WO2003100236A1

WO2003100236A1 - Spark-ignition internal combustion engine

Info

Publication number: WO2003100236A1
Application number: PCT/EP2003/003300
Authority: WO
Inventors: Klaus Rössler
Original assignee: Daimlerchrysler Ag
Priority date: 2002-05-25
Filing date: 2003-03-29
Publication date: 2003-12-04
Also published as: DE10223408A1; EP1507969A1

Abstract

The invention relates to a supercharged spark-ignition engine having direct fuel injection, in which one injector is centrally arranged inside the cylinder head with an approximately vertical mounting position. The invention provides that in the event of partial loading during a homogeneous operation of the internal combustion engine, an ignitable fuel-air mixture is formed inside the combustion chamber with an air ratio (μ) greater than 1, and in the event of high loading during homogeneous operation of the internal combustion engine, an ignitable fuel-air mixture is formed inside the combustion chamber with an air ratio (μ) less than or equal to 1.

Description

Spark ignition internal combustion engine

The invention relates to a method for operating an internal combustion engine according to the preamble of claim 1 and an internal combustion engine according to the preamble of claim 5.

In order to achieve both high torques and power values as well as low consumption in the partial load range in gasoline engines with direct injection, mixed operation is implemented within an engine map in such a way that in the upper speed and load range a homogeneous stoichiometric mixture (air ratio λ «1) and in the middle and lower speed and load range there is stratified charge operation with a largely unrestricted air supply (λ> 1) and a fuel-efficient charge stratification.

In practice, vehicle engines are operated essentially in the partial load range. For this reason, charge stratification should be carried out as economically as possible in a map area in which the engine is mainly operated. However, there are technical reasons that limit the stratified operation of the internal combustion engine in the map. For example, there is an increasing emission of soot particles from an average indicated pressure of approx. 4 bar, since the time for complete evaporation is no longer sufficient for the larger fuel masses. In stratified charge operation, non-optimized mixture formation due to tolerance deviations and cyclical fluctuations can lead to misfires, which for many reasons can be classified as very problematic with regard to exhaust gas emissions, consumption and driving comfort, especially at low engine speeds.

A concept of a turbocharged Otto engine with direct injection is known (automotive and internal combustion engines / 3rd Stuttgart Symposium: February 23-25, 1999, edited by Michael Bargend and Jochen Wiedemann -Renningen- Malmsheim, Expertverlag 1999; lecture: Concept one turbocharged DI Ottomotors, U. Mayerhofer, G. Fraidl, W. Piock and M. Wirth, AVL List GmbH, Graz; pages 171-182), which should lead to a reduction in exhaust gas emissions and fuel consumption. With this concept, the engine is operated at low and medium loads in stratified charge mode. In order to operate the engine with stratified charge at low loads, a combustion chamber design is undertaken which is not particularly suitable for homogeneous operation and which leads to some disadvantages at higher loads. Stratified charging therefore leads to theoretical consumption advantages which can only be achieved in a small area of the map due to ignition instabilities and soot problems.

The invention has for its object to design a ^'spark ignition internal combustion engine with direct injection such that a fuel-low and low exhaust emission combustion takes place at the greatest possible speed and load range.

This object is achieved by a method with the features of claim 1 and an internal combustion engine with the features of claim 5. A method for operating a spark-ignited internal combustion engine with a cylinder, a cylinder head, a piston, a combustion chamber delimited by an inside of the cylinder head and the piston, an intake valve, an exhaust valve, an ignition device, and a supercharging device is proposed air is compressed in the charging device and fed to the combustion chamber via at least one inlet valve, fuel being injected directly into the combustion chamber by an injector, and an ignitable fuel / air mixture in the combustion chamber at low and / or medium load in homogeneous operation of the internal combustion engine with an air ratio • ■ - nis (λ) greater than 1.1, and an ignitable fuel / air mixture with an air ratio (λ) less than or equal to 1 is formed in the combustion chamber at high load in homogeneous operation of the internal combustion engine.

According to the invention, the fuel / air mixture is formed in the combustion chamber with an air ratio λ greater than 1 in the lower and middle load range at least temporarily in homogeneous operation of the internal combustion engine. The combination of direct injection and charging causes the load spectrum to be shifted to higher loads, which means that lean operation in the lower and middle load range in conjunction with stoichiometric and / or rich operation at higher loads can open up greater consumption potential, while at the same time reducing the internal combustion engine space and the efficiency is increased.

In one embodiment of the invention, the fuel is injected in the intake stroke and / or in an initial part of the compression stroke of the internal combustion engine. A homogeneous mixture is formed by the early injection. In a further embodiment of the invention, the fuel is injected in a clocked manner. In this way, the fuel quantity can be introduced in partial quantities, thus preventing wetting of the wall with fuel or achieving a more favorable fuel distribution.

In order to achieve optimal homogenization, the fuel is injected with a central arrangement of the fuel injector in the combustion chamber in such a way that a fuel jet cone is formed at an angle of approximately 90 °, with an adjustment of ± 20 ° depending on the design of the combustion chamber , If the fuel injector is arranged laterally in the combustion chamber, the fuel is injected in such a way that a fuel jet cone is formed at an angle of approximately 70 °, it also being possible to make an adjustment of ± 20 ° depending on the design of the combustion chamber.

According to the invention, an internal combustion engine is also provided which has a cylinder, a cylinder head, a piston, a combustion chamber delimited by an inside of the cylinder head and the piston, an inlet valve, an exhaust valve and an ignition device, the fuel being injected directly into the combustion chamber by an injector the combustion chamber is injected. A charger is provided to compress the combustion air. The injector is arranged approximately in the central region of the cylinder head, the smallest distance between an injector outlet opening and a cylinder axis being less than 10 mm and the included angle between the injector axis and a cylinder axis being less than 20 °. Furthermore, the piston has a trough, the depth of which is preferably a maximum of 5 mm. The arrangement of the injector in the combustion chamber according to the invention enables an advantageous injection of the fuel into the combustion chamber, so that a homogeneous mixture is quickly prepared.

The advantages of developing a turbocharged gasoline engine with direct injection are that it improves driving performance, especially at low engine speeds, and at the same time reduces fuel consumption. Charging the internal combustion engine results in a noticeable increase in performance, whereby the displacement for a certain mileage can be reduced accordingly (downsizing). The air required for the combustion process is compressed in such a way that a larger mass gets into the combustion chamber per work cycle. This increases the mean specific pressure in the cylinder and increases performance. This leads to a reduction in consumption because the load spectrum shifts to higher mean pressures.

In order to achieve a homogeneous fuel / air mixture, fuel is injected very early into the combustion chamber of the reciprocating piston engine, even during the intake stroke. Alternatively, the fuel injection can extend to the initial part of the compression stroke. As a result, the amount of air sucked in is very quickly mixed with the fuel.

In one embodiment of the invention, a supercharger conveys the compressed combustion air into an intake pipe of a four-stroke internal combustion engine and further through the inlet duct into the combustion chamber. A regulating device is arranged in the intake pipe, which regulates the conveyed charged air as a function of operating parameters. In the intake pipe, internals for generating a swirl, such as swirl control valves or control flaps or suitable throttle bodies, are preferably arranged. If two inlet channels are used, a swirl can also be generated by switching off the channel. The homogenization and the charge movement of the mixture in the combustion chamber can thereby be increased. As an alternative to increasing turbulence or generating swirl, a variable tumble, ie a cylindrical charge movement in the combustion chamber, e.g. B. can be achieved by a tumble flap.

The intensification of the charge movement leads to better knocking behavior of the internal combustion engine. Furthermore, the better homogenized mixture at part load prevents misfiring and incomplete combustion. The formation of soot particles is also minimized compared to stratified charging.

A centrifugal compressor or volumetric compressor can serve as the loader. These can be driven by an exhaust gas turbine or mechanically by the internal combustion engine via a gearbox or by a separate electric motor. In order to achieve an optimal adaptation of the loader behavior to the map of the internal combustion engine, the exhaust gas turbine preferably has an integrated wastegate. A turbine with a variable turbine geometry (VTG) or with a variable sliding sleeve (VST) also enables the charging behavior to be optimally matched to the map of the internal combustion engine. The turbine wheel can consist of a ceramic material.

The charger is preferably operated as a cold air tube in the partial load (daley optimized turbo charger (DOT)), so that the exhaust gas turbocharger rotor runs at a higher speed level. As a result, an improved response behavior can be achieved when taking a load.

Further advantages result from the following description of the drawing. Show it:

1 is a schematic representation of a centrally arranged injector in the combustion chamber of a supercharged internal combustion engine,

2 is an enlarged sectional view of an arrangement of the injector of an internal combustion engine according to FIG. 1,

3 shows a schematic illustration of a laterally arranged injector in the combustion chamber of a supercharged internal combustion engine,

4 shows a schematic arrangement of exhaust or intake valves, a spark plug or spark plugs and an injector in the combustion chamber of a supercharged internal combustion engine with direct injection,

Fig. 5 shows a further schematic arrangement of outlet or. Inlet valves, a spark plug or spark plugs and an injector in the combustion chamber of a supercharged internal combustion engine with direct injection, and

6 shows a characteristic diagram of an operating strategy of an internal combustion engine.

A spark-ignited internal combustion engine 3 has, according to FIG. 1, a cylinder 4 in which a piston 6 moves up and down cyclically. The cylinder 4 is supported by a cylinder head 5 completed, in which an inlet valve 8, an outlet valve 9, a spark plug 10 and an injector 13 are arranged. A combustion chamber 7 is formed in the cylinder 4 between the piston 6 and the cylinder head 5. The piston 6 has a combustion chamber trough 14 on the upper side, the depth of which is preferably up to five millimeters. The fuel injector 13 injects the fuel in one or more fuel jets directly into the combustion chamber 7, where the fuel mixes with the combustion air and is ignited by at least one spark plug 10. The combustion air reaches the combustion chamber 7 through an intake pipe 15. The exhaust gases pass through an exhaust pipe 16 from the combustion chamber 7 via an exhaust pipe 17 to an exhaust gas turbine 18 of an exhaust gas turbocharger, which drives a charger 19. The air conveyed by the charger 19 reaches the intake pipe 15 via a charge air line 20.

The air fed into the combustion chamber 7 through the intake pipe 15 experiences an increase in turbulence when flowing through throttle bodies, which increase is largely retained in the combustion chamber. Alternatively, if two inlet valves are used, a swirl movement in combustion chamber 7 can be achieved by switching off the duct. The air conveyed to the combustion chamber can be passed through a charge air cooler, not shown, which can be configured as a water / charge air heat exchanger.

The required quantity control can be carried out by means of a variable charge air flow, which is adjusted, for example, by means of a variable blade geometry depending on the operating parameters. The exhaust gas turbocharger can be designed as a centrifugal compressor. In order to improve the response behavior of the turbocharger and to keep the so-called turbo lag low, a throttle valve 21 is arranged in front of the compressor. The composition of the mixture in the combustion chamber can also be favorably influenced by exhaust gas recirculation. For this purpose, an exhaust gas recirculation line, not shown, leads to the intake pipe 15.

2 shows an enlarged sectional view of the arrangement of the injector 13 in the cylinder head 5. The injector 13 is arranged centrally in the cylinder head 5, a distance d from an injector outlet opening 13a to the central axis 11 of the cylinder 4 being approximately 20 millimeters or less. The injector 13 is arranged such that an angle α between an injector axis 12 and the cylinder center axis 11 is less than 20 °. The combustion chamber 7 is preferably designed as a roof combustion chamber. The spark plug 10 is also arranged in the central region of the cylinder head 5. In the present exemplary embodiment, the injector has a multi-hole nozzle which is designed as an outwardly opening nozzle. The injector is driven piezoelectrically, although other injector actuations can also be expedient.

FIG. 3 also shows an internal combustion engine 3 analogous to that from FIG. 1, the injector 13 being arranged on the side here. The injector 13 is arranged inclined such that an angle β between the injector axis 12 and a horizontal is between 20 ° and 70 °.

4 and 3 show three preferred arrangements of intake and exhaust valves, injector and spark plugs. The first variant VI in FIG. 4 shows two inlet valves 8, one outlet valve 9, a double ignition 10 and a centrally arranged injector 13. Each spark plug is arranged such that it is between the injector 13 and an outer edge region of the combustion chamber 7, and at the same time is arranged approximately between an inlet valve 8 and the outlet valve 9.

The second variant V2 in FIG. 4 shows two inlet valves 8, two outlet valves 9, two spark plugs 10 and a centrally arranged injector 13. The inlet valves 8 are on one side, the outlet valves 9 on the other side and in each case one spark plug in the outer area arranged between an inlet valve 8 and an outlet valve 9.

The third variant V3 in FIG. 4 shows an inlet valve 8, an outlet valve 9, a spark plug 10 and an injector 13. The injector 13 and the spark plug are arranged laterally, so that the spark plug 10 and the injector 13 are each arranged in an outer region of the combustion chamber 7 between the inlet valve 8 and the outlet valve 9.

5 shows three further preferred arrangements of intake and exhaust valves, injector and spark plugs. The variant V4 in FIG. 5 shows two inlet valves 8, one outlet valve 9, two spark plugs 10 and a laterally arranged injector 13. Each spark plug is arranged in such a way that it lies in an outer edge region of the combustion chamber 7, in which the injector 13 is not is arranged, wherein it is simultaneously arranged between an inlet valve 8 and the outlet valve 9.

The variant V5 in FIG. 5 shows two inlet valves 8, two outlet valves 9, a centrally arranged spark plug 10 and a laterally arranged injector 13. The injector 13 is arranged in an outer area of the combustion chamber between the two inlet valves 8. The last variant V6 in FIG. 5 shows two inlet valves 8, two outlet valves 9, a centrally arranged injector 13 and a spark plug 10 arranged in the central area, which is arranged laterally from the injector 13 between the two outlet valves 9.

6 shows a characteristic diagram of an internal combustion engine, which is particularly well suited for a charged spark-ignition internal combustion engine 3 with direct injection according to FIG. 1 or FIG. 3. Two operating areas are shown. In the lower and middle speed and load range 1, the internal combustion engine is operated at least temporarily with a lean, homogeneous mixture with an air ratio λ> 1. At higher loads 2, the internal combustion engine is operated with a stoichiometric or rich mixture with an air ratio λ <1. The load L of the internal combustion engine is plotted against the speed N in the diagram according to FIG. 6. The area 1 indicates the area of a possible lean mixture, the limitation of which can be expanded by an increased charge movement, so that a larger area is covered, as a result of which the average fuel consumption of the internal combustion engine can then be significantly reduced.

In order to achieve a homogeneous fuel / air mixture, the fuel is injected in the intake stroke and / or in the initial part of the compression stroke of the internal combustion engine 3. The homogenization of the mixture is increased by the turbulence increase of the air supplied in the intake pipe 15. When using two inlet valves according to variant 1, 2, 4, 5 and 6, thereafter, a swirl movement in the combustion chamber 7 can be achieved by switching off the channel.

Claims

claims

1. Method for operating a spark ignition internal combustion engine (3) with a cylinder (4), a cylinder head (5), a piston (6),. a combustion chamber (7) bounded by an inside of the cylinder head (5) and the piston (6), an intake valve (8), an exhaust valve (9), an ignition device (10), and a charging device, with the following method steps:

- Air is compressed by means of the charging device and fed to the combustion chamber (7) via at least one inlet valve (8),

- Fuel is injected directly into the combustion chamber (7) by an injector (13), characterized in that at low and / or medium load in a homogeneous operation of the internal combustion engine, an ignitable fuel / air mixture in the combustion chamber with an air ratio (λ ) greater than 1.1, and

- At high load in homogeneous operation of the internal combustion engine, an ignitable fuel / air mixture is formed in the combustion chamber with an air ratio (λ) less than or equal to 1.

2. The method according to claim 1, characterized in that in homogeneous operation of the internal combustion engine, the fuel is injected in the intake stroke or in an initial part of the compression stroke of the internal combustion engine.

3. The method according to claim 1 or 2, characterized in that the fuel injection is clocked.

4. The method according to any one of claims 1 to 3, characterized in that in a centrally arranged injector, the fuel is injected in such a way that a fuel jet cone is formed at an angle between 70 ° and 110 °.

5. Spark ignition internal combustion engine, in particular for

Implementation of a method according to one of claims 1 to 4, with a cylinder (4), a cylinder head (5), a piston (6), a combustion chamber (7) delimited by an inside of the cylinder head (5) and the piston (6) , an inlet valve (8), an outlet valve (9), an ignition device (10), fuel being injected into the combustion chamber (7) by means of an injector (13) directly into the combustion chamber (5), and via at least one inlet valve (8 ) compressed air is fed to the combustion chamber (7) by a charger, characterized in that the injector (13) is arranged approximately in the central region of the cylinder head (5), the included angle between an injector axis (12) and a cylinder axis (11 ) is less than 20 °.

6. spark ignition internal combustion engine according to claim 5, characterized in that a smallest distance between an injector outlet opening (13a) and a cylinder axis (11) is less than 20 mm.

7. spark ignition internal combustion engine according to claim 5 or

6, characterized in that the ignition device are arranged laterally.

8. spark ignition internal combustion engine according to claim 5 or

6, characterized in that the ignition device are arranged centrally.

9. spark-ignition internal combustion engine according to claim 5 or 6, characterized in that each cylinder unit has two ignition devices.

10. Spark-ignition internal combustion engine according to one of claims 5 to 9, characterized in that each cylinder unit has 2 intake valves and an exhaust valve.

11. Spark ignition internal combustion engine according to one of claims 5 to 9, characterized in that each cylinder unit has 2 intake valves and 2 exhaust valves.