Abstract:
A bearing adjustment and monitoring system is provided for a bearing mounted between a hub and a spindle, one of which is rotatable relative to the other and one of which has a threaded end section with traversing keyway and the other of which has an abutment for limiting inward movement of the bearing. A backing washer member is arranged to removably abut the bearing on the end opposite the abutment and has a key extending into the keyway to secure it against rotation, and a calibrated nut member has threads configured for threading onto the threaded end section. One of the backing washer member and calibrated nut member has a plurality of circumferentially spaced openings and the other of the backing washer member and calibrated nut member has a plurality of openings registering with the openings in the one member but spaced apart differently therefrom, whereby to provide vernier adjustment of rotation of the calibrated nut member. A lock removably secures the backing washer member and calibrated nut member together, and a measuring device operatively interengages the hub and spindle for measuring the relative movement between them for adjusting the axial end play between the hub and spindle.

Description:
This application claims the benefit of Provisional application Ser. No. 60/089,363, filed Jun. 15, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to new and useful improvements in bearing axial free play measurement and adjustment and is particularly suitable for spindle-mounted tapered roller wheel bearings. 
     Precision adjustment of wheel bearing free axial end play, particularly of truck, trailer and bus wheel hubs is very difficult and time consuming. So difficult that precise adjustment is seldom attained, because adjustment typically is attempted by feel or experienced guess. 
     It is generally recognized by those in the industry that adjustment of tapered roller wheel bearings, such as those used in wheel hubs on trucks, trailers, buses, etc., is a major consideration in preventing excessive wheel end component wear and early wheel end component failure, including catastrophic wheel loss. Wheel bearing axial end play setting effects bearing life and the usable service life of seals, brakes and tires. 
     It is generally acknowledged in heavy duty, over-the-road equipment that the ideal method of bearing adjustment is to utilize a dial indicator to determine the point of zero axial end play, and then to preload the bearing as much as 0.001 inch and no more, to obtain optimum bearing life. Prior art devices have rendered this a trial and error task, very time consuming, and often impossible outside the test laboratory. In practice, the time consuming trial and error method with a dial indicator is rarely used. 
     Excessive bearing preload rapidly destroys the bearings. Consequently, the industry has grown to accept 0.001 to 0.020 inch end play as tolerable, and 0.001 to 0.005 inch as preferred, providing it can be verified. In practice, verification using a dial indicator is rarely performed because of the difficulty and the incompatability of parts, tools and procedures. Because optimum bearing adjustment is so difficult and bearing failure is so costly, a portion of the transportation industry is experimenting with expensive, finely machined and pre-assembled hubs in the hope of reducing operational wheel end expenses. 
     The prior art in threaded wheel bearing retaining devices is separated into three types: double nut devices with either the inner or outer nut jammed against the other, which changes the adjustment; single nut devices; and single or double nuts highly torqued to retain a pre-assembled hub and bearing unit. These prior devices are secured from further rotation by bendable tabs, peening, set screws, threaded locking fluids, keyed circular clips, spring loaded locking mechanisms, or friction. The commonly practiced prior art methods of setting axial end play are torque, torque and back off or by feel. In each case the unsure mechanic, lacking a precision device and method, can only hope for success. 
     U.S. Pat. No. 4,812,094 is typical of prior art single nut devices. In this patent, the device requires fitting a socket tool over the nut, resulting in release of the locking tab so that the nut may be rotated freely while the tool is affixed. Accordingly, fine increments of rotation cannot be indexed. This procedure further inhibits the simultaneous use of a dial indicator, whereby determining the exact zero point of axial end play is very difficult, if not impossible. The device is capable only of very coarse,  150  adjustment increments, and the process of initially removing the nut socket incurs the risk of unintentional rotation of the unpinned nut. 
     Prior art methods are extremely friction sensitive. Thread tolerance, cut, irregularity, damage, contamination and many other variables affecting the friction in on-vehicle tapered roller wheel bearing adjustment, and each individual assembly is unique in its variation. Devices dependent upon torque averaging technique inherently set excessive axial end play on those assemblies having higher than the mean average friction. On a low friction assembly, using a torque technique excessively preloads and destroys the bearings. Prior methods are dependent on a severe surface lubricant to provide a broader, forgiving tolerance of the permissible mean adjustment range. This compromise in lack of precision, is costly. 
     The prior art provides no means to either monitor or readily measure wheel bearing axial clearance without partial disassembly. Improper adjustment of over-the-road equipment frequently leads to a bearing failure that may be detected audibly, by smoking brakes, by oil seal failure, by irregular tire wear, or by wheel end separation. 
     SUMMARY OF THE INVENTION 
     In its basic concept, the bearing adjustment and monitoring system of this invention utilizes a spindle nut and keyed backing washer, both of which have cooperating vernier openings and an interengageable lock pin to secure the nut in adjusted position of rotation, to provide precise bearing preload adjustment. A wheel end hub mounted status sensor electrically communicates with a fixed spindle mounted stator to enable real time and motion analysis of wheel end structure and hub components, inclusive of bearing preload data, and remotely communicates with a hand held reader or an equipment mounted warning monitor. 
     It is the principal objective of this invention to provide a bearing adjustment and monitoring system which overcomes the aforementioned limitations and disadvantages of prior art systems. 
     Another objective of this invention is to provide a bearing adjustment and monitoring system of the class described that requires no disassembly of the wheel bearing assembly. 
     Another objective of this invention is the provision of a bearing adjustment and monitoring system of the class described that significantly reduces vehicle operational and maintenance expenses, to achieve the maximum possible wheel end component life. 
     Still another objective of this invention is to provide a bearing adjustment and monitoring system of the class described that reduces the risk of catastrophic failure by obtaining precise initial wheel bearing adjustment, wheel bearing monitoring and precise readjustment. 
     Another objective of this invention is the provision of a bearing adjustment and monitoring system of the class described that produces performance data that instantly signals the vehicle operator of impending failure data. 
     A further objective of this invention is the provision of a bearing adjustment and monitoring system of the class described that permits simultaneous use of a torque tool to “feel” and a dial indicator to “see”, the exact point of zero axial end clearance, irrespective of other unknown variances caused by the weight, type or size of mounted wheels and tires and component friction variances. 
     A still further objective of this invention is to provide a bearing adjustment and monitoring system of the class described that measures and monitors the axial preload of the bearings, to reset the preload if required, and to simplify this preventative maintenance task. 
     Still another objective of this invention is the provision of a wheel adjustment and monitoring system of the class described that affords real time monitoring of the wheel end status. 
     The foregoing and other objects and advantages of this invention will appear from the following detailed description, taken in connection with the accompanying drawings of preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary longitudinal sectional view of a hub and spindle assembly in association with a wheel bearing adjustment and monitoring system embodying the features of this invention. 
     FIG. 2 is a fragmentary sectional view, on an enlarged scale, of the calibrated nut area of FIG.  1 . 
     FIG. 3 is a fragmentary longitudinal sectional view, similar to FIG. 1, illustrating the adjustment procedure of the invention. 
     FIG. 4 is a front elevation, on an enlarged scale, showing the backing washer and calibrated nut during an adjustment procedure. 
     FIG. 5 is a front elevation, on an enlarged scale, of the keyed backing washer of FIG.  1 . 
     FIG. 6 is a front elevation, on an enlarged scale, of the calibrated nut of FIG.  1 . 
     FIG. 7 is a front elevation, on an enlarged scale, of the keyed sensor status ring of FIG.  1 . 
     FIG. 8 is a sectional view taken on the line  8 — 8  in FIG.  7 . 
     FIG. 9 is a front elevation, on an enlarged scale, of a self locking threaded sensor status ring. 
     FIG. 10 is a block diagram of an electronic status sensor for use with the system of FIG.  1 . 
     FIG. 11 is a fragmentary longitudinal sectional view, similar to FIG. 1, illustrating the inspection procedure without disassembly of the hub and spindle assembly. 
     FIG. 12 is a fragmentary longitudinal sectional view of a hub and driven axle incorporating the bearing adjustment and monitoring system of this invention. 
     FIG. 13 is a fragmentary longitudinal sectional view of the hub and drive axle assembly of FIG. 12 incorporating an inspection system without disassembly of the components. 
     FIG. 14 is a fragmentary side elevation illustrating the manner of operating the bearing adjustment system of this invention. 
     FIG. 15 is an enlarged front elevation of a modified form of keyed backing washer. 
     FIG. 16 is an enlarged front elevation of a modified form of calibrated nut for use with the backing washer of FIG.  15 . 
     FIGS. 17 and 18 are perspective views of alternate forms of the spring retaining ring. 
     FIG. 19 is a fragmentary longitudinal view, similar to FIG. 12, showing an outer bearing sealing arrangement for a re-greasing hub. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates the working form of a first embodiment of the present bearing adjustment and monitoring system of this invention, fitted to a tapered roller bearing spindle-mounted hub, as in a heavy duty trailer application. It comprises hub  10  having an outer end cap  12  with an O-ring seal  14  therebetween. The outer end of cap  12  has an opening  16  for removably receiving an electronic status sensor  18  with O-ring seal  20  in the opening. Sensor  18  has the usual small axial ventilating port  22  and is associated with sensor stator ring  24  secured to the outer end of spindle  26  which is provided with the usual keyway  28  recessed in the upper threaded portion of the spindle. 
     The hub encloses the usual outer and inner wheel bearings  30  and  12 , respectively, and includes the usual outer bearing races  34  and  36  fitted in the hub. Also shown is the usual inner races  38  and  40 , the inner bore of the usual outer wheel bearing inner race  38  being closely fitted to but easily movable lengthwise on spindle  26 . Also shown is the usual inner lubricant seal  42 . 
     A keyed inverse vernier backing washer  44 , the inner face of which is perpendicular to the spindle axes, communicates with the outer face of the usual outer bearing inner race  38 . The key  46  of the backing washer fits into the spindle keyway  28  to prevent the backing washer from turning. The inner face of specialized and calibrated nut  48 , threaded in its inner bore to turn upon the outer threaded portion of spindle  26 , communicates with the outer face of the keyed backing washer  44 . 
     With reference also to FIG. 2, the calibrated nut  48  is secured from rotation by means of lock pin  50  which communicates both with opening  52  in the circumference of nut  48  and with opening  54  through the upper circumferential body of keyed backing washer  44 . Locking pin openings  52  and  54  are in axial alignment with each other to receive lock pin  50 . The circumferential spacing between the openings  52  is different from the circumferential spacing between openings  54 , whereby to provide a vernier adjustment of rotation of calibrated nut  48 , described hereinafter. 
     The inner lengthwise portion of lock pin  50  fitting in the keyed backing washer opening  54  is of smaller cross section than the outer portion of the lock pin fitting in calibrated nut locking pin opening  52 , whereby the lock pin cannot advance further through opening  54  in an inner direction and interfere with outer bearing  30 . The specialized calibrated nut  48  has a circumferential groove  56  about its outer circumference and receives a circular spring retaining ring  58  (FIG. 1) to trap lock pin  50  in place. 
     The operation of the assembly of FIG. 1 is illustrated in FIG.  3 . With the inner bearing outer race  36  and outer bearing outer race  34  properly seated in hub  10  and the lightly lubricated inner and outer taper roller bearings  32  and  30 , respectively, and the usual inner lubricant seal  42  properly fitted in the hub, and the assembled hub placed on a lightly lubricated spindle  26 , the present wheel bearing adjustment procedure is as follows: Keyed backing washer  44  is placed on the spindle  26  and calibrated nut  48  is hand threaded onto the spindle until the nut approaches hand tight, and is in contact with keyed backing washer  44 . This washer is in contact with the outer wheel bearing inner race  38 , whereupon inward travel of nut  48  causes the same inward travel of keyed backing washer  44  and in turn causes the same inward travel of the outer wheel bearing inner race  38 . A precision measuring instrument  60 , such as a dial indicator, is fixed to hub  10  so that axial movement of the hub on spindle  26  may be easily measured in thousandths of an inch. 
     The zero point of axial end play is next determined. A usual torque wrench is used to measure rotational resistance in turning nut  48 . A nut drive tool  62  is of the open design of a spanner wrench, permitting the use of a measuring instrument such as dial indicator  60 , and simultaneous use of a torque measuring tool  64 . Referring to FIG. 4, there is shown in front elevation the spindle  26 , keyed inverse vernier backing washer  44 , calibrated nut  48  and nut drive tool  62 . This illustrates the open and accessible configuration for the adjustment. The dial indicator  60  (FIG. 3) is observed as calibrated nut  48  is rotated. This method is not torque sensitive, so the torque reading itself is not critical although variances in torque caused by assembly, thread, dimensional or bearing wear irregularities, immediately become apparent. In normal adjustment, as the nut  48  is turned the dial indicator  60  records the corresponding inward travel of the hub  10  in axial relationship to the spindle  26 . The spot at which hub movement stops and further rotation of the nut  48  requires an immediate increase in torque, is the point of zero axial end play. Should the hub continue to move with increasing torque, once an apparent zero point is reached, the nut  48  should be backed off slightly, the hub rotated and the procedure repeated. This is an excellent quality control method for determining wear or assembly irregularities. 
     With the axial end play zero point determined, lock pin openings  52  in nut  48  and lock pin openings  54  in keyed backing washer  44  are integrally sequenced to provide equal adjustment increments per uniform degree of rotation. In this example, nut  48  has  30  lock pin openings  52  and keyed backing washer  44  has six lock pin openings  54  sequenced as an inverse vernier in correspondence to calibrated nut  48 . This provides  180  adjustment increments per one revolution. To adjust axial preload to a specification of one thousandths of an inch preload maximum, on a spindle having  16  threads per inch, nut  48  is turned an additional three adjustment increments, which is 6°. One inch divided by 16 turns per inch equals 0.0625 inch per one full revolution. Having 180 adjustment increments per revolution in this illustration, each adjustment increment is 0.00035 inch (0.0625 inch divided by 180 increments). 
     With reference again to FIG. 4, the specialized nut  48  may have radial or circumferential incremental scribes  66  on its outer face adjacent the spindle  26 . Utilizing one side of spindle keyway  28  as a reference, calibrated nut  48  is tightened three scribe marks to obtain 0.001 inch preload, or backed off to obtain axial end clearance. Lock pin  50  now is installed in openings  52  and  54 , drive nut tool  62  is removed and circular spring retaining ring  58  is easily pushed by hand onto the conical outer face of nut  48  until it snaps into retaining groove  56 , securely trapping lock pin  50  in place. 
     The initial tapered roller wheel bearing axial end play adjustments having thus been made and dial indicator  60  removed from hub  10 , reference again is made to FIG.  1 . Sensor stator ring  24  is pushed or threaded onto the outer threaded end of spindle  26  until the stator ring  24  is flush with the outer face of the spindle. O-ring sealed end cap  12  next is fixed to hub  10  and O-ring sealed electronic status sensor  18  is threaded or twist-lock fitted into end cap  12  after the hub is properly lubricated. 
     Sensor stator ring  24  provides fixed magnetic poles  68  (FIGS. 7,  8  and  9 ) and is retained on the end of spindle  26 . The structure of the stator body has a key  70  and elastically pliable threaded body fragments  72  (FIG. 7) or elastically pliable ratcheting type threaded wedge fragments  74  (FIG.  9 ), whereby the sensor stator rings  24  and  24 ′ may be easily affixed to the spindle. 
     Hub-mounted wheel end status sensor  18  rotates with the hub  10 , its innermost body being closely adjacent to stator  24  but separated by an air gap  76  (FIG.  1 ). Status sensor  18  contains electronic components and circuitry shown in FIG.  10 : A dynamo  78  generates alternating current, rectifies the alternating current to direct current and powers a data processor  80  which functions as the sensor data processing brain. Battery  82  provides power for an internal timing clock  84  and power for programming and data transfer when stator sensor  18  is static. The charge on battery  82  is maintained and regulated by the dynamo. 
     Dynamo field integrator  86  derives a signal from the wave form of the dynamo field winding and sends the signal to processor  80  to effectively measure rotational characteristics and air gap  76 . Frequency counter  88  counts the dynamo field winding frequency for the processor, permitting the processor to compare rotational frequencies, such as bearing frequency and wheel mounting stud frequency. Timing device  84  provides the processor with a known reference standard and a data time stamp. Radial accelerometer  90  sends an acceleration signal to the data processor. Radial velocity integrator  92  is an operational amplifier integrating the accelerometer signal to obtain and send a velocity signal to the processor. Radial displacement integrator  94  is an operational amplifier integrating the velocity signal to obtain and send a displacement signal to the processor. 
     Axial accelerometer  96 , being in a line parallel to the hub spindle axis, sends an axial acceleration signal to processor  80 . Axial velocity integrator  98  derives the axial velocity signal for the processor and axial displacement integrator  100  derives the displacement signal for the processor. Internal transmitter  102  is powered by timed intermittent capacitive firing and the signal transmission is axially directed toward the outer end face of spindle  26 . Internal receiver  104  receives and measures the reflected signal of transmitter  102  and sends a corresponding signal to the processor  80 . Thermocouple  106  sends a millivolt signal to the processor. 
     The program data processor stores, assimilates, integrates, analyzes, interprets and compares signal patterns to predicted pre-programmed signals and to comparative data recorded signals, so that recognized and identified variations prompt responses which are sent to the programmable syntheziser  108  permitting logic analysis to eliminate internal or externally induced false signal responses. Proximity data link  110  remotely ties to a handheld reader or PC  112  so that data may be transferred during routine maintenance inspections. Transmitter  114  sends an emergency warning signal to in-cab warning monitor  116 . Formatted data of vibration characteristics may be displayed, such as bearing preload or axial end clearance, bearing condition, lubricant performance, tire carcass condition, wheel end balance, corrective action advice, maximum speed, maximum temperature, loose brake pads or shoes, miles since last reset, and total mileage. The onboard warning system may indicate impending wheel end failure, such as bearing failure, excessive temperature, loose wheel fastenings, or tire failure which prompts corrective action, whereby to avert a possible catastrohic emergency. 
     To mechanically re-measure or verify axial preload during a preventative maintenance inspection, reference is made to FIG.  11 . In a hub  10  fitted with either the electronic status sensor  18  (FIG. 1) or a vented end plug, the sensor or plug is removed and a dial indicator adapter  120  is fitted in end cap  12 . With the corresponding vehicle wheel end jacked free of the ground surface and the wheel brake released, the wheel end unit may be rotated and pried in and out to determine axial end free play, as measured by dial indicator  60 . 
     In the event bearing preload re-adjustment is required, the process is quick and easy: The exact free play in thousandths of an inch, obtained by the aforementioned full time electronic monitoring or by the dial indicator fitted in the hub end cap and the amount of preload desired being known, the end cap  12  is removed. Circular spring retaining ring  58  is removed and the nut drive tool  62  is fitted to the nut  48 . The desired calibration scribe  66  is reference marked with a chalk or pen, lock pin  50  is removed, calibrated nut  48  is turned the desired increment and the lock pin is reinstalled. The preferred exact wheel bearing preload setting accordingly has been re-established, minimizing wheel end operational expense. 
     It is important to note that in the event adjustment is required in the field, without access to special tools, the zero point of axial end play may be easily approached by tightening calibrated nut  48  in 2° increments while rotating and wiggling hub  10 . The near zero point of no bearing wiggle thereby is determined and the desired preload is set without fear of excessively preloading the bearings. 
     FIGS. 12 and 13 illustrates a drive axle configuration of this invention. Although the function and adjustment procedures are the same as in the non-driven hub, it is important to note that drive axle flange  122  becomes the outer end cap of hub  10 . The drive axle flange contains a recessed port  124  for removably receiving either an O-ring sealed plug  126 , O-ring seal  128 , dial indicator adapter  130 , or an O-ring sealed drive axle wheel end status sensor  18 ′. Recessed port  124  is centered over the outer rim face  132  of the tubular spindle so that sensor  18 ′ is not axially centered, but orbits the circumference of sensor stator ring  24  as the hub rotates. 
     FIG. 14 illustrates the unique ergonomic concept of this invention. A typical wheel end employed in the transportation industry is illustrated. The normal visual sight line  134  of the mechanic is cast downward onto the upper portion of the spindle  26 , with the mechanic&#39;s hands positioned to the left and right of the spindle. The arrangement allows the unique and simple use of a dial indicator  60  and the simultaneous use of a torque tool  64 . The inverse vernier locking pin positions of the keyed backing washer  44  (FIG.  4 ), the single specialized calibrated nut  48  and the unique open access of this integral combination keeps the entire adjustment procedure within the visual sight line. This assures equal favor of right or left-handed use, simplicity of operation and precision accuracy. 
     It is also important to note that major consideration is given to manufacturing cost. The lock pin openings  52  of calibrated nut  48 , providing the “lugged” or “sprocket” circumferential appearance, the outer circumferential spring retaining groove  56  and the incremental scribes  66 , are formed by an inexpensive manufacturing process. 
     FIGS. 15 and 16 illustrate an alternative form of keyed backing washer  44 ′ and calibrated nut  48 ′. The lock pin openings  52 ′ and  54 ′ may be less expensive to manufacture and may be of any dimension, and they may be interchangeable. Further, the sequencing of lock pin position openings, to achieve a desired inverse vernier, may be sequentially integrated to achieve ergonomic desirability. 
     FIGS. 17 and 18 illustrate alternative constructions of the lock pin and spring retaining ring. In FIG. 17 the lock pin  50 ′ is apertured to receive the retaining ring  58 ′. In FIG. 18 the lock pin  50 ″ is integral with the retaining ring  58 ″. 
     With reference to FIG. 1, in the bearing tightening and adjusting procedure, the outer bearing inner race  38  moves upon spindle  26 . However, the arrangement may be reversed, wherein the inner or outer bearing race may adjustably move upon the spindle shaft or within the hub. Also, the hub may turn rotationally upon the spindle, or the shaft may turn within the hub wherein the hub may be stationary, as a housing. Further, the shaft position may be positioned axially with respect to the hub or housing. 
     My earlier U.S. Pat. No. 5,658,053 illustrates driven hub outer lubricant sealing arrangements. With reference to FIG. 19 herein, the configuration of calibrated nut  48  allows minimal outer nut radius, providing a substantial space  136  between the outer circumference of the nut and the outer hub bore  138 . This space permits the installation of an outer lubricant seal  140  in bore  138 . Seal  140  has an inner keyed disc  142  so fitted as to not rotate on spindle  26  and is axially positioned between the hub outer bearing inner race  38  and the keyed inverse vernier backing washer  44 . This arrangement forms circumferential grease retaining cavity  144  for outer bearing  30 . Grease passage  146  in hub  10  communicates with recessed greasing port  148  and circumferential grease retaining cavity  144 . This preferred arrangement of outer seal  140  substantially reduces the manufacturing cost and simplifies installation, while affording precision bearing adjustment. 
     It will be apparent to those skilled in the art that various changes may be made in the size, shape, type, number and arrangement of parts described hereinbefore, without departing from the spirit of this invention and the scope of the appended claims.