Method for controlling and/or regulating a hybrid drive arrangement

This application is a National Stage completion of PCT/EP2008/060434 filed Aug. 8, 2008, which claims priority from German patent application serial no. 10 2007 041 569.0 filed Sep. 1, 2007.

The present invention concerns a method for controlling and/or regulating a hybrid drive arrangement for a vehicle.

Hybrid drive systems for vehicles are known from automotive technology. In the known hybrid drive systems the drivetrain of the vehicle comprises an internal combustion engine which can be coupled by a clutch to an input shaft of a transmission with variable transmission ratios. Furthermore, associated with the input shaft is at least one electric machine, the operation of which can be changed between a generator or as a motor.

Consequently, during motor operation the electric machine can be used to power the vehicle and during generator operation it can be used to charge an energy accumulator. During motor operation, the energy accumulator can supply the energy required for operating the electric machine. For charging the energy accumulator, the electric machine is operated in the generator mode and is then driven by the internal combustion engine.

After very long stationary periods or after a long time in a workshop, the energy accumulators are fully discharged and are no longer ready to operate. To bring them back to a condition of readiness to operate it is therefore necessary to re-charge them. Usually an energy accumulator is re-charged in the workshop using charging equipment. Disadvantageously, this entails having an external source of energy.

The purpose of the present invention is to propose a method of the type described at the start, by virtue of which a completely discharged energy accumulator can be charged without any external energy source.

Accordingly, a method for controlling and/or regulating a hybrid drive system having at least one internal combustion engine and at least one electric machine can be proposed, these being coupled at least some of the time by means of at least one clutch to the input shaft of an automated transmission for driving the vehicle, such that at least one energy accumulator is charged by the electric machine being driven in the generator mode by the internal combustion engine, and such that with a energized synchronizer machine as the electric machine, a nominal rotation speed, lower than an inflexion speed, is maintained during the charging process.

In this way a fully discharged energy accumulator can be charged without any additional external energy, since the nominal speed is kept within a basic speed range, i.e. below the inflexion speed or bend speed of the synchronizer machine. For example, the internal combustion engine of the vehicle can be started with the help of a conventional starter unit. The clutch is engaged and the internal combustion engine can drive the electric machine in the generator mode to begin the process of charging the energy accumulator. Since the nominal speed is below the inflexion speed, no energy is needed for the field weakening usually provided. Thus, the empty energy accumulator can be charged in the vehicle without outside assistance, so that a self-sufficient system is realized.

For speed regulation during a charging process the clutch control system can preferably be used for controlling the nominal speed. Thus, the desired speed range during charging can be kept too. The charging of the energy accumulator therefore takes place under speed regulation by the synchronizer machine, which can be done simply and steadily in terms of regulation technology.

Preferably, the clutch can be operated by the clutch control system in slipping mode to keep the nominal speed of the synchronizer machine within the basic speed range. This is necessary since the idling speed of the internal combustion engine is usually higher than the inflexion speed, which latter is usually around 300 to 400 revolutions per minute. In this way the clutch transmits a controlled appropriate torque such that the speed of the synchronizer machine is kept below the inflexion speed during charging of the energy accumulator.

Below, the invention is explained in greater detail with reference to the drawing. The single FIGURE illustrating the invention shows a diagram of a torque variation against speed, for a continually energized synchronizer machine.

From the diagram it is clear that the continually energized synchronizer machine at first shows a constant value of the torque m up to an inflexion speed or bend speed n_Eck. The section in which the torque m has a constant value is called the basic speed range I. After this the torque m decreases continuously. This region is called the field weakening range II of the continually energized synchronizer machine.

However, to operate the continually energized synchronizer machine in the field weakening range II, energy is needed in order to bring about the weakening of the field. Accordingly, when the energy accumulator is completely discharged it is proposed to carry out the charging process in the basic speed range I so that no additional external energy is needed. According to the method of the invention, this is achieved by operating the continually energized synchronizer machine under speed control with a nominal speed below the inflexion speed n_Eck during the charging of the energy accumulator.

m Torque of the synchronizer machine

n Speed of the synchronizer machine

n_Eck Inflexion speed of the synchronizer machine

I Basic speed range

II Field weakening range