PCT
`
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`
`
`
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(51) International Patent Classification 7 =
`
`(11) International Publication Number:
`
`W0 (IO/15455
`
`B60K
`
`A2
`
`.
`.
`.
`(43) International Publication Date:
`
`23 March 2000 (23.03.00)
`
`(21) International Application Number:
`
`PCT/US99/ 18844
`
`(22) International Filing Date:
`
`10 September 1999 (10.09.99)
`
`(81) Designated States: AU, BR, CA, CN, CZ, IL, JP, KR, LV,
`MX, PL, UA, Eurasian patent (AM, AZ, BY, KG, KZ, MD,
`RU, TJ, TM), European patent (AT, BE, CH, CY. DE. DK.
`ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE).
`
`(30) Priority Data:
`60/100,095
`60/ 122,296
`09/264,817
`
`14 September 1998 (14.09.98)
`1 March 1999 (01.03.99)
`9 March 1999 (09.03.99)
`
`US Published
`US
`Without international search report and to be republished
`US
`upon receipt of that report.
`
`4
`
`(71) Applicant: PAICE CORPORATION [US/US]; Suite 315, 8605
`Cameron Street, Silver Spring, MD 20910 (US).
`
`(72) Inventors: SEVERINSKY, Alex, J.; 4707 Foxhall Crescent,
`Washington, DC 20007 (US). LOUCKES, Theodore; 10398
`Appomattox, Holly, MI 48442 (US).
`
`(74) Agent: DE ANGELI, Michael; Suite 330, 1901 Research
`Boulevard, Rockville, MD 28050 (US).
`
`(54) Title: HYBRID VEHICLES
`
`
`
`
`
`
`
`(57) Abstract
`
`A hybrid vehicle comprising an internal combustion engine controllably coupled to road wheels of the vehicle by a clutch, a traction
`motor coupled to road wheels of said vehicle, a starting motor coupled to the engine, both motors being operable as generators, a battery
`bank for providing electrical energy to and accepting energy from said motors, and a microprocessor for controlling these components is
`operated in different modes, depending on the vehicle’s instantaneous torque requirements, the state of charge of the battery bank, and
`other operating parameters. The mode of operation is selected by the microprocessor in response to a control strategy resulting in improved
`fuel economy and reduced emission. The engine may be fitted with a turbocharger operated in response to a control signal for extended
`high—load operation.
`
`
`
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`FOR THE PURPOSES OF INFORMATION ONLY
`
` AL
`
`AM
`AT
`AU
`AZ
`BA
`BB
`BE
`BF
`BG
`BJ
`BR
`BY
`CA
`CF
`CG
`CH
`CI
`CM
`CN
`CU
`CZ
`DE
`DK
`EE
`
`Albania
`Armenia
`Austria
`Australia
`Azerbaijan
`Bosnia and Herzegovina
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`Cote d’Ivoire
`Cameroon
`China
`Cuba
`Czech Republic
`Germany
`Denmark
`Estonia
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT.
`Slovenia
`SI
`Lesotho
`Slovakia
`SK
`Lithuania
`SN
`Senegal
`Luxembourg
`Swaziland
`52
`Latvia
`TD
`Chad
`Monaco
`TG
`Togo
`Republic of Moldova
`TJ
`Tajikistan
`Madagascar
`TM
`Turkmenistan
`The former Yugoslav
`TR
`Turkey
`Republic of Macedonia
`TT
`Mali
`Trinidad and Tobago
`Ukraine
`UA
`Mongolia
`Mauritania
`UG
`Uganda
`US
`United States of America
`Malawi
`UZ
`Uzbekistan
`Mexico
`Viet Nam
`VN
`Niger
`YU
`Netherlands
`Yugoslavia
`ZW
`Zimbabwe
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`Sweden
`Singapore
`
`ES
`FI
`FR
`GA
`GB
`GE
`GH
`GN
`GR
`HU
`IE
`IL
`IS
`IT
`JP
`KE
`KG
`KP
`
`KR
`KZ
`LC
`LI
`LK
`LR
`
`Spain
`Finland
`France
`Gabon
`United Kingdom
`Georgia
`Ghana
`Guinea
`Greece
`Hungary
`Ireland
`Israel
`Iceland
`Italy
`Japan
`Kenya
`Kyrgyzstan
`Democratic People’s
`Republic of Korea
`Republic of Korea
`Kazakstan
`Saint Lucia
`Liechtenstein
`Sri Lanka
`Liberia
`
`LS
`LT
`LU
`LV
`MC
`MD
`MG
`MK
`
`ML
`MN
`MR
`MW
`MX
`NE
`NL
`NO
`NZ
`PL
`PT
`RO
`RU
`SD
`SE
`SG
`
`
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`WO 00/15455
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`PCT/US99Z18844
`
`HYBRID VEHICLES
`
`E' J:
`
`E
`
`I]
`
`l'
`
`4‘
`
`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
`
`10
`
`improved fuel economy and reduced pollutant emissions.
`
`'scuss'on of
`
`e
`
`'or
`
`For many years great attention has been given to the
`
`problem of reduction of fuel consumption of automobiles and other
`
`15
`
`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
`
`20
`
`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 113
`
`increase le certain undesirable pollutants,
`
`25
`
`typically NOX.
`
`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
`
`30
`
`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
`
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`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 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 a1 U.S. patent 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-
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
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`
`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,
`
`10
`
`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 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 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 locomotives can be
`
`operated at nearly full
`
`torque production. Moreover,
`
`such
`
`15
`
`20
`
`25
`
`30
`
`35
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`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
`
`10
`
`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 loaded by supplying torque to a generator
`
`charging the batteries while supplying electrical power to the
`
`15
`
`traction motor(s) as required, so as to operate efficiently. This
`
`20
`
`25
`
`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. 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 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
`
`3O
`
`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 al an internal combustion engine and an electric motor
`
`are matched through a complex gear train so that both can provide
`
`35
`
`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
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`("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
`
`10
`
`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
`
`15
`
`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
`
`20
`
`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 patent 3,566,717, and
`
`col. 2,
`
`lines 53 — 55 of patent 3,732,751.
`
`Lynch et al patent 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 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.
`
`25
`
`30
`
`35
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`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. 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 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. patent 3,923,115 also shows
`
`an 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 patent 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. 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 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. Patent Nos. 4,405,029 and 4,470,476 also disclose
`
`parallel
`
`hybrids
`
`requiring
`
`complex
`
`gearing
`
`arrangements,
`
`including multiple speed transmissions. More specifically,
`
`the
`
`10
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`
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`
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`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,
`
`load
`heavy
`be utilized under
`could
`sources
`power
`both
`conditions." Hunt also indicates that "the vehicle couldabe
`
`provided with an automatic changeover device which automatically
`
`10
`
`shifts
`
`from the electrical
`
`power
`
`source
`
`to the
`
`internal
`
`combustion power source, depending on the speed of the vehicle"
`
`15
`
`20
`
`25
`
`30
`
`35
`
`(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 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. Patents Nos. 4,305,254 and 4,407,132 show a
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`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, 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
`
`10
`
`15
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`20
`
`25
`
`30
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`35
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`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 al
`
`(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
`
`10
`
`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 al
`
`(4,697,660). Kinoshita (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 (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 al
`
`(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 (3,525,874),
`
`showing a series hybrid using a gas
`
`turbine as
`
`internal combustion engine; Yardney
`
`(3,650,345),
`
`15
`
`20
`
`25
`
`3O
`
`35
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`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
`
`(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, 3r.
`
`(3,454,122); Papst
`
`(3,211,249); Nims et a1
`
`(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 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 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
`
`10
`
`15
`
`20
`
`25
`
`30
`
`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.
`
`U.S. Patent No.
`
`4,439,989 to Yamakawa
`
`shows
`
`a
`
`system
`
`35
`
`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.
`
`10
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`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
`
`10
`
`his Fig. 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,
`
`Kalberlah indicates that mechanical combination of the torque
`
`from an internal combustion engine and an electric motor
`
`is
`
`15
`
`impractical.
`
`Gardner U.S.
`
`patents
`
`5,301,764
`
`and
`
`5,346,031
`
`follow
`
`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 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 Fig.
`
`8.
`
`Bullock also suggests the use of an internal combustion engine
`
`to drive battery charging, but does not address combining the
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`20
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`
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`engine's torque with that from the motors; see pp. 24 — 25.’
`
`Further related papers are collected in Electric and Hybrid
`
`yghigle_1gghnglggy, 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 lgfi;_§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
`
`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 a1 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-
`
`12
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`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
`
`10
`
`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
`
`15
`
`20
`
`25
`
`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 provi