Method for controlling a powershift transmission

Abstract

A method for shifting a powershift transmission for a motor vehicle, which has at least two clutch units whose transmission torque can be variably controlled, characterized in that a tractive force potential (Z*) can be generated by controlling the clutch units (K1, K2) involved in a shifting operation, by means of which a torque increase or reduction can be effected compared to a torque curve perceived as uniformly accelerating or decelerating, namely that during the time period of the shifting operation in which both clutch units (K1, K2) are active, a level of the output torque (MAB), namely by preloading the two clutch units (K1, K2) against each other, a preload torque (M*) is generated at a selectable lower or higher level than the output torque (MABbefore) before the shift, wherein this is an upshift under load.wherein a shift cycle period extends from t0 to t4, wherein when upshifting is selected a target gear is first selected at t0 and pressure is applied to an engaging clutch unit (K2), wherein due to the rapid increase of the clutch torque (MKup) of the engaging clutch unit (K2) the resulting pressure of this engaging clutch (K2) at t1 corresponds to a clutch capacity which lies between a value of the single and the double clutch capacity (MK1) of the disengaged clutch unit (K1), wherein after a predetermined time t2 or other conditions, such as falling below a predetermined speed threshold, the disengaged clutch unit (K1) is opened, wherein the disengaged clutch unit (K1) has completely transitioned into the open state at t3, wherein with unchanged pressure of the engaging clutch unit (K2) a tractive force surplus (ΔZ) arises,as long as the engine speed (nMot) is above the target speed (nZ) of the upshift, whereby with the opening of the clutch unit to be deactivated (K1) the pressure of the clutch unit to be engaged (K2) is reduced and thus any tractive force excess (ΔZ) can be set, which can be effective until the target speed (nZ) is reached at t4, whereby this tractive force excess (ΔZ) forms a tractive force potential (Z*) acting on the wheels, which is higher or lower than the normal engine torque.

Description

The invention relates to a method for controlling a powershift transmission according to the preamble of claim 1, 2, 3 or 9.In general, fluid- or electromechanically actuated clutch units are used in powershift transmissions. In such transmissions, during the transition from one transmission stage to the other, a more or less marked change in the torque transmission inevitably occurs due to the transmission step. This generally leads to oscillations in which the mass inertia assigned to the transmission and drive motor, on the one hand, works against the mass inertia moment of the drive train-essentially of the drive wheels-the transmission elements twisting according to their spring rates and acting as a torsion spring. The kinetic energy stored thereby acts on the clutch being engaged and disengaged. The consequence of this relationship is a highly undesirable jerk movement which, depending on the load case, has a tendency to swing open in a differently pronounced manner. In particular in the case of four-wheel-driven vehicles, the nominally almost twice increased mass moment of inertia of the drive train arranged downstream of the powershift transmission has a great influence on the driving comfort. Load shifting is generally referred to when an upshift is under traction or under overrun.Various methods have become known to solve the problems. DE 101 40 746 A1 proposes a method with which the gear change is carried out in accordance with characteristic maps specific to the application or in accordance with shift sequences defined as a sports, winter, eco, mountain or manual program. According to this teaching, an index is determined which corresponds to a shift program selected by the driver or determined by the transmission control. On the basis of the characteristic number, minimum and maximum values of the shift parameters are determined in each case as a function of the detected driving parameters and, on the basis of the selected or determined characteristic numbers, a shift parameter which is current as an intermediate value between the minimum and maximum values of the shift parameters which are dependent on the characteristic number is determined, on the basis of which the shift operation is then carried out.Furthermore, regions of inconsistent transitions are defined, excluding those shift parameters which excite the vehicle to jerk oscillations during the shift operation. According to DE 101 40 746 A1, therefore, a consistent, i.e., uniformly transmitting, fluctuation-free transmission of the engine torque with respect to the torque is sought, wherein merely a shortening of the gear change processes is considered to be sporting driving. The driving parameters used include, among other things, the vehicle acceleration and the inclination of the vehicle of this method. Even if the need to create characteristic maps which are dependent on a large number of driving parameters and whose characteristic curves have to be stored as nodes for access by the program control of the transmission control is dispensed with, a large number of sensors are nevertheless involved overall, which require processing in a correspondingly signal-technical and thus complicated manner. Moreover, inconsistent transitions are unavoidable in practice due to a wide variety of driving conditions.The requirement for rapid gear changing processes is based on the fact that transmissions of the generic type have hitherto had a longer response time than is the case with manually shifted transmissions. Sports oriented drivers therefore always provided the manually shifted transmissions.This circumstance has been taken up in WO 2003 / 038 315 A1 and a method for shift control of a powershift transmission of the generic type has been proposed, in which a fast, i.e. very sportally considered, execution of the desired shift is aimed at.In addition, in the case of a manually triggered load shift, the clutch unit to be engaged is filled with an increased pressure. The filling pressure is in this case of the order of magnitude of the clutch capacity of the outgoing clutch unit, i.e. of the clutch unit to be deactivated. The filling end is determined by reaching a specific filling pressure and the walking clutch unit is opened when the filling end is sensed. Due to the very short shift cycle time, a short transmission of the engine torque comparable to a manual shift and largely fluid with respect to the torque transmission is realized, wherein shift cycles can be achieved which correspond approximately to manually shifted transmissions.In contrast to manually shifted transmissions, in which the selection does not require a sequential through-shifting, this is expedient in powershift transmissions for the sufficiently rapid, providing activation of the possible clutch units. For this purpose, DE 103 21 281 A1 proposes a control method as a rapid subsequent shift for improving the shifting speed and the shifting comfort of an automatic transmission of the type in question, in which both the next descending or ascending gear following it with respect to the transmission step and the next but one descending or ascending gear following it are subjected to a pre-activation, wherein the clutch unit to be disengaged is already pressure-free when the driver executes the possible shifting request.DE 43 15 598 A1 discloses or describes a control and regulation method, wherein the output torque is to be kept as constant as possible in its value during the shifting process. A harmonic speed profile of the output torque can essentially also be reached during the shift. For the occupants of a vehicle equipped in this manner, only a barely perceptible jerk takes place during the shifting process. With the aid of torque measurement values, comfort-optimized control parameters for the further engagement and passivation of the brakes and clutches are determined during the shifting process. The control pressure of the clutch of the previous gear to be disengaged is decreased stepwise over the complete shifting process.According to DE 199 28 674 A1, shifting comfort is significantly increased by realizing an overlapping shift of the clutches for an automatic transmission. The output torque remains essentially always constant. An increase in the actuating pressure of the clutch to be engaged takes place according to a shifting ramp.The development of all automatic transmissions has so far been based on the consideration that, on the one hand, as uniform as possible an engine torque transmission is perceived as comfortable as a "perfect" gear change and, on the other hand, as quick as possible a gear change of the clutch stages is perceived as sporting. However, this progress is felt by some persons to be "long-lasting" and "emotionally".It is therefore an object of the invention to provide a method which, in a powershift transmission of the type in question, enables a fast shift on the one hand and on the other hand a driving-dynamically authentic living driving impression. Furthermore, the method should be suitable equally for comfortable low-load gearshifts and also for sport gearshifts. In addition, the driver should be able to perceive his action controlling the vehicle as the desired driving dynamics feedback without performance losses. A further object is to simplify the control or the parameters to be processed by it.The aforementioned object is achieved by the features of claims 1, 2, 3 or 9. In the respective method for shifting a powershift transmission-in particular for use in a motor vehicle-which has at least two clutch units each of which can be variably controlled in terms of their transmission torque-it is advantageous that a tractive force potential can be generated by controlling the clutch units involved in a shifting operation, as a result of which a torque increase or reduction can be effected compared to a torque profile which is perceived as uniformly dynamically accelerated or braked in terms of driving. By generating a tractive force potential, there is variable driving status of a driver's life living in dynamic driving. In addition, starting from a traction upshift, the pressure of the clutch to be engaged can advantageously be controlled in such a way that the time required to overcome the clearance of the clutch unit to be engaged is small and that the output torque after the clutch plates have been applied, that is to say the ready-to-take-over of the clutch unit to be engaged, is optionally below the stationary output torque or above the stationary output torque. Furthermore, a universal use is possible by the respective method, since all shift states can be mapped from comfortable to very sporting both with constant applied motor torque and with changing motor torque. This allows the modular use of the method for powershift transmissions of different power classes. In this respect, a large economic potential in the sense of cost optimization is thereby reduced.According to an advantageous embodiment, a function value, which embodies the clutch capacity of the clutch unit to be engaged and is derived from a function of a relative output torque with respect to a relative clutch torque of the clutch unit to be engaged, is assigned to the tractive force potential as a classification parameter.According to a further feature, the traction potential exceeds the motor torque in terms of amount during the shift.According to a further advantageous feature, the function of the classification parameter representing the clutch capacity of the clutch unit to be engaged, formed from relative output torque and relative clutch torque, has a branch having a negative gradient lying below the engine torque and a branch with a positive gradient adjoining the branch. As the relative clutch torque increases, the positive gradient branch preferably increases beyond the engine torque.According to a further feature, the function corner values of the relative clutch torque of the clutch unit to be engaged are defined for controlling the clutch units to be engaged and disengaged as a function of a predetermined gear jump. If--assuming that the clutch to be disengaged is the steady-state torque of the engine (M Ab= M Mot) - the output torque after the clutch plates are applied corresponds to the output torque after the upshift ends, the desired capacity of the clutch to be engaged should be calculated as follows:In this case, the output torque falls from the opening after the closing of the clutch to be engagedIf the output torque M Ab after the clutch plates of the clutch unit to be engaged are to be applied equal to the drive torque before the initiation of the shift, then the clutch torque of the clutch to be engaged is determined as follows:If the capacity of the clutch to be engaged lies between these values, then a torque is produced at the output during the shift, which torque lies between the output torque before the shift and the output torque after the shift.By way of example, the following applies for the case of a gear jump of 1.5:At a relative clutch torque equal to 0 or equal to 3, the relative output torque is equal to the engine torque.At a relative clutch torque in a range of 0 to 3, the relative output torque is less than 1.At a relative clutch torque in a range greater than 3, the relative output torque is greater than 1.Preferably, the relative clutch torque of the clutch unit to be engaged here does not exceed the engine torque up to a value of 3--in particular in the case of a powershift transmission with a comfortable low-load upshift--the relative output torque.The features set forth are generally suitable for powershift transmissions in which two or more clutch stages are simultaneously operatively connected to one another during the shifting process. Thus, in addition to hydraulically controlled coupling elements, in particular also coupling elements which have electromagnetically, electromechanically or pneumatically controlled coupling elements. The clutch units must of course always be designed in such a way that they reliably meet the requirements with respect to the clutch capacity.The method can also be used for controlling a powershift transmission for a motor vehicle with wet clutches, which has at least two clutch units that can be connected and disconnected, controlled by slip, each with an associated clutch capacity. In a conventional manner, during a shifting process, the clutch unit to be engaged is closed in temporal overlapping and the clutch unit to be disengaged is opened, as a result of which, after the shifting process, a drive torque provided by a drive unit is present, corresponding to the transmission ratio of the clutch unit to be engaged into a converted drive torque.The torque to be coupled by the clutch unit to be engaged is adjustable as a function of the engine torque and the clutch capacity of the clutch unit to be disengaged or / and of the clutch unit to be engaged in such a way that during the time interval of the shifting process in which both clutch units are active, the level of the output torque is at a preselectable, equal, lower or higher level than before the shifting process. This is preferably effected by temporary bracing of the load-bearing coupling units against one another.According to a further design feature, a relative output torque related to the engine torque is used for the setting of the clutch unit to be engaged. Preferably, the clutch capacity of the clutch unit to be disengaged is equal to the output motor torque.A further advantageous embodiment results if the relative output torque is related to a relative clutch torque of the connected clutch unit for the purpose of forming a classification parameter.The classification parameter preferably acts as a basis for the dimensioning for the pressure profiles of both the clutch units to be deactivated and the clutch units to be activated.The interaction of the clutch elements involved in the shift takes place independently of the means of their actuation in such a way that the acceleration or deceleration proceeds in a driving-dynamic manner as a shift action which becomes clearly perceptible.If the classification parameter is less than 1, a portion of the engine torque is supplied to the engaged clutch unit after the clutch plates have been applied, whereby a portion of the engine torque is transmitted via the transmission ratio of the clutch unit to be engaged. The range between 0 and 1 is used in the event of an overlap by increasing the capacity of the clutch to be engaged from 0 to 1. It is advantageous that, with a value of the classification parameter of equal to 1 after the load activation has taken place, the entire engine torque is transmitted via the engaged clutch, wherein the clutch to be disengaged is torque-free. As soon as the clutch to be disengaged is torque-free, it can be opened. The speed can be adjusted via the clutch to be engaged.In the case of a value of the classification parameter between 1 and 2, the resulting torque direction of the clutch unit to be disengaged is such that the torque direction of rotation of the clutch unit to be disengaged reverses until the torque of the engaged clutch unit corresponds to the sum of the output engine torque and the torque of the clutch to be disengaged. In this case, the output torque is caused to decrease. This range can be used according to the invention to generate feedback for the driver by the reduction of the output torque.If the classification parameter is between 2 and 2.5, if the torque supported by the clutch capacity of the clutch unit to be disengaged is exceeded, a portion of the energy lost in the clutch unit to be disengaged is compensated by the energy which can be obtained from the mass inertia moment of the engine by the change in speed. The clutch to be disengaged must necessarily be open until the engine speed has reached the speed level after the shift, because after this point dynamic torque can no longer be generated from the engine speed change. In this case, an output torque is established which lies between the output torque before and after the upshift, which brings about a comfortable, smooth shift.Further advantages and features will become apparent from the following description of the invention using the example of a powershift clutch with wet clutch plates in conjunction with the schematically illustrated drawing.The following are shown: FIG. 1 is a graph of the relative output torque as a function of the clutch capacity of the clutch engaged, FIGS. 2a-2c are diagrams of the time-dependent torque curve of an upshift according to the method of the invention in the case of a relative clutch torque in the range 1 to 2 and the corresponding speed curve, FIGS. 3a-3c are diagrams of the time-dependent torque curve of an upshift according to the method of the invention with a relative clutch torque in the range 2 to 2.5 and the corresponding speed curve, FIGS. 4a-4c show diagrams of the time-dependent torque curve of an upshift according to the method with a relative clutch torque in the range 2.5 to 3 and the corresponding speed curve, and FIGS. 5a-5c show the time-dependent torque curve of an upshift according to the method of the invention at a relative clutch torque in the range above 3 and the corresponding speed curve.FIG. 1 illustrates the graph of a relative output torque M rel as a function of the relative clutch torque MK rel of the clutch unit connected. In the diagram, the relative output torque M rel plotted on the ordinate, with respect to the engine torque M Mot under the boundary condition that the clutch capacity MK 1 of the clutch unit K 1 to be disengaged is equal to the output engine torque M Mot as a function of the relative clutch torque MK rel of the clutch unit K 2 plotted on the abscissa. Here, the solid line at 1 corresponds to the output torque M Abvor before the shift, the dot-dash line corresponds to the output torque M rel during the shift, and the dashed line corresponds to the output torque M Abnach after the shift. All torques are related to the motor torque M Mot during the shift. A relative output torque M rel of 1 means that the relative clutch torque MK rel is equal to the engine torque M Mot. In the example, the transmission ratio i Gang of the old gear is 1. At a gear jump of 1.5, a relative output torque of 1 / 1.5, i.e. a transmission ratio of 0.666, results after the shift has been completed.If the relative clutch torque MK rel lies between 0 and 1, the output torque M Ab falls after the clutch plates of the clutch unit K 2 to be engaged, because a portion of the engine torque M Mot is already transmitted via the engaged clutch unit K 2 on account of the transmission ratio of the higher gear i Gang+1. At a relative clutch torque MK rel of 1, the entire engine torque M Mot is transmitted via the connected clutch unit K 2 and the clutch unit K 1 to be disconnected is then torque-free.With a relative clutch torque MK rel between 1 and 2, the torque direction of the clutch unit K 1 to be deactivated reverses. The output torque M Ab decreases until the torque of the clutch unit K 2 which is switched on corresponds to the sum of the output engine torque M Mot and the torque of the outgoing clutch unit K 1.If the relative clutch torque MK rel is above 2, the torque exceeds the clutch capacity MK 1 which is supported via the clutch unit K 1 to be deactivated. The clutch unit K 1 to be disengaged therefore begins to slip and the engine speed n Mot decreases. From the energy which can be obtained from the mass inertia moment of the engine by the change in speed, a part of the energy lost in the clutch unit K 1 to be deactivated can be compensated.The resulting output torque M Ab is lower than the output torque which is present after the shift in the new gear below a relative clutch torque MK rel of 2.5.In the event that the relative clutch torque MK rel is between 2.5 and 3, an output torque M Ab can be set which is between the torque before the shift and that after the shift, so that the relative output torque M Ab moves relative to one another between the torque level before the shift (relative output torque=1) and the torque level after the shift (relative output torque=1 / gear jump) during the bracing of both clutches.Above a relative clutch torque MK rel of 3, the output torque M Ab is greater than the output torque before the upshift. Until the engine speed has entered the higher speed speed, an output torque increase can be achieved for a finite time. As soon as the engine speed n Mot has entered the target speed n Z for the higher gear i Gang+1 the clutch unit K 1 to be deactivated must be torque-free, since otherwise a strong reduction in output torque occurs.A classification parameter KP is derived from the clutch capacity MK 2 of the clutch unit K 2 to be engaged with respect to the relative clutch torque MK rel and is used as a control variable of the time sequence of engagement and disengagement of the outgoing and coming clutch elements K 1, K 2.The classification parameter represents a variable of the engine torque M Mot obtained temporally via the shift process by sensing and standardization and of the torque present at the transmission output.Intentionally, a more or less large internal stress is deliberately brought about in order to achieve an effect in which the torque transmission takes place either smoothly or a switching pulse appropriate to the switching action can be perceived as desired. The internal clamping of the clutch elements K 1 and K 2 provides a traction force potential depending on the gear ratio jump, which traction force potential permits driving dynamics which promote driver life in an optimum manner, in accordance with the gear ratio i Gang to i Gang+1 and the driving situation. In this case, the desired driving situation can also be included by sensing a pedal position of the accelerator pedal that changes by the driver.In the following figures, traction upshifts are shown by way of example for transmissions with wet multiplate clutches. This means that, in order to close the clutch to be engaged, an oil volume must be introduced into the pressure chamber of the clutch until the clutch plates lie against one another and the clutch can transmit a torque.FIG. 2 depicts the range of the classification parameter KP in the range from 1 to 2, FIG. 2a showing the speed curve of the engine speed n Mot, FIG. 2b showing the clutch torque M Kup and FIG. 2c showing the output torque M ab. The period of the switching cycle extends from t 0 to t 4. When an upshift is selected, the target gear is first selected at t 0 and a pressurization of the clutch unit K 2 to be engaged is triggered. Since it is an upshift under load, the engine speed n Mot increases still further. In the further course, a rapid increase of the clutch torque M Kup occurs in the clutch unit K 2. to be engaged. At t 1 the resulting clutch K 2 pressure corresponds to a clutch capacity that is between one value of the single and the double clutch capacity MK 4 of the clutch unit K 1 to be disengaged. When the filling of the clutch unit to be engaged is finished at t 1 the output torque M ab decreases due to the internal clamping to a value which depends on the ratio of the clutch torques MK 1, MK 2 and the gear change. After a predetermined time t 2 or other conditions, such as the speed threshold being undershot, the clutch element K 2 to be disengaged is opened, wherein the clutch element K has completely changed to the open state at t 3 and now no longer transmits torque in a unloaded manner. If the pressure of the clutch unit K 2 to be engaged remains unchanged, an excess of tractive force ΔZ occurs as long as the engine speed n Mot is above the target speed n Z of the upshift. If, with the opening of the clutch unit K 1 to be disengaged, the pressure of the clutch unit K 2 to be engaged is lowered, an arbitrary tractive force level Z can be set, which can be effective until the target rotational speed n Z is reached at t 4. This traction force excess ΔZ forms a higher or lower traction force potential Z* acting on the wheels compared to the normal engine torque, which traction force potential is shown in the figures as a hatched area.In FIG. 3, the range of the classification parameter KP is depicted in the range from 2 to 2.5. When an upshift is selected, the target gear is first selected at t 0 and a pressurization of the clutch unit K 2 to be engaged is triggered. During the power-on upshift, the engine speed n Mot continues to increase. In the further course, a very rapid increase of the clutch torque M Kup occurs in the clutch unit K 2. to be engaged. At t 1 the resulting pressure of the clutch K 2 to be engaged causes a clutch capacity MK 2 with a value which lies between twice and 2.5 times the clutch capacity MK 4 of the clutch unit K 1 to be disengaged, the engine speed n Mot falling immediately upon reaching t 1. After a predetermined time t 2 or other conditions, such as when a predetermined speed threshold is undershot, the clutch element K 1 to be disengaged is increasingly opened.At t 3 this has completely changed to its inoperative no-load state. Thus, the clutch unit K 1 to be disengaged is now relieved and no longer transmits torque. If, on the other hand, the pressure of the clutch unit K 2 to be engaged is not changed but is still somewhat maintained, an excess of tractive force ΔZ occurs, wherein this first forms a gradient between t 2 and t 3 whose gradient depends on the time interval between t 2 and t 3.As long as the engine speed n Mot is above the target speed n Z of the upshift, the traction surplus ΔZ remains. When the engine speed n Mot reaches the target speed n Z at t 4 the clutch unit K 1 to be disengaged is opened and placed in a no-load state. According to the time when after t 2 the opening of the clutch unit K 1 to be disengaged takes place and thereby the pressure of the clutch unit K 2 to be engaged is lowered again, an arbitrary tractive force level Z can be set. The hatched area in the figure represents the tractive force potential Z* which can be used for the driving dynamic effect.In FIG. 4, the range of the classification parameter is depicted in the range from 2.5 to 3. In this range, a maximum level of comfort can be achieved. In the case of a requested upshift, the target gear is first selected and a pressurization of the clutch unit K 2 to be engaged is triggered. Immediately after the upshift has been requested at t 0 the clutch unit K 2 to be engaged is activated and set to the clutch torque MK 2 wherein the torque level lies above the clutch torque MK 1 of the clutch unit K 1 to be disengaged. From the pressure curve of the clutch unit K 2 to be engaged, it can be seen that at the time t 1 the filling of the clutch unit K 2 is ended and the clutch plates are in contact. From this time on, the clutch pressure continues to increase load-bearingly. At the same time, the engine speed n Mot is released from the input shaft speed of the clutch K 1. to be disengaged. The output torque M ab at this time corresponds to the engine torque M Mot multiplied by the gear ratio i Gang+1 of the old gear. After opening the clutch unit K 1 to be disengaged at t 2 the speed adjustment can be assisted by engine torque reduction. Alternatively, the lockup may be maintained until the engine speed n Mot reaches the synchronous speed of the new gear.In FIG. 5, the range of the classification parameter KP is depicted above 3. The relative clutch torque MK rel of the clutch unit to be engaged is therefore greater than 3.After engaging the target gear of the upshift at t 0 the clutch unit K 2 to be engaged is pressurized with a pressure which corresponds to a clutch capacity which is above 3 times the clutch capacity of the clutch unit K 1 to be disengaged.When the activation given by the engagement of the clutch plates is completely completed at t 1 the engine speed n Mot is increased downward. The speed drop is caused by the bracing of the two clutches against one another, which causes a pronounced bracing torque M*. The output torque thus increases to a value above the output torque M Ab before the shift. In the time interval t 2 to t 3 the clutch unit K 1 to be disengaged is opened. In either case, a torque-free state of the off-going clutch unit K 1 should be reached before the engine speed n Mot reaches the target speed n Z at t 4. According to the manner in which the pressure of the clutch unit K 2 to be engaged is lowered, any desired tractive force level Z can be set, whereby any tractive force potential Z* that brings about the desired driving dynamic effect can be set.The presented methods allow the time between initiation and complete switching, as is effected by actuating a Tiptronic key, to be minimized. At the same time, the driver experiences a congruent, driving-dynamic, perceptible feedback of the vehicle for his measure of gear change that controls the driving behavior.In addition, the method enables comfortable torque-change-neutral shiftings in the low-load range as well as efficient upshifts in the high-load range.List of reference charactersKP classification parameter K 1 clutch unit K 2 clutch unit MK 1 clutch capacity of clutch unit K 1 MK 2 clutch capacity of clutch unit K 2 M Ab output torque M Abnach output torque after shift M Abvor output torque before shift M rel relative output torque MKrelrelative clutch torque MMotMotordrehmoment Mzudesirive capacity of the clutch unit to be engaged k 2 M* Bracing torque i Gang Transmission ratio of the old gear i Gang+1 Transmission ratio of the higher gear n Mot Engine speed n Z Target speed at the end of the shift cycle ΔZ Tractive force excess Z Tractive force level t Time t 0 Start of filling of K2 (start of the shift operation) t 1 End of filling K2 t 2 Start of clutch overlap t 3 End of clutch overlap t 4 End of speed adaptation (end of the shift operation)

Claims

Method for shifting a powershift transmission for a motor vehicle, which has at least two clutch units each of which can be variably controlled in terms of their transmission torque, characterized in that a tractive force potential (Z*) can be generated by controlling the clutch units (K 1, K 2) involved in a shifting process, by means of which tractive force potential an increase or reduction in torque can be effected in comparison with a torque profile perceived as uniformly dynamically accelerated or braked in terms of driving, namely in that during the time interval of the shifting process in which both clutch units (K 1, K 2) are active, a level of the output torque (M AB), namely by the bracing of the two clutch units (K 1, K 2) a bracing torque (M*) against one another at a preselected lower or higher level than the output torque (M ABvor) is generated before the shift, this being an upshift under load, a time period of a shift cycle extending from t 0 to t 4 a target gear being initially selected at t 0 and a pressurization of a clutch unit (K 2) to be engaged being triggered, wherein, due to the rapid increase of the clutch torque (M Kup) of the clutch unit (K 2) to be engaged, the resulting pressure of this clutch (K 2) to be engaged at t 1 corresponds to a clutch capacity which lies between a value of the single and the double clutch capacity (MK 1) of the clutch unit (K 1) to be disengaged, wherein after a predetermined time t 2 or other conditions, such as the dropping below a predetermined rotational speed threshold, the clutch unit (K 1) to be disengaged is opened, wherein the clutch unit (K 1) to be disengaged has completely changed over to the open state at t 3 wherein, with unchanged pressure of the clutch unit (K 2) to be engaged, an excess of tractive force (ΔZ) arises as long as the engine rotational speed (n Mot) is above the target rotational speed (n Z) of the upshift, wherein, with the opening of the clutch unit (K 1) to be disengaged, the pressure of the clutch unit (K 2) to be engaged is lowered and thus an arbitrary excess of tractive force (ΔZ) can be set, which can be effective until the target rotational speed (n Z) at t 4 is reached, wherein this traction excess (ΔZ) forms a traction potential (Z*) which is higher or lower than the normal engine torque acting on the wheels.Method for shifting a powershift transmission for a motor vehicle, which has at least two clutch units each of which can be variably controlled in terms of their transmission torque, characterized in that a tractive force potential (Z*) can be generated by controlling the clutch units (K 1, K 2) involved in a shifting process, by means of which tractive force potential an increase or reduction in torque can be effected in comparison with a torque profile perceived as uniformly dynamically accelerated or braked in terms of driving, namely in that during the time interval of the shifting process in which both clutch units (K 1, K 2) are active, a level of the output torque (M AB), namely by the bracing of the two clutch units (K 1, K 2) a bracing torque (M*) against one another at a preselected lower or higher level than the output torque (M ABvor) is generated before the shift, this being an upshift under load, a time period of a shift cycle extending from t 0 to t 4 a target gear being initially selected at t 0 and a pressurization of a clutch unit (K 2) to be engaged being triggered, wherein, due to the rapid increase of the clutch torque (M Kup) of the clutch unit (K 2) to be engaged, the resulting pressure of the clutch (K 2) to be engaged at t 1 corresponds to a clutch capacity which lies between a value of twice and 2.5 times the clutch capacity (MK 1) of the clutch unit (K 1) to be disengaged, wherein after a predetermined time t 2 or other conditions, such as the dropping below a predetermined rotational speed threshold, the clutch unit (K 1) to be disengaged is opened, wherein the clutch unit (K 1) to be disengaged has completely changed over to the open state at t 3 wherein, with unchanged pressure of the clutch unit (K 2) to be engaged, an excess of tractive force (ΔZ) arises as long as the engine rotational speed (n Mot) is above the target rotational speed (n Z) of the upshift, wherein, with the opening of the clutch unit (K 1) to be disengaged, the pressure of the clutch unit (K 2) to be engaged is lowered and thus an arbitrary excess of tractive force (ΔZ) can be set, which can be effective until the target rotational speed (n Z) at t 4 is reached, wherein this traction excess (ΔZ) forms a traction potential (Z*) which is higher or lower than the normal engine torque acting on the wheels.Method for shifting a powershift transmission for a motor vehicle, which has at least two clutch units each of which can be variably controlled in terms of their transmission torque, characterized in that a tractive force potential (Z*) can be generated by controlling the clutch units (K 1, K 2) involved in a shifting process, by means of which tractive force potential an increase or reduction in torque can be effected in comparison with a torque profile perceived as uniformly dynamically accelerated or braked in terms of driving, namely in that during the time interval of the shifting process in which both clutch units (K 1, K 2) are active, a level of the output torque (M AB), namely by the bracing of the two clutch units (K 1, K 2) a bracing torque (M*) against one another at a preselected lower or higher level than the output torque (M ABvor) is generated before the shift, this being an upshift under load, a time period of a shift cycle extending from t 0 to t 4 a target gear being initially selected at t 0 and a pressurization of a clutch unit (K 2) to be engaged being triggered, wherein, due to the rapid increase of the clutch torque (M Kup) of the clutch unit (K 2) to be engaged, the resulting pressure of the clutch (K 2) to be engaged at t 1 corresponds to a clutch capacity which lies between a value of 2.5 times and 3 times the clutch capacity (MK 1) of the clutch unit (K 1) to be disengaged, wherein after a predetermined time t 2 or other conditions, such as the dropping below a predetermined rotational speed threshold, the clutch unit (K 1) to be disengaged is opened, wherein the clutch unit (K 1) to be disengaged has completely changed over to the open state at t 3 wherein, with unchanged pressure of the clutch unit (K 2) to be engaged, an excess of tractive force (ΔZ) arises as long as the engine rotational speed (n Mot) is above the target rotational speed (n Z) of the upshift, wherein, with the opening of the clutch unit (K 1) to be disengaged, the pressure of the clutch unit (K 2) to be engaged is lowered and thus an arbitrary excess of tractive force (ΔZ) can be set, which can be effective until the target rotational speed (n Z) at t 4 is reached, wherein this traction excess (ΔZ) forms a traction potential (Z*) which is higher or lower than the normal engine torque acting on the wheels.Method according to one of Claims 1 to 3, characterized in that the traction force potential (Z*) is assigned a function value, which represents the clutch capacity (MK 2) of the clutch unit (K 2) to be engaged and is derived from a function of a relative output torque (M rel) with respect to a relative clutch torque (MK rel) of the clutch unit (K 2) to be engaged, as classification parameter (KP).Method according to one of Claims 1 to 4, characterized in that the traction force potential (Z*) exceeds the motor torque (M Mot) in terms of absolute value during the shift.Method according to Claim 4 or Claim 5, characterized in that the function of the classification parameter (KP) which represents the clutch capacity (MK 2) of the clutch unit (K2) to be engaged and which is formed from relative output torque (M rel) and relative clutch torque (MK rel), has a branch (A 1) which is situated below the engine torque (M Mot) and has a subsequent branch (A 2) with a positive gradient.Method according to one of Claims 4 to 6, characterized in that the corner values of the function of the relative clutch torque (MK rel) for controlling the clutch units (K 1, K 2) to be connected and disconnected are defined as a function of a predefined gear step.Method according to Claim 7, characterized - in that the clutch to be disengaged transmits the stationary torque of the engine (M Ab= MMot), - in that the torque of the desired clutch capacity of the clutch to be engaged is determined according to the equation: M Zu = M Ab * ( i gear + 1 + i gear ) / i gear + 1 if the output torque M Ab after application of the clutch to be engaged is to correspond to the output torque after the end of the upshift, where i Gang > i Gang+1 the output torque still falls from M Ab= M Mot* i Gang to M Ab= M Mot* i Gang+1 after the clutch to be engaged has been closed, or the torque of the desired clutch capacity of the clutch to be engaged is determined according to the equation: M Zu=2*M Ab*i Gear / i Gear+1 if the output torque M Ab after the clutch to be engaged is to be equal to the drive torque before the engagement of the shift.Method for controlling a powershift transmission for a motor vehicle, which has at least two clutch units (K 1, K 2) which can be switched on and off and which can be controlled by slip and each have an associated clutch capacity (MK 1, MK 2) wherein, during a shifting process, the clutch unit (K 2) to be switched on is closed in temporal overlap and the clutch unit (K 1) to be switched off is opened and, after the shifting process, a drive torque (M Mot), provided by a drive unit is produced, corresponding to the transmission ratio (i Gang+1) of the clutch unit (K 2) to be engaged into a converted output torque (M Ab) can be provided, characterized in that the torque to be coupled by the clutch unit (K 1, K 2) to be engaged can be adjusted as a function of the engine torque (M Mot) and the clutch capacity (MK 1, MK 2) of the clutch unit (K 1, K 2) to be disengaged and / or the clutch unit (K K to be engaged such that during the time period of the shifting process in which both clutch units are active, the level of the output torque (M Ab), namely a bracing torque (M*), which is produced by the mutual bracing of the clutch units (K 1, K 2) is at a pre-selectable lower or higher level than the output torque (M ABvor) before the shift, this being an upshift under load, wherein a time period of a shift cycle extends from t 0 to t 4 wherein, when the upshift is selected, a target gear is first selected at t 0 and a pressurization of the clutch unit (K 2) to be engaged is triggered, wherein, due to the rapid increase of the clutch torque (M Kup) of the clutch unit (K 2) to be engaged, the resulting pressure of the clutch (K 2) to be engaged at t 1 corresponds to a clutch capacity which lies between a value of one and twice or between a value of twice and 2.5 times or between a value of 2.5 times and 3 times the clutch capacity (MK 1) of the clutch unit (K 1) to be disengaged, wherein after a predetermined time t 2 or other conditions, such as the dropping below a predetermined rotational speed threshold, the clutch unit (K 1) to be disengaged is opened, wherein the clutch unit (K 1) to be disengaged has completely changed over to the open state at t 3 wherein, with unchanged pressure of the clutch unit (K 2) to be engaged, an excess of tractive force (ΔZ) arises as long as the engine rotational speed (n Mot) is above the target rotational speed (n Z) of the upshift, wherein, with the opening of the clutch unit (K 1) to be disengaged, the pressure of the clutch unit (K 2) to be engaged is lowered and thus an arbitrary excess of tractive force (ΔZ) can be set, which can be effective until the target rotational speed (n Z) at t 4 is reached, wherein this traction excess (ΔZ) forms a traction potential (Z*) which is higher or lower than the normal engine torque acting on the wheels.Method according to Claim 9, characterized in that a relative output torque (M rel) relating to the engine torque (M Mot) is used for setting the clutch unit (K 2) to be engaged.Method according to Claim 10, characterized in that the relative output torque (M Ab) is related to a relative clutch torque (MK reı) of the clutch unit (K 2) which is connected in order to form a classification parameter (KP).Method according to Claim 11, characterized in that, in the case of a value of the classification parameter (KP) of between 1 and 2, the resulting torque direction of the clutch unit (K 1) to be disengaged is such that the torque direction of rotation reverses until the torque of the engaged clutch unit corresponds to the sum of the output engine torque and the torque of the clutch to be disengaged.Method according to Claim 11, characterized in that, if the classification parameter (KP) value is between 2 and 2.5, when the torque supported by the clutch capacity of the clutch unit (K 1) to be disengaged is exceeded, some of the energy lost in the clutch unit (K 1) to be disengaged is compensated by the energy which can be obtained from the mass inertia torque of the engine by the change in rotational speed.Method according to Claim 11, characterized in that, if the classification parameter (KP) is between 2.5 and 3, an output torque (M Ab) is set which lies between the torque before the shift and that after the shift.

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