U.S. patent application number 09/801633 was filed with the patent office on 2001-07-19 for transmission, and vehicle and bicycle using the same.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Masaki, Ryoso.
Application Number | 20010008859 09/801633 |
Document ID | / |
Family ID | 12485595 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008859 |
Kind Code |
A1 |
Masaki, Ryoso |
July 19, 2001 |
Transmission, and vehicle and bicycle using the same
Abstract
Disclosed herein is a transmission comprising a mechanism for
distributing energy of a drive source into a plurality of
differential mechanisms; a plurality of motors connected to said
plurality of differential mechanisms, respectively; and a mechanism
for synthesizing energies outputted from said plurality of
differential mechanisms.
Inventors: |
Masaki, Ryoso; (Hitachi-shi,
JP) |
Correspondence
Address: |
EVENSON, McKEOWN, EDWARDS
& LENAHAN, P.L.L.C.
1200 G Street, N.W., Suite 700
Washington
DC
20005
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
12485595 |
Appl. No.: |
09/801633 |
Filed: |
March 9, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09801633 |
Mar 9, 2001 |
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09495720 |
Feb 1, 2000 |
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09495720 |
Feb 1, 2000 |
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09253127 |
Feb 19, 1999 |
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6053833 |
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Current U.S.
Class: |
475/5 ; 475/150;
475/221; 903/903; 903/910; 903/918; 903/946 |
Current CPC
Class: |
B60K 6/543 20130101;
B60W 20/00 20130101; F16H 3/727 20130101; B60W 10/02 20130101; F16H
2037/102 20130101; B60L 2200/26 20130101; Y10S 903/946 20130101;
B60K 6/445 20130101; F16H 2200/0008 20130101; Y02T 10/62 20130101;
B60L 2200/12 20130101; Y02T 10/70 20130101; B60W 2710/105 20130101;
B60W 2710/1022 20130101; F16H 3/725 20130101; Y02T 10/64 20130101;
B60K 1/02 20130101; B60W 10/06 20130101; B62M 6/55 20130101; F16H
61/66 20130101; Y10S 903/903 20130101; B60K 6/365 20130101; F16H
37/0826 20130101; Y10S 903/91 20130101; B60L 50/16 20190201; F16H
3/72 20130101; B60Y 2200/12 20130101; B62M 6/60 20130101; B62M
11/145 20130101; Y02T 10/7072 20130101; B60L 3/0092 20130101; B62M
6/45 20130101; B60L 2240/486 20130101; B60W 10/08 20130101; Y10S
903/918 20130101; B60W 10/26 20130101 |
Class at
Publication: |
475/5 ; 475/150;
475/221 |
International
Class: |
F16H 003/72 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 19, 1998 |
JP |
10-37005 |
Claims
What is claimed is
1. A transmission comprising: a mechanism for distributing energy
of a drive source into a plurality of differential mechanisms; a
plurality of motors connected to said plurality of differential
mechanisms, respectively; and a mechanism for synthesizing energies
outputted from said plurality of differential mechanisms.
2. A transmission comprising: a plurality of differential
mechanisms in each of which a difference in the number of rotation
between an input shaft and an output shaft is controlled by a
motor; wherein said input shafts of said plurality of differential
mechanisms are taken as a common shaft, and said output shafts of
said plurality of differential mechanisms are taken as a common
shaft.
3. A vehicle comprising: an engine for generating drive energy for
driving said vehicle; and a transmission for changing the speed of
rotation of said engine and transmitting the rotational drive force
thus speed-changed to a wheel; said transmission comprising: first
and second differential mechanisms each of which takes at least a
drive force generated by said engine as an input force and takes a
drive force for driving said wheel as an output force; and first
and second motors for controlling said first and second
differential mechanisms, respectively.
4. A vehicle comprising: an engine for generating drive energy for
driving said vehicle; first and second planetary gears each of
which is composed of a sun gear, a planetary element, and a ring
gear; and first and second motors for controlling said sun gears of
said first and second planetary gears, respectively; wherein one of
said planetary element and said ring gear of each of said first and
second planetary gears is connected to an input shaft driven by
said engine and the other is connected to an output shaft for
driving a vehicular body.
5. A vehicle according to claim 3 or 4, further comprising energy
storing means for storing energy for driving said first and second
motors.
6. A vehicle according to claim 5, wherein a gear ratio between
said common input shaft and said common output shaft of said first
differential mechanism is larger than a gear ratio between said
common input shaft and said common output shaft of said second
differential mechanism.
7. A vehicle according to claim 5, wherein said engine is started
by controlling said first and second motors using the energy of
said energy storing means.
8. A vehicle according to claim 6, wherein said engine is started
with a vehicular speed kept constant by controlling said first and
second motors.
9. A vehicle according to claim 6, wherein said vehicle is driven
with said engine stopped by controlling said first and second
motors.
10. A vehicle according to claim 6, wherein said vehicle has a
first operational mode in which said first motor is locked and said
second motor is turned into a free-run state when said vehicle is
driven by said engine, and a second operational mode in which said
first motor is turned into a free-run state and said second motor
is locked when said vehicle is driven by said engine.
11. A vehicle according to claim 10, wherein said second motor
comprises a fastening means for mechanically fastening said second
motor.
12. A vehicle according to claim 10, wherein each of said first and
second motors comprises a fastening means for mechanically
fastening said motor.
13. A vehicle according to claim 11 or 12, wherein when the
operational mode of said vehicle is changed into said first or
second operational mode, said fastening means mechanically fastens
a shaft of said first or second motor after said motor is
electrically locked.
14. A vehicle according to claim 6, wherein when said vehicle is
driven by said engine, said first motor is turned into a
power-running state, and said second motor is turned into a
power-running or regenerative state.
15. A vehicle according to claim 6, wherein when said vehicle is
driven by said engine, said first motor is turned into a
power-running state using energy generated by said second
motor.
16. A vehicle according to claim 3 or 4, wherein when said first or
second motor becomes uncontrollable, said vehicle is driven by the
controllable one of said first and second motors and said
engine.
17. A vehicle according to claim 3 or 4, wherein when it is
confirmed upon stop of said vehicle that said first or second motor
becomes uncontrollable, said engine is started by the controllable
one of said first and second motors, and thereafter said vehicle is
driven by controlling said controllable motor and said engine.
18. A vehicle according to claim 4, wherein a gear ratio between
said output side gear and said output shaft of said first planetary
gear is different from a gear ratio between said output side gear
and said output shaft of said second planetary gear.
19. A bicycle comprising: first and second differential mechanisms
each of which takes a drive force generated by a driver as an input
force and takes a drive force for driving a wheel as an output
force; and first and second motors for controlling said first and
second differential mechanisms, respectively.
20. A transmission comprising: a plurality of differential
mechanisms having input shafts taken as a common shaft and output
shafts taken as a common shaft; wherein at least one of said
plurality of differential mechanisms controls a difference in the
number of rotation between said common input shaft and said common
output shaft by a first motor, and at least one of the others of
said plurality of differential mechanisms performs torque control
by a second motor.
21. A transmission comprising: a plurality of differential
mechanisms having input shafts taken as a common shaft and output
shafts taken as a common shaft, each of said plurality of
differential mechanisms being composed of at least three gear
elements; and a plurality of motors, each of which is connected to
a shaft of one, different from those connected to said common input
shaft and said common output shaft, of said at least three gear
elements of each of said plurality of differential mechanisms.
22. A vehicle comprising: an engine; first and second planetary
gears, each being composed of a sun gear, a planetary element, and
a ring gear; and first and second motors for controlling said sun
gears of said first and second planetary gears, respectively;
wherein one of said planetary element and said ring gear of each of
said first and second planetary gears is connected to an input
shaft driven by said engine and the other is connected to an output
shaft for driving a vehicular body.
23. A vehicle comprising: an engine; a plurality of differential
mechanisms to which a drive force of said engine is inputted; a
drive mechanism for driving said vehicle by the output of said
plurality of differential mechanisms; a plurality of motors
connected to said plurality of differential mechanisms,
respectively; and a fastening device for stopping rotation of said
engine.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a transmission including
motors and differential mechanisms, and a vehicle and a bicycle
using the same.
[0002] A hybrid car utilizing a drive force of a motor has been
known as a drive system aimed at reducing a fuel consumption of an
engine. Various kinds of hybrid cars have been proposed, for
example, a series hybrid type, a parallel hybrid type, and a
series/parallel hybrid type using two motors and one planetary
gear. Concretely, Japanese Patent Laid-open No. Hei 7-135701
discloses a method in which a drive force of an engine is inputted
in a planetary gear and a vehicle is driven by a drive force
obtained by an output shaft of the planetary gear, wherein the
drive force is controlled by a generator. In this method, since
part of the energy of the engine is used for generating electric
energy by the generator and the drive force of the engine is
assisted by the motor connected to the output shaft, the engine can
be usually driven in a high-efficiency/high-torque region and the
vehicle can attain a transmission function. The same principle has
been also disclosed in Japanese Patent Laid-open Nos. Sho 49-112067
and Sho 58-191364. This known method disclosed in the above
documents is hereinafter referred to as "a first method".
[0003] As disclosed in Japanese Patent Laid-open No. Sho 60-95238,
there has been proposed a method in which a drive force of an
engine is transmitted to right and left drive wheels via planetary
gears controlled by motors, respectively. This method is
hereinafter referred to as "a second method".
[0004] As disclosed in Japanese Patent Laid-open No. Sho 57-47054,
there has been proposed a method in which a plurality of planetary
gears are driven by motors respectively and a drive force is
outputted from the selected one of the plurality of planetary
gears, so that the optimum drive of the motors can be performed in
accordance with the operational point of the vehicle at all times.
This method is hereinafter referred to as "a third method".
[0005] As disclosed in "Alternative Cars in the 21st Century--A New
Personal Transportation Paradigm--, Robert Q. Riley, Published by
Society of Automotive Engineers, Inc., 400 Commonwealth Drive
Warrendale, Pa. 15096-0001, U.S.A., p.149-P153", there has been
proposed a transmission using a continuously variable transmission
CVT in combination with a planetary gear. In this method, since the
vehicle can be stopped while the engine is rotated, without using
of any clutch, by setting a speed varying ratio of the continuously
variable transmission CVT at a specific value, it is possible to
smoothly start the vehicle only by controlling the speed varying
ratio of the continuously variable transmission CVT. This method is
hereinafter referred to as "a fourth method".
[0006] The first method, however, has a problem. Since electric
energy is generated by the generator and the vehicle is driven by
the motor for realizing the transmission function, a loss in
electric energy occurs. As a result, although the engine can be
always driven at an operational point being good in efficiency, the
efficiency of the entire vehicle is reduced correspondingly to the
loss in electric energy.
[0007] The second method, in which the planetary gears are provided
for the right and left different output shafts, respectively, has a
configuration obtained by extending the configuration of a usual
parallel hybrid car to the right and left wheels. As a result, the
second method requires the input/output of electric energy for
realizing the speed varying operation, and therefore, this method
has the same problem as described above.
[0008] The third method has a configuration obtained by extending
the configuration of the first method. As a result, this method has
the same problem as described above in terms of the loss in
electric energy.
[0009] The fourth method has a problem that since the engine must
be always rotated for driving the vehicle, there is a limitation in
reducing the fuel consumption per unit running distance over a
period, in which the engine is driven, including a stop of the
vehicle.
SUMMARY OF THE INVENTION
[0010] In view of the foregoing, the present invention has been
made, and a first object of the present invention is to provide a
transmission capable of realizing a continuously variable
transmission function using motors, and enhancing the transmission
efficiency by minimizing a loss in electric energy.
[0011] A second object of the present invention is to provide a
vehicle using the above transmission, which is capable of reducing
the fuel consumption per unit running distance.
[0012] A third object of the present invention is to provide a
bicycle capable of reducing fatigue of a driver.
[0013] The above first object can be achieved by provision of a
transmission including: a mechanism for distributing energy of a
drive source into a plurality of differential mechanisms; a
plurality of motors connected to the plurality of differential
mechanisms, respectively; and a mechanism for synthesizing energies
outputted from the plurality of differential mechanisms.
[0014] The above first object can be also achieved by provision of
a transmission including: a plurality of differential mechanisms in
each of which a difference in the number of rotation between an
input shaft and an output shaft is controlled by a motor; wherein
the input shafts of the plurality of differential mechanisms are
taken as a common shaft, and the output shafts of the plurality of
differential mechanisms are taken as a common shaft.
[0015] Gear ratios between the common input shaft and the common
output shaft of the plurality of differential mechanisms are
preferably set at different values. This makes it possible to
provide a system capable of enhancing the efficiency.
[0016] The second object can be achieved by provision of a vehicle
including: an engine for generating a drive force for driving a
vehicle; first and second planetary gears each of which is composed
of a sun gear, a planetary element, and a ring gear; and first and
second motors for controlling the sun gears of the first and second
planetary gears, respectively; wherein one of the planetary element
and the ring gear of each of the first and second planetary gears
is connected to an input shaft driven by the engine and the other
is connected to an output shaft for driving a vehicular body.
[0017] The third object can be achieved by provision of a bicycle
including: first and second differential mechanisms each of which
includes an input shaft driven by a driver and an output shaft
composed of wheels; and first and second motors for controlling the
first and second differential mechanisms, respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a configuration view showing one embodiment in
which the present invention is applied to a hybrid car of a type in
which the transmission function is realized using two planetary
gears each having a sun gear controlled by a motor;
[0019] FIG. 2 is a flow chart showing the outline of a control
method for driving the hybrid car shown in FIG. 1;
[0020] FIG. 3 is a drive force-vehicular speed characteristic
diagram showing a range of operational points for determining an
ideal mode to be operated on the basis of the existing drive
state;
[0021] FIG. 4 is a state transition diagram showing a transition
method between operational modes upon drive of the hybrid car shown
in FIG. 1;
[0022] FIG. 5 is a flow chart showing a method of controlling
ordinary modes shown in FIG. 2;
[0023] FIG. 1 is a flow chart showing a method of controlling shift
modes shown in FIG. 2;
[0024] FIGS. 7(a) to 7(e) are Torque-speed characteristic diagrams
showing the flows of energies and relationships among the speed and
torque for an engine, motor and planetary gears when the vehicle is
driven with the increased gear ratio under a CVT mode;
[0025] FIGS. 8(a) to 8(e) are Torque-speed characteristic diagrams
showing the flows of energies and relationships among the speed and
torque for the engine, motor and planetary gears when the vehicle
is driven with the decreased gear ratio under the CVT mode;
[0026] FIGS. 9(a) to 9(e) are Torque-speed characteristic diagrams
showing methods of changing the operational point of an engine for
charging a battery and assisting the motor drive by the energy of
the battery while driving the vehicle under the CVT mode,
respectively;
[0027] FIG. 10 is a flow chart showing operations performed in the
case where a motor fails;
[0028] FIG. 11 is a configuration diagram showing another
embodiment of the hybrid car in which the gear configuration is
different from that shown in FIG. 1;
[0029] FIG. 12 is a configuration diagram showing a further
embodiment of the hybrid car including two planetary gears in which
a gear ratio between the input and output sides of one planetary
gear is the same as a gear ratio between the input and output sides
of the other planetary gear;
[0030] FIG. 13 is a configuration diagram showing one embodiment in
which the present invention is applied to a bicycle; and
[0031] FIG. 14 is a configuration diagram showing another
embodiment in which the present invention is applied to a bicycle
including a drive system without use of any chain.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] Hereinafter, one embodiment of the present invention will be
described with reference to FIG. 1.
[0033] FIG. 1 shows a car of a type in which a vehicular body is
driven by rotating tires 3a and 3b via a drive shaft 2 using energy
of an engine 1. Planetary gears A4 and B6, which are essential
composing elements of the present invention, are composed of a
combination of a sun gear 4s, a planetary element 4p and a ring
gear 4r, and a combination of a sun gear 6s, a planetary element 6p
and a ring gear 6r, respectively. The sun gears 4s and 6s are
driven by motors AB and B9 controlled by power converters 10 and
11, respectively. A battery 12 is used for supplying energy
required for these motors A8 and B9 or storing energy generated by
the motors A8 and B9. The planetary elements 4p and 6p are both
fastened to the same input shaft, so that a drive torque of the
engine 1 is distributed into the planetary gears A4 and B6. On the
output sides of the ring gears 4r and 6r are arranged gears having
different gear ratios. To be more specific, a gear 5 having a large
gear ratio and a gear 7 having a small gear ratio are arranged on
the output sides of the ring gears 4r and 6r, respectively. These
gears 5 and 7 are connected to the common output shaft, so that
output torques .tau.va and .tau.vb outputted from the planetary
gears A4 and B6 are synthesized into a vehicle drive torque .tau.v
at the common output shaft. With this configuration, the vehicle
can be accelerated/decelerated as required by a driver. Also the
vehicle drive torque .tau.v and an engine speed .omega.e can be
adjusted by driving the sun gears 4a and 6s under control of motor
toques .tau.a and .tau.b and motor speeds .omega.a and .omega.b of
the motors A8 and B9 using the power convertors 10 and 11.
[0034] Next, a basic operational method for controlling the engine
1 and motors A8 and B9 shown in FIG. 1 will be described using a
flow chart shown in FIG. 2. At step 101 shown in FIG. 2, inputted
are operational commands determined by a driver, for example, an
accelerator actuated amount Xa, a brake actuated amount Xb, and a
changeover signal Xc indicating a forward, backward, or neutral
mode; and also a vehicular speed .omega.v, a charging state of the
battery 12, a temperature of each portion, and a vehicular state.
At step 102, a drive force command value .tau.r of the vehicle is
calculated on the basis of the above inputted values. Then, at step
103, a reference operational mode Mref indicating an ideal
operating method is determined on the basis of the vehicle drive
force command value .tau.r and the vehicular speed .omega.v.
[0035] For example, as shown in FIG. 3, upon running of the vehicle
at a low vehicular speed .omega.v or upon backward movement of the
vehicle, a motor drive mode is selected in which the engine 1 is
stopped and the vehicle is driven only by the motors A8 and B9. In
FIG. 3, a region other than the motor drive mode shown by hatching
involves a first speed mode, a second speed mode, and a CVT mode in
each of which the engine 1 is started and the vehicle is driven
using a drive force of the engine 1. When the vehicular speed
.omega.v is low and a drive force is required, the first speed mode
for controlling the speed-change ratio at a value equivalent to a
low gear ratio is selected. When the vehicular speed .omega.v is
medium or more and the necessary toque is low, the second speed
mode capable of enhancing the engine efficiency is selected. When
the vehicular speed .omega.v is medium or more and a high torque is
required, the CVT mode capable of obtaining a high toque drive
force by adding the drive torque of the motor is selected. In
addition, when the drive force command value .tau.r is negative,
the CVT mode may be desirably selected in order to store
regenerative energy in the battery 12 using the motors A8 and B9 as
generators.
[0036] Incidentally, the operational modes shown in FIG. 3 are not
necessarily fixed but can be suitably changed depending on the
charging state or the temperature of the battery 12. The actual
operational mode M is determined on the basis of the existing
operational mode and the reference operational mode Mref obtained
in accordance with the above manner. For example, even if the
reference operational mode Mref becomes the first speed mode in a
state in which the vehicle is driven under the motor drive mode,
since the engine 1 cannot be rapidly driven, an operation for
starting the engine 1 must be performed. Further, if the
start-up/stop of the engine 1 is excessively repeated, the fuel
consumption is rather increased. Accordingly, when the engine 1 is
started or stopped under a new operational mode changed from the
previous one, an operation for keeping the new operational mode for
a specific period of time is performed. The calculation taking the
above specific operations into account is performed at step 103, to
thus determine the operational mode M on the basis of the existing
operational mode and the reference operational mode Mref.
[0037] At step 104, it is judged whether the operational mode M is
the ordinal mode shown in FIG. 3 or a shift mode for changing an
operational mode to another one. On the basis of the judgement, the
process goes on to step 105 at which the operation under the
ordinary mode is performed or to step 106 at which the operation
under the shift mode is performed.
[0038] FIG. 4 shows a state transition diagram representative of
the state transition of the operational mode M. The ordinary modes
involve the motor drive mode, first speed mode, second speed mode,
and CVT mode. The shift modes involve an engine start mode and a
fastening device B release mode. A key-off mode represents a state
in which the key is turned off. If the key is turned on, the
key-off mode is changed into the vehicle start mode in which each
controller is turned into a controllable state. After the operation
for starting all of the controllers is completed, the vehicle start
mode is changed into the motor drive mode in which the motor A8 and
B9 are rotated by operating an accelerator by a driver and the
vehicle is turned into a drivable state. When the vehicular speed
.omega.v becomes a medium speed or more, or a large drive force is
required, it is necessary for changing the motor drive mode into
either of the first speed mode, second speed mode, and CVT mode. At
this time, the motor drive mode is changed, via the engine start
mode for starting the engine, which is one of the shift modes, into
a specific ordinary mode in which the vehicle is driven using the
drive force of the engine. The change between the first speed mode,
second speed mode and CVT mode can be basically performed not by
way of any shift mode; however, in this embodiment adopting a
fastening manner to be described later, there is used a method in
which the second speed mode is changed into another ordinary mode
by way of the fastening device B release mode which is one of the
shift modes. In addition, if there occurs any failure, the
operational mode is changed into a fail mode associated with the
failure, in which an operation suitable for coping with the failure
is performed. Further, when the key is turned off, an operation for
safely stopping the vehicle is performed, and thereafter the
control is stopped under the key-off mode.
[0039] Next, the operation under each of the ordinary modes shown
in FIG. 2 will be described in detail with reference to FIG. 5. For
an easy understanding of the description, there are shown the
following equations 1 to 10 given in the system configuration shown
in FIG. 1.
.omega.e=kp.omega.a+ka.omega.v [Equation 1]
.omega.e =kp.omega.b+kb.omega.v [Equation 2]
.tau.e=.tau.ea+.tau.eb [Equation 3]
.tau.v=.tau.va+.tau.vb [Equation 4]
.tau.ea=.tau.a/kp=.tau.va/ka [Equation 5]
.tau.eb=.tau.b/kp=.tau.vb/kb [Equation 6]
Pe=Pea+Peb [Equation 7]
Pv=Pva+Pvb [Equation 8]
Pea=Pa+Pva [Equation 9]
Peb=Pb+Pvb [Equation 10]
[0040] In the above equations, .omega.e, .omega.v, .omega.a and
.omega.b designate the engine speed, vehicular speed, motor A
speed, and motor B speed, respectively; .tau.e, .tau.ea, .tau.eb,
.tau.a, .tau.b, .tau. v, .tau.va, and .tau.vb designate the engine
torque, planetary gear A shared engine torque, planetary gear B
shared engine torque, motor A torque, motor B torque, vehicular
torque, planetary gear A shared vehicular torque, and planetary
gear B shared vehicular torque, respectively; and Pe, Pea, Peb, Pa,
Pb, Pv, Pva, and Pvb designate the engine power, planetary gear A
shared input power, planetary gear B shared input power, motor A
power, motor B power, vehicle drive power, planetary gear A output
power, and planetary gear B output power, respectively. In
addition, the relationship between the constants Ka and Kb
associated with the gear ratios is given by the following
equation.
Ka>kb [Equation 11]
[0041] This means that the gear ratio between the input side and
output side of the planetary gear A is larger than the gear ratio
between the input side and output side of the planetary gear B.
[0042] As described above, the ordinary modes involve the four
operational modes, and at step 111 shown in FIG. 5, the operational
mode M is discriminated.
[0043] In the case of the motor drive mode, operations in steps
112, 113 and 114 are performed. At step 112, in accordance with the
equation 2, the motor B speed .omega.b is controlled in such a
manner that the engine speed .omega.e becomes zero while the
vehicular speed .omega.v is kept constant. At step 113, the vehicle
drive torque .tau.v is controlled by controlling the motor A torque
.tau.a. At this time, the torque control is performed in such a
manner that, with .tau.e=0 in the equation 3, the vehicle drive
torque .tau.v is determined in accordance with the equations 4, 5
and 6.
[0044] From the equation 11, to satisfy the relationship of
.tau.v>0, the vehicle is usually driven in such a manner that
the motor A is in the power-running state and the motor B is in the
power generating state. Of course, at step 114, an operation for
continuously stopping the control of the engine is performed.
[0045] In the case of the first speed mode, an operation for
controlling the motor A speed .omega.a into zero is performed at
step 115 and an operation for stopping the control of the motor B
is performed at step 116. With these operations, the motor A is
turned into an electrically locked state and the motor B is turned
into a free-run state, and thereby the planetary gear A4 having the
large gear ratio between the input side and the output side is
driven by the engine 1 in a state in which the sun gear 4s of the
planetary gear A4 is fixed. That is to say, the speed-change ratio
in the first speed mode is equivalent to a low gear ratio of a
usual manual transmission, and accordingly, the engine torque
.tau.e can be increased in the first speed mode. Thus, by
controlling the engine at step 117, the vehicle drive torque can be
controlled into a necessary value. Further, in the first speed
mode, the input/output of energy to/from both the motors A8 and B9
is not performed, so that it is possible to minimize a loss in
electric energy.
[0046] In the case of the CVT mode, the motor A torque .tau.a is
controlled at step 118; the motor B speed .omega.b is controlled at
step 119; and the power of the engine 1 is controlled by
controlling the engine 1 at step 120, to thus realize the
continuously variable transmission function. In addition, the
operation under the CVT mode will be described in detail later with
reference to FIGS. 7 to 9.
[0047] In the case of the second speed mode, operations in steps
121 to 126 are performed. First, at step 121, it is judged whether
or not the motor B speed .omega.b becomes zero. If no, at step 122,
an operation for controlling the motor B speed .omega.b into zero
is performed. Meanwhile, at step 123, the control of the motor A is
stopped, that is, the motor A is turned into a free-run state. With
this control, reversely to the first speed mode, the sun gear 6s of
the planetary gear B6 having the small gear ratio between the input
side and the output side is fixed, and accordingly, in the second
speed mode, the speed-change ratio is equivalent to a high gear
ratio of a usual manual transmission. By controlling the engine in
such a state at step 124, the engine 1 is always driven in a high
torque region. That is to say, in the second speed mode, the highly
efficient operation of the engine 1 is made possible. At this time,
like the first speed mode, the input/output of energy to/from both
the motors A8 and B9 is not performed, so that it is possible to
minimize a loss in electric energy.
[0048] In addition, at step 121, if it is judged that the motor B
speed .omega.b is zero, the process is jumped to step 125 at which
a fastening device B13 is turned on to mechanically lock the sun
gear 6s. Next, at step 126, the control of the motors A8 and B9 is
stopped. Then, the process goes on to the above-described step 124
at which the drive force of the vehicle is controlled by
controlling the engine. With these operations, it is possible to
eliminate a loss in electric energy generated by a current flowing
when the motor B9 is electrically locked, and hence to further
reduce the fuel consumption of the vehicle. In the case where the
vehicle is driven by the engine 1, the vehicle is driven under the
second speed mode for a long period of time excluding the
accelerating operation, so that the prevention of the loss in
electric energy in the second speed mode greatly contributes to the
reduction in the fuel consumption.
[0049] Next, the shift modes for changing an ordinary mode to
another one will be described with reference to FIG. 6.
[0050] The shift modes involve the engine start mode and the
fastening device B release mode. At step 131, it is judged whether
the shift mode is the engine start mode or the fastening device B
release mode. In the case of the engine start mode, operations in
steps 132 to 135 are performed, and in the case of the fastening
device B release mode, operations in steps 136 to 139 are
performed.
[0051] By way of the engine start mode, the motor drive mode which
is one of the ordinary modes is changed into another ordinary mode
in which the engine 1 is driven First, at step 132, the speeds of
the motors A8 and B9 are controlled. From the equations 1 and 2,
the following equations 12 and 13 are given.
.omega.v=kp (.omega.a-.omega.b)/(ka-kb) [Equation 12]
.omega.e=kp (ka.omega.b-kb.omega.a)/(ka-kb) [Equation 13]
[0052] The engine 1 is gradually accelerated while the vehicular
speed .omega.v is controlled to be kept at the existing value in
accordance with the equations 12 and 13. With this control, the
engine speed be can be increased up to a specific engine start
speed without occurrence of any variation in vehicular torque due
to start-up of the engine. As is apparent from the equations 12 and
13, the above control is not dependent on the magnitude of the
vehicular speed .omega.v and the engine 1 can be started even in
the stop state or running state. In this way, although the vehicle
in this embodiment is of a clutchless type, the engine can be
usually started or stopped while preventing occurrence of shock due
to start-up of the engine. Next, at step 133, it is judged whether
or not the speed of the engine 1 reaches a specific engine start
speed. If no, at step 135, the control of the engine is left as
stopped. If the engine speed sufficiently reaches the engine start
speed, at step 134, the control of the engine is started, to
complete the change from the motor drive mode into an ordinary mode
in which the drive of the engine 1 is controlled.
[0053] The fastening device B release mode is performed to change
the second speed mode into another mode as shown in the state
transition diagram of FIG. 4. First, at step 136, the fastening
device B is turned off, to release the mechanical locking state of
the sun gear 6s. At step 137, the motor B speed .omega.b is
controlled into zero. With this control, it is possible to prevent
a variation in vehicle drive torque .tau.v due to release of the
fastening device B. At step 138, the control of the motor A is left
as stopped. And, at step 139, the vehicle drive torque .tau.v is
controlled by controlling the engine. That is to say, by carrying
out the same control as that in the second speed mode with the
fastening device B released, it is possible to prevent occurrence
of shock due to the change in operational mode.
[0054] In addition, in the case where two ordinary modes are
directly changed to each other not by way of the shift mode, the
method of controlling the motor is possibly changed, and
accordingly, upon the change in operational mode, the initial value
of the control in the new mode may be matched with the associated
value of the control in the previous mode. This is effective to
prevent a variation in torque due to the change in operational
mode.
[0055] Next, it will be described in detail how to realize the
continuously variable transmission function in the above-described
CVT mode by the system configuration shown in FIG. 1 with reference
to the flows of energies shown in FIGS. 7 and 8. In these figures,
it is assumed that the constant ka=2 and the constant kb=0.5.
Accordingly, the gear ratio in the first speed mode becomes 2, and
the gear ratio in the second speed mode becomes 0.5. And, the
operation under the CVT mode for obtaining an arbitrary speed
varying ratio in the intermediate region between the above ratios,
that is, between 0.5 to 2 will be described below.
[0056] FIGS. 7(a) to 7(e) are torque-speed characteristic diagrams
illustrating operational points of the engine, vehicle, and
planetary gears A and B in the case where the speed varying ratio
is set in a range of 0.5 to 1.0. As shown in FIG. 7(a), in the case
where with respect to an operational point X of the engine, an
operational point .smallcircle. of the vehicle to be driven is
offset on the lower speed/higher torque side (upper left side in
the figure), the planetary gear A input power Pea and the planetary
gear B input power Peb are distributed from the engine power Pe
into the planetary gears A4 and B6, respectively. The input speed
of the planetary gear A4 is the same as that of the planetary gear
B6 because both the planetary gears A4 and B6 are connected to the
common input shaft. Accordingly, the above respective powers
inputted in the planetary gears A4 and B6 are determined by
dividing the engine torque .tau.e into the planetary gear A shared
engine torque .tau.ea and the planetary gear B shared engine torque
.tau. eb. In addition, the above divided ratio of the power is
determined not by only control of one motor but by the entire
energy balance. The operational point .quadrature. of the input
side of the planetary gear A shown in FIG. 7(b) is determined by
adding the motor A power Pa inputted by drive of the sun gear 4s
using the motor A8 to the planetary gear A input power Pea inputted
from the engine. Since the input/output of the energy is carried
out by increasing/decreasing the speed of the planetary gear, the
additional energy is indicated in the abscissa (in the direction of
speed) in FIG. 7(b). As shown in FIG. 7(c), on the output side of
the planetary gear A4, the speed is reduced depending on the gear
ratio ka=2, so that the vehicular speed .omega.v becomes one-half
the value ka.omega.v, and the planetary gear A shared vehicular
torque .tau.va becomes twice the planetary gear A shared engine
torque .tau.ea. That is to say, the operational point .quadrature.
is changed into an operational point .DELTA..
[0057] Similarly, FIG. 7(d) shows the flow of the energy of an
operational point .quadrature. on the input side of the planetary
gear B. The motor B9 is operated to reduce its speed on the output
side, by the sun gear 6s to which the planetary gear B input power
Peb is applied, and therefore, the motor B9 is turned into a power
generating state. Accordingly, the operational point .quadrature.
is moved for a value equivalent to the motor B power Pb, that is,
moved to a position shown in FIG. 7(d). On the output side of the
planetary gear B6, the speed of the planetary gear B6 is increased
depending on the gear ratio kb=0.5, and accordingly, as shown by
the change from the operational point .quadrature. into an
operational point .DELTA. in FIG. 7(e), the vehicular speed
.omega.v becomes twice, and the planetary gear B shared vehicular
torque .tau.vb becomes half. The vehicular torque .tau.v is the
total of the planetary gear A shared vehicular torque .tau.va and
the planetary gear B shared vehicular torque .tau.vb, and
therefore, the vehicle is operated at an operational point
.smallcircle. shown in FIG. 7(a). With this operational principle,
the operational point of the engine 1 can be speed-changed in a low
speed/high torque region. It is revealed that the operational point
of the vehicle can be freely controlled with the operational point
of the engine 1 kept constant by controlling the power of each
motor. Also by matching the absolute value of the power Pa driven
by the motor A with the absolute value of the power Pb generated by
the motor B, it is possible to eliminate the necessity of the
operation of charging/recharging the battery 12 and hence to make
smaller the capacity of the battery. This is effective to reduce
the weight of the vehicle. In addition, the first speed mode is
equivalent to a mode in which the motor A speed .omega.a is zero
and the motor B torque .tau.b is zero in FIGS. 7(a) to 7(e). That
is to say, the first speed mode may be considered as a special case
of the CVT mode.
[0058] FIGS. 8(a) to 8(e) are torque-speed characteristic diagrams
showing operations of the engine, vehicle, and planetary gears A
and B in the case where the speed varying ratio is set in a range
of 1 to 2. FIG. 8(a) shows an operational principle in the case
where an operational point X of the engine is speed-changed into an
operational point .smallcircle. of the vehicle. Operational points
of the planetary gear A on the input and output sides shown in
FIGS. 8(b) and 8(c) are shifted to the higher speed/lower torque
sides as compared with those shown in FIGS. 7(b) and 7(c),
respectively. The motor A8 is driven at a high speed and with a low
torque. On the contrary, as shown in FIGS. 8(d) and 8(e), the
operational points of the planetary gear B on the input and output
sides are set such that the motor B speed .omega.b is smaller and
the motor B torque .tau.b is larger as compared with those shown in
FIGS. 7(d) and 7(e), respectively. In the second speed mode, the
motor A torque .tau.a is zero and the motor B speed .omega.b is
zero, and accordingly, it is possible to attain the continuously
variable transmission function by controlling the motors A and B in
a region from the first speed mode to the second speed mode. With
this configuration, since the control with the minimum gear ratio
is performed in an ordinary low torque operation, the engine 1 can
be driven at the high torque/high efficient operational point, and
also if a high torque is required, the mode is rapidly changed into
the CVT mode, with a result that there can be obtained a
comfortable driving characteristic.
[0059] FIGS. 9(a) and 9(b) show examples in each of which the
operational point of the engine is changed for controlling the
vehicle in such a manner as to realize a high output hybrid car
making effective use of the battery 12 mounted on the vehicle. FIG.
9(a) is a characteristic diagram obtained when the operational
point X of the engine shown in FIG. 7(a) is changed from a point X
to a point Y. When the motors A and B are controlled with an
operational point .smallcircle. of the vehicle kept constant, the
energy generated by the engine 1 becomes excessive, with a result
that the power Pa of the motor A necessary for driving the vehicle
is reduced and the absolute value of the power Pb of the motor B
for generating electric energy is increased. The excess energy thus
obtained by high efficient drive of the engine 1 is charged in the
battery 12.
[0060] FIG. 9(b) shows the example in which the operational point
of the engine is changed for making effective use of energy stored
in the battery 12. In this example, the operational point X of the
engine shown in FIG. 8(a) is changed from a point U to a point V by
reducing the output of the engine with the operational point
.smallcircle. of the vehicle kept constant. Concretely, to change
the operational point X of the engine from the point U to the point
V, the motor A speed .omega.a is increased to make large the motor
A power Pa and the motor B speed .omega.b is decreased to make
small the generated power. This means that the drive force of the
engine is relatively assisted by the drive force of the motor.
Actually, by controlling the input/output power of the battery such
that the engine is driven at an operational point being good in
fuel consumption, it is possible to reduce the fuel
consumption.
[0061] FIG. 10 is a flow chart showing an operational procedure
performed when either of the two motors fails. At step 141, it is
judged whether at least one of the two motors is normally
controllable or both the motors fail. If there exists a normally
operable motor, the process goes on to step 142, and if both the
motors fail, the process goes on to step 148. In the case where at
least one of the motors is normally controllable, at step 142, it
is judged whether or not the engine 1 is on rotation. If no, the
engine 1 is started by performing operations in steps 142 to 145,
and then the drive of the vehicle is controlled using the engine 1
and the normally controllable motor by performing operations in
steps 146 and 147. If it is judged that the engine 1 is on rotation
at step 142, operations in steps 146 and 147 may be performed.
[0062] At step 143, the running state of the vehicle is judged on
the basis of the vehicular speed .omega.v. If the vehicle is not on
running, the process goes on to step 144 at which an operation for
locking the tires 3a and 3b is performed to leave the vehicle as
stopped. This operation can be carried out by providing a
fastenable/openable braking device and automatically controlling
the braking device using a controller, or providing an alarm means
of informing a driver of the vehicular state, and allowing a driver
to judge actuation of the brake in accordance with an instruction
supplied from the alarm means. At step 145, the engine speed
.omega.e is increased up to the start-up speed of the engine 1 by
increasing the speed of the normally controllable motor. In the
stop of the vehicle, since the vehicle is locked at step 144, the
vehicle is prevented from being moved backward by the reaction.
Further, during running of the vehicle, the engine 1 can be started
by increasing the motor speed in accordance with the vehicular
speed .omega.v. At this time, although a negative torque is
slightly applied to the vehicle by the reaction against the force
for starting the engine 1, the drivability is not reduced because
the inertia of the vehicular body is very larger than that of the
engine 1. In this way, when the engine speed .omega.e reaches the
start-up speed, the engine 1 can be driven by controlling the
engine, for example, through fuel injection control or throttle
control. By controlling the speed of the normally drivable motor at
step 146, the engine speed .omega.e of the engine 1 can be
controlled at a specific value. Further, since the vehicular torque
.tau.v can be controlled by controlling the engine, even if one
motor fails, the running of the vehicle is made possible. In
addition, since the assisting time and power of the motor are
limited depending on the energy stored in the battery 12, the
operating method is sometimes limited by the vehicular speed
.omega.v.
[0063] At step 141, if it is judged that there is no normally
controllable motor, operations in steps 148 to 151 are performed.
First, at step 148, it is confirmed whether or not the engine 1 is
on rotation. If yes, the engine control is performed at step 149,
and the on-off control of the fastening device B13 is performed at
step 150 for preventing the engine 1 from being stopped. In the
case where the engine 1 is not stopped, for example, when the
vehicular speed .omega.v is a medium speed or more, it is desirable
to turn on the fastening device B13 to lock the sun gear 6s.
[0064] If the engine 1 is not on rotation, the vehicle cannot be
driven. In this case, at step 151, an operation of turning on a
fail lamp is performed. With these operations, since the vehicle
can be driven somewhat even in the case where the motors fail, it
is possible to enhance the reliability of the vehicle.
[0065] In this embodiment, the vehicle can be usually driven in
such a region that the input/output of electric energy is minimized
and the engine efficiency is maximized, and consequently, it is
possible to significantly reduce the fuel consumption. Also, since
the function comparable to that of a continuously variable
transmission can be obtained by controlling the two motors in
co-operation with each other, it is possible to realize a car
capable of preventing occurrence of shock due to transmission.
[0066] FIG. 11 shows another embodiment of the hybrid car different
from that shown in FIG. 1 in the configuration of the system such
as gears. In this system, a capacitor 14 is used in place of the
battery 12. Since the power per unit weight of the capacitor 14 can
be made larger than that of the battery 12, the weight of the
energy storing device mounted on the vehicle can be significantly
reduced. This is effective to reduce the weight of the vehicle and
hence to further improve the fuel consumption per unit running
distance. In addition, since the energy density of the capacitor is
smaller than that of the battery, the input/output of the energy of
the capacitor 14 may be controlled to be smaller than that of the
battery 12 of the embodiment shown in FIG. 1.
[0067] This embodiment is also different from the embodiment shown
in FIG. 1 in that fastening devices 17, 18 and 19 are provided on
rotating portions of the engine 1, motor A8 and the vehicle driving
shaft; and the gears 5 and 7, shown in FIG. 1, for making different
the gear ratio between the planetary gear A4 and the gear 5 from
the gear ratio between the planetary gear B6 and the gear 7, are
changed into gears 15 and 16.
[0068] The fastening devices 17, 18 and 19 have the following
functions. First, the fastening device 17 is used for stopping the
rotation of the engine 1. In the case where the vehicle is not
driven using the engine 1, the fastening device 17 is turned on for
fastening the engine 1. When the control under the motor drive mode
is performed in such a state, since it is not required to control
the speeds of the motors A8 and B9 in co-operation with other for
controlling the engine speed .omega.e into zero, the vehicular
torque .tau.v may be controlled by either or both of the motors.
That is to say, it is possible to significantly simplify the method
of controlling the motors. Further, in the embodiment shown in FIG.
1, if both the motors are controlled in co-operation with each
other, one motor is turned into the driving state and the other
motor is turned into the power generating state, so that the
input/output electric energy becomes large; however, in this
embodiment, the minimum electric energy necessary for driving the
vehicle may be utilized, so that the loss in electric energy can be
further reduced.
[0069] In addition, the fastening device 17 may be configured as a
one-way clutch. In the case of using the one-way clutch as the
fastening device 17, even if a torque acting to rotate the engine 1
in the reversed direction occurs during stoppage of the engine 1,
the stopping state of the engine 1 can be automatically held by the
one-way clutch as the fastening device 17. This is advantageous in
eliminating the necessity of controlling the fastening device
17.
[0070] The fastening device 18 is used for locking the motor A8. In
the first speed mode, the fastening device 18 is turned on after
the motor A speed .omega.a is controlled into zero. Then, the
control of the motor A8 is stopped. In this way, even in the first
speed mode, the engine 1 can be driven without use of any electric
energy of the motor, it is possible to further reduce the fuel
consumption.
[0071] Since the fastening device 19 can be controlled for locking
the vehicle, the vehicle locking operation at step 143 shown in
FIG. 10 can be automatically performed using a controller, so that
the start-up of the engine when the motor fails can be performed
without giving any burden to a driver.
[0072] By changing the gears 5 and 7 shown in FIG. 1 into the gears
15 and 16, not only the same effect can be obtained but also the
configuration from the output of the planetary gears A4 and B6 to
the drive shaft 2 is simplified. As a result, it is possible to
arrange a transmission portion including the motors A8 and B9
around the drive shaft in a compact manner, and hence to freely
arrange the engine in an engine room of the vehicle although the
vehicle is of the hybrid type.
[0073] As described above, according to this embodiment, it is
possible to further enhance the efficiency of the system.
[0074] FIG. 12 is a configuration diagram showing a further
embodiment different from the embodiment shown in FIG. 1. In this
system, a gear ratio between the input and output sides of the
planetary gear 20 is the same as a gear ratio between the input and
output sides of the planetary gear 21. In this system, the effect
of establishing the first speed mode and second speed mode by
changing the gear ratio is not obtained; however, a new effect can
be obtained as a parallel-hybrid car. That is to say, in the case
where the drive force of the engine 1 is assisted by the motor
using the energy of the battery 12, when the drive torque for
assisting the drive force of the engine 1 is small, only one of the
motors A8 and B9 may be driven, with a result that the motors can
be controlled at the efficient operating points; and when the drive
torque for assisting the drive force of the engine 1 is more than
the capacity of one motor, both the motors may be used to obtain
the drive torque. As a result, it is possible to make compact the
system as compared with the related art parallel hybrid car.
[0075] FIG. 13 shows an embodiment in which the transmission of the
present invention is applied to a bicycle. A transmission 23
mounted on a body 22 of the bicycle is adapted to vary the speed of
a rotational drive force obtained when pedals 24a and 24b are
actuated by a driver. The rotational drive force thus varied in its
speed is transmitted to a tire 25b of a rear wheel via a chain 30,
to thereby move the bicycle forward. The transmission 23 is
composed of thin motors 26 and 27 and planetary gears 28 and 29
controlled by the motors 26 and 27. Like the embodiment shown in
FIG. 1, it is possible to realize a first speed mode, second speed
mode, and CVT mode by making different a gear ratio between input
and output sides of the planetary gear 28 from a gear ratio between
input and output sides of the planetary gear 29. And, the motors 26
and 27 are controlled at a speed varying ratio desired by a driver
using a speed varying indicator (not shown), so that the driver
enjoys mostly comfortable operation of the vehicle. In this way,
according to this embodiment, there can be provided a bicycle
having a comfortable drivability. Also, by mounting energy storing
device on the bicycle, the bicycle can easily climb a sloping road
at the optimum speed varying ratio using energy gradually charged
during running on a down-hill or a flat road.
[0076] FIG. 14 is a further embodiment in which the rotational
direction of a transmission is changed 90.degree. from that in the
embodiment shown in FIG. 13. This embodiment is different from the
embodiment shown in FIG. 13 in that the arrangement direction of a
transmission 31 is changed 90.degree. and a drive force is
transmitted to the tire 25b via a shaft 37 in place of the chain
30. The rotational drive force of the pedals 24a and 24b is
transmitted to the shaft 36 via a bevel gear and is inputted in the
transmission 31. The transmission 31 is composed of motors 32 and
33 and planetary gears 34 and 35, and it has a transmission
function like the previous embodiment; however, the rotational
direction of the transmission is a transverse direction
perpendicular to the advancing direction of the bicycle. Since the
rotational drive force varied in its speed is transmitted to the
tire 25b via the shaft 37, it is possible to eliminate the
necessity of using the chain. This is effective to obtain a bicycle
having a good transmission efficiency with a simple structure. In
the embodiment shown in FIG. 14, since the width of the
transmission arranged between the pedals can be made smaller than
that in the embodiment shown in FIG. 13, the mounting
characteristic of the transmission on the bicycle can be also
enhanced. According to this embodiment, the driver is able to drive
the bicycle while stepping the pedals with a lighter force. In
addition, by arranging the transmission with its rotational shaft
in the vertical direction, a gyro effect can be given to the
transmission, so that the posture of the bicycle can be
stabilized.
[0077] In the above-described embodiments, the transmission
including the two planetary gears controlled by the motors, and the
hybrid car and bicycle using the transmission have been described.
Additionally, the present invention makes it possible to realize a
multi-stage (three-stage or more) transmission by use of three
pieces or more of planetary gears. In the above embodiments, there
is described the method in which the motor mainly controls the sun
gear of the planetary gear; however, there can be adopted a method
in which the motor controls another gear. Further, for example,
there can be adopted an asymmetric configuration in which the sun
gear of one planetary gear is controlled by the motor and the
planetary element of the other planetary gear is controlled by the
motor. While the planetary gear is used as the differential
mechanism in the above embodiments, it can be replaced with a
general differential gear, and further it may be replaced with a
harmonic gear by putting emphasis on the stillness. Further, the
present invention can be of course applied not only to cars but
also to ships and railcars.
[0078] According to the present invention, there is provided a
transmission including: a mechanism for distributing energy of a
drive source into a plurality of differential mechanisms; a
plurality of motors connected to the plurality of differential
mechanisms, respectively; and a mechanism for synthesizing energies
outputted from the plurality of differential mechanisms, or a
transmission including: a plurality of differential mechanisms in
each of which a difference in the number of rotation between an
input shaft and an output shaft is controlled by a motor; wherein
the input shafts of the plurality of differential mechanisms are
taken as a common shaft, and the output shafts of the plurality of
differential mechanisms are taken as a common shaft. The
transmission having the above configuration makes it possible to
realize the continuously variable transmission function using the
motors, and to enhance the efficiency by minimizing a loss in
electric energy.
[0079] According to the present invention, there is also provided a
vehicle including: an engine for generating drive energy for
driving a vehicle; first and second planetary gears each of which
is composed of a sun gear, a planetary element, and a ring gear;
and first and second motors for controlling the sun gears of the
first and second planetary gears, respectively; wherein one of the
planetary element and the ring gear of each of the first and second
planetary gears is connected to an input shaft driven by the engine
and the other is connected to an output shaft for driving a
vehicular body. The vehicle having the above configuration makes it
possible to realize a continuously variable transmission function
capable of transmitting a drive torque by the mechanical gears
without use of electric energy except for acceleration and usually
drive the engine at a high efficient operational point, and hence
to reduce the fuel consumption per unit running distance.
[0080] According to the present invention, there is also provided a
bicycle including: first and second differential mechanisms each of
which takes a drive force generated by a driver as an input force
and takes a drive force for driving a wheel as an output force; and
first and second motors for controlling the first and second
differential mechanisms, respectively. The bicycle having the above
configuration makes it possible to reduce fatigue of a driver
during running of the bicycle.
* * * * *