DE102021203949A1 - Method and control unit for operating a frictional shifting element - Google Patents

Abstract

Method for operating a frictional shifting element (4, 7) of a motor vehicle, wherein the shifting element (4, 7) is closed or opened depending on at least one operating condition of the motor vehicle, depending on a mechanical position of a movable element which is mechanically connected to the shifting element ( 4, 7) is connected, oil is passed through the switching element (4, 7) for cooling in such a way that from a defined position of the movable element, which corresponds to a torque-transmitting state of the switching element (4, 7), a first cooling capacity or cooling intensity, and otherwise a second cooling capacity or cooling intensity, which is smaller than the first cooling capacity or cooling intensity, is provided for the switching element (4, 7). When the frictional switching element (4, 7) is to be opened from a closed or at least partially closed state in which the first cooling capacity or cooling intensity is provided, the same is event-controlled and/or time-controlled only opened far enough for cooling the switching element continues to provide the first cooling capacity or cooling intensity.

Description

The invention relates to a method for operating a frictional shifting element. Furthermore, the invention relates to a control unit for operating a frictional shifting element.

Hybrid vehicles known from practice have an internal combustion engine and an electric machine as drive units. A separating clutch is connected between the internal combustion engine and the electric machine, which is designed in particular as a multi-plate clutch. This separating clutch is a frictional shifting element. Furthermore, hybrid vehicles have a transmission that converts speeds and torques and thus provides a tractive force from the drive units to an output of the hybrid vehicle. The transmission is connected between the electric machine and the output. The transmission has several shifting elements. The shifting elements of the transmission include at least several frictional shifting elements, which can be designed as clutches and/or brakes, and optionally at least one positive-locking shifting element, which can be designed as a claw.

A hybrid vehicle can be operated in different operating modes. A hybrid vehicle can be operated purely electrically, in particular when the internal combustion engine is shut down and decoupled from the output. For this purpose, the separating clutch connected between the internal combustion engine and the electric machine is open. Furthermore, a hybrid vehicle can be operated in a hybrid manner, in which case the internal combustion engine is started and coupled to the output when the separating clutch is closed.

To start the internal combustion engine from purely electric driving, the separating clutch is at least partially closed in order to tow the internal combustion engine via the electric machine. This is referred to as engine drag starting. In the case of a tow start, the separating clutch is loaded, as a result of which the separating clutch is subject to heating. In order to avoid damaging the separating clutch, the temperature of the latter must not rise too high.

A so-called continuous slip control of the separating clutch connected between the internal combustion engine and the electric machine can also cause the same to heat up considerably.

The frictionally engaged shifting elements of the transmission can also be exposed to high temperatures as a result of high loads. As already explained, in order to avoid damage to a friction-locking shifting element, an unacceptably high level of heating of the friction-locking shifting element must be avoided.

DE 10 2011 005 504 A1 discloses a frictional shifting element designed as a lamellar shifting element, which can be cooled. The same is designed in such a way that a different cooling capacity or cooling intensity is provided for the switching element depending on the switching position of the frictional switching element, ie depending on the open position and closed position of the same. When the switching element is open, oil is routed through bores into a pressure equalization space in the switching element, which allows the pressure equalization space to be filled quickly, but with a low cooling capacity of the switching element. When the shifting element is closed, the oil can be conducted into an oil dust tank, as a result of which a higher cooling capacity or cooling intensity can then be provided for the frictionally engaged shifting element.

As already stated, an impermissibly high level of heating of a friction-locking shifting element must be avoided in order to reduce the risk of damage to the friction-locking shifting element. In a switching element, as it is in particular DE 10 2011 005 504 A1 is known, is a relatively high cooling capacity or cooling intensity only available when the switching element is closed relatively far. If, on the other hand, the frictionally engaged shifting element is opened relatively widely, only a relatively small cooling capacity or cooling intensity is available, as a result of which the cooling of the shifting element is prolonged. If a switching element has not been able to cool down sufficiently, it may be necessary to temporarily block or postpone certain functions of the switching element in order to avoid damage. This reduces the availability of the shifting element and thus ultimately of functions of the drive train in which the respective frictional shifting element is integrated.

There is a need to accelerate cooling of a frictional shifting element.

The invention is based on the object of creating a novel method and control unit for operating a friction-locking shifting element.

This object is achieved by a method for operating a frictional shifting element solved according to claim 1. When the frictional shifting element is to be opened from a partially closed or at least partially closed state in which the first cooling capacity or cooling intensity is provided, the frictional shifting element is event-controlled and/or time-controlled and opened only far enough to cool the Switching element continues to provide the first cooling capacity or cooling intensity.

With the present invention, it is proposed that when a frictionally engaged shifting element is to be opened starting from an at least partially closed state in which the same is cooled with the first, relatively large cooling capacity or cooling intensity, the respective frictionally engaged shifting element should initially only be opened so far to open that the first cooling capacity or cooling intensity is still available. Here, the respective frictional shifting element can be operated in slip mode, in which the same transmits a defined torque. Alternatively, the respective frictional shifting element can also be opened up to a so-called contact point (touch point) or below the contact point, at which point the frictional shifting element no longer transmits any torque. This depends on the specific structural design of the respective frictional shifting element.

The only partial opening of the frictional shifting element to be opened to a point at which the first cooling capacity or the first cooling intensity can continue to be provided or used to cool the shifting element is event-controlled depending on at least one operating condition and/or time-controlled depending on at least a period of time.

With the invention it is possible to cool down a frictionally engaged shifting element more quickly. Therefore, the risk is reduced that the same will be damaged and/or that certain functions will have to be temporarily blocked or postponed. Overall, the availability of the frictional shifting element and thus of a drive train having the shifting element can be increased.

According to a further development, when the frictional shifting element is to be opened starting from the at least partially closed state, and when a measured or calculated temperature of the frictional shifting element is greater than a limit value, the frictional shifting element is only opened far enough that further the first cooling capacity or cooling intensity is provided. Then, when the measured or calculated temperature of the switching element is or becomes lower than a second limit value, the switching element is opened more, so that the second cooling capacity or cooling intensity is subsequently provided. This configuration is particularly preferred. The temperature of the frictional shifting element can be measured using a sensor or can also be calculated by the controller. The second limit value is particularly preferably smaller than the first limit value.

According to a further development, when the frictional shifting element is to be opened starting from the at least partially closed state, the frictional shifting element is opened for a minimum duration and/or for a maximum duration only to such an extent that the first cooling output or cooling intensity is maintained for the minimum duration and/or will continue to be provided for the maximum duration. The minimum duration can be used to ensure that the first cooling output or cooling intensity is available for the minimum duration. In the method according to the invention, the provision of the first cooling capacity or cooling intensity can be limited via the maximum duration.

A control unit according to the invention for operating a hybrid vehicle is defined in claim 6.

• 1 ein Antriebsstrangschema eines Hybridfahrzeugs;
• 2 ein erstes Zeitdiagramm zur Verdeutlichung der Erfindung;
• 3 ein zweites Zeitdiagramm zur Verdeutlichung der Erfindung.

Preferred developments result from the dependent claims 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 powertrain schematic of a hybrid vehicle;
• 2 a first timing diagram to illustrate the invention;
• 3 a second timing diagram to illustrate the invention.

Below we the invention with reference to 1 describe in connection with a hybrid vehicle. However, the invention is not limited to this application.

1 1 shows an exemplary schematic of a powertrain 1 of a hybrid vehicle. A hybrid vehicle comprises a plurality of drive units, namely an electric machine 3 as the first drive unit and an internal combustion engine 2 as the second drive unit. A separating clutch 4 is connected between the electric machine 3 and the internal combustion engine 2 . The separating clutch 4 can be designed as a multi-plate clutch. This separating clutch 4 is a frictional shifting element. Between the electric machine 3 and an output 6 of the hybrid vehicle a transmission 5 is switched. The transmission 5 has several shifting elements. The shifting elements of the transmission 5 include at least a plurality of frictional shifting elements 7, which can be embodied as clutches and/or brakes, and optionally at least one positive-locking shifting element (not shown), which can be embodied as a claw. 1 shows exemplary three frictional shifting elements 7 of the transmission 5.

When the separating clutch 4 is opened, the internal combustion engine 2 is decoupled from the electric machine 3, from the transmission 5 and from the output 6. In this case, when a non-positive gear is engaged in the transmission 5 , drive torque can be provided at the output 6 exclusively from the electric machine 3 . When the separating clutch 4 is open, the internal combustion engine 2 can be running or stopped.

Then, when the powertrain 1 of the 1 is operated with the separating clutch 4 open and the internal combustion engine 2 stopped, the state of purely electrical operation is present. When the internal combustion engine 2 is running with the separating clutch 4 open, a generator (not shown) can be driven and/or an electrical energy store (not shown) can be charged.

When the separating clutch 4 is closed, the internal combustion engine 2 is coupled to the output 6 . When a non-positive gear is engaged in the transmission 5 , drive torque can be provided at the output 6 , starting from the electric machine 3 and starting from the internal combustion engine 2 .

1 FIG. 12 also shows control-side assemblies, such as a transmission control unit 8, which controls and/or regulates the operation of the transmission 5. In particular, the transmission control unit 8 controls the shifting elements 7 of the transmission 5 . For this purpose, the transmission control unit 8 exchanges data with the transmission 5 in the direction of the double arrow shown. The separating clutch 4 connected between the internal combustion engine 2 and the electric machine 3 can also be controlled via the transmission control unit 8 .

The operation of the internal combustion engine 2 of the hybrid vehicle is controlled and/or regulated by an VM control device 9 and the operation of the electric machine 3 of the hybrid vehicle is controlled and/or regulated by an EM control device 10 . For this purpose, the VM control device 9 exchanges data with the internal combustion engine 2 and the EM control device 10 with the electric machine 3 in the direction of the dashed arrows.

Likewise, the VM control device 9 and the EM control device 10 exchange data with a hybrid control device 11 . Hybrid control unit 11 continues to exchange data with transmission control unit 8 .

Transmission control unit 8 can also communicate directly with EM control unit 10 . A direct exchange of data between the VM control device 9 and the EM control device 10 can also take place.

The hybrid control unit 11 can be part of the VM control unit 9 in terms of hardware. However, it is possible for the hybrid control unit 11 to be a hardware component of the transmission control unit 8 . Hybrid control unit 11 controls and/or regulates, in particular, a torque output from internal combustion engine 2 and electric machine 3. Transmission control unit 8 controls or regulates, in particular, the operation of transmission 5 and separating clutch 4.

Although this system architecture of the control units 8, 9, 10 and 11 is preferred, another control-side system architecture can also be implemented.

For a drag start of the internal combustion engine 2 via the electric machine 3 , the separating clutch 4 is closed at least to the extent that the separating clutch 4 transmits a sufficiently large torque in the direction of the internal combustion engine 2 for a drag start of the internal combustion engine 2 . This leads to a load and an increase in temperature on the separating clutch 4.

A so-called continuous slip operation of the separating clutch 4 can also lead to a high temperature input and thus to a large increase in temperature at the separating clutch 4 .

If the separating clutch 4 in particular like out DE 10 2011 005 504 A1 is known, executed, is only a first, relatively large cooling capacity or cooling intensity for cooling the separating clutch 4 ready when the same is closed relatively far. On the other hand, if the separating clutch 4 is opened relatively far, the same only provides a second cooling capacity or cooling intensity that is smaller than the first cooling capacity or cooling intensity.

These connections are in 2 clarified. So are in 2 several curves over time are shown, namely with a curve 12 an activation of the separating clutch 4, with a curve 13 a cooling capacity or cooling intensity that can be provided depending on the activation for the separating clutch 4 and, with a curve 14, a temperature profile that forms in particular on friction surfaces of the separating clutch 4.

In 2 before time 1, the separating clutch 4 is controlled to close and is closed to such an extent that, according to the curve 13, a first, relatively large cooling capacity and cooling intensity is available. Thus, despite the load on the at least partially closed switching element 4, the temperature increase can be limited according to curve 14. At point in time t1, the actuation of separating clutch 4 changes. Starting at point in time t1, separating clutch 4 is to be opened. According to the curve 13, this then results in a reduced cooling capacity or cooling intensity for the separating clutch 4, ie a second cooling capacity or cooling intensity that is less than the first cooling capacity or cooling intensity. According to the course of the curve 14, although the temperature of the friction clutch 14 drops beginning at time t1, it takes a relatively long time to cool down. There is a need to cool the disconnect clutch 4 faster.

With the present invention, it is proposed that when a frictional shifting element, for example the separating clutch 4, starting from a closed or at least partially closed state, in which the first, relatively large cooling capacity or cooling intensity is available for cooling the frictional shifting element , is to be opened further, the frictional shifting element, in particular the separating clutch 4, is event-controlled and/or time-controlled initially only opened far enough that the first cooling capacity or cooling intensity is initially still available for cooling the shifting element and is thus provided. This clarifies 3 .

So are in 3 Several curves are again shown over the time t, namely with the curve 12' to an activation of the separating clutch 4, with the curve 13' the available cooling intensity or cooling capacity and with the curve 14' the change as a result of the cooling intensity or cooling capacity 13 'At the separating clutch 4, namely the friction surfaces thereof, forming temperature, wherein the curve 14 of the 2 in 3 is reproduced for reference.

Up to time t1, the curves 12', 13' and 14' correspond to FIG 3 the curves 12, 13 and 14 of the 2 .

At the point in time t1, an opening of the separating clutch 4 is again requested, but in 3 in contrast to 2 the separating clutch 4 is not opened completely, but only to such an extent that the first cooling output or cooling intensity for cooling the separating clutch 4 is still available despite the separating clutch 4 being opened to a greater extent. As a result, in the time interval between times t1 and t2, in which the separating clutch 4 is closed less strongly than before time t1, the first cooling output or cooling intensity can still be used, so that the temperature drops faster according to curve 14' and thus the Separating clutch 4 can be cooled more.

Between the points in time t1 and t2, the separating clutch 4 can be operated in slip mode, in which it transmits a defined torque. Alternatively, the separating clutch 4 can be opened between the times t1 and t2 up to a so-called contact point (touch point) or below the contact point of the separating clutch 4, in which the separating clutch 4 then no longer transmits any torque. This depends in particular on the specific structural design of the separating clutch 4 . Also, the power loss at the frictional shifting element, here at the separating clutch 4, should be as low as possible during the prolonged use of the first cooling capacity or cooling intensity.

In the method according to the invention, the procedure is preferably such that a check is carried out when the respective frictional shifting element to be opened, in the exemplary embodiment shown the separating clutch 4, is to be opened starting from the at least partially closed state in which the first cooling capacity or cooling intensity can be used whether a measured or calculated temperature of the separating clutch 4 is greater than a first limit value. If this is the case, the switching element is initially only opened to such an extent that the first cooling output or cooling intensity can continue to be provided, specifically as with reference to FIG 3 described.

If, on the other hand, the measured or calculated temperature is lower than the first limit value, then the shifting element, namely the separating clutch 4, as with reference to FIG 2 described can be fully opened immediately after time t1.

A check is then carried out to determine how the measured or calculated temperature develops, with the switching element being opened more when the same is or becomes smaller than a second limit value which is smaller than the first limit value, so that the relatively small, second cooling capacity then follows or cooling intensity is provided. this is in 3 the case at time t2. In 3 it is therefore determined at time t2 that the measured or calculated temperature of the switching element, namely the separating clutch 4, becomes smaller than the second limit value.

The temperature-dependent opening of the switching element, namely the separating clutch 4, depending on the calculated or measured temperature of the switching element, corresponds to an event-controlled opening of the switching element in order to provide the first cooling capacity in an event-controlled manner.

Alternatively or additionally, time control is also possible. It is thus possible that when the shifting element, namely the separating clutch 4 in the exemplary embodiment shown, is to be opened more strongly starting at time t1, the separating clutch 4 is only opened far enough for a minimum duration and/or for a maximum duration that as before, the first, relatively large cooling capacity or cooling intensity can initially be used, namely for the minimum duration and/or for the maximum duration. Thus, for the time interval t1 to t2 3 a minimum duration and/or a maximum duration may be specified.

With reference to the above figures, the invention was described for the preferred application in which the separating clutch 4 connected between the internal combustion engine 2 and the electric machine 3 of a hybrid vehicle is to be operated as a frictional shifting element. However, the invention is not limited to this application.

Rather, the invention can also be used to operate a frictional shifting element 7 of the transmission 5, be it a transmission of a hybrid vehicle or a transmission of a purely internal combustion engine motor vehicle, in the manner described above, in order to enable rapid cooling.

The invention also relates to a control unit which is set up to carry out the method described above on the control side. This control unit is, in particular, the transmission control unit 8, which, when a frictional shifting element is to be opened starting from an at least partially closed state in which the first, relatively large cooling capacity or cooling intensity is effective, the corresponding frictional shifting element is event-controlled and / or time-controlled initially only as far to open, which continues to be effective for cooling the frictional switching element, the first cooling capacity or cooling intensity. This can take place as a function of a measured or calculated temperature of the respective switching element 4, and also as a function of a maximum duration and/or minimum duration specified by the controller. The control device 8 can calculate the temperature of the switching element based on the model. Alternatively, a sensor can be installed, which measures the temperature of the respective frictional shifting element and provides it to control unit 8 .

The control unit according to the invention is preferably an electronic control unit. This has hardware-side means and software-side means. The means on the hardware side include data interfaces in order to exchange data with the assemblies involved in the execution of the method according to the invention, for example with the corresponding frictionally engaged switching element in order to control the same. If the temperature of the frictional shifting element is detected by a sensor, control unit 8 also has a data interface for data exchange with the sensor. The hardware-side means also include a processor for data processing and a memory for data storage. The software-side means include program modules that are implemented in the control device for carrying out the method according to the invention.

The invention allows an advantageous, rapid cooling of a frictional shifting element, such as a separating clutch.

reference list

1

powertrain

2

combustion engine

3

electric machine

4

disconnect clutch

5

transmission

6

downforce

7

switching element

8th

transmission control unit

9

VM control unit

10

EM control unit

11

hybrid control unit

12

Activation of switching element

13

Cooling intensity/cooling capacity

14

Temperature switching element

12'

Activation of switching element

13'

Cooling intensity/cooling capacity

14'

Temperature switching element

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited 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

• DE 102011005504 A1 [0007, 0008, 0032]

Claims (10)

Method for operating a frictional shifting element (4, 7) of a motor vehicle, wherein the shifting element (4, 7) is closed or opened depending on at least one operating condition of the motor vehicle, depending on a mechanical position of a movable element which is mechanically connected to the shifting element ( 4, 7) is connected, oil is passed through the switching element (4, 7) for cooling in such a way that from a defined position of the movable element, which corresponds to a torque-transmitting state of the switching element (4, 7), a first cooling capacity or cooling intensity, and otherwise a second cooling capacity or cooling intensity, which is less than the first cooling capacity or cooling intensity, is provided for the switching element (4, 7), characterized in that when the frictionally engaged switching element (4, 7) starts from a closed or at least partially closed state in which the first cooling capacity or cooling interior sity is provided is to be opened, the same event-controlled and / or time-controlled is only opened so far that for cooling the switching element (4, 7) continues to be provided the first cooling capacity or cooling intensity. procedure after claim 1 , characterized in that when the switching element (4, 7) is to be opened starting from the closed or at least partially closed state, and when a measured or calculated temperature of the switching element (4, 7) is greater than a limit value, the switching element (4, 7) is only opened so far that the first cooling output or cooling intensity continues to be provided. procedure after claim 2 , characterized in that when the measured or calculated temperature of the switching element (4, 7) is or becomes smaller than a second limit value, the switching element (4, 7) is opened further, so that the second cooling capacity or cooling intensity is provided. Procedure according to one of Claims 1 until 3 , characterized in that when the switching element (4, 7) is to be opened starting from the closed or at least partially closed state, the same is only opened far enough for a minimum duration and/or maximum duration that the first cooling capacity or cooling intensity for the minimum duration and/or maximum duration continues to be provided. Procedure according to one of Claims 1 until 4 , characterized in that the switching element is a separating clutch (4) connected between an internal combustion engine (2) and an electric machine (3) of a hybrid vehicle. Control unit (8) for operating a friction-locking shifting element (4, 7) of a motor vehicle, the control unit (8) controlling the shifting element (4, 7) to close or open depending on at least one operating condition of the motor vehicle, depending on a mechanical position of a moving element, which is mechanically connected to the shifting element (4, 7), oil is passed through the shifting element (4, 7) for cooling in such a way that from a defined position of the moving element, which indicates a torque-transmitting state of the shifting element (4 7) corresponds to a first cooling capacity or cooling intensity, and otherwise a second cooling capacity or cooling intensity, which is less than the first cooling capacity or cooling intensity, is effective for the switching element (4, 7), characterized in that the control unit (8) then, if the frictional shifting element (4, 7), starting from a closed or at least partially closed state, in which the first cooling capacity or cooling intensity is effective, is to be opened, the switching element (4, 4) is event-controlled and/or time-controlled to open only to such an extent that the first cooling capacity or cooling intensity continues to be effective for cooling the switching element (4, 7). . Control unit (8) after claim 6 , characterized in that the control unit (8) when the switching element (4, 7) is to be opened starting from the closed or at least partially closed state, and when a measured or calculated temperature of the switching element (4, 7) is greater is as a limit value, the switching element (4, 7) is only activated to open to such an extent that the first cooling output or cooling intensity is still effective. Control unit (8) after claim 7 , characterized in that the control unit (8) calculates the temperature of the switching element (4, 7) based on the model. Control unit (8) after claim 7 , characterized in that the control unit (8) receives the temperature of the switching element (4, 7) from a sensor. Control unit (8) according to one of Claims 6 until 9 , characterized in that the same is set up, the method according to one of Claims 1 until 5 to execute.

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