DE19646279C1 - Method of extending travelling range of electrically-powered motor-vehicle - Google Patents

Abstract

The range extension method detects the variation in the capacity of the batteries (S1,...S3) supplying the operating current for the vehicle drive, to allow one battery to be disconnected when the capacity variation reaches a critical value, for replacement by a different battery. The disconnected battery is not used for a given time interval, for utilisation of the refreshing effect before the battery is switched back into operation.

Description

The invention relates to a method and an arrangement for increasing the range of Motor vehicles with an electric drive unit, the energy supply of which is known Accumulators are made according to the preamble of the main claim.

In motor vehicles, which are used to supply the drive systems exclusively with electrical energy from known storage units, such as lead batteries or nickel-cadmium batteries the range of the vehicles due to the high payload the accumulators limited. A range increase through redundant arrangement Several accumulators are at the expense of the possible payload.  

Solutions are also known in which electrical energy is used to drive the vehicles by using the photovoltaic effect (e.g. using solar cells) Light energy is obtained. So in DE 33 47 054 A1 an electric vehicle with an electric motor and a rechargeable battery described in which the Recharging takes place using solar cells, which are arranged on a body roof are.

There are also systems for the recovery of kinetic energy, especially of Braking energy, which is stored in temporary buffers in the vehicle, such as in Save flywheel mass, stored over relatively short periods of time. This- such Recovered energy can increase the vehicle's energy requirements (e.g. the Management of inclines or when starting off) are also provided will.

In DE 39 09 861 A1, a battery low-floor city bus is presented that its drive, in addition to a long-term storage in the form of a battery, a rotating one Flywheel used as a short-term energy storage.

DE 41 33 013 A1 describes an energy distribution system for a Road vehicle known with which depending on the particular load situation of the vehicle is fed to an electric motor or a generator can be taken with a conventional internal combustion engine are connected table (motor-generator principle).

A circuit arrangement is known from DE 41 42 863 A1, by means of which the electric motor from the control when braking the vehicle Generator is switched, which means that the delivered energy immediately Ver  is fed to the consumer. Temporary storage of the data obtained in this way There is no useful energy.

DE 40 32 606 A1 proposes a road vehicle whose internal combustion engine motor exclusively for driving a battery or for charging Battery charger is designed. This principle is also in the field of Traction vehicle technology known from rail vehicles, where by diesel engines Generators are driven, the electrical energy of which is on the wheelsets located electric traction motors is transmitted.

DE 44 46 219 A1 describes a motor vehicle with several electric motors and known at least one battery and a control device, the electrical motors operated independently of one another by the control device, Braking operation with energy recovery or braking operation for the purpose of energy destruction are adjustable. This solution is also from the field of rails Vehicle technology is known where the kinetic energy when braking a vehicle or a vehicle network depending on the current one Load situation can be fed back into the traction current network.

Circuit arrangements are known from DE 39 02 339 A1 with which vehicle Battery data from battery-powered road vehicles are recorded. These dates are used to provide business parameters for vehicle use determine. The battery data determined and recorded alongside serve the Determination of the recharge or exchange cycles of the accumulators.

A comparable solution is described in DE 195 39 695 A1. The battery Handling device for an electric vehicle is used to determine the torque The state of charge of a battery, regardless of whether the battery is in a Load state or in a resting phase.

Based on the knowledge that a previously heavily loaded battery is switched off Condition undergoes permanent discharge after a temporary recovery phase,  the battery handling device serves to determine the remaining usable capacity Signal the battery even when it is disconnected from the mains. This is supposed to enables timely recharging or replacement of the battery in question will.

For this purpose, it is proposed to use sensors that are located on or in the battery to determine the current actual capacity at intervals. For this, ins special measuring arrangements proposed that only a low energy requirement to carry out the measurements.

It is also proposed to include an autonomous battery with the help of an auxiliary battery Realize the voltage supply of the sensors. This auxiliary battery is used in particular to falsify the measurement results on the battery to be monitored to eliminate an autonomous power supply.

The known solutions are characterized by a number of disadvantages.

So motor vehicles that are powered solely by the use of solar energy be safe and only with appropriate meteorological conditions  can be used reliably. Especially in climatically changeable regions, as in Northern and Central Europe, is therefore an economical use of such Vehicles hardly possible. Added to this are the comparatively high procurement costs and the low electrical power of known solar cells.

The exclusive use of known lead, nickel-cadmium, or silver-cadmium Lithium-sulfur accumulators for the energy supply of the traction motors trigger economic limits, since high-performance batteries are disproportionately expensive are and have a relatively limited lifespan.

Known lead-acid batteries, which are characterized by a more favorable price-performance ratio have the disadvantage that the absorption capacity of the cells is comparatively low and the mass or specific density of these batteries the possible payload and the radius of action of the motor vehicle are severely limited.

The object of the invention is to develop a method and an arrangement that a Increase the range or range of action of motor vehicles at the same time Allow an increase in the normative service life of the accumulators used.

This object is achieved by the characterizing features of the main claim solved. Further developments are preferably set out in the subclaims sets.

The increase in the range of a motor vehicle is brought about by the fact that the surprising effect of "self-recovery" of the existing accumulators exploited becomes.

For this purpose, the change over time in the capacity (state of charge) of each individual battery on board the vehicle is determined at intervals. As soon as the change in the instantaneous capacity of the accumulator over time exceeds a selectable, critical setpoint, the energy flow is separated from the previously used storage (accumulator) S _i to the consumer and at the same time another storage S _{k is} selected, from which energy is obtained. This next memory S _k is selected with the proviso that that memory S _i . . . S _{n is} selected that has the optimal conditions for supplying energy to the consumer (traction motors).

A memory S _k is considered to be optimal if the actual capacity

C _cost = I _ct

corresponds to the maximum nominal capacity C _{kNenn of} this memory (state of charge full) or when an already partially discharged memory S _k has reached its instantaneous maximum charging capacity after completion of the "recovery phase".

The characteristic variable for reaching this maximum state of charge is the point Ct _max in the characteristic curve of the battery used in each case. After the point C _{tmax is reached,} the rise in the characteristic curve I _k = f (t) flattens out. This indicates the end of the self-recovery phase of the battery in question (memory S _k ). After this characteristic point, there is no significant increase in storage capacity over time.

At this time t _max , the memory S _{k in} question can be used again for delivering energy to the consumers of the vehicle. A prolonged absence of a power purchase from this memory S _k (extension of the "conservation phase" of the battery for the purpose of Refreshings) would from this point t _max disproportionate to the otherwise necessary larger number of stores S _n to the capacitive total demand of the motor vehicle to cover electrical energy.

In the manner mentioned above, the temporal changes in the capacitances C ₁ become in differently small time intervals dt. . . C _{n of} all memories S ₁ . . . S _{n of} the motor vehicle over time t detected and compared. There is thus the possibility, when the critical capacity of the residual capacity C _{iRest of} a storage S _{1 is undershot,} to choose a next partial storage S _n which temporarily has the optimal energetic requirements C _i (t) = opt.! For the energy delivery to the consumers.

An arrangement for implementing the method on a motor vehicle essentially consists of a number of memories S ₁ . . . S _n , which can have the same or different nominal capacities. The memory used can be identical or differ in size and structure. All stores S ₁ . . . S _n are electrically conductively connected to the consumer (s) [traction motor (s) including auxiliary units, lighting device, etc.] via the electrical system. A memory S _{i is connected} to the consumer via a circuit device ( 1 ) which is connected to an on-board computer ( 2 ). The on-board computer ( 2 ) determines the current capacity C ₁ (t) permanently or cyclically. . . C _n (t) of all memories S ₁ . . . S _n .

If the current capacity C _i (t) of a memory i has reached the lower permissible discharge limit C _iRest , the switchover to a memory takes place which is most suitable for the power consumption.

After each storage unit has been discharged, there is a load-free rest phase, the until the effective setpoint for regeneration (refreshing) is reached. This storage can subsequently be used again for the energy output.

The suitability of the memory S ₁ . . . S _n for renewed energy consumption can be checked by different control mechanisms:

1. Active system

The suitability of the memory S ₁ . . . S _n is determined by an on-board computer, which determines the rate of change of current and / or voltage and / or resistance of the memory over time t in all memories S _i at stochastic or determined intervals and detects the memory concerned when it falls below a predefinable limit value and released for subsequent energy extraction.

2. Passive system

The permissible change of current, voltage and / or resistance or of the product or quotient of the aforementioned parameters over time is determined for the respective memory (as a memory-specific characteristic). The associated switchover points (switch-on points EP ₁ ... Ep _n and switch-off points AP ₁ ... Ap _n ) are stored in a memory of the on-board computer before the vehicle is started up. When a determined changeover point of the characteristic curve of a memory is reached, the on-board computer determines the subsequent memory, which has the optimal energy requirements for energy delivery.

Both systems are used with the same functional principle to determine the storage S _i , which is currently suitable for energy extraction or charging.

External energy, such as B. braking energy, energy from air movement, solar Energy, etc. is fed into the storage depending on the power supplied that are most suitable for energy consumption or - depending on the current energy demand - used directly for the drive.

If the externally generated energy supply occurs abruptly (e.g. braking energy), it is not fed directly into the storage unit, but is initially used to charge one or more intermediate storage units SZ ₁ . . . SZ _i (e.g. flywheel storage), which subsequently deliver the energy supplied to the individual storage for optimal charging.

_Ges due to the division of the effective total capacitance C of the motor vehicle into a plurality of partial capacitances (.. Memory _S1. S _n) occurs after the extracting electrical energy from the respective memory S _i and the switching aufeinen new memory S _k a recovery of the memory (accumulator) S _i , as a result of which, surprisingly, a clear increase in capacity C _i (t + 1) <C _i (t) is recorded in the previously discharged memory S _i . This "recovery effect" of the unloaded memory S _i , which occurs after each load cycle, increases the current capacity of this memory by approximately 10%. Due to the careful charging and discharging of the individual storage S ₁ monitored by the on-board computer. . . S _n increases their useful life by about 20%.

Total failure of storage due to rapid discharge or falling below the permissible lower limit voltage of the accumulators are largely prevented.

The drift behavior of the individual memories can also be monitored by the temporally determined or stochastic determination of the instantaneous capacitances C _ist and their change within differently small time periods dt. In this way, memories are recognized early on, whose charging and discharging behavior is not in accordance with the standards. This defective memory can thus be replaced preventively. This increases the reliability and availability of the motor vehicle.

If such deviant charging or discharging behavior detected of a memory during operation of the vehicle so, a Umschal tung aufeinen other memory by the on-board computer (2) made of the optimality criterion C _is at this time = opt.! corresponds.

By temporarily storing the suddenly applied braking energy of the motor vehicle on one or more intermediate storage ZS ₁ . . . ZS _n can optimize the charging process of the individual memories (accumulators) S ₁ . . . S _n according to the respective discharge state [instantaneous capacitance C _1act (t). . . C _nist (t)] can be performed.

The on-board computer controls that there is no direct change from discharge to charge in any storage S _i , since otherwise the regenerative energy would not be used due to the "recovery effect" of the storage.

It was surprisingly found that the memory, which is in a regeneration phase (Recovery phase), which absorb energy more effectively than storage, energy during the energy extraction phase (e.g. in the form of Solar energy) is supplied.

Due to the temporal changes in the actual capacitances C ₁ detected at small time intervals. . . C _n the memory S ₁ . . . S _n over time and their comparison with one another and / or with stored U (t) - and / or I (t) - and / or R (t) characteristic curves of the respective memories there is the advantageous possibility of falling below the critical limit value the capacity C _{iRest of} the memory S _i to select a memory S _k from which the electrical energy can be taken for further driving. There is also a further advantageous possibility of using energy obtained on the vehicle, e.g. B. in the form of solar energy, low-loss in suitable storage S _i sen or to provide the traction motors ( 5 ) or other consumers.

The kinetic energy obtained is advantageously not fed directly into the stores S ₁ . . . S _n , but first in one or more buffers ZS ₁ . . . ZS _m , the z. B. serves as a buffer for the abruptly fed braking energy.

This results in an advantageous, more effective loading of the memories. In addition, the defined, time-dependent charging of the memories S ₁ protects. . . S _n with optimized charging currents are advantageous against thermal or chemical destruction due to excessive charging currents.

Likewise, the kinetic energy recovered by switching on the Zwi better used. In contrast, vehicles without such intermediate storage does not completely absorb the sudden braking energy be made usable for vehicle propulsion.

Another advantage of the method is that the stochastic or determined determination of the actual capacity of all memories S ₁ . . . S _n and the permissible lower limit values for the discharge of the memories in the case of a larger number of functionally independent memories S _n inoperable or in their function limited memories are recognized, which are then no longer released for further charging processes. This increases the system reliability of the vehicle equipped in this way and effectively prevents thermal or chemical destruction of individual stores.

The mode of operation of the method and the arrangement for increasing the range Motor vehicles will be described below using the exemplary embodiment of a bus explained and shown in the accompanying figures.

Show it:

Fig. 1 is a side view of a stylized the bus or coach with the components of the assembly,

Fig. 2 shows the exemplary diagram of a driving game of the bus or coach,

Fig. 3 shows the characteristic curve of U (t) and I (t) of a lead storage battery,

Fig. 4 shows the characteristic curve U (t) and I (t) of a nickel-cadmium battery.

The bus has 3 memories S ₁ . . . S ₃ with different nominal _capacities C _1Nenn which are arranged near the vehicle axles and connected to the consumers via the electrical system. All stores S ₁ . . . S ₃ are fully charged when you start driving.

Solar cells ( 3 ) for the external generation of electrical energy are arranged on the roof surface of the bus, the energy of which is fed into the vehicle electrical system. In addition, a flywheel mass storage device ( 4 ) is arranged in the rear of the bus to utilize the braking energy.

When the vehicle is started up and the control is activated, the on-board computer ( 2 ) begins with the permanent control of the capacities C _{1 actual} . . . C _{3 is} all storage S ₁ . . . S ₃ . For this purpose, the temporal change in current and / or voltage and / or resistance or the product or the quotient of the aforementioned parameters is determined over time for each memory S _i . The time interval between the check intervals is selected depending on the battery type, the current power consumption (load situation) and, if applicable, other parameters and can be between several minutes (in the case of unloaded storage, from which no energy is currently being drawn) and fractions of a second.

The on-board computer ( 2 ) controls the energy supply from the solar cells ( 3 ) and makes this available to the storage S _i , which is most suitable for charging from its capacitive state. In the present case, the supplied solar energy is used to charge the storage S ₁ . If all memories S ₁ . . . S ₅ currently have no absorption capacity, the energy is fed directly into the drive motors as driving current at the start of the journey (cf. actual state in FIG. 2).

At the start of driving (cf. switch-on point EP _{1 of} the storage characteristic according to FIG. 3), energy for accelerating the vehicle (state Z 2 in the driving game according to FIG. 2) is first taken from the storage S ₁ .

After reaching a residual capacity of about 30% of this lead-acid battery, characterized by a significant drop in voltage and current by about 20% within a time interval of one second compared to the previous measuring cycle, the on-board computer ( 2 ) switches when the Switch-off point AP ₁ (see FIG. 3) on the memory S ₂ by (state Z 3).

In the time after the switchover from memory S ₁ to S ₂ , an increase in the voltage occurs in memory S ₁ due to the refreshing effect (state Z 3). The on-board computer ( 2 ) monitors the initially steep rise in voltage until it flattens out and occurs at an empirically determined level.

During the refreshing process, additional external energy (solar energy) is fed into the memory S _{1 in} accordance with the current energy consumption (state Z 3).

After completion of the acceleration (switch-off point AP ₁ of memory S ₁ is reached, switch to memory S ₂ has been made; see state Z 3), during the subsequent rolling process (state Z 4) of the vehicle, the memory suitable for reloading is loaded by the on-board computer ( 2 ) by diagnosing the actual state of the memory S _i .

In the present example, refreshing has already been completed in memory S ₁ ; there is a further supply of solar energy. The refreshing process has not yet been completed in memory S ₂ . Due to the current energy absorption capacity of the memory S ₂ , solar energy is also supplied to this memory. The optimum charging current I _opt is specified by the on-board computer ( 2 ), on which the characteristic curves I (t), U (t), R (t) of all the accumulators (memories S ₁ ... S ₃ ) of the bus are stored (cf. Condition Z 4 of the driving game).

The vehicle is accelerated again due to traffic, the energy required for the driving motors being taken from the store S ₂ . At the same time, the store S _{1 is} recharged further by the solar cells (state Z 5).

When the vehicle is decelerated (braking process; state Z 6), the braking energy is converted into electrical energy by the drive motor ( 5 ) connected as a generator, which is used to drive the flywheel mass storage device ( 4 ).

Simultaneously with a renewed acceleration and another rolling process of the vehicle (state Z 7 and Z 8), the generator ( 6 ) converts the kinetic energy contained in the flywheel mass ( 4 ) into electrical energy and, after analyzing the state of charge and the absorption capacity from the on-board computer determined memories S ₁ and S ₂ supplied.

The flywheel mass storage device ( 4 ), which acts as a temporary storage device SZ, is used by the on-board computer ( 2 ) via the controller ( 7 ) as a function of the instantaneous energy absorption capacity of the storage device S ₁ . . . S ₃ electrical energy introduced into the individual storage. The storage is gently charged on the basis of the known characteristic curve of the individual accumulators. Changes in the characteristic curve behavior, which the on-board computer registers, result in the charging current for the memory concerned being changed.

In the subsequent braking process (state Z 9), the kinetic energy of the vehicle is used to charge the flywheel mass accumulator ( 4 ). At the same time, solar energy is stored in memory S ₁ . . . S ₃ supplied.

When the vehicle comes to a standstill (state Z 10), the kinetic energy stored in this way becomes the memory S _{1 in} accordance with the actual absorption capacity. . . S ₃ supplied. Due to the current capacity of the three memories S ₁ . . . S ₃ can also be supplied with energy from the solar cells ( 3 ).

When starting up again (acceleration phase; state Z 11), energy is again drawn from the storage S ₁ . At the same time, kinetic energy of the flywheel mass accumulator ( 4 ) converted into electrical energy is also transmitted to the accumulators S ₂ and S ₃ . At the same time, these two stores are charged with solar energy.

As at the beginning of the driving game, with further acceleration (state Z 12) there is a switch from memory S ₁ to S ₂ , from which the further energy for operating the driving motors is taken. In this phase, the refreshing effect in the memory S ₁ starts again. Due to the current absorption capacity of the memory S ₁ , this memory is supplied with solar energy at the same time. The storage S ₃ is recharged during this phase with energy from the flywheel storage and the solar cell ( 3 ).

When the vehicle finally rolls (state Z 13), the refreshing effect in memory S _{1 is} already complete. Due to the current energy absorption capacity S _{1 is} loaded in parallel with energy from the solar cells ( 3 ) and the flywheel storage ( 4 ).

The memory S ₂ is in the refreshing phase. Due to the current energy absorption capacity of the storage S ₂ , additional energy is already being supplied by the solar cells ( 3 ).

Storage S ₃ , from which energy was last drawn during the previous load cycle, has the greatest energy absorption capacity at this time. Therefore, the accumulator S ₃ is further charged with solar energy and kinetic energy, which is transferred from the flywheel mass accumulator ( 4 ).

This process is repeated until all memories S ₁ . . . S ₃ can no longer increase their permissible, minimum residual capacity C _iRest by refreshing and / or recharging solar energy or converted kinetic energy from the flywheel mass _{storage device} ( 4 ).

The driver of the bus is now signaled that a recharge of the memory S ₁ . . . S ₃ from an energy source external to the vehicle is necessary and only a reserve memory S _Res (or a defined reserve capacity of a memory S ₁ ... S ₃ ) is available for the onward journey.

Reference list

1

Circuit device

2nd

On-board computer

3rd

Solar cells

4th

Flywheel mass storage

5

Traction motor

6

generator

7

control
AP ₁

. . . AP _n

Switch-off points (points in time when a store is switched off by the consumer)
C capacity
C ₁

. . . C _n

Capacities of the first to nth memory S ₁

. . . S _n

C _total

Total capacity
C _Is

current actual capacity
C _iRest

Remaining capacity of the i-th memory
C _is

current actual capacity of the kth memory S _k

C _can

nominal nominal capacity of the kth memory S _k

C _tmax

current maximum actual capacity
EP switch-on point (time at which a store was connected to the consumer)
n Number of memories
S ₁

. . . S _i

, S _k

, S _n

Storage (accumulators)
S _Res

Reserve memory
SZ buffer
t time
t _max

Time of reaching the current maximum actual capacity of a memory
UP switchover point (switch-on or switch-off point of the characteristic curve of a memory)

Claims (9)

1. Method for increasing the range of motor vehicles with an electric drive unit, the energy supply of which is provided by accumulators,
characterized,
that the temporal change in the capacity (dC / dt) of the memories (S ₁ ... S _n ) is determined on board the motor vehicle,
that when a selectable, critical setpoint of the temporal change in the capacity (dC / dt) of a memory (S _i ) over time, the energy flow is separated from the previously used memory (S _i ) to the consumer and another memory (S _k ) is selected , from which the energy is supplied to the consumer,
the selection of this memory (S _k ) is carried out on the condition that the current actual capacity (C _kist = I _k .t) of the memory (S _k ) compared to the other memories (S ₁ ... S _n ) is a maximum
that the previously used memory (S _i ) is not selected again for energy delivery during a definable time interval in order to use the refreshing effect of the memory (S _i ),
and that the previously used memory (S _i ) not before reaching the next switch-on point (EP _i ) of the U (t) - or I (t) - or R (t) characteristic curve or a characteristic curve determined from the aforementioned characteristic variables for a renewed energy release is released. 2. Method for increasing the range of motor vehicles with an electric drive unit, the energy supply of which is provided by accumulators,
characterized,
that the permissible temporal change in current, voltage, resistance and / or capacitance or the temporal change in a parameter which can be determined from the aforementioned variables for the memory (S _i ) of a motor vehicle is determined as a load-dependent, memory-specific characteristic curve or characteristic field and is in a target-actual value -Comparer of how an on-board computer is stored,
that when driving a determined switchover point of the characteristic curve of a memory (S _i ), the target-actual comparator selects the subsequent memory which, on the basis of its characteristic curve stored in the target-actual comparator, has the optimal energetic requirements for energy delivery. 3. The method according to claim 1 or 2, characterized in that energy obtained on the motor vehicle (braking energy, solar energy) during the refreshing phase is fed to the memories (S _i ) as a function of the instantaneous energy consumption. 4. Arrangement for realizing the method according to one of claims 1 to 3,
characterized,
that n memories (S ₁ ... S _n ) are arranged in a motor vehicle,
that all memories (S ₁ ... S _n ) are electrically conductively connected to the consumer,
that a memory (S _i ) is connected to the consumer via a circuit device ( 1 ) which is connected to an on-board computer ( 2 ),
wherein the on-board computer ( 2 ) determines the instantaneous actual capacity (C _1act (t) _... C _actual (t)) of all the storage devices (S _{1 ...} S _n ) and selects the storage devices that are used for energy extraction and energy supply are optimally suited
that the motor vehicle has facilities for energy generation, which are connected via the on-board computer ( 2 ) with the memories (S ₁ ... S _n ) and / or the consumer. 5. Arrangement according to claim 4, characterized in that the memory (S _{1 ...} S _n ) have the same or different nominal _capacities (C _1Nom... C _kNom ). 6. Arrangement according to claim 4 or 5, characterized in that the memory (S ₁ ... S _n ) are identical. 7. Arrangement according to claim 4 or 5, characterized in that the memory (S _{1 ...} S _n ) have a different structure and / or different nominal capacity (S _iNenn ). 8. Arrangement according to claim 4, characterized in that the devices for energy generation are designed as solar cells ( 3 ) which are arranged on the vehicle roof and / or on the side surfaces of the vehicle. 9. Arrangement according to claim 4, characterized in that the device for energy generation as a rotating flywheel memory ( 4 ) with a generator ( 6 ) is formed, which absorbs the kinetic energy of the vehicle in the case of delayed movements, stores it and sends it to the consumer such as the drive motor ( 5 ) and / or loadable memory (S ₁ ... S _n ).