Speed-changing system with two fluid-actuated clutches
FIELD OF THE INVENTION 
     My present invention relates to a speed-changing system for transmitting torque from an engine, particularly one of the internal-combustion type, to a load such as the traction wheels of an automotive vehicle with a selectively variable speed ratio. 
     BACKGROUND OF THE INVENTION 
     In my prior U.S. Pat. No. 3,744,606 I have disclosed a dual hydraulic or pneumatic coupling for the selective fluidic actuation of two coupling devices such as clutches and/or brakes. In that prior patent I have also referred to several earlier U.S. patents, owned by the assignee of the present application, which describe a variety of planetary-gear transmissions adapted to be used in such a system, generally in series with a hydraulic torque converter. Selection of three forward speed ratios and one reverse ratio is possible in such systems which the aid of two clutches and two brakes associated with two cascaded planetary-gear trains; with the addition of further planetary-gear trains and coupling devices, the number of available speed ratios can be extended. Typically, the two clutches serve for selectively connecting an input shaft (normally driven from the engine through the aforementioned torque converter) with either or both of the two output shafts carrying, for example, the sun gears of a pair of cascaded planetary-gear trains; the coaxially nested output shafts are in line with the input shaft. With the extremities of the nested output shafts suitably staggered, they can be alternatively or jointly coupled with an adjoining extremity of the input shaft while one of these output shafts, conveniently the outer one, can also be selectively immobilized by an associated brake. 
     Certain problems have heretofore arisen in the feeding of high-pressure fluid to the two clutch housings for the displacement of their associated pistons, in view of the fact that these clutch housings are positively coupled with respective shafts for joint rotation therewith. The expedient of admitting the fluid to these clutch housings through channels in the associated shafts has the drawback of appreciably weakening the shaft structure, which therefore must be made heavier than would otherwise be required, and also necessitates the provision of special seals on opposite sides of the port through which the high-pressure fluid exits from the shaft. 
     OBJECTS OF THE INVENTION 
     The general object of my present invention is to provide an improved structural arrangement in such a system simplifying the feeding of high-pressure fluid (referred to hereinafter as oil) to a pair of clutch housings, with avoidance of any significant weakening of elements serving for the transmission of torque. 
     A more particular object of this invention is to provide improved means for pressurizing a clutch housing (referred to hereinafter as the &#34;second clutch housing&#34;) mounted on the outer one of the two aforementioned nested output shafts. 
     SUMMARY OF THE INVENTION 
     I realize these objects, in accordance with my present invention, by the provision of a stationary member adjoining the second clutch housing and defining therewith a ring channel which communicates with the interior of that clutch housing and forms part of a passage for admitting oil under pressure thereto, this member being rigid with a transmission housing surrounding the two clutch housings and being preferably a transverse wall of that transmission housing, e.g. a partition separating a clutch compartment from an adjoining brake compartment. The stationary member advantageously has a central aperture accommodating an annular bearing for the outer output shaft and also has a radial inlet terminating at the ring channel as part of an oil-supplying passage. That passage may further include an inner peripheral groove on a hub of the second clutch housing received in an annular boss of the adjoining member surrounding its central aperture. The other clutch housing (referred to hereinafter as the &#34;first clutch housing&#34;) is positively connected with the input shaft and may receive oil through a passage which includes an annular clearance formed between that shaft and a surrounding tube secured to the transmission housing, as separately claimed in my application Ser. No. 535,702 of even date. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and other features of my invention will now be described in full with reference to the accompanying drawing in which: 
     FIG. 1 is an axial sectional view of the left-hand portion of a speed-changing system embodying my invention, including two hydraulic clutches and a hydraulic brake; and 
     FIG. 2 is a view similar to FIG. 1, partly overlapping same and showing the right-hand portion of the system. 
    
    
     SPECIFIC DESCRIPTION 
     The system shown in the drawing comprises a transmission housing 1 enclosing the extremities of three coaxial shafts, namely an input shaft 7 and two nested output shafts 19, 25. Input shaft 7 is driven in the conventional way, e.g. as illustrated in commonly owned U.S. Pat. No. 3,593,599, from an internal-combustion engine via a hydraulic torque converter not further illustrated. Output shafts 19 and 25 serve as inputs for two cascaded planetary-gear trains here shown, by way of example, as being of the type disclosed in the same commonly owned patent, with sun gears S 1 , S 2 , planet gears P 1 , P 2  and ring gears R 1 , R 2 , serving to drive a load shaft O with a variable speed ratio as is well known per se. Sun gears S 1  and S 2  are keyed to outer output shaft 25 and inner output shaft 19, respectively, and can thus be driven independently or jointly under the control of hydraulic clutches K1 and K2 within transmission housing 1. This transmission housing also contains a conventional hydraulic brake B1, actuatable to arrest the outer shaft 25, and another such brake B2 illustrated only schematically and serving to immobilize the ring gear R 2 . The planetary-gear system also includes one-way couplings which have not been illustrated. 
     The clutches K1 and K2 are respectively provided with a first annular clutch housing 10, containing an axially slidable annular piston 18, and a second annular clutch housing 31, containing an axially slidable annular piston 29. Pistons 18 and 29 are normally held in a retracted position by respective Belleville springs 35, 36; when displaced by high-pressure fluid, as more fully described below, piston 18 engages a set of interleaved friction foils 37 whereas piston 29 engages a similar set of foils 38. Annular foils 37 are alternately mounted on the inner periphery of an extension 10a of first clutch housing 10 and on a collar 39 which is splined to the left-hand end of shaft 19, projecting beyond shaft 25, and effectively forms an extension thereof; annular foils 38 are alternately mounted on the outer periphery of the same clutch-housing extension 10a and on the inner periphery of the second clutch housing 28. The first clutch housing 10 is splined at 14 to the right-hand end of input shaft 7; the second clutch housing 28 is similarly splined, at 25a, to the left-hand end of shaft 25. 
     Shaft 7 is rotatably journaled in a mounting tube 6 coaxially surrounding same with formation of an annular clearance 13 therebetween, this clearance extending around the end of tube 6 between the latter and an enlarged head 7a of shaft 7 carrying the clutch housing 10. Clearance 13 is bounded by two sealing rings 8 and 9 of low-friction material, ring 8 being press-fitted into tube 6 as a journal bearing for shaft 7 whereas ring 9 is press-fitted into a central bore of clutch housing 10 to serve as a counterbearing for that clutch housing and therefore also for the supporting extremity of shaft 7. Tube 6 and shaft 7 are respectively secured to the stator and the rotor of the preceding torque converter whose housing has been partly illustrated at 3, being bolted to transmission housing 1 through an end plate 2 of the latter; tube 6 may therefore be regarded as stationary, with reference to housing structure 1-3, even though this is not essential. 
     A tubular shaft 40, rotatably carried by tube 6, forms the input for a gear pump 5 whose housing 4 is bolted to plate 2, this gear pump having relatively eccentric toothed rings 5a and 5b meshing with each other in the lower part of housing 4. Oil delivered by pump 5 enters at 41 into a high-pressure port 32 from which it is distributed to other parts of the system, in particular to a first passage 12 and to a second passage 20 leading to the interior of clutch housings 10 and 28, respectively. The admission of oil to these passages is automatically controlled, e.g. in the manner described in the aforementioned U.S. Pat. No. 3,593,599, through valves indicated diagrammatically at 33 and 34. 
     The first passage 12 extends through a radial bore 11 in tube 6 into clearance 13 and thence via an oblique bore 16 of clutch housing 10 into the interior 17 thereof, to the left of its piston 18. Second passage 20, extending radially within a partition 21, terminates inside an annular boss 21a of this partition in a ring channel 22 which is defined by confronting faces of partition 21 and of a hub 28a of clutch housing 28 surrounded by boss 21a. The passage further extends into the interior 30 of clutch housing 28 through a slanting bore 31 thereof communicating with a groove 27 on the inner periphery of hub 28a, the bore 31 lying to the right of piston 29. A sealing ring 24 in an annular groove of hub 28a prevents the escape of oil from ring space 22. Partition 21 divides the interior of transmission housing 1 into a left-hand compartment, accommodating the clutches K1 and K2, and a right-hand compartment, accommodating the brake B1. 
     Partition 21 is formed with a central bore into which a bearing ring 23, similar to rings 8 and 9, is press-fitted to serve as a journal for the left-hand end of outer output shaft 25; ring 23 also prevents leakage from ring channel 22 to the low-pressure side of the system which includes a central bore 42 of shaft 19. In order to guard against oil leakage in the opposite direction, i.e. by way of splines 25a, a sealing ring 26 is interposed between shaft 25 and clutch housing 28 to the left of this spline coupling. Similarly, a sealing ring 15 prevents the outflow of oil via spline coupling 14 from clearance 13. These sealing rings could be omitted, of course, if the corresponding spline couplings were replaced by solid welding connections or the like.