(12) United States Patent
`US 6,338,391 B1
`(10) Patent N0.:
`(45) Date of Patent:
`Severinsky et al.
`*Jan. 15, 2002
`
`USOO6338391B1
`
`(54) HYBRID VEHICLES INCORPORATING
`TURBOCHARGERS
`
`(75)
`
`Inventors: Alex J. Severinsky, Washington, DC
`(US); Theodore Louckes, Holly, MI
`(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 0 days.
`
`This patent is subject to a terminal dis-
`claimer.
`
`(21) Appl. No.: 09/392,743
`
`(22)
`
`Filed:
`
`Sep. 9, 1999
`
`(60)
`
`Related US. Application Data
`Provisional application No. 60/122,296, filed on Mar. 1,
`1999.
`
`Int. Cl.7 .................................................. B60K 6/04
`(51)
`(52) US. Cl.
`......................................... 180/652; 60/602
`(58) Field of Search ............................... 180/652, 65.3,
`180/654, 65.8, 165; 60/706, 711, 716,
`718, 602; 290/17, 40 R, 40 C; 322/16;
`477/2, 3
`
`(56)
`
`References Cited
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`.
`
`. ”, IEEE Spectrum, vol. 32,
`
`Primary Examiner—J. J. Swann
`Assistant Examiner—David R. Dunn
`
`(74) Attorney, Agent, or Firm—Michael de Angeli
`
`(57)
`
`ABSTRACT
`
`A hybrid vehicle comprising an internal combustion engine
`controllably coupled to road wheels of the vehicle by a
`clutch, and having a turbocharger that is operated only when
`extra power is needed for a extended time, 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 microproces-
`sor 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 micro-
`processor in response to a control strategy.
`
`15 Claims, 5 Drawing Sheets
`
`\\0
`
`
`
`\NVERTER/ CH NIGER
`
`
`\NVER'YER/CHARGER
`
`
`\S
`(is \6
`
`
`
`‘53
`[01
`
`
` BATTERY BANK
` 67
`
`'l'Z
`u
`
`
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`
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`

`US 6,338,391 B1
`
`Page 2
`
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`
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`10/1995 Vald1V1a
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`9/1998 Yamaguchi et al.
`
`............. 180/65.2
`
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`
`Page 3
`
`5,806,617 A
`5,820,172 A
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`7
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`“/1998 Welke
`1
`$133: 35:161.
`/
`an“ a ‘1‘
`11/1998 Tabata et a1.
`12/1998 Frank ........................ 180/652
`
`.
`12/1998 Bughone et a1.
`.......... 180/65.2
`.
`.
`12/1998 Tanlguchl et a1.
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`.
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`.
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`
`.
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`
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`............... 477/5
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`................. 60/602
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`............... 701/102
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`2/2000 Aoyarna .................... 180/65.2
`.
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`.
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`.
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`5/2000 Schmldt—Brucken
`.
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`6,098,733 A *
`............. 180/652
`6,109,025 A *
`8/2000 Murata et a1.
`60/297
`
`.
`6,131,538 A * 10/2000 Kanal ...............
`123/2
`.
`
`6,161,384 A * 12/2000 Rembold et a1.
`.
`...... 60/602
`6209 672 B1 *
`42001 s
`‘ k
`180 652
`,
`,
`/
`evenns y ................
`/
`.
`
`* cited by examiner
`
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`US 6,338,391 B1
`
`1
`HYBRID VEHICLES INCORPORATING
`TURBOCHARGERS
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application claims priority from Provisional Appli-
`cation Ser. No. 60/122,296, filed Mar. 1, 1999.
`
`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, and
`wherein turbocharging is employed under certain circum-
`stances. A preferred method of sizing the power-producing
`components of the hybrid vehicle is also disclosed.
`
`BACKGROUND OF THE INVENTION
`
`This application discloses a number of improvements
`over and enhancements to the hybrid vehicles disclosed in
`US. Pat. No. 5,343,970 (the “’970 patent”) to one of the
`present
`inventors, which is incorporated herein by this
`reference. Where differences are not mentioned, it is to be
`understood that the specifics of the vehicle design shown in
`the ’970 patent are applicable to the vehicles shown herein
`as well. Discussion of the ’970 patent herein is not to be
`construed to limit the scope of its claims.
`Generally speaking,
`the ’970 patent discloses hybrid
`vehicles wherein a controllable torque transfer unit is pro-
`vided capable of transferring torque between an internal
`combustion engine, an electric motor, and the drive wheels
`of the vehicle. The direction of torque transfer is controlled
`by a microprocessor responsive to the mode of operation of
`the vehicle, to provide highly efficient operation over a wide
`variety of operating conditions, and while providing good
`performance.
`The flow of energy—either electrical energy stored in a
`substantial battery bank, or chemical energy stored as com-
`bustible fuel—is similarly controlled by the microprocessor.
`For example, in low-speed city driving, the electric motor
`provides all torque needed responsive to energy flowing
`from the battery. In high-speed highway driving, where the
`internal-combustion engine can be operated efficiently,
`it
`typically provides all
`torque; additional
`torque may be
`provided by the electric motor as needed for acceleration,
`hill-climbing, or passing. The electric motor is also used to
`start the internal-combustion engine, and can be operated as
`a generator by appropriate connection of its windings by a
`solid-state, microprocessor-controlled inverter. For
`example, when the state of charge of the battery bank is
`relatively depleted, e.g., after a lengthy period of battery-
`only operation in city traffic, the internal combustion engine
`is started and drives the motor at between 50 and 100% of
`its maximum torque output, for efficient charging of the
`battery bank. Similarly, during braking or hill descent, the
`kinetic energy of the vehicle can be turned into stored
`electrical energy by regenerative braking.
`The hybrid drive train shown in the ’970 patent has many
`advantages with respect to the prior art which are retained by
`the present invention. For example, the electric drive motor
`is selected to be of relatively high power, specifically, equal
`to or greater than that of the internal combustion engine, and
`to have high torque output characteristics at low speeds; this
`allows the conventional multi-speed vehicle transmission to
`be eliminated. As compared to the prior art, the battery bank,
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`motor/generator, and associated power circuitry are operated
`at relatively high voltage and relatively low current, reduc-
`ing losses due to resistive heating and simplifying compo-
`nent selection and connection.
`
`Application Ser. No. 09/264,817 filed Mar. 9, 1999 (the
`“’817 application”), now US. Pat. No. 6,209,672, also
`incorporated herein by reference, discloses and claims cer-
`tain further improvements in hybrid vehicles, described
`below, with respect to the vehicles of the ’970 patent. The
`present patent application represents further improvements
`over the hybrid vehicle described in the ’817 application.
`OBJECTS OF THE INVENTION
`
`It is an object of the present invention to provide further
`improvements over the hybrid vehicles shown in the ’970
`patent and the ’817 application.
`It is a more specific object of the present invention to
`provide a hybrid drive system for vehicles that does not
`require the controllable torque-transfer unit shown in the
`’970 patent, while providing the functional advantages of
`the hybrid vehicles shown in the ’970 patent and the ”817
`application, together with further improvements.
`Other aspects of and improvements provided by the
`present invention will appear below.
`SUMMARY OF THE INVENTION
`
`According to the invention of the ’817 application, the
`controllable torque-transfer unit shown in the ’970 patent is
`eliminated by replacing the single electric motor shown
`therein by two separate motors, both operable as generators
`when appropriate, connected by a functionally-conventional
`clutch or mechanical interlock operated by the micropro-
`cessor responsive to the vehicle’s mode of operation and to
`input commands provided by the operator of the vehicle. As
`in the ’970 patent, an internal combustion engine is
`provided, sized to provide sufficient torque for the maximum
`cruising speed desired without requiring a multi-speed
`transmission, and is used for battery charging as needed.
`According to the invention of the ’817 application, a rela-
`tively high-powered “traction” motor is connected directly
`to the output shaft of the vehicle; the traction motor provides
`torque to propel the vehicle in low-speed situations, and
`provides additional
`torque when required, e.g.,
`for
`acceleration, passing, or hill-climbing during high-speed
`driving. A relatively low-powered starting motor is also
`provided, and can be used to provide torque propelling the
`vehicle when needed. This second motor is connected
`
`directly to the internal combustion engine for starting the
`engine. Unlike a conventional starter motor, which rotates an
`internal combustion engine at low speed (60—100 rpm) for
`starting, necessitating provision of a rich fuel/air mixture for
`starting, the starter motor according to the invention spins
`the engine at relatively high speed (typically 300 rpm) for
`starting;
`this allows starting the engine with a near-
`stoichiometric mixture, significantly reducing undesirable
`emissions and improving fuel economy at start-up.
`As noted, the two motors are separated by a functionally-
`conventional clutch, that is, a clutch which either joins the
`two motors together for rotation at
`the same speed, or
`separates them completely. As the motor shafts can be
`controlled to rotate at essentially the same speed when the
`clutch is engaged, the clutch need not allow for significant
`slipping before engagement. Accordingly, a friction clutch,
`as normally provided for road vehicles, may not be required,
`and a less-expensive simple mechanical interlock may alter-
`natively be employed. Engagement of the clutch is con-
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`trolled by the microprocessor, e.g., controlling a hydraulic
`actuator, responsive to the state of operation of the vehicle
`and the current operator input.
`For example, during low-speed operation, the clutch will
`be disengaged, so that the traction motor is disconnected
`from the engine; the vehicle is then operated as a simple
`electric car, i.e., power is drawn from the battery bank and
`supplied to the traction motor. If the batteries become
`depleted,
`the starter motor is used to start
`the internal
`combustion engine, which then runs at relatively high torque
`output (e.g., between about 50—100% of its maximum
`torque), for efficient use of fuel, and the starting motor is
`operated as a high-output generator to recharge the battery
`bank. If the operator calls for more power than available
`from the traction motor alone, e.g., in accelerating onto a
`highway, the starter motor starts the internal combustion
`engine, and the clutch is engaged, so that the engine and
`starter motor can provide additional torque. The engine is
`sized so that
`it provides sufficient power to maintain a
`suitable highway cruising speed while being operated in a
`torque range providing good fuel efficiency; if additional
`power is then needed, e.g., for hill-climbing or passing, the
`traction and/or starter motors can be engaged as needed.
`Both motors can be operated as generators, e. g., to transform
`the vehicle’s kinetic energy ito electrical power during
`descent or deceleration.
`
`It is also within the scope of the invention to provide
`power from the engine and starting motor to one pair of road
`wheels, through the clutch, and from the traction motor to
`another set of wheels; this provides all-wheel drive, when
`needed, without a transfer gearbox or drive shaft. See
`provisional patent application Ser. No. 60/122,478, filed
`Mar. 1, 1999, incorporated by reference herein. In a further
`embodiment, torque from the engine, starter motor, and a
`first traction motor can be provided to a first set of road
`wheels, and torque from a second traction motor to a second
`set of road wheels; this would provide maximal flexibility in
`control of the transfer of torque to the road, useful
`in
`low-traction conditions.
`
`In each of these aspects of the operation of the vehicle,
`and as in the ’970 patent, the operator of the vehicle need not
`consider
`the hybrid nature of the vehicle during its
`operation, but simply provides control inputs by operation of
`the accelerator and brake pedals. The microprocessor deter-
`mines the proper state of operation of the vehicle based on
`these and other inputs and controls the various components
`of the hybrid drive train accordingly.
`According to the present invention, the engine is further
`provided with a turbocharger, also controlled by the
`microprocessor, and operated only under extended high-load
`conditions.
`In low-speed driving,
`the turbocharger is
`bypassed and is inactive, so that the vehicle is operated as in
`the ’817 application; similarly, when the torque provided by
`the engine is inadequate for short-term high loads, such as
`during overtaking on the highway,
`the traction motor is
`employed to propel the vehicle. The starting motor may also
`be employed to provide torque as needed. However, accord-
`ing to the present invention, when conditions demand pro-
`duction of high torque for extended periods, for example,
`when towing a trailer, climbing a long hill, or driving at
`sustained high speed, or when the battery bank is relatively
`discharged, the microprocessor activates the turbocharger,
`so that additional torque is produced by the internal com-
`bustion engine when needed.
`More specifically, in the ”817 application, during substan-
`tially steady-state operation, e.g., during highway cruising,
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`the control system operates the engine at varying torque
`output levels, responsive to the operator’s commands. The
`range of permissible engine torque output levels is con-
`strained to the range in which the engine provides good fuel
`efficiency. Where the vehicle’s torque requirements exceed
`the engine’s maximum efficient torque output, e.g., during
`passing or hill-climbing, one or both of the electric motors
`are energized to provide additional torque; where the vehi-
`cle’s torque requirements are less than the minimum torque
`efficiently provided by the engine, e.g., during coasting, on
`downhills or during braking, the excess engine torque is
`used to charge the batteries. Regenerative charging may be
`performed simultaneously, as torque from the engine and the
`vehicle’s kinetic energy both drive either or both motors in
`generator mode. The rate of change of torque output by the
`engine may be controlled in accordance with the
`batteries’state of charge.
`According to the present invention, the above control
`strategy is retained and employed under substantially all
`“normal” driving conditions; addition of a turbocharger
`controlled by the microprocessor according to the invention
`allows additional control flexibility. More specifically, when
`conditions demand power in excess of the engine’s
`normally-aspirated maximum output for a relatively long
`period of time, e.g., for climbing long hills, for towing, or
`when driving at high speed,
`the turbocharger, which is
`normally bypassed and thus inactive, is energized by supply
`of the engine’s exhaust gas stream. The engine then pro-
`duces additional torque as required.
`As compared to turbochargers as conventionally
`employed, which are constantly active,
`the turbocharger
`according to the present invention is used only when needed,
`that is, as noted, only when torque in excess of that available
`from the engine when in “normally-aspirated” mode is
`required. This allows both the engine and turbocharger to be
`designed to meet relatively well-defined objectives, provid-
`ing further efficiency in use of fuel. Furthermore, because
`according to the invention the turbocharger is employed in
`a hybrid vehicle having one or more electric motors avail-
`able to provide additional torque substantially immediately
`upon demand, the vehicle overall does not exhibit the slow
`response time of conventional turbocharged vehicles.
`In a further refinement, the amount of time during which
`the motors will be used to supply torque in excess of that
`available from the engine in normally-aspirated mode before
`the turbocharger is activated is controlled responsive to the
`state of charge of the vehicle battery bank. More specifically,
`in general, when power in excess of the engine’s normally-
`aspirated capacity is required for a shorter period of time,
`e.g., when passing, at least the traction motor, or both of the
`electric motors, are energized by power from the battery.
`However, it is also within the scope of the invention to
`employ the turbocharger under circumstances calling for
`maximum acceleration, or when the state of charge of the
`battery is such that the electric motors will not be adequate
`to supply the torque required.
`In addition to the operational advantages noted, provision
`of an engine having a “turbocharger-on-demand” in a hybrid
`vehicle allows the engine to be smaller than otherwise, that
`is, to provide adequate highway performance in a vehicle of
`a given weight. As the starting motor/generator must be
`sized such that when it is driven by the engine to charge the
`batteries (e.g., in extended city driving) the engine is loaded
`adequately to be operated efficiently, employment of a
`smaller engine allows use of a smaller starting motor/
`generator. For similar reasons, provision of a smaller engine
`allows it
`to be used to efficiently propel the vehicle in
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`US 6,338,391 B1
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`5
`lower average speeds,
`highway driving commencing at
`resulting in turn in better fuel economy.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention will be better understood if reference is
`
`made to the accompanying drawings, in which:
`FIG. 1 shows a schematic diagram of the principal com-
`ponents of the hybrid vehicle drive system according to the
`invention;
`FIG. 2 is a diagram in which engine torque is plotted
`against engine speed for a typical engine in normally-
`aspirated and turbocharged modes of operation, and also
`shows typical road loads encountered;
`FIG. 3 is a diagram illustrating differing modes of vehicle
`powertrain operation, plotted on a three-dimensional chart,
`illustrating that the mode of vehicle operation is a function
`of the state of charge of the battery bank, the instantaneous
`road load, and time; and
`FIG. 4 is a timing diagram showing road load, engine
`torque output, the state of charge of the battery bank, and
`engine operation in normally-aspirated and turbocharged
`modes of operation as functions of time, thus illustrating a
`typical control strategy employed during low-speed city
`driving, highway cruising, and extended high-load driving.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`this application discloses certain
`As indicated above,
`modifications,
`improvements, and enhancements of the
`hybrid vehicles shown in US. Pat. No. 5,343,970 (the “’970
`patent”) to one of the present inventors, which is incorpo-
`rated herein by this reference; where not otherwise stated,
`the design of the vehicle of the present invention is similar
`to that shown in the ’970 patent. Components commonly
`numbered in this application and the ’970 patent are func-
`tionally similar in the corresponding systems, with detail
`differences as noted. The advantages of the system shown in
`the ’970 patent with respect to the prior art are provided by
`that of the present invention, with further improvements
`provided by the latter, as detailed herein. The present appli-
`cation also represents further improvements over the hybrid
`vehicle described in Application Ser. No. 09/264,817 filed
`Mar. 9, 1999 (the “’817 application”), also incorporated
`herein by reference.
`As shown in the ’970 patent with reference to FIGS. 1 and
`2 thereof, typical modern automobiles operate at very low
`efficiency, due principally to the fact that internal combus-
`tion engines are very inefficient except when operating at
`near peak torque output; this condition is only rarely met.
`(The same is true, to greater or lesser degree, of other road
`vehicles powered by internal combustion engines.) Accord-
`ing to an important aspect of the invention of the ’970 patent,
`substantially improved efficiency is afforded by operating
`the internal combustion engine only at relatively high torque
`output levels, typically at least 35% and preferably at least
`50% of peak torque. When the vehicle operating conditions
`require torque of this approximate magnitude, the engine is
`used to propel the vehicle; when less torque is required, an
`electric motor powered by electrical energy stored in a
`substantial battery bank drives the vehicle; when more
`power is required than provided by either the engine or the
`motor, both are operated simultaneously. The same advan-
`tages are provided by the system of the present invention,
`with further improvements and enhancements described in
`detail below.
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`In the system of the ’970 patent, torque from either or both
`the engine and motor is transferred to the drive wheels of the
`vehicle’by a controllable torque-transfer unit. This unit also
`allows torque to be transferred between the motor and
`engine, for starting the engine, and between the wheels and
`motor, for regenerative battery charging during deceleration
`of the vehicle. This unit, while entirely practical, comprises
`gears for power transfer, which are inevitably a source of
`audible noise and frictional losses. According to the inven-
`tion of the ’817 application, and the present invention, the
`controllable torque-transfer unit is eliminated. Instead, two
`electric motors are provided, each separately controlled by
`a microprocessor controller responsive to operator com-
`mands and sensed operating conditions.
`As shown in FIG. 1 of the present application, and as also
`shown in the ’817 application, a traction motor 25 is
`connected directly to the vehicle differential 32, and thence
`to the road wheels 34. A starting motor 21 is connected
`directly to the internal combustion engine 40. The motors 21
`and 25 are functional as motors or generators by appropriate
`operation of corresponding inverter/charger units 23 and 27,
`respectively. The two motors are controllably connected for
`torque transfer by a clutch 51, conventional in the sense that
`it is either engaged, wherein the shafts of motors 21 and 25
`are connected and rotate together, or disengaged, wherein
`the shafts may rotate separately. (The respective positions of
`motor 21 and engine 40 with respect to clutch 51 could be
`reversed as compared to their positions in FIGS. 1 and 2
`without affecting the function of the system, although as
`engine 40 would then require torque transmitting connection
`at both ends of its crankshaft, some additional complexity
`would result.) The clutch 51 is operated by microprocessor
`48, e.g., through a known hydraulic actuator 53, together
`with the other components of the system, in accordance with
`the operational state of the vehicle and the operator’s input
`commands.
`
`As in the case of the hybrid vehicle system shown in the
`’970 patent, and as indicated above,
`the vehicle of the
`invention is operated in different modes depending on the
`torque required, the state of charge of the batteries, and other
`variables. For example, during low-speed operation, such as
`in city traffic, the vehicle is operated as a simple electric car,
`where all power is provided to road wheels 34 by traction
`motor 25; engine 40 is run only as needed to charge battery
`bank 22. (In this connection, essentially conventional lead-
`acid batteries are currently preferred for battery bank 22,
`since the infrastructure to provide and dispose of these
`batteries is already in place; that is, lead-acid batteries are
`widely available,
`readily recycled, and so on. More
`advanced batteries may be used if and when they become
`widely available and economically competitive.) Under
`these circumstances,
`the charging current is provided by
`starting motor 21, operated as a generator by appropriate
`operation of inverter/charger 23. Accordingly, clutch 51 is
`disengaged, so that the road speed of the vehicle is inde-
`pendent of the speed of engine 40; engine 40 can thus be
`operated at high torque, for fuel efficiency. The operating
`modes of the vehicle of the invention are further discussed
`below.
`
`As shown in further detail in the ’817 application, the
`microprocessor 48 is provided with signals indicative of the
`rotational speeds of shafts 15 and 16, and controls operation
`of engine 40, motor 21, and motor 25 as necessary to ensure
`that the shafts are rotating at substantially the same speed
`before engaging clutch 51; therefore, clutch 51 need not
`necessarily be an ordinary automotive friction clutch (as
`illustrated schemati