United States Patent
`
`[19]
`
`[11] Patent Number:
`
`5,865,263
`
`Yamaguchi et al.
`[45] Date of Patent:
`Feb. 2, 1999
`
`
`U8005865263A
`
`[54] HYBRID VEHICLE
`
`[75]
`
`Inventors: K0z0 Yamaguchi; Y0shikazu
`Yamauchi; Hideki Nakashima, all of
`Aichi-ken, Japan
`
`[73] Assignee: Kabushikikaisha Equ0s Research,
`Japan
`
`[21] Appl. No.: 609,762
`
`[22]
`
`Filed:
`
`Feb. 23, 1996
`
`[30]
`
`Foreign Application Priority Data
`
`Feb. 28, 1995
`
`[JP]
`
`Japan .................................... 7—063538
`
`Int. Cl.6 ....................................................... B60K 6/00
`[51]
`[52] US. Cl.
`............................................................. 180/65.2
`[58] Field of Search .................................. 180/65.2, 65.3,
`180/654, 65.6, 65.8; 364/424026; 123/1793
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`1,848,091
`3/1932 Winther .................................. 180/65.2
`3,566,717
`3/1971 Berman et al.
`.. 180/65.2
`
`3,623,568
`11/1971 Mori ..............
`180/652
`
`3,861,484
`1/1975 Joslin et al.
`.. 180/65.2
`4,022,164
`5/1977 Fuchs ............
`. 123/1793
`
`4,122,354 10/1978 Howland .............................. 123/1793
`
`......................... 180/65.4
`4/1980 Downing, Jr.
`4,196,785
`180/65.2
`6/1982 Kawakatsu
`4,335,429
`
`.. 123/1793
`4,883,028 11/1989 Wu ...............
`5,343,970
`9/1994 Severinsky ............................. 180/652
`5,698,905
`12/1997 Ruthlein ................................. 180/65.4
`FOREIGN PATENT DOCUMENTS
`
`0570234
`4—294977
`
`5/1993 European Pat. Off..
`5/1994
`Japan .................................... 180/65.2
`
`Primary Examiner—Brian L. Johnson
`Assistant Examiner—Frank Vanaman
`
`Attorney, Agent, or Firm—Lorusso & Loud
`
`[57]
`
`ABSTRACT
`
`A hybrid vehicle has an engine and a generator/motor
`connected through a planetary gear unit to an output shaft
`and the output of the engine is distributed between the
`generator and the output shaft. The vehicle is smoothly
`started by a driving motor. When vehicle speed V reaches an
`engine starting speed V*, the speed of generator/motor is
`changed to cause the engine to rotate, the engine is ignited
`and driving continues with the output torque produced by
`the engine supplemented by the driving motor. The hybrid
`vehicle allows for a smooth start and improved driving
`comfort even if an engine interruption scheme for halting the
`engine is employed, for example, halting the vehicle while
`waiting for a traffic signal to change.
`
`19 Claims, 8 Drawing Sheets
`
`5 O
`ACCELERATOR
`
`2 P
`
`age 1 of 17
`
`1/ 42
`{/41
`,_ ___________ .1. ________
`F - - __ _ _1_ _ _ _:
`‘
`425 DRIVING FORCE INSTRUCTION
`1
`.
`a |
`I 411 Eggymox
`VALUE DETECTION UNIT
`1l
`I
`I
`I
`SENSOR
`I
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`'
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`I
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`I
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`@8111”
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`SYSTENL
`ENGINE
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`
`VEHICLE CONTROL DEVICE
`
`
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`m
`GENERATOR
`EIIJEE
`$813101
`
`SYSTEM
`
`9
`
`424
`
`I
`
`'M
`
`_____
`
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`I
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`
`——- I
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`1
`I
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`BATTERY
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`I
`1'
`.
`40
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`
`MOTOR
`
`4
`43
`
`TREE
`SENSOR
`412
`
`GENERATOR
`ROTATTONAL
`FREQUENCY
`SENSOR
`414
`ENGINE
`
`l I
`
`I
`i
`1
`1
`I
`|
`.
`I
`I
`I
`
`SENSOR
`415
`BATTERY
`SENSOR
`
`CATALYST
`TEMP.
`SENSOR
`
`4 I 6
`
`I
`I
`!
`1
`
`| :
`
`1
`L
`
`Page 1 of 17
`
`FORD 1209
`
`

`

`US. Patent
`
`Feb. 2, 1999
`
`Sheet 1 0f8
`
`5,865,263
`
`FIG.
`
`1
`
`Page 2 of 17
`
`FORD 1209
`
`Page 2 of 17
`
`FORD 1209
`
`

`

`US. Patent
`
`Feb. 2, 1999
`
`Sheet 2 0f8
`
`5,865,263
`
`F I G.
`
`2
`
`——_—_——————_J_ —._——.————q
` VEHICLE
`
` I
`
`_42_3 _
`
` ROTATIONAL
`
`GENERATOR
`
`FREQUENCY
`SENSOR
`
`' M
`
`
`
`
`II
`
`BATTERY
`
`43
`
`I
`
`[_ _ 1 _____________
`
`Il
`
`3&3?
`
`
`
`Page 3 of 17
`
`FORD 1209
`
`SPEED
`SENSOR
`
`
`
`
`
`A TM
`
`DRIVING
`GENERATOR
`ENGINE
`
`CONTROL
`ESEEOL
`€3§¥§o L
`
`DEVICE
`SYSTEM
`SYSTEM
`
`
`
`Page 3 of 17
`
`FORD 1209
`
`

`

`US. Patent
`
`Feb. 2, 1999
`
`Sheet 3 0f8
`
`5,865,263
`
`FIG. 3
`
`ENGINE STARTING
`CONTROL
`
`Sll
`
`INPUT ACCELERATOR
`OPEN DEGREE a
`INPUT VEHICLE SPEED V
`
`512¢ N
`
`ENGINE GENERATOR
`SYSTEM 0N
`
`
`
`DRIVING BY SOLE
`DRIVING MOTOR
`
`514
`
`$15
`
`$16
`
`$17
`
`$18
`
`$19
`
`INPUT GENERATOR
`
`ROTATIONAL FREQUENCY NG
`
`INPUT STORAGE RESIDUAL
`
`
`CAPACITY SOC
`
`
`
`COMPUTE GENERATOR MOTOR
`DRIVING TORQUE
`INSTRUCTION VALUE IG
`
`COMPUTE DRIVING MOTOR
`TORQUE SUPPLEMENTARY
`MWEAW
`
`OUTPUT GENERATOR MOTOR
`TORQUE. DRIVING MOTOR
`TORQUE
`
`
`
`
`INPUT ENGINE SPEED NE
`
`N Sw
`
`
`
`INGITE ENGINE
`(ENGINE ECU 0N)
`
`RETURN
`
`
`
`Page 4 of 17
`
`FORD 1209
`
`Page 4 of 17
`
`FORD 1209
`
`

`

`US. Patent
`
`Feb. 2, 1999
`
`Sheet 4 0f8
`
`5,865,263
`
`FIG. 4
`
`
`
`DRIVINGMOTORTORQUE(TM*)
`
`
`
`
`
`VEHICLE SPEED (Km/h)
`
`F I G .
`
`5
`
`soc=2o%
`
`40%
`
`60%
`
`80%
`
`’2Q.
`3-
`
`: 5000
`%
`
`a 4000
`g:
`U)
`
`% 3000
`
`5 E
`
`[— 2000
`Lt}
`(D
`
`1000
`
`% F
`
`0
`
`20
`
`40
`
`60
`
`80
`
`100
`
`THE DEGREE THE ACCELERATOR IS OPENED a (96)
`
`Page 5 of 17
`
`FORD 1209
`
`Page 5 of 17
`
`FORD 1209
`
`

`

`US. Patent
`
`Feb. 2, 1999
`
`Sheet 5 0f8
`
`5,865,263
`
`FIG.
`
`6
`
`If =1000AT
`
`
`
`
`OUTPUT VOLTAGE 228V
`
`If 2 FIELD CURRENT
`
`If = 800AT
`
`
`
`
`If = GOOAT
`
`
`If = 4OOAT
`
`Mm
`
`
`
`
`
`INPUTTORQUE(kgf)
`
`(.0
`
`N
`
`
`
`
`
`
`
`
`
`o
`
`2000
`
`4000
`
`6000
`
`8000
`
`ENGINE SPEED (rpm)
`
`F I G .
`
`7
`
`100
`
`73%
`
`Q E
`
`mD
`
`.-
`
`O Em-
`
`—I
`E"
`E—‘
`
`O 5
`
`::
`r— 50
`u.)
`:E
`E—
`u.)
`Ix.)
`n:
`IL}
`
`UL
`
`Q mL
`
`":
`F“
`
`0
`
`2000
`
`4000
`
`ENGINE SPEED NE(rpm)
`
`Page 6 of 17
`
`FORD 1209
`
`Page 6 of 17
`
`FORD 1209
`
`

`

`US. Patent
`
`Feb. 2, 1999
`
`Sheet 6 0f 8
`
`5,865,263
`
`FIG.
`
`8
`
`zepémzm—u
`
`
`
`”.535;mzHozm1.<on._.<.5~_mzHozmmos:no.5:
`
`
`
`
`ammmmmzHwzmammmm>02mzommmmaamoemaomoe”Each
` 00>summzuzohE.
`
`
`
`
`
`
`MES:mOHSmEmo02:55
`
`
`
`Page 7 of 17
`
`FORD 1209
`
`Page 7 of 17
`
`FORD 1209
`
`

`

`US. Patent
`
`Feb. 2, 1999
`
`Sheet 7 0f8
`
`5,865,263
`
`
`
`FIG. 10
`
`SPEEDv*v**
`VEHICLE
`
`0
`
`100
`SOC
`-—- ENGINE STARTING VEHICLE SPEED (V*)
`""" ENGINE HALT VEHICLE SPEED (V**)
`
`Page 8 °f 17
`
`FORD 1209
`
`Page 8 of 17
`
`FORD 1209
`
`

`

`US. Patent
`
`Feb. 2, 1999
`
`Sheet 8 0f8
`
`5,865,263
`
`F I G.
`
`1 1
`
`ENGINE STARTING
`CONTROL
`
`EHC HEATING
`
`N
`
`
`
`
`
`
`INPUT VEHICLE SPEED V,
`RESIDUAL CAPACITY SOC.
`THE DEGREE THE ACCELERATOR
`IS OPENED a
`
`
`STORAGE
`
`COMPUTE ENGINE START VEHICLE
`
`SPEED V* FOR STORAGE RESIDUAL
`CAPACITY SOC
`
`
`
`5111
`
`5112
`
`3113
`
`514
`
`ENGINE CONTROL SYSTEM ON
`
`DRIVING BY SOLE
`DRIVING MOTOR
`
`Page 9 of 17
`
`FORD 1209
`
`Page 9 of 17
`
`FORD 1209
`
`

`

`5,865,263
`
`1
`HYBRID VEHICLE
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`This invention relates to a hybrid vehicle and, more
`particularly, to a hybrid vehicle driven by a motor and an
`internal-combustion engine.
`2. Description of the Related Art
`Hybrid vehicles which use both a fuel-fed conventional
`engine and a motor using clean electric energy, have been
`developed. Various types of hybrid vehicles have been
`proposed, such as hybrid vehicles of the series type in which
`electric power generated by driving a generator by the
`output rotation of an engine, is changed into direct current
`to charge to a battery and electric power from the battery is
`changed into alternating current to drive a motor. Another
`hybrid vehicle is the parallel type in which the engine and
`the motor are connected to each other through a clutch, the
`motor is driven when starting, the clutch is subsequently
`engaged to drive the engine and the output of the motor is
`added to that of the engine when accelerating. Yet another
`type of hybrid vehicle is a combination of the series type and
`the parallel type.
`In a hybrid vehicle, as in a more conventional vehicle
`using only an engine, the engine operates in an idling state
`even though the vehicle is halted. Therefore, fuel efficiency
`is reduced by consuming fuel when the vehicle is not
`moving. Further, the idling of the engine produces noise due
`to the idling and eXhaust of gas. Consequently, an engine
`interruption system has been proposed in which the engine
`is operated only when the engine is needed for driving and,
`at other times,
`is turned off in order that the amount of
`eXhaust gas amount is decreased and fuel consumption is
`improved. The foregoing suggests that such an engine
`interruption system might be employed for the hybrid
`vehicle of the parallel
`type.
`In the engine interruption
`system,
`the operation of the engine is halted when the
`vehicle is halted,
`the engine is started again when the
`accelerator pedal is operated, and then the vehicle is started
`in motion.
`
`However, the engine interruption system inherently cre-
`ates a number of problems. Firstly, the clutch must release
`or connect whenever the engine is stopped or started, with
`the result that the load on the clutch is increased. Secondly,
`the frequency of use of the starter is increased because the
`starter must engage whenever the engine is started, so that
`durability of the starter becomes a problem. Thirdly,
`the
`driving comfort suffers due to the timelag between when the
`engine is started again after the accelerator pedal is operated
`and the torque change when the engine output is transferred
`to the output shaft. If the clutch is immediately connected in
`order to decrease the timelag, the load on the clutch is further
`increased.
`
`SUMMARY OF THE INVENTION
`
`Accordingly, the first object of the present invention is to
`provide a hybrid vehicle which is capable of smoothly
`starting and of maintaining driving comfort.
`The second object of the present invention is to provide a
`hybrid vehicle which uses an engine interruption system but
`does not use the starter and the clutch for each stop and start
`of the engine.
`To attain the aforementioned objects the present invention
`provides a hybrid vehicle which is distinguished by a
`distribution means which distributes the output torque of the
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`engine between a drive shaft and an input shaft of a
`generator/motor. The hybrid vehicle of the present invention
`further includes a motor connected to the drive shaft; a
`generator/motor control means for controlling the rotational
`speed of the generator/motor; a generator torque computa-
`tion means computing the output torque of the generator/
`motor which is controlled as the rotational speed of the
`generator/motor is controlled by the generator/motor control
`means; a driving judgment means for judging whether or not
`the vehicle is moving; and a motor torque compensating
`means for changing the output
`torque of the motor in
`accordance with the torque computed by the generator
`torque computation means, to compensate for drag imposed
`by the engine during start-up after the driving judgment
`means judges that the vehicle is moving.
`The distribution means has a differential gear device
`including a first element connected to the generator, a second
`element connected to the engine and a third element con-
`nected to the drive shaft. The differential gear device, in turn,
`may be a planetary gear unit wherein, in one embodiment,
`the first element is a sun gear, the second element is a carrier,
`and the third element is a ring gear.
`The driving judgment means includes vehicle speed
`detection means for detecting vehicle speed, and the afore-
`mentioned generator/motor control means operates to turn
`over and start the engine when the vehicle speed detected by
`the vehicle speed detection means exceeds a predetermined
`value.
`
`invention further
`The hybrid vehicle of the present
`includes means for detecting the degree of accelerator
`(throttle) opening, and the aforementioned generator/motor
`control means is responsive to change in the detected degree
`of accelerator opening. The generator/motor control means
`may also cause the vehicle speed predetermined for starting
`the engine to change in response to the temperature of the
`engine.
`invention further
`The hybrid vehicle of the present
`includes a battery and a storage residual capacity detection
`means for detecting the residual capacity of the battery. The
`vehicle speed is changed in response to the residual capacity
`of the battery as detected by the storage residual capacity
`detection means.
`
`Driving force instruction value detection means is pro-
`vided for detecting the required driving force, so that the
`engine is turned off when a signal detected by the driving
`force instruction value detection means is smaller than a
`
`predetermined value, and the engine is started when the
`signal is larger than the predetermined value.
`The aforementioned compensating torque is defined in
`accordance with the generator/motor torque, inertia of the
`generator, the gear ratio of the differential gear device and
`the counter gear ratio, where the distribution means is
`composed of the generator having a stator connected to the
`engine and a rotor connected to the drive shaft.
`Consequently,
`in the hybrid vehicle according to the
`present invention, after the engine is started, the engine
`torque is transferred to the drive shaft and to the input shaft
`of the generator by the distribution means. That is,
`the
`distribution means includes a differential gear device, for
`example, a planetary gear unit in which the sun gear as the
`first element is connected to the generator, the carrier as the
`second element is connected to the engine, and the ring gear
`as the third element is connected to the drive shaft, i.e. the
`output shaft. Alternatively, the distribution means may be
`composed of the generator having its stator connected to the
`engine and the rotor connected to the driving shaft.
`
`Page 10 OH?
`
`FORD 1209
`
`Page 10 of 17
`
`FORD 1209
`
`

`

`5,865,263
`
`3
`The generator/motor control means controls the rotational
`speed of the generator, and the controlled rotational speed of
`the generator is utilized to start the engine.
`The generator torque computation means computes the
`torque produced by the generator in controlling its rotational
`speed. When the driving judgment means judges that the
`vehicle has been started in motion and that the engine is
`being started, the motor torque supplement means increases
`the output torque of the motor to compensate for the drag
`produced by the starting of the engine, based on the torque
`computed by the generator torque computation means. The
`compensatory torque to be output by the motor is computed
`based on the generator torque, inertia of the generator, the
`gear ratio of the differential gear device and the counter gear
`ratio.
`
`According to the present invention, the vehicle can be
`smoothly operated to maintain driving comfort during the
`starting of the engine.
`Furthermore, a starter and clutch are unnecessary, even if
`an engine interruption scheme is used in operation of the
`hybrid vehicle.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a schematic view of a drive train in a hybrid
`vehicle in accordance with a preferred embodiment of the
`present invention;
`FIG. 2 is a block diagram of a control system for the
`hybrid vehicle according to an embodiment of the present
`invention;
`FIG. 3 is a flow chart of an engine starting control routine
`utilized in the first embodiment of the hybrid vehicle of the
`present invention;
`FIG. 4 is a graph (map) of the relationship between
`driving motor torque, vehicle speed, and degree of throttle
`opening (X in an embodiment of the hybrid vehicle according
`to the present invention;
`FIG. 5 is a graph (map) of the relationship between target
`rotational speed NG*, the degree of accelerator opening (X
`and storage residual capacity SOC in an embodiment of the
`hybrid vehicle according to the present invention;
`FIG. 6 is a graph (map) of generator torque versus
`rotational speed, at various values If (excitation current), for
`a generator/motor of the excitation type in an embodiment of
`the hybrid vehicle according to the present invention;
`FIG. 7 is a graph of the relationship between engine speed
`NE and the degree of throttle opening (X in an embodiment
`of the hybrid vehicle according to the present invention;
`FIG. 8 is a time chart for various operating parameters of
`an embodiment of the hybrid vehicle according to the
`present invention;
`FIG. 9 is a schematic view of a drive train in a hybrid
`vehicle in accordance with a second embodiment of the
`
`present invention;
`FIG. 10 is a graph of the relationship between engine
`starting speed V* and the storage battery residual capacity
`SOC in a third embodiment of the present invention; and
`FIG. 11 is a flow chart of an engine starting control routine
`for a fourth embodiment of the present invention.
`DETAILED DESCRIPTION OF THE
`
`PREFERRED EMBODIMENT(S)
`
`The preferred embodiments of a hybrid vehicle according
`to the present invention will be explained in detail with
`reference to FIG. 1 to FIG. 11.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`In the embodiment as shown in FIG. 1, the drive train has
`a four-shaft structure and includes an engine (EG) 1, a
`planetary gear unit 2, a generator/motor (generator G) 3, a
`driving motor (M) 4 and a differential gear unit 5.
`The first shaft is the combination of output shaft 7 of the
`engine 1 and the input/output shaft 9 of the generator/motor
`3. The planetary gear unit 2 has a carrier 22 connected to the
`output shaft 7 of the engine 1, a sun gear 21 connected to the
`input/output shaft 9 of the generator/motor 3 and a ring gear
`23 connected to the first counter drive gear 11.
`The second shaft is the output shaft 13 of the driving
`motor 4, which carries the second counter drive gear 15
`connected thereto.
`
`The third shaft is a counter shaft 31 supporting a counter
`driven gear 33 and a dif-pinion gear 35. The counter driven
`gear 33 is meshed with the first counter drive gear 11 and the
`second counter drive gear 15.
`The fourth shaft is the input shaft for the differential gear
`unit which carries a dif-ring gear 37.
`A differential gear unit 5 is driven by the dif-ring gear 37
`mounted on the fourth shaft with the dif-ring gear 37 being
`meshed with the dif-pinion gear 35.
`In the planetary gear unit 2, the rotational speed of the sun
`gear 21 defines the output rotational speed of the ring gear
`23 in response to the input rotational speed of the carrier 22.
`That is,
`the rotational speed of the sun gear 21 can be
`controlled by controlling the torque output of the generator/
`motor 3. For example, when the sun gear 21 is freely rotated,
`the rotation of the carrier 22 causes the sun gear 21 to rotate,
`but does not cause the ring gear 23 to rotate, whereby no
`rotation is output.
`In the planetary gear unit 2, the input torque to the carrier
`22 is a combined torque obtained by combining the reaction
`torque of the generator/motor 3 and the output torque of the
`engine 1.
`More specifically, the output from the engine 1 is input to
`the carrier 22, and the output from the generator/motor 3 is
`input to the sun gear 21. The output torque of the engine 1
`is output from the ring gear 23 through the counter drive
`gear 11 to drive the wheels at a gear ratio based on the engine
`efficiency. Furthermore, the output of the driving motor 4 is
`output
`through the second counter drive gear 15 to the
`driving wheels at a sufficient gear ratio for motor efficiency.
`FIG. 2 describes the structure of the control system for the
`above-described embodiment of a vehicle. As is seen from
`
`FIG. 2, the hybrid vehicle includes a driving unit 40, a sensor
`unit 41 detecting the operating parameters of the driving unit
`40 and so on, and a control unit 42 for controlling each
`element of the driving unit 40.
`The driving unit 40 includes the engine 1, the generator/
`motor 3, the driving motor 4 and a battery 43. The battery
`43 supplies electric power to the driving motor 4 and, in
`turn, is charged with regenerative electric power generated
`by the driving motor 4 and electric power generated by the
`generator/motor 3 operating in a generator mode.
`The sensor unit 41 includes an accelerator pedal sensor
`411 for detecting the degree that
`the accelerator 50 is
`opened, a vehicle speed sensor 412 for detecting vehicle
`speed V, a generator/motor rotational speed sensor 413 for
`detecting the rotational speed of the generator/motor 3, an
`engine speed sensor 414 for detecting the engine speed of
`the engine 1, a battery sensor 415 for detecting the stored
`residual capacity (SOC) of the battery 43 and an engine
`temperature sensor 416.
`The control unit 42 includes an engine control unit 421 for
`controlling the engine 4, a generator/motor control unit 422
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`for controlling the generator/motor 3, and a driving motor
`control unit 423 for controlling the driving motor 4.
`Furthermore, the control unit 42 has a vehicle control unit
`424 for controlling the movement of the vehicle by supply-
`ing a control instruction or a control value to the engine
`control unit 421, the generator/motor control unit 422, the
`driving motor control unit 423 and driving force instruction
`value detection unit 425.
`
`More specifically, the vehicle control unit 424 supplies the
`engine control system 421 with ON/OFF signals for the
`engine, in response to various detected conditions of the
`vehicle, including signals indicating that the vehicle is either
`moving or halted.
`The vehicle control system 424 supplies the generator/
`motor control unit 422 with a target rotational speed NG* for
`the generator/motor 3,
`the target rotational speed being
`based on the degree the accelerator is opened (0.), as
`detected by the accelerator pedal sensor 411, and the stored
`residual capacity (SOC), as detected by the battery sensor
`415. The vehicle control unit 424 also supplies the driving
`motor control unit 423 with a torque signal TM* based on
`the degree the accelerator is opened (X, as detected by the
`accelerator pedal sensor 411, and the vehicle speed V as
`detected by the vehicle speed sensor 412. Moreover,
`the
`vehicle control system 424 computes a ATM value based on
`the values for generator rotational speed NG and generator
`torque TG which are received from the generator/motor
`control unit 422.
`
`The engine control unit 421 controls the output of the
`engine 1 by controlling the degree of throttle opening 6,
`responsive to the ON signal received from the vehicle
`control unit 424 and an engine speed NE signal received
`from the engine speed sensor 414.
`The generator/motor control unit 422 controls the electric
`current (torque) IG to achieve a target rotational speed NG*.
`The driving motor control unit 423 controls the electric
`current (torque) IM which drives motor 4, responsive to
`signals for the torque TM* and the compensatory torque
`ATM which are received from the vehicle control unit 424.
`
`The operation of each control system of the above-
`described embodiment will now be described.
`
`The driving motor 4 starts the vehicle in motion and,
`when the vehicle speed reaches a predetermined speed, the
`engine 1 is started by controlling the rotational speed of the
`generator/motor 3, with the torque output by the driving
`motor 4 being increased by ATM to compensate for the drag
`produced by the engine 1 in starting. This drag may be
`detected as a change in torque output of the generator/motor
`3.
`
`Starting of the engine 1 by control of the speed of rotation
`of generator/motor 3 will now be explained. When the
`vehicle starts in motion, the engine 1 is not running and the
`vehicle begins moving by the torque of the driving motor 4
`alone. In this state, the output shaft (ring gear 23) is rotated
`by the driving motor 4. As can be understood, it is necessary
`that the carrier not be in orbital (planetary) motion so as not
`to rotate the output shaft 7 of the engine 1. In this initial low
`speed state, with the vehicle powered by the motor 4 only,
`the generator 3 as driven in a generator mode to generate
`electricity,
`i.e.
`the ring gear 23 drives the sun gear 21
`through the carrier 22, the carrier 22 remaining stationary.
`When the vehicle reaches a predetermined speed,
`the
`engine 1 is started. At this moment, the rotational speed of
`the sun gear 21, i.e. that of generator/motor 3, is decreased
`and, because the rotational speed of the ring gear has not
`changed,
`the carrier 22 is forced to begin its planetary
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`motion around the sun gear 21, thereby rotating the output
`shaft 7 of the engine 1. In other words, the rotational speed
`of the output shaft 7 is naturally affected by both the
`rotational speed of the sun gear 21 and that of the carrier 22.
`According, if the rotational speed of the output of motor 4
`is kept constant and the rotational speed of the sun gear 21
`is decreased,
`the rotational speed of the carrier 22 is
`increased to rotate the engine 1.
`When the rotation of the sun gear is stopped, the entire
`rotation of the motor 4 is transmitted to the carrier.
`
`Accordingly, engine 1 connected to the carrier may be
`rotated faster by driving, as a motor, the generator/motor 3
`connected to the sun gear.
`Accordingly, in the present invention the engine 1 can be
`started by controlling the generator/motor 3 to decrease its
`rotational speed in the generator mode while the vehicle is
`powered by the driving motor 4 alone, or by changing the
`generator/motor 3 over into the motor mode of rotation.
`As noted above, when the rotation of the sun gear is
`stopped, the entire rotation of the motor 4 is transmitted to
`the carrier to thereby rotate the engine 1. In other words, at
`this point in time the entire torque to rotate the engine 1 is
`provided by the drive motor 4. Accordingly, when starting
`the engine, a drop in the transmitted torque (“torque
`fluctuation”) would be expected due to the drag on the motor
`4 created by the work, i.e. compression, etc., performed in
`driving the engine (turning over the engine). In the present
`invention, this torque fluctuation is calculated and the cur-
`rent IM to the motor 4 is increased to compensate for it.
`FIG. 3 illustrates the engine starting control routine
`wherein, in step S11, the vehicle control unit 424 inputs the
`degree the accelerator opening (X received from the accel-
`erator pedal sensor 411 and the present vehicle speed V from
`the vehicle speed sensor 412. Next, in step S12, the vehicle
`control unit 424 judges whether or not the vehicle speed V
`has reached the engine starting speed V*.
`When the vehicle speed V is below the engine starting
`speed V* (“No” in S12),
`the vehicle control unit 424
`controls only the driving motor 4 (Step S13). More
`specifically, the vehicle control unit 424 supplies an OFF
`signal to the engine control unit 422 and determines the
`target driving motor torque TM* based on the values for
`accelerator opening (X and the vehicle speed V by reference
`to a driving motor torque—vehicle speed chart, as exempli-
`fied in FIG. 4, and supplies that value TM* to the driving
`motor control unit 423. The driving motor control unit 423
`controls the electric current IM to the driving motor 4 so that
`the detected driving motor torque TM becomes TM*, i.e.
`TM=TM*.
`
`On the other hand, when the vehicle speed V has been
`increased by the driving motor 4 to a value exceeding the
`engine starting speed V* (Yes in S12), the vehicle control
`unit 424 sends an ON signal to the engine control unit 421
`(Step S14).
`Next, the vehicle control unit 424 inputs a signal SOC
`representative of the storage residual capacity of the battery
`43 from the battery sensor 415, and the generator/motor
`control unit 422 inputs a generator motor rotational speed
`value NG based on the signal received from the generator/
`motor rotational speed sensor 413 (Step S15).
`A generator/motor driving torque instruction value IG is
`computed (Step S16). The vehicle control unit 424 deter-
`mines the target rotational speed NG* for the generator/
`motor 3 by reference to the chart shown in FIG. 5, applying
`the degree of accelerator opening (X input at Step 11 and the
`storage residual capacity SOC of the battery 43 input at Step
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`15, and supplies a signal for NG* to the generator/motor
`control unit 422. The generator/motor control unit 422
`computes the generator/motor torque instruction value (an
`electric current IG) for obtaining the target rotational fre-
`quency NG* by means of feedback control utilizing the
`difference between the target rotational speed NG* and the
`detected rotational speed NG of the generator/motor 3 input
`at Step S15.
`The vehicle control unit 424 computes a driving motor
`torque compensatory value ATM to compensate for the
`torque change, produced by a change in the speed of the
`generator/motor 3 upon start of turning over the engine, by
`changing the current IM to the driving motor 4 (Step 17).
`The generator/motor control unit 422 computes the
`generator/motor torque TG from the generator/motor current
`IG, because the torque of the generator/motor 3 is propor-
`tional to the electric current when the generator/motor 3 is
`the conventional magnetic type. On the other hand, when the
`generator/motor 3 is the excitation type, the generator/motor
`control unit 422 determines the generator/motor torque TG
`from a torque—rotational speed chart, as shown in FIG. 6,
`for the specific excitation current If.
`The vehicle control unit 424 computes the driving motor
`torque compensatory value ATM based on the generator/
`motor torque signal TG supplied from the generator/motor
`control unit 422. More specifically, because the generator/
`motor angular acceleration (the rotational speed change rate)
`(XG is extremely small, the generator/motor torque TG and
`the sun gear torque TS can be treated as equal (TG=TS).
`When the number of the teeth of the ring gear 23 in the
`planetary gear unit 2 is twice the number of teeth of the sun
`gear 21, the ring gear torque TR is twice the generator/motor
`torque TG (TR=2~TG), with the result that the compensatory
`torque ATM can be represented by the following equation 1
`when the counter gear ratio is defined as i.
`
`ATM=2-i'TS
`
`Incidentally, taking into account the generator/motor rota-
`tion change ratio G, when the generator/motor inertia is
`defined as InG,
`the sun gear torque TS in equation 1
`becomes TS=TG+InG~aG.
`
`As shown in FIG. 2, The vehicle control unit 424 supplies
`the driving motor control unit 423 with a signal for the
`compensating driving motor torque ATM in order to com-
`pensate for the torque TG used driving the generator/motor
`3 operating as a generator. Further, the vehicle control unit
`424 computes the target driving motor torque TM*, ignoring
`the torque acceleration, by applying the detected vehicle
`speed V to the map of FIG. 4, and supplies the signal TM*
`to the driving motor control unit 423.
`the generator/
`After the aforementioned computations,
`motor control unit 422 outputs to the generator/motor 3 a
`generator/motor driving torque instruction value IG com-
`puted at Step 16 to produce an output torque TG. The driving
`motor control unit 423 outputs to the driving motor 4 a
`torque signal (electric current) IM to produce a driving
`motor output torque TM (TM=TM*—ATM), based on the
`target driving motor torque TM* and the compensatory
`driving motor torque value ATM which are computed at
`Step 17 (Step 18).
`To start the engine 1, the rotation of generator/motor 3 is
`reversed, with the additional torque requirement for rotating
`the engine being provided by the driving motor 4.
`The engine control unit 421 receives the engine speed NE
`signal from the engine speed sensor 414 (Step S19), and
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`judges whether or not the engine speed NE has reached the
`computed engine speed NE* capable of igniting the engine
`(Step S20). When the detected engine speed has not reached
`NE* (“No” in Step S20), the routine returns to the main-
`routine and waits until there is an increase in the detected
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`engine speed NE. On the other hand, when the detected
`engine speed NE exceeds NE* (“Yes” in Step S20), the
`engine control unit 421 ignites the engine 1 by switching the
`engine ECU signal to ON (Step S21).
`Then, when the engine 1 has been started, the degree of
`throttle opening 0 is controlled in response to the engine
`speed NE to follow the relationship predetermined to pro-
`duce economy of fuel consumption as shown in FIG. 7. In
`other words, the engine control unit 421 controls the engine
`output by controlling the degree of throttle opening 0 in
`response to the detected engine speed NE as shown in FIG.
`7, with the degree of accelerator opening (X input to the
`vehicle control unit 424.
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`The aforementioned operation of each unit will now be
`described with reference to the time-chart of FIG. 8. At time
`
`t1, the vehicle starts in motion when the accelerator pedal is
`depressed. At this time, the driving motor 4 outputs a torque
`TM with TM=TM*, TM* being computed from the detected
`degree of accelerator opening (X and the detected vehicle
`speed V (zero at the start), utilizing a map as shown in FIG.
`4. This initial torque TM is indicated by Arrow A in FIG. 8.
`The generator/motor 3 is rotated by the output of the
`driving motor 4, as transmitted through the output shaft
`(“second shaft”) 13 and the ring gear 23 of the planetary gear
`unit 2. At this time, the ring gear 23 geared to the output
`shaft 13 is rotated in the positive direction, and the carrier 22
`mounted on output shaft 7 of the engine 1 is halted, whereby
`the sun gear 21, mounted