circuits 7, 9, 11 and 13 (one for each cylinder of the engine), and a common pulse source 15 for the spark plug energizing circuits.

As shown symbolically in FIG. 1, the rotor 17 of magneto 1 is driven in timed relationship to the crankshaft (not shown) of the internal combustion engine 19. The alternating current induced in the coils 21 of the magneto is rectified in the full wave diode bridge circuit 23.

Direct current from the rectifier 23 charges the main tank capacitor 25 of the common pulse source 15 to a voltage determined by zener diodes 27 at a rate determined by choke 29. Capacitors 31, 33 and 35 are also charged from the bridge circuit through resistor 37 and resistor 39, 41 or 43 respectively to a voltage controlled by zener diode 45. The capacitor 31 is shunted by resistor 49 and SCR 47 which is gated by the timing pulse circuit 3. The timing circuit includes a four vane rotor 51 driven in timed relationship to the crankshaft of the internal combustion engine 19 which induces pulses in a coil 53 shunted by a load resistor 55. A diode 57 passes positive pulses through capacitor 59 to the gate of the SCR 47. Resistor 61 and diode 65 connected gate to cathode across SCR 47 protect the switch from radio frequency interference (RFI) and from destructive negative bias.

Turn on of SCR 47 by a timing pulse discharges capacitor 31 through resistor 67 into the gate of SCR 69 which fires to discharge capacitor 33 through resistor 71 and simultaneously turn on LEDs 73, 75, 77 and 79 of the distributor 5 which are series connected by line 72. A capacitor 81 protects SCR 69 from RFI. Of course, the LEDs could also be connected in parallel for simultaneous energization.

The LEDs 73, 75, 77 and 79 are arranged in spaced confronting relation with phototransistors 83, 85, 87 and 89 respectively. An annular shutter 91 driven by the crankshaft of the engine 19 rotates in the space between the LEDs and the phototransistors thereby blocking reception of light by all the phototransistors except one opposite a slot 93 in the shutter (phototransistor 83 in the Figures).

The emitter of phototransistor 83 is connected to the gate of SCR 95 in spark plug firing circuit 7 through lead 8. The emitters of phototransistors 85, 87 and 89 are connected by leads 14, 12 and 10 to the gates of SCRs in similar spark plug firing circuits 13, 11 and 9 respectively. The collectors of the phototransistors are connected through a common junction 97 and resistor 99 to capacitor 35 which supplies the common firing pulse for the SCRs 95. The SCR 95 when turned on by the phototransistor discharges the main tank capacitor 25 through the primary of ignition coil 101 to generate the high voltage required to fire the spark plug 103 connected to the secondary of the ignition coil. The spark plug in the other spark plug firing circuits 9, 11 and 13, are fired in a similar manner when their associated phototransistors are turned on.

The SCRs 95 of the firing circuits are each protected from RFI and excessive negative bias by a capacitor 105, a resistor 107 and a diode 109. Protection is also provided against RFI turn on of the nonselected phototransistors by shunting each one with a capacitor 106. Diodes 111 and 113 prevent bleed off of the charges on capacitors 25 and 31, 33 and 35 respectively and the diode 115 blocks current from shunting through zener diodes 27 during operation of the ignition circuits as described below.

The physical arrangement of the principal components of the distributor 5 are illustrated in the exploded view of FIG. 2. The LEDs 73, 75, 77 and 79 and the corresponding phototransistors 83, 85, 87 and 89 are mounted in spaced confronting relation on mounts 117 which in turn are secured on a printed circuit board 119 with the LEDs and phototransistors arranged in concentric circles 121 and 123 respectively. The shutter 91 is in the form of a cup mounted for rotation on an engine driven shaft 125. The cup, which is shown in a raised position in FIG. 2 for clarity, rotates about the common center of the LED phototransistor array with wall 127 passing through the gaps between the LEDs and phototransistors. The cup wall 127 is opaque and therefore blocks reception of light by a phototransistor from its associated LED. However, when a slot 91 (or a transparent section) in the cup wall is adjacent an LED-phototransistor pair, energization of the LED by a timing pulse will turn on the phototransistor. Since the slot is only wide enough to uncover one LED-phototransistor pair at a time, only one phototransistor can be turned on for each timing pulse despite the fact that all of the LEDs are energized simultaneously.

The rotation of the cup 91 and the generation of timing pulses are coordinated with the rotation of the crankshaft of the engine such that successive phototransistors are sequentially turned on by successive timing pulses. As seen in FIG. 2, the shunting capacitors 106 can be mounted on the printed circuit board adjacent the phototransistors. Other components of the circuit of FIG. 1 may be mounted on the underside of the printed circuit board 119.

Adjacent LED-phototransistor pairs are angularly spaced at intervals equal to the firing angle of the engine. Since the light emitted by the LEDs can be directed in narrow beams, the LED-phototransistor pairs can be positioned in close proximity to one another and can therefore be used in distribution systems for engines having large numbers of cylinders with very small firing angles. In addition, the narrow angular sensitivity of the LED-phototransistor pairs assures that each phototransistor only responds to light emitted by its associated LED and therefore the cup 91 is only required to screen the nonselected phototransistors from their own LEDs. Thus, the slot 93 in the cup wall 127 can be nearly as wide angularly as the firing angle without causing double firing of spark plugs. Since the wide slot exposes the phototransistor to a pulse of light from its associated LED for an interval which substantially exceeds the duration of a timing pulse, full advance of the timing pulses can be accommodated by the distributor. Advance of the timing pulses can be effected by mechanical or electronic means.

Operation of the disclosed ignition system can be summarized as follows. Assume that capacitors 25, 31, 33 and 35 are all charged and that a timing pulse is generated by the rotor 51 when the slot 93 in the cup member 91 is aligned with phototransistor 83 as shown in the drawings. The timing pulse fires SCR 47 which discharges capacitor 31 into the gate of SCR 69. Firing of SCR 69 discharges capacitor 33 to turn on all of the series connected LEDs 73, 75, 77 and 79 simultaneously. The light emitted by LED 73 turns on phototransistor 83 which discharges capacitor 35 into the gate of SCR 95 in firing circuit 7. The firing of SCR 95 discharges the main tank capacitor 25 through the primary of ignition coil 101 and fires the spark plug 103 connected to the ignition coil secondary winding. With the bridge 23 alone connected across the capacitor 25, the tank circuit formed by this capacitor and the primary of the ignition coil would not ring to turn off SCR 95. However, the choke 29 drops the potential of the bridge 23 below ground so that the voltage across capacitor 25 can swing negative to cut off the SCR 95 holding current and allow capacitor 25 to recharge rapidly for the next firing pulse. The diode 115 prevents current from shunting through zeners 27 which would clamps capacitor 25 at about one 11/2 volts negative.

The other capacitors are recharged as follows. Since capacitor 33 is small and the trigger pulse applied to SCR 69 is short in duration, this switch turns off after a short interval to allow capacitor 33 to recharge. With the LEDs' current terminated, phototransistor 83 turns off to allow capacitor 35 to recharge. Capacitor 31 is recharged when the pulse applied to the gate of SCR 47 drops below the threshold voltage. While, due to the characteristics of the pulses generated by the magnetic pickup, this may not occur early enough at high speeds or small firing angles to permit capacitor 31 to charge to a voltage sufficient to turn on the LEDs, capacitor 31 will always attain the voltage required to turn on SCR 69.

With the capacitors recharged and the cup member 91 rotated counterclockwise in FIG. 1 by the engine, slot 93 will be aligned between LED 75 and phototransistor 85 when the next timing pulse is generated. This results in firing of the spark plug in plug energizing circuit 13 in a manner which is clear from the description above. Subsequently, pulses from the timing circuit will be distributed to firing circuits 11 and 9 and so on.

While one specific embodiment of the invention has been described in detail, numerous modifications fully within the spirit of the invention can be made by those skilled in the art. For instance, while the LEDs and phototransistors are arranged in concentric circles in the preferred embodiment of the invention, they can alternatively be arranged in axially spaced circles of equal diameter with a flat, slotted disc 129 disposed between them as a shutter as illustrated in FIG. 3. It can also be appreciated that more than one LED-phototransistor pair can be exposed by the shutter at one time in applications where multiple firing signals are required, such as in engines with a large number of cylinders. It is also possible, due to the narrow directional sensitivity of the devices, to arrange two rows or concentric circles of LEDs and phototransistors with each row controlled by its own trigger signals but with LED-phototransistor pairs from each row uncovered by a slot in the shutter in its row or concentric circle. For example, as shown in the exploded view of FIG. 4, additional LED-phototransistor pairs 131-139, 133-141, 135-143 and 137-145 may be arranged in concentric circles inside (or outside) the concentric circles formed by the LED-phototransistor pairs 73-83, 75-85, 77-87 and 79-89. The additional LEDs 131, 133, 135 and 137 are simultaneously energized by their own trigger signal. An additional slotted cup 147 also driven in synchronism with the engine crankshaft, allows only one of the additional phototransistors at a time to be turned on in the manner previously described. This arrangement is suitable for systems having staggered firing angles or firing angles smaller than can be physically accommodated by a single row of LED-phototransistor pairs as, for instance, systems having twenty or more spark plugs to be fired. The invention may also be applied to diesel engines wherein the timing pulses would be distributed to the solenoids of the fuel injectors rather than to spark plugs. Many other modifications to the invention could be made by those skilled in the art and therefore the scope of the invention is to be limited only by the appended claims.