SE541781C2

SE541781C2 - Method and system for controlling torque transmitting means of a vehicle

Info

Publication number: SE541781C2
Application number: SE1651283A
Authority: SE
Inventors: Erik Gustafsson; Fredrik Jarngren; Georg Åhrberg
Original assignee: Scania Cv Ab
Priority date: 2016-09-30
Filing date: 2016-09-30
Publication date: 2019-12-17
Also published as: BR102017019917A2; DE102017008737A1; DE102017008737B4; SE1651283A1

Abstract

A vehicle (100) includes torque transmitting means (106) for selectively transmitting torque to and/or from a power source (101), and driver manoeuvrable means (118) for controlling transmittable torque by the torque transmitting means (106), said driver manoeuvrable means (118) being manoeuvrable in a movement region (A-B) between a first end position (A), representing a request for a full transmissibility of torque, and a second end position (B), representing a complete interruption of the transmission of torque. The transmittable torque is controllable in a second mode independently from said position of said driver manoeuvrable means (118). The invention relates to a method including, when the transmittable torque is controlled according to said second mode: if the position of said driver manoeuvrable means (118) deviates from said first position (A), prohibiting, upon a driver initiated request for power from said power source, an automatic increase in transmitted torque by said torque transmitting means (106).

Description

METHOD AND SYSTEM FOR CONTROLLING TORQUE TRANSMITTING MEANS OF A VEHICLE Field of the invention The present invention relates to vehicles, and in particular to a method and system for controlling torque transmitting means of a vehicle. The present invention also relates to a vehicle, as well as a computer program and a computer program product that implement the method according to the invention.

Background of the invention There exist various kinds of vehicle transmissions. For example, vehicle transmissions can be of a fully automatic kind, where a vehicle control system controls gear changing operations. The gearboxes being used in these systems may consist of automated manual transmissions where the vehicle control system automatically controls gear shifting in “manual” gearboxes.

There also exist manual transmissions where the vehicle driver is in control of the gear changing operation. A change of gear in manual transmissions is often performed through the use of a driver controllable clutch, oftentimes through the use of a clutch pedal. Clutches can also be used in automated manual transmissions, in which case clutch operation when changing gear is controlled by the vehicle control system and not by the driver. There also exist systems having automated manual transmissions, where driver controllable means such as a clutch pedal is present and which may be used when starting the vehicle from standstill. When the vehicle has been set in motion, subsequent changes of gear can be arranged to be controlled completely by the vehicle control system without driver interaction and without further manoeuvring of the clutch, i.e. changes of gear being performed with the drivetrain closed. Hence, in this case, the clutch is completely controlled by the driver using a clutch pedal being directly (mechanically) linked to the clutch actuator.

The present application relates to systems where the driver manoeuvrable means such as a clutch pedal is used for controlling torque transmitting means such as a clutch, but not directly through the use of a mechanical linkage. Instead, e.g. the torque transmitting means is controlled through the use of clutch-by-wire (CBW) systems. In clutch -by-wire systems an electrical signal representing e.g. a clutch pedal position is translated into a corresponding request for torque transmission, such as a corresponding clutch movement. For example, a position sensor or other suitable means can be used to detect a position of the driver manoeuvrable means, such as e.g. the position of a clutch pedal. An electrical signal representing this position is then translated into a corresponding driver request regarding e.g. clutch operation, and the vehicle control system controls e.g. the actual clutch movement in dependence of the signal representing the position of the clutch pedal. The actual clutch movement, consequently, is not mechanically linked to movements of the driver manoeuvrable means. The responsibility for controlling the manner in which the clutch is to be manoeuvred may thereby be transferrable between driver and vehicle control system so that opening and closing of the clutch may also be completely controlled by the vehicle control system, hence independently from the position of the clutch pedal.

Systems of this kind may provide advantages in the operation of the vehicle.

Summary of the invention It would be advantageous to achieve a method and system that reduces the risk of the vehicle being unintentionally set in motion in situations when the driver may assume to be in control of the manoeuvring of torque transmitting means while in reality the torque transmitting means is controlled completely by the vehicle control system. To better address this concern a method and system having the features defined in the independent claims are provided.

According to the present invention, it is provided a method for controlling torque transmitting means of a vehicle, the vehicle including: torque transmitting means such as a clutch for selectively transmitting torque to and/or from a power source of the vehicle, and driver manoeuvrable means for controlling transmittable torque by said torque transmitting means, said driver manoeuvrable means being manoeuvrable by the driver in a movement region between a first end position, representing a full transmissibility of torque, such as e.g. a fully closed clutch, and a second end position, representing a complete interruption of the transmission of torque, such as a fully open clutch, wherein transmittable torque of said torque transmitting means is controllable in a first mode in dependence of the position of said driver manoeuvrable means, and in a second mode independently from said position of said driver manoeuvrable means, the method including, when the transmittable torque of said torque transmitting means is controlled according to said second mode: - if the position of said driver manoeuvrable means deviates from said first position, prohibiting, upon a driver initiated request for power from said power source, an automatic increase of transmittable torque of said torque transmitting means, e.g. prohibiting an automatic closing of a clutch.

With regard to automated manual transmission (AMT) systems, such systems may comprise torque transmitting means in the form of a clutch that is controlled exclusively by the vehicle control system. A vehicle comprising a system of this kind is in general a two-pedal (accelerator pedal, brake pedal) vehicle with no opportunity for the driver to manually control the clutch using a clutch pedal. When manoeuvring of the clutch is under control of the vehicle control system, performance may in some situations be improved e.g. when changing gear in comparison to a system where the clutch is manoeuvred exclusively by the driver and where e.g. changes of gear have to be performed when the clutch is closed.

Hence, AMT systems comprising an additional clutch pedal which is controlled completely by the driver of the vehicle may in some situations suffer from a reduced performance e.g. with regard to changes of gear in comparison to systems where the clutch is controlled by the vehicle control system. Vehicles comprising a clutch pedal that is mechanically linked to the clutch in general also inherently require that the driver actively manoeuvres the clutch (closes the clutch from an open state) when performing a start of the vehicle, and also opens the clutch when the vehicle is taken to a full stop. Consequently, such vehicles usually require driver operation of the clutch pedal e.g. each time the vehicle has to come to a full stop at a road crossing or traffic light etc.

However, systems of this kind may also provide advantages. For example, the use of a clutch pedal during a vehicle start may provide the vehicle control system with additional information regarding the manner in which the driver desires to perform the start e.g. by slowly closing the clutch e.g. to avoid wheel spin. The vehicle control system may then control other vehicle functions in accordance with the intention of the driver. Also, using a slipping clutch pedal, the driver may independently control both speed of the vehicle and speed of the power source. Such control is difficult to accomplish using a brake pedal and accelerator pedal only.

Consequently, it may in some situations be desirable to have a vehicle comprising a clutch that is controllable by the driver. Use of clutch-by-wire systems, i.e. systems where an electrical signal representing a position of driver manoeuvrable means for controlling the clutch, such as e.g. a clutch pedal position, may provide features of the two-pedal system and features of three-pedal systems where the clutch pedal is mechanically linked to the clutch.

Clutch-by-wire systems may be designed such that the driver may obtain (take) control of the clutch only in situations when so desired, while the vehicle control system may be left in charge of the clutch for all other situations. This means, for example, that when the vehicle stops at a traffic light it may be sufficient for the driver to only operate the brake pedal when stopping the vehicle, while the clutch will be automatically opened by the vehicle control system without driver interaction.

Still, from a driver perspective, a clutch-by-wire system may behave in a manner similar to systems having a mechanical linkage between clutch and driver manoeuvrable means according to the above, and hence the driver may be able to take control of the clutch whenever desired, e.g. when performing a start of the vehicle. It may also be comforting to the driver to know that he/she will always be capable of taking control of the clutch. The clutch-by-wire system may, however, also introduce vehicle behaviour that may not be expected by the driver.

Clutch-by-wire systems that allow driver control of the clutch has the result that manoeuvring of the clutch is under the control of either the driver or the vehicle control system. Hence, a definition of the transfer of responsibility of the control of the clutch is usually required from both a driver and control system point of view. This can be accomplished, for example, by giving control of the clutch to the vehicle control system e.g. when the clutch pedal is fully released. Correspondingly, responsibility of the clutch can be handed over to the driver when the driver manoeuvers the driver controllable means, e.g. manoeuvers the clutch pedal.

Each position of the driver manoeuvrable means (such as clutch pedal position) is in general correlated to the corresponding position of the clutch movable elements such as e.g. clutch actuator. With regard to a clutch pedal, a fully released clutch pedal may represent a fully closed clutch, and a fully depressed clutch pedal may represent a fully open clutch. Clutch pedal positions there in between may represent positions of the clutch movable elements between fully closed and fully open.

In order to take control of the clutch it may, for example, be required that the driver manoeuvers the driver manoeuvrable means to a position where the requested transmittable torque has been reduced to an extent such that said position represents a transmittable torque at most corresponding to the current transmittable torque of the clutch. That is, the driver e.g. depresses a clutch pedal to an extent at least equalling the actual degree of opening to which the clutch has been opened by the vehicle control system. The control of the clutch will then remain under the control of the driver for as long as the clutch is not fully closed.

This means, for example, that if the clutch is closed only a small movement of the driver manoeuvrable means (e.g. small depressing of the clutch pedal) by the driver will result in the driver taking control of the clutch. Conversely, if e.g. the vehicle is standing still and the clutch being manoeuvred to a fully open position by means of the vehicle control system, it is required that the driver manoeuvers the driver manoeuvrable means to a position representing fully open clutch to gain control of the clutch. Once the driver has gained/obtained control of the clutch, driver control of the clutch may be maintained for as long as the driver manoeuvrable means is not in the end position representing fully closed clutch.

Consequently, the manner in which the driver gains control of the clutch may be relatively well defined. There may exist, however, situations in which the driver may assume that control of the clutch has been acquired by appropriate manoeuvring of the driver manoeuvrable means while in reality this is not the case.

For example, if the vehicle is standing still and the clutch is fully open under the control of the vehicle control system, the driver is, in order to gain control of the clutch, required to manoeuver the driver manoeuvrable means to the second end position, e.g. fully depressing a clutch pedal. If, in this situation, the driver e.g. depresses the clutch pedal to a large extent but not completely through the movement region, the driver may assume to have taken control of the clutch while in reality the vehicle control system will remain in control of the clutch. If then the driver with the clutch pedal still depressed, e.g. accelerates the vehicle power source using an accelerator this may, from a control system point of view, equal a request for a conventional two-pedal system vehicle start. That is, the depression of the accelerator may have the consequence that closing of the clutch is commenced and the vehicle is set in motion. This, obviously, may be in complete contradiction to the vehicle behaviour expected by the driver, with potential dangerous situations arising as a consequence. The above also applies to vehicles that have torque transmitting means of other kinds than a clutch, such as e.g. of a kind as exemplified below.

In the following, aspects of the invention are described for torque transmitting means in the form of a clutch, but the aspects are applicable also for other torque transmitting means, such as e.g. as exemplified below. According to the present invention, a method and system are provided that the reduces the risk for the arising of situations similar to those described above. This is accomplished by prohibiting an automatic, i.e. control system initiated and not driver initiated, closing of the clutch upon a driver initiated request for power from said power source when the position of said driver manoeuvrable means indicates a request for at least a partial opening of the clutch.

Consequently, the risk of start of the vehicle (setting the vehicle in motion) is reduced in situations where it may be assumed that the driver believes himself/herself to be in control of the clutch while in reality this is not the case. In this way the risk of a potentially dangerous situation arising can be reduced by ensuring that the driver does not unintentionally set the vehicle in motion by depressing the accelerator pedal in a situation when the driver assumes that the clutch will remain open.

According to embodiments of the invention automatic closing of the clutch is prohibited only when a current speed, backwards or forwards, of vehicle is below a predetermined speed, such as e.g. below 3, 5 or 10 km/h, or only when the vehicle is standing still. In general, dangerous situations are more likely to arise when the vehicle is moving at low speeds or from standstill. When the vehicle is travelling at higher speeds, a closing of an open clutch will have less impact on the behaviour of the vehicle.

Furthermore, according to embodiments of the invention the automatic closing of the clutch is prohibited only when the driver manoeuvrable means, such as a clutch pedal, is manoeuvred to a position representing a movement of a predetermined percentage of said movement region, such as a movement of at least 30%, or at least 50%, or at least 70%, of the movement region from the first end position towards the second end position.

In case the driver manoeuvrable means is in the form of a clutch pedal, it may, for example, be required that the pedal is depressed to a large extent to prevent the clutch from being closed when requesting power from the power source. According to embodiments of the invention, any movement, such as any depression with regard to a clutch pedal, is sufficient.

The automatic closing of the clutch may be prohibited for as long as said driver manoeuvrable means is in a position different from said first position, e.g., in case the driver manoeuvrable means is a clutch pedal, for as long as a clutch pedal is at least partly depressed. According to embodiments of the invention, the clutch is automatically closed if the driver manoeuvrable means is returned to the first end position representing a fully closed clutch, e.g. a clutch pedal being fully released, provided that there is still a driver initiated request for power from the power source, such as by an accelerator pedal.

According to embodiments of the invention, when automatic closing of the clutch is prohibited only when the driver manoeuvrable means is manoeuvred to a position representing a movement of at least a predetermined percentage of the movement region from the first end position towards the second end position, the clutch is automatically closed if the driver manoeuvrable means is returned to a position representing a movement less than said predetermined percentage of said movement region from said first position. As above, the predetermined movement may constitute a movement of at least 30%, or at least 50%, or at least 70%, of the movement region from the first end position towards the second end position.

Furthermore, according to embodiments of the invention, a transition from said second mode to said first mode can be performed if the driver manoeuvrable means is manoeuvred to a position representing a transmittable torque that at most corresponds to the current transmittable torque of said clutch, such as e.g. if a driver manoeuvrable means in form of a clutch pedal is fully depressed while the clutch is fully open. In this way the driver will gain control of the clutch, and if the clutch is released, a corresponding closing of the clutch can be arranged to be performed.

The torque transmitting means may comprise a clutch. However, the torque transmitting means for controlling transmission of torque to/from a power source may also be of other designs. For example, a conventional clutch may be replaced by torque transmitting means comprising one or more electrical machines and suitable gearing, where such other kind of torque transmitting means still may be arranged e.g. between a power source such as an internal combustion engine and a gearbox, e.g. a gearbox comprising distinct gears. With regard to such other torque transmitting means, the gearing may e.g. comprise one or more planetary gears, or other suitable gearing, where the electrical machine(s) and power source such as an internal combustion engine may be in a torque balanced relationship such that when no torque is applied by the electrical machine, this limits torque that can be transmitted by the power source to the gearbox, and where a higher applied torque by the electrical machine allows a higher transmission of torque from the power source. In this embodiment, the vehicle may comprise a power source in the form of an internal combustion engine, while functionality resembling a slipping clutch may be obtained by controlling transmission of torque by the electrical machine. Driver manoeuvrable means such as a pedal may then be used, where a first end position, such as a released pedal, may represent a request for a high, maximally transmittable torque, similar to a closed clutch, and a second end position, such as depressed pedal, may represent an interrupted transmission, e.g. zero torque, by controlling the electrical machine to deliver e.g. zero torque. The electrical machine may be controlled to provide varying transmittable torque to/from the power source in dependence of the position of the driver manoeuvrable means. The driver may in addition control speed of rotation of the power source through the use of simultaneous operation of accelerator. Solutions of this kind may e.g. be used when the invention is implemented in hybrid vehicles, such as electric hybrid vehicles.

According to embodiments of the invention, the vehicle comprises a driver manoeuvrable gear selector, where a drive mode is selectable. For example, driving in a forward or a reverse direction may be selected using the gear selector, these modes being selected to set the vehicle in motion in a desired direction. The gear selector may also comprise e.g. a neutral mode and/or a parking mode, in which modes vehicle drivetrain is never closed to set the vehicle in motion, the parking mode e.g. applying a parking brake to keep the vehicle stationary. According to embodiments of the invention, automatic closing of the clutch is only carried out when a drive mode is selected, and the method only being carried out when a drive mode is selected by the driver. The drive mode may be a drive mode in a forward direction or a drive mode in a reverse direction.

Further, as is appreciated by the person skilled in the art, torque transmitting means such as clutches may be of various designs, and the particular design, e.g. whether the clutch is a friction clutch or not, is not of relevance to the present invention. The present invention is applicable in any system providing clutch-by-wire functionality.

Further characteristics of the present invention and advantages thereof are indicated in the detailed description of exemplary embodiments set out below and the attached drawings.

Brief description of the drawings Fig. 1A illustrates a powertrain of an exemplary vehicle; Fig. 1B illustrates an example of a control unit in a vehicle control system; Fig. 1C illustrates a clutch pedal of the exemplary vehicle of Fig. 1A.

Fig. 2 illustrates an exemplary method according to embodiments of the invention.

Fig. 3 illustrates an exemplary clutch pedal characteristic of a vehicle in which embodiments of the invention can advantageously be utilised.

Detailed description of exemplary embodiments As was mentioned above, embodiments of the invention are applicable not only to systems comprising a clutch but the invention is applicable to any kind of system where controllable torque transmitting means are used to control transmission of torque to and/or from a power source using driver manoeuvrable means. As was further mentioned above, such systems may e.g. include systems where an electrical machine and gearing are used to replace functionality of a conventional clutch, e.g. in electric hybrid vehicles.

In the following detailed description, however, for reasons of simplicity, embodiments of the invention are exemplified for a system where a clutch is controlled by driver manoeuvrable means. Furthermore, the driver controllable means for controlling a clutch is exemplified by a clutch pedal in the following detailed description. The present invention is, however, applicable for any kind of driver controllable means for controlling a clutch, where the driver controllable means is movable in a movement region.

Fig. 1A schematically depicts a powertrain of an exemplary vehicle 100. The powertrain comprises a power source, in the present example a combustion engine 101, which, in a conventional manner, is connected via an output shaft of the combustion engine 101, normally via a flywheel 102, to a gearbox 103 via a clutch 106. An output shaft 107 from the gearbox 103 propels drive wheels 113, 114 via a final drive 108, such as a common differential, and drive axles 104, 105 connected to said final drive 108.

The combustion engine 101 is controlled by the vehicle control system via a control unit 117. The clutch 106 and gearbox 103 are also controlled by the vehicle control system by means of a control unit 116. According to the present example, the clutch comprises a dry clutch where a friction element (disc) 110 is connected to, and rotates with, a first gearbox element, e.g. an input shaft 109 of the gearbox 103. The friction element 110 selectively engages the flywheel 102, or any other suitable rotating part of the combustion engine 101, to transmit torque to/from the combustion engine 101, i.e. between combustion engine 101 and powertrain components downstream of the clutch 106, such as to/from at least one of the drive wheels 113, 114 via the gearbox 103.

The engagement of the friction element 110 with the engine flywheel 102 is controlled by means of a pressure plate 111 by means of a lever arm 112, which is manoeuvred by a clutch actuator 115.

In fully mechanical systems where the clutch is controlled directly by means of a clutch pedal, the clutch pedal is mechanically linked to the clutch. For example, the clutch pedal can be mechanically linked to the lever arm in order to directly control movement of the friction element. That is, a movement of the clutch pedal is mechanically linked to the clutch, and a movable clutch element, such as friction element moves in synchronism with the clutch pedal. It is to be understood that the exemplified clutch is merely an example, and that clutches, irrespective of whether the clutch constitutes part of a clutch-by-wire system or is controlled mechanically by driver controllable means, may be of various designs. For example, the clutch actuator may be arranged coaxially with the gearbox input shaft.

According to clutch -by-wire systems, such as the presently exemplified system, opening and closing of the clutch 106 may be controlled by the driver using driver manoeuvrable means such as a clutch pedal 118. In this case, however, the clutch pedal does not directly control the influence of the clutch actuator 115 on the lever arm 112 by a mechanical link. Instead, the clutch is controlled by the vehicle control system in dependence of signals representing the clutch pedal 118 position.

Since the actual movement of the lever arm 112 is not mechanically linked to the clutch pedal 118 this means, in turn, that the clutch pedal 118 position, instead, is used as a request for a particular transmittable torque, e.g. represented by clutch friction element/actuator position, which is then, by means of the vehicle control system, translated into an actual clutch movement via the clutch actuator 115. Flence actual manoeuvring of the clutch, i.e. the positioning of the lever arm 112 in the present example, is performed by the vehicle control system when the clutch is driver controlled, where this manoeuvring is dependent on the clutch pedal 118 position.

However, since the actual manoeuvring is under the control of the vehicle control system, this allows that the clutch may also be controlled by the vehicle control system completely independent from the clutch pedal. The clutch may hence be controlled according to different modes, where actual clutch movement is always performed by the vehicle control system, but where the movement in a driver controlled mode is performed on the basis of signals representing the position of the clutch pedal, and in an automatic mode clutch movement is performed independently from the current position of the clutch pedal.

An exemplary clutch pedal 118 is schematically shown in Fig. 1C. The clutch pedal 118 is movable within a movement region defined by two end positions A, B, defining an angular range a. The clutch pedal 118 position in said movement region can be determined, e.g. by means of a suitable sensor, such as, for example, a potentiometer or an angle sensor 119 or any other suitable kind of sensor which determines the current position of the clutch pedal 118 in the movement region in which the clutch pedal is movable. When the clutch pedal 118 is fully released, i.e. not manoeuvred by the driver, it is in a state of rest in position A, e.g. by means of a spring force, where position A represents a fully closed clutch. Position B represents a fully depressed clutch pedal and hence a fully open clutch. Fig. 1 A also discloses an accelerator pedal 130 by means of which the driver requests power from the internal combustion engine 101.

As was mentioned above, the clutch may be controlled in dependence of the clutch pedal (driver manoeuvrable means). However, an advantage of clutch-by-wire systems is that the clutch may also be controlled by the vehicle control system independently from the clutch pedal. This is also often times utilized, e.g. to allow the vehicle to be driven as a two pedal (accelerator, brake pedal) vehicle if so desired, where the clutch pedal can be used to provide additional control as was described above. Embodiments of the invention provides a method and system that reduces the risk of undesired situations from occurring when both driver and control system may consider themselves as being in control of the clutch. An exemplary method 200 of embodiments of the invention is shown in Fig. 2, which method can be implemented at least partly e.g. in the control unit 116 for controlling the clutch 106 and gearbox 103. As indicated above, the functions of a vehicle are, in general, controlled by a number of control units, and control systems in vehicles of the disclosed kind generally comprise a communication bus system comprising one or more communication buses for connecting a number of electronic control units (ECUs), or controllers, to various components on board the vehicle. Such a control system may comprise a large number of control units, and the control of a specific function may be divided between two or more of them.

For the sake of simplicity, Fig. 1 A depicts only control units 116-117, but vehicles 100 of the illustrated kind are often provided with significantly more control units, as one skilled in the art will appreciate. Control units 116-117 are arranged to communicate with one another and various components via said communication bus system and other wiring, partly indicated by interconnecting lines in Fig. 1A.

Embodiments of the invention can be implemented in any suitable control unit in the vehicle 100, and hence not necessarily in the control unit 116. The control of the clutch 106 according to the present invention will usually depend on signals being received from other control units and/or vehicle components, and it is generally the case that control units of the disclosed type are normally adapted to receive sensor signals from various parts of the vehicle 100. The control unit 116 will, for example, receive signals from clutch pedal position sensor 119 and clutch actuator 115.

Further, the control unit will receive signals representing driver request for power from the internal combustion engine, such as by means of the accelerator pedal 130. Control units of the illustrated type are also usually adapted to deliver control signals to various parts and components of the vehicle, e.g. to control the clutch actuator 115.

Control of this kind is often accomplished by programmed instructions. The programmed instructions typically comprises a computer program which, when executed in a computer or control unit, causes the computer/control unit to exercise the desired control, such as method steps according to the present invention. The computer program usually constitutes a part of a computer program product, wherein said computer program product comprises a suitable storage medium 121 (see Fig. IB) with the computer program 126 stored on said storage medium 121. The computer program can be stored in a non-volatile manner on said storage medium. The digital storage medium 121 can, for example, comprise any of the group comprising: ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM), a hard disk unit etc, and be arranged in or in connection with the control unit, whereupon the computer program is executed by the control unit. The behaviour of the vehicle in a specific situation can thus be adapted by modifying the instructions of the computer program.

An exemplary control unit (the control unit 116) is shown schematically in Fig. 1 B, wherein the control unit can comprise a processing unit 120, which can comprise, for example, any suitable type of processor or microcomputer, such as a circuit for digital signal processing (Digital Signal Processor, DSP) or a circuit with a predetermined specific function (Application Specific Integrated Circuit, ASIC). The processing unit 120 is connected to a memory unit 121, which provides the processing unit 120, with e.g. the stored program code 126 and/or the stored data that the processing unit 120 requires to be able to perform calculations. The processing unit 120 is also arranged so as to store partial or final results of calculations in the memory unit 121.

Furthermore, the control unit 112 is equipped with devices 122, 123, 124, 125 for receiving and transmitting input and output signals, respectively. These input and output signals can comprise waveforms, pulses or other attributes that the devices 122, 125 for receiving input signals can detect as information for processing by the processing unit 120. The devices 123, 124 for transmitting output signals are arranged so as to convert calculation results from the processing unit 120 into output signals for transfer to other parts of the vehicle control system and/or the component (s) for which the signals are intended. Each and every one of the connections to the devices for receiving and transmitting respective input and output signals can consist of one or more of a cable; a data bus, such as a CAN bus (Controller Area Network bus), a MOST bus (Media Oriented Systems Transport) or any other bus configuration, or of a wireless connection.

Returning to the exemplary method 200 illustrated in Fig. 2, the method starts in step 201. As was mentioned above, embodiments of the invention relates to a method and system having an aim to reduce undesired situations from arising when the driver believes to be in control of the clutch while in reality the driver is not. According to embodiments of the invention, the method is carried out only when the vehicle is standing still or when the vehicle speed is below some predetermined suitable speed, in which case the determination of step 201 is only performed once such vehicle speed condition is fulfilled. According to embodiments of the invention, the method can be arranged to be carried out for all vehicle speeds, but, as was mentioned above, it is when the vehicle is standing still or traveling at only low speeds that undesired situations are most likely to occur.

Hence, step 201 can be arranged to be carried out only when the vehicle speed fulfils set criteria. Furthermore, according to embodiments of the invention, the method is only carried out when the vehicle control system is in control of the clutch and not if the driver is already in control of the clutch. In step 201 it is determined whether there is a driver request for power from the internal combustion engine 101. The method remains in step 201 for as long as this is not the case. The determination of whether there is a driver request for power can, for example, be carried out by determining whether the accelerator pedal 130 is not fully released, i.e. at least partly depressed. Information of this kind is normally available in the control system.

As was mentioned above, if the vehicle is standing still with the clutch fully open under the control of the vehicle control system, and clutch pedal fully released, the depression of the accelerator pedal would result in the vehicle performing a start, i.e. being set in motion. That is, the vehicle would behave as any two-pedal vehicle when depressing the accelerator pedal from standstill. This would also be fully expected by the driver. As was explained above, the vehicle control system may perform a start of the vehicle, i.e. close the clutch and set the vehicle in motion also in situations where the driver is not prepared for such behaviour, such as when the clutch is partially depressed.

Therefore, in step 202, it is determined whether a reduction in the transmittable torque of the clutch 106 is requested by the driver. That is, it is determined whether the clutch pedal 118 is at least partially depressed. The method returns to step 201, or alternatively being ended, when this is not the case and the vehicle may be started in a conventional manner without interruption from the present invention. On the other hand, when there is a driver initiated request for a reduction in transmittable torque, i.e. the clutch pedal is at least partially depressed, the method continues to step 203, where it is determined whether control of the clutch is under the responsibility of the driver. As was explained above, this would be the case if, when the vehicle is standing still and the clutch is fully open, the clutch pedal is fully depressed. That is, the transmittable torque of the clutch as requested by the driver does not exceed the transmittable torque as set by the vehicle control system. If, for example, the vehicle is taken to a complete standstill without using the clutch pedal, i.e. only depressing the brake pedal, the clutch will still be fully opened by the vehicle control system. This means that for as long as the clutch pedal is not, in principle, fully depressed the vehicle control system will remain in full control of the clutch and hence disregard the current position of the clutch pedal while controlling the clutch.

This is exemplified in fig. 3, which illustrates an example of a characteristic Pchan for an exemplary clutch of a kind that can be used in a vehicle of Fig. 1 A. The y-axis denotes transmittable torque T, i.e. the torque that the clutch 106 can transmit between combustion engine 101 and further powertrain components, such as drive wheels, downstream the clutch 106. In general, with regard to clutch characteristics, the x-axis denotes clutch position, such as clutch actuator position and/or lever arm position. According to the present example, however, the x-axis represent clutch pedal 118 position. Also, instead of disclosing transmittable torque as a function of the clutch pedal 118 position, the y-axis could, for example, represent actual clutch position, and the characteristic hence illustrate actual clutch position as a function of the clutch pedal 118 position.

The origin, “0”, represents the clutch open position, i.e. a position where the clutch pedal 118, and usually friction element (the lever arm/the clutch actuator) is at its one extreme position, position B in Fig. 1 C. This corresponds to a fully depressed clutch pedal 118, and the friction element 110 being completely disconnected from the combustion engine 101, i.e. being positioned to the right as in Fig. 1A. Conversely, the “closed clutch” position represents a fully released clutch pedal. That is, position A in Fig. 1 C, and the friction element 110 being as close to the flywheel as possible and thereby pressed against the flywheel, for example by the aid of a spring action. Tmax represents the maximum torque that can be transmitted. The friction element 110, when the clutch is fully open, is normally at a distance from the engine's flywheel so that closing of the clutch involves the friction element, and hence the clutch pedal, initially moving a distance x1 before actually contacting the flywheel. Once the friction element precisely contacts the flywheel, at the contact point CP, torque transfer between the engine and rest of the powertrain can commence. The more the clutch closes from this point (i.e. the more strongly the friction element 110 engages the flywheel 102), the more torque can be transmitted over the clutch 106.

If the vehicle is standing still with the clutch open, the driver would be required to depress the clutch pedal at least to the position CP, i.e. in principle all the way to the bottom (pos B), to gain control of the clutch 106. If the clutch is depressed to a position close to the position CP, such as clutch position C, the driver may assume being in control of the clutch, while in reality this is not the case.

If it is determined in step 203 that the clutch pedal is under the control of the driver, e.g. by the clutch pedal being depressed at least to position CP in fig. 3 when the vehicle is standing still, the method is ended in step 204 since in this case the driver may freely control the clutch 106, and since the clutch will be controlled according to the position of the clutch pedal the vehicle will also behave as expected by the driver. If, on the other hand, the driver is not in control of the clutch, e.g. because the clutch pedal has been depressed only to position C when the vehicle 100 is standing still with a fully open clutch 106, the method continues to step 205.

As was mentioned above, unexpected vehicle behaviour may occur in situations of this kind if the clutch pedal is not depressed to an extent being sufficient to gain driver control of the clutch. Still, by depressing the clutch pedal to a large extent the driver may assume having taken control of the clutch while in reality this is not the case. If the driver then depresses the accelerator pedal 130 to increase the speed of rotation of the internal combustion engine 101, the vehicle 100 will behave as would a two-pedal system, and hence the clutch 106 would therefore be automatically closed to set the vehicle 100 in motion. From a driver perspective, this may be highly surprising since, when assuming having taken control of the clutch 106, the driver expects to be able to increase the speed of rotation of the internal combustion engine 101 without setting the vehicle 100 in motion simply by keeping the clutch pedal 118 depressed.

If the accelerator pedal is depressed to a relatively high extent this may result in a relatively high propelling force on the vehicle drive wheels that is completely unexpected and thereby giving rise to potentially dangerous situations.

According to the present example, situations of this kind are avoided by, when it is determined in step 203 that the clutch 106 is not under the control of the driver, prohibit the clutch 106 from being closed, step 205. In this way, even though the vehicle control system in reality is in full control of the clutch 106, and in the general case should perform a closing of the clutch 106 when the driver depresses the accelerator pedal 130, the clutch will nevertheless be kept open to prevent the vehicle 100 from being set in motion.

It is then determined in step 206 whether the prohibited closing of the clutch 106 is to be maintained. This may e.g. be the case for as long as there is a driver request for power from the internal combustion engine 101 while the clutch pedal 118 is maintained at least partly depressed, and/or until either the clutch pedal 106 is released or the driver assumes control of the clutch 106, e.g. by further depressing the clutch pedal 118. The method may be arranged to return to step 205 for as long as closing of the clutch 106 is to be prohibited. When it is determined that automatic closing of the clutch no longer is to be prohibited, e.g. because the driver has taken control of the clutch or released the clutch pedal 118, the method may be ended in step 207 or be arranged to return to step 201.

Furthermore, as was stated above, the invention is applicable also when the torque transmitting means is of designs other than a clutch, such as torque transmitting means comprising one or more electrical machines and suitable gearing. Designs of this kind may provide functionality of a clutch, where such functionality may be controlled by driver manoeuvrable means e.g. in the form of a pedal. An example of a system of this kind is disclosed in the International application PCT/SE16/050538, with the title “A drive system for a vehicle” and having the same applicant as the present application. This referenced application is incorporated herein by reference.

Finally, the present invention has been described above for a particular example of a vehicle, but is applicable for any vehicle in which driver manoeuvrable means are used to control torque transmitting means e.g. in the form of a clutch, the clutch also being any kind of suitable clutch comprising any kind of elements, and hence not necessarily a clutch of the kind exemplified above, for as long as the manoeuvring of the torque transmitting means can be accomplished independently from the manoeuvring of the driver manoeuvrable means. For example, as stated above, the invention is applicable in hybrid vehicles, with or without a clutch as torque transmitting means.

Claims

1. Method for controlling torque transmitting means (106) of a vehicle (100), the vehicle (100) including: torque transmitting means (106) for selectively transmitting torque to and/or from at least one power source (101) of the vehicle (100), and driver manoeuvrable means (118) for controlling transmittable torque by the torque transmitting means (106), said driver manoeuvrable means (118) being manoeuvrable by the driver in a movement region (A-B) between a first end position (A), representing a request for a full transmissibility of torque, and a second end position (B), representing a complete interruption of the transmission of torque, wherein transmittable torque of the torque transmitting means (106) is controllable in a first mode in dependence of the position of said driver manoeuvrable means (118), and in a second mode independently from said position of said driver manoeuvrable means (118), the method including, when the transmittable torque of the torque transmitting means (106) is controlled according to said second mode: - if the position of said driver manoeuvrable means (118) deviates from said first position (A), prohibiting, upon a driver initiated request for power from said power source, an automatic increase in transmitted torque by said torque transmitting means (106).

2. Method according to claim 1, wherein said prohibition is carried out if: - a current speed of said vehicle (100) is below a predetermined speed.

3. Method according to claim 1 or 2, wherein said prohibition is carried out if: - said vehicle (100) is standing still.

4. Method according to any one of the preceding claims, wherein said prohibition is carried out if: - said driver manoeuvrable means (118) is positioned at least a predetermined percentage, such as at least 30%, or at least 50%, or at least 70%, of said movement region (A-B) from said first end position (A) towards said second end position (B).

5. Method according to claim 4, further including, after said torque transmitting means (106) has been prohibited from automatically increasing transmittable torque: - automatically increasing transmittable torque by said torque transmitting means (106) if the driver manoeuvrable means (118) is returned to a position at less than said predetermined percentage of said movement region from said first end position (A) towards said second end position (B).

6. Method according to any one of the preceding claims, further including, if an automatic increase of transmitted torque by said torque transmitting means (106) is prohibited: - prohibiting said automatic increase of transmitted torque by said torque transmitting means (106) for as long as said driver manoeuvrable means is in a position deviating from said first position (A).

7. Method according to any one of the preceding claims, wherein said prohibition is carried out if: - said driver manoeuvrable means (118) is manoeuvred to a position (C) representing a higher torque to be transmitted by said torque transmitting means (106) than being transmitted by said torque transmitting means (106) right before the manoeuvring into position (C).

8. Method according to any one of the preceding claims, further including: - performing a transition from said second mode to said first mode if said driver manoeuvrable means (118) is manoeuvred in a direction towards said second end position (B) to a position representing a transmission of torque at most amounting to the transmission of torque of the torque transmitting means as set by a vehicle control system of the vehicle.

9. Method according to any one of the preceding claims, said driver manoeuvrable means being a clutch pedal (118), wherein said prohibition is carried out only if: - said clutch pedal (118) is at least partly depressed.

10. Method according to any one of the preceding claims, wherein said prohibition is carried out only if: - the torque transmitting means is controlled according to said second mode.

11. Method according to any one of the preceding claims, further including: - when controlling said torque transmitting means in dependence of the position of said driver manoeuvrable means (118), controlling said torque transmitting means (106) according to a representation of transmission of torque of said torque transmitting means (106) as a function of an electrical signal representing the position of said driver manoeuvrable (118) means in said movement region (A-B).

12. Method according to any one of the preceding claims, the torque transmitting means being a clutch, and the method including: - if the position of said driver manoeuvrable means (118) deviates from said first position (A), prohibiting, upon a driver initiated request for power from said power source, the increase in transmitted torque by prohibiting an automatic closing of said clutch (106).

13. Method according to any one of the preceding claims, the torque transmitting means comprising at least one electrical machine and a gearing, the transmittable torque from the power source (101) to a gearbox (103) being controlled by controlling torque applied by the at least one electrical machine.

14. Computer program comprising program code that, when said program code is executed in a computer, causes said computer to carry out the method according to any one of the preceding claims.

15. Computer program product comprising a computer-readable medium and a computer program according to claim 14, wherein said computer program is contained in said computer-readable medium.

16. System for controlling torque transmitting means (106) of a vehicle (100), the vehicle (100) including: torque transmitting means (106) for selectively transmitting torque to and/or from a power source (101) of the vehicle (100), and driver manoeuvrable means (118) for controlling transmittable torque by the torque transmitting means (106), said driver manoeuvrable means (118) being manoeuvrable by the driver in a movement region (A-B) between a first end position (A), representing a request for a full transmissibility of torque, and a second end position (B), representing a complete interruption of the transmission of torque, wherein transmittable torque of the torque transmitting means (106) is controllable in a first mode in dependence of the position of said driver manoeuvrable means (118), and in a second mode independently from said position of said driver manoeuvrable means (118), the system including, when the transmittable torque of the torque transmitting means (106) is controlled according to said second mode: - means configured to, if the position of said driver manoeuvrable means (118) deviates from said first position (A), prohibit, upon a driver initiated request for power from said power source (101), an automatic increase in transmitted torque by said torque transmitting means (106) .

17. Vehicle, comprising a system according to claim 16.