SE539281C2 - A method for engine torque adaptation, a vehicle comprising an engine, a computer program for engine torque adaptation and a computer program product comprising program code - Google Patents

Abstract

23 Abstract The invention relates to a method for engine torque adaptation pertaining to anengine (2) in a powertrain (3) of a vehicle (1), the powertrain (3) furthercomprising a gearbox (6) and a clutch (4) arranged between the engine (2)and the gearbox (6), wherein the gearbox (6) comprises an input shaft (15)connected to the clutch (4), a main shaft (17), an output shaft (16), and a |ayshaft (18) connected to the input shaft (15) and the main shaft (17). Themethod comprising the steps to a) ensure that the gearbox (6) is in a neutralstate; b) control the clutch 4() to a disengaged state; c) activate at least one shaftbrake mechanism (24, 26) such that the input shaft (15) is braked and fullbraking effect is achieved; d) determine a total shaft brake torque (TQB)affecting the input shaft (15); e) control the clutch (4) to gradually reach anengaged state; f) determine an assumed engine torque (TQEA) at the point (T)when an engine torque (TQET) transmitted through the clutch (4) and the totalshaft brake torque (TQB) are substantially equal; and g) determine the enginetorque error by comparing the total shaft brake torque (TQB) and the assumed engine torque (TQEA). The invention also relates to a vehicle (1 ), a computer program (P) and acomputer programme product. (Pig. 2)

Description

A method for engine torque adaptation, a vehicle comprising an engine, acomputer program for engine torque adaptation and a computer programproduct comprising program code.

TECHNICAL FIELD The present invention relates to a method for engine torque adaptationpertaining to an engine in a powertrain of a vehicle according to the preambieof ciaim 1. The invention also relates to a vehicle comprising such an engineaccording to ciaim 12. The invention further reiates to a computer program forengine torque adaptation according to ciaim 13 and a computer programproduct comprising program code according to ciaim 14.

BACKGROUND Tiie engine torque transniitted ironi the engine to the transmission through theointon in a powertrain deoends for examoie ori oiutoit engagenient and therehyon friotion and other ioeses. The oaiouiation of transntitted engine torque istiios oompiex and the aottiaiiy iransmitted engine torque may for variousreasons difier ironi the oaioiiiated transmitted engine torque. in order toeifioientiy oontroi a potirertrain comprising iiie engine, ii is important thai tiietransrrritted engine torque is oorreot. Severai functions in a powertrain deoendon a oorreet transmitted engine torque in order to rnaintain good comfort. Forexamoie, due to oiay between components in a transmission in a driveiine it isvery important that the tranernitted engine torque is oorreot in order to avoidierks and osoiiiations in the driveiine. if too high or too iow engine torque isprovided, for examoie during take-off or gear shiiting, the oiay wiii oensesudden ierite wiiioii rnay ioe peroeived as orioieasani; ioy a driver and/or aoassenger. A oorreot transrrritted engine torque is thus soeoiiioaiiy intoortantaround iovir torque vaioee, for exarnpie around 9200 Nm. in order to ensure that the engine torque is correct, adaptation of the enginetorque may be necessary. This way, possibie errors in the engine torque areidentified and can be compensated tor. identifying and correcting errors inengine torque may be done in various ways and cotiid inyoive a comparisonbetiiveen a caictiiated engine torque and a known tordne reference. Finding areiiabie torque reference is howeyfer difiictiit and other yyeys of identifying engine torque errors are known. ififioctiinent Shit Otrtâíšilišiš A describes a ntethod tor adapting engine torqueduring regeneration of a diesei partictiiarte fiiter using an estirnatiort of theengine torque being transrriitted to a torgtie converter white regenerating theparticie fiiier. Liâêßêi "iišíš BE describes a method tor deterrnining an error inengine torque invoiving the steos to register a change in engine speed beforeand atter a predeterntined change in the engine terdoe and to coirioare thechange in engine speed with the engine torque before and efter thepredetermined citange.

SUMMARY OF THE INVENTION Despite known solutions in the field, there is still a need to develop a methodfor engine torque adaptation for an engine in a vehicle, which is reliable andthus minimizes the negative effects engine torque errors may have on the powertrain.

An object of the present invention is to achieve a method for engine torqueadaptation pertaining to an engine in a powertrain of a vehicle, which allowsadaptation at low engine torque values.

Another object of the invention is to achieve a method for engine torqueadaptation pertaining to an engine in a powertrain of a vehicle, which isreliable.

A further object of the invention is to achieve a method for engine torqueadaptation pertaining to an engine in a powertrain of a vehicle, which may beperformed both when the vehicle is still and when it is moving.

Another object of the present invention is to achieve a new and advantageouscomputer program for engine torque adaptation pertaining to an engine in apowertrain of a vehicle.

The herein mentioned objects are achieved by a method characterized by thefeatures in the characterizing part of claim 1.

The herein mentioned objects are also achieved by a vehicle characterized by the features in the characterizing part of claim 12.

The herein mentioned objects are also achieved by a computer program forengine torque adaptation characterized by the features in the characterizingpart of claim 13.

The herein mentioned objects are also achieved by a computer programproduct for engine torque adaptation characterized by the features in thecharacterizing part of claim 14.

According to an aspect of the present invention a method for engine torqueadaptation pertaining to an engine in a powertrain of a vehicle is provided. Thepowertrain comprises a gearbox and a clutch arranged between the engineand the gearbox, wherein the gearbox comprises an input shaft connected tothe clutch, a main shaft, an output shaft, and a lay shaft connected to the inputshaft and the main shaft. The method comprises the steps to: a) ensure that the gearbox is in a neutral state; b) control the clutch to a disengaged state; c) activate at least one shaft brake mechanism, such that the input shaft isbraked and full braking effect is achieved; d) determine a total shaft brake torque affecting the input shaft; e) control the clutch to gradually reach an engaged state; f) determine an assumed engine torque at the point when the engine torquetransmitted through the clutch and the total shaft brake torque are substantiallyequal; and g) determine the engine torque error by comparing the total shaft brake torque and the assumed engine torque.

The input shaft and the lay shaft are suitably connected such that if the layshaft is directly braked by a shaft brake mechanism, the input shaft will also bebraked, and vice versa. The at least one shaft brake mechanism may thus bedirectly connected to and directly affect any of the input shaft or the lay shaftand both shafts will be braked. The main shaft and the output shaft areconnected and the output shaft is connected to the driving wheels of thevehicle.

The gearbox and the clutch suitably constitute a semi-automatic transmission,such as a so called Al\/lT. The clutch is thus electronically controlled.

The engine torque is herein defined as the torque on the flywheel connected tothe engine crankshaft. The engine torque is thus the torque which istransmitted through the clutch to the input shaft of the gearbox. The enginetorque as herein defined thereby depends on friction and other losses and mayalso be called transmitted engine torque. The transmitted engine torqueincreases with the grade of clutch engagement and it is approximated that acertain position of the clutch corresponds to a certain transmitted enginetorque if the time period is so short that the clutch characteristics can beassumed constant during said time period. The assumed engine torque is theengine torque which is assumed to be transmitted through the clutch. The assumed engine torque is thus a calculated engine torque which has been compensated for friction and other losses. The friction loss and other lossesare known. The total shaft brake torque affecting the input shaft is the totaltorque provided by at least one activated shaft brake mechanism, whichaffects the input shaft.

When the at least one shaft brake mechanism is activated in step c) it takessome time before full braking effect is achieved. When full braking effect isachieved the shaft brake mechanism generates a substantially stable/fixedmaximum braking torque. The at least one shaft brake mechanism may bearranged on the input shaft or on the lay shaft and either way the maximumbraking torque affects the input shaft and thus causes a certain derivative ofthe rotational speed of the input shaft, herein also called acceleration of theinput shaft. The acceleration is negative and may also be called deceleration.lf one shaft brake mechanism is activated, the total shaft brake torque affectingthe input shaft is based on the maximum braking torque of the activated shaftbrake mechanism. lf a plurality of shaft brake mechanisms is activated, thetotal shaft brake torque is based on the sum of the maximum braking torque ofeach shaft brake mechanism. The total shaft brake torque is thus preferablydetermined while the at least one shaft brake mechanism is providing fullbraking effect. Suitably, any number of shaft brake mechanisms may beactivated. By activating at least one shaft brake mechanism such that fullbraking effect is achieved, a reliable torque reference for engine torqueadaptation is achieved. The inventive method is performed when the engine isactivated and thereby may provide an engine torque.

According to an aspect of the invention the shaft brake mechanism is activatedsuch that the input shaft and suitably also the lay shaft are braked to standstill.By maintaining the at least one shaft brake mechanism activated, such that theinput shaft and the lay shaft are held still, and controlling the clutch to graduallyreach an engaged state, the point when the engine torque transmitted throughthe clutch is substantially equal to the total shaft brake torque affecting theinput shaft may be determined as the point when the input shaft starts rotating.

The input shaft and the lay shaft will remain still until the transmitted enginetorque is greater than the total shaft brake torque. Thus, at the point when theinput shaft and thus the lay shaft start rotating, the transmitted engine torque isslightly greater but substantially equivalent to the total shaft brake torqueaffecting the input shaft. The initiation of rotation of the input shaft and the layshaft may be determined by a revolution-counter arranged at the input shaftand/or the lay shaft. At this point, an assumed engine torque is determined.Since the transmitted engine torque is substantially equivalent to the total shaftbrake torque the engine torque error can be determined by comparing theassumed engine torque and the total shaft brake torque. The engine torqueerror is thus the difference between the assumed engine torque and the totalshaft brake torque. When the engine torque error is determined the error maybe compensated for and a method for engine torque adaptation is thusachieved, which is reliable and which minimizes the effects engine torque errors may have on the powertrain.

According to an aspect of the invention the shaft brake mechanism is activatedsuch that the input shaft and suitably also the lay shaft are decelerated butrotates. By maintaining the at least one shaft brake mechanism activated, suchthat the input shaft and the lay shaft rotate with a decelerated speed, andcontrolling the clutch to gradually reach an engaged state, the point when theengine torque transmitted through the clutch is substantially equal to the totalshaft brake torque may be determined as the point when the derivative of therotational speed of the input shaft corresponds to an acceleration given by onlyfriction losses. Such an acceleration given by only friction losses is determinedbased on the known friction losses.

By performing the method according to the invention while the engine isactivated and the gearbox is in a neutral state the engine torque adaptationmay be performed both when the vehicle is standing still with the engine running and when the vehicle is moving. The method steps may suitably be performed when the vehicle is driving in an ECO-roll mode, i.e. rolling with the gearbox in a neutral state.

The at least one shaft brake mechanism, such as for example a lay shaft brakeor an input shaft brake, suitably provides a fixed total shaft brake torquearound 100 Nm. This way, since the assumed engine torque is determined atthe point when the transmitted engine torque substantially corresponds to thetotal shaft brake torque affecting the input shaft, a method for engine torqueadaptation is achieved, which allows adaptation at low engine torque valuesaround O-2OONm.

The at least one shaft brake mechanism may be a disc brake. The at least oneshaft brake mechanism may be a lay shaft brake connected to the lay shaftand thus directly affecting the lay shaft. Alternatively, the at least one shaftbrake mechanism may be an input shaft brake connected to the input shaftand thus directly affecting the input shaft.

According to an aspect of the invention two shaft brake mechanisms areactivated in step c) and brake the input shaft and the lay shaft. Suitably, oneshaft brake mechanism in form of a lay shaft brake is activated and one shaftbrake mechanism in form of an input shaft brake is activated. Alternatively, twolay shaft brakes are activated or two input shaft brakes are activated.

According to an aspect of the invention the method steps a)-g) are performedrepeatedly with different shaft brake mechanisms activated in step c). Forexample a first shaft brake mechanism generating a first total shaft braketorque may be activated in step c) in order to adapt the engine torque around afirst engine torque value corresponding to the first total shaft brake torque.Suitably a second shaft brake mechanism generating a second total shaftbrake torque may be activated when the method steps are repeated, wherebythe engine torque is adapted around a second engine torque valuecorresponding to the second total shaft brake torque.

Preferably, a control unit is arranged in communication with the engine, theclutch, the gearbox and the at least one shaft brake mechanism. The controlunit thus controls the engine, the clutch, the gearbox and the at least one shaftbrake mechanism. The assumed engine torque is, according to an aspect ofthe invention, provided by the control unit. The assumed engine torque ispreferably calculated with a predetermined algorithm in the control unit. Thus,the assumed engine torque is determined by the control unit. lf the transmittedengine torque is different from the assumed engine torque, the control unitmay incorrectly control the clutch and the gearbox based on the assumedengine torque. Adaptation of the engine torque is thus very important.

According to an aspect of the invention the determined engine torque error isregistered in the control unit and is used to adapt the engine torque. Suitably,the control unit calculates a new assumed engine torque compensating for thedetermined engine torque error. This way, the assumed engine torquebecomes equivalent to the transmitted engine torque and the engine torque is thus adapted.

According to an aspect of the invention the total shaft brake torque affectingthe input shaft is determined based on the derivative of the rotational speed ofthe input shaft and the moment of inertia of all rotating parts in the gearboxwhich are affected by the at least one activated shaft brake mechanism. Thederivative of the rotational speed of the input shaft may be determined bymeans of a revolution-counter, such as a tachometer, arranged on the inputshaft. The control unit preferably determines the total shaft brake torque.Alternatively the total shaft brake torque is provided by the control unit as aknown predetermined value. The moment of inertia of all rotating parts in thegearbox is provided by the control unit.

According to an aspect of the present invention, the total shaft brake torqueaffecting the input shaft is calculated with respect to gear ratios between the input shaft and the lay shaft. This is typically the case when an activated shaftbrake mechanism is directly connected to the lay shaft. The maximum brakingtorque provided by the shaft brake mechanism is then directly affecting the layshaft and the corresponding total shaft brake torque affecting the input shaftthereby has to be calculated such that the moment of inertia is converted torelate to the input shaft.

According to an aspect of the invention step f) further involves determining thecurrent clutch position at the point when the engine torque transmitted throughthe clutch and the total shaft brake torque are substantially equal. Clutch discsfor example may change over time due to heat, wear and tear. The clutchposition corresponding to a certain transmitted engine torque might thereforechange over time. By determining the clutch position at the point when theengine torque transmitted through the clutch and the total shaft brake torqueare substantially equal, the clutch position corresponding to the transmittedengine torque equivalent to the total shaft brake torque may be adaptivelydetermined. This way, the clutch and thus the powertrain can be controlled in acorrect and reliable way.

According to an aspect of the invention, a computer program is provided,wherein said computer program comprises programme code for causing anelectronic control unit or a computer connected to the electronic control unit toperform the steps according to the herein mentioned method for engine torqueadaptation.

According to an aspect of the invention a computer programme product isprovided, comprising a programme code stored on a computer-readablemedium for performing the method steps according to the herein mentionedmethod for engine torque adaptation, when said computer programme is runon an electronic control unit or a computer connected to the electronic control unit.

Further objects, advantages and novel features of the present invention willbecome apparent to one skilled in the art from the following details, and alsoby putting the invention into practice. Whereas the invention is describedbelow, it should be noted that it is not restricted to the specific detailsdescribed. Specialists having access to the teachings herein will recognisefurther applications, modifications and incorporations within other fields, whichare within the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS For fuller understanding of the present invention and further objects andadvantages of it, the detailed description set out below should be read togetherwith 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 ofthe invention; Figure 2 schematically illustrates a powertrain of a vehicle according to anembodiment of the invention; Figure 3 illustrates a flow chart for a method for engine torque adaptationaccording to an embodiment of the invention; Figure 4 illustrates a diagram of torque variations during a method forengine torque adaptation according to an embodiment of theinvention; and Figure 5 schematically illustrates a control unit or computer according to an embodiment of the invention. 11 DETAILED DESCRIPTION OF THE DRAWINGS Figure 1 schernaticaiiy shows a side view of a vehicle 1 according io anetnboditnent of the invention. The tfehicie 1 comprises a povtfertrain 3 with anengine 2, a clutch 4 (not shown) and a gearbox 6. The ciutch 4 is connected tothe engine 2 and the gearbox 6. The gearbox 6 is also connected to the drivingwheeis 10 of the vehicie 1 through an output shaft 16. The vehicle 1 may be aheavy vehicle, e.g. a truck or a bus. The vehicle 1 may alternatively be a passenger car.

Figure 2 schematicaiiy shows a powertrain 3 of a vehicle 1 according to anembodiment of the invention. The powertrain 3 comprises an engine 2, aclutch 4 and a gearbox 6. A flywheel 12 of the clutch 4 connects on one side tothe crankshaft 13 of the engine 2 and a clutch disc 14 connects to the inputshaft 15 of the gearbox 6 on the other side. The clutch 4 is thus arrangedbetween the engine 2 and the gearbox 6. When the clutch 4 is in an engagedstate the flywheel 12 and the clutch disc 14 are connected and the engine 2and the gearbox 6 are thus connected. When the clutch 4 is in a disengagedstate the flywheel 12 and the clutch disc 14 are separated and the engine 2 isdisconnected from the gearbox 6. The gearbox 6 comprises a main shaft 17which is connected to an output shaft 16, wherein the output shaft 16 isconnected to the driving wheels 10 of the vehicle 1. The gearbox 6 furthercomprises a lay shaft 18 arranged in connection to the input shaft 15 and themain 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 is connected tothe lay shaft 18 and a shaft brake mechanism in the form of an input shaftbrake 26 is connected to the input shaft 15. Any number of shaft brakemechanisms 24, 26 may be connected to the lay shaft 18 and/or the inputshaft 15. The input shaft 15 and the lay shaft 18 are fixedly connected such 12 that when the lay shaft brake 24 is activated the lay shaft 18 will be directlyaffected and braked and the input shaft 15 will be indirectly affected andbraked due to the connection to the lay shaft 18. Similarly, when the input shaftbrake 26 is activated the input shaft 15 will be directly affected and the layshaft 18 will be indirectly affected and both will be braked. lf the two shaftbrake mechanisms 24, 26 are activated at the same time the total shaft braketorque affecting the input shaft 15 is based on the sum of the individualmaximum braking torque of the lay shaft brake 24 and the individual maximumbraking torque of the input shaft brake 26. ln the case where the input shaft 1and the lay shaft 18 are not fixedly connected, only the input shaft brake 26may be used for engine torque adaptation.

The engine 2, the clutch 4, the gearbox 6 and the shaft brake mechanisms 24,26 are arranged in communication with a control unit 20. The control unit 20 isadapted to control the engine 2, the clutch 4, the gearbox 6 and the shaftbrake mechanisms 24, 26, for example for adapting the engine torque. Acomputer 22 may be connected to the control unit 20.

Figure 3 shows a flowchart for a method for engine torque adaptationpertaining to an engine 2 in a powertrain 3 of a vehicle 1 according to anembodiment of the invention. The powertrain 3 comprises a gearbox 6 and aclutch 4 arranged between the engine 2 and the gearbox 6, wherein thegearbox 6 comprises an input shaft 15 connected to the clutch 4, a main shaft17, an output shaft 16, and a lay shaft 18 connected to the input shaft 15 andthe main shaft 17. The powertrain 3 is suitably configured as described inFigure 2. The method comprises the steps of a) ensuring that the gearbox 6 isin a neutral state; b) controlling the clutch 4 to a disengaged state and c)activating at least one shaft brake mechanism 24, 26, such that the input shaftis braked and full braking effect is achieved. The method further comprises thesteps of d) determining a total shaft brake torque TQB affecting the input shaft15; e) controlling the clutch 4 to gradually reach an engaged state; f)determining an assumed engine torque TQEA at the point T when the engine 13 torque TQET transmitted through the clutch 4 and the total shaft brake torqueTQB are substantially equal and g) determining the engine torque error bycomparing the total shaft brake torque TQB and the assumed engine torqueTQEA. The method steps are also illustrated by torque variations in Figure 4. ln order to perform the inventive method the gearbox 6 must be in a neutralstate. Step a) may thus involve disengaging a gear if a gear is engaged whenthe method is about to be initiated. ln step b) the control unit 20 arranged in communication with the engine 2, theclutch 4, the gearbox 6 and the shaft brake mechanisms 24, 26 controls theclutch 4 to a disengaged state. By disengaging the clutch 4, the engine 2 isdisconnected from the gearbox 6 and step c) to brake the input shaft 15 and the lay shaft 18 may be performed without affecting the engine 2. ln step c) the control unit 20 activates at least one shaft brake mechanism 24,26 and the input shaft 15 and the lay shaft 18 are thus braked. According to anaspect of the invention the at least one activated shaft brake mechanism 24 isdirectly connected to the lay shaft 18. This way, the shaft brake mechanism 24(lay shaft brake) is activated in step c) and thus directly affect the lay shaft 18such that it is braked. Since the lay shaft 18 and the input shaft 15 are fixedlyconnected, the input shaft 15 is also braked when the shaft brake mechanism24 connected to the lay shaft 18 is activated. Any number of shaft brakemechanisms 24, 26 may be activated at the same time in step c). For exampletwo lay shaft brakes 24 or two input shaft brakes 26 may be activated.Alternatively, one lay shaft brake 24 is activated and one input shaft brake 26is activated. According to an aspect of the invention, the at least one shaftbrake mechanism 24, 26 is controlled to brake the input shaft 15 and the layshaft 18 to standstill. According to another aspect of the invention, the at leastone shaft brake mechanism 24, 26 is controlled to brake the input shaft 15 and the lay shaft 18 such that they rotate with a decelerated speed. The at least 14 one shaft brake mechanism 24, 26 is maintained activated with full braking effect during the subsequent method steps d)-f). ln step d) the control unit 20 determines the total shaft brake torque TQBaffecting the input shaft 15 provided by the activated shaft brake mechanisms24, 26. Step d) is suitably performed substantially simultaneously as step c).The total shaft brake torque TQB affecting the input shaft 15 may thus bedetermined while the at least one shaft brake mechanism 24, 26 is braking theinput shaft 15 and the lay shaft 18 with full braking effect. The total shaft braketorque TQB affecting the input shaft 15 may be determined based on thederivative of the rotational speed of the input shaft 15 and the moment ofinertia of all rotating parts in the gearbox 6 being affected by the activatedshaft brake mechanisms 24, 26. The total shaft brake torque TQB is suitablybased on the sum of the individual maximum braking torques of all the shaftbrake mechanisms 24, 26 activated in step c). The derivative of the rotationalspeed of the input shaft 15 is determined during the braking operation of theshaft brake mechanism 24, 26 and is thus negative, i.e. deceleration. Thederivative of the rotational speed of the input shaft 15 may be determined bymeans of a revolution-counter (not shown), such as a tachometer, arranged onthe input shaft 15. The moment of inertia of all rotating parts in the gearbox 6 isprovided by the control unit 20. The moment of inertia of all rotating parts in thegearbox 6 which are affected by the activated shaft brake mechanism 24, 26may be calculated with respect to gear ratios between the input shaft 15 andthe lay shaft 18. This is typically the case when the activated shaft brakemechanism 26 is directly connected to the lay shaft 18. The maximum brakingtorque provided by the shaft brake mechanism 26 is then directly affecting thelay shaft 18 and the corresponding total shaft brake torque TQB affecting theinput shaft 15 thereby has to be calculated such that the moment of inertia isconverted to relate to the input shaft 15. Alternatively, the total shaft braketorque TQB is provided by the control unit 20 as a predetermined fixed value. ln step e) the control unit 20 controls the clutch 4 to gradually reach anengaged state until the transmitted engine torque TQET at a point T issubstantially equal to the total shaft brake torque TQB This point T may bedetermined as the point where the input shaft 15 and the lay shaft 18 startrotating, if the input shaft 15 and the lay shaft 18 were braked to standstill instep c). Alternatively, this point T is determined as the point when theacceleration of the input shaft 15 is substantially equal to an acceleration givenby only friction losses. At this point T when the engine torque TQET transmittedthrough the clutch 4 and the total shaft brake torque TQB are substantiallyequal, the control unit 20 performs step f) and thus determines the currentassumed engine torque TQEA. The control unit 20 suitably calculates anassumed engine torque TQEA continuously whereby, in step f), the currentassumed engine torque TQEA is logged and thereby determined. ln the subsequent step g) the control unit 20 determines the engine torqueerror by comparing the total shaft brake torque TQB and the assumed enginetorque TQEA. The transmitted engine torque TQET is as establishedsubstantially equivalent to the total shaft brake torque TQB affecting the inputshaft 15 and since the total shaft brake torque TQB is known, the control unit20 can determine the engine torque error as the difference between theassumed engine torque TQEA and the total shaft brake torque TQB Thedetermined engine torque error is suitably used to adapt the engine torqueTQET by compensating for the engine torque error such that the assumedengine torque TQEA is equivalent to the transmitted engine torque TQET.

Step f) may further involve determining the current clutch position at the point Twhen the engine torque TQET transmitted through the clutch 4 and the totalshaft brake torque TQB are substantially equal. The clutch positioncorresponding to a certain transmitted engine torque TQET might for variousreasons change over time. By determining the clutch position at the point Twhen the transmitted engine torque TQET and the total shaft brake torque TQBare substantially equal, the clutch position corresponding to the transmitted 16 engine torque TQET equivalent to the total shaft brake torque TQB may beadaptively determined. This way, the clutch 4 and thus the powertrain 3 can becontrolled in a correct and reliable way.

Figure 4 shows a diagram of torque variation during a method for enginetorque adaptation pertaining to an engine 2 in a powertrain 3 of a vehicle 1according to an embodiment of the invention. The method for engine torqueadaptation is described in Figure 3 and is here further illustrated by thediagram over the torque variations. The diagram shows the transmitted enginetorque TQET varying with the clutch position. The diagram also shows the fixedtotal shaft brake torque TQB affecting the input shaft 15. The total shaft braketorque TQB is typically around 100 Nm. The input shaft 15 and the lay shaft 18are fixedly connected such that if the input shaft 15 is directly braked by a shaft brake mechanism 26, the lay shaft 18 is also braked and vice versa.

When the shaft brake mechanism 24, 26 has been activated and full brakingeffect is achieved, the input shaft 15 and the lay shaft 18 are braked and theinput shaft 15 is affected by the total shaft brake torque TQB The clutch 4 iscontrolled to gradually reach an engaged state and at a certain point T thetransmitted engine torque TQET is substantially equal to the total shaft braketorque TQB affecting the input shaft 15_.. At this point T, the control unit 20logs/determines the current assumed engine torque TQEA and possibly alsothe clutch position. The assumed engine torque TQEA is herein illustrated as aconstant value representing the assumed engine torque TQEA at this exactmoment when the transmitted engine torque TQET is substantially equal to thetotal shaft brake torque TQB affecting the input shaft 15. The assumed enginetorque TQEA typically varies with the clutch position but this is not illustrated inthis diagram. When the control unit 20 has determined the assumed enginetorque TQEA the engine torque error is determined as the difference betweenthe assumed engine torque TQEA and the transmitted engine torque TQET, which is substantially similar to the total shaft brake torque TQB affecting the 17 input shaft 15_ The control unit 20 may then adapt the engine torque TQET by compensating for the engine torque error.

Figure 5 is a diagram of a version of a device 500. The control unit 20 and/orcomputer 22 described with reference to Figure 2 may in a version comprisethe device 500. The term “link” refers herein to a communication link whichmay 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 ormicrowave link. The device 500 comprises a non-volatile memory 520, a dataprocessing unit 510 and a read/write memory 550. The non-volatile memory520 has a first memory element 530 in which a computer programme, e.g. anoperating system, is stored for controlling the function of the device 500. Thedevice 500 further comprises a bus controller, a serial communication port, I/Omeans, an A/D converter, a time and date input and transfer unit, an eventcounter and an interruption controller (not depicted). The non-volatile memory520 has also a second memory element 540.

There is provided a computer programme P which comprises routines forengine torque adaptation. The computer programme P comprises routines foridentifying a request for shifting to a reverse gear. The computer programme Pcomprises routines for ensuring that the gearbox 6 is in a neutral state. Thecomputer programme P comprises routines for controlling the clutch 4 to adisengaged stare. The computer programme P comprises routines foractivating at least one shaft brake mechanism 24, 26 such that the input shaft15 is braked and full braking effect is achieved. The computer programme Pcomprises routines for determining a total shaft brake torque affecting the inputshaft 15. The computer programme P comprises routines for controlling theclutch 4 to gradually reach an engaged state. The computer programme Pcomprises routines for determining an assumed engine torque at the pointwhen the engine torque transmitted through the clutch and the total shaft brake torque are substantially equal. The computer programme P comprises routines 18 for determining the engine torque error by comparing the total shaft brake torque and the assumed engine torque.

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

Where the data processing unit 510 is described as performing a certainfunction, it means that the data processing unit 510 effects a certain part of theprogramme 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 adata bus 515. The non-vo|ati|e memory 520 is intended for communication withthe data processing unit 510 via a data bus 512. The separate memory 560 isintended to communicate with the data processing unit 510 via a data bus 511.The read/write memory 550 is adapted to communicating with the dataprocessing unit 510 via a data bus 514.

When data are received on the data port 599, they are stored temporari|y inthe second memory element 540. When input data received have beentemporari|y stored, the data processing unit 510 is prepared to effect codeexecution as described above.

Parts of the methods herein described may be effected by the device 500 bymeans of the data processing unit 510 which runs the programme stored in thememory 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 presentinvention is provided for i||ustrative and descriptive purposes. It is not intendedto be exhaustive or to restrict the invention to the variants described. |\/|anymodifications and variations will obviously be apparent to one ski||ed in the art. 19 The embodiments have been chosen and described in order best to explainthe principles of the invention and its practical applications and hence make itpossible for specialists to understand the invention for various embodimentsand with the various modifications appropriate to the intended use.

Claims (14)

Claims

1. A method for engine torque adaptation pertaining to an engine (2) in apowertrain (3) of a vehicle (1), the powertrain (3) further comprising a gearbox(6) and a clutch (4) arranged between the engine (2) and the gearbox (6),wherein the gearbox (6) comprises an input shaft (15) connected to the clutch(4), a main shaft (17), an output shaft (16), and a |ay shaft (18) connected tothe input shaft (15) and the main shaft (17), characterized by the steps to: a) ensure that the gearbox (6) is in a neutral state; b) control the clutch (4) to a disengaged state; c) activate at least one shaft brake mechanism (24, 26) such that the inputshaft (15) is braked and full braking effect is achieved; d) determine a total shaft brake torque (TQB) affecting the input shaft (15); e) control the clutch (4) to gradually reach an engaged state; f) determine an assumed engine torque (TQEA) at the point (T) when an enginetorque (TQET) transmitted through the clutch (4) and the total shaft braketorque (TQB) are substantially equal; and g) determine the engine torque error by comparing the total shaft brake torque (TQB) and the assumed engine torque (TQEA).

2. A method according to claim 1, characterized in that step c) and step d) are performed substantially simultaneously.

3. A method according to claim 1 or 2, characterized in that the at least oneshaft brake mechanism (24, 26) maintains activated during steps d)-f).

4. A method according to any of the preceding claims, characterized in thatthe at least one activated shaft brake mechanism (24) is directly connected tothe |ay shaft (18).

5. A method according to any of the preceding claims, characterized in thatthe total shaft brake torque (TQB) affecting the input shaft (15) is determined instep d) based on the derivative of the rotational speed of the input shaft (15) 21 and the moment of inertia of all rotating parts in the gearbox (6) which are affected by the at least one activated shaft brake mechanism (24, 26).

6. A method according to c|aim 5, characterized in that the total shaft braketorque (TQB) affecting the input shaft (15) is calculated with respect to gearratios between the input shaft (15) and the lay shaft (18).

7. A method according to any of the preceding claims, characterized in thatthe point (T) when the engine torque (TQET) transmitted through the clutch (4)and the shaft brake torque (TQB) are substantially equal, is determined as thepoint when the derivative of the rotational speed of the input shaft (15) is substantially equal to an acceleration given by only friction losses.

8. A method according to claims 1-6, characterized in that the point (T) when the engine torque (TQET) transmitted through the clutch (4) and the shaft braketorque (TQB) are substantially equal, is determined as the point when the inputshaft (15) starts rotating.

9. A method according to any of the preceding claims, characterized in thatthe assumed engine torque (TQEA) is provided in step f) by a control unit (20) arranged in communication with the engine (2).

10. A method according to c|aim 9, characterized in that the control unit (20) adapts the engine torque (TQET) based on the determined engine torque error.

11. A method according to any of the preceding claims, characterized in thatstep f) further involves determining the current clutch position at the point (T)when the engine torque (TQET) transmitted through the clutch (4) and the shaftbrake torque (TQB) are substantially equal. 22

12. A vehicle (1 ), characterized in that engine torque adaptation pertaining toan engine in a powertrain of the vehicle (1) is performed according to the method in any of the claims 1-11.

13. A computer program (P), wherein said computer program comprisesprogramme code for causing an electronic control unit (20; 500) or a computer(22; 500) connected to the electronic control unit (20; 500) to perform the steps according to any of the claims 1-11.

14. A computer programme product comprising a programme code stored on acomputer-readable medium for performing the method steps according to anyof claims 1-11, when said computer programme is run on an electronic controlunit (20; 500) or a computer (22; 500) connected to the electronic control unit(18; 500).