US3721224A - Ignition circuit for spark plugs of internal-combustion engine - Google Patents

Ignition circuit for spark plugs of internal-combustion engine Download PDF

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Publication number
US3721224A
US3721224A US00124173A US3721224DA US3721224A US 3721224 A US3721224 A US 3721224A US 00124173 A US00124173 A US 00124173A US 3721224D A US3721224D A US 3721224DA US 3721224 A US3721224 A US 3721224A
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United States
Prior art keywords
base
transistor
condenser
emitter
secondary winding
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Expired - Lifetime
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US00124173A
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English (en)
Inventor
Zotto G Del
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STMicroelectronics SRL
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ATES Componenti Elettronici SpA
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P3/00—Other installations
    • F02P3/06—Other installations having capacitive energy storage
    • F02P3/08—Layout of circuits
    • F02P3/0876—Layout of circuits the storage capacitor being charged by means of an energy converter (DC-DC converter) or of an intermediate storage inductance
    • F02P3/0884—Closing the discharge circuit of the storage capacitor with semiconductor devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B75/00—Other engines
    • F02B75/02—Engines characterised by their cycles, e.g. six-stroke
    • F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
    • F02B2075/027—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle four

Definitions

  • the ignition circuit of a spark plug of an internal-combustion engine includes a storage condenser in series with a controlled rectifier which is periodically triggered under the control of an engine-driven cam switch by a blocking oscillator comprising a transistor with grounded emitter in series with the primary of a coupling transformer.
  • a blocking oscillator comprising a transistor with grounded emitter in series with the primary of a coupling transformer.
  • One secondary winding of that transformer is inserted, together with a pair of diodes, in a charging path for the storage condenser while another secondary winding lies between the emitter of the transistor and its base which is connected through a feedback resistor to the collector thereof and via an R/C network to the gate of the controlled rectifier.
  • the base is grounded through the last-mentioned secondary winding which is so poled as to intensify a firing pulse capacitively transmitted to the base upon the opening of the switch; at the same time the controlled retifier is turned on to discharge the previously charged storage condenser through the ignition circuit, whereupon the transistor cuts off and the condenser is recharged by the reversed transformer voltage.
  • My present invention relates to a system for intermittently firing a spark-discharge device, such as a spark plug in an internal-combustion engine of an automotive vehicle.
  • the ignition circuit of an automotive spark plug generally includes a storage condenser which is alternately charged from a direct-current source, such as the vehicular battery, and discharged through a step-up transformer generating the high voltage necessary to break down the spark gap.
  • the timing of the discharge is controlled by a switch operated by the cam shaft of the engine, which in a four-cylinder model may execute about 7,000 revolutions per minute.
  • a three-winding coupling transformer having its primary winding in series with the output electrode (collector) of a transistor forming part of the blocking oscillator; one secondary winding of the transformer is connected between the input electrode (base) and the common electrode (emitter) of the transistor with such a polarity as to intensify both blocking and unblocking potentials applied to that input electrode via a resistive feedback connection, another secondary winding of the same transformer lying in the charging circuit of the storage condenser whose discharge circuit includes a normally open electronic switch (such as a silicon controlled rectifier) with a control circuit extending from the transistor input to close that switch in the presence of an unblocking potential, i.e. when the transistor conducts.
  • a normally open electronic switch such as a silicon controlled rectifier
  • a reversal of the cam-operated switch to bias the transistor into conduction causes a rising current flow through the coupling transformer which regeneratively energizes the transistor input (its base) and is also communicated to the control electrode for the electronic switch (i.e. the SCR gate) to discharge the previously charged storage condenser; as the transistor and/or the core of the coupling transformers saturates, the regenerative feedback diminishes and the transistor begins to cut off, the resulting polarity reversal in the several transformer windings resulting in the flow of charging current into the condenser whose discharge circuit is broken at this point by the reopening of the electronic switch.
  • the electronic switch i.e. the SCR gate
  • the drawing shows an ignition system for a spark plug 10 of an automotive engine, not further illustrated,
  • Bus bar 14 is connected, within a blocking oscillator generally designated Ob, to the collector of an NPN transformer 01 through the primary winding N, ofa coupling transformer Tr having a core 15 with two further windings thereon, i.e., a feedback winding Np and a load winding N
  • the relative polarities of the currents flowing through these windings have been conventionally indicated by dots.
  • Switch P lies between ground and bus bar 14 in series with a leakage resistor R1.
  • the junction of this resistor with switch P is connected to the base of transistor Q1 through a circuit including, in series, a capacitor C1 and three resistors R2, R3 and R4.
  • Two diodes DI and D2 are shunted across resistors R2 and R3, respectively, with a polarity allowing positive pulses from capacitor C1 to bypass the resistors R2 and R3 in flowing to the base of the transistor 01 to unblock it.
  • This base is normally maintained at emitter potential (ground) through transformer secondary N F inserted between ground and the junction of resistors R2 and R3, the same junction being connected to the collector of the transistor by way of a feedback resiStor R6.
  • An integrating circuit consisting of a resistor R5 in parallel with a condenser C3, lies between the base and the emitter of transistor Q1 to shunt voltage transients to ground.
  • the other transformer secondary N is connected in a charging circuit for a storage condenser C4 in series with a pair of diodes D3 and D5.
  • a discharge circuit for condenser C4 includes the primary of a voltage-step-up transformer THT whose secondary feeds the spark plug 10 its primary lying in series with an SCR D4 having its gate connected to the junction of resistors R3 and R4 in the input circuit of transistor Q1 by way of an R/C network consisting of a condenser C2 and a resistor R7 in parallel therewith.
  • the bucking voltage in winding N F decreases to apply a negative-going potential to the base of transistor Q1. This reduces the current flow through primary Np and rapidly builds up a negative blocking potential in the transistor input until conduction ceases. At the same time the reversal of the polarity of the voltage developed across secondary winding N energizes the charging circuit for condenser C4 by way of diodes D3 and D5. With SCR D4 cut off by the negative potential on its gate electrode, the secondary current generated in winding N is prevented from circulating through the controlled rectifier.
  • diode D5 enables the dissipation of residual energy electromagnetically stored in the primary of transformer THT after the electronic switch D4 has opened.
  • resistor R7 in the control circuit of SCR D4 insures the presence of positive gate voltage throughout the discharge phase, thereby preventing a premature cutoff of the controlled rectifier which could otherwise occur, for example, prior to the firing of the spark plug 10 as a result of the counter-emf. developed across the primary oF transformer Tl-lT. This insures a complete discharge of the condenser C4 and prevents overcharges in subsequent cycles.
  • Resistor R3 and diode D2 protect the transistor Q1 and the controlled rectifier D4 from excessive negative voltages during switchover between saturation and cutoff.
  • the energy stored in the core of transformer Tr equals kLl where L is the inductance of primary winding N and 1,, is the peak current flowing through that winding during conduction of the transistor.
  • This energy a large part of which is transferred to the storage condenser C4, may range in magnitude between 50 and 75 mjoules with battery voltages ranging between 8 and 16 volts. With the same range of battery voltages Vb, the charging potential of storage condenser C4 may vary between 320 and 390 volts.
  • the output voltage developed across the secondary winding of step-up transformer THT may reach 24 KV if the resistance of the spark gap of spark plug 10 is on the order of 1 MO.
  • a system for intermittently igniting a sparkdischarge device comprising:
  • a blocking oscillator connected across said source, said oscillator including a transistor with an emitter, a collector and a base, a coupling transformer having a primary winding inserted between said collector and a first terminal of said source,
  • said emitter being tied to a second terminal of said source, a capacitor in series with said base, switch means for al ernately applying a blocking potential and an unblocking potential from said source to said capacitor, and a resistive connection between said base and the junction of said primary winding with said collector, said coupling transformer having a first secondary winding connected between said base and said emitter for intensifying said unblocking and blocking potentials upon incipient conduction and cutoff of said transistor;
  • an ignition circuit for said sparledischarge device including a condenser and an electronic switch in series;
  • a charging circuit including another secondary winding of said coupling transformer and diode means in series with said condensor;
  • control circuit for said electronic switch connected to said base for closing said electronic switch in the presence of said unblocking potential, thereby discharging said condenser through said ignition circuit, said other secondary winding being poled to recharge said condenser upon incipient cutoff of said transistor.
  • control circuit includes a capacitance and a resistance in parallel.
  • said ignition circuit includes a step-up transformer in series with said condenser and said electronic switch.
US00124173A 1970-03-13 1971-03-15 Ignition circuit for spark plugs of internal-combustion engine Expired - Lifetime US3721224A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT2191670 1970-03-13

Publications (1)

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US3721224A true US3721224A (en) 1973-03-20

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Application Number Title Priority Date Filing Date
US00124173A Expired - Lifetime US3721224A (en) 1970-03-13 1971-03-15 Ignition circuit for spark plugs of internal-combustion engine

Country Status (8)

Country Link
US (1) US3721224A (ru)
JP (1) JPS4922983B1 (ru)
CH (1) CH522823A (ru)
DE (1) DE2057520C3 (ru)
ES (1) ES384160A1 (ru)
FR (1) FR2066000A5 (ru)
GB (1) GB1277553A (ru)
SU (1) SU399151A3 (ru)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3838328A (en) * 1973-03-19 1974-09-24 W Lundy Capacitive discharge ignition system
US3918425A (en) * 1972-09-25 1975-11-11 Setco La Chaux De Fonds S A Electronic device serving to supply a load with constant voltage pulses
US4345576A (en) * 1979-09-24 1982-08-24 Super Shops, Inc. Multi-spark CD ignition
US6348797B1 (en) * 1999-09-16 2002-02-19 Mitsubishi Denki Kabushiki Kaisha Combustion state detecting apparatus for internal combustion engine
US20090183705A1 (en) * 2008-01-22 2009-07-23 Coates George J Hot spark injection system for diesel engines to promote complete combustion

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4046125A (en) * 1975-10-17 1977-09-06 Mackie Ronald D Capacitive discharge ignition system
FR2394686A1 (fr) * 1977-06-17 1979-01-12 Nutek Inc Systeme d'allumage par decharge de circuit capacitif pour moteurs a combustion interne

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3271593A (en) * 1963-12-05 1966-09-06 Vilbiss Alan J De Internal combustion engine ignition system
US3302629A (en) * 1964-09-21 1967-02-07 Motorola Inc Capacitor discharge ignition system with blocking oscillator charging circuit
US3415234A (en) * 1966-06-06 1968-12-10 Wilbur A. Dammann Electronic ignition system
US3487822A (en) * 1967-11-29 1970-01-06 Motorola Inc Capacitor discharge ignition system
US3520288A (en) * 1968-11-08 1970-07-14 Gen Motors Corp Dual spark capacitor discharge ignition system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3271593A (en) * 1963-12-05 1966-09-06 Vilbiss Alan J De Internal combustion engine ignition system
US3302629A (en) * 1964-09-21 1967-02-07 Motorola Inc Capacitor discharge ignition system with blocking oscillator charging circuit
US3415234A (en) * 1966-06-06 1968-12-10 Wilbur A. Dammann Electronic ignition system
US3487822A (en) * 1967-11-29 1970-01-06 Motorola Inc Capacitor discharge ignition system
US3520288A (en) * 1968-11-08 1970-07-14 Gen Motors Corp Dual spark capacitor discharge ignition system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3918425A (en) * 1972-09-25 1975-11-11 Setco La Chaux De Fonds S A Electronic device serving to supply a load with constant voltage pulses
US3838328A (en) * 1973-03-19 1974-09-24 W Lundy Capacitive discharge ignition system
US4345576A (en) * 1979-09-24 1982-08-24 Super Shops, Inc. Multi-spark CD ignition
US6348797B1 (en) * 1999-09-16 2002-02-19 Mitsubishi Denki Kabushiki Kaisha Combustion state detecting apparatus for internal combustion engine
US20090183705A1 (en) * 2008-01-22 2009-07-23 Coates George J Hot spark injection system for diesel engines to promote complete combustion

Also Published As

Publication number Publication date
DE2057520B2 (de) 1978-09-21
CH522823A (it) 1972-05-15
ES384160A1 (es) 1973-01-01
DE2057520C3 (de) 1979-05-10
DE2057520A1 (de) 1971-09-30
FR2066000A5 (ru) 1971-08-06
GB1277553A (en) 1972-06-14
JPS4922983B1 (ru) 1974-06-12
SU399151A3 (ru) 1973-09-27

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