CH708588A1 - Motor vehicle with an electric drive. - Google Patents

Abstract

The invention relates to a motor vehicle having an electric traction drive (4), an electrical energy store (3a, 3b) for providing electrical energy for the traction drive, an internal combustion engine (1) and an electric generator (2) driven exclusively by the internal combustion engine (1) Recharging the electrical energy storage device (3a, 3b). In this case, the energy store (3a, 3b) is formed with at least one first sub-battery (3a) and at least one second sub-battery (3b), and a switching element (30) is between the first sub-battery (3a), the second sub-battery (3b), the electric generator (2) and the electric traction drive (4) arranged, and designed such that the first part of battery (3a) and the second part of battery (3b) alternately the electric generator (2) or the electric traction drive (4) are switchable.

Description

description

The invention relates to a motor vehicle with electric drive according to the preamble of claim 1 and a method for operating a motor vehicle according to claim 10.

In particular, it is a motor vehicle with electric drive in which the traction drive exclusively by a, powered by an electric storage, electric motor takes place. The electric storage is designed as a multiple rechargeable batteries or accumulators, which store supplied electrical energy and can deliver it at a later date again. By battery, therefore, no single-use primary cell is meant here.

The currently available batteries have - as also apparent from the examples below - too low a memory capacity than a user-generally accepted driving range in electric-only vehicle mode (NEDC mode) would be achievable. Especially the high price, as well as the high power-to-weight ratio and power volume of electro-storage makes a more generous dimensioning of energy storage unattractive. Therefore, without massive advances in the field of electrical energy storage, vehicles with purely electric drive for the vast majority of users uninteresting.

For this purpose, for example, the South German automotive supplier Mahle has developed a 2-cylinder gasoline engine, in which a generator for converting the mechanical energy of the engine into electrical energy, directly in the crankcase of the internal combustion engine is integrated (see press release of the company Mahle in VDI News from October 2012). According to the report, this engine is intended as a "range extender" in which the generated electrical output is designed partly to charge the battery and partly directly to the electromotive traction of the vehicle. In a practical example given in this article, the battery has an energy capacity of 14 kWh, the combustion engine a maximum power of 30 kW and the electric motor a continuous power of 55 kW. The range alone from the battery is then specified in NEDC mode (ie pure battery travel without use of the range extender), at a driving speed 70 km / h, with about 70 km. With an additional use of a tank filling of 25 liters of fuel for the internal combustion engine, a total range of approximately 500 km is given.

The motor vehicle is thus further equipped with an internal combustion engine and a generator with which a charge of the electric accumulator is feasible. However, there is no direct mechanical torque transmission from the engine to the drive wheels.

In the ferry operation in this case a parallel or alternative supply of the electric motor by the internal combustion engine and / or the battery is provided. In this case, the electrical energy generated by the generator is used not only for charging the battery, but also for direct operation of the drive electric motor. As an electric drive while a permanent magnet excited synchronous motor is provided.

For example, from the Special Edition Automotive Technical Magazine ATZ Springer Verlag from October 2012, on pages 28-36 known hybrid electric vehicle with electric motor drive is also partly from a generator driven by an internal combustion engine and partly from one of the generator rechargeable Battery supplied.

WO 201 1/1124 247 shows an electric storage system for vehicles, in which of several parallel-connected accumulators are separated from the supply bus, which have a lower state of charge than the others. This is to maintain the same as possible state of charge of all accumulators during discharge and otherwise possibly occurring equalizing currents between the accumulators are avoided.

Although bring the above-mentioned range extender concepts improvements, but is a pure recollection of classic internal combustion engine, which has only a low energy efficiency, especially in part-load operation, in terms of environmental protection is not a satisfactory solution. Also, in such a concept, the ongoing, undefined change between charging and discharging of the electric storage - depending on unpredictable factors such as the traffic flow and the specific driving behavior of the user - is a burden on the energy storage, which affects its life, effectively achievable efficiency, etc. ,

It is therefore an object of the present invention to provide a motor vehicle, which is energy efficient and environmentally friendly, durable and inexpensive to purchase, but with which a sufficient, the consumer wishes corresponding range is achievable.

It is an object of the present invention to provide a motor vehicle, which achieves a high efficiency with respect to the primary energy used and low pollutant emissions.

Another object is to reduce the burden of electrical storage in the vehicle and to improve their life and continuous use efficiency.

It is therefore a specific object to provide a purely electrically driven motor vehicle with an internal combustion engine and a generator for the local generation of electrical energy, which achieves low fuel consumption and careful handling of the vehicle batteries.

[0014] A special task is also the avoidance of frequent micro-charging cycles of the batteries, which can reduce the battery life.

These objects are achieved by the realization of the characterizing features of the independent claims. Features which further develop the invention in an alternative or advantageous manner can be found in the dependent claims.

If such a vehicle with electric drive to be successful in the market, then some essential properties must be present:

First arises due to the limited capacity of currently available electrical energy storage, compared to a fuel tank significantly longer charging time and - compared to the well-developed gas station network - barely existing public charging infrastructure, especially in rural areas, the requirement that Vehicle is equipped with a range extender engine. For an economically operating vehicle with electric drive and range extender this is to charge the driving batteries on the generator only in the optimal specific fuel consumption point or operating point with minimal emissions (or a compromise of these two criteria) of its speed-torque map operate. This should be achieved with the highest possible utilization of the energy content present in the fuel tank.

For this purpose, according to the invention, the battery system in the vehicle consists of two separate sub-batteries, which each can be charged or discharged separately. It is in the sub-batteries specifically designed for the traction drive batteries, especially with at least approximately the same voltage and capacity, so not about a combination of a high-voltage traction battery and a low-voltage electrical system battery. These are also partial batteries for traction with a capacity of several hundred Wh, especially more than 1 kWh, e.g. around 5 to 100 kWh, and not around buffer transfer or rectifier capacitors with low capacitance values. While the first one of the sub-batteries is used to operate the electric motor of the traction system, a second of the sub-batteries may be separately charged by the range-extender driven generator independently of the first one. The internal combustion engine can always be operated in terms of its speed and its torque in its current fuel consumption optimum. When the partial battery to be charged is charged, the engine can be stopped. The combination battery - internal combustion engine can be designed such that the point or range of consumption optimum of the engine coincides at the same time on the electrical side with the point or range of an optimal charging curve of the sub-battery in its operating range, especially optimal with respect to their life.

The traction power is thereby according to the invention only taken from the currently not in charge sub-battery. Decreases the state of charge of the battery used for traction below a defined threshold, especially in an area whose use would have a negative effect on the life or efficiency of the battery, there is an automatic change of assignment of the sub-batteries, for example by an electrical switching. In the change, the role of the charging battery charged by the range extender becomes that of the traction battery, and the role of the spent traction previous battery becomes the charging battery.

The integrated start generator (ISG) or an additional starter device then starts the engine again to charge the previously deflated during traction battery. If the internal combustion engine is operated only in the region of the fuel consumption optimum, ie not in the much less favorable partial load range, then the energy contained in the fuel can be used with a high efficiency. The amount of electrical energy generated during optimum operation, which emits the generator of the internal combustion engine, can be tuned such that the sub-battery is charged with a substantially constant charging current, which preferably at least approximately matches the optimal charging current in terms of battery life.

According to the invention, therefore, a motor vehicle with an electric traction drive, an electrical energy storage device for providing electrical energy for the traction drive, an internal combustion engine, in particular a gasoline or diesel engine, and an exclusively driven by the internal combustion engine electric generator for recharging the electrical energy storage. In particular, the electric generator can therefore not be driven by the propulsion system, so there is no mechanical coupling or coupling possibility between the electric generator connected to the internal combustion engine and the traction drive.

The energy storage is designed as a battery system with at least a first sub-battery and at least a second sub-battery and it is a switching element between the first sub-battery, the second sub-battery, the generator and the electric drive arranged such that the first sub-battery and the second sub-battery alternately the generator or the electric traction drive are switchable.

In other words, the switching element is connected between a first operating mode in which the generator of the first sub-battery and the electric traction drive of the second sub-battery is switched on, and a second operating mode in which the generator of the second sub-battery and the electric traction drive of the first sub-battery switched on is switchable. In particular, the switching element is automatically switchable during the ferry operation, so that an alternately charging or discharging of the respective sub-battery can be performed.

[0024] An electrical energy management unit may be designed and operatively connected to the internal combustion engine such that the first sub-battery is charged in such a way that the internal combustion engine is either permanently operated in a region of its lowest specific fuel consumption in the engine map or completely is deactivated. Specifically, while the internal combustion engine is permanently operated in an optimum range with a deviation of less than 5% of the lowest specific fuel consumption of the internal combustion engine, in particular where this range of interpretation and current environmental conditions of the internal combustion engine can be adjusted. In this operation of the internal combustion engine, the first sub-battery with its, in particular with respect to a recoverable from the sub-battery maximum charging cycle number, optimal charging curve is charged by the electric generator. Specifically, the sub-battery can be charged during its entire charging process with at least approximately constant charging power and / or not the entire available capacity range of the sub-battery can be used.

So it is a mechanical drive power for the motor vehicle at any time in each case exclusively from one of the sub-batteries, which is assigned to a traction by the traction drive, removable and provided by the electric generator electrical energy is in each case exclusively another of the sub-batteries, which one Recharging is assigned by the generator, fed. Specifically, the first partial battery and the second partial battery can always be electrically separated from one another with the switching element and the first partial battery and the second partial battery can be assigned to the traction drive or the generator, in particular automatically and depending on a state of charge of the partial batteries.

The internal combustion engine can also be charged with a turbocharger or compressor, wherein specifically instead of a conventional exhaust gas turbocharger, an electrically driven turbocharger, which is fed by one of the sub-batteries or directly from the generator. Thus, e.g. Reduces the exhaust gas back pressure, improves the effect of any exhaust gas catalyst and / or a targeted control of the charge can be realized by electronic means to make the engine even more efficient.

Another important aspect of a marketable electric vehicle is the requirement that this can be manufactured inexpensively. In order to be able to provide sufficiently stored electrical energy at the currently achievable, limited energy densities of the batteries in order to be able to achieve an acceptable driving range comparable with conventional combustion engine vehicles with a purely electrically operated vehicle, the batteries are usually large, heavy and expensive. It should also be ensured that the construction costs for the charging and power electronics are as small as possible and they have only low power losses.

The inventive method and the inventive device are described below with reference to exemplary embodiments shown schematically in the drawings, purely by way of example, which also addresses further advantages of the invention. In detail show:

Fig. 1 block diagram of an electric vehicle with a combustion force range extender according to the prior art;

2 shows a first embodiment of the inventive vehicle concept in a block diagram;

3 shows a second embodiment of the inventive vehicle concept in a block diagram;

4a shows a first example of an operation of a vehicle according to the invention;

4b shows a second example of an operation of a vehicle according to the invention;

5 shows an example of a fuel consumption map of an internal combustion engine;

6 shows an example of a charging curve of an electric accumulator.

Fig. 1 shows an example of an embodiment of the structural configuration of a serial hybrid automobile of the prior art. Therein, an internal combustion engine 1 with a generator 2, which can also be embodied as an integrated starter generator (ISG), is used as a range extender, which stores the energy of the refueled fuel (eg ethanol, gasoline, diesel, biodiesel, liquefied petroleum gas, etc.). can convert into electrical energy. However, the range extender can also be designed, for example, with a free-piston linear generator as an internal combustion engine with an integrated generator.

The ISG 2 may for example be designed as an integrated crankshaft starter generator, which is usually designed as a permanent magnet synchronous machine as a three-phase motor and generator. The induction of the permanent magnets can be dimensioned according to the starting torque for the internal combustion engine 1, even at cold start, but also such that the mechanical power of the driving internal combustion engine 1 is converted into electrical power, preferably with the highest possible efficiency.

4 provided by the range extender electrical energy can then on the path 1 1 directly to the driving power converter 20, which controls one or more traction motors 4 according to predetermined driving commands 21. The torque of the traction motor 4 is optionally transmitted via a gear 5 and a differential 6 to the drive wheels 7. Alternatively, a direct drive of the wheels 7 by the electric motor 4, for example, each with a individually controlled hub motor 4a, as shown in broken lines.

However, the electrical energy provided by the range extender can also be routed via the path 12 into the electrical energy store 3 in order to charge it. Specifically, in each case that part of excess, produced by the range extender 1, 2 electrical energy, which is currently not required by the drive 4, stored in the energy storage 3.

In the reverse manner, the energy storage 3 via the path 13 electrical energy to operate the drive motor 4 are removed. The travel drive can thus be operated:

• from the energy store alone (for example, with the range extender switched off),

• from the current range extender, where excess energy is stored in the energy storage, or

• from the energy store and the current range extender (e.g., when higher power is required than either source can provide on its own).

The electrical energy management (EEM) of the motor vehicle and the engine control unit (ECU) for the traction drive 4 and the control unit for the range extender (with internal combustion engine and ISG) are designed accordingly for these tasks.

The electrical system 8 for the operation of auxiliary consumers and the comfort devices (for example, the 12V, 24V or 48V small-voltage vehicle electrical system) can be diverted with a DC-DC converter 9 of the mostly much higher battery voltage of the energy storage device 3.

In addition to the charging of the energy storage device 3 by the range extender 1, 2 installed on board the vehicle, a device 19 for charging by external energy sources, e.g. the public power grid, solar cells, wind power generators, block power plants, etc. may be provided.

Fig. 2 shows an embodiment according to the present invention in the form of a schematic structure of the drive train of a motor vehicle. As motor vehicles here are meant in particular automobiles of various types, it can - but also be motorcycles, buses, construction vehicles, agricultural vehicles, but also watercraft or aircraft, etc.

Again, an internal combustion engine 1 is coupled to a generator 2 (ISG), which is used as a range extender, with which the energy of the combustion fuel can be converted into electrical energy for an electric traction drive 4 while driving , Thus, especially if the stored electrical energy is not sufficient to cope with the desired route, conventional fuel can be used to generate the electrical energy, which can be refueled in a short time, so that no time-consuming unwanted charging stops have to be planned, as is known pure electric vehicles is the case.

According to the invention, an inefficient partial load operation of the internal combustion engine 1 should be avoided. The engine 1 should whenever possible be operated in the area in which it has the lowest fuel consumption or in which it causes the lowest emissions of pollutants, or otherwise be completely deactivated. In such optimal operation of the internal combustion engine 1, but this also has an approximately constant output power. In direct use of the engine torque for direct mechanical vehicle drive - as in classic internal combustion vehicles - such optimal operation is not permanently possible because during the ferry operation strong fluctuations in the requested performance between standstill, acceleration and braking occur.

Also in the case of serial hybrids in the prior art of the coupled to the internal combustion engine 1 generator 2 electrical power would be substantially constant in the case of optimal continuous optimal operation, and is therefore not suitable for its own use by the alone dynamically operated electric traction drive 4. The well-known practice of using a parallel-connected battery 3 to compensate for the current driving situation too much or too little generated electrical energy, this can compensate in principle, however, provides the constant alternating load and unloading for the used electrostatic accumulator 3 is a high load, which has a negative effect on its life by the many charge and discharge cycles and unsteady charging currents. A frequent renewal of the electric storage 3 is not feasible from an economic point of view, since the electric storage 3 usually accounts for a large part of the total vehicle costs. To achieve a long life of the electric storage 3 is therefore desirable.

For example, Prof. Dr. Andrea Vezzini in the book "Renewable Energy" Wiley-VCH-Verlag, 2012 considers: "If the battery is to last an auto lifetime, then it has up to a million charge and discharge cycles

5 cope. So she does not diminish appreciably, she should only up to max. 20% of their capacity will be charged and discharged. »

This general statement has been confirmed experimentally for many of the currently used in vehicles using battery technologies such as the currently most commonly used lithium-ion (Lilon) batteries - in their basic features. In particular, deep discharges should generally be avoided, for example below 20% of the nominal or maximum capacity. This lower charge limit can be determined, for example, based on the cell voltage - the so-called discharge end voltage, if necessary also taking into account the temperature.

When charging special overcharges are to be avoided, as they damage the electric storage 3. During charging, many times (for example with Lilon batteries), after a first, very fast charge up to about 80% of the maximum or nominal capacity, a significantly slower top-up charge of the remaining approx. The well-known, especially in NiCd batteries strongly pronounced memory effects play today - especially with the correct use of the battery - only a very minor role. Lilon batteries generally suffer no harm when operated only within a limited capacity range. This limited capacity range can e.g. depending on the battery type - within the above-mentioned range of about 80% of the maximum capacity as charge upper limit (or corresponding end charge voltage) and about 20% or 30% of the maximum capacity as the lower discharge limit (or the associated Entladeschussspannung) are determined. The range limits do not have to be exactly met, and can also vary, in particular with the battery temperature and / or battery type. However, in all operating scenarios, a sufficient safety distance to a deep discharge or overcharge should always be ensured.

In the prior art with a single or shared battery 3, such a procedure is often impractical. For example, as without the range extender, as good as the full capacity range usually has to be used in order to achieve even an approximately acceptable vehicle range. Even in the presence of a range extender, this will often work in inefficient partial load operation or the charging and discharging takes place almost randomly, depending on the uncontrollable change of unpredictable driving situations.

However, according to the present invention - using sub-batteries 3a, 3b separately used for charging or discharging together with a range extender - such an operation is readily realizable. The components range extender engine 1, generator 2 and part battery 3a, 3b can be matched to one another such that always an optimal charge of the battery takes place - especially where the engine is operated only in consumption or emission optimum.

In particular, the system may also be tuned such that the charging of the charging sub-battery 3a is completed to the desired state of charge (of eg 80%) before a next change due to a low 'state of charge (of eg 20%) of the traction Sub-battery 3b is required. Even if there is still enough time for a full charge of the charging sub-battery 3a through the range extender 1 up to 100% of its maximum capacity, the range extender 1 will reach the predetermined upper charge state (eg 75%, 80%, 85%). , 90% or 95%) turned off a full charge up to 100% as possible by the range extender 1 according to the invention is not sought, as this would be detrimental to the life cycle of the battery parts 3a, 3b, on the other hand by the thereby required, Reduced charging current in the upper capacity of the sub-battery 3a, 3b would lead to an inefficient partial load operation of the internal combustion engine, which according to the invention is also to be avoided. It is loaded with the RangeExtender 1 only up to a reduced end-of-charge voltage below the maximum end-of-charge voltage. The desired, defined upper charging end capacity or lower discharge limit capacity can also be made dependent on other factors, such as the temperature. In the case of an alternative grid charge at standstill, on the other hand, it is also possible to charge 100% of the battery capacity with the charge current which can be set in a readily adjustable manner.

The symbolically shown switching element 30 is designed such that the sub-batteries 3a, 3b in their assignment as a charging sub-battery 3a for recharging by the range extender or as a traction battery part 3b for discharging by the traction drive are interchangeable. The switching takes place in accordance with the state of charge (especially the traction battery 3b), ie at a time interval of many minutes and not high-frequency as in DC link capacitors in a power converter. Obvious for the person skilled in the art, this switching element according to the invention can also be implemented with modern semiconductor switches of various types.

The inventive concept can be extended to more than two sub-batteries 3a, 3b, each of which can each be decided either for charging by the range extender 1 or for discharge by the traction drive 4 each.

According to the invention, therefore, the ISG 2 may be designed so that it emits at the, the consumption optimum of the internal combustion engine 1 belonging speed, a voltage and a corresponding charging current, which is necessary for optimal charging of the charging batteries 3a. The additionally required charging electronics for the partial battery 3 a to be charged can thus be kept low, in particular in the case of a charge with an at least approximately constant charging current or constant charging power - which is indeed generated during optimum operation of the internal combustion engine - e.g. a simple circuit with monitoring of the cell voltage to determine the achievement of the desired SollLadeschlussspannung for connecting the range extender as charging current source and possibly necessary safety circuits, temperature monitoring, etc. be sufficient.

In a particularly simple embodiment of the maximum charge described in a range of less than 100%, e.g. For example, in a range of 75% to 90%, especially approximately only up to the limit at which a change to a slower top-up charge occurs in standard loading (for example, usually at about 80% in Lilon), the "Lade Intelligence »are kept particularly simple and eg to dispense with special converters to comply with a non-linear charging curve. In another embodiment, for example, only the battery temperature may be specifically considered. Especially since a variation of the charging current within a relatively small tolerance range has virtually no influence on the achievable battery life, any small adjustments required in the context of a control of the internal combustion engine towards the point of minimal fuel consumption (eg depending on the ambient conditions) can be performed without side effects become.

Since in a charge with a charging current below the maximum charging current, a further improvement life expectancy of the batteries 3a, 3b can be achieved, can also be taken in the dimensioning of the combination of range extender 1, part batteries 3a, 3b and 4 drive special care in that - with the inclusion of certain aging effects - the charging current (and consequently the power of the range extender 1 in optimum mode) tends to be kept so low that the charging time of a discharged to the lower charge line sub-battery 3a, approximately the expected travel time with the discharging traction battery part 3b corresponds, or at least to the extent that this is the battery life beneficial. Thus, to further improve battery life, there is no fastest possible charge from the range extender with maximum allowable charge current, but rather a slower charge, but which is possibly completed by the traction sub-battery 3b currently in use until discharge. However, it is generally, especially in Lilon batteries, not particularly harmful to life if a change of the sub-batteries when reaching the discharge end voltage of the traction battery 3b even before the complete reaching the desired end-of-charge voltage of the charging battery 3b. At most, a certain rest period between discharge and charge, in particular for cooling the heated by the charging or discharging sub-battery is provided. Accordingly, the components involved have to be coordinated.

Thus, according to the invention, the sub-batteries 3a, 3b are not charged and discharged at the same time, whereby the intercalation process (for example, the lithium-ion flow in the case of lithium-ion batteries) is not disturbed.

According to the invention, the traction drive 4 is purely electrical, that is, there is no connection to the direct mechanical power transmission from the engine 1 to the drive wheels 7. For the traction drive 4 come, for example. Permanent magnet synchronous motors (PMS) in question, in vehicles also asynchronous motors and hybrid synchronous motors are used. Due to the emerging scarcity of rare earth resources for the production of permanent magnets, however, it is currently also possible to evaluate extraneous motor variants as economical alternatives to permanent magnet excitation, even if their electrical-mechanical efficiency does not quite match that of permanent-magnet-excited motors. The motors 4 can be connected as direct drives or hub drives as well as indirectly via, mostly simple held mechanical gear with the drive wheels. Hub drives usually worsen the ratio of damped to undamped masses of the vehicle.

Specifically, for example, one or more single-phase AC motors may be provided for the traction drive 4. The single-phase AC rotary field synchronous motor with permanent magnetically excited rotor represents a relatively inexpensive drive, which is characterized by a high power density and high efficiency. He does not need a commutator, but only a capacitor for startup, which provides a phase shift for generating a rotating field. Its stator winding is similar to a three-phase motor, but is divided into a main line and an auxiliary line, the auxiliary line is offset in the stator against the main line by a phase angle. The rotor of such a synchronous motor can be permanently magnetically excited.

The speed control is done in a simple manner by the frequency control of an alternating current, which is supplied by the machine converter 20 from the DC voltage of the battery 3b. The effort for the power electronics is correspondingly smaller in a single-phase motor compared to a three-phase AC motor. The single-phase motor can also be designed with different numbers of poles. During the ferry operation, the vehicle speed is proportional to the engine speed supplied synchronously by the AC frequency from the engine converter 20. The power control is also done via a current position in the machine current converter 20 as well as other electric motors. The AC single-phase synchronous motor synchronous motor with magnetic rotor is due to the simple structure as a wheel hub motor, in which it depends on good cooling ability.

With regard to the discharge of the traction battery 3b, the possibilities of intervening for battery life improvement are more limited, since the discharge is primarily characterized by the respective prevailing driving situation: error: character: # not found, which can usually neither be predetermined nor influenced. Specifically, the driver expects from his vehicle a well-known, deterministic behavior to which he can trust even in extreme situations. For example, a possibly optimal, but arbitrary, for the driver 3b dynamic variation of the retrievable peak power of the vehicle could lead to dangerous traffic situations.

When braking the vehicle, a so-called recuperation, ie use of the drive motors 4 in regenerative operation and a return of electrical energy in the charging battery 3a or traction battery 4 can be used, even if this measure only a modest contribution to energy efficiency Vehicle brings.

With the concept according to the invention, optimum operation of an electric-powered vehicle with range extender, in particular with regard to energy efficiency and service life, is possible.

An embodiment of a practical example is calculated by way of example below. According to a survey alone in Berlin every day 1 million km driven, at a mean speed of only 25 km / h. One can imagine what enormous energy savings and air pollution reduction would be possible if one would generally introduce the electromobility according to the invention there. However, vehicle users would not feel constrained that vehicles have comparable range and proven refuelability as conventional internal combustion engine vehicles.

A city vehicle with a weight of 800 kg needed in the plane at a speed of 50 km / h max. a driving power of 1, 5 kW. With an efficiency of drive mechanism, 5, 6 electric motor 4 and power electronics 20 of 85% of the power demand on the traction battery 3b is thus 1, 8 kW. With a discharge of the traction battery 3b with an exemplary energy capacity of 10 kWh by only 20%, the vehicle can thus drive 2 kWh / 1, 8 kW = 1, 1 1 h, thus 67 min.

For charging the second part of the battery 3a requires a charging generator 2 with about 10 kW power only about 2 kWh / 10 kW = 0.2 h, thus only 12 min. The rest of the time, namely 55 minutes, the internal combustion engine 1 is stationary.

In the case of a diesel engine as a range extender today is the spec. Fuel consumption at the optimum point of about be = 196 g / kWh achievable. During the 67 min travel time, from which engine 1 only runs effectively for 12 min, the diesel engine (10 kW x 0, 196 kg / KWh) needs x 12 min / 60 min / h = 0.392 kg or 0.392 kg / 0, 861 / kg = 0.456 liters of diesel fuel. On 100 km distance extrapolated thus an average consumption of (100/1, 1 1 x 50) x 0.456 = 0.822 liters / 100 km. This vehicle is completely independent of plug-in dispensers that are usually not yet available and can reach more than a thousand km range with a small fuel tank of just 10 liters.

Would drive in comparison to a conventional vehicle with a 10 kW engine in partial load operation, the spec. Fuel consumption approx. Be = 280 g / kWh. While the transfer efficiency may then improve somewhat, e.g. to about 92%, but the consumption would still be with (280/196) x (0.85 / 0.92) = 1, 32 liters / 100 km about 32% higher).

In addition, the inventive electrical variant has the advantage that the batteries 3a, 3b - where appropriate infrastructure is available, even in the state of the general power grid can be charged, so that, for example. for short-haul trips, such as the daily commute with a mains charging at home and in the workplace to further reduce mileage costs and environmental emissions. For example, at the start of the journey, the destination and whether (possibly) an external charging option is available can be announced. From this it can be calculated if and how long the range extender is used. And even if at the destination, e.g. in the event of overcrowding, no mains charging is possible, the range extender can also replace the missing socket during the parking time if necessary, so that an unrestricted onward journey is nevertheless possible.

The embodiment of the invention in Fig. 3 again shows the range extender combustion engine 1 with a coupled thereto electric generator 2, which may be designed as a DC charging generator in the form of an integrated start generator for the internal combustion engine 1. The triac 40 serves as a charge - start switch for both current flow directions of sub-battery A 3a. The thyristor 41 serves as a charging switch for the sub-battery B 3b. The switching elements shown in this diagram are to be considered symbolically and can also be realized with other, electronic or mechanical switching elements fulfilling the respective function. The battery 8 for the vehicle electrical system of the vehicle, which is separate from the supply network of the traction and usually has a lower voltage, can be charged via a DC / DC converter 9. The tap of the DC / DC converter 9 can also take place elsewhere than shown.

If available, the sub-batteries 3a and 3b may also be charged via the plug-in charging rectifier 19 from the power grid or from renewable energy sources. The Ladeumschalter 44 selects one (or even both) sub-batteries 3a, 3b for charging.

The drive side consists of an electric motor 4, which transmits via its possible gear 5,6 its torque to the or the drive wheels 7. The electric motor 4 is driven by the power converter 20 in accordance with the driving command, e.g. starting from the acceleration foot pedal 21, driven. The traction switch 42 determines from which of the sub-batteries 3a or 3b of the traction drive 4 is supplied.

The parent control unit EEM 33 is inventively designed such that one of the sub-batteries 3a, 3b respectively, in particular exclusive, is selected for the discharge by the traction or charging by the range extender. The charge and discharge in each of the sub-batteries 3a, 3b can therefore take place completely independently of each other, so that either a clearly defined charging or discharging on one of the sub-batteries 3a, 3b is applied and no mixture or no continuous change between charge and discharge or with the driving situation fluctuating charging current occurs.

In this case, the EEM 33 controls the engine 1 so that it runs only in its most energy-efficient workspace, or remains completely off. An inefficient partial load operation is avoided, especially in the

8 of the range extenders 1, 2 and the sub-batteries 3a, 3b are matched to one another so that in the consumption-optimal or low-pollutant operating point or working range of the range extender internal combustion engine 1, the sub-battery 3a corresponding charged for this, in particular with respect to their life, advantageous charging function becomes.

Specifically, a change of a respectively exclusive use as a charging sub-battery 3a or traction battery 3b so controlled by the EEM 33 that the sub-batteries 3a, 3b are operated only in an advantageous for their lifetime capacity range, ie in particular deep discharges of Traction battery 3b below a lower charge threshold and overcharges of the charging battery 3a over a capacity upper limit, which is below the maximum capacity, is avoided.

Specifically, in a combination of optimum operation of the internal combustion engine 1 and optimal, undisturbed by ferry charging one of the sub-battery 3a by the internal combustion engine 1, can operate an energy-efficient motor vehicle, which has a range and a Wiederauftankkomfort of conventional vehicles, if necessary, but can also be used for short-distance journeys as a virtually emission-free plug-in vehicle.

FIG. 4a shows a first example of a vehicle concept according to the invention in operation. In the diagrams shown is an embodiment of a motor vehicle according to the present invention with two sub-batteries. The upper diagram shows the current state of charge of the first sub-battery BAT-A and the lower diagram shows the current state-of-charge of BAT-B. The changing state of charge as well as the current mode of operation of the respective energy store are displayed to the right of the time axis, which enters the modes «Charging with the Range Extender» 50, «Charging on the mains» 51, «Ferry operation (discharged)» 52 and « Break »53 breaks down. According to these modes, the respective sub-battery of either the drive unit or the (range-extender or network) charging unit is switched on or can be switched on at break 53 neither of the two.

Initially, both batteries BAT-A and BAT-B are charged, for example as described above with about 80% of their specified maximum or rated capacity. The ferry operation 52 is started as shown with BAT-A, which is connected to the traction drive, and during which BAT-A is unloaded. Meanwhile, BAT-B is in break 53, where it is neither loaded nor unloaded. When a lower capacity limit of BAT-A is reached, in particular during the ferry service and without interruption for the driver, a switchover 47 to BAT-B, which is now switched instead of BAT-A the traction drive and supplies the required for ferry operation 52 electrical energy , While energy is being drawn from BAT-B, BAT-A will charge 50 with the range extender operating in the optimum operating range, as shown in the upper diagram. If BAT-A has reached the upper capacity limit, the range extender is switched off again and BAT-A is in break 53, in which it is neither charged by the range extender nor unloaded by the traction drive. Optionally, the pausing 53 can be used thereby to cool the battery charged during charging or discharging thermally loaded. For example, the pausing 53 can also be divided by the times before and after loading 50 by the range extender. Thus, for example, it is not only possible to pause between charging 50 and next ferry operation 52, but also between ferry operation 52 and charging 50. The periods of pausing 53 may depend on the energetic requirements of ferry operation 52, and in special embodiments the pausing time may also be be reduced to zero.

If BAT-B has now reached a fixed, lower capacity limit (about 20% in the example shown), then a new switch 47 takes place and BAT-A is discharged again and BAT-B is loaded. In this exemplary scenario, however, a variant is shown in which BAT-A is not unloaded to the lower limit while driving, but the vehicle is previously Parked and connected to an external electrical energy source, by means of which energy source, a so-called network charge 51 takes place. When charging the grid, in the example shown, BAT-A and then BAT-B are loaded. Alternatively, this can also be done in reverse order or - if the external power source and the formation of the power charger allows this - BAT-A and BAT-B can also be loaded simultaneously.

Such a network charge 51 can, for example, also take place with a different charge curve (for example faster), since no optimum point of the internal combustion engine has to be taken into account here, but only a reduction of the battery life is to be avoided. Optionally, in one embodiment of the invention in the network charge 51 (as shown in the example) also a so-called top-up charge beyond the limiting in the range extender load 50 upper capacity limit out, especially since the grid charge performed with variable charging power can be faced without the disadvantages of an inefficient partial load operation. For example, the full energy capacity of the sub-batteries can be used during nighttime charging with cheap nuclear power. Alternatively, however, the same upper capacity limit as in the case of the range extender charge can also be used in the case of grid charging, e.g. if this provides life-time benefits for the energy storage used.

Following (or also interrupting the grid charge), then again the ferry operation 52 with one of the sub-batteries BAT-A or BAT-B begin, the energy management unit 33 with its control logic preferably in the medium term approximately equally distributed use and / or wear of the two sub-batteries BATA and BATB can try to achieve.

In the lower diagram to BAT-B next to the solid line of the case 45 described above, an alternative option 46 is shown with dotted lines. In this, the energy management unit 33 of the vehicle is the information available that within a range which are still safely achieved with BAT-A

9, a charge on the grid will be possible or planned. This is the case, for example, when the well-known daily commute has been selected in the car navigation system, followed by a longer parking time, in which recharging by means of a socket as an external source of energy is possible, which is cheaper and / or more environmentally friendly (for example from renewable sources). can deliver as the range extender. Accordingly, charging of BAT-B by the range extender is dispensed with and instead waits until an external power supply is established and then recharges the vehicle.

FIG. 4b shows a second example of a vehicle concept according to the invention in operation. This is similar to that of the previous figure, but in this example no mains charge is applied and BAT-A pauses before the first charge shown (e.g., to cool again at high ambient temperatures and heating by the previous discharge). Also, the lower capacity limit is about 40% higher than before due to another battery type of the sub-batteries.

Fig. 5 shows an example of a consumption map of an internal combustion engine, e.g. from a turbo diesel internal combustion engine. This map shows specific fuel consumption maps at the respective operating point. The minimum, so optimal fuel consumption (in the example shown 196g / kWh diesel fuel) is limited to a relatively small speed and torque range of the engine, which represents the optimum point 196. The significantly larger range 200 with 200g / kWh is only slightly worse and can be considered with its deviation of about 2% (or possibly even up to about 5%) from the optimum point 196 still as the optimum range 200, in which the internal combustion engine in the frame of the present invention. However, preferably the narrowest possible range around the optimum point 196 of the engine control by means of the energy management unit 33 is desired. Outside of these areas, the specific fuel consumption increases sharply, especially in the partial load range with low torque in the lower part of the map. In such a consideration, environmental influences such as temperature, etc. can also be taken into account, which can possibly lead to shifts in the consumption map or to a correspondingly parameterized group of characteristic maps. The energy management unit 33 can also perform an online optimization of the fuel consumption during operation in addition to a use of maps, for example in the form of a control loop.

Thus, according to the invention, the internal combustion engine and the electric generator connected thereto, as well as the sub-battery currently connected to it, are designed and designed in such a way that the internal combustion engine is constantly at optimum point 196 or at least at the optimal charge for the sub-battery with respect to its lifetime in the optimum range 200 is operated. Accordingly, generator is designed for such operation and also has a high efficiency in this case of operation. In this case, an electrical energy management unit 33 can be used, which is operatively connected to the internal combustion engine and controls its operation accordingly. This energy management unit 33 is designed in such a way to operate the engine at optimum consumption and to keep it permanently in this. It can also use information about the current state of the currently connected to the generator sub-battery. For example, the energy management unit 33 starts and stops the internal combustion engine according to the level and / or temperature of the sub-battery being charged, and controls the air and fuel supply during operation, as well as possibly other parameters for operating the internal combustion engine (such as the injection curve, etc.). If necessary, the energy management unit 33 can also drive a power converter between the generator and the sub-battery in order to additionally influence the electrical parameters of the charging of the sub-battery. According to the present invention, however, an additional active influencing by a power converter is not required, or only in a very small scope, in particular if the system components of the internal combustion engine / generator sub-battery are matched to one another accordingly.

FIG. 6 shows an example of a charging curve of energy storage devices, specifically an exemplary embodiment of a lithium-based energy storage device. In each case, a generic example of a voltage curve U and a current waveform I is shown at a charge of the energy storage, as well as the respectively associated stored electrical energy E. The example in the figure shows values for a single battery cell, of which in practice Several are joined together to form a sub-battery, which sub-batteries then voltages of tens or hundreds of volts and currents of tens or hundreds of amps have. In the example shown, the voltage U in the lowermost charge region only increases greatly, then increases more slowly, continuously, only to rise very slowly in the upper charge region. The charging current I is kept approximately constant in the lower range, but drops sharply after that range in which the voltage curve becomes flatter. According to the invention, a cell of a sub-battery is operated only in the marked area 50, in the example shown, for example, in an area 50 of exemplary 28% to exemplary 79% of the capacity value specified for the cell. In said region 50, the cell can be charged with approximately constant power, thus specifically the permanent operation of the supercharging internal combustion engine in the optimum point 196 and optimum range 200 can be simplified. Depending on the type of battery actually used, charging with constant charging power (and correspondingly constant generator drive power) can also be used as a charging strategy in this area (eg with correspondingly decreasing charging current I to the upper limit of 79%, so that, despite increasing voltage the power remains constant, which can be done, for example, with a power converter optimized for this area and / or by designing the entire system,

10

Claims (10)

so that such a variation by design remains within the optimum range 200), without (significantly) adversely affecting the maximum number of charging cycles achievable with the cell. The range extender is therefore operated so as to say in stop-and-go operation respectively in the optimal operating point 196 / operating range 200, or completely disabled. A part-load operation outside of the consumption optimum range 200 is avoided (if at all possible, except, for example, except for a brief start-up phase or the like). It can, for example, even when reaching a critical part battery temperature instead of a customary in the prior art reduction of the charging current I completely stop charging and only when a permissible battery condition, the charge will be resumed. claims 1. 1. Motor vehicle with An electric traction drive (4), An electrical energy store for the provision of electrical energy for the travel drive (4), • an internal combustion engine (1), in particular a gasoline or diesel engine, and • An exclusively by the internal combustion engine (1) driven electric generator (2) for recharging the electrical energy storage, characterized in that The energy store is formed with at least one first sub-battery (3a) and at least one second sub-battery (3b), and A switching element (30) is arranged between the first sub-battery (3a), the second sub-battery (3b), the electric generator (2) and the electric traction drive (4) and configured such that the first sub-battery (3a) and the second Partial battery (3b) alternately the electric generator (2) or the electric traction drive (4) are switchable. 2. Motor vehicle according to claim 1, characterized in that the switching element (30) between A first mode in which the electric generator (2) of the first part battery (3a) and the electric drive (4) of the second part battery (3b) is switched on, and • A second mode in which the electric generator (2) of the second sub-battery (3b) and the electric traction drive (4) of the first sub-battery (3a) is switched on, in particular wherein the switching element (3) is automatically switched during the ferry operation, so that a alternately either charging or discharging the respective sub-battery (3a, 3b) is feasible. 3. Motor vehicle according to one of claims 1 or 2, characterized in that an electrical energy management unit (33) is designed and is in operative connection to the internal combustion engine, that the first sub-battery (3a) is charged such that while the internal combustion engine ( 1) is permanently operated in an area of its lowest specific fuel consumption in the engine map, especially permanently in an optimum range with a deviation of less than 5% of the lowest specific fuel consumption of the internal combustion engine (1), and thereby the first sub-battery (3a) with their, in particular with respect to a maximum charging cycle number achievable by the sub-battery, optimum charging curve is charged by the electric generator (2), especially during which the sub-battery is charged with at least approximately constant charging power during its entire charging process and / or only a partial area of a total available capacity area of the sub-battery (3a) is used. 4. Motor vehicle according to one of claims 1 to 3, characterized in that a mechanical drive power for the motor vehicle at any time in each case exclusively from the second, a traction by the traction drive (4) associated sub-battery (3b) is removable, and one of the electric generator (2) provided electrical energy in each case only the first, a recharge by the electric generator (2) associated sub-battery (3a) can be fed, with the switching element (30) the first sub-battery (3a) and second sub-battery (3b), in particular always, are electrically separated from each other and with the switching element (30) the first sub-battery (3a) and the second sub-battery (3b) either the drive (4) or the electric generator (2) is assigned, in particular automatically and depending on a state of charge of the sub-batteries ( 3a, 3b). 5. Motor vehicle according to one of claims 1 to 4, characterized in that the electric generator (2) is designed as an integrated starter generator, which for starting the internal combustion engine (1) in a motor operation and during operation of the internal combustion engine (1) for generating electrical energy can be used in a regenerative operation, in particular wherein the integrated starter generator is installed in a crankcase of the internal combustion engine (1). 6. Motor vehicle according to one of claims 1 to 5, characterized in that the electric generator (2) and the Internal combustion engine (1) in its design to the sub-batteries (3a, 3b) are tuned such that for a speed and torque range in which the internal combustion engine (1) their specific fuel 11 consumption minimum, the electric generator (2) has an electrical output, which causes a charging of the sub-battery (3a) with a life-time optimal charging current. 7. Motor vehicle according to one of claims 1 to 6, characterized in that the traction drive (4). is formed with at least one permanently magnetically excited AC synchronous motor, in particular with a single-phase AC rotary field motor, and / or the traction drive (4) is formed with at least one wheel hub motor. 8. Motor vehicle according to one of claims 1 to 7, characterized in that the motor vehicle has a device (19) for charging the sub-batteries (3 a, 3 b) from an external power source, in particular at vehicle standstill from the power grid, specifically with a Charge switch (44) optionally, the first sub-battery (3a) and / or second sub-battery (3b) is charged from the external power source, and / or with a DC / DC converter (9) from a circuit of the first sub-battery (3a) or second sub-battery (3b) is a charging of a low-voltage electrical system battery (8) of the motor vehicle feasible. 9. Motor vehicle according to one of claims 1 to 8, characterized in that the internal combustion engine (1) has a turbocharger (45) which is electrically driven, in particular where this of a circuit of the first part of the battery (3a) or the second part of the battery (3b ) is supplied. 10. A method for operating an electrically driven motor vehicle with an internal combustion engine (1) as a range extender, with • an electric driving of the motor vehicle with an electric motor as a traction drive (4), wherein • Supplying the electric motor with electrical energy from a first part of battery (3a) of an electrical energy storage, takes place and • Driving an electric generator (2) for generating electrical energy, which driving exclusively by the Internal combustion engine (1) takes place, and Charging of a second sub-battery (3b) of the electrical energy store which is electrically independent of the first sub-battery (3a) with the electrical energy of the electric generator (2), an automatic, alternating connection of the first sub-battery (3a) with a switching element (30) or the second sub-battery (3b) to either the electric generator (2) or the traction drive (4), in particular wherein the charging of the first sub-battery (3a) is electrically independent of supplying the electric motor by the second sub-battery (3b), especially wherein the Charging with a permanent operation of the internal combustion engine (1) takes place in a range of their lowest specific fuel consumption or the internal combustion engine (1) is completely deactivated, preferably wherein the charging of not the traction drive (4) switched, the first sub-battery (3a) continuously, with a for the first sub-battery (3a), in particular with regard to h is a maximum charge cycle number achievable by the sub-battery, optimum charging curve is effected by the electric generator (2), in particular charging being carried out during the entire charging process with at least approximately constant charging power and / or only a partial area of a total available capacity range of the sub-battery (3a). in particular between approximately 30% and 80% of the available capacity. 12