as United States
`a2) Patent Application Publication co) Pub. No.: US 2004/0069548 A1
`
` Kira et al. (43) Pub. Date: Apr. 15, 2004
`
`
`US 20040069548A1
`
`(54) HYBRID VEHICLE
`
`(30)
`
`Foreign Application Priority Data
`
`(75)
`
`Inventors: Nobuhiro Kira, Saitama (JP); Tetsuya
`Hasebe, Saitama (JP); Ryo Nishikawa,
`Saitama (JP)
`
`Sep. 20, 2002
`
`(UP) veeciessscsssssseseesueeeenseee P.2002-274315
`
`Publication Classification
`
`Correspondence Address:
`ARENT FOX KINTNER PLOTKIN & KAHN,
`PLLC
`Suite 400
`1050 Connecticut Avenue, N.W.
`Washington, DC 20036-5339 (US)
`
`GIKEN
`(73) Assignee: HONDA
`KABUSHIKI KAISHA
`
`KOGYO
`
`(21) Appl. No.:
`
`10/663,764
`
`(CS C1A© B60K 1/00
`(52) U.S. Cd.
`coecesccssssssseerseensereseresereen 180/65.3; 180/65.4
`
`(57)
`
`ABSTRACT
`
`In a hybrid vehicle in which front wheels are driven by an
`engine and a front motor, and rear wheels are driven by a
`main rear motor and a sub rear motor, both main rear motor
`and the sub rear motor are driven whena large driving force
`is required as when the vehicle is driven at lowspeed to haul
`a trailer or the like or to run on a sandy ground, whereas
`when the required driving force is small, only the main rear
`motor is driven.
`
`(22)
`
`Filed:
`
`Sep. 17, 2003
`
`
`
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`Patent Application Publication Apr. 15,2004 Sheet 1 of 8
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`US 2004/0069548 Al
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`Patent Application Publication Apr. 15,2004 Sheet 2 of 8
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`US 2004/0069548 Al
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`FIG. 2
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`Patent Application Publication Apr. 15,2004 Sheet 3 of 8
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`Patent Application Publication Apr. 15,2004 Sheet 4 of 8
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`US 2004/0069548 Al
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`V1 MAINMOTOR+SUBMOTOR
`
`msmeeeMAINMOTOR
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`Patent Application Publication Apr. 15,2004 Sheet 5 of 8
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`US 2004/0069548 Al
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`acerMAINMOTOR
`
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`Patent Application Publication Apr. 15,2004 Sheet 6 of 8
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`US 2004/0069548 Al
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`FIG.6
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`Patent Application Publication Apr. 15,2004 Sheet 7 of 8
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`Patent Application Publication Apr. 15,2004 Sheet 8 of 8
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`US 2004/0069548 Al
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`US 2004/0069548 Al
`
`Apr. 15, 2004
`
`HYBRID VEHICLE
`
`BACKGROUND OF THE INVENTION
`
`[0001]
`
`1. Field of the Invention
`
`[0002] The present invention relates to a hybrid vehicle in
`which main driving wheels are driven by an engine and sub
`driving wheels are driven by a motor.
`
`[0003]
`
`2. Description of the Related Art
`
`[0004] A hybrid vehicle is described in JP-A-11-208304 in
`which main driving wheels are driven by an engine and/or
`a first motor and sub driving wheels are driven by a second
`motor. In the hybrid vehicle, a mode in whichthe vehicle is
`driven only by the motor and a mode in which the vehicle
`is driven by both the engine and the motor are combined in
`order to reduce its fuel consumption.
`
`Incidentally, as is often the case with this kind of
`[0005]
`hybrid vehicle when attempting to impart the vehicle a
`running through performance that is to be provided by a
`four-wheel drive vehicle, the driving force of the rear wheels
`becomes insufficient. ‘lo be specific, this unfavorable fact
`becomes conspicuous
`when the vehicle runs on a grav-
`elly road at low speed(in the order of 30 km/h) and @) when
`the vehicle climbs up an uphill road near a lakeside while
`hauling a boat.
`[0006]
`Inorder to make the running under @ possible, the
`output of the motor for the rear wheels needs to be increased,
`and in order to make the running under Q) possible, the
`torque of the motorfor the rear wheels needsto be increased.
`In either of the cases, it is unavoidable that the size of the
`motor is enlarged. However, in case the motoris enlarged,
`there are caused some problems such as that the minimum
`ground clearance is reduced, an intersecting angle with the
`drive shafts is increased, and lowering the floor level of the
`vehicle becomes difficult.
`
`SUMMARY OF THE INVENTION
`
`[0007] The invention was madein view ofthesesituations
`and an object thereofis to enable an increase in driving force
`of the sub driving wheels of the hybrid vehicle while
`suppressing to a minimum level the increase in size of the
`motor for driving the sub driving wheels.
`
`[0008] With a view to attaining the object, according to a
`first aspect of the invention,
`there is proposed a hybrid
`vehicle comprising an engine for driving main driving
`wheels and a plurality of motors for driving sub driving
`whecls, wherein at least onc motor is sclected from the
`plurality of motorsto drive the sub driving wheels according
`to a driving force required by the vehicle.
`
`[0009] According to the construction, the motor for driv-
`ing the sub driving wheels comprises the plurality of dif-
`ferent motors, so that at least one motororall the motors can
`be used to drive the sub driving wheels according to a
`driving force required by the vehicle. Therefore, when
`compared with a case where a single motor is provided
`which can supply the total of driving forces of the plurality
`of motors, the sizes of the individual motors can be made
`smaller. Due to this, the minimum ground clearance of the
`vehicle can be reduced, the intersecting angle with the drive
`shafts can be decreased, and the floor level of the vehicle can
`
`Page 10 of 16
`Page 10 of 16
`
`be lowered while enhancing the running through perfor-
`mance when the required driving force of the vehicle is
`large.
`
`In addition, according to a second aspect of the
`[0010]
`invention, there is proposed a hybrid vehicle as set forth in
`the first aspect of the invention, wherein the sub driving
`wheels are driven by all the motors at low vehicle speed
`where the driving force required by the vehicle is large.
`
`[0011] According to the construction, the running through
`performance can be enhancedsufficiently by driving the sub
`driving whecls byall the motors as when running while
`hauling the boat or the like or on the gravelly road at low
`speed where a large driving force is required.
`
`[0012] Additionally, according to a third aspect of the
`invention, there is proposed a hybrid vehicle as sct forth in
`the first aspect of the invention, wherein the plurality of
`motors comprises a main motor having a large output and a
`sub motor having a small output,
`the sub motor being
`disposed on an upstream side of the main motorrelative to
`a direction in which the driving force is transmitted to the
`sub driving wheels.
`
`[0013] According to the construction, since the sub motor
`having a small outputis disposed on the upstream side of the
`main motor relative to the direction in which the driving
`force is transmitted to the sub driving wheels, when the sub
`motor is brought to a stop since the required driving force
`can be supplied only by the main motor, there is caused no
`risk that the sub motor, which is being so stopped, resides
`along the power transmission path of the main motor to
`interrupt the transmission of power therefrom.
`
`In addition, according to a fourth aspect of the
`[0014]
`invention, there is proposed a hybrid vehicle as sct forth in
`the third aspect of the invention, wherein a clutch for
`interrupting the transmission of driving force is disposed
`between the sub motor and the main motor.
`
`[0015] According to the construction, since the clutch for
`interrupting the transmission of driving force is interposed
`between the sub motor and the main motor, when driving the
`main motor with the sub motor being brought to a stop, the
`sub motoris prevented from being drawn bythe main motor
`to thereby prevent an increase in power consumption.
`
`[0016] Additionally, according to a fifth aspect of the
`invention, there is proposed a hybrid vehicle as set forth in
`the first aspect of the invention, wherein the plurality of
`motors comprises a main motor having a large output and a
`sub motor having a small output, and wherein a high-voltage
`battery for driving the main motor is charged with regen-
`erative power of the main motor, whereas a low-voltage
`battery for driving the sub motor is charged by a generator
`driven by the engine.
`
`[0017] According to the construction, since the high-
`voltage battery for driving the main motor having a large
`output
`is charged with regenerative power of the main
`motor, whereas the low-voltage battery for driving the sub
`motor having a small output is charged by the generator
`driven by the engine, the low-voltage battery is caused to
`bearpart of the powerfor driving the sub driving wheels, so
`that the capacity of the high-voltage battery consuming more
`power can be reduced. Moreover, since the sub motor is
`driven after generated output of the generator is once stored
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`US 2004/0069548 Al
`
`Apr. 15, 2004
`
`in the low-voltage battery, when compared with a case
`where the sub motoris direct driven by the generated output
`of the generator, the control of the generator can be simpli-
`fied.
`
`In addition, according to a sixth aspect of the
`[0018]
`invention, there is provided a hybrid vehicle as set forth in
`the first aspect of the invention, wherein the plurality of
`motors comprises a main motor having a large output and a
`sub motor having a small output, and wherein a battery for
`driving the main motor is charged with regenerative power
`of the main motor, and the sub motor is driven by generated
`output of a generator driven by the engine.
`
`[0019] According to the construction, since the high-
`voltage battery for driving the main motor having a large
`output is charged with regenerative power of the main motor
`and the sub motor having a small output is driven by the
`generated output of the generator driven by the engine, the
`generated output of the generatoris suppliedfor use for part
`of the power for driving the sub driving wheels, so that the
`capacity of the high-voltage battery consuming more power
`can be reduced. Moreover, no battery for storing the gen-
`erated output of the generator is required, this contributing
`to the reduction in cost and space.
`
`[0020] Additionally, according to a seventh aspect of the
`invention, there is provided a hybrid vehicle as set forth in
`the first aspect of the invention, wherein the plurality of
`motors comprises a main motor having a large output and a
`sub motor having a small output, and wherein a batteryfor
`driving the main motor is charged with regenerative power
`of the main motor, and the sub motoris driven by lowering
`the voltage of the battery by a downverter,
`
`[0021] According to the construction, since the high-
`voltage battery for driving the main motor having a large
`output is charged with regenerative power of the main motor
`and the sub motor having a small output is driven by
`lowering the voltage of the battery by a downverter, neither
`a generator nor a battery exclusively used for driving the sub
`driving wheel
`is required, which can contribute to the
`reduction in cost and space.
`
`[0022] Additionally, according to an eights aspect of the
`invention, there is proposed a hybrid vehicle as set forth in
`the third aspect of the invention, wherein a speed reduction
`memberis disposed between the sub motor and the main
`motor.
`
`[0023] According to the construction, since the torque of
`the sub motor can be amplified by the speed reduction
`member, the sub motor can be made smaller in size, and
`moreover,
`the torque of the sub motor can be amplified
`further along a reduction path of the main motor.
`
`In addition, according to a ninth aspect of the
`[0024]
`invention, there is proposed a hybrid vehicle as set forth in
`the first aspect of the invention, further comprising a motor/
`generator which functions both as a motor to assist the
`engine for driving the main driving wheels in providing
`driving force and as a generator to generate power by being
`driven by driving force of the engine or driving force which
`is reversely transmitted from the main driving wheels.
`
`[0025] According to the construction, by provision of the
`motor/generator which functions as a motor to assist the
`engine in providing driving force, in the event that a required
`
`Page 11 of 16
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`
`driving force is not sufficiently supplied only by the engine
`for driving the main driving wheels and the motor for
`driving the sub driving wheels,
`the driving force of the
`motor/generator can assist in sufficing the required driving
`force. In addition, by provision of the motor/generator which
`functions as a generator to generate power, in the event that
`only the generative power generated by the motor using the
`driving force reversely transmitted from the sub driving
`wheels is insufficient for a requirement, the motor/generator
`can be made to function as the generator by the driving force
`of the engine or driving force reversely transmitted from the
`main driving wheels so as to increase the power generating
`capability of the vehicle.
`
`[0026] Note that a high-voltage battery Bh in an embodi-
`ment of the invention corresponds to the battery of the
`invention, an electromagnetic clutch C2 in the embodiment
`corresponds to the clutch of the invention, a front motor M
`in the embodiment correspondsto the motor/generatorofthe
`invention, a sub rear motor Ms in the embodimentcorre-
`sponds to the sub motor or the motor of the invention, front
`wheels Wf in the embodiment correspond to the main
`driving wheels of the invention, rear wheels Wr in the
`embodiment correspond to the sub driving wheels of the
`invention, and a first gear 13 and a second gear 15 in the
`embodiment correspond to the speed reduction member of
`the invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0027] FIG. 1 is a diagram showing an overall configu-
`ration of a hybrid vehicle according to a first embodiment;
`
`FIG.2 is a diagram showing the construction of a
`[0028]
`driving system for rear wheels;
`
`[0029]
`motors;
`
`FIG.3 is a diagram showing a control system of
`
`[0030] FIG. 4 is a graph showing changes in driving
`torques of main and sub rear motorsrelative to the vehicle
`speed;
`
`[0031] FIG. 5 is a graph showing changesin rotational
`speeds of the main and sub rear motorsrelative to the vehicle
`speed;
`
`FIG.6 is a diagram showing an overall configu-
`[0032]
`ration of a hybrid vehicle according to a second embodi-
`ment;
`
`[0033] FIG. 7 is a diagram showing an overall configu-
`ration of a hybrid vehicle according to a third embodiment;
`and
`
`FIG.8 is a diagram showing the construction of a
`[0034]
`driving system for rear wheels according to a fourth embodi-
`ment.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`the invention will be
`[0035] A mode for carrying out
`described below based on embodiments of the invention
`
`illustrated in the accompanying drawings.
`
`FIGS. 1 to 5 show a first embodiment of the
`[0036]
`invention. FIG. 1 is a diagram showing an overall configu-
`ration of a hybrid vehicle. FIG. 2 is a diagram showing the
`construction of a driving system for rear wheels. FIG. 3 is
`
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`US 2004/0069548 Al
`
`Apr. 15, 2004
`
`a diagram showing a control system of motors. FIG.4 is a
`graph showing changes in driving torques of main and sub
`rear motorsrelative to the vehicle speed. FIG. 5 is a graph
`showing changes in rotational speeds of the main and sub
`rear motors relative to the vehicle speed.
`
`[0042] Next, the function of the first embodimentthat is
`constructed as has been described heretofore will be
`described.
`
`[0043] As shownin FIG.1,the front motor M made up of
`the three-phase alternating-current motor is driven by con-
`verting a direct current of the high-voltage battery Bh to a
`[0037] As shownin FIG, 1, a hybrid vehicle V has left and
`three-phase alternating current at the power drive unit Pf,
`right front wheels Wf, Wf which are main driving wheels
`and similarly,
`the main rear motor Mm made up of the
`and left and right rear wheels Wr, Wr which are sub driving
`three-phase alternating-current motor is driven by convert-
`wheels. Among an engine E for driving the front wheels Wf,
`ing the direct-current of the high-voltage battery Bh to a
`Wf, a transmission T and a differential D, a front motor M
`three-phase alternating-current at the power drive unit Pr.
`constituted by a three-phase alternating-current motor is
`Whenthe vehicle is decelerated, the front motor M and the
`interposed in line between the engine E andthe transmission
`main rear motor Mm are driven by driving force from the
`T. By driving the front motor M,the engineEis assisted in
`front wheels Wf, Wf and the rear wheels Wr, Wr so that the
`providing driving force, and by making the front motor M
`front motor M and the main rear motor Mm are made to
`function as a generator, power can be generated. A main rear
`motor Mm made up of a three-phase alternating-current
`motor having a large output and a sub rear motor Ms made
`up of a direct-current brush motor having a small outputare
`connected to the rear wheels Wr, Wr via a speed reduction
`gear set R.
`
`[0038] The front motor M fordriving the front wheels Wf,
`WFis connected to a high-voltage battery Bh of 100V or
`higher via a powerdrive unit Pf and a three-phase wire L1.
`The main rear motor Mm for driving the rear wheels Wr, Wr
`is connected to the high-voltage battery Bh via a powerdrive
`unit Pr and a three-phase wire L2. In addition, the sub rear
`motor Msfor driving the rear wheels Wr, Wris connected ta
`a low-voltage battery B1 whose voltage is lower than that of
`the high-voltage battery Bh via a direct-current wire L3, and
`the low-voltage battery Bl is connected to a generator G
`driven by the engine E via a direct-current wire L4.
`
`[0039] Next, the construction of the speed reduction gear
`set R for transmitting the driving forces of the main rear
`motor Mm andthe sub rear motor Msto the rear wheels Wr,
`Wrwill be described below based on FIG.2.
`
`[0040] A first gear 13 is fixed to a first shaft 12 which is
`connected to an output shaft 11 of the sub rear motor Msvia
`an electromagnetic clutch C2, and this first gear 13 meshes
`with a second gear 15 fixed to a second shaft 14 which
`constitutes an output shaft of the main rear motor Mm. A
`third gear 16 fixed to the second shaft 14 meshes with a
`fourth gear 18 supported relatively rotatably on a third shaft
`17, and a fifth gear 19 fixed to the third shaft 17 meshes with
`a final driven gear 21 of a differential 20. The fourth gear 18
`can be connected to the third shaft 17 via a synchromesh
`clutch C1.
`
`[0041] FIG. 3 showsa control system for the front motor
`M for driving the front wheels Wf, Wf and the main rear
`motor Mmand the sub rear motor Ms for driving the rear
`wheels Wr, Wr. A managing ECU 26 into which signals are
`inputted which indicate wheel speed, engine rotational
`speed, accelerator pedal opening, forward and rearward
`accelerations, shift position, brake fluid pressure and brake
`switch communicates with a front motor ECU 27 so as to
`
`control the operation of the front motor M via the power
`drive unit Pf, communicates with a main rear motor ECU 28
`so as to control the operation of the main rear motor Mm via
`the powerdrive unit Pr, communicates with a sub rear motor
`ECU29 so as to control the operation of the sub rear motor
`Msvia the generator G, and furthermore communicates with
`a fuel injection ECU 30 and a battery ECU 31.
`
`Page 12 of 16
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`
`function as a gencrator, whereby the high-voltage battery Bh
`is charged by generated output of the motor M functioning
`as the generator. In addition, the sub rear motor Ms made up
`of the direct-current brush motoris driven by direct current
`from the low-voltage battery Bl which is charged by gen-
`erated output of the generator G driven by the engine E.
`
`[0044] As this occurs, the driving torque of the front motor
`M is controlled so as to become a target value bythe front
`motor ECU 27 and the power drive unit Pf, and the driving
`force of the main rear motor Mm is controlled so as to
`
`becomea target value by the main rear motor ECU 28 and
`the powerdrive unit Pr. In addition, the driving torque of the
`sub rear motor Msis controlled so as to become a target
`value by the sub rear motor ECU 29.
`
`[0045] As shownin FIG. 2, when the synchromesh clutch
`Cl and the electromagnetic clutch C2 are engaged,
`the
`driving force of the sub rear motor Msis transmitted to the
`left and right rear wheels Wr, Wr along a path extending
`from the electromagnetic clutch C2—thefirst shaft 12—the
`first gear 13—>the second gear 15->the second shaft 14—the
`third gear 16-+the fourth gear 18->the synchromeshclutch
`Cl-the third shaft 17-the fifth gear 19-the final driven
`gear 21-+the differential 20. On the other hand, the driving
`force of the main rear motor Mm is transmitted to the left
`
`and right rear wheels Wr, Wralong a path extending from the
`second shaft 14—the third gear 16—>the fourth gear 18—the
`synchromesh clutch Cl-the third shaft 17—the fifth gear
`19-the final driven gear 21—the differential 20.
`
`the maximum
`[0046] As is clear from FIGS. 4 and 5,
`rotational speed of the main rear motor Mm is N1, which can
`deal with vehicle speeds up to a vehicle speed V1, and the
`maximum rotational speed of the sub rear motor Msis N2,
`which can deal with vehicle speeds up to a vehicle speed V2.
`The main rear motor Mm output a torque T1 which is the
`maximumdriving force thereof in a vehicle speed range of
`0 to V3, and the driving torque gradually decreases from V3
`towards a vehicle speed V2. In addition, the sub rear motor
`Ms outputs a torque T4 which is the maximum driving
`torque thereof in a vehicle speed range from 0 to V4, and the
`driving torque gradually decreases from V4 towards the
`vehicle specd V2. A solid linc in FIG. 4 indicates total
`values resulting from addition of the driving torque of the
`main rear motor Mm and the driving torque of the sub rear
`motor Msand satisfics conditions for vehicle specd and
`driving torque which are required for hauling, as well as
`conditions for vehicle speed and driving torque which are
`required for driving on a sandy ground.
`
`BMWv.Paice, IPR2020-00994
`BMW v. Paice, IPR2020-00994
`BMW1099
`BMW1099
`Page 12 of 16
`Page 12 of 16
`
`

`

`US 2004/0069548 Al
`
`Apr. 15, 2004
`
`cl QNS Remarks
`
`ROKOOO9000axMOMOK€O6MKK
`
`hauling, driving
`on sandy ground
`
`hauling, driving
`on sandy ground
`40 km/h or lower
`40 km/h or lower
`90 km/h or higher
`40 km/h or lower
`90 km/h or higher
`
`TABLE1
`
`Vehicle Speed
`
`Driving Force
`S/MOT M/MOT Transmission
`
`When stopped
`IG OI[T
`When stopped
`IG ON
`Whenstarted forward
`(with low torque)
`Whenstarted forward
`(with high torque)
`Whenstarted reverse
`(with low torque)
`Whenstarted reverse
`(with high torque)
`PRassist
`
`Generative Braking
`
`Low, middle speed
`Tow, middle speed
`High speed
`Low, middle speed
`High speed
`
`x
`
`x
`x
`
`CCW
`
`x
`
`CW
`
`x
`ccw
`x
`x
`x
`
`x
`
`x
`cw
`
`CW
`
`CCW
`
`CCW
`
`cw
`CW
`x
`CW
`x
`
`x
`
`x
`oO
`
`oO
`
`O
`
`O
`
`O
`O
`x
`oO
`x
`
`[0047] The operating conditions of the main rear motor
`Mm,the sub rear motor Ms, the synchromeshclutch C1 and
`the electromagnetic clutch C2 in various driving conditions
`are shown in Table 1. Note that in Table 1 a symbol CW
`denotes a clockwise rotation and a symbol CCW denotes a
`counterclockwise rotation.
`
`[0048] When the vehicle is stopped with the ignition
`switch being switched off, both the syachromesh clutch C1
`and the electromagnetic clutch C2 are disengaged, and the
`main rear motor Mm and the sub rear motor Msare both
`
`stopped, whereby the transmission of driving force to the
`rear wheels Wr, Wr is stopped. Whenthe vehicle is stopped
`with the ignition switch remaining switched on,
`the syn-
`chromesh clutch Cl is engaged, whereas the electromag-
`netic clutch C2 is disengaged, and both the main rear motor
`Mm and the sub rear motor Msare stopped, whereby the
`transmission of driving force to the rear wheels Wr, Wris
`stopped. The reason why the synchromesh clutch Cl is
`caused to remain engaged is because the vehicle can start
`from the stopped condition without any delay.
`
`Mm and the sub rear motor Ms become opposite to the
`rotational directions thereof when the vehicle is started to
`move forward.
`
`{0051] There are two modes available when assisting in
`driving the rear wheels Wr, Wr in low and middle vehicle
`speeds (lower than the vehicle speed V2). A first mode is
`identical to the case where the vehicle is started to move
`
`forward with a low torque, and only the syochromeshclutch
`C1 is engaged, and only the main rear motor Mm is driven,
`whereby the driving force thereof is transmitted to the rear
`wheels Wr, Wr. A second modeis identical to the case where
`the vehicle is started to move forward with a high torque,
`and both the synchromeshclutch Cl and the electromagnetic
`clutch C2 are engaged, and both the main rear motor Mm
`and the sub rear motor Msare driven, whereby the driving
`forces thereof are transmitted to the rear wheels Wr, Wr.
`Note that from a viewpoint of protecting the sub rear motor
`Ms,in the second mode, the disengagementof the electro-
`magnetic clutch C2 is implemented according to a prede-
`termined rotational speed (N2 in FIG. 5) which is deter-
`mined based upon the performance thereof.
`
`[0049] When the vehicle is started to move forward with
`In the case of a high vehicle speed (the vehicle
`[0052]
`a low torque, only the synchromesh clutch Cl is engaged,
`speed V1 or higher), in addition to the disengagementof the
`and only the main rear motor Mm is driven, whereby the
`electromagnetic clutch C2, which has been carried out
`driving force thereof is transmitted to the rear wheels Wr,
`Wr. When the vehicle is started to move forward with a high
`before, the synchromech clutch C1 is also disengaged, so
`
`torque or when the vehicle haulsatrailer or the like or runs that the transmission of driving force to the rear wheels Wr,
`on the sandy ground, both the synchromesh clutch C1 and
`Wris stopped. The reason for this is, as with the sub rear
`motor Ms, because the main rear motor Mm should be
`the electromagnetic clutch C2 are engaged, and both the
`main rear motor Mmand the sub rear motor Msare driven,
`prevented from rotating at a speed exceeding a predeter-
`wherebythe driving forces thereof are transmitted to the rear
`mined rotational speed (N1 in FIG. 5) that is determined
`wheels Wr, Wr.
`based upon the performance thereof with a view to protect-
`ing the same motor.
`
`[0050] When the vehicle is started to reverse with a low
`torque, only the synchromeshclutch C1is engaged, and only
`the main rear motor Mmis driven, whereby the driving force
`thereof is transmitted to the rear wheels Wr, Wr. When the
`vehicle is started to reverse with a high torque or when the
`vehicle hauls a trailer or the like or runs on the sandy ground,
`both the synchromesh clutch C1 and the electromagnetic
`clutch C2 are engaged, and both the main rear motor Mm
`and the sub rear motor Msare driven, whereby the driving
`forces thereof are transmitted to the rear wheels Wr, Wr.
`However, the rotational directions of the main rear motor
`
`Page 13 of 16
`Page 13 of 16
`
`[0053] During regenerative braking in low and middle
`vehicle speeds (lower than the vehicle speed V2) only the
`synchromeshclutch C1 is engaged, and only the main rear
`motor Mm is braked in a regenerative fashion, whereby the
`kinetic energy of the vehicle body is reclaimed and stored in
`the high-voltage battery Bh as electric energy. In the case of
`a high vehicle speed (the vehicle speed V1 or higher), both
`the synchromesh clutch Cl and the electromagnetic clutch
`Cl are disengaged, and both the main rear motor Mm and
`the sub rear motor Msare stopped, whereby the regenerative
`
`BMWv.Paice, IPR2020-00994
`BMW v. Paice, IPR2020-00994
`BMW1099
`BMW1099
`Page 13 of 16
`Page 13 of 16
`
`

`

`US 2004/0069548 Al
`
`Apr. 15, 2004
`
`braking by the main rear motor Mm is not implemented. The
`reason for this is, similar to the aforesaid case where the
`driving force is transmitted, due to the viewpoint of pro-
`tecting the main rear motor Mm andthe sub rear motor Ms.
`
`[0054] Conditions for driving the sub rear motor Msare as
`below. Driving forces that are to be distributed to the front
`wheels Wf, WE and the rear wheels Wr, Wrare calculated by
`the managing ECU 26 based upon wheel speed, accelerator
`pedal opening, and forward and rearward accelerations.
`Then, in case the driving forces allocated to the rear wheels
`Wr, Wr cannot be supplied only by the main rear motor Mm,
`the sub rear motor Msis driven so as to compensate for the
`shortage of driving force.
`
`In addition, conditions for stopping the sub rear
`[0055]
`motor Msthatis so driven are described below under (1) to
`
`(1) Although the rear wheels Wr, Wr, which are the
`[0056]
`sub driving wheels,are driven to prevent the slippage of the
`front wheels Wf, Wf, which are the main driving wheels,
`when the front wheels Wf, Wf start to slip,
`the sub rear
`motor Msis stopped whenthe differential rotation between
`the front and rear wheels Wf, Wf; Wr, Wr reaches or lowers
`below a set value after the slippage of the front wheels Wf,
`Wfhas beenresolved.
`
`[0057] @ The sub rear motor Ms is stopped when the
`vehicle speed reaches or exceeds a set value (the vehicle
`speed V2 in the embodiment), and hencethe rotational speed
`thereof exceeds an upper limit rotational speed (N2 in the
`embodiment) set therefor.
`[0058] @ The sub rear motor Ms is stopped when the
`need for drastically accelerating the vehicle is obviated due
`to the accelerator opening and the rate of change thereof
`reaching or lowering below set values.
`[0059]
`(4) The sub rear motor Msis stopped when the
`need for driving the rear wheels Wr, Wr is obviated due to
`the required driving force of the vehicle being able to be
`supplied only by the front wheels Wf, Wf.
`
`[0060] Thus, since the motors for driving the rear wheels
`Wr, wr are divided into the main rear motor Mm having a
`large output and the sub rear motor Ms having a small
`output, so that both the main rear motor Mm andthe sub rear
`motor Msare driven when a large driving force is required
`as whenthe vehicle is driven at low speed to haula trailer
`or the like or to run on the sandy ground, when compared
`with a case where a single large rear motor is used whose
`capacity equalizes the total of the capacities of the main rear
`motor Mm and the sub rear motor Ms,
`the maximum
`dimensions of the main rear motor Mm andthe sub rear
`motor Ms can be made smaller than the maximum dimen-
`sions ofthe single large rear motor, respectively. As a result,
`the minimum ground clearance of the vehicle can be
`reduced, the intersecting angle with the drive shafts can be
`decreased, and the floor level of the vehicle can be lowered,
`while enhancing the running through performance at low
`vehicle speed.
`
`In addition, since the sub rear motor Msis disposed
`[0061]
`on an upstream side of the speed reduction gear sct R,
`whereas the main rear motor Mm is disposed on a down-
`stream side thereof, a sufficient reduced gear ratio from the
`sub rear motor Msto the rear wheels Wr, Wr can be secured
`
`Page 14 of 16
`Page 14 of 16
`
`to thereby increase the rate of amplifying the torque, thereby
`making it possible to use a motor having a small output for
`the sub rear moto