Method for controlling the parking process of a hybrid electric vehicle

Abstract

Method for controlling the parking process of a hybrid electric vehicle, in which an electric motor and an internal combustion engine can act on the drivetrain either individually or simultaneously, wherein the parking process is carried out with a vehicle with an automatic transmission, characterized in that - that initially only the electric motor is used as the drive for the parking process, - that if an obstacle needs to be overcome and this obstacle cannot be successfully overcome by the electric motor alone, an additional, conventional starter motor with very high torque is briefly engaged, and - that the parking procedure is used for both reversing and forward parking.

Description

[0001] The invention relates to a method for controlling the parking process of a hybrid electric vehicle, in which an electric motor and a combustion engine can be connected to the drive train either individually or simultaneously. The parking process should be possible with both an automatic and a manual transmission.

[0002] In a method known from DE 10 2013 221 904 A1, a second drive unit is switched on or off depending on the accelerator pedal position or the vehicle speed. One of the two drive types can be an electric machine, in particular a starter generator, designed for continuous operation.

[0003] DE 10 2013 212 031 A1 discloses a method intended to make maneuvering easier for the driver of a hybrid-electric vehicle when parking. In such a vehicle, where the current drive is provided either by the combustion engine or the electric motor, the second drive motor is activated when overcoming an obstacle, for example.

[0004] DE 10 2014 210 107 A1 discloses a method for operating a hybrid electric vehicle in which an internal combustion engine is combined with a starter generator. For example, to perform a parking maneuver, the electric motor is initially used exclusively. If an obstacle must be overcome and cannot be successfully overcome by the electric motor alone, the internal combustion engine is briefly activated.

[0005] DE 699 22 221 T2 discloses a hybrid vehicle equipped with an internal combustion engine and two electric motors, both of which can be operated as generators and traction motors. The two electric motors can be controlled to transmit torque to the vehicle's drive wheels individually or simultaneously. One of the motors can also function as a starter motor, driving the internal combustion engine at high speed, thus enabling the internal combustion engine to start with a lower-fuel / air mixture than usual. This motor can also be used to provide additional torque when required.

[0006] These known methods are only partially suitable for controlling the parking process, and an internal combustion engine is always involved.

[0007] The invention is based on the object of optimising the control of the parking process in a hybrid electric vehicle and, in particular, of dispensing with the use of the combustion engine.

[0008] According to the invention, this object is achieved in a vehicle with automatic transmission in that initially only the electric motor is used as the drive for the parking process, that when an obstacle has to be overcome and this obstacle cannot be successfully overcome by the electric motor alone, an additionally provided, classic starter motor with very high torque is briefly switched on, and that the parking process is applied both when parking backwards and when parking forwards.

[0009] In a vehicle with a manual transmission, the parking procedure is carried out in an identical manner, but only when parking forwards.

[0010] The starter motor to be engaged is a conventional starter motor that is not permanently engaged, but is only engaged and operated under specific conditions, such as when the combustion engine starts. This conventional starter motor is geared to such an extent that it can transmit the very high torque required when starting the combustion engine. Due to its very high gear ratio of 15:1, for example, which allows a high torque to be transmitted to the drive shaft, it is also particularly suitable for temporarily overcoming obstacles. Such a starter motor is only designed for short-term operation and can be easily mechanically decoupled after use.

[0011] The starter motor is preferably powered by a separate battery, such as a 6-volt or 12-volt battery.

[0012] The electric motor can be powered by its own battery, which has a higher voltage than the battery that powers the starter motor, in particular a 48-volt battery.

[0013] Alternatively, the electric motor can also be powered by a high-voltage battery, in particular a high-voltage battery with more than 100 volts.

[0014] In the event that the combined torque of the electric motor and the starter motor is not sufficient to overcome the obstacle, the combustion engine can be switched on as an exception.

[0015] If the parking procedure is carried out with a vehicle with an automatic transmission, the parking procedure can be used for both reversing and forward parking.

[0016] However, if the parking procedure is carried out with a vehicle with a manual transmission, the parking procedure is only applied when parking forwards.

[0017] The invention also relates to a hybrid electric vehicle in which the method according to the invention can be applied. To drive the vehicle, both an electric motor and an internal combustion engine are provided, which can act on the drive train either individually or jointly. Furthermore, a separate, conventional starter motor is provided, which is powered by a separately arranged battery and can be additionally engaged in the drive train to overcome an obstacle. The additional drive via the starter motor is particularly advantageous because the gear ratio from the starter motor to the drive shaft is very high, and thus a very strong additional torque can be generated at low speeds, such as those commonly encountered when parking.If the starter motor is connected in parallel with the electric motor intended for the electric drive, a very strong torque is generated, which is sufficient to overcome common obstacles, such as a curb.

[0018] The invention is illustrated by two diagrams and described in detail below with reference to the two diagrams. They show: Fig. 1: a diagram for the parking process using automatic gearshift and Fig. 2: a diagram for the parking process using manual transmission.

[0019] The inventive method for electric parking is particularly suitable for mild hybrid electric vehicles, which operate using both an electric motor and a combustion engine. Both motors can act on the drivetrain in the form of a parallel hybrid drive. In this operating mode, the forces and torques of the two drives are added together. This allows for a more modest design of all motors, thereby saving costs, weight, and installation space.

[0020] The electric drive unit supports the combustion engine to increase performance and / or enables fuel-efficient operation of the combustion engine. Part of the operating energy can be recovered in a regenerative brake.

[0021] In addition, a starter motor for the combustion engine is connected to the drive train.

[0022] If such a mild hybrid electric vehicle is to be parked autonomously or controlled by a driver, this is done in two ways, depending on whether the transmission is automatic or manual.

[0023] In Fig. Figure 1 illustrates the parking process of a mild hybrid electric vehicle with automatic transmission.

[0024] In this case, electric parking is initially carried out exclusively via the electric motor, which is powered, for example, by a 48-volt battery or a high-voltage battery.

[0025] If the parking maneuver is made difficult by an obstacle, such as a curb, the electric motor will first attempt to overcome the obstacle. If this is successful, the parking maneuver can be completed.

[0026] If the electric motor fails to overcome the obstacle, the starter motor, powered, for example, by a 12-volt battery, is activated. Due to its high gear ratio, the starter motor provides additional strong torque at the relatively low vehicle speed, which is usually sufficient to overcome the obstacle. The 12-volt battery provides a power source independent of the electric motor's 48-volt battery.

[0027] If the obstacle is overcome, the parking process can be completed successfully.

[0028] If the obstacle cannot be overcome even by engaging the starter motor, it is possible to engage the combustion engine. This usually involves removing the starter motor. If the obstacle is then overcome, the parking maneuver can be completed successfully.

[0029] For a vehicle with manual transmission, the parking procedure is Fig. 2. Here, too, the parking maneuver is initially attempted using the electric motor, which is powered by the 48-volt battery.

[0030] If the possible obstacle is overcome without any problems, the parking process can be completed successfully.

[0031] If the obstacle is not overcome, the starter motor, which is powered by the 12-volt battery, is switched on, just as in automatic operation.

[0032] If the obstacle is overcome and the parking process is successful with the help of the two electric motors, the parking process can be completed successfully.

[0033] If the obstacle cannot be overcome, the combustion engine can be engaged, but only for forward operation and preferably in combination with an automated clutch. The starter motor can be removed again.

[0034] If reversing is necessary to overcome the obstacle, the parking process must be aborted.

[0035] The method according to the invention significantly simplifies the electric parking of a motor vehicle and is entirely sufficient for normal operating conditions. Since parking maneuvers are primarily carried out in densely populated residential areas, the invention makes a particularly environmentally friendly contribution, as the combustion engine can normally be dispensed with.

Claims

[1] Method for controlling the parking process of a hybrid electric vehicle, in which an electric motor and an internal combustion engine can act on the drive train either individually or simultaneously, the parking process being carried out with a vehicle having an automatic transmission, characterized by , - that initially only the electric motor is used as the drive for the parking process, - that if an obstacle has to be overcome and this obstacle cannot be successfully overcome by the electric motor alone, an additional, classic starter motor with very high torque is switched on for a short time, and - that the parking procedure is applied both when reversing and when parking forward. [2] Method for controlling the parking process of a hybrid electric vehicle, in which an electric motor and an internal combustion engine can act on the drive train either individually or simultaneously, the parking process being carried out with a vehicle having a manual transmission, characterized by , - that initially only the electric motor is used as the drive for the parking process, - that if an obstacle has to be overcome and this obstacle cannot be successfully overcome by the electric motor alone, an additional, classic starter motor with very high torque is switched on for a short time, and - that the parking procedure is applied when parking forwards. [3] Method according to claim 1 or 2, characterized by that the starter motor is powered by a 6-volt battery or a 12-volt battery. [4] Method according to one of claims 1 to 3, characterized bythat the gear ratio from the starter motor to the drive shaft is very high. [5] Method according to one of claims 1 to 4, characterized by that the electric motor is powered by a battery with a higher voltage than a battery that powers the starter motor, in particular a 48-volt battery. [6] Method according to one of claims 1 to 4, characterized by that the electric motor is powered by a high-voltage battery, in particular a high-voltage battery with more than 100 volts. [7] Method according to one of claims 1 to 6, characterized by that if the combined torque of the electric motor and the starter motor is not sufficient to overcome the obstacle, the combustion engine is switched on. [8] Hybrid electric vehicle for carrying out the method according to one of claims 1 and 3 to 7, wherein an electric motor and an internal combustion engine are provided for driving the vehicle, which can act optionally individually or jointly on the drive train, and wherein the vehicle is provided with an automatic transmission, characterized by that a separate, classic starter motor with very high torque is also provided, which is fed by a separate battery, and that the starter motor can also be engaged in the drive train to overcome an obstacle, whereby the parking procedure can be used for both reversing and forward parking. [9] Hybrid electric vehicle for carrying out the method according to one of claims 2 to 7, wherein an electric motor and an internal combustion engine are provided for driving the vehicle, which can act selectively or jointly on the drive train, and wherein the vehicle is provided with a manual transmission, characterized by that a separate, classic starter motor with very high torque is also provided, which is fed by a separate battery, and that the starter motor can also be engaged in the drive train to overcome an obstacle, whereby the parking procedure can be used for forward parking. [10] Hybrid electric vehicle according to one of claims 8 or 9, characterized by that the vehicle is a mild hybrid electric vehicle. [11] Hybrid electric vehicle according to one of claims 8 to 10, characterized by that the gear ratio from the starter motor to the drive shaft is very high. [12] Hybrid electric vehicle according to one of claims 8 to 11, characterized by that in the event that the combined torque of the electric motor and the starter motor is not sufficient to overcome the obstacle, the combustion engine can be switched on.

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