LOCKING DIFFERENTIAL ASSEMBLY
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application Serial No.
61/755,939, filed January 23, 201 3, which is incorporated by reference herein in its
entirety.
BACKGROUND
[0002] A locking differential may have an additional capability compared to a
conventional "open" automotive differential. A vehicle with a locking differential may
experience increased use of traction at the drive wheels compared to a vehicle with an
"open" differential. Use of traction may be increased by restricting each of the two
drive wheels on an axle to the same rotational speed without regard to the available
traction or the road path taken at each wheel. The locking differential causes both
wheels on an axle to turn together as if on a common axle shaft.
[0003] An open differential, or unlocked locking differential allows each wheel on an
axle to rotate at different speeds. When a vehicle negotiates a turn, the wheel on the
smaller (inner) radius rotates more slowly than the wheel on the larger (outer) radius.
Without the unlocked or open differential, one of the tires may scuff in a turn. With an
open differential, when one wheel of an axle is on a slippery road surface, the wheel
on the slippery surface may tend to spin while the other wheel may not have enough
torque applied to it to move the vehicle. For example, some vehicles with open
differentials may be unable to climb a hill with wet ice under one of the wheels no
matter how dry the pavement is under the other wheel (this may be known as a splitmu
surface).
[0004] In contrast, a locked differential forces wheels on both sides of the same
axle to rotate together at the same speed. Therefore, each wheel can apply as much
torque as the wheel/road traction and the powertrain capacity will allow. In the
example of the vehicle on the hill with the split-mu surface, a locked differential may
allow the vehicle to clinnb the hill that is impossible for an otherwise identical vehicle to
climb with an open differential. Locking differentials may also provide better traction
that leads to improved vehicle performance under certain conditions, for example in
drag racing, or snow plow operations.
[0005] Some vehicles have differentials that may be reconfigured from an unlocked
state to a locked state. Such vehicles may be operated with the differential in the
unlocked state for normal conditions, for example, to prevent tire scuffing in turns, and
reconfigured for operation with a locked differential when wheel slippage is
encountered.
SUMMARY
[0006] A locking differential assembly includes a differential case defining an axis of
rotation and a gear chamber. A first side gear is at a first end of the differential case.
A second side gear is at a second end of the differential case opposite the first end for
selectable rotation relative to the differential case. At least two pinion gears are
rotatably supported in the gear chamber in meshing engagement with the first side
gear and the second side gear. A solenoid is at the first end. A plunger is selectably
magnetically actuatable by the solenoid. A lock ring is selectably engagable with the
second side gear to selectably prevent the side gear from rotating relative to the
differential case. At least two relay rods are each connected to the plunger and to the
lock ring to cause the lock ring to remain a fixed predetermined distance from the
plunger.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Features and advantages of examples of the present disclosure will become
apparent by reference to the following detailed description and drawings, in which like
reference numerals correspond to the same or similar, though perhaps not identical,
components. For the sake of brevity, reference numerals or features having a
previously described function may or may not be described in connection with other
drawings in which they appear.
[0008] Fig. 1 is a schematic view of a vehicle with a locking differential system
according to an example of the present disclosure;
[0009] Fig. 2 is a perspective view of a locking differential according to an example
of the present disclosure;
[0010] Fig. 3A is a cross-sectional perspective view of the locking differential
depicted in Fig. 2;
[001 1] Fig. 3B is an exploded view of the locking differential depicted in Fig. 2;
[0012] Fig. 3C is a cross-sectional view of a locking differential with the lock ring on
the same side as the solenoid;
[0013] Fig. 4 is a cross-sectional side view of an example of a stator according to
the present disclosure;
[0014] Fig. 5A is a cross-sectional side view of an example of a plunger according
to the present disclosure;
[0015] Fig. 5B is an exploded side view of an example of a plunger and a relay rod
according to the present disclosure;
[0016] Fig. 6A is a plan view of an example of a lock ring according to the present
disclosure;
[0017] Fig. 6B is a perspective view of an example of a locking differential with an
end cover removed according to the present disclosure;
[0018] Fig. 6C is a perspective view of an example of a lock ring, relay rods and a
plunger assembled as in the locking differential depicted in Fig. 2;
[0019] Fig. 7A is a cross-sectional view of an example of the differential assembly
with the lock ring in the disengaged position according to the present disclosure;
[0020] Fig. 7B is a cross-sectional view of an example of the differential assembly
with the lock ring in the engaged position according to the present disclosure;
[0021] Fig. 8A is a partially exploded perspective view of a differential gear set
according to the present disclosure;
[0022] Fig. 8B is an exploded perspective view of an example of a cross shaft
according to the present disclosure;
[0023] Fig. 9 is an exploded perspective view of another example of a cross shaft
according to the present disclosure;
[0024] Fig. 10 is an enlarged cross-sectional view of an example of a stator,
plunger, and position sensor according to the present disclosure; and
[0025] Fig. 11 is time graph depicting an example of a flash code according to the
present disclosure.
DETAILED DESCRIPTION
[0026] The present disclosure relates generally to locking differentials, and more
particularly to electronically controlled locking differentials used in vehicle drive axles.
As used herein, an electronically controlled locking differential means a differential that
changes between an unlocked state and a locked state in response to an electronic
signal. In the locked state, both axle shafts connected to the differential rotate
together in the same direction, at the same speed. The electronic signal may be
automatically produced in response to a vehicle condition, for example, detection of
wheel slippage. The electronic signal may also be produced in response to a demand
from an operator, for example, an operator may press a button on a control panel of
the vehicle.
[0027] Examples of the present disclosure may allow the differentials to operate at
a higher torque than similarly sized existing locking differentials. The time to actuate
the locking mechanism may also be reduced compared to existing electronic locking
differentials. Further, the status indicator may provide a more satisfactory user
experience by providing more detailed and accurate information regarding the
operation of the electronically controlled locking differential system of the present
disclosure.
[0028] Referring to Fig. 1, a powertrain 5 for a vehicle 70 includes a motor 6, a
propeller shaft 7 connected to the motor and an axle assembly 8 . The propeller shaft
7 is connected, for example, by gearing (not shown) to rotationally drive the axle shafts
13, 13' inside the axle housing 9 . The axle assembly 8 includes the axle housing 9, a
locking differential assembly 10 supported in axle housing 9 and the axle shafts 13, 13'
respectively connected to first and second drive wheels 98 and 98'. A gearset 97
disposed within a differential case 12 transfers rotational power from differential case
12 to the axle shafts 13, 13', and selectably allows relative rotation between the axle
shafts 13 and 13'. Although the locking differential assembly 10 depicted in Fig. 1 is
applied to a rear-wheel drive vehicle, the present disclosure may be used in transaxles
for use in front-wheel drive vehicles, transfer cases for use in four-wheel drive vehicles
or in any vehicle powertrain.
[0029] Referring to Figs. 2, 3A and 3B together, an example of the present
disclosure is depicted including a locking differential assembly 10. The locking
differential assembly 10 has a differential case 12 defining an axis of rotation 14 and a
gear chamber 16 . The differential case 12 rotates in the axle housing 9 (see Fig. 1)
about the axis of rotation 14 . A first side gear 18 is disposed at a first end 19 of the
differential case 12 for selectable relative rotation thereto. A second side gear 20 is
disposed at a second end 2 1 of the differential case 12 opposite the first end 19 for
selectable rotation relative to the differential case 12 .
[0030] The second side gear 20 has side gear dogs 22 defined on an outside
diameter 24 of the second side gear 20 parallel to the axis of rotation 14. At least two
pinion gears 26 are rotatably supported in the gear chamber 16 . Each of the at least
two pinion gears 26 is in meshing engagement with the first side gear 18 and the
second side gear 20.
[0031] The locking differential assembly 10 includes a solenoid 28, disposed at the
first end 19 of the differential case 12 . The stator 32 is formed from a ferromagnetic
material. The differential case 12 is rotatable relative to the stator 32 about the axis of
rotation 14. As depicted in Fig. 4, the stator 32 has an annular wall 33 with a
longitudinal axis 35 coaxial with the axis of rotation 14. Although the annular wall 33
depicted in Fig. 4 is a cylindrical wall, and the longitudinal axis 35 is a cylindrical axis,
the annular wall 33 may deviate from a cylindrical shape in examples of the present
disclosure. The annular wall 33 may, for example, have a larger diameter at one or
both ends, or the annular wall 33 may have an arcuate section. A first stator annular
flange 36 extends radially from the annular wall 33 to a first outer diameter 38 of the
first stator annular flange 36. Although Fig. 4 depicts the first stator annular flange 36
extending perpendicularly to the longitudinal axis 35, the angle that the annular flange
36 makes with the longitudinal axis 35 may deviate from 90 degrees. For example,
the angle may be 45 degrees such that the bobbin is wider at the first outer diameter
38 than at an interface between the first stator annular flange 36 and the annular wall
33. The angle between the first stator annular flange 36 and the annular wall 33 may
be any angle.
[0032] A second stator annular flange 37 extends from the annular wall 33. The
second stator annular flange 37 is spaced from the first stator annular flange 36 and
may be parallel to the first stator annular flange 36. The second stator annular flange
37 is frustoconical with an inner base annular surface 5 1 opposite the first stator
annular flange 36. An outer base annular surface 52 is distal to the first stator annular
flange 36. The inner base annular surface 5 1 has an outer edge diameter 53 equal to
the first outer diameter 38. The outer base annular surface 52 has a second outer
diameter 39 greater than the first outer diameter 38. The first stator annular flange 36,
the annular wall 33 and the second stator annular flange 37 together define an integral
bobbin 3 1 for the solenoid 28. Although Fig. 4 depicts the integral bobbin having a
substantially rectangular cross section, the surfaces may be rounded or canted in
examples of the present disclosure. The solenoid 28 is directly wound onto the stator
32. Directly winding the solenoid 28 onto the stator 32 is facilitated by having the
integral bobbin 3 1 open between the first outer diameter 38 and the second outer
diameter 39. The stator 32 with the integral bobbin 3 1 of the present disclosure differs
from other stators that open axially. A stator that opens axially may require that the
solenoid be wound on a separate bobbin and slid into the axial opening. The space
required for the separate bobbin is space that is not available for solenoid windings.
Even if a so-called bobbinless coil is used, the additional manufacturing steps required
to create the separate coil and then install the coil into the stator may be less desirable
than the stator 32 with the integral bobbin 3 1 of the present disclosure.
[0033] Fig. 3B depicts a spring 34 disposed between the differential case 12 and
the lock ring 40 to bias the lock ring 40 toward the disengaged position 44. A cover
100 is shown at the second end 2 1 of the locking differential assembly 10 . A side gear
thrust washer 10 1 is disposed between the cover 100 and the second side gear 20.
Another side gear thrust washer 10 1 is disposed between the differential case 12 and
the first side gear 18 . Thrust washers 104 are disposed between the pinion gears 26
and the differential case 12. Shaft anchor roll pins 103 are inserted through the
differential case 12 and the cross-shaft 90 and the stub shafts 92 to retain the crossshaft
90 and stub shafts 92 for supporting the pinion gears 26. Stator retaining ring
102 is inserted into a groove in the differential case 12 to prevent the stator from
moving axially relative to the differential case 12 .
[0034] Fig. 3C is a cross-sectional view of a locking differential with the lock ring 40'
on the same side as the solenoid 28. The first side gear 18' has side gear dogs 22
defined on an outside diameter 24 of the first side gear 18' parallel to the axis of
rotation 14. The lock ring 40' is the same as the lock ring 40 in the example depicted
in Fig. 3A. The relay rods 50' are shorter in the example depicted in Fig. 3C compared
to the relay rods 50 in the example depicted in Fig. 3A.
[0035] Referring to Figs. 5A and 5B, in examples of the present disclosure, a
plunger 30 is selectably magnetically actuated by the solenoid 28 (see Fig. 3A). The
plunger 30 has a ferromagnetic cylindrical body 54. The ferromagnetic cylindrical
body 54 has a cylindrical body axis 55 defined by the ferromagnetic cylindrical body 54
to be aligned with the axis of rotation 14. The ferromagnetic cylindrical body 54 has an
inner wall 56 with an annular bevel 57 at a beveled end 58 of the ferromagnetic
cylindrical body 54. The ferromagnetic cylindrical body 54 further includes an outer
wall 59 having a plunger outer diameter 6 1. An annular plunger flange 62 is defined at
a plunger end 63 distal to the beveled end 58. The annular plunger flange 62 has a
plunger flange diameter 64 smaller than the plunger outer diameter 6 1. An annular
notch 65 is defined by the ferromagnetic cylindrical body 54 and the annular plunger
flange 62.
[0036] In an example, the plunger 30 is fixed for rotation with the differential case
12, and the plunger 30 is selectably translatable relative to the differential case 12
along the axis of rotation 14 (see Figs. 2, 3A, 7A and 7B). The rotating plunger 30
rotates relative to the stator 32. Contact between the plunger 30 and the stator 32
may lead to galling of the plunger 30, the stator 32 or both.
[0037] Referring back to Figs. 5A and 5B, in examples of the present disclosure,
the locking differential assembly 10 may include a spacer 60, 60' disposed between
the plunger 30 and the differential case 12 to prevent the annular bevel 57 of the inner
wall 56 from contacting the second stator annular flange 37. In an example, the
spacer 60 may be a threaded rod 7 1 adjustably screwed into the plunger 30 to set a
predetermined gap 72 (see Fig. 7B) between the annular bevel 57 and the second
stator annular flange 37. In another example, the spacer 60' may be a plurality of
spaced raised bosses 73 on the beveled end 58 of the ferromagnetic cylindrical body
54.
[0038] A plurality of relay rod attachment bores 66 are defined in the ferromagnetic
cylindrical body 54. A plurality 67 of relay rod access slots 69 are each defined in the
beveled end 58 of the ferromagnetic cylindrical body 54 at each relay rod attachment
bore 68. Each relay rod attachment bore 68 is substantially centered in the respective
relay rod access slot 69. A shortest distance between the relay rod access slot 69 and
the annular notch 65 is equal to the lock ring thickness 4 1. Such equality of
dimensions allows each of the relay rods 50 to have end-to-end symmetry.
[0039] At least two relay rods 50 are each connected to the plunger 30 and to the
lock ring 40 to cause the lock ring 40 (see Fig. 6C) to remain a fixed predetermined
distance from the plunger 30.
[0040] The at least two relay rods 50 each include a cylindrical rod portion 74
having two ends 77, the cylindrical rod portion 74 defining a longitudinal rod axis 75 at
a center 76 of the cylindrical rod portion 74. The relay rods 50 each have a first post
78 and a second post 79 each having a smaller diameter 80 than the cylindrical rod
portion 74 defined at a respective one of the two ends 77. The first post 78 and the
second post 79 are each concentric with the cylindrical rod portion 74. An annular
groove 8 1 is defined on the first post 78 and the second post 79. The first post 78 and
the second post 79 are substantially identical, and the relay rod 50 is symmetrical endto-
end. In other words, during assembly, the relay rods 50 may be installed without
regard to which end is installed in the plunger 30 and which end is installed in the lock
ring 40. In Fig. 5B, the first post 78 and the second post 79 are given different
reference numbers for clarity in describing Fig. 5B, however, the first post 78 is
identical to the second post 79. The first post 78 is depicted as being retained in a
respective relay rod attachment bore 68 by a retention ring 82 disposed in the annular
notch 65 of the plunger 30 protruding into the annular groove 8 1 of the first post 78.
[0041] Referring now to Figs. 6A, 6B, and 6C together, in examples of the present
disclosure, the locking differential assembly 10 has a lock ring 40. The lock ring 40
includes complementary dogs 42 defined around an inside surface 43 of the lock ring
40. The complementary dogs 42 are selectably engagable with the side gear dogs 22
by translating the lock ring 40 along the axis of rotation 14 from a disengaged position
44 to an engaged position 45. The lock ring 40 has a plurality of lugs 46 defined on an
outside surface 47 of the lock ring 40. Each lug 48 is to slide in a respective
complementary slot 49 defined in the differential case 12 to guide the translation of
the lock ring 40 between the engaged position 45 and the disengaged position 44.
(See Figs. 7A and 7B.) The fit of the plurality of lugs 46 in the respective
complementary slots 49 also prevents rotation of the lock ring 40 relative to the
differential case 12.
[0042] Fig. 7A depicts an example of the present disclosure with the lock ring 40 in
the disengaged position 44. Fig. 7B depicts the example shown in Fig. 7A except the
the lock ring 40 is in the engaged position 45. In examples of the present disclosure,
the second side gear 20 is substantially prevented from rotating relative to the
differential case 12 when the lock ring 40 is in the engaged position 45. The second
side gear 20 is free to rotate relative to the differential case 12 when the lock ring 40 is
in the disengaged position 44. The lock ring 40 has a lock ring thickness 4 1 parallel to
the axis of rotation 14.
[0043] The lock ring 40 further includes extension tabs 83 on a quantity of the lugs
48 equal to a quantity of the relay rods 50. The extension tabs 83 each define a relay
rod attachment hole 84. Each relay rod 50 is retained in the respective relay rod
attachment hole 84 by a clip 85 installed in the annular groove 8 1 of the respective
second post 79 (see Fig. 5B for detail of annular groove 8 1) . In an example, the
plurality of lugs 46 is a quantity of nine lugs 48, and the quantity of relay rods 50 is
three.
[0044] Each lug 48 may have two opposed faces 86 symmetrically arranged about
a radial line 87 perpendicular to the axis of rotation 14. An angle 99 between the two
opposed faces 86 is from about 28 degrees to about 32 degrees.
[0045] Referring now to Figs. 8A and 8B, examples of the present disclosure may
have a cross-shaft 90 disposed perpendicularly to the axis of rotation 14 of the
differential case 12 to support an opposed pair 27 of the at least two pinion gears 26
for rotation of the opposed pair 27 of the at least two pinion gears 26 on the crossshaft
90. In examples of the present disclosure with a 4-pinion differential, the
differential assembly 10 may include a pair of opposed stub shafts 92, each stub shaft
92 being disposed perpendicularly to the cross-shaft 90 and perpendicularly to the axis
of rotation 14 of the differential case 12 through a yoke 9 1. The yoke 9 1 is disposed
around the cross-shaft 90. The yoke 9 1 has complementary apertures 93 for receiving
the stub shafts 92. The pair of opposed stub shafts 92 support another opposed pair
27' of the at least two pinion gears 26.
[0046] In the example depicted in Fig. 9, the cross-shaft 90' may include two
opposed central grooves 4 . Each of the opposed central grooves 4 is to receive a
complementary tongue disposed on the stub shaft 92'. Examples having the tongue in
groove joints depicted in Fig. 9 may or may not include the yoke 9 1 shown in Fig. 8B.
[0047] Examples of the present disclosure may include a locking differential system
11 that includes the locking differential assembly 10 with the solenoid 28 directly
wound on the stator 32 as described above, with control elements described below.
The locking differential system 11 may include a plunger position sensor 15 to
determine a state of the lock ring 40 by detecting the position of the plunger 30. In an
example of a plunger position sensor 15, a secondary coil 94 may be wound around
the stator 32 to detect an inductance in the solenoid 28 responsive to a position of the
plunger 30. As shown in Fig. 10, in another example, the plunger position sensor 15
may be a non-contacting position sensor 89 disposed on an anti-rotation bracket 95
connected to the stator 32. In examples of the present disclosure, the non-contacting
position sensor 5 may use any non-contacting position sensor technology. For
example, non-contacting postion sensors based on magnetostriction,
magnetoresistance, Hall-Effect, or other magnetic sensing technologies may be
included in the locking differential system 11 according to the present disclosure.
Further, non-contacting position sensors based on optical, infrared, or fluid pressure
sensing may also be used according to the present disclosure. In the example, the
non-contacting position sensor 89 detects an axial position of the plunger 30 or a
target 96 affixed to the plunger 30. As shown in Fig. 10, the retention ring 82 may be
the target 96. In examples having the retention ring 82 also operative as the target 96,
the retention ring 82 may be a double wound laminar ring. An example of a suitable
retention ring 82 is a Spirolox® part number WS-587 available from Smalley Steel
Ring Company, Lake Zurich, Illinois. The double wound laminar ring does not have a
gap along the circumference that could cause a magnetic disturbance that could be
misinterpreted as axial movement of the plunger 30 by a magnetic position detector.
The target 96 may be magnetically responsive to be detectable by the non-contacting
position sensor 89. The retention ring 82 may be formed from a magnetically
responsive low carbon steel. Fig. 10 shows three alternative locations for the noncontacting
position sensor 89. The non-contacting position sensor 89 may be
disposed in any single location shown in Fig. 10, or any combination of a plurality of
the non-contacting position sensors 89 may be used for redundancy.
[0048] Returning back to Fig. 1, an electrical switch 17 may be disposed on the
vehicle 70 to selectably close a circuit 23 to provide electrical power to the solenoid
28. The switch 17 shown in Fig. 1 is a rocker switch, however any switch capable of
controlling the flow of power through the solenoid 28 may be used. The switch 17 may
be a low current switch that controls a relay or transistor that directly controls power
through the solenoid 28. An electronic status indicator 29 may be disposed in the
vehicle 70. An electronic driver circuit 25 may be disposed on the vehicle 70 to power
the electronic status indicator 29 to indicate a status of the locking differential system
11. In an example, the status may include at least three states. For example, the
electronic status indicator 29 may be a selectably illuminated indicator 88, and the
status may be indicated by a flash code. To illustrate, the selectably illuminated
indicator 88 may include a light emitting diode, incandescent lamp, fluorescent lamp,
or other selectably illuminatable light source.
[0049] An example of a flash code may be as follows: the first state is indicated by
not illuminating the electronic status indicator 29; the second state is indicated by
continuously illuminating the electronic status indicator 29; and the third state is
indicated by sequentially illuminating and not illuminating the electronic status indicator
29 with about a 50 percent duty cycle at a frequency between 1 and 20 hertz. Fig. 11
depicts a 50 percent duty cycle at a frequency of about 3 hertz. In Fig. , "On"
means the electronic status indicator 29 is illuminated, and "Off' means the electronic
status indicator 29 is not illuminated. States other than the three states in the example
above, for example, error conditions, may be indicated by predetermined sequences of
illuminating and not illuminating the electronic status indicator 29. An electronic
diagnostic system (not shown) may be connected to the locking differential system
to determine if error conditions exist.
[0050] In an example, the status is selected from the group consisting of a first
state, a second state, and a third state. In the example, the first state is a disengaged
state having the electrical switch 7 in an open condition disconnecting power to the
solenoid 28, and the lock ring 40 is in the disengaged position 44. The second state is
an engaged state having the electrical switch 7 in a closed condition connecting
power to the solenoid 28, and the lock ring 40 is in the engaged position 45. The third
state is a transition state having the electrical switch 17 in an open condition
disconnecting power to the solenoid 28, and the lock ring 40 is in the engaged position
45 (see Fig. 7B); or the electrical switch 17 is in a closed condition connecting power
to the solenoid 28, and the lock ring 40 is in the disengaged position 44 (see Fig. 7A).
The inventors of the present disclosure believe that indicating the transition state will
reduce a tendency for an operator to continue to press a differential lock control
button, or press the button harder, while the locking differential system 11 is in the
transition state.
[0051] It is to be understood that the terms "connect/connected/connection" and/or
the like are broadly defined herein to encompass a variety of divergent connected
arrangements and assembly techniques. These arrangements and techniques
include, but are not limited to ( 1 ) the direct communication between one component
and another component with no intervening components therebetween; and (2) the
communication of one component and another component with one or more
components therebetween, provided that the one component being "connected to" the
other component is somehow in operative communication with the other component
(notwithstanding the presence of one or more additional components therebetween).
[0052] In describing and claiming the examples disclosed herein, the singular forms
"a", "an", and "the" include plural referents unless the context clearly dictates
otherwise.
[0053] It is to be understood that the ranges provided herein include the stated
range and any value or sub-range within the stated range. For example, a range from
about 28 degrees to about 32 degrees should be interpreted to include not only the
explicitly recited limits of about 28 degrees and about 32 degrees, but also to include
individual values, such as 29 degrees, 30 degrees, 3 1 degrees, etc., and sub-ranges,
such as from about 28 degrees to about 3 1 degrees, etc. Furthermore, when "about"
is utilized to describe a value, this is meant to encompass minor variations (up to +/-
0%) from the stated value.
[0054] Furthermore, reference throughout the specification to "one example",
"another example", "an example", and so forth, means that a particular element (e.g.,
feature, structure, and/or characteristic) described in connection with the example is
included in at least one example described herein, and may or may not be present in
other examples. In addition, it is to be understood that the described elements for any
example may be combined in any suitable manner in the various examples unless the
context clearly dictates otherwise.
[0055] While several examples have been described in detail, it will be apparent to
those skilled in the art that the disclosed examples may be modified. Therefore, the
foregoing description is to be considered non-limiting.
What is claimed is:
1. A locking differential assembly, comprising:
a differential case defining an axis of rotation and a gear chamber;
a first side gear disposed at a first end of the differential case for selectable
relative rotation thereto;
a second side gear disposed at a second end of the differential case
opposite the first end for selectable rotation relative to the differential case;
at least two pinion gears rotatably supported in the gear chamber each of
the at least two pinion gears in meshing engagement with the first side gear and
the second side gear;
a solenoid disposed at the first end;
a plunger selectably magnetically actuatable by the solenoid;
a lock ring selectably engagable with the second side gear to selectably
prevent the second side gear from rotating relative to the differential case; and
at least two relay rods each connected to the plunger and to the lock ring to
cause the lock ring to remain a fixed predetermined distance from the plunger.
2 . The locking differential assembly as defined in claim 1, further
comprising:
side gear dogs defined on an outside diameter of the second side gear
parallel to the axis of rotation;
complementary dogs defined around an inside surface of the lock ring, the
complementary dogs selectably engagable with the side gear dogs by translating
the lock ring along the axis of rotation from a disengaged position to an engaged
position;
a spring disposed between the differential case and the lock ring to bias the
lock ring toward the disengaged position; and
a plurality of lugs defined on an outside surface of the lock ring, each lug to
slide in a respective complementary slot defined in the differential case to guide the
lock ring translation between the engaged position and the disengaged position
and to prevent rotation of the lock ring relative to the differential case;
wherein the second side gear is substantially prevented from rotating relative
to the differential case when the lock ring is in the engaged position, and the
second side gear is free to rotate relative to the differential case when the lock ring
is in the disengaged position and wherein the lock ring has a lock ring thickness
parallel to the axis of rotation.
3 . The locking differential assembly as defined in claim 2 wherein the
solenoid is directly wound onto a stator, the stator comprising:
an annular wall having a longitudinal axis coaxial with the axis of rotation;
a first stator annular flange extending radially from the annular wall to a first
outer diameter; and
a second stator annular flange extending from the annular wall spaced from
the first stator annular flange wherein the second stator annular flange is
frustoconical with an inner base annular surface opposite the first stator annular
flange and an outer base annular surface distal to the first stator annular flange,
wherein the inner base annular surface has an outer edge diameter equal to the
first outer diameter and the outer base annular surface has a second outer
diameter greater than the first outer diameter, wherein the first stator annular
flange, the annular wall and the second stator annular flange define an integral
bobbin for the solenoid, and wherein the stator is formed from a ferromagnetic
material, wherein the differential case is rotatable relative to the stator about the
axis of rotation.
4 . The locking differential assembly as defined in claim 3 wherein:
the annular wall is a cylindrical wall;
the longitudinal axis is a cylindrical axis;
the first stator annular flange extends perpendicularly to the cylindrical axis
from the cylindrical wall;
the second stator annular flange extends from the cylindrical wall spaced
from the first stator annular flange and parallel to the first stator annular flange; and
the first stator annular flange, the cylindrical wall and the second stator
annular flange define the integral bobbin.
5 . The locking differential assembly as defined in claim 3 wherein the
plunger comprises:
a ferromagnetic cylindrical body, including:
a cylindrical body axis defined by the ferromagnetic cylindrical body to
be aligned with the axis of rotation;
an inner wall having an annular bevel at a beveled end of the
ferromagnetic cylindrical body;
an outer wall having a plunger outer diameter; and
an annular plunger flange defined at a plunger end distal to the
beveled end wherein the annular plunger flange has a plunger flange
diameter smaller than the plunger outer diameter;
an annular notch defined by the ferromagnetic cylindrical body and the
annular plunger flange;
a plurality of relay rod attachment bores defined in the ferromagnetic
cylindrical body; and
a plurality of relay rod access slots each defined in the beveled end of the
ferromagnetic cylindrical body at each relay rod attachment bore, wherein the relay
rod attachment bore is substantially centered in the relay rod access slot, wherein
a shortest distance between the relay rod access slot and the annular notch is
equal to the lock ring thickness.
6 . The locking differential assembly as defined in claim 5, further
comprising:
a spacer disposed between the plunger and the differential case to prevent
the annular bevel of the inner wall from contacting the second stator annular
flange.
7 . The locking differential assembly as defined in claim 6 wherein the
spacer is a threaded rod adjustably screwed into the plunger to set a
predetermined gap between the annular bevel and the second stator annular
flange.
8 . The locking differential assembly as defined in claim 6 wherein the
spacer is a plurality of spaced raised bosses on the beveled end of the
ferromagnetic cylindrical body.
9 . The locking differential assembly as defined in claim 5, the at least
two relay rods each comprising:
a cylindrical rod portion having two ends, the cylindrical rod portion defining
a longitudinal rod axis at a center of the cylindrical rod portion;
a first post and a second post each having a smaller diameter than the
cylindrical rod portion defined at a respective one of the two ends, the first post and
the second post each concentric with the cylindrical rod portion; and
an annular groove defined on the first post and the second post, wherein the
first and second posts are substantially identical and the relay rod is symmetrical
end-to-end, wherein the first post is retained in a respective relay rod attachment
bore by a retention ring disposed in the annular notch of the plunger protruding into
the annular groove of the first post.
10. The locking differential assembly as defined in claim 9 wherein the
lock ring further includes extension tabs on a quantity of the lugs equal to a
quantity of the relay rods, the extension tabs each having a relay rod attachment
hole therethrough wherein each relay rod is retained in the respective relay rod
attachment hole by a clip installed in the annular groove of the respective second
post.
11. The locking differential assembly as defined in claim 10 wherein the
plurality of lugs is a quantity of nine lugs and the quantity of relay rods is three.
12. The locking differential assembly as defined in claim 1 wherein:
the plunger is fixed for rotation with the differential case; and
the plunger is selectably translatable relative to the differential case along
the axis of rotation.
13. The locking differential assembly as defined in claim 2 wherein:
each lug has two opposed faces symmetrically arranged about a radial line
perpendicular to the axis of rotation; and
an angle between the two opposed faces is from about 28 degrees to about
32 degrees.
14. The locking differential assembly as defined in claim 13 wherein the
plurality of lugs is a quantity of nine lugs.
15. The locking differential assembly as defined in claim 1, further
comprising:
a cross-shaft disposed perpendicularly to the axis of rotation of the
differential case to support an opposed pair of the at least two pinion gears for
rotation of the opposed pair of the at least two pinion gears on the cross-shaft.
16. The locking differential assembly as defined in claim 14, further
comprising:
a pair of opposed stub shafts disposed perpendicularly to the cross-shaft
and perpendicularly to the axis of rotation of the differential case through a yoke,
wherein:
the yoke is disposed around the cross-shaft;
the yoke has complementary apertures for receiving the stub shafts;
and
the pair of opposed stub shafts support an other opposed pair of the
at least two pinion gears.
17. A locking differential system, comprising:
the locking differential assembly as defined in claim 1;
a plunger position sensor to determine a state of the lock ring by detecting a
position of the plunger;
an electrical switch to selectably close a circuit to provide electrical power to
the solenoid;
an electronic status indicator; and
an electronic driver circuit for powering the electronic status indicator to
indicate a status of the locking differential system wherein the status includes at
least three states.
18. The locking differential system as defined in claim 17 wherein the
electronic status indicator is a selectably illuminated indicator and the status is
indicated by a flash code.
19. The locking differential system as defined in claim 17 wherein:
the status is selected from the group consisting of a first state, a second
state, and a third state;
the first state is a disengaged state having the electrical switch in an open
condition to disconnect power to the solenoid and the lock ring is in the disengaged
position;
the second state is an engaged state having the electrical switch in a closed
condition connecting power to the solenoid and the lock ring is in the engaged
position; and
the third state is a transition state having the electrical switch in an open
condition disconnecting power to the solenoid and the lock ring is in the engaged
position or the electrical switch is in a closed condition connecting power to the
solenoid and the lock ring is in the disengaged position.
20. The locking differential system as defined in claim 17 wherein:
the electronic status indicator is a selectably illuminated indicator;
the at least three states include a first state, a second state, and a third
state;
the first state is indicated by not illuminating the electronic status indicator;
the second state is indicated by continuously illuminating the electronic
status indicator; and
the third state is indicated by sequentially illuminating and not illuminating
the electronic status indicator with about a 50 percent duty cycle at a frequency
between 1 hertz and 20 hertz.
2 1. The locking differential system as defined in claim 17, further
comprising:
a stator having the solenoid directly wound thereon, the stator including:
an annular wall having a longitudinal axis coaxial with the axis of
rotation;
a first stator annular flange extending radially from the annular wall to
a first outer diameter; and
a second stator annular flange extending from the annular wall
spaced from the first stator annular flange and parallel to the first stator
annular flange, wherein the second stator annular flange is frustoconical with
an inner base annular surface opposite the first stator annular flange and an
outer base annular surface distal to the first stator annular flange, wherein
the inner base annular surface has an outer edge diameter equal to the first
outer diameter and the outer base annular surface has a second outer
diameter greater than the first outer diameter, wherein the first stator annular
flange, the annular wall and the second stator annular flange define an
integral bobbin for the solenoid and wherein the stator is formed from a
ferromagnetic material, wherein the differential case is rotatable relative to
the stator about the axis of rotation; and
a secondary coil wound around the stator to detect an inductance in the
solenoid responsive to a position of the plunger.
22. The locking differential assembly as defined in claim 2 1 wherein:
the annular wall is a cylindrical wall;
the longitudinal axis is a cylindrical axis;
the first stator annular flange extends perpendicularly to the cylindrical axis
from the cylindrical wall;
the second stator annular flange extends from the cylindrical wall spaced
from the first stator annular flange and parallel to the first stator annular flange; and
the first stator annular flange, the cylindrical wall and the second stator
annular flange define the integral bobbin.
23. The locking differential system as defined in claim 17, further
comprising:
a stator with the solenoid directly wound thereon; and
a non-contacting position sensor disposed on an anti-rotation bracket
connected to the stator, wherein the non-contacting position sensor is to detect an
axial position of the plunger or a target affixed to the plunger.
24. The locking differential system as defined in claim 23 wherein the noncontacting
position sensor is a Hall-Effect position sensor.