SE543146C2 - Method for controlling a powertrain of a vehicle, control device, vehicle, computer program and computer-readable medium - Google Patents

Abstract

A method and a control device (100) for controlling a powertrain (3) of a vehicle (1), as well as a vehicle comprising such a control device, are disclosed. A power unit torque limitation is activated, if not already activated, when the gearbox (4) is operated in manual mode. Thereby, the power unit torque is limited to at most a predetermined gear-specific power unit threshold torque, optionally with a predetermined offset. The predetermined gear-specific power unit threshold is a function of power unit speed and is obtained by combining an energy efficiency map of the power unit (2) with an energy efficiency map of the gearbox (4).

Description

METHOD FOR CONTROLLING A POWERTRAIN OF A VEHICLE, CONTROL DEVICE, VEHICLE,COMPUTER PROGRAM AND COMPUTER-READABLE MEDIUM TECHNICAL FIELD The present disclosure relates in general to a method for controlling a vehicle powertrain, and acontrol device configured to control a vehicle powertrain. Furthermore, the present disclosurerelates in general to a vehicle comprising a vehicle powertrain. Moreover, the present disclosure relates in general to a computer program and a computer-readable medium.

BACKGROUND Vehicles are driven forward by a power unit torque produced by a power unit, such as a combustionengine or an electrical motor. The power unit torque is transmitted to the driving wheels of thevehicle through a powertrain of the vehicle. The powertrain comprises a gearbox adapted toselectively transfer torque between the power unit and the driving wheels at different gear ratios.Modern heavy vehicles are often equipped with an automated manual gearbox (AMT). There are also heavy vehicles, although less common, that are equipped with a manual gearbox.

Vehicie rnanufacturers are today striving to increase power unit efficiency to thereby reduce energyconsumption. This is specificaiiy an issue for nianufacturers of heavy vehicies, such as trucks andbuses. En case the poyver unit is a combustion engine, a reduction in energy consumption means areduced fuei consumption. in case the potyer unit is an electrical motor, reduced energyconsumption means reduced energy usage from an energy storage device. lt is a well-knownheuristic that low power unit speed, i.e. number of revolutions per minute, reduces energyconsumption. This is a rule that is generally true. However, for very low power unit speeds and hightorques, the power unit may actually have worse efficiency than on one gear down (one gear downassociated with a higher engine speed), especially if that lower gear has higher gearbox efficiency.The speed and torque limit where the prevailing gear is not the most efficient gear anymore ishowever difficult for a driver to know, inter alia since it largely depends on power unit configuration and gearbox cha racteristics. ln view of the above, there is a risk that the driver runs the power unit at a too low speed at high loads because the driver thinks it is efficient, but in reality it is not. ln case of an automated manual transmission (AMT), there is also a risk of the driver complaining on the automatic gear selectionstrategy if the driver finds that it is possible to drive the vehicle at one gear up even though theautomatic gear selection is running the powertrain in its most efficient mode. The driver could even switch to manual mode for not relying on the automatic gear selection.

SUMMARY The object of the present invention is to reduce the risk of a driver, during manual operation of a gearbox, running a power unit of a vehicle at inefficient operating points.

The object is achieved by means of the appended independent claims. ln accordance with the present disclosure, a method for controlling a powertrain of a vehicle isprovided. The powertrain comprises a power unit, such as a combustion engine. The powertrainfurther comprises a gearbox operable in manual mode and configured to selectively transfer torquebetween the power unit and at least one driving wheel. The method is performed by a control deviceand comprises the step of, when the gearbox is operated in manual mode, activating a power unittorque limitation (if not already activated) such that the power unit torque is limited to at most apredetermined gear-specific power unit threshold torque, optionally with a first predeterminedoffset, for the engaged gear. The predetermined gear-specific power unit threshold torque is afunction of power unit speed and is obtained by combining an energy efficiency map of the power unit with an energy efficiency map of the gearbox.

By means of the present method, a driver is prevented from running the power unit at inefficientoperating points that the driver may possibly believe are efficient due to low speed of the powerunit. lf the driver enables manual mode to for example upshift, the result of the power unit torquelimitation will be a reduced power output compared to the expected power output of the power unitif it is higher than the threshold. This in turn will clearly indicate to the driver that this is not a goodoperating point of the powertrain since the vehicle will lose traveling speed in relation to the desiredtraveling speed as a result of the power unit torque limitation. Thus, the driver would be motivated to select a lower gear, which in turn would lead to a more efficient operating point for power unit.

The first predetermined offset may be dependent of selection of performance mode of the vehiclepowertrain. For example, if the powertrain is run in an eco-mode, the first predetermined offset may very low, or even set to zero in order to avoid operation of the power unit above the predetermined gear-specific power unit threshold torque. However, the first predetermined offset may be greaterfor example in case the powertrain is run in power/off-road mode. A predetermined first offsetwhich is dependent of performance mode of the powertrain has the advantage of increasing theflexibility of operation of the powertrain to better suit various situations to which the vehicle may be exposed.

The first predetermined offset may be a predetermined gear-specific offset. For example, the firstpredetermined offset may be dependent of the gear number so as to be smaller for higher gearnumbers than for lower gear numbers. This has the advantage of allowing greater offsets for lowergear numbers where the problems associated with inefficient operating points may be lesspronounced than at higher gear numbers. This in turn minimises the risk of the driver experiencing disturbance during travel, as a result of the power unit torque limitation, causing irritation.

The predetermined offset may be set to zero for the highest gear number of the gearbox. Thereby,the power unit torque limitation will limit the output power unit torque to the actuallypredetermined gear-specific power unit threshold for the highest gear number of the gearbox (i.e. the lowest gear ratio of the gearbox).

The method may further comprise detecting that the gearbox is manually shifted. Furthermore, themethod may comprise, after detecting that the gearbox is manually shifted, a step of comparing aresulting power unit torque after the manual shift with the predetermined gear-specific power unitthreshold torque. lf the resulting power unit torque after the manual shift is above the gear-specificpower unit threshold torque, optionally with a second predetermined offset, the step of activatingthe power unit torque limitation such that the output power unit torque is limited to at most thepredetermined gear-specific power unit threshold torque, optionally with the first predeterminedoffset, is performed. ln other words, when a manual shift is performed, the resulting power unittorque is compared to the predetermined gear-specific power unit threshold torque for the resultinggear and if needed, the power unit torque limitation is then activated such that the output power unit torque is reduced.

The power unit torque limitation may limit the output power unit torque while maintaining theprevailing power unit speed obtained after the manual shift. Alternatively, the power unit torquelimitation may limit the output torque of the power unit while the control device controls the actualpower unit speed to the expected power unit speed which would have been achieved after the manual shift in case the power unit torque limitation would not have been activated.

The present disclosure further relates to a control device configured to control a powertrain of avehicle. The powertrain comprises a power unit, such as a combustion engine, and a gearboxoperable in manual mode and configured to selectively transfer torque between the power unit andat least one driving wheel. The control device is configured to, in response to a detection that thegearbox is operated in manual mode, activate a power unit torque limitation (if not alreadyactivated) such that the output power unit torque is limited to at most a predetermined gear-specificpower unit threshold torque, optionally with a first predetermined offset, for the engaged gear. Thepredetermined gear-specific power unit threshold torque is a function of power unit speed andobtained by combining an energy efficiency map of the power unit with an energy efficiency map of the gearbox.

The control device has the corresponding advantages as disclosed above with regard to the method for controlling a powertrain of a vehicle.

The control device may be configured to determine the first predetermined offset. Alternatively, thecontrol device may be configured to receive information regarding the first predetermined offsetfrom a separate control unit, such as a control unit remote from the vehicle. The first predetermined offset may also be programmed into the control device.

The control device may be configured to determine the first predetermined offset based on a selected performance mode of the vehicle powertrain.

The first predetermined offset may be a predetermined gear-specific offset. For example, the firstpredetermined offset may be dependent of the gear number so as to be smaller for higher gear numbers than for lower gear numbers.

The control device may be configured to set the first predetermined offset to zero for the highest gear number of the gearbox.

The control device may further be configured to, in response to the detection that the gearbox ismanually shifted, compare a resulting power unit torque after the manual gearshift with thepredetermined gear-specific power unit threshold torque, and activate the power unit torquelimitation if the resulting power unit torque after the manual gearshift is above the gear-specific power unit threshold torque, optionally with a second predetermined offset.

Moreover, the control device may be configured to activate the power unit torque limitation while controlling the power unit to maintain the power unit speed obtained after the manual gearshift.

The present disclosure also relates to a vehicle comprising a vehicle powertrain and a control device as disclosed above.

The present disclosure further relates to a computer program, wherein said computer program comprises program code for causing a control device to perform 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 perform the method described above.

BRIEF DESCRIPTION OF DRAWINGS Fig. 1 schematically illustrates a side view of an example of a vehicle, Fig. 2 schematically illustrates an exemplifying embodiment of a vehicle powertrain, Fig. 3 represents a graph of power unit torque Te versus power unit rotational speed we, the graphshowing examples of gear-specific power unit threshold torques, Fig. 4 represents a flow chart schematically illustrates an exemplifying em bodiment of a methodfor controlling a powertrain in accordance with the present disclosure, Fig. 5 schematically illustrates a device that may constitute, comprise or be a part of a control device configured to control a vehicle powertrain.

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 theappended 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.

According to a first aspect, a method for controlling a powertrain of a vehicle is provided. Themethod is performed by a control device. The powertrain comprises a power unit, such as acombustion engine. The powertrain further comprises a gearbox operable in manual mode. Thegearbox is configured to selectively transfer torque between the power unit and at least one drivingwheel. The method comprises the steps of: i) when the gearbox is manually shifted, comparing a resulting power unit torque aftersaid manual shift with a predetermined gear-specific power unit threshold torque forthe resulting gear, the predetermined gear-specific power unit threshold torquebeing a function of power unit speed and obtained by combining an energy efficiencymap of the power unit with an energy efficiency map of the gearbox; and ii) if the resulting power unit torque after the manual shift is above the predeterminedgear-specific power unit threshold torque, optionally by at least a secondpredetermined offset, activating a power unit torque limitation such that the powerunit torque is limited to at most the gear-specific power unit threshold torque, optionally with a first predetermined offset, for the resulting gear.

The manual shift may for example be a manual upshift. A manual upshift may, in case of the abovedescribed power unit torque limitation not being active, result in an inefficient operating for thepower unit. The driver may however be unaware of this and believe that the lower speed of thepower unit resulting from the upshift to be advantageous for example from a fuel saving perspective.A corresponding situation may also occur in case of a manual downshift. For example, if the gearboxis manually downshifted and the vehicle then loses traveling speed due to travelling uphill, theresulting power unit speed may become too low for the engaged gear thereby resulting in aninefficient operating point for the power unit. Another example when the situation could occur inconnection with a downshift is after having travelled downhill at a very low power unit speed anddownshifting for the continued travel after the downhill. ln accordance with the first aspect of thepresent method, the power unit torque limitation is activated if the resulting power unit torque isabove the above mentioned threshold, and the output power from the power unit will thus be lower than expected by the driver.

The predetermined gear-specific power unit threshold torque may be determined in advance andmay be programmed into the control device, be retrieved from a remote device upon request, ordetermined by the control device when needed. Since the predetermined gear-specific power unitthreshold torque is dependent of the power unit efficiency and gearbox efficiency, it need only bedetermined once. lt is however also naturally plausible to determine the gear-specific power unit threshold torque continuously or occasionally as desired.

Although the gearbox is operated in a manual mode, the power unit torque limitation is according tothe present disclosure automatically activated by the control device when appropriate. The result ofthe activation of the power unit torque limitation is that the output torque of the power unit wouldbe reduced (compared to the expected output power unit torque), which in turn reduces the torquetransmitted to the driving wheels and consequently a reduced driving torque. Thereby, the vehiclewill experience a reduced travelling speed compared to a travelling speed expected by the driver.This will indicate to the driver that there is a need for downshifting. Thus, the driver would bemotivated to manually downshift to a lower gear, and the power unit after such a downshift having a reduced energy consumption.

The power unit torque limitation may be configured to limit the output torque of the power unit toat most the gear-specific power unit threshold torque. However, it is also possible to allow a certainoffset in order not to cause irritation to the driver. lf a driver would be irritated by the activation of apower torque limitation, there is ultimately a risk that the driver would seek to avoid operating thepower unit at low power unit speeds at all instances, even when the power unit torque would bebelow a gear-specific power unit threshold torque. The aim of the present method is not to avoid thedriver to operate the power unit at low power unit speeds, but simply to avoid the specificexceptional case of inefficient operating points at very high torque and very low speed of the powerunit. Therefore, the power unit torque limitation may be configured to allow a first predeterminedoffset in torque above the gear-specific power unit threshold torque. ln other words, activation ofthe power unit torque limitation may result in a limitation of the output power unit torque to at most the gear-specific power unit threshold torque plus the first predetermined offset.

The first predetermined offset could be the same for all gears. Alternatively, the first predeterminedoffset could be gear-specific. ln other words, the first predetermined offset may be dependent of thegear number. For example, the first predetermined offset could be smaller for higher gear numbersthan for lower gear numbers. lt could for example gradually increase with decreasing gear number (i.e. decreasing gear ratio). Alternatively, the first predetermined offset could be a certain value for a first set of gears, and another value for another set of gears. Since the likelihood for an inefficientoperation of the power unit increases with increasing gear number, the first predetermined offsetcould typically be small for high gear numbers but can be higher for low gear numbers. The first predetermined offset may be set to zero for the highest gear number of the gearbox. lrrespectively of whether a first predetermined offset is allowed or not, the power unit torquelimitation could be made while maintaining the prevailing power unit speed obtained after the manual shift. ln accordance with the first aspect described above, the power unit is, when the gearbox is manuallyshifted, allowed to obtain the resulting output torque as given by its physical restraints irrespectiveof whether this output torque is above the gear-specific power unit threshold torque or not. ln otherwords, the power unit torque limitation is not activated immediately. Thereafter, the resultingoutput power unit torque is compared to the gear-specific power unit threshold torque for the gearto which the manual shift has been made. lf the resulting output torque after the manual shift is above the gear-specific power unit threshold torque, the power unit torque limitation is activated. lt may be possible to allow a certain offset in torque before activating the power unit torquelimitation in order not to cause irritation to the driver. As also disclosed above with regard to theoptional first predetermined offset, if a driver would be irritated by the activation of a power torquelimitation, there is ultimately a risk that the driver would seek to avoid operating the power unit atlow power unit speeds at all instances, even when the power unit torque would be below thethreshold power unit torque. Therefore, the power unit torque limitation may be activated if theresulting output power unit torque after the manual shift is higher than the gear-specific power unitthreshold torque plus the above mentioned second predetermined offset. However, it is alsopossible to activate the power unit torque if the resulting power unit torque is above the gear-specific power unit threshold torque, i.e. a case where the second predetermined offset is zero.Furthermore, the second predetermined offset may be the same for all of the gears or different forsome or all of the gears. By way of example, the second predetermined offset may be greater forlower gear numbers than higher gear numbers. The second predetermined offset may for examplebe gradually decreasing with increasing gear number. The second predetermined offset may be zerofor the highest gear number of the gearbox, while at lower gear numbers the predetermined offset is more than zero.

The second predetermined offset could have the same value as the first predetermined offset for thesame gear. However, the second predetermined offset could have a value different from the value ofthe first predetermined offset. For example, the second predetermined offset could have a greater value than the value of the first predetermined offset for the same gear.

The method according to the present disclosure also has the additional advantage of, if the gearboxis an automatic manual gearbox (automatic manual transmission, AMT), the driver experiencing asimilar behavior of the vehicle irrespectively of operating the gearbox in manual mode or automaticmode. The gear selection strategies in the automatic mode may already take the gear-specific powerunit threshold torques in consideration such that a gear which would result in an inefficientoperation of the power unit is never selected. Thus, since the present method automaticallyactivates a power torque limitation prompting the driver to downshift, the driver will not be annoyedby the automatic mode selecting a corresponding lower gear. Therefore, the risk of the driver not relying on the automatic gear selection is reduced.

As disclosed above, according to a first aspect of the method, the power unit is allowed to obtain theresulting output torque when manually shifted and the power unit torque limitation is activated ifthe actually resulting torque after the manual shift is above the gear-specific power unit thresholdtorque, optionally with a second predetermined offset. However, it should be recognized that themethod need for example not comprise a step of comparing an actually resulting output power unittorque with the predetermined gear-specific power unit threshold torque. Furthermore, the methodneed not be performed in conjunction with a change of gears. The problem of an inefficientoperating point of the power unit as discussed above may also occur for example if the vehicle islosing traveling speed while the prevailing gear is maintained. Therefore, there are further aspects of the method for controlling a powertrain according to the present disclosure.

According to a second aspect of the method according to the present disclosure, the power unittorque limitation is activated when a manual shift of the gearbox is detected and it is estimated thatthe future output torque of the power unit after the shift would be above the predetermined gear-specific power unit threshold torque, optionally with a third predetermined offset. The third predetermined offset corresponds to the second predetermined offset described above.

Thus, according to the second aspect, the method may comprise a step of, when detecting that thegearbox is manually shifted (for example manually upshifted), estimating a resulting output torque of the power unit that would be obtained after the manual shift. The activation of the power unit torque limitation would then be made if the estimated power unit output torque is above thepredetermined gear-specific power unit threshold torque, optionally with a third predeterminedoffset. Estimation of a resulting output power unit torque can be made is accordance with anypreviously known method for estimation thereof, i.e. based on any previously known algorithm therefore. Therefore, this will not be described in further detail herein.

According to a third aspect of the method according to the present disclosure, the power unit torquelimitation is always active when the gearbox is operated in manual mode. ln other words, when thegearbox is operated in manual mode, the power unit torque limitation will directly limit the outputpower torque of the power unit to at most the predetermined gear-specific power unit thresholdtorque, optionally with the first predetermined offset, for the engaged gear. This means that theoutput torque of the power unit will not reach the expected output torque of the resulting gear (asgiven by the physical restrains of the power unit), if the expected output torque would be above thepredetermined gear-specific power unit threshold torque, for being subject to the power unit torquelimitation. ln the case of the power unit torque limitation always being active when the gearbox isoperated in manual mode, a gearshift to a new gear will result in a new power unit threshold torquespecific for the new gear. ln other words, the power unit torque limitation will be such that theoutput power unit torque after the shift is limited to at most the gear-specific power unit thresholdtorque, optionally with a first predetermined offset, for the resulting gear. ln case the gearbox is anautomatic manual gearbox, the activation of the power unit torque limitation may be performed when it is detected that the gearbox is switched to manual mode.

As evident from the above described aspects of the method, the present disclosure provides amethod, performed by a control device, for controlling a powertrain of a vehicle. The methodcomprises the step of, when the gearbox is operated in manual mode, activating a power unit torquelimitation (if not already activated) such that the power unit torque is limited to at most apredetermined gear-specific power unit threshold torque for the engaged gear, optionally with a firstpredetermined offset. The predetermined gear-specific power unit threshold torque is a function ofpower unit speed and is obtained by combining an energy efficiency map of the power unit with an energy efficiency map of the gearbox.

The present disclosure further relates to a control device configured to perform the above describedmethod. The control device is configured to, in response to a detection that the gearbox is operatedin manual mode, activate a power unit torque limitation (if not already activated) such that the output power unit torque is limited to at most a predetermined gear-specific power unit threshold 11 torque, optionally with a first predetermined offset. The predetermined gear-specific power unitthreshold torque is a function of power unit speed and obtained by combining an energy efficiency map of the power unit with an energy efficiency map of the gearbox.

The control device may be configured to perform any of the steps of the method for controlling apowertrain as disc|osed herein. Furthermore, the control device may comprise one or more controlunits. ln case of a plurality of control units, the steps of the method may be divided between different control units of the control device.

Figure 1 schematically illustrates a side view of an example of a vehicle 1. The vehicle 1 comprises apowertrain 3 comprising a power unit 2, such as a combustion engine, and a gearbox 4. A clutch (notshown) may be arranged between the power unit 2 and the gearbox 4. The gearbox 4 is connected tothe driving wheels 5 of the vehicle 1 via an output shaft 6 of the gearbox 4. The gearbox 4 is adaptedto provide a plurality of gear ratios. The gearbox 4 may for example be an automated manual gearbox (AMT). Alternatively, the gearbox 4 may be a manual gearbox.

The vehicle 1 may be, but is not limited to, a heavy vehicle, e.g. a truck or a bus. Furthermore, thevehicle may be a hybrid vehicle comprising a second power unit in the form of an electric motor (not shown) in addition to the combustion engine 2.

Figure 2 schematically illustrates a first exemplifying embodiment of a vehicle powertrain 3, such as apowertrain of the vehicle 1 shown in Figure 1. The powertrain 3 comprises a power unit 2, such as acombustion engine. The powertrain further comprises a gearbox 4 connected to the power unit 2 viaa clutch 9. The output shaft 6 of the gearbox 4 is connected to the driving wheels 5 via for example a differential 11 and a drive shaft 12.

As shown in Figure 2, the powertrain 3 may further comprise a control device 100. The control device100 may be configured to control one or more of the constituent components of the vehiclepowertrain 3. The control device 100 may comprise one or more control units. The responsibility fora specific function or control may be divided between two or more of the control units. One or moreof the control units may be implemented in the form of a computer. The control device 100 may beconnected to the power unit 2, the gearbox 4 and optionally the clutch 9, as shown in Figure 2. Thecontrol device 100 may also be connected to any other constituent component of the vehicle powertrain 3, even though not illustrated in the figure, if desired. The connections of the control 12 device 100 to any constituent component of the vehicle powertrain 3 may be physical connection(s) and/or wireless connection(s).

The control of constituent components in the vehicle powertrain 3 may be governed by programmedinstructions. These programmed instructions typically take the forms of a computer program which,when executed in a computer or control unit, causes the computer or control unit to effect desiredforms of control action, for example the steps of the method disclosed herein. As described above, such a computer or control unit may be or constitute a part of the control device 100.

Figure 3 represents an exemplifying graph showing the power unit torque (Te) as a function ofrotational speed of the power unit (me). Merely for illustrative purposes, the limit 15 correspondingto the physical constrains of the power unit is shown in the figure. Figure 3 further shows twoexamples of gear-specific power unit threshold torques 20, 30. The threshold power unit torque 20may for example be for the n:th gear, and the threshold power unit torque 30 may be for the n+1:thgear. Here, n constitutes the gear number. As can be seen in the figure, the gear-specific power unitthreshold torques 20, 30 are each functions of the power unit speed. The gear-specific power unitthreshold torques 20, 30 are obtained by considering both the efficiency map of the power unit andan efficiency map of the gearbox. Thus, the gear-specific power unit threshold torques aredependent on the vehicle powertrain configuration. Furthermore, the gear-specific power unitthreshold torques are not altered during operation of the vehicle and can thus be determined inadvance and simply be programmed into a control device for use during operation of the vehicle.Although only two gear-specific power unit threshold torques are shown in Figure 3, each of the gears of the gearbox has a corresponding gear-specific power unit threshold torque. lt should be noted that the gear-specific power unit threshold torques are not dependent of whetherthe gearbox is operated in automatic or manual mode. lf the gearbox is shifted in automatic mode,the automatic gear selection strategy may be configured to take the gear-specific power unitthreshold torques into consideration when selecting an appropriate gear. However, in case thegearbox is manually operated, the driver is unaware of these gear-specific power unit thresholdtorques and may therefore risk selecting a gear which results in a worse power unit efficiency than if a lower gear is selected for the same desired output torque to the driving wheels.

A gear-specific power unit threshold torque defines the threshold where the power unit, if operatedabove, has an efficiency which is worse than if a lower gear would be selected. This is illustrated in Figure 3 with regard to exemplified operating points 22 and 32. Operating point 22 is an operating 13 point achieved when in the n:th gear, and operating point 32 is an operating point when in then+1:th gear, for the same output torque to the driving wheels. As can be seen in Figure 3, theoperating point 32 is above its corresponding gear-specific power unit threshold torque 30. Morespecifically, the power unit torque in the operating point 32 is above the corresponding gear-specificpower unit threshold torque 30. However, the operating point 22 is below its corresponding gear-specific power unit threshold torque 20. ln other words, if the n+1:th gear is selected by the driver,the power unit will be operated at an operating point which is not energy efficient considering thepowertrain configuration. The energy consumption of the power unit will thus be unduly high. lf thedriver instead would select the lower gear, i.e. the n:th gear in this example, the resulting torque ofthe power unit would be lower but the power unit speed higher, and the operating point is below thecorresponding gear-specific power unit threshold torque. Thus, the energy consumption of the power unit would be lower for the same torque output to the driving wheels. ln order to reduce the risk that a driver operating the gearbox in manual mode would run the powerunit at an inefficient operating point, such as the operating point 32, the method for controlling apowertrain as described herein may be used. When the power unit torque limitation is active, theoutgoing power unit torque will be limited whereby the actual torque provided by the power unitafter the manual upshift could be as illustrated by the operating point 32a in case of the firstpredetermined offset being set to zero and operating point 32b in case of the first predetermined offset 34 being greater than zero.

Figure 4 represents a flow chart of one exemplifying embodiment of the method according to thepresent disclosure. The method may comprise a step s110 of detecting that the gearbox is operatedin manual mode. Said step s110 may for example comprise detecting that a manual shift of thegearbox is performed. The method comprises a step s120 of, when the gearbox is operated inmanual mode, activating a power unit torque limitation, if not already activated, such that theoutput power unit torque is limited to at most a predetermined gear-specific power unit thresholdtorque, optionally with a first predetermined offset, for the engaged gear. The predetermined gear-specific power unit threshold torque is a function of power unit speed and is obtained by combining an energy efficiency map of the power unit with an energy efficiency map of the gearbox.

Figure 5 schematically illustrates an exemplifying embodiment of a device 500. The control device100 described above may for example comprise the device 500, consist of the device 500, or be comprised in the device 500. 14 The device 500, shown in Figure 5, comprises a non-volatile memory 520, a data processing unit 510and a read/write memory 550. The non-volatile memory 520 has a first memory element 530 inwhich a computer program, e.g. an operating system, is stored for contro||ing the function of thedevice 500. The device 500 further comprises a bus controller, a serial communication port, I/Omeans, an A/D converter, a time and date input and transfer unit, an event counter and aninterruption controller (not depicted). The non-volatile memory 520 has also a second memory element 540.

There is provided a computer program P that comprises routines for contro||ing a vehicle powertrain.Such a vehicle powertrain may comprise a power unit and a gearbox operable in manual mode andconfigured to selectively transfer torque between the power unit and at least one driving wheel. Thecomputer program comprises routines for, when the gearbox is operated in manual mode, activatinga power unit torque limitation, if not already activated, such that the output power unit torque islimited to at most a predetermined gear-specific power unit threshold torque, optionally with a firstpredetermined offset, for the engaged gear. The predetermined gear-specific power unit thresholdtorque is a function of power unit speed and is obtained by combining an energy efficiency map ofthe power unit with an energy efficiency map of the gearbox. The computer program may, if desired,further comprise routines for determining the first offset, for example in dependence of a gearnumber. The computer program may also, if desired, comprise routines for comparing a resultingpower unit torque or an estimated power unit torque after the manual shift with the predeterminedgear-specific threshold power unit threshold torque, and activating the power unit torque limitationif the resulting or estimated power unit torque after the shift is above the gear-specific power unit threshold torque.

The program P may be stored in an executable form or in a compressed form in a memory 560 and/or in a read/write memory 550.

Where the data processing unit 510 may perform certain functions. For example, the data processingunit 510 may effects a certain part of the program stored in the memory 560 or a certain part of the program stored in the read/write memory 550.

The data processing device 510 can communicate with a data port 599 via a data bus 515. The non-volatile memory 520 may be intended for communication with the data processing unit 510 via a data bus 512. The separate memory 560 may be intended to communicate with the data processing unit 510 via a data bus 511. The read/write memory 550 may be adapted to communicate with the data processing unit 510 via a data bus 514.

When data are received on the data port 599, they may be stored temporari|y in the second memoryelement 540. When input data received have been temporari|y stored, the data processing unit 510may be prepared to effect code execution according to a computer program comprising programcode for causing a control device to perform the method (or parts thereof) for contro||ing a powertrain as described herein.

Parts of the methods herein described may be effected by the device 500 by means of the dataprocessing 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 (17)

1. 6 A method for controlling a powertrain (3) of a vehicle (1),the method performed by a control device (100),the powertrain (3) comprising:a power unit (2), anda gearbox (4) operable in manual mode and configured to selectively transfer torque between the power unit (2) and at least one driving wheel (5),the method comprising the step of, when the gearbox (4) is operated in manual mode, activating a power unit torque limitation, if not already activated, such that theoutput power unit torque is limited to at most a predetermined gear-specific power unitthreshold torque (20, 30), optionally with a first predetermined offset, for the engaged gear, the predetermined gear-specific power unit threshold torque (20, 30) being afunction of power unit speed and obtained by combining an energy efficiency map of the power unit (2) with an energy efficiency map of the gearbox (4).

2. The method according to claim 1, wherein the first predetermined offset is dependent of selection of performance mode of the vehicle powertrain (3).

3. The method according to any one of the preceding claims, wherein the first predeterminedoffset is dependent of the gear number so as to be smaller for higher gear numbers than for lower gear numbers.

4. The method according to any one of the preceding claims, wherein the first predetermined offset is set to zero for the highest gear number of the gearbox (4).

5. The method according to any one of the preceding claims, wherein the gearbox (4) is an automatic manual gearbox.

6. The method according to any one of the preceding claims, further comprising,detecting that the gearbox is manually shifted,comparing a resulting power unit torque after the manual shift with the predetermined gear-specific power unit threshold torque (20, 30); and 7. 17 if the resulting power unit torque after the manual shift is above the gear-specific powerunit threshold torque (20, 30), optionally with a second predetermined offset, performingthe step of activating the power unit torque limitation such that the output power unittorque is limited to at most the predetermined gear-specific power unit threshold torque (20, 30), optionally with the first predetermined offset.

7. The method according to c|aim 6, wherein the power unit torque limitation |imits the outputpower unit torque while maintaining the prevailing power unit speed obtained after the manual shift.

8. A control device (100) configured to control a powertrain (3) of a vehicle (1),the powertrain (3) comprising: a power unit (2), and a gearbox (4) operable in manual mode and configured to selectively transfer torquebetween the power unit (2) and at least one driving wheel (5),the control device (100) configured to: in response to a detection that the gearbox (4) is operated in manual mode, activatea power unit torque limitation, if not already activated, such that the output power unittorque is limited to at most a predetermined gear-specific power unit threshold torque (20,30), optionally with a first predetermined offset, for the engaged gear, the predetermined gear-specific power unit threshold torque (20, 30) being afunction of power unit speed and obtained by combining an energy efficiency map of the power unit (2) with an energy efficiency map of the gearbox (4).

9. The control device (100) according to c|aim 8, further configured to determine the first predetermined offset based on a selected performance mode of the vehicle powertrain (3).

10. The control device (100) according to any one of claims 8 and 9, wherein the first predetermined offset is dependent of the gear number so as to be smaller for higher gear numbers than for lower gear numbers.

11. The control device (100) according to any one of claims 8 to 10, wherein the control device (100) is configured to set the first predetermined offset to zero for the highest gear number of the gearbox (4).

12.

13.

14.

15.

16.

17. 18 The control device (100) according to any one of claim 8 to 11, wherein the gearbox (4) is an automatic manual gearbox. The control device (100) according to any one of claim 8 to 12, further configured to, in response to a detection that the gearbox (4) is manually shifted,compare a resulting power unit torque after the manual gearshift with the predeterminedgear-specific power unit threshold torque (20, 30), and activate the power unit torque limitation if the resulting power unit torque after themanual gearshift is above the gear-specific power unit threshold torque (20, 30), optionally with a second predetermined offset. The control device (100) according to claim 13, further configured to activate the power unittorque limitation while controlling the power unit (2) to maintain the power unit speed obtained after the manual gearshift. A vehicle (1) comprising a vehicle powertrain (3),the vehicle powertrain (3) comprisinga power unit (2), anda gearbox (4) operable in manual mode and configured to selectively transfer torquebetween the power unit (2) and at least one driving wheel (5),the vehicle (1) further comprising a control device (100) according to any one of claims 8 to 14. A computer program comprising program code for causing a control device to perform the method according to any one of claims 1 to 7. A computer-readable medium comprising instructions, which when executed by a controldevice, cause the control device to perform the method according to any one of claims 1 to 7.