DE102008016662A1 - Method for injecting fuel in vehicle engine, involves maintaining fuel pressure in high pressure storage tank, and injecting fuel into cylinder of vehicle engine by temporally controlled injector - Google Patents

Abstract

The method involves maintaining fuel pressure in a high pressure storage tank (4). The fuel is injected into the cylinder of the vehicle engine by a temporally controlled injector (6). The injected fuel quantity is constantly determined, where the fuel quantity is calculated corresponding to the pressure signal measured by a pressure sensor (17), compared with the desired fuel quantity, and is corrected by the adjustment of an injection parameter. An independent claim is included for a fuel injection system for injecting fuel into a vehicle engine.

Description

The The invention relates to a method according to the preamble of claim 1 and a device according to the preamble of claim 8. This serve to inject fuel into a motor vehicle engine, in which the fuel pressure in a high pressure storage tank (Common Rail) maintained and the fuel through in time controlled injectors injected into the cylinders of a fuel engine becomes.

In known injection systems ( DE 10 2004 022 267 A1 ; tecnik Profi 40_2003, pages 4-8), the injection duration with maps (referred to as TI-map) is determined, the input variables of the injection pressure and the desired amount of fuel. Since such a map is created as averages of the maps measured for individual injectors, each injector injects a slightly different amount of fuel. Inaccuracies in the injection quantity are therefore unavoidable.

The Inaccuracies are reduced in practice by that the injection quantity of each injector is measured individually, and that the injectors are then classified into groups. For each group is then corrected the average map. The Correction is optimized for specified operating points and interpolated for other operating points. The correction is carried out before the start of operation of the motor vehicle and the correction values are maintained over its lifetime.

Of the Invention is based on the object, a method of the initially called type, with which the injector of each individual Injected fuel quantity individually controlled exactly and this exact control over the entire life of the injector is maintained.

The The object of the invention is achieved by a method according to claim 1 and an injection system according to claim 8 solved. In the process is the injected fuel quantity online, that is directly during operation, continuously determined by the amount of fuel calculated on the basis of a pressure signal measured by a pressure sensor, compared with the desired amount of fuel and by a Correction of an injection parameter is corrected. The pressure difference between the upper and the lower value of the rail pressure at a Injection corresponds to the injection quantity.

expedient Further developments of the invention are in the subclaims resigned.

The Advantages of the invention are in particular that production-related Deviations of the injected fuel from the injectors be compensated individually and over their lifetime. This allowed very precise control of the fuel injection reduces fuel costs and environmental impact.

embodiments The invention will be explained below with reference to the drawings. Show it:

1 an injection system in which the method according to the invention is applied, in a schematic representation;

2 a measurement diagram of the injection pressure over the angle of the high-pressure pump;

3A - 3B three diagrams illustrating the physical principles of the invention, and

4 the flowchart of a program with which the inventive method is performed.

An injection system 1 consists essentially of a pump unit 2 that fuel, for example, diesel fuel, from a fuel tank 3 sucks and under high pressure a high-pressure manifold or common rail 4 supplies. From the common rail 4 the fuel is delivered via injectors 6 injected into the individual cylinders of a motor vehicle engine. The engine is not shown here, as it is well known and is not changed by the invention in its construction.

The pump unit 2 indicates a fuel delivery pump 8th , a high pressure pump 9 , a flow valve 10 , which controls the fuel volume flow, a continuous-pressure valve 11 and a pressure relief valve 12 , The fuel gets out of the tank 3 over a line 14 holding a fuel filter 15 contains, sucked.

A signal line 16 transmits the from a pressure sensor 17 detected pressure in the common rail 4 , called in the following rail pressure, to a control unit 18 , This control unit, which contains the engine electronics, controls the flow valve 10 via a control line 20 and the continuous pressure valve 11 via a control line 21 , These control lines are for the sake of clarity in the 1 only hinted and not pulled through.

The rail pressure is with the valves 10 and 11 regulated or controlled. So, if the flow valve 10 is completely open, in the continuous-pressure valve 11 a force can be set which corresponds to a predetermined pressure value. If this value of the pressure is exceeded, the Ven til and the fuel flows through a return line 22 in the fuel tank 3 back. The rail pressure can also be controlled by the Stetigdruckventil 11 is set to a high pressure value and the flow valve 10 from the controller 18 is controlled so that the desired pressure on the high-pressure pump 9 in the common rail 4 is built.

P, PFU

Kraftstoffdruck

H

oberer (Wert)

L

unterer (Wert)

PFU_H

oberer Wert des Kraftstoffdrucks

PFU_L

unterer Wert des Kraftstoffdrucks

EOI

Ende der Einspritzung

SOP

Beginn des Pumpens

TDC

oberer Totpunkt

TDC_P

oberer Totpunkt des Kolbens der Hochdruckpumpe

Δp

Druckdifferenz PFU_H – DFU_L

From the measurement diagram of 2 is the injection pressure in megapascals (MPa) above the crankshaft angle in degrees crankshaft revolutions (° CA) can be seen. The following values and points are highlighted and the following reference numbers are used therein:

P, PFU

Fuel pressure

H

upper (value)

L

lower (value)

PFU_H

upper value of the fuel pressure

PFU_L

lower value of the fuel pressure

EOI

End of the injection

SOP

Start of pumping

TDC

Top Dead Center

TDC_P

top dead center of the piston of the high-pressure pump

Ap

Pressure difference PFU_H - DFU_L

The actual amount of fuel injected is calculated from the pressure signal. Physical basis is equation for the construction of the pressure p: dp dt = e V · ΣQ i (I) where E is the compression modulus of the fuel, V is the volume of the common rail 4 and Q _{i are} the volume flow into or out of the common rail interior. Considering a very short injection time, equation (I) can be approximated by the following equation: Δp = e V · (MF_INJ / ρ / a 0 ) (II)

Where MF_INJ are the injected fuel mass, ρ is the fuel density, and a _{0 is} an operating point-dependent, experimentally determined constant. With equation (II), the injected fuel mass can be calculated as: MF_INJ = Δp · ρ · V / E - P · a 0 (III)

The relationship Δp (INJ) → MF_INJ, that is, the implementation of an injection pressure difference in an injected fuel mass is in the 3A . 3B and 3C graphically illustrated, where a ₀ is zero in this example. In 3A is the volume flow Qp of the high-pressure pump 9 shown over time t. The arrows seg_0, seg_1 and so on indicate the beginning of the successive segments or cycles of the working cycle of the engine.

In 3B is the one from the common rail 4 emergent volume flow Qnj (in volume per unit of time) over time; it corresponds to the injection quantity (in fuel mass per injection).

In 3C the rail pressure P_RAIL is displayed over time. It can be seen from these figures that the pressure difference ΔP (INJ) between the upper and lower pressure values corresponds to the injection quantity during injection.

• Start in einem Schritt

  S1:

  eine Erfassung des Drucks durch den Drucksensor 17 mit einer hohen Messfrequenz, zum Beispiel mit einer Messung jede Millisekunde. In einem Schritt

  S2:

  erfolgt eine Ermittlung des oberen und des unteren Wertes des Kraftstoffdrucks PFU_H beziehungsweise PFU_L. Dieser Werte sind die Drücke in dem Bereich des Winkels TDC der Hochdruckpumpe. Die Messwerte werden zweckmäßigerweise gefiltert, entweder durch eine Tiefpassfilterung oder durch eine Mittelung zwischen dem Ende der Einspritzung und dem Beginn des Pumpens. In einem Schritt

  S3

  wird der Druckeinbruch Delt_PFU aufgrund der Einspritzung, das heißt die Druckdifferenz zwischen den Werten PFU_H und PFU_L berechnet. Aus dem Druckeinbruch Delt_PFU wird die eingespritzte Kraftstoffmasse MF_INJ_SUM wie beschrieben berechnet. Betriebsparameter wie die Kraftstofftemperatur TFU in dem Common-Rail 4 können dabei berücksichtigt werden. Die Kraftstoffmasse kann auch aus einem durch Kalibrierung der Einspritzanlage erstellten Kennfeld entnommen werde. In einem Schritt

  S4

  wird die Korrektur oder Änderung ΔTI der Dauer der Einspritzung TI durch eine PI-Regelung der Differenz zwischen dem aufsummierten Sollwert der eingespritzten Kraftstoffmenge SOLL_MF_INJ_SUM und dem zugehörigen Istwert MF_INJ_SUM ermittelt. Entsprechend wird als weiterer Einspritzparameter der Sollwert der Einspritzenergie EGY_SP ermittelt, was in 4 nur angedeutet ist. In einem Schritt

  S5

  werden schließlich die korrigierten Werte der Einspritzdauer TI_k und der Einspritzenergie EGY_SP_k durch addieren der ermittelten Korrekturwerte ΔTI und ΔEGY_SP zu den unkorrigierten, herkömmlich gebildeten Werten der Einspritzdauer TI beziehungsweise der Einspritzenergie EGY_SP gebildet. Damit ist ein Durchgang des Programms am

• ENDE.

At the 4 apparent flowchart of an executed in the inventive method program is carried out after the

• Start in one step

  S1:

  a detection of the pressure by the pressure sensor 17 with a high measuring frequency, for example with one measurement every millisecond. In one step

  S2:

  there is a determination of the upper and the lower value of the fuel pressure PFU_H or PFU_L. These values are the pressures in the range of the angle TDC of the high pressure pump. The readings are conveniently filtered, either by low pass filtering or by averaging between the end of the injection and the beginning of the pumping. In one step

  S3

  the pressure drop Delt_PFU is calculated on the basis of the injection, ie the pressure difference between the values PFU_H and PFU_L. From the pressure drop Delt_PFU, the injected fuel mass MF_INJ_SUM is calculated as described. Operating parameters such as the fuel temperature TFU in the common rail 4 can be taken into account. The fuel mass can also be taken from a map created by calibration of the injection system. In one step

  S4

  the correction or change .DELTA.TI the duration of the injection TI is determined by a PI control of the difference between the summed setpoint value of the injected fuel quantity SOLL_MF_INJ_SUM and the associated actual value MF_INJ_SUM. Accordingly, the desired value of the injection energy EGY_SP is determined as a further injection parameter 4 only hinted at. In one step

  S5

  Finally, the corrected values of the injection duration TI_k and the injection energy EGY_SP_k are formed by adding the determined correction values ΔTI and ΔEGY_SP to the uncorrected conventionally formed values of the injection duration TI and the injection energy EGY_SP, respectively. This is a passage of the program on

• THE END.

The Program steps S1 to S3 are performed for each segment of the active engine again processed.

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

• DE 102004022267 A1 [0002]

Claims (8)

Method for injecting fuel into an automotive engine, in which the fuel pressure in a high-pressure storage tank ( 4 ) and the fuel through time-controlled injectors ( 6 ) is injected into the cylinders of the motor vehicle engine, characterized in that - the injected fuel quantity (MF_INJ) is determined continuously by calculating the fuel quantity based on a pressure signal measured by a pressure sensor, compared with the desired fuel quantity and by a correction of an injection parameter (TI, ENY) is corrected. Method according to claim 1, characterized in that that the pressure difference (ΔP (INJ)) between the upper and the lower value of the rail pressure (P_RAIL) during an injection the injection quantity corresponds. Method according to claim 1 or 2, characterized that The upper value of the fuel pressure (PFU_H) is determined; - that the pressure drop due to the injection (Delt_PFU) is calculated, and - that from the pressure drop (Delt_PFU) the injected fuel mass MF_INJ_SUM is calculated. Method according to one of the preceding claims, characterized in that the injected fuel mass (MF_INJ) is calculated according to the equation MF_INJ = Δp · ρ · V / E - P · a ₀ , where Δp is the pressure difference between the upper value of the fuel pressure (PFU_H) and the lower value of the fuel pressure (PFU_L), ρ the density of the fuel, V the volume of the common rail ( 4 ) and E are the compression modulus of the fuel. Method according to one of the preceding claims, characterized in that the measured values of the fuel pressure (PFU_H, PFU_H) are filtered. Method according to one of the preceding claims, characterized in that a correction (ΔTI) of the duration the injection (TI) by a PI control of the difference between the setpoint (SOLL_MF_INJ_SUM) and the actual value (MF_INJ_SUM) the injected fuel quantity is determined. Method according to Claim 6, characterized that corrected values of injection duration (TI_k) and injection energy (EGY_SP_k) by adding the determined correction values (ΔTI, ΔEGY_SP) to the uncorrected values of the injection duration (TI) respectively the injection energy (EGY_SP) are formed. Injection system for injecting fuel into a motor vehicle engine with a high pressure storage tank ( 4 ), in which the fuel pressure is maintained and with time-controlled injectors ( 6 ), through which the fuel is injected through into the cylinders of an automotive engine, characterized in that the injected fuel quantity (MF_INJ) is continuously determined by the fuel quantity on the basis of a pressure sensor ( 17 ) measured pressure signal (PFU), compared with the desired amount of fuel and corrected accordingly.