Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF T~IE INVENTION
This lnvention is a ~ear system which enables
transfer of engine supplied drive power -to and between two
and four-wheel high speed drive modes while the vehicle is
in motion as well as allowing independent shi~ting of power
to a ~-wheel low speed drive mode from a stopped neutral
position.
Four-wheel drive vehicles are highly desirable
for off-road travel over rou~h terrain because o~ their
greater reliability in providing traction in such conditions,
but on the usual hard improved surface roads they can be more
economically operated as a two-wheel conventional drive
vehicle. The capability of shifting of a four-wheel drive
vehicle to two-wheel driving and return therefore is highly
desirable dependent on the conditions of traction confronted.
Gear transfer arrangements of the prior art have
enabled conversion of vehicles -to two-wheel or four wheel
d-ive modes, but in many arrangements the shifting between
such modes has not been possible while the vehicle is in
?n motion. In one such arrangemen-t the position of the locking
drive hub oE the usual non-driven wheels must be manually
locked or unlocked to correspond to the four or two-wheel
drive shift control positions desired. Thus conversion from
two-wheel to four-wheel drive and return has been cumbersome,
~5 time consuming and subject to error in combinations of
settings required to obtain the wheel driving relationships
desired.
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In another -type of prior ar-t year shif-t sys-tem,
a belt drive arrangemen-t is relied upon in which a chain
bel-t is utilized to supply power to the gear sys-tem.
The efficiency of this system suffers from greater power
consumption in that all gears of the assembly opera-te
all the time with corresponding constant splashing -through
oil without relief in shifting from one drive mocle to
another. In addition, the chain belt drive calls for
a greater amount of space in comparison to a corresponding
gear assembly.
Other all gear systems exlst which include
constant mesh gear arrangements but lac]c the simple reliable
fixed relation of gears of the present invention in addition
to lacking means for synchronizing gear speeds for a smooth
shift between two and four-wheel drive modes while the
vehicle is in motion and a single fork means effecting
shifts between operating modes.
In view of the foregoing, it is an object of the
present invention to provide an improved torque transfer
system in the form o, a gear assembly unit incorporating
a synchronizer for ma-tching gear speeds to permlt shifting
of torque from a two to a four-wheel drive mode and
return while the vehicle is in mo-tion and in which only
a single actuating fork is required to change operating
modes.
Another object of the invention is to provide an
improved rugged and long life torque -transfer unit in
which reliability is promotecl by having all the gears
rotatably in an axially fixed position in constant mesh
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relationshlp and in which torque transfers through -the
system can be effected by the movement of a single shiEt
fork.
SUM~ARY OF TEE INVE~TION
The invention is an improved vehicle torque transfer
gear mechanism in which the gear assembly includes an
input set of two constantly meshed gears in side by side
spaced relation with an output set of -three constantly
meshed gears and a gear speed synchronizer be-tween the
two gear sets associated with the output set to match
speeds of the two gear sets to enable a smooth shifting
of torque paths between two and four-wheel high drive
modes while the vehicle is in motion. Clutching collars
all movable by a single shift fork effect -the changes
in drive modes selected by way oE a shift control rod.
~he ~our-wheel low speed drive mode is set by shifting
from a stop/neutral position. A novel concentric arrangement
of clutching collars with interlocking slug means in the
form of poppet balls or palls provide a space saving means
for shifting torque paths. In addition the annular
synchronizer in applicant's arrangement is positively
piloted by support about opposite peripheral edges thereby
assuring more square and positive alignmen-t and suppor-t
of the synchronizer a~ainst wobble ~or reliable operation.
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A fea-ture oE the inven-tion is that power -transfer
is effected through an all year assembly in which only
two gears o~erate in -the two-wheel drive mode while all
five gears are called into operation only in the lesser
used four-wheel drive mode -thus promoting high efficiency
in over all operation of the power transfer unit.
Still another feature of the invention is tha-t
only a single fork is required for shift of torque -transfer
collars and for ac-tivation of the synchronlzer to effect
shifts of torque paths through the gear assembl~.
BRIEE DESCRIPTION OF T~IE DRAWI~GS
Figure 1 is a partia.l.ly schematic ~lan view
of components of a four-wheel drive system for an automotlve
vehicle including a gear transfer unit of the present
invention;
Figure 2 is an enlarged and elevational view
of the rear output end of the case for the four-wheel
gear transfer unit of Figure 1;
Figure 3 is a cross-sectional view of the transfer
case of Figure 2 as taken on line 3-3 showing -the five
gear assembly with the svnchronizer located between the
input and output gear sets;
Figure ~ is a cross-sectional view of the transfer
case shown in Figure 2 showing the gear assembly as vi.ewed
on line 4-~ illustrating the shift rod and shift ~ork for
engagement wi-th clutch collars to e.ffect chan~es in drive
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modes of -the vehicle;
Figure 5 is an enlarged somewhat schematic view
of a portion of the gear assembly oE Figure 3 showing
the clutch collar position and the synchronizer setting
to provide a two-wheel high speed drive mode for the
vehicle;
Figure 6 is a view of part of the gear assembly
of Figure 3 showin~ the shift collar and synchronizer
settings for a four-wheel high drive mode of the vehicle;
Figure 7 is a view of part of the gear assembly
o~ Figure 3 showing the shift collar and sychronizer
settings for the neutral mode of the vehicle; and
Figure 8 is a view of part of the gear assembly
of Figure 3 showing the shift clutch collar and synchronizer
lS settings for a four-wheel low drive mode of the vehicle.
BEST MODE OF CARRYING OUT I~VE~TION
Referring to the drawings in grea-ter detail,
Figure 1 shows the case 10 for the torque transfer mechanism
of the present invention positioned in a four-wheel vehicle
behind the engine 11 and its transmission 12 which has
a tail shaft (not shown) to which the unit 10 is connected
for receipt of engine driving power. Power is transmitted
from the unit 10 to the rear wheels 1~ through a rear
differential 13 and power supplied to the frcnt wheels
16 is supplied through a front wheel differential 15.
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Figure 2 shows the rear output end oE the gear
case 10 with its rear drive shaE-t por-tion 21 includiny
the rear output shaft 30, closed front drive shaft portion
22 and the closed intermediate shaf-t por-tion 23.
Figure 3 is a cross-sectional view of the case
10 as taken on line 3-3 of Figure 2 showing the input drive
shaft ~0 and the associated gear assembly for dri~7ing the
rear wheel and front wheel output shafts 30 and 32,
respectively. The input dri~7e shaft 20 is a~ially aligned
with -the rear output shaft 30, each shaf-t being rotatable
independent of the other, but interassociated by providing
the input shaft 20 with a reduced diameter end portion
extendin~ coaxially into a hollowed end portion of the
rear output shaft 30. A small gap 36 between the mated
coaxial ends of the shafts provides a space for a needle
bearing 37 t~ provide mu-tual support for the two shafts
20 and 30.
Two sets of constant mesh gears make up the torque
transfer gear assembly, namely an input gear se-t and
an output gear set. The input gear set includes an input
gear 40 in constant mesh with a larger diameter low speed
gear 45. The input gear is fixed on the input shaft 20 and
can be formed integrally with the inpu-t shaft as shown to
provide a solid constantly aligned combination. The low
~5 speed gear 45 is rotatably mounted on roller bearings on
an intermediate shaft 47.
The output gear set includes a rear drive gear
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50 in cons-tant mesh rela-tion with a smaller intermedia-te
gear 55 which in -turn is in constan-t mesh with the front
output gear 57 which is of the same .size as the rear drive
gear 50. The rear drive gear 50 is suppor-ted ro-tationally
on the rear output shaft 30 while the i.ntermediate gear
55 is rotatably mounted on roller bearings on the
intermediate shaft 47 and the front drive gear is fixed
in splined relation on a ball bea.ring supported front output
shaft 32.
The drive power paths through the gear assembly
are changed by laterally shifting of collars on and between
splines 48 and 68 at the confronting exterior ends of the
input and rear output shafts 20 and 30, respectively, splines
51 of a hub of the rea,r drive gear 50 and confronting hubs
of the in-ter~edia-te gear 55 and low speed gear ~5 on the
intermediate shaft 47.
TWO--WEIEEL HIGH MODE
Figures 5 and 6 show a coaxial collar assembly
in which in-ternal splines 61 of an annular outer collar 60
make slideable driving engagemen-t with external teeth 67 of
a smaller annular interior collar 65. The interior collar
65 has internal splines 66 which in the high speed two-wheel
drive mode of the assembly bridges the gap bet~7een t,he
confronting ends of the input and rear output shafts 20 and
30 and engages matching peripheral splines 48 and 68 about
the ends of shafts 20 and 30, respectively. A series of
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elongated cylindrical locking slugs 69 with hemi-spherical
ends, herein alternatively termed palls 69, are each snugly
fit wi-thin one of a series of apertures in a thicker e~tra
strength marginal edge 70 provided on the inner collar
65. The collar edge 70 as shown extends over -the end
portions of splines 68 on shaft 30 where the ends of the
palls 69 make engagement wi-th ma-tching locking recesses
71 in the splines 68. The palls 69 are sufficiently long
to be backed by the splines of the outer collar 60 thereby
causing the palls to positively lock the collar 65 in
its bridging relation in the two wheel drive mode until
the collar 60 is slid laterally as described hereinafter,
where an opposite series of pall matching recesses 72
in the interior splines 61 of -the outer collar 60 receive
the opposite ends of the palls to release -the palls and
the collar 65 from their locked -two-wheel position.
A pin type synchronizer 25 is mated in selective
driving relation with the rear output drive gear 50 and
has its locking ring 27 joined integrally with the outer
circumferential periphery of the collar 60 so tha-t upon
movement of collar 60, the synchronizer is activated to
establish a driving relation with the rear drive gear 50.
The synchronizer includes a cone shaped clutching ring 29
which selectively makes a locked driving communicatlon or
a disengaged non-driving relation with a finished internal
rim 35 of the rear drive gear 50. The synchronizer in the
two-wheel high mode represented in Figure 5 is illustrated
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in its disengaged rela-tion. A set oE synchronize:r blocking
pins 26 e~-tend between -the clutching ring 29 and an opposite
retaining ring 31 and in doing so, pass through separate
retaining apertures in the locking ring 27. The blocking
pins 26 each have a circumferential groove 28 which when
the synchronizer is inactive, is located in the region
of the aperture in the locking ring 27 through which i-t
passes, thus resulting in the pins 26 being held in a
released condition within the locking ring 27. The
retaining .-ing 31 in the present invention is piloted
by a residence backing groove 33 in a stationary portion
of the case for the transfer mechanism 10, which as shown
is in the form of a projecting portion 34. Thus the
synchronizer can be stably retained against possible wobble
within the assembly and maintained in dimensionally square
association with the rear drive gear 50.
When the synchronizer locking ring 27 is moved
laterally for selection of a next drive mode, which from
the two-wheel drivejarrangement represented in Figures
3 and 5 would be the four-wheel high drive mode of Figure 6,
the ring 27 passes over the shoulders of the blocking
pin grooves 28 and causes the pins to take on positions
which results in the cone shaped clutching ring 29 engaging
the rear drive gear rim surface 35 in driving relation.
The mechanism for effecting a change of drive
mode by way of a single manually operated control rod (not
shown) is illustrated in Figure 4 which is a cross-sectional
view of the torque transfer unit as taken on line 4-
~of ~igure 2. A shi:E-t rod 80 connected to and moved by
the manually opera-ted control rod has a shift fork 90
mounted thereon in close fit sliding relation by way of
a fork hub 93 which is backed by a retaining ring 98 fixed
on shaft 80. An upper arm 91 of the shift fork makes
enqagement with the rotatable synchronizer locking ring
27 which in turn is directly connected -to the outer shift
collar 60 so that upon lateral movement of the fork 90
both the locking ring and the collar 60 are correspondingly
laterally moved. An oppositely extending lower arm 92
of the fork similarly engages a low speed rotatable collar
52 to permit la-teral movement thereof bv way of an exterior
detent 54 pro~ecting therefrom. The collar 52 has internal
splines 53 which communicate in sliding relation with
mating splines 46 and 56 on the hubs of gears 45 and 55,
respectively, both rotatably mounted in side-by-side
relation on t~e intermediate shart 47.
The hub 93 of fork 90 has a hollow cup-like
opening 95 for accommodati.on of a biasing spring 94
surrounding the shaft 80 and extending outwardly from
t.he hollow hub portion 95 for spring pressure relation
against an annular spring retainer washer 96 mounted on
the shaft 80 and backed by a retaining ring 97 Eixed on
the shaft. The pressure of the spring 94 against the
washer 96 bi.ases the fork hub 93 toward and against
another retaining ring 98 also fixed on the shaft 80.
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The shaft ~0 has a series of side-by-sicle circum-
ferential mode position grooves 8~, 85, 86 and 87 for
positioning of the shift rod 80 in semi-locked pressure
relation for the two-wheel high, four-wheel high, neutral
and four-wheel low speed drive modes, respectively. An
e~tra groove 88 is provided for association with switching
means for activation or signalling of auxiliary components
if desired. At least one poppet ball 81 makes pressure
engagement with the matching rounded grooves each in turn
under the biased influence of a spring 82 which communicates
with the ball within a residence opening 83 for the spring
and ball in -the case for unit. When the shaft 80 is moved
longitudinally the pressure of the poppet ball 81
communicating with each respective groove is overcome
to effect a shift in mode. When the shift rod 80 is moved
to a position corresponding to the four-wheel high drive
where the poppet ball pressure is exerted in groove 84,
the pressure of the spring 82 is overcome and the ball
81 passes over -the ridge of groove 84 and drops into groove
85 to lock the fork 90 in this position.
Figures 5 to ~ illustrate in sequence the power
paths throu~h the effective components of the gear assembly
for -the two-wheel high, -the four-wheel high, neutral and
four-wheel low modes, respectively. The synchroni~er 25 in
the -two wheel high mode, as described above, is in active
condition represented in Fi~ure 5 while the input drive
shaft 20 is connected directly to the rear output shaft 30
by the inner collar 65, the interior splines 66 of which
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establish a locked interenyayiny drlviny relation between
splines ~8 of the input shaft and s~lines 68 o~ -the ou-tput
sha-ft 30.
FOUR--WHEEL HIGEI MODE
Upon shift of the rod 80 from its -two-wheel high
drive mode to the four-wheel high mode represented in
Figure 6, the poppe-t ball 81 is biased in-to the groove
85 to hold the shift rod 80 in position~ The synchronizer
locking ring 27 and the integrally associated external
collar 60 of the coaxial collar assembly are thereby moved
laterally toward the rear drive gear 50. In sequence,
the synchronizer 25 is first activated by movement of
its locking ring 27 over a portion of each of the blocking
pins 26 from the grooves 28 which brings the clutch ring
29 into frictional driving engagement with the rim 35
of the rear drive gear 50. The gear 50 is thereupon
gradually brought up to the rotational speed of the
interconnected input and rear output shafts 20 and 30,
respectively, whereupon the collar 60 and its splines
61 can mate and slide into positive driving relation with
the splines 51 of gear 50. The rear drive shaft 30 and
the constant mesh output gear set including rear drive
gear 50, intermediate gear 55, the front drive gear 57
and the front drive shaft on which it is fixed are thus
all driven in unison in the four-wheel high speed mode
by the input drive shaft 20.
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NEUTRAL MOD~
When the shi-Et rod 80 is moved to the neutral
mode represented in Figure 7, the fork 90 moves the
synchronizer locking ring 27 and collar 60 still another
5 step closer to -the output gear 50 over its splines 51.
This movement causes a radial inward thicker marginal pro~ecting
portion 73 of the collar 60 to engage -the ma-tching radial
outward projection 74 at the marginal edge 70 of collar 65
and to draw the collar with it away from engagement with
splines 48 of the input shaft 200 As may be seen in Figure
6, the repositioning of the collar 65 from its locked
conditlon of the two-wheel high mode releases the locking
pall 69 because o:E the p.resence of a pall recess 72 in
splines 61 which allows the locking pall 69 to be accepted
in recess 72 from the locking recess 71. This in turn
interlocks the exterior and interior collars 60 and 65 in
an eY~tended relation as illustrated in Figure 7 with the
collar 65 withdrawn from its driven communication with the
splines 48 of the input shaft 20. The output gear set is
thus placed in an idle neutral condition with neither ~he
rear or Eront output shafts 30 and 32 connected for receipt
of power.
FOUR-W~IEEL LOW MODE
Upon movement of the shift rod 80 ~rom the neutral
position to the four-wheel low drive mode represente~
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in Figure 8, -the interlocked extended collars 60 and 65
are advanced still fur-ther toward the rear outpu-t gear
50 while maintaining their connected relation with the
splines 61 and 68 and correspondingly maintaining an
interlocked relation of the output gear 50 with the rear
output shaft 30. At the same time the low speed collar
52 is moved into position to bridge splines 46 and 56
of the low speed gear 45 and intermedia-te gear 55,
respectively, thereby resulting in these two gears rotating
in unison. The torque of the input shaft 20 thus is
transmitted Erom the inpu-t gear 40 to the low speed and
intermediate gears 45 and 55, respectively, from which
it is transmitted to both the rear and front output gears
50 and 57, respectively, and correspondingly the rear
and front output shafts 30 and 32 to which they are
connected. ~hus the four wheels of the vehicle are supplied
with torque power at the same rotational speed since both
the rear drive gear 50 and front drive gear 57 are of
the same size and are both driven by the smaller
intermediate gear 55 which in turn is driven by the larger
low speed gear 45, consequently providing a higher torque
and lower speed power to the output shaft in comparison
to the power supplied to the input shaft 20.
SHIFT UNDER WINDUP STRESS
As the shift rod 80 is moved into position from
the two-wheel high mode illustrated in Figure 3~4/ and
5 to the four-wheel high, neutral and four-wheel low modes
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of Figures 6, 7,and 8, respectively, the retaining ring
98 pushes the hub 93 of the fork 90 laterally ~o activate
the synchronizer and position clutch collars for the
corresponding operating modes without significant restraint
upon movement of the shift rod 80. In reverse sequence,
however, the assembly at times has transient internal
stresses of drive wheel windup developed therein, such
as by reason of vehicle turns which result in greater
travel of the front wheels relative to the rear wheels,
which cause a restraint in movement of collars for shifts
from four-wheel drive modes. More specifically, upon
motion of the shif-t rod 80 from the four-wheel high mode
of Figure 6 to the two-wheel high mode of Figure 5, stresses
can arise between splines 51 and 61 of the rear output
gear 50 and the collar 60, respectively, such that the
collar 60 is restrained from lateral movement to effect
its disengagement from gear 50 for shift into the two-wheel
high mode illustrated in Figure 5. The shift rod 80 in
being moved under such assembly stressed conditi.ons slides
within the fork hub 93 càusing the retaining washer 96
to compress spring 95 within the hollow 94 of the fork
hub 93 and correspondingly exert pressure on the hub 93
-to promote the disengagement between collar 60 and gear
50 upon reduc-tion of the stresses therebetween with
continuing travel of vehicle. Thus the actual shift
of the fork 90 under the biasing ac-tion of the spring
95 from -the four wheel high position to the two-wheel
high position may be delayed slightly until windup
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s-tresses which may be present in the assembly are reduced
sufficien-tly that the spring 95 can move the fork arm
90 laterally a distance limited bv the retaining ring 98
and corresponding to the new mode.
Similarly when the rod 80 in being shifted
from its four-wheel low drive position to the neutral
position, like stresses between gear splines 61 and collar
splines 51 and between collar splines 66 and splines 68
at the rear output shaft 30 can restrain and delay movement
of the extended interlocked collars 60 and 65 from the
position of the four-wheel drive illustrated in Figure 8
to the position illustrated in Figure 7 where the splines
53 of the low speed collar 52 are disengaged from the
intermediate gear splines 56. The spring 95 is compressed
and is effective during such a transfer to promote the
spline disengagement upon reduction of stress between the
collar splines 61 and the gear splines 51. It will be
recognized in view of the foregoing that the spring 95 is
selected to exert sufficient force to move the fork 90 and
2n collars of the assembly upon reduction of transfer
restraining stresses, b-ut no-t so large as to exert a back
pressure against the spring retainer 96 to overcome the
locking action imparted on the shift rod 80 by the spring
82 on the poppet ball 81 in the shift rod groove of the
selected operating mode.
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Although the drawings and description of -the
invention are herein presented in relation oE -the preferred
form of the invention, it will be recognized tha-t variations
are possible within the broad scope of the invention.
For example, the synchronizer in the described embodiment
is associated with the rear output drive gear, but instead
can be included in the assembly in association wi-th the
intermediate gear or with the front output drive gear
if the latter is made free to rotate on its supporting
shaft. Still further, the pilot support for the
synchronizer can be any of a number of housing supports
built into the casing for the assembly.
In view of the foregoing it will be understood
that many variations of the arrangement of my invention
can be provided within the broad scope of the principles
embodied therein. Thus while a particular preferred
embodiment of my invention has been shown and described,
it is intended by the appended claims to cover all such
modifications which fall within the true spirit and scope
of the invention.
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