Abstract:
A breather for a driveline component such as an axle, for example, includes a rigid body portion attached to an axle housing, an extension portion attached to the rigid body portion and extending into a housing cavity, and a conical spring supported by the extension portion. The rigid body portion has an internal bore that extends from a first body end to a second body end with the first body end extending outwardly from the axle housing and the second body end being fixed to the axle housing. The extension portion has a non-uniform cross-sectional area, and includes an extension bore with a large internal diameter. The conical spring is received within the extension bore and cooperates with the extension to prevent lubricating fluid from exiting the breather while still allowing air to vent through the breather as needed.

Description:
TECHNICAL FIELD 
     The subject invention is directed to a breather for a driveline component that utilizes a body portion and a resilient member that cooperate to block lubricating fluid from exiting the breather. 
     BACKGROUND OF THE INVENTION 
     Breathers are used to release air pressure, which builds up during operation, from within a housing for driveline components such as axles, transfer cases, and transmissions. One problem with current breathers is that the breathers provide a leakage path for lubricating fluid contained within the housing. This leaking can be generated by several different operational modes, such as pumping, splashing, and spattering caused by internal driveline components enclosed within the housing. Air flow rate, fluid temperature, changes in operational speed, etc. can also affect leakage amounts. 
     Several different solutions have been proposed to address this problem but have had limited success. One solution provides a breather body that is threaded into the housing with one end extending outwardly from the housing and an opposite end being flush with an internal wall of the housing. The breather body has an internal bore that includes a pair of baffles offset from each other to block lubricating fluid from exiting the bore. During operation a thick film of fluid bridges an opening to the internal bore at the internal wall of the housing. This thick film of fluid causes fluid to collect at the breather location, which is undesirable. The baffles prevent some but not all of the lubricating fluid from exiting the breather. 
     Mesh screens have also been used in place of baffles to prevent fluid from exiting the breather. These mesh screens have a tendency to clog and do not allow fluid to drain back into the housing. 
     Another solution provides a breather body with a tube that extends into the housing cavity. The tube has the same problems identified above. A thick film of fluid bridges an opening at an internal end of the tube, which results in fluid being drawn to the breather. Further, the tube does not prevent fluid that is splashed or splattered in a direction toward the tube from exiting the breather. 
     Thus, there is a need for a breather that can prevent lubricating fluid from exiting the breather under harsh operating conditions while still allowing air to vent as needed. 
     SUMMARY OF THE INVENTION 
     A breather for a driveline component includes a rigid body portion attached to a housing and a resilient member supported by the body portion. The body portion and the resilient member cooperate to prevent lubricating fluid from exiting the breather while still allowing air to vent from the driveline component through the breather as needed. 
     In one disclosed embodiment, the breather includes an extension portion attached to the rigid body portion and extending into a housing cavity, the extension portion has a non-uniform cross-sectional area and includes an extension bore that receives the resilient member. The rigid body portion has an internal bore that extends from a first body end to a second body end with the first body end extending outwardly from the housing and the second body end being fixed to the housing. The extension bore extends through the extension portion from a first extension end to a second extension end. The first extension end is received within the internal bore and is fixed to the second body end. The second extension end extends inwardly into the housing cavity. 
     The resilient member comprises a conical spring that has a first spring end defining a first spring diameter and a second spring end defining a second spring diameter that is less than the first spring diameter. The first spring end is seated between the body and the extension portion and the second spring end is unsupported within the extension bore. 
     In one example configuration, the extension member is made from a rigid material and includes a plurality of removed areas and a plurality of slats at the second extension end. Each removed area is separated from an adjacent removed area by one of the plurality of slats to define a crowned tip. 
     The subject invention provides a unique breather for driveline components such as axles, transfer cases, transmissions, etc., which prevents lubrication leakage even under severe operating conditions while still allowing air to be vented as needed. 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. 1A  is a view of an axle assembly with a breather incorporating the subject invention. 
         FIG. 1B  is a schematic view of a driveline component with a breather incorporating the subject invention. 
         FIG. 2  is a cross-sectional view of one embodiment of the breather of  FIGS. 1A and 1B . 
         FIG. 3  is a schematic view of an alternate embodiment of a breather incorporating the subject invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1A  shows an axle  10  having a housing  12  with a central carrier portion  14  and a pair of housing legs  16 . A breather  18  is installed on the axle housing  12  at the central carrier portion  14 . The central carrier portion  14  is a typical location for the breather  18  to avoid interference with mounting of suspension components (not shown) on the housing legs  16 . However, locating the breather  18  at the central carrier portion  14  subjects the breather  18  to high levels of lubricating fluid. Internal carrier components such as a pinion gear, ring gear, and differential gear assembly (not shown) can splash, splatter, or pump lubricating fluid in a direction toward the breather  18 . With traditional breather configurations, the splatter, splash, and pump modes of operation can cause fluid lubricant to leak outwardly of the breather  18 . 
     The subject invention provides the breather  18  within a unique configuration that prevents lubricating fluid L from exiting the breather  18  even under the harshest operating conditions. While the breather  18  is beneficial for axles  10 , it should be understood that the subject breather  18  could also be used on other driveline components  20  as shown in  FIG. 1B . These other driveline components  20  could comprise transmissions, transfer cases, drop boxes, independent wheel end drive units, etc. 
     A preferred embodiment of the breather  18  is shown in greater detail in  FIG. 2 . The breather  18  includes a body  30  having an internal bore  32  extending from a first body end  34  to a second body end  36 . The breather  18  is attached to a housing wall  38  having a breather bore  40  that receives the second body end  36 . The first body end  34  extends outwardly from an external surface  42  of the housing wall  38  and the second body end  36  is fixed to the housing wall  38  at the breather bore  40 . The second body end  36  is recesses within the breather bore  40  as shown, however, the second body end  36  could also be flush with or extend just beyond an inner surface  44  of the housing wall  38 . 
     The second body end  36  preferably has a threaded outer surface that is threadably engaged within the breather bore  40 . The body  30  includes a flange portion  46  that is spaced apart from the external surface  42  of the housing wall  38 . 
     The internal bore  32  has a first portion  50  defined by a first diameter D 1  and a second portion  52  defined by a second diameter D 2 . The first portion  50  extends from within the flange portion  46 , which is located between the first  50  and second  52  portions, to an opening  54  at the first body end  34 . The second portion  52  extends from the flange portion  46  to the second body end  36 . 
     A cap  56  covers the opening  54  at the first body end  34 . The cap  56  is cup-shaped and is crimped at  58  around lip portion  60  of the first body end  34  to engage a neck portion  62 . The lip portion  60  has a greater diameter than the neck portion  62  but a smaller diameter than the flange portion  46 . 
     The cap  56  encloses a disc member  64  and a spring  66 . The spring  66  biases the disc member  64  against the opening  54 . This prevents dirt, debris, water, etc. from entering the internal bore  32 . When air pressure builds up within the housing  12 , the pressure overcomes the spring force exerted by spring  66  to move the disc member  64  away from the opening  54  to allow air to be vented or released through the internal bore  32  to atmosphere. The configuration of the spring  66  and associated spring force can be varied to meet venting needs associated with different applications. 
     Preferably, the disc member  64  is made from a felt material, however, other materials such as Viton® for example, could also be used. One concern with breather operation is vacuum relief on cool-down. Felt material is preferred because it allows pressure to equalize to zero gage pressure. 
     The breather  18  also includes an extension  70  that is received within the internal bore  32  at the second body end  36 . The extension  70  includes an extension bore  72  that extends from a first extension end  74  to a second extension end  76 . The first extension end  74  includes an outer surface  78  with a lip portion  80 . The lip portion  80  is preferably received within a groove  82  formed within the second portion  52  of the internal bore  32  in a snap-fit. While a snap fit attachment is preferred, other attachment methods such as press-fitting, for example, could also be used. 
     The extension bore  72  includes a first portion  84  defined by a diameter D 3  and a second portion  86  defined by a diameter D 4 , which is greater than diameter D 3 . The first portion  84  is received within the internal bore  32  and the second portion  86  extends inwardly beyond the inner surface  44  of the housing wall  38 . The extension  70  has a wall thickness t that is defined at the location of the diameter D 4  of the second portion  86 . The diameter D 4  of the second portion  86  is preferably made as large as possible, and the diameter D 4  plus two times the wall thickness t is approximately equal to a minor thread diameter of a threaded portion of the second body end  36 . The wall thickness t is made as small as possible. This allows the second portion  86  to have as great an internal diameter as possible while still allowing external assembly through the breather bore  40 . The extension  70  is pre-installed within the body  30  to form the breather  18 , which is then inserted through the breather bore  40  in the housing wall  38 . 
     The second extension end  76  extends to a distal tip  88  that has a crowned configuration. The crowned configuration comprises a plurality of removed areas  90  (only one is shown in  FIG. 2 ) and a plurality of slats  92  that are orientated in an alternating pattern. Each slat  92  is separated from an adjacent slat  92  by a removed area  90 . This alternating pattern preferably extends circumferentially about the distal tip  88 . Each slat  92  preferably tapers from a pointed end to a wider base portion as shown, however, other slat configurations could also be used. 
     A resilient member, shown generally at  94 , is received within the extension bore  72 . The resilient member  94  preferably comprises a conical spring  96  having a first spring end  98  defined by a first spring diameter S 1  and a second spring end  100  defined by a second spring diameter S 2  that is less than the first spring diameter S 1 . The extension bore  72  includes a third portion  102  that tapers to an increased diameter relative to the diameter D 3  to form an extension spring seat  104 . The body  30  includes a ledge portion that forms a body spring seat  106 . The first spring end  98  is held between the extension  70  and body  30  at the spring seats  104 ,  106  such that the conical spring  96  cannot fall out of the extension  70 . 
     The second spring end  100  is unsupported within the extension bore  72 . The conical spring  96  forms a discontinuous surface with spring coils catching splash particles to prevent the particles from reaching the disc member  64 . The discontinuous surface prevents capillary action and reduces oil collection at the extension  70 . 
     In this configuration, the body  30  is preferably made from a steel material and the extension  70  is preferably made from a plastic material, however, other materials could also be utilized to form the body  30  and extension  70 . By forming the body  30  from steel, temperature variations have less effect on the breather  18 . 
     Also, instead of being separately formed as shown in  FIG. 2 , the body  30  and the extension  70  could be formed as a single piece component  110  as shown in  FIG. 3 . One end  112  of the single piece component  110  would extend outwardly from the housing  12  and the opposite end  114  could be recessed with the breather bore  40 , flush with the inner surface  44  of the housing wall  38 , or extend beyond the inner surface  44  of the housing wall  38 . The single piece component  110  includes a bore  116  that at least partially receives the resilient member  94 . The resilient member  94  blocks fluid particles in the manner described above. 
     The subject breather  18  provides a unique configuration that provides several beneficial features. The breather  18  includes a large inner bore diameter in both the second extension end  76  and the second body end  36 , which overcomes a capillary effect allowing fluid to drain to sump within the housing  12 . Further, the large diameter prevents pumping of fluid out of the breather  18 , especially at low temperatures when viscosity is high. 
     The crowned configuration at the distal tip  88  of the extension  70  breaks surface tension of fluid film and prevents fluid L from pumping out of the breather  18  under pressure. Also, at higher temperatures, the viscosity of the fluid L is lower and a splash leak mode is more prevalent. The crowned configuration limits an angle of trajectory of fluid particles toward the disc member  64 . The limits are a function of the length of the extension  70  and the diameter of the extension bore  72 . Longer extensions or smaller bore diameters decrease the angle of trajectory. To prevent pumping, i.e. to reduce the capillary effect, the extension should be as long as possible with an inner bore diameter that is as large as possible. 
     The disc member  64  and spring  66  within the cap  56  cooperate to prevent water and debris ingress as well as reducing oil misting and allowing positive and negative relative pressure equalization. The conical spring  96  inside the extension  70  catches splash particles and prevents fluid L from reaching the disc member  64 . The discontinuous surface of the conical spring  96  reduces capillary action at the spring and allows fluid L to drain to sump. The conical spring  96  operates better than traditional mesh screens, which have a tendency to clog. 
     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.