U.S. patent application number 09/779181 was filed with the patent office on 2002-08-08 for dual countershaft twin clutch automated transmission with bi-directional clutches.
Invention is credited to Bowen, Thomas C..
Application Number | 20020104397 09/779181 |
Document ID | / |
Family ID | 25115590 |
Filed Date | 2002-08-08 |
United States Patent
Application |
20020104397 |
Kind Code |
A1 |
Bowen, Thomas C. |
August 8, 2002 |
DUAL COUNTERSHAFT TWIN CLUTCH AUTOMATED TRANSMISSION WITH
BI-DIRECTIONAL CLUTCHES
Abstract
An automated dual-countershaft twin-clutch multi-speed
transmission adapted to transfer power from the engine to a
driveline of a motor vehicle. The transmission includes a first
master clutch operable to establish a releasable drive connection
between the input shaft and a first countershaft shaft, a second
master clutch operable to establish a releasable drive connection
between the input driveline, and a geartrain for selectively
establishing a plurality of forward and reverse speed ratio drive
connections between the countershafts and the output shaft. The
transmission further includes power-operated shiftable overrunning
clutches for selectively engaging constant-mesh gearsets associated
with the geartrain, and a transmission controller for controlling
coordinated actuation of the first and second master clutches, and
the shiftable overrunning clutches to permit non-power interrupted
("powershift") sequential gear changes automatically without input
from the vehicle operator.
Inventors: |
Bowen, Thomas C.; (Rochester
Hills, MI) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
25115590 |
Appl. No.: |
09/779181 |
Filed: |
February 8, 2001 |
Current U.S.
Class: |
74/329 ; 903/919;
903/945; 903/946 |
Current CPC
Class: |
F16D 41/04 20130101;
B60W 10/026 20130101; B60W 20/00 20130101; B60W 10/113 20130101;
B60W 30/18 20130101; F16H 3/097 20130101; F16H 3/006 20130101; Y10T
74/19223 20150115; B60W 20/40 20130101; B60K 6/387 20130101; B60W
2540/16 20130101; Y10S 903/946 20130101; Y02T 10/62 20130101; F16H
61/688 20130101; Y10T 74/19242 20150115; Y10T 74/19233 20150115;
B60K 6/547 20130101; B60W 10/10 20130101; B60Y 2400/428 20130101;
B60W 2510/0638 20130101; B60W 10/02 20130101; F16H 63/304 20130101;
B60W 2710/1005 20130101; F16D 41/086 20130101; Y10S 903/919
20130101; B60W 2710/021 20130101; B60K 2006/268 20130101; B60K
6/485 20130101; Y10S 903/945 20130101 |
Class at
Publication: |
74/329 |
International
Class: |
F16H 003/08 |
Claims
What is claimed is:
1. A twin-clutch transmission comprising: an input shaft; an output
shaft having first and second output gears fixed thereto; a first
countershaft rotatably supporting a first speed gear meshed with
one of said first and second output gears; a first master clutch
for selectively establishing a releasable drive connection between
said input shaft and said first countershaft; a first overrunning
clutch operable in a locked mode for coupling said first speed gear
to said first countershaft and in a released mode for releasing
said first speed gear t from engagement with said first
countershaft; a first shift actuator for shifting said first
overrunning clutch between its locked and released modes; a second
countershaft rotatably supporting a second speed gear meshed with
one of said first and second output gear; a second overrunning
clutch operable in a locked mode for coupling said second speed
gear to said second countershaft and in a released mode for
releasing said second speed gear from engagement with said second
countershaft; a second shift actuator for shifting said second
overrunning clutch between its locked and released modes; and a
control system for controlling actuation of said first and second
actuators.
2. The twin-clutch transmission of claim 1 wherein said first
overrunning clutch comprises: a first inner ring rotatably
supported on said first countershaft and having a pair of end
segments defining a slot therebetween; a first outer ring fixed to
said first speed gear; a set of first locking elements disposed in
pockets formed between siad first inner ring and said first outer
ring; and a first mode shift mechanism operable in first position
to permit relative rotation between said first inner and outer
rings and in a second position to prevent such relative rotation,
whereby said first overrunning clutch operates in its locked mode
when said first mode shift mechanism is in its first position and
operating in its released mode when said first mode shift mechanism
is in its second position.
3. The twin-clutch transmission of claim 2 wherein said first shift
actuator is a power-operated device operable for moving said first
mode shift mechanism between its first and second positions.
4. The twin-clutch transmission of claim 3 wherein said second
overrunning clutch comprises: a second inner ring rotatably
supported on said second countershaft and having a pair of end
segments defining a slot therebetween; a second outer ring fixed to
said second speed gear; a set of second locking elements disposed
in pockets formed between said second inner ring and said second
outer ring; and a second mode shift mechanism operable in a first
position to permit relative rotation between said second inner and
outer rings and in a second position to prevent such relative
rotation, whereby said second overrunning clutch operates in its
locked mode when said second mode shift mechanism is in its first
position and operating in its released mode when said mode shift
mechanism is in its second position.
5. The twin-clutch transmission of claim 4 wherein said second
shift actuator is a power-operated device operable for moving said
second mode shift mechanism between its first and second
positions.
6. The twin-clutch transmission of claim 5 wherein said control
system includes a controller operable for generating electric
control signals that are supplied to said first and second shift
actuators for controlling actuation thereof.
7. The twin-clutch transmission of claim 1 further comprising: a
first electric actuator controlling activation of said first master
clutch; and a second electric actuator controlling actuation of
said second master clutch.
8. The twin-clutch transmission of claim 1 wherein said first and
second speed gears are both meshed with said first output gear.
9. The twin-clutch transmission of claim 1 further including a
first mode shift mechanism for shifting said first overrunning
clutch between its loked and released modes, and wherein said first
shift actuator is a first electrically-actuated actuator
controlling said first mode shift mechanism.
10. The twin-clutch transmission of claim 1 further including a
second mode shift mechanism for shifting said second overrunning
clutch between its locked and released modes, wherein said second
shift actuator is a second electrically-actuated actuator
controlling said second mode shift mechanism, and wherein said
control system includes a controller operable to generate electric
control signals for coordinated actuation of said first and second
actuators.
11. A transmission comprising: an input shaft; an output shaft
having an output gear fixed thereto; a countershaft rotatably
supporting a speed gear meshed with said output gear; a master
clutch for selectively establishing a releasable drive connection
between said input shaft and said countershaft; an overrunning
clutch including a first ring supported on said countershaft, a
second ring fixed to said speed gear, locking elements disposed in
pockets formed between said first and second rings, and a shift
member moveable between first and second positions, said shift
member operable in its first position to permit relative rotation
between said first and second rings for causing said locking
elements to engage locking surfaces of said pockets for coupling
said first ring to said countershaft such that said speed gear is
coupled for rotation with said countershaft, said shift member is
operable in its second position to prevent relative rotation
between said first and second rings such that said speed gear is
released from engagement with said countershaft. an electric
actuator for controlling movement of said shift member between its
first and second positions; and a controller for generating an
electric control signal and sending said control signal to said
actuator.
12. The transmission of claim 11 further comprising a second
electric actuator receiving electric control signals from said
controller for controlling actuation of said master clutch.
13. The transmission of claim 12 wherein said master clutch
includes a clutch pack operable interconnected between said input
shaft and said countershaft and a spring-biased apply plate
normally operable to engage said clutch pack and establish a drive
connection between said input shaft and said countershaft, and
wherein said second electric actuator is arranged to displace said
apply plate from engagement with said clutch pack to release said
countershaft from driven connection with said input shaft.
14. The transmission of claim 11 further comprising a second
countershaft rotatably supporting a second speed gear; a second
master clutch for selectively establishing a releasable drive
connection between said input shaft and said second countershaft; a
second overrunning clutch including a third ring supported on said
second countershaft, a fourth ring fixed to said second speed gear,
a set of second locking elements disposed in pockets formed between
said third and fourth rings, and a second shift member moveable
between first and second positions, said second shift member
operable in its first position to permit relative rotation between
said third and fourth rings for causing said second locking
elements to engage locking surfaces of said pockets for coupling
said third ring to said second countershaft such that said second
speed gear is coupled for rotation with said second countershaft,
said second shift member is operable in its second position to
prevent relative rotation between said third and fourth rings such
that said second speed gear is released from engagement with said
second countershaft; and a second electric actuator controlled by
said controller for moving said second shift member between its
first and second positions.
15. The transmission of claim 11 further comprising a third
electric actuator receiving electric control signals from said
controller for controlling said first master clutch, and a fourth
electric actuator receiving electric control signals from siad
controller for controlling said second master clutch.
16. The transmission of claim 14 wherein said second speed gear is
meshed with a second output gear fixed to said output shaft.
17. The transmission of claim 14 wherein said second speed gear is
meshed with said output gear.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to transmissions for
use in motor vehicles and, more particularly, to a twin-clutch
automated transmission applicable for use in rear-wheel drive
vehicles.
BACKGROUND OF THE INVENTION
[0002] Automobile manufacturers continuously strive to improve fuel
efficiency. This effort to improve fuel efficiency, however, is
typically offset by the need to provide enhanced comfort and
convenience to the vehicle operator. For example, it is well known
that manual transmissions are more fuel efficient than automatic
transmissions, yet a majority of all passenger vehicles are
equipped with automatic transmissions due to the increased
convenience they provide.
[0003] More recently,"automated" variants of conventional manual
transmissions have been developed which shift automatically without
any input from the vehicle operator. Such automated transmissions
typically include a plurality of power-operated actuators that are
controlled by a transmission controller to shift traditional
synchronized dog clutches. However, such automated transmissions
have the disadvantage that there is a power interruption in the
drive connection between the input shaft and the output shaft
during sequential gear shifting. Power interrupted shifting results
in a harsh shift feel which is generally considered to be
unacceptable when compared to smooth shift feel associated with
most automatic transmissions. To overcome this problem, automated
twin-clutch transmissions have been developed which can be
powershifted to permit gearshifts to be made under load. Examples
of such automated manual transmissions are shown in U.S. Pat. Nos.
5,966,989 and 5,890,392. While such powershift twin-clutch
transmissions overcome several drawbacks associated with
conventional single-clutch automated transmissions, a need exists
to develop simpler and more robust transmissions which advance the
automotive transmission technology.
SUMMARY OF THE INVENTION
[0004] Accordingly, it is an object of the present invention to
provide a dual-countershaft twin-clutch transmission and a control
system for permitting automatic shifting of transmission.
[0005] As a related object, the twin-clutch automated transmission
of the present invention has a compact geartrain and is applicable
for use in rear-wheel drive vehicles.
[0006] These and other objects of the present invention are met by
providing an automated dual-countershaft twin-clutch multi-speed
transmission adapted to transfer power from the engine to a
driveline of a motor vehicle. The transmission includes a first
master clutch operable to establish a releasable drive connection
between the input shaft and a first countershaft, a second master
clutch operable to establish a releasable drive connection between
the input shaft and a second countershaft, an output shaft adapted
to transfer power to the driveline, and a geartrain for selectively
establishing a plurality of forward and reverse speed ratio drive
connections between the countershafts and the output shaft. The
transmission further includes overrunning clutches shiftable
between locked and released modes for selectively engaging
constant-mesh gearsets associated with the geartrain, and a
transmission controller for controlling coordinated actuation of
the first and second master clutches, and shifting of the
overrunning clutches to permit non-power interrupted ("powershift")
sequential gear changes automatically without input from the
vehicle operator.
[0007] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating preferred embodiments of the invention,
are intended for purposes of illustration only, since various
changes and modifications within the scope of this invention will
become apparent to those skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic view of a twin-clutch
dual-countershaft automated transmission according to the
principles of the present invention;
[0009] FIG. 2 is a partial sectional view of one of the
controllable overrunning clutch assembly associated with the
transmission shown in FIG. 1; and
[0010] FIG. 3 is a diagrammatical illustration of the transmission
control system adapted for use with the twin-clutch automated
transmission shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] With reference to the accompanying drawings, the components
and function of a twin-clutch automated transmission 10 will now be
described. Transmission 10 is driven by the output of an engine 12
and generally includes a flywheel damper unit 14, an input shaft
16, a first master clutch 18, a second master clutch 20, a first
countershaft 22, a second countershaft 24, a geartrain 26, an
output shaft 28, and a shift control system 30.
[0012] First master clutch 18 is a power-operated spring-apply
plate-type clutch which is normally operable in its engaged state
to establish a drive connection between input shaft 16 and first
countershaft 22. Likewise, second master clutch 20 is a
power-operated spring-apply plate-type clutch which is normally
operable in its engaged state to establish a drive connection
between input shaft 16 and second countershaft 24. First master
clutch 18 includes a clutch drum 32, a hub 34 fixed to first
countershaft 22, a clutch pack 36 disposed between drum 32 and hub
34, a spring-biased apply plate assembly 38 acting on clutch pack
36, and an actuator 40 for selectively releasing apply plate 38
from engagement with clutch pack 36. Preferably, actuator 40 is an
electrically-actuated device, such as an electromagnectic solenoid,
that controls the position of apply plate 38, and thus the
magnitude of engagement of first master clutch 18, in response to
electric power being provided thereto.
[0013] Second master clutch 20 included a clutch drum 42, a hub 44
fixed to second countershaft 24, a clutch pack 46 disposed between
drum 42 and hub 44, a spring-biased apply plate assembly 48 acting
on clutch pack 46, and an actuator 50 for selectively releasing
apply plate 48 from engagement with clutch pack 46. Actuator 50 is
an electrically-actuated device that controls the position of apply
plate assembly 48, and thus the magnitude of engagement of second
master clutch 20, in response to the electric power provided
thereto. As will be detailed, shift control system 30 is operable
to control actuators 40 and 50 and, in turn, the engagement and
release of master clutches 18 and 20.
[0014] Geartrain 26 includes a headset 52 for transferring drive
torque from input shaft 16 to master clutches 18 and 20. In
particular, headset 52 includes a first transfer gear 54 rotatably
supported on first countershaft 22, a second transfer gear 56
rotatably supported on second countershaft 24, and an input gear 58
fixed for rotation with input shaft 16 which is in meshed
engagement with first transfer gear 54 and second transfer gear 56.
As seen, first transfer gear 54 is fixed to clutch drum 32 for
delivering engine power to first engine clutch 18 while second
transfer gear 56 is fixed to clutch drum 42 for delivering engine
power to second engine clutch 20. Gearset 26 also includes a first
set of speed gears rotatably supported on first countershaft 22 and
a second set of speed gears rotatably supported on second
countershaft 24, both of which are in constant mesh with a set of
output gears fixed to output shaft 28. The first set of speed gears
include a first speed gear 60 which is meshed with a first output
gear 62, a third speed gear 64 which is meshed with a second output
gear 66, and a fifth speed gear 68 which is meshed with a third
output gear 70. Similarly, the second set of speed gears includes a
second speed gear 72 which is meshed with first output gear 62, a
fourth speed gear 74 which is meshed with second output gear 66,
and a sixth speed gear 76 which is meshed with third output gear
70. Geartrain 26 also includes a reverse gearset having a reverse
input gear 78 rotatably supported on second countershaft 24, a
reverse output gear 80 fixed to output shaft 28, and a reverse
idler gear (not shown) meshed with reverse input gear 78 and
reverse output gear 80.
[0015] Shift control system 30 includes a plurality of
power-operated shift clutches which are operable for selectively
coupling a selected speed gear to its corresponding countershaft
for establishing six forward and one reverse speed ratio drive
connections with output shaft 28. According to the present
invention, these shift clutches are dual-mode "controllable"
overrunning clutches. The term "controllable" is used to define the
dual mode function of each clutch wherein operation in a "locked"
mode results in a bi-directional clutching action and operation in
a "released" mode permits freewheeling in both directions. In
particular, a first overrunning clutch 81 is operable for
selectively coupling first speed gear 60 to first countershaft 22,
a second overrunning clutch 82 is operable for selectively coupling
second speed gear 72 to second countershaft 24, and a third
overrunning clutch 83 is operable for selectively coupling third
speed gear 64 to first countershaft 22. Shift control system 30
also include a fourth overrunning clutch 84 that is operable for
selectively coupling fourth speed gear 74 to second countershaft
24, a fifth overrunning clutch 85 operable for selectively coupling
fifth speed gear 68 to first countershaft 22, a sixth overrunning
clutch 86 operable for selectively coupling sixth speed gear 76 to
second countershaft 24, and a seventh overrunning clutch 87
operable for selectively coupling reverse input gear 78 to second
countershaft 24.
[0016] Referring to FIG. 2, the components of first controllable
overrunning clutch 81 are shown in detail with the understanding
that the second through seventh overrunning clutches 82-87 have
similar structure and function. First overrunning clutch 81 is
shown to include an inner ring 81A, an outer ring 81B, and a
plurality of locking elements 81C disposed therebetween. Inner ring
81A is a C-shaped split ring which define a slot 88. Inner ring 81A
has an inner cylindrical surface 90 which is supported on outer
cylindrical surface 92 of first countershaft 22. Outer ring 81B is
fixed to first speed gear 60 for common rotation. A series of
complementary arcuate locking surfaces 94 and 96 are respectively
formed in the outer cylindrical surface of inner ring 81A and the
inner cylindrical surface of outer ring 81B and which are alignable
to define roller pockets. Preferably, locking elements 81C are
rollers that are disposed in the roller pockets.
[0017] First overrunning clutch 81 also includes a mode shift
mechanism 98 which can be selectively actuated to shift first
overrunning clutch 81 between its locked and released modes. With
first overrunning clutch 81 in its locked mode, it acts as a
self-locking clutch to prevent relative rotation between first
speed gear 60 and first countershaft 22 in either direction,
thereby coupling first speed gear 60 to first countershaft 22. In
contrast, first overrunning clutch 81 functions in its released
mode to permit bi-directional relative rotation between first speed
gear 60 and first countershaft 22.
[0018] Mode shift mechanism 98 basically functions to control
relative movement between inner ring 81A and outer ring 81B. In the
embodiment shown, mode shift mechanism 98 includes a pin 81D
extending through a radial aperture 100 formed in outer ring 81B
and a spring 81E located between outer ring 81B and a head segment
of pin 81D. Spring 81E functions to normally bias pin 81D in a
radially outward direction to a first position (shown by solid line
in FIG. 2) whereat the terminal end of pin 81D is disengaged from
slot 88 in inner ring 81A. With pin 81D in its first position,
first overrunning clutch 81 functions in its locked mode. That is,
rotation of inner ring 81A relative to outer ring 81B in either
direction causes rollers 81C to ride up and engage opposed locking
surfaces 94 and 96, frictionally clamping inner ring 81A to first
counter shaft 22. As a result, outer ring 81B is clutched to inner
ring 81A via rollers 81C such that first speed gear 60 is coupled
to first countershaft 22. The ability of inner ring 81A to index
circumferencially in either direction relative to outer ring 81B
causes locking of first speed gear 60 to first countershaft 22
regardless of the direction of relative rotation to accommodate
both drive and coast conditions.
[0019] When it is desired to shift first overrunning clutch 81 from
its locked mode into its released mode, pin 81D is moved in an
inward direction from its first position to a second position, in
opposition to the biasing of spring 81E. With pin 81D in its second
position, its terminal end is positioned within slot 88 of inner
ring 81D so as to locate and maintain inner ring 81A in a centered
position relative to outer ring 81B. As such, inner ring 8lA is
prevented from indexing relative to outer ring 81B in either
direction such that rollers 81C are centered in the roller pockets.
With follers 81C centered in the roller pockets, inner ring 81A is
released from clamped engagement with first countershaft 22 so as
to permit bi-directional relative rotation between first
countershaft 22 and first speed gear 60. Accordingly, overrunning
clutch 81 is operable in its released mode to permit freewheeling
in both directions.
[0020] To provide a means for moving pin 81D between its first and
second positions for shifting first overrunning clutch 81 between
its locked and released modes, shift control system 30 includes a
power-operated actuator 101. Clutch actuator 101 is an
electrically-activated device operable for moving pin 81D in
response to an electric control signal. Preferably, clutch actuator
101 functions in a power-off condition to hold pin 81D in its
second position and is shifted into a power on condition in
response to the electric control signal for permitting spring 81E
to forcibly urge pin 81D to its first position. To this end, clutch
actuator 101 can be any suitable two-position device, such as a
solenoid operator. As will be understood, the remaining second
through seventh controllable overrunning clutches 82 through 87 are
substantially identical in structure and function to that described
for first overrunning clutch 81. Thus, common suffixes are used
with corresponding reference numerals to identify similar
components. Moreover, power-operated clutch actuators are
schematically shown in FIG. 3 for overrunning shift clutches 82
through 87 and are designated by corresponding reference numerals
102 through 107. Power-operated clutch actuators 102 through 107
are substantially similar in function to that of clutch actuator
101.
[0021] With continued reference to FIG. 3, shift control system
further includes a transmission controller 120 and a group of
vehicle sensors 122. Controller 120 is an electronically-controlled
unit capable of receiving data from vehicle sensors 122 and
generating electric output signals in response to the sensor
signals. While not specifically limited thereto, sensors 122
include engine speed 124, throttle position 126, brake status 128,
a first countershaft speed 130, a second countershaft speed 132,
and an output shaft speed 134. Controller 120 functions to
coordinate and monitor actuation of all the electrically-controlled
devices associated with transmission 10 to permit powershifted
sequential gear changes automatically without any input from the
vehicle operator.
[0022] Geartrain 26 is shown in FIG. 1 to further include a parking
pawl wheel 138 that is fixed to output shaft 28 and a parking pawl
140 that is operable to engage wheel 138 for releasably locking
output shaft 28 to a stationary member (i.e. the housing of
transmission 10) to prevent rotation of output shaft 28. Parking
pawl 140 is operable to release output shaft 28 when the gearshift
lever is moved out of its PARK position and lock output shaft 28
when the gearshift lever is returned to its PARK position.
[0023] If desired, a manually-operable mode selector switch 142 can
be provided to shift transmission 10 from its automatic shift mode
to a manual shift mode. Mode switch 142 would, when actuated, allow
the vehicle operator to shift the gearshift lever manually to
effect sequential gear shifts (without use of a clutch pedal).
However, controller 120 would only permit the selected gearshift to
be completed if the current vehicle characteristics (i.e. engine
speed, vehicle speed, etc.) permit completion of the requested
shift.
[0024] When it is desired to operate the vehicle, engine 12 is
started with the gearshift lever in its PARK position and both
master clutches 18 and 20 engaged such that both countershafts 22
and 24 are in drive connection with the output of engine 12.
However, all of the electrically-actuated overrunning clutches are
released, whereby no drive torque is delivered through geartrain 26
to output shaft 28. When the vehicle operator moves the gearshift
lever from the PARK position to the DRIVE position, parking pawl
140 is released and first master clutch 18 is also released. In
particular, controller 120 actuates first actuator 40 for releasing
first master clutch 18, whereby the drive connection between input
shaft 16 and first countershaft 22 is released. Controller 120 then
actuates clutch actuator 101 for shifting first overrunning clutch
81 into its locked mode so as to couple first speed gear 60 to
first countershaft 22, whereby the first forward speed ratio drive
connection is established between first countershaft 22 and output
shaft 28. Controller 120 then progressively engages first master
clutch 18 for coupling input shaft 16 to first countershaft 22,
thereby accelerating the vehicle.
[0025] Thereafter, when the vehicle operating parameters indicate a
need to shift transmission 10 into the second forward gear ratio,
controller 120 actuates second actuator 50 for releasing second
master clutch 20, whereby the drive connection between engine 12
and second countershaft 24 is released. Controller 106 then
activates clutch actuator 102 for shifting second overrunning
clutch 82 into its locked mode such that second speed gear 72 is
coupled to second countershaft 24. Thereafter, controller 120
coordinates the release of first master clutch 18 and the
re-engagement of second master clutch 20. Once first master clutch
18 is released completely, controller 120 causes actuator 101 to
shift first overrunning clutch 81 into its released mode, thereby
uncoupling first speed gear 60 from first countershaft 22.
[0026] As will be appreciated, this upshift process continues
through each of the other forward speed gear ratios and likewise
works in reverse for downshifts so as to establish six forward gear
ratios. When the gearshift lever is shifted into its REVERSE
position, clutch actuator 107 is activated by controller 120 for
shifting seventh overrunning clutch 87 into its locked mode to
couple reverse gear 78 to second countershaft 24 for driving output
shaft 28 in the opposite direction. With this powershift
methodology, transmission 10 shifts between master clutches in a
power-on shift strategy (i.e. no power interruption). Transmission
10 is also shown to include a motor/generator 144 associated with
flywheel damper unit 14 and controlled by controller 120 for
starting engine 12 and charging the battery.
[0027] The shiftable overrunning clutches described above can
utilize alternative mode shift systems in place of the
spring-biased pin mechanism for controlling shifting between locked
and released modes. In particular, pivotable toggles or friction
bands can be used to control relative movement between the inner
and outer rings of each overrunning clutch. Non-limiting examples
of multi-mode shiftable clutches that can be used in substitution
for the overrunning clutches previously disclosed are shown in U.S.
Pat. No. 6,068,097 and European Application No. EP0945637.
Moreover, a coordinated shift system comprised of a rail for each
countershaft with cams for moving the pins between the first and
second positions can be employed. Each shift rail would be moveable
to various positions by an electric actuator for causing a
coordinated actuation and release of the overrunning clutches to
establish the desired sequential gearshifts.
[0028] Thus, the transmission of the present invention utilizeS the
components typically associated with a manually-shifted synchromesh
transmission in combination with shiftable overrunning clutches and
a twin clutch dual-countershaft arrangement to provide a compact
powershifted automated multi-speed transmission. The use of a
compact geartrain allows a desired speed gear to be pre-selected
and engaged while disconnected from the engine and thereafter
driven by shifting between the master clutches. Moreover, the use
of all electric powered actuators for the master clutches and shift
clutches eliminates the need for a hydraulic system and should
promote a highly efficient transmission since electric power is
only required for shifting.
[0029] While the presently preferred embodiments of the present
invention have been shown and described, it is to be understood
that these disclosures are for the purpose of illustration and that
various changes and modifications may be made without departing
from the scope of the invention as set forth in the appended
claims.
* * * * *