(12) United States Patent
`Severin sky
`
`I IIIII IIIIIIII Ill lllll lllll lllll lllll lllll lllll lllll lllll 111111111111111111
`US006209672Bl
`US 6,209,672 Bl
`Apr. 3, 2001
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) HYBRID VEHICLE
`
`(75)
`
`Inventor: Alex J. Severinsky, Washington, DC
`(US)
`
`(73) Assignee: Paice Corporation, Silver Spring, MD
`(US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by O days.
`
`(21) Appl. No.: 09/264,817
`
`(22) Filed:
`
`Mar. 9, 1999
`
`Related U.S. Application Data
`(60) Provisional application No. 60/100,095, filed on Sep. 14,
`1998.
`Int. Cl.7 ....................................................... B60K 6/04
`(51)
`(52) U.S. Cl. ........................... 180/65.2; 180/65.4; 60/711
`(58) Field of Search .................................. 180/65.2, 65.3,
`180/65.4, 65.6, 65.8, 165; 60/716, 718,
`706, 711; 290/17, 40 R, 40 C; 322/16
`
`(56)
`
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`
`Primary Examiner-]. J. Swann
`Assistant Examiner-David R. Dunn
`(74) Attorney, Agent, or Firm-Michael de Angeli
`
`(57)
`
`ABSTRACT
`
`A hybrid vehicle compnsmg 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 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 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
`strategy.
`
`33 Claims, 10 Drawing Sheets
`
`'):'.,
`
`.--------~"...--11
`
`SE,
`
`~4
`
`E,9
`
`BMW1038
`Page 1 of 34
`
`

`

`US 6,209,672 Bl
`Page 2
`
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`
`BMW1038
`Page 2 of 34
`
`

`

`US 6,209,672 Bl
`Page 3
`
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`* cited by examiner
`
`BMW1038
`Page 3 of 34
`
`

`

`U.S. Patent
`
`Apr. 3, 2001
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`BMW1038
`Page 12 of 34
`
`

`

`U.S. Patent
`
`Apr. 3, 2001
`
`Sheet 10 of 10
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`BMW1038
`Page 13 of 34
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`

`

`US 6,209,672 Bl
`
`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(cid:173)
`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
`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 economi(cid:173)
`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(cid:173)
`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, 60
`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 65
`costs per mile of driving, electric vehicles are not competi(cid:173)
`tive with ethanol-fueled vehicles, much less with conven-
`
`5
`
`2
`tional gasoline-fueled vehicles. See, generally, Simanaitis,
`"Electric Vehicles",Road & Track, May 1992, pp. 126-136;
`Reynolds, "AC Propulsion CRX",Road & Track, Oct. 1992,
`pp. 126-129.
`Brooks et al U.S. Pat. No. 5,492,192 shows such an
`electric vehicle; the invention appears to be directed to
`incorporation of antilock braking and traction control tech(cid:173)
`nologies into an otherwise conventional electric vehicle.
`Much attention has also been paid over the years to
`10 development of electric vehicles including internal combus(cid:173)
`tion engines powering generators, thus eliminating the
`defect of limited range exhibited by simple electric vehicles.
`The simplest such vehicles operate on the same general
`principle as diesel-electric locomotives used by most rail-
`15 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
`20 locomotive.
`More particularly, an internal combustion engine pro(cid:173)
`duces zero torque at zero engine speed (RPM) and reaches
`its torque peak somewhere in the middle of its operating
`25 range. Accordingly, all vehicles driven directly by an inter(cid:173)
`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
`30 torque can be matched to the road speeds and loads encoun(cid:173)
`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
`35 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
`40 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
`45 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(cid:173)
`bustion engine is most efficient when producing near its
`50 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
`55 steady speeds for long periods of time. Reasonably efficient
`fuel use is thus achieved. However, such a direct drive
`vehicle would not achieve good fuel efficiency in typical
`automotive use, involving many short trips, frequent stops in
`traffic, extended low-speed operation and the like.
`So-called "series hybrid" electric vehicles have been
`proposed for automotive use, wherein batteries are used as
`energy storage devices, so that an internal combustion
`engine provided to 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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`Page 14 of 34
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`

`US 6,209,672 Bl
`
`3
`supplying electrical power to the traction motor(s) as
`required, so as to operate efficiently. This system overcomes
`the limitations of electric vehicles noted above with respect
`to limited range and long recharge times. Thus, as compared
`to a conventional vehicle, wherein the internal combustion
`engine delivers torque directly to the wheels, in a series
`hybrid electric vehicle, torque is delivered from the engine
`to the wheels via a serially connected generator used as a
`battery charger, the battery, and the traction motor. Energy
`transfer between those components consumes at least
`approximately 25% of engine power. Further, such compo(cid:173)
`nents add substantially to the cost and weight of the vehicle;
`in particular, an electric motor capable of providing suffi(cid:173)
`cient torque to meet all expected demand, e.g., to allow
`reasonable performance under acceleration, during hill(cid:173)
`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. Pat. Nos. 3,566,717 and 3,732,751 to Berman et al. In
`Berman et al an internal combustion engine and an electric
`motor are matched through a complex gear train so that both
`can provide torque directly to the wheels.
`In Berman et al, the internal combustion engine is run in
`several different modes. Where the output of the internal
`combustion engine is more than necessary to drive the
`vehicle ("first mode operation") the engine is run at constant
`speed and excess power is converted by a first motor/
`generator ("speeder") to electrical energy for storage in a
`battery. In "second mode operation", the internal 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.
`Berman et al thus show two separate electric motor/
`generators separately powered by the internal combustion
`engine; the "speeder" charges the batteries, while the
`"torquer" propels the vehicle forward in traffic. This
`arrangement is a source of additional complexity, cost and
`difficulty, as two separate modes of engine control are
`required. Moreover, the operator must control the transition
`between the several modes of operation. Such a complex
`vehicle is unsuited for the automotive market. Automobiles
`intended for mass production can be no more complicated to
`operate than conventional vehicles, and must be essentially
`"foolproof', that is, resistant to damage that might be caused
`by operator error. Further, the gear train shown by Berman
`et al appears to be quite complex and difficult to manufacture
`economically. Berman et al also indicate that one or even
`two variable-speed transmissions may be required; see, e.g.,
`col. 3, lines 19-22 and 36-38 of U.S. Pat. No. 3,566,717,
`and col. 2, lines 53-55 of U.S. Pat. No. 3,732,751.
`Lynch et al U.S. Pat. No. 4,165,795 also shows an early
`parallel hybrid drive. Lynch argues that maximum fuel
`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 torque provided by the motor when needed and excess 65
`torque used to charge the batteries otherwise. In a first
`embodiment, torque provided by the motor is transmitted to
`
`4
`the drive wheels through the engine, while in a second
`embodiment their respective positions are reversed.
`Nishida U.S. Pat. No. 5,117,931 shows a parallel hybrid
`vehicle where torque from an electric motor may be corn-
`s 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
`10 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
`15 which would preferably be avoided.
`Helling U.S. Pat. No. 3,923,115 also shows a hybrid
`vehicle having a torque transmission unit for combining
`torque from an electric motor and an internal combustion
`engine. However, in Helling the relative rates of rotation of
`20 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
`U.S. Pat. No. 4,588,040 shows another hybrid drive scheme
`using a flywheel in addition to batteries to store excess
`25 energy; various complicated mechanical connections are
`provided between the various components. Capacitors have
`also been proposed for energy storage; see Bates et al U.S.
`Pat. No. 5,318,142.
`Fjallstrom U.S. 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(cid:173)
`ment of paired planetary gearsets, and unspecified control
`35 means are alleged to be able to allow variation of road speed
`without a variable-ratio transmission.
`Hunt U.S. Pat. Nos. 4,405,029 and 4,470,476 also dis(cid:173)
`close parallel hybrids requiring complex gearing
`arrangements, including multiple speed transmissions. More
`40 specifically, the Hunt patents disclose several embodiments
`of parallel hybrid vehicles. Hunt indicates (see col. 4, lines
`6-20 of the '476 patent) that an electric motor may drive the
`vehicle at low speeds up to 20 mph, and an internal
`combustion engine used for speeds above 20 mph, while "in
`45 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
`50 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
`ss 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
`60 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 dis(cid:173)
`closed by Hunt involves a further undesirable complexity,
`namely a turbine driving the electric motor in generator
`
`30
`
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`Page 15 of 34
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`

`US 6,209,672 Bl
`
`40
`
`45
`
`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 5
`vehicle meeting the objects of the 2-D present invention(cid:173)
`that is, a hybrid vehicle competitive with conventional
`vehicles with respect to performance, cost and complexity,
`while achieving substantially improved fuel efficiency.
`Kawakatsu U.S. Pat. Nos. 4,305,254 and 4,407,132 show 10
`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 15
`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 combus(cid:173)
`tion 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 suf(cid:173)
`ficient 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 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 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 65
`sufficient torque at low speeds. See Rosen (3,791,473);
`Rosen (4,269,280); Fiala (4,400,997); and Wu et al (4,697,
`
`6
`660). Kinoshita (3,970,163) shows a vehicle of this general
`type wherein a gas turbine engine is coupled