DE102011116132B4 - Method for operating a vehicle with hybrid drive - Google Patents

Abstract

Method for operating a vehicle having a hybrid drive with an internal combustion engine (8), at least one electric machine (9) and an energy store (10) for storing the electrical energy, wherein the energy store (10) has a storage capacity with a limited utilization range, characterized in that the limited utilization range of the storage capacity of the energy store (10) is subdivided into a predetermined number of charge states (I, II, III, IV, V), the hybrid operation has a plurality of different hybrid modes, and each hybrid mode only in predetermined charge states (I, II , III, IV, V) is allowed or restricted and is not allowed in the other states of charge (I, II, III, IV, V), the predetermined number of states of charge (I, II, III, IV, V) being five is, wherein the states of charge (I, II, II, IV, V) cover the range of use of the storage capacity of the energy store (10), w obei the first and second states of charge (I, II) the lower storage capacity range of the third state of charge (III) the average storage capacity range and the fourth and fifth state of charge (IV, V) cover the upper storage capacity range, and wherein at an intended lowering of the state of charge (I, II, III, IV, V) of the energy store in the fourth state of charge (IV) the electric machine with zero torque (B8) is operated.

Description

The invention relates to a method for operating a vehicle with hybrid drive, comprising an internal combustion engine, at least one electric machine and an energy store according to the preamble of claim 1.

Hybrid vehicles are vehicles which, in addition to the internal combustion engine, comprise at least one electric motor or one electrical machine. In hybrid serial vehicles, a generator is driven by the internal combustion engine, with the generator supplying electric power to the electric motor driving the wheels. Furthermore, parallel hybrid vehicles are known in which an addition of the torques of the internal combustion engine and at least one connectable to the internal combustion engine electric machine. In this case, the electric machines can be connected to the belt drive or to the crankshaft of the internal combustion engine. The torques generated by the internal combustion engine and / or the at least one electric machine are transmitted to the driven axle via a downstream transmission. Currently, mainly parallel hybrid vehicles are being tested and are commercially available.

The publication DE 10 2007 038 585 A1 discloses a method for load point shift in hybrid operation in a parallel hybrid vehicle with an internal combustion engine, at least one electric machine and an energy storage, wherein defined in the map of the specific consumption of the internal combustion engine, at least one limit curve and the energy storage of the vehicle at least one limit value for the state of charge is defined. Furthermore, load point shift modes are defined in which the specific consumption of the internal combustion engine and the charge state of the energy store do not exceed a predetermined limit curve or a predetermined limit value. The load point shift occurs in one of the load point shift modes or in a combination of multiple load point shift modes.

From the DE 10 2010 048 548 A1 For example, a hybrid vehicle is known that includes an internal combustion engine, an electric motor, and an energy storage device, wherein the driving torque of the vehicle may be applied by the electric motor, the internal combustion engine, or both. Depending on a target torque and an operating state of the hybrid vehicle, an operating mode of the hybrid vehicle is automatically determined, wherein the operating mode determines whether as the drive means of the hybrid vehicle, the internal combustion engine, the electric motor or the internal combustion engine and the electric motor is used. In this case, the operating mode is at least determined such that the efficiency of the drive including the selected according to the particular mode drive means is maximum. Depending on the particular operating mode, the internal combustion engine and / or the electric motor is automatically used to operate the hybrid vehicle.

The DE 10 2005 003 979 B3 discloses a device for coordinating at least one switchable vehicle function. From the DE 699 32 487 T2 is known a control system for a hybrid vehicle. The US 2007 0 118 255 A1 shows a control device for a hybrid vehicle. The DE 10 2006 034 933 A1 describes a method for controlling a hybrid vehicle drive. From the DE 10 2004 023 512 A1 a method for power management for a hybrid vehicle is known.

The memory used in hybrid vehicles, designed as high-voltage storage for storing the required electrical energy have a limited usable range, which is dependent on the type of about 30% to about 70% of the total available capacity of the memory. Within this utilization range of the high-voltage accumulator, the available charging and discharging power is not constant. In the upper area of the utilization area, the charging power is limited for component protection reasons, while the discharge capacity is limited in the lower area. The characteristic of the high-voltage accumulator is therefore to be considered when designing a hybrid operation.

The invention is therefore based on the object to provide a strategy for the operation of a hybrid vehicle, in which the consumption optimized use of the high-voltage memory is improved, the implementation of the operating strategy for the driver is always traceable and reproducible.

The object is achieved by a method for operating a hybrid vehicle with an energy store having the features of claim 1. Preferred embodiments of the invention are subject of the dependent claims.

• - ist der begrenzte Nutzungsbereich der Speicherkapazität des Energiespeichers in eine vorgegebene Anzahl von Ladezuständen unterteilt,
• - weist der Hybridbetrieb eine Mehrzahl unterschiedlicher hybridischer Betriebsarten auf, und
• - ist jede hybridische Betriebsart nur in vorgegebenen Ladezuständen erlaubt oder eingeschränkt verfügbar und in den anderen Ladezuständen nicht erlaubt.

In the method according to the invention for operating a vehicle having a hybrid drive comprising an internal combustion engine, at least one electric machine and an energy store for storing the electrical energy, the energy store having a storage capacity with a limited utilization range,

• - the limited utilization range of the storage capacity of the energy store is subdivided into a predefined number of charge states,
• the hybrid operation has a plurality of different hybrid modes, and
• - Each hybrid mode is only allowed in predetermined states of charge or limited available and not allowed in the other states of charge.

The predetermined number of states of charge is five, with the five states of charge covering the utilization range of the storage capacity of the energy store. In this case, the usable range can amount to 30% to 70% of the charge capacity of the energy store, the usable range depending on the type of energy store. The first and second charge states cover the lower storage capacity range, in particular between 30% and 40%, the third charge state the average storage capacity range, in particular between 40% and 60%, and the fourth and fifth charge state the upper storage capacity range, in particular between 60% to 70 %, from. In an intended lowering of the state of charge in the fourth state of charge, the electric machine is operated at zero torque. In other words, the internal combustion engine provides the drive torque and the electric machine runs with zero moment so that no electrical energy is generated to charge the energy storage and this then empties due to the other electrical loads.

By this measure, the invention achieves that the execution of a hybrid mode can be done only in certain states of charge of the particular designed as a high-voltage storage energy storage, whereby each mode is tuned to the current event or the current state of the energy storage. In particular, the hybrid drive is a parallel hybrid drive.

Advantageously, in the fifth state of charge of the memory, hybrid operating modes are used as a function of the required drive torque, which have the aim of lowering the state of charge of the energy store. In this case, in particular for lowering the state of charge of the memory in the fifth state of charge is a load point lowering coupled engine at higher drive requirements or a thrust takeover by the coupled internal combustion engine without fuel injection, so that the thrust torque is not provided by the electric machine, but by the internal combustion engine in the accelerator relief.

More preferably, only in the third to fifth states of charge is a purely electric driving with decoupled internal combustion engine and a boost operation with active internal combustion engine as a function of the driver's request and the state of charge of the energy storage available. In the other states of charge, this is prohibited in order not to overburden the energy store.

Furthermore, the internal combustion engine is advantageously uncoupled into the first to fourth state of charge during overrun, so that no drag losses, i. Friction power and charge exchange losses caused by the internal combustion engine. Thus, a drag torque can be generated by the electric machine, whereby a charge of the energy storage can be achieved. If an unrestrained overrun operation is to be achieved, then the electric machine generates only enough torque to supply the vehicle electrical system.

More preferably, in the range of the first to third charge state, a load point increase is performed as a function of the current operating state of the hybrid drive. As a result, the internal combustion engine generates more torque than would be necessary for the drive, so that, as a consequence, charging of the energy store by the electric machine takes place.

Advantageously, a start / stop operation including creep of the hybrid vehicle is also allowed in the second state of charge. In this state of charge is no longer sufficient energy available in the memory for an electric driving, but this is still sufficient for creeping.

More preferably, a recuperation of the braking energy in the first to fifth states of charge can take place. However, the recuperation in the upper two states of charge, namely the fourth and fifth states of charge, limits, otherwise it could lead to an overcharge of the energy storage.

More preferably generated in the nominal state of charge of the energy storage to maintain the electric machine as much electrical energy as is necessary to cover the electrical system. In this way, the desired charging state of the energy storage can be maintained.

• 1 ein paralleles Hybridfahrzeug in schematischer Darstellung, und
• 2 die Verteilung der hybridischen Betriebszustände auf die Ladezustände des Hochvoltspeichers des Hybridantriebs.

A preferred embodiment of the invention will be explained below with reference to the drawings. It shows

• 1 a parallel hybrid vehicle in a schematic representation, and
• 2 the distribution of the hybrid operating states on the states of charge of the high-voltage memory of the hybrid drive.

1 shows a schematic representation of a hybrid vehicle with a parallel hybrid drive, in this example, the vehicle is symbolized by a driven front axle 1 with wheels 2 . 3 and a non-driven rear axle 4 with wheels 5 . 6 , The hybrid powertrain 7 includes an internal combustion engine 8th , which is symbolized here as a 4-cylinder engine, an electric motor 9 with associated high-voltage storage 10 , a gearbox 11 as well as a differential 12 , which specifies the driving torque on the driven wheels 2 . 3 brings. Between the internal combustion engine 8th and the electric motor 9 is a clutch 13 arranged to disengage the internal combustion engine from the drive train can. Another clutch 14 is between the gearbox 11 and the electric motor 9 arranged to the actual drive consisting of the electric motor 9 and the internal combustion engine 8th , from the driven axle 1 to decouple. Instead of the second clutch and a torque converter can be used.

In a parallel hybrid drive both drive the internal combustion engine 8th as well as the electric motor 9 the driven wheels 2 . 3 on, the electric motor 9 depending on the operating state as a generator for charging the high-voltage accumulator 10 acts.

2 shows by way of example a distribution of the hybrid operating states on the states of charge of a high-voltage memory, as shown in the 1 is shown. In this case, in this example, the useful range of the energy storage designed as a high-voltage storage is divided between the charging states 30% and 70% in five ranges I to V according to the following Table 1: Table 1 Area SOC I 30% - 35% II 35% - 40% III 40% - 60% IV 60% - 66% V 66% - 70%

wobei im Beispiel der 2 dieser Wert bei 60% liegt.Further, a target state of charge Zielsoc of the energy storage as a function of the vehicle _speed V _Fzg and the driving resistance F _{W is} defined as: $${\text{aim}}_{\text{SOC}}=\text{f}\left({\text{v}}_{\text{veh}}{\text{, F}}_{\text{W}}\right)\text{.}$$

in the example of the 2 this value is 60%.

The following are the hybrid operating states B1 to B10 of the preferred embodiment with reference to the diagram of 2 described, which is a parallel hybrid system:

operating mode B1 "Start / stop operation incl. Creep"

This mode B1 is used in area II of the battery, ie the lower battery usage area, where due to the low availability of the discharge power for electric driving is no longer enough power available. Since the engine idling represents a very unfavorable operating condition, this is to be avoided if possible. Therefore, the area II of the battery capacity becomes explicit for the mode B1 "Start / stop operation including creep" kept. Creep is understood to mean a speed of less than 10 km / h. For example, creeping is necessary when the vehicle is stationary and the internal combustion engine is off. If, for example, in traffic jams or at a traffic light, the vehicle has to be moved a few meters further forward, starting the engine makes no sense, but the route is traveled electrically "in crawlspace". In an automatic transmission, this can be realized by starting the engine only when the driver operates the gas pedal. As long as only the brake is released, the vehicle is electrically moved by releasing the brake in crawl. In addition, by this measure, the customer will be able to increase the range in the start / stop mode because the battery is not drained by other energy consuming modes.

operating mode B2 "Electric driving"

In electric driving, the internal combustion engine is decoupled and parked. Electric driving is only possible above the range II, in other words within the ranges III to V. The power available for electric driving depends on the respective state of charge. This results in an increasing over the range of use of the high-voltage battery electric driving range.

operating mode B3 "Boost mode"

In this case, torque is controlled by the electric machine while the internal combustion engine is active. The boost mode is also possible above range II in the ranges II to V. The time that is released for the boost mode depends on the respective state of charge of the high-voltage memory.

operating mode B4 "Storing the internal combustion engine in the thrust"

In this mode, the internal combustion engine is decoupled and turned off in the overrun mode. The operating mode B4 is permissible below area V, ie in the areas I to IV, and the internal combustion engine is decoupled during thrust. At low charge state of the high-voltage storage, the engine is stored only above a speed threshold. The speed threshold is to be chosen so that a positive energy balance is ensured by the laying down of the internal combustion engine. At higher speeds, the likelihood of a longer shutdown phase is higher, so that a deposit is energetically worthwhile. At low speeds, the Abstellphase is shorter on average, whereby the energy that is necessary for the restart of the internal combustion engine exceeds the energy saved. Basically, the aim is always in thrust the mode B4 to ensure traceability and reproducibility for the driver. In unrestrained overrun operation, as a rule, only as much power is generated via the electric motor as is necessary to cover the vehicle electrical system requirement.

operating mode B5 "Thrust takeover"

The operating mode B5 relates to a state of charge of the high-voltage accumulator above the loading area IV, ie in the loading area V, and it is coupled in overrun operation of the internal combustion engine without fuel is injected. Thus, if the vehicle is in thrust and the battery has a state of charge above region IV, the internal combustion engine is coupled and uncontrolled, ie without fuel supply, rotated. This operating state B5 serves to be able to represent a drag torque independently of the electric machine, since it can no longer provide a drag torque due to a lack of storage capacity for the electric energy when the battery is full. The use of the electric machine to generate drag torque is prohibited in the area V in order to have a residual potential to use the Rekuperationsbremse available. As a result, nothing changes and the mode of operation at the current state of charge of the high-voltage memory B5 is in the diagram of 2 represented by the symbol "♦", wherein the state of charge shown is only an example. It may also be higher in the fifth region V, if, for example, an energy input into the battery has taken place by braking.

operating mode B6 "Load point raising"

The operating mode B5 "Load point boost refers to active charging of the high-voltage memory. The internal combustion engine is operated at a higher power than required for propulsion of the vehicle and as a result the electric machine compensates for this power by a generator operation. This operation B5 the load point increase is carried out in the range I to III and takes place depending on the current operating point of the entire system and the state of charge of the high-voltage memory with the aim to set a specific nominal state of charge of the memory and operate the system in the optimal operating range.

operating mode B7 "Last point reduction"

Under load point reduction is an active unloading of the high-voltage accumulator understood and the electric machine is despite active engine from a positive moment, although there is no Boostanforderung. This mode B5 "Load point reduction" is only performed in area V. The aim of the load point reduction is to lower the level of the high-voltage accumulator as quickly as possible to restore storage capacity, for example, for a Rekuperationsbremsung to create.

operating mode B8 "Zero moment"

The mode "zero torque" means a passive unloading of the memory, wherein the drive torque is generated by the internal combustion engine and the electric machine is operated at zero torque, that is, the electric machine generates no electricity. The zero moment is operated in area IV. Destination of the operating mode B8 is to reduce the state of charge of the HV battery with optimum efficiency to set the target state of charge of the HV battery. The discharge of the high-voltage storage is carried out via the electrical system consumers.

operating mode B9 "Cover electrical system"

In this mode of operation, the electrical machine generates as much electrical power as is necessary to cover the vehicle electrical system, including the need for air conditioning. This operation is used when the actual state of charge corresponds to the target state of charge of the HV battery. In the example case of the 2 the nominal charging state is 60% state of charge of the high-voltage accumulator. The drive torque is generated by the internal combustion engine. This ensures that the nominal charging state is maintained and the on-board power supply demand is displayed in an optimal manner. This operating status is symbolized in the diagram of the 2 by the symbol "•".

operating mode B10 "Recuperation"

In the operating mode B10 The electric machine generates a regenerative torque at a deceleration of the vehicle by a brake operation. Recuperation is available throughout the range of use of the high-voltage memory, although in areas IV and V the amount of available recuperation power is reduced in order to prevent overcharging of the memory. In this mode, the internal combustion engine is preferably decoupled, but this is not necessarily possible, for example, at high speeds. The decoupling and, if necessary, switching off the internal combustion engine therefore depends on external events.

Due to the distribution of the hybrid operating states to the states of charge of the high-voltage accumulator and their activation or limited activation in accordance with predetermined framework conditions, which are a function of the state of charge and the driver's request, a consumption of the high-energy storage is achieved.

LIST OF REFERENCE NUMBERS

1

Front

2

wheel

3

wheel

4

rear axle

5

wheel

6

wheel

7

Hybrid powertrain

8th

Internal combustion engine

9

electric motor

10

High-voltage battery

11

transmission

12

differential

13

clutch

14

clutch

B1

Operating mode start / stop and creep

B2

Operating mode electric driving

B3

Boost operating mode

B4

Operating mode VKM Deposition in thrust

B5

Operating mode thrust takeover

B6

Operating mode load point increase

B7

Operating mode load point reduction

B8

Operating mode zero torque

B9

Cover operating mode on-board supply system requirement

B10

Recuperation mode

Claims (9)

Method for operating a vehicle having a hybrid drive with an internal combustion engine (8), at least one electric machine (9) and an energy store (10) for storing the electrical energy, wherein the energy store (10) has a storage capacity with a limited utilization range, characterized in that the limited utilization range of the storage capacity of the energy store (10) is subdivided into a predetermined number of charge states (I, II, III, IV, V), the hybrid operation has a plurality of different hybrid modes, and each hybrid mode only in predetermined charge states (I , II, III, IV, V) is allowed or restricted and is not allowed in the other states of charge (I, II, III, IV, V), the predetermined number of states of charge (I, II, III, IV, V ) is five, wherein the states of charge (I, II, II, IV, V) cover the range of use of the storage capacity of the energy store (10) n, wherein the first and second charge states (I, II) cover the lower storage capacity range, the third charge state (III) the average storage capacity range and the fourth and fifth charge state (IV, V) the upper storage capacity range, and wherein in an intended lowering of the charge state ( I, II, III, IV, V) of the energy store in the fourth state of charge (IV), the electric machine with zero moment (B8) is operated. Method according to Claim 1 , characterized in that in the fifth state of charge (V) of the energy storage (10) hybrid modes are used as a function of the required drive torque, which have a reduction of the state of charge (I, II, III, IV, V) of the energy storage to the destination. Method according to Claim 2 , characterized in that for lowering the state of charge (I, II, III, IV, V) of the energy store (10) in the fifth state of charge (V) a load point reduction with coupled internal combustion engine (B7) or a thrust takeover by the electric machine (9) in uncoupled Internal combustion engine (B5) takes place. Method according to one of the preceding claims, characterized in that in the third to fifth states of charge (III, IV, V) a purely electric driving with decoupled internal combustion engine (B2) and a boost operation with active Internal combustion engine (B3) as a function of a driver's request and the state of charge (I, II, III, IV, V) of the energy storage (10) are available. Method according to one of the preceding claims, characterized in that in the first to fourth states of charge (I, II, III, IV) in overrun operation, the internal combustion engine (8) is decoupled (B4). Method according to one of the preceding claims, characterized in that in the range of the first to the third state of charge (I, II, III), a load point increase (B6) is performed as a function of the current operating state of the hybrid drive. Method according to one of the preceding claims, characterized in that a start / stop operation including creep (B1) in the second state of charge (II) of the energy store (10) is permitted. Method according to one of the preceding claims, characterized in that a recuperation of the braking energy (B10) in the first to fifth states of charge (I, II, III, IV, V) is possible. Method according to one of the preceding claims, characterized in that in a nominal state of charge of the energy store (10) to maintain the electric machine (9) generates as much electrical energy as is necessary to cover the electrical system.

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