VWGoA - Ex. 1001
`Volkswagen Group of America, Inc. - Petitioner
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`1
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`U.S. Patent
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`Jul. 3, 2012
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`Sheet 1 of 17
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`Jul. 3, 2012
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`1
`HYBRID VEHICLES
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`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This is a divisional application of application Ser. No.
`12/320,600, filed Jan. 29, 2009, now abandoned which was a
`divisional application of Ser. No. 11/459,458, Jul. 7, 2006
`now U.S. Pat. No. 7,520,353, which was a divisional appli-
`cation of Ser. No. 10/382,577 filed Mar. 7, 2003, now U.S.
`Pat. No. 7,104,347, which was a divisional application of Ser.
`No. 09/822,866 filed Apr. 2, 2001, now U.S. Pat. No. 6,544,
`088, which was a continuation-in-part of Ser. No. 09/264,817
`filed Mar. 9 1999, now U.S. Pat. No. 6,209,672, issuedApr. 3,
`2001, which in turn claimed priority from provisional appli-
`cation Ser. No. 60/100,095, filed Sep. 14, 1998, and was also
`a continuation-in-part of Ser. No. 09/392,743 filed Sep. 9,
`1999, now U.S. Pat. No. 6,338,391 issued Jan. 15, 2002, in
`turn claiming priority from provisional application Ser. No.
`60/122,296, filed Mar. 1, 1999.
`
`FIELD OF THE INVENTION
`
`in hybrid
`to improvements
`This application relates
`vehicles, that is, vehicles in which both an internal combus-
`tion engine and one or more electric motors are provided to
`supply torque to the driving wheels of the vehicle. More
`particularly, this invention relates to a hybrid electric vehicle
`that is fully competitive with presently conventional vehicles
`as regards performance, operating convenience, and cost,
`while achieving substantially improved fuel economy and
`reduced pollutant emissions.
`
`DISCUSSION OF THE PRIOR ART
`
`For many years great attention has been given to the prob-
`lem of reduction of fuel consumption of automobiles and
`other highway vehicles. Concomitantly very substantial
`attention has been paid to reduction of pollutants emitted by
`automobiles and other vehicles. To a degree, efforts to solve
`these problems conflict with one another. For example,
`increased thermodynamic efficiency and thus reduced fuel
`consumption can be realized if an engine is operated at higher
`temperatures. Thus there has been substantial
`interest in
`engines built of ceramic materials withstanding higher com-
`bustion temperatures than those now in use. However, higher
`combustion temperatures in gasoline-fueled engines lead to
`increase in certain undesirable pollutants, typically NOX.
`Another possibility for reducing emissions is to burn mix-
`tures of gasoline and ethanol (“gasohol”), or straight ethanol.
`However, to date ethanol has not become economically com-
`petitive with gasoline, and consumers have not accepted etha-
`nol to any great degree. Moreover, to make an alternate fuel
`such as ethanol available to the extent necessary to achieve
`appreciable improvements in nationwide air quality and fuel
`conservation would require immense costs for infrastructure
`improvements; not only the entire nation’s motor fuel pro-
`duction and delivery system, but also the vehicle manufac-
`ture, distribution, and repair system, would have to be exten-
`sively revised or substantially duplicated.
`One proposal for reducing pollution in cities is to limit the
`use of vehicles powered by internal combustion engines and
`instead employ electric vehicles powered by rechargeable
`batteries. To date, all such “straight electric” cars have had
`very limited range, typically no more than 150 miles, have
`insufficient power for acceleration and hill climbing except
`when the batteries are substantially fully charged, and require
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`substantial time for battery recharging. Thus, while there are
`many circumstances in which the limited range and extended
`recharging time of the batteries would not be an inconve-
`nience, such cars are not suitable for all the travel require-
`ments ofmost individuals. Accordingly, an electric car would
`have to be an additional vehicle for most users, posing a
`substantial economic deterrent. Moreover, it will be appreci-
`ated that in the United States most electricity is generated in
`coal-fired power plants, so that using electric vehicles merely
`moves the source of the pollution, but does not eliminate it.
`Furthermore, comparing the respective net costs per mile of
`driving, electric vehicles are not competitive with ethanol-
`fueled vehicles, much less with conventional gasoline-fueled
`vehicles. See, generally, Simanaitis, “Electric Vehicles”,
`Road & Track, May 1992, pp. 126-136; Reynolds, “AC Pro-
`pulsion CRX”, Road & Track, October 1992, pp. 126-129.
`Brooks et al U.S. Pat. No. 5,492,192 shows such an electric
`vehicle; the invention appears to be directed to incorporation
`of antilock braking and traction control technologies into an
`otherwise conventional electric vehicle.
`
`Much attention has also been paid over the years to devel-
`opment of electric vehicles including internal combustion
`engines powering generators, thus eliminating the defect of
`limited range exhibited by simple electric vehicles. The sim-
`plest such vehicles operate on the same general principle as
`diesel-electric locomotives used by most railroads. In such
`systems, an internal combustion engine drives a generator
`providing electric power to traction motors connected
`directly to the wheels of the vehicle. This system has the
`advantage that no variable gear ratio transmission is required
`between the engine and the wheels of the vehicle.
`More particularly, an internal combustion engine produces
`zero torque at zero engine speed (RPM) and reaches its torque
`peak somewhere in the middle of its operating range. Accord-
`ingly, all vehicles driven directly by an internal combustion
`engine (other than certain single-speed vehicles using friction
`or centrifugal clutches, and not useful for normal driving)
`require a variable-ratio transmission between the engine and
`the wheels, so that the engine’s torque can be matched to the
`road speeds and loads encountered. Further, some sort of
`clutch must be provided so that the engine can be mechani-
`cally decoupled from the wheels, allowing the vehicle to stop
`while the engine is still running, and to allow some slippage of
`the engine with respect to the drive train while starting from
`a stop. It would not be practical to provide a diesel locomo-
`tive, for example, with a multiple speed transmission, or a
`clutch. Accordingly, the additional complexity of the genera-
`tor and electric traction motors is accepted. Electric traction
`motors produce full torque at zero RPM and thus can be
`connected directly to the wheels; when it is desired that the
`train should accelerate, the diesel engine is simply throttled to
`increase the generator output and the train begins to move.
`The same drive system may be employed in a smaller
`vehicle such as an automobile or truck, but has several distinct
`disadvantages in this application. In particular, and as dis-
`cussed in detail below in connection with FIGS. 1 and 2, it is
`well known that a gasoline or other internal combustion
`engine is most efficient when producing near its maximum
`output torque. Typically, the number of diesel locomotives on
`a train is selected in accordance with the total tonnage to be
`moved and the grades to be overcome, so that all the locomo-
`tives can be operated at nearly full torque production. More-
`over, such locomotives tend to be run at steady speeds for long
`periods of time. Reasonably efficient
`fuel use is thus
`achieved. However, such a direct drive vehicle would not
`achieve good fuel efficiency in typical automotive use,
`
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`involving many short trips, frequent stops in traflic, extended
`low-speed operation and the like.
`So-called “series hybrid” electric vehicles have been pro-
`posed for automotive use, wherein batteries are used as
`energy storage devices, so that an internal combustion engine
`provided to power a generator can be operated in its most
`fuel-efficient output power range while still allowing the elec-
`tric traction motor(s) powering the vehicle to be operated as
`required. Thus the engine may be loaded by supplying torque
`to a generator charging the batteries while supplying electri-
`cal power to the traction motor(s) as required, so as to operate
`efliciently. This system overcomes the limitations of electric
`vehicles noted above with respect to limited range and long
`recharge times. Thus, as compared to a conventional vehicle,
`wherein the internal combustion engine delivers torque
`directly to the wheels, in a series hybrid electric vehicle,
`torque is delivered from the engine to the wheels via a serially
`connected generator used as a battery charger, the battery, and
`the traction motor. However, energy transfer between those
`components consumes at least approximately 25% of engine
`power. Further, such components add substantially to the cost
`and weight of the vehicle; in particular, an electric motor
`capable of providing suflicient torque to meet all expected
`demand, e.g., to allow reasonable performance under accel-
`eration, during hill-climbing and the like, is rather heavy and
`expensive. Thus, series hybrid vehicles have not been imme-
`diately successful.
`A more promising “parallel hybrid” approach is shown in
`U.S. Pat. Nos. 3,566,717 and 3,732,751 to Berman et al. In
`Berman et al an internal combustion engine and an electric
`motor are matched through a complex gear train so that both
`can provide torque directly to the wheels, the vehicle being
`operated in several different modes. Where the output of the
`internal combustion engine is more than necessary to drive
`the vehicle (“first mode operation”) the engine is run at con-
`stant speed and excess power is converted by a first motor/
`generator (“speeder”) to electrical energy for storage in a
`battery. In “second mode operation”, the internal combustion
`engine drives the wheels directly, and is throttled. When more
`power is needed than the engine can provide, a second motor/
`generator or “torquer” provides additional torque as needed.
`Berman et al thus show two separate electric motor/gen-
`erators separately powered by the internal combustion
`engine;
`the “speeder” charges the batteries, while the
`“torquer” propels the vehicle forward in traffic. This arrange-
`ment is a source of additional complexity, cost and difficulty,
`as two separate modes of engine control are required. More-
`over, the operator must control the transition between the
`several modes of operation. Such a complex vehicle is
`unsuited for the automotive market. Automobiles intended
`
`for mass production can be no more complicated to operate
`than conventional vehicles, and must be essentially “fool-
`proof”, that is, resistant to damage that might be caused by
`operator error. Further, the gear train shown by Berman et al
`appears to be quite complex and diflicult to manufacture
`economically. Berman et al also indicate that one or even two
`variable-speed transmissions may be required; see, e.g., col.
`3, lines 19-22 and 36-38 ofU.S. Pat. No. 3,566,717, and col.
`2, lines 53-55 ofU.S. Pat. No. 3,732,751.
`Lynch et al U.S. Pat. No. 4,165,795 also shows an early
`parallel hybrid drive. Lynch argues that maximum fuel efli-
`ciency can be realized when a relatively small internal com-
`bustion engine is provided, such that when the engine is
`operated at an efficient speed, it produces approximately the
`average power required over a typical mission. The example
`given is of an engine producing 25 hp maximum and 17 hp at
`its most eflicient speed, about 2500 rpm. This is to be com-
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`bined with an electric motor-generator of about 30 peak hp.
`This vehicle requires a variable-ratio transmission to achieve
`reasonable performance. It appears that the engine is to be run
`continuously, at a steady speed, with additional torque pro-
`vided by the motor when needed and excess torque produced
`by the engine being used to charge the batteries. In a first
`embodiment, torque provided by the motor is transmitted to
`the drive wheels through the engine, while in a second
`embodiment their respective positions are reversed.
`Nishida U.S. Pat. No. 5,117,931 shows a parallel hybrid
`vehicle where torque from an electric motor may be com-
`bined with torque from an internal combustion engine in a
`“torque transmission unit” comprising paired bevel gears and
`means for controlling the relative rates of rotation of the
`motor and engine, so that the motor can be used to start the
`engine, absorb excess torque from the engine (by charging a
`battery), or provide additional propulsive torque. A variable-
`speed transmission is coupled between the torque transmis-
`sion unit and the propelling wheels. Both the torque transmis-
`sion unit and the variable-speed transmission are complex,
`heavy, and expensive components, the use of which would
`preferably be avoided.
`Helling U.S. Pat. No. 3,923,115 also shows a hybrid
`vehicle having a torque transmission unit for combining
`torque from an electric motor and an internal combustion
`engine. However, in Helling the relative rates of rotation of
`the motor and engine input shafts are fixed; a flywheel is
`provided to store excess mechanical energy as well as a bat-
`tery to store excess electrical energy. Albright, Jr. et al U.S.
`Pat. No. 4,588,040 shows another hybrid drive scheme using
`a flywheel in addition to batteries to store excess energy;
`various complicated mechanical connections are provided
`between the various components. Capacitors have also been
`proposed for energy storage; see Bates et al U.S. Pat. No.
`5 ,3 18,142.
`Fjallstrom U.S. Pat. No. 5,120,282 shows a parallel hybrid
`drive train wherein torque from two electric motors is com-
`bined with torque produced by an internal combustion
`engine; the combination is performed by a complex arrange-
`ment of paired planetary gearsets, and unspecified control
`means are alleged to be able to allow variation of road speed
`without a variable-ratio transmission.
`Hunt U.S. Pat. Nos. 4,405,029 and 4,470,476 also disclose
`parallel hybrids requiring complex gearing arrangements,
`including multiple speed transmissions. More specifically,
`the Hunt patents disclose several embodiments of parallel
`hybrid vehicles. Hunt indicates (see col. 4, lines 6-20 of the
`’476 patent) that an electric motor may drive the vehicle at
`low speeds up to 20 mph, and an internal combustion engine
`used for speeds above 20 mph, while “in certain speed ranges,
`such as from 15-30 mph, both power sources may be ener-
`gized .
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`. Additionally, both power sources could be utilized
`under heavy load conditions.” Hunt also indicates that “the
`vehicle could be provided with an automatic changeover
`device which automatically shifts from the electrical power
`source to the internal combustion power source, depending
`on the speed of the vehicle” (col. 4, lines 12-16).
`However, the Hunt vehicle does not meet the objects ofthe
`present invention, as discussed in detail below. Hunt’s vehicle
`in each embodiment requires a conventional manual or auto-
`matic transmission. See col. 2, lines 6-7. Moreover, the inter-
`nal combustion engine is connected to the transfer case
`(wherein torque from the internal combustion engine and
`electric motor is combined) by an “fluid coupling or torque
`converter of conventional construction”. Col. 2, lines 16-17.
`Such transmissions and fluid couplings or torque converters
`are very ineflicient, are heavy, bulky, and costly, and are to be
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`5
`eliminated according to one object of the present invention,
`again as discussed in detail below.
`Furthermore, the primary means of battery charging dis-
`closed by Hunt involves a further undesirable complexity,
`namely a turbine driving the electric motor in generator con-
`figuration. The turbine is fueled by waste heat from the inter-
`nal combustion engine. See col. 3, lines 10-60. Hunt’s inter-
`nal combustion engine is also fitted with an alternator, for
`additional battery charging capability, adding yet further
`complexity. Thus it is clear that Hunt fails to teach a hybrid
`vehicle meeting the objects of the present invention—that is,
`a hybrid vehicle competitive with conventional vehicles with
`respect to performance, cost and complexity, while achieving
`substantially improved fuel efficiency.
`Kawakatsu U.S. Pat. Nos. 4,305,254 and 4,407,132 show a
`parallel hybrid involving a single internal combustion engine
`coupled to the drive wheels through a conventional variable-
`ratio transmission, an electric motor, and an alternator, to
`allow efficient use ofthe internal combustion engine. As in the
`Hunt disclosure, the engine is intended to be operated in a
`relatively efficient range of engine speeds; when it produces
`more torque than is needed to propel the vehicle, the excess is
`used to charge the batteries; where the engine provides insuf-
`ficient torque, the motor is energized as well.
`A further Kawakatsu patent, U.S. Pat. No. 4,335,429,
`shows a hybrid vehicle, in this case comprising an internal
`combustion engine and two motor/generator units. A first
`larger motor/generator, powered by a battery, is used to pro-
`vide additional torque when that provided by the engine is
`insufficient; the larger motor-generator also converts excess
`torque provided by the engine into electrical energy, to be
`stored by the battery, and is used in a regenerative braking
`mode. The second smaller motor/generator is similarly used
`to provide additional torque and additional regenerative brak-
`ing as needed.
`More particularly, the latter Kawakatsu patent asserts that
`a single electric motor sized to provide sufficient torque to
`propel the vehicle would not be capable of providing suffi-
`cient regenerative braking force; see col. 1, line 50-col. 2 line
`8. Accordingly, Kawakatsu provides two separate motor/gen-
`erators, as noted; a separate engine starting motor is also
`provided. See col. 6, lines 22-23. In the embodiment shown,
`the larger motor/generator is connected to the wheel drive
`shaft, while the engine and the smaller motor/generator are
`connected to the wheels through a complex mechanism com-
`prising three separately-controllable clutches. See col. 5,
`lines 50-62.
`
`Numerous patents disclose hybridvehicle drives tending to
`fall into one or more of the categories discussed above. A
`number of patents disclose systems wherein an operator is
`required to select between electric and internal combustion
`operation; for example, an electric motor is provided for
`operation inside buildings where exhaust fumes would be
`dangerous, and an internal combustion engine provided for
`operation outdoors. It is also known to propose a hybrid
`vehicle comprising an electric motor for use at low speeds,
`and an internal combustion engine for use at higher speed.
`The art also suggests using both when maximum torque is
`required. In several cases the electric motor drives one set of
`wheels and the internal combustion engine drives a different
`set. See generally Shea (U.S. Pat. No. 4,180,138); Fields et al
`(U.S. Pat. No. 4,351,405); Kenyon (U.S. Pat. No. 4,438,342);
`Krohling (U.S. Pat. No. 4,593,779); and Ellers (U.S. Pat. No.
`4,923,025).
`Many of these patents show hybrid vehicle drives wherein
`a variable speed transmission is required, as do numerous
`additional references. A transmission as noted above is typi-
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`cally required where the internal combustion engine and/or
`the electric motor are not capable of supplying sufficient
`torque at low speeds. See Rosen (U.S. Pat. No. 3,791,473);
`Rosen (U.S. Pat. No. 4,269,280); Fiala (U.S. Pat. No. 4,400,
`997); and Wu et al (U.S. Pat. No. 4,697,660). Kinoshita (U.S.
`Pat. No. 3,970,163) shows a vehicle of this general type
`wherein a gas turbine engine is coupled to the road wheels
`through a three-speed transmission; an electric motor is pro-
`vided to supply additional torque at low speeds.
`For further examples of series hybrid vehicles generally as
`discussed above, see Bray (U.S. Pat. No. 4,095,664); Cum-
`mings (U.S. Pat. No. 4,148,192); Monaco et al (U.S. Pat. No.
`4,306,156); Park (U.S. Pat. No. 4,313,080); McCarthy (U.S.
`Pat. No. 4,354,144); Heidemeyer (U.S. Pat. No. 4,533,011);
`Kawarnura (U.S. Pat. No. 4,951,769); and Suzuki et al (U.S.
`Pat. No. 5,053,632). Various of these address specific prob-
`lems arising in the manufacture or use of hybrid vehicles, or
`specific alleged design improvements. For example, Park
`addresses certain specifics of battery charging and discharge
`characteristics, while McCarthy shows a complex drive sys-
`tem involving an internal combustion engine driving two
`electric motors; the torque generated by the latter is combined
`in a complex differential providing continuously variable
`gear ratios. Heidemeyer shows connecting an internal com-
`bustion engine to an electric motor by a first friction clutch,
`and connecting the motor to a transmission by a second fric-
`tion clutch.
`
`Other patents of general relevance to this subject matter
`include Toy (U.S. Pat. No. 3,525,874), showing a series
`hybrid using a gas turbine as internal combustion engine;
`Yardney (U.S. Pat. No. 3,650,345), showing use of a com-
`pressed-air or similar mechanical starter for the internal com-
`bustion engine ofa series hybrid, such that batteries oflimited
`current capacity could be used; and Nakamura (U.S. Pat. No.
`3,837,419), addressing improvements in thyristor battery-
`charging and motor drive circuitry. Somewhat further afield
`but of general interest are the disclosures of Deane (U.S. Pat.
`No. 3,874,472); Horwinski (U.S. Pat. No. 4,042,056); Yang
`(U.S. Pat. No. 4,562,894); Keedy (U.S. Pat. No. 4,611,466);
`and Lexen (U.S. Pat. No. 4,815,334); Mori (U.S. Pat. No.
`3,623,568); Grady, Jr. (U.S. Pat. No. 3,454,122); Papst (U.S.
`Pat. No. 3,211,249); Nims et al (U.S. Pat. No. 2,666,492); and
`Matsukata (U.S. Pat. No. 3,502,165). Additional references
`showing parallel hybrid vehicle drive systems include
`Froelich (U.S. Pat. No. 1,824,014) and Reinbeck (U.S. Pat.
`No. 3,888,325). U.S. Pat. No. 4,578,955 to Medina shows a
`hybrid system wherein a gas turbine is used to drive a gen-
`erator as needed to charge batteries. Of particular interest to
`certain aspects of the present invention is that Medina dis-
`closes that the battery pack should have a voltage in the range
`of 144, 168 or 216 volts and the generator should deliver
`current in the range of 400 to 500 amperes. Those of skill in
`the art will recognize that these high currents involve substan-
`tial resistance heating losses, and additionally require that all
`electrical connections be made by positive mechanical means
`such as bolts and nuts, or by welding. More specifically, for
`reasons of safety and in accordance with industry practice,
`currents in excess of about 50 amperes carmot be carried by
`the conventional plug-in connectors preferred for reasons of
`convenience and economy, but must be carried by much
`heavier, more expensive and less convenient fixed connectors
`(as used on conventional starter and battery cable connec-
`tions). Accordingly, it would be desirable to operate the elec-
`tric motor of a hybrid vehicle at lower currents.
`U.S. Pat. No. 5,765,656 to Weaver also shows a series
`hybrid wherein a gas turbine is used as the internal combus-
`tion engine; hydrogen is the preferred fuel.
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`7
`U.S. Pat. No. 4,439,989 to Yamakawa shows a system
`wherein two different internal combustion engines are pro-
`vided, so that only one need be run when the load is low. This
`arrangement would be complex and expensive to manufac-
`ture.
`
`Detailed discussion of various aspects of hybrid vehicle
`drives may be found in Kalberlah, “Electric Hybrid Drive
`Systems for Passenger Cars and Taxis”, SAE Paper No.
`910247 (1991). Kalberlah first compares “straight” electric,
`series hybrid, and parallel hybrid drive trains, and concludes
`that parallel hybrids are preferable, at least when intended for
`general use (that is, straight electric vehicles may be useful
`under certain narrow conditions of low-speed, limited range
`urban driving). Kalberlah then compares various forms of
`parallel hybrids, with respect to his FIG. 4, and concludes that
`the most practical arrangement is one in which an internal
`combustion engine drives a first pair ofwheels, and an electric
`motor the second; more particularly, Kalberlah indicates that
`mechanical combination of the torque from an internal com-
`bustion engine and an electric motor is impractical.
`Gardner U.S. Pat. Nos. 5,301,764 and 5,346,031 follow
`Kalberlah’s teachings, in that Gardner shows separately driv-
`ing at least two pairs of wheels; one pair is driven by a first
`electric motor, and the second by a second electric motor or
`alternatively by a small internal combustion engine. Three
`different clutches are provided to allow various sources of
`drive torque to be connected to the wheels, and to a generator,
`depending on the vehicle’s operation mode. The internal
`combustion engine is run continuously, and provides the driv-
`ing torque when the vehicle is in a cruise mode; at other times
`it is used to charge the batteries powering the electric motors.
`Bullock, “The Technological Constraints ofMass, Volume,
`Dynamic Power Range and Energy Capacity on the Viability
`of Hybrid and Electric Vehicles”, SAE Paper No. 891659
`(1989) provides a detailed theoretical analysis of electric
`vehicles in terms of the loads thereon, and a careful analysis
`ofthe various battery types then available. Bullock concludes
`that a vehicle having two electric motors of differing charac-
`teristics, driving the wheels through a variable-speed trans-
`mission, would be optimal for automotive use; see the dis-
`cussion of FIG. 8. Bullock also suggests the use of an internal
`combustion engine to drive battery charging, but does not
`address combining the engine’s torque with that from the
`motors; see pp. 24-25.
`Further related papers are collected in Electric and Hybrid
`Vehicle Technology, volume SP-915, published by SAE in
`February 1992. See also Wouk, “Hybrids: Then and Now”;
`Bates, “On the road with a Ford HEV”, and King et al,
`“Transit Bus takes the Hybrid Route”, all in IEEE Spectrum,
`vol. 32, 7, (July 1995).
`Urban et al U.S. Pat. No. 5,667,029 shows two embodi-
`ments of parallel hybrids; a first embodiment is shown in
`FIGS. 1-9 and 11,anda second in FIGS. 12-17. Both embodi-
`ments have numerous common features, including similar
`operating modes. Referring to the first embodiment, an inter-
`nal combustion engine provides torque to the road wheels or
`to a generator; two electric motors can provide torque to the
`road wheels, or charge batteries during regenerative braking.
`Torque from the engine and motors is combined at the input
`shaft to a variable-ratio transmission. Overrunning clutches
`are provided, e.g., to allow the engine’s torque to be applied
`to the road wheels without also rotating the motors.
`As indicated at col. 6,
`lines 25-54, certain transitions
`between various operating modes are made automatically,
`responsive to the position of the accelerator pedal;
`for
`example, if the operator does not depress the pedal beyond a
`given point, only the internal combustion engine is employed
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`to propel the vehicle; ifthe operator depresses the pedal more
`fully, the electric motors are also energized. Other changes in
`the operational mode must be made by the operator directly;
`for example, the vehicle may be operated as a “straight elec-
`tric” vehicle, e.g. for short duration trips, by the operator’s
`making an appropriate control action. See col. 7, lines 49-56.
`The Urban et al design appears to suffer from a number of
`significant defects. First, the internal combustion engine is
`stated to provide all torque needed to accelerate the vehicle to
`cruising speed under normal circumstances (see col. 5, lines
`3-10), and also to propel the vehicle during cruising (see col.
`6, lines 48-54). The electric motors are to be used only during
`rapid acceleration and hill-climbing; col. 5, lines 10-13. A 20
`horsepower engine, operated through a continuously vari-
`able-ratio transmission and a torque converter, is stated to be
`adequate for this purpose. Such components are clearly com-
`plex and expensive; further, torque converters are notoriously
`inefficient. Moreover, using the internal combustion engine
`as the sole source of power for low-speed running would
`require it to be run at low speeds, e.g., at traffic lights, which
`is very inefficient and highly polluting. (Various additional
`references suggest that excess torque can be used to charge
`batteries; if this were incorporated in the Urban system, the
`engine might be run at a reasonably efficient output level
`while the