DE102012208155B4 - Method and device for performing a downshift - Google Patents

Abstract

Method for carrying out a downshift of an automatic power-shifting multi-step automatic transmission (3), in which more than one shift element (A, B, C, D, E) between the The input shaft and the output shaft of the automatic transmission (3) are closed simultaneously, with the same shift elements (A, B, C, D, E) being assigned to several gears and with the gear changes being carried out in the form of overlapping shifts in a normal mode, characterized in that in a special mode deviating from the normal mode for a multiple downshift, in which a shift element (B; D) of the current gear (G5, G4; G8) is also assigned to the next and final target gear (G4 to G2; G8 to G4) from of the control unit (6) this common switching element (B; D) is first completely opened and, at the same time or immediately afterwards, a speed specification is started, whereby i the speed specification is initially made to maintain the engine speed (n_M) of the current gear and then to set the engine speed (n_M) theoretically present in the next target gear, while the next target gear is engaged as quickly as possible via the remaining shift elements required, and after reaching the engine speed (n_M) assigned to the final target gear, the common shift element (B) is closed as quickly as possible.

Description

The invention relates to a method for carrying out a downshift process of an automatically power-shifting multi-step automatic transmission in a motor vehicle according to the preamble of claim 1 and an associated device.

For the technical background, refer to the DE 103 21 281 A1 , the DE 10 2005 012 590 A1 and the DE 103 38 624 A1 pointed out.

Automatic power-shifting multi-step automatic transmissions are to be understood in the sense of the invention as all transmissions in which a gear change takes place automatically or automatically and without interrupting the torque transmission between the output shaft of a drive motor (or the transmission input shaft) and the transmission output shaft and which have more than two loads - Have switching elements. These include in particular automatic transmissions with planetary gear sets and an automated starting clutch or converter clutch. In the following, these transmission devices are subsumed under the term automatic transmission.

In known automatic transmissions (in particular multi-step automatic transmissions with planetary gear sets), the gear changes take place in the form of so-called overlapping shifts - also called power shifts. This type of gear change is referred to below as normal mode.

From the DE 10 2006 057 666 A1 a method is known for performing an automated downshift process during vehicle deceleration with the service brake activated at least at times. According to this known method, the braking torque generated by the at least temporarily activated service brake is reduced during the downshift process, the braking torque being reduced as a function of the change in speed of the internal combustion engine or a correlating variable during the torque transmission between the drive unit and the transmission device. This is intended to enable a jerk-free downshift process during a deceleration process, in particular at higher engine speeds.

The invention is based on the object of creating a method for performing automated downshifts in a motor vehicle with an automatic transmission, in which a downshift that is as quick and jerk-free as possible is made possible, especially in the case of multiple downshifts.

According to the invention, the object is achieved by the features of claim 1, while preferred developments of the invention are specified in the subclaims.

• Bei einem Mehrfach-Rückschaltvorgang (Rückschaltungen über mehr als einen Gang), bei dem ein Schaltelement des aktuellen Ganges auch dem (jeweils nächsten sowie vorzugsweise auch dem endgültigen) Zielgang zugeordnet ist, wird von der elektronischen Getriebe-Steuereinheit zunächst dieses gemeinsame Schaltelement vollständig geöffnet und gleichzeitig oder unmittelbar anschließend eine Drehzahlvorgabe vorzugsweise an die elektronische Motor-Steuereinheit eines mit dem Automatikgetriebe zusammenwirkenden Antriebsmotor zunächst zum Halten der Motordrehzahl des aktuellen Ganges und anschließend zum Einstellen der im (jeweils nächsten oder endgültigen) Zielgang theoretisch vorliegenden Motordrehzahl vorgenommen, während über die übrigen jeweils benötigten Schaltelemente der jeweils nächste Zielgang schnellstmöglich eingelegt wird. Bei Erreichen des (endgültigen) Zielganges kann dann ein schnelles Schließen des gemeinsamen Schaltelementes durchgeführt werden, da durch die vorhergegangene Drehzahlvorgabe im Sinne einer Regelung des Motormoments und/oder der Motordrehzahl jeweils zum Erreichen des Motordrehzahlwertes, der im jeweiligen Zielgang zu erwarten ist, ein schlupffreies Schließen des gemeinsamen Schaltelementes möglich ist.

The method according to the invention for carrying out an automated downshift process of an automatic transmission, in which more than one shifting element between the input shaft and the output shaft of the automatic transmission are simultaneously closed by an electronic transmission control unit for engaging a gear, with the same shifting elements being assigned to several gears and in one Normal mode, the gear changes are carried out in the form of overlapping shifts, is characterized by the following features in a special mode that differs from the normal mode:

• In the case of a multiple downshift (downshifts over more than one gear), in which a shift element of the current gear is also assigned to the (next and preferably also the final) target gear, this common shift element is first fully opened by the electronic transmission control unit and at the same time or immediately thereafter, a speed specification is made, preferably to the electronic motor control unit of a drive motor cooperating with the automatic transmission, initially to maintain the motor speed of the current gear and then to set the engine speed theoretically present in the (next or final) target gear, while the remaining ones required shift elements the next target gear is engaged as quickly as possible. When the (final) target gear is reached, the common shifting element can be quickly closed, since the previous speed setting in the sense of regulating the engine torque and / or the engine speed means that the engine speed value that is to be expected in the respective target gear is a slip-free Closing the common switching element is possible.

According to the invention, therefore, a shift element is always selected as the common shift element that is assigned to as many gears one after the other as possible during the multiple downshift process towards smaller gears.

The method according to the invention is used in motor vehicles with a drive unit (drive motor including electronic engine control unit) designed for example as an internal combustion engine or as a hybrid drive (in particular internal combustion engine and electric motor), with a transmission device (automatic transmission including electronic transmission control unit) for carrying out automated Gear changes as well as with controllable shifting elements (so-called transmission clutches or brakes) arranged between the input shaft and the output shaft of the automatic transmission to produce a separation or a connection between the input shaft and the output shaft of the transmission device. A coupling unit between the drive motor (in particular internal combustion engine) and automatic transmission is designed, for example, as an automated separating clutch (in particular multi-plate clutches) or converter clutch.

The invention is used in particular when multiple downshifts are required during driving, in particular due to a braking intervention of the service brake. An intervention of the service brake can take place through the manual actuation of a brake pedal by the driver or on the basis of an automatic brake intervention through a driver assistance system for longitudinal and / or transverse dynamics control.

The implementation of the automatic downshift process according to the invention, as a special mode in contrast to the normal mode according to the prior art, is preferably not always carried out, but only under specified conditions, in particular if the length of the switching time in normal mode when the target gear is reached, the engine speed is below or too close to the Idle speed threatens to lie.

• Betroffen sind Automatikgetriebe in Form von Planetengetrieben, unabhängig davon ob beispielsweise in Kombination mit Wandler, Anfahrkupplung oder als Hybridmodul. Schaltungen mit diesem Getriebetyp werden üblicherweise als sogenannte Lastschaltungen oder Überschneidungsschaltungen ausgeführt, bei denen die Drehmomentübertragung während des Schaltvorgangs von einem abschaltenden auf ein zuschaltendes Schaltelement (Kupplung oder Bremse) übergeben wird, ohne dass der Kraftschluss unterbrochen wird. Aus Komfortgründen können diese Schaltungen nicht beliebig schnell durchgeführt werden. Dies führt bei stärkerem Abbremsen des Fahrzeugs zu Problemen, weil die benötigte Dauer vor allem mehrerer aufeinander folgender Rückschaltungen zum ungewollten Drücken der Motordrehzahl führen kann. Führt dies zu kritischer Unterdrehzahl, so muss für eine Entkopplung des Motors gesorgt werden, was durch Öffnen der Wandlerüberbrückungskupplung, einer eventuell vorhandenen Anfahr- oder Trennkupplung oder auch durch Neutralschalten des Getriebes (Öffnen aller oder einzelner ausgewählter Schaltelemente) geschehen kann. Bei erneuter Lastzugabe in einen dieser teilweise oder vollständig entkoppelten Zustände ergibt sich ein oftmals sehr unangenehmes Wiederanfahr-Verhalten hinsichtlich Response und Komfort, weil das oder die entkoppelnden Elemente in Verbindung mit dem Schalten eines geeigneten Ganges wieder geschlossen werden müssen.

The invention is based on the following considerations, findings and ideas:

• Automatic transmissions in the form of planetary gears are affected, regardless of whether, for example, in combination with a converter, starting clutch or as a hybrid module. Shifts with this type of transmission are usually carried out as so-called power shifts or overlapping shifts, in which the torque transmission is transferred from a disengaging to an engaging shifting element (clutch or brake) during the shifting process without the frictional connection being interrupted. For reasons of convenience, these switching operations cannot be carried out as quickly as desired. This leads to problems when the vehicle is braked harder, because the required duration, especially of several consecutive downshifts, can lead to undesired pressure on the engine speed. If this leads to critical underspeed, the engine must be decoupled, which can be done by opening the converter lock-up clutch, any starting or separating clutch that may be present, or by shifting the gearbox to neutral (opening all or individual selected shift elements). When the load is again added to one of these partially or completely decoupled states, the result is often very unpleasant restart behavior in terms of response and comfort, because the decoupling element or elements must be closed again in connection with the shifting of a suitable gear.

If the switching time required for the power shifts or overlapping shifts described above poses the risk of the engine speed dropping below a desired threshold, then according to the method proposed according to the invention, only one shift element (ideally the shift element which is used in all or most of the cases as (intermediate or end) ) Target gear is engaged, are opened in such a way that sufficient decoupling of engine (drive engine) and output is achieved. In this state, the engine is to be adjusted to the engine speed theoretically present in the current target gear by specifying torque or speed. In this state, the respective target gear should be engaged as quickly as possible via the remaining shifting elements required (with the exception of the one decoupling shifting element). In the ideal case, shifting the shifting elements and synchronous engine speed control results in little or no slip a n the switching element that remains open. As long as the braking continues, the decoupling should remain in order to be able to display the described gear changes, which can be carried out much more quickly, with parallel speed control of the motor. From this state, when the load is added or when the target gear is reached, the open shifting element can be closed directly without the risk of reducing the engine speed or when the braking is released (no slip reduction necessary) and thus a spontaneous restart behavior can be displayed.

• - Gangwechsel können deutlich schneller durchgeführt werden (Entkopplung und unterstützende Motordrehzahlregelung);
• - es kann zu keinem Drehzahldrücken kommen, da eine Entkopplung besteht und der Antriebsmotor mehr oder weniger frei drehend auf Drehzahlniveau des jeweiligen Zielgangs gestellt wird;
• - Ankoppeln bei Lastzugabe kann deutlich schneller und komfortabler dargestellt werden als beispielsweise nach Neutralschaltung oder Öffnen der Wandlerüberbrückungskupplung nach dem Stand der Technik, also ohne erfindungsgemäße Drehzahlvorgabe während geöffnetem gemeinsamen Schaltelement;
• - der Fahrer hat durch die Motordrehzahlregelung auf Zielgangniveau dieselbe Wahrnehmung als würden die Gänge normal mit bestehendem Kraftschluss geschaltet werden.

Advantages of the invention:

• - Gear changes can be carried out much faster (decoupling and supporting engine speed control);
• - There can be no speed pressure, as there is a decoupling and the drive motor is set to the speed level of the respective target gear, rotating more or less freely;
• - Coupling when the load is added can be displayed much faster and more comfortably than, for example, after a neutral shift or opening of the converter lock-up clutch according to the prior art, that is, without speed specification according to the invention while the common shift element is open;
• - Thanks to the engine speed control at the target gear level, the driver has the same perception as if the gears were being shifted normally with an existing frictional connection.

• 1 eine schematische Darstellung der in einem Kraftfahrzeug vorhandenen Komponenten zur Durchführung des erfindungsgemäßen Verfahrens,
• 2 eine tabellarische Darstellung der Zuordnung von Schaltelementen innerhalb eines Automatikgetriebes zum Einlegen der einzelnen Gänge,
• 3 eine vergleichende Gegenüberstellung der sich ergebenden Schaltzeiten bei Rückschaltvorgängen nach dem Stand der Technik (Normalmodus) und nach der Erfindung (Spezialmodus) und
• 4 eine vergleichende Gegenüberstellung der sich ergebenden Schaltzeiten bei Mehrfach-Rückschaltvorgängen mit einer komfortoptimierten Alternative und mit einer schaltzeitminimierten Alternative der Erfindung.

An exemplary embodiment of the invention is shown in the drawing. It shows

• 1 a schematic representation of the components present in a motor vehicle for carrying out the method according to the invention,
• 2 a tabular representation of the assignment of shift elements within an automatic transmission for engaging the individual gears,
• 3 a comparative comparison of the resulting shift times during downshifts according to the prior art (normal mode) and according to the invention (special mode) and
• 4th a comparative comparison of the resulting shift times for multiple downshifts with a comfort-optimized alternative and with a shift-time-minimized alternative of the invention.

In 1 at the top is a motor vehicle schematically 1 shown that has a drive motor 2 , an automatic transmission 3 and, for example, a converter clutch as a coupling unit 4th between drive motor 2 (especially internal combustion engine) and automatic transmission 3 having. The drive motor 2 is an electronic engine control unit 5 and the automatic transmission 3 is an electronic transmission control unit 6th assigned. The two control units 5 and 6th communicate with each other via a CAN data bus, for example, and thus exchange information and commands.

That about the coupling unit 4th with the drive motor 2 cooperating automatic transmission 3 includes the switching elements A. , B. , C. , D. and E. between its input shaft and its output shaft for engaging gears G1 to G8 and GR (reverse gear), which is controlled by the electronic transmission control unit 6th are controllable. Here are the switching elements A. and B. for example, transmission brakes and the shifting elements C. , D. and E. Gear couplings. The electronic control unit 6th contains a program module for carrying out the method according to the invention, there for example an interface to the engine control unit via the CAN data bus 5 to control the engine speed n_M of the drive engine 2 having.

In 2 is a table for an exemplary automatic transmission 3 which shows which of the shift elements in which gear A. , B. , C. , D. and E. are closed (= X). The invention makes use of the fact that the same shifting elements are required for several gears. In the illustrated embodiment, the switching element is in this regard B. particularly relevant for the first five gears G1 to G5. The following exemplary embodiment in accordance with the method according to the invention is based on fifth gear G5 as the current gear before a downshift process.

First, the 3 , above, the normal mode for a multiple downshift G5 => G4, G4 => G3 and G3 => G2 is shown in relation to the clutch torques M_K of the respective shift elements concerned. In parallel, the course of the engine speed n_M of the drive engine resulting from these multiple downshifts becomes 2 shown. These multiple downshifts in normal mode lead to an engine speed pressure below the idle speed n LL and can thus stall the drive engine 2 or to an emergency decoupling (power connection interruption) to prevent the drive motor from stalling 2 to lead. Furthermore, there is a relatively long shift time ts for all necessary downshifts carried out one after the other.

Based on 3 , below, the effect on the curves of the clutch torques M_K and the engine speed n_M in the special mode according to the method according to the invention is shown for comparison. According to the invention, when shifting down from gear G5, the shift element B. of the current gear G5 is also assigned to all further lower target gears G4, G3 and G2, this common shift element in a first step B. fully opened as soon as possible. At the same time, or at least immediately thereafter, the transmission control unit provides a speed specification 6th to the engine control unit 5 started and carried out in such a way that first the engine speed n_M of the (previously engaged) current gear (starting gear) is maintained and then the engine speed n_M of the next and ultimately final target gear in multiple downshifts - here from gear G5 to gear G2 - is regulated . The engine speed n_M of the respective target gear G4, G3 and G2 should be reached before or at least up to the point in time t4, t3 or t2 at which the respective other shifting elements for setting the respective target gear are ready. The specified engine speeds n_M for specifying the speed can be determined from the gear ratio of the target gear and the current vehicle speed.

• Wird ein Rückschaltvorgang über mehrere Gänge -beispielsweise ein G4 zu G2 Gangwechsel - angefordert, kann dies schaltzeitminimiert (Alternative 1) oder komfortoptimiert (Alternative 2) durchgeführt werden. Diese beiden Alternativen werden in 4 gegenübergestellt. Alternative 1 (4, unten) erreicht eine im Vergleich zum Normalmodus nach dem Stand der Technik erheblich reduzierte Schaltzeit ts3, wodurch für den Fahrer jedoch ein deutliches Aufheulen der Motordrehzahl n_M hörbar wäre (siehe strichpunktierte n_M Linie in 3. Gegenüber der Alternative 1 erreicht Alternative 2 (4, oben) zwar auch eine im Vergleich zum Normalmodus nach dem Stand der Technik reduzierte Schaltzeit ts2, die jedoch größer als ts3 ist. Durch die Alternative 2 wird trotz Schaltzeitreduzierung jedoch eine bessere und gewohntere Aktustik erreicht. Die Alternative 1 kann genutzt werden, wenn selbst die Alternative 2 zu langsam ist und somit zu Drehzahldrücken im Zielgang führen würde.

Another embodiment is based on 4th explained:

• If a downshift over several gears - for example a G4 to G2 gear change - is requested, this can be done with a minimum shift time (alternative 1 ) or comfort-optimized (alternative 2 ) be performed. These two alternatives are used in 4th juxtaposed. alternative 1 ( 4th , below) achieves a switching time ts3 that is significantly reduced compared to the normal mode according to the prior art, whereby the driver would, however, hear a clear howling of the engine speed n_M (see dash-dotted line n_M in 3 . Compared to the alternative 1 reached alternative 2 ( 4th , above) also a switching time ts2 which is reduced compared to the normal mode according to the prior art, but which is greater than ts3. With the alternative 2 However, better and more familiar acoustics are achieved despite the reduction in switching times. The alternative 1 can be used if even the alternative 2 is too slow and would therefore lead to speed pressures in the target gear.

• In einem zweiten Schritt werden bei einer Rückschaltung vom vierten Gang G4 direkt in den zweiten Gang G2 als Zielgang das andere Schaltelement D des aktuellen Ganges G4 geöffnet und das andere Schaltelemente A des Zielganges G2 geschlossen (siehe auch 1 unten, G4- zu G2-Gangwechsel). Die Verläufe der Kupplungsmomente M_K der für diese G4-zu G2-Rückschaltung relevanten Schaltelemente sind in 4 unten dargestellt. Die betroffenen Schaltelemente sind auch in 1 unten, G4- zu G2-Gangwechsel, im Zusammenhang mit der Komponentenübersicht fett dargestellt.

Second step according to the alternative 1 ( 4th below):

• In a second step, when shifting down from fourth gear G4 directly into second gear G2, the target gear is the other shift element D. of the current gear G4 open and the other switching element A. of target gear G2 closed (see also 1 below, G4 to G2 gear change). The curves of the clutch torques M_K of the shift elements relevant for this G4 to G2 downshift are shown in 4th shown below. The affected switching elements are also in 1 Below, G4 to G2 gear changes, shown in bold in connection with the component overview.

• In einem zweiten Schritt werden bei einer Rückschaltung vom vierten Gang G4 zunächst in den dritten Gang G3 als Zielgang das Schaltelement D des aktuellen Ganges G4 geöffnet und das Schaltelement C des Zielganges G3 geschlossen. Bei einer abschließenden Rückschaltung vom Gang G3 in den Gang G2 als (endgültigen) Zielgang wird das Schaltelement C des aktuellen Ganges G3 geöffnet und das Schaltelement A des Zielganges G2 geschlossen.

Second step according to the alternative 2 ( 4th above):

• In a second step, when shifting down from fourth gear G4 to third gear G3, the shift element is the target gear D. of the current gear G4 opened and the switching element C. of target gear G3 closed. In the event of a final downshift from gear G3 to gear G2 as the (final) target gear, the shift element becomes C. of the current gear G3 opened and the switching element A. of target gear G2 closed.

In the second step, the switching element remains with both alternatives B. open for traction interruption, while those related to 3 explained speed specification is carried out. In a third step, the common switching element is then used B. closed when the engine speed n_M of the final target gear G2 is reached.

The special mode is only carried out here by the corresponding constellation of the shift elements and by the advantageous effect of the special mode, especially in lower gears, if more than one downshift command is below the fifth gear G5 (in the example after 3 ) or fourth gear G4 (in the example after 4th ) is present.

Additionally or alternatively, the special mode is only carried out if, due to the length of the switching time ts in normal mode in the target gear, the engine speed n_M threatens to fall below or too close to the idle speed n_LL. This can be done by the electronic transmission control unit 6th using the information available to you in advance.

• - Zunächst wird als erstes gemeinsames Schaltelement das Schaltelement D ausgewählt, da dieses ausgehend von Gang G8 den meisten folgenden niedrigeren Gängen nacheinander zugeordnet ist. Das Schaltelement D wird somit geöffnet und bleibt bis zum Gang G4, wenn dies ein nächster oder endgültiger Zielgang wäre, geöffnet.
• - Letzter endgültiger Zielgang ist in diesem Beispiel G2, dem das Schaltelement D nicht zugeordnet ist.
• - Als nächstes gemeinsames Schaltelement wird das Schaltelement B gewählt, da dieses ausgehend vom Gang G4 den meisten folgenden niedrigeren Gängen nacheinander zugeordnet ist. Das Schaltelement B wird bei Gang G3, dem das Schaltelement D erstmalig nicht mehr zugeordnet ist, geöffnet, Schaltelement D bleibt geöffnet und das Schaltelement C wird geschlossen.

If during the multiple downshift process (e.g. by pressing the brake pedal for a longer period of time) the next or final target gear predetermined by the control unit changes in such a way that the (first or previous) common shift element is no longer assigned to the changed target gear a new common shift element is determined for the next gear and is opened for decoupling - preferably when the previous common shift element is no longer assigned to the next gear for the first time. This particularly advantageous embodiment of the invention is illustrated using the following exemplary embodiment (see also 2 ) - in the form of a multiple downshift from G8 to G2 - explained in more detail:

• - The first common switching element is the switching element D. selected because this is based on gear G8 is assigned to most of the following lower gears in sequence. The switching element D. is thus opened and remains open until aisle G4, if this were the next or final target aisle.
• - The last final target gear in this example is G2, which is the shift element D. is not assigned.
• - The next common switching element is the switching element B. selected because this is assigned to most of the following lower gears, starting from gear G4. The switching element B. is in gear G3, which the switching element D. is no longer assigned for the first time, open, switching element D. remains open and the switching element C. will be closed.

Claims (4)

Method for carrying out a downshift of an automatic power-shifting multi-step automatic transmission (3), in which more than one shift element (A, B, C, D, E) between the The input shaft and the output shaft of the automatic transmission (3) are closed simultaneously, with the same shifting elements (A, B, C, D, E) being assigned to several gears and with the gear changes being carried out in the form of overlapping shifts in a normal mode, characterized in that in a special mode deviating from the normal mode in a multiple downshift, in which a shift element (B; D) of the current gear (G5, G4; G8) is also assigned to the next and final target gear (G4 to G2; G8 to G4) from of the control unit (6) this common switching element (B; D) is first fully opened and, at the same time or immediately thereafter, a speed specification is started, whereby ei the speed specification is initially made to maintain the engine speed (n_M) of the current gear and then to set the engine speed (n_M) theoretically present in the next target gear, while the next target gear is engaged as quickly as possible via the other shift elements required, and after reaching the engine speed (n_M) assigned to the final target gear, the common shift element (B) is closed as quickly as possible. Procedure according to Claim 1 , characterized in that if during the multiple downshift process (G8 to G2) the next or final target gear (G3, G2) predetermined by the control unit (6) changes in such a way that the previous common shift element (D) corresponds to the changed target gear (G3, G2) is no longer assigned, a new common shift element (B) for the next gears is determined and opened. Method according to one of the preceding claims, characterized in that the special mode is only carried out if, due to the length of the switching time (ts) in normal mode, when the target gear is reached, the engine speed (n_M) would be below or too close to the idle speed (n_LL) . Device in a motor vehicle with a drive motor (2), with an automatic transmission (3) cooperating with the drive motor (2), which has more than one switching element (A, B, C, D, E) between its input shaft and its output shaft for inserting a Ganges (G1 to G8), and with at least one electronic control unit (6) containing a program module for performing the method according to one of the preceding claims, the program module having an interface for controlling the engine speed (n_M) of the drive motor (2 ) having.

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