Method and control unit for operating a motor vehicle

Abstract

Method for operating a motor vehicle comprising a drive unit (1) having at least one internal combustion engine (2), a transmission (4) connected between the drive unit (1) and an output (5), and a separating element (7), wherein when the separating element (7) is closed the internal combustion engine (2) is operatively connected to the transmission, and when the separating element (7) is open the internal combustion engine (2) is not operatively connected to the transmission. wherein, to execute a switching operation, a previously closed switching element (6) of the transmission (4) is opened and a previously opened switching element (6) of the transmission (4) is closed, wherein, in an overlap phase of the switching operation preceding a speed equalization phase of the switching operation, the torque that can be transmitted by the switching element to be opened is reduced and, overlapping with this, the torque that can be transmitted by the switching element to be closed is increased, where, when an upshift from an actual gear to a target gear is requested and, in parallel, the starting of the stationary combustion engine (2) and its connection to the transmission (4) is requested, a reaction time for the upshift to be performed and a start time for the internal combustion engine (2) are determined, wherein the reaction time is the time available until the end of the overlap phase of the upshift to be performed is reached, and wherein the start time is the time required until the actual speed of the internal combustion engine reaches the transmission input speed of the actual gear, then, if the start time is shorter than the reaction time, the transmission input speed of the current gear is used as the target speed of the internal combustion engine, the internal combustion engine (2) is brought to the target speed of the internal combustion engine with the separating element (7) open, and subsequently the separating element (7) is closed before the end of the load transfer phase, then, if the start time is greater than the reaction time, the transmission input speed of the target gear is used as the combustion engine target speed, the combustion engine (2) is brought to the combustion engine target speed with the separating element (7) open and subsequently the separating element (7) is closed after the end of the speed equalization phase.

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] In a hybrid vehicle, the drive unit consists of an internal combustion engine and an electric motor. A transmission is integrated between the drive unit and an output shaft of the hybrid vehicle. The transmission converts speed and torque and makes the tractive force of the drive unit available at the output shaft.

[0003] The transmission has several switching elements, which can be designed as clutches or brakes. In each selected gear, a first set of switching elements is closed and a second set is open. To perform a shift or gear change from the current gear to the target gear, a previously closed switching element is opened and a previously open switching element is closed. The switching elements can be actuated by various mechanisms, such as hydraulic, pneumatic, or electromechanical.

[0004] To open a switching element, the torque that can be transmitted by the switching element to be opened is reduced by means of a corresponding control signal. To close a switching element, the torque that can be transmitted by it is increased by means of a corresponding control signal.

[0005] The opening of the switching element to be opened and the closing of the switching element to be closed typically occur simultaneously or overlapping in an overlap phase of the switching process. This overlap phase is completed when the switching element to be closed fully transmits the transmission input torque. A speed equalization phase follows this overlap phase to transition the transmission speed from the speed of the current gear to the speed of the target gear.

[0006] In a hybrid vehicle whose drive unit comprises an internal combustion engine and an electric machine, a separating element is typically placed between the internal combustion engine and the electric machine, whereby when the separating element is open the internal combustion engine is decoupled from the transmission, i.e., it is not in operative connection with the transmission.

[0007] When an upshift from an existing gear to a target gear is to be performed in the transmission, and simultaneously a previously deactivated combustion engine is to be started and brought into operative contact with the transmission, the procedure is as follows: the combustion engine is brought up to the speed of the target gear, and the disengaging element is only closed after the speed transfer phase is complete. However, there is a need to be able to bring the combustion engine into operative contact with the transmission earlier without affecting the quality of the gear change or shifting.

[0008] The problem described above exists not only in hybrid vehicles, but also in motor vehicles whose drive system consists solely of an internal combustion engine. For example, in such a purely combustion-engine vehicle, the internal combustion engine may be switched off and decoupled from the transmission during coasting, with gears being adjusted in the transmission to perform gear selection. Here, too, it may be necessary to start the internal combustion engine and then engage it with the transmission while the transmission adjusts the coasting gear.

[0009] German patent application DE 10 2006 031 683 A1 discloses a method for operating a hybrid vehicle in which the combustion engine can be started via a tow start. In a tow start, the separating element located between the combustion engine and the electric motor is closed to allow the combustion engine to be towed by the electric motor. According to DE 10 2006 031 683 A1, this can be done during an upshift in the transmission.

[0010] DE 10 2012 224 211 A1 discloses a further method for operating a hybrid vehicle. Here too, a drag start of the combustion engine is described, whereby a target speed of the combustion engine is determined and specified for the drag start.

[0011] Based on this, the invention aims to create a novel method for operating a motor vehicle and a control unit for carrying out the method.

[0012] This problem is solved by a method for operating a motor vehicle according to claim 1.

[0013] According to the invention, when an upshift from an actual gear to a target gear is requested in the transmission, and simultaneously the previously stopped internal combustion engine is started and brought into operative contact with the transmission, the following measures are carried out: A reaction time for the upshift to be performed is determined, wherein the reaction time is the duration available until the end of the overlap phase of the upshift to be performed is reached. Furthermore, a start time for the internal combustion engine is determined, wherein the start time is the duration required until the actual speed of the internal combustion engine reaches the transmission input speed of the actual gear.

[0014] If the start time is shorter than the reaction time, the target engine speed is the transmission input speed of the current gear. The engine is brought up to this target speed with the separating element open, and the separating element is then closed before the end of the load transfer phase. If the start time is longer than the reaction time, the target engine speed is the transmission input speed of the desired gear. The engine is brought up to this target speed with the separating element open, and the separating element is then closed after the end of the speed equalization phase.

[0015] The present invention proposes that when an upshift is requested in a transmission and, simultaneously, the starting and engaging of the stationary internal combustion engine with the transmission is requested, the target engine speed for starting the internal combustion engine and the time of closing of the separating element can be determined based on a comparison between the reaction time of the shift to be performed and the start time for the internal combustion engine.

[0016] This makes it possible to start the combustion engine and engage it with the transmission as early as possible without affecting shift quality, either, if possible, before the end of the load transfer phase and before the start of the speed equalization phase, or alternatively, after the end of the speed equalization phase. Engaging the combustion engine during the speed equalization phase is avoided in any case to prevent any impact on shift quality.

[0017] According to an advantageous embodiment of the invention, the reaction time of the upshift is determined by calculating the duration of the filling phase preceding the transition phase and the duration of the transition phase itself. Preferably, the filling phase is determined based on a characteristic map. The transition phase is calculated based on the actual torque of the switching element to be closed, the torque gradient of the switching element, and the torque at the transmission input. This method allows for a particularly advantageous determination of the reaction time of the upshift.

[0018] According to an advantageous embodiment of the invention, the starting time for the internal combustion engine is calculated as a function of the transmission input speed of the current gear and the speed gradient of the internal combustion engine speed. This allows for a particularly advantageous determination of the starting time for the internal combustion engine.

[0019] When the motor vehicle is a hybrid vehicle whose drive unit, in addition to the combustion engine, has an electric machine connected between the combustion engine and the transmission input, the combustion engine is coupled to the electric machine when the separating element is closed. The electric machine is in turn coupled to the transmission input of the gearbox. The invention can be used particularly advantageously in a hybrid vehicle.

[0020] The control unit according to the invention is defined in claim 7. The control unit is configured to execute the method according to the invention on the control side.

[0021] 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 block diagram of a first motor vehicle; Fig. 2 a block diagram of a second motor vehicle; Fig. 3 a time diagram to illustrate the method according to the invention; and Fig. 4. A further time diagram to illustrate the method according to the invention.

[0022] Fig. Figure 1 shows a diagram of a motor vehicle designed as a hybrid vehicle. The hybrid vehicle of the Fig. 1 has a drive unit 1 with an internal combustion engine 2 and an electric machine 3. A transmission 4 is connected between the internal combustion engine 1 and an output 5. The transmission 4 comprises several switching elements 6, wherein in Fig. Figure 1 shows only one switching element 6 as an example. A separating element 7 is connected between the combustion engine 2 and the electric machine 3.

[0023] Then, when a gear change or a shift from an actual gear to a target gear is carried out in the transmission 4, a previously closed switching element is opened by reducing the transmission capacity of the switching element to be opened through appropriate control.

[0024] In parallel or overlapping with this, another previously opened switching element is closed by increasing the transmission capacity of this switching element through appropriate control.

[0025] The overlapping opening and closing of the switching elements occurs in a so-called overlap phase of the shifting process. This overlap phase is preceded by a filling phase of the switching elements, in which they are prepared. The overlap phase is complete when the switching element to close for the gear change fully transmits the torque applied to the input of transmission 4.

[0026] The overlap phase of the shifting process is followed by a speed equalization phase to transfer speeds from the current gear to the target gear.

[0027] Then, when dealing with the in Fig. In the hybrid vehicle shown in Figure 1, when driven purely on electric power, the separating element 7 is open and the combustion engine 2 is preferably switched off. Depending on operating conditions, it may be necessary to start the combustion engine 2 and engage it with the transmission 4 during purely electric driving. For this purpose, the combustion engine 2 is started, and after starting the combustion engine 2, the separating element 7 is closed. If an upshift is performed in the transmission 4 at the same time, it may take a long time before the combustion engine 2 can be engaged with the transmission 4. This is a disadvantage.

[0028] A similar problem arises with the motor vehicle of the Fig. 2, in which the drive unit 1 comprises only the internal combustion engine 2, but no electric machine 3. In this case, for example, sailing is possible with the separating element 7 open and the internal combustion engine 2 switched off, whereby sailing gears are engaged in the gearbox 4 during sailing, and then, if requested in parallel, the internal combustion engine 2 is started and coupled to the gearbox 4.

[0029] Fig. 1 and Fig. Figure 2 further shows control units 8, 9 and 10 for controlling and / or regulating the operation of the respective motor vehicle. Thus, they show Fig. 1 and Fig. 2 a transmission control unit 8, which controls and / or regulates the operation of the transmission 4. In Fig. 2 The transmission control unit 8 also controls and / or regulates the operation of the separating element 7. Furthermore, an engine control unit 9 is shown, which controls and / or regulates the operation of the internal combustion engine 2. The hybrid vehicle of the Fig. 1 additionally has a hybrid control unit 10 to control and / or regulate the operation of the electric machine 3 and the separating element 7. As indicated by the dashed double arrows, the control units 8, 9, and 10 exchange data with the assemblies to be controlled and / or regulated. Furthermore, the control units 8, 9, and 10 exchange data with each other.

[0030] The invention relates to details for operating a motor vehicle in order to enable, when the execution of an upshift from an actual gear to a target gear is requested in the transmission 4, and when, in parallel, the starting of the previously stopped internal combustion engine 2 and its being brought into effective contact with the transmission 4 is requested, this to be possible within the shortest possible time without negative effects on the shifting quality.

[0031] In accordance with the present invention, a reaction time for the upshifting to be carried out is determined.

[0032] The reaction time of the upshift to be performed is the time available until the end of the overlap phase of the upshift to be performed is reached. The reaction time of the upshift to be performed is determined by calculating the duration of a filling phase preceding the overlap phase and the duration of the overlap phase itself.

[0033] The duration of the filling phase can be determined based on the map-dependent data of the shift characteristics in the map of the transmission control unit.

[0034] The duration of the overlap phase is calculated based on the actual torque of the switching element to be closed, the torque gradient of the switching element to be closed, and the torque at the transmission input. The duration of the overlap phase can be easily calculated from the difference between the actual torque at the switching element to be closed and the torque at the transmission input, as well as based on the torque gradient.

[0035] In addition to the reaction time of the switching operation, a start time for the internal combustion engine 2 is determined. The start time is the duration required until the internal combustion engine 2 has started to such an extent that its actual engine speed reaches the transmission input speed of the current gear. This start time of the internal combustion engine is preferably calculated as a function of the transmission input speed of the current gear and the speed gradient of the internal combustion engine speed.

[0036] Then, if the start time of the internal combustion engine 2 is shorter than the reaction time of the upshift to be performed, i.e., if the upshift takes a relatively long time compared to starting the internal combustion engine, the transmission input speed of the current gear is used as the target speed of the internal combustion engine, the internal combustion engine 2 is brought to this target speed with the separating element 7 open, and subsequently the separating element 7 is closed before the end of the load transfer phase.

[0037] However, if the start time of the combustion engine 2 is greater than the reaction time of the upshift to be performed, i.e., if the upshift takes place relatively quickly, the transmission input speed of the target gear is used as the combustion engine target speed, the combustion engine 2 is brought to this combustion engine target speed with the separating element 7 open, and subsequently the separating element 7 is closed after the end of the speed equalization phase.

[0038] The invention allows the combustion engine to be optimally brought into operative contact with the transmission 4, depending on the situation, without affecting the switching quality.

[0039] Further details of the invention can be seen from the time diagrams of the Fig. 3 and Fig. 4, wherein in the Fig. 3 and Fig. Figure 4 shows different curves 11, 12, 13, 14, and 15 over time t. Curve 11 shows the transmission input speed. Curve 12 shows the actual internal combustion engine speed, and curve 13 shows the target internal combustion engine speed. Curve 14 corresponds to a status signal of a circuit configuration, and curve 15 to a status signal of the internal combustion engine start.

[0040] Fig. 3 and Fig. 4 can be deduced, see status signals 14 and 15, that a switching and a start of the combustion engine as well as a connection between the latter and the transmission are requested simultaneously, whereby in Fig. 3 and Fig. 4. The upshift is requested after the combustion engine 2 has been started and engaged with the transmission 4. However, this is purely illustrative. The upshift can also be requested before the combustion engine is started.

[0041] In Fig. 3 and Fig. At time t1, the combustion engine 2 is started and engaged with the transmission 4. Then, at time t2, an upshift is requested.

[0042] At time t2, the reaction time of the upshift to be performed and the start time of the combustion engine 2 are determined in the manner described above.

[0043] Fig. Figure 3 shows a situation in which the reaction time tR of the upshift to be performed is shorter than the start time tS of the internal combustion engine 2. In this case, as described above, the target speed of the internal combustion engine is the transmission input speed of the target gear, the actual speed of the internal combustion engine is brought up to the speed of the new gear according to curve 12, and at time t3 the internal combustion engine 2 is only coupled to the transmission 4 by closing the separating element 7 once the speed transfer phase is complete at time t3. Fig. 3 The circuit is completed at time t3.

[0044] Fig. Figure 4, however, shows an embodiment in which the start time tS of the internal combustion engine 2 is shorter than the reaction time tR of the upshift to be performed. In this case, with the separating element 7 open, the internal combustion engine 2 is brought up to its target speed, namely the transmission input speed of the current gear. Then, at time t3, i.e., before the end of the load transfer phase and before the start of the speed equalization phase, the separating element 7 is closed in order to couple the internal combustion engine 2 to the transmission 4 before the speed equalization phase. Fig. 4 The circuit is completed at time t4.

[0045] It is therefore in the sense of the present invention to determine the reaction time of the upshift to be performed and the start time of the internal combustion engine 2 depending on speeds, speed gradients, torques and torque gradients, and depending on these times to determine a target speed of the internal combustion engine for starting the internal combustion engine 2 and the time for coupling the internal combustion engine 2 to the transmission 4.

[0046] The invention further relates to a control unit for operating a motor vehicle, wherein the control unit which is configured to carry out the method according to the invention on the control side is in particular the transmission control unit.

[0047] Then, when an upshift from an actual gear to a target gear is requested in transmission 4, and simultaneously the starting of the stationary combustion engine 2 and its engagement with transmission 4, the control unit determines the reaction time of the upshift to be performed and the start time of the combustion engine 2 as described above. The control unit compares these times. Based on this, the control unit then determines the target engine speed, brings the combustion engine 2 to this speed, and closes the separating element 7.

[0048] The control unit has means for carrying out the method according to the invention, wherein these means are hardware-related and software-related. The hardware-related means are data interfaces for exchanging data with the assemblies involved in carrying out the method according to the invention, for example, with the internal combustion engine 2 or the engine control unit 9 and the disconnect clutch 7. The hardware-related assemblies also include a memory for data storage and a processor for data processing. Furthermore, the software-related means include program modules that serve to carry out the method according to the invention. Reference sign 1 drive unit 2 Internal combustion engine 3 Electric Machine 4 gearboxes 5 Drive 6 switching element 7 Separating element 8 Transmission control unit 9 Engine control unit 10 Hybrid control unit 11 Gearbox input speed 12 Internal combustion engine actual speed 13 Internal combustion engine target speed 14 Status signal circuit design 15 Status signal combustion engine start

Claims

Method for operating a motor vehicle with a drive unit (1) comprising at least one internal combustion engine (2), with a transmission (4) connected between the drive unit (1) and an output (5), and with a separating element (7), wherein when the separating element (7) is closed the internal combustion engine (2) is operatively connected to the transmission, wherein when the separating element (7) is open the internal combustion engine (2) is not operatively connected to the transmission, wherein, for the execution of a shift, a previously closed shift element (6) of the transmission (4) is opened and a previously opened shift element (6) of the transmission (4) is closed, wherein, in an overlap phase of the shift, which precedes a speed equalization phase of the shift, the torque transmissible by the shift element to be opened is reduced and, overlapping with this, the torque transmissible by the shift element to be closed is increased, wherein then,If an upshift from an actual gear to a target gear is requested, and in parallel, the starting of the stationary internal combustion engine (2) and its connection to the transmission (4) are requested, a reaction time for the upshift to be performed and a start time for the internal combustion engine (2) are determined, wherein the reaction time is the duration available until the end of the overlap phase of the upshift to be performed is reached, and wherein the start time is the duration required until the actual internal combustion engine speed reaches the transmission input speed of the actual gear, then, if the start time is less than the reaction time, the transmission input speed of the actual gear is used as the target internal combustion engine speed.The internal combustion engine (2) is brought to its target speed with the separating element (7) open, and the separating element (7) is subsequently closed before the end of the load transfer phase; then, if the start time is greater than the reaction time, the transmission input speed of the target gear is used as the target speed for the internal combustion engine; the internal combustion engine (2) is brought to its target speed with the separating element (7) open, and the separating element (7) is subsequently closed after the end of the speed equalization phase. Method according to claim 1, characterized in that the reaction time of the up-switching to be performed is determined by determining the duration of a filling phase preceding the overlap phase and the duration of the overlap phase. Method according to claim 2, characterized in that the duration of the filling phase is determined depending on the characteristic curve. Method according to claim 2 or 3, characterized in that the duration of the overlap phase is calculated depending on the actual torque of the switching element to be closed, depending on the torque gradient of the switching element to be closed and depending on the torque at the transmission input. Method according to one of claims 1 to 4, characterized in that the start time for the internal combustion engine (2) is calculated depending on the transmission input speed of the current gear and depending on the speed gradient of the internal combustion engine speed. Method according to one of claims 1 to 5, characterized in that when the motor vehicle is a hybrid vehicle whose drive unit (1) has an electric machine (3) connected between the combustion engine (2) and the transmission in addition to the combustion engine (2), when the separating element (7) is closed the combustion engine (2) is coupled to the electric machine (3), which in turn is coupled to the transmission input of the transmission (4). Control unit (8, 9, 10) for operating a motor vehicle with a drive unit (1) comprising at least one internal combustion engine (2), with a transmission (4) connected between the drive unit (1) and an output (5), and with a separating element (7), wherein when the separating element (7) is closed the internal combustion engine (2) is operatively connected to the transmission (4), and wherein when the separating element (7) is open the internal combustion engine (2) is not operatively connected to the transmission (4), wherein the control unit (8, 9, 10) controls a previously closed switching element (6) to open and a previously open switching element (6) to close in order to execute a switching operation in the transmission (4), wherein the control unit (8, 9, 10) for this purpose operates in an overlap phase of the switching operation, which precedes a speed equalization phase of the switching operation,the torque that can be transmitted by the switching element to be opened is reduced and, overlapping with this, the torque that can be transmitted by the switching element to be closed is increased, wherein the control unit (8, 9, 10) determines a reaction time for the upshift to be performed when an upshift from an actual gear to a target gear is requested in the transmission (4) and, in parallel, the starting of the previously stopped internal combustion engine (2) and its connection to the transmission (4), where the reaction time is the duration available until the end of the overlap phase of the upshift to be performed is reached, and determines a start time for the internal combustion engine (2), where the start time is the duration required until the actual speed of the internal combustion engine reaches the transmission input speed of the actual gear, when the start time is shorter than the reaction time,The system uses the transmission input speed of the current gear as the target engine speed, brings the combustion engine (2) to the same speed, and subsequently closes the separating element (7) before the end of the load transfer phase. Then, if the start time is greater than the reaction time, the system uses the transmission input speed of the target gear as the target engine speed, brings the combustion engine (2) to the same speed, and subsequently closes the separating element (7) after the end of the speed equalization phase. Control unit according to claim 7, characterized in that it is configured to execute the method according to one of claims 1 to 6 on the control side.

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