CA1139133A - Automatic transmission - Google Patents

Abstract

APPLICATION OF: TIMOTHY J. MORSCHIECK
FOR: AUTOMATIC TRANSMISSION

A B S T R A C T

Disclosed is a power shift transmission having two input shafts, an output shaft, two countershafts which are first synchronized and clutched with either of the input shafts, and then alternately clutched to the output shaft. Each countershaft rotatably supports a ratio gear driven by one of the input shafts, a ratio gear driven by the other input shaft, and a drive gear for driving the output shaft. A reverse gear is rotatably supported by one of the countershafts. A double acting synchronizer is disposed between the two ratio gears on each counter-shaft for synchronizing and clutching either of the ratio gears to the countershaft. A hydraulically actuated friction clutch is disposed adjacent the drive gear on each countershaft for clutching the countershaft to the driven gear. One of the input shafts is a torque converter driven shaft; this shaft drives the ratio gears which are first and second speeds and the reverse gear. The other input shaft is a torque converter bypass shaft; this shaft drives the ratio gears which are third and fourth speeds. The transmission utilizes helical gears and the helical angle direction of the ratio and drive gears on the countershafts are such that axial forces on the contact teeth of the gears impart bending stresses on the countershaft which subtract from bending stresses on the shaft caused by radial forces on the contacting teeth of the gears.

Description

~L~3~1~33 This invention relates to ratio shiftin~
transmlssions and in particular to such transmissions adapted for power shiftin~ and for use in land vehicles.
This is a dlvision oE copendin~ Canadian Pa-tent ~pplication 322,737, iled r1arch 5, 1979.
It is known in the transmission art to first synchronize and clutch an intermediate shaft or ratio gear with the transmission output and to then clutch the intermediate shaft or ratio ~e~r to the trans~ission input.
; 10 Such synchronizin~, which ~ay be referre~ to as output synchronizin~, is also known in prior art transmissic)ns havin~ plural countershafts. Many prior art transmissions, which employ plural countershafts and output s~nchronizing, power shiEt from one countershaft to another to upshiEt or downshift the transmission and synchronize a non-driving countershaft ~ith the transmission output in preparation for the next shift.
When the above prior art trans~issions are used in combination with a tor~ue converter, the sole source of power input to the transmission is throu~h the tor~ue converter ~Jhich is rather ineficient and not needed in the hi~her speed ratios of the transmission. To ne~ate this inefficiency, tor~ue converter bypass or lock out clutches have been used. Such clutches have the disadvanta~e in that they and their needed control systems may increase the cost and complexity of the trans~issions.
An object of the invention is to provide a trans-mission which is low in initial cost and economical in use.

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~:~3~33 Another object of the invention is to provide a transmission which is readily shifted without a break in power between the transmission input and output.
The present inven-tion resides in a power shift transmission of the type including an input shaft adapted to be continuously driven by an engine, an output shaft adapted to be continuousl~ connected to a load, an intermediate shaft and means mounting the shafts for rotation independently of each other. In the present invention means is operative to synchronize the intermediate shaft means with the continuously driven input shaft while the intermediate shaft means is drivingly disconnected from the output shaft. Means is operative after the synchroni~ing to positively clutch the intermediate shaEt means with the input shaft while the intermediate shaft means remains drivingly disconnected from the output shaft.
Friction clutch means is drivingly interposed between the intermediate shaft means and the output shaft and is operative after the positive clutclling to power clutch the intermediate shaft means with the output shaft.
In the specific embodiment of the invention the in-termediate shaft means includes the countershaft and there is pxovided an input gear nonrotatably fixed -to the input shaft, an output gear nonrotatably fixed to the output shaft, a driven gear rotatably supported by the countershaft and in mesh with the input gear, and a drive gear rotatably supported by the countershaft and in mesh with the output gear, the friction clutch means being interposed between the countershaft and the drive gear.
In one form of the invention the intermediate shaft means includes first and second countershafts with input ' ~ pc/~

1~3~
gear means nonrotatably Eixed to the input shaft, ou-tput gear means nonrotatably fixed to the output shaft, a driven gear rotatably supported by each countershaft and in mesh with the inpu-t gear means, and a drive gear rotatably supported by each countershaftc~nd in mesh with the output gear means, the riction clutch means being interposed between each countersha.ft and each drive gear.
BRIEF DESCRIPTION OF THE DRAWINGS
The preferred embodiment of the invention is shown in the accompanying drawings in which:
FIGIJRE ]. is a schematic view of the transmission looking in the direction of arrows 1-1 of FIGURE 2;
FIGURE 2 is a schematic view of the transmission, looking in the direction oE arrows 2-2 of FIGURE 1;
FIGURE 3 is a detailed view of the transmission of FIGURE 1, looking in the direction of arrows 1-1 of FIGURE 2;
FIGURE 4 i5 a detailed view of a portion of the -transmission, looking in the direction of arrows 3-3 of FIGURE 2; and t~./ -. -3-~:L3~3;3 FIGURE 5 is a schematic view of a portion of a countershaft assembly of FIGURES 1 and 3~
Certain terminology referring to direction and motion will be used in the following descrip-ti~n. The terminology is for convenience in describing the pre-ferred embodiment and should not be considered limiting unless explicitly used in the claims.

DE'TAILED DESCRIPTION OF TH~ PREFERRED EMBODIMENT
Looking first at FIGURF 1~ therein is schemat-ically illustrated a power shift transmission assembly 10adapted for use in an unshown land vehic:le, but not: limited to such use. Transmission 10 is preferably automatically shifted by an unshown control system, which control system f~rms no part of the instant invention. rrransmission 10 includes an input shaft 12 which may be direc-tly driven by an unshown internal combustion engine, a housiny assembly 14, a -torque converter assembly 16, a ratio change gear assembly lS which is driven by input shaft 12 through torque converter assembly 16 in first, second, and reverse ratios and is driven directly by a bypass input shaft 13 in third and fourth ratios, and an output shaft 20 axially aligned with input shafts 12 and 13.
The torque converter assembly 16 is conventional in that it includes a fluid coupling of the torque con-verter type having an impeller 22a driven by input shaft 12through a shroud 24, a turbine 22b hydraulically driven by the impeller and in turn driving a sleeve shaft 26 which extends into gear assembly 18, and a runner or stator 28 which becomes grounded to housing 14 via a one-way xol~er clutch 30 carried by a sleeve shaft 32 fixed to housing assembly 14. Shroud 24 also drives a pump 34 for pressur-izing the torque converter, for lubricating the transmission, and for selec-tively pressurizing friction clutches in gear assembly 18.
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Sleeve 26 provides a fluid power or tor~ue .
converter driven shaft for first, second, and reverse ratio gears in gear assemhly 18. Bypass shaft 13 is in continuous direct drive with inpu-t shaft 12 and provides a torque converter bypass for drivin~ third and fourth ratio gears; this arxangement of the bypass shaEt negates the need of a separate torque converter bypass clutch.
Looking now at FIGURES 1 and 2, the schematically illustrated ratio change gear assembly includes two countershaft assemblies 36 and 38, which are disposed about axes which are parallel to and radially outward o an axis defined by shafts 12, 13, and 20. Assembly 36 includes a shaft 40 rotatably supported at its elids 40a and 40b by housing assembly 14, a double acting sync:hron-izer clutch 42, first and third speed ratio gears 44 and~6 rotatable relative to`and supported b~ shaft ~Q, and a hydraulically actuated friction clutch 48. ~irst speed ratio gear 44 is driven by and in continuous mesh with an input drive gear 50 which is non-rotatably secured to : 20 bypass shaft 13. Synchronizer clutch 42 may be a conven- .
tionaI double ac-ting synchronizer having a clutch member 54 at one end which is non-rotatably secured to gear 44, a clutch member 5~ at the other end which is non-rotatably : secured to gear ~6, and a center clutch member 58 at the center which is non-rotatably secured to shaft 40. Center clutch member 58 may be slidably shifted ieftwardly or rightwardly in a conventional manner to, respectively, couple gear 44 or 46 to shaft 40.. Such slidable shifting of the center clutch member first frictionally couples countershaft 40 with one of the ratio gears and after synchronism is reached, then positively clutches the shaft with the gear via a iaw clutch shown in ~IGURE 3.
Center clutch member S8 includes a radially extending flange portion 60a which Inay be gripped by an unshown shift fork to effect the leftwdrd and rightward shifting in a aonventional mdnner. Fric~ion clutch 48 includes a housiny .l~.a~
~6--member 62 non-rotatably secured to sha:Et 40, two sets of interdigitated disks 64 and 65, and a sleeve shaft 66 rotatably supported by shaft 40. Disks 6~ ar~ non-.rotat-ably secured to sleeve shaft 66 and disks 65 are non- i S rotatably secured to housinc3 member 62. Both disk sets are axially moveable in housincJ 62 and are Erictionally intereonnected in response to hydraulic pressure beincJ
seleetively applied to an unsho~7n pi.ston in -the housing member 62. Sleeve shaft 66 is non-rotatably secured to a drive gear 68 whieh is rotatably supported by shaft ~0.
Drive gear 68 is in continuous mesh with an output gear 70 which is non-rotatabl~ secured to output sha-t 20.
Countershaft assembl~ 38 di.f~ers from assembly 36 mainly in that it also includes a :reverse ratio ~ear.
~ssembly 38 ineludes a shaft 72 rotatably supp~rted at its ends 72a and 72b by housinc3 assembly 14, a douhle actinq s~nchronizer eluteh 74 r second, fourth and reverse speed xatio c~ears 76, 78, 80 whieh are xotatable relative to and supported by shaft 72, a hydraulically aetuated friction elutch 82, and a positive type jaw eluteh assembly 84.
Clutch 84 may be a synchroniæea eluteh similar to clutches 42 and 7~. Second speed ratio gear 76 is driven b~ and in continuous mesh with an input drive gear 86 which is non-rotatably seeured to torque converter driven shaft 26.
Fourth speed xatio gear 78 is driven by and in continuous mesh with input drive gear 52 which is non-rotatably seeured to bypass shaft 13. Synchronizer elutch 74 is a double acting elutch and may be identical -to synchronizer 42. Synchronizer clutch 7~ includes a elutch member 90 at one end whi.ch is non-ro-tatably seeurea to ~ear 76, a elu-tch member 92 at the okher end which is non-rota-tably secured to gear 78, and a center clutch ~nember 9~ at the center which is non-rotatably secured to shaft 72. Center elutch member ~ includes a radially extendirlg flange portion 96a which may be ~ripped by an unshown shift fork to effect leEt-~7ard and ric~htward shif-ts in the same ~:~3~3;~

manner as described for synchronizer 42. Friction clutch 82 may be identical to fri.ction clutch 48~ Friction clutch 82 includes a housing member 98 which is non-rotatably secured to shaft 72, two setc; oE disks 100 and 101, and a sleeve shaft 102 rotatably supported by shaft 72. Disks 100 are non-rotatably secured to sleeve shaft 102 and disks 101 are non-rotatably secured to housing member 98. Both disk sets are axially moveable in housing 98 and are-frictionally interconnected in response to hydraulic pressure being selectively applied to an unshown piston in housing member 98. Sleeve shaft 102 i5 non-rotatably secured to a drive gear 104 which is rotatabl~ supported by shaft 72. Drive gea.r 104 is in continuous mesh with an output gear lQ6 which is non~rotatably secured to output shaft 20.
Reverse.gear 80 is rotatab:Ly supported by shaft 72 and is driven by an idler gear assembly 108, seen onl~ in FI~URES 2 and ~. Idler gear assembly 108 includes a shaft 110 which is non-rotatabl~ supported by housing assel~bly 14, a gear 112 which is rotatably supported on shaft llC and in continuous mesh wi-th input drive gear S0 which is driven by torque converter driven . `
shaft 26, and a gear 114 which is rotatably supported on shaft 110 and non-rotatably secured to geax 112. Gear 114 is in continuous mesh with reverse gear 80. ~aw clutch assemb~y 84 includes jaw clutch teeth 116 which are non-rotatably secured to gear 80 and a jaw clutch member 118 mounted for sliding movement relative to shaft 72 and secured against rotation relative to shaft 72.
Member 118 includes jaw clu-tch tee-th 118a which engage with teeth 116 and an annular groove 118b wh.ich receives a shift fork 152 engaging the clutch in a conventional manner. ShiEt ~ork 152 is shown in FIGURE 3.
By way of example, the ratios of ratio change gear assembly 18 are: first gear - ~.05, second gear - 2.22, third gear - 1.42, fourth gear - 1.0~, and reverse gear - ~.76.

113~133 As may be seen, bypass shaft 13 and output 20 rotate at the same speeds when drive is through fourth year.
Gear assembly 18 may also be provided with a direct drive clutch 120 at the confronting ends 13a and 20a and the bypass of output shaEts 13 and 20 for bypassing fourth speed ratio drive through countershaft 38. Such a clutch may be a non-synchronized positive type jaw clutch as illustrated herein, since herein shafts 13 and 20 rotate at the same speeds in the fourth speed drive ratio. Further, the direct drive of clutch 120 could be used to provide a fifth speed ratio by decxeasing the ratio spacing of first, second, third, and fourth ratio geaxs so that output shaft 20 would rotate slower than bypass shaft 13 when drivin~ in fourth speed. When using clutch 120 to provide a fifth speed ratio, the clutch is preferabl~ a fluid ! actuated friction clutch or a synchronized iaw clutch, both of which may be o a conventional type.
Looking now at F~GURES 3 and 4, therein the ;20 transmission of FIGU~FS 1 and 2 is disclosed in greater detail to show additional features not readily shown in a schematic. The transmission of FIGURES 3 and 4 does not include the direct drive clutch 120 but is otherwise the same as that previously described. Thus, in FIGVRES
3 and 4 the numerals corresponding to those of ~IGURES 1 and 2 will refer to parts already ~escribed.
In ~IGURE 3, housing assembly 14 includes a front housing member 14a havin~ a bell housing portion 14b formed integral therewith, a rear housing member 14c, and an intermediate plate member l~d. Members 14a, l~c, ; and 14d are secured together via plurality of b~lts 121, one of which is shown. A flan~e portion 14e of the bell housing pro~ides means for securing the transmission to the rear of an engine housing. ~ntermediate plate l~d includes through bores lgf and l~c3 ~or the passage of shafts 40 and 72, a bore 14h having a bearinc3 122 disposed :

113gl33 therein for rotatably supporting end 13a of shaft 13.
End 20a of shaft 20 extends into a blind bore 13b in shaft 13 and is supported therein by a roller bearing 124. Intermediate plate 14d also includes several unshown oil passages for directing lubrica-ting oil to various portions o~ the transmission and for directing oil to actuate clutches 48 and 82.
Shroud 24 of torque converter-assembly 16 includes a front portion 24a and a rear portion 24b which are non-rotatably secured together at 126. Front portion 24a is integrall~ formed with a cup shaped portion defining shaEt 12 and having in~ernal splines 12a which receive splines 13c for driving shaft 13. Front portion 24a also includes a plurality o~ studs 12~3 for securing the transmission input to an unshown crankshaEt or output shaft o~ an engine or mo-tor. '~he rear portion 24b is fixed to impeller 22a at 130 and is welded to a ! sleeve 132. Sleeve 132 rotatably supports the rear portion 24a via a bearing 134 and drives pump 34.
Pump 34 may be a well known crescent gear p~p. Bearing ~ 134 is supported by pump housing 34a which is bolted to ; housing portion 14a via a plurality of bolts 136.
Shafts 13 and 26 are rotatabl~ supported relative to each other and housîng assembly 14 via roller bearings 138, 139, 140, 141, and, as previously mentioned, by bearing 122. Shafts 13 and 26 are axially retained relative to housing assembly 14 and each other by a ball bearing 122 and roller bearings 142 and 144.
Looking now at cross-sectioned countershaft 38, ends 72a and 72b o:E shaft 72 are supported by ball bearings 1~6 and 1~8 which also axially retain the shaft. Reverse gear 80 is rotatably supported on shaft 72 by a roller bearing 150 and includes an axially extending portion 80a having e~ternal splines defining jaw clutch teeth 116 of the jaw clutch assembly ~4. Clutch assembly 84 fur-ther includes a ring memher l51 splined on its I D to .

shaft 72 and splined on its O.D. to jaw clutch teeth 118a of member 118. Annular groove 118b in member 118 receives a shift fo.rk 15~ which is slidably connected to a shift rod 154 of an actuator 156. Actuator 156 includes a pist.on portion 15*a ~ormed on or fixed to rod 15~ and disposed in a cylinder 14i cast.into intermediate plate 14d, and an end plate 158 for closing-the cylinder. A spring 15~ disposed between a snap ring assem~ly 160 and shift fork 152 resiliently urges clutch teeth ~8a .into engagement with clutch teeth 116 in response to leftward movement of rocl 154 and piston 154a. A snap ring 162 contacts the shift fork for disengaging the jaw clutch in response to r.i~htward movement of the rod and pi.ston. C~linder 14i is prov.ided with oil on hoth sides of piston 154a by unshown passages in intermed.iate plate 14d. H~draulic sealing of the piston and cylinder is provided by O-ring seals in a conventional manner. ~Iydraulic actuators for shifting synchronizers 42 and 74 are ~0 provi.ded in a similar manner.
. Gear 76 includes an axially extending sleeve portion 76a having external jaw clutch splines 76b which xeceive internal splines of clutch member ~0.
Gear 76 and sleeve portion 76a are rotatably supported on shaft 72 by a pair of roller bearings 164~ In a like mannex, gear 44 of countershaft assembly 36 includes an axially extending portion 44a, but of longer length, splined to clutch membex 54 and unshown roller bearings for rotatably supporting the gear and sleeve portion on shaft 40. In a similar manner, gear 78 is rotatably supported on shcaft 72 by a roller bearing 166 and includes an axially extending portion having external jaw clutch .
splines 78a which xeceive internal splines of clutch member 92. Gear ~6 is rotatably mounted on shaft 40 and c~nnected to clutch member 56 in the same manner.

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Double acting synchronizer 74, of which members 90 and 92 are part, is well known in the prior art. The synchronizer and in particular center clutch 94 includes a sleeve 167 splined on its I.D. to shaft 72 and on its S O.D. to internal jaw clutch splines 96b of a slidable positive type jaw clutch member 96 integrally formed with flange portion 96a, a pair of friction rone rin~s 168 and 170 rigidly secured together b~ three circumfer-entiall~ positioned pins 172, and a pair of internal friction conc surfaces 90a and 92a which are engageable with external cone surfaces defined by rings 16~ and 170.
Pins 172, which extend through three chamfered openings 96c circumferentially positioned in flange '~6a, have at their centers (the position of the flan~e in its neutral position) an annular groove 172a having chamfered ends. The I.D. o~ each chamfered opening 96c is slightly greater than the major O.D. of each pin 172. ~nnular t grooves 172a are slightl~ wider than the flange. Center clutch member 94 further includes three axiall~ split ~0 pins 174 extending through three chamfered openings ~6d which are alternately spaced between openings 96c. Pins 174 each consist of a pair of semicylindrical haLves which are biased apart by a leaf spring 176. Each pair of semicylindrical halves define an annular groove 17~a having chamEered ends. Annular groove 174a is formed by a semiannular groove defined by each pin half.
Spring 176 biases the semiannular grooves outward i~to engagement with openings 96d. The I.D~ of openings 96d is slightly greater than the major O.D~ of pins 174.
Annular grooves 174a closely fit the width of flange 96a.
The center clutch member 94 is shown in the neutral position, therefor both gears 76 and 88 are disenga~ed, the friction cone surfaces are slightly spaced apart, pins 17~ and 174 and their respective grooves are concentric with openings 96c and 96d, and the semiannular grooves defining grooves 174a are biased .. .. . . . . . . ...

113~133 into engagement with holes 96d. When i~ is desired to couple gear 76 to shaft 72, flange portion 96a is moved axially to the left by an appropriate shift mechanism.
Such movement, which is transmitted through split pins 174, shifts the cone surface of cone ring 168 into contact with cone surface 90a. This contact (provided gear 76 and flange 96a are no-t synchronous with each other) causes pins 172 to move out of concentric alignment with openings 96c, whereby the chamfers of the openings 96c and the chamfers of the grooves 172a engage and prevent further axial movement of the flange due to torque at the interface of the chamfers. ~s synchxonous speeds are reached, the tor~ue at the interface of the chamfers diminishes and the axial force on flange 96a moves pins 172 back into a concentric relationship with openings 96c, thereb~ allow.ing flange 1 96a and jaw member ~6 to move axially to the l.eft for ; engaging jaw clutch splines 96b with jaw clutch splines 76b. Gear 78 is coupled to shaft 72 in the same manner by moving the flange rightward.
The transmission gears are preferably helical years and as such they are axiall~ loaded with s~stantial forces when they are transmitting torque. Further, since the gears are in continuous mesh, the~ rotate at diff~
erent speeds. Hence, it is preferred that the gears be axially isolated from each other to prevent the transmittal of the axial forces across surfaces rotating at different speeds to reduce wear and energ~ losses.
Isolation and axial retention of gears 80, 76~ and 78 is as follows:
Gear 80 is retained against axial movemen-t relative to shaft 72 in the leftward direction by a thrust plate 178 and in the rightward direction through ring member 151 by a shoul~er 72c defined by a step in shaft 72. Shoulder 72c prevents axial loading being imposed on gear 76 when gear 80 is engaged Gear 76 ~, .

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~:~L3~3 L3~ ~

is retained against axîal movement relative to shaf-t 72 in the leftward direction through ring member 151 b~
a snap ring 180 and in the rightward direction through ring member 167 which abuts a shoulder 72d de~ined by a step in shaft 72~ Gear 78 is retained against axial movement relative to shaft 72 in the leftward direction through ring member 167 by a snap ring 182 and in the rightward direction by a thrush plate 184. f ~riction clutch 82, which is structurall~
and functionally conventional and identical to clutch a8, includes the housing member 98 splined to sha~t 72 at 98a, the set o~ disks 101 which are slidably splined to internal splines 98b defined by the housing member, the set of disks 100 which are slidably splined to external splines 102a defined by an extension of sleeve 102, a reaction member 186 which i9 non-rotatabl~ secured ! to housing member 98 hy splines 98b, a piston 18~ for s~ueezing the disks together in response to pressurized fluid being introduced into a chamber 190 defined by housing member 98 and piston 188, and a return spring 192 for retracting the piston. Eousing member 98 is axially retained by a .shoulder 72e defined by a step in shaft 72 and a snap ring 194. Sleeve 102 and gear 104 are rotatably supported on shaft 72 by a pair of roller bearings 196 and are axially retained by snap rings 194 and 204 through thrust bearings 198 and 200.
The gear 68 and clutch 48 o~ countershaft assembly 36 are rotatably and axially retainea on shaft 40 in a similar manner.
Out:put sha~t 20 is rotatably supported by the roller bearing 124 and a ball bearing 206. The outer race 206a of bearing 206 is supported by housing portion 14c and is axially retained thereto by a shoulder 14k and a snap ring 208 Axial retention of sha~t 20 is provided by the inner race 206b o~
beariny 206 which is sandwiched between a shoulder 20b ~3~3 defined by shaft 20 and a spacer sleeve 210. Sleeve 210 is held in place by an output yoke 212 which is splined to shaft 20 and axially retained by a bolt 21 Output gears 70 and 106 are splined to shaft 20 and are xetained in the leftward direction by a flan~e portion 20c defined by shaft 20 and in the rightward direction by the inner race 206b.

OPERATION
In reviewing the operation, it will be assumed that the transmission 10 is installed in a land vehicle - having an internal combustion en~ine, that the engine crankshaft is connected to torque converter shroud,2 by studs 1~8, that the crankshaft rotates the .shroud clockwise when view.ing the shroud from the front, and that a shift contxol system will automatically eEfect shiFting to the desired'speed ratios in the proper ! sequence. Such control systems are well known and , are oten made responsive to parameters such as engine load and vehicle speed. It will also be assumed that the control system includes a shift control lever which is selectively placed in neutral to disengage the transmission, or in drive to effect forward movement of the vehicle, or in reverse to effect reverse movement of the vehicle.
The shift control system xeferred to herein is b~ way of example only and does not form part of the invention herein or any preferred ~orm of a control system.
With the shit control lever in neutral and the engine running, bypass shaft 13 and torque converter driven shaft 26 rotate clockwise and rotate input drive gears 50, B6, and 52 clock~ise, whereby driven gears 44, 46, 76, 78 rotate counterclockwise and c3ear 80 rotates clockwise since it is driven through idler gear assembly 108~ Further, countershafts 40 and 72 are completely disconnected from the transmission input and output since synchronizers ~2 and 74 and fluid actua-ted ...

~:~3~3~9 clu-tches ~8 and ~ are disengacJed while the shift control lever is in neutral.
Assuming now that a vehicle opera-tor places the shift control lever in drive and wishes to accelera-te the vehicle in a forward direction to a speed which will cause the control s,ystem to sequentially upshift through each of the four forward ratio gears. When the shift lever is placed in drive, the control system connects the tor~ue converter driven shaft to the output shaft through the first speed ratio gear in the followiny secluence: l) Synchronîzer flange -60a is moved slightly to the left by an appropriate actuator (not shown) to effec-t a frictional connec-tion of the Eixs-t gear 4~ to shaft ~0, whereby shaft 40, which is disconnectecl from the OlltpUt shaft, is pulled up toward synchronous speed with gear 4~ thereby rotating countershat 40 relatlve to ' , gear '68'said gear 68 is unclutched a-t this time; 2) Flange 60a will then move further to the lefk and clu-tch ~ear ~4 to shaft 40 by the jaw clutch in the synchronizer when the synchronous speed is reached; and 3) Clu-tch 48 is then actuated by pressurized fluid. First gear is now fully engaged.
When engine load decreases and vehicle speed increases to predetermined amounts, the torque converter ' driven shaf-t is connected to the output through the second speed ratio gear in the following sequence: l) Synchronizer f:lange 96a is moved sli~htly to -the left by an unshown actuator to effect a frictional connection of the second gear 76 to sha-ft 72, whereby shaEt 72, which is disconnec-ted from the outpu-t shaf-t, is pulled up -toward synchronous speed with gear 76; 2) Flange 96a will then move further to the left and , cbr/~5 -15-clutch ~ear 76 to shaft 72 by the ]aw clutch in the synchronizer when the synchronous speed is reache~; 3) Clutches ~8 and ~2 are then deactua-ted and actua-ted, respectively, to drivin~ly disconnec-t shaft 40 and drivin~ly connect shaft 72; and 4) Flan~e 60a is then .

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moved back to its neutral position to clisengage the synchronizer. Second gear is now full~ engaged and first ~ear is disengayed. In the forectoing secluence '~
in upshifting to second ~ear, it shoulcl be noted that shaft 72 is synchronized with gear 76 through a drive connection wi.th the transmission input and while drive is through the first gear and shaft 40. Such synchronizing may be characterized as input synchronizing. The other ratio gears and the associated countershafts are synchronized in a like manner.
When engine load decreases and vehicle speed increases to a predeter~ined amount., bypass shaft 13 is then connected to the output shaft through third speed ratio ~ear 46 in a four step sequence simila.r to the above sequence for second gear: 1) Flange 60a is moved slightly to the right to frictionally connect gear 46 to shaft 40, 2) When synchronous speed is reached, flange 60a moves further to the right to engage the synchronizer jaw clutch; 3~ Clutches 82 and 48 are ~0 deactuated and actuated, respectively; and 4) Flange 96a is moved back to neu-tralO Third gear is now fully engaged and the torque converter is automatically b~passed.
The sequence for upshifting to four-th gear should be obvious from the foregoing and it should suffice to say that synchronizer 74 is actuated to the right, clutches 48 and 82 are deactuated and actuated, respectively, and synchronizer ~2 is disengaged.
Downshifting from fourth gear is merely the reverse of the upshift sequence in that the ne~t lower ratio gear is first synchronized with its respective shaft while drive continues in the hicJher ratio, the drive is then switched from one countershaft assembly to the other by deactuating and actuating the ~luid actuated clutches ~8 and 82.

Assuming now that the vehicle operator wishes to move the vehicle in the reverse di.rection, the shift control lever is placed in the reverse position, whereby the control system will connect the torque converter driven shaft to the outpu-t shaft through reverse gear 80 and idler assembly 108. The sequence of events to effect drive in reverse may var~; one sequence which may be automa-tically effected by the control system is as follows: 1) Tor~ue converter driven shaft 26 is pulled d~7n to a low speed by momentarily effecting a driving connection to the output shaft through countershaft assembly 36; this is done by connecting irst gear ~ to shaft 40 and momentar:ily actuating clutch 48 in the manner descri~ed for fort~7ard lS drive in first gear; and 2) Clutch member 118, of the clutch assembl~ 8~, is then resil.iently moved le~tward by actuator 156 to effect interengag~ment O:e ~aw clutch teeth 118a and 116.
The position of first gear 44 on countershaft 40 and reverse gear 80 on countershaft 7~ allows the vehicle operator to power shift between irst and reverse. Such power shifting is accomplished by moving the shift control lever between drive and re~erse and by programming the control system to momentarily delay or leave reverse clutch 84 engaged and then actuating and deactuating clutches 48 and 82 in accordance with the position of the shift control lever. This facilitates ~uick reverse to forward power s~lifting which ~reatl~
enhances the operator's abilit~ to rock the vehicle as is often necessary in sn~7 and mud conditions.
Looking n~7 at a feature provided b~ the arrangement of the helical teeth of the gears in the transmission, it .is w211 known in force analysis of gears having meshed helical teeth that forces acting on the contacting teeth of each gear ma~ be resolved i~ltO tangential, radial, and axial components. The :~13~133 -18~

tangential force component is useful si.nce it serves to rotate the driven gear~ The radial and axial force components on the other hand are not normally useful;
they merely add to bearing loads and te.nd to bend the shaft that the gear is mounted on.
Looking now at the schematic illustration of FXGURE 5, therein is shown gears 44, 46, and 68 which are mounted on countershaft 40. These gears are provided with helical teeth which are arrayed with a helical hand such that the ~endin~ moments imposed on shaft 40 by axial force components acting on gears 44, 46, and 68 will subtract from bending moments .
imposed on the shaft by radial orce components, thercb~
reducing the net bending forc~s on shaft 40 to a level less than would be caused if the gears had the opposite hana. More specificall~, gears M , 46, and 68 rotate .
counterclockwise when viewed fxom the left encl oE
shaft 40. Gears 44 and 46 are driven gears and gear 68 is a drive gear. The radial forces Erl, fr2, and fr3, acting on these gears all act in the indicated directions and tend to bend or bow the simply mounted shaf-t 40 upward. To counter the bending forces of frl, fr2, and fr3, gears 44, 46, and 6~ each have left hand helical teeth. Since gears 44 and 46 are driven gears, the 25 j axial forces fa~ and ~a2 on the helical contact teeth of each will act to the left, thereby imposing a cloc~-wise bending moment on their respective gears which tends to ~end or bow shaft 40 downward. Since gear 68 is a drive gear, the axial force fa3 will act to the right, thereb~ imposing a counterclockwise bending moment on gear 68 which tends to bend or bow shaft 40 downward. Hence, it may be seen that the axial forces subtract fxom the radial forces to decrease the net bending forces acting on shaft 40. It s~ould be kept in mind tha-t at any given t~ne, only one of gears 44 and 46 are engaged. The magnitude of the axial :Eorces ~19-acting on each of the years 44, 46, and 68 may of couxse be varied by var~in~ the degree of the helical angle on each gear to balance the forces.
Gears 80, 76, 78, and 104 of countersha~t assembly 3~ have helical teeth inclined in the sa~e direction as the gear teeth of countersha-Et assembl~
36 and ~or the s~me reasons given for sha:Et 40 oE
countershaft assembly 36.
The preferred embodimen-ts of the invention have been disclosed for illustrative purposes. Man~ ¦
variations and modifications of the preferred embodiment are balieved to ba within the spi.rit o~ the invention.
The following claims are intended to cover the inventive portions o~ the preferred embodiment and the vari.ati.on and modification within the spirit o~ the invention~

.

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a power shift transmission of the type including an input shaft adapted to be continuously driven by an engine, an output shaft adapted to be continuously connected to a load, and an intermediate shaft means, means mounting said shafts for rotation independently of each other; the improvement comprising:
means operative to synchronize said intermediate shaft means with said continuously driven input shaft while said intermediate shaft means is drivingly disconnected from said output shaft;
means operative after said synchronizing to positively clutch said intermediate shaft means with said input shaft while said intermediate shaft means remains drivingly disconnected from said output shaft;
friction clutch means drivingly interposed between said intermediate shaft means and said output shaft and operative after said positive clutching to power clutch said intermediate shaft means with said output shaft.

2. The transmission of claim 1, wherein, said intermediate shaft means comprises a countershaft and further including:
an input gear nonrotatably fixed to said input shaft;
an output gear nonrotatably fixed to said output shaft;
a driven gear rotatably supported by said countershaft and in mesh with said input gear; and a drive gear rotatably supported by said countershaft and in mesh with said output gear, said friction clutch means being interposed between said countershaft and said drive gear.

3. The transmission of claim 1, wherein said intermediate shaft means comprises first and second countershafts and further including:

input gear means nonrotatably fixed to said input shaft;
output year means nonrotatably fixed to said output shaft;
a driven gear rotatably supported by each countershaft and in mesh with said input gear means; and a drive gear rotatably supported by each counter-shaft and in mesh with said output gear means, and said friction clutch means being interposed between each countershaft and each drive gear.

4. The transmission of claim 1, further including a torque converter, adapted to be continuously driven by said engine and wherein said input shaft means comprises:
a torque converter shaft continuously driven by said torque converter;
a bypass shaft adapted to be continuously driven by said engine, said torque converter and bypass shafts being alternately connectable with said intermediate shaft means and output shaft via said synchronizing and positive clutching means, and said friction clutching means.

5. The transmission of claim 4, wherein said input gear means is nonrotatably fixed to said torque converter and bypass shafts and said intermediate shaft means comprises:
first and second countershafts including at least two ratio gears rotatably mounted thereon, one of each two ratio gears being in mesh with said input gear means fixed to said torque converter shaft and the other of each two ratio gears being in mesh with said input gear means fixed to said bypass shaft, said one ratio gears and said other ratio gears being alternately connectable with the respective countershafts (Claim 5 cont'd...) by said synchronizing and positive clutch means and said countershafts being alternately connectable with said output shaft by said friction clutch means.