Method and control device for operating a drive train

Abstract

Method for operating a drive train of a motor vehicle, wherein the drive train has a plurality of drive units (1, 2), a transmission (3) and an output (4), and wherein the transmission (3) comprises a plurality of shift elements (9), wherein, for a gear change to be carried out from an actual gear to a target gear, a switching element (9) which is closed in the actual gear and open in the target gear is opened and a switching element (9) which is open in the actual gear and closed in the target gear is closed, wherein, for the gear change to be carried out, target torques for the first and second drive units (1, 2) are determined at least as a function of a driver's desired output torque, wherein, when a positive-locking shift element (9) is opened for the gear change to be carried out, the positive-locking shift element (9) to be opened is made load-free or approximately load-free via a control of the first and second drive units (1, 2) dependent on the calculated target torques, in that the target torque on one of the drive units is reduced and the target torque on another of the drive units is increased in order to open the shift element (9) to be opened load-free or approximately load-free while providing the driver's desired output torque at the output (4), wherein the positive-locking switching element (9) to be opened is actuated in the opening direction with a defined actuation pressure or a defined actuation force before a theoretical load release or approximately theoretical load release dependent on the desired torques, wherein it is monitored whether and at which actual moments of the first and second drive units (1, 2) the positive switching element (9) to be opened begins to move, wherein the actual moments of the first and second drive units (1, 2) at which the positive-locking switching element (9) to be opened begins to move are determined as actual moments at which the positive-locking switching element (9) to be opened is actually placed load-free or approximately load-free.

Description

[0001] The invention relates to a method and a control device for operating a drive train of a motor vehicle.

[0002] Drivetrains for motor vehicles are known from hybrid vehicles, which have a plurality of drive units, a transmission, and an output. It is known that the first drive unit acts on a first drive shaft, wherein a second drive unit acts on a different, second drive shaft, and wherein a transmission output shaft is different from the first drive shaft, on which the first drive unit acts, and from the second drive shaft, on which the second drive unit acts. The first drive unit is preferably an internal combustion engine, and the second drive unit is preferably an electric machine that can be operated as a motor and as a generator. The transmission of such a drivetrain comprises a plurality of shift elements, wherein a first number of shift elements are closed and a second number of shift elements are open in each engaged gear of the transmission.To perform a gear change from an actual gear to a target gear, a shift element that is closed in the actual gear and open in the target gear is opened, and a shift element that is open in the actual gear and closed in the target gear is closed. If these are frictionally engaged shift elements, such as brakes or clutches, the opening and closing of the shift elements involved can take place while they are slipping. However, slipping operation creates frictional or drag torques that have a negative impact on the vehicle's fuel consumption. For this reason, positive-lock shift elements, such as dog-type shift elements, which do not generate any frictional torque during operation, are increasingly being used in motor vehicle transmissions. To open such a positive-lock shift element, it must be de-energized so that it can be opened with a high level of comfort.To close such a positive-locking switching element, synchronization of the respective switching element is required, which means that a differential speed at the switching element halves of the respective positive-locking switching element must be reduced before closing.

[0003] DE 10 2014 220 070 A1 discloses a method for operating a drive train with multiple drive units, wherein a first drive unit acts on a first drive shaft and a second drive unit acts on a second, different drive shaft. To perform a gear change from an actual gear to a target gear, the shift element to be opened for the target gear is made load-free via torque-controlled operation of a first drive unit and via torque-controlled operation of the second drive unit, with the load-free shift element subsequently being opened. Subsequently, the speed of the first drive unit and the speed of the second drive unit are adapted to the target gear via speed-controlled operation of the first drive unit and / or via speed-controlled operation of the second drive unit, such that the shift element to be closed for the target gear is synchronized.The switching element to be closed is then closed.

[0004] DE 10 2010 061 824 A1 discloses a further method for operating a drive train with multiple drive units and a transmission. The transmission comprises multiple positive-locking shift elements. A planetary gear train interacts with the transmission. A lock-up shift element interacts with the planetary gear train. The lock-up shift element is a positive-locking shift element that can be made load-free by setting target torques on both drive units. Once the respective target torque is reached on both drive units, the lock-up shift element can be opened load-free. It is also proposed to record those torques of the two drive units at which the lock-up shift element is actually opened. These torques are stored and used as an adaptation for the next opening process of the lock-up shift element.

[0005] Based on this, the invention is based on the object of creating a novel method for operating a drive train of a motor vehicle and a control device for carrying out the method.

[0006] This object is achieved by a method for operating a drive train according to patent claim 1.

[0007] The method according to the invention serves to operate a drive train of a motor vehicle which has a plurality of drive units, a transmission and an output, and wherein the transmission comprises a plurality of shifting elements. Preferably, a first drive unit acts on a first drive shaft, wherein a second drive unit preferably acts on a second drive shaft. The method according to the invention comprises at least the following steps: For a gear change to be carried out from an actual gear to a target gear, a shifting element which is closed in the actual gear and open in the target gear is opened and a shifting element which is open in the actual gear and closed in the target gear is closed. For the gear change to be carried out, target torques for the first and second drive units are determined at least as a function of a driver-desired output torque.When a positive-locking shift element is opened for the gear change to be carried out, the positive-locking shift element to be opened is made load-free or approximately load-free via a control of the first and second drive units that is dependent on the calculated target torques. This control is achieved by reducing the target torque on one of the drive units and increasing the target torque on another of the drive units, thereby opening the shift element to be opened load-free or approximately load-free, while providing the driver-desired output torque at the output. The positive-locking shift element to be opened is already controlled in the opening direction with a defined control pressure or a defined control force before a theoretical load release, which is dependent on the target torques, or a theoretical approximately load release, during the load transfer.This involves monitoring whether and at which actual torques of the first and second drive units the positive-locking switching element to be opened begins to move. The actual torques of the first and second drive units at which the positive-locking switching element to be opened begins to move are determined as the actual torques at which the positive-locking switching element to be opened is actually placed load-free or approximately load-free.

[0008] With the present invention, a positive-locking switching element of a transmission can be opened particularly advantageously.

[0009] To release the load, or approximately release the load, of the positive-locking switching element to be opened, a load transfer takes place based on the target torques for the two drive units. During load transfer, the target torque is increased on one of the drive units and decreased on another in order to release the load on the positive-locking switching element to be opened while maintaining the driver's desired output torque.

[0010] Even before the theoretical load release or theoretically approximately load release, the positive-locking switching element to be opened is actuated with the defined actuation pressure or the defined actuation force during load transfer.

[0011] It is monitored whether and at what actual torques of the drive units the positive-locking switching element to be opened begins to move. These torques are recorded to determine at which actual torques of the drive units the positive-locking switching element to be opened is actually load-free or approximately load-free.

[0012] According to an advantageous development of the invention, the target torques are adapted depending on a deviation between the target torques of the first and second drive units, which lead to a theoretical load-free release or a theoretical approximate load-free release of the positive-locking switching element to be opened, and the actual torques of the first and second drive units, at which the positive-locking switching element to be opened is actually made load-free or approximately load-free. This can particularly advantageously provide an adaptation for the target torques of the drive units. Upon subsequent opening of a positive-locking switching element, the opening can then occur with higher quality.

[0013] According to an advantageous development of the invention, a point in time is determined depending on the target torques of the drive units at which the positive-locking switching element to be opened is made theoretically load-free or theoretically approximately load-free. Already a defined time period before this point in time of theoretical load release or approximately load release, the switching element to be opened is actuated in the opening direction with the defined actuation pressure or the defined actuation force during load transfer. Then, when it is determined that the positive-locking switching element to be opened begins to move within this time period or at the specific point in time, the corresponding actual torques of the first and second drive units are determined, load transfer is terminated, and the positive-locking switching element to be opened is actuated with a higher actuation pressure or a higher actuation force until it is fully opened.If the switching element to be opened does not begin to move by the defined time, the switching element to be opened is actuated in the opening direction with the defined actuation pressure or the defined actuation force for a maximum of a defined period of time after this time with continued load transfer or with the target torques of the first and second drive units being increased and / or reduced in the same direction.Then, when it is determined that the positive-locking switching element to be opened begins to move within the maximum permissible time period after the specific time of the theoretical load release or approximately load release, the actual torques of the drive units are determined, the load transfer or the simultaneous increase and / or reduction of the target torques of the first and second drive units is terminated, and the positive-locking switching element to be opened is actuated with a higher actuation pressure or a higher actuation force to fully open.Then, if it is determined that the positive-locking switching element to be opened does not begin to move within the time period after the specific time of the theoretical load release or approximately load release, the load transfer or the optional simultaneous increase and / or reduction of the target torques of the first and second drive units is terminated and the positive-locking switching element to be opened is actuated with a higher actuation pressure or a higher actuation force to fully open.

[0014] These details make it particularly advantageous to determine the actual torques of the drive units, which are used to position the positive-locking shift element to be opened as actually load-free or approximately load-free. Simultaneously increasing and / or reducing the target torques for the drive units is advantageous when the torque deviations on both drive units are in the same direction, i.e., they cannot compensate for each other. Simultaneously increasing and / or reducing the target torques on the drive units is preferably performed when it could not be determined during a previous gear change that the positive-locking shift element to be disengaged would begin to move during load transfer.

[0015] The control device according to the invention is defined in claim 12.

[0016] Preferred developments emerge from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1 a diagram of a powertrain of a motor vehicle; Fig. 2 timing diagrams to illustrate the phases of a gear change; Fig. 3 timing diagrams to illustrate the invention; Fig. 4 timing diagrams to further illustrate the invention; and Fig. 5 a block diagram to further clarify the invention.

[0017] The present invention relates to a method for operating a drive train of a motor vehicle with an automatic or automated transmission and a control device for carrying out the method.

[0018] Fig. 1 shows a diagram of a drive train of a motor vehicle in which the method according to the invention is preferably used. Thus, the drive train of the Fig. 1 two drive units 1, 2, a gearbox 3 and an output 4. The gearbox 3 preferably comprises a planetary stage 5.

[0019] The two drive units 1, 2 act on different drive shafts or transmission shafts of the transmission 3, namely the first drive unit 1 on a first drive shaft 6 and the second drive unit 2 on a different second drive shaft 7. The drive units 1 and 2 do not have a constant, but rather a variable, gear ratio to each other. The two drive shafts 6, 7 are separate from a transmission output shaft 8.

[0020] In the exemplary embodiment shown, the first drive unit 1 is an internal combustion engine that acts on the first drive shaft 6, which in the exemplary embodiment shown is the transmission input shaft of the transmission 3. The second drive unit 2 in the exemplary embodiment shown is an electric machine that acts on the second drive shaft 7 or a second transmission shaft of the transmission 3, wherein the second drive shaft 7 in the exemplary embodiment shown is provided by the planetary stage 5, namely in the exemplary embodiment shown by a ring gear thereof. It should be noted that alternatively, both drive units 2 and 3 can also be electric machines.

[0021] The transmission output shaft 8 of the transmission 3 acts on an output 4 of the drive train to ultimately provide a driver-desired torque at the output 4. The transmission output shaft 8 corresponds to the output shaft. In the illustrated embodiment of the Fig. 1, the first drive unit 1 is a drive unit external to the transmission and the drive unit 2 is a drive unit internal to the transmission.

[0022] According to Fig. 1, the transmission 3 comprises several switching elements 9, wherein in Fig. 1 only two switching elements 9 are shown as examples. Thus, a first switching element 9 according to Fig. 1 is connected between the transmission input shaft 6 and the planetary stage 5, and a second shifting element 9 is connected between the planetary stage 5 and the transmission output shaft 8. In the embodiment shown, both shifting elements 9 are positive-locking shifting elements, for example, claw shifting elements.

[0023] In the exemplary embodiment, the Fig. 1, a separating clutch 10 is engaged, which is preferably designed as a frictional clutch, whereby the first drive unit 1 can be decoupled from the transmission input shaft 6 via the separating clutch. The separating clutch 10 is an optional component and can also be omitted.

[0024] Fig. 1 further shows a control device 21 which, in the embodiment shown, controls and / or regulates the operation of the first drive unit 1 and the transmission 3 including the second drive unit 2.

[0025] This control device 21 is preferably a hybrid control device. Thus, according to the dashed arrows, the control device 21 exchanges data with both the first drive unit 1 and the transmission 3 in order to control and / or regulate the operation of the first drive unit 1, the transmission 3, and the second drive unit 2.

[0026] When a gear is engaged in the transmission 3, a first number of shift elements 9 of the transmission 3 are closed and a second number of shift elements 9 of the transmission 3 are open. To perform a gear change in the transmission 3 from an actual gear to a target gear, a shift element 9 closed in the target gear must be opened and a shift element 9 open in the actual gear must be closed, wherein the invention relates to details for opening a positive-locking shift element 9 during such a gear change.

[0027] At least for the execution of a gear change and also for a journey outside the execution of the actual gear change, target torques for operating the first drive unit 1 and the second drive unit 2 are determined at least as a function of a driver-desired output torque and preferably further as a function of a target power distribution between the first drive unit 1 and the second drive unit 2 and / or as a function of an actual gear and / or as a function of a target gear and / or as a function of a target shift speed and / or as a function of an actual output speed.

[0028] In this case, it is preferably provided, at least for the execution of a gear change and preferably also for travel outside of the execution of the actual gear change, to determine the target torques for the first drive unit 1 and the second drive unit 2 in such a way that the respective target torque is composed of a static torque component and a dynamic torque component. The respective static torque component determines a basic energy distribution between the two drive units 1 and 2. The respective dynamic torque component serves for dynamic compensation.

[0029] Details of a gear change from an actual gear to a target gear are described with reference to Fig. 2, where Fig. 2 curves are shown that can develop when performing a gear change. Fig. 2 a plurality of temporal curve profiles 11 to 20 which can develop when a gear change is carried out, namely with the curve profile 11 an actual gear of a gearshift to be carried out, with the curve profile 12 a target gear of a gearshift to be carried out, with a curve profile 13 a driver-desired output torque, with a curve profile 14 a target torque of the first drive unit 1, with a curve profile 15 a target torque of the second drive unit 2, with a curve profile 16 an actual speed of the first drive unit 1, with a curve profile 17 an actual speed of the second drive unit 2, with a curve profile 18 an output speed, with a curve profile 19 the state of a shift element 9 to be opened and with the curve profile 20 the state of a shift element 9 of the transmission 3 to be closed. Fig. Figure 2 further illustrates phases P1 to P7 of the gear change, namely a P1 initialization phase, a P2 load transfer phase, a P3 decoupling phase, a P4 speed transfer phase, a P5 coupling phase, a P6 load return phase, and a P7 completion phase. Phases P2 to P6 are assigned to the actual gas exchange. Phases P1 and P7 lie outside the actual gas exchange. Phase P0 illustrates normal driving with a constant drive ratio without a gear change request. At times t1, t2, t3, t4, t5, t6, t7, and t8, a change occurs between the individual phases P0 to P7. The transition between the individual phases is based on transition conditions specified by the control system.

[0030] For a journey outside the execution of an actual gear change, i.e. for the phases P0, P1 and P7, the target torque for the first drive unit 1 is preferably determined according to the following equations (1) to (3): MVM−TARGET=MVMFG=MVMFG−stat+MVMFG−dyn MVMFG−stat=Mabw×prozhybiVMGx MVMFG−dyn=jredGx×(1−prozhyb)iVMGx×PI30×ddt(nab)

[0031] For driving outside the execution of an actual gear change, i.e. for the phases P0, P1 and P7, the target torque for the second drive unit 2 is preferably determined according to the following equations (4) to (6): MEM−TARGET=MEMFG=MEMFG−stat+MEMFG−dyn MEMFG−stat=Mabw×prozhybiEMGx MEMFG−dyn=JredGx×prozhybiEMGx×PI30×ddt(nab) where M EMFG the target torque M EM-SOLL for the second drive unit, M EMFG-stat is the static torque component of the target torque for the second drive unit, M EMFG-dyn is the dynamic torque component of the target torque for the second drive unit, M VMFG the target torque M VM-SOLL for the first drive unit, MVMFG-stat is the static torque component of the target torque for the first drive unit, M VMFG-dyn is the dynamic torque component of the target torque for the first drive unit, M abw the driver's desired output torque is process hyb the target power distribution between the first and second drive unit, i EMGx an effective gear ratio of the actual gear for the second drive unit, i VMGx is an effective gear ratio of the actual gear for the first drive unit, J redGx a reduced mass inertia of the entire drive in the current gear relative to a transmission output shaft, n ab the actual output speed is, PI is the constant π.

[0032] Determining the target torques M VM-SOLL and M EM-SOLLfor the two drive units 1, 2 according to equations (1) to (6) is in Fig. 2 is visualized by a block 22.

[0033] For the actual execution of a gear change, namely for phases P3, P4 and P5, the target torque for the first drive unit 1 is determined according to the following equations (7) to (9): MVM−TARGET=MVMGW=MVMGW-stat+MVMGW-dyn MVMGW−stat=Mabw×1iG*×i0*(i0*−1) MVMGW−dyn=(J1+J13)×iVMsoll×PI30×ddt(nab)

[0034] For the actual execution of a gear change, i.e. for phases P3, P4 and P5, the target torque for the second drive unit 2 is determined according to the following equations (10) to (12): MEM−TARGET=MEMGW=MEMGW−stat+MEMGW−dyn MEMGW−stat=Mabw×1iG*×i0*(1−i0*) MEMGW−dyn=(J3+J31)×[i0*×iVMsol1−(i0*−1)]×PI30×ddt(nab) where M EMGW the target torque M EM-SOLL for the second drive unit, M EMGW-stat is the static torque component of the target torque for the second drive unit, M EMGW-dyn is the dynamic torque component of the target torque for the second drive unit, M VMGW the target torque M VM-SOLL for the first drive unit, M VMGW-stat is the static torque component of the target torque for the first drive unit, M VMGW-dyn is the dynamic torque component of the target torque for the first drive unit, M abw the driver's desired output torque is J3 is a mass inertia of the second drive shaft, J 31 is a coupling mass inertia from a planetary gear set with respect to the first drive shaft, J1 is a mass inertia of the first drive shaft, J 13 is a coupling mass inertia from the planetary gear set with respect to the second drive shaft, i 0*a coupled ratio of the planetary gear set, i G* is an output ratio of the planetary gear set, i VMsoll a ratio for the first drive unit in the target gear, n ab the actual output speed is, PI is the constant π.

[0035] Determining the target torques M VM-SOLL and M EM-SOLL for the two drive units 1, 2 according to equations (7) to (12) is Fig. 2 is visualized by a block 23.

[0036] During phases P2 and P6, i.e. during phase P2 load transfer and phase P6 load return, the target torques M VM-SOLL and M EM-SOLL For the two drive units 1 and 2, both equations (1) to (6) and equations (7) to (12) are relevant.

[0037] During the load transfer phases P2 and P6, the first target torques for drive units 1 and 2 are determined according to equations (1) to (6), and the second target torques for drive units 1 and 2 are determined according to equations (7) to (12). The following then applies in the load transfer phases P2 and P6: MVM−TARGET=f(MVMFG,MVMGW) MEM−TARGET=f(MEMFG,MEMGW)

[0038] During the P2 load transfer phase, the first target torques of block 23 drive gear are transferred to the second target torques of block 24 power split, preferably in a time-controlled linear manner.

[0039] During phase P6 load feedback, the second target torques of block 24 power split are transferred to the first target torques of block 23 drive gear, preferably again in a time-controlled linear manner.

[0040] In the phases P4 speed transfer and P5 coupling, a speed controller 24 (see Fig. 2) can be activated in order to determine further dynamic torque components for the target torques of drive units 1 and 2 for phases P4 and P5 and, if necessary, also P6.

[0041] In the speed control, at least one actual speed curve of one of the drive units 1, 2, which develops as a result of the target torques of the drive units 1, 2, is compared with a corresponding target speed curve of the respective drive unit 1, 2. In the event of a deviation, the speed controller 24 intervenes to provide support in order to bring the actual speed of the respective drive unit to its target speed. Both the speed of the first drive unit 1, in particular the internal combustion engine, and the speed of the second drive unit 2, in particular the electric motor, can be controlled via the speed controller 24.

[0042] According to a first variant, the further dynamic torque components of the target torque for the first drive unit 1 and for the second drive unit 2 are determined via the speed controller 24 with guidance to the speed of the first drive unit 1 as follows: MEMReg=(J3+J31)×i0*×PID[nVMset−nVMact] MVMReg=(J1+J13)×PID[nVMset−nVMactual] where M EMReg the further dynamic torque component of the target torque for the second drive unit, M VMReg the further dynamic torque component of the target torque for the first drive unit is J3 is a mass inertia of the second drive shaft, J 31 is a coupling mass inertia from a planetary gear set with respect to the first drive shaft, J1 is a mass inertia of the first drive shaft, J 13is a coupling mass inertia from the planetary gear set with respect to the second drive shaft, i 0* a coupled ratio of the planetary gear set, n VMsoll is a target speed of the first drive unit for a PID control function, n VMist is an actual speed of the first drive unit for the PID control function, PID is a PID control function.

[0043] According to a second variant, the dynamic torque components of the target torques for the drive units 1 and 2 are determined via the speed controller 24 with guidance to the speed of the second drive unit 2 as follows: MEMReg=(J3+J31)×PID[nEMset−nEMact] MVMReg=(J1+J13)×1i0*×PID[nEMset−nEMact] where M EMReg the further dynamic torque component of the target torque for the second drive unit, M VMRegthe further dynamic torque component of the target torque for the first drive unit is J3 is a mass inertia of the second drive shaft, J 31 is a coupling mass inertia from a planetary gear set with respect to the first drive shaft, J1 is a mass inertia of the first drive shaft, J 13 is a coupling mass inertia from the planetary gear set with respect to the second drive shaft, i 0* a coupled ratio of the planetary gear set, n EMsoll is a target speed of the second drive unit for a PID control function, n EMist is an actual speed of the second drive unit for the PID control function, PID a PID control function.

[0044] The speed controller 24 outputs the additional dynamic torque components of the target torque of the two drive units 1 and 2. When the speed controller 24 is active, the following applies: MVMGW=MVMGW−stat+MVMGW−dyn+MVMReg MEMGW=MEMGW−stat+MEMGW−dyn+MEMReg

[0045] Fig. 2 shows the curves 11 to 20 for a special case of executing a gear change with a constant driver-desired output torque 13, wherein during phase P0 of normal travel with a fixed actual gear, the full drive torque is provided by the first drive unit 1, but no output torque is provided by the second drive unit 2. Before time t1, the switching element 20 to be engaged is opened and the switching element 19 to be opened is closed.

[0046] Before time t1, the motor vehicle is operated in phase P0 with the actual gear engaged without a gearshift request at a constant drive ratio, according to signal curve 12 there is therefore no gearshift request, according to signal curve 13 the driver's desired output torque is constant, according to signal curve 14 only the first drive unit 1 provides a torque at the output, according to signal curve 15 the second drive unit does not provide any output torque.

[0047] At time t1, a gearshift request is present. Starting at time t1, the actual gear deviates from the target gear according to curves 11 and 12, so that at time t1, the gearshift execution switches to phase P1, initialization. During phase P1, initialization, the transition from normal driving to the actual gearshift sequence, which begins with phase P2, load transfer, is coordinated. Gearshift-specific requirements such as the target gear, gearshift speed, selection of the involved gearshift elements, and the like are determined.

[0048] In addition, conditioning requests can be issued in phase P1 initialization, such as a torque lead for the first drive unit or the like.

[0049] At time t2, the system switches from phase P1 initialization to phase P2 load transfer.

[0050] During phase P2, the target torque for the first drive unit and the target torque for the second drive unit are determined both in the sense of block 22 via equations (1) to (6) and in the sense of block 23 via equations (7) to (12), whereby a transition takes place from the target torques specified by block 22 to the target torques specified by block 23. During phase P2 load transfer, the switching element to be opened or disengaged is relieved of load using the target torques of the drive units and is therefore made load-free or approximately load-free.

[0051] At time t3, the system switches to phase P3 decoupling, whereby during phase P3, according to signal curve 19, the switching element to be opened for the gear change is transferred from the closed state to the open state. In this case, transmission 3 switches from a state I coupled (see Fig. 2) into a state II decoupled (see Fig. 2). By disengaging the shift element to be opened, an additional rotational degree of freedom is provided in transmission 3 between drive units 1 and 2. This additional degree of freedom is a prerequisite for the subsequent speed transfer in phase P4 speed transfer.

[0052] In phase P4, speed transfer, the speeds are controlled to the new target speed determined from the new target gear using a transfer function, which is preferably an S-shaped transfer function. A target speed can be either a target speed of the first drive unit 1 or, alternatively, a target speed of the second drive unit 2. For stabilization, the speed controller 24 is preferably activated in phase P4.

[0053] After the speed transfer in phase P4, the system switches to phase P5 coupling at time t5, with the speed controller 24 remaining active in phase P5. In phase P5, after the speed transfer has been completed, the new ratio of the target gear is provided with the aid of the switching element to be closed in phase P5 according to signal curve 20. The additional degree of freedom gained between drive units 1 and 2 in phase P3 is canceled again in phase P5.

[0054] In phase P6, a load feedback takes place, whereby in phase P6 the target torques for the drive units are determined both in the sense of block 22 via equations (1) to (6) and in the sense of block 23 via equations (7) to (12), whereby the target torques of block 23 are then transferred to the target torques of block 22. A complete load feedback, as in Fig. 2 is not mandatory.

[0055] In phase P7, the gear change is completed and a coordinated transition back to normal driving operation in phase P0 occurs. In phase P7, special conditioning requests or feedback can be communicated to analyze the shift sequence and thus the gear change.

[0056] As already explained, the present invention relates to those details of a gear change which serve to release the load or approximately release the load of a positive shift element 9 of the transmission which is to be opened for the gear change to be carried out.

[0057] Details in this regard are given below with reference to Fig. 3, Fig. 4 in more detail, where Fig. 3, Fig. 4 for the phases P2, P3, P4, P5 and P6, in addition to the curves 14, 15 and 19, as a further curve 25 shows the activation of the switching element 9 to be opened with a defined pressure or a defined force.

[0058] As already explained, to execute a gear change for the phases described above, target torques M VM-SOLL and M EM-SOLL In order to set the positive shift element 9, which is to be opened for the gear change, to be load-free or approximately load-free during phase P2, the two drive units 1 and 2 are switched on during phase P2 depending on the calculated target torques n M VM-SOLL and M EM-SOLLcontrolled by providing a load transfer, wherein when a load is transferred to one of the drive units the target torque is reduced and the target torque is increased at another of the drive units in order to set the switching element 9 to be opened load-free or approximately load-free while maintaining the driver's desired output torque at the output 4 and subsequently to open it load-free or approximately load-free.

[0059] This shows Fig. 3, that in the embodiment shown during phase P2 according to curve 14 the target torque M VM-SOLL of the first drive unit 1 and according to curve 5 the target torque M EM-SOLL on the second drive unit 2 is increased.

[0060] Depending on the target torques M VM-SOLL and M EM-SOLL, which serve to control the two drive units 1 and 2, a time can be determined at which the positive switching element 9 to be opened is theoretically load-free or theoretically approximately load-free. This is Fig. 3 at time t3 the case that accordingly in Fig. 3 the time t3 corresponds to the time at which, depending on the target torques 14, 15 or M VM-SOLL , M EM-SOLL for the two drive units 1, 2, the positive switching element 9 to be opened is theoretically load-free or theoretically approximately load-free.

[0061] According to Fig. 3, the positive-locking switching element 9 to be opened is actuated in the opening direction with a defined actuation pressure or a defined actuation force before the time t3, i.e. before the theoretical load release or theoretical approximately load release, whereby this defined actuation pressure or this defined actuation force is relatively low or relatively small. This relatively low actuation pressure or this relative actuation force is in Fig. 3 visualized with p1 / F1.

[0062] During load transfer in phase P2, i.e., the phase in which the target torque is reduced on one of the drive units and increased on the other, and in which the positive-locking switching element 9 to be opened is already actuated with the defined actuation pressure or the defined actuation force p1 / F1, it is monitored whether and at which actual torques of the two drive units 1, 2 the positive-locking switching element 9 to be opened begins to move. Those actual torques of the drive units 1, 2 at which the positive-locking switching element 9 to be opened begins to move are determined as the actual torques at which the positive-locking switching element 9 to be opened is actually or approximately load-free.

[0063] In Fig. 3, the time at which the switching element 9 to be opened is theoretically load-free or theoretically approximately load-free, depending on the target torques 14 and 15, is marked with t3. Already during the defined first time period Δt1 before this time t3, the switching element 9 to be opened is actuated in the opening direction with the defined actuation pressure or the defined actuation force p1 / F1 during the load transfer of phase P2.

[0064] Then, when it is determined that the positive-locking switching element 9 to be opened begins to move within the first time period Δt1 or at the specific time t3, the corresponding actual torques of the first and second drive units 1, 2 are determined, the load transfer is terminated and the positive-locking switching element 9 to be opened is actuated with a higher actuation pressure or a higher actuation force to fully open.

[0065] Fig. 3 shows an embodiment in which the switching element 9 to be opened does not begin to move until the defined time t3. Therefore, according to Fig. 3 the switching element 9 to be opened is actuated in the opening direction beyond time t3 with continued load transfer with a defined actuation pressure or a defined actuation force, namely by a defined second time period Δt2 beyond time t3. This defined second time period Δt2 is maximally limited. Then, when it is determined that the positive-locking switching element 9 to be opened begins to move within the maximally limited second time period Δt2, as shown in Fig. 3 at time tx, the corresponding actual moments M VM-IST and M EM-ISTof the drive units 1, 2 is determined, the load transfer is terminated, and the positive-locking switching element 9 to be opened is activated with a higher actuation pressure or a higher actuation force p2 / F2 to fully open, thus transitioning to the decoupling phase P3. As a result of the extended load transfer up to time tx, the target torques 14 and 15 in the subsequent phases deviate from the target torques 14 and 15 that would occur if the load transfer had already been terminated at time t3.

[0066] Then, if the positive-locking switching element 9 to be opened does not begin to move even during the maximum limited, defined second time period Δt2, the load transfer is also terminated and the positive-locking switching element 9 to be opened is activated with increased actuation pressure or increased actuation force p2 / F2 to fully open in order to complete the gear change within a defined permissible maximum switching time.

[0067] According to Fig. 3, a load transfer takes place in phase P2 by setting the target torque 14 or M VM-SOLL reduced and the target torque 15 or M on the second drive unit EM-SOLLis increased. At time t3, the switching element to be opened is theoretically made load-free or approximately load-free. If it is determined that the switching element 9 to be opened does not begin to move despite being triggered to open during the time period Δt1 before time t3 is reached, the load transfer and the triggering of the switching element to be opened with the defined trigger pressure or the defined trigger force p1 / F1 is extended beyond time t3, specifically by the second time period Δt2, which is limited. If it is determined that the switching element 9 to be opened begins to move, the load transfer is terminated and the trigger pressure or the trigger force 25 p2 / F2 for the switching element 9 to be opened is increased in order to open it completely.

[0068] Those target moments M VM-SOLL and M EM-SOLL, on the basis of which the switching element 9 to be opened was theoretically load-free or theoretically approximately load-free at time t3, are in Fig. 3. Furthermore, the actual moments M VM-IST and M EM-IST visualized, at which the positive-locking switching element to be opened actually begins to move at time tx and thus becomes actually load-free or approximately load-free. Furthermore, deviations ΔM VM and ΔM EM shown, i.e. amounts by which the actual moments M VM-IST and M EM-IST of the corresponding target torques M VM-SOLL and M EM-SOLL differ.

[0069] Based on this deviation ΔM VM and ΔM EM between the target torques M VM-SOLL and M EM-SOLL of the drive units 1 and 2, which lead to a theoretical load release or theoretical approximately load release of the positive switching element 9 to be opened, and the actual moments MVM-IST and M EM-IST of the drive units 1 and 2, in which the positive switching element 9 to be opened is actually set load-free or approximately load-free, the target torques for the drive units can be adapted in order to obtain an adapted target torque M for a subsequent gear change. VM-SOLL-A and M EM-SOLL-A for the respective drive unit.

[0070] This shows Fig. 5 for the two target torques 14, 15 each a characteristic curve, which has as input the torques M VM-SOLL and M EM-SOLL be provided in order to provide an adapted target torque M as an output variable VM-SOLL-A and M EM-SOLL-A to provide, whereby Fig. 5 for a defined operating point the corresponding target torque M VM-SOLL and M EM-SOLL depending on the deviation ΔM VM and ΔM EM was adapted. The adaptation preferably takes place across all operating points.

[0071] The adaptation is preferably carried out in such a way that the deviations ΔM VM and ΔM EM not full and therefore unfiltered to correct the target torques M VM-SOLL and M EM-SOLL are not used, but are weighted with a factor k1 and k2, whereby the respective factor k1 and k2 is each less than 1.

[0072] Fig. 4 shows a modification of the Fig. 3. In Fig. 4 again shows the phases P2, P3, P4, P5 and P6 of a gear change.

[0073] Also in Fig. 4 is dependent on the target torques 14, 15 or M VM-SOLL , M EM-SOLL for the drive units 1, 2, a time t3 is determined at which the positive switching element 9 to be opened is theoretically made load-free or theoretically approximately load-free.

[0074] Also in Fig. 4, a defined time period before this time t3, referred to here as the third time period, the switching element 9 to be opened is activated with the defined control pressure or the defined control force p1 / F1 to open, whereby in Fig. 4 this defined third time period is marked with Δt3.

[0075] This involves monitoring whether the switching element 9 to be opened begins to move. If it is determined that the switching element to be opened begins to move within the time period Δt3 or at time t3, the corresponding actual torques of the drive units 1, 2 are determined, the load transfer is terminated, and the positive-locking switching element 9 to be opened is actuated with a higher actuation pressure or a higher actuation force to fully open.

[0076] In Fig. 4 is just like in Fig. 3 shows a case in which the switching element 9 does not yet begin to move until the time t3, i.e. until the time of the theoretical load release or theoretical approximately load release, despite the control of the positive switching element 9 with the defined control pressure or the defined control force p1 / F1.

[0077] Therefore, in Fig. 4 after the time t3 of the theoretical load release or theoretical approximately load release of the positive switching element 9 for a maximum limited, defined period of time Δt4 after the time t3 the target torques M VM-SOLL , M EM-SOLL the drive unit 1, 2 is increased and / or decreased in the same direction with a defined amplitude and defined frequency, e.g. sinusoidally, whereby the positive switching element 9 is further actuated in the opening direction with the defined actuation pressure or defined actuation force p1 / F1.

[0078] While in Fig. 3 following time t3 the load transfer is extended by one of the target moments M VM-SOLL or M EM-SOLL reduced and the other of the target moments M VM-SOLL or M EM-SOLL is increased in the opposite direction, Fig. 4 following time t3 the target torques M VM-SOLL , M EM-SOLL the drive unit 1, 2 is increased and / or decreased in the same direction with a defined amplitude and defined frequency.

[0079] In Fig. 4, it is again determined at time tx that the positive switching element to be opened begins to move in the defined time period Δt4, which is maximally limited on the control side, so that the simultaneous increase and / or reduction of the target torques on the first and second drive units 1, 2 is terminated at time tx.

[0080] Furthermore, starting at time tx, the positive switching element to be opened is actuated with a higher actuation pressure p2 or a higher actuation force F2 to fully open, in order to then transition from phase P2 of load transfer to phase P3 of decoupling at time tx.

[0081] As a result of the simultaneous increase and / or reduction of the target torques for the drive units 1 and 2 up to the time tx, the target torques 14 and 15 in the subsequent phases deviate from the target torques 14 and 15 that would develop if the decoupling phase P3 had been entered at the time t3.

[0082] While in the exemplary embodiment the Fig. 3 the deviations ΔM VM and ΔM EM such that they at least partially compensate each other, fall into Fig. 4 the deviations ΔM VM and ΔM EMin such a way that they reinforce each other. Fig. 4 the simultaneous increase and / or reduction of the target torques 14 and 15 for the drive units 1 and 2 with a defined amplitude and frequency is required in order to make the positive switching element 9 to be opened actually load-free or actually approximately load-free at the time tx.

[0083] Then, if despite the increase and / or reduction in the target torques 14 and 15 of the two drive units 1 and 2 in the same direction and despite the activation of the switching element 9 to be opened with the defined activation pressure or the defined activation force p1 / F1 in the direction of opening during the defined fourth time period Δt4 of the Fig. 4 the positive-locking switching element 9 to be opened does not begin to move, the simultaneous increase and / or reduction of the target torques on the first and second drive units is nevertheless terminated and the positive-locking switching torque 9 to be opened is activated with higher activation pressure and higher activation force to fully open in order to complete the gear change.

[0084] The variant of the Fig. 4 is preferably carried out when changing gears, if the variant of the Fig. 3 during a previous similar gear change has not led to the positive switching element 9 to be opened starting to move during the time period Δt1 or during the time period Δt2.

[0085] So with the variant of the Fig. 3 neither during the time period Δt1 nor during the time period Δt2 a movement of the positive switching element 9 to be opened is detected, it is concluded that the same could not be set load-free or approximately load-free, so that in a subsequent gear change the variant of the Fig. 4 is selected in order to check whether, using this variant, the positive-locking switching element 9 to be opened can be set load-free or approximately load-free.

[0086] The check as to whether the positive-locking switching element 9 to be opened can be set load-free or approximately load-free can be carried out by means of a position sensor assigned to the positive-locking switching element 9 to be opened.

[0087] With the aid of such a position sensor, it is possible to directly monitor whether a positive-locking switching element 9 to be opened begins to move.

[0088] If the corresponding positive-locking switching element 9 does not have such a position sensor, it can also be indirectly monitored whether the positive-locking switching element 9 to be opened begins to move, namely by evaluating a speed signal from the first drive unit 1 and / or a speed signal from the second drive unit 2 and / or a speed signal from the output 4. In this case, however, the defined control pressure or defined control force p1 / F1 is higher during the respective time period Δt1, Δt2, Δt3 or Δt4 than in the case in which monitoring whether a positive-locking switching element 9 to be opened begins to move is carried out using a position sensor. The increased control pressure or the increased control force p1 / F1 forces a slight tension and the speed reaction of the respective speed to be evaluated.

[0089] Since in this case the control pressure or the defined control force is selected to be higher in order to force a speed reaction on one or both drive units and / or on the output, the process is then noticeable to the driver on the output.

[0090] In order to then perform an adaptation, it is necessary to know the torque threshold at which the positive-locking switching element opens with a defined actuation pressure or a defined actuation force. This torque threshold is preferably determined in advance in testing as a function of temperature and / or aging and stored on the control side. In this case, the positive-locking switching element is set to approximately load-free and opened to approximately load-free.

[0091] The invention further relates to a control device for implementing the method on the control side. For a gear change to be executed from an actual gear to a target gear, the control device 21 controls a shift element that is closed in the actual gear and open in the target gear to open, and a shift element that is open in the actual gear and closed in the target gear to close. The control device 21 determines target torques for the first and second drive units 1, 2 for the gear change to be executed, at least as a function of a driver-desired output torque.When a positive-locking shift element 9 is opened for the gear change to be carried out, the control device 21 sets the positive-locking shift element 9 to be opened to be load-free or approximately load-free via a control of the first and second drive units 1, 2 that is dependent on the calculated target torques, in that the target torque is reduced at one of the drive units 1 or 2 while providing a load transfer and the target torque is increased at another of the drive units 2 or 1, in order to open the shift element 9 to be opened to be load-free or approximately load-free while providing the driver's desired output torque at the output 4.

[0092] The control device controls the positive-locking switching element 9 to be opened in the opening direction with a defined control pressure or a defined control force even before a theoretical load release, which depends on the target torque, or approximately theoretical load release during load transfer. The control device 21 monitors whether and at which actual torques of the first and second drive units 1, 2 the positive-locking switching element 9 to be opened begins to move.

[0093] The control device 21 determines the actual torques of the first and second drive units 1, 2 at which the positive-locking switching element 9 to be opened begins to move as the actual torques at which the positive-locking switching element 9 to be opened is actually placed load-free or approximately load-free. For further details, reference is made to the above explanations. Reference symbol 1 first drive unit 2 second drive unit 3 gearboxes 4 downforce 5 planetary stage 6 first drive shaft / transmission input shaft 7 second drive shaft 8 Gearbox output shaft 9 Switching element 10 Separating coupling 11 Curve / actual gear of a gearshift to be executed 12 Curve / target gear of a gearshift to be executed 13 Curve profile / driver desired output torque 14 Curve / target torque of the first drive unit 15 Curve / target torque of the second drive unit 16 Curve / actual speed of the first drive unit 17 Curve / actual speed of the second drive unit 18 Curve / Output speed 19 Curve / state of switching element to be opened 20 Curve / state of switching element to be closed 21 Control device 22 blocks 23 Blocks 24 speed controllers 25 Curve / control of switching element to be opened

Claims

[1] Method for operating a drive train of a motor vehicle, wherein the drive train has a plurality of drive units (1, 2), a transmission (3) and an output (4), and wherein the transmission (3) comprises a plurality of shift elements (9), wherein, for a gear change to be carried out from an actual gear to a target gear, a switching element (9) which is closed in the actual gear and open in the target gear is opened and a switching element (9) which is open in the actual gear and closed in the target gear is closed, wherein, for the gear change to be carried out, target torques for the first and second drive units (1, 2) are determined at least as a function of a driver's desired output torque, wherein, when a positive-locking shift element (9) is opened for the gear change to be carried out, the positive-locking shift element (9) to be opened is made load-free or approximately load-free via a control of the first and second drive units (1, 2) dependent on the calculated target torques, in that the target torque on one of the drive units is reduced and the target torque on another of the drive units is increased in order to open the shift element (9) to be opened load-free or approximately load-free while providing the driver's desired output torque at the output (4), wherein the positive-locking switching element (9) to be opened is actuated in the opening direction with a defined actuation pressure or a defined actuation force before a theoretical load release or approximately theoretical load release dependent on the desired torques, wherein it is monitored whether and at which actual moments of the first and second drive units (1, 2) the positive switching element (9) to be opened begins to move, wherein the actual moments of the first and second drive units (1, 2) at which the positive-locking switching element (9) to be opened begins to move are determined as actual moments at which the positive-locking switching element (9) to be opened is actually placed load-free or approximately load-free. [2] Method according to claim 1, characterized bythat depending on a deviation between the target torques of the first and second drive units (1, 2), which lead to a theoretical load-free release or theoretical approximate load-free release of the form-fitting switching element (9) to be opened, and the actual torques of the first and second drive units (1, 2), at which the form-fitting switching element (9) to be opened is actually made load-free or approximately load-free, the target torques are adapted. [3] Method according to claim 1 or 2, characterized by , that depending on the target torques of the first and second drive units (1, 2), a point in time is determined at which the positive switching element (9) to be opened is theoretically load-free or theoretically approximately load-free, the switching element (9) to be opened is already actuated in the opening direction with the defined actuating pressure or the defined actuating force a defined first time period before this time, when it is determined that the positive-locking switching element (9) to be opened begins to move within the first time period or at the specific time, the corresponding actual moments of the first and second drive units (1, 2) are determined and the positive-locking switching element (9) to be opened is actuated with a higher actuation pressure or a higher actuation force to fully open. [4] Method according to claim 3, characterized by , that then, if the switching element (9) to be opened does not begin to move until the defined time, the same is actuated in the opening direction with the defined actuating pressure or the defined actuating force for a maximum of a defined second period of time after this time, when it is determined that the positive-locking switching element (9) to be opened begins to move, the actual torques of the drive units (1, 2) are determined, the positive-locking switching element (9) to be opened is actuated with a higher actuation pressure or a higher actuation force to fully open. [5] Method according to claim 4, characterized by that if the positive-locking switching element (9) to be opened does not begin to move even during the defined second time period, the positive-locking switching element (9) to be opened is actuated with a higher actuating pressure or a higher actuating force to fully open. [6] Method according to one of claims 1 to 5, characterized by , that depending on the target torques of the first and second drive units (1, 2), a point in time is determined at which the positive switching element (9) to be opened is theoretically load-free or theoretically approximately load-free, a defined third time period before this time, the switching element (9) to be opened is actuated in the opening direction with the defined actuating pressure or the defined actuating force, then, when it is determined that the positive-locking switching element (9) to be opened begins to move within the third time period or at the specific time, the corresponding actual moments of the first and second drive units (1, 2) are determined, the positive-locking switching element (9) to be opened is actuated with a higher actuation pressure or a higher actuation force to fully open. [7] Method according to claim 6, characterized by , that then, if the switching element (9) to be opened does not begin to move until the defined time, for a maximum of a defined fourth time period after this time, the target torque on the first and second drive units (1, 2) is increased and / or reduced in the same direction with a defined amplitude and frequency and the switching element (9) to be opened is actuated in the opening direction with the defined actuation pressure or the defined actuation force, then, when it is determined that the positive-locking switching element (9) to be opened begins to move within the fourth time period, the actual torques of the drive units (1, 2) are determined and the positive-locking switching element (9) to be opened is actuated with a higher actuation pressure or a higher actuation force to fully open. [8] Method according to claim 7, characterized bythat when it is determined that the positive-locking switching element (9) to be opened does not begin to move during the fourth time period, the simultaneous increase and / or reduction of the target torques on the first and second drive units (1, 2) is terminated and the positive-locking switching element (9) to be opened is actuated with a higher actuation pressure or a higher actuation force to fully open. [9] Method according to one of claims 1 to 8, characterized by that the method steps according to one of claims 6 to 8 are carried out during a subsequent gear change if, during a current gear change, when carrying out the method steps according to one of claims 3 to 5, it is determined that the positive switching element (9) to be opened does not begin to move either during the defined first time period or during the defined second time period. [10] Method according to one of claims 1 to 9, characterized bythat with the aid of a position sensor assigned to the positive-locking switching element (9) to be opened, it is immediately monitored whether the positive-locking switching element (9) to be opened begins to move. [11] Method according to one of claims 1 to 9, characterized by that with the aid of a speed signal of the first drive unit (1) and / or the second drive unit (2) and / or the output (4) it is indirectly monitored whether the positive switching element (9) to be opened either begins to move or has already opened. [12] Control device for operating a drive train of a motor vehicle, wherein the drive train comprises a plurality of drive units (1, 2), a transmission (3) and an output (4), and wherein the transmission (3) comprises a plurality of shift elements (9), wherein the control device, for a gear change to be carried out from an actual gear to a target gear, controls a switching element (9) which is closed in the actual gear and open in the target gear to open and a switching element (9) which is open in the actual gear and closed in the target gear to close, wherein the control device determines target torques for the first and second drive units (1, 2) for the gear change to be carried out at least as a function of a driver's desired output torque, wherein the control device, when a positive-locking shift element (9) is opened for the gear change to be carried out, sets the positive-locking shift element (9) to be opened load-free or approximately load-free via a control of the first and second drive units (1, 2) dependent on the calculated target torques, in that the target torque is reduced and the target torque is increased at another of the drive units in order to open the shift element (9) to be opened load-free or approximately load-free while providing the driver's desired output torque at the output (4), wherein the control device controls the positive switching element (9) to be opened in the opening direction with a defined control pressure or a defined control force even before a theoretical load release or theoretical approximately load release dependent on the target torques, wherein the control device monitors whether and at which actual moments of the first and second drive units (1, 2) the positive switching element (9) to be opened begins to move, wherein the control device determines the actual moments of the first and second drive units (1, 2), at which the positive-locking switching element (9) to be opened begins to move, as actual moments at which the positive-locking switching element (9) to be opened is actually placed load-free or approximately load-free. [13] Control device according to claim 12, characterized by that it carries out the method according to one of claims 1 to 11 on the control side.

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