Unlted States Patent
`
`[19]
`
`[11] Patent Number:
`
`5,495,906
`
`Furutani
`
`[45] Date of Patent:
`
`Mar. 5, 1996
`
`I|I|||llllllll|||II|||I|||||||I|I||lI|I|I|I|||IlI||||||lII|II|||I|Il|||||||
`USO054-95906A
`
`[54] CONTROLLER OF HYBRID ELECTRIC
`VEHICLE
`
`‘
`
`5,176,213
`5,301,764
`5,327,987
`
`.................................. .. 180/65.4
`1/1993 Kawai
`4/1994 Gardne . .. . . . . ... ... .
`. .. . . .. 18O/65.2
`7/1994 Abdelmalek ......................... .. 180/65.4
`
`[75]
`
`Inventor: Masayuki Furutani, Susono, Japan
`
`FOREIGN PATENT DOCUMENTS
`
`[73] Assignee: Toyota Jidosha Kabushiki Kaisha,
`Toyota, Japan
`
`43-54525
`49-6619
`50-21210
`
`9/1973
`1/1974
`3/1975
`
`Japan _
`Japan .
`Japan .
`
`[21] APPL NO; 185,407
`
`[22] Filed:
`
`Jan. 24, 1994
`
`[30]
`
`Foreign Application Priority Data
`
`Japan ........................................ 5-9972
`[JP]
`Jan. 25, 1993
`[51]
`Int. Cl.“ ...................................................... B60L 11/02
`_
`_
`[:3]
`g_'Sl'dCl£_"""
`"""""" 180/652’ 180/16856jl6’51:0/2?22
`I:
`]
`1e
`0
`earc
`....................................
`I
`.
`,
`,
`180/243’ 651’ 652’ 653’ 653’ 696’ 364_/42401’
`424‘05’ 60/719
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`0232027
`
`9/1988
`
`Japan ..................................... 180/242
`
`Primary Examz'ner—Anne Marie Boehler
`Attorney, Agent, or Firm—Ob1on, Spivak, McC1e11and,
`Maia, & Neustadt
`
`ABSTRACT
`[57]
`.
`.
`.
`Amotorcominuousl
`y drives rear wheels during medlum and
`1ow—speed running, while an engine drives front wheels in a
`high_Speed
`area. In this case’ transfer of an engine_
`generated driving force to wheels is controlled by a trans-
`mission. In a medium- or low-speed running area, the engine
`1I11f)Ctdc(=)i1;11r1.}’ef10:‘)1]“Jt()W6I' generation and engine-driven running
`
`4,923,025
`
`5/1990 Ellers ..................................... 180/652
`
`7 Claims, 3 Drawing Sheets
`
`OVERALL CONSTITUTION OF EMBODIMENT
`
`°E“E““'
`
`non GEAR
`
`ELECTRONIC
`THROTTLE
`
`POWER
`19
`ACCELERATOR SIGNAL
`
`GENERATION
`CONTROLLER
`BRAKE SIGNAL
`
`Page 1 of 8
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`FORD 1205
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`FORD 1205
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`4..nef.aPQMU
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`Mar. 5, 1996
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`Sheet 1 of 3
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`5,495,906
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`m—.z_w
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`
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`eF\.m_O._.OEmm>mm._.
`
`.Em_>In.55
`
`h_.
`
`®_.NN
`
`
`
`i__________m._._._.Om:._.EEo_zoEom._m
`
`_..9...
`
`
`
`izoamE<E._m_8<mpE22
`ézoamv_$_mnwammwuww
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`
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`
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`»zms._nom_2mu_Ozo:.:.E.mzoo._._<mm>o
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`Page 2 of 8
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`FORD 1205
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`Page 2 of 8
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`FORD 1205
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`U.S. Patent
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`Mar. 5, 1996
`
`Sheet 2 of 3
`
`5,495,906
`
`VB
`
`VEHICLE SPEED [Km/h]
`
`Fig. 2A
`
`100
`
`0
`
`VEHICLE SPEED [Kmlh]
`
`Fig. 2B
`
`Page 3 of 8
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`U.S. Patent
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`Mar. 5, 1996
`
`Sheet 3 of 3
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`5,495,906
`
`S101
`
`ENGINE
`START
`
`S103
`NO
`
`EHICL
`PEEDZVB
`
`s1o4
`LOAD?-_La
`"0
`
`
`
`POWER GEN-
`ERATOR
`OUTPUT PH
`
`POWER GEN-
`ERATOR
`OUTPUT PL
`
`
`
`CLUTCH
`ON
`
`LOAD
`JUDGEMENT
`
`MIXING ENGINE
`OUTPUT WITH
`MOTOR OUTPUT
`
`
`
`
`
`
`MOTOR
`
`RUNNING
`
`Page 4 of 8
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`5,495,906
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`1
`CONTROLLER OF HYBRID ELECTRIC
`VEHICLE
`
`BACKGROUND OF THE INVENTION
`
`(i) Field of the Invention
`The present invention relates to a controller of a hybrid
`electric vehicle having an engine-driven power generator.
`(ii) Description of the Prior Art
`An electric vehicle has become prominent in view of low
`pollution in recent years. However, because it is essential for
`the electric vehicle to have a battery as its energy source and
`the battery has a considerable volume and weight, it is
`impossible to greatly increase the battery capacity. There-
`fore, a hybrid electric vehicle having an engine-driven
`power generator is proposed to charge the battery. The
`hybrid electric vehicle operates the engine-driven power
`generator when the battery charge quantity decreases in
`order to recover the battery charge state. Therefore, it is
`possible to increase the running distance per unit charge
`without greatly increasing the battery capacity. Moreover,
`engine driving for power generation can be carried out with
`a small exhaust quantity of pollutant because load fluctua-
`tion of the engine driving for power generation is smaller
`than that of engine driving for running. This type of hybrid
`electric vehicle is disclosed in the ofiicial gazette of, for
`example, Japanese Patent Laid-Open No. 21210/1975.
`For an existing hybrid electric vehicle, however, it is
`necessary to increase the electric power quantity generated
`by an engine so as to correspond to the discharge quantity at
`this time in order to prevent a battery from deteriorating due
`to over discharge during high-speed running. Therefore, the
`existing hybrid electric vehicle has a problem that the engine
`and power generator are increased in size and weight and it
`is diflicult to mount them in a vehicle.
`
`As the hybrid electric vehicle, a series hybrid electric
`vehicle using its engine only to drive its power generator is
`generally used. However, a parallel hybrid electric vehicle
`capable of using the driving force generated by the engine to
`run the vehicle is also known. The parallel hybrid electric
`vehicle makes it possible to achieve running at a high energy
`efficiency. However, the parallel hybrid electric vehicle has
`a problem that the exhaust quantity of pollutant increases
`because the engine load fluctuates.
`
`SUMMARY OF THE INVENTION
`
`The present invention is made to solve the above problem
`and its object is to provide a controller of a hybrid electric
`vehicle capable of downsizing a power generator while
`keeping the exhaust quantity of pollutant at a low level.
`The present invention is a controller of a hybrid electric
`vehicle having an engine and motor for controlling the
`engine and motor, comprising:
`a battery for supplying electric power to the motor;
`motor-generated driving-force transfer means for trans-
`ferring the driving force generated by the motor to wheels;
`a power generator driven by the engine to supply gener-
`ated electric power to the battery;
`engine-generated driving-force transfer means for trans-
`ferring the driving force generated by the engine to wheels;
`running state detection means for detecting a running state
`of a vehicle; and
`
`10
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`control means for controlling whether to transfer the
`driving force generated by the engine to the generator
`according to the detected vehicle running state.
`Therefore, a vehicle runs by driving wheels with a motor
`in a vehicle running state such as a low- or medium-speed
`running area in which the vehicle speed is comparatively
`low. That is, the vehicle operates as a series hybrid electric
`vehicle which prevents the engine from driving wheels and
`carries out only power generation control and battery charge
`by the engine. In a high-speed running area, however, the
`vehicle operates as a parallel hybrid electric vehicle which
`drives wheels with the motor and transfers the engine-
`generated driving force to wheels to replenish a required
`driving force. Therefore,
`in the low- or medium-speed
`running area,
`it
`is possible to decrease the quantity of
`unburned exhaust gas, replenish electric power with the
`engine-driven power generator, and increase the nmning
`distance. Moreover,
`it is not necessary to increase the
`quantity of electric power to be generated in order to obtain
`a driving force for high-speed running by increasing the size
`of the power generator. Therefore, it is possible to downsize
`the power generator so that the generator can easily be
`mounted in the vehicle and decrease the weight of the
`vehicle.
`
`It is preferable that the motor-generated driving-force
`transfer means transfers the driving force to either of front
`or rear wheels and the engine-generated driving-force trans-
`fer means transfers the driving force to either of the front or
`rear wheels to which no engine-generated driving force is
`transferred. Therefore, a driving mechanism can be simpli-
`fled.
`
`The control means sets a period for transferring the
`driving forces generated by both the engine and motor to
`wheels when the vehicle speed changes from a value equal
`to or less than a predetermined value to a value larger than
`the predetermined value. Thereby, it is possible to lighten a
`shock at the time of a vehicle speed change.
`It is preferable that the running state detection means
`detects vehicle speed and vehicle load.
`the control means
`In this case,
`it is preferable that
`transfers the driving force generated by the engine to the
`power generator and changes the electric power generated
`by the power generator in accordance with the vehicle load
`if the vehicle speed is the predetermined value or less.
`Moreover, it is preferable to change the predetermined value
`of the vehicle speed in accordance with the vehicle load.
`This realizes more preferable control in accordance with the
`motor output torque.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram showing the overall constitution
`of an embodiment of the present invention;
`FIGS. 2A and 2B are illustrations showing examples of
`output classification of load to vehicle speed in an embodi-
`ment of the present invention; and
`FIG. 3 is a flow chart of the operation of an embodiment
`of the present invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Embodiments of the present invention will be described
`below with reference to drawings.
`
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`5,495,906
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`In FIG. 1, an engine 1 is a motor for generating motive
`power which is connected to a power generator 2. Therefore,
`the power generator 2 generates DC power by using the
`driving force generated by the engine 1. The engine 1 is also
`connected to a transmission 5 including a clutch 3 and
`differential gear 4. The transmission 5 transfers the driving
`force generated by the engine 1 to a drive shaft 6 through the
`differential gear 4 when it connects with the clutch 3. The
`drive shaft 6 is connected to a pair of front-wheel tires and
`rotation of the drive shaft 6 is transferred to the front-wheel
`tires 8.
`
`A power cable 9 electrically connects the power generator
`2 and battery 10 and supplies generated electric power to the
`battery 10. The battery 10 is electrically connected with an
`inverter 12 comprising a plurality of switching transistors by
`a power cable 11 and the inverter 12 is connected to an AC
`induction motor 14 by a power cable 13. Therefore, DC,
`power sent from the battery 10 is converted into a desired
`AC current by the inverter 12 and the desired AC current is
`supplied to the motor 14 to drive the motor 14. The motor
`14 is connected to a pair of rear-wheel tires 17 through a
`reduction gear 15 and a drive shaft 16, and therefore the
`driving force generated by the motor 14 is transferred to the
`rear-wheel tires 17.
`This embodiment is constituted so that the front wheels 8
`are driven by the engine 1 and the rear wheels 17 are driven
`by the motor 14. However, it is also possible to constitute the
`embodiment so that the rear wheels 17 are driven by the
`engine 1 and the front wheels 8 are driven by the motor 14.
`An ECU 18 controls operations of the inverter by using
`accelerator and brake signals as inputs for accelerator and
`brake applying levels. That is, the ECU 18 calculates an
`output torque command value of the motor 14 and controls
`switching of the switching transistors of the inverter 12 in
`accordance with the output torque command value to control
`the output torque of the motor 14.
`An SOC meter 21 for detecting a state of charge (SOC) of
`the battery 18 is connected to the ECU 18 to which a signal
`for the state of charge of the battery 10 is supplied. More-
`over, the ECU 18 sends control signals for start and stop of
`power generation to a power generation controller 19 in
`accordance with the state of charge of the battery 10. The
`power generation controller 19 controls an electronic throttle
`20 of the engine 1 and carries out field control for and power
`generation of the generator 2. Moreover, a signal for vehicle
`speed sent from a vehicle sensor 22 for detecting vehicle
`speed from the wheel speed is sent to the ECU 18.
`An auxiliary battery is connected to the battery 10 through
`a DC—DC converter (not illustrated) so that the auxiliary
`battery is supplied with electric power. The auxiliary battery
`supplies electric power for turning on a lamp or driving a
`starter motor of the engine. The DC—DC converter is also
`used to drop a high voltage (e.g. 200 V) of the battery 10 to
`a low voltage (e.g. 12 V).
`FIGS. 2A and 2B show output classification of the system
`shown in FIG. 1, in which the axis of ordinates shows
`vehicle speed and the axis of abscissas shows vehicle load.
`Vehicle speed is detected with output torque obtained from
`an accelerator applying level, torque command value, or
`electric power supplied to the motor 14.
`In FIG. 2A, an area a1 is a medium- or low-speed area in
`which vehicle speed is comparatively low (equal to or less
`than VB) and vehicle load is comparatively large (equal to or
`larger than a predetermined value La). In the area a,, the
`engine 1 generates electric power by driving the power
`generator 2 and also increases the output of the power
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`generator 2. Also in this area, a vehicle runs only by the
`output of the motor 14.
`An area a2 is a medium- or low-speed area in which
`vehicle speed is comparatively low (equal to or less than VB)
`and vehicle load is comparatively small (equal to or less than
`the predetermined value La). In the area a2, the engine 1
`drives the power generator 2 and also decreases the output
`of the power generator 2. In this area also, the vehicle runs
`only by the output of the motor 14.
`Therefore,
`this embodiment only uses the engine 1 to
`drive the power generator 2 but does not use it to drive the
`vehicle in the medium- or low-speed area in which vehicle
`speed is VB or less. Therefore, the engine 1 is able to carry
`out constant—speed constant-load operation corresponding to
`a predetermined quantity of electric power to be generated
`by the power generator 2. Thus, it is possible to minimize the
`quantity of toxic matter in the exhaust gas of the engine 1.
`When the vehicle is driven by the engine 1 in this area, there
`is a greater possibility that toxic matter will be contained in
`emission matter. That is, it is generally known that a large
`amount of toxic matter (particularly, unburned matter) is
`contained in exhaust gas when a normal gasoline-powered
`vehicle starts.
`
`Outputs of the power generator 2 are changed in accor-
`dance with vehicle load. For a small vehicle load, over
`charge of the battery 10 due to excessive power generation
`can be prevented by decreasing the quantity of electric
`power to be generated because the motor 14 consumes less
`current. For a large vehicle load, it is possible to prevent the
`charge state of the battery 10 from being impaired by
`generating electric power corresponding to the vehicle load,
`because the motor 14 consumes more current.
`
`An area a3 is a high-speed area in which vehicle speed is
`VB or more. In this area, the output of the power generator
`2 is stopped and the clutch 3 is connected to transfer the
`driving force generated by the engine 1 to the front wheels
`8. In the area a3, the vehicle basically runs by the output of
`the engine 1. In this high-speed area, engine speed is equal
`to or higher than a predetermined value and toxic matter
`contained in exhaust gas can be greatly decreased. When the
`motor 14 is driven in this area, it consumes a very large
`amount of current and the charge state of the battery 10 is
`impaired. If the quantity of electric power to be generated is
`increased to compensate for the impaired charge state, a
`larger power generator is necessary. This embodiment is free
`from the above disadvantage.
`In this case, it is also preferable that the classification into
`the three areas is made as shown in FIG. 2B. In FIG. 2B, an
`area in which an engine is not driven is increased in a small
`load area even for a high speed. This is because power
`consumption of the motor 14 decreases as load decreases
`even for the same vehicle speed. Therefore, a more prefer-
`able change control can be carried out in accordance with the
`classification in FIG. 2B.
`
`Operations in the case of the area pattern in FIG. 2A will
`be described below in reference to the flow chart in FIG. 3.
`
`The system starts when a vehicle starts running due to IG
`ON (ignition key ON: S101). Then, the ECU 18 first starts
`the engine 1 through the power generation controller 19 to
`start power generation with the power generator 2 (S102).
`Then, the driving force generated by the engine 1 is trans-
`ferred only to the power generator 2 to generate electric
`power as the initial state. In this case, the power generation
`controller 19 controls fields in the electronic throttle 20 and
`the power generator and also controls power generation by
`the engine so that a predetermined electric power is gener-
`
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`ated (S102). Then, the controller judges whether vehicle
`speed is kept at a level VB (e.g. 80 Km/h) or less (S103).
`When the vehicle speed is VB or less, the engine 1 starts
`quasi-stationary operation for power generation. That is, the
`controller detects vehicle load from output torque of the
`motor 14 or the like to judge whether the vehicle load is a
`predetermined value La or more (S104). When the vehicle
`load is La or more, the controller sets the output of the power
`generator 2 to a predetermined high level PH (S105). If the
`vehicle load is less than the predetermined value, the con-
`troller sets the output to a predetermined low level PL. In
`this case, it is assumed that PH equals 10 kw and PL equals
`4 kw. Under this state, the controller keeps the clutch 3
`released and runs the vehicle with the driving force gener-
`ated by the motor 14 (S107).
`On the other hand, when vehicle speed is VB or more in
`S103, stationary operation is started and the clutch 3 is
`connected (S108). In this case, power generation by the
`driving force generated by the engine 1 stops. Then, the
`controller judges vehicle load with the accelerator applying
`level and vehicle speed (S109), decreases the output of the
`motor 14 while keeping a condition where the total output of
`the engine 1 and motor 14 is balanced with vehicle load, and
`controls mixing of the engine output with the motor output
`(S110). In this case, the controller slowly carries out the 25
`control to lighten the shock. The controller finally turns off
`the output of the motor 14 to carry out running by the engine
`1 (S111). The output of the engine 1 is improved by
`changing the number of cylinders or increasing the rota- 3o
`tional speed through control of the electronic throttle 20.
`Teen’ the eeneeeer judges ($112) Whether the ignition
`kel’ 15 turned 0ft dtmng the ntnntng by the n1°t°r (S107) 0‘
`the running by the engine (S111). If the key is not turned off,
`the controller restarts S103 to continue the control. When the 35
`ignition key is turned off, the controller turns off the engine
`1 (S113) to end the comm1_
`AS desenbed 3b°Ve: P0“/er generation by the P°WeT
`generator 2 is not Carried out in the Case of stationary 4°
`operation. In this case, it is possible to mechanically separate
`the power generator 2 from the engine 1 or prevent electric
`power from being outputted from the power generator 2.
`Moreover, when the running by the engine is changed to the 45
`nmning by the motor, it is possible to carry out mixing of the
`driving force of the engine with that of the motor, similarly
`to S110.
`
`To carry the control based on FIG. 2B, it is necessary to
`store the classification in FIG. 2B as a map and judge in
`which area the current vehicle speed and vehicle load are
`situated.
`
`Thus, according to this embodiment, a vehicle is run by
`driving an engine in a high-speed running area. Therefore, it
`is suflicient to use a power generator with a power genera-
`tion capacity corresponding to a medium- or low-speed area
`in which power consumption is comparatively small and an
`engine and power generator can be downsized. Moreover,
`because the engine 1 is used only with a large load side
`(high-speed running area) having a preferable torque char-
`acteristic, a transmission is unnecessary, and the constitution
`of a torque transfer system can be simplified. Accordingly,
`a power generator can be downsized. Moreover, the exhaust
`quantity of pollutant can be minimized because load flue-
`tuation of the engine 1 is comparatively small.
`
`50
`
`55
`
`60
`
`65
`
`6
`Though electric power is not basically generated during
`running by the engine for the above embodiment, it is
`possible to operate the power generator 2 depending on the
`charge state of the battery 10 detected by the SOC meter 21.
`For the above embodiment, the engine 1 is continuously
`driven during running. However, it is also possible to stop
`driving the engine 1 depending on the charge state of the
`battery 10.
`Moreover, it is possible to carry out regenerative braking
`by using the motor 14 while running through driving of the
`engine 1. That is, a braking force can be generated by
`operating the motor 14 as a power generator when deceler-
`ating a vehicle by operating a brake. In this case, it is
`preferable to use generated electric power for charge of the
`battery 10.
`What is claimed is:
`1. A controller of a hybrid electric vehicle having an
`engine and a motor for controlling driving of the engine and
`the motor, comprising:
`a battery for supplying electric power to the motor;
`motor-generated driving-force transfer means for trans-
`ferring the driving force generated by the motor to
`wheels;
`a power generator driven by the engine to supply gener-
`ated eteetne P0WeT t0 the battery;
`enginejgenefnted dnVtng'f0Tee transfer means for trans‘
`felfinilfthe dnvmg fefee generated by the engme t°
`W_ee 5’
`_
`_
`_
`mnrglnrllfingtittgtgeéieieee means for deteetmg e vehlele
`control means fdr controlling whether to transfer a driving
`force generated by an engine to a generator or wheels
`in accordance with a detected vehicle running state,
`wherein the control means transfers the driving force
`generated _bY the engine When Said nlnnlng State 1_S 3
`predeterrruned dviluethor more,
`transiersl
`theh driving
`orce
`enerate
`e motor to w ee s w en S31
`running state is lesis than the predetermined value, and
`transfers the driving force generated by the engine to
`the power generator, and Wherein the Controi means
`Sets 3 Pendd fol’ trnnsfernng the dnVing fofees gener-
`ated ,by b°t-h the engine and motor to Wheels when Said
`nmmng State ehengee from a value equal to er less than
`a predetermined Value to a value larger than the pre-
`determined value.
`
`2. The controller of the hybrid electric vehicle according
`to claim 1 wherein the motor-generated driving-force trans-
`fer means transfers a driving force to any one of front and
`rear wheels and the engine-generated driving-force transfer
`means transfers a driving force to that one of front and rear
`wheels to which the motor-generated driving force is not
`transferred.
`
`3. The controller of the hybrid electric vehicle according
`to claim 1 wherein the running state detection means detects
`vehicle speed.
`4. The controller of the hybrid electric vehicle according
`to claim 1 wherein the running state detection means detects
`both vehicle speed and vehicle load.
`5. The controller of the hybrid electric vehicle according
`to claim 4 wherein the control means transfers the driving
`force generated by the engine to the power generator when
`vehicle speed is the predetermined value or less and changes
`the quantity of electric power generated by the power
`generator in accordance with vehicle load.
`
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`6. The controller of the hybrid electric vehicle according
`to claim 5 wherein the control means transfers the driving
`
`force generated by the engine to wheels when vehicle speed
`
`is larger than the predetermined value, stops transfer of the 5
`driving force generated by the engine to the power generator,
`
`and also stops transfer of the driving force generated by the
`motor to wheels.
`
`7. The controller of the hybrid electric vehicle according
`to claim 6 wherein the predetermined value of vehicle speed
`is changcd in accordance with Vchiclc 1cad_
`*
`*
`*
`*
`*
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