Abstract:
An automatic transmission is specially developed for light-vehicles driven by V-Twin engines and which utilize a separate transmission housing from the engine, and where the transmission is connected with the engine output shaft by a suitable linkage. The transmission includes a main input drive shaft oriented parallel to the engine output crankshaft, and a coaxially aligned drive output shaft. The transmission contains within a gear box a ring gear, planetary gears mounted to a planetary carrier which is mounted to the output shaft, two sun gears, a pair of clutch assemblies and two braking mechanisms. A first clutch assembly includes a clutch drive coupled to the input drive shaft, and an array of clutch plate. The second other clutch assembly is used to couple or uncouple the ring gear to the input shaft for rotation therewith. A one-way clutch is engaged through the actuation of the clutch drum to engage a first ring gear. The first ring gear in turn engages at least two and preferably four groups of idle planetary gears mounted to the planetary carrier. The idle gears in turn mesh with and rotate a first diameter end of an associated compound planetary gear also provided on the planet gear carrier, and which also mesh with the ring gear. The compound planet gears also include a second diameter portion which extend axially, so as to mesh with and engage the second other output sun gear. The brake assemblies are selectively operable to engage the second sun gear and ring gear to permit and/or prevent their relative rotation. The clutch assemblies and brake assemblies are used to enable or stop rotation of ring gear and/or planetary components to change transmission ratio or direction of rotation.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims the benefit under 35 U.S.C. 119(e) to U.S. Provisional Application Serial No. 60/420,030, filed 22 Oct. 2002. 
     
    
     
       SCOPE OF THE INVENTION  
         [0002]    The present invention relates to an automatic transmission for motorcycles and other vehicles, and most preferably light weight vehicles which use a V-Twin engine such as motorcycles, snowmobiles, and other all terrain vehicles.  
         BACKGROUND OF THE INVENTION  
         [0003]    The use of a transmission is required in most vehicles which are powered by combustion engines. Conventional automatic transmissions are not usable on motorcycles and other light vehicles as a result of their typically large size and shape. In particular motorcycle drive systems require a light weight and compact construction with specific mounting arrangement. Although various automatic transmissions for motorcycles are known, as a result of sizing restrictions, heretofore conventional transmissions are provided with a reduced number of forward gears to enable the transmission to be made sufficiently small to permit their mounting on the motorcycle frame.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention seeks to overcome the disadvantages of prior art drive systems by providing a specific arrangement of transmission components for motorcycle and other light vehicle applications.  
           [0005]    Another object of the invention is to provide a transmission having a two stage planetary gear, and which provides three forward operating speeds and one reverse speed.  
           [0006]    A further object of the invention is to provide a transmission having a reverse speed to facilitate vehicle handling while parking, and which most preferably is operated by manual push-button which, for example, maybe mounted on the steering bar.  
           [0007]    Another object of the invention is to provide a transmission construction which incorporates a lock up converter for improved efficiency.  
           [0008]    To at least partially achieve some of the aforementioned objects, the present invention provides an automatic transmission which, although not restricted in use, is specially developed for light-vehicles, such as two-wheel motorcycles, ATV&#39;s, snowmobiles and the like, and most preferably light vehicles which are driven by V-Twin engines. Furthermore, the transmission is most particularly suitable for light vehicle drive systems which utilize a separate transmission housing from the engine, and where the transmission is connected with the engine output shaft by chain, timing belt, or other suitable linkage. The arrangement of the transmission advantageously facilitates retrofitting existing standard transmissions by the hereinafter disclosed automatic transmission, and provides a compact design and gearing arrangement.  
           [0009]    The transmission includes a main input drive shaft which in a most simplified construction is oriented parallel to the engine output crankshaft, and a drive output shaft. Both the engine output shaft and transmission input shaft may be connected by a suitable linkage, and most preferably by a primary synchronous belt and a torque converter. The transmission contains, planetary gears mounted to a planetary carrier, two sun gears, a clutch assembly and two braking mechanisms, all of which are mounted within a gearbox or housing. In a preferred motorcycle construction, the automatic transmission has a cylindrically shape housing which is traversly mounted, and located behind the engine.  
           [0010]    The input shaft is preferably made from alloy metals such as steel, which is hardened and tempered with the outside diameter of the input shaft, ground to close tolerances to obtain close fit with the torque converter. The torque converter which may be mounted inside of a driven synchronous sprocket and attached to starter ring gear. The torque converter is used to transmit power from the primary synchronous belt to the input drive shaft, and preferably is used to continuously rotate the input drive shaft in forward rotational movement while the engine is running.  
           [0011]    The output shaft is preferably also formed from alloy metals, such as hardened and tempered steel. The output shaft is ground to close tolerances at its outside dimensions, and is secured by means of a spline, weldment, or other suitable connecter to the planet carrier within the gearbox. The output shaft is provided with a sprocket or other suitable drive member, outside of the transmission housing and a synchronous, belt chain or other linkage is used to drive one or more wheels of the vehicle. The sprocket engages the chain or belt movement used to drive the rear wheel of the vehicle.  
           [0012]    The clutch assembly preferably includes a first clutch drive assembly, a second ring gear assembly, and a one-way clutch. The first clutch drum assembly includes, a clutch drum which is welded, splined, or otherwise connected to the input drive shaft for rotation therewith, an actuator piston, and one or more arrays of clutch plates which when engaged, couple the clutch drum to an inner end of the output shaft.  
           [0013]    The second ring gear assembly includes a ring gear which is provided radially about and spaced from the input shaft, an actuator piston and one or more clutch plate arrays used to couple the ring gear to the first clutch drum. The ring gear is made from high strength metal alloy, such as steel, machined with cut internal gear teeth disposed in the housing. When assembled, the ring gear teeth engage with one or more planet gears. The ring gear is furthermore engageable by at least one of the arrays of clutch plate. In a simplified construction clutch plates could for example, consist of sets of 3, 4, 5 or more (internal and external) clutch plates which are used to connect or disconnect two rotating members at operating speed.  
           [0014]    The one-way clutch is engaged by the input shaft to rotate the first sun gear in forward rotational movement while the input shaft is rotated forward at faster speeds than the speed of rotation of the output shaft. At least two and preferably four groups of the planetary gears and associated compound planetary gears are provided on the planet gear carrier in order to reduce load to gear teeth. In a preferred construction, the first input sun gear is engaged by first stage idle planetary gears. The first stage idle planetary gears are in turn further engaged by a respective first portion of an associated second stage compound planetary gear. The first portion of the compound planetary gears also mesh with and engage the ring gear. The compound planet gears also include a second other portion which extend axially, so as to mesh with and engage the second other output planetary sun gear. This arrangement allows reduction of transmission size and weight.  
           [0015]    The brake assemblies are selectively operable to engage the ring gear and/or output sun gear, so as to permit or prevent their rotation relative to the housing. Various possible constructions of brake assemblies are envisioned for use in the present invention. In one simplified construction, the brake assemblies may consist of band brakes made of conventional stock components. Although not essential, the braking mechanisms are preferably operated by hydraulic actuator located in an oil pan, extended from or in fluid communication with the main transmission housing. As will be described, the brakes stop rotation of planetary components to change transmission ratio or direction of rotation.  
           [0016]    In a preferred construction, the transmission has five modes of operation, including: neutral; first gear; second gear; third gear or direct drive with locked up converter; and a reverse gear. Individual operation modes are most preferably selected by programmable electronic controller (PLC) based on driver activation and vehicle operation mode. It is envisioned, however, that other types of controls, including mechanical and/or electromechanical controls could also be used. In one simplified construction, the PLC sends an electrical signal to one or two of four electromagnetically operated hydraulic valves controlling actuating clutches and/or band brakes within the transmission to selectively couple and/or uncouple the ring gear and sun gears from the transmission input and output shafts.  
           [0017]    Accordingly, in one aspect the present invention resides in a transmission comprising: an input drive shaft, the input drive shaft being elongated along and rotatable about an axis, an elongated output shaft, the output shaft being rotatable about and coaxial with the axis, an input sun gear being selectively rotatable about the axis, a one-way clutch coupled to the input shaft for rotation therewith selectively engaging the input sun gear, the one-way clutch operable to engage and rotate the input sun gear in forward rotation about the axis when the input drive shaft is rotated about the axis at a faster forward rate that the output drive shaft, an output sun gear spaced axially from the input sun gear, the output sun gear being selectively rotatable about the axis, an output gear brake assembly selectively operable to permit or prevent rotation of the output sun gear radially about the axis, a first clutch assembly including, a first clutch drum assembly including a first selectively actuable clutch piston coupled to the input shaft for rotation therewith, and a first clutch plate array activatable by said first clutch piston to couple the first drum assembly and said output drive shaft, a second clutch assembly including, an annular ring gear having an annularly extending toothed ring gear surface extending radially about and spaced from the axis, a second selectively actuable clutch piston coupled to the ring gear for rotation therewith, a second clutch plate array activatable by said second clutch piston to couple the ring gear to the first drum assembly for rotation therewith, a ring gear brake assembly selectively operable to permit or prevent rotation of the ring gear, a planetary gear assembly comprising: a planet gear carrier fixed to said output shaft for rotation therewith, a first set of planetary gears rotatably mounted on said planet gear carrier and meshing with a portion of said input sun gear, and a second set of compound planet gears rotatably mounted on said planet gear carrier, each second compound gear comprising: a first diameter portion and a second diameter portion spaced axially from the first diameter portion, the first diameter portion interposed between and meshing with an associated one of said first planetary gears and said toothed ring gear surface, the second diameter portion meshing with said output sun gear.  
           [0018]    Preferably, the second diameter portion of each compound planetary gear has a diameter selected greater than a diameter of the first diameter portion.  
           [0019]    More preferably, the input sun gear has a diameter and a number of radially extending gear teeth which is selected less than that of the output sun gear. Although not essential, the input planetary gears preferably have a diameter and number of radially extending gear teeth selected substantial equal to the diameter portion of the associated compound planetary gear.  
           [0020]    In another aspect, the present invention resides in a light vehicle drive assembly comprising: a vehicle engine having an engine output shaft, a transmission comprising, a transmission housing having an opening extending axially therethrough, an elongated input drive shaft and output drive shaft being coaxially aligned in said opening, each of the input drive shaft and output drive shaft being elongated along and rotatable about the axis, a linkage rotatably coupling the engine output shaft and the input shaft, an input sun gear being selectively rotatable about the axis, a one-way clutch coupled to the input shaft for rotation therewith, the one-way clutch engaging and rotating the input sun gear in forward rotation about the axis only when the input drive shaft is rotated about the axis at a faster forward rate than the output drive shaft, an output sun gear disposed about the axis and being selectively rotatable about the axis, an output gear brake assembly selectively engageable with the output sun gear to permit or prevent rotation of the output sun gear relative to said housing, a first clutch assembly including, a first clutch drum assembly including a clutch drum coupled to the input shaft for rotation therewith, a first selectively actuable clutch piston mounted to said first clutch drum, and a first clutch plate array activatable by said first clutch piston to rotatably couple the first drum assembly and said output drive shaft, a second clutch assembly including, an annular ring gear having an annularly extending toothed ring gear surface extending radially about and spaced from the axis, a second selectively actuable clutch piston coupled to the ring gear for rotation therewith, and a second clutch plate array activatable by said second clutch piston to couple the ring gear to the first drum assembly for rotation therewith, a ring gear brake assembly selectively operable to permit or prevent rotation of the ring gear relative to said housing, a planetary gear assembly comprising, a first set of planetary gears rotatably mounted on said planet gear carrier and meshing with a portion of said input sun gear, and a second set of compound planet gears rotatably mounted on said planet gear carrier, each second compound gear comprising, a first diameter portion and a second diameter portion spaced axially from the first diameter portion, the first diameter portion interposed between and meshing with an associated one of said first planetary gears and said toothed ring gear surface, the second diameter portion meshing with said output sun gear.  
           [0021]    In a further aspect, the present invention resides in a transmission comprising: a transmission housing having an elongated opening extending along an axis therethrough, an elongated input drive shaft rotatably disposed in said opening, an output drive shaft being coaxially aligned, an input sun gear disposed radially about the axis and being selectively rotatable, a one-way clutch coupled to the input shaft for rotation therewith, the one-way clutch engaging and rotating the input sun gear in forward rotation about the axis only when the input drive shaft is rotated about the axis at a faster forward rate than the output drive shaft, an output sun gear disposed radially about the output shaft and being selectively rotatable about the axis, an output gear brake assembly selectively engageable with the output sun gear to permit or prevent rotation of the output sun gear relative to said housing, a first clutch assembly including, a first clutch drum assembly including a clutch drum coupled to the input shaft for rotation therewith, a first selectively actuable clutch piston mounted to said first clutch drum assembly, a first clutch plate array activatable by said first clutch piston to rotatably couple the first drum assembly and said output drive shaft, a second clutch assembly including, an annular ring gear having an annularly extending gear surface extending radially about and spaced from the axis, a second selectively actuable clutch piston coupled to the ring gear for rotation therewith, and a second clutch plate array activatable by said second clutch piston to couple the ring gear to the first clutch drum for rotation therewith, a ring gear brake assembly selectively operable to permit or prevent rotation of the ring gear relative to said housing, a planetary gear assembly comprising, a planet gear carrier fixed to said output shaft for rotation therewith, a first set of planetary gears rotatably mounted on said planet gear carrier and meshing with a portion of said input sun gear, and a second set of compound planet gears rotatably mounted on said planet gear carrier, each second compound gear comprising, a first diameter portion and a second diameter portion spaced axially from the first diameter portion, the first diameter portion interposed between and meshing with an associated one of said first planetary gears and said toothed ring gear surface, the second diameter portion meshing with said output sun gear.  
           [0022]    In another aspect, the present invention resides in a vehicle drive system comprising: an axially elongated motor drive shaft, and a transmission have an input shaft rotatably coupled to the drive shaft and a coaxially aligned output shaft for providing power output to a vehicle wheel, said transmission further comprising: a first annular ring gear extending radially about the input shaft and having a first diameter, a radially extending input sun gear disposed about said axis, an output drive sun gear rotatably disposed about at least part of the output drive shaft, a planetary gear carrier coupled to the output shaft for rotation therewith and a first portion with, a first set of idle planet gears meshing with the input sun gear, and a second set of compound gears, each of the compound planet gears including a first portion with the ring gear and meshing with and interposed between an associated idle gear and ring gear, and a second portion extending axially and meshing with the output sun gear, the ring gear and driven sun gear being selectively rotatable about said axis, a respective brake assembly selectively operable to lock the ring gear and/or driven sun gear, and a one-way sprag assembly operable to rotatably engage the input sun gear when the input shaft is rotated at forward speeds faster than the forward rotational speed of the output shaft, and wherein the first and second portions of the compound planetary gears each carry a plurality of gear teeth, and whereby the number of gear teeth on the first portion is less than the number of teeth on the second portion. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    Reference may now be had to the following detailed description taken together with the accompanying drawings in which:  
         [0024]    [0024]FIG. 1 illustrates schematically a motorcycle drive system incorporating an automatic transmission assembly in accordance with a preferred embodiment of the invention;  
         [0025]    [0025]FIG. 2 illustrates a schematic cross-sectional view of the transmission assembly shown in FIG. 1, taken along line  2 - 2 ′;  
         [0026]    [0026]FIG. 3 illustrates a cross-sectional view of the brake band assembly used in transmission assembly shown in FIG. 2;  
         [0027]    [0027]FIG. 4 illustrates an enlarged partial cross-sectional view of the planetary gear assembly used in the transmission assembly show in FIG. 2;  
         [0028]    [0028]FIG. 5 illustrates a cross-sectional end view of the first stage idle planetary gears of the planetary gear assembly shown in FIG. 4, taken along  5 - 5 ′;  
         [0029]    [0029]FIG. 6 illustrates a sectional end view of the second stage planetary gears of the planetary gear assembly shown in FIG. 4, taken along  6 - 6 ′;  
         [0030]    [0030]FIG. 7 illustrates schematically the transmission assembly shown in FIG. 2 illustrating the operation of the transmission drive shaft in a first forward gear;  
         [0031]    [0031]FIG. 8 illustrates schematically the transmission assembly shown in FIG. 2 illustrating the operation of the transmission drive shaft in a second forward gear;  
         [0032]    [0032]FIG. 9 illustrates schematically the transmission assembly shown in FIG. 2 illustrating the operation of the transmission drive shaft in a third forward gear; and  
         [0033]    [0033]FIG. 10 illustrates schematically the transmission assembly shown in FIG. 2 illustrating the operation of the transmission drive shaft in a reverse gear.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]    Reference may be had to FIG. 1 which illustrates schematically a drive system  10  for a motorcycle or other light vehicles. The drive system  10  includes a V-twin engine  12  having an axially elongated engine output shaft  16 , a primary drive belt  14  and torque converter  20  used to transmit power from the engine output shaft  16  to a transmission assembly  22 , and a secondary drive belt  24  for use in driving the rear motorcycle wheel (not shown). As shown best in FIG. 1, the engine output shaft  16  is used to drive the primary drive belt  14 . The belt  14  in turn is used to rotatably engage the torque converter  20  which turns a turbine or other suitable linkage member (not shown) used to turn the transmission input shaft  28 . A starter ring gear  26 , when engaged with a starter motor, is used to start the motor  12 .  
         [0035]    As will be described, the transmission output shaft  30  is used to output power from the transmission assembly  22  to the rear wheel, and is provided with a drive sprocket  32  (FIG. 1) used to engage the secondary drive belt  24  in movement.  
         [0036]    The gearing for the automatic transmission assembly  22  is housed within a generally cylindrical housing  34 . The housing  34  provides an outer shell for the main components of the automatic transmission  22 . The housing  34  preferably is formed as a compact generally cylindrical shape. The housing  34  includes an elongated opening which extends therethrough along an axis A-A 1 , which in motorcycle applications most preferably is oriented parallel to and rearwardly from the axis of elongation (A 2 -A 2 ) of engine output shaft  16  (FIG. 1). FIG. 2 shows best the transmission assembly  22  as including the input drive shaft  28  and an output shaft  30 . The input drive shaft  28  is coupled to the torque converter  20  used to translate power from the primary drive belt  14  to the transmission assembly  22  and rotate the input shaft  28  in a forward direction about the axis A 1 -A 1 . The bottom of the housing  34  is provided with an oil pan  35  which may be made from suitable metals, such as aluminium, magnesium, or aluminium casting. The oil pan  35  is preferably made of aluminium sheet metal and is attached to the main housing  34  by bolts (not shown). As will be discussed, the oil pan  35  provides a reservoir for hydraulic oil used in operation of the automatic transmission assembly  22 . The ends of the housing  34  are sealed about the input and output shafts  28 , 30  by end covers  36 , 38  which most preferably, are formed from machined aluminium and include, respectively, axially positioned openings  40 , 42 . A bearing  43  is provided in the output opening  42  to align the output shaft  30  in position along the centre axis A 1 -A 1  of the transmission  22 .  
         [0037]    The drive input shaft  28  and output shaft  30  are most preferably provided as elongated cylindrical hardened steel members provided in a coaxially aligned orientation with each other and with the housing axis A 1 -A 1 , and extend inwardly therein through a respective opening  40 , 42 . A trust bearing  33  separates the adjacent ends of the input and output shafts  28 , 30  enabling this operation at different rotational speeds. The trust bearing  33  is most preferably selected from commercial stock.  
         [0038]    As shown best in FIG. 2, the opening  40  formed in the input side end cover  36  extends axially through an end mounted oil pump housing  41 . The opening  40  is sized thereto to receive therein a hollow stator shaft  44 . The stator shaft  44  is provided with a hollow interior adapted to receive therein in coaxially alignment input shaft  28 . An oil pump drive shaft  46  is provided as a hollow shaft which is disposed radially about the stationary shaft  44  and is rotatably supported by pump drive shaft bearings  48 . The oil pump drive shaft  46  is attached to the torque converter  20 , so as to provide constant rotation therewith to hydraulic pump gears  47 , 49  which are coupled to the pump drive shaft  46 . The pump gears  47 , 49  are disposed within the pump housing  41  for providing and porting pressurized oil from the oil pump housing  41  to or from transmission housing  34  and torque converter  20 .  
         [0039]    Within the housing  34 , the transmission assembly  22  further includes a second gear clutch housing assembly  50 , a forward drum clutch assembly  52 , an input drive sun gear  54 , an output sun gear  56 , a planetary gear assembly  58  and a one-way sprag clutch assembly  66 . FIG. 2 shows best the forward drum clutch assembly  52  as including a clutch drum assembly  60  coupled to the input shaft  28  by splines for constant rotation therewith and an array of clutch plates  62  selectively actuable to couple the clutch drum assembly to the inner end of the output shaft  30 . The clutch drum assembly  60  is further provided an axially slidable actuator pistons  68  which is moveable to engage the clutch plate array  62 .  
         [0040]    [0040]FIG. 2 shows the second gear clutch housing assembly  50  as including a second array of clutch plates  64 , an axially slidable actuator piston  70 , and a ring gear  74  which extends radially about the axis A 1 -A 1 . The ring gear  74  extends axially within the cylindrical housing  34  and is preferably disposed radially about the innermost end of the input shaft  28 . The radially inwardly created surface of the ring gear  74  is provided with gear teeth  75  which, as will be described, are engaged by the planetary gear assembly  58 .  
         [0041]    The hydraulic actuator pistons  68 , 70  are selectively moveable in the axially orientation, whereby pressure from hydraulic oil pumped or released into or out of the pump housing  41  is used to selectively move the pistons  68 , 70  in the direction of arrows  100 , 102 , into engagement against the respective arrays of clutch plates  62 , 64 , to selectively actuate each array  62 , 64 .  
         [0042]    The outer array of clutch plates  64  is selectively co-operable with the clutch drum ring gear  74  in the operation of the transmission assembly  22 . The inner array clutch plates  62  co-operable with the innermost end of the output shaft  30 . Optionally, a clutch hub  72  may be secured to the inner end of the output shaft  30 , to facilitate engagement of the clutch plate array  62 . Each of the arrays of clutch plates  62 , 64  preferably consists of five internal and external nested clutch plates which are used to connect or disconnect the operating speeds. The individual clutch plates in the arrays  62 , 64  may be made from a number of conventional materials, and for example, could include a combination of steel and fiber filled plates which are stamped and heat treated to higher hardness.  
         [0043]    The one-way sprag clutch assembly  66  is mechanically locked to the input drive sun gear  54  by the forward rotational force of the forward drum clutch assembly  52  as it rotates with the input drive shaft  28 . The one-way sprag clutch assembly  66  is selected so as to engage and rotate the input sun gear  54  about the axis A 1 -A 1  preferably only while the input shaft  28  rotates in a forward direction, about the axis A 1 -A 1 , faster than the output shaft  30 . In this manner, the sprag clutch assembly  66  is used to selectively lockup the input sun gear  54  for forward rotation with the rotation of the input shaft  28 .  
         [0044]    The ring gear  74  is selectively coupled and/or uncoupled in rotational movement about the axis A 1 -A 1 , together with the input shaft  28  by the selective operation of clutch plate array  64  and/or a brake band assembly  84  (FIG. 3). As will be described, the brake band assembly  84  includes a brake band  128   a  which, in operation, is used to engage a peripheral portion of the ring gear  74  and prevent its rotation relative to the housing  34 . Similarly, the activation of the actuator piston  70  is used to engage and actuate the clutch plate array  64 , to lockup the ring gear  74  with the forward drum clutch assembly  52  for rotation together with the input shaft  28 .  
         [0045]    FIGS.  4  to  6  show best enlarged views of the planetary gear assembly  58  used in the transmission assembly  22  of FIG. 2. The planetary gear assembly  58  is mounted for radially movement in a plane normal to and about the axis A 1 -A 1  and includes a planet gear carrier  80  (FIG. 4) used to mount first stage idle gears  110  and second stage compound planet gears  112 . Most preferably, the planet gear carrier  80  is formed from a high strength alloy steel and may, for example, consist of a welded multiple piece construction which is machined and jig-bored to provide accurate location of the individual planetary gears  110 , 112 . As shown best in FIG. 4, the planetary gear carrier  80  is secured by splines  81  to the inner end of the output shaft  30 . As will be described, the carrier  80  acts in concert with the driven or input sun gear  54  and the output sun gear  56  to transmit rotational power from the input shaft  28  to the output shaft  30 .  
         [0046]    The output sun gear  56  is mounted for relative rotation about the output shaft  30 , and is secured in rotatable alignment with the axis A-A 1  therewith by a series of plane bearings  86 . Preferably, the output sun gear  56  has a radial diameter d o  and number of peripherally extending gear teeth greater than the radial diameter d i  and number of peripheral gear teeth of the input sun gear  54 .  
         [0047]    [0047]FIGS. 5 and 6 illustrate best the planet gear carrier  80  as mounting four first stage idle planet gears  110   a ,  110   b ,  110   c  and  110   d , and four second compound planet gears  112   a ,  112   b ,  112   c  and  112   d . In a preferred construction, the planet gear carrier  80  has two compartments; one for housing the first stage planet gears  110 , and the other for housing the second stage compound planet gears  112 . Each of the planet gears  110   a ,  110   b ,  110   c ,  110   d ,  112   a ,  112   b ,  112   c ,  112   d  are rotatably mounted on a respective axially positional pin shaft  114  and roller bearings  116 . The pin shafts  114  are most preferably made from bearing tool steel and have been heat treated to high hardness sufficiently to withstand abrasion with the roller bearings  116 . The pin shafts  114  are formed as generally cylindrical pins which are elongated along a respective pin axis A p -A p  (FIG. 4) which in assembly, is parallel to the axis A 1 -A 1 . The pin shafts  114  may be pressed fitted on to the planet gear carrier  80  and secured by either button head screws (not shown), by stamping, or the like.  
         [0048]    The first stage planetary gears  110   a ,  110   b ,  110   c  and  110   d  are provided at equal radially spaced positions about the axis A 1 -A 1  meshing with the input sun gear  54 , so as to be engaged therewith. The gears  110  most preferably are made from carburizing grade steel which is machine heat treated and finish ground to precise tolerances. As shown best in FIG. 5, the first stage planet gears  110   a ,  110   b ,  110   c ,  110   d  have a diameter d 1  selected smaller than the radial spacing between the input sun gear  54  and the internal teeth  75  on the ring gear  74 .  
         [0049]    The compound planet gears  112   a ,  112   b ,  112   c ,  112   d  are axially elongated and include a first diameter pinion end  118  (FIG. 5) having a diameter d 2 , and a second diameter pinion end  12  having a diameter (FIG. 6) which is larger than diameter d 2 . The first diameter pinion end  118  which, for example, is shown best in FIG. 5, preferably has a number of radially extending gear teeth and diameter d 2  which is substantially equal to diameter d 1 . The end portion  118  of each compound gear  112   a ,  112   b ,  112   c ,  112   d  is sized and positioned for interposed engagement both with an associated first stage planet gear  110   a ,  110   b ,  110   c ,  110   d , as well as the internal toothed periphery  75  of the ring gear  74 . As shown in FIG. 6, the second pinion end  120  of each of the second compound planet gears  112   a ,  112   b ,  112   c ,  112   d  has a radial diameter d 3  and number of peripheral gear teeth selected greater than that of the first pinion end  118 . The second pinion ends  120  of the gears  112  are spaced axially outward from the ring gear  74  and matingly engage the output sun gear  56 .  
         [0050]    The ring gear  74  is provided with internal teeth  75  having a spacing (shown best in FIG. 5) which is configured for mated tooth engagement with the first diameter pinion end  118  of the second compound gears  112 .  
         [0051]    As shown best in FIGS. 2 and 3 a brake wheel  88  is coupled to the output sun gear  56  for rotation about the axis A 1 -A 1  therewith. The peripheral surface of the brake wheel  88  is selectively engageable by means of a one-way sprag clutch assembly, or more preferably the peripherally disposed brake band  128   b  which is provided as part of brake band assembly  90 . As will be described, in operation of the transmission assembly  22 , the brake band assembly  90 , may be used to lockup to engage the rotation of the output sun gear  56  relative to the housing  34  and planet gear carrier  80 .  
         [0052]    [0052]FIGS. 2 and 3 illustrate the hydraulic brake bands assemblies  84 , 90  used to selectively permit or prevent rotation of the ring gear  74  and brake wheel  88 , respectively. Within the housing  34  are disposed a pair of hydraulic cylinders  124   a ,  124   b  which, most preferably, are in fluid communication with the oil pan  35  and oil pump housing  41 . The hydraulic cylinders  124   a ,  124   b  are fabricated from suitable tubing and are welded or otherwise secured to the transmission housing  34 . More preferably, the cylinders  124   a ,  124   b  are controlled by a small programmable logic controller (PLC) that outputs an electrical signal to servo valves (not shown). The servo valves in turn direct hydraulic oil or other fluids to individual actuator pistons  68 , 70  and/or brake cylinders  124   a ,  124 , changing the ratio and/or speed direction of the rotating gears. A hydraulic actuator  126   a ,  126   b  such as a sliding piston, is provided within each hydraulic cylinder  124 ,  124   b . The actuators  126   a ,  126   b  are in turn coupled to the brake bands  128   a ,  128   b , respectively, which extend about and are engageable with a periphery of ring gear  74  and brake wheel  88 , respectively. As such, the operation of the hydraulic cylinders  124   a ,  124   b  by the PLC are selectively operable to tension or release the brake bands  128   a ,  128   b  into bearing contact with either the ring gear  74  and or brake wheel  88  in the operation of the transmission assembly  22 .  
         [0053]    The operation of the transmission assembly  22  is shown best with reference to FIGS.  7  to  10 . The transmission assembly  22  has three forward speeds with locked up converter, one reverse speed, and/or neutral operations. By selectively connecting specific clutch pack arrays  62 , 64  and/or engaging brake band assemblies  84 , 90  and disconnecting others sets, individual speeds and/or reverse or neutral operations may be achieved. Most preferably, the operation of the transmission assembly  22  is controlled by the selective actuation of the hydraulic actuators  126   a ,  126   b  within the respective cylinders  124   a ,  124   b  to activate and/or de-activate the brake bands  128   a ,  128   b . The programmable logic controller (PLC) is provided to output an electrical signal to servo valves (not shown) used to direct hydraulic oil or other suitable fluids to flow from the pump housing  41  to the actuator pistons  68 , 70  and or desired cylinder  124   a ,  124   b.    
         [0054]    [0054]FIG. 7 illustrates the transmission assembly  22  schematically, in a first operating gear with the primary drive belt  14  and torque converter  20  used to rotate the input drive shaft  28  forwardly in the direction of arrow  130  about the axis A-A 1 . First gear is obtained by the activation of the one-way sprag assembly  66  rotating the input sun gear  54  together with the drive shaft  28 . Concurrently, the band brake assembly  90  is set by its respective hydraulic actuator  126   b  to result in the engagement of brake band  128   b  with the brake wheels  88  and prevent rotation movement of the output sun gear  56  within the housing  34 .  
         [0055]    The clutch plate arrays  62 , 64  and remaining brake band assembly  84  are left open to permit relative free movement of the ring gear  74 , relative to the input shaft  28 . With this configuration, power is transmitted from the input shaft  28  to the one-way sprag clutch assembly  66  and input sun gear  54 . As the output sun gear  56  is held in a stationary position, the first stage planet gears  110   a ,  110   b ,  110   c ,  110   d  are driven by the input sun gear  54 , and in turn rotate the associated compound planet gears  112   a ,  112   b ,  112   c ,  112   d . The rotation of the compound planet gears  112  causes the ring gear  74  to rotate freely, and the planet gears  112   a ,  112   b ,  112   c  to “walk” about the output sun gear  56 . The rotational movement of the compound planet gears  112   a - d  imparts rotational movement to the planet gear carrier  80  which, as it is coupled directly to the output shaft  30 , rotates the output shaft  30  in the direction of arrow  132  to drive the secondary drive belt  24 .  
         [0056]    Operation of the transmission assembly  22  in the second gear is shown best in FIG. 8, with the formal rotation of input shaft  28  in the direction of arrow  130 , the second array of clutch plates  64  is engaged to lockup the ring gear  74  for rotation with forward drum clutch assembly  60 . In second gear, the brake band assembly  90  remains deployed to prevent rotation of the brake wheel  88  and output sun gear  56  relative to housing  34 . The brake band assembly  84  is also maintained in an inactive state. The clutch plate array  62  remains released to maintain the input drive shaft  28  in an uncoupled state from the output shaft  30 . As with first gear, the band brake  128   b  continues to prevent rotation of the output sun gear  56  relative to the housing  34 . In second gear, rotational power is transmitted by the input shaft  28  via the clutch drum  60  and clutch plate  64  to the ring gear  74 . The rotation of the ring gear  74  with the input shaft  28  rotates the compound planet gears  112   a ,  112   b ,  112   c ,  112   d  at a higher rotational speed than the input sun gear  54 , giving it a higher ratio. This in turn causes rotational movement of the compound gears  112  relative to the stationary output sun gear  56 , and transmits power to the planet gear carrier  80 , causing it to rotate at second increased speed about the stationary output sun gear  56 , driving the output shaft  30  in the direction of arrow  132 .  
         [0057]    The operation of the transmission assembly  22  in a third gear is illustrated best with reference to FIG. 9. In third gear, the inner clutch plate array  62  is engaged to couple the input drive shaft  28  and the forward clutch drum assembly  60  directly to the clutch hub  72  (FIG. 5) and output shaft  30 . Simultaneously, the brake band  90  assembly is released so as to no longer lockup the output sun gear  56  by its engagement with the brake band  128   b . The brake band assembly  84  remains deactivated to permit the rotation of ring gear  74  relative to the band brake  128   a . Although not essential, the clutch pack array  64  most preferably is maintained in engaged state. In this position, each of the input drive shaft and output shaft  30  are locked together in rotation in the direction of arrows  130 , 132 . The locking up of all of the shafts  28 , 30 , thus, achieves direct drive from the input shaft  28  to the output shaft  30  with a 1:1 transmission ratio therebetween.  
         [0058]    The transmission assembly  22  may be operated to rotate the output shaft  30  in a reverse orientation of arrow  134  for a reverse gear. Reverse gear is shown best in FIG. 10 as being achieved by engaging the ring gear brake band assembly  84  to cause the brake band  128   a  to engage the ring gear  74  and prevent its rotation within the housing  34 . The brake band assembly  90  is simultaneously deactivated to release the brake band  128   b  and permit the output sun gear  56  to rotate freely about the axis A 1 -A 1 . The clutch plate arrays  62 , 64  are both deactivated. In this configuration, power is transmitted by the input shaft  28  in the direction of arrow  130 , to the input sun gear  54  via the one-way sprag assembly  66 . The rotation of the input sun gear  54  within the planet gears  110   a - d  and  112   a - d  causes their engaging rotation. The stationary ring gear  74  results in the movement of the planetary gears  110   a ,  110   b ,  110   c ,  110   d  in the reverse direction along the teeth  75 . The reverse movement of the planetary gears  110   a ,  110   b ,  110   c ,  110   d  relative to the ring  74  rotates the planetary gear carrier  80  in the opposite direction, moving the output shaft  30  in the direction of arrow  134  therewith.  
         [0059]    It is to be appreciated that to achieve a neutral position with the transmission assembly  22 , both sets of clutch plate arrays  62 , 64  are deactivated, and both brake band assemblies  84 , 90  are released. In this configuration, the input shaft  28  and input sun gear  54  are permitted to rotate. This in turn permits free wheeling of the planetary gears  110   a ,  110   b ,  110   c ,  110   d ,  112   a ,  112   b ,  112   c ,  112   d , uncoupling the output shaft  30  from the input shaft  28 .  
         [0060]    The automatic transmission assembly  22  of the present invention provides additional simplicity and comfort to vehicle operation. It is to be appreciated that the transmission assembly  22  overcomes the disadvantages of prior art by providing an improved compact transmission construction which is sufficiently compact, so as to be suitable for use on light vehicles with a traversly mounted engine and transmission.  
         [0061]    Although the detailed description describes the transmission assembly  22  as being used in light vehicle and motorcycle applications, the invention is not so limited. The transmission assembly  22  is equally suitable for use in automotive applications with conventional V-6 and/or V-8 applications. Furthermore, the applicant has appreciated that the transmission assembly  22  may advantageously be used in racing applications, as for example in automobile off road or drag racing applications where input power may range between 500 and 2500 hp. In particular, the direct coupling of the input shaft  28  and output shaft  30  by the clutch plate array  62  in third gear, may advantageously permit the assembly  22  to continue to provide output drive power, even in the event of the failure of the ring gear  74  and/or planetary gear assembly  58 .  
         [0062]    While the detailed description discloses the transmission assembly as including a pair of brake band assemblies  88 , 90  the invention is not so limited. Those skilled in the art will appreciate that other types of clutch assemblies, including without restriction sprag clutch assemblies may be used in substitution for the brake band assemblies  88 , 90  described.  
         [0063]    Although the detailed description describes and illustrates various preferred embodiments, the invention is not so limited. Many modifications and variations will now occur to persons skilled in the art. For a definition of the invention, reference may be had to the appended claims.