KR20100066336A - Internal combustion engine - Google Patents

Abstract

PURPOSE: An internal combustion engine with an improved ignition mechanism is provided to activate the igniter at relatively low voltage, thereby extending the service life. CONSTITUTION: An internal combustion engine comprises a piston, a combustion chamber, and an igniter. The combustion chamber is defined by a cylinder head(12). The igniter lights a fuel-air mixture within the combustion chamber and includes one or more electric igniter units(20) and one or more optical igniter units(22). The electric igniter units are projected into the combustion chamber and the optical igniter units focuses light beam(26) on the combustion chamber.

Description

Internal combustion engine {INTERNAL COMBUSTION ENGINE}

The present invention relates to an internal combustion engine, in particular a gas engine, for the combustion of a gaseous fuel air mixture.

Different methods of ignition of gas engines are known in the prior art. In the diesel method, the ignition of the fuel air mixture in the combustion chamber is effected by the injection of the auto-ignition liquid ignition fuel into the compressed fuel air mixture under high pressure (pilot injection). In the Otto method, the fuel air mixture is externally ignited.

In the Otto method, the ignition of the gaseous fuel air mixture by means of an electric igniter (see eg DE 196 24 965 A1, DE 10 2005 050 435 A1) and the ignition of the gaseous fuel-gas mixture by a laser igniter (see : DE 10 2007 001 087 A1) is used. DE 101 45 944 A1 also known electric spark plugs with integrated laser ignition for multiple ignition purposes.

Ignition of the air mixture by the electric spark plug is a proven, preferred and reliable method for low pressure in the combustion chamber. The lifetime of the ignition electrode is very long when the pressure in the combustion chamber is adequate. However, the voltage required for flashover at the electrode is directly proportional to the density of the air supply mixture at the time of ignition. As the density increases, the number of free electrons for avalanche breakdown must increase. However, a higher voltage means that a very high intensity current flows during the avalanche breakdown. Therefore, the electrode of the spark plug is heated further in addition to the heat load by combustion. This limits the lifetime of the spark plugs up to about 1,000 hours in the range of average effective working pressure PME in the cylinder of about 22 bar.

Upon laser ignition of the fuel air mixture in the combustion chamber, the laser beam from the outside into the combustion chamber is focused at the defined focal point. The advantage of laser ignition is that the ignition site can be chosen almost arbitrarily in the combustion chamber and this method is particularly suitable for high average effective operating pressures. The laser energy required for laser ignition decreases significantly as the density of the air supply mixture to be ignited increases, because photon absorption of molecules in the air supply mixture is made more and more efficient according to the density.

The disadvantages of laser ignition are the cost of the laser device, the contamination of the optical combustion chamber glass and its short lifetime. Residues that occur during the combustion step can cause deposits to form in the combustion chamber glass. This deposit interferes with the beam passage of the laser light and either absorbs the laser light or scatters it back into the combustion chamber glass. Due to this, on the one hand the laser energy for ignition in the combustion chamber is lost, and on the other hand the heat load of the combustion chamber glass becomes very large. This effect is very noticeable, especially at low air supply, because the laser energy required for ignition is very high.

It is an object of the present invention to provide an internal combustion engine with an improved ignition mechanism for a fuel air mixture, and an improved ignition method for a fuel air mixture.

The problem is solved by an internal combustion engine comprising the features of claim 1 according to the first aspect. Preferred embodiments of the internal combustion engine according to the invention are presented in the dependent claims.

The internal combustion engine of the present invention includes a combustion chamber limited by a piston and a cylinder head, and an ignition device for igniting a fuel air mixture in the combustion chamber. The ignition device includes one or more electrical ignition devices and one or more optical ignition devices.

By providing an electric ignition device and an optical ignition device for ignition of the fuel air mixture in the combustion chamber, the advantages of the two systems are combined and their disadvantages are minimized, so that the ignition process can be carried out at lower energy costs and the electrical and optical ignition The life of the device can be extended.

In an embodiment of the invention, one or more electrical ignition devices protrude into the combustion chamber and the one or more optical ignition devices focus the light beam into the combustion chamber of the internal combustion engine.

In an alternative embodiment of the invention, the combustion chamber is connected with the preliminary chamber. In this case, at least one electrical ignition device protrudes into the preliminary chamber, and at least one optical ignition device focuses a light beam in the preliminary chamber.

In a preferred embodiment of the present invention, a control device is provided, wherein the control device activates one or more electric ignition devices when the average effective working pressure PME is lower than a predetermined limit, one when the average effective working pressure PME is larger than a predetermined limit. By operating the above optical ignition apparatus, the fuel air mixture in a combustion chamber is ignited. The predetermined threshold is, for example, in the range of about 12 to 18 bar, preferably in the range of about 14 to 17 bar, and more preferably about 16 bar.

According to a second aspect, the problem is solved by an ignition method for an internal combustion engine comprising the features of claim 6. Preferred embodiments of the ignition method according to the invention are given in the dependent claims.

In the ignition method for an internal combustion engine according to the present invention, when the average effective operating pressure PME is smaller than a predetermined limit, the fuel air mixture in the combustion chamber limited by the piston and the cylinder head is ignited by one or more electric ignition devices, and the average effective operating pressure If the PME is larger than the predetermined limit, it is ignited by one or more optical ignition devices.

The ignition method of the present invention combines the advantages of known electrical spark ignition with known optical ignition of the fuel air mixture in the combustion chamber of the internal combustion engine and minimizes their disadvantages. By the use of electric spark ignition only at low PME to average PME, the life of the electric ignition device can be very long. After the interruption of the electrical spark ignition, by the use of optical ignition only in high PME, optical devices with small energy can be used. Such optical devices are much cheaper. In addition, because the light beam with less energy minimizes the heat load of the combustion chamber optics, its life can be extended even further.

The predetermined threshold is, for example, in the range of about 12 to 18 bar, preferably in the range of about 14 to 17 bar, more preferably about 16 bar.

In an embodiment of the invention, the fuel air mixture is ignited in the combustion chamber of the internal combustion engine.

In an alternative embodiment of the invention, the fuel air mixture is ignited in a prechamber connected to the combustion chamber of the internal combustion engine.

The invention can be preferably used for ignition of gaseous fuel air mixtures, especially in gas engines. Basically, however, the internal combustion engine construction and the ignition method according to the invention can also be used in gasoline engines and diesel engines that ignite liquid fuel.

The above and other features and advantages of the present invention will be better understood from the following description of the preferred embodiments with reference to the accompanying drawings.

The present invention provides an internal combustion engine with an improved ignition mechanism for a fuel air mixture, and an improved ignition method for a fuel air mixture.

The invention is described below as an embodiment of a gas engine. The fuel air mixture in this case comprises gaseous fuel and air. The gaseous fuel is a combustible gas such as, for example, natural gas.

However, the present invention can also be used basically in gasoline engines and diesel engines, where the fuel air mixture comprises combustible liquids such as gasoline and air in the form of fuel mist, for example. The invention is also suitable for ignition of other combustible gases which do not contain air, such as mixtures of hydrogen and oxygen, or combustible mixtures which do not contain air and which comprise gas and liquid. "Fuel air mixture" in the context of the present invention includes all such variations.

1, a first embodiment of an internal combustion engine of the present invention will be described.

The internal combustion engine comprises a combustion chamber 14 constrained by the piston 10 and the cylinder head 12 in a known manner, which works by burning the gaseous fuel air mixture in the combustion chamber.

Ignition of the gaseous fuel air mixture takes place directly in the combustion chamber 14 in the embodiment of FIG. 1. For this purpose, an electric ignition device 20 in the form of a spark plug protruding into the combustion chamber 14 is provided. Also provided is an optical ignition device 22 in the form of a laser ignition device, which is introduced into the combustion chamber 14 through a laser device 24 for generating a laser beam 26, and a combustion chamber window 30. And a lens arrangement 28 for focusing the laser beam 26.

In the embodiment of FIG. 1, the focal point 32 of the laser ignition device 22 is near the electrode of the electrical spark plug 20. Of course, the laser beam 26 can basically be focused in almost any place within the combustion chamber 14.

In the embodiment of FIG. 1, one electrical ignition device 20 and one optical ignition device 22 are provided. Of course, a plurality of electrical ignition devices 20 and / or a plurality of optical ignition devices can be arranged in the combustion chamber 14 of the internal combustion engine.

In the embodiment of FIG. 1, the optical ignition device 22 includes a laser device 24 for generating a laser beam 26 as a laser ignition device. Basically, other optical ignition devices with other energy-rich light beams are possible.

One or more electrical ignition devices 20 and one or more optical ignition devices 22 are controlled by a control device 34. The control device 34 provides that the gaseous fuel air mixture in the combustion chamber 14 is ignited by the electric ignition device 20 if the average effective operating pressure PME is less than the predetermined limit and the average effective operating pressure PME is greater than the predetermined limit. The two ignition devices 20, 22 are controlled to be ignited by the optical ignition device 22. The predetermined threshold is, for example, in the range of about 12 to 18 bar, preferably in the range of about 14 to 17 bar, more preferably about 16 bar.

Since the electric ignition device 20 is only used at low to moderate operating pressure PME, the ignition device can be operated at a relatively low voltage, so that its life can be significantly longer. Similarly, the lifetime of the combustion chamber glass 30 can also be significantly longer, since a low energy laser beam is sufficient for the ignition process in the combustion chamber since the laser ignition device 22 is only used at high operating pressure PME. . Since less energy is needed for the electrical spark plug 20 and the laser ignition device 22, more economical components can be used and the operating cost is reduced.

2, a second embodiment of an internal combustion engine is described. The same or similar parts as in the first embodiment are denoted by the same reference numerals.

The second embodiment is characterized in that the ignition of the gaseous fuel air mixture is not in the combustion chamber 14 itself, but in the preliminary chamber 36 in the cylinder head 12, which is connected to the combustion chamber 14. It differs from an Example.

To this end, the ignition devices 20, 22 have a prechamber chamber in which the electrical spark plug 20 protrudes into the preliminary chamber 36 and the focal point 32 of the laser beam 26 generated by the laser device 22. Disposed to lie within 38. In comparison with the first embodiment, a preliminary chamber window 38 for injecting the laser beam 26 generated by the laser device 24 into the preliminary chamber 36 is provided.

The remaining features and variations correspond to the features and variations in the embodiment of FIG. 1. Also, by this embodiment, the same advantages as those obtained by the first embodiment are obtained.

The present invention is not limited to the special configurations of the combustion chamber 14, the electric ignition device 20 and the optical ignition device 22.

1 is a schematic partial sectional view of an internal combustion engine according to a first embodiment of the present invention;

2 is a schematic partial sectional view of an internal combustion engine according to a second embodiment of the present invention;

<Explanation of symbols for the main parts of the drawings>

10: piston 12: cylinder head

14 combustion chamber 16 piston head

18: recess

20: electric ignition device (ignition plug)

22: optical ignition device (laser ignition device)

24: laser device 26: laser beam

28 lens unit 30 combustion chamber window

32: focus of the laser beam 34: control device

36: preliminary chamber 38: preliminary chamber window

Claims (9)

In an internal combustion engine comprising a combustion chamber (14) limited by a piston (10) and a cylinder head (12), and an ignition device (20, 22) for igniting a fuel air mixture in the combustion chamber (14), The ignition device (20, 22) is characterized in that it comprises at least one electric ignition device (20) and at least one optical ignition device (22). The apparatus of claim 1, wherein the one or more electrical ignition devices 20 protrude into the combustion chamber 14, and the one or more optical ignition devices 22 focus the light beam 26 on the combustion chamber 14. Internal combustion engine characterized by the above. The combustion chamber (14) of claim 1, wherein the combustion chamber (14) is connected to a preliminary chamber (36), the one or more electrical ignition devices (20) protrude into the preliminary chamber (36), and the one or more optical ignition devices (22). Internal combustion engine, characterized in that for focusing the light beam (26) on the preliminary chamber (36). A control device 34 is provided, wherein the control device activates the at least one electric ignition device 20 when the average effective working pressure PME is less than a predetermined limit. And igniting the fuel air mixture in the combustion chamber (14) by operating the at least one optical ignition device (22) when the average effective operating pressure PME is greater than a predetermined limit value. 5. The internal combustion engine of claim 4, wherein the predetermined limit lies in the range of about 12 to 18 bar. As an ignition method for an internal combustion engine, If the average effective operating pressure PME is less than the predetermined limit, the fuel air mixture in the combustion chamber 14, which is limited by the piston 10 and the cylinder head 12, is ignited by one or more electric ignition devices 20, and the average effective operation An ignition method for an internal combustion engine that is ignited by one or more optical ignition devices when the pressure PME is greater than a predetermined limit. 7. The method of claim 6, wherein said predetermined limit is in the range of about 12 to 18 bar. The method of claim 6 or 7, wherein the fuel air mixture is ignited in the combustion chamber (14) of the internal combustion engine. 8. The method of claim 6 or 7, wherein the fuel air mixture is ignited in a preliminary chamber (36) connected to the combustion chamber (14) of the internal combustion engine.

Images