Note: Descriptions are shown in the official language in which they were submitted.
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AXLE SHAFT RETENTION STRUCTURE
Backqround of the Invention
The present invention relates generally to structure for
retaining an axle shaft within a housing and more particularly
to structure for preventing axial movement of the shaft in a
steerable axle where a double cardan constant velocity U-joint
is used.
On steerable axles where a double cardan constant
velocity U-joint i6 used, one end of the U-joint must be
retained and the opposite end must have freedom for end play.
; This is because a characteristic of this type of joint is that
as it moves through its operating angle, the length of the
joint changes, resulting in reciprocating motion or "plunge"
of one end of the joint as the axle is steered. It is not
functional to allow the U-joint to float or in other words,
fix both shaft ends with the U-joint not attached to either,
since the U-joint can move off of the center of the steering
axis. Therefore, it is necessary to fix or retain end play of
either the inner or outer shaft along with one end of the U-
joint.
In some applications, the shaft, inner or outer, which is
; I allowed to plunge is important. ~or example, on a steerable
mechanical front wheel drive axle with a limited slip
differential, the plunge which can occur across the steering
axis can be, depending upon the size of the unit, from 9mm to
; lOmm. If this plunge is allowed to occur on the inner part of
the shaft, it can have a substantial effect on the limited
slip action of the differential. Specifically, even though
the inner shaft is free to slide within the limited slip unit,
under load sub6tantial friction between the unit and shaft
; would still cause exces6 friction between the disks during the
shaft plunge. Therefore, it i8 extremely desirable that the
inner shaft be held axially stationary with respect to the
axial housing and that all plunge be taken on the outer side
of the universal ~oint.
In holding the axle shaft against axial movement relativeto the housing, it is also important that tolerances be held
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quite rigid since end play of .010" can be detrimental to an
oil seal unless a special oil seal which can tolerate both
axial and rotary movement is employed.
One design for preventing axial movement of the inner end
5 of a drive shaft for a steerable mechanical front wheel drive
axle is shown in U. S. Patent No. 4,693,699 which issued on 15
August 1987 and is assigned to the assignee of the present
application. In the design shown in that patent, the axle
housing and yoke are made of separate pieces and are bolted
10 together. The inner axle shaft is provided with an annular
groove and two half washers are positioned in the groove and
held between the axle housing and yoke. In this manner, axial
movement of the inner shaft is tightly controlled and all
plunge created by the universal joint is taken on the outer
15 shaft where a special oil seal arrangement is employed. The
design shown in U. S. Patent No. 4,693,699 adequately
controlled the axial movement of the inner shaft, but created
manufacturing problems due to difficulties in heat treating
the inner shaft across the groove for the retention ring.
In a design similar to that shown in U; S. Patent No.
4,693,699, the assignee of the present application eliminated
the need for a groove for the two half washers by reducing the
diameter of the shaft back to a shoulder so that the two half
washers bore against the shoulder and against a sleeve trapped
25 between the two half washers and the inner end of the
universal ~oint stub shaft. Both the design shown in the
! U. S. Patent No. 4,693,699 and that previously utilized by the
assignee of the present application relied upon the axle
housing and yoke being made of separate parts bolted together
30 in order to place the two half washers on the shaft. In some
applications, it is desirable for cost saving reasons, if for
no other reason, to have the axle housing and yoke made of a
single casting.
Another prior art design known to applicant utilized a
35 ~ingle piece axle housing and yoke and held the inner shaft
from axial movement. In this design the inner race of a ball
bearing was captured between a shoulder on the shaft and a
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snap ring in a groove of the shaft. The outer race of the
bearing was captured between two snap rings positioned in
internal grooves of a ring. The ring was then held in a fixed
position with respect to the axle housing by a dogpoint 6crew
which was threaded through the axle housing into a groove or
hole in the outside surface of the sleeve. While this design
did utilize a single piece axle housing and yoke, the use of
multiple snap rings to retain the roller bearing, and the
roller bearing itself, provided too much end play between the
axle and axle housing such that it was difficult to maintain a
seal between the axle and axle housing.
Summarv of the InYention
The principle object of the present invention is to
provide a retention structure for a rotary axle shaft which
prevents axial movement of the shaft with respect to the axle
housing.
A more specific object of the present invention is to
provide an axle shaft retention structure for a steerable
; driven axle which prevents axial movement of the driven shaft
relative to the axle housing.
The above objects are accomplished by trapping a shaft
retainer ring between a shoulder on the axle shaft and the
inner end of a hollow sleeve or stub shaft forming a part of a
universal joint. The hollow sleeve is attached to the axle
! 25 shaft by a snap ring. The retaining ring is provided with
I spherical slots which receive the spherical inner ends of
retaining screws extending through the axle housing. The
retaining screws nest into the ~pherical 610ts in the
retaining ring and force the retaining ring inward against an
internal shoulder on the axle housing. The shoulder on the
- axle housing and the retaining screws limit both axial and
rotary movement of the retainer ring. Thus, end play, which
is detrimental to oil seal life, is limited to a minimum.
The above objects and the structure of the invention will
become apparent, along with variou.s other objects and
advantages of the invention, from a reading of the following
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detailed description of the invention when taken in
conjunction with the accompanying drawing.
Brief Description of the Drawin~
In the drawing:
Figs. la and lb, taken together, are a sectional view of
a ~teerable drive axle, from the differential to an outer
planetary final drive, and incorporating the ~haft retention
structure of the present invention.
Fig. 2 i8 an enlarged view of a section of the left-hand
lo end of Fig lb.
Fig. 3 is a perspective view of a retainer ring forming
part of the present invention.
Fig. 4 i6 an elevational view of a modification of a
portion of the invention.
escrip~ion of Prefe~ed Embodiments
The invention iB shown in Fig. 1 in the context of a
~teerable drive axle assembly. This assembly includes an axle
housing 12 which includes in integral yoke 14 at its outer
end. Yoke 14 iB pivotably connected to a knuckle 16 by
kingpin a6semblies 18 and 20. The inner end of axle housing
12 is bolted to a differential housing 22 by bolts 24 (only
one shown).
A double cardan universal ~oint 26 i6 located across the
pivot axis of the kingpin as6emblies 18 and 20 and includes a
` ' 25 hollow stub shaft 28 at its yoke end which extends into a
~ I suitable openinq provided in the yoke and also a hollow stub
; shaft 30 at its knuckle end which extends into a suitable
opening provided in the knuckle 16. The hollow 6tub shaft 28
i8 rotatably mounted in the opening provided in the knuckle 14
by a bushing 32.
~ A drive shaft 34 extends through the housing 12 and has
its inner end extending into the differential housing 22 and
has ita extreme inner end splined to a bevel gear 36 which is
part of a limited ~lip differential indicated generally at 38.
The outer end of the shaft 34 extends into the opening in the
yoke 14 and into the hollow ~tub shaft 28 where it has a
splined connection with the stub shaft 28.
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A 6un ~haft 40 extends into and is ~plined to the hollow
stub shaft 30 and has an integral 6un gear 42 on its outer end
which drives a planetary gear eet indicated generally at 44.
The planetary gear set 44 drives a wheel hub 46 which i6
rotatably mounted on the knuckle 16 by bearings 48. The ~tub
shaft 30 and sun shaft 40 extend into and through a 6pecial
seal arrangement indicated generally at 50 which i8 capable of
withstanding both rotary and reciprocating motion. The
special 6eal arrangement 50, wheel hub 46, planetary gear set
44 and un shaft 42 do not form part of the present invention
and are fully described in the aforementioned U. S. Patent No.
4,693,699 which is expressly incorporated herein by reference
for a full description of the same.
With the structure thus far described, the U-joint 26 is
free to float on the two shafts 34 and 40, a situation which
would be intolerable since the U-joint could move off the axis
of rotation of the king pins 18 and 20. To prevent this
floating, the hollow 6tub shaft 28 is secured to the drive
6haft 34 by 6nap ring 52 which is engaged in internal and
external grooves provided in the hollow stub shaft 28 and the
drive shaft 34, respectively. In turn, the drive shaft 34 is
held in a fixed axial position with respect to the housing 12
by a retainer structure which includes a retainer ring 54, a
6pacer 56, an internal 6houlder 58 provided on the housing 12,
a shoulder 60 provided on the 6haft 34 and retainer screws
indicated generally at 62. The retainer ring 54 is rotatably
mounted on the shaft 34 and between the shoulder 60 and the
spacer 56 which is positioned between the retainer ring 54 and
the hollow stub shaft 28. The retainer ring 54 is made of a
sintered iron which provides a good bearing material and the
spacer ring 56 is tanged or keyed to the stub shaft 28 as at
64 60 that all relative rotation between the retainer ring 54
and hollow stub 6haft 28 takes place at the interface between
the retainer ring 54 and spacer ring 56. The spacer ring 56
is hardened 80 that with the combination of the hard material
and the sintered iron which provides a good bearing surface,
very little wear occurs.
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The retaining ring 54 is provided with a plurality of
partial spherical-shaped slots 66 which provide curved ramp
surfaces. The housing 12 is provided with a plurality of
tapped, through openings which align with the ramped surfaces.
The retainer screws 62 are each of two parts and include a
ball 70 positioned in the tapped openings 68 and a 6et screw
72 threaded into the opening. By tightening the set screw 72,
the balls 70 are forced against the ramps or partially
spherical ~lots to force the retainer ring 54 against the
shoulder 58 in the housing 12.
The retainer structure described above positively
prevents axial movement of the shaft 34 relative to the axle
housing 12 with the only looseness coming from tolerances in
the single snap ring 52 and its respective grooves and the fit
between the spacer ring 56 and the retainer ring 54 and hollow
stub shaft 28. This limits axial movement of the shaft 34 and
hollow stub shaft 28 to a very small amount so that a simple
rotary seal 74 can be used between the hollow stub shaft 28
and the yoke 14. Thus, as the angle between the drive shaft
34 and sun shaft 40 changes due to pivotal movement of the
knuckle 16 on the yoke 14, the plunge caused by the change in
effective length of the U-joint 26 must be dissipated by axial
movement of sun shaft 40 or relative movement between the sun
shaft 40 and hollow stub shaft 30. As explained in the
aforementioned U. S. Patent No. 4,693,699, the special seal 50
can survive this axial movement caused by plunge as well as
the rotary movement of the shafts. By preventing axial
movement of the shaft 34, the plunge caused by the universal
' joint 26 cannot affect the frictional $orces on the limited
slip differential and thus will not affect the action of the
limited slip differential.
Referring now to Fig. 4, an alternate embodiment of the
invention is shown. In the alternate embodiment, the set
screw 72 and balls 70 are replaced by a set screw 74 having a
rounded end 76. The rounded inner end 76 of the set screw 74
serves the same purpose as the ball 70 in the first
embodiment, but has the advantage in that no special
precautions have to be taken to remove the balls in the event
of disassembly.
Having thus described two preferred embodiments of the
invention in the context of a preferred use, various
modifications within the spirit and scope of the invention
will become obvious to those skilled in the art and can be
made without departing from the underlying principles of the
invention. Therefore, the invention should not be limited to
the 6pecific illustrated and described embodiments, but only
by the following claims.
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