Abstract:
An improved transaxle having space along an input shaft so that transmission fluid can flow along such input shaft. The input shaft is splined to a forward drum. In order for transmission fluid to be able to pass the splines of the input shaft and the mating splines of the forward drum, either one or more splines or one or more mating splines are removed. Some of each may also be eliminated. The structural integrity of the input shaft is maintained by having the splines radiate from the surface of the input shaft. Optionally, a bushing and tubes facilitate the movement of transmission fluid from the surface of the input shaft, to a cooler, and back to the surface of the input shaft. Furthermore, a variety of construction techniques are employed for, inter alia, further strengthening the improved transaxle.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to transaxles, especially a hydraulically operated semi-automatic planetary transaxle assembly. 
   2. Description of the Related Art 
   A semi-automatic transaxle comprises a differential section and a transmission section coupled to an engine with a torque converter. The transmission section contains hydraulically controlled clutches and bands. The transmission section includes a transmission fluid pump to create the requisite hydraulic pressure. This fluid pressure is regulated and directed, by a valve body assembly, to the clutches and bands in various combinations in order to provide several output gear ratios to the differential. 
   Numerous design features exist for transaxles. 
   The basic structure of a semi-automatic transaxle consists of an input shaft coming from a torque converter that is connected to the engine, an intermediate shaft, optional drop-down gears, an output or pinion shaft, a pinion gear, a ring gear, clutches, and bands. 
   In some transaxles, transmission fluid from the torque converter travels within a channel running longitudinally inside the input shaft to be used subsequently for lubrication. This is, however, not desirable because having the input shaft hollow structurally weakens the input shaft. In some other transaxles the transmission fluid travels along the surface of the input shaft before descending into a channel of the input shaft in order to travel further. Again this introduces structural weakness and is, therefore, undesirable. 
   Some transaxles place a transmission fluid pump on the front of the differential section of the transaxle, enabling the drop-down gears to be at the back of the transmission section of the transaxle. 
   In some transaxles, tapered roller bearings at the pinion gear and ring gear positions are provided with shims behind the bearing cups to allow more precise positioning. 
   The transmission fluid pump in some transaxles circulates transmission fluid to a cooler (such as a radiator or heat exchanger) in order to lower the temperature of transmission fluid coming from the torque converter, which is quite hot. 
   Billet 300M steel is utilized in the input shaft and the intermediate shaft of some transaxles in order to increase strength. 
   Clutch drums in some transaxles are machined from billet 300M steel in order to increase strength. 
   Hollow dowels are used in joining sections of some transaxles to provide precise centering and alignment. 
   For some transaxles, steel thread inserts line the cavity where a bolt is to be screwed into aluminum. 
   And in some transaxles, an oil pump provides oil to be sprayed on the ring and pinion gears as well as the drop-down gears in order to cool them. Such oil is collected in a reservoir below the transaxle and circulated through a cooler. 
   No transaxle is, however, known to the inventor which incorporates all of the preceding features other than the undesirable hollow input shaft. 
   And the only semi-automatic transaxle known by the inventor to be used in vehicles intended for off-road racing is an Audi transmission coupled with an after-market differential section designed for passenger cars having 150 to 200 horsepower. 
   In the Audi transaxle of  FIGS. 1   a  and  1   b , the input shaft  2  and the intermediate shaft  5  are hollow so that a smaller shaft  1  can pass through them to power the transmission fluid pump, which is located at the extreme rear of the transmission case. This hollow structure, as suggested above, weakens the input shaft  2  and the intermediate shaft  5 , causing them to be prone to twisting and breaking. 
   Moreover, the flow of power in the Audi transaxle is, as depicted in  FIG. 1   b , rather complicated. As illustrated in  FIG. 1   b , the input shaft  2  goes through the differential section  3  to the transmission section  4  and proceeds inside the intermediate shaft  5 . When the clutch  6  is engaged, the intermediate shaft  5  sends the power back toward the differential section  3  to the drop-down gears  7  to reach the output shaft  8  in the differential section  3 . 
   Additionally, the Audi clutch drums are made of a cast material of limited strength; and the differential section, being an after-market unit designed to be compatible with the Audi transmission unit, is similarly of limited strength. 
   There is no provision in the Audi transaxle for adjustments to the location of ring gear and pinion gear in order to achieve a wear pattern that will yield long life and reliability. Nor does the Audi transaxle provide for cooling the differential gear oil. 
   And two final disadvantage of the Audi transaxle are (a) that it does not have alignment dowels where the differential section is attached to the transmission case (or section), creating a substantial possibility of misalignment that will affect reliability and (b) that the design of the Audi transaxle creates a tendency for gear oil and transmission fluid to mix. 
   BRIEF SUMMARY OF THE INVENTION 
   The present Improved Transaxle utilizes a unique spline design in order to enable transmission fluid coming from the torque converter to flow along the surface of the input shaft in order to be available for lubrication. This enables the input shaft to be solid, thereby increasing its strength and its resistance to twisting. 
   Additionally, all of the advantageous features discussed above are present in this Improved Transaxle, a selection of features which, to the inventor&#39;s best knowledge, has never been made before and which creates a transaxle uniquely suited to the rigors of off-road racing, especially in vehicles having engines with more than 600 horsepower. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIGS. 1   a  and  1   b  show the Audi transaxle of the prior art as well as the power flow therein. 
       FIG. 2  demonstrates the overall Improved Transaxle, concentrating upon details of the differential section. 
       FIG. 3  primarily illustrates the structures utilized for the flow of transmission fluid within the Improved Transaxle. 
       FIG. 4  emphasizes the structure of the input shaft and the pathway for transmission fluid along the surface of such input shaft. 
       FIG. 5  shows the pathway for transmission fluid along the surface of the input shaft within the differential section and the transmission section of the Improved Transaxle. 
       FIG. 6  is a lateral view showing the splines on the ends of the input shaft. 
       FIGS. 7   a  and  7   b  provide end views showing the splines on the transmission end of the input shaft and on the forward hub in the forward drum. 
       FIGS. 8   a  and  8   b  show the structure for spraying oil on the ring and pinion gears and, optionally, the drop-down gears. 
       FIG. 9  illustrates the gear cover for the drop-down gear. 
       FIGS. 10   a  and  10   b  depict the placement of shims on the sides of the bearing cups for the tapered roller bearings of the pinion gear and ring gear. 
       FIG. 11   a  portrays a fastener and a steel thread insert used to line a cavity wherever a bolt is utilized,  FIG. 11   b  illustrates the hollow dowels which provide precise centering and alignment of adjoining sections,  FIG. 11   c  shows a bolt used as an example of an acceptable fastener, and  FIG. 11   d  depicts an o-ring inside the gear cover utilized positively to assure sealing with respect to fluids. 
       FIG. 12  depicts some of the locations where fasteners, steel thread inserts, hollow dowels, and o-rings are utilized in joining sections of the Improved Transaxle and connecting the gear cover to the transmission section. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As illustrated in  FIGS. 2 ,  3 ,  4 ,  5 ,  8 , and  12  the Improved Transaxle comprises a differential section  3  and a transmission section  4 . 
   And, as shown in  FIG. 2 , an input shaft  2  comes from a torque converter  9  and has a transmission end  10  splined to a forward drum  11 . An intermediate shaft  5  is splined to a forward hub  12  in the forward drum  11 . The forward clutches  13  in the forward drum  11  lock the forward drum  11  and the forward hub  12 . 
   Preferably, behind the forward drum  11  along the intermediate shaft  5  is a direct drum  14  which contains direct (third gear) clutches  15 ; and behind the direct drum  14  is a third set of (intermediate or second gear) clutches  16 , which are not located inside a drum. 
   Traditional planetary gears  17  and bands  18 ,  19  are utilized within the transmission section  4  in order to provide the desired gear ratios, as illustrated in  FIG. 2 . The intermediate shaft  5 , near the rear end  19  of such intermediate shaft  5  is connected to and powers the planetary gears  17 . 
   As indicated above, the transmission fluid pump  20  is placed on the front  21  of the differential section  3  of the transaxle  1  and is driven by the torque converter  9 . 
   The transmission fluid pump  20 , depicted in  FIG. 3 , sends transmission fluid through a tube  22  to a pressure regulator  23 . The pressure regulator  23  has three ports  24 ,  25 , and  26  connected to channels  27 ,  28 ,  29 , respectively, which respectively lead to a valve body  30 , the torque converter  9 , and the pressure side  35  of the transmission fluid pump  20  in order to release excess pressure. 
   As seen in  FIG. 3 , a shifter  31  opens and closes valves  32  in the valve body  30  to engage or disengage the various clutches  13 ,  15 , and  16 , shown in  FIG. 2 , and servos  33 , portrayed in  FIG. 4 , in order to achieve the desired output gear ratios. After being used for this purpose, transmission fluid flows into a sump  34  at the bottom  135  of the transmission section  4 . The transmission fluid pump  20  draws transmission fluid from the sump  34  through a tube  36 , located in both the transmission section  4  and the differential section  3 , into the transmission fluid pump  20 . 
   A bushing  42  supports the input shaft  2  within the torque converter  9 , and a space  37  is left between the input shaft  2  and the casing  38  of the torque converter  9  at least partially—and, preferably, completely—around the input shaft  2  so that the pressurized transmission fluid from the torque converter  9  flows from the torque converter  9  along the surface  39  of the input shaft  2  into the differential section  3 . And a space  40  exists between the input shaft  2  and the differential section  3  as does a space  41  between the input shaft  2  and the transmission section  4  in order to accommodate the flow of transmission fluid along the surface  39  of the input shaft  2  through the differential section  3  and into the transmission section  4 . 
   Since the transmission fluid from the torque converter  9  flowing along the surface  39  of the input shaft  2  tends to be quite hot, a bushing  142  is, as shown in  FIG. 4 , preferably placed around the input shaft  2  to force such transmission fluid from a first side  143  of the bushing  42  into a channel  43 . A fitting  44  connects a tube  45  to the channel  43 . The tube  45  carries the transmission fluid to a cooler  46  (such as a radiator or a heat exchanger). Another tube  47 , fitting  48 , and channel  49  return the transmission fluid to the surface  39  of the input shaft  2  on a second side  50  of the bushing  142  or of a second bushing  242  when additional structural support is desired. 
   Near, and preferably at, the transmission end  51  of the input shaft  2  splines  52  radiate outward, as seen in  FIGS. 6 ,  7   a , and  7   b  in order to connect the transmission end  51  of the input shaft  2  to the forward drum  11 . At least one, and preferably three, positions  53  which would otherwise be occupied by splines  52  are, however, left empty in order to provide for the passage of transmission fluid. The transmission fluid proceeds through the open position or positions  53 , to the center  54  of the forward drum  11 . In order to maintain the strength of the input shaft  2 , such input shaft  2  has preferably its outer diameter increased so that the spaces  53  between adjacent splines  53  have a bottom  155  that is no deeper than the surface  39  of the input shaft  2  where there are no splines  52 . Most preferably, the mating splines  252  on the forward drum  11  adjacent to the position  53  where a spline  52  has been eliminated have the sides  254  of such mating splines  252  adjacent to the position  253  that would have been occupied by the eliminated spline  52  of the input shaft  2  trimmed or otherwise narrowed in order to provide for greater flow of transmission fluid. Optionally but not preferably, the bottom  255  of the position  253  that would have been occupied by the eliminated spline  52  of the input shaft  2  may be lowered to facilitate the flow of transmission fluid. And an alternate to eliminating one or more splines  52  is the trimming described above, the lowering described above, or any combination of these techniques. Furthermore, the actions described in this paragraph, other than lowering (which would structurally weaken the input shaft  2 ), with respect to splines  52  and mating splines  252  can be reversed, e.g., one or more mating splines  252  can be eliminated on the forward drum  11  and trimming can be done on the sides  154  of the splines  52 . Also, one or more splines  52  can be removed; and one or more mating splines  252  can also be removed as long as enough splines  52  and mating splines  252  remain adequately to connect the input shaft  2  and the forward hub  12 . 
   Transmission fluid used for lubrication does not have to be returned to the transmission fluid pump  20 . 
   The upper output shaft  55  proceeds from its attachment to the planetary gears  17 , preferably through a seal  56 , to connect co-axially with the upper drop-down gear  57 . The upper drop-down gear  57  rotates against the lower drop-down gear  58 . And the lower drop-down gear  58  is co-axially attached to the pinion shaft  59 , a small portion  60  of which proceeds rearwardly to drive an oil pump  61  and the principal portion  62  of which goes forward to drive the pinion gear  63  which, in turn, moves the ring gear  64  and, ultimately, the axle drive flanges  65 . Locating the drop-down gears  57 ,  58  at the rear of the Improved Transaxle facilitates quickly changing the final drive gear ratio, which is not possible in most transaxle units. 
   Similarly, preferably oil is forced, preferably utilizing a fitting  68  in the gear cover  69  (for the drop-down gears  57 ,  58 ), portrayed in  FIG. 9 , from the oil pump  61 , through external tubes  66  and  73  to the differential section  3  in order in order to spray oil on the pinion gear  63  and the ring gear  64  to lubricate and cool them, as illustrated in  FIG. 8   a.    
   And as depicted in  FIG. 8   b , optionally the external tube  66  and the external tube  73  also take oil from the oil pump  61  to near the top of the drop-down gears  57 ,  58 , in order to spray the oil on the drop-down gears  57 ,  58  to cool them. 
   After cooling the drop-down gears  57 ,  58  the oil so used is drained to the differential sump  70  near, and preferably, at the bottom  71  of the differential section  3 . Oil used for cooling and lubricating the pinion gear  63  and the ring gear  64  also collects in the differential sump  70 . A suction tube  72  returns oil from the differential sump  70  to the oil pump  61 , preferably through a fitting  168  in the gear cover  69 . Also preferably, a cooler  67  (such as a radiator or a heat exchanger) is placed between tube  73  and tube  66 . (If there is no cooler  67 , then tube  66  and tube  73  constitute a single tube. 
   The seal  56  prevents oil used for lubrication from mixing with gear oil. 
   Placing, as portrayed in  FIG. 10   a , one or more shims  74  behind a first cup race  75  for a tapered roller bearing  76  adjacent to the front end  77  of the pinion carrier  8  which holds t the pinion gear  63  enables such pinion gear  63  to be more precisely longitudinally aligned with the ring gear  64 . Alternatively or additionally, for this same purpose, one or more shims  74  are placed behind a cup race  75  for a tapered roller bearing  76  adjacent to the rear end  79  of the pinion carrier  78 . And one or more flat shims  92  are placed adjacent to a side cover  80  behind a race  82  that holds the tapered roller bearings  83  for the ring gear  64 , as shown in  FIG. 10   b , on a first side of the ring gear  64  in order to provide more precise transverse adjustment between the ring gear  64  and the pinion gear  63 . Such flat shims  79  are available in various thicknesses, increasing in gradations of 0.002 inches. Alternatively or additionally, one or more flat shims  79  are, for the same purpose, placed adjacent to a side cover  80  behind a race  82  that holds the tapered roller bearing  83  for the ring gear  64 , as depicted in  FIG. 10   b , on the opposite side of the ring gear  64 . 
   In order to add further durability and reliability, the input shaft  2  and the intermediate shaft  5  are preferably constructed from billet 300M steel for strength; the forward drum  11  is preferably composed of billet 300M steel to prevent cracking; four hollow dowels  84  are preferably utilized, as shown in  FIG. 11 , to assure precise centering and alignment of four fasteners  85  that join the bell housing  91  to the differential section  3 , four fasteners  85  that join the differential section  3  to the transmission section  4 , and four fasteners  85  that join the gear cover  69  to the transmission section  4 ; o-rings  86  are preferably used in conjunction with each fastener  85  that joins the transmission section  4  to the differential section  3 , and in conjunction with the attachment of the gear cover  69  to the transmission section, in order to preclude leaks; and wherever bolts  85  screw into aluminum, the requisite cavity  87  is lined with a steel thread insert  88  for increased strength, as illustrated in  FIG. 12 . In the Improved Transaxle, the case  89  for the differential section  3  is preferably constructed from aluminum; and the case  90  for the transmission section  4  is preferably constructed from aluminum. 
   In many situations with respect to the present invention, it will be apparent to one of ordinary skill in the art that a channel and a tube are interchangeable. 
   As used herein, the term “preferable” or “preferably” means that a specified element or technique is more acceptable than another but not that such specified element or technique is a necessity.