Method for operating a vehicle hybrid drive train having an internal combustion engine and having an electric machine

A method of operating a hybrid drive train (1) of a vehicle which comprises an internal combustion engine (2) and an electric machine (3) which are both drivably connectable with a drive output (4) of the drive train (1), a clutch device (5) arranged in the drive train (1), between the internal combustion engine (2) and the electric machine (3) such that the internal combustion engine is rotationally fixable to the electric machine, an oil pump device (7) arranged in the drive train (1) downstream of the clutch device (5) in relation to a flow of power from the internal combustion engine (2) to the drive output (4), the oil pump device (7) drivably connectable with the internal combustion engine (2) and the electric machine (3), and a transmission (6) comprises a plurality of shifting elements which are actuatable to implement various gear steps, the method comprising the steps of:

• driving the oil pump device (7) with the electric machine (3) and adjusting a rotational speed of the electric machine (3) independent of a rotational speed of the internal combustion engine (2) to adjust the drive of the oil pump device (7) and a supply of oil to the transmission (6) and the plurality of shifting elements depending an oil volume flow required for a currently operating status of the drive train (1);
• adjusting the rotational speed of the electric machine (3), independent of the rotational speed of the internal combustion engine (2), such that when the vehicle is approximately at rest, the rotational speed of the electric machine (3) is at an at-rest speed which is lower than an idling speed of the internal combustion engine (2), such that the oil pump device (7), driven by the electric machine (3), maintains at least partial actuation of the shifting elements in a current operating status of the transmission (6);
• and
• increasing the rotational speed of the electric machine (3), to increase the drive of the oil pump device (7), when the vehicle is at rest and when a demand is made for at least one of a gear change from a starting gear to a higher gear step and a gear change from a higher gear step to the starting gear;
• and
• increasing the rotational speed of the electric machine (3), from the at-rest speed, when the vehicle is at least approximately at rest, if a demand is made for disengaging a parking lock device.

A method of operating a vehicle hybrid drive train (1) comprising an internal combustion engine (2) and an electric machine (3) whose torque is applied to a drive output (4) of the vehicle hybrid drive train (1), a clutch device (5) arranged between the internal combustion engine (2) and the electric machine (3), an oil pump device 7 arranged in the vehicle hybrid drive train (1), downstream of the clutch device (5), in relation to the internal combustion engine (2), and drivable by both the internal combustion engine (2) and by the electric machine (3), and a transmission device (6) which comprises a plurality of shifting elements for producing various gear ratios and which is supplied with hydraulic fluid by the oil pump device (7) in an operating-status-dependent manner such that a speed of the electric machine (3) is set, independently of a speed of the internal combustion engine (2), in order to supply the transmission device (6), in each case, with a hydraulic fluid volume flow required for an operating point of the transmission device (6) present at the time, the method comprising the steps of:

• corresponding the speed of the electric machine (3) to an at-rest speed value which is lower than an idling speed of the internal combustion engine (2), when the vehicle is at least approximately at rest, such that the oil pump device (7) driven by the electric machine (3) maintains the shifting elements in an at least partially engaged condition so as to maintain a current operating status of the transmission device (6),
• increasing the speed of the electric machine (3), in a range when the vehicle is at rest, when there is at least one of a shift demand for a gear change from a starting gear to a higher gear step and a shift demand for a gear change from a higher gear step to a starting gear, and
• when the vehicle is at least approximately at rest and starting from the at-rest speed value, increasing the speed of the electric machine (3) if there is a demand for disengaging a parking lock device.