U.S. patent application number 09/796727 was filed with the patent office on 2001-09-06 for drive force transmission mechanism for hybrid vehicle.
Invention is credited to Kanehisa, Takanori.
Application Number | 20010019980 09/796727 |
Document ID | / |
Family ID | 18580861 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010019980 |
Kind Code |
A1 |
Kanehisa, Takanori |
September 6, 2001 |
Drive force transmission mechanism for hybrid vehicle
Abstract
A first clutch (2) is connected to an engine (1) of a hybrid
vehicle. A motor/generator (6) is connected to an output shaft (4)
of the first clutch (2) through a planetary gear set (3). A second
clutch (10) is provided which connects an input shaft (5) of an
automatic transmission (7) to the output shaft (4) so as to move
the vehicle forward, and which connects the input shaft (5) to the
motor/generator (6) so as to move the vehicle rearward. The second
clutch (10) preferably comprises a dog clutch. When the vehicle
commences forward motion, the torque of the motor/generator which
is input to the automatic transmission (7) can be increased since
the planetary gear set (3) decreases the rotation speed of the
motor/generator (6) and transmits it to the output shaft (4).
Inventors: |
Kanehisa, Takanori;
(Hachiouji City, JP) |
Correspondence
Address: |
Richard L. Schwaab
FOLEY & LARDNER
Washington Harbour
3000 K Street, N.W., Suite 500
Washington
DC
20007-5109
US
|
Family ID: |
18580861 |
Appl. No.: |
09/796727 |
Filed: |
March 2, 2001 |
Current U.S.
Class: |
475/5 ; 475/10;
475/207; 475/218; 475/302; 903/903; 903/905; 903/906; 903/909;
903/910; 903/914; 903/918; 903/946; 903/951 |
Current CPC
Class: |
Y10S 903/903 20130101;
Y10S 903/918 20130101; Y02T 10/62 20130101; Y10S 903/905 20130101;
B60W 20/40 20130101; B60W 10/02 20130101; F16H 37/022 20130101;
B60W 10/10 20130101; B60K 17/06 20130101; Y10S 903/946 20130101;
Y10S 903/906 20130101; B60K 6/48 20130101; B60W 20/00 20130101;
Y10S 903/91 20130101; B60K 6/543 20130101; Y10S 903/909 20130101;
Y10S 903/951 20130101; B60K 6/365 20130101; B60K 2006/4833
20130101; Y10S 903/914 20130101 |
Class at
Publication: |
475/5 ; 475/10;
475/207; 475/218; 475/302 |
International
Class: |
F16H 061/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2000 |
JP |
2000-060579 |
Claims
What is claimed is:
1. A drive force transmission mechanism for a hybrid vehicle, the
hybrid vehicle comprising an engine and a motor/generator as a
motive force source, the mechanism comprising a first clutch
connected to the engine, the first clutch comprising an output
shaft that rotates together with the engine when the first clutch
is engaged; a planetary gear set connecting the motor/generator to
the output shaft; an automatic transmission comprising an input
shaft, the hybrid vehicle running in accordance with an output
rotation of the automatic transmission; and a second clutch
selectively connecting the input shaft to the motor/generator and
to the output shaft.
2. The drive force transmission mechanism as defined by claim 1,
wherein the planetary gear set comprises a sun gear connected to
the motor/generator, a ring gear connected to the output shaft, a
planet gear meshing with the sun gear and the ring gear, and a
fixed planet carrier supporting the planet gear free to rotate
while preventing the planet gear from revolving around the sun
gear.
3. The drive force transmission mechanism as defined by claim 1,
wherein the planetary gear set comprises a sun gear connected to
the motor/generator, a fixed ring gear, a planet gear comprising a
pair of intermission pinions, one of the pinions being meshed with
the sun gear and the other of the pinions being meshed with the
ring gear, and a planet carrier supporting the pinions free to
rotate and free to revolve around the sun gear as the ring gear and
the sun gear relatively rotate, the planet carrier being connected
to the output shaft.
4. The drive force transmission mechanism as defined by claim 1,
wherein a gear ratio of the planetary gear set is set to cause a
rotation speed of the motor/generator to be larger than a rotation
speed of the output shaft.
5. The drive force transmission mechanism as defined by claim 1,
wherein the second clutch comprises a dog clutch.
6. The drive force transmission mechanism as defined by claim 1,
wherein the second clutch is a clutch which switches between a
forward position in which the input shaft is connected to the
output shaft, a reverse position in which the input shaft is
connected to the motor/generator and a neutral position in which
the input shaft is not connected to any of the output shaft and the
motor/generator.
7. The drive force transmission mechanism as defined by claim 1,
wherein the automatic transmission comprises a continuously
variable transmission.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a drive force transmission in a
hybrid vehicle.
BACKGROUND OF THE INVENTION
[0002] Tokkai Hei 11-241624 published by the Japanese Patent Office
in 1999 discloses a hybrid vehicle which combines an electric motor
with an engine as a source of drive force.
[0003] A first electric motor in this hybrid vehicle is directly
connected to an input shaft of an automatic transmission. An engine
is also connected to the input shaft through a clutch. The vehicle
starts moving by using only the motive force of the first electric
motor while the clutch is disengaged.
[0004] After the vehicle has started, the engine is started by a
second electric motor. While the vehicle is running, the engine
drives the second electric motor as a generator to charge a
battery. When the load on the first electric motor increases during
acceleration, the clutch is engaged, and the motive force of the
engine is input to the automatic transmission. The motive force of
the engine increases the drive force of the vehicle by assisting
the motive force of the first electric motor.
SUMMARY OF THE INVENTION
[0005] The first electric motor and engine of the hybrid vehicle
are directly connected when the clutch is engaged and the first
electric motor rotates at the same speed as the engine.
[0006] It is often the case that high-load conditions including
vehicle acceleration coincide with low engine rotation speeds,
However, operational efficiency of the electric motor is low in low
rotation speed regions.
[0007] In other words, it is difficult to obtain a preferred
operational efficiency of the engine and of motor at the same time
when the vehicle is running on both the engine and motor.
[0008] Of course, an electric motor of a larger output can be used
in order to increase the vehicle drive force, but such a motor
generally has larger volume and weight.
[0009] Furthermore in this hybrid vehicle, it is indispensable to
provide a forward/reverse change-over mechanism between the first
electric motor and the automatic transmission so as to allow the
forward and reverse motions of the vehicle.
[0010] It is therefore an object of this invention to improve the
energy efficiency of a hybrid vehicle.
[0011] It is a further object of this invention to downsize the
electric motor while maintaining the generated torque of the
electric motor.
[0012] It is yet a further object of this invention to simplify the
structure of a forward/reverse change-over mechanism.
[0013] In order to achieve the above objects, this invention
provides a drive force transmission mechanism for such a hybrid
vehicle that comprises an engine and a motor/generator as a motive
force source. The mechanism comprises a first clutch connected to
the engine, the first clutch comprising an output shaft that
rotates together with the engine when the first clutch is
engaged;
[0014] a planetary gear set connecting the motor/generator to the
output shaft;
[0015] an automatic transmission comprising an input shaft, the
hybrid vehicle running in accordance with an output rotation of the
automatic transmission; and a second clutch selectively connecting
the input shaft to the motor/generator and to the output shaft.
[0016] The details as well as other features and advantages of this
invention are set forth in the remainder of the specification and
are shown in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic diagram of a drive force transmission
mechanism for a hybrid vehicle according to this invention.
[0018] FIG. 2 is a schematic diagram of a drive force transmission
unit into which the drive force transmission mechanism is
integrated.
[0019] FIG. 3 is a block diagram of a control system of the drive
force transmission mechanism according to this invention.
[0020] FIG. 4 is a schematic diagram of the drive force
transmission mechanism in a state where the vehicle is
stationary.
[0021] FIG. 5 is a schematic diagram of the drive force
transmission mechanism in a state where engine start-up is
performed.
[0022] FIGS. 6A-6C are schematic diagrams of the drive force
transmission mechanism showing various operating states depending
on a battery state of charge SOC when the vehicle is
stationary.
[0023] FIG. 7 is a schematic diagram of the drive force
transmission mechanism in a state where the vehicle is about to
move forward.
[0024] FIG. 8 is a schematic diagram of the drive force
transmission mechanism in a state where the vehicle is running on a
motor/generator.
[0025] FIG. 9 is a schematic diagram of the drive force
transmission mechanism during engine start-up while the vehicle is
running forward.
[0026] FIGS. 10A and 10B are schematic diagrams of the drive force
transmission mechanism showing different operation states depending
on the battery state of charge SOC when the vehicle is running
forward.
[0027] FIGS. 11A and 11B are schematic diagrams of the drive force
transmission mechanism showing different operation states depending
on the battery state of charge SOC when the vehicle is
accelerating.
[0028] FIGS. 12A-12C are schematic diagrams of the drive force
transmission mechanism showing various operation states depending
on the battery state of charge SOC when the vehicle is
decelerating.
[0029] FIGS. 13A-13C are schematic diagrams of the drive force
transmission mechanism showing various operation states when the
vehicle is in reverse motion.
[0030] FIG. 14 is a diagram describing the relationship of a
rotation speed and a direction of rotation of a sun gear, a ring
gear and a planet carrier of a planetary gear set according to this
invention.
[0031] FIG. 15 is a schematic diagram of the drive force
transmission mechanism according to another embodiment of this
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Referring to FIG. 1 of the drawings, a drive force
transmission mechanism for a hybrid vehicle according to this
invention comprises a start-up clutch 2, a planetary gear set 3, a
forward/reverse change-over clutch 10 and an automatic transmission
7.
[0033] The hybrid vehicle comprises an engine 1 and a
motor/generator 6 as sources of drive force. Drive wheels (not
shown) are provided which are rotated by the rotational output of
the automatic transmission 7. The engine 1 is a sparking ignition
gasoline engine.
[0034] The start-up clutch 2, the planetary gear set 3, the
motor/generator 6 and the forward/reverse switching clutch 10 are
housed in a casing 11 as shown in FIG. 2.
[0035] An output shaft 8 of the engine 1 is connected to the
start-up clutch 2. The start-up clutch 2 comprises for example an
oil pressure driven multi-plate clutch. An output shaft 4 of the
start-up clutch 2 is connected to a ring gear 3R of the planetary
gear set 3. The output shaft 4 is connected to an input shaft 5 of
the automatic transmission 7 through the forward/reverse
change-over clutch 10.
[0036] The motor/generator 6 is a synchronous motor/generator which
can arbitrarily select positive and reverse rotation, and comprises
a stator 6A and a rotor 6B. The stator 6A is fixed to the casing
11. The rotor 6B rotates in response to a current supplied to coils
provided in the stator 6A. The rotor 6B generates a current in the
coils of the stator 6A in response to an external rotational input.
The coils are connected to a battery 51 shown in FIG. 3 and a
current supplied from the battery 51 operates the motor/generator 6
as an electric motor. On the other hand, a current generated by the
external rotational input charges the battery 51. The operation of
the motor/generator 6 as described above is controlled by a control
current supplied to the coils from an inverter 50.
[0037] The rotor 6B comprises a rotation shaft 30. The rotation
shaft 30 is connected to the sun gear 3S of the planetary gear
mechanism 3 as shown in FIG. 1. The sun gear 3S of the planetary
gear mechanism 3 is engaged with a ring gear 3R through a plurality
of planet gears 3P. The planet gears 3P are respectively supported
by a planet carrier 3C. The planet carrier 3C is fixed to the
casing 11. As a result, the planet gears 3P rotate in response to
the relative rotation of a ring gear 3R and a sun gear 3S and
revolution about the sun gear 3S is prevented.
[0038] This structure allows the planetary gear set 3 to reduce the
rotation speed of the rotation shaft 30 and transmit it to the
output shaft 4 of the start-up clutch 2. Alternatively, the
rotation speed of the output shaft 4 is increased and transmitted
to the rotation shaft 30. This function may be realized by a simple
gear unit which meshes with the two gears. However the two gears
must not be disposed co-axially in such an arrangement. The use of
a planetary gear set 3 allows the gear 3S and 3R to be disposed
co-axially which thus reduces the volume of the drive force
transmission mechanism.
[0039] The rotation shaft 30 is connected to an input shaft 5 of
the automatic transmission 7 through the forward/reverse
change-over clutch 10. The forward/reverse change-over clutch 10
comprises a dog clutch for example.
[0040] The forward/reverse change-over clutch 10 comprises a
forward position which connects the input shaft 5 to the output
shaft 4 of the start-up clutch 2, a reverse position which engages
the input shaft 5 with the rotation shaft 30 of the motor/generator
6 and a neutral position in which the input shaft 5 is not
connected to the output shaft 4 or the rotation shaft 30. These
positions are switched by an actuator (not shown) which is driven
by a signal from a hybrid controller 100 shown in FIG. 3. A dog
clutch having this type of function is simpler in comparison to a
conventional forward/reverse change-over mechanism.
[0041] Referring now to FIG. 2 of the drawings, the automatic
transmission 7 comprises a V-belt type continuously variable
transmission,
[0042] The rotation of the input shaft 5 of the automatic
transmission 7 is transmitted to a differential 9 through a primary
pulley 71, a V-belt 73 and a secondary pulley 72. The differential
9 is connected to drive wheels (not shown) of the vehicle. The
automatic transmission 7 realizes an arbitrary speed ratio by
varying the groove width of the primary pulley 71 and the secondary
pulley 72 accommodating the V-belt 73 with an oil pressure. A
normal automatic transmission may be used instead of the
continuously variable transmission.
[0043] An oil pressure required for the operation of the start-up
clutch 2 and the automatic transmission 7 is supplied from an oil
pump 20. The oil pump 20 is driven by a designated motor to supply
an oil pressure also when the engine 1 is stopped.
[0044] A control routine for the drive force transmission mechanism
will be described below with reference to FIG. 3.
[0045] The engine 1 is controlled by an engine controller 110. The
engine controller 110 stops and starts the engine 1 based on a
signal from the hybrid controller 100. A fuel injection amount and
an ignition timing of the engine 1 are controlled in response to
operational conditions when the engine 1 is running.
[0046] For example, when the vehicle is stationary, coasting or
decelerating, fuel is economized by cutting fuel injection. Fuel
injection is also cut at low vehicle speeds below a predetermined
vehicle speed, and the vehicle runs only on the motive force of the
motor/generator 6.
[0047] In situations in which the drive force of the engine 1 is
not required for vehicle running, the hybrid controller 100 charges
the battery 51 as a state of charge SOC of the battery 51 becomes
low by starting the engine 1 with an engine controller 110 and
driving the motor/generator 6 as a generator.
[0048] The speed ratio of the automatic transmission 70 is
controlled by a transmission controller 170. A signal from a
selector switch 80 which detects an operation range of the vehicle
that is selected by a selector lever i, a command signal from the
hybrid controller 100 and a signal indicative of vehicle
operational conditions such as vehicle speed, throttle opening or
the like are input to the transmission controller 170.
[0049] The transmission controller 170 calculates a target speed
ratio on the basis of these signals and controls the speed ratio of
the automatic transmission 7 to a target speed ratio. The selector
lever comprises a D range which designates a forward running mode,
an R range which designates a reverse running mode, an N range
which designates a neutral running mode and a P range which
designates a stationary mode The selector switch 80 inputs a signal
expressing the selected operation range of the vehicle into the
transmission controller 170 and the hybrid controller 100.
[0050] The hybrid controller 100 engages and disengages the
start-up clutch 2, changes over the forward/reverse change-over
clutch 10 and controls the motor/generator 6 through the inverter
50 in response to the selected operation range of the vehicle, the
throttle opening of the engine 1 and the state of charge SOC of the
battery 51.
[0051] The hybrid controller 100, the engine controller 110 and the
transmission controller 170 respectively comprise a microcomputer
which comprises a central processing unit (CPU), a read only memory
(ROM), a random access memory (RAM) and an input/output interface
(I/O interface).
[0052] It is possible to provide the controllers 100, 110, 170 in a
single computer.
[0053] Control by the hybrid controller 100 of the drive force
transmission mechanism and the motor/generator 6 will be described
below referring to FIGS. 4-14.
[0054] Firstly referring to FIG. 4, when the select lever is in a
parking range, the hybrid controller 100 disengages the start-up
clutch 2 and maintains the forward/reverse change-over clutch 10 at
a neutral position.
[0055] The input shaft 5 of the automatic transmission 7 is
disconnected from the engine 1 and from the motor/generator 6.
[0056] In the P range, when the ignition key (not shown) which is
provided in the vehicle is in the ON position, the hybrid
controller 100 engages the start-up clutch 2 as shown in FIG. 5.
When the motor/generator 6 is operated in this state, the
rotational output is transmitted the engine 1 through the planetary
gear set 3 to start the engine 1 as shown by the arrow in the
figure.
[0057] The rotations of the motor/generator 6 are transmitted to
the ring gear 3R through the planet gears 3P from the sun gear 3S
of the planetary gear mechanism 36. Since the planet gears 3P are
prevented from revolving by the planet carrier 3C fixed to the
casing 11. The sun gear 3S and the ring gear 3R rotate in opposite
directions.
[0058] The engine 1 rotates only in one direction. Since the
motor/generator 6 is connected to the engine 1 via the planetary
gear mechanism 3, the rotation direction is reversed when the
rotation of the motor/generator 6 is transmitted to the engine 1,
or vice versa. In the following explanation, when the rotation
direction of the motor/generator 6 coincides with that of the
engine 1 after it is reversed by the planetary gear mechanism 3, it
is explained that the motor/generator 6 is operated in a reverse
mode.
[0059] In other words, the reverse mode rotation of the
motor/generator 6 corresponds to the rotation direction of the
motor/generator 6 when it drives the vehicle rearwards via the
forward/reverse change-over clutch 10 in the reverse position.
[0060] The gear ratio of the planetary gear set 3 is normally fixed
since the planet gears 3P are prevented from revolving. As a
result, as shown by the straight line in FIG. 14, the rotation
speed input to the sun gear 3S from the motor/generator 6 is
decreased by a fixed ratio and then output to the ring gear 3R.
[0061] Referring now to FIGS. 6A-6C, when the vehicle is
stationary, the hybrid controller 100 controls the start-up clutch
2, the forward/reverse change-over clutch 10 and the
motor/generator 6 in the manner described hereafter in response to
the state of charge SOC of the battery 51 and the operation range
of the vehicle detected by the selector switch 80.
[0062] When the operation range is the N range and the state of
charge SOC of the battery 51 is lower than or equal to a fixed
value, the hybrid controller 100 operates the motor/generator 6 in
reverse mode by a start-up process which is described above and
starts the engine 1. Next the engine 1 is operated with the
start-up clutch 2 engaged and the forward/reverse change-over
clutch 10 remaining in the neutral position. The inverter 50
controls the motor/generator 6 to operate as a generator using the
rotational output of the engine 1 input to the motor/generator 6
from the planetary gear set 3. The current generated by the
motor/generator 6 is fed through the inverter 50 and used to charge
the battery 51.
[0063] When the operation range is the N range and the state of
charge SOC of the battery 51 is higher than the fixed value, the
hybrid controller 100 disengages the start-up clutch 2, and the
forward/reverse change-over clutch 10 is placed in the neutral
position as shown in FIG. 6B. If the engine 1 is operating, the
hybrid controller 100 stops the operation of the engine 1.
[0064] When the operation range is the D range and the state of
charge SOC of the battery 51 is higher than the fixed value, the
hybrid controller 100 disengages the start-up clutch 2, and retains
the forward/reverse changeover clutch 10 in the forward position as
shown in FIG. 6C. If the engine 1 is operating, the hybrid
controller 100 stops the operation of the engine 1.
[0065] When the vehicle starts in the D range, that is to say, when
the accelerator pedal is depressed in the D range, if the engine 1
is stopped, the hybrid controller 100 firstly starts the engine 1
as shown in FIG. 5. Next as shown in FIG. 7, the start-up clutch 2
is engaged and the forward/reverse change-over clutch 10 is changed
over to the forward position. The motor/generator 6 continues to
operate in reverse mode as in the case of engine start-up. As a
result, the output of the engine 1 and the output of the
motor/generator 6 passing through the planetary gear set 3 are
input to the automatic transmission 7. As the rotation speed of the
engine 1 is low when it drives the vehicle to start,
thermal-efficiency of the engine 1 is also low. By assisting the
engine 1 by the motor/generator 6 to make the vehicle start, fuel
consumption of the engine 1 is minimized.
[0066] During the above control, the output of the motor/generator
6 is transmitted to the output shaft 4 of the start-up clutch 2
through the sun gear 3S, planet gears 3P and ring gear 3R of the
planetary gear mechanism 3. As shown in FIG. 14, since the rotation
speed of the motor/generator 6 is reduced by the planetary gear set
3, the torque of the motor/generator 6 is actually amplified and
output to the output shaft 4 of the start-up clutch 2. Thus in
comparison to connecting the motor/generator 6 directly to the
engine 1, the rotation speed of the motor/generator 6 is higher
when it assists the engine 1. Due to the higher rotation speed, the
motor/generator can exert a larger torque on the output shaft 4
than in the case where the motor/generator is directly connected to
the engine. In other words, a small light-weight motor/generator 6
can provide a sufficient torque according to this drive force
transmission mechanism.
[0067] Another possible operation of the drive force transmission
mechanism to start the vehicle will be described with reference to
FIG. 8. In this case, the engine 1 remains stopped, the start-up
clutch 2 is disengaged and the forward/reverse change-over clutch
10 is changed over to the forward position.
[0068] The motor/generator 6 is operated in reverse mode. Thus the
vehicle moves forward only using the motive force of the
motor/generator 6. However since torque is amplified due to the
decrease in rotation speed due to the action of the planetary gear
set 3, it is possible to obtain a required torque during start-up
or subsequent acceleration with a small light-weight
motor/generator 6. In comparison to directly connecting the
motor/generator to the engine, this arrangement also allows the
operation of the motor/generator 6 to be performed in a
high-efficiency rotation speed region since the rotation speed of
the motor/generator is high.
[0069] When the vehicle initiates start-up with the engine 1
stopped, the engine 1 is started later while the vehicle is in
travel. In this case, the hybrid controller 100 simply engages the
start-up clutch 2 as shown in FIG. 9. As a result, a part of the
rotational output of the motor/generator 6 which drives the vehicle
is used for engine start-up. Once the engine has started driving
the vehicle, the hybrid controller 100 may stop the operation of
the motor/generator 6 as a motor.
[0070] When the vehicle is in steady-state running by the drive
force of the engine 1, the hybrid controller 100 selectively
applies the two operational states of the motor/generator 6 as
shown in FIGS. 10A and 10B depending on the state of charge SOC of
the battery 51. In either case, the hybrid controller 100 engages
the start-up clutch 2 and retains the forward/reverse change-over
clutch 10 in the forward position.
[0071] When the state of charge SOC of the battery 51 is lower than
or equal to the fixed value, the hybrid controller 100 uses a part
of the rotational output of the engine 1 to use the motor/generator
6 as a generator by control of the inverter 50. This generated
current is used to charge the battery 51.
[0072] When the state of charge SOC is higher than the fixed value,
generation of electricity by the motor/generator 6 is not performed
since the hybrid controller 100 allows the motor/generator 6 to
freely rotate without generating power by the control of the
inverter 50 as shown by FIG. 10B.
[0073] When the vehicle shifts from steady-state running to
acceleration, that is to say, when the accelerator pedal is further
depressed, the hybrid controller 100 selectively applies the two
operational states of the motor/generator 6 as shown in FIGS. 11A
and 11B depending on the state of charge SOC of the battery 51. In
either case, the hybrid controller 100 engages the start-up clutch
2 and retains the forward/reverse change-over clutch 10 in the
forward position in a similar manner to control during steady-state
running.
[0074] When the state of charge SOC of the battery 51 is lower than
or equal to the fixed value, the hybrid controller 100 uses a part
of the rotational output of the engine 1 and drives the
motor/generator 6 as a generator to charge the battery 51. This is
basically the same as the state shown in FIG. 10A which is applied
to the state of charge SOC below the fixed value during
steady-state running. In this case, both the acceleration of the
vehicle and the power generation by the motor/generator 6 are
performed using the output power of the engine 1.
[0075] When the state of charge SOC is higher than the fixed value,
the hybrid controller 100 uses the motor/generator 6 as a motor in
reverse mode as shown in FIG. 11B and assists the drive force of
the engine 1 by inputting the rotations to the output shaft 4 of
the start-up clutch 2 through the planetary gear set 3.
[0076] Since the rotational output of the motor/generator 6 is
reduced by the planetary gear set 3 as explained above, amplified
torque of the motor/generator 6 is input to the output shaft 4.
Thus in comparison to connecting the motor/generator 6 directly to
the engine 1, it is possible to assist the engine 1 with a
sufficient torque with a small light-weight motor/generator 6.
[0077] During deceleration, regeneration of electrical energy is
performed by the motor/generator 6 using the rotational torque
input to the automatic transmission 7 from the drive wheels as
shown in FIGS. 12A and 12B.
[0078] During this control, when the state of charge SOC of the
battery 51 is lower than or equal to the fixed value, the hybrid
controller 10 disengages the start-up clutch 2, and retains the
forward/reverse change-over clutch 10 in the forward position as
shown in FIG. 12A. At this time, the rotation of the drive wheels
is transmitted to input shaft 5 of the automatic transmission 7.
After the rotation speed is increased by the planetary gear set 3,
it is input to the motor/generator 6. The motor/generator 6 uses
this rotational force to generate power in order to charge the
battery 51. The motor/generator 6 can therefore generate power in a
high generation-efficiency rotation speed region since the rotation
speed of the input shaft 5 is increased by the planetary gear set
3. Furthermore a regenerative braking due to the resistance of the
motor/generator 6 in power generation is applied by the
motor/generator 6 to the drive wheels.
[0079] Alternatively as shown in FIG. 12B, it is possible to engage
the start-up clutch 2 and retain the forward/reverse switching
clutch 10 in the forward position. In this case, the
motor/generator 6 is rotated by the input rotations from the
planetary gear set 3 which makes the motor/generator 6 generate
power. On the other hand, the engine 1 is also rotated by the
rotational force input from the drive wheels through the automatic
transmission 7 and thus an engine brake is applied to the drive
wheels in addition to the regenerative braking force by the
motor/generator 6.
[0080] When the state of charge SOC of the battery 51 is higher
than the fixed value, the hybrid controller 100 engages the
start-up clutch 2 and retains the forward/reverse switching clutch
10 in a forward position as shown in FIG. 12C. In this case, the
motor/generator 6 does not generate power due to control of the
inverter 50 by the hybrid controller 100. Thus in the same way as
shown in FIG. 12B, the motor/generator 6 is rotated by the input
rotations through the planetary gear set 3. However since power
generation is not performed at this time, the motor/generator 6
rotates freely without resistance. As a result, regenerative
braking does not result and only the engine brake is applied to the
drive wheels.
[0081] Finally, the operation of the drive force transmission
mechanism when the vehicle is reversing will be described with
reference to FIGS. 13A-13C.
[0082] When the vehicle is reversing, the hybrid controller 100
engages the start-up clutch 2 and changes over the forward/reverse
change-over clutch 10 to the reverse position as shown in FIG.
13A.
[0083] The drive force of the engine 1 and the drive force of the
motor/generator 6 are both input into the automatic transmission 7
through the forward/reverse change-over clutch 10 and the input
shaft 5.
[0084] Although the rotational direction of the motor/generator 6
is the same as that during forward motion, the rotations of the
motor/generator 6 are directly input to the input shaft 5 without
passing through the planetary gear set 3. As a result, the
direction of rotation of the input shaft 5 is opposite to that
during forward motion. On the other hand, since the rotation of the
engine 1 is transmitted to the input shaft 5 through the planetary
gear set 3, the direction of the rotation of the engine 1 is also
reversed before it is input to the input shaft 5. Though the
rotation directions of the motor/generator 6 and engine 1 are
identical to those in the forward motion, the direction of the
rotation of the input shaft 5 is reversed in the reverse motion. In
the reverse motion, the speed of the rotation of the engine 1 is
increased by the planetary gear set 3 before it is input to the
input shaft 5 as shown in FIG. 14.
[0085] In this situation, the rotation speed of the motor/generator
6 is transmitted to the input shaft 5 without being decreased by
the planetary gear set 3 in contrast to the case where the vehicle
starts to move forward that is shown in FIG. 7. Thus, when the
vehicle starts to move rearward it is necessary to reduce the
rotation speed of the motor/generator 6 to the same extent as in
the case where the vehicle starts to move forward. The reduction is
performed by the hybrid controller 100 by control of the inverter
50.
[0086] After the vehicle started to move rearward, the hybrid
controller 100 cuts off the supply of current to the
motor/generator 6 by controlling the inverter 50 as shown in FIG.
13B. As a result, the motor/generator rotates freely without
resistance in accordance with the rotation of the sun gear 3S and
the vehicle is driven rearward only with the drive force of the
engine
[0087] It is possible that the engine 1 can not be started up for
some reasons. In such a case, the hybrid controller 100 retains the
forward/reverse change-over clutch 10 in the reverse position and
disengages the start-up clutch 2 as shown in FIG. 13C. Thus it is
still possible to drive the vehicle rearward only with the output
of the motor/generator 6.
[0088] As described above, a drive force transmission mechanism
according to this invention connects an output shaft 4 of a
start-up clutch 2 and a rotation shaft 30 of a motor/generator 6
through a planetary gear set 3 and selectively engages the input
shaft 5 of the automatic transmission 7 to the output shaft 4 and
the rotation shaft 30 through a forward/reverse change-over clutch
10. During the forward motion of the vehicle, the rotation speed of
the output of the motor/generator 6 is decreased by the planetary
gear set 3 to assist the drive force of the engine 1. Therefore
during the forward motion of the vehicle, either for vehicle start
or acceleration, the motor/generator 6 is operated in a
high-efficiency high rotation speed region. As a result, it is
possible to obtain a suitably large torque for vehicle start or
acceleration using a small light-weight motor/generator 6.
[0089] Since the change-over of forward/reverse motion of the
vehicle is performed using, for example, a simple dog clutch in
this drive force transmission mechanism, a forward/reverse
change-over mechanism as used in the prior art device is not
required.
[0090] The planet gears 3P of the planetary gear set 3 may comprise
single pinions as in the above embodiment or double pinions as
shown in FIG. 15. In the latter case, a ring gear 3R is fixed to
the casing 11 and a planet carrier 3C is engaged with the output
shaft 4 of the start-up clutch 2.
[0091] The contents of Tokugan Hei 2000-60579 with a filing date of
Mar. 6, 2000 in Japan, are hereby incorporated by reference.
[0092] Although the invention has been described above by reference
to certain embodiments of the invention, the invention is not
limited to the embodiments described above. Modifications and
variations of the embodiments described above will occur to those
skilled in the art, in light of the above teachings.
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