Device and method for operating an internal combustion engine provided with a butterfly valve in overrun mode

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In functional block 10, the instantaneous vehicle speed vfzg 12 at the beginning of overrun mode and the instantaneous engine rpm value nmot 14 of the internal combustion engine of the motor vehicle at the beginning of overrun mode are determined, and on the basis of these values, a first value 18 for the position of a butterfly valve of the internal combustion engine is taken from a map 16 of characteristic values.
If a variable B_SA=true 20 indicates that the vehicle is in overrun mode, this first value 18 of the position of the butterfly valve is sent onward by functional block 22.
In another functional block 24, a second value 32 for the position of the butterfly valve is determined continuously and in parallel during overrun mode on the basis of the current vehicle speed vfzg 26 and the current engine rpm value nmot 28, this second value being taken from a map 30 of characteristic values.
The second value 32 corresponds to a butterfly valve position during uniform travel at the currently determined speed 26 in the sense of highway driving at partial load.
In a third functional block 34, a stopwatch 36 is used to determine the time it takes for the foot to be repositioned from the brake pedal to the gas pedal.
For this purpose, the stopwatch is initialized, i.
e.
, started, for example, by means of a state "brake contact switch off" 38 and stopped by a power demand signal (PWR signal>0) 40.
On the basis of this time difference, it is possible to predict what the driver is probably going to do.
That is, if the repositioning time is short, it is very probable that the driver wants to have a considerable level of power at the end of the overrun phase; conversely, if the repositioning time is long, it is very probable that the driver wants only a modest amount of power at the end of the overrun phase.
Accordingly, the second value 32 is corrected as needed in a collator or adder 42; that is, if the driver repositions his foot quickly from the brake pedal to the gas pedal, the second value 32 will be corrected to a value which corresponds to a butterfly valve position with a higher power demand, whereas if the driver repositions his foot slowly from the brake pedal to the gas pedal, the second value 32 is corrected to a value which corresponds to a butterfly valve position with a lower power demand