DE102017214177B3 - Device for igniting fuel by means of corona discharges - Google Patents

Abstract

A device for igniting fuel by means of corona discharges in a combustion chamber of an internal combustion engine, comprising an ignition system (1) electrically connected to a primary inductance (11) of an ignition coil (2), wherein a secondary inductance (14) of the ignition coil (2) via an ignition line (2) is electrically connected to an ignition unit (4), characterized in that the ignition system (1) is designed as a high-voltage capacitor ignition.

Description

The present invention relates to a device for igniting fuel by means of corona discharges in a combustion chamber of an internal combustion engine comprising an ignition system electrically connected to a primary inductance of an ignition coil, wherein a secondary inductance of the ignition coil is electrically connected via an ignition with an ignition unit, wherein the ignition system High-voltage capacitor igniter is formed, wherein the high-voltage capacitor ignition comprises a capacitor which is chargeable via at least one voltage source, wherein the capacitor is connected via a first switch to at least one voltage source and wherein the capacitor is connected via a second switch to the primary inductance of the ignition coil.

Devices for igniting fuel by means of corona discharges are already known in practice. These represent an alternative to the common ignition devices comprising a spark plug in which the ignition takes place via a spark which is generated between the center electrode and ground electrode.

The principle of ignition of fuel by means of corona discharges is based on the fact that a high voltage is generated at an ignition electrode in order to radiate an electric alternating field of high field strength. By the electric field, the fuel-air mixture is excited so that a plasma consisting of ions and radicals is formed. As soon as the charged particle density exceeds a critical value, visible rays of ionized gas are formed which extend into the combustion chamber and ignite the fuel. An ignition by means of corona discharges has the advantage over conventional spark ignition that the wear of the electrodes is considerably reduced and an extremely good combustion behavior is achieved.

Only, for example, is on the DE 10 2014 116 586 A1 in which a corona ignition system for an internal combustion engine is disclosed. The corona ignition system comprises a resonant circuit, which includes an ignition electrode and a high-frequency generator connected to the resonant circuit, which generates an alternating voltage for exciting the resonant circuit. Furthermore, a DC voltage source is provided in order to already set an input voltage for the high-frequency generator. The DC voltage source is controlled via a control circuit such that the resonant circuit is excited at least substantially with its resonant frequency. The control circuit is for this purpose connected to a detector circuit. The detector circuit transmits each zero crossing of the current intensity of the current flowing in the resonant circuit, so that the DC voltage source is controlled on the basis of this information.

From the US 4,136,659 A a device for igniting fuel by means of corona discharges is previously known. The device comprises an ignition coil having a primary inductance and a secondary inductance. The secondary inductance is further electrically connected via an ignition with an ignition unit.

Also the documents US 2012/0192624 A1 and US 2012/0063054 A1 disclose devices for igniting fuel by means of corona discharges.

The known corona ignition systems comprise a large number of components and, not least because of the necessary frequency control, are expensive in design and in operation.

The present invention is therefore based on the object, a device of the type mentioned in such a way and further develop that with structurally simple means a reliable generation of corona discharges can be realized.

According to the invention the above object is achieved by the features of claim 1. Thereafter, an apparatus for igniting fuel by means of corona discharges in a combustion chamber of an internal combustion engine comprising an ignition system electrically connected to a primary inductance of an ignition coil, wherein a secondary inductance of the ignition coil is electrically connected via an ignition with an ignition unit, wherein the ignition system formed as a high voltage capacitor ignition is, wherein the high-voltage capacitor ignition comprises a capacitor which is chargeable via at least one voltage source, wherein the capacitor is connected via a first switch to at least one voltage source and wherein the capacitor is connected via a second switch to the primary inductance of the ignition coil, characterized in that the first switch and the second switch are each controllable via a pulse generator.

In accordance with the invention, it has first been recognized that resonance mode with frequency control is not necessarily necessary. Rather, in the inventive manner by the arrangement of a high voltage capacitor ignition as the ignition system, a sufficiently high voltage can be generated on the secondary side of the ignition coil, even if the primary and secondary circuits do not have the same excitation frequency. Thus, the device is characterized by a surprising simple structure and a simple and therefore reliable operation.

In a further inventive manner, the high-voltage capacitor ignition on a capacitor which is rechargeable via at least one voltage source. In this case, the capacitor is connected via a first switch to the at least one voltage source. Via a second switch, the capacitor is connected to the primary inductance or primary coil of the ignition coil. By a corresponding circuit of the first and second switches, the capacitor can be selectively loaded from the voltage source and discharged via the primary side of the ignition coil. Due to the magnetic coupling between the primary side and the secondary side, a high voltage is induced on the secondary side, which is supplied to the ignition unit, so that a strong alternating electromagnetic field can be generated, which leads to the desired corona discharges. In a further inventive manner, the first switch and the second switch are each controlled by a pulse generator.

In a particularly advantageous manner, the ignition unit comprises a spark plug, in particular a prechamber spark plug. This may protrude into the combustion chamber to produce the corona discharges within the combustion chamber. The spark plug may include a center electrode and at least one ground electrode. In such an embodiment, it is further advantageous if the center electrode and the ground electrode are spaced so far apart that an electrical flashover during operation of the device is avoided. Such a construction is characterized by the fact that it is possible to make recourse essentially to already existing components, as a result of which, in addition to a reliable function, considerable cost savings can be realized. For example, the center electrode may have a distance of 1 mm to 3 mm, in particular 1.5 mm to 2.5 mm, preferably 2 mm, to the ground electrode, in particular when the capacitor of the high voltage capacitor ignition is charged by a voltage source of 150V.

In order to enable the generation of corona discharges in the most effective and simple manner possible, the center electrode can be designed such that it generates an inhomogeneous electric field. For example, it is conceivable that the center electrode comprises at its end projecting into the combustion chamber one or more arms which have a curved shape. Alternatively or additionally, the center electrode or the arms may be pointed at their free end.

In a particularly advantageous manner, the internal combustion engine is a gas engine, in particular a large gas engine.

• 1 ein Blockschaltbild einer erfindungsgemäßen Vorrichtung, und
• 2 ein Timing-Diagramm der Vorrichtung gemäß 1.

There are now various possibilities for designing and developing the teaching of the present invention in an advantageous manner. For this purpose, on the one hand to the claims subordinate to claim 1 and on the other hand to refer to the following explanation of preferred embodiments of the invention with reference to the drawings. In conjunction with the explanation of the preferred embodiments of the invention with reference to the drawings, generally preferred embodiments and developments of the teaching are explained. In the drawing show

• 1 a block diagram of a device according to the invention, and
• 2 a timing diagram of the device according to 1 ,

1 shows a block diagram of a device according to the invention. This includes an ignition system 1 , an ignition coil 2 , an ignition cable 3 as well as an ignition unit 4 ,

The ignition system 1 is realized as a high voltage capacitor ignition. This has a voltage source 5 on that the charging voltage of the capacitor 6 sets. The voltage source 5 For example, it can deliver a voltage of 150V. The capacitor 6 is from the voltage source 5 before the ignition timing, ie at time to, via the first switch 7 charged and at the ignition timing t ₁ via the second switch 8th discharged. The first switch 7 is via a first pulse generator 9 and the second switch 8th via a second pulse generator 10 controlled. About the first and second pulse generator 9 . 10 is thus determined how long the capacitor 6 is charged and when it is discharged.

By discharging the capacitor 6 via the primary inductance 11 will be on the primary side 12 the ignition coil 2 creates a voltage. Due to the magnetic coupling between the primary side 12 and the secondary side 13 This causes a high voltage at the secondary inductance 14 induced.

This high voltage leads in combination with the parasitic components of the ignition unit 4 Serving spark plug and the ignition 3 to a vibration which is conducted to the electrodes where it generates an electric field leading to the corona discharges.

2 shows a timing diagram of the device according to 1 , In the upper graph of 2 is the one on the capacitor 6 applied voltage as a function of time. At time t ₀ , the first switch 7 closed, with the second switch 8th open, leaving the capacitor 6 is loaded. At the ignition point t ₁ we are the first switch 7 opened and the second switch 8th closed, leaving the capacitor 6 on the primary side 12 discharges.

This causes that at the primary inductance 11 a voltage is generated, as shown in the middle graph of 2 can be seen. This in turn requires that at the secondary inductance 14 an alternating voltage is induced. This is in the lower graph of 2 shown. This AC voltage is via the ignition cable 3 to the ignition unit 4 which comprises the spark plug, which serves to generate the corona discharges. Consequently, with common components an extremely simple construction for generating corona discharges is realized.

With regard to further advantageous embodiments of the device according to the invention, reference is made to avoid repetition to the general part of the specification and to the appended claims.

Finally, it should be expressly understood that the above-described embodiments of the device according to the invention are only for the purpose of discussion of the claimed teaching, but not limit these to the embodiments.

LIST OF REFERENCE NUMBERS

1

ignition system

2

ignition coil

3

Ignition

4

ignition unit

5

voltage source

6

capacitor

7

first switch

8th

second switch

9

first pulse generator

10

second pulse generator

11

primary inductance

12

primary

13

secondary side

14

secondary inductance

Claims (8)

Device for igniting fuel by means of corona discharges in a combustion chamber of an internal combustion engine, comprising an ignition system (1) electrically connected to a primary inductance (11) of an ignition coil (2), wherein a secondary inductance (14) of the ignition coil (2) via an ignition line ( 2) is electrically connected to an ignition unit (4), wherein the ignition system (1) is designed as a high-voltage capacitor ignition, wherein the high-voltage capacitor ignition comprises a capacitor (6) which is chargeable via at least one voltage source (5), wherein the capacitor (6) is connected via a first switch (7) with at least one voltage source (5) and wherein the capacitor (6) via a second switch (8) to the Primärinduktivität (11) of the ignition coil (2) is connected, characterized in that the first Switch (7) and the second switch (8) in each case via a pulse generator (9, 19) are controllable. Device after Claim 1 , characterized in that the ignition unit (4) comprises a spark plug, in particular a Vorkammerzündkerze. Device after Claim 2 , characterized in that the spark plug comprises at least one center electrode and at least one ground electrode. Device after Claim 3 , characterized in that the center electrode and the ground electrode are so far apart that an electrical flashover during operation is avoided. Device after Claim 4 , characterized in that the center electrode has a distance of 1 mm to 3 mm, in particular from 1.5 mm to 2.5 mm, preferably of 2 mm, to the ground electrode. Device according to one of Claims 3 to 5 , characterized in that the center electrode is formed so as to generate an inhomogeneous electric field. Device according to one of Claims 3 to 6 , characterized in that the center electrode has a curved shape and / or is pointed formed at its free end. Device according to one of Claims 1 to 7 , characterized in that the internal combustion engine is a gas engine, in particular a large gas engine.

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