DE102009045448B4 - Vehicle for driving in stages with an electric motor and a battery and method for driving a vehicle - Google Patents

Abstract

Vehicle (2) for driving in stages between respective battery exchange bases with possible intermediate stops, with - an electric motor (14) as the main drive motor and - with an energy supply device for the electric motor (14), which has at least one rechargeable exchangeable battery (6) mounted on the roof (4) of the vehicle (2) as the basic energy source of the electric motor (14), the energy content of which, in the fully charged state, is dimensioned such that it can cover the anticipated energy requirement of the vehicle (2) for the respective current stage to the next battery exchange base with a safety margin of 150% to 250%, and - a reserve energy supply unit that can be activated as an emergency unit if necessary for providing electrical energy in the event that the energy requirement of the electric motor (14) exceeds the energy content of the rechargeable exchangeable battery (6) in order to ensure a journey to the next battery exchange base.

Description

The invention relates to a vehicle that can be used in a staged driving operation, for example, in a bus service. The vehicle is powered by an electric motor supplied with energy by a rechargeable battery.

Regular buses make a significant contribution to inner-city public transport. Regular buses are still mostly powered by fossil fuels, such as diesel. Despite their already low fuel consumption per passenger, these vehicles, which are typically used on repetitive routes in local public transport, offer significant savings potential in both energy consumption and CO2 emissions.

Various drive variants are already being used for such vehicles that reduce fossil fuel consumption or eliminate fossil fuels altogether. For example, it is known to use generator-driven combustion engines to provide electrical energy for a vehicle's electric drive. In addition, high-performance batteries or high-performance capacitors (so-called ultra-caps) can provide energy for short-term high power requirements, such as during acceleration or when driving uphill.

A further increase in efficiency can be achieved by recovering braking energy and storing it in the battery and/or capacitors. In this case, the vehicle's electric motor operates as a generator, thus acting as a "brake."

Hybrid drives that are even more optimized in terms of energy consumption use a fuel cell instead of the combustion engine, which generates chemical electrical energy. The state of the art in this regard is, for example, EP 1 868 837 B1 A fuel cell serves as the main energy source for the electric motor in this known drive system. To provide short-term peak power, both a battery acts as a "minute storage" and a number of series-connected high-performance capacitors act as "second storage." Braking energy can be stored in the battery and capacitors by the generator-driven electric motor.

What all of the energy supply systems described above have in common is that their main energy source is still fossil fuels or other continuously supplied energy sources that can be chemically converted into electrical energy. In order to almost completely do without such energy sources, vehicles that are powered by batteries as their main energy source are already in use. Scientific developments in recent years have increased the performance of batteries, such as energy content, minimum charging time and the available power, and reduced their costs to such an extent that batteries have become practical and economically interesting as the sole energy source for vehicles, especially buses. Buses have already been used in which a sufficiently large battery was installed to ensure the bus can operate throughout the entire day. To provide the energy for this operation, the battery must have a very high energy content, which leads to considerable battery costs and a very high battery weight.

Another limiting factor in this system is battery recharging. Various options are available for recharging the battery of a vehicle of the type mentioned above. With a permanently installed battery in the vehicle, the battery must be fully recharged within a typically short downtime of the bus. Such rapid charging has a detrimental effect on the battery's service life.

Inductive charging solutions have also been proposed, for example, at intermediate bus stops. However, these require a very large amount of energy to be charged into the battery in a very short time, which again brings with it the disadvantages mentioned above.

It has also been proposed to operate buses with a swappable battery, so that at the end of each day's service, the almost discharged battery is swapped for one that has been fully charged in the depot. This allows the battery to be charged much more slowly and thus increases its service life. The disadvantages of this option, however, are the large volume and very high weight of the battery and the robust battery mounts on the bus. Such heavy batteries cannot be supported on the roof of the bus, as they would overtax the roof stability and significantly shift the center of gravity upwards; instead, such batteries are usually installed in a difficult-to-access floor area of the bus.

EP 1 810 869 A1 relates to an electrically powered bus equipped with a cassette battery pack and a bus-mounted control system. A charging station is provided at a predetermined location for charging cassette batteries. ries sets. A cassette battery pack is exchanged using a charging and discharging device operated in the floor area of the bus. A charging and discharging control system, a bus-mounted control system, and a charging control system can communicate with each other. When the charging and discharging control system receives a signal sent from the bus-mounted control system that the bus is returning to the charging station, the charging and discharging device moves to a predetermined position. When the bus arrives at the predetermined position, the charging and discharging device exchanges cassette battery packs, enabling the bus to operate continuously.

DE 10 2007 004 172 A1 relates to a motor vehicle with at least one traction battery and an electric traction motor, as well as a combustion engine-driven generator. Should the traction battery be faulty or discharged and be unable to provide any or only limited power to the converter and the electric traction drive, the combustion engine-driven generator is activated, for example, and the provided electrical energy is then used to power the electric traction drive, enabling emergency operation, usually at a limited speed.

DE 198 13 146 A1 relates to a power supply system for use in an electric vehicle whose wheels are driven by a DC voltage supply comprising a combination of a rechargeable high-energy battery and a high-performance battery, and to a power supply system for use in a hybrid electric vehicle whose wheels are driven by an internal combustion engine and a DC voltage supply comprising a combination of a rechargeable high-energy battery and a high-performance battery.

EP 1 868 837 B1 relates to a drive system for an electrically powered vehicle, comprising an electric drive unit operable as a motor and generator, a first power source circuit, a second chargeable and dischargeable power source circuit connected in parallel with the drive unit, and an electrical intermediate circuit connected to the first and second power source circuits and to the drive unit. A control device is configured to set a variable setpoint for a voltage of the intermediate circuit as a function of the vehicle speed and to set the power output of the first power source circuit as a function of the setpoint and the voltage of the intermediate circuit.

The object of the present invention is to provide a vehicle with a cost-effective energy supply which largely dispenses with physically or chemically converted and continuously supplied fuels and whose energy management requires only minimal effort.

The object is achieved by a vehicle for driving in stages between respective battery exchange bases with possible intermediate stops according to patent claim 1, in particular with an electric motor as the main drive motor and with an energy supply device for the electric motor, which has at least one rechargeable exchangeable battery mounted on the roof of the vehicle as the basic energy source of the electric motor, the energy content of which in the fully charged state is dimensioned such that it can cover the anticipated energy requirement of the vehicle for the respective current stage to the next battery exchange base with a safety margin of 150%-250% and a reserve energy supply unit which can be activated as an emergency unit if necessary for providing electrical energy in the event that the energy requirement of the electric motor exceeds the energy content of the rechargeable exchangeable battery in order to ensure a journey to the next battery exchange base.

Preferably, the energy supply device additionally comprises at least one electrical capacitor for providing energy for temporary high-load operation of the electric motor.

A bus operating on a scheduled service usually travels a predetermined leg before returning to its final stop. This leg is then traveled repeatedly throughout the day. These legs are usually comparatively short and are, for example, completed in a time of approximately one hour. Since, according to the invention, a battery is installed in the vehicle whose energy content, with a certain safety margin of 150%-250%, is sufficient to supply the vehicle with energy for the leg, a much smaller, and thus lighter, and more cost-effective battery can be installed than would be necessary for operation throughout the entire day. In order to avoid completely discharging the battery during a journey and to also carry a certain reserve, the energy content of the battery is preferably dimensioned in the manner mentioned above so that it is approximately 1.5 to 2.5 times the expected energy energy requirements of the vehicle on the current stage.

To prevent the battery from becoming deeply discharged or even breaking down due to unexpectedly increased energy demand, such as can be caused by diversions along the vehicle's usual route or by persistent stop-and-go traffic, a backup power supply unit is provided that can be activated on demand but is not normally used. This backup power supply unit feeds electrical energy into the system via a generator, thus charging the battery. The backup power supply unit is preferably an internal combustion engine that drives a generator.

Preferably, the maximum power of the combustion engine is less than 60 kW, in particular less than 30 kW.

The backup power supply unit is intended solely as an emergency generator to ensure a trip to the nearest battery replacement station. The backup power supply unit should therefore be dimensioned so that it has the lowest possible power consumption, requires little space, and is lightweight. It will therefore be undersized for the vehicle's primary operation and therefore not capable of operating the vehicle in the usual manner.

To provide energy for temporary high-load operation, such as during acceleration, at least one, preferably several, series-connected electrical capacitors can be used. Due to the purely electrostatic energy storage in the capacitors, they can be charged and discharged quickly without damage and exhibit relatively low power loss while simultaneously providing almost instantaneous power.

It is particularly preferred that the energy supply device comprises a control device which is designed to automatically switch on the reserve energy supply unit when the rechargeable exchangeable battery falls below a predetermined partial discharge state.

This partial discharge state preferably corresponds to 30% to 60% of the full charge state. Furthermore, the vehicle is preferably configured to store electrically converted braking energy in the battery and/or the capacitor, preferably by operating the electric motor as a generator. The recovery of braking energy further increases the energy efficiency of the drive. Considerable braking energy is generated, especially due to the regular stops at intermediate stops in scheduled service.

Simulations by the inventor have shown that the battery's energy content should preferably be dimensioned such that, for each kilometer of travel, an energy supply of between 1.0 and 1.6 kWh, particularly 1.3 kWh, allows for optimal operation of an average public bus. This value can vary depending on the vehicle weight and may also deviate from the specified interval.

Preferably the vehicle is a regular bus.

A lithium-ion battery is particularly preferred as the primary energy source.

The object of the invention is further achieved by a method for driving a vehicle according to one of the preceding claims on a route with one or more stages, wherein each stage is delimited by a first battery exchange point as the starting point and a second battery exchange point as the end point, wherein the driving operation on a respective stage comprises the following steps: covering a stage from the first battery exchange point to the second battery exchange point; approaching any intermediate stops on the stage; repeatedly checking the charge level of the rechargeable exchangeable battery and automatically switching on the reserve energy supply unit if the charge level has fallen below a predetermined partial discharge level; exchanging the battery at the second battery exchange point with a substantially fully charged battery.

The vehicle begins its journey on a leg at a first battery swap station with a substantially fully charged battery. Any intermediate stops are made along the leg. Upon reaching the second battery swap station at the end of the leg, the battery is so significantly discharged that it requires recharging. At this second battery swap station, this discharged battery is then replaced with a substantially fully charged battery. The charge level of the rechargeable swap battery is continuously checked throughout the leg. If a predetermined partial discharge level is reached, which should not normally occur because the battery is sufficiently large, the reserve power supply unit is automatically activated.

In order to ensure the most efficient driving operation, the battery is preferably replaced automatically at each battery replacement station. This can be done, for example, by a dedicated battery replacement device into which the bus drives. At such a battery replacement station, a warehouse with charging stations for the replaced batteries can then be provided, for example. This warehouse is preferably operated automatically, and fully charged batteries that are to be replaced with discharged batteries are also selected automatically. It is particularly preferred if the first and second battery replacement stations are the same battery replacement station. This can be the case if the vehicle is operated in a scheduled service, starting from a terminal stop and traveling along a loop-shaped route and then returning to its terminal stop.

However, it is also possible for the bus to visit several different battery swap stations along its route, where rechargeable batteries are swapped as described above. The procedural steps for a single leg between two battery swap stations are the same as described above. The energy management is thus adapted to stage-drive operation, allowing the use of small, lightweight, and inexpensive standard batteries for which the recharging time is not particularly important. Therefore, there is no need to use expensive batteries with fast-charging capabilities.

• 1 zeigt einen mittels Elektromotor angetriebenen Gelenkbus mit einer Batterie auf seinem Dach als Energieversorgung;
• 2 zeigt eine elektrische Schaltung mit einer Batterie zur Energieversorgung des Elektromotors des Gelenkbusses der 1;
• 3 zeigt Verfahrensschritte für den Betrieb eines Linienbusses, der auf einer geschlossenen Etappe verkehrt, wobei jeweils an der Endhaltestelle die Batterie gewechselt wird;
• 4 zeigt die Verfahrensschritte zum Betrieb eins mit einer Batterie betriebenen Fahrzeuges auf einer Fahrstrecke mit mehreren Etappen.

Embodiments of the invention are described below with reference to the figures.

• 1 shows an articulated bus powered by an electric motor with a battery on its roof as power supply;
• 2 shows an electrical circuit with a battery for supplying energy to the electric motor of the articulated bus of the 1 ;
• 3 shows procedural steps for the operation of a scheduled bus that runs on a closed stage, with the battery being changed at each final stop;
• 4 shows the process steps for operating a battery-powered vehicle on a multi-stage route.

In the 1 An articulated bus 2 is shown, as is frequently used in scheduled service. The articulated bus 2 is driven by an electric motor (not shown). This electric motor is primarily powered by a rechargeable, replaceable battery 6 mounted on the roof 4 of the articulated bus 2. The battery 6 is attached to the roof by a fastening device 8 so that it can be easily replaced. In particular, the battery 6 is mounted so that it can be removed from the roof 4 of the bus 2 by an automatic battery changing device and replaced with an identical battery in a corresponding manner.

The battery is also provided with a protection 10 to protect it from environmental influences. Protection 10 is also designed to allow easy and quick access during automatic battery replacement using an automatic battery changing device.

Due to its favorable performance data, the battery is preferably a lithium-ion battery.

Battery 6 is the primary energy source for the electric drive of bus 2. The battery's energy content is dimensioned to be sufficient to supply bus 2 with energy during its normal scheduled service on its entire route from the final stop along the route back to the final stop. For example, a safety margin of 150%-250% can be calculated, so that under normal conditions, the bus could cover 1.5 to 2.5 times the stage distance using the battery as the energy source. A certain amount of battery reserve should be considered for vehicle air conditioning.

The 2 The circuit arrangement 12 shown, based on a battery 6 as the basic energy supply source, also enables a satisfactory energy supply to the bus 2 in almost all driving situations. The electric motor 14 of the bus 2 is controlled via a converter 16. The converter 16 converts the direct voltage provided in a circuit 18 into alternating voltage for operating the electric motor 14. The drive motor 14 can, for example, be a permanently excited synchronous machine. The drive machine 14 can also be operated as a generator, so that the power generated during generator operation, for example during a braking process, is converted into direct voltage in the converter 16 and fed into the circuit 18. Of course, several drive machines can also be used, which are placed on a respective wheel hub of the vehicle and are integrated into the circuit accordingly.

To supply energy to the drive motor 14, in addition to the battery 6, two further Energy supply systems are available. In order to be able to provide high power levels at short notice, a second energy supply unit 20 comprises several storage devices for storing electrical charge, in particular series-connected double-layer capacitors 22 (ultracaps), connected in parallel to the battery 6. The capacitors, in particular ultracaps, have a very high energy density and store energy electrostatically. In contrast to a chemical energy storage device such as a battery, a capacitor can absorb and release high power levels quickly.

The series-connected capacitors 22 serve to provide high power for a short time during acceleration or when driving uphill, particularly power that would exceed the battery's capacity. During normal operation, the capacitors 22 are charged to the battery voltage.

The energy content of the battery 6 is dimensioned such that it can supply the bus 2 with energy on its usual route from its final stop along its route back to the final stop. If unforeseen route extensions occur, such as diversions due to construction sites or energy-intensive, excessive stop-and-go traffic, the battery 6 will be discharged further than usual due to the increased energy consumption. To prevent damage to the battery and to continue to maintain sufficient power for driving, an internal combustion engine (not shown) is provided that drives a generator, such as a conventional alternator. The generator is integrated into the circuit 18 at connection points 24, 26 and is also connected in parallel to the battery 6. In situations in which the battery 6 is discharged further than permitted, the generator-driven internal combustion engine feeds energy into the circuit 18 via the connections 24, 26 and charges the battery 6.

As already described above, the drive motor 14 can also be operated as a generator, so that when the vehicle brakes, the deceleration power is generated by the generator, which feeds current into the circuit 18 via the converter 16. The energy generated is temporarily stored in the battery 6 or the capacitors 22 until their maximum charge capacity is reached. When the batteries are full, the braking power can be dissipated in a braking controller 28. The braking controller 28 consists of a braking resistor 30 and a circuit breaker 61.

The high power generated during braking does not pose a problem for the capacitors 22, but the charging power of the battery 6 must be regulated. This is done via a battery charging control circuit 34. The battery charging control circuit consists of a diode 36 and a DCDC converter 38 connected in parallel. The energy flow from the battery to the electric motor flows either via the DCDC converter 38 or, when the capacitors 22 are sufficiently discharged, via the diode 36. When energy flows from the generator-driven drive machine 14, the diode 36 blocks, and the charging power is regulated by the DCDC converter 38.

With the previously described power supply circuit 12, the operation of the bus 2 can be ensured in all driving situations. During normal load operation, the battery 6 supplies the drive motor with power. During brief periods of high power, such as during acceleration or uphill driving, the capacitors 22 support the power supply. Should the battery be excessively discharged due to unforeseen circumstances, the generator of the combustion engine provides energy to charge the battery.

During operation of a bus 2 operating in scheduled service, the energy content of the battery is selected such that the energy is sufficient to supply bus 2 with energy on its constantly repeated leg from its final stop to the turnaround stop and back to the final stop. At the final stop, battery 2, which is discharged to, for example, 40% to 50% of its full charge capacity, is exchanged for an identically charged battery. The discharged battery is then recharged at the final stop. The charging time of the battery until it is fully charged can be approximately the same as the time required by the bus to complete the entire leg. As in 3 As shown, the bus starts at the start of the stage, travels to various intermediate stops along the stage, and finally arrives at the end of the stage. For a bus traveling in a loop, the end of the stage is precisely the start of the next stage. The battery is then changed at the end of the stage or the start of the stage. The battery is changed using an automatic battery changing system. After the battery change, bus 2 travels through the stage again and returns to the start. Once again, the discharged battery is replaced with the one that has been fully charged during this time. The now discharged battery is charged at the battery changing station. This operating procedure makes it possible to operate the bus with a few, small batteries. which are constantly being changed, to operate continuously.

The bus does not necessarily have to travel in a loop-shaped stage, where it always returns to the starting point of the stage and the battery is always changed at the same battery exchange point. For longer journeys, several battery exchange points are planned along the entire route. As described in 4 As shown, the bus travels through the first stage. At the end of the first stage, the battery is swapped for a fully charged one. The discharged battery is charged at this battery swap station. The bus can now travel through a second stage to the next battery swap station, where the battery is swapped again. It is also possible, however, for the bus to return from the end of the first stage to the start of the first stage after the battery swap. Here the battery is swapped again. Once the bus has traveled through a second stage, it is possible to return from this battery swap station to the start of the second stage. The bus can also continue on to another battery swap station, for example the start of the first stage.

As in 4 As indicated, the number of stages or battery swap stations can of course be increased as desired. It is important, however, to ensure that the energy content of the battery used at each battery swap station is selected so that it is sufficient to complete the next stage.

As the previous description makes clear, the method for operating a vehicle with one or more swappable batteries is extremely flexible. Therefore, it is not limited to the operation of a regular bus that always runs the same route; it is also possible to supply such a system to a taxi or a delivery vehicle operated in the city. Especially in inner-city operations, the distances or journeys to be covered are comparatively long. Battery swapping stations in the form of taxi stands are also available.

Claims (15)

A vehicle (2) for travel in stages between respective battery exchange stations with possible intermediate stops, comprising: - an electric motor (14) as the main drive motor, and - an energy supply device for the electric motor (14), which has at least one rechargeable interchangeable battery (6) mounted on the roof (4) of the vehicle (2) as the basic energy source of the electric motor (14), the energy content of which, when fully charged, is dimensioned such that it can cover the expected energy requirements of the vehicle (2) for the respective current stage to the next battery exchange station with a safety margin of 150% to 250%, and - a reserve energy supply unit that can be activated as an emergency unit if necessary to provide electrical energy in the event that the energy requirements of the electric motor (14) exceed the energy content of the rechargeable interchangeable battery (6), in order to ensure a journey to the next battery exchange station. Vehicle (2) to Claim 1 , characterized in that the reserve energy supply unit is an internal combustion engine which drives a generator. Vehicle (2) to Claim 2 , characterized in that the maximum power of the combustion engine is less than 60 kW. Vehicle (2) to Claim 2 , characterized in that the maximum power of the combustion engine is less than 30 kW. Vehicle (2) according to one of the preceding claims, characterized in that the energy supply device further comprises at least one electrical capacitor (22) for providing energy for temporary high-load operation of the electric motor (14). Vehicle (2) according to one of the preceding claims, characterized in that the energy supply device comprises a control device which is designed to automatically switch on the reserve energy supply unit in the event of a partial discharge state of the rechargeable exchangeable battery (6). Vehicle (2) to Claim 6 , characterized in that the partial discharge state is 40%-50% of the full charge state. Vehicle (2) according to one of the preceding claims, characterized in that it is designed to store braking energy in the exchangeable battery (6) and/or the capacitor (22) by operating the electric motor (14) as a generator. Vehicle (2) according to one of the preceding claims, characterized in that the exchangeable battery (6) has an energy content which is dimensioned such that an energy of between 1.0 and 1.6 kWh can be provided for each kilometer of a route. Vehicle (2) according to one of the preceding claims, characterized in that it is a regular bus (2). Vehicle (2) according to one of the preceding claims, characterized in that the replaceable battery (6) is a Li-ion battery. A method for driving a vehicle (2) according to one of the preceding claims, on a route with one or more stages, each stage being defined by a first battery exchange point as the starting point and a second battery exchange point as the end point, wherein the driving operation on each stage comprises the steps of: covering a stage from the first battery exchange point to the second battery exchange point; approaching any intermediate stops along the stage; repeatedly checking the charge level of the rechargeable exchangeable battery (6) and automatically connecting the reserve energy supply unit when the charge level falls below a predetermined partial discharge level; replacing the exchangeable battery (6) at the second battery exchange point with a substantially fully charged exchangeable battery (6). Procedure according to Claim 12 , characterized by automatic replacement of the exchangeable battery (6) at a respective battery exchange point. Procedure according to Claim 12 or 13 , characterized by charging the replaced partially discharged battery (6) at the respective battery exchange point. Method according to one of the Claims 12 until 14 , characterized in that the first and the second battery exchange point are the same battery exchange point.