DE102011050560A1 - Method for operating electrical drive train of vehicle, involves controlling charging state of electrical energy storage by control unit between lower charging state limit and upper charging state limit - Google Patents

Abstract

The method involves controlling a charging state of an electrical energy storage (40) by a control unit (60) between a lower charging state limit and an upper charging state limit. The upper charging state limit is determined by a variable parameter of the vehicle. The area of the electrical drive train takes place in a voltage area of the electrical energy storage which is determined by the lower- and upper charging state limits. An independent claim is included for a device for operating an electrical drive train of a vehicle.

Description

The present invention relates to a method and a device for operating an electric drive train of a vehicle.

The traction batteries used in today's hybrid vehicles are designed to be frequently discharged and recharged. The battery capacity of the traction battery is usually used here in a certain capacity range.

The JP 2005210841 A describes a hybrid vehicle and a method of operating a hybrid vehicle, wherein driver-requested drive power is generated at a drive shaft of the hybrid vehicle with an engine and with an electric motor when a driver selects a sport operation as driving operation. In doing so, the used capacity of the battery increases in sports mode, so that the electric motor can provide drive energy more frequently and for a prolonged period of time.

The US Pat. No. 7,665,557 B2 describes a method for reducing the idle time of an engine in a hybrid vehicle, wherein in a hybrid powertrain, a motor, a power source, and a generator are operatively coupled. The method described therein includes a selective drive of the hybrid vehicle.

The DE 10 2005 034 147 A1 describes a system and method for efficient energy management in a hybrid vehicle. The hybrid vehicle includes a battery and an electric motor. The method described therein includes generating electrical energy by operating the engine and determining the battery temperature and the battery state of charge. The method further includes supplying electric power of the motor to the battery for simultaneously charging and heating the battery when the battery state of charge is lower than a predetermined battery charging limit and the battery temperature is higher than a lower charging efficiency temperature.

It is therefore an object of the present invention to provide an improved method and apparatus for operating a hybrid vehicle with optimized efficiency.

Accordingly, the present invention provides a method and an apparatus for operating an electric drive train of a vehicle. The method is provided for a vehicle having at least two electric machines, an internal combustion engine and an electrical energy store, wherein a state of charge of the electrical energy store is controlled by a control unit between a lower and an upper state of charge limit, which are predetermined by a variable parameter of the vehicle. Furthermore, in the method according to the invention, the operation of the electric drive train takes place in a voltage range of the electrical energy store, which is determined by the lower and the upper state of charge limit.

Further, the present invention discloses a device for operating an electric drive train of a vehicle having at least two electric machines of an internal combustion engine and an electrical energy storage, wherein a control unit is adapted to control a state of charge of the electrical energy storage between a lower and an upper state of charge limit, which by a variable parameters of the vehicle can be predetermined, and to perform the operation of the electric drive train in a voltage range, which is determined by the lower and upper state of charge limit.

The idea underlying the present invention is that the voltage level of the electrical energy store set as high as possible by choosing a high Ladezsutandsniveau to achieve an efficiency-optimized operation of the drive train with improved efficiency of the electrical components of the drive train and a higher overload capacity to achieve the electrical components, since the electrical components are operated with less power loss.

The disclosed by the present invention method and apparatus have the advantage that an optimized on the energy requirements of the vehicle operation of the electric drive train is made possible.

Advantageous embodiments and further developments emerge from the dependent claims and from the description with reference to the figures.

According to a preferred embodiment of the method, the variable parameter is determined by the control unit as a function of a driving state of the vehicle.

According to a further embodiment of the method, the variable parameter is changed by actuating a control element.

According to a further embodiment of the method, a first electric machine of the at least two electric machines for driving the hybrid vehicle is operated parallel to the internal combustion engine.

According to a further embodiment of the method, a second electric machine of the at least two electric machines is driven by the internal combustion engine as a generator.

According to a further embodiment of the method, the state of charge of the electrical energy store is regulated by the control unit by means of a control of the internal combustion engine and / or the electric machines.

According to a further embodiment of the method, the variable parameter is determined by an optimum efficiency of the power electronics.

According to a further embodiment of the method, the variable parameter is determined by an optimum efficiency of the first electric machine.

According to a further embodiment of the method, the variable parameter is determined by an optimum efficiency of the second electric machine.

According to a further embodiment of the method, the variable parameter is set to prevent overheating of the at least two electric machines.

According to a preferred embodiment of the device, a first electric machine of the at least two electric machines for driving the hybrid vehicle is designed parallel to the internal combustion engine.

According to a further embodiment of the device, a second electric machine of the at least two electric machines can be driven by the internal combustion engine as a generator.

According to a further embodiment of the device, the variable parameter is determined by an optimum efficiency of the power electronics.

According to a further embodiment of the device, the variable parameter is determined by an optimum efficiency of the first electric machine.

According to a further embodiment of the device, the variable parameter is determined by an optimum efficiency of the second electric machine.

The above embodiments and developments can, if appropriate, combine with each other as desired.

The present invention will be explained in more detail with reference to the exemplary embodiments indicated in the schematic figures of the drawings.

It shows:

1 a schematic representation of an apparatus for operating an electric drive train of a vehicle according to an embodiment of the present invention;

2 a diagram of a discharge curve of an electrical energy storage device according to an embodiment of the present invention;

3 a diagram with loading windows of an electrical energy storage in response to a variable parameter according to an embodiment of the present invention; and

4 a flow diagram of an embodiment of a method according to the invention.

In all figures, the same or functionally identical elements and devices - unless otherwise stated - have been given the same reference numerals.

The vehicle is designed, for example, as a hybrid vehicle or as a hybrid electric vehicle in micro, mild or full hybrid design.

The 1 shows a schematic representation of an apparatus for operating an electric drive train 5 of the vehicle according to an embodiment of the present invention.

The device for operating the electric drive train 5 includes a first electric machines 10 , a second electric machine 15 , an internal combustion engine 25 , an electrical energy storage 40 and a control unit 60 ,

The first electric machines 10 is for example with the internal combustion engine 25 mechanically coupled to a drive shaft, wherein the connection can be interrupted for example by means of an automatically or manually operated clutch.

The second electric machines 15 is in a hybrid drive module 20 arranged and via power electronics 45 with the electrical energy storage 40 connected.

The control unit 60 is with the power electronics 45 , with the electric energy storage 40 and the hybrid drive module 20 connected, which is the first electric machine 10 , the second electric machine 15 and the internal combustion engine 25 includes. The connection of the control unit 60 with the components of the electric drive train 5 is, for example, designed as a CAN bus.

The first electric machines 10 For example, it operates as a motor to drive the vehicle - either in addition to the engine 25 or alone - to drive.

The second electric machine 15 is used, for example, as a generator of the internal combustion engine 25 driven to generate electrical energy.

Braking energy of the vehicle can by means of a regenerative mode of operation of the first electric machines 10 and / or the second electric machines 15 be recovered.

To store the electrical energy is the electrical energy storage 40 provided, for example, as a galvanic cell, as an accumulator, flywheel storage, as a capacitor, as a lead-acid battery, lithium-ion accumulator, lithium-polymer accumulator, lithium-iron-phosphate accumulator lithium titanate accumulator, nickel-iron accumulator , Nickel-Cadmium accumulator, or is designed as a nickel-metal hydride accumulator.

The control unit 60 is designed to a state of charge SOC of the electrical energy storage 40 between a lower LSOC and an upper state of charge limit HSOC, which can be predetermined by a variable parameter SPF of the vehicle.

The operation of the electric drive train 5 is through the control unit 60 performed in a voltage range VR, which is determined by the lower LSOC and the upper state of charge limit HSOC.

The 2 shows a diagram of a discharge curve of an electrical energy storage device according to an embodiment of the present invention.

On the y-axis of the diagram is the voltage of the electrical energy store 40 Plotted in volts, on the x-axis is a relative degree of discharge of the electric energy storage 40 displayed.

The discharge curve EK is shown by way of example and describes the discharge characteristic of lithium-ion batteries or nickel-metal hydride batteries or of other metal-ion batteries having accumulators.

A sharp drop in the voltage of the electrical energy storage 40 occurs during the first quarter of the discharge of the electrical energy storage 40 , This is followed in the discharge curve EK a longer plateau to the last quarter of the total capacity of the electrical energy storage 40 , followed by a drastic drop in voltage until complete discharge.

A lower state of charge limit LSOC corresponds to a first value of a lower limit of a charging window, wherein the charging window is adapted dynamically in dependence on the variable parameter SPF.

Likewise, an upper state of charge limit HSOC is dynamically adjusted as a function of the variable parameter SPF.

An upper voltage limit HVL and a lower voltage limit LVL correspond to the upper state of charge limit HSOC and the lower state of charge limit LSOC, respectively.

By the upper voltage limit HVL and the lower voltage limit LVL is a voltage range VR of the electrical energy storage 40 Are defined.

Likewise, for a second value of the variable parameter SPF, a second upper voltage limit HVL2, a second lower voltage limit LVL2, a second upper state of charge limit HSOC2, and a second lower state of charge limit LSOC2 are defined.

A currently prevailing state of charge SOC of the electrical energy store 40 establishes a currently prevailing voltage value VL of the electrical energy store through the connection predetermined via the discharge curve EK 40 firmly.

By using a corresponding variable parameter SPF, the loading window, as limited by the upper HSOC state of charge limit and the lower state of charge limit LSOC, is raised.

The voltage range VR, which is a mean voltage level of the electrical energy store 40 is raised as well.

This increased voltage range VR, for example, increases the efficiency of the power electronics 45 and thereby the performance of the electric drive and the electric machines 10 and 15 , Semiconductor circuits often have constant loss voltages at pn junctions, at junctions between regions with different doping, or at other matrial junctions. Diffusion voltages occurring at these junctions produce a constant voltage offset within the semiconductor circuit, which typically provides power electronics with higher efficiency when operating at higher voltages.

The variable parameter SPF may be, for example, by the control unit 60 be calculated and implemented as a gradually adjustable sportiness factor, which for example characterizes a degree of driving dynamics desired by the driver.

Furthermore, a control element in the form of a button, a controller or a switch can activate a sports mode of the vehicle, which has an increased value of the variable parameter SPF.

The 3 shows a diagram with charging windows of the electrical energy storage 40 in response to the variable parameter SPF according to an embodiment of the present invention.

On the y-axis of the diagram is percentage of the state of charge of the electrical energy storage 40 applied. The x-axis represents the variable parameter SPF, wherein for two different values SPF1, SPF2 of the variable parameter SPF two different charging windows of the electrical energy storage 40 are shown.

A first value SPF1 of the variable parameter SPF is assigned the lower state of charge limit LSOC and the upper state of charge limit HSOC of the first load window.

Associated with a second value SPF2 of the variable parameter SPF, a second upper state of charge limit HSOC2 and a second lower state of charge limit LSOC2 are plotted in the diagram, whereby a second upper voltage limit HVL2, a second lower voltage limit LVL2 of the electrical energy store are defined with an associated voltage range.

In order to operate the vehicle with optimized efficiency, it is now planned to constantly maintain the highest possible state of charge SOC in the electrical energy store 40 adjust.

During the drive of the vehicle, therefore, the electrical energy storage 40 always maximally charged by the internal combustion engine 25 and the electric machines operated as a generator 10 . 15 be controlled accordingly.

As a result, the output voltage of the electrical energy storage 40 always high. This makes possible, in particular in the case of highly dynamic operation of the hybrid vehicle, better efficiency, for example of power electronics 45 to reach. In addition, it allows operation of the electric drive train 5 with lower power dissipation.

The 4 shows a flowchart of an embodiment of the method according to the invention.

In a first step S1, the state of charge SOC of the electrical energy store 40 through the control unit 60 between the lower LSOC and the upper state of charge limit HSOC, which are predetermined by the variable parameter SPF of the vehicle.

In a second step S2, the operation of the electric drive train 5 in the voltage range VR of the electrical energy storage 40 which is determined by the lower LSOC and the upper state of charge limit HSOC.

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

• JP 2005210841 A [0003]
• US 7665557 B2 [0004]
• DE 102005034147 A1 [0005]

Claims (16)

Method for operating an electric drive train ( 5 ) of a vehicle with at least two electric machines ( 10 . 15 ), an internal combustion engine ( 25 ) and an electrical energy store ( 40 ), wherein a state of charge (SOC) of the electrical energy store ( 40 ) by a control unit ( 60 ) between a lower (LSOC) and an upper state of charge limit (HSOC), which are predetermined by a variable parameter (SPF) of the vehicle; and wherein the operation of the electric drive train ( 5 ) in a voltage range (VR) of the electrical energy store ( 40 ), which is determined by the lower (LSOC) and the upper state of charge limit (HSOC). Method according to claim 1, wherein the variable parameter (SPF) is determined by the control unit ( 60 ) is determined as a function of a driving condition of the vehicle. The method of claim 1 or 2, wherein the variable parameter (SPF) is changed by operating a control element. Method according to one of claims 1-3, wherein a first electric machine ( 10 ) of the at least two electric machines ( 10 . 15 ) for driving the hybrid vehicle parallel to the internal combustion engine ( 25 ) is operated. Method according to one of claims 1-4, wherein a second electric machine ( 15 ) of the at least two electric machines ( 10 . 15 ) of the internal combustion engine ( 25 ) is driven as a generator. Method according to one of claims 1-5, wherein the state of charge (SOC) of the electrical energy store ( 40 ) by the control unit ( 60 ) by means of a control of the internal combustion engine ( 25 ) and / or the electrical machines ( 10 . 15 ) is regulated. Method according to one of Claims 1-6, wherein the variable parameter (SPF) is determined by optimum efficiency of the power electronics ( 45 ) is determined. Method according to one of claims 1-7, wherein the variable parameter (SPF) is determined by an optimal efficiency of the first electric machine ( 10 ) is determined. Method according to one of Claims 1-8, wherein the variable parameter (SPF) is determined by an optimum efficiency of the second electric machine ( 15 ) is determined. Method according to one of claims 1-9, wherein the variable parameter (SPF) for avoiding overheating of the at least two electric machines ( 10 . 15 ). Device for operating an electric drive train ( 5 ) of a vehicle with at least two electric machines ( 10 . 15 ), an internal combustion engine ( 25 ) and an electrical energy store ( 40 ), whereby a control unit ( 60 ) is adapted to a state of charge (SOC) of the electrical energy store ( 40 ) between a lower (LSOC) and an upper state of charge limit (HSOC), which can be predetermined by a variable parameter (SPF) of the vehicle, and the operation of the electric drive train ( 5 ) in a voltage range (VR) determined by the lower (LSOC) and upper state of charge limit (HSOC). Apparatus according to claim 11, wherein a first ( 10 ) of the at least two electric machines ( 10 . 15 ) for driving the hybrid vehicle parallel to the internal combustion engine ( 25 ) is designed. Apparatus according to claim 11 or 12, wherein a second ( 15 ) of the at least two electric machines ( 10 . 15 ) of the internal combustion engine ( 25 ) is generator-driven. Apparatus according to any one of claims 11-13, wherein the variable parameter (SPF) is determined by optimum efficiency of the power electronics ( 45 ). Device according to one of claims 11-14, wherein the variable parameter (SPF) is determined by an optimum efficiency of the first electric machine ( 10 ). Device according to one of Claims 11-15, the variable parameter (SPF) being determined by an optimum efficiency of the second electric machine ( 15 ).

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