DE102020202909A1 - Method and control device for operating a hybrid vehicle - Google Patents

Abstract

A method for operating a hybrid vehicle which has an electric machine (3) as the first drive source, an internal combustion engine (2) as the second drive source, a separating clutch (4) connected between the internal combustion engine (2) and the electric machine (3), and a separating clutch (4) between the electrical machine (3) and an output (6) switched gear (5). To start the internal combustion engine (2) from a purely electric drive, in which the separating clutch (4) is open and the internal combustion engine (2) is shut down, a decoupling element is first brought into slip to decouple the drive sources from the output (6) and then, When this has taken place, the separating clutch (4) is at least partially closed by the electric machine (3) for a drag start of the internal combustion engine (2). To bring the decoupling element into slippage, a target transmission capability of the same is first reduced in such a way that slip does not yet develop, with a check being made to determine when an actual transmission capability of the decoupling element intersects the target transmission capability, and if it is determined that the actual transmission capability of the decoupling element intersects the target transmission capability of the decoupling element, a timer is started, after which the target transmission capability of the decoupling element is further reduced, so that the slip develops.

Description

The invention relates to a method for operating a hybrid vehicle. The invention also relates to a control device for operating a hybrid vehicle.

A hybrid vehicle has a plurality of drive sources, a first drive source being designed as an electric machine and a second drive source being designed as an internal combustion engine. A separating clutch is connected between the internal combustion engine and the electrical machine. A hybrid vehicle also has a transmission that is connected between an output and the electric machine. When such a hybrid vehicle is operated purely electrically, the separating clutch connected between the internal combustion engine and the electrical machine is opened and the internal combustion engine is typically shut down. In this case, only the electric machine provides the drive torque at the output. A starting element, for example a starting clutch, can be connected between the electric machine and the transmission. The transmission typically has a plurality of shift elements, a first number of shift elements being closed and a second number of shift elements being opened in each frictional gear of the transmission. To carry out a shift in the transmission, at least one previously closed shift element is opened and at least one previously opened shift element is closed.

It is already known from practice that when a hybrid vehicle is operated purely electrically with the internal combustion engine stopped and the clutch disengaged and a driver's desired torque cannot be provided by the electric machine alone, the internal combustion engine is started. A starter assigned to the internal combustion engine can be used for this purpose. Furthermore, it is already known from practice to start the internal combustion engine with the help of the electrical machine via a so-called drag start, for which purpose torque from the electrical machine in the direction of is transmitted to the internal combustion engine in order to tow the internal combustion engine from the electric machine.

So that such a drag start does not have a noticeable effect on the output, it is also known from practice to compensate for the torque that the separating clutch transmits for the drag start of the internal combustion engine by providing an increased torque via the electric machine.

the US 2013/0178330 A1 discloses a hybrid vehicle with an internal combustion engine, an electric machine, a transmission and an output, wherein a first clutch is connected between the internal combustion engine and the electric machine and a second clutch is connected between the electric machine and the transmission. From this prior art it is known to start the internal combustion engine via a starter and then, when the internal combustion engine has started, to close the clutch connected between the internal combustion engine and the electrical machine. So that disturbances in the output caused by this start-up of the internal combustion engine are not noticeable, this prior art proposes slipping the clutch connected between the electric machine and the transmission when the clutch connected between the internal combustion engine and the electric machine is closed .

In a hybrid vehicle, there is a need to start an internal combustion engine quickly and with a high level of comfort from a purely electric drive using a drag start. The invention is based on the object of creating a novel method and control device for operating a hybrid vehicle. This object is achieved by a method for operating a hybrid vehicle according to patent claim 1.

According to the invention, to start the internal combustion engine from a purely electric drive, in which the separating clutch is disengaged and the internal combustion engine is shut down, first a decoupling element for decoupling the drive sources from the output is brought into slip, and then, when this has been done, the separating clutch for a drag start of the internal combustion engine is at least partially closed by the electrical machine.

In order to bring the decoupling element into slippage, according to the invention, a nominal transmission capacity of the decoupling element is first reduced in such a way that no slippage is formed on the decoupling element. It checks when an actual transmission capability of the decoupling element intersects the target transmission capability of the decoupling element. If it is determined that the actual transmission capacity of the decoupling element intersects the target transmission capability of the decoupling element, a timer is started, after which the target transmission capability of the decoupling element is further reduced, so that the slip develops on the decoupling element.

The method according to the invention enables a quick and comfortable drag start for an internal combustion engine of a hybrid vehicle from a purely electric drive. For this purpose, the drive units are first decoupled from the gearbox by slipping the decoupling element, preferably a clutch connected between the electric machine and the gearbox or a shifting element of the gearbox, so that a decoupling differential speed is then formed on the decoupling element. Only then is the separating clutch connected between the internal combustion engine and the electrical machine for the drag start of the internal combustion engine at least partially closed.

In order to bring the decoupling element connected between the electrical machine and the gearbox into slip in a defined manner before closing the disconnect clutch or to provide the decoupling differential speed on the same, the target transmission capacity of the decoupling element is first reduced, in such a way that there is still no slip on the Forms decoupling element. It is then checked when the actual transmission capability of the decoupling element intersects the target transmission capability of the decoupling element. If it is determined that the actual transmission capability intersects the target transmission capability, the timer is started, after which the target transmission capability on the decoupling element is further reduced, so that the slip then develops on the decoupling element.

As a result, a drag start for the internal combustion engine from a purely electric drive can be implemented within a short time with a high level of comfort. It is ensured that by reducing the target transmission capability, the hydraulic connection to an undershoot that develops in the actual transmission capability is not lost.

According to an advantageous development, after the timer is started, it is monitored whether the actual transmission capability of the decoupling element lies within a tolerance band around the target transmission capability of the decoupling element, the timer only running down when the actual transmission capability is within the tolerance band around the target Transferability lies. Preferably, when it is determined that after the timer has started, the actual transmission capability of the decoupling element leaves the tolerance band around the target transmission capability of the decoupling element, the timer is reset and then restarted when the actual transmission capability of the decoupling element is within the tolerance band returns to the target transmission capacity of the decoupling element. This development of the method according to the invention is particularly preferred in order to ensure the drag start of the internal combustion engine from a purely electric drive within a short time with a high level of comfort.

According to an advantageous development of the invention, when the nominal transmission capacity of the decoupling element is reduced in such a way that no slip yet forms on the decoupling element, the same is reduced in a step-like manner. Subsequently, the target transmission capability of the decoupling element is preferably changed during the expiry of the timer in such a way that a distance between the target transmission capability and a torque requested by the driver remains unchanged. Then, when the timer has expired, the nominal transmission capacity of the decoupling element is reduced in a ramp-like manner, so that the slip develops on the decoupling element. This further development of the method according to the invention also allows the internal combustion engine to be started within a very short time from a purely electric drive with a high level of comfort.

The control device according to the invention for operating a hybrid vehicle is defined in claim 8.

• 1 ein Antriebsstrangschema eines Hybridfahrzeugs; und
• 2 ein Zeitdiagramm zur Verdeutlichung des erfindungsgemäßen Verfahrens zum Betreiben eines Hybridfahrzeugs.

Preferred developments emerge from the subclaims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being restricted thereto. It shows:

• 1 a hybrid vehicle powertrain scheme; and
• 2 a time diagram to illustrate the method according to the invention for operating a hybrid vehicle.

The invention relates to a method and control device for operating a hybrid vehicle.

1 Figure 11 shows a hybrid vehicle powertrain diagram 1 . The hybrid vehicle 1 has at least two drive sources, namely an electric machine as the first drive source 3 and an internal combustion engine as the second drive source 2 , being between the internal combustion engine 2 and the electric machine 3 a disconnect clutch 4th is switched.

The hybrid vehicle 1 still has a gearbox 5 that between the electric machine 3 and a downforce 6th of the hybrid vehicle 6th is switched. In the embodiment shown is between the gear 5 and the electric machine 3 a starting clutch as a starting element 7th switched. The starting clutch 7th is optional.

The gear 5 has several switching elements 8th , of which in 1 a switching element 8th is shown as an example. In every frictional gear of the transmission 5 is a first number of switching elements 8th closed and a second number of switching elements 8th opened. To carry out a shift and thus a gear change in the transmission 5 becomes at least one previously closed switching element 8th opened and at least one previously opened switching element 8th closed.

With a purely electric drive of the hybrid vehicle 1 is the internal combustion engine 2 stopped and with disengaged clutch 4th from the gearbox 5 as well as downforce 6th disconnected. In this case, torque is used for the output 6th exclusively from the electrical machine 3 provided.

The present invention now relates to a start-up of the internal combustion engine 2 from a purely electric drive, i.e. from an initial state in which the separating clutch 4th opened and the internal combustion engine 2 is stopped, namely a start-up of the internal combustion engine in the form of a drag start 2 within a short time with a high level of comfort.

For the drag start of the combustion engine 2 from a purely electric drive, a decoupling element is initially used, preferably the one between the electric machine 3 or the transmission 5 switched clutch 7th or a switching element 8th of the transmission 5 , to decouple the two drive sources 2 , 3 from downforce 6th brought into hatch.

Then, when this has occurred, when the decoupling element has been slipped, the disconnect clutch will 4th for the actual drag start of the combustion engine 2 from the electric machine 3 from at least partially closed to this torque of the electrical machine 3 towards the internal combustion engine 2 for towing the internal combustion engine 2 transferred to.

To the decoupling element, preferably between the electrical machine 3 and the transmission 5 switched starting clutch 7th or the respective switching element 8th of the transmission 5 To bring the decoupling element into slippage, a nominal transmission capacity of the decoupling element is initially reduced in such a way that no slip develops on the decoupling element. It is checked when an actual transmission capability of the decoupling element intersects the target transmission capability, a timer being started if it is determined that the actual transmission capability of the decoupling element intersects the target transmission capability of the decoupling element.

After the timer has expired, the target transmission capacity of the decoupling element is further reduced, and there is then no slip on the decoupling element, preferably on the starting clutch 7th or the respective switching element 8th of the transmission 5 to train.

It is ensured that by reducing the nominal transmission capacity of the decoupling element, the hydraulic connection to a developing undershoot in the actual transmission capacity of the decoupling element is not lost. The decoupling element is prevented from falling shut.

Further details of the invention are provided below with reference to the timing diagram of FIG 2 described, whereby in 2 Two torque curves are plotted over time t, namely with the curve shape 9 a course of the nominal transmission capacity of the decoupling element and with the course of the curve 10 a course of the actual transferability of the decoupling element. The ability of the decoupling element to transmit corresponds to the torque that can be transmitted by the decoupling element.

In 2 becomes the decoupling element, preferably the starting clutch, before time t1 7th or the respective switching element 8th of the transmission 5 , operated in overpressure, the same is therefore completely closed.

At time t1, during purely electric travel, the internal combustion engine is in 2 shut down and the disconnect clutch 4th is open, a start request for the internal combustion engine 2 before, so that starting at time t1 first the decoupling element, preferably the starting clutch 7th or the respective switching element 8th of the transmission is to be brought into slip.

To this end, according to 2 the target transferability 9 of the decoupling element, preferably the coupling 7th or the respective switching element 8th of the transmission 5 , initially reduced, in such a way that no slip develops.

Starting at time t1, it is monitored when the actual transmission capability 10 of the decoupling element the target transmission capability 9 of the decoupling element intersects for the first time, and when it is determined that this is the case, a timer is started. This is in 2 the case at time t2.

After the timer has started at time t2, it is subsequently monitored whether the actual transmission capability 10 within a tolerance band 11 around the target transmission capability, the timer only expiring if the actual transmission capability 10 within the tolerance band 11 the target transferability 9 lies. The tolerance band 11 the target transferability 9 is due to a positive offset 12th and a negative offset 13th on the target transferability 9 defined, with positive offset 12th and negative offset 13th can be the same amount in terms of amount.

In a first advantageous embodiment of the invention, it is provided that when it is determined that the actual transmission capability is available after the timer has been started 10 the tolerance band 11 the target transferability 9 exits, the timer is reset and then restarted when the actual transmission capability 10 into the tolerance band 11 the target transferability 9 returns. This is how in 2 determined at time t3 that the actual transmission capability 10 the tolerance band 11 leaves, then in 2 the timer is reset at time t3. At time t4, the actual transferability returns 10 into the tolerance band 11 the target transferability 9 back so that in 2 the reset timer is restarted at time t4. In 2 it is determined at time t5 that the actual transmission capability 10 the tolerance band 11 the target transferability 9 leaves again, so that in 2 the timer is reset again at time t5. In 2 The actual transmission capability then returns at time t6 10 into the tolerance band 11 the target transferability 9 back so that in 2 at time t6 the timer, which has now been reset twice, is restarted. In 2 the actual transmission capability remains after time t6 10 in the tolerance band 11 the target transferability 9 so that in 2 after time t6, the timer restarted at time t6 can expire.

After the timer has expired, the target transmission capability is then set 9 again reduced what was in 2 is not shown, in order to then activate the decoupling element, in particular the starting clutch, after the timer has expired 7th or the respective switching element 8th of the transmission 5 to bring into hatch.

According to 2 the target transmission capability is reduced 9 step-like at time t1. From time t1, in remains 2 the target transferability 9 constant, to be precise until the timer expires, namely when the torque requested by the driver is also constant during this period of time. If the torque requested by the driver changes after time t1 until the timer expires, the target transmission capability becomes 9 preferably changed during the expiry of the timer so that a distance from the target transmission capability 9 remains unchanged or is constant to the driver's request moment.

Then when the timer has expired and the target transmission capability 9 is further reduced to the decoupling element, in particular the starting clutch 7th or the respective switching element 8th of the transmission 5 To bring into slippage, this reduction in the nominal transmission capability is preferably carried out in a ramp-like manner along a straight line.

It should be noted at this point that it differs from that with reference to 2 described preferred embodiment of the invention, in which if the actual transferability 10 the tolerance band 11 the target transferability 9 leaves, the timer is reset, it is also possible to stop the timer when the actual transmission capability 10 the tolerance band 11 leaves, the timer then continues if the actual transmission capability 10 into the tolerance band 11 the target transferability 9 returns.

The target transmission capability and the actual transmission capability of the decoupling element are transmittable moments that can be calculated by the control.

The invention allows a particularly advantageous, namely fast and comfortable, drag start of an internal combustion engine 2 of a hybrid vehicle 1 from a purely electric drive.

The invention also relates to a control device for carrying out the method according to the invention. This control device can be a transmission control device or a hybrid control device. The hybrid control unit can be a separate control unit or it can be integrated into the transmission control unit.

The control device according to the invention is set up to carry out the method described above on the control side. To start the internal combustion engine 2 from a purely electric drive, the control unit first controls the decoupling element, preferably the starting clutch 7th or the respective switching element 8th of the transmission 5 , in such a way that slip develops on the same, preferably with reference to the in 2 described manner. Only when the starting clutch 7th or the respective switching element 8th of the transmission 5 was brought into slip, the control unit then controls the disconnect clutch 4th for at least partial closing to the actual drag start of the internal combustion engine 2 starting from the electrical machine 3 to realize.

As stated above, the control unit reduces the starting clutch to slip 7th or the respective switching element 8th of the transmission 5 the target transmission capability of the starting clutch 7th or the respective switching element 8th initially in such a way that no slip develops yet.

The control unit then checks whether the starting clutch is actually capable of transmission 7th or the respective switching element 8th of the transmission 5 the target transferability cuts. If this is the case, the control unit starts the timer. After the timer has expired, the control unit reduces the target transmission capacity of the starting clutch 7th or the switching element 8th of the transmission 5 further, so that there is then the slip on the clutch 7th or the switching element 8th of the transmission 5 trains.

The control device which executes the method according to the invention on the control side is in particular an electronic control device. In order to carry out the method according to the invention, the control device comprises hardware-based means and software-based means. The hardware means include data interfaces in order to exchange data with the assemblies involved in the execution of the method according to the invention or to control assemblies involved in the execution of the method according to the invention. The hardware means also include a processor for data processing and a memory for data storage. The software-based means include program modules for carrying out the method according to the invention.

List of reference symbols

1

Powertrain

2

Internal combustion engine

3

electric machine

4th

Disconnect clutch

5

transmission

6th

Downforce

7th

Starting clutch

8th

Switching element

9

Target transferability

10

Actual transferability

11

Tolerance band

12th

Offset

13th

Offset

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• US 2013/0178330 A1 [0005]

Claims (9)

Method for operating a hybrid vehicle, wherein the hybrid vehicle is an electric machine (3) as the first drive source, an internal combustion engine (2) as the second drive source, a separating clutch (4) connected between the internal combustion engine (2) and the electric machine (3), and a separating clutch (4) between the electric machine (3) ) and an output (6) has switched gear (5), wherein to start the internal combustion engine (2) from a purely electric drive, in which the separating clutch (4) is open and the internal combustion engine (2) is stopped, first a decoupling element for decoupling the drive sources from the output (6), in particular one between the electrical Machine (3) and the transmission (5) switched clutch or a switching element of the transmission (5) is brought into slip and then, when this has occurred, the separating clutch (4) for a drag start of the internal combustion engine (2) from the electric machine (3) is concluded from at least partially, whereby, in order to bring the decoupling element into slippage, a nominal transmission capacity (9) of the same is first reduced so that no slip develops yet, it is checked when an actual transmission capability (10) of the decoupling element intersects the target transmission capability (9), if it is determined that the actual transmission capability (10) intersects the target transmission capability (9), a timer is started, after which the target transmission capability (9) of the decoupling element is further reduced so that the slip develops . Procedure according to Claim 1 , characterized in that after starting the timer it is monitored whether the actual transmission capability (10) of the decoupling element is within a tolerance band (11) around the target transmission capability (9) of the decoupling element, the timer only running down when that the actual transmission capability (10) lies within the tolerance band (11) around the target transmission capability (9). Procedure according to Claim 2 , characterized in that when it is determined that, after starting the timer, the actual transmission capability (10) of the decoupling element leaves the tolerance band (11) around the target transmission capability (9) of the decoupling element, the timer is reset and then restarted is when the actual transmission capability (10) returns to the tolerance band (11) around the target transmission capability (9). Procedure according to Claim 2 , characterized in that when it is determined that after starting the timer, the actual transmission capability (10) of the decoupling element leaves the tolerance band (11) around the target transmission capability (9) of the decoupling element, the timer is stopped and then continues is when the actual transmission capability (10) returns to the tolerance band (11) around the target transmission capability (9). Method according to one of the Claims 1 until 4th , characterized in that when the target transmission capacity (9) of the decoupling element is reduced so that no slip develops, the same is reduced in stages. Procedure according to Claim 5 , characterized in that the target transmission capability (9) is subsequently changed while the timer is running in such a way that a distance between the target transmission capability (9) and a torque requested by the driver remains unchanged. Method according to one of the Claims 1 until 6th , characterized in that when the timer has expired, the nominal transmission capacity (9) of the decoupling element is reduced like a ramp, so that the slip develops. Control unit for operating a hybrid vehicle, wherein the hybrid vehicle is an electric machine (3) as the first drive source, an internal combustion engine (2) as the second drive source, a separating clutch (4) connected between the internal combustion engine (2) and the electric machine (3), and a separating clutch (4) between the electric machine (3) ) and an output (6) has switched gear (5), wherein the control device for starting the internal combustion engine (2) from a purely electric drive, in which the separating clutch (4) is open and the internal combustion engine (2) is shut down, initially a decoupling element, in particular one between the electric machine (3) and the transmission (5) activated clutch or a switching element of the transmission (5), so that I develop slip on the same, and then, when this has occurred, the separating clutch (4) for a drag start of the internal combustion engine (2) from the electric machine ( 3) controls to at least partially wear, wherein the control device for bringing the decoupling element into slippage initially reduces a nominal transmission capability (9) of the same so that no slip develops yet, wherein the control device checks when an actual transmission capability of the decoupling element (10) intersects the target transmission capability (9), the control device then, when the same determines that the actual transmission capability (10) of the decoupling element intersects the target transmission capability (9) of the decoupling element, starts a timer, after which the control unit further reduces the target transmission capability (9) of the decoupling element so that the slip develops. Control unit after Claim 8 , characterized in that the same is set up the method according to one of the Claims 1 until 7th to be carried out on the control side.

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