.ffi
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`
`
`HYBRID VEHICLES
`
`Inventors: Alex J. Severinsky
`Theodore N. Louckes
`
`
`
`'This application is a
`
`continuation—in—part of Ser. No.
`
`5
`
`09/264,817, filed March 9, 1999, now U. S. patent 6,209,672,
`
`issued
`
`April 3, 2001, which in turn claims priority from provisional
`{application Ser. No.
`60/100,095, filed September 14, 1998, and is
`also a continuation-in—part of Ser. No. 09/392,743, filed September
`
`9, 1999, which in turn claims priority from provisional application
`
`10
`
`Ser. No. 60/122,296, filed March 1, 1999.
`
`dziglg of the ingention
`
`This application relates to improvements in hybrid vehicles,
`
`that is, vehicles in which both an internal combustion engine and
`
`15
`
`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
`
`20
`
`: economy and reduced pollutant emissions.
`
`.i
`
`' c 35'
`
`e
`
`'
`
`t
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`For many years great attention has been given to the problem .
`' of reduction of fuel consumption of automobiles and other highway
`
`25
`
`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
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`30
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`operated at higher temperatures. Thus there has been substantial
`
`interest in engines built of ceramic materials withstanding higher
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`combustion 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 mixtures
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`5
`
`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
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`10
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`appreciable
`achieve
`to
`necessary
`extent
`to the
`available
`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.
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`15
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`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
`
`20
`
`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
`
`25
`
`4
`
`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
`
`30
`
`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”,
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`5
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`10
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`Road & Track, May 1992, pp.
`
`126—136; Reynolds,
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`"AC Propulsion
`
`CRX", Road & Track, October 1992, pp. 126-129.
`
`Brooks et al U.S. patent 5,492,192 shows such an electric
`
`vehicle; the invention appears to be directed to incorporation of
`
`traction control
`antilock braking and
`otherwise conventional electric vehicle.
`
`technologies
`
`into an
`
`Much attention has also been paid over
`
`the years
`
`to
`
`development of electric vehicles including internal combustion
`
`thus eliminating the defect of limited
`engines powering generators,
`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.
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`15
`
`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
`
`20
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`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
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`25
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`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 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
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`30
`
`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
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`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
`
`5
`
`such as
`
`an
`
`automobile or
`
`truck,
`
`but has
`
`several distinct
`
`disadvantages in this application.
`
`In particular, and as discussed
`
`1 and 2, it is well known
`in detail below in connection with Figs.
`that
`a gasoline or other
`internal combustion engine is most
`
`10
`
`torque.
`its maximum output
`near
`producing
`efficient when
`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
`
`15
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`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
`
`20
`
`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 electric traction motor(s) powering
`
`the vehicle to be operated as required. Thus the engine may be
`
`25
`
`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
`
`30
`
`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
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`those components consumes at
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`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 sufficient torque to meet all expected demand, e.g.,
`
`to
`
`5
`
`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.
`Patent Nos. 3,566,717 and 3,732,751 to Berman et al. In Berman et
`a1 an internal combustion engine and an electric motor are matched
`
`10
`
`through :1 complex gear
`
`train so that both can provide torque
`
`directly 113
`
`the wheels,
`
`the vehicle being operated ill several
`
`different modes. Where the output of the internal combustion engine
`
`is more
`
`than necessary to drive the vehicle
`
`("first mode
`
`15
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`operation") the engine is run at constant speed and excess power is
`
`converted by a first nmtor/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,
`
`20
`
`a second motor/generator or "torquer" provides additional torque as
`needed.
`
`Berman et a1 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
`
`25
`
`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.
`vehicle is unsuited for
`the automotive market.
`
`Such a complex
`Automobiles
`
`30
`
`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
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`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
`
`patent 3,566,717, and col. 2,
`
`lines 53 — 55 of patent 3,732,751.
`
`Lynch et a1 patent 4,165,795 also shows an early parallel
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`5
`
`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
`
`The example given is of an engine producing 25
`typical mission.
`hp maximum and 17 hp at its most efficient speed, about 2500 rpm.
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`10
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`This is to be combined 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
`
`15
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`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.
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`20
`
`Nishida U.S. patent 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
`
`25
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`motor can be used to start the engine, absorb excess torque from
`
`the engine
`
`(by
`
`charging a battery),
`’
`
`or provide additional
`J
`
`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
`
`30
`
`transmission are complex, heavy, and expensive components,
`
`the use
`
`of which would preferably be avoided.
`
`Helling U.S. patent 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
`
`\/
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`Helling the relative rates of rotation of
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`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 a1 patent 4,588,040 shows another hybrid
`
`5
`
`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 a1 U.S. patent 5,318,142.
`
`Fjallstrom U.S. patent 5,120,282 shows a parallel hybrid drive
`train wherein torque from two electric motors is combined with
`
`10
`
`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.
`
`15
`
`Hunt U.S. Patent Nos. 4,405,029 and 4,470,476 also disclose
`V 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
`
`20
`
`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
`
`25
`
`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
`
`30
`
`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 the transfer case (wherein torque
`
`from the internal combustion engine and electric motor is combined)
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`’
`
`.‘
`
`conventional
`of
`converter
`torque
`"fluid coupling or
`a
`by
`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
`
`5
`
`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
`
`10
`
`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
`
`15
`
`conventional vehicles with respect
`
`to performance,
`
`cost
`
`and
`
`complexity, while achieving substantially improved fuel efficiency.
`
`Kawakatsu U.S. Patents 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
`
`20
`
`transmission,
`
`an electric “motor,1 and an alternator,
`
`to allow
`
`As in the Hunt
`efficient use of the internal combustion engine.
`disclosure,
`the engine is intended to be operated in a relatively I
`
`efficient range of engine speeds; when it produces more torque than
`
`is needed to propel the vehicle,
`
`the excess is used to charge the-
`
`25
`
`batteries; where the engine provides insufficient torque,
`
`the motor
`
`is energized as well.
`
`A further Kawakatsu patent, 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
`
`30
`
`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
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`to provide additional torque and additional regenerative braking as
`needed.
`
`the latter Kawakatsu patent asserts that
`More particularly,
`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 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 (4,180,138); Fields et a1 (4,351,405); Kenyon
`
`(4,438,342); Krohling (4,593,779); and Ellers (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
`
`(3,791,473); Rosen (4,269,280); Fiala (4,400,997); and Wu et a1
`
`(4,697,660). Kinoshita (3,970,163) shows a vehicle of this general
`
`10
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`15
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`2O
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`25
`
`30
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`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
`
`5
`
`discussed above, see Bray (4,095,664); Cummings (4,148,192); Monaco
`et
`al
`(4,306,156);
`Park
`(4,313,080); McCarthy
`(4,354,144);
`
`Heidemeyer
`
`(4,533,011); Kawamura
`
`(4,951,769);
`
`and Suzuki et a1
`
`(5,053,632). Various of these address specific problems arising in
`
`the manufacture or use of hybrid vehicles, or specific alleged
`
`10
`
`design improvements.
`
`For example, Park addresses certain specifics
`
`of battery charging and discharge characteristics, while McCarthy
`
`shows
`
`a cmmplex 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
`
`15
`
`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
`
`20
`
`iJuzlude Toy
`
`(3,525,874),
`
`showing a series hybrid using a gas
`
`turbine as internal combustion engine; Yardney (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
`
`25
`
`(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
`
`(3,874,472); Horwinski
`
`(4,042,056); Yang
`
`(4,562,894); Keedy
`
`(4,611,466);
`
`and Lexen
`
`(4,815,334); Mori
`
`(3,623,568); Grady,
`
`Jr.
`
`(3,454,122); Papst
`
`30
`
`(3,211,249); Nims et al
`
`(2,666,492); and Matsukata (3,502,165).
`
`Additional references showing parallel hybrid vehicle drive systems
`
`include Froelich (1,824,014) and Reinbeck (3,888,325).U.S. Patent
`4No. 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
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`iii . .
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`.
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`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
`
`5
`
`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 bolts and nuts, or by welding. More specifically, for
`
`reasons of
`
`safety and in accordance with industry practice,
`
`10
`
`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,
`
`15
`
`it would be desirable to operate the electric motor of a hybrid
`vehicle at lower currents.
`
`U.S. patent 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.
`
`20
`
`U.S. Patent 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
`
`25
`
`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,
`
`30
`
`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 of
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`1
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`LE
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`wheels,
`
`and an electric motor
`
`the second;
`
`more particularly,
`
`Kalberlah indicates that mechanical combination of the torque from
`
`an internal combustion engine and an electric motor is impractical.
`
`Gardner U.S.
`
`patents
`
`5,301,764
`
`and
`
`5,346,031
`
`follow
`
`5
`
`Kalberlah'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.
`
`10
`
`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.
`
`15
`
`"The Technological Constraints of Mass, Volume,
`Bullock,
`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
`
`20
`
`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 Fig.
`
`8.
`
`Bullock also
`
`suggests the use of an internal combustion engine to drive battery
`
`25
`
`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 file;trig;gnd_fiybrid
`
`yghigle_3eghnglggy, volume SP-915, published by SAE in February
`
`1992.
`
`See also Wouk, "Hybrids: Then and Now"; Bates,
`
`"On the road
`
`30
`
`with a Ford HEV", and King et a1, “Transit Bus takes the Hybrid
`
`Route", all in lEEE_§pggtrum, Vol. 32, 7,
`
`(July 1995).
`
`Urban et al U.S. patent 5,667,029 shows two embodiments of
`
`parallel hybrids; a first embodiment is shown in Figs.
`
`1 - 9 and
`
`‘
`
`11, and a second in Figs. 12 — 17. Both embodiments have numerous
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`
`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
`
`5
`
`regenerative braking.
`
`Torque
`
`from 'the engine and motors
`
`is
`
`combined at.
`
`the input shaft
`
`‘to
`
`21 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.
`
`10
`
`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
`
`15
`
`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
`
`20
`
`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 —
`
`25
`
`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
`
`30
`
`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
`I
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`
`
`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
`
`5
`
`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;
`
`10
`
`this complexity is unacceptable in a vehicle intended to be sold in
`
`quantity, as would be required in order to reach Urban's stated
`
`goals of reduction of atmospheric pollution and reduced energy
`consumption.
`As
`noted,
`hybrid vehicle operation must
`be
`
`15
`
`essentially “foolproof", or "transparent" to the user,
`chance of commercial success.
`
`to have any
`
`Urban'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.
`
`20
`
`A second Urban et a1 patent, 5,704,440,
`
`is directed to the
`
`method of operation of the vehicle of the 4029 patent and suffers
`
`the same inadequacies.
`
`Various articles describe several generations of Toyota Motor
`
`Company hybrid vehicles, believed to correspond to that available
`
`25
`
`commercially as the "Prius".
`
`See, for example, Yamaguchi, "Toyota
`
`readies gasoline/electric hybrid system", Agtgmgtiye_gnginegring,
`
`July 1997, pp. 55 — 58; Wilson,
`
`"Not Electric, Not Gasoline, But
`
`Both", Aytgweek, June 2, 1997, pp.
`
`17 — 18; Bulgin,
`
`"The Future
`
`Works, Quietly", Autgweek February 23, 1998, pp.
`
`12 and 13; and
`
`30
`
`"Toyota Electric and Hybrid Vehicles", a Toyota brochure.
`
`A more
`
`detailed discussion of the Toyota vehicle‘s powertrain is found in
`
`Nagasaka et a1,
`
`"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
`
`14
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`
`
`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
`
`5
`
`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.
`
`I
`Furutani U.S. patent 5,495,906 describes a vehicle having an
`
`10
`
`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 drivas a generator
`
`to charge
`
`batteries providing energy to the motor, and at higher speeds the
`
`15
`
`engine or hmth 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. patent 5,842,534 to Frank shows a "charge depletion"
`
`control method for hybrid vehicles;
`
`in this scheme,
`
`the internal
`
`20
`
`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
`
`25
`
`brakes are engaged in addition to regenerative braking when the
`
`pedal is depressed beyond a preset point.
`
`U.S. patent 5,823,280 to Lateur et a1 shows a parallel hybrid
`
`wherein the shafts of an internal combustion engine and