Abstract:
A gear drive assembly for a supercharger is provided. The gear drive assembly has at least one gear member rotatable about an axis of rotation and includes a cover member operable to substantially enclose the at least one gear member. A tube member extends though the cover member and is generally aligned along the axis of rotation. The tube member is operable to vent the gear drive assembly. A supercharger assembly incorporating the gear drive assembly is also disclosed.

Description:
TECHNICAL FIELD 
     The present invention relates to a vented gear drive assembly for a compressor or supercharger. 
     BACKGROUND OF THE INVENTION 
     It is known in the art to utilize positive displacement compressors, such as roots-type and screw-type compressors, having lobed rotors for supercharging internal combustion engines and for providing compressed air for other purposes. Such a compressor, when used as an automotive supercharger, may include a housing having a rotor cavity in which a pair of rotors, having interleaved lobes, rotates to transport volumes of intake air between an inlet passage of the housing and an outlet passage of the housing thereby increasing the pressure at the outlet passage. 
     Sustained high load operation of the supercharger increases the air temperature exiting the supercharger, with the highest temperatures typically reached at high engine speeds and supercharger loads. The air tends to heat lubricating oil within a gear drive assembly of the supercharger by forced convection/conduction. 
     SUMMARY OF THE INVENTION 
     A gear drive assembly for a supercharger assembly is provided. The gear drive assembly includes at least one gear member rotatable about an axis of rotation. A cover member is operable to substantially enclose the at least one gear member. A tube member extends through the cover member and is positioned substantially adjacent to the at least one gear member and is generally aligned along the axis of rotation. The cover member at least partially defines a volume within which a predetermined amount of lubricating oil is disposed. The tube member is positioned above the predetermined amount of lubricating oil when the at least one gear member is not rotating and is operable to vent the gear drive assembly. A supercharger assembly incorporating the gear drive assembly is also disclosed. 
     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 
         FIG. 1  is a bottom view of a supercharger assembly adapted for use with an internal combustion engine; 
         FIG. 2  is a cross sectional perspective view of a portion of the supercharger assembly taken along Line Z-Z of  FIG. 1 , illustrating a gear drive assembly consistent with the present invention; 
         FIG. 3  is a perspective view of a cover member for use with the gear drive assembly of  FIG. 2 ; and 
         FIG. 4  is a perspective view of an alternate embodiment of a cover member for use with the gear drive assembly of  FIG. 2 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures, there is shown in  FIG. 1  a compressor or supercharger assembly, generally indicated at  10 . The supercharger assembly  10  is adapted for use with an internal combustion engine, not shown, and is operable to increase the volumetric efficiency thereof. The supercharger  10  may be a roots-type or screw-type supercharger. The supercharger assembly includes a housing  12 . The housing  12  is preferably formed from cast metal such as, for example, aluminum, magnesium, etc. The housing  12  includes a first end  14  and an opposed second end  16 . A supercharger drive assembly  18  is mounted with respect to the first end  14  of the housing  12 , while a gear drive assembly  20  is mounted with respect to the second end  16  of the housing  12 . The supercharger drive assembly  18  includes a shaft mounted pulley  22  configured to receive a belt, not shown, thereon to transmit driving force from the internal combustion engine to the supercharger assembly  10 . Positioned substantially adjacent to the supercharger drive assembly  18  is an inlet duct  24  operable to convey intake air, indicated by arrow  26 , into the housing  12  of the supercharger assembly  10 . 
     The gear drive assembly  20  is operable to maintain rotational timing between a pair of interleaved, counter rotating rotor assemblies  28 , one of which is shown in  FIG. 2 . The gear drive assembly includes a bearing support member  30  mounted to said housing  12 , while a cover member  32  is mounted to the bearing support member  30 . The cover member  32  and bearing support member  30  are removably mounted with respect to the housing  12  by a plurality of fasteners  34 . The cover member  32  and bearing support member  30  are preferably formed from metal such as, for example, aluminum, magnesium, steel, etc. A tube member  36  extends through the cover member  32  and is operable to vent the gear drive assembly  20  to the atmosphere  38 . The tube member  36  is preferably held within the cover member  32  by interference fit or adhesive bonding; however, other methods may be employed to retain the tube member  36  with respect to the cover member  32  while remaining within the scope of that which is claimed. The construction and operation of the gear drive assembly  20  will be discussed in greater detail hereinbelow with reference to  FIGS. 2 through 4 . 
     Referring now to  FIG. 2  and with continued reference to  FIG. 1 , there is shown a sectional view of the gear drive assembly  20  of  FIG. 1 . The gear drive assembly  20  includes a gear member  40  mounted to a shaft member  42  for unitary rotation therewith. The shaft member  42  rotatably supports the rotor assembly  28  within the housing  12 , shown in  FIG. 1 . As such, the gear member  40  and rotor assembly  28  rotate unitarily. The gear member  40  is provided in meshing engagement with another gear member, not shown, and together operates to maintain rotational timing between rotor assemblies  28  within the supercharger assembly  10 . The gear member  40  has an axis of rotation  44 . The tube member  36  is generally aligned with the axis of rotation  44  of the gear member  40 . The tube member  36  includes an end portion  46  positioned substantially adjacent to the gear member  40 . In a preferred embodiment, the shaft member  42  defines a recess  48  within which the end portion  46  of the tube member  36  is at least partially received. 
     The cover member  32  partially defines a volume  50  within which a predetermined amount of lubricating oil  52  is contained. With the gear member  40  at rest, or not rotating, the lubricating oil  52  has a fill level, indicated by the phantom line  54 . The end portion  46  of the tube member  36  is positioned above the fill level  54  so as to prevent the leakage of lubricating oil  52  via the tube member  36 . 
     During operation of the supercharger assembly  10 , heating of the lubricating oil  52  occurs as a function of supercharger load and duration of operation. This temperature rise will tend to increase the pressure within the volume  50  which, if left unregulated, may damage seals, not shown, within the gear drive assembly  20 . The tube member  36  operates to vent pressure within the volume  50  to the atmosphere  38  thereby maintaining acceptable pressure limits within the volume  50 . As the gear member  40  rotates in the direction as indicated by arrow  55 , any lubricating oil  52  thereon will be forced radially outward, away from the axis of rotation  44  of the gear member  40 , thereby preventing the lubricating oil from traversing the tube member  36 . 
     Referring to  FIG. 3  and with continued reference to  FIG. 2 , there is shown an alternate embodiment of the cover member  32 , generally indicated at  32 A. The cover member  32 A includes a plurality of projections  56 , which extend axially from an inner wall  58  of the cover member  32 A toward the gear member  40  of  FIG. 2 . The projections  56  cooperate to form a plurality of radially outwardly extending channels  60  operable to channel or direct lubricating oil  52  from the axis of rotation  44  of the gear member  40 , as indicated by arrows  62 . The projections  56  are preferably curved in the direction of rotation of the gear member  40  such that the channels  60  are generally curved in the direction of rotation of the gear member  40 , as shown in  FIG. 3 . 
     Referring to  FIG. 4  and with continued reference to  FIG. 2 , there is shown an alternate embodiment of the cover members  32  of  FIGS. 2 and 32A  of  FIG. 3 , generally indicated at  32 B. The cover member  32 B includes a projecting wall  64 , which extends axially from the inner wall  58  of the cover member  32 B toward the gear member  40  of  FIG. 2 . The projecting wall  64  defines a generally outwardly spiraling channel  66  in the direction of rotation of the gear member  40 . The channel  66  is operable to substantially prevent the lubricating oil  52  from traversing the axis of rotation  44  of the gear member  40 . 
     By venting the gear drive assembly  20  via the tube member  36 , the increase in temperature and pressure within the volume  50  under sustained high load operation of the supercharger assembly  10  may be reduced. The positioning of the tube member  36  is effective in preventing or substantially limiting the loss of lubricating oil  52  through the tube member  36 . 
     While the best modes for carrying out the invention have 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.