Method and device for calibrating a pressure sensor

#The present invention relates to a method and an arrangement for calibrating a pressure sensor of a fuel-metering system of an internal combustion engine. The fuel-metering system includes: a high-pressure pump for moving fuel from a low-pressure region into a high-pressure region; injectors, which are controllable in dependence upon operating characteristic variables, for metering fuel from the high-pressure region into combustion chambers of the engine; and, the pressure sensor for measuring the pressure in the high-pressure region.

#The fuel-metering system is, for example, configured as a common-rail fuel direct-injection system with a presupply pump and a high-pressure pump controlled (open loop and/or closed loop) by demand. The presupply pump is, for example, configured as an electric fuel pump and moves fuel from a fuel supply vessel into the low-pressure region of the fuel-metering system. A prepressure of, for example, 4 bar is present in the low-pressure region. The high-pressure pump pumps the fuel from the low-pressure region into a high-pressure store in the high-pressure region of the fuel-metering system. In the high-pressure store, a pressure of 150 to 200 bar is, for example, present for gasoline fuel and a pressure of, for example, 1,500 to 2,000 bar is present for diesel fuel. Several injectors branch from the high-pressure store and, with a corresponding driving control, inject the fuel from the high-pressure store into the combustion chambers of the engine at the injection pressure present at the high-pressure store. The injectors are drivable in dependence upon specific operating characteristic variables. In the high-pressure store, a pressure sensor is furthermore mounted via which the injection pressure, which is present in the high-pressure store, is determined and a corresponding electrical signal is conducted to a control apparatus of the engine. Finally, a pressure control line branches from the high-pressure region of the fuel-metering system and this pressure control line opens via a pressure control valve into the low-pressure region. A low-pressure line branches from the low-pressure region of the fuel supply system and this low-pressure line leads via a low-pressure controller back into the fuel supply vessel.

#Pressure sensors, as they are also utilized in fuel-metering systems, conventionally include a static offset error, that is, the zero point is not reliably indicated. An offset error leads to the situation that the measured value of pressure sensors, especially in the low-pressure region, can have large relative deviations to the actual pressure value.

#A preferred embodiment of the present invention is explained in greater detail in the following with respect to the drawings wherein:

#FIG. 1 shows a sequence diagram of a method of the invention in accordance with a preferred embodiment; and,

#FIG. 2 shows a fuel-metering system of an internal combustion engine wherein a pressure sensor is calibrated by means of the method according to the invention from FIG. 1.

#In FIG. 1, a sequence diagram of a preferred embodiment of a method for calibrating a pressure sensor of a fuel-metering system of an internal combustion engine is shown. FIG. 2 shows a fuel-metering system configured as a common-rail fuel direct-injection system. The system includes a presupply pump 1 and a high-pressure pump 2 controlled (open loop and/or closed loop) in accordance with demand. The presupply pump 1 is configured as an electric fuel pump and moves fuel from a fuel supply vessel 3 in a low-pressure region ND of the fuel-metering system. A pressure of approximately 4 bar is present in the low-pressure region ND.

#The high-pressure pump 2 moves the fuel from the low-pressure region ND into a high-pressure store 4, the so-called rail, in a high-pressure region HD of the fuel-metering system. For gasoline fuel, a pressure of approximately 150 to 200 bar is present in the high-pressure store 4 and, for diesel fuel, a pressure of approximately 1,500 to 2,000 bar is present therein. Four injectors 5 branch from the high-pressure store 4 and are driven in dependence upon operating characteristic variables. For a corresponding control, the fuel is injected into the combustion chambers 6 of the engine from the high-pressure store 4 at the there present injection pressure.

#In the high-pressure store 4, a pressure sensor 7 is mounted via which the injection pressure, which is present in the high-pressure store 4, is determined and a corresponding electrical signal is conducted to a control apparatus 8 of the engine. The signal lines 9 are shown in FIG. 2 as broken lines. Finally, a pressure control line 10 branches from the high-pressure store 4 of the fuel-metering system. This pressure control line 10 opens via a pressure control valve 11 into the low-pressure region ND.