Apparatus and method for defrosting components in a transport refrigeration unit

Abstract

A transportation refrigeration unit, which is configured to defrost the evaporator coil of an evaporator, is provided with improvements to a power transfer mechanism. The power transfer mechanism incorporates a coupling mechanism that can transfer power from the condenser fan to the evaporator fan. In one embodiment, the coupling mechanism is encapsulated in a housing, which forms an interior cavity for receiving a lubricating fluid therein. The interior cavity is such that the coupling mechanism is immersed in the lubricating fluid.

1 . In a transportation refrigeration unit of the type for conditioning the environment interior of the trailer, said transportation refrigeration unit including an evaporator fan, a condenser fan, and a power transfer mechanism for simultaneously driving the evaporator fan and the condenser fan, the power transfer mechanism further comprising:
 a primary fan shaft coupled to the condenser fan;   a secondary fan shaft aligned with the primary fan shaft, the secondary fan shaft coupled to the evaporator fan;   a coupling mechanism coupling the primary fan shaft and the secondary fan shaft;   a fanshaft housing in surrounding relation to the coupling mechanism; and   a lubricating fluid disposed in the fanshaft housing.   
     
     
         2 . A transportation refrigeration unit according to  claim 1  further comprising a drive pulley in axial engagement with the primary fan shaft, wherein the coupling mechanism is operatively configured to transfer rotation of the drive pulley to the secondary fan shaft. 
     
     
         3 . A transportation refrigeration unit according to  claim 1  wherein the fan shaft housing has a evaporator end for receiving the secondary shaft and a condenser end for receiving the primary shaft, wherein each of the evaporator end and the condenser end have an axial seal, and wherein the axial seals retain the lubricating fluid in the fanshaft housing. 
     
     
         4 . A transportation refrigeration unit according to  claim 1  wherein the coupling mechanism comprise an electromagnetic clutch. 
     
     
         5 . A transportation refrigeration unit according to  claim 1  further comprising an input device coupled to the coupling mechanism, wherein the coupling mechanism changes state in response to an input from the input device. 
     
     
         6 . A transportation refrigeration unit according to  claim 1  wherein the power transfer mechanism is coupled to an internal combustion engine. 
     
     
         7 . A transportation refrigeration unit according to  claim 6  wherein the coupling mechanism operates in a plurality of states, and wherein at least one of the states disengages the evaporator fan from the internal combustion engine. 
     
     
         8 . A transportation refrigeration unit according to  claim 1  wherein the fanshaft housing comprises at least two portions coupled together to form an interior cavity, and wherein the coupling mechanism is disposed in the interior cavity so as to be immersed in the lubricating fluid. 
     
     
         9 . A power transfer mechanism for use on a transportation refrigeration unit of the type for conditioning the environment interior of the container, the transportation refrigeration unit including an evaporator fan and a condenser fan, said power transfer mechanism comprising:
 a coupling mechanism coupling a condenser fan shaft and an evaporator fan shaft, the condenser fan shaft coupled to the condenser fan and imparting rotation to the evaporator fan shaft through the coupling mechanism; and   a fanshaft housing comprising a first portion and a second portion coupled together in a manner forming a interior cavity about the coupling mechanism,   wherein the interior cavity is sealed so as to maintain a volume of a lubricating fluid therein, and   wherein the coupling mechanism is immersed in the lubricating fluid.   
     
     
         10 . A power transfer mechanism according to  claim 9  further comprising a pulley secured to the condenser fan shaft. 
     
     
         11 . A power transfer mechanism according to  claim 9  further comprising:
 a first bearing device engaging the evaporator fan shaft, and 
 a second bearing device engaging the condenser fan shaft, 
 wherein each of the first and second bearing devices are encapsulated by the interior cavity. 
 
     
     
         12 . A power transfer mechanism according to  claim 9  further comprising a seal coupled to each of the first portion and the second portion, wherein the seals retain the lubricating fluid in the interior cavity. 
     
     
         13 . A power transfer mechanism according to  claim 9  wherein the coupling mechanism comprises an electromagnetic clutch. 
     
     
         14 . A power transfer mechanism according to  claim 9  wherein the coupling mechanism is operatively configured to disengage the condenser fan shaft from the evaporator fan shaft in response to an input, and wherein the input indicates frost build-up on a portion of the transportation refrigeration unit. 
     
     
         15 . A transportation refrigeration unit comprising:
 a vapor compression refrigeration system comprising a compressor, an evaporator with an evaporator fan, and a condenser with a condenser fan; and   a fanshaft comprising a first shaft secured to the evaporator fan, a second shaft secured to the condenser fan, and a fanshaft housing in surrounding relation to an integrated coupling mechanism communicating rotational motion between the first shaft and the second shaft,   wherein the fanshaft housing forms a interior cavity about the integrated coupling mechanism, and   wherein the interior cavity is sealed so as to maintain a lubricating fluid therein.   
     
     
         16 . A transportation refrigeration unit according to  claim 15  wherein the integrated coupling mechanism comprises a clutch device disposed in the interior cavity, and wherein the clutch device communicates with one or more of the first shaft and the second shaft to disengage the condenser fan from the evaporator fan. 
     
     
         17 . A transportation refrigeration unit according to  claim 16  wherein the clutch device is an electromagnetic clutch immersed in the lubricating fluid. 
     
     
         18 . A transportation refrigeration unit according to  claim 15  further comprising a power transfer mechanism rotating the condenser fan, wherein the power transfer mechanism is coupled to an internal combustion engine. 
     
     
         19 . A transportation refrigeration unit according to  claim 18  wherein the power transfer mechanism includes a pulley disposed in axial engagement with the condenser fan. 
     
     
         20 . A transportation refrigeration unit according to  claim 15  wherein the coupling mechanism is responsive to feed back indicating frost build-up on the evaporator.