DE102010005532B4 - Method for determining a target transmission gear for a hybrid vehicle - Google Patents

Abstract

Method for determining a target transmission gear (10) for a hybrid vehicle, with at least one gear selection map (1-6) being specified and, on the basis of the at least one gear selection map (1 - 6), a target transmission gear depending on a current actual speed ( 8) and a target propulsion (9) currently requested by the driver is determined, characterized in that • the hybrid vehicle can be operated in different operating modes, a gear selection map (1-6) being specified for each of the different operating modes and based on the current operating mode assigned gear selection map (1 - 6) the target transmission gear is determined and • a determined target transmission gear (10) is actually only selected and engaged if additional, predetermined, implemented in electronics (13) secondary conditions are met, with it is provided that an upshift into a target transmission gear (10) is suppressed during a recuperation operating mode rd, if the speed of the drive motors of the hybrid vehicle are below the specified speeds.

Description

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

Such a method is from DE 102 60 007 A1 known. The relevant state of the art also includes DE 10 2004 025 460 A1 .

Vehicles with “automatically shifting transmissions”, which are collectively referred to as “automatic transmissions” in the following, have a complex shift logic that has to meet a large number of requirements. Essential boundary conditions when designing a switching logic include the resulting fuel consumption, the resulting transmission acoustics, the driving comfort, the dynamics of the vehicle etc. In conventional vehicles with automatic transmissions, the "driver's request", specified by the position of the accelerator pedal (accelerator pedal angle), and the current transmission output speed are the main input variables for the gear selection logic . The operating point of the combustion engine, determined by its speed and torque, represents the essential degree of freedom.

In vehicles with a parallel hybrid drive, ie in vehicles that can optionally be driven by an internal combustion engine and / or an electric motor, the focus in the selection of the transmission gear is also primarily on the requirements of the internal combustion engine DE 10 2006 041 155 A1 it is known to fade between a “sport” and an “eco shift characteristic” depending on the desired dynamics.

A vehicle with a parallel hybrid drive has, in addition to the internal combustion engine and the transmission, as is well known, at least one - depending on the operating mode - an electric motor or generator operating electric machine, which is powered by an electric energy store, e.g. a battery, which is fed or which charges the electrical energy store in recuperation mode.

A so-called "full hybrid" can be operated in different operating modes, e.g. in purely internal combustion engine driving mode, in purely electric motor driving mode, simultaneously in internal combustion engine and electric motor driving mode etc. In generator mode, the vehicle can recuperate energy both with the combustion engine connected and with the combustion engine disconnected. When regulating the state of charge of the electrical energy store, there is also the possibility of raising the load point of the internal combustion engine by means of a generator torque of the electrical machines (load point raising) and of charging the battery by means of the internal combustion engine. When the battery is discharged, the internal combustion engine can be supported by a motor torque from the electric machine (assist mode or load point lowering).

A design of the transmission gear selection that is primarily only matched to the operating point of the internal combustion engine and to the torque requirement specified by the driver for this does not adequately meet the requirements of a hybrid drive. In a hybrid vehicle, for example, the actual torque requirement is determined not only by the driver's request, but also by the operating state of the electric machine, which can make it necessary to increase or decrease the load point of the internal combustion engine.

The object of the invention is to create a method for determining a target transmission gear for a hybrid vehicle that takes into account the parameters or boundary conditions influencing the overall efficiency of the hybrid vehicle as comprehensively as possible.

This object is achieved by the features of patent claim 1. Advantageous configurations and developments of the invention can be found in the subclaims.

• - 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 target transmission gear for a hybrid vehicle that can be operated in different operating modes. The term "operating modes" means in particular the following operating states:

• - All-electric driving;
• - Simultaneous combustion engine and electric motor driving, with the electric machine working as an electric motor (load point lowering);
• - Simultaneous combustion engine and generator driving, the electric machine working as a generator (load point increase);
• - Pure combustion engine driving (electrical machine passive),
• - Regenerative energy recuperation when the combustion engine is disconnected; and
• - Regenerative energy recuperation with the combustion engine connected.

All of these "operating modes" are controlled or regulated 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 is that at least for some, preferably for each of the operating modes implemented in the vehicle, a so-called “gear selection map” or “gear selection logic” is specified and based on the operating mode in which the hybrid vehicle is currently operated and the assigned gear selection map or the assigned gear selection logic a target transmission gear as a function

• • from an actual speed and
• • a "target propulsion" currently requested by the driver

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 a “fixed”, reproducible shift behavior is always set in the vehicle.

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

In order to meet the requirements and degrees of freedom of a hybrid drive train, 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 a control variable for gear selection. In this way, it is possible to take into account the efficiency of the individual components or systems of a hybrid vehicle as well as the torque requirements resulting from the superordinate hybrid operating strategy when selecting a gear.

According to a further development of the invention, an individually assigned gear selection map is specified for each of the above-mentioned operating modes, which selects the currently most favorable transmission gear with regard to the overall efficiency of the drive train of the hybrid vehicle or of the entire hybrid vehicle within the respective operating mode. When changing between the individual operating modes, you can "fade over" between the relevant gear selection maps.

For the operating state "load point shift", i.e. For the operating state in which the load point of the internal combustion engine is lowered by a superimposed electromotive torque or increased by a superimposed generator torque of the electric machine, it is possible to provide different gear selection maps for certain 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;

In the following it is explained by way of example which boundary conditions or instantaneous states can be taken into account in the individual gear selection maps assigned to the various operating modes, with other approaches also being conceivable. The following abbreviations are used:

• - E-machine: electric machine;
• - SOC: "State of Charge" or state of charge of the electrical energy storage device or battery;

Gear selection map "purely electric driving"

• • Transmission:
  • - translation, f (gear)
  • - Efficiency, f (gear, speed of transmission input, torque of transmission input)
• • Separating clutch between the electric machine and the combustion engine:
  • - Drag torque, f (speed of the electric machine)
• • Electric transmission oil pump:
  • - Drag torque, f (speed of the electric machine)
• • E-machine:
  • - Maximum and minimum permissible speed
  • - efficiency, f (torque e-machine, speed e-machine)
  • - Maximum torque, f (speed of the electric machine)
• • Battery:
  • - Efficiency for discharging, f (discharging power, SOC)
• • Operating point:
  • - transmission output torque
  • - transmission output speed.

Gear selection map "load point shift"

• • Electrical power of the load point shift
• • Transmission:
  • - translation, f (gear)
  • - Efficiency, f (gear, speed of transmission input, torque of transmission input)
• • Internal combustion engine
  • - Maximum and minimum permissible speed
  • - efficiency, f (internal combustion engine torque, internal combustion engine speed)
  • - Maximum moment
• • Electric transmission oil pump:
  • - Drag torque, f (speed of the electric machine)
• • E-machine:
  • - Maximum and minimum permissible speed
  • - efficiency, f (torque e-machine, speed e-machine)
  • - Maximum torque, f (speed of the electric machine)
• • Battery:
  • - Efficiency for discharging, f (discharging power, SOC)
  • - Efficiency for charging, f (charging power, SOC)
• • Operating point:
  • - transmission output torque
  • - transmission output speed.

An individual characteristic map can be provided for different performances or performance ranges of the load point shift.

Gear selection map "pure combustion engine operation"

• • Same as load point shift, only with the load point shift power of 0 watts.

Gear selection map "Recuperation, combustion engine decoupled"

• • Transmission:
  • - translation, f (gear)
  • - Efficiency, f (gear, speed of transmission input, torque of transmission input)
• • Separating clutch between e-machine and combustion engine:
  • - Drag torque, f (speed of the electric machine)
• • Electric transmission oil pump:
  • - Drag torque, f (speed of the electric machine)
• • E-machine:
  • - Maximum and minimum permissible speed
  • - efficiency, f (torque e-machine, speed e-machine)
  • - Maximum torque, f (speed of the electric machine)
• • Battery:
  • - Efficiency for charging, f (charging power, SOC)
• • Operating point:
  • - transmission output torque
  • - transmission output speed.

Gear selection map "Recuperation, combustion engine coupled"

• • Transmission:
  • - translation, f (gear)
  • - Efficiency, f (gear, speed of transmission input, torque of transmission input)
• • E-machine:
  • - Maximum and minimum permissible speed
  • - efficiency, f (torque e-machine, speed e-machine)
  • - Maximum torque, f (speed of the electric machine)
• • Combustion engine:
  • - drag torque, f (engine speed)
• • Electric transmission oil pump:
  • - Drag torque, f (speed of the electric machine)
• • Battery:
  • - Efficiency for charging, f (charging power, SOC)
• • Operating point:
  • - transmission output torque
  • - transmission output speed.

According to a further development of the invention, the transition between individual operating modes is designed using transition functions in such a way that pendulum shifts and excessively large gear steps (e.g. gear steps over more than one or more than two gear steps) are avoided or at least temporarily suppressed.

Various restrictions can be imposed on the choice of gear.

For example, it can be provided that a target transmission gear suggested by the selection logic is not engaged if this would exceed predetermined permissible acoustic limits, i.e. if e.g. a certain predetermined minimum speed would be undershot or a predetermined maximum torque would be exceeded.

According to a further development of the invention, it can be provided to predict an imminent operating mode change on the basis of the differentiation of the characteristic variables in the control unit. Before changing from one operating mode to another operating mode, the gear selection of the “target operating mode” can be faded in to prevent a “pendulum shift”, ie switching back and forth, from occurring when the operating mode is subsequently changed.

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

An upcoming gear change is predicted on the basis of the differentiation of the characteristic variables in the control unit. If the most recently engaged gear and the desired gear calculated for the current operating point and for the extrapolated operating point are different, it can be provided that a shift is suppressed. An exception is a downshift due to the driver's desire to accelerate or multiple shifts.

According to a further development of the invention, it is provided that, in order to avoid pendulum shifts, shifts during the transition from “pulling mode” to “pushing mode” are only permitted after a predetermined time.

In order to ensure the "response" when starting up during recuperation with the combustion engine disconnected, minimum transmission input speeds can be specified depending on the vehicle speed. This ensures that the internal combustion engine is started in a speed range in which it can quickly generate torque even without a downshift that increases the response time. 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 if the speeds of the drive sources are below predetermined limit speeds.

Furthermore, upshifts can be suppressed if the driver's target propulsion requirement is only very brief, i.e. shorter than a specified period of time, is withdrawn (briefly "take off the gas").

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

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

If the method according to the invention shows that a downshift should take place when there is a desire to accelerate, it is first checked whether the desired transmission output torque is reached

1. a) in internal combustion engine driving mode
   1. a. through maximum utilization of the engine power and / or
   2. b. by an additional torque that can be applied by the electrical machine or
2. b) in the case of a load point increase by reducing the generator torque generated by the electrical machine or
3. c) can be set in the electric driving mode by making maximum use of the electric power of the electric machine.

If at least one of these alternatives is possible, it can be provided that the switching process proposed by the method according to the invention consists of e.g. "Response" or comfort reasons not carried out, i.e. 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 vom 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:

• - There is the possibility of better exploiting the fuel-saving potential of a parallel hybrid drive train. The individual vehicle components are operated through an adapted gear selection in operating points with higher efficiency, with the aim of maximizing the overall efficiency.
• - The power flows that change in the various operating modes are taken into account. Those (preferably all) components are taken into account that influence the overall efficiency of the drive train in the currently active operating mode. The abandonment of the accelerator pedal angle as a control variable enables the torque requirements of the operating strategy to be taken into account (load point shift).
• - Since the maps for the individual operating modes are generated offline, the "reproducibility" and "drivability" can be comprehensively considered and tested from in. This is a major advantage over so-called "online optimizers", which evaluate available information about the operating status of the vehicle "online" and select the gear with the lowest power loss "online" in the vehicle.

The invention is explained in more detail below in connection with the drawing.

• 1 shows in a schematic representation the logic for determining a target 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

• - "Internal combustion engine driving",
• - "load point increase",
• - "load point lowering",
• - "electric driving",
• - "Recuperation, combustion engine coupled", and
• - “Recuperation, combustion engine disconnected” is a separate gear selection map 1 - 6 intended.

Depending on which operating mode is currently being driven, based on the assigned gear selection map 1- 6 depending on a momentary actual speed 8th which can be measured or determined, for example, at the transmission output or on a drive wheel or at another point in the drive train, and a target propulsion currently required by the driver 9 a "target gear" 10 is determined, which in 1 is also referred to as "efficiency-optimized gear".

Depending on an actual torque and an actual speed of the electrical machine and the internal combustion engine of the hybrid vehicle, here in summary as an input variable 11 and the current operating mode 12 a “drive coordination module” 13 determines which target gear 14th actually should be inserted and which target torque 15th or. 16 should be applied by the electrical machine or the internal combustion engine.

Claims (4)

Method for determining a target transmission gear (10) for a hybrid vehicle, with at least one gear selection map (1-6) being specified and, on the basis of the at least one gear selection map (1 - 6), a target transmission gear depending on a current actual speed ( 8) and a target propulsion (9) currently requested by the driver is determined, characterized in that • the hybrid vehicle can be operated in different operating modes, a gear selection map (1-6) being specified for each of the different operating modes and based on the current operating mode assigned gear selection map (1 - 6) the target transmission gear is determined and • a determined target transmission gear (10) is actually only selected and engaged if additional, predetermined, implemented in electronics (13) secondary conditions are met, with it is provided that an upshift into a target transmission gear (10) is suppressed during a recuperation operating mode is when the speed of drive motors of the hybrid vehicle are below predetermined speeds. Procedure according to Claim 1 , characterized in that the gear selection maps (1-6) are designed in such a way that the target gear is the gear that gives the best overall efficiency for a drive train of the hybrid vehicle based on the boundary conditions taken into account in the gear selection maps (1-6) . Procedure according to Claim 1 or 2 , characterized in that a gear selection map (1 - 6) is specified for individual or all of the following operating modes: - Pure combustion engine driving (1), - Load point increase (2), - Load point lowering (3), - Pure electric driving (4) - Recuperation, combustion engine connected (5), - Recuperation, combustion engine decoupled (6). Method according to one of the Claims 1 to 3 , characterized in that the current operating mode is selected according to a hierarchically superordinate hybrid operating strategy of the method for determining a target transmission gear.

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