Patent ID: 7437234

Claim:
A control system for controlling an injector of a cylinder in a combustion engine where the injector is connected to a fuel accumulator of a common-rail fuel injection system, the control system comprising: a data storage medium having stored thereon an on-time calculation model or a lookup table and a fuel quantity calculation model or a lookup table; and an engine control device operable to establish an on-time value (t) for the injector with the aid of the on-time calculation model or the lookup table based on a fuel pressure value (P) and a fuel injection quantity value (δ), wherein the fuel pressure value (P) represents the fuel pressure in the fuel accumulator, the fuel injection quantity value (δ) represents a desired quantity of fuel to be injected into the cylinder and the on-time value (t) represents the associated on-time for the injector, the engine control device comprises a processor operable to execute the following steps: A) interrupt the supply of fuel to the fuel accumulator; B) execute a test injection of fuel into the cylinder with the injector by applying an on-time value (t test ) for the injector corresponding, in accordance with the on-time calculation model or the lookup table, to a fuel injection quantity (δ test ) denominated a test fuel quantity, which exceeds a maximum allowed fuel injection quantity of the cylinder, while maintaining the supply of fuel to the fuel accumulator interrupted, the test injection being executed under such conditions that no ignition of the injected fuel takes place in the cylinder; C) determine or receive a pressure drop value (ΔP) representing the pressure drop of the fuel in the fuel accumulator during the test injection and a fuel pressure value (P test ) representing the fuel pressure in the fuel accumulator at the start of the pressure drop; D) establish the actual fuel quantity (δ actual ) injected into the cylinder during the test injection with the aid of the fuel quantity calculation model or a lookup table based on the pressure drop value (ΔP) and the fuel pressure value (P test ); E) compare the actual fuel quantity (δ actual ) with the test fuel quantity (δ test ), or compare an on-time value (t a ) established with the aid of the on-time calculation model or the lookup table based on the actual fuel quantity (δ actual ) and the fuel pressure value (P test ) with the on-time value (t test ) applied for the test injection; and F) adjust the on-time calculation model or the lookup table in dependence on the result of the comparison.