Torque converter disconnect and bypass clutch structure for automatic mechanical transmission

A torque converter disconnect and bypass clutch assembly (10) for an automatic mechanical transmission system (12) of the type comprising a fluid torque converter (20) drivingly interposed a drive engine (16) and a mechanical change gear transmission (14), preferably of the type utilizing a power synchronizing device (30), is provided. The torque converter disconnect and bypass clutch structure includes an independently engageable and disengageable torque converter disconnect friction clutch (24) and torque converter bypass friction clutch (26). A connecting member (74) is fixed for rotation with the transmission input shaft (72) and includes a first portion (76) associated with the torque converter disconnect clutch and a second portion (78) associated with the torque converter bypass clutch. In the preferred embodiment, the disconnect and by-pass clutches (24 and 26) are concentric and telescopically related to provide an axially compact structure.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to automatic mechanical transmission systems 
including a throttle controlled engine, a mechanical change gear 
transmission and a fluid coupling, such as torque converter, interposed 
the engine and transmission. In particular, the present invention relates 
to a torque converter disconnect and by-pass clutch structure for such 
system. More particularly, the present invention relates to a torque 
converter disconnect and by-pass clutch structure for an automatic 
mechanical transmission system utilizing a mechanical change gear 
transmission and a power synchronizer mechanism. 
2. Description of the Prior Art 
Mechanical change gear transmissions, i.e. transmissions shifted by 
engaging selected positive jaw clutches, as opposed to friction clutches, 
are well known in the art. Examples of such transmissions may be seen by 
reference to U.S. Pat. Nos. 3,105,395; 3,611,823; 4,152,949 and 4,194,410, 
the disclosures of which are hereby incorporated by reference. 
Automatic mechanical transmission systems comprising mechanical 
transmissions and controls and actuators to automatically shift same, 
usually electronically controlled in accordance with sensed inputs and 
predetermined logic rules, are known. Examples of such systems may be seen 
by reference to U.S. Pat. Nos. 4,361,060; 4,140,031 and 4,081,065, the 
disclosures of which hereby incorporated by reference. Such systems may 
also be seen by reference to SAE Paper No. 831776 titled "AUTOMATED 
MECHANICAL TRANSMISSION CONTROLS", the disclosure of which is hereby 
incorporated by reference. 
Automatic transmission systems including a torque converter drivingly 
interposed a drive engine and a mechanical change gear transmission and/or 
including torque converter by-pass or lockup devices are also known as may 
be seen by reference to U.S. Pat. Nos. 3,593,596; 4,261,216; 4,271,724; 
4,351,205 and 4,375,171, the disclosures of which are hereby incorporated 
by reference. 
Automatic mechanical transmission systems utilizing power synchronizer 
devices, i.e. devices independent of engine speed to provide input shaft 
braking and acceleration, and not manipulation of engine speed, to 
synchronize the transmission jaw clutch members are known in the prior 
art. The acceleration portions of such devices are often output shaft 
driven through a speed increasing gear train and/or driven by an auxiliary 
motor. Examples of such systems may be seen by reference to U.S. Pat. Nos. 
3,478,851, 4,023,443 and 4,140,031, the disclosures of which are hereby 
incorporated by reference. not usable, with a minimum of modification, for 
both manual and automatic use, the advantages of torque converter starting 
and a non-slipping connection between the engine and transmission at 
higher vehicle speeds/drive ratios was not available and/or the speed of 
synchronizing the positive jaw clutches was limited to the response times 
of the engine. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, the drawbacks of the prior art 
are minimized or overcome by the provision of an automatic mechanical 
transmission system utilizing a mechanical change gear transmission of a 
structure identical or substantially identical to the structure of 
transmissions intended for manual usage, providing the advantages of a 
torque converter for vehicle start-ups and the advantages of non-slipping 
connection between the engine and transmission at higher vehicle 
speeds/gear ratios and providing relatively rapid synchronization of the 
transmission positive jaw clutches. 
The above is accomplished by providing an automatic mechanical transmission 
system based upon the same, or substantially the same, mechanical change 
gear transmission utilized for manual transmission systems. This does, of 
course, allow the same basic transmission to be utilized for both manual 
and automatic transmission systems and results in manufacturing, inventory 
and maintenance cost savings. To the transmission is added, if necessary, 
shifting mechanisms suitable for automatic control by solenoids or the 
like. An example of such a shifting mechanism may be seen by reference to 
above-mentioned U.S. Pat. Nos. 4,360,060 and 4,445,393, the disclosure of 
which is hereby incorporated by reference. A power synchronizer mechanism 
as disclosed in above-mentioned U.S. Pat. Nos. 3,478,851 or 4,023,443 is 
also added for synchronizing the transmission positive jaw clutches. It 
has been found, by way of example, that in one typical compound, 
nine-speed mechanical change gear transmission equipped with a power 
synchronizer mechanism, the input shaft may be accelerated and 
decelerated, for downshifts and upshifts, respectively, at about 2000 
RPM/second. This compares very favorably with the expected rates of about 
1500 RPM/second and 700 RPM/second, for acceleration and deceleration, 
respectively, of a transmission input shaft by utilizing only engine speed 
manipulation. Additionally, when utilizing a power synchronizer mechanism, 
the input shaft speed is not limited to the maximum governed engine speed 
as is the case when synchronizing with engine speed manipulation. 
A torque converter is drivingly interposed the drive engine and 
transmission. A torque converter disconnect and, by-pass clutch structure 
is provided comprising first and second separate, independently operable, 
clutches, preferably friction clutches, for coupling the torque converter 
driven member or turbine to the transmission input shaft and for coupling 
the torque converter input or impeller (i.e. the engine output) to the 
transmission input shaft, respectively. 
The torque converter is drivingly interconnected between the engine and 
transmission only when the first coupling is engaged and the second 
disengaged. The torque converter is by-passed, i.e. the transmission 
driven directly from the engine, whenever the second clutch is engaged, 
regardless of the condition of the first clutch. 
When both the first and second couplings are disengaged, the transmission 
input shaft is disconnected from the engine torque and also from the 
inertia of the torque converter allowing the jaw clutches to be easily 
disengaged, the power synchronizer mechanism to act quickly due to 
relatively low inertia on the input shaft and also allowing a selected 
gear to be pre-engaged with the vehicle at rest and in the drive 
condition. 
Accordingly, it is an object of the present invention to provide a new and 
improved automatic mechanical transmission system. 
Another object of the present invention is to provide a new and improved 
automatic mechanical transmission system utilizing a torque converter 
drivingly interposed the engine and mechanical transmission and further 
utilizing a torque converter disconnect and by-pass clutch structure. 
These and other objects and advantages of the present invention will become 
apparent from a reading of the description of the preferred embodiment 
taken with the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Certain terminology will be used in the following description for 
convenience and reference only and will not be limiting. The words 
"upwardly", "downwardly", "rightwardly" and "leftwardly" will designate 
directions in the drawings to which reference is made. The words 
"inwardly" and "outwardly" will refer to directions toward and away from, 
respectively, the geometric center of the described device and/or 
designated parts thereof. Said terminology will include the words above 
specifically mentioned, derivatives thereof, and words of a similar 
import. 
The torque converter disconnect and by-pass clutch assembly 10 of the 
present invention, and an automatic mechanical transmission system 12 
utilizing same, are schematically illustrated in FIGS. 1 and 2. The term 
"automatic mechanical transmission system" as used herein, shall mean a 
system comprising at least a throttle device controlled heat engine, a 
multi-speed jaw clutch type change gear transmission, a non-positive 
coupling device such as a master friction clutch and/or a fluid coupling 
interposed the engine and the transmission and a control unit for 
automatically controlling same. Such systems will, of course, also include 
sensors and/or actuators for sending input signals to and/or receiving 
command output signals from the control unit. 
The automatic mechanical transmission system 12 of the present invention is 
intended for use on a land vehicle, such as a heavy duty truck, but is not 
limited to such use. The automatic mechanical transmission system 12 
illustrated includes an automatic multi-speed mechanical change gear 
transmission 14 driven by a prime mover throttle device controlled engine 
16 (such as a diesel engine) through a fluid coupling or torque converter 
assembly 20. The output of the automatic transmission 14 is an output 
shaft 22 which is adapted for driving connection to an appropriate vehicle 
component such s the differential of a drive axle, a transfer case, or the 
like as is well known in the prior art. 
As will be discussed in greater detail below, the torque converter 
disconnect and by-pass clutch assembly 10 includes two separate, 
independently engageable clutches, preferably friction clutches, a torque 
converter disconnect clutch 24 and a torque converter by-pass clutch 26. 
The transmission 14 includes a transmission operating mechanism 28 which 
is preferably in the format of a pressurized fluid actuated shifting 
assembly of the type disclosed in above-mentioned U.S. Pat. No. 4,445,393. 
The transmission also preferably includes a power synchronizer assembly 30 
which may be of the type illustrated and disclosed in above-mentioned U.S. 
Pat. Nos. 3,478,851 or 4,023,443. 
The above-mentioned power train components are acted upon and monitored by 
several devices, each of which are known in the prior art and will be 
discussed in greater detail below. These devices may include a throttle 
position monitor assembly 32, which senses the position of the operator 
controlled vehicle throttle pedal or other fuel throttling device, a 
throttle control 34 which controls the supply of fuel to the engine, an 
engine speed sensor assembly 36 which senses the rotational speed of the 
engine, a torque converter disconnect clutch operator 38 which operates 
the torque converter disconnect clutch 24, a torque converter by-pass 
clutch operator 40 which operates the torque converter by-pass clutch 26, 
a transmission input shaft speed sensor 42, a transmission output shaft 
speed sensor 44, a transmission shifting mechanism operator 46 for 
controlling the operation of transmission shifting mechanism 28 and/or a 
power synchronizer mechanism actuator 48 for controlling the operation of 
power synchronizer mechanism 30. 
The above-mentioned devices supply information to and/or accept commands 
from an electronic central processing unit ("CPU") 50. The central 
processing unit or controller 50 is preferably based on a digital 
microprocessor, the specific configuration and structure of which form no 
part of the present invention. The central processing unit 50 also 
receives information from a shift control or mode selector assembly 52 by 
which the operator may select a reverse (R), a neutral (N) or several 
forward drive (D, D.sub.L) modes of operation of the vehicle. Typically, 
the D mode of operation is for on-highway vehicle travel while the D.sub.L 
mode of operation is for off-road operation. Alternatively, a separate 
on-highway/off-highway selector switch may be provided. An electrical 
power source (not shown) and/or source of pressurized fluid (not shown) 
provides the electrical and/or pneumatic power the various sensing, 
operating and/or processing unit. Drive train components and controls 
therefor of the type described above are known in the prior art and may be 
appreciated in greater detail by reference to U.S. Pat. Nos. 3,776,048; 
3,038,889; 4,226,295 and 4,361,060, the disclosures of which are 
incorporated by reference. 
As is known, the central processing unit 50 receives inputs from the 
various sensors and/or operating devices. In addition to these direct 
inputs, the central processing unit 50 may be provided with circuitry 
and/or logic for differentiating the input signals to provide calculated 
signals indicative of the rate of change of the various monitored devices, 
means to compare the input signals and/or memory means for storing certain 
input information, such as the direction of the last shift, and means for 
clearing the memory upon occurrence of predetermined events. Specific 
circuitry for providing the above-mentioned functions is known in the 
prior art and an example thereof may be seen by reference to 
above-mentioned U.S. Pat. No. 3,361,060 and/or by reference to a technical 
paper titled "The Automation of Mechanical Transmissions" published at 
pages 11-23 of Section IX of the published proceedings of a joint IEEE/SAE 
conference titled International Congress on Transportation Electronics, 
IEEE Catalog Number 84CH1988-5. 
As is known, a purpose of the central processing unit 50 is to select, in 
accordance with predetermined logic rules such as a program (software 
and/or firmware) and current or stored parameters, the optimum gear ratio 
at which the transmission 14 should be operating and, if necessary, to 
command a gear change, or shift, into the selected optimum gear ratio. 
Ideally, an electronically controlled transmission can be programmed to 
enhance specific vehicle characteristics, such as fuel economy or 
performance. Selection of the D (on-highway drive) mode on the shift 
selector 52 by the driver indicates to the central processing unit 52 that 
peak performance is not required. In this mode, assuming transmission 14 
provides nine selectable forward drive ratios ranging from about 12:1 to 
about 0.9:1, the gear selection subsystem may select fourth or fifth gear 
as a starting gear and select subsequent shifts, both upshifts and 
downshifts, according to what are referred to as the on-highway shift 
profiles which are intended to enhance fuel economy. Similarly, selection 
of the D.sub.1 (off-highway drive) mode on the shift selector indicates to 
the central processing unit 50 a desire to operate at peak performance at 
the expense of fuel economy. In this mode of operation, the gear selection 
subsystem may select low gear or first gear as the starting gear in 
subsequent shifts, both upshifts and downshifts, at least in the lower 
gear ratios, will be according to what are referred to as the off-highway 
shift profiles which are intended to enhance vehicle performance at the 
expense of vehicle fuel economy. 
A more detailed schematic illustration of the torque converter 20 and 
torque converter disconnect and by-pass clutch assembly 10 drivingly 
interposed engine 16 and automatic change gear transmission 14 may be seen 
by reference to FIG. 1. The torque converter assembly 20 is conventional 
in that it includes a fluid coupling of the torque converter type having 
an impeller 54 driven by the engine output or crank shaft 56 through a 
shroud 58, a turbine 60 hydraulically driven by the impeller and a stator 
or runner 62 which becomes grounded to a housing 64 via a one-way roller 
clutch 66 carried by a shaft 68 grounded to the housing 64. Shroud 58 also 
drives a pump 70 for pressurizing the torque converter, lubricating the 
transmission, selectively pressuring the transmission shifting mechanism 
28 and/or power synchronizing mechanism 30 and/or operating the disconnect 
and by-pass clutches 24 and 26. Pump 70 may be of any known structure such 
as, for example, a well known crescent gear pump. 
The transmission 14 includes an input shaft 72 driven by the engine 16 via 
the torque converter assembly 20 and/or disconnect and by-pass clutch 
assembly 10. Transmission input shaft 72 carries a connecting member 74 
fixed thereto for rotation therewith. Connecting member 74 includes a 
first portion 76 associated with the torque converter disconnect clutch 24 
and a second portion 78 associated with the torque converter by-pass 
clutch 26. Briefly, as will be described in greater detail below, torque 
converter disconnect clutch 24 may be engaged or disengaged, independently 
of engagement or disengagement of by-pass clutch 26, to frictionally 
engage or disengage, respectively, the torque converter turbine 60 from 
the transmission input shaft 72 via portion 76 of connecting member 74. 
Torque converter by-pass clutch 26 may be frictionally engaged or 
disengaged, independent of the engagement or disengagement of disconnect 
clutch 24, to frictionally engage the engine crankshaft 56, and shroud 58 
driven thereby, to the transmission input shaft 72 via member 78 of 
connecting member 74. 
Engagement of torque converter by-pass clutch 26 will engage the engine 
crankshaft 56, via shroud 58, directly with the transmission input shaft 
72, regardless of the engaged or disengaged condition of torque converter 
disconnect clutch 24, and thus provides an effective by-pass for 
by-passing the torque converter 20 and driving transmission 14 directly 
from the engine 16. If the torque converter by-pass clutch 26 is 
disconnected, and the torque converter disconnect clutch 24 is engaged, 
the transmission 14 will be driven from engine 16 via the torque converter 
fluid coupling as is well known in the prior art. If the torque converter 
by-pass clutch 26 is disengaged and the torque converter disconnect clutch 
24 is also disengaged, the transmission input shaft 72 is drivingly 
disengaged from any drive torque supplied by the engine or any inertial 
drag supplied by the torque converter. Disconnecting of the transmission 
input shaft 72 from the inertial affects of the engine and/or torque 
converter allows the rotational speed of the input shaft 72, and all 
transmission gearing drivingly connected thereto, to be accelerated or 
decelerated by the transmission power synchronizer mechanism 30 in a more 
rapid manner for purposes of more rapidly achieving synchronization during 
a downshift or upshift of the transmission and also allows the power 
sychronizer to cause the input shaft 72 to rotate at a rotational speed 
greater than any governed engine speed. 
It is noted that transmission 14 is of the mechanical transmission type 
utilizing positive jaw type clutches. Positive clutches of this type are 
relatively compact and inexpensive as compared to frictional clutches and 
are very reliable if utilized in connection with some type of 
synchronizing means such as individual synchronizers and/or a power 
synchronizing mechanism. With positive type clutches, it is necessary 
and/or highly desireable that the driving torque and inertial forces on 
input shaft 72 be minimized when the jaw clutch members are to be 
disengaged from the previously engaged gear ratio and then re-engaged in 
the selected new gear ratio. Accordingly, when a fluid coupling such as a 
fluid torque converter is drivingly interposed between a drive engine and 
a positive mechanical transmission, it is important that a means to 
disconnect the transmission input shaft from the fluid coupling be 
provided. 
The specific structural details of a preferred embodiment of the torque 
converter and torque converter disengage and by-pass clutch assembly 
structure 10 may be seen by reference to FIG. 3. Change gear transmission 
14 includes a transmission housing 80 having a bell housing portion 82 
which encloses the torque converter 20 and disconnect and by-pass 
clutches, 24 and 26, and which is provided with a flange 84 for attachment 
to the drive engine. The housing 80 is provided with bearings 86 and 88 
for rotatably supporting the input shaft 72 within the housing 80. Input 
shaft 72 carries transmission input gear 89 fixed for rotation therewith. 
As discussed above, torque converter 18 includes impeller 54, a turbine 60 
and a stator 62 as is well known in the prior art. Stator 66 is supported 
in the housing by means of a one-way roller clutch 66 as is well known in 
the prior art. The impeller 54 is fixed for rotation to a shroud member 58 
which is adapted to be driven by the engine 16 by means of engine drive 
splines 90, or the like, which are adapted for driving engagement with 
complimentary drive splines provided on the engine fly wheel. The gearing 
and positive clutch structure of transmission 14 is conventional and not 
illustrated nor described. 
The shroud 58, which surrounds assembly 10 and torque converter 20, is also 
adapted to drive pump 70 as by means of a spur gear 92 constantly engaged 
with pump drive gear 94. In addition to providing pressurized charging 
fluid for the torque converter 20, pressurized lubricant for the 
transmission 14 and actuating fluid for transmission actuating mechanisms 
28 and 30, the pump 70 may also provide pressurized fluid for selective 
engagement and disengagement of the torque converter disconnect clutch 24 
and/or torque converter by-pass clutch 26 as will be discussed in greater 
detail below. For this purpose, housing 80, shaft 72 and/or shroud end 
cover 96 are provided with fluid passage ways and rotary fluid connections 
in a manner well known in the prior art. 
Torque converter disconnect and by-pass clutch structure 10 comprises a 
torque converter disconnect clutch 24 which is concentric with and 
generally surrounded by torque converter by-pass clutch 26 to provide a 
relatively axially compact structure. The torque converter disconnect and 
by-pass clutch structure 10 includes a connecting member 74 which is fixed 
for rotation with the input shaft 72 as at splined connection 98. 
Connecting member 74 includes a generally axially extending annular shaped 
wall member 100 having a plurality of inner diameter spline members 100a 
defining portion 76 and a plurality of outer diameter spline members 100b 
defining portion 78. A plurality of friction members such as friction 
discs 102 are carried by splined member 76 for rotation therewith and 
extend radially inwardly therefrom. A plurality of friction members such 
as friction discs 104 are carried by splined member 78 and extend radially 
outwardly therefrom. Friction discs 104 are interleaved with friction 
discs 106 carried by internal splines 108 on the shroud member 58 and 
extending radially inwardly therefrom to define a friction disc pack for 
by-pass clutch 26 as is known in the prior art. Friction discs 12 are 
interleaved with friction discs 110 fixed for rotation on external splines 
112 of a member 114 fixed for rotation with the turbine 60 and extend 
radially outwardly therefrom to define a clutch disc pack for torque 
converter disconnect clutch 24. Member 114 is fixed to turbine 60 by means 
of web member 116 and is rotatably supported on a hub portion 117 of 
connecting member 74. 
An annular axially inwardly extending cylinder 120 is defined in the 
forward end wall 96 of shroud 58 and receives an annular piston member 122 
slideably and sealingly therein. Annular piston 122 and annular reaction 
member 124 receive the friction discs 104 and 106 axially therebetween for 
selective engagement and disengagement of by-pass clutch 26. Cylinder 120 
may be selectively pressurized and depressurized, to engage and disengage, 
respectively, torque converter by-pass clutch 26 to connect the engine 
driven shroud 58 directly to the input shaft 72 via portion 78 of 
connecting member 74 by pressurized fluid from pump 70 supplied through 
passages in the cover 82, shaft 72 and/or end cover 96 and controlled by 
valve structure 40. 
Connecting member 74 defines an annular axially inwardly extending cylinder 
128 in which an annular piston 130 is sealingly and slidably retained. 
Annular piston 130 and annular reaction member 132 receive the friction 
discs 102 and 110 axially therebetween for selective engagement and 
disengagement of the torque converter disconnect clutch 24. Pressurized 
fluid from pump 70 may be supplied to or vented from cylinder 128 by means 
of fluid passages defined in the hood 82, shaft 72 and/or end cover 96 and 
controlled by valve 3B controlling the flow of fluid to and from pump 70 
to cylinder 128 or an hydraulic fluid reservoir (not shown). 
As may be seen, annular cylinders 120 and 128 may be individually and 
independently pressurized and/or vented for independent engagement or 
disengagement of the torque converter disconnect 24 and/or torque 
converter by-pass 26 clutches. By utilization of concentric and 
substantially telescopic clutches 24 and 26 in clutch assembly 10, a 
relatively axially compact structure is provided allowing a drive system 
comprising a torque converter fluid coupling to be drivingly interposed a 
drive engine and a mechanical change gear transmission wherein the 
transmission may be driven directly from the engine by means of a torque 
converter by-pass clutch, the transmission may be driven by the engine 
through the torque converter fluid coupling and/or the transmission may be 
disconnected from the engine and torque converter for purposes of 
providing a break in the torque and reduction in input shaft inertia for 
purposes of more rapidly synchronizing and shifting the transmission. 
When the vehicle is at rest with the mode selector in the drive or 
off-highway drive mode, the disconnect clutch 24 will be engaged and the 
by-pass clutch 26 disengaged allowing for torque converter start-up with 
its well known advantages. At above a given vehicle speed and/or gear 
ratio, the advantages of torque converter operation are no longer 
required, and the increased efficiency of a direct drive between the drive 
engine and transmission is required. Under these conditions, the torque 
converter by-pass clutch 26 will be engaged allowing the transmission 
input shaft 72 to be driven directly from the engine via the torque 
converter shroud 58 and connecting member 74. 
As discussed above, both clutches 24 and 26 will be disengaged to shift 
from a previously engaged gear to neutral, to allow the power synchronizer 
30 to synchronize the jaw clutch members of the gear to be engaged and to 
allow engagement of the synchronized jaw clutches of the gear to be 
engaged. 
Selection of the desired gear ratio and selection of the required engaged 
or disengaged condition of the torque converter disconnect or by-pass 
clutches, as well as the issuance of command signals to the various clutch 
and transmission operators is accomplished by the central processing unit 
50 in a manner which is known in the prior art and which may be 
appreciated in greater detail by reference to above-mentioned U.S. Pat. 
No. 4,361,060. 
The power synchronizing mechanism 30 may include a shaft 136 drivingly 
connected to a transmission countershaft 138 constantly in direct or 
indirect meshing engagement with the input gear 89 and input shaft 72. 
Shaft 136 may be selectively frictionally clutched to the housing 80 to 
decelerate the input shaft 72 and the gearing driven thereby and/or may be 
selectively frictionally clutched to a speed increasing drive train, such 
as a planetary speed increasing drive train, 140, driven off the output 
shaft 22, to accelerate the input shaft 72 and the gearing driven thereby. 
To achieve and/or maintain exact or substantial synchronization of the 
transmission jaw clutch members to be engaged, the clutching of the shaft 
136 to the housing or to the gear train may be modulated as by pulse width 
modulation or the like. 
It is understood that the above description of the preferred embodiment is 
by way of example only and that various modifications, substitutions 
and/or rearrangements of the parts are possible without departing from the 
spirit and the scope of the present invention as hereinafter claimed.