Patent Application
20060170299
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).
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.
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.
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
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 18A and 18B disposed so as to cover the field winding 22, magnetic poles being formed in the segments 18A and 18B by the magnetic flux generated by the field winding 22. The segments 18A and 18B 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 18A 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 18B 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
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
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
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
In an exemplary embodiment as illustrated in
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
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.
