Procedure for reversing

Abstract

A method for reverse driving in a drive system with an electrodynamic starting element (EDA), comprising at least an internal combustion engine (1), an electric machine (2), a transmission (3), a planetary gear set (4) with the elements sun gear (10), ring gear (9) and bridge (8) and a switching element (6), wherein for electrodynamic driving one element of the planetary gear set (4) is connected to the internal combustion engine (1), another element of the planetary gear set (4) is driven by the electric machine (2) and an input shaft of the transmission (3) is driven via a third element of the planetary gear set (4), characterized in that the support torque of the internal combustion engine (1) is increased to enable reverse driving with increased torque, wherein the internal combustion engine (1) rotates at a positive speed and, in order to increase the support torque of the internal combustion engine (1), an additional brake or an engine auxiliary consumer is activated.

Description

[0001] The invention relates to a method for reversing in a drive system with an electrodynamic starting element (EDA) according to the preamble of claim 1.

[0002] From DE 10 2010 063 311 A1 a drive train of a hybrid vehicle is known, with a planetary gear having the elements ring gear, sun gear and web, wherein a first element of these elements of the planetary gear serves to permanently connect a transmission input shaft of a transmission, and wherein a second element of these elements of the planetary gear serves to permanently connect an electric machine and with a clutch, via which two of these three elements of the planetary gear can be coupled, and with a switching element, via which a third element of these elements of the planetary gear can be coupled to an internal combustion engine in a first switching position of the switching element and to the housing side or stator side in a second switching position of the switching element.The EDA function (electrodynamic starting) possible with this drive train enables comfortable starting when driving forward, since the combustion engine can apply the desired support torque precisely and precisely with its torque.

[0003] When reversing, however, the combustion engine lacks the ability to act as a brake, as only its thrust torque can provide the support torque. Consequently, reversing is possible, but only with low torque. This depends on the maximum available support torque of the combustion engine.

[0004] DE 10 2005 040 153 A1 discloses an electrodynamic drive system and an operating method for the electrodynamic drive system.

[0005] DE 11 2009 004 501 T5 discloses an engine control system for a hybrid type vehicle designed to use an internal combustion engine and motor generators to drive the vehicle.

[0006] DE 10 2008 036 048 A1 discloses a method for controlling vehicle components for automatically rocking a motor vehicle free.

[0007] The object of the present invention is therefore to provide a method with which the drivability of reversing in EDA mode is improved.

[0008] This object is achieved by a method according to claim 1. Further developments of the invention emerge from the subclaims and the following description. In the method according to the invention for reversing in a drive system with an electrodynamic starting element (EDA), comprising at least one internal combustion engine, an electric machine, a transmission, a planetary gear set with the elements sun gear, ring gear and carrier and a shifting element, for electrodynamic driving one element of the planetary gear set is connected to the internal combustion engine, another element of the planetary gear set is driven by the electric machine and the drive system is driven via a third element of the planetary gear set. The third element of the planetary gear set thus directs the power flow to the transmission and is therefore preferably connected directly to a transmission input shaft of the transmission.To enable reversing with increased torque, the support torque of the combustion engine is increased. According to the invention, this can be achieved by increasing the engine speed and / or by utilizing existing components such as activating an engine brake and / or an auxiliary brake and / or an auxiliary engine load.

[0009] To constantly increase the support torque on the combustion engine's crankshaft for reversing in EDA mode at a constant speed, the combustion engine's speed is increased to a constantly higher speed level. The electric motor is used as a variable component to set the desired speed.

[0010] The Willis equation generally applies to operation in EDA mode on the planetary gear set. The combustion engine rotates at a positive speed. The magnitude of the output torque for reversing therefore depends on the negative torque on the crankshaft or on the input element of the planetary gear set, which is connected to the electric motor. To constantly increase the thrust torque, the following options are available, which can be used either individually or in combination: Targeted increase of the engine speed to a constantly higher speed level and thus increase of the drag torque. Activation of the engine brake, for example through the exhaust flap or decompression brake. Activation of additional brakes such as a crankshaft retarder. Activation of engine auxiliary consumers such as generators, air compressors.

[0011] As described, the electric motor serves as a variable component to set the desired rpm and thus also the desired speed. This enables or improves reversing in EDA mode, even with increased torque requirements.

[0012] The increase in the support torque on the crankshaft of the combustion engine for reversing in EDA mode can also be carried out only temporarily in order to generate torque peaks, whereby dynamic output torques are generated by speed changes on the combustion engine. Here, too, the Willis equation generally applies to the planetary gear set. The combustion engine rotates at a positive speed. The level of the output torque for reversing is therefore dependent on the negative torque on the crankshaft or on the input element of the planetary gear set, which is connected to the electric machine. In contrast to the constant increase in the support torque, the temporary increase in the support torque is based on a short-term increase in the thrust torque in order to achieve the aforementioned torque peaks. For this purpose, dynamic torques are generated by targeted speed changes on the combustion engine, which are useful in certain driving situations. This can be, for example, rocking.

[0013] In the rocking-free example, the vehicle's wheels are in a trough. Leaving this trough is difficult due to spinning wheels. By repeatedly driving back and forth, alternating rapidly between forward and reverse, the vehicle gains increasing momentum, which eventually becomes sufficient to leave the trough. This rocking is called rocking-free.

[0014] To swing freely, the following steps are repeated: - The vehicle is stationary in a trough. - The speed of the combustion engine is increased to a constant level for starting in forward operation. - Due to the Willis equation, the electric motor rotates backward in EDA mode and generates positive torque, which causes the vehicle to move forward. This corresponds to an EDA start with increased engine speed. - If the vehicle cannot accelerate further, for example, because the torque can no longer be transferred to the ground, the slip limit for forward travel is reached and reverse travel is initiated. The EDA function for reverse travel is used. The electric motor accelerates further into negative direction. - The output torque is increased by allowing the engine speed to increase. Due to mass inertia, the acceleration is counteracted by a dynamic moment of inertia, which generates an additional support torque and thus provides more torque for reversing. -As soon as the slip limit for reverse travel is reached, the vehicle reaches the reversing point and the planetary gear carrier no longer rotates. EDA returns to forward operation to build up speed again. The reduced engine speed is brought back to the increased level for this purpose.

[0015] The process is illustrated by the following figures. Fig. 1: Exemplary structure of a drive system according to the invention Fig. 2a - 2c: Illustration of free swinging Fig. 3: Speed ​​and torque curve during rocking with the procedure for temporarily increasing the support torque on the crankshaft of the combustion engine for reversing in EDA mode

[0016] Fig. Figure 1 shows a known diagram of a drive train of a hybrid vehicle with an EDA arrangement, in which the method according to the invention could be used. The drive train of the Fig. 1 shows a hybrid drive or a drive unit with an internal combustion engine 1 and an electric machine 2, wherein a transmission 3 is connected between the hybrid drive or the drive unit and an output (not shown), which transmission is preferably designed as an automatic or automated manual transmission.

[0017] A device with a planetary gear in the form of a planetary gear set 4, a clutch 5 and a switching element 6 is interposed between the drive unit or the hybrid drive, which is provided by the internal combustion engine 1 and the electric machine 2, and the transmission 3. Fig. 1 also shows a torsional damper 7 assigned to the combustion engine for connecting it to the planetary gear set 4.

[0018] The planetary gear set 4 comprises at least the elements carrier 8, ring gear 9 and sun gear 10, wherein a first element of these three elements 8, 9 and 10 of the planetary gear set 4 serves for the fixed connection of a transmission input shaft 11 of the transmission 3, and wherein a second element of these three elements 8, 9 and 10 of the planetary gear set 4 serves for the fixed connection of the electric machine 2. In the embodiment of the Fig. 1, the first element, which serves to connect the transmission input shaft 11 of the transmission 3, is the web 8 of the planetary gear set 4 and the second element of the planetary gear set 4, which serves to permanently connect the electric machine 2, is the ring gear 9 of the planetary gear set 4.

[0019] Via the switching element 6, a third element of the three elements 8, 9 and 10 of the planetary gear set 4 can be coupled to the internal combustion engine 1 of the hybrid drive in a first switching position A of the switching element, whereas in a second switching position B of the switching element 6, the third element of the three elements 8, 9 and 10 of the planetary gear set 4 can be coupled to the housing side or the stator side, wherein it is Fig. 1 This third element of the planetary gear set 4 is the sun gear 10 of the planetary gear set 4. For operation in EDA mode, i.e. for electrodynamic driving, the switching element 6 must be switched to the first switching position A.

[0020] The clutch 5 can be coupled between two of these three elements 8, 9 and 10 of the planetary gear set 4, namely in the embodiment of the Fig. 1 in the switching position A of the switching element 6 between the web 8 and the sun gear 10.

[0021] In the example shown, the Fig. 1, the switching element 6 comprises, in addition to the two switching positions A and B, a further optional switching position O, wherein in the switching position O of the switching element 6, the third element of the planetary gear set 4, namely in Fig. 1 the sun gear 10, is decoupled from the combustion engine 1 as well as from the housing side, so that the third element of the planetary gear set 4, namely in Fig. 1 the sun gear 10 can rotate freely.

[0022] Fig. 2a to Fig. 2c show the general sequence of a free-rocking process. Exemplary wheels 13 of a vehicle are located in a trough 12. To leave the trough 12, momentum is gained by repeatedly driving back and forth until this momentum is sufficient to leave the trough 12. First, the vehicle is moved forward, which is Fig. 2a. The arrow indicates the direction of movement of the wheels 13. If the vehicle cannot accelerate further because the slip limit has been reached, meaning that no further torque can be transferred from the wheels 13 to the ground, a reverse movement is initiated, as shown in Fig. 2b. The vehicle reverses until it can no longer accelerate. This turning point, with the subsequent necessary change of direction, is shown in Fig. 2c.

[0023] Fig.Figure 3 shows the speed and torque curve during rocking using the method according to the invention for temporarily increasing the support torque on the crankshaft of the internal combustion engine 1 for reversing in EDA mode. In the initial situation, the vehicle is stationary in a trough 12. The torque and speed on the vehicle, which correspond to the torque T_Web and the speed at the web n_Web, are zero. The speed of the internal combustion engine n_Eng, i.e., the speed at the sun, is increased to a constant level. The electric machine (2) rotates backward due to the Willis equation in EDA mode and generates a positive torque T_EM on the ring gear, whereby the vehicle moves forward from this time t1.

[0024] If the vehicle cannot be accelerated any further, the EDA function is used for reversing. The electric motor (2) accelerates further into the negative direction (see time 2 t2). The output torque T_Bridge is increased by allowing the combustion engine speed n_Eng to increase. The acceleration is counteracted by a dynamic moment of inertia, which generates an additional support torque and thus provides more torque for reversing.

[0025] The vehicle reverses until it can no longer accelerate. At the reversal point t3, the vehicle stops (n_Steg=0), and EDA returns to forward operation to build up speed again. For this purpose, the combustion engine speed n_Eng is returned to the increased level. The process is repeated until enough momentum has been gained to exit the trough 12. Reference symbol 1 combustion engine 2 electric machine 3 gearboxes 4 planetary gear set 5 Clutch 6 Switching element 7 torsion dampers 8 first element of the planetary gear, web 9 second element of the planetary gear, ring gear 10 third element of the planetary gear, sun 11 Gearbox input shaft 12 trough 13 wheels M torque n speed n_EM speed of electric machine n_web speed web n_Eng speed of combustion engine T_EM torque electric machine T_Bridge Torque Bridge T_Eng torque combustion engine t1 Time 1 t2 Time 2 t3 Time 3 t4 Time 4

Claims

[1] Method for reversing in a drive system with an electrodynamic starting element (EDA), comprising at least one internal combustion engine (1), an electric machine (2), a transmission (3), a planetary gear set (4) with the elements sun gear (10), ring gear (9) and web (8) and a shifting element (6), wherein for electrodynamic driving, one element of the planetary gear set (4) is connected to the internal combustion engine (1), another element of the planetary gear set (4) is driven by the electric machine (2) and an input shaft of the transmission (3) is driven via a third element of the planetary gear set (4), characterized by that the support torque of the internal combustion engine (1) is increased in order to enable reversing with increased torque, wherein the internal combustion engine (1) rotates at a positive speed and, in order to increase the support torque of the internal combustion engine (1), an additional brake or an engine auxiliary consumer is activated. [2] Method for reversing in a drive system with electrodynamic starting element (EDA) according to claim 1, characterized by that the internal combustion engine (1) rotates at a positive speed and, in order to increase the support torque of the internal combustion engine (1), a speed of the internal combustion engine (1) is increased. [3] Method for reversing in a drive system with electrodynamic starting element (EDA) according to claim 1 or 2, characterized by that the combustion engine (1) rotates at a positive speed and, in order to increase the support torque of the combustion engine (1), an engine brake is activated. [4] Method for reversing in a drive system with electrodynamic starting element (EDA) according to claim 2 or 3, characterized by that the speed of the combustion engine (1) is increased to a constantly higher speed level. [5] Method for reversing in a drive system with electrodynamic starting element (EDA) according to claim 1, 2, 3 or 4, characterized by that the electric machine (2) is used as a variable component to set the desired speed. [6] Method for reversing in a drive system with electrodynamic starting element (EDA) according to claim 1 or 2, characterized by that the increase in the support torque is carried out temporarily in order to generate torque peaks, whereby dynamic output torques are generated by speed changes on the internal combustion engine (1). [7] Method for reversing in a drive system with electrodynamic starting element (EDA) according to claim 6, characterized by that the following procedure steps are repeated to swing freely: - the speed of the internal combustion engine (1) is increased to a constant level for starting in forward operation and the electric machine (2) generates a positive torque while rotating backwards, - as soon as a slip limit of the forward travel is reached, the reverse travel is initiated by the electric machine (2) accelerating further into the negative direction, whereby an output torque is increased by allowing the speed of the combustion engine (1) to increase, -as soon as a slip limit of the reverse drive is reached, the vehicle stops and the web (8) of the planetary gear set (4) no longer rotates, after which the drive system is brought back into forward operation by increasing the speed of the combustion engine (1).

Images