WO2011128320A1

WO2011128320A1 - Method for operating a drive train

Info

Publication number: WO2011128320A1
Application number: PCT/EP2011/055677
Authority: WO
Inventors: Bernd Allgaier; Peter Schiele; Michael Sohler
Original assignee: Zf Friedrichshafen Ag
Priority date: 2010-04-13
Filing date: 2011-04-12
Publication date: 2011-10-20
Also published as: DE102010003935A1

Abstract

The invention relates to a method for operating a drive train comprising a drive unit (1) and an automatic or automated transmission (2) connected between the drive unit (1) and an output (3), wherein the drive unit (1) is designed as a hybrid drive comprising an internal combustion engine (4) and an electric motor (5), wherein a cut-out clutch (6) by which the internal combustion engine (1) can be decoupled from the output (3) is connected between the internal combustion engine (4) and the electric motor (5). The transmission (2) comprises a hydraulic pump (12), which can be driven mechanically depending on a transmission input speed in order to supply hydraulic loads with hydraulic pressure. In particular when the drive train is at a standstill, and the transmission input speed is not sufficiently high to supply the hydraulic loads with hydraulic pressure via the hydraulic pump (12), the hydraulic pressure for the hydraulic loads is provided via a hydraulic volume accumulator (13) associated with the transmission (2).

Description

Method for operating a drive train

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 DE 43 23 133 A1, the basic structure of a hydraulic volume accumulator is 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:

Fig. 1 is a block diagram of a drive train;

Fig. 2 details of the drive train of Fig. 1;

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

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

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

6 shows a further diagram to illustrate the method according to the invention 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 a transmission 2 comprises an output 3. The drive unit 1 of the hybrid drive train has an internal combustion engine 4 and an electric machine 5, wherein a separating clutch 6 is connected between the internal combustion engine 4 and the electric machine, and wherein the electric motor 5 drives into a transmission input shaft of the transmission 2. Then, when the separating clutch 6 is opened, the internal combustion engine 4 is decoupled from the transmission input shaft of the transmission 2 and thus from the output 3. For coupling the internal combustion engine 4 to the output 3, the separating clutch 6 is closed. Such a drive train is also referred to as a parallel hybrid.

Fig. 2 shows details of the drive train of Fig. 1, namely in particular details of the transmission 2, wherein in the embodiment shown in FIG Gear 2 comprises a total of five switching elements 7, 8, 9, 10 and 1 1. The switching elements 7 and 8, which are also referred to as switching elements A and B, are brakes. In the switching elements 9, 10 and 1 1 of the transmission 2, which are also referred to as switching elements C, D and E, there are clutches.

In the case of the transmission 2 shown in FIG. 2, three shifting elements of the shifting elements 7 to 11 are closed in each movable gear and two shifting elements of the shifting elements 7 to 10 are opened. For starting is used in the transmission 2 of FIG. 2, one of the internal gear shift elements 7 to 1 1 as a gear-internal starting element. In contrast to this, it is also possible that a separate starting element, either a separate, internal gear starting element or a separate, gear external starting element, is present as a starting element.

1, the transmission 2 of the drive train shown there is associated with a hydraulic pump 12. In this hydraulic pump 12 of the transmission 2 is a mechanically driven hydraulic pump which is driven depending on a transmission input speed of the transmission 2 and a hydraulic pressure for hydraulic consumers, in particular for the switching elements 7 to 1 1 of the transmission 2 and the separating clutch 6, provides , Then, when under defined operating conditions of the drive train, especially at standstill of the decoupled from the output 3 internal combustion engine 4, the hydraulic pump 12 can not provide sufficient hydraulic pressure for the hydraulic consumers, according to the invention, the hydraulic pressure for the hydraulic consumers via a transmission 2 associated, hydraulic Volume memory 13 is provided, said hydraulic volume accumulator 13 is preferably integrated in the transmission 2. It is therefore within the meaning of the present invention, then, if the transmission 2 associated, mechanically driven hydraulic pump 12 can not provide sufficient hydraulic pressure to provide this via a transmission 2 associated, hydraulic volume accumulator 13.

However, since such a hydraulic volume accumulator 13 has only a limited delivery volume and can therefore only provide a limited hydraulic pressure for hydraulic consumers, will be described in detail below, which individual process steps are to be executed especially for starting or creeping such a drive train to always have sufficient oil supply to ensure the transmission or hydraulic pressure supply of the transmission 2.

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

As already stated, the drive train of FIGS. 1 and 2 at the starting element, which is operated slipping for starting or creeping, is an internal starting element, for example the starting element 8 or B of FIG. 2.

Starting from a drive train with actuated brake pedal, stationary combustion engine 4, stationary or running electrical Machine 5, open disconnect clutch 6 and non-positive gear 2 is proceeded to start the drive train so that first at time t1 (see Fig. 2 and 3), to which the brake pedal is released, or starting at the time t1 via the hydraulic Volume memory 13 hydraulic pressure, which is stored in the same is released, and further the electric machine 5 is brought to a defined speed. Thus, it can be seen from FIGS. 3 and 4 that, starting at time t1, the speed n _E M 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, completely filled via the released from the hydraulic volume accumulator 13 hydraulic pressure and thus completely closed. For example, it can be seen from FIG. 3 that at time t1, a corresponding control pressure P _S i for a first switching element and at time t 2 a triggering pressure P _S 2 for a second shift element of transmission 2 are increased both switching elements are not serving as starting elements switching elements that are completely filled and thus completely closed.

Furthermore, a starting element of the drive train, namely in the embodiment of FIGS. 1 and 2, a gear-internal switching element slipping closed via a corresponding pressure control P _A E, wherein when the driving pressure P _A E 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 _A B is greater than zero.

As can be further seen in FIG. 3, due to the slipping operation of the starting element on the starting element, which is preferably the switching element 8 or B in FIG Slip speed ΔΠ _Α Ε, wherein during the puncture in Fig. 3 course of the slip speed Δη _Α Ε of the starting element a Fülldruckadaption for the starting element can be realized.

In order to subsequently tow the combustion engine 4 of the drive train, the separating clutch 6 according to FIG. 3 is then filled according to the appropriate control pressure Ρ _Τ κ for the separating clutch 6, at the time t3, with the filling of the shifting elements of the transmission not serving as starting elements the filling of the separating clutch 6 is started and at the time t4, the separating clutch 6 is filled to a so-called Anlegpunkt, in which the separating clutch 6 is 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, the separating clutch 6 is subsequently closed by corresponding increase of the control pressure Ρτκ for the same, this being done in Fig. 3 and 4 at time t5.

By raising and subsequently keeping constant the control pressure PTK for the separating clutch 6, the combustion engine 4 can subsequently be towed to the startup, with the pressure control Ρ _Τ κ for the separating clutch 6 being reduced again as shown in FIG. 3 between the times t6 and t7, in the following beginning with the time t7 to ensure a comfortable synchronization of the engine speed n _V M and the rotational speed n _E M of the electric machine 5.

In the exemplary embodiment of FIGS. 3 and 4, the procedure for starting up the drive train is such that upon release of a brake pedal via the hydraulic volume accumulator 13 a hydraulic pressure is provided and subsequently via the hydraulic pressure, namely through the pressure Controls P _S i and Ps ₂ , the switching elements of the transmission 2, which do not serve as starting elements, are completely closed, wherein further a starting element on the pressure control P _A E slipping closed, so in slipping operation of the starting element on the speed n _E M the electric machine 5 of the drive unit 1, the hydraulic pump 1 2 of the transmission 2 can be mechanically driven. About the slip of the starting element shocks can be damped on the output 3, whereby the Anfahrkomfort is increased.

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

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

In FIG. 4, synchronous operation is already present at time t8

Combustion engine 4 and electric machine 5 of the hybrid drive 1 before, speeds n _E M and n _V M thus coincide.

If a relatively high driver's request or a relatively strong actuation of an accelerator pedal of the drive train is present, proceed as in FIG. 4 for starting in accordance with FIG. 5, wherein according to FIG. 5 for driving and towing the internal combustion engine 4 first before Filling the or each serving as a starting element switching element of the transmission 2, the separating clutch 6 is filled.

Thus, it can be seen from FIG. 5 that, at the time t1, for which a brake pedal is released, the separating clutch 6 is first filled via the pressure control Ρ _Τ κ, and that subsequently to the times t2 and t3 by the pressure controls P _s i and Ps ₂ serving not as starting elements switching elements of the transmission 2 are filled and completely closed.

Also triggered by the release of the brake pedal, the rotational speed n _E M of the electric machine 5 is raised and closed the internal gear or gear external starting element slipping on the corresponding pressure control P _A E, wherein at time t4 the torque transmitted by the starting element is sufficiently large to start off to ensure the drive train.

5 it can be seen that in this case the internal combustion engine is towed before starting, since the speed n _V M of the internal combustion engine 4 increases in front of the output rotational speed n _A B.

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

As can be seen from FIG. 5, the switching elements of the transmission 2, which do not serve as start-up elements, are nested in accordance with the pressure controls P _S i and P _S2 .

FIG. 6 shows details of the method according to the invention for operating a drive train with which a stopping process can take place. So can It can be seen from FIG. 6 that when a limit value of the speed or output rotational speed or transmission input rotational speed is reached or undershot at time t1 when the drive train is moving, the separating clutch 6 is opened by lowering the corresponding pressure control Ρ _Τ κ so as to transfer the internal combustion engine 4 from the transmission 2 and thus decoupling downforce 3 and set to 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 reached or reached, is further brought by appropriate reduction of the pressure control P _A E 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. Thus, it can be seen from FIG. 6 that a slip speed n _A E is built up by lowering the drive pressure PAE for the starting element, so that hydraulic pressure can be supplied via the rotational speed n _E M, which remains approximately constant, via the hydraulic pump 12.

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

Designation drive unit

transmission

output

internal combustion engine

electric machine

separating clutch

switching element

hydraulic pump

hydraulic volume storage

Claims

claims

1 . 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 about that of

Combustion engine can be 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 when especially at standstill of the drive train, the transmission input speed is not sufficiently high to apply hydraulic pressure to the hydraulic consumers via the hydraulic pump, hydraulic pressure to the hydraulic pumps

Consumer is provided via a hydraulic volume accumulator associated with the transmission.

2. The method according to claim 1, characterized in that when the transmission input speed is not sufficiently high to pressurize the hydraulic consumers with hydraulic pressure via the hydraulic pump, the hydraulic pressure for the hydraulic consumers is provided via a hydraulic volume accumulator integrated in the transmission.

3. The method of claim 1 or 2, characterized in that in this case for starting or creep of the drive train rotates the electric machine of the drive unit for driving the hydraulic pump and a gear internal or external gear drive element is operated in the slip.

4. The 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 gear for starting the drive train is operated so 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 shared 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.

5. The method according to claim 4, characterized in that for towing the internal combustion engine after filling or not serve as 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 State of charge of an electric energy storage is closed, so that the internal combustion engine is towed after starting.

6. The method according to claim 5, characterized in that the separating clutch initially for towing the engine on the Anlegpunkt also preferably completely closed and then opened by reducing the pressure control again, then to a comfortable synchronization of the speeds of internal combustion engine and electric machine in the subsequent Increase the pressure control to ensure the disconnect clutch.

7. The method according to claim 4, characterized in that for towing the internal combustion engine before filling the or each not serving as a 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.

8. The 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.

9. The method according to any one of claims 1 to 8, characterized in that starting from a moving drive train when reaching or falling below a first limit of the speed or a first limit of the transmission input speed, the clutch is opened to set the engine to stop regulated.

10. The method according to claim 9, characterized in that when reaching or falling below a second limit of the speed or a second limit 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.