[0001]METHOD FOR CARRYING OUT A SHIFT OF GEARS QF AN AUTOMATIC TRANSMISSION 10003] [4] The invention relates to a method for perforrning a gear shift of an automatic transmission of a vehicle while clriving, with or without utiilzation of a ciutch according to the preamble of Patent Claim 1, [5] [6] Automatic transmissions have been used for some time in different types of motor vehicles. They have a plurality of fixed transmission ratlos wfiich can be selected by means of the driver's input and/or by a transmission contro! device located in the flow of torque between a drive engine and ttie driven wheels of a vehicle. Between the drive engine of the vehicle and the automatic transmission there is a ciutch or driving ciutch vvhich allows engagement of a driving gear with the drive engine running and the vehicle stopped, This ciutch is often also automatically actuated and thus allows fully automatic or semi-automatic shifting processes. [7] Automatic transmissions can be designed ss synchronized transmissions. In this design, certain transmission elements ensure that, when engaging a gear, the invoived, cooperating, fomi-locking elements of the transmission will move without any, or only a little, deslred speed difference. Synchronization is ensured in this design by means of friction nouplings withjn the tranBm'SSion [8] Because of a plurality of different friction pairings for different transmission steps of the transmission placement of a synchronization device in the transmission is associated with fundamental disadvantages related to the costs invoived with the additional elements, the needed additional Installation space, Üie greater weight du© to the additional elements, and not lastly with regard to the possible maintenance- free life of the transmission. Since friction clutches are subject to significant wear, they have to be replaced after a particular sen/ice life, at least in vehicles with high operating power or frequent shifting, and this resutts in significant expense, due their location in the transmission, and loss of tlie vehicle during its repair in the Workshop. [9] In particular, with veiiicle types which typicaily have commercial uses and higfi annual mileage and/or a particularly large number of shift processes, unsynchronized transmissions offer certain advantages, These transmissions are usualiy designed as "claw" transmissions in which the transnnission stage iocated in the flow of torque between the drive engine and driven wheels is specified by a movement of a form-locked element. Usuaily in this type of transmission, the gear wheels are secured to a shaft in a non-rotating manner, whereas gear wheels engaging with them are at least seated on and axially fixed to a different shaft as so- called loose wheels, but can rotate radially on the shaft as loose wheels. These loose wheels can be fixed in position on their shaft by means of selector fingers or pawls, so that a flow of torque is possible from a fixed wheel arranged on a flrst shaft, to a loose wheel secured to a second shaft by a selector pawl. [10] Shifting of the selector pawls is only possible with reasonabie strain on the component and with little or no generation of noise when the loose wheel, secured to its shaft, and the associated shaft in general have roughly the same rotational speed. Since the rotational speed of th© transmission Output shaft is determined by the cruising speed of the vehicle and by the generally fixed transmission ratios between the driven wheels and the transmission input shaft, the rotational speed of the transmission drive shaft must be adjusted for a gear shift of an unsynchronized transmission in a moving vehide, so that it at least roughly con-esponds to the rotational speed which results after engagement of the claw coupling. In this regard, the drive engine can be controlied primarily in a simple manner with a transmission in the neutral position and the clutch disengaged, orthe engine rotational speed can be controlied so that the drive engine can be set to a higher or lower rotational speed than that needed for synchronization of the transmission, according to the desired acceleration or deceleration of the transmission input shaft. Now if the clutch is slowly engaged, the drive shaft of the transmission will be accelerated or decelerated accordingly. As soon as the devlation from the desired synchronous rotational speed is sufficiently small, the fornviocking elements engage, in order to hold the loose wheels, and the desired cear is seiected. [12] This method has the advantage that it wiii operate probiem-free, due to the large potential slippage in the clutch, even with very iarge differences in rotational speed between the Output rotational speed of the drive engine and th© actual er desired rotational speed of the transmission drive shaft. [13] In the case of frequent shifting and with large-weight vehicles, however, the resuitant wear on the clutch is significant and, in tum, results in expenses for replacement of the friction linfngs and also in vehicle down times resulting from the time spent in the Workshop. Furthermore, in addition to the friction iinings of the clutch the associated actuators and release bearing are placed under stress and subject to wear. [14] With this as background, there are already some designs for shtfting an unsynchronized transmission during vehicle travel with the clutch engaged. In this case it is necessary—at the notational speed of the transmission output shaft defined by the vehicle's emising speed—to relatively accurately adjust the rotational speed of the transmission drive shaft and/or of the output shaft of the drive engine connected to and rotating with the Output drive shaft via the engaged clutch, to the rotational speed necessary for the synchronization. [15] Provided this synchronization occurs by means of engine rotational speed within a reasonable time, this requtres comparatively complicated and precise engine control. The adjusted rotational speed in this case is initially dependent on the power applied by the drive engine to the pistons, and this power is, in turn, dependent on such numerous factors as the amount of fuel injected, the fuel-air ratio, the ignition angle and also on individually different engine properties within an engine serles, and on other factors as well. [16] For a determination of the engine power that is available for propulsion of the input shaft of the transmission, the engine power applied to the pistons has to be reduced, for example, by internal friction losses, which in tum are dependent not only on the particular amount of wear on the components of the drive engine and the transmission, but also change in the short term, for example, with the temperature and viscosity of the transmission- and engine eil. [17] Furthermore, It must be taken into account that adjustrneni of the synchronization speed takes place mih the gear disengaged, that is, in the neutral Position of the transmission, Owing to the very steep progression of a power- rotational speed curve in this operating State of the drive engine, even smail changes in input power or in drag torques counteracting the drive power result in considerable differences in rotational speed, so that, for example, a change in the power consumption of a generator or of an air condrttoning system can have short- term, tangible effects on the progression of adjusting the rotational speed. This control ränge of the drive engine is nonetheless satisfactorily mastered by an engine control in many cases. [18] Furthermore, adjusting a synchronous rotational speed involves a highly dynamic process in which the mass inertia of the rriasses to be acceterated or decelerated likewise piays a significant role. Whereas the masses to be accelerated or decelerated are known rather accurateiy and in general change very slowly, for example, with increasing wear on the clutch linings, it must Hirther be taken into account that the synchronization rotational speed during the shrfting process can likewise change on the transmission input side. As soon as the traction power of the engine can no longer be transferred to the driven wheels because the gear, previously engaged in the transmission, is disengaged and the transmission is thus in the neutral position, the speed of the vehicle changes according to the applied forces which depends on the inclination of the surface on which the vehide is located, the vehicle weight, roll resistance caused by vehicle components and road surface roughness, air resistance, and the speed and direction of incidentairas well as other factors. These factors are of course not within the ability of the engine control to ameliorate and must therefore be detected separately and passed to the engine control as a synchronous rotational speed needed at present or in the future. [19] For the decision whether a gear shift should be performed without disengaging the clutch and for sufficiently accurateiy setting a synchronous rotational speed, the interplay of these and other factors has to ultimately be estimated, It must be taken into account that the advantages attainable by a shifting process without disengaging of the clutch are largely based on a reduction in the wear. [20] Of course, it is sufficient in the simplest case to determine the desired synchronous rotationa! speed of the transmissicn input shaft by the rather easiiy measured rotational speed of the transmission output shaft and the transiation known by the target gear, and also to influence the output shaft of the drive engine in the desired direction by means of a controi loop. But a procedur© of this kind often leads to disproportionateiy long shift times or an undeslrable, imprecisely adjusted synchronous rotational speed during highly fluctuating vehicle operating conditions, Finally, it should be noted that there are shifting processes which cannot be, or, in any event, cannot advantageously be implemented without disengaging the dutch. Among these are not only start up processes, but also shift processes which would require, forexampie, a rotational speed ofthe drive engine belowthe normal (die rotational speed or even below the possible idie rotational speed. A shifting process of this kind can be desirable, for instance, v/hen a vehicle is moving downhill and the driver wants only a very small effect of the engine brake or in anticipation of an acceieration of the vehicle on steep inclines, when the driver wants to select a gear that will briefly cause engine Operation at or below the lower rotational speed limit, but will be at an appropriat© driving gear within a few seconds based on vehicle acceieration. [22] From DE 102 49 951 A1 a method to controi a drive train is already known in which a gear shift is nnade possible by taking into account a plurality of different factors, but without disengaging the clutch. In this regard, for each gear shift a decision Is made, whether the gear shift is to be perfonned with clutch engaged or disengaged. Provided that an analysis shows a gear shift is possible with the clutch engaged, the gear shift will also be carried out with the clutch engaged. [23] It is proposed in this regard to seiect and/or analyze the mode of gear shift based on a plurality of vehicle parameters and operating characteristics. !t should be stressed that the danger that the seiection of the nnode of gear shift will result in a wrong result is particularly low with this method. On the one hand, this is due to an extremeiy cotnplicated process sequence, both with respect to the needed computational power of an electronic transnnission controi unit, and also due to the needed sensors, and, on the other hand, because a gear shift with an engaged dutch can only be carried out when the determination method vvili predict a smooth shift with a high degree of reliabiiity. [24] For example, according to one basic variant of the method disciosed in DE 102 46 951 A1, shifting with the dutch engaged is not used when one of the involved components or its sensors happens to be malfunctioning. Du© to the mentioned large number of factors and components to be taken into account, this means in practice a significant reduction in the average availability of the System. Furthermore, after the initial start of the vehicle and afler a restart, very restrictive rules are set for aüowing a shift process with the dutch engaged, in order thus to compensate for the uncertainty regarding as yet insufficiently known current and critical influence paranfieters. [25] The security against a wrongly permitted shifting process with an engaged dutch is greatly increased, when even snnail uncertainties are detected with regard to the feasibility, the system is switched to a shifting mode with disengaged ciutch. The advantages of shifting with the ciutch engaged can thus not be realised in many cases in which they would be usefui in practice, for reasons considered in this known procedure. It is thereby important that the deoision about the mode of gear shifting (with an engaged ciutch or a disengaged ciutch) is always made before Initiation of the shift procedure. [26] Accordingly, the envistoned procedura is not able, at ieast in sonne cases, to guarantee the claimed certainty of the shifl mode decision. To be considered thereby is the daily major change of loading in commerciat vehicies and thus the Overall vehicle weight, such that after restarting the drive motor a shift with an engaged ciutch can be omitted until the basic influence factors, like, for example, the Overall vehicle weight, can be determined to a sufficiently accurate extent or can be estimated. Now, however, shutting off the drive motor is not urgently necessary for a basic change of load and is more the exception than the ruie with, for example, construction s'rte vehicies like dump trucks and cement mixers, certain tanker vehicies, but also with passenger vehicies, like school and tour buses. [27] in order to eliminate at Ieast in part the described disadvantages shown in DE 102 49 951 AI, an improvement of this process is, as proposed in the invention, to less strlngently formulate the requirements for enabling a shift procedure with an angaged clutch and thereby, with a decision made for a gsar change with an engaged clutch, to also consider the parttal step of disengaging the previously engaged gear to check the appropriateness of the decision. [28] in fact it is assumed that, If a wrong decision is made about the mode of gear shifting, the transmission cannot be placed into an essentially torque-fre© State, so that disengagement of the engaged gear Is possible at low shifting force within a default period of time. [29] Thus in the event of a decision made for a gear shift with an engaged clutch, a time limitation is introduced for disengagement of the engaged gear, and, if this time is exceeded, it is assumed that the necessary prerequisites for the process of engagement of the target gear with an engaged clutch have not been satlsfied. In this case, the shifting process will be terminated and will begin anew in a shifting mode with a disengaged clutch, or the system will switch to this mode. [0030} Thus the additional advantage of this improvement to the known method is that a shifting process already initiated can still be terminated at a relativeiy late point in time. It should be recalied, however, that the requirementg of accuracy of the engine control for the disengagement of a gear are much looser than for the successfui engagementof a gear. SuccessfuI disengagement ofa gear thus cannot be judged as a dependable sign that the subsequent engagement of a gear with an engaged clutch will be successfui or desirable. [0031] Furthermore, the requirements for a shifting process with an engaged clutch differ from gear to gear, and, for example, as a function of the driving speed and of the loading and other operating oarameters of the motor vehicle and on its environment. This is to be taken into account according to DE 102 49 951 AI, in that the threshold time until termination of the attempted gear shift with an engaged clutch is varied depending on parameters of this type, which in tum increases the complexity of the method and thus either increases its susceptibility to wrong decisions or considerably increases the needed safety margin to ensure a still advantageously implemented shifting process with an engaged clutch. [0032] [33] With this as background, the object of the invention is designing a method for performing agearshiftof an □utomatictransmission of a motor vehicle, when driving with or without utilization of a ciutch, which offers a higher reliability with r&duced expense in comparison to the known method and which can also mak® reliable predictions about the usefulness of a gear shift with an engaged ciutch—hereinafler calied briefly clutchless ahiftlng—even aftera change in vehicle Vi^eight and with the drive engine running. The attainment of the object can be seen in the features of the main claim, whiie favorable embodiments and refinements of the invention are indicated in the dependent Claims. [35] The invention is based on the knowledge that the reliability of a decision made about the advantage of clutchless shifting can be improved whsn the decision about the shifting mode—that is, a clutchless engagement of a gear or engagement of a gear with a disengaged ciutch—is niade at a later point in time of the shifting process. In particular, the invention is based on the knowledge that the decision- relevant overali effect of a plurality of factors—difficultto measure based on the prior art—can be determined by simple means and with increased reliability, as soon as the automatic transmisston is in its neutral position v^ith a disengaged gear. [36] Ultimately, the decision about the shifting mode to be used, that is, about clutchless shifting or gear engagement or disengaged ciutch shifting or gear engagement, is not based on the magnitude of the individual, named factors, but rather on the effects on the rotational speed essential to shifting which arise from the sum of factors. that is. In particular the rotational speeds of the transmission elements to be coupied so as to rotate together by a fonn-locked connecüon. [37] After disengagement of the previously engaged gear, by simple sensing of the rotational speed of the transmission Output shaft—or of a parameter in a sufficiently fixed relationship thereto, such as the driving speed or a rotational speed of another transmission element force-coupied thereto—and of the time change of this rotational speed, it can be determined precisely, reliably and at low cost whether and how the vehicle's driving speed and thus the synchronous rotational speed will change. [42] The mentioned definite, basic canditions require a more precise expianation here; They are to be understood such that the data actuaily present in tha concrete embodiment are evaluated in whole or in part to determine whether the implementation of the shifting process appears feasible with an ehgaged dutch, basically at a probability to be estimated or determined by a tedinician with ordinary skill in the art. [43] This is to be understood such that in those cases where the successfui implementation of a gear shift with closed clutch is precluded in advanoe at a sufficiently high probability, an opening of the clutch will be preferred at an earlier point in time and an otherwise necessary check of the rotationa! sp&ed and of the Speed change of the transmission Output shaft in this case can preferably be omitted, but could also be carried out based on other evaluation criteria, if necessary. The mentioned sufficiently high probability in tum is to be established in an individual case by a person having ordinary skill according to the transmission or drive train factors. [00441 It basically will not be desirabie to begin the shifting process first with an engaged clutch, for example, in those cases in which-proceeding from the instantaneous rotational speed of the transmission input shaft (or e.g. from the driving speed in combination with the known translation of the starting gear) on the one hand, and the known target gear on the other hand-it seems certain, that the drive engine cannot reach the rotational speed needed for a clutchless shifting process or cannot attain it within a desired period of time, or only under undesirable accompanying phenomena [0045] In any event, it can oniy be determined precisely in the specific, actuat case where the lower rotational speed limit of the drive engine should be. Also, it depends on the individual case and/or on the drive train, whether a constant rotational speed limit should be taken into account or whether the decision device has access to additional relevant Information, such as the engine oil temperature, the instantaneous electrical power consumption of the system, or the Operation of an air-conditioning unit. In these cases it would be usefui to specify the lower rotational speed limit under cxinsideration of these or other, or, as the case may be, additional parameters on a dynamic basis. [0046] On the other hand, the specialist with knowledge of the invention can also decide based on restrictions related to available program memor>' or the data processing capacity cfthe decision devicethat he intends io dispense with, in whole or in part, an ana!ysis of the basic conditions in the actual embodiment. In an extreme case, the definite, basIc conditions for the decision device to disengage the starting gear without disengaging the ciutch could thus also exist only after an analysls of whether the vehicle Is stationary or whether at the tinrte of shift. intent, a gear is engaged and the ciutch is engaged. [00471 It is essential to the inventive meihod that the decision device, at least where it has initiated disengagement of a starting gear without disengaging the ciutch, subsequently reads in data about ttie size and the progression of a quantity closely correiatlng with the rotationai speed of an Output shaft of the automatic transmission, and at ieast with inclusion of this data determines the shifting mode for the engagement of the target gear. [48] Now the data about the size and the progression of a value closely correiating with the rotationai speed of an Output shaft of the autonriatic transmission, as mentioned, can be the rotationai speed ofa vehicle wheel, the driving speed of the vehicle or the rotationai speed of another rotating part whose speed ratio is related to the rotationai speed of the transmission input shaft in a manner sufficientiy well- known for the present purpose. [49] From this l