Method and arrangement for detecting the end of a start operation in an internal combustion engine of a motor vehicle

#At the present time, the internal combustion engine in a motor vehicle is started with a starter which usually rotates at an rpm of 150 to 300 rpm depending upon the battery voltage and the temperature. The combustion of the air/fuel mixture in the cylinders occurs with the beginning of the injection of fuel into the cylinders of the engine and ignition of the air/fuel mixture. The internal combustion engine now generates a torque and runs up to settle at the idle rpm of approximately 800 rpm. For the engine control and the functions which run in the control, it is important to recognize whether and when the engine runs at steady state. This is recognized based on an rpm threshold which lies clearly above the starter rpm, that is, at 600 rpm, for example. When the engine exceeds this threshold, then the end of the start operation is detected and this is communicated to the engine control.

#The method and arrangement of the invention afford the advantage with the respect to the foregoing that at least one operating variable of the engine is determined which is different from the rpm of the engine and that this at least one operating variable is compared to a pregiven threshold value and that the end of the start operation is detected when the operating variable reaches or exceeds the threshold value. In this way, the end of the start operation is detected independently of the rpm of the engine. In this way, the use of starters is made possible whose rotational speeds (rpms) extend up to the idle range between approximately 700 to 1250 rpm. The method of the invention and the arrangement of the invention also make possible the detection of the end of the start operation for such starters and therefore the detection of reaching the steady-state condition of the engine.

#The use of an operating variable is especially advantageous which can be measured by means of available sensor means. These operating variables include: the combustion chamber pressure, the vibration of the engine, rpm fluctuations of the engine, the conductivity between two spark plug electrodes and the combustion chamber pressure change. The functionality of the existing sensor devices can be increased in this manner because they can be used also for the detection of the end of the start operation of the engine.

#The invention will now be described with reference to the drawings wherein:

#FIG. 1 is a block circuit diagram with an arrangement according to the invention;

#FIG. 2 is a sequence diagram explaining the method of the invention; and,

#In FIG. 1, reference numeral 1 identifies an internal combustion engine of a motor vehicle. The engine 1 is connected to a starter 25. In FIG. 1, five sensors (30, 35, 40, 45, 50) are shown which detect respective operating variables of the engine which are different from the rpm thereof. The five sensors (30, 35, 40, 45, 50) are operatively connected to the engine 1. Different sensors determine different operating variables of the engine 1. There can be more or less than the five sensors (30, 35, 40, 45, 50). In the example of FIG. 1, reference numeral 30 identifies a combustion chamber pressure sensor and 35 an optical sensor. Reference numeral 40 identifies a knock sensor or body-sound sensor and 45 identifies a rough-running sensor and 50 identifies an ion current sensor. The five sensors (30, 35, 40, 45, 50) are connected to an arrangement 5 for detecting the end of a start operation of the engine 1.

#In future, one will start at higher rpm than is usual in the present day in order to reduce the high exhaust-gas emissions when starting the internal combustion engine 1. This can be realized by correspondingly designed starters or even with the aid of a starter generator. The rpms reached therewith extend up to and into the idle range which reach approximately 700 to 1250 rpm. For this reason, the rpm of the engine can no longer be used as an index as to whether the engine is at steady state and the start operation of the engine is ended. The engine control cannot distinguish whether the conventional rpm threshold of 600 rpm for detecting the end of the start operation was exceeded because the engine is at steady state or whether the starter is still driving. For this reason, other signals for detecting the end of the start operation must be applied in order to determine whether the engine has reached its steady-state condition.

#In FIG. 3, the arrangement 5 is shown in greater detail with respect to a block circuit diagram. The arrangement 5 includes means 10 for receiving at least one operating variable of the engine 1. The operating variables, which are determined by the sensors (30, 35, 40, 45, 50), are therefore supplied to the means 10. This is shown symbolically by the three input arrows of the means 10 in FIG. 3. The arrangement 5 further includes means 15 for comparing the at least one operating variable to a pregiven threshold value. A pregiven threshold value can be stored in means 15 for each determined operating variable. The at least one operating variable is supplied from the means 10 to the means 15. The arrangement 5 further includes means 20 for detection. The comparison results from the means 15 are supplied to the means 20 and, when the at least one operating variable reaches or exceeds the particular threshold value, the means 20 detects the end of the start operation and therefore the reaching of the steady-state condition of the engine. The means 20 can output a detection signal D when detecting the end of the start operation. The detection signal D is, for example, supplied to the engine control in order to inform the engine control as to the end of the start operation and the reaching of a steady-state condition of the engine 1.