Comparison of ’455 PCT Publication and ’134 Patent Descriptions
`(“the ’455/’134 Description Comparison”)
`
`
`Field of the Invention __
`FIELD OF THE INVENTION
`
`This application relates to improvements in hybrid vehicles, that is, vehicles in which both an
`internal combustion 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 DISCUSSION OF THE PRIOR ART
`
`For many years great attention has been given to the problem 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
`combustion temperatures than those now in use. However, higher combustion temperatures in
`gasoline-fueled engines
`lead
`to
`increase
`in certain undesirable pollutants,
`typically
`NOxNO.sub.x.
`
`Another possibility for reducing emissions is to burn mixtures of gasoline and ethanol
`("gasohol") ,"), or straight ethanol. However, to date ethanol has not become economically
`competitive with gasoline, and consumers have not accepted ethanol 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
`production and delivery system, but also the vehicle manufacture, distribution, and repair system,
`would have to be extensively 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 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 inconvenience, such cars are not suitable for all the travel requirements of most
`individuals. Accordingly, an electric car would have to be an additional vehicle for most users,
`posing a substantial economic deterrent. Moreover, it will be appreciated 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
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`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 Propulsion CRX" ,",
`Road & Track, October 1992, pp. 126-129.
`
`Brooks et al U.S. patentPat. 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 development of electric vehicles including
`internal combustion engines powering generators, thus eliminating the defect of limited range
`exhibited by simple electric vehicles. The simplest 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. Accordingly,
`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 ' sengine'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 mechanically 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 locomotive, for example, with a multiple speed transmission, or a clutch. Accordingly, the
`additional complexity of the generator 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 discussed in detail
`below in connection with FigsFIGS. 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 locomotives can be operated at nearly full
`torque production. Moreover, 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, involving many short trips,
`frequent stops in traffic, extended low-speed operation and the like.
`
`So-called "series hybrid" electric vehicles have been proposed for automotive use, wherein
`batteries are used as energy storage devices, so that an internal combustion engine provided to
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`power a generator can be operated in its most fuel-efficient output power range while still
`allowing the electric 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
`electrical power to the traction motor (s) as required, so as to operate efficiently. 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. EnergyHowever, energy transfer between those
`components consumes at least approximately 25%2-5-% of engine power. Further, such
`components add substantially to the cost and weight of the vehicle; in particular, an electric
`motor capable of providing sufficient torque to meet all expected demand, e.g. ,., to allow
`reasonable performance under acceleration, during hill-climbing and the like, is rather heavy and
`expensive. Thus, series hybrid vehicles have not been immediately successful.
`
` A
`
` more promising "parallel hybrid" approach is shown in U.S. PatentPat. 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 constant 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/generators separately powered by the internal
`combustion engine; the "speeder" charges the batteries, while the "torquer" propels the vehicle
`forward in traffic. This arrangement is a source of additional complexity, cost and difficulty, as
`two separate modes of engine control are required. Moreover, 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 "foolproof", 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 difficult 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 of patentU.S. Pat. No. 3,566,717, and col. 2, lines 53 - -55 of patentU.S.
`Pat. No. 3,732,751.
`
`Lynch et al patentU.S. Pat. No. 4,165,795 also shows an early parallel hybrid drive. Lynch
`argues that maximum fuel efficiency can be realized when a relatively small internal combustion
`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 efficient speed, about 2500 rpm. This is
`to be combined with an electric motor-generator of about 30 peak hp. This vehicle requires a
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`variable-ratio transmission to achieve reasonable performance. It appears that the engine is to be
`run continuously, at a steady speed, with additional torque provided 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. patentPat. No. 5,117,931 shows a parallel hybrid vehicle where torque from an
`electric motor may be combined 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 transmission unit and the propelling
`wheels. Both the torque transmission unit and the variable-speed transmission are complex,
`heavy, and expensive components, the use of which would preferably be avoided.
`
`Helling U.S. patentPat. 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 battery to store excess electrical energy.
`Albright, Jr. et al patentU.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. patentPat. No. 5,318,142.
`Fjallstrδm
`Fjallstrom U.S. patentPat. No. 5,120,282 shows a parallel hybrid drive train wherein torque from
`two electric motors is combined with torque produced by an internal combustion engine; the
`combination is performed by a complex arrangement 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. PatentPat. 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 energized.... 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 of the present invention, as discussed in
`detail below. Hunt's vehicle in each embodiment requires a conventional manual or automatic
`transmission. See col. 2, lines 6 - -7. Moreover, the internal combustion engine is connected to
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`the transfer case (wherein torque from the internal combustion engine and electric motor is
`combined) by a "fluid coupling or torque converter of conventional construction". Col. 2, lines
`16 - -17. Such transmissions and fluid couplings or torque converters are very inefficient, are
`heavy, bulky, and costly, and are to be eliminated according to one object of the present
`invention, again as discussed in detail below.
`
`Furthermore, the primary means of battery charging disclosed by Hunt involves a further
`undesirable complexity, namely a turbine driving the electric motor in generator configuration.
`The turbine is fueled by waste heat from the internal combustion engine. See col. 3, lines 10 - -
`60. Hunt's internal 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. PatentsPat. 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 of the 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
`insufficient 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 provide 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 braking 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 sufficient regenerative
`braking force; see col. 1, line 50 - --col. 2 line 8. Accordingly, Kawakatsu provides two separate
`motor/generators, 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 comprising three separately-controllable clutches. See col. 5, lines 50 - -62.
`
`Numerous patents disclose hybrid vehicle 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
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`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 typically
`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
`provided 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); Cummings (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); Kawamura (U.S. Pat. No. 4,951,769); and Suzuki et al (U.S. Pat. No. 5,053,632).
`Various of these address specific problems 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 system 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 combustion engine to an electric motor by a first friction clutch,
`and connecting the motor to a transmission by a second friction 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 compressed-air or similar mechanical starter for the internal
`combustion engine of a series hybrid, such that batteries of limited 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. PatentPat. No.
`4,578,955 to Medina shows a hybrid system wherein a gas turbine is used to drive a generator as
`needed to charge batteries. Of particular interest to certain aspects of the present invention is that
`Medina discloses 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 substantial resistance heating losses, and
`additionally require that all electrical connections be made by positive mechanical means such as
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`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 cannot 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 connections) .). Accordingly, it would be desirable to operate the
`electric motor of a hybrid vehicle at lower currents.
`
`U.S. patentPat. No. 5,765,656 to Weaver also shows a series hybrid wherein a gas turbine is used
`as the internal combustion engine; hydrogen is the preferred fuel.
`
`U.S. PatentPat. No. 4,439,989 to Yamakawa shows a system wherein two different internal
`combustion engines are provided, so that only one need be run when the load is low. This
`arrangement would be complex and expensive to manufacture.
`
`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) . Kalberϊah). Kalberlah then compares various forms of parallel hybrids,
`with respect to his FigFIG. 4, and concludes that the most practical arrangement is one in which
`an internal combustion engine drives a first pair of wheels, and an electric motor the second;
`more particularly, KalberlahKalberiah indicates that mechanical combination of the torque from
`an internal combustion engine and an electric motor is impractical.
`
`Gardner U.S. patentsPat. Nos. 5,301,764 and 5,346,031 follow Kalberlah 'sKalberlah's teachings,
`in that Gardner shows separately driving 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 driving 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 of Mass, 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 of the various battery types then available. Bullock concludes that a vehicle
`having two electric motors of differing characteristics, driving the wheels through a variable-
`speed transmission, would be optimal for automotive use; see the discussion of FigFIG. 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
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` 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. patentPat. No. 5,667,029 shows two embodiments of parallel hybrids; a first
`embodiment is shown in FigsFIGS. 1 - -9 and 111, and a second in FigsFIGS. 12 - -17. Both
`embodiments have numerous common features, including similar operating modes. Referring to
`the first embodiment, an internal 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 to propel the vehicle; if the 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 electric" 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 variable-ratio transmission and a torque converter, is stated to be adequate for this
`purpose. Such components are clearly complex 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 vehicle was stationary, but this would lead
`to high levels of noise and vibration. In any event Urban does not appear to consider this
`possibility. ).)
`
`On the other hand, Urban does suggest that the vehicle can be operated as a "straight electric"
`under low-speed conditions, but this requires the operator to provide an explicit control input;
`this complexity is unacceptable in a vehicle intended to be sold in quantity, as would be required
`in order to reach Urban 'sUrban's stated goals of reduction of atmospheric pollution and reduced
`energy consumption. As noted, hybrid vehicle operation must be essentially "foolproof", or
`"transparent" to the user, to have any chance of commercial success.
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`Urban *sUrban's second embodiment is mechanically simpler, employing but a single
`"dynamotor", through which torque is transmitted from the engine to the variable-ratio
`transmission, but suffers from the same operational deficiencies.
`
` A
`
` second Urban et al patent,, U.S. Pat. No. 5,704,440, is directed to the method of operation of
`the vehicle of the '029 patent and suffers the same inadequacies.
`
`Various articles describe several generations of Toyota Motor Company hybrid vehicles, stated
`soonbelieved to becorrespond to that available commercially. as the "Prius". See, for example,
`Yamaguchi, "Toyota readies gasoline/electric hybrid system", Automotive Engineering,,, July
`1997, pp. 55 - -58; Wilson, "Not Electric, Not Gasoline, But Both", Autoweek . June, Jun. 2,
`1997, pp. 17 - -18; Bulgin, "The Future Works, Quietly", Autoweek FebruaryFeb. 23, 1998, pp.
`12 and 13; and
`
`"Toyota Electric and Hybrid Vehicles", a Toyota brochure. A more detailed discussion of the
`Toyota vehicle's powertrain is found in Nagasaka et al, "Development of the Hybrid/Battery
`ECU for the Toyota Hybrid System", SAE paper 981122 (1998), pp. 19 - -27. According to the
`Wilson article, Toyota describes this vehicle as a "series-parallel hybrid"; regardless of the label
`applied, its powertrain appears to be similar to that of the Berman patents described above, that
`is, torque from either or both of an internal combustion engine and an electric motor are
`controllably combined in a "power-split mechanism" and transmitted to the drive wheels through
`a planetary gearset providing the functionality of a variable-ratio transmission. See the Nagasaka
`article at pp. 19 - -20.
`
`Furutani U.S. patentPat. No. 5,495,906 describes a vehicle having an internal combustion engine
`driving a first set of wheels through a variable-ratio transmission and an electric motor driving a
`second set of wheels. The engine is apparently intended to be run continuously; at low speeds, it
`drives a generator to charge batteries providing energy to the motor, and at higher speeds the
`engine or both engine and motor propel the vehicle. In some circumstances the transmission may
`not be required; compare, for example, col. 3, lines 4 - -8 with col. 5, lines 59 -64.
`
`U.S. patentPat. No. 5,842,534 to Frank shows a "charge depletion" control method for hybrid
`vehicles; in this scheme, the internal combustion engine is essentially used only when the state of
`the batteries is such that the vehicle cannot otherwise reach a recharging point. See col. 3, lines
`50 - -55. In normal operation, the batteries are recharged from an external power source. Frank
`also discusses two-mode brake pedal operation, wherein mechanical brakes are engaged in
`addition to regenerative braking when the pedal is depressed beyond a preset point.
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`U.S. patentPat. No. 5,823,280 to Lateur et al shows a parallel hybrid wherein the shafts of an
`internal combustion engine and first and second electric motors are all coaxial; the engine is
`connected to the first motor by a clutch, and the first motor to the second by a planetary gearset,
`allowing the speeds of the motors to be varied so as to operate them in their most efficient range.
`See col. 4, line 57 - --col. 5, line 60.
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`U.S. patentPat. No. 5,826,671 to Nakae et al shows a parallel hybrid wherein torque from an
`internal combustion engine is combined with that from a motor in a planetary gearset; a clutch is
`provided therebetween. The specific invention relates to sensing of engine warmup conditions,
`so as to limit emission of unburnt fuel and thus lower emissions.
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`U.S. patentPat. No. 5