O
`(12) Umted States Patent
`Severinsky
`
`(54)
`
`(75)
`
`(73)
`
`HYBRII) VEHICLE
`
`lnventor: Alex J. Severinsky, Washington, DC
`(US)
`
`Assignee:
`
`(Page: Corporation, Silver Spring, Ml)
`
`("l
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21)
`
`A 1. No.1 09 264 817
`pp
`/
`’
`Filed:
`Mar. 9, 1999
`
`.
`.
`Related U-S-APPI'cat'O“ Data
`Provisional application No. 60,400,095, filed on Sep. 14,
`1998.
`
`
`
`
`
`U8006209672B1
`
`(16) Patent No.:
`(45) Date of Patent:
`
`US 6,209,672 B1
`Apr. 3, 2001
`
`3,888,325
`3,923,115
`3,970,163
`4,042,056
`4,095,664
`
`611975 Reinbeck.
`1211975 llclling.
`71"1976 KillOShita .
`811977 llorwinski .
`6;"1978 Bray .
`
`(List continued on next page.)
`OTHER PUBLICATIONS
`.
`I
`I
`I
`I
`Simonams, "Electnc Vehtcles", Road & Track, May 1992,
`PP~ 126—136-
`Reynolds, “AC Propulsion CRX", Road & Track, Oct. 1992,
`,
`26—129.
`PP 1
`Kalberlah, "Electric Hybrid Drive Systems .
`No. 910247, 1991.
`Bullock, “The Technological Constraints of Mass, Volume,
`Dynamic Power Range and Energy Capacity .
`.
`.
`SAE
`Paper No. 891659 1989.
`
`.
`
`.
`
`SAE Paper
`
`(60)
`
`(51)
`(52)
`(58)
`
`(56)
`
`Int. 0.7
`
`860K 6/04
`
`(List continued on next page.)
`
`
`
`180/652; 180/654; 601/711
`..................
`U.S. Cl.
`ISO/65.2, 65.3,
`Field of Search
`180/654, 65.6, 65.8, 165; 60f716, 718,
`706, 711; 290117, 40 R, 40 C; 322/16
`
`Primary Examiner—J. J. Swann
`Assistant Examiner—David R. Dunn
`(74) Attorney, Agent, or Firm—Michael de Angeli
`
`References Clted
`
`9
`
`U.S. PATENT DOCUMENTS
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`i
`10/1965 Papst .
`.
`[1969 Grady, Jr.
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`11/1?“ Mon-
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`
`'
`
`.
`
`1,824,014
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`3,566,217
`3923908
`3,650,345
`3,732,751
`3,791,473
`3,837,419
`3,874,472
`
`(57)
`
`ABSTRACT
`.
`.
`.
`.
`.
`.
`A hybnd vehicle comprtstng an 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 engme, 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 difi‘erent modes, depending on its 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
`5mm:
`'
`
`gy‘
`
`33 Claims, 10 Drawing Sheets
`
`
`
`\NVERTEQ / CHARGER
`
`
`
`Page 1 of 34
`
`FORD 1233
`
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`
`

`

`US 6,209,672 B1
`Page 2
`
`US. PATENT DOCUMENTS
`
`4,148,192
`4,165,795
`4,180,138
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`4,400,997
`4,405,029
`4,407,132
`4,438,342
`4,439,989
`4,444,285
`4,470,476
`4,495,45 1
`4,51 1,012
`4,533,011
`4,562,894
`4,578,955
`4,583,505
`4,588,040
`4,593,779
`4,597,463
`4,61 1,466
`4,631,456
`4,680,986
`4,697,660
`4,765,656
`4,815,334
`4,862,009
`4,923,025
`4,95 1,769
`4,953,646
`5,053,632
`5,117,931
`5,120,282
`5,125,469
`5,172,784
`5,176,213
`5,193,634
`5,249,637
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`5,291,960
`5,301,764
`5,318,142
`5,323,868
`5,327,987
`5,327,992
`5,337,848
`5,343,970
`5,345,154
`5,345,761
`5,346,031
`5,350,031
`5,372,213
`5,415,245
`5,427,196
`5,433,282
`5,441,122
`5,463,294
`5,489,001
`5,492,189
`5,492,190
`5,492,192
`5,495,906
`5,495,907
`5,495,912
`
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`8/1979
`12/1070
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`12/1081
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`1/1082
`6/1982
`0/1082
`10/1982
`8/1083
`9/1983
`10/1983
`3/1984
`4/1984
`4/1984
`9/1984
`1/1985
`4/1985
`8/1985
`1/1986
`4/1986
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`5/1986
`6/1986
`7/1986
`9/1986
`12/1986
`7/1987
`10/1987
`8/1988
`3/1989
`8/1989
`5/1990
`8/1990
`9/1990
`10/1991
`6/1992
`6/1992
`6/1992
`12/1992
`1/1993
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`3/1994
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`6/1994
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`7/1994
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`8/1994
`9/1994
`9/1994
`9/1994
`9/1994
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`10/1995
`2/1996
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`
`*
`
`"
`
`.
`
`.
`
`Cummings .
`Lynch el al. .
`Shea .
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`.
`Frank et al.
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`.
`Varela, Jr.
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`.
`Hammond .
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`Dala .
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`
`.
`
`.
`
`.
`
`180/652
`
`180/652
`
`5,513,718
`5,513,719
`5 ,5 15,937
`5,545,928
`5,550,445
`5558,173
`5,558,175
`5,558,588
`5,558,595
`5,562,565
`5566,774
`5,568,023
`5586,613
`5588,498
`5,589,743
`5,608,308
`5,614,809
`5,621,304
`5,632,352
`5.635805
`5,637,987
`5.643.119
`5,644,200
`5.6SU,713
`5,650,931
`5,653,302
`5,656,921
`5,664,635
`5,667,029
`5,672,920
`5,697,466
`5,704,440
`5,705,859
`5,713,425
`5,713,426
`5,713,814
`5,722,91 1
`5,725,064
`5,755,303
`5,757,151
`5,767,637
`5,773,904
`5,775,449
`5,778,326
`5,778,997
`5,785,136
`5,785,137
`5,785,138
`5,786,640
`5,788,003
`5,788,006
`5,788,597
`5,789,881
`5,789,882
`5,791,426
`5,791,427
`5,799,744
`5,806,617
`5,820,172
`5,823,280
`5,823,281
`5,826,671
`5,831,341
`5,833,022
`5,830,530
`5,839,533
`5,841,201
`5,842,534
`5,845,731
`5,846,155
`5,862,497
`
`5719965
`5/1 996
`5/1996
`8,-‘1996
`8/1996
`9,-‘1996
`9/1996
`9/1996
`0/1006
`10/1996
`10/1996
`10/ 1996
`12/1996
`12/1996
`12/1996
`3/1997
`3/1997
`4/1997
`5/1997
`6/1997
`6/1997
`7/1997
`7/ 1997
`7/1997
`7/1997
`8/1997
`8/1997
`9/1997
`9/1997
`9/1997
`‘ 12/1997
`1/1998
`1/1998
`2/1998
`2/1998
`2/1998
`3/1998
`3/1998
`5/1998
`5/1998
`6,-‘1998
`6/ 1998
`7/1998
`7/1998
`7/1998
`7/1998
`7/1998
`7/1998
`7/1998
`8/1998
`8/1998
`8/1998
`8/1998
`8/1998
`8/1998
`8/1998
`9,-‘1098
`9,"1998
`10,-‘1098
`"‘ 10/1998
`10,-‘1098
`10/1998
`11/1098
`11/1998
`11/1008
`11/1998
`12,-‘1008
`* 12/ 1998
`" 12/1098
`12/1998
`1/1999
`
`‘
`
`.
`
`............. 180/652
`
`318/146
`
`.
`
`Suzuki cl al. .
`Moroto et al. .
`Adler el al. .
`Kolani .
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`Sherman .
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`.
`Kiuchi et al.
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`.
`Jcnncrcl .
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`.........
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`.
`Lansberry
`Schiebold et a1.
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`.
`Falkenmayer el al. .
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`.
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`.
`Lateur ...................
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`.
`Selfors et al. .
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`.
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`Buglione et a].
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`.
`
`.............. 180/652
`
`180/652
`............. 180/652
`
`......
`.
`
`Page 2 of 34
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`

`US 6,209,672 B1
`Page 3
`
`5,865,263
`5,887,670
`5,890,555
`5,893,895
`5,898,282
`5,899,286
`5,908,077
`5,934,395
`5,969,624
`5,986,376
`5,993,351
`6,018,198
`6,018,694
`6,054,844
`6,059,059
`
`2/1999
`3/1999
`4/1999
`4/1999
`4/1999
`5/1999
`6/1999
`8/1999
`10/1999
`11/1999
`11/1999
`1/2000
`1/2000
`4/2000
`5/2000
`
`x
`
`.
`
`Yamaguchi et a1.
`'l'abata et al. .
`Miller .
`lbaraki ,
`.
`Drozdz ct a].
`Yamaguchi et al. .
`Moore .
`Koide et al.
`........................ 180/652
`
`Sakai et al.
`340/636
`Werson
`310/186
`
`chuchii ct al.
`477/5
`'l'suzuki et al.
`..
`.. 290/17
`
`Egami ct al.
`701/102
`Frank
`...... 322/16
`Schmidt-Brucken ............... 180/653
`
`.
`
`.
`
`.
`
`IEEE
`
`. ", IEEE Spectrum, vol. 32,
`
`Wouk, “Hybrids: Then and Now”, IEEE Spectrum, v01. 32,
`7, Jul. 1995.
`Bates, "Getting a Ford HEV On the road .
`Spectrum, vol. 32, 7, Jul. 1995.
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`.
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`tem”, Automotive Engineering, Jul. 1997, pp. 55—58.
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`.
`. Autoweek, Jun. 2,
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`1998 pp. 12—13.
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`
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`
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`Feb, 1992.
`
`the Hybrid/Battery
`a1, "Development of
`Nagasaka et
`EUC .
`.
`. ”, SAE paper 981122, 1998, pp. 19—27.
`
`* cited by examiner
`
`Page 3 of 34
`
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`FORD 1233
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`

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`US. Patent
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`Apr. 3, 2001
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`Sheet 5 0f 10
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`US 6,209,672 B1
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`FORD 1233
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`US. Patent
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`US. Patent
`
`Apr. 3, 2001
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`US. Patent
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`Apr. 3, 2001
`
`Sheet 10 0f 10
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`US 6,209,672 B1
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`F/é. 9(a)
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`1
`HYBRID VEHICLE
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`This application claims priority from Provisional Appli-
`cation Ser. No. 60!100,095, filed Sep. 14, 1998.
`
`FIELD OF THE INVENTION
`
`This application relates to improvements in hybrid
`vehicles, that is, vehicles in which both an internal combus-
`tion engine and one or more electric motors are provided to
`supply torque to the driving wheels of the vehicle. More
`particularly, this invention relates to a hybrid electric vehicle
`that
`is fully competitive with presently conventional
`vehicles as regards performance, operating convenience,
`and cost, while achieving substantially improved fuel
`economy and reduced pollutant emissions.
`
`DISCUSSION OF THE PRIOR ART
`
`For many years great attention has been given to the
`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
`NON.
`Another possibility for reducing emissions is to burn
`mixtures of gasoline and ethanol (“gasohol”), or straight
`ethanol. However, to date ethanol has not become economi-
`cally 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 neces-
`
`sary 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 respective net
`costs per mile of driving, electric vehicles are not competi-
`tive with ethanol-fueled vehicles, much less with conven-
`
`10
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`US 6,209,672 B1
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`2
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`tional gasoline-fueled vehicles. See, generally, Simanaitis,
`“Electric Vehicles”, Road & Truck, May 1992, pp. 126—136;
`Reynolds, "AC Propulsion CRX”,R0ad & Track, Oct. 1992,
`pp. 126—129.
`Brooks et al US. Pat. No. 5,492,192 shows such an
`electric vehicle;
`the invention appears to be directed to
`incorporation of antilock braking and traction control tech-
`nologies into an otherwise conventional electric vehicle.
`Much attention has also been paid over the years to
`development of electric vehicles including internal combus-
`tion engines powering generators,
`thus eliminating the
`defect of limited range exhibited by simple electric vehicles.
`The sitnplest such vehicles operate on the same general
`principle as dieselelectric locomotives used by most rail—
`roads. 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 diesel engine and the wheels of the
`locomotive.
`
`More particularly, an internal combustion engine pro-
`duces 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 inter-
`nal 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 encoun-
`tered. 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 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 com-
`bustion engine is most eflicient 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 periocb of time. Reasonably eflicient
`fuel use is thus achieved. However, such a direct drive
`vehicle would not achieve good fuel elliciency in typical
`automotive use, involving many short trips, frequent stops in
`trafiic, extended low-speed operation and the like.
`So-callec “series hybric” electric vehicles have been
`proposed 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 loaded by
`supplying torque to a generator charging the batteries while
`
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`US 6,209,672 B1
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`3
`supplying electrical power to the traction motor(s) as
`required, so as to operate etficiently. 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. Energy
`transfer between those components consumes at
`least
`approximately 25% of engine power. Further, such compo-
`nents add substantially to the cost and weight of the vehicle;
`in particular, an electric motor capable of providing sufii-
`cient 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
`US. Pat. 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 through a complex gear train so that both
`can provide torque directly to the wheels.
`In Berman et al, the internal combustion engine is run in
`several ditferent 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 convened by a first motor/
`generator (“Speeder”) to electrical energy for storage in a
`battery. In “second mode operation”, the internal combus-
`tion 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.
`
`thus show two separate electric motor/
`Berman et a]
`generators separately powered by the internal combustion
`engine;
`the “Speeder” charges the batteries, while the
`"torquer" propels the vehicle forward in tratfic. 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 difiicult 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 US. Pat. No. 3,566,717,
`and col. 2, lines 53—55 of U.S. Pat. No. 3,732,751.
`
`Lynch et a1 U.S. Pat. No. 4,165,795 also shows an early
`parallel hybrid drive. Lynch argues that maximum fuel
`efliciency can be realized when a relatively small internal
`combustion engine is provided, such that when the engine is
`operated at an eflicient 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 iLs most eflicient 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 torque provided by the motor when needed and excess
`torque used to charge the batteries otherwise.
`In a first
`embodiment, torque provided by the motor is transmitted to
`
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`
`LnLII
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`60
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`4
`
`the drive wheels through the engine, while in a second
`embodiment their respective positions are reversed.
`Nishida US. Pat. No. 5,117,931 shows a parallel hybrid
`vehicle where torque from an electric motor may be com-
`bined with torque from an internal combustion engine in a
`“torque transmission unit” comprising paired bevel gears
`and means for controlling the relative rates of rotation of the
`motor and engine, so that the motor can be used to start the
`engine, absorb excess torque from the engine (by charging
`a battery), or provide additional propulsive torque. A
`variable-speed transmission is coupled between the torque
`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.
`IIelIing US. Pat. No. 3,923,115 also shows a hybrid
`vehicle having a torque transmission unit for combining
`torque from an electric motor and an internal combustion
`engine. However, in IIelIing 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. ct al
`US. 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 US.
`Pat. No. 5,318,142.
`
`Fjallstrom US. Pat. 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 arrange-
`ment of paired planetary gearsets, and unspecified control
`means are alleged to be able to allow variation of road speed
`without a variable-ratio transmission.
`
`Hunt US. Pat. Nos. 4,405,029 and 4,470,476 also dis-
`close 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 speech 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 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 inefiicient, 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 dis-
`closed hy Hunt involves a further undesirable complexity,
`namely a turbine driving the electric motor in generator
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`5
`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 2-D present invention—
`that
`is, a hybrid vehicle competitive with conventional
`vehicles with respect to performance, cost and complexity,
`while achieving substantially improved fuel elficiency.
`Kawakatsu US. Pat. Nos. 4,305,254 and 4,407,132 show
`a parallel hybrid involving a single internal combustion
`engine coupled to the drive wheels through a conventional
`variable—ratio transmission, an electric motor, and an
`alternator, to allow efficient use 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 insuflicient 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 combus-
`tion engine and two motorigenerator 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 suflicient torque to
`propel the vehicle would not be capable of providing suf-
`ficient regenerative braking force; see 001. 1, line 50 - col. 2
`line 8. Accordingly, Kawakatsu provides two separate
`motor/generators, as noted; a separate engine starting motor
`is also provided. Sec 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 dill‘erent
`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 al (4,697,
`
`5
`
`10
`
`15
`
`45
`
`60
`
`65
`
`6
`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 a1 (5,053,632). Various of these
`address specific problems arising in the manufacture or use
`ofhybrid 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 com-
`bustion engine driving two electric motors; the torque gen-
`erated 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),
`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. Some-
`what 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 (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).
`US. Pat. No. 4,578,955 to Medina shows a hybrid system
`wherein a gas turbine is used as the internal combustion
`engine 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,