U.S. patent application number 10/050550 was filed with the patent office on 2002-05-30 for transmission and vehicle using same.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Kaneko, Satoru, Masaki, Ryoso, Matsunobu, Yutaka.
Application Number | 20020065162 10/050550 |
Document ID | / |
Family ID | 14729835 |
Filed Date | 2002-05-30 |
United States Patent
Application |
20020065162 |
Kind Code |
A1 |
Kaneko, Satoru ; et
al. |
May 30, 2002 |
Transmission and vehicle using same
Abstract
A vehicle provided with an engine 1 which generates a driving
energy for the vehicle, planetary gears 4 and 6 comprising sun
gears, planet gears and ring gears, motors 8 and 9 for respectively
controlling the sun gears, and a clutch 14, the planet gears being
connected to an input shaft driven by the engine and the ring gears
connected to an output shaft for driving wheels, wherein gear
ratios from the input shafts to the output shafts in the planetary
gears 4 and 6 are set at a value different to each other. A
stepless speed changing function which permits vehicular operation
in a high engine efficiency region while minimizing an electrical
energy loss is realized by a small-sized transmission using
small-sized motors. The vehicle, which uses the transmission, can
be operated in a high engine efficiency region while keeping an
electrical energy loss to a minimum.
Inventors: |
Kaneko, Satoru; (Naka-gun,
JP) ; Matsunobu, Yutaka; (Hitachinaka, JP) ;
Masaki, Ryoso; (Hitachi, JP) |
Correspondence
Address: |
CROWELL & MORING, L.L.P.
P.O. Box 14300
Washington
DC
20044-4300
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
14729835 |
Appl. No.: |
10/050550 |
Filed: |
January 18, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10050550 |
Jan 18, 2002 |
|
|
|
09805573 |
Mar 14, 2001 |
|
|
|
Current U.S.
Class: |
475/2 ; 903/903;
903/946 |
Current CPC
Class: |
B60W 10/02 20130101;
B60W 10/06 20130101; Y02T 10/62 20130101; Y02T 10/64 20130101; B60W
10/26 20130101; Y02T 10/7072 20130101; B60W 20/30 20130101; B60L
50/16 20190201; Y02T 10/70 20130101; F16H 3/72 20130101; B60L
2200/26 20130101; B60L 2220/14 20130101; F16H 3/725 20130101; F16H
2037/102 20130101; F16H 3/727 20130101; B60W 10/08 20130101; B60W
20/00 20130101; Y02T 10/72 20130101; Y10S 903/946 20130101; B60L
2220/12 20130101; B60K 1/02 20130101; B60L 15/2054 20130101; Y02T
10/40 20130101; B60L 50/61 20190201; B60K 6/445 20130101 |
Class at
Publication: |
475/2 |
International
Class: |
F16H 003/72 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 1998 |
JP |
10-118169 |
Claims
1. A transmission including a plurality of differential mechanisms
in which motors control a difference in the number of revolutions
between an input shaft and an output shaft thereof, said input
shaft and said output shaft for said plural differential mechanisms
being used in common, wherein gear ratios from said input shafts to
said output shafts in said plural differential mechanisms are set
at a value different to each other, and gear ratios from said input
shafts to the motors in said plural differential mechanisms are set
at a value different to each other.
2. A transmission including first and second planetary gears each
comprising at least three components of a sun gear, a planet gear
and a ring gear; first and second motors for respectively
controlling the sun gears in said first and second planetary gears;
input shafts connected to the planet gears in said first and second
planetary gears; and output shafts connected to the ring gears in
said first and second planetary gears; wherein gear ratios from
said input shaft to said first and second motors are set at a value
different to each other.
3. A transmission including first and second planetary gears each
comprising at least three components of a sun gear, a planet gear
and a ring gear; first and second motors for respectively
controlling the sun gears in said first and second planetary gears;
input shafts connected to the ring gears in said first and second
planetary gears; and output shafts connected to the planet gears in
said first and second planetary gears; wherein gear ratios from
said input shafts to said first and second motors are set at a
value different to each other.
4. A transmission including an input shaft which inputs a driving
force; an output shaft which outputs a driving force; first and
second planetary gears each comprising a sun gear, a planetary gear
and a ring gear; and first and second motors for respectively
controlling the sun gears in said first and second planetary gears;
wherein the planet gear in said first planetary gear and the ring
gear in said second planetary gear are connected to said input
shaft, while the ring gear in said first planetary gear and the
planet gear in said second planetary gear are connected to said
output shaft.
5. A transmission including a plurality of differential mechanisms
in which motor shafts driven by motors control a difference in the
number of revolutions between an input shaft and an output shaft
thereof, said input shaft and said output shaft for said plural
differential mechanisms being used in common, wherein gear ratios
from said input shafts to said output shafts in said plural
differential mechanisms are set at a value different to each other,
and there is further included a locking/unlocking mechanism for
locking and unlocking the motor shaft in at least a differential
mechanism of a larger gear ratio of said plural differential
mechanisms.
6. A vehicle including an engine which generates a driving energy
for driving the vehicle and a transmission which changes the
rotational speed of said engine and transmits a driving force to
wheels, said transmission including at least first and second
differential mechanisms which input a driving force generated by
said engine and which output a driving force for the wheels, and
first and second motors for respectively controlling said first and
second differential mechanisms, wherein gear ratios from input
shafts to output shafts in said first and second differential
mechanisms are set at a value different to each other, and gear
ratios from said input shafts to said first and second motors are
set at a value different to each other.
7. A vehicle including an engine which generates a driving energy
for driving the vehicle and a transmission which changes the
rotational speed of said engine and transmits a driving force to
wheels, said transmission including at least first and second
differential mechanisms which input a driving force generated by
said engine and which output a driving force for the wheels, and
first and second motors for respectively controlling said first and
second differential mechanisms, wherein a gear ratio from an input
shaft to an output shaft in said first differential mechanism is
set at a value larger than a gear ratio from the input shaft to the
output shaft in said second differential mechanism, and there is
further included a locking/unlocking mechanism for locking and
unlocking a motor shaft which transmits a driving force of at least
said first motor to said first differential mechanism.
8. A vehicle according to claim 7, wherein said locking/unlocking
mechanism is unlocked when the rotational speed of said motor shaft
is at a predetermined value or more.
9. A vehicle according to claim 7, wherein said locking/unlocking
mechanism is unlocked when said first motor stops generation of a
torque.
10. A vehicle according to claim 7, wherein said locking/unlocking
mechanism is locked after the rotational speed of the motor shaft
in the locking/unlocking mechanism has been subjected to even speed
control by said first motor.
11. A vehicle according to claim 7, further including a failure
detecting means for detecting a failure of said locking/unlocking
mechanism, and a speed limiting means which limits the speed of the
vehicle or of the engine in accordance with a signal provided from
said failure detecting means.
12. A vehicle according to claim 7, further including a failure
detecting means for detecting a failure of said locking/unlocking
mechanism, and a voltage suppressing means which suppresses a
counter electromotive force of said first motor in accordance with
a signal provided from said failure detecting means.
Description
TECHNICAL FIELD
[0001] The present invention relates to a transmission comprising
motors and differential mechanisms, as well as a vehicle using the
same.
BACKGROUND ART
[0002] As a drive system capable of reducing the fuel consumption
of an engine there is known a hybrid vehicle which utilizes a motor
drive force.
[0003] Various types of hybrid vehicles such as series type and
parallel type have been proposed, among which is included a
series-parallel hybrid type using two motors and one planetary
gear. For example, in Japanese Patent Laid-open No. Hei 7-135701
there is disclosed a method wherein a driving force of an engine is
inputted to a planetary gear and control is made by a generator so
that a vehicle is driven with a driving force obtained from an
output shaft of the planetary gear. While a part of energy of the
engine is generated by a generator, a driving force is assisted
from a motor connected to the output shaft to drive the engine
always in a high torque region of a high efficiency, and at the
same time a speed change function can be attained.
[0004] The same principle as above is also described in Japanese
Patent Laid-open Nos. Sho 49-112067 and Sho 58-191364.
[0005] According to the methods disclosed therein, power is
generated by a generator and a driving force is obtained by a motor
for realizing a speed change function, so that there occurs an
electrical energy loss. Consequently, there occurs reduction in
efficiency by an amount corresponding to the electrical energy loss
with respect to the whole of the vehicle concerned despite the
engine can be driven always at a highly efficient operating
point.
[0006] The present invention has been accomplished in view of the
above-mentioned problems and it is the first object of the
invention to provide a small-sized transmission constituted by
small-sized motors, thereby realizing a stepless speed change
function which permits vehicular operation in a region of a high
engine efficiency while minimizing an electrical energy loss.
[0007] It is the second object of the present invention to provide
a vehicle capable of being driven in a region of a high engine
efficiency while minimizing an electrical energy loss.
DISCLOSURE OF THE INVENTION
[0008] The above first object of the present invention is achieved
by a transmission having a plurality of differential mechanisms in
which motors control a difference in the number of revolutions
between an input shaft and an output shaft thereof, the input and
output shafts for the plural differential mechanisms being used in
common, wherein gear ratios from the input shafts to the output
shafts in the plural differential mechanisms are set at a value
different to each other, and gear ratios from the input shafts to
the motors in the plural differential mechanisms are set at a value
different to each other.
[0009] Particularly, this construction is effective in reducing the
size of the motor which controls the differential mechanism smaller
in the gear ratio from the input shafts to the output shafts.
[0010] The above first object is achieved also by a transmission
having a plurality of differential mechanisms in which motor shafts
driven by motors control a difference in the number of revolutions
between an input shaft and an output shaft thereof, the input and
output shafts for the plural differential mechanisms being used in
common, wherein gear ratios from the input shafts to the output
shafts in the plural differential mechanisms are set at a value
different to each other, the transmission further having a
locking/unlocking mechanism for locking and unlocking the motor
shaft in at least the differential mechanism larger in the gear
ratio of the plural differential mechanisms.
[0011] According to this construction it is possible to reduce the
size of the motor disposed on the side where the locking/unlocking
mechanism is provided. Thus, by using both means described above in
combination it is made possible to provide a transmission still
smaller in size.
[0012] The above second object of the present invention is achieved
by a vehicle having an engine which generates a driving energy for
driving the vehicle and a transmission which changes the rotational
speed of the engine and transmits a driving force to wheels, the
transmission having at least first and second differential
mechanisms which input the driving force from the engine and output
a driving force for the wheels, and also having first and second
motors for controlling the first and second differential
mechanisms, respectively, wherein gear ratios from input shafts to
output shafts in the first and second differential mechanisms are
set at a value different to each other and gear ratios from the
input shafts to the first and second motors are set at a value
different to each other.
[0013] The above second object of the present invention is achieved
also by a vehicle having an engine which generates a driving energy
for driving the vehicle and a transmission which changes the
rotational speed of the engine and transmits a driving force to
wheels, the transmission having at least first and second
differential mechanisms which input the driving force from the
engine and output a driving force for the wheels, and also having
first and second motors for controlling the first and second
differential mechanisms, respectively, wherein a gear ratio from an
input shaft to an output shaft in the first differential mechanism
is set at a value larger than a gear ratio from an input shaft to
an output shaft in the second differential mechanism, the
transmission further having a locking/unlocking mechanism for
locking and unlocking a motor shaft which transmits the driving
force of at least the first motor to the first differential
mechanism.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a construction diagram of a hybrid vehicle
according to an embodiment of the present invention which realizes
a speed change function with use of two planetary gears whose sun
gears are controlled by motors.
[0015] FIGS. 2A and 2B are speed-torque characteristic diagrams of
motors 8 and 9 shown in FIG. 1.
[0016] FIGS. 3A and 3B are speed-torque characteristic diagrams of
motors 8 and 9 with a clutch 14 omitted in FIG. 1 and with the same
gear ratio on an input side.
[0017] FIG. 4 is a control flowchart for the hybrid vehicle shown
in FIG. 1.
[0018] FIG. 5 is a control flowchart for the motor 8 and clutch 14
shown in FIG. 4.
[0019] FIG. 6 is a processing flowchart with a trouble occurring in
the clutch 14 shown in FIG. 4.
[0020] FIG. 7 is a construction diagram of a hybrid vehicle
according to another embodiment of the present invention wherein
input and output gears of a planetary gear 4 are constructed in a
manner different from that in FIG. 1.
[0021] FIG. 8 is a construction diagram of a hybrid vehicle
according to a further embodiment of the present invention wherein
a sun gear 4s is used on an input side of a planetary gear 4.
[0022] FIG. 9 is a construction diagram of a hybrid vehicle
according to a still further embodiment of the present invention
wherein the number of constituent gears is decreased.
[0023] FIG. 10 is a processing flowchart showing a further
embodiment of the control processing illustrated in FIG. 4.
BEST MODE FOR CARRYING OUT THE INVENTION
[0024] An embodiment of the present invention will be described
below with reference to FIG. 1.
[0025] FIG. 1 illustrates an automobile wherein, with use of energy
of an engine 1, tires 3a and 3b are rotated through drive shafts 2a
and 2b to drive a body of the automobile. Planetary gears 4 and 6,
which are important components in the present invention,
respectively comprise sun gears 4s and 6s, planetary gears 4p and
6p, and ring gears 4r and 6r. The sun gears 4s and 6s are driven
respectively by motors 8 and 9 which are controlled by power
converters 10 and 11, respectively. As a motor for an automobile, a
permanent magnet synchronous motor is most suitable from the
standpoint of attaining a high efficiency and a small size. A
battery 12 is used for the supply of energy required by the motors
8 and 9 and for the storage of energy generated by the motors.
Rotation of the engine 1 is transmitted to the planet gear 6p of
the planetary gear 6 via gears 15, 16 and 17 and is also
transmitted to the planet gear 4p of the planetary gear 4 via gears
19 and 20 which are connected to the gears 16. Thus, the driving
torque of the engine 1 is distributed to the planetary gears 4 and
6 by the construction from the gear 15 to the gear 20. What is
important in the present invention is that a gear ratio from the
gear 15 to the gear 17 and that from the gear 15 to the gear 20 are
different from each other. As to the operation concerned, the
details thereof will be described later.
[0026] Also as to the ring gears, gears different in gear ratio are
disposed on the output side. A gear 21 is connected to the ring
gear 4r to rotate a gear 5, while a gear 18 is connected to the
ring gear 6r to rotate a gear 7. The gears 5 and 7 are clamped to
each other and the tires 3a and 3b are driven with a torque
transmitted from both gears. A gear ratio from the gear 15 located
on the input side to the gear 5 on the output side via the
planetary gear 4, which gear ratio means the ratio of a rotation
cycle of the gear 5 to that of the gear 15 in a locked state of the
sun gear 4s and will hereinafter be referred to as gear ratio L, is
set at a value larger than a gear ratio (gear ratio H hereinafter)
from the gear 15 to the gear 7 via the planetary gear 6. Generally,
it is desirable to set the gear ratio L at a value three to six
times as large as the gear ratio H. Particularly when the
transmission of the invention is applied to an automobile, it is
desirable to set the gear ratio L at a value four to five times as
large as the gear ratio H, which value is advantageous to the
improvement of the vehicular driving performance and the reduction
in size of the transmission.
[0027] A description will now be given of one method for driving
the vehicle with use of a controller 23 shown in FIG. 1. The
control unit 23 makes control so that when the vehicle is driven at
a low speed and a low torque, the clutch 14 is engaged and a
locking/unlocking device 13 is released, thereby permitting the
vehicle to be driven with a torque of the motors 8 and 9. By a
cooperative speed control with both motors 8 and 9 the vehicle is
driven while keeping the engine speed .omega.e zero. When the
driver presses down on an accelerator to accelerate the vehicle,
the engine 1 is rotated up to a startable speed and is started by a
cooperative speed control of both motors 8 and 9 so as to permit a
high-torque drive. After start-up of the engine 1, the motor 9 is
brought into a free running condition, while the motor 8 is locked
electrically. As a result, the vehicle comes to be driven at the
gear ratio L from the gear 15 to the gear 5 and therefore a driving
force of high speed and high torque can be generated in the tires
3a and 3b. This speed change ratio can be regarded as being equal
to that of a low gear in a manual transmission.
[0028] When the vehicle is to be driven by the engine 1 while
running at a medium or higher speed, the motor 8 is brought into a
free running condition electrically, while the motor 9 is locked
electrically and is thereafter locked mechanically by the
locking/unlocking device 13. As a result, the vehicle is driven at
the gear ratio H from the gear 15 to the gear 7. Therefore, the
engine 1 operates in a low speed, high torque region and a change
in speed is made to a high speed side by the transmission to drive
the vehicle. In this steady state the engine 1 operates in a high
efficiency region of a high torque. Besides, since the electrical
energy is not utilized by the motors 8 and 9, there is no
electrical loss and the vehicular running distance can be made
longer at a low fuel consumption. When the vehicle is to be
accelerated while running at a medium or higher speed, the motor 8
is brought into a driving condition and the motor 9 into a driving
or power generating condition to attain the same function as in a
continuously variable transmission or there can be attained a
function of adding motor assisting torque to the engine drive force
as in a hybrid automobile.
[0029] In the case where the vehicle speed exceeds a predetermined
speed in a high-speed running, a control is made to release the
clutch 14. If the motor 9 is locked, the motor 8 will be rotated at
a high speed, which is therefore prevented by releasing the clutch
14. If a permanent magnet synchronous motor suitable for an
automobile is used as the motor 8, an excessive counter
electromotive force is generated by a high-speed rotation. Since an
excessive counter electromotive force will result in destruction of
the power converters, so it is necessary to make a design while
paying attention to this point. In designing a motor so as to
prevent the generation of an excessive counter electromotive force
there is adopted a method wherein the number of turns of winding is
made small, while an electric current to be passed through the
winding is enhanced to ensure a required torque. By adopting such a
high-speed rotation preventing construction as in this embodiment
it is possible to make a motor design with a larger number of turns
of winding. Thus, in this embodiment it is possible to make the
electric current flowing in the motor 8 small and therefore it is
possible to attain the reduction in size of the motor 8 and in
capacity of the power converter 10 from the standpoint of a thermal
design.
[0030] Setting the gear ratio from the gear 15 to the gear 17
smaller than the gear ratio from the gear 15 to the gear 20 is
advantageous in carrying out the above operations. This point will
now be described. The gear ratio L from the gear 15 to the gear 5
is set several times larger than the gear ratio H from the gear 15
to the gear 7. Besides, the gears 5 and 7 are coupled together
through a common shaft.
[0031] If both gear ratios are set at the same value, the motor 9
comes to operate in a narrow speed range relative to the speed
range of the motor 8. In view of this point, if the gear ratio from
the gear 15 to the gear 17 is set smaller than the gear ratio from
the gear 15 to the gear 20, the maximum operating speed of the
motor 9 becomes high, so that the maximum torque of the motor 9 can
be kept small and thus the size of the motor 9 can be reduced by
changing the gear ratios. Since in this embodiment the gear ratio
from the planet gear 4p in the planetary gear 4 to the motor 8 and
the gear ratio from the planet gear 6p in the planetary gear 6 to
the motor 9 are the same, the above description covered only the
components up to the input portions of the planetary gears.
[0032] FIGS. 2A and 2B show speed-torque characteristics (N-T
characteristics) of the motors 8 and 9 both used in the embodiment
of FIG. 1. For comparison, FIGS. 3A and 3B show speed-torque
characteristics of both motors obtained without using the clutch 14
in FIG. 1 and with the gear ratio from the gear 15 to the gear 17
and that from the gear 15 to the gear 20 set equal to each other.
With the clutch 14, the motor 8 exhibits such a characteristic as
shown in FIG. 2A in which a high speed region is cut in comparison
with FIG. 3A, thus permitting a motor design so as to increase the
number of turns of winding and decrease the motor current, whereby
the motor 8 and the power converter 10 can be reduced in size. In
comparison with the characteristic shown in FIG. 3B, the
characteristic shown in FIG. 2B indicates that the maximum torque
of the motor 9 can be diminished. This is effective in reducing the
size of the motor 9. As a matter of course, that the maximum torque
of the motor 9 can be made small leads to a decrease of the motor
current, thus permitting the reduction in size of the power
converter 11.
[0033] FIG. 4 is a flowchart showing a control method for the
system of FIG. 1 in which the control is made by the control unit
23. In step 101 in FIG. 4, the control unit 23 inputs operation
commands intended by the vehicular driver such as an accelerator
depression quantity Xa, a brake depression quantity Xb, and a
change-over signal Xc which instructs forward, reverse, or neutral,
as well as vehicular conditions such as vehicle velocity .omega.v,
charging condition of the battery 12, and temperatures of various
components. In step 102, the control unit 23 judges whether the
clutch 14 is in normal condition or not on the basis of a signal
provided from a failure detector 24 shown in FIG. 1. If the answer
is affirmative, there are performed normal control operations from
step 103 to step 107, while if the answer is negative, a clutch
trouble processing is executed in step 108. As to the contents of
the processing performed in step 108, it will be described later
with reference to FIG. 6.
[0034] When the clutch 14 is judged to be normal, processings are
performed successively from step 103. In step 103, a vehicular
driving force command value .tau.r is calculated on the basis of
information values indicative of vehicle conditions and operation
commands which were inputted in step 101. Next, in step 104, a
decision is made as to in what manner the driving forces of the
engine 1 and motors 8, 9 are to be distributed, including which of
opening and closing commands for the clutch 14 is to be issued, on
the basis of the vehicular driving force command value .tau.r and
the vehicle velocity .omega.v. As a result there are determined
drive command values (torque or speed command values). In step 105,
an engine control calculation is conducted on the basis of a
driving force command value for the engine 1 and the engine is
controlled to satisfy the driving force command value. In step 106,
a motor control calculation is conducted on the basis of a driving
force command value for the motor 9 and a predetermined driving
force is generated. Further, in step 107, a control is made to
satisfy a driving force command value for the motor 8. In this
case, it is necessary that the processing should include the
control for the clutch 14, and the details of this processing are
shown in FIG. 5. As noted in the previous operational description
in connection with FIG. 1, it is when the vehicle speed exceeds a
predetermined value that the clutch should be released. Even if the
clutch is released when the motor rotating speed exceeds a
predetermined value, instead of using the vehicle speed, there will
be obtained an equivalent effect. Even when the torque command
value of the motor 8 is zero, if a command for releasing the clutch
14 is given, it is possible to diminish a mechanical loss caused by
follow-up rotation of the motor.
[0035] In FIG. 5, the present state of the clutch 14 is judged in
step 111, and if the clutch is engaged, the processing of step 112
is performed, while if the clutch is released, the processing of
step 116 is conducted. In step 112, if a command issued for the
clutch 14 is an engaging command, it suffices for the clutch to be
kept engaged, so a control processing is performed to give a
driving force command for the motor 8 in step 113. If the command
for the clutch 14 is a release command in step 112, a processing
for releasing the clutch is carried out in step 114. Next, in step
115 the control for the motor 8 is stopped since the clutch 14 is
released.
[0036] If the present state of the clutch 14 is a released state, a
shift is made from step 111 to step 116, in which a judgment is
made about a command value for the clutch 14. If the command is a
clutch release command, a processing is performed to stop the
control for the motor 8 in step 115 because it suffices for the
clutch 14 to be kept released. If the clutch command is an engaging
command in step 116, an even speed control is made for the motor 8
in step 117 so that the rotational speed of the motor 8 is made
coincident with that of the sun gear 4s. Next, in step 118 there is
made judgment as to whether the speed control has been completed or
not in step 118, and only when the speed control has been
completed, a processing for engaging the clutch 14 is performed in
step 119. The driving force from the motor 8 is controlled by
performing the above processings.
[0037] The clutch trouble processing method shown in FIG. 4 will
now be described with reference to the flowchart of FIG. 6. In step
121 it is determined whether the clutch 14 is improperly engaged or
not. If the clutch is found to be improperly engaged, a processing
is made in step 122 to limit a maximum torque capable of being
generated by the vehicle. The maximum torque is transferred from
the engine 1 and the motor 8 via the planetary gear 4, but in the
case where the clutch 14 cannot be engaged, the torque generated
from the engine 1 and the motor 9 is transferred via the planetary
gear 6 alone and serves as a driving torque for driving the
vehicle. Thus, a limitation is made on the maximum torque capable
of being generated from gear ratio setting conditions. Therefore,
it is notified to the vehicle driver that the maximum torque is
limited, and at the same time a processing is performed to also
limit the torque command value. If the clutch 14 is properly
engaged, a processing is made in step 123 to cancel the limitation
on the maximum torque.
[0038] Next, in step 124 it is judged whether the clutch 14 is
improperly released or not, and if the clutch is improperly
released, there are performed processings from step 125 to step
127. In step 125 a processing is made to limit the maximum vehicle
speed. It is assumed that the limited maximum speed is not higher
than the vehicle speed obtained when the motor speed shown in FIG.
2A exceeds 1. Next, in step 126, the control for the motor 8 is
stopped, and in step 127 a control for the engine 1 and the motor 9
is executed within limited speed range and torque range. By
performing such processings the power converter 10 can be prevented
from being damaged by a counter electromotive force at a high-speed
rotation in an improperly released condition of the clutch 14. On
the other hand, if it is judged in step 124 that the clutch 14 is
properly released, the limitation on the maximum speed is cancelled
in step 128, then in step 129 a control for the engine 1 and motors
8, 9 is made in a limited state of the maximum torque.
[0039] Thus, according to this embodiment it is possible to provide
a transmission of small size and low cost possessing a stepless
speed changing function and a motor assisting function. Besides,
this transmission is applicable not only to ordinary types of
automobiles but also to hybrid automobiles. Although the method
adopted in this embodiment is limiting the maximum vehicle speed,
the same effect as above can also be obtained even by adopting a
method of limiting the maximum engine speed.
[0040] FIG. 7 illustrates another embodiment of the present
invention which is different from the embodiment shown in FIG. 1 in
point of how to construct gears in an automobile. More
specifically, the construction shown in FIG. 7 is different from
the construction shown in FIG. 1 in a method of connecting gears of
a planetary gear 4 on input and output sides. In FIG. 7, a gear 20
meshing with an input-side gear 19 is connected to a ring gear 4r
in a planetary gear 4. Further, a gear 21 engaged with a planet
gear 4p is connected to an output-side gear 5. Thus, the gears of
the planetary gear 4 connected to input and output sides in FIG. 7
are reverse to those in FIG. 1. Since the gear ratio from the ring
gear to the planet gear in the planetary gear is larger than 1.0,
the gear ratio from the gear 15 to the gear 20 and that from the
gear 21 to the gear 5 can be set smaller than in FIG. 1.
[0041] It has been described previously that in the embodiment
shown in FIG. 1 the gear ratio L from the gear 15 to the gear 5 is
set at a value several times larger than the gear ratio H from the
gear 15 to the gear 7. If the same setting is made in the
embodiment shown in FIG. 7, the gear ratios on input and output
sides of the planetary gear 4 can be made closer to the gear ratios
on input and output sides of the planetary gear 6. Consequently,
the gears can be designed more easily and can be arranged in a
compact form, thus permitting the realization of a transmission
smaller in size.
[0042] FIG. 8 illustrates a further embodiment of the present
invention which is different in how to construct gears from the
embodiment shown in FIG. 7. This embodiment is characteristic in
that a gear 15 is in mesh with a gear 17 and that the gear 17 is
engaged with a planet gear 6p and also with a sun gear 4s in a
planetary gear 4. It is a planet gear 4p in the planetary gear that
is connected to a motor 8 through a clutch 14, with a ring gear 4r
being connected to an output-side gear 5 through a gear 22 which is
for reverse rotation. The gear ratio from the sun gear 4s in the
planetary gear 4 to the planet gear 4p is usually several times
larger than the gear ratio from the ring gear 4r to the planet gear
4p. Therefore, by connecting the gear 17 to the sun gear 4s it is
possible to obtain a larger gear ratio than in the embodiments
illustrated in FIGS. 1 and 7 and hence possible to omit the gears
16, 19 and 20 used in those previous embodiments. As a matter of
course, the effect of reducing the motor size by setting the gear
ratios on the input side of the two planetary gears in FIG. 1 at
different values can also be obtained in the embodiment illustrated
in FIG. 8. In the planetary gear 4, since the rotational direction
of the sun gear 4s and that of the ring gear 4r rotated thereby are
opposite to each other, the gear 22 is used to obtain a reverse
rotation. As a result, upon operation of the engine 1, the rotation
of the gear 5 and that of the gear 7 become coincident with each
other within the usual speed range of each motor.
[0043] Thus, according to this embodiment it is possible to
decrease the number of gears used and hence it is possible to
realize a more compact transmission.
[0044] FIG. 9 illustrates an automobile using a still smaller
number of gears according to a further embodiment of the present
invention. Since a basic method for constructing planetary gears is
the same as in the system of FIG. 7, a description will now be
given while making comparison with FIG. 7. A rotating shaft of an
engine 1 is connected to a planet gear 6p in a planetary gear 6 and
causes a gear 21 to rotate via a gear 15. The gear 21 is engaged
with a ring gear 4r in a planetary gear 4. This construction
corresponds to the construction of FIG. 7 in which the gear ratio
from the gear 15 to the gear 17 is set at 1.0. The gear ratio from
the gear 15 to the gear 20 in FIG. 9 corresponds to the gear ratio
from the gear 15 to the gear 20 in FIG. 7. Thus, equal
characteristics can be obtained by making these set values
coincident with each other.
[0045] In this embodiment, a ring gear 6r in the planetary gear 6
outputs a torque to a gear 7 via a gear 18 which is engaged with
the ring gear 6r. The planetary gear 4 is connected to the same
shaft as that of the gear 7 through a planet gear 4p. A driving
torque is outputted from this shaft to tires 3a and 3b. Thus, also
as to the output-side construction of the planetary gears, the
construction shown in FIG. 9 can be made corresponding to the
construction shown in FIG. 7. More specifically, the gear ratio
from the gear 18 to the gear 7 in FIG. 9 corresponds to the gear
ratio from the gear 18 to the gear 7 in FIG. 7, and if the gear
ratio from the gear 21 to the gear 5 in FIG. 7 is set at 1.0, this
construction is equal to that shown in FIG. 9.
[0046] In this way a similar performance to that in FIG. 7 can be
attained by a system configuration with a smaller number of gears
and thus this embodiment is characteristic in that a hydbrid
automobile capable of attaining a speed changing function at low
cost can be realized.
[0047] FIG. 10 shows another example of the clutch trouble
processing method shown in FIG. 4, which is different from that
shown in FIG. 6. This processing method is different from that of
FIG. 6 in that step 130 is provided instead of steps 125 and 126 in
FIG. 6. The processing of step 130 is performed when the clutch 14
is not properly released. In this case, a field weakening control
is conducted for the motor 8. According to this field weakening
control, a field magnet generated by the permanent magnet of the
motor 8 as a permanent magnet synchronous motor is cancelled to
some extent by the motor current. With this control, even if the
motor 8 is rotated at a high speed, there is no fear that a counter
electromotive force may become excessive, because of a substantial
decrease of magnetic flux. Thus, even if the maximum vehicle speed
is not limited, there is no fear of damage to the power converter
10, so that the driving performance in clutch failure can be
improved.
[0048] Transmissions using two planetary gears controlled by motors
and hybrid vehicles using the same, both embodying the present
invention, have been described above. The present invention is also
applicable to the case where three or more planetary gears are
used, so that a still more steps of a transmission can also be
constituted. Although the motors referred to above are mainly
synchronous motors using a permanent magnet, there may be used a DC
motor using a permanent magnet as a field magnet. The present
invention is further applicable to the case where a permanent
magnet-free induction motor or synchronous motor is used. It goes
without saying that a combination of the motors referred to above
can also be used effectively. Although the control method described
above mainly control the sun gear in each planetary gear with a
motor, there may be adopted another method controlling another
gear. Thus, the present invention can be practices using any of
various combined methods. As to the differential mechanisms,
planetary gears are used in the above embodiments, they may be
substituted by commonly-used differential gears, or when importance
is attached to quietness, there may be used harmonic gears. It is
needless to say that the transmission according to the present
invention is applicable not only to automobiles but also to ships
and various other vehicles, including rolling stock and
bicycles.
[0049] In the present invention, there are used a plurality of
differential mechanisms in which motors control a difference in the
number of revolutions between an input shaft and an output shaft
thereof, the input and output shafts for the plural differential
mechanisms being used in common, gear ratios from the input shafts
to the output shafts in the plural differential mechanisms are set
at a value different to each other, and gear ratios from the input
shafts to the motors of the plural differential mechanisms are set
at a value different to each other, whereby it is possible to
provide a transmission having a small-sized motor of a low torque
and a motor prevented from high revolution and having a stepless
speed changing function which permits operation in a high engine
efficiency region while minimizing an electrical energy loss.
[0050] According to the present invention, in another aspect
thereof, there are used a plurality of differential mechanisms in
which motor shafts driven by motors control a difference in the
number of revolutions between an input shaft and an output shaft
thereof, the input and output shafts for the plural differential
mechanisms being used in common, gear ratios from the input shafts
to the output shafts in the plural differential mechanisms are set
at a value different to each other, and there is provided a
locking/unlocking mechanism for locking and unlocking the motor
shaft in a differential mechanism which is larger at least in its
gear ratio, whereby there can be provided a transmission having a
small-sized motor of a low torque and a motor prevented from high
revolution and having a stepless speed changing function which
permits operation in a high engine efficiency region while
minimizing an electrical energy loss.
[0051] According to the present invention, in a further aspect
thereof, in a vehicle having an engine which generates a driving
energy for driving the vehicle and a transmission which changes the
rotational speed of the engine and transmits a driving force for
wheels, the transmission is provided with at least first and second
differential mechanisms which input a driving force generated by
the engine and which output a driving force for the wheels, and is
also provided with first and second motors for controlling the
first and second differential mechanisms, respectively, wherein
gear ratios from the input shafts to the output shafts in the first
and second differential mechanisms are set at a value different to
each other and gear ratios from the input shafts to the first and
second motors are also set at a value different to each other. With
this construction it is possible to provide a vehicle of a low cost
and a reduced fuel consumption.
[0052] According to the present invention, in a still further
aspect thereof, in a vehicle having an engine which generates a
driving energy for driving the vehicle and a transmission which
changes the rotational speed of the engine and transmits a driving
force to wheels, the transmission is provided with at least first
and second differential mechanisms which input a driving force
generated by the engine and which output a driving force for the
wheels, and is also provided with first and second motors for
controlling the first and second differential mechanisms,
respectively, wherein a gear ratio from the input shaft to the
output shaft in the first differential mechanism is set at a value
larger than a gear ratio from the input shaft to the output shaft
in the second differential mechanism, and there is provided with a
locking/unlocking mechanism for locking and unlocking a motor shaft
which transmits the driving force of at least the first motor to
the first differential mechanism. Also with this construction it is
possible to provide a vehicle of a low cost and a reduced fuel
consumption.
* * * * *