DE102010005532A1 - Method for determining a desired transmission gear for a hybrid vehicle - Google Patents

Abstract

Method for determining a target transmission gear for a hybrid vehicle that can be operated in different operating modes. A gear selection map is predefined for the different operating modes. On the basis of the gear selection map associated with the current operating mode, a target gear is determined as a function of a current actual speed and a target propulsion currently requested by the driver.

Description

The present invention relates to a method for determining a desired transmission gear for a hybrid vehicle according to the preamble of claim 1.

Vehicles with "automatic transmissions", which are collectively referred to as "automatic transmission" below, have a complex switching logic that must meet a variety of requirements. Essential boundary conditions in the design of a switching logic u. a. the resulting fuel consumption, the geared-up transmission acoustics, the ride comfort, the dynamics of the vehicle, etc. In conventional vehicles with automatic transmissions, the "driver's request", determined by the position of the accelerator pedal (accelerator pedal angle), and the current transmission output speed are the essential input variables for the gear selection logic , The operating point of the internal combustion engine, determined by its speed and its torque, thereby represents the essential degree of freedom.

In vehicles with a parallel hybrid drive, ie in vehicles that are optional internal combustion engine and / or electric motor driven, the focus in the transmission gear selection is primarily also on the requirements of the engine, with z. B. from the DE 10 2006 041 155 A1 is known, depending on the desired dynamics between a "sports" and an "Eco-switching characteristic" überzublenden.

A vehicle with a parallel hybrid drive, in addition to the internal combustion engine and the transmission also known to have at least one - depending on the operating mode - electric motor or regenerative electric machine, which from an electrical energy storage, eg. As a battery, is powered or which loads the electrical energy storage in Rekuperationsbetrieb.

A so-called "full hybrid" can be operated in different operating modes, eg. B. in purely internal combustion engine driving, in the purely electric motor driving, simultaneously in internal combustion engine and electromotive driving, etc. In generator mode, the vehicle can recuperate both with coupled combustion engine and decoupled combustion engine energy. In the regulation of the state of charge of the electric energy storage device, it is also possible to increase the load point of the internal combustion engine by a regenerative moment of the electric machines (load point increase) and to charge the battery by means of the internal combustion engine. When discharging the battery, the internal combustion engine can be assisted by a motor torque of the electrical machine (Assist mode or load point reduction).

An interpretation of the transmission gear selection, which is tuned primarily only to the operating point of the internal combustion engine and the torque requirement specified by the driver for this, does not meet the requirements of a hybrid drive sufficiently. Thus, in a hybrid vehicle, the actual torque request is determined not only by the driver's request but also by the operating state of the electric machine, which may necessitate an increase or a decrease in the load point of the internal combustion engine.

The object of the invention is to provide a method for determining a desired transmission gear for a hybrid vehicle, which takes into account, as far as possible, the parameters or boundary conditions influencing the overall efficiency of the hybrid vehicle.

This object is solved by the features of claim 1. Advantageous embodiments and further developments of the invention can be found in the dependent claims.

• – Rein elektrisches Fahren;
• – Gleichzeitiges verbrennungsmotorisches und elektromotorisches Fahren, wobei die elektrische Maschine als Elektromotor arbeitet (Lastpunktabsenkung);
• – Gleichzeitiges verbrennungsmotorisches und generatorisches Fahren, wobei die elektrische Maschine als Generator arbeitet (Lastpunkanhebung);
• – Rein verbrennungsmotorisches Fahren (elektrische Maschine passiv),
• – Generatorische Energierekuperation bei abgekoppeltem Verbrennungsmotor; und
• – Generatorische Energierekuperation bei angekoppeltem Verbrennungsmotor.

The starting point of the invention is a method for determining a desired transmission gear for a hybrid vehicle, which can be operated in different operating modes. The term "operating modes" is understood to mean in particular the following operating states:

• - purely electric driving;
• - Simultaneous combustion engine and electric motor driving, the electric machine works as an electric motor (load point reduction);
• - Simultaneous combustion engine and regenerative driving, the electric machine works as a generator (load point boosting);
• - pure combustion engine driving (electrical machine passive),
• - regenerative energy recuperation with decoupled internal combustion engine; and
• - Regenerative energy recuperation with coupled combustion engine.

All of these "operating modes" are controlled by control electronics according to a higher-level "hybrid operating strategy".

• – von einer Ist-Drehzahl und
• – einem vom Fahrer aktuell angeforderten „Soll-Vortrieb”

ermittelt wird. Der Begriff „Gangwahlkennfeld” ist äußerst breit auszulegen und ganz allgemein im Sinne einer Zuordnungsvorschrift zu verstehen.The essence of the invention consists in that at least for some, preferably for each of the operating modes implemented in the vehicle, a so-called "gear selection map" or a "gear selection logic" is specified in each case and that based on the Operating mode in which the hybrid vehicle is currently operated and the assigned gear selection map or the associated gear selection logic a desired transmission gear in dependence

• - from an actual speed and
• A driver-requested "target propulsion"

is determined. The term "gear selection map" is to be interpreted extremely broadly and generally understood in the sense of an assignment rule.

The gear selection maps can be generated in an "offline simulation tool", so that the vehicle always sets a "solid", reproducible switching behavior.

With a method for determining a desired transmission gear, which is based on several different gear selection maps, the overall efficiency of the powertrain can be optimized. Theoretically, it is even possible to always choose the most favorable in terms of the overall efficiency of the hybrid vehicle gear.

In order to meet the requirements and degrees of freedom of a hybrid powertrain, instead of the input parameter "accelerator pedal angle" used in conventional vehicles, a "desired transmission output torque" or a "desired wheel torque" is used as the control variable for the gear selection. In this way, it is possible to take into account the efficiency of the individual components or systems of a hybrid vehicle and the torque requirements resulting from the parent hybrid operating strategy in the gear selection.

According to a development of the invention, an individually assigned gear selection map is predefined for all the above-mentioned operating modes, which selects the most favorable transmission gear currently within the respective operating mode with regard to the overall efficiency of the drive train of the hybrid vehicle or the entire hybrid vehicle. When switching between individual operating modes, it is possible to "crossfade" between the relevant gear selection characteristics.

For the operating state "load point shift", d. H. For the operating state in which the load point of the internal combustion engine is lowered by a superimposed electromotive torque or raised by a superimposed regenerative torque of the electric machine, it is possible to provide different gear selection maps for specific powers or power ranges of the load point shift or the electric machine.

• – E-Maschine: elektrische Maschine;
• – SOC: „State of Charge” bzw. Ladezustand elektrischen des Energiespeichers bzw. der Batterie;

• 1. Gangwahlkennfeld „Rein elektrisches Fahren” • Getriebe: – Übersetzung, f(Gang) – Wirkungsgrad, f(Gang, Drehzahl Getriebeeingang, Moment Getriebeeingang) • Trennkupplung zwischen E-Maschine und Verbrennungsmotor: – Schleppmoment, f(Drehzahl E-Maschine) • Elektrische Getriebeölpumpe: – Schleppmoment, f(Drehzahl E-Maschine) • E-Maschine: – Maximal und minimal zulässige Drehzahl – Wirkungsgrad, f(Moment E-Maschine, Drehzahl E-Maschine) – Maximales Moment, f(Drehzahl E-Maschine) • Batterie: – Wirkungsgrad für Entladen, f(Entladeleistung, SOC) • Betriebspunkt: – Getriebeausgangsmoment – Getriebeausgangsdrehzahl.
• 2. Gangwahlkennfeld „Lastpunktverschiebung” • Elektrische Leistung der Lastpunktverschiebung • Getriebe: – Übersetzung, f(Gang) – Wirkungsgrad, f(Gang, Drehzahl Getriebeeingang, Moment Getriebeeingang) • Verbrennungsmotor: – Maximal und minimal zulässige Drehzahl – Wirkungsgrad, f(Moment Verbrennungsmotor, Drehzahl Verbrennungsmotor) – Maximales Moment • Elektrische Getriebeölpumpe: – Schleppmoment, f(Drehzahl E-Maschine) • E-Maschine: – Maximal und minimal zulässige Drehzahl – Wirkungsgrad, f(Moment E-Maschine, Drehzahl E-Maschine) – Maximales Moment, f(Drehzahl E-Maschine) • Batterie: – Wirkungsgrad für Entladen, f(Entladeleistung, SOC) – Wirkungsgrad für Laden, f(Ladeleistung, SOC) • Betriebspunkt: – Getriebeausgangsmoment – Getriebeausgangsdrehzahl.

The text below explains by way of example which boundary conditions or instantaneous states in the individual gear selection maps associated with the different operating modes can be taken into account, although other approaches are also conceivable. The following abbreviations are used:

• - E machine: electric machine;
• - SOC: "State of charge" or state of charge of the energy store or the battery;

• 1st gear selection map "purely electric driving" • Transmission: - gear ratio, f (gear) - efficiency, f (gear, speed gear input, moment transmission input) • Disconnect between electric motor and combustion engine: - drag torque, f (speed electric motor) • Electric transmission oil pump: - Drag torque, f (E-motor speed) • E-machine: - Maximum and minimum permitted speed - Efficiency, f (torque E machine, speed E machine) - Maximum torque, f (speed E machine ) • Battery: - Efficiency for unloading, f (discharge capacity, SOC) • Operating point: - Transmission output torque - Transmission output speed.
• 2nd gear selection map "load point shift" • Electrical power of load point shift • Transmission: - gear ratio, f (gear) - efficiency, f (gear, speed gear input, moment transmission input) • Internal combustion engine: - Maximum and minimum permissible speed - efficiency, f (moment internal combustion engine , Internal combustion engine speed) - Maximum torque • Electric gear oil pump: - drag torque, f (electric motor speed) • E machine: - maximum and minimum permitted speed - efficiency, f (torque E machine, speed E machine) - maximum torque , f (E-machine speed) • Battery: - discharge efficiency, f (discharge capacity, SOC) - charge efficiency, f (charging power, SOC) • Operating point: - transmission output torque - transmission output speed.

• 3. Gangwahlkennfeld „reiner Verbrennungsmotorbetrieb” • Wie Lastpunktverschiebung, nur mit Leistung der Lastpunktverschiebung von 0 Watt.
• 4. Gangwahlkennfeld „Rekuperation, Verbrennungsmotor abgekoppelt” • Getriebe: – Übersetzung, f(Gang) – Wirkungsgrad, f(Gang, Drehzahl Getriebeeingang, Moment Getriebeeingang) • Trennkupplung zw. E-Maschine und Verbrennungsmotor: – Schleppmoment, f(Drehzahl E-Maschine) • Elektrische Getriebeölpumpe: – Schleppmoment, f(Drehzahl E-Maschine) • E-Maschine: – Maximal und minimal zulässige Drehzahl – Wirkungsgrad, f(Moment E-Maschine, Drehzahl E-Maschine) – Maximales Moment, f(Drehzahl E-Maschine) • Batterie: – Wirkungsgrad für Laden, f(Ladeleistung, SOC) • Betriebspunkt: – Getriebeausgangsmoment – Getriebeausgangsdrehzahl.
• 5. Gangwahlkennfeld „Rekuperation, Verbrennungsmotor angekoppelt” • Getriebe: – Übersetzung, f(Gang) – Wirkungsgrad, f(Gang, Drehzahl Getriebeeingang, Moment Getriebeeingang) • E-Maschine: – Maximal und minimal zulässige Drehzahl – Wirkungsgrad, f(Moment E-Maschine, Drehzahl E-Maschine) – Maximales Moment, f(Drehzahl E-Maschine) • Verbrennungsmotor: – Schleppmoment, f(Drehzahl Verbrennungsmotor) • Elektrische Getriebeölpumpe: – Schleppmoment, f(Drehzahl E-Maschine) • Batterie: – Wirkungsgrad für Laden, f(Ladeleistung, SOC) • Betriebspunkt: – Getriebeausgangsmoment – Getriebeausgangsdrehzahl.

In each case, an individual characteristic field can be provided for different powers or power ranges of the load point shift.

• 3rd gear selection map "pure combustion engine operation" • Like load point shift, only with power of the load point shift of 0 watts.
• 4th gear selection map "Recuperation, internal combustion engine decoupled" • Gearbox: - gear ratio, f (gear) - efficiency, f (gear, speed gearbox input, torque transmission input) • Disconnect between electric motor and combustion engine: - drag torque, f (engine speed) Machine) • Electric gearbox oil pump: - drag torque, f (speed E machine) • E machine: - maximum and minimum permissible speed - efficiency, f (torque E machine, speed E machine) - maximum torque, f (speed E Machine) • Battery: - Efficiency for charging, f (charging power, SOC) • Operating point: - Transmission output torque - Transmission output speed.
• 5. Gear selection map "Recuperation, internal combustion engine coupled" • Gearbox: - gear ratio, f (gear) - efficiency, f (gear, gearbox input speed, gearbox input torque) • E machine: - maximum and minimum permissible speed - efficiency, f (torque E -Machine, speed electric motor) - Maximum torque, f (speed electric motor) • Internal combustion engine: - drag torque, f (engine speed) • Electric gear oil pump: - drag torque, f (speed electric motor) • Battery: - Efficiency for Charging, f (charging power, SOC) • Operating point: - Transmission output torque - Transmission output speed.

According to a development of the invention, the transition between individual operating modes is designed by way of transition functions such that pendulum circuits and overshoots (eg gear steps over more than one or more than two gear steps) are avoided or at least temporarily suppressed.

Regarding the gear selection, various restrictions may be provided.

Thus, it can be provided that a desired transmission gear proposed by the selection logic is not engaged if this would exceed predetermined permissible acoustic limits, ie. H. if z. B. falls below a certain predetermined minimum speed or a predetermined maximum torque would be exceeded.

According to a development of the invention, it may be provided to predict an imminent change of operating mode based on the differentiation of the characteristic variables in the control unit. Thus, even before a change from one operating mode to another operating mode, the gear selection of the "target operating mode" can be blended in order to prevent a "shuttle circuit", that is to say the subsequent change of the operating mode. H. a back and forth, takes place.

Furthermore, a start of the internal combustion engine can be predicted. It is thus possible to avoid a gear change when the internal combustion engine is started by preselecting an associated gear even in the operating mode "purely electric driving".

An upcoming gear change is predicated on the differentiation of the characteristic quantities in the control unit. If the last gear engaged and the desired gear calculated for the current and the extrapolated operating point are different, it can be provided that a shift is suppressed. An exception is a downshift due to a driver's acceleration request or multiple circuits.

According to a development of the invention, it is provided that, to avoid pendulum circuits, circuits are allowed to transition from the "train operation" in the "overrun" only after a predetermined time.

In order to ensure the "response" during a halt during recuperation with the combustion engine disconnected, minimum transmission input speeds can be specified depending on the vehicle speed. In this way, it is ensured that the internal combustion engine is also started without a response time extending downshift in a speed range in which it can generate torque quickly. At low vehicle speeds, the electric machine can compensate for the dynamics.

Furthermore, it can be provided that upshifts are suppressed during the recuperation operation when the rotational speeds of the drive sources are below predetermined limit rotational speeds.

Furthermore, upshifts can be suppressed if the driver's target propulsion request is only withdrawn for a very short time, ie shorter than a predetermined period of time (short "out of gas").

In addition, it can be provided that after a successful downshift an upshift for a predetermined period of time is suppressed.

• a) im verbrennungsmotorischen Fahrmodus a. durch maximales Ausnutzen der Motorleistung und/oder b. durch ein zusätzliches von der elektrischen Maschine aufbringbares Drehmoment oder
• b) im Falle einer Lastpunktanhebung durch eine Reduzierung des von der elektrischen Maschine erzeugten Generatormoments oder
• c) im elektrischen Fahrmodus durch maximales Ausnutzen der elektrischen Leistung der elektrischen Maschine

eingestellt werden kann.If the method according to the invention results in that a downshift should occur in the presence of an acceleration request, it is first checked whether the desired transmission output torque

• a) in the IC engine mode a. by maximum utilization of engine power and / or b. by an additional applied by the electric machine torque or
• b) in the case of a load point increase by reducing the generator torque generated by the electric machine, or
• c) in the electric driving mode by maximum utilization of the electrical power of the electric machine

can be adjusted.

If at least one of these alternatives is possible, then it can be provided that the switching process proposed by the method according to the invention can be selected from, for example, B. "Response" or comfort reasons not performed, d. H. is suppressed.

• – Es besteht die Möglichkeit, die Verbrauchseinsparpotentiale eines Parallelhybridantriebstrangs besser auszuschöpfen. Die einzelnen Fahrzeugkomponenten werden durch eine angepasste Gangwahl in Betriebspunkten höheren Wirkungsgrades betrieben, mit dem Ziel, den Gesamtwirkungsgrad zu maximieren.
• – Dabei werden die sich in den verschiedenen Betriebsmodi ändernden Leistungsflüsse berücksichtigt. Es werden diejenigen (vorzugsweise all diejenigen) Komponenten berücksichtigt, die in der aktuell aktiven Betriebsart den Gesamtwirkungsgrad des Antriebsstrangs beeinflussen. Die Abkehr vom Gaspedalwinkel als Steuergröße ermöglicht eine übergeordnete Berücksichtigung der Momentenanforderungen der Betriebsstrategie (Lastpunktver-schiebung).
• – Da die Kennfelder für die einzelnen Betriebsmodi offline erzeugt werden, kann die „Reproduzierbarkeit” und „Fahrbarkeit” von vorn herein umfassend berücksichtigt und getestet werden. Dies ist ein wesentlicher Vorteil gegenüber sogenannten „Online-Optimierern”, die verfügbare Informationen über den Betriebszustand des Fahrzeugs „online” auswerten und den Gang mit der geringsten Verlustleistung „online” im Fahrzeug wählen.

In summary, the invention achieves the following advantages in particular:

• - It is possible to better exploit the fuel savings potential of a parallel hybrid powertrain. The individual vehicle components are operated by an adapted gear selection in operating points of higher efficiency, with the aim of maximizing the overall efficiency.
• - This takes into account the changing power flows in the different operating modes. It takes into account those (preferably all those) components that affect the overall efficiency of the powertrain in the currently active mode. The departure from the accelerator angle as a control variable allows a higher-level consideration of the torque requirements of the operating strategy (load point shift).
• - Since the maps for the individual operating modes are generated offline, the "reproducibility" and "driveability" from the outset can be fully considered and tested. This is a significant advantage over so-called "online optimizers", which evaluate available information about the operating state of the vehicle "online" and select the gear with the lowest power loss "online" in the vehicle.

In the following the invention will be explained in connection with the drawing.

1 shows a schematic representation of the logic for determining a desired transmission gear for a hybrid vehicle according to the invention.

• – „Verbrennungsmotorisches Fahren”,
• – „Lastpunktanhebung”,
• – „Lastpunktabsenkung”,
• – „elektrisches Fahren”,
• – „Rekuperation, Verbrennungsmotor angekoppelt”, und
• – „Rekuperation, Verbrennungsmotor abgekoppelt”,

ist jeweils ein separates Gangwahlkennfeld 1–6 vorgesehen.For the different operating modes

• - "Combustion Driving",
• - "load point increase",
• - "load point reduction",
• - "electric driving",
• - "Recuperation, internal combustion engine coupled", and
• - "Recuperation, decoupled combustion engine",

is each a separate gear selection map 1 - 6 intended.

Depending on which mode of operation is currently being run, based on the assigned gear selection map 1 - 6 depending on a current actual speed 8th that z. B. measured at the transmission output or on a drive wheel or elsewhere in the drive train or can be determined, and a currently required by the driver target propulsion 9 a "target gear" 10 determined in 1 Also referred to as "efficiency optimal gear".

Depending on an actual torque and an actual speed of the electric machine and the internal combustion engine of the hybrid vehicle, in summary here as an input variable 11 referred to, and the current operating mode 12 is in a "drive coordination module" 13 determines which nominal gear 14 should actually be inserted and what target torque 15 respectively. 16 to be applied by the electric machine or the internal combustion engine.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006041155 A1 [0003]

Claims (5)

Method for determining a desired transmission gear ( 10 ) for a hybrid vehicle which is operable in different operating modes, characterized in that for the different operating modes in each case a gear selection map ( 1 - 6 ) and based on the gear selection map associated with the current operating mode ( 1 - 6 ) a desired transmission gear as a function of - a current actual speed ( 8th ) and - a currently requested by the driver target propulsion ( 9 ) is determined. A method according to claim 1, characterized in that the gear selection maps ( 1 - 6 ) are designed so that the desired transmission gear is the one transmission gear in which, based on the in the gear selection maps ( 1 - 6 ) takes into account the best overall efficiency for a powertrain of the hybrid vehicle. A method according to claim 1 or 2, characterized in that for each or all of the following operating modes each have a gear selection map ( 1 - 6 ): - pure combustion engine driving ( 1 ), - load point increase ( 2 ), - load point reduction ( 3 ), - purely electric driving ( 4 ), - recuperation, internal combustion engine coupled (5), - recuperation, internal combustion engine decoupled (6). Method according to one of claims 1 to 3, characterized in that the current operating mode is selected according to a method for determining a desired transmission gear hierarchically superior hybrid operating strategy. Method for selecting a transmission gear for a hybrid vehicle, characterized in that a set transmission gear (1) determined according to one of Claims 1-4 ( 10 ) is actually only selected and inserted if additional, predetermined, in an electronics ( 13 ) are implemented.

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