Control device and method for controlling a vehicle to disengage a gear

Abstract

A control arrangement (100) and a method for controlling a vehicle (1) to disengage a gear of a transmission arrangement (5), said transmission arrangement (5) having an input shaft (5a) operatively connected to one or more power units (3, 4) of the vehicle, are provided. The method comprises a step of, when a request for disengagement of the gear has been generated, and it is determined that torque transmitted trough the transmission arrangement cannot be reduced through control of the one or more power units (3, 4) to a torque or a torque range appropriate for disengagement of the gear, braking (S110) an output shaft (5b) of the transmission arrangement (5) to reduce the torque transmitted through the transmission arrangement (5) to said torque or torque range appropriate for disengagement of the gear.

Description

[0001] CONTROL DEVICE AND METHOD FOR CONTROLLING A VEHICLE TO DISENGAGE A GEAR

[0002] TECHNICAL FIELD

[0003] The present disclosure relates in general to a method for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle. The present disclosure also relates in general to a control arrangement configured to control a vehicle to disengage a gear of a transmission arrangement of the vehicle, and a vehicle comprising the control arrangement.

[0004] The present disclosure also relates in general to a computer program as well as a computer readable medium.

[0005] BACKGROUND

[0006] Damage of hardware of a vehicle’s powertrain can be every costly, and often requires replacement of the damaged constituent component of the powertrain. Damage may for example occur due to overrewing of the constituent component. For example, overrewing of a power unit of the powertrain may lead to mechanical failure and / or thermal damage. In case of the power unit being an electrical machine, electrical failure may also occur due to overrewing. Another example of a constituent component of a vehicle’s powertrain that may be damaged due to overrewing is a clutch. At excessively high rotational speeds, the clutch disc may suffer from e.g., mechanical damage as a result of the high centrifugal forces. Overrewing of a constituent component of a vehicle’s powertrain may, for example, be caused by an inappropriate gear selection in a transmission arrangement of the vehicle given the prevailing circumstances.

[0007] It has previously been proposed to put a transmission arrangement in neutral for the purpose of protecting one or more constituent components, arranged upstream of the transmission arrangement, from damage. Thereby, the rotational speed of the vehicle’s drive wheels cannot contribute to an increase of the rotational speed of a constituent component arranged upstream of the transmission arrangement. Putting the transmission arrangement in neutral requires that the currently engaged gear is disengaged, which may be performed in the same way as during a normal gear shifting procedure. It is well known that, in order to allowdisengagement of a currently engaged gear, the (positive or negative) torque transmitted over said gear has to be reduced, typically to substantially zero, to allow a gearshift actuator to execute said disengagement. This is achieved through control of a torque output from the powertrain’s power unit(s), allowing the torque transmitted through the transmission arrangement to be ramped down.

[0008] Disengagement of a currently engaged gear of the transmission arrangement is an efficient way for protecting a constituent component arranged upstream of the transmission arrangement from damage. However, in some situations, the torque transmitted through the transmission arrangement cannot be (at least not sufficiently) reduced using a power unit of the powertrain. An example of such a situation is when the currently engaged gear of the vehicle is a reverse gear, and the vehicle accelerates downhill with an open clutch. This could, for example, occur when a vehicle has been reversed uphill to a stop at which a parking brake orthe like has been activated and the clutch opened to allow a combustion engine to idle during the stop. When the parking brake is released, the vehicle may start to accelerate downhill by the gravitational force while still having the reverse gear engaged. In such a situation, the output shaft of a combustion engine will inherently rotate in a direction opposite to the rotational direction of the input shaft of the transmission arrangement, which in turn means that the clutch may not be closed. As the clutch remains open, the torque trough the transmission arrangement cannot be reduced by the combustion engine and the rotational speed of the clutch disc will increase with increasing speed of the vehicle. Eventually, the clutch disc will reach a rotational speed at which the centrifugal force is too high (such as at about 6000-8000 rpm for many of today’s clutch discs of heavy vehicles) and mechanical damage therefore will occur.

[0009] SUMMARY

[0010] The object of the present invention is to further reduce the risk of damage of hardware arranged upstream of a transmission arrangement in a vehicle’s powertrain.

[0011] The object is achieved by the subject-matter of the appended independent claim(s).

[0012] The present disclosure provides a method, performed by a control arrangement, for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle, said transmission arrangement having an input shaft operatively connected to one or more power units of thevehicle. The method comprises a step of, when a request for disengagement of the gear has been generated, and it is determined that torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units to a torque or torque range appropriate for disengagement of the gear, braking an output shaft of the transmission arrangement to reduce the torque transmitted through the transmission arrangement to said torque or torque range appropriate for disengagement of the gear.

[0013] The herein described method allows for disengaging a gear of the transmission arrangement even in such situations where e.g., the one or more power units for some reason may not be controlled freely for the purpose of reducing the torque, transmitted through the transmission arrangement, sufficiently low to enable disengagement of the gear, as well as in other situations where it might not be possible to utilize the one or more power units for said purpose. In contrast to during a normal gear shifting procedure, in which the torque is ramped-down through control of the one or more power units, a sufficiently low torque through the transmission arrangement is accordingto the present method instead achieved by brakingthe output shaft of the transmission arrangement.

[0014] Thereby, the herein described method reduces the number of different type of situations in which it is not possible to disengage a gear of the transmission arrangement. In otherwords, the herein described method increases the number of different types of situations in which the gear may be disengaged, and thus also the number of different types of situations in which the transmission arrangement may be put in neutral for the purpose of protecting such constituent components of a vehicle’s powertrain that are arranged upstream of the transmission arrangement against damage, e.g. caused by overrewing of the constituent component.

[0015] Damage of a constituent component arranged upstream of the transmission arrangement may be very costly, and may often require replacement of the damaged constituent component. Thus, the herein described method contributes to improved total cost of operation of the vehicle, a factor which is very important to a vehicle owner.

[0016] The method may further comprise a step of, in parallel with the step of braking the output shaft of the transmission arrangement, controlling a gearshift actuator of the transmission arrangement to apply a preselected maneuvering force to the gear. By applying such a preselected maneuvering force to the gear to be disengaged, simultaneously with at least a part of the step of brakingthe output shaft of the transmission arrangement, it is not necessary to determine when a sufficiently lowtorque through the transmission arrangement has beenachieved. Instead, the gear will inherently be disengaged as soon as such a state has been achieved by the transmission arrangement. This also means that the time until which the gear has been disengaged may be reduced, compared to a case where the maneuvering force is only applied when it is established or predicted that the torque is sufficiently low. A reduced time for disengagement of the gear naturally reduces the risk of damage, or at least severity of the damage, to the constituent component of the powertrain to be protected.

[0017] The above described step of braking the output shaft of the transmission arrangement may suitably comprise braking the vehicle through usage of a service brake system of the vehicle. Braking the vehicle through usage of a service brake system will inherently lead to a braking of the output shaft of the transmission arrangement. Furthermore, usage of the service brake system for this purpose has the advantage that braking of the output shaft of the transmission arrangement can be initiated quickly as a result of the service brake system having a short response time compared to for example auxiliary brake systems of the vehicle. Moreover, a service brake system can brake the vehicle independently of the vehicle speed and the operational state of the one or more power units of the vehicle.

[0018] The step of braking the output shaft of the transmission arrangement may comprise braking the vehicle through usage of an auxiliary brake system of the vehicle, said auxiliary brake system being arranged downstream of the transmission arrangement. Usage of such an auxiliary brake system may in some cases provide a somewhat smoother braking action of the output shaft of the transmission arrangement compared to usage of a service brake system. However, one drawback is that today’s auxiliary brake systems are typically not designed to be used at lower vehicle speeds.

[0019] Naturally, the step of braking the output shaft of the transmission arrangement may be performed through braking the vehicle through usage of both the service brake system and an auxiliary brake system arranged downstream of the transmission arrangement, if desired.

[0020] The herein described method may further comprise a step of determining that torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units to a torque or torque range appropriate for disengagement of the gear when it is predicted that a maximum currently available torque output from the one or more power units is insufficient for reaching said torque or torque range appropriate for disengagement of the gear. In case the maximum available torque output from the one or morepower units is not sufficient for reducingthe torque transmitted by the transmission arrangement to allow disengagement of the gear, it is necessary to take other action to allow disengagement of the gear as soon as possible, in particular in case the torque transmitted through the transmission arrangement unintentionally continues to increase.

[0021] Alternatively, or additionally, the herein described method may further comprise a step of determiningthat torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units to a torque or torque range appropriate for disengagement of the gearwhen the one or more power units is / are operated in a failure mode. Such a failure mode may be a failure mode of a power unit in which the output torque therefrom cannot, or can only partly, be controlled. In other words, such a failure mode of a power unit may be a failure mode in which the output torque from the power unit cannot be freely controlled. In case a power unit, such as an electrical machine, is operated in a failure mode for some reason such that the torque output therefrom cannot be freely controlled, it may not be used for reducingthe torque transmitted through the transmission arrangement to allow disengagement of the gear. If no other power unit of the vehicle may be controlled so as to reduce the torque transmitted through the transmission arrangement to allow disengagement of the gear, then the gear cannot be disengaged while the vehicle is in motion unless the torque may be reduced through braking of the output shaft of the transmission arrangement in accordance with the herein described method.

[0022] According to one exemplifying embodiment of the herein described vehicle, the one or more power units may comprise a combustion engine operatively connected to the input shaft of the transmission arrangement via a clutch. In such a case, the method may further comprise a step of determiningthat torque transmitted through the transmission arrangement cannot be reduced through control of combustion engine to a torque ortorque range appropriate for disengagement of the gearwhen the clutch is in an open state and an output shaft of the combustion engine rotates in an opposite direction to a rotational direction of the input shaft of the transmission arrangement. When an output shaft of the combustion engine rotates in an opposite direction to the rotational direction of the input shaft of the transmission arrangement, the clutch cannot be closed without causing damage thereto and the combustion engine can therefore not be used for reducingthe torque transmitted through the transmission arrangement to allow disengagement of the gear. Thus, unless another power unit may be controlled to sufficiently reduce the torque transmitted through the transmission arrangement, the torque transmitted through the transmission arrangement should instead be reducedthrough braking of the output shaft of the transmission arrangement in accordance with the present method.

[0023] The herein described method may further comprise a step of generating the above described request for disengagement of the gear when it is predicted that a constituent component, arranged upstream of the transmission arrangement, of a powertrain of the vehicle will reach a critical rotational speed threshold for said constituent component unless the gear is disengaged, or when it is determined that said constituent component has reached said critical rotational speed threshold. Said constituent component, arranged upstream of the transmission arrangement, of the powertrain of the vehicle may for example be a clutch, or an electrical machine of the one or more power units.

[0024] The above described step of braking the output shaft of the transmission arrangement to reduce the torque transmitted through the transmission arrangement may comprise braking the output shaft of the transmission arrangement to achieve a substantially zero torque transmitted through the transmission arrangement. In otherwords, the step of brakingthe output shaft of the transmission arrangement may comprise brakingthe output shaft of the transmission arrangement to achieve a substantially torque-less state of the transmission arrangement.

[0025] The present disclosure also relates to a control arrangement configured to control a vehicle to disengage a gear of a transmission arrangement of the vehicle, said transmission arrangement having an input shaft operatively connected to one or more power units of the vehicle. The control arrangement is configured to, when a request for disengagement of the gear has been generated, and it is determined that torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units to a torque or torque range appropriate for disengagement of the gear, brake an output shaft of the transmission arrangement to reduce the torque transmitted through the transmission arrangement to said torque or torque range appropriate for disengagement of the gear.

[0026] The herein described control arrangement provides the same advantages as described above with regard to the corresponding method for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle.

[0027] The control arrangement may further be configured to control a gearshift actuator of the transmission arrangement to apply a preselected maneuvering force to the gear while theoutput shaft of the transmission arrangement is braked to reduce the torque transmitted through the transmission arrangement to the torque or torque range appropriate for disengagement of the gear.

[0028] Moreover, the control arrangement may be configured to brake the output shaft of the transmission arrangement to reduce the torque transmitted through the transmission arrangement to said torque or torque range appropriate for disengagement of the gear through control of a service brake system of the vehicle and / or an auxiliary brake system of the vehicle, said auxiliary brake system being arranged downstream of the transmission arrangement.

[0029] The control arrangement may further be configured to determine whether torque transmitted through the transmission arrangement can be reduced through control of the one or more power units to a torque or torque range appropriate for disengagement of the gear based on an operating mode of the one or more power units and / or a prediction of whether a maximum currently available torque output is sufficient for reaching said torque or torque range appropriate for disengagement of the gear.

[0030] The present disclosure also relates to a computer program comprising instructions which, when executed by the control arrangement described above, cause the control arrangement to carry out the above described method for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle.

[0031] The present disclosure also relates to a computer-readable medium having stored thereon the computer program as described above.

[0032] Furthermore, the present disclosure relates to a vehicle comprising the above described control arrangement. The vehicle may comprise a powertrain comprising one or more power units and a transmission arrangement. The transmission arrangement is a transmission arrangement configured to selectively transmit torque at different gear ratios. The vehicle further comprises one or more brake systems, such as a service brake system and one or more an auxiliary brake systems. At least one of said auxiliary brake systems may be arranged downstream of the transmission arrangement.

[0033] The vehicle may be a land-based medium-duty or heavy-duty vehicle, such as a truck or a bus, but is not limited thereto. The vehicle may be a vehicle driven solely by a combustion engine, bea hybrid vehicle (such as a plug-in hybrid, PHEV, or a mild hybrid, mHEV), be a fully electric vehicle (such as a battery electric vehicle, BEV). The vehicle could alternatively be a fuel cell vehicle (FCV).

[0034] BRIEF DESCRIPTION OF DRAWINGS

[0035] Fig. 1 schematically illustrates an example of a vehicle,

[0036] Fig. 2 schematically illustrates the powertrain of the vehicle shown in Fig. 1 ,

[0037] Fig. 3 schematically illustrates an example of a transmission arrangement which may be comprised in the powertrain shown in Fig. 2,

[0038] Fig. 4 schematically illustrates a second example of a powertrain of a vehicle,

[0039] Fig. 5 represents a flowchart schematically illustrating a first exemplifying embodiment of the herein described method for controlling a vehicle for the purpose of disengaging a gear of a transmission arrangement of the vehicle,

[0040] Fig. 6 represents a flowchart schematically illustrating a second exemplifying embodiment of the herein described method for controlling a vehicle for the purpose of disengaging a gear of a transmission arrangement of the vehicle,

[0041] Fig. 7 schematically illustrates a device that may comprise, consist of, or be comprised in the herein described control arrangement configured to control a vehicle to disengage a gear of a transmission arrangement of the vehicle.

[0042] DETAILED DESCRIPTION

[0043] 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 toscale as some features may be exaggerated in order to more clearly illustrate the invention or features thereof.

[0044] In the present disclosure, the expression “operatively connected” is used to describe a functional arrangement / relationship between different constituent components of a powertrain, more specifically between a power unit and an input shaft of a transmission arrangement. It should here be noted that the expression “operatively connected” should be interpreted as a capability of functional interaction as part of the powertrain, and is not limited to a constant physical connection between the power unit and the input shaft of the transmission arrangement. In other words, “operatively connected” is intended to also encompass a possibility for selective engagement / disengagement of the power unit and the input shaft of the transmission arrangement. Furthermore, the expression “operatively connected” is intended to encompass both the alternative of the power unit being directly connectable to the input shaft of the transmission arrangement as well as the alternative of a presence of one or more constituent components arranged between the power unit and the input shaft of the transmission arrangement. One example of the latter is a power unit operatively connected to the input shaft of the transmission arrangement via a clutch, which allows for selective engagement of the power unit to the input shaft of the transmission arrangement.

[0045] The terms “upstream” and “downstream”, respectively, shall in the present disclosure be considered to refer to a relative arrangement of constituent components within a powertrain as seen in the direction of torque transfer from a power unit to the drive wheels of a vehicle comprising the powertrain.

[0046] The present disclosure relates to a method for controlling a vehicle in order to disengage a (currently engaged) gear of a transmission arrangement of a powertrain of the vehicle for the purpose of protecting one or more constituent components, arranged upstream of the transmission arrangement, of the powertrain against damage. In addition to the transmission arrangement, the vehicle’s powertrain comprises one or more power units. The one or more power units may comprise one or more electrical machines, a combustion engine, or a combustion engine plus one or more electrical machines. The transmission arrangement has an input shaft operatively connected, optionally via a clutch, to the one or more power units of the vehicle. The transmission arrangement may be configured to selectively transfer torque at least two different gear ratios to one or more drive wheels of the vehicle. The transmissionarrangement may for example comprise, or consist of, an automated manual transmission (AMT), but is not limited thereto.

[0047] As evident from the above, the herein described method may be a method for controlling a vehicle in order to disengage a gear of the transmission arrangement for the purpose of protecting at least one power unit of the one or more power units from damage. This is because each of said one or more power units is arranged upstream of the transmission arrangement. The herein described method is particularly suitable for protecting a power unit from damage in case of the power unit constituting an electrical machine. Alternatively, the herein described method may be a method for controlling a vehicle in order to disengage a gear of the transmission arrangement for the purpose of protecting a clutch (if present) arranged upstream of the transmission arrangement, or more specifically a clutch disc of said clutch, against damage.

[0048] The herein described method for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle comprises a step of, when (i) a request for disengagement of the (currently engaged) gear has been generated and (ii) it is determined that torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units to a torque or a torque range appropriate for disengagement of the gear, braking an output shaft of the transmission arrangement to reduce the torque transmitted through the transmission arrangement to a torque, or a torque range, appropriate for disengagement of the gear.

[0049] In other words, by means of the herein described method, a sufficiently low torque transmittal through the transmission arrangement (and thus also over the currently engaged gear) to allow disengagement of the currently engaged gear is achieved through braking of the output shaft of the transmission arrangement. This is in contrast to e.g., a conventional procedure for disengagement of a gear during gearshifting, in which the torque transmitted through the transmission arrangement is ramped down through control of the one or more power units to allow disengagement of the gear to be shifted. However, the herein described method allows for disengagement of a gear even in some situations where the torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units. Thus, the method extends the number of situations in which disengagement of a gear for the purpose of protecting constituent components, arranged upstream of the transmission arrangement, (such as a power unit or a clutch, if present) may be performed.A torque (or torque range) appropriate for disengagement of the gear is in the present disclosure considered to mean a torque (or torque range) that is sufficiently low that a gearshift actuator, by applying an available maneuvering force thereof to the gear, to disengage the gear without risking damage to the gear. For many configurations of transmission arrangements, but not all, such a torque may correspond to a substantially zero torque.

[0050] The method may further comprise a step of, in parallel with the step of braking the output shaft of the transmission arrangement, controlling a gearshift actuator of the transmission arrangement to apply a preselected maneuvering force to the gear. By applying such a preselected maneuvering force to the gear to be disengaged, simultaneously with at least a part of the step of braking the output shaft of the transmission arrangement, it is not necessary to determine when a sufficiently low torque through the transmission arrangement has actually been achieved. Instead, the gear will inherently be disengaged as soon as such a state has been achieved by the transmission arrangement. This also means that the time until which the gear has been disengaged may be reduced, compared to a case where the maneuvering force is only applied when it is established or predicted that the torque is sufficiently low. A reduced time for disengagement of the gear naturally reduces the risk of damage, or at least severity of the damage, to the constituent component of the powertrain to be protected. The preselected maneuvering force may suitably correspond to a maximum maneuvering force that the actuator can apply, but the present disclosure is not limited thereto. For example, according to one exemplifying embodiment, the preselected maneuvering force may be at least 80% of the maximum maneuvering force that the actuator can apply to the gear. A higher preselected maneuvering force may reduce the time needed for disengagement of the gear and thereby further contribute to reduced risk for damage of a constituent component arranged upstream of the transmission arrangement.

[0051] In case the method does not comprise a step of controlling a gearshift actuator of the transmission arrangement to apply a preselected maneuvering force to the gear in parallel with at least part of the step of braking the output shaft of the transmission arrangement to reduce the torque transmitted through the transmission arrangement, the method may comprise controlling the gearshift actuator of the transmission arrangement to apply an appropriate maneuvering force to the gear when a sufficiently low torque through the transmission arrangement has been reached.The step of braking the output shaft of the transmission arrangement may be achieved through braking of the vehicle through usage of a service brake system of the vehicle. Alternatively, or additionally, the step of braking the output shaft of the transmission arrangement may be achieved through braking the vehicle through usage of an auxiliary brake system of the vehicle, said auxiliary brake system being arranged downstream of the transmission arrangement. Braking of the vehicle by the service brake system and / or the auxiliary brake system arranged downstream of the transmission arrangement will inherently brake the output shaft of the transmission arrangement in view of the drive wheels of the vehicle being operatively connected to the output shaft of the transmission arrangement. It should here be noted that braking of the vehicle does not necessarily lead to a reduction of the vehicle speed. For example, if braking of a vehicle (independently of the brake system used) is performed while travelling downhill, the vehicle speed may alternatively simply be maintained, or even increased, due to the gravitational force acting on the vehicle.

[0052] The braking of the output shaft of the transmission arrangement may for example be interrupted as soon as the gear has been disengaged. Alternatively, braking of the output shaft of the transmission arrangement may be continued, if this is appropriate consideringthe current driving situation of the vehicle. In the latter case however, the braking of the output shaft of the transmission arrangement is performed for another purpose than to disengage the gear.

[0053] In some situations, the torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units of the vehicle due to the maximum currently available torque output from the one or more power units being insufficient for reaching the torque, or torque range, appropriate for disengagement of the gear. This may for example occur when the gear to be disengaged is a lower gear (i.e. a gear having a higher gear ratio) of the transmission arrangement, and the vehicle is accelerating in a steep downhill. In particular, the maximum currently available torque output from the one or more power units may be insufficient for sufficiently reducing the torque transmitted through the transmission arrangement in case of the one or more power units constituting one or more electrical machines. This is because electrical machines used in medium-duty or heavy-duty vehicles today often have a more limited maximum available torque output compared to a e.g. combustion engine. This could also be the case because of an electrical machine temporarily being operated in a mode at which the maximum available torque output may be limited for some reason, e.g., to limit heat generation in the electrical machine. It should however be noted that a situation in which the maximum available torque output from the one or more power unitsmay be insufficient for reducing the torque transmitted through the transmission arrangement to allow disengagement of a gear may occur also in vehicles driven solely or partly by a combustion engine (i.e. for vehicles in which the one or more power units comprises a combustion engine).

[0054] For this reason, the herein described method may comprise a step of determining that torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units to a torque, or torque range, appropriate for disengagement of the gear when it is predicted that a maximum currently available torque output from the one or more power units is insufficient for reaching said torque, or torque range, appropriate for disengagement of the gear. In case the maximum available torque output from the one or more power units is insufficient for reducing the torque transmitted by the transmission arrangement to allow disengagement of the gear, it is necessary to take other action to allow disengagement of the gear as soon as possible; in particular in case the torque transmitted through the transmission arrangement unintentionally continues to increase. Therefore, the output shaft of the transmission arrangement should be braked in accordance with the present method to allow the needed of reduction of torque transmission through the transmission arrangement to disengage the gear.

[0055] Another example of a situation in which the one or more power units may not be controlled so as to sufficiently reduce the torque transmitted through the transmission arrangement to allow disengagement of the gear may be when at least one of the one or more power units is operated in a failure mode. Such a failure mode may be a failure mode of a power unit in which the output torque therefrom cannot, or can only partly, be controlled. In other words, such a failure mode of a power unit may be a failure mode in which the output torque from the power unit cannot be freely controlled. For example, a power unit in the form of an electrical machine may be operated in a failure mode in which an inverter associated therewith switches the electrical machine into operation as a generator, e.g. to avoid further heating of the electrical machine. It should be noted that, although the electrical machine is operated in such a failure mode, damage could still occur to the electrical machine e.g., in case of acceleration of the vehicle since torque transmitted in the powertrain from drive wheels of the vehicle may counteract the purpose of the failure mode, and even lead to an undesired acceleration of the electrical machine. This could however be prevented by putting the transmission arrangement in neutral through disengagement of the currently engaged gear.For this reason, the method may comprise a step of determining that torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units to a torque, or torque range, appropriate for disengagement of the gear with the one or more power units is / are operated in a failure mode. It should here be noted that when the one or more power units is / are operated in a failure mode in which the torque output therefrom cannot be freely controlled, this will in most cases also mean that the maximum current available torque output (if any) therefrom will be significantly reduced compared to a maximum available torque output if the one or more power units where operated in a default mode in which the full capacity thereof may be utilized.

[0056] According to one exemplifying embodiment of the herein described vehicle, the one or more power units may comprise a combustion engine operatively connected to the input shaft of the transmission arrangement via a clutch. In such a case, the method may further comprise a step of determiningthat torque transmitted through the transmission arrangement cannot be reduced through control of combustion engine to a torque ortorque range appropriate for disengagement of the gear when the clutch is in an open state and an output shaft of the combustion engine rotates in an opposite direction to a rotational direction of the input shaft of the transmission arrangement. When an output shaft of the combustion engine rotates in an opposite direction to the rotational direction of the input shaft of the transmission arrangement, the clutch cannot be closed without causing damage thereto and the combustion engine can therefore not be used for reducingthe torque transmitted through the transmission arrangement to allow disengagement of the gear. This may for example occur when the vehicle travels forward downhill with a reverse gear engaged. Unless the vehicle comprises an electrical machine, directly operatively connected to the input shaft of the transmission arrangement, and which is capable of delivering sufficient torque to allow the needed reduction of torque transmitted through the transmission arrangement, the gear may not be disengaged while the vehicle continues to travel downhill unless the torque transmitted through the transmission arrangement is reduced by braking the output shaft of the transmission arrangement in accordance with the herein described method.

[0057] As previously described, the step of braking the output shaft of the transmission arrangement to reduce the torque transmitted through the transmission arrangement is performed (only) in case a request for disengagement of the gear has been generated. Such a request may be generated by another controller than the control arrangement configured to perform the herein described method. Alternatively, said request may be generated by the herein described controlarrangement, in which case the generation of the request is also part of the herein described method. For example, the herein described method may comprise a step of generating the request for disengagement of the gear when it is predicted that a constituent component, arranged upstream of the transmission arrangement in a powertrain of the vehicle (such as a clutch, or an electrical machine of the one or more power units), will reach a critical rotational speed threshold for said constituent component unless the gear is disengaged, or when it is determined that said constituent component has reached said critical rotational speed threshold.

[0058] The performance of the herein described method for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle may be governed by programmed instructions. These programmed instructions may take the form of a computer program which, when executed by a computer, cause the computer to effect desired forms of control action. Such a computer may for example be comprised in the control arrangement as described herein. A computer is in the present disclosure considered to mean any hardware or hardware / firmware device implemented using processing circuity such as, but not limited to, a processor, Central Processing Unit (CPU), a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, an application-specific integrated circuit, or any other device capable of electronically performing operations in a defined manner.

[0059] The above described programmed instructions, which may take the form of a computer program, may be stored on a computer-readable medium. Hence, the present disclosure also relates to a computer-readable medium storing instructions, which when executed by a computer, cause the computer to carry out the herein described method for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle. The computer-readable medium may be a non-transitory computer-readable medium, such as a tangible electronic, magnetic, optical, infrared, electromagnetic, and / or semiconductor system, apparatus, and / or device.

[0060] The present disclosure further relates to a control arrangement configured to control a vehicle to disengage a gear of a transmission arrangement of the vehicle. The control arrangement may be configured to perform any one of the above described steps of the method for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle.More specifically, in accordance with the present disclosure, a control arrangement configured to control a vehicle to disengage a gear of a transmission arrangement of the vehicle is provided. Said transmission arrangement has an input shaft operatively connected, optionally via a clutch, to one or more power units of the vehicle. The control arrangement is configured to, (i) when a request for disengagement of the gear has been generated, and (ii) it is determined that torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units to a torque or torque range appropriate for disengagement of the gear, brake an output shaft of the transmission arrangement to reduce the torque transmitted through the transmission arrangement to said torque or torque range appropriate for disengagement of the gear.

[0061] The control arrangement may be configured to receive the generated request for disengagement of the gear from another controller of the vehicle through any previously known communication means suitable therefore. Alternatively, or additionally, the control arrangement may be configured to generate the request for disengagement of the gear. For example, the control arrangement may be configured to generate a request for disengagement of a gear of the transmission arrangement when it is predicted that a constituent component, arranged upstream of the transmission arrangement, of a powertrain of the vehicle will reach a critical rotational speed threshold for said constituent component unless the gear is disengaged, or when it is determined that said constituent component has reached said critical rotational speed threshold. Said critical rotational speed threshold may correspond to a rotational speed at which there is a riskfor damage of the constituent component.

[0062] The control arrangement may further be configured to determine whether the one or more power units, given the current circumstances when the request for disengagement of the gear has been generated, may be controlled so as to reduce the torque transmitted through the transmission arrangement to a torque, or a torque range, appropriate for disengagement of the gear. In case the control arrangement is not configured to determine whether the one or more power units may be controlled accordingly, the control arrangement may be configured to communicate with another controller of the vehicle capable of making such a determination and thereby derive such information. Examples of situations in which the one or more power units may not be controlled so as to reduce the torque transmitted through the transmission arrangement may be when a power unit is operated in a failure mode in which the torque output therefrom cannot be freely controlled and / or when the maximum available torque output from the power unit is insufficient for sufficiently reducing the torque transmitted by the transmissionarrangement. Yet another example of a situation in which the one or more power units cannot be controlled to reduce the torque transmitted through the transmission arrangement is where a clutch, interposed between a combustion engine and the transmission arrangement, is in an open state and the input shaft of the transmission arrangement rotates in an opposite direction to the rotation direction of the output shaft of the combustion engine. The latter may occur when a reverse gear is engaged in the transmission arrangement and the vehicle is accelerating in a forward direction downhill with the clutch open.

[0063] The control arrangement may suitably be configured to, while braking the output shaft of the transmission arrangement to reduce the torque transmitted through the transmission arrangement, control a gearshift actuator of the transmission arrangement to apply a preselected maneuvering force to the gear. Thereby, the gear will be disengaged as soon as the torque transmitted through the transmission arrangement is sufficiently low to allow such a disengagement. The preselected maneuvering force could, for example, correspond to a maximum maneuvering force that the gearshift actuator may apply. In case the control arrangement is not configured to control a gearshift actuator to apply a preselected maneuvering force simultaneously with at least part of the step of braking the output shaft to reduce the torque transmitted through the transmission arrangement, the control arrangement may instead be configured to control the gearshift actuator to apply a maneuvering force when a sufficiently low torque transmittal through the transmission arrangement to be appropriate for disengagement of the gear has been reached.

[0064] Moreover, the control arrangement may be configured to brake the output shaft of the transmission to reduce the torque transmitted thereto through control of a service brake system and / or an auxiliary brake system of the vehicle, said auxiliary brake system being arranged downstream of the transmission arrangement. It should here be noted that controlling the service brake system and / or the auxiliary brake system (which is arranged downstream of the transmission arrangement) will also inherently lead to a braking of the vehicle as such.

[0065] Depending on the circumstances, this braking of the vehicle may, or may not, lead to a reduction of the vehicle speed.

[0066] The control arrangement may further be configured to interrupt the braking of the output shaft of the transmission arrangement when it is determined that the gear has been disengaged.The herein described control arrangement may comprise one or more control units. In case of the control arrangement comprising a plurality of control units, each control unit may be configured to control a certain function / step or a certain function / step may be divided between more than one control units. The control arrangement may be a control arrangement of a powertrain of the vehicle. Alternatively, the control arrangement may be any other control arrangement of the vehicle, but configured to communicate with the vehicle’s powertrain for the purpose of performing the herein described method. Suitably, the control arrangement is further configured to communicate with a service brake system of the vehicle for the purpose of performingthe herein described method.

[0067] Figure 1 schematically illustrates an example of a vehicle 1 , here shown in a side view. The vehicle 1 may for example be a heavy-duty vehicle or a medium-duty vehicle, but is not limited thereto. In the figure, the vehicle 1 is illustrated as a tractor truck.

[0068] The vehicle 1 comprises a plurality of wheels, including drive wheels 10 (also known as driven wheels), front wheels 12, and optionally also rear wheels 14. The drive wheels 10 are equally distributed on both sides of a longitudinal axis A of the vehicle, and therefore only one drive wheel 10 is visible in the figure. Similarly, each of the front wheels 12 and the optional rear wheels 14 are equally distributed on opposing sides of the longitudinal axis A of the vehicle 1. The drive wheels 10 are associated with a (first) powertrain 2 of the vehicle, which will be described in more detail below. The optional rear wheels 14 may for example be non-driven tag axle wheels, or could be associated with a second powertrain (not shown) that is mechanically independent from the powertrain 2 (such as an electrical drive axle as shown in Figure 4).

[0069] Alternatively, the optional rear wheels 14 may be a second set of drive wheels of the powertrain 2. The front wheels 12 are typically non-driven wheels, but may in some cases also be drive wheels.

[0070] As mentioned above, the vehicle 1 comprises at least one powertrain 2. The powertrain 2 of the exemplified vehicle 1 comprises a first power unit 3 and a second power unit 4, each serving as a propulsion unit for the vehicle 1. The first power unit 3 of the exemplified powertrain 2 constitutes a combustion engine, whereas the second power unit 4 constitutes an electrical machine. The powertrain 2 further comprises a transmission arrangement 5 configured to transfer torque from the first and second power units 3, 4, to a set of drive wheels 10 of the vehicle 1. The first power unit 3 and the second power unit 4 are therefore operatively connected to an input shaft (not shown) of the transmission arrangement 5. More specifically, thecombustion engine is operatively connected to the transmission arrangement 5 via a clutch (see Figure 2). In contrast, a power unit in the form of an electrical machine need typically not be connected via an intermediate clutch to the transmission arrangement 5. The output shaft 5b of the transmission arrangement 5 may be connected to the drive wheels 10 as will be described in more detail with reference to Figure 2.

[0071] The powertrain 2 of the vehicle 1 may further comprise an auxiliary brake system 6. Said auxiliary brake 6 system is arranged to brake the output shaft 5b of the transmission arrangement 5. In other words, the auxiliary brake system 6 is arranged downstream of the transmission arrangement 5. The auxiliary brake system 6 may for example be a hydraulic brake system (such as a retarder), or an electromagnetic brake system. It should be noted that, although not illustrated in the figure, the vehicle 1 may comprise one or more further auxiliary brake systems arranged upstream of the transmission arrangement 5. Examples of such auxiliary brake systems that are arranged upstream of the transmission arrangement 5 include a regenerative brake system (which utilizes the electrical machine 4 as a generator for converting kinetic energy to electrical energy), a compression release brake system, a variable vane brake system, and an exhaust brake system.

[0072] The vehicle 1 further comprises a service brake system 16. The service brake system 16 is configured to brake the drive wheels 10. The service brake system 16 may typically be configured to brake also the front wheels 12 and / or the optional rear wheels 14. Alternatively, the front wheels 12 and / or the optional rear wheels 14 may be braked by additional service brake system(s) of the vehicle. Service brake systems are typically not considered to be part of a vehicle’s powertrain.

[0073] The vehicle 1 further comprises a control arrangement 100 configured to control at least parts of the vehicle 1. More specifically, the control arrangement 100 may be configured to control the powertrain 2, and suitably also the service brake system 16. The control arrangement 100 may be configured to perform the herein described method for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle.

[0074] It should here be noted that although Figure 1 illustrates an example of a hybrid vehicle (in view of comprising both a combustion engine and an electrical machine), the present disclosure is not limited thereto. The vehicle 1 may for example constitute a vehicle driven solely by a combustion engine, in which case the powertrain 2 does not comprise any electrical machine.Alternatively, the vehicle 1 may be a fully electric vehicle, in which case it does not comprise any combustion engine but only one or more electrical machines serving as power units.

[0075] Alternatively, the vehicle 1 may be a primarily electric vehicle but which, in addition to one or more primary electrical machines, comprises a range extender in the form of a smaller combustion engine.

[0076] Figure 2 schematically illustrates the powertrain 2 of the vehicle 1 , as shown Figure 1, in more detail. As already mentioned above, the powertrain 2 comprises a first power unit 3, in the form of a combustion engine, and a transmission arrangement 5. The output shaft 3b of the combustion engine 3 is operatively connected to the input shaft 5a of the transmission arrangement 5 via a clutch 9. The clutch 9 allows for selectively disconnecting the combustion engine 3 from the transmission arrangement. The powertrain 2 further comprises a second power unit 4 in the form of an electrical machine 4. The electrical machine 4 is arranged at the input shaft 5a of the transmission arrangement 5, and thus operatively connected thereto. Furthermore, as shown in the figure, the output shaft 5b of the transmission arrangement 5 is connected to a set of drive wheels 10 via a differential 7 and a drive shaft 8. Moreover, an auxiliary brake system 6 may be arranged at the output shaft 5b of the transmission arrangement. Said auxiliary brake system 6, if present, is thus arranged downstream of the transmission arrangement 5. Each of the first power unit 3, the clutch 9, the second power unit 4, the transmission arrangement 5, the auxiliary brake system 6, the differential 7, the drive shaft 8, and the drive wheels 10 are constituent components of the powertrain 2.

[0077] The transmission arrangement 5 of the powertrain 2 may have various configurations without departingfrom the scope of the present disclosure. However, in each case, the transmission arrangement 5 is a so called multi-speed transmission arrangement. In other words, the transmission arrangement is a transmission arrangement which allows for shifting between different gears to thereby allow different gear ratios. The transmission arrangement 5 may for example comprise an automated manual transmission (AMT), but is not limited thereto.

[0078] As already mentioned above, the powertrain 2 shown in Figure 2 is intended merely to serve as an example. The powertrain 2 shown in the figure need for example not comprise the second power unit 4, or may be supplemented with further power units in the form of electrical machines. Alternatively, the powertrain 2 need not comprise a combustion engine (in which case the clutch 9 may also be omitted), but comprise one or more electrical machines serving as power units (compare with the second power unit 4).Figure 3 schematically illustrates an example of a transmission arrangement 5 which may be comprised in a powertrain, such as the powertrain 2 shown in Figure 2. The illustrated transmission arrangement 5 is an example of a previously known automated manual transmission (AMT), but the present disclosure is not limited thereto.

[0079] The transmission arrangement 5 according to the example comprises two transmission units, more specifically a main gearbox 26 and a split gearbox 28. The main gearbox 26 can be set to three different forward gear pairs and a reverse gear pair. The split gearbox 28 is arranged upstream of the main gearbox 26 as seen in a direction of torque from a power unit towards the drive wheels of a vehicle comprisingthe transmission arrangement 5. The split gearbox 28 divides each gear pair of the main gearbox 26 into two gear steps with different gear ratios in order to provide further gear ratios of the transmission arrangement 5. The transmission arrangement 5 may also, although not illustrated in the figure, comprise further transmission units. For example, a third transmission unit, such as a planetary gearset, may be arranged downstream of the main gearbox 26.

[0080] The exemplified transmission arrangement 5 comprises three different shafts, more specifically an input shaft 20, a main shaft 22, and a layshaft 24. The input shaft 20 corresponds to the input shaft 5a shown in Figure 2, unless there is a furthertransmission unit arranged upstream of the split gearbox 28. Similarly, the main shaft 22 may correspond to the output shaft 5B shown in Figure 2, unless the transmission arrangement comprises a further transmission unit arranged downstream of the main gearbox 26.

[0081] The main gearbox 26 comprises a plurality of gear pairs, each representing a different gear ratio. More specifically, a first gear pair 31 is formed of a first cogwheel 31 A and a second cogwheel 31 B that engages with the first cogwheel 31 A. Similarly, a second gear pair 32 is formed of a third cogwheel 32A which engages with a fourth cogwheel 32B. A third gear pair 33 is formed of a fifth cogwheel 33A which engages with a sixth cogwheel 33B. The first cogwheel 31 A, the third cogwheel 32A, and the fifth cogwheel 33A, are each rotatably fixed to the layshaft 24. The second cogwheel 31 B, the fourth cogwheel 32B, and the sixth cogwheel 33B, are each rotatably arranged about the main shaft 22, but can be selectively locked for rotation with the main shaft 22 to engage a gear. For example, the first gear pair 31 may be engaged by maneuvering a first coupling unit 41 , arranged to rotate with the main shaft 22, to a position where it engages with the second cogwheel 31 B (i.e. to the left in the figure). Thereby, the second cogwheel 31 B will belocked for rotation with the main shaft 22 and the layshaft 24 thereby being engaged with the main shaft 22 via the first cogwheel 31 A. The first coupling unit 41 may be maneuvered by a first gearshift actuator 42 configured therefore.

[0082] Shifting from the first gear pair 31 to the second gear pair 32 may be achieved by moving the first coupling unit 41 to a position at which the second cogwheel 31 B is disengaged from the main shaft 22 so as to be freely rotatable about the main shaft 22, and thereafter moving a second coupling unit 43, maneuverable by a second gearshift actuator 44, to a position at which the fourth cogwheel 32B is locked for rotation with the main shaft 22. Shifting from the second gear pair 32 to the third gear pair 33 may be achieved by moving the second coupling unit 43 to a position at which the fourth cogwheel 32B is freely rotatable about the main shaft 22, and thereafter locking the sixth cogwheel 33B for rotation with the main shaft 22. In the exemplified transmission arrangement 5, the sixth cogwheel 33B may be locked for rotation with the main shaft 22 by means of the second coupling unit 43. In other words, the second coupling unit 43 may selectively lock each of the fourth cogwheel 32B and the sixth cogwheel 33B for rotation with the main shaft 22. It should however be noted that the fourth cogwheel 32B and the sixth cogwheel 33B may be locked to the main shaft 22 by separate coupling units, if desired.

[0083] The transmission arrangement 5 further comprises a fourth gear pair 34, which is arranged in the split gearbox 28. The fourth gear pair 34 comprises a seventh cogwheel 34A, rotationally locked to the layshaft 24, engaging with an eight cogwheel 34B. The eight cogwheel 34B is arranged to be freely rotatable about the input shaft 20, but which may be selectively coupled thereto so as to be locked for rotation with the input shaft 20. More specifically, the eight cogwheel 34B may be locked for rotation with the input shaft 20 by means of a third coupling unit 45, maneuverable by a third gearshift actuator 46. As shown in the figure, the third coupling unit 45 may also be used for connecting the input shaft 20 of the transmission arrangement 5 directly to the sixth cogwheel 33B. Thereby, each of the gear pairs 31 , 32, 33 may be split into two different gear ratios for the transmission arrangement 5 as a whole, depending on whether the third coupling unit 45 is controlled so as to lock the cogwheel 34B or the cogwheel 33B for rotation with the input shaft 20. It should further be noted that in case of the transmission arrangement comprising further transmission units than the ones illustrated in the figure, such as a planetary gear arranged downstream of the main gearbox 26, each of the gear pairs 31 , 32, 33 (in high split or low split) may be divided into further gear ratios, as is well known in the art.The transmission arrangement 5 further provides a reverse gear. This is achieved by cogwheel arrangement 35 in the main gearbox 26. Said cogwheel arrangement 35 comprises a ninth cogwheel 35A rotationally locked to the layshaft 24 and tenth cogwheel 35B which may be selectively locked for rotation with the main shaft 22. The change of rotational direction in order for reversing a vehicle comprising the transmission arrangement 5 is achieved by an intermediate cogwheel 35C of the cogwheel arrangement 35. The intermediate cogwheel 35C engages with both the ninth cogwheel 35A and the tenth cogwheel 36B, and thus provides the operational connection between the ninth and tenth cogwheels 35A, 35B.

[0084] It should be noted that the illustrated transmission arrangement 5 is only one possible alternative of an automated manual transmission, and the present disclosure is not limited to the illustrated example.

[0085] Figure 4 schematically illustrates a second example of a powertrain 2 of a vehicle, as seen in a top view. The powertrain 2 according to the second example is an electric drive axle (also known in the art as an electric axle or e-axle). In the figure, the drive wheel(s) of the powertrain have been omitted for simplification of the disclosure.

[0086] As is well known in the art, an electric drive axle is based on a powertrain configuration wherein an electrical machine, serving as a propulsion unit of the vehicle, and a transmission arrangement are arranged at the drive shaft. Thereby, there is for example no need for a propeller shaft for transferring propulsion power from the propulsion unit to the drive wheels of the vehicle. One of the advantages of an electric drive axle is that it typically occupies less space compared to a powertrain such as the one shown in Figure 2, and thereby leaves more available space onboard the vehicle for accommodating, for example, batteries. Furthermore, an electric drive axle typically provides a greater flexibility in vehicle configurations. In some cases, a vehicle may comprise a plurality of mechanically independent powertrains, such as a plurality of electric drive axles, or a conventional powertrain of the type shown in Figure 2 and an electric drive axle. In such cases, each of the mechanically independent powertrains comprise their own set of drive wheels.

[0087] The powertrain 2 shown in Figure 4 comprises a power unit 4 in the form of electrical machine, and a transmission assembly 5. The transmission assembly 5 is directly connected to a drive shaft 50 (as will be further described below) and comprises a main shaft 51 and a layshaft 52. The drive shaft 50, the main shaft 51 and the lay shaft 52 are each arranged substantially inparallel to each other. The transmission assembly 5 further comprises a first gearwheel pair 56, a second gearwheel pair 57 and a final gearwheel pair 58. An input shaft 5a of the transmission assembly is operatively connected to the first power unit 4. The first power unit 4 is directly connected to the input shaft 5a of the transmission arrangement, and the input shaft 5a of the transmission arrangement 5 may thus also be considered to serve as an output shaft of the power unit 4.

[0088] The transmission assembly 5 comprises a first gear wheel 55 rotationally locked to the input shaft 5a. In other words, the first gear wheel 55 is fixedly connected to the input shaft 5a of the transmission arrangement 5 and will therefore rotate with the same rotational speed as the input shaft 5a. The first gearwheel 55 may, as shown in the figure, be connected to the first gear wheel pair 56 by being arranged to engage with one of the gearwheels of the first gearwheel pair 56. Alternatively, the first gearwheel 55 may be connected to the second gearwheel pair 57, if desired, by engaging with one of the gearwheels of the second gearwheel pair 57.

[0089] The first gearwheel pair 56 comprises a second gearwheel 56a and a third gearwheel 56b engaged with each other. The second gear wheel 56a is arranged on the lay shaft 52. More specifically, the second gearwheel 56a is rotationally locked to the lay shaft 52. In other words, the second gear wheel 56a is fixedly connected to the lay shaft 52. The third gear wheel 56b is arranged on, and connectable to, the main shaft 51. More specifically, the third gearwheel 56b is selectively rotationally coupled to the main shaft 51. In other words, when the third gear wheel 56b is rotationally coupled to the main shaft 51 , the third gear wheel 56b is rotationally locked to the main shaft 51 , and the main shaft 51 and the third gearwheel 56b will thereby rotate with the same rotational speed. The connection of the third gearwheel 56b to the main shaft 51 to rotationally lock the third gear wheel thereto may be made by any previously known means therefore, such as a coupling unit in the form of a coupling sleeve, a dog clutch, or the like. Such means may be controlled by a gearshift actuator (not shown). When the third gear wheel 56b is not rotationally coupled to the main shaft 51 , the main shaft 51 and the third gear wheel 56b may rotate with different rotational speeds.

[0090] In a similar way as for the first gearwheel pair 56, the second gearwheel pair 57 comprises a fourth gear wheel 57a and a fifth gear wheel 57b engaged with each other. The fourth gear wheel 57a is fixedly connected, i.e. rotationally locked to, the lay shaft 52. The fifth gear wheel 57b is arranged on the main shaft 51 and connectable thereto. In other words, the fifth gear wheel is selectively rotationally coupled to the main shaft 51. The connection of the fifth gear wheel 57bto the main shaft 51 to rotationally lock the fifth gear wheel 57b thereto may be made by any previously known means therefore, such as described above with regard to locking of the third gearwheel 56b to the main shaft 51. The first gearwheel pair 56 and the second gearwheel pair 57 are configured to provide two different gear ratios, and thus provides two different gear steps.

[0091] The transmission assembly 5 further comprises a final gear wheel pair 58 comprising a sixth gear wheel 58a and a final gear wheel 58b (which may alternatively be described as a seventh gearwheel). The sixth gearwheel 58a is fixedly connected to, i.e. rotationally locked to, the main shaft 51. The final gear wheel 58b is arranged on the drive shaft 50.

[0092] When transmission arrangement 5 is arranged in a vehicle, for example a vehicle 1 such as shown in Figure 1 , the drive shaft 50 is configured to be connected to at least one drive wheel of the vehicle for the purpose of transmitting driving power thereto. In case the drive shaft 50 is connected to only one drive wheel of the vehicle, the final gearwheel 58b may be directly and fixedly connected to the drive shaft 50. However, in the example shown in Figure 4, the drive shaft 50 is configured to be connected to two opposing drive wheels of the vehicle. In other words, the drive shaft 50 is configured to be connected to a first drive wheel at a first longitudinal end of the drive shaft 50, and a second drive wheel at a second longitudinal end of the drive shaft 50. In such a case, the drive shaft 50 may comprise, or consist of, a first drive shaft half-shaft 50a and a second drive shaft half-shaft 50b as shown in Figure 4. The first drive shaft half-shaft 50a is configured to be connected to said first drive wheel of the vehicle, and the second drive shaft half-shaft 50b is configured to be connected to said second drive wheel of the vehicle. The first and second drive shaft half-shafts 50a, 50b may optionally have a substantially equal length (i.e. longitudinal extension). However, the lengths of the first and second drive shaft half-shafts 50a, 50b are typically not the same. When the drive shaft 50 comprises a first drive shaft half-shaft 50a and a second drive shaft half-shaft 50b, the final gear wheel 58b is suitably connected to the drive shaft 50 via a differential (not shown).

[0093] The transmission assembly 5 may, if desired, further comprise a planetary gear 59 arranged on the main shaft 51 between the first gearwheel pair 56 and the second gearwheel pair 57. In case the transmission assembly 5 comprises the planetary gear 29, the main shaft 51 comprises or consists of two main shaft half-shafts. One of the two main shaft half-shafts forming the main shaft 51 may be connected to a sun gear of the planetary gear 59 and the other one of said two main shaft half-shafts may be connected to a planet wheel carrier of the planetary gear 59, although other configurations are also possible.Figure 5 represents a flowchart schematically illustrating a first exemplifying embodiment of the herein described method for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle. The vehicle comprises, in addition to the transmission arrangement, one or more power units operatively connected to an input shaft of the transmission arrangement. The one or more power units and the transmission arrangement are constituent components of a powertrain of the vehicle.

[0094] The method according to the first exemplifying embodiment comprises a step S101 of determining whether a request for disengagement of the gear of the transmission arrangement has been generated. If not, the method may revert to start as shown in the figure. However, in case it is determined that a request for disengagement of the gear has been generated, the method proceeds to step S104.

[0095] Step S104 comprises determining whether one or more power units of the vehicle may be controlled so as to reduce the (positive or negative) torque transmitted through the transmission arrangement to a torque, or torque range, appropriate for disengagement of the gear. If this is the case, the method may proceed to a normal procedure for disengagement of a gear, such a procedure typically comprising steps S105 and S106. Step S105 comprises controlling the one or more power units so as to reduce the torque transmitted through the transmission arrangement to a torque appropriate for disengagement of the gear (such as a substantially zero torque), and a step S106 comprises disengaging the gear. Step S106 may comprise controlling a gearshift actuator of the transmission arrangement to apply a suitable maneuvering force to the gear. After step S106, the method may be ended as shown in the figure (or alternatively be reverted to start).

[0096] However, in case it is determined in step S104 that torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units to a torque, or torque range, appropriate for disengagement of the gear, the method proceeds to a step S110 of braking an output shaft of the transmission arrangement to reduce the torque transmitted through the transmission arrangement to the torque, or torque range, appropriate for disengagement of the gear.

[0097] Step S110 may comprise (or be achieved by) a step S110a of braking the vehicle through usage of a service brake system of the vehicle. Alternatively, or additionally, step S110 may comprise(or be achieved by) a step S110b of braking the vehicle through usage of an auxiliary brake system of the vehicle, said auxiliary brake system being arranged downstream of the transmission arrangement.

[0098] The method accordingto the exemplifying embodiment further comprises a step S112 of controlling a gearshift actuator of the transmission arrangement to apply a preselected maneuvering force to the gear, which in turn causes a disengagement of the gear. It should here be noted that although step S112 is illustrated in the figure as being performed after step S110, step S112 is suitably performed in parallel with (at least a part) of step S110. Thereby, the gear will disengaged as soon as the torque transmitted through the transmission arrangement has been reduced sufficiently low that the maneuvering force, applied by the gearshift actuator, is sufficient to disengage the gear.

[0099] After step S112, the method may be ended as shown in the figure (or alternatively be reverted to start). The braking of the output shaft of the transmission arrangement, performed in step S110, may suitably be interrupted as soon as the gear has been disengaged, but the present disclosure is not limited thereto.

[0100] Figure 6 represents a flowchart schematically illustrating a second exemplifying embodiment of the herein described method for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle. The second exemplifying embodiment of the method corresponds to the first exemplifying embodiment shown in Figure 5, except that it comprises steps S102 and S103 instead of step S101. It should however be noted that the second exemplifying embodiment may be modified to also include step S101, in which case step S101 is to be performed after step S103 but prior to step S104.

[0101] The method accordingto the second exemplifying embodiment comprises a step S102 of predicting whether a constituent component, arranged upstream of the transmission arrangement, of a powertrain of the vehicle will reach a critical rotational speed threshold for said constituent component unless the gear is disengaged, and / or determining whether said constituent component has already reached said critical rotational speed threshold. The constituent component, arranged upstream of the transmission arrangement, may for example be an electrical machine of the one or more power units or a clutch, depending on the configuration of the powertrain. Moreover, the critical rotational speed threshold maycorrespond to a rotational speed at which there is a risk for damage of the constituent component.

[0102] In case it is determined, through step S102, that the constituent component, arranged upstream of the transmission arrangement, has not reach the critical rotational speed threshold and is not predicted to do so, the method may revert to start as shown in the figure.

[0103] However, in case it, in step S102, is predicted that the constituent component, arranged upstream of the transmission arrangement, will reach the critical rotational speed threshold therefore unless the gear is disengaged, or has already reached said critical rotational speed threshold, the method proceeds to a step S103 of generating a request for disengagement of the gear.

[0104] After step S103, the method proceeds to step S104, and the steps following thereafter, as already described above with regard to the first exemplifying embodiment as illustrated in Figure 5.

[0105] Figure 7 schematically illustrates an exemplifying embodiment of a device 500. The control arrangement 100 described above may comprise the device 500, consist of the device 500, or be comprised in the device 500.

[0106] 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 540.

[0107] There is provided a computer program P that comprises instructions for controlling a vehicle to disengage a gear of a transmission arrangement of the vehicle, said transmission arrangement having an input shaft operatively connected to one or more power units of the vehicle. The computer program comprises instructions for, when (i) a request for disengagement of the gear has been generated and (ii) it is determined that torque transmitted through the transmission arrangement cannot be reduced through control of the one or more power units to a torque ortorque range appropriate for disengagement of the gear, braking an output shaft of the transmission arrangement to reduce the torque transmitted through the transmission arrangement to said torque or torque range appropriate for disengagement of the gear.

[0108] 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.

[0109] 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 550.

[0110] 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.

[0111] 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 unit 510 is prepared to effect code execution as described above.

[0112] Parts of the methods herein described may be effected 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

CLAIMS1. A method, performed by a control arrangement (100), for controlling a vehicle (1 ) to disengage a gear of a transmission arrangement (5) of the vehicle (1 ),said transmission arrangement (5) having an input shaft (5a) operatively connected to one or more power units (3, 4) of the vehicle (1 ),the method comprising a step of:when a request for disengagement of the gear has been generated, and it is determined that torque transmitted through the transmission arrangement (5) cannot be reduced through control of the one or more power units (3, 4) to a torque or torque range appropriate for disengagement of the gear, braking (S110) an output shaft (5b) of the transmission arrangement (5) to reduce the torque transmitted through the transmission arrangement (5) to said torque or torque range appropriate for disengagement of the gear.

2. The method according to claim 1 , further comprising a step of:in parallel with the step of braking (S110) the output shaft (5b) of the transmission arrangement (5), controlling (S112) a gearshift actuator (42, 44, 46) of the transmission arrangement (5) to apply a preselected maneuvering force to the gear.

3. The method according to according to anyone of claims 1 or 2, wherein the step of braking (S110) the output shaft (5b) of the transmission arrangement (5) comprises braking (S110a) the vehicle (1 ) through usage of a service brake system (16) of the vehicle d).

4. The method according to any one of the preceding claims, wherein the step of braking (S110) the output shaft (5b) of the transmission arrangement (5) comprises braking (S110b) the vehicle (1 ) through usage of an auxiliary brake system (6) of the vehicle (1 ), said auxiliary brake system (6) being arranged downstream of the transmission arrangement (5).

5. The method according to any one of the preceding claims, further comprising a step of:determiningthat torque transmitted through the transmission arrangement (5) cannot be reduced through control of the one or more power units (3, 4) to a torque or torque range appropriate for disengagement of the gear when it is predicted that amaximum currently available torque output from the one or more power units (3, 4) is insufficient for reaching said torque or torque range appropriate for disengagement of the gear.

6. The method according to any one of the preceding claims, further comprising a step of:determiningthat torque transmitted through the transmission arrangement (5) cannot be reduced through control of the one or more power units (3, 4) to a torque or torque range appropriate for disengagement of the gear when the one or more power units (3, 4) is / are operated in a failure mode.

7. The method according to any one of the preceding claims, whereinthe one or more power units (3, 4) comprises a combustion engine (3) operatively connected to the input shaft (5a) of the transmission arrangement (5) via a clutch (9), andthe method further comprising a step of:determiningthat torque transmitted through the transmission arrangement (5) cannot be reduced through control of combustion engine (3) to a torque or torque range appropriate for disengagement of the gear when the clutch (9) is in an open state and an output shaft (3b) of the combustion engine (3) rotates in an opposite direction to a rotational direction of the input shaft (5a) of the transmission arrangement (5).

8. The method according to any one of the preceding claims, further comprising a step of:generating (S103) the request for disengagement of the gear when it is predicted that a constituent component, arranged upstream of the transmission arrangement (5), of a powertrain (2) of the vehicle (1 ) will reach a critical rotational speed threshold for said constituent component unless the gear is disengaged, or when it is determined that said constituent component has reached said critical rotational speed threshold;optionally wherein said constituent component, arranged upstream of the transmission arrangement (5), of the powertrain (2) of the vehicle (1) is a clutch (9) or an electrical machine of the one or more power units (3, 4).

9. The method according to any one of the preceding claims, wherein the step of braking (S110) the output shaft (5b) of the transmission arrangement (5) to reduce the torque transmitted through the transmission arrangement (5) comprises brakingthe outputshaft (5b) of the transmission arrangement (5) to achieve a substantially zero torque transmitted through the transmission arrangement (5).

10. A control arrangement (100) configured to control a vehicle (1 ) to disengage a gear of a transmission arrangement (5) of the vehicle (1),said transmission arrangement (5) having an input shaft (5a) operatively connected to one or more power units (3, 4) of the vehicle (1),the control arrangement (100) being configured to:when a request for disengagement of the gear has been generated, and it is determined that torque transmitted through the transmission arrangement (5) cannot be reduced through control of the one or more power units (3, 4) to a torque or torque range appropriate for disengagement of the gear, brake an output shaft (5b) of the transmission arrangement (5) to reduce the torque transmitted through the transmission arrangement (5) to said torque or torque range appropriate for disengagement of the gear.

11. The control arrangement (100) according to claim 10, wherein the control arrangement (100) further is configured to:control a gearshift actuator (42, 44, 46) of the transmission arrangement (5) to apply a preselected maneuvering force to the gear while the output shaft (5b) of the transmission arrangement (5) is braked to reduce the torque transmitted through the transmission arrangement (5) to the torque ortorque range appropriate for disengagement of the gear.

12. The control arrangement (100) according to any one of claims 10 and 11, wherein the control arrangement (100) is configured to brake the output shaft (5b) of the transmission arrangement (5) to reduce the torque transmitted through the transmission arrangement (5) to said torque or torque range appropriate for disengagement of the gear through control of a service brake system (16) of the vehicle (1 ) and / or an auxiliary brake system (6) of the vehicle (1 ), said auxiliary brake system (6) being arranged downstream of the transmission arrangement (5).

13. The control arrangement (100) according to any one of claims 10 to 12, further configured to determine whether torque transmitted through the transmission arrangement (5) can be reduced through control of the one or more power units (3, 4) toa torque or torque range appropriate for disengagement of the gear based on an operating mode of the one or more power units (3, 4) and / or a prediction of whether a maximum currently available torque output is sufficient for reaching said torque or torque range appropriate for disengagement of the gear.

14. A computer program comprising instructions which, when executed by a control arrangement (100) according to any one of claims 10 to 13, cause the control arrangement (100) to carry out the method according to any one of claims 1 to 9.

15. A computer-readable medium having stored thereon the computer program according to claim 14.

16. A vehicle (1) comprising a control arrangement (100) according to any one of claims 10

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