Method and control device for operating a drive train

Abstract

The invention relates to a method for operating a drive train of a motor vehicle, wherein the drive train has a drive unit (1), an automated group transmission (2) connected between the drive unit (1) and an output (3), and a decoupling clutch (5) connected between the drive unit (1) and the group transmission (2), wherein the group transmission (2) has a plurality of partial transmissions, namely at least a main transmission (9) and also a sub-transmission (10) which is located upstream in terms of drive technology from the main transmission (9) and a range group (11) which is located downstream in terms of drive technology from the main transmission (9), wherein, when the decoupling clutch (5) cannot be utilized, i.e. cannot be opened and closed, when a shift is carried out in the group transmission (2), an emergency shift program is activated, wherein, in the emergency shift program, a shift from an actual gear of the group transmission (2) to a target gear of the group transmission (2) with the decoupling clutch (5) closed is carried out only in the main transmission (9) and / or in the range group (11) which is located downstream in terms of drive technology from the main transmission (9) and not in the sub-transmission (10) which is located upstream in terms of drive technology from the main transmission (9), depending on an input rotational speed of the group transmission (2) or depending on a rotational speed of the drive unit (1).

Description

TECHNICAL FIELD

[0001] The invention relates to a method for operating a drive train of a motor vehicle, wherein the drive train has a drive unit, an automated group transmission which is connected between the drive unit and an output, and a disconnect clutch which is connected between the drive unit and the group transmission, and wherein the group transmission has a plurality of partial transmissions, i.e. at least a main transmission and also a range group which is located upstream of the main transmission in terms of drive technology and a sub-transmission which is located downstream of the main transmission in terms of drive technology. The invention also relates to a control device for operating such a drive train. BACKGROUND

[0002] DE 10 2006 054 277 A1 discloses a method for performing a shift in an automated manual transmission. In the proposed method, a shift can be performed either with the use of a disconnect clutch or without the use of a disconnect clutch and thus either with or without the disconnect clutch being open. Therefore, it is checked whether the basic conditions for a shift, i.e. a switch, with the disconnect clutch closed are fulfilled and, when these basic conditions are fulfilled, the out of the original gear with the disconnect clutch closed is permitted. If this out of the original gear with the disconnect clutch closed is not successful, a change is made to a switch mode for the in of the target gear with the disconnect clutch open. If the out of the original gear with the disconnect clutch closed is successful, it is checked whether the conditions for the in of the target gear with the disconnect clutch closed are fulfilled, wherein, if this is not the case, a diversion is made again to the switch mode for the in of the target gear with the disconnect clutch open. The prerequisite of the method according to DE 10 2006 054 277 A1 is therefore that the disconnect clutch can be provided and thus utilized, i.e. opened and closed, when a switch is implemented in the automated manual transmission.

[0003] The method known from DE 2006 054 277 A1 is not suitable for implementing a switch, i.e. a shift, when the disconnect clutch cannot be utilized, i.e. cannot be opened and closed.

[0004] There is a need for a method for operating a drive train of a motor vehicle with an automated group transmission in which a switch, i.e. a shift, from an actual gear to a target gear can be performed even when the disconnect clutch cannot be utilized, i.e. cannot be opened and closed. SUMMARY

[0005] On the basis of this, the task on which the invention is based is to provide a novel method for operating a drive train of a motor vehicle and a control device for performing the method. This task is solved by a method for operating a drive train according to claim 1.

[0006] When the shift in the group transmission cannot be implemented with the disengagement clutch, i.e. cannot be opened and closed, an emergency shift program is activated. In the emergency shift program, the shift from the actual gear of the group transmission to the target gear of the group transmission with the disengagement clutch closed is only implemented automatically in the main transmission and / or in the range group downstream of the main transmission in terms of drive technology, but not in the auxiliary transmission upstream of the main transmission in terms of drive technology, depending on the input rotational speed of the group transmission or depending on the rotational speed of the drive unit.

[0007] According to the invention, it is proposed that, in the case of a drive train with an automated group transmission, when the shift in the group transmission cannot be opened and closed, an emergency shift program is activated. In the emergency shift program, the shift from the actual gear of the group transmission to the target gear of the group transmission with the disengagement clutch closed is implemented, i.e. a gear change, however, only in the case of the main transmission and / or the range group participating. The auxiliary transmission remains unchanged in its state. With the invention, the availability of a motor vehicle with a group transmission can be improved in that the shift is implemented even when the disengagement clutch cannot be opened and closed.

[0008] Preferably, if the motor vehicle is accelerating, i.e. the input rotational speed of the group transmission or the rotational speed of the drive unit is increasing and reaches or exceeds a first limit value, an upshift is implemented automatically in the group transmission with the main transmission participating and / or with the range group participating. If the motor vehicle is decelerating, i.e. the input rotational speed of the group transmission or the rotational speed of the drive unit is decreasing and reaches or falls below a second limit value, a downshift is implemented automatically in the group transmission with the main transmission participating and / or with the range group participating. The method is particularly preferred for implementing the shift, i.e. the gear change, in the group transmission when the disengagement clutch cannot be opened and closed. Thus, both an upshift and a downshift in the group transmission can be performed with the main transmission and / or the range group participating.

[0009] Preferably, the target gear of the group transmission is determined depending on the respective limit value, the actual gear and a desired target rotational speed for the input rotational speed of the group transmission or the rotational speed of the drive unit, in particular in such a way that the target rotational speed of the input rotational speed of the group transmission or the rotational speed of the drive unit is in a range around the middle between the permissible maximum rotational speed of the drive unit and the idling rotational speed of the drive unit. This is particularly preferred in order to improve the availability of the motor vehicle when the disengagement clutch cannot be opened and closed.

[0010] The control device according to the invention is defined in claim 8. BRIEF DESCRIPTION OF DRAWINGS

[0011] Preferred refinements result from the dependent claims and the following description. Embodiments of the application are explained in more detail below without being restricted thereto, in conjunction with the attached drawings. Therein:

[0012] Figure 1 An exemplary diagram of a drive train of a motor vehicle is shown;

[0013] Figure 2 A signal flow chart for illustrating the application is shown; and

[0014] Figure 3 A timing diagram for a downshift is shown. DETAILED DESCRIPTION

[0015] The application relates to a method for operating a drive train of a motor vehicle having an automated group transmission and a control device for carrying out the method.

[0016] Figure 1 A diagram of a drive train of a motor vehicle is shown, which has a drive unit 1, an automated group transmission 2 and an output 3. The drive unit 1 can be coupled to an input shaft 6 of the group transmission 2 via a separating clutch 5, also referred to as a launch clutch. The output 3 is coupled to an output shaft 8 of the group transmission 2. In the embodiment shown, the group transmission 2 has a main transmission 9, a sub-transmission 10 upstream of the main transmission 9 in terms of drive technology, and a range group 11 downstream of the main transmission 9 in terms of drive technology. The main transmission 9 is also referred to as a main group.

[0017] The main transmission 9 of the group transmission 2 is embodied as a direct-shift transmission of the intermediate shaft type and has two intermediate shafts 21, 22. In the embodiment shown, the main transmission 9 is configured to have three gear ratio stages Gl, G2, G3 for forward travel and a gear ratio stage R for reverse travel. The ring gears of the gear ratio stages Gl, G2 and R are each rotatably supported on a main shaft and can be shifted via the associated shift elements 15, 16, 18 and 19, which are configured as dog clutches. The associated fixed gears are arranged on the intermediate shafts 21, 22 against rotation. The two shift elements 15, 16 and the two shift elements 18, 19 each form a shift assembly 17 or 20. The main transmission 9 can be shifted unsynchronized.

[0018] In the embodiment shown, the sub-transmission 10 of the group transmission 2 is configured as two-stage and is likewise embodied in the intermediate shaft type, wherein the two gear ratio stages Kl and K2 of the sub-transmission 10 form two switchable input constants of the main transmission 9. The two gear ratio stages Kl, K2 have a small gear ratio difference.

[0019] The loose gearwheel of the first gear step K1 is rotatably supported on the input shaft 6. The loose gearwheel of the second gear step K2 is rotatably supported on the main shaft. The fixed gearwheels of the two gear steps K1, K2 of the auxiliary transmission 10 are each arranged in a rotationally fixed manner with the intermediate shafts 21, 22 of the main transmission 9, which are extended on the input side. The switching elements 12, 13 of the synchronization constitution of the auxiliary transmission 10, the so-called synchro switching elements, are combined into a common switching assembly 14.

[0020] The range gear group 11 of the group transmission 2, which is arranged downstream of the main transmission 9, is likewise designed as a two-stage transmission, however, as a planetary gear 24. The sun wheel 25 is coupled in a rotationally fixed manner with the main shaft of the main transmission 9, which is extended on the output side. The planet carrier 27 is coupled in a rotationally fixed manner with the output shaft 8 of the group transmission 2. The ring gear 26 is connected with a switching assembly 23 having two synchronized switching clutches, by means of which the range gear group 11 can be alternately switched into the low-speed travel stage L by connecting the ring gear 26 with the fixed housing part 7 and into the high-speed travel stage S by connecting the ring gear 26 with the planet carrier 27. The range gear group 11 can be switched synchronously. Figure 1 An optional transmission brake 4 acting on the intermediate shaft 21 is also shown. Via the transmission brake 4, the intermediate shaft 21 can be braked.

[0021] It is pointed out here that the group transmission 2, which is shown in Figure 1 The embodiment shown in Fig. 1 is preferred, but is optional. The application can also be used in connection with other group transmissions comprising a main gear group 9, a range gear group 11 and an auxiliary transmission 10.

[0022] The application now relates to a method for operating a drive train having an automated group transmission 2, with which a shift or gear change from an actual gear of the group transmission 2 to a target gear of the group transmission 2 can be carried out if a disconnect clutch 5, which is connected between a drive unit 1 and the input shaft 6 of the group transmission 2, cannot be opened and then reclosed when a shift is carried out in the group transmission 2.

[0023] The emergency shift program is activated when the decoupling clutch 5 cannot be utilized, i.e. cannot be opened and closed, when a shift is carried out in the transmission 2. In the emergency shift program, depending on the input rotational speed of the group transmission 2, i.e. depending on the rotational speed of the input shaft 6 of the group transmission 2, or depending on the rotational speed of the drive unit 1, the shift from the actual gear of the group transmission 2 to the target gear of the group transmission 2 is carried out only in the main transmission 9 and / or in the range gear group 11 which is located downstream of the main transmission 9 in terms of drive technology, but not in the auxiliary transmission 10 which is located upstream of the main transmission 9 in terms of drive technology, with the decoupling clutch 5 closed. Thus, only the main transmission 9 and / or the range gear group 11 participate in the implementation of the shift or gear change of the group transmission 2 in the emergency shift program with the decoupling clutch 5 closed, while the auxiliary transmission 10 does not participate. Further details of the application will be described below with reference to the signal flow diagram of Figure 2 and the timing diagram of Figure 3 .

[0024] In block 28 of the signal flow diagram of Figure 2 , it is checked whether the decoupling clutch 5 can be used, i.e. can be opened and closed. If the decoupling clutch 5 can be opened and closed, the flow branches back to block 28 from block 28. If, in contrast, the decoupling clutch 5 cannot be opened and closed when a shift is carried out in the group transmission 2, the flow branches from block 28 to block 29. In block 29, the regular shift program is deactivated. Subsequently, the emergency shift program is activated in block 30.

[0025] Subsequently, with the emergency shift program activated, it is checked whether the motor vehicle is accelerating, i.e. whether the input rotational speed of the group transmission 2 or the rotational speed of the drive unit 1 is increasing. If this is the case, the flow branches from block 31 to block 32. If, in contrast, this is not the case, i.e. it is ascertained in block 31 that the motor vehicle is decelerating, i.e. the input rotational speed of the group transmission 2 or the rotational speed of the drive unit 1 is decreasing, the flow branches from block 31 to block 33.

[0026] In block 32, it is checked whether the input rotational speed of the group transmission 2 or the rotational speed of the drive unit 1 reaches or exceeds a first limit value. Preferably, this first limit value is a rotational speed which is smaller than the maximum permissible rotational speed of the drive unit 1 by a defined offset.

[0027] If it is ascertained in block 32 that the rotational speed of the drive unit 1 or the input rotational speed of the group transmission 2 does not reach or does not exceed the first limit value, a branch is made from block 32 back to block 32. If, in contrast, it is ascertained in block 32 that the rotational speed of the drive unit 1 or the input rotational speed of the group transmission 2 reaches or exceeds the first limit value, a branch is made from block 32 to block 34, in which, in block 34, a shift from the actual gear to the target gear is then automatically implemented in the group transmission 2 only with the participation of the main transmission 9 and / or with the participation of the range gear group 11, more precisely as an upshift switch with the separation clutch 5 closed.

[0028] In block 33, it is checked whether the input rotational speed of the group transmission 2 or the rotational speed of the drive unit 1 reaches or falls below a second limit value. This second limit value is a rotational speed which is greater than the idling rotational speed of the drive unit 1 by a defined offset.

[0029] If it is ascertained in block 33 that this is not the case, i.e. the input rotational speed of the group transmission 2 or the rotational speed of the drive unit 1 does not reach or does not fall below this second limit value, a branch is made back to block 33. If, in contrast, it is ascertained in block 33 that the input rotational speed of the group transmission 2 or the rotational speed of the drive unit 1 reaches or falls below this second limit value in the case of a deceleration of the motor vehicle, a branch is made from block 33 to block 35. In block 35, a switch is then automatically implemented in the group transmission 2 only with the participation of the main transmission 9 and / or with the participation of the range gear group 11, i.e. as a downshift switch with the separation clutch 5 closed.

[0030] The target gear of the group transmission 2 to be implemented in the case of a closed separation clutch 5 which cannot be opened and closed depends on the respective limit value, i.e. the first limit value or the second limit value, the actual gear and the desired target rotational speed for the input rotational speed of the group transmission 2 or the rotational speed of the drive unit 1. Here, the target gear of the group transmission 2 is ascertained in such a way that the target rotational speed for the input rotational speed of the group transmission 2 or the rotational speed of the drive unit 1 lies in a range around the middle between the permissible maximum rotational speed of the drive unit 1 and the idling rotational speed of the drive unit 1. For this target rotational speed, the target gear with the appropriate transmission ratio is then selected, such that after the engagement of this target gear the input rotational speed of the group transmission 2 or the rotational speed of the drive unit 1 is as close as possible to this target rotational speed.

[0031] Figure 3The signal development over time with respect to the time t is shown, more precisely for the case in which a downshift is implemented in the group transmission 2. The curve development 36 corresponds to the rotational speed of the drive unit 1, and the curve development 37 corresponds to the input rotational speed of the group transmission 2, wherein the curve developments 36 and 37 coincide since the decoupling clutch 5 is closed.

[0032] In Figure 3 , the motor vehicle is slowing down, i.e. both the input rotational speed 37 of the group transmission 2 and the rotational speed 36 of the drive unit 1 are decreasing. At the time point ti, the input rotational speed of the group transmission 2 or the rotational speed of the drive unit 1 reaches a limit value which is greater than the idling rotational speed 39 of the drive unit 1 by a defined offset. As a result, at the time point ti, the target gear of the group transmission 2 is changed, wherein a gear shift from the old target gear to the new target gear and thus from the actual gear in the group transmission 2, which is shown by the curve development 40, is carried out with the decoupling clutch 5 closed. It can be seen from the curve development 40 that, in order to change the group transmission 2 from the actual gear to the new target gear, the actual gear is first disengaged and the group transmission 2 is changed to a neutral gear, and the new target gear is then engaged in the group transmission 2 starting from the neutral gear.

[0033] As has already been explained, the gear shift implemented in the group transmission 2 in the case of a closed decoupling clutch 5 is only realized with the participation of the main transmission 9 and / or with the participation of the range gear group 11, while the sub-transmission 10 does not participate.

[0034] Figure 3 The development of the speed 41 of the motor vehicle over time is also visualized. In Figure 3 , this speed 41 is the calculated driving speed of the motor vehicle.

[0035] Both the upshift and the downshift which can be implemented in the emergency shift program with the decoupling clutch 5 closed in the case of use of the method according to the application can be carried out as a single-gear jump shift or as a multi-gear jump shift.

[0036] As has already been explained, the respective shift in the group transmission 2 is carried out in such a way that the target rotational speed which occurs at the input shaft 6 of the group transmission 2 and thus the rotational speed of the drive unit 1 after the shift is implemented lies in the range around the middle between the maximum engine rotational speed and the idling rotational speed of the drive unit 1.

[0037] The application also relates to a control device for operating a drive train having an automated group transmission. Preferably, the control device is an electrical or electronic transmission control device which has hardware-side and software-side means for carrying out the method according to the application. The hardware-side means comprise a data interface for exchanging data with structural components which participate in carrying out the method according to the application, for example with the group transmission 2. Furthermore, the hardware-side means comprise a memory for data storage and a processor for data processing. The software-side means comprise program modules which are implemented in the control device to carry out the method according to the application.

[0038] The method according to the application is set up to automatically carry out the above-described method. When the separating clutch 5 cannot be utilized, i.e. cannot be opened and closed, when a shift is carried out in the group transmission 2, the control device activates an emergency shift program. In the emergency shift program, the control device automatically triggers a shift from the actual gear of the group transmission to the target gear of the group transmission 2 with the separating clutch 5 closed, depending on the input rotational speed of the group transmission 2 or depending on the rotational speed of the drive unit 1, more precisely only in the case of participation of the main transmission 9 and / or in the case of participation of the range gear group 11 which is located downstream of the main transmission 9 in terms of drive technology, but without participation of the auxiliary transmission 10 which is located upstream of the main transmission 9 in terms of drive technology.

[0039] The application allows to improve the availability of a motor vehicle, more precisely the availability of a shift in the group transmission 2 with the separating clutch 5 closed, in the case where the separating clutch 5 cannot be opened and closed, i.e. cannot be disconnected and subsequently cannot be closed again, wherein in these shifts only the main transmission 9 and / or the range gear group 11 participate, while the auxiliary transmission 10 does not participate.

[0040] List of reference signs

[0041] 1 drive unit

[0042] 2 group transmission

[0043] 3 output end

[0044] 4 transmission brake

[0045] 5 separating clutch

[0046] 6 input shaft

[0047] 7 housing part

[0048] 8 output shaft

[0049] 9 main transmission

[0050] 10 auxiliary transmission

[0051] 11 range stop group

[0052] 12 synchronizing shift element

[0053] 13 synchronizing shift element

[0054] 14 shift assembly

[0055] 15 shift element

[0056] 16 shift element

[0057] 17 shift assembly

[0058] 18 shift element

[0059] 19 shift element

[0060] 20 shift assembly

[0061] 21 intermediate shaft

[0062] 22 intermediate shaft

[0063] 23 shift assembly

[0064] 24 planetary gear

[0065] 25 sun gear

[0066] 26 ring gear

[0067] 27 planet carrier

[0068] 28 frame

[0069] 29 frame

[0070] 30 frame

[0071] 31 frame

[0072] 32 frame

[0073] 33 frame

[0074] 34 frame

[0075] 35 frame

[0076] 36 transmission input rotational speed

[0077] 37 drive unit rotational speed

[0078] 38 target gear

[0079] 39 idle rotational speed

[0080] 40 actual gear

[0081] 41 vehicle speed

Claims

1. Method for operating a drive train of a motor vehicle, the drive train having a drive unit (1), an automated group transmission (2) connected between the drive unit (1) and an output (3), and a separating clutch (5) connected between the drive unit (1) and the group transmission (2), wherein the group transmission (2) has a plurality of partial transmissions, namely at least a main transmission (9) and also a sub-transmission (10) upstream of the main transmission (9) in terms of drive technology and a range group (11) downstream of the main transmission (9) in terms of drive technology, wherein, in the event of a shift in the group transmission (2) when the separating clutch (5) cannot be utilized, i.e. cannot be switched, an emergency shift program is activated, in the event of a non-zero travel speed of the motor vehicle, wherein, in the emergency shift program, a shift from an actual gear of the group transmission (2) to a target gear of the group transmission (2) with the separating clutch (5) closed is only carried out automatically in the main transmission (9) and / or in the range group (11) downstream of the main transmission (9) in terms of drive technology, but not in the sub-transmission (10) upstream of the main transmission (9) in terms of drive technology, depending on an input rotational speed of the group transmission (2) or on a rotational speed of the drive unit (1). wherein 2. Method according to claim 1, characterized in that, if the motor vehicle is accelerating, i.e. the input rotational speed of the group transmission (2) or the rotational speed of the drive unit (1) is increasing and reaches or exceeds a first limit value, an upshift is carried out automatically in the group transmission (2) with participation of the main transmission (9) and / or with participation of the range group (11).

3. Method according to claim 2, characterized in that the first limit value is greater than the maximum permissible rotational speed of the drive unit (1) by a defined offset.

4. Method according to any one of claims 1 to 3, characterized in that, if the motor vehicle is decelerating, i.e. the input rotational speed of the group transmission (2) or the rotational speed of the drive unit (1) is decreasing and reaches or falls below a second limit value, a downshift is carried out automatically in the group transmission (2) with participation of the main transmission (9) and / or with participation of the range group (11).

5. Method according to claim 4, characterized in that the second limit value is greater than the idling rotational speed of the drive unit (1) by a defined offset.

6. Method according to any one of claims 1 to 3, characterized in that the target gear of the group transmission (2) is ascertained depending on the respective limit value, the actual gear and a desired target rotational speed of the input rotational speed of the group transmission (2) or of the rotational speed of the drive unit (1).

7. Method according to claim 6, characterized in that ​ ​ ​ ​ ​ ​ ​ ​ ​ The target gear of the group transmission (2) is ascertained in such a way that the target rotational speed of the input rotational speed of the group transmission (2) or of the rotational speed of the drive unit (1) lies in a range that is in the middle between the maximum permissible rotational speed of the drive unit (1) and the idling rotational speed of the drive unit (1).

8. Control device for operating a drive train of a motor vehicle, wherein which drive train has a drive unit (1), an automated group transmission (2) which is connected between the drive unit (1) and an output (3), and a separating clutch (5) which is connected between the drive unit (1) and the group transmission (2), wherein the group transmission (2) has a plurality of partial transmissions, namely at least a main transmission (9) and also a sub-transmission (10) which is located upstream in terms of drive technology and a range group (11) which is located downstream in terms of drive technology from the main transmission (9), wherein, in the event of a driving speed of the motor vehicle which is not zero, the control device activates an emergency shift program when the separating clutch (5) cannot be utilized, i.e. cannot be shifted, for implementing a shift in the group transmission (2), wherein, in the emergency shift program, the control device automatically triggers a shift from an actual gear of the group transmission (2) to a target gear of the group transmission (2) only in the main transmission (9) and / or in the range group (11) which is located downstream in terms of drive technology from the main transmission (9) and not in the sub-transmission (10) which is located upstream in terms of drive technology from the main transmission (9) with the separating clutch (5) closed, depending on the input rotational speed of the group transmission (2) or on the rotational speed of the drive unit (1).

9. The control device according to claim 8, characterized by The control device is set up to automatically implement the method according to any one of claims 1 to 3.

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