Method and control unit for operating a powertrain

Abstract

Method for operating a drivetrain of a motor vehicle, wherein the drive train comprises a drive unit (1), a group transmission (2) connected between the drive unit (1) and an output (3) and a disconnect clutch (5) connected between the drive unit (1) and the group transmission (2), wherein the group transmission (2) comprises several sub-transmissions, namely at least one main transmission (9) and furthermore a split group (10) connected upstream of the main transmission (9) and / or a range group (11) connected downstream of the main transmission (9) wherein, when the speed of the motor vehicle falls below a limit value, the disconnect clutch (5) is opened and, for gear selection, one of the sub-transmissions is moved to or towards neutral and the other sub-transmission or sub-transmissions is moved to or towards a friction-locked state, whereupon the disconnecting coupling (5) is at least partially closed and the drive unit (1) is brought to a defined rotational speed, where it is then checked whether, when a force-locking group transmission (2) is requested, a starting gear shift or a driver request shift for the group transmission (2) is requested, where, when a driver request is made, it is checked whether a target speed of the drive unit (1) is greater or less than the current input speed of the group transmission (2), wherein, when a starting gear shift is requested, and then, when the driver's desired shift is requested, the target speed of the drive unit (1) is less than the current input speed of the group transmission (2), the disconnect clutch (5) is opened and the sub-transmission in neutral is synchronized via a transmission brake (4) and, after synchronization, this sub-transmission is brought into a friction-locked state, where, when the driver requests a shift, the target speed of the drive unit (1) is greater than the current input speed of the group transmission (2), the sub-transmission in neutral is synchronized via the drive unit (1) and, after synchronization, this sub-transmission is brought into a friction-locked state.

Description

[0001] The invention relates to a method for operating a drive train of a motor vehicle, wherein the drive train comprises a drive unit, a group transmission connected between the drive unit and an output, and a separating clutch connected between the drive unit and the group transmission. The group transmission comprises a plurality of sub-transmissions, namely at least one main transmission and furthermore a splitter group connected upstream of the main transmission in terms of drive technology and / or a range-change group connected downstream of the main transmission in terms of drive technology. Furthermore, the invention relates to a control unit for operating such a drive train.

[0002] Motor vehicle drivetrains that utilize a range-change transmission as their transmission are known from the prior art. A range-change transmission comprises a main transmission, a splitter group upstream of the main transmission, and / or a range-change transmission downstream of the main transmission. The main transmission is also referred to as the main group. DE 10 2007 007 257 A1 discloses the use of an electric motor as a synchronization device during gearshifts in a range-change transmission.

[0003] When a motor vehicle with a range transmission is decelerated, i.e. slows down, the separating clutch is opened when the vehicle speed falls below a certain threshold, thus decoupling the drive unit from the transmission. If the range transmission is to be transferred from such a state into a non-positive state, either by executing a starting gear shift or by executing a driver-initiated gear shift in the range transmission, long synchronization times can occur under certain circumstances, and thus transferring the range transmission into a non-positive state can take a very long time, because when the separating clutch is opened and the range transmission is not in a non-positive state, one of the range transmission's input shafts coasts to a stop. Long synchronization times for the range transmission lead to a loss of comfort.

[0004] There is a need to synchronize a group transmission more quickly and thus to transfer a group transmission from a non-positive state to a positive state more quickly.

[0005] DE 10 2007 012 875 A1 discloses a method for operating a drive train, in which, when the motor vehicle rolls with the starting clutch open, a gear matching the current speed of the motor vehicle is engaged in the transmission in order to provide, upon subsequent engagement of the starting clutch, a gear matching the speed of the motor vehicle prevailing when the starting clutch is engaged.

[0006] DE 10 2007 010 295 A1 discloses a further method for operating a drive train of a motor vehicle, namely for carrying out so-called overrun downshifts in the overrun mode of the motor vehicle.

[0007] A method for controlling a transmission of a vehicle, in particular a truck, in a starting phase is disclosed by DE 10 2014 012 984 A1.

[0008] DE 10 2011 088 833 B4 discloses a method for synchronizing an automated transmission.

[0009] 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.

[0010] This object is achieved by a method for operating a drive train according to patent claim 1.

[0011] Then, when a speed of the motor vehicle becomes lower than a limit value, the separating clutch is opened and, for gear pre-selection, one of the sub-transmissions is moved to neutral or towards neutral and the or any other sub-transmission is moved to a force-locking state or towards a force-locking state.

[0012] The separating clutch is then at least partially closed and the drive unit is brought to a defined speed.

[0013] It is then checked whether, when a force-locking group transmission is requested, a starting gear shift or a driver-desired gear shift is requested for the group transmission.

[0014] Then, when a driver-initiated shift is requested, a check is carried out to determine whether a target speed of the drive unit is greater or less than the current input speed of the group transmission.

[0015] When a starting gearshift is requested, and when the target speed of the drive unit is lower than the current input speed of the group transmission when the driver's desired gearshift is requested, the separating clutch is opened and the sub-transmission in neutral is synchronized via a transmission brake. After synchronization, this sub-transmission is transferred to a non-positive state. When the target speed of the drive unit is higher than the current input speed of the group transmission when the driver's desired gearshift is requested, the sub-transmission in neutral is synchronized via the drive unit and, after synchronization, this sub-transmission is transferred to a non-positive state.

[0016] The method according to the invention proposes that when a speed of the motor vehicle is lower than a limit value, when the separating clutch is open and when one of the partial transmissions of the group transmission is transferred to neutral or in the direction of neutral, but the or each other partial transmission of the group transmission is transferred to a force-locking state or in the direction of a force-locking state, the separating clutch is to be closed at least partially and the drive unit is to be brought to a defined speed and then to check whether the group transmission is to be transferred to a force-locking state by executing a starting gear shift or by executing a driver-initiated gear shift.Depending on this, a defined synchronization of the partial transmission of the group transmission, which is in neutral, takes place, followed by a transition of the partial transmission and thus of the entire group transmission into a force-locking state. The invention makes it possible to shorten the time required to transition a group transmission from a non-force-locking state to a force-locking state. When shifting gears while the vehicle is stationary, tooth-on-tooth positions on the shift elements of the group transmission can be prevented.

[0017] Preferably, in order to check whether a starting gearshift is requested when a force-locking group transmission is requested, it is checked whether a current speed of the motor vehicle is less than a second limit value, wherein if the current speed of the motor vehicle is less than the second limit value, a starting gearshift is requested. Preferably, in order to check whether a driver-desired gearshift for the group transmission is requested when a force-locking group transmission is requested, in addition to the speed of the motor vehicle, a driver-side accelerator pedal actuation and / or driver-side brake pedal actuation is checked, wherein if the current speed of the motor vehicle is greater than the second limit value and if a brake pedal is no longer actuated by the driver and / or an accelerator pedal is actuated by the driver, a driver-desired gearshift is requested.This procedure is particularly suitable for checking whether the group transmission can be brought into a force-locking state by executing a starting gear shift or by executing a driver-initiated gear shift.

[0018] Preferably, when a driver-initiated gearshift is requested, a target gear for the group transmission is determined based on the current operating conditions of the motor vehicle, and the target speed of the drive unit is determined based on the target gear. After determining the target gear, a check is carried out to determine whether the gear preselection matches the target gear. If it is determined that the gear preselection does not match the target gear, the process is aborted. If it is determined that the gear preselection does match the target gear, the process is not aborted. This allows the process to be further improved.

[0019] The control device according to the invention is defined in claim 7.

[0020] 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 an exemplary diagram of a drive train of a motor vehicle, and Fig. 2 a signal flow diagram to illustrate the invention.

[0021] The present invention relates to a method for operating a drive train of a motor vehicle and a control device for carrying out the method.

[0022] Fig. 1 shows a diagram of a drive train of a motor vehicle with a drive unit 1, with a group transmission 2 and with an output 3.

[0023] The drive unit 1 can be coupled to an input shaft 6 of the group transmission 2 via a separating clutch 5, also referred to as a starting clutch. The output 3 is coupled to an output shaft 8 of the group transmission 2.

[0024] In the illustrated embodiment, the group transmission 2 comprises a main transmission 9, a splitter group 10 arranged upstream of the main transmission 9 in terms of drive technology, and a range group 11 arranged downstream of the main transmission 9 in terms of drive technology. In addition to the main transmission 9, only the range group 11 or only the splitter group 10 may be present. The main transmission 9 is also referred to as the main group.

[0025] The main gearbox 9 of the group gearbox 2 is designed as a direct-gear gearbox in countershaft design and has two countershafts 21, 22.

[0026] In the illustrated embodiment, the main transmission 9 is designed with three gear ratios G1, G2, and G3 for forward travel and one gear ratio R for reverse travel. Idler gears of the gear ratios G1, G2, and R are each rotatably mounted on a main shaft and can be shifted via associated shift elements 15, 16, 18, and 19, designed as claw clutches. The associated fixed gears are arranged in a rotationally fixed manner on the countershafts 21, 22. The two shift elements 15, 16 and the two shift elements 18, 19 each form a shift assembly 17 and 20, respectively. The main transmission 9 can be shifted unsynchronously.

[0027] In the illustrated embodiment, the splitter group 10 of the group transmission 2 is designed as a two-stage unit and also as a countershaft unit, with the two gear ratios K1 and K2 of the splitter group 10 forming two switchable input constants of the main transmission 9. The two gear ratios K1, K2 have a smaller gear ratio difference.

[0028] The idler gear of the first gear stage K1 is rotatably mounted on the input shaft 6. The idler gear of the second gear stage K2 is rotatably mounted on the main shaft. The fixed gears of both gear stages K1, K2 of the splitter group 10 are each arranged in a rotationally fixed manner with the input-side extended countershafts 21, 22 of the main transmission 9. Synchronized shift elements 12, 13, so-called synchronous shift elements, of the splitter group 10 are combined into a common shift assembly 14.

[0029] The range group 11 of the group transmission 2, which is arranged downstream of the main transmission 9, is also designed as a two-stage, but as a planetary gear 24. The sun gear 25 is connected in a rotationally fixed manner to the main shaft of the main transmission 9, which is extended on the output side. The planet carrier 27 is coupled in a rotationally fixed manner to the output shaft 8 of the group transmission 2. The ring gear 26 is connected to a shift assembly 23 with two synchronized shift clutches, by means of which the range group 11 can be alternately shifted into a low-speed stage L by connecting the ring gear 26 to a stationary housing part 7, and into a high-speed stage S by connecting the ring gear 26 to the planet carrier 27. The range group 11 can be shifted in a synchronized manner.

[0030] Fig. 1 also shows a transmission brake 4 that engages the countershaft 21. The transmission brake 4 can brake the countershaft 21.

[0031] It should be noted at this point that the Fig. The embodiment of the group transmission 2 shown in Figure 1 is preferred, but optional. The invention can also be used in conjunction with other group transmissions.

[0032] Thus, the group transmission 2 can comprise only the main group 9 and the range group 11 or only the main group 9 and the splitter group 10. It is also possible for claw shift elements to be used in the area of ​​the splitter group 10 and / or in the area of ​​the range group 11.

[0033] The invention now relates to a method for operating a drive train with a group transmission 2 starting from a state in which, when the speed of the motor vehicle is lower than a limit value, the separating clutch 5 is opened and, for gear preselection, a partial transmission of the group transmission 2 is transferred to neutral or towards neutral and the or each other partial transmission of the group transmission 2 is transferred to a force-locking state or towards a force-locking state, to quickly transfer the group transmission 2 into a force-locking state. The partial transmission of the group transmission 2 which is transferred to neutral for gear preselection is the group transmission 2 of the Fig. 1 preferably around the main transmission 9. The splitter group 10 and range group 11 are transferred to a force-locking state or towards a force-locking state for gear preselection; they are therefore engaged or are in a tooth-on-tooth position. Starting from such a state, it should be possible to transfer the group transmission 2 into a force-locking state in a short time, i.e. the partial transmission which is still in neutral. The method according to the invention is described below with reference to the signal flow diagram of the Fig. 2 described.

[0034] In block 28, a check is made to determine whether the speed of the motor vehicle is below a limit value. If this is the case, the process branches from block 28 to block 29, where in block 29 the separating clutch 5 is opened and, in order to preselect the gear of the group transmission 2, one sub-transmission of the group transmission 2 is moved into neutral or towards neutral, whereas the or each other sub-transmission of the group transmission 2 is moved into a non-positive state or towards a non-positive state. In block 30, a check is made to determine whether the respective sub-transmission to be moved into neutral is in neutral and whether the or each other sub-transmission has been moved towards a non-positive state. This can be checked using position sensors that interact with shift elements.

[0035] If it is determined in block 30 that the gear preselection is completed, the separating clutch 5 is subsequently at least partially closed in a block 31 and the drive unit 1 is brought to a defined speed in a block 32, which can, for example, correspond to the idle speed of the drive unit 1 or can be greater than the idle speed of the drive unit 1 by a defined offset.

[0036] Subsequently, a check is carried out in a block 33 as to whether, when a force-locking group transmission 2 is requested, a starting gear shift or a driver-desired shift is requested for the group transmission 2 in order to transfer the not yet force-locking group transmission 2 into a force-locking state.

[0037] In block 33, a check is made to determine whether the current speed of the motor vehicle is less than a second threshold. If the current speed of the motor vehicle is less than the second threshold, it is concluded that a starting gear shift is requested, and the system then branches to block 34.

[0038] If, however, it is determined in block 33 that the speed of the motor vehicle is greater than a second limit value, the system branches from block 33 to block 35, where block 35 checks for driver-side accelerator pedal actuation and / or driver-side brake pedal actuation. If, after checking block 33, the current speed of the motor vehicle is greater than a second limit value, and if, after checking in block 35, it is determined that a brake pedal is not being actuated or is no longer being actuated by the driver and / or an accelerator pedal is being actuated by the driver, a driver-initiated shift is requested and the system branches to block 36.

[0039] In block 36, a target gear for the group transmission 2 is determined for a driver-initiated shift depending on the current operating conditions of the motor vehicle and, depending on this target gear, the target speed of the drive unit 1 is determined.

[0040] A current road gradient and / or a current vehicle mass can be taken into account as the current operating condition of the motor vehicle, depending on which the target gear of the group transmission 2 is determined.

[0041] After determining the target gear for the driver's desired gearshift and the target speed of the drive unit 1, a block 37 checks whether the gear preselection of block 29 matches the target gear determined in block 36.

[0042] If it is determined that the gear preselection does not match the target gear, the system branches from block 37 to block 38 and aborts the process. However, if it is determined that the gear preselection does match the target gear of the requested driver shift, the system branches from block 37 to block 39 and continues the process.

[0043] In block 39, a check is carried out to determine whether, when a driver-selected gearshift is requested with a target gear that matches the transmission preselection, the target speed of the drive unit is greater or less than the current transmission input speed at the input shaft 6 of the group transmission 2.

[0044] If it is determined in block 39 that the target speed of drive unit 1 is lower than the current transmission input speed, the system branches from block 39 to block 34.

[0045] If, however, it is determined in block 39 that the target speed of drive unit 1 is greater than the current transmission input speed, the system branches from block 39 to block 40.

[0046] In block 34, in order to execute the respective gear shift, the separating clutch 5 is opened and the partial transmission of the group transmission 2, which is in neutral and is to be transferred into a force-locking state, is synchronized via the transmission brake 4, whereby after this synchronization, this partial transmission is transferred into a force-locking state.

[0047] To carry out a respective shift in block 40, the separating clutch 5 remains at least partially closed and the synchronization of the partial transmission in neutral takes place via the drive unit 1 by setting a defined target speed on the drive unit 1, wherein after synchronization via the drive unit 1, the now synchronized partial transmission can be transferred from neutral to the non-positive state.

[0048] With the method according to the invention, a group transmission 2 can be converted into a force-locking state within a short time, starting from a non-positive state in which a partial transmission of the group transmission 2 is in neutral and the or each other partial transmission is converted into a force-locking state, so that drive torque can then be transmitted via the group transmission 2 in the direction of the output 3.

[0049] The invention further relates to a control device for carrying out the method described above, which is set up to carry out the method described above automatically.

[0050] The control unit is preferably an electrical or electronic transmission control unit that has hardware and software components. The hardware components include data interfaces for exchanging data with the modules involved in executing the method according to the invention. Furthermore, the hardware components include a processor for data processing and a memory for data storage. The software components include program modules implemented in the control unit to carry out the method according to the invention.

[0051] Then, when a speed of the motor vehicle becomes lower than a limit value, the control unit controls the separating clutch 5 to open, furthermore the control unit controls the group transmission for transmission pre-selection in such a way that one of the sub-transmissions of the group transmission 2 is controlled to transfer to neutral and the or each other sub-transmission is controlled to transfer to a non-positive state.

[0052] The control unit then controls the separating clutch 5 to at least partially close it and the drive unit 1 to provide a defined speed, wherein the drive unit 1 is controlled either directly or indirectly via another control unit.

[0053] The control unit then checks whether, when a force-locking group transmission is requested, a starting shift or a driver-initiated shift is requested for group transmission 2 in order to transfer group transmission 2 into a force-locking state, i.e. to engage a gear in the partial transmission that was previously in neutral.

[0054] Then, when a driver-initiated shift is to be carried out, the control unit checks whether a target speed of the drive unit 1 for the driver-initiated shift is greater or less than the current input speed of the group transmission 2.

[0055] When a start-up shift is requested, and when the target speed of drive unit 1 is lower than the current input speed of group transmission 2 when a driver-input shift is requested, the control unit controls the disconnect clutch to open and the transmission brake 4 to synchronize the sub-transmission in neutral. After synchronizing this sub-transmission, the control unit controls the same via the transmission brake 4 to transfer it to a non-positive state. When the target speed of drive unit 1 is higher than the current input speed of group transmission 2 when a driver-input shift is requested, the sub-transmission, which is still in neutral, is synchronized via drive unit 1, and the control unit subsequently controls this synchronized sub-transmission to transfer it to a non-positive state. Reference symbol 1 drive unit 2 group transmissions 3 Downforce 4 Transmission brake 5 Separating clutch 6 Input shaft 7 Housing part 8 Output shaft 9 Main gearbox 10 split group 11 Area group 12 Synchronous switching element 13 Synchronous switching element 14 Switch package 15 Switching element 16 Switching element 17 Switch package 18 Switching element 19 Switching element 20 switching package 21 Countershaft 22 Countershaft 23 Switch package 24 planetary gears 25 Sun gear 26 ring gear 27 planet carriers 28 blocks 29 Block 30 blocks 31 Block 32 blocks 33 Block 34 Blocks 35 Block 36 blocks 37 Block 38 Block 39 Block 40 Block

Claims

[1] Method for operating a drive train of a motor vehicle, wherein the drive train comprises a drive unit (1), a group transmission (2) connected between the drive unit (1) and an output (3) and a separating clutch (5) connected between the drive unit (1) and the group transmission (2), wherein the group transmission (2) comprises a plurality of sub-transmissions, namely at least one main transmission (9) and furthermore a splitter group (10) connected upstream of the main transmission (9) in terms of drive technology and / or a range group (11) connected downstream of the main transmission (9), wherein, when a speed of the motor vehicle becomes lower than a limit value, the separating clutch (5) is opened and, for gear pre-selection, one of the partial transmissions is transferred into or towards neutral and the or each other partial transmission is transferred into or towards a force-locking state, wherein the separating clutch (5) is then at least partially closed and the drive unit (1) is brought to a defined speed, wherein it is subsequently checked whether, when a force-locking group transmission (2) is requested, a starting gear shift or a driver-desired gear shift for the group transmission (2) is requested, wherein, when a driver-initiated shift is requested, it is checked whether a target speed of the drive unit (1) is greater or less than the current input speed of the group transmission (2), When a starting gear shift is requested, and when the target speed of the drive unit (1) is lower than the current input speed of the group transmission (2) when the driver's desired gear shift is requested, the separating clutch (5) is opened and the partial transmission in neutral is synchronized via a transmission brake (4) and, after synchronization, this partial transmission is transferred into a force-locking state, wherein, when the target speed of the drive unit (1) is greater than the current input speed of the group transmission (2) when the driver's desired shift is requested, the partial transmission located in neutral is synchronized via the drive unit (1) and, after synchronization, this partial transmission is transferred into a force-locking state. [2] Method according to claim 1, characterized byin that, in order to check whether a starting gear shift is requested when a force-locking group transmission (2) is requested, it is checked whether a current speed of the motor vehicle is less than a second limit value, wherein if the current speed of the motor vehicle is less than the second limit value, a starting gear shift is requested. [3] Method according to claim 2, characterized byin that, in order to check whether a driver-desired shift for the group transmission (2) is requested when a force-locking group transmission (2) is requested, in addition to the speed of the motor vehicle, a driver-side accelerator pedal actuation and / or driver-side brake pedal actuation is checked, wherein if the current speed of the motor vehicle is greater than the second limit value and if a brake pedal is no longer actuated by the driver and / or an accelerator pedal is actuated by the driver, a driver-desired shift is requested. [4] Method according to one of claims 1 to 3, characterized by that when a driver-initiated gearshift is requested, a target gear for the group transmission (2) is determined depending on the current operating conditions of the motor vehicle and the target speed of the drive unit (1) is determined depending on the target gear. [5] Method according to claim 4, characterized bythat the target gear for the group transmission (2) is determined depending on a current road gradient and / or depending on a current vehicle mass. [6] Method according to claim 4 or 5, characterized by , that after determining the target gear, it is checked whether the gear preselection matches the target gear, If it is determined that the gear preselection does not match the target gear, the procedure is aborted, If it is determined that the gear preselection matches the target gear, the procedure is not aborted. [7] Control unit for operating a drive train of a motor vehicle, wherein the drive train comprises a drive unit (1), a group transmission (2) connected between the drive unit (1) and an output (3) and a separating clutch (5) connected between the drive unit (1) and the group transmission (2), wherein the group transmission (2) comprises a plurality of sub-transmissions, namely at least one main transmission (9) and furthermore a splitter group (10) connected upstream of the main transmission (9) in terms of drive technology and / or a range group (11) connected downstream of the main transmission (9), wherein, when a speed of the motor vehicle becomes lower than a limit value, the control unit controls the separating clutch (5) to open and to preselect the gear of one of the partial transmissions to transfer to or towards neutral and the or each other partial transmission to transfer to or towards a non-positive state, wherein the control unit subsequently controls the separating clutch (5) to at least partially close it and the drive unit (1) to provide a defined speed, wherein the control unit subsequently checks whether, when a force-locking group transmission (2) is requested, a starting gear shift or a driver-desired gear shift is requested for the group transmission (2), wherein the control unit checks, when a driver-input shift is requested, whether a target speed of the drive unit (1) is greater or less than the current input speed of the group transmission (2), wherein the control unit, when a starting gear shift is requested, and when the target speed of the drive unit (1) is lower than the current input speed of the group transmission (2) when a driver-input shift is requested, activates the separating clutch (5) to open and synchronises the partial transmission in neutral via a transmission brake (4) and, after synchronisation, activates this partial transmission to transfer it into a force-locking state, wherein the control unit, when the target speed of the drive unit (1) is greater than the current input speed of the group transmission (2) when a driver-input shift is requested, synchronizes the partial transmission located in neutral via the drive unit (1) and, after synchronization, controls this partial transmission to transfer it into a force-locking state. [8] Control device according to claim 7, characterized bythat it is arranged to carry out the method according to one of claims 1 to 6.

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