DE102007028959A1 - Combustion engine e.g. petrol engine, operating method, involves automatically modeling counter pressure inside cylinder of combustion engine in real time, based on drive parameters of engine - Google Patents

Abstract

The method involves automatically modeling counter pressure inside a cylinder (1) of a combustion engine e.g. petrol engine, in real time, based on drive parameters of the engine that includes a dwell angle and an exhaust valve (AV). The modeling of counter pressure includes an interpolation of characteristic zone of counter pressure over a crank shaft angle. Injection amount of an injection valve (12) in the engine depends on the counter pressure. The injection valve is provided for fuel injection in a combustion chamber (2) of the cylinder. Independent claims are also included for the following: (1) a device, in particular control device or combustion engine, which is provided for executing a method for operating a combustion engine (2) a computer program with a program code for executing a method for operating a combustion engine.

Description

The The present invention relates to a method for operating an internal combustion engine, in particular a gasoline engine with gasoline direct injection in controlled Self-ignition. The invention further relates to a Control device and a computer program for implementation of the procedure.

When operating an internal combustion engine in HCCI mode (Homogeneous Charge Compression Ignition), sometimes also referred to as CAI (Controlled Auto Ignition), ATAC (Active Thermo Atmosphere Combustion) or TS (Toyota Soken), the ignition of the air / fuel Mixture not by spark ignition, but by controlled auto-ignition. The HCCI combustion process can be caused for example by a high proportion of hot residual gases and / or by a high compression and / or a high inlet air temperature. The prerequisite for auto-ignition is a sufficiently high energy level in the cylinder. In HCCI mode operable internal combustion engines or methods for their operation are z. B. from the US 6,260,520 . DE 199 27 479 or WO 98/10179 known.

The HCCI combustion has over a conventional one spark-ignition combustion the advantage of a reduced Fuel consumption and lower pollutant emissions.

So far was the pressure correction of the injection pressure in gasoline direct injection over the fuel rail pressure less the intake manifold pressure performed or during injections in the compression phase the fuel rail pressure minus a characteristic curve which includes the cylinder pressure over the crankshaft angle, corrected. This characteristic is in addition to the intake manifold pressure weighted, as in the conventional engine, the cylinder pressure correlated with the intake manifold pressure. If there is a combustion chamber pressure sensor, so the measured value can be used directly to correct the injection pressure be deducted by this deducted from the fuel rail pressure becomes.

at HCCI engines carry those known in the art Method does not produce sufficient results because in the charge cycle OT often residual gas is retained in the cylinder and is compressed again.

Disclosure of the invention

A Object of the present invention is therefore, the combustion chamber back pressure easier and more accurate to determine and so the quantity accuracy of Improve injections in HCCI operation.

This Problem is solved by a method, a device and a computer program according to the independent claims. The problem is solved in particular by a method for operating an internal combustion engine, in particular a gasoline engine with gasoline direct injection in controlled auto-ignition, wherein the internal combustion engine at least one injection valve for Includes fuel injection into a combustion chamber of a cylinder, wherein the injection quantity of the injection valve of the back pressure within the cylinder, with the back pressure based on of operating parameters of the internal combustion engine automatically in real time is modeled.

One This method can be carried out particularly well with a gasoline direct injection gasoline engine, which is a fully variable Valve drive includes. Through this, the residual gas through internal Exhaust gas recirculation can be controlled as required. alternative Such a method can also be carried out For example, with a supercharged gasoline engine or diesel engine with external exhaust gas recirculation. The determination the combustion chamber back pressure can with any internal combustion engine, So both in a gasoline and a diesel engine, application Find. Preferably, the invention Method Application in a gasoline engine operated in HCCI mode becomes. Under real time here is in particular a cycle synchronous Understood modeling, ie the injection back pressure based the present in each cycle combustion chamber pressure cycle synchronous is determined.

Preferably is provided that the operating parameters a closing angle an exhaust valve.

Of the Closing angle of the exhaust valve determined by internal Exhaust gas recirculation the amount of residual gas. Will be additional or alternatively an external exhaust gas recirculation used, so can the corresponding parameters of the external Exhaust gas recirculation such. B. a position of a Throttle valve or the like can be used.

The Modeling of the back pressure preferably comprises an interpolation at least one characteristic map of the back pressure over the crankshaft angle. Preferably, it is provided that the modeling of the back pressure an interpolation between two maps of the back pressure over includes the crankshaft angle.

Between the two maps of the back pressure above the crankshaft is preferably interpolated linearly.

Preferably, it is provided that one the maps a map of the back pressure on the crankshaft angle at the earliest outlet valve-closes position and / or that one of the maps is a map of the back pressure on the crankshaft angle at the latest outlet valve-closes position.

The The above measures offer the advantage of being easy to be determined and easily stored data relatively accurate Determine values for back pressure or combustion chamber pressure to be able to.

Preferably is provided, the modeled back pressure from a modeled Combustion chamber pressure corrected with a temperature dependent value is determined. The temperature-dependent value is preferably a factor with which the modeled back pressure multiplies becomes. Next has proved to be advantageous with another Factor to weight. It has been shown that not all injectors immediately react to the back pressure. Therefore, still a rail pressure-dependent valve factor introduced.

The The problem mentioned at the outset is also solved by a device, In particular, control unit or internal combustion engine, the Carrying out an inventive Procedure is set up.

The The problem mentioned at the outset is also solved by a computer program with program code to perform all steps after one inventive method when the program running in a computer.

Brief description of the drawings

following becomes an embodiment of the present invention explained in more detail with reference to the accompanying drawings. Showing:

1 a sketch of a cylinder of an internal combustion engine;

2 a diagram of the combustion chamber pressure over the crankshaft angle;

3 a diagram of the valve opening and closing angle;

4 a logic diagram of an embodiment of a method according to the invention.

Embodiment of the invention

Based on 1 to 3 First, the technological environment of the invention will be described. In 1 is a cylinder 1 an internal combustion engine, not shown in detail, which generally consists of several cylinders. The cylinder 1 includes a combustion chamber 2 in which a piston 3 with a connecting rod 4 slidably arranged. The connecting rod 4 is connected to a crankshaft, not shown. In the combustion chamber 2 opens an inlet 5 with an inlet valve EV. Furthermore, it flows into the combustion chamber 2 an outlet 7 with an outlet valve AV. Both the inlet valve EV and the outlet valve AV are controlled electro-hydraulically, so the internal combustion engine is equipped with a so-called electro-hydraulic valve control (EHVS). An electro-hydraulic valve control allows control of the valves independent of the crankshaft position. About the inlet 5 is air from the environment in the combustion chamber 2 sucked. The combustion gases are discharged via the outlet 7 returned to the environment. By a suitable opening time of the exhaust valve AV, z. As an opening of the exhaust valve AV during the intake stroke of the internal combustion engine, a so-called internal exhaust gas recirculation can be realized who, namely by the intake stroke of the cylinder 1 Exhaust from the outlet 7 in the combustion chamber 2 flows back or is sucked back.

In the combustion chamber 2 open in a known manner a spark plug 11 and an injection valve or injector 12 , The injector 12 is preferably a piezoelectric injector or an electrohydraulic injector. The injector 12 is via a high pressure line 10 with a high pressure rail 8th the internal combustion engine connected. The high pressure line 10 leads fuel to the injector 12 , The injector 12 is electrically controlled by a control unit 9 are controlled accordingly by the control unit 9 also the spark plug 11 and the intake valve EV and the exhaust valve AV are controlled. Instead of an intake valve EV and an exhaust valve AV, a plurality of intake valves EV and a plurality of exhaust valves AV may also be provided here.

For electro-hydraulic, camshaft-less valve controls (EHVS), as z. B. from the DE 10127205 and the DE 10134644 are known, stroke and timing of the gas exchange valves of an internal combustion engine can be freely programmed in principle. Here, the gas exchange valves are the inlet valve (s) EV and the outlet valve (s) AV.

2 shows a diagram of the combustion chamber pressure in the combustion chamber 2 the engine above the crankshaft angle in degrees crankshaft (° CA). Shown above the ordinate is a crankshaft angle of -180 ° to 540 °, above the abscissa, the combustion chamber pressure is plotted in bar. With 0 °, the top dead center in the charge change L-OT is arbitrarily chosen here. The charge change serves in be known way the emission of burned exhaust gases, this takes place between -180 ° and 0 ° crankshaft, and the intake of fresh ambient air or a fuel-air mixture, this takes place here in the crankshaft angle range of 0-180 °. One crankshaft revolution continues, at 360 ° crankshaft, the top dead center of the ignition (ignition TDC) is reached. Between 180 ° crankshaft and 360 ° crankshaft angle, the compression stroke V takes place between 360 ° crankshaft angle and 540 ° crankshaft angle takes place the expansion E of the combusting gases. The individual bars are in 2 designated with the exhaust stroke AU of -180 ° to 0 °, the intake stroke AN from 0 ° to 180 °, the compression stroke (compression) V of 180 ° to 360 ° and the expansion stroke (combustion) E of 360 ° to 540 °. In the compression stroke V, the air or fuel-air mixture or fuel-air-exhaust gas mixture is compressed and heated. The mixture is usually ignited shortly before reaching the ignition TDC. This can be done as usual in the Otto engine by spark ignition or by a controlled auto-ignition. The ignition of the mixture leads in a known manner to a pressure increase, which is converted in the adjoining power stroke of the expansion E into mechanical energy.

In order to accurately measure the required injection quantity of an internal combustion engine, it is important to know what the back pressure at the injection valve (injector) is at the time of injection. In conventional BDE engines and combustion methods, in the charge exchange OT (L-OT), the back pressure Po at the injector is equal to the intake manifold pressure P _s since the intake valve is open at this time. In HCCI engines, various types of charge cycle control are known from the literature. One of them retains exhaust gas from the last combustion by closing the exhaust valve early in the combustion chamber and compresses it already in the charge exchange TDC, thus also causing a pressure increase of up to 25 bar in the charge exchange TDC. Such a valve strategy is in 3 shown.

In 3 the opening and closing of the intake valve EV and the exhaust valve AV is shown. The exhaust valve AV is normally opened in the exhaust stroke, for example, between -180 ° to 0 ° crankshaft in a 4-stroke engine, accordingly, the intake valve EV is opened in the range of the intake stroke between 0 ° crankshaft and 180 ° crankshaft angle. In 3 is the one valve opening strategy shown, in which the exhaust valve AV is opened shortly before reaching the bottom dead center UT and remains open at about to -90 ° crankshaft. This leaves part of the burned exhaust gases in the combustion chamber 2 , The inlet valve EV is only opened at approximately 90 ° crankshaft angle once pressure equilibrium between the combustion chamber 2 and intake tract remains and remains open until about the bottom dead center. In this way, a so-called negative valve overlap is effected, which ensures that some of the burned exhaust gases in the combustion chamber 2 remains and for heating the in the intake stroke in the combustion chamber 2 introduced fuel-air mixture is used.

The increase in pressure in the combustion chamber caused by the early closing of the exhaust valve must be taken into account as a back pressure during injection if it is necessary to inject in the TDC. This is often the case because in HCCI operation, pilot injection around the charge cycle TDC is used to control the cylinders. The injections must be accurately metered in their quantity. To meet this requirement, the pressure curve at the earliest exhaust valve closing position and at the latest exhaust valve closing position in a map BRP, which is spanned by the crankshaft angle ° KW, stored in two rows. Between the two extreme positions is linearly interpolated. This reflects the quasi-linear relationship between exhaust valve position and residual gas filling, cylinder filling and cylinder pressure in the combustion chamber. In order to do justice to the dependence on the exhaust gas temperature T_A, the output of the characteristic is multiplied by a further characteristic T_R above the exhaust gas temperature. The characteristic curve is neutral at the temperature, that is to say the factor 1 at which the characteristic map BRP shown above or the two characteristics maps were stored. For all other temperatures, multiply by the quotient to the neutral temperature. 4 shows an associated logic diagram. On the map with the pressure curve at the earliest exhaust valve closing position and the latest exhaust valve closing position, the map is referred to here as BRP, the crankshaft angle at which the exhaust valve (s) close, KW_A and the current crankshaft angle ° KW switched. At the output of the map BRP is the modeled combustion chamber pressure PBr. A correction map T_K the exhaust gas temperature T_A is switched on, at the output of the map T_K is a correction factor k on. These are used to multiply the modeled combustion chamber pressure PBr, previously determined by the map BRP, so that the combustion chamber back pressure P_G is obtained.

There the back pressure needed at the time of injection ° KW is the mean injection angle of the just calculated Injection. The map V-K takes into account that different Valves probably differ depending on the hole diameter react to the back pressure. Depending on the rail pressure, the combustion chamber back pressure has an effect sometimes only up to 10% off.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 6260520 [0002]
• - DE 19927479 [0002]
• WO 98/10179 [0002]
• - DE 10127205 [0025]
• - DE 10134644 [0025]

Claims (11)

Method for operating an internal combustion engine, in particular a gasoline engine with gasoline direct injection in controlled self-ignition, wherein the internal combustion engine at least one injection valve ( 12 ) for fuel injection into a combustion chamber ( 2 ) of a cylinder, wherein the injection quantity of the injection valve ( 12 ) depends on the backpressure (P_G) within the cylinder, characterized in that the backpressure (P_G) is automatically modeled in real time on the basis of operating parameters of the internal combustion engine. Method according to claim 1, characterized in that that the operating parameters a closing angle (KW_A) of a Exhaust valve (AV) include. Method according to claim 1 or 2, characterized that the modeling of the back pressure (P_G) is an interpolation at least one characteristic map (BRP) of the back pressure over the crankshaft angle (° CA) includes. Method according to one of claims 1 to 3, characterized in that the modeling of the back pressure (P_G) an interpolation between two maps of the back pressure on includes the crankshaft angle. Method according to claim 4, characterized in that that between the two maps of the back pressure over the crankshafts are linearly interpolated. Method according to claim 4 or 5, characterized that one of the maps a map of the back pressure over the crankshaft angle at the earliest outlet valve closes Position is. Method according to one of claims 4 to 6, characterized in that one of the maps a map the backpressure over the crankshaft angle at the latest Outlet valve-closes position. Method according to one of claims 1 to 7, characterized in that the modeled back pressure (P_G) from a modeled combustion chamber pressure (P_Br), which has a temperature-dependent value is corrected, is determined. Method according to one of claims 1 to 8, characterized in that the modeled back pressure (P_G) from a modeled combustion chamber pressure (P_Br), which is associated with a valve-dependent Value (V_K) is corrected, is determined. Device, in particular control device or internal combustion engine, for carrying out a method according to one of the claims 1 to 9 is set up. Computer program with program code for execution all the steps according to one of claims 1 to 9, when the Program is running in a computer.