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`HYBRID VEHICLES
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`Inventors: Alex J. Severinsky
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`Theodore N. Louckes
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`continuation-in—part of Ser. No.
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`This appliCation is
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`999, now U. S. patent 6,209,672,
`issued
`' 09/264,817, filed March 9,
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`April 3, 2001, which '
`turn claims priority from provisional
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`application Ser. No.
`0/100,095, filed September 14, 1998, and is
`also a continuation- n—part of Ser. No; 09/392,743, filed September
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`9, 1999, which in urn claims priority from provisional application
`Ser. NO. 60/12 ,296, filed March 1, 1999.
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`This application relates to improvements in hybrid vehicles,
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`n]
`that is, vehicles in which both an internal combustion engine and
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`one or more electric motors are provided to supply torque to the
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`driving wheels of the vehicle. More particularly, this invention
`a;
`relates to-a hybrid electric vehicle that is fully competitive with
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`$1
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`presently conventional vehicles as regards performance, operating
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`convenience, and cost, while achieving substantially improved fuel
`E)
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`economy and reduced pollutant emissions.
`2|}
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`For many years great attention has been given to the problem
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`of reduction of fuel consumption of automobiles and other highway
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`vehicles. Concomitantly very substantial attention has been paid
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`to reduction of pollutants emitted by automobiles
`and other
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`vehicles. To a degree, efforts to solve these problems Conflict
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`with one another. For example,
`increased thermodynamic efficiency
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`and thus reduced fuel consumption can be realized if an engine is
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`operated at higher temperatures. Thus there has been substantial
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`interest in engines built of ceramic materials withstanding higher
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`combustion temperatures than those now in use. However, higher
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`combustion temperatures in gasoline—fueled engines lead to increase
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`in certain undesirable pollutants, typically NOX.
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`Another possibility for reducing emissions is to burn mixtures
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`of gasoline and ethanol ("gasohol"), or straight ethanol. However,
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`to date ethanol has not become economically competitive with
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`gasoline, and consumers have not accepted ethanol
`to any great
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`degree. Moreover,
`to make an alternate fuel such as ethanol
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`available
`appreciable
`extent
`to the
`necessary .to achieve
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`improvements in nationwide air quality and fuel conservation would
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`require immense costs for infrastructure improvements; not only the
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`entire nation's motor fuel production and delivery system, but also
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`the vehicle manufacture, distribution, and repair system, would
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`have to be extensively revised or substantially duplicated.
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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
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`employ electric vehicles powered by rechargeable batteries. To
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`date, all such "straight electric" cars have had very limited
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`range,
`typically no more than 150 miles, have insufficient power
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`for acceleration and hill climbing except when the batteries are
`substantially fully charged,
`and require substantial
`time for
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`battery recharging. Thus, while there are many circumstances in
`which Ithe limited: range and extended recharging time of
`the
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`batteries would not be an inconvenience, such cars are not suitable
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`for all the travel requirements of most individuals. Accordingly,
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`an electric car would have to be an additional vehicle for most
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`users, posing a substantial economic deterrent. Moreover, it will
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`be appreciated that
`‘in the United States most electricity is
`generated in Icoal-fired. power plants,
`so that using electric
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`vehicles merely moves the source of the pollution, but does not
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`eliminate it. Furthermore, comparing the respective net costs per
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`mile of driving, electric vehicles are not competitive with
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`ethanol—fueled vehicles, much less with conventional gasoline-
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`fueled vehicles. See, generally, Simanaitis, "Electric Vehicles",
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`Reynolds,
`Road & ITack, May 1992, pp. 126-136;
`"AC Propulsion
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`CRX", Road & Track, October 1992, pp. 126-129.
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`Brooks et a1 U.S. patent 5,492,192 shows such an electric
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`'vehicle; the,invention appears to be directed to incorporation of
`antilock braking and
`traction control
`technologies
`into an
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`otherwise conventional electric vehicle.
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`to
`Much attention has also been paid over
`the years
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`development of electric vehicles including internal combustion
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`engines powering generators,
`thus eliminating the defect of limited
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`range exhibited by simple electric vehicles. The simplest such
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`vehicles operate on the same general principle as diesel—electric
`locomotives used by most railroads.
`In such systems, an internal
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`combustion engine drives a generator providing electric power to
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`traction motors connected directly to the wheels of the vehicle.
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`system has
`the advantage that
`no variable gear
`ratio
`This
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`transmission is required between the engine and the wheels of the
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`vehicle.
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`More particularly, an internal combustion engine produces zero
`torque at zero engine speed (RPM) and.reaches its torque peak
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`somewhere in the middle of its operating rangeT'Accordingly, all
`vehicles driven directly by an internal combustion engine (other
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`than certain single-speed vehicles using friction or centrifugal
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`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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`engine's torque can be matched to the road speeds and loads
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`encountered. Further,
`some sort of clutch must be provided so that
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`the engine can be mechanically decoupled from the wheels, allowing
`the vehicle to stop while the engine is still running, and to allow
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`some slippage of the engine with respect to the drive train while
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`starting from a stop. ~It would not be practical
`to provide a
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`diesel locomotive,,for example, with a multiple speed transmission,,
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`a clutch. Accordingly,
`the’ additional
`complexity of
`the
`or
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`generator
`and electric traction motors
`is accepted. Electric
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`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
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`should accelerate,
`the diesel engine
`is simply throttled to
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`increase the generator output and the train begins to move.
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`The same drive system may be employed in a smaller vehicle
`as _an
`automobile or
`truck,
`but has
`several distinct
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`disadvantages in this application. In particular, and as discussed
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`in detail below in connection with Figs. 1 and 2, it is well known
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`that
`a gasoline or other
`internal combustion- engine is most
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`efficient when
`producing
`its maximum output
`torque.
`near
`Typically, the number of diesel locomotives on a train is selected
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`in accordance with the total tonnage to be moved and the grades to
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`be overcome, so that all the locomotives can be operated at nearly
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`full torque production. Moreover, such locomotives tend to be run
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`at steady speeds for long periods of time. Reasonably efficient
`15;;
`fuel use is thus achieved. However,
`such a direct drive vehicle
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`a) would not achieve good fuel efficiency in typical automotive use,
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`involving many short trips,
`frequent stops in traffic, extended
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`low-speed operation and the like.
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`So-called "series hybrid" electric vehicles Have been proposed
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`for automotive use, wherein batteries are used as energy storage
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`devices, so that an internal combustion engine provided to power a
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`generator can be operated in its most fuel—efficient output power
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`range while still allowing the electric traction motor(s) powering
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`the vehicle to be operated as required. Thus the engine may be
`loaded by supplying torque to a generator charging the batteries
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`while supplying electrical power
`to the traction motor(s)
`as
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`required, so as to operate efficiently. This system overcomes the
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`limitations of electric vehicles noted above with respect
`to
`limited range and long recharge times.
`Thus, as compared to a
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`conventional vehicle, wherein the internal
`combustion engine
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`delivers torque directly to the wheels,
`in a series hybrid electric
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`vehicle,
`torque is delivered from the engine to the wheels via a
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`serially connected generator used as
`a battery charger,
`the
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`battery, and the traction motor. Howaver, energy transfer between
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`least approximately 25% of engine
`those components consumes at
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`power. Further, such components add substantially to the cost and
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`weight of the vehicle;
`in particular, an electric motor capable of
`providing sufficient torque to meet all expected demand, e.g.,
`to
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`allow reasonable performance under acceleration, during hill-
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`climbing and the like, is rather heavy and expensive. Thus, series
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`hybrid vehicles have not been immediately successful.
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`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
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`a1 an internal combustion engine and an electric motor are matched
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`through a complex gear
`train so that both can provide torque
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`directly to the wheels,
`the vehicle being operated in several
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`different modes. Where the output of the internal combustion engine
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`than necessary to drive the vehicle
`("first mode
`is more
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`operation") the engine is run at constant speed and excess power is
`converted by a first motor/generator
`("Speeder")
`to electrical
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`energy for storage in a battery. In “second mode operation",
`the
`internal combustion engine drives the wheels directly,
`and is
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`throttled. When more power is needed than the engine can provide,
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`a second motor/generator or "torquer" provides additional torque as
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`needed}
`N
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`' Berman et a1 thus show two separate electric motor/generators
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`separately powered by the internal combustion engine; the "Speeder"
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`charges the batteries, while the “torquer” propels the vehicle
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`forward in traffic. This arrangement
`is a source of additional
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`complexity, cost and difficulty, as two separate modes of engine
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`control are required. Moreover,
`the operator must control
`the
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`transition between the several modes of operation.
`Such a complex
`vehicle is unsuited for
`the automotive market.
`Automobiles
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`intended for mass production can be no more complicated to operate
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`than conventional vehicles, and mhst be essentially "foolproof",
`resistant
`to damage that might be caused by operator
`is,
`that
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`error. Further,
`the gear train shown by Berman et a1 appears to be
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`quite complex and difficult to manufacture economically. Berman at
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`if!
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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
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`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
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`hybrid drive.
`Lynch argues that maximum fuel efficiency can be
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`realized when a relatively small
`internal combustion engine is
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`provided,
`such that when the engine is operated at an efficient
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`speed, it produces approximately the average power required over a
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`typical mission.
`The example given is of an engine producing 25
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`hp maximum and 17 hp at its most efficient speed, about 2500 rpm.
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`This is to be combined with an electric motor-generator of about 30
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`peak hp. This vehicle requires a variable-ratio transmission to
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`achieve reasonable performance. It appears that the engine is to be
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`run continuously, at
`steady speed, with additional
`torque
`a
`provided by the motor when needed and excess torque produced by the
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`engine being used to charge the batteries.
`In a first embodiment,
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`torque provided by the motor is transmitted to the drive wheels
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`through the engine, while in a second embodiment their respective
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`positions are reversed.
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`Nishida U.S. patent 5,117,931 shows a parallel hybrid vehicle
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`where torque from an electric motor may be combined with torque
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`from an internal combustion engine in a "torque transmission unit"
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`comprising paired bevel“ gears
`and means
`for controlling the
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`relatiVe rates of rotation of the motor and engine, so that the
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`motor can be used to start the engine, absorb excess torque from
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`the engine
`(by
`charging a battery),
`or provide additional
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`propulsive torque.
`A variable—speed transmission is coupled
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`between the torque transmission unit and the propelling wheels.
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`the
`torque "transmission unit
`and
`the variable-speed
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`transmission are complex, heavy, and expensive components,
`the use
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`of which would preferably be avoided.
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`Belling U.S. patent 3,923,115 also shows a hybrid vehicle
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`having a torque transmission unit for combining torque from an-
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`electric motor and an internal combustion engine.
`However,
`in
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`Both
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`Helling the relative rates of rotation of
`the motor and engine
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`input shafts are fixed;
`a flywheel is provided to store excess
`mechanical energy as well as a battery to store excess electrical
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`energy. Albright, Jr. et a1 patent 4,588,040 shows another hybrid
`drive scheme using a flywheel
`in addition to batteries to store
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`excess energy; various complicated »mechanica1 connections are
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`provided between the various components. Capacitors have also been
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`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
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`train wherein torque from two electric motors is combined with
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`torque produced by an internal combustion engine; the combination
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`is performed by a complex arrangement of paired planetary gearsets,
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`and unspecified control means are alleged to be able to allow
`variation of road speed without a variable-ratio transmission.
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`i”
`Hunt U.S. Patent Nos. 4,405,029 and 4,470,476 also disclose
`
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`fl! parallel hybrids.requiring complex gearing arrangements,
`including
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`multiple speed transmissions. More specifically,
`the Hunt patents
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`a}
`disclose several embodiments of parallel hybrid vehicles. Hunt
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`indicates (see col. 4,
`lines 6 - 20 of the '47§_patent)
`that an
`$1
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`2Q
`electric motor may drive the vehicle at low speeds up to 20 mph,
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`and an internal combustion engine used for speeds above 20 mph,
`C?
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`:5 while "in'certain speed ranges,
`such as from 15 - 30 mph, both
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`power sources may be energized... Additionally, both power sources
`f:
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`could be utilized under heavy load conditions." Hunt also indicates
`I?
`that “the vehicle could be provided with an automatic changeover
`Zil-
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`device which automatically shifts from the electrical power source
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`to the internal combustion power source, depending on the speed of
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`the vehicle" (coll 4,
`lines 12 - 16).
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`I However,-the Hunt vehicle does not meet the objects of the
`present invention, as discussed in detail below. Hunt's vehicle in
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`each embodiment
`requires
`a conventional manual or automatic
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`transmission. See col. 2,
`lines 6 - 7. Moreover,
`the internal
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`combustion engine is connected to the transfer case (wherein torque
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`from the internal combustion engine and electric motor is combined)
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`1 2
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`fl}
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`F11.
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`1
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`Q1
`2%”
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`£1
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`'5
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`fl!
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`[H
`2;“
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`30
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`by
`converter
`of
`conventional
`a
`"fluid coupling or
`torque
`construction". Col. 2,
`lines 16 — 17. Such transmissions and fluid
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`couplings or torque converters are very inefficient, are heavy,
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`bulky, and costly, and are to be eliminated according to one object
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`of the present invention, again as discussed in detail below.
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`Furthermore,
`the primary means of battery charging disclosed
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`by Hunt involves a further undesirable complexity, namely a turbine
`driving the electric motor in generator configuration. The turbine
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`is fueled by waste heat from the internal combustion engine. See
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`col. 3,
`lines 10 - 60. Hunt‘s internal combustion engine is also
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`fitted with an alternator,
`for additional battery charging
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`capability, adding yet further complexity. Thus it is clear that
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`Hunt fails to teach a hybrid vehicle meeting the objects of the
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`present
`invention - that
`a hybrid vehicle competitive with
`is,
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`conventional vehicles with respect
`to performance,
`cost
`and
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`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
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`coupled to the drive wheels through a conventional variable-ratio
`transmission,
`an electric 'motor,
`and an alternator,
`to allow
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`efficient use of the internal combustion engine:' As in the Hunt
`disclosure,
`the engine is intended to be operated in a relatively
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`efficient range of engine speeds; when it produces more torque than
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`is needed to propel the vehicle,
`the excess is used to charge the
`batteries; where the engine provides insufficient torque,
`the motor
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`is energized as well.
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`shows a hybrid
`A further Kawakatsu patent, No. 4,335,429,
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`vehicle,
`in this case comprising an internal combustion engine and
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`two motor/generator units.
`A first larger motor/generator, powered
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`by a battery,
`is used
`to provide additional
`torque when that
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`provided by the engine is insufficient; the larger motor-generator
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`also converts excess torque provided by the engine into electrical
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`energy,
`to be stored by the battery, and is used in a regenerative
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`braking mode. The second smaller motor/generator is similarly used
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`to provide additional torque and additional regenerative braking as
`needed.
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`More particularly,
`the latter Kawakatsu patent asserts that
`a single electric motor sized to provide sufficient
`torque to
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`propel
`the vehicle would not be capable of providing sufficient
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`regenerative braking force; see col.-1,
`line 50 - col.
`2 line 8.
`Accordingly, Kawakatsu provides two separate motor/generators, as
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`noted; a separate engine starting motor is also provided.
`See col.
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`
`
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`6,
`lines
`the
`embodiment
`shown,
`the
`larger
`22
`—
`In
`23.
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`motor/generator is connected to the wheel drive shaft, while the
`engine and the smaller motor/generator are connected to the wheels
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`through
`a
`complex mechanism comprising
`three
`separately-
`controllable clutches. See col. 5,
`lines 50 - 62.
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`Numerous patents disclose hybrid vehicle drives tending to
`fall into one or more of the categories discussed above. A number
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`of patents disclose systems wherein an operator is required to
`select between electric and internal combustion operation;
`for
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`
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`example,
`an electric motor
`is provided for operation inside
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`buildings where exhaust fumes would be dangerous, and an internal
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`combustion engine provided for operation outdoors.
`It is also
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`known to propose a hybrid vehicle comprising an electric motor for
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`use at low speeds, and an internal combustion engine for use at
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`higher speed.
`The art also suggests using both when maximum torque
`is reguired.
`In several cases the electric motor drives one set of
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`wheels and the internal combustion engine drives a different set.
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`
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`See generally Shea (4,180,138); Fields et a1 (4,351,405); Kenyon
`
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`
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`(4,438,342); Krohling (4,593,779); and Ellers (4,923,025).
`
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`Many of these patents show hybrid vehicle drives wherein a
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`variable speed transmission is required, as do numerous additional
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`references. A transmission as noted above is typically required
`
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`where the internal combustion engine and/or the electric motor are
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`not capable of supplYing sufficient torque at low speeds. See Rosen
`
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`(3,791,473); Rosen (4,269,280); Fiala (4,400,997); and Wu et al
`
`
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`
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`(4,697,660). Kinoshita (3,970,163) shows a vehicle of this general
`
`10
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`29
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`£11
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`:12
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`E)
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`(I)
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`f31
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`(I)
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`25
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`30
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`5-
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`type wherein a gas turbine engine is coupled to the road wheels
`
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`through a three-speed transmission; an electric motor is provided
`
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`to supply additional torque at low speeds.
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`For further examples of series hybrid vehicles generally as
`
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`discussed above, see Bray (4,095,664); Cummings (4,148,192); Monaco
`
`
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`et
`(4,306,156);
`Park
`(4,313,080); McCarthy
`(4,354,144);
`a1
`
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`
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`Heidemeyer
`(4,533,011); Kawamura
`(4,951,769); and Suzuki et a1
`
`
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`
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`(5,053,632). Various of these address specific problems arising in
`
`
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`
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`the manufacture or use of hybrid Vehicles, or specific alleged
`
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`
`
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`design improvements.
`For example, Park addresses certain specifics
`
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`of battery charging and discharge characteristics, while McCarthy
`
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`shows a complex: drive system involving an internal combustion
`
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`engine driving two electric motors;
`the torque generated by the
`
`
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`
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`latter is combined in a complex differential providing continuously
`,
`
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`variable gear ratios.
`Heidemeyer
`shows connecting an internal
`HE,
`combustion engine to an electric motor by a first friction clutch,
`g;
`
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`and connecting the motor to a transmission by a second friction
`3!
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`clutch.
`a:
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`
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`
`
`other patents of general relevance to this_subject matter
`$1
`include Toy
`(3,525,874),
`showing a series hybrid using a gas
`26“
`
`
`
`
`
`
`
`
`
`
`
`
`
`
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`a;
`turbine as-internal combustion engine; Yardney (3,650,345), showing
`
`
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`
`
`
`use of a compressed-air or similar mechanical starter for the
`a:
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`
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`internal combustion engine of a series hybrid, such that batteries
`g!
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`
`
`
`
`E3
`limited current
`capacity could be used;
`and Nakamura
`of
`(3,837,419), addressing improvements in thyristor battery-charging
`2%L
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`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); Mari
`(3,623,568); Grady,
`Jr.
`(3,454,122); Papst
`
`
`
`
`
`(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
`
`
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`
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`.No. 4,578,955 to Medina shows a hybrid system wherein a gas turbine
`
`
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`
`
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`is used to drive a generator as needed to charge batteries. Of
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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
`
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`in the range of 144,
`168 or 216 volts and the generator should
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`
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`deliver current in the range of 400 to 500 amperes. Those of skill
`
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`
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`in the art will
`recognize that
`these high currents
`involve
`substantial resistance heating losses, and additionally require
`
`
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`
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`that all electrical connections be made by positive mechanical
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`
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`means such as bolts and nuts, or by welding. More specifically, for
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`reasons of safety and in accordance with industry practice,
`
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`currents in excess of about 50 amperes cannot be carried by the
`
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`
`conventional
`plug-in
`connectors
`preferred
`for
`reasons
`of
`
`
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`
`
`
`
`
`
`convenience and economy, but must be carried by much heavier, more
`
`
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`
`
`expensive and
`convenient
`fixed connectors
`(as used on
`less
`
`
`
`
`
`
`
`.
`conventional starter and battery cable connections). Accordingly,
`it would be desirable to operate the electric motor of a hybrid
`15%}
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`
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`vehicle at lower currents.
`fl}
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`
`
`U.S. patent 5,765,656 to Weaver also shows a series hybrid
`fig
`
`
`
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`
`
`x .
`
`
`
`
`
`
`
`
`fl) wherein a gas turbine is used as the internal combustion engine;
`
`in
`
`
`
`
`
`hydrogen is the preferred fuel.
`fil
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`
`
`
`2%
`U.S. Patent No. 4,439,989 to Yamakawa shows a system wherein
`
`
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`
`
`
`
`
`
`€Q'
`two different
`internal combustion engines are provided,
`so that
`
`
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`
`
`
`
`
`
`only one need be run when the load is low. This arrangement would
`Ej
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`be complex and expensive to manufacture.
`F3
`
`Detailed discussion of various aspects of hybrid vehicle
`SEE
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`drives may be found in Kalberlah, "Electric Hybrid Drive Systems
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`for Passenger Cars
`and Taxis",
`SAE Paper No.
`910247
`(1991).
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`Kalberlah first compares "straight" electric, series hybrid, and
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`parallel hybrid drive trains, and concludes that parallel hybrids
`are preferable, at least when intended for general use (that is,
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`straight electric vehicles may be useful under certain narrow
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`conditions qf'low-speed,
`limited.range urban driving). Ka1ber1ah
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`then compares various forms of parallel hybrids, with respect to
`his Fig. 4, and concludes that the most practical arrangement is
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`one in which an internal combustion engine drives a first pair of
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`wheels,
`the second; more particularly,
`and an electric motor
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`Kalberlah indicates that mechanical combination of the torque from
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`an internal combustion engine and an electric motor is impractical.
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`Gardner U.S.
`patents
`5,301,764
`and
`5,346,031
`follow
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`Kalberlah's teachings,
`in that Gardner shows separately driving at
`least two pairs of wheels; one pair is driven by a first electric
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`motor, and the second by a second electric motor or alternatively
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`by a small internal combustion engine. Three different clutches
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`are provided to allow various sources of drive torque to be
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`connected to the wheels, and to a generator, dependimg on the
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`vehicle's operation mode.
`The internal combustion engine is run
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`continuously, and provides the driving torque when the vehicle is
`in a cruise mode; at other times it is used to charge the batteries
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`powaring the electric motors.
`Bullock,
`"The Technological Constraints of Mass, Volume,
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`Dynamic Power Range and Energy Capacity on the Viability of Hybrid
`and Electric Vehicles",
`SAE Paper No. 891659 (1989) provides a
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`detailed theoretical analysis of electric vehicles in terms of the
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`loads thereon, and a careful analysis of the various battery types
`then available.
`Bullock concludes that a vehicle having two
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`electric motors of differing characteristics, driving the wheels
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`through a variable—speed transmission, would be optimal
`for
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`automotive use;
`see the discussion of Fig.
`8.
`Bullock also
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`suggests the use of an internal combustion engine to drive battery
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`charging, but does not address combining the engi