Transistorized ignition system

Claim 2

An ignition system for an internal combustion engine having an ignition coil with a primary winding and a secondary winding and a current source comprising: means driven by said engine for generating timing signals synchRonized with the speed of said engine, said timing signals characterized by slow rise and fall times; pulse-shaping means responsive to said timing means for generating a square pulse train having a frequency and pulse width determined by said timing signals; and switching means in series with said primary winding, said switching means opening and closing in response to said square pulse train generated by said pulse-shaping means, said switching means allowing current flow from said current source through said primary winding when closed and interrupting said current flow from said current source when open, said pulseshaping means causing said switching means to operate very rapidly to interrupt the flow of current through said primary winding so that the magnitude of the ignition pulse output from said secondary winding is increased and dissipation of energy stored within said ignition coil into said switching means is prevented.

Claim 3

The system of claim 1 wherein said means for generating timing signals comprises: a light source and a photocell in optical communication; and a shutter wheel having spaced arcuate segments intermediate said light source and said photocell and adapted to be rotated in synchronism with said engine.

Claim 4

The system of claim 1 wherein said pulse-shaping means comprises: first and second transistors interconnected to have complementary conduction states, said transistors changing from a first to a second conduction state by regenerative action when the magnitude of said timing pulses reach a first value and said transistors returning to said first conduction state when the magnitude of said timing pulses reaches a second value.

Claim 5

The system of claim 3 wherein said transistors are PNP transistors having base, emitter and collector electrodes, said first transistor being normally conductive and connected between the emitter and base electrodes of said second transistor to bias said second transistor normally nonconductive, said first transistor having said timing pulses applied to its base electrode causing it to become nonconductive when the magnitude of said timing pulse reaches said first value, as said first transistor transitions from a conductive to a nonconductive state said second transistor transitions from a nonconductive to a conductive state accelerating the transition of said first transistor, when said timing pulse reaches said second value said first transistor becomes conductive causing said second transistor to become nonconductive accelerating the transition of said first transistor to a conductive state.

Claim 6

The system of claim 3 wherein said transistors are PNP transistors having base, emitter and collector electrodes, said second transistor having a first resistor connected to its collector electrode, and a third resistor having a value greater than the value of said second resistor connected to its base electrode, said first transistor being normally conductive and having its emitter and collector electrodes connected to the emitter and base electrodes respectively of said second transistor to bias said second transistor normally nonconductive, said first transistor having said timing pulses applied to its base electrode to bias said first transistor nonconductive when the magnitude of said timing pulses reaches said first value, as said first transistor becomes nonconductive said second transistor becomes conductive reducing the voltage potential at the emitter electrodes of said transistors due to the increased current flow through said first resistor accelerating the transition of said first transistor from a conductive to a nonconductive state and thereby accelerating the transition of said second transistor from nonconductive to a conductive state, said first transistor becoming conductive when said timing pulse reaches said second value causing said second transistor to become nonconductive increasing the voltage potential at the emitter electrodes of said transistors acceleraTing the nonconductive to conductive transition of said first transistor.

Claim 7

The system of claim 5 wherein said switching means includes: a driver transistor controlled by the output current flow through said second transistor; and, a switching transistor in series with said primary winding and responsively connected to said driver transistor.

Claim 8

The system of claim 6 wherein said pulse-shaping means further includes a fourth resistor in series with said series connected second transistor collector electrode and second resistor and wherein the base of said driver transistor in said switching means is connected between said second resistor and said fourth resistor, said fourth resistor having a magnitude sufficiently large so that current flow through said second transistor during said second conduction state develops a voltage potential across said fourth resistor to forward bias said driver transistor to a conductive state, said driver transistor being biased to a nonconductive state during said first conduction state of said second transistor, the magnitude of said fourth resistor being sufficiently small to provide a rapid discharge path for reverse base current in said driver transistor resulting from the collector to base capacitance when said driver transistor is biased to a nonconductive state.

Claim 9

The system of claim 1 wherein said switching means includes: a switching transistor having its collector and emitter electrodes connected to said primary winding and ground respectively, said switching transistor allowing current to flow through said primary winding when conductive and interrupting said current flow when nonconductive; a driver resistor connected between the base of said switching transistor and a direct current source so that said switching transistor is conductive; and, a driver transistor having its collector and emitter electrodes connected between the base of said switching transistor and ground respectively and having said square pulses output from said pulse-shaping means applied to its base, said driver transistor becoming conductive while said square pulses are present on its base, said driver transistor shunting the current through said driver resistor to ground when conductive causing said switching transistor to become nonconductive interrupting said current flow through said primary winding.

Claim 10

The system of claim 1 further including a parallel connected capacitor and voltage limiting diode said parallel connected capacitor and diode being connected across said switching means, said capacitor increasing the energy output from said ignition coil and also increasing the reliability of said switching means, said voltage-limiting diode protecting said switching means from damage resulting from voltage transients in excess of the breakdown voltage of said switching means.

Claim 11

An ignition system for an internal combustion engine having a direct current source connected in series with a primary winding of an ignition coil also having a secondary winding connected through a distributor to spark plugs for the engine comprising: a shutter wheel rotated by the distributor shaft; a light source and juxtaposed photocell, said rotating shutter wheel interrupting the light impinging on said photocell at a rate proportional to the engine speed; a first resistor connecting said direct current power source to said photocell; an amplifier transistor having its base and emitter electrodes coupled to opposite terminals of said photocell and its collector electrode serially connected with second and third resistors to said current source; first and second pulse-squaring transistors having their emitter electrodes connected together with said first transistor having its base electrode connected between said second and third resistors, a fourth resistor connected between said current source and the common emitter electrode connection of said pulse-squaring transistors and a fifth resistor connected between the collector electrode of said first pulse-squaring transistor and ground said second pulse shaping transistor having its base electrode connected to the collector electrode of said first pulse shaping transistor and its collector electrode connected to ground through serially connected sixth and seventh resistors; a driver transistor having its base electrode connected intermediate said sixth and seventh resistors its emitter electrode connected to ground and its collector electrode connected in series with a driver resistor to said direct current power source; a ballast resistor in series between said current source and said primary winding; and, a switching transistor having its base electrode connected to the collector electrode of said driver transistor, the emitter and collector electrodes of said switching transistor being connected in series with said primary winding of said ignition coil and said ballast resistor to said direct current power source said emitter electrode being connected to ground.

Claim 12

An ignition system for an internal combustion engine having a direct current source connected in series with a primary winding of an ignition coil also having a secondary winding connected through a distributor to spark plugs for the engine comprising: a shutter wheel rotated by the distributor shaft; a light source and juxtaposed photocell, said rotating shutter wheel interrupting the light impinging on said photocell at a rate proportional to the engine speed; a first resistor connecting said direct current power source to said photocell; an amplifier transistor having its base and emitter electrodes coupled to opposite terminals of said photocell and its collector electrode serially connected with second and third resistors to said current source; first and second pulse-squaring transistors having their emitter electrodes connected together with said first transistor having its base electrode connected between said second and third resistors, a fourth resistor connected between said current source and the common emitter electrode connection of said pulse-squaring transistors and a fifth resistor connected between the collector electrode of said first pulse-squaring transistor and ground said second pulse shaping transistor having its base electrode connected to the collector electrode of said first pulse shaping transistor and its collector electrode connected to ground through serially connected sixth and seventh resistors; a driver transistor having its base electrode connected intermediate said sixth and seventh resistors its emitter electrode connected to ground and its collector electrode connected in series with a driver resistor to said direct current power source; a ballast resistor in series between said current source and said primary winding; and, a switching transistor having its base electrode connected to the collector electrode of said driver transistor, the emitter and collector electrodes of said switching transistor being connected in series with said primary winding of said ignition coil and said ballast resistor to said direct current power source said emitter electrode being connected to ground.

Claim 13

The system of claim 10 wherein said seventh resistor is given a sufficiently high value such that said drive transistor turns on when said second pulse-squaring transistor is turned on and a low enough value such that it will prevent a collector-base current through said driver transistor from causing the driver transistor to remain conductive as the second pulse-squaring transistor is being turned off.

Claim 14

The system of claim 11 further including a parallel connected capacitor and voltage limiting diode having its anode electrode connected to ground said parallel connected capacitor and diode being connected in parallel to the collector and emitter electrodes of said switching transistor.

Claim 15

An ignition system for an internal combustion engine having an ignition coil with a primary winding and a secondary winding and a current source comprising: means driven by said engine for generating timing signals synchronized with the speed of said engine, said timing signals characterized by slow rise and fall times, said means for generating timing signals comprising: a light source and a photocell in optical communication, said light source connected in series with a current-limiting resistor to said current source; a diode connected in parallel with said light source, said diode providing voltage variation across said light source as a function of environmental temperature to increase the energy emitted by said light source when the environmental temperature reduces the sensitivity of said photocell and to decrease the emitted energy when the environmental temperature increases the sensitivity of the photocell; a shutter wheel having spaced arcuate segments intermediate said light source and said photocell and adapted to be rotated in synchronism with said engine; pulse-shaping means responsive to said timing means for generating a square pulse train having a frequency and pulse width determined by said timing signals: and switching means in series with said primary winding, said switching means opening and closing in response to said square pulse train generated by said pulse-shaping means, said switching means allowing current flow from said current source through said primary winding when closed and interrupting said current flow from said current source when open, said pulse-shaping means causing said switching means to operate very rapidly to interrupt the flow of current through said primary winding so that the magnitude of the ignition pulse output from said secondary winding is increased and dissipation of energy stored within said ignition coil into said switching means is prevented.

Claim 16

An ignition system for an internal combustion engine having an ignition coil with a primary winding and a secondary winding and a current source comprising: means driven by said engine for generating timing signals synchronized with the speed of said engine, said timing signals characterized by slow rise and fall times, said means for generating timing signals comprising: a light source and a photocell in optical communication, said light source connected in series with a current-limiting resistor to said current source; a diode connected in parallel with said light source, said diode providing voltage variation across said light source as a function of environmental temperature to increase the energy emitted by said light source when the environmental temperature reduces the sensitivity of said photocell and to decrease the emitted energy when the environmental temperature increases the sensitivity of the photocell; a shutter wheel having spaced arcuate segments intermediate said light source and said photocell and adapted to be rotated in synchronism with said engine; pulse-shaping means responsive to said timing means for generating a square pulse train having a frequency and pulse width determined by said timing signals: and switching means in series with said primary winding, said switching means opening and closing in response to said square pulse train generated by said pulse-shaping means, said switching means allowing current flow from said current source through said primary winding when closed and interrupting said current flow from said current source when open, said pulse-shaping means causing said switching means to operate very rapidly to interrupt the flow of current through said primary winding so that the magnitude of the ignition pulse output from said secondary winding is increased and dissipation of energy stored within said ignition coil into said switching means is prevented.

Claim 17

The system as described in claim 7 wherein said ignition system and said ignition coil are contained in a a housing member adapted to be mounted on an internal combustion engine distributor camshaft and which includes a mounting plate journaled around said camshaft and wherein said means for generating timing signals comprises a shutter wheel coupled to sad camshaft to rotate in accordance therewith, a light source and photocell juxtaposed radially from said camshaft and mounted on said mounting plate said shutter wheel rotating between said light source and photocell to interrupt the light energy emitted by said light source incident upon said photocell at a frequency proportional to said engine speed.