METHOD FOR OPERATING A DRIVE APPARATUS AND CORRESPONDING DRIVE APPARATUS

Abstract

A method for operating a drive apparatus including an internal combustion engine and an electric engine. An output shaft of the drive apparatus can be operatively connected to the internal combustion engine by way of a shifting clutch and can be permanently operatively connected to the electric engine, so that the output shaft is disengaged from the internal combustion engine in a first shifting state of the shifting clutch and is engaged with it in a second shifting state.

Claims

1. A method for operating a drive apparatus comprising: an internal combustion engine and an electric engine, wherein an output shaft of the chive apparatus can be operatively connected to the internal combustion engine by way of a shifting clutch and is permanently operatively connected to the electric engine, so that the output shaft is disengaged from the internal combustion engine in a first shifting state of the shifting clutch and is engaged with the internal combustion engine in a second shifting state, wherein, during a starting of the internal combustion engine from a standstill, a clutch adaptation is carried out in an adaptation operating mode, wherein a target clutch torque is adjusted on the shifting clutch in such a way that clutch slip is present, and the internal combustion engine is towed without firing to a first target rotational speed and subsequently towed without firing with a constant target clutch torque to a second target rotational speed, and wherein, after the clutch adaptation, the shifting clutch is completely disengaged, and the internal combustion engine is operated with firing to a synchronous speed, which corresponds to an actual speed of the output shaft.

2. The method according to claim 1, wherein, with the clutch adaptation from a rotational speed gradient of the internal combustion engine, an actual clutch torque is determined and is compared to the target clutch torque, wherein, in the event of a deviation between the actual clutch torque and the target clutch torque, an adaptation of a clutch characteristic diagram of the shifting clutch is carried out.

3. The method according to claim 1, wherein, before the second target rotational speed is achieved by the internal combustion engine, fuel injection into the internal combustion engine is suppressed, and then released after the second target rotational speed is achieved.

4. The method according to claim 2, wherein a linear rotational speed curve is used between the first target rotational speed and the second target rotational speed to determine the actual clutch torque.

5. The method according to claim 1, wherein the drive apparatus is operated in a normal operating mode and then is only switched into the adaptation operating mode when a certain number of clutch actuations of the shifting clutch is exceeded since the last clutch adaptation or an adaptation request is present, wherein, after starting of the internal combustion engine, during which the clutch adaptation is carried out, there is a switch back to normal operating mode.

6. The method according to claim 5, wherein the starting of the internal combustion engine in normal operating mode is carried out optionally without firing or with firing, wherein the starting is selected without firing or with &hut based on at least one state parameter.

7. The method according to claim 5, wherein the internal combustion engine is towed in normal operating mode for the start without firing via the shifting clutch up to the synchronous rotational speed and only then is the fuel injection released.

8. The method according to claim 5, wherein the internal combustion engine is towed in normal operating mode for the start with firing via the shifting clutch upon released fuel injection until a minimum speed is reached that is less than the second target rotational speed, and subsequently, the shifting clutch disengages, and the internal combustion engine is then operated with firing to the synchronous rotational speed.

9. The method according to claim 1, wherein, after the synchronous speed is reached by the internal combustion engine, the shifting clutch is completely engaged.

10. A drive apparatus comprising; an internal combustion engine and an electric engine, wherein an output shaft of the drive apparatus can be operatively connected to the internal combustion engine by way of a shifting clutch and is permanently operatively connected to the electric engine, so that the output shaft is disengaged from the internal combustion engine in a first shifting state of the shifting clutch and is engaged with the internal combustion engine in a second shifting state, wherein the drive apparatus is designed to carry out a clutch adaptation in an adaptation operating mode during a starting of the internal combustion engine from a standstill, wherein a target clutch torque is adjusted on the shifting clutch in such a way that clutch slip is present, and the internal combustion engine is towed without firing to a first target rotational speed, and subsequently towed without firing with a constant target clutch torque to a second target rotational speed, and wherein, after the clutch adaptation, the shifting clutch is completely disengaged and the internal combustion engine is operated with firing to a synchronous speed, which corresponds to an actual speed of the output shaft.

Description

DETAILED DESCRIPTION

[0032] FIG. 1 shows a pan of a drive train 1 of a motor vehicle, which is not shown in further detail. The drive train 1 has a drive apparatus 2, which, in turn, has an internal combustion engine 3, an electric engine 4, and an output shaft 5. The drive apparatus 2 is used to drive at least one axle 6 of the motor vehicle, which is composed of two sub axles 7 and 8, and which is connected to a gearbox output shaft 10 of a multi-gear transmission 11 via a differential gear 9. An optional shifting clutch 12 may be present between the gearbox output shaft 10 and the differential gear 9.

[0033] A torque convener 13, which may have a converter lockup clutch 14, may be allocated to the multi-gear transmission 11. The multi-gear transmission 11 has a gearbox output shaft 15, which is preferably permanently connected to the torque converter 13. The gearbox input shaft 15 may be directly connected to the output shaft 5 of the drive apparatus 2 or—as shown here—connected by way of a damping apparatus 16, for example, a torsional vibration damper, particularly rigidly and/or permanently.

[0034] The electric engine 4 is coaxially arranged with respect to the output shaft 5 and preferably rigidly and/or permanently connected to it. In contrast, an operative connection between the internal combustion engine 3 and the output shaft 5 can be adjusted by a shifting clutch 17. For example, the internal combustion engine 3 is completely disengaged from the output shaft 5 in a first shifting state of the shifting clutch 17, and consequently from the electric engine 4. On the other hand, the internal combustion engine 3 is connected to the output shaft 5 and the electric engine 4, respectively, in a second shifting state of the shifting, clutch 17. The shifting clutch 17 can be connected to the internal combustion engine 3 either directly or indirectly by means of an additional damping apparatus 18. The damping apparatus 18 is preferably designed as a dual mass flywheel.

[0035] The drive apparatus 2 may essentially be operated in different operating modes, particularly in a normal operating mode and an adaptation operating mode. In normal operating mode, the internal combustion engine 3 can be started, for example, from a standstill, with the assistance of different start modes, namely optionally without firing or with tiring. With a start of the internal combustion engine 3 without firing, initially the shifting clutch 17 is partially engaged, so that clutch slip is present at the shifting clutch 17. To this end, a corresponding target clutch torque is set on the shifting clutch 17. The actual clutch torque transferred from the output shaft 5 and/or the electric engine 4 by way of the shifting clutch 17 is used to tow the internal combustion engine 3 in the direction of a synchronous speed.

[0036] During the start without firing, the internal combustion engine 3 is then towed up to this synchronous speed without firing and fuel injection of the internal combustion engine 3 is not released until then. The target, clutch torque is adjusted on the shifting clutch 17 until the internal combustion engine 3 has reached the synchronous speed. Once this is the case, the shifting clutch 17 can be completely engaged. The shifting clutch 17 is thus always at least partially engaged during the start of the internal combustion engine 3 without firing, so that an actual clutch torque is transferred by way of it, which is greater than zero.

[0037] Alternatively, a starting of the internal combustion engine 3 with firing may be provided. To this end the shifting clutch 17 may likewise be at least partially engaged in that a target clutch torque is adjusted on it. This clutch torque is, in turn, selected in such a way that clutch slip occurs. With the assistance of the actual torque transferred by means of the shifting clutch 17, the internal combustion engine 3 is towed without firing up to a minimum speed. If the internal combustion engine 3 has reached the minimum speed, the shifting clutch 17 is disengaged and the internal combustion engine 3 is operated with firing upon released fuel inject on and accelerates in the direction of the synchronous speed. The minimum speed is less than the synchronous speed and/or the second target rotational speed. For example, it corresponds to that minimum speed starting from which the internal combustion engine 3 can accelerate autonomously provided it is operated with firing.

[0038] From time to time, it may be necessary to undertake a clutch adaptation during which a clutch characteristic diagram of the shifting clutch 17 is adapted and/or corrected. To this end, a switch is made horn normal operating mode to the adaptation operating mode. If the internal combustion engine 3 is supposed to be started in adaptation operating mode, the clutch adaptation is carried out during the start. In order to start the internal combustion engine 3 in the adaptation operating mode, the target clutch torque is adjusted on the shifting clutch 17 in such a way that clutch slip is present. With the assistance of the actual clutch torque transferred by way of the shifting clutch 17, the internal combustion engine 3 is towed without firing to a first target rotational speed, and subsequently towed without firing with constant target clutch torque to a second target rotational speed. The second target rotational speed can, correspond to the previously mentioned minimum speed.

[0039] During the towing from the first target rotational speed to the second target rotational speed, the clutch adaptation is carried out. After the second target rotational speed is reached by the internal combustion engine 3, that is, after completion of the clutch adaptation, the shifting clutch 17 is completely disengaged and the internal combustion engine 3 is operated with firing to the synchronous speed. This corresponds to the actual speed of the output shaft 5. Despite the implementation of the clutch adaptation, a significantly faster start of the internal combustion engine 3 is possible in this manner than in the normal operating mode by means of the start without firing. In addition, there is significantly less clutch load.

[0040] FIG. 2 shows two diagrams, wherein the upper diagram reflects the torque curves of a torque M over time t, and the lower diagram shows the rotational speed curves of a speed n over time t. One curve 19 describes a default torque, which is specified by a driver of the motor vehicle. This default torque is initially provided solely by the electric engine 4, the torque curve of which is represented over time by curve 20. The internal combustion engine 3 here is not in operation; thus it is initially not providing any torque. The torque curve of the internal combustion engine 3 is indicated by curve 21. A frictional torque of the internal combustion engine with the respective actual speed of the internal combustion engine 3 is indicated by curve 22. Finally, curve 23 shows the curve of an actual clutch torque of the shifting clutch 17. Curve 24 describes the rotational speed curve of the electric engine 4, curve 25 shows the rotational speed curve of the internal combustion engine 3, and curve 26 describes the speed curve of the output shaft 5 and/or the gearbox input shaft 15.

[0041] It is obvious that the torque provided by the electric engine 4 initially corresponds to the default torque. This is the case for t<t.sub.1. The internal combustion engine 3 is not in operation, so that its rotational speed is equal to zero. If the internal combustion engine 3 is started in adaptation operating mode, the torque initially provided by the electric engine 4 and consequently its rotational speed is increased for t.sub.1≦t<t.sub.2. Subsequently, a first target clutch torque that is greater than zero is set on the shifting clutch 17. This means that the actual clutch torque, which is preferably equal to the target clutch torque, is impressed on the internal combustion engine 3 via the shifting clutch 17. Correspondingly, the rotational speed starts to increase starting at t=t.sub.2.

[0042] After the adjustment of the target clutch torque on the shifting clutch 17 at the time t=t.sub.2, the actual clutch torque continues to increase during the time period t.sub.2≦t<t.sub.3. Accordingly, the increase in rotational speed of the internal combustion engine 3 also begins to accelerate. The torque provided by the electric engine 4 can be further increased, particularly up to a torque that corresponds to the total of the default torque and of the target clutch torque, in addition, a speed controller portion may be contained in the torque in order to maintain the slip between the electric engine 4 and the gearbox input shaft 15. This is relevant fir any torque errors of the shifting clutch 17 or timing problems between the electric engine 4 and the shifting clutch 17. The internal combustion engine 3 is then towed until it has reached a first target rotational speed. This is the case for time t=t.sub.4.

[0043] Subsequently, a practically linear increase in the rotational speed of the internal combustion engine 3 results until a second target rotational speed is reached. This is the case for time t=t.sub.5. During the time period t.sub.4<t<t.sub.5, the clutch adaptation of the shifting clutch 17 is carried out. After the second target rotational speed is reached, the shifting clutch 17 is completely disengaged and the internal combustion engine 3 is further accelerated with firing. The disengagement of the shifting clutch 17 starts, for example, at time t=t.sub.6 and is completed at time t=t.sub.7. It can be seen that the rotational speed of the internal combustion engine 3 reaches the rotational speed of the electric engine 4 in the time period t.sub.8≦t<t.sub.9 and subsequently synchronizes with it. Accordingly, the shifting clutch 17 starts to engage, starting from time t=t.sub.8. The engaged state of the shifting clutch 17 is achieved at time t=t.sub.9. In doing so, a target clutch torque is adjusted that is greater than the target clutch torque previously used to start the internal combustion engine 3.

[0044] With the assistance of the described procedure, a quick start of the internal combustion engine 3 with the assistance of the electric engine 4 and the implementation of the clutch adaptation are possible, without anything further. In addition, the clutch adaptation is implemented solely in adaptation operating mode, i.e. not for each start of the internal combustion engine 3.