U.S. patent application number 09/981417 was filed with the patent office on 2003-04-24 for three-mode, compound-split, electrically-variable transmission.
Invention is credited to Holmes, Alan G., Klemen, Donald, Schmidt, Michael Roland.
Application Number | 20030078126 09/981417 |
Document ID | / |
Family ID | 25528346 |
Filed Date | 2003-04-24 |
United States Patent
Application |
20030078126 |
Kind Code |
A1 |
Holmes, Alan G. ; et
al. |
April 24, 2003 |
THREE-MODE, COMPOUND-SPLIT, ELECTRICALLY-VARIABLE TRANSMISSION
Abstract
An electrically-variable transmission has three modes of
operation. The power in each of the modes of operation is split by
differential gearing into a mechanical path and an electrical path
between the input shaft of the transmission and the output shaft of
the transmission. This is accomplished with three planetary
gearsets and four torque-transmitting mechanisms that are
judiciously engaged to provide the three modes of operation, which
are an input-split mode and two compound-split modes. The
transmission can be part of a system with electrical storage
devices, which will supplement the engine power during some periods
of operation.
Inventors: |
Holmes, Alan G.; (Fishers,
IN) ; Schmidt, Michael Roland; (Carmel, IN) ;
Klemen, Donald; (Carmel, IN) |
Correspondence
Address: |
LESLIE C. HODGES
General Motors Corporation
Legal Staff, Mail Code 482-C23-B21
P.O. Box 300
Detroit
MI
48265-3000
US
|
Family ID: |
25528346 |
Appl. No.: |
09/981417 |
Filed: |
October 18, 2001 |
Current U.S.
Class: |
475/5 ; 475/275;
475/282; 903/910; 903/951 |
Current CPC
Class: |
F16H 2037/0866 20130101;
B60K 6/40 20130101; Y02T 10/62 20130101; B60K 6/365 20130101; Y10S
903/91 20130101; F16H 2037/107 20130101; B60K 6/445 20130101; Y10S
903/951 20130101; F16H 2037/104 20130101; Y02T 10/6239 20130101;
F16H 2200/2041 20130101; F16H 3/728 20130101; F16H 2200/201
20130101 |
Class at
Publication: |
475/5 ; 475/275;
475/282 |
International
Class: |
F16H 003/72; F16H
003/62; F16H 003/44 |
Claims
1. An electrically-variable transmission comprising: a transmission
input shaft; a first planetary gear set having first, second, and
third members, said first member being continuously interconnected
with said input shaft; a first electrical power unit continuously
interconnected with said second member of said first planetary gear
set; a second planetary gear set having first, second, and third
members with said first member being continuously interconnected
with said third member of said first planetary gear set; a second
electrical power unit continuously interconnected with said second
member of said second planetary gear set; a third planetary gear
set having three members, said first member being continuously
interconnected with both said third member of said first planetary
gear set and with said first member of said second planetary gear
set, said second member of said third planetary gear set being
continuously interconnected with a transmission output shaft; a
first torque transmitting mechanism selectively interconnecting
said first electrical power unit and said third member of said
second planetary gear set for common rotation; a second torque
transmitting mechanism selectively interconnecting said third
member of said second planetary gear set with a stationary member;
a third torque transmitting mechanism selectively interconnecting
said second electrical power unit with said third member of said
third planetary gear set for common rotation; a fourth torque
transmitting mechanism selectively interconnecting said third
member of said third planetary gear set with said stationary
member; and said torque transmitting mechanisms being operated in
combinations of two to establish three modes of power transmission
between said input shaft and said output shaft.
2. The electrically-variable transmission defined in claim 1
further comprising: said second and fourth of said torque
transmitting mechanisms being engaged to establish an input split
mode of power transmission; said first and fourth of said torque
transmitting mechanisms being engaged to establish a first compound
split mode of power transmission; and said first and third of said
torque transmitting mechanisms being engaged to establish a second
compound split mode of power transmission.
3. The electrically-variable transmission defined in claim 2
further comprising: said first electrical power unit and said third
member of said second planetary gear set being substantially
stationary during an interchange between said input split mode and
said first compound split mode; and said second electrical unit and
said third member of said third planetary gear set being
substantially stationary during and interchange between said first
compound split mode and said second compound split mode.
4. The electrically-variable transmission defined in claim 2
further comprising: said torque transmitting mechanisms each being
selectively engageable fluid-operated friction torque transmitting
mechanisms, said first and third torque transmitting mechanisms
being clutches and said second and fourth torque transmitting
mechanisms being brakes.
5. The electrically-variable transmission defined in claim 2
further comprising: said first torque transmitting mechanism being
a mechanical sliding clutch and said second torque transmitting
mechanisms being mechanical sliding brake, said first and second
torque transmitting mechanisms having a central overlapping
condition wherein both of said torque transmitting mechanisms are
operable to hold the second member of said first planetary gear set
stationary.
6. The electrically-variable transmission defined in claim 2
further comprising: a source of mechanical power for supplying
power to said input shaft; means for connecting said source of
mechanical power to said input shaft; and an electrical storage
means for supplying electrical power to and receiving electrical
power from said first and second electrical power units.
7. The electrically-variable transmission defined in claim 1
further comprising: said first member of first planetary gear set
and said third member of said second planetary gear set both being
ring gear members; said third member of said first planetary gear
set, said first member of said second planetary gear set, and said
second member of said third planetary gear set each being planet
carrier assembly members; said second member of said first
planetary gear set and said second member of said second planetary
gear set both being sun gear members; said first member of said
third planetary gear set being any one of a group consisting of a
ring gear member and a sun gear member; and said third member of
said third planetary gear set being the member of the group that is
not said first member.
8. An electrically-variable propulsion system comprising: a
transmission input shaft; a source of mechanical power for
supplying power to said input shaft; means for connecting said
source of mechanical power to said input shaft; a first planetary
gear set having first, second, and third members, said first member
being continuously interconnected with said input shaft; a first
electrical power unit continuously interconnected with said second
member of said first planetary gear set; a second planetary gear
set having first, second, and third members with said first member
being continuously interconnected with said third member of said
first planetary gear set; a second electrical power unit
continuously interconnected with said second member of said second
planetary gear set; an electrical power storage means for supplying
electrical power to and receiving electrical from said first and
second electrical power units; a third planetary gear set having
three members, said first member being continuously interconnected
with both said third member of said first planetary gear set and
with said first member of said second planetary gear set, said
second member of said third planetary gear set being continuously
interconnected with a transmission output shaft; a first torque
transmitting mechanism selectively interconnecting said first
electrical power unit and said third member of said second
planetary gear set for common rotation; a second torque
transmitting mechanism selectively interconnecting said third
member of said second planetary gear set with a stationary member;
a third torque transmitting mechanism selectively interconnecting
said second electrical power unit with said third member of said
third planetary gear set for common rotation; a fourth torque
transmitting mechanism selectively interconnecting said third
member of said third planetary gear set with said stationary
member; and said torque transmitting mechanisms being operated in
combinations of two to establish three modes of power transmission
between said input shaft and said output shaft.
Description
TECHNICAL FIELD
[0001] The present invention relates to vehicular transmissions
and, more particularly, to vehicular transmissions having both
electrical and mechanical drive paths to provide split-mode
operation within the transmission between an input shaft and an
output shaft.
BACKGROUND OF THE INVENTION
[0002] The electrically-variable transmission (EVT) has been
proposed for vehicles to improve fuel economy and reduce emissions.
The EVT splits mechanical power between an input shaft and an
output shaft into a mechanical power path and an electrical power
by means of differential gearing. The mechanical power path may
include clutches and additional gears. The electrical power path
may employ two electrical power units, each of which may operate as
a motor or as a generator. With an electric storage battery, the
EVT can be incorporated into a propulsion system for a hybrid
electric vehicle.
[0003] The hybrid vehicle or hybrid propulsion system uses an
electrical power source, such as batteries, as well as an engine
power source. The batteries are connected with the electrical drive
units through an electronic control unit (ECU), which distributes
the electrical power as required. The ECU also has connections with
the engine and vehicle to determine operating characteristics, or
operating demand, so that the electrical power units are operated
properly as either a motor or a generator. When operating as a
generator, the electrical power unit accepts power from either the
vehicle or the engine and stores power in the battery, or provides
that power to operate another electrical device or another
electrical power unit on the vehicle or on the transmission.
[0004] There have been a number of electrically-variable
transmissions proposed for vehicle operation. Examples of proposed
electrically-variable transmissions are shown in U.S. Pat. No.
5,558,589 issued to Schmidt on Sep. 24, 1996, and assigned to the
assignee of the present invention; U.S. Pat. No. 6,090,005 issued
to Schmidt et al. on Jul. 18, 2000, and assigned to the assignee of
the present invention; and U.S. Pat. No. 5,931,757 issued to
Schmidt on Aug. 3, 1999, and assigned to the assignee of the
present invention. The above-identified U.S. Pat. No. 5,931,757
defines the structure and operation of a variable two-mode,
input-split, electromechanical transmission for a parallel hybrid
electric propulsion system. The U.S. Pat. No. 5,558,589 discloses a
two-mode, compound-split, electromechanical vehicular transmission,
and U.S. Pat. No. 5,558,595 issued to Schmidt et al. on Sep. 24,
1996, discloses a one-mode, input-split transmission. These, and
many other patents, describe various electrically-variable type
transmissions.
[0005] One of the benefits of having an electrically-variable
transmission incorporating more than one mode of operation is that
each mode of operation will generally incorporate at least one
mechanical point where one of the electrical power units is
stationary, thereby reducing the electrical power input and
providing a pure mechanical power flow path which is, of course,
more efficient than a pure electrical power flow path.
[0006] Other hybrid type power transmissions are shown in U.S. Pat.
No. 5,571,058 issued to Schmidt on Nov. 5, 1996; U.S. Pat. No.
5,577,973 issued to Schmidt on Nov. 26, 1996; U.S. Pat. No.
5,558,173 issued to Sherman on Sep. 24, 1996; and U.S. Pat. No.
5,558,175 issued to Sherman on Sep. 24, 1996, all of which are
assigned to the assignee of the present invention.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to provide an
improved three-mode, input-split and compound-split
electrically-variable transmission.
[0008] In one aspect of the present invention, the
electrically-variable transmission has an input-split first mode of
operation.
[0009] In another aspect of the present invention, the
electrically-variable transmission has a compound-split mode during
the second mode of operation.
[0010] In still another aspect of the present invention, the
electrically-variable transmission has another compound-split power
path during a third mode of operation.
[0011] In yet still another aspect of the present invention, the
electrically-variable transmission incorporates a mechanical power
source, two electrical power units, and three planetary gear
sets.
[0012] In a further aspect of the present invention, the
electrically-variable transmission incorporates four
torque-transmitting mechanisms that are selectively engageable to
provide the three modes of operation.
[0013] In yet a further aspect of the present invention, the four
torque-transmitting mechanisms are operated in combinations of two
to provide the three modes of operation.
[0014] In yet still a further aspect of the present invention, the
electrically-variable transmission has a neutral condition with two
of the torque-transmitting mechanisms engaged, wherein the
transmission can operate in either the forward mode or a reverse
mode from the neutral condition depending on the speed of one of
the electrical power units.
DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic representation of one embodiment of
the present invention incorporated in a hybrid electric vehicle
propulsion system.
[0016] FIG. 2 is a plurality of curves representing the speeds of
components of the electrically-variable transmission of FIG. 1
versus the speed of the vehicle or output speed of the
transmission.
[0017] FIG. 3 is a schematic representation of an alternative
embodiment of the present invention incorporated in a hybrid
powertrain.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
[0018] Referring to the drawings, wherein like characters represent
the same or corresponding parts throughout the several views, there
is seen in FIG. 1 a powertrain 10 incorporating an engine 12, an
electrically-variable transmission 14, and a final drive mechanism
16. The electrically-variable transmission 14 has an input shaft 18
continuously connected with the engine 12 and driving a main pump
20, and a power takeoff (PTO) gear unit 22. The power takeoff gear
unit 22 drives a conventional PTO, which supplies mechanical power
for accessory mechanisms that might be connected with the
transmission.
[0019] The transmission 14 includes three planetary gearsets 24,
26, and 28. The planetary gearset 24 includes a sun gear member 30,
a ring gear member 32, and planet carrier assembly member 34. The
planet carrier assembly member 34 includes a plurality of pinion
gears 36 that are rotatably mounted on a planet carrier 38 disposed
in meshing relationship with both the sun gear member 30 and the
ring gear member 32.
[0020] The planetary gearset 26 includes a sun gear member 40, a
ring gear member 42, and a planet carrier assembly member 44. The
planet carrier assembly member 44 includes a plurality of pinion
gears 46 that are rotatably mounted on planet carrier 48 and
disposed in meshing relationship with both the sun gear member 40
and the ring gear member 42.
[0021] The planetary gearset 28 includes a sun gear member 50, a
ring gear member 52, and a planet carrier assembly member 54. The
planet carrier assembly member 54 includes a plurality of pinion
gears 56 that are rotatably mounted on a planet carrier 58 and
disposed in meshing relationship with the sun gear member 50 and
the ring gear member 52.
[0022] Further incorporated into the electrically-variable
transmission 14 is a pair of electrical power units 60 and 62 that
are controlled by a conventional electronic control unit (ECU). The
ECU is connected with the electrical power unit 60 through a pair
of electrical conductors 64 and 66, and is connected with the
electrical power unit 62 through a pair of electrical conductors 68
and 70. The ECU is also communicated with an electrical storage
device 72, which is connected with the ECU through a pair of
electrical conductors 74 and 76. The electrical storage device is
generally one or more electrical batteries.
[0023] The electrical power units 60 and 62 are preferably
motor/generator units, which, as is well known, can operate as
either a power supplier or as a power generator. In operating as a
motor or power supplier, the electrical power units will supply
power to the transmission and, when operating as generators, will
take electrical power from the transmission, and the ECU will
either distribute the power in the electrical storage device 72
and/or distribute the power to the other power unit which is
operating as a motor at that time.
[0024] The electrically-variable transmission 14 employs four
torque-transmitting mechanisms 78, 80, 82, and 84. The
torque-transmitting mechanisms 78 and 82 are rotating-type
torque-transmitting mechanisms, commonly termed clutches, and the
torque-transmitting mechanisms 80 and 84 are stationary-type
torque-transmitting mechanisms, commonly termed brakes. Each of the
torque-transmitting mechanisms 78, 80, 82, and 84, as shown in FIG.
1, are hydraulically-operated, selectively engageable friction
devices. The hydraulic power to operate the clutches is supplied by
the pump 20. The ECU provides electronic control signals that are
effective on conventional valve mechanisms to distribute fluid to
and exhaust fluid from the torque-transmitting mechanisms in a
well-known manner.
[0025] The input shaft 18 is continuously connected with the ring
gear member 32, and the sun gear member 30 is continuously
connected with the electrical power unit 60. The planet carrier
assembly member 34 is connected through a main shaft 86 with both
the planet carrier assembly member 44 and the ring gear member 42.
The sun gear member 40 is continuously connected with the
electrical power unit 62. The planet carrier assembly member 54 is
continuously connected with the final drive mechanism 16 through an
output shaft 88.
[0026] The torque-transmitting mechanism 78 selectively
interconnects the sun gear member 30 and the electrical power unit
60 with the ring gear member 42 of the planetary gearset 26. The
torque-transmitting mechanism 80 selectively connects the ring gear
member 42 with a stationary transmission housing 90 of the
powertrain 10. The torque-transmitting mechanism 82 selectively
interconnects the sun gear member 40 and electrical power unit 62
with the sun gear member 50. The torque-transmitting mechanism 84
selectively connects the sun gear member 50 with the stationary
housing 90.
[0027] As is well known in electrical controls of power
transmissions, the ECU receives a number of electrical signals from
the vehicle and transmission, such as engine speed, vehicle speed,
throttle demand, to name a few. These electrical signals are used
as input signals for the programmable-type digital computer, which
is incorporated within the ECU. The computer is then effective to
distribute the electrical power as required to permit the operation
of the transmission in a controlled manner.
[0028] During normal operation, the engine 12 supplies mechanical
power to the ring gear member 32. The electrical power unit 60
either supplies power to the sun gear member 30 or accepts power
from the sun gear member 30. The electrical power unit 62 either
supplies to the sun gear member 40 or accepts power from the sun
gear member 40.
[0029] If the torque-transmitting mechanism 78 is engaged, the
electrical power unit 60 is connected with the ring gear member 42
and either supplies or accepts power through the ring gear member
42 as well as the sun gear member 30. When the torque-transmitting
mechanism 82 is engaged, the electrical power unit 62 accepts power
from or delivers power to the sun gear member 50 as well as the sun
gear member 40. When the torque-transmitting mechanism 80 is
engaged, the sun gear member 40 is held stationary and becomes a
reaction member within the planetary gearset 26. When the
torque-transmitting mechanism 84 is engaged, the sun gear member 50
becomes a reaction member within the planetary gearset 28. When the
torque-transmitting mechanism 84 is engaged, the sun gear member 50
is a reaction member and the power of the main shaft 86 will be
transmitted through the ring gear member 52 to the planet carrier
assembly member 54 and therefore to the output shaft 88. When the
torque-transmitting mechanism 80 is engaged, the electrical power
unit can either accept power from or deliver power to the main
shaft 86 through the planetary gearset 26.
[0030] The judicious selection of the engagement of the
torque-transmitting mechanisms 78, 80, 82, and 84 in combinations
of two will establish three modes of operation within the
electrically-variable transmission 14. The engagement of the
torque-transmitting mechanisms 80 and 84 establishes a first mode
of operation; the engagement of the torque-transmitting mechanisms
78 and 84 establishes a second mode of operation, and the
engagement of the torque-transmitting mechanisms 78 and 82
establishes a third mode of operation.
[0031] The first mode of operation is an input-split mode of
operation, while the second and third modes are compound-split
modes of operation. There are, of course, other combinations of
engagements of the torque-transmitting mechanisms that will permit
other operating conditions. For example, with the
torque-transmitting mechanisms 78 and 80 engaged simultaneously,
the electrical power unit 62 can be utilized as a motor to supply
power to the main shaft 86 and thereby provide starting torque for
the engine 12. If all four of the torque-transmitting mechanisms
are engaged simultaneously, the input shaft 18 and the output shaft
88 are effectively grounded and therefore no power can be
transmitted, thus producing a "park gear" arrangement if desired.
The simultaneous disengagement of all of the torque-transmitting
mechanisms provides a positive neutral condition.
[0032] The curve or chart shown in FIG. 2 provides a graphical
illustration of the speeds of the various components within the
transmission, as well as the speed of the engine, during the three
modes of operation and during an idle condition.
[0033] For purposes of the following discussion, the rotational
direction of the engine will be considered forward or positive, and
the rotational direction opposite the engine will be considered
reverse or negative. During the first mode of operation, the
torque-transmitting mechanisms 80 and 84 are engaged. In a neutral
condition, the engine is at an idle speed as depicted in FIG. 2,
and the speed of the electrical power unit 60 is negative or
reverse, such that the speed of the planet carrier assembly member
34 is zero, as shown at the zero-to-zero point on the curve of FIG.
2. Also, curve of FIG. 2, the engine speed is represented by a line
92, the speed of electrical power unit 60 is represented by the
line 94, the speed of the electrical power unit 62 is represented
by the line 96, and the speed of the transmission output shaft 18
is represented by the line 98.
[0034] When the powertrain 10 is being operated in the neutral
condition, the vehicle can be moved in either a forward direction
or a reverse direction. For movement in the reverse direction, the
negative or reverse speed of the electrical power unit 62 is
permitted to increase, thereby increasing the speed of the planet
carrier assembly member 34 in the negative direction. The
electrical power unit 62 is operated as a motor to assist in
driving the vehicle and therefore adding power to the transmission
at the sun gear member 40, which is distributed to the main shaft
86 by the planet carrier assembly member 44. This power is
transmitted to the ring gear member 52 by planetary gearset 28 and
then through the planet carrier assembly member 54 through the
output shaft 88. As is noted, the vehicle can be moved in the
reverse direction from the neutral condition. Also, during the
reverse operation, the speed of the engine 12 is increased from the
idle speed to an elevated speed.
[0035] To operate in the forward direction, the engine 12 is
accelerated from the idle speed, the speed of the electrical power
unit 94 (operating as a generator) is decreased, and the speed of
the electrical power unit 62 operating as a motor is increased.
This operation will continue until the point 100 is reached. This
is the end of the first mode of operation. This first mode of
operation is an input-split type of power transmission.
[0036] At the point 100 on curve of FIG. 2, the ring gear member 42
is stationary as held by the torque-transmitting mechanism 80, and
as noted on curve of line 94, the speed of the electrical power
unit 62 is also zero. At this point, the torque-transmitting
mechanisms 80 and 78 can be interchanged in a synchronous
condition, such that there is no slippage involved in either the
engagement or disengagement of these devices. It should also be
noted that at this point, the transmission is operating in a
substantially mechanical power flow arrangement and the electrical
losses from either unit 60 or 62 are small and negligible. At this
interchange point from mode one to mode two, the operation of the
electrical power unit 62 is changed from being a motor to being a
generator. Also at this interchange point, the operation of
electrical power unit 60 changes from a generator mode to a motor
mode. It will be noted from the curve line 92 that the engine speed
is essentially fixed at this point. That is, the engine is
operating at its governed speed.
[0037] To continue to accelerate the vehicle during the second mode
of operation, which is a compound-split mode, the speed of the
electrical power unit 60 (operating as a motor) is increased and
the speed of the electrical power unit 62 (operating as a
generator) is decreased. Both the electrical power unit 60 and the
engine 12 impart positive or forward rotation to the planet carrier
assembly member 36, and the electrical power unit 62 provides a
rotating reaction member at the sun gear member 40 of the planetary
gearset 26. The electrical energy generated by the electrical power
unit 62 can be utilized to either recharge the electrical storage
device 72, provide electrical power to drive the electrical power
unit 60, or to do both depending upon the amount of power needed at
the electrical power unit 60 and the level of charge of the
electrical storage device 72.
[0038] The powertrain 10 continues to operate in the second mode
until the point 102 is reached in FIG. 2. At this point, the speed
of the electrical power unit 62 has decreased to zero and the speed
of the electrical power unit 60 has increased to a maximum value.
At this point, the electrical power unit 62 has a zero speed, which
is equal to the speed of the sun gear member 50 as held stationary
by the torque-transmitting mechanism 84. Therefore, at this
interchange point, the torque-transmitting mechanisms 82 and 84 can
be interchanged in a synchronous manner, wherein no slippage occurs
during the ratio interchange. This is the end of the second mode of
operation and the beginning of the third mode of operation.
[0039] The third mode of operation is also a compound-split mode of
operation. During the third mode of operation, the electrical power
unit 60 is operated as a generator and the electrical power unit 62
is operated as a motor. As can be seen in FIG. 2, the speed of the
electrical power unit 60 is decreasing while the speed of the
electrical power unit 62 is increasing. The sun gear member 50 and
the planet carrier assembly member 54 are both driven in a forward
or positive direction. The sun gear member 50 is driven by the
electrical power unit 62, and the ring gear member 52 is driven by
both the engine 12 through the planetary gearset 24 and the
electrical power unit 62 through the planetary gearset 26. During
the third mode of operation, the electrical power unit 60 supplies
electrical power to the system which can be utilized to power the
electrical power unit 62 as a motor and/or provide energy to the
electrical storage device 72 to increase the storage charge of that
member. The third mode of operation can continue until the vehicle
reaches a maximum speed point at 104 on the curve of FIG. 2.
[0040] The curves shown on FIG. 2 are for maximum power flow
through the vehicle. That is, the engine is operated at its maximum
throttle condition and each of the electrical power units is
operating at its maximum electrical generation and/or power output
conditions. The powertrain 10 can be operated at lesser power flows
if the engine throttle is reduced to below the maximum throttle
condition shown in FIG. 2. If the engine speed is reduced, the ECU
will accommodate with lesser engine speed and provide the desired
control signals to the electrical power units 60 and 62, as well as
the torque-transmitting mechanisms 78, 80, 82, and 84, such that
the operating points 100, 102, and 104 will still be achieved but
at lesser vehicle speeds. The operating points 100, 102, and 104
are important operating points in that each of these is a
mechanical operating point where the amount of electrical energy
being distributed through the powertrain 10 is at a minimum and the
mechanical power flow is a maximum or greater percentage of the
total power flow. As is well known, this results in a substantial
increase in operating efficiency for the powertrain 10.
[0041] A powertrain 110, shown in FIG. 3, provides an alternative
embodiment for the present invention. Powertrain 110 includes the
engine 12, the pump 20, the final drive mechanism 16, and an
alternative electrically-variable transmission 114. The
transmission 114 includes three planetary gearsets 124, 126, and
128.
[0042] The planetary gearset 124 includes a sun gear member 130, a
ring gear member 132, and a planet carrier assembly member 134. The
planet carrier assembly member 134 includes a plurality of pinion
gears 136 that are rotatably mounted on a planet carrier 138 and
disposed in meshing relationship with both the sun gear member 130
and the ring gear member 132.
[0043] The planetary gearset 126 includes a sun gear member 140, a
ring gear member 142, and a planet carrier assembly member 144. The
planet carrier assembly member 144 includes a plurality of pinion
gears 146 that are rotatably mounted on a planet carrier 148 and
disposed in meshing relationship with both the sun gear member 140
and the ring gear member 142.
[0044] The planetary gearset 128 includes a sun gear member 150, a
ring gear member 152, and a planet carrier assembly member 154. The
planet carrier assembly member 154 includes a plurality of pinion
gears 156 that are rotatably mounted on a planet carrier 158 and
disposed in meshing relationship with both the sun gear member 150
and the ring gear member 152.
[0045] The electrically-variable transmission 114 also includes two
electrical power units 160 and 162, which are communicated with the
ECU, the same as the electrical power units 60 and 62, shown in
FIG. 1. The electrically-variable transmission 114 also includes a
plurality of torque-transmitting mechanisms 178, 180, 182, and 184.
The torque-transmitting mechanisms 182 and 184 are friction-type
torque-transmitting mechanisms, similar to those shown as 82 and
84, respectively, in FIG. 1. The torque-transmitting mechanisms 178
and 180 are preferably sliding mechanical-type torque-transmitting
mechanisms.
[0046] The torque-transmitting mechanism 178 will provide a drive
engagement between the electrical power unit 160 and the ring gear
member 142. The torque-transmitting mechanism 180 will provide a
connection between the ring gear member 142 and the transmission
housing 90. The torque-transmitting mechanisms 178 and 180 are
designed such that they will simultaneously engage their respective
members when in a middle or neutral condition. Under this
circumstance, the electrical power unit 60 and therefore sun gear
member 30 is held stationary, which will permit the electrical
power unit 62 to provide starting torque for the engine 12. The
torque-transmitting mechanisms 178 and 180 can be moved from there
to engage the first mode of operation in which the
torque-transmitting mechanisms 180 and 184 are simultaneously
engaged. The operation of the powertrain 110 is the same as the
operation of the powertrain 10, depicted in FIG. 1.
[0047] The planetary gearset 128 is slightly different from the
planetary gearset 28 in that the connections are arranged
differently. The sun gear member 150 is continuously connected with
a main transmission shaft 186, while the ring gear member 152 is
selectively connectible with either the transmission housing 90 or
the electrical power unit 162. The planet carrier assembly member
154 is connected with the output shaft 88, the same as the planet
carrier assembly member 54 is connected with the output shaft 88.
This change in mechanical connections does not affect the operation
of the powertrain 110. It merely changes the power flow in the
planetary gearset 128 such that power flows through the sun gear
member 150 to the planet carrier assembly member 154 during the
first and second modes of operation, and through both the sun gear
member 150 and ring gear member 152 during the third mode of
operation.
[0048] Other configurations of the planetary gearsets are possible
without changing the spirit or scope of the present invention. For
example, the planetary gearset at the output shaft, that is 28 or
128, can be a compound-type planetary gearset wherein meshing
pinion gears are arranged on a single carrier and disposed between
the sun gear member and the ring gear member. These minor changes
will be well known to those skilled in the art of power
transmissions.
[0049] In both of the embodiments shown, the electrically-variable
transmission has three modes of operation: an input power split
mode for launching the vehicle from rest; a compound power split
mode for low speed ratio cruising; and a second compound-split mode
for high speed cruising. Each of the transmissions incorporate
three planetary gearsets and two electrical power units that can
operate as either motors or generators, and four
torque-transmitting mechanisms that are operable to selectively
interconnect the electrical power units in the planetary gearsets
in the desired fashion to accomplish the three modes of
operation.
[0050] In both of the embodiments shown, the input power split
requires only one gearset, which provides a differential gearset
between the first of the electrical power units and the power input
from the engine. The second of the electrical power units absorbs
power from the transmission and does not contribute to the power
flow between the input shaft of the transmission and the output
shaft of the transmission. Each of the compound-split modes
requires more than one planetary gearset. The torque-transmitting
mechanisms are interchanged judiciously to connect the planetary
gearsets in the desired arrangement for each of the higher two
modes of operation. The interchanges from the input power split
mode to the first compound-split mode, and from the first
compound-split mode to the second compound-split mode, are each
accomplished at a synchronous shift point. At these shift points,
the on-coming and off-going torque-transmitting devices control a
number that is at essentially speed, thereby reducing or
eliminating any slippage between the components to be controlled by
the torque-transmitting mechanism during the ratio interchange as
in the mode interchange.
[0051] Those skilled in the art will recognize that the
transmissions described above provide an electrically-variable
transmission that has three modes of operation, an input-split mode
and two compound-split modes, that are accomplished with three
planetary gearsets and four torque-transmitting mechanisms.
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