SE542258C2

SE542258C2 - A method for clutch torque adaptation, a control unit for clutch torque adaptation, a vehicle comprising such a control unit, a computer program and a computer-readable medium

Info

Publication number: SE542258C2
Application number: SE1651400A
Authority: SE
Inventors: Erik Gustafsson; Fredrik Jarngren
Original assignee: Scania Cv Ab
Priority date: 2016-10-26
Filing date: 2016-10-26
Publication date: 2020-03-24
Also published as: SE1651400A1; BR102017019844A2; DE102017009297A1

Description

A method for clutch torque adaptation, a control unit for clutch torque adaptation, a vehicle comprising such a control unit, a computer program and a computer-readable medium.

TECHNICAL FIELD The present invention relates to a method for clutch torque adaptation pertaining to a powertrain of a vehicle, a control unit for clutch torque adaptation, a vehicle, a computer program and a computer-readable medium according to the appended claims.

BACKGROUND Vehicles today typically comprise electronically controlled clutches. A vehicle control unit then suitably controls the clutch, such that torque is transmitted through the clutch according to a control strategy depending on the driving situation. The torque transferred from the engine to the transmission by the clutch, depends on the position of the clutch. In order to be able to control the amount of torque that is transmitted through the clutch, the control unit needs to know how the position of the clutch and the transmitted torque relates to one another. Generally, the torque transmitted through the clutch (clutch torque) increases with the applied clutch force. However, the transmitted clutch torque also depends on for example the temperature and the friction coefficient of the clutch and calculation of the transmitted clutch torque is therefore complex. By performing a clutch torque adaptation the relationship between the transmitted clutch torque and the clutch position can be determined in an easier way. The relationship between the transmitted clutch torque and the clutch position is typically adapted during normal clutch use, for example during gear shifts and take offs. During such operating conditions the control of the clutch may be very fast, which may result in high torque derivatives and thereby cause poor sampling of signals for the adaptation. Adaptation during normal clutch use may therefore be difficult and often leads to disadvantageous results.

Document US2009/0090591 A1 describes a method for adapting an existing torque characteristic of a friction clutch of a powertrain. The method comprises to determine at least two marker points of a regulating-path-dependent torque characteristic, of which at least one marker point is determined at a slippage limit of the friction clutch. The method is initiated with the clutch engaged and the transmission in neutral, where a first marker point suitably is determined.

SUMMARY OF THE INVENTION Despite known solutions in the field, it would be desirable to develop a method for clutch torque adaptation, which overcomes or at least alleviates the drawbacks mentioned above. It would thus be advantageous to achieve a method for clutch torque adaptation which increases the quality of the adaptation and thereby increases the control over the torque transmission of the clutch.

An object of the present invention is therefore to achieve a method for clutch torque adaptation pertaining to a powertrain of a vehicle, which increases the quality of the adaptation. Another object of the invention is to achieve a method for clutch torque adaptation pertaining to a powertrain of a vehicle, which determines the relationship between clutch torque and clutch position in a less complex way compared to previously known methods.

Another object of the present invention is to achieve a control unit for clutch torque adaptation, which increases the quality of the adaptation and which determines the relationship between clutch torque and clutch position in a less complex way.

The herein mentioned objects are achieved by a method for clutch torque adaptation, a control unit for clutch torque adaptation, a vehicle, a computer program and a computer-readable medium according to the independent claims.

Hence, according to an aspect of the present invention a method for clutch torque adaptation pertaining to a powertrain of a vehicle is provided. The powertrain comprising an engine; a gearbox comprising an input shaft; and a clutch arranged to selectively transfer torque between the engine and the gearbox. The method comprising, if the vehicle is at standstill with the engine active and the clutch in a disengaged state: - preventing rotation of the input shaft; - controlling the clutch such that the torque transmitted through the clutch is gradually increased; and - determining the torque transmitted through the clutch at different clutch positions.

The torque transmitted from the engine to the gearbox through the clutch, depends on the position of the clutch. The clutch position is herein defined as the position of a clutch actuator of the clutch. The position of the clutch actuator affects the applied clutch force which in turn affects the torque transmitted through the clutch. However, the transmitted clutch torque also depends on for example the temperature, the friction coefficient and other losses. By clutch torque adaptation the relationship between the transmitted clutch torque and the clutch position can be determined without complex calculations. By preventing rotation of the input shaft of the gearbox when the vehicle is at standstill with the engine active and the clutch in a disengaged state, a stable state of the powertrain is achieved. The driveline of the vehicle is thereby locked and no torque is transferred to the driving wheels of the vehicle. The risk for oscillations in the driveline during adaptation is thereby reduced and the quality of the adaptation will be increased. The clutch and thus the powertrain can thereby be controlled in a more correct and more reliable way based on the result of the adaptation.

It is to be understood that controlling the clutch such that the torque transmitted through the clutch is gradually increased includes gradually controlling the clutch position. Controlling the clutch, such that the torque transmitted through the clutch is gradually increased suitably comprises controlling the clutch actuator gradually to different positions, such that more and more torque is transmitted through the clutch. In order to enable torque transmission through the clutch, the clutch is suitably controlled to an at least partially engaged state.

According to embodiments, the gearbox and the clutch may constitute a semiautomatic transmission, such as a so called AMT. The clutch may thus be electronically controlled. The method for clutch torque adaptation may be performed by means of a control unit for clutch torque adaptation. The clutch position may e.g. be determined by means of a position sensor arranged in association with the clutch actuator according to conventional methods. The control unit for clutch torque adaptation may be arranged in communication with such position sensor. The control unit may be arranged to receive information regarding the clutch position from other components or systems of the vehicle.

The gearbox may comprise at least one input shaft connected to the clutch and an output shaft. The gearbox may further comprise a main shaft, and a lay shaft connected to the input shaft and the main shaft. The lay shaft may be connected to the input shaft and the main shaft via gear wheels, such that torque may be transferred between the lay shaft, the input shaft and the main shaft. The main shaft may be connected to the output shaft. The main shaft may be connected to the output shaft via gear wheels, such that torque may be transferred between the main shaft and the output shaft. The output shaft may be connected to the driving wheels of the vehicle, such that torque may be transferred to the driving wheels. The gearbox may be electronically controlled.

According to an embodiment of the invention the method may comprise to determine if the vehicle is at standstill with the engine active and the clutch in a disengaged state. By active engine means that the engine is running and thus provides an engine torque. The engine may suitably be active with an idling speed. That the vehicle is at standstill may be determined based on the rotational speed of the front wheels of the vehicle. The rotational speeds of the front wheels may be determined by means of conventional sensors arranged on the vehicle. The control unit for clutch torque adaptation may determine if the vehicle is at standstill with the engine active and the clutch in a disengaged state.

According to an embodiment of the invention the torque transmitted through the clutch at a certain clutch position may be determined based on a torque provided by the engine at that clutch position. The torque provided by the engine may be defined as the torque on the flywheel connected to the engine crankshaft. When the input shaft is prevented from rotating and the clutch is gradually engaged the clutch will start slipping and the load on the flywheel, and thus the engine, will increase. An increased engine torque is thereby required to maintain the idling speed of the engine. It can be proven that as long as the clutch is slipping, the torque transmitted through the clutch is substantially the same as the torque provided by the engine (flywheel torque), as long as the engine has a constant rotational speed and no other load is acting on the engine. Thus, the torque transmitted through the clutch increases with the applied clutch force as long as the clutch is slipping. By knowing the engine torque at a certain clutch position, the torque transmitted through the clutch can be determined. The provided engine torque may be determined by means of an engine control system as known in the art. The torque transmitted through the clutch at a certain clutch position may thus be determined based on a known torque provided by the engine. The information regarding the provided engine torque may be available for the control unit for clutch torque adaptation. Alternatively, the provided engine torque may be determined by means of a torque sensor arranged in association with the engine flywheel.

Alternatively, the torque transmitted through the clutch at a certain clutch position may be determined by means of a torque sensor arranged in association with the input shaft of the gearbox.

According to an embodiment of the invention, preventing rotation of the input shaft may comprise activating at least one shaft brake mechanism. The input shaft may be prevented from rotating by locking the driveline to the chassis of the vehicle by means of components in the gearbox. The at least one activated shaft brake mechanism may be directly connected to the lay shaft or the at least one activated shaft brake mechanism may be directly connected to the input shaft. The input shaft and the lay shaft may be connected such that if the lay shaft is directly braked by a shaft brake mechanism, the input shaft will also be braked, and vice versa. The at least one shaft brake mechanism may thus be directly connected to and directly affect any of the input shaft or the lay shaft and the input shaft will be prevented from rotating upon activation of the shaft brake mechanism. The at least one shaft brake mechanism may be a disc brake. A shaft brake mechanism connected to the lay shaft may be referred to as a lay shaft brake and a shaft brake mechanism connected to the input shaft may be referred to as an input shaft brake. The method may comprise to activate two shaft brake mechanisms, for example one lay shaft brake and one input shaft brake.

Alternatively or additionally, the activated at least one shaft brake mechanism is directly connected to the main shaft. The main shaft and the output shaft are connected and the output shaft is connected to the driving wheels of the vehicle. In this case, the method may comprise to ensure that a gear is engaged such that the input shaft is connected to the main shaft and thereby is prevented from rotating When the input shaft is prevented from rotating by means of a shaft brake mechanism on the lay shaft, the input shaft or the main shaft the method may comprise to ensure that the output shaft is disconnected from the input shaft.

In this way, it is ensured that no torque will be transferred to the driving wheels even if the engine torque becomes larger than the braking force provided by the shaft brake mechanism and the input shaft starts rotating. Safety is thereby enhanced. The output shaft is disconnected from the input shaft (such that no torque is transmitted there between) when the gearbox is in neutral, and thus when no gear is engaged. The method may comprise to ensure that the gearbox is in neutral, such that no gear is engaged downstream of the at least one shaft brake mechanism. The method may thus comprise to ensure that no torque can be transferred from the input shaft to the driving wheels through the gearbox. In the present specification, downstream means the direction of a torque transmission path reaching in direction from the engine towards the driving wheels of the vehicle.

According to an embodiment of the invention preventing rotation of the input shaft comprises ensuring that the output shaft is connected to the input shaft and ensuring braking of the driving wheels of the vehicle. By braking the driving wheels of the vehicle the output shaft will be prevented from rotating. Since the output shaft is connected to the input shaft, the input shaft is also prevented from rotating. The output shaft may be connected to the input shaft by means of an engaged gear in the gearbox. Preventing rotation of the input shaft may thus comprise ensuring that the output shaft is connected to the input shaft via gear wheels, such that torque may be transferred between the input shaft and the output shaft, and ensuring braking of the driving wheels. The driving wheels of the vehicle are suitably braked by activation of a wheel brake mechanism. The wheel brake mechanism may be a parking brake or a service brake of the vehicle. By applying a wheel brake mechanism to prevent rotation of the input shaft a larger braking force can be applied on the input shaft. This way, larger engine torque may be provided before the input shaft starts rotating. Clutch torque adaptation at larger torque values is thereby possible.

The method may comprise to prevent rotation of the input shaft by activating at least one shaft brake mechanism and/or a wheel brake mechanism.

According to an embodiment of the invention the torque transmitted through the clutch is determined for any number of different clutch positions. By determining the transmitted clutch torque at a plurality of different clutch positions the relationship between the transmitted clutch torque and the clutch position may be mapped. The transmitted clutch torque and the clutch position are suitably determined (at least essentially) simultaneously to ensure that the relationship between the determined clutch torque and clutch position is accurate. According to an embodiment of the invention the torque transmitted through the clutch is determined for at least five different clutch positions. The torque transmitted through the clutch may be determined for at least ten different clutch positions. The method may comprise to determine the transmitted clutch torque for a number of predetermined clutch positions. The clutch may then be controlled to a predetermined position whereafter the transmitted clutch torque at said clutch position is determined. Alternatively, the torque transmitted through the clutch at different clutch positions is determined for a number of predetermined transmitted clutch torque values. The clutch may then be controlled such that a predetermined torque value is transmitted through the clutch, whereafter the clutch position corresponding to said transmitted clutch torque is determined. Alternatively, the method comprises to determine the transmitted clutch torque at different clutch positions according to a predetermined time interval. Thus, at a certain point in time the current transmitted clutch torque and the current clutch position is determined. The result of the adaptation (the determined torque and position values) may be compiled in a graph showing the relationship between clutch torque and clutch positions.

The clutch torque adaptation may be performed when the vehicle is at standstill with the engine active and the clutch in a disengaged state. However, this does not mean that the adaptation is performed every time these conditions are met. The clutch torque adaptation method may be performed only when a suitable situation for adaptation has been identified. Such a suitable situation may be when the vehicle is expected to be at standstill for a certain time period. This is typically the case when the vehicle is at standstill with the gearbox in neutral and the parking brake activated. The clutch torque adaptation may be performed at predetermined intervals and/or when it has been identified that it was a long time since the last adaptation was performed. Alternatively or additionally, the clutch torque adaptation may be performed when the clutch has been frequently used or has been subject to great stress, which thereby may affect the torque transmitted through the clutch. The method may thus comprise to identify a suitable situation for clutch torque adaptation.

According to an embodiment of the invention the method for clutch torque adaptation constitutes a part of a workshop clutch testing method. For example, if it is identified that a vehicle has a problem associated with the clutch, such as problems during gear shifting or take off, the clutch torque adaptation may be performed in order to determine if there is something wrong with the clutch. When a problem associated with the clutch has been identified by a diagnostic tool, the diagnostic tool may request a workshop test whereby the clutch torque adaptation is performed. As part of a workshop testing method the clutch torque adaptation may be performed repeatedly in order to achieve a better basis for decision.

According to an embodiment of the invention a control unit for clutch torque adaptation pertaining to a powertrain of a vehicle is provided. The powertrain comprising an engine; a gearbox comprising an input shaft; and a clutch arranged to selectively transfer torque between the engine and the gearbox, the control unit being configured to, if the vehicle is at standstill with the engine active and the clutch in a disengaged state: prevent rotation of the input shaft; control the clutch such that the torque transmitted through the clutch is gradually increased; and determine the torque transmitted through the clutch at different clutch positions. The control unit may comprise an algorithm for clutch torque adaptation according to the herein mentioned method. The control unit may comprise a module for preventing rotation of the input shaft, a module for controlling the clutch such that the torque transmitted through the clutch is gradually increased and a module for determining the torque transmitted through the clutch at different clutch positions.

The control unit may be a control unit of a transmission control system or any other vehicle control unit. The control unit may comprise a plurality of different vehicle control units. The control unit is suitably arranged in communication with the engine, the clutch and the gearbox.

The embodiments of the herein disclosed method for clutch torque adaptation are applicable also for the control unit.

According to an aspect of the invention, a computer program is provided, wherein said computer program comprises programme code for causing an electronic control unit or a computer connected to the electronic control unit to perform the steps according to the herein mentioned method for clutch torque adaptation.

According to an aspect of the invention a computer-readable medium is provided, wherein said computer-readable medium comprises instructions, which when executed by a control unit or a computer connected to the control unit, cause the control unit or the computer to perform the herein mentioned method for clutch torque adaptation.

Further objects, advantages and novel features of the present invention will become apparent to one skilled in the art from the following details, and also by putting the invention into practice. Whereas embodiments of the invention are described below, it should be noted that it is not restricted to the specific details described. Specialists having access to the teachings herein will recognise further applications, modifications and incorporations within other fields, which are within the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS For fuller understanding of the present invention and further objects and advantages of it, the detailed description set out below should be read together with the accompanying drawings, in which the same reference notations denote similar items in the various diagrams, and in which: Figure 1 schematically illustrates a vehicle according to an embodiment of the invention; Figure 2 schematically illustrates a powertrain of a vehicle according to an embodiment of the invention; Figure 3 illustrates a flow chart for a method for clutch torque adaptation according to an embodiment of the invention; Figure 4 illustrates a diagram of the relationship between clutch torque and clutch position according to an embodiment of the invention; and Figure 5 schematically illustrates a control unit or computer according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS Figure 1 schematically shows a side view of a vehicle 1 according to an embodiment of the invention. The vehicle 1 comprises a powertrain 3 with an engine 2, a clutch (not shown) and a gearbox 6. The clutch is connected to the engine 2 and the gearbox 6. The gearbox 6 is also connected to the driving wheels 10 of the vehicle 1 through an output shaft 16 of the gearbox 6. The vehicle 1 may further comprise a control unit 20 for clutch torque adaptation. The vehicle 1 may be a heavy vehicle, e.g. a truck or a bus. The vehicle 1 may alternatively be a passenger car.

Figure 2 schematically shows a powertrain 3 of a vehicle according to an embodiment of the invention. The vehicle may be the vehicle 1 as disclosed in Figure 1. The powertrain 3 may comprise an engine 2, a gearbox 6 comprising an input shaft 15 and a lay shaft 18 and a clutch 4 arranged to selectively transfer torque between the engine 2 and the gearbox 6. The clutch 4 may comprise a flywheel 12 and a clutch disc 14. The flywheel 12 is connected to the crankshaft 13 of the engine 2 and the clutch disc 14 is connected to the input shaft 15 of the gearbox 6. The clutch 4 is thus arranged between the engine 2 and the gearbox 6. When the clutch 4 is engaged the clutch 4 is in a position where the flywheel 12 and the clutch disc 14 are engaged and the engine 2 and the gearbox 6 are thus connected. When the clutch 4 is disengaged the clutch 4 is in a position where the flywheel 12 and the clutch disc 14 are separated, and the engine 2 is disconnected from the gearbox 6. For clutch positions between the disengaged state and the engaged state, that is partially engaged states, the clutch 4 is slipping. That is, the flywheel 12 and the clutch disc 14 are slipping against each other. The gearbox 6 comprises a main shaft 17 which is connected to an output shaft 16, wherein the output shaft 16 is connected to the driving wheels 10 of the vehicle 1. The lay shaft 18 is arranged in connection to the input shaft 15 and the main shaft 17. Only two driving wheels 10 are illustrated in Figure 2, however, any number of driving wheels 10 may be driven by the powertrain 3 within the scope of the invention.

A shaft brake mechanism in the form of a lay shaft brake 24 may be connected to the lay shaft 18 and a shaft brake mechanism in the form of an input shaft brake 26 may be connected to the input shaft 15. Any number of shaft brake mechanisms 24, 26 may be connected to the lay shaft 18 and/or the input shaft 15. The input shaft 15 and the lay shaft 18 may be connected such that when the lay shaft brake 24 is activated the lay shaft 18 will be directly affected and braked and the input shaft 15 will be indirectly affected and braked due to the connection to the lay shaft 18. Similarly, when the input shaft brake 26 is activated the input shaft 15 will be directly affected and the lay shaft 18 will be indirectly affected and both will be braked.

A shaft brake mechanism in the form of a main shaft brake 28 may be connected to the main shaft 17. With a gear engaged such that the input shaft 15 is connected to the main shaft 17, the input shaft 15 can be prevented from rotating when the main shaft brake 28 is activated.

At least one wheel brake mechanism 32 may be arranged in connection to each driving wheel 10 of the vehicle 1. The at least one wheel brake mechanism 32 may be a parking brake or a service brake.

The engine 2, the clutch 4, the gearbox 6, the shaft brake mechanisms 24, 26, 28 and the wheel brake mechanisms 32 may be arranged in communication with a control unit for clutch torque adaptation 20. The control unit 20 may be adapted to control the engine 2, the clutch 4, the gearbox 6, the shaft brake mechanisms 24, 26, 28 and/or the wheel brake mechanisms 32 for adapting the clutch torque. A computer 22 may be connected to the control unit 20. The control unit 20 is suitably adapted to, if the vehicle is at standstill with the engine 2 active and the clutch 4 in a disengaged state: prevent rotation of the input shaft 15; control the clutch 4 such that the torque transmitted through the clutch 4 is gradually increased and determine the torque transmitted through the clutch 4 at different clutch positions. The control unit 20 may thus be adapted to determine the relationship between transmitted clutch torque and clutch position by clutch torque adaptation.

Figure 3 shows a flowchart for a method for clutch torque adaptation pertaining to a powertrain of a vehicle according to an embodiment of the invention. The powertrain may be the powertrain 3 as disclosed in Figure 2. The vehicle may be the vehicle 1 as disclosed in Figure 1. The powertrain 3 may comprise an engine 2, a gearbox 6 comprising an input shaft 15, and a clutch 4 arranged to selectively transfer torque between the engine 2 and the gearbox 6. The method comprising, if the vehicle 1 is at standstill with the engine 2 active and the clutch 4 in a disengaged state; preventing s101 rotation of the input shaft 15; controlling s102 the clutch 4 such that the torque transmitted through the clutch 4 is gradually increased; and determining s103 the torque transmitted through the clutch 4 at different clutch positions. The method may comprise to determine if the vehicle 1 is at standstill with the engine 2 active and the clutch 4 in a disengaged state.

The method may be performed by means of a control unit for clutch torque adaptation 20. Determining s103 the torque transmitted through the clutch 4 may be performed essentially simultaneously as the corresponding clutch position is determined.

The torque transmitted through the clutch 4 at a certain clutch position may be determined based on a torque provided by the engine 2 at that clutch position. The provided engine torque is typically determined by means of an engine control system and is communicated to the control unit for clutch torque adaptation 20. The torque transmitted through the clutch 4 at a certain clutch position may be determined by means of a torque sensor arranged in association with the engine flywheel 12 or in association with the clutch disc 14 and the input shaft 15.

Preventing s101 rotation of the input shaft 15 may comprise activating at least one shaft brake mechanism 24, 26, 28. The at least one shaft brake mechanism 24, 26, 28 may be a shaft brake mechanism directly connected to the input shaft 15, the lay shaft 18 or the main shaft 17 of the gearbox 6. The method may further comprise ensuring that the output shaft 16 is disconnected from the input shaft 15, when the activated shaft brake mechanism 24, 26, 28 is directly connected to the input haft 15, the lay shaft 18 or the main shaft 17. The method may thus comprise ensuring that no gear is engaged in the gearbox 6. More specifically, the method may comprise ensuring that no gear is engaged in the gearbox 6 downstream of the activated shaft brake mechanism 24, 26, 28. The torque/force flow is defined to go from the engine 2 to the driving wheels 10. A gear downstream of a shaft brake mechanism 24, 26, 28 thus means a gear closer to the driving wheels 10 than the shaft brake mechanism 24, 26, 28. When the output shaft 16 is disconnected from the input shaft 15 no torque can be transmitted to the driving wheels 10 even if the input shaft 15 starts rotating. The method may thus comprise ensuring that no torque can be transmitted from the input shaft 15 to the output shaft 16 via the gearbox 6. This way, the risk that the vehicle 1 will start moving during the clutch torque adaptation is avoided.

Preventing s101 rotation of the input shaft 15 may comprise ensuring that the output shaft 16 is connected to the input shaft 15 and ensuring braking of the driving wheels 10 of the vehicle 1. The method may thus comprise activating a wheel brake mechanism 32, such as a parking brake or a service brake. The method may thus also comprise ensuring that a gear is engaged in the gearbox 6. With a gear engaged in the gearbox 6 the output shaft and the main shaft 17 are connected to the input shaft 15. By activating a wheel brake mechanism 32 the output shaft 16 is prevented from rotating and the input shaft 15 is thereby also prevented from rotating.

The method may comprise to determine the torque transmitted through the clutch 4 for any number of clutch positions. The method may comprise to determine the torque transmitted through the clutch 4 for at least five different clutch positions. The method may comprise to determine the torque transmitted through the clutch 4 for at least ten different clutch positions. The method may comprise to determine the torque transmitted through the clutch 4 at different clutch positions for any number of predetermined clutch torque values. Thus, the method may comprise to determine the transmitted clutch torque and the corresponding clutch position for a number of predetermined measurement points (clutch torque values/clutch positions). The more measurement points, the better adaptation result. The result of the adaptation may be compiled in a diagram showing the relationship between the transmitted torque through the clutch and the clutch position as a curve. An example of such a diagram is shown in Figure 4. A new relationship may be determined from scratch each time the clutch torque adaptation is performed or the new relationship may be based on a previously determined relationship.

The method for clutch torque adaptation may according to an aspect of the invention be part of a workshop clutch testing method.

The method for clutch torque adaptation may be ended when the torque transmitted through the clutch 4 is similar to the torque that the shaft brake mechanism 24, 26, 28 and/or the wheel brake mechanism 32 applies. The method for clutch torque adaptation may be ended when the torque transmitted through the clutch 4 is within a predetermined range from the torque applied by the shaft brake mechanism 24, 26, 28 and/or the wheel brake mechanism 32.

Figure 4 shows a diagram of a relationship between transmitted clutch torque and clutch position according to an embodiment of the invention. The diagram shows the transmitted clutch torque TQc varying with the clutch position. The diagram may show the result of a method for clutch torque adaptation pertaining to a powertrain 3 of a vehicle 1 as disclosed in Figure 3. By determining the torque transmitted through the clutch 4 at different clutch positions the results can be compiled in a diagram like this, showing the relationship as a curve. Due to wear of the clutch 4, the operating temperature, friction losses and other factors the relationship between transmitted clutch torque and clutch position varies over time. If this is not considered when controlling the clutch 4, driving situations where the clutch 4 is used may be poorly performed. By performing a clutch torque adaptation according to the method disclosed in Figure 3 a more accurate relationship is determined and an improved control of the clutch 4 can be achieved.

Figure 5 is a diagram of a version of a device 500. The control unit 20 and/or computer 22 described with reference to Figure 2 may in a version comprise the device 500. The term “link” refers herein to a communication link which may be a physical connection such as an optoelectronic communication line, or a non-physical connection such as a wireless connection, e.g. a radio link or microwave link. The device 500 comprises a non-volatile memory 520, a data processing unit 510 and a read/write memory 550. The non-volatile memory 520 has a first memory element 530 in which a computer programme, e.g. an operating system, is stored for controlling the function of the device 500. The device 500 further comprises a bus controller, a serial communication port, I/O means, an A/D converter, a time and date input and transfer unit, an event counter and an interruption controller (not depicted). The non-volatile memory 520 has also a second memory element 540.

There is provided a computer programme P which comprises routines for clutch torque adaptation. The computer programme P comprises routines for preventing rotation of the input shaft. The computer programme P comprises routines for controlling the clutch such that the torque transmitted through the clutch is gradually increased. The computer programme P comprises routines for determining the torque transmitted through the clutch at different clutch positions. The computer programme P comprises routines for activating at least one shaft brake mechanism. The computer programme P comprises routines for activating at least one wheel brake mechanism. The computer programme P comprises routines for determining if the vehicle is at standstill with the engine active and the clutch in a disengaged state. The computer programme P comprises routines for ensuring that the output shaft is disconnected from the input shaft.

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

Where the data processing unit 510 is described as performing a certain function, it means that the data processing unit 510 effects a certain part of the programme stored in the memory 560 or a certain part of the programme stored in the read/write memory 550.

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

When data are received on the data port 599, they are stored temporarily in the second memory element 540. When input data received have been temporarily stored, the data processing unit 510 is prepared to effect code execution as described above.

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

The foregoing description of the preferred embodiments of the present invention is provided for illustrative and descriptive purposes. It is not intended to be exhaustive or to restrict the invention to the variants described. Many modifications and variations will obviously be apparent to one skilled in the art. The embodiments have been chosen and described in order best to explain the principles of the invention and its practical applications and hence make it possible for specialists to understand the invention for various embodiments and with the various modifications appropriate to the intended use.

Claims

1. A method for clutch torque adaptation pertaining to a powertrain (3) of a vehicle (1), the powertrain (3) comprising: an engine (2); a gearbox (6) comprising an input shaft (15); and a clutch (4) arranged to selectively transfer torque between the engine (2) and the gearbox (6), the method comprising, if the vehicle (1) is at standstill with the engine (2) active and the clutch (4) in a disengaged state: - preventing (s102) rotation of the input shaft (15); - controlling (s103) the clutch (4), such that the torque (TQc) transmitted through the clutch (4) is gradually increased; and - determining (s104) the torque (TQc) transmitted through the clutch (4) at different clutch positions.

2. The method according to claim 1, wherein the torque (TQc) transmitted through the clutch (4) at a certain clutch position is determined based on a torque provided by the engine (2) at that clutch position.

3. The method according to any one of the preceding claims, wherein preventing (s102) rotation of the input shaft (15) comprises activating at least one shaft brake mechanism (24, 26; 28).

4. The method according to claim 3, wherein the at least one activated shaft brake mechanism (24) is directly connected to the input shaft (15).

5. The method according to claim 3, wherein the at least one activated shaft brake mechanism (26) is directly connected to a lay shaft (18) of the gear box (6).

6. The method according to any one of claims 3-5, further comprising ensuring that an output shaft (16) of the gearbox (6) is disconnected from the input shaft (15).

7. The method according to any one of claims 1 -5, wherein preventing (s102) rotation of the input shaft (15) comprises ensuring that the output shaft (16) is connected to the input shaft (15) and ensuring braking of the driving wheels (10) of the vehicle (1).

8. The method according to any one of the preceding claims, wherein the torque (TQc) transmitted through the clutch (4) is determined for at least five different clutch positions.

9. The method according to any one of the preceding claims, wherein the method constitutes a part of a workshop clutch testing method.

10. A computer program (P), wherein said computer program comprises programme code for causing a control unit (20; 500) or a computer (22; 500) connected to the control unit (20; 500) to perform the method according to any one of the preceding claims.

11. A computer-readable medium comprising instructions, which when executed by a control unit (20; 500) or a computer (22; 500) connected to the control unit (20; 500), cause the control unit (20; 500) or the computer (22; 500) to perform the method according to any one of claims 1-9.

12. A control unit for clutch torque adaptation (20) pertaining to a powertrain (3) of a vehicle (1), the powertrain (3) comprising: an engine (2); a gearbox (6) comprising an input shaft (15); and a clutch (4) arranged to selectively transfer torque between the engine (2) and the gearbox (6), the control unit (20) being configured to, if the vehicle (1) is at standstill with the engine (2) active and the clutch (4) in a disengaged state: - prevent rotation of the input shaft (15); - control the clutch (4), such that the torque (TQc) transmitted through the clutch (4) is gradually increased; and - determine the torque transmitted by the clutch (4) at different clutch positions.

13. A vehicle (1) comprising a control unit (20) according to claim 12.