Method for controlling a hybrid powertrain of a hybrid vehicle

Abstract

A method for controlling a hybrid drivetrain (1) of a hybrid vehicle, wherein the hybrid drivetrain (1) has a dual-clutch transmission (2) with two sub-transmissions (3, 4), the transmission input shafts (5, 6) of the two sub-transmissions being respectively driveably coupled to a first drive unit (9) by means of friction clutches (7, 8), wherein one of the two transmission input shafts (5, 6) is coupled or can be coupled to a second drive unit (10) in a driveably coupled manner, and is characterized in that, in the event of a failure of the second drive unit (10) during a synchronization process for preparing a gear shift, the friction clutch (7, 8) associated with the sub-transmission (3, 4) slips at least briefly, so that the sub-transmissions (3, 4) and the second drive unit (10) are set to a synchronous speed via the first drive unit (9), and the transmission input shafts (5, 6) of the sub-transmissions are coupled or can be coupled to the second drive unit (10) in a driveably coupled manner.

Description

Technical Field

[0001] The present invention relates to a method for controlling a hybrid drivetrain of a hybrid motor vehicle, wherein the hybrid drivetrain has a dual-clutch transmission with two sub-transmissions, whose transmission input shafts can each be coupled in a drivingly effective manner to a first drive unit by means of a friction clutch, wherein one of the two transmission input shafts is coupled or can be coupled in a drivingly effective manner to a second drive unit. Background Art

[0002] Dual-clutch transmissions of this type are well known in the field of vehicle transmissions. They feature a dual clutch with first and second friction clutches, as well as first and second sub-transmissions. Each friction clutch is functionally associated with a sub-transmission. Each sub-transmission can be operatively connected to the drive unit via its associated friction clutch. Providing two power transmission paths allows for gear changes without interrupting tractive force. The drive torque provided by the drive unit is transferred continuously from one power transmission path to the other through overlapping operation without interrupting tractive force.

[0003] It is also known to hybridize the powertrain of a motor vehicle. This is understood to be the combination of at least two different drive units that provide the drive power for operating the motor vehicle. In the most common embodiment, a hybrid motor vehicle has an internal combustion engine and at least one electric machine that can be operated both electrically and in a generator-like manner.

[0004] Various design concepts are known for hybridizing a powertrain with a dual-clutch transmission. For example, it is known to connect an electric motor to one of the two sub-transmissions of a dual-clutch transmission—in this case, the electric motor is arranged downstream of the corresponding friction clutch associated with the sub-transmission, as viewed in terms of power flow. This arrangement is described, for example, in DE 10 2010 004 711 A1.

[0005] It is also known that in this type of hybrid drivetrain design, the electric machine is used, in particular, to assist in the synchronization of the gears during the shifting process in order to compensate for the increased inertia of the sub-transmissions connected to the electric machine and thus protect the synchronization unit from excessive mechanical loads. In particular, failures of the electric machine and the associated failures of the synchronization assistance on the electric machine must be considered in this design variant of the hybrid drivetrain.

[0006] DE 10 2007 042 724 A1 discloses a method for controlling a hybrid drivetrain of a hybrid motor vehicle, wherein the hybrid drivetrain has a dual-clutch transmission with two sub-transmissions, the transmission input shafts of which can each be coupled in a drivingly effective manner to a first drive unit by means of a friction clutch, wherein one of the two transmission input shafts is coupled or can be coupled in a drivingly effective manner to a second drive unit.

[0007] DE 10 2004 035 534 A1 discloses, in the context of a synchronization process for preparing a gear shift, that when a reverse gear is to be engaged in the event of a failure of the second drive unit, a friction clutch associated with a sub-transmission, the transmission input shaft of which is coupled or can be coupled in a drivingly active manner to the second drive unit, is at least briefly slipped. Summary of the Invention

[0008] One object of the present invention is to provide a method for controlling a hybrid drivetrain, which method enables a sub-transmission of a dual-clutch transmission, which is connected in a drivingly active manner to a second drive unit, to reach a desired synchronous speed even in the event of a failure or malfunction of the second drive unit, without subjecting the synchronous unit to excessive mechanical loads. The second drive unit is, for example, an electric motor.

[0009] The object is achieved by a method for controlling a hybrid drivetrain of a hybrid motor vehicle, wherein the hybrid drivetrain has a dual-clutch transmission with two sub-transmissions, the transmission input shafts of the two sub-transmissions being respectively coupled to a first drive unit in a drivingly effective manner by means of a friction clutch, wherein one of the two transmission input shafts (5, 6) is coupled or can be coupled to a second drive unit in a drivingly effective manner, wherein in the event of a failure of the second drive unit during a synchronization process for preparing a gear shift, the friction clutch associated with the sub-transmission slips at least briefly, so that the sub-transmission and the second drive unit are set to a synchronous speed via the first drive unit, the transmission input shaft of the sub-transmission being coupled or can be coupled to the second drive unit in a drivingly effective manner.

[0010] The method according to the invention for controlling a hybrid powertrain of a hybrid motor vehicle is used in a hybrid powertrain having the following features:

[0011] - a first drive unit,

[0012] - a second drive unit, and

[0013] A dual-clutch transmission comprising two sub-transmissions, the transmission input shafts of which can each be coupled in a drivingly active manner to a first drive unit by means of a friction clutch.

[0014] According to the invention, the second drive unit is coupled or can be coupled in a drivingly active manner to one of the two transmission input shafts.

[0015] Furthermore, according to the invention, in the event of a fault in the second drive unit during the synchronization process for preparing a gear shift, the friction clutch associated with the sub-transmission slips at least briefly, so that the sub-transmission and the second drive unit are set to a synchronous speed via the first drive unit, and the transmission input shaft of the sub-transmission is coupled or can be coupled to the second drive unit in a drive-effective manner.

[0016] Developments of the invention are specified in the dependent claims, the description and the drawings.

[0017] Particularly preferably, the first drive unit is designed as an internal combustion engine and the second drive unit is designed as an electric machine that can be operated both as an electric motor and as a generator.

[0018] According to the present invention, if the speed of the first drive unit is less than or equal to the synchronous speed to be set, i.e., the target synchronous speed, when an upshift is required, or if the speed of the first drive unit is greater than or equal to the synchronous speed to be set, when a downshift is required, the speed jump required for setting the synchronous speed is fully set by means of the corresponding friction clutch ("fullintermediate clutching"). If the speed of the first drive unit is greater than the synchronous speed to be set, when an upshift is required, or if the speed of the first drive unit is less than the synchronous speed to be set, when a downshift is required, the speed jump required for setting the synchronous speed is preferably substantially halved by means of the corresponding friction clutch ("half intermediate clutching").

[0019] Preferably, in the case of traction upshifts and overrunning downshifts, the speed jump required for setting the synchronous speed is set essentially in half by means of the corresponding friction clutches without interruption of traction.

[0020] According to the invention, in the case of traction downshifts and overrun upshifts, the speed jump required for setting the synchronous speed is fully set without traction interruption by means of the corresponding friction clutch.

[0021] The dual-clutch transmission preferably has a first sub-transmission and a second sub-transmission, wherein the first sub-transmission comprises a first transmission input shaft and the second sub-transmission comprises a second transmission input shaft, wherein the first transmission input shaft can be coupled to the first drive unit by means of a first friction clutch, and the second transmission input shaft can be coupled to the first drive unit by means of a second friction clutch, and wherein the second transmission input shaft is coupled or can be coupled to the second drive unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is described below by way of example with reference to the accompanying drawings.

[0023] Figure 1 A schematic diagram of a hybrid powertrain is shown.

[0024] Figure 2 The diagram shows “speed vs. time” in the “traction upshift” operating state of a hybrid vehicle.

[0025] Figure 3 The diagram shows “speed vs. time” in the “overdrive upshift” operating state of a hybrid vehicle.

[0026] Figure 4 The diagram shows “speed vs. time” in the “traction downshift” operating state of a hybrid vehicle.

[0027] Figure 5 The diagram shows “speed vs. time” in the “overdrive downshift” operating state of a hybrid vehicle. DETAILED DESCRIPTION

[0028] Figure 1 An exemplary hybrid drivetrain 1 for a hybrid motor vehicle is shown, in which the method according to the invention is used.

[0029] exist Figure 1 The hybrid drivetrain 1 shown in FIG has a first drive unit 9 , namely an internal combustion engine 9 ′; a second drive unit 10 , namely an electric motor 10 ′; and a dual-clutch transmission 2 .

[0030] The dual-clutch transmission 2 has a first sub-transmission 3 with a first transmission input shaft 5 and a second sub-transmission 4 with a second transmission input shaft 6 .

[0031] The first transmission input shaft 5 of the first sub-transmission 3 can be connected to the crankshaft 11 via the first friction clutch 7. Figure 1 As shown in FIG, , the first clutch 7 is connected to the internal combustion engine 9' in a drivingly active manner, either directly or via a decoupling element. All odd-numbered gears of the dual-clutch transmission 2 are associated with the first sub-transmission 3. The first friction clutch 7 and the first sub-transmission 3 form a first power transmission path. Downstream of the first sub-transmission 3 is the first shifting clutch S1 for decoupling the driven shaft from the differential D.

[0032] The second transmission input shaft 6 of the second sub-transmission 4 can be connected in a drivingly effective manner to the crankshaft 11 via the second friction clutch 8. The crankshaft 11 is also connected in a drivingly effective manner to the internal combustion engine 9'. All even-numbered gears of the dual-clutch transmission 2 are assigned to the second sub-transmission 4. The second friction clutch 8 and the second sub-transmission 4 form a second power transmission path together with the second shifting clutch S2.

[0033] The electric machine 10 ′ is connected in a drive-operable manner to the second transmission input shaft 6 .

[0034] The drive torque provided by the internal combustion engine 9' and / or the electric machine 10' is transferred alternately via the sub-transmissions 3 and 4 activated by engaging the associated friction clutches 7 and 8, i.e., alternately via the first and second power transmission paths. By overlapping operation of the first and second friction clutches 7 and 8, with the shifting clutches S1 and S2 open and closed, the drive torque is shifted from the first sub-transmission 3 to the second sub-transmission 4, and vice versa.

[0035] In the event of a failure of the electric motor 10 ′, during a synchronization process to prepare for a gear shift, for example, when switching the drive torque from the first sub-transmission 3 to the second sub-transmission 4 , the second friction clutch 8 is at least briefly slipped or engaged, so that the second sub-transmission 4 and the electric motor 10 ′ are set to a synchronous speed via the first drive unit 9 , i.e., the internal combustion engine 9 ′. During this time, the drive power for operating the hybrid vehicle is transmitted uninterrupted via the first power transmission path.

[0036] In the following, in order to describe the method according to the invention in more detail, a distinction is made between four operating states of the hybrid vehicle, namely in traction upshift ( Figure 2 ), Overspeed downshift ( Figure 3 ), Traction downshift ( Figure 4 ) and overdrive upshift ( Figure 5 ) are distinguished between them.

[0037] exist Figures 2 to 5 In each case one of the above operating states is shown, wherein in all diagrams the time in seconds is plotted on the abscissa and the time in seconds is plotted on the ordinate. -1 The speed is plotted in units of 1 / 2. The curves marked with "12" describe the speed profile of the second transmission input shaft 6 over time. The curves marked with "13" describe the speed profile of the crankshaft 11 over time.

[0038] Figure 2The "Drag Upshift" operating state is shown. The shifting process in a dual-clutch transmission is performed by shifting from an odd-numbered gear with a lower transmission ratio to an even-numbered gear with a higher transmission ratio. For example, the odd-numbered gear with a lower transmission ratio is engaged in the first sub-transmission, while the friction clutch between the internal combustion engine and the first transmission input shaft is engaged. Drive torque is thus transmitted via the first power transmission path of the dual-clutch transmission. During this time, while the second friction clutch between the internal combustion engine and the second transmission input shaft is disengaged, the next gear, an even-numbered gear with a higher transmission ratio, is engaged on the second transmission input shaft. Synchronization of the second transmission input shaft is assisted by the slipping engagement of the second friction clutch. During the synchronization process, in the current "Drag Upshift" operating situation, the speed of the internal combustion engine 9 ′ or crankshaft 11 is lower than the speed of the second transmission input shaft 6 only in the first half, that is, during the first time interval a. Due to the slipping engagement of the second friction clutch 8 during the first time interval a, the speed of the second transmission input shaft 6 is reduced by the internal combustion engine 9' or crankshaft 11. Here, the internal combustion engine 9' provides a negative torque, and the second transmission input shaft 6 is braked. During the second time interval b, the speed of the internal combustion engine 9' or crankshaft 11 is higher than the speed of the second transmission input shaft 6. Here, the internal combustion engine 9' provides a positive torque, and the second transmission input shaft 6 is accelerated due to the slipping engagement of the second friction clutch 8. During this second time interval b, the second friction clutch 8 is disengaged to prevent the second transmission input shaft 6 from accelerating during this time interval. During the second time interval b, the synchronization unit takes over further synchronization work.

[0039] Figure 3 The "overdrive downshift" operating state is shown. In this operating condition, during the synchronization process, the speed of the internal combustion engine 9' or crankshaft 11 is higher than the speed of the second transmission input shaft 6 only in the first half, that is, in the first time interval a. Due to the slipping contact of the second friction clutch 8 in the first time interval a, the speed of the second transmission input shaft 6 is increased by the internal combustion engine 9' or crankshaft 11. In this case, the internal combustion engine 9' provides positive torque, and the second transmission input shaft 6 is accelerated. In the second time interval b, the speed of the internal combustion engine 9' or crankshaft 11 falls below the speed of the second transmission input shaft 6. In this case, the internal combustion engine 9' provides negative torque, and the second transmission input shaft 6 is braked due to the slipping contact of the second friction clutch 8. In this second time interval b, the second friction clutch 8 is disengaged to prevent the second transmission input shaft 6 from braking during this time interval.

[0040] Therefore, for Figure 2 and Figure 3In the operating state shown in FIG, a so-called “half intermediate clutching” is necessary for synchronization, ie the speed jump required for setting the synchronous speed is essentially set to half by means of the second friction clutch 8 .

[0041] Figure 4 The "Drag Downshift" operating state is shown. In this operating situation, the speed of the internal combustion engine 9 ′ or the crankshaft 11 is lower than the speed of the second transmission input shaft 6 during the entire synchronization process - the internal combustion engine 9 ′ provides a negative torque, and the second transmission input shaft 6 is braked during the entire synchronization process due to the slipping contact of the second friction clutch 8.

[0042] Figure 5 The "overdrive upshift" operating state is shown. In this operating situation, the rotational speed of the internal combustion engine 9 ′ or the crankshaft 11 is higher than the rotational speed of the second transmission input shaft 6 during the entire synchronization process—the internal combustion engine 9 ′ provides positive torque and the second transmission input shaft 6 is accelerated during the entire synchronization process due to the slipping contact of the second friction clutch 8 .

[0043] Therefore, for Figure 4 and Figure 5 In the operating state shown in FIG, a so-called “full intermediate clutching” is necessary for synchronization, ie the speed jump required for setting the synchronous speed is set completely by means of the second friction clutch 8 .

[0044] The degree to which the second transmission input shaft 6 is braked or accelerated depends in each case on the synchronous speed of the second transmission input shaft 6 to be set.

[0045] List of reference numerals:

[0046] 1 Hybrid powertrain

[0047] 2 Dual-clutch transmission

[0048] 3 First sub-transmission

[0049] 4 Second sub-transmission

[0050] 5 First transmission input shaft

[0051] 6 Second transmission input shaft

[0052] 7 First friction clutch

[0053] 8 Second friction clutch

[0054] 9 First drive unit

[0055] 9' internal combustion engine

[0056] 10 Second drive unit

[0057] 10' motor

[0058] 11 Crankshaft

[0059] 12 Speed ​​variation curve of the second transmission input shaft (secondary side of the second friction clutch)

[0060] 13 Crankshaft speed curve (primary side of the second friction clutch)

[0061] a First time interval

[0062] b Second time interval

Claims

1. A method for controlling a hybrid drivetrain (1) of a hybrid vehicle, wherein the hybrid drivetrain (1) has a dual-clutch transmission (2) with two sub-transmissions (3, 4), the transmission input shafts (5, 6) of the two sub-transmissions being respectively driveably coupled to a first drive unit (9) by means of friction clutches (7, 8), wherein one of the two transmission input shafts (5, 6) is coupled or can be coupled to a second drive unit (10) in a driveably coupled manner, wherein in the event of a fault in the second drive unit (10) during a synchronization process for preparing a gear shift, the friction clutch (7, 8) associated with the sub-transmission (3, 4) slips at least briefly, so that the sub-transmissions (3, 4) and the second drive unit (10) are set to a synchronous speed via the first drive unit (9), and the transmission input shafts (5, 6) of the sub-transmissions are coupled or can be coupled to the second drive unit (10) in a driveably coupled manner, characterized in that If the speed of the first drive unit (9) is greater than the synchronous speed to be set when an upshift is required, or if the speed of the first drive unit (9) is less than the synchronous speed to be set when a downshift is required, the speed jump required for setting the synchronous speed is essentially set to half by means of the corresponding friction clutch (7, 8).

2. The method according to claim 1, characterized in that The first drive unit (9) is designed as an internal combustion engine (9').

3. The method according to claim 1 or 2, characterized in that The second drive unit (10) is configured as an electric motor (10').

4. The method according to claim 1 or 2, characterized in that If the speed of the first drive unit (9) is less than or equal to the synchronous speed to be set when an upshift is required, or if the speed of the first drive unit (9) is greater than or equal to the synchronous speed to be set when a downshift is required, the speed jump required for setting the synchronous speed is completely reduced by means of the corresponding friction clutch (7, 8).

5. The method according to claim 1 or 2, characterized in that In the case of a drag upshift and an overrun downshift, the speed jump required for setting the synchronous speed is essentially halved by means of the corresponding friction clutches (7, 8).

6. The method according to claim 1 or 2, characterized in that The dual-clutch transmission (2) has a first sub-transmission (3) and a second sub-transmission (4), wherein the first sub-transmission (3) includes a first transmission input shaft (5) and the second sub-transmission (4) includes a second transmission input shaft (6), wherein the first transmission input shaft (5) can be coupled to the first drive unit (9) by means of a first friction clutch (7), and the second transmission input shaft (6) can be coupled to the first drive unit (9) by means of a second friction clutch (8), and wherein the second transmission input shaft (6) is coupled or can be coupled to the second drive unit (10).

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