Five-speed transmission assembly employing compounded planetary gear sets

A transmission assembly having an input shaft, an output shaft as well as first and second planetary gear sets. The first and second planetary gear sets each have three gear members. Two of the gear members in each planetary gear set are a sun gear and a ring gear. As such, the sun and ring gears, one in each planetary gear set, are paired. The sun and ring gears in each of the first and second planetary gear sets are operatively connected in each respective planetary gear set through the third gear members, which are in the nature of a plurality of planet gears mounted on respective first and second carriers. In one of the planetary gear sets the planet gears are themselves compounded. One of the pairs of sun and ring gears is continuously connected, and the carrier in the first planetary gear set is selectively, and independently, connected to two gear members in the second planetary gear set. The carrier in the second planetary gear set is continuously connected to the output shaft means.

TECHNICAL FIELD 
The present invention relates generally to automatic transmissions for 
vehicles. More particularly, the present invention relates to a planetary 
or epicyclic transmission assembly, wherein a pair of compounded planetary 
gear sets provide five forward speeds and one reverse speed by selective 
actuation of one or more of a plurality of torque transfer devices in the 
nature of clutch members and brake members. Specifically, the present 
invention relates to a five-speed planetary transmission assembly having a 
pair of planetary gear sets; one of the planetary gear sets includes 
compounded planet gears, and the planetary gear sets have either conjoined 
sun gears or conjoined ring gears. 
BACKGROUND OF THE INVENTION 
The present invention relates to what is commonly designated as a 
five-speed automatic transmission that is particularly adapted for 
vehicular usage. That is, the transmission provides five forward speeds or 
gear ratios, and one reverse speed or gear ratio. By way of introduction, 
and to clarify the discussion which follows, the forward gear ratios are 
defined as those ratios which causes the vehicle to move forwardly, and, 
for simplicity, it will be assumed that the configuration of the planetary 
gear sets is such that in a forward gear ratio the output member rotates 
in the same direction as the input member. Conversely, the reverse ratio 
causes the vehicle to move rearwardly, and it will also be assumed that 
the output member rotates in a direction opposite to that of the input 
member. 
As is also known, an input member is a connecting mechanism (normally a 
shaft in the transmission) which receives its driving force or torque from 
the vehicular engine--as through a well known torque converter--and 
imparts the driving torque to the planetary gear sets which comprise the 
epicyclic transmission. The output member operatively connects the 
transmission to the differential from which the drive wheels are rotated. 
"Torque transfer device" is another term commonly employed in the 
description of planetary gear sets. Two forms of torque transfer devices 
are commonly recognized--viz.: clutch members and brake members. An input 
clutch member is employed selectively to interconnect two members that are 
normally relatively rotatable so that they move in unison. A brake member 
is employed selectively to preclude rotation of a member that is mounted 
so as be rotatable. Typically, a brake member is presented from the 
housing in which the transmission is encased, and the brake member thereby 
serves to "ground" a normally rotatable member to the housing so that 
member cannot rotate. As will be hereinafter described, in one embodiment 
of the present invention at least one torque transfer device sometimes 
operates as a clutch an sometimes as a brake. 
A planetary gear set typically consists of a sun gear, which is a small 
gear located in the center of the planetary set, and a ring gear which, as 
the outermost member, circumscribes the set and has inwardly-facing teeth. 
A plurality of planet gears or pinions are interposed between the 
aforementioned sun and ring gears to be rotatable and/or circumferentially 
translatable. The planet gears in each planetary gear set are normally 
supported from a carrier that will rotate in response to translation of 
the planet gears. Conversely, the carrier may be rotated to effect a 
desired movement of the planet gears. 
Rotation of the sun gear will cause all of the other elements in the 
planetary set to move, as well, unless one of the other elements is held 
stationary by a torque transfer device such as a brake member which may be 
presented from the transmission housing. When a brake member grounds one 
of the components in a planetary gear set to the housing, the grounded 
member will be forcibly held in position so that all the other members are 
movable relative thereto. Selectively grounding the members of a planetary 
gear set in combination with selectively connecting the input shaft to the 
desired component of the planetary gear set constitutes the typical means 
by which different gear ratios are achieved from a planetary gear 
set--i.e.: different members are selected to be rotated or grounded so the 
speed and direction of the output can be appropriately changed to 
accommodate the existing conditions. 
There is, however, a limit to the number of variations which can be 
provided by a single planetary set. As a result, planetary gear sets have 
been compounded to provide a greater number of individual speeds or gear 
ratios. When planetary gear sets are compounded, various torque transfer 
devices are provided to effect selective interconnection between the 
members of the individual gear sets as well as to ground one or more of 
the components of the gear sets to the transmission housing. These 
arrangements, while successful, do tend to increase the length of the 
housing required to encase not only the gear sets but also the torque 
transfer devices required to provide the desired number of gear ratios. 
SUMMARY OF THE INVENTION 
It is, therefore, a primary object of the present invention to provide an 
improved five-speed transmission by selectively compounding only two 
planetary gear sets. 
It is another object of the present invention to provide an improved 
five-speed transmission, as above, which may be readily incorporated in a 
housing having lesser overall dimensions than might be expected from the 
prior art. 
It is a farther object of the present invention to provide an improved 
five-speed transmission, as above, which employs a pair of compounded 
planetary gear sets wherein at least one of the planetary gear sets has 
compounded planet gears--i.e.: one set of planet gears meshingly engage 
the sun gear and a second set of planet gears meshingly engage the ring 
gear, but both sets of planet gears meshingly engage each other. 
It is still another object of the present invention to provide an improved 
five-speed invention, as above, wherein the compounded planetary gear sets 
are operated by the selective actuation of seven torque transfer devices. 
It is an even further object of the present invention to provide an 
improved five-speed transmission, as above, wherein the sun gears of the 
two planetary gear sets are continuously conjoined in one embodiment and 
the ring gears of the two planetary gear sets are continuously conjoined 
in an alternative embodiment. 
These and other objects of the invention, as well as the advantages thereof 
over existing and prior art forms, which will be apparent in view of the 
following detailed specification, are accomplished by means hereinafter 
described and claimed. 
In general, a transmission assembly embodying the concepts of the present 
invention may be categorized as a five-speed epicyclic gear train that has 
an input shaft means, an output shaft means and first and second planetary 
gear sets. The first and second planetary gear sets each have three gear 
means. Two of the gear means in each planetary gear set are a sun gear and 
a ring gear. The sun and ring gears in each of the first and second 
planetary gear sets are operatively connected in each respective planetary 
gear set through the third gear means, which is in the nature of a 
plurality of planet gears mounted on respective first and second carriers. 
In one of the planetary gear sets the planet gears are themselves 
compounded. 
One of the pairs of sun and ring gears is continuously connected, and the 
carrier in the first planetary gear set is selectively, and independently, 
connected to two gear means in the second planetary gear set. One of the 
carriers is continuously connected to the output shaft means. 
To acquaint persons skilled in the arts most closely related to the present 
invention, two preferred embodiments of a transmission assembly that 
illustrate two best modes now contemplated for putting the invention into 
practice are described herein by, and with reference to, the annexed 
drawings that form a part of the specification. The exemplary transmission 
assemblies are described in detail without attempting to show all of the 
various forms and modifications in which the invention might be embodied. 
As such, the embodiments shown and described herein are illustrative, and 
as will become apparent to those skilled in these arts can be modified in 
numerous ways within the spirit and scope of the invention; the invention 
being measured by the appended claims and not by the details of the 
specification.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT 
One representative form of a vehicular transmission assembly embodying the 
concepts of the present invention is designated generally by the numeral 
10 on FIG. 1 of the accompanying drawings. The representative vehicular 
transmission assembly 10 employs a compounded epicyclic--or 
planetary--gear set which, as is well known to the art, typically receives 
input torque from an engine 12 that is drivingly connected--as through a 
chain drive assembly 14--to an input shaft 16. As is also commonly known, 
an output shaft 18 extends outwardly from the transmission assembly 10 and 
may be connected, as through a differential 20, to the right and left 
drive axles 22A and 22B, respectively, of the vehicle (not shown), the 
right and left drive wheels 24A and 24B being mounted on the respective 
left and right axles 22A and 22B. 
As previewed in the previous paragraph, a particular structural member, 
component or arrangement may be employed at more than one location. When 
referring generally to that type of structural member, component or 
arrangement a common numerical designation shall be employed. However, 
when one of the structural members, components or arrangements so 
identified is to be individually identified, it shall be referenced by 
virtue of a letter suffix employed in combination with the numerical 
designation employed for general identification of that structural member, 
component or arrangement. Thus, them are at least two axles which are 
generally identified by the numeral 22, but the specific individual axles 
are, therefore, identified as 22A and 22B in the specification and on the 
drawings. This suffix convention shall be employed throughout the 
specification. 
With continued reference to FIG. 1, the transmission assembly 10 utilizes 
compounded first and second planetary gear sets 26 and 28, and the first 
planetary gear set 26 may have a compounded plurality of planet gears 30 
and 32 supported on a single carrier 34. As such, the sun gear 36 of the 
first planetary gear set 26 is in continuous meshing engagement with the 
planet gears 30, and the ring gear 38 of the first planetary gear set 26 
is in continuous meshing engagement with the planet gears 32. The planet 
gears 30 and 32 are also in continuous meshing engagement with each other. 
The second planetary gear set 28 is a standard arrangement in that the sun 
gear 40 and ring gear 42 both meshingly engage a plurality of planet gears 
44 that are rotatably supported on a carrier 46. 
In the first exemplary embodiment of the transmission assembly 10, the sun 
gear 36 of the first planetary gear set 26 is permanently secured to the 
sun gear 40 of the second planetary gear set 28, as by a common sun gear 
shaft 48. 
The input shaft 16 is selectively connectable to the common sun gear shaft 
48 by a torque transfer device 50A which, as depicted, may be in the 
nature of a clutch. The input shaft 16 is also selectively connectable to 
the ring gear 38 of the first planetary gear set 26 by a torque transfer 
device 50B which, as depicted, may also be in the nature of a clutch. The 
common sun gear shaft 48, in addition to being selectively connectable to 
the input shaft 16 through torque transfer device 50A, is also selectively 
connectable to ground, designated at 52, by a torque transfer device 50C 
which, as depicted, may be in the nature of a brake. 
The ring gear 38 of the first planetary gear set 26, as well as the ring 
gear 42 of the second planetary gear set 28, are also selectively, and 
individually, connectable to ground 52 by the torque transfer devices 50D 
and 50E, respectively, which may, as depicted, be in the nature of brakes. 
The first and second planetary gear sets 26 and 28 are further compounded 
in that the carrier 34 of the first planetary gear set 26 is selectively, 
and individually, connectable to the carrier 46 of the second planetary 
gear set 28, as by a torque transfer device 50F, which, as depicted, is in 
the nature of a clutch. The carrier 34 of the first planetary gear set 26 
is also selectively, and individually, connectable to the ring gear 42 of 
the second planetary gear set 28 by a torque transfer device 50G which, as 
depicted, serves as either a clutch or a brake depending upon the state of 
the ring gear 42--i.e.: whether the ring gears 42 is rotatable or 
grounded. 
General Observations on Operation 
By way of background, it should be understood that motor vehicle 
transmissions generally include selectively operable gear elements for 
providing multiple forward speed ratios through which the output torque of 
the engine is applied to the drive wheels of the vehicle. In automatic 
transmissions employing planetary gear sets, the gear members in the 
planetary gear sets are selectively interconnected to each other and/or 
grounded in order to provide the various speed ratios. The selective 
interconnection may be readily accomplished through torque transfer 
devices such as clutches and brakes. 
Thus, shifting from one speed ratio to another generally involves releasing 
(disengaging) the torque transfer device(s) associated with the current 
speed ratio and applying (engaging) the torque transfer device(s) 
associated with the desired speed ratio. Any torque transfer device to be 
released during a particular shift sequence is conventionally referred to 
as the off-going torque transfer device while the torque transfer device 
to be applied during that same shift sequence is referred to as the 
on-coming torque transfer device. 
There is generally a slight overlap between the "release" and "apply" of 
the torque transfer devices involved in a shift sequence, and high quality 
shifts are achieved only when the "release" and "apply" operations are 
properly timed and executed. 
Conventionally, the shifting control effected by an automatic transmission 
is performed in conjunction with a logic control map and various inputs 
which reflect such system parameters as vehicle speed, engine throttle 
position and engine torque. Fluid pressure signals representative of the 
various system parameters are processed in an on-board computer and/or 
microprocessor to determine when a shift is in order and to actuate, in 
accordance with the logic control map, electronically controlled valves in 
the hydraulic control system which respond to the signals received from 
the computer to effect the required engagement and/or disengagement (and 
in the proper order) of the appropriate torque transfer devices necessary 
to secure the desired speed ratio changes to the output shaft of the 
transmission. 
To facilitate an understanding of the sequencing for the torque transfer 
devices 50 by which the drive range, forward or reverse, as well as the 
drive ratios in the forward drive range are accomplished in the improved 
transmission assembly 10, a sequencing chart is provided in FIG. 2. Those 
torque transfer devices which must be engaged in order to effect each 
drive ratio are designated with an "X" on FIG. 2. One can, therefore, 
refer either to the chart in FIG. 2 and/or the description which follows 
to determine how each drive ratio is achieved. 
It will be observed from the chart set forth on FIG. 2 that the present 
transmission assembly 10 employs what is commonly designated as a single 
transition shift. That is, only one torque transfer device 50 is off-going 
and one torque transfer device 50 is on-coming to effect a change to the 
next successive drive ratio, during either an up-shift or a down-shift. 
Operation of the First Exemplary Embodiment 
Actuation of the First Forward Drive Ratio 
The first gear ratio (the highest torque, lowest speed output) is enabled 
by establishing a driving connection between the input shaft 16 and the 
common sun drive shaft 48 through the engagement of torque transfer device 
50A. As such, the conjoined sun gears 36 and 40 constitute the input 
member. The torque transfer device 50E is engaged to ground the ring gear 
42 in the second planetary gear set 28 and thereby establish the ring gear 
42 as the reaction member. The torque transfer device 50F is also enabled 
to connect the carrier 34 of the first planetary gear set to the carrier 
46 of the second planetary gear set 28, thereby further compounding the 
two planetary gear sets 26 and 28. The aforesaid arrangement achieves the 
slowest forward movement of the vehicle with the highest torque output 
delivered by the output shaft 18. 
Actuation of the Second Forward Drive Ratio 
To achieve the second forward drive ratio, the single transition shift 
effects a release of torque transfer device 50A and a timed engagement of 
torque transfer device 50B. In this arrangement, the ring gear 42 in the 
second planetary gear set 28 remains the reaction member, but the input 
changes from the conjoined sun gears 36 and 40 to the ring gear 38 in the 
first planetary gear set 26. Hence, the single transition is the change of 
the input member. 
In the operation of the second drive ratio, it should be appreciated that 
the conjoined sun gears 36 and 40 interact, through the planet gears 44, 
with the load on the output shaft 18 to provide the necessary reaction 
against the compounded planet gears 30 and 32 on the single carrier 34 in 
the first planetary gear set 26 to convert the input applied to the ring 
gear 38 to a driving output through the output shaft 18. As such, the 
system incorporates a regenerative aspect. 
Actuation of the Third Forward Drive Ratio 
To achieve the third forward drive ratio, the single transition shift 
effects a release of torque transfer device 50F and a timed engagement of 
torque transfer device 50G. In this arrangement, the ring gear 42 in the 
second planetary gear set 28 remains the reaction member, but the 
engagement of torque transfer device 50G includes the carrier 34 as an 
integral component of the reaction member. The input member remains the 
ring gear 38 in the first planetary gear set 26. Hence, the single 
transition shift is the disengagement of the carrier 46 from the carrier 
34 in conjunction with the engagement of the ring gear 42 with the carrier 
34. As such, the input to the ring gear 38 in the first planetary gear set 
26 is transmitted through the compounded planet gears 30 and 32 to the 
conjoined sun gears 36 and 40, and the sun gear 40 drives the carrier 46 
against the direct reaction of the grounded ring gear 42 to provide the 
third forward drive ratio. 
Actuation of the Fourth Forward Drive Ratio 
To achieve the fourth forward drive ratio, the single transition shift 
effects a release of torque transfer device 50E and a timed engagement of 
torque transfer device 50A. In this arrangement, the input shaft 16 
simultaneously drives not only the conjoined sun gears 36 and 40 but also 
the ring gear 38 in the first planetary gear set 26. Under that 
arrangement, the carrier 34 in the first planetary gear set 26 rotates in 
unison with the sun and ring gears 36 and 38, respectively. By having 
disengaged the ring gear 42 of the second planetary gear set 28 from 
ground 52, and having effected a driving connection between the carrier 34 
in the first planetary gear set 26 with the ring gear 42 of the second 
planetary gear set 28, the sun and ring gears 40 and 42, respectively, in 
the second planetary gear set 28 also rotate in unison with the sun and 
ring gears 36 and 38 in the first planetary gear set 26. This rotates the 
carrier 46 in the second planetary gear set 28 at a 1:1 ratio with the 
carrier 34 in the first planetary gear set 26. Accordingly, the fourth 
forward drive ratio is a direct drive. 
Actuation of the Fifth Forward Drive Ratio 
To achieve the fifth forward drive ratio, the single transition shift 
effects a release of torque transfer device 50A and a timed engagement of 
torque transfer device 50C. In this arrangement, the conjoined sun gears 
36 and 40 are disconnected from the input shaft 16 and are grounded. As 
such, only the ring gear 38 in the first planetary gear set 26 remains as 
the input member, and the driving connection between the carrier 34 in the 
first planetary gear set 26 is maintained. Accordingly, the ring 38 in the 
first planetary gear set 26 drives the compounded planet gears 30 and 32 
against the grounded sun gear 36 to rotate the carrier 34. The carrier 34, 
in turn rotates the ring gear 42 in the second planetary gear set 28, and 
with the sun gear 40 grounded, rotation of the ring gear 42 co-rotates the 
carrier 46 to drive the output shaft 18 in the fifth forward drive ratio. 
The fifth forward drive ratio is an overdrive. 
One should be careful in analyzing the rotation of the carrier 34 in the 
fifth forward drive range because, without an accurate analysis, it may 
not appear to rotate in the direction required to effect operation of the 
transmission in the forward drive range. Should one wish to verify the 
true direction in which the carrier 34 rotates, it is suggested that a 
stick diagram analysis be employed, as is well known to the art. 
Actuation of the Reverse Drive Range 
To achieve the reverse drive range, torque transfer devices 50A, 50D and 
50F are engaged. Torque transfer device 50A connects the input shaft 16 to 
the conjoined sun gears 36 and 40 through sun shaft 48, making the sun 
gears the input members. Engagement of torque transfer device 50D grounds 
the ring gear 38 of the first planetary gear set 26 such that it becomes 
the reaction member. Engagement of torque transfer device 50F connects the 
carriers 34 and 46. In this arrangement, the carrier 34 rotates in a 
direction opposite to the direction in which the sun gear 36 is rotating, 
and that rotation is transferred directly to the carrier 46 of the second 
planetary gear set 28 through torque transfer device 50F. Inasmuch as ring 
gear 42 is free to rotate, the rotation of the sun gear 40 has no effect 
on the rotation of the carrier 46. Accordingly, the carrier 46 rotates in 
the same direction as the carrier 34, thus effecting the reverse drive 
range. 
Description of an Alternative Embodiment 
A second representative form of a vehicular transmission assembly embodying 
the concepts of the present invention is designated generally by the 
numeral 110 on FIG. 3 of the accompanying drawings. The representative 
vehicular transmission assembly 110 also employs a compounded 
epicyclic--or planetary--gear set which, as is well known to the art, 
typically receives input torque from an engine 12 that is drivingly 
connected--as through a chain drive assembly 14--to an input shaft 16. As 
is also commonly known, an output shaft 18 extends outwardly from the 
transmission assembly 110 and may be connected, as through a differential 
20, to the right and left drive axles 22A and 22B, respectively, of the 
vehicle (not shown)--the right and left drive wheels 24A and 24B being 
mounted on the respective right and left axles 22A and 22B. 
The transmission assembly 110 utilizes compounded first and second 
planetary gear sets 126 and 128, and the first planetary gear set 126 may 
have compounded planet gears 130 and 132 supported on a single carrier 
134. As such, the sun gear 136 of the first planetary gear set 126 is in 
continuous meshing engagement with the planet gears 130, and the ring gear 
138 of the first planetary gear set 126 is in continuous meshing 
engagement with the planet gears 132. The planet gears 130 and 132 are 
also in continuous meshing engagement with each other. 
The second planetary gear set 128 is a standard arrangement in that the sun 
gear 140 and ring gear 142 both meshingly engage a plurality of planet 
gears 144 that are rotatably supported on a carrier 146. 
In the second exemplary embodiment of the transmission assembly 110, the 
ring gear 138 of the first planetary gear set 126 is permanently secured 
to the ring gear 142 of the second planetary gear set 128, as by a common 
ring gear shaft 154. 
The input shaft 16 is selectively connectable to the shaft portion 156 of 
sun gear 136 by a torque transfer device 150A which, as depicted, may be 
in the nature of a clutch. The input shaft 16 is also selectively 
connectable to the carrier 134 of the first planetary gear set 126 by a 
torque transfer device 150B which, as depicted, may also be in the nature 
of a clutch. The common ring gear shaft 154, in addition to being 
selectively connectable to the input shaft 16 through torque transfer 
device 150C, is also selectively connectable to ground, designated at 52, 
by a torque transfer device 150E which, as depicted, may be in the nature 
of a brake. 
The sun gear 136 of the first planetary gear set 126 is also selectively 
connectable to ground 52 by the torque transfer device 150D which may, as 
depicted, be in the nature of a brake. 
The first and second planetary gear sets 126 and 128 are further compounded 
in that the carrier 134 of the first planetary gear set 126 is selectively 
connectable to the carrier 146 of the second planetary gear set 128, as by 
the torque transfer device 150F, which, as depicted, is in the nature of a 
clutch. The carrier 134 of the first planetary gear set 126 is also 
selectively, and individually, connectable to the sun gear 140 of the 
second planetary gear set 128 by torque transfer device 150G which, as 
depicted, serves as a clutch. 
Operation of the Alternative Embodiment 
Actuation of the First Forward Drive Ratio 
The first gear ratio (the highest torque, lowest speed output) is enabled 
by establishing a driving connection between the input shaft 16 and the 
carrier 134 through the engagement of torque transfer device 150B. As 
such, the carrier 134 constitute the input member. The torque transfer 
device 150E is engaged to ground the conjoined ring gears 138 and 142 and 
thereby establish those conjoined gears as the reaction member. The torque 
transfer device 150G is engaged to connect the carrier 134 of the first 
planetary gear set 126 to the sun gear 140 of the second planetary gear 
set 128. The aforesaid arrangement achieves the slowest forward movement 
of the vehicle with the highest torque output delivered by the output 
shaft 18. 
Actuation of the Second Forward Drive Ratio 
To achieve the second forward drive ratio, the single transition shift 
effects a release of torque transfer device 150E and a timed engagement of 
torque transfer device 150D. In this arrangement, the sun gear 136 in the 
first planetary gear set 126 is grounded to become the reaction member, 
but the input member remains the carrier 134 in the first planetary gear 
set 126. Hence, the single transition effects a change of the reaction 
member. 
In the operation of the second drive ratio, the planet gears 130 supported 
from the carrier 134 react against the grounded sun gear 136 in the first 
planetary gear set 126 to rotate the carrier 134 unfettered from any 
reaction with the conjoined ring gears 138 and 142 which are free to 
rotate. The carrier 134 thus rotates the sun gear 140 in the second 
planetary gear set 128. The sun gear 140, in turn, rotates the planet 
gears 144 supported from the carrier 146 in the second planetary gear set 
128. However, a reaction is imposed on the planet gears 144 by the fact 
that the ring gears 138 and 142 are conjoined. Thus, the attempt of the 
ring gear 142 to rotate freely is resisted by the meshing engagement of 
the ring gear 138 with the planet gears 132--the rotation of which is 
controlled by rotation of the planet gear 130 against the grounded sun 
gear 136. Accordingly, the input applied to the carrier 134 is converted 
to a driving output through the output shaft 18. It should be recognized, 
therefore, that the present transmission assembly also incorporates a 
regenerative aspect. 
Actuation of the Third Forward Drive Ratio 
To achieve the third forward drive ratio, the single transition shift 
effects a release of torque transfer device 150D and a timed engagement of 
torque transfer device 150C. In this arrangement, a direct drive is 
achieved. Specifically, the carrier 134 and the ring gear 138 in the first 
planetary gear set 126 are both rotated in unison against a free sun gear 
136. The fact that the ring gears 138 and 142 are conjoined causes both 
ring gears to rotate at the same rate. Moreover, the rotatable connection 
of the carrier 134 in the first planetary gear set 126 with the sun gear 
140 in the second planetary gear set 128 causes the sun gear 140 to rotate 
at the same rate as the ring gear 142. This drives the carrier 146 at the 
same rate. Hence, the rotational rate of the input shaft 16 is equal to 
the rotational rate of the output shaft 18, and a direct drive is provided 
by the third drive ratio. 
Actuation of the Fourth Forward Drive Ratio 
To achieve the fourth forward drive ratio, the single transition shift 
effects a release of torque transfer device 150B and a timed engagement of 
torque transfer device 150D. In this arrangement, the input shaft 16 
continues to drive the conjoined ring gears 138 and 142 in the respective 
first and second planetary gear sets 126 and 128. The ring gears 138 and 
142 thus remain the input members. Engagement of torque transfer device 
150D serves to ground the sun gear 136 in the first planetary gear set 
126, which, therefore, becomes the reaction member. Under that 
arrangement, rotation of the ring gear 138 relative to the grounded sun 
gear 136 rotates the sun gear 140 in the second planetary gear set 128. 
With both the ring gear 142 and the sun gear 140 in the second planetary 
gear set 128 rotating in the same direction, but at different rates (as 
determined by the ratio of the teeth on the compounded planet gears 130 
and 132 in the first planetary gear set 126), the carrier 146 in the 
second planetary gear set 128 may rotate at even a faster rate that the 
ring 142, thus causing the fourth forward drive ratio to be an overdrive 
ratio. 
Actuation of the Fifth Forward Drive Ratio 
To achieve the fifth forward drive ratio, the single transition shift 
effects a release of torque transfer device 150G and a timed engagement of 
torque transfer device 150F. In this arrangement, the conjoined ring gears 
138 and 142 remain the input member and the grounded sun gear 136 remains 
the reaction member. However, the carrier 134 in the first planetary gear 
set 126 is connected to the carrier 146 in the second planetary gear set 
128. Accordingly, the ring gear 138 in the first planetary gear set 126 
drives the compounded planet gears 130 and 132 against the grounded sun 
gear 136 to rotate the carrier 134. The carrier 134, in turn, rotates the 
carrier 146 in the second planetary gear set 128 relative to the ring gear 
142 that is already rotating with the conjoined ring gear 138 at the input 
rate. Hence, if the planet gears 130 and 132 are chosen to provide an 
overdrive ratio in the fourth forward drive ratio, the fifth drive ratio 
is a second overdrive ratio. 
Actuation of the Reverse Drive Range 
To achieve the reverse drive range, torque transfer devices 150A, 150E and 
150F are engaged. Torque transfer device 150A connects the input shaft 16 
to the sun gear 136 in the first planetary gear set 126, making the sun 
gear 136 the input member. Engagement of torque transfer device 150E 
grounds the conjoined ring gears 138 and 142 such that the ring gears 
become the reaction member. Engagement of torque transfer device 150F 
connects the carriers 134 and 146 to conclude the compounding of the first 
and second planetary gear sets 126 and 128. In this arrangement, the 
carrier 134 rotates in a direction opposite to the direction in which the 
sun gear 136 is driven by the input shaft 16, and that rotation is 
transferred to the connected carrier 146 of the second planetary gear set 
128. Inasmuch as the sun gear 140 of the second planetary gear set 128 is 
free to rotate and the ring gear 142 of that same planetary gears set is 
grounded, the carrier 146 rotates in the same direction as the carrier 
134, thus effecting the reverse drive range. 
Closing 
While only two preferred embodiments of the present invention are 
disclosed, it is to be clearly understood that the same is susceptible to 
numerous changes apparent to one skilled in the art. Therefore, the scope 
of the present invention is not to be limited to the details shown and 
described but is intended to include all changes and modifications which 
come within the scope of the appended claims. 
As should now be apparent, the present invention teaches that a five-speed 
transmission assembly may employ an epicyclic gear train having two 
uniquely compounded planetary gear sets to accomplish the objects of the 
invention.