Note: Descriptions are shown in the official language in which they were submitted.
D-2G43 C-3006
POWER TRANSI`IISSION HAVING A DIRECTIO~ALLY
SE~SITIVE T~ANSMITTING DEVICE
This invention relates to power transmissions with
a drive establishing mechanism haviny a higher torque capacity
in one rotational direction of torque transmission.
In power transrnissions, a gear ratio change is achieved
by engaging one friction device such as a clutch or brake
while simultaneously disen~aging another friction device.
The engagement and disengagement of these devices must be con-
trolled during the ratio change to prevent engine flare or
unnecessary tie-up. Engine flare occurs, during a ratio
change, when the offcoming device releases its controlled
element prior to the oncoming device having established
suffieient torque transmitting capacity to accept the input
load. If the o~erlap time between the devices is extensive,
transmission tie-up can occur resulting in engine or vehicle
stuttering.
The pres~nt invention seeks to prevent these conditions
from occurring by limiting in one rotational directionr the -~
maximum torque capacity of one of the devices being inter-
changed so that tie-u~ eannot occur. Thus, the time required
for interchanging the devices i5- less critical and overlapping
of-the devices is permitted.
- It is therefore~an object of this inven-tion to provide
an improved torque transmitting device for a power transmission
having a higher toxque eapaeity in one rotational direction~
Another object of this invention is to provide an
improved torque transmitting device for a power transmission
having a friction torque transrnitting device in series drive
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rela~ion with a one-wa~ torque transmittiny device ana ~
lesser torque capacity friction torque transmittiny device in
parallel drive ~elation with the one-~ay device.
~ further object of t~lis invention is to provide an
improved torque transmitting device for a power transmission
wherein a friction drive establishing device and a one-way
drive establishing device are in series torque transmittiny
relation to provide a high capacity of torque transmission in
one rotational direction and a lesser capacity friction drive
establishing device is in parallel drive relation with the
one-way drive establishing device to provide a lower torque
transmitting capacity upon a torque reversal within the torque
transmitting device and wherein both of the friction drive
esta~lishing devices are actuated by a single pressure respon-
sive member.
Other objects and advantages of the present invention
will be more apparent from the following description and
drawings wherein~
Figure 1 is a schematic diagram of a power trans-
2~ mission incorporating the present invention, and
Figure 2 is an elevational view of a torque trans~
mitting device incorporating the present invention.
Referring to the drawings, there is seen in Figure 1,
a power transmission having an input shaft 10, an output shaft
12, a pair of~ planetary gear sets 14~and 16, three selectively
engageable fric~ion clutches 18, 20 and 22, a pair of selec-
tively engageable~friction brakes 24 and 26 and a pair of
one-way drive devices 28~and 30. The input shaft 10 has formed
thereon a clutch hub 32 which forms the inner drum 34 of clutch
18, and the outer drum 36 of clutches 20 and 22. The clutches
and brakes are preferably actuated by fluid pressure.
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~573B
The planetary gear set 14 includes a sun gear 38,
a ring gear 40 and a carrier member 42 on which is rotatably
mounted a plurality of pinion gears 44 meshi~g with the sun
year 38 and ring gear 40. The planetary gear se~ 16 has a
sun gear 46, a ring gear 48 and a carrier 50 on which is
mounted a plurality of pinion gears 52 meshing with the sun
gear 46 and ring gear 48. The carrier 42 and ring gear 48
are driving].y connected through an intermediate shaft 54 to the
output shaft 12. The sun gear 46 is connected through a shaft
56 and hub 58 to an outer drum 60 of clutch 18. The ring gear
40 is connected through a hub 62 and an intermediate sleeve
shaft 64 to the carrier 50 which in turn is connected to -the
outer race 66 of one-way device 30 and drum 68 which is
operatively associated with b~ake 26A The ring gear 40 is
also connected with an inner clutch hub 70 of clutch 22. .The
inner race 72 of one-way device 30 is connected to the trans- ,-
mission housing 74,
The clutch 20 has a plural.ity of plates 75 connected
to an inner clutch drum 76 w-hich is also connected to an outer
race 78 of one-way device 28. The one-way device 28 has an
inner race 80 which is connected through a shaft 82 to the
sun gear 38 and is also connected to a single plate 84 of
clutch 20. Interleaved wi~h the plates 75 is a plurality of
plates 85 splined to the outer drum 36.
The transmission gearing and~the operation thereof
is-similar to that shown i~ United States Patent 4,086,827 to
Chana issued May 2, 1978, and assigned to the assignee of the
: present invention~ By selective engagement of combinations of
the various clutches and brakes, four forward speeds and a
-. 30 reverse speed can be accomplished between the input shaft lO
and -th~. output shaf~ 12. With the particular gearing shown,
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573B
the highest forward ratio is an overdri~/e ratio and is accom-
plished through the engager,ent of ciutch 22 and brake 24. The
clutch 22 connects the input shaft 10 to the carrier 50, while
the brake 24 prevents rotation of sun year 46 throuyh outer
drum 60 of hub 58 and shaft 56.
The third forward speed is a direct drive ratio which
is accomplished by the enyagement of clutches 20 and 22. On
forward torque transmission, the one-way device 28 transmits
the torque input from clutch 20 to sun year 38 while the
clutch 22 transmits input torque to the riny gear 40 so that
the planetary gear set 14 is in a 1:1 ratio.
The single plate 84 of clutch 20 provides a con-
tinuous drive connection between sun year 38 and input shaft
10 when clutch 20 is engaged such that during coasting in the
direct drive ratio, engine braking is available.
On an upshift from the third ratio to the fourth ratio,
the brake 24 is engaged and when it has sufficient capacity to
permit the interchange to proceed, the sun gear 38 attempts to -~
rotate faster than the input shaft 10. The one-way device 28
would normally permit the sun gear 38 to overrun, however, the
single plate 84 of clutch 20 establishes a torque transmitting
connection bypassing the one-way device 28 such that the sun gea
38 will not overrun the input shaft 10 until the brake 24 has
sufficient capacity to overcome the residual capacity of the
single plate 84 and permit the interchange to proceed. The
clutch 20 is then fully disengaged after the ratio change is
completed~
On a downshift from fourth gear to third gear, the
c1utch 2a i5 engaged while the bra~e 24 is disengaged. ~lowever,
the overlap timing is not critical since the single plate 84
will permit slippag~ within the clutch 20 during the shift
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inte~change to permit a smoo-th ratio chanye even though the
clutch 20 has more torque capacity than is considered desirable
for a smooth ratio interch~nye because of the action of one-r~Jay
~evice 28.
Referring to Figure 2, there is seen an input shaft 10'
and an ou-tput shaft 82'. Intermediate these shafts lO' and 82',
is a fric-tion clutch 20' and a one-way device 28'. The clutch
20' includes a housing 86 whi.cll is drivingly connected to the
shaft 10' and has slidably disposed ~herein, a fluid operated
piston 88. The clutch 20' also has an inner drum 90 which serves
as the outer race for the one-way device 28'. The one-way device
28' has an inner race 92 drivinyly connected to the shaft 82'and
which inner race 92 has formed thereon a spline surface 94 to
: which is drivingly connected a single clutch plate or disc 96.
The single clutch plate 96 is a member of clutch 20'.
A plurality of friction plates or discs 98 are splined
at lO0 to the inner surface of clutch housing 86, while a
plurality of clutch plates 102 are splined at 104 to the inner
drum 90. The clutch plates 98 and 102 are alternately spaced
and along with clutch plate 96 are limited in movement to the
riyht by a backing plate 106 which is splined to the clutch
housing 86. The piston 88~cooperates with the clutch housing
86 to form a clutch apply chamber 108 which is adapted to be
selectively pressurized and depressuri~ed wi~h hydraulic
fluid in a conventional manner. ~hen the chamber 108 is
pressuri~ed, the piston 88 is moved into abutting relationship
with one of the plates 98 and causes frictional enga~ement of
the adjacent plates 98 and 102 and simultaneous frictional
~ engagem~nt of plate 96. The one-way device 28' is capable of
; 30 transmittin~ torque in one direction only such that when torque
is transmitted from the shaft lO' to the shaft 82', the one~way
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s~73~
device 28' is operative. This is termed the ~orward direction
of torque transmission.
On a torque reversal, that is, when torque is trans-
mitted from shaft 82' to shaft 10', the one-way device 28' is
inoperable and with the clutch ~n ~ enqa~ed, all the torque
must be transmitted through the single plate 96. Thus, it is
apparent that the combination of clutch 20' and one-way device
28' have a high torque capacity during the forward torque
transmitting direction and a low torque capacity in the reverse
10 torque capacity. The ratio of torque capacities during forward
- and reverse directions is controlled by the number of plates in
each of the sections of clutch 20'. If the device is desired
to transmit, on torque reversal, 50% of the forward torque, the
number of friction plates connected to the outer race, o~ one-
way device 28', will be equal to the number of clutch plates
that bypass the one-way device 28'. He~ce, the ratio of clutch
plates bypassing the one-way device to the total number of
plates in the clutch establishes the capacity ratio of the
clutch. It should be apparent to those skilled in the art
20 that this device would not be limited to friction-clutches but
could also be used with a disc type friction brake.
It will be apparent to those skilled in the art that
the above described device acts similar to a double wrap band
which has one level of torque capacity in the self-energizing
direction of rotation and a lower level of torque capacity in
the opposite direction of rotation~
Obviously, many modificatlons and variations of the
- present invention are possible in light of the above teaching.
It is therefore to be understood, that within the scope of the
3~ appended claims, the invention may be practiced otherwise than
as specificall~ described.
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