Abstract:
A bearing assembly includes a bearing housing; a rotatable shaft extending through the bearing housing; a bearing having an outer race and an inner race with a bearing seal therebetween, the outer race operably coupled to the bearing housing and the inner race operably coupled to the rotatable shaft; and a slinger operably coupled to an outside edge defining the inner race and rotatable therewith while an external periphery defining the slinger is disposed within a groove configured in the housing, wherein the slinger protects the bearing from contamination from the elements while freely spinning absent contact with the housing, the outer race, and the bearing seal.

Description:
TECHNICAL FIELD 
     This application relates generally to contamination protection of bearing assemblies. More specifically, this application relates to a method and apparatus for contamination protection of ball or roller bearings, for example, in rotating electrical machines, especially dynamoelectric machines such as automotive alternators (generators). 
     BACKGROUND 
     Rotating electrical machines such as automotive alternators (dynamoelectric machines) (also commonly referred to as “generators”) having a stator secured within the housing of the machine and a rotor assembly that extends axially through the motor or generator are well known. The housing often includes two spaced apart frames which provide the main structural elements of the alternator. The frame closest to a pulley, which powers the alternator via a belt drive is commonly referred to as the drive end frame. The opposite frame is commonly referred to as the slip ring end frame. The two frames support between them the rotor assembly comprising a rotor shaft with a connected rotor winding. Support bearings for the rotor assembly are typically positioned “inboard” of the pulley that turns the rotor of the generator via a fan belt from the engine, the pulley also being attached to the rotor assembly. The frames are held together typically by three or four bolts which are attached axially between ears or bosses on the outside of the frames. 
     Each frame has a hub. The hub includes an inner core having a central axial opening (sometimes referred to as the bearing bore). The inner core axial opening provides mounting support for an outer race of a roller or ball bearing which mounts the rotor shaft to the hub. The outer race of the bearing is typically press fitted within this central opening of the core. Extending radially outward from the core is a series of hub ribs forming ventilation openings between contiguous hub ribs. The hub ribs connect the core with a rim of the hub. 
     Mounted on the shaft of the rotor in a position adjacent to the hub will be a fan. During operation of the alternator fan blades pass close by the hub ribs, essentially shearing the air as the blades pass near the hub ribs. 
     Presently, bearings that support the rotor assembly are exposed to the elements subjecting them to contamination, thus reducing the life of the bearings and the pulley. Present technology depends on one of two items for protection from contamination: the pulley or an external/outboard drive end fan. 
     Dual internal fan (DIF) alternators are especially susceptible to contamination of the drive end ball bearing because the ball bearing is placed in a location that is more exposed to the elements compared to prior art alternators. This is aggravated further by the large variation in customer pulleys that are often used in alternators. In particular, smaller diameter pulleys increase exposure of the drive end bearing to contamination. 
     Accordingly, contamination protection for the drive end bearing is desired that provides unrivalled protection with no sensitivity to the pulley used by the end-user. 
     BRIEF SUMMARY OF THE INVENTION 
     The above discussed and other drawbacks and deficiencies are overcome or alleviated by a bearing assembly that includes a bearing housing; a rotatable shaft extending through the bearing housing; a bearing having an outer race and an inner race with a bearing seal therebetween, the outer race operably coupled to the bearing housing and the inner race operably coupled to the rotatable shaft; and a slinger operably coupled to an outside edge defining the inner race and rotatable therewith while an external periphery defining the slinger is disposed within a groove configured in the housing, wherein the slinger protects the bearing from contamination from the elements while freely spinning absent contact with the housing, the outer race, and the bearing seal. 
     In another embodiment, a rotating electrical machine is disclosed. The rotating electrical machine includes a rotor rotatable about a rotor shaft; a fan operably connected to the rotor shaft; a stator surrounding the rotor; front and rear frames rotatably supporting the rotor, at least one of the frames having a hub with a core with an opening for receiving a bearing mounting the rotor with the hub, the bearing having an outer race and an inner race with a bearing seal therebetween, the outer race operably coupled to the hub and the inner race operably coupled to the rotor shaft; and a slinger operably coupled to an outside edge defining the inner race and rotatable therewith while an external periphery defining the slinger is disposed within a groove configured in the hub, wherein the slinger protects the bearing from contamination from the elements while freely spinning absent contact with the hub, the outer race, and the bearing seal. 
     In yet another embodiment, a method to suppress contamination of a bearing assembly in a brush type rotor of a wound-field electrical machine is disclosed. The method includes configuring a groove in a bearing housing having a rotatable shaft extending therethrough via a bearing, the bearing having an outer race and an inner race with a bearing seal therebetween, the outer race operably coupled to the bearing housing and the inner race operably coupled to the rotatable shaft; and operably coupling a slinger to an outside edge defining the inner race and rotatable therewith while an external periphery defining the slinger is disposed within a groove configured in the housing, wherein the slinger protects the bearing from contamination from the elements while freely spinning absent contact with the housing, the outer race, and the bearing seal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view through a Lundell alternator illustrating a contamination protection apparatus operably coupled to a drive end bearing assembly in accordance with an exemplary embodiment; 
         FIG. 2  is an enlarged partial cross sectional view of the drive end bearing assembly of  FIG. 1  in accordance with an exemplary embodiment; 
         FIG. 3  is a front elevation view of a slinger used in the contamination protection apparatus of  FIGS. 1 and 2 ; 
         FIG. 4  is a side elevation view of the slinger of  FIG. 3   
         FIG. 5  is a cross section view of a spacer having a slinger integrally molded thereto in accordance with an exemplary alternative embodiment; and 
         FIG. 6  is a cross section view of a cast integral spacer and slinger in accordance with another exemplary alternative embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     This disclosure relates to a method and apparatus for contamination protection of a bearing, and more particularly, to a slinger mounted on the rotor of a wound-field electrical machine and proximate a drive end bearing to limit exposure of the elements to the drive end bearing. The slinger significantly reduces contamination of the drive end bearing with no sensitivity to a pulley used by the end-user. In particular, the slinger is in operable contact with the rotor shaft and inner race of the drive end bearing, as well as being rotatable therewith to which it is attached, while the outer race and bearing housing are stationary and remain out of contact with the slinger. 
     The present method and apparatus for contamination protection of a bearing provides an improvement over previous designs in that it includes features from the rotating members (e.g., spacer(s) and/or slinger(s)) working in conjunction with features of the stationary member(s) to provide more effective protection to the bearing than can be accomplished by either a flat rotating spacer and/or slinger, or features of the stationary members. In addition to the synergy described above, the disclosure includes making use of a shallow-draw lip design to significantly increase the level of protection by lengthening the distance contaminants must travel to affect the bearing, as well as forcing contaminants to make several direction changes in order to come in proximity with the seal of the bearing. 
     Referring now to  FIG. 1 , an alternator  10  has a rotor assembly generally designated by the reference numeral  12  and stator assembly generally designated by the reference numeral  14 . The rotor assembly  12  includes a shaft  16  supporting all rotating magnetic circuit structures thereof including conventional pole-members or segments  18 A and  18 B, rotor core  20  and field coil  22  wound upon bobbin  24 . Each segment  18 A and  18 B has P/2 claw poles where P is an even number and representative of the total number of poles. Additionally, all other non-magnetic circuit rotating structures are carried thereby, including air circulation fans  26  located at axially opposite sides of the pole-members, and a slip ring assembly  30  located at one extreme end of the shaft. One fan  26  is formed from sheet metal stock and spot welded to pole-member  18 B while the other fan  26  is formed from an appropriate thermoplastic material and heat staked to tower extensions (not shown) from the field coil bobbin  24 . However, it will be recognized that fans  26  may be formed and attached in various other ways and is not limited to those discussed above. The shaft  16  in turn is rotatably supported within a housing  32  by a pair of bearings  34 ,  36 . Bearing  34  is a slip ring end bearing located between the slip ring assembly  30  and the fan  26 . Bearing  36  is a drive end bearing located between a pulley section  38  on shaft  16  and a drive end shoulder  40  on shat  16 . 
     As described above, the rotor assembly  12  is constituted by: the field winding  22  for generating a magnetic flux on passage of an electric current; and pole cores or segments  18 A and  18 B disposed so as to cover the field winding  22 , magnetic poles being formed in the segments  18 A and  18 B by the magnetic flux generated by the field winding  22 . The segments  18 A and  18 B are preferably made of iron, having two first and second claw-shaped magnetic poles (only one shown) disposed on an outer circumferential edge and offsetly aligned with each other in a circumferential direction so as to project axially, and the end segment pole cores  42  are fixed to the shaft  16  facing each other such that the claw pole of one core is aligned with a gap defined between contiguous claw poles of the other core and intermesh with the opposing magnetic poles of the other core as is well known in the art of Lundell rotor assemblies. 
     In the dynamoelectric machine  10  constructed in this manner, an electric current is supplied to the field winding  22  during start up from a storage battery through brushes (both not shown) and the slip rings  30 , generating a magnetic flux. After the alternator turns on and begins to produce power, the alternator internally provides the field current. The first claw-shaped magnetic poles  42  of segment  18 A are magnetized into a fixed polarity by this magnetic flux (such as North seeking (N) poles), and the second claw-shaped magnetic poles  42  (not shown) of segment  18 B are magnetized into the opposite polarity (such as South-seeking (S) poles). At the same time, rotational torque from the engine is transmitted to the shaft  16 , by means of the belt (not shown) and the pulley (not shown), rotating the rotor assembly  12 . Thus, a rotating magnetic field is imparted to the armature winding (not shown) of stator assembly  14 , inducing a voltage across the armature winding. An alternating-current electromotive force from induced voltage across armature winding passes through a rectifier and is converted into direct current, the magnitude thereof is adjusted by a voltage regulator, the storage battery is charged, and the current is supplied to an electrical load (all not shown). 
     Referring now to  FIGS. 1 and 2 , support and sealing of rotor shaft  16  at the drive end frame  50  of housing  32  will be described in more detail. Drive end bearing  36  includes an inner race  52  fitted to shaft  16  and an outer race  54  is fitted at a core opening  56  defined by drive end frame  50 . A ball or roller bearing, for example, is disposed between inner and outer races  52 ,  54 , respectively, allowing shaft  16  to rotate with respect to stationary frame  50 . A pair of opposing seals  60  may be included to further seal the ball or roller bearing between inner and outer races  52 ,  54 , respectively. 
     In an exemplary embodiment, a flat washer or spacer  62  can be used to protect the seal  60  on bearing  36  on one, or both sides thereof. Each spacer  62  abuts the inner race  52  but remains out of contact with a respective seal  60 . Each spacer  62  extends radially outwardly a distance shy of the outer race to avoid contact therewith, as each spacer  60  rotates with shaft  16  and inner race  52  while outer race  54  remains stationary along with frame  50 . 
     Referring now to  FIGS. 1–4 , a metallic slinger  64  is used on one or both sides of bearing  36  to offer additional protection over that of spacers  62 . In an exemplary embodiment as illustrated, slinger  64  is shaped like a Frisbee or is shaped like a saucer having a centrally located aperture  66  for shaft  16  to be disposed therethrough. Slingers are cupped pieces of sheet metal that may be used to act as oil filters and also to keep dirt and other contaminants from getting into a bearing. 
     Slinger  64  is defined by a first member  68  having a second member  70  extending from a terminal end defining first member  68 . An opposite terminal end of first member  68  defines aperture  66 . First member  68  is disc shaped such that one surface thereof abuts a corresponding spacer  62 . Second member  70  extends from first member  68  forming a bight  72 . Second member  70  defines a “rim” portion or flange that rotates within a complimentary configured groove  74  machined or cast into the bearing housing  32  illustrated as drive end frame  50  in  FIGS. 1 and 2 . Groove  74  is configured in the bearing&#39;s housing or retainer, without making contact, and prevents contaminants from getting to the bearing seal  60 . 
     Second member  70  and groove  74  cooperate in defining a tortuous path  76  to provide an effective contamination protection to bearing  36  as best seen in  FIG. 2 . Path  76  delimits a labyrinth seal arrangement defined by groove  74  in housing  32  and the rotatable second member  70  that rotates as a unit with shaft  16 . Use of a shallow-draw lip design of slinger  64  in conjunction with groove  74  significantly increases the level of protection by lengthening the distance contaminants must travel via path  76  to affect the bearing, as well as forcing contaminants to make several direction changes in order to come in proximity with seal  60  of bearing  36 . In particular, one embodiment of path  76  is a serpentine path  76  which includes a plurality of 90° bends whereby a liquid contaminant, for example, is caused to make abrupt direction changes. 
     In an exemplary embodiment as illustrated in  FIG. 2 , it can be seen that spacer  62  provides a second serpentine path  80  which adds another 90° bend generally indicated at  82 , whereby a liquid contaminant, for example, is caused to make another abrupt direction change. Use of a flat spacer  62  provides close-up protection to bearing  36  from contaminants such as dust, and liquid contaminants, for example. The shallow-draw lip  70  of slinger  64  provides significant additional protection from contaminants in cooperation with the cast-in or machined groove  74  in the non-rotating member(s), which makes a significant improvement in the protection from contaminants, including liquid from high-pressure washers, which may be directed at the bearing area. 
     In one embodiment, it should be noted that is envisioned that the contamination protection device disclosed herein uses stamped components (e.g., spacer  62  and slinger  64 ) working in conjunction with cast-in or machined features (e.g., grooves) to provide effective contamination protection to a ball bearing or roller bearing, including other types of bearing assemblies. In other embodiments referring to  FIGS. 5 and 6 , it is contemplated that spacer  62  and slinger  64  are integral. 
       FIG. 5  illustrates a slinger  164  comprising a metallic spacer  162  like spacer  62  having a second member  170  and a first member  168  molded thereto forming a slinger portion  172 . Second member  170  and first member  168  correspond with second member  70  and a portion of first member  68 , respectively, in  FIG. 4 . It is contemplated that slinger portion  172  may be a polymer (e.g., plastic) inserted molded with spacer  162 , but is not limited thereto. 
       FIG. 6  illustrates a slinger  264  comprising an integrally cast metallic spacer  262  like spacer  62  having a second member  270  and a first member  268  integrally cast with spacer  262 . Second member  270  and first member  268  correspond with second member  70  and a portion of first member  68 , respectively, in  FIG. 4 . 
     The disclosure specifically covers the use of such components and features to protect the drive end bearing of an automotive alternator, but generally includes the use in any application where a sealed or shielded bearing is used in a severe contamination environment. While incorporation of the exemplary contamination protection device at a drive end frame has been described for use with generators associated with vehicles, the same may also be used and incorporated in applications other than generators for a vehicle where suppression or reduction of contamination in a bearing assembly is desired. 
     The slinger  64  and/or spacer  62  may be used to protect one, or both sides of a bearing. The bearing being protected will generally be a double seal design, but significant improvements in contamination protection will be achieved when used on any type of bearing, with or without bearing seals or shields. 
     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.