DE861622C - Ignition device, especially for internal combustion engines with one or more sliding spark plugs, via which a capacitor is discharged - Google Patents

Description

Ignition device, especially for internal combustion engines with one or several sliding spark spark plugs through which a capacitor is discharged. The invention relates to an ignition device, in particular for internal combustion engines that with one or more sliding spark ignition plugs through which a capacitor discharges will be equipped.

With such spark plugs a. Creepage formed by a wide discharge path that is short in the discharge direction. at every discharge of the capacitor through this path is always a part along it Break through the path, while the creepage path extends over another part along the Railway is renewed again by the fact that it is then electric. deposit conductive parts on it.

The favorable properties of a sliding spark plug, which makes it differs from a high voltage spark plug are characterized by the fact that the creepage path is broken through with every occurring spark, whereas with the high-voltage ignition! Spark from flashover between the electrodes.

In the event of impurities that cannot be avoided, the The high-voltage spark plug is not able to penetrate the creepage distance that is then present and cause a flashover to initiate ignition, whereas the contaminants in the case of sliding spark plugs primarily the restoration of the creepage distance support financially.

Furthermore, impurities in the sliding spark spark plug shorten the discharge time of the; Kottdensiators through the then existing smaller resistance of the creepage distance, so that the larger mean discharge current necessary for the breakdown increases and ignition remains secured by a breakdown.

In the case of sliding spark plugs, the breakdown depends on the creepage distance from the current and is the burn-up of the electrodes, which is essential for the life of the spark plug is decisive, determined by the charge or the number of coulombs that occur during the breakdown flow via the creepage distance of the spark plug, the problem., according to the invention is solved, is based on the considerations, that., albeit on the one hand a low tension in order to maintain the favorable properties of the Gleitfunkenzüudkerze serves the advantage, on the other hand in connection with the Size of the capacitor to store the energy and the burn-up or that of it Depending on the service life, a higher voltage is desired. To this extent, however, how the voltage of the sliding spark plug is selected to be higher, .go with the same: charge the very favorable properties of sliding spark plugs or low-voltage spark plugs lost.

In the case of the ignition device for a high-voltage spark plug, this is Spark plug directly connected to the power source at the moment of ignition, and efforts are made to keep the voltage of the power source so high at the moment of ignition to do as possible: In the case of the ignition device for a sliding spark spark plug - against it At the moment of ignition, the capacitor is only connected to the spark plug in connection, and the current must be large enough for a breakdown to occur allow. -The invention is based on the knowledge that one in the data of the capacitor has a means at hand to make the life of the sliding spark plug substantial to extend.

Corresponding. the invention is marked the ignition device by means of a capacitor that delivers an energy of at least o, oi joules to the spark plug and emits a maximum of 2 joules per spark at a voltage of at least 215o volts and at most 5,000 V.

The invention is illustrated below using a few examples. explained in more detail: The energy stored in a capacitor of 1 microfarad at a voltage of zooo V is calculated using the formula I / 2 CV = and amounts to 2 joules: Die Capacity of a capacitor at a voltage of 4000 V for storing the The same amount of energy of 21 joules is only 0.25 microfarads and is accordingly considerably smaller than in the former case.

The application of high voltage to sliding spark plugs has the Advantage of a very small capacitor, but the disadvantage that it is for high voltage suitable capacitor is more expensive to purchase.

The capacitor charge Q = CTl is smaller for a higher voltage than for a lower voltage for the same energy stored in the capacitor.

In the case dealt with first, the charge on the capacitor is those about the. Creepage distance of the sliding spark spark plug flows, o, oo2, coulomb and in the second Case o, ooi Coulomb.

The erosion of the electrodes of the sliding spark plug is therefore at 4000 V. Be considerably less than at zoooV, so that the life of the spark plug at: higher voltage becomes greater.

The mean discharge current is calculated from the formula and this is at a discharge time of z. B. io microseconds for the i microfarad capacitor at a voltage of 2ooo V is about ioo "amps.

The discharge time, which is proportional to the point CR, is the same -Resistance of the creepage distance of the sliding spark plug is shorter to the same extent as the Capacitor capacity is smaller. In the second case, the capacity is four times that small as in the first case, sb that the discharge time for the conidenser of 0.25 microfarads at a voltage of 4000 V will be about 2 microseconds.

The mean discharge current for the latter capacitor is approximately 20o amps.

The breakdown of a sliding spark plug therefore also remains smaller charge of the capacitor.

However, such currents are not permitted for high-voltage spark plugs and would completely melt away the electrodes. For a high voltage spark plug with a normal distance between the electrodes, the withstand voltage is at a compression pressure of 7 at about 5oao volts.

Assuming only i 9 / o of the aforementioned zoo amps; then this results in 2 amps. The released energy would then amount to E # I - t = 5ooo - 2 - o "ooo3- Joule. At high voltage, however, the spark plug will surely become oily at 2 amperes of overturning current.

The difference that occurs corresponds to the discharge time of the capacitor The invention has little or no effect on the efficiency of the internal combustion engine, in which the ignition device is built, even at speeds of more than, 8ooa Revolutions per minute.

Claims (1)

Claim: Ignition device, in particular for internal combustion engines, which are equipped with one or more sliding spark spark plugs, via which a capacitor is discharged, characterized by a capacitor which gives the spark plug an energy of at least o; oz joules and a maximum of 2 joules per spark at a voltage of at least 50 volts and at most 5,000 volts. Cited publications: German Patent No. 683 661; Fiat report 624 BC December 15 z945.