Planetary transmission having a rotating-type torque-transmitting mechanism with a stationary piston

A planetary transmission has a plurality of rotating-type torque-transmitting mechanism that are operable to connect a rotating input mechanism with one or more planetary gear members. At least two of the rotating-type torque-transmitting mechanisms are radially stacked and axially aligned. At least one of the radially stacked rotating torque-transmitting mechanisms has an apply piston that is slidably mounted in a stationary transmission housing, an apply plate that is rotatable with a portion of the torque-transmitting mechanism, and a bearing disposed therebetween to accommodate relative rotation therebetween.

TECHNICAL FIELD

This invention relates to rotating-type torque-transmitting mechanisms in power transmissions, especially rotating-type torque-transmitting mechanisms having a stationary piston.

BACKGROUND OF THE INVENTION

Power transmissions generally utilize one or more rotating-type torque-transmitting mechanisms, commonly termed clutches. The clutch assembly generally includes a piston slidably disposed in a housing, a plurality of interdigitated friction discs, one splined with a housing and the other splined with a hub, and a backup plate splined to one of the members.

The piston is normally rotated with one of the housing members. A fluid pressure is applied between the housing and the piston into an apply chamber to cause the piston to engage with a pressure plate which abuts one of the friction plates. The friction plates are placed into frictional contact such that rotating power is transmitted between the two housing members or hub members of the clutch. The piston apply chamber is generally full of oil when the piston is not actuated and is subjected in many cases to centrifugal force which could cause the piston to apply, thereby partially engaging the clutch and inducing wear on the friction plates. To compensate for this centrifugal pressure, some clutches employ a ball dump valve placed within the piston or within the housing rotating with the piston. The ball dump valve is effective to open at a predetermined speed of the rotating speed of the piston or housing, thereby relieving the fluid within the apply chamber, provided the pressure within the apply chamber is at or below a predetermined value. The use of these ball dump valves is well known.

Other clutch assemblies use what is termed a centrifugal dam, which is a chamber on the side of the piston opposite the apply chamber. The centrifugal dam is permitted to fill with lubrication oil such that the centrifugal force within the centrifugal dam portion will counterbalance whatever centrifugal force is present within the apply chamber. Both of these systems are effective to prevent centrifugal apply of the piston.

Another element that is of interest in rotating-type torque-transmitting mechanisms is the shaft seal assembly, which is present between the rotating housing and a rotating shaft. At times during operation, these two members will be rotating at different speeds, thereby creating a frictional loss within the seal assembly, which is termed as a drive loss within the transmission.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved rotating-type torque-transmitting mechanism for use in a power transmission wherein the rotating-type torque-transmitting mechanism has a stationary (i.e., non-rotating) piston member.

In one aspect of the present invention, a power transmission includes two rotating-type torque-transmitting mechanisms that are radially aligned and at least partially axially overlapping and wherein one of the rotating-type torque-transmitting mechanisms has a stationary piston which is slidably disposed in a stationary housing.

In another aspect of the present invention, a power transmission includes three radially aligned rotating-type torque-transmitting mechanisms wherein each rotating-type torque-transmitting mechanism has a stationary piston slidably disposed in a stationary housing.

In yet another aspect of the present invention, a power transmission includes three torque-transmitting mechanisms that are radially aligned and wherein two of the torque-transmitting mechanisms are of the rotating-type, each having a stationary piston slidably disposed in a stationary housing.

In still yet another aspect of the present invention, a power transmission has three rotating-type torque-transmitting mechanisms that are selectively connectible with a planetary gear arrangement, and wherein two of the torque-transmitting mechanisms are disposed on one axial side of the planetary gear set, and the third is disposed on the opposite axial side of the planetary gear set, and further wherein each of the rotating-type torque-transmitting mechanisms includes a respective stationary piston that is slidably disposed in respective stationary housings.

In a further aspect of the present invention, each of the rotating-type torque-transmitting mechanisms having stationary pistons includes a rotary bearing disposed between the stationary piston and a rotating member of the torque-transmitting mechanism.

In a further aspect of the present invention, the transmission housing forms first, second and third stationary piston chambers which are positioned radially outward of each other, sequentially.

In a yet further aspect of the present invention, a power transmission includes a plurality of stationary pistons for rotating-type torque-transmitting mechanisms, wherein centrifugal forces are eliminated from the system during discontinuance of operation of the torque-transmitting mechanisms.

In yet still a further aspect of the present invention, a power transmission having a plurality of stationary piston-type rotating torque-transmitting mechanisms provides an improved packaging arrangement by reducing the axial space requirement for the torque-transmitting mechanisms.

The present invention provides rotating-type torque-transmitting mechanisms (clutches) each having a stationary piston. The stationary piston eliminates the need for rotating-type oil transfer structures and also the need for reducing or eliminating centrifugal forces that the oil might apply to the piston. The rotating-type torque-transmitting mechanisms with stationary pistons require less space and reduced mass, and they eliminate drag losses between the rotating shaft seals and the rotating housing. By reducing or eliminating the centrifugal effects, an improved controllability is permitted with the transmission system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, there is shown inFIGS. 1aand1ba planetary transmission10, which includes a conventional torque converter12, planetary gear arrangement14, and a final drive mechanism16. The torque converter12includes an impeller18, a turbine20, and a stator22. The impeller18is connected with an engine crankshaft24through a flex plate26and an input shell28. A conventional torque converter clutch30is disposed between the turbine20and the input shell28. The torque converter clutch30has one portion secured to the turbine20and includes a hub32, which is splined to a transmission input shaft34. The torque converter clutch30has an apply plate36, which includes a friction surface38that engages the inner surface of the input shell28. When the torque converter clutch is applied, as is well known, a direct drive between the engine crankshaft24and the transmission input shaft34is provided. During torque converter operation, a hydrodynamic drive is present between the engine crankshaft24and the transmission input shaft34. These hydrodynamic-type drives are well known in the art.

The planetary gear arrangement14includes two planetary gear sets40and42. The planetary gear set40has a sun gear member44, a ring gear member46, and planet carrier assembly member48. The planet carrier assembly member48includes a plurality of pinion gears50rotatably mounted on a planet carrier member52. The planetary gear set42includes a sun gear member54, a ring gear member56, and a planet carrier assembly member58. The planet carrier assembly member58includes a plurality of pinion gears60rotatably mounted on a planet carrier member62.

The input shaft34has an end section64that is rotatably supported on a housing extension68that is secured to a transmission housing70. The housing extension68is stationary as is the housing70relative to the rotation of the transmission input shaft34. The end section64has drivingly connected therewith a clutch housing or hub72.

The planetary gear arrangement14includes three rotating-type torque-transmitting mechanisms or clutches74,76, and78, and three stationary-type torque-transmitting mechanisms or brakes80,82, and84. The clutch74has a plurality of friction or clutch plates86that are splined to the hub or housing70, and a plurality of friction plates88that are splined with a hub90. The clutch74also includes an apply piston92that is slidably supported in the housing70and cooperates therewith to form an apply chamber94. The clutch74also includes a wall member96that cooperates with the apply piston92to create a centrifugal dam cavity98. The clutch74also has a pressure plate100and a backing plate102that are splined to the housing74for common rotation therewith. The hub90is splined or otherwise drivingly connected with a sleeve shaft104that is drivingly connected with the carrier member62of the planet carrier assembly member58. Thus, when the apply chamber94is pressurized sufficiently, the clutch74will engage thereby connecting the input shaft34with the carrier62of the planet carrier assembly member58. The backing plate102is splined or otherwise drivingly connected with the sun gear member44, such that the sun gear member44rotates in unison with the input shaft34.

The clutch76includes a plurality of clutch plates106that are splined with or otherwise drivingly connected to a hub108. The clutch76also includes a plurality of friction plates110that are splined with or otherwise drivingly connected to the housing70, which rotates in unison with the input shaft34. Other components of the clutch76include a piston112, a roller or thrust bearing assembly114, and a plurality of return springs116. The bearing114is disposed between the piston112, which is slidably disposed in the transmission housing70, and the leftmost of the clutch plates106. The piston112has an extension118that abuts the return springs116to urge the piston112into the housing70whenever an apply chamber120formed between the piston112and the housing70is not pressurized. When the chamber120is pressurized, the piston112will engage the clutch76such that a drive connection is established between the input shaft34and the hub108. The hub108is splined to or otherwise drivingly connected with the planet carrier52of the planet carrier assembly member48. Thus, whenever the clutch76is applied, the planet carrier assembly member52and the sun gear member44are interconnected for common rotation with the input shaft34. When the clutch76is engaged, the planetary gear set40will rotate in unison, that is, as a single unit.

The ring gear member46of the planetary gear set40is drivingly connected with a hub or shell122which is, in turn, drivingly connected with or otherwise secured to the sun gear member54. Therefore, the ring gear member46and the sun gear member54will operate as a single unit. Thus, when one of these members rotates, the other member rotates, and when one of these members is held stationary, the other member is held stationary.

The clutch78has an inner hub portion124integral with the planet carrier52, an outer hub portion126drivingly connected with the sleeve shaft104, a plurality of clutch plates128splined to the hub126, a plurality of friction plates130splined to the hub124, and an apply piston132. The apply piston132is slidably supported in the hub126and cooperates therewith to form an apply chamber or cavity134.

A wall or dam member136is supported on the sleeve shaft104and slidably disposed within the piston132. The dam wall136and piston132cooperate to form a centrifugal dam cavity138. A return spring140, in the form of a Belleville-type spring, is disposed between the dam wall136and the piston132to encourage disengagement of the piston when the cavity134is not pressurized. The dam cavity138is available to be filled with lubrication fluid to counterbalance any centrifugal fluid pressure that is generated within the cavity134. When the cavity134is pressurized, the planet carrier assembly member48and the planet carrier assembly member58will rotate in unison.

The brake80includes an apply piston142slidably disposed in the transmission housing70, a plurality of brake plates144splined to the transmission housing70, and a plurality of friction plates146splined to a hub148that is drivingly connected with the carrier62of the planet carrier assembly member58. A Belleville-type return spring150is disposed between a retaining ring152secured in the housing70and the piston142to urge disengagement of the piston whenever an apply chamber154, formed between the piston142and the housing70, is not pressurized. When the apply chamber154is pressurized, the brake80will be applied to retard rotation of the planet carrier62.

The brake82includes an apply piston155that is slidably disposed in the transmission housing70, a plurality of friction plates156splined to the housing70, a plurality of friction plates158splined to the hub122, a return spring160disposed between the housing70and the piston154. The piston154cooperates with the housing70to form an apply chamber162which when pressurized will cause engagement of the brake82. When the brake82is pressurized, the hub122will be held stationary, thereby retarding rotation of both the ring gear member46and the sun gear member54.

The brake84includes an apply piston164that is slidably disposed in the housing70, a plurality of brake plates166splined to the housing70, and a plurality of friction plates168splined to a hub170that is drivingly connected with the planet carrier52of the planet carrier assembly member48. The piston164cooperates with the housing70to create an apply chamber172. A return spring174is disposed between the housing70and the piston164to urge the piston164into the chamber172and out of engagement with the brake plates166. When the piston164is energized with pressure in the chamber172, the brake84is effective to retard rotation of the carrier52of planet carrier assembly member48.

The ring gear member56is drivingly connected with a transfer gear176, which meshes with another transfer gear178. The transfer gear178is splined with or otherwise drivingly connected to a shaft180on which is formed a final drive gear182. The final drive gear182meshes with a final drive gear184that is drivingly connected with a housing186of a conventional final drive differential188. The differential188includes two output shafts190and192, which are operatively connected in a well-known manner to drive the wheels of a vehicle, not shown.

As can be seen inFIGS. 1aand1band understood from the foregoing description, the clutch76is disposed radially outboard of the clutch74. The clutch76includes the stationary piston112which has the apply chamber120supplied with fluid through passages, not shown, formed in the housing70. Thus, the piston112does not require any rotating-type seals. The clutch74is supported on the end section64, which is rotatably supported on the housing extension68. The apply chamber94of the clutch74is supplied with fluid through radial passages194that are formed in the end section64. In order to eliminate leakage from the passages194, a pair of seals196and198are supplied which effectively prevent leakage of fluid between the end section64and the housing extension68.

The rotating torque-transmitting mechanism or clutch78also has rotating-type seal structures199and201which seal on opposite sides of a feed passage203that supplies pressurized fluid to the chamber134when it is desired to engage the clutch78. The three rotating-type torque-transmitting mechanisms or clutches74,76, and78reduce the overall axial space requirement by radially stacking the clutches74and76and by placing the clutch78on the opposite side of the planetary gear set40. It should also be apparent to those skilled in the art that the drag losses in the transmission are reduced due to the fact that the piston112is not a rotating structure, and therefore does not require the rotating-type seal assemblies. The thrust bearing114does provide some increased drag; however, it is greatly reduced from the constant drag that is present when rotating-type seals must be provided.

The use of the stationary piston112also simplifies the oil routing from the control system represented at205. This control system is an electro-hydraulic control system, which is generally controlled by an electronic control unit, which might include a programmable digital computer. This controller205, as is well known, supplies hydraulic fluid to control the engagement of the various clutches and brakes within the transmission. The fluid must be routed from the control205to the various friction devices that are to be controlled. By providing the clutch76with a stationary piston, the routing passages can be formed within the stationary transmission housing70, which greatly simplifies the routing of oil and the reduction of the need for rotating-type seals.

The planetary transmission10provides five forward speeds and one reverse speed between the input shaft34and the transfer gear176. The reverse speed ratio is provided with the engagement of the torque-transmitting mechanism76and the torque-transmitting mechanism80. The first and lowest forward speed ratio is established with the engagement of the torque-transmitting mechanism78and the torque-transmitting mechanism80. The second forward speed ratio is established with the engagement of the torque-transmitting mechanism78and the torque-transmitting mechanism82. The third forward speed ratio is established with the engagement of the torque-transmitting mechanism78and the torque-transmitting mechanism74. The fourth forward speed ratio is established with the engagement of the torque-transmitting mechanism74and the torque-transmitting mechanism82. The fifth forward speed ratio is established with the engagement of the torque-transmitting mechanism74and the torque-transmitting mechanism84.

A planetary transmission200shown inFIG. 2includes an input shaft202, a planetary gear arrangement204, and a final drive transfer gear206. The planetary gear arrangement204includes two planetary gear sets208and210, three rotating-type torque-transmitting mechanisms or clutches212,214, and216, and three stationary torque-transmitting mechanisms or brakes218,220, and222. A hub or wall member224is splined or otherwise drivingly connected with the input shaft202. The wall224has splined thereto or drivingly connected therewith a housing or shell226. The shell226is drivingly connected with a sun gear member228, which is a member of the planetary gear set208. The planetary gear set208also includes a ring gear member230and a planet carrier assembly member232. The planet carrier assembly member232includes a plurality of pinion gears234that are rotatably mounted in a planet carrier236. The ring gear member230is formed integrally with or drivingly connected to a hub238that is secured to a sun gear member240of the planetary gear set210. The planetary gear set210also includes a ring gear member242and a planet carrier assembly member244. The planet carrier assembly member244includes a plurality of pinion gears246that are rotatably mounted on a planet carrier248. The ring gear member242is formed integrally with or otherwise secured to the transfer gear206.

The rotating-type torque-transmitting mechanism or clutch212includes a fluid-operated piston250, a plurality of clutch plates252, which are splined to the wall224, and a plurality of friction plates254that are splined to a hub256, which is drivingly connected with the planet carrier248of the planet carrier assembly member244. The piston250includes a nonrotating member258, which is slidably disposed in a cavity260formed in a transmission housing262. The piston250also includes a rotating member264, which includes a plurality of pegs266that extend from a plate portion268through an opening in the wall224and engage with a pressure plate270through a bearing member272. A thrust roller bearing member274is disposed between the nonrotating piston member258and the rotating member264. Thus, the piston member258is stationary and the member264rotates in unison with the wall224.

The rotating torque-transmitting mechanism or clutch214includes a plurality of friction plates276that are splined with the hub256, a plurality of clutch plates278that are splined with a hub280, which is drivingly connected with the planet carrier236of the planet carrier assembly member232. The rotating torque-transmitting mechanism214also includes a fluid-operated piston282, which has a stationary piston portion284and a rotating portion286. The rotating portion286includes a plurality of posts288which extend through openings in the wall224and engage a pressure plate290through a bearing292. A thrust bearing294is disposed between the stationary piston284and the rotating portion286to accommodate relative rotation between these members. The rotating portion286rotates in unison with the wall224.

The rotating-type torque-transmitting mechanism216includes a stationary piston296that is slidably disposed in a cavity298formed in the transmission housing262. The rotating-type torque-transmitting mechanism216also includes a plurality of clutch plates300that are splined and/or drivingly connected with the planet carrier236of the planet carrier assembly member232, and a plurality of friction plates302that are splined with or otherwise drivingly connected with the shell226. Therefore, the friction plates302rotate in unison with the wall224and input shaft202. The torque-transmitting mechanism216has a roller thrust bearing304disposed between the stationary piston296and a pressure plate306. The roller thrust bearing304will accommodate relative rotation between the pressure plate306and the stationary piston296, hence the pressure plate306will rotate in unison with the planet carrier236whether the torque-transmitting mechanism216is engaged or not.

The rotating-type torque-transmitting mechanism212has an apply chamber308formed between the piston250and the transmission housing262. The rotating-type torque-transmitting mechanism214has an apply chamber310formed between the stationary piston284and the housing262. The rotating-type torque-transmitting mechanism216has an apply chamber312formed between the piston296and the transmission housing262.

When the torque-transmitting mechanism212is engaged, the planet carrier248and ring gear member230will rotate in unison with the input shaft202. When the torque-transmitting mechanism214is engaged, due to pressurization of the chamber310, the planet carriers236and248will rotate in unison. These members can rotate relative to the input shaft due to the presence of the bearing292. When the torque-transmitting mechanism216is engaged, the planet carrier236will rotate in unison with the input shaft202.

The stationary type torque-transmitting mechanism218includes an apply piston314, which is slidably disposed in the transmission housing262and cooperates therewith to form an apply chamber316. The torque-transmitting mechanism218further includes a plurality of brake plates318that are splined to a stationary hub320, and a plurality of friction plates322that are splined to the planet carrier236. When the torque-transmitting mechanism218is engaged, the planet carrier236will be held stationary.

The stationary type torque-transmitting mechanism220includes a piston324that is slidably engaged in the transmission housing262and cooperates therewith to form an apply chamber326. The torque-transmitting mechanism220also includes a plurality of brake plates328that are splined with or otherwise drivingly connected to the hub320, and a plurality of friction plates330that are splined with or otherwise drivingly connected with the hub238, which interconnects the ring gear member230with the sun gear member240. When the torque-transmitting mechanism220is engaged, the ring gear member230and sun gear member240will be held stationary.

The stationary-type torque-transmitting mechanism222includes a piston332that is slidably disposed in the housing226and cooperates therewith to form an apply chamber334. The torque-transmitting mechanism222also includes a plurality of brake plates336that are splined with or otherwise connected to the housing226, and a plurality of friction plates338which are splined to a hub339formed on the planet carrier248. Thus, when the torque-transmitting mechanism222is engaged, the planet carrier248will be held stationary.

The torque-transmitting mechanisms212,214, and216have respective return spring assemblies or spring packs340,342, and344, which are effective to disengage the respective torque-transmitting mechanisms whenever the respective apply chambers308,310, and312are not pressurized. The torque-transmitting mechanisms218and220employ a common return spring assembly or spring pack346which will ensure that these torque-transmitting mechanisms are disengaged when their respective pistons314and324are not supplied with fluid pressure in their respective apply chambers. The torque-transmitting mechanism222has a single large spring348when encircles a hub350which is secured or drivingly connected with the transmission housing262.

As is evident from the above description and reviewing the drawings, the torque-transmitting mechanisms212,214, and216are rotating-type torque-transmitting mechanisms each having a stationary apply piston. The use of the stationary apply pistons permits the simple distribution of fluid pressure to the respective apply chambers308,310, and312without the need for rotating-type seal assemblies. Also, these stationary pistons permit radial stacking of the three torque-transmitting mechanisms, thereby saving considerable axial space within the transmission assembly.

The planetary gear arrangement204supplies essentially the same five forward speeds and one reverse speed as are available with the transmission described inFIGS. 1aand1b. For the reverse speed ratio, the torque-transmitting mechanism216and the torque-transmitting mechanism222are selectively engaged. During the first and lowest forward speed ratio, the torque-transmitting mechanism214and the torque-transmitting mechanism222are engaged. During the second forward speed ratio, the torque-transmitting mechanism214and the torque-transmitting mechanism220are engaged. During the third forward speed ratio, the torque-transmitting mechanism214and the torque-transmitting mechanism212are engaged. During the fourth forward speed ratio, the torque-transmitting mechanism212and the torque-transmitting mechanism220are engaged. To establish the fifth forward speed ratio, the torque-transmitting mechanisms212and218are engaged.

A planetary transmission400is shown inFIGS. 3aand3b. The transmission400includes a conventional torque converter and torque converter clutch assembly402, a planetary gear arrangement404, and a final drive mechanism406. The torque converter and clutch assembly402is drivingly connected with an engine crankshaft408, which delivers power to the torque converter402.

The torque converter402is drivingly connected with a transmission input shaft410which in turn is drivingly connected with a sun gear member412disposed in meshing relationship with a plurality of pinion gears414which also mesh with a sun gear member416. The sun gear member416is drivingly connected with an input sleeve shaft418. The pinion gears414are rotatably mounted on a planet carrier assembly member420, which has a planet carrier422drivingly connected with a transmission output shaft424, and with a sun gear member426of a differential planetary gear set428. The differential planetary gear set428also includes a ring gear member430, a plurality of pinion gears432disposed in meshing relationship with the sun gear member426, and a plurality of pinion gears434disposed in meshing relationship with both the pinion gears432and the ring gear member430.

The pinion gears432and434are rotatably mounted in a planet carrier436, which is drivingly connected with a sprocket or gear438, which is a component of the final drive mechanism406. The final drive mechanism406also includes a second sprocket or gear440, which is drivingly connected with the sprocket or gear438through a conventional chain442. The sprocket440drives a shaft444, which is operatively or drivingly connected with a drive mechanism for at least one pair of driving wheels for a passenger vehicle. The output shaft424is also drivingly connected with a final drive mechanism, not shown, for another pair of the driving wheels for a passenger vehicle.

The input sleeve shaft418is secured to or drivingly connected with a hub446, which is secured to a hub448that is drivingly connected to a ring gear member450, which is a component of an input planetary gear set452. The hub448also has a spline portion454, which is drivingly connected with a plurality of clutch plates456which are components of a rotating torque-transmitting mechanism or clutch458. The torque-transmitting mechanism458also includes an inner hub459and plurality of friction plates461.

The planetary gear set452also includes a sun gear member460and a planet carrier assembly member462. The planet carrier assembly member462includes a plurality of pinion gears464that are rotatably mounted on planet carrier466and disposed in meshing relationship with both the sun gear member460and the ring gear member450. The planet carrier466is drivingly connected with a hub468that is a component of a rotating-type torque-transmitting mechanism470. The hub468is also connected through a portion of a rotating-type torque-transmitting mechanism472. Thus, the planet carrier466is drivingly connected with two rotating-type torque-transmitting mechanisms470and472.

The transmission404includes a ratio planetary arrangement474, which is comprised of two planetary gear sets476and478. The planetary gear set476includes a sun gear member480, a ring gear member482, and a planet carrier assembly member484. The planet carrier assembly member484includes a plurality of pinion gears486that are rotatably supported on a planet carrier488and disposed in meshing relationship with both the sun gear member480and the ring gear member482. The planet carrier488is drivingly connected with the hub459.

The planetary gear set478includes a sun gear member490, a ring gear member492, and a planet carrier assembly member494. The planet carrier assembly member494includes intermeshing pinion gears496and498that are rotatably mounted on a planet carrier500. The pinion gears496mesh with the sun gear member490and the pinion gears498mesh with the ring gear member492. The ring gear member492is continuously connected with the ring gear member482, both of which are continuously connected with the ring gear member430.

The planet carrier488is operatively connected with a stationary-type torque-transmitting mechanism502. The sun gear member480is drivingly connected with a hub504, which is drivingly connected with both the torque-transmitting mechanism472and a torque-transmitting mechanism506. The sun gear member490is drivingly connected with a hub508, which is also drivingly connected with the torque-transmitting mechanism470.

The torque-transmitting mechanism470, as previously mentioned, is a rotating-type torque-transmitting mechanism or clutch. The torque-transmitting mechanism470includes a piston510, which is slidably disposed in a housing512of the planetary transmission400. The piston510is therefore stationary. The torque-transmitting mechanism470has a rotating member514that is operated by the piston510through a conventional roller thrust bearing516. The torque-transmitting mechanism470includes a plurality of interdigitated friction plates518and clutch plates520. The friction plates518are splined to the hub468and the clutch plates520are splined to the hub508. The piston510cooperates with the housing512to form an apply chamber522which when pressurized will cause the friction plates518and clutch plates520to frictionally engage, thereby transmitting rotating power between the planet carrier466and the sun gear member480.

The torque-transmitting mechanism472includes a piston524, which is slidably disposed in the housing512and therefore remains nonrotating during operation. The torque-transmitting mechanism472includes a conventional thrust roller or needle bearing526which is disposed between the piston524and an apply plate528. The torque-transmitting mechanism472also includes a plurality of friction plates530interdigitated with a plurality of clutch plates532, which are drivingly connected with the planet carrier466and the hub504, respectively.

The torque-transmitting mechanism458includes a piston534, which is disposed in a stationary housing536that is splined to an extension538of the transmission housing512. This same extension also secures the sun gear member460from rotation. The torque-transmitting mechanism458also includes a rotating apply member540that is operable to cause engagement of the plates456and461whenever an apply chamber542formed between the housing536and the piston534is pressurized.

The torque-transmitting mechanism502is a stationary-type torque-transmitting mechanism and includes an apply piston544that is slidably disposed in a cavity546formed in the housing512. The torque-transmitting mechanism502also includes a plurality of brake plates548and friction plates550that are splined with the housing512and the planet carrier488, respectively. Whenever the torque-transmitting mechanism502is engaged, the planet carrier488will be held stationary.

The torque-transmitting mechanism506includes an apply piston552, which is slidably disposed in a cavity554formed in the housing512, a plurality of brake plates556, and a plurality of friction plates558, which are drivingly connected with the housing512and the hub504, respectively. Whenever the torque-transmitting mechanism506is engaged, the sun gear member480will be held stationary.

The torque-transmitting mechanisms470,472, and458are rotating-type torque-transmitting mechanisms each having a nonrotating piston. The torque-transmitting mechanisms470,472, and506are radially stacked on one side of the input planetary gear set452, and the torque-transmitting mechanisms458and502are substantially relatively radially disposed on the opposite side of the input planetary gear set452. The use of nonrotating pistons permits the easy supply of fluid pressure from a conventional control system, not shown, to each of the apply chambers for the torque-transmitting mechanisms. The apply pressures for the torque-transmitting mechanisms458,470,472, and506are supplied through the end surface of the left end of the transmission housing512and through the extension538. Thus, the passages are easily installed with cross-drilled passages in the housing and extension. The torque-transmitting mechanism502is supplied with fluid pressure through a passage formed in the housing512and communicated with the control assembly, not shown.

The use of these stationary or nonrotating piston-type torque-transmitting mechanisms requires less axial space than rotating-type torque-transmitting mechanisms with rotating pistons, and also eliminates the need for rotating-type seal assemblies which are known to impose drag losses on a planetary transmission.

The planetary transmission400provides six forward speed ratios and one reverse speed ratio through judicious selection of the torque-transmitting mechanisms458,470,472,502, and506in combinations of two. The reverse speed ratio is established with the engagement of the torque-transmitting mechanisms472and502. The first forward speed ratio is established with the engagement of the torque-transmitting mechanisms470and502. The second forward speed ratio is established with the engagement of the torque-transmitting mechanisms470and506. The third forward speed ratio is established with the engagement of the torque-transmitting mechanisms470and472. The fourth forward speed ratio is established with the engagement of the torque-transmitting mechanisms470and458. The fifth forward speed ratio is established with the engagement of the torque-transmitting mechanisms458and472. The sixth and highest forward speed ratio is established with the engagement of the torque-transmitting mechanisms458and506.

By the nesting of the torque-transmitting mechanisms about the input planetary gear set452, a considerable amount of axial space is saved in the overall length of the transmission assembly.

A planetary transmission600shown inFIG. 4includes an input shaft602(a/k/a an input), a planetary gear arrangement604, and an output shaft606(a/k/a an output) supported within a transmission housing630. The planetary gear arrangement604includes a planetary gear set608, four rotating-type torque-transmitting mechanisms612,614,616,618, and one stationary-type torque-transmitting mechanism or brake620.

The planetary gear set608includes a stationary sun gear622, a carrier624, and a ring gear626.

The stationary transmission housing630forms first, second and third stationary piston chambers632,642,652which are positioned radially outboard of each other, sequentially. The piston chambers632and642are positioned axially overlapping each other (i.e., piston chamber642substantially circumscribes piston chamber632), and the piston chamber652partially axially overlaps the piston chambers632,642with respect to the transmission axis633.

Fluid in the piston chamber632is operative to actuate movement of the piston634to the right as viewed inFIG. 4against the force of the return spring636for moving the apply member637toward the apply plate638to apply the clutch612. A bearing639is positioned between the piston component634aand the apply member637to accommodate rotation therebetween, and a bearing640is positioned between the apply member637and the apply plate638to accommodate rotation therebetween.

Pressurized fluid in the piston chamber642is operative to actuate movement of the piston644to the right as viewed inFIG. 4against the force of the return spring646to actuate movement of the apply member647to engage the apply plate648for applying the clutch614. A bearing649is positioned between the piston component644aand the apply member647to accommodate rotation therebetween. As shown, the apply member647is castellated to protrude through the housing member641.

Pressurized fluid in the piston chamber652causes movement of the piston654to the right as viewed inFIG. 4against the force of the return spring656to actuate movement of the apply member657toward the apply plate658for engaging the clutch616. A bearing659is positioned between the piston654and the apply member657to accommodate rotation therebetween.

Actuation of the clutch612operatively connects the ring gear626with the output member672. Actuation of the clutch614operatively connects the housing member641with the output member672. Actuation of the clutch616operatively connects the housing member641with the output member674. Actuation of the clutch618operatively connects the clutch housing676with the clutch hub678. Actuation of the brake620connects the output member680with the transmission housing630.

In view of the foregoing disclosure, many modifications and variations are possible in light of this disclosure. It is therefore to be understood that the invention is only to be limited by the scope of the appended claims.