CA1158069A - Multiple ratio overdrive transmission - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A multiple ratio automotive vehicle transmission having a hydrokinetic torque converter and a compound plane-tary gear unit that establish a plurality of underdrive ratios, a direct drive ratio and an overdrive ratio, the ratio changes from the first underdrive ratio to a second underdrive ratio from the second underdrive ratio to the direct drive ratio each being established by engagement by a single torque establishing device, brake means for controlling application and release of the torque establishing devices to effect transmission of reaction torque from a reaction element of the gearing to a stationary portion of the mechanism, said controlling means being adapted to establish optimum shift points during ratio changes regardless of the magnitude of the torque being delivered at the instant a ratio shift occurs. The latter is achieved using an orifice control valve which has different sizes of orifice and direc-ting fluid through the different orifices to the shift valve depending on the torque load at the time of ratio shift.

Description

," 11~0~g MUI.TIPLE RATIO OVERDRIVE TRANSMISSION- DIV. III
Our invention comprises improvements in a hydro-kinetic multiple ratio power transmission mechanism having two underdrive ratios, a direct drive ratio, an overdrive ratio and a control system for establishing the various drive ranges and shift patterns; more particularly it is an improve-ment in transmission mechanisms of the kind described in Konrad U.S. Patent No. 3,491,617 and in Egbert U.S. Patent No. 3,31~,307. Those patent disclosures, as well as this disclosure, relate to transmission mechanisms for use with automotive internal combustion engines.
The present application is a division of copending Canadian application ~erial No. 359,390 filed August 28, 1980.
The present invention provides a power transmission mechanism having gear elements including a ring gear, sun gear, planetary pinion and carrier for the planetary pinion.
The gear elements define plural torque delivery paths from a driving member to a driven member to effect multiple ratio torque ratios including an overdrive ratio and a direct drive ratio. Clutches and brakes including a forward drive clutch means and an overdrive brake means control the relative motion of the gear elements and an overdrlve clutch means dellvers input torque to the carrier as an overdrive reaction gear element is braked by the overdrive brake means. The forward drive clutch means, when applied, connects the gear elements together for rotation in unison.
A valve control circuit controls engagement and release of the clutches and brakes and includes a pressure source and an overdrive and direct shift valve means for controlling application and release of the forward drive clutch means as the overdrive brake is released and applied, respectively. A feed passage for the forward drive clutch means communicates with the shift valve means, so that the shift valve means controls application of the forward drive clutch means. A pair of flow control orifices of different size and located in the feed passages and orifice control valve means including a 2-3 backout valve directs fluid through the larger orifice during ratio shifts under torque ,.

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~rom the overdrive ratio to the direct drive ratio and -through the smaller orifice duri,ng a corresponding ratio shift with reduced torque. A source of torque dependent throttle pres-sure is provided and means subjec~s portions of the orifice control valve means to the throttle pressure to actuate the same.
The overdrive brake preferably has a double acting brake servo with a piston that defines in part a servo release presure chamber and a servo apply pressure chamber. The overdrive servo is released when both pressure chambers are pressurized. The shift valve means provides an exhaust flow path for the release chamber when it is shifted to the over-drive ratio position.
The forward drive clutch means preferably is adap-ted to connect the driving member of the mechanism to a torqueinput gear element during forward drive operation. Parallel portions of a forward drive clutch means feed passage commun-icated with the orifice control valve means with one parallel portion providing a greater flow restriction than the other.
The orifice control valve means is in communication with the throttle pressure source and ~esponds to thro~tle pressure to actuate the orific~ control valve means to a position causing fluid to be distributed to the forward drive cIutch means through the reduced flow restriction passage portion with a reduction in throttle pressure below a caIibrated low valve causing the oriflce control valve means to be con-ditioned for distribution of fluid to the forward drive clutch '~' means through the higher flow restriction passage portion.
Other features of the invention will become apparent from the following description, which is made with reference to the accompanying drawings, wherein:
Figures lA, lB and lC show, respectively, the torque converter portion, the main gearing portion and the tailshaft extension housing for an automatic power transmission mechanism capable of embodying the improvements of the invention;
Figure lD is a schematic representation of the transmission mechanism of Figures lA, lB and IC;
Figure lE is a chart that shows the clutch engagement and release pattern during ratio changes for the transmission mechanism of Figures lA, lB and lC;
Figure ~ is a cross-sectional view of a partial assembly o~ a cover and damper which form a part of the converter mechanism shown in Figure lA;
Figure 3 is a cross-sectional view as seen .rom the plane of section line 3-3 of Figure 2;
Figure 4 is a cross-section view as seen from the plane o section line 4-4 of Figure 2;
Figure 5 is a chart that shows the relationship between carburetor throttle angle at the engine and the throttle valve pressure at the transmission;
Figure 6 is a chart that shows the relationship bett~een line pressure and throttle pressure for reverse ~ :~

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drive operation, first and second speed operation and cutback operation in third and fourth ratios;
Figures 7A and 7B show a control valve circuit for controlling the ratio shift pattern for the transmission mechanism of Figures lA, lB and lC;
Figure 8 is a subassembly view of the valve arrangement for Figures 7A and 7B illustrating the valve positions during initial engagement of the forward drive clutch;
10Figure 9 is a partial drawing of the valve circuit showing the valve positions during start-up in the manual-low range;
Figure 9A shows an enlarged view of the low servo modulator valve seen in Figure 9;
- 15Figure 10 shows the control valve circuit condition for second ratio lockout in the manual-low range;
Figure lOA is an enlarged view of the 2-1 scheduling valve shown in the circuit of Figure 10;
20Figure 11 is a partial valve diagram of the valve system when it is conditioned for~ distribution of a scheduling pressure to the 1-2 shift valve; :
Figure llA shows the operation ~of the 2-1 scheduling valve during the mode of operation of Figure 11;
Figure 12 shows a partial valve diagram illustrating the reverse brake servo and clutch when the valve system is conditioned for reverse drive range;
Figure 13 shows the ~throttle valve system in combination with the~valve circuit as a~whole;
: Figures 13A, 13B and liC show a subassembly view of the throttle valve elements for the system of Figure 13;
Figure 14 is a partial valve diagram showing -~ 35 the modulated mv pressures used for ,delaying upshlfts to the second ratio, to the third ratio and to the fourth overdrive ratio;
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Figures 14A and 14B show the operation of the

2-3 shift valve and the 3-4 shift valve, respectively, during delay of the upshifts;
Figure 15 shows the valves conditioned for upshift control in the overdrive range when the gearing is adapted for low speed ratio operation;
Figure 16 is a view similar to Figure 15 with the valves in the overdrive range and conditioned for an automatic 1-2 upshift;
Figures 16A, 16~ and 16C show the function of the 1-2 capacity modulator valve and the 1-2 accumulator valve;
Figure 17 shows a valve system in the overdrive range when it is in condition for a 2-3 upshift at part throttle;
Figure 18 is a partial view of the valve system in the overdrive range when it is in condition for a 3-4 upshift;
Figure 19 shows a kick-down valve system when the throttle valve is advanced to its maximum setting;
Figure 20 is a view of the valve system~when it is in condition for manual-low, first gear: ratio operation;
Figure 21: shows the valve system when it is in 2S condition for first gear engagement in the overdrive range at closed throttle;
Figure 22 shows the valve system when it is in condition for second~gear: operation in part throttle in the overdrive range;
Figure 23 shows the valve system when it is in condition for third:gear operation at 3/4 engine throttle setting in the overdrive range;
~Figure 24 is a view of the valve system when it is in condition for third gear operation at 3/4 engine 35 throttle in drive range number 3;
Figure 25 is a view of the valve system when it is in condition for fourth gear operation at part:
throttle;

`` ll~t)B9 Figure 26 is a view of the valve system when it is in condition for reverse drive operation at initial engagement at a closed engine throttle;
Figure 27 is a view of the valve system when it is in condition for manual low operation at closed throttle above the 2-1 downshift speed;
Figure 28 is a chart that shows the orifices in the 2-3 backout valve that are effective ~or various driving conditions indicated in the chart;
Figure 29 is a partial view of the valve system showing the 2-3 capacity modulator valve and the orifice control valve during closed throttle engagement of the direct drive clutch, as well as during closed throttle clutch engagement under torque;
lS Figure 30 is a view similar to Figure 29 showing the valve positions during a 4-3 torque demand downshift; and Figure 31 shows a coasting downshift condition for the orifice control va}ve on the 2-3 capacity modulator as the downshift occurs from the overdrive ratio to the direct drive ratio.
The operation of the converter, the gearing and - the clutch-and-brake engagement and release sequences will be described with reference to Figure lA through~lE.
Reference numeral 10 in Figure lA shows the end of an engine ~cranksha~t for an internal combustion engine.
Reference numeral 12 generally designates a unitary cast aluminum ~ousing which encloses a hydrokine~tic~torque converter 14 and a planetary gear portiôn~ 16. A
tailshaft extension housing 18 is mounted on the~
right-hand end of the housing 12 and is secured thereto bv bolts 20.
~ Crankshaft lO is bolted at 22 to impel1er drive ~;
plate 24, which carries~a starter ring gear 26 on its periphery. Impeller housing 28 is bolted~at a~radially outward location 30 to the drive plate 24. Impeller housing 28 encloses a bladed turbine 32 and a bladed stator 34, the latter being situated between ~the flow exit region of the : ' ~ ' ' , :

, 0 ~ g turbine 32 at the ~low entrance re~ion o~ the impeller blades sh~wn at 36. The hub of impeller housing 28 is drivably connected to impeller suppor~ sleeve shaft 38 which is journallea in an opening formed in the pump s hou~ing 40. ~ou~ing 40 is ~ecured by bolts 42 agai~st an internal shoulder 44 ~ormed in the transmissi~n hous-ing 12. ~ ~ta~or support sleeve shaft 46 i~ disposed within impeller 31ee~e shat 38. It form~ a part of p~p cover plate 48. Bladed stator 34 is mounted on 10 the stator sleeye sha~t 46 by overrunning brake assembly .50, the latter permitting freewheeling motion of the bladed stator ~4 in the dixection o~ rotation o~ the impeller but preventing rotation of the bladed stator in the oppo~ite directi~n~
TurbLne 32 include~ an outer shroud 52 which is secured to turhine hub 5 4, which in turn is splined to turb~ne ~leeve ~ha~t 56 located concentrically within the slee~e shaft 46. Direct drive shaft 58 is splined at 60 to the hub 62 of an internal damper assem~ly 64.
This damper assem~ly 64 forms a resilie~t co~nection ~et-ween the direct dri~e shaft 58 and the impe}ler hou~ing 28.
~ he damper asse~bly can best be seen by reer-ring ~o Figures 2, 3 and 4. It includes a spring retainer plate 66 which has recesses on one side thereof, a~ seen at 68, f~r retai~ing damper springs 70. The hub 62 form~
a part of a radially outward drlve pl~te 72 which is formed with angularly di posed openings 74 for receiving the springs 70. The outar margin o~ plate 72 is formed with recesses or no~ches 76 which receive drive tabs 78 formed on drive plate 80, the latte~ in turn being spot welded at 82 to the inner wall of the impeller housing. -Drive plate 80, the radial plate 72~and the end plate 66 are joined together by ri~ets 84 to form a unitary assembly. The plate 8~ and the plate 66 form an assembly that is adapted to ve angularly with respect to the plate 72. That movement is resisted by the springs 70 .

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which are ~eated with a preload on the ends ~ the spring openings i4. The plate 72 is provided with eLongated slots 86 through which the rivets or pins extend thereby accommodating relative motion between the plate-~ 78 and 5 66 with respect to the plate 72.
~ fric~ion washer 88 with friction material on one side thereof is urged ~nto engagemen~ with the damper hub 62 by a circular Belleville ~pring wash~r so situated betwQen the hub 62 and the plate 66. Friction material 92 is formed also on the oppo~ite side of the hub 62.
Thus the 3ell~Yilla washer 90 provid~Y a so-called coloumb effect to pro~ide fric~ional energy absorption whiGh, in combination with t~e damping effect o~ the spri~g~ ?0, provide~ an inertia damper for cushioning the ratio shi~t ~ro~ a ~ydrokinetic drive to either a partial or a ~echa~aldriv~ aq the transmissio~ ls~in condition for direct driVQ operation or o~erdrive operation.
A wa~her 88 ha~ tabs that are received in rece~ses 94 formed in a c~ntxal opening 96 of the plate 66. The right-hand end o~ the tur~ine sleeve ~haft 56 i~ splined at 98 to the hub of clutch member 100, which is journalled at 102 on 3tationa~y support sleeve sha~t 104 that forms a part of pump cover plate 4a bolted by bolts 106 to the pus:lp housing 40. Clutch member 100 de~ine5 an annular cylinder 108 ~or forward clutch assembly 110. An annular pi~ton 112 iq situated in the cylinder 108 and defines a pressure cham~er that can be pressurized selec~i~ely by th~ control y~tem to effect engagement of the clu~ch assembly 110. Clutch mem~er 100 is pro~ided with internal spl~nes that carry externally splined olutch discs 114. These register with internally splined clutch discc 116 carr~ed by externally splined clutch member 118, ~ ~:
the latter in turn being splined to sun gear slee~e sha~t 120 for the planetary gear unit:16. Clutch return spring 35 122 situated between the clutch member 118 and the piston 112 normally urge the piston 112 out of engagement with the clutch disc , .
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Clutch member 100 is provided also with an externally splined portion that carries in~ernally splined clutch discs 124. The~a are arranged in regi5try with externally splined clutch disc3 126 that are carried by an internally ~plined porkion o~ the rever~e clutch element 12a, which is journalled rotatably ~n the qtation-ary sleeve sha~t 104. Clutch discs 124 and 126 form a part of a reverse clutch asgembly identified by re~erence character 130.
Reverse clutch element 128 deines an annular - cyli~der 132 whic~ receive~ an annular piston 134. Belle-ville spring lever 13~ provides a ~orce multiplying con-nection between the piston 134 and the pres~u~e plate 138 that acti~ate~ the clutch discs.
A21 intermediate clutch or brake assembly 140 comprisas externally 3p~ined friction disc~ that register with splines or groo~es formed in the housing 12. A
stationary bac~up ring ~or the intermedi~te clutch or brake, which i~ shown at 141,engages an in~ernal shoulder on the housing 12. Internally splined ~riction di~c~ of the clutch or brake a.~3embly. 140 are carried by an exter-nally splined overrunning brake race 142 of an overrunning brake a~qembly 144. The inner rac 146 for the brake assem~ly 144 i~ secured to the reverse clutch element 128.
The friction discs for the clutch ar brake assem~ly 140 can be applied by an annular piston 148 located in an annular cylinder lS0 formed in the pump housing 40.
Whe~ fluid pressuxe is admit~ed to the annular 30 cylinder 150i the forca developed on the piston 148 applies the intermediate clutch or brake thereby anchoring 5un gear 152 of the planetary geax assemb}y 16. Sun gear 152 ~ con-nected to reverse clutch element 128 through a dri~e shell 154, which is a sheet metal torque transfer member surround-ing th- iorward clutch sJem~ly llO.

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B g The compound planetary gear assem~ly 16 includa~,in addition to ~he ~un gear 152, a sun gear 156 which is of a smaller pitch diameter than the sun gear 152. A ~ir~t se~ of planeta~y pinions 158 engages ~un gear 152 and a 3econd set of planetary pinions 160 engage~ the sun gear 156. The pinions 158 and 160 engage each other. Al~o pinion~ 158 engage ring gear 162. Both sets of pinions 15~ and 160 are journalled on plnion sha~ts that are ~h~wn at 164 and 166, which ~orm a part o~ carrier assembly 168.
A bra~e drum 170 i~ formed integrally wi~h the carrier a~s`embly 16~. It is surrounded ~y multiple wrap brake band 112. A ~luid pressure operated bxake ser~o which is shown schema~icalLy in the circuit drawings to be described later, is adapted to apply and release the brak~ band 172. The reaction torque for the braXe band 172 i~ absorbed by the transmission housing 12.
An overrunning bxa~e 174 i9 ~ituated in series di~position with respect to ~he brake band 172. It 20 includaq an outer race 176 carried by brake drum 170, an inner raca L78 and overxunning bra~e rollers 180 that register with ca~ urface formed in the race 176. Inner race 178 is secured to the housing I2 by brake suppor~
plate 182.
Brake drum 170 forms a part o~ a compound plane- -~
tary gear carrier 168. Carrier 168 includes a sleeve that is journalled on sun gear shaft 18Ç. It includes also an end plate 184 which is journalled on sleeve la7 which formc a part of direct drive clutch element 188.
Sle~ve 187 is splined directly to the direct drive shaft 58. Plate 184 is splined also to dire~t dri~e clutch element l90, which carrïes inter~ally splined clutch discs 192 which are situated~adjacent to exte~lly splined disc }94, the latter being carried by element la8.
: 35 Element 188 defines an annular cylinder 196 within which is situated an annular piston 198 which is adapted to ': :

g engage the discs 192 and 194 when fluid pressure is admitted to the cylinder 196. Piston return spring 200 urges normally the piston 198 to A clutch release position.
output shaf~ 202 is provided with an extension 204 that is received within sleeve 187 and journals the clutch element 188. Shaft 202 is supported by a bushing within a ~earing sleeve 206 which forms a part of the end wall 208 of the housing 12.
The converter and gear system disclosed in Figures lA, lB and lC is illustrated schematically in Figure lD. The mode of operation of the converter and gear system can best bé understood by referring to Figures lD and lE. To condition the mechanism for 15 operation in the lowest speed ratio, it merely is necessary to engage the forward clutch identified by the symbols Cl in Figures lD and lE. At that time turbine torque from the converter 14 is distributed through the clutch Cl to the smaIl sun gear 156. The:overall speed 20 reduction that occurs is 2.4:1 as the ring gear drives the output shaft, and the carrier torque is: absorbed through the overrunning clutch ~174 (C4). If torque reaction in the opposite direction is desired, it merely is necessary to engage brake band 172, which is the 2S driving mode that is referred to in the following description of the control circuit as the manual low drive range.
To effect an automatic upshift from the lowest ratio to the intermediate second speed ratio, it merely 30 is necessary to engage the intermedlate clutch or brake 140. Reaction torque then is distributed from reaction sun gear 152 through the overrunning clutch~or brake 144 - to the engaged friction 140 (C5). The overrunning clutch 174 (C4) freewheels~ under these conditlons, ~thus 35 providing an automatic pick-up shift. A speed ratio change to the third speed ratio, ~hich is approximately a direct drive is achieved by engaging the direct drive clutch 192 (C3). Clutches 192 and 110 being engaged simultaneously, the transmission mechanism is in 6 ~

condition Eor operation with a 1:1 ratio, except for the effect of converter strip, since all the elements of the gearing rotate together in unison. At that time, however, torque is distributed directly from tne input shaft 10 to the carrier through the direct drive clutch 192 ~C3). The balance of the torque is distxibuted hydrokinetically through the turbine 14 since the turbine of the converter 14 is connected through the forward clutch 110 (Cl) to the small sun gear 156. Because only a portion of the driving torque is distributed hydrokinetically, the resulting increase in the overall mechanical efficiency of the transmission is improved in comparison to transmission mechanisms of the kind disclosed in the previously described reference patents lS where the hydrokinetic torque converter is fully active in each of the four driving ranges.
During a ratio change from the second ratio to the third ratio, it is necessar~y to engage only a single friction device, namely the clutch 192 (C3). The clutch 20 overrunning clutch 144 (C6) automatically freewheels as the clutch 192 (C3) is engaged. Thus an automatic pickup shift from the second ratio to the third ratio is achieved in a nonsynchronous fashion. The valve mechanism that is used ~to establish this shift will be 25 described subsequently.
A ratio change from the third direct drive ratio to the overdrive ratio is obtained by engaging the overdrive brake band shown at 210 in Figure lA and by releasing the front clutch. The corresponding reference 30 symbol in~Figure lD and lE is Bl.
The overdrive brake band 210~surrounds clutch member 130; and since clutch member 130 is connected through the drive shelI 154 to the larger sun gear 152, sun gear 152 acts as a reaction point during overdrive 35 operation as torque is delivered from the engine crankshaft through the shaft 58 and through the clutch 192 (C3) to the carrier for the planetary gear unit.
This overruns the ring gear 162 and the output shaft 202 relative to the speed of the crankshaft.

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Reverse drive is obtained by engaging clutch 130 ~C2) and engaging brake band 172 (B2). With the carrier braked by the brake band B2, it acts as reaction point and the sun gear 152 acts as a torque input element thus driving the ring gear 162 in a reverse - direction.
The control valve system for controlling the ratio changes and driving modes for the transmission mechanism of Figures lA, lB and lC is illustrated schematically in Figures 7A and 7B. The function of the various valve elements of Figures 7A and 7B will be described subsequently with reference to .Figures 8 through 27. For purposes of identifying the various valve elements of the circuit, refer~nce now will be made in a general fashion to Figures 7A and 7B.
The source of pump pressure for the control circuit is pump 212. It comprises internal pump gear teeth 214 which mesh with the external pump gear teeth for pump 216, the gear teeth 216 being driven by impeller 20 support sleeve shaft 38 as shown in Figure lA.
The pressure developed by the pump 212 is regulated by the main pressure regulator valve 218. A
first regulated output pressure from the main oil pressure regulator valve 218 is distributed to the 25 converter 14. The fluid supplied to the converter 14 circulates through the converter and transfers to cooler 220 and to the lubrication circuit for the transmission mechanism. Converter relief valve 222 located on the upstream side of the converter 14 prevents overprèssure 30 in the converter torus circuit.
One of the elements of the control circuit that :controls the timing of the ratio change from direct to ~:overdrive is the aacumulator 224 which has a piston, one side of which is subjected to the apply pressure on one 35 side of an overdrive servo 227 for brake band 210, the other side of which is subjected to pressure regulated by the main regulator valve 218. ~
A ratio change from the lowest ~atio to the intermediate ratio occurs upon application of the ~' '' ~ '' '.
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intermediate clutch 140, the shift quality and timing of that shift is controlled by 1-2 capacity modulator valve 226 and by the 1-2 accumulator valve 228. During operation in the manual low range to be de~cribed, a ratio change from the intermediate ratio ~o the lowest ratio is timed by 2-1 scheduling valve 230, which is a regulator valve that distributes a pressure to the lower end of the 1-2 shift valve 232, the latter in turn controlling distribution of pressure to the intermediate clutch 140 through the 1-2 capacity modulator valve.
Ratio changes from intermediate to the direct drive ratio are controlled by the 2-3 shift valve 234, which is in communication with manual valve 236, the latter receiving regulated pressure from the pump and distributing it to the 2-3 shift valve and the 1-2 shift valve. The manual valve selects the drive mode that is desired, as will be explained subsequently.
Ratio changes from the direct drive ratio, which is a split torque drive as explained previouslyj to the overdrive ratio is controlled by 3-4 shift valve 238 through the intermediary o~ the 3-4 shuttle valve 240 and the overdrive servo regulator valve 242.
~ Reduced throttle and zero throttIe ratio changes from the third ratio to the fourth ratio are 25 controlled by 3-4 upshift; pressure control backout valve 244, which is sensitive to throttle pressure received ~rom throttle valve pressure limit valve 246. A reduced engine throttle or zero~engine throttle ratio change~from the second~ratio to the third ratio is controlled by 2-3 30 upshift pressure control backout valve 248 which regulates the timing of the engagement and disengagement~
of the direct clutch 192.
The timing and shift timing of the ratio change from the~intermediate ratio to the direct drive ratio 35 upon movement of the 2-3 shift valve, the quality of the shift being control~led in part by 2-3 accumul~ator 252.~ A
speed signal which ;is used for the various shift functions is developed by a governor assembly 254 which, as explained ;previously, is drivably connected to the :
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1 15~0~9 output shaft 202 shown in Figure lC. That signal cooperates with a torque signal referred to in the sp~cification as a throttle valve signal which is developed by throttle valve 256. The torque signal received from the throttle valve 256 acts upon the shit valves, more particularly the modulator valves for the shift valves. A ratio change from the second ratio to the direct drive ratio is timed by the output signal received from 2-3 modulator valve 258 which regulates the TV limit pressure received from the TV limit valve 246 before it is distributed to the spring side of the 2-3 shift valve 234. Similarly, TV modulator valve 260 controls the magnitude of the throttle pressure made available to the 3-4 shift valve 238, thus providing the 15 necessary shift delay during acceleration, The 2 3 throttle pressure modulator valve 258 also is directed to the 1-2 shift valve 232 and similarly delays the 1-2 upshift.
The pressure made available to low-and-reverse 20 brake servo 130 is regulated by a low servo modulator valve 262 which reduces the magnitude of ~he pressure in the servo as the mechanism is conditioned for low speed ratio operation but which allows a pressure build-up to occur during reverse drive operation. Brake band 172 is 25 applied both in low and reverse.
Referring next to Fiyure 8, there is shown a composite view of the valve elements and have indicated by appropriate shading those elements that are actuated and which are pertinent to the conditioning of the~
30 mechanism for forward drive operation following initial engagement of the forward drive clutch. The pump 212 distributes pressure to the main regulator valve 218 which comprises a valve spool having three spaced valve lands 264, 266 and 268. The valve spool regulates the 35 pressure at a value that is determined by the value of the force of springs 270 acting in an upward direction on the valve spool. That force is complemented by the forces distributed to the valve spool by oil pressure booster valve 272, wrlch comprises three spaced velve ,~

, O ~ g lands 274, 276 and 278 of progressively decreasing diameter. Pressure is regulated by the main regulator valve 218 and distributes the regulated pressure to passage 280. The pressure is made available to the main pressure regulator valve 218 in passage 282, which extends to the converter 14. Passage 280, which contains regulated pressure, communicates through a check valve control orifice plate 284 with the 3-4 accumula~or which comprises a piston 286 that cooperates with accumulator chamber 288 to define opposed pressure chambers. When the lower pressure chamber is pressurized, the piston 286 moves upwardly against the force of aGcumulator spring 290. Pressure is distributed to the upper end of the accumulator piston through passage 292.
Line pressure passage 294 extends from regulated line pressure passage 280 to the manual valve 236 which includes a valve spool 296 having valve lands 298, 300 and 302. Valve spool 296 can be~shifted to any one of the positions indicated in Figure 8 by reference characters P, R, N~ D, 3 and 1. When the manual valve 236 is positioned as-shown in Figure 8, it is capable of conditioning the control valve system for automatic operation in any of the four forward drive ranges.
Control pressure is distributed to the manual valve 236 from line 280 through passage 294 to the space between the valve lands 296 and 298, which causes control pressure to be distributed to throttle valve 256 and to the 2-3 shift valve 234. Pressure is distributed through the 2-3 shift valve 234 through passage 304 and through~
that valve to passage 306 which extends to the oil pressure booster valve 272. The pressure in passage 306 acts on the differential area of lands 274 and 276 which produces a force that augments the force of the valve spring 270 so that upon a 2-3 upshift the regulated 35 pressure made available to the control circuit is reduced to a value that is not in excess of the pressure that is required to maintain direct clutch engagement.
Line pressure from the main pressure regulator valve 218 is distributed also through the~ manual valve ` - - ' - ' .
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g 236 to passage 308 which extends to the governor assembly 254 and to the 3-4 shift valve 238, That pressure passes through the 3-4 shift valve 238 to the orifice control valve 250, passage 310 providing the fluid communication between the 3-4 shift valve and the orifice control valve. Pressure in passage 310 passes directly from the orifice control valve 250 to the 2-3 backout valve 248 through passage 312. The fluid connection on the downstream side of the 2-3 backout valve 248 is provided by passage 314 which extends to the forward clutch 110 and pressurizes the annular piston for the forward clutch. The same pressure is distributed through check valve 316 to the upper side of piston 318 for the 2-3 accumulator 252. The pressure in the accumulator chamber on the upper side of the piston 318 develops a force that opposes the accumulator spring ~orce of spring 320. As the clutch pressure builds up in the forward clutch, corresponding pressure builds up on the top side of the piston 318 and strokes the piston 318 in a downward direction against the opposing force of the spring 320 thus providing a gradual pressure increase that cushions clutch engagement.
An orifice A (see Figures 29 - 31) is located in passage 314 and pressure distributed through the 2-3 backout valve 248 from passage 312 to passage 314 must pass through that orifice, which controls the rate of engagement of the forward clutch.
Regulated line pressure is distributed to the governor assembly 254. This governor assembly 254 3Q comprises a pair of spaced valve lands 322 and 324 of differential area. It includes also an exhaust orifice 326 controlled by valve land 324. A valve spring urges the valve lands in a radially inward direction, thus producing a modulated pressure in governor pressure 35 passage 327. This is a measure of the rotating speed of the output shaft 202. For a particular description of a governor assembly of the kind shown in Figure 8, reference may be made to U.S. patents Nos. 3,431~,928;
2,711,749; 2,889,844; 2,911,987; 3,048,184 and 3,139,102.
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0 ~ 9 Governor pressure in passage 327 is distributed to the upper end of both the 1-2 shift valve 232 and the upper end of the 3 4 shift valve 238. Governor pressure is distributed also through governor pressure passage 330 to the lower end of the valve spool for the 2-3 shift valve 234.
Reference will be made in the following description of Figures 9 through 27 to the various control functions. Some of these functions are similar to those functions described in prior art U.S. patents Nos. 3,336,815; 3,424,037; 3,327,554; 3,400,612;

3,593,598; 3,095,755; 3,446,098; 3,393,585 and 3,295,387.
Those functions that are not described in those prior art patents will be described more particula~ly in this lS specification. More particularly this specification will describe the function and operation of the throttle valve system and the relationship of the throttle valve system to the 2-3 backout valve 248 and the 3-4 backout valve 244, the fail-safe feature of the throttle valve system 20 and the throttle pressure versus travel characteristic of the throttle valve assembly. It will describe -also the function of TV limit valve 246, the 3-~ bac~out valve 244, the 2-3 backout valve 248, and the 2-3~ capacity modulator 248 and its'relationship to the 2-3 accumulator 25 252. The orifice control valve 250 which acts in combination with the 2-3 capacity modulator valve 558 and the 2-3 accumulator 252 also will be described in particular.
The overdrive brake band is applied by servo 30 227 as explained previously. That servo includes a piston 328 (see Figure 7A) positioned in an overdrive servo cylinder in cooperation with a cylinder to define two pressure chambers indicated in Figure 7A as the release pressure chamber and the apply pressure chamber, 35 the former being above the piston 328 and the latter being below the piston 328. Pressure is distributed from the manual valve 236 when it is positioned as shown in Figure 8 to the~2-3 shift valve 234 through passage 331 and through the 2-3 shi~t valve 234 to passage 332 and ,- :
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' ,' a ~ s the release side of the servo piston 328 thereby disengaging the overdrive servo 227 and maintaining it in a~ cff position. Line pressure from the manual vaLve 236 is dis~ributed also through passage 334 to the 1-2 accumulator valve 238 and through connecting passage 336 to the 1-2 shift valve 232. The presence of pressure in passage 334 will cause the 1-2 accumulator valve 228 to be stroked in an upward direction to condition the accumulator valve 228 for controlling the subsequent upshift from the low ratio to the intermediate ratio as will be explained subsequently.
The 2-3 backout valve 248 comprises a valve spool having spaced valve lands 338, 340, 342, 344 and 346 . A valve spring acts on the land 346 to urge 15 normally the valve spool of the 2-3 backout valve 248 in the left-hand direction as seen in Figure 8. When it is in that position, communication is established between passages 312 and 314 through the orifice A (Figures 29 to 31) as explained previously. In Figure 9, there is shown 20 the condition of the valve elements for a control system when the manual low valve 236 is shifted to the manual low start position No. 1. At that time regulated line pressure from passage 294 is distributed to passage 308 through the space between valve lands 298 and 300, thus 25 controlling the application of the forward clutch 110 as explained previously wi~h reference to Figure 8. When the manual valve spool 296 is positioned as shown, however, pressure is distributed around valve land 300 to line pressure passage 348 which extends to the 1-2 shift~
30 valve 232. Shift valve 232 comprises a valve spooI
having a valve land 350 and a valve land 352 which accommodate transfer of pressure from passage 348 to passage 354 extending to the low servo modulator valve 262.
Modulator valve 262 is best seen in Figure 9A.
It comprises a valve spool having lands 356 and 358 of differential diameter. The pressure of pas~sage 362 creates a pressure force on the differential diamèter which opposes the force of valve sprlnq 36'. Thls :'`

.

produces a regulated reduced pressure in passage 362 on the downstream side of the valve 262, reverse pressure passage 364 acting at this time as an exhaust port. The regulated pressure in passage 362 is distributed to the low and reverse servo 172. The reduced pressure in passage 362 acts on the top of land 358 ko oppose the force of the spring 365. Thus the low-and-reverse servo becomes applied with a reduced pr0ssure that is sufficient to maintain manual low operation. The pressure that is applied to the low and reverse servo 172 is lower than the pressure that is necessary for reverse drive operation. Hence, excessive pressure is not used because of the operation of the low servo modulator valve 262. The overrunning brake 174 will not overrun when the band is applied. Thus the transmission is capable of engine braking. When the valve system is in a condition as shown in Figure 9, the mechanism is incapable of shifting to the second ratio. This function can be understood best by referring to Figure 10. As seen in Figure 10, the control pressure is made available to passage 348 and is distributed to the 1-2 shift valve 232. It passes through the 1-2 shift valve 232 to the passage 354, as explained previously. Pressure in passage 348 is distributed through 3-way check valve 366 to passage 368 to the lower end of the 1-2 shift valve 232.
The 1-2 shift valve 232 includes, in addition to the valve lands 350 and 352, a valve land 370 of larger diameter than the diameter of land 352, a land 372 30 and a land 374. Pressure in passage 368 is distributed to the lower end of the land 374 and urges the 1-2 shift valve 232 in an upward direction against the opposing force of governor pressure acting on the upper end of the land 370. Line pressure also is distributed from passage 35 348 and through passage 376 to the 2-3 TV modulator valve 258. It passes through that valve to the differential area of lands 352 and 370, thus contributing to the upward force acting on the 1-2 shift valve spool 232.

'" I 1 ~0~9 Pressure passes through passage 354 to the 2-1 scheduling valve 230 as described earlier. Pressure from passage 368 is distributed also to the lower end of land 374 to supplement the upward hydraulic force on the 1-2 shift valve 232. When the 2-1 scheduling valve is in the downward position, line pressure from passage 352 is distributed directly to passage 377, which causes the 1-2 shift valve 232 to move in an upward direction and to be locked in that position. For purposes of clarity the 2-l scheduling valve 230 has been shown in an enlarged form in Figure 10A~ The 1-2 shift valve 232 then will be incapable of effecting a ratio change to the intermediate ratio regardless of the magnitude of the governor pressure acting on the upper end of the land 370.
If the manual valve 236 is moved to the manual low position from either the overdrive range of the direct drive range, the transmission will shift first to the second ratio, assuming that the vehicle is travelling at a cruising speed in third or fourth ratio. As the 20 speed decreases; an automatic downshift will occur to the first ratlo. To control this shift the 2-l scheduling valve 23Q shown in Figure 11 and in Figure llA is used.
The 2-l scheduling valve 230 determines the pressure under which a 1-2 shift valve wilI move to the downshift 25 or first ratio position.
In Figures 11 and llA it i5 seen that the 1-2 shift ualve 232 first is moved during cruising in the third ratio or the fourth ratio to the upshift position under the influence of governor pressure. When it is 30 upshifted, passage 354 ;becomes exhausted through exhaust orifice 380 in the 1-2 shift valve. Passage 376, which~
is pressurized with line pressure as explained~ with reference to Figure~lO, communicates with passage 382 through the 2-3 modulator valve~ 258, thus distributing ` 35 pressure to the 2-l scheduling valve 230. The pressure~
acts on the differential area of land 384 and 386 of~the 2-1 scheduling valve~ 230. The force produced by ~the pressure on that diffential area is opposed by the force of valve sprlng 388~ Thus the valve 230 acts as a ~` :
~:
~ , , ~

`

regulator valve to produce a 2-1 scheduling valve pressure in passage 3so which is distributed to the lower end of the 1-2 shift valve land 374. The 1-2 shift valve is controlled by the magnitude of the 2-1 scheduling valve pressure in passage 390, line pressure is made available to the 2-1 scheduling valve through passage 354.
With the regulated pressure acting on the shift valve land 374, the shift valve will move to tha low ratio position. Thus the transmission will be locked in the low ratio as explained with reference to Figure 10.
Full line pressure thus acts on the lower end of land 374 since passage 382 is brought into communication with passage 390 and with passage 377.
The 2-1 scheduling valve acts as a pressure regulator for producing a shift point establishing pressuxe for the 1-2 shift valve 232 as the vehicle is coasted from a cruising condition to a low speed condition following movement of the manual valve to the 20 number 1 range. Upon a decrease in governor pressure to a calibrated value, the 2-1 scheduling valve 230 functions merely to transmit line pressure to the lower end of the land 374 as shown in Figures lOA and 10.
Figure 12 shows the condition of the control 25 circuit` when it is in a condition for reverse drive operation with the reverse clutch 130 engaged and the low-and-reverse brake band 172 applied. The manual valve 236 is shifted to the position R as indicated in Figure 12. Line pressure from the line pressure llne 294 is 30 transferred through the manual valve space between lands 300 and 302, thus pressurizing passage 348 which extends to the space between the lands 350 and 352 of the 1-2 shift valve 232. That pressurizes passage 354 which ~ extends to the low servo modulatox valve~ 262. Pressure 35 is distributed also from line pressure passage 294 through the manual valve 236 to the passage 394, which also extends to the low servo~modulator valve 262. A
fluid connection to the low servo modulator valve 262 and the 1-2 shift valve 232 at this time is established by the pressurized passage 354. The output side of the low servo modulator valve 262 communicates with the low-and-reverse brake servo 172 through passage 362 previously described, so that the low-and-reverse servo 172 is pressurized with a maximum line pressure, unreduced by the low servo modulator valve 306.
Passage 394 which is pressurized upon movement of the manual valve 236 to the reverse position R
communicates with reverse clutch feed passage 396.
Passage 394 also communicates with the oil pressure booster valve 272 and acts on the differential area of lands 276 and 278, thereby supplementing the force of the valve spring 270 to produce an augmented circuit pressure during operation in reverse drive.
In Figures 13, 13A, 13B and 13C, there is shown the throttle valve system and its relationship to the other elements of the circuit. Throttle valve assembly 256 is supplied with line pressure through passage 294, as explained previously. Throttle valve pressure passage 400 communicates with the output side of the throttle valve assembly 256. The throttle pressure in passage 400 is distributed to the left hand side of 2-3 backout valve 248 and acts on the end of valve land 338 to urge the 2-3 backout valve in a right hand direction as seen in Figure 13. Passage 400 distributes also throttle pressure to the lower end of the 3-4 TV modulator valve 260 at the base of the 3-4 shift valve 238. The 3-4 TV modulator valve 260 is a valve spool that is subjected to the spring force of valve spring 402 in the 3-4 shift valve assembly. The same spring 402 acts in an upward direction on the 3-4 shift valve 238. Passage 404 communicates with the valve chamber in which the 3-4 TV
modulator valve 260 is situated and extends to the orifice control valve 250. In the condition shown in Figure 13, passage 404 is exhausted through the orifice control valve 250 and through passage 406, which communicates with passage 408 through 3-way check valve 410, passage 408 being exhausked through the manual valve exhaust port 412. Thus the 3-4 TV modulator valve 260 80Bg modulates the pressure in throttle pressure passage 400 ~o produce the shift pressure signal in passage 414 which acts on the lower end of the 3 4 shift valve 238 to supplement the force of the valve spring 402.
Passage ,400 communicates directly with the TV
limit valve 246. This valve comprises a valve spool 416 having spaced valve lands which provides communication between passage 400 and the TV limit pressure passage 418 and which provides also a differential diameter on which the output pressure in passage 418 may act to oppose the force of the spring 420.
The TV limit valve 246 establishes an upper limit for the pressure in passage 418. When the pressure in passage 400 exceeds an established Iimit d,etermined by the calibration of the TV limit valve 246,~ the vaIve spool 416 will move upwardly so that it begins to regulate and produce a modified pressure in passage 418.
Passage 418 extends to the 2-3 TV modulator valve 258 located at one end of the 2-3 shift valve 234. : Valve 20 spring 422 acts on the 2-3 shift valve:as well as the 2-3 modulator valve 258. The 2-3 modulator valve 25~ thus is capable of establishing a modulated pressure in passage 424, which acts:on the upper end of the 2-3 shift valve 234 and on the differential area of the 1-2::sh~lft valve 25 defined by valve lands~352 and 370, thus producing a shift delay force on the 1-2 shift valve~ Under the condition shown in Figu:re 13, the exhaust path: fo~r passage 424 is passage: 376 since it communicates wi:th exhausted passage 408.
The TV limit pressure in passage 418 is distributed:also:to one end of~the 3-4 backout valve 244.
That valve comprlses a valve spool :having differential~
diamèter valve lands 426 and 428. The TV limit valve ~' pressure in passage 418 is distributed also to the~:lower end of the oil pressure booster valve 272 and acts on the differential diameter of lands~ 274 and 276, : t-hus providing an:increased circuit pressure upon an increase in the value of the throttle pressure. The influence of the throttle pressure on the circuit pressure, however,~

., , `
' , ' ', 8~9 is limited by the TV limit valve 246. Line pressure from the pump is supplied to the throttle valve 256 whenever the engine is running and throttle pressure is developed in passage 400. As soon as the engine throttle is opened slightly, the ~hrottle pressure tha~ is developed ir.
passage 400 produces a force on the 2-3 backout valve 248 that causes the 2-3 backout valve 248 to move in a right-hand direction. The upper limit for the throttle pressure that is established by the TV limit valve 246 in one operating embodiment of this invention is about 85 psi. If the TV pressure falls below 85 psi, it will distribute unregulated TV pressure to the passaga 418.
If the TV pressure in passage 400 exceeds 85 psi, the pressure in passage 418 will not rise above that value.
The TV pressure is applied also to the 3-4 TV modulator valve 260 to produce the 3-4 shift and the output of the TV limit valve 246 is applied to the 2-3 modulator valve 258 to produce a modulated TV pressure for controlling the 2-3 shift and the 1-2 shift. The 3-4 backout valve 244 also is controlled by the TV pressure at closed throttle when the TV pressure in passage 400 is zero.
The 3-4 backout valve regulates the pressure in the overdrive servo release chamber as apply pressure is applied to the overdrive servo as will be explained subsequently, thereby cushioning the operation of. the overdrive servo 227 during a so-called minimum of zero throttle bac~out ratio change from the third ratio to the fourth ratio.
TV limit pressure in passage 418 acts on the~
30 differential diameter of lands 276 and 278 of the oil pressure booster valve 272, thereby increasing the circuit pressure as throttle pressure increases, thus Line pressure will be boosted in proportion to TV
pressure up to about 85 psi TV pressure. But beyond that 35 there ~is no other boost due to increases in throttle valve pressure. This avoids the possibility of development of excessive line pressures which will~cause damage to the pump and to the clutches and brake servos.

0 ~ 9 As seen in Figures 13A, 13B and 13C the throttle valve 256 comprises a valve spool with two spaced valve lands 430 and 432. A third valve land 434 on a separate valve element is situated in a valve sleeve which defines a pre~sure chamber 436 in which is disposed throttle valve spring 438. A throttle valve plunger 440 is located in alignment with the valve spool of throttle valve 256, and it comprises a single valve land slidably situated in the throttle valve bore. Pressure is distributed through the throttle valve bore to passage 294. Exhaust ports are located in the throttle valve bore adjacent land 430, as shown at 442, and at a location intermediate lands 440 and 430 as shown at 444.
Valve spring 446 is located between the thro~ttle plunger that carries land 440 and the valve spool for throttle valve 256.
Pressure chamber 436 communicates with pressure chamber 448 and with the space between the valve lands 430 and 432, crossover passage 450 providing such communicating. Passage 450 communicates also with the space between lands 440 and 430. An orifice 452 is located between crossover passage 450 and the space between lands 440 and 430.
As the engine throttle control 453 (Figure 13A) is advance, the throttle plunger moves the land 440 and compresses the spring 446 thereby causing the throttIe valve spool 256 to modulate the pressure in passage 294 to produce a resultant throttle pressure in passage 400.
The regulated throttle pressure acts on the left hand side of the land 440 thereby assisting in the movement of the throttle plunger and eliminating the high driver effort that is sometimes necessary to actuate a transmission throttle valve upon movement of the engine throttle.
A mechanical linkage mechanism is disposed between the engine carburetor throttle and the throttle plunger and the magnitude of the TV pressure is determined by the force of the TV spring 446. The effort required to compress the spring is reduced by the 1 1~8089 so-called pressure feedback feature and a uniform actuating ~orce then is available since the greater compressio~ of spring 446 is offset by the increase in the pressure force acting on the left hand side of the valve land 440. The linkage interposed between the throttle plunger and the engine carburetor throttle includes a torsion spring (schematically shown at 455 in Figure 13A) which tends to move the throttle plunger toward the wide open throttle position if the linkage from the carburetor should become disconnected. The torsion spring, whenever the engine is running, will move the plunger towards the wide open throttle position thus tending to increase the throttle pressure to its maximum value. This, of course, results in a maximum line pressure and that maximum line pressure is then available whenever a linkage failure occurs, thereby preventing the clutches and brake bands of the transmission from slipping and failing if the engine is operated under these conditions at heavy throttle.
Figure 13A illustrates the closed throttle condition. At that time the throttle plunger assumes its maximum leftward position. The force of the spring 446, even when the engine throttle is closed, is sufficient to overcome the force of the preload~spring 436 acting on the right hand end of the throttle valve land 434. The regulated throt~le pressure acts on the right hand end of the land 434 to resist the movement of the plunger thus producing a regulating action. The orifice 452 at closed throttle tends to leak a certain amount of~ throttle 30 pressure through the exhaust port 444. At closed throttle passage 400 is in communication with the space between lands 440 and 430, and since that space is exhausted through exhaust port 444 the magnitude of the throttle pressure in passage 400 made available to the control circuit also is zero. Movement of the engine throttle from the closed throttle setting to an initial small movement will cause the land 440 to bIock the flow through the orifice 452. Thus the throttle valve pressure in passage 400 will rise immediately from a value zero to whatever value exists in the passage 450.
This is ~he condition that exists in the Figure 13B.
~ igure 13C shows ~he condition of the valves during wide open throt~le or kick down condition. When the engine is operated at full throttle, the throttle linkage positions the plunger as shown in Figure 13C and the plunger contacts the throttle valve 256 and moves it out of its regulating position so that it opens up the line pressure in passage 294 to the throttle pressure passage 400. Thus the throttle pressure in passage 400 immediately arises to the full line pressure that exists in passage 294.
In Figure 14, 14A and 14B, there is illustrated the modulated pressures and other pressures that are used to delay the automatic upshifts for the 2-3 shi~t valve and the 3-4 shift valve 238 as well as for the 1-2 shift - valve. Governor pressure in passage 452 acts on lower land 454 of the 2-3 shift valve 234. That valve includes also valve lands 456, 458, 460 and 462.
The 2-3 shift valve 234 is urged in a downward direction as~ seen in Figure 14 by the valve spring disposed between the 2-3 modulator valve 258 and the land 462 and by a valve spring that acts on the upper side of the land 460. Line pressure from passage 304 is 25 distributed through the space between lands 456 and~ 454 to the passage 306 extending through the booster valve 272 as explained previously. Passage 330 extends to the space between lands 460 and 458, such space communicating with the valve in the position shown in Figure 14 with 30 passage 332 extending to the overdrive servo release chamber on the upper side of the piston 328 of servo 227.
The 3-4 shift valve 238 has three valve lands as shown at 464, 466 and 468 in Figure 14. It includes also a valve~spring 470 that moves the valve 238 in an 35 upward direction as seen in Figure 14 against the opposing force of governor pressure. Governor pressure passage 328 transfers governor pressure to the upper end of the land 454. The modulated throttle valve pressure in passage 414, previously described with reference to Figure 13, establishes a downshift force on valve land 468. Passage 404 acts as an exhaust passage for 3-4 TV
modulator valve 260 since it is exhausted under the conditions shown in Figure 14 through the orifice control valve 250, 3-way check valve 410 and passage 408. The 3-way check valve 410 communicates with the orifice control valve 25~ in passage 406.
The 2-3 modulator valve 258 is a single diameter valve spool that that is subjected to the TV
limit pressure in passage 418. I~ produces a pressure force on the 2-3 shift valve that opposes the governor pressure force due to the governor pressure in passage 452. The magnitude of the modulated pressure acting on land 462 is determined by the TV limit pressure and the spring force.
The modulated pressure in passage 424 for the 2-3 shift valve ,34 acts also on the 1-2 shift valve 232.
The 1-2 shift valve comprises spaced valve lands 370, 352, -350, 372 and 374 as seen in Figure 14. The 20 modulated pressure in passage 424 acts on the differential area defined by lands 370 and 352 to create a downshift force or a shift delay force on the 1-2 shift valve 232 that opposes the force of the governor pressure in passage 328. Line pressure in passage 334 and in passage 336 acts on the differential area of lands 372 and 374 to create a further shift delay. Passage 334 is not shown in a pressurized state in Figure 14, however, since the manual valve 236 in that Figure is shifted to the neutral position rather than position D.
A shift delay pressure on the 2-3 shif~ valve 234, in addition to the shift delay produced by the modulated pressure in passage 42A, is developed by the line pressure in passage 304 which acts on the differential area of shift valve lands 456 and 454.
Shift delay pressures acting on the 3-4 shift valve 238, in addition to the shift delay pressure developed by the modulated pressure in ~line 414,~are the pressure forces due to the pressure in passage 308. That pressure acts on tbe differential area of~lands 464 an~

0 ~ 9 466 and on the separate differential area defined by lands 466 and 468.
In Figure lS there is shown an operating mode of the con~rol valve circuit when tha manual valve 236 is shifted to the drive range position when the vehicle is in first gear ratio. This is the operating mode that conditions the mechanism for automatic ratio changes as will be explained with reference to Figures 16, 17 and 18. Line pressure in the Figure lS mode is distributed to the 1-2 shift valve 232 through passage 336 and 334 and that line pressure is blocked by lands 372 and 374.
Pressure is distributed also from passage 336 to the lower end of the 1-2 accumulator valve 228 thus causing the 1-2 accumulator valve piston 482 to be stroked in an lS upward direction against the opposing force of spring 484 in preparation for a 1-2 automatic upshift.
Line pressure is distributed also from passage 304 to the 2-3 shift valve 234 at the space between valve lands 456 and 454 as seen in Figure 15. Line pressure 20 from passage 330 extends through the 2-3 shift valve 234 to the passage 323 which extends to the release side of the overdrive servo 227. The forward clutch also is applied as pressure is distributed through passage 308, through the 3-~ shift valve to crossover passage 310 and 25 through the orifice control valve to passage 312 and hence through the 2-3 backout valve 248 to the passage 314. This circuit was described previously with reference to Figure 8. It should be noted that the orifice control valve 250 is urged in an upward direction 30 at this time, as seen in Figure 15 as the pressure in passaqe 310 acts on lower valve land 486. The orifice control valve 250 includes, in addition to the land 486, valve land 488 and a valve spring 490 which urges the valve in a downward direction as seen in Figure 15.
35 Pressure in passage 310, which is distributed to the forward clutch 110 through the circuit previously described, is made available also to the upper end of the 2-3 accumulator 252 which was described also with reference to Figure 8. The accumulator 252, as shown in 0~

Fiqure 15, is fully stroked in contrast to the position that is illustrated in ~igure 8.
During initial engagement of the forward clutch the time required to stroke the accumulator piston delays the pressure buildup in the forward clutch 110 and causes a cushioned clutch application. The 3-4 shuttle valve 240 also is in condition for operation. It is comprised of a valve spool 494 having spaced valve lands 496 and 498. The valve spool is biased in an upward direction, as seen in Figure 15, by valve spring 500 seen in Figure 8 but not in Figure 15. The 3-4 shuttle valve spool 494 is pressurized at its upper end with line pressure which is distributed to it through passage 502. This passage communicates with passage 314 through one-way check valve 504, passage 314 being pressurized as described previously with reference to Figure 8.
The shi~t valves receive a speed signal pressure as described in Figure 8, but the magnitude of that signal is not sufficient to cause them to shift against the opposing shift delay pressures~and against the opposing forces of the shift valve springs, It will be observed in Figure 15 that the forward clutch 110 receives its pressure ~hrough the 3-4 shift valve 238 so that when the latter is upshifted to fourth ratio 25 position, the forward clutch 110 will become disengaged.~
The throttle pressure developed by~the throttle pressure valve 256 is distributed in the condition shown in Figure 15 throughout the valve circuit in~the same fashion described previously with reference ko Figure 13.
30 Throttle pressure causes the backout valves, both the 3-4 backout valve and khe 2-3 backout vaIve to be shifted against their respective springs. It should be noted also in Figure 15 that distribution of control pressure through the 2-3 shift valve 234 to passage 306 occurs to 35 develop a line pressure boost. Diskribukion cf pressure khrough that passage 306 is interrupted, however, immediately upon ~upshifk of kh~e 2-3 ~shift valve 234 to iks direck drive position, thus causing a cutback in the magnitude of th regulated line pressure output of the ;

.: ` :
,' ~ ' main regulator valve, It should be noted also in Figure 15 that throttle pressure from the throttle valve 256 is distributed to the lower end of the land 278 of the oil pressure booster valve.
hine pressure is distributed from passage 334 to passage 336 to the space between lands 37~ and 374 on the 1-2 shift valve thereby conditioning the 1-2 shift valve for a subsequent 1-2 upshift.
Line pressure from pump 212 is distributed through the passage 280 to the differential area on the 3-4 accumulator 224 in the manner described with reference to Figure 8.
The condition of the automatic control valves during an automatic 1-2 upshift, when the manual valve 236 is in the overdrive range position D, is shown in Figure 16. The 1-2 shift valve 232 responds to an increased governor pressure in passage 328 and shifts to the upshift position against the force of the shift valve spring acting on the lower end of the 1-2 shift valve 232. This allows control pressure to be distributed from passage 334 to the overdrive servo regulator valve 242 through passage 504. Line pressure~ passes through that valve to passage 506 which extends to the 1-2 capacity modulator valve 226. Before a 1-2 ratio shift begins, the 1-2 capacity moduLator; valve and the 1-2 accumulator valve shown at 226 and 2~28, respectively, assume the positions shown in Figure 16A. After the 1-2 shift begins but before it is completed the 1 2 capacity modulator valve 226 and the 1-2 accumulator valve 228 assume the position shown in Figure 16B. At that instant in the shift interval line pressure is distributed to the 1-2 capacity ~modulator valve spool 508 which has two regulating valve lands S10 and 512. Valve ~spool 508 is urged in an upward direction by valve spring 511.
35 Pressure i5 fed bac~ to the top to land 510 through the capacity modulator output~ passage 514 and to the lower end of the land Sl The regulated pressure that lS~ produced ln passage 514 is distributed to the upper end of the :; ' . ' , ' ' 0 ~ 9 cylinder 520 of the 1-2 accumulator valve 228. The magnitude of the pressure in line 514 is about 5 psi higher than the pressure on piston 520. The upper side of the accumulator piston 520 is supplied through the orifice 522. The pressure in the top of the 1-2 accumulator valve forces the accumulator piston 520 in a downward direction and assists the accumulator valve spring 524. Those forces are opposed by the force produced by the pressure in passage 334 which is applied to the di,fferential area of the two lands for th accumulator piston 520. This pressure regulation continues during intermediate clutch pressure buildup until the accumulator piston 520 is fully bottomed. When that occurs, there is no longer any pressure,increase in lS passage 514 and the capacity modulator valve 226 then ceases to modulate. The pressures in the 1-2 capacity modulator valve 226 and the 1-2 accumulator valve 228 - then rlse to the full line pressure value. This condition is shown in Figure 16C.
The condition of the valves during an automatic 2-3 upshift while the manual valve 236 is in the overdrive range is shown in Figure 17. Governor pressure acts on the base of the 2-3 shift valve 258 and moves it to the upshift position. This allows pressure to pass from line 331 to passage 528 which extends to the 2-3 backout valve 248. Vent port 526 then is sealed from passage 528.
Line pressure from passage 528 passes through ' lands 342 and 344 of the 2-3 backout valve 248 and~
through orifice K (see Figures 29 to 31) in the 2-3 backout valve 248, to direct clutch feed passage 530. The pressure in passage 530 is distributed to the top of the orifice control valve 250 to cause the latter to move in ' a downward direction. That pressure is applied also to 35 the lower end of the piston for the 2-3 accumulator 252 causing that piston to~stroke in an upward direction, the effective pressure area on the lower end of the piston being greater than the effective pressure on the upper end of the piston. Pressure is forced through orifice K

- , ~ ,, ~ecause of the fact that check valve 532 in the 2-3 backout valve 248 which normally bypasses the orifice K
as well as orifice E, is closed by the pressure in passage 528.
As explained with reference to Figures 15 and 16, the piston of the 2-3 accumulator 252 was held in a downward direction by the clutch pressure in the forward clutch during operation in the first and second ratios.
During the 2-3 upshiEt, however, the accumulator moves up and the pressure downstream of the orifice K assists the accumulator spring to force the accumulator 252 upward.
This causes an intensified back pressure flow from the smaller upper end of the accumulator chamber. This seats the check valve 316. The only escape for the-flow from the upper side of the 2-3 accumulator is past the 2-3 capacity modulator valve 558. The modulator valve 554 moves outwardly and regulates that pressure. This regulation controls the force on the accumulator valve 558 and, therefore, controls the direct clutch apply 20 p~essure during the 2-3 shift interval. When the~
accumulator piston reaches the end of its travel, there is no longer any flow from the upper end of the accumulator piston; and direct clutch apply pressure then rises to the full line pressure.
A shift to the overdrive range during the automatic upshift mode i5 illustrated in Figure 18. This requires a release Oe the forward clutch, the exhausting of the overdrive servo release pressure and the control of the overdrive servo apply pressure. The direct clutch 30 remains applied, as explained with reference to Figure 17. The 3-4 shift valve 238 moves under the influence of governor pressure in passage 328 which acts on the land 464 of the 3-4 shift valve assembly. That opens the forward clutch circuit to restricted exhaust. As the exhaust port 534 in the 3-4 shift valve assembly is brought into communication with passage 502, check valve 504 opens and permits flow from the forward clutch to the ` ` passage 502 and to the 3-4 shift valve exhaust port 534.

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:
,~ ' . ' ~t the same time it blocks distribution of line pressure from passage 308 to the forward clutch.
The exhausting of pressure from the forward clutch takes place through the check valve 504 and through the 3-4 shift valve 238. The flow path for this exhausting of fluid is designated in Figure 18 by arrows.
The exhaust flow path for the release side of the overdrive servo 227 takes place as flow from the release side is passed through passage 332, through the 2-3 shift valve 234 and then through the 3-4 backout valve 244, the 2-3 backout valve 248 and the check valve 504 to the exhaust orifice 534 in the 3-4 shift valve 238. The pressure that acts on the upper end of the 3-4 shuttle valve land 496 also communicates through the same flow 15 path followed by fluid from the forward clutch 110 to the 3-4 shift valve vent port 534.
The 3-4 shuttle valve 240, which is in the downward position during operation in the first, second and third ratios in the overdrive range, moves up under 20 the influence of the spring 500 at the base of the valve during a ratio change to the fourth ratio position. This allows the output pressure from the overdrive servo regulator valve 242 to pass through the shuttle valve 240 to the base on the overdrive servo regulator vaLve 242 25 causing it to cease regulating. Pressure~ then is distributed through orifice 528 and passage 536.
Pressure from the overdrive servo regulator valve 242 to the apply side of the overdrive servo 227 passes through orifice 538 as well as to the upper side of the 3-4 30 accumulator plston 286. This causes the accumulator piston 286 to move downwardly, thereby causing the pressure to be less than line pressure during its movement; The pressure on the underside of the 3-4 accumulator piston 286 is line pressure. The control 35 pressure on the upper side of the 3-4 accumulat~or piston is applied to the overdrive servo piston and provides a controlled and cushioned overdrive band engagement to effect a smooth 3-4 upshift. As soon as the accumulator : ~
`

224 is fully stroked, the control pressure rises to full line pressure.
Prior to the 3-4 upshift sequence, the overdrive regulaLor valve functions as a regulator valve and produces i~ the passage 536 a regulated pressure.
This regulatior occurs by the spaced valve lands 540 and 542. The lower end of the land 540 is connected to the upper end of the overdrive servo regulator valve 242 by an internal orifice that is shown in dotted lines in Figure 18. The valve is urged normally downwardly by a valve spring as indicated. Land 542 is larger than land 540 so that the line pressure supplied to the overdrive servo regulator valve 242 is modulated to produce a controlled, reduced pressure in passage 536. This 15 modified servo-apply pressure is available whenever the 1-2 shift valve 232 moves to the upshift position as line pressura is distributed through the space between valve lands 372 and 380 of the 1-2 shift valve 232 to the regulator valve 218.
In Figure 19, there is illustrated the condition of the valves when the throttle valve is moved to the full wide-open engine throttle position. At that time line pressure in passage 294 is distributed directly through the throttle valve assembly 256 to the throttle 25 pressure passage 400 so that throttle pressure is equal to line pressure. The output side of the TV limit valve 246 continues to distribute modified TV limit pressure in passage 418, as previously descri~ed, regardless of the rise in the magnitude of the pressure in passage 400 to 30 full line pressure which comes through the bore in the orifice control valve during kickdown. In the Figure 19 condition the high pressure passes through the 3-~4 TV
modulator valve 260 to the base of the 3-4 shift valve 238 causing it to upshift against the opposing influence of governor pressure. This, as explained previously, causes release of the overdrive brake servo 227. Line pressure is distributed also through 3-way check valves 366 and 410 to the upper end of the 2-3 shift valve 234 and to the differential area on the lower two lands 372 , 1 .1 5 ~ 9 and 374 of the 1-2 shift valve 232 as well as to the lower end of the 3-4 shift valve 238 through the orifice control v~lve 250. If the speed of the vehicle is sufficient so that the increased downshift forces on the 2-3 shift 234 valve and the 1-2 shift valve 232 are cufficient to overcome governor pressure, downshifts will occur to the second ratio or the first ratio. The condition shown in Figure 19, however, illustrates merely a downshift from the fourth ratio to the third ratio.
Figure 20 illustrates the condition of the valve circuit when the transmission manual valve 236 is moved to the manual low position at closed throttle while the vehicle is standing still. The forward clutch 110 is applied at that time as well as the low-and-r.everse brake band 172 to permit engine braking. The overrunning clutch or brake 174 complements the braking ~orque of the brake band 172 during forward drive operation in manual low under torque. The 3-4 accumuIator 224 is stroked in an upward direction since the upper side of the piston 286 is exhausted through passage 292~ and through the exhaust port in the 1-2 shift valve located between lands 350 and 372 on the 1-2 shift valve 232. Line pressure acts on the lower ends of the 3-4 shift valve 238, the 1-2 shift valve 232 and on the upper end of the 2-3 shift 25 valve 258 forcing these valves to their downshift positions. When the 2-3 shift valve 258 is ~so positioned, line boost pressure is distributed to the~oil pressure booster valve land 278 through passage 306,~thus~
causing an increase in the regulated circuit pressure 30 during manual low operation in low speed range (the same is true for the overdrive~range).
Since the engine throttle is at the zero throttle setting in the Figure 20 addition, ~throttle pressure is zero as explained previously.
The low servo modulator~valve feed passage 546 is exhausted through the right hand end of the manual valve 236 so that the low servo modulator valve ~262 cannot distribute line pressure to the apply side of;the low and reverse servo ~172. Pressure is distributed, .

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I 1 ~8(~i9 however, to the low servo modulator valve 262 through the passage 354 which is pressurized by reason of the connection between passage 348 and passage 354 that is provided by the 1-2 shift valve 232. The low servo modulator valve 262 produces a low and reverse modulated pressure in passage 548 which extends to the low and reverse brake servo 172.
The low servo modulator valve 262 has a pair of regulating valve lands 550 and 552. The reverse servo feed passage 546 is exhausted and ac~s as an exhaust port for the low servo modulator valve 262. The regulating valve lands of the low servo modulator valve 262 are biased in an upward direction, as seen in Figure 20, by a valve ~pring, thus causing the valve to regulate to produce a reduced pressure in passage 548, the magnitude of which is dependent upon the value of the spring for any given line pressure.
The forward clutch 110 is pressurized by line pressure distributed through the 3-4 shift valve 238 and the orifice control valve 250 in the fashion previously described.
The 1-2 shift valve 232 is locked in the position shown in Figure 20-by line pressure acting on the spring end of the valve and to the line pressure acting on the differential areas of the valve lands.
Similarly the 2-3 shift valve 234 is locked in place by the full line pressure extending to the upper end of that valve through the 2-3 TV modulator valve, and to the line pressure acting on the differential area of the valve~
lands of the 2-3 shift valve.
~ igure 21 shows the condition of the valve system during first gear engagement in overdrive range at closed throttle. The forward clutch 110 is applied as described previously with reference to Figure 8 ~and the 35 2-3 accumulator 252 is fully stroked as shown as is the 3-4 accumulator 224.
Figure 22 shows the condition of the valve system that exists during operation in second gear at part throttle in the overdrive range. Figure 22, and I 1 ~80S~

also Figure 21, show the valves in their respective posltions just after the shift has been completed. The condition that exists during the shift interval for Figure 22 was described previousLy with reference to Figure 16, and Figure 22 should be viewed simultaneously with Figures 16, 16A, 16B and 16C.
Main line pressure is regulated by the main oil pressure regulator valve 218 and distributed throughout the converter and lubrication system, as explained previouslyO The 3-4 accumulator valve 224 is moved upwardly by line pressure against the force of the accumulator valve spring. Since the 2-3 shift valve still is in the downshift position at thi~ time, line pressure still is distributed to the boost valve 272 to cause an increase in the main oil pressure regulator valve output. 5ince throttle pressure now is available, as indicated in Figure 22 in the passage 400, an auxiliary TV pressure force is exerted on the oil pressure booster valve 262 causing an increase in the line pressure because of the engine torque that accompanies the increased throttle pressure at this instant.
The TV pressure is now sufficient to actuate the TV modulator valves ~o produce a delayed upshift signal. The 3-4 backout valve 244 and the 2-3 backout valve 248 both are shifted to their inoperative positions as shown since throttle pressure acts on each of the back valve ends.
Orifice A in the 2-3 backout valve 248 is 30 bypassed through the shifted orifice control valve 250, passage 312, the 2-3 backout valve and to the forward clutch 110. Clutch apply pressure continues to hold the 2-3 accumulator valve 252 downward and to hold the 3-4 shuttle valve 240 against its spring force.
The governor pressure acting on the upper end of the l-2 shift valve 232 is sufficient to move that valve against the opposing spring and hydraulic forces to permit a feed of line pressure through the overdrive servo regulator valve 242 and the 1--2 capacity modulator .

L lr)~9 valve 226 to the intermediate clutch 140. The clutch apply pressure is distributed khrough orifice 522 (orifice F) to the spring end o~ the piston of the 1-2 accumulator valve 228. The accumulator 228, upon movement in a downward direction, cushions the application of the intermediate clutch 140. The release side of the overdrive servo 227 is pressurized because of the pressure that is distributed to it through passage 331 and the downshifted 2-3 shift valve 234 which connects passage 331 to passage 332. The overdrive servo regulator valve 242 continues to supply a modulated pressure to the apply side of the overdrive servo 227 as explained previously.
Figure 23 shows the valve condition for third 15 gear operation at 3/4 engine throttle setting in the overdrive range after the shift has been completed.
Figure 17, in contrast, shows the upshift from the second ratio to the third ratio in the overdrive range at part throttle during the shift interval. Under the Figure 23 20 condition, the 3~4 accumulator 224 is forced in an upward direction so that it can be conditioned for a subsequent 3-4 upshift. TV Iimit pressure from the TV limit valve 246 continues to be supplied to the main oil pressure booster valve 272 to provide a line pressure boost. The 25 line boost pressure in passage 306 is exhausted through the exhaust port in the 2-3 shift valve 234 located between the lower valve land 454 and 456 on the 2-3 shift valve 234 which results in a reduction in the main oil pressure regulator valve output.
The 3-4 TV modulator valve 260 assumes a regulating condition under the influence of the throttle pressure acting on the lower end of that valve. This regulating action was explained with reference to Figures 14 and 15.
It will be seen that orifice K is in the fluid circuit that feeds the direct clutch as pressure is distributed to the 2-3 backout valve 248 through passage 528. Direct clutch pressure is distributed also at this instant to the bottom of the piston of the 2-3 0 ~ ~

accumulator 252 to cushion the shift to the third ratio as explained previously.
In Figure 24 there is illustrated the condition that exists during operation in third gear at 3/4 throttle when the manual valve 236 is in Range 3. The condition of the valves in Figure 24 is similar to the condition of the valves in ~igure 23, but the fourth gear lockou~ is actuated through the passage 554 which communicates through check valve 410 and through the orifice control valve 250 to force the 3-4 shift valve 238 in an upward direction. The pressure that exists on the lower end of the 3-4 shift 238 valve is distributed through the check valve 410 and locks the shift valve 238 to prevent overdrive from occurring.
The upshift from the third ratio to the overdrive ra~io is described with reference to Figure 18.
The valve system following the completion of that shift assumes the condition shown in Figure 25. That is the condition that exists during normal cruising operation 20 under steady state conditions with the transmission in the overdrive range. The 3-4 shift valve~ 238 in Figure has been shifted under the influence ;of governor pressure to its upshift position. This exhausts the forward clutch 110 through~the exhaust port 534 in the 25 3~4 shift valve 238. The upper side of ~the 2-3 accumulator piston also is exhausted. Exhaust flow paths for the forward clutch 110 and the 2-3 accumulator piston are common and have been;designated by arrows in~Figure 25. Similarly, the overdrive servo rele~ase~ pressure is 30 e~xhausted through;~he 2-3 shift valve, through the 3-4 backout ~alve ~and through the 2-3 backout valve 248 as indicated also by the arrows in Figure 25 that originate at the overdrive servo~227 and terminate at the 3-4 shift~
valve 238.
~ The 3-4; shift valve 238 has been moved downwardly in Figure~25 against the opposing ~orce of the spring by governor pressure as indicated~thereby opening the exhaust flow path for the ~release aide of the overdrive servo 227. Line pressure is supplied, as - , , ,~ :
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~2 previously described, to the apply side of the overdrive servo ~27 through the orifice 538 (orifice D). The 3-4 accumulator 224 cushions the shift since the accumulator piston has been stroked, as indicated, by the apply pressure for the overdrive servo 227.
Figure 26 shows the condition of the valve system during reverse drive at initial engagement with the throttle closed. The initiation of that shift before it is completed was illustrated in Figure 12 and described earlier. In the Figure 26 condition the low servo modulator valve 262 is moved to establish a direct connection for delivering line pressure to the rever~e servo feed passage 362. Governor pressure is absent in this drive mode and throttle pressure th~oughout the 15 circuit is absent because of the closed throttle condition. Line pressure is distributed directly from the manual valve 236, which is in the reverse drive position R, to the check valve 410 and through the orifice control valve 250 to lock the 3-4 shift valve 238 20 in place. Pressure is distributed also through the check valve 366 to the various pressure lands on the 1-2 shift valve 232 which locks it in place. Similarly, the 2-3 shift valve 234 is locked in place by the same control pressure that is made available to the other shift 25 valve Figure 27 shows the condition of the valves during manual low operation with the manual valve in the No. 1 position at closed throttle when the vehicle is moving sufficiently fast so that the 2-l downshift point 30 has not been reached and the transmission operates in the second ratio. The throttle pressure in passage 400 under these conditions is absent because the engine throttle is closed. Thus the 2-3 backout valve 248 shifts in a left hand direction under force of its spring, and the 3-4 35 backout valve 244 shifts in an upward direction under the influence of its spring force. The forward clutch 110 remains applied under these conditions as it is supplied with fluid through the 3-4 shift valve 238, the orifice control valve 250, the 2-3 backout valve 248 and the .
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orifice A (see Figures 29-31) in the 2-3 backout valve 248. Since the governor pressure is high enough to keép the 1-2 shift valve 232 in the upshif~ position, line pressure thus is available to hold ~he intermediake clutch 140 applied.
Line pressure is distributed from passage 348 and across the 2-3 shift valve 234 to the lower end of the 3-4 shuttle valve 240 so that the 3-4 shuttle valve 240 is held in an upward position. Line pressure acts on the overdrive servo regulator valve and holds it in a nonregulating condition, which is the downward position shown in Figure 27. The line pressure on the apply side of the overdirve servo 227 thus is able to apply the overdrive servo 227. The release side of the overdrive servo 227 is e~hausted through the flow path provided by passage 332 as idicated by the arrows. Thls flow path is define in part by the 2-3 shift valve 234 and the end of the manual valve 236.
The 2-1 scheduling valve 230 produces a 20 regulated pressure as described with reference to Figure 11. That regulated pressure acts on the base~of the 1-2 shift valve 232. This will cause the 1-2 shift valve 232 to downshift as governor pressure is reduced at lower road speeds.
In Figure 6, there is illustrated the relationship between circuit pressure and throttle pressure during the reverse drive mode, during operation in first and second ratios, neutral and park modes and during operation in the third and fourth ratios. During 30 operation in reverse, the reverse line pressure is effective on the main oil pressure booster valve 272 to augment the circuit pressure as explained ~Jith reference to Figure 12. During~operation in the third and fourth ratios, the q-3 shift v~lve q34, upon moving, causes a 35 cutback without the necessity for providing~an additional cutback valve as in some conventional control circuits such as those illustrated in the re~erence citations mentioned in the beginning of this specification. The sharp rise in the curves of Figure 6 beginning at a point ', ~
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l 1~80~9 corresponding approximately to 25 psi on the abscissa is due to the fact ~hat the throttle pressure developed by the throttle valve system is not made available to the circuit until after the engine throttle advances to the preselected minimum travel condition which is described with reference to Figure 13A, 13B and 13C. That TV
characteristic is shown, as mentioned earlier, in Figure where throttle pressure is plotted against plunger travel.
The operation of the orifice control valve 250, which has been described previously, can be understood more clearly if reference is made to Figures 29, 30 and 31. During idle engagement of the front clutch, the flow path through the orifice control path is shown in Figure 29 by the arrows. Pressure passes through the downshifted 3-4 shift valve 238 to the lower end of the orifice control valve 250 and hence to the 2-3 backout valve 244 and orifice A to the forward clutch 110.
Throttle pressure during such closed throttle engagement is removed from the 2-3 backout valve 248 and~that valve shifts in a left-hand direction as indicated in Figure 29. The dotted lines and the dotted arrow in Figure 29 show the flow path and the valve position during advance throttle engagement when the throttle pressure is sufficient to shift the 2-3 backout valve 248 in a right-hand position.
During a 4-3 torque demand downshift, the orifice control valve 250 ~functions as shown in Figure 30. It moves in a downward direction under the force of the orifice control valve spring line pressure feed flow thus passes through the~ downshifted 3-4 shift valve 238 and through the space between the upper valve lands on the orifice control valve 250 and through the 2-3 backout valve 248 and orifice B to the overdrive servo release 35 pressure passage 332 and to the forward clutch llO. The 2-3 backout valve 248 is shifted in a right-hand direction because OL the presence of throttle pressure on the left-hand end under a driving condition with torque applied. ~ ~

' Orifice C in the 2-3 backout valve 250 functions as shown in Figure 31. This is the condition that exists during a coastiny downshift from overdrive to the third ratio. The feed passage extends through the 3-4 shift valve 23~ and through the orifice control valve 250, which is shifted downward in Figure 31, and hence through the 2-3 baclcout valve 248 and orifice C to khe forward clutch 110. The overdrive servo release circuit is fed be~ore the flow passes throu~h the orifice C (see Figure 2A) so that the servo releases quickly.
Engagement o the forward clutch 110 with advanced engine throttle occurs as previously explained.
Under those conditions the 2-3 backout valve 248 is shifted in a right-hand direction and pressure i5 distributed through the 2-3 backout valve 248, as described with reference to Figure 22. The feed passage in that case is the passage 556 as shown in Figure 22.
Orifice A is bypassed.
Figure 28 is a chart that shows the functions f the various orifices A, B, C, E and K for the 2-3 backout valve 248. Orific~ K is effective as explained with reference to Figure 17 during a 2-3~upshift. As pressure is distributed from passage 528 through the 2-3 backout valve 248 to the feed passage 530 for the direct clutch 192. Passage 530 communicates with the lower end of the 2-3 accumuiator 252. Thus the accumulator 252 is capable of two functions: namely, it cushions direct clutch application on an automatic 2-3 upshift~and al~so cushions the front clutch application during the initiation of the shif~ sequence. It cushions the direct clutch application since the lower side of the accumulator piston communicates with the passage 530 as indicated in Figure 17. This creates a pressure on the upper side of the piston that is in excess of the 35 magnitude of the pressure on the lower side of the piston. The pressure Gn the upper side of the piston is regulated by the 2-3 capacity modulator valve 558 which comprises a valve spool having valve lands 560 and 562 that ar3 urged in a downward direction by valve springs ~' :

1 1~81~69 as indicated. The regulated pressure on the upper side of the accumulator piston is transmitted through passage 564, as shown in F.igure 17, to the lower side of the land 560 thereby allowing pressure regulation to occur as fluid flows out of the upper end of the 2-3 accumulator 252. When the accumulator piston reaches the end of its travel, there no longer is any flow, and direct clutch apply pressure rises ~o its full value.

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Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a power transmission mechanism having gear ele-ments including a ring gear, sun gear, planetary pinion and carrier for said planetary pinion, said gear elements defining plural torque delivery paths from a driving member to a driven member to effect multiple ratio torque ratios including an overdrive ratio and a direct drive ratio, clutches and brakes including a forward drive clutch means and an overdrive brake means for controlling the relative motion of said gear elements and an overdrive clutch means for delivering input torque to said carrier as an overdrive reaction gear element is braked by said overdrive brake means, said forward drive clutch means when applied connecting said gear elements to-gether for rotation in unison, a valve control circuit for controlling engagement and release of said clutches and brakes including a pressure source and an overdrive and direct shift valve means for controlling application and release of said forward drive clutch means as said overdrive brake is released and applied, respectively, a feed passage for said forward drive clutch means communicating with said shift valve means whereby said shift valve means controls application of said forward drive clutch means, a pair of flow control orifices of different size in said feed passages and orifice control valve means including 2-3 backout valve for directing fluid through the larger orifice during ratio shifts under torque from said overdrive ratio to said direct drive ratio and through the smaller orifice during a corresponding ratio shift with reduced torque, a source of a torque dependent throttle pressure and means for subjecting portions of said orifice control valve means to said throttle pressure to actuate the same.

2. The transmission mechanism of claim 1 wherein said overdrive brake has a double acting brake servo with a piston that defines in part a servo release pressure chamber and a servo apply pressure chamber, said overdrive servo being released when both pressure chambers are pressurized, said shift valve means providing an exhaust flow path for said release chamber when it is shifted to the overdrive ratio position.

3. The transmission mechanism in claim 1 wherein said forward drive clutch means is adapted to connect the driving member of said mechanism to a torque input gear element during forward drive operation, a feed passage for said forward drive clutch means, parallel portions of said forward drive clutch means feed passage communicating with said orifice control valve means, one parallel portion providing a greater flow restriction than the other, said orifice control valve means being in communication with said throttle pressure source and responding to throttle pressure to actuate said orifice control valve means to a position causing fluid to be distributed to said forward drive clutch means through the reduced flow restriction passage portion, a reduction in throttle pressure below a calibrated low value causing said orifice control valve means to be conditioned for dis-tribution of fluid to said forward drive clutch means through the higher flow restriction passage portion.