The spark plug (2) is intended for internal combustion engines and has an ignition chamber (11) which is connected via a transfer passage (28, 12) to a main combustion space (13) of the internal combustion engine and contains ignition electrodes (7, 29). The ignition chamber (11) is designed as an annular space. The transfer passage (28) opens essentially into the centre plane of the cross-section of the annular space (11), mutually adjacent swirl rings (33, 34) comprising quantities of fuel/air mixture which have flowed in circulating in opposite directions. In relation to their volume, these swirl rings (33, 34) have very small cross-sections, with the result that very high centrifugal accelerations occur in them and within their quantities of mixture each effect a very pronounced charge stratification. Ignition takes place close to one wall (29) of the ignition chamber (11), where the swirl rings (33, 34) form a stagnant zone (35). Within the stagnant zone (35), highly fuel-enriched mixture is virtually at rest, with the result that its ignition takes place with great reliability and the subsequent development of the flame progresses quickly. In the transfer passage (28), there is a glass window for the analysis of the development of the flame. The surface of the window lies in the region of high gas velocities and as a result is kept free of dirt deposits.

Spark plug for internal combustion engines

To increase the spark intensity delivered from a spark plug, an auxiliary spark gap (33) is serially connected with an auxiliary capacitor (37) and the main spark gap (42), the auxiliary capacitor being charged through a charging circuit including a resistor (45) connected in shunt to the auxiliary spark gap (33) and the auxiliary capacitor, and a further or second resistor (46) connected in shunt across the auxiliary capacitor and the ground or chassis electrode (15), and a shunt capacitor (51) is connected between the main spark plug terminal (27) and the ground or chassis or counter electrode (11, 15) so that, upon breakdown of the auxiliary spark gap, the main spark gap will have a voltage thereacross formed by the charge voltage of the main or shunt capacitor (51) and the additional voltage on the auxiliary capacitor (37) which had been charged through the resistors connected across the auxiliary capacitor and to the main spark plug terminal (27) and the ground terminal or electrode (15) respectively.

Spark plug for externally ignited internal combustion engine

A spark plug which has a capacitor located therein, connected in parallel to the main or ignition spark gap (13), additional includes a pilot or pre-spark gap (12) located within the insulator (18) of the spark gap, to control discharge of the capacitor (14) through the main spark gap (13). In accordance with the invention, the pre-spark gap (12) is located within a chamber (34) in the insulator which is filled with a pressurized gas, preferably nitrogen under pressure of between 2 to 100 bar, preferably 5 to 30 bar, with the electrodes (27, 27) defining the pre-spark gap being spaced, preferably, between about 0.1 to 1 mm from each other. Placing the pre-spark gap electrodes within a pressurized gas chamber increases the energy available at the main spark gap (13) for ignition even of very lean fuel-air mixtures. Preferably, an inductive-resistive circuit (15) is connected in shunt across the main electrode (13) to prevent arcing and glow discharges across the main spark gap (13) after the initial ignition spark.

Spark plug with capacitor spark discharge

To increase the spark energy being transferred from a spark plug to a fuel-air mixture, so that the maximum energy transfer occurs during the initial breakdown phase and electrode deterioration at the spark plug is prevented upon occurrence of subsequent arc conduction and glow phases, an inductive circuit is connected in parallel to the spark gap which is so dimensioned that the inductance has a time constant which inhibits substantial current flow through the shunt circuit upon breakdown of the spark gap, but permits flow of current during an arc and glow phase of the spark at the spark gap through the shunt circuit so that energy is drained from the spark gap during the plasma and glow phase.

Spark plug for an internal combustion engine, having a pilot breakdown gap

The connector permits firing of the sparking plug by a sudden high energy discharge without the need for modification to either the plug itself or the distributor system. The insulated plug housing (1) contains a h.f. capacitor (8) between the cable connector (3) and the snap-on clio (5) for the plug terminal. Between the conductor ends is a spark gap (19). One terminal of the capacitor (10) can be connected to a screen (2) on the body of the housing. The capacitor is preferably of the ceramic type. A suppression resistor (4) is normally included in the circuit. The connector has rubber seals (6,7) at each end to give a close fit on the HT cable and the sparking plug insulator. The components inserted in the housing are typically cast in insulating resin.

Connector for IC engine sparking plug - has HF capacitor and discharge gap inside housing

In the igniting process a high voltage capacitor is charged, and discharged across a spark gap and ignition electrodes when a threshold value voltage has been attained. This voltage is higher than the breakdown voltage at the ignition electrodes. The energy transfer takes place in the starting phase of the ignition spark, i.e. possibly in the breakdown phase of the ignition start. In an appropriate spark plug the presparking path is as near as possible to the ignition electrodes. It has the lowest possible ohmic and inductive resistance, and its threshold value voltage is externally controllable. Between the capacitor and the ignition electrodes the inductance and ohmic resistance of the supply line to the electrodes is as low as possible, at least at frequencies exceeding 50 MHz.

Gottfried Dipl Ing Bauer

Papers

Spark plug for igniting Otto engine mixt. - uses HV capacitor discharged on reaching threshold voltage, higher than breakdown voltage of electrodes