DE102021117441A1 - Method for switching off an internal combustion engine in an automatic stop and hybrid drive train - Google Patents

Abstract

The invention relates to a method (30) for switching off an internal combustion engine (12) in an automatic stop via a switching off process (31), in which the internal combustion engine (12) assigned to a drive train is switched off and an existing engine speed (nm) of the internal combustion engine (12) via a counter-torque (Mg) counteracting the rotational movement of the internal combustion engine (12) of an electric motor (14) connected in a torque-transmitting manner to the internal combustion engine (12), in that the electric motor (14) uses the counter-torque (Mg) to convert energy into energy recovery, in which a kinetic energy of the rotary movement is converted into electrical energy, with the counter-torque (Mg) of the electric motor (14) during the switch-off process (31) being adjusted as a function of an electrical power parameter (PI) of the energy recovery and as a function of the engine speed (nm). The invention also relates to a hybrid drive train (10).

Description

The invention relates to a method for switching off an internal combustion engine in the case of an automatic stop according to the preamble of claim 1. The invention also relates to a hybrid drive train.

In DE 10 2019 111 758 A1 describes a method for energy recovery in which, when a hybrid vehicle is being driven, the mechanical energy that occurs when an internal combustion engine is switched off is converted into electrical energy by an electric motor.

The object of the present invention is to carry out a shutdown process of an internal combustion engine in a more comfortable, gentler and more efficient manner.

At least one of these objects is solved by a method for switching off an internal combustion engine in the case of an automatic stop with the features of claim 1 . As a result, the combustion engine can be switched off more gently, quietly and more efficiently.

The internal combustion engine can be arranged in a vehicle. The vehicle may be a hybrid vehicle. The engine may provide drive torque to propel the vehicle. The electric motor can provide additional or alternative drive torque to propel the vehicle. The powertrain may be a hybrid powertrain.

The internal combustion engine can be switched off by cutting off fuel supply to the combustion chamber and/or suspending an ignition process. The stopped engine may stop outputting drive torque. The existing engine speed can slowly decrease due to the mass inertia of the moving engine components if there is no counter-torque from the electric motor acting on the internal combustion engine.

The electric motor can be connected to the internal combustion engine via a separating clutch. When the countertorque acts on the internal combustion engine, the separating clutch can be closed. The separating clutch can be designed as a K0 clutch. The electric motor can have a rotor, which is fixed to rotate relative to a crankshaft of the internal combustion engine.

The drive train can have a further electric motor. The additional electric motor can be connected to the internal combustion engine via a separating clutch. The further electric motor can additionally or alternatively bring about a further drive torque for the locomotion of the vehicle. The additional electric motor can carry out energy recovery.

The automatic stop can be part of an automatic start-stop system of the vehicle. The energy consumption of the vehicle can be reduced with the automatic start-stop system.

During the switch-off process, the counter-torque of the electric motor is preferably actively controlled, in particular regulated. The regulation can include a detection, for example a calculation and/or measurement, of the applied counter-torque of the electric motor.

The counter-torque can be set to be greater, the greater the electrical power parameter. The electrical power parameter can be a maximum value of an electrical parameter that generates, processes, stores or uses the electrical energy generated during the energy recovery, which maximum value can be used during the energy recovery.

The counter-torque can also be set as a function of a speed gradient of the engine speed and/or the speed of the electric motor and/or a torque gradient of the counter-torque. For example, the counter-torque can be set during the shutdown process at least in a speed range of the engine speed so that the engine speed falls below a maximum speed gradient.

In a preferred embodiment of the invention, it is advantageous if the electrical power parameter includes a maximum electrical power of the electric motor generated during and with the energy recovery. The drive train can include a further electric motor in addition to the electric motor. The electric motor, in particular also the further electric motor, can be connected to an energy store for providing electrical energy for operating the electric motor and for absorbing the electrical energy generated by the energy recovery.

The electrical power parameter can include an electrical consumption power of electrical consumers of the vehicle. If there is a greater power consumption, then the electrical power generated by the electric motor and thus the counter-torque can also be increased.

A preferred embodiment of the invention is advantageous in which, in addition to the electric motor, at least one other electric motor of the drive train simultaneously carries out energy recovery during the switch-off process, providing electrical power that is reduced at least temporarily during the switch-off process. As a result, the electric motor applying the counter-torque for implementing the energy recovery can be given preference over other electric motors in which energy recovery is carried out during the switch-off process. The electric power of the electric motor applying the counter-torque can be higher than that of the other electric motors during energy recovery.

In a preferred embodiment of the invention, it is provided that the electrical power parameter includes a maximum charging power of an energy store that is electrically connected to the electric motor for storing the electrical energy that is obtained, which can be used during energy recovery. The energy store can be designed as a rechargeable battery.

A preferred embodiment of the invention is advantageous in which the electrical power parameter includes a maximum electrical transmission power, at least during the energy recovery, of transmission means electrically connected to the electric motor. The transmission means can include electrical components, electronic components, cables and/or conductor tracks.

In a specific embodiment of the invention, it is advantageous if a greater counter-torque is set in a first speed range of the engine speed during the switch-off process than at adjacent higher engine speeds. The first speed range may include a torsional resonance range of at least a portion of the powertrain.

In a special embodiment of the invention, torsional vibrations originating from the internal combustion engine are greater in the first speed range than in the adjacent, higher engine speeds. The torsional vibrations in the first speed range can also be greater than at adjacent lower engine speeds.

In a specific embodiment of the invention, it is advantageous if an electrical short circuit of motor phases of the electric motor is carried out in a target speed range of the motor speed during the switch-off process. The target speed range may be immediately preceding a stall of the engine. As a result, an overshoot beyond the standstill of the internal combustion engine can be prevented.

In a specific embodiment of the invention, it is advantageous if, at the end of the shutdown process, a final remaining rotational position of the internal combustion engine is set via the electric motor. As a result, the combustion engine can be started more gently and quietly when restarted.

Furthermore, at least one of the above-mentioned objects is achieved by a hybrid drive train, with an internal combustion engine and an electric motor connected to it in a torque-transmitting manner, which is set up to deliver a counter-torque to the internal combustion engine using a shutdown process of the internal combustion engine that is carried out using a method with at least one of the preceding features .

Further advantages and advantageous configurations of the invention result from the description of the figures and the illustrations.

character list

• 1: Ein Funktionsschaltbild eines Hybridantriebsstrangs in einer speziellen Ausführungsform der Erfindung.
• 2: Ein Funktionsschaltbild eines Verfahrens in einer speziellen Ausführungsform der Erfindung.
• 3: Ein Zeitdiagramm einer Motordrehzahl und eines Gegendrehmoments bei Ausführung eines Verfahrens in einer weiteren speziellen Ausführungsform der Erfindung.

The invention is described in detail below with reference to the figures. They show in detail:

• 1 : A functional diagram of a hybrid drive train in a specific embodiment of the invention.
• 2 : A functional diagram of a method in a special embodiment of the invention.
• 3 : A timing chart of a motor speed and a counter torque when a method in another specific embodiment of the invention is carried out.

1 shows a functional circuit diagram of a hybrid drive train in a special embodiment of the invention. The hybrid drive train 10 is arranged in a vehicle and comprises an internal combustion engine 12, which provides a drive torque for the locomotion of the vehicle and an electric motor 14, which alternatively or additionally provides a further drive torque for the locomotion of the vehicle. The electric motor 14 has a rotor 16 which is rotatable in relation to a stator 18 and fixed in a co-rotating manner in relation to a crankshaft 20 of the internal combustion engine 12 . The internal combustion engine 12 and the electric motor 14 are connected to a transmission 24 via a separating clutch 22 . The transmission 24 is connected to at least one vehicle wheel 26 for locomotion tion of the vehicle in a torque-transmitting manner.

Another electric motor 28 is operatively disposed between the transmission 24 and the disconnect clutch 22 . The additional electric motor 28 can carry out energy recovery, in which the kinetic energy of the vehicle wheels is converted into electrical energy, which is transferred to an energy store.

The electric motor 14 can also carry out energy recovery, in which it exerts a counter-torque Mg which, when the internal combustion engine 12 is switched off, counteracts the rotational movement of the crankshaft 20 via an automatic stop mechanism, thereby reducing an engine speed nm of the internal combustion engine 12 .

2 shows a functional circuit diagram of a method in a special embodiment of the invention. The method 30 for switching off the internal combustion engine 12 is carried out via a switch-off process 31 which is started by an instruction 32 to initiate the switch-off process 31 . The internal combustion engine 12 is switched off by the switch-off process 31 via a switch-off signal 34, for example by cutting off fuel supply to the combustion chamber and/or suspending an ignition process. During the switch-off process 31, the counter-torque Mg of the electric motor 14, which is connected in a torque-transmitting manner to the internal combustion engine 12, is set as a function of a number of input values.

During the switch-off process 31, the torque Mm and the engine speed nm of the internal combustion engine 12 and the applied counter-torque Mg and the speed ne of the electric motor 14 and at least one electrical power parameter PI of energy recovery and a maximum speed gradient of the engine speed Gnmax are included as input values. The electrical power parameter PI can be a maximum electrical power Pemax of the electric motor 14 generated during and with the energy recovery, a maximum charging power Plmax that can be used during the energy recovery of an energy store electrically connected to the electric motor 14 for storing the electrical energy obtained and/or at least during the Include energy recovery maximum electrical transmission power Ptmax from transmission means electrically connected to the electric motor 14 .

The counter-torque Mg to be set at the electric motor 14 is calculated as a function thereof, preferably among other things, and output to the electric motor 14 as the target counter-torque Mgsetpoint, on which the counter-torque Mg for reducing the engine speed nm is present as a function.

3 Fig. 12 shows a time chart of a motor speed and a counter torque when a method in a further specific embodiment of the invention is carried out. The time diagram forms the engine speed nm of the internal combustion engine and a time-associated counter-torque Mg of the electric motor when using the switch-off process 31 according to a method in a special embodiment of the invention, compared to a curve of the engine speed nmr and the counter-torque Mgr when a switch-off process 38 is carried out which the counter-torque Mgr is set exclusively as a function of the engine speed nmr. During the switch-off process 31, the counter-torque Mg is set as a function of the electrical power parameter and the engine speed nm.

At the beginning of the switch-off process 31, the counter-torque Mg of the electric motor is built up in a first time range T1, with the result that the motor speed nm decreases. The counter-torque Mg is lower than the comparative counter-torque Mgr because the counter-torque Mg is set in the first time range T1 depending on the electrical power parameter that limits the counter-torque Mg in the first time range T1. As a result, for example, the maximum electrical power output of the electric motor during energy recovery can be reduced and overloading of the electrical components and/or an energy store connected to the electric motor can be prevented.

At a lower engine speed nm in the second time range T2, the counter-torque Mg is set higher than the counter-torque Mgr, since at a lower engine speed and thus a lower speed of the electric motor, the electrical power generated during energy recovery of the electric motor is lower than at a higher speed of the electric motor. Due to the higher counter-torque Mg, the engine speed nm can decrease more than the engine speed nmr. The second time range T2 includes a first speed range n1, which corresponds to a torsional vibration resonance range of at least one section of the drive train. The torsional vibrations that occur at an engine speed nm in the first speed range n1 and are caused by the internal combustion engine are therefore greater than at engine speeds nm outside of the first speed range n1. With the greater counter-torque Mg in the first speed range n1, a greater speed gradient of the engine speed nm is implemented. The torsional vibration resonance range can thus be faster during the switch-off process 31 be run through and the shutdown process 31 can be carried out quieter and more pleasantly.

In a subsequent third time range T3, the counter-torque Mg is set with a specification to restrict the speed gradient of the engine speed nm to a maximum speed gradient Gnmax in order to carry out the transition to a standstill of the internal combustion engine more gently and comfortably. In this case, an electrical short circuit of motor phases of the electric motor is carried out in a target speed range ng of the motor speed nm in order to prevent overshooting beyond the standstill of the internal combustion engine. The target speed range ng is immediately adjacent to a standstill of the internal combustion engine.

At the end of the switch-off process 31 in a fourth time range T4, a finally remaining rotational position of the internal combustion engine is set via the electric motor. As a result, the combustion engine can be started more gently and quietly when restarted.

reference list

10

hybrid powertrain

12

combustion engine

14

electric motor

16

rotor

18

stator

20

crankshaft

22

disconnect clutch

24

transmission

26

vehicle wheel

28

electric motor

30

procedure

32

Instruction

34

shutdown signal

31

shutdown process

38

shutdown process

mg

counter torque

mm

torque

nm

engine speed

no

rotational speed

PI

performance parameters

pemax

maximum electrical power

Plmax

maximum charging power

Pt max

maximum transmission power

mg target

target counter torque

Gnmax

maximum speed gradient

T1

first time range

T2

second time range

T3

third time range

T4

fourth time range

n1

first speed range

ng

target speed range

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102019111758 A1 [0002]

Claims (10)

Method (30) for switching off an internal combustion engine (12) in the case of an automatic stop via a switching off process (31), in which the internal combustion engine (12) assigned to a drive train is switched off and an existing engine speed (nm) of the internal combustion engine (12) via a rotational movement of the internal combustion engine (12) counteracting counter-torque (Mg) of an electric motor (14) connected in a torque-transmitting manner to the internal combustion engine (12) is reduced in that the electric motor (14) converts energy recovery via the counter-torque (Mg) in which a kinetic energy of the rotary movement is converted into a electrical energy is converted, characterized in that the counter-torque (Mg) of the electric motor (14) during the shutdown process (31) is set as a function of an electrical power parameter (PI) of the energy recovery and as a function of the engine speed (nm). Method (30) for switching off an internal combustion engine (12) in an automatic stop claim 1 , characterized in that the electric power parameter (PI) includes a maximum electric power (Pemax) of the electric motor (14) generated during and with the energy regeneration. Method (30) for switching off an internal combustion engine (12) in an automatic stop claim 1 or 2 , characterized in that during the switch-off process (31), in addition to the electric motor (14), at least one further electric motor (28) of the drive train simultaneously carries out energy recovery, providing electrical power which is reduced at least temporarily during the switch-off process (31). Method (30) for switching off an internal combustion engine (12) in the case of an automatic stop according to one of the preceding claims, characterized in that the electrical power parameter (PI) is a maximum charging power (Plmax) that can be used in energy recovery of a motor with the electric motor (14) electrically connected energy store for storing the generated electrical energy includes. Method (30) for switching off an internal combustion engine (12) in the case of an automatic stop according to one of the preceding claims, characterized in that the electrical power parameter (PI) has a maximum electrical transmission power (Ptmax), at least during energy recovery, from electrically connected to the electric motor (14 ) associated means of transmission. Method (30) for switching off an internal combustion engine (12) in the case of an automatic stop according to one of the preceding claims, characterized in that in a first speed range (n1) of the engine speed (nm) during the switching-off process (31) a greater counter-torque (Mg) is set than at adjacent higher engine speeds (nm). Method (30) for switching off an internal combustion engine (12) in an automatic stop claim 6 , characterized in that from the internal combustion engine (12) emanating torsional vibrations in the first speed range (n1) are greater than in the adjacent higher engine speeds (nm). Method (30) for shutting down an internal combustion engine (12) with an automatic stop according to one of the preceding claims, characterized in that during the shutdown process (31) an electrical short circuit of motor phases of the electric motor (14) in a target speed range (ng) of the engine speed (nm) is performed. Method (30) for switching off an internal combustion engine (12) in the case of an automatic stop according to one of the preceding claims, characterized in that at the end of the switching-off process (31) a final remaining rotational position of the internal combustion engine (12) is set via the electric motor (14). . Hybrid drive train (10) with an internal combustion engine (12) and an electric motor (14) connected to it in a torque-transmitting manner, which is set up to apply a counter-torque (Mg) to the internal combustion engine (12) using a method (30) according to one of the preceding claims carried out shutdown process (31) of the internal combustion engine (12) to deliver.

Images