DE102009001293A1 - Drive train operating method for motor vehicle, involves presetting speed reference value such that reference value is increased starting from initial value to final value when crawling operation is started to limit torque to maximum value - Google Patents

Abstract

The method involves operating a drive train in a speed-controlled crawling operation when an accelerator pedal (5) and a brake pedal (6) are not operated such that a speed actual value is compared with a speed reference value. Crawling torque is produced as correcting variable based on deviation between the values such that the speed actual value approximates the speed reference value. The reference value is preset such that the speed reference value is increased starting from an initial value to a final value when the crawling operation is started to limit the torque to a maximum value.

Description

The The invention relates to a method for operating a drive train of a motor vehicle.

The Main components of a drive train of a motor vehicle are a drive unit and a transmission. The present invention relates a method of operating a powertrain. The invention Method is in a motor vehicle with a purely internal combustion engine Drive unit, in a pure electric vehicle whose drive unit exclusively formed by an electric machine is, as well as in a hybrid vehicle, the drive unit of an electric machine and an internal combustion engine formed becomes usable. In a pure electric vehicle, the transmission possibly omitted.

Out the prior art, it is already known, the drive train of a motor vehicle when in an automatic or automated Transmission of the powertrain is a gear engaged and a driver's pedal and a brake pedal of the drive train is not actuated are to operate in a creep operation, creeping in a Creep is provided so that the creep operated Motor vehicle can roll at a low speed.

From the DE 10 2006 003 714 A1 is a speed-controlled creep operation of a drive train known. In the speed-controlled creeping operation of a motor vehicle, a speed setpoint is preset, which is compared with a metrologically detected speed actual value, wherein a creep torque is generated on the basis of the deviation between the speed setpoint and the actual speed value as a manipulated variable for the drive unit of the motor vehicle.

One Such speed-controlled creep operation can be used as cause uncomfortable perceived driving behavior of the motor vehicle.

Of these, Based on the present invention, the problem underlying a novel method for operating a drive train of a To create motor vehicle.

This Problem is solved by a method according to claim 1 solved. According to the invention, if creeping operation is started, the speed command value is so given that the same starting from an initial value to a Final value is increased, with the generated creep on a maximum value is limited.

At the inventive method for operating a Drive train is in creep on the one hand, a target value for given the creep speed and on the other hand, the manipulated variable or The creep torque is limited, which makes it possible for the To increase comfort in speed-controlled creep. About that In addition, this can increase driving safety in creeping operation become.

preferred Further developments of the invention will become apparent from the dependent claims and the description below. An embodiment The invention is but not limited to Hand of the drawing explained in more detail. Showing:

1 a schematic drive train scheme of a motor vehicle, in which the inventive method is used.

1 shows a highly schematic diagram of a powertrain of a motor vehicle, in which the inventive method for operating a drive train can be used.

The in 1 The highly schematic drive train has a drive unit 1 and one between the drive unit 1 and a downforce 2 switched gear 3 , With the drive unit 1 It may be a pure combustion engine, a pure electric machine or a hybrid drive, which then includes both an electric machine and an internal combustion engine. Between the drive unit 1 and the gearbox 3 is a clutch 4 switched, via which the drive unit 1 from the downforce 2 can be disconnected. In a pure electric vehicle, the transmission may be omitted.

The powertrain of 1 also includes an accelerator pedal 5 , which can also be referred to as an accelerator pedal, wherein the operation of the accelerator pedal 5 In particular influence on the drive unit 1 Has. Furthermore, the drive train includes the 1 a brake pedal 6 where the operation of the brake pedal 6 in particular influence on a brake system 7 of the drive train has, which when pressing the brake pedal 6 at the output 2 provides a braking torque. The brake system 7 at the output 2 provided braking torque is thus on the operation of the brake pedal 6 dependent.

Then if at the in 1 shown drive train in the transmission 3 a gear is engaged and the accelerator pedal 5 as well as the brake pedal 6 are not operated, the drive train is operated in a creep operation, wherein in creep operation, the drive aggregate 1 Provides a creep, so that the motor vehicle can roll at low speed in crawl mode. In creeping operation, the present invention is a speed controlled creep operation.

When speed-controlled creep, as in 2 shown, proceeded so that a metrologically detected _actual speed _value V _{IST is} compared with a speed setpoint v _SOLL , wherein a deviation .DELTA.v between the speed setpoint v _SOLL and the _actual speed _value v _IST a controller 8th is supplied as input. The regulator 8th is output variable as a manipulated variable, namely a creep torque M for the drive unit 1 the powertrain, the regulator 8th the output creep torque M is such that the _actual speed value v _IST approaches the speed setpoint v _SOLL , or the deviation Δv between the _actual speed value v _IST and the speed setpoint v _{SOLL is} zero. According to 2 gives a setpoint generation unit 9 the speed setpoint v _SOLL .

For the purposes of the present invention, when a creeping operation of the drive train is started, the speed setpoint v _SOLL for the creep operation is set in such a way that the same is increased from an initial value to an end value. The increase of the speed setpoint v _SOLL from the initial value to the end value is preferably linear, the initial value for the speed setpoint v _{SOLL being} zero and the end value for the speed setpoint v _SOLL corresponding to a so-called step speed. After increasing the speed setpoint v _SOLL from the initial value to the final value, the speed setpoint v _{SOLL is} kept approximately constant in creep _mode at the final value.

The above provision of the speed _command value v _SHOULD at the start of creep operation by the command value generation unit 9 is in 3 shown schematically, wherein at time t _{0 of} the creep operation is started and between the times t ₀ and t _1, the speed setpoint v _SOLL for the creep from the initial value to the final value v _{MAX is increased} linearly or ramped.

After reaching the final value v _{MAX of} the speed setpoint v _SOLL , the speed setpoint is kept constant at the final value v _MAX .

Parallel to this setpoint specification is carried out in the sense of the present invention, a further limitation of the controller 8th output manipulated variable and thus a limitation of the controller 8th output creep torque M to a maximum value M _MAX .

With this limitation of the manipulated variable or of the controller 8th output creep torque is ensured that the drive train does not try to reach the speed setpoint v _SOLL with maximum possible starting torque. As a result, both a perceived as uncomfortable noise development and an unnecessarily high consumption of the motor vehicle can be avoided. Furthermore, such a setpoint limitation for safety reasons is advantageous.

In the 3 shown variant is when the creep operation at time t _2, for example, by pressing the brake pedal 6 should be terminated, the speed setpoint v _SOLL reduced from the final value v _MAX to the initial value, this reduction of the speed setpoint v _SOLL according to 3 between the times t ₂ and t ₃ again takes place linearly along a ramp.

Alternatively, it is possible that when the creep operation in particular by pressing the brake pedal 6 should be stopped, the speed control is terminated and that of the controller 8th output creep torque M is reduced to zero, in particular again linearly along a ramp.

Alternatively, it is also possible that the creep operation is not by pressing the brake pedal 6 but rather by pressing the accelerator pedal 5 is terminated, in which case the creep, which in creep mode by the controller 8th is output, is replaced by a dependent of the accelerator operation, predetermined by a driving strategy control torque. In this case, then a control torque for the drive unit 1 output, which is higher than the creep torque of the creep operation.

The limitation of creep operation by the controller 8th output creep torque M to a maximum value M _MAX is carried out using a manipulated variable limiting unit 10 , the maximum value M _MAX for the creep torque of the creep operation the regulator 8th provides.

The manipulated variable limiting unit 10 determines the creep maximum value M _MAX for limiting the creep torque M, preferably depending on a roadway inclination. In this case, when a motor vehicle is traveling uphill, a larger maximum value M _{MAX is given} for the creep torque M than in the case where the motor vehicle is traveling in a plane.

Alternatively or additionally, the manipulated variable limiting unit 10 the maximum value M valid in creep mode for limiting the controller 8th Issued creep M also depending on a slip between a road and wheels of the motor vehicle, in particular the driven wheels of the same, determine. In this case, when slip is detected between the road surface and the driven wheels of the motor vehicle, the maximum value M _MAX for the creep torque M is reduced. When slip is detected, therefore, a smaller maximum value M _{MAX is} output for limiting the creep torque M than in the case in which there is no slippage between the roadway and the driven wheels of the motor vehicle.

Alternatively or additionally, it is also possible that the manipulated variable limiting unit 10 in creep mode, the maximum value M _MAX for limiting the controller 8th determined certain creep torque depending on an identified by vehicle sensors travel obstruction. It is thus possible, for example, to detect driving obstacles with the aid of a camera and, depending thereon, that of the command value limiting unit 10 determined maximum creep torque M _MAX .

Becomes for example, using a camera, a lowered curb is detected, so can a higher maximum value for the creep output as if an uncut curb is detected, so as to ensure, for example, that in creep the motor vehicle overcome a lowered curb can, whereas the motor vehicle has a not lowered curb can not overcome in crawl.

Furthermore, it is alternatively or additionally possible in the sense of limiting the setting torque or creep torque M that the manipulated variable limiting unit 10 the maximum value M _MAX valid in creep mode for limiting the controller 8th output creep torque determined depending on a time history of creep operation. If it is determined, for example, that the motor vehicle does not reach the speed setpoint value v _TARG during creep operation within a predetermined time, then the control variable limiting unit can then be used 10 the maximum value M _MAX for the creep torque can be reduced in order to save energy, for example.

Only after another driver reaction, for example by pressing or releasing the brake pedal 6 , then becomes that of the manipulated variable limiting unit 10 output maximum creep torque M _MAX increased again.

It is therefore within the meaning of the present invention, for a speed-controlled creep operation of a powertrain of a motor vehicle on the one hand to specify the speed setpoint v _SOLL and on the other hand to limit the creep M in creep to a maximum value M _MAX .

1

power unit

2

output

3

transmission

4

clutch

5

accelerator

6

brake pedal

7

braking system

8th

regulator

9

Setpoint generation unit

10

Output limiting unit

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 102006003714 A1 [0004]

Claims (12)

Method for operating a drive train of a motor vehicle, wherein the drive train comprises a drive unit, an accelerator pedal and a brake pedal, wherein when the accelerator pedal and the brake pedal are not actuated, the drive train is operated in a speed-controlled creep operation such that a speed setpoint with a speed actual value and, based on the deviation between the speed command value and the actual speed value, a creep torque is generated so that the actual speed value approaches the speed command value, characterized in that, when a creep operation is started, the speed command value is set to be from a Initial value is increased to a final value, wherein the generated creep torque is limited to a maximum value. Method according to claim 1, characterized in that that the speed setpoint starts from the initial value the final value is increased linearly. Method according to claim 1 or 2, characterized that in creep mode after increasing the speed setpoint from the initial value to the final value of the speed reference is kept approximately constant at the final value. Method according to one of claims 1 to 3, characterized in that when the creep operation in particular is terminated by pressing the brake pedal, the speed setpoint is specified such that the same starting from the final value on the initial value is reduced. Method according to claim 4, characterized in that that the speed setpoint from the end value to the Initial value is reduced linearly. Method according to one of claims 1 to 3, characterized in that when the creep operation in particular is terminated by pressing the brake pedal, the cruise control finished and the creep torque is reduced. Method according to Claim 6, characterized that the creep torque is reduced linearly. Method according to one of claims 1 to 7, characterized in that when the creep operation in particular is terminated by pressing the accelerator pedal, the creep by a dependent of the accelerator operation Stellmoment is replaced. Method according to one of claims 1 to 8, characterized in that the valid in creep maximum value to limit the creep torque depending on a roadway inclination is determined. Method according to one of claims 1 to 9, characterized in that the valid in creep maximum value to limit the creep torque depending on a slip between a carriageway and wheels is determined. Method according to one of claims 1 to 10, characterized in that the valid in creep maximum value to limit the creep torque depending on a detected obstacle is determined. Method according to one of claims 1 to 11, characterized in that the valid in creep maximum value to limit the creep depending on determined whether the speed setpoint is in creep mode within a defined time is reached.