Method for accelerating the decoupling of the starting clutch, which detachably connects the electric machine to the transmission input, in a hybrid powertrain of a motor vehicle.

Abstract

Method for accelerating the decoupling of the starting clutch (5) which detachably connects the electric machine (2) to the transmission input in a hybrid powertrain of a motor vehicle, wherein, when a decoupling request is present, the electric machine (2) is controlled simultaneously with the start of the control of the starting clutch for the purpose of decoupling or a predetermined time after the start of the control of the starting clutch in such a way that a torque is built up, thereby accelerating the transition to sliding friction and thus the decoupling while maintaining a target driving torque, characterized in that a target speed for the electric machine (2) is output by a control unit, wherein a speed controller of the electric machine builds up the torque corresponding to the target speed.

Description

[0001] The invention relates to a method for accelerating the decoupling of the starting clutch which detachably connects the electric machine to the transmission input in a hybrid powertrain of a motor vehicle, in particular in a parallel hybrid powertrain, according to the preamble of claim 1.

[0002] Vehicles comprising a parallel hybrid drivetrain are known from the prior art, in which the torques of the internal combustion engine and at least one electric machine connectable to the internal combustion engine are added, preferably by means of a summing transmission, for example, a planetary gear set. In this configuration, the at least one electric machine can be connected to the belt drive or the crankshaft of the internal combustion engine by means of a first clutch. The torques generated by the internal combustion engine and / or the at least one electric machine are transmitted to the driven axle via a downstream transmission. Furthermore, it is known from the prior art to arrange the internal combustion engine and the electric machine in series.

[0003] According to the current state of the art, parallel hybrid drive trains can be equipped with an optional additional clutch that detachably connects the transmission to the drive unit consisting of the combustion engine and electric motor and can serve as a starting clutch. In this case, the transmission can be detachably connected to the electric motor via the starting clutch.

[0004] In a parallel hybrid powertrain, depending on the operating strategy, the vehicle's drive mode can switch between combustion engine drive, electric motor drive and mixed drive, often resulting in the combustion engine being started from purely electric motor driving.

[0005] It is known from the prior art to start the internal combustion engine using so-called drag starts; in this process, with the clutch between the electric motor and the internal combustion engine engaged, the torque of the electric motor overcomes the drag resistance of the internal combustion engine, thus accelerating the internal combustion engine to the starting speed. Preferably, to perform a drag start of the internal combustion engine, the starting clutch provided between the electric motor and the vehicle transmission is operated with a predetermined slip.

[0006] When the starting clutch is in the engaged state and slip is to be created by reducing the torque transmitted by the starting clutch during decoupling (i.e., releasing the rotationally fixed connection between the electric motor and the vehicle transmission), for example, to start the combustion engine using a drag start, the current torque of the starting clutch is reduced by appropriate control until the desired slip is achieved, according to the state of the art. For this purpose, the starting clutch must be controlled in such a way that the transmitted torque is less than the torque corresponding to the desired slip.

[0007] This results in a detrimental delay in the drivetrain, as the clutch must transition from static friction to sliding friction. This delay can be perceived as unpleasant, especially if the desired slip is only established after a long time interval, which can be the case, for example, when the torque to be transmitted is around 0 Nm; in this case, the torque to be transmitted by the starting clutch must be reduced significantly.

[0008] From DE 10 2004 001 381 A1 of the applicant, a method for increasing the spontaneity of overlapping switching in an automatic transmission is known, in which motor firing is specified with or immediately thereafter of the switching command, by which a breaking open of the switching element provided in the transmission and / or an increase of the speed gradient of the turbine speed is achieved, wherein the motor firing is effected by specifying a target speed to be set or by specifying a target motor torque to be set.

[0009] Furthermore, WO 2007 / 093 249 A1 describes a method for decoupling at least one torque source from at least one other torque source of a drive train which, for generating an output torque, extends at its rear end over a plurality of torque sources arranged one behind the other and mechanically connected to each other by rotating shafts, wherein a disconnect coupling is arranged between at least one pair of adjacent torque sources, which is opened to disconnect the torque sources arranged in front of the disconnect coupling from the remainder of the drive train located behind the disconnect coupling, and wherein at least one torque source on each side of the disconnect coupling is controllable with respect to its torque output to the drive train in order to generate a required output torque profile.

[0010] In the known method, the at least two controllable torque sources arranged on opposite sides of the disconnect coupling are controlled during a disconnect preparation period before the disconnect coupling is opened, such that the sum of the torques acting on the disconnect coupling at the end of the disconnect preparation period cancels out, and the required output torque profile is maintained during the disconnect preparation period. Preferably, an internal combustion engine and an electric machine are detachably connected to each other by means of the disconnect coupling.

[0011] The method known from WO 2007 / 093 249 A1 is intended to reduce the jerky fluctuations in output torque that occur when the combustion engine is decoupled, which can lead to a jerky (positive or negative) acceleration of the entire vehicle.

[0012] From EP 1 502 791 A2, a hybrid powertrain for a motor vehicle is known in which a clutch is arranged between an internal combustion engine and a transmission, by means of which the internal combustion engine can be decoupled from the powertrain. It is provided that, when the clutch is to be opened, the torque transmitted by the clutch and, optionally, the gradient of the torque transmitted by the clutch are reduced before the clutch is opened.

[0013] In DE 10 2004 023 673 A1 a method for controlling the powertrain of a hybrid vehicle is disclosed.

[0014] DE 10 2007 001 424 A1 describes a method for starting a piston engine of a hybrid drive.

[0015] In DE 10 2007 049 137 A1, a method for controlling and / or regulating a starting process in a hybrid drive arrangement of a vehicle is proposed.

[0016] The present invention is based on the objective of providing a method for accelerating the decoupling of the starting clutch which detachably connects the electric machine to the transmission input in a hybrid powertrain of a motor vehicle, in particular in a parallel hybrid powertrain, by the implementation of which the aforementioned delays in the powertrain are largely avoided.

[0017] This problem is solved by the features of claim 1. Further embodiments and advantages of the invention are set out in the dependent claims.

[0018] Accordingly, a method is proposed for accelerating the decoupling of the starting clutch, which detachably connects the electric machine to the transmission input, in a hybrid powertrain of a motor vehicle. Within this method, when a decoupling request is present, the electric machine is controlled either simultaneously with the start of the control of the starting clutch for the purpose of decoupling or a predetermined time after the start of the control of the starting clutch, in such a way that a torque is built up by the electric machine, thereby accelerating the transition to sliding friction and thus the decoupling and the establishment of a slip while maintaining the target driving torque.

[0019] According to a first particularly advantageous embodiment of the invention, the control system outputs a target speed for the electric machine, whereby the speed controller of the electric machine builds up the torque corresponding to the target speed. If no slip occurs after a predetermined time, the speed and thus the torque of the electric machine is reduced. This prevents undesirable acceleration of the vehicle due to the additional torque of the electric machine.

[0020] According to a second particularly advantageous embodiment of the invention, the control unit outputs a target torque for the electric machine, which is transmitted to the electric machine as a feedforward torque. If no slip occurs after a predetermined time, the feedforward torque of the electric machine is reduced and the decoupling is terminated, thereby preventing undesired acceleration of the vehicle due to the additional torque of the electric machine, as already explained.

[0021] The control of the electric machine according to the invention accelerates the decoupling of the starting clutch; furthermore, the target driving torque is advantageously maintained, so that no undesirable delays occur in the drive train.

[0022] The target speed or torque value depends on the respective operating point of the drive train and can be stored in the control system as a characteristic map.

[0023] The invention is explained in more detail below with reference to the accompanying figures. These show: Fig. 1: A schematic representation of a parallel hybrid drive train of a motor vehicle including a starting clutch; Fig. 2: A diagram containing the curves of the status of the starting clutch, the target speed of the electric machine, the actual speed of the primary side of the starting clutch, the actual speed of the secondary side of the starting clutch, the target driving torque and the clutch torque as a function of time according to a first variant of the method according to the invention when the starting clutch has been decoupled within a predetermined time; Fig. 3: A diagram containing the curves of the status of the starting clutch, the target speed of the electric machine, the actual speed of the primary side of the starting clutch, the actual speed of the secondary side of the starting clutch, the target driving torque and the clutch torque as a function of time according to the first variant of the method according to the invention if the starting clutch has not been decoupled within a predetermined time; Fig. 4: A diagram containing the curves of the status of the starting clutch, the target speed of the electric machine, the actual speed of the primary side of the starting clutch, the actual speed of the secondary side of the starting clutch, the target driving torque and the clutch torque as a function of time according to a second variant of the method according to the invention, after decoupling of the starting clutch within a predetermined time; and Fig. 5: A diagram containing the curves of the status of the starting clutch, the target speed of the electric machine, the actual speed of the primary side of the starting clutch, the actual speed of the secondary side of the starting clutch, the target driving torque and the clutch torque as a function of time according to a second variant of the method according to the invention when the starting clutch has not been decoupled within a predetermined time.

[0024] In Fig. In the following, the internal combustion engine is designated 1, the electric machine 2, and the vehicle transmission 3. A first coupling 4 is arranged between the internal combustion engine 1 and the electric machine 2, by which the internal combustion engine 1 can be detachably connected to the electric machine 2. The internal combustion engine 1 and the electric machine 2 are arranged in series.

[0025] Furthermore, a second clutch 5, serving as a starting clutch, is arranged between the electric machine 2 and the vehicle transmission 3, through which the electric machine 2 can be detachably connected to the transmission input. Fig. 1 The primary side of the starting clutch is designated with reference numeral 6 and the secondary side with reference numeral 7.

[0026] The method according to the invention is explained using the example of decoupling the starting clutch for the purpose of performing a drag start of the internal combustion engine.

[0027] In Fig. 2, Fig. 3, Fig. 4 and Fig. Curve 5 represents the time course of the status of the starting clutch 5 (curve A), the time course of the actual speed of the primary side 6 of the starting clutch 5 (curve C), the time course of the actual speed of the secondary side 7 of the starting clutch 5 (i.e., the electric machine 2) (curve D), the time course of the target driving torque (i.e., the target torque at the output) (curve E), and the time course of the clutch torque (curve F). Furthermore, curve G represents the status of the "drag start" function, curve H the status of the "decoupling request" function, and curve I the status of the timer initialization, with curve J representing the status of the "target speed setting activation" function (in Fig. 2 and Fig. 3) or “activation of pre-control torque” (in Fig. 4 and Fig. 5). The time course of the timer is illustrated by curve K.

[0028] Furthermore, in Fig. 2 and Fig. 3. The time course of the target speed of the electric machine 2 is represented by curve B; in Fig. 4 and Fig. Figure 5 shows the curve L as the course of the feedforward torque of the electric machine 2 as a function of time.

[0029] Referring to Fig. 2, Fig. 3, Fig. 4 and Fig. 5 At time t_0, a tow start of the combustion engine is requested, while at the same time a decoupling request for the starting clutch 2 is issued, so that the starting clutch 2 is controlled for the purpose of decoupling, thereby reducing the clutch torque (curve F).

[0030] According to the invention and with reference to Fig. 2. A defined time after the start of the activation of the starting clutch 5, a target speed for the electric machine 2 is output for the purpose of decoupling. The electric machine 2 is then controlled in such a way that the target speed, and thus a corresponding torque, is built up. The activation of the electric machine 2 begins at time t_1. Simultaneously with the start of the activation of the electric machine 2, a timer is initialized.

[0031] At the in Fig. In the example shown, the decoupling of the starting clutch, which is illustrated by the difference in rotational speed between the primary side 6 and the secondary side 7 of the starting clutch 5, takes place at time t_3, i.e. before the timer expires.

[0032] If no decoupling occurs within the specified time, i.e., before the timer expires, the rotational speed and thus the torque of the electric machine 2 are reduced immediately after the timer expires, as shown by Fig. 3 illustrates this; it breaks the decoupling. In the Fig. In the example shown in 3, the timer runs at time t_4, and it can be seen from the curves of the actual speed of the primary side 6 and the secondary side 7 of the starting clutch 5 that no decoupling of the starting clutch 5 has taken place at this time.

[0033] The in Fig. The example shown in section 4 differs from the embodiment shown in the illustration. Fig. 2 by the fact that, for a defined time after the start of the control of the starting clutch 5, instead of a target speed, a target torque is output for the control of the electric machine 2, which is passed to the electric machine 2 as a pre-control torque.

[0034] Analogous to after Fig. 2. The control of the electric machine 2 begins at time t_1, and a timer is initialized simultaneously with the start of the control of the electric machine 2. The decoupling of the starting clutch occurs at time t_3, i.e., before the timer expires. In the example shown, the pre-control torque is reduced after the decoupling of the starting clutch 5.

[0035] If the starting clutch 5 is not disengaged within the specified time, i.e., before the timer expires, the feedforward torque of the electric machine 2 is reduced immediately after the timer expires, as shown by Fig. Figure 5 illustrates the timer's execution at time t_4, where it can be seen from the curves of the actual speed of the primary side 6 and the secondary side 7 of the starting clutch 5 that no decoupling has taken place at this time.

[0036] The concept according to the invention allows the decoupling of the starting clutch to be accelerated while simultaneously maintaining the target driving torque, thus increasing driving comfort. Reference sign 1 Internal combustion engine 2 Electric Machine 3 gearboxes 4 first clutch 5 Starting clutch 6 Primary side of the starting clutch 7 Secondary side of the starting clutch AG Time course of the status of the starting clutch 5 B Time course of the target speed of the electric machine 2 C Time course of the actual speed of the primary side 6 of the starting clutch 5 D of the actual speed of the secondary side 7 of the starting clutch 5 E time course of the target driving torque F Time course of the clutch torque Status of the "drag start" function H Status of the "Decoupling Request" function I. Timer initialization status J Status of the function “Activation of target speed setting” K time course of the timer L Time course of the feedforward torque of the electric machine 2

Claims

[1] Method for accelerating the decoupling of the starting clutch (5) which detachably connects the electric machine (2) to the transmission input in a hybrid powertrain of a motor vehicle, wherein, when a decoupling request is present, the electric machine (2) is controlled simultaneously with the start of the control of the starting clutch for the purpose of decoupling or a predetermined time after the start of the control of the starting clutch in such a way that a torque is built up, thereby accelerating the transition to sliding friction and thus the decoupling while maintaining a target driving torque, characterized by , that a control system outputs a target speed for the electric machine (2), wherein a speed controller of the electric machine builds up the torque corresponding to the target speed. [2] Method for accelerating the decoupling of the starting clutch (5) which detachably connects the electric machine (2) to the transmission input in a hybrid powertrain of a motor vehicle, according to claim 1, characterized by , that the value of the target speed depends on the respective operating point of the drive train and can be stored in the control system as a characteristic map. [3] Method for accelerating the decoupling of the starting clutch (5) which detachably connects the electric machine (2) to the transmission input in a hybrid powertrain of a motor vehicle, according to one of the preceding claims, characterized by , that if no decoupling occurs within a specified time, the rotational speed or the feedforward torque of the electric machine (2) is reduced in order to avoid an undesirable acceleration of the vehicle due to the additional torque of the electric machine (2).

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