DE102016217370A1 - Method and device for operating a motor vehicle with a hybrid drive - Google Patents

Abstract

The hybrid drive comprises an internal combustion engine (3) and an electric machine (4), which is mechanically coupled to the internal combustion engine (3) and which operates in a generator mode for converting a torque generated by the internal combustion engine (3) into electrical energy and in an engine mode for converting electrical energy into a torque for driving the internal combustion engine (3), wherein when switching from generator operation to engine operation and vice versa, a change in sign of the torque of the electric machine (4). A torque change required at an operating point change of the hybrid drive (1) takes place via a torque intervention of the electric machine (4) only up to a defined distance value from the change of sign of the torque of the electric machine (4).

Description

The invention relates to a method and a device for operating a motor vehicle with a hybrid drive, consisting of an internal combustion engine and an electric machine, both of which act on a common drive train.

There are hybrid drives for motor vehicles are known and these are increasingly being used to increase the performance of motor vehicles and the ride comfort and their efficiency by reducing fuel consumption. In this case, in a hybrid drive, an internal combustion engine and at least one electric machine are combined in such a way that both the type-specific properties of an internal combustion engine and that of an electric machine for driving the vehicle can be utilized. For this purpose, the electric machine can be arranged in various ways in the motor vehicle depending on the configuration of the hybrid drive train. The term electric machine is to be understood in the context of the invention, a combination of an electric motor with an electric generator, in particular in the form of a starter generator.

Such electric machines are preferably used in hybrid systems for motor vehicles because of their high reaction speed for torque interventions, such as torque boosting or torque reduction for vehicle, powertrain or engine management functions. This is particularly known in full hybrid systems with a powerful electric machine. However, even smaller electric machines offer z. In 48V Mild Hybrid systems, for example, it is possible to implement torque intervention to a limited extent. If these electric machines are coupled by means of a belt drive with the internal combustion engine, one usually speaks of a belt starter generator (RSG) or belt driven starter generator (BSG).

The torque interventions are, for example, switching interventions, ie the execution of a gear change (torque reduction for upshifts, torque increase for downshifts, mostly for automatic transmissions) or interventions for stability or traction control (torque reduction for traction control (ASR), torque increase for engine drag torque control (MSR) ). Also for the speed synchronization in deactivation of a so-called sailing function, which opens the drive train with passive driver request, torque interventions on the electric machine can be used advantageously. In a torque reduction in this case electrical energy is generated simultaneously in the generator mode, while in the usual torque reduction via a Zündwinkeleingriff (shift of the ignition angle to late) in an Otto internal combustion engine lost energy or in all types of internal combustion engines unsteady operating conditions arise, which is unfavorable affect fuel economy and / or emissions.

In systems with a belt starter generator as an electric machine this is connected via a belt drive to the internal combustion engine. This belt drive must be sufficiently tensioned to transfer the forces. This is ensured by belt tensioning systems. Such a belt tensioning system is for example in the DE 10 2012 209 028 A1 described. When changing between motor and generator mode of the electric machine in this case changes the more strained belt side (Lasttrum) and the less strained belt side (empty strand) back and forth. This requires compensatory movements of the belt tensioning system, for example a pendulum movement of a decoupling tensioner of the belt tensioning system. This pendulum movement can adversely affect the dynamic response of the electric drive, which may be expressed in a poorer quality of implementation of the torque intervention, such as in a delayed torque build-up, vibrations or jerking, with the result of poorer shift quality.

The object of the present invention is therefore to provide a method and a device for operating a motor vehicle with a hybrid drive, consisting of an internal combustion engine and an electric machine, which largely prevents the occurrence of transient operating conditions even during torque interventions via the electric machine.

This object is achieved by the subject matter of the independent claims. Advantageous developments are the subject of the dependent claims.

The invention is characterized by a method and a corresponding device for operating a motor vehicle with a hybrid drive, consisting of an internal combustion engine and an electric machine, both of which act on a common drive train. The electric machine is mechanically coupled to the internal combustion engine and operates in a generator mode for converting a torque generated by the internal combustion engine into electrical energy and operates in a motor operation for converting electrical energy into a torque for driving the Internal combustion engine, wherein when switching from the generator mode in the engine operation and vice versa a sign change of the torque of the electric machine. A required at a change in operating point of the hybrid drive torque change of the hybrid drive is a torque intervention via the electric machine only up to a predetermined distance from the sign change of the torque of the electric machine.

If this change of the torque by means of the electric machine is insufficient, then the remaining residual value of the torque change is carried out via the internal combustion engine.

Thus, there is a division of a torque intervention in a proportion which is converted via the electric machine and in a proportion which is converted via the internal combustion engine, taking into account the physically possible torque limits of the individual machines.

The use of the torque engagement of the electric machine takes place only to the extent in which a defined distance from the sign change of the torque setpoint of the electric machine is maintained. If this distance is equal to zero, an engagement occurs exactly up to the zero moment of the electric machine 4 ,

The zero moment may correspond to a state in which the electric machine is electrically passive, i. is neither in motor nor in generator mode. Due to mechanical frictional losses, a slight mechanical torque acts on the belt drive in this state, which, however, is neglected. Alternatively, the zero moment may correspond to a state in which the electric machine, taking into account the frictional losses, gives no moment, and the electric machine may then be in the motor or generator mode.

If a belt starter generator with a belt tensioning system is used as the electric machine and is coupled to the internal combustion engine by means of a belt, the invention avoids a change between the load side and the back side of the belt. Due to the specified distance from the zero moment (eg applicable as a function of the speed), the compensatory movement of the belt drive can be limited to a level which has no negative effects on the quality of the implementation of the intervention (speed and accuracy) or driveability ( from the driver perceptible vibrations or jerking) with it brings. Possibly. can be avoided by the process negative effects of torque interventions on the electric machine on the life of the belt drive.

The limits of the torque of the electric machine, which are to be observed in the distribution of the torque engagement, may include the torque at the allowable current limits of an energy storage (eg maximum discharge current or charging current of a battery, taking into account any consumers such as DC / DC converter ) can be displayed.

In order to avoid or reduce the negative effects of the compensation process of the belt tensioning system when changing the electric machine between motor and generator mode, interventions on the electric machine so only up to a defined distance from the sign change of the torque of the electric machine.

An advantageous embodiment of the invention will be explained in more detail with reference to the accompanying drawings. In the individual figures, only those components are shown which are necessary for the understanding of the invention. Show it:

1 a schematic view of components of a equipped with a hybrid powertrain motor vehicle and

2 in a schematic view of an electric machine with a belt tensioner when the electric machine and

3 a schematic view of an electric machine with a belt tensioner during the starting process of the internal combustion engine or when boosting by means of the electric machine.

The 1 shows very schematically a typical configuration of a mild hybrid system for a motor vehicle 2 , A hybrid powertrain 1 has an internal combustion engine 3 conventional design (diesel engine, gasoline engine, gas-powered engine or flex-fuel engine) and an electric machine 4 on. The electric machine 4 In this example, it is designed as a belt starter generator (RSG) that has a drive wheel 43 and a belt around it 44 with a drive wheel 45 a crankshaft 6 the internal combustion engine 3 connected is.

The hybrid powertrain 1 also has a coupling 5 on, which is designed for example as a dog clutch or friction clutch. The coupling 5 is on the one hand with a crankshaft 6 the internal combustion engine 3 and on the other hand with a transmission input shaft 7 a gearbox 8th connected so that this connection can be closed or disconnected depending on demand. The gear 8th is designed as an automatic transmission or manual transmission. A transmission output shaft 9 of the transmission 8th is mechanical with one differential gear 10 a drive axle 11 of the motor vehicle 2 connected.

For controlling or regulating the electric machine 4 are a vehicle electrical system 14 and a hybrid battery 15 intended. Preferably, the hybrid battery is designed as a 48-volt hybrid battery, in particular as a lithium-ion battery as energy storage.

However, the aspects of the invention are not limited in principle to the use of a nominal voltage of 48 volts. For example, it is also conceivable that the nominal voltage is only 42 volts, or even more than 48 volts. Furthermore, in the motor vehicle 2 preferably still a conventional 12-volt electrical system with a 12-volt vehicle battery arranged (not shown), by means of which various electrical consumers are supplied.

With the 48-volt vehicle electrical system voltage compared to the conventional 12-volt vehicle electrical system voltage higher performance and a relatively high torque of the electric machine 4 be achieved. Furthermore, the increased vehicle electrical system voltage results in lower electrical losses and higher efficiency, with no additional load on the conventional 12-volt vehicle electrical system, in particular during the starting process. Furthermore, the hybrid drive system is adapted to automatically perform a recuperation of energy, or a change from a normal driving situation to a recuperation mode or vice versa.

For controlling and controlling the internal combustion engine 3 , as well as their ancillaries is an electronic control device 21 provided, which are assigned to different sensors, capture the measured variables and determine the measured values of the measured variable. Operating variables include not only the measured variables but also derived from these variables. The control device 21 controls the actuators, that of the internal combustion engine depending on at least one of the operating variables 3 are assigned, and each associated with corresponding actuators, by generating actuating signals for the actuators.

The control device 21 is for the exchange of data with the electrical system 14 the electric machine 4 coupled, for example via a CAN bus.

The electronic control device 21 can also be referred to as engine control unit. Such control devices 21 , which usually include one or more microprocessors, are known per se, so that in the following only the relevant in connection with the invention structure and its operation will be discussed.

The control device 21 preferably comprises a computing unit 25 (Processor) using a program memory 26 and a value memory 27 (Data memory) is coupled. In the program memory and the value memory programs or values are stored, which are for the operation of the internal combustion engine 3 are necessary. Among other things, in the program memory software is a function for controlling the hybrid powertrain 1 , in particular for the control of torque interventions (torque reduction or torque increase) implemented, as described below with reference to the description of 2 and 3 will be explained in more detail.

In the 2 and 3 is the electric machine 4 shown in more detail. It is a belt starter generator equipped with a belt tensioning device 40 is combined into a structural unit. The belt starter generator has a machine housing 41 on, at the front of the belt tensioning device 40 is mounted. The belt tensioning device 40 is designed as a so-called decoupling tensioner. On a wave 42 is a bolted drive wheel 43 for an endlessly circulating belt 44 intended. The belt 44 connects this drive wheel 43 with one on the crankshaft 6 the internal combustion engine 4 attached drive wheel 45 and with another driving wheel 46 which drives an accessory, such as an air conditioning compressor. The driving wheels 45 . 46 are also referred to as pulleys. As a belt 44 is preferably a V-ribbed belt or a poly-V belt.

The drive wheel 45 the crankshaft 6 is used to start the internal combustion engine 3 from the drive wheel 43 the belt starter generator then driven at started internal combustion engine 3 the drive wheel 43 to power generation. The alternately torque-releasing or torque-receiving drive wheel 43 causes a synchronous change of traction (load space) and slack side in the belt drive, which on the drive wheel 43 drawn circumferential direction of the belt ( 3 ). The load belt is generally the strapped side of the belt, and the back is the less strained side of the belt.

The belt tensioning device 40 has a tensioner housing 47 with two tension rollers 48 . 49 on which one around the shaft 42 of the drive wheel 43 is pivotally mounted. The tension roller 48 is fixed to the tensioner housing 47 mounted, the tension roller 49 sits on a movable, arc-shaped lever 50 and is about an unillustrated bow spring package opposite the tensioner housing 47 sprung. The tension roller 49 thus generates the necessary preload force for the belt 44 ,

Due to the pivotable mounting of the entire belt tensioning device 40 makes it possible that in a change of operation (generator mode, motor mode) of the belt starter generator and concomitant permutation of Zugtrum with idle strand in the belt drive the tensioner housing with the tensioners 48 . 49 around the shaft 42 of the drive wheel 43 pivoted.

When the belt starter generator switches from engine operation (starter operation or boosting) to generator operation or recuperation, the belt core changes on the tensioner housing side moving tensioner pulley 49 from empty strand to tensile strand and on the part of the tensioner housing side stationary tensioning roller 48 from Zugtrum to Leertrum. As a result, this change of operation leads to a pivoting of the belt tensioning device 40 from the then current tension on the part of the tension pulley 49 out into the then current slack side of the tensioner 48 into it. This means that at the in 3 drawn circumferential direction of the belt 44 a pivoting counter to the direction of rotation takes place.

While the 2 the belt drive at standstill of the internal combustion engine 3 shows is in 3 the state of the belt drive shown, as he was at the start of the internal combustion engine 3 or when booting sets. The belt starter generator is thus in engine operation and drives the internal combustion engine. At the in 3 drawn circumferential direction of the belt 44 Based on the above-described operation change now takes place a permutation between slack side and Zugtrum instead and there is a pivoting of the belt tensioning device 40 in the direction of rotation of the belt 44 , The train is in the 3 with the reference number 44Z and the empty strand with the reference numeral 44L characterized.

To the negative effects of the compensation process of the belt tensioning device 40 when changing the electric machine 4 between engine and generator operation, commonly referred to as mode switching, to avoid, but at least reduce, interventions take place via the electric machine 4 only up to a specified distance from the sign change of the torque of the electric machine 4 ,

Is the electric machine 4 Before the torque intervention in generator mode (= negative torque torque, eg recuperation mode and if the total torque is to be increased, the torque of the electric machine becomes 4 increased only up to a definable, negative torque value, possibly to zero torque. If this increase in torque is insufficient, the remaining remainder of the torque increase will continue to be transmitted via the internal combustion engine 3 executed. The limit, ie the distance from the sign change of the torque, for that of the electric machine 4 demanded, negative torque is determined experimentally and is in the value memory 27 the control device 21 stored depending on the speed of the electric machine or the internal combustion engine.

Is the electric machine 4 before torque intervention in motor mode (= positive torque, eg boost mode) and if the total torque is to be reduced, the torque of the electric machine becomes 4 only reduced to a defined, positive torque value, if necessary, to zero torque. If this reduction in torque is insufficient, then the remainder of the torque reduction will continue to be transmitted via the internal combustion engine 3 executed. The limit, ie the distance from the sign change of the torque, for that of the electric machine 4 applied, positive torque is also determined experimentally and is in the value memory 27 the control device 21 stored depending on the speed of the electric machine or the internal combustion engine.

Thus, there is a division of a torque intervention into a share, via the electric machine 4 is implemented and in a share, via the internal combustion engine 3 is implemented, taking into account the physically possible torque limits of the individual machines.

The use of the torque intervention of the electric machine 4 takes place only to the extent in which a defined distance from the sign change of the torque setpoint of the electric machine 4 is complied with. If this distance is equal to zero, an engagement occurs exactly up to the zero moment of the electric machine 4 ,

By the invention it is avoided that a change takes place between load strand and empty strand. Due to the specified distance from the zero moment (eg applicable as a function of the speed), the compensatory movement of the belt drive can be limited to a level which has no negative effects on the quality of the implementation of the intervention (speed and accuracy) or driveability ( from the driver perceptible vibrations or jerking) with it brings. Possibly. This procedure can negatively affect the momentary intervention via the electric machine be avoided on the life of the belt drive.

At the same time, the method makes it possible to use the energetic advantage of torque intervention via the electric machine also in systems with belt starter generator. With a torque reduction via the electric machine, which is in the motor mode (eg boost case), previously generated electrical energy can be saved. With a torque boost across the electric machine that is in generator mode (eg, downshifting during recuperation), said strategy may reduce the amount of fuel required for the engagement. In addition, a smaller change in the operating point of the internal combustion engine, which z. B. may have emission advantages.

The invention has been explained with reference to an example in which the belt tensioning device is designed as a decoupling tensioner. However, the type of belt tensioning device is not important for the implementation of the method, it can for example be applied in the presence of a commuter tensioner with two independent tensioners (idlers), which do not form an integral unit with the electric machine.

In addition, an application of the invention in the case of other types of mechanical connection except a belt drive between electric machine and internal combustion engine is possible in which a change in the sign of the torque of the electric machine brings adverse effects, such. B. by gearless when connected directly via gears or gears and chain drive.

LIST OF REFERENCE NUMBERS

1

Hybrid powertrain

2

motor vehicle

3

Internal combustion engine

4

Electric machine, belt starter generator (RSG)

5

clutch

6

crankshaft

7

Transmission input shaft

8th

transmission

9

Transmission output shaft

10

differential gear

11

drive axle

14

Bordnetzelekronik

15

hybrid battery

21

electronic control device

25

Arithmetic unit, processor

26

program memory

27

Value memory, data memory

40

Belt tensioner

41

machine housing

42

Shaft of the belt starter generator

43

Drive wheel of the belt starter generator

44

belt

44Z

Pulling the belt

44L

Slack of the belt

45

Drive wheel crankshaft

46

Drive wheel accessory

47

tensioner housing

48

firmly mounted tension pulley

49

movably mounted tension pulley

50

curved lever

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 102012209028 A1 [0005]

Claims (7)

Method for operating a motor vehicle ( 2 ) with a hybrid drive, the an internal combustion engine ( 3 ) and an electric machine ( 4 ), which mechanically with the internal combustion engine ( 3 ) and in a generator mode for converting one of the internal combustion engine ( 3 ) in electrical energy and in an engine operation for converting electrical energy into a torque for driving the internal combustion engine ( 3 ), wherein when switching from generator mode in the engine operation and vice versa, a change of sign of the torque of the electric machine ( 4 ), characterized in that at an operating point change of the hybrid drive ( 1 ) required torque change of the hybrid drive ( 1 ) via a torque intervention of the electric machine ( 4 ) only up to a predetermined distance from the sign change of the torque of the electric machine ( 4 ) he follows. Method according to Claim 1, characterized in that the distance value depends on the rotational speed of the internal combustion engine ( 3 ) or the electric machine ( 4 ). A method according to claim 1 or 2, characterized in that in the determination of the distance value, the permissible limits with respect to charging current and discharge current of one with the electric machine ( 4 ) coupled energy storage are taken into account. A method according to claim 1, characterized in that the remaining necessary torque change to implement the required torque value of the hybrid drive ( 1 ) taking into account the distance value from the internal combustion engine ( 3 ) is applied. Device for operating a motor vehicle ( 2 ) with a hybrid drive, which is designed to carry out a method according to one of claims 1 to 4, characterized in that the electric machine ( 4 ) is designed as a belt starter generator, which by means of a belt ( 44 ) with a drive wheel ( 45 ) of the internal combustion engine ( 3 ) and a belt tensioning device ( 40 ) with two tension rollers ( 48 . 49 ) for tensioning the belt ( 44 ) having. Method according to claim 5, characterized in that the belt tensioning device ( 40 ) is designed as a decoupling tensioner, which directly on the electric machine ( 4 ) is attached. Method according to claim 5, characterized in that the belt tensioning device ( 40 ) is designed as a pendulum clamp.

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