DE102010039375A1 - Powertrain operating method for motor car, involves selecting hybrid driving operation as operating mode of drive train via electric machine and internal combustion engine when accelerator pedal operation is larger than threshold value - Google Patents

Abstract

The method involves selectively changing required accelerator pedal actuation force or gradient by operation of an accelerator pedal of a drive train. An electric driving operation is selected as an operating mode of the drive train via an electric machine (3) and an internal combustion engine (2) when the accelerator pedal operation is less than a threshold value. A hybrid driving operation is selected as the operating mode of the drive train via the electric machine and the internal combustion engine when the accelerator pedal operation is larger than the threshold value.

Description

The invention relates to a method for operating a drive train according to the preamble of claim 1.

A drive train with a drive unit designed as a hybrid drive has an internal combustion engine and an electric machine. Between the drive unit and an output of such a drive train with a hybrid drive, a transmission is connected. In a purely electric drive, a drive torque is provided exclusively by the electric machine of the hybrid drive at the output of the drive train. In a hybrid ride, a drive torque is provided both at the output by the electric machine and the engine. The present invention relates to a method for operating such a drive train with a hybrid drive, wherein the internal combustion engine in purely electric driving, in which only the electric machine of the hybrid drive at the output of the drive train provides a drive torque, can be decoupled from the output and stopped. If, in such a drive train, the internal combustion engine is to be started starting from a purely electric drive with the internal combustion engine stopped, this can be done via the electric machine of the hybrid drive by using a torque provided by the electric machine to start the internal combustion engine. This can then form a collapse of the available drive torque at the output of the drive train.

A powertrain having a hybrid drive further includes a controller that selects an operating mode for the powertrain based on operating parameters of the powertrain, such as based on driver-side actuation of an accelerator pedal of the powertrain.

In this case, the control device, which can also be referred to as a hybrid control, select as operating mode for the drive train at least purely electric driving exclusively via the electric machine or hybrid driving over the electric machine and the internal combustion engine, decoupled from the output during purely electric driving of the engine and preferably is shut down or stands still. The selection of the operating mode for the drive train is therefore carried out automatically via the control device, with no possibility for the driver to specify reproducible and safe purely electric driving via an actuation of the accelerator pedal. Rather, additional operating devices are installed for this purpose in motor vehicles with a hybrid drive, such as buttons or switches in the vehicle cockpit, via which the driver can specify as operating mode purely electric driving with the internal combustion engine stopped.

On this basis, the present invention based on the problem to provide a novel method for operating a drive train. This problem is solved by a method according to claim 1. According to the invention, when the drive train has an accelerator pedal in which the required accelerator pedal actuation force or the gradient thereof changes discontinuously at least selectively and the accelerator pedal actuation is still less than a limit value, the operating mode of the powertrain is purely electric driving exclusively via the electric machine is selected with the internal combustion engine stopped, whereas when the accelerator pedal operation is greater than a limit value in such an accelerator pedal, as the operating mode of the powertrain hybrid driving over the electric machine and the internal combustion engine is selected.

With the method according to the invention, the possibility is opened up for the first time that the driver can select safe and reliable purely as an operating mode purely electric driving with the internal combustion engine switched off purely via the actuation of the accelerator pedal. For this purpose, an accelerator pedal is used, in which the accelerator pedal actuation required for actuating the accelerator pedal accelerator pedal actuation force or a gradient of the same points discontinuously changes, namely to form at least one pressure point to be overcome. Then, when the accelerator operation is smaller than a lower limit, that is below a pressure point to be overcome, is selected as the operating mode of the powertrain purely electric driving only via the electric machine with the engine stopped shutdown. Then, on the other hand, when the accelerator pedal operation is greater than an upper limit value, ie above the pressure point to be overcome, hybrid mode is selected as the operating mode of the powertrain via the electric machine and the internal combustion engine, for which purpose the internal combustion engine is automatically started or started becomes.

Accordingly, there is a safe and reproducible possibility for the driver to select purely electric driving with the internal combustion engine switched off or the internal combustion engine switched off via the actuation of the accelerator pedal without any additional operating devices exclusively via a defined accelerator pedal actuation.

According to an advantageous embodiment of the invention, this selection of the operating mode is dependent on the accelerator pedal actuation speed dependent, namely only when the vehicle speed is less than a limit. Then, when the vehicle speed is above the threshold, accelerator operation is interpreted by the powertrain controller as in a conventional driving strategy.

Preferably, if based on the above evaluation of the accelerator pedal operation as operating mode of the powertrain purely electric driving is selected exclusively via the electric machine with the engine stopped, depending on the accelerator pedal operation of the electric machine maximum torque provided on the drive, which corresponds to the maximum torque of the electric Machine minus a torque required to start the engine corresponds. The above limitation of the torque provided by the electric machine at the output ensures that in a subsequent starting of the internal combustion engine via the electric machine no tensile force intrusion occurs at the output, since then the electric machine safe the starting torque required to start the engine in addition to the provided drive torque can muster. This allows a particularly comfortable starting of the internal combustion engine from a purely electric drive with the internal combustion engine stopped.

Preferred embodiments of the invention will become apparent from the dependent claims and the description below. Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. Showing:

1 a schematic of a drive train to illustrate the method according to the invention for operating a drive train;

2 a diagram for further clarification of the method according to the invention.

The present invention relates to a method for operating a drive train of a motor vehicle with a drive unit designed as a hybrid drive.

1 shows very schematically an exemplary drive train scheme of a motor vehicle with hybrid drive, in which the inventive method can be used.

So shows 1 a schematic of a powertrain with a drive unit 1 , which is designed as a hybrid drive and an internal combustion engine 2 as well as an electric machine 3 includes. Between the drive unit 1 , namely in the embodiment shown between the electric machine 3 the same, and an output 4 is a transmission 5 switched, it is the gearbox 5 For example, it may be an automated manual transmission or an automatic powershift transmission or a continuously variable transmission.

The internal combustion engine 2 of the drive unit 1 is for purely electric driving from the output 4 decoupled and can be stopped, including in the embodiment shown the 1 between the internal combustion engine 2 and the electric machine 3 the hybrid drive a clutch 6 is switched. Then, when the clutch 6 is open, is the internal combustion engine 2 from the downforce 4 decoupled. Then, on the other hand, when the clutch 6 is closed, is the internal combustion engine 2 to the output 4 decoupled. The coupling 6 can also be replaced by a planetary gear.

The powertrain of 1 further comprises a control device 7 which selects a drive train operating mode based on powertrain operational parameters. Thus, the control device 7 as operating mode, for example, purely electric driving over the electric machine 3 when the internal combustion engine is stopped 2 choose. Furthermore, the control device 7 as operating mode hybrid driving over the electric machine 3 and the internal combustion engine 2 choose.

As already stated, the controller determines 7 the mode of operation for the drive train depending on operating parameters of the drive train, as well as dependent on a driver-side operation of an accelerator pedal 8th of the powertrain. The accelerator pedal 8th is also called accelerator pedal.

The inventive method for operating a drive train requires that in the drive train an accelerator pedal 8th is used, in which above an accelerator operation x (see 2 ) for operating the accelerator pedal 8th required accelerator operation force F or a gradient of the accelerator operation force F selectively changes discontinuously.

So take according to 2 via the accelerator pedal actuation x, the required accelerator operation force F zu, but with different gradients, namely in a first range for accelerator operation x between 0% and x1 with a relatively flat gradient, in a second range between x1 and x2 with a relatively steep gradient and in a third range between x2 and 100% with a middle gradient, which lies between the relatively flat gradient of the first region and the relatively steep gradient of the second region. Accordingly, in the points x1 and x2 of the accelerator pedal operation in which the respective accelerator pedal operating forces F1 and F2 act, a gradient of the accelerator opening force F changes discontinuously. It is possible that the points x1 and x2 coincide, in which case accelerator operation force would change discontinuously.

Such a dependency of the accelerator pedal operating force F on the accelerator operation x can, as 1 shows, for example, be provided by the accelerator pedal 8th two spring elements 9 and 10 comprising, namely a first spring element 9 which is active over the entire accelerator operation x, and a second spring element 10 , which is only active when the accelerator pedal 8th has already been operated by a defined amount.

With reference to 2 This means that the spring element 9 is active over the entire accelerator pedal actuation x between 0% and 100%, the spring element 10 On the other hand, it only becomes active or effective from accelerator pedal actuation x1. In this way, in the accelerator pedal travel x of the accelerator pedal 8th provided a pressure point with an increased accelerator operation force F, this pressure point is determined by the accelerator pedal operations x1 and x2. As already mentioned, x1 and x2 can also coincide.

According to the invention, it is now proposed that if the accelerator pedal actuation x is smaller than a limit value, then, for example, smaller than the limit value x1 in FIG 2 , as the operating mode for the drive train purely electric driving exclusively via the electric machine 3 when the internal combustion engine is stopped 2 is selected. In this case, then is the shutdown internal combustion engine 2 from the downforce 4 decoupled.

Then, on the other hand, when the accelerator operation is greater than a threshold, for example, greater than the in 2 shown limit x2, is used as the operating mode for the powertrain hybrid driving over the internal combustion engine 2 and the electric machine 3 selected, then the internal combustion engine 2 to the output 4 is coupled.

When accelerator pedal operations x between x1 and x2 is preferably as the operating mode and purely electric driving exclusively on the electric machine 3 when the internal combustion engine is stopped 2 selected. In the case of accelerator pedal actuations x between x1 and x2, hybrid mode can alternatively be used as operating mode via the electric machine 3 and the internal combustion engine 2 to be selected.

The above limits x1 and x2 may also coincide.

Then, when the accelerator pedal operation x is smaller than the limit value x2, pure electric driving is selected as the operation mode. On the other hand, when the accelerator operation x is greater than the limit value x2, hybrid driving is selected as the drive train operating mode.

Below a pressure point to be overcome in the accelerator operation, therefore, as the operating mode purely electric driving exclusively on the electric machine 3 when the internal combustion engine is stopped 2 whereas when the pressure point in the accelerator operation is exceeded as the operating mode of the powertrain, hybrid driving via the electric machine is selected 3 and the internal combustion engine 2 is selected.

In this way can be selected by the driver exclusively on the operation of the accelerator pedal without the need for an additional control element purely electric driving with the internal combustion engine stopped as the operating mode for the drive unit.

The lower the power of the electric machine 3 of the hybrid drive, the closer the limit values x1 and x2 should be to 0%. In a reasonable example, x1 is 10% and x2 is 15%. Until the accelerator operation x1 or x2, a start of the internal combustion engine is suppressed.

Preferably, this inventive selection of the operating mode is dependent on the accelerator operation of the accelerator pedal 8th speed-dependent, namely only when the driving speed of the drive train is less than a limit value. By contrast, at driving speeds above the limit, an accelerator operation is conventionally interpreted to automatically select a powertrain operating mode therefrom.

Then, if in the manner according to the invention at relatively low driving speeds based on the above evaluation of the accelerator operation of the accelerator pedal 8th as operating mode of the powertrain purely electric driving exclusively via the electric machine 3 when the internal combustion engine is stopped 2 is selected by the electric machine 3 at the output 4 provided a maximum of a moment, which is the maximum torque of the electric machine 3 less one to start the internal combustion engine 2 required moments corresponds.

This ensures that, when the limit value is exceeded in the accelerator operation, starting from which the internal combustion engine 2 is started from the electric machine 3 even that for starting the internal combustion engine 2 required moment can be deployed without being at the output 4 the drive train sets a reduction in the traction.

In this way, a particularly comfortable transition from the operating mode of the purely electric driving to the operating mode of the hybrid driving takes place, wherein the states of the internal combustion engine 2 over the electric machine 3 in the powertrain of 1 the between the internal combustion engine 2 and the electric machine 3 switched clutch 6 is closed.

Preferably, this is the purely electric driving of the electric machine 3 at the output 4 provided moment, which maximum the maximum torque of the electric machine 3 minus that for starting the internal combustion engine 2 required torque, with increasing accelerator pedal operation x between 0% and in particular the lower limit x1 continuously constructed, ie until reaching the pressure point in the accelerator pedal actuation.

According to a further advantageous embodiment of the invention can be provided that, if based on the evaluation of the accelerator pedal operation of the accelerator pedal according to the invention 8th as operating mode for the drive train purely electric driving exclusively via the electric machine 3 when the internal combustion engine is stopped 2 is selected, depending on the accelerator operation at low speeds in the accelerator pedal operating range between 0% and in particular the lower limit x1 depending on the accelerator pedal actuation set a speed setpoint for the vehicle speed and the drive train is operated speed controlled.

It is then preferably the speed setpoint for the speed-controlled operation depending on the accelerator pedal operation in particular until reaching the lower limit x1 and thus increased until reaching the pressure point continuously.

In this speed-controlled operation, that is at the output 4 provided drive torque and / or the acceleration of the drive train limited to a limit in order to ensure a high ride comfort.

It is therefore within the meaning of the present invention that a driver exclusively via the operation of the accelerator pedal 8th especially at driving speeds that are less than a limit, as the operating mode purely electric driving over the electric machine 3 at the output 4 coupled and stopped internal combustion engine 2 can pretend driver. This makes it possible, driver side a Zustart the engine 2 to suppress the driver's side emission-free, low-noise operation of the powertrain.

In the event that, when in such a driver selected operating mode, a state of charge of one with the electric machine 3 can cooperate, electrical energy storage drops below a threshold, it can be provided that the motor vehicle is stopped or, alternatively, the internal combustion engine 2 is forcibly started to allow continued operation of the motor vehicle.

LIST OF REFERENCE NUMBERS

1

power unit

2

internal combustion engine

3

electric machine

4

output

5

transmission

6

clutch

7

control device

8th

accelerator

9

spring element

10

spring element

Claims (9)

Method for operating a drive train of a motor vehicle, wherein the drive train comprises a designed as a hybrid drive unit with an internal combustion engine and an electric machine and a switched between the drive unit and an output gear, wherein the internal combustion engine in purely electric driving via the electric machine from the output and decoupled can be stopped, depending on a driver-side accelerator operation as the operating mode of the drive train at least purely electric driving exclusively on the electric machine or hybrid driving on the electric machine and the internal combustion engine is selected, characterized in that when the drive train has an accelerator pedal, in which the required accelerator pedal actuation force or the gradient thereof changes discontinuously over the accelerator pedal actuation at least occasionally, and if, furthermore, the accelerator pedal actuation is smaller than a ls is a limit, is selected as the operating mode of the powertrain purely electric driving exclusively via the electric machine with the engine stopped, whereas when the accelerator pedal operation is greater than a threshold value in such an accelerator pedal, as the drive train operating mode, hybrid driving is selected via the electric machine and the engine. A method according to claim 1, characterized in that the accelerator pedal has to be overcome in the accelerator operation to pressure point to be selected in an accelerator pedal operation below the pressure point as the operating mode of the powertrain purely electric driving exclusively via the electric machine with the internal combustion engine, whereas with exceeding the pressure point is selected as the operating mode of the powertrain hybrid driving over the electric machine and the internal combustion engine. A method according to claim 2, characterized in that when the pressure point is exceeded, the previously stopped internal combustion engine is started automatically, in particular via the electric machine. Method according to one of claims 1 to 3, characterized in that when based on the above evaluation of the accelerator pedal operation as the operating mode of the powertrain purely electric driving is selected exclusively via the electric machine with the engine stopped, depending on the accelerator pedal operation of the electric machine maximum a moment is provided on the output, which corresponds to the maximum torque of the electric machine less a torque required for starting the internal combustion engine. A method according to claim 4, characterized in that in this case the provided by the electric machine at the output torque is increased depending on the accelerator operation until reaching the pressure point. Method according to one of claims 1 to 5, characterized in that when based on the above evaluation of the accelerator pedal operation as the operating mode of the powertrain purely electric driving is selected exclusively via the electric machine with the engine stopped, depending on the accelerator operation, a speed setpoint for the driving speed specified and the drive train is operated speed controlled. A method according to claim 6, characterized in that in this case the speed setpoint for the speed-controlled operation is increased depending on the accelerator operation until reaching the pressure point. A method according to claim 6 or 7, characterized in that in this case a provided on the drive torque and / or acceleration of the drive train is limited. Method according to one of claims 1 to 8, characterized in that this selection of the operating mode is dependent on the accelerator pedal actuation speed-dependent, namely only when the vehicle speed is less than a threshold.

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