WO2002079622A1

WO2002079622A1 - Method of operating a self-ignited internal combustion engine

Info

Publication number: WO2002079622A1
Application number: PCT/DE2002/000888
Authority: WO
Inventors: Gernot Wuerfel
Original assignee: Robert Bosch Gmbh
Priority date: 2001-03-29
Filing date: 2002-03-14
Publication date: 2002-10-10
Also published as: DE10115608A1

Abstract

The invention relates to a method of operating an internal combustion engine (1), especially a motor vehicle. In order to allow for a safe and reliable self-ignition of the fuel-air mixture present in a combustion chamber (4) of the internal combustion engine (1), the air present in a combustion chamber (4) of the internal combustion engine (1) is heated up and fuel is directly injected into the combustion chamber (4) during a compression phase of the internal combustion engine (1) where it forms a self-ignited fuel-air mixture with the compressed, heated up air. The inventive method further suggests measures supplementary to the heating up of air, such as an increased compression ratio, exhaust gas recirculation or pressure charging.

Description

METHOD FOR OPERATING A AUTO IGNITION COMBUSTION ENGINE

The present invention relates to a method for operating an internal combustion engine, in particular a motor vehicle.

The invention also relates to a memory element for a control unit of an internal combustion engine, in particular a motor vehicle. A computer program is stored on the memory element and can be run on a computing device, in particular on a microprocessor. The storage element is e.g. as. a read-only memory, a random access memory or as a flash memory.

The present invention further relates to a computer program that can run on a computing device, in particular on a microprocessor.

The invention also relates to a control device for an internal combustion engine, in particular a motor vehicle. The control unit is used to control and / or regulate the

Injection of gasoline into a combustion chamber of the internal combustion engine.

Finally, the present invention relates to an internal combustion engine, in particular of a motor vehicle. ^'The internal combustion engine has a fuel injection system for directly injecting fuel into a combustion chamber of Internal combustion engine on.

State of the art

Approaches for generating a self-ignitable gasoline-air mixture charge are known from the prior art for internal combustion engines with intake manifold injection, in which a gasoline-air mixture is sucked in by the piston of the internal combustion engine and with the inclusion of additional measures that heat the mixture in the The combustion chamber is used to ignite.

Additional measures for heating the mixture are known: 1. Varying the filling of the combustion chamber via a variable valve train. The compressed gasoline-air mixture heats up from a defined amount of air that can be influenced via the opening times of the inlet valves. This measure, however, shows stroke-to-stroke scattering of the respective individual cylinders, as well as cylinder-specific deviations of an internal combustion engine. In addition, the start of combustion of the respective work cycles and the individual cylinders is difficult to control. 2. High exhaust gas recirculation rate. By returning hot exhaust gases to the combustion chamber, the temperature of the fuel / combustion air mixture enclosed in the combustion chamber can be significantly increased before the onset of combustion. The actual combustion temperature during the combustion of the

However, gasoline-air mixture is reduced by the exhaust gas recirculation since the oxygen content in the combustion chamber is reduced by the exhaust gas. This reduces nitrogen oxide emissions. The exhaust gas serves as an inert gas, through which the temperature of the

Combustion air is increased and that during the Combustion is located in the combustion chamber, but is hardly involved in the actual combustion reaction. The disadvantage of this measure is that the suitable amount of exhaust gas is difficult to control. It is a sluggish system that has stroke-to-stroke scattering and an uneven distribution across the combustion chambers of all cylinders. 3. Charging the combustion air. Charging compresses the combustion air and raises its temperature. However, this measure also has the disadvantage that it is a relatively sluggish system that has filling differences in the combustion chambers of the individual cylinders.

In direct-injection gasoline internal combustion engines known from the prior art, gasoline is injected directly into the combustion chamber of a cylinder of the internal combustion engine. The gasoline-air mixture compressed in the combustion chamber is then ignited by igniting an ignition spark in the combustion chamber. The volume of the ignited gasoline-air mixture expands explosively and sets a piston that can be moved back and forth in the cylinder in motion. The reciprocation of the piston is transmitted to a crankshaft of the internal combustion engine.

Direct-injection internal combustion engines can be operated in various operating modes. A so-called shift operation is known as a first operating mode, which is used in particular for smaller loads. A so-called homogeneous operation is known as a second operating mode, which is used for larger loads applied to the internal combustion engine. The different operating modes differ in particular in the injection timing and the injection duration as well as in the ignition timing. In stratified operation, the gasoline is injected into the combustion chamber during the compression phase of the internal combustion engine in such a way that a cloud of fuel is in the immediate vicinity of a spark plug at the time of ignition. This injection can take place in different ways. It is thus possible that the injected fuel cloud is already at the spark plug during or immediately after the injection and is ignited by the latter. It is also possible that the injected fuel cloud is guided to the spark plug by a charge movement and only then ignited. In both combustion processes, there is no uniform fuel distribution in the combustion chamber, but a stratified charge.

The advantage of shift operation is that the applied smaller loads can be carried out by the internal combustion engine with a very small amount of fuel. However, larger loads cannot be met by shift operation.

With gasoline direct injection using the jet-guided combustion process, full load can also be operated in shift operation with a stoichiometric fuel-air mixture. In this case, shift operation - as in target load operation - means injection near the ignition point.

In the homogeneous operation provided for such larger loads, the gasoline is injected during the intake phase of the internal combustion engine, so that swirling and thus distribution of the gasoline in the combustion chamber can take place easily before the ignition. In this respect, the homogeneous operation corresponds approximately to the operating mode of internal combustion engines, in the conventional way

Fuel is injected into the intake pipe. If necessary

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high pressure can build up that an uncontrolled self-ignition occurs even before the flame front can detect the remaining unburned gasoline-air mixture. If the burning speed is fast enough, the flame front also detects this end gas area before this high auto-ignition pressure can build up in the unburned zone.

The present invention is based on the object of increasing the ignitability of a fuel-air mixture in a combustion chamber of the internal combustion engine by means of suitable additional measures while avoiding the disadvantages of the prior art and at least after reaching the operating temperature of the internal combustion engine a safe and reliable self-ignition of the mixture.

To achieve this object, the invention proposes, based on the method for operating an internal combustion engine of the type mentioned, that in a combustion chamber

Air located in the internal combustion engine is heated and fuel is injected directly into the combustion chamber during a compression phase of the internal combustion engine, where it forms a self-ignitable fuel-air mixture together with the compressed, heated air.

Advantages of the invention

The present invention is not only for gasoline-powered internal combustion engines, but also for such

Internal combustion engines suitable with other liquid fuels that have relied on spark ignition in previous applications, e.g. B. Alcohol-based fuels such as methanol, ethanol, etc. or LPG.

An essential aspect of the present invention is one L to H in o in o LΠ o in

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the fact that the combustion is no longer initiated by the spark plug and spreads in a flame front from the spark plug, but only by heating a fuel-air mixture enclosed in the combustion chamber.

The initiation of combustion via self-ignition has the properties of a predominantly premixed combustion with low diffusion fractions. This creates several ignition sources at the same time, which can be distributed throughout the combustion chamber, where there is a well-prepared ignitable fuel-air mixture. The further flame spread is supported by the air warming also in possibly existing extremely lean mixture zones. This ignitable gasoline-air mixture can be easily generated using today's injection technology (e.g. smaller

Injection hole diameter of an injection valve in the range of 0.12mm, multiple injection, variation of the rail pressure or heating of the fuel shortly before the injection).

There are various possibilities within the scope of the present invention to heat the combustion air in the combustion chamber, some of which are explained in more detail below.

According to an advantageous development of the present invention, it is proposed that a higher compression ratio be provided for heating the air in the combustion chamber. That increased

Compression ratio ensures that the combustion can take place immediately after the injection, taking into account a slight ignition delay. The late injection shortly before the top ignition dead point effectively prevents knocking, which is damaging to the engine, since there is no fuel in the gusset spaces between the piston and

Oxygen content in the combustion chamber is reduced. This reduces nitrogen oxide emissions.

According to a preferred embodiment of the present invention, it is proposed that pre-compressed air is sucked into the combustion chamber to heat up the air in the combustion chamber during an intake phase of the internal combustion engine. Charging compresses the combustion air and increases its temperature.

The formation of a flame front during the combustion of the fuel-air mixture in the combustion chamber can in particular be prevented by injecting the fuel into the combustion chamber in a finely divided manner.

The fuel is advantageously injected into the combustion chamber with the aid of an A valve that opens in the forward direction. Alternatively, the fuel can be supplied with an I-valve that opens against the direction of passage with several, preferably with at least six,

Injection holes are injected into the combustion chamber, which are arranged on an ellipse or a circular line with the injector tip as the center or some other suitable shape in coordination with the combustion chamber geometry. The spray holes are preferably arranged such that the fuel can be distributed as evenly as possible in the combustion chamber. A uniform distribution of the fuel in the combustion chamber and reliable combustion can thus be achieved. As a result, a flame core, which has formed in the region of the injection jet, can spread directly to adjacent zones without the flame propagation speed being delayed by more or less large lean zones. The design of the hole pattern of the injection valves largely corresponds to the hole pattern for jet-guided combustion processes (cf. "Automotive engineering Taschenbuch / Bosch ", 22nd edition, Springer-Verlag, 1998, p. 369), to which express reference is made.

According to another preferred embodiment of the present invention, it is proposed that the fuel is injected into the combustion chamber via an injector, the cone opening angle of which is at least 60 °. The injection jets span an approximate lateral surface of an injection cone. The more injection jets there are in multi-hole injectors, the more perfect the cone jacket is. With multi-hole valves, a variable jet cone can also be represented, which has a different cone angle in the longitudinal direction of the engine than in the transverse direction of the engine. This property is important for roof-shaped combustion chambers, because due to intensive jet ventilation in the direction of the roof ridge, a larger cone angle is more advantageous than in the direction of the roof pitch. Instead of multi-hole injectors, it is also possible, for example, to use outwardly opening screen jet nozzles that build up a perfect jet cone.

The heating of the combustion air in the combustion chamber can be further improved in that a glow plug protrudes into the combustion chamber, which, when the engine is cold-started

Internal combustion engine is activated. This ensures safe and reliable ignition and ignition of the fuel-air mixture even during a cold start at extremely low ambient temperatures. With the help of the glow plug, the self-ignition of the fuel-air mixture can be additionally supported. The glow plug can be deactivated as soon as the internal combustion engine runs smoothly.

Finally, another is preferred

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As a further solution to the object of the present invention, starting from the control device of the type mentioned at the outset, it is proposed that the control device cause heating of air in the combustion chamber of the internal combustion engine and injection of the fuel directly into the combustion chamber during a compression phase of the internal combustion engine, where it forms a self-igniting fuel-air mixture together with the compressed, heated air.

Finally, as yet another solution to the object of the present invention, starting from the internal combustion engine of the type mentioned at the outset, it is proposed that the internal combustion engine have means for heating air located in the combustion chamber of the internal combustion engine and that the fuel injection system delivers fuel directly into the engine during a compression phase of the internal combustion engine

Injects combustion chamber, where it forms a self-ignitable fuel-air mixture together with the compressed, heated air.

According to an advantageous development of the present invention, it is proposed that the internal combustion engine have means for heating the fuel in the fuel injection system and the fuel injection system injects the heated fuel into the combustion chamber.

drawings

Further features, possible applications and advantages of the invention result from the following description of exemplary embodiments of the invention, which are described in the Drawing are shown. All of the features described or illustrated, individually or in any combination, form the subject matter of the invention, regardless of their summary in the patent claims or their dependency, and regardless of their formulation or representation in the description or in the drawing. Show it :

Figure 1 shows a direct injection internal combustion engine according to the invention according to a preferred

embodiment;

FIG. 2 shows a flow chart of a method according to the invention in accordance with a preferred embodiment; and

3 shows an example of a time sequence of the method according to the invention from FIG. 2 as a function of an angle of rotation position ° KW of a crankshaft of the internal combustion engine.

Description of the embodiments

1 shows a direct-injection gasoline internal combustion engine 1 of a motor vehicle according to the invention, in which a piston 2 can be moved back and forth in a cylinder 3. The present invention is not only suitable for petrol-operated internal combustion engines 1, but also for those internal combustion engines which are compatible with other liquid fuels which have relied on spark ignition in previous applications, e.g. B. alcohol-based fuels such as methanol, ethanol or the like or LPG. The cylinder 3 is provided with a combustion chamber 4, which is delimited inter alia by the piston 2, an inlet valve 5 and an outlet valve 6. Several inlet valves 5 and / or several can also be used Exhaust valves 6 can be provided per combustion chamber 4. An intake pipe 7 is coupled to the inlet valve 5 and an exhaust pipe 8 is coupled to the outlet valve.

In the area of the inlet valve 5 and the outlet valve 6, an injection valve 9 projects into the combustion chamber 4. Gasoline can be injected into the combustion chamber 4 via the injection valve 9.

In the intake pipe 7, a rotatable throttle valve 11 is accommodated, via which air can be fed to the intake pipe 7. The amount of air supplied is dependent on the angular position of the throttle valve 11. A catalytic converter 12 is accommodated in the exhaust pipe 8 and serves to clean the exhaust gases resulting from the combustion of the fuel-air mixture.

The combustion of the fuel-air mixture 4 causes the piston 2 to move back and forth, which is transmitted to a crankshaft (not shown) and exerts a torque thereon. A combustion chamber trough 23 is provided on the top of the piston 2. The injection valve 9 is arranged centrally to the combustion chamber trough 23 and has a multi-hole nozzle. Through the combustion chamber trough 23 and the specially trained

Injection valve 9, a jet-guided combustion process can be implemented. The internal combustion engine 1 is operated in shift operation.

A control device 18 for controlling and / or regulating the direct-injection internal combustion engine 1 is acted upon by input signals 19, which represent operating variables of the internal combustion engine 1 measured by sensors. For example. the control unit 18 is connected to an air mass sensor, a lambda sensor, a speed sensor and the like. Furthermore, the control unit lυ t H in o in o in

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Internal combustion engine can also be operated in full shift operation.

2 shows a flow chart of a method according to the invention. The process begins in one

Function block 30. In a function block 31, air is sucked from the intake pipe 7 via the inlet valve 5 into the combustion chamber 4 of the internal combustion engine. The sucked-in combustion air is heated in a function block 32. This can be done in different ways, for example by an increased compression ratio, by charging or by exhaust gas recirculation. In a function block 33, gasoline is then injected into the compressed and heated combustion air via the injection valve 9. Together with the combustion air, the gasoline forms a self-igniting gasoline-air mixture that ignites itself after a short delay in ignition. To shorten the ignition delay, for example, a glow plug can be arranged in the combustion chamber 4, which is switched on if necessary for additional heating of the combustion air. The ignition delay can also be reduced by an advantageous embodiment of the injection valve, for example a multi-hole valve or an outwardly opening screen jet nozzle. The method according to the invention is then ended in a function block 34.

FIG. 3 shows an example of a chronological sequence of the method according to the invention, from FIG. 2 as a function of an angular position ° KW of the crankshaft of the internal combustion engine 1. The exact times for

The start and end of activation depend on the injector and the

Claims

Expectations

1. A method for operating an internal combustion engine (1), in particular a motor vehicle, characterized in that air located in a combustion chamber (4) of the internal combustion engine (1) is heated and fuel is injected directly into the combustion chamber (4) during a compression phase of the internal combustion engine (1) ) is injected, where it forms a self-ignitable fuel-air mixture together with the compressed, heated air.

2. The method according to claim 1, characterized in that for heating the located in the combustion chamber (4)

Air a higher compression ratio is provided.

3. The method according to claim 2, characterized in that a higher geometric compression ratio (egeom) is provided.

, A method according to claim 2 or 3, characterized in that a higher effective compression ratio (eeff) is provided.

5. The method according to any one of claims 1 to 4, characterized in that partially burned exhaust gases are sucked into the combustion chamber (4) for heating the air in the combustion chamber (4i) during a suction phase of the internal combustion engine (1).

S. Method according to one of claims 1 to 5, characterized in that for heating the air located in the combustion chamber (4) during a suction phase of the internal combustion engine (1) pre-compressed air is sucked into the combustion chamber (4).

7. The method according to any one of claims 1 to 6, characterized in that the fuel is injected finely divided into the combustion chamber (4).

8. The method according to claim 7, characterized in that the fuel is injected into the combustion chamber (4) with the aid of an A valve opening in the forward direction.

9. The method according to claim 7, characterized in that the fuel is injected into the combustion chamber (4) with the aid of an I-valve opening counter to the passage direction with several, preferably with at least ^' six, spray holes, which are on an ellipse or a circular line the injector tip are arranged as the center.

10. The method according to any one of claims 7 to 9, characterized in that the fuel is injected into the combustion chamber via an injector, the cone opening angle of which is at least 60 °.

11. The method according to any one of claims 1 to 10, characterized in that a glow plug protrudes into the combustion chamber, which is activated when the internal combustion engine (1) is cold started.

12. The method according to any one of claims 1 to 11, characterized in that before the injection of fuel during the compression phase, a small amount of fuel directly into the combustion chamber (4) of the internal combustion engine (1) is pre-injected.

13. Memory element (22), in particular read-only memory, random access memory or flash memory, for a control device (18) of an internal combustion engine (1), in particular a motor vehicle, on which a computer program is stored, which is stored on a computing device (21), in particular on a microprocessor, is executable and suitable for executing a method according to one of claims 1 to 12.

14. Computer program that can run on a computing device (21), in particular on a microprocessor, characterized in that the computer program is suitable for executing a method according to one of claims 1 to 12 when it runs on the computing device (21).

15. Computer program according to claim 14, characterized in that the computer program is stored on a memory element (22), in particular on a flash memory.

16. Control unit (18) for an internal combustion engine (1), in particular of a motor vehicle, for controlling and / or regulating the injection of fuel into a combustion chamber (4) of the internal combustion engine, characterized in that the control unit (18) heats up in the combustion chamber ( 4) of the internal combustion engine (1) and an injection of the fuel during a compression phase of the internal combustion engine (1) directly into the combustion chamber (4), where it forms a self-ignitable fuel-air mixture together with the compressed, heated air.

17. Internal combustion engine (1), in particular a motor vehicle, the internal combustion engine (1) being a

Fuel injection system for direct injection of Fuel in a combustion chamber (4) of the internal combustion engine (1), characterized in that the internal combustion engine (1) has means for heating air in the combustion chamber (4) of the internal combustion engine (1) and the fuel injection system of the fuel during a compression phase of the Brennkra tmaschine (1) injected directly into the combustion chamber (4), where it forms a self-ignitable fuel-air mixture together with the compressed, heated air.

18. Internal combustion engine (1) according to claim 17, characterized in that the internal combustion engine (1) has means for heating the fuel in the fuel injection system and the fuel injection system injects the heated fuel into the combustion chamber (4).