Method and control device for operating a drive train

Abstract

The invention relates to a method for operating a drive train of a motor vehicle, wherein the drive train has an internal combustion engine (1), an electric machine (4) and a group transmission (2) with a main transmission (9) and a range group (11), wherein the internal combustion engine (1) is coupled to an input shaft (6) of the group transmission (2) via a shiftable disconnect clutch (5), wherein the electric machine (4) is also coupled to the input shaft (6). Then, when the motor vehicle travels with the disconnect clutch (5) engaged, a downshift is to be carried out at least with the involvement of the range group (1) and the main transmission (9), and the electric machine (4) cannot be used to synchronise the shifting elements, the following is carried out: the motor vehicle is braked in such a way that a rotational speed of the internal combustion engine (1) is brought to a target rotational speed. Subsequently, a load reduction is carried out on a shifting element of the main transmission (9) to be disengaged to carry out the downshift, and same is disengaged. Subsequently, the input shaft (6) is synchronised to a first target rotational speed and the shifting element of the main transmission (9) to be engaged in order to carry out the downshift is engaged. At the same time or subsequently, the range group (11) is transferred into neutral, the input shaft (6) is synchronised to a second target rotational speed, and a shifting element of the range group (11) to be engaged to carry out the downshift is engaged.

Description

[0001] ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0002] Method and control unit for operating a drive train

[0003] The invention relates to a method for operating the drivetrain of a motor vehicle, wherein the drivetrain comprises an internal combustion engine as the first drive unit, an electric machine as the second drive unit, and an automated transmission group connected between the drive units and an output shaft, wherein the internal combustion engine is coupled to an input shaft of the transmission group via a switchable disconnect clutch, wherein the electric machine is also coupled to the input shaft of the transmission group, and wherein the transmission group comprises several sub-transmissions, namely at least one main transmission and a range group connected downstream of the main transmission. The invention further relates to a control unit for operating such a drivetrain.

[0004] DE 10 2007 043 694 A1 discloses a group transmission comprising a main transmission, a range group connected downstream of the main transmission, and a splitter group connected upstream of the main transmission. The main transmission and splitter group are designed as reduction gears with countershafts, one of which has a transmission brake engaged. An internal combustion engine is coupled to an input shaft of the group transmission via a disconnect clutch, and an output shaft is coupled to an output shaft of the group transmission. Shifting is possible within the group transmission, and according to DE 10 2007 043 694 A1, the transmission brake is used to synchronize the shifting elements.

[0005] DE 10 2013 211 225 A1 discloses a group transmission for a motor vehicle, which in turn comprises a main transmission, a range group connected downstream of the main transmission, and a splitter group connected upstream of the main transmission, wherein an internal combustion engine and an electric machine are coupled to the input shaft of the group transmission. The internal combustion engine is coupled to the input shaft of the group transmission via a disconnect clutch, while the electric machine is permanently coupled to the input shaft of the group transmission via a planetary gear stage. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0006] The group transmission for a hybrid drive arrangement disclosed in DE 10 2013 211 225 A1 does not include a transmission brake. In one version, the electric machine is used to synchronize the switching elements.

[0007] If the electric machine for synchronizing the switching elements is unavailable, for example due to a malfunction or failure of a high-voltage system, it is currently not possible to reliably execute shifts in the transmission. This can then lead to the vehicle breaking down.

[0008] Based on this, there is a need for a method for operating a motor vehicle drive train with an automated group transmission, in which a downshift can be reliably carried out even when the electric machine cannot be used for switching element synchronization, with the involvement of the range group and the main transmission.

[0009] The invention is based on the objective of creating a novel method for operating a drive train of a motor vehicle and a control unit for carrying out the method.

[0010] This problem is solved by a method for operating a drive train according to claim 1 and by a control unit according to claim 9.

[0011] Then, when the vehicle is driving with the disconnect clutch engaged, and a downshift is to be performed in the range transmission, at least involving the range group and the main transmission, and the electric machine cannot be used for shift element synchronization, the following steps are carried out to perform the downshift:

[0012] The vehicle is braked in such a way that the combustion engine speed is reduced to a target speed. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0013] Subsequently, a load reduction is carried out on a positive-locking switching element of the main gearbox designed to execute the downshift, and the same is then designed to bring the main gearbox into neutral.

[0014] Subsequently, the input shaft is synchronized to a first target speed, and then the positive-locking switching element of the main gearbox, which is to be inserted to execute the downshift, is inserted.

[0015] Simultaneously with the insertion of the positive-locking switching element of the main transmission or subsequently thereafter, the range group is moved into neutral, the input shaft is synchronized to a second target speed and a positive-locking switching element of the range group to be inserted for the execution of the downshift is inserted.

[0016] The invention enables reliable downshifting in the range transmission even when the range transmission has neither a transmission brake nor can the electric motor be used for shift element synchronization. The downshift occurs at a relatively low engine speed to ensure the smallest possible differential speed at the shift element to be closed for downshifting in the range group. Synchronization does not rely on the engine braking system of the combustion engine.

[0017] Preferably, when the vehicle decelerates, the internal combustion engine speed is reduced to a minimum speed that corresponds to the idle speed of the internal combustion engine multiplied by a predetermined offset and the gear ratio of the downshift to be performed, or to a speed dependent on this, which is greater than the minimum speed by an offset or a factor. Such an engine speed, to which the engine is reduced when the vehicle decelerates, is preferred in order to ensure that the downshift can be reliably executed within a relatively short shift time with the smallest possible differential speed at the switching element of the range group to be closed, and that sufficient torque reserve adapted to the current driving situation is still available. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0018] Preferably, the synchronization of the input shaft of the group transmission to the first target speed is achieved via friction losses of the group transmission and / or the internal combustion engine.

[0019] First, the disconnect clutch is held closed, and then, when the input shaft of the group transmission reaches the first target speed before the internal combustion engine reaches its idle speed, the positive-locking switching element of the main transmission, which is to be engaged to perform the downshift, is activated.

[0020] However, if the combustion engine reaches its idle speed before the input shaft of the group transmission reaches the first target speed, the disconnect clutch is opened, and then, when the input shaft of the group transmission subsequently reaches the first target speed, the positive-locking shift element of the main transmission to be engaged for downshifting is activated, and after the positive-locking shift element of the main transmission to be engaged for downshifting has been activated, the disconnect clutch is closed again.

[0021] Then, if the input shaft of the group transmission reaches the first target speed before the internal combustion engine reaches its idle speed, the disconnect clutch can be kept closed and the synchronization of the input shaft of the group transmission to the first target speed takes place via friction losses or drag losses of the group transmission and internal combustion engine.

[0022] If, however, the combustion engine reaches its idle speed before the input shaft of the transmission has been synchronized, the disconnect clutch is opened to prevent intervention by the combustion engine's idle speed governor. After the disconnect clutch opens, the transmission's input shaft is synchronized via the transmission's friction losses and no longer via the combustion engine's friction losses. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0023] Preferably, the internal combustion engine is used to synchronize the input shaft of the group transmission to the second target speed, such that the input shaft of the group transmission is accelerated to the second target speed via the internal combustion engine.

[0024] Preferably, when a splitter group upstream of the main transmission is also involved in the execution of the downshift, a positive-locking switching element designed for executing the downshift is installed in the splitter group after the range group has been shifted into neutral and before the input shaft of the range transmission has been synchronized to the second target speed. This allows the splitter group to be advantageously integrated into the shifting mechanism during the downshift.

[0025] Preferably, downshifting is performed when, after a downshift request is received, it is determined, based on current and / or future driving resistance and / or road gradient, that downshifting can be performed without assistance from the electric motor. This further development of the invention is based on the understanding that downshifting should only be performed if, after a downshift request is received, it is determined, based on the current and / or future driving situation, that downshifting can actually be performed without synchronization of the switching element by the electric motor. If, upon a downshift request, it is determined that this is not possible, then the execution of the downshift is prevented.

[0026] Preferred embodiments are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. The drawing shows:

[0027] Fig. 1 shows an exemplary scheme of a motor vehicle powertrain, namely a hybrid drive arrangement with a group transmission;

[0028] Fig. 2 is a signal flow diagram to illustrate the invention. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0029] The invention relates to a method for operating a drive train of a motor vehicle with a hybrid drive and with an automated group transmission, as well as a control device for carrying out the method.

[0030] Fig. 1 shows a schematic of a motor vehicle drivetrain comprising a first drive unit designed as an internal combustion engine 1, an automated transmission 2, an output shaft 3, and a second drive unit designed as an electric machine 4. The internal combustion engine 1 is coupled to an input shaft 6 of the transmission 2 via a disconnect clutch 5, also referred to as a starting clutch. The disconnect clutch 5 is a friction-based switching element. When the disconnect clutch 5 is open, the internal combustion engine 1 is disengaged from the input shaft 6 of the transmission 2. When the disconnect clutch 5 is closed, either fully or partially closed, the internal combustion engine 1 is coupled to the input shaft 6 of the transmission 2.

[0031] In the illustrated embodiment, the electric machine 4 is permanently coupled to the input shaft 6 of the transmission 2, specifically via a planetary gear 30 as shown in Fig. 1. In addition to the planetary gear 30, a disconnect clutch (not shown) can also be connected between the electric machine 4 and the input shaft 6 of the transmission 2. The output 3 is coupled to an output shaft 8 of the transmission 2.

[0032] In the illustrated embodiment, the group transmission 2 comprises a main transmission 9, a splitter group 10 upstream of the main transmission 9, and a range group 11 downstream of the main transmission 9. The main transmission 9 is also referred to as the main group. The main transmission 9 of the group transmission 2 is designed as a direct-drive transmission with a reduction gear and has two countershafts 21 and 22. In the illustrated embodiment, the main transmission 9 has three gear ratios G1, G2, and G3 for forward travel and one gear ratio R for reverse travel. The loose gears of the gear ratios G1, G2, and R are each rotatably mounted on a main shaft and can be switched via associated switching elements 15, 16, 18, and 19, which are designed as positive-locking claw switching elements. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0033] In Fig. 1, switching element 15 is designated as switching element C, switching element 16 as switching element D, switching element 18 as switching element E, and switching element 19 as switching element F. The associated fixed gears are arranged non-rotating on the countershafts 21 and 22. The two switching elements 15 and 16 (or C and D) and the two switching elements 18 and 19 (or E and F) each form a switching assembly 17 or 20, respectively.

[0034] The split group 10 of the transmission 2, which is upstream of the main transmission 9, is designed in two stages in the illustrated embodiment and is also of reduction gear construction, with the two gear ratio stages K1 and K2 of the split group 10 forming two switchable input constants of the main transmission 9. The two gear ratio stages K1 and K2 have a smaller gear ratio difference. The split group 10 of the transmission 2 is optional and can also be omitted.

[0035] The loose gear of the first transmission stage K1 is rotatably mounted on the input shaft 6. The loose gear of the second transmission stage K2 is rotatably mounted on the main shaft. The fixed gears of both transmission stages K1 and K2 of the splitter assembly 10 are each rotationally fixed to the input-side extended countershafts 21 and 22 of the main gearbox 9. Synchronized switching elements 12 and 13, so-called synchronous switching elements, of the splitter assembly 10 are combined into a common switching unit 14. In Fig. 1, switching element 12 is designated as switching element A and switching element 13 as switching element B. The switching elements 12 and 13 are designed as positive-locking claw switching elements.

[0036] The range group 1 1 of the range gearbox 2, which is downstream of the main gearbox 9, is also designed as a two-stage system, but as a planetary gearbox 24. The sun gear 25 is non-rotatably connected to the main shaft of the main gearbox 9, which is extended on the output side. The planet carrier 27 is non-rotatably coupled to the output shaft 8 of the range gearbox 2. The ring gear 26 is connected to a shift unit 23 with two synchronized shift elements 28, 29, by which the range group 11 can be alternately shifted into a low-speed stage by connecting the ring gear 26 to a stationary housing part 7 and into a high-speed stage by connecting the ring gear 26 to the planet carrier 27. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0037] In Fig. 1, switching element 28 is designated as switching element G and switching element 29 as switching element H. Switching elements 28 and 29 are designed as positive-locking claw switching elements.

[0038] In Fig. 1, an optional oil pump 31 engages the countershaft 22 and can be driven from the countershaft 22.

[0039] It should be noted here that the embodiment of the group transmission 2 shown in Fig. 1 is preferred, but optional. The invention can also be used in conjunction with other group transmissions.

[0040] The present invention relates to a method by which it is possible to reliably execute a shift, namely a downshift, at least with the involvement of the range group 11 and the main transmission 9, in a range transmission 2, which is part of a hybrid powertrain configuration of a motor vehicle, and in which, due to the absence of a transmission brake, the electric machine 4 is used for synchronizing shifting elements, even when, for example, the electric machine 4 cannot be used for shifting element synchronization due to a fault or failure of a high-voltage system. The invention is described in detail below with reference to the range transmission 2 shown in Fig. 1.

[0041] In its initial state, the motor vehicle travels with a gear engaged in the transmission 2 and the disconnect clutch 5 closed. The speed of the internal combustion engine 1 corresponds to the speed of the input shaft 6 of the transmission 2.

[0042] If a downshift request is detected, it is preferably first checked whether, based on a current and / or future driving situation, in particular driving resistance and / or road gradient, the downshift can be carried out by the electric machine 4 without switching element synchronization, ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0043] To determine driving resistance and / or road gradient, sensors installed in the drivetrain, such as tilt sensors, as well as models for calculating or estimating the vehicle mass, can be used. Furthermore, GPS data about the road ahead can be provided by a GPS system. Based on these input parameters, driving resistance and / or road gradient can be determined in order to estimate, depending on these parameters, whether a downshift can be performed when a downshift is requested, specifically when the electric motor 4 is not available for synchronizing the shift element.

[0044] A downshift request can be detected, in particular, depending on the driver's accelerator pedal input. For example, if the driver reduces the accelerator pedal position, it can be inferred that a lower speed is desired and that the driver wishes to downshift. A downshift request can also be inferred from the driver's use of the brake pedal.

[0045] If it has been determined that the downshift can be performed even without the assistance of the electric machine 4 for synchronizing the switching element, the drivetrain is first preconditioned for the downshift by braking the vehicle in such a way that the speed of the internal combustion engine 1 is reduced to a target speed.

[0046] When the vehicle decelerates, the speed of the internal combustion engine 1 is reduced to a minimum speed, which corresponds to the idle speed of the internal combustion engine 1 increased by a predetermined offset and multiplied by the gear ratio of the downshift to be performed, or to a speed dependent on this, which is greater than the minimum speed by an offset or a factor. This ensures the smallest possible differential speed at a positive-locking shift element of the main transmission 9, which is to be engaged for the downshift to be performed. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0047] Following the preconditioning of the drivetrain, the positive-locking switching element of the main transmission 9, designed to perform the downshift, is first de-loaded by reducing the load on it. This load reduction is achieved by reducing the torque supplied by the internal combustion engine, preferably at a constant engine speed of the internal combustion engine 1. After the positive-locking switching element of the main transmission 9, designed for the downshift, has been de-loaded, it is engaged, thereby moving the main transmission 9 into neutral.

[0048] The input shaft 6 of the group transmission 2 is then synchronized to a first target speed. This is done without the involvement of the electric machine 4 and without the engine braking device of the internal combustion engine 1, i.e., without the decompression brake or retarder brake of the internal combustion engine 1, and without the transmission brake. Instead, this synchronization of the input shaft 6 of the group transmission 2 to the first target speed is achieved via friction losses and drag losses of the group transmission 2 and / or the internal combustion engine 1.

[0049] To synchronize the input shaft 6 of the range gearbox 2 to the first target speed, the disconnect clutch 5 is initially held closed. Then, when the input shaft 6 of the range gearbox 2 reaches the first target speed before the internal combustion engine 1 reaches its idle speed, the disconnect clutch 5 can be held permanently closed, and with the disconnect clutch closed, the positive-locking shift element of the main gearbox 9 can be actuated to engage for downshifting.

[0050] However, if the internal combustion engine 1 reaches its idle speed before the input shaft 6 of the transmission 2 reaches the first target speed, the disconnect clutch 5 is opened to synchronize the transmission input shaft 6. This occurs when the speed of the internal combustion engine 1 has reached a limit speed, which is preferably higher than the idle speed of the internal combustion engine 1 by an offset. The synchronization of the input shaft 6 of the transmission 2 to the first target speed then takes place exclusively via friction losses of the transmission 2. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0051] When the input shaft 6 of the group gearbox 2 reaches the first target speed, the positive-locking shift element of the main gearbox 9, which is required to perform the downshift, is activated. The disconnect clutch 5 can then be closed again.

[0052] The first target speed, to which the input shaft 6 of the group transmission 2 is synchronized, is dimensioned such that the differential speed at the positive-locking shift element of the main transmission 9, which is to be engaged for the downshift, is less than 300 rpm, and in particular lies in a range between 200 and 300 rpm. At such a differential speed at the positive-locking shift element of the main transmission 9, which is to be closed for the downshift, it can be reliably engaged by ratcheting, in such a way that the ratcheting action is kept as short as possible, i.e., that the positive-locking shift element of the main transmission 9 is engaged in the shortest possible time.

[0053] Simultaneously with the engagement of the positive-locking switching element of the main transmission 9 for the execution of the downshift, or immediately thereafter, the range group 11 is shifted into neutral by opening the positive-locking switching element of range group 11 for the downshift to be performed. After the range group 11 has been shifted into neutral, the input shaft 6 of the range transmission 2 is synchronized to a second target speed, namely for synchronizing the positive-locking switching element of range group 11 for the downshift, with this synchronization being carried out by means of the internal combustion engine 1. Thus, the input shaft 6 of the range transmission 2 is accelerated to the second target speed by the internal combustion engine 1.After the input shaft 6 of the transmission group 2 has accelerated to the second target speed and the positive-locking switching element of range group 11, which is to be closed for the downshift to be performed, has therefore been synchronized, the positive-locking switching element of range group 11 to be engaged for the downshift is subsequently engaged, so that range group 11 is then frictionally locked again and the downshift is finally completed. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30.

[0054] Should the split group also be involved in the execution of the downshift, i.e., should the split group 10 have to be switched, then after the range group 11 has been moved to neutral and before the input shaft 6 of the group transmission 2 has been synchronized to the second target speed, the split group 10 is switched by removing a positive-locking switching element of the split group 10 to be designed for the execution of the downshift and inserting a positive-locking switching element of the split group 10 to be used for the execution of the downshift.

[0055] The downshifting described above therefore takes place without switching element synchronization by the electric machine 4, without switching element synchronization by an engine braking device of the internal combustion engine 1, i.e. without decompression brake or retarder brake, and without switching element synchronization by a transmission brake.

[0056] Further details of the invention are described below with reference to Fig. 2, namely for a downshift, with which a downshift from gear 7, in which the shifting elements A, E and G are engaged, to gear 6, in which the shifting elements B, C and H are engaged, is to take place in the group transmission 2 of Fig. 1.

[0057] Block 32 corresponds to an initial state of the motor vehicle in which it is driving with the disconnect clutch 5 closed and gear 7 engaged, i.e. with the shift elements A, E and G in the group transmission 2 closed, and in which a downshift request exists, for which it is determined that it can be carried out without shift element synchronization by the electric machine 4.

[0058] Starting from this point, in block 33 the drivetrain is first conditioned by braking the vehicle using the internal combustion engine 1 to reduce the engine speed to the target speed. Furthermore, in block 33, the positive-locking shift element of the main transmission 9, designed for the downshift operation (shift element E in the case of downshifting from gear 7 to gear 6), is de-energized and disengaged, so that in block 33 the main transmission 9 is moved into neutral. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0059] Subsequently, in blocks 34, 35, and 36, the input shaft 6 of the group transmission 2 is synchronized to the first target speed. In block 34, this occurs with the disconnect clutch 5 initially closed, by utilizing friction and drag losses in the group transmission 2 and the internal combustion engine 1. Then, when the first target speed of the internal combustion engine 1 is lower than its idle speed, the disconnect clutch 5 is opened in block 35, and further synchronization of the input shaft 6 of the group transmission 2 takes place exclusively by utilizing friction and drag losses in the group transmission 2.Subsequently, in block 36, once the speed of the input shaft 6 of the group transmission 2 has been synchronized to the first target speed, the positive-locking shift element to be engaged in the main transmission 9 for the execution of the downshift is activated. In the case of downshifting from gear 7 to gear 6, this engagement of shift element C occurs. In block 36, ratchets can be specifically used to engage shift element C of the main transmission 9.

[0060] Block 37 of Fig. 2 illustrates that the switching of the main transmission 9 is completed, i.e., that the positive-locking switching element to be inserted in the main transmission 9 for the execution of the downshift to be carried out, in the case of the execution of the downshift from gear 7 to gear 6, the switching element C of the main transmission 9, is inserted.

[0061] In block 38, overlapping with the engagement of the main transmission 9, range group 11 is moved to neutral by deploying the positive-locking shift element in range group 11 for downshifting; in the case of downshifting from gear 7 to gear 6, this is shift element G. Thus, in block 38, range group 11 is moved to neutral. When downshifting from gear 6 to gear 7, split group 10 is also involved. Therefore, in block 39, split group 10 is switched by first deploying the positive-locking shift element A of split group 10 for downshifting from gear 7 to gear 6, and subsequently engaging the positive-locking shift element B of split group 10. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0062] Following the switching of the split group in block 39, the input shaft 6 of the group transmission 2 is synchronized to the second target speed in block 40. This synchronizes the positive-locking switching element of range group 11 required for downshifting; in the case of downshifting from gear 7 to gear 6, this is the positive-locking switching element H of range group 11. After this synchronization, the positive-locking switching element required for downshifting is engaged in block 41; in the case of downshifting from gear 7 to gear 6, this is the positive-locking switching element H of range group 11, thus closing the engagement. Subsequently, in block 42, the vehicle is traveling in gear 7, and the downshift is therefore complete.

[0063] Block 39 is only executed if the splitter group 10 needs to be switched during the downshift. This is the case with the downshift from gear 7 to gear 6 described above. However, if a downshift from gear 7, in which shift elements A, E, and G are closed, to gear 5, in which shift elements A, C, and H are closed, is to be performed in the transmission group 2 of Fig. 1, the splitter group 10 is not switched, and therefore block 39 is omitted. The same applies to the downshift from gear 7, in which shift elements A, E, and G are closed, to gear 3, in which shift elements A, D, and H are closed. Block 39 is also omitted for the downshift from gear 7 to gear 3, since the splitter group 10 is not involved and does not need to be switched.

[0064] Furthermore, block 35 is important when the first target speed for synchronizing the input shaft 6 of the group gearbox 2 is lower than the idle speed of the internal combustion engine 1. If, on the other hand, the first target speed is higher than the idle speed of the internal combustion engine 1, the disconnect clutch 5 does not need to be opened and block 35 is omitted.

[0065] The invention further relates to a control unit configured to automatically execute the above-described method. The control unit has hardware and software means for this purpose. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0066] Hardware components include data interfaces for exchanging data with the assemblies involved in carrying out the method according to the invention, for example, for controlling the combustion engine 1 and the switching elements involved in executing the upshift. Hardware components also include a processor for data processing and a memory for data storage. Software components include program modules implemented in the control unit for carrying out the method.

[0067] ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0068] Reference mark

[0069] 1 Internal combustion engine

[0070] 2-group gearbox

[0071] 3 Drive

[0072] 4 electric machine

[0073] 5 Disconnect coupling

[0074] 6 Input wave

[0075] 7 Housing part

[0076] 8 Output wave

[0077] 9 Main gearboxes

[0078] 10 Split group

[0079] 11 Area Group

[0080] 12 Synchronous switching element

[0081] 13 Synchronous switching element

[0082] 14 shift package

[0083] 15 switching element

[0084] 16 switching element

[0085] 17 shift package

[0086] 18 switching element

[0087] 19 Switching element

[0088] 20 shift package

[0089] 21 Countershaft

[0090] 22 Countershaft

[0091] 23 Shift package

[0092] 24 planetary gears

[0093] 25 sun wheel

[0094] 26 Ring gear

[0095] 27 planetary carriers

[0096] 28 switching element

[0097] 29 Switching element

[0098] 30 planetary gears

[0099] 31 Oil pump

[0100] 32 Block ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30

[0101] Block 33

[0102] Block 34

[0103] 35 Block

[0104] 36 Block

[0105] Block 37

[0106] 38 Block

[0107] Block 39

[0108] 40 blocks

[0109] Block 41

[0110] 42 Block

Claims

ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30 Patent claims 1. A method for operating a drivetrain of a motor vehicle, wherein the drivetrain comprises an internal combustion engine (1) as the first drive unit, an electric machine (4) as the second drive unit, and an automated transmission (2) connected between the drive units and an output (3), wherein the internal combustion engine (1) is coupled to an input shaft (6) of the transmission (2) via a switchable disconnect clutch (5), wherein the electric machine (4) is also coupled to the input shaft (6) of the transmission (2), wherein the transmission (2) comprises several sub-transmissions, namely at least one main transmission (9) and a range group (11) connected downstream of the main transmission (9), characterized in that when the motor vehicle is driving with the disconnect clutch (5) engaged,In the group transmission (2), a downshift is to be carried out at least with the involvement of the range group (11) and the main transmission (9), and the electric machine (4) cannot be used for shift element synchronization. The following steps are carried out to execute the downshift: the vehicle is braked in such a way that the speed of the internal combustion engine (1) is reduced to a target speed; subsequently, a load reduction is carried out on a positive-locking shift element of the main transmission (9) designed to execute the downshift, and the same is subsequently engaged to bring the main transmission (9) into neutral; subsequently, the input shaft (6) is synchronized to a first target speed, and subsequently the positive-locking shift element of the main transmission (9) to be engaged to execute the downshift is engaged; overlapping or subsequently, the range group (11) is brought into neutral.the input shaft (6) is synchronized to a second target speed and a positive-locking switching element of the range group (11) to be inserted for the execution of the reverse switching is inserted. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30 2. Method according to claim 1, characterized in that when the motor vehicle is decelerated, the speed of the internal combustion engine (1) is reduced as a target speed to a minimum speed which corresponds to the idle speed of the internal combustion engine increased by a predetermined offset and multiplied by the gear step of the downshift to be performed, or to a speed dependent thereon which is greater than the minimum speed by an offset or a factor.

3. Method according to claim 1 or 2, characterized in that by synchronizing the input shaft (6) of the group transmission (2) to the first target speed, the positive-locking switching element of the main transmission (9) to be inserted for carrying out the downshift is synchronized.

4. Method according to claim 1, 2 or 3, characterized in that the synchronization of the input shaft (6) of the range transmission (2) to the first target speed is effected via friction losses of the range transmission (2) and / or the internal combustion engine (1), such that the disconnect clutch (5) is initially held closed, and then, when the input shaft (6) of the range transmission (2) reaches the first target speed before the internal combustion engine (1) reaches its idle speed, the positive-locking shift element of the main transmission (9) to be engaged for downshifting is actuated, and that, conversely, when the internal combustion engine (1) reaches its idle speed before the input shaft (6) of the range transmission (2) reaches the first target speed, the disconnect clutch (5) is opened before the internal combustion engine (1) reaches its idle speed, and then, when the input shaft (6) of the range transmission (2) subsequently reaches the first target speed,The positive-locking switching element of the main transmission (9), which is to be engaged to execute the downshift, is activated, and after the positive-locking switching element of the main transmission (9), which is to be engaged to execute the downshift, the disconnecting clutch (5) is closed again. ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30 5. Method according to one of claims 1 to 4, characterized in that by synchronizing the input shaft (6) of the group transmission (2) to the second target speed, the positive-locking switching element of the range group (1 1 ) to be inserted for carrying out the downshift is synchronized.

6. Method according to one of claims 1 to 5, characterized in that the internal combustion engine (1 ) is used to synchronize the input shaft (6) of the group transmission (2) to the second target speed, such that the input shaft (5) of the group transmission (2) is accelerated to the second target speed via the internal combustion engine (1 ).

7. Method according to one of claims 1 to 6, characterized in that, when a split group (10) upstream of the main transmission (9) is also involved in the execution of the downshift, a positive-locking switching element to be designed for the execution of the downshift is designed and a positive-locking switching element to be inserted for the execution of the downshift is designed in the split group (10) after the range group (11) has been moved to neutral and before the input shaft (6) of the range transmission (2) has been synchronized to the second target speed.

8. Method according to one of claims 1 to 7, characterized in that the downshifting is then carried out when, after a downshifting request has been made based on a current and / or future driving situation, in particular a driving resistance and / or a road gradient, it is recognized that the downshifting can be carried out without switching element synchronization by the electric machine (4).

9. Control unit for operating a drive train of a motor vehicle, wherein the drive train comprises as a first drive unit an internal combustion engine (1), as a second drive unit an electric machine (4), and an automated group transmission (2) connected between the drive units and an output (3), wherein the internal combustion engine (1) is coupled to an input shaft (6) of the group transmission (2) via a switchable disconnect clutch (5), ZF Friedrichshafen AG File 305281 Friedrichshafen 2024-10-30 wherein the electric machine (4) is also coupled to the input shaft (6), wherein the group transmission (2) has several sub-transmissions, namely at least one main transmission (9) and a range group (11) connected downstream of the main transmission (9) in terms of drive technology, characterized in that the control unit is set up for the automatic, control-side execution of the method according to one of claims 1 to 8.

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