Abstract:
A speed sensor for a wheel end that has an interior that is substantially isolated from an atmosphere around the wheel end. The speed sensor is carried by a housing of the wheel end for monitoring the rotation of the wheel end and indicating the angular velocity of the wheel end. The speed sensor includes a cable leading from the sensor to a location remote from the wheel end and further includes leads that transmit a signal and a sheath that encloses the leads. The sheath is open enough to allow a fluid to flow through its interior. A vent channel provides communication between the interior of the wheel end and the interior of the sheath on the cable.

Description:
[0001]     The present application claims priority to U.S. Provisional Patent Application Ser. No. 60/795,066, filed Apr. 26, 2006, the content of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates in general to wheel ends, and more particularly to a wheel end provided with a sensor and cable that together serve as a vent for a bearing in the wheel end.  
         [0003]     More and more components of automotive vehicles are being furnished by outside suppliers as packaged assemblies. Typical are wheel ends used to couple the road wheels of the vehicles to suspension uprights that form part of the suspension systems for such vehicles. The typical wheel end has a housing that is bolted to a suspension upright, a hub provided with a spindle that projects into the housing, and an antifriction bearing located between the housing and spindle to enable the hub to rotate with respect to the housing. The road wheel is secured to a flange at the end of the spindle on the hub. The assembly procedure is such that upon completion the bearing has the correct setting—normally slight preload—and a measured quantity of grease for lubrication. A seal pressed into the outboard end of the housing and another seal or end cap pressed into the inboard end of the housing retains the lubricant in the bearing and excludes contaminants. Conditions may exist, such as a change in temperature or elevation, that cause the pressure within the bearing to increase. Indeed, if an end cap is pressed into the housing, it will function as a pump during assembly and increase the pressure within the bearing. Moreover, oils used in the manufacture of the bearing and in the assembly of the wheel end leach some of the oil out of the grease. The elevated pressure produced within the bearing may drive some of the free oil past the lips of the seals and out of the bearing.  
         [0004]     Many wheel ends have speed sensors to monitor the angular velocity of their hubs. Active sensors are preferred. This type of sensor has a barrel that projects into the interior of the housing from a head, and both the head and barrel have electronic components embedded in them. The electronic components are totally isolated from contaminants, such as moisture, to which the wheel end may be subjected. As a consequence, the sensor has no through passage through which the interior of the bearing may be vented.  
       SUMMARY OF THE INVENTION  
       [0005]     A speed sensor for a wheel end that has an interior that is substantially isolated from an atmosphere around the wheel end. The speed sensor is carried by a housing of the wheel end for monitoring the rotation of the wheel end and indicating the angular velocity of the wheel end. The speed sensor includes a cable leading from the sensor to a location remote from the wheel end and further includes leads that transmit a signal and a sheath that encloses the leads. The sheath is open enough to allow a fluid to flow through its interior. A vent channel provides communication between the interior of the wheel end and the interior of the sheath on the cable.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a side section view of a wheel end according to an embodiment of the present invention;  
         [0007]      FIG. 2  is a side section view of a wheel end according to another embodiment of the present invention;  
         [0008]      FIG. 3  is a perspective section view of speed sensor according to an embodiment of the present invention;  
         [0009]      FIG. 4  is a side section view of a speed sensor according to an embodiment of the present invention;  
         [0010]      FIG. 5  is a side section view of a speed sensor according to another embodiment of the present invention; and  
         [0011]      FIG. 6  is a side section view of a speed sensor according to another embodiment of the present invention; 
     
    
     DESCRIPTION OF THE INVENTION  
       [0012]     Referring now to  FIGS. 1 and 2 , a wheel end A couples a road wheel to a suspension upright for an automotive vehicle, enabling the wheel to rotate about an axis X. The wheel end A includes a housing  2  that is bolted to the suspension upright, and a rotatable hub  4  to which the road wheel is secured, an antifriction bearing  6  between the housing  2  and the hub  4  to accommodate the rotation, seals  8  at the ends of the bearing  6 , and a speed sensor  10  fitted to the housing  2 .  
         [0013]     The housing  2  encloses the bearing  6  and at its ends has end bores  16  that receive the seals  8 . Both are pressed into their respective end bores  16 . The housing  2  also has an oblique bore  18  that receives the speed sensor  10 .  
         [0014]     The hub  4  has a drive flange  20  located beyond the outboard end of the housing  2  and a spindle  22  that projects from the flange  20  into the housing  2 . The spindle  22  is for the most part solid, and its end is turned outwardly in a roll forming procedure to provide a formed end  24  that captures the bearing  6  on the spindle  22 .  
         [0015]     The bearing  6  includes two outer raceways  30  that are machined into the housing  2  and two inner races in the form of cones  32  that are fitted over the spindle  22  of the hub  4 , with each having an inner raceway  34  and a thrust rib  38  at the large end of its raceway  34 . In addition, the bearing  6  has rolling elements in the form of tapered rollers  36  that are located in two rows between the inner and outer raceways  30  and  34 .  
         [0016]     The rollers  36  along their tapered side faces contact the raceways  30  and  34 —there being line contact—and at their large end faces bear against the thrust ribs  38  of the cones. The rollers  36  are on apex, so pure rolling contact exists between the rollers  36  and the raceways  30  and  34 . One of the cones  32  has an extension  40  that abuts the other cone  32 , and the length of the extension controls the setting of the bearing  6 . It should be slight preload.  
         [0017]     The extension  40  of the one cone  32  carries a tone wheel  42  that is monitored by the speed sensor  10 . Being pressed over the spindle  22  of the hub  4 , the cones  32  rotate with the hub  4  at the same angular velocity as the hub  4 , and the same holds true for the tone wheel  42 , which is pressed over the extension  40  on the one cone  32 .  
         [0018]     The seals  8  fit into the end bores  16  ( FIG. 1 ) with press fits and surround the thrust ribs  38  of the two cones  32 . Here they establish dynamic fluid barriers which isolate the interior of the housing  2  and bearing  6  that is in it. On the other hand, the inboard seal  8  may be replaced by an end cap  46  ( FIG. 2 ) that is pressed into the inboard end bore  16 . For the end cap  46  to be effective, the spindle  22  should not be hollow.  
         [0019]     The sensor  10  includes a barrel  50  that fits into the oblique bore  18  of the housing  2  and projects toward the tone wheel  46  that revolves with the bearing cones  32  and the hub  4 . Indeed, its end lies close to the rotating tone wheel  42 . The sensor  10  also includes a head  52  that lies outside the housing  2 , yet is joined to the barrel  50  so that the barrel  50  and head  52  are an integral unit. The sensor  10  contains electronic components that are completely encased and embedded in the barrel  50  and head  52 , and they enable the sensor  10  to monitor rotation of the tone wheel  42  and produce an electrical signal that reflects the angular velocity of the tone wheel  42 .  
         [0020]     That signal is delivered to a cable  54  that is connected to the head  52  through a boot  56  and leads to a processor at a location remote from the wheel end A—a location generally free of moisture and other contaminants that might damage electronic components such as those in the sensor  10 . The cable  54  contains leads that actually transmit the signals and a sheath that surrounds the leads. Enough space exists between the wall of the sheath and the enclosed leads to enable a fluid to flow through the cable  54 .  
         [0021]     Referring to  FIGS. 3-4 , the barrel  50  of the sensor  10  fits snugly into the oblique bore  18  of the housing  2 , and an O-ring seal  58  located between the barrel  50  and the wall of the bore  18  excludes contaminants, including moisture. The sensor  10  contains a vent channel  60  that at one end opens out of the barrel  50  inwardly from the O-ring seal  58 , so that here the channel  60  communicates with the interior of the housing  2  where the bearing  6  is located. The other end of the vent channel  60  opens into the boot  56  which is in turn is in communication with the interior of the sheath for the cable  54 . The opposite end of the sheath is vented to the atmosphere at the location that is generally free of contaminants. Thus, the interior of the housing  2 , where the bearing  6  is located, is vented to the atmosphere through the sensor  10  and through the cable  54 .  
         [0022]     As shown in  FIGS. 5-6 , a modified sensor  70  is similar to the sensor  10 , but lacks the vent channel  60  in its barrel  50  and head  52 . It does have a flange  72  that lies over the exterior surface of the housing  2  and it contains a hole  74  that aligns with a partially threaded bore  76  in the housing  2 . The bore  76  lies parallel to the oblique bore  18  and like the oblique bore  18  passes from the exterior surface to the interior surface of the housing  2  and thus communicate with the interior of the housing  2  and the bearing  6 . The threads of the threaded bore  76  extend inwardly from the exterior surface that the flange  72  overlies.  
         [0023]     The hole  74  in the flange  72  of the modified sensor  70  receives a cap screw  78 , which threads into the bore  76  in the housing  2  and secures the sensor  70  firmly to the housing  2 . The cap screw  78  in turn has a head  80  that overlies the flange  72  of the sensor  70  and also a small diameter hole  82  that extends axially through the screw  78  from one end to the other.  
         [0024]     Apart from that, the sensor  70  has a cap  84  that fits over the head  80  of the screw  78 , effecting a seal with the head  80 , and a connecting tube  86  that leads from the cap  84  to the boot  56  at which the cable  54  enters the sensor  70 . At one end the tube  86  communicates with the interior of the cap  84  and the small diameter bore  82  in the screw  78 . At its other end, the tube  86  communicates with the interior of the boot  56  and the interior of the sheath on the cable  54 . Thus, the interior of the housing  2  and the bearing  6  within it communicates with the interior of the sheath on the cable  54  through the vent channel formed by the bore  82  in the screw  78 , the interior of the cap  84  that is over the head  80  of the screw  78 , and the tube  86  that connects the cap  84  with the boot  56  of the cable  54 .