1. Field of the Invention
The present invention generally relates to a method and a device for operating a hybrid drive system having multiple drives, and relates particularly to the execution of learning functions in order to adapt regulation of the drives of the hybrid drive system to changed physical behavior of the drives.
2. Description of the Related Art
For previous drives having internal combustion engines, the internal combustion engines are activated by an appropriate engine control unit in order to provide the desired output variables such as rotational speed or torque, for example. Since the physical behavior of the internal combustion engine may change over time due to various influences, for example aging, temperature fluctuations, or the like, adaptation functions are usually implemented in the engine control unit. These adaptation functions may be triggered as a function of operating data, for example the operating time of the internal combustion engine, the distance traveled, the number of driving cycles, or the number of revolutions of the engine shaft, and as a function of a specified operating range of the internal combustion engine. If the specified operating range is operated for a minimum period of time which is necessary for completely executing the adaptation function, specific parameters may be adjusted or adapted with the aid of the adaptation function.
In hybrid drive systems, two or more than two types of drives are generally used in parallel. A higher-level hybrid control unit is used to select a subdivision of the torque to be provided, according to a drive strategy, as a function of the driver's specifications and as a function of the instantaneous operating states of the vehicle or of the drive system. Depending on the drive strategy provided, the operating control unit may provide that in the specific operating range of the motor vehicle and in specific ranges of driver specifications the load is distributed between the drives so that the drives are each operated in preferred operating ranges. However, this may result in certain operating ranges no longer being included in a drive, since the drive strategy which is implemented in the hybrid control unit keeps one or more of the drives in a preferred operating range.
In the example of the internal combustion engine as the drive, current drive strategies of the hybrid control units provide that the hybrid control units are operated in a medium load range so that, for example, operating modes such as coasting mode or idle speed occur rarely or not at all.
If this is the case, the engine control unit is no longer able to carry out the adaptation function, even when a suitable testing time is established, since the internal combustion engine no longer reaches the operating range which is necessary for executing the adaptation function.
An object of the present invention, therefore, is to provide a method and a device for operating a hybrid drive system via which, also for a hybrid drive system, it may be ensured that necessary adaptation functions for the individual drives are executed.