Abstract:
A power take-off assembly for transmitting rotary power from the powertrain of a motor vehicle includes a torque converter for an automatic transmission and including an impeller shaft connected driveably to a power source, a housing having a opening through a wall of the housing, and a power takeoff gear secured to the impeller shaft, located in the housing, aligned with the opening, and supported for rotation about an axis.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to a motor vehicle powertrain and, in particular, to use of the powertrain as a power source for equipment that is onboard or extrinsic to the vehicle. 
   2. Description of the Prior Art 
   The engine of a motor vehicle can be used to supply power through a power take-off (PTO) to onboard equipment, such as a hydraulic pump that provides pressure to support and move a snowplow blade or a bucket boom, and to extrinsic equipment, such as a water pump or electric generator at a construction site, ranch or farm. 
   A conventional PTO is driven downstream of a torque converter turbine, which is hydrokinetically coupled to the engine shaft through an impeller, driveably coupled to the engine. A conventional PTO unit transmits no power when the vehicle is stopped, though the selected position of the transmission gear selector is either the reverse-range or drive-range because. For a conventional PTO to provide power to a user, the transmission must transmit power to its output 
   In heavy truck applications, a PTO assembly generally is located axially between a transmission bell housing and the gearbox. But this arrangement does not package well in light trucks. It requires changing the rear position of the transmission, which causes mount/cross and drive shaft complexities, and is incompatible with high volume manufacturing. 
   A need exists in the light truck industry for a live PTO that is driven directly by the engine output regardless of the operating state of the transmission, and permits a one-piece transmission case and common driveshafts whether the vehicle is equipped with an optional PTO or the PTO is not incorporated in the vehicle. 
   SUMMARY OF THE INVENTION 
   A power take-off assembly for transmitting rotary power from the powertrain of a motor vehicle includes a torque converter for an automatic transmission and including an impeller shaft connected driveably to a power source, a housing having a opening through a wall of the housing, and a power takeoff gear secured to the impeller shaft, located in the housing, aligned with the opening, and supported for rotation about an axis. 
   The live PTO gear is located within the pump/stator support assembly. This arrangement eliminates complexity and the associated cost. The hydraulic feeds to pump/stator assembly go directly to the valve body and allow for a thin mounting flange. Consequently, the opening in the PTO mounting flange is positioned axially towards the bell housing, thereby allowing the PTO gear, mounted inside the pump/stator assembly, to have direct access to the PTO opening. 
   This arrangement also provides a one piece case or separate bell housing, alternative pump/PTO drive configurations that allow isolation the pump from the converter hub. The PTO idler gear can be integrated with pump housing or can be a separate drop-in unit that is installed when customer installs the PTO unit. 
   The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 

   
     DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
       FIG. 1  is a cross sectional side view showing a torque converter, hydraulic pump and PTO unit; 
       FIG. 2  is a cross section showing a second embodiment of the PTO unit; 
       FIG. 3  is a partial front view of the transmission oil pump assembly; PTO unit and idler; 
       FIG. 4  is a schematic diagram showing a motor vehicle powertrain to which the PTO unit can be applied; and 
       FIG. 5  is a cross sectional side view showing a third embodiment of the PTO unit. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring first to  FIG. 1 , a torque converter  10 , located along an axis  11  between an engine and the front of an automatic transmission, includes an impeller  12  surrounded by a torque converter cover  14 , which is secured to the blades of the impeller and connected driveably to the crankshaft of the engine. An impeller shaft  16 , welded to the cover  14 , is supported for rotation on a pump body  18  by a bearing  20 . The pump body  18  is fitted into a pump support  22 , which is secured by bolts  23  to the front cover  24  of the transmission. The pump body  18  contains a hydraulic pump, whose gear or rotor  26  is connected by an external spline  28  to impeller shaft  16 . 
   An internal spline  30  on impeller shaft  16  connects that shaft to the pinion  32  of a PTO. Gear  32  is supported by a bearing  34  located on a shoulder of a stator shaft  36 , which extends axially from the stator of torque converter  10 . PTO gear  32  meshes with a PTO idler gear  38 , which is supported on a bearing  40  and a stub shaft  42 , fitted into the lugs  44 ,  46  of PTO idler gear support  48 . A snap ring  49  secures shaft  42  in position on the support  48 . 
   The transmission housing  56  is formed with a covered opening  50  surrounded by a mounting surface  52 . The cover is removed when the PTO unit is installed. The idler support  48  is removeably attached to and supported on mounting surface  52  while the PTO is being used. The PTO idler gear  38  is located such that it engages with an output gear  54 , located on equipment  55  (seen best in  FIG. 2 ) that is to be driven by the PTO. Output gear  54  extends through the opening  50  into the space enclosed by the transmission housing  56 . Front cover  24  may be separate from transmission housing  56  such that the opening  50  is integrated solely in the housing  56 , or cover  24  and housing  56  may be integral comprising a single housing. 
   In operation with the engine running, impeller  12 , impeller shaft  16  and PTO gear  32  are driven by the engine in rotation about axis  11 . PTO idler gear  38  is driven by gear  32  and rotates on the idler support  48  about axis  58 . Power from the engine is transmitted through the PTO assembly, PTO idler gear  38  and output gear  54  to the subject equipment  55 . 
     FIG. 2  illustrates a second embodiment, in which the PTO gear  32  is formed integrally with a pump drive or an impeller shaft  60 . A transmission torque converter stator support assembly  62  is spaced axially from the rear face  64  of pump support  22 , thereby providing a space in which the PTO gear  32  is located and the PTO idler gear  38  extends through the opening  50  to engage gear  32  and gear  54 . 
     FIG. 3  shows the teeth of PTO gear  32  meshing with the teeth of PTO idler  38  at a radial line extending from axis  11 . External radial access to PTO gear  32  is provided to PTO idler  38  through the opening  50  in the wall of housing  56 . 
     FIG. 4  is a schematic diagram showing a portion of a vehicle powertrain, whose power source is an engine  70  having a crankshaft  72  driveably connected to the impeller cover and impeller  12 . The impeller shaft  16  is connected driveably to the rotor in the pump body  18 . A bladed turbine  74  is hydrokinetically coupled to impeller  12  and is driven by hydraulic fluid exiting the impeller. A lock-up clutch  76  engages and disengages alternately in response to control of a transmission controller. When clutch  76  is engaged, a mechanical connection between engine crankshaft  72  and the transmission input shaft  78  is produced, such that the hydrokinetically coupling is inoperative. The input shaft  78  of transmission  66  transmits power to a gear box containing gears, shafts, solenoids, clutch and brakes, which cooperate to produce various gear ratio of the transmission  66 . The wheels of the vehicle are driven from the transmission output shaft  82 . 
     FIG. 5  illustrates a third embodiment in which an idler support  90  is integrated with both the stator support  62  and the pump support  22  by bolts  92 ,  93  that is secured in position within the transmission  66 . The idler gear  38 , bearing  40 , shaft  42  are not removed from the transmission housing  56  when the PTO is not being used to transmit power. Instead, the output gear  54  and its engagement with PTO idler gear  38  are removed from the housing  56  when the PTO is not being used to transmit power. Then the opening  50  in housing  56  is closed with a cover. 
   Impeller shaft  96  is formed with teeth  98  at its axial end, which engage teeth  100  formed on the adjacent end of PTO gear  32 , thereby driveably connecting shaft  96  and gear  32  mutually. 
   In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.