SE544764C2 - Control device and method for controlling a powertrain of a vehicle while the vehicle is in motion, related computer program and computer readable medium, and a vehicle comprising the control device - Google Patents

Abstract

A control device (100), a method for controlling a powertrain (3) of a vehicle, as well as a vehicle (1), are provided. The powertrain (3) comprises a gearbox (2) configured to allow a secondary gear to be engaged while a primary gear is transferring propulsion torque from a propulsion unit (4, 14, 16) of the powertrain (3) to an output shaft (20) of the gearbox. The method comprises, in response to a determination that a predicted time until shift of primary gear exceeds a first predetermined time limit, disengaging a secondary gear of the gearbox. A computer program and computer readable medium, and a vehicle comprising the control device are also provided.

Description

TECHNICAL FIELD The present disclosure relates in general to a method for controlling a powertrain of a vehicle while the vehicle is in motion. The present disclosure further relates in general to a control device configured to control a powertrain of a vehicle while the vehicle is in motion. The present disclosure also relates in general to a computer program and a computer-readable medium. Moreover, the present disclosure relates in general to a vehicle.

BACKGROUND Gearboxes conventionally used in vehicle powertrains may have many different configurations. One example of a frequently used gearbox in heavy vehicles is an automated manual transmission (AMT). When performing a gearshift in an AMT, an interruption in propulsion torque transmitted to the driving wheels of the vehicle necessarily occurs due to the configuration of the gearbox. Naturally, such an interruption in propulsion torque may (depending on the circumstances) lead to a loss of vehicle speed, which may have to be compensated for after the gearshift has been completed. To overcome this problem, gearboxes configured to allow gearshifts without interruption in propulsion torque have been developed.

One example of a gearbox configured to allow gearshifts without interruption in propulsion torque is a hydraulic automatic transmission, which uses planetary gears instead of gears lined up along an input shaft, a layshaft and an output shaft as used in a manual transmission such as AMT. Another example of a gearbox configured to allow gearshifts without interruption in propulsion torque is a so called dual clutch transmission (DCT), which uses two separate clutches for odd and even gears sets. Each of the clutches is connected to a respective input shaft, which in turn is connected to the output shaft via a layshaft. By timing the engagement of one clutch to the disengagement of the other clutch, a DCT can shift gears without interrupting the propulsion torque to the driving wheels. Yet another example of a gearbox capa ble of allowing gearshifts without interruption in propulsion torque is described in US 2016/0053864 A1. ln contrast to the DCT, the gearbox described in US 2016/0053864 relies on the principle of two main shafts, each connected to a respective planetary gear. Furthermore, the two planetary gears are connected to each other.

Both the DCT and the gearbox comprises two possible mechanical paths for transferring propulsion torque from a propulsion unit to an output shaft of the gearbox. ln order to shift gear without interruption in propulsion torque, both the DCT as well as the gearbox described in US 2016/0053864 rely on the possibility of having a secondary gear engaged in the mechanical path of the gearbox not currently transferring propulsion torque from a propulsion unit to the output shaft of the gearbox. When the gearbox should be shifted, the engaged secondary gear is thereby ready to transfer propulsion torque from the propulsion unit and the gearbox can thus be shifted such that the secondary gear becomes the primary gear. More specifically, shifting of the primary gear is achieved by changing the mechanical path through which propulsion torque is transferred in the gearbox. ln case no secondary gear is engaged, an interruption in propulsion torque during gearshift cannot be avoided. Furthermore, in case an unsuitable secondary gear is engaged when the gearbox is to be shifted, the gearbox may need to be pre-shifted to a more appropriate secondary gear before the gearbox may be shifted to a new primary gear. Naturally, this causes a delay in the intended gearshift of the gearbox. Alternatively, an interruption in propulsion torque may have to be accepted when shifting the gearbox to new primary gear in case the currently engaged secondary gear is not an appropriate gear selection for the continued operation of the vehicle. An interruption in propulsion torque during gearshift or a delayed gearshift may have to be compensated for after the gearshift, which in turn may increase the energy consumption of the vehicle and therefore lead to for example increased fuel consumption.

SUMMARY The object of the present invention is to enable an energy efficient operation of a vehicle having a powertrain comprising a gearbox configured to perform gearshifts without interruption in propulsion torque.

The object is achieved by the subject-matter of the appended independent claim(s). ln accordance with the present disclosure, a method for controlling a powertrain of a vehicle while the vehicle is in motion is provided. The method is performed by a control device. The powertrain comprises a gearbox configured to allow a secondary gear to be engaged while a primary gear is transferring propulsion torque from a propulsion unit of the powertrain to an output shaft of the gearbox. The method comprises a step of, in response to a determination that a predicted time until shift of primary gear exceeds a first predetermined time limit, disengaging a secondary gear of the gearbox.

By disengaging the secondary gear, energy |osses in the powertrain may be significantly reduced. Thereby, the method may lead to a lower energy consumption from an energy storage device in case the powertrain is powered by an electrical machine and/or a reduction in fuel consumption and exhaust gas emissions in case the powertrain is powered by a combustion engine. Furthermore, since the disengagement of the secondary gear is performed in response to a determination that the predicted time until shift of primary gear exceeds a first predetermined time limit, the risk of the disengagement of the secondary gear resulting in having to perform a shift of primary gear with an interruption in propulsion torque is significantly reduced. Thus, the present method leads to an improved energy efficiency in the operation of a powertrain comprising a gearbox capable of performing gearshifts without interruption in propulsion torque.

The method may further comprise a step of, when the secondary gear has been disengaged, maintaining the gearbox in a state wherein no secondary gear is engaged during at least a portion of said predicted time until shift of primary gear. Thereby, the energy loss in the powertrain is further reduced.

The step of disengaging the secondary gear may be performed in response to a determination that an estimated amount of energy that may be saved by said disengagement of the secondary gear exceeds a preselected energy threshold value. Thereby, disengagement of secondary gear in situations where there is no or only little possibility for energy savings can be avoided. This may in turn improve the comfort for a driver of the vehicle as well as reduce the possible wear of the constituent components of the gearbox for reducing the number of disengagements and engagements of gears, by avoiding disengagement of the secondary gear in situations where the possible energy savings are not justified.

According to one aspect, the gearbox comprises a first planetary gear connected to a first main shaft of the gearbox and a second planetary gear connected to the first planetary gear and a second main shaft of the gearbox. The gearbox according to the aspect further comprises a layshaft connectable to an output shaft of the gearbox, a first set of gear pairs arranged between the first main shaft and the layshaft, and a second set of gear pairs arranged between the second main shaft and the layshaft. Moreover, according to said aspect, the powertrain further comprises a first propulsion unit in the form of a first electrical machine connecta ble to the first planetary gear and a second propulsion unit in the form of a second electrical machine connectable to the second planetary gear. Such a powertrain inter alia has the advantage of, in addition to allowing gearshifts without interruption in propulsion torque, enabling a large number of gear steps, which in turn makes it suitable for use in a heavy vehicle. Furthermore, it allows for a large variety gear selection strategies depending on the circumstances, which in turn improves the performance of the powertrain and thus also the vehicle. The configuration of the powertrain also enables an independent control of the first main shaft and the second main shaft. Such a powertrain may also have a relatively compact design. Furthermore, the powertrain has the advantage of enabling electric drive of a vehicle, even in case the vehicle is a heavy vehicle, as well as the ability to use regenerative braking for controlling the vehicle speed. Furthermore, this gearbox overcomes the disadvantage associated with a dual clutch of considera ble wear of the clutches and possible energy losses associated with gearshifts due to the timing of the connection and disconnection of the two clutches.

The method may further comprise a step of, after the secondary gear has been disengaged, interrupting power supply to the electrical machine of the first electrical machine and the second electrical machine that is not currently connected to the output shaft of the gearbox via the primary gear. Thereby, further energy savings may be made by not having the one of the electrical machines not currently acting as a propulsion unit consuming energy by being operated in idle speed.

The method may further comprise a step of, in response to a determination that a predicted time until shift of primary gear is equal to or below a second predetermined time limit, pre-shifting the gearbox by engaging a secondary gear. Thereby, the risk of having to perform a gearshift resulting in an interruption in propulsion torque is significantly reduced.

The present disclosure further relates to a computer program comprising instructions which, when executed by a control device, cause the control device to carry out the method as described above.

The present disclosure further relates to a computer-readable medium comprising instructions which, when executed by a control device, cause the control device to carry out the method as described above.

Moreover, in accordance with the present disclosure, a control device configured to control a powertrain of a vehicle while the vehicle is in motion is provided. The powertrain comprises a gearbox configured to allow a secondary gear to be engaged while a primary gear is transferring propulsion torque from a propulsion unit of the powertrain to an output shaft of the gearbox. The control device is configured to, in response to a determination that a predicted time until shift of primary gear exceeds a first predetermined time limit, disengage a secondary gear of the gearbox.

The control device has the same advantages as described above with regard to the corresponding method of controlling a powertrain of a vehicle while the vehicle is motion.

The control device may further be configured to, when the secondary gear has been disengaged, maintain the gearbox in a state wherein no secondary gear is engaged during at least a portion of said predicted time until shift of primary gear.

The control device may further be configured to perform said disengagement of the secondary gear in response to a determination that an estimated amount of energy that may be saved by said disengagement of the secondary gear exceeds a preselected energy threshold value.

As mentioned above, the gearbox may according to one aspect comprise a first planetary gear connected to a first main shaft of the gearbox and a second planetary gear connected to the first planetary gear and a second main shaft of the gearbox. The gearbox according to the aspect further comprises a layshaft connecta ble to an output shaft of the gearbox, a first set of gear pairs arranged between the first main shaft and the layshaft, and a second set of gear pairs arranged between the second main shaft and the layshaft. Moreover, according to said aspect, the powertrain further comprises a first propulsion unit in the form of a first electrical machine connectable to the first planetary gear and a second propulsion unit in the form of a second electrical machine connectable to the second planetary gear.

The control device may further be configured to, after the secondary gear has been disengaged, interrupt power supply to the electrical machine of the first electrical machine and the second electrical machine that is not currently connected to the output shaft of the gearbox via the primary gear The control device may further be configured to, in response to a determination that a predicted time until shift of primary gear is equal to or below a second predetermined time limit, pre-shift the gearbox by engaging a secondary gear.

The present disclosure further provides a vehicle comprising the control device as described above. The vehicle may further comprise a powertrain comprising a gearbox configured to allow a secondary gear to be engaged while a primary gear is transferring propulsion torque from a propulsion unit of the powertrain to an output shaft of the gearbox. The vehicle may be a heavy vehicle, such as a truck or a bus. The vehicle may for example be a hybrid vehicle or a fully electric vehicle.

BRIEF DESCRIPTION OF DRAWINGS Fig. 1 schematically illustrates a side view of one example of a vehicle, Fig. 2 schematically illustrates a first exemplifying embodiment of a vehicle powertrain that may be controlled by the method as described herein, Fig. 3 schematically illustrates a second exemplifying embodiment of a vehicle powertrain that may be controlled by the method as described herein, Fig. 4 represents a flowchart schematically illustrating a method for controlling a powertrain of a vehicle, while the vehicle is in motion, in accordance with an exemplifying em bodiment of the present disclosu re, Fig. 5 schematically illustrates a device that may constitute, comprise or be a part of a control device configured to control a powertrain of a vehicle.

DETAILED DESCRIPTION The invention will be described in more detail below with reference to exemplifying embodiments and the accompanying drawings. The invention is however not limited to the exemplifying embodiments discussed and/or shown in the drawings, but may be varied within the scope of the appended claims. Furthermore, the drawings shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate the invention or features thereof.

The term ”secondary gear" is in the present disclosure considered to mean a gear which is engaged in the gearbox, but not currently used for transfer of propulsion torque from any propulsion unit to the driving wheels of the vehicle. ln contrast, a ”primary gear” is an engaged gear which is currently used for transfer of propulsion torque from one or more propulsion units to the drive wheels of the vehicle. lt should here be noted that an engaged secondary gear may still transfer torque, for example to a power take-off connected to the gearbox.

Furthermore, the terms "pre-shift", "pre-shifting", or similar expressions, refer to a gearshift in the gearbox which does not alter the mechanical path through which propulsion torque is transferred in the gearbox from one or more propulsion units to the output shaft of the gearbox (and thus the driving wheels of the vehicle).

Moreover, in the present disclosure, the term ”vehicle speed profile” is used. This should not be construed as limited to a specific vehicle speed in every geographical point, but may typically comprise a vehicle speed interval within which the vehicle should travel for a defined or undefined road segment. Such a road segment may also be divided into a plurality of sub-segments having different desired or targeted vehicle speed intervals, together forming the vehicle speed profile. A vehicle speed profile may for example be selected by a control system of the vehicle, and may for example be dependent of possible input from a driver of the vehicle, speed limits of the road Segment etC. .

Furthermore, the term ”map data” is in the present context considered to comprise both geographical data and topographic data. ln accordance with the present disclosure, a method for controlling a powertrain of a vehicle is provided. The method is performed when the vehicle is in motion. ln other words, the method is performed when the vehicle is travelling. The method is performed by a control device. The powertrain of the vehicle comprises a gearbox configured to allow a secondary gear to be engaged while a primary gear is transferring propulsion torque from a propulsion unit of the powertrain to an output shaft of the gearbox. The gearbox is capa ble of performing gearshifts without interruption in propulsion torque to an output shaft of the gearbox (and thus without interruption in propulsion torque to the drive wheels of the vehicle). The method comprises a step of, in response to a determination that a predicted time until shift of primary gear exceeds a first predetermined time limit, disengaging a secondary gear of the gearbox (if not already disengaged).

When the secondary gear has been disengaged, the gearbox may be maintained in a state wherein no secondary gear is engaged during a certain period of time as will be further discussed below. ln other words, the method may comprise, when the secondary gear has been disengaged, inhibiting an engagement of a secondary gear (i.e. pre-shifting) for a certain period of time.

Having a secondary gear engaged, while a primary gear is transferring propulsion torque from one or more propulsion units of the powertrain to the output shaft of the gearbox, has the advantage of reducing the risk of having to perform a gearshift which entails an interruption in propulsion torque to the drive wheels of the vehicle. For said reason, the gearbox of the herein described kind is usually pre-shifted by engaging a new secondary gear shortly after the gearbox has been shifted to a new primary gear. The secondary gear is selected to be the most likely appropriate new primary gear and the selection thereof may thus be based on predictions of the future operation of the powertrain. Such predictions may typically take into account a desired vehicle speed profile for an upcoming road section as well as map data relating to said upcoming road section. However, having a secondary gear engaged may also lead to an energy loss in the powertrain due to for example friction losses. Said loss of energy therefore has to be compensated for by one or more propulsion units of the powertrain in order to for example maintain a desired vehicle speed profile.

However, by means of the present method, the secondary gear is disengaged if the predicted time until next shift of primary gear is longer than a first predetermined time limit. By disengaging the secondary gear, such that only the primary gear is engaged, the above-described energy loss is essentially removed or at least significantly reduced. This may in turn lead to lower fuel consumption of the vehicle in case of a propulsion unit in the form of a combustion engine and/or less power consumption from an energy storage device of the vehicle in case of a propulsion unit in the form of an electrical machine. Since the secondary gear is disengaged in response to a determination that the predicted time until shift of primary gear exceeds the first predetermined time limit, it is ensured that the operational conditions of the vehicle are such that the likelihood of needing a secondary gear in the near future is minimal and that it therefore is acceptable to temporarily disengage the secondary gear.

The method may comprise a step of predicting the time until shift of primary gear. This may be performed based on configuration of the powertrain and/or the vehicle, as well as map data relating to an upcoming road section. Moreover, the current vehicle speed and/or a desired vehicle speed profile may be taken into account when predicting the time until shift of primary gear. Other factors, such as vehicle load, may also be taken into account when predicting the time until shift of primary gear. The step of predicting the time until shift of primary gear may suitably be repeated continuously, or be performed at regular time intervals. The method may further comprise a step of determining whether such a predicted time unit shift of primary gear exceeds the first predetermined time limit.

As an alternative to the above-mentioned steps of predicting the time until shift of primary gear and determining whether said predicted time exceeds the first predetermined time limit, the method may comprise obtaining information that a determination that a predicted time unit shift of primary gear exceeds the first predetermined time limit has been made. Such information may be obtained from a separate control arrangement (other than the control device configured to perform the herein described method), which in turn is configured to determine whether a predicted time until shift of primary gear exceeds the first predetermined time limit. The step of disengaging the secondary gear may then be performed upon the control device receiving information that a determination has been made of the predicted time until shift of primary gear exceeding the first predetermined time limit. Thus, also in such a case the step of disengaging the secondary gear is performed in response to a determination that a predicted time unit shift of primary gear exceeds the first predetermined time limit.

As mentioned above, the disengagement of the secondary gear is performed in response to a determination that the predicted time until shift of primary gear exceeds the first predetermined time limit. The first predetermined time limit may be a preselected time limit, selected based on various factors. Examples of such factors include powertrain and/or vehicle configuration, possibility for sufficient time for having no secondary gear engaged for the purpose of reducing energy loss, a desired maximum number of disengagement/engagement of gears per time unit based on for example desired service life of constituent components of the gearbox and/or driver comfort, etc., but is not limited thereto. Said first predetermined time limit may for example be selected to be about 5 seconds, about 10 seconds or about 15 seconds, but is not limited thereto.

The method may further comprise a step of determining an expected time that the gearbox may be maintained in a state wherein no secondary gear is engaged without risking that an upcoming shift of primary gear may have to be performed with an interruption in propulsion torque. Such a determination of the expected time that the gearbox may be maintained in a state wherein no secondary gear is engaged may be made based on the predicted time until shift of primary gear, also taking into account the time it would take to engage a secondary gear. For the purpose of minimizing energy losses (as described above) in the powertrain, the gearbox would ideally be maintained in the state wherein no secondary gear is engaged during such a determined expected time. However, in reality, it may be necessary to incorporate a certain safety margin to reduce the risk of having to perform a gearshift of primary gear with an interruption in propulsion torque. Furthermore, it may in some cases not be suitable to maintain the gearbox in a state wherein no secondary gear is engaged for the whole expected duration, for example in case of an unexpected a|teration in the operational condition of the powertrain. For said reason, a more appropriate approach may in many cases be to, while the secondary gear is disengaged, monitoring the operational conditions of the powertrain as well as map data of upcoming road section(s) to determine if the gearbox may be maintained in the state wherein no secondary gear is engaged for essentially the whole expected time determined as described above (minus the potential safety margin). ln case the situation would be changed from what was expected when disengaging the secondary gear, the step of inhibiting engagement of secondary gear (i.e. the step of inhibiting pre-shifting of the gearbox) may then be terminated. lt should however be recognized that in certain situations, it may be disadvantageous to terminate a step of inhibiting engagement of a (new) secondary gear too early for example due to the risk of leading to an undesired higher number of engagements and disengagements of secondary gear. Moreover, in case it has been determined that the predicted time until shift of primary gear exceeds the first predetermined time limit, the likelihood of the time until an actual need for shift of primary gear being significantly different from the predicted time immediately after disengagement of the secondary gear is low. Therefore, the method may comprise a step of, when the secondary gear has been disengaged, maintaining the gearbox in a state wherein no secondary gear is engaged during at least a portion of the (previously) predicted time until shift of primary gear. ln other words, the method may comprise inhibiting pre-shifting of the gearbox, i.e. engaging a secondary gear, during at least a portion of the predicted time (on which the determination that it exceeds the first predetermined time limit is based) until shift of primary gear. Such a portion may for example be a percentage of the predicted time until shift of primary gear. lt should here be noted that in case of the predicted time until shift of primary gear being comparatively short, a higher percentage may be allowed compared to a case of the predicted time until shift of primary gear being very long (for example in case the vehicle would be travelling at essentially constant speed on a road having an essentially constant road gradient for a long time). Therefore, the percentage may be selected based on the length of the predicted time. Such percentages dependent of the length of the predicted time may for example be determined in advance and stored in a look-up table in the control device or at a remote control center from which data can be retrieved by the control device. ln certain situations, it may not be necessary or desired to disengage the secondary gear although the predicted time until next shift of primary gear exceeds the first predetermined time limit. By way of example, one such situation may be if the amount of energy that may be saved by disengagementof the secondary gear does not justify the increased number of pre-shifts with the associated possible wear of the constituent components of the gearbox and/or reduced driver comfort. Therefore, the step of disengaging the secondary gear may, if desired, further be performed in response to a determination that an estimated amount of energy that may be saved by said disengagement of the secondary gear exceeds a prese|ected energy threshold value. The estimation of the amount of energy that may be saved by disengagement of the secondary gear may be made based on the expected time that the secondary gear may be disengaged without risking having to perform an upcoming shift of primary gear with an interruption in propu|sion torque.

After the above-described step of disengaging the secondary gear and maintaining the gearbox in a state wherein no secondary gear is engaged, the method may comprise a step of pre-shifting the gearbox by engaging a secondary gear. This is performed by engaging an appropriate gear (other than the currently engaged primary gear) as a secondary gear. This gear may be the same gear of the gearbox as constituted the secondary gear previously disengaged, or another gear that, based on the current operation of the powertrain and an upcoming road section, now is a more appropriate selection as secondary gear.

The step of pre-shifting the gearbox by engaging a secondary gear may be performed in response to a determination that the predicted time until shift of primary gear is equal to or below a second predetermined time limit. The second predetermined time limit may be shorter than the first predetermined time limit. Alternatively, the second predetermined time limit may be selected to be equal to the first predetermined time limit. By way of example, the second predetermined time limit may correspond to the time it would take to identify the gear to be engaged as secondary gear, engaging said gear as secondary gear, plus an appropriate safety margin. The second predetermined time limit may typically be in the order of one or a few seconds, but is not limited thereto.

Alternatively, the step of pre-shifting the gearbox by engaging a secondary gear may be performed in response to a detection that the powertrain approaches a shift limit for shifting the primary gear. The shift limit may for example correspond to speed limits for at least one propu|sion unit of the powertrain. lf the powertrain approaches a shift limit, there might be a risk of having to perform a shift of primary gear within short, and a secondary gear may therefore be engaged as a safety mGHSUFG.

The present method has primarily been developed for the control of a powertrain comprising a gearbox comprising two planetary gears, each connected to a respective main shaft. Morespecifically, the said gearbox comprises a first planetary gear connected to a first main shaft of the gearbox, and a second planetary gear connected to the first planetary gear and a second main shaft of the gearbox. Said gearbox further comprises a layshaft connectable to an output shaft of the gearbox, a first set of gear pairs arranged between the first main shaft and the layshaft, and a second set of gear pairs arranged between the second main shaft and the layshaft. The first planetary gear is connectable to a first electrical machine, which constitutes a first propulsion unit of the plurality of propulsion units. The second planetary gear is connectable to a second electrical machine, which constitutes a second propulsion unit of the plurality of propulsion units. This powertrain inter alia has the advantage of enabling two parallel main shafts that may transfer torque independently of each other without the need for a dual clutch configuration for connecting the gearbox to a propulsion unit. One disadvantage of a dual clutch configuration, which may also enable gearshifts without interruption in propulsion torque, is that the clutches are generally subjected to considerable wear and the powertrain may suffer from considera ble energy losses for ena bling the gearshifts without interruption in propulsion torque. Furthermore, in comparison with a dual clutch configuration, this powertrain has the advantage of at least two propulsion units that independently of each other may influence the transfer of propulsion torque via the gearbox to driving wheels of the vehicle.

Moreover, it enables electric drive and therefore reduces fuel consumption and emissions.

The above-described powertrain comprising two planetary gears and two electrical machines may further comprise a third propulsion unit in the form of a combustion engine. ln such a case, a hybrid powertrain is provided. The combustion engine may be connectable to an input shaft of the gearbox, which in turn is connected to the first planetary gear. The combustion engine may be permanently connected to the input shaft of the gearbox, or may be connected/disconnected from the gearbox by a clutch arranged between the input shaft and the combustion engine. lt should however be noted that the present method may also be utilized for control of other powertrains comprising a gearbox configured to allow a secondary gear to be engaged while a primary gear is transferring propulsion torque from a propulsion unit of the powertrain to an output shaft of the gearbox, such as a powertrain comprising a dual clutch transmission, if desired. ln case the powertrain comprises the above-described gearbox comprising two planetary gears, each connected to a respective electrical machine, it may in certain situations be possible to reduce energy consumption even further when the secondary gear has been disengaged. More specifically, by reducing the energy consumption of the electrical machine that is not currently acting as a propulsion unit, less energy consumption from an energy storage device (powering said electricalmachine, or both of the electrical machines) may be achieved. Therefore, the method may comprise a step of, after the secondary gear has been disengaged, interrupting power supply to the electrical machine not currently connected to the output shaft of the gearbox via the primary gear. ln other words, the method may comprise interrupting power supply to the electrical machine not currently providing propulsion torque to the drive wheels of the vehicle. This may be achieved by turning off an inverter arranged between said electrical machine and the energy storage device.

The performance of the herein described method for controlling a powertrain of a vehicle may be governed by programmed instructions. These programmed instructions typically take the form of a computer program which, when executed in or by a control device, cause the control device to effect desired forms of control action. Such instructions may typically be stored on a computer-readable medium.

The present disclosure further relates to a control device configured to control a powertrain of a vehicle in accordance with the method as described herein. The control device may be configured to perform any one of the steps of the method for controlling a powertrain of a vehicle as described herein.

More specifically, a control device configured to control a powertrain of a vehicle is provided. The control device is configured to control the powertrain at least when the vehicle is in motion, but may also be configured to control the powertrain in other situations, if desired. Said powertrain comprises a gearbox configured to allow a secondary gear to be engaged while a primary gear is transferring propulsion torque from a propulsion unit of the powertrain to an output shaft of the gearbox. The control device is configured to, in response to a determination that a predicted time until shift of primary gear exceeds a first predetermined time limit, disengage a secondary gear of the gearbox. More specifically, the control device is configured to perform said disengagement of the secondary gear when the vehicle is in motion.

The control device may further be configured to predict the time until shift of primary gear, prefera bly continuously or at selected time intervals. The control device may further be configured to, when the secondary gear has been disengaged, maintain the gearbox in a state wherein no secondary gear is engaged during a certain period of time. Said period of time may for example be dependent of the predicted time until shift of primary gear. For example, the control device may be configured to inhibit pre-shifting of the gearbox after the secondary gear has been disengaged. The control device may further be configured to, in response to a determination that a predicted timeuntil shift of primary gear is equal to or below a second predetermined time limit, pre-shift the gearbox by engaging a secondary gear.

The control device may comprise one or more control units. ln case of the control device comprising a plurality of control units, each control unit may be configured to control a certain function or a certain function may be divided between more than one control units.

The control device may be a control device of the powertrain and/or comprised in the vehicle. Alternatively, parts of the control device may be arranged remote from the vehicle, for example at a remote control center or the like. The control device may further be configured to communicate with external units, which in turn may be arranged at a remote control center or the like, for example for the purpose of obtaining map data or the like. The control device may further be configured to determine the geographical position of the vehicle in accordance with any previously known method therefore, such as by GPS or the like.

The present disclosure further relates to a vehicle the control device described above. The vehicle may comprise a powertrain comprising a gearbox configured to allow a secondary gear to be engaged while a primary gear is transferring propulsion torque from one or more propulsion units of the powertrain to an output shaft of the gearbox. The vehicle may be a heavy, land-based, vehicle, such as a bus or a truck. The vehicle may for example be a hybrid vehicle or a fully electric vehicle.

Figure 1 schematically illustrates a side view of an example of a vehicle 1. The vehicle 1 comprises a vehicle powertrain 3. The vehicle powertrain 3 comprises a gearbox 2 and at least one propulsion unit, such as a combustion engine 4 and/or a first electrical machine 14, connectable to the gearbox. The an output shaft of the gearbox 2 may be connected to drive wheels 5 of the vehicle via a propeller shaft 6. The vehicle may be a heavy land-based vehicle, such as a truck or a bus, but is not limited thereto.

Figure 2 schematically illustrates a first exemplifying embodiment of a powertrain 3. The powertrain 3 may be comprised in a vehicle, such as the vehicle 1 shown in Fig. 1. The powertrain 3 comprises a plurality of propulsion units. The plurality of propulsion units may comprise a combustion engine 4, a first electrical machine 14 and a second electrical machine 16. The combustion engine 4 may be connected to the gearbox 2 via an input shaft 8 of the gearbox 2. More specifically, an output shaft 9 of the combustion engine 4 may be connected to the input shaft 8 of the gearbox 2 via a clutch 7 or the like. The purpose of the clutch 7 is to enable disconnecting the combustion engine 4 from the gearbox 2, for example during shut down of the com bustion engine 4 for the purpose of saving fuel and/or reducing emissions by operating the vehicle electrically.

The gearbox 2 comprises a first planetary gear 10, a second planetary gear 12, and an output shaft 20. The first planetary gear 10 is connected to the input shaft 8 of the gearbox 2, and the second planetary gear 12 is connected to the first planetary gear The first planetary gear 10 comprises a first ring gear 22, to which a rotor 24 of the first electrical machine 14 is connected. The first planetary gear 10 further comprises a first sun gear 26, a first set of planet wheels 52, and a first planet wheel carrier 50. The first set of planetary wheels 52 is mounted to the first planetary wheel carrier 50. The first set of planet wheels 52 interacts with the first ring gear 22 and the first sun gear The second planetary gear 12 comprises a second ring gear 28, to which a rotor 30 of the second electrical machine 16 is connected. The second planetary gear 12 further comprises a second sun gear 32, a second set of planet wheels 54, and a second planet wheel carrier 51. The second set of planet wheels 54 interacts with the second ring gear 28 and the second sun gear 32. The second set of planetary wheels 54 is mounted to the second planetary wheel carrier 51. The first and second sun gears 26, 32, may be arranged coaxially, as shown in Figure The input shaft 8 of the gearbox 2 is connected to the first planet wheel carrier 50. The first planet wheel carrier 50 is directly connected to the second sun gear 32 of the second planetary gear 12 such that the first planet wheel carrier 50 and the second sun gear 32 will always have the same rotational speed.

Furthermore, a first coupling device 56 is arranged between the first sun gear 26 and the first planet wheel carrier 50. By arranging the first coupling device 56 such that the first sun gear 26 and the first planet wheel carrier 50 are connected to each other, and thus not able to rotate relative to each other, the first planet wheel carrier 50 and the first sun gear 26 will rotate with the same rotational speed. ln Figure 2, the coupling device 56 is shown in an open (disengaged) state, whereby the planet wheel carrier 50 and the first sun gear 26 are not connected to each other.

A second coupling device 58 is arranged between the second sun gear 32 and the second planet wheel carrier 51. By arranging the second coupling device 58 such that the second sun gear 32 and the second planet wheel carrier 51 are connected to each other and thus not able to rotate relativeto each other, the second planet wheel carrier 51 and the second sun gear 32 will rotate with the same rotational speed. ln Figure 2, the second coupling device 58 is shown in an open (disengaged) state and does therefore not connect the second wheel carrier 51 and the second sun gear The first and second coupling devices 56, 58 may each comprise a splines-equipped coupling sleeve, which is axially displaceable on a splines-equipped section on the first and second planetary wheel carrier 50, 51, respectively, and on a splines-equipped section on the respective sun wheels 26, The gearbox 2 further comprises a first main shaft 34 and a second main shaft 36. The first main shaft 34 is connected to the first sun wheel 26 of the first planetary gear 10. The second main shaft 36 is connected to the second planetary wheel carrier 51. As shown in Figure 2, the first main shaft 34 may be arranged so as to extend inside the second main shaft 36. For this purpose, the second main shaft 36 may comprise a central bore. Alternatively, the first main shaft 34 may be arranged in parallel and at the side of the second main shaft 36 (which in such a case need not have a central bore). The first main shaft 34 and the second main shaft 36 are connected to the output shaft 20 through a transmission arrangement 19, which will be described in more detail below. The transmission arrangement 19 can comprise a freely chosen number of gear steps.

The first electrical machine 14 comprises a first stator 40, which may be connected to a housing 42 that surrounds the gearbox 2. The second electrical machine 16 comprises a second stator 44, which may be connected to the housing 42. The first electrical machine 14 and the second electrical machine 16 are connected to an energy storage device (not shown), such as a battery, that may drive the electrical machines 14, 16 depending on the operating conditions of the vehicle. Alternatively, the first and second electrical machines 14, 16 may each have a separate energy storage, if desired, for the same purpose. ln certain operating conditions, the electrical machines 14, 16 can function as generators, whereby current is supplied to the energy storage(s). ln certain operating conditions, the electrical machines 14, 16 may also drive each other. ln such a case, electrical energy is then led from one of the electrical machines to the other electrical machine via a switch (not shown). Thereby, it is possible to achieve a power balance between the electrical machines 14, The transmission arrangement 19 comprises, in addition to the first main shaft 34 and the second main shaft 36, a layshaft 18. The transmission arrangement 19 further comprises a plurality of gear pairs. For example, the transmission arrangement may comprise a first gear pair G1, a second gear pair G2, a third gear pair G3 and a fourth gear pair G4. The first gear pair G1 may comprise a first pinion gear 62 and a first cogwheel 64, which are in engagement with each other. The first piniongear 62 may be arranged on the first main shaft 34 and the first cogwheel 64 may be arranged on the layshaft 18. The second gear pair G2 comprises a second pinion gear 68 and a second cogwheel 70, which are in engagement with each other. The second pinion gear 68 may be arranged on the second main shaft 36 and the second cogwheel 70 may be arranged on the layshaft 18. The third gear pair G3 may comprise a third pinion gear 74 and a third cogwheel 76, which are in engagement with each other. The third pinion gear 74 may be arranged on the first main shaft 34 and the third cogwheel 76 may be arranged on the layshaft 18. The fourth gear pair G4 may comprise a fourth pinion gear 80 and a fourth cogwheel 82, which are in engagement with each other. The fourth pinion gear 80 may be arranged on the second main shaft 36 and the fourth cogwheel 82 may be arranged on the layshaft The first and the third pinion gears 62, 74 may be fixedly connected to the first main shaft 34, so that they cannot rotate in relation to the first main shaft 34. The second and the fourth pinion gears 68, 80 may be fixedly connected with the second main shaft 36, so that they cannot rotate in relation to the second main shaft The first, second, third and fourth cogwheels 64, 70, 76, 82 may be individually connected to and disconnected from the layshaft 18 by means of a third coupling device 83 and a fourth coupling device 85, respectively. The coupling devices 83, 85 may each comprise coupling s|eeves configured to mechanically engage with splines-equipped sections on the cogwheels 64, 70, 76, 82 and on the layshaft 18. The first and third cogwheels 64, 76 may be connected/disconnected with a common coupling device 83, and the second and fourth cogwheels 70, 82 may be connected/disconnected with a common coupling device 85. ln a disconnected state, a relative rotation may occur between a disconnected cogwheel, of the cogwheels 64, 70, 76, 82, and the layshaft 18. ln a connected state, a connected cogwheel, of the cogwheels 64, 70, 76, 82, will rotate together with the layshaft The gearbox 2 shown in Figure 2 also comprises a fifth gear pair G5. The fifth gear pair G5 comprises a fifth cogwheel 92 arranged on the layshaft 18 and a fifth pinion gear 94 arranged on the output shaft 20. Thus, the layshaft 18 is connected to the output shaft 20 via the fifth gear pair G5. The fifth cogwheel 92 is arranged so it may be connected with and disconnected from the layshaft 18 by means of a fifth coupling device 87. The fifth coupling device 87 may comprise a coupling sleeve configured to interact with splines-equipped sections on the fifth cogwheel 92 and the layshaft 18. ln the disconnected state, a relative rotation may occur between the fifth cogwheel 92 and the layshaftPropelling torque may be transferred to the output shaft 20 of the gearbox 2 via the first planetary gear 10, or the second planetary gear 12, and the layshaft 18. The torque transfer may also occur directly via the first planetary gear 10 and the first main shaft 34 to the output shaft 20 via a sixth coupling device 48. The sixth coupling device 48 may comprise a splines-equipped coupling sleeve, which is axially displaceable on the first main shaft 34 and on splines-equipped sections of the output shaft 20. By disp|acing the coupling s|eeve of the sixth coupling device 48, so that the first main shaft 34 is connected to the output shaft 20, the first main shaft 34 and the output shaft 20 will have the same rotationa| speed. By disconnecting the fifth cogwheel 92 from the layshaft 18, torque from the second planetary gear 12 may (via the second main shaft 36) be transferred to the layshaft 18, from the layshaft 18 to the first main shaft 34, and finally to the output shaft 20 via the sixth coupling device During operation, the gearbox 2 may in certain operating modes operate so that one of the sun gears 26 or 32 is locked against the first or second planet wheel carrier 50 or 51 with the aid of the first or second coupling device 56 or 58. The first or second main shaft 34 or 36 will then be given the same rotationa| speed as the input shaft 8, depending on which sun gear 22 or 28 that has been fixedly locked at the relevant planet wheel carrier 50 or 51. One or both of the electrical machines 14, 16 may function as a generator in order to generate energy to the energy storage device. Alternatively, the electrical machines 14, 16 whose ring gear 22 or 28 is connected to the planet wheel carrier 50 may provide an increase in torque in order to in this way increase the torque at the output shaftof the gearbox. ln order to disengage a sun gear and a planet wheel carrier at one of the first and second planetary gears, at least one of the first and second electrical machines may be controlled such that torque balance is prevalent in the relevant planetary gear. When torque balance has been achieved, the relevant one of the first and second coupling devices may be displaced such that the sun gear and the planet wheel carrier are no longer mechanically connected to each other. The term "torque balance” is here used to denote a condition in which a torque acts on a ring gear of the planetary gear, corresponding to the product of the torque that acts on the planet wheel carrier of the planetary gear, while at the same time a torque acts on the sun gear of the planetary gear, corresponding to the product of the torque that acts on the planet wheel carrier and (1-the gear ratio of planetary gear). ln the case in which two of the constituent components of the planetary gear are connected by means of one of the first and second coupling devices, this coupling device transfers no torque between the constituent components of the planetary gear when torque balanceis prevalent. The relevant coupling device can in this way be displaced in a simple manner, and the constituent components of the planetary gear disengaged.

The configuration of the vehicle powertrain 3 according to the exemplified embodiment illustrated in Figure 2 allows gear changes to be performed without interruption of propelling torque to the output shaft 20. The configuration of the vehicle powertrain 3 also enables the first main shaft 34 to be controlled independently of the second main shaft 36 and vice versa. This in turn enables a higher flexibility in the control of the gearbox The powertrain 3 further comprises a control device 100. The control device 100 may be configured to control one or more of the constituent components of the vehicle powertrain 3. The control device 100 may comprise one or more control units. The responsibility for a specific function or control may be divided between two or more of the control units. One or more of the control units may be implemented in the form of a computer. The control device 100 may for example be connected to the first electrical machine 14 and the second electrical machine 16 of the gearbox 2, and the combustion engine 4. The control device 100 may also be connected to any other constituent component of the vehicle powertrain 3. The connections of the control device 100 to any constituent component of the vehicle powertrain 3 may be in the form of physical connection(s) and/or wireless connection(s).

The exemplifying embodiment shown in Figure 2 shows a transmission arrangement 19 comprising four gear pairs G1, G2, G3, G4, and two planetary gears 10, 12 with associated electrical machines 14, 16. However, it is possible to configure the gearbox 2 with more or fewer pinion gears and cogwheels, and with more planetary gears with associated electrical machines.

Furthermore, although Figure 2 illustrates an exemplifying embodiment wherein a combustion engine 4 may be disconnected from the input shaft 8 of the gearbox, a combustion engine may alternatively be permanently connected to the input shaft 8 of the gearbox. lt should also be noted that the vehicle powertrain 3 may be a fully electric powertrain, in which case the powertrain 3 does not comprise the combustion engine 4 illustrated in Figure The configuration of the gearbox 2 shown in Figure 2 enables a simultaneous engagement of a primary gear, through which the propulsion torque is transmitted from one or more of the propulsion units to the output shaft 20, and a secondary gear, which is not transmitting propulsion torque to the output shaft 20, in the transmission arrangement 19. By way of example only, the second gear pair G2 may be engaged as a primary gear simultaneously with either first gear pair G1 or third gear pair G3 being engaged as a secondary gear. ln such a case, propulsion torque may be transferred from the first and/or second electrical machine 14, 16 via the second main shaft 36, and further via the |ayshaft 18 to the output shaft 20. The secondary gear, according to this example either gear pair G1 or gear pair G3, is however not transferring any propulsion torque to the output shaft 20, even though they are locked for rotation with the |ayshaft Figure 3 schematically illustrates a second exemplifying embodiment of a powertrain 3. The second exemplifying embodiment of the powertrain 3 corresponds to the first exemplifying em bodiment described above and shown in Figure 2, with the exemption that the gearbox further comprises a range gearbox unit The range gearbox unit 11 is in the form of a third planetary gear comprising a third sun gear 96, a third planet wheel carrier 97 on which a third set of planetary wheels 98 is mounted, and a third ring gear 99. The third set of planetary wheels 98 interacts with the third ring gear 99 and the third sun gear 96. The input shaft 95 of the range gearbox unit 11 is connected with the third sun gear 96. The output shaft 20 is connected with the third planet wheel carrier A sixth cogwheel 93 may be locked and released on the lay shaft 18 with the help of the fifth coupling device 87 or by a separate coupling device (not shown). ln a released state, a relative motion may occur between the sixth cogwheel 93 and the lay shaft 18. The sixth cogwheel 93 engages with a seventh cogwheel 88 which is fixedly connected to the third planet wheel carrier 97. Thus, when the sixth cogwheel 93 is locked on the lay shaft 18, rotational movement and torque may be transferred between the lay shaft 18 and the third planetary wheel carrier 97. Thereby, a high range position may be obtained.

The third ring gear 99 may be connected, in a low range position, with a second housing 43 by means of a locking device 46. A downshift of the rotational speed then takes place via the range gearbox unit 11, which entails a torque increase in the output shaft 20. The second housing 43 may be the same as the housing 42 or a separate housing for the range gearbox unit.

The third sun gear 96 may be connected with the third planet wheel carrier 97 via a seventh coupling device 90, and thereby achieve a high range position. ln the engaged state of the seventh coupling device 90, the gear ratio through the range gearbox unit 11 is thereby 1:Figure 4 represents a flowchart schematically illustrating one exemplifying em bodiment of the method for controlling a powertrain of a vehicle according to the present disclosure. Optional steps are in the figure illustrated by dashed boxes and/or lines. The method is performed while the vehicle is in motion, i.e. while the vehicle is travelling. The method is performed by a control device configured to perform the method. The powertrain may have a configuration as described above, such as the configuration shown in Figure 2 or the configuration shown Figure 3. Alternatively, the powertrain may have a dual clutch configuration.

The method may comprise a step S101 of predicting the time until a shift of primary gear is to be performed. The prediction of the time until shift of primary gear may be performed in accordance with any previously known method therefore. For example, said prediction of time until shift of primary gear may be made based on the configuration of the powertrain and the vehicle and/or current vehicle mass, and may take into account map data relating to one or more upcoming road sections.

The method may further comprise a step S102 of determining whether the predicted time obtained in step S101 exceeds a first predetermined time limit. lf the predicted time until shift of primary gear does not exceed the first predetermined time limit, the method may be returned to start. However, in case it is determined that the predicted time until shift of primary gear exceeds the first predetermined time limit, the method proceeds to subsequent step(s) of the method. lt should here be noted that steps S101 and S102 may, if desired, be replaced with a step of obtaining information from a control arrangement (other than the control device configured to perform the herein described method) that a determination has been made that the predicted time until shift of primary gear exceeds the first predetermined time limit.

The method may further comprise a step S103 of estimating the amount of energy that may be saved by disengaging the secondary gear. Said estimation may for example take into account an expected time that the secondary gear may be disengaged (i.e. an expected time that the gearbox may be maintained in a state wherein no secondary gear is engaged) without risking having to perform a shift of the primary gear with an interruption in propulsion torque. Said estimation of the amount of energy that may be saved may also take into account the operating mode of the vehicle powertrain and/or map data regarding one or more upcoming road sections.The method may further comprise a step S104 of determining whether the estimated amount of energy that may be saved by disengaging the secondary gear exceeds a preselected energy threshold value. lf the estimated amount of energy that may be saved by disengaging the secondary gear does not exceed the preselected energy threshold value, the method may be reverted to start since in such a case, disengagement of the secondary gear may not be desired or needed. By way of example only, in case the amount of energy that may be saved is very low, it may be disadvantageous to disengage the secondary gear for increasing the wear of the constituent components of the gearbox and/or from a driver comfort perspective. However, in case the estimated amount of energy that may be saved by disengaging the secondary gear exceeds the preselected energy threshold value, the method proceeds to subsequent step(s) of the method.

The method comprises a step S105 of, in response to a determination that the predicted time until shift of primary gear exceeds the first predetermined time limit (provided by step S102 or from a separate control arrangement as described above), disengaging the secondary gear currently engaged in the gearbox.

When the secondary gear has been disengaged, the method may further comprise a step S106 of monitoring predicted time until shift of primary gear. This may be performed by continuously or intermittently predicting the time until shift of primary gear.

The method may further comprise a step S107 of determining whether the predicted time until shift of primary gear is equal to or lower than a second predetermined time limit. ln case the predicted time until shift of primary gear is not equal to or lower than the second predetermined time limit, the method may be reverted back to step S106. However, in case the predicted time until shift or primary gear is equal to or lower than the second predetermined time limit, the method may proceed to step S The method may comprise a step S108 of pre-shifting the gearbox by engaging a secondary gear. The secondary gear that is engaged in step S108 may be the same gear as previously engaged as secondary gear or a new gear that is now a more appropriate selection as secondary gear. The step S108 may typically be performed after a certain period of time after the step S105 of disengaging the (previous) secondary gear. When the gearbox has been pre-shifted in step S108, the gearbox will be ready for a shift of primary gear without interruption in propulsion torque.

After step S108, the method may suitably be reverted to start or, if desired, terminated.Figure 5 schematically illustrates an exemplifying embodiment of a device 500. The control device 100 described above may for example comprise the device 500, consist of the device 500, or be comprised in the device The device 500 comprises a non-volatile memory 520, a data processing unit 510 and a read/write memory 550. The non-volatile memory 520 has a first memory element 530 in which a computer program, e.g. an operating system, is stored for controlling the function of the device 500. The device 500 further comprises a bus controller, a serial communication port, I/O means, an A/D converter, a time and date input and transfer unit, an event counter and an interruption controller (not depicted).

The non-volatile memory 520 has also a second memory element There is provided a computer program P that comprises instructions for controlling a powertrain of a vehicle while the vehicle is in motion. Said powertrain comprises a gearbox configured to allow a secondary gear to be engaged while a primary gear is transferring propulsion torque from a propulsion unit of the powertrain to an output shaft of the gearbox. The computer program comprises instructions for, in response to a determination that a predicted time until shift of primary gear exceeds a first predetermined time limit, disengaging a secondary gear of the gearbox.

The program P may be stored in an executable form or in a compressed form in a memoryand/or in a read/write memory The data processing unit 510 may perform one or more functions, i.e. the data processing unit 510 may effect a certain part of the program P stored in the memory 560 or a certain part of the program P stored in the read/write memory The data processing device 510 can communicate with a data port 599 via a data bus 515. The non- volatile memory 520 is intended for communication with the data processing unit 510 via a data bus 512. The separate memory 560 is intended to communicate with the data processing unit 510 via a data bus 511. The read/write memory 550 is adapted to communicate with the data processing unit 510 via a data bus 514. The communication between the constituent components may be implemented by a communication link. A communication link may be a physical connection such as an optoelectronic communication line, or a non-physical connection such as a wireless connection, e.g. a radio link or microwave link.When data are received on the data port 599, they may be stored temporarily in the second memory element 540. When input data received have been temporarily stored, the data processing unitis prepared to effect code execution as described above.

Parts of the methods herein described may be executed by the device 500 by means of the data processing unit 510 which runs the program stored in the memory 560 or the read/write memory 550. When the device 500 runs the program, methods herein described are executed.

Claims (10)

1. A method, performed by a control device (100), for controlling a powertrain (3) of a vehicle (1) while the vehicle (1) is in motion, the powertrain (3) comprising: a gearbox (2) configured to allow a secondary gear to be engaged while a primary gear is transferring propulsion torque from a propulsion unit (4, 14, 16) of the powertrain (3) to an output shaft (20) of the gearbox (2), the method comprising a step of: in response to a determination that a predicted time until shift of primary gear exceeds a first predetermined time limit, disengaging the secondary gear of the gearbox (2).

2. The method according to claim 1, further comprising a step of: when the secondary gear has been disengaged, maintaining the gearbox (2) in a state wherein no secondary gear is engaged during at least a portion of said predicted time until shift of primary gear.

3. The method according to any one of the preceding claims, wherein the step of disengaging the secondary gear is performed in response to a determination that an estimated amount of energy that may be saved by said disengagement of the secondary gear exceeds a preselected energy threshold value.

4. The method according to any one of the preceding claims, wherein the gearbox (2) comprises: a first planetary gear (10) connected to a first main shaft (34) of the gearbox (2), a second planetary gear (12) connected to the first planetary gear (10) and a second main shaft (36) of the gearbox (2), a layshaft (18) connectable to an output shaft (20) of the gearbox (2), a first set of gear pairs arranged between the first main shaft (34) and the layshaft (18), and a second set of gear pairs arranged between the second main shaft (36) and the layshaft (18), and wherein the powertrain further comprises: a first propulsion unit in the form of a first electrical machine (14) connectable to the first planetary gear (10), anda second propulsion unit in the form of a second electrical machine (16) connectable to the second planetary gear (12).

5. The method according to claim 4, further comprising a step of: after the secondary gear has been disengaged, interrupting power supply to the first electrical machine (14) and the second electrical machine (16) that is not currently connected to the output shaft (20) of the gearbox (2) via the primary gear.

6. The method according to any one of the preceding claims, further comprising a step of: in response to a determination that a predicted time until shift of primary gear is equal to or below a second predetermined time limit, pre-shifting the gearbox (2) by engaging a secondary gea r.

7. A computer program comprising instructions which, when executed by a control device (100), cause the control device (100) to carry out the method according to any one of the preceding claims.

8. A computer-readable medium comprising instructions which, when executed by a control device (100), cause the control device (100) to carry out the method according to any one of claims 1 to

9. A control device (100) configured to control a powertrain (3) of a vehicle (1) while the vehicle (1) is in motion, the powertrain (3) comprising: a gearbox (2) configured to allow a secondary gear to be engaged while a primary gear is transferring propulsion torque from a propulsion unit (4, 14, 16) of the powertrain (3) to an output shaft (20) of the gearbox (2), wherein the control device (100) is configured to, in response to a determination that a predicted time until shift of primary gear exceeds a first predetermined time limit, disengage the secondary gear of the gearbox.

10. The control device (100) according to claim 9, further configured to, when the secondary gear has been disengaged, maintain the gearbox (2) in a state wherein no secondary gear is engaged during at least a portion of said predicted time until shift of primary gear.The control device (100) according to any one of claims 9 or 10, further configured to perform said disengagement of the secondary gear in response to a determination that an estimated amount of energy that may be saved by said disengagement of the secondary gear exceeds a preselected energy threshold value. The control device according to any one of claims 9 to 11, wherein the gearbox (2) comprises: a first planetary gear (10) connected to a first main shaft (34) of the gearbox (2), a second planetary gear (12) connected to the first planetary gear (10) and a second main shaft (36) of the gearbox (2), a layshaft (18) connectable to an output shaft (20) of the gearbox (2), a first set of gear pairs arranged between the first main shaft (34) and the layshaft (18), and a second set of gear pairs arranged between the second main shaft (36) and the layshaft (18), and wherein the powertrain further comprises: a first propulsion unit in the form of a first electrical machine (14) connectable to the first planetary gear (10), and a second propulsion unit in the form of a second electrical machine (16) connectable to the second planetary gear (12). The control device (100) according to claim 12, further configured to: after the secondary gear has been disengaged, interrupt power supply to the first electrical machine (14) and the second electrical machine (16) that is not currently connected to the output shaft (20) of the gearbox (2) via the primary gear. The control device according to any one of claims 9 to 13, further configured to: in response to a determination that a predicted time until shift of primary gear is equal to or below a second predetermined time limit, pre-shift the gearbox (2) by engaging a secondary gea r. A vehicle (1) comprising the control device (100) according to any one of claims 9 to 14.