III IIII
`USOO5533583A
`Patent Number:
`11)
`5,533,583
`(45) Date of Patent:
`Jul. 9, 1996
`
`1/1985 Barnard .................................. 180/65.5
`4,495,451
`5/1986 Albright, Jr. etal
`... 80/65.4
`4,588,040
`5,224,563 7/1993 Iizuka et al. ........................... 180/65.5
`5,418,437 5/1995 Couture et al. ........................ 180/65.5
`FOREIGN PATENT DOCUMENTS
`2943554 5/1981 Germany.
`2. 10/1982 Germany .
`228589 10/1985 Germany.
`3714151 10/1987 Germany.
`4000678 7/1991 Germany
`Primary Examiner-Richard M. Camby
`Attorney, Agent, or Firm-Cohen, Pontani, Lieberman, Pav
`al
`ABSTRACT
`(57)
`A passenger automobile or truck contains a unit which is
`formed by an internal combustion engine and a generator
`and which powers electric motors coupled with driving
`wheels of the vehicle via an energy distributor in the form
`of power electronics. An accumulator which can likewise be
`coupled with the electric motors via the energy distributor is
`provided as an additional power source. An electronic con
`trol unit receives driving signals from an accelerator pedal,
`in particular a position signal and a speed signal. The
`position signal of the throttle is interpreted as a request for
`a determined permanent output to be supplied by the internal
`combustion engine.
`
`The internal combustion engine is revved up to a new
`operating point in an "optimal' manner (e.g. with favorable
`fuel consumption), for example when a higher output is
`requested, while the generator is entirely or partially
`uncoupled from the load. Energy for accelerating the vehicle
`is provided in the meantime by the accumulator. The speed
`signal determines the amount of acceleration. By means of
`a selector switch, an operation powered exclusively by
`stored energy may be switched on when the internal com
`bustion engine is turned off if no special sensors are pro
`vided for this purpose.
`15 Claims, 3 Drawing Sheets
`
`United States Patent 19
`Adler et al.
`
`(54) NON-TRACKBOUND VEHICLE WITH AN
`ELECTRODYNAMIC CONVERTER AND A
`THROTTLE
`
`(75) Inventors: Uwe Adler, Schweinfurt; Hans-Jirgen
`Drexl, Schonungen; Dieter Lutz,
`Schweinfurt; Franz Nagler, Ottendorf;
`Martin Ochs, Stefan Schiebold, both
`of Schweinfurt, Hans-Joachim
`sa.
`Schmidt-Bricken, Geldersheim;
`Wolfgang Thieler, Hassfurt; Michael
`Wagner, Niederwerrn; Holger
`Westendorf, Hambach; Rainer
`Wychnanek, Madenhausen, all of
`Germany
`(73) Assignee: Mannesmann Aktiengesellschaft,
`Dusseldorf, Germany
`Appl. No.:
`211,141
`21
`22 PCT Filed:
`Sep. 30, 1992
`86 PCT No.:
`PCTIDE92/00834
`S371 Date:
`Jun. 22, 1994
`S 102(e) Date: Jun. 22, 1994
`87, PCT Pub. No.: WO93/07020
`PCT Pub. Date: Apr. 15, 1993
`A
`Foreign Application Priority Data
`30
`Oct. 4, 1991 (DE) Germany .......................... 41 33 0145
`6
`51) Int. Cl. ....................................................... B6OK 1/04
`52 U.S. C. .............................................. 80/65.4; 318/150
`58) Field of Search .................................. 180/65.5, 65.4,
`180/165, 55.2; 318/150, 139
`
`56
`
`References Cited
`U.S. PATENT DOCUMENTS
`3,837,419 9/1974 Nakamura .............................. 180/65.5
`
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`U.S. Patent
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`Jul. 9, 1996
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`Sheet 1 of 3
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`5,533,583
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`U.S. Patent
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`Jul. 9, 1996
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`Sheet 2 of 3
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`5,533,583
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`U.S. Patent
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`Sheet 3 of 3
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`FIG.3 f
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`when the electric motors are operating as generators, energy
`is obtained from the latter and can be stored in the flywheel
`as mechanical energy.
`In practice, however, former proposals for providing a
`vehicle having an internal combustion engine with a gen
`erator and associated driving electric motors have only been
`realized in part.
`A non-trackbound vehicle is known from DE 4000 678
`A1. This vehicle has an internal combustion engine, an
`electric generator driven by the latter, an electrically charge
`able and dischargeable flywheel storage, at least one electric
`drive motor, and an energy distributor which is controlled by
`a control unit and constructed as power electronics. The
`electric drive motor is powered by the energy distributor
`with electric current from the generator and/or the flywheel
`storage. Depending on the charge state of the flywheel
`storage, the electronic control unit allows the internal com
`bustion engine to run either at idling speed (when the storage
`is extensively charged) or at a second speed (when the
`storage is mostly discharged). This second speed represents
`a quantity which is selected on the basis of optimization
`criteria (e.g. fuel consumption, pollutant emission).
`The concept of a vehicle with electrodynamic converter
`discussed above is very promising with regard to economiz
`ing on energy, pollution abatement and other requirements.
`However, the driver's readjustment from the customary
`vehicle with internal combustion engine to a vehicle with
`quasi-electric drive may be a possible source of problems in
`the use of such vehicles. Since the vehicle is ultimately
`driven by electric motors, the vehicle behaves very much
`like a vehicle with a purely electric drive.
`It is therefore an object of the present invention to provide
`a non-trackbound vehicle of the type mentioned above in
`which the driver's commands, as expressed by the move
`ment of the throttle, in particular the accelerator pedal, are
`correctly interpreted and in which means are employed for
`converting the driver's commands into available output
`allowing the vehicle to behave in conformity to the driver's
`commands.
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`1.
`NON-TRACKBOUND VEHICLE WITH AN
`ELECTRODYNAMC CONVERTER AND A
`THROTTLE
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`FIELD OF THE INVENTION
`The invention relates to non-trackbound vehicles, gener
`ally, and more particularly to vehicles having at least one
`wheel coupled to an electric motor which drives the wheel
`and which is supplied with current via an energy distributor
`depending on control signals generated by a control unit, the
`current being supplied by a generator coupled with an
`internal combustion engine and the control unit receiving
`from a throttle a driving signal which is at least represen
`tative of the position of the throttle.
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`DESCRIPTION OF THE PRIOR ART
`The most common non-trackbound vehicles are passenger
`automobiles and trucks. These vehicles were hitherto con
`ventionally operated by internal combustion engines. Inter
`nal combustion engines have a characteristic torque/speed
`curve which, at a determined speed range, has a more or less
`pronounced torque maximum bordered by regions with
`greatly reduced torque at higher speeds and especially at
`lower speeds.
`Engine output is calculated as the product of torque and
`speed. To achieve the fastest possible acceleration of a
`vehicle, the maximum available output must be transmitted
`to the driving wheels. When the vehicle engine is operating
`in a low speed range, only a relatively slow acceleration can
`take place even at the maximum throttle valve opening,
`since there is insufficient available output. The output for
`acceleration can be increased by shifting into a lower gear,
`since higher speed and accordingly a higher available output
`are provided in a lower gear. Practically all vehicles having
`an internal combustion engine are outfitted with a gear shift
`or automatic transmission to make use of the available
`output of the engine.
`Electric drives which are chiefly used in trackbound
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`vehicles, e.g. in locomotives, have the advantage that the
`dependency of the output on speed is considerably less -
`pronounced than in internal combustion engines. For this
`reason, electric drives can generally be utilized without a
`transmission.
`It has already been proposed to drive non-trackbound
`vehicles, i.e. passenger automobiles, trucks and busses, by
`means of one or more electric motors which are directly
`coupled with the wheels. The electric motors are powered by
`an internal combustion engine/generator unit via an energy
`distributor constructed as power electronics. A hybrid engine
`of this kind has a number of advantages. When the wheels
`are driven by means of electric motors, not only can a gear
`shift or automatic transmission be dispensed with, but it is
`also possible with thrusting engine or during a braking
`process to operate the electric motors as generators so that
`the occurring electrical output can be used, e.g., for heating
`or the like.
`It has also already been suggested to couple an internal
`combustion engine with an energy storage constructed as a
`flywheel in a vehicle. In this case, the internal combustion
`engine can always be operated in an optimum operating
`state, e.g. in a range of the most favorable specific fuel
`consumption. The generator coupled with the internal com
`bustion engine supplies electrical energy to the driving
`65
`electric motors. When the vehicle is accelerated, additional
`energy is drawn from the flywheel. During a braking process
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`SUMMARY OF THE INVENTION
`The aforementioned object, as well as others which will
`become apparent from the description provided herein, is
`met by a vehicle in which an energy storage means is
`provided which is electrically connected, via the energy
`distributor, with the electric motor and with the generators in
`that the control unit processes the driving signal in the form
`of a control signal for the internal combustion engine in
`order to bring the internal combustion engine to the output
`corresponding to the position of the throttle or in order to
`maintain it at this output, and in that the control unit further
`generates a control signal for taking energy from the energy
`storage at least so as to allow the internal combustion engine
`to accelerate to a new operating point in an optimal manner
`and/or to achieve maximum acceleration of the vehicle
`and/or to further increase the maximum speed of the vehicle
`at full engine output.
`In accordance with the present invention a determined
`drive output to is produced fundamentally by the internal
`combustion engine be allocated to the driving signal, i.e. in
`particular to the respective angular position of the throttle
`(accelerator pedal). The driver requests a certain output by
`actuating the accelerator pedal. The characteristic curve
`between the demanded output and the position of the accel
`erator pedal is preferably nonlinear and is relatively fiat in
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`the initial region so as to enable an easy proportioning of
`output in a slow moving vehicle.
`The output selected according to the position of the
`accelerator pedal should be viewed as permanent output
`which is basically to be provided by the internal combustion
`engine. The energy storage means, according to the inven
`tion, is provided in conjunction with the control unit to
`enable the transition between a given driving speed and a
`new driving speed. When the vehicle is traveling at a given
`initial speed v, the drive sources, i.e. the internal combus
`tion engine/generator unit and the energy storage means,
`supply an output P, designated here as initial output, which
`is in equilibrium with the resistance, particularly air resis
`tance, rolling resistance of the tires and the like, acting on
`the vehicle at constant speed. A continued depression of the
`accelerator pedal in this stationary state of the vehicle is
`interpreted as a demand for increased output. In providing
`this increased output, the vehicle is accelerated until reach
`ing a final speed v at which the increased output P is in
`equilibrium with the resistance acting on the vehicle.
`According to the invention, the control unit uses the
`energy storage means in a very specific manner to organize
`the transition from an output P produced in stationary
`driving operation to a new output P.
`In accordance with one aspect of the present invention,
`the internal combustion engine is "optimally” accelerated to
`a new operating point. An internal combustion engine has a
`family of characteristic curves. More particularly, a curve
`for optimal specific fuel consumption may be identified in
`the speed/torque characteristic field. Assuming that the
`internal combustion engine is running at a relatively low
`speed and a demand for increased output is made by the
`driver by further depressing the accelerator pedal, the engine
`must be brought to a higher speed since the newly selected
`output is interpreted as a permanent output to be provided by
`the internal combustion engine. As is well known, when the
`throttle valve opening increases while the burden on the
`engine remains the same in other respects, the speed only
`increases very slowly depending on the loading of the
`engine. The invention makes it possible to increase the speed
`from an operating point located on the above-mentioned
`curve of optimal specific fuel consumption to a second
`operating point also located on this curve in such a way that
`very little fuel is consumed. In so doing, a continuous or
`stepwise increase in speed is effected with a corresponding
`adjustment of the torque and output. For this purpose, the
`generator can be decoupled entirely or partially from the
`electric motor so that the generator runs completely or
`partially on idle in practice. Accordingly, the speed of the
`internal combustion engine can be increased quite rapidly
`when the load on the generator is reduced, specifically so as
`to enable an increase in the vicinity of the curve of the
`optimal specific fuel consumption mentioned above.
`In accordance with a further aspect of the present inven
`tion, the internal combustion engine can also be revved up
`quickly to the desired speed with the generator on idle,
`whereupon the generator is coupled with the electric motor
`again gradually, that is, slowly enough so that the speed does
`not decrease again. In the meantime, the drive of the electric
`motor is powered by the energy storage means. This results
`in a smooth transition from power supplied by the internal
`combustion/generator to power supplied by the energy stor
`age means.
`In addition to an "optimal' acceleration of the internal
`combustion engine, the drawing of power from the energy
`storage means can also be controlled in such a way that the
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`vehicle achieves maximum acceleration. In so doing, it is
`necessary to ensure that the acceleration is adapted to the
`total charge stored in the energy storage means so that the
`storage means is not depleted during the acceleration pro
`cess, which could lead to dangerous situations in traffic.
`There is a certain similarity between maximum accelera
`tion of the vehicle and the step by which the maximum speed
`of the vehicle determined, perse, by the maximum output of
`the internal combustion engine is further increased by draw
`ing additional power from the energy storage means at
`maximum output of the internal combustion engine and
`supplying it to the electric motor.
`Warning devices which notify the driver when the avail
`able energy in the energy storage means has dropped to a
`residual amount are provided in order to avoid dangerous
`situations.
`The steps discussed above for making optimal use of the
`energy storage means in certain situations relate to special
`driving signals which will be discussed more fully in the
`following. These driving signals notwithstanding, energy
`can be supplied, according to the invention, from the energy
`storage means to the electric motor in order to make extra
`energy available for negotiating ascending grades at roughly
`constant speed without a change in the engine torque and/or
`to replace a part of the engine output by drawing on stored
`energy and/or to enable driving operation when the engine
`is turned off. The latter variant is of particular importance for
`city traffic and for so-called stop-and-go driving in backed
`up traffic, since a maximum abatement of pollution can be
`achieved at relatively low fuel consumption. The vehicle is
`preferably provided with a selector switch. When the selec
`tor switch is actuated, the internal combustion engine is
`turned off assuming that there is sufficient energy in the
`energy storage means for operating purely on stored energy.
`In principle, the energy storage means according to the
`invention can be a mechanical storage device, e.g. a fly
`wheel, but is preferably a storage battery or accumulator for
`storing electrical energy.
`The factors discussed above, e.g. fastest possible accel
`eration of the internal combustion engine, low fuel con
`sumption, low pollutant emission and the like, may be taken
`into account simultaneously, advisably by weighting the
`individual parameters.
`As indicated above, the invention provides that the gen
`erator is electrically decoupled from the electric motor
`entirely or partially and the internal combustion engine,
`together with the generator, is gradually coupled with the
`electric motor again when reaching the new operating point
`and that energy is fed to the electric motor from the energy
`storage means during the decoupling phase in such a way
`that the transitions are effected smoothly during the cou
`pling.
`As discussed above, the driving signal plays a special part
`in the controlled use of the energy storage means. In the
`simplest case, a position sensor located at the throttle, i.e.
`particularly at the accelerator pedal, transmits a position
`signal O. to the control unit. The control unit can then
`determine a speed signal O. and an acceleration signal O. for
`the movement of the accelerator pedal from the time curve
`of this position signal or by differentiation. The speed signal
`and acceleration signal for the accelerator pedal can also be
`supplied directly by corresponding sensors at the accelerator
`pedal.
`In addition to the driving signals mentioned above, which
`depend on the actuation of the accelerator pedal, the inven
`tion also provides a transmitter for a maximum acceleration
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`requirement (kickdown) and possibly another selector
`switch for intermittent operation (city traffic).
`The energy storage is outfitted with a charge status sensor
`which transmits to the storage means means a signal repre
`senting the energy still contained in the energy storage
`means. Based on these values and other values which are
`already stored, the control unit can determine how much
`energy per time unit (output) may be taken from the energy
`storage means so that the acceleration leads to the desired
`new final vehicle speed without depleting the energy storage
`means during the acceleration process and so as to prevent
`dangerous situations which may occur as a result of decreas
`ing acceleration.
`Switching on additional output from the energy storage
`means at maximum engine output permits a further increase
`in the maximum speed as determined by the maximum
`output of the internal combustion engine. According to the
`invention, the last range of the throttle path is provided for
`obtaining this additional thrust by means of additional
`output from the energy storage means. The internal com
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`bustion engine and energy storage means are both used for
`driving the vehicle only when the accelerator pedal is
`completely depressed.
`As will be clear from the foregoing discussion, energy is
`taken from the storage means on the one hand without
`conscious effort on the part of the driver merely by appro
`priate operation of the control device which, apart from the
`driving signal, contains status signals from the internal
`combustion engine, generator, storage means, and driving
`electric motors so that permanent signals relating to the
`speed and torque of the internal combustion engine or
`generator, the charge state of the storage means, and the
`speed of the electric motors are available at the control unit.
`On the other hand, the driver may also actively take energy
`from the storage means, e.g., by selecting a drive by means
`of the above-mentioned selector switch in city traffic also
`when the internal combustion engine is stopped.
`The invention can also be used advantageously in a
`vehicle which is outfitted with a device for automatically
`regulating speed. Each time the actual driving speed
`diverges from the adjusted reference driving speed by more
`than a predetermined value, stored energy can be used to
`maintain constant speed.
`The above-mentioned possibility for switching to a quasi
`exclusively electrical operating mode of the vehicle in city
`traffic by means of selector switches can also be linked to a
`learning function of the control unit. The control unit counts
`the occurrence of braking and accelerating processes within
`a determined time window. If the average occurrence
`exceeds a threshold value, a "city driving mode, i.e. a quasi
`exclusive electromotive drive, is automatically switched on,
`wherein, depending on its charge state, the storage is only
`charged occasionally by switching on the internal combus
`tion engine.
`A certain set of problems arises in relation to the naturally
`limited capacity of the energy storage means. If the vehicle
`is very sharply accelerated when passing another vehicle and
`energy is taken from the energy storage means for this
`purpose, it must be ensured that the stored energy will be
`sufficient for the entire passing process. The energy required
`for passing depends on the required acceleration of the
`vehicle, the mass of the vehicle, the road configuration
`(grade) and other influencing variables. Of course, there are
`certain output limits which must be allowed for by the
`driver-as is also the case in conventional vehicles with
`internal combustion engines-so that he does not begin a
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`passing process which is impossible to complete based on
`the vehicle power.
`However, in the case of the vehicles under discussion, it
`may happen that the energy storage means is rather radically
`discharged just after considerable energy is consumed. In
`this case, a maximum acceleration of the vehicle for a
`passing process would be impossible under certain circum
`stances. For this reason, the invention provides a signalling
`device for the charge state of the energy storage means. This
`signalling device may be realized as a visual or acoustic
`device, but is preferably realized as a tactile signalling
`device, in particular, as resistance in the accelerator pedal. If
`the charge state of the energy storage means is insufficient,
`the driver will perceive an unusually high resistance when
`actuating the accelerator pedal. This alerts the driver of
`insufficient stored energy for maximum vehicle acceleration.
`In addition, the driver can be warned by a visual or acoustic
`signal whose intensity depends on the discharge state of the
`energy storage.
`The various features of novelty which characterize the
`invention are pointed out with particularity in the claims
`annexed to and forming a part of the disclosure. For a better
`understanding of the invention, its operating advantages, and
`specific object attained by its use, reference should be had to
`the drawings and descriptive matter in which there are
`illustrated and described preferred embodiments of the
`invention.
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`BRIEF DESCRIPTION OF THE DRAWINGS
`An illustrative embodiment of the present invention will
`be explained in more detail in the following with reference
`to the drawings, in which
`FIG. 1 shows a schematic view of essential elements of a
`passenger automobile outfitted with an electrodynamic con
`verter and an accumulator as energy Storage;
`FIG. 2 shows a characteristic field of an internal combus
`tion engine;
`FIG.3 shows a characteristic curve for output/accelerator
`pedal position; and
`FIG. 4 shows an output/speed characteristic curve at a
`speed o. of the accelerator pedal as parameter.
`
`DETALED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`FIG. 1 is a schematic view of essential drive elements of
`a passenger car. An internal combustion engine/generator
`unit (hereinafter VGE) 2 formed by an internal combustion
`engine 4 and an electric generator 6 supplies electric power,
`via a line L1, to an energy distributor 8 which is constructed
`as power electronics and which supplies electric power, via
`lines L2 and L3, to two electric motors 12 and 16 which are
`directly coupled to the rear wheels 14 and 18. The rear
`wheels 14 and 18 are accordingly driven depending on the
`current supplied to the electric motors 12 and 16 by the
`energy distributor 8.
`The vehicle 10 can also be outfitted with an all-wheel
`drive as indicated in the lower left-hand portion of FIG. 1 by
`dashed lines leading to additional electric motors which are
`coupled with the rest of the wheels of the vehicle.
`The current supplied to the electric motors 12 and 16 via
`the energy distributor 8 is controlled by a control unit 20
`which includes a microprocessor and data storage means.
`Control programs, characteristic curves and the like are
`stored in the storage means.
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`In addition to the VGE 2, an energy storage 23 con
`structed in this instance as an accumulator 22 is provided as
`an additional energy source and is coupled with the energy
`distributor 8 via lines L4 and L5. Electrical energy is stored
`in the accumulator 22 and electrical energy is supplied by
`the accumulator 22 to the energy distributor 8, respectively,
`via lines LA and L5.
`A sensor 24 which transmits a signal representing the
`charge state of the accumulator 22 to the control unit 20 is
`associated with the accumulator 22. Moreover, the control
`unit 20 receives speed signals in from the two electric motors
`12 and 16, a speed signal n and a torque signal M from the
`VGE 2, as well as driving signals from an accelerator pedal
`27.
`The accelerator pedal 27 is outfitted with a sensor
`arrangement 30 which sends the control unit 20 a position
`signal O. representing the angular position O. of the accel
`erator pedal 27, a speed signal O, and an acceleration signal
`O. The signals O, O, and O, respectively, represent the
`position of the accelerator pedal 27, its actuating speed and
`its acceleration.
`Further, a sensor 28 which supplies a "kickdown” signal
`kd to the control unit 20 is coupled with the acceleratorpedal
`27. The driver can also send a signal w to the control unit 20
`via a selector switch 26 to inform the control unit 20 of the
`driver's request that current be supplied to the electric
`motors 12 and 16 exclusively from the accumulator (city
`driving).
`Based on the signals fed to the control unit 20, the control
`unit 20 calculates control signals for the VGE 2 (in particu
`lar, the internal combustion engine) on the one hand and for
`the energy distributor 8 on the other hand. When the driver
`depresses the accelerator pedal 27 from a first position into
`a second position at a determined speed o, the control unit
`20 interprets this as a request for a higher permanent output
`on the part of the VGE 2 so that the control unit 20 supplies
`control signals to the VGE 2 for revving the internal
`combustion engine to an operating point corresponding to
`the required permanent output.
`The ratio between the accelerator pedal position and the
`required output is nonlinear, as shown, for example, in FIG.
`3. With small accelerator pedal displacements o, the
`required output changes only slightly. This enables an easy
`proportioning of the output requirement at low speeds.
`As is shown in principle in FIG. 4, the manner in which
`the vehicle is accelerated is determined by depressing the
`accelerator pedal 27 by a certain distance into a new
`accelerator pedal position O. at a determined actuating speed
`O. as mentioned above. A higher, new constant speed v of
`the vehicle corresponds to the requested increased output. In
`order to attain this speed proceeding from the previous
`constant speed v, wherein the internal combustion engine
`supplies the total output after reaching speed v, additional
`output which is at least equal to the previous output of the
`internal combustion engine (P) is first provided immedi
`ately by the energy storage 22. The speed of the internal
`combustion engine is then driven up until reaching a value
`corresponding to the aimed for output P. Acceleration of the
`vehicle by means of the stored energy is effected on the basis
`of the actuating speed o. of the accelerator pedal 27 as shown
`in FIG. 4. The faster the accelerator pedal 27 is actuated, the
`more energy is provided for accelerating the vehicle.
`In this preferred embodiment example, the generator 6 is
`decoupled from the driving electric motors 12 and 16 when
`the internal combustion engine is revved up to a new
`operating point.
`
`8
`FIG. 2 shows characteristic performance data for a 100
`kW internal combustion engine. The torque is plotted over
`speed. A dashed line by represents the most favorable
`specific fuel consumption as a function of speed. For
`example, a point be
`with the most favorable fuel con
`sumption of all results at speed n=2200. Although fuel
`consumption is lower at lower speeds, the torque is dispro
`portionately smaller. At higher speeds, there is increased fuel
`consumption with a disproportionately small increase in
`torque.
`It is assumed in the preceding example that at a vehicle
`speed V during which output is applied entirely by the
`internal combustion engine 4, the internal combustion
`engine 4 operates at a speed of 3000 rpm which corresponds
`to the operating point A* on line by in FIG. 2. If the driver
`continues to depress the accelerator pedal 27, which corre
`sponds to a requested permanent output P, the internal
`combustion engine 4 must be revved up to a new operating
`point B* on line b.
`This revving of the internal combustion engine 4 is
`preferably effected when the generator 6 is decoupled from
`the load. For this purpose, the energy distributor 8 is
`controlled in such a way that the electric motors 12 and 8
`which are powered in order to move the vehicle forward are
`no longer powered completely by the generator 6, but rather
`entirely or partially from the energy storage 2. In this state,
`the internal combustion engine 4 is revved up along the line
`b to the new operating point B*. There follows a gradual
`coupling of the generator 6 to the electric motors 12 and 16.
`These coupling processes are controlled by the control unit
`20 in such away that they proceed gradually so that the drive
`is continued smoothly.
`In the example discussed above with reference to FIG. 2,
`the energy storage 22 is used to accelerate the vehicle
`allowing for favorable fuel consumption. Alternatively or in
`addition, other parameters may also be taken into account,
`e.g. the emission of pollutants, noise development, loading
`of the unit and the like.
`When the vehicle travels at a certain constant speed and
`the driver desires a maximum acceleration, he fully
`depresses the acceleratorpedal 27. In so doing, the sensor 28
`generates the "kickdown” signal kd. Consequently, the
`maximum available output is supplied to the electric motors
`12 and 16: the internal combustion engine 4 is revved up to
`maximum output on the one hand, and a certain maximum
`output is taken from the energy storage 22 on the other hand.
`Thus-as was described above-avery high output which is
`higher than the maximum output of the internal combustion
`engine 4 can be drawn from the energy storage 22 first.
`When the internal combustion engine 4 is then operated in
`a range of the highest output, the proportion of the output
`taken from the energy storage 22 can be reduced, but in such
`a way that an output which is greater than the maximum
`output applied by the internal combustion engine is still
`supplied to the electric motors 12 and 16.
`The above-mentioned process provides an extremely
`powerful acceleration of the vehicle (kickdown). If the
`vehicle is already traveling at a maximum speed correspond
`ing to the maximum output of the internal combustion
`engine 4, additional thrust can still be achieved by m