Electronic ignition system with means for limiting engine speed

Claim 2

In the ignition system of an internal combustion engine, in combination, electrical igniting means operative for igniting a fuel-air mixture in a cylinder of the engine; ignition capacitor means operative for storing the electrical energy required by said igniting means for effecting ignition of said mixture; energy transfer means operative for causing said ignition means to ignite said mixture by transferring to said igniting means electrical energy stored in said ignition capacitor means; ignition-capacitor-charging means connected to said ignition capacitor means and operative for charging the latter; timing means for timing the transfer of energy from said capacitor means to said igniting means; and engine-speedlimiting means including speed-monitoring capacitor means, speed-dependent charging means for charging said speed-monitoring capacitor means by applying thereto substantially identical charging pulses having a pulse repetition frequency proportional to engine speed, discharge means connected to said speed-monitoring capacitor means and operative for discharging said speed-monitoring capacitor means at such a rate that the voltage across the latter can build up to a predetermined value only if the engine speed reaches a predetermined speed, and voltage-responsive means connected to said speed-monitoring capacitor means and operative when the voltage across the latter exceeds said predetermined value for preventing said igniting means from igniting said mixture, wherein said discharge means comprises a discharge circuit branch connected across said speed-monitoring capacitor means and including resistor means for dissipating energy stored in said speed-monitoring capacitor means, wherein said voltage-responsive means has an input, and wherein said discharge circuit branch comprises a voltage divider having a voltage-divider tap connected to said input of said voltage-responsive means, wherein said voltage divider is comprised of a first portion and a second portion joined together at said voltage-divider tap, and wherein one of said portions is comprised of parallel-connected ohmic resistance means and negative-temperature-coefficient resistance means and a further resistance means connected in series with the parallel combination of said ohmic and negative-temperature-coefficient resistance means.

Claim 3

In the ignition system of an internal combustion engine, in combination, electrical igniting means operative for igniting a fuel-air mixture in a cylinder of the engine; ignition capacitor means operative for storing the electrical energy required by said igniting means for effecting ignition of said mixture; energy transfer means operative for causing said igniting means to ignite said mixture by transferring to said igniting means electrical energy stored in said ignition capacitor means; ignition-capacitor-charging means connected to said ignition capacitor means and operative for charging the latter timing means for timing the transfer of energy from said capacitor means to said igniting means; and engine-speed-limiting means including speed-monitoring capacitor means, speed-dependent charging means for charging said speed-monitoring capacitor means by applying thereto substantially identical charging pulses having a pulse repetition frequency proportional to engine speed, discharge means connected to said speed-monitoring capacitor means and operative for discharging said speed-monitoring capacitor means at such a rate that the voltage across the latter can build up to a predetermined value only if the engine speed reaches a predetermined speed, and voltage-responsive means connected to said speed-monitoring capacitor means and operative when the voltage across the latter exceeds said predetermined value for preventIng said igniting means from igniting said mixture, wherein said energy transfer means includes a transformer comprised of a secondary winding connected across said igniting means and a primary winding, and means connecting said primary winding in circuit with said ignition capacitor means and including a first electronic switch for preventing discharge of said ignition capacitor means through said primary winding except when said switch is conductive, and wherein said ignition-capacitor-charging means includes a charging transformer comprised of a primary winding and a secondary winding, a source of D.C. current connected across said primary winding of said charging transformer, and a second electronic switch connected in circuit with said source and said primary winding of said charging transformer for preventing flow of current through said primary winding of said charging transformer except when said second electronic switch is conductive, and wherein said timing means comprises means for applying a brief turn-on voltage pulse to said second-electronic switch to initiate the build-up of current flow through said primary winding of said charging transformer, and inductive positive-feedback means operative in response to build-up of current flow through said primary winding of said charging transformer for applying to said second electronic switch a control voltage maintaining the latter conductive accordingly effecting further build-up of current flow through said primary winding of said charging transformer, and wherein said ignition-capacitor-charging means comprises cut-off means automatically operative after the build-up of current in said primary winding of said charging transformer has proceeded to a predetermined extent for terminating the flow of such current by terminating the positive-feedback action of said positive-feedback means, to thereby induce a voltage pulse across said secondary winding of said charging transformer, and wherein said ignition-capacitor-charging means further comprises means connecting said secondary winding of said charging transformer in circuit with said ignition capacitor means and including charging rectifier means operative for permitting current flow through said ignition capacitor means from said secondary winding of said charging transformer only when the voltage generated across the latter is of a predetermined polarity, and wherein said voltage-responsive means of said engine-speed-limiting means comprises ignition-prevention means operative when the voltage across said speed-monitoring capacitor means exceeds said predetermined value for preventing the build-up of current flow through said primary winding of said charging transformer by preventing positive-feedback action by said positive-feedback means.

Claim 4

In the ignition system of an internal combustion engine, in combination, electrical igniting means operative for igniting a fuel-air mixture in a cylinder of the engine; ignition capacitor means operative for storing the electrical energy required by said igniting means for effecting ignition of said mixture; energy transfer means operative for causing said igniting means to ignite said mixture by transferring to said igniting means electrical energy stored in said ignition capacitor means; ignition-capacitor-charging means connected to said ignition capacitor means and operative for charging the latter timing means for timing the transfer of energy from said capacitor means to said igniting means; and engine-speed-limiting means including speed-monitoring capacitor means, speed-dependent charging means for charging said speed-monitoring capacitor means by applying thereto substantially identical charging pulses having a pulse repetition frequency proportional to engine speed, discharge means connected to said speed-monitoring capacitor means and operative for discharging said speed-monitoring capacitor means at such a rate that the voltage across the latter can build up to a predetermined value only if the engine speed reaches a predetermined speed, and voltage-responsive means connected to said speed-monitoring capacitor means and operative when the voltage across the latter exceeds said predetermined value for preventIng said igniting means from igniting said mixture, wherein said energy transfer means includes a transformer comprised of a secondary winding connected across said igniting means and a primary winding, and means connecting said primary winding in circuit with said ignition capacitor means and including a first electronic switch for preventing discharge of said ignition capacitor means through said primary winding except when said switch is conductive, and wherein said ignition-capacitor-charging means includes a charging transformer comprised of a primary winding and a secondary winding, a source of D.C. current connected across said primary winding of said charging transformer, and a second electronic switch connected in circuit with said source and said primary winding of said charging transformer for preventing flow of current through said primary winding of said charging transformer except when said second electronic switch is conductive, and wherein said timing means comprises means for applying a brief turn-on voltage pulse to said second-electronic switch to initiate the build-up of current flow through said primary winding of said charging transformer, and inductive positive-feedback means operative in response to build-up of current flow through said primary winding of said charging transformer for applying to said second electronic switch a control voltage maintaining the latter conductive accordingly effecting further build-up of current flow through said primary winding of said charging transformer, and wherein said ignition-capacitor-charging means comprises cut-off means automatically operative after the build-up of current in said primary winding of said charging transformer has proceeded to a predetermined extent for terminating the flow of such current by terminating the positive-feedback action of said positive-feedback means, to thereby induce a voltage pulse across said secondary winding of said charging transformer, and wherein said ignition-capacitor-charging means further comprises means connecting said secondary winding of said charging transformer in circuit with said ignition capacitor means and including charging rectifier means operative for permitting current flow through said ignition capacitor means from said secondary winding of said charging transformer only when the voltage generated across the latter is of a predetermined polarity, and wherein said voltage-responsive means of said engine-speed-limiting means comprises ignition-prevention means operative when the voltage across said speed-monitoring capacitor means exceeds said predetermined value for preventing the build-up of current flow through said primary winding of said charging transformer by preventing positive-feedback action by said positive-feedback means.

Claim 5

A system as defined in claim 2, wherein said discharge means comprises a discharge circuit branch connected across said speed-monitoring capacitor means and including resistor means for dissipating energy stored in said speed-monitoring capacitor means.

Claim 6

A system as defined in claim 3, wherein said voltage-responsive means has an input, and wherein said discharge circuit branch comprises a voltage divider having a voltage-divider tap connected to said input of said voltage-responsive means.

Claim 7

A system as defined in claim 4, wherein said voltage divider is an adjustable voltage divider applying to said input of said voltage-responsive means an adjustable fraction of the voltage across said speed-monitoring capacitor means, whereby to permit adjustment of the engine speed above which ignition is prevented.

Claim 8

A system as defined in claim 4, wherein said voltage divider is comprised of a first portion and a second portion joined together at said voltage-divider tap, and wherein one of said portions is comprised of parallel-connected ohmic resistance means and negative-temperature-coefficient resistance means and a further resistance means connected in series with the parallel combination of said ohmic and negaTive-temperature-coefficient resistance means.

Claim 9

A system as defined in claim 6, wherein said further resistance means is comprised of the series connection of an ohmic resistor and a negative-temperature-coefficient resistor.

Claim 10

A system as defined in claim 2, wherein said timing means comprises signal-generating means for generating timing signals for controlling said energy-transfer means and said ignition-capacitor-charging means, and wherein sid speed-dependent charging means comprises means operative for deriving said substantially identical charging pulses from timing pulses generated by said signal-generating means.

Claim 11

A system as defined in claim 8, wherein said means operative for deriving said charging pulses from said timing signals comprises a pulse-transmitting circuit branch onnected between said signal-generating and said speed-monitoring capacitor means and including half-wave rectifier means for permitting the flow of charging current into said speed-monitoring capacitor means while preventing discharge of said speed-monitoring capacitor means through said pulse-transmitting circuit branch.

Claim 12

A system as defined in claim 9, wherein said pulse-transmitting circuit branch further includes a resistor connected in series with said half-wave rectifier means.

Claim 13

A system as defined in claim 9, wherein said speed-dependent charging means further comprises Zener diode means connected across said speed-monitoring capacitor means with such a polarity that a charging pulse applied to said speed-monitoring capacitor means will cause breakdown of said Zener diode means and shunt further charging current of said charging pulse away from said speed-monitoring capacitor means when the voltage level of such charging pulse exceeds a predetermined value, whereby to establish an upper limit on the voltage level of the charging pulses actually charging said speed-monitoring capacitor means.

Claim 14

A system as defined in claim 2, wherein said inductive positive-feedback means comprises inductor means so positioned as to have induced thereacross a voltage dependent upon the build-up of current flow through said primary winding of said charging transformer, said inductor means being so connected to said second electronic switch as to apply to the latter a control voltage maintaining the latter conductive and effecting further build-up of current flow through said primary winding of said charging transformer, and wherein said cut-off means comprises a third electronic switch connected across said inductor and operative when conductive for short-circuiting said inductor to prevent the latter from applying to said second electronic switch a control voltage sufficient to maintain said second switch conductive, and wherein said ignition-preventing means comprises means for biasing said third electronic switch for conduction when the voltage across said speed-monitoring capacitor means reaches said predetermined value.

Claim 15

A system as defined in claim 12, wherein said third electronic switch has two terminals between which current flows when said third switch is conductive and also a control terminal, and wherein said cut-off means comprises a voltage divider connected across said inductor means and having a voltage-divider impedance portion connected between said control terminal of said third switch and one of said two terminals of said third switch, to render said third switch conductive when the voltage across said inductor means increases to a predetermined extent.

Claim 16

A system as defined in claim 12, wherein said third electronic switch is a thyristor.

Claim 17

A system as defined in claim 12, wherein said ignition-preventing means comprises standby circuit means connected across said source of D.C. current and normally operative for carrying a standby current but operative when the voltage across said speed-monitoring capacitor means exceeds said predetermined value for diverting said standby current to said third electronic switch and applying said standby current to said third electronic switch as a biasing current.

Claim 18

A system as defined in claim 15, wherein said standby circuit means comprises a first current path for standby current and a second current path for conducting current to said third electronic switch, and wherein said second current path includes a diode having a polarity such as to permit current flow along said second path only in a direction which will bias said third electronic switch for conduction.

Claim 19

A system as defined in claim 16, wherein said first current path is connected in series with a stabilizing resistor and with such stabilizing resistor connected across said source of D.C. current, and a Zener diode connected across said first current path.

Claim 20

A system as defined in claim 16, wherein said first current path includes the anode-cathode current path of a thyristor.

Claim 21

A system as defined in claim 18, wherein said standby circuit means further includes a Zener diode having a cathode connected to the anode of said thyristor and an anode connected to the cathode of said thyristor.

Claim 22

A system as defined in claim 19, wherein said standby circuit means further comprises a transistor having a base-emitter junction connected across said speed-monitoring capacitor means and having a collector-emitter path connected across the cathode-gate control path of said thyristor.

Claim 23

A system as defined in claim 2, wherein said timing means comprises crankshaft coupled means for generating crankshaft-position-synchronized pulses, and differentiating means for converting such crankshaft-position-synchronized pulses into voltage spikes, and wherein said speed-dependent charging means comprises means for charging said speed-monitoring capacitor means by applying thereto charging pulses derived from said voltage spikes.

Claim 24

In the ignition system of an internal combustion engine, in combination, electrical igniting means operative for igniting a fuel-air mixture in a cylinder of the engine; ignition capacitor means operative for storing the electrical energy required by said igniting means for effecting ignition of said mixture; energy transfer means operative for causing said igniting means to ignite said mixture by transferring to said igniting means electrical energy stored in said ignition capacitor means; ignition-capacitor-charging means connected to said ignition capacitor means and operative for charging the latter; timing means for timing the transfer of energy from said capacitor means to said igniting means; and engine-speed-limiting means including speed-monitoring capacitor means, speed-dependent charging means for charging said speed-monitoring capacitor means by applying thereto substantially identical charging pulses having a pulse repetition frequency proportional to engine speed, discharge means connected to said speed-monitoring capacitor means and operative for discharging said speed-monitoring capacitor means at such a rate that the voltage across the latter can build up to a predetermined value only if the engine speed reaches a predetermined speed, and voltage-responsive means connected to said speed-monitoring capacitor means and operative when the voltage across the latter exceeds said predetermined value for preventing said igniting means from igniting said mixture, wherein said timing means comprises crankshaft coupled means for generating crankshaft-position-synchronized pulses, and differentiating means for converting such crankshaft-positionsynchronized pulses into voltage spikes, and wherein said speeddependent charging means comprises means for charging said speedmonitoring capacitor means by applying thereto charging pulses derived from said voltage spikes.

Claim 25

In the ignition system of an internal combustion engine, in combination, electrical igniting means operative for igniting a fuel-air mixture in a cylinder of the engine; ignition capacitor means operative for storing the electrical energy required by said igniting means for effecting ignition of said mixture; energy transfer means operative for causing said igniting means to ignite said mixture by transferring to said igniting means electrical energy stored in said ignition capacitor means; ignition-capacitor-charging means connected to said ignition capacitor means and operative for charging the latter; timing means for timing the transfer of energy from said capacitor means to said igniting means; and engine-speed-limiting means including speed-monitoring capacitor means, speed-dependent charging means for charging said speed-monitoring capacitor means by applying thereto substantially identical charging pulses having a pulse repetition frequency proportional to engine speed, discharge means connected to said speed-monitoring capacitor means and operative for discharging said speed-monitoring capacitor means at such a rate that the voltage across the latter can build up to a predetermined value only if the engine speed reaches a predetermined speed, and voltage-responsive means connected to said speed-monitoring capacitor means and operative when the voltage across the latter exceeds said predetermined value for preventing said igniting means from igniting said mixture, wherein said timing means comprises crankshaft coupled means for generating crankshaft-position-synchronized pulses, and differentiating means for converting such crankshaft-positionsynchronized pulses into voltage spikes, and wherein said speeddependent charging means comprises means for charging said speedmonitoring capacitor means by applying thereto charging pulses derived from said voltage spikes.