DE102010003935A1 - Method for operating a drive train - Google Patents

Abstract

Method for operating a drive train with a drive unit (1) and an automatic or automated transmission (2) connected between the drive unit (1) and an output (3), the drive unit (1) being a hybrid drive with an internal combustion engine (4) and an electric machine (5) is formed, wherein a disconnect clutch (6) is connected between the internal combustion engine (4) and the electrical machine (5), via which the internal combustion engine (1) can be decoupled from the output (3), the transmission (2) comprises a hydraulic pump (12) which can be driven mechanically as a function of a transmission input speed in order to apply hydraulic pressure to hydraulic consumers, and if the transmission input speed is not high enough, especially when the drive train is at a standstill, to use the hydraulic pump (12) to to apply hydraulic pressure to hydraulic consumers, the hydraulic pressure for the hydraulic consumers via a the hydraulic volume accumulator (13) assigned to the transmission (2) is provided.

Description

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

A drive train of a hybrid vehicle has a drive unit designed as a hybrid drive with an internal combustion engine and an electric machine, wherein a transmission, namely an automatic or automated transmission, is connected between the hybrid drive and an output. In a so-called parallel hybrid powertrain, a disconnect clutch is connected between the internal combustion engine of the hybrid drive and the electric machine thereof, via which the internal combustion engine can be completely decoupled from the output. In addition, such a drive train has a starting element, wherein the starting element may be a gear-internal starting element or a gear-external starting element.

The transmission of such a powertrain has a hydraulic pump which can be mechanically driven depending on a transmission input speed of the transmission. Then, when the engine is decoupled from the output and the vehicle is stationary, the transmission hydraulic pump can not be driven to provide hydraulic pressure to hydraulic consumers. Therefore, it is already known in practice known drive trains with a hybrid drive, the transmission in addition to the mechanically driven hydraulic pump additionally assign an electrically driven hydraulic pump, which, if no sufficient hydraulic pressure for hydraulic consumers can be provided by the mechanically driven hydraulic pump, the mechanical Hydraulic pump supported.

However, such an auxiliary electric hydraulic pump is needed only for some operating states of the drive train and thus only for a small proportion of the total operating time of the drive train. Since such an electric auxiliary hydraulic pump on the one hand is costly and on the other hand requires a relatively large amount of space, there is a need for a method for operating a drive train with which such an electric auxiliary hydraulic pump can be dispensed with.

From the DE 43 23 133 A1 is the basic structure of a hydraulic volume memory known.

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 transmission input speed is not sufficiently high, in particular when the drive train is at a standstill, to apply hydraulic pressure to the hydraulic consumers via the hydraulic pump, the hydraulic pressure for the hydraulic consumers is made available via a hydraulic volume accumulator assigned to the transmission.

With the present invention, it is first proposed, then, if the mechanically driven hydraulic pump of the transmission can not provide sufficient hydraulic pressure for hydraulic consumers to provide the hydraulic pressure via a hydraulic volume accumulator associated with the transmission, whereby it is then possible to complete an electric auxiliary hydraulic pump to renounce. This not only saves costs and installation space, but also reduces the electrical energy requirement, since a hydraulic volume accumulator requires less electrical energy than an electric auxiliary hydraulic pump.

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 block diagram of a drive train;

2 Details of the powertrain of 1 ;

3 a diagram for illustrating the method according to the invention for operating a drive train;

4 a further diagram for illustrating the method according to the invention for operating a drive train;

5 a further diagram for illustrating the method according to the invention for operating a drive train; and

6 a further diagram to illustrate the inventive method for operating a drive train.

The present invention relates to a method for operating a drive train of a hybrid vehicle, wherein such a drive train in addition to a drive unit 1 and one transmission 2 an output 3 includes. The drive unit 1 The hybrid powertrain has an internal combustion engine 4 and an electric machine 5 , being between the internal combustion engine 4 and the electric machine a disconnect clutch 6 is switched, and wherein the electric motor 5 in a transmission input shaft of the transmission 2 one rubs. Then, when the disconnect clutch 6 is open, is the internal combustion engine 4 from the transmission input shaft of the transmission 2 and thus the downforce 3 decoupled. For coupling the internal combustion engine 4 to the output 3 is the disconnect clutch 6 closed. Such a drive train is also referred to as a parallel hybrid.

2 shows details of the powertrain of the 1 , namely in particular details of the transmission 2 , where im in 2 shown embodiment of the transmission 2 a total of five switching elements 7 . 8th . 9 . 10 and 11 includes. At the switching elements 7 and 8th , which are also referred to as switching elements A and B, are brakes. At the switching elements 9 . 10 and 11 of the transmission 2 , which are also referred to as switching elements C, D and E, are couplings.

At the in 2 shown gear 2 are in each movable gear three switching elements of the switching elements 7 to 11 closed and two switching element of the switching elements 7 to 10 open. To start serves in the transmission 2 of the 2 one of the internal gear shift elements 7 to 11 As an internal gear starting element In contrast, it is also possible that as a starting element, a separate starting element, either a separate, internal gear starting element or a separate, gear-external starting element, is present.

As 1 can still be removed is the transmission 2 of the drive train shown there, a hydraulic pump 12 assigned. In this hydraulic pump 12 of the transmission 2 it is a mechanically driven hydraulic pump, which depends on a transmission input speed of the transmission 2 is driven and a hydraulic pressure for hydraulic consumers, in particular for the switching elements 7 to 11 of the transmission 2 as well as the separating clutch 6 , provides. Then, if under defined operating conditions of the drive train, especially at standstill of the same at the output 3 uncoupled combustion engine 4 , the hydraulic pump 12 can provide sufficient hydraulic pressure for the hydraulic consumers, according to the invention, the hydraulic pressure for the hydraulic consumers via the transmission 2 assigned, hydraulic volume storage 13 provided, this hydraulic volume accumulator 13 preferably in the transmission 2 is integrated.

It is therefore within the meaning of the present invention then, if the the transmission 2 assigned, mechanically driven hydraulic pump 12 can not provide sufficient hydraulic pressure, this one through the gearbox 2 assigned, hydraulic volume storage 13 provide.

Because such a hydraulic volume storage 13 However, only has a limited flow and thus has limited hydraulic pressure for hydraulic consumers can provide, will be described in detail below, which are to execute particular process steps in particular for starting or creeping such a drive train to always have sufficient oil supply to the transmission or hydraulic pressure supply transmission 2 to ensure.

Thus, to start or creep the drive train initially a hydraulic pressure on the hydraulic volume accumulator 13 provided, further wherein the electric machine 5 of the drive unit 1 is operated at a defined speed and a gear-internal starting element or gear-external starting element is operated in the slip, so as the mechanical hydraulic pump 12 of the transmission 2 to drive and at each operating point of the drive train sufficient hydraulic pressure for the hydraulic consumers, in particular for the switching elements 7 to 11 of the transmission 2 as well as the separating clutch 6 to provide.

As already stated, the powertrain is the 1 and 2 the starting element, which is operated slipping to start or creep to an internal gear starting element, for example, the starting element 8th or B the 2 ,

Starting from a drive train with actuated brake pedal, stationary internal combustion engine 4 , resting or running electric machine 5 , open disconnect clutch 6 and non-positive gear 2 is used to start the drive train so that initially at time t1 (see 2 and 3 ), to which the brake pedal is released, or starting at the time t1 via the hydraulic volume accumulator 13 Hydraulic pressure that is stored in the same is released, and continue the electric machine 5 is brought to a defined speed. So can 3 and 4 are taken, that starting at time t1, the speed n _{EM of} the electric machine 4 of the drive unit 1 is raised.

Also triggered by the release of the brake pedal is at least one internal gear shift element of the transmission, which does not serve as a starting element, on the hydraulic volume memory 13 released hydraulic pressure completely filled and thus completely closed. So can 3 can be taken that at time t1, a corresponding drive pressure P _S1 for a first switching element and at time t2, a drive pressure P _S2 for a second switching element of the transmission 2 is increased, which is not serving as starting elements switching elements in these two switching elements, which are completely filled and thus completely closed.

Furthermore, a starting element of the drive train, namely in the embodiment of 1 and 2 a gear-internal switching element, slipping closed via a corresponding pressure control P _AE , in which case, when the control pressure P _AE for the starting element of the drive train is sufficiently large, the motor vehicle anfährt, and wherein at an approaching motor vehicle, the output speed n _{AB is} greater than zero.

As 3 can still be removed, builds up due to the slipping operation of the starting element on the starting element, in which it is in 2 preferably around the switching element 8th or B, a slip speed Δn _AE , wherein during the in 3 Dotted course of the slip speed .DELTA.n _{AE of} the starting element a Fülldruckadaption for the starting element can be realized.

To follow the startup of the internal combustion engine 4 to tow the powertrain is according to 3 subsequent to the filling of the non-starting elements serving as switching elements of the transmission, the separating clutch 6 according to the corresponding drive pressure P _TK for the disconnect clutch 6 filled, at the time t3 with the filling of the separating clutch 6 is started and at time t4, the separating clutch is filled up to a so-called Anlegpunkt, in which the separating clutch 6 partially closed, but still no moment transmits.

Depending on an operation of an accelerator pedal of the drive train and / or depending on a state of charge of an electrical energy storage of the same is the separating clutch 6 subsequently closed by corresponding increase of the control pressure P _TK for the same, this being in 3 and 4 takes place at time t5.

By raising and subsequently keeping constant the control pressure P _TK for the disconnect clutch 6 can follow the approach of the combustion engine 4 be towed, according to 3 between the times t6 and t7, the pressure control P _TK for the separating clutch 6 is again reduced to below starting from the time t7 a comfortable synchronization of the engine speed n _VM and the speed n _{EM of} the electric machine 5 to ensure.

In the embodiment of 3 and 4 Accordingly, the procedure for starting the drive train is such that when releasing a brake pedal via the hydraulic volume accumulator 13 a hydraulic pressure is provided and subsequently via the hydraulic pressure, namely by the pressure controls P _S1 and P _S2 , the switching elements of the transmission 2 , which do not serve as starting elements, are completely closed, wherein furthermore a starting element on the pressure control P _AE is closed slipping, so in slipping operation of the starting element on the speed n _{EM of} the electric machine 5 of the drive unit 1 the hydraulic pump 12 of the transmission 2 can be mechanically driven. About the slip of the starting element can shocks on the output 3 be damped, whereby the starting comfort is increased.

For subsequent towing the internal combustion engine 4 becomes the disconnect clutch 6 closed by the pressure control P _TK first to the Anlegpunkt and then closed depending on the driver's request and / or state of charge of an electrical energy storage at time t5, then the internal combustion engine 4 of the drive unit 1 actually towing.

4 shows a variant of the invention in which he is a greater driver's desire or a stronger operation of an accelerator pedal, so according to 4 between times t4 and t5 is a shorter period than in 3 so ultimately the internal combustion engine 4 of the drive unit 1 is towed faster or earlier.

In 4 is already at time t8 a synchronous operation between the internal combustion engine 4 and electric machine 5 the hybrid drive 1 before, speeds n _EM and n _VM thus coincide.

If a relatively high driver's request or a relatively strong operation of an accelerator pedal of the drive train is present, can be used for starting unlike 4 also according to 5 be proceeded according to 5 for driving and towing the internal combustion engine 4 first before filling the or each not serving as a starting element switching element of the transmission 2 the separating clutch 6 is filled.

So can 5 can be taken that at time t1, to which a brake pedal is released, first via the pressure control P _TK the disconnect clutch 6 is filled, and that subsequent to the times t2 and t3 by the pressure controls P _S1 and P _S2 serving not as starting elements switching elements of the transmission 2 filled and completely closed.

Also triggered by the release of the brake pedal is the speed n _{EM of} the electric machine 5 raised and the transmission internal or external gear starting element slipping closed via the corresponding pressure control P _AE , wherein at time t4 the torque transmitted by the starting element is sufficiently large to ensure a drive-off of the drive train.

5 can be seen that in this case the internal combustion engine is towed before starting, since the speed n _{VM of} the internal combustion engine 4 before the output speed n _AB increases.

In the embodiments of the 3 and 4 the towing of the internal combustion engine takes place 4 however, only after starting the drive train.

As 5 can be removed, which are not used as starting elements switching elements of the transmission 2 nested closed according to the pressure controls P _S1 and P _S2 .

6 shows details of the method according to the invention for operating a drive train with which a stop operation can take place. So can 6 can be taken that when at the time t1 when the drive train is running a limit value of the speed or output speed or transmission input speed is reached or fallen below, the disconnect clutch 6 is lowered by lowering the corresponding pressure control P _TK , so as to the internal combustion engine 4 from the gearbox 2 and thus downforce 3 disconnect and settle quietly.

Then, if below the time t2, a second limit value of the speed or the output speed or the transmission input speed is below or reached, is further brought by appropriate reduction of the pressure control P _AE for the internal gear or gear external starting element in slippage to the mechanically operated oil pump 12 of the transmission 2 to ensure a sufficient hydraulic pressure supply of the hydraulic consumers. So can 6 can be taken that a slip speed n _{AE is} built up by the lowering of the control pressure P _AE for the starting element on the same, so on the speed n _EM , which remains approximately constant, via the hydraulic pump 12 Hydraulic pressure can be provided.

At standstill of the motor vehicle then the electric machine 5 of the drive unit 1 switched off or shut down.

LIST OF REFERENCE NUMBERS

1

power unit

2

transmission

3

output

4

internal combustion engine

5

electric machine

6

separating clutch

7

switching element

8th

switching element

9

switching element

10

switching element

11

switching element

12

hydraulic pump

13

hydraulic volume storage

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 4323133 A1 [0005]

Claims (10)

Method for operating a drive train with a drive unit and a switched between the drive unit and an output, automatic or automated transmission, wherein the drive unit is designed as a hybrid drive with an internal combustion engine and an electric machine, wherein connected between the internal combustion engine and the electric machine, a separating clutch is, via which the engine is decoupled from the output, wherein the transmission comprises a hydraulic pump which is driven mechanically dependent on a transmission input speed to pressurize hydraulic consumers with hydraulic pressure, characterized in that, especially when the drive train is not the transmission input speed is sufficiently high to pressurize the hydraulic consumers with hydraulic pressure via the hydraulic pump, the hydraulic pressure for the hydraulic consumers via a transmission associated with the hydrau is provided. A method according to claim 1, characterized in that when the transmission input speed is not sufficiently high to apply hydraulic pressure to the hydraulic consumers via the hydraulic pump, the hydraulic pressure for the hydraulic consumers is provided via a hydraulic volume accumulator integrated in the transmission. A method according to claim 1 or 2, characterized in that in this case for starting or creeping of the drive train rotates the electric machine of the drive unit for driving the hydraulic pump and an internal gear or gear external starting element is operated in the slip. A method according to claim 3, characterized in that, proceeding from a drive train with actuated brake pedal, stationary internal combustion engine, stationary or running electric machine, open disconnect clutch and non-positive transmission for starting the drive train is so proceeded that a) released by releasing the brake pedal first stored in the hydraulic volume accumulator hydraulic pressure and the electric machine is brought to a defined speed; b) then at least one internal gear shift element of the transmission, which does not serve as a starting element, completely filled via the released hydraulic pressure of the hydraulic volume accumulator and thus completely closed, whereas the internal gear or gear external starting element partially filled via the shared hydraulic pressure of the hydraulic volume accumulator and thus closed slipping becomes. A method according to claim 4, characterized in that for towing the internal combustion engine following the filling of the or each non-starting element switching element of the transmission, the separating clutch first filled up to the Anlegpunkt the same and then depending on an operation of an accelerator pedal and / or depending on the state of charge electric energy storage is closed, so that the internal combustion engine is towed after starting. A method according to claim 5, characterized in that the separating clutch is initially closed for towing the engine beyond the Anlegepunkt also completely closed and then opened by reducing the pressure control again, then a comfortable synchronization of the speeds of the internal combustion engine and electric machine during subsequent increase of the pressure control to ensure for the separating clutch. A method according to claim 4, characterized in that for towing the internal combustion engine before filling the or each non-starting element switching element of the transmission, the separating clutch is filled and that is then approached by partial filling and slipping closing of the internal gear or gear external starting element, so that the internal combustion engine is towed before starting. A method according to claim 7, characterized in that not serving as a starting element switching elements of the transmission are then nested closed to the filling of the separating clutch. Method according to one of claims 1 to 8, characterized in that starting from a moving drive train when reaching or falling below a first limit value of the speed or a first limit value of the transmission input speed, the separating clutch is opened to set the internal combustion engine regulated to stop. A method according to claim 9, characterized in that when reaching or falling below a second limit value of the speed or a second limit value of the transmission input speed, the internal transmission or gear external starting element is opened in the slip to continue to drive the hydraulic pump of the transmission via the electric machine.

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