Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION
Hybrid drive train for vehicle
FIELD OF THE INVENTION
[0001] The present invention relates to drive trains for vehicles. More
specifically, the present invention is concerned with a hybrid drive train and
to modes
of operations of such a drive train.
BACKGROUND OF THE INVENTION
[0002] Vehicles having a hybrid drive train are well known in the art. They
are usually provided with an' internal combustion engine (ICE), an electric
traction
motor that may transmit power to at least one wheel of the vehicle and an
electric
generator used to supply electricity to the traction motor and/or to recharge
batteries
of the vehicle.
[0003] On the one hand, a hybrid drive train is said to be a series hybrid
drive train when the traction motor is used to drive the wheels and the ICE is
exclusively used to drive the electric generator to recharge the vehicle's
batteries
and/or supply electric power directly to the traction motor.
[0004] On the other hand, a hybrid drive train is said to be a parallel
hybrids drive train when both the traction motor and the ICE may be used
simultaneously or individually to drive the wheels of the vehicle. In parallel
hybrid
drive trains, the ICE may also~be used to recharge the batteries through the
electric
generator.
[0005] Series/parallel hybrid vehicles (SPHV) are also known in the art.
Conventionally, these vehicles include drive trains that may be switched
between a
series mode and a parallel mode, as described hereinabove.
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[0006] Early parallel hybrid drive included electric motors associated with
the front wheels and an ICE associated with the rear wheels. This arrangement
has
the drawback of taking much space in the vehicle.
[0007] Often, parallel hybrid drive trains include an interconnection
between the ICE, the traction motor,and the electric generator. This
interconnection
is often provided by a planetary gear assembly. A drawback of such an
interconnection is its mechanical complexity and inherent inefficiency.
OBJECTS OF THE INVENTION
[0008] An object of the present invention is therefore to provide an
improved hybrid drive train for vehicle.
SUMMARY OF THE INVENTION
[0009] More specifically, in accordance with the present invention, there is
provided a hybrid drive for a vehicle including at least one driving wheel;
said hybrid
drive comprising
an engine having an output shaft;
an electric motor having an output shaft connected to the at least
one driving wheel;
an electric motorlgenerator having an output/input shaft;
a clutch assembly selectively interconnecting said outpufi/input
shaft of said electric motor/generator to said output shaft of said engine and
to said
output shaft of said electric motor; said clutch assembly being actuatable
between a
first position where said output/input shaft is connected to said output shaft
of the
electric motor to thereby supplement the electric motor by using said
motorlgenerator as a motor, a second position where said output/input shaft is
connected to said output shaft of said engine to thereby use said electric
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motor/generator as an electric generator, and a third position where said
output/input
shaft is freewheeling;
a controller so connected to said electric motor, said electric
motor/generator and said clutch assembly as to control their operation.
[0010] A hybrid drive for a vehicle including at least one driving wheel and
an engine having an output shaft; said hybrid drive comprising
an electric traction motor having an, output shaft connected to the
at least one driving wheel;
an electric motor/generator having an output/input shaft;
a clutch assembly selectively interconnecting said output/input
shaft of said electric motor/generator to the output shaft of the engine and
to said
output shaft of said electric motor; said clutch assembly being actuatable
between, a
first position where said output/input shaft is connected to said output shaft
of the
electric motor to thereby supplement the electric motor by using said
motor/generator as a motor, a second position where said output/input shaft is
connected to the output shaft of the engine to thereby use said electric
motor/generator as an electric generator, and a third position where said
output/input
shaft is freewheeling; and
a controller so connected to said electric motor, said electric
motor/generator and said clutch assembly as to control their operation.
[0011] A clutch assembly for a hybrid drive of a vehicle including at least
one driving wheel, an engine having an output shaft, an electric motor having
an
output shaft associated with the at least one driving wheel, an electric
motor/generator having an output/input shaft and a controller so connected to
the
electric motor, the electric motor/generator and said clutch assembly as to
control
their operation; said clutch assembly selectively interconnecting the
output/input
shaft of the electric mofior/generator to the output shaft of the engine and
to the
output shaft of the electric motor; said clutch assembly being actuatable
between a
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first position where the output/input shaft is connected to the output shaft
of the
electric motor, a second position where the output/input shaft is connected to
the
output shaft of the engine, and a third position where the output/input shaft
is
freewheeling.
[0012] A method for operating a drive train of a hybrid vehicle provided
with user controls, an ICE, a traction motor, an electric generator and a
clutch
assembly selectively interconnecting the electric generator to the ICE and to
the
traction motor; said method including the steps of:
providing a controller connected to the user controls to receive
data therefrom, to the ICE and to the clutch assembly;
providing at least one sensor for sensing at least one characteristic
of the hybrid vehicle; the at least one sensor supplying sensed data to the
controller;
and
via the controller, controlling the clutch assembly so as to
interconnect the electric generator either to the ICE and to the traction
motor,
depending on the data supplied from the at least one sensor and from the user
controls.
[0013] It is to be noted that the expressions "neutral state", "mechanical
power generating state" and "electrical power generating state" used herein
and in
the appended claims refer to the state of the generator of the drive train and
not to
the state of the drive train, as will easily be understood by one skilled in
the art.
[0014] Other objects, advantages and features of the present invention
will become more apparent upon reading of the following non-restrictive
description
of preferred embodiments thereof, given by way of example only with reference
to
the accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In the appended drawings:
[0016] Figure 1 is a schematic view of a hybrid drive train according to an
embodiment of the present invention, shown in a neutral state;
[0017] Figure 2 is a schematic view similar to Figure 1, illustrating the
hybrid drive train in a generation state;
[0018] Figure 3 is a schematic view similar to Figure 1, illustrating the
hybrid drive train in a traction state;
[0019] Figure 4 is an exemplary schematic flowchart of various modes of
operation of the hybrid drive train of Figure 1;
[0020] Figure 5 is a schematic view illustrating a possible arrangement of
the various elements of the clutch used in the drive train of Figure 1; and
[0021] Figure 6 is a schematic view of a hybrid drive train according to a
second embodiment of the present invention, shown in a parallel mode.
DETAILED DESCRIPTION
[0022] Generally stated, a first aspect of the present invention is
concerned with a series hybrid drive train for a vehicle comprising a traction
motor (in
the form of an electric motor), an electric generator (in the form of. an
electric
motor/generator), a three position clutch and a controller. The three position
clutch
allows the generator to be connected to an iCE of the vehicle, to the traction
motor.
or to remain freewheeling. In a second aspect of the present invention, a four
position clutch is used to further allow the ICE to be connected directly to
the wheels
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to thereby yield a series/parallel hybrid drive train. A third aspect of the
present
invention is concerned with the modes of operation of such hybrid drive
trains.
. [0023] Turning now to Figure 1 of the . appended drawings, there is
provided a hybrid drive train 10 to which an ICE 12, a battery 14 and wheels
(not
shown) of the vehicle may be directly or indirectly connected.
[0024] The drive train 10 includes a traction motor 16, an electric
generator 18, a three-position clutch 20 a disk actuating mechanism 21 and a
controller 22 connected to the ICE 12, the battery 14, the traction motor 16,
the
electric generator 18 and the disk actuating mechanism 21. The controller 22
may
thus control the entire drive train 10 and send and receive data about the
operational
state of the ICE and the state of charge of the battery 14.
[0025] The three position clutch 20 includes a first disk 24 connected to
the shaft of the ICE 12, a second disk 26 connected to the shaft of the
traction motor
16 and a movable disk 28 connected to the shaft of the electric generator 18.
The
disk actuating mechanism 21 is controlled by the controller 22 and includes
mechanical elements (not shown) to move the movable disk 28 between its three
positions. The disk moving arrangement may operate via magnetism, a fork or a
solenoid, for example.
[0026] It is to be noted that Figure 1 is very schematic. Many other
components are required to operate the drive train 10. For example, the
controller
22 includes power electronics (not shown). Similarly, the battery 14, the
traction
motor 16 and the electric generator 18 all include different sensors to supply
data to
the controller 22.
(0027] Figure 1 shows the drive train 10 in a neutral state, i.e. that the
shaft of electric generator 18, connected to the movable disk 28, is
freewheeling.
This is the default state of the drive train 10.
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[0028] Figure 2 shows the drive train 10 in an electrical power generation
state, i.e. that the shaft of the electric generator is connected to the ICE
12 via the
three-position clutch 20. Indeed, the movable disk 28 has been brought in
contact
with the first disk 24 under the control of the actuating mechanism 21.
[0029] As will easily be understood by one skilled in the art, when the
drive train 10 is in this state, the rotation of the shaft of the ICE 12 will
cause the
rotation of the shaft of the electric generator 18. This mechanical energy
generated
by the ICE 12 may be transformed info electric energy by the electric
generator 18
according to known techniques. Since these techniques are believed well known
to
those skilled in the art, they will not be discussed in greater detail herein.
[0030] Turning now to Figure 3 of the appended drawings, the drive train
is shown in a mechanical power generating state. Indeed, the movable disk 28
is
brought into contact with the second disk 26, therefore linking the shaft of
the electric
generator 18 and the shaft of the traction motor 16.
[0031] , When the drive train 10 is in such a mechanical power generating
state, the electric generator 18 is used in a motor mode and may generate
mechanical power and .transfer this mechanical power to the shaft of the
tractiorr
motor and therefore to the wheels (not shown) of the vehicle.
[0032] In other words, the hybrid drive train 10 described herein has three
mechanical states. A neutral state where the outputlinput shaft of the
generator 18
is freewheeling (Figure 1 ); an electrical power generating state where the
output/input shaft of the generator 18 is connected to the output shaft of the
ICE 12
(Figure 2) and a mechanical power generating state where the output/input
shaft of
the generator 18 is connected to the output shaft of the electric motor 16
(Figure 3).
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[0033] As will be understood upon further reading of the present
document, the mechanical power generating state of Figure 3 may also allow
regenerative braking.
[0034] According to another aspect of the present invention, the controller
22 of the drive train 10 controls the various elements of the drive train so
that,.from
the three mechanical states of the drive train, seven modes are available.
Mode 1: Priority charge mode
[0035] This is an electrical power generating mode. Accordingly, when
the controller ~2 determines that this mode is required, the drive train 10 is
placed in
the electrical power generating state of Figure 2.
[0036] Generally, the priority charge mode is used when the State Of
Charge (SOC) of the battery 14 falls below a predetermined value. For example,
the
controller 22 could be so configured that when the SOC falls below 20%, the
priority
charge mode is requested.
[0037] When the drive train 10 is in the priority charge mode, the electric
generator 10 generates as much power as it can to supply as much electrical
power
as possible to the traction motor and to recharge the battery. Of course, the
electrical power generated may be limited by the battery limitations (power
and/or
current). However, it is possible that, depending on the power rating of the
various
elements of the drive train, the controller limits the performances of the
vehicle for
example by limiting the maximum speed, torque and/or power allowed when the
drive train is in this mode.
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Mode 2: Power increase mode
[0038] This is an electrical power generating mode. Accordingly, when
the controller 22 determines that this mode is required, the drive train 10 is
placed in
the electrical power generating state of Figure 2.
[0039] This mode is generally used when the controller determines that
the electrical power present in the battery 14 is not sufficient to allow the
traction
motor 18 to develop the required mechanical power, mainly because high
performances are demanded of the drive train by the user or because the SOC of
the battery is not sufficient to reach the requested performance. The
electrical power
generated by the electric generator 18 is transferred to the traction motor 18
to
supplement the power delivered by the battery 14.
[0040] This power increase mode is most often used when the vehicle
travels at high speed and the user desires to accelerate, when there is strong
head
wind or when the vehicle reaches an upward slope.
[0041] The level of electrical power generation in the power increase
mode may vary. indeed, the controller 22 may control the electric generator 18
so
as to: a) generate the minimum required electrical power; b) generate the
maximum
electrical power; and c) obtain the best power efficiency.
[0042] When the electric generator 18 generates the minimum required
electrical power, the goal is to use as little fuel as possible.
[0043] When it is desired to leeep a minimum adequate level of SOC of
the battery 14, the controller 22 controls the electric generator 18 so that
it generates
the maximum electrical power.
[0044] The third option is used when it is desired to maintain the best
power efficiency for the drive train
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[0045] It is to be noted that the three options of the power increase mode
may be automatically selected by the controller 22 or may be selected by the
user of
the vehicle via user's controls (not shown).
Mode 3: Torque increase mode
[0046] This is a mechanical power generating mode. Accordingly, when
the controller 22 determines that this mode is required, the drive train 10 is
placed in
the mechanical power generating state of Figure 3.
[0047] This mode is used when the torque required from the drive train 10
is greater than the maximum torque that may be developed by the traction motor
16
alone. Therefore, this mode is most often used when the vehicle starts, when a
' strong acceleration is requested by the user, when there is strong head wind
or
when the vehicle reaches an upward slope.
[0048] The level of mechanical power generation in the torque increase
mode may vary. Indeed, the controller 22 may coritrol the electric generator
18 so
as to: a) prevent excessive overheating of the various elements of the
traction motor
16; or b) obtain the best overall power efficiency.
[0049] In the first case, temperature sensors (not shown) may be installed
to monitor the temperature of various elements of the traction motor 16 and of
the
electric generator 18. Depending on the data supplied by these sensors, the
controller 22 may determine the amount of torque to be generated by the
traction
motor 16 and by the electric generator 18 to prevent overheating.
[0050] When the controller determines that there is no overheating, for
example when the speed of the vehicle is constant, the controller may
determine that
the required torque may be split between the traction motor 16 and the
electric
generator 18. One skilled in the art will be in a position to determine the
adequate
ratio.
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Mode 4: Normal charge mode
[0051] This is an electrical power generating mode. Accordingly, when
the controller 22 determines that this mode is required, the drive train 10 is
placed in
the electrical power generating state of Figure 2.
[0052] Generally, the normal charge mode is used when the SOC of the
battery 14 falls below a predetermined value that is greater that the value of
the SOC
that dictates the priority charge mode described hereinabove. For example, the
controller 22 could be so configured that when the SOC falls below 40%, the
normal
charge mode is requested.
[0053] It is to be noted that the electrical power generated by the electric
generator 18 may vary when the drive train 10 is in the normal charge mode. On
the
one hand, if the battery is to be charged as fast as possible, the electric
generator 18
is so controlled as to supply as much electric power as possible. On the other
hand,
the amount of fuel may be minimized by selecting a 'more efficient level of
electrical
power generation. Alternatively, the controller may allow a quiet mode where
the
ICE 12 is operated at a level that is a function of the ground speed of tfle
vehicle to
thereby minimize the noise perceived by the user.
[0054] It is to be noted that the three options of the normal charge mode
may be automatically selected by the controller 22 or may be selected by the
user of
the vehicle via user's controls (not shown).
Mode 5: Torque sharing mode
[0055] This is a mechanical power generating mode. Accordingly, when
the controller 22 determines that this mode is required, the drive train 10 is
placed in
the mechanical power generating state of Figure 3.
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[0056] In some instances, it may then be desirable to place the drive train
in the torque sharing mode and dynamically split the requested torque between
the traction motor 16 and the electric generator 18. For example, it has been
found
that this torque splitting is efFicient when the torque developed by the
traction motor
16 is about its nominal torque and the torque developed by the electric
generator 18
is about its nominal torque.
[0057] This mode may also ,be used when the temperature of the traction
motor 18, or one of its associated components, exceeds a predetermined value.
[0058] It is to be noted that the ratio of torque requested from the traction
motor 16 and the electric generator 18 may vary without going over the maximum
torque rating, for example depending on the temperature reading of these
elements.
Alternatively, the ratio may be fixed at their nominal torque so as to yield
the best
drive train efficiency.
Mode 6: Power sharing mode
[0059] This is an electrical power generating mode very similar to the
power increase mode described hereinabove. Accordingly, when the controller 22
determines that this mode is required, the drive firain 10 is placed in the
electrical
power generating state of Figure 2.
[0060] The Power Sharing Mode is generally used to increase the life of
the battery by dividing the electric power required by the traction motor
between the
battery and the electric generator.
[0061] One skilled in the art will.understand that to increase the life of the
battery, it is best not to draw more power than the optimum power available.
The
optimum power of the battery changes from one battery technology to another
and
usually decreases wifih the SOC of the battery. Accordingly, an optimum power
curve with respect to the SOC is entered in the controller.
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[0062] The Power Sharing Mode is therefore used when the power
requested by the drive train is greater than the optimum power available from
the
battery. .
j0063] It is to be noted that when the drive train is in this mode, the
controller aims at preventing the drive train from falling to the priority
charge mode
level of SOC. Therefore, the electric generator is so controlled that it
generates the
maximum electric power possible.
Mode 7: Neutral mode
[0064] This is the default state of the drive train 10. When the controller
22 determines that the drive train 10 is to be placed in this mode, it places
the clutch
20 in its neutral state illustrated in Figure 1.
[0065] It is to be noted that, in some cases, when the clutch 20 is in the
electric power generating state and has to be changed to the mechanical power
generating state, or vice-versa, the clutch 20 is advantageously first placed
in its
neutral state to prevent any undesired sensations to the driver and to limit
the
mechanical stress of the drive train.
[0066] It is to be noted that the user controls may include an optional
mode selector (not shown) to allow the driver to request any of the modes
described
hereinabove manually.
[0067] Figure 4 of the appended drawings illustrates a schematic block
diagram of the seven modes described hereinabove and their priority, according
to
an aspect of the present invention. This block diagram will be used
hereinbelow to
describe a control method of the drive train 10 according to an embodiment of
the
present invention. As will easily be understood by one skilled in the art,
this control
method may be implemented by the controller 22.
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(0068] Generally stated, after the decision process is started, the method
separately tests, the seven modes to determine all the modes that are
adequate.
These tests are made in parallel and fihe results are then compared to
determine
which mode should be selected.
[0069] Step 100 is the start of the decision process. Then, in steps ~ 02 to
112, the controller determines all the modes that are adequate depending on
the
various characteristics of the vehicle.
[0070] For each non-neutral mode, a variable is set to a predetermined
value if the method determines that the mode is adequate and if set to the
value
seven (7) if the method determines that the mode is not adequate.
[0071] Accordingly:
~ the variable "Priority Charge Mode" is set to one (1 ) if the
method determines that the SOC is below 20% (step 114); if not
this variable is set to seven (7) (step 116);
~ the variable "Power Increase Mode" is set to two (2) if the
method determines that the power requested by the traction
motor is greater than the power available from the battery (step
118); if not this variable is set fio seven (7) (step 120);
~ the variable "Torque Increase Mode" is set to three (3) if the
method determines that the torque requested by the drive train
is greater than the torque available from the traction motor (step
122); if not this variable is set to seven (7) (step 124);
~ the variable "Normal Charge Mode" is set to four (4) if the
method determines that the SOC is below 40% (step 126); if not
this variable is set to seven (7) (step 128);
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~ the variable "Torque Sharing Mode" is set to five (5) if the
method determines that overheating has been detected in the
traction motor (step 130); if not this variable is set to seven (7)
(step 132); and
~ the variable "Power Sharing Mode" is set to six (6) if the method
determines that the power requested by the drive train is greater
than the optimum power available from the traction motor (step
134); if not this variable is set to seven (7) (step 136).
[0072] Finally, in step 138, the method selects and activates a mode of
operation of the drive train by finding the variable that has the lowest
value. Then,
the method returns to step 100.
[0073] It is to be noted that the percentages of the SOC given herein are
example only and that these percentages can be changed depending on the
performance requirements of the vehicle and the power rating of the different
elements of the vehicle, for example.
[0074] As will easily be understood by one skilled in the art, the selection
method described hereinabove is interesting since, to change the priority
between
the different modes during the design stage of the drive train, one simply has
to
change the values given to the variables when the corresponding modes are
found
adequate. Of course, these values could be changed after the design stage, if
necessary.
[0075] Of course, one skilled in the art will understand that other control
strategies could be used. For example, instead of doing the decision process
as a
parallel process as described hereinabove, it could be done in series, by
using a IF-
THEN-ELSE strategy, for example.
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[0076] A possible modification to the control method presented
hereinabove would be to treat the Power Increase Mode (Mode 2) and the Torque
Increase Mode (Mode 3) as optional modes fihat would be manually triggered by
the
user. More specifically, the user's control of the vehicle could include a
"Sports"
button that, when depressed would enable these two modes.
[0077] Turning now to Figure 5 of the appended drawings, a schematic
representation of a three-position clutch 20 according to an aspect of the
present
invention will be described.
[0078] As can be seen from this figure, the shafts 26A and 28A,
respectively finked to the second disk 26 and the movable disk 28 are
concentric.
Accordingly, since shaft 28A can telescopically slide into shaft 26A, the
movable disk
28 may be moved by the actuating mechanism 21 while remaining linked to the
electric generator 18. One skilled in the art will have no problem linking the
shaft
28A to the electric generator 18 and the shaft 26A to the tracfiion motor 16.
[0079] ~ Alternatively, in another configuration (not shown), shafts
associated with the electric generator 18 and with the ICE 12 could be
concentric to
yield similar results.
[0080] Turning now to Figure 6 of the appended drawings, a drive train
10' according to an alternative embodiment of the present invention will be
described. Since the drive train 10' is very similar to the drive train 10
described
hereinabove with reference to Figures 1 to 3, only the differences between
these
drive trains wilt be described.
[0081] The main difference between the drive train 10 of Figure 1 and the
drive train 10' of Figure 6 concerns the clutch. Indeed, while the clutch 20
of Figure
1 is a three-position clutch, the clutch 20' of Figure 6 is a four-position
clutch.
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Indeed, while clutch 20' may be positioned in the three positions illustrated
in Figure
1 to 3, a fourth position, illustrated in Figure 6, is also possible.
[0082] This fourth position allows the electric generator 18 to be
simultaneously connected to both the ICE 12 and to the traction motor 16.
Accordingly, this enables a parallel hybrid mode where at least a portion of
the
mechanical power can be transferred from the ICE 12 to the wheels of the
vehicle
through the two-part (28' and 28") movable disk.
[0083] One skilled in the art will understand that the two parts 28' and 28"
of the two-part movable disk may be engaged to one another to realize the
three
states illustrated in Figures 1 to 3.
[0084] It is to be noted that while the three-position clutch has been
described hereinabove as a generic clutch, a conventional friction clutch, a
jaw
clutch or other clutch technologies could be used.
[0085] It is to be noted that while the power rating of the various elements
of the drive train 10 have not been specified herein, it is believed that one
skilled in
the art of hybrid drive trains would have no problem selecting or designing
the
appropriate elements according to the desired performances of the vehicle.
[0086] It is mentioned hereinabove that some of the modes may be
controlled so as to improve efficiency. However, no exact indication of the
method of
control required to obtain such an improved efficiency is given since the
efficiency
level is dependent on the power rating and other characteristics of the
various
elements of the drive train _10. One skilled in the art will be in a position
to configure
the controller 22 according to the elements used in the drive train to yield
the best
efficiency. '
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[0087] It is to be noted that while the traction motor 16 is primarily
designed to drive the wheels of the vehicle, when the vehicle is decelerating,
the
traction motor 16 may also be used ~as an electric generator to recuperate
energy
and store it in the batteries.
[0088] It is also to be noted that while the engine has been described as
being an internal combustion engine, other types of engine could be used.
[0089] Although the present invention has been described hereinabove by
way of preferred embodiments thereof, it can be modified, without departing
from the
spirit and nature of the subject invention as defined in the appended claims.
