Patent Publication Number: US-8968141-B2

Title: Uninterruptible oil supply in planetary system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of U.S. application Ser. No. 13/568,400 filed on Aug. 7, 2012, which is a continuation of U.S. application Ser. No. 11/080,175 filed on Mar. 15, 2005, now U.S. Pat. No. 8,267,826 granted on Sep. 18, 2012. 
    
    
     BACKGROUND OF THE INVENTION 
     This application generally relates to an oil supply system for a planetary gear system. More particularly, this application relates to an uninterruptible oil supply system for a planetary gear system. 
     Conventional planetary gear assemblies include a carrier housing supporting rotation of various gears. Each gear is supported on a journal shaft and supplied with lubricant through passages within the journal shaft. Lubricant is delivered to the journal shaft by a primary delivery system. A secondary delivery system is typically included to provide lubricant if the primary delivery system fails. Although, the secondary system will continue lubricant delivery to the journal shaft and thereby to the gears, there is inevitably a time delay between failure of the primary delivery system and reestablishment of lubricant flow provided by the secondary delivery system. During the time delay lubricant is not provided to the journal shaft. The absence of lubricant can have undesired affects, especially in high-speed applications such as those commonly used in aircraft drive train applications. 
     Lubricant delivered to the journal shaft generates a lubricant film between the journal shaft and the gear supported thereon. The lubricant film is necessary to prevent undesirable contact between the gear and the journal shaft. During the interim between failure of the primary lubricant delivery system and engagement of the secondary system it is possible that the lubricant film will dissipate due to the temporary absence of lubricant, thereby allowing contact between with the gear and the journal shaft. This undesirable touchdown of the gear can cause undesirable damage and premature wear. 
     The carrier housing body typically experiences some degree of twisting caused by transmission of torque to the gears supported thereon, which can result in undesirable bearing misalignment. Such misalignment can cause premature wear or damage to the journal shaft. Typically, the effect of torsional twisting of the carrier housing is minimized by the application of a torque frame system. The torque frame provides support for the carrier housing and transmits torque through a shaft to an engine system. However, such a system does not provide an accommodation for the interim time period between failure of a primary lubricant system and engagement of the secondary lubricant system. 
     Accordingly it is desirable to design and develop a lubricant supply system that provides effective and reliable lubricant delivery in the interval between failure of the primary system and reestablishment of lubricant flow by a secondary system. 
     SUMMARY OF THE INVENTION 
     This invention is a system for providing and ensuring continuous lubricant delivery to a journal bearing in an interim period between failure of a primary lubricant delivery system and reestablishment of lubricant flow by a secondary lubricant delivery system. 
     The system of this invention includes a planetary carrier housing supporting a plurality of journal shafts, that in turn support a plurality of planetary gears. The journal shafts receive lubricant to produce a lubricant film that supports the gear. A torque frame is part of the carrier system and provides support for the carrier and transmits torque via a shaft to an engine supporting structure. The torque frame includes a lubricant passage that communicates lubricant starting from a first radial distance to the carrier housing body at a second radial distance. The carrier housing body supplies lubricant to journal shafts. Lubricant is delivered through the torque frame lubricant passages by a positive pressure. The torque frame includes several lubricant communication passages to provide lubricant to each of the separate journal shafts. 
     Each of the lubricant communication passages includes an accumulator for storing lubricant during normal operation. The accumulator stores a desired amount of lubricant to provide necessary lubricant to the adjacent journal shaft for the interim period between primary system failure and secondary system engagement. Lubricant from the accumulator is forced to the journal shaft by centrifugal force generated by rotation of the carrier housing body and torque frame. Flow of lubricant from the accumulator maintains a desired lubricant flow to each of the journal shafts until the secondary system can provided lubricant at desired pressures and flows. 
     Accordingly, the system and method of this invention includes a lubricant accumulator within the torque frame that provides lubricant supply to the journal shaft in the interim period prior to actuation of the secondary lubricant delivery system. 
     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a planetary gear carrier according to this invention. 
         FIG. 2  is a cross-sectional view of a torque frame according to this invention. 
         FIG. 3  is a cross-sectional view of another torque frame according to this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1  a planetary gear system  10  includes a carrier  12  and a torque frame  14  for transmitting torque to an output shaft (not shown) without imparting twisting the carrier  12 . The carrier  12  supports a plurality of journal bearing shafts  16  that in turn support a corresponding plurality of planetary gears (not shown). Lubricant is provided through passages within the torque frame  14  to smooth operation of each of the planetary gears. Lubricant is provided by a primary system  15  ( FIG. 2 ) that is supplemented with a secondary system  17  ( FIG. 2 ). In the event that the primary system  15  can no longer supply lubricant, the secondary back-up system  17  engages and continues the supply of lubricant such that there is substantially little interruption of lubricant flow. 
     Even in optimal circumstances there is a delay in lubricant flow in the interim period between stoppage of the primary system and reestablishment of lubricant flow provided by the secondary back-up system  17 . The torque frame  14  includes a plurality of accumulators  38  disposed adjacent lubricant passages to store lubricant during normal operation and provide lubricant in the interim period prior to engagement of the secondary system  17 . The torque frame  14  includes a plurality of spokes  20  that extend radially outward from an outer hub  26 . Each of the spokes  20  includes a boss  28  that attaches to the carrier  12 . Lubricant is communicated through openings  25  in the outer hub  26  through a passage within each of the spokes  20 , and bosses  28  to the carrier  12 . Lubricant may be supplied directly from lubricant jets to the torque frame 
     Referring to  FIG. 2  one spoke  20  of the torque frame  14  is shown and includes the hub  26  that is attached to a shaft  32  rotating about an axis  22 . Lubricant is supplied to the outer hub  26  and into the lubricant main passage  30 . The accumulator  38  is disposed adjacent the main passage  30  and includes an inlet  40  and an outlet  42 . The inlet  40  is disposed at a radial location  41  spaced apart from the axis  22 . The radial distance provides for lubricant flow caused by centrifugal forces produced during rotation of the planetary gear system  10 . During normal operation lubricant flows through the main passage  30  and into the carrier passage  52 . The carrier passage  52  includes an opening  50  that communicates lubricant to the journal bearings  16  ( FIG. 1 ). 
     A desired amount of lubricant determined by the volume of the accumulator  38  fills the accumulator  38 . Lubricant within the accumulator  38  is continuously replenished such that there is a constant flow of lubricant through the accumulator  38 . The outlet  42  can include an orifice  48  sized to limit the flow of lubricant. The orifice  48  is sized to provide a lower flow of lubricant than would otherwise be provided through the main passage  30 . 
     In the event of primary system fault, lubricant will empty from the main passage  30  and begin being drawn from the accumulator  38 . The outlet  42  is spaced radially apart a distance  54  from a portion of the passage  35  parallel to the axis  22  to create a positive pressure or head that drives the flow of lubricant. The inlet  40  is spaced apart from the axis  22 . The distance from the axis  22  along with rotation of the planetary gear system  10  generates a centrifugal force that causes lubricant to flow radially outward. 
     The accumulator  38  includes a volume that is calculated to provide a desired amount of lubricant for a desired time. The desired time corresponds with the time delay that occurs prior to reestablishment of lubricant flow by the secondary system  17 . The flow rate of lubricant from the accumulator  38  in this example can be set to the minimum flow rate required to maintain the journal bearing shaft  16  functions. The lower flow rate provides a greater duration of lubricant availability from the stored lubricant within the accumulator  38 . Lubricant flow to the journal bearing shafts  16  may be reduced to provide the additional time. 
     Referring to  FIG. 3 , another example torque frame  14  according to this invention is shown in cross-section and includes an accumulator  60  that is an integral portion of the passage  62 . The accumulator  60  defines a portion of the passage  62  for lubricant between the hub  26  and the boss  28 . Lubricant flows radially outward through the spokes  20  from the hub  26  to the boss  28  and into the carrier  12 . Lubricant fills the accumulator  60  due to a restriction  66  in the passage  64  that creates a slight backpressure that results in filling of the accumulator  60 . Lubricant continuously fills the accumulator  60  during normal operation and empties when lubricant flow from the primary system  15  is interrupted. 
     The torque frame  14  can be connected through the boss  28  to the carrier housing body by fasteners such as bolts or screws (not shown). As the torque frame  14  and the carrier  12  are continuously rotating and generating centrifugal forces, the lubricant is forced into the carrier  12 . The outlet  66  between the accumulator  60  and the passage  64  controls the flow of lubricant such that the accumulator  60  fills during normal operation, and to regulate emptying of lubricant at a predetermined desired flow rate during the interim period before reestablishment of lubricant flow by the secondary system  17 . 
     In operation, lubricant is supplied by the primary system  15  by a positive pressure head or jets at a lower radial location such as at the hub  26  of the torque frame  14 . The lubricant is then driven radially outward through the passage  62  in the torque frame  14  by centrifugal forces generated by rotation of the planetary gear system  10 . Lubricant is restricted at the outlet  66  to provide for the continuous filling of the accumulator  60 . In the event that the primary system  15  no longer functions and lubricant pressure and flow to the accumulator  60  is interrupted, flow from the accumulator  60  will continue for a predetermined period after the primary system  15  is no long providing lubricant. The duration that the accumulator  60  can supply flow to the journal bearing shaft  16  is determined to coincide with the time required to reestablish lubricant flow by with the secondary system  17 . This provides for uninterrupted supply of lubricant to the journal bearing shafts  16 . 
     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.