SE541560C2

SE541560C2 - Method and system for controlling torque transmitting means of a vehicle

Info

Publication number: SE541560C2
Application number: SE1750354A
Authority: SE
Inventors: Erik Gustafsson; Fredrik Jarngren; Georg Åhrberg
Original assignee: Scania Cv Ab
Priority date: 2017-03-24
Filing date: 2017-03-24
Publication date: 2019-10-29
Also published as: DE102018001845A1; SE1750354A1

Abstract

The present invention relates to a method for a vehicle (100),the vehicle (100) including:a drivetrain for transferring torque between a power source (101) and at least one drive wheel of the vehicle (101),torque transmitting means (106) for selectively transmitting torque between the power source (101) and the at least one drive wheel of the vehicle (100), anddriver manoeuvrable means (118), wherein transmittable torque of the torque transmitting means (106) is controllable in dependence of an electrical signal representing a position of the driver manoeuvrable means (118),the method including:- detecting if disengagement of the torque transmitting means (106) is initiated by means of the driver manoeuvrable means (118), and- based on said detection, influencing the torque delivered by the power source and/or the timing of an interruption of transmission of torque caused by the disengagement of the torque transmitting means (106) such that torque transmitted by the drivetrain, when transmittable torque of the torque transmitting means falls below the torque currently transmitted by the drivetrain, is reduced.

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-readable medium 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 comprise 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 specification relates to systems where the driver manoeuvrable means such as a clutch pedal or other means is used to control torque transmitting means such as a clutch or other torque transmitting means, 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.

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 increases driver comfortability in situations when the driver disengages torque transmission between a power source and vehicle drive wheels through control of torque transmission means using driver manoeuvrable means. 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 a vehicle, the vehicle including: a drivetrain for transferring torque between a power source and at least one drive wheel of the vehicle, torque transmitting means for selectively transmitting torque between the power source and the at least one drive wheel of the vehicle, and driver manoeuvrable means, wherein transmittable torque of the torque transmitting means is controllable in dependence of an electrical signal representing a position of the driver manoeuvrable means, the method including: - detecting if disengagement of the torque transmitting means is initiated by means of the driver manoeuvrable means, and - based on said detection, influencing the torque delivered by the power source and/or the timing of an interruption of transmission of torque caused by the disengagement of the torque transmitting means such that torque transmitted by the drivetrain, at the time when transmittable torque of the torque transmitting means falls below a currently transmitted torque, is reduced.

There exist various kinds of transmission systems, where a change of gear may be performed manually or automatically. The transmission systems, irrespective whether of a manual gearshift or automatic gearshift kind, may include a clutch or other torque transmission means that can be used to selectively disengage, i.e. interrupt, torque transmission through the drivetrain. Such systems may further comprise driver manoeuvrable means for allowing driver manoeuvring of the torque transmitting means. For example, a further pedal in addition to e.g. an accelerator and a brake pedal may be utilised. Such driver manoeuvrable means for controlling torque transmitting means may also be present in hybrid vehicles.

The torque transmitting means may be controlled by the driver manoeuvrable means where a signal, such as an electrical signal, may be used to represent a position of the driver manoeuvrable means, such as e.g. a clutch pedal position, where the vehicle control system then controls the torque transmitting means on the basis of the position signals.

When the drivetrain of the vehicle is closed by the torque transmitting means being fully engaged, it may transmit full torque from the power source towards the driving wheels. When the torque transmitting means starts to disengage (e.g. by the force of a friction element of a clutch acting on a flywheel of the power source starting to reduce) it may still transmit full torque from the power source for a while, until a later point in time (such as until the point in time when the force of the friction element acting on the flywheel is small enough to cause a slip there between). The time (or point in time) when transmittable torque of the torque transmitting means falls below a currently transmitted torque may be this later point in time.

Torque transmitting means may be disengaged from an engaged state, and when the transmission of torque is disengaged, there is an interruption in the transmission of torque between power source and vehicle drive wheels. If the transmittable torque of the torque transmitting means falls below a still ongoing transmission of torque, this may give rise to e.g. jerks, drivetrain oscillations etc., which may be perceived as uncomfortable to the driver and increase wear on components. For this reason, the driver may make an effort to reduce the transmission of torque over the torque transmission means prior to disengaging the torque transmission means.

For example, the driver may control the request for torque from the power source, e.g. using means for requesting power in the form of an accelerator pedal, in an attempt to meet the torque applied by the vehicle drive wheels, so that the drivetrain may be relieved from transmission of torque prior to the torque transmitting means being disengaged, thereby allowing the torque transmitting means to be disengaged in a more comfortable manner.

However, the prevailing driving conditions when torque transmitting means are disengaged may vary substantially, e.g. depending on the current road inclination and/or load of the vehicle. It may therefore be difficult to control the power source in a manner that reduces drivetrain torque at the time transmittable torque of the torque transmitting means falls below a currently transmitted torque to an extent that results in a comfortable disengagement of the torque transmitting means. Jerks and/or drivetrain oscillations may therefor still occur as a result of the disengagement.

According to the present invention, such discomforts may be reduced.

According to the invention, it is detected if disengagement of the torque transmitting means is initiated by means of the driver manoeuvrable means. For example, this detection may be accomplished by the vehicle control system monitoring the electrical signal representing the position of the driver manoeuvrable means, wherein changes in the electrical signal may be translated into a corresponding movement (i.e. change in position) of the driver manoeuvrable means. The detection may be performed by the vehicle control system, or in any other suitable way.

The present inventive concept is based on the idea of obtaining a reduced ongoing transmission of torque at the time transmittable torque of the torque transmitting means falls below the torque that is currently transmitted by the drivetrain.

Alternatively or in addition, the rate of change in the transmission of torque when transmittable torque of the torque transmitting means falls below the torque that is currently transmitted by the drivetrain may be reduced. This is obtained by influencing the torque delivered by the power source and/or the timing of the interruption of transmission of torque caused by the disengagement of the torque transmitting means.

If the transmittable torque of the torque transmitting means falls below the torque that currently is being transmitted by the drivetrain, this may give rise to jerks and/or oscillations. Furthermore, the magnitude of the jerks/oscillations may depend at least in part on the rate of change (derivative) of the torque being transmitted by the drivetrain, and hence the faster the transmittable torque is reduced, the higher the magnitude of the jerks/oscillations may be.

Consequently, according to embodiments of the invention, control may be performed such that the rate of change of the transmittable torque of the torque transmitting means is reduced, which may reduce the magnitude of possible jerks/oscillations. Alternatively or in addition, the torque currently being transmitted by the drivetrain when transmittable torque of the torque transmitting means falls below this currently torque may be reduced, which thereby also reduces the risks for jerks/oscillations arising.

In this way, jerks and/or drivetrain oscillations that otherwise may occur due to a still ongoing transmission of torque at the point in time when the transmittable torque of the torque transmitting means falls below the torque currently being transmitted may be reduced, e.g. as a consequence of the reduced ongoing transmission of torque prior to this situation occurring. Consequently, a more comfortable disengagement of the torque transmitting means may be obtained.

In particular, the influencing may be performed such that torque transmitted by the drivetrain at the time transmittable torque of the torque transmitting means falls below a currently transmitted torque is reduced in relation to if the disengagement had been controlled according to the driver manoeuvrable means. Hence, a more comfortable disengagement may be provided in comparison to a disengagement being controlled completely according to the driver request.

According to embodiments of the invention, the influencing may include the actual time of interruption of transmission of torque in relation to the time of interruption of transmission of torque requested by means of the driver manoeuvrable means being delayed or advanced. That is, the interruption of the transmission of torque may be controlled such that it occurs either earlier or later than the time of interruption that would prevail if the disengagement were controlled according to the driver manoeuvrable means.

In this way, the interruption of the transmission of torque may be controlled such that the torque being transmitted by the drivetrain when transmittable torque of the torque transmitting means falls below a currently transmitted torque is less than the torque would have been if the interruption had been controlled according to the driver manoeuvrable means.

According to embodiments of the invention, the influencing may include controlling the power source such that the torque delivered by the power source is increased or decreased in relation to the driver request for torque to reduce torque transmitted by the drivetrain at the time transmittable torque of the torque transmitting means falls below a currently transmitted torque. In this way, the torque delivered by the power source may be increased if required to reduce torque being transmitted by the drivetrain at the time the transmittable torque of the torque transmitting means falls below a currently transmitted torque. Alternatively, the torque being delivered by the power source may be decreased if required to reduce torque being transmitted by the drivetrain at the time the transmittable torque of the torque transmitting means falls below a currently transmitted torque.

The torque that would be transmitted by the drivetrain at the time transmittable torque of the torque transmitting means falls below a currently transmitted torque if the transmission of torque is interrupted according to the driver manoeuvrable means may be estimated before the transmission of torque is actually interrupted, and the influencing of the interruption of the transmission of torque may then be based on this estimation.

According to embodiments of the invention, it may be estimated if the torque transmitted by the drivetrain, if controlling the torque transmitting means according to the driver manoeuvrable means, will reduce to zero prior to the point in time at which the transmission of torque will be interrupted, where this point in time also may be estimated. If this is the case, the interruption may be advanced in relation to the time of interruption if controlled according to the manoeuvring of the driver manoeuvrable means. That is, the interruption of torque may be arranged to occur at an earlier point in time that is closer to the point in time where the transmitted torque is reduced to zero so that e.g. a negative torque, such as a braking torque applied by the vehicle drive wheels, does not arise or does not increase to an undesired level.

The advancing may be accomplished by controlling the torque transmitting means differently from the request by the driver manoeuvrable means.

Alternatively, or in addition, the torque delivered by the power source may be increased in order to delay the point in time at which torque transmitted by the drivetrain is reduced to zero so that drivetrain torque reduces to zero at a time that is closer to the time that the transmittable torque of the torque transmitting means falls below the currently transmitted torque.

According to embodiments of the invention, it may be estimated if transmission of torque of the torque transmitting means, if controlled according to the driver manoeuvrable means, will be interrupted prior to the torque transmitted by the drivetrain is reduced to zero. If this is the case, the time of interruption of the transmission of torque of the torque transmitting means in relation to the time of interruption if controlled according to the driver manoeuvrable means may be delayed. That is, the torque transmitting means may be controlled in a manner that deviates from the control as requested by the driver manoeuvrable means so that interruption of torque occurs at a point in time closer to the point in time at which transmission of torque would reduce to zero if the torque transmitting means were still engaged.

The delaying may be accomplished by controlling the torque transmitting means differently from the request by the driver manoeuvrable means.

Alternatively, or in addition, torque delivered by the power source may be reduced in relation to e.g. the driver request for torque in order to advance the point in time at which torque transmitted by the drivetrain is reduced to zero so that less torque is transmitted at the time transmittable torque of the torque transmitting means falls below the currently transmitted torque.

The initiation of the disengagement of the torque transmitting means may be detected, for example, if a movement of the driver manoeuvrable means is detected. Oftentimes the driver manoeuvrable means may not be manoeuvred at all when the torque transmission between power source and vehicle drive wheels is fully engaged. Hence, it may be detected if there is any movement of the driver manoeuvrable means, since any movement of e.g. a clutch pedal from a fully released position may be seen as an initiation of a reduction of the transmission of torque.

The driver manoeuvrable means may, for example, be manoeuvrable by the driver in a movement region between a first end position, representing a request for a full transmissibility of torque and a second end position, representing a complete interruption of the transmission of torque. Hence, initiation of disengagement of the torque transmitting means may be detected when it is detected a change in position of the driver manoeuvrable means from the position representing a request for a full transmissibility of the transmission of torque of the torque transmitting means.

The torque transmitting means may be controllable according to a first (e.g. predetermined) dependency being a representation of transmittable torque of the torque transmitting means as a function of an electrical signal representing a position of the driver manoeuvrable means in a movement region of the driver manoeuvrable means, such as a movement region according to the above. When performing influencing according to embodiments of the invention, the dependency of the transmittable torque of the torque transmitting means in relation to the position of the driver manoeuvrable means may be changed such that the torque transmitting means is set to a different transmittable torque in comparison to said first dependency. This may be utilised to delay or advance interruption of the transmission of torque according to the above by manoeuvring the torque transmitting means different from the request by the driver.

Each position of the driver manoeuvrable means may correspond to a particular transmittable torque. When influencing transmission of torque according to the invention, a transmittable torque caused by the influencing and which differs from the transmittable torque requested by the driver may therefore correspond to a different position of the driver manoeuvrable means than the current position of the driver manoeuvrable means. The influencing can be controlled such that this difference at most correspond to a predetermined difference in position of the driver manoeuvrable means. In this way, the actual transmittable torque may be controlled such that it does not deviate from the driver expected behaviour to an extent that highly surprises the driver.

Alternatively or in addition, the transmittable torque of the torque transmitting means may be controlled such that the actual transmittable torque of the torque transmitting means differs at most by a predetermined difference in transmittable torque in relation to the transmittable torque represented by the position of said driver manoeuvrable means. Again, this may be used to ensure that the vehicle behaviour does not deviate from the driver expected behaviour to an extent that highly surprises the driver.

Similarly, according to embodiments of the invention, the power source may be arranged to be controlled such that the difference in torque delivered by the power source differs at most by a predetermined difference in relation to the driver request for torque from the power source. Also in this case this may be utilised to avoid vehicle behaviours that may surprise the driver.

According to embodiments of the invention, the driver manoeuvrable means may be a clutch pedal and the torque transmitting means may be a clutch.

According to embodiments of the invention, the driver manoeuvrable means comprises a pedal to be manoeuvred by a foot of the driver, for example a clutch pedal.

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 arranged in a torque balanced relationship such that when no torque is applied by the electrical machine, this limits the torque that can be transmitted by the power source to the gearbox to essentially zero, and where a higher applied torque by the electrical machine allows a higher transmission of torque from the power source, where the torque that can be applied by the power source may be the torque applied by the electrical machine times a factor. 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 an accelerator. Solutions of this kind allows different speeds of rotation of the power source and gearbox input shaft, where the speeds of rotation will be brought into synchronism as higher torque is applied. Solutions of this kind may e.g. be used when embodiments of the invention is implemented in hybrid vehicles, such as electric hybrid vehicles.

Further, as is appreciated by the person skilled in the art, torque transmitting means such as clutches and other means 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 may be applicable in any system providing clutch-by-wire functionality, irrespective of whether an actual clutch is present.

It will be appreciated that the embodiments described in relation to the method aspect of the present invention are all applicable also for the vehicle system aspect of the present invention. That is, the vehicle system may be configured to perform the method as defined in any of the above described embodiments. Further, the method may be a computer implemented method.

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 the present invention may advantageously be utilised.

Figs. 4A-E illustrate exemplary control methods according to embodiments of the invention.

Detailed description of exemplary embodiments As was mentioned above, embodiments of the invention are applicable not only to systems comprising a clutch but 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.

However, in the following detailed description, 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. However, the present invention and the embodiments described in the following are 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 a 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 one or more 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. Hence 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 may be determined, e.g. by means of a suitable sensor, such as 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. 1A 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 may be used to provide additional control. According to embodiments of the invention, it is provided a method and system that may increase driver comfortability and that may reduce wear on components. An exemplary method 200 of the present invention is shown in Fig. 2, which method may 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 consisting of 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. 1A 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 the communication bus system and other wiring, partly indicated by interconnecting lines in Fig. 1A.

Embodiments of the invention may 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 embodiments of the 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 adapted to receive sensor signals from various parts of the vehicle 100. The control unit 116 may, for example, receive signals from clutch pedal position sensor 119 and clutch actuator 115. Further, the control unit may 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 embodiments of the present invention. The computer program usually constitutes a part of a computer-readable medium, wherein said computer-readable medium comprises a suitable storage medium 121 (see Fig. 1B) with the computer program 126 stored on said storage medium 121. The computer program may be stored in a non-volatile manner on said storage medium. The digital storage medium 121 may, 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 may thus be adapted by modifying the instructions of the computer program.

An exemplary control unit (the control unit 116) is shown schematically in Fig. 1B, wherein the control unit may comprise a processing unit 120, which may 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 may comprise waveforms, pulses or other attributes that the devices 122, 125 for receiving input signals may 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 may comprise 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 relate to a method and system having an aim to reduce discomforting jerks/drivetrain oscillations when disengaging torque transmission between a power source, such as the internal combustion engine 101, and one or more vehicle drive wheels, such as drive wheels 113, 114. In addition, wear of components may be reduced.

In step 201, it is determined whether a disengagement of the clutch 106 is initiated. The method remains in step 201 for as long as this is not the case, while the method continues to step 202 when it is determined that a disengagement of the clutch 106 is initiated.

Whether or not a disengagement of the clutch is initiated may be detected, for example, by detecting a movement of the clutch pedal 118 from the position A (Fig. 1C) representing a request for a full transmissibility of torque, i.e. closed drivetrain towards the position B representing a complete interruption of the transmission of torque. The movement may further be detected by the vehicle control system monitoring an electrical signal representing the position of the clutch pedal 118.

According to embodiments of the invention, it may be required that a clutch motion constituting at least a predetermined portion of the movement region A-B is detected, such as e.g. 5% or 10% of the total movement region. However, according to embodiments of the invention it may be sufficient that any motion is detected from position A is detected, since oftentimes a movement from a released clutch pedal 118 indicates that transmission of torque is to be disengaged.

In step 202 it is determined whether the interruption of the transmission of torque is to be influenced. According to embodiments of the invention, interruption of the transmission of torque may be arranged to always be influenced, while according to embodiments of the invention the transmission of torque may be arranged to be influenced only when some criteria is fulfilled.

For example, the interruption of the transmission of torque may be arranged to be influenced only if it is estimated that the transmission of torque that is still ongoing right before the transmission of torque is completely interrupted exceeds some predetermined torque. For example, it may be determined a remaining torque for which it is determined that driver comfortability and/or wear is affected only to some extent, and which therefore may be accepted. However, according to the present example the interruption of torque is always influenced if it is determined that there will be a still ongoing transmission of torque at the time of complete interruption and/or at the time transmittable torque of the torque transmitting means falls below the currently transmitted torque.

Hence, if it is determined that the interruption is to be influenced, the method continues to step 203 while otherwise the method returns to step 201 as in fig. 2, or is ended.

In step 203 it is determined the manner in which the interruption of the transmission of torque is to be influenced. This may be performed in different ways.

The time at which the clutch disengages completely may, for example, be the point in time at which the friction plate 106 is positioned such that it no longer contacts the flywheel 102. It may also be a time at which the friction plate 106 contacts the flywheel 102 to some extent. The point in time at which the clutch disengages completely may be estimated by the vehicle control system e.g. using a clutch characteristic and an estimation of the torque being transmitted by the drivetrain as well as an estimation of when the clutch will reach a particular position, such as e.g. the point at which the friction plate no longer contacts the flywheel.

Clutch characteristics may be used to determine when and to which extent a clutch engages. Fig. 3 illustrates an example of a characteristic Pchan for an exemplary clutch of a kind that may be used in a vehicle of Fig. 1A. The y-axis denotes transmittable torque T, i.e. the torque that the clutch 106 can transmit between the internal combustion engine 101 and the vehicle drive wheels 113, 114. In general, with regard to clutch characteristics, the x-axis denotes clutch position, such as clutch actuator position and/or lever arm position. The x-axis may also represent clutch pedal 118 position.

The origin, “0”, represents the clutch open position, i.e. a position where the clutch pedal 118 is at its one extreme position, position B in Fig. 1C. 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. 1C, and the friction element 110 being as close to the flywheel as possible to and 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, when opening the clutch, the friction element will be moved to a position where it no longer is contacting the flywheel before the clutch pedal reaches position B. This also means that the transmission of torque is completely interrupted prior to the clutch pedal reaches positon B. The position at which this occurs is represented by the contact point CP in fig. 3. The more the clutch is opened towards this point, the less torque can be transmitted over the clutch 106. The torque transmission may be completely interrupted before the point CP is reached, e.g. if a high torque is still transmitted by the drivetrain.

A characteristic of the kind shown in fig. 3 may be used to determine when the clutch will disengage, e.g. by monitoring signals representing clutch pedal position.

Consequently, a point in time at which interruption of the transmission of torque will occur may be determined by estimating e.g. when the contact point CP will be reached.

Furthermore, the torque being transmitted by the drivetrain may also be estimated, and the time at which the drivetrain torque reaches zero may also be estimated. In general, when torque transmitting means such as a clutch is disengaged, the driver attempts to control the vehicle in a manner that reduces the transmission of torque between the power source and the vehicle drive wheels as close as possible to zero prior to the transmission of torque being completely interrupted. Vehicle control systems in general comprises various functions for estimating the torque that currently is being transmitted by the drivetrain, and e.g. by comparing consecutive estimations of the torque being transmitted a point in time at which the drivetrain torque would reach zero may also be estimated in a straightforward manner. There exist various methods for estimating drivetrain torque as is known to the person skilled in the art, and any such method may be utilized according to embodiments of the invention. This is not described more in detail herein.

Hence, in step 202 it may therefore be determined a point in time at which the transmission of torque will be interrupted and e.g. the drivetrain torque that will prevail at this point in time, and/or the point in time at which the drivetrain torque will reach zero and/or the point in time transmittable torque of the torque transmitting means falls below the currently transmitted torque. On the basis of these estimations it may be determined whether the interruption of torque is to be influenced, and in step 203 the manner in which the interruption of torque is to be influenced may also be determined on the basis of such estimations.

Exemplary manners in which the interruption of torque may be influenced will be described with reference to figs 4A-E. In figs. 4A-E the x-axis represents time t and the y- axis represents torque T. Positive values (i.e. exceeding zero) of torque represents torque being transmitted from the internal combustion engine 101 towards the vehicle drive wheels 113, 114, and negative values below zero represents negative torque, i.e. torque is being transmitted from the vehicle drive wheels towards the internal combustion engine.

Dashed line 401 represents an estimation of the torque that is being transmitted by the drivetrain as a function of time, and solid line 402 represents transmittable torque by the torque transmitting means, i.e. clutch 106. The disengagement of the torque transmitting means may be initiated at time to by the driver starting to depress the clutch pedaM 18, and the initiation of the disengagement may be detected e.g. at time ti by the vehicle control system. According to the above, the point in time at which the transmission of torque of the drivetrain reaches zero may be estimated by the vehicle control system, which time is represented by time tyin fig. 4A. Similarly, the time txat which the transmission of torque will be interrupted due to the clutch completely disengaging may also be estimated. According to the present example, when the transmittable torque of the clutch, solid line 402, falls below the torque that currently is being transmitted by the drivetrain, i.e. when solid line 402 crosses dashed line 401, the clutch will start slipping. This clutch slip may give rise to jerks and/or oscillations. Consequently, according to the example of fig. 4A, discomforting jerks/oscillations may arise at time ts. Furthermore, the magnitude of the jerks/oscillations will at least in part depend on the rate of change (derivative) of the torque being transmitted by the drivetrain when lines 401 and 402 intersect.

According to the present example, the rate of change of the transmittable torque of the clutch, solid line 402, is higher than the rate of change of the torque that is transmitted by the drivetrain, dashed line 401, and hence the jerks/oscillations will depend on the rate of change of the clutch in this example. The faster the clutch is opened, i.e. the steeper the solid line 402 is, the higher the magnitude of the jerks/oscillations may be.

According to the present example, therefore, measures are taken to reduce the rate of change of the transmission of torque by the drivetrain. This is commenced at time t2where the disengagement of the clutch 106 is delayed by controlling the clutch actuator/friction element to move more slowly so that interruption occurs closer to, or at, time ty. That is, the clutch is controlled by the vehicle control system to open more slowly than the driver requests by the clutch pedal 118. This is indicated in fig. 4A by dotted line 403 starting from time t2, which represents the actual movement of the clutch when influenced according to the present example, such that the clutch is fully disengaged at time tyinstead of at the time tx. Consequently, according to the example, disengagement of the clutch is delayed such that transmission of torque is interrupted substantially at the point in time at which the transmission of torque reaches zero. This provides two advantages. Firstly, the rate of change of the transmittable torque of the clutch is reduced, which in itself reduces the magnitude of possible jerks/oscillations. Hence, even if the line 401 would still intersect line 403 prior to the drivetrain torque being reduced to zero, the impact on comfortability would be less severe due to the reduced derivative of line 403. Secondly, the torque currently being transmitted by the drivetrain when lines 401 and 403 intersect is reduced, preferably to zero as in the example, which thereby also reduces the risks for jerks/oscillations arising.

Figure 4B discloses the same situation as in fig. 4A, however with the difference that instead of delaying the disengagement of the clutch 106, the torque delivered by the internal combustion engine 106 is instead controlled such that torque transmitted by the drivetrain reaches zero at an earlier point in time. This is illustrated by dashdotted line 404, according to which the speed at which the drivetrain torque reduces is increased starting from time t2such that the drivetrain torque reaches zero essentially at time txinstead of at time ty. In this way, also, intersection of lines 401 and 402 at time tsis effectively prevented. This may be accomplished, for example, by controlling the internal combustion engine 106 such that it delivers less torque than e.g. is requested by the driver, or by the low idle speed governor of the engine, thereby accomplishing the faster reduction of the drivetrain torque of fig. 4B.

According to this example, the possible negative impact of increasing the derivative of the reduction in drivetrain torque is compensated for by substantially reducing the drivetrain torque to essentially zero when the clutch start slipping so that jerks/oscillations are effectively reduced since only little or no torque remain in the drivetrain when the clutch starts slipping.

Fig. 4C discloses a further example where dashed line 405 represents an estimation of the torque that is being transmitted by the drivetrain as a function of time, and solid line 406 represents transmittable torque by the clutch 106. According to the example of fig. 4C, the drivetrain torque 405 is estimated to reduce to zero at time txwhile the clutch is estimated to completely disengage only at time ty. Hence, in this case the drivetrain torque is estimated to reduce to zero prior to the clutch completely disengages. In this case, therefore, the drivetrain will instead transmit a negative torque -Tyat the time of interruption of the transmission of torque, which again will be abruptly reduced to zero, thereby possibly giving rise to jerks and/or oscillations. According to the present example, measures are also taken and commenced at time t2where the disengagement of the clutch 106 is instead advanced by controlling the clutch actuator/friction element to open faster than requested by the driver by means of the clutch pedal 118. This is indicated in fig. 4C by dotted line 407 starting from time t2, which represents the actual movement of the clutch 106 when influenced according to the present example, such that the clutch 106 is disengaged earlier at time tx instead of at the later point in time ty. Consequently, disengagement of the clutch is advanced such that transmission of torque is interrupted substantially at the point in time at which the transmission of torque reaches zero, thereby allowing a smooth disengagement of the clutch also in this case.

Figure 4D discloses the same situation as in fig. 4C, however with the difference that instead of advancing the disengagement of the clutch 106, the torque delivered by the internal combustion engine 106 is instead controlled such that torque transmitted by the drivetrain reaches zero at a later point in time. This is illustrated by dashdotted line 408. In this case, the speed at which the drivetrain torque reduces is reduced starting from time t2. In this way the drivetrain torque may be controlled to reach zero torque essentially at time tyinstead of at time tx. This may be accomplished, for example, by controlling the internal combustion engine 106 such that it delivers more torque than e.g. is requested by the driver, thereby accomplishing the slower reduction of the drivetrain torque of fig. 4C.

Figure 4E illustrates an alternative to the control of fig. 4D. According to this example, the torque delivered by the internal combustion engine 106 is instead controlled such that torque transmitted by the drivetrain is allowed to reach zero at time tx, but the internal combustion engine is then controlled to maintain the drivetrain torque at essentially zero, dash-dotted line 409, so that when the transmittable torque of the clutch reaches zero at time tya smooth opening of the clutch is still obtained.

The described measures may also be combined, such that e.g. with reference to the figs. 4A-B example, the opening of the clutch may be delayed while simultaneously the drivetrain torque may be controlled to reduce faster, so that an actual point of interruption occurs between time txand time ty. This applies analogously to the example of figs. 4C-E.

Returning to fig. 2, when a suitable manner of influencing the interruption of the transmission of torque has been determined in step 203, e.g. according to any of the above examples, the actual influencing is commenced, step 204, and in step 205 it may be determined if the influence is to be continued, e.g. because the clutch has not yet disengaged. The method may be arranged to return to step 204, or step 203 to adjust, if necessary, the influence, e.g. if a new estimation differs from a previous estimation. When the disengagement no longer is to be continued, e.g. because the clutch has completely disengaged, the method is ended in step 206.

Furthermore, as was stated above, embodiments of the invention are 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.

In systems of this kind an internal combustion engine may e.g. be connected to a gearbox input shaft through a planetary gearing, where an electrical machine is also connected to the planetary gearing. The internal combustion engine may be connected e.g. to a sun gear of the planetary gearing, while the gearbox may be connected to a carrier, and the electrical machine is connected to a ring gear.

According to solutions of the referenced application, the internal combustion engine may be rotating independently from the speed of rotation of the gearbox input gear. Further, the electrical machine and internal combustion engine may be arranged in a torque balanced relationship such that when no torque is applied by the electrical machine, this limits the torque that can be transmitted by the internal combustion engine to zero.

When applied torque is increased by the electrical machine, a higher torque can be transmitted by the internal combustion engine to the gearbox input shaft, and the higher the transmission of torque the closer the speeds of rotation will be. When the electrical machine applies a torque equal to or exceeding the torque that will be transmitted by the drivetrain the speeds of rotation of the internal combustion engine and gearbox will be in synchronisation.

Consequently, the interruption of the transmission of torque can be influenced according to embodiments of the invention also in systems of this kind when disengaging the torque transmitting means, such as when decreasing the torque applied by the electrical machine in response to e.g. a driver manoeuvred pedal that provides functions similar to that of a clutch pedal. The vehicle may be a hybrid vehicle, such as an electric hybrid vehicle, or any other kind of vehicle having torque transmitting means of this kind.

Finally, embodiments of the present invention have been described above mainly 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. The torque transmitting means may be of any suitable kind comprising any kind of elements, such as a clutch or other kind of solution, for as long as the manoeuvring of the torque transmitting means may be accomplished independently from the manoeuvring of the driver manoeuvrable means.

Claims

1. Method for a vehicle (100), the vehicle (100) including: a drivetrain for transferring torque between a power source (101) and at least one drive wheel of the vehicle (101), torque transmitting means (106) for selectively transmitting torque between the power source (101) and the at least one drive wheel of the vehicle (100), and driver manoeuvrable means (118), wherein transmittable torque of the torque transmitting means (106) is controllable in dependence of an electrical signal representing a position of the driver manoeuvrable means (118), the method including: - detecting if disengagement of the torque transmitting means (106) is initiated by means of the driver manoeuvrable means (118), and - based on said detection, influencing the torque delivered by the power source and/or the timing of an interruption of transmission of torque caused by the disengagement of the torque transmitting means (106) such that torque transmitted by the drivetrain, at the time when transmittable torque of the torque transmitting means falls below a currently transmitted torque, is reduced.

2. Method according to claim 1, further including: - performing said influencing such that torque transmitted by the drivetrain at the time when transmittable torque falls below a currently transmitted torque is reduced in relation to if controlling disengagement according to the driver manoeuvrable means (118).

3. Method according to claim 1 or 2, further including: - delaying or advancing the time of interruption of transmission of torque in relation to the time of interruption of transmission of torque requested by means of the driver manoeuvrable means (118).

4. Method according to any one of the preceding claims, further including: - increasing or decreasing torque delivered by the power source (101) to reduce torque transmitted by the drivetrain at the time when transmittable torque falls below a currently transmitted torque.

5. Method according to any one of the preceding claims, wherein initiation of disengagement of the torque transmitting means (106) is detected if: - detecting a movement of the driver manoeuvrable means (118).

6. Method according to any one of the preceding claims, further including, prior to the transmission of torque is interrupted: - estimating the torque that would be transmitted by the drivetrain at the time when transmittable torque falls below a currently transmitted torque if the transmission of torque is interrupted according to the driver manoeuvrable means (118), and performing said influencing based on this estimation.

7. Method according to any one of the preceding claims, further including: - estimating if the torque transmitted by the drivetrain, if controlling the torque transmitting means (106) according to the driver manoeuvrable means (118), will reduce to zero prior to the transmission of torque is interrupted; and - if it is estimated that the torque transmitted by the drivetrain will reduce to zero prior to the transmission of torque is interrupted: - advancing the time of interruption of the transmission of torque of the torque transmitting means (106) in relation to the time of interruption if controlled according to the manoeuvring of the driver manoeuvrable means (118), and/or - increasing the torque delivered by the power source (101) in order to delay the point in time at which torque transmitted by the drivetrain is reduced to zero.

8. Method according to any one of the preceding claims, further including: - estimating if transmission of torque of the torque transmitting means (106), if controlled according to the driver manoeuvrable means (118), will be interrupted prior to the torque transmitted by the drivetrain is reduced to zero, and if estimating that transmission of torque will be interrupted prior to torque transmitted by the drivetrain is reduced to zero: - delaying the time of interruption of the transmission of torque of the torque transmitting means (106) in relation to the time of interruption if controlled according to the driver manoeuvrable means (118), and/or - reducing torque delivered by the power source (101) in order to advance the point in time at which torque transmitted by the drivetrain is reduced to zero.

9. Method according to any one of the preceding claims, performing said influencing such that: - a difference in transmittable torque of the torque transmitting means corresponds to at most a predetermined difference in position of the driver manoeuvrable means (118) in relation to the actual position of said driver manoeuvrable means (118), and/or - a difference in torque delivered by said power source (101) differs at most by a predetermined difference in relation to the driver request for torque from the power source (101).

10. Method according to any one of the preceding claims, the torque transmitting means being a clutch (106).

11. Method according to any one of the preceding claims, the driver manoeuvrable means being a clutch pedal (118).

12. Computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any one of the preceding claims.

13. Computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of the claims 1-11.

14. System for a vehicle (100), the vehicle (100) including: a drivetrain for transferring torque between a power source (101) and at least one drive wheel of the vehicle (101), torque transmitting means (106) for selectively transmitting torque between the power source (101) and the at least one drive wheel of the vehicle (100), and driver manoeuvrable means (118), wherein transmittable torque of the torque transmitting means (106) is controllable in dependence of an electrical signal representing a position of the driver manoeuvrable means (118), the system including means for: - detecting if disengagement of the torque transmitting means (106) is initiated by means of the driver manoeuvrable means (118), and - based on said detection, influencing the torque delivered by the power source and/or the timing of an interruption of transmission of torque caused by the disengagement of the torque transmitting means (106) such that torque transmitted by the drivetrain, at the time when transmittable torque of the torque transmitting means falls below the torque currently transmitted by the drivetrain, is reduced.

15. Vehicle comprising a system according to claim 14.