Universal bearing pre-load tool and method for using thereof

[0002] 1. Field of the Invention

[0003] The present invention relates to bearing preload tools, and more particularly to a bearing preload tool for differential assembly for motor vehicles, and a method for using thereof.

[0004] 2. Description of the Prior Art

[0005] Differentials for automotive or similar uses are well known in the prior art, and generally comprise a differential case rotatably mounted in a differential housing or differential carrier by axially spaced differential bearing assemblies. The differential bearings are typically preloaded to provide the desired amount of backlash between a drive pinion and the ring gear of the drive gear assembly or to eliminate end play of the rotor have presented problems, particularly as the bearing assemblies or gears wear. Proper engagement of the ring gear carried by the differential case with the input drive pinion is necessary, and subsequent wear of the gears or bearings will result in misadjustment of backlash and possibly end play in the rotor. This in turn normally requires adjustment of the bearings. Generally, prior art differential case bearings have been made adjustable by use of adjustment shims or the like, with it many times being necessary to remove the differential case from the differential housing, select shims having appropriate thickness, then reassemble the differential case to affect adjustment of backlash or bearing preload. The selection of the shims is, currently, practically guesswork, and depends on a workmen's experience. Typically, it requires several disassembling-reassembling operations before the correct bearing preload is achieved. Such labor-intensive procedures add cost and complexity to the adjustment procedure.

[0006] Thus, there is a need for a tool that is simple and inexpensive that would allow reducing time for selecting shims of appropriate thickness for properly preloading differential bearings in accordance with manufacturer's specifications.

[0007] The present invention provides a novel universal differential bearing preload tool and a method for using thereof for mounting a differential case in a differential housing with a predetermined bearing preload,

[0008] In one preferred embodiment, the universal differential bearing preload tool includes a pair of opposite cylindrical discs simulating differential bearing cups, a disc spreading device for adjusting a distance between the discs for simulating a bearing preload, and a force measuring device associated with said disc spreading device. The opposite cylindrical discs are removably fastened to the preload tool, and may be selected from a plurality of discs having assorted external diameters simulating differential bearing cups of different sizes and manufacturers.

[0009] The bearing preload tool is used in a method for mounting a differential case in a differential housing providing a predetermined bearing preload. The method comprises the steps of placing a bearing preload tool into the differential housing by spreading the discs until the discs are snug fit against a bearing bores, then measuring a first distance between certain base points on the differential housing in a non-preloaded condition. Next, the discs are spread outwardly until a desired preload force is achieved. A second distance between the base points in a preloaded condition that defines a desired spread is measured, and bearing preload tool is removed from the differential housing. Then, the bearing preload shim is selected based on a difference between the first and second distances, and a differential case along with the shim is mounted in the differential housing through differential support bearings.

[0010] Therefore, the present invention provides a novel universal bearing preload tool and method for mounting the differential assembly in the differential housing using the universal bearing preload tool with a predetermined bearing preload, which is simple, cost effective, and substantially reduces time and labor expenses.

[0011] Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in light of the accompanying drawings, wherein:

[0012] FIG. 1 is a fragmentary, partial sectional view of a differential assembly;

[0013] FIG. 2 is a partial view of a differential housing with removed cover plate;

[0014] FIG. 3 is a view showing a differential case without a ring gear, with two bearing assemblies and without shims;

[0015] FIG. 4 is a view, partially in phantom and partially in cross-section, of a preloaded differential case assembly with bearings and inboard shims;

[0016] FIG. 5 is an elevational view of a universal bearing preload tool in accordance with the preferred embodiment of the present invention;

[0017] FIG. 6 shows parts of the universal bearing preload tool in accordance with the preferred embodiment of the present invention.

[0018] The preferred embodiments of the present invention will now be described with the reference to accompanying drawings.

[0019] Referring now to the drawings, a vehicular axle assembly 1 is shown in FIG. 1, and includes a differential housing 2 carried on the underside of a vehicle (not shown). The differential housing 2 may include left and right axle tubes 3aand 3brespectively, projecting coaxially from opposite sides, or could be part of an independent suspension axle which would not require axle tubes 3aand 3b.The differential housing 2 defines a cavity 4 adapted for receiving a differential assembly 14 therewithin. The axle assembly 1 further includes a power input pinion gear 7 secured to a drive shaft. The pinion gear 7 meshes with a ring gear 10, which in turn is secured to a ring gear flange 18 associated with a differential case 16. The differential case 16 along with the ring gear 10 is rotatably mounted in the axle housing 2.

[0020] As illustrated in FIG. 2, provided within the cavity 4 are two spaced apart bearing blocks 6aand 6bdefining bearing bores 8aand 8b,respectively, when complementary bearing caps 28aand 28b,are fastened to the bearing blocks 6aand 6b.

[0021] The differential assembly 14, illustrated in FIGS. 3 and 4, is a conventional differential assembly well known in the art. The differential assembly 14 includes the differential case 16 having the flange 18, and two opposite cylindrical bearing hubs 20aand 20bat each lateral end thereof. The ring gear 10 is fastened to the flange 18, typically by a plurality of bolts (not shown).

[0022] The differential case 16 is rotatably supported in the bearing bores 8aand 8b,by means of anti-friction bearings. Preferably, the anti-friction bearings are tapered roller bearings 22aand 22bthat are pre-assembled units including associated bearing caps 26aand 26b.The bearing caps 26a,26bare secured to bearing blocks 6aand 6bformed in the differential housing 2.

[0023] The bearing 22ais disposed between the bearing bore 8aand the bearing hub 20a.Correspondingly, the bearing 22bis disposed between the bearing bore 8b,and the bearing hub 20b.Each of the bearings 22aand 22bincludes an inner race (24aand 24b) mounted to the associated bearing hub (20aor 20b), the bearing cup (26aand 26b) and a plurality of tapered rolling elements (27aand 27b) disposed therebetween.

[0024] For preloading of the bearings 22aand 22b,adjustment shims are conventionally used. The exemplary embodiment of the axle assembly illustrated in FIG. 1, shows an inboard shim 30aand an outboard shim 30b.It will be appreciated that FIG. 1 is merely a schematic illustration to show that differential assemblies may have inboard shims, as well as outboard shims, and the differential assembly 14 will have either inboard shims or outboard shims, but will not have the combination of the inboard and outboard shims, as illustrated in FIG. 1.

[0025] First aspect of the present invention is described with the reference to FIGS. 5 and 6 wherein there is disclosed a bearing preload tool 40 in accordance with the preferred embodiment of the present invention. The bearing preload tool 40 comprises a pair of opposite cylindrical discs 42aand 42bsimulating bearing cups 26aand 26b.Secured to each of the discs 42aand 42bare rigid rods 44aand 44b.A spring device in the form of a resilient annular band 46 is disposed between the discs 42aand 42b.The disc 42ais operatively connected to the resilient annular band 46 by means of a rod 44a.It would be appreciated that the rod 44ais attached to the disc 42aand the annular band 46 by any appropriate means well known in the art, such as welding, threaded connection, etc. In accordance with the preferred embodiment of the present invention, illustrated in FIG. 5, the disc 42ais removably fastened to the rod 44aby means of the threaded connection. As illustrated in FIG. 5, the rod 44ahas a threaded end 44a′ fastened to the disc 42aby means of a nut 45a.Alternatively, the disc 42amay have a threaded bore (not shown) complimentary to the threaded end 44a′ of the rod 44a.The rod 44ais preferably welded to the annular band 46. Alternatively, the 44amay be removably connected to the annular band 46.

[0026] The disc 42bis operatively connected to the resilient annular band 46 by means of a rod 44b,a threaded stud 48 and a nut member 52 interposed therebetween.

[0027] In accordance with the preferred embodiment of the present invention, illustrated in FIG. 5, the disc 42bis removably fastened to the rod 44bby means of the threaded connection. As illustrated in FIG. 5, the rod 44bhas a threaded end 44b′ fastened to the disc 42bby means of a bolt 45b.Alternatively, the disc 42bmay have a threaded bore (not shown) complimentary to the threaded end 44b′ of the rod 44b.A stud 48 is fixed to the annular band 46, opposite to the rod 44a,at one end thereof, preferably by welding. Alternatively, the stud 48 may be removably fastened to the annular band 46. The other end of the stud 48 is provided with threads 50 engaging internal threads of one end the nut member 52. The other end of the nut member 50 is connected to the rod 44bby any appropriate means known in the prior art, that allows relative rotation between the nut member 52 and the rod 44b.The nut member 52 is provided with a wrench-engaging surface 54 having polygonal cross-section, typically hexagonal. Combination of the rod 44b,the threaded stud 48 and the nut member 52 defines a disc-spreading device 56 that allows for adjustment a distance between the discs 42aand 42bby rotating the nut member 52.

[0028] Moreover, a measuring gauge 58 is positioned within the band 46 by means of mounting brackets 60 of any appropriate construction. Preferably, the measuring gauge 58 is a force measuring gauge. However, a dial indicator for measuring a deflection of the annular band 46, may be used if the technician knows a value of the deflection of the annular band 46 corresponding to a desired bearing preload.

[0029] Thus, the present invention discloses a novel arrangement of the bearing preload tool 40. As noted hereinabove, in accordance with the preferred embodiment of the present invention, the bearing simulating discs 42aand 42bare removably fastened to the bearing preload tool 40, that allows using the discs 42aand 42bfrom a set of a plurality of discs having assorted external diameters simulating differential bearing cups of different sizes and manufacturers. This provision makes the bearing preload tool 40 universal so that it can be used for virtually all axle designs.

[0030] The second aspect of the present invention is a method for mounting the differential case 16 in the differential housing 2 that provides a predetermined bearing preload. The method employs the bearing preload tool 40 described in detail hereinabove.

[0031] First, the bearing preload tool 40 is placed into the differential housing 2 by mounting the discs 42aand 42binto the bearing bores 8aand 8b,correspondingly. Using any appropriate conventional wrench (not shown) engaging the wrench-engaging surface 54, torque is applied to the nut member 52 for spreading the discs 42aand 42buntil they snug against the bearing bores 8aand 8b.Then the bearing caps 28aand 28bare bolted to the bearing blocks 6aand 6band tightened to their torque specifications. Next, a distance S₀between two opposite base points each associated with the corresponding bearing block 6aor 6b,is measured using a conventional spread gauge (not shown). Preferably, spreader holes 10aand 10bon the differential housing 2, shown in FIG. 2, are used as the base points. Alternatively, any appropriate opposite points on the bearing blocks 6aand 6bor the bearing caps 28aand 28bmay be used as the base points.

[0032] After that, the wrench torque is again applied to the nut member 52 of the disc-spreading device 56 until the force measuring gauge 58 positioned within the band 46, shows a predetermined desired bearing pre-load force F_PLknown to a technician through a chart. In this position, the bearing preload tool 40 simulates the differential assembly 14 with properly pre-loaded bearings 22aand 22b.The spread gauge is then placed back on the differential housing 2 to measure a distance S_PLbetween the spreader holes 10aand 10bin order to determine the spread between the base points when the bearings are properly pre-loaded. The difference between S_Oand S_PLallows estimating the shim thickness that would provide a desired bearing pre-load. Then, the bearing preload tool 40 is removed from the differential housing 2, and the differential case 16, the bearings 22aand 22b,and the shims 30aand 30bof estimated thickness are mounted to the differential housing 2. Placing the spread gauge on the differential housing 2, distance S_dbetween the spreader holes is again measured in order to determine an actual spread between the base points when the differential assembly 14 is mounted to the differential housing 2. If the shims of the appropriate thickness are selected, then the distance S_dis substantially equals to the distance S_PL. However, if the bearings 22aand 22bare not properly pre-loaded, then the distance S_ddiffers from the distance S_PL. In this case, the differential assembly 14 is removed from the differential housing 2, the shim thickness is appropriately adjusted, the differential assembly 14 is mounted back to the differential housing 2, and distance S_dbetween the spreader holes 10aand 10bis again measured. The last couple of steps are repeated until the distance S_dis substantially equal to the distance S_PLthat indicates that the bearings 22aand 22bare properly pre-loaded.

[0033] Therefore, the present invention provides a novel universal bearing preload tool and method for mounting the differential assembly in the differential housing using the universal bearing preload tool with a predetermined bearing preload, which is simple, cost effective, and substantially reduces time and labor expenses.

[0034] The foregoing description of the preferred embodiments of the present invention has been presented for the purpose of illustration in accordance with the provisions of the Patent Statutes. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. The embodiments disclosed hereinabove were chosen in order to best illustrate the principles of the present invention and its practical application to thereby enable those of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated, as long as the principles described herein are followed. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application as intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains. Thus, changes can be made in the above-described invention without departing from the intent and scope thereof. It is also intended that the scope of the present invention be defined by the claims appended thereto.