Procedure for operating a motor vehicle and control unit for carrying out the procedure

Abstract

Method for operating a motor vehicle with a drive unit (10) and a transmission (12) which has several switching elements (13), wherein, in order to execute a gear change from an actual gear to a target gear, a switching element (13) closed in the actual gear is opened and a switching element (13) open in the actual gear is closed, wherein, between disengaging the actual gear and engaging the target gear, the speed of the drive unit (10) is synchronized from an actual speed to a target speed in the following steps: After disengaging the actual gear, in a first phase, the actual speed of the drive unit (10) is changed parabolically by specifying a linear change in the torque of the drive unit (10) until a target torque is reached.Once the target torque is reached, in a second phase the torque of the drive unit is held constant at the target torque, and its rotational speed is linearly varied until it reaches a target speed that is a defined speed difference from the target speed. Once the target speed is reached, in a third speed synchronization phase, the rotational speed of the drive unit is parabolically varied by applying a linear change in torque from the target torque to the starting torque using a superimposed speed control, in order to bring the rotational speed of the drive unit (10) to the target speed.

Description

[0001] The invention relates to a method for operating a motor vehicle. Furthermore, the invention relates to a control unit for carrying out the method.

[0002] A motor vehicle has at least one drive unit and a transmission positioned between the at least one drive unit and an output shaft. The transmission converts the rotational speed and torque of the at least one drive unit and provides the tractive force at the output shaft.

[0003] When a gear is engaged in the transmission, a first set of shift elements are closed and a second set of shift elements are open. To perform a gear change from the current gear to the target gear, at least one shift element that was closed in the current gear is opened to disengage the current gear. To engage the target gear, at least one shift element that was open in the current gear is closed. Between disengaging the current gear and engaging the target gear, the rotational speed of at least one drive unit is synchronized, starting from the current rotational speed of the engaged current gear and increasing towards the target rotational speed of the target gear.

[0004] The invention presented here relates to a method for operating a motor vehicle, namely a method for synchronizing the rotational speed of the at least one drive unit of the motor vehicle during the execution of a gear change between disengaging the current gear and engaging the target gear.

[0005] DE 10 2019 214 986 A1 discloses a drive axle of an electric vehicle and a power-shifting method for this drive axle. The drive axle comprises two electric machines which provide their drive torque to an output of the drive axle via a multi-stage planetary gearbox.

[0006] The present invention is based on the objective of providing a method for operating a motor vehicle during the execution of a gear change, by means of which the speed of the at least one drive unit can be advantageously synchronized during the execution of the gear change between engaging the current gear and engaging the target gear, in particular during the execution of a power shift without a disturbing increase or reduction of the torque at the output.

[0007] This problem is solved by a method according to claim 1 and a control unit according to claim 9.

[0008] According to the invention, the following steps are carried out to synchronize the rotational speed of at least one drive unit: After the actual gear ratio has been determined, in a first phase of speed synchronization, the actual speed of the respective drive unit is changed parabolically by specifying a linear change in the torque of the respective drive unit, until the torque of the respective drive unit, starting from a starting torque, has reached a target torque.

[0009] After the torque of the respective drive unit has reached the target torque, in a second phase of speed synchronization the torque of the respective drive unit is kept constant at the target torque and the speed of the respective drive unit is changed linearly until the speed of the respective drive unit has reached a target speed that has a defined speed difference from the target speed of the speed synchronization.

[0010] After the speed of the respective drive unit has reached the target speed, in a third phase of speed synchronization, the speed of the respective drive unit is changed parabolically by specifying a linear change in the torque of the respective drive unit from the target torque towards the starting torque, and a speed control is superimposed on this parabolic change in order to bring the speed of the drive unit to the target speed.

[0011] The invention presented here allows for an advantageous speed synchronization, which is subdivided into three phases.

[0012] In the first and third phases of speed synchronization, the torque of the respective drive unit is changed linearly and the speed of the respective drive unit is changed parabolically.

[0013] In the second phase of speed synchronization, which lies between the first phase of speed synchronization and the third phase of speed synchronization, the torque of the respective drive unit is kept constant and the speed of the respective drive unit is changed linearly.

[0014] At least in the third phase of speed synchronization, a speed control is superimposed on the speed change caused by the specification of the torque for the drive unit in order to bring the speed of the respective drive unit to the target speed.

[0015] If the drive train comprises several, especially two, drive units, the above steps or phases are performed separately on each drive unit. This allows for a particularly advantageous load switching operation without any disruptive increase or decrease in output torque when two drive units are present.

[0016] Preferably, the target torque for speed synchronization is determined as a function of a specified speed gradient for speed synchronization and a specified moment of inertia of the respective drive unit. For the first phase of speed synchronization, either its duration or its time gradient for the torque of the respective drive unit is specified. This allows for a particularly advantageous determination of the target torque for speed synchronization, which is present at the end of the first phase and kept constant during the second phase.

[0017] Preferably, the defined speed difference from the target speed is determined based on the starting torque of the first phase of speed synchronization and the target torque of the first and second phases of speed synchronization. Preferably, either the duration or the time gradient of the third phase of speed synchronization is specified for the torque of the respective drive unit. This allows for a particularly advantageous definition of the transition from the second to the third phase of speed synchronization, namely the speed of the respective drive unit at which the second phase ends and the third phase of speed synchronization begins.

[0018] Preferably, at the beginning of the third phase of speed synchronization, a target speed profile for speed control during the third phase is calculated based on the speed of the respective drive unit at the beginning of the third phase, the target speed for speed synchronization, and the duration of the third phase. This is particularly advantageous for speed control during the third phase of speed synchronization in order to achieve the target speed with high precision.

[0019] Preferably, the start of the third phase of speed synchronization is brought forward depending on the latency times between a momentary demand on the drive unit and its subsequent torque delivery. By taking these latencies into account, the target speed can be achieved with particularly high accuracy.

[0020] Then, if the motor vehicle has a first drive unit and a second drive unit, which, when performing a load shift, provide their respective drive torque at different transmission input shafts at the transmission output, the synchronization of the speed is carried out on both drive units.

[0021] The invention is particularly advantageous when the motor vehicle has two drive units that can provide torque at different shafts of the transmission to perform a load shift. In this case, the method according to the invention is then carried out on each drive unit separately, thereby avoiding a disruptive increase or decrease in torque at the output of the transmission.

[0022] 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: Fig. 1 a highly schematic representation of a motor vehicle's drivetrain, Fig. 2 a signal flow diagram to illustrate the inventive method for operating a motor vehicle, Fig. 3 a time diagram to further illustrate the inventive method for operating a motor vehicle, Fig. 4 a highly schematic representation of a drive train of a motor vehicle with two drive units, in which the method according to the invention can be advantageously used; Fig. 5 a highly schematic representation of a drive train of a motor vehicle with two drive units, in which the method according to the invention can be advantageously used.

[0023] Fig. Figure 1 shows a highly schematic representation of a motor vehicle drivetrain with a drive unit 10 and a transmission 12 connected between the drive unit 10 and an output 11. The transmission 12 converts rotational speeds and torques and provides the tractive force of the drive unit 10 at the output 11. The transmission 12 has shifting elements, wherein Fig. Figure 1 shows an exemplary switching element 13. In the case of the Fig. The switching element 13 shown in Figure 1 is a positive-locking switching element, in particular a claw. The transmission 12 can also have friction-locking switching elements, such as clutches or brakes, in addition to or as an alternative to positive-locking switching elements.

[0024] In each engaged gear of the transmission 12, a first number of switching elements 13 are closed and a second number of switching elements 13 are open. If a gear change is to be performed in the transmission 12 from an engaged current gear to a target gear, at least one switching element 13 of the transmission 12 that is closed in the current gear is opened to disengage the current gear, and at least one switching element 13 of the transmission 12 that is open in the current gear is closed to engage the target gear.

[0025] Fig. Figure 1 further shows an engine control unit 14 for controlling and / or regulating the operation of the drive unit 10 and a transmission control unit 15 for controlling and / or regulating the operation of the transmission 12. The engine control unit 14 exchanges data with the drive unit 10, and the transmission control unit 15 exchanges data with the transmission 12, as indicated by the dashed double arrows. Furthermore, the engine control unit 14 and the transmission control unit 15 exchange data with each other.

[0026] Fig. 4 and Fig. Figure 5 shows possible design variations for the gearbox 12, which is located in Fig. 4 and Fig. 5 is connected between the output shaft 11 and two drive units 10a, 10b. The gearbox 12 of the Fig. 4, Fig. 5 comprises two planetary stages 16, 17 each, with a ring gear 16a, 17a, a sun gear 16b, 17b, and a bridge 16c, 17c. The gears 12 of the Fig. 4, Fig. The 5 differ in the interconnection of the elements of their planetary levels 16, 17 and their connection to the in Fig. 4, Fig. 5 shown switching elements 13, which are in Fig. 4 and Fig. 5 are also referred to as switching elements A, B, C, D, and E. Switching elements D and E are designed as double switching elements, and switching elements A, B, and C are combined into a switching package. Of the switching elements D and E forming the double switching element, only one of the switching elements D and E can be closed at any given time. Likewise, of the switching elements A, B, and C, only one of the switching elements can be closed at any given time. Fig. 4 and Fig. In each case, switching element D is closed, the remaining switching elements A, B, C and E are open. Fig. 4, Fig. 5 are open, thus assuming a neutral position.

[0027] In Fig. 4 and Fig. In section 5, the drive unit 10b is permanently connected to the sun gear 16b of the planetary stage 16. The drive unit 10a can be connected to different shafts of the gearbox 12 depending on the switching position of the switching elements. When the switching element E is closed, the drive unit 10a, together with the drive unit 10b, is connected to the sun gear 16b of the planetary stage 16. However, if in Fig. 4 and Fig. 5. If the switching element D is closed, the drive unit 10a can be coupled to another shaft of the gearbox, namely in Fig. 5 to the sun wheel 17b of planetary stage 17. In Fig. 4 When the switching element D is closed, the drive unit 10a is connected to the ring gear 16a of the planetary stage 16.

[0028] Should a gear change in the drivetrain of the Fig. 1 for the drive unit 10 or in the case of the drive trains of the Fig. 4, Fig. 5 For the drive units 10a, 10b in connection with the execution of a gear change in the transmission 12 from an actual gear to a target gear, after the actual gear has been disengaged and before the target gear has been engaged, the rotational speed of the respective drive unit 10, 10a, 10b is transferred from the actual rotational speed of the actual gear to be disengaged to the target rotational speed of the target gear to be engaged and thus synchronized, the following steps are carried out for the rotational speed synchronization of the respective drive unit 10, 10a, 10b, which are described below with reference to the signal flow diagram of the Fig. 2 and on the time diagram of the Fig. 3 will be described.

[0029] Block 18 of the Fig. Figure 2 visualizes the requirement for speed synchronization of a respective drive unit 10, 10a, 10b, whereby the speed synchronization in block 18 is requested when the actual gear of the shift to be performed or the gear change to be performed is designed.

[0030] In Fig. 3 is the actual gear at time t0 designed so that the speed synchronization is carried out at the respective drive unit 10, 10a, 10b after time t0.

[0031] In block 19 of the Fig. 2 In a first step of speed synchronization, the actual speed of each drive unit 10, 10a, 10b is changed parabolically by specifying a linear change in the torque of the respective drive unit 10, 10a, 10b. This is carried out until the torque of the drive unit, starting from a starting torque provided by drive unit 10, 10a, 10b when the actual gear is selected, has been changed towards a target torque. In block 20 of the Fig. Step 2 checks whether, after the start of the first speed synchronization phase, the torque M of the drive unit has reached the target torque M1. If this is the case, the first speed synchronization phase ends and the process switches to block 21, which corresponds to the second speed synchronization phase, in which the torque M is constantly maintained at the target torque M1.

[0032] In Fig. 3. The first phase of speed synchronization is executed between times t0 and t1. The actual speed of the current gear is displayed in Fig. Figure 3 shows the curve nIST and the curve nZIEL the target speed of the target gear. Starting at time t0, the speed n of the respective drive unit 10, 10a, 10b is changed parabolically in the first phase of speed synchronization between times t0 and t1 by the linear change of the torque M provided by the drive unit 10, 10a, 10b. The first phase ends at time t1 when the torque M has changed from the starting torque M0 to the target torque M1. Thus, when the torque M reaches the torque M1, the first phase of speed synchronization ends at time t1.

[0033] The target torque M1, which is to be achieved by the end of the first phase to achieve speed synchronization, is determined in particular as a function of a speed gradient specified for speed synchronization and as a function of a specified moment of inertia of the respective drive unit 10, 10a, 10b. The speed gradient over time for the change in speed during speed synchronization corresponds to the speed gradient with which the speed n of the drive unit 10, 10a, 10b is to be linearly changed in the second phase of speed synchronization following the first phase.

[0034] If this speed gradient is known, the target torque M1 can be calculated depending on the speed gradient and depending on the moment of inertia of the respective drive unit 10, 10a, 10b.

[0035] For the first phase of speed synchronization, which ends when the target torque M1 is reached at the respective drive unit 10, 10a, 10b, either its duration Δt1 or the time gradient for the change in torque M of the drive unit 10, 10a, 10b can be specified directly.

[0036] As already explained, the first phase for speed synchronization ends when the torque M of the respective drive unit 10, 10a, 10b has changed from the starting torque M0 to the target torque M1, i.e., when the torque of the respective drive unit M has reached the respective target torque M1. This is in Fig. 3 at time t1, so that therefore in Fig. 3 at time t1 the parabolic change of the rotational speed n of the drive unit ends at time t1 and subsequently the rotational speed n of the drive unit 10, 10a, 10b changes linearly or ramp-like, depending on the target torque M1.

[0037] In the second phase of speed synchronization, which follows the first phase of speed synchronization, and which is Fig. 3. At time t1, the torque M of the respective drive unit is held constant at the respective target torque M1, and the rotational speed n of the respective drive unit is changed linearly until the rotational speed n of the respective drive unit reaches a target rotational speed n2 that has a defined rotational speed difference Δn2 from the target rotational speed nTARGET of the target gear and thus from the target rotational speed nTARGET of the speed synchronization. This is in Fig. 3 at time t2 the case in which the rotational speed n of the drive unit has reached the target rotational speed n2, which has the defined rotational speed difference Δn2 from the target rotational speed nTARGET.

[0038] In Fig. 3 is the duration of the second phase of speed synchronization, denoted by Δt2.

[0039] Then, when the rotational speed n of the respective drive unit has reached the target rotational speed n2, the second phase of speed synchronization ends and the third phase of speed synchronization begins at time t2, with the third phase of speed synchronization in Fig. 3 lasts until time t3, so that the third phase of speed synchronization takes up the time interval Δt3.

[0040] As already explained, the third phase of speed synchronization begins at time t2, i.e., when in block 22 of the Fig. It was determined that the rotational speed n of the respective drive unit has reached the target rotational speed n2, which exhibits the defined rotational speed difference Δn2 from the target rotational speed nZIEL of the speed synchronization. The defined rotational speed difference Δn2 from the target rotational speed nZIEL is determined during speed synchronization depending on the starting torque M0 and target torque M1 of the drive unit 10, 10a, 10b, assuming that the torque M of the respective drive unit is fed back from the target torque M1 to the starting torque M0. For the third phase of speed synchronization, its duration Δt3 or, alternatively, the time gradient for the change in the torque M of the drive unit 10, 10a, 10b can be specified directly.

[0041] As previously explained, the third phase of speed synchronization begins at time t2 when block 22 has determined that the speed of the respective drive unit 10, 10a, 10b has reached the target speed n2. The third phase of speed synchronization then starts, branching from block 22 to block 23 and then to block 24, with both blocks 23 and 24 being executed in the third phase. Block 23 corresponds to the transition of the torque M of the drive unit 10, 10a, 10b from the target torque M1 of the second phase to the starting torque M0. This transition of torque M from torque M1 to torque M0 occurs linearly between times t2 and t3 in the third phase.

[0042] In addition, in the third phase of speed synchronization according to block 24, a speed control of the speed n of the respective drive unit takes place, which is superimposed on the change in speed dependent on the torque change of block 23, in order to ultimately transfer the speed n of the respective drive unit to the target speed nTARGET of the target gear with high accuracy.

[0043] For this purpose, in block 24, preferably at the beginning of the third phase of speed synchronization, i.e. at time t2, a target speed profile for the parabolic change of speed is calculated depending on the speed n of the respective drive unit at the beginning of the third phase of speed synchronization, which corresponds to the speed n2, depending on the target speed nTARGET of the speed synchronization and depending on the duration Δt3 of the third phase of speed synchronization, whereby this target speed profile is used for speed control in the third phase of speed synchronization.

[0044] In the third phase of speed synchronization, block 23, in which the speed n of the respective drive unit 10, 10a, 10b is changed in a torque-controlled manner, corresponds to a torque feedforward control; block 24 corresponds to a speed control superimposed on the torque feedforward control. This allows the target speed nTARGET to be achieved with particularly high precision.

[0045] Fig. Figure 3 further shows that the target speed nTARGET can change during speed synchronization. This shows Fig. 3. A target speed nTARGET', which has changed during the second phase of speed synchronization compared to the original target speed nTARGET. In this case, the time required for the second phase is extended to Δt2', since the speed n' of the drive unit 10, 10a, 10b only reaches the target speed n2' at time t2'. The third phase of speed synchronization then takes place for the changed target speed nTARGET' between times t2' and t3' again by the torque-controlled speed change of block 23 with the superimposed speed control of block 24.

[0046] During speed synchronization, latency times between a torque demand on the respective drive unit and the torque delivery by the respective drive unit can be taken into account. This can be done particularly for the third phase of speed synchronization. Depending on the latency between a torque demand and the torque delivery of the respective drive unit 10, 10a, 10b, the third phase for the return of the torque of the respective drive unit from the target torque M1 to the start torque M0 can be brought forward by the known latency time. This further improves speed synchronization. The target speed profile for the speed controller then matches the actual torque of the respective drive unit 10, 10a, 10b.

[0047] The invention is particularly applicable to motor vehicles. Fig. 4, Fig. 5. Application in which two drive units 10a, 10b can provide a drive torque at the output 11 via the transmission 12. Thus, the invention provides an advantageous power shift without undesirable increases or reductions in the torque applied to the output 11. This is achieved when the motor vehicle, as in Fig. 4 and Fig. As shown in Figure 5, which has two drive units 10a and 10b, during the first and second phases of speed synchronization, only the torque for the speed change of the respective drive unit 10a and 10b is specified for the respective torques of the drive units 10a and 10b, so that the speed adjustment at the output 11 is not noticeable. Only in the third phase does the speed control of block 24, which is superimposed on the torque feedforward control of block 23, become important in order to compensate for any speed deviations. In a load-shift operation, the following applies to motor vehicles: Fig. 4 and Fig.5. The amount of torque required for speed synchronization is known over the entire duration of the speed synchronization process. The remaining torque can be used at the output 11. The invention can also be used in motor vehicles with traction-interrupted transmissions. In this case, it is then possible to perform the speed control of block 24, which is superimposed on the torque feedforward control of block 23, not only in the third phase of speed synchronization, but also in the first and second phases of speed synchronization.

[0048] The invention further relates to a control unit configured to automatically execute the above-described method. This control unit is an electronic control unit that has hardware and software means for carrying out the method according to the invention. The hardware means include data interfaces for exchanging data with the assemblies involved in carrying out the method according to the invention. Furthermore, the hardware means include a processor for data processing and a memory for data storage. The software means include program modules that are implemented in the control unit for carrying out the method according to the invention. The control unit according to the invention can, for example, be the engine control unit 14. Reference sign 10 Drive unit 10a Drive units 10b Drive units 11 Drive 12 gearboxes 13 Switching element 14 Engine control unit 15 Transmission control unit 16th planetary stage 16a Ring gear 16b Sun wheel 16c Bridge 17th planetary stage 17a Ring gear 17b Sun wheel 17c Bridge 18 Block Requirement Speed ​​Synchronization 19 Block first phase speed synchronization 20 Block Moment Check 21 Block second phase speed synchronization 22 Block Speed ​​Check 23 Block third phase speed synchronization 24 Block third phase speed synchronization QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 214 986 A1

[0005]

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