Internal-combustion engines – High tension ignition system – Using capacitive storage and discharge for spark energy
Patent
1999-07-02
2000-10-31
Kwon, John
Internal-combustion engines
High tension ignition system
Using capacitive storage and discharge for spark energy
123620, 123644, F02P 100
Patent
active
061386537
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an electric ignition device according to the preamble of Claim 1 and to a method for operating an ignition device.
Such ignition devices are used for igniting fuel-air mixtures in internal combustion engines. Fuel-air mixtures which have a stoichiometric ratio require little igniting energy and burn up reliably. However, internal combustion engines are increasingly being operated with lean mixtures, as a result of which the fuel consumption and the emission of pollutants can be drastically reduced. Such lean fuel-air mixtures require higher igniting energies and a longer lasting ignition spark in order to ensure reliable ignition of the fuel-air mixture.
Furthermore, particular ignition problems arise in the case of special applications such as, for example, in engines for motor boats. Thus, the air-fuel mixture can be ignitable only with difficulty because of moisture components, or soot particles which impair the ignition collect in an idling operation of relatively lengthy duration.
Ignition problems arise with internal combustion engines particularly in the case of low speeds and during the starting operation.
Fundamentally, two types of ignition devices are known, specifically inductive ignition devices (Coil Ignition=CI) and capacitive ignition devices (Capacitive Discharge Ignition=CDI). Capacitive ignition devices are distinguished by a high ignition voltage and a rapid ignition voltage rise, with the result that an ignition spark can be produced even in the case of non-ideal spark gaps. However, the intensive ignition spark of a capacitive ignition device is only very short-lasting, with the result that poorly flammable mixtures often cannot be ignited.
Inductive ignition devices, by contrast, produce a relatively long-lasting ignition spark, it being the case, however, that the maximum ignition voltage is substantially lower than in the case of capacitive ignition devices.
WO 93/04279 has disclosed an ignition device in which two energy sources are used in order to produce an ignition spark which has a high ignition voltage and, at the same time, is relatively long-lasting. In this case, a distinction is drawn between the actual spark, to produce which a high voltage is required, and the arc following thereupon, which is kept burning by means of a relatively low voltage.
This ignition device has an inherently conventional design with a primary capacitor which serves as first energy source or energy store and is arranged in a primary circuit. The primary circuit is coupled via a transformer to a secondary circuit in which a spark plug is provided. The primary capacitor is charged by means of a current source to a predetermined voltage value, and discharged suddenly by means of a trigger device. The discharging pulse is coupled into the secondary circuit via the transformer and causes a high voltage pulse for producing a spark at the spark plug or spark gap. To this extent, this ignition device corresponds to a conventional capacitive ignition device.
Moreover, as a second energy source a secondary capacitor is connected in series with the spark plug in the secondary circuit. This secondary capacitor is charged via the same current source as the primary capacitor or via a further current source, the secondary capacitor subsequently being discharged at the spark produced by the primary capacitor, since the secondary circuit is closed by the formation of a plasma in the spark gap. The arc is kept burning by the second energy source, the secondary capacitor.
Furthermore, U.S. Pat. No. 4,083,347 and U.S. Pat. No. 4,506,650 have disclosed further ignition devices which contain additional electronic subassemblies in the secondary circuit in order to maintain a pulsed or capacitive ignition with a high ignition voltage over a lengthy period.
Because of the high voltages (>3000 V) and high currents (>250 mA) occurring in the secondary circuit, it is not possible, or is possible only with an exceptionally high technical outlay, for additional energy to be fed into the secondar
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Ficht GmbH & Co. KG
Kwon John
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