LOCKING DIFFERENTIAL
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention is directed toward differentials, generally, and more
specifically, toward locking differentials that operatively couple a pair of axle half shafts during
most driving conditions and that automatically disengage one half shaft in response to
predetermined speed differentials between the axles.
2. Description of the Related Art
[0002] A differential is a component of an axle assembly and is used to couple a pair of
rotating half shafts which make up a portion of the axle assembly. The differential is driven by
the driveshaft via a pinion gear that meshes with a ring gear mounted to the differential. In
automotive applications, the differential allows the tires mounted at either end of an axle
assembly to rotate at different speeds. This becomes important, for example, when the vehicle is
turning. The outer tire travels over an arc ofgreater distance than the inner tire. Thus, the outer
tire must rotate at faster speeds than the inner tire to compensate for the greater distance travelled.
[0003] There are a number of differential mechanisms that are known in the related art for
use in distributing torque between the output shafts. One such differential functions to lock the
axle half shafts together during most driving conditions, while disengaging the axles during
predetermined conditions, such as in response to differences in axle speed when, for example, the
vehicle is turning. These devices are commonly known as "locking differentials."
[0004] Many locking differentials include a housing that supports a pair of side gears.
The side gears are splined for rotation with a pair of axle half shafts. A central driver or spider is
mounted for rotation with the differential housing and drives a pair of clutch members disposed
on each side of the central driver. A cam member is operatively coupled for rotation with the
central driver and also includes camming teeth in meshing relationship with a portion of the
driven teeth of each of the clutch members. During most driving conditions, the central driver, clutches and side gears are operatively coupled together so that the axle half shafts rotate
together. In the event of a predetermined desired difference in speed between the axle half shafts, such as when the vehicle is turning, portions of the teeth on the clutch associated with the faster
turning axle, ride up the cam teeth such that the clutch is moved out of engagement with the
central driver. This allows the associated axle half shaft to rotate at a different speed than the
other axle half shaft that is still driven by the central driver. Once the speed differential is
eliminated, the clutch member is moved back to its original position allowing the drive teeth to
be meshingly engaged with the driven teeth on the associated clutch member.
[0005] While locking differentials of this type have generally worked for their intended
purposes, certain disadvantages remain. For example, locking differentials of the type commonly
known in the art are relatively mechanically complex and this complexity adds to the cost of
manufacturing the devices. In addition, the interaction between the cam teeth and a portion of the
driven teeth on the clutch is less than ideal because the driven teeth function to transmit torque
from the central driver as well as respond to speed differentials to ride up the surfaces of the cam
teeth. The drive teeth on the central driver and the driven teeth on the clutches are usually
designed to cause the teeth to remain in meshing engagement. The interaction between the
portion of the driven teeth on the clutch member with the cam teeth act against these meshing
forces. This results in the creation of noise and vibration during conditions when there is a speed
differential between the axle half shafts.
[0006] Thus, there remains a need in the art for a locking differential that has a reduced
number of components, is mechanically efficient, may be manufactured at a reduced cost, and
that, at the same time, reduces the noise and vibration generated when there is a speed differential
between the axle half shafts.
SUMMARY OF THE INVENTION
[0007] The present invention overcomes the disadvantages in the related art in a locking
differential mechanism for supplying torque from a driveshaft to a pair of aligned output shafts.
The locking differential mechanism includes a pair of side gears mounted for rotation with the
corresponding pair of aligned output shafts about a common axis. A central driver is operatively
coupled to the driveshaft and has a pair of opposed annular faces. Each of the pair of opposed
annular faces includes a plurality of drive teeth. A pair of clutch members are operatively
coupled for rotation with a corresponding one of the pair of side gears. Each of the pair of clutch
members includes a plurality of driven teeth. Each of the pair of clutch members is axially
movable between a first position where the driven teeth are adapted for meshing engagement in
driven relationship with the drive teeth of the central driver so as to translate torque from the
central driver through the clutch members and to the side gears and a second position where the
driven teeth are moved out of meshing engagement with the drive teeth on the central driver such
that the associated side gear may rotate at a speed different than the central driver. The locking
differential mechanism also includes a cam assembly having a pair of opposed cam members.
Each of the cam members is mounted for rotation with a corresponding one of the pair of side
gears and is disposed in abutting contact with a corresponding one of the pair of clutch members.
Each of the pair of opposed cam members includes a plurality of camming teeth extending
toward the corresponding teeth on the opposed cam member. Each of the cam members is
movable from a first position wherein the camming teeth are disposed in meshing relationship
with respect to each other when the pair of side gears are rotating at substantially the same speed
and a second position spaced axially from the first position along the associated side gear so as to
move an associated clutch member from its first position to its second position. In this way, the
camming members move the associated clutch member out of driven relationship with the central
driver in response to a variation in rotational speed of the associated one of the pair of side gears.
[0008] Because the cam assembly includes a pair of cam members that have teeth
specially designed to interact with each other to provide a corresponding camming action thereby
moving the clutch members axially away from the central driver, this arrangement results in less
internal wear in the locking differential mechanism as well as quieter and smoother operation.
The locking differential also has a reduced number of hold out rings when compared to the
devices known in the related art. Thus, the present invention is mechanically efficient and may
be manufactured at a reduced cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Other objects, features and advantages of the present invention will be readily
appreciated, as the sante becomes better understood after reading the subsequent description
taken in connection with the accompanying drawings wherein:
[0010] Figure 1 is a cross-sectional side view of the locking differential of the present
invention;
[0011] Figure 2 is a cross-sectional side view of the locking mechanism of the locking
differential of the present invention;
[0012] Figure 3 is an exploded view of the locking mechanism of the locking differential
of the present invention;
[0013] Figure 4 is a cross-sectional side view of the cam assembly of the present
invention;
[0014] Figure 5 -10 are diagrams illustrating the relative disposition of the components
of the cam assembly and the associated clutch members when the axle half shafts are locked
together as well as during other driving conditions when there is a speed differential between the
axle half shafts.
DETAILED DESCRIPTION
[0015] A representative portion of a vehicle drive train for supplying torque from a
driveshaft (not shown) to a pair of aligned output shafts (shown in phantom at 26, 28 in Figures 1
and 2) is generally illustrated in Figures 1 - 4, where like numerals are used to designate like
structure throughout the drawings. Those having ordinary skill in the art will appreciate from the
description that follows that the purpose of the figures is to illustrate one example of the
invention and are not meant to limit it. The drive train includes a locking differential mechanism, generally indicated at 12 in Figures 1 and 2, that is operatively supported in a differential
housing, generally indicated at 14 in Figure 1. The housing 14 may be configured in any suitable
way commonly known in the art. For example, in the representative example illustrated in Figure
1, the housing is defined by two pieces 16, 18 that are operatively mounted together at a flange
coupling, generally indicated at 20. A ring gear (not shown) is mounted to the flanged coupling
20 via fasteners such as a nut/bolt arrangement, not shown but commonly known in the art. The
housing 14 may also define a pair of openings 22, 24 that are adapted to support a pair of axle
half shafts illustrated in phantom in Figures 1 and 2 at 26 and 28. To this end, the housing 14
also defines a pair of bearing hubs 30, 32 that the axle half shafts 26, 28 extend therethrough. In
most operational environments, a driveshaft has a pinion gear that is disposed in meshing
relationship with the ring gear to drive the housing 14 and thus the axle half shafts 26, 28 as will
be described in greater detail below.
[0016] More specifically, the differential mechanism 12 includes a pair of side gears 34, 36 that are supported for rotation within the housing 14 on bearings as is commonly known in the
art. Each of the side gears 34, 36 has a splined inner circumference 38, 40 that cooperates with
splines 42, 44 formed on the outer circumference of the axle half shafts 26, 28. In this way, the
side gears 34, 36 are fixed to their respective half shafts 26, 28 and the side gears 34, 36 and axle
half shafts 26, 28 rotate about a common axis A. Each of the side gears 34, 36 includes an inner
terminal end 46, 48. The locking differential mechanism 12 further includes a spacer 50 disposed
between the opposed pair of terminal ends 46, 48 of the pair of side gears 34, 36.
[0017] The locking differential mechanism also includes a central driver, generally
indicated at 52. The central driver 52 includes an outer surface having a plurality of splines 54
that cooperate with splines 56 formed on the inner surface of the housing 14 as shown in Figure 1
to fix the central driver 52 for rotation with the housing 14. Alternatively, those having ordinary
skill in the art will appreciate that a spider may be employed in place of the central driver 52.
The spider has the same function as the central driver, except that a spider is operatively
connected to the housing 14 typically via four trunions that are inserted into mating holes formed
in the housing. Thus, for purposes of the discussion that follows, those having ordinary skill in
the art will appreciate that the central driver 52 and spider are interchangeable. As best shown in
Figure 3, the central driver 52 also has a pair of opposed annular feces 58. Each of the pair of
opposed annular faces includes a plurality of drive teeth 60. The locking differential mechanism
12 also includes a pair of clutch members, generally indicated at 62, 64, that are operatively
coupled for rotation with a corresponding one of a pair of side gears 34, 36. To this end, each of
the pair of side gears 34, 36 includes a splined outer circumference 66, 68, respectively (Figure
3). Each of the pair of clutch members 62, 64 includes a corresponding splined inner
circumference 70, 72. Each of the pair of clutch members 62, 64 is supported for rotation via the
respective splines with an associated one of the pair of side gears 34, 36, respectively. In
addition, each of the pair of clutch members 62, 64 is disposed on opposite sides of the central
driver 52. Each of the pair of clutch members 62, 64 also includes a plurality of driven teeth 74, 76. Each of the pair of clutch members 62, 64 is axially movable relative to its associated side
gear 34, 36 between a first position (Figures 1, 2, 5 and 8) and a second position (Figures 6, 7, 9
and 10). In the first position, the driven teeth 74, 76 of the clutch member 62, 64 are adapted for
meshing engagement in driven relationship with the drive teeth 60 of the central driver 52. In
this way, the central driver 52 acts to translate torque from the housing 14, through the central
driver 52 and the clutch members 62, 64 and thus to the side gears 34, 36. In the second position, the clutch members 62, 64 are moved axially along the outer circumference of the side gears 34, 36 such that the driven teeth 74, 76 are moved out of meshing engagement with the drive teeth 60
on the central driver 52. When a clutch member 62 or 64 is disposed in its second position, the
associated side gear 34 or 36, respectively, may rotate at a speed different than the central driver
52, as will be described in greater detail below.
[0018] As best shown in Figures 1, 2 and 4, the locking differential mechanism 12 also
includes a cam assembly, generally indicated at 78. The cam assembly 78 includes a pair of
opposed cam members 80, 82. As best illustrated in Figure 3, the cam member 80 illustrated to
the left of the central driver 52 may be referred to as the "small cam" and the cam member 82
illustrated to the right of the central driver 52 may be referred to as the "large cam." This
nomenclature may be employed because the large cam member 82 has a greater radial dimension
than the small cam member 80 as will be described in further detail below. Those having
ordinary skill in the art will appreciate that the relative location of the large and small cam
members 80, 82 with respect to the central driver 52 may be reversed without departing from the
scope of the present invention. In any event, each of the cam members 80, 82 is mounted for
rotation with a corresponding one of the pair of side gears 34, 36, respectively. Moreover, each
of the cam members 80, 82 is disposed in abutting contact with a corresponding one of the pair of
clutch members 62, 64. Each of the cam members 80, 82 also include a splined inner
circumference 84, 86 which corresponds with and is mating received by the splines 66, 68 on a
portion of the outer circumference of the associated side gear 34, 36, respectively.
[00191 As best shown in Figure 3, each of the pair of opposed cam members 80, 82 also
includes a plurality of camming 88, 90 teeth extending toward the corresponding teeth on the
opposed cam member. Each of the cam members 80, 82 is movable axially along the splines 66, 68 on the outer circumference of its associated side gear 34, 36 between a first position (Figures
1, 2, 4, 5 and 8) and a second position (Figures 6, 7, 9 and 10). In the first position, illustrated for
example in Figures 1, 2, 4, 5 and 8, the camming teeth 88, 90 are disposed in meshing
relationship with respect to each other when the pair of side gears 34, 36 are rotating at
substantially the same speed. When one of the cam members 80, 82 is disposed in its second
position illustrated for example in Figures 6, 7, 9 and 10, it becomes spaced axially from the first
position along the associated side gear 34, 36. In this way, the cam member 80 or 82 also acts to
move an associated clutch member 62 or 64 from its first position to its second position thereby
moving the clutch member 62, 64 out of driven relationship with the central driver 52 in response
to a difference in rotational speed between the associated one of the pair of side gears 34, 36.
This occurs, for example, when the vehicle is turning and the outer wheel subscribes an arc of
greater radius than the inner wheel.
[0020] More specifically, under these circumstances, the camming teeth 88, 90 cause the
cam member 80, 82 associated with the side gear 34, 36 rotating at a different speed to move
axially relative to the other such that the camming teeth 88, 90 and the associated cam member
80, 82 is moved out of meshing relationship with the opposed cam member. To this end, each of
the pair of clutch members 62, 64 defines a smooth annular surface 92, 94 that is disposed
radially inward of the plurality of driven teeth 74, 76. The smooth annular surface 92, 94 also
faces the direction of the associated cam member 80, 82. On the other hand, each of the cam
members 80, 82 includes a correspondingly outwardly directed smooth annular surface 96, 98
disposed in abutting contact with the annular surface 92, 94 on the corresponding one of the
clutch members 62, 64. Axial movement of one of the pair of cam members 80, 82 causes
similar movement by the associated clutch member 62, 64 via interaction between these mating
annular surfaces 92, 94, 96, 98.
[0021 ] The locking differential mechanism 12 also includes a single holdout ring 100 that
is mounted for rotation with one of the pair of opposed cam members 80, 82. In the embodiment
illustrated herein, the holdout ring 100 is mounted for rotation with the small cam 80. The hold
out ring 100 includes a plurality of lugs 102 disposed in annularly spaced positions about the
outer circumference of the holdout ring 100. The holdout ring 100 is indexable about the axis of
rotation A between a first position and a second position. In the first position, the pair of side
gears 34, 36 rotate at the same rotational speed. In the second position, at least one of the cam
members 80, 82 is disposed in its second, axially spaced position. In this position, the holdout
ring 100 is indexed to its second position and thereby prevents re-engagement of the camming
teeth when there is a rotational speed difference between the side gears. More specifically, the
lugs 102 act to prevent the re-engagement of the cam members 80, 82 when the holdout ring 100
has been indexed to its second position. As best shown in Figures 2 and 3, the large cam 82 has
camming teeth 90 of greater radial length than the camming teeth 88 on the small cam 80. When
the large cam 82 has moved to its second position, the teem 90 engage the lugs 102 on the
holdout ring 100 and act to index to its second position.
[0022] As best shown in Figure 2, the locking differential mechanism 12 also defines a
center line CL that bisects it and extends perpendicularly to the axis of rotation A. As noted
above, in the representative example illustrated herein, the holdout ring 100 is mounted about the
outer circumference of the small cam member 80 and is biased or located to one side of the center
line CL. The holdout ring 100 also includes an inner annular rib 104 that is received in a
corresponding groove 106 disposed on the outer circumference of the small cam 80. On the other
hand, the central driver 52 defines an inner diameter 108 having a key 110 located biased to one
side of the center line CL. The holdout ring 100 includes a slot that is adapted to engage the key
110 when the holdout ring 100 has been indexed to its second position so as to block re-
engagement of the camming teeth 88, 90 on the pair of cam members 80, 82. In the
representative example illustrated herein, the holdout ring is mounted to the outer circumference
of the small cam member 80 so as to be biased to the left of the centerline. Similarly, the key 110
is located on the inner circumference of the central driver at a location biased to the left side of
the center line as illustrated in Figures 1 and 2. However, those having ordinary skill in the art
will appreciate from thedescription herein that both the holdout ring 100 and the key 110 may be
biased to the right of the centerline without departing from the scope of the present invention.
[0023] The locking differential mechanism 12 also includes a pair of annular retainers
112, 114 operatively mounted to a corresponding one of the pair of side gears 34, 36, respectively. More specifically, the retainers 112, 114 are mounted against shoulders 116, 118
formed on the side gears 34, 36. A pair of biasing members 120, 122 is disposed between each
one of the pair of retainers 112, 114 and one of the pair of clutch members 62, 64. To this end, each of the clutch members 62, 64 includes an annular retaining groove 124, 126 that is adapted
to receive and retain one end of the biasing members 120, 122. The pair of biasing members 120, 122 act to bias the pair of clutch members 62, 64 toward the clutch members' first position and
into engagement with the central driver 52. In one embodiment, the biasing members 120, 122
may include a pair of coiled springs. However, those having ordinary skill in the art will
appreciate that any suitable biasing member may be employed for this purpose.
[0024] The key 110 defined on the inner circumference of the central driver 52 has a
predetermined axial width. The holdout ring 100 is supported for axial movement with one 80 of
the pair of cam members 80, 82. As noted above, in the embodiment illustrated herein, this cam

member 80 is the smaller of the two. The second position of the pair of clutch members 62, 64 is
limited by the pair of annular retainers. The axial width of the key 110 is designed such that the
distance of travel of the pair of clutch members 62, 64 to the second position is less than the axial
width of the key. In this way, the holdout ring 100 is prevented from being moved axially out of
engagement with the key 110 when the holdout ring 100 is indexed to its second position. This
feature prevents the problem where the holdout ring "jumps the key." When the holdout ring
jumps the key as can happen with differential mechanisms known in the related art, other
components of the differential mechanism can become axially skewed and this results in failure
of the components. Thus, the present invention is specifically designed to prevent this problem
from occurring.
[0025] Figures 5-10 illustrate the different operational modes of the locking differential
mechanism 12 of the present invention. More specifically, as illustrated in Figure 5, when both
axle half shafts 26, 28 and associated side gears 34, 36 are driven at the same speed, the central
driver 52, clutch member 62, 64, cam assembly 78, and side gears 34, 36 all rotate together. As
illustrated in Figure 6, when the right wheel is over-running, the side gear 36 and axle half shaft
28 associated with the right wheel will rotate at a greater speed. Under these circumstances, the
cam member 82 will move its associated clutch member 64 out of engagement with the central
driver 52. In this way, the side gear 36 and its associated axle half shaft 28 will be able to rotate
at a faster rotational speed than the side gear 34 associated with the left-hand tire. As best shown
in Figure 7, the locking differential mechanism 12 of the present invention operates in the same
way when the left hand wheel is over-running, except that the cam member 80 and the associated
clutch member 62 is moved out of engagement with the central driver 52 to allow the side gear
34 and associated axle half shafts 26 to rotate at a faster rotational speed.
[0026] Figure 8 illustrates the operational conditions when both wheels are drive at the
same rotational velocity but in a coast condition. Under these circumstances, the central driver
52, clutch members 62, 64, cam assembly 78 and side gears 34, 36 all rotate together in a locked
condition.
[0027] Figures 9 and 10 illustrate the operation of the locking differential mechanism 12
of the present invention when the axles 26, 28 are in contact and the right and left wheels are
under-running, respectively. In each case, and as similarly described above, the cam member 80, 82 associated with the side gear 34, 36 rotating at a lower rotational velocity, moves the
associated clutch member 62, 64 out of engagement with the central driver 52 to allow the side
gear 34, 36 to rotate at a slower speed.
[0028] The locking differential mechanism 12 of the present invention achieves these
results using only one hold out ring when compared to locking differentials known in the related
art. In addition, the locking differential mechanism 12 of the present invention prevents the
holdout ring 100 from "jumping the key" 110 and causing damage to the assembly. Moreover, the present invention is mechanically efficient and may be manufactured at a reduced cost. At
the same time, because the camming teeth 88, 90 are designed for meshing and camming action
relative to each other, the noise and vibration generated by the locking differential mechanism 12
of the present invention is reduced when there is a speed differential between the axle half shafts.
[0029] The invention has been described in great detail in the foregoing specification, and
it is believed that various alterations and modifications of the invention will become apparent to
those having ordinary skill in the art from a reading and understanding of the specification. It is
intended that all such alterations and modifications are included in the invention, insofar as they
come within the scope of the appended claims.
WE CLAIM:
1. A locking differential mechanism (12) for supplying torque from a driveshaft to a
pair of aligned output shafts (26, 28), said locking differential mechanism comprising:
a pair of side gears (34, 36) mounted for rotation with the corresponding pair of aligned
output shafts (26, 28) about a common axis (A);
a central driver (52) operatively coupled to the driveshaft and having a pair of opposed
annular faces (58), each of said pair of opposed annular faces including a plurality of drive teeth
(60);
a pair of clutch members (62, 64) operatively coupled for rotation with a corresponding
one of said pair of side gears (34, 36), each of said pair of clutch members (62, 64) including a
plurality of driven teeth (74, 76), each of said pair of clutch members (62, 64) is axially movable
between a first position where said driven teeth (74, 76) are adapted for meshing engagement in
driven relationship with said drive teeth (60) of said central driver (52) so as to translate torque
from said central driver{52) through said clutch members (62, 64) and to said side gears (34, 36)
and a second position wherein said driven teeth (74, 76) are moved out of meshing engagement
with said drive teeth (60) on said central driver (52) such that the associated side gear may rotate
at a speed different than said central driver;
a cam assembly (78) including a pair of opposed cam members (80, 82), each of said cam
members mounted for rotation with a corresponding one of said pair of side gears (34, 36) and
disposed in abutting contact with the corresponding one of said pair of clutch members (62, 64);
each of said pair of opposed cam members (80, 82) including a plurality of camming teeth
(88, 90) extending toward the corresponding teeth (74, 76) on the opposed cam member (62, 64), each of said cam members (62, 64) movable from a first position wherein said camming teeth
(88, 90) are disposed in meshing relationship with respect to each other when said pair of side
gears (34, 36) are rotating at substantially the same speed, and a second position spaced axially

from said first position along the associated side gear so as to move an associated clutch member
(62, 64) from said first position to said second position thereby moving its associated clutch
member out of driven relationship with said central driver (52) in response to a variation in
rotational speed of the associated one of said pair of side gears (34, 36).
2. A locking differential mechanism (12) as set forth in claim 1 wherein said
camming teeth (88, 90) cause said cam member (82) associated with the side gear rotating at a
t
different speed to move axially relative to the other such that said camming teeth (88, 90) and
said associated cam member (80, 82) is moved out of meshing relationship with the opposed cam
member.
3. A locking differential mechanism (12) as set forth in claim 1 further including a
single holdout ring (100) mounted for rotation with one of said pair of opposed cam members
(80, 82), said holdout ring (100) indexable about the axis of rotation between a first position
wherein said pair of side gears (34, 36) rotate at the same rotational speed and a second position
wherein at least one cam member (80, 82) is disposed in said second axially spaced position and
said holdout ring (100) prevents re-engagement of said camming teeth (88, 90) when there is a
rotational speed difference between said side gears.
4. A locking differential mechanism (12) as set forth in claim 3 wherein said holdout
ring (100) includes a plurality of lugs (102) disposed in annularly spaced positions about the
outer circumference of said holdout ring (100), said lugs (102) acting to prevent re-engagement
of said cam members (80, 82) when said holdout ring (100) has been indexed to its second
position.
5. A locking differential (12) mechanism as set forth in claim 3 wherein said locking
differential mechanism defines a center line (CL) bisecting said differential mechanism, said
holdout ring (100) being mounted about one of said cam members (80, 82) and biased to one side
of said center line.
6. A-locking differential mechanism (12) as set forth in claim 5 wherein said central
driver (52) defines an inner diameter (108) having a key (110) located biased to one side of said
center line (CL), said holdout ring (100) including a slot that is adapted to engage said key (110)
when said holdout ring (100) has been indexed to its second position so as to block re-
engagement of the camming teeth (88, 90) on the pair of cam members (80, 82).
7. A locking differential mechanism (12) as set forth in claim 6 further including a
pair of annular retainers (112, 114) operatively mounted to a corresponding one of said pair of
side gears (34, 36), a pair of biasing members (120, 122) disposed between each one of said pair
of retainers (112, 114) and each one of said pair of clutch members (62, 64), said pair of biasing
member (120, 122) acting to bias said pair of clutch members (62, 64) toward said first position.
8. A locking differential mechanism (12) as set forth in claim 7 wherein said key
(110) has a predetermined axial width, said holdout ring (100) supported for axial movement
with one (80) of said pair of cam members (80, 82), said second position of said pair of clutch
members (62, 64) being limited by said pair of annular retainers (112, 114) such that the distance
of travel of said pair of clutch members (62, 64) to said second position is less than the axial
width of said key (110) such that said holdout ring (100) is prevented from being moved axially
out of engagement with said key (110) when said holdout ring (100) is indexed to said second
position.
9. A locking differential mechanism (12) as set forth in claim 1 wherein each of said
pair of clutch members (62, 64) defines a smooth annular surface (92, 94) disposed radially
inward of said plurality of driven teeth (74, 76) and in the direction of the associated cam
member, each of an associated one of said cam members (82, 84) including a corresponding
outwardly directed smooth annular face (96, 98) disposed in abutting contact with said annular
surface (92, 94) on said corresponding one of said clutch members (62, 64).
10. A locking differential mechanism (12) as set forth in claim 1 wherein the
camming teeth (90) of one (82) of said pair of cam members (80, 82) extends for a longer radial
length than the camming teeth (88) on the opposed cam member (80).
11. A locking differential mechanism (12) as set forth in claim 1 wherein each of said
side gears (34, 36) includes an inner terminal end (46, 48), and wherein said locking differential
mechanism further includes a spacer (50) disposed between the opposed pair of terminal ends
(46, 48) of each of said pair of side gears (34, 36).
12. A locking differential mechanism (12) as set forth in claim 1 further including a
housing (14), said locking differential mechanism operatively supported within said housing (14), said housing including an inner surface having a plurality of splines (56), said central driver (52)
including an outer surface having a corresponding plurality of splines (54) that cooperate with
said splines (56) on the inner surface of said housing (14) to fix said central driver (52) for
rotation with said housing (14).

13. A locking differential for supplying torque from a driveshaft to a pair of aligned
output shafts, said locking differential comprising:
a housing (14) and a locking differential mechanism (12) operatively supported within
said housing (14), said housing (14) including an inner surface having a plurality of splines (56);
said differential mechanism (12) including a pair of side gears (34, 36) supported for
rotation within said housing (14) with the corresponding pair of aligned output shafts (26, 28)
about a common axis;
a central driver (52) including an outer surface having a corresponding plurality of splines
(54) that cooperate with said splines (56) on said inner surface of said housing (14) to fix said
central driver (52) for rotation with said housing (14), said central driver (52) having a pair of
opposed annular faces (58), each of said pair of opposed annular faces (58) including a plurality
of drive teeth (60);
a pair of clutch members (62, 64) operatively coupled for rotation with a corresponding
one of said pair of side gears (34, 36), each of said pair of clutch members (62, 64) including a
plurality of driven teeth (74, 76), each of said pair of clutch members (62, 64) axially movable
between a first position where said driven teeth (74, 76) are adapted for meshing engagement in
driven relationship with said drive teeth (60) of said central driver (52) so as to translate torque
from said central driver (52) through said clutch members (62, 64) and to said side gears (34, 36)
and a second position wherein said driven teeth (74, 76) are moved out of meshing engagement
with said drive teeth (60) on said central driver (52) such that the associated side gear (34, 36)
may rotate at a speed different than said central driver (52);
a cam assembly (78) including a pair of opposed cam members (80, 82), each of said cam
members (80, 82) mounted for rotation with a corresponding one of said pair of side gears (34, 36) and disposed in abutting contact with the corresponding one of said pair of clutch members
(62, 64);
each of said pair of opposed cam members (80, 82) including a plurality of camming teeth
(88, 90) extending toward the corresponding teeth on the opposed cam member, each of said cam
members (80, 82) movable from a first position wherein said camming teeth (88, 90) are disposed
in meshing relationship with respect to each other when said pair of side gears (34, 36) are
rotating at substantially the same speed, and a second position spaced axiaily from said first
position along the associated side gear (34, 36) so as to move an associated clutch member (62, 64) from said first position to said second position thereby moving its associated clutch member
(62, 64) out of driven relationship with said central driver (52) in response to a variation in
rotational speed of the associated one of said pair of side gears (34, 36).
14. A locking differential mechanism as set forth in claim 13 wherein said camming
teeth (88, 90) cause said cam member (80, 82) associated with the side gear (34, 36) rotating at a
different speed to move axiaily relative to the other such that said camming teeth (88, 90) and
said associated cam member (80, 82) is moved out of meshing relationship with the opposed cam
member.
15. A locking differential mechanism as set forth in claim 13 further including a
single holdout ring (100) mounted for rotation with one (80) of said pair of opposed cam
members (80, 82), said holdout ring (100) indexable about the axis of rotation between a first
position wherein said pair of side gears (34, 36) rotate at the same rotational speed and a second
position wherein at least one cam member is disposed in said second axiaily spaced position and
said holdout ring (100) prevents re-engagement of said camming teeth (88, 90) when there is a
rotational speed difference between said side gears (34, 36).
16. A locking differential mechanism as set forth in claim 15 wherein said holdout
ring (100) includes a plurality of lugs (102) disposed in annularly spaced positions about the
outer circumference of said holdout ring, said lugs (102) acting to prevent re-engagement of said
cam members (80, 82) when said holdout ring (100) has been indexed to its second position.
17. A locking differential mechanism as set forth in claim 15 wherein said locking
differential mechanism (12) defines a center line (CL) bisecting said differential mechanism, said
holdout ring (100) being mounted about one (80) of said cam members (80, 82) and biased to one
side of said center line (CL).
18. A locking differential mechanism as set forth in claim 17 wherein said central
driver (52) defines an inner diameter having a key (110) located biased to one side of said center
line (CL), said holdout ring (100) including a slot that is adapted to engage said key (110) when
said holdout ring (100) has been indexed to its second position so as to block re-engagement of
the camming teeth (88, 90) on the pair of cam members (80, 82).
19. A locking differential mechanism as set forth in claim 18 further including a pair
of annular retainers (112, 114) operatively mounted to a corresponding one of said pair of side
gears (34, 36), a pair of biasing members (120, 122) disposed between each one of said pair of
retainers (112, 114) and one of said pair of clutch members (62, 64), said pair of biasing members
(120, 122) acting to bias said pair of clutch members (62, 64) toward said first position of said
pair of clutch members.
20. A locking differential mechanism as set forth in claim 19 wherein said key (110)
has a predetermined axial width, said holdout ring (100) supported for axial movement with one
(80) of said pair of cam members (80, 82), said second position of said pair of clutch members
(62, 64) being limited by said pair of annular retainers (112, 114) such that the distance of travel
of said pair of clutch members (62, 64) to said second position is less than the axial width of said
key (110) such that said holdout ring (100) is prevented from being moved axially out of
engagement with said key (110) when said holdout ring (100) is indexed to said second position.

A locking differential mechanism (12) for supplying
torque from a driveshaft to a pair of aligned output
shafts (26, 28) including a pair of side gears (34,
36), a central driver (52), and a pair of clutch
members (62, 64) operatively coupled for rotation with
the corresponding one of the pair of side gears (34,
36). A cam assembly (78) includes a pair of cam members
(80, 82). Each of the pair of cam members (80, 82)
includes a plurality of camming teeth (88, 90)
extending toward the corresponding teeth on the opposed
cam member. Each of the cam members (80, 82) is movable
from a first position where the cam teeth (88, 90) are
disposed in meshing relationship with respect to each
other when the pair of side gears (34, 36), are
rotating at substantially the same speed and a second
position spaced axially from the first position along
the associated side gear (34, 36) so as to move an
associated clutch member (62, 64) from its first
position to its second position out of driven
relationship with the central driver (52) in response
to a difference in rotational speed of the associated
pair of side gears (34, 36).