Abstract:
A transmission lubrication system for a vehicle transmission includes a fluid collection chamber positioned to collect fluid thrown by a rotatable member within the transmission. Structure forming a flow passage extending from the fluid collection chamber is in fluid communication with a transmission component so that the collected fluid flows from the fluid collection chamber via the flow passage to the transmission component to lubricate the transmission component.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/589,281, filed Jul. 20, 2004, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     The invention relates to the lubrication of a power transmission, especially during towing.  
       BACKGROUND OF THE INVENTION  
       [0003]     A power transmission for a vehicle contains many moving components that require lubrication. A typical transmission lubrication system includes lubricating oil circulated by a pump. The pump is powered by the vehicle engine. When the engine is turned off, such as during towing of the vehicle, the pump does not run and cannot circulate lubricating fluid to the transmission.  
       SUMMARY OF THE INVENTION  
       [0004]     A transmission lubrication system for a vehicle transmission is provided that lubricates transmission components, especially those that move during vehicle towing, when a power source for the vehicle is turned off. The transmission lubrication system includes a transmission component and structure forming a fluid collection chamber that is positioned with respect to the transmission component to collect fluid thrown by rotation of a rotating member within the transmission. Structure such as the transmission casing forms a flow passage which extends from the fluid collection chamber and is in fluid communication with the transmission component so that the collected fluid flows by gravity from the fluid collection chamber via the flow passage to lubricate the transmission component.  
         [0005]     In one aspect of the invention the rotatable member, which may be an output chain or a gear, is located in the interior space of the transmission and is connected to the power source and to the wheels. The rotatable member rotates by the power source when the power source is on and rotates by rotation of the wheels when the power source is off and the vehicle is being towed. The rotatable member contacts fluid contained in the transmission and throws the fluid such that it is collected in the fluid collection chamber. The fluid collection chamber may include a spill feature permitting the collected fluid to spill out of the fluid collection chamber when a predetermined level of fluid is collected.  
         [0006]     In another aspect of the invention, the transmission casing includes an extension positioned so that the projected fluid coats the extension and is then dripped from the extension into the fluid collection chamber.  
         [0007]     In yet another aspect of the invention, the flow passage includes a valve that restricts flow when the power source is powering the vehicle and is selectively openable to permit flow from the fluid collection chamber to the transmission component when the power source is not powering the vehicle (i.e., when the vehicle is being towed).  
         [0008]     In still another aspect of the invention, the branch passage extends from the flow passage and permits fluid to flow from the flow passage to another transmission component for lubrication thereof. A valve may be located in the branch passage that is selectively operable to permit flow to the other transmission components when a predetermined level of fluid pressure exists in the flow passage.  
         [0009]     A method for lubricating a vehicle transmission during towing of the vehicle includes towing the vehicle such that wheels on the vehicle rotate. A rotatable member located within the transmission rotates through lubricating fluid contained in the transmission in response to the rotation of the wheels to throw the lubricating fluid off of the rotatable member. The method then includes collecting the thrown fluid. Finally, the method includes directing the collected fluid onto a transmission component for lubrication thereof.  
         [0010]     Optionally, after the rotating step, the method may include coating the casing with the thrown fluid and dripping the thrown fluid from the coated casing such that the dripped fluid is collected.  
         [0011]     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a schematic illustration of a first vehicle being towed by a second vehicle;  
         [0013]      FIG. 2  is a schematic perspective illustration of a transmission lubrication system including a rotating member for lubricating the transmission of the towed vehicle of  FIG. 1 ; and  
         [0014]      FIG. 3  is a schematic illustration in partial perspective and partial cross-sectional view of the transmission lubrication system of  FIG. 2 , with the rotating member not shown. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]     Referring to the drawings, wherein like reference numbers refer to like components,  FIG. 1  shows a towed vehicle  100  being towed by a towing vehicle  101 . The towed vehicle  100  includes a power source, such as an engine  102  that during normal driving operation powers the transmission  104  to rotate the wheels  108 . A rotating member, such as an output chain  106 , drives a differential mechanism (not shown) operatively connected to the wheels  108  to rotate the wheels, as is typical. As an alternative to the output chain  106 , the rotating member may be a gear  143  (or multiple gears) shown in phantom and rotating about the same axis I as the left hand side of the chain  106 . During normal driving operation, a pump (not shown) is powered via the engine  102  to provide lubrication to internal moving components of the transmission  104  to prevent frictional heat damage to the components. During towing, the pump is not powered and therefore cannot supply lubricant to the moving components in the transmission  104 .  
         [0016]     Referring to  FIG. 2 , a transmission lubrication system  110  includes a fluid collection chamber  112 , also referred to herein as a tub. Any structure capable of collecting fluid as described herein, whether or not having a tub-like formation, may serve as a fluid collection chamber within the scope of the invention. The tub  112  is mounted to or integrally formed on an internal casing wall  114  (shown in phantom) of the transmission  104 . The tub  112  is located generally above the chain  106 . A lower portion  116  of the chain  106  contacts fluid  117  collected toward the bottom of the transmission as it rotates clockwise as indicated by the arrow A. As the chain continues to rotate, centrifugal force throws some of the fluid off of the chain  106 . The thrown fluid may splash against the wall  114 , coating the wall  114  or splash off of the wall  114  into the tub  112 , as indicate by the path of arrow B. Thrown fluid that coats the wall  114  may collect on an extension  118  (i.e., a detent) formed on or mounted to the wall  114  and positioned to drip the collected fluid into the tub  112  located below. (It should be noted that the lubrication system  110  would also function if the chain  106  were rotating counterclockwise, as it would be if the vehicle  100  of  FIG. 1  were facing the opposite direction than that shown during towing. In that instance, fluid would be thrown from the chain  106  in a different pattern, but would still be collected in the tub  112 ). The tub  112  is formed with a spillover lip  120 , which causes collected fluid  132  to spill out from the tub when it reaches a predetermined level (i.e., the bottom of the lip  120 ) to maintain no more than the predetermined level of fluid in the tub  112 .  
         [0017]     Referring to  FIG. 3 , a tube  122  extends downward from an opening  124  in the tub  112  and connects to structure  126 , the tube  122  and the structure  126  together forming a first flow passage  128 . The structure  126  may be the transmission casing or other structure within the transmission forming a flow passage. A first ball check valve  130  prevents flow in the first flow passage  128  when the engine  102  is powering the vehicle and opens to permit flow (via gravity from tube  122  to structure  126 ) when the engine  102  is not powering the vehicle, but the wheels are nevertheless turning (i.e., during towing). Fluid  132  collected in the tub  112  flows down the first flow passage  128  to travel along a connected lower passage  134  formed in the structure  126  to transmission components such as bearings  136  for the chain  106  (fluid flow is represented by arrows shown in the various passages). The lower passage  134  may be the passage used during normal driving operation to transfer lubricating fluid from a pump  138  to the bearings  136 . However, as discussed above, the pump  138  is not powered during towing, and does not assist in lubricating the bearings or other transmission components (such as gears, bearings, washers, clutch plates and bushings) during towing.  
         [0018]     A branch passage  140  is fluidly connected to the first flow passage  128 . A second ball check valve  142  which is preferably spring loaded is housed in the branch passage  140 . When the pressure in the first flow passage  128  downstream of the first check valve  130  reaches a predetermined level, the second check valve  142  permits flow through the branch passage  140  and beyond the valve  142  toward other transmission components  144 .  
         [0019]     Accordingly, the lubrication system  110  permits lubrication of transmission components during vehicle towing (i.e., during an engine off condition) by allowing fluid collected in the tub  112  to flow through the first flow passage  128 . Additionally, the branched formation of the flow passages  128  and  140  permits lubrication of transmission components  136  and  144  which may be located on separate axes within the transmission  104 .  
         [0020]     While the best modes for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.