DE102014202058A1 - Reduction of drag torque fluctuations during electrical starting - Google Patents

Abstract

The invention relates to a method for operating a motor vehicle (2), in which the electric motor (8) is driven to output a torque during a starting operation with an electric motor (8) coupled to an internal combustion engine (6) of the motor vehicle (2) the torque output by the electric motor contains a crankshaft angle-dependent component (MSM) which counteracts fluctuations in the crankshaft angle of a drag torque of the internal combustion engine (6). A corresponding Anfahrregler (14) and a computer program are also the subject of the invention.

Description

The present invention relates to a method for operating a motor vehicle, a computing unit for its implementation and a computer program for operating a motor vehicle.

State of the art

For a comfortable start of an internal combustion engine of a motor vehicle from a standstill, it is necessary to decouple the internal combustion engine from the drive wheels or a transmission of the motor vehicle. This is done by opening a clutch arranged between the internal combustion engine and the drive wheels or selecting a neutral gear of the transmission. A start without clutch by means of an electric motor is known in electric vehicles. In contrast, in hybrid vehicles, it is necessary to decouple the internal combustion engine for its start from a standstill out of a drive axle or the drive wheels.

In a starting operation with an electric motor with a coupled internal combustion engine vibrations are excited in the motor vehicle by the uneven course of the engine drag torque of the internal combustion engine, e.g. by compression and decompression processes in the compression or power stroke of the internal combustion engine. These vibrations and thus caused shaking and noise caused the starting process is uncomfortable.

There is therefore a need to show ways, such as a comfortable starting and starting an internal combustion engine with the aid of an electric motor with the drive train closed, i. can be made possible with direct coupling with the internal combustion engine without actuation of the clutch.

Disclosure of the invention

According to the invention, a method for operating a motor vehicle, a computing unit and a computer program having the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

An essential aspect of the present invention is that in a starting process with a coupled to an internal combustion engine of the motor vehicle, the electric motor output torque from the crankshaft angle is determined so that it contains a proportion counteracts the crankshaft angle dependent fluctuations in the drag torque of the engine and compensated as possible , Appropriately, the drag torque to be compensated is determined as dependent on the crankshaft angle for the determination of the proportion.

Here, under a starting operation of a motor vehicle, the section between standstill of the motor vehicle and reaching a vehicle speed at which the internal combustion engine can record the fired operation, understood with an engaged forward or reverse gear. This ensures that a comfortable starting and starting an internal combustion engine smoothly by means of the electric motor with the drive train closed, i. in direct coupling with the internal combustion engine, is made possible. Smooth-free is understood to mean an acceleration that is perceived by occupants of the motor vehicle as uniform and without fluctuation. In particular, the acceleration of occupants of the motor vehicle over a longer period of time is perceived as steadily increasing.

Preferably, the control of the electric motor takes place depending on the crankshaft angle by means of feedforward control, in particular without detecting the engine drag moment in real time. The dependence of the drag torque of the internal combustion engine on the crankshaft angle can be detected, for example, on a test bench and stored in a map.

Advantageously, the drag torque to be compensated is determined as a function of an engine temperature and / or an engine speed and / or a cylinder fill level.

During the starting operation, an engine starting position (i.e., crankshaft angle) is appropriately detected. By detecting the engine starting position, for example, a starting resistance (force that must be overcome to set the engine in motion) can be considered. The dependence of the starting resistance of the internal combustion engine from the starting position can be detected, for example, on a test bench and stored in a map.

According to one embodiment, a throttle valve of the internal combustion engine is controlled in a closed position during the starting process. This ensures that by reducing the cylinder filling the engine drag torque is made uniform. This leads to a further homogenization. Furthermore, the method can be used, for example, in a hybrid drive with a small electric motor, such as in a micro hybrid with a power of eg 2.7 kW / t to 4 kW / t (specific power to weight in kilowatts of electric power per ton Vehicle mass) or a mild hybrid with a power of eg 6 kW / t to 14 kW / t.

According to a further embodiment, intake and / or exhaust valves of the internal combustion engine are controlled to a closed position during a starting process. In this way it is also achieved that the internal combustion engine drag torque is made uniform by reducing the cylinder charge. This leads to a further homogenization. Again, the method can be used e.g. also be used in a hybrid drive with a small electric motor, such. in a microhybrid or a mild hybrid.

According to a further embodiment, an engaged gear of a transmission of the motor vehicle is detected and controlled in dependence on the engaged gear, the electric motor. This ensures that in the control of the electric motor and the selected gear ratio can be taken into account by the engaged gear. This improves the determination of the torque to be delivered.

According to a further embodiment, a road gradient angle is detected and controlled in dependence on the road gradient angle of the electric motor. In this way it is achieved that in the control of the electric motor and a road incline angle can be taken into account, if, for. a startup takes place on a mountain. It is readily apparent from known physical contexts how the road grade, in particular in connection with the vehicle weight, influences the torque to be delivered via a downhill force. This improves the determination of the torque to be delivered.

According to a further embodiment, a motor vehicle weight of the motor vehicle is detected, for example by axle load sensors, and driven in dependence on the motor vehicle weight of the electric motor. Both downgrade force and rolling resistance and starting resistance of the vehicle are dependent on the vehicle weight, so that with knowledge of the torque to be delivered can be calculated more accurately.

According to a further embodiment, a gas actuation element position (for example accelerator pedal position) of the motor vehicle is detected and the electric motor is activated as a function of the gas actuation element position. It is thereby achieved that when the electric motor is actuated, the speed desired by the driver can also be taken into account by actuating the gas actuating element for acceleration, that is to say in particular of the accelerator pedal.

According to a further embodiment, a speed actual value and / or a time and / or a crankshaft angle and / or an engine temperature and / or an engine speed and / or a cylinder fill level are detected and the electric motor is activated in dependence thereon. In this way it is achieved that during the control of the electric motor, a speed actual value and / or a time and / or a crankshaft angle and / or an engine temperature and / or an engine speed and / or a cylinder fill level can also be taken into account. This leads to a further homogenization.

An arithmetic unit according to the invention, e.g. a Anfahrregler a motor vehicle is, in particular programmatically, adapted to perform a method according to the invention.

The implementation of the method in the form of software is also advantageous, since this causes particularly low costs, in particular if an executing computing unit, e.g. with such a start-up controller, is still used for other tasks and therefore already exists. Suitable data carriers for providing the computer program are, in particular, floppy disks, hard disks, flash memories, EEPROMs, CD-ROMs, DVDs and the like. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described in detail below with reference to the drawing.

Brief description of the drawings

1 shows a motor vehicle in a schematic representation,

2 shows a Anfahrregler for such a motor vehicle in a schematic representation, and

3 shows a further component of the Anfahrreglers in a schematic representation.

Embodiment (s) of the invention

The 1 shows a motor vehicle 2 , which is formed in the present embodiment as a passenger car. Deviating from this, the motor vehicle 2 but also be designed as a commercial vehicle, for example.

The car 2 has a hybrid drive 4 with an internal combustion engine 6 and an electric motor 8th on. In the present embodiment, the hybrid drive is a mild hybrid and the internal combustion engine 6 is a gasoline or diesel engine. The hybrid drive 4 is in the present embodiment via a manual clutch 10 with a manual gearbox 12 driving force transmitting connected. With the manual clutch 10 can be a powertrain of the motor vehicle 2 from the hybrid drive 4 As is known, a gear change with the manual transmission 12 perform. In other words, the motor vehicle 2 a manual transmission. Alternatively, the motor vehicle 2 also have an automatic or semi-automatic transmission.

Furthermore, the motor vehicle 2 one in 2 schematically illustrated Anfahrregler 14 for a starting process and start of the internal combustion engine 6 with the help of the electric motor 8th with the drive train closed, ie with the manual clutch closed 10 , on. The approach controller 14 is preferably implemented by programming in a control unit.

The approach controller 14 has in the present embodiment, a target speed determination unit 16 , a regulator 18 , an engine drag torque determination unit 20 and a torque pilot control unit 22 on. The regulator 18 essentially serves that purpose by the electric motor 8th given torque so that the desired speed is reached. The engine drag torque determination unit 20 is used together with the torque pilot control unit 22 essentially, that of the electric motor 8th Torque output to vary so that there are crankshaft angle-dependent fluctuations in a drag torque of the internal combustion engine 6 counteracts, ideally compensated for this to zero.

Furthermore, the Anfahrregler 14 a control unit 24 for controlling the electric motor 8th the hybrid drive 4 on.

The target speed determination unit 16 in the present exemplary embodiment is designed or set up to read in as input variables a time t, a road gradient angle w, a motor vehicle weight m and a gas actuator element position x, in particular of the accelerator pedal. From these input variables, the target speed determination unit determines 16 a speed setpoint GSW. Preferably, the target speed determination unit 16 adapted to determine the speed setpoint GSW so that the starting process is pleasant for occupants, ie an adequate vehicle acceleration is achieved. In particular, too large torques and too low torques should be avoided. Excessively high torque causes too much acceleration, which is not pleasant for occupants (unless it is desired by the driver) (kickdown or too much throttle)), too low torque can promote vibration at startup because the powertrain and engine block will last longer be operated in their own resonance band.

The speed setpoint GSW is an input variable of the controller 18 which has a PID controller in the present embodiment. Another input is the controller 18 a detected actual speed value GIW of the motor vehicle 2 fed. The controller supplies as output 18 a manipulated variable STG, that of the control unit 24 is supplied. It should be emphasized that setpoint speed determination unit and controller in the exemplary embodiment are shown by way of example only and represent only advantageous, but not mandatory features of the invention.

The engine drag torque determination unit 20 In the present exemplary embodiment, it is designed or set up to read in as input variables a crankshaft angle α, an engine temperature T, an engine rpm n and a cylinder fill factor f. The engine drag torque determination unit determines from these input variables 20 an engine drag torque MSM, in particular using maps that the control unit 24 is supplied. It should be emphasized that, apart from the crankshaft angle α, all other input variables are optional.

The torque pilot control unit 22 is designed or set up in the present embodiment, as inputs an inlaid gear g of the transmission 12 to read in an engine starting position p, the road gradient angle w and the vehicle weight m. The torque feedforward control unit determines from these input variables 22 a torque control variable DST, that of the control unit 24 is supplied. The torque pilot control unit 22 essentially serves to take account of variables (ie to counteract or ideally to compensate for zero), which in a crankshaft angle-independent manner affect the torque to be delivered, in particular the starting resistance, rolling resistance, downgrade. It should be emphasized that the torque pilot control unit in the exemplary embodiment is shown by way of example only and does not constitute an obligatory feature of the invention.

The control unit 24 is designed or set up to evaluate the manipulated variable STG, the engine drag torque MSM and the torque manipulated variable DST, and the electric motor 8th the hybrid drive 4 to control such that the engine drag as possible compensated and thereby a start-up and starting the engine 6 the hybrid drive 4 is uniformed, that is essentially smooth. Smooth-free is understood to be an acceleration that is used by occupants of the motor vehicle 2 is perceived as even and without fluctuation. In particular, the acceleration is perceived as continuous over a longer period of, for example, several seconds.

The approach controller 14 , the target speed determination unit 16 , the regulator 18 , the engine drag torque determination unit 20 , the torque pilot control unit 22 and the control unit 24 may include hardware and / or software components.

In 3 is another possible component of the start-up controller 14 shown in a schematic representation, namely a ventilation regulator 26 ,

The ventilation controller 26 is adapted to read in a stop signal s that is logical 1 is when the internal combustion engine 6 the hybrid drive 4 stands still. On the output side is the aeration controller 26 for controlling at least one throttle valve 28 and / or intake / exhaust valves 30 the internal combustion engine 6 the hybrid drive 4 educated.

Also the ventilation regulator 26 may include hardware and / or software components.

In operation, the target speed determination unit reads 16 the time t, the road gradient angle w, the vehicle weight m and the gas actuator element position x and determines therefrom the speed setpoint GSW.

The speed setpoint GSW and the detected actual speed value GIW become the controller 18 supplied, which determines therefrom the manipulated variable STG, the control unit 24 is supplied.

The engine drag torque determination unit 20 reads the crankshaft angle α and optionally the engine temperature T, the engine speed n and the cylinder filling degree f and determines therefrom the engine drag torque MSM, that of the control unit 24 is supplied.

The torque pilot control unit 22 reads the engaged gear g of the transmission 12 , the engine starting position p, the road gradient angle w and the vehicle weight m, and determines therefrom the torque manipulated variable DST, that of the control unit 24 is supplied.

The control unit 24 then controls the electric motor based on the manipulated variable STG, the engine drag torque MSM and the torque control variable DST 8th the hybrid drive 4 such that a substantially smooth starting and starting of the internal combustion engine 6 the hybrid drive 4 be effected.

Before the control unit 24 the electric motor 8th the hybrid drive 4 controls, reads the aeration controller 26 the stop signal s on, the logical 1 is when the internal combustion engine 6 the hybrid drive 4 stands still. The ventilation controller then controls 26 the throttle 28 in a closed position and / or the intake / exhaust valves 30 in a closed position to reduce engine drag torque unevenness, thus causing further equalization of torque, in that acceleration is judged to be smooth.

Claims (12)

Method for operating a motor vehicle ( 2 ), in which at a starting process with a to an internal combustion engine ( 6 ) of the motor vehicle ( 2 ) coupled electric motor ( 8th ) the electric motor ( 8th ) is driven so as to deliver a torque, that of the electric motor ( 8th ) torque contains a crankshaft angle-dependent component (MSM), the crankshaft angle-dependent fluctuations in a drag torque of the internal combustion engine ( 6 ) counteracts. Method according to Claim 1, in which the determination of the crankshaft angle-dependent component (MSM) takes place by means of precontrol. Method according to Claim 1 or 2, in which the crankshaft angle-dependent component (MSM) is determined as a function of an internal combustion engine temperature and / or an engine rotational speed and / or a cylinder fill level. Method according to one of the preceding claims, in which a throttle valve ( 28 ) of the internal combustion engine ( 6 ) is controlled in a closed position. Method according to one of the preceding claims, in which intake and / or exhaust valves ( 30 ) of the internal combustion engine ( 6 ) are controlled in a closed position. Method according to one of the preceding claims, in which that of the electric motor ( 8th ) torque contains a crankshaft angle independent component (DST), which counteracts quantities that act in crankshaft angle independent manner on the torque to be delivered. Method according to Claim 6, in which the crankshaft angle-independent component (DST) is determined as a function of an engine start position (p). Method according to Claim 6 or 7, in which the crankshaft angle-independent component (DST) is dependent on an engaged gear (g) of a transmission ( 12 ) of the motor vehicle ( 2 ) and / or in dependence on a road gradient angle (w) and / or in dependence on a motor vehicle weight (m) of the motor vehicle ( 2 ) is determined. Method according to one of the preceding claims, in which a gas actuation element position (x) of the motor vehicle ( 2 ) and depending on the gas actuator element position (x) of the electric motor ( 8th ) is driven. Arithmetic unit ( 14 ), which is adapted to perform a method according to any one of claims 1 to 9. Computer program comprising a computing unit ( 14 ) to perform a method according to any one of claims 1 to 9, when it on the computing unit ( 14 ) is performed. Machine-readable storage medium with a computer program stored thereon according to claim 11.

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