Note: Descriptions are shown in the official language in which they were submitted.
Il 1281559
AUTOMATIC TR~SMISSION ~IT~ ADD-~ OV~RDRIV~
B~C~GROUND DP T~e Iive~
This invention relates generally to an automatic power
transmission for use ln motor vehicles and more particularly
to an add-on overdrive unit adapted to provide a fourth
forward-driving speed ratio for an existing three speed
automatic transmission.
The U.S. Pat. No. 4,095,487 issued June 20, 1980 to
Cartwright et al discloses a three forward speed and reverse
drive motor vehicle automatic transmission adapted for use
with an engine which extends transversely on the vehicle.
There have been numerous overdrive devices proposed for
establishing a reduction gear ratio of less than one for
automatic transmissions of the type disclosed in the
Cartwright patent. The advantages of such overdrive units
include less engine noise during high speed operation and
improved fuel consumption. Examples of overdrive
arrangements for automatic transmissions are found in U.S.
Pat. Nos. 4,453,429; 4,455,890; and 4,567,788.
SUMMARY OF TE8 INVBNTION
Briefly, this invention comprises an add-on overdrive unit
for an automatic transmission wherein an overdrive ratio is
achieved. The add-on unit is located on an extended portion
of the transmission's output shaft and includes a single
planetary gear set unit having its annulus gear splined to an
outer race of an overrunning one-way clutch. The carrier of
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the planet~ry 9ear set has one c~rrler rlng spl1ned to the
transmls610n output shaft. ~he one-way clutch outer race 1B
dlrectly connected w1th the ~verdrlve output shaft ~hlch
shaft i6 coaxlolly allgned wlth the transmlsslon output
shaft. The one-way clutch lnner race i5 splined to the
transmisslon output shaft.
A feature of the overdrlve unit is the use of a single
hydraulically stroked spring biased piston to control a first
direct drive friction clutch pack and a second overdrive
friction clutch pack. The piston is normally biased by the
spring to a non-pressurized or destroked position engaging
the direct-drive clutch pack. This provides a direct-drive
mode of the overdrive unit upon the transmission output shaft
being driven in a first rotational direction. With the
direct-drive clutch pack engaged, the planetary sun gear is
locked to the annulus gear. Further, an outer sleeve
drivingly interconnects the direct-drive clutch pack with the
planetary annulus. As a result the one-way clutch outer race
is driven into engagement with the inner race via coupling
means located therebetween, thus, establishing a one-to-one
drive ratio. Drive torque, however, is transferred directly
from the transmission output shaft to the inner race and
thence to the overdrive output shaft via the engaged one-way
clutch outer race obviating the transmission of drive torque
through the direct-drive clutch pack.
1,
Upon hydraulic pressure from the transmission being
supplied to the piston, the piston is moved to its stroked
position against the spring biasing force. This disengages
the direct-drive clutch pack and engages the overdrive clutch
pack grounding the planetary sun gear to the overdrive unit
case. As a result, drive torque is transferred from the
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tran~mifislon output shaft to one pl~net~ry carrler rlng
6pllned thereto. Drlve torque 1B then tr~nsferred from the
I carrier rlng to the planetary plnlon gears ~nd the annulu6
gear overdriving the one-way clutch outer race thereby
transferring an overdrive speed ratio to the overdrive output
shaft.
Another feature of the invention is that upon the
transmission being placed in its reverse mode the piston,
! which is biased in its de-stroked position by the spring,
engages the direct-drive clutch pack and disengages the
overdrive clutch pack. With the transmission output shaft
now being rotated in its opposite or reverse direction the
one-way clutch inner race is also driven in the reverse
direction. At the same time a carrier ring splined to the
transmission output shaft is rotated in the reverse direction
together with the pinion gears and annulus gear. ~owever,
the engaged direct-drive clutch pack, by means of the outer
sleeve, is also driving the outer race in the reverse
direction in unison with the inner race even though the one-
way clutch coupling means are not engaged. Thus, a one-to-
one gear ratio drive torque is transferred to the overdrive
output shaft through the direct drive clutch pack only in the
reverse mode of the transmission, thereby minimizing wear on
the overdrive unit.
A~other feature of the present invention is the
incorporation of external parking sprag teeth on the
planetary annulus gear member thereby enabling the positive
locki~g of the transmission's main shaft against rotation
with the transmission's selector in its park mode obviating
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~als~s
locking the transmission through its clutch packs or brake bands.
Other features and advantages of this invention will be
made apparent by reference to the following description and accompanying
drawings in which one of the various possible embodiments is illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a cross-sectional view of a three speed automatic
transmission together with a fragmentary portion of the overdrive
unit;
Fig. 2 is an enlarged framentary cross-sectional view of
the overdrive unit forward portion; and
Fig. 3 is an enlarged fragmentary cross-sectional view of
the overdrive unit aft portion.
DETAILED DESCRIPTI OF THE INVENTIO
Referring now to the drawings~ there is shown in Fig. 1 a
longitudinal sectional view of a vehicle's automatic transmission
generally indicated at 10. The end portion of a driving member, such
as a vehicle crankshaft, is indicated at 12 in Fig. 1. Reference may
be made to the above-mentioned patent 4,095,487 which diagramatically
shows a motor vehicle engine and drive train of a type suitable for
use with the present invention.
The crankshaft 12 is drivingly connected to a drive
transmitting ring 13 by fasteners 14 and the ring 13 is
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~ultably connec~ed to a torque converter casl~g 16 by bolts
18. An englne starter rlng 20 1B mo~nted on and extends
around the perlphery of the torque converter caslng 16.
~ he torque converter caslng 16 contains a conventional
turbine 22 and stator or reaction member 24, as well as an
impeller 26, with the impeller being 1ntegrally connected to
the casings 16 and the turbine member 22 being drivingly
connected by a hub 28 to an input shaft 30. The stator 24 is
connected by a one-way brake device, having an inner hub 32,
to an axial sleeve 34 secured to a wall or partition 36
attached to the interior of a housing 38. The construction
of a torque converter is well-known and reference may be had
to the above mentioned 4,095,487 patent for a more detailed
description of the transmission 10.
A bydraulic pump 40 has its driving element 42 connected
to a rearwardly projecting end portion of torque converter
casing flange portion 44- The pump 40 draws fluid from a
supply sump 45 through conduit means ~not shown) and
circulates fluid through the torque converter, the
trans~ission lubricating system, and the various
hydraulically operated control mechanisms associated with
this power transmission.
The gear box includes a forward drive clutch Cl, a reverse
and direct drive clutch C2, and a pair of planetary gear sets
47 and 48. The gearbox is adapted to cooperate with the
torque converter to provide a means for the transmission of
three forward drives and a reverse dri~e to a speed change
section output shaft 50. The forward drive clutch Cl. is
engaged whenever any of the three forward speeds are being
used, and is di~engaged when the transmission controls are
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~I set in elther Neutral or Reverse. ~he direct dr~ve clutch C2
I 1B engaged only when the thlrd dlrect forw~rd speed 1~ belng
transmitted and whenever reverse drlve 1B belng tran~ltted.
~ he clutches Cl and C2 and the one rear planetary gear set
48 are located in the rear portion of the speed change
section. ~he front portion of the speed change section
! houses the front planetary gear set 47. The front end of the
jl converter driven gear box input shaft 30 is concentric with
the forward end of the speed change section output shaft 50.
! The transmission input shaft 30 i8 drivingly connected at
60 to a retainer member 62 which carries friction clutch disc
elements 64 of the reverse and direct drive clutch C2. The
set of clutch discs 64 are adapted to a drivingly engaged
with the use of clutch discs 66 drivingly connected to the
interior surface of a drum 68. The drum 68 is journalled on
the rearwardly projecting collar 70 on gearbox housing wall
36. A brake band B2 is arranged to be selectively applied to
the drum 68 to prevent rotation thereof. The drum 68
includes a backing plate 71 which cooperates with an axially
¦ shiftable piston 72 to effect drive transmitting engagement
of tbe clutch discs 64 and 66. An annular spring 74 normally
I urges the piston 72 forwardly to a clutch disengaged
position. Pressure fluid for operation of the clutch C2 is
supplied to the piston bore for piston 72 through conduit 76
connected to the hydraulically operated control system.
The retainer 62 has a rearwardly extending clutch drum 77
at its periphery. Clutch drum 77 has drivingly and shiftably
mounted on as its interior face one or more clutch discs 78.
The clutch discs 7B are drivingly engaged with the clutch
discs 80 which are carried by the exterior surface of annular
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me~ber ~1 connected to annular gear 82 of the planetary 9eDr
set 8. Clutch d1BC6 70 and 8~ are arranged to be drlvlngly
compressed agaln5t a backing plate 84 by a pressure plate
~ember 86 actuated by a lever sprlng plate 88. Lever sprlng
plate 88 is operated by a piston 90 which reciprocates in a
cylinder bore 92 formed in the rearside of the retalner
member 62. Pressure fluid is supplied to the cylinder bore
92 through a conduit 94 connected to the hydraulically
operated control system.
Arranged concentrically within the forward drive clutch
Cl, is the planetary gear set 48. This gear set comprises
the annular gear 82, a sun gear 96, a planet pinion gear 98,
connecting gears 82 and 96, and a planet pinion gear carrier
100 v~ich rotatably supports the pinion gearing. Carrier 100
is splined to the speed change output ~haft S0 at 102.
Annulus gear 82 is supported on an annular member 81
rotatably mounted by bushing 106 at the hub portion of the
carrier 100. The sun gear 96 is an integral part of a double
sun gear sleeve 108, with the sun gear 96 being formed on the
front end and a sun gear 110 of the planetary set 47 being
formed on the rear end thereof. Bearings 112 mount the sun
gear sleeve 108 on the output shaft 50.
The rearwardly located gear set 47 includes the sun gear
110 aDd annulus gear 114, planet pinion gearing 116, which
conne_ts gears 110 and 114, and a planet pinion carrier 118
I rotatably supporting pinion gearing 116. Annulus gear 114 is
! drivingly connected to the output shaft 50 by splines 120.
Pinio~ gear carrier 118 is drivingly connected at 115 to the
brake dru~ 122. Brake bands Bl, are arranged to be
selectively applled to the brake drum 122 to prevent rotation
thereof. The brake drum 122 is restrained against reverse
12~ S9
rotat~on, counterclockwlse when looklng from the left towar~6
the rlght of the transm1sslon, by mean6 of a conventlon~l
one-vay brake dev~ce lndlcated at WBl.
Inter-connection between the two axially spaced adjacent
gear set6 47 and 48 is by way of the common gear ~leeve 108
and by the dual connectlons of the front carrier 100 and the
rear annulus gear 114 to the common speed change section
output shaft 50. The drum 68 is connected by the bell-shaped
member 128 to the sun gear sleeve 108.
As best seen in Figs. 1 and 2, an add-on overdrive unit,
indicated generally at 130, is adapted for coupling to the
aft end of the three speed transmission 10. The overdrive
unit 130 provides a higher gear ratio of less than one and
reduces noise of the engine during operation at high speed
while improving vehicle fuel consumption.
The overdrive unit 130 includes a one-piece casing 132
removably secured to aft end wall 134 of the transmission
housing such as by machine bolts (not shown). The
transmission output shaft 50 extends rearwardly through an
axial passage 136 in a central hub portion 138 of overdrive
i casing forward bulkhead generally indicated at 140 in Fig. 1.
The transmission housing aft end wall 134 is formed with a
central boss 144 having an axial bore 146 slidably receiving
therein the bulkhead central hub portion 138. The casing
bulkhead 140 is secured to the transmission housing aft wall
134 by a plurality of machine bolts, one of which is shown at
148.
As ~est seen in Fig. 2 the overdrive portion of the
trans~ission includes an axially movable annular piston 150
which is slidably received in a piston cup or cylinder
lZ8155~ ~
portlon 152. ~he cyl1nder port1on 152 ls forme~ ln the
bulk~ead 140 by mean6 of lts perlpheral rearwardly extendlng
outer annular flange ~53 and lnner ~nnular flange 154
disposed ln concentrlc relatlon. A dual w~lled clutch spool,
generally lndicated at 156 ln Fig. 2, i8 concentrlcally
disposed about a rearwardly extending portlon of the
transmission's main shaft 50. The clutch spool 156 has an
inner cylindrical wall lS8 formed with lnternal splines 160
meshed with external ~plines 162 of an inner sleeve member
164. Outer cylindrical wall 166 of the clutch spool 156 has
external splines 168 splined to an inner set of clutch pack
discs 170. The inner discs 170 are interleaved with a set of
outer companion discs 172 of a first multiple disc direct
drive clutch pack 174.
The outer wall external splines 168 are also splined to a
set of inner discs 176 interleaved with a set of outer
i companion discs 178 of a second multiple disc overdrive
clutch pack generally indicated at 180. It will be noted
that the outer discs 178 are splined to internal splines 182
formed integral with the inner wall of the overdrive casing
132. Further, the outer discs 172 of the direct drive clutch
pack 174 are splined to internal splines 184 of an outer
sleeve member 186. The outer sleeve member 186 has its
internal splines 184 in engagement with external splines 188
formed on the forward end of annulus member 190. A pair of
! fore and aft annular wire rings 192 and 194 respectively, are
received in associated internal grooves on either side of
outer sleeve member 186 capturing annulus external splines
188 therebetween. The annular wire rings 192 and 194 retain
the outer sleeve member 186 against axial movement relative
to the annulus member 190.
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81559
ingle coll compresslon sprlng 196 ls concentrlcally
dlsposed 1ntermedlate the inner 158 ~nd outer 166 ~11B ~f
the clutch BPOO1 156. ~he coll prlng 196 1B COmPreBBed
bet~een annular spool ba~e wall 198 ~nd sprlng ~butment means
ln the form of a compresslon ring 200. The r~ng 200 ~s
fixedly mounted on inner sleeve 164 by ~eans of reta1ning
ring 202. A needle bearing assembly 204 iB positioned
inter~ediate the compression ring 200 and a planetary gear
unit to be described. The sp~ol base wall 198 is ~paced from
the piston 150 by means of a needle bearing assembly 206 and
an annular select spacer ring 208.
The compression spring 196, as shown in Fig. 2, is
operative to bias the direct drive clutch pack 174 into its
clamped or engaged state. That is, the ring 196 normally
biases the direct drive clutch pack inner discs 170 into
contact with the outer discs 172 by means of the forward or
leftward travel of pressure plate member 210 against the
resistance o~ fixed backing plate 212. The pressure plate
210 has a step 213 locked to the spool outer wall 166 by
abutment with annular wall collar 214 while the pressure
plate 212 is fixedly positioned to the outer sleeve 186 by
retaining ring 216.
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The overdrive clutch pack 180 has the outer periphery of a
¦ backing plate 218 splined to the casing splines 182 against ¦
¦ which the overdrive clutch discs 176 and 178 are drivingly
¦I compressed by pressure plate 219 as the piston 150 is stroked
j rearwardly or rightwardly upon pressure chamber 220 being
¦¦ pressurized. Pressure chamber 220, defined by the cylinder
,¦ portion 152 and piston 150, is sealed by piston outer
resilient ring 221 contacting bulkhead outer flange 153 and
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plston lnner res~llent r~ng 222 contactlng bulkhe~d lnner
flange 154.
Fig. 2 shows lnner sleeve member 164 belng ~ourna~ly
supported on the exten~ion of the transmission output shaft
50 for relatlve rotation therewith by means of axially ~paced
bushings 223. The aft or rightward end of sleeve member 164
is formed with external teeth 224 defining a sun gear portion
of a planetary gear set unit generally indicated at 226. The
planetary gear set unit includes a plurality of planet pinion
I gears 228 journally mounted on pinion shafts 230 having their
ends rotatably supported in fore and aft carrier rings 232
and 234, respectively. The pinion gears 230 mesh with both
I the sun gear teeth 224 and annulus internal gear teeth
portion 236 of the annulus member 190. The carrier aft ring
! member 234 has internal splines 238 on an integral rearwardly
extending cylindrical neck portion 240 splined to e~ternal
splines 242 on the transmission output shaft 50.
An overrunning coupling or one-way clutch assembly,
generally indicated at 244, has an integrally combined inner
race and hub member 245 including inner race portion 246 and
cylindrical hub portion 247. The hub portion 247 has an
axial bore formed with internal splines 248 engaging the
transmission output shaft external splines 242 rearwardly of
the aft carrier ring neck portion internal splines 238. The
one-way clutch outer race member comprises an outer race
portion integral with an overdrive output shaft portion.
Thus, the outer race member includes an outer race portion
! 249 and an overdrive output shaft 250 interconnected to a
. j stepped shoulder having an axial portion 251 and a radial
portion 252. The outer race portion 249 of the one-way
clutch has external splines 253 splined to annulus internal
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splines 254 adjacent the aft or rightward end of the annulus member
190. Coupling means in the form of plurality of rollers 256 are
inserted between the outer race portion 249 and the inner race 246 of
the one-way clutch in a conventional manner. It will be noted that
the annulus member 190 includes external parking sprag teeth 257
formed thereon. Further the stepped shoulder portions 251 and 252
define an external notch 258 for reception of a ball bearing assembly
259 journally supporting the one-way clutch assembly.
Because the parking sprag teeth 257 are located on the
annulus member 190 a positive transmission park-locking position is
provided via engaged splines 253 and 254 to the outer race portion
249 and thence to the overdrive output shaft 250. That is, the park-
locking path is not transferred through any clutch packs of brake
bands reducing wear on the transmission. An example of a parking
mechanism suitable for use with the present invention is shown in
U.S. Patent 4,223,768 issued September 23, 1980 to Iwanage.
The outer race member of the one-way clutch stepped axial
shoulder 252 is journalled at 262 on the reduced axially extending
pilot hub portion 247 of the inner race 246. The stepped axial
shoulder portions define an axially extending cup-shaped bore 266
sized to journally receive the inner race hub portion 247 therein.
In a like manner the one-way clutch inner race member forward face is
formed with an axially extending countersunk pilot bore 268 sized to
slidably receive or pilot the aft carrier ring neck portion 240
therein. This structural arrangement insures concentric
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allgnment of the planetary carr1er rings 232 an~ 234 relatlve
to the transmlsslon output ~h~ft 50. A conventlon~l ~peed
governor ~ssembly, generally lndlcated at 272 ln ~19. 3, i8
concentrically mounted on the overdr~ve output shaft 251.
In operation, the add-on overdrive unit 130 i6 shown ln
its normal or ~fail-safe~ direct drive mode wherein the
spring 196 biases the direct drive clutch pack 174 in it6
engaged or on state. In this direct drive mode tor~ue from
the transmission output shaft 50 is transferred directly to
the one-way clutch inner race portion 246 by means of the
transmission output shaft 50 and inner race engaged splines
242 and 248, respectively. The engine torque or mechanical
drive then is transferred from the inner race portion 246 to
the engaged rollers 256 and thus to the one-way clutch outer
race portion 249 for delivery to integral overdrive output
shaft 2S0. It will be noted that in the direct drive mode
turbine torque is not transmitted through the engaged direct
clutch pack 174 thus reducing wear on the overdrive unit.
~owever, because the direct clutch pack is engaged, the
planetary annulus member 190 is rotated in unison with the
sleeve 164 which includes the sun gear teeth 224 thus
insuring a one-to-one drive ratio being transferred to the
overdrive output shaft 250 during the direct drive mode.
With the transmission placed in its reverse mode the
transmission output shaft 50 is driven in an opposite or
counter-clockwise rotational direction when viewed lo~king
rearward or rightward in Fig. 2. In the reverse drive mode
torque from the transmission output shaft 50 is transferred
to the aft carrier ring 240 by means of the engaged splines
242 and 238, respectively. As the one-way integral clutch
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lnner r~ce ~nd hub ~ember 245 are rot~ted ln the Opp~8~ te or
counter-clockwise dlrectlon the one-way clutch 244 i8
overdriven. ~hat ls, the one-way clutch freewheels ~n~
transm1ts no torque because the clutch rollers 256 are out of
engagement. However, drlve torque i8 transferred to the
pinion gears 221 and then to the annulus member 190. As the
direct drive clutch pack 174 is engaged in the rever~e mode
the annulus member 190 and the sleeve member 164, including
its aft portion formed with the 6un gear teeth 224, are
locked together. Thus, the engaged clutch pack 174 causes
the sleeve member 186 and the clutch spool 156 to rotate in
unison.
By virtue of applicant's arrangement the annulus member
190, splined to the sleeve 186, transfers reverse drive
torque to the one-way clutch outer race portion 249 and thus
to its integral overdrive output shaft 250. It will be noted
that in the reverse mode driving torque is transmitted
through the direct clutch pack 174, while in the direct mode
driving tor~ue bypasses the direct clutch pack. Because the
vehicle is operated primarily in its forward drive mode, the
service life of the clutch pack 174 is greatly enhanced.
~ 2~n the chamber 220 being pressurized, the piston 150 is
moved rearwardly or to the right further compressing spring
196 and causing the clutch spool 156 to travel rearwardly.
As a result, the overdrive clutch pack pressure plate 219 is
contacted by the piston 150 and the overdrive clutch pack 180
is ap21ied. This causes the inner sleeve 164 and sun gear
teetb 224 to be held against rotation while the planetary
carrier rings 232, 234; planetary gears 228 and annulus
member 190 are rotated by the transmission output shaft 50.
The annulus member 190, in turn, overdrives the outer race
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1~815~9
i 250 of the one way clutch at a speed exceedlng that of the
lntegral lnner race and hub member 245. With the one-way
clutch ln lts freewheellng conditlon an overdrlve gear ratlo
I¦ i8 dellvered to the overdrlve output shaft 250. In the
¦¦ disclosed embodiment the overdrlve ratlo 1~ of the order of
0.69 to 1Ø
l Although only one embodiment of the invention has been
! disclosed and described, it is apparent that other
emb~d ments and modlfications of the invention are posslble.
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